Showing papers on "Shell (structure) published in 2003"

Application of double negative materials to increase the power radiated by electrically small antennas

Abstract: The effect of surrounding an electrically small dipole antenna with a shell of double negative (DNG) material (/spl epsiv//sub r/<0 and /spl mu//sub r/<0) has been investigated both analytically and numerically. The problem of an infinitesimal electric dipole embedded in a homogeneous DNG medium is treated; its analytical solution shows that this electrically small antenna acts inductively rather than capacitively as it would in free space. It is then shown that a properly designed dipole-DNG shell combination increases the real power radiated by more than an order of magnitude over the corresponding free space case. The reactance of the antenna is shown to have a corresponding decrease. Analysis of the reactive power within this dipole-DNG shell system indicates that the DNG shell acts as a natural matching network for the dipole. An equivalent circuit model is introduced that confirms this explanation. Several cases are presented to illustrate these results. The difficult problem of interpreting the energy stored in this dipole-DNG shell system when the DNG medium is frequency independent and, hence, of calculating the radiation Q is discussed from several points of view.

Heat-transfer and solidification model of continuous slab casting: CON1D

Abstract: A simple, but comprehensive model of heat transfer and solidification of the continuous casting of steel slabs is described, including phenomena in the mold and spray regions. The model includes a one-dimensional (1-D) transient finite-difference calculation of heat conduction within the solidifying steel shell coupled with two-dimensional (2-D) steady-state heat conduction within the mold wall. The model features a detailed treatment of the interfacial gap between the shell and mold, including mass and momentum balances on the solid and liquid interfacial slag layers, and the effect of oscillation marks. The model predicts the shell thickness, temperature distributions in the mold and shell, thickness of the resolidified and liquid powder layers, heat-flux profiles down the wide and narrow faces, mold water temperature rise, ideal taper of the mold walls, and other related phenomena. The important effect of the nonuniform distribution of superheat is incorporated using the results from previous three-dimensional (3-D) turbulent fluid-flow calculations within the liquid pool. The FORTRAN program CONID has a user-friendly interface and executes in less than 1 minute on a personal computer. Calibration of the model with several different experimental measurements on operating slab casters is presented along with several example applications. In particular, the model demonstrates that the increase in heat flux throughout the mold at higher casting speeds is caused by two combined effects: a thinner interfacial gap near the top of the mold and a thinner shell toward the bottom. This modeling tool can be applied to a wide range of practical problems in continuous casters.

LED lamp heat sink

Abstract: An LED lamp includes an exterior shell that has the same form factor as a conventional incandescent light bulb, such as a PAR type bulb. The LED lamp includes an optical reflector that is disposed within the shell and that directs the light emitted from one or more LEDs. The optical reflector and shell define a space that is used to channel air to cool the device. The LED is mounted on a heat sink that is disposed within the shell. A fan moves air over the heat sink and through the spaced defined by the optical reflector and the shell. The shell includes one or more apertures that serve as air inlet or exhaust apertures. One or more apertures defined by the optical reflector and shell at the opening of the shell can also be used as air exhaust or inlet apertures.

Freely Dispersible Au@TiO2, Au@ZrO2, Ag@TiO2, and Ag@ZrO2 Core−Shell Nanoparticles: One-Step Synthesis, Characterization, Spectroscopy, and Optical Limiting Properties

Abstract: We report a one-step route for the synthesis of Au@TiO2, Au@ZrO2, Ag@TiO2, and Ag@ZrO2 particles in nanometer dimensions, with controllable shell thickness. This scalable procedure leads to stable and freely dispersible particles, and bulk nanocomposite materials have been made this way. The procedure leads to particles of various morphologies, with a crystalline core in the size range of 30−60 nm diameter and an amorphous shell of ∼3 nm thickness in a typical synthesis. The core diameter and shell thickness (in the range of 1−10 nm) can be varied, leading to different absorption maxima. The material has been characterized with microscopic, diffraction, and spectroscopic techniques. The metal particle growth occurs by the carbamic acid reduction route followed by hydrolysis of the metal oxide precursor, resulting in the oxide cover. The particles could be precipitated and redispersed. The shell, upon thermal treatment, gets converted to crystalline oxides. Cyclic voltammetric studies confirm the core−shel...

Growth of three-shell onionlike bimetallic nanoparticles.

