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.
Dynamics of tilted cylindrical geometry
NASA Astrophysics Data System (ADS)
Sharif, M.; Sadiq, Sobia
2016-09-01
In this paper, we study the dynamics of tilted cylindrical model with imperfect matter distribution. We formulate the field equations and develop relations between tilted and non-tilted variables. We evaluate kinematical as well as dynamical quantities and discuss the inhomogeneity factor. We also obtain the Raychaudhuri equation to study evolution of expansion scalar. The solutions of field equations are also investigated for static cylinder under isotropy and conformally flat condition. Finally, we analyze some thermoinertial aspects of the system.
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.
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.
Non-modal analysis of the diocotron instability: Cylindrical geometry
Mikhailenko, V. V.; Lee, Hae June; Mikhailenko, V. S.; Azarenkov, N. A.
2013-04-15
The temporal evolution of the linear diocotron instability of the cylindrical annular plasma column is investigated by employing the extension of the shearing modes methodology to the cylindrical geometry. It was obtained that the spatial time-dependent distortion of the electron density initial perturbations by shear flows leads to the non-modal evolution of the potential, which was referred to as the manifestation of the continuous spectrum. The evolution process leads toward the convergence to the phase-locking configuration of the mutually growing normal modes.
Rayleigh-Taylor instability experiments in a cylindrically convergent geometry
Goodwin, B.; Weir, S.
1995-08-25
Due to the sensitivity of Rayleigh-Taylor instabilities to initial conditions and due to the difficulty of forming well controlled cylindrical or spherical fluid interfaces, Rayleigh-Taylor experiments are often performed with simple, planar interfaces. Rayleigh-Taylor instability phenomena of practical interest, however, (e.g., underwater explosions, supernova core collapses, and inertial confinement fusion capsule implosions) are typically associated with cylindrical or spherical interfaces in which convergent flow effects have an important influence on the dynamics of instability growth. Recently, Meshkov et.al. have developed a novel technique for studying Rayleigh-Taylor instability growth in a cylindrically convergent geometry. Their experiments utilized low-strength gelatin rings which are imploded by a detonating gas mixture of oxygen and acetylene. Since the gelatin itself has sufficient strength to resist significant deformation by gravity, no membranes are needed to define the ring shape. This experimental technique is attractive because it offers a high degree of control over the interfacial geometry and over the material`s strength and rigidity, which can be varied by adjusting the gelatin concentration. Finally, since both the gelatin and the explosive product gases are transparent, optical diagnostics can be used.
Finite and infinite wavelength elastocapillary instabilities with cylindrical geometry
NASA Astrophysics Data System (ADS)
Biggins, John; Xuan, Chen
In an elastic cylinder with shear modulus μ, radius R0 and surface tension γ we can define an emergent elastocapillary length l = γ / μ . When this length becomes comparable to R0 the cylinder becomes undergoes a Rayleigh-Plateaux type instability, but surprisingly, with infinite wavelength λ rather than with wavelength λ ~R0 ~ l . Here we take advantage of this infinite wavelength behaviour to construct a simple 1-D model of the elastocapillary instability in a cylindrical gel which permits a high-amplitude fully non-linear treatment. In particular, we show that the instability is sub-critical and entirely dependent on the elastic cylinder being subject to tension. We also discuss elastocapillary instabilities in a range of other cylindrical geometries, such a cylindrical cavities through a bulk elastic solid, or a solid cylinder embedded in a bulk elastic solid, and show that in these cases instability has finite wavelength. Thus infinite wavelength behaviour is a curiosity of elastic cylinders rather than the generic behaviour or elasto-capiliarity. Also Fudan University Shanghai.
Reversed Field Pinch Dynamics in Toroidal and Cylindrical Geometries
NASA Astrophysics Data System (ADS)
Morales, Jorge A.; Bos, Wouter J. T.; Schneider, Kai; Montgomery, David C.
2014-10-01
The effect of the curvature of the imposed magnetic field on Reversed Field Pinch dynamics is investigated by comparing the flow of a magnetofluid in a torus with aspect ratio 1.83, with the flow in a periodic cylinder. It is found that an axisymmetric toroidal mode is always present in the toroidal, but absent in the cylindrical configuration. In particular, in contrast to the cylinder, the toroidal case presents a double poloidal recirculation cell with a shear localized at the plasma edge. Quasi-single-helicity states are found to be more persistent in toroidal than in periodic cylinder geometry. This work was supported by the contract SiCoMHD (ANR-Blanc 2011-045), computing time was supplied by IDRIS, project 22206.
High-m kink/tearing modes in cylindrical geometry
NASA Astrophysics Data System (ADS)
Connor, J. W.; Hastie, R. J.; Pusztai, I.; Catto, P. J.; Barnes, M.
2014-12-01
The global ideal kink equation, for cylindrical geometry and zero beta, is simplified in the high poloidal mode number limit and used to determine the tearing stability parameter, Δ‧. In the presence of a steep monotonic current gradient, Δ‧ becomes a function of a parameter, σ0, characterising the ratio of the maximum current gradient to magnetic shear and xs, characterising the separation of the resonant surface from the maximum of the current gradient. In equilibria containing a current ‘spike’, so that there is a non-monotonic current profile, Δ‧ also depends on two parameters: κ, related to the ratio of the curvature of the current density at its maximum to the magnetic shear and xs, which now represents the separation of the resonance from the point of maximum current density. The relation of our results to earlier studies of tearing modes and to recent gyrokinetic calculations of current driven instabilities, is discussed, together with potential implications for the stability of the tokamak pedestal.
Selective decay in a long cylindrical geometry in SSX
NASA Astrophysics Data System (ADS)
Gray, T.; Brown, M.; Dandurand, D.; Zhang, X.
2010-11-01
A helical, minimum-energy relaxed plasma state has been observed in a long cylindrical volume. The cylinder is long enough (L/R = 13) so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v >=50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1--2 axial Alfvén times after initiation of the plasma. Magnetic data is favorably compared with an analytical model. Magnetic data exhibits broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement to the minimum energy eigenstate of ∇xB = λB. Merging experiments are planned and additional data will be presented if available.
The Athena Astrophysical MHD Code in Cylindrical Geometry
NASA Astrophysics Data System (ADS)
Skinner, M. A.; Ostriker, E. C.
2011-10-01
We have developed a method for implementing cylindrical coordinates in the Athena MHD code (Skinner & Ostriker 2010). The extension has been designed to alter the existing Cartesian-coordinates code (Stone et al. 2008) as minimally and transparently as possible. The numerical equations in cylindrical coordinates are formulated to maintain consistency with constrained transport, a central feature of the Athena algorithm, while making use of previously implemented code modules such as the eigensystems and Riemann solvers. Angular-momentum transport, which is critical in astrophysical disk systems dominated by rotation, is treated carefully. We describe modifications for cylindrical coordinates of the higher-order spatial reconstruction and characteristic evolution steps as well as the finite-volume and constrained transport updates. Finally, we have developed a test suite of standard and novel problems in one-, two-, and three-dimensions designed to validate our algorithms and implementation and to be of use to other code developers. The code is suitable for use in a wide variety of astrophysical applications and is freely available for download on the web.
THE ATHENA ASTROPHYSICAL MAGNETOHYDRODYNAMICS CODE IN CYLINDRICAL GEOMETRY
Skinner, M. Aaron; Ostriker, Eve C. E-mail: ostriker@astro.umd.ed
2010-05-15
A method for implementing cylindrical coordinates in the Athena magnetohydrodynamics (MHD) code is described. The extension follows the approach of Athena's original developers and has been designed to alter the existing Cartesian-coordinates code as minimally and transparently as possible. The numerical equations in cylindrical coordinates are formulated to maintain consistency with constrained transport (CT), a central feature of the Athena algorithm, while making use of previously implemented code modules such as the Riemann solvers. Angular momentum transport, which is critical in astrophysical disk systems dominated by rotation, is treated carefully. We describe modifications for cylindrical coordinates of the higher-order spatial reconstruction and characteristic evolution steps as well as the finite-volume and CT updates. Finally, we present a test suite of standard and novel problems in one, two, and three dimensions designed to validate our algorithms and implementation and to be of use to other code developers. The code is suitable for use in a wide variety of astrophysical applications and is freely available for download on the Web.
Friedberg, Richard; Manassah, Jamal T.
2011-08-15
We obtain in both the scalar and vector photon models the analytical expressions for the initial cooperative decay rate and the cooperative Lamb shift for an ensemble of resonant atoms distributed uniformly in an infinite cylindrical geometry for the case that the initial state of the system is prepared in a phased state modulated in the direction of the cylindrical axis. We find that qualitatively the scalar and vector theories give different results.
Lewis, Brent J.; Husain, Aamir
2002-12-15
A general methodology was developed to estimate geometry factors for internal gamma dose rate calculations within a cylindrical radioactive waste container. In particular, an average geometry factor is needed to calculate the average energy deposition rate within the container for determination of the internal gas generation rate. Such a calculation is required in order to assess the potential for radioactive waste packages to radiolytically generate combustible gases.This work therefore provides a method for estimating the point and average geometry factors for internal dose assessment for a cylindrical geometry. This analysis is compared to other results where it is shown that the classical work of Hine and Brownell do not correspond to the average geometry factors for a cylindrical body but rather to values at the center of its top or bottom end. The current treatment was further developed into a prototype computer code (PC-CAGE) that calculates the geometry factors numerically for a cylindrical body of any size and material, accounting both for gamma absorption and buildup effects.
Non-modal analysis of the diocotron instability for cylindrical geometry with conducting boundary
Mikhailenko, V. V.; Seok Kim, Jin; Jo, Younghyun; June Lee, Hae; Mikhailenko, V. S.
2014-05-15
The temporal evolution of the linear diocotron instability of a cylindrical annular plasma column surrounded by a conducting boundary has been investigated by using the methodology of the cylindrical shearing modes. The linear solution of the initial and boundary-value problems is obtained which is valid for any time at which linear effects dominate. The solution reveals that the initial perturbations of the electron density pass through the stage of the non-modal evolution when the perturbation experiences spatio-temporal distortion pertinent to the considered geometry of the electron column. The result is confirmed by a two-dimensional cylindrical particle-in-cell simulation.
Stationary premixed flames in spherical and cylindrical geometries
NASA Technical Reports Server (NTRS)
Ronney, P. D.; Whaling, K. N.; Abbud-Madrid, A.; Gatto, J. L.; Pisowiscz, V. L.
1994-01-01
Stationary source-free spherical flames ('flame balls') in premixed combustible gases were studied by employing low-gravity (micro-g) environments in a drop tower and an aircraft flying parabolic trajectories to diminish the impact of buoyancy-induced convective flow. Flame balls were found in all mixture families tested when: (1) the Lewis number Le of the deficient reactant was sufficiently low; and (2) the compositions were sufficiently close to the flammability limits. Probably as a consequence of the reduction in buoyant convection, the flammability limits at micro-g were significantly more dilute than those at Earth gravity; for example, 3.35% H2 vs 4.0% H2 in lean H2-air mixtures. By comparison with analytical and computational models, it is inferred that the phenomenon is probably related to diffusive-thermal effects in low-Le mixtures in conjunction with flame-front curvature and radiative heat losses from the combustion products. The chemical reaction mechanism appears to play no qualitative role. In the aircraft experiments, the gravity levels (approximately equal 10(exp -2)g(sub 0)) were found to cause noticeable motion of flame balls due to buoyancy, which in turn influenced the behavior of flame balls. At these g levels, a new type of transient, nearly cylindrical flame structure, termed 'flame strings,' was observed.
Onset of buoyancy-driven convection in Cartesian and cylindrical geometries
NASA Astrophysics Data System (ADS)
Myint, Philip C.; Firoozabadi, Abbas
2013-04-01
We perform a linear stability analysis to examine the onset of buoyancy-driven convection relevant to subsurface carbon dioxide sequestration in confined, porous Cartesian and cylindrical domains. Our work amends the analysis in an earlier study on cylindrical geometries. We consider Cartesian geometries where the aspect ratio between the two horizontal dimensions is not necessarily equal to one. Two key elements of the stability analysis are: (1) the critical time and (2) the critical wavenumber. Lateral boundaries have a much greater influence on the critical wavenumber than on the critical time. The confinement due to these boundaries impedes the onset of convection to the extent that convection cannot even occur in domains that are smaller than a certain size. Large aspect ratios can significantly reduce boundary effects. Patterns of the earliest-growing perturbation mode in the horizontal plane reveal many interesting dynamics which have not been examined in previous stability analyses. We illustrate several differences between patterns in Cartesian geometries and patterns in cylindrical geometries. Based on observations from earlier papers, we hypothesize that the contrasts between the Cartesian and cylindrical patterns may lead to significantly different behavior in the two geometries after the onset of convection. Our results may guide future numerical studies that can investigate this hypothesis and may help with understanding the onset of buoyancy-driven convection in real systems where lateral boundary effects are significant.
Energy Science and Technology Software Center (ESTSC)
1980-10-15
Version 00 PALLAS-2DCY-FX is a code for direct integration of the transport equation in two-dimensional (r,z) geometry. It solves the energy and angular-dependent Boltzmann transport equation with general anisotropic scattering in cylindrical geometry. Its principal applications are to neutron or gamma-ray transport problems in the forward mode. The code is particularly designed for and suited to the solution of deep penetration radiation transport problems with an external (fixed) source.
Simulations of plasma dynamo in cylindrical and spherical geometries
NASA Astrophysics Data System (ADS)
Khalzov, Ivan; Forest, Cary; Schnack, Dalton; Ebrahimi, Fatima
2010-11-01
We have performed the numerical investigation of plasma flow and possibility of dynamo effect in Madison Plasma Couette Experiment (MPCX) and Madison Plasma Dynamo Experiment (MPDX), which are being installed at the University of Wisconsin- Madison. Using the extended MHD code, NIMROD, we have studied several types of plasma flows appropriate for dynamo excitation. Calculations are done for isothermal compressible plasma model including two-fluid effects (Hall term), which is beyond the standard incompressible MHD picture. It is found that for magnetic Reynolds numbers exceeding the critical one the counter-rotating Von Karman flow (in cylinder) and Dudley- James flow (in sphere) result in self-generation of magnetic field. Depending on geometry and plasma parameters this field can either saturate at certain amplitude corresponding to a new stable equilibrium (laminar dynamo) or lead to turbulent dynamo. It is shown that plasma compressibility results in increase of the critical magnetic Reynolds number while two- fluid effects change the level of saturated dynamo field. The work is supported by NSF.
Khirevich, Siarhei; Höltzel, Alexandra; Tallarek, Ulrich
2011-06-28
We study the time and length scales of hydrodynamic dispersion in confined monodisperse sphere packings as a function of the conduit geometry. By a modified Jodrey-Tory algorithm, we generated packings at a bed porosity (interstitial void fraction) of ε=0.40 in conduits with circular, rectangular, or semicircular cross section of area 100πd(p)(2) (where d(p) is the sphere diameter) and dimensions of about 20d(p) (cylinder diameter) by 6553.6d(p) (length), 25d(p) by 12.5d(p) (rectangle sides) by 8192d(p) or 14.1d(p) (radius of semicircle) by 8192d(p), respectively. The fluid-flow velocity field in the generated packings was calculated by the lattice Boltzmann method for Péclet numbers of up to 500, and convective-diffusive mass transport of 4×10(6) inert tracers was modelled with a random-walk particle-tracking technique. We present lateral porosity and velocity distributions for all packings and monitor the time evolution of longitudinal dispersion up to the asymptotic (long-time) limit. The characteristic length scales for asymptotic behaviour are explained from the symmetry of each conduit's velocity field. Finally, we quantify the influence of the confinement and of a specific conduit geometry on the velocity dependence of the asymptotic dispersion coefficients. PMID:21576163
A quadrupole ion trap with cylindrical geometry operated in the mass-selective instability mode.
Wells, J M; Badman, E R; Cooks, R G
1998-02-01
A cylindrical geometry ion trap is used to record mass spectra in the mass-selective instability mode. The geometry of the cylindrical ion trap has been optimized to maximize the quadrupole field component relative to the higher-order field content through field calculations using the Poisson/Superfish code and through experimental variation of the electrode structure. The results correspond well with predictions of the calculations. The trap has been used to record mass spectra with better than unit mass resolution, high sensitivity, and a mass/charge range of ∼600 Th. Multistage (MS(3)) experiments have been performed, and the Mathieu stability region has been experimentally mapped. The performance of this device compares satisfactorily with that of the hyperbolic ion trap. PMID:21644742
Multi-Group Reductions of LTE Air Plasma Radiative Transfer in Cylindrical Geometries
NASA Technical Reports Server (NTRS)
Scoggins, James; Magin, Thierry Edouard Bertran; Wray, Alan; Mansour, Nagi N.
2013-01-01
Air plasma radiation in Local Thermodynamic Equilibrium (LTE) within cylindrical geometries is studied with an application towards modeling the radiative transfer inside arc-constrictors, a central component of constricted-arc arc jets. A detailed database of spectral absorption coefficients for LTE air is formulated using the NEQAIR code developed at NASA Ames Research Center. The database stores calculated absorption coefficients for 1,051,755 wavelengths between 0.04 µm and 200 µm over a wide temperature (500K to 15 000K) and pressure (0.1 atm to 10.0 atm) range. The multi-group method for spectral reduction is studied by generating a range of reductions including pure binning and banding reductions from the detailed absorption coefficient database. The accuracy of each reduction is compared to line-by-line calculations for cylindrical temperature profiles resembling typical profiles found in arc-constrictors. It is found that a reduction of only 1000 groups is sufficient to accurately model the LTE air radiation over a large temperature and pressure range. In addition to the reduction comparison, the cylindrical-slab formulation is compared with the finite-volume method for the numerical integration of the radiative flux inside cylinders with varying length. It is determined that cylindrical-slabs can be used to accurately model most arc-constrictors due to their high length to radius ratios.
NASA Astrophysics Data System (ADS)
Oguic, Romain; Viazzo, Stéphane; Poncet, Sébastien
2015-11-01
We present an efficient parallelized multidomain algorithm for solving the 3D Navier-Stokes equations in cylindrical geometries. The numerical method is based on fourth-order compact schemes in the two non-homogeneous directions and Fourier series expansion in the azimuthal direction. The temporal scheme is a second-order semi-implicit projection scheme leading to the solution of five Helmholtz/Poisson equations. To handle the singularity appearing at the axis in cylindrical coordinates, while being able to have a thinner or conversely a coarser mesh in this zone, parity conditions are imposed at r = 0 for each flow variable and azimuthal Fourier mode. To simulate flows in irregularly shaped cylindrical geometries and benefit from a hybrid OpenMP/MPI parallelization, an accurate perfectly free-divergence multidomain method based on the influence matrix technique is proposed. First, the accuracy of the present solver is checked by comparison with analytical solutions and the scalability is then evaluated. Simulations using the present code are then compared to reliable experimental and numerical results of the literature showing good quantitative agreements in the cases of the axisymmetric and 3D unsteady vortex breakdowns in a cylinder and turbulent pipe flow. Finally to show the capability of the algorithm to deal with more complex flows relevant of turbomachineries, the turbulent flow inside a simplified stage of High-Pressure compressor is considered.
Geometry optimization for the cylindrical ion trap: field calculations, simulations and experiments
NASA Astrophysics Data System (ADS)
Wu, Guangxiang; Cooks, R. Graham; Ouyang, Zheng
2005-03-01
Optimization of ion trap geometries for best analytical performance was studied in the specific case of the cylindrical ion trap (CIT). An optimization procedure was developed based on field calculations and simulations of ion motion. The electric field inside the CIT was calculated by using the Poisson/Superfish software package and geometrical effects, specifically the half thickness of the ring electrode (zb), the spacing (ds) between the ring electrode and the end-cap electrode, and the end-cap hole radius (rH), were systematically investigated. Appropriate compensation for higher-order field components, namely octapolar and dodecapolar fields, was achieved by refining the CIT geometry and improved mass resolution in scans using boundary and resonance ejection. Resolution for different CIT geometries was measured in both simulations and experiments and was evaluated from the separation between the major isotope peaks of 1,3-dichlorobenzene at m/z 146 and 148. Optimization of the CIT electric field via simple geometry changes involved exploration of several geometries and simulations using the ion trap simulation program (ITSIM) were used to confirm the results for each geometry and to predict experimental performance. Experiments are reported that confirm the enhanced performance achieved using the CITs optimized using the procedure developed in this study.
The influence of triggers geometry upon the stiffness of cylindrical thin walled tubes
NASA Astrophysics Data System (ADS)
Soica, Adrian; Radu, Gheorghe N.
2014-06-01
Today's automobile manufacturers are increasingly using lightweight materials to reduce weight; these include plastics, composites, aluminium, magnesium alloys, and also new types of high strength steels. Many of these materials have limited strength or ductility, therefore in many cases the rupture being serious consequences during crashes, underscore Picketta et al. in their studies. Automotive structures must deform plastically in a short period of time, a few milliseconds, to absorb the crash energy in a controllable manner. It must be light and enable economically mass-production [1]. FE models rapidly gained acceptance among engineers. Many other factors facilitated the development of vehicle models by shell finite elements since most of the geometry of the structural surfaces was already on computer graphic files. Kee Poong Kim and Hoon Huh emphasize that the crashworthiness of each vehicle part needs to be evaluated at the initial stage of design for good performance of an assembled vehicle. As the dynamic behaviour of structural members is different from the static one, the crashworthiness of the vehicle structures has to be assessed by impact analysis. The paper analyzes the influence of trigger geometry upon the compression of thin-walled cylindrical tubes. Simulations performed on a simple model showed the dependence between triggers area and deformation times as well as the maximum deformations obtained for various speeds at which the simulations ware carried out. Likewise, the geometry of trigger leads to different results.
LI, BO; SUN, HUI; ZHOU, SHENGGAO
2015-01-01
The solute-solvent interface that separates biological molecules from their surrounding aqueous solvent characterizes the conformation and dynamics of such molecules. In this work, we construct a solvent fluid dielectric boundary model for the solvation of charged molecules and apply it to study the stability of a model cylindrical solute-solvent interface. The motion of the solute-solvent interface is defined to be the same as that of solvent fluid at the interface. The solvent fluid is assumed to be incompressible and is described by the Stokes equation. The solute is modeled simply by the ideal-gas law. All the viscous force, hydrostatic pressure, solute-solvent van der Waals interaction, surface tension, and electrostatic force are balanced at the solute-solvent interface. We model the electrostatics by Poisson’s equation in which the solute-solvent interface is treated as a dielectric boundary that separates the low-dielectric solute from the high-dielectric solvent. For a cylindrical geometry, we find multiple cylindrically shaped equilibrium interfaces that describe polymodal (e.g., dry and wet) states of hydration of an underlying molecular system. These steady-state solutions exhibit bifurcation behavior with respect to the charge density. For their linearized systems, we use the projection method to solve the fluid equation and find the dispersion relation. Our asymptotic analysis shows that, for large wavenumbers, the decay rate is proportional to wavenumber with the proportionality half of the ratio of surface tension to solvent viscosity, indicating that the solvent viscosity does affect the stability of a solute-solvent interface. Consequences of our analysis in the context of biomolecular interactions are discussed. PMID:26877555
Electron Raman scattering in semiconductor quantum well wire of cylindrical ring geometry
NASA Astrophysics Data System (ADS)
Re., Betancourt-Riera; Ri., Betancourt-Riera; M. Nieto Jalil, J.; Riera, R.
2015-11-01
We study the electron states and the differential cross section for an electron Raman scattering process in a semiconductor quantum well wire of cylindrical ring geometry. The electron Raman scattering developed here can be used to provide direct information about the electron band structures of these confinement systems. We assume that the system grows in a GaAs/Al0.35Ga0.65As matrix. The system is modeled by considering T = 0 K and also a single parabolic conduction band, which is split into a sub-band system due to the confinement. The emission spectra are discussed for different scattering configurations, and the selection rules for the processes are also studied. Singularities in the spectra are found and interpreted.
