Generating perfect fluid spheres in general relativity
Boonserm, Petarpa; Visser, Matt; Weinfurtner, Silke
2005-06-01
Ever since Karl Schwarzschild’s 1916 discovery of the spacetime geometry describing the interior of a particular idealized general relativistic star—a static spherically symmetric blob of fluid with position-independent density—the general relativity community has continued to devote considerable time and energy to understanding the general-relativistic static perfect fluid sphere. Over the last 90 years a tangle of specific perfect fluid spheres has been discovered, with most of these specific examples seemingly independent from each other. To bring some order to this collection, in this article we develop several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. These transformation theorems sometimes lead to unexpected connections between previously known perfect fluid spheres, sometimes lead to new previously unknown perfect fluid spheres, and in general can be used to develop a systematic way of classifying the set of all perfect fluid spheres.
Generating perfect fluid spheres in general relativity
International Nuclear Information System (INIS)
Boonserm, Petarpa; Visser, Matt; Weinfurtner, Silke
2005-01-01
Ever since Karl Schwarzschild's 1916 discovery of the spacetime geometry describing the interior of a particular idealized general relativistic star--a static spherically symmetric blob of fluid with position-independent density--the general relativity community has continued to devote considerable time and energy to understanding the general-relativistic static perfect fluid sphere. Over the last 90 years a tangle of specific perfect fluid spheres has been discovered, with most of these specific examples seemingly independent from each other. To bring some order to this collection, in this article we develop several new transformation theorems that map perfect fluid spheres into perfect fluid spheres. These transformation theorems sometimes lead to unexpected connections between previously known perfect fluid spheres, sometimes lead to new previously unknown perfect fluid spheres, and in general can be used to develop a systematic way of classifying the set of all perfect fluid spheres
Some results on rotating fluid balls of Petrov type D
Energy Technology Data Exchange (ETDEWEB)
Bradley, M [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Eriksson, D [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Fodor, G [KFKI Research Institute for Particle and Nuclear Physics, H-1525, Budapest 114, P.O.B. 49 (Hungary); Racz, I [KFKI Research Institute for Particle and Nuclear Physics, H-1525, Budapest 114, P.O.B. 49 (Hungary)
2007-05-15
The second order perturbative field equations for slowly and rigidly rotating perfect fluid balls of Petrov type D are solved numerically. It is found that all the slowly and rigidly rotating perfect fluid balls up to second order, irrespective of Petrov type, may be matched to a possibly non-asymptotically flat stationary axisymmetric vacuum exterior. A subspace of the parameter space is identified for which the solutions can be matched to an asymptotically flat exterior vacuum region. The physical properties like equations of state, shapes and speeds of sound are determined for a number of solutions.
Hamiltonian formalism for perfect fluids in general relativity
International Nuclear Information System (INIS)
Demaret, J.; Moncrief, V.
1980-01-01
Schutz's Hamiltonian theory of a relativistic perfect fluid, based on the velocity-potential version of classical perfect fluid hydrodynamics as formulated by Seliger and Whitham, is used to derive, in the framework of the Arnowitt, Deser, and Misner (ADM) method, a general partially reduced Hamiltonian for relativistic systems filled with a perfect fluid. The time coordinate is chosen, as in Lund's treatment of collapsing balls of dust, as minus the only velocity potential different from zero in the case of an irrotational and isentropic fluid. A ''semi-Dirac'' method can be applied to quantize astrophysical and cosmological models in the framework of this partially reduced formalism. If one chooses Taub's adapted comoving coordinate system, it is possible to derive a fully reduced ADM Hamiltonian, which is equal to minus the total baryon number of the fluid, generalizing a result previously obtained by Moncrief in the more particular framework of Taub's variational principle, valid for self-gravitating barotropic relativistic perfect fluids. An unconstrained Hamiltonian density is then explicitly derived for a fluid obeying the equation of state p=(gamma-1)rho (1 < or = γ < or = 2), which can adequately describe the phases of very high density attained in a catastrophic collapse or during the early stages of the Universe. This Hamiltonian density, shown to be equivalent to Moncrief's in the particular case of an isentropic fluid, can be simplified for fluid-filled class-A diagonal Bianchi-type cosmological models and appears as a suitable starting point for the study of the canonical quantization of these models
Nonminimal coupling of perfect fluids to curvature
International Nuclear Information System (INIS)
Bertolami, Orfeu; Lobo, Francisco S. N.; Paramos, Jorge
2008-01-01
In this work, we consider different forms of relativistic perfect fluid Lagrangian densities that yield the same gravitational field equations in general relativity (GR). A particularly intriguing example is the case with couplings of the form [1+f 2 (R)]L m , where R is the scalar curvature, which induces an extra force that depends on the form of the Lagrangian density. It has been found that, considering the Lagrangian density L m =p, where p is the pressure, the extra-force vanishes. We argue that this is not the unique choice for the matter Lagrangian density, and that more natural forms for L m do not imply the vanishing of the extra force. Particular attention is paid to the impact on the classical equivalence between different Lagrangian descriptions of a perfect fluid.
Thermodynamical stability for a perfect fluid
Energy Technology Data Exchange (ETDEWEB)
Fang, Xiongjun; Jing, Jiliang [Hunan Normal University, Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Synergetic Innovation Center for Quantum Effects and Applications, Changsha, Hunan (China); He, Xiaokai [Hunan Normal University, Department of Physics, Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Synergetic Innovation Center for Quantum Effects and Applications, Changsha, Hunan (China); Hunan First Normal University, School of Mathematics and Computational Science, Changsha (China)
2017-12-15
According to the maximum entropy principle, it has been proved that the gravitational field equations could be derived by the extrema of the total entropy for a perfect fluid, which implies that thermodynamic relations contain information as regards gravity. In this manuscript, we obtain a criterion for the thermodynamical stability of an adiabatic, self-gravitating perfect fluid system by the second variation of the total entropy. We show, for Einstein's gravity with spherical symmetry spacetime, that the criterion is consistent with that for the dynamical stability derived by Chandrasekhar and Wald. We also find that the criterion could be applied to cases without spherical symmetry, or under general perturbations. The result further establishes the connection between thermodynamics and gravity. (orig.)
Perfect Fluid Theory and its Extensions
Jackiw, R.; Nair, V. P.; Pi, S. -Y.; Polychronakos, A. P.
2004-01-01
We review the canonical theory for perfect fluids, in Eulerian and Lagrangian formulations. The theory is related to a description of extended structures in higher dimensions. Internal symmetry and supersymmetry degrees of freedom are incorporated. Additional miscellaneous subjects that are covered include physical topics concerning quantization, as well as mathematical issues of volume preserving diffeomorphisms and representations of Chern-Simons terms (= vortex or magnetic helicity).
Perfect fluid cosmology with geodesic world lines
International Nuclear Information System (INIS)
Raychaudhuri, A.K.; Maity, S.R.
1978-01-01
It is shown that for a perfect fluid with an equation of state p = p (rho), if the world lines are geodesics, then they are hypersurface orthogonal and the scalars p, rho, sigma 2 , and theta 2 are all constants over these hypersurfaces, irrespective of any spatial-homogeneity assumption. However, an examination of some simple cases does not reveal any spatially nonhomogeneous solution with these properties
Black hole formation in perfect fluid collapse
International Nuclear Information System (INIS)
Goswami, Rituparno; Joshi, Pankaj S
2004-01-01
We construct here a special class of perfect fluid collapse models which generalizes the homogeneous dust collapse solution in order to include nonzero pressures and inhomogeneities into evolution. It is shown that a black hole is necessarily generated as the end product of continued gravitational collapse, rather than a naked singularity. We examine the nature of the central singularity forming as a result of endless collapse and it is shown that no nonspacelike trajectories can escape from the central singularity. Our results provide some insights into how the dynamical collapse works and into the possible formulations of the cosmic censorship hypothesis, which is as yet a major unsolved problem in black hole physics
Two-perfect fluid interpretation of an energy tensor
International Nuclear Information System (INIS)
Ferrando, J.J.; Morales, J.A.; Portilla, M.
1990-01-01
There are many topics in General Relativity where matter is represented by a mixture of two fluids. In fact, some astrophysical and cosmological situations need to be described by an energy tensor made up of the sum of two or more perfect fluids rather than that with only one. The paper contains the necessary and sufficient conditions for a given energy tensor to be interpreted as a sum of two perfect fluids. Given a tensor of this class, the decomposition in two perfect fluids (which is determined up to a couple of real functions) is obtained
Gauge freedom in perfect fluid spatially homogeneous spacetimes
International Nuclear Information System (INIS)
Jantzen, R.T.
1983-01-01
The class of reference systems compatible with the symmetry of a spatially homogeneous perfect fluid spacetime is discussed together with the associated class of symmetry adapted comoving ADM frames (or computational frames). The fluid equations of motion are related to the four functions on the space of fluid flow lines discovered by Taub and which characterize an isentropic flow. (Auth.)
Lattice fluid dynamics from perfect discretizations of continuum flows
International Nuclear Information System (INIS)
Katz, E.; Wiese, U.
1998-01-01
We use renormalization group methods to derive equations of motion for large scale variables in fluid dynamics. The large scale variables are averages of the underlying continuum variables over cubic volumes and naturally exist on a lattice. The resulting lattice dynamics represents a perfect discretization of continuum physics, i.e., grid artifacts are completely eliminated. Perfect equations of motion are derived for static, slow flows of incompressible, viscous fluids. For Hagen-Poiseuille flow in a channel with a square cross section the equations reduce to a perfect discretization of the Poisson equation for the velocity field with Dirichlet boundary conditions. The perfect large scale Poisson equation is used in a numerical simulation and is shown to represent the continuum flow exactly. For nonsquare cross sections one can use a numerical iterative procedure to derive flow equations that are approximately perfect. copyright 1998 The American Physical Society
On perfect fluids and black holes in static equilibrium
Energy Technology Data Exchange (ETDEWEB)
Carrasco, Alberto; Mars, Marc; Simon, Walter [Facultad de Ciencias, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain)
2007-05-15
Proofs of spherical symmetry of static black holes and of spherical symmetry of static perfect fluids normally require, a priori, 'black holes only' or 'fluid only'. In a recent paper Shiromizu, Yamada and Yoshino admit a priori (and exclude) coexistence of fluids and holes. This work assumes connectedness of the fluid region and the same assumptions on the equation of state as earlier papers on the 'fluid only' case, and requires in addition an upper bound for the fluid mass in terms of the black holes masses. We discuss this paper. As a new result we show that there cannot exist static fluid shells (i.e. fluid regions of the topology of an annulus) even if one a priori admits, inside and outside the shell, any arrangement of black holes or additional matter which satisfies the energy condition.
On perfect fluids and black holes in static equilibrium
International Nuclear Information System (INIS)
Carrasco, Alberto; Mars, Marc; Simon, Walter
2007-01-01
Proofs of spherical symmetry of static black holes and of spherical symmetry of static perfect fluids normally require, a priori, 'black holes only' or 'fluid only'. In a recent paper Shiromizu, Yamada and Yoshino admit a priori (and exclude) coexistence of fluids and holes. This work assumes connectedness of the fluid region and the same assumptions on the equation of state as earlier papers on the 'fluid only' case, and requires in addition an upper bound for the fluid mass in terms of the black holes masses. We discuss this paper. As a new result we show that there cannot exist static fluid shells (i.e. fluid regions of the topology of an annulus) even if one a priori admits, inside and outside the shell, any arrangement of black holes or additional matter which satisfies the energy condition
Inhomogeneous generalizations of Bianchi type VIh models with perfect fluid
Roy, S. R.; Prasad, A.
1991-07-01
Inhomogeneous universes admitting an Abelian G2 of isometry and filled with perfect fluid have been derived. These contain as special cases exact homogeneous universes of Bianchi type VIh. Many of these universes asymptotically tend to homogeneous Bianchi VIh universes. The models have been discussed for their physical and kinematical behaviors.
Helicity and other conservation laws in perfect fluid motion
Serre, Denis
2018-03-01
In this review paper, we discuss helicity from a geometrical point of view and see how it applies to the motion of a perfect fluid. We discuss its relation with the Hamiltonian structure, and then its extension to arbitrary space dimensions. We also comment about the existence of additional conservation laws for the Euler equation, and its unlikely integrability in Liouville's sense.
On a ''conformal'' perfect fluid in the classical vacuum
International Nuclear Information System (INIS)
Culetu, H.
1993-02-01
A possible existence of a conformal perfect fluid in the classical vacuum is investigated in this letter. It is shown, contrary to Madsen's opinion, that the scalar field stress tensor acquires a perfect fluid form even with a nonminimal coupling (ξ = 1/6) in the Einstein Lagrangian, provided the geometry is the Lorentzian analogue of the Euclidean Hawking wormhole. In addition, our T μν equals (up to a constant factor) the vacuum expectation value of the Fulling stress tensor for a massless scalar field and Visser's one concerning transversible wormholes. On the other side of the light cone, there is a coordinate system (the dimensionally reduced Witten bubble) where the stress tensor becomes diagonal. (author). 13 refs
Thermodynamics of perfect fluids from scalar field theory
Ballesteros, Guillermo; Pilo, Luigi
2016-01-01
The low-energy dynamics of relativistic continuous media is given by a shift-symmetric effective theory of four scalar fields. These scalars describe the embedding in spacetime of the medium and play the role of Stuckelberg fields for spontaneously broken spatial and time translations. Perfect fluids are selected imposing a stronger symmetry group or reducing the field content to a single scalar. We explore the relation between the field theory description of perfect fluids to thermodynamics. By drawing the correspondence between the allowed operators at leading order in derivatives and the thermodynamic variables, we find that a complete thermodynamic picture requires the four Stuckelberg fields. We show that thermodynamic stability plus the null energy condition imply dynamical stability. We also argue that a consistent thermodynamic interpretation is not possible if any of the shift symmetries is explicitly broken.
The Hamiltonian structure of general relativistic perfect fluids
International Nuclear Information System (INIS)
Bao, D.; Houston Univ., TX; Marsden, J.; Walton, R.
1985-01-01
We show that the evolution equations for a perfect fluid coupled to general relativity in a general lapse and shift, are Hamiltonian relative to a certain Poisson structure. For the fluid variables, a Lie-Poisson structure associated to the dual of a semi-direct product Lie algebra is used, while the bracket for the gravitational variables has the usual canonical symplectic structure. The evolution is governed by a Hamiltonian which is equivalent to that obtained from a canonical analysis. The relationship of our Hamiltonian structure with other approaches in the literature, such as Clebsch potentials, Lagrangian to Eulerian transformations, and its use in clarifying linearization stability, are discussed. (orig.)
Shear-free perfect fluids with zero magnetic Weyl tensor
International Nuclear Information System (INIS)
Collins, C.B.
1984-01-01
Rotating, shear-free general-relativistic perfect fluids are investigated. It is first shown that, if the fluid pressure, p, and energy density, μ, are related by a barotropic equation of state p = p( μ) satifying μ+pnot =0, and if the magnetic part of the Weyl tensor (with respect to the fluid flow) vanishes, then the fluid's volume expansion is zero. The class of all such fluids is subsequently characterized. Further analysis of the solutions shows that, in general, the space-times may be regarded as being locally stationary and axisymmetric (they admit a two-dimensional Abelian isometry group with timelike orbits, which is in fact orthogonally transistive), although various specializations can occur, with the ''most special'' case being the well-known Goedel model, which is space-time homogeneous (it admits a five-dimensional isometry group acting multiply transitively on the space-time). all solutions are of Petrov type D. The fact that there are any solutions in the class at all means that a theorem appearing in the literature is invalid, and the existence of some special solutions in which the fluid's vorticity vector is orthogonal to the acceleration reveals the incompleteness of a previous study of a class of space-times, in which there are Killing vectors parallel to the fluid four-velocity and to the vorticity vector
Non-adiabatic perturbations in multi-component perfect fluids
Energy Technology Data Exchange (ETDEWEB)
Koshelev, N.A., E-mail: koshna71@inbox.ru [Ulyanovsk State University, Leo Tolstoy str 42, 432970 (Russian Federation)
2011-04-01
The evolution of non-adiabatic perturbations in models with multiple coupled perfect fluids with non-adiabatic sound speed is considered. Instead of splitting the entropy perturbation into relative and intrinsic parts, we introduce a set of symmetric quantities, which also govern the non-adiabatic pressure perturbation in models with energy transfer. We write the gauge invariant equations for the variables that determine on a large scale the non-adiabatic pressure perturbation and the rate of changes of the comoving curvature perturbation. The analysis of evolution of the non-adiabatic pressure perturbation has been made for several particular models.
Non-adiabatic perturbations in multi-component perfect fluids
International Nuclear Information System (INIS)
Koshelev, N.A.
2011-01-01
The evolution of non-adiabatic perturbations in models with multiple coupled perfect fluids with non-adiabatic sound speed is considered. Instead of splitting the entropy perturbation into relative and intrinsic parts, we introduce a set of symmetric quantities, which also govern the non-adiabatic pressure perturbation in models with energy transfer. We write the gauge invariant equations for the variables that determine on a large scale the non-adiabatic pressure perturbation and the rate of changes of the comoving curvature perturbation. The analysis of evolution of the non-adiabatic pressure perturbation has been made for several particular models
Gravitational perfect fluid collapse in Gauss-Bonnet gravity
Energy Technology Data Exchange (ETDEWEB)
Abbas, G.; Tahir, M. [The Islamia University of Bahawalpur, Department of Mathematics, Bahawalpur (Pakistan)
2017-08-15
The Einstein Gauss-Bonnet theory of gravity is the low-energy limit of heterotic super-symmetric string theory. This paper deals with gravitational collapse of a perfect fluid in Einstein-Gauss-Bonnet gravity by considering the Lemaitre-Tolman-Bondi metric. For this purpose, the closed form of the exact solution of the equations of motion has been determined by using the conservation of the stress-energy tensor and the condition of marginally bound shells. It has been investigated that the presence of a Gauss-Bonnet coupling term α > 0 and the pressure of the fluid modifies the structure and time formation of singularity. In this analysis a singularity forms earlier than a horizon, so the end state of the collapse is a naked singularity depending on the initial data. But this singularity is weak and timelike, which goes against the investigation of general relativity. (orig.)
Perfect fluid tori orbiting Kehagias-Sfetsos naked singularities
Stuchlík, Z.; Pugliese, D.; Schee, J.; Kučáková, H.
2015-09-01
We construct perfect fluid tori in the field of the Kehagias-Sfetsos (K-S) naked singularities. These are spherically symmetric vacuum solutions of the modified Hořava quantum gravity, characterized by a dimensionless parameter ω M^2, combining the gravitational mass parameter M of the spacetime with the Hořava parameter ω reflecting the role of the quantum corrections. In dependence on the value of ω M^2, the K-S naked singularities demonstrate a variety of qualitatively different behavior of their circular geodesics that is fully reflected in the properties of the toroidal structures, demonstrating clear distinction to the properties of the torii in the Schwarzschild spacetimes. In all of the K-S naked singularity spacetimes the tori are located above an "antigravity" sphere where matter can stay in a stable equilibrium position, which is relevant for the stability of the orbiting fluid toroidal accretion structures. The signature of the K-S naked singularity is given by the properties of marginally stable tori orbiting with the uniform distribution of the specific angular momentum of the fluid, l= const. In the K-S naked singularity spacetimes with ω M^2 > 0.2811, doubled tori with the same l= const can exist; mass transfer between the outer torus and the inner one is possible under appropriate conditions, while only outflow to the outer space is allowed in complementary conditions. In the K-S spacetimes with ω M^2 < 0.2811, accretion from cusped perfect fluid tori is not possible due to the non-existence of unstable circular geodesics.
Perfect fluid tori orbiting Kehagias-Sfetsos naked singularities
Energy Technology Data Exchange (ETDEWEB)
Stuchlik, Z.; Pugliese, D.; Schee, J.; Kucakova, H. [Silesian University in Opava, Faculty of Philosophy and Science, Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Opava (Czech Republic)
2015-09-15
We construct perfect fluid tori in the field of the Kehagias-Sfetsos (K-S) naked singularities. These are spherically symmetric vacuum solutions of the modified Horava quantum gravity, characterized by a dimensionless parameter ωM{sup 2}, combining the gravitational mass parameter M of the spacetime with the Horava parameter ω, reflecting the role of the quantum corrections. In dependence on the value of ωM{sup 2}, the K-S naked singularities demonstrate a variety of qualitatively different behavior of their circular geodesics that is fully reflected in the properties of the toroidal structures, demonstrating clear distinction to the properties of the torii in the Schwarzschild spacetimes. In all of the K-S naked singularity spacetimes the tori are located above an @gantigravity@h sphere where matter can stay in a stable equilibrium position, which is relevant for the stability of the orbiting fluid toroidal accretion structures. The signature of the K-S naked singularity is given by the properties of marginally stable tori orbiting with the uniform distribution of the specific angular momentum of the fluid, l = const. In the K-S naked singularity spacetimes with ωM{sup 2} > 0.2811, doubled tori with the same l = const can exist; mass transfer between the outer torus and the inner one is possible under appropriate conditions, while only outflow to the outer space is allowed in complementary conditions. In the K-S spacetimes with ωM{sup 2} < 0.2811, accretion from cusped perfect fluid tori is not possible due to the non-existence of unstable circular geodesics. (orig.)
Spherically symmetric Einstein-aether perfect fluid models
Energy Technology Data Exchange (ETDEWEB)
Coley, Alan A.; Latta, Joey [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia, B3H 3J5 (Canada); Leon, Genly [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4950, Valparaíso (Chile); Sandin, Patrik, E-mail: aac@mathstat.dal.ca, E-mail: genly.leon@ucv.cl, E-mail: patrik.sandin@aei.mpg.de, E-mail: lattaj@mathstat.dal.ca [Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut), Am Mühlenberg 1, D-14476 Potsdam (Germany)
2015-12-01
We investigate spherically symmetric cosmological models in Einstein-aether theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame formalism and adopt the comoving aether gauge to derive the evolution equations, which form a well-posed system of first order partial differential equations in two variables. We then introduce normalized variables. The formalism is particularly well-suited for numerical computations and the study of the qualitative properties of the models, which are also solutions of Horava gravity. We study the local stability of the equilibrium points of the resulting dynamical system corresponding to physically realistic inhomogeneous cosmological models and astrophysical objects with values for the parameters which are consistent with current constraints. In particular, we consider dust models in (β−) normalized variables and derive a reduced (closed) evolution system and we obtain the general evolution equations for the spatially homogeneous Kantowski-Sachs models using appropriate bounded normalized variables. We then analyse these models, with special emphasis on the future asymptotic behaviour for different values of the parameters. Finally, we investigate static models for a mixture of a (necessarily non-tilted) perfect fluid with a barotropic equations of state and a scalar field.
Cosmological coevolution of Yang-Mills fields and perfect fluids
International Nuclear Information System (INIS)
Barrow, John D.; Jin, Yoshida; Maeda, Kei-ichi
2005-01-01
We study the coevolution of Yang-Mills fields and perfect fluids in Bianchi type I universes. We investigate numerically the evolution of the universe and the Yang-Mills fields during the radiation and dust eras of a universe that is almost isotropic. The Yang-Mills field undergoes small amplitude chaotic oscillations, as do the three expansion scale factors which are also displayed by the expansion scale factors of the universe. The results of the numerical simulations are interpreted analytically and compared with past studies of the cosmological evolution of magnetic fields in radiation and dust universes. We find that, whereas magnetic universes are strongly constrained by the microwave background anisotropy, Yang-Mills universes are principally constrained by primordial nucleosynthesis but the bound is comparatively weak with Ω YM rad
Expanding perfect fluid generalizations of the C metric
International Nuclear Information System (INIS)
Wylleman, Lode; Beke, David
2010-01-01
Petrov type D gravitational fields, generated by a perfect fluid with spatially homogeneous energy density and with flow lines which form a nonshearing and nonrotating timelike congruence, are reexamined. It turns out that the anisotropic such spacetimes, which comprise the vacuum C metric as a limit case, can have nonzero expansion, contrary to the conclusion in the original investigation by Barnes [A. Barnes, Gen. Relativ. Gravit. 4, 105 (1973).]. Apart from the static members, this class consists of cosmological models with precisely one symmetry. The general line element is constructed and some important properties are discussed. It is also shown that purely electric Petrov type D vacuum spacetimes admit shear-free normal timelike congruences everywhere, even in the nonstatic regions. This result incited to deduce intrinsic, easily testable criteria regarding shear-free normality and staticity of Petrov type D spacetimes in general, which are added in an appendix.
Perfect fluid models in noncomoving observational spherical coordinates
International Nuclear Information System (INIS)
Ishak, Mustapha
2004-01-01
We use null spherical (observational) coordinates to describe a class of inhomogeneous cosmological models. The proposed cosmological construction is based on the observer past null cone. A known difficulty in using inhomogeneous models is that the null geodesic equation is not integrable in general. Our choice of null coordinates solves the radial ingoing null geodesic by construction. Furthermore, we use an approach where the velocity field is uniquely calculated from the metric rather than put in by hand. Conveniently, this allows us to explore models in a noncomoving frame of reference. In this frame, we find that the velocity field has shear, acceleration, and expansion rate in general. We show that a comoving frame is not compatible with expanding perfect fluid models in the coordinates proposed and dust models are simply not possible. We describe the models in a noncomoving frame. We use the dust models in a noncomoving frame to outline a fitting procedure
Exact EGB models for spherical static perfect fluids
Energy Technology Data Exchange (ETDEWEB)
Hansraj, Sudan; Chilambwe, Brian; Maharaj, Sunil D. [University of KwaZulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, Private Bag 54001, Durban (South Africa)
2015-06-15
We obtain a new exact solution to the field equations for a 5-dimensional spherically symmetric static distribution in the Einstein-Gauss-Bonnet modified theory of gravity. By using a transformation, the study is reduced to the analysis of a single second order nonlinear differential equation. In general the condition of pressure isotropy produces a first order differential equation which is an Abel equation of the second kind. An exact solution is found. The solution is examined for physical admissibility. In particular a set of constants is found which ensures that a pressure-free hypersurface exists which defines the boundary of the distribution. Additionally the isotropic pressure and the energy density are shown to be positive within the radius of the sphere. The adiabatic sound-speed criterion is also satisfied within the fluid ensuring a subluminal sound speed. Furthermore, the weak, strong and dominant conditions hold throughout the distribution. On setting the Gauss-Bonnet coupling to zero, an exact solution for 5-dimensional perfect fluids in the standard Einstein theory is obtained. Plots of the dynamical quantities for the Gauss-Bonnet and the Einstein case reveal that the pressure is unaffected, while the energy density increases under the influence of the Gauss-Bonnet term. (orig.)
Kantowski-Sachs Einstein-æther perfect fluid models
Energy Technology Data Exchange (ETDEWEB)
Latta, Joey [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia, B3H 3J5 (Canada); Leon, Genly [Instituto de Física, Pontificia Universidad de Católica de Valparaíso, Casilla 4950, Valparaíso (Chile); Paliathanasis, Andronikos, E-mail: lattaj@mathstat.dal.ca, E-mail: genly.leon@pucv.cl, E-mail: anpaliat@phys.uoa.gr [Instituto de Ciencias Físicas y Matemáticas, Universidad Austral de Chile, Valdivia (Chile)
2016-11-01
We investigate Kantowski-Sachs models in Einstein-æ ther theory with a perfect fluid source using the singularity analysis to prove the integrability of the field equations and dynamical system tools to study the evolution. We find an inflationary source at early times, and an inflationary sink at late times, for a wide region in the parameter space. The results by A.A. Coley, G. Leon, P. Sandin and J. Latta ( JCAP 12 (2015) 010), are then re-obtained as particular cases. Additionally, we select other values for the non-GR parameters which are consistent with current constraints, getting a very rich phenomenology. In particular, we find solutions with infinite shear, zero curvature, and infinite matter energy density in comparison with the Hubble scalar. We also have stiff-like future attractors, anisotropic late-time attractors, or both, in some special cases. Such results are developed analytically, and then verified by numerics. Finally, the physical interpretation of the new critical points is discussed.
A global conformal extension theorem for perfect fluid Bianchi space-times
International Nuclear Information System (INIS)
Luebbe, Christian; Tod, Paul
2008-01-01
A global extension theorem is established for isotropic singularities in polytropic perfect fluid Bianchi space-times. When an extension is possible, the limiting behaviour of the physical space-time near the singularity is analysed
Hypersurface-homogeneous Universe filled with perfect fluid in f ( R ...
Indian Academy of Sciences (India)
homogeneous Universe filled with perfect fluid in the framework of f ( R , T ) theory of gravity (Harko et al, \\emph{Phys. Rev.} D 84, 024020 (2011)) is derived. The physical behaviour of the cosmological model is studied.
Shear-free flows of a perfect fluid
International Nuclear Information System (INIS)
Barnes, A.
1984-01-01
Previous results on shear-free fluid flows are reviewed. Attention is then restricted to flows which satisfy the additional condition that the Weyl tensor is purely electric: Hsub(ac)=*Csub(abcd)usup(b)usup(d)=O where usup(a) is the velocity vector of the fluid. The analysis is also applied to Einstein spaces admitting a shear-free timelike vector field usup(a). If the Weyl tensor is purely electric or purely magnetic, it is shown that usup(a) is necessarily irrotational unless the spacetime has constant curvature. (author)
Noether and Lie symmetries for charged perfect fluids
International Nuclear Information System (INIS)
Kweyama, M C; Govinder, K S; Maharaj, S D
2011-01-01
We study the underlying nonlinear partial differential equation that governs the behaviour of spherically symmetric charged fluids in general relativity. We investigate the conditions for the equation to admit a first integral or be reduced to quadratures using symmetry methods for differential equations. A general Noether first integral is found. We also undertake a comprehensive group analysis of the underlying equation using Lie point symmetries. The existence of a Lie symmetry is subject to solving an integro-differential equation in general; we investigate the conditions under which it can be reduced to quadratures. Earlier results for uncharged fluids and particular first integrals for charged matter are regained as special cases of our treatment.
Anti-collapse mechanism of CBM fuzzy-ball drilling fluid
Directory of Open Access Journals (Sweden)
Lihui Zheng
2016-03-01
Full Text Available Although fuzzy-ball drilling fluid has been successfully applied in CBM well drilling, it is necessary to study its anti-collapse mechanism so that adjustable coalbed sealing effects, controllable sealing strength, rational sealing cost and controllable reservoir damage degree can be realized. In this paper, laboratory measurement was performed on the uniaxial compressive strength of the plungers of No. 3 coalbed in the Qinshui Basin and the inlet pressure of Ø38 mm coal plunger displacement. The strengths of coal plungers were tested and compared after 2% potassium chloride solution, low-solids polymer drilling fluid and fuzzy-ball drilling fluid were injected into the coal plungers respectively. It is shown that coal strength rises by 38.46% after the fuzzy-ball drilling fluid is injected (in three groups; and that no fuzzy-ball drilling fluid is lost at the displacement pressures of 20.73 and 21.46 MPa, nor 2% potassium chloride solution is leaked at such pressures of 24.79 and 25.64 MPa after the plunger was sealed by the fuzzy-ball drilling fluid. This indicates that the fuzzy-ball drilling fluid can increase the formation resistance to fluid. Indoor microscopic observation was conducted on the sealing process of the fuzzy-ball drilling fluid in sand packs with coal cuttings of three grain sizes (60–80, 80–100 and 100–120 mesh. It is shown that the leakage pathways of different sizes are sealed by the vesicles in the form of accumulation, stretch and blockage. And there are vesicles at the inlet ends of the flowing pathways in the shape of beaded blanket. The impact force of drilling tools on the sidewalls is absorbed by the vesicles due to their elasticity and tenacity, so the sidewall instability caused by drilling tools is relieved. It is concluded that the main anti-collapse mechanisms of the CBM fuzzy-ball drilling fluid are to raise the coal strength, increase the formation resistance to fluid, and buffer the impact of
New family of simple solutions of relativistic perfect fluid hydrodynamics
International Nuclear Information System (INIS)
Csoergo, T.; Nagy, M.I.; Csanad, M.
2008-01-01
A new class of accelerating, exact and explicit solutions of relativistic hydrodynamics is found-more than 50 years after the previous similar result, the Landau-Khalatnikov solution. Surprisingly, the new solutions have a simple form, that generalizes the renowned, but accelerationless, Hwa-Bjorken solution. These new solutions take into account the work done by the fluid elements on each other, and work not only in one temporal and one spatial dimensions, but also in arbitrary number of spatial dimensions. They are applied here for an advanced estimation of initial energy density and life-time of the reaction in ultra-relativistic heavy ion collisions. New formulas are also conjectured, that yield further important increase of the initial energy density estimate and the measured life-time of the reaction if the value of the speed of sound is in the realistic range
Inhomogeneous generalizations of Bianchi Type VIh universes with stiff perfect fluid and radiation
Roy, S. R.; Prasad, A.
1995-03-01
Families of inhomogeneous models filled with a stiff perfect fluid and radiation have been derived in which there is no flow of total momentum. The models are generalizations of those of Bianchi Type VIh and are discussed for some particular forms of the arbitrary functions appearing in them.
Polytropic solutions of a perfect fluid in spatial n-dimensions
International Nuclear Information System (INIS)
Luiz, Fabricio Casarejos Lopes; Rocha, Jaime F. Villas da
2005-01-01
We found all the solutions of a polytropic state equation for a n-dimensional metric associated to a perfect fluid. Some of them represent gravitational collapse with black hole or naked singularity formation. We found also an accelerating cosmological model. (author)
On some properties of Einstein equations with the perfect fluid energy-momentum tensor
International Nuclear Information System (INIS)
Biesiada, M.; Szydlowski, M.; Szczesny, J.
1989-01-01
We discuss the symmetries of Einstein equations with the perfect fluid energy momentum tensor. We show that the symmetries inherited from vacuum equations enforce the equation of state in the form p p 0 = γρ which is the most often used one and contains models with the cosmological constant. 9 refs. (author)
Collapsing perfect fluid in self-similar five dimensional space-time and cosmic censorship
International Nuclear Information System (INIS)
Ghosh, S.G.; Sarwe, S.B.; Saraykar, R.V.