Abstract: We show by molecular dynamics simulations on three systems (B/A=Pd/Ag, Cu/Ag, and Ni/Ag) that three-shell metallic nanoparticles made by a core of a metal A, an intermediate shell of metal B and an external shell of metal A (A-B-A nanoparticles) can be grown by deposition of B atoms onto an A core. The growth of the intermediate B shell is triggered by the fact that the most favorable positions for isolated B impurities inside A clusters are located just one layer below the cluster surface.

Effect of ZnS shell thickness on the phonon spectra in CdSe quantum dots

Abstract: The evolution of the optical phonon spectra of colloidal core/shell CdSe/ZnS quantum dots with an increase of the shell thickness from 0.5 to 3.4 monolayers has been studied by resonant Raman spectroscopy. The results obtained suggest that the ZnS shell changes its structure from amorphous to partly crystalline as the thickness increases. Simultaneously, an increase in Raman scattering by surface (core/shell interface) phonons and the redshift of the corresponding phonon band have been observed and assigned to variations in the shell structure. The disorder present in the shell provides a major contribution to the line shape of the Raman spectra at higher ZnS coverage. A method to control the quality of quantum dots based on Raman spectroscopy is proposed.

Trash can assembly

Abstract: A trash can assembly has a shell, a lid fitted over the top end of the shell, a pedal positioned adjacent the bottom end of the shell, a link assembly coupling the pedal and the lid, and a motion damper coupled to the link assembly for slowing the closing motion of the lid. The assembly also includes an inner liner that is retained inside the shell, with a support frame secured to the top end of the shell and having a ridge on which a peripheral lip of the inner liner rests. Two or more inner liners can be provided inside the shell. In addition, the lid can be pivotably connected to the upper edge of the outer shell by a connector which has a sleeve that is coupled to the upper edge of the outer shell, a non-metal tube that is positioned inside the sleeve, and a shaft received inside the bore of the tube.

Microtopography and antifouling properties of the shell surface of the bivalve molluscs mytilus galloprovincialis and pinctada imbricata

Abstract: Biofouling rapidly covers most submerged surfaces in the marine environment. However, some marine organisms remain clean despite strong fouling pressure. Potential physical inhibitors of fouling were investigated by comparing the thickness, cover, and microtopographic structure of the periostracum of two bivalve molluscs, the blue mussel, Mytilus galloprovincialis , and the pearl oyster, Pinctada imbricata . The cover and thickness of the periostracum were measured on four size classes of each species using histological and microscopic techniques. The periostracum of M. galloprovincialis was significantly thicker than that of P. imbricata and did not differ significantly between size classes. In contrast, the periostracum of P. imbricata decreased significantly with increasing size in both thickness and cover. The microtopography of the shell surface of both species was measured using atomic force microscopy (AFM) and scanning electron microscopy (SEM), which revealed a homogeneous ridged surface for M. g...

A Non-Incremental Finite Element Procedure for the Analysis of Large Deformation of Plates and Shells in Mechanical System Applications

Abstract: In this investigation, a non-incremental solution procedure for the finite rotationand large deformation analysis of plates is presented. The method, whichis based on the absolute nodal coordinate formulation, leads to plateelements capable of representing exact rigid body motion. In thismethod, continuity conditions on all the displacement gradients areimposed. Therefore, non-smoothness of the plate mid-surface at the nodalpoints is avoided. Unlike other existing finite element formulationsthat lead to a highly nonlinear inertial forces for three-dimensionalelements, the proposed formulation leads to a constant mass matrix, andas a result, the centrifugal and Coriolis inertia forces are identicallyequal to zero. Furthermore, the method relaxes some of the assumptionsused in the classical and Mindlin plate models and automatically satisfiesthe objectivity requirements. By using a generalcontinuum mechanics approach, a relatively simple expression for theelastic forces is obtained. Generalization of the formulation to thecase of shell elements is discussed. As examples of the implementationof the proposed method, two different plate elements are presented; oneplate element does not guarantee the continuity of the displacementgradients between the nodal points, while the other plate elementguarantees this continuity. Numerical results are presented in order todemonstrate the use of the proposed method in the large rotation anddeformation analysis of plates and shells. The numerical results, whichare compared with the results obtained using existing incrementalprocedures, show that the solution obtained using the proposed methodsatisfies the principle of work and energy. These results are obtainedusing explicit numerical integration method. Potential applications ofthe proposed method include high-speed metal forming, vehiclecrashworthiness, rotor blades, and tires.