RECENT RESULTS OF RADIATION HYDRODYNAMICS AND TURBULENCE EXPERIMENTS IN CYLINDRICAL GEOMETRY.
Magelssen G. R.; Scott, J. M.; Batha, S. H.; Holmes, R. L.; Lanier, N. E.; Tubbs, D. L.; Elliott, N. E.; Dunne, A. M.; Rothman, S.; Parker, K. W.; Youngs, D.
2001-01-01
Cylindrical implosion experiments at the University of Rochester laser facility, OMEGA, were performed to study radiation hydrodynamics and compressible turbulence in convergent geometry. Laser beams were used to directly drive a cylinder with either a gold (AU) or dichloropolystyrene (C6H8CL2) marker layer placed between a solid CH ablator and a foam cushion. When the cylinder is imploded the Richtmyer-Meshkov instability and convergence cause the marker layer to increase in thickness. Marker thickness measurements were made by x-ray backlighting along the cylinder axis. Experimental results of the effect of surface roughness will be presented. Computational results with an AMR code are in good agreement with the experimental results from targets with the roughest surface. Computational results suggest that marker layer 'end effects' and bowing increase the effective thickness of the marker layer at lower levels of roughness.
NASA Technical Reports Server (NTRS)
Kiefer, Walter S.; Hager, Bradford H.
1992-01-01
A variety of evidence suggests that at least some hotspots are formed by quasi-cylindrical mantle plumes upwelling from deep in the mantle. Such plumes are modeled in cylindrical, axisymmetric geometry with depth-dependent, Newtonian viscosity. Cylindrical and sheet-like, Cartesian upwellings have significantly different geoid and topography signatures. However, Rayleigh number-Nusselt number systematics in the two geometries are quite similar. The geoid anomaly and topographic uplift over a plume are insensitive to the viscosity of the surface layer, provided that it is at least 1000 times the interior viscosity. Increasing the Rayleigh number or including a low-viscosity asthenosphere decreases the geoid anomaly and the topographic uplift associated with an upwelling plume.
Zakharov-Kuznestov-Burger Equation for Ion-Acoustic Waves in Cylindrical Geometry
NASA Astrophysics Data System (ADS)
Mandal, Pankaj Kumar; Ghosh, Uday Narayan; Chaterjee, Prasanta
2015-07-01
The nonlinear wave structures of ion acoustic waves in magnetized plasma comprising ions, non-extensive distributed electrons and kinematic viscosity are investigated through dynamical study. In a bounded cylindrical geometry Zakharov-Kuznestov-Burger (ZKB) equation is derived, for the first time, using reductive perturbation technic. System of coupled nonlinear ordinary differential equations is derived from ZKB equation and is solved numerically using fourth order Runge-kutta method. Equilibrium points are obtained and the features are studied dynamically in the neighbourhood of these points. With the variation of the non-extensive parameter and the kinematic viscosity parameter some important features in the nonlinear waves like oscillatory shocks to steady state propagation and vis-a-vis steady state propagation to oscillatory shocks emerge. When the values of the non-extensive parameter decrease, the phase portrait of the system shows that the change from stable spiral to stable closed and stable to unstable equilibrium happens . When the effect of dissipative term i.e. kinematic viscosity is considered some other significant features also evolve .The reduction of the value of kinematic viscosity results the change in nature of the waves from oscillatory shocks to periodic one.
Han, B.S.; Lee, K.J.; Hwang, Y.S.
1995-12-01
Numerical simulation of radionuclide migration as a form of colloid in two dimentional cylindrical geometry were conducted. Due to the relatively strong filtration phenomena in backfill material of waste repository, colloid concentrations decay out very rapidly along the geosphere. Inside the backfill material, diffusional transport of radiocolloid is known to be relatively dominant than that of advection. The flow conditions of the waste repository groundwater can be represented with a dimensionless Peclet number. If the Peclet number is lower than 2, which means diffusion is dominant transport mechanism, general Finite Difference Method (FDM) cannot predict the migration behavior of the colloid exactly due to the numerical error. Instead, so called Central Difference Method (CDM) is applicable for the low Peclet number problems. outside the backfill media, where advection is the controlling transport process with Peclet number being greater than 2, the upwind numerical scheme would be a powerful tool. Most of the experiments simulating the radionuclide migration were conducted at high flow conditions, and the theoretical modelling about the experiments typically neglected the role of the diffusion in filtration mechanism. In this paper the two-dimensional CDM scheme and CDM-upwind scheme are developed to describe radio-colloid migration in two-dimensional porous media using potential flow theorem. Then the mass fluxes at a given position inside the backfill are predicted.
Gheisari, R.; Firoozabadi, M. M.; Mohammadi, H.
2014-01-15
A new idea to calculate ultracold neutron (UCN) production by using Monte Carlo simulation method to calculate the cold neutron (CN) flux and an analytical approach to calculate the UCN production from the simulated CN flux was given. A super-thermal source (UCN source) was modeled based on an arrangement of D{sub 2}O and solid D{sub 2} (sD{sub 2}). The D{sub 2}O was investigated as the neutron moderator, and sD{sub 2} as the converter. In order to determine the required parameters, a two-dimensional (2D) neutron balance equation written in Matlab was combined with the MCNPX simulation code. The 2D neutron-transport equation in cylindrical (ρ − z) geometry was considered for 330 neutron energy groups in the sD{sub 2}. The 2D balance equation for UCN and CN was solved using simulated CN flux as boundary value. The UCN source dimensions were calculated for the development of the next UCN source. In the optimal condition, the UCN flux and the UCN production rate (averaged over the sD{sub 2} volume) equal to 6.79 × 10{sup 6} cm{sup −2}s{sup −1} and 2.20 ×10{sup 5} cm{sup −3}s{sup −1}, respectively.
Task order #24 update: exploration of damage mechanisms in cylindrical geometry
Kaul, Ann M
2011-01-14
A typical method of failure for ductile materials is spallation damage, which is caused by the nucleation, growth and coalescence of voids due to the presence of high tensile stress in the material. Spallation damage models, such as TEPLA, are currently implemented in hydrodynamic computer codes used at Los Alamos National Laboratory (LANL). Parameters for such constitutive models are derived from data sets obtained primarily from gas gun and shock-driven experiments, which are designed to allow one-dimensional analysis of the evolution of the failure characteristics. However, in a non-planar geometry, advanced failure models predict failure to be a multi-dimensional process. Additionally, a limited amount of data exists for the process of void nucleation, growth and coalescence. Another lightly researched area is the state of the material in the event that the spallation layer is recollected and voids are closed. The experiments described here are being conducted as part of a Campaign-l effort to provide data addressing these issues. The Russian Damage Experimental Series is designed to provide fundamental non-planar (cylindrical) spallation damage data, including early time processes (void nucleation, growth and coalescence) and late time processes (recollection of the spallation layer). Previous experiments produced data addressing some of the early time processes. This presentation will be provided to LANL and VNIIEF colleagues as a means of assessing the status of Task Order No.24 at the current time.
A plastic miniature x-ray emission spectrometer based on the cylindrical von Hamos geometry
NASA Astrophysics Data System (ADS)
Mattern, B. A.; Seidler, G. T.; Haave, M.; Pacold, J. I.; Gordon, R. A.; Planillo, J.; Quintana, J.; Rusthoven, B.
2012-02-01
We present a short working distance miniature x-ray emission spectrometer (miniXES) based on the cylindrical von Hamos geometry. We describe the general design principles for the spectrometer and detail a specific implementation that covers Kβ and valence level emission from Fe. Large spatial and angular access to the sample region provides compatibility with environmental chambers, microprobe, and pump/probe measurements. The primary spectrometer structure and optic is plastic, printed using a 3-dimensional rapid-prototype machine. The spectrometer is inexpensive to construct and is portable; it can be quickly set up at any focused beamline with a tunable narrow bandwidth monochromator. The sample clearance is over 27 mm, providing compatibility with a variety of environment chambers. An overview is also given of the calibration and data processing procedures, which are implemented by a multiplatform user-friendly software package. Finally, representative measurements are presented. Background levels are below the level of the Kβ2, 5 valence emission, the weakest diagram line in the system, and photometric analysis of count rates finds that the instrument is performing at the theoretical limit.
NASA Astrophysics Data System (ADS)
Bedington, Robert; Kataria, Dhiren; Smith, Alan
2015-09-01
The CATS (Cylindrical And Tiny Spectrometer) electrostatic optics geometry features multiple nested cylindrical analysers to simultaneously measure multiple energies of electron and multiple energies of ion in a configuration that is targeted at miniaturisation and MEMS fabrication. In the prototyped model, two configurations of cylindrical analyser were used, featuring terminating side-plates that caused particle trajectories to either converge (C type) or diverge (D type) in the axial direction. Simulations show how these different electrode configurations affect the particle focussing and instrument parameters; C-type providing greater throughputs but D-type providing higher resolving powers. The simulations were additionally used to investigate unexpected plate spacing variations in the as-built model, revealing that the k-factors are most sensitive to the width of the inter-electrode spacing at its narrowest point.
NASA Astrophysics Data System (ADS)
Agashe, Janhavi S.; Arnold, David P.
2008-05-01
Kelvin's formula is used to calculate forces acting on a permanent magnet in the presence of an external magnetic field from a second permanent magnet. This approach is used to derive explicit analytical solutions for the axial and lateral forces between cuboidal and cylindrical permanent magnets as functions of magnet dimensions and separation. While exact solutions can be found for cuboidal magnets, a hypergeometric expansion is used to approximate the elliptic integrals in solving for the fields and forces for the cylindrical magnets. The resulting equations are applied over a range of magnet sizes and geometries to explore scaling laws and other geometrical effects. It is shown that cuboidal magnets provide larger forces than equivalently sized cylindrical magnets. Also, the aspect ratio of the magnets significantly affects the forces. These results are intended to benefit the design and optimization of sensors, actuators and systems that rely on magnetic forces, particularly at the microscale.
Torres-Diaz, I.; Cortes, A.; Rinaldi, C.; Cedeño-Mattei, Y.; Perales-Perez, O.
2014-01-15
Ferrofluid flow in cylindrical and annular geometries under the influence of a uniform rotating magnetic field was studied experimentally using aqueous ferrofluids consisting of low concentrations (<0.01 v/v) of cobalt ferrite nanoparticles with Brownian relaxation to test the ferrohydrodynamic equations, elucidate the existence of couple stresses, and determine the value of the spin viscosity in these fluids. An ultrasound technique was used to measure bulk velocity profiles in the spin-up (cylindrical) and annular geometries, varying the intensity and frequency of the rotating magnetic field generated by a two pole stator winding. Additionally, torque measurements in the cylindrical geometry were made. Results show rigid-body like velocity profiles in the bulk, and no dependence on the axial direction. Experimental velocity profiles were in quantitative agreement with the predictions of the spin diffusion theory, with a value of the spin viscosity of ∼10{sup −8} kg m/s, two orders of magnitude larger than the value estimated earlier for iron oxide based ferrofluids, and 12 orders of magnitude larger than estimated using dimensional arguments valid in the infinite dilution limit. These results provide further evidence of the existence of couple stresses in ferrofluids and their role in driving the spin-up flow phenomenon.
NASA Technical Reports Server (NTRS)
Romesser, T. E.
1974-01-01
Ion acoustic phenomena are studied in a cylindrical geometry for two distinct cases. A large amplitude compressive pulse is seen to evolve into solitons. The evolution of these solitons and their dependence on initial conditions show a similarity to previous work on one dimensional solitons. Dimensionless scaling arguments are used to distinguish the two cases. In the presence of a steady state uniform cylindrical beam, approximated by a ring in V sub r, V sub phi, an ion-ion beam instability is observed. This instability exists for a limited range of beam velocities and shows a marked similarity to the strictly one dimensional ion-ion beam instability. Solution of the appropriate dispersion relation shows agreement with the observed phenomenon.
Ritchie, R.H.; Sakakura, A.Y.
1956-01-01
The formal solutions of problems involving transient heat conduction in infinite internally bounded cylindrical solids may be obtained by the Laplace transform method. Asymptotic series representing the solutions for large values of time are given in terms of functions related to the derivatives of the reciprocal gamma function. The results are applied to the case of the internally bounded infinite cylindrical medium with, (a) the boundary held at constant temperature; (b) with constant heat flow over the boundary; and (c) with the "radiation" boundary condition. A problem in the flow of gas through a porous medium is considered in detail.
Bailey, T S; Adams, M L; Chang, J H
2008-10-01
We present a new spatial discretization of the discrete-ordinates transport equation in two-dimensional cylindrical (RZ) geometry for arbitrary polygonal meshes. This discretization is a discontinuous finite element method that utilizes the piecewise linear basis functions developed by Stone and Adams. We describe an asymptotic analysis that shows this method to be accurate for many problems in the thick diffusion limit on arbitrary polygons, allowing this method to be applied to radiative transfer problems with these types of meshes. We also present numerical results for multiple problems on quadrilateral grids and compare these results to the well-known bi-linear discontinuous finite element method.
NASA Technical Reports Server (NTRS)
Egan, Michael P.; Leung, Chun Ming; Spagna, George F., Jr.
1988-01-01
The program solves the radiation transport problem in a dusty medium with one-dimensional planar, spherical or cylindrical geometry. It determines self-consistently the effects of multiple scattering, absorption, and re-emission of photons on the temperature of dust grains and the characteristics of the internal radiation field. The program can treat radiation field anisotropy, linear anisotropic scattering, and multi-grain components. The program output consists of the dust-temperature distribution, flux spectrum, surface brightness at each frequency and the observed intensities (involving a convolution with a telescope beam pattern).
NASA Astrophysics Data System (ADS)
Koenig, Anne; Planat-Chrétien, Anne; Coutard, Jean-Guillaume; Hervé, Lionel; Brambilla, Marco; Josserand, Véronique; Coll, Jean-Luc; Dinten, Jean-Marc
2011-03-01
An instrument dedicated to the co-registration of optical and X-ray measurements is presented: specific acquisition protocol and reconstruction software have been developed for carrying out fluorescence diffuse optical tomography in a cylindrical geometry consistent with XCT. Actual animal geometry provided by the X-ray tomography is used to give animal boundaries to the diffuse optical tomography reconstruction algorithm. To evaluate performances of this new optical imaging system, experiments have been conducted on phantoms, mice with fluorescent capillaries, and finally on mice bearing tumors. The fluorescence reconstructions are shown to be geometrically consistent with X-ray ones. We determined that the sensibility limit of the system to detect fluorescence signal over intrinsic ones is 2 pmol for lungs area and 5 pmol for the abdomen area.
NASA Astrophysics Data System (ADS)
Blas, Felipe J.; Mendiboure, Bruno
2013-04-01
We extend the well-known Test-Area methodology of Gloor et al. [J. Chem. Phys. 123, 134703 (2005)], 10.1063/1.2038827, originally proposed to evaluate the surface tension of planar fluid-fluid interfaces along a computer simulation in the canonical ensemble, to deal with the solid-fluid interfacial tension of systems adsorbed on cylindrical pores. The common method used to evaluate the solid-fluid interfacial tension invokes the mechanical relation in terms of the tangential and normal components of the pressure tensor relative to the interface. Unfortunately, this procedure is difficult to implement in the case of cylindrical geometry, and particularly complex in case of nonspherical molecules. Following the original work of Gloor et al., we perform free-energy perturbations due to virtual changes in the solid-fluid surface. In this particular case, the radius and length of the cylindrical pore are varied to ensure constant-volume virtual changes of the solid-fluid surface area along the simulation. We apply the modified methodology for determining the interfacial tension of a system of spherical Lennard-Jones molecules adsorbed inside cylindrical pores that interact with fluid molecules through the generalized 10-4-3 Steele potential recently proposed by Siderius and Gelb [J. Chem. Phys. 135, 084703 (2011)], 10.1063/1.3626804. We analyze the effect of pore diameter, density of adsorbed molecules, and fluid-fluid cutoff distance of the Lennard-Jones intermolecular potential on the solid-fluid interfacial tension. This extension, as the original Test-Area formulation, offers clear advantages over the classical mechanical route of computational efficiency, easy of implementation, and generality.
Self-organization of helically forced MHD flow in confined cylindrical geometries
NASA Astrophysics Data System (ADS)
Roberts, Malcolm; Leroy, Matthieu; Morales, Jorge; Bos, Wouter; Schneider, Kai
2014-12-01
The dynamics of a magnetically forced conducting fluid in confined geometries is studied. A pseudospectral method with volume penalisation is used to solve the resistive magnetohydrodynamic equations. A helical magnetic field is imposed via boundary conditions, which generates a response in the velocity field for large enough magnitudes. Different helical structures are observed in the flow depending on the magnitude and direction of the forcing and the cross-sectional geometry of the fluid domain. A computational technique for finding a solenoidal vector field which can be used in complex geometries is also proposed.
NASA Astrophysics Data System (ADS)
Pérez-Barrera, James; Pérez-Espinoza, José Enrique; Ortíz, Alejandro; Cuevas, Sergio; Ramos, Eduardo
2014-11-01
We present numerical simulations of the flow produced by an azimuthal Lorentz force in an electromagnetic stirrer. The stirrer consists of a cylindrical cavity with two copper concentric cylindrical electrodes, filled with an electrolytic solution. Underneath the cavity, a permanent magnet creates an almost uniform magnetic field, perpendicular to the circular section of the stirrer. An electric potential difference between the electrodes produces a radial D.C. current that passes through the fluid and interacts with the axial magnetic field, generating an azimuthal Lorentz force that drives the fluid. Experiments have shown the appearance of a flow instability that gives rise to a varying number of anticyclonic vortices for given values of the current intensity and fluid layer thickness. The MHD governing equations are expressed in terms of the velocity, pressure and electric potential. Numerical simulations are carried out using a hybrid Finite volume-Fourier method to ensure periodicity in the azimuthal direction. Numerical results show the formation of different modes of perturbation in the velocity field, which give rise to a varying number of traveling vortical structures. Work supported by CONACYT, Mexico under Project 131399. JPB acknowledges a Grant from CONACYT.
Numerical study of laminar plasma dynamo in cylindrical and spherical geometries
NASA Astrophysics Data System (ADS)
Khalzov, Ivan; Bayliss, Adam; Ebrahimi, Fatima; Forest, Cary; Schnack, Dalton
2009-05-01
We have performed the numerical investigation of possibility of laminar dynamo in two new experiments, Plasma Couette and Plasma Dynamo, which have been designed at the University of Wisconsin-Madison. The plasma is confined by a strong multipole magnetic field localized at the boundary of cylindrical (Plasma Couette) or spherical (Plasma Dynamo) chamber. Electrodes positioned between the magnet rings can be biased with arbitrary potentials so that Lorenz force ExB drives any given toroidal velocity profile at the surface. Using the extended MHD code, NIMROD, we have modeled several types of plasma flows appropriate for dynamo excitation. It is found that for high magnetic Reynolds numbers the counter-rotating von Karman flow (in cylinder) and Dudley-James flow (in sphere) can lead to self-generation of non-axisymmetric magnetic field. This field saturates at certain amplitude corresponding to a new stable equilibrium. The structure of this equilibrium is considered.
Study of neoclassical tearing modes based on a reduced MHD model in cylindrical geometry
NASA Astrophysics Data System (ADS)
Sato, M.; Wakatani, M.
2005-02-01
Neoclassical tearing modes (NTMs) are examined with a reduced MHD model including the bootstrap current as a simple model, JBS vprop - dP/dr, in cylindrical tokamaks. It is found that linear instabilities due to the perturbation of bootstrap current appear for large JBS cases with large parallel thermal diffusivity, χpar, under small perpendicular thermal diffusivity, χbottom, in the pressure evolution equation. Here, other dissipations such as resistivity and viscosity are also finite. Although the linear growth rate of this unstable mode is small, the growth of magnetic energy of this unstable mode is usually accelerated after the saturation of kinetic energy. Its nonlinear behaviour shown by the evolution of magnetic islands is consistent with the standard nonlinear NTM theory.
NASA Astrophysics Data System (ADS)
Seip, Ralf; Chen, Wohsing; Carlson, Roy; Frizzell, Leon; Warren, Gary; Smith, Nadine; Saleh, Khaldon; Gerber, Gene; Shung, Kirk; Guo, Hongkai; Sanghvi, Narendra T.
2005-03-01
This paper presents engineering progress and the latest in-vitro and in-vivo results obtained with a 4.0 MHz, 20 element, PZT annular transrectal HIFU array and several 4.0 MHz, 211 element, PZT and piezocomposite cylindrical transrectal HIFU arrays for the treatment of prostate cancer. The geometries of both arrays were designed and analyzed to steer the HIFU beams to the desired sites in the prostate volume using multi-channel electronic drivers, with the intent to increase treatment efficiency and reliability for the next generation of HIFU systems. The annular array is able to focus in depth from 25 mm to 50 mm, generate total acoustic powers in excess of 60W, and has been integrated into a modified Sonablate®500 HIFU system capable of controlling such an applicator through custom treatment planning and execution software. Both PZT- and piezocomposite cylindrical arrays were constructed and their characteristics were compared for the transrectal applications. These arrays have been installed into appropriate transducer housings, and have undergone characterization tests to determine their total acoustic power output, focusing range (in depth and laterally), focus quality, efficiency, and comparison tests to determine the material and technology of choice (PZT or piezocomposite) for intra-cavity HIFU applications. Array descriptions, characterization results, in-vitro and in-vivo results, and an overview of their intended use through the application software is shown.
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.
2015-11-19
In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As amore » result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.« less
NASA Astrophysics Data System (ADS)
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.
2015-11-01
In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ˜600 kA with ˜200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.
Yager-Elorriaga, D A; Steiner, A M; Patel, S G; Jordan, N M; Lau, Y Y; Gilgenbach, R M
2015-11-01
In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ∼600 kA with ∼200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines. PMID:26628134
Yager-Elorriaga, D. A.; Steiner, A. M.; Patel, S. G.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.
2015-11-19
In this study, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ~600 kA with ~200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. As a result, this technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.
Gravier, E.; Plaut, E.
2013-04-15
Collisional drift waves and ion temperature gradient (ITG) instabilities are studied using a linear water-bag kinetic model [P. Morel et al., Phys. Plasmas 14, 112109 (2007)]. An efficient spectral method, already validated in the case of drift waves instabilities [E. Gravier et al., Eur. Phys. J. D 67, 7 (2013)], allows a fast solving of the global linear problem in cylindrical geometry. The comparison between the linear ITG instability properties thus computed and the ones given by the COLUMBIA experiment [R. G. Greaves et al., Plasma Phys. Controlled Fusion 34, 1253 (1992)] shows a qualitative agreement. Moreover, the transition between collisional drift waves and ITG instabilities is studied theoretically as a function of the ion temperature profile.
NASA Technical Reports Server (NTRS)
Litvin, Faydor L.; Nava, Alessandro; Fan, Qi; Fuentes, Alfonso
2002-01-01
New geometry of face worm gear drives with conical and cylindrical worms is proposed. The generation of the face worm-gear is based on application of a tilted head-cutter (grinding tool) instead of application of a hob applied at present. The generation of a conjugated worm is based on application of a tilted head-cutter (grinding tool) as well. The bearing contact of the gear drive is localized and is oriented longitudinally. A predesigned parabolic function of transmission errors for reduction of noise and vibration is provided. The stress analysis of the gear drive is performed using a three-dimensional finite element analysis. The contacting model is automatically generated. The developed theory is illustrated with numerical examples.
Thermal contact resistance for a CU/G-10CR interface in a cylindrical geometry
Phelan, P.E.; Niemann, R.C.; Nicol, T.H.
