Statistical Mechanics of Thin Spherical Shells
Directory of Open Access Journals (Sweden)
Andrej Košmrlj
2017-01-01
Full Text Available We explore how thermal fluctuations affect the mechanics of thin amorphous spherical shells. In flat membranes with a shear modulus, thermal fluctuations increase the bending rigidity and reduce the in-plane elastic moduli in a scale-dependent fashion. This is still true for spherical shells. However, the additional coupling between the shell curvature, the local in-plane stretching modes, and the local out-of-plane undulations leads to novel phenomena. In spherical shells, thermal fluctuations produce a radius-dependent negative effective surface tension, equivalent to applying an inward external pressure. By adapting renormalization group calculations to allow for a spherical background curvature, we show that while small spherical shells are stable, sufficiently large shells are crushed by this thermally generated “pressure.” Such shells can be stabilized by an outward osmotic pressure, but the effective shell size grows nonlinearly with increasing outward pressure, with the same universal power-law exponent that characterizes the response of fluctuating flat membranes to a uniform tension.
Stability of transparent spherically symmetric thin shells and wormholes
International Nuclear Information System (INIS)
Ishak, Mustapha; Lake, Kayll
2002-01-01
The stability of transparent spherically symmetric thin shells (and wormholes) to linearized spherically symmetric perturbations about static equilibrium is examined. This work generalizes and systematizes previous studies and explores the consequences of including the cosmological constant. The approach shows how the existence (or not) of a domain wall dominates the landscape of possible equilibrium configurations
Spherical thin-shell wormholes and modified Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Azam, M., E-mail: msharif.math@pu.edu.pk, E-mail: azammath@gmail.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2013-05-01
The purpose of this paper is to construct spherical thin-shell wormhole solutions through cut and paste technique and investigate the stability of these solutions in the vicinity of modified Chaplygin gas. The Darmois-Israel formalism is used to formulate the stresses of the surface concentrating the exotic matter. We explore the stability of the wormhole solutions by using the standard potential method. We conclude that there exist more stable as well as unstable solutions than the previous study with generalized Chaplygin gas [19].
Cell membrane wrapping of a spherical thin elastic shell.
Yi, Xin; Gao, Huajian
2015-02-14
Nanocapsules that can be tailored intelligently and specifically have drawn considerable attention in the fields of drug delivery and bioimaging. Here we conduct a theoretical study on cell uptake of a spherical nanocapsule which is modeled as a linear elastic solid thin shell in three dimensions. It is found that there exist five wrapping phases based on the stability of three wrapping states: no wrapping, partial wrapping and full wrapping. The wrapping phase diagrams are strongly dependent on the capsule size, adhesion energy, cell membrane tension, and bending rigidity ratio between the capsule and membrane. Discussion is made on similarities and differences between the cell uptake of solid nanocapsules and fluid vesicles. The reported results may have important implications for biomedical applications of nanotechnology.
On Perturbation Solutions for Axisymmetric Bending Boundary Values of a Deep Thin Spherical Shell
Directory of Open Access Journals (Sweden)
Rong Xiao
2014-01-01
Full Text Available On the basis of the general theory of elastic thin shells and the Kirchhoff-Love hypothesis, a fundamental equation for a thin shell under the moment theory is established. In this study, the author derives Reissner’s equation with a transverse shear force Q1 and the displacement component w. These basic unknown quantities are derived considering the axisymmetry of the deep, thin spherical shell and manage to constitute a boundary value question of axisymmetric bending of the deep thin spherical shell under boundary conditions. The asymptotic solution is obtained by the composite expansion method. At the end of this paper, to prove the correctness and accuracy of the derivation, an example is given to compare the numerical solution by ANSYS and the perturbation solution. Meanwhile, the effects of material and geometric parameters on the nonlinear response of axisymmetric deep thin spherical shell under uniform external pressure are also analyzed in this paper.
SOUND FIELD SHIELDING BY FLAT ELASTIC LAYER AND THIN UNCLOSED SPHERICAL SHELL
Directory of Open Access Journals (Sweden)
G. Ch. Shushkevich
2014-01-01
Full Text Available An analytical solution of a boundary problem describing the process of penetration of a sound field of a spherical radiator located inside a thin unclosed spherical shell through a flat elastic layer is constructed. An influence of some parameters of the problem on the value of the attenuation coeffi-cient (screening of the sound field was studied by using a numerical simulation.
Dynamic behaviors of visco-elastic thin-walled spherical shells impact onto a rigid plate
Directory of Open Access Journals (Sweden)
X.W. Zhang
Full Text Available As a representative structure, ping-pong balls are usually used to study the mechanical properties of thin-walled spherical shells. In a previous study, the dynamic behaviors of ping-pong balls impinged onto a rigid plate were investigated. It was found that the dynamic deformation energy of the balls could be several times higher than that under quasi-static compression, which could not be completely explained by elastic-plastic material property, strain-rate and inertial effects. In this paper, more impact tests were conducted and the details including the contact time, deformation and rebound behaviors with different impact velocities were reinvestigated. Based on the experimental results, visco-elastic material model is applied and the numerical simulation of thin-walled spherical shells impact onto a plate is performed, in which the influences of the visco-elastic parameters and the impact velocity on the dynamic behaviors are studied. By adjusting the visco-elastic parameters, the contact time, deformation, and the coefficient of restitution agree well with the experimental results.
Onset of low Prandtl number thermal convection in thin spherical shells
Garcia, F.; Chambers, F. R. N.; Watts, A. L.
2018-02-01
This study considers the onset of stress-free Boussinesq thermal convection in rotating spherical shells with an aspect ratio η =ri/ro=0.9 (ri and ro being the inner and outer radius), Prandtl numbers Pr∈[10-4,10-1] , and Taylor numbers Ta ∈[104,1012] . We are particularly interested in the form of the convective cell pattern that develops, and in its time scales, since this may have observational consequences. For a fixed Ta 3 ×109 , the unicellular polar modes become also preferred at moderate Pr˜10-2 because two new transition curves between EA and AP/SP and between AP/SP and SC modes are born at a triple-point bifurcation. The dependence on Pr and Ta of the transitions is studied to estimate the types of modes, and their critical parameters, preferred at different stellar regimes.
PENETRATION OF A SOUND FIELD THROUGH A MULTILAYERED SPHERICAL SHELL
Directory of Open Access Journals (Sweden)
G. Ch. Shushkevich
2013-01-01
Full Text Available An analytical solution of the boundary problem describing the process of penetration of thesound field of a spherical emitter located inside a thin unclosed spherical shell through a permeable multilayered spherical shell is considered. The influence of some parameters of the problem on the value of the sound field weakening (screening coefficient is studied via a numerical simulation.
PENETRATION OF A SOUND FIELD THROUGH A MULTILAYERED SPHERICAL SHELL
G. Ch. Shushkevich; N. N. Kiselyova
2013-01-01
An analytical solution of the boundary problem describing the process of penetration of thesound field of a spherical emitter located inside a thin unclosed spherical shell through a permeable multilayered spherical shell is considered. The influence of some parameters of the problem on the value of the sound field weakening (screening) coefficient is studied via a numerical simulation.
Galileon radiation from a spherical collapsing shell
Energy Technology Data Exchange (ETDEWEB)
Martín-García, Javier [Instituto de Física Teórica UAM/CSIC,C/ Nicolás Cabrera 15, E-28049 Madrid (Spain); Vázquez-Mozo, Miguel Á. [Instituto Universitario de Física Fundamental y Matemáticas (IUFFyM),Universidad de Salamanca, Plaza de la Merced s/n, E-37008 Salamanca (Spain)
2017-01-17
Galileon radiation in the collapse of a thin spherical shell of matter is analyzed. In the framework of a cubic Galileon theory, we compute the field profile produced at large distances by a short collapse, finding that the radiated field has two peaks traveling ahead of light fronts. The total energy radiated during the collapse follows a power law scaling with the shell’s physical width and results from two competing effects: a Vainshtein suppression of the emission and an enhancement due to the thinness of the shell.
Ibragimov, Ranis N.
2018-03-01
The nonlinear Euler equations are used to model two-dimensional atmosphere dynamics in a thin rotating spherical shell. The energy balance is deduced on the basis of two classes of functorially independent invariant solutions associated with the model. It it shown that the energy balance is exactly the conservation law for one class of the solutions whereas the second class of invariant solutions provides and asymptotic convergence of the energy balance to the conservation law.
Solutocapillary convection in spherical shells
Subramanian, Pravin; Zebib, Abdelfattah; McQuillan, Barry
2005-01-01
A linear stability study of solutocapillary driven Marangoni instabilities in small spherical shells is presented. The shells contain a binary fluid with an evaporating solvent. The viscosity is a strong function of the solvent concentration, the inner surface of the shell is assumed impermeable and stress free, while nonlinear boundary conditions are modeled and prescribed at the receding outer boundary. A time-dependent diffusive state is possible and may lose stability through the Marangoni mechanism due to surface tension dependence on solvent concentration (buoyant forces are negligible in this microscale problem). A frozen-time or quasisteady state linear stability analysis is performed to compute the critical Reynolds number and degree of surface harmonics, as well as the maximum growth rate of perturbations at specified parameters. The development of maximum growth rates in time was also computed by solving the initial value problem with random initial conditions. Results from both approaches are in good agreement except at short times where there is dependence on initial conditions. The physical problem models the manufacturing of spherical shells used as targets in inertial confinement fusion experiments where perfect sphericity is demanded for efficient fusion ignition. It is proposed that the Marangoni instability might be the source of observed surface roughness. Comparisons with the available experiments are made with reasonable qualitative and quantitative agreement.
Casimir effect in spherical shells
International Nuclear Information System (INIS)
Ruggiero, J.R.
1985-01-01
The analytic regularization method is applied to study the Casimir effect for spherical cavities. Although many works have been presented in the past few years, problems related to the elimination of the regulator parameter still remain. A way to calculate the zero point energy of a perfectly conducting spherical shell which is a miscellaneous of those presented early is here proposed, How a cancelation of divergent terms occurs and how a finite parte is obtained after the elimination of the regulator parameter is shown. As a by-product the zero point energy of the interior vibration modes is obtained and this has some relevance to the quarks bag model. This relev ance is also discussed. The calculation of the energy fom the density view is also discussed. Some works in this field are criticized. The logarithmic divergent terms in the zero point energy are studied when the interior and exterior of the sphere are considered as a medium not dispersive and characterized by a dielectric constants ε 1 and ε 2 and peermeability constants μ 1 and μ 2 respectivelly. The logarithmic divergent terms are not present in the case of ε i μ i =K, with K some constant and i=1,2. (author) [pt
Collapsing spherical null shells in general relativity
Directory of Open Access Journals (Sweden)
S Khakshournia
2011-03-01
Full Text Available In this work, the gravitational collapse of a spherically symmetric null shell with the flat interior and a charged Vaidya exterior spacetimes is studied. There is no gravitational impulsive wave present on the null hypersurface which is shear-free and contracting. It follows that there is a critical radius at which the shell bounces and starts expanding.
Energy Technology Data Exchange (ETDEWEB)
Martin-Moruno, Prado; Visser, Matt [School of Mathematics, Statistics, and Operations Research, Victoria University of Wellington, PO Box 600, Wellington 6140 (New Zealand); Garcia, Nadiezhda Montelongo [Departamento de Física, Centro de Investigación y Estudios avanzados del I.P.N., A.P. 14-700,07000 México, DF (Mexico); Lobo, Francisco S.N., E-mail: prado@msor.vuw.ac.nz, E-mail: nmontelongo@fis.cinvestav.mx, E-mail: flobo@cii.fc.ul.pt, E-mail: matt.visser@msor.vuw.ac.nz [Centro de Astronomia e Astrofísica da Universidade de Lisboa, Campo Grande, Edifício C8 1749-016 Lisboa (Portugal)
2012-03-01
We construct generic spherically symmetric thin-shell gravastars by using the cut-and-paste procedure. We take considerable effort to make the analysis as general and unified as practicable; investigating both the internal physics of the transition layer and its interaction with 'external forces' arising due to interactions between the transition layer and the bulk spacetime. Furthermore, we discuss both the dynamic and static situations. In particular, we consider 'bounded excursion' dynamical configurations, and probe the stability of static configurations. For gravastars there is always a particularly compelling configuration in which the surface energy density is zero, while surface tension is nonzero.
Statistical mechanics of microscopically thin thermalized shells
Kosmrlj, Andrej
Recent explosion in fabrication of microscopically thin free standing structures made from graphene and other two-dimensional materials has led to a renewed interest in the mechanics of such structures in presence of thermal fluctuations. Since late 1980s it has been known that for flat solid sheets thermal fluctuations effectively increase the bending rigidity and reduce the bulk and shear moduli in a scale-dependent fashion. However, much is still unknown about the mechanics of thermalized flat sheets of complex geometries and about the mechanics of thermalized shells with non-zero background curvature. In this talk I will present recent development in the mechanics of thermalized ribbons, spherical shells and cylindrical tubes. Long ribbons are found to behave like hybrids between flat sheets with renormalized elastic constants and semi-flexible polymers, and these results can be used to predict the mechanics of graphene kirigami structures. Contrary to the anticipated behavior for ribbons, the non-zero background curvature of shells leads to remarkable novel phenomena. In shells, thermal fluctuations effectively generate negative surface tension, which can significantly reduce the critical buckling pressure for spherical shells and the critical axial load for cylindrical tubes. For large shells this thermally generated load becomes big enough to spontaneously crush spherical shells and cylindrical tubes even in the absence of external loads. I will comment on the relevance for crushing of microscopic shells (viral capsids, bacteria, microcapsules) due to osmotic shocks and for crushing of nanotubes.
Stability of charged thin shell wormhole supported by polytropic gas
Eid, A.
2017-05-01
In the framework of Darmois-Israel formalism, the general equations describing the motion of thin shell wormhole with a general form of equation of state of a polytropic gas are derived. The mechanical stability analysis of thin shell wormhole with charge in Reissner-Nordstrom (RN) to linearized spherically symmetric perturbation about static equilibrium solution is carried out.
Spherical shells buckling to the sound of music
Lee, Anna; Marthelot, Joel; Reis, Pedro
We study how the critical buckling load of spherical elastic shells can be modified by a fluctuating external pressure field. In our experiments, we employ thin elastomeric shells of nearly uniform thickness fabricated by the coating of a hemispherical mold with a polymer solution, which upon curing yields elastic structures. A shell is submerged in a water bath and loaded quasi-statically until buckling occurs by reducing its inner volume with a syringe pump. Simultaneously, a plunger connected to an electromagnetic shaker is placed above the shell and driven sinusoidally to create a fluctuating external pressure field that can excite dynamic vibration modes of the shell. These dynamic modes induce effective compressive stresses, in addition to those from the inner pressure loading, which can modify the critical conditions for the onset of buckling. We systematically quantify how the frequency and amplitude of the external driving affects the buckling strength of our shells. In specific regions of the parameter space, we find that pressure fluctuations can result in large reductions of the critical buckling pressure. This is analogous to the classic knock-down effect in shells due to intrinsic geometric imperfections, albeit now in a way that can be controlled externally.
Convection patterns in a spherical fluid shell
Feudel, F.; Bergemann, K.; Tuckerman, L. S.; Egbers, C.; Futterer, B.; Gellert, M.; Hollerbach, R.
2011-04-01
Symmetry-breaking bifurcations have been studied for convection in a nonrotating spherical shell whose outer radius is twice the inner radius, under the influence of an externally applied central force field with a radial dependence proportional to 1/r5. This work is motivated by the GeoFlow experiment, which is performed under microgravity condition at the International Space Station where this particular central force can be generated. In order to predict the observable patterns, simulations together with path-following techniques and stability computations have been applied. Branches of axisymmetric, octahedral, and seven-cell solutions have been traced. The bifurcations producing them have been identified and their stability ranges determined. At higher Rayleigh numbers, time-periodic states with a complex spatiotemporal symmetry are found, which we call breathing patterns.
Creep stresses in a spherical shell under steady state temperature
Verma, Gaurav; Rana, Puneet
2017-10-01
The paper investigates the problem of creep of a spherical structure under the influence of steady state temperature. The problem of creep in spherical shell is solved by using the concept of generalized strain measures and transition hypothesis given by Seth. The problem has reduced to non-linear differential equation for creep transition. This paper deals with the non-linear behaviour of spherical shell under thermal condition. The spherical shell structures are easily vulnerable to creep, shrinkage and thermal effects; a thorough understanding of their time-dependent behaviour has been fully established. The paper aims to provide thermal creep analysis to enhance the effective design and long life of shells, and a theoretical model is developed for calculating creep stresses and strains in a spherical shell with purpose. Results obtained for the problem are depicted graphically.
Optical properties of spherical and oblate spheroidal gold shell colloids
Penninkhof, J.J.; Moroz, A.; van Blaaderen, A.; Polman, A.
2008-01-01
The surface plasmon modes of spherical and oblate spheroidal core−shell colloids composed of a 312 nm diameter silica core and a 20 nm thick Au shell are investigated. Large arrays of uniaxially aligned core−shell colloids with size aspect ratios ranging from 1.0 to 1.7 are fabricated using a novel
A KIRCHHOFF THIN SHELL THEORY,
imposing the principal of virtual work on the calss of deformations which satisfy the Kirchhoff hypotheses, i.e. those deformations which carry normals to...physically realistic unless the shell is in fact thin. Imposing the principal of virtual work yields a system of differential equations for the three
Shell closure at {ital N}=164: Spherical or deformed?
Energy Technology Data Exchange (ETDEWEB)
Rigol, J. [Joint Institute for Nuclear Research, 141980 Dubna (Russia)
1997-02-01
Brenner {ital et al}. [1] recently reported the apparent evidence for a spherical shell at {ital N}=164. Some arguments are given which may make it necessary to reconsider this conclusion. {copyright} {ital 1997} {ital The American Physical Society}
Thin-shell wormholes in Einstein-Yang-Mills-Gauss-Bonnet theory
Energy Technology Data Exchange (ETDEWEB)
Bandyopadhyay, Tanwi; Chakraborty, Subenoy, E-mail: tanwib@gmail.co, E-mail: schakraborty@math.jdvu.ac.i [Department of Mathematics, Jadavpur University, Kolkata 32 (India)
2009-04-21
A thin-shell Lorentzian wormhole with spherical symmetry has been constructed in Einstein-Yang-Mills-Gauss-Bonnet theory. The generalized Darmois-Israel matching conditions are applied to the bounding shell and energy localized on the shell has been calculated. The amount of exotic matter for the existence of the wormhole has been evaluated and it has been shown graphically for certain choices of the parameters involved that ordinary matter is sufficient for the formation of thin-shell wormholes.
Influence of initial imperfections on ultimate strength of spherical shells
Directory of Open Access Journals (Sweden)
Chang-Li Yu
2017-09-01
Full Text Available Comprehensive consideration regarding influence mechanisms of initial imperfections on ultimate strength of spherical shells is taken to satisfy requirement of deep-sea structural design. The feasibility of innovative numerical procedure that combines welding simulation and non-linear buckling analysis is verified by a good agreement to experimental and theoretical results. Spherical shells with a series of wall thicknesses to radius ratios are studied. Residual stress and deformations from welding process are investigated separately. Variant influence mechanisms are discovered. Residual stress is demonstrated to be influential to stress field and buckling behavior but not to the ultimate strength. Deformations are proved to have a significant impact on ultimate strength. When central angles are less than critical value, concave magnitudes reduce ultimate strengths linearly. However, deformations with central angles above critical value are of much greater harm. Less imperfection susceptibility is found in spherical shells with larger wall thicknesses to radius ratios.
Stability of Thin Shell Wormholes in Born-Infeld Theory Supported by Polytropic Phantom Energy
Energy Technology Data Exchange (ETDEWEB)
Eid, Ali [Cairo University, Giza (Egypt)
2017-02-15
In the framework of the Darmois-Israel formalism, the dynamical equations of motion of spherically-symmetric thin-shell wormholes supported by a polytropic phantom energy in Einstein-Born-Infeld theory are constructed. A stability analysis of the spherically-symmetric thin-shell wormhole by using the standard potential method is carried out. The existence of stable, static solutions depends on the values of some parameters.
Stability of thin shell wormholes in Born-Infeld theory supported by polytropic phantom energy
Eid, Ali
2017-02-01
In the framework of the Darmois-Israel formalism, the dynamical equations of motion of spherically-symmetric thin-shell wormholes supported by a polytropic phantom energy in Einstein- Born-Infeld theory are constructed. A stability analysis of the spherically-symmetric thin-shell wormhole by using the standard potential method is carried out. The existence of stable, static solutions depends on the values of some parameters.
Axisymmetric bifurcations of thick spherical shells under inflation and compression
deBotton, G.
2013-01-01
Incremental equilibrium equations and corresponding boundary conditions for an isotropic, hyperelastic and incompressible material are summarized and then specialized to a form suitable for the analysis of a spherical shell subject to an internal or an external pressure. A thick-walled spherical shell during inflation is analyzed using four different material models. Specifically, one and two terms in the Ogden energy formulation, the Gent model and an I1 formulation recently proposed by Lopez-Pamies. We investigate the existence of local pressure maxima and minima and the dependence of the corresponding stretches on the material model and on shell thickness. These results are then used to investigate axisymmetric bifurcations of the inflated shell. The analysis is extended to determine the behavior of a thick-walled spherical shell subject to an external pressure. We find that the results of the two terms Ogden formulation, the Gent and the Lopez-Pamies models are very similar, for the one term Ogden material we identify additional critical stretches, which have not been reported in the literature before.© 2012 Published by Elsevier Ltd.
Energy Technology Data Exchange (ETDEWEB)
Toyoda, K.; Yasuzawa, Y.; Kagawa, K.; Sugimoto, S. [Kyushu University, Fukuoka (Japan). Faculty of Engineering
1997-10-01
Vibration characteristics of the semi-spherical shell fixed in water with bidirectional curvatures were studied experimentally. Various marine structures have been devised as relay station for life spaces or submarine resource excavation. As compared with land structures, marine structures are constantly under a severe condition subjected to hydrostatic pressure, and requires advanced technologies. The experimental result, numerical computation result by analytical code DASOR (Dynamic Analysis of Shell of Revolution) and theoretical analysis result were compared with each other. FEM and BEM were used in DASOR computation for the axisymmetric thin semi-spherical shell and circumferential liquid, respectively. Due to an added mass effect, the natural frequency decreased with an increase in water level regardless of mode orders. However, the water level over the top of the semi-spherical shell caused the nearly constant natural frequencies of 30-40% of that in the air. The computation result by DASOR well agreed with the experimental result demonstrating its validity. 4 refs., 13 figs., 1 tab.
A theory of thin shells with orbiting constituents
Berezin, V A; Berezin, Victor; Okhrimenko, Maxim
2001-01-01
The self-gravitating, spherically symmetric thin shells built of orbiting particles are sstudied. Two new features are found. One is the minimal possible value for an angular momentum of particles, above which elleptic orbits become possible. The second is the coexistence of both the wormhole solutions and the elleptic or hyperbolic orbits for the same values of the parameters (but different initial conditions). Possible applications of these results to astrophysics and quantum black holes are briefly discussed.
Porous spherical shells and microspheres by electrodispersion precipitation
Energy Technology Data Exchange (ETDEWEB)
Harris, M.T.; Sisson, W.G.; Basaran, O.A.; Hayes, S.M.; Bobrowski, S.J.
1994-12-31
The ability to reproduce the synthesis of dense- and porous-microspheres and micron-sized spherical shells is very important in (a) the development of ceramics for structural, electronic, catalyst and thermal applications; and (b) the encapsulation of products for controlled-release of drugs, flavors and perfumes, and inks and dyes, and the protection of light-sensitive components and mechanical support of fragile materials. Larger metallic- and ceramic-spherical shells have been used in inertial confinement fusion (ICF) experiments and as catalyst supports. The current paper will focus on a recent technique that has been developed for synthesizing ceramic microspheres and micro-shells. Pulsed electric fields have been used to enhance the dispersion of aqueous metal (Zr and Al) salt solutions from a nozzle and into a nonconducting liquid continuous phase that is immiscible with the aqueous phase. The diameter of the resulting microdroplets ranged in size from approximately 0.1 to 10 {mu}m. Precipitation of hydrous metal oxides occurred as ammonia, which was dissolved in varying amounts in the continuous phase, diffused into the aqueous microdroplets. Spherical shells were formed at higher ammonia concentrations and microspheres were produced at lower ammonia concentrations. Upon drying, dimples appeared in the particles that were synthesized at higher ammonia concentrations. The latter result accords with the well known fact that under certain conditions spherical shells collapse when a fluid is extracted from the core of the particle. No dimples were observed in the microspheres that were produced at lower ammonia concentrations. Analog X-ray dot maps for aluminum and zirconium were done to determine the spatial distribution of each metal in the particles.
Porous spherical shells and microspheres by electrodispersion precipitation
International Nuclear Information System (INIS)
Harris, M.T.; Sisson, W.G.; Basaran, O.A.; Hayes, S.M.; Bobrowski, S.J.
1994-01-01
The ability to reproduce the synthesis of dense- and porous-microspheres and micron-sized spherical shells is very important in (a) the development of ceramics for structural, electronic, catalyst and thermal applications; and (b) the encapsulation of products for controlled-release of drugs, flavors and perfumes, and inks and dyes, and the protection of light-sensitive components and mechanical support of fragile materials. Larger metallic- and ceramic-spherical shells have been used in inertial confinement fusion (ICF) experiments and as catalyst supports. The current paper will focus on a recent technique that has been developed for synthesizing ceramic microspheres and micro-shells. Pulsed electric fields have been used to enhance the dispersion of aqueous metal (Zr and Al) salt solutions from a nozzle and into a nonconducting liquid continuous phase that is immiscible with the aqueous phase. The diameter of the resulting microdroplets ranged in size from approximately 0.1 to 10 μm. Precipitation of hydrous metal oxides occurred as ammonia, which was dissolved in varying amounts in the continuous phase, diffused into the aqueous microdroplets. Spherical shells were formed at higher ammonia concentrations and microspheres were produced at lower ammonia concentrations. Upon drying, dimples appeared in the particles that were synthesized at higher ammonia concentrations. The latter result accords with the well known fact that under certain conditions spherical shells collapse when a fluid is extracted from the core of the particle. No dimples were observed in the microspheres that were produced at lower ammonia concentrations. Analog X-ray dot maps for aluminum and zirconium were done to determine the spatial distribution of each metal in the particles
Attractive electromagnetic Casimir stress on a spherical dielectric shell
International Nuclear Information System (INIS)
Graham, N.; Quandt, M.; Weigel, H.
2013-01-01
Based on calculations involving an idealized boundary condition, it has long been assumed that the stress on a spherical conducting shell is repulsive. We use the more realistic case of a Drude dielectric to show that the stress is attractive, matching the generic behavior of Casimir forces in electromagnetism. We trace the discrepancy between these two cases to interactions between the electromagnetic quantum fluctuations and the dielectric material
Numerical Simulations of Thermal Convection in Rapidly Rotating Spherical Shell
Energy Technology Data Exchange (ETDEWEB)
Nenkov, Constantine; Peltier, Richard, E-mail: nenkov@atmosp.physics.utoronto.ca, E-mail: peltier@atmosp.physics.utoronto.ca [Department of Physics, University of Toronto Toronto, Ontario, M5S 1A7 (Canada)
2010-11-01
We present a novel numerical model used to simulate convection in the atmospheres of the Gas Giant planets Jupiter and Saturn. Nonlinear, three-dimensional, time-dependant solutions of the anelastic hydrodynamic equations are presented for a stratified, rotating spherical fluid shell heated from below. This new model is specified in terms of a grid-point based methodology which employs a hierarchy of tessellations of the regular icosahedron onto the sphere through the process of recurrent dyadic refinements of the spherical surface. We describe discretizations of the governing equations in which all calculations are performed in Cartesian coordinates in the local neighborhoods of the almost uniform icosahedral grid, a methodology which avoids the potential mathematical and numerical difficulties associated with the pole problem in spherical geometry. Using this methodology we have built our model in primitive equations formulation, whereas the three-dimensional vector velocity field and temperature are directly advanced in time. We show results of thermal convection in rapidly rotating spherical shell which leads to the formation of well pronounced prograde zonal jets at the equator, results which previous experiments with two-dimensional models in the limit of freely evolving turbulence were not able to achieve.
Thin-shell wormholes supported by ordinary matter in Einstein--Gauss--Bonnet gravity
Richarte, Martin; Simeone, Claudio
2007-01-01
The generalized Darmois--Israel formalism for Einstein--Gauss--Bonnet theory is applied to construct thin-shell Lorentzian wormholes with spherical symmetry. We calculate the energy localized on the shell, and we find that for certain values of the parameters wormholes could be supported by matter not violating the energy conditions.
The secondary buckling transition: wrinkling of buckled spherical shells.
Knoche, Sebastian; Kierfeld, Jan
2014-07-01
We theoretically explain the complete sequence of shapes of deflated spherical shells. Decreasing the volume, the shell remains spherical initially, then undergoes the classical buckling instability, where an axisymmetric dimple appears, and, finally, loses its axisymmetry by wrinkles developing in the vicinity of the dimple edge in a secondary buckling transition. We describe the first axisymmetric buckling transition by numerical integration of the complete set of shape equations and an approximate analytic model due to Pogorelov. In the buckled shape, both approaches exhibit a locally compressive hoop stress in a region where experiments and simulations show the development of polygonal wrinkles, along the dimple edge. In a simplified model based on the stability equations of shallow shells, a critical value for the compressive hoop stress is derived, for which the compressed circumferential fibres will buckle out of their circular shape in order to release the compression. By applying this wrinkling criterion to the solutions of the axisymmetric models, we can calculate the critical volume for the secondary buckling transition. Using the Pogorelov approach, we also obtain an analytical expression for the critical volume at the secondary buckling transition: The critical volume difference scales linearly with the bending stiffness, whereas the critical volume reduction at the classical axisymmetric buckling transition scales with the square root of the bending stiffness. These results are confirmed by another stability analysis in the framework of Donnel, Mushtari and Vlasov (DMV) shell theory, and by numerical simulations available in the literature.
Thin shells joining local cosmic string geometries
Energy Technology Data Exchange (ETDEWEB)
Eiroa, Ernesto F. [Universidad de Buenos Aires, Ciudad Universitaria Pabellon I, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Rubin de Celis, Emilio; Simeone, Claudio [Universidad de Buenos Aires, Ciudad Universitaria Pabellon I, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Ciudad Universitaria Pabellon I, IFIBA-CONICET, Buenos Aires (Argentina)
2016-10-15
In this article we present a theoretical construction of spacetimes with a thin shell that joins two different local cosmic string geometries. We study two types of global manifolds, one representing spacetimes with a thin shell surrounding a cosmic string or an empty region with Minkowski metric, and the other corresponding to wormholes which are not symmetric across the throat located at the shell. We analyze the stability of the static configurations under perturbations preserving the cylindrical symmetry. For both types of geometries we find that the static configurations can be stable for suitable values of the parameters. (orig.)
Static and dynamic snap-through behaviour of an elastic spherical shell
Karagiozova, D.; Zhang, X.-W.; Yu, T.-X.
2012-06-01
The deformation and snap-through behaviour of a thin-walled elastic spherical shell statically compressed on a flat surface or impacted against a flat surface are studied theoretically and numerically in order to estimate the influence of the dynamic effects on the response. A table tennis ball is considered as an example of a thin-walled elastic shell. It is shown that the increase of the impact velocity leads to a variation of the deformed shape thus resulting in larger deformation energy. The increase of the contact force is caused by both the increased contribution of the inertia forces and contribution of the increased deformation energy. The contact force resulted from deformation/inertia of the ball and the shape of the deformed region are calculated by the proposed theoretical models and compared with the results from both the finite element analysis and some previously obtained experimental data. Good agreement is demonstrated.
Circumferential-wave phase velocities for empty, fluid-immersed spherical metal shells
DEFF Research Database (Denmark)
Überall, Herbert; Ahyi, A. C.; Raju, P. K.
2002-01-01
-loaded, evacuated spherical metal shells of aluminum, stainless steel, and tungsten carbide. In particular, the characteristic upturn of the dispersion curves of low-order shell-borne circumferential waves (A or A0 waves) which takes place on spherical shells when the frequency tends towards very low values...
Traveling waves in low and intermediate rotating spherical shell convection
International Nuclear Information System (INIS)
Futterer, B; Koch, S; Egbers, C
2011-01-01
The spherical shell convection in the lower rotational regime is discussed with numerical simulation by the use of a pseudo-spectral code and experimental observation by the use of a microgravity experiment in self-gravitating force field. While a low Coriolis force produces traveling waves of cubic, five-fold and frozen tetrahedral symmetry with a prograde drift, in the transition zone to chaos an axisymmetric flow is visible. The chaotic fluid flow does neither show a specific drift nor a dominating pattern of convection. Numerical and experimental data are in a good agreement.
The fuzzy C spherical shells algorithm - A new approach
Krishnapuram, Raghu; Nasraoui, Olfa; Frigui, Hichem
1992-01-01
The fuzzy c spherical shells (FCSS) algorithm is specially designed to search for clusters that can be described by circular arcs or, more generally, by shells of hyperspheres. In this paper, a new approach to the FCSS algorithm is presented. This algorithm is computationally and implementationally simpler than other clustering algorithms that have been suggested for this purpose. An unsupervised algorithm which automatically finds the optimum number of clusters is also proposed. This algorithm can be used when the number of clusters is not known. It uses a cluster validity measure to identify good clusters, merges all compatible clusters, and eliminates spurious clusters to achieve the final result. Experimental results on several data sets are presented.
DEFF Research Database (Denmark)
Niordson, Christian F.; Nielsen, S.B.
2006-01-01
of the transverse deflection is modified by in-plane tectonic forces originating e.g. at plate boundaries. However, geoscience applications of the coupling between transverse deflections and boundary conditions have been restricted to the one-dimensional thin-plate model. In this paper we extend the model...... to a spherical thin elastic shell. This configuration is required when geoscience studies move from local scenarios, where the flat-Earth approximation holds, to plate-scale or global scenarios, where the correct application of far-field boundary conditions and the spherical geometry becomes of primary...
Exciton states and optical absorption in core/shell/shell spherical quantum dot
Hayrapetyan, D. B.; Baghdasaryan, D. A.; Kazaryan, E. M.; Pokutnyi, S. I.; Sarkisyan, H. A.
2018-04-01
The exciton states in core/shell/shell spherical quantum dot with three-dimensional Winternitz-Smorodinsky confinement potential are considered. The problem is discussed in the framework of adiabatic approximation when the heavy hole is situated in the effective potential well caused by the electron. The interband optical transitions caused by incident light polarized in z-direction have been considered in such systems. The oscillator strengths and selection rules for the quantum transitions have been obtained. The ensemble of quantum dots and their size dispersion have been taken into account in the calculations. The Gaussian distribution has been chosen to describe the size dispersion of the core/shell/shell quantum dots thickness. The dependence of the absorption coefficient and photoluminescence spectra on the energy of incident light of interband transitions have been obtained.
Thin-shell wormholes supported by total normal matter
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S.H.; Halilsoy, M. [Eastern Mediterranean University, Department of Physics, Gazimagusa (Turkey)
2014-09-15
The Zipoy-Voorhees-Weyl (ZVW) spacetime characterized by mass (M) and oblateness (δ) is proposed in the construction of viable thin-shell wormholes (TSWs). A departure from spherical/cylindrical symmetry yields a positive total energy in spite of the fact that the local energy density may take negative values. We show that oblateness of the bumpy sources/black holes can be incorporated as a new degree of freedom that may play a role in the resolution of the exotic matter problem in TSWs. A small velocity perturbation reveals, however, that the resulting TSW is unstable. (orig.)
International Nuclear Information System (INIS)
Jain, R.K.; Nath, Y.
1986-01-01
Interaction of clamped orthotropic shallow spherical shells with nonlinear elastic foundations is studied under transient loads. The effect of softening and hardening foundation nonlinearities on the response behaviour of shallow shells has been investigated. Detailed analysis depicting the influence of hardening type foundation nonlinearity on the maximum response of orthotropic shallow spherical shells has been conducted. The numerical results suggest that for the shell-foundation interaction problems undergoing moderately large deformations, the nonlinear model for the foundation must be considered. (orig.) [de
Eid, A.
2017-11-01
In the framework of Darmois-Israel formalism, the dynamics of motion equations of spherically symmetric thin shell wormholes that are supported by a modified Chaplygin gas in Einstein-Hoffman-Born-Infeld theory are constructed. The stability analysis of a thin shell wormhole is also discussed using a linearized radial perturbation around static solutions at the wormhole throat. The existence of stable static solutions depends on the value of some parameters of dynamical shell.
Relativistic Bose-Einstein condensates thin-shell wormholes
Richarte, M. G.; Salako, I. G.; Graça, J. P. Morais; Moradpour, H.; Övgün, Ali
2017-10-01
We construct traversable thin-shell wormholes which are asymptotically Ads/dS applying the cut and paste procedure for the case of an acoustic metric created by a relativistic Bose-Einstein condensate. We examine several definitions of the flare-out condition along with the violation or not of the energy conditions for such relativistic geometries. Under reasonable assumptions about the equation of state of the matter located at the shell, we concentrate on the mechanical stability of wormholes under radial perturbation preserving the original spherical symmetry. To do so, we consider linearized perturbations around static solutions. We obtain that dS acoustic wormholes remain stable under radial perturbations as long as they have small radius; such wormholes with finite radius do not violate the strong/null energy condition. Besides, we show that stable Ads wormhole satisfy some of the energy conditions whereas unstable Ads wormhole with large radii violate them.
Gravito-inertial modes in a differentially rotating spherical shell
Directory of Open Access Journals (Sweden)
Mirouh Giovanni M.
2015-01-01
Full Text Available While many intermediate- and high-mass main sequence stars are rapidly and differentially rotating, the effects of rotation on oscillation modes are poorly known. In this communication we present a first study of axisymmetric gravito-inertial modes in the radiative zone of a differentially rotating star. We consider a simplified model where the radiative zone of the star is a linearly stratified rotating fluid within a spherical shell, with differential rotation due to baroclinic effects. We solve the eigenvalue problem with high-resolution spectral computations and determine the propagation domain of the waves through the theory of characteristics. We explore the propagation properties of two kinds of modes: those that can propagate in the entire shell and those that are restricted to a sub-domain. Some of the modes that we find concentrate kinetic energy around short-period shear layers known as attractors. We describe various geometries for the propagation domains, conditioning the surface visibility of the corresponding modes.
Thin-shell wormholes from the regular Hayward black hole
Energy Technology Data Exchange (ETDEWEB)
Halilsoy, M.; Ovgun, A.; Mazharimousavi, S.H. [Eastern Mediterranean University, Department of Physics, Mersin 10 (Turkey)
2014-03-15
We revisit the regular black hole found by Hayward in 4-dimensional static, spherically symmetric spacetime. To find a possible source for such a spacetime we resort to the nonlinear electrodynamics in general relativity. It is found that a magnetic field within this context gives rise to the regular Hayward black hole. By employing such a regular black hole we construct a thin-shell wormhole for the case of various equations of state on the shell. We abbreviate a general equation of state by p = ψ(σ) where p is the surface pressure which is a function of the mass density (σ). In particular, linear, logarithmic, Chaplygin, etc. forms of equations of state are considered. In each case we study the stability of the thin shell against linear perturbations.We plot the stability regions by tuning the parameters of the theory. It is observed that the role of the Hayward parameter is to make the TSW more stable. Perturbations of the throat with small velocity condition are also studied. The matter of our TSWs, however, remains exotic. (orig.)
Quantum corrected Schwarzschild thin-shell wormhole
Jusufi, Kimet
2016-01-01
Recently, Ali and Khalil (Nucl Phys B, 909, 173–185, 2016 ), based on Bohmian quantum mechanics, derived a quantum corrected version of the Schwarzschild metric. In this paper, we construct a quantum corrected Schwarzschild thin-shell wormhole (QSTSW) and investigate the stability of this wormhole. First we compute the surface stress at the wormhole throat by applying the Darmois–Israel formalism to the modified Schwarzschild metric and show that exotic matter is required at the throat to kee...
Enceladus's crust as a non-uniform thin shell: I tidal deformations
Beuthe, Mikael
2018-03-01
The geologic activity at Enceladus's south pole remains unexplained, though tidal deformations are probably the ultimate cause. Recent gravity and libration data indicate that Enceladus's icy crust floats on a global ocean, is rather thin, and has a strongly non-uniform thickness. Tidal effects are enhanced by crustal thinning at the south pole, so that realistic models of tidal tectonics and dissipation should take into account the lateral variations of shell structure. I construct here the theory of non-uniform viscoelastic thin shells, allowing for depth-dependent rheology and large lateral variations of shell thickness and rheology. Coupling to tides yields two 2D linear partial differential equations of the fourth order on the sphere which take into account self-gravity, density stratification below the shell, and core viscoelasticity. If the shell is laterally uniform, the solution agrees with analytical formulas for tidal Love numbers; errors on displacements and stresses are less than 5% and 15%, respectively, if the thickness is less than 10% of the radius. If the shell is non-uniform, the tidal thin shell equations are solved as a system of coupled linear equations in a spherical harmonic basis. Compared to finite element models, thin shell predictions are similar for the deformations due to Enceladus's pressurized ocean, but differ for the tides of Ganymede. If Enceladus's shell is conductive with isostatic thickness variations, surface stresses are approximately inversely proportional to the local shell thickness. The radial tide is only moderately enhanced at the south pole. The combination of crustal thinning and convection below the poles can amplify south polar stresses by a factor of 10, but it cannot explain the apparent time lag between the maximum plume brightness and the opening of tiger stripes. In a second paper, I will study the impact of a non-uniform crust on tidal dissipation.
Cr/alpha-Cr2O3 monodispersed spherical core-shell particles based solar absorbers
CSIR Research Space (South Africa)
Khamlich, S
2011-07-01
Full Text Available Monodispersed spherical core-shell particles of Cr/alpha-Cr2O3 cermet ACG coatings investigated within this contribution could be successfully employed in thermal converters. Their selectivity depends on their chemical, physical and structural...
Circumferential-wave phase velocities for empty, fluid-immersed spherical metal shells
DEFF Research Database (Denmark)
Überall, Herbert; Claude Ahyi, A.; Raju, P. K.
2001-01-01
frequency/elasticity-theory connection, and we obtain comparative dispersion-curve results for water-loaded, evacuated spherical shells of various metals. In particular, the characteristic upturn of the dispersion curves of low-order shell-borne circumferential waves (A or A0 waves) which takes place...
Temperature Condition and Spherical Shell Shape Variation of Space Gauge-Alignment Spacecraft
Directory of Open Access Journals (Sweden)
V. S. Zarubin
2016-01-01
Full Text Available A high precision spherical shell is one of the geometrical shape embodiments of a gaugealignment spacecraft to determine and control a radar channel energy potential of the ground-based complex for the traffic control of space objects. Passive relays of signals and some types of smallsized instrumentation standard reflectors used for radar gauge and alignment have the same shape. Orbits of the considered spacecraft can be either circular with a height of about 1000 km, including those close to the polar, or elliptical with an apogee of up to 2200 km.In case there is no thermal control system in spacecrafts of these types the solar radiation is a major factor to define the thermal state of a spherical shell in the illuminated orbit area. With the shell in fixed position with respect to direction towards the Sun an arising uneven temperature distribution over its surface leads to variation of the spherically ideal shell shape, which may affect the functional characteristics of the spacecraft. The shell rotation about an axis perpendicular to the direction towards the Sun may reduce an unevenness degree of the temperature distribution.The uneven temperature distribution over the spherical shell surface in conditions of the lowEarth space and this unevenness impact on the shell shape variation against its spherical shape can be quantively estimated by the appropriate methods of mathematical modeling using modification of a previously developed mathematical model to describe steady temperature state of such shell on the low-Earth orbit. The paper considers the shell made from a polymeric composite material. Its original spherical shape is defined by rather low internal pressure. It is assumed that equipment in the shell, if any, is quite small-sized. This allows us to ignore its impact on the radiative transfer in the shell cavity. Along with defining the steady temperature distribution over the shell surface at its fixed orientation with respect to
Reissner-Nordstroem thin-shell wormholes with generalized cosmic Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); University of Education, Division of Science and Technology, Lahore (Pakistan)
2013-09-15
Following Visser's approach (Visser in Phys. Rev. D 39:3182, 1989; Nucl. Phys. B 328:203, 1989; Lorentzian wormholes. AIP Press, New York, 1996) of cut and paste, we construct Reissner-Nordstroem thin-shell wormholes by taking the generalized cosmic Chaplygin gas for the exotic matter located at the wormhole throat. The Darmois-Israel conditions are used to determine the dynamical quantities of the system. The viability of the thin-shell wormholes is explored with respect to radial perturbations preserving the spherical symmetry. We find stable as well as unstable Reissner-Nordstroem thin-shell wormhole solutions depending upon the model parameters. Finally, we compare our results with both generalized and modified Chaplygin gases. (orig.)
Higher-dimensional thin-shell wormholes in Einstein-Yang-Mills-Gauss-Bonnet gravity
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S Habib; Halilsoy, M; Amirabi, Z, E-mail: habib.mazhari@emu.edu.tr, E-mail: mustafa.halilsoy@emu.edu.tr, E-mail: zahra.amirabi@emu.edu.tr [Department of Physics, Eastern Mediterranean University, G. Magusa, North Cyprus, Mersin 10 (Turkey)
2011-01-21
We present thin-shell wormhole solutions in the Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory in higher dimensions d {>=} 5. Exact black hole solutions are employed for this purpose where the radius of the thin shell lies outside the event horizon. For some reasons the cases d = 5 and d > 5 are treated separately. The surface energy-momentum of the thin shell creates surface pressures to resist against collapse and rendering stable wormholes possible. We test the stability of the wormholes against spherical perturbations through a linear energy-pressure relation and plot stability regions. Apart from this restricted stability we investigate the possibility of normal (i.e. non-exotic) matter which satisfies the energy conditions. For negative values of the Gauss-Bonnet (GB) parameter we obtain such physical wormholes.
Nonlinear buckling behaviour of spherical shells: barriers and symmetry-breaking dimples.
Hutchinson, John W; Thompson, J Michael T
2017-05-13
The nonlinear axisymmetric post-buckling behaviour of perfect, thin, elastic spherical shells subject to external pressure and their asymmetric bifurcations are characterized, providing results for a structure/loading combination with an exceptionally nonlinear buckling response. Immediately after the onset of buckling, the buckling mode localizes into a dimple at the poles. The relations among the pressure, the dimple amplitude and the change in volume of the shell are determined over a large range of pole deflections. These results allow accurate evaluation of criteria such as the Maxwell condition for which the energies in the unbuckled and buckled states are the same and evaluation of the influences of pressure versus volume-controlled loadings. Non-axisymmetric bifurcation from the axisymmetric state, which occurs deep into the post-buckling regime in the form of multi-lobed dimples, is also established and discussed.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.' © 2017 The Author(s).
Su, Zhu; Jin, Guoyong
2016-11-01
This paper presents a Fourier spectral element method (FSEM) to analyze the free vibration of conical-cylindrical-spherical shells with arbitrary boundary conditions. Cylindrical-conical and cylindrical-spherical shells as special cases are also considered. In this method, each fundamental shell component (i.e., cylindrical, conical, and spherical shells) is divided into appropriate elements. The variational principle in conjunction with first-order shear deformation shell theory is employed to model the shell elements. Since the displacement and rotation components of each element are expressed as a linear superposition of nodeless Fourier sine functions and nodal Lagrangian polynomials, the global equations of the coupled shell structure can be obtained by adopting the assembly procedure. The Fourier sine series in the displacement field is introduced to enhance the accuracy and convergence of the solution. Numerical results show that the FSEM can be effectively applied to vibration analysis of the coupled shell structures. Numerous results for coupled shell structures with general boundary conditions are presented. Furthermore, the effects of geometric parameters and boundary conditions on the frequencies are investigated.
Thin-shell wormholes constrained by cosmological observations
Wang, Deng; Meng, Xin-He
2017-09-01
We investigate the thin-shell wormholes constrained by cosmological observations for the first time in the literature. Without loss of generality, we study the thin-shell wormholes in ωCDM model and analyze their stability under perturbations preserving the symmetry. Firstly, we constrain the ωCDM model using a combination of Union 2.1 SNe Ia data, the latest H(z) data and CMB data. Secondly, we use the constrained dark energy equation of state (EoS) ω which lies in [ - 1 . 05 , - 0 . 89 ] to investigate thin-shell wormholes generated by various black hole spacetimes. We find that the stable Schwarzschild and Reinssner-Nordström thin-shell wormholes constrained by cosmological observations do not exist. In addition, the method we developed can be applied in exploring the stable thin-shell wormholes from any black hole spacetime in the framework of any cosmological theory.
Quantum corrected Schwarzschild thin-shell wormhole
Energy Technology Data Exchange (ETDEWEB)
Jusufi, Kimet [State University of Tetovo, Physics Department, Tetovo (Macedonia, The Former Yugoslav Republic of)
2016-11-15
Recently, Ali and Khalil (Nucl Phys B, 909, 173-185, 2016), based on Bohmian quantum mechanics, derived a quantum corrected version of the Schwarzschild metric. In this paper, we construct a quantum corrected Schwarzschild thin-shell wormhole (QSTSW) and investigate the stability of this wormhole. First we compute the surface stress at the wormhole throat by applying the Darmois-Israel formalism to the modified Schwarzschild metric and show that exotic matter is required at the throat to keep the wormhole stable. We then study the stability analysis of the wormhole by considering phantom-energy for the exotic matter, generalized Chaplygin gas (GCG), and the linearized stability analysis. It is argued that quantum corrections can affect the stability domain of the wormhole. (orig.)
On the dynamic buckling of thin shells
International Nuclear Information System (INIS)
Combescure, A.; Hoffmann, A.; Homan, R.
1986-10-01
The shells of a pool type reactor like Super Phenix 1 or the Super Phenix 2 project are relatively thin compared to the diameter. Normal loads and mainly seismic loads due to strong fluid-structure interaction and giving pressure of the same order then static collapse pressure. This is a main difficulty for a good and safe design of LMFBR. The paper describes the experimental results obtained at CEA-DEMT on the seismic buckling of structures filled with fluid. A general tendency is given on all experimental results. The experimental results are analysed by two simple models and the main results are explained. A strategy to design a structure against dynamic buckling is then presented. 7 refs
Stable Dyonic Thin-Shell Wormholes in Low-Energy String Theory
Directory of Open Access Journals (Sweden)
Ali Övgün
2017-01-01
Full Text Available Considerable attention has been devoted to the wormhole physics in the past 30 years by exploring the possibilities of finding traversable wormholes without the need for exotic matter. In particular, the thin-shell wormhole formalism has been widely investigated by exploiting the cut-and-paste technique to merge two space-time regions and to research the stability of these wormholes developed by Visser. This method helps us to minimize the amount of the exotic matter. In this paper, we construct a four-dimensional, spherically symmetric, dyonic thin-shell wormhole with electric charge Q, magnetic charge P, and dilaton charge Σ, in the context of Einstein-Maxwell-dilaton theory. We have applied Darmois-Israel formalism and the cut-and-paste method by joining together two identical space-time solutions. We carry out the dyonic thin-shell wormhole stability analyses by using a linear barotropic gas, Chaplygin gas, and logarithmic gas for the exotic matter. It is shown that, by choosing suitable parameter values as well as equation of state parameter, under specific conditions, we obtain a stable dyonic thin-shell wormhole solution. Finally, we argue that the stability domain of the dyonic thin-shell wormhole can be increased in terms of electric charge, magnetic charge, and dilaton charge.
Dilaton thin-shell wormholes supported by a generalized Chaplygin gas
Bejarano, Cecilia; Eiroa, Ernesto F.
2011-09-01
In this article, we construct spherical thin-shell wormholes with charge in dilaton gravity. The exotic matter required for the construction is provided by a generalized Chaplygin gas. We study the stability under perturbations preserving the symmetry. We find that the increase of the coupling between the dilaton and the electromagnetic fields reduces the range of the parameters for which stable configurations are possible.
Thin-shell wormholes with charge in F(R) gravity
Energy Technology Data Exchange (ETDEWEB)
Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Figueroa Aguirre, Griselda [Instituto de Astronomia y Fisica del Espacio (IAFE, CONICET-UBA), Buenos Aires (Argentina)
2016-03-15
In this article, we construct a class of constant curvature and spherically symmetric thin-shell Lorentzian wormholes in F(R) theories of gravity and we analyze their stability under perturbations preserving the symmetry. We find that the junction conditions determine the equation of state of the matter at the throat. As a particular case, we consider configurations with mass and charge. We obtain that stable static solutions are possible for suitable values of the parameters of the model. (orig.)
Evidence of Marangoni Convection Cells on Spherical Shells
McQuillan, Barry
2001-11-01
1 and 2 mm OD plastic shells show surface bumps. The origin of the bumps are Marangoni convection cells created during the formation of the shells. The L mode number for these bumps is consistent with the mode number predicted from a calculation of Lebon and Pirotte. The bumps can be eliminated by suitable changes in the processing, changes which are guided by the presumption of Marangoni convection cells.
