Buckling of angle-ply laminated circular cylindrical shells
NASA Technical Reports Server (NTRS)
Hirano, Y.
1979-01-01
This note presents closed-form solutions for axisymmetrical and axially unsymmetrical buckling of angle-ply laminated circular cylindrical shells under axial compression. The axisymmetrical and axially unsymmetrical buckling stress are found to be different from each other, and the best lamination angles which give the highest buckling stress are obtained.
Wave propagation in laminated orthotropic circular cylindrical shells
NASA Technical Reports Server (NTRS)
Srinivas, S.
1976-01-01
An exact three-dimensional analysis of wave propagation in laminated orthotropic circular cylindrical-shells is developed. Numerical results are presented for three-ply shells, and for various axial wave lengths, circumferential wave numbers, and thicknesses. Results from a thin shell theory and a refined approximate theory are compared with the exact results.
Internal resonance of axially moving laminated circular cylindrical shells
NASA Astrophysics Data System (ADS)
Wang, Yan Qing; Liang, Li; Guo, Xing Hui
2013-11-01
The nonlinear vibrations of a thin, elastic, laminated composite circular cylindrical shell, moving in axial direction and having an internal resonance, are investigated in this study. Nonlinearities due to large-amplitude shell motion are considered by using Donnell's nonlinear shallow-shell theory, with consideration of the effect of viscous structure damping. Differently from conventional Donnell's nonlinear shallow-shell equations, an improved nonlinear model without employing Airy stress function is developed to study the nonlinear dynamics of thin shells. The system is discretized by Galerkin's method while a model involving four degrees of freedom, allowing for the traveling wave response of the shell, is adopted. The method of harmonic balance is applied to study the nonlinear dynamic responses of the multi-degrees-of-freedom system. When the structure is excited close to a resonant frequency, very intricate frequency-response curves are obtained, which show strong modal interactions and one-to-one-to-one-to-one internal resonance phenomenon. The effects of different parameters on the complex dynamic response are investigated in this study. The stability of steady-state solutions is also analyzed in detail.
Bending Boundary Layers in Laminated-Composite Circular Cylindrical Shells
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.; Smeltzer, Stanley S., III
2000-01-01
An analytical, parametric study of the attenuation of bending boundary layers or edge effects in balanced and unbalanced, symmetrically and unsymmetrically laminated thin cylindrical shells is presented for nine contemporary material systems. The analysis is based on the linear Sanders-Koiter shell equations and specializations to the Love-Kirchhoff shell equations and Donnell's equations are included. Two nondimensional parameters are identified that characterize and quantify the effects of laminate orthotropy and laminate anisotropy on the bending boundary-layer decay length in a very general and encompassing manner. A substantial number of structural design technology results are presented for a wide range of laminated-composite cylinders. For all the laminate constructions considered, the results show that the differences between results that were obtained with the Sanders-Koiter shell equations, the Love-Kirchhoff shell equations, and Donnell's equations are negligible. The results also show that the effect of anisotropy in the form of coupling between pure bending and twisting has a negligible effect on the size of the bending boundary-layer decay length of the balanced, symmetrically laminated cylinders considered. Moreover, the results show that coupling between the various types of shell anisotropies has a negligible effect on the calculation of the bending boundary-layer decay length in most cases. The results also show that in some cases neglecting the shell anisotropy results in underestimating the bending boundary-layer decay length and in other cases it results in an overestimation.
Bending Boundary Layers in Laminated-Composite Circular Cylindrical Shells
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.; Smeltzer, Stanley S., III
2000-01-01
A study of the attenuation of bending boundary layers in balanced and unbalanced, symmetrically and unsymmetrically laminated cylindrical shells is presented for nine contemporary material systems. The analysis is based on the linear Sanders-Koiter shell equations and specializations to the Love-Kirchhoff shell equations and Donnell's equations are included. Two nondimensional parameters are identified that characterize the effects of laminate orthotropy and anisotropy on the bending boundary-layer decay length in a very general manner. A substantial number of structural design technology results are presented for a wide range of laminated-composite cylinders. For all laminates considered, the results show that the differences between results obtained with the Sanders-Koiter shell equations, the Love-Kirchhoff shell equations, and Donnell's equations are negligible. The results also show that the effect of anisotropy in the form of coupling between pure bending and twisting has a negligible effect on the size of the bending boundary-layer decay length of the balanced, symmetrically laminated cylinders considered. Moreover, the results show that coupling between the various types of shell anisotropies has a negligible effect on the calculation of the bending boundary-layer decay length in most cases. The results also show that, in some cases, neglecting the shell anisotropy results in underestimating the bending boundary-layer decay length and, in other cases, results in an overestimation.
Analysis of laminated, composite, circular cylindrical shells with general boundary conditions
NASA Technical Reports Server (NTRS)
Srinivas, S.
1974-01-01
This report develops: (1) a refined approximate theory for the static and dynamic analyses of finite, laminated, composite, circular cylindrical shells with general boundary conditions; (2) an exact three-dimensional analysis of simply supported, laminated, composite, circular cylindrical shells, and (3) a thin-shell theory for laminated, composite, circular cylindrical shells. In the refined approximate theory the displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and transverse normal stress are included. A variational approach is followed to obtain the governing differential equations and boundary conditions. A general solution of the governing differential equations is also presented. The results obtained by using the refined approximate theory and the thin-shell theory are compared with the exact results for the case of free vibrations of simply supported, laminated, composite, circular cylindrical shells. The refined approximate theory is very accurate, even for thick shells with short nodal distances, whereas thin-shell theory is reasonably accurate only for thin shells at moderate nodal distances and wave number less than 2.
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.; Schultz, Marc R.
2012-01-01
A detailed exact solution is presented for laminated-composite circular cylinders with general wall construction and that undergo axisymmetric deformations. The overall solution is formulated in a general, systematic way and is based on the solution of a single fourth-order, nonhomogeneous ordinary differential equation with constant coefficients in which the radial displacement is the dependent variable. Moreover, the effects of general anisotropy are included and positive-definiteness of the strain energy is used to define uniquely the form of the basis functions spanning the solution space of the ordinary differential equation. Loading conditions are considered that include axisymmetric edge loads, surface tractions, and temperature fields. Likewise, all possible axisymmetric boundary conditions are considered. Results are presented for five examples that demonstrate a wide range of behavior for specially orthotropic and fully anisotropic cylinders.
Exact solutions for laminated composite cylindrical shells in cylindrical bending
NASA Technical Reports Server (NTRS)
Yuan, F. G.
1992-01-01
Analytic elasticity solutions for laminated composite cylindrical shells under cylindrical bending are presented. The material of the shell is assumed to be general cylindrically anisotropic. Based on the theory of cylindrical anisotropic elasticity, coupled governing partial differential equations are developed. The general expressions for the stresses and displacements in the laminated composite cylinders are discussed. The closed form solutions based on Classical Shell Theory (CST) and Donnell's (1933) theory are also derived for comparison purposes. Three examples illustrate the effect of radius-to-thickness ratio, coupling and stacking sequence. The results show that, in general, CST yields poor stress and displacement distributions for thick-section composite shells, but converges to the exact elasticity solution as the radius-to-thickness ratio increases. It is also shown that Donnell's theory significantly underestimates the stress and displacement response.
Arbitrarily laminated, anisotropic cylindrical shell under internal pressure
NASA Technical Reports Server (NTRS)
Chaudhuri, Reaz Z.; Balaraman, K.; Kunukkasseril, Vincent X.
1986-01-01
An arbitrarily laminated, anisotropic cylindrical shell of finite length, under uniform internal pressure, is analyzed using Love-Timoshenko's kinematic relations and under the framework of classical lamination theory. The previously obtained solutions for asymmetrically laminated orthotropic (cross-ply) as well as unbalanced-symmetric and balanced-unsymmetric (angle-ply) cylindrical shells under the same loading conditions have been shown to be special cases of the present closed-form solution. Numerical results have been presented for a two-layer cylindrical shell and compared with those obtained using finite element solutions based on the layerwise constant shear-angle theory. These are expected to serve as benchmark solutions for future comparisons and to facilitate the use of unsymmetric lamination in design.
A higher order theory of laminated composite cylindrical shells
NASA Technical Reports Server (NTRS)
Krishna Murthy, A. V.; Reddy, T. S. R.
1986-01-01
A new higher order theory has been proposed for the analysis of composite cylindrical shells. The formulation allows for arbitrary variation of inplane displacements. Governing equations are presented in the form of a hierarchy of sets of partial differential equations. Each set describes the shell behavior to a certain degree of approximation. The natural frequencies of simply-supported isotropic and laminated shells and stresses in a ring loaded composite shell have been determined to various orders of approximation and compared with three dimensional solutions. These numerical studies indicate the improvements achievable in estimating the natural frequencies and the interlaminar shear stresses in laminated composite cylinders.
Buckling of circular cylindrical shells under dynamically applied axial loads
NASA Technical Reports Server (NTRS)
Tulk, J. D.
1972-01-01
A theoretical and experimental study was made of the buckling characteristics of perfect and imperfect circular cylindrical shells subjected to dynamic axial loading. Experimental data included dynamic buckling loads (124 data points), high speed photographs of buckling mode shapes and observations of the dynamic stability of shells subjected to rapidly applied sub-critical loads. A mathematical model was developed to describe the dynamic behavior of perfect and imperfect shells. This model was based on the Donnell-Von Karman compatibility and equilibrium equations and had a wall deflection function incorporating five separate modes of deflection. Close agreement between theory and experiment was found for both dynamic buckling strength and buckling mode shapes.
NASA Astrophysics Data System (ADS)
Amabili, M.
2003-07-01
Large-amplitude (geometrically non-linear) vibrations of circular cylindrical shells subjected to radial harmonic excitation in the spectral neighbourhood of the lowest resonances are investigated. The Lagrange equations of motion are obtained by an energy approach, retaining damping through Rayleigh's dissipation function. Four different non-linear thin shell theories, namely Donnell's, Sanders-Koiter, Flügge-Lur'e-Byrne and Novozhilov's theories, which neglect rotary inertia and shear deformation, are used to calculate the elastic strain energy. The formulation is also valid for orthotropic and symmetric cross-ply laminated composite shells. The large-amplitude response of perfect and imperfect, simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of the lowest natural frequency is computed for all these shell theories. Numerical responses obtained by using these four non-linear shell theories are also compared to results obtained by using the Donnell's non-linear shallow-shell equation of motion. A validation of calculations by comparison with experimental results is also performed. Both empty and fluid-filled shells are investigated by using a potential fluid model. The effects of radial pressure and axial load are also studied. Boundary conditions for simply supported shells are exactly satisfied. Different expansions involving from 14 to 48 generalized co-ordinates, associated with natural modes of simply supported shells, are used. The non-linear equations of motion are studied by using a code based on an arclength continuation method allowing bifurcation analysis.
Nicols, R.O.
1985-08-15
A 2-D optical analysis is described that allows determination of the intensity distribution on a circular cylinder located in the focal zone of nonperfect concentrators. We call nonperfect concentrators those in which the normal to each differential element of the specular surface departs from its correct position by an angle epsilon, the possible values of which follow a Gaussian distribution of mean value epsilon-bar and standard deviation sigma. The analysis is based on a previous one developed to calculate the intensity distribution at the receiver plane of nonperfect cylindrical concentrators. The analysis permits the consideration of circular receivers displaced from the focus by distance delta/sub f/ in any direction and directions of the incident rays nonparallel to the parabola's symmetry plane. Results for different sets of parameters characterizing the behavior of a given concentrator are shown and compared.
Nonobvious features of dynamics of circular cylindrical shells
NASA Astrophysics Data System (ADS)
Leizerovich, G. S.; Taranukha, N. A.
2008-04-01
In the framework of the nonlinear theory of flexible shallow shells, we study free bending vibrations of a thin-walled circular cylindrical shell hinged at the end faces. The finite-dimensional shell model assumes that the excitation of large-amplitude bending vibrations inevitably results in the appearance of radial vibrations of the shell. The modal equations are obtained by the Bubnov-Galerkin method. The periodic solutions are found by the Krylov-Bogolyubov method. We show that if the tangential boundary conditions are satisfied "in the mean," then, for a shell of finite length, significant errors arise in determining its nonlinear dynamic characteristics. We prove that small initial irregularities split the bending frequency spectrum, the basic frequency being smaller than in the case of an ideal shell.
Finite deformations of an electroelastic circular cylindrical tube
NASA Astrophysics Data System (ADS)
Melnikov, Andrey; Ogden, Ray W.
2016-12-01
In this paper the theory of nonlinear electroelasticity is used to examine deformations of a pressurized thick-walled circular cylindrical tube of soft dielectric material with closed ends and compliant electrodes on its curved boundaries. Expressions for the dependence of the pressure and reduced axial load on the deformation and a potential difference between, or uniform surface charge distributions on, the electrodes are obtained in respect of a general isotropic electroelastic energy function. To illustrate the behaviour of the tube, specific forms of energy functions accounting for different mechanical properties coupled with a deformation independent quadratic dependence on the electric field are used for numerical purposes, for a given potential difference and separately for a given charge distribution. Numerical dependences of the non-dimensional pressure and reduced axial load on the deformation are obtained for the considered energy functions. Results are then given for the thin-walled approximation as a limiting case of a thick-walled cylindrical tube without restriction on the energy function. The theory described herein provides a general basis for the detailed analysis of the electroelastic response of tubular dielectric elastomer actuators, which is illustrated for a fixed axial load in the absence of internal pressure and fixed internal pressure in the absence of an applied axial load.
Acoustic radiation from single and double ribbed circular cylindrical shells
NASA Astrophysics Data System (ADS)
Burroughs, C. B.; Hayek, S. I.; Hallander, J. E.; Bostian, D. A.
1984-03-01
Measurements of the acoustic radiation from single and double ribbed circular cylindrical shells were made on the NUSC Transducer Calibration Platform (TCP) in Lake Seneca, NY. Six different types of mechanical drives were used at each of three locations inside the inner shell. Measurements of the shell vibration and acoustic radiation were made with and without outer shells installed around the inner shell structure. For two types of drives, measurements were made with a pressure release layer installed between the inner and outer shell surfaces. Acoustic radiation measurements were made as a function of frequency from 20 to 5,000 Hz and as a function of observation direction at several frequencies for each shell and drive measurement configuration. Measured acoustic radiation data as a function of frequency have been processed. Analysis of the processed data is presented and discussed. It is shown that the location of the drive had a significant effect on the acoustic radiation. The outer shell reduced the acoustic radiation at shell resonant frequencies, but had little effect on other frequencies. The pressure release layer in the double shell had little effect on the acoustic radiation.
Free vibration analysis of skewed open circular cylindrical shells
NASA Astrophysics Data System (ADS)
Kandasamy, Selvakumar; Singh, Anand V.
2006-03-01
In this paper, a numerical study is presented for the free vibration of skewed open circular cylindrical deep shells. The formulation considers first-order shear deformation theory of shells and includes rotary inertia and shear deformation so that thin-to-moderately thick shells can be analyzed. A set of grid points, the number of which depends upon the orders of the polynomials chosen for the displacement and rotation components, on the middle surface of the shell is defined first. For a particular displacement component, the field functions are derived corresponding to each node from the above-mentioned set of points and are used in the Rayleigh-Ritz method to calculate frequencies and mode shapes. Convergence study with reference to the order of the polynomials used for the displacement fields was performed first. Numerical results obtained from the present method are compared with those from the finite element method and very good agreement is observed. Additional results are presented and discussed in this paper for skewed panels clamped at the curved edges and free at the straight parallel edges.
Buckling characteristic of multi-laminated composite elliptical cylindrical shells
NASA Astrophysics Data System (ADS)
Kassegne, Samuel Kinde; Chun, Kyoung-Sik
2015-03-01
Fiber-reinforced composite materials continue to experience increased adoption in aerospace, marine, automobile, and civil structures due to their high specific strength, high stiffness, and light weight. This increased use has been accompanied by applications involving non-traditional configurations such as compression members with elliptical cross-sections. To model such shapes, we develop and report an improved generalized shell element called 4EAS-FS through a combination of enhanced assumed strain and the substitute shear strain fields. A flat shell element has been developed by combining a membrane element with drilling degree-of-freedom and a plate bending element. We use the element developed to determine specifically buckling loads and mode shapes of composite laminates with elliptical cross-section including transverse shear deformations. The combined influence of shell geometry and elliptical cross-sectional parameters, fiber angle, and lay-up on the buckling loads of an elliptical cylinder is examined. It is hoped that the critical buckling loads and mode shapes presented here will serve as a benchmark for future investigations.
Flow-Induced Vibration of Circular Cylindrical Structures
Chen, Shoei-Sheng
1985-06-01
of heat exchanger tube banks are typical examples. Recently, flow-induced vibration has been studied extensively for several reasons. First, with the use of high-strength materials, structures become more slender and more susceptible to vibration. Second, the development of advanced nuclear power reactors requires high-velocity fluid flowing through components, which can cause detrimental vibrations. Third, the dynamic interaction of structure and fluid is one of the most fascinating problems in engineering mechanics. The increasing study is evidenced by many conferences directed to this subject and numerous publications, including reviews and books. In a broad sense, flow-induced vibration encompasses all topics on the dynamic responses of structures submerged in fluid, containing fluid, or subjected to external flow. In this report, discussions focus on circular cylindrical structures with emphasis on nuclear reactor system components.
NASA Technical Reports Server (NTRS)
Carper, D. M.; Johnson, E. R.; Hyer, M. W.
1983-01-01
Equations are developed which govern the deflection response of long cylindrical panels subjected to a line load. The line load is directed toward the center of curvature of the panel, is located at an arbitrary point along the arc length of the panel, and is included at an arbitrary angle relative to the radial direction. Only the geometrically linear problem is considered and the spatial dependence in the problem is reduced to one independent variable, specifically, the arc length along the panel. The problem is thus solvable in closed form. Both symmetrically laminated and the less common unsymmetrically laminated simply supported panels are studied. The unsymmetrically laminated case was considered because the natural shape of an unsymmetric laminate is cylindrical. Results are presented which show the influence of the location and inclination of the line load on panel deflection. Shallow and deep panels are considered. Both the symmetric and unsymmetric panels exhibit similar behavior, the unsymmetric configurations being less stiff. Limited experimental results are presented.
NASA Astrophysics Data System (ADS)
Lakshminarayana, A.; Vijayakumar, R.; Krishnamohana Rao, G.
2016-09-01
The progressive failure analysis of symmetrically laminated composite plate [0°/+45°/-45°/90°]2s with circular or elliptical cutout under uniform uniaxial compression loading is carried out using finite element method. Hashin's failure criterion is used to predict the lamina failure. A parametric study has been carried out to study the effect of elliptical / circular cutout orientation, cutout size and plate thickness on the ultimate failure load of laminated composite plate under uni-axial compression loading. It is noticed that elliptical cutout orientation has influence on the strength of the notched composite plates. It is observed that the laminate size of the elliptical/circular cutout and plate thickness has substantial influence on the ultimate failure load of notched composite plates.
Postbuckling behavior of graphite/epoxy laminated cylindrical panels under axial compression
Hong, C.S.; Kweon, J.H.
1993-12-31
The buckling and postbuckling behavior of graphite/epoxy laminated cylindrical panels under axial compression are investigated by the nonlinear finite element method. For the finite element analysis, the updated Lagrangian formulation and the eight-node degenerated shell element are utilized. Improved load-increment and iteration strategies based on the deflection mode of panel are proposed for the incremental nonlinear finite element analysis along the postbuckling equilibrium path. Using the developed finite element program, the composite cylindrical panels are analyzed with various stacking sequences. The characteristics of buckling and postbuckling behavior is discussed in the view of load-carrying capacities and deformation. The behavior of axially compressed composite panels are largely dependent on the stacking sequence, and there exist some differences between the initial buckling loads and the postbuckling load-carrying capacities.
NASA Astrophysics Data System (ADS)
Cao, Xiongtao; Shi, Lei; Zhang, Xusheng; Jiang, Guohe
2013-06-01
Active control of sound radiation from piezoelectric laminated cylindrical shells is theoretically investigated in the wavenumber domain. The governing equations of the smart cylindrical shells are derived by using first-order shear deformation theory. The smart layer is divided into lots of actuator patches, each of which is coated with two very thin electrodes at its inner and outer surfaces. Proportional derivative negative feedback control is applied to the actuator patches and the stiffness of the controlled layer is derived in the wavenumber domain. The equivalent driving forces and moments generated by the piezoelectric layer can produce distinct sound radiation. Large actuator patches cause strong wavenumber conversion and fluctuation of the far-field sound pressure, and do not make any contribution to sound reduction. Nevertheless, suitable small actuator patches induce weak wavenumber conversion and play an important role in the suppression of vibration and acoustic power. The derivative gain of the active control can effectively suppress sound radiation from smart cylindrical shells. The effects of small proportional gain on the sound field can be neglected, but large proportional gain has a great impact on the acoustic radiation of cylindrical shells. The influence of different piezoelectric materials on the acoustic power is described in the numerical results.
Buckling of circular cylindrical shells under axial compression.
NASA Technical Reports Server (NTRS)
Budiansky, B.; Hutchinson, J. W.
1972-01-01
The infinitely long cylindrical shell under axial compression with axisymmetric sinusoidal imperfections is considered. The bifurcation problem is formulated exactly, and a complete family of buckling modes is identified. Koiter's (1963) upper bound pertains to the critical stress associated with one restricted set of modes, and the critical stress for a set of long wavelength modes reproduces some numerical results obtained by Almroth (1966). The initial postbuckling analysis is also formulated exactly. An exact analytical solution is obtained for the limiting case of modes with infinitely long wavelengths, and numerical analysis is used to solve the equations for the other cases. An appendix gives the details of the analysis.
Simplified dispersion curves for circular cylindrical shells using shallow shell theory
NASA Astrophysics Data System (ADS)
Sarkar, Abhijit; Sonti, Venkata R.
2009-04-01
An alternative derivation of the dispersion relation for the transverse vibration of a circular cylindrical shell is presented. The use of the shallow shell theory model leads to a simpler derivation of the same result. Further, the applicability of the dispersion relation is extended to the axisymmetric mode and the high frequency beam mode.
NASA Technical Reports Server (NTRS)
Smull, Leland K.
1943-01-01
Four circular cylindrical grids were tested under axial compression to investigate the validity of a theoretical formula for the critical load for such structures. The chief result of the investigation was to throw light on some difficulties connected with the experimental validation of such formulas.
NASA Technical Reports Server (NTRS)
Hong, C. S.; Crews, J. H., Jr.
1979-01-01
Stresses were calculated for finite-width orthotropic laminates with a circular hole and remote uniaxial loading using a two-dimensional finite element analysis with both uniform stress and uniform displacement boundary conditions. Five different laminates were analyzed. Computed results are presented for selected combinations of hole diameter/sheet-width ratio d/w and length-to-width ratio L/w. For small L/w values, the stress-concentration factors K sub tn were significantly different for the uniform stress and uniform displacement boundary conditions. Typically, for the uniform stress condition, the K sub tn values were much larger than for the infinite strip reference condition; however, for the uniform displacement condition, they were only slightly smaller than for this reference. The results for long strips are also presented as width correction factors. For d/w less or = 0.33, these width correction factors are nearly equal for all five laminates.
Vibrations of cantilevered circular cylindrical shells Shallow versus deep shell theory
NASA Technical Reports Server (NTRS)
Lee, J. K.; Leissa, A. W.; Wang, A. J.
1983-01-01
Free vibrations of cantilevered circular cylindrical shells having rectangular planforms are studied in this paper by means of the Ritz method. The deep shell theory of Novozhilov and Goldenveizer is used and compared with the usual shallow shell theory for a wide range of shell parameters. A thorough convergence study is presented along with comparisons to previously published finite element solutions and experimental results. Accurately computed frequency parameters and mode shapes for various shell configurations are presented. The present paper appears to be the first comprehensive study presenting rigorous comparisons between the two shell theories in dealing with free vibrations of cantilevered cylindrical shells.
Huang, C-Y; Trask, R S; Bond, I P
2010-08-06
A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension.
Huang, C.-Y.; Trask, R. S.; Bond, I. P.
2010-01-01
A study of the influence of embedded circular hollow vascules on structural performance of a fibre-reinforced polymer (FRP) composite laminate is presented. Incorporating such vascules will lead to multi-functional composites by bestowing functions such as self-healing and active thermal management. However, the presence of off-axis vascules leads to localized disruption to the fibre architecture, i.e. resin-rich pockets, which are regarded as internal defects and may cause stress concentrations within the structure. Engineering approaches for creating these simple vascule geometries in conventional FRP laminates are proposed and demonstrated. This study includes development of a manufacturing method for forming vascules, microscopic characterization of their effect on the laminate, finite element (FE) analysis of crack initiation and failure under load, and validation of the FE results via mechanical testing observed using high-speed photography. The failure behaviour predicted by FE modelling is in good agreement with experimental results. The reduction in compressive strength owing to the embedding of circular vascules ranges from 13 to 70 per cent, which correlates with vascule dimension. PMID:20150337
Dispersion analysis and measurement of circular cylindrical wedge-like acoustic waveguides.
Yu, Tai-Ho
2015-09-01
This study investigated the propagation of flexural waves along the outer edge of a circular cylindrical wedge, the phase velocities, and the corresponding mode displacements. Thus far, only approximate solutions have been derived because the corresponding boundary-value problems are complex. In this study, dispersion curves were determined using the bi-dimensional finite element method and derived through the separation of variables and the Hamilton principle. Modal displacement calculations clarified that the maximal deformations appeared at the outer edge of the wedge tip. Numerical examples indicated how distinct thin-film materials deposited on the outer surface of the circular cylindrical wedge influenced the dispersion curves. Additionally, dispersion curves were measured using a laser-induced guided wave, a knife-edge measurement scheme, and a two-dimensional fast Fourier transform method. Both the numerical and experimental results correlated closely, thus validating the numerical solution.
Prediction of impact force and duration during low velocity impact on circular composite laminates
NASA Technical Reports Server (NTRS)
Shivakumar, K. N.; Elber, W.; Illg, W.
1983-01-01
Two simple and improved models--energy-balance and spring-mass--were developed to calculate impact force and duration during low velocity impact of circular composite plates. Both models include the contact deformation of the plate and the impactor as well as bending, transverse shear, and membrane deformations of the plate. The plate was transversely isotropic graphite/epoxy composite laminate and the impactor was a steel sphere. Calculated impact forces from the two analyses agreed with each other. The analyses were verified by comparing the results with reported test data.
NASA Technical Reports Server (NTRS)
Webster, J. D.
1981-01-01
The compressive behavior of T300/5208 graphite-epoxy laminates containing circular delaminations was studied to determine the flaw criticality of two types of implanted defect, Kapton bag and Teflon film, on several laminate configurations. Defect size was varied. Results, presented in the form of residual strength curves, indicate that the Teflon film defect reduced strength more than the Kapton bad defect in 12-ply samples, but that two laminates (+ or - 45) sub 2s and (90/+ or - 45) sub s were insensitive to any implanted defect. A clear thickness effect was shown to exist for the (o/+ pr 45) sub ns laminate and was attributed to failure mode transition. The analytically predicted buckling loads show excellent agreement with experimental results and are useful in predicting failure mode transition.
Failure analysis of composite laminated plates with circular holes under bending
NASA Astrophysics Data System (ADS)
Bradshaw, R. D.; Pang, S. S.
The purpose of this study is to investigate the failure of composite laminated plates with centrally located circular holes under bending. The stress state at any point in an orthotropic lamina with a circular hole was developed in terms of a stress concentration factor matrix multiplied by the stress vector at a point far from the hole. Classical lamination theory was applied to determine the ply-level stresses under bending. By applying the Tsai-Wu failure criterion to each ply at the hole edge, the crack modes were determined for various plate configurations. Knowledge of the crack direction and the stress concentration factor matrix led to a failure criterion based upon the ply-level hoop stress at some distance away from the hole. Point stress and average stress criteria were developed to determine the failure loading for any hole size, based on an experimental data point. Both criteria predicted the average failure load for other experimental points within 3 percent, but the point stress criteria was the more accurate of the two. The material used was a T650-42 graphite fiber with EYMYD polyimide resin system. Three stacking sequences were studied under four-point bending. In each case, three hole sizes were analyzed.
A Circular-cylindrical Flux-rope Analytical Model for Magnetic Clouds
NASA Astrophysics Data System (ADS)
Nieves-Chinchilla, T.; Linton, M. G.; Hidalgo, M. A.; Vourlidas, A.; Savani, N. P.; Szabo, A.; Farrugia, C.; Yu, W.
2016-05-01
We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds (MCs). Our model extends the circular-cylindrical concept of Hidalgo et al. by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation. The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in situ observations. Four Earth-directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic field and plasma in situ observations and with a new parameter (EPP, the Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of the plasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical. An extension of our current modeling framework to account for such non-circular CMEs will be presented in a forthcoming publication.
The input mobility of an infinite circular cylindrical elastic shell filled with fluid
NASA Technical Reports Server (NTRS)
Fuller, C. R.
1983-01-01
The force input mobility of an infinite elastic circular cylindrical shell filled with fluid is derived by using the spectral equations of motion. Mobilities are evaluated and their physical interpretations are discussed for a steel shell of thickness h/a = 0.05 filled with water and vibrating in the n = 0, 1 and 2 circumferential modes. The results are subsequently used to analyze the related situations of wave transmission through a radial ring constraint and the far field vibrational energy distributions between the contained fluid and the shell wall for line and point driving forces.
Instability of the vertically forced surface wave in a circular cylindrical container
NASA Astrophysics Data System (ADS)
Jian, Yong-Jun; E, Xue-Quan
2004-10-01
The nonlinear amplitude equation, which was derived by Jian Yongjun employing expansion of two-time scales in inviscid fluids in a vertically oscillating circular cylindrical vessel, is modified by introducing a damping term due to the viscous dissipation of this system. Instability of the surface wave is analysed and properties of the solutions of the modified equation are determined together with phase-plane trajectories. A necessary condition of forming a stable surface wave is obtained and unstable regions are illustrated. Research results show that the stable pattern of surface wave will not lose its stability to an infinitesimal disturbance.
NASA Astrophysics Data System (ADS)
Wang, Y. Q.; Guo, X. H.; Li, Y. G.; Li, J.
2010-03-01
This is a study of nonlinear traveling wave response of a cantilever circular cylindrical shell subjected to a concentrated harmonic force moving in a concentric circular path at a constant velocity. Donnell's shallow-shell theory is used, so that moderately large vibrations are analyzed. The problem is reduced to a system of ordinary differential equations by means of the Galerkin method. Frequency-responses for six different mode expansions are studied and compared with that for single mode to find the more contracted and accurate mode expansion investigating traveling wave vibration. The method of harmonic balance is applied to study the nonlinear dynamic response in forced oscillations of this system. Results obtained with analytical method are compared with numerical simulation, and the agreement between them bespeaks the validity of the method developed in this paper. The stability of the period solutions is also examined in detail.
NASA Astrophysics Data System (ADS)
Lee, Min Jin; Hong, Helen; Chung, Jin Wook
2014-03-01
We propose an automatic vessel segmentation method of vertebral arteries in CT angiography using combined circular and cylindrical model fitting. First, to generate multi-segmented volumes, whole volume is automatically divided into four segments by anatomical properties of bone structures along z-axis of head and neck. To define an optimal volume circumscribing vertebral arteries, anterior-posterior bounding and side boundaries are defined as initial extracted vessel region. Second, the initial vessel candidates are tracked using circular model fitting. Since boundaries of the vertebral arteries are ambiguous in case the arteries pass through the transverse foramen in the cervical vertebra, the circle model is extended along z-axis to cylinder model for considering additional vessel information of neighboring slices. Finally, the boundaries of the vertebral arteries are detected using graph-cut optimization. From the experiments, the proposed method provides accurate results without bone artifacts and eroded vessels in the cervical vertebra.
NASA Astrophysics Data System (ADS)
Yuan, Li-Yun; Xiang, Yu; Lu, Jing; Jiang, Hong-Hua
2015-12-01
Based on the transfer matrix method of exploring the circular cylindrical shell treated with active constrained layer damping (i.e., ACLD), combined with the analytical solution of the Helmholtz equation for a point source, a multi-point multipole virtual source simulation method is for the first time proposed for solving the acoustic radiation problem of a submerged ACLD shell. This approach, wherein some virtual point sources are assumed to be evenly distributed on the axial line of the cylindrical shell, and the sound pressure could be written in the form of the sum of the wave functions series with the undetermined coefficients, is demonstrated to be accurate to achieve the radiation acoustic pressure of the pulsating and oscillating spheres respectively. Meanwhile, this approach is proved to be accurate to obtain the radiation acoustic pressure for a stiffened cylindrical shell. Then, the chosen number of the virtual distributed point sources and truncated number of the wave functions series are discussed to achieve the approximate radiation acoustic pressure of an ACLD cylindrical shell. Applying this method, different radiation acoustic pressures of a submerged ACLD cylindrical shell with different boundary conditions, different thickness values of viscoelastic and piezoelectric layer, different feedback gains for the piezoelectric layer and coverage of ACLD are discussed in detail. Results show that a thicker thickness and larger velocity gain for the piezoelectric layer and larger coverage of the ACLD layer can obtain a better damping effect for the whole structure in general. Whereas, laying a thicker viscoelastic layer is not always a better treatment to achieve a better acoustic characteristic. Project supported by the National Natural Science Foundation of China (Grant Nos. 11162001, 11502056, and 51105083), the Natural Science Foundation of Guangxi Zhuang Autonomous Region, China (Grant No. 2012GXNSFAA053207), the Doctor Foundation of Guangxi
Loading-unloading response of circular GLARE fiber-metal laminates under lateral indentation
NASA Astrophysics Data System (ADS)
Tsamasphyros, George J.; Bikakis, George S.
2015-01-01
GLARE is a Fiber-Metal laminated material used in aerospace structures which are frequently subjected to various impact damages. Hence, the response of GLARE plates subjected to lateral indentation is very important. In this paper, analytical expressions are derived and a non-linear finite element modeling procedure is proposed in order to predict the static load-indentation curves of circular GLARE plates during loading and unloading by a hemispherical indentor. We have recently published analytical formulas and a finite element procedure for the static indentation of circular GLARE plates which are now used during the loading stage. Here, considering that aluminum layers are in a state of membrane yield and employing energy balance during unloading, the unloading path is determined. Using this unloading path, an algebraic equation is derived for calculating the permanent dent depth of the GLARE plate after the indentor's withdrawal. Furthermore, our finite element procedure is modified in order to simulate the unloading stage as well. The derived formulas and the proposed finite element modeling procedure are applied successfully to GLARE 2-2/1-0.3 and to GLARE 3-3/2-0.4 circular plates. The analytical results are compared with corresponding FEM results and a good agreement is found. The analytically calculated permanent dent depth is within 6 % for the GLARE 2 plate, and within 7 % for the GLARE 3 plate, of the corresponding numerically calculated result. No other solution of this problem is known to the authors.
NASA Astrophysics Data System (ADS)
Amabili, M.; Garziera, R.; Carra, S.
2005-12-01
This paper completes a study of Amabili and Garziera [2000, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part I: empty and fluid-filled shells. J. Fluids Struct. 14, 669 690; 2002a, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part II: shells containing or immersed in axial flow. J. Fluids Struct. 16, 31 51; 2002b, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part III: steady viscous effects on shells conveying fluid. J. Fluids Struct. 16, 795 809] by adding the effect of rotary inertia of added masses to the DIVA code, based on the Rayleigh Ritz method and developed to study free vibrations of circular cylindrical shells with nonuniform boundary conditions, added masses, partial elastic bed, initial pre-stress, conveying flow or immersed in axial flow. The effect of rotary inertia has also been evaluated by commercial FEM software and experiments in order to validate the DIVA code. Calculations and experiments show that the effect of rotary inertia of added masses is generally negligible, except for additional local modes; this is in contrast with what has been found for thin plates, due to the geometric stiffness of the circular cylindrical shell.
Hydrothermoelastic Stability of Functionally Graded Circular Cylindrical Shells Containing a Fluid
NASA Astrophysics Data System (ADS)
Bochkarev, S. A.; Lekomtsev, S. V.; Matveenko, V. P.
2016-09-01
The thermoelastic and hydroelastic stability of heated circular cylindrical shells made of functionally graded materials and interacting with an internal flow of an ideal compressible fluid was investigated. The effective properties of the material vary across the shell thickness according to a power law and depend on temperature. By way of a mathematical formulation the problem on dynamics the elastic structure, the classical theory of shells and the principle of virtual displacements are used. The radial temperature distribution is determined by solving the one-dimensional heat conduction equation. Behavior of the fluid is described using the potential theory. The corresponding wave equation, together with impermeability and boundary conditions, are transformed to a system of equations with the use of the Bubnov-Galerkin method. The solution of the problem, found by employing a semianalytical version of the finite-element method, is reduced to computing the complex eigenvalues of a coupled system of equations. A comparative analysis of the circular cylindrical shells is carried out at different boundary conditions and for different values of the consistency index of the functionally graded material. The effect of a thermal load on the critical speed of the loss of stability and of flow speed on the thermoelastic stability is estimated. It is shown that a flowing fluid has the greatest effect on the stability boundaries of heated cantilevered shells.
Circular-cylindrical flux-rope analytical model for Magnetic Clouds
NASA Astrophysics Data System (ADS)
Nieves-Chinchilla, Teresa; Linton, Mark; Hidalgo, Miguel A.; Vourlidas, Angelos; Savani, Neel P.; Szabo, Adam; Farrugia, Charlie; Yu, Wenyuan
2016-05-01
We present an analytical model to describe magnetic flux-rope topologies. When these structures are observed embedded in Interplanetary Coronal Mass Ejections (ICMEs) with a depressed proton temperature, they are called Magnetic Clouds ( MCs). The model extends the circular-cylindrical concept of Hidalgo et al. (2000) by introducing a general form for the radial dependence of the current density. This generalization provides information on the force distribution inside the flux rope in addition to the usual parameters of MC geometrical information and orientation.The generalized model provides flexibility for implementation in 3D MHD simulations. Here, we evaluate its performance in the reconstruction of MCs in in-situ observations. Four Earth directed ICME events, observed by the Wind spacecraft, are used to validate the technique. The events are selected from the ICME Wind list with the magnetic obstacle boundaries chosen consistently with the magnetic fi eld and plasma in situ observations and with a new parameter (EPP, Electron Pitch angle distribution Parameter) which quantifies the bidirectionally of theplasma electrons. The goodness of the fit is evaluated with a single correlation parameter to enable comparative analysis of the events. In general, at first glance, the model fits the selected events very well. However, a detailed analysis of events with signatures of significant compression indicates the need to explore geometries other than the circular-cylindrical.
Kelker, D.; Langenberg, C.W.
1988-08-01
A folded surface can be represented by the orientation of normals to the surface measured at several locations. When plotted on the unit sphere, the pattern of normals determines the type of fold. Poles from a cylindrical fold give a great circle on the unit sphere, whereas poles of a circular conical fold give a small circle, and poles from an elliptical conical fold give the projection of an ellipse onto the surface of the sphere. Several statistical tests that appear in the literature for classifying folds are discussed and compared. All but one of the tests use quantities obtained from an iterative least-squares procedure that fits the appropriate curve on the sphere. The classification procedure is illustrated with folds from the Canadian Rocky Mountains and uses for examples a cylindrical fold and a circular conical fold from the Smoky River coal field near Grande Cache, Alberta, and an elliptical conical fold near Jasper, Alberta. This methodology has resulted in new coal reserves in the Grande Cache area.
NASA Astrophysics Data System (ADS)
Russo, A.; Zuccarello, B.
2007-07-01
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups; in particular, the experimental results have shown that a combined use of the method proposed and the well-know point-stress criterion leads to reliable strength predictions for GFRP or CFRP laminates with a circular hole.
The axisymmetric elasticity problem for a laminated plate containing a circular hole
NASA Technical Reports Server (NTRS)
Delale, F.; Erdogan, F.
1981-01-01
The elasticity problem for a laminated thick plate which consists of two bonded dissimilar layers and which contains a circular hole is considered. The problem is formulated for arbitrary axisymmetric tractions on the hole surface by using the Love strain function. Through the expansion of the boundary conditions into Fourier series the problem is reduced to an infinite system of algebraic equations which is solved by the method of reduction. Of particular interest in the problem are the stresses along the interface as they relate to the question of delamination failure of the composite plate. These stresses are calculated and are observed to become unbounded at the hole boundary. An approximate treatment of the singular behavior of the stress state is presented and the stress intensity factors are calculated.
NASA Astrophysics Data System (ADS)
Guo, Zhangxin; Han, Xiaoping; Zhu, Xiping
2012-06-01
An approach is proposed to numerically study the composite laminates stitched around a circular hole. The local structure of stitching region is simplified and the finite element analysis (FEA) is carried out. With this approach, the interlaminar stresses are calculated, and the effects of stitching parameters such as edge distance, stitching needle span and row spacing of yarn are discussed on the interlaminar stresses. The effect of the reinforcement can be enhanced by properly reducing the edge distance or needle span when stitching at the hole edge. Compared with unstitching, there is an evident decrease for interlaminar stresses at the hole after stitching enforcement. The distribution of the interlaminar stresses around the hole is related with layers.
On the mechanism of buckling of a circular cylindrical shell under axial compression
NASA Technical Reports Server (NTRS)
Yoshimura, Yoshimaru
1955-01-01
The present paper deals with the buckling of a circular cylindrical shell under axial compression from the viewpoint of energy and the characteristics of deformation. It is shown first, both theoretically and experimentally, that the reason why the buckling of a cylindrical shell is quite different from that of a flat plate is attributable to the existence of a nearly developable surface far apart from the original cylindrical surface. Based upon this result, the experimental fact that the buckling is really not general but local, that is, that the buckled region is limited axially to a range of 1.5 times the wave length of the lobe, is explained by the theoretical result that the minimum buckling load is smaller in the local buckling than in the general buckling case. The occurrence of local buckling is affirmed also from the viewpoint of the energy barrier to be jumped over during buckling, and from a comparison of the theoretical post-buckling state with the experimental results. Finally, the local buckling with the load applied by a spring is analyzed, and it is proved that the minimum buckling load increased with an increase of rigidity of the spring.
Cylindrical acoustic levitator/concentrator having non-circular cross-section
Kaduchak, Gregory; Sinha, Dipen N.
2003-11-11
A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow piezoelectric crystal which has been formed with a cylindrical cross-section to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. By deforming the circular cross-section of the transducer, the acoustic force is concentrated along axial regions parallel to the axis of the transducer. The cylinder does not require accurate alignment of a resonant cavity. The concentrated regions of acoustic force cause particles in the fluid to concentrate within the regions of acoustic force for separation from the fluid.
NASA Astrophysics Data System (ADS)
Lepedat, Karin; Wagner, Robert; Lang, Jürgen
The use of phenolic resin for the impregnation of a carrier material such as paper or fabric based on either organic or inorganic fibers was and still is one of the most important application areas for liquid phenolic resins. Substrates like paper, cotton, or glass fabric impregnated with phenolic resins are used as core layers for decorative and technical laminates and for many other different industrial applications. Nowadays, phenolic resins for decorative laminates used for furniture, flooring, or in the construction and transportation industry have gained significant market share. The Laminates chapter mainly describes the manufacture of decorative laminates especially the impregnation and pressing process with special emphasis to new technological developments and recent trends. Moreover, the different types of laminates are introduced, combined with some brief comments as they relate to the market for decorative surfaces.
NASA Technical Reports Server (NTRS)
Ramsey, J. W., Jr.
1975-01-01
The effect on stresses in a cylindrical shell with a circular penetration subject to internal pressure was investigated in thin, shallow linearly, elastic cylindrical shells. Results provide numerical predictions of peak stress concentration factors around nonreinforced and reinforced penetrations in pressurized cylindrical shells. Analytical results were correlated with published formulas, as well as theoretical and experimental results. An accuracy study was made of the finite element program for each of the configurations considered important in pressure vessel technology. A formula is developed to predict the peak stress concentration factor for analysis and/or design in conjunction with the ASME Boiler and Pressure Vessel Code.
Effect of a circular hole on the buckling of cylindrical shells loaded by axial compression.
NASA Technical Reports Server (NTRS)
Starnes, J. H., Jr.
1972-01-01
An experimental and analytical investigation of the effect of a circular hole on the buckling of thin cylindrical shells under axial compression was carried out. The experimental results were obtained from tests performed on seamless electroformed copper shells and Mylar shells with a lap joint seam. These results indicated that the character of the shell buckling was dependent on a parameter which is proportional to the hole radius divided by the square root of the product of the shell radius and thickness. For small values of this parameter, there was no apparent effect of the hole on the buckling load. For slightly larger values of the parameter, the shells still buckled into a general collapse configuration, but the buckling loads were sharply reduced as the parameter increased. For still larger values of the parameter, the buckling loads were further reduced, and the shells buckled into a stable local buckling configuration.
Nonlinear response of infinitely long circular cylindrical shells to subharmonic radial loads
NASA Technical Reports Server (NTRS)
Nayfeh, Ali H.; Nayfeh, Jamal F.; Raouf, Raouf A.
1991-01-01
The nonlinear response of infinitely long circular cylindrical shells (thin circular rings) in the presence of a two-to-one internal (autoparametric) resonance to a subharmonic excitation of order one-half of the higher mode is analyzed with the multiple-scale method. Four autonomous first-order ordinary differential equations are derived for the modulation of the amplitudes and phases of the interacting models. These modulation equations are used to determine the fixed points and their stability. The fixed points correspond to periodic oscillations of the shell, whereas the limit-cycle solutions of the modulation equations correspond to amplitude and phase-modulated oscillations of the shell. The force response curves exhibit saturation, jumps, and Hopf bifurcation. As excitation frequency changes, all limit cycles deform and lose stability through either pitchfork or cyclic-fold (saddle-node) bifurcations. Some of these saddle-node bifurcations cause a transition to chaos. The pitchfork bifurcations break the symmetry of the limit cycles.
NASA Astrophysics Data System (ADS)
Villalobos Mendoza, Brenda; Cordero Dávila, Alberto; González García, Jorge
2011-01-01
This paper describes the construction of an elliptical-cylindrical model without spherical aberration using vertical rotating tools. The engine of the circular tool is placed on one arm so that the tool fits on the surface and this in turn is moved by an X-Y table. The test method and computer algorithms that predict the desired wear are described.
Williams, Todd O
2009-01-01
The exact solution for the history-dependent behavior of laminated plates subjected to cylindrical bending is presented. The solution represents the extension of Pagano's solution to consider arbitrary types of constitutive behaviors for the individual lamina as well as arbitrary types of cohesive zones models for delamination behavior. Examples of the possible types of material behavior are plasticity, viscoelasticity, viscoplasticity, and damaging. Examples of possible CZMs that can be considered are linear, nonlinear hardening, as well as nonlinear with softening. The resulting solution is intended as a benchmark solution for considering the predictive capabilities of different plate theories. Initial results are presented for several types of history-dependent material behaviors. It is shown that the plate response in the presence of history-dependent behaviors can differ dramatically from the elastic response. These results have strong implications for what constitutes an appropriate plate theory for modeling such behaviors.
NASA Astrophysics Data System (ADS)
Afshin, M.; Sadighi, M.; Shakeri, M.
2010-12-01
In the present study, the static response of cylindrical sandwich panels with a flexible core is investigated. The face sheets are considered as composite laminates with a cross-ply lay-up and the core as a flexible elastic medium. The flexibility of the low-strength core leads to high stress concentrations in terms of peeling stresses between the face sheets and the core at edges of the sandwich panel. To take into account the compressibility of the core and to determine the free-edge stresses of sandwich structures accurately, the Reddy layerwise theory (LWT) is used in this paper. The paper outlines the mathematical formulation, along with a numerical study, of a cylindrical sandwich panel with two simply supported and two free edges under a transverse load. The formulation includes the derivation of field equations along with boundary conditions. A Levy-type solution procedure is performed to determine the distributions of stresses and strains. In the numerical study, first a comparison is made with results from the commercial finite-element software ANSYS to verify the LWT results. Finally, a parametric study is conducted, and the effect caused by varying different parameters, such as the radii of curvature and the core to face sheet thickness ratio, on the results are investigated. The results obtained demonstrate a good agreement between LWT and FEM solutions and show increasing interlaminar stresses in the free edge of the sandwich panel
Convective heat transfer from circular cylinders located within perforated cylindrical shrouds
NASA Technical Reports Server (NTRS)
Daryabeigi, K.; Ash, R. L.
1986-01-01
The influence of perforated cylindrical shrouds on the convective heat transfer to circular cylinders in transverse flow has been studied experimentally. Geometries studied were similar to those used in industrial platinum resistance thermometers. The influence of Reynolds number, ventilation factor (ratio of the open area to the total surface area of shroud), radius ratio (ratio of shroud's inside radius to bare cylinder's radius), and shroud orientation with respect to flow were studied. The experiments showed that perforated shrouds with ventilation factors in the range 0.1 to 0.4 and radius ratios in the range 1.1 to 2.1 could enhance the convective heat transfer to bare cylinders up to 50%. The maximum enhancement occurred for a radius ratio of 1.4 and ventilation factors between 0.2 and 0.3. It was found that shroud orientation influenced the heat transfer, with maximum heat transfer generally occurring when the shroud's holes were centered on either side of the stagnation line. However, the hole orientation effect is of second order compared to the influence of ventilation factor and radius ratio.
Analysis of soft and hard strip-loaded horns using a circular cylindrical model
NASA Astrophysics Data System (ADS)
Lier, Erik
1990-06-01
Strip-loaded horns with transverse (soft) and longitudinal (hard) strips are analyzed theoretically. The method is based on a circular cylindrical and uniform waveguide model with a periodic strip structure. The field is represented by an infinite series of space harmonics (Floquet modes) in the air-filled central region and in the dielectrically filled wall region. The tangential field is forced to be continuous across the air-dielectric boundary. The propagation constant and the total field (including the hybrid factor) can be determined by solving the resulting matrix equations. The convergence of the solution has been accelerated by calculating the higher-order terms analytically. It is shown that the soft-strip-loaded horn in principle exhibits the same electrical behavior as a corrugated horn. The horn represents an interesting alternative to the corrugated horn in wide-band or dual-band applications, in particular for millimeter waves and for lightweight applications onboard satellites. The hard-strip-loaded horn has potentially high gain and low cross polarization over a certain frequency range, dependent on the horn dimensions, thickness of the dielectric wall and on how strongly the stripline modes are being excited.
NASA Astrophysics Data System (ADS)
AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.
1999-08-01
The study presented is an investigation of the non-linear dynamics and stability of simply supported, circular cylindrical shells containing inviscid incompressible fluid flow. Non-linearities due to large-amplitude shell motion are considered by using the non-linear Donnell's shallow shell theory, with account taken of the effect of viscous structural damping. Linear potential flow theory is applied to describe the fluid-structure interaction. The system is discretiszd by Galerkin's method, and is investigated by using a model involving seven degrees of freedom, allowing for travelling wave response of the shell and shell axisymmetric contraction. Two different boundary conditions are applied to the fluid flow beyond the shell, corresponding to: (i) infinite baffles (rigid extensions of the shell), and (ii) connection with a flexible wall of infinite extent in the longitudinal direction, permitting solution by separation of variables; they give two different kinds of dynamical behaviour of the system, as a consequence of the fact that axisymmetric contraction, responsible for the softening non-linear dynamical behaviour of shells, is not allowed if the fluid flow beyond the shell is constrained by rigid baffles. Results show that the system loses stability by divergence.
Extension, inflation and torsion of a residually stressed circular cylindrical tube
NASA Astrophysics Data System (ADS)
Merodio, José; Ogden, Ray W.
2016-03-01
In this paper, we provide a new example of the solution of a finite deformation boundary-value problem for a residually stressed elastic body. Specifically, we analyse the problem of the combined extension, inflation and torsion of a circular cylindrical tube subject to radial and circumferential residual stresses and governed by a residual-stress dependent nonlinear elastic constitutive law. The problem is first of all formulated for a general elastic strain-energy function, and compact expressions in the form of integrals are obtained for the pressure, axial load and torsional moment required to maintain the given deformation. For two specific simple prototype strain-energy functions that include residual stress, the integrals are evaluated to give explicit closed-form expressions for the pressure, axial load and torsional moment. The dependence of these quantities on a measure of the radial strain is illustrated graphically for different values of the parameters (in dimensionless form) involved, in particular the tube thickness, the amount of torsion and the strength of the residual stress. The results for the two strain-energy functions are compared and also compared with results when there is no residual stress.