1996-07-01
A major component of a high-T[sub c] superconductor current lead designed to provide current to low-T[sub c] superconductor magnets is the heat intercept connection, which is a cylindrical structure consisting of an inner Cu disk, a thin-walled G-10CR composite tube, and an outer Cu ring, assembled by a thermal interference fit. It was determined in a previous study that the thermal contact resistance (R[sub c]) between the composite tube and the two Cu pieces contributed a substantial portion of the total thermal resistance between the inner and outer Cu pieces. This report emphasizes the analysis of the data for the third and final design of the heat intercept connection. In particular, it is found that R[sub c] decreases dramatically with increasing heat flux, a result consistent with earlier studies of composite cylinders. However, for the present data, the thermal contact conductance [=1/R{sub c}]varies with the calculated contact pressure with a power-law exponent of approximately 10, as compared to a theoretical value near 1. In addition, the presence of He or N[sub 2] gas substantially reduces R [sub c] even though the contacting surfaces are coated with a thermal grease.
Experimental investigation of the shock wave in a fast discharge with cylindrical geometry
Antsiferov, P. S.; Dorokhin, L. A.
2013-08-15
The work is devoted to the registration and the study of the properties of cylindrical shock waves generated in the fast discharge (dI/dt ∼ 10{sup 12} A/s) inside the ceramic tube (Al{sub 2}O{sub 3}) filled by argon at pressures of 100 and 300 Pa. The shock wave appears at the inner wall of the insulator and moves to the discharge axis with a velocity of about (3−4) × 10{sup 6} cm/s with subsequent cumulation. The plasma behind the front is heated enough to produce radiation in the vacuum ultraviolet (VUV) region, which makes it possible to study its structure by means of a pinhole camera with a microchannel plate detector. The time resolution of the registration system was 10 ns. The analysis of VUV spectra of the plasma shows that the electron temperature behind the shock wave front is about several eV; after the moment of cumulation, its temperature increases to 20–30 eV.
Proton radiography of laser-driven imploding target in cylindrical geometry
Volpe, L.; Batani, D.; Vauzour, B.; Nicolai, Ph.; Santos, J. J.; Regan, C.; Dorchies, F.; Fourment, C.; Hulin, S.; Morace, A.; Perez, F.; Baton, S.; Lancaster, K.; Galimberti, M.; Heathcote, R.; Tolley, M.; Spindloe, Ch.; Koester, P.; Labate, L.; Gizzi, L. A.
2011-01-15
An experiment was done at the Rutherford Appleton Laboratory (Vulcan laser petawatt laser) to study fast electron propagation in cylindrically compressed targets, a subject of interest for fast ignition. This was performed in the framework of the experimental road map of HiPER (the European high power laser energy research facility project). In the experiment, protons accelerated by a picosecond-laser pulse were used to radiograph a 220 {mu}m diameter cylinder (20 {mu}m wall, filled with low density foam), imploded with {approx}200 J of green laser light in four symmetrically incident beams of pulse length 1 ns. Point projection proton backlighting was used to get the compression history and the stagnation time. Results are also compared to those from hard x-ray radiography. Detailed comparison with two-dimensional numerical hydrosimulations has been done using a Monte Carlo code adapted to describe multiple scattering and plasma effects. Finally we develop a simple analytical model to estimate the performance of proton radiography for given implosion conditions.
Optimization of Orifice Geometry for Cross-Flow Mixing in a Cylindrical Duct
NASA Technical Reports Server (NTRS)
Kroll, J. T.; Sowa, W. A.; Samuelsen, G. S.
1996-01-01
Mixing of gaseous jets in a cross-flow has significant applications in engineering, one example of which is the dilution zone of a gas turbine combustor. Despite years of study, the design of the jet injection in combustors is largely based on practical experience. The emergence of NO(x) regulations for stationary gas turbines and the anticipation of aero-engine regulations requires an improved understanding of jet mixing as new combustor concepts are introduced. For example, the success of the staged combustor to reduce the emission of NO(x) is almost entirely dependent upon the rapid and complete dilution of the rich zone products within the mixing section. It is these mixing challenges to which the present study is directed. A series of experiments was undertaken to delineate the optimal mixer orifice geometry. A cross-flow to core-flow momentum-flux ratio of 40 and a mass flow ratio of 2.5 were selected as representative of a conventional design. An experimental test matrix was designed around three variables: the number of orifices, the orifice length-to- width ratio, and the orifice angle. A regression analysis was performed on the data to arrive at an interpolating equation that predicted the mixing performance of orifice geometry combinations within the range of the test matrix parameters. Results indicate that the best mixing orifice geometry tested involves eight orifices with a long-to-short side aspect ratio of 3.5 at a twenty-three degree inclination from the center-line of the mixing section.
Optimization of orifice geometry for cross-flow mixing in a cylindrical duct
NASA Technical Reports Server (NTRS)
Sowa, W. A.; Kroll, J. T.; Samuelsen, G. S.; Holdeman, J. D.
1994-01-01
Mixing of gaseous jets in a cross-flow has significant applications in engineering, one example of which is the dilution zone of a gas turbine combustor. Despite years of study, the design of jet injection in combustors is largely based on practical experience. A series of experiments was undertaken to delineate the optimal mixer orifice geometry. A cross-flow to core-flow momentum-flux ratio of 40 and a mass flow ratio of 2.5 were selected as representative of an advanced design. An experimental test matrix was designed around three variables: the number of orifices, the orifice aspect ratio (long-to-short dimension), and the orifice angle. A regression analysis was performed on the data to arrive at an interpolating equation that predicted the mixing performance of orifice geometry combinations within the range of the test matrix parameters. Results indicate that mixture uniformity is a non-linear function of the number of orifices, the orifice aspect ratio, and the orifice angle. Optimum mixing occurs when the asymptotic mean jet trajectories are in the range of 0.35 less than r/R less than 0.5 (where r = 0 is at the mixer wall) at z/R = 1.0. At the optimum number of orifices, the difference between shallow-angled slots with large aspect ratios and round holes is minimal and either approach will lead to good mixing performance. At the optimum number of orifices, it appears possible to have two local optimums where one corresponds to an aspect ratio of 1.0 and the other to a high aspect ratio.
Geometry effects on cooling in a standing wave cylindrical thermoacousic resonator
NASA Astrophysics Data System (ADS)
Mohd-Ghazali, Normah; Ghazali, Ahmad Dairobi; Ali, Irwan Shah; Rahman, Muhammad Aminullah A.
2012-06-01
Numerous reports have established the refrigeration applications of thermoacoustic cooling without compressors and refrigerants. Significant cooling effects can be obtained in a thermoacoustic resonator fitted with a heat exchanging stack and operated at resonance frequency. Past studies, however, have hardly referred to the fundamental relationship between resonant frequency and the resonator geometry. This paper reports the thermoacoustic cooling effects at resonance obtained by changing the diameter of the resonator while holding the length constant and vice versa. Experiments were completed at atmospheric pressure with air as the working fluid using a number of pvc tubes having parallel plate stack from Mylar. The temperature difference measured across the stack showed that a volume increase in the working fluid in general increases the temperature gradient for the quarter-and half-wavelength resonators. Doubling the diameter from 30 mm to 60 mm produced the highest temperature difference due to the greater number of stack plates resulting in a higher overall thermoacaoustic cooling. Increasing the resonator length only produced a small increase in temperature gradient since the resonant frequency at operation is only slightly changed. Investigation on the aspect ratio exhibits no influence on the temperature difference across the stack. This study have shown that the resonator length and diameter do affect the temperature difference across the thermoacoustic stack, and further research should be done to consider the contribution of the stack mass on the overall desired thermoacoustic cooling.
NASA Astrophysics Data System (ADS)
Sambasivan, Shiv Kumar; Shashkov, Mikhail J.; Burton, Donald E.
2013-03-01
A finite volume cell-centered Lagrangian formulation is presented for solving large deformation problems in cylindrical axisymmetric geometries. Since solid materials can sustain significant shear deformation, evolution equations for stress and strain fields are solved in addition to mass, momentum and energy conservation laws. The total strain-rate realized in the material is split into an elastic and plastic response. The elastic and plastic components in turn are modeled using hypo-elastic theory. In accordance with the hypo-elastic model, a predictor-corrector algorithm is employed for evolving the deviatoric component of the stress tensor. A trial elastic deviatoric stress state is obtained by integrating a rate equation, cast in the form of an objective (Jaumann) derivative, based on Hooke's law. The dilatational response of the material is modeled using an equation of state of the Mie-Grüneisen form. The plastic deformation is accounted for via an iterative radial return algorithm constructed from the J2 von Mises yield condition. Several benchmark example problems with non-linear strain hardening and thermal softening yield models are presented. Extensive comparisons with representative Eulerian and Lagrangian hydrocodes in addition to analytical and experimental results are made to validate the current approach.
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.
NASA Astrophysics Data System (ADS)
Maccioni, Maurizio; Orgiu, Emanuele; Cosseddu, Piero; Locci, Simone; Bonfiglio, Annalisa
2006-10-01
Cylindrical organic field effect transistors have been obtained starting from a metallic fiber used in textile processes. The metal core of the yarn, covered with a thin polyimide layer, is the gate of the structure. A top-contact device can be obtained by depositing a layer of organic semiconductor followed by the deposition of source and drain top contacts, made by metals or conductive polymers, deposited by evaporation or soft lithography. Thanks to the flexibility of the structure and the low cost of technologies, this device is a meaningful step towards innovative applications of textile electronics.
NASA Astrophysics Data System (ADS)
Buschinelli, Pedro D. V.; Melo, João. Ricardo C.; Albertazzi, Armando; Santos, João. M. C.; Camerini, Claudio S.
2013-04-01
An axis-symmetrical optical laser triangulation system was developed by the authors to measure the inner geometry of long pipes used in the oil industry. It has a special optical configuration able to acquire shape information of the inner geometry of a section of a pipe from a single image frame. A collimated laser beam is pointed to the tip of a 45° conical mirror. The laser light is reflected in such a way that a radial light sheet is formed and intercepts the inner geometry and forms a bright laser line on a section of the inspected pipe. A camera acquires the image of the laser line through a wide angle lens. An odometer-based triggering system is used to shot the camera to acquire a set of equally spaced images at high speed while the device is moved along the pipe's axis. Image processing is done in real-time (between images acquisitions) thanks to the use of parallel computing technology. The measured geometry is analyzed to identify corrosion damages. The measured geometry and results are graphically presented using virtual reality techniques and devices as 3D glasses and head-mounted displays. The paper describes the measurement principles, calibration strategies, laboratory evaluation of the developed device, as well as, a practical example of a corroded pipe used in an industrial gas production plant.
Lloyd, RC
1988-04-01
A series of critical experiments was completed with mixed plutonium-uranium solutions having Pu/(Pu + U) ratios of approximately 0.5. These experiments were a part of the Criticality Data Development Program between the United States Department of Energy (USDOE), and the Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan. A complete description of, and data from, the experiments are included in this report. The experiments were performed with mixed plutonium-uranium solutions in annular cylindrical geometry. The measurements were made with a water reflector. The central region included a concrete annular cylinder containing B{sub 4}C. Interior to the concrete insert was a stainless steel bottle containing plutonium-uranium solution. The concentration of the solution in the annular region was varied from 116 to 433 g (Pu + U)/liter. The ratio of plutonium to total heavy metal (plutonium plus uranium) was 52% for all experiments.
Lloyd, R.C.
1986-12-01
A series of critical experiments was completed with mixed plutonium-uranium solutions having Pu/(Pu + U) ratios of approximately 0.5. These experiments were a part of the Criticality Data Development Program between the United States Department of Energy (USDOE), and the Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan. A complete description of, and data from, the experiments are included in this report. The experiments were performed with mixed plutonium-uranium solutions in cylindrical and slab geometries and included measurements with a water reflector, a concrete reflector, and without an added reflector. The concentration was varied from 112 to 332 g (Pu + U)/liter. The ratio of plutonium to total heavy metal (plutonium plus uranium) was 52% for all experiments.
NASA Astrophysics Data System (ADS)
Dantu, Subbarao; Ramanathan, Uma
2000-04-01
The nonlinear Schrodinger equation with saturating nonlinearity like the ponderomotive nonlinearity in a plasma is analysed with the help of Symmetry Group Analysis. The symmetry group of the equation is deduced and a fiber-preserving subgroup of linear transformations are identified that leave such a nonlinear Schrodinger equation invariant. The MACSYMA-based Lie algebra of the symmetry group is realized to the extent possible. The theory results in an ordinary differential equation apart from a dictated beam profile. The resulting ordinary differential equation for self-focusing is compared with similar equations obtained from other existing theories of self-focusing in cylindrical geometry like the moments theory, the variational theory and the modified paraxial theory based on harmonic-oscillator modes. New types of solutions are identified and the limitations of the different methods are indicated.Acknowledgements: Financial assistance of CSIR(India)(Research Project,03(0815)/97/ EMR-II) for this work is acknowledged.
NASA Astrophysics Data System (ADS)
Han, Qing; Zhang, Chi; Xu, Bo; Chen, Jiangping
2013-07-01
The hydrodynamic flow behavior, effects of geometry and working conditions of a gas-liquid cylindrical cyclone separator with a new structure are investigated by computational fluid dynamic and experiment. Gas liquid cylindrical cyclone separator is widely used in oil industry, refrigeration system because of its simple structure, high separating efficiency, little maintenance and no moving parts nor internal devices. In this work, a gas liquid cylindrical cyclone separator with new structure used before evaporator in refrigeration system can remove the vapor from the mixture and make evaporator compact by improving its heat exchange efficiency with the lower inlet quality. It also decreases evaporator pressure drop and reduces compressor work. The two pipes are placed symmetrically which makes each of them can be treated as inlet. It means when the fluids flow reverse, the separator performance will not be influence. Four samples with different geometry parameters are tested by experiment with different inlet quality (0.18-0.33), inlet mass flow rate (65-100kg/h). Compared with the experimental data, CFD simulation results show a good agreement. Eulerian multiphase model and Reynolds Stress Turbulence model are applied in the CFD simulation and obtained the inner flow field such as phase path lines, tangential velocity profiles and pressure and volume of fraction distribution contours. The separator body diameter (24, 36, 48mm) and inlet diameter (3.84, 4.8, 5.76mm) decide the maximum tangential velocity which results in the centrifugal force. The tangential velocity profiles are simulated and compared among different models. The higher tangential velocity makes higher quality of gas outlet but high pressure drop at the same time. Decreasing the inlet diameter increases quality of gas outlet pipe and pressure drop. High gas outlet quality is cost at high pressure drop. Increasing of separator diameter makes gas outlet quality increase first and then decrease but
Yanuka, D.; Zinowits, H. E.; Krasik, Ya. E.; Kozlov, M.
2015-10-15
The results of experiments and numerical simulations of a shock wave propagating between either conical or parabolic bounding walls are presented. The shock wave was generated by a microsecond timescale underwater electrical explosion of a cylindrical wire array supplied by a current pulse having an amplitude of ∼230 kA and a rise time of ∼1 μs. It is shown that with the same energy density deposition into the exploding wire array, the shock wave converges faster between parabolic walls, and as a result, the pressure in the vicinity of convergence is ∼2.3 times higher than in the case of conical walls. The results obtained are compared to those of earlier experiments [Antonov et al., Appl. Phys. Lett. 102, 124104 (2013)] with explosions of spherical wire arrays. It is shown that at a distance of ∼400 μm from the implosion origin the pressure obtained in the current experiments is higher than for the case of spherical wire arrays.
NASA Astrophysics Data System (ADS)
Yanuka, D.; Kozlov, M.; Zinowits, H. E.; Krasik, Ya. E.
2015-10-01
The results of experiments and numerical simulations of a shock wave propagating between either conical or parabolic bounding walls are presented. The shock wave was generated by a microsecond timescale underwater electrical explosion of a cylindrical wire array supplied by a current pulse having an amplitude of ˜230 kA and a rise time of ˜1 μs. It is shown that with the same energy density deposition into the exploding wire array, the shock wave converges faster between parabolic walls, and as a result, the pressure in the vicinity of convergence is ˜2.3 times higher than in the case of conical walls. The results obtained are compared to those of earlier experiments [Antonov et al., Appl. Phys. Lett. 102, 124104 (2013)] with explosions of spherical wire arrays. It is shown that at a distance of ˜400 μm from the implosion origin the pressure obtained in the current experiments is higher than for the case of spherical wire arrays.
Conformal approach to cylindrical DLA
NASA Astrophysics Data System (ADS)
Taloni, A.; Caglioti, E.; Loreto, V.; Pietronero, L.
2006-09-01
We extend the conformal mapping approach elaborated for the radial diffusion limited aggregation model (DLA) to cylindrical geometry. We introduce in particular a complex function which allows a cylindrical cluster to be grown using as an intermediate step a radial aggregate. The aggregate grown exhibits the same self-affine features as the original cylindrical DLA. The specific choice of the transformation allows us to study the relationship between the radial and the cylindrical geometry. In particular the cylindrical aggregate can be seen as a radial aggregate with particles of size increasing with the radius. On the other hand, the radial aggregate can be seen as a cylindrical aggregate with particles of size decreasing with the height. This framework, which shifts the point of view from the geometry to the size of the particles, can open the way to more quantitative studies on the relationship between radial and cylindrical DLA.
Light collectors in cylindrical geometry
Winston, Roland
1976-01-01
A device is provided for collecting electromagnetic energy developed by an energy source of finite dimension and of finite distance from the collection device. It includes an energy absorber positioned between two side walls which reflects substantially all incident energy received from the energy source onto the energy absorber.
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.
Lloyd, RC
1988-04-01
A series of critical experiments was completed with mixed plutonium-uranium solutions having Pu/(Pu + U) ratios of approximately 0.4. These experiments were a part of the Criticality Data Development Program between the United States Department of Energy (USDOE), and the Power Reactor and Nuclear Fuel Development Corporation (PNC) of Japan. A complete description of, and data from, the experiments are included in this report. The experiments were performed with mixed plutonium-uranium solutions in cylinqrical and slab geometries and included measurements with a water reflector, a concrete reflector, and without an added reflector. The concentration was varied from 105 to 436 g (Pu + U)/liter. The ratio of plutonium to total heavy metal (plutonium plus uranium) was 0.4 for all experiments.
Energy Science and Technology Software Center (ESTSC)
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 sendmore » 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.« less
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.
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.
Input space-dependent controller for multi-hazard mitigation
NASA Astrophysics Data System (ADS)
Cao, Liang; Laflamme, Simon
2016-04-01
Semi-active and active structural control systems are advanced mechanical devices and systems capable of high damping performance, ideal for mitigation of multi-hazards. The implementation of these devices within structural systems is still in its infancy, because of the complexity in designing a robust closed-loop control system that can ensure reliable and high mitigation performance. Particular challenges in designing a controller for multi-hazard mitigation include: 1) very large uncertainties on dynamic parameters and unknown excitations; 2) limited measurements with probabilities of sensor failure; 3) immediate performance requirements; and 4) unavailable sets of input-output during design. To facilitate the implementation of structural control systems, a new type of controllers with high adaptive capabilities is proposed. It is based on real-time identification of an embedding that represents the essential dynamics found in the input space, or in the sensors measurements. This type of controller is termed input-space dependent controllers (ISDC). In this paper, the principle of ISDC is presented, their stability and performance derived analytically for the case of harmonic inputs, and their performance demonstrated in the case of different types of hazards. Results show the promise of this new type of controller at mitigating multi-hazards by 1) relying on local and limited sensors only; 2) not requiring prior evaluation or training; and 3) adapting to systems non-stationarities.
Evolution of space dependent growth in the teleost Astyanax mexicanus.
Gallo, Natalya D; Jeffery, William R
2012-01-01
The relationship between growth rate and environmental space is an unresolved issue in teleosts. While it is known from aquaculture studies that stocking density has a negative relationship to growth, the underlying mechanisms have not been elucidated, primarily because the growth rate of populations rather than individual fish were the subject of all previous studies. Here we investigate this problem in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling form (surface fish) and several blind cave-dwelling (cavefish) forms. Surface fish and cavefish are distinguished by living in spatially contrasting environments and therefore are excellent models to study the effects of environmental size on growth. Multiple controlled growth experiments with individual fish raised in confined or unconfined spaces showed that environmental size has a major impact on growth rate in surface fish, a trait we have termed space dependent growth (SDG). In contrast, SDG has regressed to different degrees in the Pachón and Tinaja populations of cavefish. Mating experiments between surface and Pachón cavefish show that SDG is inherited as a dominant trait and is controlled by multiple genetic factors. Despite its regression in blind cavefish, SDG is not affected when sighted surface fish are raised in darkness, indicating that vision is not required to perceive and react to environmental space. Analysis of plasma cortisol levels showed that an elevation above basal levels occurred soon after surface fish were exposed to confined space. This initial cortisol peak was absent in Pachón cavefish, suggesting that the effects of confined space on growth may be mediated partly through a stress response. We conclude that Astyanax reacts to confined spaces by exhibiting SDG, which has a genetic component and shows evolutionary regression during adaptation of cavefish to confined environments. PMID:22870223
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.
Multi-stable cylindrical lattices
NASA Astrophysics Data System (ADS)
Pirrera, Alberto; Lachenal, Xavier; Daynes, Stephen; Weaver, Paul M.; Chenchiah, Isaac V.
2013-11-01
We present a cylindrical lattice structure that mimics the behaviour of the virus bacteriophage T4 in having two (or more) stable states which differ in their radii and length. While the virus achieves bistability through molecular mechanisms we use composite materials to exploit the interplay between pre-stress, material properties and structural geometry. We demonstrate (computationally) that multi-stability is a robust phenomenon. We also show (analytically) that it is possible to choose the design variables so that the energy is independent of the radius, thus resulting in every state of the structure being stable.
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
NASA Technical Reports Server (NTRS)
Kruse, R. L.; Keener, E. R.; Chapman, G. T.; Claser, G.
1979-01-01
Wind-tunnel tests were conducted to investigate the side forces and yawing moments that can occur at high angles of attack and zero sideslip for cylindrical bodies of revolution. Two bodies having several tangent ogive forebodies with fineness ratios of 0.5, 1.5, 2.5, and 3.5 were tested. The forebodies with fineness ratios of 2.5 and 3.5 had several bluntnesses. The cylindrical afterbodies had fineness ratios of 7 and 13. The model components - tip, forebody, and afterbody - were tested in various rotational positions about their axes of symmetry. Most of the tests were conducted at a Mach number of 0.25, a Reynolds number of 0.32 x 10 to the 6th power, and with the afterbody that had a fineness ratio of 7 and with selected forebodies. The effect of Mach number was determined with the afterbody that had a fineness ratio of 13 and with selected forebodies at mach numbers from 0.25 to 2 at Reynolds number = 0.32 X 10 to the 6th power. Maximum angle of attack was 58 deg.
NASA Astrophysics Data System (ADS)
Morales Crespo, R.
2015-08-01
This paper solves and analyses the complete characterization of the plasma-sheath transition and the characteristic I-V curves of an active and collisional plasma close to a cylindrical or spherical wall considering a wide range of the parameter which describe the model to be useful for experimental measures. Despite the difficulty of including the three possible pre-sheath mechanisms, this characterization is obtained from a self-consistent model using three easily measurable parameters, namely the electric potential of the wall, the positive ion current collected by the wall, and the radius of the wall. These parameters are easy to measure and facilitate the diagnosis of plasmas from an experimental point of view.
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.
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.
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.
High convergence implosion symmetry in cylindrical hohlraums
Amendt, P A; Bradley, D K; Hammel, B A; Landen, O L; Suter, L J; Turner, R E; Wallace, R J
1999-09-01
High convergence, hohlraum-driven implosions will require control of time-integrated drive asymmetries to 1% levels for ignition to succeed on the NIF. We review how core imaging provides such asymmetry measurement accuracy for the lowest order asymmetry modes, and describe recent improvements in imaging techniques that should allow detection of higher order asymmetry modes. We also present a simple analytic model explaining how the sensitivity of symmetry control to beam pointing scales as we progress from single ring per side Nova cylindrical hohlraum illumination geometries to NIF-like multiple rings per side Omega hohlraum illumination geometries and ultimately to NIF-scale hohlraums.