3 + 1-dimensional thin shell wormhole with deformed throat can be supported by normal matter
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S.H.; Halilsoy, M. [Eastern Mediterranean University, Department of Physics, Gazimagusa (Turkey)
2015-06-15
From the physics standpoint the exotic matter problem is a major difficulty in thin shell wormholes (TSWs) with spherical/cylindrical throat topologies.We aim to circumvent this handicap by considering angle dependent throats in 3 + 1 dimensions. By considering the throat of the TSW to be deformed spherical, i.e., a function of θ and φ, we present general conditions which are to be satisfied by the shape of the throat in order to have the wormhole supported by matter with positive density in the static reference frame. We provide particular solutions/examples to the constraint conditions. (orig.)
Fast ignition upon the implosion of a thin shell onto a precompressed deuterium-tritium ball
Gus'kov, S. Yu.; Zmitrenko, N. V.
2012-11-01
Fast ignition of a precompressed inertial confinement fusion (ICF) target by a hydrodynamic material flux is investigated. A model system of hydrodynamic objects consisting of a central deuterium-tritium (DT) ball and a concentric two-layer shell separated by a vacuum gap is analyzed. The outer layer of the shell is an ablator, while the inner layer consists of DT ice. The igniting hydrodynamic flux forms as a result of laser-driven acceleration and compression of the shell toward the system center. A series of one-dimensional numerical simulations of the shell implosion, the collision of the shell with the DT ball, and the generation and propagation of thermonuclear burn waves in both parts of the system are performed. Analytic models are developed that describe the implosion of a thin shell onto a central homogeneous ball of arbitrary radius and density and the initiation and propagation of a thermonuclear burn wave induced by such an implosion. Application of the solution of a model problem to analyzing the implosion of a segment of a spherical shell in a conical channel indicates the possibility of fast ignition of a spherical ICF target from a conical target driven by a laser pulse with an energy of 500-700 kJ.
Spherical-shell boundaries for two-dimensional compressible convection in a star
Pratt, J.; Baraffe, I.; Goffrey, T.; Geroux, C.; Viallet, M.; Folini, D.; Constantino, T.; Popov, M.; Walder, R.
2016-10-01
Context. Studies of stellar convection typically use a spherical-shell geometry. The radial extent of the shell and the boundary conditions applied are based on the model of the star investigated. We study the impact of different two-dimensional spherical shells on compressible convection. Realistic profiles for density and temperature from an established one-dimensional stellar evolution code are used to produce a model of a large stellar convection zone representative of a young low-mass star, like our sun at 106 years of age. Aims: We analyze how the radial extent of the spherical shell changes the convective dynamics that result in the deep interior of the young sun model, far from the surface. In the near-surface layers, simple small-scale convection develops from the profiles of temperature and density. A central radiative zone below the convection zone provides a lower boundary on the convection zone. The inclusion of either of these physically distinct layers in the spherical shell can potentially affect the characteristics of deep convection. Methods: We perform hydrodynamic implicit large eddy simulations of compressible convection using the MUltidimensional Stellar Implicit Code (MUSIC). Because MUSIC has been designed to use realistic stellar models produced from one-dimensional stellar evolution calculations, MUSIC simulations are capable of seamlessly modeling a whole star. Simulations in two-dimensional spherical shells that have different radial extents are performed over tens or even hundreds of convective turnover times, permitting the collection of well-converged statistics. Results: To measure the impact of the spherical-shell geometry and our treatment of boundaries, we evaluate basic statistics of the convective turnover time, the convective velocity, and the overshooting layer. These quantities are selected for their relevance to one-dimensional stellar evolution calculations, so that our results are focused toward studies exploiting the so
Mechanical stability of cylindrical thin-shell wormholes
Energy Technology Data Exchange (ETDEWEB)
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Azam, M. [University of Education, Division of Science and Technology, Lahore (Pakistan)
2013-04-15
In this paper, we apply the cut and paste procedure to the charged black string for the construction of a thin-shell wormhole. We consider the Darmois-Israel formalism to determine the surface stresses of the shell. We take the Chaplygin gas to deal with the matter distribution on shell. The radial perturbation approach (preserving the symmetry) is used to investigate the stability of static solutions. We conclude that stable static solutions exist both for uncharged and charged black string thin-shell wormholes for particular values of the parameters. (orig.)
Stability of generic thin shells in conformally flat spacetimes
Energy Technology Data Exchange (ETDEWEB)
Amirabi, Z. [Eastern Mediterranean Univ., Gazimagusa (Turkey). Dept. of Physics
2017-07-15
Some important spacetimes are conformally flat; examples are the Robertson-Walker cosmological metric, the Einstein-de Sitter spacetime, and the Levi-Civita-Bertotti-Robinson and Mannheim metrics. In this paper we construct generic thin shells in conformally flat spacetime supported by a perfect fluid with a linear equation of state, i.e., p = ωσ. It is shown that, for the physical domain of ω, i.e., 0 < ω ≤ 1, such thin shells are not dynamically stable. The stability of the timelike thin shells with the Mannheim spacetime as the outer region is also investigated. (orig.)
Övgün, Ali; Jusufi, Kimet
2017-12-01
In this paper, we construct generic, spherically symmetric thin-shell wormholes and check their stabilities using the unified dark sector, including dark energy and dark matter. We give a master equation, from which one can recover, as a special case, other stability solutions for generic spherically symmetric thin-shell wormholes. In this context, we consider a particular solution; namely we construct an effective thin-shell wormhole under Lorentz symmetry breaking. We explore stability analyses using different models of the modified Chaplygin gas with constraints from cosmological observations, such as seventh-year full Wilkinson microwave anisotropy probe data points, type Ia supernovae, and baryon acoustic oscillation. In all these models we find stable solutions by choosing suitable values for the parameters of the Lorentz symmetry breaking effect.
Vibrations of Thin Piezoelectric Shallow Shells
Indian Academy of Sciences (India)
Abstract. In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two-dimensional eigenvalue problem.
Symmetry-dictated trucation: Solutions of the spherical shell model for heavy nuclei
International Nuclear Information System (INIS)
Guidry, M.W.
1992-01-01
Principles of dynamical symmetry are used to simplify the spherical shell model. The resulting symmetry-dictated truncation leads to dynamical symmetry solutions that are often in quantitative agreement with a variety of observables. Numerical calculations, including terms that break the dynamical symmetries, are shown that correspond to shell model calculations for heavy deformed nuclei. The effective residual interaction is simple, well-behaved, and can be determined from basic observables. With this approach, we intend to apply the shell model in systematic fashion to all nuclei. The implications for nuclear structure far from stability and for nuclear masses and other quantities of interest in astrophysics are discussed
Shape evolution of a core-shell spherical particle under hydrostatic pressure.
Colin, Jérôme
2012-03-01
The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core.
Neutron leakage from Pb and Bc spherical shells with 14 MeV central neutron source
International Nuclear Information System (INIS)
Antonov, S.; Daskalov, G.; Ilieva, K.; Jordanova, J.; Prodanova, R.; Zagryadskij, V.A.; Novikov, V.M.; Chuvilin, D.Yu.
1988-01-01
Results of measuring neutron leakage from spherical shells of different thickness, made of Pb and Be with a point neutron source in the sphere centrum are presented. The experiment results are compared to calculations according to different programs using data of various nuclear data libraies. The comparison has shown that all the calculations understate the neutron leakage from Pb assmebly. 9 refs.; 2 tabs
OWL: A code for the two-center shell model with spherical Woods-Saxon potentials
Diaz-Torres, Alexis
2018-03-01
A Fortran-90 code for solving the two-center nuclear shell model problem is presented. The model is based on two spherical Woods-Saxon potentials and the potential separable expansion method. It describes the single-particle motion in low-energy nuclear collisions, and is useful for characterizing a broad range of phenomena from fusion to nuclear molecular structures.
Analytical solution for viscous incompressible Stokes flow in a spherical shell
Thieulot, Cedric
2017-01-01
I present a new family of analytical flow solutions to the incompressible Stokes equation in a spherical shell. The velocity is tangential to both inner and outer boundaries, the viscosity is radial and of the power-law type, and the solution has been designed so that the expressions for velocity,
On the dynamic buckling load of spherical shells trapped by a ...
African Journals Online (AJOL)
In this paper, the dynamic buckling load of an imperfect discretized spherical shell subjected to a slowly varying time dependent sinusoidal load is determined by means of regular perturbation The results which are given in two levels of approximation are valid for small amplitudes of the imperfection. All results are strictly ...
Şahan, Mehmet Fatih
2017-11-01
In this paper, the viscoelastic damped response of cross-ply laminated shallow spherical shells is investigated numerically in a transformed Laplace space. In the proposed approach, the governing differential equations of cross-ply laminated shallow spherical shell are derived using the dynamic version of the principle of virtual displacements. Following this, the Laplace transform is employed in the transient analysis of viscoelastic laminated shell problem. Also, damping can be incorporated with ease in the transformed domain. The transformed time-independent equations in spatial coordinate are solved numerically by Gauss elimination. Numerical inverse transformation of the results into the real domain are operated by the modified Durbin transform method. Verification of the presented method is carried out by comparing the results with those obtained by the Newmark method and ANSYS finite element software. Furthermore, the developed solution approach is applied to problems with several impulsive loads. The novelty of the present study lies in the fact that a combination of the Navier method and Laplace transform is employed in the analysis of cross-ply laminated shallow spherical viscoelastic shells. The numerical sample results have proved that the presented method constitutes a highly accurate and efficient solution, which can be easily applied to the laminated viscoelastic shell problems.
Theory of elastic thin shells solid and structural mechanics
Gol'Denveizer, A L; Dryden, H L
1961-01-01
Theory of Elastic Thin Shells discusses the mathematical foundations of shell theory and the approximate methods of solution. The present volume was originally published in Russian in 1953, and remains the only text which formulates as completely as possible the different sets of basic equations and various approximate methods of shell analysis emphasizing asymptotic integration. The book is organized into five parts. Part I presents the general formulation and equations of the theory of shells, which are based on the well-known hypothesis of the preservation of the normal element. Part II is
Thin-shell wormholes in Born–Infeld electrodynamics with modified Chaplygin gas
Energy Technology Data Exchange (ETDEWEB)
Sharif, M., E-mail: msharif.math@pu.edu.pk [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan); Azam, M., E-mail: azam.math@ue.edu.pk [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan); Division of Science and Technology, University of Education, Township Campus, Lahore-54590 (Pakistan)
2014-07-25
In this paper, we construct spherically symmetric thin-shell wormholes in the scenario of Born–Infeld electrodynamics theory. We take the modified Chaplygin gas for the description of exotic matter around the wormhole throat. The stability of static wormhole solutions with different values of charge and Born–Infeld parameter is investigated. We compare our results with those obtained for generalized Chaplygin gas [36] and conclude that stable static wormhole solutions also exist even for large value of Born–Infeld parameter. - Highlights: • Constructed thin-shell wormholes in Born–Infeld electrodynamics for modified Chaplygin. • Studied its stability with different values of charge and Born–Infeld parameter. • New stable solutions are found even for large value of Born–Infeld parameter. • Selection of EoS significantly changes the presence and stability of static solutions.
Construction of thin shell wormholes from metric f(R) gravity
Bhatti, M. Zaeem-Ul-Haq; Anwar, A.; Ashraf, S.
2017-06-01
In this paper, we have constructed spherically symmetric thin-shell wormholes (WHs) by surgically grafting two geometries of charged black hole in the framework of f(R) higher curvature invariants (threaded by exotic matter). We have investigated the stable/unstable regimes for couple of f(R) models using the potential approach formulated by Eiroa with radial perturbation. We have categorized our analysis for different values of charge as well as the parameters involved in the particular mode of f(R) gravity. We have found both stable and unstable regions using modified Chaplygin gas in this scenario and the results are shown through plots. We found that there exists a parametric space for equation of state and quadratic as well as cubic gravities in which one can accommodate more stable thin-shell WHs.
A curved finite element for general thin shell structures
International Nuclear Information System (INIS)
Jones, R.F. Jr.
1978-01-01
This work describes the development of a curved quadrilateral shell finite element which demonstrates very good convergence properties. A general description is used in deriving the element so that it may be applied to any thin shell problem. The element is shown to be very efficient. It has a total of 36 degrees-of-freedom with 9 at each of the corners of the element. There are several distinct advantages that the element offers for practical applications. Most of the shell elements that have been presented in the past are limited to problems in which the coordinates on the shell surface are orthogonal. The element that is described in the paper is derived using a general description so that it may be applied to any thin shell problem including those in which the shell coordinates are not orthogonal. The degree-of-freedom at each of the four nodes are the three Cartesian displacements and their first derivatives with respect to the two surface coordinates. The imposition of boundary conditions is simplified since each of the degrees-of-freedom can be can be associated with a quantity which has a simple physical meaning. During the course of the derivation of the element, the strain displacement relationships are derived in a very simple manner consistent with Love's first approximation for thin shells. The derivation in the paper starts from basic principles and should help to shed some light on the proper form for the bending strain. Two primary contributions are presented in this work. The first is the presentation of a procedure for the development of a general quadrilateral shell element. The second is the simple derivation of the bending strain for the thin shells which apparently has not been presented previously. (Auth.)
Preparation of non-spherical particles by shell-shield etching for near-field nanopatterning
International Nuclear Information System (INIS)
Ye, Jian; Liesbet, Lagae
2014-01-01
The shape of polymer particles plays an important role in determining their function. In this paper, we describe a simple and unconventional method called shell-shield etching (SSE) that allows us to prepare freestanding submicrometer- or micrometer-sized polymer particles with various shapes. By precisely varying the time of ultraviolet ozone treatment under the partial shielding effect of the silica shell, we controllably reshape polymer spheres into symmetry-reduced polymer peaches, mushrooms, bowls, and plates. Finite difference time domain simulations indicate that the non-spherical particles obtained from the SSE method might have potential for near-field nanopatterning applications. (papers)
Charged black string thin-shell wormholes in modified gravity
Zaeem-ul-Haq Bhatti, M.; Yousaf, Z.; Ashraf, Sara
2017-08-01
In this paper, we explore the possibility for the existence of thin-shell wormholes for the charged black string in the framework of f(R) gravity theory. We have carried out our analysis by keeping linear perturbations about static equilibrium solutions where we have surgically pasted the interior spacetime to an exterior vacuum geometry. We have assumed logarithmic as well as exponential form of well-known f(R) models and investigated their role in the modeling of stable/unstable thin-shell wormholes. As a specific case, we perform our analysis through distributions of mass, charge and equation of state parameter. We found that various static thin-shell wormhole backgrounds are possible for different parametric values of f(R) models. We also concluded that modified gravity induced by logarithmic and exponential f(R) models could likely to host wide range of wormholes.
Elastic stresses at reinforced nozzles in spherical shells with pressure and moment loading
International Nuclear Information System (INIS)
Rodabaugh, E.C.; Gwaltney, R.D.
1976-01-01
Calculated elastic stresses at reinforced nozzles in spherical shells with pressure and moment loading are presented. The models used in the calculations represent a wide variety of reinforced shapes; all meeting Code requirements. The results show Code stress indices for pressure loading for nozzles with local reinforcement are acceptable with some modification in coverage. Simple equations for stress indices for moment loading are developed. Potential application of the moment-loading stress indices is discussed. Several recommendations for Code changes are included
Shell and pairing effects in spherical nuclei close to the nucleon drip lines
International Nuclear Information System (INIS)
Beiner, M.; Lombard, R.J.
1975-01-01
The unstability against nucleon emission of light and medium exotic spherical nuclei is investigated systematically using an extended version of the energy density formalism which reproduces correctly shell and pairing effects in stable nuclei. The reliability of the predictions of this microscopic, self-consistent and weakly parametrized model should not decrease significantly with the distance of the nuclei from the β-stability line, what is not the case for conventional mass formulae or mass tables [fr
Charged thin-shell gravastars in noncommutative geometry
Energy Technology Data Exchange (ETDEWEB)
Oevguen, Ali [Pontificia Universidad Catolica de Valparaiso, Instituto de Fisica, Valparaiso (Chile); Eastern Mediterranean University, Physics Department, Famagusta, Northern Cyprus (Turkey); Banerjee, Ayan [Jadavpur University, Department of Mathematics, Kolkata, West Bengal (India); Jusufi, Kimet [State University of Tetovo, Physics Department, Tetovo (Macedonia, The Former Yugoslav Republic of); Institute of Physics, Ss. Cyril and Methodius University, Faculty of Natural Sciences and Mathematics, Skopje (Macedonia, The Former Yugoslav Republic of)
2017-08-15
In this paper we construct a charged thin-shell gravastar model within the context of noncommutative geometry. To do so, we choose the interior of the nonsingular de Sitter spacetime with an exterior charged noncommutative solution by cut-and-paste technique and apply the generalized junction conditions. We then investigate the stability of a charged thin-shell gravastar under linear perturbations around the static equilibrium solutions as well as the thermodynamical stability of the charged gravastar. We find the stability regions, by choosing appropriate parameter values, located sufficiently close to the event horizon. (orig.)
Thin-shell wormholes constrained by cosmological observations
Wang, Deng; Meng, Xin-He
2017-01-01
We investigate the thin-shell wormholes constrained by cosmological observations for the first time in the literature. Without loss of generality, we study the thin-shell wormholes in $\\omega$CDM model and analyze their stability under perturbations preserving the symmetry. Firstly, we constrain the $\\omega$CDM model using a combination of Union 2.1 SNe Ia data, the latest $H(z)$ data and CMB data. Secondly, we use the constrained dark energy equation of state (EoS) $\\omega$ which lies in $[-...
Thin-shell wormholes with a generalized Chaplygin gas in Einstein-Born-Infeld theory
Energy Technology Data Exchange (ETDEWEB)
Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Figueroa Aguirre, Griselda [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina)
2012-11-15
We construct spherically symmetric thin-shell wormholes supported by a generalized Chaplygin gas in Born-Infeld electrodynamics coupled to Einstein gravity, and we analyze their stability under radial perturbations. For different values of the Born-Infeld parameter and the charge, we compare the results with those obtained in a previous work for Maxwell electrodynamics. The stability region in the parameter space reduces and then disappears as the value of the Born-Infeld parameter is modified in the sense of a larger departure from Maxwell theory. (orig.)
Stabilization of thin shell modes by a rotating secondary wall
International Nuclear Information System (INIS)
Gimblett, C.G.
1989-01-01
A simple model is developed to investigate if and under what circumstances the thin shell instabilities of a Reverse Field Pinch can be stabilized by a rotating secondary wall. The principles may be applicable to reactor designs that utilize a flowing liquid blanket (author)
Thin-shell wormholes associated with global cosmic strings
Bejarano, Cecilia; Eiroa, Ernesto F.; Simeone, Claudio
2007-01-01
In this article we construct cylindrical thin-shell wormholes in the context of global cosmic strings. We study the stability of static configurations under perturbations preserving the symmetry and we find that the throat tends to collapse or expand, depending only on the direction of the velocity perturbation.
Stability analysis of thin-shell wormholes from charged black string
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Azam, M., E-mail: msharif.math@pu.edu.pk, E-mail: azammath@gmail.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2013-04-01
In this paper, we construct thin-shell wormholes from charged black string through cut and paste procedure and investigate its stability. We assume modified generalized Chaplygin gas as a dark energy fluid (exotic matter) present in the thin layer of matter-shell. The stability of these constructed thin-shell wormholes is investigated in the scenario of linear perturbations. We conclude that static stable as well as unstable configurations are possible for cylindrical thin-shell wormholes.
Directory of Open Access Journals (Sweden)
Shen Fei
2016-12-01
Full Text Available We have investigated the scattering properties of an individual core-shell nanoparticle using the Mie theory, which can be tuned to support both electric and magnetic modes simultaneously. In general, the suppression of forward scattering can be realized by the second Kerker condition. Here, a novel mechanism has to be adopted to explain zero-forward scattering, which originates from the complex interactions between dipolar and quadrupolar modes. However, for lossy and lossless core-shell spherical nanoparticles, zero-forward scattering can never be achieved because the real parts of Mie expansion coefficients are always positive. By adding proper gain in dielectric shell, zero-forward scattering can be found at certain incident wavelengths, which means that all electric and magnetic responses in Mie scattering can be counteracted totally in the forward direction. In addition, if the absolute values of dipolar and quadrupolar terms are in the same order of magnitude, the local scattering minimum and maximum can be produced away from the forward and backward directions due to the interacting effect between the dipolar and quadrupolar terms. Furthermore, by adding suitable gain in shell, super-forward scattering can also be realized at certain incident wavelengths. We also demonstrated that anomalously weak scattering or superscattering could be obtained for the core-shell nanoparticles with suitable gain in shell. In particular, for such a choice of suitable gain in shell, we can obtain zero-forward scattering and anomalously weak scattering at the same wavelength as well as super-forward scattering at another wavelength. These features may provide new opportunities for cloaking, plasmonic lasers, optical antennas, and so on.
Shen, Fei; An, Ning; Tao, Yifei; Zhou, Hongping; Jiang, Zhaoneng; Guo, Zhongyi
2017-08-01
We have investigated the scattering properties of an individual core-shell nanoparticle using the Mie theory, which can be tuned to support both electric and magnetic modes simultaneously. In general, the suppression of forward scattering can be realized by the second Kerker condition. Here, a novel mechanism has to be adopted to explain zero-forward scattering, which originates from the complex interactions between dipolar and quadrupolar modes. However, for lossy and lossless core-shell spherical nanoparticles, zero-forward scattering can never be achieved because the real parts of Mie expansion coefficients are always positive. By adding proper gain in dielectric shell, zero-forward scattering can be found at certain incident wavelengths, which means that all electric and magnetic responses in Mie scattering can be counteracted totally in the forward direction. In addition, if the absolute values of dipolar and quadrupolar terms are in the same order of magnitude, the local scattering minimum and maximum can be produced away from the forward and backward directions due to the interacting effect between the dipolar and quadrupolar terms. Furthermore, by adding suitable gain in shell, super-forward scattering can also be realized at certain incident wavelengths. We also demonstrated that anomalously weak scattering or superscattering could be obtained for the core-shell nanoparticles with suitable gain in shell. In particular, for such a choice of suitable gain in shell, we can obtain zero-forward scattering and anomalously weak scattering at the same wavelength as well as super-forward scattering at another wavelength. These features may provide new opportunities for cloaking, plasmonic lasers, optical antennas, and so on.
Stability of the Regular Hayward Thin-Shell Wormholes
Directory of Open Access Journals (Sweden)
M. Sharif
2016-01-01
Full Text Available The aim of this paper is to construct regular Hayward thin-shell wormholes and analyze their stability. We adopt Israel formalism to calculate surface stresses of the shell and check the null and weak energy conditions for the constructed wormholes. It is found that the stress-energy tensor components violate the null and weak energy conditions leading to the presence of exotic matter at the throat. We analyze the attractive and repulsive characteristics of wormholes corresponding to ar>0 and ar<0, respectively. We also explore stability conditions for the existence of traversable thin-shell wormholes with arbitrarily small amount of fluid describing cosmic expansion. We find that the space-time has nonphysical regions which give rise to event horizon for 0
Lebiedzik, Catherine
1995-01-01
Development of design tools to furnish optimal acoustic environments for lightweight aircraft demands the ability to simulate the acoustic system on a workstation. In order to form an effective mathematical model of the phenomena at hand, we have begun by studying the propagation of acoustic waves inside closed spherical shells. Using a fully-coupled fluid-structure interaction model based upon variational principles, we have written a finite element analysis program and are in the process of examining several test cases. Future investigations are planned to increase model accuracy by incorporating non-linear and viscous effects.
Pattern recognition in RICH counters using the Possibilistic C- Spherical Shell algorithm
Massone, A M; Masulli, F
2000-01-01
The pattern recognition problem in RICH counters concerns the identification of an unknown number of imperfect roughly-circular rings made of a low number of discrete points in presence of background. We present some preliminary results obtained using the Possibilistic C-Spherical Shell algorithm. In particular, we show that the algorithm is very tolerant and robust to noise (outliers rate) level. Moreover, for complex images full of rings, we introduce an iterative scheme that greatly improves performance. Also, the rings are not required to be complete, arcs are sufficient to recognize the underlying rings. (4 refs).
International Nuclear Information System (INIS)
Ibral, Asmaa; Zouitine, Asmaa; Assaid, El Mahdi
2015-01-01
Poisson equation is solved analytically in the case of a point charge placed anywhere in a spherical core/shell nanostructure, immersed in aqueous or organic solution or embedded in semiconducting or insulating matrix. Conduction and valence band-edge alignments between core and shell are described by finite height barriers. Influence of polarization charges induced at the surfaces where two adjacent materials meet is taken into account. Original expressions of electrostatic potential created everywhere in the space by a source point charge are derived. Expressions of self-polarization potential describing the interaction of a point charge with its own image–charge are deduced. Contributions of double dielectric constant mismatch to electron and hole ground state energies as well as nanostructure effective gap are calculated via first order perturbation theory and also by finite difference approach. Dependencies of electron, hole and gap energies against core to shell radii ratio are determined in the case of ZnS/CdSe core/shell nanostructure immersed in water or in toluene. It appears that finite difference approach is more efficient than first order perturbation method and that the effect of polarization charge may in no case be neglected as its contribution can reach a significant proportion of the value of nanostructure gap
Entropy of an extremal electrically charged thin shell and the extremal black hole
Directory of Open Access Journals (Sweden)
José P.S. Lemos
2015-11-01
Full Text Available There is a debate as to what is the value of the entropy S of extremal black holes. There are approaches that yield zero entropy S=0, while there are others that yield the Bekenstein–Hawking entropy S=A+/4, in Planck units. There are still other approaches that give that S is proportional to r+ or even that S is a generic well-behaved function of r+. Here r+ is the black hole horizon radius and A+=4πr+2 is its horizon area. Using a spherically symmetric thin matter shell with extremal electric charge, we find the entropy expression for the extremal thin shell spacetime. When the shell's radius approaches its own gravitational radius, and thus turns into an extremal black hole, we encounter that the entropy is S=S(r+, i.e., the entropy of an extremal black hole is a function of r+ alone. We speculate that the range of values for an extremal black hole is 0≤S(r+≤A+/4.
International Nuclear Information System (INIS)
Civalek, Ö.
2014-01-01
In the present study nonlinear static and dynamic responses of shallow spherical shells resting on Winkler–Pasternak elastic foundations are carried out. The formulation of the shells is based on the Donnell theory. The nonlinear governing equations of motion of shallow shells are discretized in space and time domains using the discrete singular convolution and the differential quadrature methods, respectively. The validity of the present method is demonstrated by comparing the present results with those available in the open literature. The effects of the Winkler and Pasternak foundation parameters on nonlinear static and dynamic response of shells are investigated. Some results are also presented for circular plate as special case. Damping effect on nonlinear dynamic response of shells is studied. It is important to state that the increase in damping parameter causes decrease in the dynamic response of the shells. It is shown that the shear parameter of the foundation has a significant influence on the dynamic and static response of the shells. Also, the response of the shell is decreased with the increasing value of the shear parameter of the foundation. Parametric studies considering different geometric variables have also been investigated. -- Highlights: • Nonlinear responses of shallow spherical shells are presented. • The effects of foundation parameters are investigated. • Damping effect on nonlinear dynamic response of shells is also studied
Spherical core-shell magnetic particles constructed by main-chain palladium N-heterocyclic carbenes
Zhao, Huaixia; Li, Liuyi; Wang, Jinyun; Wang, Ruihu
2015-02-01
The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core-shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core-shell palladium N-heterocyclic carbene (NHC) particles (Fe3O4@PNP1 and Fe3O4@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe3O4@PNP2 shows better recyclability than Fe3O4@PNP1. Unexpectedly, Pd(ii) is well maintained after six consecutive catalytic runs in Fe3O4@PNP2, and Pd(0) and Pd(ii) coexist in Fe3O4@PNP1 under the same conditions; moreover, the morphologies of these spherical core-shell particles show no significant variation after six consecutive catalytic runs.The encapsulation of the functional species on magnetic core is a facile approach for the synthesis of core-shell magnetic materials, and surface encapsulating matrices play crucial roles in regulating their properties and applications. In this study, two core-shell palladium N-heterocyclic carbene (NHC) particles (Fe3O4@PNP1 and Fe3O4@PNP2) were prepared by a one-pot reaction of semi-rigid tripodal imidazolium salts and palladium acetate in the presence of magnetite nanoparticles. The magnetite nanoparticles are encapsulated inside the main-chain palladium, which act as cores. The conjugated effects of triphenyltriazine and triphenylbenzene in the imidazolium salts have important influence on their physical properties and catalytic performances. Fe3O4@PNP2 shows better recyclability than Fe3O4@PNP1. Unexpectedly, Pd(ii) is well maintained after six consecutive catalytic runs in
Mitri, Farid G
2012-08-01
This work presents the general theory of resonance scattering (GTRS) by an elastic spherical shell immersed in a nonviscous fluid and placed arbitrarily in an acoustic beam. The GTRS formulation is valid for a spherical shell of any size and material regardless of its location relative to the incident beam. It is shown here that the scattering coefficients derived for a spherical shell immersed in water and placed in an arbitrary beam equal those obtained for plane wave incidence. Numerical examples for an elastic shell placed in the field of acoustical Bessel beams of different types, namely, a zero-order Bessel beam and first-order Bessel vortex and trigonometric (nonvortex) beams are provided. The scattered pressure is expressed using a generalized partial-wave series expansion involving the beam-shape coefficients (BSCs), the scattering coefficients of the spherical shell, and the half-cone angle of the beam. The BSCs are evaluated using the numerical discrete spherical harmonics transform (DSHT). The far-field acoustic resonance scattering directivity diagrams are calculated for an albuminoidal shell immersed in water and filled with perfluoropropane gas, by subtracting an appropriate background from the total far-field form function. The properties related to the arbitrary scattering are analyzed and discussed. The results are of particular importance in acoustical scattering applications involving imaging and beam-forming for transducer design. Moreover, the GTRS method can be applied to investigate the scattering of any beam of arbitrary shape that satisfies the source-free Helmholtz equation, and the method can be readily adapted to viscoelastic spherical shells or spheres.
Buckling Capacity Curves for Steel Spherical Shells Loaded by the External Pressure
Błażejewski, Paweł; Marcinowski, Jakub
2015-03-01
Assessment of buckling resistance of pressurised spherical cap is not an easy task. There exist two different approaches which allow to achieve this goal. The first approach involves performing advanced numerical analyses in which material and geometrical nonlinearities would be taken into account as well as considering the worst imperfections of the defined amplitude. This kind of analysis is customarily called GMNIA and is carried out by means of the computer software based on FEM. The other, comparatively easier approach, relies on the utilisation of earlier prepared procedures which enable determination of the critical resistance pRcr, the plastic resistance pRpl and buckling parameters a, b, h, l 0 needed to the definition of the standard buckling resistance curve. The determination of the buckling capacity curve for the particular class of spherical caps is the principal goal of this work. The method of determination of the critical pressure and the plastic resistance were described by the authors in [1] whereas the worst imperfection mode for the considered class of spherical shells was found in [2]. The determination of buckling parameters defining the buckling capacity curve for the whole class of shells is more complicated task. For this reason the authors focused their attention on spherical steel caps with the radius to thickness ratio of R/t = 500, the semi angle j = 30o and the boundary condition BC2 (the clamped supporting edge). Taking into account all imperfection forms considered in [2] and different amplitudes expressed by the multiple of the shell thickness, sets of buckling parameters defining the capacity curve were determined. These parameters were determined by the methods proposed by Rotter in [3] and [4] where the method of determination of the exponent h by means of additional parameter k was presented. As a result of the performed analyses the standard capacity curves for all considered imperfection modes and amplitudes 0.5t, 1.0t, 1.5t
Reversed field pinch operation with a thin shell
International Nuclear Information System (INIS)
Ortolani, S.; Antoni, V.; Martini, S.; LaHaye, R.; Schaffer, M.; Tamano, T.; Taylor, P.; GA Technologies, San Diego, CA)
1987-01-01
The pulse length in OHTE, operating with a thin conducting shell, has been prolonged by finer control of the plasma position. The plasma sensitivity to equilibrium control further proves the absence of any intrinsic limitation on the plasma performance due to the lack of the perfectly conducting shell. The addition of the external vertical field control has extended the discharge lengths from ∼8 ms to ∼14 ms, with a simultaneous increase in discharge reproducibility. Although MHD linear theory predicts that RFP plasmas are unstable with a resistive shell boundary, no change in gross MHD modes is observed experimentally. However, a toroidally localized kink mode (slinky'' mode) due to nonlinear couplings of several internal kink modes has been found. The experimental indication that a relatively resistive shell (tau/sub shell/ ≅ 1/10 tau/sub pulse/) can provide an adequate MHD stability boundary introduces the possibility of major simplifications and optimizations in the design and construction of the next generation of RFP experiments. In particular, field error constraints on gaps and portholes become much less important and active accurate plasma positioning becomes possible. The latter may prove to be a crucial issue in RFP research where the dissipation in the outer plasma regions can largely determine the loop voltage and therefore the energy confinement time. 7 refs., 4 figs
Directory of Open Access Journals (Sweden)
Astafyeva Liudmila
2011-01-01
Full Text Available Abstract Nonlinear thermo-optical properties of two-layered spherical system of gold nanoparticle core and water vapor shell, created under laser heating of nanoparticle in water, were theoretically investigated. Vapor shell expansion leads to decreasing up to one to two orders of magnitude in comparison with initial values of scattering and extinction of the radiation with wavelengths 532 and 633 nm by system while shell radius is increased up to value of about two radii of nanoparticle. Subsequent increasing of shell radius more than two radii of nanoparticle leads to rise of scattering and extinction properties of system over initial values. The significant decrease of radiation scattering and extinction by system of nanoparticle-vapor shell can be used for experimental detection of the energy threshold of vapor shell formation and investigation of the first stages of its expansion. PACS: 42.62.BE. 78.67. BF
Tank measurements of scattering from a resin-filled fiberglass spherical shell with internal flaws.
Tesei, Alessandra; Guerrini, Piero; Zampolli, Mario
2008-08-01
This paper presents results of acoustic inversion and structural health monitoring achieved by means of low to midfrequency elastic scattering analysis of simple, curved objects, insonified in a water tank. Acoustic elastic scattering measurements were conducted between 15 and 100 kHz on a 60-mm-radius fiberglass spherical shell, filled with a low-shear-speed epoxy resin. Preliminary measurements were conducted also on the void shell before filling, and on a solid sphere of the same material as the filler. These data were used to estimate the constituent material parameters via acoustic inversion. The objects were measured in the backscatter direction, suspended at midwater, and insonified by a broadband directional transducer. From the inspection of the response of the solid-filled shell it was possible to detect and characterize significant inhomogeneities of the interior (air pockets), the presence of which were later confirmed by x-ray CT scan and ultrasound measurements. Elastic wave analysis and a model-data comparison study support the physical interpretation of the measurements.
Limit load carrying capacity for spherical laminated shells under external pressure
Muc, A.; Rys, J.; Latas, W.
The aim of the present paper is to discuss possible failure modes encountered in the analysis of multilayered laminated spherical shells having different shallowness parameters and subjected to external pressure. Two various approaches are proposed: the first based on the global buckling analysis and local determination of FPF for each individual layer in a laminate and the second postulating global investigations of both buckling as well as failure (in the sense of LPF) phenomena in laminated structures. The intersection of two curves corresponding to bifurcation buckling and breaking of fibers forms the limit load carrying capacity curve for the analyzed shells. The first part of the work is devoted to the analytical prediction of the LLCC curves. Next, the theoretical results are compared with the numerical ones obtained with the use of strict geometrically nonlinear formulation for composite shells. Various types of materials are analyzed herein, i.e., both unidirectional as well as woven roving composite materials. The analysis includes also some remarks dealing with the possibility of composite topology optimization in order to obtain the maximal LLCC.
Malekshahi Byranvand, Mahdi; Nemati Kharat, Ali; Taghavinia, Nima; Dabirian, Ali
2016-06-29
Dielectric scattering particles have widely been used as embedded scattering elements in dye-sensitized solar cells (DSCs) to improve the optical absorption of the device. Here we systematically study rodlike and spherical core-shell silica@Ag particles as more effective alternatives to the dielectric scattering particles. The wavelength-scale silica@Ag particles with sufficiently thin Ag shell support hybrid plasmonic-photonic resonance modes that have low parasitic absorption losses and a broadband optical response. Both of these features lead to their successful deployment in light trapping in high-efficiency DSCs. Optimized rodlike silica@Ag@silica particles improve the power conversion efficiency of a DSC from 6.33 to 8.91%. The dimension, surface morphology, and concentration of these particles are optimized to achieve maximal efficiency enhancement. The rodlike silica particles are prepared in a simple one-pot synthesis process and then are coated with Ag in a liquid-phase deposition process by reducing an Ag salt. The aspect ratio of silica rods is tuned by adjusting the temperature and duration of the growth process, whereas the morphology of Ag shell is tailored by controlling the reduction rate of Ag salt, where slower reduction in a polyol process gives a smoother Ag shell. Using optical calculations, the superior performance of the plasmonic core-shell particles is related to the large number of hybrid photonic-plasmonic resonance modes that they support.
Analytical solution for viscous incompressible Stokes flow in a spherical shell
Directory of Open Access Journals (Sweden)
C. Thieulot
2017-11-01
Full Text Available I present a new family of analytical flow solutions to the incompressible Stokes equation in a spherical shell. The velocity is tangential to both inner and outer boundaries, the viscosity is radial and of the power-law type, and the solution has been designed so that the expressions for velocity, pressure, and body force are simple polynomials and therefore simple to implement in (geodynamics codes. Various flow average values, e.g., the root mean square velocity, are analytically computed. This forms the basis of a numerical benchmark for convection codes and I have implemented it in two finite-element codes: ASPECT and ELEFANT. I report error convergence rates for velocity and pressure.
NIF-Scale Hohlraum Asymmetry Studies Using Point-Projection Radiograph of Thin Shells
International Nuclear Information System (INIS)
Pollaine, S.; Bradley, D.; Landen, O.; Wallace, R.; Jones, O.
2000-01-01
Our current OMEGA experimental campaign is developing the thin shell diagnostic for use on NIF with the needed accuracy. The thin shell diagnostic has the advantage of linearity over alternative measurement techniques, so that low-order modes will not corrupt the measurement of high-order modes. Although our random measurement errors are adequate, we need to monitor beam balance and ensure that the thin shells have a uniform thickness
Hypocycloidal throat for 2 + 1-dimensional thin-shell wormholes
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S.H.; Halilsoy, M. [Eastern Mediterranean University, Department of Physics, Gazimagusa (Turkey)
2015-11-15
Recently we have shown that for 2 + 1-dimensional thin-shell wormholes a non-circular throat may lead to a physical wormhole in the sense that the energy conditions are satisfied. By the same token, herein we consider an angular dependent throat geometry embedded in a 2 + 1-dimensional flat spacetime in polar coordinates. It is shown that, remarkably, a generic, natural example of the throat geometry is provided by a hypocycloid. That is, two flat 2 + 1 dimensions are glued together along a hypocycloid. The energy required in each hypocycloid increases with the frequency of the roller circle inside the large one. (orig.)
Transient Response of a Fluid-Filled, Thick-Walled Spherical Shell Embedded in an Elastic Medium
Directory of Open Access Journals (Sweden)
Bahari Ako
2016-01-01
Full Text Available The paper addresses the problem of transient elastodynamics analysis of a thick-walled, fluid-filled spherical shell embedded in an elastic medium with an analytical approach. This configuration is investigated at first step for a full-space case. Different constitutive relations for the elastic medium, shell material and filling fluid can be considered, as well as different excitation sources (including S/P wave or plane/spherical incident wave at different locations. With mapmaking visualisation, the wave propagation phenomena can be described and better understood. The methodology is going to be applied to analysis of the tunnels or other shell like structures under the effect of nearby underground explosion.
Multi-layer adaptive thin shells for future space telescopes
International Nuclear Information System (INIS)
Bastaits, R; Preumont, A; Rodrigues, G; Jetteur, Ph; Hagedorn, P
2012-01-01
This paper examines the morphing capability of doubly curved elastic shells with various layers of active materials with strain actuation capability. The equivalent piezoelectric loads of an orthotropic multi-layer shell is established and it is demonstrated that a set of four active layers offer independent control of the in-plane forces and bending moments, which guarantees optimum morphing with arbitrary profile. This is illustrated by a numerical example which compares a unimorph configuration (single layer of active material) with a twin-bimorph (two pairs of symmetrical layers of active material with orthotropic properties). Numerical simulations indicate that the optical (Zernike) modes with shapes where the curvatures in orthogonal directions have opposite signs (e.g. astigmatism, trefoil, tetrafoil) are fairly easy to control with both configurations and that substantial amplitudes may be achieved. However, the optical modes with shapes where the curvatures in orthogonal directions have the same sign (e.g. defocus, coma, spherical aberration) are difficult to control with the unimorph configuration, and they lead to the appearance of slope discontinuities at the interface between the independent electrodes. As expected, a much better morphing is achieved with a twin-bimorph configuration. (paper)
Directory of Open Access Journals (Sweden)
Jiang Wenming
2010-08-01
Full Text Available Aiming at the cracking phenomenon of the thin shell mould in the expendable pattern shell casting during the pattern removing process, some systemic researches are presented. The influence of the pattern removing method and temperature on the pattern removing were investigated. The shell mould cracking mechanism was analyzed by using thermo-gravimetric analysis (TGA, and combining the temperature field and the volume change of the expanded polystyrene (EPS foam pattern being tested. The results indicated that the shell mould was not easily cracked when the pattern removing process was carried out with the furnace being heated little by little because of the shell slowly shrinking with dehydration and shell strength gradually increasing. The shell mould was soon destroyed when it was set directly into the furnace at above 400 ℃ because of the thin shell mould rapidly shrinking and the foam pattern hindering. However, the shell mould had no cracking when it had been preheated for a long time even if the furnace temperature was above 400 篊 and the shell was put into the furnace directly. Moreover, when the shell mould was directly set into the furnace at lower temperatures, 250 to 300 ℃, the shell would shrink slowly and the foam pattern would stay at the maximum expansion stage temperature of 100 to 110 ℃ for a long time; and the shell mould would experience an expansion force from the foam pattern for a long time. The expansion force is related to the pattern removing temperature, holding time, foam pattern thickness and density. Therefore, the foam pattern with higher density could make the shell crack.
Shiloh, Roy; Remez, Roei; Lu, Peng-Han; Jin, Lei; Lereah, Yossi; Tavabi, Amir H; Dunin-Borkowski, Rafal E; Arie, Ady
2018-03-27
Nearly eighty years ago, Scherzer showed that rotationally symmetric, charge-free, static electron lenses are limited by an unavoidable, positive spherical aberration. Following a long struggle, a major breakthrough in the spatial resolution of electron microscopes was reached two decades ago by abandoning the first of these conditions, with the successful development of multipole aberration correctors. Here, we use a refractive silicon nitride thin film to tackle the second of Scherzer's constraints and demonstrate an alternative method for correcting spherical aberration in a scanning transmission electron microscope. We reveal features in Si and Cu samples that cannot be resolved in an uncorrected microscope. Our thin film corrector can be implemented as an immediate low cost upgrade to existing electron microscopes without re-engineering of the electron column or complicated operation protocols and can be extended to the correction of additional aberrations. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Pustovalov, V.K.; Astafyeva, L.G.; Zharov, V.P.
2013-01-01
Modeling of nonlinear dependences of optical properties of spherical two-layered gold core and some material shell nanoparticles (NPs) placed in water on parameters of core and shell was carried out on the basis of the extended Mie theory. Efficiency cross-sections of absorption, scattering and extinction of radiation with wavelength 532 nm by core–shell NPs in the ranges of core radii r 00 =5–40 nm and of relative NP radii r 1 /r 00 =1–8 were calculated (r 1 —radius of two-layered nanoparticle). Shell materials were used with optical indexes in the ranges of refraction n 1 =0.2–1.5 and absorption k 1 =0–3.5 for the presentation of optical properties of wide classes of shell materials (including dielectrics, metals, polymers, vapor shell around gold core). Results show nonlinear dependences of optical properties of two-layered NPs on optical indexes of shell material, core r 00 and relative NP r 1 /r 00 radii. Regions with sharp decrease and increase of absorption, scattering and extinction efficiency cross-sections with changing of core and shell parameters were investigated. These dependences should be taken into account for applications of two-layered NPs in laser nanomedicine and optical diagnostics of tissues. The results can be used for experimental investigation of shell formation on NP core and optical determination of geometrical parameters of core and shell of two-layered NPs. -- Highlights: • Absorption, scattering and extinction of two-layered nanoparticles are studied. • Shell materials change in wide regions of materials (metals, dielectrics, vapor). • Effect of sharp decrease and increase of optical characteristics is established. • Explanation of sharp decreasing and increasing optical characteristics is presented
Perturbative dynamics of thin-shell wormholes beyond general relativity: An alternative approach
Rubín de Celis, Emilio; Tomasini, Cecilia; Simeone, Claudio
Recent studies relating the approximations for the equations-of-state for thin shells and their consequent perturbative evolution are extended to thin-shell wormholes in theories beyond general relativity and more than four spacetime dimensions. The assumption of equations-of-state of the same form for static and slowly evolving shells appears as a strong restriction excluding the possibility of oscillatory evolutions. Then the new results considerably differ from previous ones obtained within the usual linearized approach.
Communication: Programmable self-assembly of thin-shell mesostructures
Halverson, Jonathan D.; Tkachenko, Alexei V.
2017-10-01
We study numerically the possibility of programmable self-assembly of various thin-shell architectures. They include clusters isomorphic to fullerenes C20 and C60, finite and infinite sheets, tube-shaped and toroidal mesostructures. Our approach is based on the recently introduced directionally functionalized nanoparticle platform, for which we employ a hybrid technique of Brownian dynamics with stochastic bond formation. By combining a number of strategies, we were able to achieve a near-perfect yield of the desired structures with a reduced "alphabet" of building blocks. Among those strategies are the following: the use of bending rigidity of the interparticle bond as a control parameter, programming the morphology with a seed architecture, use of chirality-preserving symmetries for reduction of the particle alphabet, and the hierarchic approach.
Microscopic thin-shell wormholes in magnetic Melvin universe
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S.H.; Halilsoy, M.; Amirabi, Z. [Eastern Mediterranean University, Department of Physics, North Cyprus, Mersin 10 (Turkey)
2014-05-15
We construct thin-shell wormholes in the magnetic Melvin universe. It is shown that in order to make a TSW in the Melvin spacetime the radius of the throat cannot be larger than (2)/(B{sub 0}), in which B{sub 0} is the magnetic field constant. We also analyze the stability of the constructed wormhole in terms of a linear perturbation around the equilibrium point. In our stability analysis we scan a full set of the Equation of States such as Linear Gas, Chaplygin Gas, Generalized Chaplygin Gas, Modified Generalized Chaplygin Gas, and Logarithmic Gas. Finally we extend our study to the wormhole solution in the unified Melvin and Bertotti-Robinson spacetime. In this extension we show that for some specific cases, the local energy density is partially positive but the total energy which supports the wormhole is positive. (orig.)
Thin-shell wormholes in neo-Newtonian theory
Övgün, Ali; Salako, Ines G.
2017-07-01
In this paper, we constructed an acoustic thin-shell wormhole (ATW) under neo-Newtonian theory using the Darmois-Israel junction conditions. To determine the stability of the ATW by applying the cut-and-paste method, we found the surface density and surface pressure of the ATW under neo-Newtonian hydrodynamics just after obtaining an analog acoustic neo-Newtonian solution. We focused on the effects of the neo-Newtonian parameters by performing stability analyses using different types of fluids, such as a linear barotropic fluid (LBF), a Chaplygin fluid (CF), a logarithmic fluid (LogF) and a polytropic fluid (PF). We showed that a fluid with negative energy is required at the throat to keep the wormhole stable. The ATW can be stable if suitable values of the neo-Newtonian parameters ς, A and B are chosen.
Nonlinear behaviour and stability of thin-walled shells
Obodan, Natalia I; Gromov, Vasilii A
2013-01-01
This book focuses on the nonlinear behaviour of thin-wall shells (single- and multilayered with delamination areas) under various uniform and non-uniform loadings. The dependence of critical (buckling) load upon load variability is revealed to be highly non-monotonous, showing minima when load variability is close to the eigenmode variabilities of solution branching points of the respective nonlinear boundary problem. A novel numerical approach is employed to analyze branching points and to build primary, secondary, and tertiary bifurcation paths of the nonlinear boundary problem for the case of uniform loading. The load levels of singular points belonging to the paths are considered to be critical load estimates for the case of non-uniform loadings.
Geometric Nonlinear Computation of Thin Rods and Shells
Grinspun, Eitan
2011-03-01
We develop simple, fast numerical codes for the dynamics of thin elastic rods and shells, by exploiting the connection between physics, geometry, and computation. By building a discrete mechanical picture from the ground up, mimicking the axioms, structures, and symmetries of the smooth setting, we produce numerical codes that not only are consistent in a classical sense, but also reproduce qualitative, characteristic behavior of a physical system----such as exact preservation of conservation laws----even for very coarse discretizations. As two recent examples, we present discrete computational models of elastic rods and shells, with straightforward extensions to the viscous setting. Even at coarse discretizations, the resulting simulations capture characteristic geometric instabilities. The numerical codes we describe are used in experimental mechanics, cinema, and consumer software products. This is joint work with Miklós Bergou, Basile Audoly, Max Wardetzky, and Etienne Vouga. This research is supported in part by the Sloan Foundation, the NSF, Adobe, Autodesk, Intel, the Walt Disney Company, and Weta Digital.
Experimental Observation of Thin-shell Instability in a Collisionless Plasma
Energy Technology Data Exchange (ETDEWEB)
Ahmed, H.; Doria, D.; Sarri, G.; Ianni, E.; Kar, S.; Quinn, K.; Borghesi, M. [Centre for Plasma Physics, Queen’s University of Belfast, Belfast BT7 1NN (United Kingdom); Dieckmann, M. E. [Department of Science and Technology, Linkoping University, SE-60174 Norrkoping (Sweden); Romagnani, L. [LULI, École Polytechnique, CNRS, CEA, UPMC, Palaiseau (France); Bret, A. [ETSI Industriales, Universidad Castilla La Mancha, E-13 071 Ciudad Real (Spain); Cerchez, M.; Giesecke, A. L.; Prasad, R.; Willi, O. [Institute for Laser and Plasma Physics, University of Düsseldorf (Germany); Notley, M., E-mail: d.doria@qub.ac.uk, E-mail: m.borghesi@qub.ac.uk [Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom)
2017-01-10
We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.
International Nuclear Information System (INIS)
NIKROO, A; CZECHOWICZ, DG; CASTILLO, ER; PONTELANDOLFO, JM
2002-01-01
OAK A271 PRODUCTION OF HIGHER STRENGTH THIN WALLED GLOW DISCHARGE POLYMER SHELLS FOR CRYOGENIC EXPERIMENTS AT OMEGA. Thin walled polymer shells are needed for OMEGA cryogenic laser experiments. These capsules need to be about 900 (micro)m in diameter and as thin as possible (approx 1-2 (micro)m), while having enough strength to be filled with DT as fast as possible to about 1000 atm. The authors have found that by optimizing the coating parameters in the glow discharge polymer (GDP) deposition system, traditionally used for making ICF targets, they can routinely make robust, ∼ 1.5 (micro)m thick, 900 (micro)m diameter GDP shells with buckle strengths of over 0.3 atm. This is twice the strength of shells made prior to the optimization and is comparable to values quoted for polyimide shells. In addition, these shells were found to be approximately three times more permeable and over 20% denser than previously made GDP shells. The combination of higher strength and permeability is ideal for direct drive cryogenic targets at OMEGA. Shells as thin as 0.5 (micro)m have been made. In this paper, the authors discuss the shell fabrication process, effects of modifying various GDP deposition parameters on shell properties and chemical composition
Park, Gi Dae; Kang, Yun Chan
2018-03-01
Micrometer-sized spherical aggregates of Sn and Co components containing core-shell, yolk-shell, hollow nanospheres are synthesized by applying nanoscale Kirkendall diffusion in the large-scale spray drying process. The Sn 2 Co 3 -Co 3 SnC 0.7 -C composite microspheres uniformly dispersed with Sn 2 Co 3 -Co 3 SnC 0.7 mixed nanocrystals are formed by the first-step reduction of spray-dried precursor powders at 900 °C. The second-step oxidation process transforms the Sn 2 Co 3 -Co 3 SnC 0.7 -C composite into the porous microsphere composed of Sn-Sn 2 Co 3 @CoSnO 3 -Co 3 O 4 core-shell, Sn-Sn 2 Co 3 @CoSnO 3 -Co 3 O 4 yolk-shell, and CoSnO 3 -Co 3 O 4 hollow nanospheres at 300, 400, and 500 °C, respectively. The discharge capacity of the microspheres with Sn-Sn 2 Co 3 @CoSnO 3 -Co 3 O 4 core-shell, Sn-Sn 2 Co 3 @CoSnO 3 -Co 3 O 4 yolk-shell, and CoSnO 3 -Co 3 O 4 hollow nanospheres for the 200 th cycle at a current density of 1 A g -1 is 1265, 987, and 569 mA h g -1 , respectively. The ultrafine primary nanoparticles with a core-shell structure improve the structural stability of the porous-structured microspheres during repeated lithium insertion and desertion processes. The porous Sn-Sn 2 Co 3 @CoSnO 3 -Co 3 O 4 microspheres with core-shell primary nanoparticles show excellent cycling and rate performances as anode materials for lithium-ion batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Axisymmetric thermoviscoelastoplastic state of thin laminated shells made of a damageable material
Galishin, A. Z.