2002-01-01
We investigate the occurrence and nature of naked singularities in the gravitational collapse of a self-similar adiabatic perfect fluid in a five dimensional space-time. The naked singularities are found to be gravitationally strong in the sense of Tipler and thus violate the cosmic censorship conjecture
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
Abstract. Bianchi Type-I cosmological models containing perfect fluid with time vary- ing G and Λ have been presented. The solutions obtained represent an expansion scalar θ bearing a constant ratio to the anisotropy in the direction of space-like unit vector λi. Of the two models obtained, one has negative vacuum energy ...
Scalar-metric quantum cosmology with Chaplygin gas and perfect fluid
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Saumya; Panigrahi, Prasanta K. [Indian Institute of Science Education and Research Kolkata, Nadia, West Bengal (India); Gangopadhyay, Sunandan [Indian Institute of Science Education and Research Kolkata, Nadia, West Bengal (India); S.N. Bose National Centre for Basic Sciences, Kolkata (India)
2018-01-15
In this paper we consider the flat FRW cosmology with a scalar field coupled with the metric along with generalized Chaplygin gas and perfect fluid comprising the matter sector. We use the Schutz's formalism to deal with the generalized Chaplygin gas sector. The full theory is then quantized canonically using the Wheeler-DeWitt Hamiltonian formalism. We then solve the WD equation with appropriate boundary conditions. Then by defining a proper completeness relation for the self-adjointness of the WD equation we arrive at the wave packet for the universe. It is observed that the peak in the probability density gets affected due to both fluids in the matter sector, namely, the Chaplygin gas and perfect fluid. (orig.)
Binary Mixture of Perfect Fluid and Dark Energy in Modified Theory of Gravity
Shaikh, A. Y.
2016-07-01
A self consistent system of Plane Symmetric gravitational field and a binary mixture of perfect fluid and dark energy in a modified theory of gravity are considered. The gravitational field plays crucial role in the formation of soliton-like solutions, i.e., solutions with limited total energy, spin, and charge. The perfect fluid is taken to be the one obeying the usual equation of state, i.e., p = γρ with γ∈ [0, 1] whereas, the dark energy is considered to be either the quintessence like equation of state or Chaplygin gas. The exact solutions to the corresponding field equations are obtained for power-law and exponential volumetric expansion. The geometrical and physical parameters for both the models are studied.
Quantum FRW cosmological solutions in the presence of Chaplygin gas and perfect fluid
International Nuclear Information System (INIS)
Pedram, P.; Jalalzadeh, S.
2008-01-01
We present a Friedmann-Robertson-Walker quantum cosmological model in the presence of Chaplygin gas and perfect fluid for early and late time epochs. In this work, we consider perfect fluid as an effective potential and apply Schutz's variational formalism to the Chaplygin gas which recovers the notion of time. These give rise to Schroedinger-Wheeler-DeWitt equation for the scale factor. We use the eigenfunctions in order to construct wave packets and study the time dependent behavior of the expectation value of the scale factor using the many-worlds interpretation of quantum mechanics. We show that contrary to the classical case, the expectation value of the scale factor avoids singularity at quantum level. Moreover, this model predicts that the expansion of Universe is accelerating for the late times
All static spherically symmetric perfect-fluid solutions of Einstein's equations
International Nuclear Information System (INIS)
Lake, Kayll
2003-01-01
An algorithm based on the choice of a single monotone function (subject to boundary conditions) is presented which generates all regular static spherically symmetric perfect-fluid solutions of Einstein's equations. For physically relevant solutions the generating functions must be restricted by nontrivial integral-differential inequalities. Nonetheless, the algorithm is demonstrated here by the construction of an infinite number of previously unknown physically interesting exact solutions
International Nuclear Information System (INIS)
Tupper, B.O.J.
1983-01-01
The work of a previous article is extended to show that space-times which are the exact solutions of the field equations for a perfect fluid also may be exact solutions of the field equations for a viscous magnetohydrodynamic fluid. Conditions are found for this equivalence to exist and viscous magnetohydrodynamic solutions are found for a number of known perfect fluid space-times. (author)
International Nuclear Information System (INIS)
Chakraborty, Sumanta
2015-01-01
The hydrodynamic behavior of perfect fluid orbiting around black holes in spherically symmetric spacetime for various alternative gravity theories has been investigated. For this purpose we have assumed a uniform distribution for the angular momentum density of the rotating perfect fluid. The contours of equipotential surfaces are illustrated in order to obtain the nature of inflow and outflow of matter. It has been noticed that the marginally stable circular orbits originating from decreasing angular momentum density lead to closed equipotential surfaces along with cusps, allowing the existence of accretion disks. On the other hand, the growing part of the angular momentum density exhibits central rings for which stable configurations are possible. However, inflow of matter is prohibited. Among the solutions discussed in this work, the charged F(R) gravity and Einstein–Maxwell–Gauss–Bonnet solutions exhibit inflow and outflow of matter with central rings present. These varied accretion disk structures of perfect fluid attribute astrophysical importance to these spacetimes. The effect of higher curvature terms predominantly arises from the region near the black hole horizon. Hence the structural difference of the accretion disk in modified gravity theories in comparison to general relativity may act as an experimental probe for these alternative gravity theories. (paper)
The 'spontaneous' acoustic emission of the shock front in a perfect fluid: solving a riddle
International Nuclear Information System (INIS)
Brun, Louis
2013-06-01
In the fifties, S. D'yakov discovered that theory allows for suitable EOS shock fronts to emit acoustic waves 'spontaneously'. Section 90 of Fluid Mechanics of Landau and Lifshitz, 2. Ed., deals with the phenomenon, leaving it unexplained. This open question was chosen to introduce a monograph in progress about 'the shock front in the perfect fluid'. The novelty of our approach consists in having the phenomenon generated - which means it is non-spontaneous -- from an appropriate solicitation of the front and studying its development analytically. The non classical source and mechanism of the emission are thus brought to light. (author)
On the variational principle for the equations of perfect fluid dynamics
International Nuclear Information System (INIS)
Serre, D.
1993-01-01
One gives a new version of the variational principle δL = 0, L being the usual Lagrangian, for the perfect fluid mechanics. It is formally equivalent to the well-known principle but it gives the first rigorous derivation of the conservation laws (momentum and energy), including the discontinuous case (shock waves, contact discontinuities). Thanks to a new formulation of the constraints, we do not involve any Lagrange multiplier, which in previous works were neither physically relevant, since they do not appear in the Euler equations, nor mathematically relevant. We even give a variational interpretation of the entropy inequality when shock waves occur. Our method covers all aspects of the perfect fluids, including stationary and unstationary motion, compressible and incompressible fluids, axisymmetric case. When the velocity field admits a stream function, the variational principle gives rise to extremal points of the Lagrangian on various infinite dimensional manifolds. For a suitable choice of this manifold, the flow is itself periodic, that is all the fluid particles have a periodic motion with the same period. The flow describes a closed geodesic on some group of diffeomorphisms. (author). 10 refs
Beyond the perfect fluid hypothesis for the dark energy equation of state
International Nuclear Information System (INIS)
Cardone, V.F.; Troisi, A.; Tortora, C.; Capozziello, S.
2006-01-01
Abandoning the perfect fluid hypothesis, we investigate here the possibility that the dark energy equation of state (EoS) w is a nonlinear function of the energy density ρ. To this aim, we consider four different EoS describing classical fluids near thermodynamical critical points and discuss the main features of cosmological models made out of dust matter and a dark energy term with the given EoS. Each model is tested against the data on the dimensionless coordinate distance to Type Ia Supernovae and radio galaxies, the shift and the acoustic peak parameters and the positions of the first three peaks in the anisotropy spectrum of the comic microwave background radiation. We propose a possible interpretation of each model in the framework of scalar field quintessence determining the shape of the self-interaction potential V(φ) that gives rise to each one of the considered thermodynamical EoS. As a general result, we demonstrate that replacing the perfect fluid EoS with more general expressions gives both the possibility of successfully solving the problem of cosmic acceleration escaping the resort to phantom models
Kerr–anti-de Sitter/de Sitter black hole in perfect fluid dark matter background
Xu, Zhaoyi; Hou, Xian; Wang, Jiancheng
2018-06-01
We obtain the Kerr–anti-de-sitter (Kerr–AdS) and Kerr–de-sitter (Kerr–dS) black hole (BH) solutions to the Einstein field equation in the perfect fluid dark matter background using the Newman–Janis method and Mathematica package. We discuss in detail the black hole properties and obtain the following main results: (i) From the horizon equation g rr = 0, we derive the relation between the perfect fluid dark matter parameter α and the cosmological constant Λ when the cosmological horizon exists. For , we find that α is in the range for and for . For positive cosmological constant Λ (Kerr–AdS BH), decreases if , and increases if . For negative cosmological constant (Kerr–dS BH), increases if and decreases if ; (ii) An ergosphere exists between the event horizon and the outer static limit surface. The size of the ergosphere evolves oppositely for and , while decreasing with the increasing . When there is sufficient dark matter around the black hole, the black hole spacetime changes remarkably; (iii) The singularity of these black holes is the same as that of rotational black holes. In addition, we study the geodesic motion using the Hamilton–Jacobi formalism and find that when α is in the above ranges for , stable orbits exist. Furthermore, the rotational velocity of the black hole in the equatorial plane has different behaviour for different α and the black hole spin a. It is asymptotically flat and independent of α if while is asymptotically flat only when α is close to zero if . We anticipate that Kerr–Ads/dS black holes could exist in the universe and our future work will focus on the observational effects of the perfect fluid dark matter on these black holes.
On the spherical symmetry of static perfect fluids in general relativity
International Nuclear Information System (INIS)
Beig, R.; Simon, W.
1990-01-01
We present a theorem which establishes uniqueness, in particular spherical symmetry, of a wide class of general relativistic, static perfect-fluid models provided there exists a spherically symmetric model with the same equation of state and surface potential. The method of proof, which is inspired by recent work of Masood-ul-Alam, is illustrated by demonstrating uniqueness of a class of solutions due to Buchdahl which correspond to an extreme case of the inequality on the equation of state required by our theorem. 16 refs. (Authors)
Equilibrium points of the tilted perfect fluid Bianchi VIh state space
Apostolopoulos, Pantelis S.
2005-05-01
We present the full set of evolution equations for the spatially homogeneous cosmologies of type VIh filled with a tilted perfect fluid and we provide the corresponding equilibrium points of the resulting dynamical state space. It is found that only when the group parameter satisfies h > -1 a self-similar solution exists. In particular we show that for h > -{1/9} there exists a self-similar equilibrium point provided that γ ∈ ({2(3+sqrt{-h})/5+3sqrt{-h}},{3/2}) whereas for h VIh.
New class of inhomogeneous cosmological perfect-fluid solutions without big-bang singularity
Energy Technology Data Exchange (ETDEWEB)
Senovilla, J.M.M. (Grupo de Fisica Teorica, Departamento de Fisica, Ingenieria y Radiologia Medica, Facultad de Ciencias, Universidad de Salamanca, 37008 Salmanaca (Spain))
1990-05-07
A new class of exact solutions to Einstein's field equations with a perfect-fluid source is presented. The solutions describe spatially inhomogeneous cosmological models and have a realistic equation of state {ital p}={rho}/3. The properties of the solutions are discussed. The most remarkable feature is the absence of an initial singularity, the curvature and matter invariants being regular and smooth everywhere. We also present an alternative interpretation of the solution as a globally regular cylindrically symmetric space-time.
On the uniqueness of static perfect-fluid solutions in general relativity
International Nuclear Information System (INIS)
Beig, R.; Simon, W.
1990-01-01
Following earlier work of Masood-ul-Alam, we consider a uniqueness problem for nonrotating stellar models. Given a static, asymptotically flat perfect-fluid spacetime with barotropic equation of state ρ(p), and given another such spacetime which is spherically symmetric and has the same ρ(p) and the same surface potential: we prove that both are identical provided ρ(p) satisfies a certain differential inequality. This inequality is more natural and less restrictive that the conditions required by Masood-ul-Alam. 30 refs. (Authors)
Spectra of primordial fluctuations in two-perfect-fluid regular bounces
International Nuclear Information System (INIS)
Finelli, Fabio; Peter, Patrick; Pinto-Neto, Nelson
2008-01-01
We introduce analytic solutions for a class of two components bouncing models, where the bounce is triggered by a negative energy density perfect fluid. The equation of state of the two components are constant in time, but otherwise unrelated. By numerically integrating regular equations for scalar cosmological perturbations, we find that the (would-be) growing mode of the Newtonian potential before the bounce never matches with the growing mode in the expanding stage. For the particular case of a negative energy density component with a stiff equation of state we give a detailed analytic study, which is in complete agreement with the numerical results. We also perform analytic and numerical calculations for long wavelength tensor perturbations, obtaining that, in most cases of interest, the tensor spectral index is independent of the negative energy fluid and given by the spectral index of the growing mode in the contracting stage. We compare our results with previous investigations in the literature
Transport tensors in perfectly aligned low-density fluids: Self-diffusion and thermal conductivity
International Nuclear Information System (INIS)
Singh, G. S.; Kumar, B.
2001-01-01
The modified Taxman equation for the kinetic theory of low-density fluids composed of rigid aspherical molecules possessing internal degrees of freedom is generalized to obtain the transport tensors in a fluid of aligned molecules. The theory takes care of the shape of the particles exactly but the solution has been obtained only for the case of perfectly aligned hard spheroids within the framework of the first Sonine polynomial approximation. The expressions for the thermal-conductivity components have been obtained for the first time whereas the self-diffusion components obtained here turn out to be exactly the same as those derived by Kumar and Masters [Mol. Phys. >81, 491 (1994)] through the solution of the Lorentz-Boltzmann equation. All our expressions yield correct results in the hard-sphere limit
Classical and quantum dynamics of a perfect fluid scalar-metric cosmology
International Nuclear Information System (INIS)
Vakili, Babak
2010-01-01
We study the classical and quantum models of a Friedmann-Robertson-Walker (FRW) cosmology, coupled to a perfect fluid, in the context of the scalar-metric gravity. Using the Schutz' representation for the perfect fluid, we show that, under a particular gauge choice, it may lead to the identification of a time parameter for the corresponding dynamical system. It is shown that the evolution of the universe based on the classical cosmology represents a late time power law expansion coming from a big-bang singularity in which the scale factor goes to zero while the scalar field blows up. Moreover, this formalism gives rise to a Schroedinger-Wheeler-DeWitt (SWD) equation for the quantum-mechanical description of the model under consideration, the eigenfunctions of which can be used to construct the wave function of the universe. We use the resulting wave function in order to investigate the possibility of the avoidance of classical singularities due to quantum effects by means of the many-worlds and ontological interpretation of quantum cosmology.
Perfect fluid of p-branes, 2D dilaton gravity and the big-bang
International Nuclear Information System (INIS)
Borlaf, J.
2001-01-01
This paper starts by building the energy-momentum tensor of a perfect fluid of p-branes coupled to (p+4)-dimensional general relativity. Having three homogeneous and isotropic macroscopical spatial dimensions, the system gravity/fluid can be reduced to an effective theory over the branes. For the string fluid (p=1) the effective theory is nothing but the 2D dilaton gravity where the potential for the scalar field, which is the scale factor of the macroscopical space, is fixed by the state equation and the three-dimensional geometry. This theory can be solved allowing us to compare some relevant aspects in our homogeneous and isotropic string cosmologies with those of the Robertson-Walker ones. In particular, unlike the point-particle models, the existence of an initial singularity is strongly sensitive to the state equation, and it is remarkable that this model picks out the radiation state equation as the canonical case where the big-bang is kinematically forbidden. Moreover, we cannot reduce the Robertson-Walker cosmologies to the limit when the string size approaches to zero, because the existence of an upper bound on the string size is not compatible with the big-bang. Some examples are presented
Perfect fluid of p-branes, 2D dilaton gravity and the big-bang
Energy Technology Data Exchange (ETDEWEB)
Borlaf, J. E-mail: jborlaf@redestb.es
2001-01-15
This paper starts by building the energy-momentum tensor of a perfect fluid of p-branes coupled to (p+4)-dimensional general relativity. Having three homogeneous and isotropic macroscopical spatial dimensions, the system gravity/fluid can be reduced to an effective theory over the branes. For the string fluid (p=1) the effective theory is nothing but the 2D dilaton gravity where the potential for the scalar field, which is the scale factor of the macroscopical space, is fixed by the state equation and the three-dimensional geometry. This theory can be solved allowing us to compare some relevant aspects in our homogeneous and isotropic string cosmologies with those of the Robertson-Walker ones. In particular, unlike the point-particle models, the existence of an initial singularity is strongly sensitive to the state equation, and it is remarkable that this model picks out the radiation state equation as the canonical case where the big-bang is kinematically forbidden. Moreover, we cannot reduce the Robertson-Walker cosmologies to the limit when the string size approaches to zero, because the existence of an upper bound on the string size is not compatible with the big-bang. Some examples are presented.
General exact solution for homogeneous time-dependent self-gravitating perfect fluids
International Nuclear Information System (INIS)
Gaete, P.; Hojman, R.
1988-01-01
A procedure to obtain the general exact solution of Einstein equations for a self-gravitating spherically-symmetric static perfect fluid obeying an arbitrary equation of state, is applied to time-dependent Kantowsky-Sachs line elements (with spherical, planar and hyperbolic symmetry). As in the static case, the solution is generated by an arbitrary function of the independent variable and its first derivative. To illustrate the results, the whole family of (plane-symmetric) solutions with a ''gamma-law'' equation of state is explicity obtained in terms of simple known functions. It is also shown that, while in the static plane-symmtric line elements, every metric is in one to one correspondence with a ''partner-metric'' (both originated from the same generatrix function), in this case every generatrix function univocally determines one metric. (author) [pt
Directory of Open Access Journals (Sweden)
Jinfeng Wang
2016-01-01
Full Text Available During well-killing operations for the workover of low-pressure gas wells, formation pressure should be balanced so as to guarantee well control safety by preventing natural gas overflow. In this paper, a laboratory evaluation was conducted with fuzzy-ball fluids as killing fluids. The results show that, the fuzzy-ball fluid, with a density of 0.5–1.5 g/cm3 and a viscosity up to 78,50,000 mPa·s at a low shear rate, realizes controllable performance and forms piston-like plugging slugs of solid-free high structural strength on natural gas wellbore after bonding. During well workover, multiple fluid column pressures were set up by injecting fuzzy-ball fluids with different densities at various rates. Owing to high structural strength of the fluids at a low shear rate, natural gas breaks through only inside the piston-like slug and cannot flow upwards to the ground, so the pathways of natural gas in the wellbore are isolated from the ground surface. Moreover, the fluid can wholly move up and down like a piston-like plug, with the change of formation pressures or the tripping of pipe strings. Like the conventional operations, the production can be restored after the workover, so long as the fluid in wellbore is cleaned by means of gas lift. In a natural gas field in NW China, where the formation pressure coefficient dropped to 0.60–0.82, three wells were fully filled with fuzzy-ball workover fluids for 7 days and another three wells were treated with the piston-like plugs of fuzzy-ball workover fluids for only 3 days. They all presented better technical results. The technology provides a new way for low-pressure gas well workover.
Lorentz invariant noncommutative algebra for cosmological models coupled to a perfect fluid
Energy Technology Data Exchange (ETDEWEB)
Abreu, Everton M.C.; Marcial, Mateus V.; Mendes, Albert C.R.; Oliveira, Wilson [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Seropedica, RJ (Brazil); Universidade Federal de Juiz de Fora, MG (Brazil)
2013-07-01
Full text: In current theoretical physics there is a relevant number of theoretical investigations that lead to believe that at the first moments of our Universe, the geometry was not commutative and the dominating physics at that time was ruled by the laws of noncommutative (NC) geometry. Therefore, the idea is that the physics of the early moments can be constructed based on these concepts. The first published work using the idea of a NC spacetime were carried out by Snyder who believed that NC principles could make the quantum field theory infinities disappear. However, it did not occur and Snyder's ideas were put to sleep for a long time. The main modern motivations that rekindle the investigation about NC field theories came from string theory and quantum gravity. In the context of quantum mechanics for example, R. Banerjee discussed how NC structures appear in planar quantum mechanics providing a useful way for obtaining them. The analysis was based on the NC algebra used in planar quantum mechanics that was originated from 't Hooft's analysis on dissipation and quantization. In this work we carry out a NC algebra analysis of the Friedmann-Robert-Walker model, coupled to a perfect fluid and in the presence of a cosmological constant. The classical field equations are modified, by the introduction of a shift operator, in order to introduce noncommutativity in these models. (author)
Searching for perfect fluids: quantum viscosity in a universal Fermi gas
International Nuclear Information System (INIS)
Cao, C; Elliott, E; Wu, H; Thomas, J E
2011-01-01
We measure the shear viscosity in a two-component Fermi gas of atoms, tuned to a broad s-wave collisional (Feshbach) resonance. At resonance, the atoms strongly interact and exhibit universal behavior, where the equilibrium thermodynamic properties and transport coefficients are universal functions of density n and temperature T. We present a new calibration of the temperature as a function of global energy, which is directly measured from the cloud profiles. Using the calibration, the trap-averaged shear viscosity in units of ℎn is determined as a function of the reduced temperature at the trap center, from nearly the ground state to the unitary two-body regime. Low-temperature data are obtained from the damping rate of the radial breathing mode, whereas high-temperature data are obtained from hydrodynamic expansion measurements. We also show that the best fit to the high-temperature expansion data is obtained for a vanishing bulk viscosity. The measured trap-averaged entropy per particle and shear viscosity are used to estimate the ratio of shear viscosity to entropy density, which is compared with that conjectured for a perfect fluid.
Reviving the shear-free perfect fluid conjecture in general relativity
Sikhonde, Muzikayise E.; Dunsby, Peter K. S.
2017-12-01
Employing a Mathematica symbolic computer algebra package called xTensor, we present (1+3) -covariant special case proofs of the shear-free perfect fluid conjecture in general relativity. We first present the case where the pressure is constant, and where the acceleration is parallel to the vorticity vector. These cases were first presented in their covariant form by Senovilla et al. We then provide a covariant proof for the case where the acceleration and vorticity vectors are orthogonal, which leads to the existence of a Killing vector along the vorticity. This Killing vector satisfies the new constraint equations resulting from the vanishing of the shear. Furthermore, it is shown that in order for the conjecture to be true, this Killing vector must have a vanishing spatially projected directional covariant derivative along the velocity vector field. This in turn implies the existence of another basic vector field along the direction of the vorticity for the conjecture to hold. Finally, we show that in general, there exists a basic vector field parallel to the acceleration for which the conjecture is true.
Lorentz invariant noncommutative algebra for cosmological models coupled to a perfect fluid
International Nuclear Information System (INIS)
Abreu, Everton M.C.; Marcial, Mateus V.; Mendes, Albert C.R.; Oliveira, Wilson
2013-01-01
Full text: In current theoretical physics there is a relevant number of theoretical investigations that lead to believe that at the first moments of our Universe, the geometry was not commutative and the dominating physics at that time was ruled by the laws of noncommutative (NC) geometry. Therefore, the idea is that the physics of the early moments can be constructed based on these concepts. The first published work using the idea of a NC spacetime were carried out by Snyder who believed that NC principles could make the quantum field theory infinities disappear. However, it did not occur and Snyder's ideas were put to sleep for a long time. The main modern motivations that rekindle the investigation about NC field theories came from string theory and quantum gravity. In the context of quantum mechanics for example, R. Banerjee discussed how NC structures appear in planar quantum mechanics providing a useful way for obtaining them. The analysis was based on the NC algebra used in planar quantum mechanics that was originated from 't Hooft's analysis on dissipation and quantization. In this work we carry out a NC algebra analysis of the Friedmann-Robert-Walker model, coupled to a perfect fluid and in the presence of a cosmological constant. The classical field equations are modified, by the introduction of a shift operator, in order to introduce noncommutativity in these models. (author)
Static and radiating solutions of Lovelock gravity in the presence of a perfect fluid
International Nuclear Information System (INIS)
Dehghani, M.H.; Farhangkhah, N.
2009-01-01
We present a general solution of third order Lovelock gravity in the presence of a specific type II perfect fluid. This solution for linear equation of state, p=w(ρ-4B) contains all the known solutions of third order Lovelock gravity in the literature and some new static and radiating solutions for different values of w and B. Specially, we consider the properties of static and radiating solutions for w=0 and w=(n-2) -1 with B=0 and B≠0. These solutions are asymptotically flat for B=0, while they are asymptotically (anti-)de Sitter for B≠0. The new static solutions for these choices of B and w present black holes with one or two horizons, extreme black holes or naked singularities provided the parameters of the solutions are chosen suitable. The static solution with w=0 and vanishing geometrical mass (m=0) may present a black hole with two inner and outer horizons. This is a peculiar feature of the third order Lovelock gravity, which does not occur in lower order Lovelock gravity. We also, investigate the properties of radiating solutions for these values of B and w, and compare the singularity strengths of them with the known radiating solutions of third order Lovelock gravity.
International Nuclear Information System (INIS)
Gaikwad, N. P.; Borkar, M. S.; Charjan, S. S.
2011-01-01
We investigate the Bianchi type-I massive string magnetized barotropic perfect fluid cosmological model in Rosen's bimetric theory of gravitation with and without a magnetic field by applying the techniques used by Latelier (1979, 1980) and Stachel (1983). To obtain a deterministic model of the universe, it is assumed that the universe is filled with barotropic perfect fluid distribution. The physical and geometrical significance of the model are discussed. By comparing our model with the model of Bali et al. (2007), it is realized that there are no big-bang and big-crunch singularities in our model and T = 0 is not the time of the big bang, whereas the model of Bali et al. starts with a big bang at T = 0. Further, our model is in agreement with Bali et al. (2007) as time increases in the presence, as well as in the absence, of a magnetic field. (geophysics, astronomy, and astrophysics)
International Nuclear Information System (INIS)
McLerran, L.
1985-01-01
The author discusses the applicability of a hydrodynamic description of high energy hadronic collisions. The author reviews the results of recent computations of the mean free paths of quarks and gluons in a quark-gluon plasma, and the corresponding results for viscous coefficients. These quantities are employed to evaluate the limits to the application of perfect fluid hydrodynamics as a description of the time evolution of matter produced in various hardronic collisions
Yang, Jubiao; Yu, Feimi; Krane, Michael; Zhang, Lucy T
2018-01-01
In this work, a non-reflective boundary condition, the Perfectly Matched Layer (PML) technique, is adapted and implemented in a fluid-structure interaction numerical framework to demonstrate that proper boundary conditions are not only necessary to capture correct wave propagations in a flow field, but also its interacted solid behavior and responses. While most research on the topics of the non-reflective boundary conditions are focused on fluids, little effort has been done in a fluid-structure interaction setting. In this study, the effectiveness of the PML is closely examined in both pure fluid and fluid-structure interaction settings upon incorporating the PML algorithm in a fully-coupled fluid-structure interaction framework, the Immersed Finite Element Method. The performance of the PML boundary condition is evaluated and compared to reference solutions with a variety of benchmark test cases including known and expected solutions of aeroacoustic wave propagation as well as vortex shedding and advection. The application of the PML in numerical simulations of fluid-structure interaction is then investigated to demonstrate the efficacy and necessity of such boundary treatment in order to capture the correct solid deformation and flow field without the requirement of a significantly large computational domain.
Bianchi Type-V model with a perfect fluid and Λ-term
Indian Academy of Sciences (India)
A self-consistent system of gravitational field with a binary mixture of perfect ... a form of quintessence, may explain the coincidence, adding a new motivation for .... hand, with the expansion of the universe, i.e., with the increase of V , the ...
Perfect-fluid models admitting a non-Abelian and maximal two-parameter group of isometries
International Nuclear Information System (INIS)
Van den Bergh, N.
1988-01-01
A proof is given that, when a spacetime admits an invariant timelike congruence orthogonal to the orbits of a non-Abelian two-parameter group of isometries, the given congruence is vorticity-free provided the group is maximal. The result is used to derive a canonical coordinate form for perfect-fluid solutions satisfying the above condition. It is also shown that such a group of isometries cannot be orthogonally transitive and a brief discussion is given of the self-similar case. (author)
DEFF Research Database (Denmark)
Xie, Zhinan; Matzen, René; Cristini, Paul
2016-01-01
A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range-dependent a......A time-domain Legendre spectral-element method is described for full-wave simulation of ocean acoustics models, i.e., coupled fluid-solid problems in unbounded or semi-infinite domains, taking into account shear wave propagation in the ocean bottom. The technique can accommodate range......-dependent and depth-dependent wave speed and density, as well as steep ocean floor topography. For truncation of the infinite domain, to efficiently absorb outgoing waves, a fluid-solid complex-frequency-shifted unsplit perfectly matched layer is introduced based on the complex coordinate stretching technique....... The complex stretching is rigorously taken into account in the derivation of the fluid-solid matching condition inside the absorbing layer, which has never been done before in the time domain. Two implementations are designed: a convolutional formulation and an auxiliary differential equation formulation...
Bianchi type-V cosmological models with perfect fluid and heat flow ...
Indian Academy of Sciences (India)
In the cosmology with the power-law, the solutions correspond to a cos- mological model .... where ρ is the energy density, p is the thermodynamic pressure, uµ is the four- velocity of the fluid and ..... In the first category of models, the. Universe ...
Self-propulsion of a body with rigid surface and variable coefficient of lift in a perfect fluid
Ramodanov, Sergey M.; Tenenev, Valentin A.; Treschev, Dmitry V.
2012-11-01
We study the system of a 2D rigid body moving in an unbounded volume of incompressible, vortex-free perfect fluid which is at rest at infinity. The body is equipped with a gyrostat and a so-called Flettner rotor. Due to the latter the body is subject to a lifting force (Magnus effect). The rotational velocities of the gyrostat and the rotor are assumed to be known functions of time (control inputs). The equations of motion are presented in the form of the Kirchhoff equations. The integrals of motion are given in the case of piecewise continuous control. Using these integrals we obtain a (reduced) system of first-order differential equations on the configuration space. Then an optimal control problem for several types of the inputs is solved using genetic algorithms.
International Nuclear Information System (INIS)
Sussman, R.A.
1988-01-01
The topology of the solutions derived in Part I [J. Math. Phys. 28, 1118 (1987)] is discussed in detail using suitable topological embeddings. It is found that these solutions are homeomorphic to S 3 x R, R 4 , or S 2 x R 2 . Singularities and boundaries in these manifolds are examined within a global framework. One of these boundaries (mentioned but not examined in Part II) is regular (though unphysical), and is associated with an ''asymptotically de Sitter'' behavior characterized by an exponential form of the Hubble scale factor. Solutions with S 2 x R 2 topology lack a center of symmetry [fixed point of SO(3)] and present a null boundary at an infinite affine parameter distance along hypersurfaces orthogonal to the four-velocity. This boundary, which in most cases is singular, can be identified as a null I-script surface arising as an asymptotical null limit of timelike hypersurfaces. Solutions with this topology, matched to a Schwarzschild or Reissner--Nordstr≅m region, describe collapsing fluid spheres whose ''surface'' (as seen by observers in the vacuum region) has finite proper radius, but whose ''interior'' is a fluid region of cosmological proportions. In the case when the null boundary of the fluid region is singular, it behaves as a sort of ''white hole.'' Uniform density solutions which are not conformally flat are all homeomorphic to S 2 x R 2 . Conformally flat solutions are also examined in detail. Their global structure has common features with those of FRW and de Sitter solutions. The static limits of all nonstatic solutions are discussed. In particular, under suitable parameter restrictions, some of these static solutions, together with the nonstatic conformally flat subclass, are the less physically objectionable of all solutions
The ideal relativistic rotating gas as a perfect fluid with spin
International Nuclear Information System (INIS)
Becattini, F.; Tinti, L.
2010-01-01
We show that the ideal relativistic spinning gas at complete thermodynamical equilibrium is a fluid with a non-vanishing spin density tensor σ μν . After having obtained the expression of the local spin-dependent phase-space density f(x, p) στ in the Boltzmann approximation, we derive the spin density tensor and show that it is proportional to the acceleration tensor Ω μν constructed with the Frenet-Serret tetrad. We recover the proper generalization of the fundamental thermodynamical relation, involving an additional term -(1/2)Ω μν σ μν . We also show that the spin density tensor has a non-vanishing projection onto the four-velocity field, i.e. t μ = σ μν u ν ≠ 0, in contrast to the common assumption t μ = 0, known as Frenkel condition, in the thus-far proposed theories of relativistic fluids with spin. We briefly address the viewpoint of the accelerated observer and inertial spin effects.
International Nuclear Information System (INIS)
Dupeux, Guillaume; Le Goff, Anne; Quere, David; Clanet, Christophe
2010-01-01
We discuss the trajectory of a fast revolving solid ball moving in a fluid of comparable density. As the ball slows down owing to drag, its trajectory follows an exponential spiral as long as the rotation speed remains constant: at the characteristic distance L where the ball speed is significantly affected by the drag, the bending of the trajectory increases, surprisingly. Later, the rotation speed decreases, which makes the ball follow a second kind of spiral, also described in the paper. Finally, the use of these highly curved trajectories is shown to be relevant to sports.
International Nuclear Information System (INIS)
Portugal, R.
1984-01-01
Three processes of solutions of the Einstein-Maxwell equations for Bianchi - I, II, VIII, IX and Kantowski-Sachs-like cosmological models with perfect fluid in magnetohydrolodynamical regimem are presented. Diagonal Bianchi-like models are considered with two anisotropy direction in the maximum. Solutions are found for Bianchi-II and IX-like models with energy conditions to be analyzed. Solutions are found for Bianchi-IX and Kantowski-Sachs-Like models with positive electric conductivity and satisfering to the predominant energy conditions. Solutions are formed for isotropic Kantowski-Sachs-Like models satisfering to the equation of state p=λρ, 0 0, admiting, in addition to the perfect fluid, electric field only. It is shown that a class of Bertotti-Robinson-like solutions is unstable by perturbations and it is carried in Kantowski-Sachs-like models with non-null electric conductivity. (L.C.) [pt
Slowly rotating charged fluid balls and their matching to an exterior domain
International Nuclear Information System (INIS)
Fodor, Gyula; Perjes, Zoltan; Bradley, Michael
2002-01-01
The slow-rotation approximation of Hartle is developed to a setting where a charged rotating fluid is present. The linearized Einstein-Maxwell equations are solved on the background of the Reissner-Nordstroem space-time in the exterior electrovacuum region. The theory is put to action for the charged generalization of the Wahlquist solution found by Garcia. The Garcia solution is transformed to coordinates suitable for the matching and expanded in powers of the angular velocity. The two domains are then matched along the zero pressure surface using the Darmois-Israel procedure. We prove a theorem to the effect that the exterior region is asymptotically flat if and only if the parameter C 2 , characterizing the magnitude of an external magnetic field, vanishes. We obtain the form of the constant C 2 for the Garcia solution. We conjecture that the Garcia metric cannot be matched to an asymptotically flat exterior electrovacuum region even to first order in the angular velocity. This conjecture is supported by a high precision numerical analysis
Virta, R.L.