Hexatic undulations in curved geometries.
Lenz, Peter; Nelson, David R
2003-03-01
We discuss the influence of two-dimensional hexatic order on capillary waves and undulation modes in spherical and cylindrical geometries. In planar geometries, extended bond-orientational order has only a minor effect on the fluctuations of liquid surfaces or lipid bilayers. However, in curved geometries, the long-wavelength spectrum of these ripples is altered. We calculate this frequency shift and discuss applications to spherical vesicles, liquid metal droplets, bubbles and cylindrical jets coated with surface-active molecules, and to multielectron bubbles in liquid helium at low temperatures. Hexatic order also leads to a shift in the threshold for the fission instability of charged droplets and bubbles, and for the Plateau-Rayleigh instability of liquid jets. PMID:12689068
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.
ERIC Educational Resources Information Center
Jones, Dustin L.
2009-01-01
The author describes an activity where prospective mathematics teachers made hypotheses about the dimensions of a fair cylindrical die and conducted experiments with different cylinders. He also provides a model that estimates the probability that a cylinder would land on the lateral surface, depending on the height and diameter of the cylinder.…
Development of the Cylindrical Wire Electrical Discharge Machining Process.
McSpadden, SB
2002-01-22
Results of applying the wire Electrical Discharge Machining (EDM) process to generate precise cylindrical forms on hard, difficult-to-machine materials are presented. A precise, flexible, and corrosion-resistant underwater rotary spindle was designed and added to a conventional two-axis wire EDM machine to enable the generation of free-form cylindrical geometries. A detailed spindle error analysis identifies the major source of error at different frequency. The mathematical model for the material removal of cylindrical wire EDM process is derived. Experiments were conducted to explore the maximum material removal rate for cylindrical and 2D wire EDM of carbide and brass work-materials. Compared to the 2D wire EDM, higher maximum material removal rates may be achieved in the cylindrical wire EDM. This study also investigates the surface integrity and roundness of parts created by the cylindrical wire EDM process. For carbide parts, an arithmetic average surface roughness and roundness as low as 0.68 and 1.7 {micro}m, respectively, can be achieved. Surfaces of the cylindrical EDM parts were examined using Scanning Electron Microscopy (SEM) to identify the craters, sub-surface recast layers and heat-affected zones under various process parameters. This study has demonstrated that the cylindrical wire EDM process parameters can be adjusted to achieve either high material removal rate or good surface integrity.
Cylindrically symmetric electrohydrodynamic patterning.
Deshpande, Paru; Pease, Leonard F; Chen, Lei; Chou, Stephen Y; Russel, William B
2004-10-01
Cylindrically symmetric structures such as concentric rings and rosettes arise out of thin polymeric films subjected to strong electric fields. Experiments that formed concentric rings and theory capable of explaining these and other cylindrical structures are presented. These rings represent an additional member of a class of structures, including pillars and holes, formed by electrohydrodynamic patterning of thin films, occasionally referred to as lithographically induced self-assembly. Fabrication of a set of concentric rings begins by spin coating a thin poly(methyl methacrylate) film onto a silicon wafer. A mask is superimposed parallel to the film leaving a similarly thin air gap. Electric fields, acting in opposition to surface tension, destabilize the free interface when raised above the glass transition temperature. Central pillars nucleate under small cylindrical protrusions patterned on the mask. Rings then emerge sequentially, with larger systems having as many as 10 fully formed rings. Ring-to-ring spacings and annular widths, typically on the order of a micron, are approximately constant within a concentric cluster. The formation rate is proportional to the viscosity and, consequently, has the expected Williams-Landel-Ferry dependence on temperature. In light of these developments we have undertaken a linear stability analysis in cylindrical coordinates to describe these rings and ringlike structures. The salient feature of this analysis is the use of perturbations that incorporate their radial dependence in terms of Bessel functions as opposed to the traditional sinusoids of Cartesian coordinates. The theory predicts approximately constant ring-to-ring spacings, constant annular widths, and growth rates that agree with experiment. A secondary instability is observed at higher temperatures, which causes the rings to segment into arcs or pillar arrays. The cylindrical theory may be generalized to describe hexagonal pillar/hole packing, gratings, and
Quantum Cylindrical Waves and Parametrized Field Theory
NASA Astrophysics Data System (ADS)
Varadarajan, Madhavan
In this article, we review some illustrative results in the study of two related toy models for quantum gravity, namely cylindrical waves (which are cylindrically symmetric gravitational fields)and parametrized field theory (which is just free scalar field theory on a flat space-time in generally covariant disguise). In the former, we focus on the phenomenon of unexpected large quantum gravity effects in regions of weak classical gravitational fields and on an analysis of causality in a quantum geometry. In the latter, we focus on Dirac quantization, argue that this is related to the unitary implementability of free scalar field evolution along curved foliations of the flat space-time and review the relevant results for unitary implementability.
Cylindrically polarized nondiffracting optical pulses
NASA Astrophysics Data System (ADS)
Ornigotti, Marco; Conti, Claudio; Szameit, Alexander
2016-07-01
We extend the concept of radially and azimuthally polarized optical beams to the polychromatic domain by introducing cylindrically polarized nondiffracting optical pulses. In particular, we discuss in detail the case of cylindrically polarized X-waves, both in the paraxial and nonparaxial regime. The explicit expressions for the electric and magnetic fields of cylindrically polarized X-waves are also reported.
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.
Wang, L. F.; He, X. T.; Wu, J. F.; Zhang, W. Y.; Ye, W. H.
2013-04-15
A weakly nonlinear (WN) model has been developed for the incompressible Rayleigh-Taylor instability (RTI) in cylindrical geometry. The transition from linear to nonlinear growth is analytically investigated via a third-order solutions for the cylindrical RTI initiated by a single-mode velocity perturbation. The third-order solutions can depict the early stage of the interface asymmetry due to the bubble-spike formation, as well as the saturation of the linear (exponential) growth of the fundamental mode. The WN results in planar RTI [Wang et al., Phys. Plasmas 19, 112706 (2012)] are recovered in the limit of high-mode number perturbations. The difference between the WN growth of the RTI in cylindrical geometry and in planar geometry is discussed. It is found that the interface of the inward (outward) development spike/bubble is extruded (stretched) by the additional inertial force in cylindrical geometry compared with that in planar geometry. For interfaces with small density ratios, the inward growth bubble can grow fast than the outward growth spike in cylindrical RTI. Moreover, a reduced formula is proposed to describe the WN growth of the RTI in cylindrical geometry with an acceptable precision, especially for small-amplitude perturbations. Using the reduced formula, the nonlinear saturation amplitude of the fundamental mode and the phases of the Fourier harmonics are studied. Thus, it should be included in applications where converging geometry effects play an important role, such as the supernova explosions and inertial confinement fusion implosions.
Drag coefficient and settling velocity for particles of cylindrical shape
Gabitto, Jorge; Tsouris, Costas
2008-01-01
Solid particles of cylindrical shape play a significant role in many separations processes. Explicit equations for the drag coefficient and the terminal velocity of free-falling cylindrical particles have been developed in this work. The developed equations are based on available experimental data for falling cylindrical particles in all flow regimes. The aspect ratio (i.e., length-over-diameter ratio) has been used to account for the particle shape. Comparisons with correlations proposed by other researchers using different parameters to account for the geometry are presented. Good agreement is found for small aspect ratios, and increasing differences appear when the aspect ratio increases. The aspect ratio of cylindrical particles satisfactorily accounts for the geometrical influence on fluid flow of settling particles.
Cylindrical effects in weakly nonlinear Rayleigh-Taylor instability
NASA Astrophysics Data System (ADS)
Liu, Wan-Hai; Ma, Wen-Fang; Wang, Xu-Lin
2015-01-01
The classical Rayleigh-Taylor instability (RTI) at the interface between two variable density fluids in the cylindrical geometry is explicitly investigated by the formal perturbation method up to the second order. Two styles of RTI, convergent (i.e., gravity pointing inward) and divergent (i.e., gravity pointing outwards) configurations, compared with RTI in Cartesian geometry, are taken into account. Our explicit results show that the interface function in the cylindrical geometry consists of two parts: oscillatory part similar to the result of the Cartesian geometry, and non-oscillatory one contributing nothing to the result of the Cartesian geometry. The velocity resulting only from the non-oscillatory term is followed with interest in this paper. It is found that both the convergent and the divergent configurations have the same zeroth-order velocity, whose magnitude increases with the Atwood number, while decreases with the initial radius of the interface or mode number. The occurrence of non-oscillation terms is an essential character of the RTI in the cylindrical geometry different from Cartesian one. Project supported by the National Basic Research Program of China (Grant No. 10835003), the National Natural Science Foundation of China (Grant No. 11274026), the Scientific Research Foundation of Mianyang Normal University, China (Grant Nos. QD2014A009 and 2014A02), and the National High-Tech ICF Committee.
Double focusing ion mass spectrometer of cylindrical symmetry
NASA Technical Reports Server (NTRS)
Coplan, M. A.; Moore, J. H.; Hoffman, R. A.
1984-01-01
A mass spectrometer consisting of an electric sector followed by a magnetic sector is described. The geometry is a cylindrically symmetric generalization of the Mattauch-Herzog spectrometer (1934). With its large annular entrance aperture and a position-sensitive detector, the instrument provides a large geometric factor and 100-percent duty factor, making it appropriate for spacecraft experiments.
ul Haq, Muhammad Noaman; Saeed, R.; Shah, Asif
2010-08-15
The propagation of ion acoustic shock waves in cylindrical and spherical geometries has been investigated. The plasma system consists of cold ions, Boltzmannian electrons and positrons. Spherical, cylindrical Korteweg-de Vries-Burger equations have been derived by reductive perturbation technique and their shock behavior is studied by employing finite difference method. Our main emphasis is on the behavior of shock as it moves toward and away from center of spherical and cylindrical geometries. It is noticed, that the shock wave strength and steepness accrues with time as it moves toward the center and shock enervates as it moves away from center. The strength of shock in spherical geometry is found to dominate over shock strength in cylindrical geometry. Positron concentration, kinematic viscosity are also found to have significant effect on the shock structure and propagation. The results may have relevance in the inertial confinement fusion plasmas.
Coatings for Energy Efficient Lamps with Cylindrical Geometry
NASA Astrophysics Data System (ADS)
Rancourt, James; Martin, Robert
1986-09-01
During the past several years, a high level of activity has been directed toward developing more efficient lighting products to meet consumer demand in the face of energy scarcity and its high cost. Without major redesign of lamps, manufacturers have been able to achieve modest gains of 5 to 10 percent in incandescent lamp efficacy by optimizing standard features such as filament design, gas fill, etc. What was desired for incandescent lamps was a major jump in efficacy of 30% or more. Much encouraging work, notably by Philips in the Netherlands, has already been accomplished in the laboratory using thin film reflectors to recycle the wasted infrared radiation from incandescent lamps. Indium tin oxide (ITO) films, which are transparent in the visible and reflect well at wavelengths greater than 2 micrometers, is a most attractive material for its simplicity and apparent high performance. It Â°has a serious drawback, however, in its inability to reflect adequately when its temperature exceeds 800 C. A separate outer jacket surrounding the lamp itself is required in order to keep the ITO coating cool and thereby take advantage of its properties. The use of this extra component makes this solution to the energy problem more expensive and complex. In the United States, the Duratest Corporation has developed a sophisticated silver coating which is deposited inside domestic type A-line lamps. About six years ago, the General Electric Co., a major U.S. lamp manufacturer, approached 0.C.L.I. and requested assistance in improving the quartz-halogen lamp. The G.E.-0.C.L.I. method that was developed for improving the efficacy of an incandescent lamp product consists of coating quartz-halogen lamps with infrared reflectors. These reflectors are interference reflector stacks made of refractory metal oxides using conventional thermal evaporation technology. These products have been available commercially for about three years.
Ultrasound Imaging Using Diffraction Tomography in a Cylindrical Geometry
Chambers, D H; Littrup, P
2002-01-24
Tomographic images of tissue phantoms and a sample of breast tissue have been produced from an acoustic synthetic array system for frequencies near 500 kHz. The images for sound speed and attenuation show millimeter resolution and demonstrate the feasibility of obtaining high-resolution tomographic images with frequencies that can deeply penetrate tissue. The image reconstruction method is based on the Born approximation to acoustic scattering and is a simplified version of a method previously used by Andre (Andre, et. al., Int. J. Imaging Systems and Technology, Vol 8, No. 1, 1997) for a circular acoustic array system. The images have comparable resolution to conventional ultrasound images at much higher frequencies (3-5 MHz) but with lower speckle noise. This shows the potential of low frequency, deeply penetrating, ultrasound for high-resolution quantitative imaging.
Measurement of cylindrical parts
NASA Astrophysics Data System (ADS)
Knight, Paul Douglas, Jr.
The form of cylindrical parts has been traditionally evaluated using stylus-based mechanical instruments. The Tropel Corporation has developed a grazing incidence interferometer (GII) for the measurement of cylindrical parts. The repeatability of this instrument due to various instrument uncertainties was measured. Differing instrument configurations that produce the same systematic error were determined to produce a zonal calibration method for determining systematic error over the full range of the instrument, given knowledge of the error in a single zone. The effect of the aperture stop on the response of the imaging system to axially sinusoidal artifacts was simulated. Diamond-turned axially sinusoidal artifacts, with amplitude of order1 um and spatial wavelength of order10 mm, were measured to test the axial response of the interferometer. The modulation transfer function of the instrument's imaging system, measured using a knife edge test, predicts the response observed with the sinusoidal artifacts. A diffraction analysis predicts that the measured axial form is modified by a second order envelope function with phase that varies with the relative position of the imaging system focal plane and part position. A compensation method is proposed for this effect. A comparison of roundness measurements by both a traditional stylus-based instrument and the GII was performed demonstrating that the roundness measurements of the two instruments are equivalent when the measurements are properly corrected for the differing effects of surface finish.
NASA Astrophysics Data System (ADS)
Honeycutt, T. E.; Roberts, T. G.
1986-05-01
Brass retainer rings are currently fastened to artillery shells by spinning each shell at a high rate and then jamming the ring on it so that it is fastened or welded by friction between the two objects. This is an energy-inefficient process which heats and weakens more material than is desirable. The shell spinning at a high rate is also potentially dangerous. A laser welder is provided that generates output energy focused on a circular or cylindrical shape for simultaneously welding around a 360 degs circumference without unnecessarily heating large amounts of material. The welder may be used to fasten cylindrical shaped objects, gears and shafts together, which is difficult to do by conventional means. The welder may also be used to fasten one cylinder to another. To accomplish the welding, a laser has an unstable optical cavity arranged with its feedback mirror centered to generate a circular output beam having an obscuration in the center. A circularly-symmetric, off-axis concave mirror focuses the output beam onto the objects being fastened and away from the center line or axis of the circular beam.
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).
NASA Technical Reports Server (NTRS)
Kleckner, R. J.; Pirvics, J.
1981-01-01
Program CYBEAN computes behavior of rolling-element bearings including effects of bearing geometry, shaft misalinement, and temperature. Accurate assessment is possible for various outer-ring and housing configurations. CYBEAN is structured for coordinated execution of modules that perform specific analytical tasks. It is written in FORTRAN IV for use on the UNIVAC 1100/40 computer.
Parametric Investigations of Miniaturized Cylindrical and Annular Hall Thrusters
A. Smirnov; Y. Raitses; N.J. Fisch
2001-10-16
A cylindrical geometry Hall thruster may overcome certain physical and technological limitations in scaling down of Hall thrusters to miniature sizes. The absence of the inner wall and use of the cusp magnetic field can potentially reduce heating of the thruster parts and erosion of the channel. A 2.6 cm miniaturized Hall thruster of a flexible design was built and successfully operated in the power range of 50-300 W. Comparison of preliminary results obtained for cylindrical and annular thruster configurations is presented.
2DEG on a cylindrical shell with a screw dislocation
NASA Astrophysics Data System (ADS)
Filgueiras, Cleverson; Silva, Edilberto O.
2015-09-01
A two dimensional electron gas on a cylindrical surface with a screw dislocation is considered. More precisely, we investigate how both the geometry and the deformed potential due to a lattice distortion affect the Landau levels of such system. The case showing the deformed potential can be thought in the context of 3D common semiconductors where the electrons are confined on a cylindrical shell. We will show that important quantitative differences exist due to this lattice distortion. For instance, the effective cyclotron frequency is diminished by the deformed potential, which in turn enhances the Hall conductivity.
Incorrectness of the usual gyrokinetic treatment in cylindrically symmetric systems
Linsker, R.
1980-07-01
It is shown that the usual gyrokinetic theory does not consistently retain all terms of leading order in the expansion parameter epsilon = gyroradius/equilibrium scale length. This is illustrated for cylindrically symmetric systems by comparing the perturbed distribution function calculated by the gyrokinetic method with that obtained by explicitly integrating the Vlasov equation over the unperturbed orbit. The integral equation used in some recent treatments of drift waves in sheared-slab geometry is shown to be incorrect. The correct calculation of the ion density perturbation for a collisionless ..beta.. = 0 plasma with cylindrical symmetry is presented.
Propagation and Separation of Charged Colloids by Cylindrical Passivated Gel Electrophoresis.
Bikos, Dimitri; Mason, Thomas G
2016-07-01
We explore the electrophoretic propagation of charged colloidal objects, monodisperse anionically stabilized polystyrene spheres, in large-pore agarose gels that have been passivated using polyethylene glycol (PEG) when a radial electric field is applied in a cylindrical geometry. By contrast to standard Cartesian gel-electrophoresis geometries, in a cylindrical geometry, charged particles that start at a ring well near the central axis propagate outward more rapidly initially and then slow down as they move further away from the axis. By building a full-ring cylindrical gel electrophoresis chamber and taking movies of scattered light from propagating nanospheres undergoing electrophoresis, we experimentally demonstrate that the ring-like front of monodisperse nanospheres propagates stably in PEG-passivated agarose gels and that the measured ring radius as a function of time agrees with a simple model that incorporates the electric field of a cylindrical geometry. Moreover, we show that this cylindrical geometry offers a potential advantage when performing electrophoretic separations of objects that have widely different sizes: smaller objects can still be retained in a cylindrical gel that has a limited size over long electrophoretic run times required for separating larger objects. PMID:27109865
Geometric Hall Effect of ^{23}Na Condensate in a Time- and Space-Dependent Magnetic Field
NASA Astrophysics Data System (ADS)
Zheng, Gong-Ping; Yang, Ling-Ling; Chang, Gao-Zhan; Wu, Zhe
2016-04-01
We simulate numerically the dynamics of ^{23}Na condensate in a time- and space-dependent magnetic field with a variational approach. It is shown to be an efficient method to describe the complex dynamics of the system, which may excite the breather mode, the scissor mode, and the dipole mode simultaneously. Our results agree with the experimental observations of Choi et al. (Phys Rev Lett 111:245301, 2013). We reproduce qualitatively the geometric Hall effect and resonance behavior. We also find that the condensate shows a scissor-mode-like motion, which may play the shearing force to deform the condensate and consequently leads to the dynamical nucleation of quantized vortices.
New optical cylindrical microresonators
NASA Astrophysics Data System (ADS)
Gun'ko, Yurii K.; Balakrishnan, Sivakumar; McCarthy, Joseph E.; Rakovich, Yuri P.; Donegan, John F.; Perova, Tatiana S.; Melnikov, Vasily
2007-10-01
In this paper we describe a novel technique for the fabrication of aluminosilicate microfibres and microtubes which are shown to act as optical cylindrical microresonators. The alumosilicate microfibres and microtubes were fabricated by using vacuum-assisted wetting and filtration of silica gel through a microchannel glass matrix. The microfibres and microtubes were studied using Scanning Electron Microscopy (SEM), micro-photoluminescence spectroscopy and fluorescence lifetime imaging confocal microscopy. In the emission spectra of the micro-resonators we find very narrow periodic peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors up to 3200. A strong enhancement in photoluminescence decay rates at high excitation power demonstrates the occurrence of amplified spontaneous emission from a single microtube. These microtubes show a large evanescent field extending many microns beyond the tube radius. Potential applications for these novel microresonators will be in the area of optical microsensors for a single molecule detection of biological and chemical species, including anti-terrorism and defense sectors.
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.
Particle-counting statistics of time- and space-dependent fields
NASA Astrophysics Data System (ADS)
Braungardt, Sibylle; Rodríguez, Mirta; Glauber, Roy J.; Lewenstein, Maciej
2012-03-01
The counting statistics give insight into the properties of quantum states of light and other quantum states of matter such as ultracold atoms or electrons. The theoretical description of photon counting was derived in the 1960s and was extended to massive particles more recently. Typically, the interaction between each particle and the detector is assumed to be limited to short time intervals, and the probability of counting particles in one interval is independent of the measurements in previous intervals. There has been some effort to describe particle counting as a continuous measurement, where the detector and the field to be counted interact continuously. However, the formalism based on continuous measurements does not provide a formula applicable to general time- and space-dependent fields. In our work, we derive a fully time- and space-dependent description of the counting process for linear quantum many-body systems, taking into account the back-action of the detector on the field. We apply our formalism to an expanding Bose-Einstein condensate of ultracold atoms, and show that it describes the process correctly, whereas the standard approach gives unphysical results in some limits. The example illustrates that, in certain situations, the back-action of the detector cannot be neglected and has to be included in the description.
ERIC Educational Resources Information Center
Desseyn, H. O.; And Others
1985-01-01
Compares linear-nonlinear and planar-nonplanar geometry through the valence-shell electron pairs repulsion (V.S.E.P.R.), Mulliken-Walsh, and electrostatic force theories. Indicates that although the V.S.E.P.R. theory has more advantages for elementary courses, an explanation of the best features of the different theories offers students a better…
Rayleigh-Taylor and Richtmyer-Meshkov Instabilities and Mixing in Stratified Cylindrical Shells
Mikaelian, K O
2004-04-15
We study the linear stability of an arbitrary number N of cylindrical concentric shells undergoing a radial implosion or explosion.We derive the evolution equation for the perturbation {eta}{sub i} at interface i; it is coupled to the two adjacent interfaces via {eta}{sub i{+-}1}. For N=2, where there is only one interface, we verify Bell's conjecture as to the form of the evolution equation for arbitrary {rho}{sub 1} and {rho}{sub 2}, the fluid densities on either side of the interface. We obtain several analytic solutions for the N=2 and 3 cases. We discuss freeze-out, a phenomenon that can occur in all three geometries (planar, cylindrical, or spherical), and ''critical modes'' that are stable for any implosion or explosion history and occur only in cylindrical or spherical geometries. We present numerical simulations of possible gelatin-ring experiments illustrating perturbation feedthrough from one interface to another. We also develop a simple model for the evolution of turbulent mix in cylindrical geometry and define a geometrical factor G as the ratio h{sub cylindrical}/h{sub planar} between cylindrical and planar mixing layers. We find that G is a decreasing function of R/R{sub o}, implying that in our model h{sub cylindrical} evolves faster (slower) than h{sub planar} during an implosion (explosion).