2008-04-01
A technique for the determination of the axisymmetric thermoviscoelastoplastic state of laminated thin shells made of a damageable material is developed. The technique is based on the kinematic equations of the theory of thin shells that account for transverse shear strains. The thermoviscoplastic equations, which describe the deformation of a shell element along paths of small curvature, are used as the constitutive equations. The equivalent stress that appears in the kinetic equations of damage and creep is determined from a failure criterion that accounts for the stress mode. The thermoviscoplastic deformation of a two-layer shell that models an element of a rocket engine nozzle is considered as an example
Energy Technology Data Exchange (ETDEWEB)
Kirkwood, R K; Milovich, J; Bradley, D K; Schmitt, M; Goldman, S R; Kalantar, D H; Meeker, D; Jones, O S; Pollaine, S M; Amendt, P A; Dewald, E; Edwards, J; Landen, O L; Nikroo, A
2008-07-28
A necessary condition for igniting indirectly-driven inertial confinement fusion (ICF) spherical capsules on the National Ignition Facility (NIF) is controlling drive flux asymmetry to the 1% level time-integrated over the pulse and with < 10%/ns swings during the pulse [J. D. Lindl et al., 'The Physics Basis for Ignition using Indirect Drive Targets on the National Ignition Facility', Physics of Plasmas 11, 339 (2003)]. While drive symmetry during the first 2 ns of the pulse can be inferred by using the re-emission pattern from a surrogate high Z sphere [E. Dewald et al. to be published in Rev. Sci. Inst.] and symmetry during the last 5 ns inferred from the shape of fully imploded capsules [A. Hauer, N. Delamater, D. Ress et al. Rev. Sci. Instrum. 66, 672-7 (1995)], the midportion ({approx} 2-10 ns) has been shown to be amenable to detection by the in-flight shape of x-ray backlit thin shell capsules [Pollaine et. al., Physics of Plasmas 8 2357 (2001)]. In this paper, we present sensitivity studies conducted on the University of Rochester's OMEGA laser of the thin shell symmetry measurement technique at near NIF-scale for two candidate capsule ablator materials, Ge-doped CH and Cu-doped Be. These experiments use both point and area backlighting to cast 4.7 keV radiographs of thin 1.4 mm initial-diameter Ge-doped CH and Cu-doped Be shells when converged a factor of {approx} 0.5 x in radius. Distortions in the position of the transmission limb of the shells resulting from drive asymmetries are measured to an accuracy of a few {micro}ms, meeting requirements. The promising results to date allow us to compare measured and predicted distortions and by inference drive asymmetries for the first 4 asymmetry modes as a function of hohlraum illumination conditions.
Problems with tunneling of thin shells from black holes
Indian Academy of Sciences (India)
the manifolds inside and outside the shell. In this paper we choose Eddington–. Finkelstein coordinates. The coordinates and transformation laws are explained in. Appendix B and here we summarize the equations of motion. As explained in §4 we use the symbol ⊘ to mean + for outgoing shells and − for ingoing shells.
Vibrations of thin piezoelectric shallow shells: Two-dimensional ...
Indian Academy of Sciences (India)
In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two-dimensional eigenvalue problem.
Vibrations of thin piezoelectric shallow shells: Two-dimensional ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
In this paper we consider the eigenvalue problem for piezoelectric shallow shells and we show that, as the thickness of the shell goes to zero, the eigensolutions of the three-dimensional piezoelectric shells converge to the eigensolutions of a two- dimensional eigenvalue problem. Keywords. Vibrations; piezoelectricity ...
Thin-shell wormhole solutions in Einstein-Hoffmann-Born-Infeld theory
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S. Habib, E-mail: habib.mazhari@emu.edu.tr [Department of Physics, Eastern Mediterranean University, G. Magusa, North Cyprus, Mersin 10 (Turkey); Halilsoy, M., E-mail: mustafa.halilsoy@emu.edu.tr [Department of Physics, Eastern Mediterranean University, G. Magusa, North Cyprus, Mersin 10 (Turkey); Amirabi, Z., E-mail: zahra.amirabi@emu.edu.tr [Department of Physics, Eastern Mediterranean University, G. Magusa, North Cyprus, Mersin 10 (Turkey)
2011-10-03
We adopt the Hoffmann-Born-Infeld's (HBI) double Lagrangian approach in general relativity to find black holes and investigate the possibility of viable thin-shell wormholes. By virtue of the non-linear electromagnetic parameter, the matching hypersurfaces of the two regions with two Lagrangians provide a natural, lower-bound radius for the thin-shell wormholes which provides the main motivation to the present study. In particular, the stability of thin-shell wormholes supported by normal matter in higher-dimensional Einstein-HBI-Gauss-Bonnet (EHBIGB) gravity is highlighted. -- Highlights: → We extend the Hoffmann-Born-Infeld Lagrangian to higher dimensions. → We found higher-dimensional black hole solutions for Einstein-Hoffmann-Born-Infeld-Gauss-Bonnet (EHBIGB) gravity. → We obtained thin-shell wormholes in the EHBIGB gravity which are supported by ordinary matter and stable.
Energy Technology Data Exchange (ETDEWEB)
Pettersen, Sigurd R., E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang; He, Jianying, E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Kristiansen, Helge [NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), NO-7491 Trondheim (Norway); Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway); Njagi, John; Goia, Dan V. [Center for Advanced Materials Processing, Clarkson University, Potsdam, New York 13699-5814 (United States); Redford, Keith [Conpart AS, Dragonveien 54, NO-2013 Skjetten (Norway)
2016-07-25
Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental results with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.
International Nuclear Information System (INIS)
Clementi, Luis A.; Vega, Jorge R.; Gugliotta, Luis M.; Quirantes, Arturo
2012-01-01
A numerical method is proposed for the characterization of core–shell spherical particles from static light scattering (SLS) measurements. The method is able to estimate the core size distribution (CSD) and the particle size distribution (PSD), through the following two-step procedure: (i) the estimation of the bivariate core–particle size distribution (C–PSD), by solving a linear ill-conditioned inverse problem through a generalized Tikhonov regularization strategy, and (ii) the calculation of the CSD and the PSD from the estimated C–PSD. First, the method was evaluated on the basis of several simulated examples, with polystyrene–poly(methyl methacrylate) core–shell particles of different CSDs and PSDs. Then, two samples of hematite–Yttrium basic carbonate core–shell particles were successfully characterized. In all analyzed examples, acceptable estimates of the PSD and the average diameter of the CSD were obtained. Based on the single-scattering Mie theory, the proposed method is an effective tool for characterizing core–shell colloidal particles larger than their Rayleigh limits without requiring any a-priori assumption on the shapes of the size distributions. Under such conditions, the PSDs can always be adequately estimated, while acceptable CSD estimates are obtained when the core/shell particles exhibit either a high optical contrast, or a moderate optical contrast but with a high ‘average core diameter’/‘average particle diameter’ ratio. -- Highlights: ► Particles with core–shell morphology are characterized by static light scattering. ► Core size distribution and particle size distribution are successfully estimated. ► Simulated and experimental examples are used to validate the numerical method. ► The positive effect of a large core/shell optical contrast is investigated. ► No a-priori assumption on the shapes of the size distributions is required.
Thin-shell wormholes in (2 + 1)-dimensional Einstein-scalar theory
Mazharimousavi, S. Habib; Amirabi, Z.; Halilsoy, M.
2017-03-01
We present an infinite class of one-parameter scalar field extensions to the Bañados, Teitelboim and Zanelli (BTZ) black hole in 2 + 1 dimensions. By virtue of the scalar charge, the thin-shell wormhole supported by a linear fluid at the throat becomes stable against linear perturbations. More interestingly, we provide an example of thin-shell wormhole which is strictly stable in the sense that it is confined in between two classically intransmissible potential barriers.
Static black hole and vacuum energy: thin shell and incompressible fluid
Ho, Pei-Ming; Matsuo, Yoshinori
2018-03-01
With the back reaction of the vacuum energy-momentum tensor consistently taken into account, we study static spherically symmetric black-hole-like solutions to the semi-classical Einstein equation. The vacuum energy is assumed to be given by that of 2-dimensional massless scalar fields, as a widely used model in the literature for black holes. The solutions have no horizon. Instead, there is a local minimum in the radius. We consider thin shells as well as incompressible fluid as the matter content of the black-hole-like geometry. The geometry has several interesting features due to the back reaction of vacuum energy. In particular, Buchdahl's inequality can be violated without divergence in pressure, even if the surface is below the Schwarzschild radius. At the same time, the surface of the star can not be far below the Schwarzschild radius for a density not much higher than the Planck scale, and the proper distance from its surface to the origin can be very short even for very large Schwarzschild radius. The results also imply that, contrary to the folklore, in principle the Boulware vacuum can be physical for black holes.
Sasaki, Youhei; Takehiro, Shin-ichi; Ishiwatari, Masaki; Yamada, Michio
2018-03-01
Linear stability analysis of anelastic thermal convection in a rotating spherical shell with entropy diffusivities varying in the radial direction is performed. The structures of critical convection are obtained in the cases of four different radial distributions of entropy diffusivity; (1) κ is constant, (2) κT0 is constant, (3) κρ0 is constant, and (4) κρ0T0 is constant, where κ is the entropy diffusivity, T0 is the temperature of basic state, and ρ0 is the density of basic state, respectively. The ratio of inner and outer radii, the Prandtl number, the polytropic index, and the density ratio are 0.35, 1, 2, and 5, respectively. The value of the Ekman number is 10-3 or 10-5 . In the case of (1), where the setup is same as that of the anelastic dynamo benchmark (Jones et al., 2011), the structure of critical convection is concentrated near the outer boundary of the spherical shell around the equator. However, in the cases of (2), (3) and (4), the convection columns attach the inner boundary of the spherical shell. A rapidly rotating annulus model for anelastic systems is developed by assuming that convection structure is uniform in the axial direction taking into account the strong effect of Coriolis force. The annulus model well explains the characteristics of critical convection obtained numerically, such as critical azimuthal wavenumber, frequency, Rayleigh number, and the cylindrically radial location of convection columns. The radial distribution of entropy diffusivity, or more generally, diffusion properties in the entropy equation, is important for convection structure, because it determines the distribution of radial basic entropy gradient which is crucial for location of convection columns.
Spherical nano-SnSb/MCMB/carbon core–shell composite for high stability lithium ion battery anodes
International Nuclear Information System (INIS)
Li, Juan; Ru, Qiang; Hu, Shejun; Sun, Dawei; Zhang, Beibei; Hou, Xianhua
2013-01-01
A novel multi-step design of spherical nano-SnSb/MCMB/carbon core–shell composite for high stability and long life lithium battery electrodes has been introduced. The core–shell composite was successfully synthesized via co-precipitation and subsequent pyrolysis. The resultant composite sphere consisted of nanosized SnSb alloy and mesophase carbon microbeads (MCMB, 10 μm) embedded in a carbon matrix pyrolyzed from glucose and petroleum pitch, in which the MCMB was treated to be the inner core to offer mechanical support and efficient electron conducting pathway. The composite material exhibited a unique stability with a retention discharge capacity rate of 83.52% with reversible capacity of 422.5 mAh g −1 after 100 cycles and a high initial coulombic efficiency of 83.53%. The enhanced electrochemical performance is attributed to the structural stability of the composite sphere during the charging–discharging process
Problems with tunneling of thin shells from black holes
Indian Academy of Sciences (India)
Specifically for shells tunneling out of black holes, this quantity is not invariant under canonical transformations. It can be interpreted as the transmission coefficient only in the cases in which it is invariant under canonical transformations. Although such cases include alpha decay, they do not include the tunneling of shells ...
On the mechanics of elastic lines in thin shells
Benet, Eduard; Vernerey, Franck
The deformation of soft shells in nature and engineering is often conditioned by the presence of lines whose mechanical properties are different from the shell. For instance, the deformation of tree leaves is conditioned by the presence of harder stems, and cell mitosis is driven by a stiffening line along its membrane. From an experimental standpoint, many groups have taken advantage of this feature to develop self-actuated shells with prescribed deformations. Examples include the polymerization of gels along certain lines, or the inclusion of stiffer lines via 3D printing. However, there is not yet a general continuum theory that accounts for this type of discontinuity within the membrane. Hence, we extend the general shell theory to account for the inclusion of a line that potentially induces jumps in stresses, couple stresses and moments, across its thickness. This is achieved via coupling the rod and the membrane deformations, and ensuring continuity of displacements. The model is then applied to three important problems: a constriction disc inside a shell of revolution, the induced twisting of a shell via the torsion of an embedded line, and the effect of an helicoidal line on the uni-axial deformation of a cylindrical shell. National Science Foundation CAREER award 1350090.
Elasto/visco-plastic deformations of thin shells of revolution
International Nuclear Information System (INIS)
Takezono, S.; Akashi, T.
1979-01-01
This paper is concerned with the numerical analysis of large elasto/visco-plastic deformations of this shells of revolution under axi-symmetrical loading with applications to pressure vessels. (orig.)
OPTIMIZATION OF INHOMOGENEOUS THICK-WALLED SPHERICAL SHELL IN THE TEMPERATURE FIELD
Directory of Open Access Journals (Sweden)
Andreev Vladimir Igorevich
2012-12-01
Full Text Available The authors consider the central symmetric problem of the theory of elasticity of inhomogeneous bodies for thick-walled spheres exposed to the external pressure in a stationary temperature field. The essence of the inverse problem lies in the identification of such dependence of the elastic modulus on the radius whereby the stress state of the sphere is the same as the pre-set one. Maximal stresses in thick-walled shells exposed to internal or external pressures occur in the proximity to the internal contour. Thus, destruction in this area is initiated upon the achievement of the limit state, while the rest of the shell is underused. The essence of the problem solved in the paper is the following. The problems are solved using the simultaneous exposure to forces and temperature loads.The two theories of strength are considered at once: a maximum normal stress theory and a maximum shear stress theory. It is proven that according to the first theory maximum stresses in an inhomogeneous shell are 1.35 times smaller than those in the homogeneous shell. The stress reduction rate equals to 2.5, if the maximum shear stress theory is employed. Thus, the introduction of artificial inhomogeneity leads to the optimization of shells by reducing their thickness or increasing loads.
A thin-shelled reptile from the Late Triassic of North America and the origin of the turtle shell
Joyce, Walter G.; Lucas, Spencer G.; Scheyer, Torsten M.; Heckert, Andrew B.; Hunt, Adrian P.
2008-01-01
A new, thin-shelled fossil from the Upper Triassic (Revueltian: Norian) Chinle Group of New Mexico, Chinlechelys tenertesta, is one of the most primitive known unambiguous members of the turtle stem lineage. The thin-shelled nature of the new turtle combined with its likely terrestrial habitat preference hint at taphonomic filters that basal turtles had to overcome before entering the fossil record. Chinlechelys tenertesta possesses neck spines formed by multiple osteoderms, indicating that the earliest known turtles were covered with rows of dermal armour. More importantly, the primitive, vertically oriented dorsal ribs of the new turtle are only poorly associated with the overlying costal bones, indicating that these two structures are independent ossifications in basal turtles. These novel observations lend support to the hypothesis that the turtle shell was originally a complex composite in which dermal armour fused with the endoskeletal ribs and vertebrae of an ancestral lineage instead of forming de novo. The critical shell elements (i.e. costals and neurals) are thus not simple outgrowths of the bone of the endoskeletal elements as has been hypothesized from some embryological observations. PMID:18842543
Energy Technology Data Exchange (ETDEWEB)
Ibral, Asmaa [Equipe d’Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B.P. 20 El Jadida Principale, El Jadida 24000 (Morocco); Laboratoire d’Instrumentation, Mesure et Contrôle, Département de Physique, Université Chouaïb Doukkali, B.P. 20 El Jadida Principale, El Jadida (Morocco); Zouitine, Asmae [Département de Physique, Ecole Nationale Supérieure d’Enseignement Technique, Université Mohammed V Souissi, B.P. 6207 Rabat-Instituts, Rabat (Morocco); Assaid, El Mahdi, E-mail: eassaid@yahoo.fr [Equipe d’Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B.P. 20 El Jadida Principale, El Jadida 24000 (Morocco); Laboratoire d’Instrumentation, Mesure et Contrôle, Département de Physique, Université Chouaïb Doukkali, B.P. 20 El Jadida Principale, El Jadida (Morocco); Feddi, El Mustapha [Département de Physique, Ecole Nationale Supérieure d’Enseignement Technique, Université Mohammed V Souissi, B.P. 6207 Rabat-Instituts, Rabat (Morocco); and others
2014-09-15
Ground state energy and wave function of a hydrogen-like off-centre donor impurity, confined anywhere in a ZnS/CdSe spherical core/shell nanostructure are determined in the framework of the envelope function approximation. Conduction band-edge alignment between core and shell of nanostructure is described by a finite height barrier. Dielectric constant mismatch at the surface where core and shell materials meet is taken into account. Electron effective mass mismatch at the inner surface between core and shell is considered. A trial wave function where coulomb attraction between electron and off-centre ionized donor is used to calculate ground state energy via the Ritz variational principle. The numerical approach developed enables access to the dependence of binding energy, coulomb correlation parameter, spatial extension and radial probability density with respect to core radius, shell radius and impurity position inside ZnS/CdSe core/shell nanostructure.
1991-04-01
Adnan H. Navfeh 1521 anisotropic media Plane acoustic %aves in linear viscoelastic porous media: Energy , Patrick N. J. Rasolofosaon 1532 particle...xx) Ivs n. The frequency x replaced by A (bsr), where I ( bsg , for most metal shells in can be chosen to be a resonance frequency x,,, of the body, or
Counter-rotational effects on stability of 2 + 1-dimensional thin-shell wormholes
Energy Technology Data Exchange (ETDEWEB)
Mazharimousavi, S.H.; Halilsoy, M. [Eastern Mediterranean University, Department of Physics, Gazimagusa (Turkey)
2014-09-15
The role of angular momentum in a 2 + 1-dimensional rotating thin-shell wormhole (TSW) is considered. Particular emphasis is given to stability when the shells (rings) are counter-rotating. We find that counter-rotating halves make the TSW supported by the equation of state of a linear gas more stable. Under a small velocity dependent perturbation, however, it becomes unstable. (orig.)
MECHANICAL PROPERTIES OF THIN GDP SHELLS USED AS CRYOGENIC DIRECT DRIVE TARGETS AT OMEGA
International Nuclear Information System (INIS)
NIKROO, A.; CZECHOWICZ, D.; CHEN, K.C.; DICKEN, M.; MORRIS, C.; ANDREWS, R.; GREENWOOD, A.L; CASTILLO, E.
2003-09-01
OAK-B135 Thin glow discharge polymer (GDP) shells are currently used as the targets for cryogenic direct drive laser fusion experiments. These shells need to be filled with nearly 1000 atm of D 2 and cooled to cryogenic temperatures without failing due to buckling and bursting pressures they experience in this process. Therefore, the mechanical and permeation properties of these shells are of utmost importance in successful and rapid filling with D 2 . In this paper, they present an overview of buckle and burst pressures of several different types of GDP shells. These include those made using traditional GDP deposition parameters (standard GDP) using a high deposition pressure and using modified parameters (strong GDP) of low deposition pressure that leads to more robust shells
Creep bending of thin-walled shells and plates by consideration of finite deflections
Altenbach, H.; Naumenko, K.
A phenomenological constitutive model for the characterization of creep-damage processes of metals is applied to the numerical analysis of thin-walled shells and plates. The governing equations of the theory of shallow shells are used taking into account geometrical nonlinearities connected with finite time-dependent deflections by moderate bending. The solutions of the initial-boundary value problem are obtained for thin rectangular plates in order to show the influence of geometrical nonlinearity on results of time-dependent deformation and stress redistribution as well as on estimations of the failure time.
Critical stability of almost adiabatic convection in a rapidly rotating thick spherical shell
Energy Technology Data Exchange (ETDEWEB)
Starchenko, S. V., E-mail: sstarchenko@mail.ru [Russian Academy of Sciences, Institute of Terrestrial Magnetism, the Ionosphere, and Radiowave Propagation (Russian Federation); Kotelnikova, M. S. [Lavrentyev Institute of Hydrodynamics (Russian Federation)
2013-02-15
In this work, the convection equations in the almost adiabatic approximation is studied for which the choice of physical parameters is primarily based on possible applications to the hydrodynamics of the deep interiors of the Earth and planets and moons of the terrestrial group. The initial system of partial differential equations (PDEs) was simplified to a single second-order ordinary differential equation for the pressure or vertical velocity component to investigate the linear stability of convection. The critical frequencies, modified Rayleigh numbers, and distributions of convection are obtained at various possible Prandtl numbers and in different thick fluid shells. An analytical WKB-type solution was obtained for the case when the inner radius of the shell is much smaller than the outer radius and convective sources are concentrated along the inner boundary.
Takehiro, Shin-ichi; Sasaki, Youhei
2018-03-01
Penetration of steady magneto-hydrodynamic (MHD) disturbances into an upper strongly stratified stable layer excited by MHD thermal convection in rotating spherical shells is investigated. The theoretical model proposed by Takehiro (2015) is reexamined in the case of steady fluid motion below the bottom boundary. Steady disturbances penetrate into a density stratified MHD fluid existing in the semi-infinite region in the vertical direction. The axis of rotation of the system is tilted with respect to the vertical. The basic magnetic field is uniform and may be tilted with respect to the vertical and the rotation axis. Linear dispersion relation shows that the penetration distance with zero frequency depends on the amplitude of Alfvén wave speed. When Alfvén wave speed is small, viscous diffusion becomes dominant and penetration distance is similar to the horizontal scale of the disturbance at the lower boundary. In contrast, when Alfvén wave speed becomes larger, disturbance can penetrate deeper, and penetration distance becomes proportional to the Alfvén wave speed and inversely proportional to the geometric average of viscous and magnetic diffusion coefficients and to the total horizontal wavenumber. The analytic expression of penetration distance is in good agreement with the extent of penetration of mean zonal flow induced by finite amplitude convection in a rotating spherical shell with an upper stably stratified layer embedded in an axially uniform basic magnetic field. The theory expects that the stable layer suggested in the upper part of the outer core of the earth could be penetrated completely by mean zonal flows excited by thermal/compositional convection developing below the stable layer.
Thin shell morphology in the circumstellar medium of massive binaries
van Marle, A. J.; Keppens, R.; Meliani, Z.
2011-01-01
Context. In massive binaries, the powerful stellar winds of the two stars collide, leading to the formation of shock-dominated environments that can be modeled only in 3D. Aims. We investigate the morphology of the collision-front shell between the stellar winds of binary components in two
Problems with tunneling of thin shells from black holes
Indian Academy of Sciences (India)
p dr)) is not invariant under canonical transfor- mations in general. Specifically for shells tunneling out of black holes, this quantity is not invariant under canonical transformations. It can be interpreted as the transmission coef- ficient only in the cases in which it is invariant under canonical transformations. Although.
Facile and Scalable Synthesis of Monodispersed Spherical Capsules with a Mesoporous Shell
Qi, Genggeng
2010-05-11
Monodispersed HMSs with tunable particle size and shell thickness were successfully synthesized using relatively concentrated polystyrene latex templates and a silica precursor in a weakly basic ethanol/water mixture. The particle size of the capsules can vary from 100 nm to micrometers. These highly engineered monodispersed capsules synthesized by a facile and scalable process may find applications in drug delivery, catalysis, separationm or as biological and chemical microreactors. © 2010 American Chemical Society.
Directory of Open Access Journals (Sweden)
Boonlamp, M.
2005-03-01
Full Text Available A spherical double shell model (SDM for a single cell has been developed, using Laplace’s equation in spherical coordinates and boundary conditions. Electric field intensities and dielectric constants of each region inside and outside of the cell have been estimated. The dielectrophoretic spectrum of the real part of a complex function (Re[f ( ω] were computed using Visual Foxpro Version 6, which gave calculated values pertaining to electrical properties of the cell model as compared with experimental values. The process was repeated until the error percentile was in an acceptable range. The calculated parameters were the dielectric constants and the conductivities of the inner cytoplasm ( εic, σic, the outer cytoplasm ( εoc, σoc, the inner membrane ( εim, σim, the outer membrane ( εom, σom, the suspending solution( εs, σs and the thickness of each layer (dom, doc, dim, respectively. This computer program provides estimated values of cell electrical properties with high accuracy and required minimal computational time.
Kiranda, Hanan Karimah; Mahmud, Rozi; Abubakar, Danmaigoro; Zakaria, Zuki Abubakar
2018-01-01
The evolution of nanomaterial in science has brought about a growing increase in nanotechnology, biomedicine, and engineering fields. This study was aimed at fabrication and characterization of conjugated gold-cockle shell-derived calcium carbonate nanoparticles (Au-CSCaCO3NPs) for biomedical application. The synthetic technique employed used gold nanoparticle citrate reduction method and a simple precipitation method coupled with mechanical use of a Programmable roller-ball mill. The synthesized conjugated nanomaterial was characterized for its physicochemical properties using transmission electron microscope (TEM), field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). However, the intricacy of cellular mechanisms can prove challenging for nanomaterial like Au-CSCaCO3NPs and thus, the need for cytotoxicity assessment. The obtained spherical-shaped nanoparticles (light-green purplish) have an average diameter size of 35 ± 16 nm, high carbon and oxygen composition. The conjugated nanomaterial, also possesses a unique spectra for aragonite polymorph and carboxylic bond significantly supporting interactions between conjugated nanoparticles. The negative surface charge and spectra absorbance highlighted their stability. The resultant spherical shaped conjugated Au-CSCaCO3NPs could be a great nanomaterial for biomedical applications.
A hybrid radial basis function-pseudospectral method for thermal convection in a 3-D spherical shell
Wright, G. B.
2010-07-01
A novel hybrid spectral method that combines radial basis function (RBF) and Chebyshev pseudospectral methods in a "2 + 1" approach is presented for numerically simulating thermal convection in a 3-D spherical shell. This is the first study to apply RBFs to a full 3-D physical model in spherical geometry. In addition to being spectrally accurate, RBFs are not defined in terms of any surface-based coordinate system such as spherical coordinates. As a result, when used in the lateral directions, as in this study, they completely circumvent the pole issue with the further advantage that nodes can be "scattered" over the surface of a sphere. In the radial direction, Chebyshev polynomials are used, which are also spectrally accurate and provide the necessary clustering near the boundaries to resolve boundary layers. Applications of this new hybrid methodology are given to the problem of convection in the Earth\\'s mantle, which is modeled by a Boussinesq fluid at infinite Prandtl number. To see whether this numerical technique warrants further investigation, the study limits itself to an isoviscous mantle. Benchmark comparisons are presented with other currently used mantle convection codes for Rayleigh number (Ra) 7 × 10^{3} and 10^{5}. Results from a Ra = 10^{6} simulation are also given. The algorithmic simplicity of the code (mostly due to RBFs) allows it to be written in less than 400 lines of MATLAB and run on a single workstation. We find that our method is very competitive with those currently used in the literature. Copyright 2010 by the American Geophysical Union.
Fang, Baizeng; Kim, Jung Ho; Kim, Minsik; Kim, Minwoo; Yu, Jong-Sung
2009-03-07
Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.
Directory of Open Access Journals (Sweden)
Seyyed M. Hasheminejad
2003-01-01
Full Text Available An analysis for sound scattering by fluid-filled spherical and cylindrical viscoelastic shells immersed in viscous fluids is outlined. The dynamic viscoelastic properties of the scatterer and the viscosity of the surrounding and core fluids are rigorously taken into account in the solution of the acoustic scattering problem. The novel features of Havriliak-Negami model for viscoelastic material dynamic behaviour description along with the appropriate wave-harmonic field expansions and the pertinent boundary conditions are employed to develop a closed-form solution in form of infinite series. Subsequently, the associated acoustic field quantities such as the scattered far-field pressure directivity pattern, form function amplitude, transmitted intensity ratio, and acoustic force magnitude are evaluated for given sets of medium physical properties. Numerical results clearly indicate that in addition to the traditional fluid viscosity-related mechanisms, the dynamic viscoelastic properties of the shell material as well as its thickness can be of major significance in sound scattering. Limiting cases are examined and fair agreements with well-known solutions are established.
Holovatsky, V. A.; Voitsekhivska, O. M.; Yakhnevych, M. Ya
2018-04-01
The effect of homogeneous magnetic field and location of donor impurity on the electron energy spectrum and distribution of its probability density in spherical core-shell quantum dot is investigated. In the framework of the effective mass approximation and rectangular infinitely deep potential well, the solutions of the Schrodinger equation are found using the matrix method. The wave functions are expanded over the complete set of exact functions obtained without the magnetic field and impurity. It is shown that when the induction of magnetic field increases, the ground state of electron in the nanostructure without impurity or on-center impurity is successively formed by the states with m = 0, -1, -2, … (Aharonov-Bohm effect). When donor impurity is located in the shell of the nanostructure the Aharonov-Bohm effect vanishes. The dependences of electron energy spectrum and its wave functions on the location of impurity, placed along the direction of magnetic field or perpendicularly to it, are studied. It is shown, that in the first case, the quantum states are characterized by the certain value of magnetic quantum number m and the expansion contains the wave functions of the states with it only. In the second case, the cylindrical symmetry of the problem is broken and the new quantum states are formed from the states with different values of all three quantum numbers n, l, m and electron energy spectrum weakly depends on the magnetic field induction.
Lin, Cuikun; Kong, Deyan; Liu, Xiaoming; Wang, Huan; Yu, Min; Lin, Jun
2007-04-02
Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields.
International Nuclear Information System (INIS)
Sun, Z.; Schubert, G.
1995-01-01
In this study, we carry out numerical simulations of thermal convection in a rapidly rotating spherical fluid shell at high Taylor number Ta and Rayleigh number R with a nonlinear, three-dimensional, time-dependent, spectral-transform code. The parameters used in the simulations are chosen to be in a range which allows us to study two different types of convection, i.e., single column and multi-layered types, and the transition between them. Numerical solutions feature highly time-dependent north--south open columnar convective cells. The cells occur irregularly in longitude, are quasi-layered in cylindrical radius, and maintain alternating bands of mean zonal flow. The complex convective structure and the banded mean zonal flow are results of the high Taylor and Rayleigh numbers. The transition between the two types of convection appears to occur gradually with increasing Rayleigh and Taylor numbers. At a Taylor number of 10 7 the differential rotation pattern consists of an inner cylindrical region of subrotation and an outer cylindrical shell of superrotation manifest at the outer boundary as an equatorial superrotation and a high latitude subrotation. The differential rotation pattern is similar at Ta=10 8 and low Rayleigh number. Cylindrical shells of alternately directed mean zonal flow begin to develop at Ta=10 8 and R=50R c and at Ta=10 9 and R=25R c . This pattern is seen on the outer surface as a latitudinally-banded zonal flow consisting of an equatorial superrotation, a middle and high latitude subrotation, and a polar superrotation. At Ta=10 9 and R=50R c the differential rotation appears at the surface as a broad eastward flow in the equatorial region with alternating bands of westward and eastward flow at high latitudes. copyright 1995 American Institute of Physics
Directory of Open Access Journals (Sweden)
H. Huang
1995-01-01
Full Text Available The nonlinear interaction problem is analyzed by simultaneously solving the mass, momentum, and energy conservation equations together .with appropriate material constitutive equations governing the fluid dynamics of the explosion gaseous product and the water and the structural dynamics of the compliant shell. A finite difference technique in a coupled Eulerian–Lagrangian scheme is used. The computer program PISCES 2DELK is employed to carry out the numerical computations. The results demonstrate that to rigorously analyze the response of a submerged structure to a nearby explosion, the interactions among the explosion shock wave, the structure, its surrounding media, and the explosion bubble need to be considered.
Thin Static Charged Dust Majumdar–Papapetrou Shells with High Symmetry in D ≥ 4
Czech Academy of Sciences Publication Activity Database
Čermák, Martin; Zouhar, M.
2012-01-01
Roč. 51, č. 8 (2012), s. 2455-2469 ISSN 0020-7748 Institutional research plan: CEZ:AV0Z20410507 Keywords : Majumdar–Papapetrou * Kastor–Traschen * higher dimensional thin charged shell Subject RIV: BE - Theoretical Physics Impact factor: 1.086, year: 2012
Note on a thin-shell wormhole in extremal Reissner-Nordström geometry
Mazharimousavi, S. Habib; Halilsoy, M.
We show that the cold near horizon of the extremal Reissner-Nordström can be considered as the throat of a thin-shell wormhole with arbitrarily small exotic matter and positive angular pressure. Such a wormhole is physical and stable against radial perturbations provided an appropriate perfect fluid exists at the throat.
Contribution of apparently non-operating loadings to the buckling of thin shells and plates
International Nuclear Information System (INIS)
Delaigue, Didier.
1980-02-01
This work includes four parts: in the first part, the Kirchhoff-Love theory of thin shells is described, a theory taken up and developed by Koiter and whose modelling seems to meet the problems of engineers. The second part deals with the buckling of a thin plate subjected to a load along a part of its edge, of which a part or all is seemingly inoperative. In the third part the study is extended to shells of any shape subjected to a conservative loading of the ''dead-loading'' type along part of their edges. On the basis of the results of the previous study, a study is then made on the taking into account of any load applied to the edge of a thin shell. In the fourth part the previous results are applied to the study of the buckling of a thin shell with a circular base subjected along a part of its edge to a normal prestress and to twisting moments linear density [fr
Local effects in thin elastic shell due to thermal and mechanical loadings
International Nuclear Information System (INIS)
Taheri, S.
1987-01-01
For a thick cylinder (1/15)<(h/rm)<(1/3) the local effect is represented by the same field. When the local effect is negligible the Love-Kirchhoff solution is valid for a thick cylinder. A shear effect shell theory may give for a thin cylinder a large error compared to the exact 3D solution on a thermal shock. The Love-Kirchhoff solution is generally not valid in the vicinity of a clamped or simply supported edge. A finite element program of thin shell with shear effect or thick shell ist not really reliable. A combination of 3D local solution and Love-Kirchhoff global solution through a transition zone may replace a complete 3D solution for not very thick structures. (orig./GL)
International Nuclear Information System (INIS)
Penner, Joyce E; Andronova, Natalia; Oehmke, Robert C; Brown, Jonathan; Stout, Quentin F; Jablonowski, Christiane; Leer, Bram van; Powell, Kenneth G; Herzog, Michael
2007-01-01
One of the most important advances needed in global climate models is the development of atmospheric General Circulation Models (GCMs) that can reliably treat convection. Such GCMs require high resolution in local convectively active regions, both in the horizontal and vertical directions. During previous research we have developed an Adaptive Mesh Refinement (AMR) dynamical core that can adapt its grid resolution horizontally. Our approach utilizes a finite volume numerical representation of the partial differential equations with floating Lagrangian vertical coordinates and requires resolving dynamical processes on small spatial scales. For the latter it uses a newly developed general-purpose library, which facilitates 3D block-structured AMR on spherical grids. The library manages neighbor information as the blocks adapt, and handles the parallel communication and load balancing, freeing the user to concentrate on the scientific modeling aspects of their code. In particular, this library defines and manages adaptive blocks on the sphere, provides user interfaces for interpolation routines and supports the communication and load-balancing aspects for parallel applications. We have successfully tested the library in a 2-D (longitude-latitude) implementation. During the past year, we have extended the library to treat adaptive mesh refinement in the vertical direction. Preliminary results are discussed. This research project is characterized by an interdisciplinary approach involving atmospheric science, computer science and mathematical/numerical aspects. The work is done in close collaboration between the Atmospheric Science, Computer Science and Aerospace Engineering Departments at the University of Michigan and NOAA GFDL
GEOFLOW: simulation of convection in a spherical shell under central force field
Directory of Open Access Journals (Sweden)
P. Beltrame
2006-01-01
Full Text Available Time-dependent dynamical simulations related to convective motion in a spherical gap under a central force field due to the dielectrophoretic effect are discussed. This work is part of the preparation of the GEOFLOW-experiment which is planned to run in a microgravity environment. The goal of this experiment is the simulation of large-scale convective motion in a geophysical or astrophysical framework. This problem is new because of, on the one hand, the nature of the force field (dielectrophoretic effect and, on another hand, the high degree of symmetries of the system, e.g. the top-bottom reflection. Thus, the validation of this simulation with well-known results is not possible. The questions concerning the influence of the dielectrophoretic force and the possibility to reproduce the theoretically expected motions in the astrophysical framework, are open. In the first part, we study the system in terrestrial conditions: the unidirectional Earth's force is superimposed on the central dielectrophoretic force field to compare with the laboratory experiments during the development of the equipment. In the second part, the GEOFLOW-experiment simulations in weightless conditions are compared with theoretical studies in the astrophysical framework's, in the first instance a fluid under a self-gravitating force field. We present complex time-dependent dynamics, where the dielectrophoretic force field causes significant differences in the flow compared to the case that does not involve this force field.
Planktic foraminiferal shell thinning in the Arabian Sea due to anthropogenic ocean acidification?
Directory of Open Access Journals (Sweden)
H. de Moel
2009-09-01
Full Text Available About one third of the anthropogenic carbon dioxide (CO_{2} released into the atmosphere in the past two centuries has been taken up by the ocean. As CO_{2} invades the surface ocean, carbonate ion concentrations and pH are lowered. Laboratory studies indicate that this reduces the calcification rates of marine calcifying organisms, including planktic foraminifera. Such a reduction in calcification resulting from anthropogenic CO_{2} emissions has not been observed, or quantified in the field yet. Here we present the findings of a study in the Western Arabian Sea that uses shells of the surface water dwelling planktic foraminifer Globigerinoides ruber in order to test the hypothesis that anthropogenically induced acidification has reduced shell calcification of this species. We found that light, thin-walled shells from the surface sediment are younger (based on ^{14}C and δ^{13}C measurements than the heavier, thicker-walled shells. Shells in the upper, bioturbated, sediment layer were significantly lighter compared to shells found below this layer. These observations are consistent with a scenario where anthropogenically induced ocean acidification reduced the rate at which foraminifera calcify, resulting in lighter shells. On the other hand, we show that seasonal upwelling in the area also influences their calcification and the stable isotope (δ^{13}C and δ^{18}O signatures recorded by the foraminifera shells. Plankton tow and sediment trap data show that lighter shells were produced during upwelling and heavier ones during non-upwelling periods. Seasonality alone, however, cannot explain the ^{14}C results, or the increase in shell weight below the bioturbated sediment layer. We therefore must conclude that probably both the processes of acidification and seasonal upwelling are responsible for the presence of light shells in the top of the sediment and the age
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 3
International Nuclear Information System (INIS)
Gwaltney, R.C.; Bolt, S.E.; Corum, J.M.; Bryson, J.W.
1975-06-01
The third in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models are idealized thin-shell structures consisting of two circular cylindrical shells that intersect at right angles. There are no transitions, reinforcements, or fillets in the junction region. This series of model tests serves two basic purposes: the experimental data provide design information directly applicable to nozzles in cylindrical vessels; and the idealized models provide test results for use in developing and evaluating theoretical analyses applicable to nozzles in cylindrical vessels and to thin piping tees. The cylinder of model 3 had a 10 in. OD and the nozzle had a 1.29 in. OD, giving a d 0 /D 0 ratio of 0.129. The OD/thickness ratios for the cylinder and the nozzle were 50 and 7.68 respectively. Thirteen separate loading cases were analyzed. In each, one end of the cylinder was rigidly held. In addition to an internal pressure loading, three mutually perpendicular force components and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. The experimental stress distributions for all the loadings were obtained using 158 three-gage strain rosettes located on the inner and outer surfaces. The loading cases were also analyzed theoretically using a finite-element shell analysis developed at the University of California, Berkeley. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good agreement for this model. (U.S.)
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 4
International Nuclear Information System (INIS)
Gwaltney, R.C.; Bolt, S.E.; Bryson, J.W.
1975-06-01
The last in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. The models in the series are idealized thin-shell structures consisting of two circular cylindrical shells that intersect at right angles. There are no transitions, reinforcements, or fillets in the junction region. This series of model tests serves two basic purposes: (1) the experimental data provide design information directly applicable to nozzles in cylindrical vessels, and (2) the idealized models provide test results for use in developing and evaluating theoretical analyses applicable to nozzles in cylindrical vessels and to thin piping tees. The cylinder of model 4 had an outside diameter of 10 in., and the nozzle had an outside diameter of 1.29 in., giving a d 0 /D 0 ratio of 0.129. The OD/thickness ratios were 50 and 20.2 for the cylinder and nozzle respectively. Thirteen separate loading cases were analyzed. For each loading condition one end of the cylinder was rigidly held. In addition to an internal pressure loading, three mutually perpendicular force components and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. The experimental stress distributions for each of the 13 loadings were obtained using 157 three-gage strain rosettes located on the inner and outer surfaces. Each of the 13 loading cases was also analyzed theoretically using a finite-element shell analysis developed at the University of California, Berkeley. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good agreement for this model. (U.S.)
Numerical study of stress concentration in localized axisymmetric thinnings in shells and plates
International Nuclear Information System (INIS)
Neoberdin, Yu.A.; Maslenok, B.A.; Borintsev, A.B.; Egorov, M.F.; Shvetsov, A.V.
1981-01-01
Based on the method of finite elements and that of central composition orthogonal planning, regression equations are obtained for stress concentration coefficients for three different forms of localized thinning of a ring plate subjected to axisymmetric tension. The equations obtained allow the stress concentration coefficients to be determined in a plate and with a sufficient accuracy for practice, in shells over a wide range of changes in the hollow depth, grinding spot diameter and the plate or shell thickness. Recommendations are given as to the hollow shape securing the least stress concentration
Design and development by direct polishing of the WFXT thin polynomial mirror shells
Proserpio, L.; Campana, S.; Citterio, O.; Civitani, M.; Combrinck, H.; Conconi, P.; Cotroneo, V.; Freeman, R.; Mattini, E.; Langstrof, P.; Morton, R.; Motta, G.; Oberle, O.; Pareschi, G.; Parodi, G.; Pels, C.; Schenk, C.; Stock, R.; Tagliaferri, G.
2017-11-01
The Wide Field X-ray Telescope (WFXT) is a medium class mission proposed to address key questions about cosmic origins and physics of the cosmos through an unprecedented survey of the sky in the soft X-ray band (0.2-6 keV) [1], [2]. In order to get the desired angular resolution of 10 arcsec (5 arcsec goal) on the entire 1 degrees Field Of View (FOV), the design of the optical system is based on nested grazing-incidence polynomial profiles mirrors, and assumes a focal plane curvature and plate scale corrections among the shells. This design guarantees an increased angular resolution also at large off-axis positions with respect to the usually adopted Wolter I configuration. In order to meet the requirements in terms of mass and effective area (less than 1200 kg, 6000 cm2 @ 1 keV), the nested shells are thin and made of quartz glass. The telescope assembly is composed by three identical modules of 78 nested shells each, with diameter up to 1.1 m, length in the range of 200-440 mm and thickness of less than 2.2 mm. At this regard, a deterministic direct polishing method is under investigation to manufacture the WFXT thin grazing-incidence mirrors made of quartz. The direct polishing method has already been used for past missions (as Einstein, Rosat, Chandra) but based on much thicker shells (10 mm ore more). The technological challenge for WFXT is to apply the same approach but for 510 times thinner shells. The proposed approach is based on two main steps: first, quartz glass tubes available on the market are ground to conical profiles; second the pre-shaped shells are polished to the required polynomial profiles using a CNC polishing machine. In this paper, preliminary results on the direct grinding and polishing of prototypes shells made by quartz glass with low thickness, representative of the WFXT optical design, are presented.
Spherical Collapse in Chameleon Models
Brax, Ph; Steer, D A
2010-01-01
We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse depends on the initial comoving size of the inhomogeneity.
Spherical collapse in chameleon models
International Nuclear Information System (INIS)
Brax, Ph.; Rosenfeld, R.; Steer, D.A.
2010-01-01
We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse in principle depends on the initial comoving size of the inhomogeneity
A simple triangular finite element for nonlinear thin shells: statics, dynamics and anisotropy
Viebahn, Nils; Pimenta, Paulo M.; Schröder, Jörg
2017-02-01
This work presents a simple finite element implementation of a geometrically exact and fully nonlinear Kirchhoff-Love shell model. Thus, the kinematics are based on a deformation gradient written in terms of the first- and second-order derivatives of the displacements. The resulting finite element formulation provides C^1-continuity using a penalty approach, which penalizes the kinking at the edges of neighboring elements. This approach enables the application of well-known C^0-continuous interpolations for the displacements, which leads to a simple finite element formulation, where the only unknowns are the nodal displacements. On the basis of polyconvex strain energy functions, the numerical framework for the simulation of isotropic and anisotropic thin shells is presented. A consistent plane stress condition is incorporated at the constitutive level of the model. A triangular finite element, with a quadratic interpolation for the displacements and a one-point integration for the enforcement of the C^1-continuity at the element interfaces leads to a robust shell element. Due to the simple nature of the element, even complex geometries can be meshed easily, which include folded and branched shells. The reliability and flexibility of the element formulation is shown in a couple of numerical examples, including also time dependent boundary value problems. A plane reference configuration is assumed for the shell mid-surface, but initially curved shells can be accomplished if one regards the initial configuration as a stress-free deformed state from the plane position, as done in previous works.
International Nuclear Information System (INIS)
Kimura, Keiji; Takehiro, Shin-ichi; Yamada, Michio
2014-01-01
We investigate properties of convective solutions of the Boussinesq thermal convection in a moderately rotating spherical shell allowing the respective rotation of the inner and outer spheres due to the viscous torque of the fluid. The ratio of the inner and outer radii of the spheres, the Prandtl number, and the Taylor number are fixed to 0.4, 1, and 500 2 , respectively. The Rayleigh number is varied from 2.6 × 10 4 to 3.4 × 10 4 . In this parameter range, the behaviours of obtained asymptotic convective solutions are almost similar to those in the system whose inner and outer spheres are restricted to rotate with the same constant angular velocity, although the difference is found in the transition process to chaotic solutions. The convective solution changes from an equatorially symmetric quasi-periodic one to an equatorially symmetric chaotic one, and further to an equatorially asymmetric chaotic one, as the Rayleigh number is increased. This is in contrast to the transition in the system whose inner and outer spheres are assumed to rotate with the same constant angular velocity, where the convective solution changes from an equatorially symmetric quasi-periodic one, to an equatorially asymmetric quasi-periodic one, and to equatorially asymmetric chaotic one. The inner sphere rotates in the retrograde direction on average in the parameter range; however, it sometimes undergoes the prograde rotation when the convective solution becomes chaotic
El Haouari, M.; Feddi, E.; Dujardin, F.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.
2017-11-01
The ground state of a conduction electron coupled to an off-center impurity donor in a AlAS/GaAs spherical core/shell quantum dot is investigated theoretically. The image-charge effect and the influence of the electron-polar-LO-phonon interaction are considered. The electron-impurity binding energy is calculated via a variational procedure and is reported both as a function of the shell width and of the radial position of the donor atom. The polaronic effects on this quantity are particularly discussed.
Nemeth, Michael P.
2010-01-01
A comprehensive development of nondimensional parameters and equations for nonlinear and bifurcations analyses of quasi-shallow shells, based on the Donnell-Mushtari-Vlasov theory for thin anisotropic shells, is presented. A complete set of field equations for geometrically imperfect shells is presented in terms general of lines-of-curvature coordinates. A systematic nondimensionalization of these equations is developed, several new nondimensional parameters are defined, and a comprehensive stress-function formulation is presented that includes variational principles for equilibrium and compatibility. Bifurcation analysis is applied to the nondimensional nonlinear field equations and a comprehensive set of bifurcation equations are presented. An extensive collection of tables and figures are presented that show the effects of lamina material properties and stacking sequence on the nondimensional parameters.
General formalism for the stability of thin-shell wormholes in dimensions
Bejarano, Cecilia; Eiroa, Ernesto F.; Simeone, Claudio
2014-08-01
In this article we theoretically construct circular thin-shell wormholes in a 2+1 dimensional spacetime. The construction is symmetric with respect to the throat. We present a general formalism for the study of the mechanical stability under perturbations preserving the circular symmetry of the configurations, adopting a linearized equation of state for the exotic matter at the throat. We apply the formalism to several examples.
General formalism for the stability of thin-shell wormholes in 2 + 1 dimensions
Energy Technology Data Exchange (ETDEWEB)
Bejarano, Cecilia [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina); Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); Simeone, Claudio [Universidad de Buenos Aires, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina); IFIBA-CONICET, Buenos Aires (Argentina)
2014-08-15
In this article we theoretically construct circular thin-shell wormholes in a 2 + 1-dimensional spacetime. The construction is symmetric with respect to the throat. We present a general formalism for the study of the mechanical stability under perturbations preserving the circular symmetry of the configurations, adopting a linearized equation of state for the exotic matter at the throat. We apply the formalism to several examples. (orig.)
Geometric method for stability of non-linear elastic thin shells
Ivanova, Jordanka
2002-01-01
PREFACE This book deals with the new developments and applications of the geometric method to the nonlinear stability problem for thin non-elastic shells. There are no other published books on this subject except the basic ones of A. V. Pogorelov (1966,1967,1986), where variational principles defined over isometric surfaces, are postulated, and applied mainly to static and dynamic problems of elastic isotropic thin shells. A. V. Pogorelov (Harkov, Ukraine) was the first to provide in his monographs the geometric construction of the deformed shell surface in a post-critical stage and deriving explicitely the asymptotic formulas for the upper and lower critical loads. In most cases, these formulas were presented in a closed analytical form, and confirmed by experimental data. The geometric method by Pogorelov is one of the most important analytical methods developed during the last century. Its power consists in its ability to provide a clear geometric picture of the postcritical form of a deformed shell surfac...
Effect of a cylindrical thin-shell of matter on the electrostatic self-force on a charge
Energy Technology Data Exchange (ETDEWEB)
Rubin de Celis, Emilio [Universidad de Buenos Aires y IFIBA, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Buenos Aires (Argentina)
2016-02-15
The electrostatic self-force on a point charge in cylindrical thin-shell space-times is interpreted as the sum of a bulk field and a shell field. The bulk part corresponds to a field sourced by the test charge placed in a space-time without the shell. The shell field accounts for the discontinuity of the extrinsic curvature κ{sup p}{sub q}. An equivalent electric problem is stated, in which the effect of the shell of matter on the field is reconstructed with the electric potential produced by a non-gravitating charge distribution of total image charge Q, to interpret the shell field in both the interior and exterior regions of the space-time. The self-force on a point charge q in a locally flat geometry with a cylindrical thin-shell of matter is calculated. The charge is repelled from the shell if κ{sup p}{sub q} = κ < 0 (ordinarymatter) and attracted toward the shell if κ > 0 (exotic matter). The total image charge is zero for exterior problems, while for interior problems Q/q = κr{sub e}, with re the external radius of the shell. The procedure is general and can be applied to interpret self-forces in other space-times with shells, e.g., for locally flat wormholes we found Q{sub -+}{sup wh}/q = -1/(κ{sub wh}r{sub ±}). (orig.)
d-Dimensional non-asymptotically flat thin-shell wormholes in Einstein-Yang-Mills-dilaton gravity
Energy Technology Data Exchange (ETDEWEB)
Habib Mazharimousavi, S., E-mail: habib.mazhari@emu.edu.t [Department of Physics, Eastern Mediterranean University, G. Magusa, north Cyprus, Mersin 10 (Turkey); Halilsoy, M., E-mail: mustafa.halilsoy@emu.edu.t [Department of Physics, Eastern Mediterranean University, G. Magusa, north Cyprus, Mersin 10 (Turkey); Amirabi, Z., E-mail: zahra.amirabi@emu.edu.t [Department of Physics, Eastern Mediterranean University, G. Magusa, north Cyprus, Mersin 10 (Turkey)
2011-01-17
Thin-shell wormholes in Einstein-Yang-Mills-dilaton (EYMD) gravity are considered. We show that a non-asymptotically flat (NAF) black hole solution of the d-dimensional EYMD theory provides stable thin-shell wormholes which are supported entirely by exotic matter. The presence of dilaton makes the spacetime naturally NAF, and with our conclusion it remains still open to construct wormholes supported by normal matter between two such spacetimes.
International Nuclear Information System (INIS)
Kozlov, E.A.; Brichikov, S.A.; Gorbachev, D.M.; Brodova, I.G.; Yablonskikh, T.I.