2001-01-01
Part of the 2000 annual review of the industrial minerals sector. A general overview of the ball clay industry is provided. In 2000, sales of ball clay reached record levels, with sanitary ware and tile applications accounting for the largest sales. Ball clay production, consumption, prices, foreign trade, and industry news are summarized. The outlook for the ball clay industry is also outlined.
Perfect imaging without negative refraction
Energy Technology Data Exchange (ETDEWEB)
Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)], E-mail: ulf@st-andrews.ac.uk
2009-09-15
Perfect imaging has been believed to rely on negative refraction, but here we show that an ordinary positively refracting optical medium may form perfect images as well. In particular, we establish a mathematical proof that Maxwell's fish eye in two-dimensional (2D) integrated optics makes a perfect instrument with a resolution not limited by the wavelength of light. We also show how to modify the fish eye such that perfect imaging devices can be made in practice. Our method of perfect focusing may also find applications outside of optics, in acoustics, fluid mechanics or quantum physics, wherever waves obey the 2D Helmholtz equation.
DEFF Research Database (Denmark)
Pless, Mette; Sørensen, Niels Ulrik
’Picture perfect’ – when perfection becomes the new normal This paper draws on perspectives from three different studies. One study, which focuses on youth life and lack of well-being (Sørensen et al 2011), one study on youth life on the margins of society (Katznelson et al 2015) and one study...
1998-01-01
The Ultra 500 Series golf balls, introduced in 1995 by Wilson Sporting Goods Company, has 500 dimples arranged in a pattern of 60 spherical triangles. The design employs NASA's aerodynamics technology analysis of air loads of the tank and Shuttle orbiter that was performed under the Space Shuttle External Tank program. According to Wilson, this technology provides 'the most symmetrical ball surface available, sustaining initial velocity longer and producing the most stable ball flight for unmatched accuracy and distance.' The dimples are in three sizes, shapes and depths mathematically positioned for the best effect. The selection of dimples and their placement optimizes the interaction of opposing forces of lift and drag. Large dimples reduce air drag, enhance lift, and maintain spin for distance. Small dimples prevent excessive lift that destabilizes the ball flight and the medium size dimples blend the other two.
International Nuclear Information System (INIS)
Nouicer, R.
2013-01-01
This thesis for the 'Accreditation to lead research' diploma consists of six chapters. Chapter I provides an overview of my scientific career, including a summary of my research tasks, professional experiences, and scientific output, list of my oral presentations at international conferences and my publications history. Chapter II introduces the background and goals of research in relativistic heavy ion physics, the main axis of research at the RHIC collider facility. Chapter III describes the context of Quarks-Gluon Plasma (QGP) physics including theoretical aspects, experimental aspects, the signatures of deconfinement and the evolution of QGP physics from fixed-target (SPS) to collider (RHIC) beam energies. Chapter IV details my personal contribution to the construction, assembly, installation, operation, evaluation of the signals and the maintenance of (i) the silicon pixel detectors used for the measurements of the charged particles multiplicity in PHOBOS experiment, and also (ii) the silicon vertex tracker (VTX) in PHENIX, with the main goal being to differentiate measurements of the heavy quarks charm and beauty. Chapter V presents my analysis work using the 'hit-counting' method which allows the measurement of the pseudorapidity density distributions of charged particles in PHOBOS at several RHIC energies. This chapter also illustrates my predictions for the LHC as well my publications as principal author and my responsibilities as 'Co-convenor' of the multiplicity group in PHOBOS. Finally, chapter VI presents the highlights of the RHIC results: 'Nearly Perfect Fluid of Quarks and Gluons'. This chapter illustrates a great wealth of scientific discoveries, and some great surprises encountered in the RHIC era which provided new perspectives in quantum chromodynamics (QCD) calculations. At the end of this chapter, I concluded while answering the question about what we have learnt and where we are. (author)
Flight trajectory of a rotating golf ball with grooves
Baek, Moonheum; Kim, Jooha; Choi, Haecheon
2014-11-01
Dimples are known to reduce drag on a sphere by the amount of 50% as compared to a smooth surface. Despite the advantage of reducing drag, dimples deteriorate the putting accuracy owing to their sharp edges. To minimize this putting error but maintain the same flight distance, we have devised a grooved golf ball (called G ball hereafter) for several years. In this study, we modify the shape and pattern of grooves, and investigate the flow characteristics of the G ball by performing wind-tunnel experiments at the Reynolds numbers of 0 . 5 ×105 - 2 . 5 ×105 and the spin ratios (ratio of surface velocity to the free-stream velocity) of 0 - 0.6 that include the real golf-ball velocity and rotational speed. We measure the drag and lift forces on the rotating G ball and compare them with those of a smooth ball and two well-known dimpled balls. The lift-to-drag ratio of the G ball is much higher than that of a smooth ball and is in between those of the two dimpled balls. The trajectories of flying golf balls are computed. The flight distance of G ball is almost the same as that of one dimpled ball but slightly shorter than that of the other dimpled ball. The fluid-dynamic aspects of these differences will be discussed at the talk. Supported by 2011-0028032, 2014M3C1B1033980.
Having a Ball with Fitness Balls
McNulty, Betty
2011-01-01
Fitness programs can be greatly enhanced with the addition of fitness balls. They are a fun, challenging, economical, and safe way to incorporate a cardiovascular, strength, and stretching program for all fitness levels in a physical education setting. The use of these balls has become more popular during the last decade, and their benefits and…
Fischer, Richard B.
1974-01-01
The paper presents a generalized life history of the goldenrod ball gall, a ball-shaped swelling found almost exclusively on the Canada goldenrod, Solidago canadensis, and caused by a peacock fly know as Eurosta soldiaginis. (KM)
Energy Technology Data Exchange (ETDEWEB)
Smith, Maurice
2011-12-15
In the oil and gas industry, the implementation of fracture systems using ball and seat technology helped make multistage fracturing possible. However, frac balls can obstruct later production flow by staying in the well. Baker Hughes Inc. developed a technology to solve this problem: IN-Tallic frac balls. The unique feature of these frac balls is that they are made of an electrolytic metallic nanostructured material which is light and strong and which melts away with salt water or brine through a decomposition process governed by electrochemical reactions controlled by nanoscale coatings. These balls need to be kept away from moisture in order to prevent degradation. This technology is more expensive than traditional frac balls but it prevents the need to mill out obstructions created by the balls. The IN-Tallic frac balls are a new technology which provides operators with peace of mind.
International Nuclear Information System (INIS)
Ozawa, Masanao
2006-01-01
The notion of perfect correlations between arbitrary observables, or more generally arbitrary POVMs, is introduced in the standard formulation of quantum mechanics, and characterized by several well-established statistical conditions. The transitivity of perfect correlations is proved to generally hold, and applied to a simple articulation for the failure of Hardy's nonlocality proof for maximally entangled states. The notion of perfect correlations between observables and POVMs is used for defining the notion of a precise measurement of a given observable in a given state. A longstanding misconception on the correlation made by the measuring interaction is resolved in the light of the new theory of quantum perfect correlations
Ball Screw Actuator Including a Compliant Ball Screw Stop
Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)
2017-01-01
An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.
Directory of Open Access Journals (Sweden)
Jacek NOWICKI
2008-05-01
Full Text Available The behaviour of weaners after mixing housed in pens equipped with hanging wooden ball, aromatized with vanilla fluid hanging wooden ball and without enrichment was evaluated. It was found that both enrichments reduced aggression, however the most interesting for weaners was the aromatized wooden ball.
Two balls and a string: from ordered motion to chaos
International Nuclear Information System (INIS)
Sacks, William; Mauger, Alain
2013-01-01
Two spherical balls are connected by a taught string passing through a small hole in a perfectly planar table: the first ball, subject to a central force, moves without friction on a two-dimensional plane, while the second ball moves only along the vertical axis directly below the hole. The pedagogical aspects of this novel two-body problem are given particular attention: Newton’s laws, central force motion, conservation laws, angular momentum, constraints, etc. The dynamics of the system is considered under various initial conditions wherein the ball on the table moves qualitatively in rotating ellipses or hypotrochoids. The conditions for closed or periodic orbits are examined. The more complex case of the inclined plane is then considered, revealing a rich variety of periodic, aperiodic and chaotic solutions as a function of the ball mass ratio and the plane inclination angle. The associated Poincaré phase-space maps are discussed. (paper)
Directory of Open Access Journals (Sweden)
Alexander Yu. Sulimov
2015-01-01
Full Text Available The article is devoted to technique «Perfect demand illusion», which allows to strengthen the competitive advantageof retailers. Also in the paper spells out the golden rules of visual merchandising.The deﬁnition of the method «Demand illusion», formulated the conditions of its functioning, and is determined by the mainhypothesis of the existence of this method.Furthermore, given the deﬁnition of the «Perfect demand illusion», and describes its additional conditions. Also spells out the advantages of the «Perfect demandillusion», before the «Demand illusion».
Everybody's Different Nobody's Perfect
... traten ni qué edad tengan — eso se llama “DISCAPACIDAD.” Some kids have a disability because their muscles ... have one? ¿Conoces a alguien que tenga una discapacidad? ¿Tienes una tú? Everybody’s different, nobody’s perfect. So ...
Bacon, David
2010-01-01
The United States today faces an economic crisis worse than any since the Great Depression of the 1930s. Nowhere is it sharper than in the nation's schools. Last year, California saw a perfect storm of protest in virtually every part of its education system. K-12 teachers built coalitions with parents and students to fight for their jobs and their…
Russo, Ruth
1998-01-01
A chemistry teacher describes the elements of the ideal chemistry textbook. The perfect text is focused and helps students draw a coherent whole out of the myriad fragments of information and interpretation. The text would show chemistry as the central science necessary for understanding other sciences and would also root chemistry firmly in the…
Energy Technology Data Exchange (ETDEWEB)
Bazeia, D., E-mail: bazeia@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, 58051-970 João Pessoa, PB (Brazil); Losano, L.; Marques, M.A. [Departamento de Física, Universidade Federal da Paraíba, 58051-970 João Pessoa, PB (Brazil); Menezes, R. [Departamento de Ciências Exatas, Universidade Federal da Paraíba, 58297-000 Rio Tinto, PB (Brazil); Departamento de Física, Universidade Federal de Campina Grande, 58109-970 Campina Grande, PB (Brazil); Rocha, R. da [Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, 09210-580 Santo André (Brazil)
2016-07-10
In this work we deal with non-topological solutions of the Q-ball type in two space–time dimensions, in models described by a single complex scalar field that engenders global symmetry. The main novelty is the presence of stable Q-balls solutions that live in a compact interval of the real line and appear from a family of models controlled by two distinct parameters. We find analytical solutions and study their charge and energy, and show how to control the parameters to make the Q-balls classically and quantum mechanically stable.
Casimir Energies for Isorefractive or Diaphanous Balls
Directory of Open Access Journals (Sweden)
Kimball A. Milton
2018-03-01
Full Text Available It is known that the Casimir self-energy of a homogeneous dielectric ball is divergent, although a finite self-energy can be extracted through second order in the deviation of the permittivity from the vacuum value. The exception occurs when the speed of light inside the spherical boundary is the same as that outside, so the self-energy of a perfectly conducting spherical shell is finite, as is the energy of a dielectric-diamagnetic sphere with ε μ = 1 , a so-called isorefractive or diaphanous ball. Here we re-examine that example and attempt to extend it to an electromagnetic δ -function sphere, where the electric and magnetic couplings are equal and opposite. Unfortunately, although the energy expression is superficially ultraviolet finite, additional divergences appear that render it difficult to extract a meaningful result in general, but some limited results are presented.
CERN Bulletin
2010-01-01
10 November 1972: CERN’s Bent Stumpe places an order for 12 bowling balls for a total cost of 95 US dollars. Although not evident at first sight, he is buying the heart of some of the first tracking devices to be used in the SPS control room. Today, Bent Stumpe’s device would be called a desktop mouse… The first order for 4 bowling balls later changed to 12 balls. The bowling balls became the heart of Bent Stumpe's mouse. Almost 40 years ago, the web, Wikipedia and Google did not exist and it was much more difficult to know whether other people in other parts of the world or even in the same laboratory were facing the same problems or developing the same tools. At that time, Bent Stumpe was an electronics engineer, newly recruited to work on developments for the SPS Central Control room. One of the things his supervisor asked him to build as soon as possible was a device to control a pointer on a screen, also called a tracker ball. The heart of the device was the...
CFD Study of Drag and Lift of Sepak Takraw Ball at Different Face Orientations
Directory of Open Access Journals (Sweden)
Abdul Syakir Abdul Mubin
2015-01-01
Full Text Available There have been a significant number of researches on computational fluid dynamic (CFD analysis of balls used in sports such as golf balls, tennis balls, and soccer balls. Sepak takraw is a high speed court game predominantly played in Southeast Asia using mainly the legs and head. The sepak takraw ball is unique because it is not enclosed and made of woven plastic. Hence a study of its aerodynamicswould give insight into its behaviour under different conditions of play. In this study the dynamics of the fluid around a static sepak takraw ball was investigated at different wind speeds for three different orientations using CFD. It was found that although the drag did not differ very much, increasing the wind velocity causes an increase in drag. The lift coefficientvaries as the velocity increases and does not show a regular pattern. The drag and lift coefficients are influenced by the orientation of the sepak takraw ball.
Thompson, Robert Bruce
2006-01-01
This popular Build-It-Yourself (BIY) PC book covers everything you want to know about building your own system: Planning and picking out the right components, step-by-step instructions for assembling your perfect PC, and an insightful discussion of why you'd want to do it in the first place. Most big brand computers from HP, Dell and others use lower-quality components so they can meet their aggressive pricing targets. But component manufacturers also make high-quality parts that you can either purchase directly, or obtain through distributors and resellers. Consumers and corporations
Perfect imaging without negative refraction
Leonhardt, Ulf
2009-01-01
Perfect imaging has been believed to rely on negative refraction, but here we show that an ordinary positively-refracting optical medium may form perfect images as well. In particular, we establish a mathematical proof that Maxwell's fish eye in two-dimensional integrated optics makes a perfect instrument with a resolution not limited by the wavelength of light. We also show how to modify the fish eye such that perfect imaging devices can be made in practice. Our method of perfect focusing ma...
Laboratory demonstration of ball lightning
International Nuclear Information System (INIS)
Egorov, Anton I; Stepanov, Sergei I; Shabanov, Gennadii D
2004-01-01
A common laboratory facility for creating glowing flying plasmoids akin to a natural ball lightning, allowing a number of experiments to be performed to investigate the main properties of ball lightning, is described. (methodological notes)
Directory of Open Access Journals (Sweden)
Nikitović Aleksandar
2013-01-01
Full Text Available Early Greek ethics embodied in Cretan and Spartan mores, served as a model for Plato`s political theory. Plato theorized the contents of early Greek ethics, aspiring to justify and revitalize the fundamental principles of a traditional view of the world. However, according to Plato`s new insight, deed is further from the truth than a thought i.e. theory. The dorian model had to renounce its position to the perfect prototype of a righteous state, which is a result of the inner logic of philosophical theorizing in early Greek ethics. Prototype and model of philosophical reflection, in comparison to philosophical theory, becomes minor and deficient. Philosophical theorizing of early Greek ethics philosophically formatted Greek heritage, initiating substantial changes to the content of traditional ethics. Replacement of the myth with ontology, as a new foundation of politics, transformed early Greek ethics in various relevant ways. [Projekat Ministarstva nauke Republike Srbije, br. 179049
Moulton, Calum
2014-10-01
Perfect pitch, or absolute pitch (AP), is defined as the ability to identify or produce the pitch of a sound without need for a reference pitch, and is generally regarded as a valuable asset to the musician. However, there has been no recent review of the literature examining its aetiology and its utility taking into account emerging scientific advances in AP research, notably in functional imaging. This review analyses the key empirical research on AP, focusing on genetic and neuroimaging studies. The review concludes that: AP probably has a genetic predisposition, although this is based on limited evidence; early musical training is almost certainly essential for AP acquisition; and, although there is evidence that it may be relevant to speech processing, AP can interfere with relative pitch, an ability on which humans rely to communicate effectively. The review calls into question the value of AP to musicians and non-musicians alike. © 2014 Royal College of Physicians.
Metamaterials for perfect absorption
Lee, Young Pak; Yoo, Young Joon; Kim, Ki Won
2016-01-01
This book provides a comprehensive overview of the theory and practical development of metamaterial-based perfect absorbers (MMPAs). It begins with a brief history of MMPAs which reviews the various theoretical and experimental milestones in their development. The theoretical background and fundamental working principles of MMPAs are then discussed, providing the necessary background on how MMPAs work and are constructed. There then follows a section describing how different MMPAs are designed and built according to the operating frequency of the electromagnetic wave, and how their behavior is changed. Methods of fabricating and characterizing MMPAs are then presented. The book elaborates on the performance and characteristics of MMPAs, including electromagnetically-induced transparency (EIT). It also covers recent advances in MMPAs and their applications, including multi-band, broadband, tunability, polarization independence and incidence independence. Suitable for graduate students in optical sciences and e...
Supermassive dark-matter Q-balls in galactic centers?
Energy Technology Data Exchange (ETDEWEB)
Troitsky, Sergey [Institute for Nuclear Research of the Russian Academy of Sciences,60th October Anniversary Prospect 7a, Moscow 117312 (Russian Federation); Moscow Institute for Physics and Technology,Institutskii per. 9, 141700, Dolgoprudny, Moscow Region (Russian Federation)
2016-11-11
Though widely accepted, it is not proven that supermassive compact objects (SMCOs) residing in galactic centers are black holes. In particular, the Milky Way’s SMCO can be a giant nontopological soliton, Q-ball, made of a scalar field: this fits perfectly all observational data. Similar but tiny Q-balls produced in the early Universe may constitute, partly or fully, the dark matter. This picture explains in a natural way, why our SMCO has very low accretion rate and why the observed angular size of the corresponding radio source is much smaller than expected. Interactions between dark-matter Q-balls may explain how SMCOs were seeded in galaxies and resolve well-known problems of standard (non-interacting) dark matter.
Perfect simulation of Hawkes processes
DEFF Research Database (Denmark)
Møller, Jesper; Rasmussen, Jakob Gulddahl
This article concerns a perfect simulation algorithm for unmarked and marked Hawkes processes. The usual stratihtforward simulation algorithm suffers from edge effects, whereas our perfect simulation algorithm does not. By viewing Hawkes processes as Poisson cluster processes and using...... their branching and conditional independence structure, useful approximations of the distribution function for the length of a cluster are derived. This is used to construct upper and lower processes for the perfect simulation algorithm. Examples of applications and empirical results are presented....
Perfect simulation of Hawkes processes
DEFF Research Database (Denmark)
Møller, Jesper; Rasmussen, Jakob Gulddahl
2005-01-01
Our objective is to construct a perfect simulation algorithm for unmarked and marked Hawkes processes. The usual straightforward simulation algorithm suffers from edge effects, whereas our perfect simulation algorithm does not. By viewing Hawkes processes as Poisson cluster processes and using...... their branching and conditional independence structures, useful approximations of the distribution function for the length of a cluster are derived. This is used to construct upper and lower processes for the perfect simulation algorithm. A tail-lightness condition turns out to be of importance...... for the applicability of the perfect simulation algorithm. Examples of applications and empirical results are presented....
Frictional performance of ball screw
International Nuclear Information System (INIS)
Nakashima, Katuhiro; Takafuji, Kazuki
1985-01-01
As feed screws, ball screws have become to be adopted in place of trapezoidal threads. The structure of ball screws is complex, but those are the indispensable component of NC machine tools and machining centers, and are frequently used for industrial robots. As the problems in the operation of ball screws, there are damage, life and the performance related to friction. As to the damage and life, though there is the problem of the load distribution on balls, the results of the research on rolling bearings are applied. The friction of ball screws consists of the friction of balls and a spiral groove, the friction of a ball and a ball, the friction in a ball-circulating mechanism and the viscous friction of lubricating oil. It was decided to synthetically examine the frictional performance of ball screws, such as driving torque, the variation of driving torque, efficiency, the formation of oil film and so on, under the working condition of wide range, using the screws with different accuracy and the nuts of various circuit number. The experimental setup and the processing of the experimental data, the driving performance of ball screws and so on are reported. (Kako, I.)
International Nuclear Information System (INIS)
Bevilacqua, F.
1978-01-01
A pressurized nuclear reactor having an instrument assembly sheathed in a metallic tube which is extended vertically upward into the reactor core by traversing a metallic guide tube which is welded to the wall of the vessel is described. Sensors in each instrument assembly are connected to instruments outside the vessel to manifest the conditions within the core. Each instrument assembly probe is moved into position within a metallic guide channel. The guide channel penetrates the wall of the vessel and forms part of the barrier to the environment within the pressure vessel. Each channel includes a ball check valve which is opened by the instrument assembly probe when the probe passes through the valve. A ball valve element is moved from its seat by the probe to a position lateral of the bore of the channel and is guided to its seat along a sloped path within the valve body when the probe is removed. 5 claims, 3 figures
Directory of Open Access Journals (Sweden)
BONET Maria Angeles
2014-05-01
Full Text Available Posidonia Oceanic is a seaweed from Mediterranean Sea and it is more concentrated at the Balerian SEA. This implies the Valencian Community also. It forms vaste underwater meadows in the sea and are part of the Mediterranean ecosystem. It is a sea-grass specie with fruits and flowers. Leaves are ribbon-like and they grow in winter and at the end of summer some of them are separated and arrive to some sea line. Fuit is separated and can floate, it is known as “the olive of the sea” mainly in Italy, or as the Neptune Balls. As it can be used in different fields, it is is being studied in order ro have the precitice tests. Some authors have reported the manufacturing of fully bio-based comites with a gluten matrix by hot-press molding. And it has been considered as an effective insulator for building industry or even though to determine the presence of mercure in the Mediterranean sea some years ago. As many applications can be designed from that fibers, it has been considered to be bleached in order to used them in fashionable products. Consequently, its original brown color is not the most suitable one and it should be bleached as many other cellulosic fibers. The aim of this paper is to bleache neptune balls however, the inner fibers were not accessible at all and it implied not to bleach the inner fibers in the neptune ball. Further studiesd will consider bleaching the individualized fibers.
A note on perfect scalar fields
International Nuclear Information System (INIS)
Unnikrishnan, Sanil; Sriramkumar, L.
2010-01-01
We derive a condition on the Lagrangian density describing a generic, single, noncanonical scalar field, by demanding that the intrinsic, nonadiabatic pressure perturbation associated with the scalar field vanishes identically. Based on the analogy with perfect fluids, we refer to such fields as perfect scalar fields. It is common knowledge that models that depend only on the kinetic energy of the scalar field (often referred to as pure kinetic models) possess no nonadiabatic pressure perturbation. While we are able to construct models that seemingly depend on the scalar field and also do not contain any nonadiabatic pressure perturbation, we find that all such models that we construct allow a redefinition of the field under which they reduce to pure kinetic models. We show that, if a perfect scalar field drives inflation, then, in such situations, the first slow roll parameter will always be a monotonically decreasing function of time. We point out that this behavior implies that these scalar fields cannot lead to features in the inflationary, scalar perturbation spectrum.
Liang, Shiuan-Ni; Lan, Boon Leong
The dynamics of a bouncing ball undergoing repeated inelastic impacts with a table oscillating vertically in a sinusoidal fashion is studied using Newtonian mechanics and general relativistic mechanics. An exact mapping describes the bouncing ball dynamics in each theory. We show, contrary to expectation, that the trajectories predicted by Newtonian mechanics and general relativistic mechanics from the same parameters and initial conditions for the ball bouncing at low speed in a weak gravitational field can rapidly disagree completely. The bouncing ball system could be realized experimentally to test which of the two different predicted trajectories is correct.
Individual ball possession in soccer.
Directory of Open Access Journals (Sweden)
Daniel Link
Full Text Available This paper describes models for detecting individual and team ball possession in soccer based on position data. The types of ball possession are classified as Individual Ball Possession (IBC, Individual Ball Action (IBA, Individual Ball Control (IBC, Team Ball Possession (TBP, Team Ball Control (TBC und Team Playmaking (TPM according to different starting points and endpoints and the type of ball control involved. The machine learning approach used is able to determine how long the ball spends in the sphere of influence of a player based on the distance between the players and the ball together with their direction of motion, speed and the acceleration of the ball. The degree of ball control exhibited during this phase is classified based on the spatio-temporal configuration of the player controlling the ball, the ball itself and opposing players using a Bayesian network. The evaluation and application of this approach uses data from 60 matches in the German Bundesliga season of 2013/14, including 69,667 IBA intervals. The identification rate was F = .88 for IBA and F = .83 for IBP, and the classification rate for IBC was κ = .67. Match analysis showed the following mean values per match: TBP 56:04 ± 5:12 min, TPM 50:01 ± 7:05 min and TBC 17:49 ± 8:13 min. There were 836 ± 424 IBC intervals per match and their number was significantly reduced by -5.1% from the 1st to 2nd half. The analysis of ball possession at the player level indicates shortest accumulated IBC times for the central forwards (0:49 ± 0:43 min and the longest for goalkeepers (1:38 ± 0:58 min, central defenders (1:38 ± 1:09 min and central midfielders (1:27 ± 1:08 min. The results could improve performance analysis in soccer, help to detect match events automatically, and allow discernment of higher value tactical structures, which is based on individual ball possession.
Ovarian cystic teratoma containing balls of fat. A case report
International Nuclear Information System (INIS)
Salinas, A.; Rebolledo, M.; Escribano, M.; Alejo, J. P.; Morenom, J.
1998-01-01
We present the case of a ovarian cystic teratoma characterized predominantly by the mobile balls floating in the intra cystic fluid. Ultrasonography demonstrated their marked echo reflectivity and computed tomography revealed that they had the density of fat. We establish a relationship among the ultrasound, computed tomography and histological findings in this uncommon type of ovarian cystic teratoma. (Author) 6 refs
Experimental research on ball lightning
International Nuclear Information System (INIS)
Ofuruton, H.; Ohtsuki, Y.H.
1990-01-01
Experiments on producing ball lightning were made with discharge in flammable gas and/or aerosol. A long lifetime (2 s) ball lightning was observed in 2.7 % ethane and 100 cm 3 cotton fibers, and in 1.5 % methane and 1.9 % ethane
International Nuclear Information System (INIS)
Bartel, W.; Bulos, F.; Luke, D.; Peck, C.; Strauch, K.
1975-01-01
The modifications to the SPEAR version of the Crystal Ball required by the higher energies at PEP are discussed. Since the hadron multiplicity is expected to rise as log s, their average energy must rise. On the other hand, if the hadrons are produced in jets, the low energy part of their spectrum is not heavily depleted. This implies that modifications for high energy particles should not deteriorate low energy performance. An external iron calorimeter for measuring the high energy hadrons, charged and neutral, is considered. To improve the angular resolution on γ's, an active internal converter has been studied, estimates have been made of its expected performance, and difficulties requiring further study have been outlined
Holographic perfect fluidity, Cotton energy-momentum duality and transport properties
Energy Technology Data Exchange (ETDEWEB)
Mukhopadhyay, Ayan [Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644,Route de Saclay, 91128 Palaiseau Cedex (France); Institut de Physique Théorique, CEA, CNRS URA 2306,91191 Gif-sur-Yvette (France); Petkou, Anastasios C. [Institute of Theoretical Physics, Department of Physics, Aristotle University of Thessaloniki,54124 Thessaloniki (Greece); Petropoulos, P. Marios; Pozzoli, Valentina [Centre de Physique Théorique, Ecole Polytechnique, CNRS UMR 7644,Route de Saclay, 91128 Palaiseau Cedex (France); Siampos, Konstadinos [Service de Mécanique et Gravitation, Université de Mons, UMONS,20 Place du Parc, 7000 Mons (Belgium)
2014-04-23
We investigate background metrics for 2+1-dimensional holographic theories where the equilibrium solution behaves as a perfect fluid, and admits thus a thermodynamic description. We introduce stationary perfect-Cotton geometries, where the Cotton-York tensor takes the form of the energy-momentum tensor of a perfect fluid, i.e. they are of Petrov type D{sub t}. Fluids in equilibrium in such boundary geometries have non-trivial vorticity. The corresponding bulk can be exactly reconstructed to obtain 3+1-dimensional stationary black-hole solutions with no naked singularities for appropriate values of the black-hole mass. It follows that an infinite number of transport coefficients vanish for holographic fluids. Our results imply an intimate relationship between black-hole uniqueness and holographic perfect equilibrium. They also point towards a Cotton/energy-momentum tensor duality constraining the fluid vorticity, as an intriguing boundary manifestation of the bulk mass/nut duality.
Holographic perfect fluidity, Cotton energy-momentum duality and transport properties
International Nuclear Information System (INIS)
Mukhopadhyay, Ayan; Petkou, Anastasios C.; Petropoulos, P. Marios; Pozzoli, Valentina; Siampos, Konstadinos
2014-01-01
We investigate background metrics for 2+1-dimensional holographic theories where the equilibrium solution behaves as a perfect fluid, and admits thus a thermodynamic description. We introduce stationary perfect-Cotton geometries, where the Cotton-York tensor takes the form of the energy-momentum tensor of a perfect fluid, i.e. they are of Petrov type D t . Fluids in equilibrium in such boundary geometries have non-trivial vorticity. The corresponding bulk can be exactly reconstructed to obtain 3+1-dimensional stationary black-hole solutions with no naked singularities for appropriate values of the black-hole mass. It follows that an infinite number of transport coefficients vanish for holographic fluids. Our results imply an intimate relationship between black-hole uniqueness and holographic perfect equilibrium. They also point towards a Cotton/energy-momentum tensor duality constraining the fluid vorticity, as an intriguing boundary manifestation of the bulk mass/nut duality
Perfect secure domination in graphs
Directory of Open Access Journals (Sweden)
S.V. Divya Rashmi
2017-07-01
Full Text Available Let $G=(V,E$ be a graph. A subset $S$ of $V$ is a dominating set of $G$ if every vertex in $Vsetminus S$ is adjacent to a vertex in $S.$ A dominating set $S$ is called a secure dominating set if for each $vin Vsetminus S$ there exists $uin S$ such that $v$ is adjacent to $u$ and $S_1=(Ssetminus{u}cup {v}$ is a dominating set. If further the vertex $uin S$ is unique, then $S$ is called a perfect secure dominating set. The minimum cardinality of a perfect secure dominating set of $G$ is called the perfect secure domination number of $G$ and is denoted by $gamma_{ps}(G.$ In this paper we initiate a study of this parameter and present several basic results.
Bradas, James C.; Fennelly, Alphonsus J.; Smalley, Larry L.
1987-01-01
It is shown that a generalized (or 'power law') inflationary phase arises naturally and inevitably in a simple (Bianchi type-I) anisotropic cosmological model in the self-consistent Einstein-Cartan gravitation theory with the improved stress-energy-momentum tensor with the spin density of Ray and Smalley (1982, 1983). This is made explicit by an analytical solution of the field equations of motion of the fluid variables. The inflation is caused by the angular kinetic energy density due to spin. The model further elucidates the relationship between fluid vorticity, the angular velocity of the inertially dragged tetrads, and the precession of the principal axes of the shear ellipsoid. Shear is not effective in damping the inflation.
2007-01-01
A technique involving a small ball with a transmitter embedded inside it has been successfully tested in Sector 7-8. The ball is sent through the LHC beam pipes to check the LHC interconnections. The multidisciplinary team responsible for the RF ball project to check the interconnections. From left to right: Rhodri Jones (AB/BI), Eva Calvo (AB/BI), Francesco Bertinelli (AT/MCS), Sonia Bartolome Jimenez (TS/IC), Sylvain Weisz (TS/IC), Paul Cruikshank (AT/VAC), Willemjan Maan (AT/VAC), Alain Poncet (AT/MCS), Marek Gasior (AB/BI). During the tests the ball is inserted very carefully into the vacuum chamber.A game of ping-pong at the LHC? On 13 September a rather unusual test was carried out in Sector 7-8 of the accelerator. A ball just a bit smaller than a ping-pong ball was carefully introduced into one of the accelerator’s two vacuum pipes, where it travelled 800 metres in the space of a few mi...
Acquisition and reduction of data obtained from tank 101-SY in-situ ball rheometer
International Nuclear Information System (INIS)
Shepard, C.L.; Chieda, M.A.; Kirihara, L.J.; Phillips, J.R.; Shekarriz, A.; Terrones, G.; Abbott, J.; Unal, C.; Pasamehmetoglu, K.O.; Graham, A.