Cylindrical Projection of Jupiter
NASA Technical Reports Server (NTRS)
1979-01-01
This computer generated map of Jupiter was made from 10 color images of Jupiter taken Feb. 1, 1979, by Voyager 1, during a single, 10 hour rotation of the planet. Computers at Jet Propulsion Laboratory's Image Processing Lab then turned the photos into this cylindrical projection. Such a projection is invaluable as an instantaneous view of the entire planet. Along the northern edge of the north equatorial belt (NEB) are four dark brown, oblong regions believed by some scientists to be openings in the more colorful upper cloud decks, allowing the darker clouds beneath to be seen. The broad equatorial zone (EZ) is dominated by a series of plumes, possibly regions of intense convective activity, encircling the entire planet. In the southern hemisphere the Great Red Spot is located at about 75 degrees longitude. South of the Great Red Spot in the south temperate zone (STeZ) three large white ovals, seen from Earth-based observatories for the past few decades, are located at 5 degrees, 85 degrees and 170 degrees longitude. Resolution in this map is 375 miles (600 kilometers). Since Jupiter's atmospheric features drift around the planet, longitude is based on the orientation of the planet's magnetic field. Symbols at right edge of photo denote major atmospheric features (dark belts and light zones): NTeZ - north temperate zone; NTrZ - north tropical zone; NEB - north equatorial belt; EZ - equatorial zone; SEB - south equatorial belt; STrZ - south tropical zone; and STeZ - south temperate zone. Voyager belt; EZ - equatorial zone; SEB - south tropical zone; Voyager is managed for NASA's Office of Space Science by Jet Propulsion Laboratory.
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.
Thermal stress in high temperature cylindrical fasteners
NASA Technical Reports Server (NTRS)
Blosser, Max L.
1988-01-01
Uninsulated structures fabricated from carbon or silicon-based materials, which are allowed to become hot during flight, are attractive for the design of some components of hypersonic vehicles. They have the potential to reduce weight and increase vehicle efficiency. Because of manufacturing contraints, these structures will consist of parts which must be fastened together. The thermal expansion mismatch between conventional metal fasteners and carbon or silicon-based structural materials may make it difficult to design a structural joint which is tight over the operational temperature range without exceeding allowable stress limits. In this study, algebraic, closed-form solutions for calculating the thermal stresses resulting from radial thermal expansion mismatch around a cylindrical fastener are developed. These solutions permit a designer to quickly evaluate many combinations of materials for the fastener and the structure. Using the algebraic equations developed, material properties and joint geometry were varied to determine their effect on thermal stresses. Finite element analyses were used to verify that the closed-form solutions derived give the correct thermal stress distribution around a cylindrical fastener and to investigate the effect of some of the simplifying assumptions made in developing the closed-form solutions for thermal stresses.
Evaluation of direct-exchange areas for a cylindrical enclosure
Sika, J. )
1991-11-01
This paper reports on a method for calculating the radiative heat transfer direct-exchange areas for surface-to-surface, volume-to-surface, and volume-to-volume pairs of zones in axisymmetric cylindrical geometries. With this method the calculation of the direct-exchange areas can be transformed from the original four-, five-, and sixfold integrals in the defining relations to just single and/or double integrals. Gray gas with absorption coefficient K is assumed.
Kim, Joshua; Ionascu, Dan; Zhang, Tiezhi
2013-01-01
Purpose: To accelerate iterative algebraic reconstruction algorithms using a cylindrical image grid. Methods: Tetrahedron beam computed tomography (TBCT) is designed to overcome the scatter and detector problems of cone beam computed tomography (CBCT). Iterative algebraic reconstruction algorithms have been shown to mitigate approximate reconstruction artifacts that appear at large cone angles, but clinical implementation is limited by their high computational cost. In this study, a cylindrical voxelization method on a cylindrical grid is developed in order to take advantage of the symmetries of the cylindrical geometry. The cylindrical geometry is a natural fit for the circular scanning trajectory employed in volumetric CT methods such as CBCT and TBCT. This method was implemented in combination with the simultaneous algebraic reconstruction technique (SART). Both two- and three-dimensional numerical phantoms as well as a patient CT image were utilized to generate the projection sets used for reconstruction. The reconstructed images were compared to the original phantoms using a set of three figures of merit (FOM). Results: The cylindrical voxelization on a cylindrical reconstruction grid was successfully implemented in combination with the SART reconstruction algorithm. The FOM results showed that the cylindrical reconstructions were able to maintain the accuracy of the Cartesian reconstructions. In three dimensions, the cylindrical method provided better accuracy than the Cartesian methods. At the same time, the cylindrical method was able to provide a speedup factor of approximately 40 while also reducing the system matrix storage size by 2 orders of magnitude. Conclusions: TBCT image reconstruction using a cylindrical image grid was able to provide a significant improvement in the reconstruction time and a more compact system matrix for storage on the hard drive and in memory while maintaining the image quality provided by the Cartesian voxelization on a
NASA Astrophysics Data System (ADS)
Cembranos, J. A. R.; Dobado, A.; Maroto, A. L.
Extra-dimensional theories contain additional degrees of freedom related to the geometry of the extra space which can be interpreted as new particles. Such theories allow to reformulate most of the fundamental problems of physics from a completely different point of view. In this essay, we concentrate on the brane fluctuations which are present in brane-worlds, and how such oscillations of the own space-time geometry along curved extra dimensions can help to resolve the Universe missing mass problem. The energy scales involved in these models are low compared to the Planck scale, and this means that some of the brane fluctuations distinctive signals could be detected in future colliders and in direct or indirect dark matter searches.
Concentration profiles in drying cylindrical filaments
NASA Astrophysics Data System (ADS)
Czaputa, Klaus; Brenn, Günter; Meile, Walter
2008-12-01
We analyze theoretically the drying of cylindrical filaments. For modelling the mass transfer on the gas side of the liquid-gas interface of the shrinking circular cylindrical filament, we apply the model of Abramzon and Sirignano, which was originally developed for spherical geometry. As a consequence of mass transfer at constant Sherwood number, we obtain a d2-law for the shrinkage of the cylinder as in the case of the spherical geometry, which expresses that the cross-sectional area of the cylinder shrinks at a constant rate with time. For this situation, the diffusion equation for the liquid phase mixture components becomes separable upon transformation into similarity coordinates and is solved analytically to obtain the concentration profiles inside the filament as functions of time. The dependency of the profiles on the radial coordinate is determined by a series of Kummer’s functions. Applying this result, we study the evolution of the concentration profiles in the liquid phase with time as dependent on a parameter given as the ratio of rate of shrinkage of the cross-sectional area of the cylinder to liquid-phase diffusion coefficient, which was identified as relevant for the shape of the concentration profiles formed in the liquid during the drying process. As an example, we present computed results for the constant evaporation rate regime in the dry-spinning process of a polyvinyl-alcohol (PVA)-water system. Comparison of our analytical results with full numerical solutions of the diffusion equation from the literature, achieved with concentration-dependent diffusion coefficient, reveals very good agreement.
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.
Cylindrical and spherical electron acoustic solitary waves with nonextensive hot electrons
Pakzad, Hamid Reza
2011-08-15
Nonlinear propagation of cylindrical and spherical electron-acoustic solitons in an unmagnetized plasma consisting cold electron fluid, hot electrons obeying a nonextensive distribution and stationary ions, are investigated. For this purpose, the standard reductive perturbation method is employed to derive the cylindrical/spherical Korteweg-de-Vries equation, which governs the dynamics of electron-acoustic solitons. The effects of nonplanar geometry and nonextensive hot electrons on the behavior of cylindrical and spherical electron acoustic solitons are also studied by numerical simulations.
Cylindrical and Spherical Positron-Acoustic Shock Waves in Nonthermal Electron-Positron-Ion Plasmas
NASA Astrophysics Data System (ADS)
Rahman, M. M.; Alam, M. S.; Mamun, A. A.
2015-06-01
The nonlinear propagation of cylindrical and spherical positron-acoustic shock waves (PASWs) in an unmagnetized four-component plasma (containing nonthermal distributed hot positrons and electrons, cold mobile viscous positron fluid, and immobile positive ions) is investigated theoretically. The modified Burgers equation is derived by employing the reductive perturbation method. Analytically, the effects of cylindrical and spherical geometries, nonthermality of electrons and hot positrons, relative number density and temperature ratios, and cold mobile positron kinematic viscosity on the basic features (viz. polarity, amplitude, width, phase speed, etc.) of PASWs are briefly addressed. It is examined that the PASWs in nonplanar (cylindrical and spherical) geometry significantly differ from those in planar geometry. The relevance of our results may be useful in understanding the basic characteristics of PASWs in astrophysical and laboratory plasmas.
Cylindrical Implosion Experiments using Laser Direct Drive
NASA Astrophysics Data System (ADS)
Tubbs, David
1998-11-01
Development of high-gain targets for the National Ignition Facility relies considerably on computational modeling, and it is important that our codes are validated against relevant experimental data in convergent geometry.(W. J. Krauser et al., Phys. Plasmas 3, 2084 (1996); D. C. Wilson et al., Phys. Plasmas 5, 1953 (1998)) In collaboration with the University of Rochester, we have begun a campaign of hydrodynamic instability experiments in cylindrical geometry using direct drive,(D. L. Tubbs et al., submitted to Laser and Particle Beams (1998); C. W. Barnes et al., submitted to Rev. Sci. Instrm. (1998)) building on our success in indirect drive.( W. W. Hsing et al., Phys. Plasmas 5, 1832 (1997); W. W. Hsing and N. M. Hoffman, Phys. Rev. Lett., 3876 (1997)) Cylindrical targets facilitate direct diagnostic access to the convergent, hydrodynamic flow. The energy advantage of direct drive and its excellent target-illumination symmetry (achieved at OMEGA through use of Distributed Phase Plates and SSD) permit more energetic implosions, larger target scale (hence greater diagnostic resolution), longer acceleration timescales, and higher convergence than were possible using indirect drive. We estimate that specific laser energy delivered to the target for direct drive at OMEGA is roughly 4 times that achieved for indirect drive at Nova. Our first experiments (January 1998) yield excellent data for the first highly symmetrical direct-drive implosions, with which we benchmark zeroth-order hydrodynamic simulations. Two-dimensional (2-D) LASNEX calculations, using as-shot laser power histories and no further physics adjustments, match measured target-implosion data within theoretical and experimental errors. In addition, 2-D LASNEX simulations of single-mode (m=28, azimuthally symmetric) perturbation growth agree well with data obtained during our first week of experiments. For 1.5-micron initial perturbation amplitude, we observe Rayleigh-Taylor growth factors of order 10
Advanced nodal neutron diffusion method with space-dependent cross sections: ILLICO-VX
Rajic, H.L.; Ougouag, A.M.
1987-01-01
Advanced transverse integrated nodal methods for neutron diffusion developed since the 1970s require that node- or assembly-homogenized cross sections be known. The underlying structural heterogeneity can be accurately accounted for in homogenization procedures by the use of heterogeneity or discontinuity factors. Other (milder) types of heterogeneity, burnup-induced or due to thermal-hydraulic feedback, can be resolved by explicitly accounting for the spatial variations of material properties. This can be done during the nodal computations via nonlinear iterations. The new method has been implemented in the code ILLICO-VX (ILLICO variable cross-section method). Numerous numerical tests were performed. As expected, the convergence rate of ILLICO-VX is lower than that of ILLICO, requiring approx. 30% more outer iterations per k/sub eff/ computation. The methodology has also been implemented as the NOMAD-VX option of the NOMAD, multicycle, multigroup, two- and three-dimensional nodal diffusion depletion code. The burnup-induced heterogeneities (space dependence of cross sections) are calculated during the burnup steps.
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.
JKR adhesion in cylindrical contacts
NASA Astrophysics Data System (ADS)
Sundaram, Narayan; Farris, T. N.; Chandrasekar, S.
2012-01-01
Planar JKR adhesive solutions use the half-plane assumption and do not permit calculation of indenter approach or visualization of adhesive force-displacement curves unless the contact is periodic. By considering a conforming cylindrical contact and using an arc crack analogy, we obtain closed-form indenter approach and load-contact size relations for a planar adhesive problem. The contact pressure distribution is also obtained in closed-form. The solutions reduce to known cases in both the adhesion-free and small-contact solution ( Barquins, 1988) limits. The cylindrical system shows two distinct regimes of adhesive behavior; in particular, contact sizes exceeding the critical (maximum) size seen in adhesionless contacts are possible. The effects of contact confinement on adhesive behavior are investigated. Some special cases are considered, including contact with an initial neat-fit and the detachment of a rubbery cylinder from a rigid cradle. A comparison of the cylindrical solution with the half-plane adhesive solution is carried out, and it indicates that the latter typically underestimates the adherence force. The cylindrical adhesive system is novel in that it possesses stable contact states that may not be attained even on applying an infinite load in the absence of adhesion.
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…
Vibration of perforated cylindrical shells
NASA Astrophysics Data System (ADS)
Cousseau, Peter L.
For a credible design of an inertial confinement fusion (ICF) target chamber, the vibration characteristics of the chamber must be completely understood. Target chambers are usually cylindrical or spherical in shape and contain hundreds of perforations (called ports) to allow access to the inside of the chamber. The fusion reaction within the chamber creates a uniform impulsive loading, which the chamber walls must be designed to contain. Also prior to an implosion, a delicate alignment process of the drivers and diagnostics takes place. The vibration of the chamber from rotating machinery, e.g., vacuum pumps, and ambient sources must be completely understood and accounted for during these alignment procedures. This dissertation examines the vibration characteristics of perforated cylindrical shells. Because the target chambers' thickness-to-radius ratio is small, such chambers can be modeled as thin shells. Included in the text is a literature review of perforated plates and shells and examples of the use of perforated structures in constructed and proposed ICF target chambers. The natural frequencies and corresponding mode shapes of perforated and unperforated cylindrical shells are studied analytically, numerically (via finite elements) and experimentally. Conclusions and comparisons between the different solution methods are made for both the perforated and unperforated cases. In addition, the dynamic response of perforated cylindrical shells to an axisymmetric impulsive loading has been identified. A demonstration showing how the convolution integral can be used to determine the response of a cylinder to a non-impulsive loading is presented.
Cylindrical magnets and ideal solenoids
NASA Astrophysics Data System (ADS)
Derby, Norman; Olbert, Stanislaw
2010-03-01
Both wire-wound solenoids and cylindrical magnets can be approximated as ideal azimuthally symmetric solenoids. We present an exact solution for the magnetic field of an ideal solenoid in an easy to use form. The field is expressed in terms of a single function that can be rapidly computed by means of a compact efficient algorithm, which can be coded as an add-in function to a spreadsheet, making field calculations accessible to introductory students. These expressions are not only accurate but are also as fast as most approximate expressions. We demonstrate their utility by simulating the dropping of a cylindrical magnet through a nonmagnetic conducting tube and comparing the calculation with data obtained from experiments suitable for an undergraduate laboratory.
Cylindrical solutions in mimetic gravity
NASA Astrophysics Data System (ADS)
Momeni, Davood; Myrzakulov, Kairat; Myrzakulov, Ratbay; Raza, Muhammad
2016-06-01
This paper is devoted to investigate cylindrical solutions in mimetic gravity. The explicit forms of the metric of this theory, namely mimetic-Kasner (say) have been obtained. In this study we have noticed that the Kasner's family of exact solutions needs to be reconsidered under this type of modified gravity. A no-go theorem is proposed for the exact solutions in the presence of a cosmological constant.
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)
Cylindrical solutions in braneworld gravity
Khoeini-Moghaddam, S.; Nouri-Zonoz, M.
2005-09-15
In this article we investigate exact cylindrically symmetric solutions to the modified Einstein field equations in the braneworld gravity scenarios. It is shown that for the special choice of the equation of state 2U+P=0 for the dark energy and dark pressure, the solutions found could be considered formally as solutions of the Einstein-Maxwell equations in 4-D general relativity.
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.
Jet mixing in a reacting cylindrical crossflow
NASA Technical Reports Server (NTRS)
Leong, M. Y.; Samuelsen, G. S.; Holdeman, J. D.
1995-01-01
This paper addresses the mixing of air jets into the hot, fuel-rich products of a gas turbine primary zone. The mixing, as a result, occurs in a reacting environment with chemical conversion and substantial heat release. The geometry is a crossflow confined in a cylindrical duct with side-wall injection of jets issuing from round orifices. A specially designed reactor, operating on propane, presents a uniform mixture without swirl to mixing modules consisting of 8, 9, 10, and 12 holes at a momentum-flux ratio of 57 and a jet-to-mainstream mass-flow ratio of 2.5. Concentrations of O2, CO2, CO, and HC are obtained upstream, downstream, and within the orifice plane. O2 profiles indicate jet penetration while CO2, CO, and HC profiles depict the extent of reaction. Jet penetration is observed to be a function of the number of orifices and is found to affect the mixing in the reacting system. The results demonstrate that one module (the 12-hole) produces near-optimal penetration defined here as a jet penetration closest to the module half-radius, and hence the best uniform mixture at a plane one duct radius from the orifice leading edge.
Capillary effects on floating cylindrical particles
NASA Astrophysics Data System (ADS)
Dixit, Harish N.; Homsy, G. M.
2012-12-01
In this study, we develop a systematic perturbation procedure in the small parameter, B1/2, where B is the Bond number, to study capillary effects on small cylindrical particles at interfaces. Such a framework allows us to address many problems involving particles on flat and curved interfaces. In particular, we address four specific problems: (i) capillary attraction between cylinders on flat interface, in which we recover the classical approximate result of Nicolson ["The interaction between floating particles," Proc. Cambridge Philos. Soc. 45, 288-295 (1949), 10.1017/S0305004100024841], thus putting it on a rational basis; (ii) capillary attraction and aggregation for an infinite array of cylinders arranged on a periodic lattice, where we show that the resulting Gibbs elasticity obtained for an array can be significantly larger than the two cylinder case; (iii) capillary force on a cylinder floating on an arbitrary curved interface, where we show that in the absence of gravity, the cylinder experiences a lateral force which is proportional to the gradient of curvature; and (iv) capillary attraction between two cylinders floating on an arbitrary curved interface. The present perturbation procedure does not require any restrictions on the nature of curvature of the background interface and can be extended to other geometries.
Sound transmission into a laminated composite cylindrical shell
NASA Technical Reports Server (NTRS)
Koval, L. R.
1980-01-01
In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a laminated composite circular cylindrical shell. Numerical results are obtained for geometry typical of a narrow-bodied jet transport. Results indicate that from the viewpoint of noise attenuation on laminated composite shell does not appear to offer any significant advantage over an aluminum shell. However, the transmission loss of a laminated composite shell is sensitive to the orientation of the fibers and this suggests the possibility of using a laminated composite shell to tailor the noise attenuation characteristics to meet a specific need.
Spectrum of resistive MHD modes in cylindrical plasmas
Ryu, C.M.; Grimm, R.C.
1983-07-01
A numerical study of the normal modes of a compressible resistive MHD fluid in cylindrical geometry is presented. Resistivity resolves the shear Alfven and slow magnetosonic continua of ideal MHD into discrete spectra and gives rise to heavily damped modes whose frequencies lie on specific lines in the complex plane. Fast magnetosonic waves are less affected but are also damped. Overstable modes arise from the shear Alfven spectrum. The stabilizing effect of favorable average curvature is shown. Eigenfunctions illustrating the nature of typical normal modes are displayed.
Axial jet mixing of ethanol in cylindrical containers during weightlessness
NASA Technical Reports Server (NTRS)
Aydelott, J. C.
1979-01-01
An experimental program was conducted to examine the liquid flow patterns that result from the axial jet mixing of ethanol in 10-centimeter-diameter cylindrical tanks in weightlessness. A convex hemispherically ended tank and two Centaur liquid-hydrogen-tank models were used for the study. Four distinct liquid flow patterns were observed to be a function of the tank geometry, the liquid-jet velocity, the volume of liquid in the tank, and the location of the tube from which the liquid jet exited.
Parallel algorithms for 2-D cylindrical transport equations of Eigenvalue problem
Wei, J.; Yang, S.
2013-07-01
In this paper, aimed at the neutron transport equations of eigenvalue problem under 2-D cylindrical geometry on unstructured grid, the discrete scheme of Sn discrete ordinate and discontinuous finite is built, and the parallel computation for the scheme is realized on MPI systems. Numerical experiments indicate that the designed parallel algorithm can reach perfect speedup, it has good practicality and scalability. (authors)
Supercooling Water in Cylindrical Capsules
NASA Astrophysics Data System (ADS)
Guzman, J. J. Milón; Braga, S. L.
2005-11-01
An experimental apparatus was developed to investigate the supercooling phenomenon of water inside cylindrical capsules used for a cold storage process. The coolant is a water-alcohol mixture controlled by a constant temperature bath (CTB). Temperatures varying with time are measured inside and outside the capsule. Cylinders with an internal diameter and thickness of 45 and 1.5 mm, respectively, were made from four different materials: acrylic, PVC, brass, and aluminum. The supercooling period of the water and the nucleation temperature were investigated for different coolant temperatures. The supercooling and nucleation probabilities are shown as a function of the coolant temperature for the four different materials.
Planar and cylindrical active microwave temperature imaging: numerical simulations.
Rius, J M; Pichot, C; Jofre, L; Bolomey, J C; Joachimowicz, N; Broquetas, A; Ferrando, M
1992-01-01
A comparative study at 2.45 GHz concerning both measurement and reconstruction parameters for planar and cylindrical configurations is presented. For the sake of comparison, a numerical model consisting of two nonconcentric cylinders is considered and reconstructed using both geometries from simulated experimental data. The scattered fields and reconstructed images permit extraction of very useful information about dynamic range, sensitivity, resolution, and quantitative image accuracy for the choice of the configuration in a particular application. Both geometries can measure forward and backward scattered fields. The backscattering measurement improves the image resolution and reconstruction in lossy mediums, but, on the other hand, has several dynamic range difficulties. This tradeoff between forward only and forward-backward field measurement is analyzed. As differential temperature imaging is a weakly scattering problem, Born approximation algorithms can be used. The simplicity of Born reconstruction algorithms and the use of FFT make them very attractive for real-time biomedical imaging systems. PMID:18222887
Inflation of stressed cylindrical tubes: an experimental study
NASA Astrophysics Data System (ADS)
Guo, Zhiming; Wang, Shibin; Li, Linan; Ji, Hongwei; Wang, Zhiyong; Cai, Songbao
2014-06-01
The inflation of an initially stressed cylindrical shell provides a good illustration of the phenomenon of the initiation and propagation of an instability, which shares the same mathematical and mechanical features with a variety of other strain localization phenomena in engineering structures and materials. The high speed CCD camera and digital image processing system were used to measure the 3D shape of the inflated cylindrical tube. The localized bulge of a cylindrical tube with closed ends forms when the internal pressure reaches a critical value Pcr. As more air is filled into the tube, the pressure drops but the radius at the centre of the bulge will increase until it reaches a maximum value rmax. With continued inflation, the pressure stays at a constant value Pp. The purpose of this study is to investigate the critical and propagation pressures in the tubes and the profile outside when the shells under axial tension and internal pressure were inflating. We focus on the influence of the axial tension on the critical pressure. In this paper the problem is explored through experimental efforts. A series of experiments were conducted on commercially available natural rubber latex tubes involving different geometries and initial axial tensions, which were regarded as isotropic, homogeneous, incompressible and hyper-elastic materials.
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
Propagation Mechanism of Cylindrical Cellular Detonation
NASA Astrophysics Data System (ADS)
Han, Wen-Hu; Wang, Cheng; Ning, Jian-Guo
2012-10-01
We investigate the evolution of cylindrical cellular detonation with different instabilities. The numerical results show that with decreasing initial temperature, detonation becomes more unstable and the cells of the cylindrical detonation tend to be irregular. For stable detonation, a divergence of cylindrical detonation cells is formed eventually due to detonation instability resulting from a curved detonation front. For mildly unstable detonation, local overdriven detonation occurs. The detonation cell diverges and its size decreases. For highly unstable detonation, locally driven detonation is more obvious and the front is highly wrinkled. As a result, the diverging cylindrical detonation cell becomes highly irregular.
Numerical study of cathode emission constraints on cylindrical self-field MPD thruster performance
NASA Technical Reports Server (NTRS)
Lapointe, Michael R.