Cylindrical matrix device with a circular release area with inhomogeneous diffusivity
NASA Astrophysics Data System (ADS)
Cuartas Velez, Carlos Alfredo
2013-05-01
A cylindrical matrix device with a circular release area with inhomogeneous diffusivity was analyzed using a Laplace transform-based method, using Bromwich integral and residue theorem. The two-dimensional model represented a pharmaceutical agent uniformly distributed in a polymeric matrix with a diffusivity spatially modulated, surrounded by an impermeable layer. The pharmaceutical agent could be transferred only through a small hole centered at the top surface of the cylinder. A closed-form solution was obtained in terms of Bessel functions with the aim to help study the effects of design parameters and geometries on the cumulative amount of pharmaceutical agent released. The cumulative flux of pharmaceutical agent increased with the mass transfer and diffusion coefficients and decreased with any increment in the device's length and variations of the diffusivity coefficients. The delivery rate was described by an effective time constant calculated from Laplace transforms and using Bessel functions and their zeros. Reducing the orifice diameter or fabricating a longer system would delay transport of the medication. Simplified expressions for the release profile and the time constant were derived for special design cases.
Optimization of circular orifice jets mixing into a heated cross flow in a cylindrical duct
NASA Technical Reports Server (NTRS)
Kroll, J. T.; Sowa, W. A.; Samuelsen, G. S.; Holdeman, J. D.
1993-01-01
To examine the mixing characteristics of circular jets in an axisymmetric can geometry, temperature measurements were obtained downstream of a row of cold jet injected into a heated cross stream. The objective was to obtain uniform mixing within one duct radius downstream of the leading edge of the jet orifices. An area weighted standard deviation of the mixture fraction was used to help quantify the degree of mixedness at a given plane. Non-reacting experiments were conducted to determine the influence of the number of jets on the mixedness in a cylindrical configuration. Results show that the number of orifices significantly impacts the mixing characteristics of jets injected from round hole orifices in a can geometry. Optimum mixing occurs when the mean jet trajectory aligns with the radius which divides the cross sectional area of the can into two equal parts at one mixer radius downstream of the leading edge of the orifice. The optimum number of holes at momentum-flux ratios of 25 and 52 is 10 and 15 respectively.
NASA Astrophysics Data System (ADS)
Sabri, Farhad
circular cylindrical shell or truncated conical shell subjected to internal/external pressure and axial compression loading. This is a typical example of external liquid propellant tanks of space shuttles and re-entry vehicles where they may experience this kind of loading during the flight. In the current work, different end boundary conditions of a circular cylindrical shell with different filling ratios were analyzed. To the best author' knowledge this is the first study where this kind of complex loading and boundary conditions are treated together during such an analysis. Only static instability, divergence, was observed where it showed that the fluid filling ratio does not have any effect on the critical buckling pressure and axial compression. It only reduces the vibration frequencies. It also revealed that the pressurized shell loses its stability at a higher critical axial load. (ii) Aeroelastic analysis of empty or partially liquid filled circular cylindrical and conical shells. Different boundary conditions with different geometries of shells subjected to supersonic air flow are studied here. In all of cases shell loses its stability though the coupled mode flutter. The results showed that internal pressure has a stabilizing effect and increases the critical flutter speed. It is seen that the value of critical dynamic pressure changes rapidly and widely as the filling ratio increases from a low value. In addition, by increasing the length ratio the decrement of flutter speed is decreased and vanishes. This rapid change in critical dynamic pressure at low filling ratios and its almost steady behaviour at large filling ratios indicate that the fluid near the bottom of the shell is largely influenced by elastic deformation when a shell is subjected to external subsonic flow. Based on comparison with the existing numerical, analytical and experimental data and the power of capabilities of this hybrid finite element method to model different boundary conditions and
NASA Astrophysics Data System (ADS)
GARDONIO, P.; FERGUSON, N. S.; FAHY, F. J.
2001-07-01
This paper covers the development and application of a modal interaction analysis (MIA) to investigate the plane wave transmission characteristics of a circular cylindrical sandwich shell of the type used in the aerospace industry for satellite launch vehicles. The model is capable of handling many high order structural and acoustic modes, and can be used to investigate the sensitivity to different structural stiffness configurations, angles of incidence, damping and cavity absorption. The model has been developed to predict the structural response and transmitted noise when a number of discrete masses are applied to the shell. The study presented considers a set of cases where blocking masses, having a total weight equal to 8% of the cylinder weight, are attached to the cylinder. The simulations carried out show a substantial reduction of the sound transmission in many of the first 15 one-third octave frequency bands (frequency range 22·4-707 Hz). The blocking masses act on the shape of the cylinder normal modes and their orientations with respect to the plane of the incident wavenumber vector. In particular, the circumferential re-orientation reduces the coupling between the incident acoustic field and the structural modes of the cylinder. The modification of the structural mode shapes, both in axial and circumferential directions, also reduces the coupling between the cylinder modes and the acoustic modes of the interior.Simulations show the effect of the number of structural and acoustic modes included on the calculated frequency response, and indicate the number necessary for an accurate prediction of the resonant and non-resonant sound transmission through the structure. In particular, the effect of neglecting off-resonance acoustic and structural modes is investigated. It is shown that restricting the acoustic and structural modes to those having natural frequencies within an interval of ±40 and ±60 Hz, respectively, of the excitation frequency produces
Strength and Failure Analysis of Composite Laminate Containing a Circular Hole with Reinforcement
1987-12-01
0.733 -0.885 14 0.1 73718 0.753 1.771 -0.582 a. 15 70528 0.720 -2.633 1 _ 16 49572 0.506 -8.200 17 Plexi - 0.2 55625 0.568 3.009 -1.604 18 glass 54205...Characteristic Length, al, of the Effective Average Stress Model ..... ............. .. 26 5. Strength Reduction Factor of GR/EP Laminate with an Open Hole...Typical Failure Mode of Compression Test. . . 48 15(a). Comparison of Strength Reduction Factor (SRF) of the Open Hole versus Bonded Reinforcement
NASA Astrophysics Data System (ADS)
Bich, Dao Huy; Xuan Nguyen, Nguyen
2012-12-01
In the present work, the study of the nonlinear vibration of a functionally graded cylindrical shell subjected to axial and transverse mechanical loads is presented. Material properties are graded in the thickness direction of the shell according to a simple power law distribution in terms of volume fractions of the material constituents. Governing equations are derived using improved Donnell shell theory ignoring the shallowness of cylindrical shells and kinematic nonlinearity is taken into consideration. One-term approximate solution is assumed to satisfy simply supported boundary conditions. The Galerkin method, the Volmir's assumption and fourth-order Runge-Kutta method are used for dynamical analysis of shells to give explicit expressions of natural frequencies, nonlinear frequency-amplitude relation and nonlinear dynamic responses. Numerical results show the effects of characteristics of functionally graded materials, pre-loaded axial compression and dimensional ratios on the dynamical behavior of shells. The proposed results are validated by comparing with those in the literature.
NASA Technical Reports Server (NTRS)
Saravanos, Dimitris A.
1996-01-01
Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors.
NASA Astrophysics Data System (ADS)
Lee, HyunWook; Kwak, Moon K.
2015-09-01
This study uses the Rayleigh-Ritz method to derive a dynamic model for the free vibration analysis of a circular cylindrical shell. In particular, explicit expressions for the mass and stiffness matrices are obtained to easily implement a computer simulation under different shell theories and boundary conditions. The dynamic model is constructed according to the Donnell-Mushtari theory, which is fully discussed herein, and then, dynamic models are constructed by using Sanders theory, Love-Timoshenko theory, Reissner theory, Flügge theory, and Vlasov theory. This paper also discusses the use of eigenfunctions of a uniform beam as admissible functions that produce compact expressions for the mass and stiffness matrices. The numerical results indicate that the Donnell-Mushtari theory is not sufficiently accurate to calculate the natural frequencies and that there is no discernible difference between the other shell theories considered in this study.
NASA Astrophysics Data System (ADS)
Pellicano, F.; Amabili, M.
2006-05-01
In the present paper the dynamic stability of circular cylindrical shells subjected to static and dynamic axial loads is investigated. Both Donnell's nonlinear shallow shell and Sanders-Koiter shell theories have been applied to model finite-amplitude static and dynamic deformations. Results are compared in order to evaluate the accuracy of these theories in predicting instability onset and post-critical nonlinear response. The effect of a contained fluid on the stability and the post-critical behaviour is analyzed in detail. Geometric imperfections are considered and their influence on the dynamic instability and post-critical behaviour is investigated. Chaotic dynamics of pre-compressed shells is investigated by means of nonlinear time-series techniques, extracting correlation dimension and Lyapunov exponents.
Estève, Simon J; Johnson, Marty E
2002-12-01
A modal expansion method is used to model a cylindrical enclosure excited by an external plane wave. A set of distributed vibration absorbers (DVAs) and Helmholtz resonators (HRs) are applied to the structure to control the interior acoustic levels. Using an impedance matching method, the structure, the acoustic cavity, and the noise reduction devices are fully coupled to yield an analytical formulation of the structural kinetic energy and acoustic potential energy of a treated cylindrical cavity. Lightweight DVAs and small HRs tuned to the natural frequencies of the targeted structural and acoustic modes, respectively, result in significant acoustic and structural attenuation when the devices are optimally damped. Simulations show that significant interior noise reduction can only be achieved by adding damping to both structural and acoustic modes, which are resonant in the frequency bandwidth of interest. In order to be independent of the azimuth angle of the excitation and to avoid unwanted modal interactions, the devices are distributed evenly around the cylinder in rings. This treatment can only achieve good performance if the structure and the acoustic cavity are lightly damped.
NASA Astrophysics Data System (ADS)
Estève, Simon J.; Johnson, Marty E.
2002-12-01
A modal expansion method is used to model a cylindrical enclosure excited by an external plane wave. A set of distributed vibration absorbers (DVAs) and Helmholtz resonators (HRs) are applied to the structure to control the interior acoustic levels. Using an impedance matching method, the structure, the acoustic cavity, and the noise reduction devices are fully coupled to yield an analytical formulation of the structural kinetic energy and acoustic potential energy of a treated cylindrical cavity. Lightweight DVAs and small HRs tuned to the natural frequencies of the targeted structural and acoustic modes, respectively, result in significant acoustic and structural attenuation when the devices are optimally damped. Simulations show that significant interior noise reduction can only be achieved by adding damping to both structural and acoustic modes, which are resonant in the frequency bandwidth of interest. In order to be independent of the azimuth angle of the excitation and to avoid unwanted modal interactions, the devices are distributed evenly around the cylinder in rings. This treatment can only achieve good performance if the structure and the acoustic cavity are lightly damped.
Analysis of progressive damage in thin circular laminates due to static-equivalent impact loads
NASA Technical Reports Server (NTRS)
Shivakumar, K. N.; Elber, W.; Illg, W.
1983-01-01
Clamped circular graphite/epoxy plates (25.4, 38.1, and 50.8 mm radii) with an 8-ply quasi-isotropic layup were analyzed for static-equivalent impact loads using the minimum-total-potential-energy method and the von Karman strain-displacement equations. A step-by-step incremental transverse displacement procedure was used to calculate plate load and ply stresses. The ply failure region was calculated using the Tsai-Wu criterion. The corresponding failure modes (splitting and fiber failure) were determined using the maximum stress criteria. The first-failure mode was splitting and initiated first in the bottom ply. The splitting-failure thresholds were relatively low and tended to be lower for larger plates than for small plates. The splitting-damage region in each ply was elongated in its fiber direction; the bottom ply had the largest damage region. The calculated damage region for the 25.4-mm-radius plate agreed with limited static test results from the literature.
NASA Astrophysics Data System (ADS)
Amabili, Marco; Balasubramanian, Prabakaran; Ferrari, Giovanni
2016-10-01
The nonlinear vibrations of a water-filled circular cylindrical shell subjected to radial harmonic excitation in the spectral neighbourhood of the lowest resonances are investigated experimentally and numerically by using a seamless aluminium sample. The experimental boundary conditions are close to simply supported edges. The presence of exact one-to-one internal resonance, giving rise to a travelling wave response around the shell circumference and non-stationary vibrations, is experimentally observed and the nonlinear response is numerically reproduced. The travelling wave is measured by means of state-of-the-art laser Doppler vibrometers applied to multiple points on the structure simultaneously. Chaos is detected in the frequency region where the travelling wave response is present. The reduced-order model is based on the Novozhilov nonlinear shell theory retaining in-plane inertia and the nonlinear equations of motion are numerically studied (i) by using a code based on arclength continuation method that allows bifurcation analysis in case of stationary vibrations, (ii) by a continuation code based on direct integration and Poincaré maps that evaluates also the maximum Lyapunov exponent in case of non-stationary vibrations. The comparison of experimental and numerical results is particularly satisfactory.
NASA Technical Reports Server (NTRS)
Mushtari, K. M.; Sachenkov, A. V.
1958-01-01
We consider in this report the determination of the upper limit of critical loads in the case of simultaneous action of a compressive force, uniformly distributed over plane cross sections, and of isotropic external normal pressure on cylindrical or conical shells of circular cross section. As a starting point we use the differential equations for neutral equilibrium of conical shells which have been used for the solution of the problem of stability of conical shells under torsion and under axial compression; upon solution of the problem it is possible to satisfy all boundary conditions, in contrast to the report where no attention is paid to the fulfillment of the boundary conditions, and to the report where only part of the boundary conditions are satisfied by solution of the problem according to Galerkin's method. Approximate formulas are used for the determination of the critical external normal pressure with simultaneous action of longituninal compression. Let us note that the formulas suggested in reference 5 are not well founded and may lead, in a number of cases, to a substantial mistake in the magnitude of the critical load.
NASA Astrophysics Data System (ADS)
Amabili, M.
2003-05-01
The large-amplitude response of perfect and imperfect, simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of some of the lowest natural frequencies is investigated. Donnell's non-linear shallow-shell theory is used and the solution is obtained by the Galerkin method. Several expansions involving 16 or more natural modes of the shell are used. The boundary conditions on the radial displacement and the continuity of circumferential displacement are exactly satisfied. The effect of internal quiescent, incompressible and inviscid fluid is investigated. The non-linear equations of motion are studied by using a code based on the arclength continuation method. A series of accurate experiments on forced vibrations of an empty and water-filled stainless-steel shell have been performed. Several modes have been intensively investigated for different vibration amplitudes. A closed loop control of the force excitation has been used. The actual geometry of the test shell has been measured and the geometric imperfections have been introduced in the theoretical model. Several interesting non-linear phenomena have been experimentally observed and numerically reproduced, such as softening-type non-linearity, different types of travelling wave response in the proximity of resonances, interaction among modes with different numbers of circumferential waves and amplitude-modulated response. For all the modes investigated, the theoretical and experimental results are in strong agreement.
NASA Astrophysics Data System (ADS)
Amabili, M.; Sarkar, A.; Païdoussis, M. P.
2006-03-01
The geometric nonlinear response of a water-filled, simply supported circular cylindrical shell to harmonic excitation in the spectral neighbourhood of the fundamental natural frequency is investigated. The response is investigated for a fixed excitation frequency by using the excitation amplitude as bifurcation parameter for a wide range of variation. Bifurcation diagrams of Poincaré maps obtained from direct time integration and calculation of the Lyapunov exponents and Lyapunov dimension have been used to study the system. By increasing the excitation amplitude, the response undergoes (i) a period-doubling bifurcation, (ii) subharmonic response, (iii) quasi-periodic response and (iv) chaotic behaviour with up to 16 positive Lyapunov exponents (hyperchaos). The model is based on Donnell's nonlinear shallow-shell theory, and the reference solution is obtained by the Galerkin method. The proper orthogonal decomposition (POD) method is used to extract proper orthogonal modes that describe the system behaviour from time-series response data. These time-series have been obtained via the conventional Galerkin approach (using normal modes as a projection basis) with an accurate model involving 16 degrees of freedom (dofs), validated in previous studies. The POD method, in conjunction with the Galerkin approach, permits to build a lower-dimensional model as compared to those obtainable via the conventional Galerkin approach. Periodic and quasi-periodic response around the fundamental resonance for fixed excitation amplitude, can be very successfully simulated with a 3-dof reduced-order model. However, in the case of large variation of the excitation, even a 5-dof reduced-order model is not fully accurate. Results show that the POD methodology is not as "robust" as the Galerkin method.
NASA Astrophysics Data System (ADS)
AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.
2000-11-01
The response of simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of one of the lowest natural frequencies is investigated by using improved mode expansions with respect to those assumed in Parts I and II of the present study. Two cases are studied: (1) shells in vacuo; and (2) shells filled with stagnant water. The improved expansions allow checking the accuracy of the solutions previously obtained and giving definitive results within the limits of Donnell's non-linear shallow-shell theory. The improved mode expansions include: (1) harmonics of the circumferential mode number n under consideration, and (2) only the principal n, but with harmonics of the longitudinal mode included. The effect of additional longitudinal modes is absolutely insignificant in both the driven and companion mode responses. The effect of modes with 2 n circumferential waves is very limited on the trend of non-linearity, but is significant in the response with companion mode participation in the case of lightly damped shells (empty shells). In particular, the travelling wave response appears for much lower vibration amplitudes and presents a frequency range without stable responses, corresponding to a beating phenomenon. A liquid (water) contained in the shell generates a much stronger softening behaviour of the system. Experiments with a water-filled circular cylindrical shell made of steel are in very good agreement with the present theory.
NASA Astrophysics Data System (ADS)
Leonov, V. I.
A cylindrical shell is considered which is loaded via a round rigid bracket by a force normal to its middle surface and also by a bending moment relative to the generatrix. The shell is reinforced by an annular patch around the bracket. The stressed state of the shell is analyzed as a function of the geometrical parameters of the reinforcement.
Zhang, Anqi; Xu, Guan; Daluwatte, Chathuri; Yao, Gang; Bunting, Charles F; Pogue, Brian W; Piao, Daqing
2011-02-01
This is Part II of the work that examines photon diffusion in a homogenous medium enclosed by a concave circular cylindrical applicator or enclosing a convex circular cylindrical applicator. Part I of this work [J. Opt. Soc. Am. A 27, 648 (2010)] analytically examined the steady-state photon diffusion between a source and a detector for two specific cases: (1) the detector is placed only azimuthally with respect to the source, and (2) the detector is placed only longitudinally with respect to the source, in the infinitely long concave and convex applicator geometries. For the first case, it was predicted that the decay rate of photon fluence would become smaller in the concave geometry and greater in the convex geometry than that in the semi-infinite geometry for the same source-detector distance. For the second case, it was projected that the decay rate of photon fluence would be greater in the concave geometry and smaller in the convex geometry than that in the semi-infinite geometry for the same source-detector distance. This Part II of the work quantitatively examines these predictions from Part I through several approaches, including (a) the finite-element method, (b) the Monte Carlo simulation, and (c) experimental measurement. Despite that the quantitative examinations have to be conducted for finite cylinder applicators with large length-to-radius ratio to approximate the infinite-length condition modeled in Part I, the results obtained by these quantitative methods for two concave and three convex applicator dimensions validated the qualitative trend predicted by Part I and verified the quantitative accuracy of the analytic treatment of Part I in the diffusion regime of the measurement, at a given set of absorption and reduced scattering coefficients of the medium.
NASA Astrophysics Data System (ADS)
AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.
2000-11-01
The response of a shell conveying fluid to harmonic excitation, in the spectral neighbourhood of one of the lowest natural frequencies, is investigated for different flow velocities. The theoretical model has already been presented in Part I of the present study. Non-linearities due to moderately large-amplitude shell motion are considered by using Donnell's non-linear shallow-shell theory. Linear potential flow theory is applied to describe the fluid-structure interaction by using the model proposed by Paı̈doussis and Denise. For different amplitudes and frequencies of the excitation and for different flow velocities, the following are investigated numerically: (1) periodic response of the system; (2) unsteady and stochastic motion; (3) loss of stability by jumps to bifurcated branches. The effect of the flow velocity on the non-linear periodic response of the system has also been investigated. Poincaré maps and bifurcation diagrams are used to study the unsteady and stochastic dynamics of the system. Amplitude modulated motions, multi-periodic solutions, chaotic responses, cascades of bifurcations as the route to chaos and the so-called “blue sky catastrophe” phenomenon have all been observed for different values of the system parameters; the latter two have been predicted here probably for the first time for the dynamics of circular cylindrical shells.
NASA Astrophysics Data System (ADS)
AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.
1999-12-01
The non-linear response of empty and fluid-filled circular cylindrical shells to harmonic excitations is investigated. Both modal and point excitations have been considered. The model is suitable to study simply supported shells with and without axial constraints. Donnell's non-linear shallow-shell theory is used. The boundary conditions on radial displacement and the continuity of circumferential displacement are exactly satisfied. The radial deflection of the shell is expanded by using a basis of seven linear modes. The effect of internal quiescent, incompressible and inviscid fluid is investigated. The equations of motion, obtained in Part I of this study, are studied by using a code based on the collocation method. The validation of the present model is obtained by comparison with other authoritative results. The effect of the number of axisymmetric modes used in the expansion on the response of the shell is investigated, clarifying questions open for a long time. The results show the occurrence of travelling wave response in the proximity of the resonance frequency, the fundamental role of the first and third axisymmetric modes in the expansion of the radial deflection with one longitudinal half-wave, and limit cycle responses. Modes with two longitudinal half-waves are also investigated.
Cup Cylindrical Waveguide Antenna
NASA Technical Reports Server (NTRS)
Acosta, Roberto J.; Darby, William G.; Kory, Carol L.; Lambert, Kevin M.; Breen, Daniel P.
2008-01-01
The cup cylindrical waveguide antenna (CCWA) is a short backfire microwave antenna capable of simultaneously supporting the transmission or reception of two distinct signals having opposite circular polarizations. Short backfire antennas are widely used in mobile/satellite communications, tracking, telemetry, and wireless local area networks because of their compactness and excellent radiation characteristics. A typical prior short backfire antenna contains a half-wavelength dipole excitation element for linear polarization or crossed half-wavelength dipole elements for circular polarization. In order to achieve simultaneous dual circular polarization, it would be necessary to integrate, into the antenna feed structure, a network of hybrid components, which would introduce significant losses. The CCWA embodies an alternate approach that entails relatively low losses and affords the additional advantage of compactness. The CCWA includes a circular cylindrical cup, a circular disk subreflector, and a circular waveguide that serves as the excitation element. The components that make it possible to obtain simultaneous dual circular polarization are integrated into the circular waveguide. These components are a sixpost polarizer and an orthomode transducer (OMT) with two orthogonal coaxial ports. The overall length of the OMT and polarizer (for the nominal middle design frequency of 2.25 GHz) is about 11 in. (approximately equal to 28 cm), whereas the length of a commercially available OMT and polarizer for the same frequency is about 32 in. (approximately equal to 81 cm).
Zhang, Anqi; Piao, Daqing; Bunting, Charles F
2012-04-01
This is Part III of the work that examines photon diffusion in a scattering-dominant medium enclosed by a "concave" circular cylindrical applicator or enclosing a "convex" circular cylindrical applicator. In Part II of this work Zhang et al. [J. Opt. Soc. Am. A, 66 (2011)] predicted that, on the tissue-applicator interface of either "concave" or "convex" geometry, there exists a unique set of spiral paths, along which the steady-state photon fluence rate decays at a rate equal to that along a straight line on a planar semi-infinite interface, for the same line-of-sight source-detector distance. This phenomenon of steady-state photon diffusion is referred to as "straight-line-resembling-spiral paths" (abbreviated as "spiral paths"). This Part III study develops analytic approaches to the spiral paths associated with geometry of a large radial dimension and presents spiral paths found numerically for geometry of a small radial dimension. This Part III study also examines whether the spiral paths associated with a homogeneous medium are a good approximation for the medium containing heterogeneity. The heterogeneity is limited to an anomaly that is aligned azimuthally with the spiral paths and has either positive or negative contrast of the absorption or scattering coefficient over the background medium. For a weak-contrast anomaly the perturbation by it to the photon fluence rate along the spiral paths is found by applying a well-established perturbation analysis in cylindrical coordinates. For a strong-contrast anomaly the change by it to the photon fluence rate along the spiral paths is computed using the finite-element method. For the investigated heterogeneous-medium cases the photon fluence rate along the homogeneous-medium associated spiral paths is macroscopically indistinguishable from, and microscopically close to, that along a straight line on a planar semi-infinite interface.
Melcer, Shai; Gruenbaum, Yosef . E-mail: gru@vms.huji.ac.il; Krohne, Georg . E-mail: krohne@biozentrum.uni-wuerzburg.de
2007-06-10
Lamins are the main component of the nuclear lamina and considered to be the ancestors of all intermediate filament proteins. They are localized mainly at the nuclear periphery where they form protein complexes with integral proteins of the nuclear inner membrane, transcriptional regulators, histones and chromatin modifiers. Studying lamins in invertebrate species has unique advantages including the smaller number of lamin genes in the invertebrate genomes and powerful genetic analyses in Caenorhabditis elegans and Drosophila melanogaster. These simpler nuclear lamina systems allow direct analyses of their structure and functions. Here we give an overview of recent advances in the field of invertebrate nuclear lamins with special emphasis on their evolution, assembly and functions.
Response of long shallow cylindrical panels to radial line loads
NASA Technical Reports Server (NTRS)
Johnson, E. R.; Hyer, M. W.; Carper, D. M.
1984-01-01
The large displacement static response of shallow orthotropic panels subjected to lateral loading is examined both theoretically and experimentally. The panels are circular cylindrical open shells which are also thin and long. The straight edges are simply supported at a fixed distance apart, and the curved edges are free. The lateral load is a spatially uniform line load acting along the generator direction of the cylinder, and is directed radially inward toward the center of curvature. The load induces a circumferential thrust, and the panel can, and does, snap-through to an inverted configuration at the buckling load. The effect of load position on the response is also examined. The test panels discussed in the paper are /(90/0)3/S graphite-epoxy laminates. Nominal dimensions are a radius of 60 in., a thickness of 0.060 in., and an arc length of 12 in. Very good agreement between theory and experiment is achieved.
Large Deformation Behavior of Long Shallow Cylindrical Composite Panels
NASA Technical Reports Server (NTRS)
Carper, Douglas M.; Hyer, Michael W.; Johnson, Eric R.
1991-01-01
An exact solution is presented for the large deformation response of a simply supported orthotropic cylindrical panel subjected to a uniform line load along a cylinder generator. The cross section of the cylinder is circular and deformations up to the fully snapped through position are investigated. The orthotropic axes are parallel to the generator and circumferential directions. The governing equations are derived using laminated plate theory, nonlinear strain-displacement relations, and applying variational principles. The response is investigated for the case of a panel loaded exactly at midspan and for a panel with the load offset from midspan. The mathematical formulation is one dimensional in the circumferential coordinate. Solutions are obtained in closed-form. An experimental apparatus was designed to load the panels. Experimental results of displacement controlled tests performed on graphite-epoxy curved panels are compared with analytical predictions.
Vibration of cylindrical shells of bimodulus composite materials
NASA Astrophysics Data System (ADS)
Bert, C. W.; Kumar, M.
1982-03-01
A theory is formulated for the small amplitude free vibration of thick, circular cylindrical shells laminated of bimodulus composite materials, which have different elastic properties depending upon whether the fiber-direction strain is tensile or compressive. The theory used is the dynamic, shear deformable (moderately thick shell) analog of the Sanders best first approximation thin shell theory. By means of tracers, the analysis can be reduced to that of various simpler shell theories, namely Love's first approximation, and Donnell's shallow shell theory. As an example of the application of the theory, a closed form solution is presented for a freely supported panel or complete shell. To validate the analysis, numerical results are compared with existing results for various special cases. Also, the effects of the various shell theories, thickness shear flexibility, and bimodulus action are investigated.
Thermographic validation of a novel, laminate body, analytical heat conduction model
NASA Astrophysics Data System (ADS)
Desgrosseilliers, Louis; Groulx, Dominic; White, Mary Anne
2014-07-01
The two-region fin model captures the heat spreading behaviour in multilayered composite bodies (i.e., laminates), heated only over a small part of their domains (finite heat source), where there is an inner layer that has a substantial capacity for heat conduction parallel to the heat exchange surface (convection cooling). This resulting heat conduction behaviour improves the overall heat transfer process when compared to heat conduction in homogeneous bodies. Long-term heat storage using supercooling salt hydrate phase change materials, stovetop cookware, and electronics cooling applications could all benefit from this kind of heat-spreading in laminates. Experiments using laminate films reclaimed from post-consumer Tetra Brik cartons were conducted with thin rectangular and circular heaters to confirm the laminate body, steady-state, heat conduction behaviour predicted by the two-region fin model. Medium to high accuracy experimental validation of the two-region fin model was achieved in Cartesian and cylindrical coordinates for forced external convection and natural convection, the latter for Cartesian only. These were conducted using constant heat flux finite heat source temperature profiles that were measured by infrared thermography. This validation is also deemed valid for constant temperature heat sources.
NASA Astrophysics Data System (ADS)
Narita, Y.; Nitta, T.
1998-07-01
Free vibration and corresponding optimal design problems are solved for laminated composite shallow shells of rectangular planform. The shells have symmetric laminated construction and are supported by shear diaphragms along the edges. The first-order transverse shear deformation is assumed in the Donnell type shell theory to account for the thickness shear effect, and an analytical solution is presented which is exact for cross-ply laminates and is approximate for angle-ply laminates. A simplified formula is also derived by neglecting inplane inertia terms. Analytical solutions with/without the inplane inertia terms from the classical thin shell theory are also shown. In numerical examples, natural frequencies are presented for various types of shell curvature, e.g., circular cylindrical, spherical and hyperbolic paraboloidal shells. Fibre orientation angles, which cause the maximized fundamental frequencies of the alternating angle-ply shells, are determined, and effects of using the four different vibration solutions are discussed on the optimal frequencies and fibre orientation angles. Questions of how the different solutions quantitatively affect the optimal design results and which solution is recommended in the present type of optimization problems are clarified in the conclusions.
Thermal buckling of laminated composite shells
Thangaratnam, R.K.; Palaninathan, R.; Ramachandran, J. )
1990-05-01
The linear buckling analysis of laminated composite cylindrical and conical shells under thermal load using the finite element method is reported here. Critical temperatures are presented for various cases of cross-ply and angly-ply laminated shells. The effects of radius/thickness ratio, number of layers, ratio of coefficients of thermal expansion, and the angle of fiber orientation have been studied. The results indicate that the buckling behavior of laminated shell under thermal load is different from that of mechanically loaded shell with respect to the angle of fiber orientation. 6 refs.
Baxter, G M
1994-12-01
Laminitis is an inflammation of the sensitive laminae along the dorsal aspect of the digit and is considered to be a secondary complication of several predisposing or primary factors. Affected horses are usually very lame, have increased digital pulses, are painful to hoof testers along the toe of the foot, and have evidence of downward rotation or distal displacement of the distal phalanx present on radiographs. Treatments for acute laminitis include anti-inflammatory drugs, anti-endotoxin therapy, vasodilators, antithrombotic therapy, corrective trimming and shoeing, and surgical procedures. Treatment regimens are very controversial and the true efficacy of these treatments is unknown. The quality of laminae damage that occurs with laminitis, however, probably has greater influence on the success of treatment and outcome of the horse than the treatment regimen itself.
The room-temperature shapes of four-layer unsymmetric cross-ply laminates
NASA Technical Reports Server (NTRS)
Hyer, M. W.
1982-01-01
A geometrically nonlinear extension of classical lamination theory developed by Hyer (1981) for predicting the room-temperature shapes of unsymmetric laminates is reformulated using relaxed restrictions regarding the inplane strains. The inplane residual strains of unsymmetric laminates which have cooled from curing into a cylindrical room-temperature shape are examined numerically. Results show that the residual strains are compressive and practically independent of spatial location on the laminate. In addition, the room temperature shapes of the four-layer unsymmetric cross-ply laminates are predicted, and it is shown that the temperature shapes are a strong function of their size and their stacking arrangement. It is demonstrated that, depending on the parameters selected, the room-temperature shape of a four-layer cross-ply unsymmetric laminate can be a unique saddle shape, a unique cylindrical shape, or a cylindrical shape that can be snapped through to another cylindrical shape.
Andrade, A.D.; Galbraith, L.K.
1979-10-01
The disclosure relates to a laminated negative dry-film photoresist for the production of thick, as well as thin, patterns with vertical sidewalls. Uniform depthwise exposure in a photoresist layer is effected by the use of an ultraviolet filtering top layer.
Williams, Robert K.; Paranthaman, Mariappan; Chirayil, Thomas G.; Lee, Dominic F.; Goyal, Amit; Feenstra, Roeland
2002-01-01
A laminate article comprises a substrate and a biaxially textured (RE.sub.x A.sub.(1-x)).sub.2 O.sub.2-(x/2) buffer layer over the substrate, wherein 0
Bronnikov, K. A.; Lemos, Jose P. S.
2009-05-15
It is shown that the existence of static, cylindrically symmetric wormholes does not require violation of the weak or null energy conditions near the throat, and cylindrically symmetric wormhole geometries can appear with less exotic sources than wormholes whose throats have a spherical topology. Examples of exact wormhole solutions are given with scalar, spinor and electromagnetic fields as sources, and these fields are not necessarily phantom. In particular, there are wormhole solutions for a massless, minimally coupled scalar field in the presence of a negative cosmological constant, and for an azimuthal Maxwell electromagnetic field. All these solutions are not asymptotically flat. A no-go theorem is proved, according to which a flat (or string) asymptotic behavior on both sides of a cylindrical wormhole throat is impossible if the energy density of matter is everywhere nonnegative.
Hybrid composite laminate structures
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Lark, R. F. (Inventor)
1977-01-01
An invention which relates to laminate structures and specifically to essentially anisotropic fiber composite laminates is described. Metal foils are selectively disposed within the laminate to produce increased resistance to high velocity impact, fracture, surface erosion, and other stresses within the laminate.
NASA Astrophysics Data System (ADS)
Soldatos, K. P.
1987-11-01
This paper is concerned with the influence of thickness shear deformation and rotatory inertia on the free vibrations of antisymmetric angle-ply laminated circular cylindrical panels. Two kinds of thickness shear deformable shell theories are considered. In the first one, uniformly distributed thickness shear strains through the shell thickness and, therefore, thickness shear correction factors are used. In the second theory a parabolic variation of thickness shear strains and stresses with zero values at the inner and outer shell surfaces is assumed. The analysis is mainly based on Love's approximations but, for purposes of comparison, Donnell's shallow shell approximations are also considered. For a simply supported panel, the equations of motion of the aforementioned theories, as well as of the corresponding classical theories, are solved by using Galerkin's method. For a family of graphite-epoxy angle-ply laminated plates and circular cylindrical panels, numerical results are obtained, compared and discussed and some interesting conclusions are made regarding the shell theories considered as well as the mathematical method employed.
Farriery for chronic laminitis.
O'Grady, Stephen E
2010-08-01
Laminitis is considered chronic once the distal phalanx has displaced within the hoof capsule. Chronic laminitis generally occurs as a direct sequel to acute laminitis. Clinical evaluation of chronic laminitis is best performed with a thorough clinical examination and radiography. The mainstay of hoof care is therapeutic farriery. In this article, the goals and principles of hoof care, the appropriate trim and various shoes that form the bulk of farriery for chronic laminitis, and surgical treatments are discussed.
NASA Technical Reports Server (NTRS)
Rosu, Grigore; Goguen, Joseph; Norvig, Peter (Technical Monitor)
2001-01-01
Circular coinduction is a technique for behavioral reasoning that extends cobasis coinduction to specifications with circularities. Because behavioral satisfaction is not recursively enumerable, no algorithm can work for every behavioral statement. However. algorithms using circular coinduction can prove every practical behavioral result that we know. This paper proves the correctness of circular coinduction and some consequences.
Hall, Thomas E.
1999-04-29
The CS system is designed to provide a very fast imaging system in order to search for weapons on persons in an airport environment. The Cylindrical Scanner moves a vertical transceiver array rapidly around a person standing stationary. The software can be segmented in to three specific tasks. The first task is data acquisition and scanner control. At the operator's request, this task commands the scanner to move and the radar transceiver array to send data to the computer system in a known and well-ordered manner. The array is moved over the complete aperture in 10 to 12 seconds. At the completion of the array movement the second software task automatically reconstructs the high-resolution image from the radar data utilizing the integrated DSP boards. The third task displays the resulting images, as they become available, to the computer screen for user review and analysis.
Behavior of curved laminated composite panels and shells under axial compression
NASA Astrophysics Data System (ADS)
Abramovich, H.; Bisagni, C.
2015-10-01
The buckling and post-buckling behavior of curved cylindrical stringer-stiffened laminated composite and metal panels had been investigated both numerically and experimentally. The results were compared to those of cylindrical stringer-stiffened laminated composite shells to yield a way of determining the optimal structure to be used for axial compression loading. For the present tested structures, the composite panels showed the best load-weight ratio.
NASA Technical Reports Server (NTRS)
Nemeth, Michael P.
2014-01-01
Nonlinear and bifurcation buckling equations for elastic, stiffened, geometrically perfect, right-circular cylindrical, anisotropic shells subjected to combined loads are presented that are based on Sanders' shell theory. Based on these equations, a three-parameter approximate Rayleigh-Ritz solution and a classical solution to the buckling problem are presented for cylinders with simply supported edges. Extensive comparisons of results obtained from these solutions with published results are also presented for a wide range of cylinder constructions. These comparisons include laminated-composite cylinders with a wide variety of shell-wall orthotropies and anisotropies. Numerous results are also given that show the discrepancies between the results obtained by using Donnell's equations and variants of Sanders' equations. For some cases, nondimensional parameters are identified and "master" curves are presented that facilitate the concise representation of results.
NASA Technical Reports Server (NTRS)
Gerhard, Craig Steven; Gurdal, Zafer; Kapania, Rakesh K.
1996-01-01
Layerwise finite element analyses of geodesically stiffened cylindrical shells are presented. The layerwise laminate theory of Reddy (LWTR) is developed and adapted to circular cylindrical shells. The Ritz variational method is used to develop an analytical approach for studying the buckling of simply supported geodesically stiffened shells with discrete stiffeners. This method utilizes a Lagrange multiplier technique to attach the stiffeners to the shell. The development of the layerwise shells couples a one-dimensional finite element through the thickness with a Navier solution that satisfies the boundary conditions. The buckling results from the Ritz discrete analytical method are compared with smeared buckling results and with NASA Testbed finite element results. The development of layerwise shell and beam finite elements is presented and these elements are used to perform the displacement field, stress, and first-ply failure analyses. The layerwise shell elements are used to model the shell skin and the layerwise beam elements are used to model the stiffeners. This arrangement allows the beam stiffeners to be assembled directly into the global stiffness matrix. A series of analytical studies are made to compare the response of geodesically stiffened shells as a function of loading, shell geometry, shell radii, shell laminate thickness, stiffener height, and geometric nonlinearity. Comparisons of the structural response of geodesically stiffened shells, axial and ring stiffened shells, and unstiffened shells are provided. In addition, interlaminar stress results near the stiffener intersection are presented. First-ply failure analyses for geodesically stiffened shells utilizing the Tsai-Wu failure criterion are presented for a few selected cases.
Rippel, Wally E.; Kobayashi, Daryl M.
2005-10-11
An electric motor, transformer or inductor having a lamination cooling system including a stack of laminations, each defining a plurality of apertures at least partially coincident with apertures of adjacent laminations. The apertures define a plurality of cooling-fluid passageways through the lamination stack, and gaps between the adjacent laminations are sealed to prevent a liquid cooling fluid in the passageways from escaping between the laminations. The gaps are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. The apertures of each lamination can be coincident with the same-sized apertures of adjacent laminations to form straight passageways, or they can vary in size, shape and/or position to form non-axial passageways, angled passageways, bidirectional passageways, and manifold sections of passageways that connect a plurality of different passageway sections. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.
Hood, D M
1999-08-01
This article serves as an introduction to this issue on laminitis. As such, it contains the general perspectives and terminology that will be used in all subsequent articles. This article separates the clinical problem of laminitis into developmental, acute, subacute, and chronic phases and defines the criteria, duration, clinical goals, and implications of these phases. The basis for the significance of laminitis to the horse industry and the horseman is reviewed. Lastly, the organization of this issue is described.
Polar symmetry in three-dimensional analysis of laminates with angle plies
NASA Technical Reports Server (NTRS)
Raju, I. S.; Crews, J. H., Jr.
1980-01-01
An improved procedure for the three dimensional finite element analysis of an angle ply laminate with a circular hole is discussed. The procecure exploits polar symmetry and is the basis for a new finite element computer code. For the broad class of laminates that contain angle plies, this code requires only one half as much computing capacity as conventional codes.
Calculation of the room-temperature shapes of unsymmetric laminates
NASA Technical Reports Server (NTRS)
Hyer, M. W.
1981-01-01
A theory explaining the characteristics of the cured shapes of unsymmetric laminates is presented. The theory is based on an extension of classical lamination theory which accounts for geometric nonlinearities. A Rayleigh-Ritz approach to minimizing the total potential energy is used to obtain quantitative information regarding the room temperature shapes of square T300/5208 (0(2)/90(2))T and (0(4)/90(4))T graphite-epoxy laminates. It is shown that, depending on the thickness of the laminate and the length of the side the square, the saddle shape configuration is actually unstable. For values of length and thickness that render the saddle shape unstable, it is shown that two stable cylindrical shapes exist. The predictions of the theory are compared with existing experimental data.
Nuclear lamins and neurobiology.
Young, Stephen G; Jung, Hea-Jin; Lee, John M; Fong, Loren G
2014-08-01
Much of the work on nuclear lamins during the past 15 years has focused on mutations in LMNA (the gene for prelamin A and lamin C) that cause particular muscular dystrophy, cardiomyopathy, partial lipodystrophy, and progeroid syndromes. These disorders, often called "laminopathies," mainly affect mesenchymal tissues (e.g., striated muscle, bone, and fibrous tissue). Recently, however, a series of papers have identified important roles for nuclear lamins in the central nervous system. Studies of knockout mice uncovered a key role for B-type lamins (lamins B1 and B2) in neuronal migration in the developing brain. Also, duplications of LMNB1 (the gene for lamin B1) have been shown to cause autosome-dominant leukodystrophy. Finally, recent studies have uncovered a peculiar pattern of nuclear lamin expression in the brain. Lamin C transcripts are present at high levels in the brain, but prelamin A expression levels are very low-due to regulation of prelamin A transcripts by microRNA 9. This form of prelamin A regulation likely explains why "prelamin A diseases" such as Hutchinson-Gilford progeria syndrome spare the central nervous system. In this review, we summarize recent progress in elucidating links between nuclear lamins and neurobiology.
NASA Astrophysics Data System (ADS)
Mahadev, Sthanu
Continued research and development efforts devoted in recent years have generated novel avenues towards the advancement of efficient and effective, slender laminated fiber-reinforced composite members. Numerous studies have focused on the modeling and response characterization of composite structures with particular relevance to thin-walled cylindrical composite shells. This class of shell configurations is being actively explored to fully determine their mechanical efficacy as primary aerospace structural members. The proposed research is targeted towards formulating a composite shell theory based prognosis methodology that entails an elaborate analysis and investigation of thin-walled cylindrical shell type laminated composite configurations that are highly desirable in increasing number of mechanical and aerospace applications. The prime motivation to adopt this theory arises from its superior ability to generate simple yet viable closed-form analytical solution procedure to numerous geometrically intense, inherent curvature possessing composite structures. This analytical evaluative routine offers to acquire a first-hand insight on the primary mechanical characteristics that essentially govern the behavior of slender composite shells under typical static loading conditions. Current work exposes the robustness of this mathematical framework via demonstrating its potential towards the prediction of structural properties such as axial stiffness and bending stiffness respectively. Longitudinal ply-stress computations are investigated upon deriving the global stiffness matrix model for composite cylindrical tubes with circular cross-sections. Additionally, this work employs a finite element based numerical technique to substantiate the analytical results reported for cylindrically shaped circular composite tubes. Furthermore, this concept development is extended to the study of thin-walled, open cross-sectioned, curved laminated shells that are geometrically
Buckling analysis of laminated thin shells in a hot environment
NASA Technical Reports Server (NTRS)
Gotsis, Pascal K.; Guptil, James D.
1993-01-01
Results are presented of parametric studies to assess the effects of various parameters on the buckling behavior of angle-ply, laminated thin shells in a hot environment. These results were obtained by using a three-dimensional finite element analysis. An angle-ply, laminated thin shell with fiber orientation of (theta/-theta)(sub 2) was subjected to compressive mechanical loads. The laminated thin shell had a cylindrical geometry. The laminate contained T300 graphite fibers embedded in an intermediate-modulus, high-strength (IMHS) matrix. The fiber volume fraction was 55 percent and the moisture content was 2 percent. The residual stresses induced into the laminate structure during the curing were taken into account. Parametric studies were performed to examine the effect on the critical buckling load of the following parameters: cylinder length and thickness, internal hydrostatic pressure, different ply thicknesses, different temperature profiles through the thickness of the structure, and different lay up configurations and fiber volume fractions. In conjunction with these parameters the ply orientation was varied from 0 deg to 90 deg. Seven ply angles were examined: 0 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. The results show that the ply angle theta and the laminate thickness had significant effects on the critical buckling load. The fiber volume fraction, the fiber orientations, and the internal hydrostatic pressure had important effects on the critical buckling load. The cylinder length had a moderate influence on the buckling load. The thin shell with (theta/-theta)(sub 2) or (theta/-theta)(sub s) angle-ply laminate had better buckling-load performance than the thin shell with (theta)(sub 4) angle-ply laminate. The temperature profiles through the laminate thickness and various laminates with the different ply thicknesses has insignificant effects on the buckling behavior of the thin shells.
Self-referenced interferometer for cylindrical surfaces.
Šarbort, Martin; Řeřucha, Šimon; Holá, Miroslava; Buchta, Zdeněk; Lazar, Josef
2015-11-20
We present a new interferometric method for shape measurement of hollow cylindrical tubes. We propose a simple and robust self-referenced interferometer where the reference and object waves are represented by the central and peripheral parts, respectively, of the conical wave generated by a single axicon lens. The interferogram detected by a digital camera is characterized by a closed-fringe pattern with a circular carrier. The interference phase is demodulated using spatial synchronous detection. The capabilities of the interferometer are experimentally tested for various hollow cylindrical tubes with lengths up to 600 mm.
Cylindrical Piezoelectric Fiber Composite Actuators
NASA Technical Reports Server (NTRS)
Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.
2008-01-01
The use of piezoelectric devices has become widespread since Pierre and Jacques Curie discovered the piezoelectric effect in 1880. Examples of current applications of piezoelectric devices include ultrasonic transducers, micro-positioning devices, buzzers, strain sensors, and clocks. The invention of such lightweight, relatively inexpensive piezoceramic-fiber-composite actuators as macro fiber composite (MFC) actuators has made it possible to obtain strains and displacements greater than those that could be generated by prior actuators based on monolithic piezoceramic sheet materials. MFC actuators are flat, flexible actuators designed for bonding to structures to apply or detect strains. Bonding multiple layers of MFC actuators together could increase force capability, but not strain or displacement capability. Cylindrical piezoelectric fiber composite (CPFC) actuators have been invented as alternatives to MFC actuators for applications in which greater forces and/or strains or displacements may be required. In essence, a CPFC actuator is an MFC or other piezoceramic fiber composite actuator fabricated in a cylindrical instead of its conventional flat shape. Cylindrical is used here in the general sense, encompassing shapes that can have circular, elliptical, rectangular or other cross-sectional shapes in the planes perpendicular to their longitudinal axes.
Low cost and high performance screen laminate regenerator matrix
NASA Astrophysics Data System (ADS)
Bin-Nun, Uri; Manitakos, Dan
2004-06-01
A laminate screen matrix regenerator with 47 elements has been designed, analyzed, fabricated and tested. The laminate was fabricated from stainless steel screen sheets that were stacked on top of each other at certain angular orientation and then bonded at high temperature and pressure environment utilizing a sintering process. This laminate is a porous structure media with highly repeatable properties that can be controlled by varying mesh size, weave type, wire size and laminate sheet to sheet orientation. The flow direction in relation to the weave plan can be varied by cutting a cylindrical or rectangular laminate element along or across the weave. The regenerator flow resistance, thermal conductance losses, dead volume, surface area and heat transfer coefficient are analyzed. Regenerator cost and performance comparison data between the conventional widely used method of stacked screens and the new stacked laminate matrix regenerator is discussed. Also, a square stainless steel screen laminate was manufactured in a way which permits gas to flow along the screen wire instead of across it.
NASA Technical Reports Server (NTRS)
Keenan, R.
1985-01-01
Two-piece unit heats and presses protective layers to form laminate. Rubber diaphragm between upper and lower vacuum chambers alternates between neutral position and one that presses against solar-cell array, supplying distributed force necessary to press layers of laminate together. Encapsulation helps to protect cells from environment and to ensure long panel life while allowing efficient generation of electricity from Sunlight.
ERIC Educational Resources Information Center
Lee, Paul D.
1995-01-01
Provides a period-long activity using battery powered cars rolling in a circular motion on a tile floor. Students measure the time and distance as the car moves to derive the equation for centripetal acceleration. (MVL)
Honeycomb-laminate composite structure
NASA Technical Reports Server (NTRS)
Gilwee, W. J., Jr.; Parker, J. A. (Inventor)
1977-01-01
A honeycomb-laminate composite structure was comprised of: (1) a cellular core of a polyquinoxaline foam in a honeycomb structure, and (2) a layer of a noncombustible fibrous material impregnated with a polyimide resin laminated on the cellular core. A process for producing the honeycomb-laminate composite structure and articles containing the honeycomb-laminate composite structure is described.
Mixed FE analysis of viscoelastic cylindrical helixes
NASA Astrophysics Data System (ADS)
Arıbaş, Ü. N.; Omurtag, M. H.
2012-09-01
In this study, analysis of viscoelastic cylindrical helixes with circular and square cross section is investigated by using the mixed FEM based on Timoshenko beam theory. The Kelvin model is used for the viscoelastic behavior. The analysis is performed in the Laplace domain and the results are transformed back to time domain numerically by Modified Durbin algorithm. The outcome is quite satisfactory besides the necessary engineering precision.
Beamtracking in cylindrical and cartesian coordinates
Schillinger, B.; Weiland, T.
1997-02-01
For the design of devices with circular optical axes, e.g. bending magnets or spectrometers, the use of cylindrical coordinates for field calculations could be favourable. Additionally, in case of applications like bending systems with nonorthogonal entry and exit faces, the coupling of cylindrical and cartesian coordinates improves the simulation of fringe fields. In this context we have implemented a consistent coupling between the two coordinate systems and have extended the tracking code of the electromagnetic simulator MAFIA to cylindrical coordinates. This extensions could be of interest for the calculation of transfer maps of ionoptical devices using the tracked particle orbit as reference trajectory and including fringe field effects in a more general manner. We will give a short introduction to the extensions and show some examples for bending systems with nonorthogonal entries.
Distributed neural signals on parabolic cylindrical shells
NASA Astrophysics Data System (ADS)
Hu, S. D.; Li, H.; Tzou, H. S.
2013-06-01
Parabolic cylindrical shells are commonly used as key components in communication antennas, space telescopes, solar collectors, etc. This study focuses on distributed modal neural sensing signals on a flexible simply-supported parabolic cylindrical shell panel. The parabolic cylindrical shell is fully laminated with a piezoelectric layer on its outer surface and the piezoelectric layer is segmented into infinitesimal elements (neurons) to investigate the microscopic distributed neural sensing signals. Since the dominant vibration component of the shell is usually the transverse oscillation, a new transverse mode shape function is defined. Two shell cases, i.e., the ratio of the meridian height to the half span distance of a parabola at 1:4 (shallow) and 1:1 (deep), are studied to reveal the curvature effect to the neural sensing signals. Studies suggest that the membrane signal component dominates for lower natural modes and the bending signal component dominates for higher natural modes. The meridional membrane and bending signal components are mostly concentrated on the high-curvature areas, while the longitudinal bending component is mostly concentrated on the relatively flat areas. The concentration behavior becomes more prominent as the parabolic cylindrical shell deepens, primarily resulting from the enhanced membrane effect due to the increased curvature.
NASA Technical Reports Server (NTRS)
Dawn, F. S.; Sauers, D. G.
1977-01-01
Lightweight flexible laminate of interwoven conducting and insulating yarns, designed to provide localized controlled heating for propellant tanks on space vehicles, is useful for nonspace applications where weight, bulk, and flexibility are critical concerns.
Historical perspectives on laminitis.
Wagner, I P; Heymering, H
1999-08-01
This article attempts to provide a historical perspective regarding equine laminitis. It is designed to cover, as completely as possible, the historical record of, and the research advances made, in regards to acute and chronic laminitis. With respect to the historical record, the names given to this disease, the postulated etiologies, and the various treatment protocols are discussed. This article demonstrates the historical longevity of this disease and establishes a background for the current understanding of the disease's pathologic mechanisms and treatments.
Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks
NASA Technical Reports Server (NTRS)
Saravanos, Dimitris A.
1999-01-01
Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.
Lamination cooling system formation method
Rippel, Wally E; Kobayashi, Daryl M
2012-06-19
An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.
Multipole Analysis of Circular Cylindircal Magnetic Systems
Selvaggi, Jerry P.