2007-01-01
Results of comparative metallographic examination of recovered shells exposed to explosive loading in two modes (with and without a heavy casing confining explosion products scatter) are presented. The shells were made of high-purity and technical-grade unalloyed iron with the initial grain size 250 and 125 μm, steel 30KhGSA in delivery state and quenched up to HR C 35...40, austenitic stainless steel 12Kh18N10T. The heavy casing used in experiments is demonstrated to ensure a rather compact convergence of shells destroyed at high radii. In the described comparative experiments, one managed to compile the 12Kh18N10T steel shell, after it was spalled at high radii and exposed to shear fracture and spallation layer fragmentation at medium radii, into a compact sphere but failed to do the same with the 30KhGSA quenched steel shell after it was fractured according to spall and shear mechanisms at high and medium radii. Polar zones of this steel shell have obvious undercompressed areas due to significant dissipative losses to overcome the shear strength. Occurrence, development, and re-compaction of spall and shear fractures in spherically-convergent shells made of materials, which were already carefully investigated in 1D- and 2D-geometry experiments, were systematically studied in order to verify and validate new physical models of dynamic fractures, as well as up-to-date used in 1D-, 2D- and 3D-numerical algorithms [ru
The challenge of developing thin mirror shells for future x-ray telescopes
Döhring, Thorsten; Stollenwerk, Manfred; Gong, Qingqing; Proserpio, Laura; Winter, Anita; Friedrich, Peter
2015-09-01
Previously used mirror technologies are not able to fulfil the requirements of future X-ray telescopes due to challenging requests from the scientific community. Consequently new technical approaches for X-ray mirror production are under development. In Europe the technical baseline for the planned X-ray observatory ATHENA is the radical new approach of silicon pore optics. NASÁs recently launched NuSTAR mission uses segmented mirrors shells made from thin bended glasses, successfully demonstrating the feasibility of the glass forming technology for X-ray mirrors. For risk mitigation also in Europe the hot slumping of thin glasses is being developed as an alternative technology for lightweight X-ray telescopes. The high precision mirror manufacturing requires challenging technical developments; several design trades and trend-setting decisions need to be made and are discussed within this paper. Some new technical and economic aspects of the intended glass mirror serial production are also studied within the recently started interdisciplinary project INTRAAST, an acronym for "industry transfer of astronomical mirror technologies". The goal of the project, embedded in a cooperation of the Max-Planck-Institute for extraterrestrial Physics and the University of Applied Sciences Aschaffenburg, is to master the challenge of producing thin mirror shells for future X-ray telescopes. As a first project task the development of low stress coatings for thin glass mirror substrates have been started, the corresponding technical approach and first results are presented.
Huang, Wen Deng; Bao, Li Fu; Ren, Ya Jie; Yuan, Zhao Lin
2018-04-01
The properties of interface optical phonons and their electron-phonon interactions in ZnS/CdS multi-shell spherical quantum dots are studied by adopting dielectric continuum model. The dispersion curves and electron-phonon coupling strengths for interface optical phonons in ZnS/CdS multi-shell dots are calculated and analyzed in detail. It is shown that the number of interface optical phonon branches increase with the increase of layers of multi-shell quantum dots. The number of interface optical phonons increase two branches for increasing one layer material. The dispersions of interface optical phonon with low quantum number l are weak. The electron-interface optical phonon interactions are mainly localized at hetero-interfaces. The interface optical phonons with low quantum number l have important contribution to electron-interface optical phonon interactions.
Ogi, Takashi; Dani Nandiyanto, Asep Bayu; Kisakibaru, Yutaka; Iwaki, Toru; Nakamura, Keitaro; Okuyama, Kikuo
2013-04-01
When nitrogen was inserted into the spherical α-Fe/Al2O3 core shell of 45 nm nanoparticles, the XRD pattern showed a clear change in the crystal modification from a body-centered cubic crystal to that of a single-phase α″-Fe16N2 structure. SEM, TEM, and energy-dispersive X-ray spectroscopy mapping analysis gave the particle size distributions, the shell thickness, and the Fe and Al elements. An examination of the total electron yield (surface sensitive) and fluorescence yield (bulk sensitive) of X-ray absorption fine structure on Fe and N atoms of these core shell nanoparticles confirmed the nitriding of the core iron and showed iron oxide formations on the core surface, indicating stability and resistivity performance. The nitriding process also changed the magnetic properties from paramagnetic to ferromagnetic with a coercivity above 3000 Oe, indicating a promising material for a "rear-earth-free" giant magnet.
Theoretical and experimental stress analyses of ORNL thin-shell cylinder-to-cylinder model 2
International Nuclear Information System (INIS)
Gwaltney, R.C.; Bolt, S.E.; Bryson, J.W.
1975-10-01
Model 2 in a series of four thin-shell cylinder-to-cylinder models was tested, and the experimentally determined elastic stress distributions were compared with theoretical predictions obtained from a thin-shell finite-element analysis. Both the cylinder and the nozzle of model 2 had outside diameters of 10 in., giving a d 0 /D 0 ratio of 1.0, and both had outside diameter/thickness ratios of 100. Sixteen separate loading cases in which one end of the cylinder was rigidly held were analyzed. An internal pressure loading, three mutually perpendicular force components, and three mutually perpendicular moment components were individually applied at the free end of the cylinder and at the end of the nozzle. In addition to these 13 loadings, 3 additional loads were applied to the nozzle (in-plane bending moment, out-of-plane bending moment, and axial force) with the free end of the cylinder restrained. The experimental stress distributions for each of the 16 loadings were obtained using 152 three-gage strain rosettes located on the inner and outer surfaces. All the 16 loading cases were also analyzed theoretically using a finite-element shell analysis. The analysis used flat-plate elements and considered five degrees of freedom per node in the final assembled equations. The comparisons between theory and experiment show reasonably good general agreement, and it is felt that the analysis would be satisfactory for most engineering purposes. (auth)
Directory of Open Access Journals (Sweden)
Xudong Chen
2016-01-01
Full Text Available Comparison study on free vibration of circular cylindrical shells between thin and moderately thick shell theories when using the exact dynamic stiffness method (DSM formulation is presented. Firstly, both the thin and moderately thick dynamic stiffness formulations are examined. Based on the strain and kinetic energy, the vibration governing equations are expressed in the Hamilton form for both thin and moderately thick circular cylindrical shells. The dynamic stiffness is assembled in a similar way as that in classic skeletal theory. With the employment of the Wittrick-Williams algorithm, natural frequencies of circular cylindrical shells can be obtained. A FORTRAN code is written and used to compute the modal characteristics. Numerical examples are presented, verifying the proposed computational framework. Since the DSM is an exact approach, the advantages of high accuracy, no-missing frequencies, and good adaptability to various geometries and boundary conditions are demonstrated. Comprehensive parametric studies on the thickness to radius ratio (h/r and the length to radius ratio (L/r are performed. Applicable ranges of h/r are found for both thin and moderately thick DSM formulations, and influences of L/r on frequencies are also investigated. The following conclusions are reached: frequencies of moderately thick shells can be considered as alternatives to those of thin shells with high accuracy where h/r is small and L/r is large, without any observation of shear locking.
Self-force on an arbitrarily coupled scalar charge in cylindrical thin-shell spacetimes
Tomasini, C.; Rubín de Celis, E.; Simeone, C.
2018-02-01
We consider the arbitrarily coupled field and self-force of a static massless scalar charge in cylindrical spacetimes with one or two asymptotic regions, with the only matter content concentrated in a thin-shell characterized by the trace of the extrinsic curvature jump κ . The self-force is studied numerically and analytically in terms of the curvature coupling ξ . We found the critical values ξ _c^{(n)} = n/( ρ (r_s) κ ) , with n \\in N and ρ (r_s) the metric's profile function at the position of the shell, for which the scalar field is divergent in the background configuration. The pathological behavior is removed by restricting the coupling to a domain of stability. The coupling has a significant influence over the self-force at the vicinities of the shell, and we identified ξ =1/4 as the value for which the scalar force changes sign at a neighborhood of r_s; if κ (1-4ξ )>0 the shell acts repulsively as an effective potential barrier, while if κ (1-4ξ )force only depends on whether there is an angle deficit or not on the external region where the charge is placed; conical asymptotics produce a leading attractive force, while Minkowski regions produce a repulsive asymptotic self-force.
Numerical Investigation of Shell Formation in Thin Slab Casting of Funnel-Type Mold
Vakhrushev, A.; Wu, M.; Ludwig, A.; Tang, Y.; Hackl, G.; Nitzl, G.
2014-06-01
The key issue for modeling thin slab casting (TSC) process is to consider the evolution of the solid shell including fully solidified strand and partially solidified dendritic mushy zone, which strongly interacts with the turbulent flow and in the meantime is subject to continuous deformation due to the funnel-type mold. Here an enthalpy-based mixture solidification model that considers turbulent flow [Prescott and Incropera, ASME HTD, 1994, vol. 280, pp. 59-69] is employed and further enhanced by including the motion of the solidifying and deforming solid shell. The motion of the solid phase is calculated with an incompressible rigid viscoplastic model on the basis of an assumed moving boundary velocity condition. In the first part, a 2D benchmark is simulated to mimic the solidification and motion of the solid shell. The importance of numerical treatment of the advection of latent heat in the deforming solid shell (mushy zone) is specially addressed, and some interesting phenomena of interaction between the turbulent flow and the growing mushy zone are presented. In the second part, an example of 3D TSC is presented to demonstrate the model suitability. Finally, techniques for the improvement of calculation accuracy and computation efficiency as well as experimental evaluations are also discussed.
Design and modeling of an additive manufactured thin shell for x-ray astronomy
Feldman, Charlotte; Atkins, Carolyn; Brooks, David; Watson, Stephen; Cochrane, William; Roulet, Melanie; Willingale, Richard; Doel, Peter
2017-09-01
Future X-ray astronomy missions require light-weight thin shells to provide large collecting areas within the weight limits of launch vehicles, whilst still delivering angular resolutions close to that of Chandra (0.5 arc seconds). Additive manufacturing (AM), also known as 3D printing, is a well-established technology with the ability to construct or `print' intricate support structures, which can be both integral and light-weight, and is therefore a candidate technique for producing shells for space-based X-ray telescopes. The work described here is a feasibility study into this technology for precision X-ray optics for astronomy and has been sponsored by the UK Space Agency's National Space Technology Programme. The goal of the project is to use a series of test samples to trial different materials and processes with the aim of developing a viable path for the production of an X-ray reflecting prototype for astronomical applications. The initial design of an AM prototype X-ray shell is presented with ray-trace modelling and analysis of the X-ray performance. The polishing process may cause print-through from the light-weight support structure on to the reflecting surface. Investigations in to the effect of the print-through on the X-ray performance of the shell are also presented.
Eurov, Daniil A.; Kurdyukov, Dmitry A.; Kirilenko, Demid A.; Kukushkina, Julia A.; Nashchekin, Alexei V.; Smirnov, Alexander N.; Golubev, Valery G.
2015-02-01
Core-shell nanoparticles with diameters in the range 100-500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5-100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m2 g-1) and pore volume (0.3 cm3 g-1), and are bright solid phosphor with superior stability in aqueous media. The core-shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent.
Vacuum thin shells in Einstein–Gauss–Bonnet brane-world cosmology
Ramirez, Marcos A.
2018-04-01
In this paper we construct new solutions of the Einstein–Gauss–Bonnet field equations in an isotropic Shiromizu–Maeda–Sasaki brane-world setting which represent a couple of Z 2-symmetric vacuum thin shells splitting from the central brane, and explore the main properties of the dynamics of the system. The matching of the separating vacuum shells with the brane-world is as smooth as possible and all matter fields are restricted to the brane. We prove the existence of these solutions, derive the criteria for their existence, analyse some fundamental aspects or their evolution and demonstrate the possibility of constructing cosmological examples that exhibit this feature at early times. We also comment on the possible implications for cosmology and the relation of this system with the thermodynamic instability of highly symmetric vacuum solutions of Lovelock theory.
Linear dynamic analysis of arbitrary thin shells modal superposition by using finite element method
International Nuclear Information System (INIS)
Goncalves Filho, O.J.A.
1978-11-01
The linear dynamic behaviour of arbitrary thin shells by the Finite Element Method is studied. Plane triangular elements with eighteen degrees of freedom each are used. The general equations of movement are obtained from the Hamilton Principle and solved by the Modal Superposition Method. The presence of a viscous type damping can be considered by means of percentages of the critical damping. An automatic computer program was developed to provide the vibratory properties and the dynamic response to several types of deterministic loadings, including temperature effects. The program was written in FORTRAN IV for the Burroughs B-6700 computer. (author)
X-ray Multilayers and Thin-Shell Substrate Surface-Figure Correction
Windt, David
We propose a comprehensive experimental research program whose two main goals are (a) to improve the performance of hard X-ray multilayer coatings and (b) to develop a high-throughput method to correct mid-frequency surface errors in thin-shell mirror substrates. Achieving these goals will enable the cost-effective construction of light- weight, highly-nested X-ray telescopes having greater observational sensitivity, wider energy coverage, and higher angular resolution than can be achieved at present. The realization of this technology will thus benefit the development of a variety of Explorer- class NASA X-ray astronomy missions now being formulated for both the soft and hard X-ray bands, and will enable the construction of future facility-class X-ray missions that will require both high sensitivity and high resolution. Building on the success of our previous APRA-funded research, we plan to investigate new thin-film growth techniques, new materials, and new aperiodic coating designs in order to develop new hard X-ray multilayers that have higher X-ray reflectance, wider energy response, lower film stress, and good stability, and that can be produced more quickly, at reduced cost. Additionally, we propose to build upon our extensive experience in sub-nm film-thickness control using velocity modulation and masked deposition techniques, and in the recent development of low-roughness, low-stress films grown by reactive sputtering, in order to develop new methods for correcting mid-frequency surface errors in thin-shell mirror substrates using both differential deposition and ion-beam figuring, either alone or in combination. These two surface-correction techniques already being used for sub-nm figuring of precision optics in a variety of disciplines, including diffraction-limited EUV lithography and synchrotron applications requiring sub-micron focusing are ideally suited for controlling mm-scale surface errors in the thin-shell substrates used for astronomical X
Behavior of thin rectangular ANCF shell elements in various mesh configurations
DEFF Research Database (Denmark)
Hyldahl, Per; Mikkola, Aki M.; Balling, Ole
2014-01-01
The absolute nodal coordinate formulation (ANCF) is characterized by being developed specifically for dynamic analysis of large deformation problems. The objective of the study is to investigate how the shape of the initial mesh configuration influences the obtained numerical solution. After......, the ability of the ANCF method to describe curved structures is evaluated. This study concludes that thin ANCF shell elements are sensitive to both the initial shape and their loading condition. Furthermore, both the initial configuration and the loading condition affect how the ANCF-based models converge...
Optimisation of thin shell parts by using particle swarm optimisation (PSO) method
Hidayah, M. H. N.; Shayfull, Z.; Nasir, S. M.; Sazli, S. M.; Fathullah, M.
2017-09-01
This paper proposes an optimization model of process parameters in Plastic Injection Moulding (PIM) in which the quality characteristics for the plastic injection product that been study are warpage. In this study, plastic dispenser of dental floss (thin shell part) has been analysed with thermoplastic material of Polypropylene (PP) used as the moulded material. Design of Experiment (DOE), Response surface methodology (RSM) and Particle Swarm Optimisation (PSO) method were used to analyse the optimal process parameters setting. From optimal processing parameter, the value of warpage inx, y and z-axis have been optimised by 22.1%, 27.34% and 23.81%, respectively.
Xia, Xinhui; Xiong, Qinqin; Zhang, Yongqi; Tu, Jiangping; Ng, Chin Fan; Fan, Hong Jin
2014-06-25
High-performance electrochemical energy storage (EES) devices require the ability to modify and assemble electrode materials with superior reactivity and structural stability. The fabrication of different oxide/metal core-branch nanoarrays with adjustable components and morphologies (e.g., nanowire and nanoflake) is reported on different conductive substrates. Hollow metal branches (or shells) wrapped around oxide cores are realized by electrodeposition using ZnO nanorods as a sacrificial template. In battery electrode application, the thin hollow metal branches can provide a mechanical protection of the oxide core and a highly conductive path for charges. As a demonstration, arrays of Co3O4/Ni core-branch nanowires are evaluated as the anode for lithium ion batteries. The thin metal branches evidently improve the electrochemical performance with higher specific capacity, rate capability, and capacity retention than the unmodified Co3O4 counterparts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Nonlinear Shell Modeling of Thin Membranes with Emphasis on Structural Wrinkling
Tessler, Alexander; Sleight, David W.; Wang, John T.
2003-01-01
Thin solar sail membranes of very large span are being envisioned for near-term space missions. One major design issue that is inherent to these very flexible structures is the formation of wrinkling patterns. Structural wrinkles may deteriorate a solar sail's performance and, in certain cases, structural integrity. In this paper, a geometrically nonlinear, updated Lagrangian shell formulation is employed using the ABAQUS finite element code to simulate the formation of wrinkled deformations in thin-film membranes. The restrictive assumptions of true membranes, i.e. Tension Field theory (TF), are not invoked. Two effective modeling strategies are introduced to facilitate convergent solutions of wrinkled equilibrium states. Several numerical studies are carried out, and the results are compared with recent experimental data. Good agreement is observed between the numerical simulations and experimental data.
Calculation of Eddy currents in the ETE spherical torus
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto
2002-07-01
A circuit model based on a Green's function method was developed to evaluate the currents induced during startup in the vessel of ETE (Spherical Tokamak Experiment). The eddy currents distribution is calculated using a thin shell approximation for the vacuum vessel and local curvilinear coordinates. The results are compared with values of the eddy currents measured in ETE. (author)
The chocolate-egg problem: Fabrication of thin elastic shells through coating
Lee, Anna; Marthelot, Joel; Brun, Pierre-Thomas; Reis, Pedro M.
2015-03-01
We study the fabrication of thin polymeric shells based on the coating of a curved surface by a viscous fluid. Upon polymerization of the resulting thin film, a slender solid structure is delivered after demolding. This technique is extensively used, empirically, in manufacturing, where it is known as rotational molding, as well as in the food industry, e.g. for chocolate-eggs. This problem is analogous to the Landau-Levich-Derjaguin coating of plates and fibers and Bretherton's problem of film deposition in cylindrical channels, albeit now on a double-curved geometry. Here, the balance between gravity, viscosity, surface tension and polymerization rate can yield a constant thickness film. We seek to identify the physical ingredients that govern the final film thickness and its profile. In our experiments using organosilicon, we systematically vary the properties of the fluid, as well as the curvature of the substrate onto which the film is coated, and characterize the final thickness profile of the shells. A reduced model is developed to rationalize the process.
Hydrothermal core-shell carbon nanoparticle films: thinning the shell leads to dramatic pH response.
Xia, Fengjie; Pan, Mu; Mu, Shichun; Xiong, Yuli; Edler, Karen J; Idini, Ilaria; Jones, Matthew D; Tsang, Shik Chi; Marken, Frank
2012-12-05
Carbon nanoparticles with phenylsulfonate negative surface functionality (Emperor 2000, Cabot Corp.) are coated with positive chitosan followed by hydrothermal carbonization to give highly pH-responsive core-shell nanocarbon composite materials. With optimised core-shell ratio (resulting in an average shell thickness of ca. 4 nm, estimated from SANS data) modified electrodes exhibit highly pH-sensitive resistance, capacitance, and Faradaic electron transfer responses (solution based, covalently bound, or hydrothermally embedded). A shell "double layer exclusion" mechanism is discussed to explain the observed pH switching effects. Based on this mechanism, a broader range of future applications of responsive core-shell nanoparticles are envisaged.
The origin of flow-induced alignment of spherical colloids in shear-thinning viscoelastic fluids
Santos de Oliveira, I.S.; den Otter, Wouter K.; Briels, Willem J.
2012-01-01
We have studied the poorly understood process of flow-induced structure formation by colloids suspended in shear-thinning fluids. These viscoelastic fluids contain long flexible chains whose entanglements appear and disappear continuously as a result of Brownian motion and the applied shear flow.
Research on dual-parameter optical fiber sensor based on thin-core fiber and spherical structure
Tong, Zhengrong; Wang, Xue; Zhang, Weihua; Xue, Lifang
2018-04-01
A novel dual-parameter optical fiber sensor is proposed and experimentally demonstrated. The proposed sensor is based on a fiber in-line Mach-Zehnder interferometer, which is fabricated by sandwiching a section of thin-core fiber between two spherical structures made of single-mode fibers. The transmission spectrum exhibits the response of the interference between the core and the different cladding modes. Due to the different wavelength shifts of the two selected dips, the simultaneous measurement of temperature and the surrounding refractive index can be achieved. The measured temperature sensitivities are 0.067 nm/°C and 0.050 nm/°C, and the refractive index sensitivities are -119.9 nm/RIU and -69.71 nm/RIU, respectively. In addition, the compact size, simple fabrication and cost-effectiveness of the fiber sensor are also advantages.
Expeditious low-temperature sintering of copper nanoparticles with thin defective carbon shells
Kim, Changkyu; Lee, Gyoungja; Rhee, Changkyu; Lee, Minku
2015-04-01
The realization of air-stable nanoparticles, well-formulated nanoinks, and conductive patterns based on copper is a great challenge in low-cost and large-area flexible printed electronics. This work reports the synthesis of a conductively interconnected copper structure via thermal sintering of copper inks at a low temperature for a short period of time, with the help of thin defective carbon shells coated onto the copper nanoparticles. Air-stable copper/carbon core/shell nanoparticles (typical size ~23 nm, shell thickness ~1.0 nm) are prepared by means of an electric explosion of wires. Gaseous oxidation of the carbon shells with a defective structure occurs at 180 °C, impacting the choice of organic solvents as well as the sintering conditions to create a crucial neck formation. Isothermal oxidation and reduction treatment at 200 °C for only about 10 min yields an oxide-free copper network structure with an electrical resistivity of 25.1 μΩ cm (14.0 μΩ cm at 250 °C). Finally, conductive copper line patterns are achieved down to a 50 μm width with an excellent printing resolution (standard deviation ~4.0%) onto a polyimide substrate using screen printing of the optimized inks.The realization of air-stable nanoparticles, well-formulated nanoinks, and conductive patterns based on copper is a great challenge in low-cost and large-area flexible printed electronics. This work reports the synthesis of a conductively interconnected copper structure via thermal sintering of copper inks at a low temperature for a short period of time, with the help of thin defective carbon shells coated onto the copper nanoparticles. Air-stable copper/carbon core/shell nanoparticles (typical size ~23 nm, shell thickness ~1.0 nm) are prepared by means of an electric explosion of wires. Gaseous oxidation of the carbon shells with a defective structure occurs at 180 °C, impacting the choice of organic solvents as well as the sintering conditions to create a crucial neck formation
Malhotra, Sahil; Sharma, Mukul M
2014-01-03
An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data. The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.(1) Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.
Civitani, M. M.; Hołyszko, J.; Vecchi, G.; Basso, S.; Citterio, O.; Ghigo, M.; Pareschi, G.; Parodi, G.; Incorvaia, S.
2017-09-01
The implementation of an X-ray mission with high imaging capabilities, similar to those achieved with Chandra (studied in USA, with the participation of international partners. In order to figure out the challenging technological task of the mirror fabrication, different approaches are considered, based on monolithic and segmented shells. Starting from the experience done on the glass prototypal shell realized in the past years, the direct polishing of thin (2 mm thick) fused silica monolithic shells is being investigated as a possible solution. A temporary stiffening structure is designed to support the shell during the figuring and polishing operations and to manage the handling up to its integration in the telescope structure. After the grinding and the polishing phases, in order to achieve the required surface accuracy, a final ion beam figuring correction is foreseen. In this paper, we present the technological process and the results achieved so far on a prototypal shell under development.
DEFF Research Database (Denmark)
Luan, Yu; Ohlrich, Mogens; Jacobsen, Finn
2011-01-01
a number of stiffened plates are combined in a complicated assembly composed of many plate panels. However, whereas the equivalent smeared plate technique is well established and recently improved for flat panels, there is no similar established technique for doubly curved stiffened shells. In this paper...... the improved smeared plate technique is combined with the equation of motion for a doubly curved thin rectangular shell, and a solution is offered for using the smearing technique for stiffened shell structures. The developed prediction technique is validated by comparing natural frequencies and mode shapes...
Predicting the failure of a thin liquid film loaded with spherical particles.
Morris, Gareth; Neethling, S J; Cilliers, Jan J
2014-02-04
A model is presented for predicting the failure of a thin liquid film stabilized by attached inert particles. A statistical analysis of roughly 3500 Surface Evolver1 simulations was used to identify the relationship between the packing density of the particles on the film, their contact angle distribution, and the capillary pressure required to rupture the film. The model presented allows a fast and simple method of calculating the range of pressures a thin film in a three-phase froth will fail at based upon three variables: the film loading, mean particle contact angle, and the standard distribution of contact angles round the mean. The predicted range of failure pressures can be used in simulations of bulk froth properties where bubble coalescence is an important factor governing the froth properties.
International Nuclear Information System (INIS)
Simpson, E.M.; Kim, Kyekyoon
1994-05-01
A numerical model has been developed to describe the thermally induced behavior of a liquid layer of hydrogen isotopes inside a spherical Inertial Confinement Fusion (ICF) target and to calculate the far-field temperature gradient which will sustain a uniform liquid layer. This method is much faster than the trial-and-error method previously employed. The governing equations are the equations of continuity, momentum, energy, mass diffusion-convection, and conservation of the individual isotopic species. Ordinary and thermal diffusion equations for the diffusion of fluxes of the species are included. These coupled equations are solved by a finite-difference method using upwind schemes, variable mesh, and rigorous boundary conditions. The solution methodology unique to the present problem is discussed in detail. in particular, the significance of the surface tension gradient driven flows (also called Marangoni flows) in forming uniform liquid layers inside ICF targets is demonstrated. Using the theoretical model, the values of the externally applied thermal gradients that give rise to uniform liquid layers of hydrogen inside a cryogenic spherical-shell ICF target are calculated, and the results compared with the existing experimental data
DEFF Research Database (Denmark)
Engelbrekt, Christian; Seselj, Nedjeljko; Poreddy, Raju
2016-01-01
We present a facile synthesis protocol for atomically thin platinum (Pt) shells on top of gold (Au) nanoparticles (NPs) (Au@PtNPs) in one pot under mild conditions. The Au@PtNPs exhibited remarkable stability (> 2 years) at room temperature. The synthesis, bimetallic nanostructures and catalytic ...... activity for the direct production of γ-valerolactone, an alternative biofuel/fuel additive, from levulinic acid and methyl levulinate was finally demonstrated....... in electrooxidation of sustainable fuels (i.e. formic acid, methanol and ethanol), and selective hydrogenation of benzene derivatives. Especially high activity was achieved for formic acid oxidation, 549 mA (mgPt)−1 (at 0.6 V vs. SCE), which is 3.5 fold higher than a commercial
International Nuclear Information System (INIS)
Marinković, D; Köppe, H; Gabbert, U
2008-01-01
Active piezoelectric thin-walled structures, especially those with a notably higher membrane than bending stiffness, are susceptible to large rotations and transverse deflections. Recent investigations conducted by a number of researchers have shown that the predicted behavior of piezoelectric structures can be significantly influenced by the assumption of large displacements and rotations of the structure, thus demanding a geometrically nonlinear formulation in order to investigate it. This paper offers a degenerated shell element and a simplified formulation that relies on small incremental steps for the geometrically nonlinear analysis of piezoelectric composite structures. A set of purely mechanical static cases is followed by a set of piezoelectric coupled static cases, both demonstrating the applicability of the proposed formulation
Seismic design method of clamped-free thin cylindrical shells immersed in fluid
International Nuclear Information System (INIS)
Fukuyama, Mayumi; Nakagawa, Masaki; Yashiro, Takeshi; Toyoda, Yukihoro; Akiyama, Hiroshi
2001-01-01
We carried out excitation experiments on clamped-free thin cylindrical shells immersed in fluid that represented thermal baffles of a fast breeder reactor. At a certain excitation level, occurred external pressure buckling. We also observed that parametric vibration, which involved high-order circumferential vibration modes, occurred at a certain combination of excitation frequency and excitation level. Concerning seismic design of the thermal baffles, we, therefore, take not only the buckling but also the effect of the parametric vibration into consideration. We adopt buckling eigenvalue analyses to estimate buckling pressure and propose a formula to prevent the buckling. Further, we discuss important factors such as buckling strength reduction caused by initial shape imperfections and interaction between horizontal and vertical seismic response. Concerning the parametric vibration, a significant deformation of cylinders should be prevented. A practical method applying the dynamic stability theory is proposed to obtain the condition, under which the parametric vibration takes place
International Nuclear Information System (INIS)
La Haye, R.J.; Lee, P.S.; Schaffer, M.J.; Tamano, T.; Taylor, P.L.
1988-01-01
A small set of magnetic pickup coils inside the thin resistive shell and an extensive set outside are used to monitor high frequency (3-50 kHz) MHD activity in a reversed field pinch discharge of duration long compared to the shell time constant. The MHD activity is dominated by nearly equal amplitude m=0 and m=-1 poloidal modes both of whose frequency spectra peak near the drift frequency, i.e. about 8 to 10 kHz. The m=0 and m=-1 activities are uncorrelated and exhibit strong turbulence; the autocorrelation times for both are about 40 μs, and the toroidal correlation lengths are about equal to the 20 cm shell minor radius b. The toroidal variation of the m=0 activity at a given time when Fourier analysed in toroidal mode n has a power spectrum peaking at n=4-5 or nb/R 0 approx.= 1. The n spectrum for m=-1 is nearly zero up to n=10 and substantial at 11 ≤ n ≤ 16, i.e. those modes which are pitch resonant in the plasma interior. The aperiodic development of a localized helical kink, the slinky mode, stabilizes, i.e. turns off, in turn the m=-1 high frequency activities of the n=11 and 12 modes. This is postulated to be due to the slinky mode flattening the gradient in μ near the axis (μ is the ratio between current density parallel to the magnetic field and the magnetic field strength). (author). Letter-to-the-editor. 11 refs, 5 figs
Wiemeyer, Stanley N.; Bunck, C.M.; Krynitsky, A.J.
1988-01-01
Osprey (Pandion haliaetus) eggs were collected in 14 states in 1970-79 and analyzed for organochlorine pesticides, polychlorinated biphenyls (PCBs), and mercury. Moderate shell thinning occurred in eggs from several areas. DDE was detected in all eggs, PCBs in 99%, DDD in 96%, dieldrin in 52%, and other compounds less frequently. Concentrations of DDT and its metabolites declined in eggs from Cape May County, New Jersey between 1970-72 and 1978-79. Eggs .from New Jersey in the early 1970s contained the highest concentrations of DDE. Dieldrin concentrations declined in eggs from the Potomac River, Maryland during 1971-77. Five different contaminants were significantly negatively correlated with shell thickness; DDE was most closely correlated. Ten percent shell thinning was associated with 2.0 ppm DDE, 15% with 4.2 ppm, and 20% with 8.7 ppm in eggs collected from randomly selected nests before egg loss. Shell thickness could not be accurately predicted from DDE concentrations in eggs collected after failure to hatch, presumably because the eggs with the thinnest shells had been broken and were unavailable for sampling. DDE was also significantly negatively correlated with brood size. Other contaminants did not appear to adversely affect shell thickness or reproductive success.
Thin-shell bubbles and information loss problem in anti de Sitter background
Energy Technology Data Exchange (ETDEWEB)
Sasaki, Misao [Yukawa Institute for Theoretical Physics,Kyoto University, Kyoto 606-8502 (Japan); Tomsk State Pedagogical University,634050 Tomsk (Russian Federation); Yeom, Dong-han [Yukawa Institute for Theoretical Physics,Kyoto University, Kyoto 606-8502 (Japan); Leung Center for Cosmology and Particle Astrophysics, National Taiwan University,Taipei 10617, Taiwan (China)
2014-12-24
We study the motion of thin-shell bubbles and their tunneling in anti de Sitter (AdS) background. We are interested in the case when the outside of a shell is a Schwarzschild-AdS space (false vacuum) and the inside of it is an AdS space with a lower vacuum energy (true vacuum). If a collapsing true vacuum bubble is created, classically it will form a Schwarzschild-AdS black hole. However, this collapsing bubble can tunnel to a bouncing bubble that moves out to spatial infinity. Then, although the classical causal structure of a collapsing true vacuum bubble has the singularity and the event horizon, quantum mechanically the wavefunction has support for a history without any singularity nor event horizon which is mediated by the non-perturbative, quantum tunneling effect. This may be regarded an explicit example that shows the unitarity of an asymptotic observer in AdS, while a classical observer who only follows the most probable history effectively lose information due to the formation of an event horizon.
Nonlinear analysis of dynamic stability for the thin cylindrical shells of supercavitating vehicles
Directory of Open Access Journals (Sweden)
Hai An
2016-12-01
Full Text Available The dynamic stability of supercavitating vehicles under periodic axial loading is investigated in this article. The supercavitating vehicle is simulated as a long and thin cylindrical shell subjected to periodic axial loading and simply supported boundary conditions. The nonlinear transverse vibration differential equation is obtained in terms of nonlinear geometric equations, physical equations, and balance equations of cylindrical shells. Mathieu equation with periodic coefficients and nonlinear term is derived by employing Galerkin variational method and Bolotin method. The analytical expressions of the steady-state amplitudes of vibrations in the first- and second-order instable regions are obtained by solving nonlinear Mathieu equation derived in this article. Numerical results are presented to analyze the influence of the sailing speed, ratio of loads, the frequency of axial loads, and the mode of vibration on parametric resonance curves and to show the nonlinear parametric resonance curves incline toward the side where it is greater than the excitation frequency, which significantly extends the range of the exciting region. The presented results indicate the enlargement of the exciting region will cause shrinkage of the safe frequency range of external loads and decrease in dynamic stability of supercavitating vehicle.
The Influence on Modal Parameters of Thin Cylindrical Shell under Bolt Looseness Boundary
Directory of Open Access Journals (Sweden)
Hui Li
2016-01-01
Full Text Available The influence on modal parameters of thin cylindrical shell (TCS under bolt looseness boundary is investigated. Firstly, bolt looseness boundary of the shell is divided into two types, that is, different bolt looseness numbers and different bolt looseness levels, and natural frequencies and mode shapes are calculated by finite element method to roughly master vibration characteristics of TCS under these conditions. Then, the following measurements and identification techniques are used to get precise frequency, damping, and shape results; for example, noncontact laser Doppler vibrometer and vibration shaker with excitation level being precisely controlled are used in the test system; “preexperiment” is adopted to determine the required tightening torque and verify fixed constraint boundary; the small-segment FFT processing technique is employed to accurately measure nature frequency and laser rotating scanning technique is used to get shape results with high efficiency. Finally, based on the measured results obtained by the above techniques, the influence on modal parameters of TCS under two types of bolt looseness boundaries is analyzed and discussed. It can be found that bolt looseness boundary can significantly affect frequency and damping results which might be caused by changes of nonlinear stiffness and damping and in bolt looseness positions.
The origin of flow-induced alignment of spherical colloids in shear-thinning viscoelastic fluids.
Santos de Oliveira, I S; den Otter, W K; Briels, W J
2012-11-28
We have studied the poorly understood process of flow-induced structure formation by colloids suspended in shear-thinning fluids. These viscoelastic fluids contain long flexible chains whose entanglements appear and disappear continuously as a result of brownian motion and the applied shear flow. Responsive particle dynamics simulates each chain as a single smooth brownian particle, with slowly evolving inter-particle degrees of freedom accounting for the entanglements. The colloids mixed homogeneously in all simulated quiescent dispersions and they remain dispersed under slow shear flow. Beyond a critical shear rate, which varies depending on the fluid, the colloids aggregate and form flow-aligned strings in the bulk of the fluid. In this work we explore the physical origins of this hitherto unexplained ordering phenomena, both by systematically varying the parameters of the simulated fluids and by analyzing the flow-induced effective colloidal interactions. We also present an expression for the critical shear rate of the studied fluids.
Aslam, Umar; Linic, Suljo
2017-12-13
Bimetallic nanoparticles in which a metal is coated with an ultrathin (∼1 nm) layer of a second metal are often desired for their unique chemical and physical properties. Current synthesis methods for producing such core-shell nanostructures often require incremental addition of a shell metal precursor which is rapidly reduced onto metal cores. A major shortcoming of this approach is that it necessitates precise concentrations of chemical reagents, making it difficult to perform at large scales. To address this issue, we considered an approach whereby the reduction of the shell metal precursor was controlled through in situ chemical modification of the precursor. We used this approach to develop a highly scalable synthesis for coating atomic layers of Pt onto Ag nanocubes. We show that Ag-Pt core-shell nanostructures are synthesized in high yields and that these structures effectively combine the optical properties of the plasmonic Ag nanocube core with the surface properties of the thin Pt shell. Additionally, we demonstrate the scalability of the synthesis by performing a 10 times scale-up.
Energy Technology Data Exchange (ETDEWEB)
Khani, Omid, E-mail: omidkhani@mut-es.ac.ir [Department of Physics, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran (Iran, Islamic Republic of); Shoushtari, Morteza Zargar [Department of Physics, Shahid Chamran University of Ahvaz, Ahvaz, Islamic Republic of Iran (Iran, Islamic Republic of); Ackland, Karl; Stamenov, Plamen [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland)
2017-04-15
An increase in microwave permeability is a prerequisite for reducing the thickness of radar absorber coatings. The aim of this paper is to increase the magnetic loss of commercial carbonyl iron particles for fabricating wideband microwave absorbers with a multilayer structure. For this purpose, carbonyl iron particles were milled and their static and dynamic magnetic properties were studied before and after milling. A distinct morphological change from spherical to flake-like particles is measured with increased milling time, whereas no distinct changes in magnetic properties are measured with increased milling time. The imaginary part of the permeability (µ'') of the milled carbonyl iron particles increased from 1.23 to 1.88 and showed a very broad peak over the entire frequency range 1–18 GHz. The experimental results were modeled using the Rousselle effective medium theory (EMT) in the Neo formulation. The theoretical predictions showed good agreement with the experimental results. Two layer absorbers were designed according to the measured microwave parameters and the multilayer design. The results revealed that a thin multilayer with a thickness of 1.75 mm can effectively absorb microwaves in both the entire X and Ku frequency bands. The results suggest that microwave absorbers with excellent absorption properties could be mass-produced, using commercial carbonyl iron particles. - Highlights: • The microwave properties of carbonyl iron particles can be controlled effectively by particles shape. • Milling process transforms the carbonyl iron particle morphology from spherical to flake-like. • No appreciable differences in the magnetic and chemical local environments were detected by means of Mossbauer spectroscopy. • The two layer design showed appropriate absorptions in a rather wide frequency range.
A study on the relief of shell wall thinning of high pressure feedwater heater
International Nuclear Information System (INIS)
Kim, Hyung Joon; Park, Sang Hoon; Seo, Hyuk Ki; Kim, Kyung Hoon; Hwang, Kyung Mo
2008-01-01
Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle-installed downstream of the high pressure turbine extraction stream line- inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes operation of experience and numerical analysis composed similar condition with real high pressure feedwater heater. This study applied squared, curved and new type impingement baffle plates to feedwater heater same as previous study. In addition, it shows difference of pressure distribution and value between single phase and two phase based on experience and numerical analysis
Energy Technology Data Exchange (ETDEWEB)
Myagkov, N. N., E-mail: nn-myagkov@mail.ru [Russian Academy of Sciences, Institute of Applied Mechanics (Russian Federation)
2017-01-15
The problem of aluminum projectile fragmentation upon high-velocity impact on a thin aluminum shield is considered. A distinctive feature of this description is that the fragmentation has been numerically simulated using the complete system of equations of deformed solid mechanics by a method of smoothed particle hydrodynamics in three-dimensional setting. The transition from damage to fragmentation is analyzed and scaling relations are derived in terms of the impact velocity (V), ratio of shield thickness to projectile diameter (h/D), and ultimate strength (σ{sub p}) in the criterion of projectile and shield fracture. Analysis shows that the critical impact velocity V{sub c} (separating the damage and fragmentation regions) is a power function of σ{sub p} and h/D. In the supercritical region (V > V{sub c}), the weight-average fragment mass asymptotically tends to a power function of the impact velocity with exponent independent of h/D and σ{sub p}. Mean cumulative fragment mass distributions at the critical point are scale-invariant with respect to parameters h/D and σ{sub p}. Average masses of the largest fragments are also scale-invariant at V > V{sub c}, but only with respect to variable parameter σ{sub p}.
Greenhouse Effect: Temperature of a Metal Sphere Surrounded by a Glass Shell and Heated by Sunlight
Nguyen, Phuc H.; Matzner, Richard A.
2012-01-01
We study the greenhouse effect on a model satellite consisting of a tungsten sphere surrounded by a thin spherical, concentric glass shell, with a small gap between the sphere and the shell. The system sits in vacuum and is heated by sunlight incident along the "z"-axis. This development is a generalization of the simple treatment of the…
El Haouari, M.; Talbi, A.; Feddi, E.; El Ghazi, H.; Oukerroum, A.; Dujardin, F.
2017-01-01
The hydrostatic pressure influence on the binding energy and on the optical properties (linear and third nonlinear) associated to the 1 s - 1 p intersubband transition of single dopant in a AlAs / GaAs spherical core/shell structure is investigated. The combined effects of the problem variables such as the core and shell sizes, the donor position in the structure and the pressure dependence of the physical parameters of the material have been analyzed. Our calculations are performed in the framework of the effective mass approximation and the energies are obtained by using a variational method. The results show that the linear and nonlinear parts of the absorption coefficient and the refractive index associated to the intersubband 1 s - 1 p transition undergo important changes. There are several interesting results to point out such as the shift of the absorption coefficients and refractive index to high values of photon energy. Another significant result is that the donor position considerably affects the optical properties and their corresponding amplitude.
Enceladus Plume Activity Consistent with Eruptions from Sources within a Thin Shell
Hurford, Terry; Spitale, Joseph N.; Rhoden, Alyssa R.; Henning, Wade
2017-10-01
Enceladus is a small (radius 250 km) moon that orbits Saturn between the moons Mimas and Tethys with a period of 1.37 days. A 2:1 mean motion resonance with the moon Dione, which orbits just beyond Tethys, excites its orbital eccentricity to the observed value of 0.0047, which in turn produces periodic tidal stress on the surface.In 2005, Cassini detected the eruption of material from warm regions, which correlated with the large Tiger Stripe fractures near the south pole of Enceladus. A 2007 analysis of tidal stress postulated that the eruptive activity might be linked to tidal tension across these fractures and predicted that activity should vary on the orbital timescale such that greatest activity should be observed near apocenter (Hurford et al., 2007). In 2013, results from analysis of Cassini’s Visual and Infrared Map- ping Spectrometer (VIMS) data detected variability of the erupting material in the orbital cycle and qualitatively confirmed the predictions of variable activity from 2007 (Hedman et al., 2013; Hurford et al. 2007).Since then, work has been done to refine models for tidal control of plume activity. Nimmo et al. (2014) found that the plume activity could track the fraction of fractures under tension, but required a ~5 hr lag in Enceladus’ tidal response. This lag seemed plausible in a 24km ice shell. Behounkova et al. (2105) confirmed this result with a slightly improved model that linked tidal activity to normalize average tensile stress on the fracture.In this work, we illustrate how reservoir depth combines with a lag in tidal response to mimic larger delays in tidal activity. Taking into account the depth of the volatile reservoir, we find that the response of Enceladus to tidal deformation needs only be ~3 hrs and is more consistent with eruptions from a thin ice shell (≤10 km). This result is more consistent with recent revisions in ice shell thickness (Iess et al., 2014; Thomas et al., 2016).Hurford et al., 2007, Nature 447, 292
Mitri, F G
2010-03-01
Acoustic scattering properties of ultrasound contrast agents are useful in extending existing or developing new techniques for biomedical imaging applications. A useful first step in this direction is to investigate the acoustic scattering of a new class of acoustic beams, known as helicoidal high-order Bessel beams, to improve the understanding of their scattering characteristics by an ultrasound contrast agent, which at present is very limited. The transverse acoustic scattering of a commercially available albuminoidal ultrasound contrast agent shell filled with air or a denser gas such as perfluoropropane and placed in a helicoidal Bessel beam of any order is examined numerically. The shell is assumed to possess an outer radius a=3.5 microns and a thickness of approximately 105 nm. Moduli of the total and resonance transverse acoustic scattering form functions are numerically evaluated in the bandwidth 0scattering of a helicoidal Bessel beam of order m1 so that the dynamics of contrast agents would be significantly altered. The main finding of the present theory is the suppression or enhancement for a particular resonance that may be used to advantage in imaging with ultrasound contrast agents for clinical applications. 2009 Elsevier B.V. All rights reserved.
Liquid metal actuators: correctable mounting and assembly of thin-shell x-ray telescope mirrors
Bruccoleri, Alexander R.; Klingensmith, Martin; Chalifoux, Brandon; Heilmann, Ralf K.; Schattenburg, Mark L.
2015-09-01
An ideal bonding agent for thin-shell x-ray mirrors could be quickly applied to joints and set with deterministic and stable properties. Unfortunately, mirror assembly methods have typically utilized various epoxy formulations which are messy, slow to apply and cure, and far from deterministic or stable. Problems include shrinkage, creep and high thermal and humidity sensitivity. Once the bond is set errors are frozen in and cannot be corrected. We are developing a new method for bonding thin-foil mirrors that has the potential to solve these problems. Our process to bond mirrors to housing reference points is achieved via small beads of a low-melting-point bonding agent (such as solder or thermoset). The mirror is bonded to small contact surface points under real-time metrology. If the position of the mirror needs to be adjusted after bonding, a small force is applied normal or parallel to the contact surface and a pulsed fiber laser is used to melt an ultrathin layer of the solder for a very short time. The joint is then compressed, stretched or sheared while molten before refreezing in a new position, enabling repeatable and stable mirror position adjustments along the direction of the force in nm-level steps with minimal heat input. We present results from our prototype apparatus demonstrating proof of principle. The initial experiment includes developing a technique to bond D263 glass to Kovar, designing and building a one-dimensional stage to precisely apply force, and using an infrared laser pulse to heat the joint while measuring position and force.
Energy Technology Data Exchange (ETDEWEB)
Kim, K.; Feng, Q.; Ryu, C.K. [Univ. of Illinois, Urbana, IL (United States)
1995-12-31
A novel gas-dynamic levitation (GDL) technique has been developed to facilitate noncontact coating of spherical ICF targets. Preliminary test has been performed on a novel coating method known as the Charged Liquid Cluster Beam (CLB) technique, which is compatible with the levitation scheme, to assess its feasibility as an ICF target coating technique. Using the GDL technique three metal balls 450 {micro}m, 650 {micro}m, and 950 {micro}m in diameter were levitated very stably for several hours, with the balls rotating continuously. The CLCB coating technique utilizes the flow-limited field-injection electrostatic spraying to produce a spray of charged nanodrops of the coating material which, in turn, is directed toward the levitated ICF target. The apparatus and preliminary data demonstrating the capability of the levitation scheme and the coating technique are presented.
International Nuclear Information System (INIS)
Kim, K.; Feng, Q.; Ryu, C.K.
1995-01-01
A novel gas-dynamic levitation (GDL) technique has been developed to facilitate noncontact coating of spherical ICF targets. Preliminary test has been performed on a novel coating method known as the Charged Liquid Cluster Beam (CLB) technique, which is compatible with the levitation scheme, to assess its feasibility as an ICF target coating technique. Using the GDL technique three metal balls 450 microm, 650 microm, and 950 microm in diameter were levitated very stably for several hours, with the balls rotating continuously. The CLCB coating technique utilizes the flow-limited field-injection electrostatic spraying to produce a spray of charged nanodrops of the coating material which, in turn, is directed toward the levitated ICF target. The apparatus and preliminary data demonstrating the capability of the levitation scheme and the coating technique are presented
Directory of Open Access Journals (Sweden)
F. Spada
2006-01-01
Full Text Available A new multiple-scattering Monte Carlo 3-D radiative transfer model named McSCIA (Monte Carlo for SCIAmachy is presented. The backward technique is used to efficiently simulate narrow field of view instruments. The McSCIA algorithm has been formulated as a function of the Earth's radius, and can thus perform simulations for both plane-parallel and spherical atmospheres. The latter geometry is essential for the interpretation of limb satellite measurements, as performed by SCIAMACHY on board of ESA's Envisat. The model can simulate UV-vis-NIR radiation. First the ray-tracing algorithm is presented in detail, and then successfully validated against literature references, both in plane-parallel and in spherical geometry. A simple 1-D model is used to explain two different ways of treating absorption. One method uses the single scattering albedo while the other uses the equivalence theorem. The equivalence theorem is based on a separation of absorption and scattering. It is shown that both methods give, in a statistical way, identical results for a wide variety of scenarios. Both absorption methods are included in McSCIA, and it is shown that also for a 3-D case both formulations give identical results. McSCIA limb profiles for atmospheres with and without absorption compare well with the one of the state of the art Monte Carlo radiative transfer model MCC++. A simplification of the photon statistics may lead to very fast calculations of absorption features in the atmosphere. However, these simplifications potentially introduce biases in the results. McSCIA does not use simplifications and is therefore a relatively slow implementation of the equivalence theorem.
A spherical Taylor-Couette dynamo
Marcotte, Florence; Gissinger, Christophe
2016-04-01
We present a new scenario for magnetic field amplification in the planetary interiors where an electrically conducting fluid is confined in a differentially rotating, spherical shell (spherical Couette flow) with thin aspect-ratio. When the angular momentum sufficiently decreases outwards, a primary hydrodynamic instability is widely known to develop in the equatorial region, characterized by pairs of counter-rotating, axisymmetric toroidal vortices (Taylor vortices) similar to those observed in cylindrical Couette flow. We characterize the subcritical dynamo bifurcation due to this spherical Taylor-Couette flow and study its evolution as the flow successively breaks into wavy and turbulent Taylor vortices for increasing Reynolds number. We show that the critical magnetic Reynolds number seems to reach a constant value as the Reynolds number is gradually increased. The role of global rotation on the dynamo threshold and the implications for planetary interiors are finally discussed.
Ultrasonic-Assisted Incremental Microforming of Thin Shell Pyramids of Metallic Foil
Directory of Open Access Journals (Sweden)
Toshiyuki Obikawa
2017-05-01
Full Text Available Single point incremental forming is used for rapid prototyping of sheet metal parts. This forming technology was applied to the fabrication of thin shell micropyramids of aluminum, stainless steel, and titanium foils. A single point tool used had a tip radius of 0.1 mm or 0.01 mm. An ultrasonic spindle with axial vibration was implemented for improving the shape accuracy of micropyramids formed on 5–12 micrometers-thick aluminum, stainless steel, and titanium foils. The formability was also investigated by comparing the forming limits of micropyramids of aluminum foil formed with and without ultrasonic vibration. The shapes of pyramids incrementally formed were truncated pyramids, twisted pyramids, stepwise pyramids, and star pyramids about 1 mm in size. A much smaller truncated pyramid was formed only for titanium foil for qualitative investigation of the size reduction on forming accuracy. It was found that the ultrasonic vibration improved the shape accuracy of the formed pyramids. In addition, laser heating increased the forming limit of aluminum foil and it is more effective when both the ultrasonic vibration and laser heating are applied.
International Nuclear Information System (INIS)
Combescure, A.
1986-04-01
During the last ten years, the French Research Institute for Nuclear Energy (Commissariat a l'Energie Atomique) achieved many theoretical as well as experimental studies for designing the first large size pool type fast breeder reactor. Many of the sensitive parts of this reactor are thin shells subjected to high temperatures and loads. Special care has been given to buckling, because it often governs design. Most of the thin shells structures of the french breeder reactor are axisymmetric. However, imperfections have to be accounted for. In order to keep the advantage of an axisymmetric analysis (low computational costs), a special element has been implemented and used with considerable success in the recent years. This element (COMU) is described in the first chapter, its main features are: either non axisymmetric imperfection or non axisymmetric load, large displacement, non linear material behaviour, computational costs about ten times cheaper than the equivalent three dimensional analysis. This paper based on a careful comparison between experimental and computational results, obtained with the COMU, will analyse three problems: First: design procedure against buckling of thin shells structures subjected to primary loads; Second: static post buckling; Third: buckling under seismic loads [fr
Leung, Ka-Ngo
2006-11-21
A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.
Tackley, Paul J.
2008-12-01
Here it is documented how an existing code for modelling mantle convection in a cartesian domain, Stag3D, has been converted to model a 3D spherical shell by using the recently introduced yin-yang grid. StagYY is thus the latest evolution of a code that has been in continuous use and development for about 15 years so incorporates much physics and several features including compressibility, phase transitions, compositional variations, non-linear rheology, parallelisation, tracers to track composition, partial melting and melt migration, and the ability to also model spherical patches, cartesian boxes, and various 2D geometries by changing one input switch. StagYY uses a multigrid solver to obtain a velocity-pressure solution at each timestep on a staggered grid, a finite-volume scheme for advection of temperature and tracers to track composition. Convergence of multigrid solvers in the presence of realistically large viscosity variations has always been a problem; here a new pressure interpolation scheme is presented that can dramatically improve the robustness of the iterations to large viscosity variations, with up to 19 orders of magnitude variation in presented tests. Benchmark tests show that StagYY produces results that are consistent with those produced by other codes. Performance tests show reasonable scaling on a parallel Beowulf cluster up to 64 CPUs, with up to 1.2 billion unknowns solved for in a few minutes. StagYY is designed to be a stand-alone application with no libraries required and if MPI is installed it can be run in parallel. Technical issues and goals for the future are discussed.