1993-01-01
A stability equation relating thruster discharge current, argon propellant mass flow rate, and electrode geometry has been solved for a variety of cylindrical self-field MPD thruster configurations and discharge currents. Realistic values for cathode emission current densities were used to provide additional constraints on the thruster geometries. A two-dimensional MPD code was employed to provide better estimates of the maximum achievable specific impulse, thrust, and flow efficiency for cases of interest. The model results indicate that long life, cylindrical self-field MPD thrusters operated with argon propellant may not be able to provide specific impulse values in excess of 2100s. Alternate electrode geometries, applied magnetic fields, and/or low molecular weight propellants may be necessary to achieve higher values of specific impulse.
Transient Eddy Current Response Due to a Conductive Cylindrical Rod
NASA Astrophysics Data System (ADS)
Fu, Fangwei; Bowler, J. R.
2007-03-01
Transient eddy current test systems have been developed for the inspection of aircraft structures and for oil and gas pipelines. This work is supported by theoretical developments in which transient fields and time domain signals are determined for the geometry of interest. However most of the models to date have been aimed at structures that are planar, relatively little attention being paid to the corresponding problems in cylindrical geometries. In order to rectify this deficiency, we have examined theoretically the transient probe signal response due to a cylindrical conductive rod excited by an encircling coil. The transient fields can be calculated from a Fourier transform of the frequency domain solutions for infinite rods or tubes but, as with planar structures, we have found that it is better to use series solutions in the time domain since these provide more accurate and flexible representations of transient fields. Two types of series are used; one which converges faster at short times and one which converges faster at longer times. Calculations using these series show that they are in mutual agreement and agree with results computed using the fast Fourier transform.
ERIC Educational Resources Information Center
Kuntz, Gilles
The first section of this paper on World Wide Web applications related to dynamic geometry addresses dynamic geometry and teaching, including the relationship between dynamic geometry and direct manipulation, key features of dynamic geometry environments, the importance of direct engagement of the learner using construction software for…
ERIC Educational Resources Information Center
Cukier, Mimi; Asdourian, Tony; Thakker, Anand
2012-01-01
Geometry provides a natural window into what it is like to do mathematics. In the world of geometry, playful experimentation is often more fruitful than following a procedure, and logic plus a few axioms can open new worlds. Nonetheless, teaching a geometry course in a way that combines both rigor and play can be difficult. Many geometry courses…
NASA Astrophysics Data System (ADS)
Khalifa, H. E.; Deck, C. P.; Gutierrez, O.; Jacobsen, G. M.; Back, C. A.
2015-02-01
The use of silicon carbide (SiC) composites as structural materials in nuclear applications necessitates the development of a viable joining method. One critical application for nuclear-grade joining is the sealing of fuel within a cylindrical cladding. This paper demonstrates cylindrical joint feasibility using a low activation nuclear-grade joint material comprised entirely of β-SiC. While many papers have considered joining material, this paper takes into consideration the joint geometry and component form factor, as well as the material performance. Work focused specifically on characterizing the strength and permeability performance of joints between cylindrical SiC-SiC composites and monolithic SiC endplugs. The effects of environment and neutron irradiation were not evaluated in this study. Joint test specimens of different geometries were evaluated in their as-fabricated state, as well as after being subjected to thermal cycling and partial mechanical loading. A butted scarf geometry supplied the best combination of high strength and low permeability. A leak rate performance of 2 × 10-9 mbar l s-1 was maintained after thermal cycling and partial mechanical loading and sustained applied force of 3.4 kN, or an apparent strength of 77 MPa. This work shows that a cylindrical SiC-SiC composite tube sealed with a butted scarf endplug provides out-of-pile strength and permeability performance that meets light water reactor design requirements.
Velocity Inversion In Cylindrical Couette Gas Flows
NASA Astrophysics Data System (ADS)
Dongari, Nishanth; Barber, Robert W.; Emerson, David R.; Zhang, Yonghao; Reese, Jason M.
2012-05-01
We investigate a power-law probability distribution function to describe the mean free path of rarefied gas molecules in non-planar geometries. A new curvature-dependent model is derived by taking into account the boundary-limiting effects on the molecular mean free path for surfaces with both convex and concave curvatures. In comparison to a planar wall, we find that the mean free path for a convex surface is higher at the wall and exhibits a sharper gradient within the Knudsen layer. In contrast, a concave wall exhibits a lower mean free path near the surface and the gradients in the Knudsen layer are shallower. The Navier-Stokes constitutive relations and velocity-slip boundary conditions are modified based on a power-law scaling to describe the mean free path, in accordance with the kinetic theory of gases, i.e. transport properties can be described in terms of the mean free path. Velocity profiles for isothermal cylindrical Couette flow are obtained using the power-law model. We demonstrate that our model is more accurate than the classical slip solution, especially in the transition regime, and we are able to capture important non-linear trends associated with the non-equilibrium physics of the Knudsen layer. In addition, we establish a new criterion for the critical accommodation coefficient that leads to the non-intuitive phenomena of velocity-inversion. Our results are compared with conventional hydrodynamic models and direct simulation Monte Carlo data. The power-law model predicts that the critical accommodation coefficient is significantly lower than that calculated using the classical slip solution and is in good agreement with available DSMC data. Our proposed constitutive scaling for non-planar surfaces is based on simple physical arguments and can be readily implemented in conventional fluid dynamics codes for arbitrary geometric configurations.
High speed cylindrical roller bearing analysis, SKF computer program CYBEAN. Volume 2: User's manual
NASA Technical Reports Server (NTRS)
Kleckner, R. J.; Pirvics, J.
1978-01-01
The CYBEAN (Cylindrical Bearing Analysis) was created to detail radially loaded, aligned and misaligned cylindrical roller bearing performance under a variety of operating conditions. Emphasis was placed on detailing the effects of high speed, preload and system thermal coupling. Roller tilt, skew, radial, circumferential and axial displacement as well as flange contact were considered. Variable housing and flexible out-of-round outer ring geometries, and both steady state and time transient temperature calculations were enabled. The complete range of elastohydrodynamic contact considerations, employing full and partial film conditions were treated in the computation of raceway and flange contacts. Input and output architectures containing guidelines for use and a sample execution are detailed.
NASA Technical Reports Server (NTRS)
Walowit, Jed A.; Shapiro, Wibur
2005-01-01
This is the source listing of the computer code SPIRALI which predicts the performance characteristics of incompressible cylindrical and face seals with or without the inclusion of spiral grooves. Performance characteristics include load capacity (for face seals), leakage flow, power requirements and dynamic characteristics in the form of stiffness, damping and apparent mass coefficients in 4 degrees of freedom for cylindrical seals and 3 degrees of freedom for face seals. These performance characteristics are computed as functions of seal and groove geometry, load or film thickness, running and disturbance speeds, fluid viscosity, and boundary pressures.
The space-dependent model and output characteristics of intra-cavity pumped dual-wavelength lasers
NASA Astrophysics Data System (ADS)
He, Jin-Qi; Dong, Yuan; Zhang, Feng-Dong; Yu, Yong-Ji; Jin, Guang-Yong; Liu, Li-Da
2016-01-01
The intra-cavity pumping scheme which is used to simultaneously generate dual-wavelength lasers was proposed and published by us and the space-independent model of quasi-three-level and four-level intra-cavity pumped dual-wavelength lasers was constructed based on this scheme. In this paper, to make the previous study more rigorous, the space-dependent model is adopted. As an example, the output characteristics of 946 nm and 1064 nm dual-wavelength lasers under the conditions of different output mirror transmittances are numerically simulated by using the derived formula and the results are nearly identical to what was previously reported.
Observations of ion-acoustic cylindrical solitons
NASA Technical Reports Server (NTRS)
Hershkowitz, N.; Romesser, T.
1974-01-01
Experimental observations of cylindrical solitons in a collisionless plasma are presented. The data obtained show that cylindrical solitonlike objects exist and that their properties are consistent with those of one- and three-dimensional solitons. It is found that compressive density perturbations evolve into solitons. The number of the solitons is determined by the width and amplitude of the applied pulse.
Learning Geometry through Dynamic Geometry Software
ERIC Educational Resources Information Center
Forsythe, Sue
2007-01-01
In this article, the author investigates effective teaching and learning of geometrical concepts using dynamic geometry software (DGS). Based from her students' reactions to her project, the author found that her students' understanding of the concepts was better than if they had learned geometry through paper-based tasks. However, mixing computer…
Intrinsic cylindrical and spherical waves
NASA Astrophysics Data System (ADS)
Ludlow, I. K.
2008-02-01
Intrinsic waveforms associated with cylindrical and spherical Bessel functions are obtained by eliminating the factors responsible for the inverse radius and inverse square radius laws of wave power per unit area of wavefront. The resulting expressions are Riccati-Bessel functions for both cases and these can be written in terms of amplitude and phase functions of order v and wave variable z. When z is real, it is shown that a spatial phase angle of the intrinsic wave can be defined and this, together with its amplitude function, is systematically investigated for a range of fixed orders and varying z. The derivatives of Riccati-Bessel functions are also examined. All the component functions exhibit different behaviour in the near field depending on the order being less than, equal to or greater than 1/2. Plots of the phase angle can be used to display the locations of the zeros of the general Riccati-Bessel functions and lead to new relations concerning the ordering of the real zeros of Bessel functions and the occurrence of multiple zeros when the argument of the Bessel function is fixed.
Growing Yeast into Cylindrical Colonies
Vulin, Clément; Di Meglio, Jean-Marc; Lindner, Ariel B.; Daerr, Adrian; Murray, Andrew; Hersen, Pascal
2014-01-01
Microorganisms often form complex multicellular assemblies such as biofilms and colonies. Understanding the interplay between assembly expansion, metabolic yield, and nutrient diffusion within a freely growing colony remains a challenge. Most available data on microorganisms are from planktonic cultures, due to the lack of experimental tools to control the growth of multicellular assemblies. Here, we propose a method to constrain the growth of yeast colonies into simple geometric shapes such as cylinders. To this end, we designed a simple, versatile culture system to control the location of nutrient delivery below a growing colony. Under such culture conditions, yeast colonies grow vertically and only at the locations where nutrients are delivered. Colonies increase in height at a steady growth rate that is inversely proportional to the cylinder radius. We show that the vertical growth rate of cylindrical colonies is not defined by the single-cell division rate, but rather by the colony metabolic yield. This contrasts with cells in liquid culture, in which the single-cell division rate is the only parameter that defines the population growth rate. This method also provides a direct, simple method to estimate the metabolic yield of a colony. Our study further demonstrates the importance of the shape of colonies on setting their expansion. We anticipate that our approach will be a starting point for elaborate studies of the population dynamics, evolution, and ecology of microbial colonies in complex landscapes. PMID:24853750
Filling of charged cylindrical capillaries.
Das, Siddhartha; Chanda, Sourayon; Eijkel, J C T; Tas, N R; Chakraborty, Suman; Mitra, Sushanta K
2014-10-01
We provide an analytical model to describe the filling dynamics of horizontal cylindrical capillaries having charged walls. The presence of surface charge leads to two distinct effects: It leads to a retarding electrical force on the liquid column and also causes a reduced viscous drag force because of decreased velocity gradients at the wall. Both these effects essentially stem from the spontaneous formation of an electric double layer (EDL) and the resulting streaming potential caused by the net capillary-flow-driven advection of ionic species within the EDL. Our results demonstrate that filling of charged capillaries also exhibits the well-known linear and Washburn regimes witnessed for uncharged capillaries, although the filling rate is always lower than that of the uncharged capillary. We attribute this to a competitive success of the lowering of the driving forces (because of electroviscous effects), in comparison to the effect of weaker drag forces. We further reveal that the time at which the transition between the linear and the Washburn regime occurs may become significantly altered with the introduction of surface charges, thereby altering the resultant capillary dynamics in a rather intricate manner. PMID:25375597
Efficient method for analyzing multiple circular cylindrical nanoparticles on a substrate
NASA Astrophysics Data System (ADS)
Lu, Xun; Lu, Ya Yan
2016-05-01
Due to the existing nanofabrication techniques, many metallic or dielectric nanoparticles are cylindrical objects with top and bottom surfaces parallel to a substrate and side boundaries perpendicular to the substrate. In this paper, we develop a relatively simple and efficient semi-analytic method for analyzing the scattering of light by a set of circular cylindrical objects (of finite height) on a layered background. The method relies on expanding the field in one-dimensional modes in layered regions where the material properties change with one spatial variable only, to establish a linear system on the boundaries separating the layered regions. Although the ‘expansion coefficients’ are two-dimensional (2D) functions, they satisfy scalar 2D Helmholtz equations which have analytic solutions due to the special geometry. The method is used to analyze dielectric and metallic circular cylindrical nanoparticles on a substrate or in free space.
NASA Technical Reports Server (NTRS)
Koval, L. R.
1980-01-01
In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a finite cylindrical shell stiffened by stringers and ring frames. The rings and stringers are modeled as discrete structural elements. The numerical case studied was typical of a narrow-bodied jet transport fuselage. The numerical results show that the ring-frequency dip in the transmission loss curve that is present for a monocoque shell is still present in the case of a stiffened shell. The ring frequency effect is a result of the cylindrical geometry of the shell. Below the ring frequency, stiffening does not appear to have any significant effect on transmission loss, but above the ring frequency, stiffeners can enhance the transmission loss of a cylindrical shell.
Plastic Limit Load Analysis of Cylindrical Pressure Vessels with Different Nozzle Inclination
NASA Astrophysics Data System (ADS)
Prakash, Anupam; Raval, Harit Kishorchandra; Gandhi, Anish; Pawar, Dipak Bapu
2016-04-01
Sudden change in geometry of pressure vessel due to nozzle cutout, leads to local stress concentration and deformation, decreasing its strength. Elastic plastic analysis of cylindrical pressure vessels with different inclination angles of nozzle is important to estimate plastic limit load. In the present study, cylindrical pressure vessels with combined inclination of nozzles (i.e. in longitudinal and radial plane) are considered for elastic plastic limit load analysis. Three dimensional static nonlinear finite element analyses of cylindrical pressure vessels with nozzle are performed for incremental pressure loading. The von Mises stress distribution on pressure vessel shows higher stress zones at shell-nozzle junction. Approximate plastic limit load is obtained by twice elastic slope method. Variation in limit pressure with different combined inclination angle of nozzle is analyzed and found to be distinct in nature. Reported results can be helpful in optimizing pressure vessel design.
Generation of scalable terahertz radiation from cylindrically focused two-color laser pulses in air
NASA Astrophysics Data System (ADS)
Kuk, D.; Yoo, Y. J.; Rosenthal, E. W.; Jhajj, N.; Milchberg, H. M.; Kim, K. Y.
2016-03-01
We demonstrate scalable terahertz (THz) generation by focusing terawatt, two-color laser pulses in air with a cylindrical lens. This focusing geometry creates a two-dimensional air plasma sheet, which yields two diverging THz lobe profiles in the far field. This setup can avoid plasma-induced laser defocusing and subsequent THz saturation, previously observed with spherical lens focusing of high-power laser pulses. By expanding the plasma source into a two-dimensional sheet, cylindrical focusing can lead to scalable THz generation. This scheme provides an energy conversion efficiency of 7 × 10-4, ˜7 times better than spherical lens focusing. The diverging THz lobes are refocused with a combination of cylindrical and parabolic mirrors to produce strong THz fields (>21 MV/cm) at the focal point.
Substrate heating rates for planar and cylindrical-post magnetron sputtering sources
NASA Technical Reports Server (NTRS)
Thornton, J. A.; Lamb, J. L.
1984-01-01
Results are presented for the substrate heating energy/atom required in the planar magnetron sputtering of Al, Cr, Ni, Cu, Mo, In, Ta, W, and Pt in Ar, as well as Al and Cr in O2. Data are also obtained for cylindrical magnetron sputtering of Nb, Ag, Ta, W, and Pb-Sn in Ar, and Mo sputtered in Ne, Ar, Kr, and Xe. Planar and cylindrical magnetron heating rates were comparable. Special experiments were conducted to examine the contributions to substrate heating of plasma species and ion neutralization and reflection at the cathode; the results obtained indicate that charged plasma species do not significantly contribute to the heating, but that neutralized and reflected ions play a significant role in the planar as well as cylindrical cases despite the differences in cathode geometry.
NASA Technical Reports Server (NTRS)
Walowit, Jed A.; Shapiro, Wilbur
2005-01-01
The SPIRALI code predicts the performance characteristics of incompressible cylindrical and face seals with or without the inclusion of spiral grooves. Performance characteristics include load capacity (for face seals), leakage flow, power requirements and dynamic characteristics in the form of stiffness, damping and apparent mass coefficients in 4 degrees of freedom for cylindrical seals and 3 degrees of freedom for face seals. These performance characteristics are computed as functions of seal and groove geometry, load or film thickness, running and disturbance speeds, fluid viscosity, and boundary pressures. A derivation of the equations governing the performance of turbulent, incompressible, spiral groove cylindrical and face seals along with a description of their solution is given. The computer codes are described, including an input description, sample cases, and comparisons with results of other codes.
Combinatorial Geometry Printer Plotting.
Energy Science and Technology Software Center (ESTSC)
1987-01-05
Picture generates plots of two-dimensional slices through the three-dimensional geometry described by the combinatorial geometry (CG) package used in such codes as MORSE and QAD-CG. These plots are printed on a standard line printer.
NASA Astrophysics Data System (ADS)
Taylor, Marika
2006-03-01
Two charge BPS horizon free supergravity geometries are important in proposals for understanding black hole microstates. In this paper we construct a new class of geometries in the NS1-P system, corresponding to solitonic strings carrying fermionic as well as bosonic condensates. Such geometries are required to account for the full microscopic entropy of the NS1-P system. We then briefly discuss the properties of the corresponding geometries in the dual D1-D5 system.
Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water.
Lau, Gabriel V; Ford, Ian J; Hunt, Patricia A; Müller, Erich A; Jackson, George
2015-03-21
The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large
Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water
Lau, Gabriel V.; Müller, Erich A.; Jackson, George; Ford, Ian J.; Hunt, Patricia A.
2015-03-21
The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large
ERIC Educational Resources Information Center
McDonald, Nathaniel J.
2001-01-01
Chronicles a teacher's first year teaching geometry at the Hershey Montessori Farm School in Huntsburg, Ohio. Instructional methods relied on Euclid primary readings and combined pure abstract logic with practical applications of geometry on the land. The course included geometry background imparted by Montessori elementary materials as well as…
Nondestructive Strain Tensor Scanning within Samples of Cylindrical Symmetry
Lienert, U.; Almer, J.; Haeffner, D.; Gao, Y.; Carter, W.
2004-05-12
The radial (i.e., depth below the surface) dependence of the residual strain tensor within shot-peened samples of cylindrical geometry is measured nondestructively using high-energy synchrotron radiation (80 keV). Transmission geometry is employed in combination with a triangulation slit and area detector. Thus, a radial gauge length is defined directly by the beam size rather than cumulatively as in conventional reflection geometry. A narrow incident beam of 30 micrometer diameter is used, and we demonstrate that macroscopic grain averaging is achieved even in the bulk, where the grain size is large, by oscillating the samples in two dimensions. Therefore, the samples are rotated with high frequency around the cylinder axis and translated with low frequency parallel to the axis. We argue that the combination of a narrow incident beam, a two-dimensional sample oscillation, and area detector provides a versatile technique to overcome insufficient grain averaging as the gauge volumes can be flexibly chosen by the combined translation and/or rotation oscillations. The methodology is discussed and experimental results are presented for a shot-peened steel sample. The achieved radial resolution is 30 micrometers, and the radial dependences of five strain tensor components are measured.
Vlad, Marcel O.; Szedlacsek, Stefan E.; Pourmand, Nader; Cavalli-Sforza, L. Luca; Oefner, Peter; Ross, John
2005-01-01
We study different physical, chemical, or biological processes involving replication, transformation, and disappearance processes, as well as transport processes, and assume that the time and space dependence of the species densities are known. We derive two types of Fisher equations. The first type relates the average value of the time derivative of the relative time-specific rates of growth of the different species to the variance of the relative, time-specific rates of growth. A second type relates the average value of the gradient or the divergence of the relative, space-specific rates of growth to the space correlation matrix of the relative, space-specific rates of growth. These Fisher equations are exact results, which are independent of the detailed kinetics of the process: they are valid whether the evolution equations are linear or nonlinear, local or nonlocal in space and/or time and can be applied for the study of a large class of physical, chemical, and biological systems described in terms of time- and/or space-dependent density fields. We examine the implications of our generalized Fisher relations in population genetics, biochemistry, and chemical kinetics (reaction–diffusion systems). We show that there is a connection between the enhanced (hydrodynamic) transport of mutations induced by population growth and space-specific rate vectors: the velocity of enhanced transport is proportional to the product of the diffusion coefficient of the species and the space rate vector; this relation is similar to a fluctuation–dissipation relation in statistical mechanics. PMID:15994224
Three-step cylindrical seal for high-performance turbomachines
NASA Technical Reports Server (NTRS)
Hendricks, Robert C.
1987-01-01
A three-step cylindrical seal configuration representing the seal for a high performance turbopump (e.g., the space shuttle main engine fuel pump) was tested under static (nonrotating) conditions. The test data included critical mass flux and pressure profiles over a wide range of inlet temperatures and pressures for fluid nitrogen and fluid hydrogen with the seal in concentric and fully eccentric positions. The critical mass flux (leakage rate) was 70% that of an equivalent straight cylindrical seal with a correspondingly higher pressure drop based on the same flow areas of 0.3569 sq cm but 85% that of the straight seal based on the third-step flow area of 0.3044 sq cm. The mass flow rates for the three step cylindrical seal in the fully eccentric and concentric positions were essentially the same, and the trends in flow coefficient followed those of a simple axisymmetric inlet configuration. However, for inlet stagnation temperatures less than the thermodynamic critical temperature the pressure profiles exhibited a flat region throughout the third step of the seal, with the pressure magnitude dependent on the inlet stagnation temperature. Such profiles represent an extreme positive direct stiffness. These conditions engendered a crossover in the pressure profile upstream of the postulated choke that resulted in a local negative stiffness. Flat and crossover profiles resulting from choking within the seal are practically unknown to the seal designer. However, they are of critical importance to turbomachine stability and must be integrated into any dynamic analysis of a seal of this configuration. In addition, choking is highly dependent on geometry, inlet-to-backpressure ratio, and inlet temperature and can occur within the seal even though the backpressure is above the critical pressure.
Three-step cylindrical seal for high-performance turbomachines
NASA Astrophysics Data System (ADS)
Hendricks, Robert C.
1987-06-01
A three-step cylindrical seal configuration representing the seal for a high performance turbopump (e.g., the space shuttle main engine fuel pump) was tested under static (nonrotating) conditions. The test data included critical mass flux and pressure profiles over a wide range of inlet temperatures and pressures for fluid nitrogen and fluid hydrogen with the seal in concentric and fully eccentric positions. The critical mass flux (leakage rate) was 70% that of an equivalent straight cylindrical seal with a correspondingly higher pressure drop based on the same flow areas of 0.3569 sq cm but 85% that of the straight seal based on the third-step flow area of 0.3044 sq cm. The mass flow rates for the three step cylindrical seal in the fully eccentric and concentric positions were essentially the same, and the trends in flow coefficient followed those of a simple axisymmetric inlet configuration. However, for inlet stagnation temperatures less than the thermodynamic critical temperature the pressure profiles exhibited a flat region throughout the third step of the seal, with the pressure magnitude dependent on the inlet stagnation temperature. Such profiles represent an extreme positive direct stiffness. These conditions engendered a crossover in the pressure profile upstream of the postulated choke that resulted in a local negative stiffness. Flat and crossover profiles resulting from choking within the seal are practically unknown to the seal designer. However, they are of critical importance to turbomachine stability and must be integrated into any dynamic analysis of a seal of this configuration. In addition, choking is highly dependent on geometry, inlet-to-backpressure ratio, and inlet temperature and can occur within the seal even though the backpressure is above the critical pressure.
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].
Linac mechanic QA using a cylindrical phantom
NASA Astrophysics Data System (ADS)
Mamalui-Hunter, Maria; Li, Harold; Low, Daniel A.