2005-12-01
This thesis deals with an alternate method for computing the external magnetic field from a circular cylindrical magnetic source. The primary objective is to characterize the magnetic source in terms of its equivalent multipole distribution. This multipole distribution must be valid at points close to the cylindrical source and a spherical multipole expansion is ill-equipped to handle this problem; therefore a new method must be introduced. This method, based upon the free-space Green's function in cylindrical coordinates, is developed as an alternative to the more familiar spherical harmonic expansion. A family of special functions, called the toroidal functions or Q-functions, are found to exhibit the necessary properties for analyzing circular cylindrical geometries. In particular, the toroidal function of zeroth order, which comes from the integral formulation of the free-space Green's function in cylindrical coordinates, is employed to handle magnetic sources which exhibit circular cylindrical symmetry. The toroidal functions, also called Q-functions, are the weighting coefficients in a ''Fourier series-like'' expansion which represents the free-space Green's function. It is also called a toroidal expansion. This expansion can be directly employed in electrostatic, magnetostatic, and electrodynamic problems which exhibit cylindrical symmetry. Also, it is shown that they can be used as an alternative to the Elliptic integral formulation. In fact, anywhere that an Elliptic integral appears, one can replace it with its corresponding Q-function representation. A number of problems, using the toroidal expansion formulation, are analyzed and compared to existing known methods in order to validate the results. Also, the equivalent multipole distribution is found for most of the solved problems along with its corresponding physical interpretation. The main application is to characterize the external magnetic field due to a six-pole permanent magnet motor in terms of
Three dimensional inelastic finite element analysis of laminated composites
NASA Technical Reports Server (NTRS)
Griffin, O. H., Jr.; Kamat, M. P.
1980-01-01
Formulations of the inelastic response of laminated composites to thermal and mechanical loading are used as the basis for development of the computer NALCOM (Nonlinear Analysis of Laminated Composites) computer program which uses a fully three dimensional isoparametric finite element with 24 nodes and 72 degrees of freedom. An incremental solution is performed with nonlinearities introduced as pseudoloads computed for initial strains. Equilibrium iteration may be performed at every step. Elastic and elastic-plastic response of boron/epoxy and graphite/epoxy graphite/epoxy and problems of curing 0/90 sub s Gr/Ep laminates with and without circular holes are analyzed. Mechanical loading of + or - 45sub s Gr/Ep laminates is modeled and symmetry conditions which exist in angle-ply laminates are discussed. Results are compared to experiments and other analytical models when possible. All models are seen to agree reasonably well with experimetnal results for off-axis tensile coupons. The laminate analyses show the three dimensional effects which are present near holes and free corners.
Laminate armor and related methods
Chu, Henry S; Lillo, Thomas M; Zagula, Thomas M
2013-02-26
Laminate armor and methods of manufacturing laminate armor. Specifically, laminate armor plates comprising a commercially pure titanium layer and a titanium alloy layer bonded to the commercially pure titanium outer layer are disclosed, wherein an average thickness of the titanium alloy inner layer is about four times an average thickness of the commercially pure titanium outer layer. In use, the titanium alloy layer is positioned facing an area to be protected. Additionally, roll-bonding methods for manufacturing laminate armor plates are disclosed.
Laminates and reinforced metals
NASA Technical Reports Server (NTRS)
Chamis, C. C.
1980-01-01
A selective review is presented of the state of the art of metallic laminates and fiber reinforced metals called metallic matrix laminates (MMLs). Design and analysis procedures that are used for, and typical structural components that have been made from MMLs are emphasized. Selected MMLs, constituent materials, typical material properties and fabrication procedures are briefly described, including hybrids and superhybrids. Advantages, disadvantages, and special considerations required during design, analysis, and fabrication of MMLs are examined. Tabular and graphical data are included to illustrate key aspects of MMLs. Appropriate references are cited to provide a selective bibliography of a rapidly expanding and very promising research and development field.
NASA Technical Reports Server (NTRS)
Johnson, W. S.; Bigelow, C. A.; Bahei-El-din, Y. A.
1983-01-01
Experimental results for five laminate orientations of boron/aluminum composites containing either circular holes or crack-like slits are presented. Specimen stress-strain behavior, stress at first fiber failure, and ultimate strength were determined. Radiographs were used to monitor the fracture process. The specimens were analyzed with a three-dimensional elastic-elastic finite-element model. The first fiber failures in notched specimens with laminate orientation occurred at or very near the specimen ultimate strength. For notched unidirectional specimens, the first fiber failure occurred at approximately one-half of the specimen ultimate strength. Acoustic emission events correlated with fiber breaks in unidirectional composites, but did not for other laminates. Circular holes and crack-like slits of the same characteristic length were found to produce approximately the same strength reduction. The predicted stress-strain responses and stress at first fiber failure compared very well with test data for laminates containing 0 deg fibers.
Leung, Ka-Ngo
2005-06-14
A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.
Leung, Ka-Ngo
2009-12-29
A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.
Leung, Ka-Ngo
2008-04-22
A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.
Cylindrically symmetric wormholes
Kuhfittig, Peter K.F.
2005-05-15
This paper discusses traversable wormholes that differ slightly but significantly from those of the Morris-Thorne type under the assumption of cylindrical symmetry. The throat is a piecewise smooth cylindrical surface resulting in a shape function that is not differentiable at some value. It is proposed that the regular derivative be replaced by a one-sided derivative at this value. The resulting wormhole geometry satisfies the weak energy condition.
Transparent polymeric laminates
NASA Technical Reports Server (NTRS)
Parker, J. A.; Fohlen, G. M.; Sawko, P. M.
1973-01-01
Laminate prepared from epoxy-boroxine and phenolphthalein polycarbonate has high mechanical strength at elevated temperature and is resistant to impact, fire, and high-energy thermal radiation. Polycarbonate is prepared by reaction of phenolphthalein with phosgene in presence of amine catalyst and immiscible organic solvent phase.
Cylindrical coordinate representation for multiband Hamiltonians
NASA Astrophysics Data System (ADS)
Takhtamirov, Eduard
2012-10-01
Rotationally invariant combinations of the Brillouin zone-center Bloch functions are used as basis function to express in cylindrical coordinates the valence-band and Kane envelope-function Hamiltonians for wurtzite and zinc-blende semiconductor heterostructures. For cylindrically symmetric systems, this basis allows to treat the envelope functions as eigenstates of the operator of projection of total angular momentum on the symmetry axis, with the operator's eigenvalue conventionally entering the Hamiltonians as a parameter. Complementing the Hamiltonians with boundary conditions for the envelope functions on the symmetry axis, we present for the first time a complete formalism for efficient modeling and description of multiband electron states in low-dimensional semiconductor structures with cylindrical symmetry. To demonstrate the potency of the cylindrical symmetry approximation and establish a criterion of its applicability for actual structures, we map the ground and several excited valence-band states in an isolated wurtzite GaN quantum wire of a hexagonal cross-section to the states in an equivalent quantum wire of a circular cross-section.
Analysis of delamination growth in compressively loaded composite laminates
NASA Astrophysics Data System (ADS)
Tratt, Matthew D.
The present analytical and empirical study of composite structure delamination has attempted to predict the threshold stress for the initiation of delamination growth in compressively loaded composite laminates. The strain-energy release-rate distributions around circular delaminations are computed via MSC/NASTRAN analysis in conjunction with a virtual crack-opening technique. Static compression tests were conducted on specimens of graphite fiber-reinforced epoxy having circular delaminations of various sizes. Computed delamination growth threshold-stress prediction results were at substantial variance with the test data, but confirmed trends and gave qualitative insight into quasi-static delamination growth.
Development of a realistic stress analysis for fatigue analysis of notched composite laminates
NASA Technical Reports Server (NTRS)
Humphreys, E. A.; Rosen, B. W.
1979-01-01
A finite element stress analysis which consists of a membrane and interlaminar shear spring analysis was developed. This approach was utilized in order to model physically realistic failure mechanisms while maintaining a high degree of computational economy. The accuracy of the stress analysis predictions is verified through comparisons with other solutions to the composite laminate edge effect problem. The stress analysis model was incorporated into an existing fatigue analysis methodology and the entire procedure computerized. A fatigue analysis is performed upon a square laminated composite plate with a circular central hole. A complete description and users guide for the computer code FLAC (Fatigue of Laminated Composites) is included as an appendix.
Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-28
... COMMISSION Certain Products Having Laminated Packaging, Laminated Packaging, and Components Thereof.... 1337, on behalf of Lamina Packaging Innovations LLC of Longview, Texas. An amended complaint was filed... importation of certain products having laminated packaging, laminated packaging, and components thereof...
Chronic laminitis: foot management.
Morrison, Scott
2010-08-01
Laminitis is a disease of the suspensory apparatus of the distal phalanx, which can advance to the chronic stage with varying degrees of structural failure. Because the disease may ultimately lead to mechanical failure of the digit, a foot management plan is required to effectively and mechanically treat these cases. Many laminitis cases can be successfully rehabilitated back to athletic soundness, light use, breeding, or pasture soundness, whereas others suffer from permanent instability and never enjoy an acceptable level of comfort. To understand how to minimize damage in the acute laminitic foot or rehabilitate the chronic laminitic foot, the veterinarian should have an understanding of the normal supporting structures of the digit, the biomechanical forces acting on the foot, and the structural failure that results when these otherwise normal forces act on a diseased, damaged foot.
Laminated piezoelectric transformer
NASA Technical Reports Server (NTRS)
Vazquez Carazo, Alfredo (Inventor)
2006-01-01
A laminated piezoelectric transformer is provided using the longitudinal vibration modes for step-up voltage conversion applications. The input portions are polarized to deform in a longitudinal plane and are bonded to an output portion. The deformation of the input portions is mechanically coupled to the output portion, which deforms in the same longitudinal direction relative to the input portion. The output portion is polarized in the thickness direction relative its electrodes, and piezoelectrically generates a stepped-up output voltage.
Thermally stable laminating resins
NASA Technical Reports Server (NTRS)
Jones, R. J.; Vaughan, R. W.; Burns, E. A.
1972-01-01
Improved thermally stable laminating resins were developed based on the addition-type pyrolytic polymerization. Detailed monomer and polymer synthesis and characterization studies identified formulations which facilitate press molding processing and autoclave fabrication of glass and graphite fiber reinforced composites. A specific resin formulation, termed P10P was utilized to prepare a Courtaulds HMS reinforced simulated airfoil demonstration part by an autoclave molding process.
Laminates for Ballistic Protection
1975-02-01
Textile Research &Inginearing Division 1S. NUM11ER OF PAGES N I ,aN4MotN.lInNOfDoe ISANSUITY CLASS. (of this eport0) 1 ~~,fICATIONf DOVINGRA3DING5 WS...Kevlar and glass laminates using an areal density of 11.6 kg/m and a maximn load of 82N (200 lb.). The Kevlar lamintes survived 1000 cycles but
Jebens, R.W.
1980-04-01
A fabrication method for making plastic-on-glass laminated Fresnel lenses is discussed. These Fresnel lenses are for application in an RCA solar photovoltaic concentrator array now in the prototype stage of development. This laminated Fresnel lens fabrication method consists of making a Dow Corning J RTV silastic rubber mold of a master lens array. This mold is used to vacuum cast only the lens facets onto a low-iron tempered-glass substrate with an epoxy resin such as Hysol 0S 1000, a bisphenol-A resin with a flexibilizer that is anhydride cured. Cast acrylic Fresnel lens arrays commercialy available have potential cleaning and abrasion problems, have very large thermal expansion, and have dimensional uncertainties in their manufacture. The laminated lens is dimensionally stable with low thermal expansion, has good cleaning characteristics, and is very inexpensive in materials cost. The measured transmission of such a lens on low-iron glass is 80.4% compared with 85.1% for a cast acrylic lens, and the optical quality is good enough for application in the 100X to 200X concentration range. An approach to making large lens arrays (3 by 6 ft) on a commercial scale is explored.
Solar cell module lamination process
Carey, Paul G.; Thompson, Jesse B.; Aceves, Randy C.
2002-01-01
A solar cell module lamination process using fluoropolymers to provide protection from adverse environmental conditions and thus enable more extended use of solar cells, particularly in space applications. A laminate of fluoropolymer material provides a hermetically sealed solar cell module structure that is flexible and very durable. The laminate is virtually chemically inert, highly transmissive in the visible spectrum, dimensionally stable at temperatures up to about 200.degree. C. highly abrasion resistant, and exhibits very little ultra-violet degradation.
A Higher-Order Bending Theory for Laminated Composite and Sandwich Beams
NASA Technical Reports Server (NTRS)
Cook, Geoffrey M.
1997-01-01
A higher-order bending theory is derived for laminated composite and sandwich beams. This is accomplished by assuming a special form for the axial and transverse displacement expansions. An independent expansion is also assumed for the transverse normal stress. Appropriate shear correction factors based on energy considerations are used to adjust the shear stiffness. A set of transverse normal correction factors is introduced, leading to significant improvements in the transverse normal strain and stress for laminated composite and sandwich beams. A closed-form solution to the cylindrical elasticity solutions for a wide range of beam aspect ratios and commonly used material systems. Accurate shear stresses for a wide range of laminates, including the challenging unsymmetric composite and sandwich laminates, are obtained using an original corrected integration scheme. For application of the theory to a wider range of problems, guidelines for finite element approximations are presented.
Laminitis in the geriatric horse.
Hunt, Robert J
2002-12-01
There are few diseases that instill a comparable sense of doom in the mind of a treating veterinarian as laminitis. There is a feeling of cautious optimism when a horse with laminitis responds favorably to treatment. Although this optimism all too often proves false when treating laminitic patients, management of the patient afflicted with chronic laminitis can be rewarding. Through diligent and careful client communication and instruction, many geriatric patients with chronic laminitis can be maintained for years as comfortable companions, for light riding use, or as productive breeding animals.
Microfabricated cylindrical ion trap
Blain, Matthew G.
2005-03-22
A microscale cylindrical ion trap, having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale cylindrical ion trap to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The microscale CIT has a reduced ion mean free path, allowing operation at higher pressures with less expensive and less bulky vacuum pumping system, and with lower battery power than conventional- and miniature-sized ion traps. The reduced electrode voltage enables integration of the microscale cylindrical ion trap with on-chip integrated circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of microscale cylindrical ion traps can be realized in truly field portable, handheld microanalysis systems.
A General Study of Hybrid Composite Laminates.
1977-12-01
appeared to have little effect on the overall properties of a laminate. Hybrid composite laminates obey classical laminate theory and can, in certain ply configurations, develop considerable free edge effect stresses. (Author)
Simple Analytic Expressions for the Magnetic Field of a Circular Current Loop
NASA Technical Reports Server (NTRS)
Simpson, James C.; Lane, John E.; Immer, Christopher D.; Youngquist, Robert C.; Steinrock, Todd (Technical Monitor)
2001-01-01
Analytic expressions for the magnetic induction and its spatial derivatives for a circular loop carrying a static current are presented in Cartesian, spherical and cylindrical coordinates. The solutions are exact throughout all space outside the conductor.
Laminated Thin Shell Structures Subjected to Free Vibration in a Hygrothermal Environment
NASA Technical Reports Server (NTRS)
Gotsis, Pascal K.; Guptill, James D.
1994-01-01
Parametric studies were performed to assess the effects of various parameters on the free-vibration behavior (natural frequencies) of (+/- theta)(sub 2) angle-ply, fiber composite, thin shell structures in a hygrothermal environment. Knowledge of the natural frequencies of structures is important in considering their response to various kinds of excitation, especially when structures and force systems are complex and when excitations are not periodic. The three dimensional, finite element structural analysis computer code CSTEM was used in the Cray YMP computer environment. The fiber composite shell was assumed to be cylindrical and made from T300 graphite fibers embedded in an intermediate-modulus, high-strength matrix. The following parameters were investigated: the length and the laminate thickness of the shell, the fiber orientation, the fiber volume fraction, the temperature profile through the thickness of the laminate, and laminates with different ply thicknesses. The results indicate that the fiber orientation and the length of the laminated shell had significant effects on the natural frequencies. The fiber volume fraction, the laminate thickness, and the temperature profile through the shell thickness had weak effects on the natural frequencies. Finally, the laminates with different ply thicknesses had an insignificant influence on the behavior of the vibrated laminated shell. Also, a single through-the-thickness, eight-node, three dimensional composite finite element analysis appears to be sufficient for investigating the free-vibration behavior of thin, composite, angle-ply shell structures.
The Development of Laminated Armor
1948-09-27
band saw, By using a piece of soft wood under the laminate while it was being cut, fraying of the edge was reduced to a minimum, especially in paneJs of...c. ’ LEGEND L LUMITE (SARAN) * ALL LAMINATE Rf RAYON (FQRTISAN) 20-30 OZ/FT 0-- Rc RAYON (CELANESE) ... 20-30...... X× GwLOss GLASS FLOSS Ir
Thermal conductivity of graphene laminate.
Malekpour, H; Chang, K-H; Chen, J-C; Lu, C-Y; Nika, D L; Novoselov, K S; Balandin, A A
2014-09-10
We have investigated thermal conductivity of graphene laminate films deposited on polyethylene terephthalate substrates. Two types of graphene laminate were studied, as deposited and compressed, in order to determine the physical parameters affecting the heat conduction the most. The measurements were performed using the optothermal Raman technique and a set of suspended samples with the graphene laminate thickness from 9 to 44 μm. The thermal conductivity of graphene laminate was found to be in the range from 40 to 90 W/mK at room temperature. It was found unexpectedly that the average size and the alignment of graphene flakes are more important parameters defining the heat conduction than the mass density of the graphene laminate. The thermal conductivity scales up linearly with the average graphene flake size in both uncompressed and compressed laminates. The compressed laminates have higher thermal conductivity for the same average flake size owing to better flake alignment. Coating plastic materials with thin graphene laminate films that have up to 600× higher thermal conductivity than plastics may have important practical implications.
NASA Technical Reports Server (NTRS)
Beiermann, Brett A. (Inventor); Keller, Michael W. (Inventor); White, Scott R. (Inventor); Sottos, Nancy R. (Inventor)
2016-01-01
A laminate material may include a first flexible layer, and a self-healing composite layer in contact with the first flexible layer. The composite layer includes an elastomer matrix, a plurality of first capsules including a polymerizer, and a corresponding activator for the polymerizer. The laminate material may self-heal when subjected to a puncture or a tear.
Finite element analysis of laminated plates and shells, volume 1
NASA Technical Reports Server (NTRS)
Seide, P.; Chang, P. N. H.
1978-01-01
The finite element method is used to investigate the static behavior of laminated composite flat plates and cylindrical shells. The analysis incorporates the effects of transverse shear deformation in each layer through the assumption that the normals to the undeformed layer midsurface remain straight but need not be normal to the mid-surface after deformation. A digital computer program was developed to perform the required computations. The program includes a very efficient equation solution code which permits the analysis of large size problems. The method is applied to the problem of stretching and bending of a perforated curved plate.
Olins, Ada L; Rhodes, Gale; Welch, David B Mark; Zwerger, Monika
2010-01-01
Lamin B receptor (LBR) is an integral membrane protein of the interphase nuclear envelope (NE). The N-terminal end resides in the nucleoplasm, binding to lamin B and heterochromatin, with the interactions disrupted during mitosis. The C-terminal end resides within the inner nuclear membrane, retreating with the ER away from condensing chromosomes during mitotic NE breakdown. Some of these properties are interpretable in terms of our current structural knowledge of LBR, but many of the structural features remain unknown. LBR apparently has an evolutionary history which brought together at least two ancient conserved structural domains (i.e., Tudor and sterol reductase). This convergence may have occurred with the emergence of the chordates and echinoderms. It is not clear what survival values have maintained LBR structure during evolution. But it seems likely that roles in post-mitotic nuclear reformation, interphase NE growth and compartmentalization of nuclear architecture might have provided some evolutionary advantage to preservation of the LBR gene. PMID:21327105
Hilly Surroundings (cylindrical)
NASA Technical Reports Server (NTRS)
2004-01-01
This 360-degree view of the terrain surrounding NASA's Mars Exploration Rover Spirit was taken on the rover's 189th sol on Mars (July 15, 2004). It was assembled from images taken by the rover's navigation camera at a position referred to as Site 72, which is at the base of the 'West Spur' portion of the 'Columbia Hills.' The view is presented in a cylindrical projection with geometrical seam correction.
Static cylindrically symmetric spacetimes
NASA Astrophysics Data System (ADS)
Fjällborg, Mikael
2007-05-01
We prove the existence of static solutions to the cylindrically symmetric Einstein Vlasov system, and we show that the matter cylinder has finite extension in two of the three spatial dimensions. The same results are also proved for a quite general class of equations of state for perfect fluids coupled to the Einstein equations, extending the class of equations of state considered by Bicak et al (2004 Class. Quantum Grav.21 1583). We also obtain this result for the Vlasov Poisson system.
Analysis of laminated composite shells under internal pressure
NASA Technical Reports Server (NTRS)
Yuan, F. G.
1991-01-01
A closed form solution is presented that predicts the response of filament wound composite shells subjected to internal pressure. The material of the shell is assumed to be general cylindrically anisotropic. Based on the theory of cylindrical anisotropic elasticity coupled differential equations are developed using Lekhnitskii's stress function approach. Two composite systems, graphite/epoxy and glass/epoxy, are selected to demonstrate the influence of degree of material anisotropy and fiber orientations on the axial and induced twisting deformation. Detailed stress distributions of (45) off-axis unidirectional and (45/-45)s symmetric angle-ply fiber-reinforced laminated shells are shown to illustrate the effect of radius-to-thickness ratio and stacking sequence.
Polar POLICRYPS diffractive structures generate cylindrical vector beams
Alj, Domenico; Caputo, Roberto Umeton, Cesare; Paladugu, Sathyanarayana; Volpe, Giovanni
2015-11-16
Local shaping of the polarization state of a light beam is appealing for a number of applications. This can be achieved by employing devices containing birefringent materials. In this article, we present one such enables converting a uniformly circularly polarized beam into a cylindrical vector beam (CVB). This device has been fabricated by exploiting the POLICRYPS (POlymer-LIquid CRYstals-Polymer-Slices) photocuring technique. It is a liquid-crystal-based optical diffraction grating featuring polar symmetry of the director alignment. We have characterized the resulting CVB profile and polarization for the cases of left and right circularly polarized incoming beams.
NASA Astrophysics Data System (ADS)
Lee, S. J.; Reddy, J. N.
2004-10-01
Third-order shear deformation theories of laminated composite shells are developed using the strain-displacement relations of Donnell and Sanders theories. These theories also account for geometric nonlinearity in the von Kármán sense. Analytical (Navier) solutions for vibration suppression in cross-ply laminated composite shells with surface mounted smart material layers are developed using the linear versions of the two shell theories and for simply supported boundary conditions. Numerical results are presented to bring out the parametric effects of shell types (cylindrical, spherical, and doubly curved shells) and material properties on vibration suppression. A simple negative velocity feedback control in a closed loop is used.
A {3,2}-Order Bending Theory for Laminated Composite and Sandwich Beams
NASA Technical Reports Server (NTRS)
Cook, Geoffrey M.; Tessler, Alexander
1998-01-01
A higher-order bending theory is derived for laminated composite and sandwich beams thus extending the recent {1,2}-order theory to include third-order axial effect without introducing additional kinematic variables. The present theory is of order {3,2} and includes both transverse shear and transverse normal deformations. A closed-form solution to the cylindrical bending problem is derived and compared with the corresponding exact elasticity solution. The numerical comparisons are focused on the most challenging material systems and beam aspect ratios which include moderate-to-thick unsymmetric composite and sandwich laminates. Advantages and limitations of the theory are discussed.
Stress-concentration factors for finite orthotropic laminates with a pin-loaded hole
NASA Technical Reports Server (NTRS)
Crews, J. H., Jr.; Hong, C. S.; Raju, I. S.
1981-01-01
Stresses were calculated for finite size orthotropic laminates loaded by a frictionless steel pin in a circular hole of the same diameter. The calculations were based on finite element analyses for six laminates. Stress concentration factors, based on nominal bearing stress, were determined for wide ranges of the ratios of width to diameter, w/d and edge distance to diameter, e/d. An infinite laminate case was analyzed for each laminate. Orthotropy had a significant influence on the tensile stress concentration at the hole. For example, the stress concentration factors for the infinite laminate cases ranged from 0.82 to 2.16, compared with 0.87 for the quasi-isotropic laminate. The finite widths and edge distances strongly influenced the tensile stress concentration. For the practical range w/d or = 3, the peak tensile stresses were as much as 80% larger than the infinite laminate reference value. For e/d or = 3, these stresses were amplified by as much as 50%. In contrast, the finite width and edge distance had little effect on shear-out and bearing stress concentrations.
Tests on Stiffened Circular Cylinders
NASA Technical Reports Server (NTRS)
Holt, Marshall
1941-01-01
Compressive tests were made of two series of stiffened circular cylindrical shells under axial load. All the shells were 16 inches in diameter by 24 inches in length and were made of aluminum-alloy sheet curved to the proper radius and welded with one longitudinal weld. The ratios of diameter to thickness of shell wall in the two series of specimens were 258 and 572. Strains were measured with Huggenberger tensometers at a number of gage lines on the stiffeners and shell. The results of these tests indicate that a spacing of circumferential stiffeners equal to 0.67 times the radius is too great to strengthen the shell wall appreciably. The results are not inclusive enough to show the optimum in stiffeners. Plain cylinders without stiffeners developed ultimate strengths approximately half as great as the buckling strengths computed by the equation resulting from the classical theory and slightly greater than those computed by Donnell's large deflection theory.
NASA Technical Reports Server (NTRS)
Sova, J. A.; Crews, J. H., Jr.
1974-01-01
A semianalytical method was developed for determining elastoplastic cyclic stresses and strains at notch roots in metallurgically bonded metal laminates. The method is based on the Neuber equation, which was used with an effective stress-strain curve for the laminate. It was applied to laminates containing a circular hole which were subjected to one cycle of reversed loading. The laminates consisted of two elasto-perfectly-plastic materials with different yield strengths and with either equal or different Young's moduli. A laminate of high-strength titanium alloy with alternate layers of commercially pure titanium was also analyzed. The accuracy of the method was evaluated by comparing the stresses and strains with those calculated from a finite-element analysis. The results estimated by the simple method based on the Neuber equation agreed closely with the results computed from the more elaborate finite-element analysis.
Axisymmetric buckling of laminated thick annular spherical cap
NASA Astrophysics Data System (ADS)
Dumir, P. C.; Dube, G. P.; Mallick, A.
2005-03-01
Axisymmetric buckling analysis is presented for moderately thick laminated shallow annular spherical cap under transverse load. Buckling under central ring load and uniformly distributed transverse load, applied statically or as a step function load is considered. The central circular opening is either free or plugged by a rigid central mass or reinforced by a rigid ring. Annular spherical caps have been analysed for clamped and simple supports with movable and immovable inplane edge conditions. The governing equations of the Marguerre-type, first order shear deformation shallow shell theory (FSDT), formulated in terms of transverse deflection w, the rotation ψ of the normal to the midsurface and the stress function Φ, are solved by the orthogonal point collocation method. Typical numerical results for static and dynamic buckling loads for FSDT are compared with the classical lamination theory and the dependence of the effect of the shear deformation on the thickness parameter for various boundary conditions is investigated.
Vacuum lamination of photovoltaic modules
NASA Technical Reports Server (NTRS)
Burger, D. R.
1982-01-01
Vacuum lamination of terrestrial photovoltaic modules is a new high volume process requiring new equipment and newly develop materials. Equipment development, materials research, and some research in related fields and testing methods are discussed.
Internal Stresses in Laminated Construction
NASA Technical Reports Server (NTRS)
Heim, A L; Knauss, A C; Seutter, Louis
1923-01-01
This report reviews the procedure employed in an investigation of the sources and influence of internal stresses in laminated construction, and discusses the influence of shrinkage and swelling stresses caused by atmospheric conditions upon the tensile strength across grain in laminated construction with special reference to airplane propellers. The investigation covered three sources of internal stress, namely, the combination of plain-sawed and quarter-sawed material in the same construction, the gluing together of laminations of different moisture contents, and the gluing together of laminations of different densities. Glued specimens and free specimens, made up under various manufacturing conditions, were subjected to various climatic changes inducing internal stresses and then were tested.
Sudden bending of cracked laminates
NASA Technical Reports Server (NTRS)
Sih, G. C.; Chen, E. P.
1980-01-01
A dynamic approximate laminated plate theory is developed with emphasis placed on obtaining effective solution for the crack configuration where the 1/square root of r stress singularity and the condition of plane strain are preserved. The radial distance r is measured from the crack edge. The results obtained show that the crack moment intensity tends to decrease as the crack length to laminate plate thickness is increased. Hence, a laminated plate has the desirable feature of stabilizing a through crack as it increases its length at constant load. Also, the level of the average load intensity transmitted to a through crack can be reduced by making the inner layers to be stiffer than the outer layers. The present theory, although approximate, is useful for analyzing laminate failure to crack propagation under dynamic load conditions.
Cylindrical holographic radar camera
NASA Astrophysics Data System (ADS)
McMakin, Douglas L.; Sheen, David M.; Hall, Thomas E.; Severtsen, Ronald H.
1998-12-01
A novel personnel surveillance system has been developed to rapidly obtain 360 degree, full-body images of humans for the detection and identification of concealed threats. Detectable threats include weapons fabricated with metal, plastic, and ceramic, as well as explosive solids and liquids. This new system uses a cylindrical mechanical scanner to move a seven-foot, 384 element, Ka band (26 - 30 GHz) array circumferentially around a person in four to seven seconds. Low power millimeter-waves, which are nonionizing and not harmful to humans, are employed because they readily penetrate clothing barriers and reflect from concealed threats. The reflected waves provide information that is reconstructed into 3-D cylindrical holographic images with high-speed, digital signal processing (DSP) boards. This system is capable of displaying in an animation format eight, sixteen, thirty-two or sixty-four image frames at various aspect angles around the person under surveillance. This new prototype surveillance system is operational and is presently under laboratory testing and evaluation.
Laminated electromagnetic pump stator core
Fanning, Alan W.
1995-01-01
A stator core for an electromagnetic pump includes a plurality of circumferentially abutting tapered laminations extending radially outwardly from a centerline axis to collectively define a radially inner bore and a radially outer circumference. Each of the laminations includes radially inner and outer edges and has a thickness increasing from the inner edge toward the outer edge to provide a substantially continuous path adjacent the circumference.
Laminated electromagnetic pump stator core
Fanning, A.W.
1995-08-08
A stator core for an electromagnetic pump includes a plurality of circumferentially abutting tapered laminations extending radially outwardly from a centerline axis to collectively define a radially inner bore and a radially outer circumference. Each of the laminations includes radially inner and outer edges and has a thickness increasing from the inner edge toward the outer edge to provide a substantially continuous path adjacent the circumference. This pump is used in nuclear fission reactors. 19 figs.
Metamaterial properties of periodic laminates
NASA Astrophysics Data System (ADS)
Srivastava, Ankit
2016-11-01
In this paper we show that a 1-D phononic crystal (laminate) can exhibit metamaterial wave phenomena which are traditionally associated with 2- and 3-D crystals. Moreover, due to the absence of a length scale in 2 of its dimensions, it can outperform higher dimensional crystals on some measures. This includes allowing only negative refraction over large frequency ranges and serving as a near-omnidirectional high-pass filter up to a large frequency value. First we provide a theoretical discussion on the salient characteristics of the dispersion relation of a laminate and formulate the solution of an interface problem by the application of the normal mode decomposition technique. We present a methodology with which to induce a pure negative refraction in the laminate. As a corollary to our approach of negative refraction, we show how the laminate can be used to steer beams over large angles for small changes in the incident angles (beam steering). Furthermore, we clarify how the transmitted modes in the laminate can be switched on and off by varying the angle of the incident wave by a small amount. Finally, we show that the laminate can be used as a remarkably efficient high-pass frequency filter. An appropriately designed laminate will reflect all plane waves from quasi-static to a large frequency, incident at it from all angles except for a small set of near-normal incidences. This will be true even if the homogeneous medium is impedance matched with the laminate. Due to the similarities between SH waves and electromagnetic (EM) waves it is expected that some or all of these results may also apply to EM waves in a layered periodic dielectric.
Buckling of cylindrical panels under axial compression
NASA Technical Reports Server (NTRS)
Sobel, L. H.; Weller, T.; Agarwal, B. L.
1976-01-01
This paper investigates the effects of boundary conditions and panel width on the axially compressive buckling behavior of unstiffened, isotropic, circular cylindrical panels. Numerical results are presented for eight different sets of boundary conditions along the straight edges of the panels. For all sets of boundary conditions except one (SS1), the results show that the panel buckling loads monotonically approach the complete cylinder buckling load from above as the panel width is increased. Low buckling loads, sometimes less than half the complete cylinder buckling load, are found for simply supported panels with free in-plane edge displacements (SS1). It is observed that the prevention of circumferential edge displacement is the most important in-plane boundary condition from the point of view of increasing the buckling load; and that the prevention of edge rotation in the circumferential direction also significantly increases the buckling load.
Chirped microlens arrays for diode laser circularization and beam expansion
NASA Astrophysics Data System (ADS)
Schreiber, Peter; Dannberg, Peter; Hoefer, Bernd; Beckert, Erik
2005-08-01
Single-mode diode lasers are well-established light sources for a huge number of applications but suffer from astigmatism, beam ellipticity and large manufacturing tolerances of beam parameters. To compensate for these shortcomings, various approaches like anamorphic prism pairs and cylindrical telescopes for circularization as well as variable beam expanders based on zoomed telescopes for precise adjustment of output beam parameters have been employed in the past. The presented new approach for both beam circularization and expansion is based on the use of microlens arrays with chirped focal length: Selection of lenslets of crossed cylindrical microlens arrays as part of an anamorphic telescope enables circularization, astigmatism correction and divergence tolerance compensation of diode lasers simultaneously. Another promising application of chirped spherical lens array telescopes is stepwise variable beam expansion for circular laser beams of fiber or solid-state lasers. In this article we describe design and manufacturing of beam shaping systems with chirped microlens arrays fabricated by polymer-on-glass replication of reflow lenses. A miniaturized diode laser module with beam circularization and astigmatism correction assembled on a structured ceramics motherboard and a modulated RGB laser-source for photofinishing applications equipped with both cylindrical and spherical chirped lens arrays demonstrate the feasibility of the proposed system design approach.
Vibrations of fiber-reinforced laminated deep shells
Kumar, V.; Singh, A.V.
1996-11-01
This paper deals with a numerical method for the free vibrational analysis of laminated deep shells. The strain-displacement relations are obtained for a general laminated shell geometry described by orthogonal curvilinear coordinates. Parabolic variation of transverse shear stresses along the thickness and the effects of rotary inertia are included in the formulation. The displacement fields are represented by Bezier patches. The shape and size of these patches are controlled by certain arbitrary points called control points. Owing to the special characteristics of these control points, the treatment of displacements, slopes, curvatures, etc., at a particular edge becomes very simple. Hence, the enforcement of boundary conditions along the edges is straightforward. Ritz-type solution procedure is used for the eigen-analysis of the shell structure. Numerical examples involving laminated spherical, conical, and cylindrical shells are investigated in detail. Such shell geometries usually have planes of symmetry; hence, only one-quarter of the shell is analyzed in this study. Good convergence of the natural frequencies is observed by using eight-order Bezier functions. The results are compared with the existing sources in the literature. The influences of material strength and number of layers on the natural frequencies are also examined.
Cylindrical geometry hall thruster
Raitses, Yevgeny; Fisch, Nathaniel J.
2002-01-01
An apparatus and method for thrusting plasma, utilizing a Hall thruster with a cylindrical geometry, wherein ions are accelerated in substantially the axial direction. The apparatus is suitable for operation at low power. It employs small size thruster components, including a ceramic channel, with the center pole piece of the conventional annular design thruster eliminated or greatly reduced. Efficient operation is accomplished through magnetic fields with a substantial radial component. The propellant gas is ionized at an optimal location in the thruster. A further improvement is accomplished by segmented electrodes, which produce localized voltage drops within the thruster at optimally prescribed locations. The apparatus differs from a conventional Hall thruster, which has an annular geometry, not well suited to scaling to small size, because the small size for an annular design has a great deal of surface area relative to the volume.
Coupling into and scattering from cylindrical structures covered periodically with metallic patches
NASA Technical Reports Server (NTRS)
Cwik, Tom
1990-01-01
Circular cylindrical structures covered periodically with metallic patches are considered. After an analogy to planar periodic surfaces is shown, formulations are presented for calculating induced currents on the curved surface. The equations are solved and results calculated for the specific case of periodic strips on the cylindrical surface. For a cylindrical structure a two-dimensional periodicity exists, as in a planar structure, while a spherical structure allows only a rotational periodicity. When the cylindrical structure is excited by the characteristic harmonic of the system, the spectral response of the transmitted field exhibits resonances that depend on the surface periodicity, as is known for planar structures. Since the cylindrical structure contains finite closed regions, the effects of resonances internal to the structure are seen and give additional information as compared to planar structures.
Cylindrical quasi-Gaussian beams.
Mitri, F G
2013-11-15
Making use of the complex-source-point method in cylindrical coordinates, an exact solution representing a cylindrical quasi-Gaussian beam of arbitrary waist w(0) satisfying both the Helmholtz and Maxwell's equations is introduced. The Cartesian components of the electromagnetic field are derived stemming from different polarizations of the magnetic and electric vector potentials based on Maxwell's vectorial equations and Lorenz's gauge condition, without any approximations. Computations illustrate the theory for tightly focused and quasi-collimated cylindrical beams. The results are particularly useful in beam-forming design using high-aperture or collimated cylindrical laser beams in imaging microscopy, particle manipulation, optical tweezers, and the study of scattering, radiation forces, and torque on cylindrical structures.
Lamin A, farnesylation and aging
Reddy, Sita; Comai, Lucio
2012-01-01
Lamin A is a component of the nuclear envelope that is synthesized as a precursor prelamin A molecule and then processed into mature lamin A through sequential steps of posttranslational modifications and proteolytic cleavages. Remarkably, over 400 distinct point mutations have been so far identified throughout the LMNA gene, which result in the development of at least ten distinct human disorders, collectively known as laminopathies, among which is the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS). The majority of HGPS cases are associated with a single point mutation in the LMNA gene that causes the production of a permanently farnesylated mutant lamin A protein termed progerin. The mechanism by which progerin leads to premature aging and the classical HGPS disease phenotype as well as the relationship between this disorder and the onset of analogous symptoms during the lifespan of a normal individual are not well understood. Yet, recent studies have provided critical insights on the cellular processes that are affected by accumulation of progerin and have suggested that cellular alterations in the lamin A processing pathway leading to the accumulation of farnesylated prelamin A intermediates may play a role in the aging process in the general population. In this review we provide a short background on lamin A and its maturation pathway and discuss the current knowledge of how progerin or alterations in the prelamin A processing pathway are thought to influence cell function and contribute to human aging.
Broers, Jos L.V. . E-mail: jos.broers@molcelb.unimaas.nl; Kuijpers, H.J.H.; Oestlund, C.; Worman, H.J.; Endert, J.; Ramaekers, F.C.S.
2005-04-01
We have applied the fluorescence loss of intensity after photobleaching (FLIP) technique to study the molecular dynamics and organization of nuclear lamin proteins in cell lines stably transfected with green fluorescent protein (GFP)-tagged A-type lamin cDNA. Normal lamin A and C proteins show abundant decoration of the inner layer of the nuclear membrane, the nuclear lamina, and a generally diffuse localization in the nuclear interior. Bleaching studies revealed that, while the GFP-tagged lamins in the lamina were virtually immobile, the intranuclear fraction of these molecules was partially mobile. Intranuclear lamin C was significantly more mobile than intranuclear lamina A. In search of a structural cause for the variety of inherited diseases caused by A-type lamin mutations, we have studied the molecular organization of GFP-tagged lamin A and lamin C mutants R453W and R386K, found in Emery-Dreifuss muscular dystrophy (EDMD), and lamin A and lamin C mutant R482W, found in patients with Dunnigan-type familial partial lipodystrophy (FPLD). In all mutants, a prominent increase in lamin mobility was observed, indicating loss of structural stability of lamin polymers, both at the perinuclear lamina and in the intranuclear lamin organization. While the lamin rod domain mutant showed overall increased mobility, the tail domain mutants showed mainly intranuclear destabilization, possibly as a result of loss of interaction with chromatin. Decreased stability of lamin mutant polymers was confirmed by flow cytometric analyses and immunoblotting of nuclear extracts. Our findings suggest a loss of function of A-type lamin mutant proteins in the organization of intranuclear chromatin and predict the loss of gene regulatory function in laminopathies.
Stage Cylindrical Immersive Display
NASA Technical Reports Server (NTRS)
Abramyan, Lucy; Norris, Jeffrey S.; Powell, Mark W.; Mittman, David S.; Shams, Khawaja S.
2011-01-01
Panoramic images with a wide field of view intend to provide a better understanding of an environment by placing objects of the environment on one seamless image. However, understanding the sizes and relative positions of the objects in a panorama is not intuitive and prone to errors because the field of view is unnatural to human perception. Scientists are often faced with the difficult task of interpreting the sizes and relative positions of objects in an environment when viewing an image of the environment on computer monitors or prints. A panorama can display an object that appears to be to the right of the viewer when it is, in fact, behind the viewer. This misinterpretation can be very costly, especially when the environment is remote and/or only accessible by unmanned vehicles. A 270 cylindrical display has been developed that surrounds the viewer with carefully calibrated panoramic imagery that correctly engages their natural kinesthetic senses and provides a more accurate awareness of the environment. The cylindrical immersive display offers a more natural window to the environment than a standard cubic CAVE (Cave Automatic Virtual Environment), and the geometry allows multiple collocated users to simultaneously view data and share important decision-making tasks. A CAVE is an immersive virtual reality environment that allows one or more users to absorb themselves in a virtual environment. A common CAVE setup is a room-sized cube where the cube sides act as projection planes. By nature, all cubic CAVEs face a problem with edge matching at edges and corners of the display. Modern immersive displays have found ways to minimize seams by creating very tight edges, and rely on the user to ignore the seam. One significant deficiency of flat-walled CAVEs is that the sense of orientation and perspective within the scene is broken across adjacent walls. On any single wall, parallel lines properly converge at their vanishing point as they should, and the sense of
Cylindrically symmetric dust spacetime
NASA Astrophysics Data System (ADS)
Senovilla, José M. M.
2000-07-01
We present an explicit exact solution of Einstein's equations for an inhomogeneous dust universe with cylindrical symmetry. The spacetime is extremely simple but nonetheless it has surprising new features. The universe is `closed' in the sense that the dust expands from a big-bang singularity but recollapses to a big-crunch singularity. In fact, both singularities are connected so that the whole spacetime is `enclosed' within a single singularity of general character. The big-bang is not simultaneous for the dust, and in fact the age of the universe as measured by the dust particles depends on the spatial position, an effect due to the inhomogeneity, and their total lifetime has no non-zero lower limit. Part of the big-crunch singularity is naked. The metric depends on a parameter and contains flat spacetime as a non-singular particular case. For appropriate values of the parameter the spacetime is a small perturbation of Minkowski spacetime. This seems to indicate that flat spacetime may be unstable against some global non-vacuum perturbations.
Shearfree cylindrical gravitational collapse
Di Prisco, A.; Herrera, L.; MacCallum, M. A. H.; Santos, N. O.
2009-09-15
We consider diagonal cylindrically symmetric metrics, with an interior representing a general nonrotating fluid with anisotropic pressures. An exterior vacuum Einstein-Rosen spacetime is matched to this using Darmois matching conditions. We show that the matching conditions can be explicitly solved for the boundary values of metric components and their derivatives, either for the interior or exterior. Specializing to shearfree interiors, a static exterior can only be matched to a static interior, and the evolution in the nonstatic case is found to be given in general by an elliptic function of time. For a collapsing shearfree isotropic fluid, only a Robertson-Walker dust interior is possible, and we show that all such cases were included in Cocke's discussion. For these metrics, Nolan and Nolan have shown that the matching breaks down before collapse is complete, and Tod and Mena have shown that the spacetime is not asymptotically flat in the sense of Berger, Chrusciel, and Moncrief. The issues about energy that then arise are revisited, and it is shown that the exterior is not in an intrinsic gravitational or superenergy radiative state at the boundary.
Shearfree cylindrical gravitational collapse
NASA Astrophysics Data System (ADS)
di Prisco, A.; Herrera, L.; MacCallum, M. A. H.; Santos, N. O.
2009-09-01
We consider diagonal cylindrically symmetric metrics, with an interior representing a general nonrotating fluid with anisotropic pressures. An exterior vacuum Einstein-Rosen spacetime is matched to this using Darmois matching conditions. We show that the matching conditions can be explicitly solved for the boundary values of metric components and their derivatives, either for the interior or exterior. Specializing to shearfree interiors, a static exterior can only be matched to a static interior, and the evolution in the nonstatic case is found to be given in general by an elliptic function of time. For a collapsing shearfree isotropic fluid, only a Robertson-Walker dust interior is possible, and we show that all such cases were included in Cocke’s discussion. For these metrics, Nolan and Nolan have shown that the matching breaks down before collapse is complete, and Tod and Mena have shown that the spacetime is not asymptotically flat in the sense of Berger, Chrusciel, and Moncrief. The issues about energy that then arise are revisited, and it is shown that the exterior is not in an intrinsic gravitational or superenergy radiative state at the boundary.
Cylindrical rotating triboelectric nanogenerator.
Bai, Peng; Zhu, Guang; Liu, Ying; Chen, Jun; Jing, Qingshen; Yang, Weiqing; Ma, Jusheng; Zhang, Gong; Wang, Zhong Lin
2013-07-23
We demonstrate a cylindrical rotating triboelectric nanogenerator (TENG) based on sliding electrification for harvesting mechanical energy from rotational motion. The rotating TENG is based on a core-shell structure that is made of distinctly different triboelectric materials with alternative strip structures on the surface. The charge transfer is strengthened with the formation of polymer nanoparticles on surfaces. During coaxial rotation, a contact-induced electrification and the relative sliding between the contact surfaces of the core and the shell result in an "in-plane" lateral polarization, which drives the flow of electrons in the external load. A power density of 36.9 W/m(2) (short-circuit current of 90 μA and open-circuit voltage of 410 V) has been achieved by a rotating TENG with 8 strip units at a linear rotational velocity of 1.33 m/s (a rotation rate of 1000 r/min). The output can be further enhanced by integrating more strip units and/or applying larger linear rotational velocity. This rotating TENG can be used as a direct power source to drive small electronics, such as LED bulbs. This study proves the possibility to harvest mechanical energy by TENGs from rotational motion, demonstrating its potential for harvesting the flow energy of air or water for applications such as self-powered environmental sensors and wildlife tracking devices.
1990-12-01
1920, A. E. Love published a set of equations for the midsurface displacement of circular, 3 cylindrical thin shells. Perhaps the first useful...and if rotations of the midsurface greater than fifteen degrees occur then accuracy suffers. Another major milestone in shell theory occurred in 31959
[Circular migration in Indonesia].
Mantra, I B
1979-12-01
The author examines circular migration in Indonesia, with primary focus on the 1970s. It is found that circular, or repeated return migration, generally occurs over short distances and for short periods and is more frequent than lifetime migration. The relationships between improvements in the national transport system, access to labor force opportunities in both the formal and informal sectors of the economy, and circular migration are discussed.
Closed form solution to the semi-infinite cylindrical shell problem.
NASA Technical Reports Server (NTRS)
Sanders, J. L., Jr.
1972-01-01
Reconsideration of the problem of a complete semiinfinite circular cylindrical shell with a square cage investigated earlier by Reissner and Simmonds (1966). It is shown that the solution can be found in closed form rather than in the form of Fourier series, provided that the boundary data on the end of the shell are 'slowly varying.'
NASA Astrophysics Data System (ADS)
Raybould, T. A.; Fedotov, V. A.; Papasimakis, N.; Kuprov, I.; Youngs, I. J.; Chen, W. T.; Tsai, D. P.; Zheludev, N. I.
2016-07-01
We demonstrate that the induced toroidal dipole, represented by currents flowing on the surface of a torus, makes a distinct and indispensable contribution to circular dichroism. We show that toroidal circular dichroism supplements the well-known mechanism involving electric dipole and magnetic dipole transitions. We illustrate this with rigorous analysis of the experimentally measured polarization-sensitive transmission spectra of an artificial metamaterial, constructed from elements of toroidal symmetry. We argue that toroidal circular dichroism will be found in large biomolecules with elements of toroidal symmetry and should be taken into account in the interpretation of circular dichroism spectra of organics.
Optimization of Cylindrical Hall Thrusters
Yevgeny Raitses, Artem Smirnov, Erik Granstedt, and Nathaniel J. Fi
2007-07-24
The cylindrical Hall thruster features high ionization efficiency, quiet operation, and ion acceleration in a large volume-to-surface ratio channel with performance comparable with the state-of-the-art annular Hall thrusters. These characteristics were demonstrated in low and medium power ranges. Optimization of miniaturized cylindrical thrusters led to performance improvements in the 50-200W input power range, including plume narrowing, increased thruster efficiency, reliable discharge initiation, and stable operation. __________________________________________________
Optimization of Cylindrical Hall Thrusters
Yevgeny Raitses, Artem Smirnov, Erik Granstedt, and Nathaniel J. Fisch
2007-11-27
The cylindrical Hall thruster features high ionization efficiency, quiet operation, and ion acceleration in a large volume-to-surface ratio channel with performance comparable with the state-of-the-art annular Hall thrusters. These characteristics were demonstrated in low and medium power ranges. Optimization of miniaturized cylindrical thrusters led to performance improvements in the 50-200W input power range, including plume narrowing, increased thruster efficiency, reliable discharge initiation, and stable operation.
Electron diffraction from cylindrical nanotubes
Qin, L.C. )
1994-09-01
Electron diffraction intensities from cylindrical objects can be conveniently analyzed using Bessel functions. Analytic formulas and geometry of the diffraction patterns from cylindrical carbon nanotubes are presented in general forms in terms of structural parameters, such as the pitch angle and the radius of a tubule. As an example the Fraunhofer diffraction pattern from a graphitic tubule of structure [18,2] has been simulated to illustrate the characteristics of such diffraction patterns. The validity of the projection approximation is also discussed.
Analysis of bolt-loaded elliptical holes in laminated composite joints
NASA Astrophysics Data System (ADS)
Wang, J. T.; Lotts, C. G.; Davis, D. D., Jr.
1993-02-01
The feasibility of changing the bolt shape from circular to elliptical in order to increase the joint strength was investigated. An analytical method using a cosine series to represent the bearing stress was derived, and a boundary collocation method was used to determine the unknown coefficients of this cosine series. Stresses at the hole edge predicted by the analytical method agreed very well with finite element solutions. Failure analyses of joints in two different laminates were performed, and each laminate exhibited a different joint failure mode. Results demonstrate that the joint strength of both laminates can be improved substantially by changing the bolt shape to elliptical. The joint that failed in a bearing mode showed a greater strength increase compared to the joint that failed in a shearing mode.
Analysis of bolt-loaded elliptical holes in laminated composite joints
NASA Technical Reports Server (NTRS)
Wang, J. T.; Lotts, C. G.; Davis, D. D., Jr.
1993-01-01
The feasibility of changing the bolt shape from circular to elliptical in order to increase the joint strength was investigated. An analytical method using a cosine series to represent the bearing stress was derived, and a boundary collocation method was used to determine the unknown coefficients of this cosine series. Stresses at the hole edge predicted by the analytical method agreed very well with finite element solutions. Failure analyses of joints in two different laminates were performed, and each laminate exhibited a different joint failure mode. Results demonstrate that the joint strength of both laminates can be improved substantially by changing the bolt shape to elliptical. The joint that failed in a bearing mode showed a greater strength increase compared to the joint that failed in a shearing mode.
Cylindrical millimeter-wave imaging technique and applications
NASA Astrophysics Data System (ADS)
Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.
2006-05-01
The wideband microwave or millimeter-wave cylindrical imaging technique has been developed at Pacific Northwest National Laboratory (PNNL) for several applications including concealed weapon detection and automated body measurement for apparel fitting. This technique forms a fully-focused, diffraction-limited, three-dimensional image of the person or imaging target by scanning an inward-directed vertical array around the person or imaging target. The array is switched electronically to sequence across the array at high-speed, so that a full 360 degree mechanical scan over the cylindrical aperture can occur in 2-10 seconds. Wideband, coherent reflection data from each antenna position are recorded in a computer and subsequently reconstructed using an FFT-based image reconstruction algorithm developed at PNNL. The cylindrical scanning configuration is designed to optimize the illumination of the target and minimize non-returns due to specular reflection of the illumination away from the array. In this paper, simulated modeling data are used to explore imaging issues that affect the cylindrical imaging technique. Physical optics scattering simulations are used to model realistic returns from curved surfaces to determine the extent to which specular reflection affects the signal return and subsequent image reconstruction from these surfaces. This is a particularly important issue for the body measurement application. Also, an artifact in the imaging technique, referred to as "circular convolution aliasing" is discussed including methods to reduce or eliminate it. Numerous simulated and laboratory measured imaging results are presented.