Thermal buckling of functionally graded cylindrical shell

Abstract: In this article, the thermal buckling loads of cylindrical shells of functionally graded material are considered. Derivation of equations are based on the first-order shell theory and the Sanders kinematic equations. The derived equilibrium and stability equations for the functionally graded cylindrical shell are identical with the equations for homogeneous shells expressed in the form of forces and moments per unit length. Assuming that the material properties vary linearly through the thickness direction, the system of fundamental partial differential equations in terms of the displacement components is established. Buckling analysis of functionally graded cylindrical shells under two types of thermal loads with simply supported boundary conditions are carried out. Results are obtained in the analytical form. The results are validated with the known data in the literature.

Nonlinear structural mechanics based modeling of carbon nanotube deformation.

Abstract: A nonlinear structural mechanics based approach for modeling the structure and the deformation of single-wall and multiwall carbon nanotubes (CNTs) is presented. Individual tubes are modeled using shell finite elements, where a specific pairing of elastic properties and mechanical thickness of the tube wall is identified to enable successful modeling with shell theory. The effects of van der Waals forces are simulated with special interaction elements. This new CNT modeling approach is verified by comparison with molecular dynamics simulations and high-resolution micrographs available in the literature. The mechanics of wrinkling of multiwall CNTs are studied, demonstrating the role of the multiwalled shell structure and interwall van der Waals interactions in governing buckling and postbuckling behavior.

Method of forming a tubular blank into a structural component and die therefor

Abstract: A method of forming an elongated tubular blank into a tubular structural component having a predetermined outer configuration, the method comprising: providing a shape imparting shell formed from a low permeability, rigid material which includes an inner surface defining the predetermined shape, plugging the open ends of the tubular blank, placing the plugged blank into the shell, and forming the tubular blank into the tubular component by inductively heating axial portions of the blank by axially spaced conductors adjacent the shell while or before forcing gas at a high pressure into the plugged blank until the blank conforms to at least a portion of the inner surface of the shell to form the structural component.

Electrostatic latent image developing toner

Abstract: An electrostatic latent-image developing toner comprising: a core particle and a shell layer formed on an outer portion thereof, wherein the shell layer comprises a crystalline polyester resin having a softening point from 60 to 120° C. at 70 to 100% by weight of the entire shell-layer constituent resin, and an image-forming method using the toner.

Passivated Iron as Core−Shell Nanoparticles

Abstract: Using reverse micelles as reaction vessels, it is possible to synthesize iron nanoparticles that are coated with a native oxide shell. The nanoparticles presented here consist of a metallic iron glass surrounded by a disordered oxide shell. This shell protects the metallic core from oxidation for at least 6 weeks.

Structure and phase diagram of high-density water: the role of interstitial molecules.

Abstract: The structural transformations occurring to water from the low- to the high-density regimes have been studied by classical molecular dynamics calculations. The local structure is analyzed through a proper choice of the relevant orientational distribution functions. This approach sheds light on the key role played by the interstitial molecules in the second coordination shell and identifies a clear structural fingerprint of high-density water. As a consequence, the analogy between the structure of high-density water and those of high-density ices is evidenced.

Dependence of Shell Thickness on Core Compression in Acrylic Acid Modified Poly(N-isopropylacrylamide) Core/Shell Microgels

Abstract: The swelling properties of poly(N-isopropylacrylamide) (pNIPAm)-based core/shell microgels are investigated as a function of shell thickness. Core particles composed of cross-linked pNIPAm-co-acrylic acid serve as nuclei for subsequent polymerization of a cross-linked pNIPAm shell. The thickness of the shell component is varied by changing the amount of monomer present during the shell addition polymerization. Photon correlation spectroscopy results indicate that the thickness of the shell greatly impacts the swelling properties of the core as a function of polymer network density, solution pH, and temperature. Previously reported results on this core/shell polymer combination show that the core is restricted from swelling to its native volume in the presence of the shell below the polymer phase transition temperature of 31 °C. The shell also compresses the core above the polymer phase transition temperature in pH solutions above the acid pKa by inducing a volume change, despite the fact that the core is ...