1995-02-01
Development of the ball rheometer to measure rheological properties and density of the waste in Hanford Tank 241-SY-101 will be completed around September 1994. This instrument is expected to provide the first-of-its-kind in-situ measurements of the fluid properties of the waste contained within this tank. A mixer pump has been installed in this tank, and this pump has been very successful at mitigating the flammable gas problem associated with Tank 101-SY. The ball rheometer will serve as a diagnostic tool for judging the effectiveness of mixing in Tank 101-SY and others and will be one of few in-situ probes available for diagnostic measurements. Based on experiments performed at Los Alamos National Laboratory and Pacific Northwest Laboratory, it is believed that a generalized Bingham fluid model (Herschel-Bulkley fluid model) may be useful for describing at least some of the waste contained in Tank 101-SY, and data obtained in the tank will initially be reduced using this fluid model. The single largest uncertainty in the determination of the drag force on the ball is the drag force which will be experienced by the cable attached to the ball. This drag can be a substantial fraction of the total drag when the ball is deep within the tank. It is expected that the fluid properties may be history dependent, thus rheological properties of the undisturbed fluid may be different from the same properties after the fluid has been disturbed by passage of the ball. The data collection strategy allows the determination of the waste fluid rheology both in the undisturbed state and after it has been disturbed by the ball. Unlike the rheological parameters, measurement of density requires no model for its interpretation; however, the effects of yield stress may need to be accounted for. This measurement can be made with fairly good accuracy and may provide the most useful data in determination of mixer pump effectiveness
Perfect sequences over the real quaternions
Kuznetsov, Oleg
2017-01-01
In this Thesis, perfect sequences over the real quaternions are first considered. Definitions for the right and left periodic autocorrelation functions are given, and right and left perfect sequences introduced. It is shown that the right (left) perfection of any sequence implies the left (right) perfection, so concepts of right and left perfect sequences over the real quaternions are equivalent. Unitary transformations of the quaternion space ℍ are then considered. Using the equivalence of t...
Relativistic fluids in spherically symmetric space
International Nuclear Information System (INIS)
Dipankar, R.
1977-12-01
Some of McVittie and Wiltshire's (1977) solutions of Walker's (1935) isotropy conditions for relativistic perfect fluid spheres are generalized. Solutions are spherically symmetric and conformally flat
Visible light broadband perfect absorbers
Energy Technology Data Exchange (ETDEWEB)
Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O., E-mail: wxo@hit.edu.cn [School of Science, Harbin Institute of Technology, Harbin 150001 (China)
2016-03-15
The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.
Perfect Liberty or Natural Liberty?
DEFF Research Database (Denmark)
Jacobsen, Stefan Gaarsmand
2012-01-01
The article investigates the concept of natural order as it is used by François Quesnay and Adam Smith in their respective economic writings. While Smith used the concept only after having visited Quesnay and the Physiocrats in France in the 1760s, in The Wealth of Nations he sought to negotiate...... the meaning of what was “natural” about economic life. The Physiocrats believed it possible to identify a model or a perfect regime of natural order – an order that they in fact thought to exist and function in China due to a rigorous system of economic laws. Smith sided with contemporary critics...... of this metaphysical vision of economic perfection (and of Chinese governance), but he suggested that the economic mechanisms of the physiocratic theories would remain intact even with a minimum of control by state laws. However, Smith’s balancing act on these questions remained disputed even by his Scottish...
Looking beyond the perfect lens
International Nuclear Information System (INIS)
Wee, W H; Pendry, J B
2010-01-01
The holy grail of imaging is the ability to see through anything. From the conservation of energy, we can easily see that to see through a lossy material would require lenses with gain. The aim of this paper therefore is to propose a simple scheme by which we can construct a general perfect lens, with gain-one that can restore both the phases and amplitudes of near and far fields.
International Nuclear Information System (INIS)
Diamond, R.M.
1984-10-01
Criteria for a high-resolution γ-ray system are discussed. Desirable properties are high resolution, good response function, and moderate solid angle so as to achieve not only double- but triple-coincidences with good statistics. The Berkeley High-Resolution Ball involved the first use of bismuth germanate (BGO) for anti-Compton shield for Ge detectors. The resulting compact shield permitted rather close packing of 21 detectors around a target. In addition, a small central BGO ball gives the total γ-ray energy and multiplicity, as well as the angular pattern of the γ rays. The 21-detector array is nearly complete, and the central ball has been designed, but not yet constructed. First results taken with 9 detector modules are shown for the nucleus 156 Er. The complex decay scheme indicates a transition from collective rotation (prolate shape) to single- particle states (possibly oblate) near spin 30 h, and has other interesting features
Critical phenomena at perfect and non-perfect surfaces
International Nuclear Information System (INIS)
Pleimling, M
2004-01-01
In the past, perfect surfaces have been shown to yield local critical behaviour that differs from bulk critical behaviour. On the other hand, surface defects, whether they are of natural origin or created artificially, are known to modify local quantities. It is therefore important to clarify whether these defects are relevant or irrelevant for the surface critical behaviour. The purpose of this review is two-fold. In the first part we summarize some of the important results on surface criticality at perfect surfaces. Special attention is thereby paid to new developments such as for example the study of the surface critical behaviour in systems with competing interactions or of surface critical dynamics. In the second part the effect of surface defects (presence of edges, steps, quenched randomness, lines of adatoms, regular geometric patterns) on local critical behaviour in semi-infinite systems and in thin films is discussed in detail. Whereas most of the defects commonly encountered are shown to be irrelevant, some notable exceptions are highlighted. It is shown furthermore that under certain circumstances non-universal local critical behaviour may be observed at surfaces. (topical review)
2007-01-01
1. The multidisciplinary team responsible for the RF ball project to check the interconnections. From left to right: Rhodri Jones (AB/BI), Eva Calvo (AB/BI), Francesco Bertinelli (AT/MCS), Sonia Bartolome Jimenez (TS/IC), Sylvain Weisz (TS/IC), Paul Cruikshank (AT/VAC), Willemjan Maan (AT/VAC), Alain Poncet (AT/MCS), Marek Gasior (AB/BI).2. During the tests the ball is inserted very carefully into the vacuum chamber.1. Le groupe pluridisciplinaire qui a mené le projet de balle RF pour vérifier les interconnexions avec, de gauche à droite, Rhodri Jones (AB/BI), Eva Calvo (AB/BI), Francesco Bertinelli (AT/MCS), Sonia Bartolome Jimenez (TS/IC), Sylvain Weisz (TS/IC), Paul Cruikshank (AT/VAC), Willemjan Maan (AT/VAC), Alain Poncet (AT/MCS) et Marek Gasior (AB/BI).2. Lors des tests, la balle est insérée dans la chambre à vide avec beaucoup de précaution.
The correct "ball bearings" data.
Caroni, C
2002-12-01
The famous data on fatigue failure times of ball bearings have been quoted incorrectly from Lieblein and Zelen's original paper. The correct data include censored values, as well as non-fatigue failures that must be handled appropriately. They could be described by a mixture of Weibull distributions, corresponding to different modes of failure.
Ribeiro, Jair Lúcio Prados
2016-01-01
A disco ball is a spherical object covered with small plane mirrors. When light reflects on these mirrors, it is scattered in many directions, producing a novel effect. The mirror globe is usually set to rotate, creating a profusion of moving spots (Fig. 1). In this article, we present a geometrical description of the movement of these spots and…
Encapsulated Ball Bearings for Rotary Micro Machines
2007-01-01
occurrence as well as the overall tribological properties of the bearing mechanism. Firstly, the number of stainless steel balls influences not only the load...stacks.iop.org/JMM/17/S224 Abstract We report on the first encapsulated rotary ball bearing mechanism using silicon microfabrication and stainless steel balls...The method of capturing stainless steel balls within a silicon race to support a silicon rotor both axially and radially is developed for rotary micro
2012 Problem 15: Frustrating Golf Ball
Huang, Shan; Zhu, Zheyuan; Gao, Wenli; Wang, Sihui
2015-10-01
This paper studies the condition for a golf ball to escape from a hole. The two determining factors are the ball's initial velocity v0 and its deviation from the center of the hole d. There is a critical escaping velocity vc for every deviation d. The ball's motion is analyzed by calculating the change of velocity whenever the ball collides with the hole. The critical conditions predicted by our theory are verified through experiment.
Acquisition and reduction of data obtained from Tank 101-SY in-situ ball rheometer
International Nuclear Information System (INIS)
Shepard, C.L.; Chieda, M.A.; Kirihara, L.J.
1994-12-01
Development of the ball rheometer to measure rheological properties and density of the waste in Hanford Tank 241-SY-101 will be completed around September 1994. Since the ball rheometer project began, a mixer pump has been installed in this tank, and by all accounts this pump has been very successful at mitigating the flammable gas problem associated with Tank 101-SY. Present plans now call for the use of mixer pumps in several other tanks. The ball rheometer will serve as a diagnostic tool for judging the effectiveness of mixing in Tank 101-SY and others and will be one of few in-situ probes available for diagnostic measurements. The in-situ data collection strategy and the methods of data analysis and reduction are presented in this final report concerning this instrument. It is believed that a generalized Bingham fluid model (Herschel-Bulkley fluid model) may be useful for describing at least some of the waste contained in Tank 101-SY, and data obtained in the tank will initially be reduced using this fluid model. The single largest uncertainty in the determination of the drag force on the ball is the drag force which will be experienced by the cable attached to the ball. This drag can be a substantial fraction of the total drag when the ball is deep within the tank. Careful accounting of the cable drag will be important in the reduction of the data. The data collection strategy allows the determination of the waste fluid rheology both in the undisturbed state and after it has been disturbed by the ball. Fluid density will be measured at regular intervals
Ceramic ball grid array package stress analysis
Badri, S. H. B. S.; Aziz, M. H. A.; Ong, N. R.; Sauli, Z.; Alcain, J. B.; Retnasamy, V.
2017-09-01
The ball grid array (BGA), a form of chip scale package (CSP), was developed as one of the most advanced surface mount devices, which may be assembled by an ordinary surface ball bumps are used instead of plated nickel and gold (Ni/Au) bumps. Assembly and reliability of the BGA's printed circuit board (PCB), which is soldered by conventional surface mount technology is considered in this study. The Ceramic Ball Grid Array (CBGA) is a rectangular ceramic package or square-shaped that will use the solder ball for external electrical connections instead of leads or wire for connections. The solder balls will be arranged in an array or grid at the bottom of the ceramic package body. In this study, ANSYS software is used to investigate the stress on the package for 2 balls and 4 balls of the CBGA package with the various force range of 1-3 Newton applied to the top of the die, top of the substrate and side of the substrate. The highest maximum stress was analyzed and the maximum equivalent stress was observed on the solder ball and the die. From the simulation result, the CBGA package with less solder balls experience higher stress compared to the package with many solder balls. Therefore, less number of solder ball on the CBGA package results higher stress and critically affect the reliability of the solder balls itself, substrate and die which can lead to the solder crack and also die crack.
Supersymmetric Q-balls theory and cosmology
Kusenko, A
1999-01-01
MSSM predicts the existence of Q-balls, some of which can be entirely stable. Both stable and unstable Q-balls can play an important role in cosmology. In particular, Affleck-Dine baryogenesis can result in a copious production of stable baryonic Q-balls, which can presently exist as a form of dark matter.
Breast milk is conditionally perfect.
Erick, Miriam
2018-02-01
Breast milk is the universal preferred nutrition for the newborn human infant. New mother have been encouraged to exclusively breastfeed by health care professionals and consumer-advocacy forums for years, citing "breast milk is the perfect food". The benefits are numerous and include psychological, convenience, economical, ecological and nutritionally superior. Human milk is a composite of nutritional choices of the mother, commencing in the pre-conceptual era. Events influencing the eventual nutritional profile of breast milk for the neonate start with pre-conceptual dietary habits through pregnancy and finally to postpartum. Food choices do affect the nutritional profile of human breast milk. It is not known who coined the phrase "breast milk is the perfect food" but it is widely prevalent in the literature. While breast milk is highly nutritive, containing important immunological and growth factors, scientific investigation reveals a few short-falls. Overall, human breast milk has been found to be low in certain nutrients in developed countries: vitamin D, iodine, iron, and vitamin K. Additional nutrient deficiencies have been documented in resource-poor countries: vitamin A, vitamin B 12, zinc, and vitamin B 1/thiamin. Given these findings, isn't it more accurate to describe breast milk as "conditionally perfect"? Correcting the impression that breast milk is an inherently, automatically comprehensive enriched product would encourage women who plan to breastfeed an opportunity to concentrate on dietary improvement to optimizes nutrient benefits ultimately to the neonate. The more immediate result would improve pre-conceptual nutritional status. Here, we explore the nutritional status of groups of young women; some of whom will become pregnant and eventually produce breast milk. We will review the available literature profiling vitamin, mineral, protein and caloric content of breast milk. We highlight pre-existing situations needing correction to optimize
The pursuit of perfect packing
Weaire, Denis
2008-01-01
Coauthored by one of the creators of the most efficient space packing solution, the Weaire-Phelan structure, The Pursuit of Perfect Packing, Second Edition explores a problem of importance in physics, mathematics, chemistry, biology, and engineering: the packing of structures. Maintaining its mathematical core, this edition continues and revises some of the stories from its predecessor while adding several new examples and applications. The book focuses on both scientific and everyday problems ranging from atoms to honeycombs. It describes packing models, such as the Kepler conjecture, Voronoï decomposition, and Delaunay decomposition, as well as actual structure models, such as the Kelvin cell and the Weaire-Phelan structure. The authors discuss numerous historical aspects and provide biographical details on influential contributors to the field, including emails from Thomas Hales and Ken Brakke. With examples from physics, crystallography, engineering, and biology, this accessible and whimsical bo...
The pursuit of perfect packing
Weaire, Denis
2000-01-01
In 1998 Thomas Hales dramatically announced the solution of a problem that has long teased eminent mathematicians: what is the densest possible arrangement of identical spheres? The Pursuit of Perfect Packing recounts the story of this problem and many others that have to do with packing things together. The examples are taken from mathematics, physics, biology, and engineering, including the arrangement of soap bubbles in foam, atoms in a crystal, the architecture of the bee''s honeycomb, and the structure of the Giant''s Causeway. Using an informal style and with key references, the book also includes brief accounts of the lives of many of the scientists who devoted themselves to problems of packing over many centuries, together with wry comments on their efforts. It is an entertaining introduction to the field for both specialists and the more general public.
The swimming of a perfect deforming helix
Koens, Lyndon; Zhang, Hang; Mourran, Ahmed; Lauga, Eric
2017-11-01
Many bacteria rotate helical flagellar filaments in order to swim. When at rest or rotated counter-clockwise these flagella are left handed helices but they undergo polymorphic transformations to right-handed helices when the motor is reversed. These helical deformations themselves can generate motion, with for example Rhodobacter sphaeroides using the polymorphic transformation of the flagellum to generate rotation, or Spiroplasma propagating a change of helix handedness across its body's length to generate forward motion. Recent experiments reported on an artificial helical microswimmer generating motion without a propagating change in handedness. Made of a temperature sensitive gel, these swimmers moved by changing the dimensions of the helix in a non-reciprocal way. Inspired by these results and helix's ubiquitous presence in the bacterial world, we investigate how a deforming helix moves within a viscous fluid. Maintaining a single handedness along its entire length, we discuss how a perfect deforming helix can create a non-reciprocal swimming stroke, identify its principle directions of motion, and calculate the swimming kinematics asymptotically.
Ball mounting fixture for a roundness gage
Gauler, Allen L.; Pasieka, Donald F.
1983-01-01
A ball mounting fixture for a roundness gage is disclosed. The fixture includes a pair of chuck assemblies oriented substantially transversely with respect to one another and mounted on a common base. Each chuck assembly preferably includes a rotary stage and a wobble plate affixed thereto. A ball chuck affixed to each wobble plate is operable to selectively support a ball to be measured for roundness, with the wobble plate permitting the ball chuck to be tilted to center the ball on the axis of rotation of the rotary stage. In a preferred embodiment, each chuck assembly includes a vacuum chuck operable to selectively support the ball to be measured for roundness. The mounting fixture enables a series of roundness measurements to be taken with a conventional rotating gagehead roundness instrument, which measurements can be utilized to determine the sphericity of the ball.
Ceramic Rail-Race Ball Bearings
Balzer, Mark A.; Mungas, Greg S.; Peters, Gregory H.
2010-01-01
Non-lubricated ball bearings featuring rail races have been proposed for use in mechanisms that are required to function in the presence of mineral dust particles in very low-pressure, dry environments with extended life. Like a conventional ball bearing, the proposed bearing would include an inner and an outer ring separated by balls in rolling contact with the races. However, unlike a conventional ball bearing, the balls would not roll in semi-circular or gothic arch race grooves in the rings: instead, the races would be shaped to form two or more rails (see figure). During operation, the motion of the balls would push dust particles into the spaces between the rails where the particles could not generate rolling resistance for the balls
Equilibrium states for a plane incompressible perfect fluid
Energy Technology Data Exchange (ETDEWEB)
Boldrighini, C; Frigio, S [Camerino Univ. (Italy). Istituto di Matematica
1980-01-01
We associate to the plane incompressible Euler equation with periodic conditions the corresponding Hopf equation, as an equation for measures on the space of solenoidal distributions. We define equilibrium states as the solutions of the stationary Hopf equation. We find a class of equilibrium states which corresponds to a class of infinitely divisible distributions, and investigate the properties of gaussian and poissonian states. Equilibrium dynamics for a class of poissonian states is constructed by means of the Onsager vortex equations.
Singularity free non-rotating cosmological solutions for perfect fluids ...
Indian Academy of Sciences (India)
Singularity free cosmological solutions of the type stated in the title known so far are of a very special class and have the following characteristics: (a) The space time is cylindrically symmetric. (b) In case the metric is diagonal, the μ's are of the form μ = a function of time multiplied by a function of the radial coordinate.
Perfect fluid cosmological Universes: One equation of state and the ...
Indian Academy of Sciences (India)
Anadijiban Das
2018-01-04
Jan 4, 2018 ... equation of state, one may calculate the geometric vari- ables, such as the ... connected by any analytic function ψ, the evolutions equations, mainly ... [3] J E Marsden and A J Tromba, Vector calculus, 3rd edn. (W. H. Freeman ...
Relativistic thermodynamics of fluids
International Nuclear Information System (INIS)
Souriau, J.-M.
1977-05-01
The relativistic covariant definition of a statistical equilibrium, applied to a perfect gas, involves a 'temperature four-vector', whose direction is the mean velocity of the fluid, and whose length is the reciprocal temperature. The hypothesis of this 'temperature four-vector' being a relevant variable for the description of the dissipative motions of a simple fluid is discussed. The kinematics is defined by using a vector field and measuring the number of molecules. Such a dissipative fluid is subject to motions involving null entropy generation; the 'temperature four-vector' is then a Killing vector; the equations of motion can be completely integrated. Perfect fluids can be studied by this way and the classical results of Lichnerowicz are obtained. In weakly dissipative motions two viscosity coefficient appear together with the heat conductibility coefficient. Two other coefficients perharps measurable on real fluids. Phase transitions and shock waves are described with using the model [fr
Obsession with perfection: Body dysmorphia.
Vashi, Neelam A
The deeply rooted fascination with beauty penetrates society worldwide. The indulgence to look and feel beautiful pervades all ages, genders, and nationalities, with research conferring a remarkable tendency to agree on measures of attractiveness among these disparate groups. Research has found that beautiful people do, in fact, receive more desirable outcomes in life and job satisfaction, family formation, and overall happiness. Humans have a tendency to respond to attractive persons more favorably, driving many patients to our clinics. Although some dissatisfaction with one's appearance is common and normal, excessive concern with certain facial or body attributes can be sign of an underlying disorder. Body dysmorphic disorder (BDD) is a disorder of self-perception. It is the obsession with perfection. Defined as the impairing preoccupation with a nonexistent or minimal flaw in appearance, BDD affects 0.7-2.4% of the general population and a much larger percentage of those attempting to receive aesthetic treatments. Clinicians should be aware of this disorder and remain vigilant because such patients will not be satisfied with corrective procedures. Although not involving cosmetic intervention, the treatment of BDD does involve psychiatric referral and psychopharmacologic therapy, with patients receiving these having a much better prognosis. Copyright © 2016 Elsevier Inc. All rights reserved.
Ball Screw Actuator Including a Stop with an Integral Guide
Wingett, Paul T. (Inventor); Perek, John (Inventor); Geck, Kellan (Inventor)
2015-01-01
An actuator includes a housing assembly, a ball nut, a ball screw, and a ball screw stop. The ball nut is rotationally mounted in the housing assembly, is adapted to receive an input torque, and is configured, upon receipt thereof, to rotate and supply a drive force. The ball screw is mounted within the housing assembly and extends through the ball nut. The ball screw has a first end and a second end, and is coupled to receive the drive force from the ball nut. The ball screw is configured, upon receipt of the drive force, to selectively translate between a stow position and a deploy position. The ball screw stop is mounted on the ball screw to translate therewith and is configured to at selectively engage the housing assembly while the ball screw is translating, and engage the ball nut when the ball screw is in the deploy position.
Looking for the Perfect Mentor.
Sá, Ana Pinheiro; Teixeira-Pinto, Cristina; Veríssimo, Rafaela; Vilas-Boas, Andreia; Firmino-Machado, João
2015-01-01
The authors established the profile of the Internal Medicine clinical teachers in Portugal aiming to define a future interventional strategy plan as adequate as possible to the target group and to the problems identified by the residents. Observational, transversal, analytic study. An online anonymous questionnaire was defined, evaluating the demographic characteristics of the clinical teachers, their path in Internal Medicine and their involvement in the residents learning process. We collected 213 valid questionnaires, making for an estimated response rate of 28.4%. Median global satisfaction with the clinical teacher was 4.52 (± 1.33 points) and the classification of the relationship between resident and clinical teacher was 4.86 ± 1.04 points. The perfect clinical teacher is defined by high standards of dedication and responsibility (4.9 ± 1.37 points), practical (4.8 ± 1.12 points) and theoretical skills (4.8 ± 1.07 points). The multiple linear regression model allowed to determine predictors of the residentâs satisfaction with their clinical teacher, justifying 82,5% of the variation of satisfaction with the clinical teacher (R2 = 0.83; R2 a = 0.82). Postgraduate medical education consists of an interaction between several areas of knowledge and intervening variables in the learning process having the clinical teacher in the central role. Overall, the pedagogical abilities were the most valued by the Internal Medicine residents regarding their clinical teacher, as determinants of a quality residentship. This study demonstrates the critical relevance of the clinical teacher in the satisfaction of residents with their residentship. The established multiple linear regression model highlights the impact of the clinical and pedagogical relantionship with the clinical teacher in a relevant increase in the satisfaction with the latter.
A new characterization of trivially perfect graphs
Directory of Open Access Journals (Sweden)
Christian Rubio Montiel
2015-03-01
Full Text Available A graph $G$ is \\emph{trivially perfect} if for every induced subgraph the cardinality of the largest set of pairwise nonadjacent vertices (the stability number $\\alpha(G$ equals the number of (maximal cliques $m(G$. We characterize the trivially perfect graphs in terms of vertex-coloring and we extend some definitions to infinite graphs.
Apparatus Would Measure Temperatures Of Ball Bearings
Gibson, John C.; Fredricks, Thomas H.
1995-01-01
Rig for testing ball bearings under radial and axial loads and measuring surface temperatures undergoing development. Includes extensible thermocouples: by means of bellows as longitudinal positioners, thermocouples driven into contact with bearing balls to sense temperatures immediately after test run. Not necessary to disassemble rig or to section balls to obtain indirect indications of maximum temperatures reached. Thermocouple measurements indicate temperatures better than temperature-sensitive paints.
Multifractal properties of ball milling dynamics
Energy Technology Data Exchange (ETDEWEB)
Budroni, M. A., E-mail: mabudroni@uniss.it; Pilosu, V.; Rustici, M. [Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, Via Vienna 2, Sassari 07100 (Italy); Delogu, F. [Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, Cagliari 09123 (Italy)
2014-06-15
This work focuses on the dynamics of a ball inside the reactor of a ball mill. We show that the distribution of collisions at the reactor walls exhibits multifractal properties in a wide region of the parameter space defining the geometrical characteristics of the reactor and the collision elasticity. This feature points to the presence of restricted self-organized zones of the reactor walls where the ball preferentially collides and the mechanical energy is mainly dissipated.
Physical applications of homogeneous balls
Scarr, Tzvi
2005-01-01
One of the mathematical challenges of modern physics lies in the development of new tools to efficiently describe different branches of physics within one mathematical framework. This text introduces precisely such a broad mathematical model, one that gives a clear geometric expression of the symmetry of physical laws and is entirely determined by that symmetry. The first three chapters discuss the occurrence of bounded symmetric domains (BSDs) or homogeneous balls and their algebraic structure in physics. The book further provides a discussion of how to obtain a triple algebraic structure ass
Hossenfelder, Sabine
2014-07-01
The idea that Lorentz-symmetry in momentum space could be modified but still remain observer-independent has received quite some attention in the recent years. This modified Lorentz-symmetry, which has been argued to arise in Loop Quantum Gravity, is being used as a phenomenological model to test possibly observable effects of quantum gravity. The most pressing problem in these models is the treatment of multi-particle states, known as the 'soccer-ball problem'. This article briefly reviews the problem and the status of existing solution attempts.
Crystal ball data acquisition system
International Nuclear Information System (INIS)
Chestnut, R.; Kiesling, C.; Bloom, E.; Bulos, F.; Gaiser, J.; Godfrey, G.; Oreglia, M.; Partridge, R.; Peck, C.; Porter, F.; Aschman, D.; Cavali-Sforza, M.; Coyne, D.; Sadrozinski, H.; Kollmann, W.; Richardson, M.
1979-01-01
The data acquisition system for the Crystal Ball project at SLAC is described. A PDP-11/t55 using RSX-11M connected to the SLAC Triplex is the basis of the system. A ''physics pipeline'' allows physicists to write their own equipment-monitoring or physics tasks which require event sampling. As well, an interactive analysis package (MULTI) is in the pipeline. Histogram collection and display on the PDP are implemented using the Triplex histogramming package. Various interactive event displays are also implemented
Ball Nut Preload Diagnosis of the Hollow Ball Screw through Support Vector Machine
Directory of Open Access Journals (Sweden)
Yi-Cheng Huang
2018-01-01
Full Text Available This paper studies the diagnostic results of hollow ball screws with different ball nut preload through the support vector machine (SVM process. The method is testified by considering the use of ball screw pretension and different ball nut preload. SVM was used to discriminate the hollow ball screw preload status through the vibration signals and servo motor current signals. Maximum dynamic preloads of 2%, 4%, and 6% ball screws were predesigned, manufactured, and conducted experimentally. Signal patterns with different preload features are separatedby SVM. The irregularity development of the ball screw driving motion current and rolling balls vibration of the ball screw can be discriminated via SVM based on complexity perception. The experimental results successfully show that the prognostic status of ball nut preload can be envisaged by the proposed methodology. The smart reasoning for the health of the ball screw is available based on classification of SVM. This diagnostic method satisfies the purposes of prognostic effectiveness on knowing the ball nut preload status
Characterization of two-qubit perfect entanglers
International Nuclear Information System (INIS)
Rezakhani, A.T.
2004-01-01
Here we consider perfect entanglers from another perspective. It is shown that there are some special perfect entanglers which can maximally entangle a full product basis. We explicitly construct a one-parameter family of such entanglers together with the proper product basis that they maximally entangle. This special family of perfect entanglers contains some well-known operators such as controlled-NOT (CNOT) and double-CNOT, but not √(SWAP). In addition, it is shown that all perfect entanglers with entangling power equal to the maximal value (2/9) are also special perfect entanglers. It is proved that the one-parameter family is the only possible set of special perfect entanglers. Also we provide an analytic way to implement any arbitrary two-qubit gate, given a proper special perfect entangler supplemented with single-qubit gates. Such gates are shown to provide a minimum universal gate construction in that just two of them are necessary and sufficient in implementation of a generic two-qubit gate
Bifurcation of plasma balls and black holes to Lobed configurations
International Nuclear Information System (INIS)
Cardoso, Vitor; Dias, Oscar J.C.
2009-01-01
At high energy densities any quantum field theory is expected to have an effective hydrodynamic description. When combined with the gravity/gauge duality an unified picture emerges, where gravity itself can have a formal holographic hydrodynamic description. This provides a powerful tool to study black holes in a hydrodynamic setup. We study the stability of plasma balls, holographic duals of Scherck-Schwarz (SS) AdS black holes. We find that rotating plasma balls are unstable against m-lobed perturbations for rotation rates higher than a critical value. This unstable mode signals a bifurcation to a new branch of non-axisymmetric stationary solutions which resemble a 'peanut-like' rotating plasma. The gravitational dual of the rotating plasma ball must then be unstable and possibly decay to a non-axisymmetric long-lived SS AdS black hole. This instability provides therefore a mechanism that bounds the rotation of SS black holes. Our results are strictly valid for the SS AdS gravity theory dual to a SS gauge theory. The latter is particularly important because it shares common features with QCD, namely it is non-conformal, non-supersymmetric and has a confinement/deconfinement phase transition. We focus our analysis in 3-dimensional plasmas dual to SS AdS 5 black holes, but many of our results should extend to higher dimensions and to other gauge theory/gravity dualities with confined/deconfined phases and admitting a fluid description.
Multi-channel coherent perfect absorbers
Bai, Ping
2016-05-18
The absorption efficiency of a coherent perfect absorber usually depends on the phase coherence of the incident waves on the surfaces. Here, we present a scheme to create a multi-channel coherent perfect absorber in which the constraint of phase coherence is loosened. The scheme has a multi-layer structure such that incident waves in different channels with different angular momenta can be simultaneously and perfectly absorbed. This absorber is robust in achieving high absorption efficiency even if the incident waves become "incoherent" and possess "random" wave fronts. Our work demonstrates a unique approach to designing highly efficient metamaterial absorbers. © CopyrightEPLA, 2016.
On 4-critical t-perfect graphs
Benchetrit, Yohann
2016-01-01
It is an open question whether the chromatic number of $t$-perfect graphs is bounded by a constant. The largest known value for this parameter is 4, and the only example of a 4-critical $t$-perfect graph, due to Laurent and Seymour, is the complement of the line graph of the prism $\\Pi$ (a graph is 4-critical if it has chromatic number 4 and all its proper induced subgraphs are 3-colorable). In this paper, we show a new example of a 4-critical $t$-perfect graph: the complement of the line gra...
Multi-channel coherent perfect absorbers
Bai, Ping; Wu, Ying; Lai, Yun
2016-01-01
The absorption efficiency of a coherent perfect absorber usually depends on the phase coherence of the incident waves on the surfaces. Here, we present a scheme to create a multi-channel coherent perfect absorber in which the constraint of phase coherence is loosened. The scheme has a multi-layer structure such that incident waves in different channels with different angular momenta can be simultaneously and perfectly absorbed. This absorber is robust in achieving high absorption efficiency even if the incident waves become "incoherent" and possess "random" wave fronts. Our work demonstrates a unique approach to designing highly efficient metamaterial absorbers. © CopyrightEPLA, 2016.
Structural and dynamical properties of Yukawa balls
International Nuclear Information System (INIS)
Block, D; Kroll, M; Arp, O; Piel, A; Kaeding, S; Ivanov, Y; Melzer, A; Henning, C; Baumgartner, H; Ludwig, P; Bonitz, M
2007-01-01
To study the structural and dynamical properties of finite 3D dust clouds (Yukawa balls) new diagnostic tools have been developed. This contribution describes the progress towards 3D diagnostics for measuring the particle positions. It is shown that these diagnostics are capable of investigating the structural and dynamical properties of Yukawa balls and gaining insight into their basic construction principles
Soccer Ball Lift Coefficients via Trajectory Analysis
Goff, John Eric; Carre, Matt J.
2010-01-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin…
Study of soccer ball flight trajectory
Directory of Open Access Journals (Sweden)
Javorova Juliana
2018-01-01
Full Text Available In this paper the trajectories of a soccer ball for the most important kicks in the football game - a corner kick and a direct free kick are studied. The soccer ball is modelled as an ideal rigid hollow spherical body with six degrees of freedom, which performs a general motion in an immovable air environment with constant parameters. The ball 3D orientation is determined by the three Cardan angles. The aerodynamic forces and moments with which the air environment acts to the ball are taken into account. Two of the most dangerous areas of the football goal are defined. Differential equations which describe the motion of the soccer ball are solved numerically by MatLab-Simulink.
International Nuclear Information System (INIS)
Fryberger, D.
1994-10-01
A model for ball lightning (BL) is described. It is based upon the vorton model for elementary particles, which exploits the symmetry between electricity and magnetism. The core, or driving engine, of BL in this model is comprised of a vorton-antivorton plasma. The energy of BL, which derives from nucleon decay catalyzed by this plasma, leads, through various mechanisms, to BL luminosity as well as to other BL features. It is argued that this model could also be a suitable explanation for other luminous phenomena, such as the unidentified atmospheric light phenomena seen at Hessdalen. It is predicted that BL and similar atmospheric luminous phenomena should manifest certain features unique to this model, which would be observable with suitable instrumentation
Directory of Open Access Journals (Sweden)
Peter Marquis
2012-06-01
Full Text Available Fin octobre 2008, la nouvelle fit l’effet d’une bombe : Barack Obama, alors candidat à la présidence américaine, demanda à la chaîne câblée Fox News de retarder le début du sixième match de la World Series de base-ball afin de diffuser un spot de campagne. Son adversaire, John McCain, soutenu par le camp républicain et une partie de la population, monta aussitôt au créneau pour dénoncer l’hérésie : s’arroger le droit de perturber cette grande finale du championnat au déroulement immuable reve...