Cylindrical Millemeter-Wave Imaging Technique and Applications
Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.
2006-08-01
The wideband microwave or millimeter-wave cylindrical imaging technique has been developed at Pacific Northwest National Laboratory (PNNL) for several applications including concealed weapon detection and automated body measurements for apparel fitting. This technique forms a fully-focused, diffraction-limited, three-dimensional image of the person or imaging target by scanning an inward-directed vertical array around the person or imaging target. The array is switched electronically to sequence across the array at high-speed, so that a full 360 degree mechanical scan over the cylindrical aperture can occur in 2-10 seconds. Wideband, coherent reflection data from each antenna position are recorded in a computer and subsequently reconstructed using an FFT-based image reconstruction algorithm developed at PNNL. The cylindrical scanning configuration is designed to optimize the illumination of the target and minimize non-returns due to specular reflection of the illumination away from the array. In this paper, simulated modeling data is used to explore imaging issues that affect the cylindrical imaging technique. Physical optics scattering simulations are used to model realistic returns from curved surfaces to determine the extent to which specular reflection affects the signal return and subsequent image reconstruction from these surfaces. This is a particularly important issue for the body measurement application. Also, an artifact in the imaging technique, referred to as "circular convolution aliasing" is discussed including methods to reduce or eliminate it. Numerous simulated and laboratory measured imaging results are presented.
Chronic laminitis: current treatment strategies.
Parks, Andrew; O'Grady, Stephen E
2003-08-01
Laminitis is divided into four different phases: developmental, acute, subacute, and chronic. The focus of this article is on treating the laminitic horse after the cessation of therapy for the acute phase, that is, usually 2 to 4 weeks after the onset of clinical signs.
Laminitis as a systemic disease.
Hood, D M
1999-08-01
This article presents the clinical pathology and the involvement of the cardiovascular, renal, endocrine, and immunologic systems in laminitis. The data available on these systems are presented with respect to the disease phase and severity. The nutritional and metabolic alterations realized in the chronically affected horse are also presented. In this discussion, the origins and clinical implications of these systemic findings are discussed.
Steady state response of unsymmetrically laminated plates
Hosokawa, Kenji; Kawashima, Katsuya; Sakata, Toshiyuki
1995-11-01
A numerical approach for analyzing the forced vibration problem of a symmetrically laminated FRP (fiber reinforced plastic) composite plate was proposed by the authors. In the present paper, this approach is modified for application to an unsymmetrically laminated FRP composite plate. Numerical calculations are carried out for the clamped antisymmetrically laminated rectangular and elliptical plates which are a kind of unsymmetrically laminated plate. Then,, the effects of the lamina material and the fiber orientation angle on the steady state response are discussed. Furthermore, it is investigated that what structural damping factor is most influenced on the steady state response of an antisymmetrically laminated plate.
Precise DOA Estimation Using SAGE Algorithm with a Cylindrical Array
NASA Astrophysics Data System (ADS)
Takanashi, Masaki; Nishimura, Toshihiko; Ogawa, Yasutaka; Ohgane, Takeo
A uniform circular array (UCA) is a well-known array configuration which can accomplish estimation of 360° field of view with identical accuracy. However, a UCA cannot estimate coherent signals because we cannot apply the SSP owing to the structure of UCA. Although a variety of studies on UCA in coherent multipath environments have been done, it is impossible to estimate the DOA of coherent signals with different incident polar angles. Then, we have proposed Root-MUSIC algorithm with a cylindrical array. However, the estimation performance is degraded when incident signals arrive with close polar angles. To solve this problem, in the letter, we propose to use SAGE algorithm with a cylindrical array. Here, we adopt a CLA Root-MUSIC for the initial estimation and decompose two-dimensional search to double one-dimensional search to reduce the calculation load. The results show that the proposal achieves high resolution with low complexity.
Plug Repairs of Marine Glass Fiber / Vinyl Ester Laminates Subjected to Uniaxial Tension
2009-06-01
framed single-skin designs. The sandwich construction consists of thin FRP face skins over a thick core of medium density polyvinyl chloride foam or...with a circular hole is used. The laminate’s engineering constants in the formulation are the Young’s modulus in the x-direction Ex, the Young’s...Gardiner, "Marine Applications," ASM Handbook Vol. 21, ASM International Handbook Committee, ASM International, 2001. [2] A.P. Mouritz, E. Gellert, P
Warping of unsymmetric cross-ply graphite/epoxy laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.
1981-01-01
Warping in unsymmetric graphite/epoxy laminates was studied with particular attention given to the change of residual stresses resulting from long term environmental exposure. Square, cured prepreg sheets were measured for edge deflection with a cathetometer, then quartered and remeasured. Two postcuring durations were then used, 7.5 and one hr at 177 C; varying cooldown rates after curing were used for other samples, and one set was stored in vacuum at 75 C. Maximum deflections and weight changes were measured periodically at room temperature. Average curvatures, the effect of postcure, and the effect of long-term exposure were determined. Larger panels exhibited cylindrical warping and smaller panels underwent anticlastic warping. The deflections were related to weight changes, i.e. moisture absorption, and the lower the moisture content, the higher the deflection. Relaxation of residual stresses at 75 C was neglibible after 220 days.
Structural similitude and scaling laws for laminated beam-plates
NASA Technical Reports Server (NTRS)
Simitses, George J.; Rezaeepazhand, Jalil
1992-01-01
The establishment of similarity conditions between two structural systems is discussed. Similarity conditions provide the relationship between a scale model and its prototype and can be used to predict the behavior of the prototype by extrapolating the experimental data of the corresponding small-scale model. Since satisfying all the similarity conditions simultaneously is difficult or even impossible, distorted models with partial similarity (with at least one similarity condition relaxed) are more practical. Establishing similarity conditions based on both dimensional analysis and direct use of governing equations is discussed, and the possibility of designing distorted models is investigated. The method is demonstrated through analysis of the cylindrical bending of orthotropic laminated beam-plates subjected to transverse line loads.
Generalized offset surfaces of cylindrical surfaces
NASA Astrophysics Data System (ADS)
Georgiev, Georgi Hristov
2016-12-01
Cylindrical surfaces play an important role in geometric modeling and architecture. In this paper, we describe a way for constructing a new cylindrical surface from a given cylindrical surface. Our approach is based on the differential geometry of cylindrical surfaces and a generalization of the notion of offset surface. We examine the case of a similarity offset of an arbitrary cylindrical surface which is closely related to direct similarities of Euclidean 3-space. Some illustrative examples are included.
Lamination residual strains and stresses in hybrid laminates
NASA Technical Reports Server (NTRS)
Daniel, I. M.; Liber, T.
1977-01-01
An investigation is conducted of the effects of hybridization on the magnitude of lamination residual stresses. Eight-ply graphite/Kevlar 49/epoxy and graphite/S-glass/epoxy laminates were studied. The same matrix resin was selected for all basic materials to ensure compatibility and uniform curing of the various plies. The specimens, with inserted strain gages and thermocouples, were subjected to curing and postcuring cycles in an autoclave. Subsequently, the specimens were subjected to a thermal cycle from room temperature to 444 K and down to room temperature. It was found that hydridizing reduces apparently residual strains and stresses in the graphite plies. However, these strains were not affected much by the type and degree of hybridization.
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Sullivan, T. L.
1974-01-01
An approximate computational procedure is described for the analysis of angleplied laminates with residual nonlinear strains. The procedure consists of a combination of linear composite mechanics and incremental linear laminate theory. The procedure accounts for initial nonlinear strains, unloading, and in-situ matrix orthotropic nonlinear behavior. The results obtained in applying the procedure to boron/aluminum angleplied laminates show that this is a convenient means to accurately predict the initial tangent properties of angleplied laminates in which the matrix has been strained nonlinearly by the lamination residual stresses. The procedure predicted initial tangent properties results which were in good agreement with measured data obtained from boron/aluminum angleplied laminates.
Evaluation of hybrid composite materials in cylindrical specimen geometries
NASA Technical Reports Server (NTRS)
Liber, T.; Daniel, I. M.
1976-01-01
Static and fatigue properties of three composite materials and hybrids were examined. The materials investigated were graphite/epoxy, S-glass/epoxy, PRD-49 (Kevlar 49)/epoxy, and hybrids in angle-ply configurations. A new type of edgeless cylindrical specimen was developed. It is a flattened tube with two flat sides connected by curved sections and it is handled much like the standard flat coupon. Special specimen fabrication, tabbing, and tab region reinforcing techniques were developed. Axial modulus, Poisson's ratio, strength, and ultimate strain were obtained under static loading from flattened tube specimens of nine laminate configurations. In the case of graphite/epoxy the tubular specimens appeared to yield somewhat higher strength and ultimate strain values than flat specimens. Tensile fatigue tests were conducted with all nine types of specimens and S-N curves obtained. Specimens surviving 10 million cycles of tensile loading were subsequently tested statically to failure to determine residual properties.
1997-10-01
plane wave by a circular cylindrical shell. Results of computations. Acustica - Acta Acustica , 82, 1996: 689-697. [5] de Billy M., Determination of the...circumferential waves on cylindrical elastic shells. Acustica - Acta Acustica , 82, 1996: 707-716. [14] Bhattacharyya G.K., and Johnson R.A., Statistical...22] Batard H, Talmant M., and Quentin G.J., The Acoustical Characteristics Estimation Method (MECA) applied to cylinders and shells. Acta Acustica
Specific contribution of lamin A and lamin C in the development of laminopathies
Sylvius, Nicolas Hathaway, Andrea; Boudreau, Emilie; Gupta, Pallavi; Labib, Sarah; Bolongo, Pierrette M.; Rippstein, Peter; McBride, Heidi; Bilinska, Zofia T.; Tesson, Frederique
2008-08-01
Mutations in the lamin A/C gene are involved in multiple human disorders for which the pathophysiological mechanisms are partially understood. Conflicting results prevail regarding the organization of lamin A and C mutants within the nuclear envelope (NE) and on the interactions of each lamin to its counterpart. We over-expressed various lamin A and C mutants both independently and together in COS7 cells. When expressed alone, lamin A with cardiac/muscular disorder mutations forms abnormal aggregates inside the NE and not inside the nucleoplasm. Conversely, the equivalent lamin C organizes as intranucleoplasmic aggregates that never connect to the NE as opposed to wild type lamin C. Interestingly, the lamin C molecules present within these aggregates exhibit an abnormal increased mobility. When co-expressed, the complex formed by lamin A/C aggregates in the NE. Lamin A and C mutants for lipodystrophy behave similarly to the wild type. These findings reveal that lamins A and C may be differentially affected depending on the mutation. This results in multiple possible physiological consequences which likely contribute in the phenotypic variability of laminopathies. The inability of lamin C mutants to join the nuclear rim in the absence of lamin A is a potential pathophysiological mechanism for laminopathies.
Plastic Laminate Pulsed Power Development
ALEXANDER,JEFF A.; SHOPE,STEVEN L.; PATE,RONALD C.; RINEHART,LARRY F.; JOJOLA,JOHN M.; RUEBUSH,MITCHELL H.; CROWE,WAYNE; LUNDSTROM,J.; SMITH,T.; ZAGAR,D.; PRESTWICH,K.
2000-09-01
The desire to move high-energy Pulsed Power systems from the laboratory to practical field systems requires the development of compact lightweight drivers. This paper concerns an effort to develop such a system based on a plastic laminate strip Blumlein as the final pulseshaping stage for a 600 kV, 50ns, 5-ohm driver. A lifetime and breakdown study conducted with small-area samples identified Kapton sheet impregnated with Propylene Carbonate as the best material combination of those evaluated. The program has successfully demonstrated techniques for folding large area systems into compact geometry's and vacuum impregnating the laminate in the folded systems. The major operational challenges encountered revolve around edge grading and low inductance, low impedance switching. The design iterations and lessons learned are discussed. A multistage prototype testing program has demonstrated 600kV operation on a short 6ns line. Full-scale prototypes are currently undergoing development and testing.
Cylindrical acoustic levitator/concentrator
Kaduchak, Gregory; Sinha, Dipen N.
2002-01-01
A low-power, inexpensive acoustic apparatus for levitation and/or concentration of aerosols and small liquid/solid samples having particulates up to several millimeters in diameter in air or other fluids is described. It is constructed from a commercially available, hollow cylindrical piezoelectric crystal which has been modified to tune the resonance frequency of the breathing mode resonance of the crystal to that of the interior cavity of the cylinder. When the resonance frequency of the interior cylindrical cavity is matched to the breathing mode resonance of the cylindrical piezoelectric transducer, the acoustic efficiency for establishing a standing wave pattern in the cavity is high. The cylinder does not require accurate alignment of a resonant cavity. Water droplets having diameters greater than 1 mm have been levitated against the force of gravity using; less than 1 W of input electrical power. Concentration of aerosol particles in air is also demonstrated.
Stress Analysis of Composite Cylindrical Shells with an Elliptical Cutout
NASA Technical Reports Server (NTRS)
Oterkus, E.; Madenci, E.; Nemeth, M. P.
2007-01-01
A special-purpose, semi-analytical solution method for determining the stress and deformation fields in a thin laminated-composite cylindrical shell with an elliptical cutout is presented. The analysis includes the effects of cutout size, shape, and orientation; non-uniform wall thickness; oval-cross-section eccentricity; and loading conditions. The loading conditions include uniform tension, uniform torsion, and pure bending. The analysis approach is based on the principle of stationary potential energy and uses Lagrange multipliers to relax the kinematic admissibility requirements on the displacement representations through the use of idealized elastic edge restraints. Specifying appropriate stiffness values for the elastic extensional and rotational edge restraints (springs) allows the imposition of the kinematic boundary conditions in an indirect manner, which enables the use of a broader set of functions for representing the displacement fields. Selected results of parametric studies are presented for several geometric parameters that demonstrate that analysis approach is a powerful means for developing design criteria for laminated-composite shells.
Stress Analysis of Composite Cylindrical Shells With an Elliptical Cutout
NASA Technical Reports Server (NTRS)
Nemeth, M. P.; Oterkus, E.; Madenci, E.
2005-01-01
A special-purpose, semi-analytical solution method for determining the stress and deformation fields in a thin laminated-composite cylindrical shell with an elliptical cutout is presented. The analysis includes the effects of cutout size, shape, and orientation; nonuniform wall thickness; oval-cross-section eccentricity; and loading conditions. The loading conditions include uniform tension, uniform torsion, and pure bending. The analysis approach is based on the principle of stationary potential energy and uses Lagrange multipliers to relax the kinematic admissibility requirements on the displacement representations through the use of idealized elastic edge restraints. Specifying appropriate stiffness values for the elastic extensional and rotational edge restraints (springs) allows the imposition of the kinematic boundary conditions in an indirect manner, which enables the use of a broader set of functions for representing the displacement fields. Selected results of parametric studies are presented for several geometric parameters that demonstrate that analysis approach is a powerful means for developing design criteria for laminated-composite shells.
Postbuckling of laminated anisotropic panels
NASA Technical Reports Server (NTRS)
Jeffrey, Glenda L.
1987-01-01
A two-part study of the buckling and postbuckling of laminated anisotropic plates with bending-extensional coupling is presented. The first part involves the development and application of a modified Rayleigh-Ritz analysis technique. Modifications made to the classical technique can be grouped into three areas. First, known symmetries of anisotropic panels are exploited in the selection of approximation functions. Second, a reduced basis technique based on these same symmetries is applied in the linear range. Finally, geometric boundary conditions are enforced via an exterior penalty function approach, rather than relying on choice of approximation functions to satisfy these boundary conditions. Numerical results are presented for both the linear and nonlinear range, with additional studies made to determine the effect of variation in penalty parameter and number of basis vectors. In the second part, six panels possessing anisotropy and bending-extensional coupling are tested. Detailed comparisons are made between experiment and finite element results in order to gain insight into the postbuckling and failure characteristics of such panels. The panels are constructed using two different lamination sequences, and panels with three different aspect ratios were constructed for each lamination sequence.
Frequency spectra of laminated piezoelectric cylinders
NASA Astrophysics Data System (ADS)
Siao, J. C.-T.; Dong, S. B.; Song, J.
1994-07-01
A finite-element method is presented for determining the vibrational characteristics of a circular cylinder composed of bonded piezoelectric layers. Finite-element modeling occurs in the radial direction only using quadratic polynomials and the variationally derived partial differential equations are functions of the hoop and axial coordinates (theta, z) and time t. Using solution form Q exp (i(xi(z) + n(theta) + (omega)t)), with Q as the nodal amplitudes, leads to an algebraic eigensystem where any one of the three parameters (n, xi, omega), the circumferential or axial wave number or natural frequency, can act as the eigenvalue. Integer values always are assigned to n, leaving two possible eigenvalue problems. With omega as the eigenvalue and real values assigned to xi, the solutions represent propagating waves or harmonic standing vibrations in an infinite cylinder. When xi is the eigenvalue and real values assigned to omega, this eigensystem admits both real and complex eigendata. Real xi's represent propagating waves or harmonic standing vibrations as noted before. Complex conjugate pairs of xi 's describe end vibrations, which arise when an incident wave impinges upon a free end of a cylindrical bar. They are standing waves whose amplitudes decay sinusoidally or exponentially from the free end into the interior. Two examples are given to illustrate the method of analysis, viz., a solid piezoelectric cylinder of PZT-4 ceramic material and a two-layer cylinder of PZT-4 covering an isotropic material.
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-12
... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Products Having Laminated Packaging, Laminated Packaging, and Components Thereof... & Spirits Group of Cognac, France (``Camus''). Camus, Sidney Frank, and L'Oreal have since been...
Mammalian telomeres and their partnership with lamins
Burla, Romina; La Torre, Mattia; Saggio, Isabella
2016-01-01
ABSTRACT Chromosome ends are complex structures, which require a panel of factors for their elongation, replication, and protection. We describe here the mechanics of mammalian telomeres, dynamics and maintainance in relation to lamins. Multiple biochemical connections, including association of telomeres to the nuclear envelope and matrix, of telomeric proteins to lamins, and of lamin-associated proteins to chromosome ends, underline the interplay between lamins and telomeres. Paths toward senescence, such as defective telomere replication, altered heterochromatin organization, and impaired DNA repair, are common to lamins' and telomeres' dysfunction. The convergence of phenotypes can be interpreted through a model of dynamic, lamin-controlled functional platforms dedicated to the function of telomeres as fragile sites. The features of telomeropathies and laminopathies, and of animal models underline further overlapping aspects, including the alteration of stem cell compartments. We expect that future studies of basic biology and on aging will benefit from the analysis of this telomere-lamina interplay. PMID:27116558
ERIC Educational Resources Information Center
Gordon, Russell
2008-01-01
Consider a circular segment (the smaller portion of a circle cut off by one of its chords) with chord length c and height h (the greatest distance from a point on the arc of the circle to the chord). Is there a simple formula involving c and h that can be used to closely approximate the area of this circular segment? Ancient Chinese and Egyptian…
Telescoping cylindrical piezoelectric fiber composite actuator assemblies
NASA Technical Reports Server (NTRS)
Allison, Sidney G. (Inventor); Shams, Qamar A. (Inventor); Fox, Robert L. (Inventor); Fox, legal representative, Christopher L. (Inventor); Fox Chattin, legal representative, Melanie L. (Inventor)
2010-01-01
A telescoping actuator assembly includes a plurality of cylindrical actuators in a concentric arrangement. Each cylindrical actuator is at least one piezoelectric fiber composite actuator having a plurality of piezoelectric fibers extending parallel to one another and to the concentric arrangement's longitudinal axis. Each cylindrical actuator is coupled to concentrically-adjacent ones of the cylindrical actuators such that the plurality of cylindrical actuators can experience telescopic movement. An electrical energy source coupled to the cylindrical actuators applies actuation energy thereto to generate the telescopic movement.
Glucocorticoids and laminitis in the horse.
Johnson, Philip J; Slight, Simon H; Ganjam, Venkataseshu K; Kreeger, John M
2002-08-01
The administration of exogenously administered GCs and syndromes associated with GC excess are both attended by increased risk for the development of laminitis in adult horses. However, there exists substantial controversy as to whether excess GCs cause laminitis de novo. If true, the pathogenesis of laminitis arising from the effects of GC excess is probably different from that associated with diseases of the gastrointestinal tract and endotoxemia. Although a satisfactory explanation for the development of laminitis as a consequence of GC action is currently lacking, numerous possible and plausible theoretical mechanisms do exist. Veterinarians must exert caution with respect to the use of GCs in adult horses. The extent to which individual horses are predisposed to laminitis as a result of GC effect cannot be predicted based on current information. However, the administration of systemic GCs to horses that have been previously affected by laminitis should be used only with extreme caution, and should be accompanied by careful monitoring for further signs of laminitis. The risk of laminitis appears to be greater during treatment using some GCs (especially dexamethasone and triamcinalone) compared with others (prednisone and prednisolone). Whenever possible, to reduce the risk of laminitis, GCs should be administered locally. For example, the risk of GC-associated laminitis is evidently considerably reduced in horses affected with chronic obstructive pulmonary disease (COPD) if GC treatment is administered via inhalation. We have hypothesized that structural changes in the equine hoof that resemble laminitis may arise as a consequence of excess GC effect. Although these changes are not painful per se, and are not associated with inflammation, they could likely predispose affected horses to the development of bona fide laminitis for other reasons. Moreover, the gross morphological appearance of the chronically GC-affected hoof resembles that of a chronically
The pathophysiology of developmental and acute laminitis.
Hood, D M
1999-08-01
This review implies that although we know more regarding the enigma of developmental and acute laminitis today than previously, there is still more to investigate. As these investigations are conducted and interpreted, new and more effective preventive and therapeutic regimens are likely to be developed, tested, and made available. As this occurs, the impact of laminitis should undoubtedly decrease. Unfortunately, due to the lack of clinical symptoms in the developmental phase and the shortness of the acute phase, it is also evident that the two sequelae of acute laminitis, subacute and chronic laminitis, are likely to continue to pose a major problem for some time.
Geometrically nonlinear analysis of laminated elastic structures
NASA Technical Reports Server (NTRS)
Reddy, J. N.
1984-01-01
Laminated composite plates and shells that can be used to model automobile bodies, aircraft wings and fuselages, and pressure vessels among many other were analyzed. The finite element method, a numerical technique for engineering analysis of structures, is used to model the geometry and approximate the solution. Various alternative formulations for analyzing laminated plates and shells are developed and their finite element models are tested for accuracy and economy in computation. These include the shear deformation laminate theory and degenerated 3-D elasticity theory for laminates.
Optics Demonstrations Using Cylindrical Lenses
ERIC Educational Resources Information Center
Ivanov, Dragia; Nikolov, Stefan
2015-01-01
In this paper we consider the main properties of cylindrical lenses and propose several demonstrational experiments that can be performed with them. Specifically we use simple glasses full of water to demonstrate some basic geometrical optics principles and phenomena. We also present some less standard experiments that can be performed with such…
Blast waves from cylindrical charges
NASA Astrophysics Data System (ADS)
Knock, C.; Davies, N.
2013-07-01
Comparisons of explosives are often carried out using TNT equivalency which is based on data for spherical charges, despite the fact that many explosive charges are not spherical in shape, but cylindrical. Previous work has shown that it is possible to predict the over pressure and impulse from the curved surface of cylindrical charges using simple empirical formulae for the case when the length-to-diameter ( L/ D) ratio is greater or equal to 2/1. In this paper, by examining data for all length-to-diameter ratios, it is shown that it is possible to predict the peak over pressure, P, for any length-to-diameter ratio from the curved side of a bare cylindrical charge of explosive using the equation P=K_PM(L/D)^{1/3}/R^3, where M is the mass of explosive, R the distance from the charge and K_P is an explosive-dependent constant. Further out where the cylindrical blast wave `heals' into a spherical one, the more complex equation P=C_1(Z^' ' })^{-3}+C_2(Z^' ' })^{-2}+C_3(Z^' ' })^{-1} gives a better fit to experimental data, where Z^' ' } = M^{1/3}(L/D)^{1/9}/D and C_1, C_2 and C_3 are explosive-dependent constants. The impulse is found to be independent of the L/ D ratio.
Effect of Er:YAG laser on debonding strength of laminate veneers
Iseri, Ufuk; Oztoprak, Mehmet Oguz; Ozkurt, Zeynep; Kazazoglu, Ender; Arun, Tulin
2014-01-01
Objective: The purpose of this study was to evaluate the debonding strength of laminate veneers after using erbium-doped: yttrium aluminium garnet (Er:YAG) laser. Materials and Methods: A total of 60 bovine mandibular incisor teeth were divided into two groups (n = 30). Cylindrical specimens (0.7 mm × 5 mm) were fabricated from Empress II ceramic. Then, they were cemented to incisors using dual-cured resin cement (Variolink II). In the first group, no laser application was performed. The Er:YAG laser was applied on each laminate veneer at the test group for 9 s by using the scanning method. Shear force to remove the laminate veneers were applied with universal testing machine at a crosshead speed of 1 mm/min. Results: Results of this study exhibited significant differences between the control (27.28 ± 2.24 MPa) and test group (3.44 ± 0.69 MPa) (P < 0.05). Conclusion: This study shows that application of Er:YAG laser decreased the bond strength of laminate veneers. PMID:24966747
Weaver, P. M.
2016-01-01
The safe design of primary load-bearing structures requires accurate prediction of stresses, especially in the vicinity of geometric discontinuities where deleterious three-dimensional stress fields can be induced. Even for thin-walled structures significant through-thickness stresses arise at edges and boundaries, and this is especially precarious for laminates of advanced fibre-reinforced composites because through-thickness stresses are the predominant drivers in delamination failure. Here, we use a higher-order equivalent single-layer model derived from the Hellinger–Reissner mixed variational principle to examine boundary layer effects in laminated plates comprising constant-stiffness and variable-stiffness laminae and deforming statically in cylindrical bending. The results show that zigzag deformations, which arise due to layerwise differences in the transverse shear moduli, drive boundary layers towards clamped edges and are therefore critically important in quantifying localized stress gradients. The relative significance of the boundary layer scales with the degree of layerwise anisotropy and the thickness to characteristic length ratio. Finally, we demonstrate that the phenomenon of alternating positive and negative transverse shearing deformation through the thickness of composite laminates, previously only observed at clamped boundaries, can also occur at other locations as a result of smoothly varying the material properties over the in-plane dimensions of the laminate. PMID:27843401
NASA Technical Reports Server (NTRS)
Walowit, Jed A.
1994-01-01
A viewgraph presentation is made showing the capabilities of the computer code SPIRALI. Overall capabilities of SPIRALI include: computes rotor dynamic coefficients, flow, and power loss for cylindrical and face seals; treats turbulent, laminar, Couette, and Poiseuille dominated flows; fluid inertia effects are included; rotor dynamic coefficients in three (face) or four (cylindrical) degrees of freedom; includes effects of spiral grooves; user definable transverse film geometry including circular steps and grooves; independent user definable friction factor models for rotor and stator; and user definable loss coefficients for sudden expansions and contractions.
Buckling and Failure of Compression-Loaded Composite Laminated Shells With Cutouts
NASA Technical Reports Server (NTRS)
Hilburger, Mark W.
2007-01-01
Results from a numerical and experimental study that illustrate the effects of laminate orthotropy on the buckling and failure response of compression-loaded composite cylindrical shells with a cutout are presented. The effects of orthotropy on the overall response of compression-loaded shells is described. In general, preliminary numerical results appear to accurately predict the buckling and failure characteristics of the shell considered herein. In particular, some of the shells exhibit stable post-local-buckling behavior accompanied by interlaminar material failures near the free edges of the cutout. In contrast another shell with a different laminate stacking sequence appears to exhibit catastrophic interlaminar material failure at the onset of local buckling near the cutout and this behavior correlates well with corresponding experimental results.
Brau, Charles A.; Kurnit, Norman A.; Cooper, Richard K.
1984-01-01
A high efficiency, free electron laser utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.
Machining of fiber-reinforced composite laminates
NASA Astrophysics Data System (ADS)
Won, Myong-Shik
As fiber-reinforced composite laminates are becoming considerably popular in a wide range of applications, the necessity for machining such materials is increasing rapidly. Due to their microscopical inhomogeneity, anisotropy, and highly abrasive nature, composite laminates exhibit some peculiar types of machining damage. Consequently, the machining of composite laminates requires a different approach from that used for metals and offers a challenge from both an academic and application point of view. In the present work, the drilling of composite laminated plates and the edge trimming of tubular composite laminates were investigated through theoretical analyses and their experimental verification. First, a drilling process model using linear elastic fracture mechanics and classical plate bending theory was developed to predict the critical thrust value responsible for the onset of delamination during the drilling of composite laminates with pre-drilled pilot holes. Experiments using stepped drills, which can utilize the effectiveness of such pilot holes, were conducted on composite laminates. Reasonably good agreement was found between the results of the process model and the tests. Second, the development of a model-based intelligent control strategy for the efficient drilling of composite laminates was explored by experiments and analyses. In this investigation, mathematical models were created to relate the drilling forces to cutting parameters and to identify the different process stages. These models predicted the degree of thrust force regulation to prevent delamination. Third, the edge trimming of thin-walled tubular composite laminates was modeled and analyzed for estimating the critical cutting force at the initiation of longitudinal cracking. A series of full-scale edge trimming tests were conducted on tubular composite specimens to assess the current approach and to obtain basic machining data for various composite laminates. The present study provides
Effect of laminate thickness and specimen configuration on the fracture of laminated composites
NASA Technical Reports Server (NTRS)
Harris, C. E.; Morris, D. H.
1986-01-01
Attention is given to the effect of laminate thickness on graphite/epoxy laminates in the present measurements of fracture toughness in center cracked tension specimens, compact tension specimens, and three-point bend specimens. Crack tip damage development prior to fracture is also studied. The results obtained show fracture toughness to be a function of laminate thickness, being in all cases independent of crack size. The fracture surface of all thick laminates was uniform in the interior and self-similar with the starter notch. With only one exception, the fracture toughness of the thicker laminates was relatively independent of specimen configuration.
Negative refraction in a laminate
NASA Astrophysics Data System (ADS)
Willis, J. R.
2016-12-01
This work is concerned with the reflection and transmission of waves at a plane interface between a homogeneous elastic half-space and a half-space of elastic material that is periodically laminated. The lamination is always in the direction of the x1-coordinate axis and the displacement is always longitudinal shear, so that the only non-zero displacement component is u3(x1 ,x2 , t). After an initial discussion of Floquet-Bloch waves in the laminated material, brief consideration is given to the reflection-transmission problem, when the interface between the two media is the plane x1 = 0. Nothing unusual emerges: there are just a single reflected wave and a single transmitted wave, undergoing positive group-velocity refraction. Then, the problem is considered when the interface between the two media is the plane x2 = 0. The periodic structure of the interface induces an infinite set of reflected waves and an infinite set of transmitted waves. All need to be taken into account, but most decay exponentially away from the interface. It had previously been recognized that, if the incident wave had appropriate frequency and angle of incidence, a propagating transmitted wave would be generated that would undergo negative group-velocity refraction - behaviour usually associated with a metamaterial. It is established by an example in this work that there is, in addition, a propagating transmitted wave with smaller wavelength but larger group velocity that undergoes positive group-velocity refraction. The work concludes with a brief discussion of this finding, including its implications for the utility (or not) of "effective medium" theory.
Compact waveguide circular polarizer
Tantawi, Sami G.
2016-08-16
A multi-port waveguide is provided having a rectangular waveguide that includes a Y-shape structure with first top arm having a first rectangular waveguide port, a second top arm with second rectangular waveguide port, and a base arm with a third rectangular waveguide port for supporting a TE.sub.10 mode and a TE.sub.20 mode, where the end of the third rectangular waveguide port includes rounded edges that are parallel to a z-axis of the waveguide, a circular waveguide having a circular waveguide port for supporting a left hand and a right hand circular polarization TE.sub.11 mode and is coupled to a base arm broad wall, and a matching feature disposed on the base arm broad wall opposite of the circular waveguide for terminating the third rectangular waveguide port, where the first rectangular waveguide port, the second rectangular waveguide port and the circular waveguide port are capable of supporting 4-modes of operation.
Symmetries in laminated composite plates
NASA Technical Reports Server (NTRS)
Noor, A. K.
1976-01-01
The different types of symmetry exhibited by laminated anisotropic fibrous composite plates are identified and contrasted with the symmetries of isotropic and homogeneous orthotropic plates. The effects of variations in the fiber orientation and the stacking sequence of the layers on the symmetries exhibited by composite plates are discussed. Both the linear and geometrically nonlinear responses of the plates are considered. A simple procedure is presented for exploiting the symmetries in the finite element analysis. Examples are given of square, skew and polygonal plates where use of symmetry concepts can significantly reduce the scope and cost of analysis.
Maggot debridement therapy for laminitis.
Morrison, Scott
2010-08-01
Maggot debridement therapy is a nontraumatic, minimally invasive method to treat infections in a foot compromised by chronic laminitis. A mechanical strategy must first be in place to address the instability of the distal phalanx and hoof capsule. Adverse reactions to maggot debridement therapy are uncommon and the only side effect observed has been irritation or hypersensitivity at the site. Chronic laminitic cases of sepsis/necrosis within the hoof benefit from this procedure due to the noninvasive, continuous debridement and healing properties provided by the larvae.
The Influences of Lamination Angles on the Interior Noise Levels of an Aircraft
NASA Technical Reports Server (NTRS)
Fernholz, Christian M.; Robinson, Jay H.
1996-01-01
The feasibility of reducing the interior noise levels of an aircraft passenger cabin through optimization of the composite lay up of the fuselage is investigated. MSC/NASTRAN, a commercially available finite element code, is used to perform the dynamic analysis and subsequent optimization of the fuselage. The numerical calculation of sensitivity of acoustic pressure to lamination angle is verified using a simple thin, cylindrical shell with point force excitations as noise sources. The thin shell used represents a geometry similar to the fuselage and analytic solutions are available for the cylindrical thin shell equations of motion. Optimization of lamination angle for the reduction of interior noise is performed using a finite element model of an actual aircraft fuselage. The aircraft modeled for this study is the Beech Starship. Point forces simulate the structure borne noise produced by the engines and are applied to the fuselage at the wing mounting locations. These forces are the noise source for the optimization problem. The acoustic pressure response is reduced at a number of points in the fuselage and over a number of frequencies. The objective function is minimized with the constraint that it be larger than the maximum sound pressure level at the response points in the passenger cabin for all excitation frequencies in the range of interest. Results from the study of the fuselage model indicate that a reduction in interior noise levels is possible over a finite frequency range through optimal configuration of the lamination angles in the fuselage. Noise reductions of roughly 4 dB were attained. For frequencies outside the optimization range, the acoustic pressure response may increase after optimization. The effects of changing lamination angle on the overall structural integrity of the airframe are not considered in this study.
Residual stresses in angleplied laminates and their effects on laminate behavior
NASA Technical Reports Server (NTRS)
Chamis, C. C.
1978-01-01
Evidence of the presence of lamination residual stresses in angleplied laminates were transply cracks and warpage of unsymmetric laminates which occur prior to application of any mechanical load. Lamination residual strains were measured using the embedded strain gage technique. These strains result from the temperature differences between cure and room temperature and vary linearly within this temperature range. Lamination residual stresses were usually present in angleplied fiber composites laminates; they were also present in unidirectional hybrids and superhybrids. For specific applications, the magnitudes of lamination residual stresses were determined and evaluated relative to the anticipated applied stresses. Particular attention was given to cyclic thermal loadings in applications where the thermal cycling takes place over a wide temperature range.
Silicone modified resins for graphite fiber laminates
NASA Technical Reports Server (NTRS)
Frost, L. W.; Bower, G. M.
1980-01-01
Six silicone modified resins were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 6-63%. The highest flexural values measured for the laminates were a strength of 1,220 MPa and a modulus of 105 GPa. The highest interlaminar shear strength was 72 MPa.
NASA Astrophysics Data System (ADS)
Clauss, D. B.; Reuter, R. C., Jr.
1983-02-01
A simplified theory for the bending behavior of a thin flat bilamina panel was developed which includes the effects of shear deformation in the central adhesive layer. Static equilibrium equations for elastic thermomechanical cylindrical bending of a thin plate are used. A solution form is proposed which greatly facilitates application of this theory to structural panels with numerous discrete property changes in the variable direction. The influence of adhesive shear stiffness parameters upon overall laminate behavior is characterized through numerical examples typifying various thermal and mechanical loading conditions.
Stability of Laminated Composite Shells Subjected to Uniform Axial Compression and Torsion.
1982-11-01
Simitses lzhak Sheinman and Dein Shaw School of Engineering Science and Mechanics GEORGIA INSTITUTE OF TECHNOLOGY A Unit of the University System of...system can easily be computed by -D~ rreT", (C-I?) i I Reference C.1 Tene y. Epstein M., and Sheinman I. "A generalization of potters method" Computer...References D.1 Sheinman , I., Shaw, D., and Simitses, G. J., "Nonlenear Analysis of Axially-Loaded Laminated Cylindrical Shells". Proceedings of the
Wettability of graphene-laminated micropillar structures
NASA Astrophysics Data System (ADS)
Bong, Jihye; Seo, Keumyoung; Park, Ji-Hoon; Ahn, Joung Real; Ju, Sanghyun
2014-12-01
The wetting control of graphene is of great interest for electronic, mechanical, architectural, and bionic applications. In this study, the wettability of graphene-laminated micropillar structures was manipulated by changing the height of graphene-laminated structures and employing the trichlorosilane (HDF-S)-based self-assembly monolayer. Graphene-laminated micropillar structures with HDF-S exhibited higher hydrophobicity (contact angle of 129.5°) than pristine graphene thin film (78.8°), pristine graphene-laminated micropillar structures (97.5°), and HDF-S self-assembled graphene thin film (98.5°). Wetting states of the graphene-laminated micropillar structure with HDF-S was also examined by using a urea solution, which flowed across the surface without leaving any residues.
Universality of the frequency spectrum of laminates
NASA Astrophysics Data System (ADS)
Shmuel, Gal; Band, Ram
2016-07-01
We show that the frequency spectrum of two-component elastic laminates admits a universal structure, independent of the geometry of the periodic-cell and the specific physical properties. The compactness of the structure enables us to rigorously derive the maximal width, the expected width, and the density of the band-gaps - ranges of frequencies at which waves cannot propagate. In particular, we find that the density of these band-gaps is a universal property of classes of laminates. Rules for tailoring laminates according to desired spectrum properties thereby follow. We show that the frequency spectrum of various finitely deformed laminates are also endowed with the same compact structure. Finally, we explain how our results generalize for laminates with an arbitrary number of components, based on the form of their dispersion relation.
Steady compression characteristics of laminated MRE isolator
NASA Astrophysics Data System (ADS)
Wahab, N. A. A.; Mazlan, S. A.; Ubaidillah; Sharif, A. H. R.; Kamaruddin, S.
2016-11-01
This paper focused on an experimental setup on laminated magnetorheological elastomer (MRE) isolator under steady state compression test. An isotropic type natural rubber (NR) based MRE were fabricated and layered with a steel plate to form a multilayer sandwich structure adopted from the conventional laminated rubber bearing design. A set of static compression test was conducted to explore the potential of semi-active laminated MRE isolator in field-dependent stiffness properties. Stress versus strain relationship was assessed under different magnetic fields application. Based on the examination, the stress altered as the application of magnetic fields. Consequently, the effective stiffness of isolator also influenced by the magnetic fields induction. The experimental results show that the proposed laminated MRE isolator can effectively alter the compression stiffness up to the 14.56%. The preliminary results have confirmed the tunability of the semi-active laminated MRE isolator in which it would be beneficial for improving building isolator in general.
Stationary turbine component with laminated skin
James, Allister W [Orlando, FL
2012-08-14
A stationary turbine engine component, such as a turbine vane, includes a internal spar and an external skin. The internal spar is made of a plurality of spar laminates, and the external skin is made of a plurality of skin laminates. The plurality of skin laminates interlockingly engage the plurality of spar laminates such that the external skin is located and held in place. This arrangement allows alternative high temperature materials to be used on turbine engine components in areas where their properties are needed without having to make the entire component out of such material. Thus, the manufacturing difficulties associated with making an entire component of such a material and the attendant high costs are avoided. The skin laminates can be made of advanced generation single crystal superalloys, intermetallics and refractory alloys.
Wettability of graphene-laminated micropillar structures
Bong, Jihye; Seo, Keumyoung; Ju, Sanghyun E-mail: shju@kgu.ac.kr; Park, Ji-Hoon; Ahn, Joung Real E-mail: shju@kgu.ac.kr
2014-12-21
The wetting control of graphene is of great interest for electronic, mechanical, architectural, and bionic applications. In this study, the wettability of graphene-laminated micropillar structures was manipulated by changing the height of graphene-laminated structures and employing the trichlorosilane (HDF-S)-based self-assembly monolayer. Graphene-laminated micropillar structures with HDF-S exhibited higher hydrophobicity (contact angle of 129.5°) than pristine graphene thin film (78.8°), pristine graphene-laminated micropillar structures (97.5°), and HDF-S self-assembled graphene thin film (98.5°). Wetting states of the graphene-laminated micropillar structure with HDF-S was also examined by using a urea solution, which flowed across the surface without leaving any residues.
Gao, Nan; Zhang, Yuchao; Xie, Changqing
2011-11-01
We introduce circular Fibonacci gratings (CFGs) that combine the concept of circular gratings and Fibonacci structures. Theoretical analysis shows that the diffraction pattern of CFGs is composed of fractal distributions of impulse rings. Numerical simulations are performed with two-dimensional fast Fourier transform to reveal the fractal behavior of the diffraction rings. Experimental results are also presented and agree well with the numerical results. The fractal nature of the diffraction field should be of great theoretical interest, and shows potential to be further developed into practical applications, such as in laser measurement with wideband illumination.
Plastic buckling of cylindrical shells
Bandyopadhyay, K.; Xu, J.; Shteyngart, S.; Eckert, H.
1994-05-01
Cylindrical shells exhibit buckling under axial loads at stresses much less than the respective theoretical critical stresses. This is due primarily to the presence of geometrical imperfections even through such imperfections could be very small (e.g., comparable to thickness). Under internal pressure, the shell regains some of its buckling strength. For a relatively large radius-to-tickness ratio and low internal pressure, the effect can be reasonably estimated by an elastic analysis. However, for low radius-to-thickness ratios and greater pressures, the elastic-plastic collapse controls the failure load. In order to quantify the elastic-plastic buckling capacity of cylindrical shells, an analysis program was carried out by use of the computer code BOSOR5 developed by Bushnell of Lockheed Missiles and Space company. The analysis was performed for various radius-to- thickness ratios and imperfection amplitudes. The analysis results are presented in this paper.
GRIPPING DEVICE FOR CYLINDRICAL OBJECTS
Pilger, J.P.
1964-01-21
A gripping device is designed for fragile cylindrical objects such as for drawing thin-walled tubes. The gripping is done by multiple jaw members held in position by two sets of slots, one defined by keystone-shaped extensions of the outer shell of the device and the other in a movable sleeve held slidably by the extensions. Forward movement oi the sleeve advances the jaws, thereby exerting a controlled, radial pressure on the object being gripped. (AEC)
Bremsstrahlung from cylindrical beta sources.
NASA Technical Reports Server (NTRS)
Harris, D. W.; Silverman, J.
1972-01-01
Refined experimental measurements of the bremsstrahlung number and energy fluxes from thick cylindrical sources of several nuclides are presented, dose rates calculated from experimental energy fluxes are compared with theoretical results based on Wyard's thick-target approximation, and experiments are correlated with both thick- and thin-target bremsstrahlung theory to obtain accurate values of bremsstrahlung yields. The data presented should prove useful for the design of radioisotope power supplies, particularly those used in spacecraft and in biological applications.
Solutions of the cylindrical nonlinear Maxwell equations.
Xiong, Hao; Si, Liu-Gang; Ding, Chunling; Lü, Xin-You; Yang, Xiaoxue; Wu, Ying
2012-01-01
Cylindrical nonlinear optics is a burgeoning research area which describes cylindrical electromagnetic wave propagation in nonlinear media. Finding new exact solutions for different types of nonlinearity and inhomogeneity to describe cylindrical electromagnetic wave propagation is of great interest and meaningful for theory and application. This paper gives exact solutions for the cylindrical nonlinear Maxwell equations and presents an interesting connection between the exact solutions for different cylindrical nonlinear Maxwell equations. We also provide some examples and discussion to show the application of the results we obtained. Our results provide the basis for solving complex systems of nonlinearity and inhomogeneity with simple systems.
Active Control of Vibrations and Noise of Double Wall Cylindrical Shells
NASA Astrophysics Data System (ADS)
Wang, C.-Y.; Vaicaitis, R.
1998-10-01
Active control of vibrations and noise transmissions of double wall composite cylindrical shells using pairs of spatially discrete piezoelectric actuators is investigated. The velocity feedback and sound pressure rate feedback control procedures are developed. The inner and outer shells which are separated by a soft core are modelled by Love's thin shell theory for laminate composite materials and the inputs are taken as stationary random pressures and/or random point forces. A galerkin-like procedure is used to obtain solutions of the governing structural-acoustic equations. Parametric studies are performed to demonstrate the effect of actuator placement, actuator size, control gains, spillover, structural and acoustic damping characteristics
NASA Technical Reports Server (NTRS)
Nielsen, Jack N
1955-01-01
A theoretical method is presented for calculating the flow field about wing-body combinations employing bodies deviating only slightly in shape from a circular cylinder. The method is applied to the calculation of the pressure field acting between a circular cylindrical body and a rectangular wing. The case of zero body angle of attack and variable wing incidence is considered as well as the case of zero wing incidence and variable body angle of attack. An experiment was performed especially for the purpose of checking the calculative examples.
Monitoring damage development around stress raisers in carbon/epoxy laminates
NASA Astrophysics Data System (ADS)
Sripragash, L.; Smith, C.; Kumaran, G.; Sundaresan, M.
2013-04-01
An experimental and numerical investigation was carried out for the feasibility of determining damage development in carbon/epoxy composite laminates with a circular hole. The study involved flash thermography to map the damaged region in these specimens. First, thermographic response of implanted delaminations in composite laminates was examined using both numerical and experimental approaches. Next, damage development around a circular hole in a composite specimen was examined using thermography. The specimen was cyclically loaded until fracture to generate different levels of damage near the center of the specimen. Thermographic images of damage development at different fractions of fatigue life were recorded. Numerical models of thermal response of the region with evolving damage were also examined to assess the effectiveness of flash thermography under different conditions. The carbon/epoxy composite laminate was pulsed and examined using laser vibrometry in order to characterize the modes of stress wave propagation. Numerical simulations of a similarly excited carbon/epoxy panel were carried out as well.
Wiimote Experiments: Circular Motion
ERIC Educational Resources Information Center
Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary
2013-01-01
The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a…
Wiimote Experiments: Circular Motion
NASA Astrophysics Data System (ADS)
Kouh, Minjoon; Holz, Danielle; Kawam, Alae; Lamont, Mary
2013-03-01
The advent of new sensor technologies can provide new ways of exploring fundamental physics. In this paper, we show how a Wiimote, which is a handheld remote controller for the Nintendo Wii video game system with an accelerometer, can be used to study the dynamics of circular motion with a very simple setup such as an old record player or a bicycle wheel.
ERIC Educational Resources Information Center
Library of Congress, Washington, DC. Copyright Office.
This circular answers some of the questions that are frequently asked about copyright, a form of protection provided by the laws of the United States to authors of "original works of authorship" including library, dramatic musical, artistic, and certain other intellectual works. The Copyright Act of 1976 (title 17 of the United States…
Transposable elements and circular DNAs
2016-01-01
ABSTRACT Circular DNAs are extra-chromosomal fragments that become circularized by genomic recombination events. We have recently shown that yeast LTR elements generate circular DNAs through recombination events between their flanking long terminal repeats (LTRs). Similarly, circular DNAs can be generated by recombination between LTRs residing at different genomic loci, in which case the circular DNA will contain the intervening sequence. In yeast, this can result in gene copy number variations when circles contain genes and origins of replication. Here, I speculate on the potential and implications of circular DNAs generated through recombination between human transposable elements. PMID:28090380
NASA Astrophysics Data System (ADS)
Giasin, Khaled; Ayvar-Soberanis, Sabino; French, Toby; Phadnis, Vaibhav
2017-02-01
Machining Glass fibre aluminium reinforced epoxy (GLARE) is cumbersome due to distinctively different mechanical and thermal properties of its constituents, which makes it challenging to achieve damage-free holes with the acceptable surface quality. The proposed work focuses on the study of the machinability of thin ( 2.5 mm) GLARE laminate. Drilling trials were conducted to analyse the effect of feed rate and spindle speed on the cutting forces and hole quality. The resulting hole quality metrics (surface roughness, hole size, circularity error, burr formation and delamination) were assessed using surface profilometry and optical scanning techniques. A three dimensional (3D) finite-element (FE) model of drilling GLARE laminate was also developed using ABAQUS/Explicit to help understand the mechanism of drilling GLARE. The homogenised ply-level response of GLARE laminate was considered in the FE model to predict cutting forces in the drilling process.
NASA Technical Reports Server (NTRS)
Wang, S. S.
1985-01-01
A three-dimensional hybrid-stress finite element analysis of composite laminates containing cutouts and cracks is presented. Fully three-dimensional, hexahedral isoparametric elements of the hybrid-stress model are formulated on the basis of the Hellinger-Reissner variational principle. Traction-free edges, cutouts, and crack surfaces are modeled by imposition of exact traction boundary conditions along element surfaces. Special boundary and surface elements are constructed by introducing proper constraints on assumed stress functions. The Lagrangian multiplier technique is used to enforce ply-interface continuity conditions in hybrid bimaterial composite elements for modeling the interface region in a composite laminate. Two examples are given to illustrate the capability of the present method of approach: (1) the well-known delamination problem in an angle-ply laminate, and (2) the important problem of a composite laminate containing a circular hole. Results are presented in detail for each case. Implications of interlaminar and intralaminar crack initiation, growth and fracture in composites containing cracks and cutouts are discussed.
Oztoprak, Mehmet Oguz; Tozlu, Murat; Iseri, Ufuk; Ulkur, Feyza; Arun, Tulin
2012-07-01
Porcelain laminate veneers as esthetic and minimally invasive restorations are being used as an alternative to full veneer crowns. However, the removal of porcelain veneers that have failed may be an uncomfortable and time-consuming procedure because of the high bond strength between the porcelain laminate veneers and the tooth surface. The purpose of this study was to prepare a simple and reliable method for porcelain laminate veneer debonding by using an Er:YAG laser with the scanning method and to determine the amount of lasing time required. Eighty cylindrical specimens with a thickness of 0.7 mm and a diameter of 5 mm were fabricated from Empress II ceramic material. They were cemented on the labial surface of extracted bovine mandibular incisors using Variolink II (Ivoclar Vivadent AG, Schaan, Liechtenstein) and light cured for 40 s. The specimens were randomly divided into four groups of 20. The first group was assigned as the control group and no laser application was performed. The Er:YAG laser was applied on each specimen in the other three study groups for 3, 6, and 9 s by using the scanning method. One second after the lasing, a mechanical force was applied to remove the laminate veneers by using an Instron Universal Testing machine. Results of this study exhibited statistically significant differences between the control group and the three study groups. Intergroup comparison of shear bond strengths of the three study groups showed a statistically significant difference (p = 0.0001). This study showed that all three application times of Er-YAG laser were effective for debonding ceramic laminate veneers by softening the adhesive resin.
Direct Composite Laminate Veneers: Three Case Reports
Korkut, Bora; Yanıkoğlu, Funda; Günday, Mahir
2013-01-01
Re-establishing a patient’s lost dental esthetic appearance is one of the most important topics for contemporary dentistry. New treatment materials and methods have been coming on the scene, day by day, in order to achieve such an aim. Most dentists prefer more conservative and aesthetic approaches, such as direct and indirect laminate veneer restorations, instead of full-ceramic crowns for anteriors where aesthetics is really important. Laminate veneers are restorations which are envisioned to correct existing abnormalities, esthetic deficiencies and discolo-rations. Laminate veneer restorations may be processed in two different ways: direct or indirect. Direct laminate veneers have no need to be prepared in the laboratory and are based on the principle of application of a composite material directly to the prepared tooth surface in the dental clinic. Indirect laminate veneers may be produced from composite materials or ceramics, which are cemented to the tooth with an adhesive resin. In this case report, direct composite laminate veneer technique used for three patients with esthetic problems related to fractures, discolorations and an old prolapsed restoration, is described and six-month follow-ups are discussed. As a conclusion, direct laminate veneer restorations may be a treatment option for patients with the esthetic problems of anterior teeth in cases similar to those reported here. PMID:23875090
Laminitis and the equine metabolic syndrome.