Energy Technology Data Exchange (ETDEWEB)
Cristescu, R., E-mail: rodica.cristescu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, P.O. Box MG-36, Bucharest-Magurele (Romania); Popescu, C.; Socol, G.; Iordache, I.; Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, P.O. Box MG-36, Bucharest-Magurele (Romania); Mihaiescu, D.E.; Grumezescu, A.M. [Faculty of Applied Chemistry and Materials Science, ' Politehnica' University of Bucharest, 1-7 Polizu Street, 011061 Bucharest (Romania); Balan, A.; Stamatin, I. [University of Bucharest, 3Nano-SAE Research Center, PO Box MG-38, Bucharest-Magurele (Romania); Chifiriuc, C. [Faculty of Biology, University of Bucharest, Microbiology Immunology Department, Aleea Portocalilor 1-3, Sector 5, 77206 Bucharest (Romania); Bleotu, C. [Stefan S. Nicolau Institute of Virology, 285 Mihai Bravu, 030304 Bucharest (Romania); Saviuc, C.; Popa, M. [Faculty of Biology, University of Bucharest, Microbiology Immunology Department, Aleea Portocalilor 1-3, Sector 5, 77206 Bucharest (Romania); Chrisey, D.B. [Rensselaer Polytechnic Institute, School of Engineering, Departments of Materials Science and Biomedical Engineering, Troy, 12180-3590, NY (United States)
2012-09-15
Highlights: Black-Right-Pointing-Pointer We deposit magnetic Fe{sub 3}O{sub 4}/oleic acid/cephalosporin nanoparticle thin films by MAPLE. Black-Right-Pointing-Pointer Thin films have a chemical structure similar to the starting material. Black-Right-Pointing-Pointer Cephalosporins have an additive effect on the grain size and induce changes in grain shape. Black-Right-Pointing-Pointer MAPLE can be used to develop novel strategies for fighting medical biofilms associated with chronic infections. - Abstract: We report on thin film deposition of nanostructured Fe{sub 3}O{sub 4}/oleic acid/ceftriaxone and Fe{sub 3}O{sub 4}/oleic acid/cefepime nanoparticles (core/shell/adsorption-shell) were fabricated by matrix assisted pulsed laser evaporation (MAPLE) onto inert substrates. The thin films were characterized by profilometry, Fourier transform infrared spectroscopy, atomic force microscopy, and investigated by in vitro biological assays. The biological properties tested included the investigation of the microbial viability and the microbial adherence to the glass coverslip nanoparticle film, using Gram-negative and Gram-positive bacterial strains with known antibiotic susceptibility behavior, the microbial adherence to the HeLa cells monolayer grown on the nanoparticle pellicle, and the cytotoxicity on eukaryotic cells. The proposed system, based on MAPLE, could be used for the development of novel anti-microbial materials or strategies for fighting pathogenic biofilms frequently implicated in the etiology of biofilm associated chronic infections.
Neotectonics of Asia: Thin-shell finite-element models with faults
Kong, Xianghong; Bird, Peter
1994-01-01
As India pushed into and beneath the south margin of Asia in Cenozoic time, it added a great volume of crust, which may have been (1) emplaced locally beneath Tibet, (2) distributed as regional crustal thickening of Asia, (3) converted to mantle eclogite by high-pressure metamorphism, or (4) extruded eastward to increase the area of Asia. The amount of eastward extrusion is especially controversial: plane-stress computer models of finite strain in a continuum lithosphere show minimal escape, while laboratory and theoretical plane-strain models of finite strain in a faulted lithosphere show escape as the dominant mode. We suggest computing the present (or neo)tectonics by use of the known fault network and available data on fault activity, geodesy, and stress to select the best model. We apply a new thin-shell method which can represent a faulted lithosphere of realistic rheology on a sphere, and provided predictions of present velocities, fault slip rates, and stresses for various trial rheologies and boundary conditions. To minimize artificial boundaries, the models include all of Asia east of 40 deg E and span 100 deg on the globe. The primary unknowns are the friction coefficient of faults within Asia and the amounts of shear traction applied to Asia in the Himalayan and oceanic subduction zones at its margins. Data on Quaternary fault activity prove to be most useful in rating the models. Best results are obtained with a very low fault friction of 0.085. This major heterogeneity shows that unfaulted continum models cannot be expected to give accurate simulations of the orogeny. But, even with such weak faults, only a fraction of the internal deformation is expressed as fault slip; this means that rigid microplate models cannot represent the kinematics either. A universal feature of the better models is that eastern China and southeast Asia flow rapidly eastward with respect to Siberia. The rate of escape is very sensitive to the level of shear traction in the
Salazar-Albornoz, Salvador; Sánchez, Ariel G.; Padilla, Nelson D.; Baugh, Carlton M.
2014-10-01
We test the cosmological implications of studying galaxy clustering using a tomographic approach, by computing the galaxy two-point angular correlation function ω(θ) in thin redshift shells using a spectroscopic redshift galaxy survey. The advantages of this procedure are that it is not necessary to assume a fiducial cosmology in order to convert measured angular positions and redshifts into distances, and that it gives several (less accurate) measurements of the angular diameter distance DA(z) instead of only one (more precise) measurement of the effective average distance DV(z), which results in better constraints on the expansion history of the Universe. We test our model for ω(θ) and its covariance matrix against a set of mock galaxy catalogues and show that this technique is able to extract unbiased cosmological constraints. Also, assuming the best-fitting Λ cold dark matter (ΛCDM) cosmology from the cosmic microwave background measurements from the Planck satellite, we forecast the result of applying this tomographic approach to the final Baryon Oscillation Spectroscopic Survey catalogue in combination with Planck for three flat cosmological models, and compare them with the expected results of the isotropic baryon acoustic oscillation (BAO) measurements post-reconstruction on the same galaxy catalogue combined with Planck. While BAOs are more accurate for constraining cosmological parameters for the standard ΛCDM model, the tomographic technique gives better results when we allow the dark energy equation of state wDE to deviate from -1, resulting in a performance similar to BAOs in the case of a constant value of wDE, and a moderate improvement in the case of a time-dependent value of wDE, increasing the value of the figure of merit in the w0-wa plane up to 15 per cent.
International Nuclear Information System (INIS)
Chien, Wen-Chen; Yu, Yang-Yen; Chen, Po-Kan; Yu, Hui-Huan
2011-01-01
In this study, poly(acrylic)/SiO 2 -TiO 2 core-shell nanoparticle hybrid thin films were successfully synthesized by microwave-assisted polymerization. The coupling agent 3-(trimethoxysilyl) propyl methacrylate (MSMA) was hydrolyzed with colloidal SiO 2 -TiO 2 core-shell nanoparticles, and then polymerized with two acrylic monomers and initiator to form a precursor solution. The results of this study showed that the spin-coated hybrid films had relatively good surface planarity, high thermal stability, a tunable refractive index (1.525 2 -TiO 2 core-shell nanoparticle hybrid thin films, for potential use in optical applications.
International Nuclear Information System (INIS)
Belolipetskiy, A.A.; Lalinina, E.A.; Panina, L.V.
2010-01-01
Complete text of publication follows. Current stage in the IFE research has passed to a closing stage: creation of the experimental reactor and realization of electric power generation. HiPER is a proposed European High Power laser Energy Research facility dedicated to demonstrating the feasibility of laser driven fusion for IFE reactor. The HiPER facility operation requires the formation and delivery of spherical shock ignition cryogenic targets with a rate of several Hz. The targets must be free-standing, or un-mounted. At the Lebedev Physical Institute (LPI), significant progress has been made in the technology development based on rapid fuel layering inside moving free-standing targets which refers to as FST layering method. It allows one to form cryogenic targets with a required rate. In this report, we present the results of a feasibility study on high rep-rate formation of HiPER-class targets by FST. We consider two types of the baseline target for shock ignition. The first one (BT-2) is a 2.094-mm diameter compact polymer shell with a 3 μm thick wall. The solid layer thickness is 211 μm. The second (BT-2a) consists of a 2.046-mm diameter compact polymer shell (3 μm thick also) having a DT-filled CH foam (70 μm) on its inner surface, and then a 120 μm thick solid layer of pure DT. The work addresses the physical concept, and the modeling results of the major stages of FST technologies for different shell materials: Filling stage optimization (computation): optimal filling of a target batch up to ∼ 1000 atm at 300 K requires minimizing the diffusion fill time due to using the ramp filling method for both BT-2 and BT-2a; Depressurization stage optimization (computation and experiments): it requires providing the shell container leak proofness during the process of its cooling down to a depressurization temperature. This allows one to fulfill the technical requirements on the risks minimization associated with the damage of the HiPER-class targets
Structural shell analysis understanding and application
Blaauwendraad, Johan
2014-01-01
The mathematical description of the properties of a shell is much more elaborate than those of beam and plate structures. Therefore many engineers and architects are unacquainted with aspects of shell behaviour and design, and are not familiar with sufficiently reliable shell theories for the different shell types as derived in the middle of the 20th century. Rather than contributing to theory development, this university textbook focuses on architectural and civil engineering schools. Of course, practising professionals will profit from it as well. The book deals with thin elastic shells, in particular with cylindrical, conical and spherical types, and with elliptic and hyperbolic paraboloids. The focus is on roofs, chimneys, pressure vessels and storage tanks. Special attention is paid to edge bending disturbance zones, which is indispensable knowledge in FE meshing. A substantial part of the book results from research efforts in the mid 20th century at Delft University of Technology. As such, it is a valua...
CSIR Research Space (South Africa)
Shatalov, M
2009-05-01
Full Text Available stream_source_info Shatalov2_2009.pdf.txt stream_content_type text/plain stream_size 22572 Content-Encoding UTF-8 stream_name Shatalov2_2009.pdf.txt Content-Type text/plain; charset=UTF-8 1 DYNAMICS OF ROTATING... AND VIBRATING THIN HEMISPHERICAL SHELL WITH MASS AND DAMPING IMPERFECTIONS AND PARAMETRICALLY DRIVEN BY DISCRETE ELECTRODES Michael Shatalov1,2 and Charlotta Coetzee2 1Sensor Science and Technology (SST) of CSIR Material Science and Manufacturing (MSM...
International Nuclear Information System (INIS)
Wu, Hua.
1989-01-01
One of the most elusive quantum system in nature is the nucleus, which is a strongly interacting many body system. In the hadronic (a la neutrons and protons) phase, the primary concern of this thesis, the nucleus' single particle excitations are intertwined with their various collective excitations. Although the underpinning of the nucleus is the spherical shell model, it is rendered powerless without a severe, but intelligent truncation of the infinite Hilbert space. The recently proposed Fermion Dynamical Symmetry Model (FDSM) is precisely such a truncation scheme and in which a symmetry-dictated truncation scheme is introduced in nuclear physics for the first time. In this thesis, extensions and explorations of the FDSM are made to specifically study the odd mass (where the most intricate mixing of the single particle and the collective excitations are observed) and the neutron-proton systems. In particular, the author finds that the previously successful phenomenological particle-rotor-model of the Copenhagen school can now be well understood microscopically via the FDSM. Furthermore, the well known Coriolis attenuation and variable moment of inertia effects are naturally understood from the model as well. A computer code FDUO was written by one of us to study, for the first time, the numerical implications of the FDSM. Several collective modes were found even when the system does not admit a group chain description. In addition, the code is most suitable to study the connection between level statistical behavior (a at Gaussian Orthogonal Ensemble) and dynamical symmetry. It is found that there exist critical region of the interaction parameter space were the system behaves chaotically. This information is certainly crucial to understanding quantum chaotic behavior
Scheler, Gabriela; Fischer, Michael J M; Genow, Alexandra; Hummel, Cornelia; Rampp, Stefan; Paulini, Andrea; Hopfengärtner, Rüdiger; Kaltenhäuser, Martin; Stefan, Hermann
2007-04-01
Epilepsy surgery is an option for patients with pharmacoresistant focal epilepsies, but it requires a precise focus localization procedure. Magnetoencephalography (MEG) and electroencephalography (EEG) can be used for analysis of interictal activity. The aim of this prospective study was to compare clusters of source localization results with MEG and EEG using a three spherical shells (3SS) and a boundary element method (BEM) volume conductor model. The study was closed when 100 patients met the inclusion criteria. Simultaneous MEG and EEG were recorded during presurgical evaluation. Epileptiform signals were analyzed using an equivalent current dipole model. Centroids of source localizations from MEG, EEG, 3SS, and BEM in their respective combinations were compared. In a 3SS model, MEG source localizations were 5.6 mm inferior to those obtained by EEG, while in a BEM model MEG source localizations were 6.3 mm anterior and 4.8 mm superior. The mean scattering of source localizations between both volume conductor models was 19.5 mm for EEG and 9.6 mm for MEG. For MEG no systematic difference between BEM and 3SS source localizations was found. For EEG, source localizations with BEM were 5.9 mm posterior and 11.7 mm inferior to those determined using 3SS. No differences were found between the 46 temporal and the 54 extratemporal lobe epilepsy patients. The observed systematic differences of source localizations of epileptic spikes due to the applied source signal modality and volume conductor model should be considered in presurgical evaluation when only one source signal and volume conductor model is available. (c) 2006 Wiley-Liss, Inc.
Malmberg, J.-A.; Brunsell, P. R.
2002-01-01
Observations of resistive wall instabilities and tearing mode dynamics in the EXTRAP T2R thin shell (τw=6 ms) reversed field pinch are described. A nonresonant mode (m=1,n=-10) with the same handedness as the internal field grows nearly exponentially with an average growth time of about 2.6 ms (less than 1/2 of the shell time) consistent with linear stability theory. The externally nonresonant unstable modes (m=1,n>0), predicted by linear stability theory, are observed to have only low amplitudes (in the normal low-Θ operation mode of the device). The radial field of the dominant internally resonant tearing modes (m=1,n=-15 to n=-12) remain low due to spontaneous fast mode rotation, corresponding to angular phase velocities up to 280 krad/s. Phase aligned mode structures are observed to rotate toroidally with an average angular velocity of 40 krad/s, in the opposite direction of the plasma current. Toward the end of the discharge, the radial field of the internally resonant modes grows as the modes slow down and become wall-locked, in agreement with nonlinear computations. Fast rotation of the internally resonant modes has been observed only recently and is attributed to a change of the front-end system (vacuum vessel, shell, and TF coil) of the device.
Shell thinning and reproductive impairment in black ducks after cessation of DDE dosage
Longcore, J.R.; Stendell, R.C.
1977-01-01
Captive black ducks (anas rubripes) were fed dietary DDE [1,1-dichloro-2,2-bis (p-chlorophenyl)ethylene] at 10 ppm (dry weight; about 2 ppm on a natural diet basis) for 2 breeding seasons, then untreated feed for 2 succeeding years. Residues of DDE in the carcasses of adults declined 90% during the 2-year clean-up period. Following 2 years of dietary DDE, mean residues in eggs reached 64.9 ppm. Even after 2 years on clean feed, DDE residues in the eggs averaged 6.2 ppm or 9.5% of the mean DDE level reached after 2 years on treated feed. Shells of eggs from treated hens were about 20% thinner than shells of eggs from controls. Stoppage of DDE dosage resulted in progressively thicker shells, yet even after 2 years on untreated feed hens laid eggs with shells about 10% thinner than control hens. After DDE was removed from the diet, DDE residues in the eggs decreased, shell thickness increased, and reproductive success improved. Hens previously exposed to DDE, but then fed clean feed for 2 years, still produced significantly fewer surviving ducklings than did control hens.
Curvature-driven morphing of non-Euclidean shells
Pezzulla, Matteo; Stoop, Norbert; Jiang, Xin; Holmes, D. P.
2017-05-01
We investigate how thin structures change their shape in response to non-mechanical stimuli that can be interpreted as variations in the structure's natural curvature. Starting from the theory of non-Euclidean plates and shells, we derive an effective model that reduces a three-dimensional stimulus to the natural fundamental forms of the mid-surface of the structure, incorporating expansion, or growth, in the thickness. Then, we apply the model to a variety of thin bodies, from flat plates to spherical shells, obtaining excellent agreement between theory and numerics. We show how cylinders and cones can either bend more or unroll, and eventually snap and rotate. We also study the nearly isometric deformations of a spherical shell and describe how this shape change is ruled by the geometry of a spindle. As the derived results stem from a purely geometrical model, they are general and scalable.
Mori, Y.; Nishimura, Y.; Hanayama, R.; Nakayama, S.; Ishii, K.; Kitagawa, Y.; Sekine, T.; Takeuchi, Y.; Kurita, T.; Satoh, N.; Kawashima, T.; Komeda, O.; Nishi, T.; Azuma, H.; Hioki, T.; Motohiro, T.; Sunahara, A.; Sentoku, Y.; Miura, E.
2017-11-01
Fast heating is a method of heating an assembled high-density plasma into a hot state by irradiating it with short-duration (sub-picosecond), high-intensity (> 1018 W cm-2 ) laser pulses before the plasma expands and dissolves hydrodynamically. In this paper, we present detailed experimental results of fast heating fuel assembled in a spherical deuterated polystyrene shell target of 500 μ m diameter and 7 μm thickness with counterbeam illumination by using a HAMA 1 Hz, 5.9 J inertial confinement fusion laser driver with pulse tailoring. These tailored pulses contain three pulses in sequence: a ‘foot’ pulse of 2.4 J/25 ns, a ‘spike’ pulse of 0.5 J/300 ps and a ‘heater’ pulse of 0.4 J/110 fs; these pulses are designed to assemble the fuel and heat it. By varying the energy of the foot pulse, we find that fast heating the fuel is achieved only if the fuel is weakly ablated by the foot pulse and then shock-assembled by the spike pulse into the target centre so that the heater pulse can access the fuel with a focal intensity greater than 1018 W cm-2 . Without a foot pulse, the heater pulse contributes to assembling the fuel. For higher foot-pulse energies, the heater pulse drives a hydrodynamic motion with speeds of the order 107 cm s-1 with intensities of the order 1017 W cm-2 , resulting in re-assembling and additional heating of the pre-assembled fuel. Once a shock-assembled core is achieved at the target centre, we succeed qualitatively in fast heating the core for shots in sequence with variations of laser energy within 18%. The coupling efficiency from the heating laser to the core is inferred to be (10 +/- 2) % in total: (8 +/- 1.6) % for the ionized bulk electrons and (2 +/- 0.4) % for the bulk ions. The fusion neutron spectrum detected on the laser axis exhibits peaks at 1.0 MeV, 1.7 MeV and 3.8 MeV. These peaks are attributed to the C(d, n){\\hspace{0pt}}13 N and d(d, n){\\hspace{0pt}}3 He reactions induced by counterpropagating fast deuterons
Minn, Khant; Anopchenko, Aleksei; Yang, Jingyi; Lee, Ho Wai Howard
2018-02-05
We report a novel optical waveguide design of a hollow step index fiber modified with a thin layer of indium tin oxide (ITO). We show an excitation of highly confined waveguide mode in the proposed fiber near the wavelength where permittivity of ITO approaches zero. Due to the high field confinement within thin ITO shell inside the fiber, the epsilon-near-zero (ENZ) mode can be characterized by a peak in modal loss of the hybrid waveguide. Our results show that such in-fiber excitation of ENZ mode is due to the coupling of the guided core mode to the thin-film ENZ mode. We also show that the phase matching wavelength, where the coupling takes place, varies depending on the refractive index of the constituents inside the central bore of the fiber. These ENZ nanostructured optical fibers have many potential applications, for example, in ENZ nonlinear and magneto-optics, as in-fiber wavelength-dependent filters, and as subwavelength fluid channel for optical and bio-photonic sensing.
Comparison of beam and shell theories for the vibrations of thin turbomachinery blades
Leissa, A. W.; Ewing, M. S.
1982-01-01
Vibration analysis of turbomachinery blades has traditionally been carried out by means of beam theory. In recent years two-dimensional methods of blade vibration analysis have been developed, most of which utilize finite elements and tend to require considerable computation time. More recently a two-dimensional method of blade analysis has evolved which does not require finite elements and is based upon shell equations. The present investigation has the primary objective to demonstrate the accuracy and limitations of blade vibration analyses which utilize one-dimensional, beam theories. It is found that beam theory is generally inadequate to determine the free vibration frequencies and mode shapes of moderate to low aspect ratio turbomachinery blades. The shallow shell theory, by contrast, is capable of representing all the vibration modes accurately. However, the one-dimensional beam theory has an important advantage over the two-dimensional shell theory for blades and vibration modes. It uses fewer degrees of freedom, thus requiring less computer time.
Koval, L. R.
1978-01-01
In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the effects of internal cavity resonances on sound transmission into a thin cylindrical shell. The 'noise reduction' of the cylinder is defined and computed, with and without including the effects of internal cavity resonances. As would be expected, the noise reduction in the absence of cavity resonances follows the same qualitative pattern as does transmission loss. Numerical results show that cavity resonances lead to wide fluctuations and a general decrease of noise reduction, especially at cavity resonances. Modest internal absorption is shown to greatly reduce the effect of cavity resonances. The effects of external airflow, internal cabin pressurization, and different acoustical properties inside and outside the cylinder are also included and briefly examined.
Asyirah, B. N.; Shayfull, Z.; Nasir, S. M.; Fathullah, M.; Hazwan, M. H. M.
2017-09-01
In manufacturing a variety of parts, plastic injection moulding is widely use. The injection moulding process parameters have played important role that affects the product's quality and productivity. There are many approaches in minimising the warpage ans shrinkage such as artificial neural network, genetic algorithm, glowworm swarm optimisation and hybrid approaches are addressed. In this paper, a systematic methodology for determining a warpage and shrinkage in injection moulding process especially in thin shell plastic parts are presented. To identify the effects of the machining parameters on the warpage and shrinkage value, response surface methodology is applied. In thos study, a part of electronic night lamp are chosen as the model. Firstly, experimental design were used to determine the injection parameters on warpage for different thickness value. The software used to analyse the warpage is Autodesk Moldflow Insight (AMI) 2012.
Wang, Wenxin
2015-06-16
An operational strategy for the synthesis of atomically smooth Pt skin by a defect-mediated thin film growth method is reported. Extended ultrathin core-shell structured Pd@Ptmonolayer nanosheets (thickness below 5 nm) exhibit a seven-fold enhancement in mass-activity and surprisingly good durability toward oxygen reduction reaction as compared with the commercial Pt/C catalyst.
Electromagnetic response of a thin type-II superconducting cylindrical shell
International Nuclear Information System (INIS)
Perez-Gonzalez, A.; Clem, J.R.
1991-01-01
The general critical-state model, which includes the effects of both flux-line cutting and flux pinning, is used for calculating the response of a type-II superconducting cylindrical shell subjected to applied magnetic fields that change in both magnitude and orientation. Analytic expressions for the ac losses are obtained for the case that the applied field has a small-amplitude oscillating component. For the regime of partial penetration of the changing B field, the ac-loss expression reduces, for large cylinder radius, to that in slab geometry. When full penetration occurs, the ac-loss expressions depend upon the cylinder outer radius
Geometrically Nonlinear Shell Analysis of Wrinkled Thin-Film Membranes with Stress Concentrations
Tessler, Alexander; Sleight, David W.
2006-01-01
Geometrically nonlinear shell finite element analysis has recently been applied to solar-sail membrane problems in order to model the out-of-plane deformations due to structural wrinkling. Whereas certain problems lend themselves to achieving converged nonlinear solutions that compare favorably with experimental observations, solutions to tensioned membranes exhibiting high stress concentrations have been difficult to obtain even with the best nonlinear finite element codes and advanced shell element technology. In this paper, two numerical studies are presented that pave the way to improving the modeling of this class of nonlinear problems. The studies address the issues of mesh refinement and stress-concentration alleviation, and the effects of these modeling strategies on the ability to attain converged nonlinear deformations due to wrinkling. The numerical studies demonstrate that excessive mesh refinement in the regions of stress concentration may be disadvantageous to achieving wrinkled equilibrium states, causing the nonlinear solution to lock in the membrane response mode, while totally discarding the very low-energy bending response that is necessary to cause wrinkling deformation patterns.
Energy Technology Data Exchange (ETDEWEB)
Gilmanov, Anvar, E-mail: agilmano@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Le, Trung Bao, E-mail: lebao002@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Sotiropoulos, Fotis, E-mail: fotis@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Department of Civil, Environmental and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414 (United States)
2015-11-01
We present a new numerical methodology for simulating fluid–structure interaction (FSI) problems involving thin flexible bodies in an incompressible fluid. The FSI algorithm uses the Dirichlet–Neumann partitioning technique. The curvilinear immersed boundary method (CURVIB) is coupled with a rotation-free finite element (FE) model for thin shells enabling the efficient simulation of FSI problems with arbitrarily large deformation. Turbulent flow problems are handled using large-eddy simulation with the dynamic Smagorinsky model in conjunction with a wall model to reconstruct boundary conditions near immersed boundaries. The CURVIB and FE solvers are coupled together on the flexible solid–fluid interfaces where the structural nodal positions, displacements, velocities and loads are calculated and exchanged between the two solvers. Loose and strong coupling FSI schemes are employed enhanced by the Aitken acceleration technique to ensure robust coupling and fast convergence especially for low mass ratio problems. The coupled CURVIB-FE-FSI method is validated by applying it to simulate two FSI problems involving thin flexible structures: 1) vortex-induced vibrations of a cantilever mounted in the wake of a square cylinder at different mass ratios and at low Reynolds number; and 2) the more challenging high Reynolds number problem involving the oscillation of an inverted elastic flag. For both cases the computed results are in excellent agreement with previous numerical simulations and/or experiential measurements. Grid convergence tests/studies are carried out for both the cantilever and inverted flag problems, which show that the CURVIB-FE-FSI method provides their convergence. Finally, the capability of the new methodology in simulations of complex cardiovascular flows is demonstrated by applying it to simulate the FSI of a tri-leaflet, prosthetic heart valve in an anatomic aorta and under physiologic pulsatile conditions.
Buckling of thin walled composite cylindrical shell filled with solid propellant
Dash, A. P.; Velmurugan, R.; Prasad, M. S. R.
2017-12-01
This paper investigates the buckling of thin walled composite cylindrical tubes that are partially filled with solid propellant equivalent elastic filler. Experimental investigation is conducted on thin composite tubes made out of S2-glass epoxy, which is made by using filament winding technique. The composite tubes are filled with elastic filler having similar mechanical properties as that of a typical solid propellant used in rocket motors. The tubes are tested for their buckling strength against the external pressure in the presence of the filler. Experimental data confirms the enhancement of external pressure carrying capacity of the composite tubes by up to three times as that of empty tubes for a volumetric loading fraction (VLF) of 0.9. Furthermore, the finite element based geometric nonlinearity analysis predicts the buckling behaviour of the partially filled composite tubes close to the experimental results.
International Nuclear Information System (INIS)
Zulhijah, Rizka; Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Iwaki, Toru; Nakamura, Keitaro; Okuyama, Kikuo
2015-01-01
The introduction of an oxidation treatment to the synthesis of spherical and core–shell α″-Fe 16 N 2 /Al 2 O 3 nanoparticles (~62 nm) from plasma-synthesized core–shell α-Fe/Al 2 O 3 nanoparticles has been found to result in a high yield of α″-Fe 16 N 2 phase of up to 98%. The oxidation treatment leads the formation of a maghemite phase with open channeled structures along the c-axis, facilitating penetration of H 2 and NH 3 gases during the hydrogen reduction and nitridation steps. The saturation magnetization and magnetic coercivity of the core–shell α″-Fe 16 N 2 /Al 2 O 3 magnetic nanoparticles were found to be 156 emu/g and 1450 Oe, respectively. The detailed effects of the oxidation on the formation of α″-Fe 16 N 2 phase were investigated by characterizing the morphology (SEM, TEM and BET), elemental composition (EDX, EELS, and XAFS) and magnetic properties (Mössbauer and MSPS) of the prepared particles. The good magnetic properties obtained have the potential for future applications such as rare-earth-free magnetic materials. - Highlights: • High yield of α″-Fe 16 N 2 up to 98% was prepared from core–shell α-Fe/Al 2 O 3 NPs. • Introduction of oxidation improved yield of α″-Fe 16 N 2 for large size of NPs. • Oxidation forming microporous structured maghemite facilitated nitridation process. • Particle morphology changed during the nitrogen process due to atomic dislocation. • Core–shell α″-Fe 16 N 2 /Al 2 O 3 nanoparticles showed good magnetic performances
Pokhrel, Madhab; Burger, Arnold; Groza, Michael; Mao, Yuanbing
2017-06-01
We report the generation of La2Zr2O7:5%Eu3+@Y2O3 (LZO5E@YO) core@shell crystalline inorganic-inorganic heterogeneous nanoparticles (NPs). The Y2O3 (YO) shell coating process based on a chemical sol-gel method led to the growth of a thin YO shell on the ordered pyrochlore La2Zr2O7:5%Eu3+ (LZO5E) core NPs. Photoluminescence (PL) analyses demonstrated a blue shift of 15 nm on charge transfer (CT) excitation band of the core@shell NPs from that of the core NPs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) along x-ray diffraction (XRD), Fourier-transform Infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) studies confirmed the formation of the thin YO layer over the LZO5E core NPs. The PL intensity of the LZO5E@YO core@shell NPs was enhanced by three fold compared to that of the LZO5E core NPs, and higher quantum yield (QY) was observed for the former compared to the original NPs by more than 70%. Higher radioluminescence (RL) emission was also observed for the core@shell NPs compared to the core NPs. Our ability of obtaining near-perfect core@shell heterostructure with enhanced luminescence performance opens the door for the development of efficient La2Zr2O7:5%Eu3+@Y2O3 NPs for both optical and x-ray scintillation applications.
Zulhijah, Rizka; Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Iwaki, Toru; Nakamura, Keitaro; Okuyama, Kikuo
2015-05-01
The introduction of an oxidation treatment to the synthesis of spherical and core-shell α″-Fe16N2/Al2O3 nanoparticles (~62 nm) from plasma-synthesized core-shell α-Fe/Al2O3 nanoparticles has been found to result in a high yield of α″-Fe16N2 phase of up to 98%. The oxidation treatment leads the formation of a maghemite phase with open channeled structures along the c-axis, facilitating penetration of H2 and NH3 gases during the hydrogen reduction and nitridation steps. The saturation magnetization and magnetic coercivity of the core-shell α″-Fe16N2/Al2O3 magnetic nanoparticles were found to be 156 emu/g and 1450 Oe, respectively. The detailed effects of the oxidation on the formation of α″-Fe16N2 phase were investigated by characterizing the morphology (SEM, TEM and BET), elemental composition (EDX, EELS, and XAFS) and magnetic properties (Mössbauer and MSPS) of the prepared particles. The good magnetic properties obtained have the potential for future applications such as rare-earth-free magnetic materials.
Li, Xue; Niitsoo, Olivia; Couzis, Alexander
2016-03-01
An electrostatically-assisted strategy for fabrication of thin film composite capacitors with controllable dielectric constant (k) has been developed. The capacitor is composed of metal-dielectric core/shell nanoparticle (silver/silica, Ag@SiO2) multilayer films, and a backfilling polymer. Compared with the simple metal particle-polymer mixtures where the metal nanoparticles (NP) are randomly dispersed in the polymer matrix, the metal volume fraction in our capacitor was significantly increased, owing to the densely packed NP multilayers formed by the electrostatically assisted assembly process. Moreover, the insulating layer of silica shell provides a potential barrier that reduces the tunneling current between neighboring Ag cores, endowing the core/shell nanocomposites with a stable and relatively high dielectric constant (k) and low dielectric loss (D). Our work also shows that the thickness of the SiO2 shell plays a dominant role in controlling the dielectric properties of the nanocomposites. Control over metal NP separation distance was realized not only by variation the shell thickness of the core/shell NPs but also by introducing a high k nanoparticle, barium strontium titanate (BST) of relatively smaller size (∼8nm) compared to 80-160nm of the core/shell Ag@SiO2 NPs. The BST assemble between the Ag@SiO2 and fill the void space between the closely packed core/shell NPs leading to significant enhancement of the dielectric constant. This electrostatically assisted assembly method is promising for generating multilayer films of a large variety of NPs over large areas at low cost. Copyright © 2015 Elsevier Inc. All rights reserved.
LOW-FREQUENCY MAGNETIC FIELD SHIELDING BY A CIRCULAR PASSIVE LOOP AND CLOSED SHELLS
Directory of Open Access Journals (Sweden)
V.S. Grinchenko
2016-05-01
Full Text Available Purpose. To analyze the shielding factors for a circular passive loop and conductive closed shells placed in a homogeneous low-frequency magnetic field. Methodology. We have obtained simplified expressions for the shielding factors for a circular passive loop and a thin spherical shell. In addition, we have developed the numerical model of a thin cubical shell in a magnetic field, which allows exploring its shielding characteristics. Results. We have obtained dependences of the shielding factors for passive loops and shells on the frequency of the external field. Analytically determined frequency of the external magnetic field, below which field shielding of a passive loop is expedient to use, above which it is advisable to use a shielding shell.
Wang, Wenxin; Zhao, Yunfeng; Ding, Yi
2015-07-01
An operational strategy for the synthesis of atomically smooth Pt skin by a defect-mediated thin film growth method is reported. Extended ultrathin core-shell structured d@Ptmonolayer nanosheets (thickness below 5 nm) exhibit nearly seven-fold enhancement in mass-activity and surprisingly good durability toward oxygen reduction reaction as compared with the commercial Pt/C catalyst.An operational strategy for the synthesis of atomically smooth Pt skin by a defect-mediated thin film growth method is reported. Extended ultrathin core-shell structured d@Ptmonolayer nanosheets (thickness below 5 nm) exhibit nearly seven-fold enhancement in mass-activity and surprisingly good durability toward oxygen reduction reaction as compared with the commercial Pt/C catalyst. Electronic supplementary information (ESI) available: Sample preparation, physical and electrochemical characterization, Fig. S1 to S11. See DOI: 10.1039/c5nr02748a
Chai, Geun Seok; Yoon, Suk Bon; Kim, Jung Ho; Yu, Jong-Sung
2004-12-07
Carbon capsules with hollow core and mesoporous shell (HCMS) structures were used as a support material for Pt(50)-Ru(50) catalyst, and the catalytic performance of the HCMS supported catalyst in the direct methanol fuel cell was described; the HCMS carbon supported catalysts exhibited much higher specific activity for methanol oxidation than the commonly used E-TEK catalyst by about 80%, proving that the HCMS carbon capsules are an excellent support for electrode catalysts in DMFC.
Directory of Open Access Journals (Sweden)
Zhong Luo
2015-02-01
Full Text Available This study investigates a method of designing a simplified cylindrical shell model. This model accurately predicts the dynamic characteristics of a prototype cylindrical shell with sealing teeth accurately. The significance of this study is that it provides an acceptable process which guides the design of test models. Firstly, an equivalent cylindrical shell with rectangular rings is designed by combining the energy equation and numerical analysis. Then the transfer matrixes of the stiffened cylindrical shell and the cylindrical shell are employed to calculate the equivalent thickness of the simplified cylindrical shell commonly used in model tests. Further, the equivalent thicknesses are normalized by introducing an average equivalent thickness. The distorted scaling laws and size applicable intervals are investigated to reduce the errors caused by the normalization. Finally, a 42CrMo cylindrical shell with sealing teeth is used as a prototype and a number 45 steel scaled-down cylindrical shell is used as a distorted test model. The accuracy of the prediction is verified by using experimental data, and the results indicate that the distorted model can predict the characteristics of the stiffened cylindrical shell prototype with good accuracy.
Wenninger, Magnus J
2012-01-01
Well-illustrated, practical approach to creating star-faced spherical forms that can serve as basic structures for geodesic domes. Complete instructions for making models from circular bands of paper with just a ruler and compass. Discusses tessellation, or tiling, and how to make spherical models of the semiregular solids and concludes with a discussion of the relationship of polyhedra to geodesic domes and directions for building models of domes. "". . . very pleasant reading."" - Science. 1979 edition.
Cohen, Taco S.; Geiger, Mario; Koehler, Jonas; Welling, Max
2018-01-01
Convolutional Neural Networks (CNNs) have become the method of choice for learning problems involving 2D planar images. However, a number of problems of recent interest have created a demand for models that can analyze spherical images. Examples include omnidirectional vision for drones, robots, and autonomous cars, molecular regression problems, and global weather and climate modelling. A naive application of convolutional networks to a planar projection of the spherical signal is destined t...
Facile Synthesis of ZnO@TiO2 Core-Shell Nanorod Thin Films for Dye-Sensitized Solar Cells
Directory of Open Access Journals (Sweden)
Xiaoxu Ji
2015-01-01
Full Text Available ZnO nanorod thin films grown on fluorine-doped tin oxide (FTO glasses have been synthesized via facile thermal evaporation. To optimize the performance of dye-sensitized solar cells (DSSCs, we fabricated ZnO@TiO2 core-shell composite by a simple dip-coating method immersed in the mixed solution of Ti(OC4H9 and ethanol. Results of solar cell testing showed that ZnO@TiO2 core-shell nanorod thin films on FTO significantly increased open circuit voltage (from 0.47 V to 0.53 V, short circuit current (from 10.78 mA/cm2 to 13.98 mA/cm2, and fill factor (from 51% to 55%. The photoelectric conversion efficiency (PEC increased from 3.3% for bare ZnO DSSCs to 4.85% for ZnO@TiO2 core-shell structured DSSCs. This is mainly ascribed to the improvement in light harvesting efficiency, electron transfer, and the effective suppression of charge recombination.
Cooperative effects in spherical spasers
DEFF Research Database (Denmark)
Bordo, Vladimir
2017-01-01
A fully analytical semiclassical theory of cooperative optical processes which occur in an ensemble of molecules embedded in a spherical core-shell nanoparticle is developed from first principles. Both the plasmonic Dicke effect and spaser generation are investigated for the designs in which...
Energy Technology Data Exchange (ETDEWEB)
Kim, Min-Gyu; Lee, Hye-Jung; Oh, Yong-Jun [Hanbat National Univ., Daejeon (Korea, Republic of)
2016-07-15
Au-Pd bimetallic nanoparticles (NPs) have received a lot of attention in the fields of catalysts and hydrogen sensors. In this study, Au-Pd core-shell NP arrays were successfully fabricated using two steps: formation of the ordered array of Au NPs cores via solid-state dewetting of a Au thin film on a topographic silica substrate, and Pd shell formation via chemical synthesis using two different surfactants (CTAB and CTAC). Using the CTAB surfactant in particular, a 2-D composite structure comprised of an ordered array of Au-Pd NPs, with smaller Pd NPs on the nanoscopic gaps between the Au-Pd NPs, could be formed. This structure is expected to have potential application in resistance-base hydrogen sensors.
How Spherical Is a Cube (Gravitationally)?
Sanny, Jeff; Smith, David
2015-01-01
An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center. By integrating over ring elements of a spherical shell, we show that the…
Neff, P.
2004-10-01
This contribution is concerned with a consistent formal dimensional reduction of a previously introduced finite-strain three-dimensional Cosserat micropolar elasticity model to the two-dimensional situation of thin plates and shells. Contrary to the direct modelling of a shell as a Cosserat surface with additional directors, we obtain the shell model from the Cosserat bulk model which already includes a triad of rigid directors. The reduction is achieved by assumed kinematics, quadratic through the thickness. The three-dimensional transverse boundary conditions can be evaluated analytically in terms of the assumed kinematics and determines exactly two appearing coefficients in the chosen ansatz. Further simplifications with subsequent analytical integration through the thickness determine the reduced model in a variational setting. The resulting membrane energy turns out to be a quadratic, elliptic, first order, non degenerate energy in contrast to classical approaches. The bending contribution is augmented by a curvature term representing an additional stiffness of the Cosserat model and the corresponding system of balance equations remains of second order. The lateral boundary conditions for simple support are non-standard. The model includes size-effects, transverse shear resistance, drilling degrees of freedom and accounts implicitly for thickness extension and asymmetric shift of the midsurface. The formal thin shell “membrane” limit without classical h 3-bending term is non-degenerate due to the additional Cosserat curvature stiffness and control of drill rotations. In our formulation, the drill-rotations are strictly related to the size-effects of the bulk model and not introduced artificially for numerical convenience. Upon linearization with zero Cosserat couple modulus μ_c = 0 we recover the well known infinitesimal-displacement Reissner-Mindlin model without size-effects and without drill-rotations. It is shown that the dimensionally reduced
International Nuclear Information System (INIS)
Rattanapan, Anuchit; Limtong, Savitree; Phisalaphong, Muenduen
2011-01-01
Highlights: → Thin-shell silk cocoons for immobilization of Saccharomycescerevisiae. → Advantages: high mechanical strength, light weight, biocompatibility and high surface area. → Enhanced cell stability and ethanol productivity by the immobilization system. -- Abstract: A thin-shell silk cocoon (TSC), a residual from the silk industry, is used as a support material for the immobilization of Saccharomyces cerevisiae M30 in ethanol fermentation because of its properties such as high mechanical strength, light weight, biocompatibility and high surface area. In batch fermentation with blackstrap molasses as the main fermentation substrate, an optimal ethanol concentration of 98.6 g/L was obtained using a TSC-immobilized cell system at an initial reducing sugar concentration of 240 g/L. The ethanol concentration produced by the immobilized cells was 11.5% higher than that produced by the free cells. Ethanol production in five-cycle repeated batch fermentation demonstrated the enhanced stability of the immobilized yeast cells. Under continuous fermentation in a packed-bed reactor, a maximum ethanol productivity of 19.0 g/(L h) with an ethanol concentration of 52.8 g/L was observed at a 0.36 h -1 dilution rate.
Gravitational Field of Spherical Branes
Gogberashvili, Merab
The warped solution of Einstein's equations corresponding to the spherical brane in five-dimensional AdS is considered. This metric represents interiors of black holes on both sides of the brane and can provide gravitational trapping of physical fields on the shell. It is found that the analytic form of the coordinate transformations from the Schwarzschild to co-moving frame that exists only in five dimensions. It is shown that in the static coordinates active gravitational mass of the spherical brane, in agreement with Tolman's formula, is negative, i.e. such objects are gravitationally repulsive.
1997-10-01
cylindrical shells. Journal Acoustique , 4, 1991: 509-523. [13] Magand F., and Chevret P., Time frequency analysis of energy distribution for...application a 1’etude des ondes de Lamb Journal Acoustique , 3, 1990: 273-280. [17] Kay S.M., Modem spectral estimation: theory and application, New York
Francesco Tornabene; Nicholas Fantuzzi; Michele Bacciocchi; Junuthula N. Reddy
2016-01-01
The main purpose of the paper is to present an innovative higher-order structural theory to accurately evaluate the natural frequencies of laminated composite shells. A new kinematic model is developed starting from the theoretical framework given by a unified formulation. The kinematic expansion is taken as a free parameter, and the three-dimensional displacement field is described by using alternatively the Legendre or Lagrange polynomials, following the key points of the most typical Layer...
International Nuclear Information System (INIS)
Toyoda, Yukihiro; Matsuura, Shinichi
1997-01-01
The demonstration FBRs' reactor vessel wall protective structures, which are composed of thin shell structures, may fail by dynamic buckling due to seismically induced hydrodynamic effects. In order to clarify the dynamic buckling characteristics of the shells, numerical analysis can be a useful tool. However, it generally takes an enormous amount of computational time to execute dynamic buckling analysis by the finite element method. Therefore, one of the authors has developed an elastic-plastic large displacement analysis computer program for shells of revolution with high efficiency. The objectives of this study are to investigate the buckling behaviour of a partially liquid-filled cantilevered thin cylindrical shell subjected to harmonic excitation, and to validate the applicability of the improved computer program which has the capability of elastic-plastic dynamic buckling analysis including fluid-structure interaction. Numerical simulations were performed using the computer program under the conditions corresponding to shaking table tests of the tank. It is confirmed that the dynamic buckling analyses of the liquid-filled thin shell are possible by using the computer program within reasonable computational time. (author)
DNA nanoparticles with core-shell morphology.
Chandran, Preethi L; Dimitriadis, Emilios K; Lisziewicz, Julianna; Speransky, Vlad; Horkay, Ferenc
2014-10-14
Mannobiose-modified polyethylenimines (PEI) are used in gene therapy to generate nanoparticles of DNA that can be targeted to the antigen-presenting cells of the immune system. We report that the sugar modification alters the DNA organization within the nanoparticles from homogenous to shell-like packing. The depth-dependent packing of DNA within the nanoparticles was probed using AFM nano-indentation. Unmodified PEI-DNA nanoparticles display linear elastic properties and depth-independent mechanics, characteristic of homogenous materials. Mannobiose-modified nanoparticles, however, showed distinct force regimes that were dependent on indentation depth, with 'buckling'-like response that is reproducible and not due to particle failure. By comparison with theoretical studies of spherical shell mechanics, the structure of mannobiosylated particles was deduced to be a thin shell with wall thickness in the order of few nanometers, and a fluid-filled core. The shell-core structure is also consistent with observations of nanoparticle denting in altered solution conditions, with measurements of nanoparticle water content from AFM images, and with images of DNA distribution in Transmission Electron Microscopy.
Energy Technology Data Exchange (ETDEWEB)
Yahia, I.S. [Nano-Science & Semiconductor Labs, Metallurgical Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Ganesh, V. [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Shkir, M., E-mail: shkirphysics@gmail.com [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); AlFaify, S. [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Zahran, H.Y. [Nano-Science & Semiconductor Labs, Metallurgical Lab., Department of Physics, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Algarni, H. [Advanced Functional Materials & Optoelectronic Laboratory (AFMOL), Department of Physics, Faculty of Science, King Khalid University, P.O. Box 9004, Abha (Saudi Arabia); Abutalib, M.M.; Al-Ghamdi, Attieh A. [Centre of Nanotechnology, Physics Department-Faculty of Science-AL Faisaliah Campus, King Abdulaziz University, Jeddah (Saudi Arabia); El-Naggar, A.M.; AlBassam, A.M. [Research Chair of Exploitation of Renewable Energy Applications in Saudi Arabia, Physics & Astronomy Dept., College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)
2016-09-01
In the current work, the authors present the systematic study on linear and nonlinear optical properties of Copper-phathalocyanine thin film deposited by thermal evaporation system for the first time. The thickness of the prepared thin film was measured and found to be ~300 nm. X-ray diffraction and AFM study confirms that the prepared thin film possess good quality. The orientation of the grown thin film is found to be along (100). UV–vis-NIR study shows that the deposited thin film is highly transparent (>80%) in the wavelength range of 700–2500 nm. Further, the recorded optical data was used to determine the various linear and nonlinear optical parameters. The calculated value of refractive index is found to be in the range of 0.4–1.0. The direct and indirect band gap value is found to be 2.9 and 3.25 eV, respectively. The value of linear and nonlinear susceptibilities is found to be in order of 10{sup −12}. The higher value of linear and nonlinear parameters makes it suitable for optoelectronic applications.
Yahia, I. S.; Ganesh, V.; Shkir, M.; AlFaify, S.; Zahran, H. Y.; Algarni, H.; Abutalib, M. M.; Al-Ghamdi, Attieh A.; El-Naggar, A. M.; AlBassam, A. M.
2016-09-01
In the current work, the authors present the systematic study on linear and nonlinear optical properties of Copper-phathalocyanine thin film deposited by thermal evaporation system for the first time. The thickness of the prepared thin film was measured and found to be ~300 nm. X-ray diffraction and AFM study confirms that the prepared thin film possess good quality. The orientation of the grown thin film is found to be along (100). UV-vis-NIR study shows that the deposited thin film is highly transparent (>80%) in the wavelength range of 700-2500 nm. Further, the recorded optical data was used to determine the various linear and nonlinear optical parameters. The calculated value of refractive index is found to be in the range of 0.4-1.0. The direct and indirect band gap value is found to be 2.9 and 3.25 eV, respectively. The value of linear and nonlinear susceptibilities is found to be in order of 10-12. The higher value of linear and nonlinear parameters makes it suitable for optoelectronic applications.
Critical Buckling Load on Large Spherical Shells
DEFF Research Database (Denmark)
Wedellsborg, B. W.
1962-01-01
Approximate evaluation for watertanks, hortonspheres, vapor containers, containment vessels for nuclear reactors, and so forth, has been computed, taking into account out-of-roundness and local flattened areas; graphs have been plotted giving critical buckling load as function of maximum radial...
Directory of Open Access Journals (Sweden)
Elif Peksu
2015-01-01
Full Text Available In this investigation, hydrothermal technique was employed for the synthesis of well-aligned dense arrays of ZnO nanowires (NWs on a wide range of substrates including silicon, soda-lime glass (SLG, indium tin oxide, and polyethylene terephthalate (PET. Results showed that ZnO NWs can be successfully grown on any substrate that can withstand the growth temperature (~90°C and precursor solution chemicals. Results also revealed that there was a strong impact of growth time and ZnO seed layer deposition route on the orientation, density, diameter, and uniformity of the synthesized nanowires. A core-shell n-ZnO NWs/p-AgGaSe2 (AGS thin film solar cell was fabricated as a device application of synthesized ZnO nanowires by decoration of nanowires with ~700 nm thick sputtering deposited AGS thin film layer, which demonstrated an energy conversion efficiency of 1.74% under 100 mW/cm2 of simulated solar illumination.
Simple spherical ablative-implosion model
Energy Technology Data Exchange (ETDEWEB)
Mayer, F.J.; Steele, J.T.; Larsen, J.T.
1980-06-23
A simple model of the ablative implosion of a high-aspect-ratio (shell radius to shell thickness ratio) spherical shell is described. The model is similar in spirit to Rosenbluth's snowplow model. The scaling of the implosion time was determined in terms of the ablation pressure and the shell parameters such as diameter, wall thickness, and shell density, and compared these to complete hydrodynamic code calculations. The energy transfer efficiency from ablation pressure to shell implosion kinetic energy was examined and found to be very efficient. It may be possible to attach a simple heat-transport calculation to our implosion model to describe the laser-driven ablation-implosion process. The model may be useful for determining other energy driven (e.g., ion beam) implosion scaling.
Synthesis and Enhanced Formaldehyde-Sensing Properties of In2O3 Hollow Spheres with Thin Shells
Zou, Yanzhao; Wang, Hong; Lai, Xiaoyong; Li, Xuefei; Zhou, Xiaofei; Lin, Guo; Liu, Di; Chen, Jian; Xin, Hong
2018-03-01
Uniform-size In2O3 hollow spheres were synthesized using carbon microspheres as sacrificial template and In(NO3)3 as the indium resource. The effects of different solvents on the structure and morphology of as-prepared samples were discussed, and it was found that the shell thickness of In2O3 hollow microspheres could be controlled by changing solvents. The formation mechanism of the In2O3 hollow microspheres was also investigated. The gas-sensing results indicated that all of the as-prepared samples showed high gas-sensing response and excellent selectivity to formaldehyde and In2O3 hollow microspheres had an advantage over the bulk In2O3. Notably, In2O3 hollow microspheres with the shell thickness of 20 nm were fabricated by methanol solution and showed a higher response value of 41 toward 100 ppm HCHO than those of In2O3 hollow microspheres obtained by using other solvents. In2O3 hollow microspheres had good selectivity, high response and fast response-recovery, which made this product a promising gas-sensing material for detecting formaldehyde.
Synthesis and Enhanced Formaldehyde-Sensing Properties of In2O3 Hollow Spheres with Thin Shells
Zou, Yanzhao; Wang, Hong; Lai, Xiaoyong; Li, Xuefei; Zhou, Xiaofei; Lin, Guo; Liu, Di; Chen, Jian; Xin, Hong
2017-12-01
Uniform-size In2O3 hollow spheres were synthesized using carbon microspheres as sacrificial template and In(NO3)3 as the indium resource. The effects of different solvents on the structure and morphology of as-prepared samples were discussed, and it was found that the shell thickness of In2O3 hollow microspheres could be controlled by changing solvents. The formation mechanism of the In2O3 hollow microspheres was also investigated. The gas-sensing results indicated that all of the as-prepared samples showed high gas-sensing response and excellent selectivity to formaldehyde and In2O3 hollow microspheres had an advantage over the bulk In2O3. Notably, In2O3 hollow microspheres with the shell thickness of 20 nm were fabricated by methanol solution and showed a higher response value of 41 toward 100 ppm HCHO than those of In2O3 hollow microspheres obtained by using other solvents. In2O3 hollow microspheres had good selectivity, high response and fast response-recovery, which made this product a promising gas-sensing material for detecting formaldehyde.
Directory of Open Access Journals (Sweden)
Francesco Tornabene
2016-12-01
Full Text Available The main purpose of the paper is to present an innovative higher-order structural theory to accurately evaluate the natural frequencies of laminated composite shells. A new kinematic model is developed starting from the theoretical framework given by a unified formulation. The kinematic expansion is taken as a free parameter, and the three-dimensional displacement field is described by using alternatively the Legendre or Lagrange polynomials, following the key points of the most typical Layer-wise (LW approaches. The structure is considered as a unique body and all the geometric and mechanical properties are evaluated on the shell middle surface, following the idea of the well-known Equivalent Single Layer (ESL models. For this purpose, the name Equivalent Layer-Wise (ELW is introduced to define the present approach. The governing equations are solved numerically by means of the Generalized Differential Quadrature (GDQ method and the solutions are compared with the results available in the literature or obtained through a commercial finite element program. Due to the generality of the current method, several boundary conditions and various mechanical and geometric configurations are considered. Finally, it should be underlined that different doubly-curved surfaces may be considered following the mathematical framework given by the differential geometry.