2008-09-01
Precise mechanical operation of a linear accelerator (linac) is critical for accurate radiation therapy dose delivery. Quantitative procedures for linac mechanical quality assurance (QA) used in the standard of care are time consuming and therefore conducted on a relatively infrequent basis. We present a method for evaluating the mechanical performance of a linac based on a series of projection portal images of a prototype cylindrical phantom with embedded radiopaque fiducial markers. The marker autodetection process included modeling imager response to the radiation beam where the projected cylinder attenuation yielded a non-uniform image background. The linac mechanical characteristics were estimated based on nonlinear multi-objective optimization of the projected marker locations. The estimated geometry parameters for the tested commercial model were gantry angle deviation 0.075 ± 0.076° (1 SD), gantry sag 0.026 ± 0.02°, source-to-axis distance SAD 998.3 ± 1.7 mm, source-to-detector distance SDD 1493 ± 5.0 mm, couch vertical motion 0.6 ± 0.45 mm, couch rotation 0.154 ± 0.1° and average linac rotation center (1.02, -0.27, -0.37) ± (0.36,0.333,1.20) mm relative to the laser intersection. The imager shift was [-0.44, 2.6] ± [0.20, 1.1] mm and the imager orientation was in-plane rotation 0.05 ± 0.03°, roll -0.14 ± 0.09° and pitch -0.9 ± 0.604°. The performance of this procedure concerning marker detection and optimization was examined by comparing the detected set of marker coordinates to its back-calculated counterpart for three subgroups of markers: central, wall and intermediate relative to the center of the phantom. The maximum difference was less than 0.25 mm with a mean of 0.146 mm and a standard deviation of 0.07 mm. The clinical use of this automated procedure will allow more efficient, more thorough, and more frequent mechanical linac QA.
Linac mechanic QA using a cylindrical phantom.
Mamalui-Hunter, Maria; Li, Harold; Low, Daniel A
2008-09-21
Precise mechanical operation of a linear accelerator (linac) is critical for accurate radiation therapy dose delivery. Quantitative procedures for linac mechanical quality assurance (QA) used in the standard of care are time consuming and therefore conducted on a relatively infrequent basis. We present a method for evaluating the mechanical performance of a linac based on a series of projection portal images of a prototype cylindrical phantom with embedded radiopaque fiducial markers. The marker autodetection process included modeling imager response to the radiation beam where the projected cylinder attenuation yielded a non-uniform image background. The linac mechanical characteristics were estimated based on nonlinear multi-objective optimization of the projected marker locations. The estimated geometry parameters for the tested commercial model were gantry angle deviation 0.075 +/- 0.076 degrees (1 SD), gantry sag 0.026 +/- 0.02 degrees , source-to-axis distance SAD 998.3 +/- 1.7 mm, source-to-detector distance SDD 1493 +/- 5.0 mm, couch vertical motion 0.6 +/- 0.45 mm, couch rotation 0.154 +/- 0.1 degrees and average linac rotation center (1.02, -0.27, -0.37) +/- (0.36,0.333,1.20) mm relative to the laser intersection. The imager shift was [-0.44, 2.6] +/- [0.20, 1.1] mm and the imager orientation was in-plane rotation 0.05 +/- 0.03 degrees , roll -0.14 +/- 0.09 degrees and pitch -0.9 +/- 0.604 degrees . The performance of this procedure concerning marker detection and optimization was examined by comparing the detected set of marker coordinates to its back-calculated counterpart for three subgroups of markers: central, wall and intermediate relative to the center of the phantom. The maximum difference was less than 0.25 mm with a mean of 0.146 mm and a standard deviation of 0.07 mm. The clinical use of this automated procedure will allow more efficient, more thorough, and more frequent mechanical linac QA. PMID:18723927
A cylindrical SPECT camera with de-centralized readout scheme
NASA Astrophysics Data System (ADS)
Habte, F.; Stenström, P.; Rillbert, A.; Bousselham, A.; Bohm, C.; Larsson, S. A.
2001-09-01
An optimized brain single photon emission computed tomograph (SPECT) camera is being designed at Stockholm University and Karolinska Hospital. The design goal is to achieve high sensitivity, high-count rate and high spatial resolution. The sensitivity is achieved by using a cylindrical crystal, which gives a closed geometry with large solid angles. A de-centralized readout scheme where only a local environment around the light excitation is readout supports high-count rates. The high resolution is achieved by using an optimized crystal configuration. A 12 mm crystal plus 12 mm light guide combination gave an intrinsic spatial resolution better than 3.5 mm (140 keV) in a prototype system. Simulations show that a modified configuration can improve this value. A cylindrical configuration with a rotating collimator significantly simplifies the mechanical design of the gantry. The data acquisition and control system uses early digitization and subsequent digital signal processing to extract timing and amplitude information, and monitors the position of the collimator. The readout system consists of 12 or more modules each based on programmable logic and a digital signal processor. The modules send data to a PC file server-reconstruction engine via a Firewire (IEEE-1394) network.
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)
Lai, Changliang; Wang, Junbiao; Liu, Chuang
2014-10-01
Six typical composite grid cylindrical shells are constructed by superimposing three basic types of ribs. Then buckling behavior and structural efficiency of these shells are analyzed under axial compression, pure bending, torsion and transverse bending by finite element (FE) models. The FE models are created by a parametrical FE modeling approach that defines FE models with original natural twisted geometry and orients cross-sections of beam elements exactly. And the approach is parameterized and coded by Patran Command Language (PCL). The demonstrations of FE modeling indicate the program enables efficient generation of FE models and facilitates parametric studies and design of grid shells. Using the program, the effects of helical angles on the buckling behavior of six typical grid cylindrical shells are determined. The results of these studies indicate that the triangle grid and rotated triangle grid cylindrical shell are more efficient than others under axial compression and pure bending, whereas under torsion and transverse bending, the hexagon grid cylindrical shell is most efficient. Additionally, buckling mode shapes are compared and provide an understanding of composite grid cylindrical shells that is useful in preliminary design of such structures.
Au cylindrical nanocup: A geometrically, tunable optical nanoresonator
NASA Astrophysics Data System (ADS)
Kovylina, M.; Alayo, N.; Conde-Rubio, A.; Borrisé, X.; Hibbard, G.; Labarta, A.; Batlle, X.; Pérez-Murano, F.
2015-07-01
The optical response of Au cylindrical metallic nanostructures (nanocups) with very thin walls is studied by means of finite difference time domain simulations. The simulations predict that, by changing the geometry of the nanocups, they behave as tunable optical nanoresonators with strong near-field enhancement. This opens up the possibility to use them simultaneously as container and field enhancer. Nanocups have been produced by an on-purpose designed fabrication route that combines nanoimprint lithography, definition of an intermediate hard mask, and metal lift-off. The fabrication route offers a manifold of supplementary advantages: thorough control of geometrical parameters; versatility of compositional design, including multishell nanocups; precise positioning of nanocups over the substrate; and low-cost and fast manufacturing of large areas of desirable density without loss of resolution, all processes being compatible with high throughput, low cost production, thus enabling future commercial applications.
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.
Cylindrical microlasers and light emitting devices from conducting polymers
Frolov, S.V.; Fujii, A.; Chinn, D.; Vardeny, Z.V.; Yoshino, K.; Gregory, R.V.
1998-06-01
Substantially improved, photopumped polymer lasers are demonstrated using microrings and microdisks of various diameters D ranging from 5 to 200 {mu}m. Various cavity-dependent laser modes were observed, which for D{lt}10{mu}m were dominated by a single longitudinal mode with linewidth of less than 1 {Angstrom}. These microlasers were also characterized by Q of order 5000, low threshold excitation energy of order 100 pJ/pulse for pulse duration ranging from 100 ps to sub-{mu}s, and an abrupt increase in the emission directionality and polarization degree. Light emitting diodes with cylindrical geometry, fully compatible with these microlasers are also demonstrated. {copyright} {ital 1998 American Institute of Physics.}
Ductile fracture of cylindrical vessels containing a large flaw
NASA Technical Reports Server (NTRS)
Erdogan, F.; Irwin, G. R.; Ratwani, M.
1976-01-01
The fracture process in pressurized cylindrical vessels containing a relatively large flaw is considered. The flaw is assumed to be a part-through or through meridional crack. The flaw geometry, the yield behavior of the material, and the internal pressure are assumed to be such that in the neighborhood of the flaw the cylinder wall undergoes large-scale plastic deformations. Thus, the problem falls outside the range of applicability of conventional brittle fracture theories. To study the problem, plasticity considerations are introduced into the shell theory through the assumptions of fully-yielded net ligaments using a plastic strip model. Then a ductile fracture criterion is developed which is based on the concept of net ligament plastic instability. A limited verification is attempted by comparing the theoretical predictions with some existing experimental results.
Nonlinear saturation amplitude of cylindrical Rayleigh—Taylor instability
NASA Astrophysics Data System (ADS)
Liu, Wan-Hai; Yu, Chang-Ping; Ye, Wen-Hua; Wang, Li-Feng
2014-09-01
The nonlinear saturation amplitude (NSA) of the fundamental mode in the classical Rayleigh—Taylor instability with a cylindrical geometry for an arbitrary Atwood number is analytically investigated by considering the nonlinear corrections up to the third order. The analytic results indicate that the effects of the initial radius of the interface (r0) and the Atwood number (A) play an important role in the NSA of the fundamental mode. The NSA of the fundamental mode first increases gently and then decreases quickly with increasing A. For a given A, the smaller the r0/λ (λ is the perturbation wavelength), the larger the NSA of the fundamental mode. When r0/λ is large enough (r0 ≫ λ), the NSA of the fundamental mode is reduced to the prediction in the previous literatures within the framework of the third-order perturbation theory.
Shear stabilization of the capillary breakup of a cylindrical interface
NASA Technical Reports Server (NTRS)
Russo, Mathew J.; Steen, Paul H.
1989-01-01
A cylindrical interface containing a viscous liquid set into axial motion is subject to a capillary and to a surface-wave instability. Clues from previous studies suggest that, even though both mechanisms separately are destabilizing, under certain circumstances their mutual interaction can lead to a stable interface; shear can stabilize capillary breakup. Here, an axial flow through an annular cross section bounded on the inside by a rigid rod and on the outside by a deformable interface is considered. The competition between the two mechanisms is studied through the temporal growth of infinitesimal axisymmetric and nonaxisymmetric disturbances. This examination of temporal stability shows that, indeed, for geometries corresponding to thin annular layers both instabilities can be completely suppressed (disturbances of all wavelengths decay).
Rigid-drift magnetohydrodynamic equilibria for cylindrical screw pinches
NASA Technical Reports Server (NTRS)
Turner, L.
1979-01-01
The rigid-drift equations of MHD equilibria in cylindrical geometry are solved analytically in terms of an infinite series of hypergeometric functions for the case where the pressure is proportional to the square of number density and the current density is arbitrarily pitched. Solutions are obtained for a pure Z pinch, a pure theta pinch, and a general screw pinch. It is found that the shapes of the pressure and magnetic-field profiles are completely determined by the model once two parameters are specified: the local plasma beta on the axis and a quantity related to the pitch of the current density. A set of profiles that resemble those observed experimentally in reversed-field pinches is presented. The results also indicate that hollow pressure profiles and reversed Bz profiles can occur either simultaneously or independently and that the pressure always falls to zero at a finite value of the radius.
Magnetic stress anisotropy field in plated cylindrical Permalloy films.
NASA Technical Reports Server (NTRS)
Lutes, O. S.
1971-01-01
An analysis is made of the magnetic stress anisotropy field (Hks) arising from internal and external stress sources in plated-wire memory elements. The analysis takes into consideration circumferential composition variation and cylindrical geometry of the Permalloy film. Expressions are derived relating Hks to uniaxial film stress, average composition, and amplitude of composition variation. A result of particular importance is that even for average zeromagnetostrictive composition (ZMC) films, Hks may still make an appreciable contribution to the total anisotropy field if the composition is not uniform. Calculated Hks characteristics are shown to correlate with anisotropy field changes observed in annealing experiments. Examples are given to show the importance of composition uniformity in determining the stability of the anisotropy field. The utility of the analysis is extended by the inclusion of data expressing the inverse relation between anisotropy field and easy-axis dispersion in the film.
Intensity and absorbed-power distribution in a cylindrical solar-pumped dye laser
NASA Technical Reports Server (NTRS)
Williams, M. D.
1984-01-01
The internal intensity and absorbed-power distribution of a simplified hypothetical dye laser of cylindrical geometry is calculated. Total absorbed power is also calculated and compared with laboratory measurements of lasing-threshold energy deposition in a dye cell to determine the suitability of solar radiation as a pump source or, alternatively, what modifications, if any, are necessary to the hypothetical system for solar pumping.
Changing the Structure Boundary Geometry
Karasev, Viktor; Dzlieva, Elena; Ivanov, Artyom
2008-09-07
Analysis of previously obtained results shows that hexagonal crystal lattice is the dominant type of ordering, in particular, in striated glow discharges. We explore the possibility for changing the dust distribution in horizontal cross sections of relatively highly ordered structures in a glow-discharge. Presuming that boundary geometry can affect dust distribution, we used cylindrical coolers held at 0 deg. C and placed against a striation containing a structure, to change the geometry of its outer boundary. By varying the number of coolers, their positions, and their separations from the tube wall, azimuthally asymmetric thermophoretic forces can be used to form polygonal boundaries and vary the angles between their segments (in a horizontal cross section). The corner in the structure's boundary of 60 deg. stimulates formation of hexagonal cells. The structure between the supported parallel boundaries is also characterized by stable hexagonal ordering. We found that a single linear boundary segment does not give rise to any sizable domain, but generates a lattice extending from the boundary (without edge defects). A square lattice can be formed by setting the angle equal to 90 deg. . However, angles of 45 deg. and 135 deg. turned out easier to form. Square lattice was created by forming a near-135 deg. corner with four coolers. It was noted that no grain ordering is observed in the region adjacent to corners of angles smaller than 30 deg. , which do not promote ordering into cells of any shape. Thus, manipulation of a structure boundary can be used to change dust distribution, create structures free of the ubiquitous edge defects that destroy orientation order, and probably change the crystal lattice type.
Numerical study of cathode emission constraints on cylindrical, self-field MPD thruster performance
LaPointe, M.R. )
1993-01-20
A stability equation relating thruster discharge current, argon propellant mass flow rate, and electrode geometry has been solved for a variety of cylindrical self-field MPD thruster configurations and discharge currents code was employed to provide better estimates of the maximum achievable specific impulse, thrust, and flow efficiency for cases of interest. The model results indicate that long life, cyclindrical self-field MPD thrusters operated with argon propellant may not be able to provide specific impulse values in excess of 2100 s. Alternate electrode geometries, applied magnetic fields, and/or low molecular weight propellants may be necessary to achieve higher values of specific impulse.
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.
Investigation of Surface Phenomena in Shocked Tin in Converging Geometry
Rousculp, Christopher L.; Oro, David Michael; Margolin, Len G.; Griego, Jeffrey Randall; Reinovsky, Robert Emil; Turchi, Peter John
2015-08-06
There is great interest in the behavior of the free surface of tin under shock loading. While it is known that meso-scale surface imperfections can seed the Richtmyer-Meshkov Instability (RMI) for a surface that is melted on release, much less is known about a tin surface that is solid, but plastically deforming. Here material properties such as shear and yield strength come into play especially in converging geometry. Previous experiments have been driven by direct contact HE. Usually a thin, flat target coupon is fielded with various single-mode, sinusoidal, machined, profiles on the free surface. The free surface is adjacent to either vacuum or an inert receiver gas. Most of these previous driver/target configurations have been nominal planer geometry. With modern HE it has been straightforward to shock tin into melt on release. However it has been challenging to achieve a low enough pressure for solid state on release. Here we propose to extend the existing base of knowledge to include the behavior of the free surface of tin in cylindrical converging geometry. By shock loading a cylindrical tin shell with a magnetically driven cylindrical liner impactor, the free surface evolution can be diagnosed with proton radiography. With the PHELIX capacitor bank, the drive can easily be varied to span the pressure range to achieve solid, mixed, and liquid states on release.
ERIC Educational Resources Information Center
Lyublinskaya, Irina; Funsch, Dan
2012-01-01
Several interactive geometry software packages are available today to secondary school teachers. An example is The Geometer's Sketchpad[R] (GSP), also known as Dynamic Geometry[R] software, developed by Key Curriculum Press. This numeric based technology has been widely adopted in the last twenty years, and a vast amount of creativity has been…
ERIC Educational Resources Information Center
Morris, Barbara H.
2004-01-01
This article describes a geometry project that used the beauty of stained-glass-window designs to teach middle school students about geometric figures and concepts. Three honors prealgebra teachers and a middle school mathematics gifted intervention specialist created a geometry project that covered the curriculum and also assessed students'…
Geometry of multihadron production
Bjorken, J.D.
1994-10-01
This summary talk only reviews a small sample of topics featured at this symposium: Introduction; The Geometry and Geography of Phase space; Space-Time Geometry and HBT; Multiplicities, Intermittency, Correlations; Disoriented Chiral Condensate; Deep Inelastic Scattering at HERA; and Other Contributions.
ERIC Educational Resources Information Center
Kaufmann, Matthew L.; Bomer, Megan A.; Powell, Nancy Norem
2009-01-01
Students enter the geometry classroom with a strong concept of fairness and a sense of what it means to "play by the rules," yet many students have difficulty understanding the postulates, or rules, of geometry and their implications. Although they may never have articulated the properties of an axiomatic system, they have gained a practical…
Euclidean Geometry via Programming.
ERIC Educational Resources Information Center
Filimonov, Rossen; Kreith, Kurt
1992-01-01
Describes the Plane Geometry System computer software developed at the Educational Computer Systems laboratory in Sofia, Bulgaria. The system enables students to use the concept of "algorithm" to correspond to the process of "deductive proof" in the development of plane geometry. Provides an example of the software's capability and compares it to…
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.
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.
Frambati, S.; Firpo, G.; Frignani, M.
2012-07-01
MANCINTAP [1], a fully automated tool for determining the activation patterns in complex 4D scenarios and evaluating the distribution of the ensuing radiation fields, has been improved. The constraint of forcing the user to define a single global mesh in order to approximate the whole problem, a limitation which prevented an accurate description of detail-rich geometries, has been overcome. The algorithm was improved and many limitations were relaxed. MANCINTAP is now capable of handling many different geometry elements in a given area at once, even if they have very different geometries and characteristic dimensions, thus allowing a vastly more complete and detailed analysis. Different meshes can be superimposed to the 3D geometry, allowing for an appropriate, dedicated treatment of all the relevant features of the problem, and the results are automatically combined in order to provide a global perspective. These new capabilities were accurately tested by applying the tool to the study of time-dependent radiation levels during shutdown in the upper reactor cavity and nozzle gallery regions of a 2-loop PWR reactor. (authors)
Roller bearing geometry design
NASA Technical Reports Server (NTRS)
Savage, M.; Pinkston, B. H. W.
1976-01-01
A theory of kinematic stabilization of rolling cylinders is extended and applied to the design of cylindrical roller bearings. The kinematic stabilization mechanism puts a reverse skew into the rolling elements by changing the roller taper. Twelve basic bearing modification designs are identified amd modeled. Four have single transverse convex curvature in their rollers while eight have rollers which have compound transverse curvature made up of a central cylindrical band surrounded by symmetric bands with slope and transverse curvature. The bearing designs are modeled for restoring torque per unit axial displacement, contact stress capacity, and contact area including dynamic loading, misalignment sensitivity and roller proportion. Design programs are available which size the single transverse curvature roller designs for a series of roller slopes and load separations and which design the compound roller bearings for a series of slopes and transverse radii of curvature. The compound rollers are proportioned to have equal contact stresses and minimum size. Design examples are also given.
Light scattering from cylindrical structures on surfaces.
Taubenblatt, M A
1990-03-01
Light scattering from a dielectric cylindrical structure on a surface by a plane wave with field vector along the cylinder axis is calculated with a modification of the coupled-dipole method. The interaction matrix is calculated with the use of both the direct contribution of a polarization current filament and its reflection from the surface. The reflected cylindrical waves are computed with the use of the Sommerfeld-type integral expression. Light scattering from structures of arbitrary cross section and the size of the order of a wavelength can be quickly determined with this method. PMID:19759774
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. PMID:26836560
Cheng, Juan; Shu, Chi-Wang
2014-09-01
In applications such as astrophysics and inertial confinement fusion, there are many three-dimensional cylindrical-symmetric multi-material problems which are usually simulated by Lagrangian schemes in the two-dimensional cylindrical coordinates. For this type of simulation, a critical issue for the schemes is to keep spherical symmetry in the cylindrical coordinate system if the original physical problem has this symmetry. In the past decades, several Lagrangian schemes with such symmetry property have been developed, but all of them are only first order accurate. In this paper, we develop a second order cell-centered Lagrangian scheme for solving compressible Euler equations in cylindrical coordinates, based on the control volume discretizations, which is designed to have uniformly second order accuracy and capability to preserve one-dimensional spherical symmetry in a two-dimensional cylindrical geometry when computed on an equal-angle-zoned initial grid. The scheme maintains several good properties such as conservation for mass, momentum and total energy, and the geometric conservation law. Several two-dimensional numerical examples in cylindrical coordinates are presented to demonstrate the good performance of the scheme in terms of accuracy, symmetry, non-oscillation and robustness. The advantage of higher order accuracy is demonstrated in these examples.
NASA Astrophysics Data System (ADS)
Weis, Matthew R.
Cylindrical liner implosions in the Magnetized Liner Inertial Fusion (MagLIF) concept are susceptible to the magneto-Rayleigh-Taylor instability (MRT). The danger of MRT enters in two phases, (1) during the main implosion, the outer surface of the liner is MRT unstable, and (2) during the short time period when the liner decelerates onto hot fuel, the inner surface becomes unstable. Growth of MRT on the outer surface may also feedthrough, which may seed the inner surface leading to high MRT growth in the second phase. If MRT growth becomes large enough, confinement of the fuel is lost. To characterize MRT we solve the linearized, ideal MHD equations in both planar and cylindrical geometries, including the presence of an axial magnetic field and the effects of sausage and kink modes (present in cylindrical coordinates only). In general, the total instability growth rates in cylindrical geometry are found to be larger than those in planar geometry. MRT and feedthrough is shown to be suppressed by strong magnetic field line bending (tension). However, for the same amount of field line bending, feedthrough is the most stabilized. Application of the planar and the cylindrical model to results from the Z-machine at Sandia National Laboratories is presented. Analytic MRT growth rates for a typical magnetized MagLIF-like implosion show the kink mode to be the fastest growing early and very late in the liner implosion (during deceleration). 1D HYDRA MHD simulations are used to generate realistic, evolving profiles (in density, pressure, and magnetic field) during the implosion from which instantaneous growth rates can be computed exactly, using either the planar or cylindrical analytic formulae developed in this thesis. Sophisticated 2D HYDRA MHD simulations were also performed to compare with the analytic theory and experimental results. In 2D, highly compressed axial magnetic fields can reduce the growth of perturbations at the fuel/liner interface during the implosion
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).
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.
Conformal cylindrically symmetric spacetimes in modified gravity
NASA Astrophysics Data System (ADS)
Türkog˜lu, Murat Metehan; Dog˜ru, Melis Ulu
2015-11-01
We investigate cylindrically symmetric spacetimes in the context of f(R) gravity. We firstly attain conformal symmetry of the cylindrically symmetric spacetime. We obtain solutions to use features of the conformal symmetry, field equations and their solutions for cylindrically symmetric spacetime filled with various cosmic matters such as vacuum state, perfect fluid, anisotropic fluid, massive scalar field and their combinations. With the vacuum state solutions, we show that source of the spacetime curvature is considered as Casimir effect. Casimir force for given spacetime is found using Wald’s axiomatic analysis. We expose that the Casimir force for Boulware, Hartle-Hawking and Unruh vacuum states could have attractive, repulsive and ineffective features. In the perfect fluid state, we show that matter form of the perfect fluid in given spacetime must only be dark energy. Also, we offer that potential of massive and massless scalar field are developed as an exact solution from the modified field equations. All solutions of field equations for vacuum case, perfect fluid and scalar field give a special f(R) function convenient to Λ-CDM model. In addition to these solutions, we introduce conformal cylindrical symmetric solutions in the cases of different f(R) models. Finally, geometrical and physical results of the solutions are discussed.