Johnson, Philip J; Wiedmeyer, Charles E; LaCarrubba, Alison; Ganjam, V K Seshu; Messer, Nat T
2010-08-01
Although much has been written about laminitis in the context of its association with inflammatory processes, recognition is growing that most cases of laminitis examined by veterinarians in private practice are those associated with pasture grazing, obesity, and insulin resistance (IR). The term 'endocrinopathic laminitis' has been adopted to classify the instances of laminitis in which the origin seems to be more strongly associated with an underlying endocrinopathy, such as either IR or the influence of corticosteroids. Results of a recent study suggest that obesity and IR represent the most common metabolic and endocrinopathic predispositions for laminitis in horses. IR also plays an important role in the pathogenesis of laminitis that develops when some horses or ponies are allowed to graze pastures at certain times of the year. The term equine metabolic syndrome (EMS) has been proposed as a label for horses whose clinical examination results (including both physical examination and laboratory testing) suggest heightened risk for developing laminitis as a result of underlying IR.
Damage of hybrid composite laminates
NASA Astrophysics Data System (ADS)
Haery, Haleh A.; Kim, Ho Sung
2013-08-01
Hybrid laminates consisting of woven glass fabric/epoxy composite plies and woven carbon fabric/epoxy composite plies are studied for fatigue damage and residual strength. A theoretical framework based on the systems approach is proposed as a guide to deal with the complexity involving uncertainties and a large number of variables in the hybrid composite system. A relative damage sensitivity factor expression was developed for quantitative comparisons between non-hybrid and hybrid composites. Hypotheses derived from the theoretical framework were tested and verified. The first hypothesis was that the difference between two different sets of properties produces shear stress in interface between carbon fibre reinforced plastics (CRP) and glass fibre reinforced plastics (GRP), and eventually become a source for CRP/GRP interfacial delamination or longitudinal cracking. The second hypothesis was that inter-fibre bundle delamination occurs more severely to CRP sub-system than GRP sub-system.
Method of laminating structural members
NASA Technical Reports Server (NTRS)
Heier, W. C. (Inventor)
1974-01-01
A laminate is obtained by providing a lightweight core material, such as a honeycombed plastic or metal, within the cavity defined by an annular mold cavity frame. Face sheets, which are to be bonded to the core material, are provided on opposite sides of the frame and extend over the frame, thus sealing the core material in the cavity. An adhesive is provided between the core material and the face sheets and the combined thickness of the core material and adhesive is a close fit within the opposed face sheets. A gas tight seal, such as an O-ring gasket, is provided between the frame and the face sheet members to form a gas tight cavity between the face sheet members and the frame. External heat and pressure are used to bond the face sheets to the core material. Gas pressure is introduced into the sealed cavity to minimize out-gasing of the adhesive.
Indentation law for composite laminates
NASA Technical Reports Server (NTRS)
Yang, S. H.
1981-01-01
Static indentation tests are described for glass/epoxy and graphite/epoxy composite laminates with steel balls as the indentor. Beam specimens clamped at various spans were used for the tests. Loading, unloading, and reloading data were obtained and fitted into power laws. Results show that: (1) contact behavior is not appreciably affected by the span; (2) loading and reloading curves seem to follow the 1.5 power law; and (3) unloading curves are described quite well by a 2.5 power law. In addition, values were determined for the critical indentation, alpha sub cr which can be used to predict permanent indentations in unloading. Since alpha sub cr only depends on composite material properties, only the loading and an unloading curve are needed to establish the complete loading-unloading-reloading behavior.
Flat laminated microbial mat communities
NASA Astrophysics Data System (ADS)
Franks, Jonathan; Stolz, John F.
2009-10-01
Flat laminated microbial mats are complex microbial ecosystems that inhabit a wide range of environments (e.g., caves, iron springs, thermal springs and pools, salt marshes, hypersaline ponds and lagoons, methane and petroleum seeps, sea mounts, deep sea vents, arctic dry valleys). Their community structure is defined by physical (e.g., light quantity and quality, temperature, density and pressure) and chemical (e.g., oxygen, oxidation/reduction potential, salinity, pH, available electron acceptors and donors, chemical species) parameters as well as species interactions. The main primary producers may be photoautotrophs (e.g., cyanobacteria, purple phototrophs, green phototrophs) or chemolithoautophs (e.g., colorless sulfur oxidizing bacteria). Anaerobic phototrophy may predominate in organic rich environments that support high rates of respiration. These communities are dynamic systems exhibiting both spatial and temporal heterogeneity. They are characterized by steep gradients with microenvironments on the submillimeter scale. Diel oscillations in the physical-chemical profile (e.g., oxygen, hydrogen sulfide, pH) and species distribution are typical for phototroph-dominated communities. Flat laminated microbial mats are often sites of robust biogeochemical cycling. In addition to well-established modes of metabolism for phototrophy (oxygenic and non-oxygenic), respiration (both aerobic and anaerobic), and fermentation, novel energetic pathways have been discovered (e.g., nitrate reduction couple to the oxidation of ammonia, sulfur, or arsenite). The application of culture-independent techniques (e.g., 16S rRNA clonal libraries, metagenomics), continue to expand our understanding of species composition and metabolic functions of these complex ecosystems.
NOLIN: A nonlinear laminate analysis program
NASA Technical Reports Server (NTRS)
Kibler, J. J.
1975-01-01
A nonlinear, plane-stress, laminate analysis program, NOLIN, was developed which accounts for laminae nonlinearity under inplane shear and transverse extensional stress. The program determines the nonlinear stress-strain behavior of symmetric laminates subjected to any combination of inplane shear and biaxial extensional loadings. The program has the ability to treat different stress-strain behavior in tension and compression, and predicts laminate failure using any or all of maximum stress, maximum strain, and quadratic interaction failure criteria. A brief description of the program is presented including discussion of the flow of information and details of the input required. Sample problems and a complete listing of the program is also provided.
Neuropathic pain management in chronic laminitis.
Driessen, Bernd; Bauquier, Sébastien H; Zarucco, Laura
2010-08-01
Managing pain in horses afflicted by chronic laminitis is one of the greatest challenges in equine clinical practice because it is the dreadful suffering of the animals that most often forces the veterinarian to end the battle with this disease. The purpose of this review is to summarize our current understanding of the complex mechanisms involved in generating and amplifying pain in animals with laminitis and, based on this information, to propose a modified approach to pain therapy. Furthermore, a recently developed pain scoring technique is presented that may help better quantify pain and the monitoring of responses to analgesic treatment in horses with laminitis.
NASA Astrophysics Data System (ADS)
Okabe, Tomonaga; Yashiro, Shigeki
This study proposes the cohesive zone model (CZM) for predicting fatigue damage growth in notched carbon-fiber-reinforced composite plastic (CFRP) cross-ply laminates. In this model, damage growth in the fracture process of cohesive elements due to cyclic loading is represented by the conventional damage mechanics model. We preliminarily investigated whether this model can appropriately express fatigue damage growth for a circular crack embedded in isotropic solid material. This investigation demonstrated that this model could reproduce the results with the well-established fracture mechanics model plus the Paris' law by tuning adjustable parameters. We then numerically investigated the damage process in notched CFRP cross-ply laminates under tensile cyclic loading and compared the predicted damage patterns with those in experiments reported by Spearing et al. (Compos. Sci. Technol. 1992). The predicted damage patterns agreed with the experiment results, which exhibited the extension of multiple types of damage (e.g., splits, transverse cracks and delaminations) near the notches.
Radial Internal Material Handling System (RIMS) for Circular Habitat Volumes
NASA Technical Reports Server (NTRS)
Howe, A. Scott; Haselschwardt, Sally
2012-01-01
A Radial Internal Material Handling System (RIMS) has been developed to service a circular floor area in variable gravity. On planetary surfaces, pressurized human habitable volumes will require a means to carry heavy equipment between various locations within the volume of the habitat, regardless of the partial gravity (Earth, moon, Mars, etc). On the NASA Habitat Demonstration Unit (HDU), a vertical cylindrical volume, it was determined that a variety of heavy items would need to be carried back and forth from deployed locations to the General Maintenance Work Station (GMWS) when in need of repair, and other equipment may need to be carried inside for repairs, such as rover parts and other external equipment. The vertical cylindrical volume of the HDU lent itself to a circular overhead track and hoist system that allows lifting of heavy objects from anywhere in the habitat to any other point in the habitat interior. In addition, the system is able to hand off lifted items to other material handling systems through the side hatches, such as through an airlock. This paper describes the RIMS system which is scalable for application in a variety of circular habitat volumes.
The compressive failure of graphite/epoxy plates with circular holes
NASA Technical Reports Server (NTRS)
Knauss, J. F.; Starnes, J. H., Jr.; Henneke, E. G., II
1978-01-01
The behavior of fiber reinforced composite plates containing a circular cutout was characterized in terms of geometry (thickness, width, hole diameter), and material properties (bending/extensional stiffness). Results were incorporated in a data base for use by designers in determining the ultimate strength of such a structure. Two thicknesses, 24 plies and 48 plies were chosen to differentiate between buckling and strength failures due to the presence of a cutout. Consistent post-buckling strength was exhibited by both laminate configurations.
Loads for pulsed power cylindrical implosion experiments
Anderson, W.E.; Armijo, E.V.; Barthell, B.L.; Bartos, J.J.; Bush, H.; Foreman, L.R.; Garcia, F.P.; Gobby, P.L.; Gomez, V.M.; Gurule, V.A.
1994-07-01
Pulse power can be used to generate high energy density conditions in convergent hollow cylindrical geometry through the use of appropriate electrode configuration and cylindrical loads. Cylindrically symmetric experiments are conducted with the Pegasus-H inductive store, capacitor energized pulse power facility at Los Alamos using both precision machined cylindrical liner loads and low mass vapor deposited cylindrical foil loads. The liner experiments investigate solid density hydrodynamic topics. Foil loads vaporize from Joule heating to generate an imploding cylindrical plasma which can be used to simulate some fluxes associated with fusion energy processes. Similar experiments are conducted with {open_quotes}Procyon{close_quotes} inductive store pulse power assemblies energized by explosively driven magnetic flux compression.
Circular inferences in schizophrenia.
Jardri, Renaud; Denève, Sophie
2013-11-01
A considerable number of recent experimental and computational studies suggest that subtle impairments of excitatory to inhibitory balance or regulation are involved in many neurological and psychiatric conditions. The current paper aims to relate, specifically and quantitatively, excitatory to inhibitory imbalance with psychotic symptoms in schizophrenia. Considering that the brain constructs hierarchical causal models of the external world, we show that the failure to maintain the excitatory to inhibitory balance results in hallucinations as well as in the formation and subsequent consolidation of delusional beliefs. Indeed, the consequence of excitatory to inhibitory imbalance in a hierarchical neural network is equated to a pathological form of causal inference called 'circular belief propagation'. In circular belief propagation, bottom-up sensory information and top-down predictions are reverberated, i.e. prior beliefs are misinterpreted as sensory observations and vice versa. As a result, these predictions are counted multiple times. Circular inference explains the emergence of erroneous percepts, the patient's overconfidence when facing probabilistic choices, the learning of 'unshakable' causal relationships between unrelated events and a paradoxical immunity to perceptual illusions, which are all known to be associated with schizophrenia.
Method for fabricating laminated uranium composites
Chapman, L.R.
1983-08-03
The present invention is directed to a process for fabricating laminated composites of uranium or uranium alloys and at least one other metal or alloy. The laminated composites are fabricated by forming a casting of the molten uranium with the other metal or alloy which is selectively positioned in the casting and then hot-rolling the casting into a laminated plate in or around which the casting components are metallurgically bonded to one another to form the composite. The process of the present invention provides strong metallurgical bonds between the laminate components primarily since the bond disrupting surface oxides on the uranium or uranium alloy float to the surface of the casting to effectively remove the oxides from the bonding surfaces of the components.
Home care for horses with chronic laminitis.
Orsini, James A; Wrigley, Jennifer; Riley, Patrick
2010-04-01
Home care for horses with chronic laminitis has been discussed rarely in the veterinary literature even though, at any given time, most of us have at least 1 chronic laminitis case in our care that is being managed at home by the owner. Almost all of our knowledge on this aspect of laminitis treatment has been gleaned through experience, by individually working through the medical, ethical, financial, and emotional challenges these cases can present. Much has already been presented on the medical management of the laminitic horse and on strategies for trimming and shoeing the laminitic foot. This article focuses on the other challenges so often faced when directing the home care of a horse with chronic laminitis.
Pattern recognition of laminated sediments methodology
NASA Astrophysics Data System (ADS)
Barba-Rojo, Perla Karina; Solorza-Calderón, Selene; González-Fernández, Antonio
2016-12-01
This work presents a different aproach for laminae counting and thickness measurements on laminated sediment images. This is done by the use of morphological operations and minimum variance quantization.
Evaluation of transmitting performance of cylindrical polycapillary
NASA Astrophysics Data System (ADS)
Xiaoyan, Lin; Yude, Li; Guotai, Tan; Tianxi, Sun
2007-03-01
Based on a detailed ray-tracing code for capillary optics, a MATLAB program for the simulation of X-ray transmission in a cylindrical polycapillary is described. The simulated and experimental results for the spatial distributions and power density gain of the X-rays in the beam guided through a cylindrical polycapillary are in good agreement, and the results show that the spatial distribution of the X-rays in the beam guided through a cylindrical polycapillary is uneven.
Models of cylindrical bubble pulsation
Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hay, Todd A.; Hamilton, Mark F.
2012-01-01
Three models are considered for describing the dynamics of a pulsating cylindrical bubble. A linear solution is derived for a cylindrical bubble in an infinite compressible liquid. The solution accounts for losses due to viscosity, heat conduction, and acoustic radiation. It reveals that radiation is the dominant loss mechanism, and that it is 22 times greater than for a spherical bubble of the same radius. The predicted resonance frequency provides a basis of comparison for limiting forms of other models. The second model considered is a commonly used equation in Rayleigh-Plesset form that requires an incompressible liquid to be finite in extent in order for bubble pulsation to occur. The radial extent of the liquid becomes a fitting parameter, and it is found that considerably different values of the parameter are required for modeling inertial motion versus acoustical oscillations. The third model was developed by V. K. Kedrinskii [Hydrodynamics of Explosion (Springer, New York, 2005), pp. 23–26] in the form of the Gilmore equation for compressible liquids of infinite extent. While the correct resonance frequency and loss factor are not recovered from this model in the linear approximation, it provides reasonable agreement with observations of inertial motion. PMID:22978863
Fatigue crack growth in aluminum laminate composites
Hoffman, P.B.; Carpenter, R.D.; Gibeling, J.C.
1996-12-31
Fatigue crack growth has been measured in a laminated metal composite (LMC) consisting of alternating layers of AA6090/SiC/25p metal matrix composite (MMC) and AA5182 alloy. This material was tested in both as-pressed (F temper) and aged (T6 temper) conditions. Corresponding crack growth measurements were made in self-laminates of both the MMC and AA5182 materials to examine the role of the interfaces.
Vibrations of cantilevered shallow cylindrical shells of rectangular planform
NASA Technical Reports Server (NTRS)
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-01-01
A cantilevered, shallow shell of circular cylindrical curvature and rectangular planform exhibits free vibration behavior which differs considerably from that of a cantilevered beam or of a flat plate. Some numerical results can be found for the problem in the previously published literature, mainly obtained by using various finite element methods. The present paper is the first definitive study of the problem, presenting accurate non-dimensional frequency parameters for wide ranges of aspect ratio, shallowness ratio and thickness ratio. The analysis is based upon shallow shell theory. Numerical results are obtained by using the Ritz method, with algebraic polynomial trial functions for the displacements. Convergence is investigated, with attention being given both to the number of terms taken for each co-ordinate direction and for each of the three components of displacement. Accuracy of the results is also established by comparison with finite element results for shallow shells and with other accurate flat plate solutions.
Scaling Instability in Buckling of Axially Compressed Cylindrical Shells
NASA Astrophysics Data System (ADS)
Grabovsky, Yury; Harutyunyan, Davit
2016-02-01
In this paper, we continue the development of mathematically rigorous theory of "near-flip" buckling of slender bodies of arbitrary geometry, based on hyperelasticity. In order to showcase the capabilities of this theory, we apply it to buckling of axially compressed circular cylindrical shells. The theory confirms the classical formula for the buckling load, whereby the perfect structure buckles at the stress that scales as the first power of shell's thickness. However, in the case of imperfections of load, the theory predicts scaling instability of the buckling stress. Depending on the type of load imperfections, buckling may occur at stresses that scale as thickness to the power 1.5 or 1.25, corresponding to the lower and upper ends, respectively, of the historically accumulated experimental data.
The cylindrical magnetic Rayleigh-Taylor instability for viscous fluids
Chambers, K.; Forbes, L. K.
2012-10-15
This paper considers a cylindrical Rayleigh-Taylor instability, in which a heavy fluid surrounds a light fluid, and gravity is directed radially inwards. A massive object is located at the centre of the light fluid, and it behaves like a line dipole both for fluid flow and magnetic field strength. The initially circular interface between the two conducting fluids evolves into plumes, dependent on the magnetic and fluid dipole strengths and the nature of the initial disturbance to the interface. A spectral method is presented to solve the time-dependent interface shapes, and results are presented and discussed. Bipolar solutions are possible, and these are of particular relevance to astrophysics. The solutions obtained resemble structures of some HII regions and nebulae.
Vibrations of cantilevered shallow cylindrical shells of rectangular planform
NASA Astrophysics Data System (ADS)
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-10-01
A cantilevered, shallow shell of circular cylindrical curvature and rectangular planform exhibits free vibration behavior which differs considerably from that of a cantilevered beam or of a flat plate. Some numerical results can be found for the problem in the previously published literature, mainly obtained by using various finite element methods. The present paper is the first definitive study of the problem, presenting accurate non-dimensional frequency parameters for wide ranges of aspect ratio, shallowness ratio and thickness ratio. The analysis is based upon shallow shell theory. Numerical results are obtained by using the Ritz method, with algebraic polynomial trial functions for the displacements. Convergence is investigated, with attention being given both to the number of terms taken for each co-ordinate direction and for each of the three components of displacement. Accuracy of the results is also established by comparison with finite element results for shallow shells and with other accurate flat plate solutions.
Descriptive epidemiological study of equine laminitis.
Slater, M R; Hood, D M; Carter, G K
1995-09-01
A descriptive and matched case-control study of laminitis was conducted in 7 private practices and at the Texas Veterinary Medical Centre (TVMC) between May 1992 and July 1993. Out of 108 horses with laminitis, 19 acute (49%) and 20 chronic (51%) cases were seen in private practice and 16 acute (23%) and 53 (77%) cases at the TVMC. Gastrointestinal disease was the most common problem in 19/35 horses (54%), occurring just prior to the onset of acute laminitis in all hospitals. Among all horses in the study, most commonly used drugs were phenylbutazone (68%), acepromazine (34%), dimethyl sulphoxide (DMSO) (27%), antibiotics of various types (19%) and flunixin meglumine (19%). Acepromazine, DMSO and flunixin meglumine were used more commonly in acute cases of laminitis compared to chronic cases. In acutely affected horses, DMSO and flunixin meglumine were used significantly more often at the TVMC. In chronic cases, phenylbutazone and antibiotics were used more often in private practice. Shoeing and trimming were more commonly part of the treatment protocol for chronic cases. There were no significant associations between age, breed, sex or weight and the occurrence of acute laminitis. Horses with chronic laminitis were significantly older (P=0.04) and more females tended to be affected (P=0.08).
78 FR 14620 - Joint Development: Proposed Circular
Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-06
... Federal Transit Administration Joint Development: Proposed Circular AGENCY: Federal Transit Administration... the form of a circular, on joint development. This circular provides guidance to recipients of Federal... joint development. This circular: (1) Defines the term ``joint development''; ] (2) explains how...
Microwave Imaging and Holographic Diagnostic to Antennas in Cylindrical Near-Field Measurement
NASA Technical Reports Server (NTRS)
Hussein, Ziad A.
1995-01-01
In this paper, the issues pertaining to microwave imaging and holographic diagnostic to antennas in cylindrical near-field measurements are addressed. The theoretical approach is based on expanding the work in [1] and [2] where a cylindrical wave expansion of the field on a cylindrical near-field surface is given. The sampling probe is modeled by its equivalent aperture current (idealized circular aperture) and incorporated into the near-field to far-field transformation. The method of steepest decent is applied to obtain the far-field. In its implementation, however, one could specify directly the angular spectrum at which the far-field is desired to be calculated without resorting to interpolation. The microwave imaging and holographic diagnostic is based on back projection where a plane wave expansion of the far-field is obtained. This approach necessitates the knowledge of the far-field at exact angular spectrum resulting from application of 2-D FFT. Hence, we were able to construct simply the near-field on a plane not necessarily on the aperture plane of the test antenna but also on planes perpendicular to the aperture plane [3]. And a 3-D high resolution and high precision antenna imaging of the test antenna is obtained from cylindrical near-field simulated measurements. In addition microwave holographic diagnostic of large NASA scatterometer radar antenna obtained from measured near-field on a cylindrical surface will be given if time permits.
Vibration of in-vacuo elliptic cylindrical shells
NASA Astrophysics Data System (ADS)
Boisvert, Jeffrey E.; Hayek, Sabih I.
2003-10-01
The equations of motion for the vibration of elliptic cylindrical shells of constant thickness were derived using a Galerkin approach. The elastic strain energy density used in this derivation has seven independent kinematic variables: three displacements, two thickness-shear, and two thickness-stretch. The resulting seven coupled algebraic equations are symmetric and positive definite. The shell has a constant thickness, h, finite length, L, and is simply supported at its ends, (z=0,L), where z is the axial coordinate. The elliptic cross-section is defined by the shape parameter, a, and the half-length of the major axis, l. The modal solutions are expanded in a doubly infinite series of comparison functions in terms of circular functions in the angular and axial coordinates. The natural frequencies and the mode shapes were obtained by the Galerkin method. Numerical results were obtained for several h/l and L/l ratios, and various shape parameters, including the limiting case of a simply supported cylindrical shell (a=100). [Work supported by ONR and the Navy/ASEE Summer Faculty Program.
Teixidó, Mercè; Pallejà, Tomàs; Font, Davinia; Tresanchez, Marcel; Moreno, Javier; Palacín, Jordi
2012-01-01
This paper presents the use of an external fixed two-dimensional laser scanner to detect cylindrical targets attached to moving devices, such as a mobile robot. This proposal is based on the detection of circular markers in the raw data provided by the laser scanner by applying an algorithm for outlier avoidance and a least-squares circular fitting. Some experiments have been developed to empirically validate the proposal with different cylindrical targets in order to estimate the location and tracking errors achieved, which are generally less than 20 mm in the area covered by the laser sensor. As a result of the validation experiments, several error maps have been obtained in order to give an estimate of the uncertainty of any location computed. This proposal has been validated with a medium-sized mobile robot with an attached cylindrical target (diameter 200 mm). The trajectory of the mobile robot was estimated with an average location error of less than 15 mm, and the real location error in each individual circular fitting was similar to the error estimated with the obtained error maps. The radial area covered in this validation experiment was up to 10 m, a value that depends on the radius of the cylindrical target and the radial density of the distance range points provided by the laser scanner but this area can be increased by combining the information of additional external laser scanners. PMID:23443390
Boosman, R; Németh, F; Gruys, E
1991-07-01
This review deals with the features of clinical and subclinical laminitis in cattle. Prominent clinical signs of acute laminitis are a tender gait and arched back. The sole horn reveals red and yellowish discolourations within five days. In subacute and chronic cases clinical signs are less severe. In chronic laminitis the shape of the claws is altered. Laminitis is frequently followed by sole ulceration and white zone lesions. Blood tests showed no significant changes for laminitic animals. Arteriographic studies of claws affected by laminitis indicated that blood vessels had narrowed lumens. Gross pathology revealed congestion of the corium and rotation of the distal phalanx. Histopathologic studies indicate that laminitis is associated with changes of the vasculature. Peripartum management and nutrition are important factors in its aetiology. It is hypothesised that laminitis is evoked by disturbed digital circulation. In the pathogenesis of acute laminitis three factors are considered important: the occurrence of thrombosis, haemodynamic aspects of the corium, and endotoxins which trigger these pathologic events.
Effect of laminate edge conditions on the formation of microvoids in composite laminates
NASA Astrophysics Data System (ADS)
Anderson, J. P.; Altan, M. C.
2015-05-01
Manufacturing defects such as microvoids are common in thermoset composite components and are known to negatively affect their strength. The resin pressure developed in and the resin flow out from the laminates during cure have been reported to be the primary factors influencing the final void content of a composite component. In this work, the effect of laminate edge conditions during the cure process on the formation of microvoids was experimentally investigated. This was achieved by fabricating eight-ply laminates from TenCate® BT250/7781 prepreg in a hot-press at a constant cure pressure of 170 kPa while limiting the laminate perimeter available for resin flow by 0%, 25%, 50%, 75%, and 100%. The individual plies of these five laminates were conditioned at 99% relative humidity before curing to maximize the moisture present in the lay-up before fabrication. The presence of moisture in the lay-ups was expected to promote void formation and allow the effect of restricting flow at the edges of a laminate to be better identified. The restriction of resin outflow was found to cause the average characteristic void diameter to decrease by 17% and void content to rise by 33%. This phenomenon was identified to be a result of the outflow restriction increasing the number of voids trapped within the laminate and indicates that for laminates cured at low pressures resin outflow is the dominant mechanism for void reduction.
Propagation of light in a circular array of elliptical fibres
NASA Astrophysics Data System (ADS)
Alexeyev, C. N.; Milione, G.; Pogrebnaya, A. O.; Yavorsky, M. A.
2016-02-01
We have studied transformation of discrete light beams in circular arrays of elliptical fibres, in which the orientation of ellipses' axes linearly depends on the angular position of the fibre in the array and makes an half-integer number p of full rotations while tracing along its contour. We have derived analytical expressions for the spectra and supermodes that allow for evanescent coupling between the fibres in the next-neighbour approximation. We have studied the transformative properties of such an array and shown that it can generate cylindrical vector beams (CVBs) of TE and TM types. We have shown that the type of generated beam depends on the orientation of linear polarization of the incident beam. In this way, the circular array of strongly elliptical fibres enables polarization control over the type of the generated CVB. We have also shown that such arrays can change the topological charge of an incoming discrete optical vortex by the doubled array's index p.
Scattering of antiplane shear waves by layered circular elastic cylinder.
Cai, Liang-Wu
2004-02-01
An exact analytical solution for the scattering of antiplane elastic waves by a layered elastic circular cylinder is obtained. The solution and its degenerate cases are compared with other simpler models of circular cylindrical scatterers. The effects of the geometrical and physical properties of the interphase are studied. Numerical results confirm the existence of a resonance mode in which the scatterer's core undergoes a rigid-body motion when the outer layer of the scatterer is very compliant. This resonance mode has been attributed [Liu et al., Science 289, 1734 (2000)] to a new mechanism for the band gap formed in the extremely low frequency range for phononic crystals made of layered spherical scatterers. Numerical results also show the existence of a similar resonance mode when the outer layer of the scatterer has very high mass density.
NASA Astrophysics Data System (ADS)
Khan, Z. M.; Adams, D. O.; Anas, S.
2016-01-01
As advanced composite materials having superior physical and mechanical properties are being developed, the optimization of their processing techniques is eagerly sought. One of the most common defects arising during processing of structural composites is layer waviness. The layer waviness is more pronounced in thick-section flat and cylindrical laminates, which are extensively used in large wind turbine blades, submersibles, and space platforms. The layer waviness undulates the entire layer of a multidirectional laminate in the throughthe-thickness direction, leading to a gross deterioration of its compressive strength. This research investigates the influence of multiple layer waviness in a double nest formation on the compression strength of a composite laminate. Different wave fractions of wavy 0° layers were fabricated in an IM/8551-7 carbon-epoxy composite laminate on a steel mold by using a single-step fabrication procedure. The test laminates were cured on a heated press according to the specific curing cycle of epoxy. Their static compression testing was performed using a NASA short block compression fixture on an MTS servohydraulic machine. The purpose of these tests was to determine the effects of multiple layer wave regions on the compression strength of the composite laminate. The experimental and analytical results obtained revealed that the reduction in the compression strength of composite laminate was constant after the fraction of the wavy 0° layers exceeded 35%. This analysis indicated that the percentage of the 0° wavy layer may be used to estimate the reduction in the compression strength of a double nested wave formation in a composite laminate.
Casimir torque on a cylindrical gear
NASA Astrophysics Data System (ADS)
Vaidya, Varun
2014-08-01
I utilize effective field theory(EFT) techniques to calculate the Casimir torque on a cylindrical gear in the presence of a polarizable but neutral object and present results for the energy and torque as a function of angle for a gear with multiple cogs, as well as for the case of a concentric cylindrical gear.
Treating laminitis: beyond the mechanics of trimming and shoeing.
Baker, William R
2012-08-01
Laminitis is typically classified into developmental or prodromal, acute, subacute, and chronic phases. Scientific evidence regarding the pathophysiology of laminitis does exist, but it is often conflicting and dependent on the clinician's interpretation/understanding of the study or the model used for inducing laminitis. The diagnosis of laminitis consists of obtaining an accurate history, performing a thorough physical examination, and taking good-quality radiographs. The use of radiographs for diagnosis and interpretation of laminitis is an absolute necessity for the clinician. Laminitis is one disease that requires the assembly of a team consisting of the veterinarian, the farrier, and the owner to be successfully treated.
Lamin B1 and lamin B2 are long-lived proteins with distinct functions in retinal development
Razafsky, David; Ward, Candace; Potter, Chloe; Zhu, Wanqiu; Xue, Yunlu; Kefalov, Vladimir J.; Fong, Loren G.; Young, Stephen G.; Hodzic, Didier
2016-01-01
Lamin B1 and lamin B2 are essential building blocks of the nuclear lamina, a filamentous meshwork lining the nucleoplasmic side of the inner nuclear membrane. Deficiencies in lamin B1 and lamin B2 impair neurodevelopment, but distinct functions for the two proteins in the development and homeostasis of the CNS have been elusive. Here we show that embryonic depletion of lamin B1 in retinal progenitors and postmitotic neurons affects nuclear integrity, leads to the collapse of the laminB2 meshwork, impairs neuronal survival, and markedly reduces the cellularity of adult retinas. In stark contrast, a deficiency of lamin B2 in the embryonic retina has no obvious effect on lamin B1 localization or nuclear integrity in embryonic retinas, suggesting that lamin B1, but not lamin B2, is strictly required for nucleokinesis during embryonic neurogenesis. However, the absence of lamin B2 prevents proper lamination of adult retinal neurons, impairs synaptogenesis, and reduces cone photoreceptor survival. We also show that lamin B1 and lamin B2 are extremely long-lived proteins in rod and cone photoreceptors. OF interest, a complete absence of both proteins during postnatal life has little or no effect on the survival and function of cone photoreceptors. PMID:27075175
Free Vibrations Of Delaminated Composite Cylindrical Shell Roofs
NASA Astrophysics Data System (ADS)
Acharyya, A. Kumar; Chakraborty, Dipankar; Karmakar, Amit
Recently laminated composites are widely used in civil engineering, which may suffer from delamination damage resulting from improper fabrication and overloading at service. A review of literature that exists on composite shells reveals that the research reports on delaminated shells are very few in number. Hence the present endeavor is to work on delaminated simply supported cylindrical shell with different extents of delaminations. An eight noded isoparametric element with five degrees of freedom per node is used together with Sander's strain displacement relationships and multipoint constraint equations to satisfy the compatibility of displacements and rotations along the cracked edges. The study reveals that there is a consistent decrease in the fundamental frequency value as the area of the delamination damage increases. Further the fundamental frequency of angle ply shells undergo relatively more prominent decrease compared to that of cross ply shells. It seems that delamination damage brings about greater reduction in frequency values as the number of layers increases for angle ply shells, especially for symmetric ones.
Development of laser finishing for non-circular profiles
Liu, K.W.; Sheng, P.S.
1995-03-01
A laser-based technique for finishing of non-circular cylindrical parts is presented. In this process, the frequency characteristics of a desired non-circular shape is extracted from a CAD through a Fast Fourier Transform algorithm and implemented through a CO{sub 2} laser machining system. A galvanometer-based scanner is used in the process to achieve programmable beam trajectories and high-speed finishing. An error estimation scheme can be developed to determine the final dimensional error of the non-circular profile. This process can be selected as both a batch production tool and a rapid prototyping tool based on the designated processing rate and precision. Initial experimental results include the production of two- and three-lobed profiles, as well as definition of part feature using higher-order harmonics, in polymethylmethacrylate (PMMA) with corresponding R{sub a} values of less than 1 {mu}m. The machine tool elements and general procedure for non-circular laser finishing are also presented.
Theoretical, Experimental, and Computational Evaluation of Disk-Loaded Circular Wave Guides
NASA Technical Reports Server (NTRS)
Wallett, Thomas M.; Qureshi, A. Haq
1994-01-01
A disk-loaded circular wave guide structure and test fixture were fabricated. The dispersion characteristics were found by theoretical analysis, experimental testing, and computer simulation using the codes ARGUS and SOS. Interaction impedances were computed based on the corresponding dispersion characteristics. Finally, an equivalent circuit model for one period of the structure was chosen using equivalent circuit models for cylindrical wave guides of different radii. Optimum values for the discrete capacitors and inductors describing discontinuities between cylindrical wave guides were found using the computer code TOUCHSTONE.
Evaluation of Behaviours of Laminated Glass
NASA Astrophysics Data System (ADS)
Sable, L.; Japins, G.; Kalnins, K.
2015-11-01
Visual appearance of building facades and other load bearing structures, which now are part of modern architecture, is the reason why it is important to investigate in more detail the reliability of laminated glass for civil structures. Laminated glass in particular has become one of the trendy materials, for example Apple© stores have both load carrying capacity and transparent appearance. Glass has high mechanical strength and relatively medium density, however, the risk of sudden brittle failure like concrete or other ceramics determine relatively high conservatism in design practice of glass structures. This should be changed as consumer requirements evolve calling for a safe and reliable design methodology and corresponding building standards. A design methodology for glass and glass laminates should be urgently developed and included as a chapter in Eurocode. This paper presents initial experimental investigation of behaviour of simple glass sheets and laminated glass samples in 4-point bending test. The aim of the current research is to investigate laminated glass characteristic values and to verify the obtained experimental results with finite element method for glass and EVA material in line with future European Structural Design of Glass Components code.
Lamination residual stresses in fiber composites
NASA Technical Reports Server (NTRS)
Daniel, I. M.; Liber, T.
1975-01-01
An experimental investigation was conducted to determine the magnitude of lamination residual stresses in angle-ply composites and to evaluate their effects on composite structural integrity. The materials investigated were boron/epoxy, boron/polyimide, graphite/low modulus epoxy, graphite/high modulus epoxy, graphite/polyimide and s-glass/epoxy. These materials were fully characterized. Static properties of laminates were also determined. Experimental techniques using embedded strain gages were developed and used to measure residual strains during curing. The extent of relaxation of lamination residual stresses was investigated. It was concluded that the degree of such relaxation is low. The behavior of angle-ply laminates subjected to thermal cycling, tensile load cycling, and combined thermal cycling with tensile load was investigated. In most cases these cycling programs did not have any measurable influence on residual strength and stiffness of the laminates. In the tensile load cycling tests, the graphite/polyimide shows the highest endurance with 10 million cycle runouts at loads up to 90 percent of the static strength.
Fracture behavior of hybrid composite laminates
NASA Technical Reports Server (NTRS)
Kennedy, J. M.
1983-01-01
The tensile fracture behavior of 15 center-notched hybrid laminates was studied. Three basic laminate groups were tested: (1) a baseline group with graphite/epoxy plies, (2) a group with the same stacking sequence but where the zero-deg plies were one or two plies of S-glass or Kevlar, and (3) a group with graphite plies but where the zero-deg plies were sandwiched between layers of perforated Mylar. Specimens were loaded linearly with time; load, far field strain, and crack opening displacement (COD) were monitored. The loading was stopped periodically and the notched region was radiographed to reveal the extent and type of damage (failure progression). Results of the tests showed that the hybrid laminates had higher fracture toughnesses than comparable all-graphite laminates. The higher fracture toughness was due primarily to the larger damage region at the ends of the slit; delamination and splitting lowered the stress concentration in the primary load-carrying plies. A linear elastic fracture analysis, which ignored delamination and splitting, underestimated the fracture toughness. For almost all of the laminates, the tests showed that the fracture toughness increased with crack length. The size of the damage region at the ends of the slit and COD measurements also increased with crack length.
NASA Astrophysics Data System (ADS)
Liu, Z.-C.; Li, C.-Y.; Lesselier, D.; Zhong, Y.
2016-12-01
Modeling of periodically-structured, fiber-reinforced laminates with fibers missing is investigated, this applying as well to similarly disorganized photonic crystals at optical frequencies. Parallel cylindrical fibers are periodically embedded within a layer sandwiched between two half-spaces. Absent fibers destroy the periodicity. The supercell concept involving an auxiliary periodic structure provides subsidiary solutions, wherein plane-wave illumination can be analyzed with the help of the Floquet theorem, while the field response due to a line source can be calculated from the pertinent plane-wave expansion. Accuracy, computational efficacy and versatility of the above approaches are illustrated by comprehensive numerical simulations with in particular comparisons to results provided by a finite-element code, all-purpose but computationally demanding, this work seen as the first step to the localization of missing fibers in a damaged laminate and imaging thereof.
Kerley, P.L.
1959-01-01
A small-size antenna having a doughnut-shaped field pattern and which can act both as an antenna and a resonant circuit is described. The antenna is of the slotted type and comprises a resonant cavity with a center hole. A circular slot is provided in one wall of the cavity concentric with the hole and a radio frequency source is connected across the slot. The pattern and loading of the antenna are adjusted by varying the position and shape of a center element slidably disposed within the hole and projecting from the slotted side of the resonant cavity. The disclosed structure may also be used to propagate the oscillator signal down a transniission line by replacing the center element with one leg of the transmission line in a spaced relation from the walls of the cavity.
Nonlinear effects on composite laminate thermal expansion
NASA Technical Reports Server (NTRS)
Hashin, Z.; Rosen, B. W.; Pipes, R. B.
1979-01-01
Analyses of Graphite/Polyimide laminates shown that the thermomechanical strains cannot be separated into mechanical strain and free thermal expansion strain. Elastic properties and thermal expansion coefficients of unidirectional Graphite/Polyimide specimens were measured as a function of temperature to provide inputs for the analysis. The + or - 45 degrees symmetric Graphite/Polyimide laminates were tested to obtain free thermal expansion coefficients and thermal expansion coefficients under various uniaxial loads. The experimental results demonstrated the effects predicted by the analysis, namely dependence of thermal expansion coefficients on load, and anisotropy of thermal expansion under load. The significance of time dependence on thermal expansion was demonstrated by comparison of measured laminate free expansion coefficients with and without 15 day delay at intermediate temperature.
Structural reliability analysis of laminated CMC components
NASA Technical Reports Server (NTRS)
Duffy, Stephen F.; Palko, Joseph L.; Gyekenyesi, John P.
1991-01-01
For laminated ceramic matrix composite (CMC) materials to realize their full potential in aerospace applications, design methods and protocols are a necessity. The time independent failure response of these materials is focussed on and a reliability analysis is presented associated with the initiation of matrix cracking. A public domain computer algorithm is highlighted that was coupled with the laminate analysis of a finite element code and which serves as a design aid to analyze structural components made from laminated CMC materials. Issues relevant to the effect of the size of the component are discussed, and a parameter estimation procedure is presented. The estimation procedure allows three parameters to be calculated from a failure population that has an underlying Weibull distribution.
Preliminary evaluation of hybrid titanium composite laminates
NASA Technical Reports Server (NTRS)
Miller, J. L.; Progar, D. J.; Johnson, W. S.; St.clair, T. L.
1994-01-01
In this study, the mechanical response of hybrid titanium composite laminates (HTCL) was evaluated at room and elevated temperatures. Also, the use of an elastic-plastic laminate analysis program for predicting the tensile response from constituent properties was verified. The improvement in mechanical properties achieved by the laminates was assessed by comparing the results of static strength and constant amplitude fatigue tests to those for monolithic titanium sheet. Two HTCL were fabricated with different fiber volume fractions, resin layer thicknesses, and resins. One panel was thicker and was more poorly bonded in comparison to other. Consequently, the former had a lower tensile strength, while fewer cracks grew in this panel and at a slower rate. Both panels showed an improvement in fatigue life of almost two orders of magnitude. The model predictions were also in good agreement with the experimental results for both HTCL panels.
Stochastic damage evolution in textile laminates
NASA Technical Reports Server (NTRS)
Dzenis, Yuris A.; Bogdanovich, Alexander E.; Pastore, Christopher M.
1993-01-01
A probabilistic model utilizing random material characteristics to predict damage evolution in textile laminates is presented. Model is based on a division of each ply into two sublaminas consisting of cells. The probability of cell failure is calculated using stochastic function theory and maximal strain failure criterion. Three modes of failure, i.e. fiber breakage, matrix failure in transverse direction, as well as matrix or interface shear cracking, are taken into account. Computed failure probabilities are utilized in reducing cell stiffness based on the mesovolume concept. A numerical algorithm is developed predicting the damage evolution and deformation history of textile laminates. Effect of scatter of fiber orientation on cell properties is discussed. Weave influence on damage accumulation is illustrated with the help of an example of a Kevlar/epoxy laminate.
Development of tough, moisture resistant laminating resins
NASA Technical Reports Server (NTRS)
Brand, R. A.; Harrison, E. S.
1982-01-01
Tough, moisture resistant laminating resins for employment with graphite fibers were developed. The new laminating resins exhibited cost, handleability and processing characteristics equivalent to 394K (250 F) curing epoxies. The laminating resins were based on bisphenol A dicyanate and monofunctional cyanates with hydrophobic substituents. These resins sorb only small quantities of moisture at equilibrium (0.5% or less) with minimal glass transition temperature depression and represent an improvement over epoxies which sorb around 2% moisture at equilibrium. Toughening was accomplished by the precipitation of small diameter particles of butadiene nitrile rubber throughout the resin matrix. The rubber domains act as microcrack termini and energy dissipation sites, allowing increased stress accommodation prior to catastrophic failure. A unique blend of amine terminated butadiene nitrile elastomer (MW 2,000) and a high nitrile content butadiene nitrile rubber yielded the desired resin morphology.
Plated lamination structures for integrated magnetic devices
Webb, Bucknell C.
2014-06-17
Semiconductor integrated magnetic devices such as inductors, transformers, etc., having laminated magnetic-insulator stack structures are provided, wherein the laminated magnetic-insulator stack structures are formed using electroplating techniques. For example, an integrated laminated magnetic device includes a multilayer stack structure having alternating magnetic and insulating layers formed on a substrate, wherein each magnetic layer in the multilayer stack structure is separated from another magnetic layer in the multilayer stack structure by an insulating layer, and a local shorting structure to electrically connect each magnetic layer in the multilayer stack structure to an underlying magnetic layer in the multilayer stack structure to facilitate electroplating of the magnetic layers using an underlying conductive layer (magnetic or seed layer) in the stack as an electrical cathode/anode for each electroplated magnetic layer in the stack structure.
Flutter of laminated plates in supersonic flow
NASA Technical Reports Server (NTRS)
Sawyer, J. W.
1975-01-01
A solution procedure was developed using linear small deflection theory for the flutter of simply supported laminated plates. For such plates, the bending and extensional governing equations are coupled and have cross-stiffness terms which do not appear in classical plate theory. An extended Galerkin method is used to obtain approximate solutions to the governing equations, and the aerodynamic pressure loading used in the analysis is that given by linear piston theory with flow at arbitrary cross-flow angle. A limited parametric study was conducted for typical laminated composite plates. The calculations show that both the bending-extensional coupling and the cross-stiffness terms have a large destabilizing effect on flutter. Since classical plate theory does not consider bending-extensional coupling and cross stiffness terms, it usually gives inaccurate and nonconservative flutter boundaries for laminated plates.
Hybrid Laminates for Application in North Conditions
NASA Astrophysics Data System (ADS)
Antipov, V. V.; Oreshko, E. I.; Erasov, V. S.; Serebrennikova, N. Yu.
2016-11-01
A hybrid aluminum-lithium alloy/SIAL laminate as a possible material for application in structures operated in North conditions is considered. The finite-element method is used for a buckling stability analysis of hybrid panels, bars, and plates. A technique allowing one to compare the buckling stability of multilayered hybrid plates is offered. Compression tests were run on a hybrid laminate wing panel as a prototype of the top panel of TU-204SM airplane made from a high-strength B95T2 aluminum alloy. It turned out that the lighter composite panel had a higher load-carrying capacity than the aluminum one. Results of investigation into the properties the hybrid aluminum-lithium alloy/SIAL laminate and an analysis of scientific-technical data on this subject showed that this composite material could be used in the elements of airframes, including those operated in north conditions.
Silicone modified resins for graphite fiber laminates
NASA Technical Reports Server (NTRS)
Frost, L. W.; Bower, G. M.
1979-01-01
The development of silicon modified resins for graphite fiber laminates which will prevent the dispersal of graphite fibers when the composites are burned is discussed. Eighty-five silicone modified resins were synthesized and evaluated including unsaturated polyesters, thermosetting methacrylates, epoxies, polyimides, and phenolics. Neat resins were judged in terms of Si content, homogeneity, hardness, Char formation, and thermal stability. Char formation was estimated by thermogravimetry to 1,000 C in air and in N2. Thermal stability was evaluated by isothermal weight loss measurements for 200 hrs in air at three temperatures. Four silicone modified epoxies were selected for evaluation in unidirectional filament wound graphite laminates. Neat samples of these resins had 1,000 C char residues of 25 to 50%. The highest flexural values measured for the laminates were a strength of 140 kpsi and a modulus of 10 Mpsi. The highest interlaminar shear strength was 5.3 kpsi.
Circularly Polarized MHOHG with Bichromatic Circularly Polarized Laser Pulses
NASA Astrophysics Data System (ADS)
Bandrauk, Andre D.; Mauger, Francois; Uzer, Turgay
2016-05-01
Circularly polarized MHOHG-Molecular High Order Harmonic Generation is shown to occur efficiently with intense ultrashort bichromatic circularly polarized pulses due to frequent electron-parent -ion recollision with co-or counter-rotating incident circular pulses as predicted in 1995. We show in this context that molecules offer a very robust and efficient frameworkfor the production of circularly polarized harmonics for the generation of single circularly polarized ``attosecond'' pulses. The efficiency of such new MHOHG is shown to depend on the compatibility of the symmetry of the molecular medium with the net electric field generated by the combination of the laser pulses.Using a time-dependent symmetry analysis with concrete examples such as H 2 + vs H 3 + we show how all the features(harmonic order and ∧ polarization) of MHOHG can be explained and predicted.
Free vibration of composite skewed cylindrical shell panel by finite element method
NASA Astrophysics Data System (ADS)
Haldar, Salil
2008-03-01
In this paper a composite triangular shallow shell element has been used for free vibration analysis of laminated composite skewed cylindrical shell panels. In the present element first-order shear deformation theory has been incorporated by taking transverse displacement and bending rotations as independent field variables. The interpolation function used to approximate transverse displacement is one order higher than for bending rotations. This has made the element free from locking in shear. Two types of mass lumping schemes have been recommended. In one of the mass lumping scheme the effect of rotary inertia has been incorporated in the element formulations. Free vibration of skewed composite cylindrical shell panels having different thickness to radius ratios ( h/R=0.01-0.2), length to radius ratios ( L/R), number of layers and fiber orientation angles have been analyzed following the shallow shell method. The results for few examples obtained in the present analysis have compared with the published results. Some new results of composite skewed cylindrical shell panels have been presented which are expected to be useful to future research in this direction.
Wang, Fei; Gong, Haoran; Chen, Xi; Chen, C. Q.
2016-01-01
Origami structures enrich the field of mechanical metamaterials with the ability to convert morphologically and systematically between two-dimensional (2D) thin sheets and three-dimensional (3D) spatial structures. In this study, an in-plane design method is proposed to approximate curved surfaces of interest with generalized Miura-ori units. Using this method, two combination types of crease lines are unified in one reprogrammable procedure, generating multiple types of cylindrical structures. Structural completeness conditions of the finite-thickness counterparts to the two types are also proposed. As an example of the design method, the kinematics and elastic properties of an origami-based circular cylindrical shell are analysed. The concept of Poisson’s ratio is extended to the cylindrical structures, demonstrating their auxetic property. An analytical model of rigid plates linked by elastic hinges, consistent with numerical simulations, is employed to describe the mechanical response of the structures. Under particular load patterns, the circular shells display novel mechanical behaviour such as snap-through and limiting folding positions. By analysing the geometry and mechanics of the origami structures, we extend the design space of mechanical metamaterials and provide a basis for their practical applications in science and engineering. PMID:27624892
Wang, Fei; Gong, Haoran; Chen, Xi; Chen, C Q
2016-09-14
Origami structures enrich the field of mechanical metamaterials with the ability to convert morphologically and systematically between two-dimensional (2D) thin sheets and three-dimensional (3D) spatial structures. In this study, an in-plane design method is proposed to approximate curved surfaces of interest with generalized Miura-ori units. Using this method, two combination types of crease lines are unified in one reprogrammable procedure, generating multiple types of cylindrical structures. Structural completeness conditions of the finite-thickness counterparts to the two types are also proposed. As an example of the design method, the kinematics and elastic properties of an origami-based circular cylindrical shell are analysed. The concept of Poisson's ratio is extended to the cylindrical structures, demonstrating their auxetic property. An analytical model of rigid plates linked by elastic hinges, consistent with numerical simulations, is employed to describe the mechanical response of the structures. Under particular load patterns, the circular shells display novel mechanical behaviour such as snap-through and limiting folding positions. By analysing the geometry and mechanics of the origami structures, we extend the design space of mechanical metamaterials and provide a basis for their practical applications in science and engineering.
NASA Astrophysics Data System (ADS)
Wang, Fei; Gong, Haoran; Chen, Xi; Chen, C. Q.
2016-09-01
Origami structures enrich the field of mechanical metamaterials with the ability to convert morphologically and systematically between two-dimensional (2D) thin sheets and three-dimensional (3D) spatial structures. In this study, an in-plane design method is proposed to approximate curved surfaces of interest with generalized Miura-ori units. Using this method, two combination types of crease lines are unified in one reprogrammable procedure, generating multiple types of cylindrical structures. Structural completeness conditions of the finite-thickness counterparts to the two types are also proposed. As an example of the design method, the kinematics and elastic properties of an origami-based circular cylindrical shell are analysed. The concept of Poisson’s ratio is extended to the cylindrical structures, demonstrating their auxetic property. An analytical model of rigid plates linked by elastic hinges, consistent with numerical simulations, is employed to describe the mechanical response of the structures. Under particular load patterns, the circular shells display novel mechanical behaviour such as snap-through and limiting folding positions. By analysing the geometry and mechanics of the origami structures, we extend the design space of mechanical metamaterials and provide a basis for their practical applications in science and engineering.
Thin cylindrical sheets of air
NASA Astrophysics Data System (ADS)
Thoroddsen, Sigurdur; Beilharz, Daniel; Guyon, Axel; Li, Er Qiang; Thoraval, Marie-Jean
2014-11-01
Drops impacting at low velocities onto a pool surface can stretch out thin hemispheric sheets of air. These air sheets can remain intact until they reach submicron thicknesses, whereby they rupture to form myriad of microbubbles. By impacting a higher-viscosity drop onto a lower-viscosity pool, we have explored new geometries of such air films. In this way we are able to maintain stable air-layers which can wrap around the entire drop to form anti-bubbles, i.e. spherical air layers bounded by inner and outer liquid masses. Furthermore, for the most viscous drops they enter the pool trailing a viscous thread from the pinch-off from the nozzle. The air sheet can also wrap around these treads and remain stable over extended time to form a cylindrical air sheet. We study the parameter regime where these structures appear and their subsequent breakup. The stability of these air cylinders is inconsistent with inviscid stability theory, suggesting stabilization by lubrication forces within the submicron air layer.
Radially sandwiched cylindrical piezoelectric transducer
NASA Astrophysics Data System (ADS)
Lin, Shuyu; Fu, Zhiqiang; Zhang, Xiaoli; Wang, Yong; Hu, Jing
2013-01-01
A new type of radially sandwiched piezoelectric short cylindrical transducer is developed and its radial vibration is studied. The transducer is composed of a solid metal disk, a radially polarized piezoelectric ceramic short tube and a metal tube. The radial vibrations of the solid metal disk, the radially polarized piezoelectric tube and the metal tube are analyzed and their electromechanical equivalent circuits are introduced. Based on the mechanical boundary conditions among the metal disk, the piezoelectric tube and the metal tube, a three-port electromechanical equivalent circuit for the radially sandwiched transducer is obtained and the frequency equation is given. The theoretical relationship of the resonance and anti-resonance frequencies and the effective electromechanical coupling coefficient with the geometrical dimensions is analyzed. The radial vibration of the sandwiched transducer is simulated by using two different numerical methods. It is shown that the analytical resonance and anti-resonance frequencies are in good agreement with the numerically simulated results. The transducer is expected to be used in piezoelectric resonators, actuators and ultrasonic radiators in ultrasonic and underwater sound applications.