Altenbach, Holm
2011-01-01
In this volume, scientists and researchers from industry discuss the new trends in simulation and computing shell-like structures. The focus is put on the following problems: new theories (based on two-dimensional field equations but describing non-classical effects), new constitutive equations (for materials like sandwiches, foams, etc. and which can be combined with the two-dimensional shell equations), complex structures (folded, branching and/or self intersecting shell structures, etc.) and shell-like structures on different scales (for example: nano-tubes) or very thin structures (similar
Investigation of spherical and concentric mechanism of compound droplets
Directory of Open Access Journals (Sweden)
Meifang Liu
2016-07-01
Full Text Available Polymer shells with high sphericity and uniform wall thickness are always needed in the inertial confined fusion (ICF experiments. Driven by the need to control the shape of water-in-oil (W1/O compound droplets, the effects of the density matching level, the interfacial tension and the rotation speed of the continuing fluid field on the sphericity and wall thickness uniformity of the resulting polymer shells were investigated and the spherical and concentric mechanisms were also discussed. The centering of W1/O compound droplets, the location and movement of W1/O compound droplets in the external phase (W2 were significantly affected by the density matching level of the key stage and the rotation speed of the continuing fluid field. Therefore, by optimizing the density matching level and rotation speed, the batch yield of polystyrene (PS shells with high sphericity and uniform wall thickness increased. Moreover, the sphericity also increased by raising the oil/water (O/W2 interfacial tension, which drove a droplet to be spherical. The experimental results show that the spherical driving force is from the interfacial tension affected by the two relative phases, while the concentric driving force, as a resultant force, is not only affected by the three phases, but also by the continuing fluid field. The understanding of spherical and concentric mechanism can provide some guidance for preparing polymer shells with high sphericity and uniform wall thickness.
Korala, Lasantha; Wang, Zhijie; Liu, Yi; Maldonado, Stephen; Brock, Stephanie L
2013-02-26
Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) nonradiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic, and microscopic studies. Further enhancement of interparticle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications.
Korala, Lasantha; Wang, Zhijie; Liu, Yi; Maldonado, Stephen; Brock, Stephanie L.
2013-01-01
Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) non-radiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic and microscopic studies. Further enhancement of inter-particle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications. PMID:23350924
Shell model studies in the N = 54 isotones 99Rh, 100Pd
International Nuclear Information System (INIS)
Ghugre, S.S.; Sarkar, S.; Chintalapudi, S.N.
1996-01-01
The shell model in reproducing the observed level is used to investigate the observed level sequences in 99 Rh and 100 Pd within the spherical shell model framework. Shell model calculations have been performed using the code OXBASH
Design aids for stiffened composite shells with cutouts
Sahoo, Sarmila
2017-01-01
This book focuses on the free vibrations of graphite-epoxy laminated composite stiffened shells with cutout both in terms of the natural frequencies and mode shapes. The dynamic analysis of shell structures, which may have complex geometry and arbitrary loading and boundary conditions, is solved efficiently by the finite element method, even including cutouts in shells. The results may be readily used by practicing engineers dealing with stiffened composite shells with cutouts. Several shell forms viz. cylindrical shell, hypar shell, conoidal shell, spherical shell, saddle shell, hyperbolic paraboloidal shell and elliptic paraboloidal shell are considered in the book. The dynamic characteristics of stiffened composite shells with cutout are described in terms of the natural frequency and mode shapes. The size of the cutouts and their positions with respect to the shell centre are varied for different edge constraints of cross-ply and angle-ply laminated composite shells. The effects of these parametric variat...
Preparations of spherical polymeric particles from Tanzanian ...
African Journals Online (AJOL)
Spherical Polymeric Particles (SPP) have been prepared from Tanzanian Cashew Nut Shell Liquid (CNSL) by suspension polymerization technique involving either step-growth or chain- growth polymerization mechanisms. The sizes of the SPP, which ranged from 0.1 to 2.0 mm were strongly influenced by the amounts of ...
Design aids for fixed support reinforced concrete cylindrical shells ...
African Journals Online (AJOL)
Shells are objects considered as materialization of the curved surface. Despite structural advantages and architectural aesthetics possessed by shells, relative degree of unacquaintance with shell behavior and design is high. Thin shells are examples of strength through form as opposed to strength through mass; their thin ...
Curvature-Induced Instabilities of Shells
Pezzulla, Matteo; Stoop, Norbert; Steranka, Mark P.; Bade, Abdikhalaq J.; Holmes, Douglas P.
2018-01-01
Induced by proteins within the cell membrane or by differential growth, heating, or swelling, spontaneous curvatures can drastically affect the morphology of thin bodies and induce mechanical instabilities. Yet, the interaction of spontaneous curvature and geometric frustration in curved shells remains poorly understood. Via a combination of precision experiments on elastomeric spherical shells, simulations, and theory, we show how a spontaneous curvature induces a rotational symmetry-breaking buckling as well as a snapping instability reminiscent of the Venus fly trap closure mechanism. The instabilities, and their dependence on geometry, are rationalized by reducing the spontaneous curvature to an effective mechanical load. This formulation reveals a combined pressurelike term in the bulk and a torquelike term in the boundary, allowing scaling predictions for the instabilities that are in excellent agreement with experiments and simulations. Moreover, the effective pressure analogy suggests a curvature-induced subcritical buckling in closed shells. We determine the critical buckling curvature via a linear stability analysis that accounts for the combination of residual membrane and bending stresses. The prominent role of geometry in our findings suggests the applicability of the results over a wide range of scales.
Osmotic buckling of spherical capsules.
Knoche, Sebastian; Kierfeld, Jan
2014-11-07
We study the buckling of elastic spherical shells under osmotic pressure with the osmolyte concentration of the exterior solution as a control parameter. We compare our results for the bifurcation behavior with results for buckling under mechanical pressure control, that is, with an empty capsule interior. We find striking differences for the buckling states between osmotic and mechanical buckling. Mechanical pressure control always leads to fully collapsed states with opposite sides in contact, whereas uncollapsed states with a single finite dimple are generic for osmotic pressure control. For sufficiently large interior osmolyte concentrations, osmotic pressure control is qualitatively similar to buckling under volume control with the volume prescribed by the osmolyte concentrations inside and outside the shell. We present a quantitative theory which also captures the influence of shell elasticity on the relationship between osmotic pressure and volume. These findings are relevant for the control of buckled shapes in applications. We show how the osmolyte concentration can be used to control the volume of buckled shells. An accurate analytical formula is derived for the relationship between the osmotic pressure, the elastic moduli and the volume of buckled capsules. This also allows use of elastic capsules as osmotic pressure sensors or deduction of elastic properties and the internal osmolyte concentration from shape changes in response to osmotic pressure changes. We apply our findings to published experimental data on polyelectrolyte capsules.
Determination of shell energies. Nuclear deformations and fission barriers
International Nuclear Information System (INIS)
Koura, Hiroyuki; Tachibana, Takahiro; Uno, Masahiro; Yamada, Masami.
1996-01-01
We have been studying a method of determining nuclear shell energies and incorporating them into a mass formula. The main feature of this method lies in estimating shell energies of deformed nuclei from spherical shell energies. We adopt three assumptions, from which the shell energy of a deformed nucleus is deduced to be a weighted sum of spherical shell energies of its neighboring nuclei. This shell energy should be called intrinsic shell energy since the average deformation energy also acts as an effective shell energy. The ground-state shell energy of a deformed nucleus and its equilibrium shape can be obtained by minimizing the sum of these two energies with respect to variation of deformation parameters. In addition, we investigate the existence of fission isomers for heavy nuclei with use of the obtained shell energies. (author)
Magnetic field-dependent of binding energy in GaN/InGaN/GaN spherical QDQW nanoparticles
International Nuclear Information System (INIS)
El Ghazi, Haddou; Jorio, Anouar; Zorkani, Izeddine
2013-01-01
Simultaneous study of magnetic field and impurity's position effects on the ground-state shallow-donor binding energy in GaN|InGaN|GaN (core|well|shell) spherical quantum dot–quantum well (SQDQW) as a function of the ratio of the inner and the outer radius is reported. The calculations are investigated within the framework of the effective-mass approximation and an infinite deep potential describing the quantum confinement effect. A Ritz variational approach is used taking into account of the electron-impurity correlation and the magnetic field effect in the trial wave-function. It appears that the binding energy depends strongly on the external magnetic field, the impurity's position and the structure radius. It has been found that: (i) the magnetic field effect is more marked in large layer than in thin layer and (ii) it is more pronounced in the spherical layer center than in its extremities
Energy Technology Data Exchange (ETDEWEB)
Boyadjiev, Stefan I., E-mail: boiajiev@gmail.com [MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Santos, Gustavo dos Lopes; Szűcs, Júlia [Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Szilágyi, Imre M., E-mail: imre.szilagyi@mail.bme.hu [MTA-BME Technical Analytical Chemistry Research Group, Szent Gellért tér 4, Budapest, H-1111 (Hungary); Budapest University of Technology and Economics, Department of Inorganic and Analytical Chemistry, Szent Gellért tér 4, Budapest, H-1111 (Hungary)
2016-03-25
In this study, monoclinic WO{sub 3} nanoparticles were obtained by thermal decomposition of (NH{sub 4}){sub x}WO{sub 3} in air at 600 °C. On them by atomic layer deposition (ALD) TiO{sub 2} films were deposited, and thus core/shell WO{sub 3}/TiO{sub 2} nanocomposites were prepared. We prepared composites of WO{sub 3} nanoparticles with conductive polymer as PEDOT:PSS, and deposited thin films of them on glass and ITO substrates by spin coating. The formation, morphology, composition and structure of the as-prepared pure and composite nanoparticles, as well thin films, were studied by TEM, SEM-EDX and XRD. The photocatalytic activity of both the WO{sub 3} and core/shell WO{sub 3}/TiO{sub 2} nanoparticles was studied by decomposing methyl orange in aqueous solution under UV light irradiation. Cyclic voltammetry measurements were performed on the composite PEDOT:PSS/WO{sub 3} thin films, and the coloring and bleaching states were studied.
Silica@layered double hydroxide core-shell hybrid materials.
Kwok, Wing L J; Crivoi, Dana-Georgiana; Chen, Chunping; Buffet, Jean-Charles; O'Hare, Dermot
2017-12-19
A series of silica@layered double hydroxides (SiO 2 @Mg 2 Al-CO 3 -AMO-LDHs) have been synthesised by in situ precipitation of Mg 2 Al-CO 3 -LDH at room temperature in the presence of amorphous spherical silica particles (∼500 nm). We have systematically investigated a number of synthetic parameters in order to evaluate their effects on the composition, morphological and physical properties of the isolated materials. Syntheses carried out at moderate stirring speeds (e.g. 500 rpm) were found to promote the formation of vertically aligned LDH platelets with respect to the silica surface. Addition rates of the metal solutions slower than 0.43 mmol h -1 were found to create a thicker LDH shell consisting of vertically aligned LDH platelets. When the metal solutions were added rapidly (0.86 mmol h -1 ), we observed that for both slow and fast stirring speeds the synthesised core-shell materials had thin LDH shells and the majority of the LDH precipitated independent of the silica, forming unbound "free" LDH.
Fang, Honghua; Balazs, Daniel M.; Protesescu, Loredana; Kovalenko, Maksym V.; Loi, Maria Antonietta
2015-01-01
Colloidal semiconductor quantum dots (QDs) are extraordinarily appealing for the development of cheap and large area solar cells due to high absorption efficiency; tunable bandgap energies; and solution processability. Understanding:and controlling electronic wave function delocalitation in QD thin
Vibrational analysis of submerged cylindrical shells based on elastic foundations
International Nuclear Information System (INIS)
Shah, A.G.; Naeem, M.N.
2014-01-01
In this study a vibration analysis was performed of an isotropic cylindrical shell submerged in fluid, resting on Winkler and Pasternak elastic foundations for simply supported boundary condition. Love's thin shell theory was exploited for strain- and curvature- displacement relationship. Shell problem was solved by using wave propagation approach. Influence of fluid and Winkler as well as Pasternak elastic foundations were studied on the natural frequencies of submerged isotropic cylindrical shells. Results were validated by comparing with the existing results in literature. Vibration, Submerged cylindrical shell, Love's thin shell theory, Wave propagation method, Winkler and Pasternak foundations. (author)
Quasi-spherical direct drive fusion.
Energy Technology Data Exchange (ETDEWEB)
VanDevender, J. Pace; Abbott, Lucas M.; Langston, William L.; McDaniel, Dillon Heirman; Nash, Thomas J.; Roderick, Norman Frederick; Silva, M.
2007-01-01
The authors present designs of quasi-spherical direction drive z-pinch loads for machines such as ZR at 28 MA load current with a 150 ns implosion time (QSDDI). A double shell system for ZR has produced a 2D simulated yield of 12 MJ, but the drive for this system on ZR has essentially no margin. A double shell system for a 56 MA driver at 150 ns implosion has produced a simulated yield of 130 MJ with considerable margin in attaining the necessary temperature and density-radius product for ignition. They also represent designs for a magnetically insulated current amplifier, (MICA), that modify the attainable ZR load current to 36 MA with a 28 ns rise time. The faster pulse provided by a MICA makes it possible to drive quasi-spherical single shell implosions (QSDD2). They present results from 1D LASNEX and 2D MACH2 simulations of promising low-adiabat cryogenic QSDD2 capsules and 1D LASNEX results of high-adiabat cryogenic QSDD2 capsules.
Hydrate Shell Growth Measured Using NMR.
Haber, Agnes; Akhfash, Masoumeh; Loh, Charles K; Aman, Zachary M; Fridjonsson, Einar O; May, Eric F; Johns, Michael L
2015-08-18
Benchtop nuclear magnetic resonance (NMR) pulsed field gradient (PFG) and relaxation measurements were used to monitor the clathrate hydrate shell growth occurring in water droplets dispersed in a continuous cyclopentane phase. These techniques allowed the growth of hydrate inside the opaque exterior shell to be monitored and, hence, information about the evolution of the shell's morphology to be deduced. NMR relaxation measurements were primarily used to monitor the hydrate shell growth kinetics, while PFG NMR diffusion experiments were used to determine the nominal droplet size distribution (DSD) of the unconverted water inside the shell core. A comparison of mean droplet sizes obtained directly via PFG NMR and independently deduced from relaxation measurements showed that the assumption of the shell model-a perfect spherical core of unconverted water-for these hydrate droplet systems is correct, but only after approximately 24 h of shell growth. Initially, hydrate growth is faster and heat-transfer-limited, leading to porous shells with surface areas larger than that of spheres with equivalent volumes. Subsequently, the hydrate growth rate becomes mass-transfer-limited, and the shells become thicker, spherical, and less porous.
Abnavi, Amin; Sadati Faramarzi, Mojtaba; Abdollahi, Ali; Ramzani, Reza; Ghasemi, Shahnaz; Sanaee, Zeinab
2017-06-01
Here, we report 3D hierarchical SnO2 nanowire (NW) core-amorphous silicon shell on free-standing carbon nanotube paper (SnO2@a-Si/CNT paper) as an effective anode for flexible lithium-ion battery (LIB) application. This binder-free electrode exhibits a high initial discharge capacity of 3020 mAh g-1 with a large reversible charge capacity of 1250 mAh g-1 at a current density of 250 mA g-1. Compared to other SnO2 NW or its core-shell nanostructured anodes, the fabricated SnO2@a-Si/CNT structure demonstrates an outstanding performance with high mass loading (˜5.9 mg cm-2), high areal capacity (˜5.2 mAh cm-2), and large volumetric capacity (˜1750 mAh cm-3) after 25 cycles. Due to the incorporation of CNT paper as the current collector, the weight and thickness of the total electrode is effectively reduced with respect to the conventional LIB anodes. The fabricated electrode has a total thickness of only 30 μm and considering the total weight of the electrode (active mass + current collector), an initial discharge/charge capacity of 2460/1018 mAh g-1 is obtained. Hence, this thin, lightweight and highly flexible structure is proposed as an excellent candidate for high-performance LIB anode materials, especially in flexible electronics.
Peeples, Steven
2015-01-01
A three degree of freedom (DOF) spherical actuator is proposed that will replace functions requiring three single DOF actuators in robotic manipulators providing space and weight savings while reducing the overall failure rate. Exploration satellites, Space Station payload manipulators, and rovers requiring pan, tilt, and rotate movements need an actuator for each function. Not only does each actuator introduce additional failure modes and require bulky mechanical gimbals, each contains many moving parts, decreasing mean time to failure. A conventional robotic manipulator is shown in figure 1. Spherical motors perform all three actuation functions, i.e., three DOF, with only one moving part. Given a standard three actuator system whose actuators have a given failure rate compared to a spherical motor with an equal failure rate, the three actuator system is three times as likely to fail over the latter. The Jet Propulsion Laboratory reliability studies of NASA robotic spacecraft have shown that mechanical hardware/mechanism failures are more frequent and more likely to significantly affect mission success than are electronic failures. Unfortunately, previously designed spherical motors have been unable to provide the performance needed by space missions. This inadequacy is also why they are unavailable commercially. An improved patentable spherically actuated motor (SAM) is proposed to provide the performance and versatility required by NASA missions.
Spherical geodesic mesh generation
Energy Technology Data Exchange (ETDEWEB)
Fung, Jimmy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kenamond, Mark Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burton, Donald E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Shashkov, Mikhail Jurievich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-02-27
In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.
Preparation and characteristics of core-shell structure cobalt/silica nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Fu Wuyou [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Yang Haibin [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China) and Henan Polytechnic University, Hennan Jiaozuo 454000 (China)]. E-mail: yanghb@jlu.edu.cn; Hari-Bala [College of Chemistry, Jilin University, Changchun 130023 (China); Liu Shikai [Henan Polytechnic University, Hennan Jiaozuo 454000 (China); Li, Minghui [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zou Guangtian [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)
2006-12-10
The silica nanolayer with different thickness was coated on the spherical cobalt nanoparticles (an average diameter of 67 nm) to form core-shell structure by the controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS). This coating process was based on the use of silane coupling agent 3-mercaptopropyltrimethoxysilane (HS-(CH{sub 2}){sub 3}Si(OCH{sub 3}){sub 3}, MPTS) as a primer to render the cobalt surface vitreophilic, thus rendering cobalt surface compatible with silica. The control over the silica coating layer thickness can be achieved by varying the reaction time. The cobalt nanoparticles and the cobalt coated with silica shell were confirmed by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. Result of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicate that the thermal stability of cobalt/silica is better than that of pure cobalt nanoparticles. Magnetic properties of these powders have been evaluated. These cobalt/silica core-shell nanoparticles can be utilized as precursors for making property-tunable magnetic nanoparticles, thin films, and multilayered core-shell structure nanocomposites.
Indentation of Ellipsoidal and Cylindrical Elastic Shells
Vella, Dominic
2012-10-01
Thin shells are found in nature at scales ranging from viruses to hens\\' eggs; the stiffness of such shells is essential for their function. We present the results of numerical simulations and theoretical analyses for the indentation of ellipsoidal and cylindrical elastic shells, considering both pressurized and unpressurized shells. We provide a theoretical foundation for the experimental findings of Lazarus etal. [following paper, Phys. Rev. Lett. 109, 144301 (2012)PRLTAO0031-9007] and for previous work inferring the turgor pressure of bacteria from measurements of their indentation stiffness; we also identify a new regime at large indentation. We show that the indentation stiffness of convex shells is dominated by either the mean or Gaussian curvature of the shell depending on the pressurization and indentation depth. Our results reveal how geometry rules the rigidity of shells. © 2012 American Physical Society.
Simulation of spatial distribution of absorbed laser energy in spherical microcapsules
Geints, Yu E.; Zemlyanov, A. A.; Panina, E. K.
2016-09-01
Specific features of optical field distribution in composite spherical particles consisting of a liquid core and nanocomposite absorbing shell are theoretically studied at different wavelengths of incident radiation. Using the numerical simulation it is shown that the thickness of the shell of the spherical microcapsule particle and its intrinsic absorption coefficient determine the character of the spatial distribution and the absorbed power. The variation of these parameters allows one to change the spatial position of efficient volume absorption regions and peak absorption values. This provides favourable conditions for opening the shells in appropriate spatial zones to release the contents of the microcapsules.
Neutron and proton shell closure in the superheavy region via ...
Indian Academy of Sciences (India)
... = 162, 172 and 184. Isotopic and isobaric mass parabolas are studied for various cluster emissions and minima of parabola indicate neutron shell closure at = 162, 184 and proton shell closure at = 114. Our study shows that 162 276 114 is the deformed doubly magic and 184 298 114 is the spherical doubly magic ...
Method of fabricating nested shells and resulting product
Henderson, Timothy M.; Kool, Lawrence B.
1982-01-01
A multiple shell structure and a method of manufacturing such structure wherein a hollow glass microsphere is surface treated in an organosilane solution so as to render the shell outer surface hydrophobic. The surface treated glass shell is then suspended in the oil phase of an oil-aqueous phase dispersion. The oil phase includes an organic film-forming monomer, a polymerization initiator and a blowing agent. A polymeric film forms at each phase boundary of the dispersion and is then expanded in a blowing operation so as to form an outer homogeneously integral monocellular substantially spherical thermoplastic shell encapsulating an inner glass shell of lesser diameter.
DEFF Research Database (Denmark)
Almegaard, Henrik
2004-01-01
A new statical and conceptual model for membrane shell structures - the stringer system - has been found. The principle was first published at the IASS conference in Copenhagen (OHL91), and later the theory has been further developed (ALMO3)(ALMO4). From the analysis of the stringer model it can...... be concluded that all membrane shells can be described by a limited number of basic configurations of which quite a few have free edges....
Borghi, Riccardo
2014-03-01
In the present letter, Newton’s theorem for the gravitational field outside a uniform spherical shell is considered. In particular, a purely geometric proof of proposition LXXI/theorem XXXI of Newton’s Principia, which is suitable for undergraduates and even skilled high-school students, is proposed. Minimal knowledge of elementary calculus and three-dimensional Euclidean geometry are required.
Zuo, Heng E.; Yao, Youwei; Chalifoux, Brandon D.; DeTienne, Michael D.; Heilmann, Ralf K.; Schattenburg, Mark L.
2017-08-01
Slumping (or thermal-shaping) of thin glass sheets onto high precision mandrels was used successfully by NASA Goddard Space Flight Center to fabricate the NuSTAR telescope. But this process requires long thermal cycles and produces mid-range spatial frequency errors due to the anti-stick mandrel coatings. Over the last few years, we have designed and tested non-contact horizontal slumping of round flat glass sheets floating on thin layers of nitrogen between porous air-bearings using fast position control algorithms and precise fiber sensing techniques during short thermal cycles. We recently built a finite element model with ADINA to simulate the viscoelastic behavior of glass during the slumping process. The model utilizes fluid-structure interaction (FSI) to understand the deformation and motion of glass under the influence of air flow. We showed that for the 2D axisymmetric model, experimental and numerical approaches have comparable results. We also investigated the impact of bearing permeability on the resulting shape of the wafers. A novel vertical slumping set-up is also under development to eliminate the undesirable influence of gravity. Progress towards generating mirrors for good angular resolution and low mid-range spatial frequency errors is reported.
Self-similar spherical metrics with tangential pressure
Gair, J R
2002-01-01
A family of spherically symmetric spacetimes is discussed, which have anisotropic pressure and possess a homothetic Killing vector. The spacetimes are composed of dust with a tangential pressure provided by angular momentum of the dust particles. The solution is given implicitly by an elliptic integral and depends on four arbitrary functions. These represent the initial configurations of angular momentum, mass, energy and position of the shells. The solution is derived by imposing self-similarity in the coordinates R, the shell label, and tau, the proper time experienced by the dust. Conditions for evolution without shell crossing and a description of singularity formation are given and types of solution discussed. General properties of the solutions are illustrated by reference to a particular case, which represents a universe that exists for an infinite time, but in which every shell expands and recollapses in a finite time.
International Nuclear Information System (INIS)
Hsieh, B.J.
1977-01-01
A rectilinear shell element formulated in the convected (co-rotational) coordinates is used to investigate the effects of edge conditions on the behaviors of thin shells of revolution under suddenly applied uniform loading. The equivalent generalized nodal forces under uniform loading are computed to the third order of the length of each element. A dynamic buckling load is defined as the load at which a great change in the response is observed for a small change in the loading. The problem studied is a shallow spherical cap. The cap is discretized into a finite number of elements. This discretization introduces some initial imperfections into the shell model. Nonetheless, the effect of this artificial imperfection is isolated from the effect of the edge conditions provided the same number of elements is used in all the cases. Four different edge conditions for the cap are used. These boundary conditions are fixed edge, hinged edge, roller edge and free edge. The apex displacement of the cap is taken as the measure for the response of the cap, and the dynamic buckling load is obtained by examining the response of the cap under different levels of loadings. Dynamic buckling loads can be found for all cases but for the free edge case. They are 0.28q for both fixed and hinged cases and 0.13 q for the roller case, where q is the classic static buckling load of a complete spherical shell with the same geometric dimensions and material properties. In the case of free edge, the motions of the cap are composed of mostly rigid body motion and small vibrations. The vibration of the cap is stable up to 1 q loading. The cap does snap through at higher loading. However, no loading can be clearly identified as buckling load
International Nuclear Information System (INIS)
Berg, S.; Semmes, P.B.; Nazarewicz, W.
1997-01-01
Various theoretical approaches to proton emission from spherical nuclei are investigated, and it is found that all the methods employed give very similar results. The calculated decay widths are found to be qualitatively insensitive to the parameters of the proton-nucleus potential, i.e., changing the potential parameters over a fairly large range typically changes the decay width by no more than a factor of ∼3. Proton half-lives of observed heavy proton emitters are, in general, well reproduced by spherical calculations with the spectroscopic factors calculated in the independent quasiparticle approximation. The quantitative agreement with experimental data obtained in our study requires that the parameters of the proton-nucleus potential be chosen carefully. It also suggests that deformed proton emitters will provide invaluable spectroscopic information on the angular momentum decomposition of single-proton orbitals in deformed nuclei. copyright 1997 The American Physical Society
Spherical rhenium metal powder
International Nuclear Information System (INIS)
Leonhardt, T.; Moore, N.; Hamister, M.
2001-01-01
The development of a high-density, spherical rhenium powder (SReP) possessing excellent flow characteristics has enabled the use of advanced processing techniques for the manufacture of rhenium components. The techniques that were investigated were vacuum plasma spraying (VPS), direct-hot isostatic pressing (D-HIP), and various other traditional powder metallurgy processing methods of forming rhenium powder into near-net shaped components. The principal disadvantages of standard rhenium metal powder (RMP) for advanced consolidation applications include: poor flow characteristics; high oxygen content; and low and varying packing densities. SReP will lower costs, reduce processing times, and improve yields when manufacturing powder metallurgy rhenium components. The results of the powder characterization of spherical rhenium powder and the consolidation of the SReP are further discussed. (author)
The Spherical Deformation Model
DEFF Research Database (Denmark)
Hobolth, Asgar
2003-01-01
Miller et al. (1994) describe a model for representing spatial objects with no obvious landmarks. Each object is represented by a global translation and a normal deformation of a sphere. The normal deformation is defined via the orthonormal spherical-harmonic basis. In this paper we analyse the s...... a single central section of the object. We use maximum-likelihood-based inference for this purpose and demonstrate the suggested methods on real data....
Teh, Chee Keng; Muaz, Siti Dalila; Tangaya, Praveena; Fong, Po-Yee; Ong, Ai Ling; Mayes, Sean; Chew, Fook Tim; Kulaveerasingam, Harikrishna; Appleton, David Ross
2017-01-01
The fundamental trait in selective breeding of oil palm (Eleais guineensis Jacq.) is the shell thickness surrounding the kernel. The monogenic shell thickness is inversely correlated to mesocarp thickness, where the crude palm oil accumulates. Commercial thin-shelled tenera derived from thick-shelled dura???shell-less pisifera generally contain 30% higher oil per bunch. Two mutations, sh MPOB (M1) and sh AVROS (M2) in the SHELL gene ? a type II MADS-box transcription factor mainly present in ...
Hung, Jenny; Kok, Mang Hin; Tam, Wing Yim
2009-01-01
We have fabricated spherical layer structures that exhibit complete photonic bandgaps in the visible range in dichromate gelatin emulsions by holographic interference. The complete bandgap was not a result of the high dielectric contrast but was due to the fact that the spherical layer structure was isotropic with equal spacing in all accessible directions. Angular dependence spectral measurements of the spherical layer structures were in good agreement with the expected results from an ideal structure of dielectric concentric spherical shells with equal spacing. Our fabrication technique and results could pave the way for new applications using complete bandgap photonic crystals.
Indian Academy of Sciences (India)
If the particles size is larger than the quasistatic limit, the Mie theory is applicable and higher multipole modes dom- .... electromagnetic fields are expressed in terms of a set of spherical vector basis functions such that each term in ... scattering modes, each of which has a contribution depending on the particle size. Higher-.
Indian Academy of Sciences (India)
nanoparticles the quasistatic approximation is not appropriate and Mie theory illustrates SPR due to dipole and quadrupole in extinction ... The time-dependent local density approximation (TDLDA) [19] .... satile technique for determining the optical properties of nanoshells or any other spherical particles of any dimension.
Foam shell project: Progress report
International Nuclear Information System (INIS)
Overturf, G.; Reibold, B.; Cook, B.; Schroen-Carey, D.
1994-01-01
The authors report on their work to produce a foam shell target for two possible applications: (1) as liquid-layered cryogenic target on Omega Upgrade, and (2) as a back-up design for the NIF. This target consists of a roughly 1 mm diameter and 100 μm thick spherical low-density foam shell surrounding a central void. The foam will be slightly overfilled with liquid D 2 or DT, the overfilled excess being symmetrically distributed on the inside of the shell and supported by thermal gradient techniques. The outside of the foam is overcoated with full density polymer which must be topologically smooth. The technology for manufacturing this style of foam shell involves microencapsulation techniques and has been developed by the Japanese at ILE. Their goal is to determine whether this technology can be successfully adapted to meet US ICF objectives. To this end a program of foam shell development has been initiated at LLNL in collaboration with both the General Atomics DOE Target Fabrication Contract Corporation and the Target Fabrication Group at LLE
Inertial waves in spherical shells at low Ekman numbers
Czech Academy of Sciences Publication Activity Database
Šimkanin, Ján; Hejda, Pavel; Jankovičová, Dana
2010-01-01
Roč. 54, č. 2 (2010), s. 291-298 ISSN 0039-3169 R&D Projects: GA AV ČR IAA300120704 Institutional research plan: CEZ:AV0Z30120515; CEZ:AV0Z30420517 Keywords : inertial waves * shear layers * Ekman layers * zonal flow s Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 1.123, year: 2010
Ocean Engineering Studies. Volume 5. Acrylic Windows. Spherical Shell Configurations
1991-01-01
with polishing of all surfaces and annealing at 1750F for 6 hours. Flanges for the windows were fabricated (figure 12) from st- el with a minimum yield...increase in radial apex displacement. The radial apex displacement becomes almost a step function just prior to plastico -elastic instability failure of...20,000 0 / 0 / 0.10 - ,, ,,/ ,0~/ ,oo El , ,--E implosion 2,000 4 ,000 5,000 8,000 PRESSURE (psi) Figure 15. -Iu.,ured Strain aid Displacement at the
G7 BiSpherical Acetabular Shell PMCF Study
2017-11-22
Rheumatoid Arthritis; Osteoarthritis; Noninflammatory Degenerative Joint Disease; Avascular Necrosis; Correction of Functional Deformity; Non-Union Fracture; Femoral Neck Fractures; Trochanteric Fractures
A Study of the Nearfield of an Excited Spherical Shell.
1980-03-17
advisor, for his constant inspiration throughout this work with his fresh enthusiasm; Professor Jiri Tichy , Professor Eugen J. Skudrzyk, Professor...Frequency Scattering by an Impenetrable Sphere," Annals of Physics 34, 23-95 (1965). 24. Franz , W., "Uber die Greeschen Funktionen des Zylinders und der Kugel
Probabilistic dynamic stability of a damped spherical shell ...
African Journals Online (AJOL)
Such stochastic and random characterizations of the dynamic load function confer some element of randomness on the normal displacement whose statistical mean we shall first seek for the determination of the dynamic buckling load . Lastly, the dynamic buckling load is determined via a suitable maximization and certain ...
Fundamentals of spherical array processing
Rafaely, Boaz
2015-01-01
This book provides a comprehensive introduction to the theory and practice of spherical microphone arrays. It is written for graduate students, researchers and engineers who work with spherical microphone arrays in a wide range of applications. The first two chapters provide the reader with the necessary mathematical and physical background, including an introduction to the spherical Fourier transform and the formulation of plane-wave sound fields in the spherical harmonic domain. The third chapter covers the theory of spatial sampling, employed when selecting the positions of microphones to sample sound pressure functions in space. Subsequent chapters present various spherical array configurations, including the popular rigid-sphere-based configuration. Beamforming (spatial filtering) in the spherical harmonics domain, including axis-symmetric beamforming, and the performance measures of directivity index and white noise gain are introduced, and a range of optimal beamformers for spherical arrays, includi...
Free vibration analysis of delaminated composite shells using different shell theories
International Nuclear Information System (INIS)
Nanda, Namita; Sahu, S.K.
2012-01-01
Free vibration response of laminated composite shells with delamination is presented using the finite element method based on first order shear deformation theory. The shell theory used is the extension of dynamic, shear deformable theory according to the Sanders' first approximation for doubly curved shells, which can be reduced to Love's and Donnell's theories by means of tracers. An eight-noded C 0 continuity, isoparametric quadrilateral element with five degrees of freedom per node is used in the formulation. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. The natural frequencies of the delaminated cylindrical (CYL), spherical (SPH) and hyperbolic paraboloid (HYP) shells are determined by using the above mentioned shell theories, namely Sanders', Love's, and Donnell's. The validity of the present approach is established by comparing the authors' results with those available in the literature. Additional studies on free vibration response of CYL, SPH and HYP shells are conducted to assess the effects of delamination size and number of layers considering all three shell theories. It is shown that shell theories according to Sanders and Love always predict practically identical frequencies. Donnell's theory gives reliable results only for shallow shells. Moreover, the natural frequency is found to be very sensitive to delamination size and number of layers in the shell.
Spherical fusion plasma-confinement field of Surmac type
Energy Technology Data Exchange (ETDEWEB)
Wipf, S.L.
1981-01-01
The concept of a Surmac confinement field that can be completely closed is presented. The internal conductor is magnetically suspended inside large corrugations of a superconducting spherical shell structure that carries the return current. Presently available superconductor technology using superfluid helium cooling allows fields above 1.5T throughout the wall region. Such a Surmac has potential for the study of advanced fuel cycles.
Ooi, Leslie C.-L.; Low, Eng-Ti L.; Abdullah, Meilina O.; Nookiah, Rajanaidu; Ting, Ngoot C.; Nagappan, Jayanthi; Manaf, Mohamad A. A.; Chan, Kuang-Lim; Halim, Mohd A.; Azizi, Norazah; Omar, Wahid; Murad, Abdul J.; Lakey, Nathan; Ordway, Jared M.; Favello, Anthony
2016-01-01
Oil palm (Elaeis guineensis) is the most productive oil bearing crop worldwide. It has three fruit forms, namely dura (thick-shelled), pisifera (shell-less) and tenera (thin-shelled), which are controlled by the SHELL gene. The fruit forms exhibit monogenic co-dominant inheritance, where tenera is a hybrid obtained by crossing maternal dura and paternal pisifera palms. Commercial palm oil production is based on planting thin-shelled tenera palms, which typically yield 30% more oil than dura p...
Magnetic actuation and transition shapes of a bistable spherical cap
Directory of Open Access Journals (Sweden)
E.G. Loukaides
2014-10-01
Full Text Available Multistable shells have been proposed for a variety of applications; however, their actuation is almost exclusively addressed through embedded piezoelectric patches. Additional actuation techniques are needed for applications requiring high strains or where remote actuation is desirable. Part of the reason for the lack of research in this area is the absence of appropriate models describing the detailed deformation and energetics of such shells. This work presents a bistable spherical cap made of iron carbonyl-infused polydimethylsiloxane. The magnetizable structure can be actuated remotely through permanent magnets while the transition is recorded with a high-speed camera. Moreover, the experiment is reproduced in a finite element (FE dynamic model for comparison with the physical observations. High-speed footage of the physical cap inversion together with the FE modeling gives valuable insight on preferable intermediate geometries. Both methods return similar values for the magnetic field strength required for the snap-through. High-strain multistable spherical cap transformation is demonstrated, based on informed material selection. We discover that non-axisymmetric transition shapes are preferred in intermediate geometries by bistable spherical caps. We develop the methods for design and analysis of such actuators, including the feasibility of remote actuation methods for multistable shells.
Spherical magnetic nanoparticles fabricated by laser target evaporation
Directory of Open Access Journals (Sweden)
A. P. Safronov
2013-05-01
Full Text Available Magnetic nanoparticles of iron oxide (MNPs were prepared by the laser target evaporation technique (LTE. The main focus was on the fabrication of de-aggregated spherical maghemite MNPs with a narrow size distribution and enhanced effective magnetization. X-ray diffraction, transmission electron microscopy, magnetization and microwave absorption measurements were comparatively analyzed. The shape of the MNPs (mean diameter of 9 nm was very close to being spherical. The lattice constant of the crystalline phase was substantially smaller than that of stoichiometric magnetite but larger than the lattice constant of maghemite. High value of Ms up to 300 K was established. The 300 K ferromagnetic resonance signal is a single line located at a field expected from spherical magnetic particles with negligible magnetic anisotropy. The maximum obtained concentration of water based ferrofluid was as high as 10g/l of magnetic material. In order to understand the temperature and field dependence of MNPs magnetization, we invoke the core-shell model. The nanoparticles is said to have a ferrimagnetic core (roughly 70 percent of the caliper size while the shell consists of surface layers in which the spins are frozen having no long range magnetic order. The core-shell interactions were estimated in frame of random anisotropy model. The obtained assembly of de-aggregated nanoparticles is an example of magnetic nanofluid stable under ambient conditions even without an electrostatic stabilizer.
Fabrication of Foam Shells for ICF Experiments
Czechowicz, D. G.; Acenas, O.; Flowers, J. S.; Nikroo, A.; Paguio, R. R.; Schroen, D. G.; Streit, J.; Takagi, M.
2004-11-01
The General Atomics/Schafer team has developed processes to fabricate foam shells targets suitable for ICF experiments. The two most common chemical systems used to produce foam shells have been resorcinol-formaldehyde (R/F) aerogel and divinylbenzene (DVB). Spherical targets have been made in the form of shells and beads having diameters ranging from approximately 0.5 mm to 4.0 mm, and having densities from approximately 100 mg/cc to 250 mg/cc. The work on R/F foam shells has been concentrated on 1) shell fabrication process improvement to obtain high yields ( ˜25%) and 2) depositing a reliable permeation barrier to provide shells for ongoing direct drive experiments at LLE. Development of divinylbenzene foam shells has been mainly directed towards Inertial Fusion Energy applications (at densities as low as 30 mg/cc) and recently for shells for experiments at LLE. Details of the relevant metrology and properties of these foams as well as the range of targets currently available will be discussed.
Strength Calculation of Locally Loaded Orthotropic Shells
Directory of Open Access Journals (Sweden)
Yu. I. Vinogradov
2015-01-01
Full Text Available The article studies laminated orthotropic cylindrical, conic, spherical, and toroidal shells, which are often locally loaded in the aircraft designs over small areas of their surfaces.The aim of this work is to determine stress concentration in shells versus structure of orthotropic composite material, shell form and parameters, forms of loading areas, which borders do not coincide with lines of main curvatures of shells. For this purpose, an analytical computing algorithm to estimate strength of shells in terms of stress is developed. It enables us to have solution results of the boundary value problem with a controlled error. To solve differential equations an analytical method is used. An algorithm of the boundary value problem solution is multiplicative.The main results of researches are graphs of stress concentration in the orthotropic shells versus their parameters and areas of loading lineated by circles and ellipses.Among the other works aimed at determination of stress concentration in shells, the place of this one is defined by the analytical solution of applied problems for strength estimation in terms of shell stresses of classical forms.The developed effective analytical algorithm to solve the boundary value problem and received results are useful in research and development.
Rayleigh-Taylor instability in multi-structured spherical targets
International Nuclear Information System (INIS)
Gupta, N.K.; Lawande, S.V.
1986-01-01
An eigenvalue equation for the exponential growth rate of the Rayleigh-Taylor instability is derived in spherical geometry. The free surface and jump boundary conditions are obtained from the eigenvalue equation. The eigenvalue equation is solved in the cases where the initial fluid density profile has a step function or exponential variation in space and analytical formulae for growth rate of the instability are obtained. The solutions for the step function are generalized for any number N of spherical zones forming an arbitrary fluid density profile. The results of the numerical calculations for N spherical zones are compared with the exact analytical results for exponential fluid density profile with N=10 and a good agreement is observed. The formalism is further used to study the effects of density gradients on Rayleigh-Taylor instability in spherical geometry. Also analytical formulae are presented for a particular case of N=3 and shell targets. The formalism developed here can be used to study the growth of the instability in present day multi-structured shell targets. (author)
Restricted Three-Body Dynamics and Morphologies of Early Novae Shells and their Spectral Signatures
Lynch, D. K.; Mazuk, S.; Campbell, E.; Venturini, C. C.
2003-08-01
The goal of this work is to calculate emission line profiles of classical novae systems for comparison to line profiles we observe in an attempt to deduce geometrical and dynamical properties of the system from the spectra. The material ejected by the thermonuclear runaway on the surface of the white dwarf (WD) is modeled as a large number of massless particles that are launched instantaneously and move ballistically thereafter. Each particle's position is propagated independently in three-dimensional space with a particle's track terminating if it impacts the WD or the secondary. Predicted line profiles, assuming an optically thin shell, are generated by computing a histogram of the number of particles in radial velocity space for a given observing projection. At high ejection velocities, a nearly spherical shell is produced. At ejection speeds near the WD's escape velocity, very complicated and ever changing geometries result and the material remains close to the system's barycenter. We present animations of computer simulations of novae shell development and the associated line profiles. This work supported by The Aerospace Corporation's Independent Research and Development program and by the US Air Force Space and Missile Systems Center through the Mission Oriented Investigation and Experimentation program, under contract F4701-00-C-0009 with the US Air Force.
Nuclear structure investigations on spherical nuclei
International Nuclear Information System (INIS)
Heisenberg, J.; Calarco, J.; Dawson, J.; Hersman, F.W.
1989-09-01
This report discusses the following topics: electron scattering studies on spherical nuclei; electron scattering from collective states in deformed nuclei; proton and pion scattering studies; 12 C(e,e'p) and 16 O(e,e'p); 12 C(e,e'α) and 16 O(e,e'α); studies at high q at Bates; measurements with rvec e at Bates; 12 C(γ,p); future directions in giant resonance studies; proton knockout from 16 O; quasielastic studies at Bates; triple coincidence studies of nuclear correlations; contributions to (e,e'2p) at KIKHEF; contributions to instrumentation at CEBAF; instrumentation development at UNH; the Bates large acceptance spectrometer toroid; shell model and core polarization calculations; and the relativistic nuclear model
Spherical tokamak development in Brazil
International Nuclear Information System (INIS)
Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes
2003-01-01
The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Spherical tokamak development in Brazil
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] (and others)
2003-07-01
The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
The ETE spherical Tokamak project
International Nuclear Information System (INIS)
Ludwig, Gerson Otto; Andrade, Maria Celia Ramos de; Barbosa, Luis Filipe Wiltgen
1999-01-01
This paper describes the general characteristics of spherical tokamaks, with a brief overview of work in the area of spherical torus already performed or in progress at several institutions. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and status of construction in September, 1998 at the Associated plasma Laboratory (LAP) of the National Institute for Space Research (INPE) in Brazil. (author)
The ETE spherical Tokamak project
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto; Andrade, Maria Celia Ramos de; Barbosa, Luis Filipe Wiltgen [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] [and others]. E-mail: ludwig@plasma.inpe.br
1999-07-01
This paper describes the general characteristics of spherical tokamaks, with a brief overview of work in the area of spherical torus already performed or in progress at several institutions. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and status of construction in September, 1998 at the Associated plasma Laboratory (LAP) of the National Institute for Space Research (INPE) in Brazil. (author)
Spherical grating spectrometers
O'Donoghue, Darragh; Clemens, J. Christopher
2014-07-01
We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.
Roy, Kenneth I.; Kennedy, Robert G., III; Fields, David E.
2013-02-01
The traditional concept of terraforming assumes ready availability of candidate planets with acceptable qualities: orbiting a star in its "Goldilocks zone", liquid water, enough mass, years longer than days, magnetic field, etc. But even stipulating affordable interstellar travel, we still might never find a good candidate elsewhere. Whatever we found likely would require centuries of heavy terraforming, just as Mars or Venus would here. Our increasing appreciation of the ubiquity of life suggests that any terra nova would already possess it. We would then face the dilemma of introducing alien life forms (us, our microbes) into another living world. Instead, we propose a novel method to create habitable environments for humanity by enclosing airless, sterile, otherwise useless planets, moons, and even large asteroids within engineered shells, which avoids the conundrum. These shells are subject to two opposing internal stresses: compression due to the primary's gravity, and tension from atmospheric pressure contained inside. By careful design, these two cancel each other resulting in zero net shell stress. Beneath the shell an Earth-like environment could be created similar in almost all respects to that of Home, except for gravity, regardless of the distance to the sun or other star. Englobing a small planet, moon, or even a dwarf planet like Ceres, would require astronomical amounts of material (quadrillions of tons) and energy, plus a great deal of time. It would be a quantum leap in difficulty over building Dyson Dots or industrializing our solar system, perhaps comparable to a mission across interstellar space with a living crew within their lifetime. But when accomplished, these constructs would be complete (albeit small) worlds, not merely large habitats. They could be stable across historic timescales, possibly geologic. Each would contain a full, self-sustaining ecology, which might evolve in curious directions over time. This has interesting implications
Effect of multiple resistive shells on the dynamics of the slinky mode in RFP plasmas
Guo, S. C.; Chu, M. S.
2002-11-01
The effects of multiple resistive shells and transient electromagnetic torque on the dynamics of mode locking in the RFP plasmas are studied. We study the EM torque acting on the tearing modes produced by a system of resistive shells. These shells may consist of several nested thin shells or several thin shells enclosed within a thick shell. Both the steady state theory and the time dependent theory are developed. The steady state theory is shown to provide accurate account of the resultant EM torque if (dω/dt)ω-2 slinky mode and its dynamics in the presence of resistive walls are discussed.
Isogeometric shell formulation based on a classical shell model
Niemi, Antti
2012-09-04
This paper constitutes the first steps in our work concerning isogeometric shell analysis. An isogeometric shell model of the Reissner-Mindlin type is introduced and a study of its accuracy in the classical pinched cylinder benchmark problem presented. In contrast to earlier works [1,2,3,4], the formulation is based on a shell model where the displacement, strain and stress fields are defined in terms of a curvilinear coordinate system arising from the NURBS description of the shell middle surface. The isogeometric shell formulation is implemented using the PetIGA and igakit software packages developed by the authors. The igakit package is a Python package used to generate NURBS representations of geometries that can be utilised by the PetIGA finite element framework. The latter utilises data structures and routines of the portable, extensible toolkit for scientific computation (PETSc), [5,6]. The current shell implementation is valid for static, linear problems only, but the software package is well suited for future extensions to geometrically and materially nonlinear regime as well as to dynamic problems. The accuracy of the approach in the pinched cylinder benchmark problem and present comparisons against the h-version of the finite element method with bilinear elements. Quadratic, cubic and quartic NURBS discretizations are compared against the isoparametric bilinear discretization introduced in [7]. The results show that the quadratic and cubic NURBS approximations exhibit notably slower convergence under uniform mesh refinement as the thickness decreases but the quartic approximation converges relatively quickly within the standard variational framework. The authors future work is concerned with building an isogeometric finite element method for modelling nonlinear structural response of thin-walled shells undergoing large rigid-body motions. The aim is to use the model in a aeroelastic framework for the simulation of flapping wings.
Tidal deformation of Enceladus' ice shell with variable thickness and Maxwell rheology
Soucek, Ondrej; Behounkova, Marie; Cadek, Ondrej; Tobie, Gabriel; Choblet, Gael
2017-04-01
Tidal deformation of icy moons has been traditionally studied using the spectral approach which is very efficient for perfectly spherical bodies with radially dependent rheological structure. Measurements of Enceladus' topography (Nimmo et al., 2011) and low-degree gravity (Iess et al., 2014) indicate that the ice shell is significantly thinned in the southern hemisphere (Iess et al., 2014; McKinnon, 2015) and according to recent gravity, shape and libration inversion, it may be only a few kilometers thick at the south pole (Cadek et al., 2016). These variations may potentially have a significant effect on the amplitude and pattern of tidal deformation, stress and associated heating inside the shell, but cannot be straightforwardly incorporated into the existing spectral codes. In order to circumvent this difficulty and to quantify the effects of ice-shell thickness variations, we have developed a three-dimensional finite element code in the framework of FEniCS package (Alnaes et al., 2015). Using this numerical tool, we address the changes in tidally-induced deformation amplitude, stresses and tidal heating for structural models of Enceladus' ice shell of various complexity. Considering Maxwell viscoelastic rheology of the shell, we compare models with uniform thickness consistent with the libration data and with constant viscosity, synthetic models with analytically parameterized thinning in the south polar region and depth-dependent viscosity varying over several orders of magnitude, and finally, models with the shell topography and thickness based on the recent model of Cadek et al. (2016). We find that the thinning of the ice shell around the south pole may lead to amplification of the stress and displacement in this region region by a factor of up to 2 and 4, respectively, depending on the average ice shell thickness, the amplitude of thinning and the viscosity structure. Our results also suggest that lateral variations of ice thickness can induce significant
Miniaturization of Spherical Magnetodielectric Antennas
DEFF Research Database (Denmark)
Hansen, Troels Vejle
; Arbitrary order of the spherical wave, arbitrary radius of the spherical antenna, as well as arbitrarily large core permeability and/or permittivity, given an inversely proportional frequency variation of the imaginary part(s) and an arbitrary dispersion of the real part(s) - thus describing both lossless...
Adiabatic Quasi-Spherical Compressions Driven by Magnetic Pressure for Inertial Confinement Fusion
International Nuclear Information System (INIS)
Nash, Thomas J.
2000-01-01
The magnetic implosion of a high-Z quasi-spherical shell filled with DT fuel by the 20-MA Z accelerator can heat the fuel to near-ignition temperature. The attainable implosion velocity on Z, 13-cm/micros, is fast enough that thermal losses from the fuel to the shell are small. The high-Z shell traps radiation losses from the fuel, and the fuel reaches a high enough density to reabsorb the trapped radiation. The implosion is then nearly adiabatic. In this case the temperature of the fuel increases as the square of the convergence. The initial temperature of the fuel is set by the heating of an ion acoustic wave to be about 200-eV after a convergence of 4. To reach the ignition temperature of 5-keV an additional convergence of 5 is required. The implosion dynamics of the quasi-spherical implosion is modeled with the 2-D radiation hydrodynamic code LASNEX. LASNEX shows an 8-mm diameter quasi-spherical tungsten shell on Z driving 6-atmospheres of DT fuel nearly to ignition at 3.5-keV with a convergence of 20. The convergence is limited by mass flow along the surface of the quasi-spherical shell. With a convergence of 20 the final spot size is 400-microm in diameter
Simulation of the stress computation in shells
Salama, M.; Utku, S.
1978-01-01
A self-teaching computer program is described, whereby the stresses in thin shells can be computed with good accuracy using the best fit approach. The program is designed for use in interactive game mode to allow the structural engineer to learn about (1) the major sources of difficulties and associated errors in the computation of stresses in thin shells, (2) possible ways to reduce the errors, and (3) trade-off between computational cost and accuracy. Included are derivation of the computational approach, program description, and several examples illustrating the program usage.
Analysis of anisotropic shells containing flowing fluid
International Nuclear Information System (INIS)
Lakis, A.A.
1983-01-01
A general theory for the dynamic analysis of anisotropic thin cylindrical shells containing flowing fluid is presented. The shell may be uniform or non-uniform, provided it is geometrically axially symmetric. This is a finite- element theory, using cylindrical finite elements, but the displacement functions are determined by using classical shell theory. A new solution of the wave equation of the liquid finite element leads to an expression of the fluid pressure, p, as a function of the nodal displacements of the element and three operative forces (inertia, centrifugal and Coriolis) of the moving fluid. (Author) [pt
Audet, Pascal
2014-01-01
consistent manner, the expressions for the admittance and coherency from flexural equations for the loading of thin elastic plates and shells and show that they result in similar spectra, except at the longest wavelengths where the shell membrane stresses dominate. We then estimate global grids of Earth's continentalTe by inverting the planar and spherical admittance and coherency functions, both separately and jointly, using either free air or Bouguer gravity anomalies. The correspondence between the Cartesian and spherical approaches and the similarity of Te results for the Earth's continents indicate that the spherical methods are robust. Results obtained from the joint inversion of admittance and coherency show that simple lithospheric loading models fail to capture the complexity of the data, with adverse effects on the estimated parameters. Finally, we extend the analysis to the Moon and other terrestrial planets and discuss limitations and future applications of the fully spherical techniques.