Planar shock focusing through perfect gas lens: First experimental demonstration
International Nuclear Information System (INIS)
Biamino, Laurent; Mariani, Christian; Jourdan, Georges; Houas, Lazhar; Vandenboomgaerde, Marc; Souffland, Denis
2014-01-01
When a shock wave crosses an interface between two materials, this interface becomes unstable and the Richtmyer-Meshkov instability develops. Such instability has been extensively studied in the planar case, and numerous results were presented during the previous workshops. But the Richtmyer-Meshkov (Richtmyer, 1960, 'Taylor Instability in Shock Acceleration of Compressible Fluids,' Commun. Pure Appl. Math., 13(2), pp. 297-319; Meshkov, 1969, 'Interface of Two Gases Accelerated by a Shock Wave,' Fluid Dyn., 4(5), pp. 101-104) instability also occurs in a spherical case where the convergence effects must be taken into account. As far as we know, no conventional (straight section) shock tube facility has been used to experimentally study the Richtmyer-Meshkov instability in spherical geometry. The idea originally proposed by Dimotakis and Samtaney (2006, 'Planar Shock Cylindrical Focusing by a Perfect-Gas Lens,' Phys. Fluid., 18(3), pp. 031705-031708) and later generalized by Vandenboomgaerde and Aymard (2011, 'Analytical Theory for Planar Shock Focusing Through Perfect Gas Lens and Shock Tube Experiment Designs,' Phys. Fluid., 23(1), pp. 016101-016113) was to retain the flexibility of a conventional shock tube to convert a planar shock wave into a cylindrical one through a perfect gas lens. This can be done when a planar shock wave passes through a shaped interface between two gases. By coupling the shape with the impedance mismatch at the interface, it is possible to generate a circular transmitted shock wave. In order to experimentally check the feasibility of this approach, we have implemented the gas lens technique on a conventional shock tube with the help of a convergent test section, an elliptic stereo lithographed grid, and a nitrocellulose membrane. First experimental sequences of Schlieren images have been obtained for an incident shock wave Mach number equal to 1.15 and an air/SF_6-shaped interface. Experimental results indicate that the shock that moves
BALL - biochemical algorithms library 1.3
Directory of Open Access Journals (Sweden)
Stöckel Daniel
2010-10-01
Full Text Available Abstract Background The Biochemical Algorithms Library (BALL is a comprehensive rapid application development framework for structural bioinformatics. It provides an extensive C++ class library of data structures and algorithms for molecular modeling and structural bioinformatics. Using BALL as a programming toolbox does not only allow to greatly reduce application development times but also helps in ensuring stability and correctness by avoiding the error-prone reimplementation of complex algorithms and replacing them with calls into the library that has been well-tested by a large number of developers. In the ten years since its original publication, BALL has seen a substantial increase in functionality and numerous other improvements. Results Here, we discuss BALL's current functionality and highlight the key additions and improvements: support for additional file formats, molecular edit-functionality, new molecular mechanics force fields, novel energy minimization techniques, docking algorithms, and support for cheminformatics. Conclusions BALL is available for all major operating systems, including Linux, Windows, and MacOS X. It is available free of charge under the Lesser GNU Public License (LPGL. Parts of the code are distributed under the GNU Public License (GPL. BALL is available as source code and binary packages from the project web site at http://www.ball-project.org. Recently, it has been accepted into the debian project; integration into further distributions is currently pursued.
International Nuclear Information System (INIS)
Jang, Byeong Ju
1984-01-01
This book is made up of 5 chapters. They are fluid mechanics, fluid machines, Industrial thermodynamics, steam boiler and steam turbine. It introduces hydrostatics, basic theory of fluid movement and law of momentum. It also deals with centrifugal pump, axial flow pump, general hydraulic turbine, and all phenomena happening in the pump. It covers the law of thermodynamics, perfect gas, properties of steam, and flow of gas and steam and water tube boiler. Lastly it explains basic format, theory, loss and performance as well as principle part of steam turbine.
Estimating Wear Of Installed Ball Bearings
Keba, John E.; Mcvey, Scott E.
1993-01-01
Simple inspection and measurement technique makes possible to estimate wear of balls in ball bearing, without removing bearing from shaft on which installed. To perform measurement, one observes bearing cage while turning shaft by hand to obtain integral number of cage rotations and to measure, to nearest 2 degrees, number of shaft rotations producing cage rotations. Ratio between numbers of cages and shaft rotations depends only on internal geometry of bearing and applied load. Changes in turns ratio reflect changes in internal geometry of bearing provided measurements made with similar bearing loads. By assuming all wear occurs on balls, one computes effective value for this wear from change in turns ratio.
International Nuclear Information System (INIS)
Copeland, Edmund J.; Tsumagari, Mitsuo I.
2009-01-01
We study the classical and absolute stability of Q-balls in scalar field theories with flat potentials arising in both gravity-mediated and gauge-mediated models. We show that the associated Q-matter formed in gravity-mediated potentials can be stable against decay into their own free particles as long as the coupling constant of the nonrenormalizable term is small, and that all of the possible three-dimensional Q-ball configurations are classically stable against linear fluctuations. Three-dimensional gauge-mediated Q-balls can be absolutely stable in the thin-wall limit, but are completely unstable in the thick-wall limit.
Crystal ball single event display
International Nuclear Information System (INIS)
Grosnick, D.; Gibson, A.; Allgower, C.; Alyea, J.; Argonne National Lab., IL
1997-01-01
The Single Event Display (SED) is a routine that is designed to provide information graphically about a triggered event within the Crystal Ball. The SED is written entirely in FORTRAN and uses the CERN-based HICZ graphing package. The primary display shows the amount of energy deposited in each of the NaI crystals on a Mercator-like projection of the crystals. Ten different shades and colors correspond to varying amounts of energy deposited within a crystal. Information about energy clusters is displayed on the crystal map by outlining in red the thirteen (or twelve) crystals contained within a cluster and assigning each cluster a number. Additional information about energy clusters is provided in a series of boxes containing useful data about the energy distribution among the crystals within the cluster. Other information shown on the event display include the event trigger type and data about π o 's and η's formed from pairs of clusters as found by the analyzer. A description of the major features is given, along with some information on how to install the SED into the analyzer
Overlapped optics induced perfect coherent effects
Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin
2013-12-01
For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.
Static Load Distribution in Ball Bearings
Ricci, Mario
2010-01-01
A numerical procedure for computing the internal loading distribution in statically loaded, single-row, angular-contact ball bearings when subjected to a known combined radial and thrust load is presented. The combined radial and thrust load must be applied in order to avoid tilting between inner and outer rings. The numerical procedure requires the iterative solution of Z + 2 simultaneous nonlinear equations - where Z is the number of the balls - to yield an exact solution for axial and radial deflections, and contact angles. Numerical results for a 218 angular-contact ball bearing have been compared with those from the literature and show significant differences in the magnitudes of the ball loads, contact angles, and the extent of the loading zone.
On the formation of ball lightning
International Nuclear Information System (INIS)
Silberg, P.A.
1981-01-01
A plasma continuum model for the formation of ball lightning is developed based on a substantial number of reports that the ball is often in the discharge column of a previous lightning stroke. The usual method of setting up the plasma equation for a one-component electron plasma is used. An approximate equation for the plasma is derived from the describing equation which is then solved exactly in terms of the Jacobi elliptic functions. The formation of the ball is based on a nonlinearity of the plasma equation which uner certain circumstances permits the field to collapse into a small region. This collapse is interpreted to be ball lightning. The approximate equation derived for the plasma has the same form as a previous equation used to describe the formation of the fireball plasma. (author)
Dolphin underwater bait-balling behaviors in relation to group and prey ball sizes.
Vaughn-Hirshorn, Robin L; Muzi, Elisa; Richardson, Jessica L; Fox, Gabriella J; Hansen, Lauren N; Salley, Alyce M; Dudzinski, Kathleen M; Würsig, Bernd
2013-09-01
We characterized dusky dolphin (Lagenorhynchus obscurus) feeding behaviors recorded on underwater video, and related behaviors to variation in prey ball sizes, dolphin group sizes, and study site (Argentina versus New Zealand, NZ). Herding behaviors most often involved dolphins swimming around the side or under prey balls, but dolphins in Argentina more often swam under prey balls (48% of passes) than did dolphins in NZ (34% of passes). This result may have been due to differences in group sizes between sites, since groups are larger in Argentina. Additionally, in NZ, group size was positively correlated with proportion of passes that occurred under prey balls (pdolphins in Argentina more often swam through prey balls (8% of attempts) than did dolphins in NZ (4% of attempts). This result may have been due to differences in prey ball sizes between sites, since dolphins fed on larger prey balls in Argentina (>74m(2)) than in NZ (maximum 33m(2)). Additionally, in NZ, dolphins were more likely to swim through prey balls to capture fish when they fed on larger prey balls (p=0.025). Copyright © 2013 Elsevier B.V. All rights reserved.
Hermitian harmonic maps into convex balls
International Nuclear Information System (INIS)
Li Zhenyang; Xi Zhang
2004-07-01
In this paper, we consider Hermitian harmonic maps from Hermitian manifolds into convex balls. We prove that there exist no non-trivial Hermitian harmonic maps from closed Hermitian manifolds into convex balls, and we use the heat flow method to solve the Dirichlet problem for Hermitian harmonic maps when the domain is compact Hermitian manifold with non-empty boundary. The case where the domain manifold is complete(noncompact) is also studied. (author)
Thermoelastoplastic Deformation of a Multilayer Ball
Murashkin, E. V.; Dats, E. P.
2017-09-01
The problem of centrally symmetric deformation of a multilayer elastoplastic ball in the process of successive accretion of preheated layers to its outer surface is considered in the framework of small elastoplastic deformations. The problems of residual stress formation in the elastoplastic ball with an inclusion and a cavity are solved under various mechanical boundary conditions on the inner surface and for prescribed thermal compression distributions. The graphs of residual stress and displacement fields are constructed.
Optimal simulation of a perfect entangler
International Nuclear Information System (INIS)
Yu Nengkun; Duan Runyao; Ying Mingsheng
2010-01-01
A 2 x 2 unitary operation is called a perfect entangler if it can generate a maximally entangled state from some unentangled input. We study the following question: How many runs of a given two-qubit entangling unitary operation are required to simulate some perfect entangler with one-qubit unitary operations as free resources? We completely solve this problem by presenting an analytical formula for the optimal number of runs of the entangling operation. Our result reveals an entanglement strength of two-qubit unitary operations.
Perfect 800 Advanced Strategies for Top Students
Celenti, Dan
2010-01-01
Getting into the nation's most competitive universities requires more than a good SAT score, it requires a perfect score. Perfect 800: SAT Math gives advanced students the tools needed to master the SAT math test. Covering areas including arithmetic concepts; algebra; geometry; and additional topics such as probability and weighted average, the book offers exposure to a wide range of degrees of difficulty in a holistic approach that allows students to experience the "real thing," including the impact of time constraints on their performance. By emphasizing critical thinking and analytic skills
A Hypergraph Dictatorship Test with Perfect Completeness
Chen, Victor
A hypergraph dictatorship test is first introduced by Samorodnitsky and Trevisan and serves as a key component in their unique games based {operatorname{PCP}} construction. Such a test has oracle access to a collection of functions and determines whether all the functions are the same dictatorship, or all their low degree influences are o(1). Their test makes q ≥ 3 queries, has amortized query complexity 1+Oleft(log q/qright), but has an inherent loss of perfect completeness. In this paper we give an (adaptive) hypergraph dictatorship test that achieves both perfect completeness and amortized query complexity 1+Oleft(log q/qright).
Perfect and Periphrastic Passive Constructions in Danish
DEFF Research Database (Denmark)
Bjerre, Tavs; Bjerre, Anne
2007-01-01
This paper gives an account of the event and argument structure of past participles and the linking between argument structure and valence structure. It further accounts for how participles form perfect and passiv constructions with auxiliaries. We assume that the same participle form is used...... in both types of construction. Our claim is that the valence structure of a past participle is predictable from its semantic type, and that the valence structure predicts with which auciliary a past participle combines in perfect constructions and whether the past participle may occur in passiv...
Optically Modulated Multiband Terahertz Perfect Absorber
DEFF Research Database (Denmark)
Seren, Huseyin R.; Keiser, George R.; Cao, Lingyue
2014-01-01
response of resonant metamaterials continues to be a challengingendeavor. Resonant perfect absorbers have flourished as one of the mostpromising metamaterial devices with applications ranging from power har-vesting to terahertz imaging. Here, an optically modulated resonant perfectabsorber is presented....... Utilizing photo-excited free carriers in silicon padsplaced in the capacitive gaps of split ring resonators, a dynamically modu-lated perfect absorber is designed and fabricated to operate in reflection.Large modulation depth (38% and 91%) in two absorption bands (with 97%and 92% peak absorption...
Optimization of Perfect Absorbers with Multilayer Structures
Li Voti, Roberto
2018-02-01
We study wide-angle and broadband perfect absorbers with compact multilayer structures made of a sequence of ITO and TiN layers deposited onto a silver thick layer. An optimization procedure is introduced for searching the optimal thicknesses of the layers so as to design a perfect broadband absorber from 400 nm to 750 nm, for a wide range of angles of incidence from 0{°} to 50{°}, for both polarizations and with a low emissivity in the mid-infrared. We eventually compare the performances of several optimal structures that can be very promising for solar thermal energy harvesting and collectors.
Electromagnetic Detection of a Perfect Invisibility Cloak
International Nuclear Information System (INIS)
Zhang Baile; Wu, Bae-Ian
2009-01-01
A perfect invisibility cloak is commonly believed to be undetectable from electromagnetic (EM) detection because it is equivalent to a curved but empty EM space created from coordinate transformation. Based on the intrinsic asymmetry of coordinate transformation applied to motions of photons and charges, we propose a method to detect this curved EM space by shooting a fast-moving charged particle through it. A broadband radiation generated in this process makes a cloak visible. Our method is the only known EM mechanism so far to detect an ideal perfect cloak (curved EM space) within its working band.
Lattice-Like Total Perfect Codes
Directory of Open Access Journals (Sweden)
Araujo Carlos
2014-02-01
Full Text Available A contribution is made to the classification of lattice-like total perfect codes in integer lattices Λn via pairs (G, Φ formed by abelian groups G and homomorphisms Φ: Zn → G. A conjecture is posed that the cited contribution covers all possible cases. A related conjecture on the unfinished work on open problems on lattice-like perfect dominating sets in Λn with induced components that are parallel paths of length > 1 is posed as well.
Mechanical Energy Changes in Perfectly Inelastic Collisions
Mungan, Carl E.
2013-01-01
Suppose a block of mass "m"[subscript 1] traveling at speed "v"[subscript 1] makes a one-dimensional perfectly inelastic collision with another block of mass "m"[subscript 2]. What else does one need to know to calculate the fraction of the mechanical energy that is dissipated in the collision? (Contains 1 figure.)
The Present Perfect in World Englishes
Yao, Xinyue; Collins, Peter
2012-01-01
This paper reports on a comprehensive corpus-based study of regional and stylistic variation in the distribution of the English present perfect. The data represents ten English varieties of both the Inner Circle and Outer Circle, covering four major text types: conversation, news reportage, academic and fictional writing. The results are discussed…
Le Perfectionnement en Phonetique (Perfecting Phonetics)
Laroche-Bouvy, Danielle
1975-01-01
This article describes the programs of the Institut d'Etudes Linguistiques et Phonetiques, located in Paris. The program focuses on perfecting the students' phonetic production of French. Both curriculum and teaching methods are described, as well as a course in phonetics for future teachers of French. (Text is in French.) (CLK)
Maple Explorations, Perfect Numbers, and Mersenne Primes
Ghusayni, B.
2005-01-01
Some examples from different areas of mathematics are explored to give a working knowledge of the computer algebra system Maple. Perfect numbers and Mersenne primes, which have fascinated people for a very long time and continue to do so, are studied using Maple and some questions are posed that still await answers.
Perfectly Secure Oblivious RAM without Random Oracles
DEFF Research Database (Denmark)
Damgård, Ivan Bjerre; Meldgaard, Sigurd Torkel; Nielsen, Jesper Buus
2011-01-01
We present an algorithm for implementing a secure oblivious RAM where the access pattern is perfectly hidden in the information theoretic sense, without assuming that the CPU has access to a random oracle. In addition we prove a lower bound on the amount of randomness needed for implementing...
Reshaping the perfect electrical conductor cylinder arbitrarily
International Nuclear Information System (INIS)
Chen Huanyang; Zhang Xiaohe; Luo Xudong; Ma Hongru; Chan Cheting
2008-01-01
A general method is proposed to design a cylindrical cloak, concentrator and superscatterer with an arbitrary cross section. The method is demonstrated by the design of a perfect electrical conductor (PEC) reshaper which is able to reshape a PEC cylinder arbitrarily by combining the concept of cloak, concentrator and superscatterer together. Numerical simulations are performed to demonstrate its properties.
What is anthropological about The Perfect Human?
DEFF Research Database (Denmark)
Thomsen, Line Hassall
2015-01-01
Jørgen Leth has classified The Perfect Human as an anthropological film. But is the film anthropological at all? This article explores Leth’s connections with anthropology and finds that he is more inspired by anthropological framing than he is by anthropological research methods....
Aerodynamic drag of modern soccer balls.
Asai, Takeshi; Seo, Kazuya
2013-12-01
Soccer balls such as the Adidas Roteiro that have been used in soccer tournaments thus far had 32 pentagonal and hexagonal panels. Recently, the Adidas Teamgeist II and Adidas Jabulani, respectively having 14 and 8 panels, have been used at tournaments; the aerodynamic characteristics of these balls have not yet been verified. Now, the Adidas Tango 12, having 32 panels, has been developed for use at tournaments; therefore, it is necessary to understand its aerodynamic characteristics. Through a wind tunnel test and ball trajectory simulations, this study shows that the aerodynamic resistance of the new 32-panel soccer ball is larger in the high-speed region and lower in the middle-speed region than that of the previous 14- and 8-panel balls. The critical Reynolds number of the Roteiro, Teamgeist II, Jabulani, and Tango 12 was ~2.2 × 10(5) (drag coefficient, C d ≈ 0.12), ~2.8 × 10(5) (C d ≈ 0.13), ~3.3 × 10(5) (C d ≈ 0.13), and ~2.4 × 10(5) (C d ≈ 0.15), respectively. The flight trajectory simulation suggested that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can thus easily acquire large initial velocity in this region. It is considered that the critical Reynolds number of a soccer ball, as considered within the scope of this experiment, depends on the extended total distance of the panel bonds rather than the small designs on the panel surfaces.
Effect of a ball skill intervention on children's ball skills and cognitive functions
Westendorp-Haverdings, Marieke; Houwen, Suzanne; Hartman, Esther; Mombarg, Remo; Smith, Joanne; Visscher, Chris
Purpose: This study examined the effect of a 16-wk ball skill intervention on the ball skills, executive functioning (in terms of problem solving and cognitive flexibility), and in how far improved executive functioning leads to improved reading and mathematics performance of children with learning
Optical and Acoustic Sensor-Based 3D Ball Motion Estimation for Ball Sport Simulators †
Directory of Open Access Journals (Sweden)
Sang-Woo Seo
2018-04-01
Full Text Available Estimation of the motion of ball-shaped objects is essential for the operation of ball sport simulators. In this paper, we propose an estimation system for 3D ball motion, including speed and angle of projection, by using acoustic vector and infrared (IR scanning sensors. Our system is comprised of three steps to estimate a ball motion: sound-based ball firing detection, sound source localization, and IR scanning for motion analysis. First, an impulsive sound classification based on the mel-frequency cepstrum and feed-forward neural network is introduced to detect the ball launch sound. An impulsive sound source localization using a 2D microelectromechanical system (MEMS microphones and delay-and-sum beamforming is presented to estimate the firing position. The time and position of a ball in 3D space is determined from a high-speed infrared scanning method. Our experimental results demonstrate that the estimation of ball motion based on sound allows a wider activity area than similar camera-based methods. Thus, it can be practically applied to various simulations in sports such as soccer and baseball.
Effect of a ball skill intervention on children's ball skills and cognitive functions.
Westendorp, Marieke; Houwen, Suzanne; Hartman, Esther; Mombarg, Remo; Smith, Joanne; Visscher, Chris
2014-02-01
This study examined the effect of a 16-wk ball skill intervention on the ball skills, executive functioning (in terms of problem solving and cognitive flexibility), and in how far improved executive functioning leads to improved reading and mathematics performance of children with learning disorders. Ninety-one children with learning disorders (age 7-11 yr old) were recruited from six classes in a Dutch special-needs primary school. The six classes were assigned randomly either to the intervention or to the control group. The control group received the school's regular physical education lessons. In the intervention group, ball skills were practiced in relative static, simple settings as well as in more dynamic and cognitive demanding settings. Both groups received two 40-min lessons per week. Children's scores on the Test of Gross Motor Development-2 (ball skills), Tower of London (problem solving), Trail Making Test (cognitive flexibility), Dutch Analysis of Individual Word Forms (reading), and the Dutch World in Numbers test (mathematics) at pretest, posttest, and retention test were used to examine intervention effects. The results showed that the intervention group significantly improved their ball skills, whereas the control group did not. No intervention effects were found on the cognitive parameters. However, within the intervention group, a positive relationship (r = 0.41, P = 0.007) was found between the change in ball skill performance and the change in problem solving: the larger children's improvement in ball skills, the larger their improvement in problem solving. The present ball skill intervention is an effective instrument to improve the ball skills of children with learning disorders. Further research is needed to examine the effect of the ball skill intervention on the cognitive parameters in this population.
Laser Sintering Technology and Balling Phenomenon.
Oyar, Perihan
2018-02-01
The aim of this review was to evaluate the balling phenomenon which occurs typically in Selective Laser Sintering (SLS). The balling phenomenon is a typical SLS defect, and observed in laser sintered powder, significantly reduces the quality of SLS, and hinders the further development of SLS Technology. Electronic database searches were performed using Google Scholar. The keywords "laser sintering, selective laser sintering, direct metal laser melting, and balling phenomenon" were searched in title/abstract of publications, limited to December 31, 2016. The inclusion criteria were SLS, balling phenomenon, some alloys (such as Cr-Co, iron, stainless steel, and Cu-based alloys) mechanical properties, microstructure and bond strength between metal-ceramic crown, laboratory studies, full text, and in English language. A total of 100 articles were found the initial search and yielded a total of 50 studies, 30 of which did not fulfill the inclusion criteria and were therefore excluded. In addition, 20 studies were found by screening the reference list of all included publications. Finally, 40 studies were selected for this review. The method in question is regulated by powder material characteristics and the conditions of laser processing. The procedure of formation, affecting factors, and the mechanism of the balling effect are very complex.
Electrostatic charge bounds for ball lightning models
International Nuclear Information System (INIS)
Stephan, Karl D
2008-01-01
Several current theories concerning the nature of ball lightning predict a substantial electrostatic charge in order to account for its observed motion and shape (Turner 1998 Phys. Rep. 293 1; Abrahamson and Dinniss 2000 Nature 403 519). Using charged soap bubbles as a physical model for ball lightning, we show that the magnitude of charge predicted by some of these theories is too high to allow for the types of motion commonly observed in natural ball lightning, which includes horizontal motion above the ground and movement near grounded conductors. Experiments show that at charge levels of only 10-15 nC, 3-cm-diameter soap bubbles tend to be attracted by induced charges to the nearest grounded conductor and rupture. We conclude with a scaling rule that can be used to extrapolate these results to larger objects and surroundings
International Nuclear Information System (INIS)
Pistoia, F.; Ozonoff, M.B.; Wintz, P.; Hartford Hospital, CT
1987-01-01
The ball-and-socket ankle joint is a malformation of the ankle in which the articular surface of the talus is hemispherical in both the anteroposterior and lateral projections and has a congruent, concave tibial articular surface. Fourteen patients with this condition were identified retrospectively. Thirteen patients were thought to have the congenital type of ball-and-socket ankle joint which in many was associated with tarsal coalition, short limb, and ray fusion and deletion anomalies. One case of the acquired type, demonstrating less geometric rounding of the talar margins, was seen in a patient with myelomeningocele, probably resulting from sensory and motor deficits. Although the exact etiology of the congenital type is unknown, its association with other malformations suggests that the ball-and-socket ankle joint results from an overall maldevelopment of the ankle and foot. (orig.)
Physicotechnical potentialities of perfecting roentgenographic research
International Nuclear Information System (INIS)
Chikirdin, Eh.G.; Mishkinis, B.Ya.
1991-01-01
Physicotechnical potentialities of perfecting image quality in X-ray examinations are enumerated. Realization of these potentialities demands interrelated decision of two problems: substantiation of optimizing conditions of survey (postures of a patient, geometry of investigation, image converters, electric regimes), creation of adequate hardware and software components. It is shown that introduction of X-ray feeding device with microprocessor control permits to upgrade the quality of X-ray images and to reduce radiation loads of a patient
Comment on 'Perfect imaging without negative refraction'
Blaikie, R. J.
2010-05-01
The prediction of 'perfect' imaging without negative refraction for Maxwell's fish-eye lens (Leonhardt U 2009 New J. Phys. 11 093040) is a consequence of imposing an active localized 'drain' at the image point rather than being a general property of the lens. This work then becomes analogous to other work using time-reversal symmetry and/or structured antennae to achieve super-resolution, which can be applied to many types of imaging system beyond the fish-eye lens.
Comment on 'Perfect imaging without negative refraction'
International Nuclear Information System (INIS)
Blaikie, R J
2010-01-01
The prediction of 'perfect' imaging without negative refraction for Maxwell's fish-eye lens (Leonhardt U 2009 New J. Phys. 11 093040) is a consequence of imposing an active localized 'drain' at the image point rather than being a general property of the lens. This work then becomes analogous to other work using time-reversal symmetry and/or structured antennae to achieve super-resolution, which can be applied to many types of imaging system beyond the fish-eye lens.
Inequivalent quantizations and fundamentally perfect spaces
International Nuclear Information System (INIS)
Imbo, T.D.; Sudarshan, E.C.G.
1987-06-01
We investigate the problem of inequivalent quantizations of a physical system with multiply connected configuration space X. For scalar quantum theory on X we show that state vectors must be single-valued if and only if the first homology group H 1 (X) is trivial, or equivalently the fundamental group π 1 (X) is perfect. The θ-structure of quantum gauge and gravitational theories is discussed in light of this result
Another Class of Perfect Nonlinear Polynomial Functions
Directory of Open Access Journals (Sweden)
Menglong Su
2013-01-01
Full Text Available Perfect nonlinear (PN functions have been an interesting subject of study for a long time and have applications in coding theory, cryptography, combinatorial designs, and so on. In this paper, the planarity of the trinomials xpk+1+ux2+vx2pk over GF(p2k are presented. This class of PN functions are all EA-equivalent to x2.
On longevity of I-ball/oscillon
Energy Technology Data Exchange (ETDEWEB)
Mukaida, Kyohei [Kavli IPMU (WPI), UTIAS, The University of Tokyo,Kashiwa, Chiba 277-8583 (Japan); Takimoto, Masahiro [Theory Center, KEK,1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Department of Particle Physics and Astrophysics, Weizmann Institute of Science,Rehovot 7610001 (Israel); Yamada, Masaki [Institute of Cosmology, Department of Physics and Astronomy, Tufts University,Medford, MA 02155 (United States); Department of Physics, Tohoku University,Sendai, Miyagi 980-8578 (Japan)
2017-03-23
We study I-balls/oscillons, which are long-lived, quasi-periodic, and spatially localized solutions in real scalar field theories. Contrary to the case of Q-balls, there is no evident conserved charge that stabilizes the localized configuration. Nevertheless, in many classical numerical simulations, it has been shown that they are extremely long-lived. In this paper, we clarify the reason for the longevity, and show how the exponential separation of time scales emerges dynamically. Those solutions are time-periodic with a typical frequency of a mass scale of a scalar field. This observation implies that they can be understood by the effective theory after integrating out relativistic modes. We find that the resulting effective theory has an approximate global U(1) symmetry reflecting an approximate number conservation in the non-relativistic regime. As a result, the profile of those solutions is obtained via the bounce method, just like Q-balls, as long as the breaking of the U(1) symmetry is small enough. We then discuss the decay processes of the I-ball/oscillon by the breaking of the U(1) symmetry, namely the production of relativistic modes via number violating processes. We show that the imaginary part is exponentially suppressed, which explains the extraordinary longevity of I-ball/oscillon. In addition, we find that there are some attractor behaviors during the evolution of I-ball/oscillon that further enhance the lifetime. The validity of our effective theory is confirmed by classical numerical simulations. Our formalism may also be useful to study condensates of ultra light bosonic dark matter, such as fuzzy dark matter, and axion stars, for instance.
Soccer ball lift coefficients via trajectory analysis
International Nuclear Information System (INIS)
Goff, John Eric; Carre, Matt J
2010-01-01
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin parameters that have not been obtained by today's wind tunnels. Our trajectory analysis technique is not only a valuable tool for professional sports scientists, it is also accessible to students with a background in undergraduate-level classical mechanics.
Soccer ball lift coefficients via trajectory analysis
Energy Technology Data Exchange (ETDEWEB)
Goff, John Eric [Department of Physics, Lynchburg College, Lynchburg, VA 24501 (United States); Carre, Matt J, E-mail: goff@lynchburg.ed [Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)
2010-07-15
We performed experiments in which a soccer ball was launched from a machine while two high-speed cameras recorded portions of the trajectory. Using the trajectory data and published drag coefficients, we extracted lift coefficients for a soccer ball. We determined lift coefficients for a wide range of spin parameters, including several spin parameters that have not been obtained by today's wind tunnels. Our trajectory analysis technique is not only a valuable tool for professional sports scientists, it is also accessible to students with a background in undergraduate-level classical mechanics.
Prakash, E.; Sivakumar, K.
2015-12-01
Experimental analysis of damping capacity and tribological characteristics of nano CuO added Servosystem 68 lubricant is attempted. CuO nano particles were synthesized by aqueous precipitation method and characterized. Prior to dispersion into lubricant, CuO nano particles were coated with 0.2 wt.% surfactant (Span-80) to stabilize the nano fluid. Tribological characteristics of particle added lubricant were tested in ASTM D 4172 four ball wear tester. Scanning electron microscopy test results of worn surfaces of nano CuO particle added lubricant were smoother than base lubricant. The particle added lubricant was applied in a new ball bearing and three defected ball bearings. When particle added lubricant was used, the ball defected bearing's vibration amplitude was reduced by 21.94% whereas it was 16.46% for new bearing and was ≤ 11% for other defected bearings. The formation of protection film of CuO over ball surface and regime of full film lubrication near the ball zone were observed to be reason for improved damping of vibrations.
Spheres settling in an Oldroyd-B fluid
Pan, Tsorng-Whay; Glowinski, Roland
2017-11-01
In this talk we present a numerical study of the dynamics of balls settling in a vertical channel with a square cross-section filled with an Oldroyd-B fluid. For the case of two balls, two typical kinds of particle dynamics are obtained: (i) periodic interaction between two balls and (ii) the formation of a vertical chain of two balls. For the periodic interaction of two balls occurred at lower values of the elasticity number, two balls draft, kiss and break away periodically and the chain is not formed due to not strong enough elastic force. For slightly higher values of the elasticity number, two balls draft, kiss and break away a couple times first and then form a chain. Such chain finally becomes a vertical one after the oscillation damps out. For higher values of the elasticity number, two balls draft, kiss and form a vertical chain right away. The formation of three ball chain can be obtained at higher values of the elasticity number. This work was supported by NSF (Grant DMS-1418308).
Protein profiling of cerebrospinal fluid
DEFF Research Database (Denmark)
Simonsen, Anja H
2012-01-01
The cerebrospinal fluid (CSF) perfuses the brain and spinal cord. CSF contains proteins and peptides important for brain physiology and potentially also relevant for brain pathology. Hence, CSF is the perfect source to search for new biomarkers to improve diagnosis of neurological diseases as well...
From a Ball Game to Incompleteness
Indian Academy of Sciences (India)
We present a ball game that can be continued as long as wewish. It looks as though the game would never end. But byapplying a result on trees, we show that the game nonethelessends in some finite number of moves. We then point out somedeep results on the natural number system connected withthe game.
4 π physics with the plastic ball
International Nuclear Information System (INIS)
Gutbrod, H.H.; Loehner, H.; Poskanzer, A.M.; Renner, T.; Riedesel, H.; Ritter, H.G.; Warwick, A.; Weik, F.; Wieman, H.
1982-10-01
4 π data taken with the Plastic Ball show that cluster production in relativistic nuclear collisions depends on both the size of the participant volume and the finite size of the cluster. The measurement of the degree of thermalization and the search for collective flow will permit the study of the applicability of macroscopic concepts such as temperature and density
Crystal Ball results on tau decays
International Nuclear Information System (INIS)
Lowe, S.T.
1987-10-01
This report reviews measurements and upper limit determinations for a number of exclusive 1-prong tau decay modes using the Crystal Ball detector. These results are important input to the apparent discrepancy between the topological and sum-of-exclusive branching fractions in 1-prong tau decays
A plasma ball in the Microcosm museum
Maximilien Brice
2005-01-01
Plasma balls, like the one shown here, are displayed in the Microcosm exhibition where families can visit to learn more about the experiments carried out in a research institute like CERN. Hands-on activities allow visitors to get a step closer to the research activities carried out at CERN.
Fractal Aggregates in Tennis Ball Systems
Sabin, J.; Bandin, M.; Prieto, G.; Sarmiento, F.
2009-01-01
We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the…
Soccer Ball Production for Nike in Pakistan
K.A. Siegmann (Karin Astrid)
2008-01-01
textabstractThis paper looks at how Nike’s soccer ball suppliers (previous and current) in Sialkot (Pakistan) fare in relation to the company’s code of ethics. While minimum required working conditions are implemented, the criteria for social and environmental compliance are not met with. The
Kulp, Christopher W.; Biermann, Mark L.; Howard, Timothy; Klingenberg, Kurtis; Ramsey, Paul
2008-01-01
A camcorder can be a powerful tool in pedagogical settings, such as in an introductory physics course or in introducing undergraduates to data collection. In this paper, we discuss our experience using a Panasonic PV-GS150 digital camcorder to analyze the motion of a falling steel ball, with the goal of determining the acceleration due to gravity,…
On the dynamics of ball bearings
Wensing, J.A.
1998-01-01
This investigation on the dynamic behaviour of ball bearings was motivated by the demand for silent bearings in noise-sensitive applications, especially in the household appliance and automotive industry. The present investigations are intended to provide a clear understanding of the role of the
On the perfect hexagonal packing of rods
International Nuclear Information System (INIS)
Starostin, E L
2006-01-01
In most cases the hexagonal packing of fibrous structures or rods extremizes the energy of interaction between strands. If the strands are not straight, then it is still possible to form a perfect hexatic bundle. Conditions under which the perfect hexagonal packing of curved tubular structures may exist are formulated. Particular attention is given to closed or cycled arrangements of the rods like in the DNA toroids and spools. The closure or return constraints of the bundle result in an allowable group of automorphisms of the cross-sectional hexagonal lattice. The structure of this group is explored. Examples of open helical-like and closed toroidal-like bundles are presented. An expression for the elastic energy of a perfectly packed bundle of thin elastic rods is derived. The energy accounts for both the bending and torsional stiffnesses of the rods. It is shown that equilibria of the bundle correspond to solutions of a variational problem formulated for the curve representing the axis of the bundle. The functional involves a function of the squared curvature under the constraints on the total torsion and the length. The Euler-Lagrange equations are obtained in terms of curvature and torsion and due to the existence of the first integrals the problem is reduced to the quadrature. The three-dimensional shape of the bundle may be readily reconstructed by integration of the Ilyukhin-type equations in special cylindrical coordinates. The results are of universal nature and are applicable to various fibrous structures, in particular, to intramolecular liquid crystals formed by DNA condensed in toroids or packed inside the viral capsids
Neutrons and the crystal ball experiments
International Nuclear Information System (INIS)
Alyea, J.; Grosnick, D.; Koetke, D.; Manweiler, R.; Spinka, H.; Stanislaus, S.