Fracture behavior of laminated discontinuously reinforced aluminum material
Osman, T.M. |; Lewandowski, J.J.; Lesuer, D.R.; Syn, C.K.; Hunt, W.H. Jr
1994-05-01
Laminated metallic composites are being developed for applications which require high specific stiffness and fracture resistance. Recent work with laminated discontinuously reinforced aluminum (DRA) materials has demonstrated the potential for marked improvements in stable crack growth resistance via extrinsic toughening. The purpose of this work is to compare the fracture mechanisms and fracture resistance of laminated DRA materials to unlaminated DRA materials. In particular, the production of extensive stable crack growth and the associated improvement in damage tolerance in DRA laminates is documented.
Small Laminated Axial Turbine Design and Test Program.
1980-12-01
the Disk Rim During Startup and Shutdown 112 74 CME Rotor Burst Ratio 114 75 PCM Laminate Tool No. 21 115 76 Small Cruise Missile Laminated Turbine 117...Jr., H. R. Fisk and J. A. Vonada, ’Demonstration of a Cooled Laminated Integral Axial Turbine," AIAA Paper 77-949. Reprinted in Journal of Aircraft... Tooling (PC0) for the small diameter laminated rotor. 3 4. .< ,.C, DESIGN ANALYSIS Heat-Ttansfer Performance Predictions The expected metal temperature
Ultrahigh Carbon Steels and Their Laminates
1990-02-01
PROGRAM PROJECT TASK WORK UNIT 11LitME NT NO. No. NO. NO I I TITLE tiAtluda Seca.r.ty Ck~iaialasonJ Ultrahigh Carbon Steels and their laminates...PROM Aug. 1984 To- Fe~r--9O February 1, 1906 1S. SUPPLEMENTARY NOTATION Amore coinpetc tte of tie-program is: Low Density and Tough Steels with High...Hardenabihzty: Processing, Testing and Evaluation of UHC steels and their laminates 17 COSATI CODES Is.. SUBJECT TERMS (CoAtInai" on uvwrue iroleemary
Ultrasonic transducer with laminated coupling wedge
Karplus, Henry H. B.
1976-08-03
An ultrasonic transducer capable of use in a high-temperature environment incorporates a laminated metal coupling wedge including a reflecting edge shaped as a double sloping roof and a transducer crystal backed by a laminated metal sound absorber disposed so as to direct sound waves through the coupling wedge and into a work piece, reflections from the interface between the coupling wedge and the work piece passing to the reflecting edge. Preferably the angle of inclination of the two halves of the reflecting edge are different.
Multi-layer laminate structure and manufacturing method
Keenihan, James R.; Cleereman, Robert J.; Eurich, Gerald; Graham, Andrew T.; Langmaid, Joe A.
2013-01-29
The present invention is premised upon a multi-layer laminate structure and method of manufacture, more particularly to a method of constructing the multi-layer laminate structure utilizing a laminate frame and at least one energy activated flowable polymer.
Multi-layer laminate structure and manufacturing method
Keenihan, James R [Midland, MI; Cleereman, Robert J [Midland, MI; Eurich, Gerald [Merrill, MI; Graham, Andrew T [Midland, MI; Langmaid, Joe A [Caro, MI
2012-04-24
The present invention is premised upon a multi-layer laminate structure and method of manufacture, more particularly to a method of constructing the multi-layer laminate structure utilizing a laminate frame and at least one energy activated flowable polymer.
Price, Matthew A.
2005-05-01
An understanding of the detonation phenomenon and airblast behavior for cylindrical high-explosive charges is essential in developing predictive capabilities for tests and scenarios involving these charge geometries. Internal tests on reinforced concrete structures allowed for the analysis of cylindrical charges and the effect of secondary reactions occurring in confined structures. The pressure profiles that occur close to a cylindrical explosive charge are strongly dependent on the length-to-diameter ratio (L/D) of the charge. This study presents a comparison of finite-element code models (i.e., AUTODYN) to empirical methods for predicting airblast behavior from cylindrical charges. Current finite element analysis (FEA) and blast prediction codes fail to account for the effects of secondary reactions (fireballs) that occur with underoxidized explosives. Theoretical models were developed for TNT and validated against literature. These models were then applied to PBX 9501 for predictions of the spherical fireball diameter and time duration. The following relationships for PBX 9501 were derived from this analysis (units of ft, lb, s). Comparison of centrally located equivalent weight charges using cylindrical and spherical geometries showed that the average impulse on the interior of the structure is ~3%–5% higher for the spherical charge. Circular regions of high impulse that occur along the axial direction of the cylindrical charge must be considered when analyzing structural response.
Aerodynamic modification to a circular cylinder to enhance the piezoelectric wind energy harvesting
NASA Astrophysics Data System (ADS)
Hu, Gang; Tse, K. T.; Kwok, K. C. S.; Song, Jie; Lyu, Yuan
2016-11-01
This study aims to expand the aeroelastic unstable range of a circular cylinder for improving the efficiency of a vortex-induced vibration (VIV)-based wind energy harvester. The kinetic energy of the harvester is provided by flow-induced vibration of a circular cylinder. Two small-diameter cylindrical rods were attached on two sides of the circular cylinder parallel to the cylinder axis and symmetrical to the stagnation line at a series of circumferential locations. This was inspired by rain-wind-induced vibrations of stay-cables of cable-stayed bridges. It was found that attaching two small-diameter cylindrical rods at the circumferential location θ = 60° significantly expands the aeroelastic unstable range for the circular cylinder. The wind energy harvester with this configuration harnesses the wind energy beyond the VIV onset wind speed and is sustained over the range of wind speed. Therefore, this configuration possesses a dramatic superiority over a plain circular cylinder as the kinetic source of a wind energy harvester.
Circular chemiresistors for microchemical sensors
Ho, Clifford K.
2007-03-13
A circular chemiresistor for use in microchemical sensors. A pair of electrodes is fabricated on an electrically insulating substrate. The pattern of electrodes is arranged in a circle-filling geometry, such as a concentric, dual-track spiral design, or a circular interdigitated design. A drop of a chemically sensitive polymer (i.e., chemiresistive ink) is deposited on the insulating substrate on the electrodes, which spreads out into a thin, circular disk contacting the pair of electrodes. This circularly-shaped electrode geometry maximizes the contact area between the pair of electrodes and the polymer deposit, which provides a lower and more stable baseline resistance than with linear-trace designs. The circularly-shaped electrode pattern also serves to minimize batch-to-batch variations in the baseline resistance due to non-uniform distributions of conductive particles in the chemiresistive polymer film.
Resonantly guided modes in microstructured optical fibers with a circular array of high-index rods.
Ohtera, Yasuo; Hirose, Haruka; Yamada, Hirohito
2013-08-01
A microstructured optical fiber with a new type of waveguiding mechanism is proposed. The fiber consists of a circular rod array of high index material (n=3.48) embedded in a low index background (n=1.44). The rod array exhibits guided-mode resonance (GMR) for cylindrical waves arriving from inside the array, and thus functions as a highly reflective circular wall. Through finite-difference time-domain (FDTD) simulations, we confirmed light confinement and guidance near the GMR wavelength. Basic optical characteristics such as dispersion relations, loss spectra, and mode field profiles were calculated.
Crack problems in cylindrical and spherical shells
NASA Technical Reports Server (NTRS)
Erdogan, F.
1976-01-01
Standard plate or shell theories were used as a starting point to study the fracture problems in thin-walled cylindrical and spherical shells, assuming that the plane of the crack is perpendicular to the surface of the sheet. Since recent studies have shown that local shell curvatures may have a rather considerable effect on the stress intensity factor, the crack problem was considered in conjunction with a shell rather than a plate theory. The material was assumed to be isotropic and homogeneous, so that approximate solutions may be obtained by approximating the local shell crack geometry with an ideal shell which has a solution, namely a spherical shell with a meridional crack, a cylindrical shell with a circumferential crack, or a cylindrical shell with an axial crack. A method of solution for the specially orthotropic shells containing a crack was described; symmetric and skew-symmetric problems are considered in cylindrical shells with an axial crack.
Reciprocal knock-in mice to investigate the functional redundancy of lamin B1 and lamin B2
Lee, John M.; Tu, Yiping; Tatar, Angelica; Wu, Daniel; Nobumori, Chika; Jung, Hea-Jin; Yoshinaga, Yuko; Coffinier, Catherine; de Jong, Pieter J.; Fong, Loren G.; Young, Stephen G.
2014-01-01
Lamins B1 and B2 (B-type lamins) have very similar sequences and are expressed ubiquitously. In addition, both Lmnb1- and Lmnb2-deficient mice die soon after birth with neuronal layering abnormalities in the cerebral cortex, a consequence of defective neuronal migration. The similarities in amino acid sequences, expression patterns, and knockout phenotypes raise the question of whether the two proteins have redundant functions. To investigate this topic, we generated “reciprocal knock-in mice”—mice that make lamin B2 from the Lmnb1 locus (Lmnb1B2/B2) and mice that make lamin B1 from the Lmnb2 locus (Lmnb2B1/B1). Lmnb1B2/B2 mice produced increased amounts of lamin B2 but no lamin B1; they died soon after birth with neuronal layering abnormalities in the cerebral cortex. However, the defects in Lmnb1B2/B2 mice were less severe than those in Lmnb1-knockout mice, indicating that increased amounts of lamin B2 partially ameliorate the abnormalities associated with lamin B1 deficiency. Similarly, increased amounts of lamin B1 in Lmnb2B1/B1 mice did not prevent the neurodevelopmental defects elicited by lamin B2 deficiency. We conclude that lamins B1 and B2 have unique roles in the developing brain and that increased production of one B-type lamin does not fully complement loss of the other. PMID:24672053
Damage experiments in cylindrical geometry update
Kaul, Anne; Holtkamp, David; Rodriguez, George
2009-01-01
Using a cylindrical configuration to study spallation damage allows for a natural recollection of the damaged material under proper driving conditions. Previous experiments provided data about failure initiation in aluminum in a cylindrical geometry and the behavior of material recollected after damage from pressures in the damage initiation regime. The current series of experiments studied the behavior of material recollected after complete failure. Results from the current experiments will be presented.
Object recognition using cylindrical harmonic filter.
Guerrero Bermúdez, Jáder
2004-06-28
We present the cylindrical harmonic filter for three-dimensional (3D) discrete correlation between range data. The filter guarantees invariance of the correlation peak intensity under target rotation around z-axis. It can be considered a harmonic decomposition, in cylindrical coordinates, of the 3D Fourier spectrum of the target. Some simulation results confirm the in-plane rotation invariance and the discrimination of the filter.
View factors of cylindrical spiral surfaces
NASA Astrophysics Data System (ADS)
Lebedev, Vladimir A.; Solovjov, Vladimir P.
2016-03-01
Analytical expressions are presented for the view factors (radiative configuration factors) associated with the flat right cylindrical spiral surface. Such cylindrical spiral systems are widely applied as electrical resistance heating elements for lighting devices, electronic radio tubes, high-speed gas flow heaters, and other appliances used for scientific, industrial and domestic purposes. Derivation of the view factors is based on the invariant principles and the results presented in Lebedev (2000, 2003,1988) [1-3].
Cylindrical Antenna Using Near Zero Index Metamaterial
2012-07-24
device for enhancing the directivity and port isolation of a dual-frequency dual- polarization (DFDP) microstrip antenna by using metamaterial... Directivity Microstrip Patch Antenna Based on Zero-Index Metamaterial," IEEE Antennas and Wireless Prop. Letters, vol.8, no., pp.538-541, 2009. [0008...Invention [0003] The present invention is generally directed towards a cylindrical antenna and more specifically directed towards a cylindrical
Spontaneous transition from flat to cylindrical solitons
Frycz, P.; Infeld, E. )
1989-07-24
Flat, cylindrical, and spherical soliton solutions to various model equations are known. Many of these exact solutions have been seen in numerical simulations. However, there are few simulations that actually show that exact flat solitons can break up into an array of exact cylindrical or spherical solitons and follow this on a step by step basis. This Letter presents the first of these two kinds of transition for the Zakharov-Kuznetsov equation governing ion acoustic solitons in strongly magnetized plasmas.
Structural similitude and design of scaled down laminated models
NASA Technical Reports Server (NTRS)
Simitses, G. J.; Rezaeepazhand, J.
1993-01-01
similarity are discussed. The procedure consists of systematically observing the effect of each parameter and corresponding scaling laws. Then acceptable intervals and limitations for these parameters and scaling laws are discussed. In each case, a set of valid scaling factors and corresponding response scaling laws that accurately predict the response of prototypes from experimental models is introduced. The examples used include rectangular laminated plates under destabilizing loads, applied individually, vibrational characteristics of same plates, as well as cylindrical bending of beam-plates.
1983-09-01
circu- ’ lar hole stretched uniaxially while the surface moisture is changed suddenly at a constant surface temperature. The stresses near the hole...S + AP 3C (8) -at at where AP = P-Po Application of the Onsager principle [2,3] leads to the follow- ing expressions for the moisture and heat flux...vectors f = Ll l x f + L12 x q (9) " = L21xf + L22Xq -5- with Lij (ij - 1,2) being the Onsager coefficients such that L 0, L22 > 0, L12 L < (10) The
Development and verification of global/local analysis techniques for laminated composites
NASA Technical Reports Server (NTRS)
Thompson, Danniella Muheim; Griffin, O. Hayden, Jr.
1991-01-01
A two-dimensional to three-dimensional global/local finite element approach was developed, verified, and applied to a laminated composite plate of finite width and length containing a central circular hole. The resulting stress fields for axial compression loads were examined for several symmetric stacking sequences and hole sizes. Verification was based on comparison of the displacements and the stress fields with those accepted trends from previous free edge investigations and a complete three-dimensional finite element solution of the plate. The laminates in the compression study included symmetric cross-ply, angle-ply and quasi-isotropic stacking sequences. The entire plate was selected as the global model and analyzed with two-dimensional finite elements. Displacements along a region identified as the global/local interface were applied in a kinematically consistent fashion to independent three-dimensional local models. Local areas of interest in the plate included a portion of the straight free edge near the hole, and the immediate area around the hole. Interlaminar stress results obtained from the global/local analyses compares well with previously reported trends, and some new conclusions about interlaminar stress fields in plates with different laminate orientations and hole sizes are presented for compressive loading. The effectiveness of the global/local procedure in reducing the computational effort required to solve these problems is clearly demonstrated through examination of the computer time required to formulate and solve the linear, static system of equations which result for the global and local analyses to those required for a complete three-dimensional formulation for a cross-ply laminate. Specific processors used during the analyses are described in general terms. The application of this global/local technique is not limited software system, and was developed and described in as general a manner as possible.
Simulating flow and segregation of cylindrical particles
NASA Astrophysics Data System (ADS)
Zhao, Yongzhi; Umbanhowar, Paul B.; Lueptow, Richard M.
2015-11-01
Efficient and accurate simulation of cylindrical particles using discrete element method (DEM) is a challenge. Typical approaches to simulating cylindrical particle systems are based on the glued spheres method, which has low accuracy, or real shape models, which have high computational cost. In this work we utilize super-ellipsoids, which belong to super-quadrics, to model cylindrical particles in DEM simulations. Simulations of a single cylinder impacting a flat wall indicate that super-ellipsoids provide the same accuracy as real shape models and much better accuracy than the glued sphere method. Simulations of super-ellipsoid cylindrical particles in rotating tumblers result in nearly the same angle of repose as experiments and real shape simulations, demonstrating the accuracy of super-ellipsoid DEM simulations for multi-particle systems. The segregation of bidisperse cylindrical particles differing in length in a bounded heap was simulated by super-ellipsoid DEM, and the results are similar to the experiment. In spite of these advantages of using super-ellipsoid cylindrical particles, simulations of filling a box with particles indicate that the simulation times for super-ellipsoid cylinders is about an order of magnitude longer than that for the same number of spherical particles.
NASA Astrophysics Data System (ADS)
Yin, J. J.; Chang, F.; Li, S. L.; Yao, X. L.; Sun, J. R.; Xiao, Y.
2017-02-01
To clarify the evolution of damage for typical carbon woven fabric/epoxy laminates exposed to lightning strike, artificial lightning testing on carbon woven fabric/epoxy laminates were conducted, damage was assessed using visual inspection and damage peeling approaches. Relationships between damage size and action integral were also elucidated. Results showed that damage appearance of carbon woven fabric/epoxy laminate presents circular distribution, and center of the circle located at the lightning attachment point approximately, there exist no damage projected area dislocations for different layers, visual damage territory represents maximum damage scope; visible damage can be categorized into five modes: resin ablation, fiber fracture and sublimation, delamination, ablation scallops and block-shaped ply-lift; delamination damage due to resin pyrolysis and internal pressure exist obvious distinguish; project area of total damage is linear with action integral for the same type specimens, that of resin ablation damage is linear with action integral, but no correlation with specimen type, for all specimens, damage depth is linear with logarithm of action integral. The coupled thermal-electrical model constructed is capable to simulate the ablation damage for carbon woven fabric/epoxy laminates exposed to simulated lightning current through experimental verification.
Doped LZO buffer layers for laminated conductors
Paranthaman, Mariappan Parans [Knoxville, TN; Schoop, Urs [Westborough, MA; Goyal, Amit [Knoxville, TN; Thieme, Cornelis Leo Hans [Westborough, MA; Verebelyi, Darren T [Oxford, MA; Rupich, Martin W [Framingham, MA
2010-03-23
A laminated conductor includes a metallic substrate having a surface, a biaxially textured buffer layer supported by the surface of the substrate, the biaxially textured buffer layer comprising LZO and a dopant for mitigating metal diffusion through the LZO, and a biaxially textured conductor layer supported by the biaxially textured buffer layer.
Micro-Cracking Detection in Laminated Composites
NASA Technical Reports Server (NTRS)
Chu, Tsuchin; Leyte, Alma; DiGregorio, Anthony; Russell, Samuel S.; Walker, James L.; Thom, Robert (Technical Monitor)
2002-01-01
Porosity and fatigue cracking are two critical factors that affect the performance and safety of cryogenic fuel tanks and feedlines made from unlined laminated or weaved carbon/epoxy materials. This paper presents the experiments to induce fatigue cracking of laminated composites through thermal cycling as well as the feasibility of using Thermography and Ultrasound Spectroscopy technology (UT) to detect and measure such micro-cracking. Carbon/epoxy laminated composite panels were built and cut into strips. These specimens were partially submerged in liquid nitrogen while subjected to various loads on a test machine. Edges of some specimens were polished and etched to determine the degree of micro-cracking. The rest of specimens were then examined with Thermography and Ultrasound Spectroscopy NDE systems to investigate the feasibility of finding such micro-cracking in the laminated composites. Thermography is utilized to determine changes in thermal diffusivity. The degree of cracking may reduce the apparent thermal diffusivity and therefore change the thermal response on the surface. Thermography testing was conducted on a group of specimens where it is desired to have some correlation between the predetermined stress and the thermography data. Ultrasound Spectroscopy was used to determine peak changes between the pre-stressed and stressed samples. Data from the inspections were analyzed and the results are presented in this paper.
[Laminitis in cattle: a literature review].
Lischer, C; Ossent, P
1994-10-01
Worldwide afflictions of the claws belong to the economically important diseases in dairy cattle. The significance of laminitis has gained importance in the last years since the condition is regarded as the most important predisposing factor for the development of lesions such as sole ulcer, white line disease and heel horn erosion. Apart from the clinical stages (acute, subacute, chronic, chronic-recurrent) there is also a subclinical form of laminitis which does not cause lameness. It is characterized by soft yellowish sole and heel horn with haemorrhages in the sole and along the white line. Laminitis is a multifactorial event in which nutrition, genetic disposition and the perinatal period, combined with the associated diseases of high-yielding cows, have a particular significance. Currently, two principally different hypotheses on the pathogenesis are discussed. The generally accepted theory bases on a disturbance in the microcirculation of the corium. According to the other theory the circulatory disturbances are secondary to changes which occur in the horn producing cells of the stratum basale of the epidermis. The predisposing factors and the pathogenesis of laminitis are discussed in the light of possible therapeutic and prophylactic measures.
Laminated insulators having heat dissipation means
Niemann, R.C.; Mataya, K.F.; Gonczy, J.D.
1980-04-24
A laminated body is provided with heat dissipation capabilities. The insulator body is formed by dielectric layers interleaved with heat conductive layers, and bonded by an adhesive to form a composite structure. The heat conductive layers include provision for connection to an external thermal circuit.
Nuclear spin circular dichroism
Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia
2014-04-07
Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.
NASA Astrophysics Data System (ADS)
Kwak, Moon K.; Yang, Dong-Ho
2013-09-01
This paper is concerned with the suppression of vibrations and radiated sound of a ring-stiffened circular cylindrical shell in contact with unbounded external fluid by means of piezoelectric sensors and actuators. The dynamic model of a circular cylindrical shell based on the Sanders shell theory was considered together with a ring stiffener model. The mass and stiffness matrices for a ring stiffener were newly derived in this study and added to the mass and stiffness matrices of the cylindrical shell, respectively. The fluid-added mass matrix, which was derived by using the baffled shell theory, was also added to the mass matrix. Finally, the equations representing the piezoelectric sensor measurement and piezoelectric actuation complete the theoretical model for the addressed problem. The natural vibration characteristics of the ring-stiffened cylindrical shell both in air and in water were investigated both theoretically and experimentally. The theoretical predictions were in good agreement with the experimental results. An active vibration controller which can cope with a harmonic disturbance was designed by considering the modified higher harmonic control, which is, in fact, a band rejection filter. An active vibration control experiment on the submerged cylindrical shell was carried out in a water tank and the digital control system was used. The experimental results showed that both vibrations and radiation sound of the submerged cylindrical shell were suppressed by a pair of piezoelectric sensor and actuator.
Prediction of Composite Laminate Fracture: Micromechanics and Progressive Fracture
NASA Technical Reports Server (NTRS)
Gotsis, P. K.; Chamis, C. C.; Minnetyan, L.
1996-01-01
This report describes an investigation to predict first-ply failure and final fracture in selected composite laminates subjected to inplane loads. The laminates were composed of glass fiber and graphite fibers in epoxy matrices. Failure envelopes based on first-ply failure and laminate fracture were generated for combined loading of these laminates. Predictions were evaluated by micromechanics-based theory and progressive fracture. The results show that, for most cases, combined tensile loading significantly enhanced the laminate fracture stress in comparison to the uniaxial loading.
Composite laminates with negative through-the-thickness Poisson's ratios
NASA Technical Reports Server (NTRS)
Herakovich, C. T.
1984-01-01
A simple analysis using two dimensional lamination theory combined with the appropriate three dimensional anisotropic constitutive equation is presented to show some rather surprising results for the range of values of the through-the-thickness effective Poisson's ratio nu sub xz for angle ply laminates. Results for graphite-epoxy show that the through-the-thickness effective Poisson's ratio can range from a high of 0.49 for a 90 laminate to a low of -0.21 for a + or - 25s laminate. It is shown that negative values of nu sub xz are also possible for other laminates.
Composite laminates with negative through-the-thickness Poisson's ratios
NASA Technical Reports Server (NTRS)
Herakovich, C. T.
1984-01-01
A simple analysis using two-dimensional lamination theory combined with the appropriate three-dimensional anisotropic constitutive equation is presented to show some rather surprising results for the range of values of the through-the-thickness effective Poisson's ratio nu sub xz for angle ply laminates. Results for graphite-epoxy show that the through-the-thickness effective Poisson's ratio can range from a high of 0.49 for a 90 laminate to a low of -0.21 for a + or - 25s laminate. It is shown that negative values of nu sub xz are also possible for other laminates.
Nonlinear laminate analysis for metal matrix fiber composites
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Sinclair, J. H.
1981-01-01
A nonlinear laminate analysis is described for predicting the mechanical behavior (stress-strain relationships) of angleplied laminates in which the matrix is strained nonlinearly by both the residual stress and the mechanical load and in which additional nonlinearities are induced due to progressive fiber fractures and ply relative rotations. The nonlinear laminate analysis (NLA) is based on linear composite mechanics and a piece wise linear laminate analysis to handle the nonlinear responses. Results obtained by using this nonlinear analysis on boron fiber/aluminum matrix angleplied laminates agree well with experimental data. The results shown illustrate the in situ ply stress-strain behavior and synergistic strength enhancement.
Progressive delamination in polymer matrix composite laminates: A new approach
NASA Technical Reports Server (NTRS)
Chamis, C. C.; Murthy, P. L. N.; Minnetyan, L.
1992-01-01
A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive delamination in polymer matrix composite laminates. The damage stages are quantified based on physics via composite mechanics while the degradation of the laminate behavior is quantified via the finite element method. The approach accounts for all types of composite behavior, laminate configuration, load conditions, and delamination processes starting from damage initiation, to unstable propagation, and to laminate fracture. Results of laminate fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach.
Fatigue damage development of various CFRP-laminates
NASA Technical Reports Server (NTRS)
Schulte, K.; Baron, CH.
1988-01-01
The chronic strength and fatigue behavior of a woven carbon-fiber reinforced laminate in a balanced eight-shaft satin weave style was compared to nonwoven laminates with an equivalent cross-ply layup. Half the fibers were arranged in the direction of the load and the other half perpendicular to it. Two types of nonwoven laminates consisting of continuous fibers and aligned discontinuous fibers, both produced from carbon fiber prepregs, were studied. The cross-ply laminate with continuous fiber showed the best characteristics with regard to both static strength and fatigue. The similarities and differences in damage mechanisms in the laminates are described.
Compression failure of angle-ply laminates
NASA Technical Reports Server (NTRS)
Peel, Larry D.; Hyer, Michael W.; Shuart, Mark J.
1991-01-01
The present work deals with modes and mechanisms of failure in compression of angle-ply laminates. Experimental results were obtained from 42 angle-ply IM7/8551-7a specimens with a lay-up of ((plus or minus theta)/(plus or minus theta)) sub 6s where theta, the off-axis angle, ranged from 0 degrees to 90 degrees. The results showed four failure modes, these modes being a function of off-axis angle. Failure modes include fiber compression, inplane transverse tension, inplane shear, and inplane transverse compression. Excessive interlaminar shear strain was also considered as an important mode of failure. At low off-axis angles, experimentally observed values were considerably lower than published strengths. It was determined that laminate imperfections in the form of layer waviness could be a major factor in reducing compression strength. Previously developed linear buckling and geometrically nonlinear theories were used, with modifications and enhancements, to examine the influence of layer waviness on compression response. The wavy layer is described by a wave amplitude and a wave length. Linear elastic stress-strain response is assumed. The geometrically nonlinear theory, in conjunction with the maximum stress failure criterion, was used to predict compression failure and failure modes for the angle-ply laminates. A range of wave length and amplitudes were used. It was found that for 0 less than or equal to theta less than or equal to 15 degrees failure was most likely due to fiber compression. For 15 degrees less than theta less than or equal to 35 degrees, failure was most likely due to inplane transverse tension. For 35 degrees less than theta less than or equal to 70 degrees, failure was most likely due to inplane shear. For theta less than 70 degrees, failure was most likely due to inplane transverse compression. The fiber compression and transverse tension failure modes depended more heavily on wave length than on wave amplitude. Thus using a single
Determining Shear Stress Distribution in a Laminate
NASA Technical Reports Server (NTRS)
Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.
2010-01-01
A "simplified shear solution" method approximates the through-thickness shear stress distribution within a composite laminate based on an extension of laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather, it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply-level stresses can be efficiently determined from global load resultants at a given location in a structure and used to evaluate the margin of safety on a ply-by-ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. The method has been incorporated within the HyperSizer commercial structural sizing software to improve its predictive capability for designing composite structures. The HyperSizer structural sizing software is used extensively by NASA to design composite structures. In the case of through-thickness shear loading on panels, HyperSizer previously included a basic, industry-standard, method for approximating the resulting shear stress distribution in sandwich panels. However, no such method was employed for solid laminate panels. The purpose of the innovation is to provide an approximation of the through-thickness shear stresses in a solid laminate given the through-thickness shear loads (Qx and Qy) on the panel. The method was needed for implementation within the HyperSizer structural sizing software so that the approximated ply-level shear stresses could be utilized in a failure theory to assess the adequacy of a panel design. The simplified shear solution method was developed based on extending and generalizing bi-material beam theory to plate-like structures. It is assumed that the through-thickness shear stresses arise due to local bending of the laminate induced by the through-thickness shear load, and by imposing
NASA Technical Reports Server (NTRS)
Harrison, Peter N.; Johnson, Eric R.; Starnes, James H., Jr.
1994-01-01
A mixed method of approximation based on Reissner's variational principle is developed for the linear analysis of interlaminar stresses in laminated composites, with special interest in laminates that contain terminated internal plies (dropped-ply laminates). Two models are derived, one for problems of generalized plane deformation and the other for the axisymmetric response of shells of revolution. A layerwise approach is taken in which the stress field is assumed with an explicit dependence on the thickness coordinate in each layer. The dependence of the stress field on the thickness coordinate is determined such that the three-dimensional equilibrium equations are satisfied by the approximation. The solution domain is reduced to one dimension by integration through the thickness. Continuity of tractions and displacements between layers is imposed. The governing two-point boundary value problem is composed of a system of both differential and algebraic equations (DAE's) and their associated boundary conditions. Careful evaluation of the system of DAE's was required to arrive at a form that allowed application of a one-step finite difference approximation. A two-stage Gauss implicit Runge-Kutta finite difference scheme was used for the solution because of its relatively high degree of accuracy. Patch tests of the two models revealed problems with solution accuracy for the axisymmetric model of a cylindrical shell loaded by internal pressure. Parametric studies of dropped-ply laminate characteristics and their influence on the interlaminar stresses were performed using the generalized plane deformation model. Eccentricity of the middle surface of the laminate through the ply drop-off was found to have a minimal effect on the interlaminar stresses under longitudinal compression, transverse tension, and in-plane shear. A second study found the stiffness change across the ply termination to have a much greater influence on the interlaminar stresses.
Electroosmosis in a Finite Cylindrical Pore: Simple Models of End Effects
2015-01-01
A theoretical model of electroosmosis through a circular pore of radius a that traverses a membrane of thickness h is investigated. Both the cylindrical surface of the pore and the outer surfaces of the membrane are charged. When h ≫ a, end effects are negligible, and the results of full numerical computations of electroosmosis in an infinite pore agree with theory. When h = 0, end effects dominate, and computations again agree with analysis. For intermediate values of h/a, an approximate analysis that combines these two limiting cases captures the main features of computational results when the Debye length κ–1 is small compared with the pore radius a. However, the approximate analysis fails when κ–1 ≫ a, when the charge cloud due to the charged cylindrical walls of the pore spills out of the ends of the pore, and the electroosmotic flow is reduced. When this spilling out is included in the analysis, agreement with computation is restored. PMID:25020257
Free vibrations of circular cylindrical shells with a small added concentrated mass
NASA Astrophysics Data System (ADS)
Leizerovich, G. S.; Seregin, S. V.
2016-09-01
The effect of a small added mass on the frequency and shape of free vibrations of a thin shell is studied using shallow shell theory. The proposed mathematical model assumes that mass asymmetry even in a linear formulation leads to coupled radial flexural vibrations. The interaction of shape-generating waves is studied using modal equations obtained by the Bubnov-Galerkin method. Splitting of the flexural frequency spectrum is found, which is caused not only by the added mass but also by the wave-formation parameters of the shell. The ranges of the relative lengths and shell thicknesses are determined in which the interaction of flexural and radial vibrations can be neglected.
Dimensional crossover of hard parallel cylinders confined on cylindrical surfaces.
Martínez-Ratón, Yuri; Velasco, Enrique
2013-05-01
We derive, from the dimensional-crossover criterion, a fundamental-measure density functional for parallel hard curved rectangles moving on a cylindrical surface. We derive it from the density functional of circular arcs of length σ with centers of mass located on an external circumference of radius R(0). The latter functional in turn is obtained from the corresponding two-dimensional functional for a fluid of hard disks of radius R on a flat surface with centers of mass confined onto a circumference of radius R(0). Thus the curved length of closest approach between the two centers of mass of hard disks on this circumference is σ=2R(0)sin(-1)(R/R(0)), the length of the circular arcs. From the density functional of circular arcs, and by applying a dimensional expansion procedure to the spatial dimension orthogonal to the plane of the circumference, we finally obtain the density functional of curved rectangles of edge lengths σ and L. Along with the derivation, we show that, when the centers of mass of the disks are confined to the exterior circumference of a circle of radius R(0),(i) for R(0)>R, the exact Percus one-dimensional (1D) density functional of circular arcs of length 2R(0)sin(-1)(R/R(0)) is obtained, and (ii) for R(0)
Novel Remanufacturing Process of Recycled Polytetrafluoroethylene(PTFE)/GF Laminate
NASA Astrophysics Data System (ADS)
Xi, Z.; Ghita, O. R.; Johnston, P.; Evans, K. E.
2011-01-01
Currently, the PTFE/GF laminate and PTFE PCB manufacturers are under considerable pressure to address the recycling issues due to Waste Electrical and Electronic Equipment (WEEE) Directive, shortage of landfill capacity and cost of disposal. This study is proposing a novel manufacture method for reuse of the mechanical ground PTFE/Glass fibre (GF) laminate and production of the first reconstitute PTFE/GF laminate. The reconstitute PTFE/GF laminate proposed here consists of a layer of recycled sub-sheet, additional layers of PTFE and PTFE coated glass cloth, also covered by copper foils. The reconstitute PTFE/GF laminate showed good dielectric properties. Therefore, there is potential to use the mechanical ground PTFE/GF laminate powder to produce reconstitute PTFE/GF laminate, for use in high frequencies PCB applications.
Tensile stress-strain behavior of boron/aluminum laminates
NASA Technical Reports Server (NTRS)
Sova, J. A.; Poe, C. C., Jr.
1978-01-01
The tensile stress-strain behavior of five types of boron/aluminum laminates was investigated. Longitudinal and transverse stress-strain curves were obtained for monotonic loading to failure and for three cycles of loading to successively higher load levels. The laminate strengths predicted by assuming that the zero deg plies failed first correlated well with the experimental results. The stress-strain curves for all the boron/aluminum laminates were nonlinear except at very small strains. Within the small linear regions, elastic constants calculated from laminate theory corresponded to those obtained experimentally to within 10 to 20 percent. A limited amount of cyclic loading did not affect the ultimate strength and strain for the boron/aluminum laminates. The laminates, however, exhibited a permanent strain on unloading. The Ramberg-Osgood equation was fitted to the stress-strain curves to obtain average curves for the various laminates.
Circular Scan Streak Tube Development
NASA Technical Reports Server (NTRS)
Nevin, S.
1980-01-01
A streak tube having circular scan was designed, built and tested. Continuous circular scan, easily derived from out of phase sine waves applied to the conventional deflection plates, permits the timing of pulses traveling long baselines. At the tube's output a circular array of 720 elements is scanned to provide 30 to 40 picosecond resolution. Initial difficulties with electron bombarded silicon arrays were circumvented by using microchannel plates within the streak tube to provide the needed electronic amplification and digital sensitivity and coupling the 720 element arrays to the electron beam by means of a phosphor on a fiber optics. Two ceramic body tubes with S-20 photocathodes were tested and delivered.
Digitalizing the Circular Economy
NASA Astrophysics Data System (ADS)
Reuter, Markus A.
2016-12-01
Metallurgy is a key enabler of a circular economy (CE), its digitalization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitalization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure. This will be illustrated through the following: (1) System optimization models for multimetal metallurgical processing. These map large-scale m-IoT systems linked to computer-aided design tools of the original equipment manufacturers and then establish a recycling index through the quantification of RE. (2) Reactor optimization and industrial system solutions to realize the "CE (within a) Corporation—CEC," realizing the CE of society. (3) Real-time measurement of ore and scrap properties in intelligent plant structures, linked to the modeling, simulation, and optimization of industrial extractive process
Towards future circular colliders
NASA Astrophysics Data System (ADS)
Benedikt, Michael; Zimmermann, Frank
2016-09-01
The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) presently provides proton-proton collisions at a center-of-mass (c.m.) energy of 13 TeV. The LHC design was started more than 30 years ago, and its physics program will extend through the second half of the 2030's. The global Future Circular Collider (FCC) study is now preparing for a post-LHC project. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh) in a new ˜100 km tunnel. It also includes the design of a high-luminosity electron-positron collider (FCCee) as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb3 S n superconductor, for the FCC-hh hadron collider, and a highly-efficient superconducting radiofrequency system for the FCC-ee lepton collider. Following the FCC concept, the Institute of High Energy Physics (IHEP) in Beijing has initiated a parallel design study for an e + e - Higgs factory in China (CEPC), which is to be succeeded by a high-energy hadron collider (SPPC). At present a tunnel circumference of 54 km and a hadron collider c.m. energy of about 70 TeV are being considered. After a brief look at the LHC, this article reports the motivation and the present status of the FCC study, some of the primary design challenges and R&D subjects, as well as the emerging global collaboration.
Quantitative validation of carbon-fiber laminate low velocity impact simulations
English, Shawn A.; Briggs, Timothy M.; Nelson, Stacy M.
2015-09-26
Simulations of low velocity impact with a flat cylindrical indenter upon a carbon fiber fabric reinforced polymer laminate are rigorously validated. Comparison of the impact energy absorption between the model and experiment is used as the validation metric. Additionally, non-destructive evaluation, including ultrasonic scans and three-dimensional computed tomography, provide qualitative validation of the models. The simulations include delamination, matrix cracks and fiber breaks. An orthotropic damage and failure constitutive model, capable of predicting progressive damage and failure, is developed in conjunction and described. An ensemble of simulations incorporating model parameter uncertainties is used to predict a response distribution which ismore » then compared to experimental output using appropriate statistical methods. Lastly, the model form errors are exposed and corrected for use in an additional blind validation analysis. The result is a quantifiable confidence in material characterization and model physics when simulating low velocity impact in structures of interest.« less
Quantitative validation of carbon-fiber laminate low velocity impact simulations
English, Shawn A.; Briggs, Timothy M.; Nelson, Stacy M.
2015-09-26
Simulations of low velocity impact with a flat cylindrical indenter upon a carbon fiber fabric reinforced polymer laminate are rigorously validated. Comparison of the impact energy absorption between the model and experiment is used as the validation metric. Additionally, non-destructive evaluation, including ultrasonic scans and three-dimensional computed tomography, provide qualitative validation of the models. The simulations include delamination, matrix cracks and fiber breaks. An orthotropic damage and failure constitutive model, capable of predicting progressive damage and failure, is developed in conjunction and described. An ensemble of simulations incorporating model parameter uncertainties is used to predict a response distribution which is then compared to experimental output using appropriate statistical methods. Lastly, the model form errors are exposed and corrected for use in an additional blind validation analysis. The result is a quantifiable confidence in material characterization and model physics when simulating low velocity impact in structures of interest.
NASA Astrophysics Data System (ADS)
Nakata, K.; Matsuda, T.; Kawai, M.
In this study, multi-scale creep analysis of plain-woven GFRP laminates is performed using the time-dependent homogenization theory developed by the present authors. First, point-symmetry of internal structures of plain-woven laminates is utilized for a boundary condition of unit cell problems, reducing the domain of analysis to 1/4 and 1/8 for in-phase and out-of-phase laminate configurations, respectively. The time-dependent homogenization theory is then reconstructed for these domains of analysis. Using the present method, in-plane creep behavior of plain-woven glass fiber/epoxy laminates subjected to a constant stress is analyzed. The results are summarized as follows: (1) The in-plane creep behavior of the plain-woven GFRP laminates exhibits marked anisotropy. (2) The laminate configurations considerably affect the creep behavior of the laminates.
A note on the low-frequency noise reduction of cylindrical capsules (L).
Ungar, Eric E
2006-12-01
The noise reductions provided by capsules consisting of uniform cylindrical shells whose two ends are closed off by like circular plates are analyzed for the low-frequency regime in which a capsule acts quasi-statically, much like a pressure vessel. The change in the confined volume is determined from the structural deflections produced by a net pressure difference, taking account of the interactions of the shell and end plates. Expressions for the noise reduction of a single capsule and of two nested capsules are derived. Some insights into the noise reduction effects of interaction between the shell and end plates are discussed, as are the contributions of these components.
Cylindrical vector beams of light from an electrically excited plasmonic lens
Cao, Shuiyan Le Moal, Eric; Boer-Duchemin, Elizabeth; Dujardin, Gérald; Drezet, Aurélien; Huant, Serge
2014-09-15
The production of cylindrical vector beams from a low-energy, electric, microscale light source is demonstrated both experimentally and theoretically. This is achieved by combining a “plasmonic lens” with the ability to locally and electrically excite propagating surface plasmons on gold films. The plasmonic lens consists of concentric circular subwavelength slits that are etched in a thick gold film. The local excitation arises from the inelastic tunneling of electrons from the tip of a scanning tunneling microscope. We report on the emission of radially polarized beams with an angular divergence of less than ±4°.
1983-10-01
following basic equations can be deduced for orthotropic circular cylindrical shells. Let a be the radius of the midsurface of the shell, x, y, z the...axial, circumferential and radial coordinates and a, a the dimensionless midsurface coordinates along lines of curvatures (a - , a - . The threea a...8217The components of strain at an arbitrary point of the shell are related to the midsurface displacements by [8,15,16] e ( 1 v , 3 2w e a a a ,2)- 0 a
Beam Rounders for Circular Colliders
A. Burov; S. Nagaitsev; Ya. Derbenev
2001-07-01
By means of linear optics, an arbitrary uncoupled beam can be locally transformed into a round (rotation-invariant) state and then back. This provides an efficient way to round beams in the interaction region of circular colliders.
Beam rounders for circular colliders
A. Burov and S. Nagaitsev
2002-12-10
By means of linear optics, an arbitrary uncoupled beam can be locally transformed into a round (rotation-invariant) state and then back. This provides an efficient way to round beams in the interaction region of circular colliders.
Beach vortices near circular topography
NASA Astrophysics Data System (ADS)
Hinds, A. K.; Johnson, E. R.; McDonald, N. R.
2016-10-01
Finite-area monopolar vortices which propagate around topography without change in shape are computed for circular seamounts and wells including the limiting cases of each: islands and infinitely deep wells. The time-dependent behaviour of vortex pairs propagating toward circular topography is also examined. Trajectories of point-vortex pairs exterior to the topography are found and compared to trajectories of vortex patches computed using contour dynamics.
NASA Technical Reports Server (NTRS)
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.
NASA Astrophysics Data System (ADS)
Zitouni, Gley
1992-09-01
The propagation and stability of converging cylindrical shocks produced in an annular shock tube equipped with a three increment area contraction were investigated for various cylindrical chamber widths and two annular shock Mach numbers of 1.26 and 1.44. The method of characteristics, integrated using the Hartree scheme, was employed to determine the shock Mach number and pressure-time variations in the cylindrical chamber. These numerical values were verified experimentally by employing a set of piezoelectric pressure transducers placed at five different locations. In narrow cylindrical chambers, a new test section was used to determine the boundary layer effect on the shock strength. For a cylindrical chamber width of 2.5 mm, experimental results were found to be in excellent agreement with the inviscid numerical solution. For smaller widths, an empirical equation of the shock Mach number variation was developed. Stability of the converging shocks was examined from the series of spark shadowgraphs taken near the geometric center.
The Dizzying Depths of the Cylindrical Mirror
NASA Astrophysics Data System (ADS)
DeWeerd, Alan J.; Hill, S. Eric
2005-02-01
A typical introduction to geometrical optics treats plane and spherical mirrors. At first glance, it may be surprising that texts seldom mention the cylindrical mirror, except for the occasional reference to use in fun houses and to viewing anamorphic art.1,2 However, even a cursory treatment reveals its complexity. Holzberlein used an extended object to qualitatively illustrate that images are produced both before and behind a concave cylindrical mirror.3 He also speculated on how this extreme astigmatism results in an observer's dizziness. By considering a simple point object, we make a more detailed analysis of the cylindrical mirror and the dizziness it induces. First, we illustrate how rays from a point object reflect to form not one point image but two line images. Next, we describe how an observer perceives a likeness of the object. Finally, we suggest how confusing depth cues induce dizziness. Although we focus on the concave cylindrical mirror, the discussion is easy to generalize to the convex cylindrical mirror.
The structural response of unsymmetrically laminated composite cylinders
NASA Technical Reports Server (NTRS)
Butler, T. A.; Hyer, M. W.
1989-01-01
The responses of an unsymmetrically laminated fiber-reinforced composite cylinder to an axial compressive load, a torsional load, and the temperature change associated with cooling from the processing temperature to the service temperature are investigated. These problems are considered axisymmetric and the response is studied in the context of linear elastic material behavior and geometrically linear kinematics. Four different laminates are studied: a general unsymmetric laminate; two unsymmetric but more conventional laminates; and a conventional quasi-isotropic symmetric laminate. The responses based on closed-form solutions for different boundary conditions are computed and studied in detail. Particular emphasis is directed at understanding the influence of elastic couplings in the laminates. The influence of coupling decreased from a large effect in the general unsymmetric laminate, to practically no effect in the quasi-isotropic laminate. For example, the torsional loading of the general unsymmetric laminate resulted in a radial displacement. The temperature change also caused a significant radial displacement to occur near the ends of the cylinder. On the other hand, the more conventional unsymmetric laminate and the quasi-isotropic cylinder did not deform radially when subjected to a torsional load. From the results obtained, it is clear the degree of elastic coupling can be controlled and indeed designed into a cylinder, the degree and character of the coupling being dictated by the application.
Micromechanical Modeling of Impact Damage Mechanisms in Unidirectional Composite Laminates
NASA Astrophysics Data System (ADS)
Meng, Qinghua; Wang, Zhenqing
2016-12-01
Composite laminates are susceptible to the transverse impact loads resulting in significant damage such as matrix cracking, fiber breakage and delamination. In this paper, a micromechanical model is developed to predict the impact damage of composite laminates based on microstructure and various failure models of laminates. The fiber and matrix are represented by the isotropic and elastic-plastic solid, and their impact failure behaviors are modeled based on shear damage model. The delaminaton failure is modeling by the interface element controlled by cohesive damage model. Impact damage mechanisms of laminate are analyzed by using the micromechanical model proposed. In addition, the effects of impact energy and laminated type on impact damage behavior of laminates are investigated. Due to the damage of the surrounding matrix near the impact point caused by the fiber deformation, the surface damage area of laminate is larger than the area of impact projectile. The shape of the damage area is roughly rectangle or elliptical with the major axis extending parallel to the fiber direction in the surface layer of laminate. The alternating laminated type with two fiber directions is more propitious to improve the impact resistance of laminates.
Verification and Validation of Carbon-Fiber Laminate Low Velocity Impact Simulations.
English, Shawn Allen; Nelson, Stacy Michelle; Briggs, Timothy; Brown, Arthur A.
2014-10-01
Presented is a model verification and validation effort using low - velocity impact (LVI) of carbon fiber reinforced polymer laminate experiments. A flat cylindrical indenter impacts the laminate with enough energy to produce delamination, matrix cracks and fiber breaks. Included in the experimental efforts are ultrasonic scans of the damage for qualitative validation of the models. However, the primary quantitative metrics of validation are the force time history measured through the instrumented indenter and initial and final velocities. The simulations, whi ch are run on Sandia's Sierra finite element codes , consist of all physics and material parameters of importance as determined by a sensitivity analysis conducted on the LVI simulation. A novel orthotropic damage and failure constitutive model that is cap able of predicting progressive composite damage and failure is described in detail and material properties are measured, estimated from micromechanics or optimized through calibration. A thorough verification and calibration to the accompanying experiment s are presented. Specia l emphasis is given to the four - point bend experiment. For all simulations of interest, the mesh and material behavior is verified through extensive convergence studies. An ensemble of simulations incorporating model parameter unc ertainties is used to predict a response distribution which is then compared to experimental output. The result is a quantifiable confidence in material characterization and model physics when simulating this phenomenon in structures of interest.
An improved plate theory of order (1,2) for thick composite laminates
NASA Technical Reports Server (NTRS)
Tessler, A.
1992-01-01
A new (1,2)-order theory is proposed for the linear elasto-static analysis of laminated composite plates. The basic assumptions are those concerning the distribution through the laminate thickness of the displacements, transverse shear strains and the transverse normal stress, with these quantities regarded as some weighted averages of their exact elasticity theory representations. The displacement expansions are linear for the inplane components and quadratic for the transverse component, whereas the transverse shear strains and transverse normal stress are respectively quadratic and cubic through the thickness. The main distinguishing feature of the theory is that all strain and stress components are expressed in terms of the assumed displacements prior to the application of a variational principle. This is accomplished by an a priori least-square compatibility requirement for the transverse strains and by requiring exact stress boundary conditions at the top and bottom plate surfaces. Equations of equilibrium and associated Poisson boundary conditions are derived from the virtual work principle. It is shown that the theory is particularly suited for finite element discretization as it requires simple C(sup 0)- and C(sup -1)-continuous displacement interpolation fields. Analytic solutions for the problem of cylindrical bending are derived and compared with the exact elasticity solutions and those of our earlier (1,2)-order theory based on the assumed displacements and transverse strains.
Investigating Delamination Migration in Composite Tape Laminates
NASA Technical Reports Server (NTRS)
Ratcliffe, James G.; DeCarvalho, Nelson V.
2014-01-01
A modification to a recently developed test specimen designed to investigate migration of a delamination between neighboring ply interfaces in tape laminates is presented. The specimen is a cross-ply laminated beam consisting of 40 plies with a polytetrafluoroethylene insert spanning part way along its length. The insert is located between a lower 0-degree ply (specimen length direction) and a stack of four 90-degree plies (specimen width direction). The modification involved a stacking sequence that promotes stable delamination growth prior to migration, and included a relocation of the insert from the specimen midplane to the interface between plies 14 and 15. Specimens were clamped at both ends onto a rigid baseplate and loaded on their upper surface via a piano hinge assembly, resulting in a predominantly flexural loading condition. Tests were conducted with the load-application point positioned at various locations along a specimen's span. This position affected the sequence of damage events during a test.
High energy impact on woven laminates
NASA Astrophysics Data System (ADS)
López-Puente, J.; Zaera, R.; Navarro, C.
2003-09-01
The influence of high velocity impacts on CFRPs was studied by launching Spherical steel masses, at velocities from 60 m/s to 550 m/s, against carbon fiber/epoxy woven laminates. The extension of the damage induced in the laminate was measured by C-Scan. Finite element numerical simulation of the impact test used a failure model based on the Chang-Chang model. A comparison was made of the damaged areas resulting from non-destructive inspection of the specimens and those predicted by numerical simulation. To conclue the analysis, an analytical model developed by Cantwell-Morton was used to calculate the residual velocity of the projectile after perforation. The residual velocities predicted by numerical and by analytical models, were also compared.
Fabrication of CFRP/Al Active Laminates
NASA Astrophysics Data System (ADS)
Asanuma, Hiroshi; Haga, Osamu; Ohira, Junichiro; Takemoto, Kyosuke; Imori, Masataka
This paper describes fabrication and evaluation of the active laminate. It was made by hot-pressing of an aluminum plate as a high CTE material, a unidirectional CFRP prepreg as a low CTE material and an electric resistance heater, a KFRP prepreg as a low CTE material and an insulator between them, and copper foils as electrodes. In this study, fabricating conditions and performances such as curvature change and output force were examined. Under optimized fabricating conditions, it became clear that 1) the curvature of the active laminate linearly changes as a function of temperature, between room temperature and its hot pressing temperature without hysteresis by electric resistance heating of carbon fiber in the CFRP layer and cooling, and 2) the output force against a fixed punch almost linearly increases with increasing temperature during heating from 313K up to around the glass transition temperature of the epoxy matrix.
Current pulse effects on cylindrical damage experiments
Kaul, Ann M; Rousculp, Christopher L
2009-01-01
A series of joint experiments between LANL and VNIIEF use a VNIIEF-designed helical generator to provide currents for driving a LANL-designed cylindrical spallation experimental load. Under proper driving conditions, a cylindrical configuration allows for a natural recollection of the damaged material. In addition, the damaged material is able to come to a complete stop due to its strength, avoiding application of further forces. Thus far, experiments have provided data about failure initiation of a well-characterized material (aluminum) in a cylindrical geometry, behavior of material recollected after damage from pressures in the damage initiation regime, and behavior of material recollected after complete failure. In addition to post-shot collection of the damaged target material for subsequent metallographic analysis, dynamic in-situ experimental diagnostics include velocimetry and transverse radial radiography. This paper will focus on the effects of tailoring the driving current pulse to obtain the desired data.