Design steel spherical tank height H = 44m according to Eurocode
Directory of Open Access Journals (Sweden)
Bešević Miroslav T.
2016-01-01
Full Text Available This paper presents the design of the steel water tower with spherical water tank height H = 44m. Spherical tank is located at the top of the steel tubular column, with diameter F = 128cm. The construction of the water tower was modeled using the ABAQUS software package, to give a realistic picture of the stress-strain states in all points of the tank shell and the tubular column. Analysis of the load of construction was carried out based on European standards, with special attention to the influence of the earthquake on the spherical tank.
Metal shell technology based upon hollow jet instability
International Nuclear Information System (INIS)
Kendall, J.M.; Lee, M.C.; Wang, T.G.
1982-01-01
Spherical shells of submillimeter size are sought as ICF targets. Such shells must be dimensionally precise, smooth, of high strength, and composed of a high atomic number material. We describe a technology for the production of shells based upon the hydrodynamic instability of an annular jet of molten metal. We have produced shells in the 0.7--2.0 mm size range using tin as a test material. Specimens exhibit good sphericity, fair concentricity, and excellent finish over most of the surface. Work involving a gold--lead--antimony alloy is in progress. Droplets of this are amorphous and possess superior surface finish. The flow of tin models that of the alloy well; experiments on both metals show that the technique holds considerable promise
Preparation of hollow shell ICF targets using a depolymerizing model
International Nuclear Information System (INIS)
Letts, S.A.; Fearon, E.M.; Buckley, S.R.
1994-11-01
A new technique for producing hollow shell laser fusion capsules was developed that starts with a depolymerizable mandrel. In this technique we use poly(alpha-methylstyrene) (PAMS) beads or shells as mandrels which are overcoated with plasma polymer. The PAMS mandrel is thermally depolymerized to gas phase monomer, which diffuses through the permeable and thermally more stable plasma polymer coating, leaving a hollow shell. We have developed methods for controlling the size of the PAMS mandrel by either grinding to make smaller sizes or melt sintering to form larger mandrels. Sphericity and surface finish are improved by heating the PAMS mandrels in hot water using a surfactant to prevent aggregation. Using this technique we have made shells from 200 μm to 5 mm diameter with 15 to 100 μm wall thickness having sphericity better than 2 μm and surface finish better than 10 nm RMS
International Nuclear Information System (INIS)
Borghi, Riccardo
2014-01-01
In the present letter, Newton’s theorem for the gravitational field outside a uniform spherical shell is considered. In particular, a purely geometric proof of proposition LXXI/theorem XXXI of Newton’s Principia, which is suitable for undergraduates and even skilled high-school students, is proposed. Minimal knowledge of elementary calculus and three-dimensional Euclidean geometry are required. (letters and comments)
static analysis of circular cylindrical shell under hydrostatic and ring ...
African Journals Online (AJOL)
DEPT OF AGRICULTURAL ENGINEERING
University of Nigeria, Nsukka. ABSTRACT. Analysis of circular cylindrical shell under the action of hydrostatic and stiffening ring forces is ... The economy or feasibility of many modern constructions necessitates lightweight, thin- ... concerned with the analysis of circular cylindri- cal shell subjected to hydrostatic pressure in.
Sinusoidal velaroidal shell – numerical modelling of the nonlinear ...
African Journals Online (AJOL)
Many works are devoted to linear and nonlinear analyses of shells of classical form. But for thin shells of complex geometry, many things remained to do. Four different sources of nonlinearity exist in solid mechanics. The geometric nonlinearity, the material nonlinearity, the kinetic nonlinearity and the force nonlinearity.
JUST: Joint Upgraded Spherical Tokamak
International Nuclear Information System (INIS)
Azizov, E.A.; Dvorkin, N.Ya.; Filatov, O.G.
1997-01-01
The main goals, ideas and the programme of JUST, spherical tokamak (ST) for the plasma burn investigation, are presented. The place and prospects of JUST in thermonuclear investigations are discussed. (author)
Spherical Primary Optical Telescope Testbed
National Aeronautics and Space Administration — This IRAD proposes to continue operation of the Spherical Primary Optical Telescope (SPOT) testbed as an image-based wavefront sensing demonstrator. In addition to...
Optical absorption of carbon-gold core-shell nanoparticles
Wang, Zhaolong; Quan, Xiaojun; Zhang, Zhuomin; Cheng, Ping
2018-01-01
In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.
Micromagnetic studies of three-dimensional pyramidal shell structures
International Nuclear Information System (INIS)
Knittel, A; Franchin, M; Fischbacher, T; Fangohr, H; Nasirpouri, F; Bending, S J
2010-01-01
We present a systematic numerical analysis of the magnetic properties of pyramidal-shaped core-shell structures in a size range below 400 nm. These are three-dimensional structures consisting of a ferromagnetic shell which is grown on top of a non-magnetic core. The standard micromagnetic model without the magnetocrystalline anisotropy term is used to describe the properties of the shell. We vary the thickness of the shell between the limiting cases of an ultra-thin shell and a conventional pyramid and delineate different stable magnetic configurations. We find different kinds of single-domain states, which predominantly occur at smaller system sizes. In analogy to equivalent states in thin square films we term these onion, flower, C and S states. At larger system sizes, we also observe two types of vortex states, which we refer to as symmetric and asymmetric vortex states. For a classification of the observed states, we derive a phase diagram that specifies the magnetic ground state as a function of structure size and shell thickness. The transitions between different ground states can be understood qualitatively. We address the issue of metastability by investigating the stability of all occurring configurations for different shell thicknesses. For selected geometries and directions hysteresis measurements are analysed and discussed. We observe that the magnetic behaviour changes distinctively in the limit of ultra-thin shells. The study has been motivated by the recent progress made in the growth of faceted core-shell structures.
Spherical tokamak development in Brazil
Energy Technology Data Exchange (ETDEWEB)
Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma; Barbosa, L.F.W. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil). Faculdade de Engenharia, Arquitetura e Urbanismo; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Div. de Mecanica Espacial e Controle; The high-power microwave sources group
2003-12-01
This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Spherical tokamak development in Brazil
International Nuclear Information System (INIS)
Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J.; Barbosa, L.F.W.; Patire Junior, H.; The high-power microwave sources group
2003-01-01
This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Conical shell edge disturbance : An engineer's derivation
Blaauwendraad, J.; Hoefakker, JH
2016-01-01
Because a rigorous bending theory for thin shells of revolution is complicated, attempts have been made for reliable approximations of the edge disturbance problem under axisymmetric loading. A well-known one was published by Geckeler [1, 2], who obtained his approximation by mathematical
Anticavitation and Differential Growth in Elastic Shells
Moulton, Derek E.
2010-07-22
Elastic anticavitation is the phenomenon of a void in an elastic solid collapsing on itself. Under the action of mechanical loading alone typical materials do not admit anticavitation. We study the possibility of anticavitation as a consequence of an imposed differential growth. Working in the geometry of a spherical shell, we seek radial growth functions which cause the shell to deform to a solid sphere. It is shown, surprisingly, that most material models do not admit full anticavitation, even when infinite growth or resorption is imposed at the inner surface of the shell. However, void collapse can occur in a limiting sense when radial and circumferential growth are properly balanced. Growth functions which diverge or vanish at a point arise naturally in a cumulative growth process. © 2010 Springer Science+Business Media B.V.
Rodríguez-Dorado, Rosalia; Landín, Mariana; Altai, Ayça; Russo, Paola; Aquino, Rita P; Del Gaudio, Pasquale
2018-03-01
Numerous studies have been focused on hydrophobic compounds encapsulation as oils. In fact, oils can provide numerous health benefits as synergic ingredient combined with other hydrophobic active ingredients. However, stable microparticles for pharmaceutical purposes are difficult to achieve when commonly techniques are used. In this work, sunflower oil was encapsulated in calcium-alginate capsules by prilling technique in co-axial configuration. Core-shell beads were produced by inverse gelation directly at the nozzle using a w/o emulsion containing aqueous calcium chloride solution in sunflower oil pumped through the inner nozzle while an aqueous alginate solution, coming out from the annular nozzle, produced the beads shell. To optimize process parameters artificial intelligence tools were proposed to optimize the numerous prilling process variables. Homogeneous and spherical microcapsules with narrow size distribution and a thin alginate shell were obtained when the parameters as w/o constituents, polymer concentrations, flow rates and frequency of vibration were optimized by two commercial software, FormRules® and INForm®, which implement neurofuzzy logic and Artificial Neural Networks together with genetic algorithms, respectively. This technique constitutes an innovative approach for hydrophobic compounds microencapsulation. Copyright © 2018 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Salvatore Brischetto
2014-01-01
equilibrium written in orthogonal curvilinear coordinates for the free vibrations of simply supported structures. These equations consider an exact geometry for shells without simplifications. The main novelty is the possibility of a general formulation for different geometries. The equations written in general orthogonal curvilinear coordinates allow the analysis of spherical shell panels and they automatically degenerate into cylindrical shell panel, cylindrical closed shell, and plate cases. Results are proposed for isotropic and orthotropic structures. An exhaustive overview is given of the vibration modes for a number of thickness ratios, imposed wave numbers, geometries, embedded materials, and angles of orthotropy. These results can also be used as reference solutions to validate two-dimensional models for plates and shells in both analytical and numerical form (e.g., closed solutions, finite element method, differential quadrature method, and global collocation method.
Tasker, Alison L; Hitchcock, James; Baxter, Elaine A; Cayre, Dr Olivier J; Biggs, Simon
2017-07-04
Polymer microcapsules have been used commercially for decades, however they have an inherent flaw which renders them impractical as a carrier of small, volatile molecules. The porous nature of the polymer shell allows for diffusion of the encapsulated molecules into the bulk. The use of metal shells is an innovative way to prevent undesired loss of small molecules from the core of microcapsules, however it is important, particularly when using expensive metals to ensure that the resulting shell is as thin as possible. Here we investigate the fundamental mechanisms controlling the gold shell thickness when a fragrance oil is encapsulated in a poly(methyl methacrylate) shell. We consider the distribution of the nanoparticles on the capsule surface, and from quantification of the adsorbed nanoparticle (NP) density and resulting shell thickness, we propose mechanisms to describe the gold shell growth for systems with high and low NP surface coverage. We suggest from our observations that the gold grows to fill in the gaps between NPs. At low NP concentrations, thicker metal shells form. We postulate that this is due to the low NP density on the surface, forcing the gold clusters to grow larger before they meet the adjacent ones. Thus, to grow the thinnest possible shells a densely packed monolayer of platinum nanoparticles is required on the capsule surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
A direct approach to nonlinear shells with application to surface-substrate interactions
Šilhavý, M. (Miroslav)
2013-01-01
International audience; he paper develops a direct, intrinsic approach to the equilibrium equations of bodies coated by a thin film with a nonlinear shell like structure. The forms of the equations in the reference and actual configurations are considered. The equations are shown to coincide with those obtained by using coordinate systems on the film or on the thin shell.
Shielding of electromagnetic fields of current sources by spherical enclosures
Shastry, S. V. K.; Rao, M. N.; Katti, V. R.
Expressions for the shielding effectiveness of a conductive spherical enclosure excited by a Hertzian dipole have been derived using the dyadic Green's function technique. This technique has the advantage that the fields inside or outside the enclosure due to arbitrary current distribution may be found by employing the same set of dyadic Green's functions. The shielding effectiveness for plane wave incidence has been determined by considering the limiting case of the current source external to the spherical shell. Computed values of shielding effectiveness deduced in this manner have been compared with those obtained by the numerical evaluation of the expressions derived by earlier authors. The theory presented here may be useful to EMC (electromagnetic compatibility) engineers who must consider electromagnetic coupling from current sources in the vicinity of shielding enclosures.
Directory of Open Access Journals (Sweden)
Woo-Young Jung
2015-04-01
Full Text Available For the solution of geometrically nonlinear analysis of plates and shells, the formulation of a nonlinear nine-node refined first-order shear deformable element-based Lagrangian shell element is presented. Natural co-ordinate-based higher order transverse shear strains are used in present shell element. Using the assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. Furthermore, a refined first-order shear deformation theory for thin and thick shells, which results in parabolic through-thickness distribution of the transverse shear strains from the formulation based on the third-order shear deformation theory, is proposed. This formulation eliminates the need for shear correction factors in the first-order theory. To avoid difficulties resulting from large increments of the rotations, a scheme of attached reference system is used for the expression of rotations of shell normal. Numerical examples demonstrate that the present element behaves reasonably satisfactorily either for the linear or for geometrically nonlinear analysis of thin and thick plates and shells with large displacement but small strain. Especially, the nonlinear results of slit annular plates with various loads provided the benchmark to test the accuracy of related numerical solutions.
Some engineering properties of shelled and kernel tea ( Camellia ...
African Journals Online (AJOL)
Some engineering properties (size dimensions, sphericity, volume, bulk and true densities, friction coefficient, colour characteristics and mechanical behaviour as rupture ... The static coefficients of friction of shelled and kernel tea seeds for the large and small sizes higher values for rubber than the other friction surfaces.
Hilburger, Mark W.; Starnes, James H., Jr.
2004-01-01
The results of an experimental and numerical study of the effects of initial imperfections on the buckling response and failure of unstiffened thin-walled compression-loaded graphite-epoxy cylindrical shells are presented. The shells considered in the study have six different orthotropic or quasi-isotropic shell-wall laminates and two different shell-radius-to-thickness ratios. The numerical results include the effects of geometric shell-wall mid-surface imperfections, shell-wall thickness variations, local shell-wall ply-gaps associated with the fabrication process, shell-end geometric imperfections, nonuniform end loads, and the effects of elastic boundary conditions. Selected cylinder parameter uncertainties were also considered. Results that illustrate the effects of imperfections and uncertainties on the nonlinear response characteristics, buckling loads and failure the shells are presented. In addition, a common failure analysis is used to predict material failures in the shells.
Axisymmetric vibrations of thick shells of revolution
International Nuclear Information System (INIS)
Suzuki, Katsuyoshi; Kosawada, Tadashi; Takahashi, Shin
1983-01-01
Axisymmetric shells of revolution are used for chemical plants, nuclear power plants, aircrafts, structures and so on, and the elucidation of their free vibration is important for the design. In this study, the axisymmetric vibration of a barrel-shaped shell was analyzed by the modified thick shell theory. The Lagrangian during one period of the vibration of a shell of revolution was determined, and from its stopping condition, the vibration equations and the boundary conditions were derived. The vibration equations were analyzed strictly by using the series solution. Moreover, the basic equations for the strain of a shell and others were based on those of Love. As the examples of numerical calculation, the natural frequency and vibration mode of the symmetrical shells of revolution fixed at both ends and supported at both ends were determined, and their characteristics were clarified. By comparing the results of this study with the results by thin shell theory, the effects of shearing deformation and rotary inertia on the natural frequency and vibration mode were clarified. The theoretical analysis and the numerical calculation are described. The effects of shearing deformation and rotary inertia on the natural frequency became larger in the higher order vibration. The vibration mode did not much change in both theories. (Kako, I.)
Spherical Demons: Fast Surface Registration
Yeo, B.T. Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina
2009-01-01
We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast – registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces. PMID:18979813
Gravitational collapse of a cylindrical null shell in vacuum
Directory of Open Access Journals (Sweden)
S. Khakshournia
2008-03-01
Full Text Available Barrabès-Israel null shell formalism is used to study the gravitational collapse of a thin cylindrical null shell in vacuum. In general the lightlike matter shell whose history coincides with a null hypersurface is characterized by a surface energy density. In addition, a gravitational impulsive wave is present on this null hypersurface whose generators admit both the shear and expansion. In the case of imposing the cylindrical flatness the surface energy-momentum tensor of the matter shell on the null hypersurface vanishes and the null hyper- surface is just the history of the gravitational wave .
Spherical agglomeration of acetylsalicylic acid
Directory of Open Access Journals (Sweden)
Polowczyk Izabela
2016-01-01
Full Text Available In this paper spherical agglomeration of acetylsalicylic acid was described. In the first step, the system of good and poor solvents as well as bridging liquid was selected. As a result of a preliminary study, ethyl alcohol, water and carbon tetrachloride were used as the good solvent, poor one, and bridging liquid, respectively. Then, the amount of acetylsalicylic acid and the ratio of the solvents as well as the volume of the bridging liquid were examined. In the last step, the agglomeration conditions, such as mixing intensity and time, were investigated. The spherical agglomerates obtained under optimum conditions could be subjected to a tableting process afterwards.
Jin, Congrui; Davoodabadi, Ali; Li, Jianlin; Wang, Yanli; Singler, Timothy
2017-03-01
Due to the development of novel micro-fabrication techniques to produce ultra-thin materials and increasing interest in thin biological membranes, in recent years, the mechanical characterization of thin films has received a significant amount of attention. To provide a more accurate solution for the relationship among contact radius, load and deflection, the fundamental and widely applicable problem of spherical indentation of a freestanding circular membrane have been revisited. The work presented here significantly extends the previous contributions by providing an exact analytical solution to the governing equations of Föppl-Hecky membrane indented by a frictionless spherical indenter. In this study, experiments of spherical indentation has been performed, and the exact analytical solution presented in this paper is compared against experimental data from existing literature as well as our own experimental results.
CSIR Research Space (South Africa)
Jule, L
2015-07-01
Full Text Available We investigate light scattering by core–shell consisting of metal/dielectric composites considering spherical and cylindrical nanoinclusions, within the framework of the conventional Rayleigh approximation. By writing the electric potential...
Ground state instabilities of protein shells are eliminated by buckling.
Singh, Amit R; Perotti, Luigi E; Bruinsma, Robijn F; Rudnick, Joseph; Klug, William S
2017-11-15
We propose a hybrid discrete-continuum model to study the ground state of protein shells. The model allows for shape transformation of the shell and buckling transitions as well as the competition between states with different symmetries that characterize discrete particle models with radial pair potentials. Our main results are as follows. For large Föppl-von Kármán (FvK) numbers the shells have stable isometric ground states. As the FvK number is reduced, shells undergo a buckling transition resembling that of thin-shell elasticity theory. When the width of the pair potential is reduced below a critical value, then buckling coincides with the onset of structural instability triggered by over-stretched pair potentials. Chiral shells are found to be more prone to structural instability than achiral shells. It is argued that the well-width appropriate for protein shells lies below the structural instability threshold. This means that the self-assembly of protein shells with a well-defined, stable structure is possible only if the bending energy of the shell is sufficiently low so that the FvK number of the assembled shell is above the buckling threshold.
Sheet-like assemblies of spherical particles with point-symmetrical patches.
Mani, Ethayaraja; Sanz, Eduardo; Roy, Soumyajit; Dijkstra, Marjolein; Groenewold, Jan; Kegel, Willem K
2012-04-14
We report a computational study on the spontaneous self-assembly of spherical particles into two-dimensional crystals. The experimental observation of such structures stabilized by spherical objects appeared paradoxical so far. We implement patchy interactions with the patches point-symmetrically (icosahedral and cubic) arranged on the surface of the particle. In these conditions, preference for self-assembly into sheet-like structures is observed. We explain our findings in terms of the inherent symmetry of the patches and the competition between binding energy and vibrational entropy. The simulation results explain why hollow spherical shells observed in some Keplerate-type polyoxometalates (POM) appear. Our results also provide an explanation for the experimentally observed layer-by-layer growth of apoferritin--a quasi-spherical protein.
Delamination of Compressed Thin Layers at Corners
DEFF Research Database (Denmark)
Sørensen, Kim D.; Jensen, Henrik Myhre; Clausen, Johan
2008-01-01
An analysis of delamination for a thin elastic layer under compression, attached to a substrate at a corner is carried out. The analysis is performed by combining results from interface fracture mechanics and the theory of thin shells. In contrast with earlier results for delamination on a flat...
Delamination of Compressed thin Layers at Corners
DEFF Research Database (Denmark)
Clausen, Johan; Jensen, Henrik Myhre; Sørensen, Kim Dalsten
2008-01-01
An analysis of delamination for a thin elastic film, attached to a substrate with a corner, is carried out. The film is in compression and the analysis is performed by combining results from fracture mechanics and the theory of thin shells. The results show a very strong dependency of the angle...
CIRCUMSTELLAR SHELL FORMATION IN SYMBIOTIC RECURRENT NOVAE
Energy Technology Data Exchange (ETDEWEB)
Moore, Kevin; Bildsten, Lars [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)
2012-12-20
We present models of spherically symmetric recurrent nova shells interacting with circumstellar material (CSM) in a symbiotic system composed of a red giant (RG) expelling a wind and a white dwarf accreting from this material. Recurrent nova eruptions periodically eject material at high velocities ({approx}> 10{sup 3} km s{sup -1}) into the RG wind profile, creating a decelerating shock wave as CSM is swept up. High CSM densities cause the shocked wind and ejecta to have very short cooling times of days to weeks. Thus, the late-time evolution of the shell is determined by momentum conservation instead of energy conservation. We compute and show evolutionary tracks of shell deceleration, as well as post-shock structure. After sweeping up all the RG wind, the shell coasts at a velocity {approx}100 km s{sup -1}, depending on system parameters. These velocities are similar to those measured in blueshifted CSM from the symbiotic nova RS Oph, as well as a few Type Ia supernovae that show evidence of CSM, such as 2006X, 2007le, and PTF 11kx. Supernovae occurring in such systems may not show CSM interaction until the inner nova shell gets hit by the supernova ejecta, days to months after the explosion.
Spherical Pendulum, Actions, and Spin
Richter, Peter H.; Dullin, Holger R.; Waalkens, Holger; Wiersig, Jan
1996-01-01
The classical and quantum mechanics of a spherical pendulum are worked out, including the dynamics of a suspending frame with moment of inertia θ. The presence of two separatrices in the bifurcation diagram of the energy-momentum mapping has its mathematical expression in the hyperelliptic nature of
Testing for Bivariate Spherical Symmetry
Einmahl, J.H.J.; Gantner, M.
2010-01-01
An omnibus test for spherical symmetry in R2 is proposed, employing localized empirical likelihood. The thus obtained test statistic is distri- bution-free under the null hypothesis. The asymptotic null distribution is established and critical values for typical sample sizes, as well as the
A charged spherically symmetric solution
Indian Academy of Sciences (India)
A charged spherically symmetric solution. K MOODLEY, S D MAHARAJ and K S GOVINDER. School of Mathematical and Statistical Sciences, University of Natal, Durban 4041, South Africa. Email: maharaj@nu.ac.za. MS received 8 April 2002; revised 7 April 2003; accepted 23 June 2003. Abstract. We find a solution of the ...
Testing for bivariate spherical symmetry
Einmahl, J.H.J.; Gantner, M.
2012-01-01
An omnibus test for spherical symmetry in R2 is proposed, employing localized empirical likelihood. The thus obtained test statistic is distribution free under the null hypothesis. The asymptotic null distribution is established and critical values for typical sample sizes, as well as the asymptotic
Laplacian eigenmodes for spherical spaces
International Nuclear Information System (INIS)
Lachieze-Rey, M; Caillerie, S
2005-01-01
The possibility that our space is multi-rather than singly-connected has gained renewed interest after the discovery of the low power for the first multipoles of the CMB by WMAP. To test the possibility that our space is a multi-connected spherical space, it is necessary to know the eigenmodes of such spaces. Except for lens and prism space, and to some extent for dodecahedral space, this remains an open problem. Here we derive the eigenmodes of all spherical spaces. For dodecahedral space, the demonstration is much shorter, and the calculation method much simpler than before. We also apply our method to tetrahedric, octahedric and icosahedric spaces. This completes the knowledge of eigenmodes for spherical spaces, and opens the door to new observational tests of the cosmic topology. The vector space V k of the eigenfunctions of the Laplacian on the 3-sphere S 3 , corresponding to the same eigenvalue λ k = -k(k + 2), has dimension (k + 1) 2 . We show that the Wigner functions provide a basis for such a space. Using the properties of the latter, we express the behaviour of a general function of V k under an arbitrary rotation G of SO(4). This offers the possibility of selecting those functions of V k which remain invariant under G. Specifying G to be a generator of the holonomy group of a spherical space X, we give the expression of the vector space V x k of the eigenfunctions of X. We provide a method to calculate the eigenmodes up to an arbitrary order. As an illustration, we give the first modes for the spherical spaces mentioned
Shell ontogeny in radiolarians
Digital Repository Service at National Institute of Oceanography (India)
Anderson, O.R.; Gupta, S.M.
The ontogeny of the shells in modern and ancient radiolarian species, Acrosphaera cyrtodon were observed by scanning and transmission electron microscopy. The shells of A. cyrtodon were obtained from core samples collected from the Central Indian...
Directory of Open Access Journals (Sweden)
Fang Wu
2017-05-01
Full Text Available Due to their efficient locomotion and natural tolerance to hazardous environments, spherical robots have wide applications in security surveillance, exploration of unknown territory and emergency response. Numerous studies have been conducted on the driving mechanism, motion planning and trajectory tracking methods of spherical robots, yet very limited studies have been conducted regarding the obstacle avoidance capability of spherical robots. Most of the existing spherical robots rely on the “hit and run” technique, which has been argued to be a reasonable strategy because spherical robots have an inherent ability to recover from collisions. Without protruding components, they will not become stuck and can simply roll back after running into bstacles. However, for small scale spherical robots that contain sensitive surveillance sensors and cannot afford to utilize heavy protective shells, the absence of obstacle avoidance solutions would leave the robot at the mercy of potentially dangerous obstacles. In this paper, a compact magnetic field-based obstacle detection and avoidance system has been developed for miniature spherical robots. It utilizes a passive magnetic field so that the system is both compact and power efficient. The proposed system can detect not only the presence, but also the approaching direction of a ferromagnetic obstacle, therefore, an intelligent avoidance behavior can be generated by adapting the trajectory tracking method with the detection information. Design optimization is conducted to enhance the obstacle detection performance and detailed avoidance strategies are devised. Experimental results are also presented for validation purposes.
Wu, Fang; Vibhute, Akash; Soh, Gim Song; Wood, Kristin L; Foong, Shaohui
2017-05-28
Due to their efficient locomotion and natural tolerance to hazardous environments, spherical robots have wide applications in security surveillance, exploration of unknown territory and emergency response. Numerous studies have been conducted on the driving mechanism, motion planning and trajectory tracking methods of spherical robots, yet very limited studies have been conducted regarding the obstacle avoidance capability of spherical robots. Most of the existing spherical robots rely on the "hit and run" technique, which has been argued to be a reasonable strategy because spherical robots have an inherent ability to recover from collisions. Without protruding components, they will not become stuck and can simply roll back after running into bstacles. However, for small scale spherical robots that contain sensitive surveillance sensors and cannot afford to utilize heavy protective shells, the absence of obstacle avoidance solutions would leave the robot at the mercy of potentially dangerous obstacles. In this paper, a compact magnetic field-based obstacle detection and avoidance system has been developed for miniature spherical robots. It utilizes a passive magnetic field so that the system is both compact and power efficient. The proposed system can detect not only the presence, but also the approaching direction of a ferromagnetic obstacle, therefore, an intelligent avoidance behavior can be generated by adapting the trajectory tracking method with the detection information. Design optimization is conducted to enhance the obstacle detection performance and detailed avoidance strategies are devised. Experimental results are also presented for validation purposes.
International Nuclear Information System (INIS)
Clarisse, J.M.
2007-01-01
A numerical scheme for computing linear Lagrangian perturbations of spherically symmetric flows of gas dynamics is proposed. This explicit first-order scheme uses the Roe method in Lagrangian coordinates, for computing the radial spherically symmetric mean flow, and its linearized version, for treating the three-dimensional linear perturbations. Fulfillment of the geometric conservation law discrete formulations for both the mean flow and its perturbation is ensured. This scheme capabilities are illustrated by the computation of free-surface mode evolutions at the boundaries of a spherical hollow shell undergoing an homogeneous cumulative compression, showing excellent agreement with reference results. (author)
Small angle-rotated detector emission tomography for measuring holdup in spherical container
International Nuclear Information System (INIS)
Deng Jingshan; Li Ze; Gan Lin; Lu Wenguang; Dong Mingli
2007-01-01
Some special nuclear material (SNM) is inevitably deposited in the facilities (mixer, reactor) of nuclear material process line. Exactly knowing the quantity of nuclear material holdup is very important for nuclear material accountability and critical safety. The small angle-rotated emission tomography method was presented for SNM holdup measurement of spherical container. Because of other equipments exist at the left, right and back side of the container, so that the detectors can be put only in front of container for measurement. The nuclear material deposited in the spherical container can be looked as spherical shell source, which is divided into many voxels. The detectors scanning spherical shell source are rotated around the container at small angle at each layer to obtain projection data, with which deposited material distribution can be reconstructed by using least square (LS) method or maximum likelihood (ML) method. Based on these methods accurate total holdup can be obtained by summing up all the voxel values reconstructed. The measurement method for holdup in the spherical container was verified with Monte-Carlo simulation calculation. (authors)
Svalbonas, V.
1973-01-01
A procedure for the structural analysis of stiffened shells of revolution is presented. A digital computer program based on the Love-Reissner first order shell theory was developed. The computer program can analyze orthotropic thin shells of revolution, subjected to unsymmetric distributed loading or concentrated line loads, as well as thermal strains. The geometrical shapes of the shells which may be analyzed are described. The shell wall cross section can be a sheet, sandwich, or reinforced sheet or sandwich. General stiffness input options are also available.
Spherically symmetric elasticity in relativity
Energy Technology Data Exchange (ETDEWEB)
Carot, J [Departament de Fisica, Universitat de les Illes Balears, Cra Valldemossa pk 7.5, E-07122 Palma (Spain); Brito, I; Vaz, E G L R, E-mail: jcarot@uib.ca, E-mail: ireneb@mct.uminho.p, E-mail: evaz@mct.uminho.p
2010-05-01
The relativistic theory of elasticity is reviewed within the spherically symmetric context with a view towards the modelling of star interiors possessing elastic properties such as the ones expected in neutron stars. Emphasis is placed on generality in the main sections of the paper, and the results are then applied to specific examples. Along the way, a few general results for spacetimes admitting isometries are deduced, and their consequences are fully exploited in the case of spherical symmetry relating them next to the the case in which the material content of the spacetime is some elastic material. This paper extends and generalizes the pioneering work by Magli and Kijowski [1], Magli [2] and [3], and complements, in a sense, that by Karlovini and Samuelsson in their interesting series of papers [4], [5] and [6].
Testing for bivariate spherical symmetry
Einmahl, J.H.J.; Gantner, M.
2012-01-01
An omnibus test for spherical symmetry in R2 is proposed, employing localized empirical likelihood. The thus obtained test statistic is distri- bution-free under the null hypothesis. The asymptotic null distribution is established and critical values for typical sample sizes, as well as the asymptotic ones, are presented. In a simulation study, the good perfor- mance of the test is demonstrated. Furthermore, a real data example is presented.
Lithography-free shell-substrate isolation for core-shell GaAs nanowires.
Haggren, Tuomas; Perros, Alexander Pyymaki; Jiang, Hua; Huhtio, Teppo; Kakko, Joona-Pekko; Dhaka, Veer; Kauppinen, Esko; Lipsanen, Harri
2016-07-08
A facile and scalable lithography-free technique(5) for the rapid construction of GaAs core-shell nanowires incorporating shell isolation from the substrate is reported. The process is based on interrupting NW growth and applying a thin spin-on-glass (SOG) layer to the base of the NWs and resuming core-shell NW growth. NW growth occurred in an atmospheric pressure metalorganic vapour phase epitaxy (MOVPE) system with gold nanoparticles used as catalysts for the vapour-liquid-solid growth. It is shown that NW axial core growth and radial shell growth can be resumed after interruption and even exposure to air. The SOG residues and native oxide layer that forms on the NW surface are shown to prevent or perturb resumption of epitaxial NW growth if not removed. Both HF etching and in situ annealing of the air-exposed NWs in the MOVPE were shown to remove the SOG residues and native oxide layer. While both procedures are shown capable of removing the native oxide and enabling resumption of epitaxial NW growth, in situ annealing produced the best results and allowed construction of pristine core-shell NWs. No growth occurred on SOG and it was observed that axial NW growth was more rapid when a SOG layer covered the substrate. The fabricated p-core/n-shell NWs exhibited diode behaviour upon electrical testing. The isolation of the NW shells from the substrate was confirmed by scanning electron microscopy and electrical measurements. The crystal quality of the regrown core-shell NWs was verified with a high resolution transmission electron microscope. The reported technique potentially provides a pathway using MOVPE for scalable and high-throughput production of shell-substrate isolated core-shell NWs on an industrial scale.
Shell thickness effects on quantum dot brightness and energy transfer.
Chern, Margaret; Nguyen, Thuy T; Mahler, Andrew H; Dennis, Allison M
2017-11-02
Heterostructured core/shell quantum dots (QDs) are prized in biomedical imaging and biosensing applications because of their bright, photostable emission and effectiveness as Förster resonance energy transfer (FRET) donors. However, as nanomaterials chemistry has progressed beyond traditional QDs to incorporate new compositions, ultra-thick shells, and alloyed structures, few of these materials have had their optical properties systematically characterized for effective application. For example, thick-shelled QDs, also known as 'giant' QDs (gQDs) are useful in single-particle tracking microscopy because of their reduced blinking, but we know only that CdSe/CdS gQDs are qualitatively brighter than thin-shelled CdSe/CdS in aqueous media. In this study, we quantify the impact of shell thickness on the nanoparticle molar extinction coefficient, quantum yield, brightness, and effectiveness as a FRET donor for CdSe/xCdS core/shell and CdSe/xCdS/ZnS core/shell/shell QDs, with variable thicknesses of the CdS shell (x). Molar extinction coefficients up to three orders of magnitude higher than conventional dyes and forty-fold greater than traditional QDs are reported. When thick CdS shells are combined with ZnS capping, quantum yields following thiol ligand exchange reach nearly 40%-5-10× higher than either the commercially available QDs or gQDs without ZnS caps treated the same way. These results clearly show that thick CdS shells and ZnS capping shells work in concert to provide the brightest possible CdSe-based QDs for bioimaging applications. We demonstrate that thicker shelled gQDs are over 50-fold brighter than their thin-shelled counterparts because of significant increases in their absorption cross-sections and higher quantum yield in aqueous milieu. Consistent with the point-dipole approximation commonly used for QD-FRET, these data show that thick shells contribute to the donor-acceptor distance, reducing FRET efficiency. Despite the reduction in FRET efficiency
Binding of Lysozyme to Spherical Poly(styrenesulfonate Gels
Directory of Open Access Journals (Sweden)
Martin Andersson
2018-01-01
Full Text Available Polyelectrolyte gels are useful as carriers of proteins and other biomacromolecules in, e.g., drug delivery. The rational design of such systems requires knowledge about how the binding and release are affected by electrostatic and hydrophobic interactions between the components. To this end we have investigated the uptake of lysozyme by weakly crosslinked spherical poly(styrenesulfonate (PSS microgels and macrogels by means of micromanipulator assisted light microscopy and small angle X-ray scattering (SAXS in an aqueous environment. The results show that the binding process is an order of magnitude slower than for cytochrome c and for lysozyme binding to sodium polyacrylate gels under the same conditions. This is attributed to the formation of very dense protein-rich shells in the outer layers of the microgels with low permeability to the protein. The shells in macrogels contain 60 wt % water and nearly charge stoichiometric amounts of lysozyme and PSS in the form of dense complexes of radius 8 nm comprising 30–60 lysozyme molecules. With support from kinetic modelling results we propose that the rate of protein binding and the relaxation rate of the microgel are controlled by the protein mass transport through the shell, which is strongly affected by hydrophobic and electrostatic interactions. The mechanism explains, in turn, an observed dependence of the diffusion rate on the apparent degree of crosslinking of the networks.
Plasmonic and silicon spherical nanoparticle antireflective coatings.
Baryshnikova, K V; Petrov, M I; Babicheva, V E; Belov, P A
2016-03-01
Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes.
Modeling of microencapsulated polymer shell solidification
International Nuclear Information System (INIS)
Boone, T.; Cheung, L.; Nelson, D.; Soane, D.; Wilemski, G.; Cook, R.
1995-01-01
A finite element transport model has been developed and implemented to complement experimental efforts to improve the quality of ICF target shells produced via controlled-mass microencapsulation. The model provides an efficient means to explore the effect of processing variables on the dynamics of shell dimensions, concentricity, and phase behavior. Comparisons with experiments showed that the model successfully predicts the evolution of wall thinning and core/wall density differences. The model was used to efficiently explore and identify initial wall compositions and processing temperatures which resulted in concentricity improvements from 65 to 99%. The evolution of trace amounts of water entering into the shell wall was also tracked in the simulations. Comparisons with phase envelope estimations from modified UNIFAP calculations suggest that the water content trajectory approaches the two-phase region where vacuole formation via microphase separation may occur
Spherical Accretion in a Uniformly Expanding Universe
Colpi, Monica; Shapiro, Stuart L.; Wasserman, Ira
1996-10-01
We consider spherically symmetric accretion of material from an initially homogeneous, uniformly expanding medium onto a Newtonian point mass M. The gas is assumed to evolve adiabatically with a constant adiabatic index F, which we vary over the range Γ ɛ [1, 5/3]. We use a one-dimensional Lagrangian code to follow the spherical infall of material as a function of time. Outflowing shells gravitationally bound to the point mass fall back, giving rise to a inflow rate that, after a rapid rise, declines as a power law in time. If there were no outflow initially, Bondi accretion would result, with a characteristic accretion time-scale ta,0. For gas initially expanding at a uniform rate, with a radial velocity U = R/t0 at radius R, the behavior of the flow at all subsequent times is determined by ta,0/t0. If ta,0/t0 ≫ 1, the gas has no time to respond to pressure forces, so the fluid motion is nearly collisionless. In this case, only loosely bound shells are influenced by pressure gradients and are pushed outward. The late-time evolution of the mass accretion rate Mdot is close to the result for pure dust, and we develop a semianalytic model that accurately accounts for the small effect of pressure gradients in this limit. In the opposite regime, ta,0/t0 ≪ 1, pressure forces significantly affect the motion of the gas. At sufficiently early times, t ≤ ttr, the flow evolved along a sequence of quasi-stationary, Bondi-like states, with a time-dependent Mdot determined by the slowly varying gas density at large distances. However, at later times, t ≥ ttr, the fluid flow enters a dustllke regime; ttr is the time when the instantaneous Bondi accretion radius reaches the marginally bound radius. The transition time ttr depends sensitively on ta,0/t0 for a given Γ and can greatly exceed t0. We show that there exists a critical value Γ = 11/9, below which the transition from fluid to ballistic motion disappears. As one application of our calculations, we consider the
Amplified Photon Upconversion by Photonic Shell of Cholesteric Liquid Crystals.
Kang, Ji-Hwan; Kim, Shin-Hyun; Fernandez-Nieves, Alberto; Reichmanis, Elsa
2017-04-26
As an effective platform to exploit triplet-triplet-annihilation-based photon upconversion (TTA-UC), microcapsules composed of a fluidic UC core and photonic shell are microfluidically prepared using a triple emulsion as the template. The photonic shell consists of cholesteric liquid crystals (CLCs) with a periodic helical structure, exhibiting a photonic band gap. Combined with planar anchoring at the boundaries, the shell serves as a resonance cavity for TTA-UC emission and enables spectral tuning of the UC under low-power-density excitation. The CLC shell can be stabilized by introducing a polymerizable mesogen in the LC host. Because of the microcapsule spherical symmetry, spontaneous emission of the delayed fluorescence is omnidirectionally amplified at the edge of the stop band. These results demonstrate the range of opportunities provided by TTA-UC systems for the future design of low-threshold photonic devices.
Near spherical illumination of ion-beam and laser targets
International Nuclear Information System (INIS)
Mark, J.W.K.
1985-01-01
A procedure is developed for reducing energy-deposition asymmetry in spherical targets driven directly by ion or laser beams. This work is part of a strategy for achieving illumination symmetry in such targets, which is proposed as an alternative to those in the literature. This strategy allows an axially symmetric placement of beamlets, which would be convenient for some driven or reactor scenarios. It also allows the use of beam currents or energy fluxes and beam transverse profiles to help reduce deposition asymmetry with fewer beamlets. In the ideal limit of thin deposition layers and controlled beam profiles, at most six beamlets are needed for target symmetry
Nuclear moments of nuclei near sphericity
International Nuclear Information System (INIS)
El Hajjaji, O.
1987-05-01
Magnetic and electric hyperfine interactions are studied by means of low temperature nuclear orientation. The magnetic moment of the 149 Gd isotope and that of 151 Gd are determined. The values follow the same trend as literature values of neighbouring nuclei. The calculated moments of the 7/2 - states using the Mottelson-Nilsson model without configuration mixing are nearly independent of deformation. Thus we assign the decrease of the magnetic moment versus neutron number to many particle coupling in the f shell. The Moessbauer effect detection of nuclear orientation is discussed. Two series of experiences are performed with different finalities. In the first one we determined the electric quadrupole moments of 125m Te and 129 Te. The quadrupole moments confirm the nearly spherical shape of these nuclei. In the second series we describe the Moessbauer effect of the radiation emitted by the daigleter nucleus of 125 I, implanted in two semiconductor matrices, locally oriented at low temperature by the electric field gradient of impurity-vacancy coupling. Despite the difficulty of the cooling down of Te nuclei to lattice temperature, we have shown the existence of the electric field gradient of implanted I into Si and α-Sn and determined their signs. The level mixing resonance is applied on oriented nuclei technique to determine the weak prolate deformation of silver nuclei. Studying the Δm = 3 resonance of 107 Ag m , we etablished the quadrupole moment of this state, which is in good agreement with the theoretical estimations of Moeller and Nix [fr
Evolution of bulk strain solitons in cylindrical inhomogeneous shells
Energy Technology Data Exchange (ETDEWEB)
Shvartz, A., E-mail: andrew.shvartz@mail.ioffe.ru; Samsonov, A.; Dreiden, G.; Semenova, I. [Ioffe Institute, 26 Politekhnicheskaya, St Petersburg 194021 (Russian Federation)
2015-10-28
Bulk strain solitary waves in nonlinearly elastic thin-walled cylindrical shells with variable geometrical and physical parameters are studied, and equation for the longitudinal strain component with the variable coefficients is derived. A conservative finite difference scheme is proposed, and the results of numerical simulation of the strain soliton evolution in a shell with the abrupt variations of cross section and physical properties of the material are presented.
Future Directions and Challenges in Shell Stability Analysis
Arbocz, Johann
1998-01-01
An answer is sought to the question of today, in 1997, after so many years of concentrated research effort in designing buckling critical thin walled shells, why one cannot do any better than using the rather conservative Lower Bound Design Philosophy of the sixties. It will be shown that with the establishment of Initial Imperfection Data Banks and the introduction of Probabilistic Design Procedures one has a viable alternative, that when used judiciously, may lead to improved shell design recommendations.
Behavior of self-confined spherical layer of light radiation in the air atmosphere
Energy Technology Data Exchange (ETDEWEB)
Torchigin, V.P.; Torchigin, A.V
2004-07-26
Behavior of thin spherical layer of intensive light in an inhomogeneous atmosphere is considered. It is shown that the behavior is similar to puzzling and mysterious behavior of ball lightnings. Under assumption that ball lightning moves along the gradient of atmosphere air density process of ball lightning penetration in a salon of a flying airplane is analyzed.
Behavior of self-confined spherical layer of light radiation in the air atmosphere
International Nuclear Information System (INIS)
Torchigin, V.P.; Torchigin, A.V.
2004-01-01
Behavior of thin spherical layer of intensive light in an inhomogeneous atmosphere is considered. It is shown that the behavior is similar to puzzling and mysterious behavior of ball lightnings. Under assumption that ball lightning moves along the gradient of atmosphere air density process of ball lightning penetration in a salon of a flying airplane is analyzed
Double-shell inertial confinement fusion target fabrication
Energy Technology Data Exchange (ETDEWEB)
Hatcher, C.W.; Lorensen, L.E.; Weinstein, B.W.
1980-08-26
First generation hemishells, from which spherical shells are constructed, were fabricated by micromachining coated mandrels and by molding. The remachining of coated mandrels are described in detail. Techniques were developed for coating the microsized mandrels with polymeric and metallic materials by methods including conformal coating, vapor deposition, plasma polymerization and thermoforming. Micropositioning equipment and bonding techniques have also been developed to assemble the hemishells about a fuel pellet maintaining a spherical concentricity of better than 2 ..mu..m and voids in the hemishell bonding line of a few hundred angstroms or less.
A Spherical Aerial Terrestrial Robot
Dudley, Christopher J.
This thesis focuses on the design of a novel, ultra-lightweight spherical aerial terrestrial robot (ATR). The ATR has the ability to fly through the air or roll on the ground, for applications that include search and rescue, mapping, surveillance, environmental sensing, and entertainment. The design centers around a micro-quadcopter encased in a lightweight spherical exoskeleton that can rotate about the quadcopter. The spherical exoskeleton offers agile ground locomotion while maintaining characteristics of a basic aerial robot in flying mode. A model of the system dynamics for both modes of locomotion is presented and utilized in simulations to generate potential trajectories for aerial and terrestrial locomotion. Details of the quadcopter and exoskeleton design and fabrication are discussed, including the robot's turning characteristic over ground and the spring-steel exoskeleton with carbon fiber axle. The capabilities of the ATR are experimentally tested and are in good agreement with model-simulated performance. An energy analysis is presented to validate the overall efficiency of the robot in both modes of locomotion. Experimentally-supported estimates show that the ATR can roll along the ground for over 12 minutes and cover the distance of 1.7 km, or it can fly for 4.82 minutes and travel 469 m, on a single 350 mAh battery. Compared to a traditional flying-only robot, the ATR traveling over the same distance in rolling mode is 2.63-times more efficient, and in flying mode the system is only 39 percent less efficient. Experimental results also demonstrate the ATR's transition from rolling to flying mode.
Collisions in spherical stellar systems
Energy Technology Data Exchange (ETDEWEB)
Polyachenko, V.L.; Shukhman, I.G. (AN SSSR, Irkutsk. Sibirskij Inst. Zemnogo Magnetizma Ionosfery i Rasprostraneniya Radiovoln)
From the set of the equations for the stellar distribution function and for the two-particle correlation in the action- angle variables, by averaging over fast finite motions the general expression for the collisional term of a finite stellar system with ''rare'' Coulomb collisions is obtained. In the case of a spherically symmetrical system with the distribution function f/sub 0/=f/sub 0/(E, L) (E, L being the energy and the angular momentum of a star), the kinetic equation is reduced to the standard form of the two-dimensional Fokker-Planck equations.
Spherical Orbifolds for Cosmic Topology
International Nuclear Information System (INIS)
Kramer, Peter
2012-01-01
Harmonic analysis is a tool to infer cosmic topology from the measured astrophysical cosmic microwave background CMB radiation. For overall positive curvature, Platonic spherical manifolds are candidates for this analysis. We combine the specific point symmetry of the Platonic manifolds with their deck transformations. This analysis in topology leads from manifolds to orbifolds. We discuss the deck transformations of the orbifolds and give eigenmodes for the harmonic analysis as linear combinations of Wigner polynomials on the 3-sphere. These provide new tools for detecting cosmic topology from the CMB radiation.
Petrov, Alexey; Lehmann, Hauke; Finsel, Maik; Klinke, Christian; Weller, Horst; Vossmeyer, Tobias
2016-01-26
Metallodielectric nanostructured core-shell-shell particles are particularly desirable for enabling novel types of optical components, including narrow-band absorbers, narrow-band photodetectors, and thermal emitters, as well as new types of sensors and catalysts. Here, we present a facile approach for the preparation of submicron SiO2@Pt@SiO2 core-shell-shell particles. As shown by transmission and scanning electron microscopy, the first steps of this approach allow for the deposition of closed and almost perfectly smooth platinum shells onto silica cores via a seeded growth mechanism. By choosing appropriate conditions, the shell thickness could be adjusted precisely, ranging from ∼3 to ∼32 nm. As determined by X-ray diffraction, the crystalline domain sizes of the polycrystalline metal shells were ∼4 nm, regardless of the shell thickness. The platinum content of the particles was determined by atomic absorption spectroscopy and for thin shells consistent with a dense metal layer of the TEM-measured thickness. In addition, we show that the roughness of the platinum shell strongly depends on the storage time of the gold seeds used to initiate reductive platinum deposition. Further, using polyvinylpyrrolidone as adhesion layer, it was possible to coat the metallic shells with very homogeneous and smooth insulating silica shells of well-controlled thicknesses between ∼2 and ∼43 nm. After depositing the particles onto silicon substrates equipped with interdigitated electrode structures, the metallic character of the SiO2@Pt particles and the insulating character of the SiO2 shells of the SiO2@Pt@SiO2 particles were successfully demonstrated by charge transport measurements at variable temperatures.
Directory of Open Access Journals (Sweden)
Mahdi Ghazanfari
2014-12-01
Full Text Available This paper is a report on the synthesis of the Fe3O4@Ag core-shell with high saturation magnetization of magnetite nanoparticles as the core, by using polyol route and silver shell by chemical reduction. X-ray diffraction (XRD and Fourier transform infrared spectroscopy analyses confirmed that the particles so produced were monophase. The magnetic properties of the product were investigated by using a vibrating sample magnetometer. Magnetic saturation of magnetite was 91 emu/g that around about bulk magnetization. This high saturation magnetization can be attributed to the thin dead layer. By using polyethylene glycol as a surfactant to separate and restrict the growth of the particles, magnetostatic interactions are in good agreement with the remanence ratio analysis. Morphology and the average size of the particles were determined with field emission scanning electron microscope (FESEM. Spherical aggregates of Fe3O4 (size around 73 nm are composed of a small primary particle size of about 16 nm. Silver deposition was done using butylamine as the reductant of AgNO3 in ethanol with different ratio. The silver layers were estimated using statistical histogram images of FESEM. Silver-coated iron oxide nanohybrids have been used in a broad range of applications, including chemical and biological sensing, due to the broad absorption in the optical region associated with localized surface plasmon resonance.
Huang, Suping; Li, Chunxia; Xiao, Qi
2017-12-01
In this paper, yolk-shell hollow nanospheres of amorphous calcium phosphate (ACP) are prepared, and its loading capacity is investigated by comparing with that of solid-shell hollow structure ACP and cage-shell hollow structure ACP. Results show that the products are yolk @ cage-shell of ACP with large shell's pores size (15-40 nm) and large cavity volume. Adsorption results show that the loading capacity of yolk @ cage-shell hollow spherical ACP is very high, which is more than twice that of hollow ACP and 1.5 times of cage-like ACP. The main reasons are that the big shell's pore size contributes the large molecular doxorubicin hydrochloride (DOX · HCl) to enter the inner of hollow spheres easier, and the yolk-shell structure provides larger interior space and more adsorption sites for loading drugs.
K I 7699 A emission from the Betelgeuse shell
Bernat, A. P.; Lambert, D. L.
1976-01-01
A map of the circumstellar gas shell around Betelgeuse is presented from observations of the fluorescent emission in the K I 7699 A resonance line. The observations obtained at 3 sec and 5 sec from the star indicate approximate spherical symmetry in the 10 km/s expanding shell responsible for the blueshifted sharp cores seen in strong resonance and low excitation lines. Calculations show that the density of neutral K atoms is approximately constant between 3 sec and 5 sec from the star. The emission profiles in the west show a second, higher velocity, component at 5 sec from the star.
National Spherical Torus Experiment (NSTX)
International Nuclear Information System (INIS)
Masayuki Ono
2000-01-01
The main aim of National Spherical Torus Experiment (NSTX) is to establish the fusion physics principles of the innovative spherical torus (ST) concept. Physics outcome of the NSTX research program is relevant to near-term applications such as the Volume Neutron Source (VNS) and burning plasmas, and future applications such as the pilot and power plants. The NSTX device began plasma operations in February 1999 and the plasma current was successfully ramped up to the design value of 1 million amperes (MA) on December 14, 1999. The CHI (Coaxial Helicity Injection) and HHFW (High Harmonic Fast Wave) experiments have also started. Stable CHI discharges of up to 133 kA and 130-msec duration have been produced using 20 kA of injected current. Using eight antennas connected to two transmitters, up to 2 MW of HHFW power was successfully coupled to the plasma. The Neutral-beam Injection (NBI) heating system and associated NBI-based diagnostics such as the Charge-exchange Recombination Spectrometer (CHERS) will be operational in October 2000
Progress in octahedral spherical hohlraum study
Directory of Open Access Journals (Sweden)
Ke Lan
2016-01-01
Full Text Available In this paper, we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study. From our theoretical study, the octahedral spherical hohlraums with 6 Laser Entrance Holes (LEHs of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7. In addition, the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology. We studied the laser arrangement and constraints of the octahedral spherical hohlraums, and gave a design on the laser arrangement for ignition octahedral hohlraums. As a result, the injection angle of laser beams of 50°–60° was proposed as the optimum candidate range for the octahedral spherical hohlraums. We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields, in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport. We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums, the rugby hohlraums and the cylindrical hohlraums, and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive. Up till to now, we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG laser facilities, including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums, spherical hohlraum energetics on the SGIII prototype laser facility, and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.
Ma, Yanyun; Li, Weiyang; Cho, Eun Chul; Li, Zhiyuan; Yu, Taekyung; Zeng, Jie; Xie, Zhaoxiong; Xia, Younan
2010-01-01
This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4 to 50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO3 precursor to Au se...