1997-01-01
The Crystal Ball detector, as originally constructed, consisted of a set of 672 optically-isolated NaI crystals, forming an approximately spherical shell and each crystal viewed by a photomultiplier, a charged-particle tracker within the NaI shell, and two endcaps to cover angles close to two colliding beams. The detector geometry subtends a solid angle of about 93% of 4π st (20 degree le θ le 160degree and 0degree le φ le 360degree) from the center. The Crystal Ball detector was used for two long series of experiments at the e + e - colliding beam accelerators SPEAR [1, 2, 3, 4] at SLAC and DORIS [5, 6, 7, 8] at DESY. A new set of measurements using the Crystal Ball detector is planned at the Brookhaven National Laboratory Alternating Gradient Synchrotrons (BNL AGS). These new experiments will use the 672 NaI crystals from the original detector, but neither the tracker nor endcaps. The ''Crystal Ball'' in this note will refer only to the set of NaI crystals. Initially, the reactions to be studied will include π - pr a rrow neutrals with pion beam momenta approximately400-750 MeV/c and K - pr a rrow neutrals with kaon beam momenta approximately600-750 MeV/c. Each of these reactions will include a neutron in the final state. whereas the fraction of e + e - interactions with neutrons at SLAC or DESY was quite small. Consequently, there is relatively little experience understanding the behavior of neutrons in the Crystal Ball
Diamagnetic expansions for perfect quantum gases
DEFF Research Database (Denmark)
Briet, Philippe; Cornean, Horia; Louis, Delphine
2006-01-01
In this work we study the diamagnetic properties of a perfect quantum gas in the presence of a constant magnetic field of intensity B. We investigate the Gibbs semigroup associated with the one particle operator at finite volume, and study its Taylor series with respect to the field parameter ome......:=eB/c in different topologies. This allows us to prove the existence of the thermodynamic limit for the pressure and for all its derivatives with respect to omega (the so-called generalized susceptibilities)....
Explaining evolution via constrained persistent perfect phylogeny
2014-01-01
Background The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. Results We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. Conclusions A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to
Validity and Reliability of a Medicine Ball Explosive Power Test.
Stockbrugger, Barry A.; Haennel, Robert G.
2001-01-01
Evaluated the validity and reliability of a medicine ball throw test to evaluate explosive power. Data on competitive sand volleyball players who performed a medicine ball throw and a standard countermovement jump indicated that the medicine ball throw test was a valid and reliable way to assess explosive power for an analogous total-body movement…
Apnea of prematurity--perfect storm.
Di Fiore, Juliann M; Martin, Richard J; Gauda, Estelle B
2013-11-01
With increased survival of preterm infants as young as 23 weeks gestation, maintaining adequate respiration and corresponding oxygenation represents a clinical challenge in this unique patient cohort. Respiratory instability characterized by apnea and periodic breathing occurs in premature infants because of immature development of the respiratory network. While short respiratory pauses and apnea may be of minimal consequence if oxygenation is maintained, they can be problematic if accompanied by chronic intermittent hypoxemia. Underdevelopment of the lung and the resultant lung injury that occurs in this population concurrent with respiratory instability creates the perfect storm leading to frequent episodes of profound and recurrent hypoxemia. Chronic intermittent hypoxemia contributes to the immediate and long term co-morbidities that occur in this population. In this review we discuss the pathophysiology leading to the perfect storm, diagnostic assessment of breathing instability in this unique population and therapeutic interventions that aim to stabilize breathing without contributing to tissue injury. Copyright © 2013. Published by Elsevier B.V.
How does gravity save or kill Q-balls?
International Nuclear Information System (INIS)
Tamaki, Takashi; Sakai, Nobuyuki
2011-01-01
We explore stability of gravitating Q-balls with potential V 4 (φ)=(m 2 /2)φ 2 -λφ 4 +(φ 6 /M 2 ) via catastrophe theory, as an extension of our previous work on Q-balls with potential V 3 (φ)=(m 2 /2)φ 2 -μφ 3 +λφ 4 . In flat spacetime Q-balls with V 4 in the thick-wall limit are unstable and there is a minimum charge Q min , where Q-balls with Q min are nonexistent. If we take self-gravity into account, on the other hand, there exist stable Q-balls with arbitrarily small charge, no matter how weak gravity is. That is, gravity saves Q-balls with small charge. We also show how stability of Q-balls changes as gravity becomes strong.
Quantum field theory of fluids.
Gripaios, Ben; Sutherland, Dave
2015-02-20
The quantum theory of fields is largely based on studying perturbations around noninteracting, or free, field theories, which correspond to a collection of quantum-mechanical harmonic oscillators. The quantum theory of an ordinary fluid is "freer", in the sense that the noninteracting theory also contains an infinite collection of quantum-mechanical free particles, corresponding to vortex modes. By computing a variety of correlation functions at tree and loop level, we give evidence that a quantum perfect fluid can be consistently formulated as a low-energy, effective field theory. We speculate that the quantum behavior is radically different from both classical fluids and quantum fields.
Ball assisted device for analytical surface sampling
ElNaggar, Mariam S; Van Berkel, Gary J; Covey, Thomas R
2015-11-03
A system for sampling a surface includes a sampling probe having a housing and a socket, and a rolling sampling sphere within the socket. The housing has a sampling fluid supply conduit and a sampling fluid exhaust conduit. The sampling fluid supply conduit supplies sampling fluid to the sampling sphere. The sampling fluid exhaust conduit has an inlet opening for receiving sampling fluid carried from the surface by the sampling sphere. A surface sampling probe and a method for sampling a surface are also disclosed.
Relative locality and the soccer ball problem
International Nuclear Information System (INIS)
Amelino-Camelia, Giovanni; Freidel, Laurent; Smolin, Lee; Kowalski-Glikman, Jerzy
2011-01-01
We consider the behavior of macroscopic bodies within the framework of relative locality [G. Amelino-Camelia, L. Freidel, J. Kowalski-Glikman, and L. Smolin, arXiv:1101.0931]. This is a recent proposal for Planck scale modifications of the relativistic dynamics of particles which are described as arising from deformations in the geometry of momentum space. We consider and resolve a common objection against such proposals, which is that, even if the corrections are small for elementary particles in current experiments, they are huge when applied to composite systems such as soccer balls, planets, and stars, with energies E macro much larger than M P . We show that this soccer ball problem does not arise within the framework of relative locality because the nonlinear effects for the dynamics of a composite system with N elementary particles appear at most of order E macro /N·M P .
Relativistic charged fluids: hydrodynamic and kinetic approaches
International Nuclear Information System (INIS)
Debbasch, F.; Bonnaud, G.
1991-10-01
This report gives a rigorous and consistent hydrodynamic and kinetic description of a charged fluid and the basis equations, in a relativistic context. This study should lead to a reliable model, as much analytical as numerical, of relativistic plasmas which will appear in the interaction of a strong laser field with a plasma. For simplicity, we limited our study to a perfect fluid or, in other words, we disregarded the energy dissipation processes inside the fluid [fr
Ball-thrower's fracture of the humerus
International Nuclear Information System (INIS)
Callaghan, Eric B.; Bennett, D. Lee; El-Khoury, Georges Y.; Ohashi, Kenjirou
2004-01-01
A relatively rare case of ball-thrower's fracture of the humerus is presented. Severe muscular action is an uncommon cause of humeral fractures but has been well documented in the orthopedic literature. To our knowledge, this fracture has not been described in the radiology literature, and awareness of this entity could preclude further unnecessary workup. The mechanism of injury and its typical radiographic appearance is described. (orig.)
From a Ball Game to Incompleteness
Indian Academy of Sciences (India)
tree is a tree in which each node has a finite number of children. In a rooted tree, the sequence of nodes from the root to a leaf, where the (j + 1)th node is a child of the jth node, is called a. 'path'. For instance, in the above tree, the root contains 2, and all leafs are the nodes that contain 0. Since any ball is replaced with a fi-.
Electromagnetic Detection of a Perfect Carpet Cloak
Shi, Xihang; Gao, Fei; Lin, Xiao; Zhang, Baile
2015-05-01
It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)]. However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible. On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters. In this paper, we numerically investigate the electromagnetic radiation from a charged particle passing through a perfect carpet cloak and propose an experimentally verifiable model to demonstrate symmetry breaking of transformation optics.
A perfect launch viewed across Banana Creek
2000-01-01
Billows of smoke and steam surround Space Shuttle Discovery as it lifts off from Launch Pad 39A on mission STS-92 to the International Space Station. The perfect on-time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.
The surveyors' quest for perfect alignment
2003-01-01
Photogrammetry of a CMS endcap and part of the hadronic calorimeter.The structure was covered with targets photographed by digital cameras. Perfect alignment.... Although CERN's surveyors do not claim to achieve it, they are constantly striving for it and deploy all necessary means to come as close as they can. In their highly specialised field of large-scale metrology, the solution lies in geodesy and photogrammetry, both of which are based on increasingly sophisticated instruments and systems. In civil engineering, these techniques are used for non-destructive inspection of bridges, dams and other structures, while industrial applications include dimensional verification and deformation measurement in large mechanical assemblies. The same techniques also come into play for the metrology of research tools such as large telescopes and of course, particle accelerators. Particle physics laboratories are especially demanding customers, and CERN has often asked for the impossible. As a result, the alignment metro...
A Dream of the Perfect Map – Calvino’s Invisible Cities
Directory of Open Access Journals (Sweden)
Mario Vrbančić
2012-06-01
Full Text Available The cartographer’s dream is that of a perfect map: a map that perfectly represents a territory, a dream of Divine knowledge; a map that has haunted the ideology of representation throughout history; a map so detailed that it coincides with real space. In a short parable, ‘Museum, on Exactitude in Science’, Borges describes the mysterious gild of cartographers which charts such a map. Although Borges’ narrative finishes with a nostalgic conclusion about a superfluous and forgotten discipline, the cartographer’s dream of a perfect map has never ceased: it has merely varied throughout history. For medieval cartographers the perfect map included the physical cosmos and the spiritual one. In Dante’s time the European ‘mappa mundi’ depicted one single landmass, the Northern Hemisphere, with Jerusalem in the middle and the world is variously shown as dominated or held by God. In the Psalter mappa mundi, which is surmounted by an illustration of the Last Judgement, God holds a little dark red ball, the size of a golf ball – the world. Its size reminds us of the world’s shrinkage due to the advancing technology of transport and communications of the 20th century. Borges’ mystical Aleph on the other hand contains the whole cosmos within its confines (no bigger than the globe held by God on the Hereford map. In a sense the Aleph is a goal of cartography, its theology. Instead of God’s gaze into the unknown distance (as on the Hereford map, Renaissance cartographers imagined the Ptolemaic human gaze looking down on the Earth. The cartographer’s ‘organ of sight’ began to shift from the inner eye of the soul to the physical eye of the body: the idea of the globe as a whole observed by a ‘roving human eye’ is connected to the Renaissance idea of perspectivism. In many respects Renaissance concepts of space laid the foundations for the Enlightenment project. Maps were stripped of spiritual space, of their angels and their
CVD carbon powders modified by ball milling
Directory of Open Access Journals (Sweden)
Kazmierczak Tomasz
2015-09-01
Full Text Available Carbon powders produced using a plasma assisted chemical vapor deposition (CVD methods are an interesting subject of research. One of the most interesting methods of synthesizing these powders is using radio frequency plasma. This method, originally used in deposition of carbon films containing different sp2/sp3 ratios, also makes possible to produce carbon structures in the form of powder. Results of research related to the mechanical modification of these powders have been presented. The powders were modified using a planetary ball mill with varying parameters, such as milling speed, time, ball/powder mass ratio and additional liquids. Changes in morphology and particle sizes were measured using scanning electron microscopy and dynamic light scattering. Phase composition was analyzed using Raman spectroscopy. The influence of individual parameters on the modification outcome was estimated using statistical method. The research proved that the size of obtained powders is mostly influenced by the milling speed and the amount of balls. Powders tend to form conglomerates sized up to hundreds of micrometers. Additionally, it is possible to obtain nanopowders with the size around 100 nm. Furthermore, application of additional liquid, i.e. water in the process reduces the graphitization of the powder, which takes place during dry milling.
3D Printing of Ball Grid Arrays
Sinha, Shayandev; Hines, Daniel; Dasgupta, Abhijit; Das, Siddhartha
Ball grid arrays (BGA) are interconnects between an integrated circuit (IC) and a printed circuit board (PCB), that are used for surface mounting electronic components. Typically, lead free alloys are used to make solder balls which, after a reflow process, establish a mechanical and electrical connection between the IC and the PCB. High temperature processing is required for most of these alloys leading to thermal shock causing damage to ICs. For producing flexible circuits on a polymer substrate, there is a requirement for low temperature processing capabilities (around 150 C) and for reducing strain from mechanical stresses. Additive manufacturing techniques can provide an alternative methodology for fabricating BGAs as a direct replacement for standard solder bumped BGAs. We have developed aerosol jet (AJ) printing methods to fabricate a polymer bumped BGA. As a demonstration of the process developed, a daisy chain test chip was polymer bumped using an AJ printed ultra violet (UV) curable polymer ink that was then coated with an AJ printed silver nanoparticle laden ink as a conducting layer printed over the polymer bump. The structure for the balls were achieved by printing the polymer ink using a specific toolpath coupled with in-situ UV curing of the polymer which provided good control over the shape, resulting in well-formed spherical bumps on the order of 200 um wide by 200 um tall for this initial demonstration. A detailed discussion of the AJ printing method and results from accelerated life-time testing will be presented
Relation Between Hertz Stress-Life Exponent, Ball-Race Conformity, and Ball Bearing Life
Zaretsky, Erwin V.; Poplawski, Joseph V.; Root, Lawrence E.
2008-01-01
ANSI/ABMA and ISO standards based on Lundberg-Palmgren bearing life theory are normalized for ball bearings having inner- and outerrace conformities of 52 percent (0.52) and made from pre-1940 bearing steel. The Lundberg-Palmgren theory incorporates an inverse 9th power relation between Hertz stress and fatigue life for ball bearings. The effect of race conformity on ball set life independent of race life is not incorporated into the Lundberg-Palmgren theory. In addition, post-1960 vacuum-processed bearing steel exhibits a 12th power relation between Hertz stress and life. The work reported extends the previous work of Zaretsky, Poplawski, and Root to calculate changes in bearing life--that includes the life of the ball set--caused by race conformity, Hertz stress-life exponent, ball bearing type and bearing series. The bearing fatigue life in actual application will usually be equal to or greater than that calculated using the ANSI/ABMA and ISO standards that incorporate the Lundberg-Palmgren theory. The relative fatigue life of an individual race is more sensitive to changes in race conformity for Hertz stress-life exponent n of 12 than where n = 9. However, when the effects are combined to predict actual bearing life for a specified set of conditions and bearing geometry, the predicted life of the bearing will be greater for a value of n = 12 than n = 9.
Inter-Faith Reading of Perfect Man With Mystical Approach
Directory of Open Access Journals (Sweden)
Fatemeh Musavi
2010-12-01
Full Text Available The expression Insan –e kamil (perfect man is often said to have first been used by Muhyiddin ibn 'Arabi (1165 -1240AD, though the concept of the term is much older. In his theosophical teaching, the doctrine of insan e- kamil, is held a prominent place. After him two other great Sufis, Aziz Nasafi (1300AD and 'Abd al- karim ibn Ibrahim al- Jili (1366 – 1424 AD, each wrote a work on this very issue. These works are regarded as explanations of Ibn Arabi’s teachings on human perfection. In Islamic mysticism, Perfect man is the one who within their soul possesses all God's names and attributes. Thus the perfect man’s existence, reality and inner might become a clear mirror and a complete reflection of the Perfection, Beauty and Glory of the Essence of the One, so that he becomes Godlike. However, the idea of human perfectibility going back to other religions and human schools even before Islam. In Abrahimic religions there are some joint teachings that could be considered as main statements for the doctrine of Perfect Man In Jewish scriptures the notion of human creation in God's image suggests that the human being is able to be God's like and the perfection is available to him. However, Jews do not believe a perfect man. They hold that even Moses is not a perfect man. In Christianity, Although Jesus encourages his followers to be perfect like their heavenly fathers, the doctrine of original sin to be considered as an obstacle for human perfectibility.This essay examines some significant element in human perfectibility from the view points of some scholars of Judaism, Christianity and Islam and presents some similarities and differences of their view points.
Inter-Faith Reading of Perfect Man With Mystical Approach
Directory of Open Access Journals (Sweden)
Mohammadkazem Shaker
2011-01-01
Full Text Available The expression Insan –e kamil (perfect man is often said to have first been used by Muhyiddin ibn 'Arabi (1165 -1240AD, though the concept of the term is much older. In his theosophical teaching, the doctrine of insan e- kamil, is held a prominent place. After him two other great Sufis, Aziz Nasafi (1300AD and 'Abd al- karim ibn Ibrahim al- Jili (1366 – 1424 AD, each wrote a work on this very issue. These works are regarded as explanations of Ibn Arabi’s teachings on human perfection. In Islamic mysticism, Perfect man is the one who within their soul possesses all God's names and attributes. Thus the perfect man’s existence, reality and inner might become a clear mirror and a complete reflection of the Perfection, Beauty and Glory of the Essence of the One, so that he becomes Godlike. However, the idea of human perfectibility going back to other religions and human schools even before Islam. In Abrahimic religions there are some joint teachings that could be considered as main statements for the doctrine of Perfect Man In Jewish scriptures the notion of human creation in God's image suggests that the human being is able to be God's like and the perfection is available to him. However, Jews do not believe a perfect man. They hold that even Moses is not a perfect man. In Christianity, Although Jesus encourages his followers to be perfect like their heavenly fathers, the doctrine of original sin to be considered as an obstacle for human perfectibility.This essay examines some significant element in human perfectibility from the view points of some scholars of Judaism, Christianity and Islam and presents some similarities and differences of their view points.
Inter-Faith Reading of Perfect Man With Mystical Approach
Directory of Open Access Journals (Sweden)
Shaker, M.K
2011-01-01
Full Text Available The expression Insan –e kamil (perfect man is often said to have first been used by Muhyiddin ibn 'Arabi (1165 -1240AD, though the concept of the term is much older. In his theosophical teaching, the doctrine of insan e- kamil, is held a prominent place. After him two other great Sufis, Aziz Nasafi (1300AD and 'Abd al- karim ibn Ibrahim al- Jili (1366 – 1424 AD, each wrote a work on this very issue. These works are regarded as explanations of Ibn Arabi’s teachings on human perfection. In Islamic mysticism, Perfect man is the one who within their soul possesses all God's names and attributes. Thus the perfect man’s existence, reality and inner might become a clear mirror and a complete reflection of the Perfection, Beauty and Glory of the Essence of the One, so that he becomes Godlike. However, the idea of human perfectibility going back to other religions and human schools even before Islam. In Abrahimic religions there are some joint teachings that could be considered as main statements for the doctrine of Perfect Man In Jewish scriptures the notion of human creation in God's image suggests that the human being is able to be God's like and the perfection is available to him. However, Jews do not believe a perfect man. They hold that even Moses is not a perfect man. In Christianity, Although Jesus encourages his followers to be perfect like their heavenly fathers, the doctrine of original sin to be considered as an obstacle for human perfectibility.This essay examines some significant element in human perfectibility from the view points of some scholars of Judaism, Christianity and Islam and presents some similarities and differences of their view points.
Nearly perfect fluidity: from cold atomic gases to hot quark gluon plasmas
International Nuclear Information System (INIS)
Schaefer, Thomas; Teaney, Derek
2009-01-01
Shear viscosity is a measure of the amount of dissipation in a simple fluid. In kinetic theory shear viscosity is related to the rate of momentum transport by quasi-particles, and the uncertainty relation suggests that the ratio of shear viscosity η to entropy density s in units of ℎ/k B is bounded by a constant. Here, ℎ is Planck's constant and k B is Boltzmann's constant. A specific bound has been proposed on the basis of string theory where, for a large class of theories, one can show that η/s ≥ ℎ/(4πk B ). We will refer to a fluid that saturates the string theory bound as a perfect fluid. In this review we summarize theoretical and experimental information on the properties of the three main classes of quantum fluids that are known to have values of η/s that are smaller than ℎ/k B . These fluids are strongly coupled Bose fluids, in particular liquid helium, strongly correlated ultracold Fermi gases and the quark gluon plasma. We discuss the main theoretical approaches to transport properties of these fluids: kinetic theory, numerical simulations based on linear response theory and holographic dualities. We also summarize the experimental situation, in particular with regard to the observation of hydrodynamic behavior in ultracold Fermi gases and the quark gluon plasma.
Aerodynamics in the classroom and at the ball park
Cross, Rod
2012-04-01
Experiments suitable for classroom projects or demonstrations are described concerning the aerodynamics of polystyrene balls. A light ball with sufficient backspin can curve vertically upward through the air, defying gravity and providing a dramatic visual demonstration of the Magnus effect. A ball projected with backspin can also curve downward with a vertical acceleration greater than that due to gravity if the Magnus force is negative. These effects were investigated by filming the flight of balls projected in an approximately horizontal direction so that the lift and drag forces could be easily measured. The balls were also fitted with artificial raised seams and projected with backspin toward a vertical target in order to measure the sideways deflection over a known horizontal distance. It was found that (a) a ball with a seam on one side can deflect either left or right depending on its launch speed and (b) a ball with a baseball seam can also deflect sideways even when there is no sideways component of the drag or lift forces acting on the ball. Depending on the orientations of the seam and the spin axis, a sideways force on a baseball can arise either if there is rough patch on one side of the ball or if there is a smooth patch. A scuff ball with a rough patch on one side is illegal in baseball. The effect of a smooth patch is a surprising new observation.
Biomechanics of Heading a Soccer Ball: Implications for Player Safety
Directory of Open Access Journals (Sweden)
Charles F. Babbs
2001-01-01
Full Text Available To better understand the risk and safety of heading a soccer ball, the author created a set of simple mathematical models based upon Newton�s second law of motion to describe the physics of heading. These models describe the player, the ball, the flight of the ball before impact, the motion of the head and ball during impact, and the effects of all of these upon the intensity and the duration of acceleration of the head. The calculated head accelerations were compared to those during presumably safe daily activities of jumping, dancing, and head nodding and also were related to established criteria for serious head injury from the motor vehicle crash literature. The results suggest heading is usually safe but occasionally dangerous, depending on key characteristics of both the player and the ball. Safety is greatly improved when players head the ball with greater effective body mass, which is determined by a player�s size, strength, and technique. Smaller youth players, because of their lesser body mass, are more at risk of potentially dangerous headers than are adults, even when using current youth size balls. Lower ball inflation pressure reduces risk of dangerous head accelerations. Lower pressure balls also have greater “touch” and “playability”, measured in terms of contact time and contact area between foot and ball during a kick. Focus on teaching proper technique, the re-design of age-appropriate balls for young players with reduced weight and inflation pressure, and avoidance of head contact with fast, rising balls kicked at close range can substantially reduce risk of subtle brain injury in players who head soccer balls.
A general theory for ball lightning structure and light output
Morrow, R.
2018-03-01
A general theory for free-floating ball lightning is presented which unifies the phantom plasma ball theory involving the production of very little light, with theories for ball lightning involving light output produced by burning particles from the soil. The mechanism for the formation of plasma balls is shown to be quite general, producing very similar plasma balls independent of initial ion densities over four orders of magnitude. All that is required is an excess of positive ions in the initial ball of ions. The central plasma density after 1 s is shown to be the reciprocal of the ion neutralization coefficient for all cases, both analytically and computationally. Further, the plasma region has zero electric field in all cases. Surrounding the plasma ball is a sphere of positive ions moving away from the centre via their own space-charge field; this space-charge field, which is the same in all cases near the plasma ball, drives negative ions and negative particles towards the plasma centre. The connection with burning particle theories is the proposition that the burning particles are highly-charged which is very likely after a lightning strike. Burning negatively charged particles would be driven into the plasma ball region and trapped while any positively charged particles would be driven away. The plasma ball structure is shown to last more than 10 s and the ‘burnout time’ for a typical coal particle (as an example) has been measured at 5-10 s this is comparable with the lifetimes observed for ball lightning. The light output from a few hundred particles is estimated to be ~1 W, a typical output for ball lightning. Finally, suggestions are made for the generation of ball lightning in the laboratory.
Modern problems of perfection of elite light athletic sportsmen’s technical skillfulness perfection
Directory of Open Access Journals (Sweden)
A.V. Kolot
2016-04-01
Full Text Available Purpose: perfection of elite sportsmen’s technical skillfulness in competition kinds of light athletic. Material: the data of more than 60 literature sources were systemized. Expert questioning of 36 coaches, having experience of work with elite sportsmen, was carried out; documents of training process planning were analyzed as well as sportsmen’s diaries (n=244. Results: we have presented main principles of sportsmen’s technical skillfulness perfection and elucidated characteristics of technical training methodic. We have determined main priorities of technical training building for light athletes at every stage of many years’ perfection. Dynamic of competition practice volume has been found as well as main requirements to selection of training means of technical orientation. The data of bio-mechanical criteria of sportsmen’s technical skillfulness assessment have been supplemented. Conclusions: effectiveness of sportsmen’s training methodic is determined by realization of previous stages’ technical potential in final competition results. It can be achieved by determination of means of and methods of different orientation rational correlation.
Modern problems of perfection of elite light athletic sportsmen’s technical skillfulness perfection
Directory of Open Access Journals (Sweden)
Kolot A.V.
2016-02-01
Full Text Available Purpose: perfection of elite sportsmen’s technical skillfulness in competition kinds of light athletic. Material: the data of more than 60 literature sources were systemized. Expert questioning of 36 coaches, having experience of work with elite sportsmen, was carried out; documents of training process planning were analyzed as well as sportsmen’s diaries (n=244. Results: we have presented main principles of sportsmen’s technical skillfulness perfection and elucidated characteristics of technical training methodic. We have determined main priorities of technical training building for light athletes at every stage of many years’ perfection. Dynamic of competition practice volume has been found as well as main requirements to selection of training means of technical orientation. The data of bio-mechanical criteria of sportsmen’s technical skillfulness assessment have been supplemented. Conclusions: effectiveness of sportsmen’s training methodic is determined by realization of previous stages’ technical potential in final competition results. It can be achieved by determination of means of and methods of different orientation rational correlation.
Long, Dan; Niu, Meng; Tan, Longfei; Fu, Changhui; Ren, Xiangling; Xu, Ke; Zhong, Hongshan; Wang, Jingzhuo; Li, Laifeng; Meng, Xianwei
2017-06-29
Combined thermo-chemotherapy displays outstanding synergically therapeutic efficiency when compared with standalone thermotherapy and chemotherapy. Herein, we developed a smart tri-stimuli-responsive drug delivery system involving X@BB-ZrO 2 NPs (X represents loaded IL, DOX, keratin and tetradecanol) based on novel ball-in-ball-structured ZrO 2 nanoparticles (BB-ZrO 2 NPs). The microwave energy conversion efficiency of BB-ZrO 2 NPs was 41.2% higher than that of traditional single-layer NPs due to the cooperative action of self-reflection and spatial confinement effect of the special two-layer hollow nanostructure. The tri-stimuli-responsive controlled release strategy indicate that integrated pH, redox and microwaves in single NPs based on keratin and tetradecanol could effectively enhance the specific controlled release of DOX. The release of DOX was only 8.1% in PBS with pH = 7.2 and GSH = 20 μM. However, the release could reach about 50% at the tumor site (pH = 5.5, GSH = 13 mM) under microwave ablation. The as-made X@BB-ZrO 2 NPs exhibited perfect synergic therapy effect of chemotherapy and microwave ablation both in subcutaneous tumors (H22 tumor-bearing mice) and deep tumors (liver transplantation VX2 tumor-bearing rabbit model). There was no recurrence and death in the X@BB-ZrO 2 + MW group during the therapy of subcutaneous tumors even on the 42 nd day. The growth rates in the deep tumor of the control, MW and X@BB-ZrO 2 + MW groups were 290.1%, 14.1% and -42% 6 days after ablation, respectively. Dual-source CT was used to monitor the metabolism behavior of the as-made BB-ZrO 2 NPs and traditional CT was utilized to monitor the tumor growth in rabbits. Frozen section examination and ICP results indicated the precise control of drug delivery and enhanced cytotoxicity by the tri-stimuli-responsive controlled release strategy. The ball-in-ball ZrO 2 NPs with high microwave energy conversion efficiency were first developed for synergic microwave ablation and
Mucormycosis (Mucor fungus ball) of the maxillary sinus.
Cho, Hang Sun; Yang, Hoon Shik; Kim, Kyung Soo
2014-01-01
A fungus ball is an extramucosal fungal proliferation that completely fills one or more paranasal sinuses and usually occurs as a unilateral infection. It is mainly caused by Aspergillus spp in an immunocompetent host, but some cases of paranasal fungal balls reportedly have been caused by Mucor spp. A Mucor fungus ball is usually found in the maxillary sinus and/or the sphenoid sinus and may be black in color. Patients with mucormycosis, or a Mucor fungal ball infection, usually present with facial pain or headache. On computed tomography, there are no pathognomonic findings that are conclusive for a diagnosis of mucormycosis. In this article we report a case of mucormycosis in a 56-year-old woman and provide a comprehensive review of the literature on the "Mucor fungus ball." To the best of our knowledge, 5 case reports (8 patients) have been published in which the fungus ball was thought to be caused by Mucor spp.
Micro structrual characterization and analysis of ball milled silicon carbide
Madhusudan, B. M.; Raju, H. P.; Ghanaraja., S.
2018-04-01
Mechanical alloying has been one of the prominent methods of powder synthesis technique in solid state involving cyclic deformation, cold welding and fracturing of powder particles. Powder particles in this method are subjected to greater mechanical deformation due to the impact of ball-powder-ball and ball-powder-container collisions that occurs during mechanical alloying. Strain hardening and fracture of particles decreases the size of the particles and creates new surfaces. The objective of this Present work is to use ball milling of SiC powder for different duration of 5, 10, 15 and 20 hours by High energy planetary ball milling machine and to evaluate the effect of ball milling on SiC powder. Micro structural Studies using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and EDAX has been investigated.
Perfect crystal interferometer and its applications
Energy Technology Data Exchange (ETDEWEB)
Hasegawa, Yuji [Atominstitut der Oesterreichischen Universitaeten, Vienna (Austria)
1996-08-01
The interferometry with angstrom scale wavelength has developed steadily, and various types of interferometers have been investigated. Among them, LLL interferometers are widely used. The first neutron interferometry was achieved in 1962 by Maier-Leibnitz et al. A new type of neutron interferometers was constructed with a perfect crystal, and experimentally performed in 1974 by Rauch et al. The precise measurements with LLL neutron interferometers were performed on scattering length, gravitational effect, coherence, Fizeau effects, spin superposition, complementarity, and post-selection effects. Since the early stage of quantum physics, the double-slit experiment has served as the example of the epistemologically strange features of quantum phenomena, and its course of study is described. The time-delayed interferometry with nuclear resonant scattering of synchrotron radiation and phase transfer in time-delayed interferometry with nuclear resonant scattering were experimented, and are briefly reported. A geometric phase factor was derived for a split beam experiment as an example of cyclic evolution. The geometric phase was observed with a two-loop neutron interferometer. All the experimental results showed complete agreement with the theoretical treatment. (K.I.)
Memory and Perfection in Ferroelastic Inclusion Compounds
International Nuclear Information System (INIS)
Hollingsworth, M.; Peterson, M.; Rush, J.; Brown, M.; Abel, M.; Black, A.; Dudley, M.; Raghothamachar, B.; Werner-Zwanziger, U.
2005-01-01
In a series of ferroelastic urea inclusion compounds (UICs), in which domain reorientation occurs upon application of an external anisotropic force, introduction of a relaxive impurity that disrupts a specific hydrogen-bonding network transforms a plastic (irreversible) domain-switching process into one that exhibits a striking memory effect and 'rubber-like behavior', a form of pseudoelasticity. As expected for a highly cooperative process, the ferroelastic response to the impurity concentration exhibits a critical threshold. Through synchrotron white-beam X-ray topography (SWBXT) of crystals under stress, videomicroscopy of spontaneous repair during crystal growth, acoustomechanical relaxation of daughter domains, kinetic measurements of spontaneous domain reversion, and solid-state 2 H NMR of labeled guests, this work shows how relaxive impurities lower the barrier to domain switching and how differences in perfection between mother and daughter domains provide the driving force for the memory effects. Although the interfacial effects implicated here are different from the volume effects that operate in certain shape memory materials, the twinning and defect phenomena responsible for the rubber-like behavior and memory effects should be generally applicable to domain switching in ferroelastic and ferroelectric crystals and to other solid-state processes
Natural death and the work of perfection.
Young, Alexey
1998-08-01
The historic or traditional Christian view of pain (suffering) and death, especially as preserved by the Christians East (i.e., the Orthodox), is radically opposed to the modern secular obsession with avoidance of pain. Everything about this life has its goal or aim in a mystical reality, the Kingdom of Heaven, for which earthly life is a preparation. While neither illness nor health are seen as ends in themselves, both are viewed as proceeding from the will of God for our benefit and have no ultimate meaning or purpose outside of eternal life. Death may be a relief or an ending of suffering, but in itself it is not "good" but evil. Because they are the embodiment of lived theology, saints' lives can be a sure guide to understanding how to die as a traditional Christian. To illustrate this, I have chosen some examples from the lives of relatively recent saints. I myself am from the Russian Orthodox spiritual tradition, so all but one of my examples come from pre-Revolutionary Russia. The question is not so much whether or not a traditional Christian can countenance physician-assisted suicide, but rather, what is the meaning or purpose of pain and suffering in general. Is it part of the "work of perfection" required of those who wish to enter the Kingdom of Heaven and therefore not to be completely denied?