Analysis of 3D problems using a new enhanced strain hexahedral element

Abstract: The now classical enhanced strain technique, employed with success for more than 10 years in solid, both 2D and 3D and shell finite elements, is here explored in a versatile 3D low-order element which is identified as HIS. The quest for accurate results in a wide range of problems, from solid analysis including near-incompressibility to the analysis of locking-prone beam and shell bending problems leads to a general 3D element. This element, put here to test in various contexts, is found to be suitable in the analysis of both linear problems and general non-linear problems including finite strain plasticity. The formulation is based on the enrichment of the deformation gradient and approximations to the shape function material derivatives. Both the equilibrium equations and their variation are completely exposed and deduced, from which internal forces and consistent tangent stiffness follow. A stabilizing term is included, in a simple and natural form. Two sets of examples are detailed: the accuracy tests in the linear elastic regime and several finite strain tests. Some examples involve finite strain plasticity. In both sets the element behaves very well, as is illustrated in numerous examples. Copyright © 2003 John Wiley & Sons, Ltd.

Compositions comprising encapsulated material

Abstract: A composition such as a water-based consumer product comprises material (e.g. perfume) encapsulated within shell capsules, each capsule comprising an encapsulating wall having an inner surface and an outer surface, with a coating on the inner surface and/or outer surface of the shell wall, the composition further comprising surfactant and/or solvent. The coating can improve the barrier properties of the shell and can enhance retention of the encapsulated materials within the shell.

Devices and methods for manipulation of organ tissue

Abstract: The invention provides techniques for holding a moving organ, such as a beating heart (10). A manipulation device (12) that holds the organ includes an outer shell (16) and an inner shell (14). Vacuum pressure applied to the outer shell draws the organ into the inner shell. The vacuum pressure is communicated to the inner shell chamber via one or more apertures (58) in the inner shell. The inner shell may have a structure and a texture that enhances the hold on the organ, and the manipulation device may also include a skirt-like member (18) to improve the seal between the manipulation device and the organ.

Brushless permanent magnet wheel motor with variable axial rotor/stator alignment

Abstract: A brushless permanent magnet electric machine with a fixed radial air gap is operated to a much higher speed than normal maximum speed by the reduction in effective magnet pole strength. Permanent magnets are supported on the inner surface of an axially movable cylindrical shell. A plurality of magnetic poles provided with wire coils are supported on a stationary cylindrical member cooperate with the permanent magnets on the axially movable cylindrical shell to either cause, or react to, rotation of the axially movable cylindrical shell. The axially movable cylindrical shell and cylindrical member are coaxial. The cylindrical shell is axially movable with respect to the cylindrical member.

Transition zone in wind turbine blade

Abstract: The invention relates to a wind turbine blade and a transitional shell blank for the manufacture of the shell of a wind turbine blade, the blade or the transitional shell blank being made of fibre-reinforced polymer including a first type of fibres (1, 3, 6) of a first stiffness and a first elongation at breakage, and a second type of fibres (2, 5, 7) of a different stiffness and a different elongation at breakage. According to the invention the two types of fibres are distributed in the polymer matrix. When seen in a sectional view perpendicular to longitudinal direction of the blade or the transitional shell blank, the quantitative ratio of the two types of fibres varies continuously in the longitudinal direction of the blade or of the transition shell blank.

Cylindrical shell buckling: a characterization of localization and periodicity

Abstract: A hypothesis for the prediction of the circumferential wavenumber of buckling of the thin axially-compressed cylindrical shell is presented, based on the addition of a length effect to the classical (Koiter circle) critical load result. Checks against physical and numerical experiments, both by direct comparison of wavenumbers and via a scaling law, provide strong evidence that the hypothesis is correct.

Functionally Graded Cylindrical Shell Thermal Instability Based on Improved Donnell Equations

Abstract: The thermal instability of cylindrical shells of functionally graded material is considered. The derivation of equations is based on first-order shell theory and the complete Sanders kinematic equations. The resulting equilibrium and the stability equations contain the rotations in the x and θ directions and the transverse shear force in the θ direction, in addition to the conventional Donnell equations. When it is assumed that the material properties vary linearly through the thickness direction, the system of fundamental partial differential equations in terms of the displacement components is is established. Instability analysis of functionally graded cylindrical shells under two types of thermal loads with simply supported boundary conditions is carried out. Results are obtained in analytical form. The results are validated with the known data in the literature.