Laser diode assembly including a cylindrical lens
Snyder, James J.; Reichert, Patrick
1992-01-01
The present invention provides a diffraction limited, high numerical aperture (fast) cylindrical microlens. The method for making the microlens is adaptable to produce a cylindrical lens that has almost any shape on its optical surfaces. The cylindrical lens may have a shape, such as elliptical or hyperbolic, designed to transform some particular given input light distribution into some desired output light distribution. In the method, the desired shape is first formed in a glass preform. Then, the preform is heated to the minimum drawing temperature and a fiber is drawn from it. The cross-sectional shape of the fiber bears a direct relation to the shape of the preform from which it was drawn. During the drawing process, the surfaces become optically smooth due to fire polishing.
Laser diode assembly including a cylindrical lens
Snyder, J.J.; Reichert, P.
1992-01-14
The present invention provides a diffraction limited, high numerical aperture (fast) cylindrical microlens. The method for making the microlens is adaptable to produce a cylindrical lens that has almost any shape on its optical surfaces. The cylindrical lens may have a shape, such as elliptical or hyperbolic, designed to transform some particular given input light distribution into some desired output light distribution. In the method, the desired shape is first formed in a glass preform. Then, the preform is heated to the minimum drawing temperature and a fiber is drawn from it. The cross-sectional shape of the fiber bears a direct relation to the shape of the preform from which it was drawn. During the drawing process, the surfaces become optically smooth due to fire polishing. 11 figs.
Cylindrical polarization symmetry for nondestructive nanocharacterization
NASA Astrophysics Data System (ADS)
Zhan, Qiwen
2003-07-01
Recently there is an increasing interest in laser beams with radial symmetry in polarization. Due to the cylindrical symmetry in polarization, these beams have unique focusing properties, which may find wide applications in a variety of nanometer scale applications, including high-resolution metrology, high-density data storage, and multi-functional optical microtool. In this paper, simple method of generating cylindrically polarized beams is presented and their potential applications to nondestructive nano-characterization are discussed. A high resolution surface plasmon microscope and a surface plasmon enhanced apertureless near-field scanning optical microscope are proposed. An automatic scanning microellipsometer that uses the cylindrical symmetry to enhance the signal-to-noise-ratio in high-spatial-resolution ellipsometric measurement will also be presented.
Thermomechanical fracture on pressurized cylindrical vessels
NASA Astrophysics Data System (ADS)
Tzou, Robert D. Y.; Chiu, Kwong S.; Beraun, Jorge E.; Chen, Jinn Kuen
1998-09-01
This work studies the rapid fracture developed on the surface of a pressurized cylindrical vessel when heated by an intensified energy source. The primary concerns are the interactions between the rapid thermal expansion and the internal pressure that exerts on the interior surface. From a mechanical point of view, the thermal loading tends to develop a crack along the circumferential direction of the cylindrical vessel. The excessive internal pressure established within the cylindrical vessel, on the other hand, tends to develop a crack in the axial direction. Combination of the two mechanisms results in a capricious pattern of rapid fracture that needs to be fully understood in thermal processing. Special features in this work include the dynamics plasticity induced by the combined thermomechanical loading at short times, as well as the temperature-dependent thermomechanical properties that evolve in the load-time history.
Dewetting processes in a cylindrical geometry.
Callegari, G; Calvo, A; Hulin, J P
2005-03-01
Dewetting of liquid films of water-glycerol solutions of different viscosities has been studied experimentally in PVC cylindrical tubes. In contrast with plane surfaces, the dewetting capillary number Ca(vd) increases with the film thickness ho over a large part of the experimental range and follows a same global trend independent of viscosity as a function of ho. This increase is only partly explained by variations of the capillary driving force predicted in a recent theoretical work for a cylindrical geometry. An additional explanation is suggested, based on different spatial distributions of the viscous dissipation in the dewetting bump in the planar and cylindrical geometries. This mechanism is investigated for films of different thicknesses in a numerical model assuming a polynomial variation of the liquid thickness with distance in the bump region.
Design of tunable cylindrical dielectric nanoantenna
NASA Astrophysics Data System (ADS)
Devi, Inder; Reena; Kalra, Yogita; Sinha, R. K.
2016-09-01
A tunable cylindrical all dielectric optical nanoantenna has been proposed. A silicon nanocylinder of radius 60 nm and height 150 nm has been considered. The azimuthally symmetric, complete forward scattering at first Kerker's condition and backward scattering with minimum forward scattering at second generalized Kerker's condition in near infra-red region has been observed for the proposed design which makes silicon nanocylinder a promising candidate for optical nanoantenna applications. The effect of the dimensions of the dielectric nanocylinder on the scattering properties of the cylindrical nanoantenna has been analyzed using finite element method. We have analyzed that the variation in diameter of nanocylinder has great influence on the strength of interference of electric and magnetic dipolar resonances. Further, we have observed tuning ability of the cylindrical nanoantenna with respect to the variation in its radius.
Residual stresses in polymer matrix composite laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.
1976-01-01
Residual stresses in composites are induced during fabrication and by environmental exposure. The theory formulated can describe the shrinkage commonly observed after a thermal expansion test. Comparison between the analysis and experimental data for laminates of various material systems indicates that the residual stress-free temperature can be lower than the curing temperature, depending on the curing process. Effects of residual stresses on ply failure including the acoustic emission characteristics are discussed.
Laminated grid and web magnetic cores
Sefko, John; Pavlik, Norman M.
1984-01-01
A laminated magnetic core characterized by an electromagnetic core having core legs which comprise elongated apertures and edge notches disposed transversely to the longitudinal axis of the legs, such as high reluctance cores with linear magnetization characteristics for high voltage shunt reactors. In one embodiment the apertures include compact bodies of microlaminations for more flexibility and control in adjusting permeability and/or core reluctance.
Digital holographic nondestructive testing of laminate composite
NASA Astrophysics Data System (ADS)
Karray, Mayssa; Christophe, Poilane; Gargouri, Mohamed; Picart, Pascal
2016-09-01
Optical digital holographic techniques can be used for nondestructive testing of materials. Digital holographic nondestructive testing essentially measures deformations on the surface of the object. However, there is sufficient sensitivity to detect subsurface and internal defects in metallic and composite specimens. We investigate and discuss the vibration analysis of laminated composite glass-epoxy using time averaging in digital Fresnel holography to visualize the modes of vibration and to test the integrity of the structures of studied materials.
Process Yields Strong, Void-Free Laminates
NASA Technical Reports Server (NTRS)
Bryant, L. E.; Covington, E. W., III; Dale, W. J.; Hall, E. T., Jr; Justice, J. E.; Taylor, E. C.; Wilson, M. L.
1983-01-01
Need for lightweight materials as structural components for future space transportation systems stimulated development of systematic method for manufacturing a polyimide/graphite composite. Laminates manufactured by process are void-free, exhibit excellent thermo-oxidative stability up to 315 degrees C (600 degrees F) and are 40 percent lighter than aluminum. Process is precise, repeatable, and ideally suited for researchers and small-lot producers of composite materials.
Delamination stresses in semicircular laminated composite bars
NASA Technical Reports Server (NTRS)
Ko, William L.
1988-01-01
Using anisotropic elasticity theory, delamination stresses in a semicircular laminated composite curved bar subjected to end forces and end moments were calculated, and their radial locations determined. A family of design curves was presented, showing variation of the intensity of delamination stresses and their radial locations with different geometry and different degrees of anisotropy of the curved bar. The effect of anisotropy on the location of peak delamination stress was found to be small.
Modeling Composite Laminate Crushing for Crash Analysis
NASA Technical Reports Server (NTRS)
Fleming, David C.; Jones, Lisa (Technical Monitor)
2002-01-01
Crash modeling of composite structures remains limited in application and has not been effectively demonstrated as a predictive tool. While the global response of composite structures may be well modeled, when composite structures act as energy-absorbing members through direct laminate crushing the modeling accuracy is greatly reduced. The most efficient composite energy absorbing structures, in terms of energy absorbed per unit mass, are those that absorb energy through a complex progressive crushing response in which fiber and matrix fractures on a small scale dominate the behavior. Such failure modes simultaneously include delamination of plies, failure of the matrix to produce fiber bundles, and subsequent failure of fiber bundles either in bending or in shear. In addition, the response may include the significant action of friction, both internally (between delaminated plies or fiber bundles) or externally (between the laminate and the crushing surface). A figure shows the crushing damage observed in a fiberglass composite tube specimen, illustrating the complexity of the response. To achieve a finite element model of such complex behavior is an extremely challenging problem. A practical crushing model based on detailed modeling of the physical mechanisms of crushing behavior is not expected in the foreseeable future. The present research describes attempts to model composite crushing behavior using a novel hybrid modeling procedure. Experimental testing is done is support of the modeling efforts, and a test specimen is developed to provide data for validating laminate crushing models.
Eastern Guaymas Basin: laminated but not anoxic
NASA Astrophysics Data System (ADS)
Cheshire, H.; Thurow, J. W.
2009-12-01
Site MD02-2513, eastern Guaymas Basin, challenges the accepted hypothesis about the circumstances and sequence of events leading to the occurrence of annually laminated (varved) sediment. By convention, under a climate regime of strong seasonal contrast, high productivity in a restricted basin enhances a preformed OMZ and inhibits bioturbation, resulting in the preservation of varves. The comparison of the high-resolution log of the sediment fabric and continuous XRF data from Core MD02-2513 reveal that laminated intervals over the last ~90 ka BP are characterised by an increase of oxygenation above background levels and are accompanied by lows of terrestrial and biogenic flux indicating that the preserving factor is rapid burial rather than high sedimentation rate (ie high seasonality and low rainfall). Intervals of diffuse/discontinuous laminations are times of high terrestrial and biogenic flux indicating comparatively low seasonality and high rainfall. Brief periods of relatively high anoxic conditions occur within homogeneous intervals and are accompanied by exceptionally high biogenic flux, indicating there was no seasonal contrast. Long homogenous intervals occur during the last glacial due to lowered sea level and the consequent removal of the upwelling cell offshore. The changes in Guaymas Basin seasonality are most probably caused by alterations to the migration pattern of the North Pacific Subtropical High due to the growth and decay of the North American ice sheets.
Superconductivity in Ca-doped graphene laminates
Chapman, J.; Su, Y.; Howard, C. A.; Kundys, D.; Grigorenko, A. N.; Guinea, F.; Geim, A. K.; Grigorieva, I. V.; Nair, R. R.
2016-01-01
Despite graphene’s long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc’s strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp. PMID:26979564
Superconductivity in Ca-doped graphene laminates.
Chapman, J; Su, Y; Howard, C A; Kundys, D; Grigorenko, A N; Guinea, F; Geim, A K; Grigorieva, I V; Nair, R R
2016-03-16
Despite graphene's long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc's strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.
Vascular perfusion in horses with chronic laminitis.
Hood, D M; Grosenbaugh, D A; Slater, M R
1994-05-01
Vascular perfusion casts were used to define and characterise the macroscopic perfusion defects present in the distal digit of 11 horses affected by chronic laminitis. Five clinically normal horses were used as controls. Based on clinical history and clinical status, horses with chronic laminitis were classified as being potentially treatable or clinically refractory. Eleven macroscopic vascular defects were noted in the casts from horses with laminitis. Four types of lesions were identified in the submural laminar circulation, 3 in the coronary bed and 4 were associated with the solar circulation. Multiple defects were present and a definite trend was noted for the perfusion defects to be worse in the casts of clinically refractory subjects than in those considered treatable. This information suggests that evaluation of circulatory status should add significantly to the ability to separate treatable from clinically refractory patients. Results also indicated that ventral displacement of the third phalanx (sinkers) and compression of the solar vasculature are more prevalent than is presently thought.
Laminate articles on biaxially textured metal substrates
Beach, David B.; Morrell, Jonathan S.; Paranthaman, Mariappan; Chirayil, Thomas; Specht, Eliot D.; Goyal, Amit
2003-12-16
A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0
Superconductivity in Ca-doped graphene laminates
NASA Astrophysics Data System (ADS)
Chapman, J.; Su, Y.; Howard, C. A.; Kundys, D.; Grigorenko, A. N.; Guinea, F.; Geim, A. K.; Grigorieva, I. V.; Nair, R. R.
2016-03-01
Despite graphene’s long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures (Tc) between ≈4 and ≈6 K, with Tc’s strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.
The tail domain of lamin B1 is more strongly modulated by divalent cations than lamin A
Ganesh, Sairaam; Qin, Zhao; Spagnol, Stephen T; Biegler, Matthew T; Coffey, Kelli A; Kalinowski, Agnieszka; Buehler, Markus J; Dahl, Kris Noel
2015-01-01
The nucleoskeleton contains mainly nuclear intermediate filaments made of lamin proteins. Lamins provide nuclear structure and also play a role in various nuclear processes including signal transduction, transcription regulation and chromatin organization. The disparate functions of lamins may be related to the intrinsic disorder of the tail domains, which allows for altered and promiscuous binding. Here, we show modulation of lamin tail domain structures in the presence of divalent cations. We utilize changes in fluorescence of tryptophan residues within the Ig-fold flanked by disordered regions to experimentally measure protein thermodynamics. Using spectroscopy experiments and molecular dynamics simulations, we show that the tail domain of lamin B1 shows enhanced association with both Ca2+ and Mg2+ compared to the tail domain of lamin A. Binding curves show a similar KD between protein and ion (250–300 μM) for both proteins with both ions. However, we observe a maximum binding of ions to lamin B1 tail domain which is 2–3 times greater than that for lamin A tail domain by both experiment and simulation. Using simulations, we show that divalent ion association alters the Ig-fold by pinning flanking regions. With cells in culture, we observe altered lamin B1 organization in the presence of excess Mg2+ more so than for lamin A. We suggest that the differential sensitivity to divalent cations contributes to the vastly different functionalities and binding of the 2 proteins. PMID:25807068
Karikoski, N P; Horn, I; McGowan, T W; McGowan, C M
2011-10-01
Endocrinopathic causes of laminitis may be a common underlying causative pathogenesis in first-opinion or field cases presenting with laminitis, as opposed to laminitis produced in inflammatory research models. This study aimed to determine whether evidence of an underlying endocrinopathy was present in horses presented for laminitis to a first-opinion/referral veterinary teaching hospital. A second aim was to compare the signalment of horses and ponies with laminitis with the equine hospital population during the same period. All horses presenting for laminitis at Helsinki University Equine Teaching Hospital, Finland, over a 16-month period were examined for an underlying endocrinopathy. Horses presenting for laminitis were compared with the hospitalized population over the same period. There were 36 horses presented for laminitis, and evidence of endocrinopathy was present in 89%. Of the horses showing an underlying endocrinopathy, one-third had a diagnosis of pituitary pars intermedia dysfunction, and two-thirds showed basal hyperinsulinemia indicative of insulin resistance, without evidence of hirsutism. Phenotypic indicators of obesity were present in 95% of horses with basal hyperinsulinemia without hirsutism. Compared with the hospital population during the same period, horses with laminitis associated with an underlying endocrinopathy were significantly older and more likely to be pony breeds. Our data support that endocrine testing should be performed on all cases of laminitis that do not have a clear inflammatory or gastrointestinal origin.
Cylindrical roller bearings with profiled contacting surfaces
NASA Astrophysics Data System (ADS)
Creţu, S. S.
2017-02-01
An initial loading of cylindrical roller bearings in the elastic-plastic domain was performed to induce elastic shakedown phenomena able to change the basic profiles of both, rollers and raceways, which endorses a different value for the basic reference rating life. Fatigue life tests carried out on four lots of NJ206 cylindrical roller bearings revealed much higher values of L10 and Lm criteria for the bearings lots which experienced a suitable initial loading operation in the elastic-plastic domain. The reference rating lives, evaluated by using the lamina technique, confirmed the superiority of bearings lots which undergone an appropriate primary loading in the elastic-plastic domain.
NASA Technical Reports Server (NTRS)
Guynn, E. Gail; Bradley, Walter L.
1989-01-01
An understanding was developed of the factors that determine the semi-circular edge-notched compressive strength and the associated failure mode(s) were identified of thermoplastic composite laminates with multidirectional stacking sequences. The experimental observations and the detailed literature review suggest at least four factors that affected the determination of the strain levels at which fiber microbuckling initiates and thus, partially control the composite's compression strength. The dependent variables studied are the compressive strength of a reduced gage section compression specimen and the compression strength of a compression specimen with two semi-circular edge notches (no opposite free edges) centered along the gage section. In this research, specimens containing two semi-circular edge notches (no opposite free edges) were loaded in compression at a relatively slow rate to provide more stable development of fiber microbuckling damage. The results indicate that the local constraints (free surfaces, supporting ply orientation, and resin-rich regions) significantly affect the strain level for the initiation of in-plane fiber microbuckling. Preliminary results at an elevated temperature, 77 C, showed the shear stress yield strength of the resin was reduced and consequently, the resistance to fiber microbuckling was also reduced. The finite element analysis of the perfectly straight fiber problem indicates that the free surface effect causes a 10 percent reduction in the critical buckling strain. However, the experimentally measured reduction for fibers with an initial fiber curvature, was 35 percent.
Homogenized Creep Behavior of CFRP Laminates at High Temperature
NASA Astrophysics Data System (ADS)
Fukuta, Y.; Matsuda, T.; Kawai, M.
In this study, creep behavior of a CFRP laminate subjected to a constant stress is analyzed based on the time-dependent homogenization theory developed by the present authors. The laminate is a unidirectional carbon fiber/epoxy laminate T800H/#3631 manufactured by Toray Industries, Inc. Two kinds of creep analyses are performed. First, 45° off-axis creep deformation of the laminate at high temperature (100°C) is analyzed with three kinds of creep stress levels, respectively. It is shown that the present theory accurately predicts macroscopic creep behavior of the unidirectional CFRP laminate observed in experiments. Then, high temperature creep deformations at a constant creep stress are simulated with seven kinds of off-axis angles, i.e., θ = 0°, 10°, 30°, 45°, 60°, 75°, 90°. It is shown that the laminate has marked in-plane anisotropy with respect to the creep behavior.
Waved core lamination techniques on large and bulb hydroelectric machinery
Lehoczky, K.N. )
1988-12-01
Stator core lamination of large hydroelectric generators and motors and especially bulb type machines are often exposed to heat expansion forces causing severe damages. The temperature difference between the warm core lamination and the relatively colder stator frame, creates both radial and tangential stresses in these components. The consequence of these stresses depends on the axial prestressing of lamination and the internal design of the core. An overriding of some critical combination of these stresses may result in buckling of lamination, fracture of core tensioning and supporting components or cracks in the stator frame. The present waved lamination technique reduces the tangential and radial spring constant of core and prevents the damages. The research performed through theoretical and experimental methods, indicates a fundamental change in the behavior of core. The waved lamination was successfully used in a large number of machines, providing the reliability and wide application range of the method.
Phosphorylation of lamins determine their structural properties and signaling functions
Torvaldson, Elin; Kochin, Vitaly; Eriksson, John E
2015-01-01
Lamin A/C is part of the nuclear lamina, a meshwork of intermediate filaments underlying the inner nuclear membrane. The lamin network is anchoring a complex set of structural and linker proteins and is either directly or through partner proteins also associated or interacting with a number of signaling protein and transcription factors. During mitosis the nuclear lamina is dissociated by well established phosphorylation- dependent mechanisms. A-type lamins are, however, also phosphorylated during interphase. A recent study identified 20 interphase phosphorylation sites on lamin A/C and explored their functions related to lamin dynamics; movements, localization and solubility. Here we discuss these findings in the light of lamin functions in health and disease. PMID:25793944
Broken nuclei--lamins, nuclear mechanics, and disease.
Davidson, Patricia M; Lammerding, Jan
2014-04-01
Mutations in lamins, which are ubiquitous nuclear intermediate filaments, lead to a variety of disorders including muscular dystrophy and dilated cardiomyopathy. Lamins provide nuclear stability, help connect the nucleus to the cytoskeleton, and can modulate chromatin organization and gene expression. Nonetheless, the diverse functions of lamins remain incompletely understood. We focus here on the role of lamins on nuclear mechanics and their involvement in human diseases. Recent findings suggest that lamin mutations can decrease nuclear stability, increase nuclear fragility, and disturb mechanotransduction signaling, possibly explaining the muscle-specific defects in many laminopathies. At the same time, altered lamin expression has been reported in many cancers, where the resulting increased nuclear deformability could enhance the ability of cells to transit tight interstitial spaces, thereby promoting metastasis.
Circular codes, symmetries and transformations.
Fimmel, Elena; Giannerini, Simone; Gonzalez, Diego Luis; Strüngmann, Lutz
2015-06-01
Circular codes, putative remnants of primeval comma-free codes, have gained considerable attention in the last years. In fact they represent a second kind of genetic code potentially involved in detecting and maintaining the normal reading frame in protein coding sequences. The discovering of an universal code across species suggested many theoretical and experimental questions. However, there is a key aspect that relates circular codes to symmetries and transformations that remains to a large extent unexplored. In this article we aim at addressing the issue by studying the symmetries and transformations that connect different circular codes. The main result is that the class of 216 C3 maximal self-complementary codes can be partitioned into 27 equivalence classes defined by a particular set of transformations. We show that such transformations can be put in a group theoretic framework with an intuitive geometric interpretation. More general mathematical results about symmetry transformations which are valid for any kind of circular codes are also presented. Our results pave the way to the study of the biological consequences of the mathematical structure behind circular codes and contribute to shed light on the evolutionary steps that led to the observed symmetries of present codes.
Optoacoustic sensing for target detection inside cylindrical catheters
NASA Astrophysics Data System (ADS)
Tavakoli, Behnoosh; Guo, Xiaoyu; Taylor, Russell H.; Kang, Jin U.; Boctor, Emad M.
2014-03-01
Optoacoustic sensing is a hybrid technique that combines the advantages of high sensing depth of ultrasound with contrast of optical absorption. In this study a miniature optoacoustic probe that can characterize the target properties located at the distal end of a catheter is investigated. The probe includes an optical fiber to illuminate the target with the pulsed laser light and a hydrophone to detect the generated optoacoustic signal. The probe is designed for the forwardsensing and therefore the acoustic signal propagates along the tube before being detected. Due to the circular geometry, the waves inside the tube are highly complex. A three dimensional numerical simulation is performed to model the optoacoustic wave generation and propagation inside the water filled cylindrical tubes. The effect of the boundary condition, tube diameter and target size on the detected signal is systematically evaluated. A prototype of the probe is made and tested for detecting an absorbing target inside a 2mm diameter tube submerged in water. The preliminary experimental results corresponding to the simulation is acquired. Although many different medical applications for this miniature probe may exist, our main focus is on detecting the occlusion inside the ventricular shunts. These catheters are used to divert the excess cerebrospinal fluid to the absorption site and regulate inter cranial pressure of hydrocephalous patients. Unfortunately the malfunction rate of these catheters due to blockage is very high. This sensing tool could locate the occluding tissue non-invasively and can potentially characterize the occlusion composites by scanning at different wavelengths of the light.
A cylindrical standing wave ultrasonic motor using bending vibration transducer.
Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun
2011-07-01
A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms).
Thermal Behavior of Cylindrical Buckling Restrained Braces at Elevated Temperatures
Talebi, Elnaz; Tahir, Mahmood Md.; Yasreen, Airil
2014-01-01
The primary focus of this investigation was to analyze sequentially coupled nonlinear thermal stress, using a three-dimensional model. It was meant to shed light on the behavior of Buckling Restraint Brace (BRB) elements with circular cross section, at elevated temperature. Such bracing systems were comprised of a cylindrical steel core encased in a strong concrete-filled steel hollow casing. A debonding agent was rubbed on the core's surface to avoid shear stress transition to the restraining system. The numerical model was verified by the analytical solutions developed by the other researchers. Performance of BRB system under seismic loading at ambient temperature has been well documented. However, its performance in case of fire has yet to be explored. This study showed that the failure of brace may be attributed to material strength reduction and high compressive forces, both due to temperature rise. Furthermore, limiting temperatures in the linear behavior of steel casing and concrete in BRB element for both numerical and analytical simulations were about 196°C and 225°C, respectively. Finally it is concluded that the performance of BRB at elevated temperatures was the same as that seen at room temperature; that is, the steel core yields prior to the restraining system. PMID:24526915
Processing and mechanical characterization of alumina laminates
NASA Astrophysics Data System (ADS)
Montgomery, John K.
2002-08-01
Single-phase ceramics that combine property gradients or steps in monolithic bodies are sought as alternatives to ceramic composites made of dissimilar materials. This work describes novel processing methods to produce stepped-density (or laminated) alumina single-phase bodies that maintain their mechanical integrity. One arrangement consists of a stiff, dense bulk material with a thin, flaw tolerant, porous exterior layer. Another configuration consists of a lightweight, low-density bulk material with a thin, hard, wear resistant exterior layer. Alumina laminates with strong interfaces have been successfully produced in this work using two different direct-casting processes. Gelcasting is a useful near-net shape processing technique that has been combined with several techniques, such as reaction bonding of aluminum oxide and the use of starch as a fugative filler, to successfully produced stepped-density alumina laminates. The other direct casting process that has been developed in this work is thermoreversible gelcasting (TRG). This is a reversible gelation process that has been used to produce near-net shape dense ceramic bodies. Also, individual layers can be stacked together and heated to produce laminates. Bilayer laminate samples were produced with varied thickness of porous and dense layers. It was shown that due to the difference in modulus and hardness, transverse cracking is found upon Hertzian contact when the dense layer is on the exterior. In the opposite arrangement, compacted damage zones formed in the porous material and no damage occurred in the underlying dense layer. Flaw tolerant behavior of the porous exterior/dense underlayer was examined by measuring biaxial strength as a function of Vickers indentation load. It was found that the thinnest layer of porous material results in the greatest flaw tolerance. Also, higher strength was exhibited at large indentation loads when compared to dense monoliths. The calculated stresses on the surfaces
Peter, Annette; Khandekar, Shaunak; Deakin, Janine E; Stick, Reimer
2015-11-01
Platypus (Ornithorhynchus anatinus) holds a unique phylogenetic position at the base of the mammalian lineage due to an amalgamation of mammalian and sauropsid-like features. Here we describe the set of four lamin genes for platypus. Lamins are major components of the nuclear lamina, which constitutes a main component of the nucleoskeleton and is involved in a wide range of nuclear functions. Vertebrate evolution was accompanied by an increase in the number of lamin genes from a single gene in their closest relatives, the tunicates and cephalochordates, to four genes in the vertebrate lineage. Of the four genes the LIII gene is characterized by the presence of two alternatively spliced CaaX-encoding exons. In amphibians and fish LIII is the major lamin protein in oocytes and early embryos. The LIII gene is conserved throughout the vertebrate lineage, with the notable exception of marsupials and placental mammals, which have lost the LIII gene. Here we show that platypus has retained an LIII gene, albeit with a significantly altered structure and with a radically different expression pattern. The platypus LIII gene contains only a single CaaX-encoding exon and the head domain together with coil 1a and part of coil1b of the platypus LIII protein is replaced by a novel short non-helical N-terminus. It is expressed exclusively in the testis. These features resemble those of male germ cell-specific lamins in placental mammals, in particular those of lamin C2. Our data suggest (i) that the specific functions of LIII, which it fulfills in all other vertebrates, is no longer required in mammals and (ii) once it had been freed from these functions has undergone structural alterations and has adopted a new functionality in monotremes.
Energy Saving Glass Lamination via Selective Radio-Frequency Heating
Shulman, Holly S.; Allan, Shawn M.
2009-11-11
This Inventions and Innovations program supported the technical and commercial research and development needed to elevate Ceralink's energy saving process for flat glass lamination from bench scale to a self-supporting technology with significant potential for growth. Radio-frequency heating was any un-explored option for laminating glass prior to this program. With significant commercial success through time and energy savings in the wood, paper, and plastics industries, RF heating was found to have significant promise for the energy intensive glass lamination industry. A major technical goal of the program was to demonstrate RF lamination across a wide range of laminate sizes and materials. This was successfully accomplished, dispelling many skeptics' concerns about the abilities of the technology. Ceralink laminated panels up to 2 ft x 3 ft, with four sets processed simultaneously, in a 3 minute cycle. All major categories of interlayer materials were found to work with RF lamination. In addition to laminating glass, other materials including photovoltaic silicon solar cells, light emitting diodes, metallized glass, plastics (acrylic and polycarbonate), and ceramics (alumina) were found compatible with the RF process. This opens up a wide range of commercial opportunities beyond the initially targeted automotive industry. The dramatic energy savings reported for RF lamination at the bench scale were found to be maintained through the scale up of the process. Even at 2 ft x 3 ft panel sizes, energy savings are estimated to be at least 90% compared to autoclaving or vacuum lamination. With targeted promotion through conference presentations, press releases and internet presence, RF lamination has gained significant attention, drawing large audiences at American Ceramic Society meetings. The commercialization success of the project includes the establishment of a revenue-generating business model for providing process development and demonstrations for potential RF
Fracture behavior of thick, laminated graphite/epoxy composites
NASA Technical Reports Server (NTRS)
Harris, C. E.; Morris, D. H.
1984-01-01
The effect of laminate thickness on the fracture behavior of laminated graphite epoxy (T300/5208) composites was studied. The predominantly experimental research program included the study of the 0/+ or - 45/90 sub ns and 0/90 sub ns laminates with thickness of 8, 32, 64, 96 and 120 plies and the 0/+ or - 45 sub ns laminate with thickness of 6, 30, 60, 90 and 120 plies. The research concentrated on the measurement of fracture toughness utilizing the center-cracked tension, compact tension and three point bend specimen configurations. The development of subcritical damage at the crack tip was studied nondestructively using enhanced X-ray radiography and destructively using the laminate deply technique. The test results showed fracture toughness to be a function of laminate thickness. The fracture toughness of the 0 + or - 45/90 sub ns and 0/90 sub ns laminates decreased with increasing thickness and asymptotically approached lower bound values of 30 ksi square root of in. (1043 MPa square root of mm and 25 ksi square root of in (869 MPa square root of mm respectively. In contrast to the other two laminates, the fracture toughness of the 0/+ or - 45 sub ns laminate increased sharply with increasing thickness but reached an upper plateau value of 40 ksi square root of in (1390 MPa square root of mm) at 30 plies. Fracture toughness was independent of crack size for both thin and thick laminates for all three laminate types except for the 0/90 sub 2s laminate which spilt extensively. The center cracked tension, three point bend and compact tension specimens gave comparable results.
Impact Damage Tolerance of a Carbon Fibre Composite Laminate.
1984-05-01
design of composite structures. 8 CONCLUSIONS These carbon fibre/ epoxy resin laminates are susceptible :: low e ;rt., - .. impact damage, especially...ROYAL AIRCRAFT ESTABLISHMENT0 Technical Report 84049 May 1984 GARTEUR/TP-007 IMPACT DAMAGE TOLERANCE OF A CARBON FIBRE COMPOSITE LAMINATE by DTIC G...007 Received for printing 3 May 1984 IMPACT DAMAGE TOLERANCE OF A CARBON FIBRE COMPOSITE LAMINATE by G. Dorey P. Sigety* K. Stellbrink** W. G. J. ’t
Arteriographical and pathological changes in chronic laminitis in dairy cattle.
Boosman, R; Nemeth, F; Gruys, E; Klarenbeek, A
1989-07-01
The arteriographic appearance of 76 bovine hind digits, obtained from a slaughterhouse, was related to the macroscopic signs of chronic laminitis in the digits. There were statistically significant correlations between the macroscopic and the arteriographic appearance of the claws. Subsequent histological examination of the radiographically abnormal arteries revealed features indicative of arteriosclerosis. The results of this study indicate that chronic laminitis develops following a subclinical attack of laminitis due to a continous hypoperfusion of the digit.
Methods for Preparing Nanoparticle-Containing Thermoplastic Composite Laminates
NASA Technical Reports Server (NTRS)
Gruber, Mark B. (Inventor); Jensen, Brian J. (Inventor); Cano, Roberto J. (Inventor)
2016-01-01
High quality thermoplastic composites and composite laminates containing nanoparticles and/or nanofibers, and methods of producing such composites and laminates are disclosed. The composites comprise a thermoplastic polymer and a plurality of nanoparticles, and may include a fibrous structural reinforcement. The composite laminates are formed from a plurality of nanoparticle-containing composite layers and may be fused to one another via an automated process.
Direct actin binding to A- and B-type lamin tails and actin filament bundling by the lamin A tail
Simon, Dan N; Zastrow, Michael S
2010-01-01
Nuclear intermediate filament networks formed by A- and B-type lamins are major components of the nucleoskeleton. Lamins have growing links to human physiology and disease including Emery-Dreifuss muscular dystrophy (EDMD), lipodystrophy, cardiomyopathy, neuropathy, cerebellar disorders and segmental accelerated ‘aging’ syndromes. How lamins interact with other nucleoskeletal components, and even the identities of these other components, are open questions. Previous studies suggested lamins might bind actin. We report that the recombinant C-terminal tail domain of human A- and B-type lamins binds directly to purified actin in high-speed pelleting assays. This interaction maps to a conserved Actin Binding site (AB-1) comprising lamin A residues 461–536 in the Ig-fold domain, which are 54% identical in lamin B1. Two EDMD-causing missense mutations (R527P and L530P) in lamin A that are predicted to disrupt the Ig-fold, each reduced F-actin binding by ∼66%, whereas the surface-exposed lipodystrophy-causing R482Q mutation had no significant effect. The lamin A tail was unique among lamins in having a second actin-binding site (AB-2). This second site was mapped to lamin A tail residues 564–608, based on actin-binding results for the lamin C tail and internal deletions in the lamin A tail that cause Hutchinson-Gilford Progeria Syndrome (Δ35, Δ50) or restrictive dermopathy (Δ90). Supporting the presence of two actin-binding sites, recombinant precursor (unmodified) and mature lamin A tails (not C or B1 tails) each bundled F-actin in vitro: furthermore F-actin bundling was reduced 25–40% by the R527P, L530P, Δ35 and Δ50 mutations, and was abolished by Δ90. Unexpectedly, the mature lamin A tail bound F-actin significantly more efficiently than did the prelamin A tail; this suggested unmodified residues 647–664, unique to prelamin A, might auto-inhibit binding to actin (and potentially other partners). These biochemical results suggest direct mechanisms
Energy Saving Glass Lamination via Selective Radio Frequency Heating
Allan, Shawn M; Baranova, Inessa; Poley, Joseph; Reis, Henrique
2012-02-27
This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North
Energy Saving Glass Lamination via Selective Radio Frequency Heating
Allan, Shawn M.
2012-02-27
This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North
An Elastic Model of Blebbing in Nuclear Lamin Meshworks
NASA Astrophysics Data System (ADS)
Funkhouser, Chloe; Sknepnek, Rastko; Shimi, Takeshi; Goldman, Anne; Goldman, Robert; Olvera de La Cruz, Monica
2013-03-01
A two-component continuum elastic model is introduced to analyze a nuclear lamin meshwork, a structural element of the lamina of the nuclear envelope. The main component of the lamina is a meshwork of lamin protein filaments providing mechanical support to the nucleus and also playing a role in gene expression. Abnormalities in nuclear shape are associated with a variety of pathologies, including some forms of cancer and Hutchinson-Gilford progeria syndrome, and are often characterized by protruding structures termed nuclear blebs. Nuclear blebs are rich in A-type lamins and may be related to pathological gene expression. We apply the two-dimensional elastic shell model to determine which characteristics of the meshwork could be responsible for blebbing, including heterogeneities in the meshwork thickness and mesh size. We find that if one component of the lamin meshwork, rich in A-type lamins, has a tendency to form a larger mesh size than that rich in B-type lamins, this is sufficient to cause segregation of the lamin components and also to form blebs rich in A-type lamins. The model produces structures with comparable morphologies and mesh size distributions as the lamin meshworks of real, pathological nuclei. Funded by US DoE Award DEFG02-08ER46539 and by the DDR&E and AFOSR under Award FA9550-10-1-0167; simulations performed on NU Quest cluster
Residual stress and crack propagation in laminated composites
Yttergren, R.M.F.; Zeng, K.; Rowcliffe, D.J.
1994-12-31
Residual stress distributions in several laminated ceramic composites were measured by an indentation technique. The material included alumina-zirconia laminated composites, containing strong interfaces, and alumina-porcelain laminated composites with both weak and strong interfaces. The residual stress in these material originates from the mismatch of the thermal properties, differences in elastic properties, and different shrinkage of the laminates during sintering. An experimental technique is presented which gives a direct view of the residual stress state in the materials. Values of residual tensile stress are presented as a function of position relative to the interface in each material.
Impact damage resistance of thin stitched carbon/epoxy laminates
NASA Astrophysics Data System (ADS)
Francesconi, L.; Aymerich, F.
2015-07-01
The study examines the influence of through-thickness stitching on the damage response of thin cross-ply carbon/epoxy laminates subjected to low-velocity impacts. Instrumented impact tests were carried out on unstitched and polyethylene stitched laminates and the resulting damage was assessed in detail by X-radiography analyses. The results of the observations carried out during the experimental analyses are illustrated and discussed to identify the mechanical role played by through-thickness reinforcement and to highlight the influence of the laminate layup on the impact resistance of stitched laminates.
Circular piezoelectric bender laser tuners
NASA Technical Reports Server (NTRS)
Mcelroy, J. H.; Thompson, P. E.; Walker, H. E.; Johnson, E. H.; Radecki, D. J.; Reynolds, R. S.
1972-01-01
The circular piezoelectric bender laser tuner to replace conventional laser tuners when mirror diameters up to 0.50 inch are sufficient is described. The circular piezoelectric bender laser tuner offers much higher displacements per applied volt and permits laser control circuits to be fabricated using standard operational amplifiers, rather than the expensive high-voltage amplifiers required by conventional tuners. The cost of the device is more than one order of magnitude lower than conventional tuners and the device is very rugged with all mechanical resonances easily designed to be greater than 3kHz. In addition to its use as a laser frequency tuner, the circular bender tuner should find many applications in interferometers and similar devices.
Photoelectron circular dichroism of isopropanolamine
NASA Astrophysics Data System (ADS)
Catone, D.; Turchini, S.; Contini, G.; Prosperi, T.; Stener, M.; Decleva, P.; Zema, N.
2017-01-01
Spectroscopies based on circular polarized light are sensitive to the electronic and structural properties of chiral molecules. Photoelectron circular dichroism (PECD) is a powerful technique that combines the chiral sensitivity of the circular polarized light and the electronic information obtained by photoelectron spectroscopy. An experimental and theoretical PECD study of the outer valence and C 1s core states of 1-amino-2-propanol in the gas phase is presented. The experimental dichroic dispersions in the photoelectron kinetic energy are compared with theoretical calculations employing a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian. In order to understand analogies and differences in the dichroism of structural isomers bearing the same functional groups, a comparison with previous PECD study of valence band of 2-amino-1-propanol is carried out.
Cylindrical Mixing Layer Model in Stellar Jet
NASA Astrophysics Data System (ADS)
Choe, Seung-Urn; Yu, Kyoung Hee
1994-12-01
We have developed a cylindrical mixing layer model of a stellar jet including cooling effect in order to understand an optical emission mechanism along collimated high velocity stellar jets associated with young stellar objects. The cylindrical results have been calculated to be the same as the 2D ones presented by Canto & Raga(1991) because the entrainment efficiency in our cylindrical model has been obtained to be the same value as the 2D model has given. We have discussed the morphological and physical characteristics of the mixing layers by the cooling effect. As the jet Mach number increases, the initial temperature of the mixing layer goes high because the kinetic energy of the jet partly converts to the thermal energy of the mixing layer. The initial cooling of the mixing layer is very severe, changing its outer boundary radius. A subsequent change becomes adiabatic. The number of the Mach disks in the stellar jet and the total radiative luminosity of the mixing layer, based on our cylindrical calculation, have quite agreed with the observation.
Cylindrical Induction Melter Modicon Control System
Weeks, G.E.
1998-04-01
In the last several years an extensive R{ampersand}D program has been underway to develop a vitrification system to stabilize Americium (Am) and Curium (Cm) inventories at SRS. This report documents the Modicon control system designed for the 3 inch Cylindrical Induction Melter (CIM).
Tamm plasmon polaritons in multilayered cylindrical structures
NASA Astrophysics Data System (ADS)
Little, C. E.; Anufriev, R.; Iorsh, I.; Kaliteevski, M. A.; Abram, R. A.; Brand, S.
2012-12-01
It is shown that cylindrical Bragg reflector structures with either a metal core, a metal cladding, or both can support Tamm plasmon polaritons (TPPs) that can propagate axially along the interface between the metallic layer and the adjacent dielectric. A transfer matrix formalism for cylindrical multilayered structures is used in association with cavity phase matching considerations to design structures that support Tamm plasmon polaritons at specified frequencies, and to explore the field distributions and the dispersion relations of the excitations. The cylindrical TPPs can exist in both the TE and TM polarizations for the special cases of modes with either azimuthal isotropy or zero axial propagation constant and also as hybrid cylindrical modes when neither of those conditions applies. In the cases considered the TPPs have low effective masses and low group velocities. Also, when there is both metallic core and cladding, near degenerate modes localized at each metallic interface can couple to produce symmetric and antisymmetric combinations whose frequency difference is in the terahertz regime.
NASA Astrophysics Data System (ADS)
Casado, Victor M.; Hinsch, Svend; Garcia, Jesus Gomez; Castro, Saullo G. P.
2014-06-01
The impact of geometrical imperfections on the general instability of laminated cylindrical sandwich shells was assessed by means of a numerical investigation. Five forms of 'ideal' initial geometrical imperfection patterns were studied: eigen-mode shaped, axisymmetric dimple, geometric dimple, single perturbation load and single stress-free dimple. Implementation of such imperfections, despite their simplicity, can provide a method for predicting lower-bound buckling loads during the preliminary design phase, when the structural defects of the real hardware are unknown. Numerical prediction of the non- linear instability of the cylinders under axial compression was performed using the finite element method. A typical launcher Inter Stage Skirt (ISS) structure is used as the basis for the chosen geometry and materials. In order to make design and qualification tests more affordable, it is common to use representative sub-scaled hardware. This paper verifies the validity of the chosen sub-scaling method of an ISS cylindrical shell. Buckling mechanisms are described and the different lower-bound methods are discussed.
Thin cylindrical slot in an optical microdisk cavity for sensing biomaterials
NASA Astrophysics Data System (ADS)
Daraei, Ahmadreza; Daraei, Mohammad Esmaeil
2017-04-01
In this paper, we propose and investigate a thin cylindrical slot etched into a disk shape optical microcavity (MC) aiming for sensing biomaterials in a label-free style. Supporting whispering gallery modes (WGMs), with remarkably large quality factor to modal volume ratio (Q/Vm) of the optical MC structures that penetrate in the slot region, enables us to perform sensing. Three different geometries for the side walls of host microdisk cavities, including vertical, 60° wedged, and half-circular cross section, are selected for investigations. In each individual case, the radial position, width, and height of the thin cylindrical slot are varied. The electromagnetic (EM) field intensity distributions (mode mapping profiles) of the WGMs show funneling of the intensified fields into the slot area that possessing nearly the same high Q values. Tuning the slot position, width, and depth for a suitably chosen WGM, sensing could be optimized for different biomaterials. Sensitivity value as high as 75 nm/RIU is calculated for the half-circular side wall microdisk. The proposed WGM-based slotted microdisk, as a state-of-the-art device which can operate, such as lab-on-chip structure, would function as a sensitive biosensor, even down to the single biomolecule levels.
A parallel 3D poisson solver for space charge simulation in cylindrical coordinates.
Xu, J.; Ostroumov, P. N.; Nolen, J.; Physics
2008-02-01
This paper presents the development of a parallel three-dimensional Poisson solver in cylindrical coordinate system for the electrostatic potential of a charged particle beam in a circular tube. The Poisson solver uses Fourier expansions in the longitudinal and azimuthal directions, and Spectral Element discretization in the radial direction. A Dirichlet boundary condition is used on the cylinder wall, a natural boundary condition is used on the cylinder axis and a Dirichlet or periodic boundary condition is used in the longitudinal direction. A parallel 2D domain decomposition was implemented in the (r,{theta}) plane. This solver was incorporated into the parallel code PTRACK for beam dynamics simulations. Detailed benchmark results for the parallel solver and a beam dynamics simulation in a high-intensity proton LINAC are presented. When the transverse beam size is small relative to the aperture of the accelerator line, using the Poisson solver in a Cartesian coordinate system and a Cylindrical coordinate system produced similar results. When the transverse beam size is large or beam center located off-axis, the result from Poisson solver in Cartesian coordinate system is not accurate because different boundary condition used. While using the new solver, we can apply circular boundary condition easily and accurately for beam dynamic simulations in accelerator devices.
Paired circularly polarized heterodyne ellipsometer
Yu, C.-J.; Lin, C.-E.; Yu, L.-P.; Chou, C
2009-02-01
We develop a paired circularly polarized heterodyne ellipsometer (PCPHE), in which a heterodyne interferometer based on a two-frequency circularly polarized laser beam is set up. It belongs to an amplitude-sensitive ellipsometer that is able to provide not only a wider dynamic range of polarization modulation frequency but also a higher detection sensitivity than that of a conventional photometric ellipsometer. A real-time and precise measurement of ellipsometric parameters, which demonstrated an accuracy of less than 1 nm on thickness measurement of SiO2 thin film deposited on silicon substrate, can be applied with the PCPHE.
Maximal dinucleotide and trinucleotide circular codes.
Michel, Christian J; Pellegrini, Marco; Pirillo, Giuseppe
2016-01-21
We determine here the number and the list of maximal dinucleotide and trinucleotide circular codes. We prove that there is no maximal dinucleotide circular code having strictly less than 6 elements (maximum size of dinucleotide circular codes). On the other hand, a computer calculus shows that there are maximal trinucleotide circular codes with less than 20 elements (maximum size of trinucleotide circular codes). More precisely, there are maximal trinucleotide circular codes with 14, 15, 16, 17, 18 and 19 elements and no maximal trinucleotide circular code having less than 14 elements. We give the same information for the maximal self-complementary dinucleotide and trinucleotide circular codes. The amino acid distribution of maximal trinucleotide circular codes is also determined.
Radial Internal Material Handling System (RIMS) for Circular Habitat Volumes
NASA Technical Reports Server (NTRS)
Howe, Alan S.; Haselschwardt, Sally; Bogatko, Alex; Humphrey, Brian; Patel, Amit
2013-01-01
On planetary surfaces, pressurized human habitable volumes will require a means to carry equipment around within the volume of the habitat, regardless of the partial gravity (Earth, Moon, Mars, etc.). On the NASA Habitat Demonstration Unit (HDU), a vertical cylindrical volume, it was determined that a variety of heavy items would need to be carried back and forth from deployed locations to the General Maintenance Work Station (GMWS) when in need of repair, and other equipment may need to be carried inside for repairs, such as rover parts and other external equipment. The vertical cylindrical volume of the HDU lent itself to a circular overhead track and hoist system that allows lifting of heavy objects from anywhere in the habitat to any other point in the habitat interior. In addition, the system is able to hand-off lifted items to other material handling systems through the side hatches, such as through an airlock. The overhead system consists of two concentric circle tracks that have a movable beam between them. The beam has a hoist carriage that can move back and forth on the beam. Therefore, the entire system acts like a bridge crane curved around to meet itself in a circle. The novelty of the system is in its configuration, and how it interfaces with the volume of the HDU habitat. Similar to how a bridge crane allows coverage for an entire rectangular volume, the RIMS system covers a circular volume. The RIMS system is the first generation of what may be applied to future planetary surface vertical cylinder habitats on the Moon or on Mars.
Joergensen, O.; Horsewell, A.
1997-08-01
Elastic and elasto-plastic modelling of indentation in CFRP cross-ply laminates has been performed. Detailed knowledge of the field solutions in the volume below the indentor forms the basis for the reported micromechanical interpretation of the observed damage in test specimens. The analysis shows that matrix cracks originate at sites of maximum tensile stress perpendicular to fibers. The predicted stress fields due to indentation show that stress concentrations occur in the interface between alternating plies. It is found that microcracking in this zone is a precursor to the observed failure. This analysis is supported by in-situ scanning electron microscopy during loading by a cylindrical indentor onto the laminate supported on a rigid substrate. The microscopy reveals microdamage in the region of interfacial tensile stress concentrations. The onset of indentation failure in these layered composites suggests that plastic interleaves would delay failure. It is shown numerically that plastic deformation of the interleaves redistributes stresses and thereby weakens the tensile stress concentrations which arise during indentation. Experimentally it is shown that aluminium interleaves affect the formation of indentation failure. In a cross-ply laminate, where alternating ply groups are separated by aluminium sheets, matrix cracking and delamination failures are suppressed by the occurrence of plastic deformation. Since the aluminium is likely to be weakly bonded to the plies, it is seen that weak interlaminar fracture toughness does not necessarily cause delaminations, nor lead to a lower indentation strength. High indentation strength and delamination resistance are complex qualities which, among others, seem to be achieved in laminate geometries which have a minimum of stress concentration at interfaces between ply groups of different orientation.
Dynamic stability of simply supported composite cylindrical shells under partial axial loading
NASA Astrophysics Data System (ADS)
Dey, Tanish; Ramachandra, L. S.
2015-09-01
The parametric vibration of a simply supported composite circular cylindrical shell under periodic partial edge loadings is discussed in this article. Donnell's nonlinear shallow shell theory considering first order shear deformation theory is used to model the shell. The applied partial edge loading is represented in terms of a Fourier series and stress distributions within the cylindrical shell are determined by prebuckling analysis. The governing equations of the dynamic instability of shells are derived in terms of displacements (u-v-w) and rotations (φx, φθ). Employing the Galerkin and Bolotin methods the dynamic instability regions are computed. Using the expression for the stress function derived in this paper, the pre-buckling stresses in the cylindrical shell due to partial loading can be calculated explicitly. Numerical results are presented to show the influence of radius-to-thickness ratio, different partial edge loading distributions and shear deformation on the dynamic instability regions. The linear and nonlinear responses in the stable and unstable regions are presented to bring out the characteristic features of the dynamic instability regions, such as the existence of beats, its dependence on forcing frequency and effect of nonlinearity on the response. The effect of dynamic load amplitude on the nonlinear response is also studied. It is found that for higher values of dynamic loading, the shell exhibits chaotic behavior.
Angles-Only Initial Relative Orbit Determination Performance Analysis using Cylindrical Coordinates
NASA Astrophysics Data System (ADS)
Geller, David K.; Lovell, T. Alan
2017-03-01
The solution of the initial relative orbit determination problem using angles-only measurements is important for orbital proximity operations, satellite inspection and servicing, and the identification of unknown space objects in similar orbits. In this paper, a preliminary relative orbit determination performance analysis is conducted utilizing the linearized relative orbital equations of motion in cylindrical coordinates. The relative orbital equations of motion in cylindrical coordinates are rigorously derived in several forms included the exact nonlinear two-body differential equations of motion, the linear-time-varying differential equations of motion for an elliptical orbit chief, and the linear-time-invariant differential equations of motion for a circular orbit chief. Using the nonlinear angles-only measurement equation in cylindrical coordinates, evidence of full-relative-state observability is found, contrary to the range observability problem exhibited in Cartesian coordinates. Based on these results, a geometric approach to assess initial relative orbit determination performance is formulated. To facilitate a better understanding of the problem, the focus is on the 2-dimensional initial orbit determination problem. The results clearly show the dependence of the relative orbit determination performance on the geometry of the relative motion and on the time-interval between observations. Analysis is conducted for leader-follower orbits and flyby orbits where the deputy passes directly above or below the chief.
NASA Technical Reports Server (NTRS)
Rao, P. V.; Buckley, D. H.
1983-01-01
The erosion characteristics of aluminum cylinders sand-blasted with both spherical and angular erodent particles were studied and compared with results from previously studied flat surfaces. The cylindrical results are discussed with respect to impact conditions. The relationship between erosion rate and pit morphology (width, depth, and width to depth ratio) is established. The aspects of (1) erosion rate versus time curves on cylindrical surfaces; (2) long-term exposures; and (3) erosion rate versus time curves with spherical and angular particles are presented. The erosion morphology and characteristics of aluminum surfaces with pre-existing circular cylindrical and conical holes of different sizes were examined using weight loss measurements, scanning electron microscopy, a profilometer, and a depth gage. The morphological features (radial and concentric rings) are discussed with reference to flat surfaces, and the erosion features with spherical microglass beads. The similarities and differences of erosion and morphological features are highlighted. The erosion versus time curves of various shapes of holes are discussed and are compared with those of a flat surface. The erosion process at slits is considered.
Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates
NASA Technical Reports Server (NTRS)
Hiel, Clement; Brinson, H. F.
1993-01-01
Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.
Effect of Impact Damage and Open Hole on Compressive Strength of Hybrid Composite Laminates
Hiel, C.; Brinson, H.F.