LOW COMPRESSION TENNIS BALLS AND SKILL DEVELOPMENT
Directory of Open Access Journals (Sweden)
John Hammond
2006-12-01
Full Text Available Coaching aims to improve player performance and coaches have a number of coaching methods and strategies they use to enhance this process. If new methods and ideas can be determined to improve player performance they will change coaching practices and processes. This study investigated the effects of using low compression balls (LCBs during coaching sessions with beginning tennis players. In order to assess the effectiveness of LCBs on skill learning the study employed a quasi-experimental design supported by qualitative and descriptive data. Beginner tennis players took part in coaching sessions, one group using the LCBs while the other group used standard tennis balls. Both groups were administered a skills at the beginning of a series of coaching sessions and again at the end. A statistical investigation of the difference between pre and post-test results was carried out to determine the effect of LCBs on skill learning. Additional qualitative data was obtained through interviews, video capture and the use of performance analysis of typical coaching sessions for each group. The skill test results indicated no difference in skill learning when comparing beginners using the LCBs to those using the standard balls. Coaches reported that the LCBs appeared to have a positive effect on technique development, including aspects of technique that are related to improving power of the shot. Additional benefits were that rallies went on longer and more opportunity for positive reinforcement. In order to provide a more conclusive answer to the effects of LCBs on skill learning and technique development recommendations for future research were established including a more controlled experimental environment and larger sample sizes across a longer period of time
The methodology of composing the exercises system with fit balls.
Directory of Open Access Journals (Sweden)
Voronov N.P.
2011-02-01
Full Text Available The original methodology of composing the exercises system with fit balls was considered. More than 10 publications were analysed. On the lesson with fit balls the problem was revealed. In the experiment took part 30 students at the age from 18 till 21. All the famous exercises were systematized. As a result, a big attractiveness and assimilability of the proposed complex was revealed. The effectiveness of the complex of physical exercises with fit balls for students was proved.
Random power series in the unit ball of Cn
International Nuclear Information System (INIS)
Shi Jihuai.
1989-07-01
The random power series in the unit disc has been studied by many authors. In this paper, we studied the random power series in the unit ball of C n and generalized some results in the unit disc to the unit ball, in particular, the result obtained recently by Duren has been generalized to the unit ball. The main tool used here is the generalized Salem-Zygmund's theorem. (author). 12 refs
Amebiasis in four ball pythons, Python reginus.
Kojimoto, A; Uchida, K; Horii, Y; Okumura, S; Yamaguch, R; Tateyama, S
2001-12-01
Between September 13th and November 18th in 1999, four ball pythons, Python reginus kept in the same display, showed anorexia and died one after another. At necropsy, all four snakes had severe hemorrhagic colitis. Microscopically, all snakes had severe necrotizing hemorrhagic colitis, in association with ameba-like protozoa. Some of the protozoa had macrophage-like morphology and others formed protozoal cysts with thickened walls. These protozoa were distributed throughout the wall in the large intestine. Based on the pathological findings, these snakes were infested with a member of Entamoeba sp., presumably with infection by Entamoeba invadens, the most prevalent type of reptilian amoebae.
Collective flow measured with the Plastic Ball
International Nuclear Information System (INIS)
Ritter, H.G.; Gutbrod, H.H.; Kampert, K.H.; Kolb, B.; Poskanzer, A.M.; Schicker, R.; Schmidt, H.R.; Siemiarczuk, T.
1989-08-01
The experimental results from the Plastic Ball detector have contributed vastly to the understanding of the reaction mechanism of nuclear collisions at several hundred MeV per nucleon. The discovery of the collective flow phenomena (bounce-off of spectator fragments, side-splash in the reaction plane, and squeeze-out out of the reaction plane), as they were predicted by hydrodynamical models, has led to the experimental observation of compressed nuclear matter, which is a necessary condition before one can study the equation of state in detail and search for phase transitions at higher energies. 39 refs., 9 figs., 1 tab
A proposed experiment on ball lightning model
International Nuclear Information System (INIS)
Ignatovich, Vladimir K.; Ignatovich, Filipp V.
2011-01-01
Highlights: → We propose to put a glass sphere inside an excited gas. → Then to put a light ray inside the glass in a whispering gallery mode. → If the light is resonant to gas excitation, it will be amplified at every reflection. → In ms time the light in the glass will be amplified, and will melt the glass. → A liquid shell kept integer by electrostriction forces is the ball lightning model. -- Abstract: We propose an experiment for strong light amplification at multiple total reflections from active gaseous media.
Quenching simulation of steel grinding balls
Energy Technology Data Exchange (ETDEWEB)
Zapata-Hernandez, O.; Reyes, L. A.; Camurri, C.; Carrasco, C.; Garza-Monte-de-Oca, F.; Colas, R.
2015-07-01
The phase transformations of high carbon steel during quenching and equalizing were modelled using commercial computer packages based on the finite element method and the kinetic transformation of steel. The model was used to predict the temperature and microstructural changes taking place within balls of two different sizes that are used for grinding mineral ores. A good correlation between the temperatures measured by inserted thermocouples and those predicted by the model was obtained after modifying the thermal conductivity of the steel within the temperature domain at which mixed phases are present. The phase transformations predicted were confirmed by metallographic analyses. (Author)
Crystal Ball evidence for new states
International Nuclear Information System (INIS)
Coyne, D.G.
1981-09-01
Evidence for three new particles observed in the Crystal Ball detector is presented. The first particle, at 3592 MeV, is seen inclusively in γ transitions from psi', and is thus a candidate for eta/sub c/'. The other two, at 1440 and 1640 MeV, are best seen in exclusive decays of psi involving a prompt γ, and are thus candidates for bound states of two gluons. Detailed reasons are presented to support the contention that these states are distinct from previously observed candidates such as E(1420). Alternative hypotheses are discussed
Results on charmonium from the Crystal Ball
Partridge, R; Bloom, Elliott D; Bulos, F; Burnett, T; Cavalli-Sforza, M; Chestnut, R; Coyne, D; Gaiser, J; Godfrey, G; Hofstadter, R; Kiesling, C; Kirkbride, I; Kolanoski, H; Kollmann, W; Liberman, A; O'Reilly, J; Oreglia, M J; Peck, C; Porter, F; Richardson, M; Sadrozinski, H F W; Strauch, K; Tompkins, J; Wacker, K
1979-01-01
Results from the Crystal Ball experiment at SPEAR are presented. A preliminary analysis of the 3 photon final state from the J/ psi (3095) and of the cascade decays of the psi '(3684) yield new upper limits on the controversial states X(2820), chi (3455) and the even C- parity state at 3.59 GeV. From inclusive gamma -ray spectra of the J/ psi and psi ' preliminary branching ratios for psi ' to chi states and upper limits for J/ psi , psi ' to eta /sub c/, eta /sub c/' are given. (15 refs).
Ball Bearing Analysis with the ORBIS Tool
Halpin, Jacob D.
2016-01-01
Ball bearing design is critical to the success of aerospace mechanisms. Key bearing performance parameters, such as load capability, stiffness, torque, and life all depend on accurate determination of the internal load distribution. Hence, a good analytical bearing tool that provides both comprehensive capabilities and reliable results becomes a significant asset to the engineer. This paper introduces the ORBIS bearing tool. A discussion of key modeling assumptions and a technical overview is provided. Numerous validation studies and case studies using the ORBIS tool are presented. All results suggest the ORBIS code closely correlates to predictions on bearing internal load distributions, stiffness, deflection and stresses.
Simulation of ball motion and energy transfer in a planetary ball mill
International Nuclear Information System (INIS)
Lu Sheng-Yong; Mao Qiong-Jing; Li Xiao-Dong; Yan Jian-Hua; Peng Zheng
2012-01-01
A kinetic model is proposed for simulating the trajectory of a single milling ball in a planetary ball mill, and a model is also proposed for simulating the local energy transfer during the ball milling process under no-slip conditions. Based on the kinematics of ball motion, the collision frequency and power are described, and the normal impact forces and effective power are derived from analyses of collision geometry. The Hertzian impact theory is applied to formulate these models after having established some relationships among the geometric, dynamic, and thermophysical parameters. Simulation is carried out based on two models, and the effects of the rotation velocity of the planetary disk Ω and the vial-to-disk speed ratio ω/Ω on other kinetic parameters is investigated. As a result, the optimal ratio ω/Ω to obtain high impact energy in the standard operating condition at Ω = 800 rpm is estimated, and is equal to 1.15. (interdisciplinary physics and related areas of science and technology)
Hoon-Hanks, Laura L; Layton, Marylee L; Ossiboff, Robert J; Parker, John S L; Dubovi, Edward J; Stenglein, Mark D
2018-04-01
Circumstantial evidence has linked a new group of nidoviruses with respiratory disease in pythons, lizards, and cattle. We conducted experimental infections in ball pythons (Python regius) to test the hypothesis that ball python nidovirus (BPNV) infection results in respiratory disease. Three ball pythons were inoculated orally and intratracheally with cell culture isolated BPNV and two were sham inoculated. Antemortem choanal, oroesophageal, and cloacal swabs and postmortem tissues of infected snakes were positive for viral RNA, protein, and infectious virus by qRT-PCR, immunohistochemistry, western blot and virus isolation. Clinical signs included oral mucosal reddening, abundant mucus secretions, open-mouthed breathing, and anorexia. Histologic lesions included chronic-active mucinous rhinitis, stomatitis, tracheitis, esophagitis and proliferative interstitial pneumonia. Control snakes remained negative and free of clinical signs throughout the experiment. Our findings establish a causal relationship between nidovirus infection and respiratory disease in ball pythons and shed light on disease progression and transmission. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
CFD Analysis of Swing of Cricket Ball and Trajectory Prediction
G, Jithin; Tom, Josin; Ruishikesh, Kamat; Jose, Jyothish; Kumar, Sanjay
2013-11-01
This work aims to understand the aerodynamics associated with the flight and swing of a cricket ball and predict its flight trajectory over the course of the game: at start (smooth ball) and as the game progresses (rough ball). Asymmetric airflow over the ball due to seam orientation and surface roughness can cause flight deviation (swing). The values of Drag, Lift and Side forces which are crucial for determining the trajectory of the ball were found with the help of FLUENT using the standard K- ɛ model. Analysis was done to study how the ball velocity, spin imparted to be ball and the tilt of the seam affects the movement of the ball through air. The governing force balance equations in 3 dimensions in combination a MATLAB code which used Heun's method was used for obtaining the trajectory of the ball. The conditions for the conventional swing and reverse swing to occur were deduced from the analysis and found to be in alignment with the real life situation. Critical seam angle for maximum swing and transition speed for normal to reverse swing were found out. The obtained trajectories were compared to real life hawk eye trajectories for validation. The analysis results were in good agreement with the real life situation.
Two Balls' Collision of Mass Ratio 3:1
Ogawara, Yasuo; Hull, Michael M.
2018-04-01
Students will sometimes ask why momentum and kinetic energy concepts are both necessary. When physics teachers demonstrate situations that require both an understanding of kinetic energy and momentum, a favorite is Newton's cradle, or a comparable demonstration of two balls of equal mass hitting each other. However, in addition to the case of two balls of equal mass, if a ball hits another ball of three times the mass with equal speed, the results are also interesting, and, like the equal-mass demonstration, both kinetic energy and momentum are critical for understanding the motion.
An early record of ball lightning: Oliva (Spain), 1619
Domínguez-Castro, Fernando
2018-05-01
In a primary documentary source we found an early record of ball lightning (BL), which was observed in the monastery of Pi (Oliva, southeastern Spain) on 18 October 1619. The ball lightning was observed by at least three people and was described as a rolling burning vessel and a ball of fire. The ball lightning appeared following a lightning flash, showed a mainly horizontal motion, crossed a wall, smudged an image of the Lady of Rebollet (then known as Lady of Pi) and burnt her ruff, and overturned a cross.
How does gravity save or kill Q-balls?
Tamaki, Takashi; Sakai, Nobuyuki
2011-01-01
We explore stability of gravitating Q-balls with potential $V_4(\\phi)={m^2\\over2}\\phi^2-\\lambda\\phi^4+\\frac{\\phi^6}{M^2}$ via catastrophe theory, as an extension of our previous work on Q-balls with potential $V_3(\\phi)={m^2\\over2}\\phi^2-\\mu\\phi^3+\\lambda\\phi^4$. In flat spacetime Q-balls with $V_4$ in the thick-wall limit are unstable and there is a minimum charge $Q_{{\\rm min}}$, where Q-balls with $Q
Fouling research and cleaning effect by sponge ball on condencer tubes
Energy Technology Data Exchange (ETDEWEB)
Matsumoto, S; Sano, A [Kansai Electric Power Co., Inc., Osaka (Japan); Minamoto, K; Mimura, K; Kyohara, S
1978-07-01
Systematic research has been performed to investigate the cleaning effect on condensers cooled by sea water. The test has been done for a year using the test condenser at the Kainan Power Station, Kansai Electric Power Company. The main purpose of this research was to see the effect of cleaning inner walls of condenser tubes with sponge balls on the prevention of adhesion of marine creatures such as barnacles and other shellfishes. As the test tubes, the aluminum-brass and titanium tubes with 25.4 mm diameter, 1.245 mm thickness and 170 mm length were used. Frequency of cleaning and flow rate were chosen as the variable parameters. The effect of seasons was also investigated. Major conclusions drawn from this research were as follows. (1) More adhesion of barnacles was observed at slower flow speed and in titanium tubes rather than aluminum brass tubes. (2) At the flow speed of 1 m/sec. cleaning frequency of more than twice a week was necessary to perfectly avoid the adhesion. (3) In summer, the adhesion was most intensive, whereas in winter, it was the least. (4) Barnacles were the most predominant organism. (5) Cleaning with sponge balls was effective.
Fouling research and cleaning effect by sponge ball on condencer tubes
International Nuclear Information System (INIS)
Matsumoto, Seizo; Sano, Akira; Minamoto, Kenju; Mimura, Keisuke; Kyohara, Shigeru.
1978-01-01
Systematic research has been performed to investigate the cleaning effect on condensers cooled by sea water. The test has been done for a year using the test condenser at the Kainan Power Station, Kansai Electric Power Company. The main purpose of this research was to see the effect of cleaning inner walls of condenser tubes with sponge balls on the prevention of adhesion of marine creatures such as barnacles and other shellfishes. As the test tubes, the aluminum-brass and titanium tubes with 25.4 mm diameter, 1.245 mm thickness and 170 mm length were used. Frequency of cleaning and flow rate were chosen as the variable parameters. The effect of seasons was also investigated. Major conclusions drawn from this research were as follows. (1) More adhesion of barnacles was observed at slower flow speed and in titanium tubes rather than aluminum brass tubes. (2) At the flow speed of 1 m/sec. cleaning frequency of more than twice a week was necessary to perfectly avoid the adhesion. (3) In summer, the adhesion was most intensive, whereas in winter, it was the least. (4) Barnacles were the most predominant organism. (5) Cleaning with sponge balls was effective. (Aoki, K.)
Development of a perfect prognosis probabilistic model for ...
Indian Academy of Sciences (India)
A prediction model based on the perfect prognosis method was developed to predict the probability of lightning and probable time of its occurrence over the south-east Indian region. In the perfect prognosis method, statistical relationships are established using past observed data. For real time applications, the predictors ...
A cross-linguistic discourse analysis of the perfect
Swart, Henriëtte de
2007-01-01
Since Reichenbach (1947), the Present Perfect has been discussed in relation to the Simple Past. The Reichenbachian characterization E-R,S has led to the view that the English Present Perfect, with its restrictions on modification by time adverbials and its resistance to narrative structure is the
James Moores Ball: Ophthalmologist, medical historian, bibliophile.
Feibel, Robert M
2016-08-01
James Moores Ball (1862-1929) was an ophthalmologist in St. Louis, Missouri, who excelled as a medical historian and collector of rare and historic books about the history of anatomy. During his lifetime, he was best known as the author of a comprehensive, authoritative, and popular textbook titled Modern Ophthalmology First published in 1904, there were five further editions. Ball was very interested in the history of anatomy and wrote two books on this subject, the first being a biography of Andreas Vesalius, one of the earliest in English, and the second a history of the resurrection men or grave robbers who sold corpses to professors of anatomy and surgery for teaching purposes. His legacy today is the 470 volumes of his personal library, which are now in the Archives and Rare Books department of the Becker Medical Library of the Washington University School of Medicine. These texts are one of their major collections, concentrating on the history of anatomy, beginning with a first edition of Vesalius's De Humani Corporis Fabrica and holding many important and beautiful landmark volumes of anatomical atlases. © The Author(s) 2016.
Crises in a dissipative bouncing ball model
Energy Technology Data Exchange (ETDEWEB)
Livorati, André L.P., E-mail: livorati@usp.br [Departamento de Física, UNESP, Universidade Estadual Paulista, Av. 24A, 1515, Bela Vista, 13506-900, Rio Claro, SP (Brazil); School of Mathematics, University of Bristol, Bristol, BS8 1TW (United Kingdom); Instituto de Física, IFUSP, Universidade de São Paulo, USP, Rua do Matão, Tr.R 187, Cidade Universitária, 05314-970, São Paulo, SP (Brazil); Caldas, Iberê L. [Instituto de Física, IFUSP, Universidade de São Paulo, USP, Rua do Matão, Tr.R 187, Cidade Universitária, 05314-970, São Paulo, SP (Brazil); Dettmann, Carl P. [School of Mathematics, University of Bristol, Bristol, BS8 1TW (United Kingdom); Leonel, Edson D. [Departamento de Física, UNESP, Universidade Estadual Paulista, Av. 24A, 1515, Bela Vista, 13506-900, Rio Claro, SP (Brazil)
2015-11-06
Highlights: • We studied a dissipative bouncing ball dynamics. • A two-dimensional nonlinear mapping describes the dynamics. • Crises between attractors and its manifolds were characterized. • A new physical crisis between vibrating platform and an attractor was characterized. • The existence of a ‘robust’ chaotic attractor was set. - Abstract: The dynamics of a bouncing ball model under the influence of dissipation is investigated by using a two-dimensional nonlinear mapping. When high dissipation is considered, the dynamics evolves to different attractors. The evolution of the basins of the attracting fixed points is characterized, as we vary the control parameters. Crises between the attractors and their boundaries are observed. We found that the multiple attractors are intertwined, and when the boundary crisis between their stable and unstable manifolds occurs, it creates a successive mechanism of destruction for all attractors originated by the sinks. Also, a physical impact crisis is described, an important mechanism in the reduction of the number of attractors.
Hausmann, J C; Mans, C; Dreyfus, J; Reavill, D R; Lucio-Forster, A; Bowman, D D
2015-01-01
Subspectacular nematodiasis was diagnosed in three captive-bred juvenile ball pythons (Python regius) from two unrelated facilities within a 6-month period. The snakes were presented with similar lesions, including swelling of facial, periocular and oral tissues. Bilaterally, the subspectacular spaces were distended and filled with an opaque fluid, which contained nematodes and eggs. Histopathology showed nematodes throughout the periocular tissue, subspectacular space and subcutaneous tissue of the head. The nematodes from both facilities were morphologically indistinguishable and most closely resembled Serpentirhabdias species. Morphological characterization and genetic sequencing indicate this is a previously undescribed rhabdiasid nematode. Copyright © 2014 Elsevier Ltd. All rights reserved.
Residual stresses analysis in ball end milling of nickel-based superalloy Inconel 718
Energy Technology Data Exchange (ETDEWEB)
Wang, Junteng; Zhang, Dinghua; Wu, Baohai; Luo, Ming [Key Laboratory of Contemporary Design and Integrated Manufacturing Technology, Northwestern Polytechnical University (China)
2017-11-15
Inconel 718 is widely used in the aviation, space, automotive and biomedical industries because of its outstanding properties. Near-surface residual stresses that are induced by ball end milling in Inconel 718 can be crucial for the performance and service time of the machined parts. In this paper, the influences of cutting conditions, including the use of cutting parameters, cutting fluid and spindle angles, on the residual stresses in the ball end milling process of Inconel 718 alloy were investigated experimentally. X-ray diffraction measurements reveal that residual stress distributions are highly influenced by cutting parameters, especially the depth of cut and cutting speed. The milling operation with cooling induces more compressive stresses trend and the magnitude of the residual stresses increases in the tensile direction with the increase of spindle angles. These cutting induced effects were further discussed with respect to thermal- mechanical coupling theory and some observations made by optical microscopy. From this investigation, it is suggested that the machining process parameters are not the smaller the better for the control of residual stresses in the ball end milling process of Inconel 718. (author)
Czech Academy of Sciences Publication Activity Database
Zanáška, M.; Adámek, Jiří; Peterka, Matěj; Kudrna, P.; Tichý, M.
2015-01-01
Roč. 22, č. 3 (2015), č. článku 033516. ISSN 1070-664X Institutional support: RVO:61389021 Keywords : plasma * tokamak * ball- pen probe (BPP) Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.207, year: 2015 http://scitation.aip.org/content/aip/journal/pop/22/3/10.1063/1.4916572
Modeling and Analyzing the Slipping of the Ball Screw
Directory of Open Access Journals (Sweden)
Nannan Xu
Full Text Available AbstractThis paper aims to set up the ball systematic slipping model and analyze the slipping characteristics caused by different factors for a ball screw operating at high speeds. To investigate the ball screw slipping mechanism, transformed coordinate system should be established firstly. Then it is used to set up mathematical modeling for the ball slipping caused by the three main reasons and the speed of slipping can be calculated. Later, the influence of the contact angle, helix angle and screw diameter for ball screw slipping will be analyzed according to the ball slipping model and slipping speeds equation and the slipping analysis will be obtained. Finally, curve of slipping analysis and that of mechanical efficiency of the ball screw analysis by Lin are compared, which will indirectly verify the correctness of the slipping model. The slipping model and the curve of slipping analysis established in this paper will provide theory basis for reducing slipping and improving the mechanical efficiency of a ball screw operating at high speeds.
Linearly convergent stochastic heavy ball method for minimizing generalization error
Loizou, Nicolas; Richtarik, Peter
2017-01-01
In this work we establish the first linear convergence result for the stochastic heavy ball method. The method performs SGD steps with a fixed stepsize, amended by a heavy ball momentum term. In the analysis, we focus on minimizing the expected loss
Exact solutions, energy, and charge of stable Q-balls
Energy Technology Data Exchange (ETDEWEB)
Bazeia, D.; Marques, M.A. [Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, PB (Brazil); Menezes, R. [Universidade Federal da Paraiba, Departamento de Ciencias Exatas, Rio Tinto, PB (Brazil); Universidade Federal de Campina Grande, Departamento de Fisica, Campina Grande, PB (Brazil)
2016-05-15
In this work we deal with nontopological solutions of the Q-ball type in two spacetime dimensions. We study models of current interest, described by a Higgs-like and other, similar potentials which unveil the presence of exact solutions. We use the analytic results to investigate how to control the energy and charge to make the Q-balls stable. (orig.)
Attempted - to -Phase Conversion of Croconic Acid via Ball Milling
2017-05-18
ARL-TN-0824 MAY 2017 US Army Research Laboratory Attempted α- to β-Phase Conversion of Croconic Acid via Ball Milling by...Laboratory Attempted α- to β-Phase Conversion of Croconic Acid via Ball Milling by Steven W Dean, Rose A Pesce-Rodriguez, and Jennifer A Ciezak...
Wear numbers for ball cup and journal bearings
Ligterink, D.J.; Moes, H.
1980-01-01
A wear number is defined for ball cup bearings and for journal bearings where the cup and the cylindrical bearing are made of soft material. This dimensionless wear number provides a relation between the following five quantities: the radius of the ball or the length of the journal bearing in
Between Traditions: Stephen Ball and the Critical Sociology of Education
Apple, Michael W.
2013-01-01
Stephen Ball's work has deservedly received a good deal of attention. In this article, I detail a number of tasks in which the critical sociologist of education--as a "public intellectual"--should engage. I then place Ball's work within these tasks and evaluate his contributions to them. In the process, I show that one of the…
Launch Creativity with Ping-Pong Ball Challenge
Kornoelje, Joanne; Roman, Harry T.
2011-01-01
Educators at Thomas A. Edison Middle School have worked together to bring invention information and activities to life. One activity in particular, Ping-Pong Ball Invention Challenge, has proven a great success. The Ping-Pong Ball Invention Challenge was inspired by the basic rules for PBS's "Design Squad"'s "Pop Fly" activity. In this article,…
International Nuclear Information System (INIS)
Nie, Junwu; Han, Xianghua; Du, Juan; Xia, Weixing; Zhang, Jian; Guo, Zhaohui; Yan, Aru; Li, Wei; Ping Liu, J.
2013-01-01
Anisotropic magnetic SmCo 5 nanoflakes have been fabricated by surfactant-assisted ball milling (SABM) using hardened steel balls of one of the following sizes: 4, 6.5, 9.5 and 12.7 mm in diameters. The magnetic properties of SmCo 5 particles prepared by SABM with different milling ball sizes in diameters were investigated systematically. It was showed that the nanoflakes milled by amount of small size balls had a higher coercivity and lower anisotropy, i.e., worse grain orientation although in a short milling time while the nanoflakes prepared with same weight of big balls tend to have a lower coercivity, better grain orientation. The coercivity mechanism of the nanoflake was studied and it was mainly dominated with the domain-wall pinning. The SEM analysis shows that the morphology of nanoflakes prepared with different ball sizes are almost the same when the balls to powder weight ratio is fixed. The different magnetic properties caused by different ball sizes are mainly due to the different microstructure changes, i.e, grain refinement and c-axis orientation, which are demonstrated by X-ray diffraction (XRD) analysis and transmission electron microscope (TEM). Based on the experiments above, a combined milling process was suggested and done to improve magnetic properties as your need. - Highlights: • We fabricated anisotropic magnetic SmCo 5 nanoflakes by surfactant-assisted ball milling (SABM). • We investigated the magnetic properties of SmCo 5 particles systematically. It was showed that the coercivity, high or low, and grain orientation, good or bad, were influenced strongly by balls size. The different magnetisms caused by different ball sizes is mainly due to the different microstructure changes. • The coercivity mechanism of the nanoflake was studied and it was mainly dominated with the domain-wall pinning
Niu, Linkai; Cao, Hongrui; He, Zhengjia; Li, Yamin
2015-11-01
Ball passing frequencies (BPFs) are very important features for condition monitoring and fault diagnosis of rolling ball bearings. The ball passing frequency on outer raceway (BPFO) and the ball passing frequency on inner raceway (BPFI) are usually calculated by two well-known kinematics equations. In this paper, a systematic study of BPFs of rolling ball bearings is carried out. A novel method for accurately calculating BPFs based on a complete dynamic model of rolling ball bearings with localized surface defects is proposed. In the used dynamic model, three-dimensional motions, relative slippage, cage effects and localized surface defects are all considered. Moreover, localized surface defects are modeled accurately with consideration of the finite size of the ball, the additional clearance due to material absence, and changes of contact force directions. The reasonability of the proposed method for the prediction of dynamic behaviors of actual ball bearings with localized surface defects and for the calculation of BPFs is discussed by investigating the motion characteristics of a ball when it rolls through a defect. Parametric investigation shows that the shaft speed, external loads, the friction coefficient, raceway groove curvature factors, the initial contact angle, and defect sizes have great effects on BPFs. For a loaded ball bearing, the combination of rolling and sliding in contact region occurs, and the BPFs calculated by simple kinematical relationships are inaccurate, especially for high speed, low external load, and large initial contact angle conditions where severe skidding occurs. The hypothesis that the percentage variation of the spacing between impulses in a defective ball bearing was about 1-2% reported in previous investigations can be satisfied only for the conditions where the skidding effect in a bearing is slight. Finally, the proposed method is verified with two experiments.
Higher-dimensional relativistic-fluid spheres
International Nuclear Information System (INIS)
Patel, L. K.; Ahmedabad, Gujarat Univ.
1997-01-01
They consider the hydrostatic equilibrium of relativistic-fluid spheres for a D-dimensional space-time. Three physically viable interior solutions of the Einstein field equations corresponding to perfect-fluid spheres in a D-dimensional space-time are obtained. When D = 4 they reduce to the Tolman IV solution, the Mehra solution and the Finch-Skea solution. The solutions are smoothly matched with the D-dimensional Schwarzschild exterior solution at the boundary r = a of the fluid sphere. Some physical features and other related details of the solutions are briefly discussed. A brief description of two other new solutions for higher-dimensional perfect-fluid spheres is also given
Fluid observers and tilting cosmology
International Nuclear Information System (INIS)
Coley, A A; Hervik, S; Lim, W C
2006-01-01
We study perfect fluid cosmological models with a constant equation of state parameter γ in which there are two naturally defined timelike congruences, a geometrically defined geodesic congruence and a non-geodesic fluid congruence. We establish an appropriate set of boost formulae relating the physical variables, and consequently the observed quantities, in the two frames. We study expanding spatially homogeneous tilted perfect fluid models, with an emphasis on future evolution with extreme tilt. We show that for ultra-radiative equations of state (i.e. γ > 4/3), generically the tilt becomes extreme at late times and the fluid observers will reach infinite expansion within a finite proper time and experience a singularity similar to that of the big rip. In addition, we show that for sub-radiative equations of state (i.e. γ < 4/3), the tilt can become extreme at late times and give rise to an effective quintessential equation of state. To establish the connection with phantom cosmology and quintessence, we calculate the effective equation of state in the models under consideration and we determine the future asymptotic behaviour of the tilting models in the fluid frame variables using the boost formulae. We also discuss spatially inhomogeneous models and tilting spatially homogeneous models with a cosmological constant
Improved hydrogen sorption kinetics in wet ball milled Mg hydrides
Energy Technology Data Exchange (ETDEWEB)
Meng, Li
2011-05-04
In this work, wet ball milling method is used in order to improve hydrogen sorption behaviour due to its improved microstructure of solid hydrogen materials. Compared to traditional ball milling method, wet ball milling has benefits on improvement of MgH{sub 2} microstructure and further influences on its hydrogen sorption behavior. With the help of solvent tetrahydrofuran (THF), wet ball milled MgH{sub 2} powder has much smaller particle size and its specific surface area is 7 times as large as that of dry ball milled MgH{sub 2} powder. Although after ball milling the grain size is decreased a lot compared to as-received MgH{sub 2} powder, the grain size of wet ball milled MgH{sub 2} powder is larger than that of dry ball milled MgH{sub 2} powder due to the lubricant effect of solvent THF during wet ball milling. The improved particle size and specific surface area of wet ball milled MgH{sub 2} powder is found to be determining its hydrogen sorption kinetics especially at relatively low temperatures. And it also shows good cycling sorption behavior, which decides on its industrial applicability. With three different catalysts MgH{sub 2} powder shows improved hydrogen sorption behavior as well as the cyclic sorption behavior. Among them, the Nb{sub 2}O{sub 5} catalyst is found to be the most effective one in this work. Compared to the wet ball milled MgH{sub 2} powder, the particle size and specific surface area of the MgH{sub 2} powder with catalysts are similar to the previous ones, while the grain size of the MgH{sub 2} with catalysts is much finer. In this case, two reasons for hydrogen sorption improvement are suggested: one is the reduction of the grain size. The other may be as pointed out in some literatures that formation of new oxidation could enhance the hydrogen sorption kinetics, which is also the reason why its hydrogen capacity is decreased compared to without catalysts. After further ball milling, the specific surface area of wet ball milled Mg
Friction torque in thrust ball bearings grease lubricated
Ianuş, G.; Dumitraşcu, A. C.; Cârlescu, V.; Olaru, D. N.
2016-08-01
The authors investigated experimentally and theoretically the friction torque in a modified thrust ball bearing having only 3 balls operating at low axial load and lubricated with NGLI-00 and NGLI-2 greases. The experiments were made by using spin-down methodology and the results were compared with the theoretical values based on Biboulet&Houpert's rolling friction equations. Also, the results were compared with the theoretical values obtained with SKF friction model adapted for 3 balls. A very good correlation between experiments and Biboulet_&_Houpert's predicted results was obtained for the two greases. Also was observed that the theoretical values for the friction torque calculated with SKF model adapted for a thrust ball bearing having only 3 balls are smaller that the experimental values.
Ball Screw Actuator Including an Axial Soft Stop
Wingett, Paul T. (Inventor); Forrest, Steven Talbert (Inventor); Abel, Steve (Inventor); Woessner, George (Inventor); Hanlon, Casey (Inventor)
2016-01-01
An actuator includes an actuator housing, a ball screw, and an axial soft stop assembly. The ball screw extends through the actuator housing and has a first end and a second end. The ball screw is coupled to receive a drive force and is configured, upon receipt of the drive force, to selectively move in a retract direction and an extend direction. The axial soft stop assembly is disposed within the actuator housing. The axial soft stop assembly is configured to be selectively engaged by the ball screw and, upon being engaged thereby, to translate, with compliance, a predetermined distance in the extend direction, and to prevent further movement of the ball screw upon translating the predetermined distance.
Stability of a Fermi ball against deformation from spherical shape
International Nuclear Information System (INIS)
Yoshida, T.; Ogure, K.; Arafune, J.