Magnetization processes in core/shell exchange-spring structures.
Energy Technology Data Exchange (ETDEWEB)
Jiang, J. S.
2015-03-27
The magnetization reversal processes in cylindrical and spherical soft core/hard shell exchange-spring structures are investigated via the analytical nucleation theory, and are verified with numerical micromagnetic simulations. At small core sizes, the nucleation of magnetic reversal proceeds via the modified bulging mode, where the transverse component of the magnetization is only semi-coherent in direction and the nucleation field contains a contribution from self-demagnetization. For large core sizes, the modified curling mode, where the magnetization configuration is vortex-like, is favored at nucleation. The preference for the modified curling mode is beneficial in that the fluxclosure allows cylindrical and spherical core/shell exchange-spring elements to be densely packed into bulk permanent magnets without affecting the nucleation field, thereby offering the potential for high energy product.
Precision Membrane Optical Shell (PMOS) Technology for Lightweight LIDAR Apertures, Phase I
National Aeronautics and Space Administration — Precision membrane optical shell (PMOS) technology is an innovative combination of 1) ultra lightweight optically smooth membrane thin films, 2) advanced mold based...
Magnetic-luminescent spherical particles synthesized by ultrasonic spray pyrolysis
International Nuclear Information System (INIS)
Michel, Norma L; Hirata, Gustavo A; Flores, Dora L
2015-01-01
The combination of magnetic and luminescent properties in a single particle system, opens-up a wide range of potential applications in biotechnology and biomedicine. In this work, we performed the synthesis of magnetic-luminescent Gd 2 O 3 :Eu 3+ @Fe 2 O 3 particles by ultrasonic spray pyrolysis performed in a tubular furnace. In order to achieve the composite formation, commercial superparamagnetic Fe 3 O 4 nanoparticles were coated with a luminescent Eu 3+ -doped Gd 2 O 3 shell in a low-cost one-step process. The spray pyrolysis method yields deagglomerated spherical shape magneto/luminescent particles. The photoluminescence spectra under UV excitation (λ Exc = 265 nm) of the magnetic Gd 2 O 3 :Eu 3+ @Fe 2 O 3 compound showed the characteristic red emission of Eu 3+ (λ Em = 612 nm). This magneto/luminescent system will find applications in biomedicine and biotechnology. (paper)
The ETE spherical Tokamak project. IAEA report
Energy Technology Data Exchange (ETDEWEB)
Ludwig, Gerson Otto; Del Bosco, E.; Berni, L.A.; Ferreira, J.G.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Barroso, J.J.; Castro, P.J.; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: ludwig@plasma.inpe.br
2002-07-01
This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and operating conditions as of October, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)
Relationships between solid spherical and toroidal harmonics
Majic, Matt; Ru, Eric C. Le
2018-01-01
We derive new relationships expressing solid spherical harmonics as series of toroidal harmonics and vice versa. The expansions include regular and irregular spherical harmonics, ring and axial toroidal harmonics of even and odd parity about the plane of the torus. The expansion coefficients are given in terms of a recurrence relation. As an example application we apply one of the expansions to express the potential of a charged conducting torus on a basis of spherical harmonics.
Self-assembly morphology effects on the crystallization of semicrystalline block copolymer thin film
Wei, Yuhan; Pan, Caiyuan; Li, Binyao; Han, Yanchun
2007-03-01
Self-assembly morphology effects on the crystalline behavior of asymmetric semicrystalline block copolymer polystyrene-block-poly(L-lactic acid) thin film were investigated. Firstly, a series of distinctive self-assembly aggregates, from spherical to ellipsoid and rhombic lamellar micelles (two different kinds of rhombic micelles, defined as rhomb 1 and rhomb 2) was prepared by means of promoting the solvent selectivity. Then, the effects of these self-assembly aggregates on crystallization at the early stage of film evolution were investigated by in situ hot stage atomic force microscopy. Heterogeneous nucleation initiated from the spherical micelles and dendrites with flat on crystals appeared with increasing temperature. At high temperature, protruding structures were observed due to the thickening of the flat-on crystals and finally more thermodynamically stable crystallization formed. Annealing the rhombic lamellar micelles resulted in different phenomena. Turtle-shell-like crystalline structure initiated from the periphery of the rhombic micelle 1 and spread over the whole film surface in the presence of mostly noncrystalline domain interior. Erosion and small hole appeared at the surface of the rhombic lamellar micelle 2; no crystallization like that in rhomb 1 occurred. It indicated that the chain-folding degree was different in these two micelles, which resulted in different annealing behaviors.
Development of high quality plastic fuel shells for laser fusion energy
International Nuclear Information System (INIS)
Norimatsu, T.; Nagai, K.; Yamanaka, T.
2001-01-01
An overview of the emulsion process to make fuel capsules for a laser fusion power plant is presented, emphasizing the fact that high quality shells, of which sphericity is close to the extrapolated NIF standard, were successfully fabricated. A simulation model for the centering process, by which uniformly thick shells were formed, was compared with the experiment, and showed good agreement. It was indicated that the water core approaches the center by repeated instantaneous deformations. (author)
The shallow shell approach to Pogorelov's problem and the breakdown of 'mirror buckling'.
Gomez, Michael; Moulton, Derek E; Vella, Dominic
2016-03-01
We present a detailed asymptotic analysis of the point indentation of an unpressurized, spherical elastic shell. Previous analyses of this classic problem have assumed that for sufficiently large indentation depths, such a shell deforms by 'mirror buckling'-a portion of the shell inverts to become a spherical cap with equal but opposite curvature to the undeformed shell. The energy of deformation is then localized in a ridge in which the deformed and undeformed portions of the shell join together, commonly referred to as Pogorelov's ridge. Rather than using an energy formulation, we revisit this problem from the point of view of the shallow shell equations and perform an asymptotic analysis that exploits the largeness of the indentation depth. This reveals first that the stress profile associated with mirror buckling is singular as the indenter is approached. This consequence of point indentation means that mirror buckling must be modified to incorporate the shell's bending stiffness close to the indenter and gives rise to an intricate asymptotic structure with seven different spatial regions. This is in contrast with the three regions (mirror-buckled, ridge and undeformed) that are usually assumed and yields new insight into the large compressive hoop stress that ultimately causes the secondary buckling of the shell.
Dynamics of Inhomogeneous Shell Systems Under Non-Stationary Loading (Survey)
Lugovoi, P. Z.; Meish, V. F.
2017-09-01
Experimental works on the determination of dynamics of smooth and stiffened cylindrical shells contacting with a soil medium under various non-stationary loading are reviewed. The results of studying three-layer shells of revolution whose motion equations are obtained within the framework of the hypotheses of the Timoshenko geometrically nonlinear theory are stated. The numerical results for shells with a piecewise or discrete filler enable the analysis of estimation of the influence of geometrical and physical-mechanical parameters of structures on their dynamics and reveal new mechanical effects. Basing on the classical theory of shells and rods, the effect of the discrete arrangement of ribs and coefficients of the Winkler or Pasternak elastic foundation on the normal frequencies and modes of rectangular planar cylindrical and spherical shells is studied. The number and shape of dispersion curves for longitudinal harmonic waves in a stiffened cylindrical shell are determined. The equations of vibrations of ribbed shells of revolution on Winkler or Pasternak elastic foundation are obtained using the geometrically nonlinear theory and the Timoshenko hypotheses. On applying the integral-interpolational method, numerical algorithms are developed and the corresponding non-stationary problems are solved. The special attention is paid to the statement and solution of coupled problems on the dynamical interaction of cylindrical or spherical shells with the soil water-saturated medium of different structure.
Morphology and film formation of poly(butyl methacrylate)-polypyrrole core-shell latex particles
Huijs, F; Lang, J
Core-shell latex particles made of a poly(butyl methacrylate) (PBMA) core and a thin polypyrrole (PPy) shell were synthesized by two-stage polymerization. In the first stage, PBMA latex particles were synthesized in a semicontinuous process by free-radical polymerization. PBMA latex particles were
Core–shell Au/Ag nanoparticles embedded in silicate sol–gel ...
Indian Academy of Sciences (India)
Administrator
catalytic reduction and sensing of hydrogen peroxide in comparison to monometal Au and Ag nanoparticles ... metal catalyst. It has been reported in many cases that bimetallic systems display a core–shell struc- ture, where a thin shell of second metal surrounds a ... The homogeneous MTMOS sol–gel matrix was pre- pared.
Validation of annual growth rings in freshwater mussel shells using cross dating .Can
Andrew L. Rypel; Wendell R. Haag; Robert H. Findlay
2009-01-01
We examined the usefulness of dendrochronological cross-dating methods for studying long-term, interannual growth patterns in freshwater mussels, including validation of annual shell ring formation. Using 13 species from three rivers, we measured increment widths between putative annual rings on shell thin sections and then removed age-related variation by...
Stress analysis for shells with double curvature by finite element method
International Nuclear Information System (INIS)
Mueller, A.
1981-08-01
A simple triangular finite element for plates and shells, is presented. Since the rotation fields are assumed independent of the displacement fields, simple shape functions of second and third degree were used. An implicit penalty method allows one to solve thin shell problems since the Kirchoff-Love hypothesis are automatically satisfied. (Author) [pt
Transitions of Spherical Thermohaline Circulation to Multiple Equilibria
Özer, Saadet; Şengül, Taylan
2017-06-01
The main aim of the paper is to investigate the transitions of the thermohaline circulation in a spherical shell in a parameter regime which only allows transitions to multiple equilibria. We find that the first transition is either continuous (Type-I) or drastic (Type-II) depending on the sign of the transition number. The transition number depends on the system parameters and l_c , which is the common degree of spherical harmonics of the first critical eigenmodes, and it can be written as a sum of terms describing the nonlinear interactions of various modes with the critical modes. We obtain the exact formulas of this transition number for l_c=1 and l_c=2 cases. Numerically, we find that the main contribution to the transition number is due to nonlinear interactions with modes having zero wave number and the contribution from the nonlinear interactions with higher frequency modes is negligible. In our numerical experiments we encountered both types of transition for Le1 . In the continuous transition scenario, we rigorously prove that an attractor in the phase space bifurcates which is homeomorphic to the 2l_c dimensional sphere and consists entirely of degenerate steady state solutions.
Rings and filaments: The remarkable detached CO shell of U Antliae
Kerschbaum, F.; Maercker, M.; Brunner, M.; Lindqvist, M.; Olofsson, H.; Mecina, M.; De Beck, E.; Groenewegen, M. A. T.; Lagadec, E.; Mohamed, S.; Paladini, C.; Ramstedt, S.; Vlemmings, W. H. T.; Wittkowski, M.
2017-09-01
Aims: Our goal is to characterize the intermediate age, detached shell carbon star U Antliae morphologically and physically in order to study the mass-loss evolution after a possible thermal pulse. Methods: High spatial resolution ALMA observations of unprecedented quality in thermal CO lines allow us to derive first critical spatial and temporal scales and constrain modeling efforts to estimate mass-loss rates for both the present day as well as the ejection period of the detached shell. Results: The detached shell is remarkably thin, overall spherically symmetric, and shows a barely resolved filamentary substructure possibly caused by instabilities in the interaction zone of winds with different outflow velocities. The expansion age of the detached shell is of the order of 2700 yr and its overall width indicates a high expansion-velocity and high mass-loss period of only a few hundred years at an average mass-loss rate of ≈10-5 M⊙ yr-1. The post-high-mass-loss-rate-epoch evolution of U Ant shows a significant decline to a substantially lower gas expansion velocity and a mass-loss rate amounting to 4 × 10-8 M⊙ yr-1, at present being consistent with evolutionary changes as predicted for the period between thermal pulses. This paper makes use of the following ALMA data: ADS/JAO.ALMA2015.1.00007.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.The reduced ALMA FITS data cubes are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A116The movie is available at http://www.aanda.org
Fischer, Stefan; Swabeck, Joseph K; Alivisatos, A Paul
2017-09-06
Precise morphology and composition control is vital for designing multifunctional lanthanide-doped core/shell nanocrystals. Herein, we report controlled isotropic and anisotropic shell growth techniques in hexagonal sodium rare-earth tetrafluoride (β-NaLnF 4 ) nanocrystals by exploiting the kinetics of the shell growth. A drastic change of the shell morphology was observed by changing the injection rate of the shell precursors while keeping all other reaction conditions constant. We obtained isotropic shell growth for fast sequential injection and a preferred growth of the shell layers along the crystal's c-axis [001] for slow dropwise injection. Using this slow shell growth technique, we have grown rod-like shells around different almost spherical core nanocrystals. Bright and efficient upconversion was measured for both isotropic and rod-like shells around β-NaYF 4 nanocrystals doped with Yb 3+ /Er 3+ and Yb 3+ /Tm 3+ . Photoluminescence upconversion quantum yield and lifetime measurements reveal the high quality of the core/shell nanocrystal. Furthermore, multishell rod-like nanostructures have been prepared with optically active cores and tips separated by an inert intermediate shell layer. The controlled anisotropic shell growth allows the design of new core/multishell nanostructures and enables independent investigations of the chemistry and physics of different nanocrystal facets.
Fluorescent nanodiamonds embedded in biocompatible translucent shells.
Rehor, Ivan; Slegerova, Jitka; Kucka, Jan; Proks, Vladimir; Petrakova, Vladimira; Adam, Marie-Pierre; Treussart, François; Turner, Stuart; Bals, Sara; Sacha, Pavel; Ledvina, Miroslav; Wen, Amy M; Steinmetz, Nicole F; Cigler, Petr
2014-03-26
High pressure high temperature (HPHT) nanodiamonds (NDs) represent extremely promising materials for construction of fluorescent nanoprobes and nanosensors. However, some properties of bare NDs limit their direct use in these applications: they precipitate in biological solutions, only a limited set of bio-orthogonal conjugation techniques is available and the accessible material is greatly polydisperse in shape. In this work, we encapsulate bright 30-nm fluorescent nanodiamonds (FNDs) in 10-20-nm thick translucent (i.e., not altering FND fluorescence) silica shells, yielding monodisperse near-spherical particles of mean diameter 66 nm. High yield modification of the shells with PEG chains stabilizes the particles in ionic solutions, making them applicable in biological environments. We further modify the opposite ends of PEG chains with fluorescent dyes or vectoring peptide using click chemistry. High conversion of this bio-orthogonal coupling yielded circa 2000 dye or peptide molecules on a single FND. We demonstrate the superior properties of these particles by in vitro interaction with human prostate cancer cells: while bare nanodiamonds strongly aggregate in the buffer and adsorb onto the cell membrane, the shell encapsulated NDs do not adsorb nonspecifically and they penetrate inside the cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Williams, Suzanne T
2017-05-01
The phylum Mollusca is highly speciose, and is the largest phylum in the marine realm. The great majority of molluscs are shelled, including nearly all bivalves, most gastropods and some cephalopods. The fabulous and diverse colours and patterns of molluscan shells are widely recognised and have been appreciated for hundreds of years by collectors and scientists alike. They serve taxonomists as characters that can be used to recognise and distinguish species, however their function for the animal is sometimes less clear and has been the focus of many ecological and evolutionary studies. Despite these studies, almost nothing is known about the evolution of colour in molluscan shells. This review summarises for the first time major findings of disparate studies relevant to the evolution of shell colour in Mollusca and discusses the importance of colour, including the effects of visual and non-visual selection, diet and abiotic factors. I also summarise the evidence for the heritability of shell colour in some taxa and recent efforts to understand the molecular mechanisms underpinning synthesis of shell colours. I describe some of the main shell pigments found in Mollusca (carotenoids, melanin and tetrapyrroles, including porphyrins and bile pigments), and their durability in the fossil record. Finally I suggest that pigments appear to be distributed in a phylogenetically relevant manner and that the synthesis of colour is likely to be energetically costly. © 2016 Cambridge Philosophical Society.
Stability of the spherical form of nuclei
International Nuclear Information System (INIS)
Sabry, A.A.
1976-08-01
An extension of the mass formula for a spherical nucleus in the drop model to include a largely deformed nucleus of different forms is investigated. It is found that although the spherical form is stable under small deformations from equilibrium, there exists for heavier nuclei another more favourable stable form, which can be approximated by two, or three touching prolate ellipsoids of revolution
Spherically symmetric inhomogeneous dust collapse in higher ...
Indian Academy of Sciences (India)
We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. ... The existence of strong curvature naked singularities in gravitational collapse of spherically symmetric space-times ... where an over dot denotes partial derivative with respect to t. The functions F(r) and f(r).
Inertial modes and their transition to turbulence in a differentially rotating spherical gap flow
Hoff, Michael; Harlander, Uwe; Andrés Triana, Santiago; Egbers, Christoph
2016-04-01
We present a study of inertial modes in a spherical shell experiment. Inertial modes are Coriolis-restored linear wave modes, often arise in rapidly-rotating fluids (e.g. in the Earth's liquid outer core [1]). Recent experimental works showed that inertial modes exist in differentially rotating spherical shells. A set of particular inertial modes, characterized by (l,m,ˆω), where l, m is the polar and azimuthal wavenumber and ˆω = ω/Ωout the dimensionless frequency [2], has been found. It is known that they arise due to eruptions in the Ekman boundary layer of the outer shell. But it is an open issue why only a few modes develop and how they get enhanced. Kelley et al. 2010 [3] showed that some modes draw their energy from detached shear layers (e.g. Stewartson layers) via over-reflection. Additionally, Rieutord et al. (2012) [4] found critical layers within the shear layers below which most of the modes cannot exist. In contrast to other spherical shell experiments, we have a full optical access to the flow. Therefore, we present an experimental study of inertial modes, based on Particle-Image-Velocimetry (PIV) data, in a differentially rotating spherical gap flow where the inner sphere is subrotating or counter-rotating at Ωin with respect to the outer spherical shell at Ωout, characterized by the Rossby number Ro = (Ωin - Ωout)/Ωout. The radius ratio of η = 1/3, with rin = 40mm and rout = 120mm, is close to that of the Earth's core. Our apparatus is running at Ekman numbers (E ≈ 10-5, with E = ν/(Ωoutrout2), two orders of magnitude higher than most of the other experiments. Based on a frequency-Rossby number spectrogram, we can partly confirm previous considerations with respect to the onset of inertial modes. In contrast, the behavior of the modes in the counter-rotation regime is different. We found a triad interaction between three dominant inertial modes, where one is a slow axisymmetric Rossby mode [5]. We show that the amplitude of the most
Functional buckling behavior of silicone rubber shells for biomedical use.
van der Houwen, E B; Kuiper, L H; Burgerhof, J G M; van der Laan, B F A M; Verkerke, G J
2013-12-01
The use of soft elastic biomaterials in medical devices enables substantial function integration. The consequent increased simplification in design can improve reliability at a lower cost in comparison to traditional (hard) biomaterials. Functional bi-stable buckling is one of the many new mechanisms made possible by soft materials. The buckling behavior of shells, however, is typically described from a structural failure point of view: the collapse of arches or rupture of steam vessels, for example. There is little or no literature about the functional elastic buckling of small-sized silicone rubber shells, and it is unknown whether or not theory can predict their behavior. Is functional buckling possible within the scale, material and pressure normally associated with physiological applications? An automatic speech valve is used as an example application. Silicone rubber spherical shells (diameter 30mm) with hinged and double-hinged boundaries were subjected to air pressure loading. Twelve different geometrical configurations were tested for buckling and reverse buckling pressures. Data were compared with the theory. Buckling pressure increases linearly with shell thickness and shell height. Reverse buckling shows these same relations, with pressures always below normal buckling pressure. Secondary hinges change normal/reverse buckling pressure ratios and promote symmetrical buckling. All tested configurations buckled within or closely around physiological pressures. Functional bi-stable buckling of silicone rubber shells is possible with adjustable properties in the physiological pressure range. Results can be predicted using the proposed relations and equations. Copyright © 2013 Elsevier Ltd. All rights reserved.
de-Shalit, Amos; Massey, H S W
1963-01-01
Nuclear Shell Theory is a comprehensive textbook dealing with modern methods of the nuclear shell model. This book deals with the mathematical theory of a system of Fermions in a central field. It is divided into three parts. Part I discusses the single particle shell model. The second part focuses on the tensor algebra, two-particle systems. The last part covers three or more particle systems. Chapters on wave functions in a central field, tensor fields, and the m-Scheme are also presented. Physicists, graduate students, and teachers of nuclear physics will find the book invaluable.
The effect of mesh size on failure for shell structures
Walters, C.L.; Schipperen, J.H.A.
2012-01-01
More than any other application, simulation of crash events depends on the precise representation of fracture. At the same time, practical considerations typically force the crash analyst to use shell elements for many types of thin-walled structures, such as cars, aircraft, and ships. For these
Photonic crystals of core-shell colloidal particles
Velikov, K.P.; Moroz, A.; Blaaderen, A. van
2001-01-01
We report on the fabrication and optical transmission studies of thin three-dimensional (3D) photonic crystals of high-dielectric ZnS-core and low-dielectric SiO2-shell colloidal particles. These samples were fabricated using a vertical controlled drying method. The spectral position and width of a
Sloshing effect on the dynamic behavior of horizontal cylindrical shells
International Nuclear Information System (INIS)
Lakis, A.A.; Bursuc, G.; Toorani, M.H.
2009-01-01
The present study investigates the effect of free surface motion of a fluid on the dynamic behavior of thin-walled cylindrical shells. This paper outlines a semi-analytical approach to dynamic analysis of a fluid-filled horizontal cylindrical shell taking into account free surface motion; sloshing. The aim of the method is to provide a general approach that can be used for both analysis and synthesis of fluid/structure interaction problems in horizontal cylindrical shells focusing on the dynamic interaction between a flexible structure and incompressible and inviscid flow. The approach is very general; it allows dynamic analysis of both uniform and non-uniform cylindrical shells and considers the fluid forces and includes the sloshing effect exerted on the structure. The hybrid method developed in this work incorporates a combination of the classic finite element approach and thin shell theory to determine the specific displacement functions. Mass and stiffness matrices of the shell are determined by precise analytical integration. A potential function is applied to develop the dynamic pressure due to the fluid. The kinetic and potential energies are evaluated for a range of fluid heights to find the influence of the fluid on the dynamic responses of the structure. The influence of physical and geometrical parameters on the fluid-structure system has been considered in the numerical solutions. When these results are compared with corresponding results available in the literature, both theoretical and experimental, very good agreement is obtained.
Acoustic resonances in two-dimensional radial sonic crystal shells
Energy Technology Data Exchange (ETDEWEB)
Torrent, Daniel; Sanchez-Dehesa, Jose, E-mail: jsdehesa@upvnet.upv.e [Wave Phenomena Group, Departamento de Ingenieria Electronica, Universidad Politecnica de Valencia, C/Camino de Vera s.n., E-46022 Valencia (Spain)
2010-07-15
Radial sonic crystals (RSC) are fluidlike structures infinitely periodic along the radial direction that verify the Bloch theorem and are possible only if certain specially designed acoustic metamaterials with mass density anisotropy can be engineered (see Torrent and Sanchez-Dehesa 2009 Phys. Rev. Lett. 103 064301). A comprehensive analysis of two-dimensional (2D) RSC shells is reported here. A given shell is in fact a circular slab with a central cavity. These finite crystal structures contain Fabry-Perot-like resonances and modes strongly localized at the central cavity. Semi-analytical expressions are developed to obtain the quality factors of the different resonances, their symmetry features and their excitation properties. The results reported here are completely general and can be extended to equivalent 3D spherical shells and to their photonic counterparts.
Acoustic resonances in two-dimensional radial sonic crystal shells
Torrent, Daniel; Sánchez-Dehesa, José
2010-07-01
Radial sonic crystals (RSC) are fluidlike structures infinitely periodic along the radial direction that verify the Bloch theorem and are possible only if certain specially designed acoustic metamaterials with mass density anisotropy can be engineered (see Torrent and Sánchez-Dehesa 2009 Phys. Rev. Lett. 103 064301). A comprehensive analysis of two-dimensional (2D) RSC shells is reported here. A given shell is in fact a circular slab with a central cavity. These finite crystal structures contain Fabry-Perot-like resonances and modes strongly localized at the central cavity. Semi-analytical expressions are developed to obtain the quality factors of the different resonances, their symmetry features and their excitation properties. The results reported here are completely general and can be extended to equivalent 3D spherical shells and to their photonic counterparts.
Intrinsic cylindrical and spherical waves
International Nuclear Information System (INIS)
Ludlow, I K
2008-01-01
Intrinsic waveforms associated with cylindrical and spherical Bessel functions are obtained by eliminating the factors responsible for the inverse radius and inverse square radius laws of wave power per unit area of wavefront. The resulting expressions are Riccati-Bessel functions for both cases and these can be written in terms of amplitude and phase functions of order v and wave variable z. When z is real, it is shown that a spatial phase angle of the intrinsic wave can be defined and this, together with its amplitude function, is systematically investigated for a range of fixed orders and varying z. The derivatives of Riccati-Bessel functions are also examined. All the component functions exhibit different behaviour in the near field depending on the order being less than, equal to or greater than 1/2. Plots of the phase angle can be used to display the locations of the zeros of the general Riccati-Bessel functions and lead to new relations concerning the ordering of the real zeros of Bessel functions and the occurrence of multiple zeros when the argument of the Bessel function is fixed
The energy of a prolate spheroidal shell in a uniform magnetic field
Koksharov, Yu. A.
2017-04-01
The problem of the energy of a spheroidal magnetic shell, solved by methods of classical electrodynamics, arises, in particular, upon the study of thin-wall biocompatible microcapsules in connection with a pressing issue of targeted drug delivery. The drug inside a microcapsule should be released from the shell at a required instant of time by destroying the capsule's shell. The placement inside a shell of magnetic nanoparticles sensitive to an external magnetic field theoretically makes it possible to solve both problems: to transport a capsule to the required place and to destroy its shell. In particular, the shell can be destroyed under the action of internal stress when the shape of a capsule is changed. In this paper, the analysis of the model of a magnetic microcapsule in the form of a prolate spheroidal shell is performed and formulas for the magnetostatic and magnetic free energy when the magnetic field is directed along the major axis of the spheroid are derived.
Pfister, Catherine A.; Roy, Kaustuv; Wootton, Timothy J.; McCoy, Sophie J.; Paine, Robert T.; Suchanek, Tom; Sanford, Eric
2016-01-01
Seawater pH and the availability of carbonate ions are decreasing due to anthropogenic carbon dioxide emissions, posing challenges for calcifying marine species. Marine mussels are of particular concern given their role as foundation species worldwide. Here, we document shell growth and calcification patterns in Mytilus californianus, the California mussel, over millennial and decadal scales. By comparing shell thickness across the largest modern shells, the largest mussels collected in the 1960s–1970s and shells from two Native American midden sites (∼1000–2420 years BP), we found that modern shells are thinner overall, thinner per age category and thinner per unit length. Thus, the largest individuals of this species are calcifying less now than in the past. Comparisons of shell thickness in smaller individuals over the past 10–40 years, however, do not show significant shell thinning. Given our sampling strategy, these results are unlikely to simply reflect within-site variability or preservation effects. Review of environmental and biotic drivers known to affect shell calcification suggests declining ocean pH as a likely explanation for the observed shell thinning. Further future decreases in shell thickness could have significant negative impacts on M. californianus survival and, in turn, negatively impact the species-rich complex that occupies mussel beds..
Shell Buckling Knockdown Factors
National Aeronautics and Space Administration — The Shell Buckling Knockdown Factor (SBKF) Project, NASA Engineering and Safety Center (NESC) Assessment #: 07-010-E, was established in March of 2007 by the NESC in...
African Journals Online (AJOL)
THE LAND SNAIL LIMICOLARIA KAMBEUL CHUDEAUI GERMAIN. IN THE ETHIOPIAN RIFT VALLEY: HABITAT, ECOLOGY AND. SHELL ISOTOPE GEOCHEMISTRY. Melanie J. Lengl, Henry F. Lamb',. Mohammed Umer Mohammed''* and Elias Dadebo4. 'NERC Isotope Geosciences Laboratory, Keyworth, Nottingham, ...
Grimm, U
2005-01-01
A homogeneous medium is characterised by a point set in Euclidean space (for the atomic positions, say), together with some self-averaging property. Crystals and quasicrystals are homogeneous, but also many structures with disorder still are. The corresponding shelling is concerned with the number of points on shells around an arbitrary, but fixed centre. For non-periodic point sets, where the shelling depends on the chosen centre, a more adequate quantity is the averaged shelling, obtained by averaging over points of the set as centres. For homogeneous media, such an average is still well defined, at least almost surely (in the probabilistic sense). Here, we present a two-step approach for planar model sets.
Liquid-drop technique for generation of organic glass and metal shells
International Nuclear Information System (INIS)
Hendricks, C.D.
1981-01-01
We have for several years utilized the technique of capillary wave synchronization of the break-up of single and multiple component jets to produce uniform sized liquid drops and solid particles, and hollow liquid and solid shells. The technique has also been used to encapsulate a number of liquids in impermeable spherical shells. Highly uniform glass shells have been made by generating uniform drops of glass forming materials in an aqueous solution, subsequently evaporating the water, and then fusing and blowing the remaining solids in a high temperature vertical tube furnace. Experimental results will be presented and the critical problems in further research in this field will be discussed
Numerical code for fitting radial emission profile of a shell supernova remnant: Application
Directory of Open Access Journals (Sweden)
Opsenica Slobodan
2011-01-01
Full Text Available We present IDL (Interactive Data Language codes for fitting a theoretical emission profile of a shell supernova remnant (SNR to the mean profile of an SNR obtained from radio observations. Two considered theoretical models are: 1 a shell with constant emissivity and 2 a synchrotron shell with radially aligned magnetic field. The codes were applied to several observed supernova remnants. Good results are obtained in five considered cases, which justify the use of our code for remnants that are bright (so that observational errors are not large and spherically symmetric enough.
Temperature and angular momentum dependence of the quadrupole deformation in sd-shell
Ganai, P. A.; Sheikh, J. A.; Maqbool, I.; Singh, R. P.
2009-12-01
Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard USD interaction and the canonical partition function constructed from the calculated eigen-solutions. It is shown that the extracted average quadrupole moments show a transitional behavior as a function of temperature and the inferred transitional temperature is shown to vary with angular-momentum. The quadrupole deformation of the individual eigen-states is also analyzed.
Sutley, Jane
2009-01-01
"Shells and Patterns" was a project the author felt would easily put smiles on the faces of her fifth-graders, and teach them about unity and the use of watercolor pencils as well. It was thrilling to see the excitement in her students as they made their line drawings of shells come to life. For the most part, they quickly got the hang of…
Contemporary nuclear shell models
Luo Yan An; Zhang Xia; Tan Yu Hong; Ning Ping Zhi
2002-01-01
The current status on the theoretical investigations of the nuclear shell model is reviewed, and the fundamental problems in shell-model studies are mentioned. Basically the shell-model uses a very intuitive approach to study the nuclear many-body dynamics in terms of valence particles. It assumes that the nucleons, belonging to a closed core, do not participate in the establishment of the nuclear spectrum. One of the main problems in the (traditional) shell model is to make a calculation feasible. With the explosive growth of the computational power, it is possible to carry out a 'Very Large Scale' shell model calculation. Nevertheless, whether such a calculation really helps authors' understanding of physics is still an open question. Furthermore, the case of the medium weight and heavy nuclei with configurations of 10 sup 1 sup 4 -10 sup 1 sup 8 remains out of reach. For these nuclei one still needs to truncate the huge shell model space to a manageable subspace. Recently, a useful formalism has been descr...
Spherical aberration in contact lens wear.
Lindskoog Pettersson, A; Jarkö, C; Alvin, A; Unsbo, P; Brautaset, R
2008-08-01
The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. A wavefront analyser (Zywave, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (plenses. Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.
A finite element model for nonlinear shells of revolution
International Nuclear Information System (INIS)
Cook, W.A.
1979-01-01
A shell-of-revolution model was developed to analyze impact problems associated with the safety analysis of nuclear material shipping containers. The nonlinear shell theory presented by Eric Reissner in 1972 was used to develop our model. Reissner's approach includes transverse shear deformation and moments turning about the middle surface normal. With these features, this approach is valid for both thin and thick shells. His theory is formulated in terms of strain and stress resultants that refer to the undeformed geometry. This nonlinear shell model is developed using the virtual work principle associated with Reissner's equilibrium equations. First, the virtual work principle is modified for incremental loading; then it is linearized by assuming that the nonlinear portions of the strains are known. By iteration, equilibrium is then approximated for each increment. A benefit of this approach is that this iteration process makes it possible to use nonlinear material properties. (orig.)
Oscillating shells and oscillating balls in AdS
Banerjee, Avik; Kundu, Arnab; Roy, Pratik; Virmani, Amitabh
2017-07-01
It has recently been reported that certain thin timelike shells undergo oscillatory motion in AdS. In this paper, we compute two-point function of a probe field in the geodesic approximation in such an oscillating shell background. We confirm that the two-point function exhibits an oscillatory behaviour following the motion of the shell. We show that similar oscillatory dynamics is possible when the perfect fluid on the shell has a polytropic equation of state. Moreover, we show that certain ball like configurations in AdS also exhibit oscillatory motion and comment on how such a solution can be smoothly matched to an appropriate exterior solution. We also demonstrate that the weak energy condition is satisfied for these oscillatory configurations.
Injection Moulding Simulation and Experimental Validation of Hearing Aid Shells
DEFF Research Database (Denmark)
Islam, Aminul; Li, Xiaoliu
) mode was adopted in this work to simulate the injection molding process of a hearing aid shell made of Polybutylene Terephthalate (PBT) filled with 30% glass fiber. The typical hearing aid shells are complex thin-walled structures made by injection molding. Highly sophisticated molds and lots...... of process optimizations by trial and errors are needed to make successful shells for hearing aids. In this context, a dedicated simulation tool can be very useful to reduce the time and cost for developing the new hearing aids. In this work, the injection molding experimental validation of the Moldex3D...... simulation was conducted for the upper shell of a hearing aid. With the pressure sensors integrated in the molding tool, real cavity pressure data was collected and the real filling time was estimated to replicate the processing conditions in the simulation. Injection time, injection pressure; pressure loss...
HST/ACS observations of shell galaxies : inner shells, shell colours and dust
Sikkema, G.; Carter, D.; Peletier, R. F.; Balcells, M.; Del Burgo, C.; Valentijn, E. A.
Context. Shells in Elliptical Galaxies are faint, sharp-edged features, believed to provide evidence for a merger event. Accurate photometry at high spatial resolution is needed to learn on presence of inner shells, population properties of shells, and dust in shell galaxies. Aims. Learn more about
Novel Electrically Small Spherical Electric Dipole Antenna
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2010-01-01
This paper introduces a novel electrically small spherical meander antenna. Horizontal sections of the meander are composed of wire loops, radii of which are chosen so that the whole structure is conformal to a sphere of radius a. To form the meander the loops are connected by wires at a meridian...... plane. The antenna operates as an electric dipole, i.e. it radiates the TM10 spherical mode. The antenna is self-resonant and can be matched to a wide range of input feed lines without an external matching network. In this paper, a spherical meander antenna of the size ka = 0.27 and the input impedance...
An integral transform of Green's function, off-shell Jost solution and T ...
Indian Academy of Sciences (India)
integral transform of the Green's function for motion in Coulomb–Yamaguchi potential is derived via the r-space ... use in the calculation of the corresponding off-shell quantities without the explicit use of two-potential theorem and ..... (x), spherical Bessel function and gli(βli,r)s, the form factors of the sep- arable potential the ...
Emulsion preparation for novel micro-porous polymeric hemi-shells
CSIR Research Space (South Africa)
Naidoo, Kersch
2008-01-01
Full Text Available A modified oil-in-water (O/W) emulsion process was developed to produce novel micro-porous hemi-spherical polycaprolactone (PCL) micro-particles called "hemi-shells". By addition of a porogen such as sodium bicarbonate (NaHCO3) into the PCL...
The shell structure effects in neutron cross section calculation by a ...
African Journals Online (AJOL)
The role of the shell structure properties of the nucleus in the calculation of neutron-induced reaction cross-section data based on nuclear reaction theory has been investigated. In this investigation, measured, evaluated and calculated (n.p) reaction cross-section data on la spherical nucleus (i.e. 112Sn) and a deformed ...
Multi-Shell Hollow Nanogels with Responsive Shell Permeability
Schmid, Andreas J.; Dubbert, Janine; Rudov, Andrey A.; Pedersen, Jan Skov; Lindner, Peter; Karg, Matthias; Potemkin, Igor I.; Richtering, Walter
2016-01-01
We report on hollow shell-shell nanogels with two polymer shells that have different volume phase transition temperatures. By means of small angle neutron scattering (SANS) employing contrast variation and molecular dynamics (MD) simulations we show that hollow shell-shell nanocontainers are ideal systems for controlled drug delivery: The temperature responsive swelling of the inner shell controls the uptake and release, while the thermoresponsive swelling of the outer shell controls the size of the void and the colloidal stability. At temperatures between 32 °C shell. Computer simulations showed, that temperature induced switching of the permeability of the inner shell allows for the encapsulation in and release of molecules from the cavity. PMID:26984478
Finite deformations of functionally graded shell under outer pressure with steady state temperature
Sharma, Sanjeev; Panchal, Rekha; Sahni, Manoj; Sharma, Richa
2017-10-01
In this paper, finite elastic and plastic stresses have been determined for functionally graded shell using the concepts of transition theory and generalized measure of strain i.e. nonlinear terms in the displacements are also considered while in classical theory only infinitesimal strain theory concept has been applied. In this problem of spherical shell, temperature has been applied at the internal surface while pressure is considered to be applied at the external surface. From the detailed analysis, it has been noticed that temperature and pressure have significant effects on functionally graded shell. In this paper, it is found that external pressure required for the fully plastic state from initial yielding is on the higher side for the shell made up of highly functionally graded material as compared to the shell made up of less functionally graded material.
Progress in High-Capacity Core-Shell Cathode Materials for Rechargeable Lithium Batteries.
Myung, Seung-Taek; Noh, Hyung-Joo; Yoon, Sung-June; Lee, Eung-Ju; Sun, Yang-Kook
2014-02-20
High-energy-density rechargeable batteries are needed to fulfill various demands such as self-monitoring analysis and reporting technology (SMART) devices, energy storage systems, and (hybrid) electric vehicles. As a result, high-energy electrode materials enabling a long cycle life and reliable safety need to be developed. To ensure these requirements, new material chemistries can be derived from combinations of at least two compounds in a secondary particle with varying chemical composition and primary particle morphologies having a core-shell structure and spherical cathode-active materials, specifically a nanoparticle core and shell, nanoparticle core and nanorod shell, and nanorod core and shell. To this end, several layer core-shell cathode materials were developed to ensure high capacity, reliability, and safety.
Fabrication of slender elastic shells by the coating of curved surfaces
Lee, A.; Brun, P.-T.; Marthelot, J.; Balestra, G.; Gallaire, F.; Reis, P. M.
2016-04-01
Various manufacturing techniques exist to produce double-curvature shells, including injection, rotational and blow molding, as well as dip coating. However, these industrial processes are typically geared for mass production and are not directly applicable to laboratory research settings, where adaptable, inexpensive and predictable prototyping tools are desirable. Here, we study the rapid fabrication of hemispherical elastic shells by coating a curved surface with a polymer solution that yields a nearly uniform shell, upon polymerization of the resulting thin film. We experimentally characterize how the curing of the polymer affects its drainage dynamics and eventually selects the shell thickness. The coating process is then rationalized through a theoretical analysis that predicts the final thickness, in quantitative agreement with experiments and numerical simulations of the lubrication flow field. This robust fabrication framework should be invaluable for future studies on the mechanics of thin elastic shells and their intrinsic geometric nonlinearities.
Vibrations of a fluid filled cylindrical shell excited by an oscillating piston in the fluid
International Nuclear Information System (INIS)
Hailfinger, G.; Eberle, F.; Kadlec, J.; Krieg, R.
1987-01-01
A water filled thin walled cylindrical shell was excited to vibrate by a piston displacing the water. The near-wall water pressures and the accelerations of the wall were measured and compared with corresponding computations. It was stated that the dynamic system behavior was dominated by the structure dynamics. A major finding was that a relatively small imperfection caused by a weld seam of the cylindrical shell (out-of-roundness 0.36% of the diameter) exerted a decisive influence on the dynamic behavior of the shell. Pressures and accelerations were changed by a multiple of the value calculated for the perfect cylindrical shell. (orig.)
Ma, Yanyun; Li, Weiyang; Cho, Eun Chul; Li, Zhiyuan; Yu, Taekyung; Zeng, Jie; Xie, Zhaoxiong; Xia, Younan
2010-11-23
This paper describes a facile method for generating Au@Ag core-shell nanocubes with edge lengths controllable in the range of 13.4-50 nm. The synthesis involved the use of single-crystal, spherical Au nanocrystals of 11 nm in size as the seeds in an aqueous system, with ascorbic acid serving as the reductant and cetyltrimethylammonium chloride (CTAC) as the capping agent. The thickness of the Ag shells could be finely tuned from 1.2 to 20 nm by varying the ratio of AgNO(3) precursor to Au seeds. We also investigated the growth mechanism by examining the effects of seeds (capped by CTAC or cetyltrimethylammonium bromide(CTAB)) and capping agent (CTAC vs CTAB) on both size and shape of the resultant core-shell nanocrystals. Our results clearly indicate that CTAC worked much better than CTAB as a capping agent in both the syntheses of Au seeds and Au@Ag core-shell nanocubes. We further studied the localized surface plasmon resonance properties of the Au@Ag nanocubes as a function of the Ag shell thickness. By comparing with the extinction spectra obtained from theoretical calculations, we derived a critical value of ca. 3 nm for the shell thickness at which the plasmon excitation of the Au cores would be completely screened by the Ag shells. Moreover, these Au@Ag core-shell nanocubes could be converted into Au-based hollow nanostructures containing the original Au seeds in the interiors through a galvanic replacement reaction.
3D Printing Electrically Small Spherical Antennas
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2013-01-01
3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations....
Spherically symmetric inhomogeneous dust collapse in higher ...
Indian Academy of Sciences (India)
We consider a collapsing spherically symmetric inhomogeneous dust cloud in higher dimensional space-time. We show that the central singularity of collapse can be a strong curvature or a weak curvature naked singularity depending on the initial density distribution.
Spherical designs and anticoherent spin states
International Nuclear Information System (INIS)
Crann, Jason; Pereira, Rajesh; Kribs, David W
2010-01-01
Anticoherent spin states are quantum states that exhibit maximally nonclassical behaviour in a certain sense. Any spin state whose Majorana representation is a Platonic solid is called a perfect state. By direct calculation, it has been shown that any perfect state is an anticoherent spin state. We show that any spin state whose Majorana representation is both the orbit of a finite subgroup of O(3) and a spherical t-design must be an anticoherent spin state of order t. Since all Platonic solids are spherical designs, this result gives an explanation of the anticoherence of perfect states and explains their observed order. We also show that any spin state whose Majorana representation lies in any single open hemisphere cannot be anticoherent of any order. This result is then used to give further relations between spherical designs and anticoherent spin states. We also pose some questions relating spherical designs and geometric entanglement.
Transformation of Real Spherical Harmonics under Rotations
Romanowski, Z.; Krukowski, St.; Jalbout, A. F.
2008-08-01
The algorithm rotating the real spherical harmonics is presented. The convenient and ready to use formulae for l = 0, 1, 2, 3 are listed. The rotation in R3 space is determined by the rotation axis and the rotation angle; the Euler angles are not used. The proposed algorithm consists of three steps. (i) Express the real spherical harmonics as the linear combination of canonical polynomials. (ii) Rotate the canonical polynomials. (iii) Express the rotated canonical polynomials as the linear combination of real spherical harmonics. Since the three step procedure can be treated as a superposition of rotations, the searched rotation matrix for real spherical harmonics is a product of three matrices. The explicit formulae of matrix elements are given for l = 0, 1, 2, 3, what corresponds to s, p, d, f atomic orbitals.
Spherical stochastic neighbor embedding of hyperspectral data
CSIR Research Space (South Africa)
Lunga, D
2012-07-01
Full Text Available of spherical coordinates. This allows the use of an Exit probability distribution to discover the nonlinear characteristics that are inherent in hyperspectral data. In addition, the method directly learns the probability distribution over neighboring pixel maps...
Feasibility study for the Spherical Torus Experiment
International Nuclear Information System (INIS)
Lazarus, E.A.; Attenberger, S.E.; Baylor, L.R.
1985-10-01
The design of the Spherical Torus Experiment (STX) is discussed. The physics of the plasma are given in a magnetohydrodynamic model. The structural aspects and instrumentation of the device are described. 19 refs., 103 figs
Spiral CT manifestations of spherical pneumonia
International Nuclear Information System (INIS)
Li Xiaohong; Yang Hongwei; Xu Chunmin; Qin Xiu
2008-01-01
Objective: To explore the Spiral CT manifestations and differential diagnosis of spherical pneumonia. Methods: 18 cases of spherical pneumonia and 20 cases of peripheral pulmonary carcinoma were selected, both of them were confirmed by clinic and/or pathology. The SCT findings of both groups were compared retrospectively. Results: Main spiral CT findings of spherical pneumonia were showed as followings: square or triangular lesions adjacent to pleura; with irregular shape, blurry, slightly lobulated margin, sometimes with halo sign. Small inflammatory patches and intensified vascular markings around the lesions were seen. Lesions became smaller or vanished after short-term anti-inflammatory treatment. Conclusion: Spherical pneumonia showed some characteristics on Spiral CT scan, which are helpful in diagnosis and differential diagnosis of this disease. (authors)
The confinement effect in spherical inhomogeneous quantum dots and stability of excitons
Directory of Open Access Journals (Sweden)
F. Benhaddou
2017-06-01
Full Text Available We investigate in this work the quantum confinement effect of exciton in spherical inhomogeneous quantum dots IQDs. The spherical core is enveloped by two shells. The inner shell is a semiconductor characterized by a small band-gap. The core and the outer shell are the same semiconductor characterized by a large band-gap. So there is a significant gap-offset creating a deep potential well where the excitons are localized and strongly confined. We have adopted the Ritz variational method to calculate numerically the excitonic ground state energy and its binding energy in the strong, moderate and low confinement regimes. The results show that the Ritz variational method is in good agreement with the perturbation method in strong confinement. There is a double confinement effect and dual control. The calculation checks the effective Rydberg R* at the asymptotic limit of bulk semiconductor when the thickness takes very large values. The excitonic binding energy increases, Thus giving the excitons a high stability even at ambient temperature. These nanosystems are promising in several applications: lighting, detection, biological labeling and quantum computing.
3D Printing Electrically Small Spherical Antennas
DEFF Research Database (Denmark)
Kim, Oleksiy S.
2013-01-01
3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations.......3D printing is applied for rapid prototyping of an electrically small spherical wire antenna. The model is first printed in plastic and subsequently covered with several layers of conductive paint. Measured results are in good agreement with simulations....
A Spherical Electro Optic High Voltage Sensor
1989-06-01
the application of an electric field applied to the EO crystal, and a photodetector senses the pattern movement. The sensor can be made small (e.g...spherical symmetry simplifies analysis; a uniform£ exists within a spherical dielectric when immursed in a uniform E; conoscopic light production...of an electric field applied to the EO crystal, and a photodetector senses the pattern movement. The sensor can be made small (e.g. < 3mm diam
Yu, Jong-Sung; Yoon, Suk Bon; Lee, Yun Jo; Yoon, Kyung Byung
2005-04-21
In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases.
Nuclear mass formula with the shell energies obtained by a new method
International Nuclear Information System (INIS)
Koura, H.; Tachibana, T.; Yamada, M.; Uno, M.
1998-01-01
Nuclear shapes and masses are estimated by a new method. The main feature of this method lies in estimating shell energies of deformed nuclei from spherical shell energies by mixing them with appropriate weights. The spherical shell energies are calculated from single-particle potentials, and, till now, two mass formulas have been constructed from two different sets of potential parameters. The standard deviation of the calculated masses from all the experimental masses of the 1995 Mass Evaluation is about 760 keV. Contrary to the mass formula by Tachibana, Uno, Yamada and Yamada in the 1987-1988 Atomic Mass Predictions, the present formulas can give nuclear shapes and predict on super-heavy elements
Conjugated polymer shells on colloidal templates by seeded Suzuki–Miyaura dispersion polymerization.
ten Hove, Jan Bart; Appel, Jeroen; van den Broek, Johanna M; Kuehne, Alexander J C; Sprakel, Joris
2014-03-12
The self-assembly of colloidal conjugated polymers presents a versatile and powerful oute towards new functional optoelectronic materials and devices. However, this strategy relies on the existence of chemical protocols to prepare highly monodisperse colloids of conjugated polymers in high yields. Here, a recently developed Suzuki–Miyaura dispersion polymerization method is adopted to synthesize core–shell particles, in which a conjugated polymer shell is grown onto non-conjugated organic and inorganic colloidal templates. By chemically anchoring aryl halide groups at the particle surface, a conjugated polymer shell can be attached to a wide variety of organic and inorganic microparticles. In this way, both spherical and non-spherical hybrid conjugated polymer particles are prepared, and it is shown that the method can be applied to a variety of conjugated polymers. This new method offers independent control of the size, shape and photophysical properties of these novel conjugated polymer particles.
Three-dimensional flat shell-to-shell coupling: numerical challenges
Guo, Kuo; Haikal, Ghadir
2017-11-01
The node-to-surface formulation is widely used in contact simulations with finite elements because it is relatively easy to implement using different types of element discretizations. This approach, however, has a number of well-known drawbacks, including locking due to over-constraint when this formulation is used as a twopass method. Most studies on the node-to-surface contact formulation, however, have been conducted using solid elements and little has been done to investigate the effectiveness of this approach for beam or shell elements. In this paper we show that locking can also be observed with the node-to-surface contact formulation when applied to plate and flat shell elements even with a singlepass implementation with distinct master/slave designations, which is the standard solution to locking with solid elements. In our study, we use the quadrilateral four node flat shell element for thin (Kirchhoff-Love) plate and thick (Reissner-Mindlin) plate theory, both in their standard forms and with improved formulations such as the linked interpolation [1] and the Discrete Kirchhoff [2] elements for thick and thin plates, respectively. The Lagrange multiplier method is used to enforce the node-to-surface constraints for all elements. The results show clear locking when compared to those obtained using a conforming mesh configuration.
NIF Double Shell outer/inner shell collision experiments
Merritt, E. C.; Loomis, E. N.; Wilson, D. C.; Cardenas, T.; Montgomery, D. S.; Daughton, W. S.; Dodd, E. S.; Desjardins, T.; Renner, D. B.; Palaniyappan, S.; Batha, S. H.; Khan, S. F.; Smalyuk, V.; Ping, Y.; Amendt, P.; Schoff, M.; Hoppe, M.
2017-10-01
Double shell capsules are a potential low convergence path to substantial alpha-heating and ignition on NIF, since they are predicted to ignite and burn at relatively low temperatures via volume ignition. Current LANL NIF double shell designs consist of a low-Z ablator, low-density foam cushion, and high-Z inner shell with liquid DT fill. Central to the Double Shell concept is kinetic energy transfer from the outer to inner shell via collision. The collision determines maximum energy available for compression and implosion shape of the fuel. We present results of a NIF shape-transfer study: two experiments comparing shape and trajectory of the outer and inner shells at post-collision times. An outer-shell-only target shot measured the no-impact shell conditions, while an `imaging' double shell shot measured shell conditions with impact. The `imaging' target uses a low-Z inner shell and is designed to perform in similar collision physics space to a high-Z double shell but can be radiographed at 16keV, near the viable 2DConA BL energy limit. Work conducted under the auspices of the U.S. DOE by LANL under contract DE-AC52-06NA25396.
Application of spherically bent crystals spectrometer to X-ray diagnosis
International Nuclear Information System (INIS)
Liu Lifeng; Xiao Shali; Wang Hongjian; Shi Jun; Qian Jiayu; Liu Shenye; Wei Minxi; Chen Bolun
2010-01-01
In order to diagnose X-ray emitted from the plasma, a spherically bent crystals spectrometer was developed based on the X-ray Bragg diffraction theory. In the experiment, the dispersive element of crystal analyzer was quartz, the bent radius was 250 mm and the range of Bragg angle of the crystal was 30 degree to 67.5 degree. The X-ray film, as its principal detector, obtained spectra information which had an effective area of 10 mm x 50 mm. The experiment was carried out at the anode accelerator. The detector obtained the X-ray spectra information of the K-shell Ti spectra. By the analysis of spectra information, the spectral resolution of spherically bent quartz crystals can be achieved for more than 1000, and the spectral passband is 0.43 eV. (authors)
A 20-DOF hybrid stress general shell element
Kang, David S.; Pian, Theodore H. H.
1988-01-01
A hybrid-stress general shell element is developed based on the Hellinger-Reissner principle modified for relaxed element compatibility conditions. The element is based on a thin-shell theory with Love-Kirchhoff hypothesis. It is of quadrilateral shape with only four corner nodes and five degrees of freedom per node. The geometry of the element is approximated through a cubic polynomial surface patch. Numerical examples consisting of torsion-loaded slit cylinder and pinched cylinders with open ends and rigid diaphragmed ends demonstrate excellent performance of the present element.