Optical methods for cylindrical rough surface testing
NASA Astrophysics Data System (ADS)
Perez Quintian, F.; Rebollo, Maria A.; Gaggioli, Nestor G.; Raffo, C. A.
1999-07-01
This work studies theoretically the scattering of light from cylindrical rough surfaces. It is shown, for the conical diffraction configuration, that the mean intensity on an observation plane perpendicular to the cylinder longitudinal axis, is related to the statistical parameters that characterize the surface: the roughness (sigma) and the correlation length T.
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.
Light Transmission Through Reflecting Cylindrical Tubes
ERIC Educational Resources Information Center
Cohen, D. K.; Potts, J. E.
1978-01-01
Describes an experiment in which a point source of light, when viewed through a cylindrical tube having reflecting inner walls, appears as a series of sharply defined rings, due to the multiple reflections from the inner walls of the tube. ( GA)
ERIC Educational Resources Information Center
Chern, Shiing-Shen
1990-01-01
Discussed are the major historical developments of geometry. Euclid, Descartes, Klein's Erlanger Program, Gaus and Riemann, globalization, topology, Elie Cartan, and an application to molecular biology are included as topics. (KR)
ERIC Educational Resources Information Center
Emenaker, Charles E.
1999-01-01
Describes a sixth-grade interdisciplinary geometry unit based on Charles Dickens's "A Christmas Carol". Focuses on finding area, volume, and perimeter, and working with estimation, decimals, and fractions in the context of making gingerbread houses. (ASK)
Noncommutative Geometry and Physics
NASA Astrophysics Data System (ADS)
Connes, Alain
2006-11-01
In this very short essay we shall describe a "spectral" point of view on geometry which allows to start taking into account the lessons from both renormalization and of general relativity. We shall first do that for renormalization and explain in rough outline the content of our recent collaborations with Dirk Kreimer and Matilde Marcolli leading to the universal Galois symmetry of renormalizable quantum field theories provided by the renormalization group in its cosmic Galois group incarnation. As far as general relativity is concerned, since the functional integral cannot be treated in the traditional perturbative manner, it relies heavily as a "sum over geometries" on the chosen paradigm of geometric space. This will give us the occasion to discuss, in the light of noncommutative geometry, the issue of "observables" in gravity and our joint work with Ali Chamseddine on the spectral action, with a first attempt to write down a functional integral on the space of noncommutative geometries.
Proof in Transformation Geometry
ERIC Educational Resources Information Center
Bell, A. W.
1971-01-01
The first of three articles showing how inductively-obtained results in transformation geometry may be organized into a deductive system. This article discusses two approaches to enlargement (dilatation), one using coordinates and the other using synthetic methods. (MM)
Detonation diffraction through different geometries
NASA Astrophysics Data System (ADS)
Sorin, Rémy; Zitoun, Ratiba; Khasainov, Boris; Desbordes, Daniel
2009-04-01
We performed the study of the diffraction of a self-sustained detonation from a cylindrical tube (of inner diameter d) through different geometric configurations in order to characterise the transmission processes and to quantify the transmission criteria to the reception chamber. For the diffraction from a tube to the open space the transmission criteria is expressed by d c = k c · λ (with λ the detonation cell size and k c depending on the mixture and on the operture configuration, classically 13 for alkane mixtures with oxygen). The studied geometries are: (a) a sharp increase of diameter ( D/ d > 1) with and without a central obstacle in the diffracting section, (b) a conical divergent with a central obstacle in the diffracting section and (c) an inversed intermediate one end closed tube insuring a double reflection before a final diffraction between the initiator tube and the reception chamber. The results for case A show that the reinitiation process depends on the ratio d/ λ. For ratios below k c the re-ignition takes place at the receptor tube wall and at a fixed distance from the step, i.e. closely after the diffracted shock reflection shows a Mach stem configuration. For ratios below a limit ratio k lim (which depends on D/ d) the re-ignition distance increases with the decrease of d/λ. For both case A and B the introduction of a central obstacle (of blockage ratio BR = 0.5) at the exit of the initiator tube decreases the critical transmission ratio k c by 50%. The results in configuration C show that the re-ignition process depends both on d/ λ and the geometric conditions. Optimal configuration is found that provides the transmission through the two successive reflections (from d = 26 mm to D ch = 200 mm) at as small d/ λ as 2.2 whatever the intermediate diameter D is. This configuration provides a significant improvement in the detonation transmission conditions.
Experimental and theoretical studies of cylindrical Hall thrusters
Smirnov, Artem; Raitses, Yegeny; Fisch, Nathaniel J.
2007-05-15
The Hall thruster is a mature electric propulsion device that holds considerable promise in terms of the propellant saving potential. The annular design of the conventional Hall thruster, however, does not naturally scale to low power. The efficiency tends to be lower and the lifetime issues are more aggravated. Cylindrical geometry Hall thrusters have lower surface-to-volume ratio than conventional thrusters and, thus, seem to be more promising for scaling down. The cylindrical Hall thruster (CHT) is fundamentally different from the conventional design in the way the electrons are confined and the ion space charge is neutralized. The performances of both the large (9-cm channel diameter, 600-1000 W) and miniaturized (2.6-cm channel diameter, 50-300 W) CHTs are comparable with those of the state-of-the-art conventional (annular) design Hall thrusters of similar sizes. A comprehensive experimental and theoretical study of the CHT physics has been conducted, addressing the questions of electron cross-field transport, propellant ionization, plasma-wall interaction, and formation of the electron distribution function. Probe measurements in the harsh plasma environment of the microthruster were performed. Several interesting effects, such as the unusually high ionization efficiency and enhanced electron transport, were observed. Kinetic simulations suggest the existence of the strong fluctuation-enhanced electron diffusion and predict the non-Maxwellian shape of the electron distribution function. Through the acquired understanding of the new physics, ways for further optimization of this means for low-power space propulsion are suggested. Substantial flexibility in the magnetic field configuration of the CHT is the key tool in achieving the high-efficiency operation.
Energy Science and Technology Software Center (ESTSC)
2005-01-01
The Common Geometry Module (CGM) is a code library which provides geometry functionality used for mesh generation and other applications. This functionality includes that commonly found in solid modeling engines, like geometry creation, query and modification; CGM also includes capabilities not commonly found in solid modeling engines, like geometry decomposition tools and support for shared material interfaces. CGM is built upon the ACIS solid modeling engine, but also includes geometry capability developed beside and onmore » top of ACIS. CGM can be used as-is to provide geometry functionality for codes needing this capability. However, CGM can also be extended using derived classes in C++, allowing the geometric model to serve as the basis for other applications, for example mesh generation. CGM is supported on Sun Solaris, SGI, HP, IBM, DEC, Linux and Windows NT platforms. CGM also indudes support for loading ACIS models on parallel computers, using MPI-based communication. Future plans for CGM are to port it to different solid modeling engines, including Pro/Engineer or SolidWorks. CGM is being released into the public domain under an LGPL license; the ACIS-based engine is available to ACIS licensees on request.« less
NASA Astrophysics Data System (ADS)
Osborne, I.; Brownson, E.; Eulisse, G.; Jones, C. D.; Lange, D. J.; Sexton-Kennedy, E.
2014-06-01
CMS faces real challenges with upgrade of the CMS detector through 2020 and beyond. One of the challenges, from the software point of view, is managing upgrade simulations with the same software release as the 2013 scenario. We present the CMS geometry description software model, its integration with the CMS event setup and core software. The CMS geometry configuration and selection is implemented in Python. The tools collect the Python configuration fragments into a script used in CMS workflow. This flexible and automated geometry configuration allows choosing either transient or persistent version of the same scenario and specific version of the same scenario. We describe how the geometries are integrated and validated, and how we define and handle different geometry scenarios in simulation and reconstruction. We discuss how to transparently manage multiple incompatible geometries in the same software release. Several examples are shown based on current implementation assuring consistent choice of scenario conditions. The consequences and implications for multiple/different code algorithms are discussed.
Technology Transfer Automated Retrieval System (TEKTRAN)
There is growing interest in using fillers in plastic products to displace petroleum components, reduce cost, and improve mechanical properties. Many studies have examined the use of materials such as clay, talc, paper, wood flour, lignin, flax, and bamboo, to name just a few. For successful utili...
Observation of a free-Shercliff-layer instability in cylindrical geometry.
Roach, Austin H; Spence, Erik J; Gissinger, Christophe; Edlund, Eric M; Sloboda, Peter; Goodman, Jeremy; Ji, Hantao
2012-04-13
We report on observations of a free-Shercliff-layer instability in a Taylor-Couette experiment using a liquid metal over a wide range of Reynolds numbers, Re∼10(3)-10(6). The free Shercliff layer is formed by imposing a sufficiently strong axial magnetic field across a pair of differentially rotating axial end cap rings. This layer is destabilized by a hydrodynamic Kelvin-Helmholtz-type instability, characterized by velocity fluctuations in the r-θ plane. The instability appears with an Elsasser number above unity, and saturates with an azimuthal mode number m which increases with the Elsasser number. Measurements of the structure agree well with 2D global linear mode analyses and 3D global nonlinear simulations. These observations have implications for a range of rotating MHD systems in which similar shear layers may be produced. PMID:22587259
A cylindrical-section ultrasound phased-array applicator for hyperthermia cancer therapy.
Ebbini, E S; Umemura, S I; Ibbini, M; Cain, C A
1988-01-01
A phased-array applicator geometry for deep localized hyperthermia is presented. The array consists of rectangular transducer elements forming a section of a cylinder that conforms to the body portals in the abdominal and pelvic regions. Focusing and scanning properties of the cylindrical-section array are investigated in homogeneous lossy media using appropriate computer simulations. The characteristic focus of this array is shown to be spatially limited in both transverse and longitudinal directions with intensity gain values suitable for deep hyperthermia applications. The ability of the cylindrical-section phased array to generate multiple foci using the field conjugation method is examined. The effect of the grating lobes on the power deposition pattern of the scanned field is shown to be minimal. Steady-state temperature distributions are simulated using a three-dimensional thermal model of the normal tissue layers surrounding a tumor of typical volume. The advantages and the limitations of this array configuration are discussed. PMID:18290188
Effects of Shell-Buckling Knockdown Factors in Large Cylindrical Shells
NASA Technical Reports Server (NTRS)
Hrinda, Glenn A.
2012-01-01
Shell-buckling knockdown factors (SBKF) have been used in large cylindrical shell structures to account for uncertainty in buckling loads. As the diameter of the cylinder increases, achieving the manufacturing tolerances becomes increasingly more difficult. Knockdown factors account for manufacturing imperfections in the shell geometry by decreasing the allowable buckling load of the cylinder. In this paper, large-diameter (33 ft) cylinders are investigated by using various SBKF's. An investigation that is based on finite-element analysis (FEA) is used to develop design sensitivity relationships. Different manufacturing imperfections are modeled into a perfect cylinder to investigate the effects of these imperfections on buckling. The analysis results may be applicable to large- diameter rockets, cylindrical tower structures, bulk storage tanks, and silos.
NASA Astrophysics Data System (ADS)
Salazar-Aravena, D.; Corona, R. M.; Goerlitz, D.; Nielsch, K.; Escrig, J.
2013-11-01
The magnetic properties in multisegmented cylindrical nanostructures comprised of nanowire and nanotube segments are investigated numerically as a function of their geometry. In this work we report systematic changes in the coercivity and remanence in these systems. Besides, we have found the ideal conditions for a magnetic configuration with two antiparallel domains that could be used to help to stabilize magnetic nanoparticles inside ferromagnetic multisegmented cylindrical nanoparticles. This magnetic behavior is due to the fact that the tube segment reverses its magnetization before the wire segment, allowing the control of the magnetic domain walls motion between two segments. In this way, these magnetic nanoobjects can be an alternative to store information or even perform logic functions.
Puckett, A.D.
2000-09-01
The ability to model wave propagation in circular cylindrical bars of finite length numerically or analytically has many applications. In this thesis the capability of an explicit finite element method to model longitudinal waves in cylindrical rods with circular cross-sections is explored. Dispersion curves for the first four modes are compared to the analytical solution to determine the accuracy of various element sizes and time steps. Values for the time step and element size are determined that retain accuracy while minimizing computational time. The modeling parameters are validated by calculating a signal propagated with a broadband input force. Limitations on the applicability are considered along with modeling parameters that should be applicable to more general geometries.
Impact of a shearless flow and cylindricity on interchange instability in magnetized plasma
Benilov, E.S.
2005-05-15
The stability of magnetically confined plasmas is sometimes examined using the so-called 'slab' model, where the toroidal geometry of the problem is approximated locally by the Cartesian one. In the present paper, a (more accurate) cylindrical approximation is considered and shown to yield results which are qualitatively different from those of the slab model. In particular, if the slab model is applied to the outboard region of the tokamak (where the gradient of the plasma's density and that of the magnetic field are of the same sign), disturbances remain unstable at all times. In the cylindrical model, on the other hand, the ExB flow carries disturbances around the cylinder and they alternate between the unstable and stable regions. Naturally, this reduces the growth rate of instability and makes it dependent on the angular velocity of the flow.
Elastic-plastic fracture of cylindrical shells containing a part-through circumferential crack
Ezzat, H.; Erdogan, F.
1982-11-01
The problem of fatigue crack propagation and ductile fracture of a cylindrical shell containing a macroscopic circumferential flaw is considered. The main interest in the study is in applications to line pipes and other cylindrical containers under secondary axial stresses in addition to the primary stresses coming from the internal pressure. The stress intensity factor for the part-through crack used in analyzing and correlating the fatigue crack propagation rate is obtained by using a line spring model in conjunction with Reissner's shell theory. To analyze the ductile fracture instability and to correlate the experimental and theoretical results, the crack mouth opening displacement is used as the parameter. The limited data on fatigue crack propagation give the expected result, namely that the crack propagation rate in pipes may be predicted from the fatigue results performed on simpler geometries provided the stress intensity factors in pipes are calculated with sufficient accuracy. 14 references.
NASA Technical Reports Server (NTRS)
Bain, D. B.; Smith, C. E.; Holdeman, J. D.
1995-01-01
Three dimensional turbulent reacting CFD analyses were performed on transverse jets injected into annular and cylindrical (can) confined crossflows. The goal was to identify and assess mixing differences between annular and can geometries. The approach taken was to optimize both annular and can configurations by systematically varying orifice spacing until lowest emissions were achieved, and then compare the results. Numerical test conditions consisted of a jet-to-mainstream mass-flow ratio of 3.2 and a jet-to-mainstream momentum-flux ratio (J) of 30. The computational results showed that the optimized geometries had similar emission levels at the exit of the mixing section although the annular configuration did mix-out faster. For lowest emissions, the density correlation parameter (C = (S/H) square root of J) was 2.35 for the annular geometry and 3.5 for the can geometry. For the annular geometry, the constant was about twice the value seen for jet mixing at low mass-flow ratios (i.e., MR less than 0.5). For the can geometry, the constant was about 1 1/2 times the value seen for low mass-flow ratios.
Ablation Front Rayleigh-Taylor Growth Experiments in Spherically Convergent Geometry
Glendinning, S.G.; Cherfils, C.; Colvin, J.; Divol, L.; Galmiche, D.; Haan, S.; Marinak, M.M.; Remington, B.A.; Richard, A.L.; Wallace, R.
1999-11-03
Experiments were performed on the Nova laser, using indirectly driven capsules mounted in cylindrical gold hohlraums, to measure the Rayleigh-Taylor growth at the ablation front by time-resolved radiography. Modulations were preformed on the surface of Ge-doped plastic capsules. With initial modulations of 4 {micro}m, growth factors of about 6 in optical depth were seen, in agreement with simulations using the radiation hydrocode FCI2. With initial modulations of 1 {micro}m, growth factors of about 100-150 in optical depth were seen. The Rayleigh-Taylor (RT) instability at the ablation front in an inertial confinement fusion capsule has been the subject of considerable investigation. Much of this research has been concentrated on planar experiments, in which RT growth is inferred from radiography. The evolution is somewhat different in a converging geometry; the spatial wavelength decreases (affecting the onset of nonlinear saturation), and the shell thickens and compresses rather than decompressing as in a planar geometry. In a cylindrically convergent geometry, the latter effect is proportional to the radius, while in spherically convergent geometry, the latter effect is proportional to the radius squared. Experiments were performed on the Nova and Omega lasers in cylindrical geometry (using both direct and indirect drive) and have been performed in spherical geometry using direct drive.
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.
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. PMID:25658139
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.
Nonaxisymmetric radiative transfer in cylindrical enclosures
Moder, J.P.; Lee, H.S.; Chai, J.C.; Parthasarathy, G.; Patankar, S.V.
1996-12-31
A finite-volume method for radiative transfer in cylindrical enclosures is presented. Angular redistribution terms in the equation of transfer are avoided by defining radiation directions in terms of angular coordinates measured with respect to Cartesian base vectors; this definition of radiation directions can result in control angles which overlap control-volume faces, depending on the type of spatial and angular grids used in the azimuthal direction. A simple treatment for such control-angle overlaps is presented which is also applicable to nonorthogonal curvilinear spatial-coordinates. A comparison of the present procedure with other similar methods is given. Solutions are presented for axisymmetric transfer through a cylinder and nonaxisymmetric transfer through two- and three-dimensional annular sectors. Results show that the procedure produces reasonable solutions for transparent and participating media in axisymmetric and nonaxisymmetric cylindrical enclosures.
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.
Cylindrically converging blast waves in air
NASA Astrophysics Data System (ADS)
Matsuo, H.; Nakamura, Y.
1981-07-01
Cylindrically converging shock waves are produced by utilizing the detonation of cylindrical explosive shells. The production and the propagation of shock waves are observed by framing and streak camera photographs, and the trajectory of shock propagations is determined by using an electrical ionization probing system. The effect of the quantity of explosives on the stability, or the axial symmetry, of shock fronts and on the strength of shocks produced is investigated. It has been shown that, for practical purposes, the approximation of shock trajectories by Guderley's formulas would be sufficiently acceptable in an unexpectedly wide region near the implosion center, and that the axial symmetry of the shock front is improved by increasing the quantity of explosives, and thus, strong shocks are produced by merely increasing the quantity of explosives. The reflected diverging shock seems to be very stable. Piezoelectric elements have also been used to detect reflected diverging waves.
Jamming of Cylindrical Grains in Vertical Channels
NASA Astrophysics Data System (ADS)
Baxter, G. William; Spier, Gregory; Barr, Nicholas; Steel, Fiona
2012-02-01
We study jamming of low aspect-ratio cylindrical Delrin grains in a vertical channel. These cylindrical grains resemble antacid tablets, poker chips, or coins since their height is less than their diameter. Grains are allowed to fall through a vertical channel with a square cross section where the channel width is greater than the diameter of a grain and constant throughout the length of the channel with no obstructions or constrictions. Within this channel, grains are sometimes observed to form jams, stable structures supported by the channel walls with no support beneath them. The probability of jam occurrence and the strength or robustness of a jam is effected by the grain dimensions and channel size. We will present experimental measurements of the jamming probability and jam strength in this system and discuss the relationship of these results to other experiments and theories.
Multiple Bifurcations of a Cylindrical Dynamical System
NASA Astrophysics Data System (ADS)
Han, Ning; Cao, Qingjie
2016-03-01
This paper focuses on multiple bifurcations of a cylindrical dynamical system, which is evolved from a rotating pendulum with SD oscillator. The rotating pendulum system exhibits the coupling dynamics property of the bistable state and conventional pendulum with the ho- moclinic orbits of the first and second type. A double Andronov-Hopf bifurcation, two saddle-node bifurcations of periodic orbits and a pair of homoclinic bifurcations are detected by using analytical analysis and nu- merical calculation. It is found that the homoclinic orbits of the second type can bifurcate into a pair of rotational limit cycles, coexisting with the oscillating limit cycle. Additionally, the results obtained herein, are helpful to explore different types of limit cycles and the complex dynamic bifurcation of cylindrical dynamical system.
Omnidirectional, circularly polarized, cylindrical microstrip antenna
NASA Technical Reports Server (NTRS)
Stanton, Philip H. (Inventor)
1985-01-01
A microstrip cylindrical antenna comprised of two concentric subelements on a ground cylinder, a vertically polarized (E-field parallel to the axis of the antenna cylinder) subelement on the inside and a horizontally polarized (E-field perpendicular to the axis) subelement on the outside. The vertical subelement is a wraparound microstrip radiator. A Y-shaped microstrip patch configuration is used for the horizontally polarized radiator that is wrapped 1.5 times to provide radiating edges on opposite sides of the cylindrical antenna for improved azimuthal pattern uniformity. When these subelements are so fed that their far fields are equal in amplitude and phased 90.degree. from each other, a circularly polarized EM wave results. By stacking a plurality of like antenna elements on the ground cylinder, a linear phased array antenna is provided that can be beam steered to the desired elevation angle.
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.
Domain wall dynamics in cylindrical nanomagnet
NASA Astrophysics Data System (ADS)
Mukhopadhyay, Soumik; Singh, Amrita; Ghosh, Arindam
2011-06-01
The stochasticity associated with domain wall nucleation and propagation in a cylinderical nanowire has been studied using time resolved resistance measurement in presence of magnetic field. We have shown that the propagation stochasticity of domain wall in a cylindrical nanowire is reflected in the magnetic field dependent velocity distribution whereas the stochasticity involved in the domain wall nucleation can be effectively tuned by varying the angle between the direction of applied magnetic field and the long axis of the cylinder.
Moiré effect in cylindrical objects
NASA Astrophysics Data System (ADS)
Saveljev, Vladimir
2016-05-01
The moiré effect in single-walled cylindrical objects (gridshells) is investigated. The surface of such an object is a rolled-up periodic grating (mesh). Analytical formulae are obtained for the period of the moiré patterns, which depends particularly on the direction of the wavevector of the grating. The experiments confirm the theory. The results can be applied to nanoparticles and to three-dimensional autostereoscopic displays.
Numerical dynamo action in cylindrical containers
NASA Astrophysics Data System (ADS)
Nore, Caroline; Castanon Quiroz, Daniel; Guermond, Jean-Luc; Léorat, Jacques; Luddens, Francky
2015-06-01
The purpose of this paper is to present results from numerical simulations of dynamo action in relation with two magnetohydrodynamics (MHD) experiments using liquid sodium in cylindrical containers. The first one is the von Kármán sodium (VKS) experiment from Cadarache (France), the second one is a precession-driven dynamo experiment from the DREsden sodium facility for DYNamo and thermohydraulic studies (DRESDYN). Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014) - Elected submissions", edited by Adel Razek
Cylindrical multilayer metal-dielectric structures
NASA Astrophysics Data System (ADS)
Sasin, M. E.; Il'inskaya, N. D.; Zadiranov, Yu. M.; Kaliteevskaya, N. A.; Lazarenko, A. A.; Mazlin, V. A.; Brunkov, P. N.; Pavlov, S. I.; Kaliteevski, M. A.
2015-11-01
A method of creating a cylindrical structures consisting of thin metallic layer and dielectric multilayer Bragg reflector is described. Formation of the structures is observed experimentally as a result of separation and twisting away from the substrate a thin layer of gold coated with a multilayer SiO2/TiO2 Bragg reflector. It is suggested that such structures may be of interest for the creation of novel optoelectronic devices.