1993-05-01
Impact damage tolerance is a frequently listed design requirement for composites hardware. The effect of impact damage and open hole size on laminate compressive strength was studied on sandwich beam specimens which combine CFRP-GFRP hybrid skins and a syntactic foam core. Three test specimen configurations have been investigated for this study. The first two were sandwich beams which were loaded in pure bending (by four point flexure). One series had a skin damaged by impact, and the second series had a circular hole machined through one of the skins. The reduction of compressive strength with increasing damage (hole) size was compared. Additionally a third series of uniaxially loaded open hole compression coupons were tested to generate baseline data for comparison with both series of sandwich beams.
Acoustic resonance scattering from a multilayered cylindrical shell with imperfect bonding.
Rajabi, M; Hasheminejad, Seyyed M
2009-12-01
The method of wave function expansion is adopted to study the three dimensional scattering of a time-harmonic plane progressive sound field obliquely incident upon a multi-layered hollow cylinder with interlaminar bonding imperfection. For the generality of solution, each layer is assumed to be cylindrically orthotropic. An approximate laminate model in the context of the modal state equations with variable coefficients along with the classical T-matrix solution technique is set up for each layer to solve for the unknown modal scattering and transmission coefficients. A linear spring model is used to describe the interlaminar adhesive bonding whose effects are incorporated into the global transfer matrix by introduction of proper interfacial transfer matrices. Following the classic acoustic resonance scattering theory (RST), the scattered field and response to surface waves are determined by constructing the partial waves and obtaining the non-resonance (backgrounds) and resonance components. The solution is first used to investigate the effect of interlayer imperfection of an air-filled and water submerged bilaminate aluminium cylindrical shell on the resonances associated with various modes of wave propagation (i.e., symmetric/asymmetric Lamb waves, fluid-borne A-type waves, Rayleigh and Whispering Gallery waves) appearing in the backscattered spectrum, according to their polarization and state of stress. An illustrative numerical example is also given for a multi-layered (five-layered) cylindrical shell for which the stiffness of the adhesive interlayers is artificially varied. The sensitivity of resonance frequencies associated with higher mode numbers to the stiffness coefficients is demonstrated to be a good measure of the bonding strength. Limiting cases are considered and fair agreements with solutions available in the literature are established.
1981-05-01
difference two of the Li DF-L tension lamina- other test material in this study and between the average of the unad - tions were chosen for that reason...MOE data, adjusted to a 12 per- of tension lamination had a signifi- should be combined to determine the cent moisture content, and the unad - cant
Cylindrical isomorphic mapping applied to invariant manifold dynamics for Earth-Moon Missions
NASA Astrophysics Data System (ADS)
Giancotti, Marco; Pontani, Mauro; Teofilatto, Paolo
2014-11-01
Several families of periodic orbits exist in the context of the circular restricted three-body problem. This work studies orbital motion of a spacecraft among these periodic orbits in the Earth-Moon system, using the planar circular restricted three-body problem model. A new cylindrical representation of the spacecraft phase space (i.e., position and velocity) is described, and allows representing periodic orbits and the related invariant manifolds. In the proximity of the libration points, the manifolds form a four-fold surface, if the cylindrical coordinates are employed. Orbits departing from the Earth and transiting toward the Moon correspond to the trajectories located inside this four-fold surface. The isomorphic mapping under consideration is also useful for describing the topology of the invariant manifolds, which exhibit a complex geometrical stretch-and-folding behavior as the associated trajectories reach increasing distances from the libration orbit. Moreover, the cylindrical representation reveals extremely useful for detecting periodic orbits around the primaries and the libration points, as well as the possible existence of heteroclinic connections. These are asymptotic trajectories that are ideally traveled at zero-propellant cost. This circumstance implies the possibility of performing concretely a variety of complex Earth-Moon missions, by combining different types of trajectory arcs belonging to the manifolds. This work studies also the possible application of manifold dynamics to defining a suitable, convenient end-of-life strategy for spacecraft placed in any of the unstable orbits. The final disposal orbit is an externally confined trajectory, never approaching the Earth or the Moon, and can be entered by means of a single velocity impulse (of modest magnitude) along the right unstable manifold that emanates from the Lyapunov orbit at L_2.
Accelerator Science: Circular vs. Linear
Lincoln, Don
2016-12-14
Particle accelerator are scientific instruments that allow scientists to collide particles together at incredible energies to study the secrets of the universe. However, there are many manners in which particle accelerators can be constructed. In this video, Fermilabâs Dr. Don Lincoln explains the pros and cons of circular and linear accelerators.
Accelerator Science: Circular vs. Linear
Lincoln, Don
2016-11-10
Particle accelerator are scientific instruments that allow scientists to collide particles together at incredible energies to study the secrets of the universe. However, there are many manners in which particle accelerators can be constructed. In this video, Fermilab’s Dr. Don Lincoln explains the pros and cons of circular and linear accelerators.
Class IIc or Circular Bacteriocins
NASA Astrophysics Data System (ADS)
Martin-Visscher, Leah A.; van Belkum, Marco J.; Vederas, John C.
The circular bacteriocins produced by Gram-positive bacteria represent a diverse class of antimicrobial peptides. These bacteriocins display enhanced stability compared to linear bacteriocins, which arises from their characteristic circular backbone. Currently, eight unique circular bacteriocins have been identified, and analysis of their gene clusters indicates that they likely utilize complex mechanisms for maturation and secretion, as well as for immunity. These bacteriocins target the cytoplasmic membrane of sensitive cells, leading to pore formation that results in loss of ions, dissipation of membrane potential, and ultimately, cell death. Structural studies suggest that despite variation in their sequences, most of these bacteriocins likely adopt a common three-dimensional architecture, consisting of four or five tightly packed helices encompassing a hydrophobic core. There are many mysteries surrounding the biosynthesis of these peptides, particularly in regard to the mechanism by which they are cyclized. Elucidation of such a mechanism may provide exciting new approaches to the bioengineering of new, stable, and antimicrobially active circular peptides.
Stress Analysis of Circular Frames
NASA Technical Reports Server (NTRS)
Fahlbusch, H; Wegner, W
1941-01-01
The stresses in circular frames of constant bending stiffnesses, as encountered in thin-wall shells, are investigated from the point of view of finite depth of sectional area of frame. The solution is carried out for four fundamental load conditions. The method is illustrated on a worked out example.
Neuropathic changes in equine laminitis pain.
Jones, Emma; Viñuela-Fernandez, Ignacio; Eager, Rachel A; Delaney, Ada; Anderson, Heather; Patel, Anisha; Robertson, Darren C; Allchorne, Andrew; Sirinathsinghji, Eva C; Milne, Elspeth M; MacIntyre, Neil; Shaw, Darren J; Waran, Natalie K; Mayhew, Joe; Fleetwood-Walker, Susan M
2007-12-05
Laminitis is a common debilitating disease in horses that involves painful disruption of the lamellar dermo-epidermal junction within the hoof. This condition is often refractory to conventional anti-inflammatory analgesia and results in unremitting pain, which in severe cases requires euthanasia. The mechanisms underlying pain in laminitis were investigated using quantification of behavioural pain indicators in conjunction with histological studies of peripheral nerves innervating the hoof. Laminitic horses displayed consistently altered or abnormal behaviours such as increased forelimb lifting and an increased proportion of time spent at the back of the box compared to normal horses. Electron micrographic analysis of the digital nerve of laminitic horses showed peripheral nerve morphology to be abnormal, as well as having reduced numbers of unmyelinated (43.2%) and myelinated fibers (34.6%) compared to normal horses. Sensory nerve cell bodies innervating the hoof, in cervical, C8 dorsal root ganglia (DRG), showed an upregulated expression of the neuronal injury marker, activating transcription factor-3 (ATF3) in both large NF-200-immunopositive neurons and small neurons that were either peripherin- or IB4-positive. A significantly increased expression of neuropeptide Y (NPY) was also observed in myelinated afferent neurons. These changes are similar to those reported in other neuropathic pain states and were not observed in the C4 DRG of laminitic horses, which is not associated with innervation of the forelimb. This study provides novel evidence for a neuropathic component to the chronic pain state associated with equine laminitis, indicating that anti-neuropathic analgesic treatment may well have a role in the management of this condition.
Laminated anisotropic reinforced plastic plates and shells
NASA Technical Reports Server (NTRS)
Korolev, V. I.
1981-01-01
Basic technical theories and engineering calculation equations for anisotropic plates and shells made of rigid reinforced plastics, mainly laminated fiberglass, are presented and discussed. Solutions are given for many problems of design of structural plates and shells, including curved sections and tanks, as well as two chapters on selection of the optimum materials, are given. Accounting for interlayer shearing and transverse separation, which are new engineering properties, are discussed. Application of the results obtained to thin three ply plates and shells wth a light elastic filler is presented and discussed.
Micromechanics of composite laminate compression failures
NASA Technical Reports Server (NTRS)
Guynn, E. Gail; Bradley, Walter L.
1988-01-01
The purpose of this annual progress report is to summarize the work effort and results accomplished from July 1987 through July 1988 on NASA Research Grant NAG1-659 entitled Micromechanics of Composite Laminate Compressive Failure. The report contains: (1) the objective of the proposed research, (2) the summary of accomplishments, (3) a more extensive review of compression literature, (4) the planned material (and corresponding properties) received to date, (5) the results for three possible specimen geometries, experimental procedures planned, and current status of the experiments, and (6) the work planned for the next contract year.
Tailoring Laminates For Protection Against Projectiles
NASA Technical Reports Server (NTRS)
Gassner, John J.; Boyce, Joseph S.; Smirlock, Martin E.; Evans, David A.
1992-01-01
Fiber/matrix composite laminates developed to protect military land vehicles against projectiles and spacecraft against impacts by micrometeroids. Although types, sizes, and velocities of expected incident objects differ between terrestrial and outer-space cases, general protection problems and solutions exhibit some common features. Configurations of fibers and matrices optimized with respect to protection, bulk, and weight, to obtain shield that breaks rapidly moving incident object into harmless smaller, more-slowly-moving pieces, containing debris, vaporizes debris, and/or otherwise absorbs kinetic energy of object to prevent harm to vehicle and occupants.
Adhesive characterization in prestressed piezoelectric laminates
NASA Astrophysics Data System (ADS)
Hodges, Charles A.; Mossi, Karla M.; Scott, Lisa A.
2003-08-01
Pre-stressed piezoelectric laminates, consisting of one or more metal layers and a piezoelectric material bonded together with an adhesive, have been widely studied over the past few years, both numerically and experimentally. Most of the current research has concentrated on the effect of the metal layers, types and geometry, along with variations in the active layer of the laminate. Historically, the adhesive layer has been neglected as a contributing factor in the overall performance of the final device. This paper attempts to address the effect of the adhesive line thickness and its influence on the performance of pre-stressed piezoelectric laminates under specific boundary conditions. All laminates tested were constructed with the following lay-up: 0.354 mm thick stainless steel, adhesive, 0.381 mm PZT ceramic, adhesive, and a 0.0254 mm aluminum layer. The devices having an adhesive line thickness of 0.169 mm were classified as group A, and group B were the devices with an adhesive line thickness of 0.036 mm. The adhesive line thickness for group A was approximately 21% more than the line thickness of group B. The devices were tested in a simply supported, free-free condition under a series of loads at a constant frequency of 5 Hz over a voltage range from 400 to 800 Volts peak-to-peak. Displacement was measured using loads of 25, 50, 75, 100, and 200 grams for each actuator. The data from each group was averaged and compared. The results showed group B generated more displacement at the same "arm weight" applied as compared to group A. However, only three samples for group B were measured since the rest of the samples failed during testing. Failure of the devices of group B may be due to the ultimate stress of the devices and their ability to lift a load under those conditions. The study demonstrated that adhesive layer thickness, along with the manufacturing process, has to be taken into account when developing an application that requires load
Expression of endothelin in equine laminitis.
Katwa, L C; Johnson, P J; Ganjam, V K; Kreeger, J M; Messer, N T
1999-05-01
Biosynthesis of endothelin-1 (ET-1), the most potent endogenous vasoconstrictor yet identified, is increased following myocardial infarction (MI) in man. Pathological events which occur in the connective tissues of the equine hoof during laminitis are similar in some respects, to changes occurring in the myocardial connective tissues following MI in man. The objective of this study was to determine whether ET-1 expression in connective tissues obtained from the hoof of laminitic horses is increased compared with tissues obtained from healthy horses. Expression of ET-1 in connective tissues of the equine hoof was measured following tissue extraction from 3 groups of horses: horses in which acute laminitis had been induced by the administration of starch; chronically foundered horses; nonlaminitic horses. The concentration of ET-1 in laminar connective tissues obtained from all laminitic horses (1573.0 +/- 392.8 pg/g of tissue; n = 10) was increased when compared with tissues obtained from nonlaminitic horses (392.5 +/- 117.4 pg/g of tissue; n = 5) (P<0.05). The concentration of ET-1 in laminar connective tissues obtained from the experimentally induced, acute laminitic horses (1043.6 +/- 254.4 pg/g of tissue; n = 7) and from the spontaneously affected, chronic laminitic horses (2808.3 +/- 878.6 pg/g of tissue; n = 3) was increased compared with the control group (P<0.05, P<0.01, respectively). The concentration of ET-1 in laminar connective tissues obtained from the chronic laminitic horses was greater than that of the experimentally induced, acute laminitic group (P<0.05). It is suggested that the data provide a strong argument that increased ET-1 expression in the connective tissues of the equine hoof represent a potentially important and hitherto unrecognised component of the pathophysiology of equine laminitis. Further studies are needed to determine whether inhibitors of ET-1 converting enzyme or antagonists of ET-1 receptors might be useful in the treatment
Better Thermal Insulation in Solar-Array Laminators
NASA Technical Reports Server (NTRS)
Burger, D. R.; Knox, J. F.
1984-01-01
Glass marbles improve temperature control. Modified vacuum laminator for photovoltaic solar arrays includes thermal insulation made of conventional glass marbles. Marbles serve as insulation for temperature control of lamination process at cure temperatures as high as 350 degrees F. Used to replace original insulation made of asbestos cement.
Laminated sheet composites reinforced with modular filament sheet
NASA Technical Reports Server (NTRS)
Reece, O. Y.
1968-01-01
Aluminum and magnesium composite sheet laminates reinforced with low density, high strength modular filament sheets are produced by diffusion bonding and explosive bonding. Both processes are accomplished in normal atmosphere and require no special tooling or cleaning other than wire brushing the metal surfaces just prior to laminating.
The pharmacologic basis for the treatment of endocrinopathic laminitis.
Durham, Andy
2010-08-01
Although the treatment and management of laminitis in the horse requires a holistic and often multidisciplinary approach from the veterinarian, farrier, and nutritionist, this review focuses on pharmacologic interventions that might have prophylactic benefit, specifically in the horse with laminitis as a result of pituitary pars intermedia dysfunction and equine metabolic syndrome.
The nucleoporin Nup88 is interacting with nuclear lamin A
Lussi, Yvonne C.; Hügi, Ilona; Laurell, Eva; Kutay, Ulrike; Fahrenkrog, Birthe
2011-01-01
Nuclear pore complexes (NPCs) are embedded in the nuclear envelope (NE) and mediate bidirectional nucleocytoplasmic transport. Their spatial distribution in the NE is organized by the nuclear lamina, a meshwork of nuclear intermediate filament proteins. Major constituents of the nuclear lamina are A- and B-type lamins. In this work we show that the nuclear pore protein Nup88 binds lamin A in vitro and in vivo. The interaction is mediated by the N-terminus of Nup88, and Nup88 specifically binds the tail domain of lamin A but not of lamins B1 and B2. Expression of green fluorescent protein–tagged lamin A in cells causes a masking of binding sites for Nup88 antibodies in immunofluorescence assays, supporting the interaction of lamin A with Nup88 in a cellular context. The epitope masking disappears in cells expressing mutants of lamin A that are associated with laminopathic diseases. Consistently, an interaction of Nup88 with these mutants is disrupted in vitro. Immunoelectron microscopy using Xenopus laevis oocyte nuclei further revealed that Nup88 localizes to the cytoplasmic and nuclear face of the NPC. Together our data suggest that a pool of Nup88 on the nuclear side of the NPC provides a novel, unexpected binding site for nuclear lamin A. PMID:21289091
A Laminated Track for the Inductrack System: Theory and Experiment
Post, R F; Hoburg, J F
2004-01-12
A laminated structure, composed of stacks of thin conducting sheets, has several advantages over a litz-wire ladder as the ''track'' wherein levitating currents are induced by a permanent magnet array on a moving vehicle. Modeling and experimental results for the laminated track are described and evaluated in this paper.
Hole-thru-laminate mounting supports for photovoltaic modules
Wexler, Jason; Botkin, Jonathan; Culligan, Matthew; Detrick, Adam
2015-02-17
A mounting support for a photovoltaic module is described. The mounting support includes a pedestal having a surface adaptable to receive a flat side of a photovoltaic module laminate. A hole is disposed in the pedestal, the hole adaptable to receive a bolt or a pin used to couple the pedestal to the flat side of the photovoltaic module laminate.
Processing of thermoset prepreg laminate via exposure to microwave radiation
Paulauskas, F.L.; Meek, T.T.
1994-06-01
Studies of microwave-assisted curing of neat resins (epoxy) and unidirectional glass and carbon fiber laminates have shown that a substantial reduction in the curing time was obtained. This may be explained by the penetration of microwave energy directly and throughout the laminate with enhancement of the kinetics of the chemical reaction. Results of this work indicate that the microwave assisted curing of glass fiber laminates also shows a substantial reduction of the required curing time. Microwave radiation of 2.45 GHz has been demonstrated to be an acceptable method to cure unidirectional carbon fiber laminates. Also, effective curing of crossply (0/90) laminates through this method was observed when proper rotation of the parts accompanied the curing process. This is in accordance with previous work. Multidirectional carbon fiber/epoxy laminates demonstrate a lack of coupling during the curing process. A direct curing of these laminates was not possible by microwave radiation with the experimental approach used, in agreement with previous work. Nevertheless, a moderate reduction in the curing time of these thin laminates was observed due to hybrid curing.
A MEMS lamination technology based on sequential multilayer electrodeposition
Kim, M; Kim, J; Herrault, F; Schafer, R; Allen, MG
2013-08-06
A MEMS lamination technology based on sequential multilayer electrodeposition is presented. The process comprises three main steps: (1) automated sequential electrodeposition of permalloy (Ni80Fe20) structural and copper sacrificial layers to form multilayer structures of significant total thickness; (2) fabrication of polymeric anchor structures through the thickness of the multilayer structures and (3) selective removal of copper. The resulting structure is a set of air-insulated permalloy laminations, the separation of which is sustained by insulating polymeric anchor structures. Individual laminations have precisely controllable thicknesses ranging from 500 nm to 5 mu m, and each lamination layer is electrically isolated from adjacent layers by narrow air gaps of similar scale. In addition to air, interlamination insulators based on polymers are investigated. Interlamination air gaps with very high aspect ratio (>1:100) can be filled with polyvinylalcohol and polydimethylsiloxane. The laminated structures are characterized using scanning electron microscopy and atomic force microscopy to directly examine properties such as the roughness and the thickness uniformity of the layers. In addition, the quality of the electrical insulation between the laminations is evaluated by quantifying the eddy current within the sample as a function of frequency. Fabricated laminations are comprised of uniform, smooth (surface roughness < 100 nm) layers with effective electrical insulation for all layer thicknesses and insulator approaches studied. Such highly laminated structures have potential uses ranging from energy conversion to applications where composite materials with highly anisotropic mechanical or thermal properties are required.
Histopathology of oligofructose-induced acute laminitis in heifers.
Thoefner, M B; Wattle, O; Pollitt, C C; French, K R; Nielsen, S S
2005-08-01
Histopathology of the dermo-epidermal junction in the lamellar region of front claws was examined in 6 dairy heifers given an alimentary oligofructose overload and compared with sections from a control group of 6 heifers. Four of the 6 heifers administered oligofructose developed clinical signs of acute laminitis before they were euthanized. Postmortem samples from front claws were processed for histology. Eleven histopathologic characteristics were selected from the existing literature and used in a blinded evaluation of sections. In total, 104 front claw samples, including 8 samples from 2 cows having spontaneously occurring acute laminitis, were evaluated histologically using hematoxylin and eosin as well as periodic acid-Schiff staining. The major morphological features associated with oligofructose-induced acute clinical laminitis were stretching of lamellae, dermal edema, hemorrhage, changes in basal cell morphology, presence of white blood cells in dermis, and signs of basement membrane detachment. Changes at the lamellar junction of claw tissue affected by oligofructose-induced clinical laminitis resembled tissue from the 2 cows suffering from spontaneous acute clinical laminitis, and generally were consistent with existing descriptions of laminitis histopathology. Important exceptions to existing descriptions in the literature were stretching of lamellae and basement membrane changes. Not previously described, we considered these early signs of acute laminitis. In conclusion, this study documents that oligofructose-induced clinical laminitis is associated with histopathological changes at the lamellar interface. A weakened dermo-epidermal junction is a possible intermediate stage in the pathophysiology of bovine sole ulceration at the typical site.
Vibration suppression of composite laminated plate with nonlinear energy sink
NASA Astrophysics Data System (ADS)
Zhang, Ye-Wei; Zhang, Hao; Hou, Shuai; Xu, Ke-Fan; Chen, Li-Qun
2016-06-01
The composite laminated plate is widely used in supersonic aircraft. So, there are many researches about the vibration suppression of composite laminated plate. In this paper, nonlinear energy sink (NES) as an effective method to suppress vibration is studied. The coupled partial differential governing equations of the composite laminated plate with the nonlinear energy sink (NES) are established by using the Hamilton principle. The fourth-order Galerkin discrete method is used to truncate the partial differential equations, which are solved by numerical integration method. Meanwhile study about the precise effectiveness of the nonlinear energy sink (NES) by discussing the different installation location of the nonlinear energy sink (NES) at the same speed. The results indicate that the nonlinear energy sink (NES) can significantly suppress the severe vibration of the composite laminated plate with speed wind loadings in to protect the composite laminated plate from excessive vibration.
Design of composite laminates by a Monte Carlo method
NASA Astrophysics Data System (ADS)
Fang, Chin; Springer, George S.
1993-01-01
A Monte Carlo procedure was developed for optimizing symmetric fiber reinforced composite laminates such that the weight is minimum and the Tsai-Wu strength failure criterion is satisfied in each ply. The laminate may consist of several materials including an idealized core, and may be subjected to several sets of combined in-plane and bending loads. The procedure yields the number of plies, the fiber orientation, and the material of each ply and the material and thickness of the core. A user friendly computer code was written for performing the numerical calculations. Laminates optimized by the code were compared to laminates resulting from existing optimization methods. These comparisons showed that the present Monte Carlo procedure is a useful and efficient tool for the design of composite laminates.
Residual stresses and their effects in composite laminates
NASA Technical Reports Server (NTRS)
Hahn, H. T.; Hwang, D. G.
1983-01-01
Residual stresses in composite laminates are caused by the anisotropy in expansional properties of constituent unidirectional plies. The effect of these residual stresses on dimensional stability is studied through the warping of unsymmetric (0 sub 4/90 sub 4)sub T graphite/epoxy laminates while their effect on ply failure is analyzed for (0/90)sub 2s Kevlar 49/epoxy laminate. The classical laminated plate theory is used to predict the warping of small and large panels. The change of warping does not indicate a noticeable stress relaxation at 75 C while it is very sensitive to moisture content and hence to environment. A prolonged gellation at the initial cure temperature reduces residual stresses while postcure does not. The matrix/interface cracking in dry (0/90)sub 2s Kevlar 49/epoxy laminate is shown to be the result of the residual stress exceeding the transverse strength.
Deposition of laminated shale: A field and experimental study
NASA Astrophysics Data System (ADS)
Carey, Daniel L.; Roy, David C.
1985-03-01
Intermittently laminated shale of the Jemtland Formation in Maine is characterized by thin lenticular silt segregations interlaced with argillaceous and organic material (including graptolites). This shale is thinly interbedded with nonlaminated shale, siltstone, and thicker turbidite graywacke beds. Experiments suggest that the intermittently laminated shale was deposited by silt/clay-laden currents and may have been part of an upward turbidite progression from parallel-laminated silt (>60% silt), through intermittently laminated mud (40 to 60% silt), to nonlaminated mud (20 to 40% silt). Intermittently laminated mud may be produced from silt/clay flows that are: decelerating at a constant silt content, losing silt at constant velocity; or both decelerating and losing silt.
The strength of laminated composite materials under repeated impact loading
NASA Technical Reports Server (NTRS)
Rotem, Assa
1988-01-01
When low velocity and energy impact is exerted on a laminated composite material, in a perpendicular direction to the plane of the laminate, invisible damage may develop. It is shown analytically and experimentally that the invisible damage occurs during the first stage of contact between the impactor and the laminate and is a result of the contact stresses. However, the residual flexural strength changes only slightly, because it depends mainly on the outer layers, and these remain undamaged. Repeated impact intensifies the damage inside the laminate and causes larger bending under equivalent impact load. Finally, when the damage is most severe, even though it is still invisible, the laminate fails because of bending on the tension side. If the repeated impact is halted before final fracture occurs the residual strength and modulus would decrease by a certain amount.
Matrix cracking in laminated composites under monotonic and cyclic loadings
NASA Technical Reports Server (NTRS)
Allen, David H.; Lee, Jong-Won
1991-01-01
An analytical model based on the internal state variable (ISV) concept and the strain energy method is proposed for characterizing the monotonic and cyclic response of laminated composites containing matrix cracks. A modified constitution is formulated for angle-ply laminates under general in-plane mechanical loading and constant temperature change. A monotonic matrix cracking criterion is developed for predicting the crack density in cross-ply laminates as a function of the applied laminate axial stress. An initial formulation for a cyclic matrix cracking criterion for cross-ply laminates is also discussed. For the monotonic loading case, a number of experimental data and well-known models are compared with the present study for validating the practical applicability of the ISV approach.
Diverse lamin-dependent mechanisms interact to control chromatin dynamics
Camozzi, Daria; Capanni, Cristina; Cenni, Vittoria; Mattioli, Elisabetta; Columbaro, Marta; Squarzoni, Stefano; Lattanzi, Giovanna
2014-01-01
Interconnected functional strategies govern chromatin dynamics in eukaryotic cells. In this context, A and B type lamins, the nuclear intermediate filaments, act on diverse platforms involved in tissue homeostasis. On the nuclear side, lamins elicit large scale or fine chromatin conformational changes, affect DNA damage response factors and transcription factor shuttling. On the cytoplasmic side, bridging-molecules, the LINC complex, associate with lamins to coordinate chromatin dynamics with cytoskeleton and extra-cellular signals. Consistent with such a fine tuning, lamin mutations and/or defects in their expression or post-translational processing, as well as mutations in lamin partner genes, cause a heterogeneous group of diseases known as laminopathies. They include muscular dystrophies, cardiomyopathy, lipodystrophies, neuropathies, and progeroid syndromes. The study of chromatin dynamics under pathological conditions, which is summarized in this review, is shedding light on the complex and fascinating role of the nuclear lamina in chromatin regulation. PMID:25482195
Observing of tree trunks and other cylindrical objects using GPR
NASA Astrophysics Data System (ADS)
Jezova, Jana; Lambot, Sebastien
2016-04-01
Trees are a part of our everyday life, hence it is important to prevent their collapse to protect people and urban infrastructures. It is also important to characterize tree wood properties for usages in construction. In order to investigate internal parts of tree trunks non-invasively, ground-penetrating radar (GPR), or in this case, ultra-wideband microwave radar as a general tool, appears to be a very promising technology. Nevertheless, tree trunk tomography using microwave radar is a complicated task due to the circular shape of the trunk and the very complex (heterogeneous and anisotropic) internal structures of the trunk. Microwave sensing of tree trunks is also complicated due to the electromagnetic properties of living wood, which strongly depend on water content, density and temperature of wood. The objective of this study is to describe tree trunk radar cross sections including specific features originating from the particular circumferential data acquisition geometry. In that respect, three experiments were performed: (1) numerical simulations using a finite-difference time-domain software, namely, gprMax 2D, (2) measurements on a simplified laboratory trunk model including plastic and cardboard pipes, sand and air, and (3) measurements over a real tree trunk. The analysis was further deepened by considering: (1) common zero-offset reflection imaging, (2) imaging with a planar perfect electrical conductor (PEC) at the opposite side of the trunk, and (3) imaging with a PEC arc at the opposite side of the trunk. Furthermore, the shape of the reflection curve of a cylindrical target was analytically derived based on the straight-ray propagation approximation. Subsequently, the total internal reflection (TIR) phenomenon occurring in cylindrical objects was observed and analytically described. Both the straight-ray reflection curve and TIR were well observed on the simulated and laboratory radar data. A comparison between all experiments and radar
Cylindrically converging shock and detonation waves
NASA Astrophysics Data System (ADS)
Matsuo, H.
1983-07-01
The non-self-similar implosion of cylindrical shock and detonation waves generated by an instantaneous energy release at a cylindrical wall is analyzed theoretically by the method of integral relations. The analysis shows that as the wave propagates towards the axis, the solutions tend to approach but never reach the self-similar implosion limit. The rate of approach appears to be slower than expected, and the region of applicability of the self-similar solution appears to be restricted to a very small region behind the front. This tendency is more pronounced for the detonation case. It is also demonstrated that for detonations where the initiation energy is negligible in comparison with the chemical energy, the Chapman-Jouguet detonation jump conditions apply at the front except near the axis and near the outer wall. The chemical heating in the detonation process increases the pressure and the temperature but considerably reduces the density near the front.
Dynamic Buckling of Composite Cylindrical Shells
NASA Astrophysics Data System (ADS)
Cheng, Sai-Wei; Wang, Xiao-Jun
2016-05-01
Considering the effect of stress wave, the dynamic buckling governing equations and boundary conditions of composite cylindrical shells under axial step load are derived based on the Hamilton principle. The expression of radial displacement function along the circumferential direction is assumed since the cylindrical shell is closed. The solutions of the governing equations are obtained by the state-space technique. The determinant of the coefficient matrix must be equal to zero if the linear equations have a non-trivial solution. The relationship between the critical load and length and the influences of boundary conditions, modes, etc. on critical load are obtained by programming with MATLAB software before and after the reflection of stress wave.
Surface superconductivity in thin cylindrical Bi nanowire.
Tian, Mingliang; Wang, Jian; Ning, Wei; Mallouk, Thomas E; Chan, Moses H W
2015-03-11
The physical origin and the nature of superconductivity in nanostructured Bi remains puzzling. Here, we report transport measurements of individual cylindrical single-crystal Bi nanowires, 20 and 32 nm in diameter. In contrast to nonsuperconducting Bi nanoribbons with two flat surfaces, cylindrical Bi nanowires show superconductivity below 1.3 K. However, their superconducting critical magnetic fields decrease with their diameter, which is the opposite of the expected behavior for thin superconducting wires. Quasiperiodic oscillations of magnetoresistance were observed in perpendicular fields but were not seen in the parallel orientation. These results can be understood by a model of surface superconductivity with an enhanced surface-to-bulk volume in small diameter wires, where the superconductivity originates from the strained surface states of the nanowires due to the surface curvature-induced stress.
Experimental study of cylindrical air electrodes
NASA Astrophysics Data System (ADS)
Viitanen, M.; Lamminen, J.; Lampinen, M. J.
1991-11-01
The electrodes studied here are cylindrical and prepared to be placed inside the inner surface of a sintered brass tube, which is nickel-plated. Previously we have reported on the preparation of flat air electrodes and also on long run tests carried out with these electrodes. The electrode material was prepared by the so-called wet method to obtain a carbon dough which is easy to handle. The material preparation remains the same, but owing to the different geometrical shape, the preparation of the electrode itself is quite different. We have studied here the long-term performance of these new cylindrical air electrodes and at the same time measured the carbonate content of the electrolyte. We have also analyzed by comparative methods which property of the electrode lowers the performance after a fairly long period.
Variable-focus cylindrical liquid lens array
NASA Astrophysics Data System (ADS)
Zhao, Wu-xiang; Liang, Dong; Zhang, Jie; Liu, Chao; Zang, Shang-fei; Wang, Qiong-hua
2013-06-01
A variable-focus cylindrical liquid lens array based on two transparent liquids of different refractive index is demonstrated. An elastic membrane divides a transparent reservoir into two chambers. The two chambers are filled with liquid 1 and liquid 2, respectively, which are of different refractive index. The micro-clapboards help liquid 1, liquid 2 and the elastic membrane form a cylindrical lens array. Driving these two liquids to flow can change the shape of the elastic membrane as well as the focal length. In this design, the gravity effect of liquid can be overcome. A demo lens array of positive optical power is developed and tested. Moreover, a potential application of the proposed lens array for autostereoscopic 3D displays is emphasized.
Buckling optimisation of sandwich cylindrical panels
NASA Astrophysics Data System (ADS)
Abouhamzeh, M.; Sadighi, M.
2016-06-01
In this paper, the buckling load optimisation is performed on sandwich cylindrical panels. A finite element program is developed in MATLAB to solve the governing differential equations of the global buckling of the structure. In order to find the optimal solution, the genetic algorithm Toolbox in MATLAB is implemented. Verifications are made for both the buckling finite element code and also the results from the genetic algorithm by comparisons to the results available in literature. Sandwich cylindrical panels are optimised for the buckling strength with isotropic or orthotropic cores with different boundary conditions. Results are presented in terms of stacking sequence of fibers in the face sheets and core to face sheet thickness ratio.
Nanolaminate Membranes as Cylindrical Telescope Reflectors
NASA Technical Reports Server (NTRS)
Dooley, Jennifer; Dragovan, Mark; Hickey, Gregory; Lih, Shyh-Shiu Lih
2010-01-01
A document discusses a proposal to use axially stretched metal nanolaminate membranes as lightweight parabolic cylindrical reflectors in the Dual Anamorphic Reflector Telescope (DART) - a planned spaceborne telescope in which the cylindrical reflectors would be arranged to obtain a point focus. The discussion brings together a combination of concepts reported separately in several prior NASA Tech Briefs articles, the most relevant being "Nanolaminate Mirrors With Integral Figure-Control Actuators" NPO -30221, Vol. 26, No. 5 (May 2002), page 90; and "Reflectors Made From Membranes Stretched Between Beams" NPO -30571, Vol. 33, No. 10 (October 2009), page 11a. The engineering issues receiving the greatest emphasis in the instant document are (1) the change in curvature associated with the Poisson contraction of a stretched nanolaminate reflector membrane and (2) the feasibility of using patches of poly(vinylidene fluoride) on the rear membrane surface as piezoelectric actuators to correct the surface figure for the effect of Poisson contraction and other shape errors.
Damage experiments in a cylindrical geometry
Kaul, Ann M
2010-09-21
Studying spallation damage with a cylindrical configuration allows for a natural recollection of the damaged material under proper driving conditions. Additionally, the damaged material can come to a complete rest without the application of further stopping forces. Specific areas of research include the damage initiation regime in convergent geometry, behavior of material recollected after damage, and effects of convergent geometry on the material response. Such experiments produce unique strain and shear stress states, motivating improvements in existing computational material models and increasing the predictive capabilities of codes. A LANL/VNIIEF joint experimental series has produced cylindrical aluminum failure initiation data and studied the behavior of material recollected after damage initiation and after complete failure. In addition to post-shot collection of the damaged target material for subsequent metallographic analysis, dynamic in-situ experimental diagnostics include velocimetry and transverse radial radiography. This paper will discuss the current experimental status.
Gravitational radiation from a cylindrical naked singularity
Nakao, Ken-ichi; Morisawa, Yoshiyuki
2005-06-15
We construct an approximate solution which describes the gravitational emission from a naked singularity formed by the gravitational collapse of a cylindrical thick shell composed of dust. The assumed situation is that the collapsing speed of the dust is very large. In this situation, the metric variables are obtained approximately by a kind of linear perturbation analysis in the background Morgan solution which describes the motion of cylindrical null dust. The most important problem in this study is what boundary conditions for metric and matter variables should be imposed at the naked singularity. We find a boundary condition that all the metric and matter variables are everywhere finite at least up to the first order approximation. This implies that the spacetime singularity formed by this high-speed dust collapse is very similar to that formed by the null dust and the final singularity will be a conical one. Weyl curvature is completely released from the collapsed dust.
Effect of a rotor wake on the local heat transfer on the forward half of a circular cylinder
NASA Astrophysics Data System (ADS)
Morehouse, Kim A.; Simoneau, Robert J.
Turbine rotor-stator wake dynamics was simulated by a spoked wheel rotating in annular flow, generating rotor wakes. Spanwise averaged circumferentially local heat transfer in the circular cylindrical leading edge region of a turbine airfoil was obtained. Reynolds numbers ranged from 35,000 to 175,000. Strouhal numbers ranged from 0.63 to 2.50. Wakes were generated by 2 sets of circular cylindrical bars, 1.59 and 3.18 mm in diameter. The rotor could be rotated either clockwise or counterclockwise. Grid turbulence was introduced upstream yielding freestream turbulence of 1.0 to 2.5 percent at the stator. Data represented an extensive body of local heat transfer coefficients, which can be used to model the leading edge region of a turbine airfoil. In the presence of rotor wakes, an asymmetry from the leeward to windward side was noted. Windward side levels were 30 to 40 percent higher than the corresonding leeward side.
77 FR 42077 - Environmental Justice: Final Circular
Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-17
... TRANSPORTATION Federal Transit Administration Environmental Justice: Final Circular AGENCY: Federal Transit... (hereinafter ``EJ Circular'') on incorporating environmental justice principles into plans, projects, and... recipients of FTA funds on how to fully engage environmental justice populations in the public...
Machining Thin-Walled Cylindrical Parts
NASA Technical Reports Server (NTRS)
Cimbak, Joe; Spagnolo, Jim; Kraus, Dan
1988-01-01
Cylindrical walls only few thousandths of inch thick machined accurately and without tears or punctures with aid of beryllium copper mandrel. Chilled so it contracts, then inserted in cylinder. As comes to room temperature, mandrel expands and fits snugly inside cylinder. Will not allow part to slide and provides solid backup to prevent deflection when part machined by grinding wheel. When machining finished, cylinder-and-mandrel assembly inserted in dry ice, mandrel contracts and removed from part.
Aberrations of sphero-cylindrical ophthalmic lenses.
Malacara, Z; Malacara, D
1990-04-01
The authors have presented in two previous articles the graphic solutions resembling Tscherning ellipses, for spherical as well as for aspherical ophthalmic lenses free of astigmatism or power error. These solutions were exact, inasmuch as they were based on exact ray tracing, and not third-order theory as frequently done. In this paper sphero-cylindrical lenses are now analyzed, also using exact ray tracing. The functional dependence of the astigmatism and the power error for these lenses is described extensively.
Residual stress characterization for laminated composites
NASA Astrophysics Data System (ADS)
Liu, Shao-Chun
With increasing applications of advanced laminated composites, process-induced residual stress has drawn more and more attention in recent years. Efforts have been devoted to understanding residual stress both quantitatively and qualitatively. In the current study, a novel technique called the Cure Referencing Method was developed which has the capability for measuring the residual stress on the symmetric laminated composite plates. It can also differentiate residual stress into two components: one is due to the mismatch of the coefficient of thermal expansion, the other is caused by the matrix chemical curing shrinkage. The chemical curing shrinkage of the polymer matrix was investigated in further detail. A technique was developed to measure the post-gel chemical curing shrinkage which is the portion of curing shrinkage that really induces the residual stress in the polymer matrix composites. Time-dependent material property is another issue associated with polymer matrix composite materials. The data of several short-term tensile creep tests run at different temperature were used to construct a linear viscoelastic: model for describing the behavior of the composites over a long period of time. It was found that physical aging of the polymer matrix needs to be taken into account in order to have a more accurate representation of the long-term behavior. A fair agreement was obtained between the result of the long-term creep test and the master curve constructed from several momentary creep tests.
Lamins as mediators of oxidative stress
Sieprath, Tom; Darwiche, Rabih; De Vos, Winnok H.
2012-05-18
Highlights: Black-Right-Pointing-Pointer The nuclear lamina defines structural and functional properties of the cell nucleus. Black-Right-Pointing-Pointer Lamina dysfunction leads to a broad spectrum of laminopathies. Black-Right-Pointing-Pointer Recent data is reviewed connecting laminopathies to oxidative stress. Black-Right-Pointing-Pointer A framework is proposed to explain interactions between lamins and oxidative stress. -- Abstract: The nuclear lamina defines both structural and functional properties of the eukaryotic cell nucleus. Mutations in the LMNA gene, encoding A-type lamins, lead to a broad spectrum of diseases termed laminopathies. While different hypotheses have been postulated to explain disease development, there is still no unified view on the mechanistic basis of laminopathies. Recent observations indicate that laminopathies are often accompanied by altered levels of reactive oxygen species and a higher susceptibility to oxidative stress at the cellular level. In this review, we highlight the role of reactive oxygen species for cell function and disease development in the context of laminopathies and present a framework of non-exclusive mechanisms to explain the reciprocal interactions between a dysfunctional lamina and altered redox homeostasis.
Geometrically nonlinear behavior of piezoelectric laminated plates
NASA Astrophysics Data System (ADS)
Rabinovitch, Oded
2005-08-01
The geometrically nonlinear behavior of piezo-laminated plates actuated with isotropic or anisotropic piezoelectric layers is analytically investigated. The analytical model is derived using the variational principle of virtual work along with the lamination and plate theories, the von Karman large displacement and moderate rotation kinematic relations, and the anisotropic piezoelectric constitutive laws. A solution strategy that combines the approach of the method of lines, the advantages of the finite element concept, and the variational formulation is developed. This approach yields a set of nonlinear ordinary differential equations with nonlinear boundary conditions, which are solved using the multiple-shooting method. Convergence and verification of the model are examined through comparison with linear and nonlinear results of other approximation methods. The nonlinear response of two active plate structures is investigated numerically. The first plate is actuated in bending using monolithic piezoceramic layers and the second one is actuated in twist using macro-fiber composites. The results quantitatively reveal the complicated in-plane stress state associated with the piezoelectric actuation and the geometrically nonlinear coupling of the in-plane and out-of-plane responses of the plate. The influence of the nonlinear effects ranges from significant stiffening in certain combinations of electrical loads and boundary conditions to amplifications of the induced deflections in others. The paper closes with a summary and conclusions.
Interlaminar interaction in paper thermoplastic laminate composites
NASA Astrophysics Data System (ADS)
Prambauer, M.; Paulik, C.; Burgstaller, C.
2016-07-01
Bio-based composites are a research topic since several decades, which aims for sustainable and durable materials. In the scope of this research, many different sources for biobased reinforcements have been investigated. Typical issues associated with the use of such are property variations due to cultivation area and climate, besides the influences of the type, pretreatment and fibre geometry. Another issue can be the availability of such natural fibres. Due to these reasons, we started using paper sheets as reinforcements in laminate composites with thermoplastic materials. In preliminary studies with polypropylene composites, we found good mechanical properties, even higher than could be expected by estimating the composite properties from the constituents by applying simple rule of mixtures type models. We suspect, besides some effect of paper compaction, interlaminar effects to be the reason for this. Therefore, the aim of this work is to investigate the effects of the interfacial interaction on the different paper laminate properties due to different matrix polymers. For this work, we used polypropylene, polyamide 6 and 12 as well as polystyrene. Composites were produced via compression moulding and samples for mechanical testing and density evaluation were cut from the moulded plates. The results from mechanical tests show, that there is a reinforcing effect, regardless of matrix polymer used. Simple rule of mixtures evaluations show, that the different matrices exhibit different degrees of interaction, based on their chemical structure. In addition, also influences due to processing were found.
Free Vibration of Uncertain Unsymmetrically Laminated Beams
NASA Technical Reports Server (NTRS)
Kapania, Rakesh K.; Goyal, Vijay K.
2001-01-01
Monte Carlo Simulation and Stochastic FEA are used to predict randomness in the free vibration response of thin unsymmetrically laminated beams. For the present study, it is assumed that randomness in the response is only caused by uncertainties in the ply orientations. The ply orientations may become random or uncertain during the manufacturing process. A new 16-dof beam element, based on the first-order shear deformation beam theory, is used to study the stochastic nature of the natural frequencies. Using variational principles, the element stiffness matrix and mass matrix are obtained through analytical integration. Using a random sequence a large data set is generated, containing possible random ply-orientations. This data is assumed to be symmetric. The stochastic-based finite element model for free vibrations predicts the relation between the randomness in fundamental natural frequencies and the randomness in ply-orientation. The sensitivity derivatives are calculated numerically through an exact formulation. The squared fundamental natural frequencies are expressed in terms of deterministic and probabilistic quantities, allowing to determine how sensitive they are to variations in ply angles. The predicted mean-valued fundamental natural frequency squared and the variance of the present model are in good agreement with Monte Carlo Simulation. Results, also, show that variations between plus or minus 5 degrees in ply-angles can affect free vibration response of unsymmetrically and symmetrically laminated beams.
Integration of sensing networks into laminated composites
NASA Astrophysics Data System (ADS)
Ghezzo, Fabrizia; Rye, Patrick; Huang, Yi; Nemat-Nasser, Sia
2008-03-01
We summarize the methodology that we have used to address integrating sensing network into composite materials for structural self diagnosis. First, we have examined the effect of stress concentration that arises due to the embedment of sensors and external devices on the strength and endurance of laminated glass fiber composites. To analyze the mechanical response of the composite material under study subjected to in-plane or impact loads, we have fabricated a series of samples, with and without embedded (dummy) sensors/micro-processors, using S2 glass fiber/epoxy, and have characterized their response by acoustic emission. Guided by the corresponding results, we can select sensors and other necessary components in such way as to minimize the impact of the embedded electronics on the material integrity and, at the same time, to implement acoustic sensing monitoring functionalities within the material. A 4-tree hierarchical network of PVDF sensors capable of acquiring signals typically related to resin micro cracking phenomena has been developed and partially integrated into a cross ply laminate. The achieved results and ongoing research will be discussed.
Development of a heterogeneous laminating resin system
NASA Technical Reports Server (NTRS)
Biermann, T. F.; Hopper, L. C.
1985-01-01
The factors which effect the impact resistance of laminating resin systems and yet retain equivalent performance with the conventional 450 K curing epoxy matrix systems in other areas were studied. Formulation work was conducted on two systems, an all-epoxy and an epoxy/bismaleimide, to gain fundamental information on the effect formulation changes have upon neat resin and composite properties. The all-epoxy work involved formulations with various amounts and combinations of eight different epoxy resins, four different hardeners, fifteen different toughening agents, a filler, and a catalyst. The epoxy/bismaleimide effort improved formulations with various amounts and combinations of nine different resins, four different hardeners, eight different toughening agents, four different catalysts, and a filler. When a formulation appeared to offer the proper combination of properties required for a laminating resin Celion 3K-70P fabric was prepregged. Initial screening tests on composites primarily involved Gardner type impact and measurement of short beam shear strengths under dry and hot/wet conditions.
Failure and deformation analyses of smart laminated composites
NASA Astrophysics Data System (ADS)
Hasan, Z.; Muliana, A.
2012-09-01
The present study focuses on the failure analysis and shape control of smart composite laminates under coupled thermal (hygro), electric, and mechanical stimuli. A linear thermo(hygro)electroelastic constitutive model for transversely isotropic materials is used for each ply in the composite laminate and for the piezoelectric materials that are integrated with laminates of the composite. Piezoelectric materials, such as lead zirconate titanate, and piezoelectric fiber composites, such as an active fiber composite or a microfiber composite, are considered as actuators for controlling unwanted bending deformations to avoid failure in such composite laminates. Due to the high stress concentrations at the interfaces between an active layer and the host structure, which may cause debonding, embedded actuators in which the active material is placed as part of the plies to form geometrically continuous plies are considered in order to minimize the stress concentration while improving the actuation capability. The first-ply failure and the ultimate laminate failure criteria of composite laminates are used to predict the failure stress and mode of the smart composite laminates, where commonly known macroscopic failure criteria, such as the Tsai-Hill, Tsai-Wu, and maximum stress criteria, are employed for each lamina. Piezoelectric materials can be used to prevent the failure from hygrothermal and mechanical loadings by applying an electric voltage in order to counteract laminate deformations. Based on the deformation and failure analyzes of smart composite laminates having various stacking sequences, fiber and matrix constituents, and piezoelectric materials, we could estimate the overall properties and failure envelopes of the laminates, which is useful in the preliminary design of smart composite structures.
Experimental study of noise emitted by circular cylinders with large roughness
NASA Astrophysics Data System (ADS)
Alomar, Antoni; Angland, David; Zhang, Xin; Molin, Nicolas
2014-12-01
The aerodynamic noise generated by high Reynolds number flow around a bluff body with large surface roughness was investigated. This is a relevant problem in many applications, in particular aircraft landing gear noise. A circular cylinder in cross-flow and a zero-pressure-gradient turbulent boundary layer with various types of roughness was tested in a series of wind tunnel experiments. It has been shown that distributed roughness covering a circular cylinder affects the spectra over the entire frequency range. Roughness noise is dominant at high frequencies, and the peak frequency is well described by Howe's roughness noise model when scaled with the maximum outer velocity. There are differences between hemispherical and cylindrical roughness elements for both the circular cylinder and the zero-pressure-gradient turbulent boundary layer cases, indicating a dependence on roughness shape, not described by the considered roughness noise models. Cylindrical roughness generates higher noise levels at the highest frequencies, especially for the zero-pressure-gradient turbulent boundary layer case. Cable-type roughness aligned with the mean flow does not generate roughness noise, and its spectrum has been found to collapse with the smooth cylinder at medium and high frequencies. At low and medium frequencies the noise spectra have the same features as the smooth cylinder, but with higher shedding peak levels and fall-off levels, despite the decrease in spanwise correlation length. Roughness induces early separation, and thus a shift of the spectra to lower frequencies.
Circular on planned parenthood, 1987.
1987-01-01
In 1987 fourteen units of the Government of Henan issued a Circular stating that: "Planned parenthood must be publicized deep into the grass roots and among the people, and importance must be attached to results." The Circular stresses: "In the propaganda drive, it is necessary to successfully grasp three key links: 1. It is necessary to disseminate intensively the important directive on population problems that is contained in the report of the 13th CPC National Congress and the seriousness of the population situation of our country and province so that the cadres and the masses can understand the relationship between population control and the achievement of the strategic target of the three big steps, understand the reason for carrying out planned parenthood, understand that the one-child policy is still advocated, and conscientiously carry out planned parenthood. 2. It is essential to succeed in propagating knowledge of contraception, sterilization, childbirth, and child care and in conducting ideological education for those who undergo operations and for their family members. 3. It is imperative to visit those who have undergone operations and to help them solve practically their difficulties in making a living." The Circular concludes by demanding that under the unified leadership of party committees and governments at all levels, the propaganda drive be carried out by relying on the efforts of all of society. In conjunction with their own work, departments, including the propaganda, education, public health, and cultural departments, must carry out propaganda and education for planned parenthood.
A novel replicating circular DNAzyme
Chen, Fei; Wang, Ruijian; Li, Zhe; Liu, Bin; Wang, Xiaoping; Sun, Yanhong; Hao, Dongyun; Zhang, Jin
2004-01-01
10–23 DNAzyme has the potential to suppress gene expressions through sequence-specific mRNA cleavage. However, the dependence on exogenous delivery limits its applications. The objective of this work is to establish a replicating DNAzyme in bacteria using a single-stranded DNA vector. By cloning the 10–23 DNAzyme into the M13mp18 vector, we constructed two circular DNAzymes, C-Dz7 and C-Dz482, targeting the β-lactamase mRNA. These circular DNAzymes showed in vitro catalytic efficiencies (kcat/KM) of 7.82 × 106 and 1.36 × 107 M–1·min–1, respectively. Their dependence on divalent metal ions is similar to that found with linear 10–23 DNAzyme. Importantly, the circular DNAzymes were not only capable of replicating in bacteria but also exhibited high activities in inhibiting β-lactamase and bacterial growth. This study thus provides a novel strategy to produce replicating DNAzymes which may find widespread applications. PMID:15115797
NASA Astrophysics Data System (ADS)
Herper, J. C.; Hessel, A.; Tomasic, B.
1985-03-01
It is pointed out that circular cylindrical antenna arrays are of interest for radar and communication applications because of the uniformity of their circumferential radiation characteristics. In surveys of state-of-the-art arrays, most of the cited bibliographies deal with aperture arrays. On the other hand, a dipole element is an attractive choice for an array radiator due to its simplicity of manufacture, reasonably wide bandwidth and polarization purity. For this reason, a two-phase study has been conducted, taking into account a theoretical and experimental investigation. In the first phase, cylindrical stacked ring antenna arrays of uniformly spaced axial dipoles were investigated to establish the mutually coupled element pattern characteristics. The first part of the present paper is concerned with details of this investigation. The second part of the paper will provide an account of the second phase of the study, which consisted of experiments supporting the theoretical phase.