2003-01-01
The stability of a Fermi ball (F ball), which is a kind of nontopological soliton accompanying the breakdown of the approximate Z 2 symmetry, is investigated in three situations: when it is electrically neutral, when it is electrically charged and unscreened, and when it is electrically charged and screened. We argue only that the third case is physically meaningful since the neutral F ball is unstable and the case of an unscreened charged F ball is observationally excluded when it has a sizable contribution to CDM. We find that the energy scale of the breakdown of the approximate Z 2 symmetry v should satisfy v 6 GeV if the F ball is the main component of CDM
Unpredictable Property of a Kicked Billiard Ball
International Nuclear Information System (INIS)
Shen Ying; Dai Jun; Jiang Yumei; He Yue; He Daren
2006-01-01
A simultaneous change in the systemic property of a kicked billiard ball is observed from an entirely smooth and conservative state to a piecewise smooth and quasi-dissipative state when a single controlling parameter has been adjusted. The transition induces a sudden change of a typical conservative stochastic web into a transient web. The iterations on the transient web eventually escape to some elliptic islands. In the meantime, a fat fractal forbidden web, which appears also at the threshold, grows up and cuts away increasingly more parts from the original conservative stochastic web. We numerically show that the initial conditions that generated different attractors are mixed in a random manner and the pattern remains unchanged even when smaller and smaller scales are used for examination, indicating a riddle-like basin structure that practically rules out the possibility of predicting the attractors from a given initial condition
Poincare ball embeddings of the optical geometry
International Nuclear Information System (INIS)
Abramowicz, M A; Bengtsson, I; Karas, V; Rosquist, K
2002-01-01
It is shown that the optical geometry of the Reissner-Nordstroem exterior metric can be embedded in a hyperbolic space all the way down to its outer horizon. The adopted embedding procedure removes a breakdown of flat-space embeddings which occurs outside the horizon, at and below the Buchdahl-Bondi limit (R/M=9/4 in the Schwarzschild case). In particular, the horizon can be captured in the optical geometry embedding diagram. Moreover, by using the compact Poincare ball representation of the hyperbolic space, the embedding diagram can cover the whole extent of radius from spatial infinity down to the horizon. Attention is drawn to the advantages of such embeddings in an appropriately curved space: this approach gives compact embeddings and it clearly distinguishes the case of an extremal black hole from a non-extremal one in terms of the topology of the embedded horizon
Grinding arrangement for ball nose milling cutters
Burch, C. F. (Inventor)
1974-01-01
A grinding arrangement for spiral fluted ball nose end mills and like tools includes a tool holder for positioning the tool relative to a grinding wheel. The tool is mounted in a spindle within the tool holder for rotation about its centerline and the tool holder is pivotably mounted for angular movement about an axis which intersects that centerline. A follower arm of a cam follower secured to the spindle cooperates with a specially shaped cam to provide rotation of the tool during the angular movement of the tool holder during the grinding cycle, by an amount determined by the cam profile. In this way the surface of the cutting edge in contact with the grinding wheel is maintained at the same height on the grinding wheel throughout the angular movement of the tool holder during the grinding cycle.
Recent results from the Crystal Ball
International Nuclear Information System (INIS)
Porter, F.C.
1981-09-01
During the past year, the Crystal Ball experiment has continued the investigation of e + e - interactions at SPEAR. In the course of the year, we have slightly more than doubled the available datasets at the J/psi (to 2.2 x 10 6 produced J/psi) and the psi' (to 1.8 x 10 6 produced psi') resonances, and have increased the data in the 5.2 to 7.4 GeV center-of-mass (E/sub c.m./) region. The present discussion is limited to recent results obtained with the J/psi and psi' datasets, primarily dealing with transitions among the charmonium bound states
Peploe, C; McErlain-Naylor, S A; Harland, A R; King, M A
2018-06-01
Three-dimensional kinematic data of bat and ball were recorded for 239 individual shots performed by twenty batsmen ranging from club to international standard. The impact location of the ball on the bat face was determined and assessed against the resultant instantaneous post-impact ball speed and measures of post-impact bat torsion and ball direction. Significant negative linear relationships were found between post-impact ball speed and the absolute distance of impact from the midline medio-laterally and sweetspot longitudinally. Significant cubic relationships were found between the distance of impact from the midline of the bat medio-laterally and both a measure of bat torsion and the post-impact ball direction. A "sweet region" on the bat face was identified whereby impacts within 2 cm of the sweetspot in the medio-lateral direction, and 4.5 cm in the longitudinal direction, caused reductions in ball speed of less than 6% from the optimal value, and deviations in ball direction of less than 10° from the intended target. This study provides a greater understanding of the margin for error afforded to batsmen, allowing researchers to assess shot success in more detail, and highlights the importance of players generating consistently central impact locations when hitting for optimal performance.
Scheme for achieving coherent perfect absorption by anisotropic metamaterials
Zhang, Xiujuan
2017-02-22
We propose a unified scheme to achieve coherent perfect absorption of electromagnetic waves by anisotropic metamaterials. The scheme describes the condition on perfect absorption and offers an inverse design route based on effective medium theory in conjunction with retrieval method to determine practical metamaterial absorbers. The scheme is scalable to frequencies and applicable to various incident angles. Numerical simulations show that perfect absorption is achieved in the designed absorbers over a wide range of incident angles, verifying the scheme. By integrating these absorbers, we further propose an absorber to absorb energy from two coherent point sources.
The Ideology of the Perfect Dictionary: How Efficient Can a ...
African Journals Online (AJOL)
friendly material which will improve both their fluency in and understanding of the target language, and embed acquired lexis in their long-term memory. Lexicographers, in their search for perfection and in compliance with users' wishes, are ...
Perfect 3-colorings of the cubic graphs of order 10
Directory of Open Access Journals (Sweden)
Mehdi Alaeiyan
2017-10-01
Full Text Available Perfect coloring is a generalization of the notion of completely regular codes, given by Delsarte. A perfect m-coloring of a graph G with m colors is a partition of the vertex set of G into m parts A_1, A_2, ..., A_m such that, for all $ i,j \\in \\lbrace 1, ... , m \\rbrace $, every vertex of A_i is adjacent to the same number of vertices, namely, a_{ij} vertices, of A_j. The matrix $A=(a_{ij}_{i,j\\in \\lbrace 1,... ,m\\rbrace }$, is called the parameter matrix. We study the perfect 3-colorings (also known as the equitable partitions into three parts of the cubic graphs of order 10. In particular, we classify all the realizable parameter matrices of perfect 3-colorings for the cubic graphs of order 10.
Perfect imaging with positive refraction in three dimensions
International Nuclear Information System (INIS)
Leonhardt, Ulf; Philbin, Thomas G.
2010-01-01
Maxwell's fish eye has been known to be a perfect lens within the validity range of ray optics since 1854. Solving Maxwell's equations, we show that the fish-eye lens in three dimensions has unlimited resolution for electromagnetic waves.
Simulation of MILD combustion using Perfectly Stirred Reactor model
Chen, Z.; Vanteru, Mahendra Reddy; Ruan, S.; Doan, N. A K; Roberts, William L.; Swaminathan, N.
2016-01-01
A simple model based on a Perfectly Stirred Reactor (PSR) is proposed for moderate or intense low-oxygen dilution (MILD) combustion. The PSR calculation is performed covering the entire flammability range and the tabulated chemistry approach is used
Scheme for achieving coherent perfect absorption by anisotropic metamaterials
Zhang, Xiujuan; Wu, Ying
2017-01-01
in conjunction with retrieval method to determine practical metamaterial absorbers. The scheme is scalable to frequencies and applicable to various incident angles. Numerical simulations show that perfect absorption is achieved in the designed absorbers over a
Astroseismology of neutron stars from gravitational waves in the limit of perfect measurement
Suvorov, A. G.
2018-04-01
The oscillation spectrum of a perturbed neutron star is intimately related to the physical properties of the star, such as the equation of state. Observing pulsating neutron stars therefore allows one to place constraints on these physical properties. However, it is not obvious exactly how much can be learnt from such measurements. If we observe for long enough, and precisely enough, is it possible to learn everything about the star? A classical result in the theory of spectral geometry states that one cannot uniquely `hear the shape of a drum'. More formally, it is known that an eigenfrequency spectrum may not uniquely correspond to a particular geometry; some `drums' may be indistinguishable from a normal-mode perspective. In contrast, we show that the drum result does not extend to perturbations of simple neutron stars within general relativity - in the case of axial (toroidal) perturbations of static, perfect fluid stars, a quasi-normal mode spectrum uniquely corresponds to a stellar profile. We show in this paper that it is not possible for two neutron stars, with distinct fluid profiles, to oscillate in an identical manner. This result has the information-theoretic consequence that gravitational waves completely encode the properties of any given oscillating star: unique identifications are possible in the limit of perfect measurement.
Zeroth Poisson Homology, Foliated Cohomology and Perfect Poisson Manifolds
Martínez-Torres, David; Miranda, Eva
2018-01-01
We prove that, for compact regular Poisson manifolds, the zeroth homology group is isomorphic to the top foliated cohomology group, and we give some applications. In particular, we show that, for regular unimodular Poisson manifolds, top Poisson and foliated cohomology groups are isomorphic. Inspired by the symplectic setting, we define what a perfect Poisson manifold is. We use these Poisson homology computations to provide families of perfect Poisson manifolds.
Perfect 2-colorings of the generalized Petersen graph
Indian Academy of Sciences (India)
There are no perfect 2-colorings of GP(n, 2) with the matrix A3. Proof. Suppose, contrary to our claim, there is a perfect 2-coloring of GP(n, 2) with the matrix A3. By Lemma 3.4, there are 2 vertices ai and bi, for some 0 ≤ i ≤ n−1, such that they are the same color. By symmetry, without loss of generality, we can assume T (a0) ...
Tracking of ball and players in beach volleyball videos.
Directory of Open Access Journals (Sweden)
Gabriel Gomez
Full Text Available This paper presents methods for the determination of players' positions and contact time points by tracking the players and the ball in beach volleyball videos. Two player tracking methods are compared, a classical particle filter and a rigid grid integral histogram tracker. Due to mutual occlusion of the players and the camera perspective, results are best for the front players, with 74,6% and 82,6% of correctly tracked frames for the particle method and the integral histogram method, respectively. Results suggest an improved robustness against player confusion between different particle sets when tracking with a rigid grid approach. Faster processing and less player confusions make this method superior to the classical particle filter. Two different ball tracking methods are used that detect ball candidates from movement difference images using a background subtraction algorithm. Ball trajectories are estimated and interpolated from parabolic flight equations. The tracking accuracy of the ball is 54,2% for the trajectory growth method and 42,1% for the Hough line detection method. Tracking results of over 90% from the literature could not be confirmed. Ball contact frames were estimated from parabolic trajectory intersection, resulting in 48,9% of correctly estimated ball contact points.
Tracking of Ball and Players in Beach Volleyball Videos
Gomez, Gabriel; Herrera López, Patricia; Link, Daniel; Eskofier, Bjoern
2014-01-01
This paper presents methods for the determination of players' positions and contact time points by tracking the players and the ball in beach volleyball videos. Two player tracking methods are compared, a classical particle filter and a rigid grid integral histogram tracker. Due to mutual occlusion of the players and the camera perspective, results are best for the front players, with 74,6% and 82,6% of correctly tracked frames for the particle method and the integral histogram method, respectively. Results suggest an improved robustness against player confusion between different particle sets when tracking with a rigid grid approach. Faster processing and less player confusions make this method superior to the classical particle filter. Two different ball tracking methods are used that detect ball candidates from movement difference images using a background subtraction algorithm. Ball trajectories are estimated and interpolated from parabolic flight equations. The tracking accuracy of the ball is 54,2% for the trajectory growth method and 42,1% for the Hough line detection method. Tracking results of over 90% from the literature could not be confirmed. Ball contact frames were estimated from parabolic trajectory intersection, resulting in 48,9% of correctly estimated ball contact points. PMID:25426936
Circuital model for the spherical geodesic waveguide perfect drain
González, Juan C.; Grabovičkić, Dejan; Benítez, Pablo; Miñano, Juan C.
2012-08-01
The perfect drain for the Maxwell fish eye (MFE) is a non-magnetic dissipative region placed in the focal point to absorb all the incident radiation without reflection or scattering. The perfect drain was recently designed as a material with complex permittivity that depends on frequency. However, this material is only a theoretical material, so it cannot be used in practical devices. The perfect drain has been claimed as necessary for achieving super-resolution (Leonhardt 2009 New J. Phys. 11 093040), which has increased the interest in practical perfect drains suitable for manufacturing. Here, we present a practical perfect drain that is designed using a simple circuit (made of a resistance and a capacitor) connected to the coaxial line. Moreover, we analyze the super-resolution properties of a device equivalent to the MFE, known as a spherical geodesic waveguide, loaded with this perfect drain. The super-resolution analysis for this device is carried out using COMSOL Multiphysics. The results of simulations predict a super-resolution of up to λ/3000.
Circuital model for the spherical geodesic waveguide perfect drain
International Nuclear Information System (INIS)
González, Juan C; Grabovičkić, Dejan; Benítez, Pablo; Miñano, Juan C
2012-01-01
The perfect drain for the Maxwell fish eye (MFE) is a non-magnetic dissipative region placed in the focal point to absorb all the incident radiation without reflection or scattering. The perfect drain was recently designed as a material with complex permittivity that depends on frequency. However, this material is only a theoretical material, so it cannot be used in practical devices. The perfect drain has been claimed as necessary for achieving super-resolution (Leonhardt 2009 New J. Phys. 11 093040), which has increased the interest in practical perfect drains suitable for manufacturing. Here, we present a practical perfect drain that is designed using a simple circuit (made of a resistance and a capacitor) connected to the coaxial line. Moreover, we analyze the super-resolution properties of a device equivalent to the MFE, known as a spherical geodesic waveguide, loaded with this perfect drain. The super-resolution analysis for this device is carried out using COMSOL Multiphysics. The results of simulations predict a super-resolution of up to λ/3000. (paper)
Water Bouncing Balls: how material stiffness affects water entry
Truscott, Tadd
2014-03-01
It is well known that one can skip a stone across the water surface, but less well known that a ball can also be skipped on water. Even though 17th century ship gunners were aware that cannonballs could be skipped on the water surface, they did not know that using elastic spheres rather than rigid ones could greatly improve skipping performance (yet would have made for more peaceful volleys). The water bouncing ball (Waboba®) is an elastic ball used in a game of aquatic keep away in which players pass the ball by skipping it along the water surface. The ball skips easily along the surface creating a sense that breaking the world record for number of skips could easily be achieved (51 rock skips Russell Byers 2007). We investigate the physics of skipping elastic balls to elucidate the mechanisms by which they bounce off of the water. High-speed video reveals that, upon impact with the water, the balls create a cavity and deform significantly due to the extreme elasticity; the flattened spheres resemble skipping stones. With an increased wetted surface area, a large hydrodynamic lift force is generated causing the ball to launch back into the air. Unlike stone skipping, the elasticity of the ball plays an important roll in determining the success of the skip. Through experimentation, we demonstrate that the deformation timescale during impact must be longer than the collision time in order to achieve a successful skip. Further, several material deformation modes can be excited upon free surface impact. The effect of impact velocity and angle on the two governing timescales and material wave modes are also experimentally investigated. Scaling for the deformation and collision times are derived and used to establish criteria for skipping in terms of relevant physical parameters.
Surface transport in plasma-balls
Energy Technology Data Exchange (ETDEWEB)
Armas, Jay [Physique Théorique et Mathématique, Université Libre de Bruxelles andInternational Solvay Institutes,ULB-Campus Plaine CP231, B-1050 Brussels (Belgium); Bhattacharya, Jyotirmoy [Centre for Particle Theory & Department of Mathematical Sciences, Durham University,South Road, Durham DH1 3LE (United Kingdom); Kundu, Nilay [Harish-Chandra Research Institute,Chhatnag Road, Jhunsi, Allahabad 211019 (India)
2016-06-06
We study the surface transport properties of stationary localized configurations of relativistic fluids to the first two non-trivial orders in a derivative expansion. By demanding that these finite lumps of relativistic fluid are described by a thermal partition function with arbitrary stationary background metric and gauge fields, we are able to find several constraints among surface transport coefficients. At leading order, besides recovering the surface thermodynamics, we obtain a generalization of the Young-Laplace equation for relativistic fluid surfaces, by considering a temperature dependence in the surface tension, which is further generalized in the context of superfluids. At the next order, for uncharged fluids in 3+1 dimensions, we show that besides the 3 independent bulk transport coefficients previously known, a generic localized configuration is characterized by 3 additional surface transport coefficients, one of which may be identified with the surface modulus of rigidity. Finally, as an application, we study the effect of temperature dependence of surface tension on some explicit examples of localized fluid configurations, which are dual to certain non-trivial black hole solutions via the AdS/CFT correspondence.
Dry grinding of talc in a stirred ball mill
Directory of Open Access Journals (Sweden)
Cayirli Serkan
2016-01-01
Full Text Available The aim of this work was to investigate micro fine size dry grindability of talc in a stirred ball mill. The effects of various parameters such as grinding time, stirrer speed, powder filling ratio and ball filling ratio were investigated. Alumina balls were used as grinding media. Experiments were carried out using the 24 full factorial design. The main and interaction effects were evaluated using the Yates method. Test results were evaluated on the basis of product size and surface area.
Gas-discharge particle detector with ball-tipped anodes
International Nuclear Information System (INIS)
Travkin, V.I.; Khazins, D.M.
1987-01-01
A new gas-discharge particle detector, whose anode is a set of balls 2mm in diameter is investigated. The chamber is blowing down by the argon-methane-methylal gas mixture with the ratio 3:1:1. The detector operates in the self-quenching streamer mode, has high efficiency and a wide counting characteristic plateau. The maximum counting rate of particles at one ball is ∼ 2.5x10 4 s -1 . The ball-tipped anodes allow making reliable complex-shaped detectors. Two-coordinate detection of multiparticle events can be naturally organized in detectors like that
Numerical study of Q-ball formation in gravity mediation
International Nuclear Information System (INIS)
Hiramatsu, Takashi; Kawasaki, Masahiro; Takahashi, Fuminobu
2010-01-01
We study Q-ball formation in the expanding universe on 1D, 2D and 3D lattice simulations. We obtain detailed Q-ball charge distributions, and find that the distribution is peaked at Q 3D peak ≅ 1.9 × 10 −2 (|Φ in |/m) 2 , which is greater than the existing result by about 60%. Based on the numerical simulations, we discuss how the Q-ball formation proceeds. Also we make a comment on possible deviation of the charge distributions from what was conjectured in the past
The development of cobalt-base alloy ball bearing
International Nuclear Information System (INIS)
Yu Xinshui; Chen Jianting; Wang Zaishu; Wang Ximei; Huang Chongming.
1986-01-01
The main technologies and experiences in developing a Cobalt-base alloy ball bearing are described. In the hardfacing of bearing races, a lower-hardness alloy of type St-6 is used rather than an alloy with hardness similar to that of the ball and finally the hardness of race is increased to match that of the ball by heat treatment. This improvement has certain advantages. The experience of whole developing technology indicates that strict control of the technology in the bearing-race hardfacing is the key problem in the quality assurance of bearings
Traumatic eye ball luxation: A stepwise approach to globe salvage
Directory of Open Access Journals (Sweden)
Himika Gupta
2017-10-01
Full Text Available Craniofacial trauma is often associated with orbital and ocular injuries. We report a case of a 21-year-old male with motor vehicular accident, orbital roof blow-in fracture, cerebrospinal fluid (CSF leak, and left sided globe luxation with corneal abrasion and complete conjunctival denuding. The patient was managed by a multispeciality team and the eyeball was protected by amniotic membrane graft (AMG biological dressing with novel use of inverted sterile metallic bowl as mechanical protection till the patient stabilized. During surgery, eyeball was reposited and ocular surface was reconstructed using amniotic membrane and symblepharon ring. Surgical correction and plating of the facial fractures and dural repair with autologus tensor fascia lata was done. Post surgery ocular surface was intact, ocular motility was well preserved and the globe was prephthisical. Traumatic eyeball luxation is a rare, but dramatic presentation which may occur in a blow in fracture when the intra orbital volume reduces and expels the eye ball out of the socket. This may be associated with extra ocular muscle rupture or optic nerve avulsion. The visual prognosis is nil in majority cases. However, the management is targeted towards globe preservation in view of psychological benefit and ease of cosmetic or prosthetic rehabilitation. Knowing the mechanism of luxation helps to plan the management. A stepwise approach for globe salvage is recommended. Team efforts to take care of various morbidities with special steps to safeguard the eye help to optimize outcomes. Keywords: Traumatic eyeball luxation, Blow in orbital fractures, Amniotic membrane graft for ocular surface, Globe reposition
Sources and components of ball lightning theory
Nikitin, A. I.; Bychkov, V. L.; Nikitina, T. F.; Velichko, A. M.; Abakumov, V. I.
2018-03-01
The article describes the cases when ball lightning (BL) exhibited an extremely high specific energy store (up to 1010 J/m3), a presence of uncompensated electric charge (up to 10‑3 C) and an ability to generate high frequency pulses (up to 10 MW). It is shown that the realization of a combination of these properties of BL is possible if to consider it as a heterogeneous system consisting of a unipolarly charged core and a dielectric shell. In the electric field of the core charge, arises a force owing to the polarization of the shell that opposes the Coulomb repulsion force of the charges. BL models constructed according to the indicated principle are described: the electrodynamic model and the chemical-thermal model, which treats BL as a hollow sphere filled with steam. The requirement to take into account the main three properties of BL makes it possible to reduce the number of models of this natural phenomenon. Detailed cases of observations of high-energy lightning are analyzed.
Directory of Open Access Journals (Sweden)
Charikova K.M.
2012-03-01
Full Text Available Technical devices which used in basket-ball are considered. The features of constructing of trainers and method of their application are selected in a training process. A trainer is offered for teaching a technique to the long transmission of ball in basket-ball. A trainer is a moving on a rope imitator of basket-ball ball. This construction allows to design initial position, замах for implementation of transmission and line of acceleration of ball in the final phase of motion. The method of the use of trainer is developed in an educational process.
Noncommutative geometry and fluid dynamics
International Nuclear Information System (INIS)
Das, Praloy; Ghosh, Subir
2016-01-01
In the present paper we have developed a Non-Commutative (NC) generalization of perfect fluid model from first principles, in a Hamiltonian framework. The noncommutativity is introduced at the Lagrangian (particle) coordinate space brackets and the induced NC fluid bracket algebra for the Eulerian (fluid) field variables is derived. Together with a Hamiltonian this NC algebra generates the generalized fluid dynamics that satisfies exact local conservation laws for mass and energy, thereby maintaining mass and energy conservation. However, nontrivial NC correction terms appear in the charge and energy fluxes. Other non-relativistic spacetime symmetries of the NC fluid are also discussed in detail. This constitutes the study of kinematics and dynamics of NC fluid. In the second part we construct an extension of the Friedmann-Robertson-Walker (FRW) cosmological model based on the NC fluid dynamics presented here. We outline the way in which NC effects generate cosmological perturbations bringing about anisotropy and inhomogeneity in the model. We also derive a NC extended Friedmann equation. (orig.)
Noncommutative geometry and fluid dynamics
Energy Technology Data Exchange (ETDEWEB)
Das, Praloy; Ghosh, Subir [Indian Statistical Institute, Physics and Applied Mathematics Unit, Kolkata (India)
2016-11-15
In the present paper we have developed a Non-Commutative (NC) generalization of perfect fluid model from first principles, in a Hamiltonian framework. The noncommutativity is introduced at the Lagrangian (particle) coordinate space brackets and the induced NC fluid bracket algebra for the Eulerian (fluid) field variables is derived. Together with a Hamiltonian this NC algebra generates the generalized fluid dynamics that satisfies exact local conservation laws for mass and energy, thereby maintaining mass and energy conservation. However, nontrivial NC correction terms appear in the charge and energy fluxes. Other non-relativistic spacetime symmetries of the NC fluid are also discussed in detail. This constitutes the study of kinematics and dynamics of NC fluid. In the second part we construct an extension of the Friedmann-Robertson-Walker (FRW) cosmological model based on the NC fluid dynamics presented here. We outline the way in which NC effects generate cosmological perturbations bringing about anisotropy and inhomogeneity in the model. We also derive a NC extended Friedmann equation. (orig.)
Ball lightning as a route to fusion energy
International Nuclear Information System (INIS)
Roth, J.R.
1989-01-01
The reality of ball lightning is attested to by observations reported in surveys of large populations, which are the subject of several books. These observations indicate that its characteristics may be relevant to fusion energy applications. Ball lightning can have a diameter up to several meters, a lifetime of over 100 seconds, an energy content in excess of 10 megajoules, and an energy density and a kinetic pressure greater than that of a reacting DT plasma. This paper reviews some of the properties of ball lightning which commend it to the attention of the fusion community, and it discusses some potential advantages and applications of ball lightning fusion reactors. 11 refs., 6 figs., 1 tab
An experiment on a ball-lightning model
International Nuclear Information System (INIS)
Ignatovich, F.V.; Ignatovich, V.K.
2010-01-01
We discuss total internal reflection (TIR) from an interface between glass and gainy gaseous media and propose an experiment for strong light amplification related to investigation of a ball-lightning model
An aerodynamic analysis of recent FIFA world cup balls
Kiratidis, Adrian L.; Leinweber, Derek B.
2018-05-01
Drag and lift coefficients of recent FIFA world cup balls are examined. We fit a novel functional form to drag coefficient curves and in the absence of empirical data provide estimates of lift coefficient behaviour via a consideration of the physics of the boundary layer. Differences in both these coefficients for recent balls, which result from surface texture modification, can significantly alter trajectories. Numerical simulations are used to quantify the effect these changes have on the flight paths of various balls. Altitude and temperature variations at recent world cup events are also discussed. We conclude by quantifying the influence these variations have on the three most recent world cup balls, the Brazuca, the Jabulani and the Teamgeist. While our paper presents findings of interest to the professional sports scientist, it remains accessible to students at the undergraduate level.
On the isoperimetric rigidity of extrinsic minimal balls
DEFF Research Database (Denmark)
Markvorsen, Steen; Palmer, V.
2003-01-01
We consider an m-dimensional minimal submanifold P and a metric R-sphere in the Euclidean space R-n. If the sphere has its center p on P, then it will cut out a well defined connected component of P which contains this center point. We call this connected component an extrinsic minimal R-ball of P....... The quotient of the volume of the extrinsic ball and the volume of its boundary is not larger than the corresponding quotient obtained in the space form standard situation, where the minimal submanifold is the totally geodesic linear subspace R-m. Here we show that if the minimal submanifold has dimension...... larger than 3, if P is not too curved along the boundary of an extrinsic minimal R-ball, and if the inequality alluded to above is an equality for the extrinsic minimal ball, then the minimal submanifold is totally geodesic....
An overview of Ball Aerospace cryogen storage and delivery systems
International Nuclear Information System (INIS)
Marquardt, J; Keller, J; Mills, G; Schmidt, J
2015-01-01
Starting on the Gemini program in the 1960s, Beech Aircraft (now Ball Aerospace) has been designing and manufacturing dewars for a variety of cryogens including liquid hydrogen and oxygen. These dewars flew on the Apollo, Skylab and Space Shuttle spacecraft providing fuel cell reactants resulting in over 150 manned spaceflights. Since Space Shuttle, Ball has also built the liquid hydrogen fuel tanks for the Boeing Phantom Eye unmanned aerial vehicle. Returning back to its fuel cell days, Ball has designed, built and tested a volume-constrained liquid hydrogen and oxygen tank system for reactant delivery to fuel cells on unmanned undersea vehicles (UUVs). Herein past history of Ball technology is described. Testing has been completed on the UUV specific design, which will be described. (paper)
Severe wear behaviour of alumina balls sliding against diamond ...
Indian Academy of Sciences (India)
study, alumina ball was chosen as the counter body material to show better performance of the ... Tribology is a relatively new science that considers ... The science is applied in ... for example, in hip prosthesis, instead of existing alumina.
Drazin, Philip
1987-01-01
Outlines the contents of Volume II of "Principia" by Sir Isaac Newton. Reviews the contributions of subsequent scientists to the physics of fluid dynamics. Discusses the treatment of fluid mechanics in physics curricula. Highlights a few of the problems of modern research in fluid dynamics. Shows that problems still remain. (CW)
Falling balls and simple shearing strain
International Nuclear Information System (INIS)
Brun, J L; Pacheco, A F
2006-01-01
The problem of particles falling under gravity allows us to relate Hamiltonian mechanics to such different subjects as elasticity and fluid mechanics. It is with this in mind that mechanics gives us the opportunity of introducing, in a rather simple and unusual form, some concepts such as vorticity, the incompressibility condition or simple shear strain to physics students at the undergraduate level
Fang, Chen; Zhao, Bin Yuan; Chen, LeSheng; Wu, Qing; Liu, Nan; Hu, Ke Ao
2005-02-01
Magnetorheological (MR) fluid containing guar gum was prepared for the first time by ball-milling the guar gum powder together with silicone oil and carbonyl iron powder. By forming a coating layer over the ground carbonyl iron powder, the guar gum improves the sedimentation stability and thixotropy of the MR fluid effectively.
Dijkstra, T.M.H.; Katsumata, H.; Rugy, A. de; Sternad, D.
2004-01-01
We investigate the skill of rhythmically bouncing a ball on a racket with a focus on the mathematical modeling of the stability of performance. As a first step we derive the deterministic ball bouncing map as a Poincar´e section of a sinusoidally driven bouncing ball. Subsequently, we show the ball
The head tracks and gaze predicts: how the world's best batters hit the ball
Mann, D.L.; Spratford, W.; Abernethy, B.
2013-01-01
Hitters in fast ball-sports do not align their gaze with the ball throughout ball-flight; rather, they use predictive eye movement strategies that contribute towards their level of interceptive skill. Existing studies claim that (i) baseball and cricket batters cannot track the ball because it moves
DEFF Research Database (Denmark)
Andersen, Thomas B.; Krustrup, Peter; Bendiksen, Mads
2016-01-01
The present study evaluated the effect of a smaller, lighter ball on kicking speed and technical-tactical and physical match performance in high-level adult female footballers. In the laboratory test setting, the peak ball velocity was 6% higher with the new ball (NB) than the standard ball (SB...
Comparison of exit time moment spectra for extrinsic metric balls
DEFF Research Database (Denmark)
Hurtado, Ana; Markvorsen, Steen; Palmer, Vicente
2012-01-01
We prove explicit upper and lower bounds for the $L^1$-moment spectra for the Brownian motion exit time from extrinsic metric balls of submanifolds $P^m$ in ambient Riemannian spaces $N^n$. We assume that $P$ and $N$ both have controlled radial curvatures (mean curvature and sectional curvature...... obtain new intrinsic comparison results for the exit time spectra for metric balls in the ambient manifolds $N^n$ themselves....
Patient satisfaction of tooth supported overdentures utilizing ball attachments
Nassar, Hossam I.
2016-01-01
Statement of problem: Teeth retained overdenture therapy is an alternative treatment rarely used in cases with few remaining teeth. Purpose: The aim of this study was to evaluate the patient satisfaction associated with teeth retained maxillary and mandibular overdentures utilizing ready made ball attachment. Materials and methods: Thirty patients treated with teeth retained overdenture utilizing ready made ball attachment. Participants completed a series of questionnaires (OHIP-14 ques...
Linearly convergent stochastic heavy ball method for minimizing generalization error
Loizou, Nicolas
2017-10-30
In this work we establish the first linear convergence result for the stochastic heavy ball method. The method performs SGD steps with a fixed stepsize, amended by a heavy ball momentum term. In the analysis, we focus on minimizing the expected loss and not on finite-sum minimization, which is typically a much harder problem. While in the analysis we constrain ourselves to quadratic loss, the overall objective is not necessarily strongly convex.
Forbidden Structures for Planar Perfect Consecutively Colourable Graphs
Directory of Open Access Journals (Sweden)
Borowiecka-Olszewska Marta
2017-05-01
Full Text Available A consecutive colouring of a graph is a proper edge colouring with posi- tive integers in which the colours of edges incident with each vertex form an interval of integers. The idea of this colouring was introduced in 1987 by Asratian and Kamalian under the name of interval colouring. Sevast- janov showed that the corresponding decision problem is NP-complete even restricted to the class of bipartite graphs. We focus our attention on the class of consecutively colourable graphs whose all induced subgraphs are consecutively colourable, too. We call elements of this class perfect consecutively colourable to emphasise the conceptual similarity to perfect graphs. Obviously, the class of perfect consecutively colourable graphs is induced hereditary, so it can be characterized by the family of induced forbidden graphs. In this work we give a necessary and sufficient conditions that must be satisfied by the generalized Sevastjanov rosette to be an induced forbid- den graph for the class of perfect consecutively colourable graphs. Along the way, we show the exact values of the deficiency of all generalized Sevastjanov rosettes, which improves the earlier known estimating result. It should be mentioned that the deficiency of a graph measures its closeness to the class of consecutively colourable graphs. We motivate the investigation of graphs considered here by showing their connection to the class of planar perfect consecutively colourable graphs.
Biaxial testing for nuclear grade graphite by ball on three balls assessment
International Nuclear Information System (INIS)
Mohd Reusmaazran Yusof; Yusof Abdullah
2012-01-01
Nuclear grade (high-purity) graphite for fuel element and moderator material in Advanced Gas Cooling Reactors (AGR) displays large scatter in strength and a non-linear stress-strain response from the damage accumulation. These responses can be characterized as quasi-brittle behaviour. Current assessments of fracture in core graphite components are based on the linear elastic approximation and thus represent a major assumption. The quasi-brittle behaviour gives challenge to assess the real nuclear graphite component. The selected test method would help to bridge the gap between microscale to macro-scale in real reactor component. The small scale tests presented here can contribute some statistical data to manifests the failure in real component. The evaluation and choice of different solution design of biaxial test will be discussed in this paper. The ball on-three ball test method was used for assessment test follows by numerous of analytical method. The results shown that biaxial strength of the EY9 grade graphite depends on the method used for evaluation. Some of the analytical methods use to calculate biaxial strength were found not to be valid and therefore should not be used to assess the mechanical properties of nuclear graphite. (author)
Quenching simulation of steel grinding balls
Directory of Open Access Journals (Sweden)
Zapata-Hernández, Oscar
2015-09-01
Full Text Available The phase transformations of high carbon steel during quenching and equalizing were modelled using commercial computer packages based on the finite element method and the kinetic transformation of steel. The model was used to predict the temperature and microstructural changes taking place within balls of two different sizes that are used for grinding mineral ores. A good correlation between the temperatures measured by inserted thermocouples and those predicted by the model was obtained after modifying the thermal conductivity of the steel within the temperature domain at which mixed phases are present. The phase transformations predicted were confirmed by metallographic analyses.Las transformaciones de fase en aceros de alto carbono durante su temple y un posterior periodo de estabilización fueron modelizadas por medio del uso de paquetes computacionales basados en el método del elemento finito y de la transformación cinética de los aceros. El modelo se usó para predecir los cambios de temperatura y microestructura que se presentan en bolas de dos diferentes tamaños empleadas en estaciones de molienda de minerales. Se encontró una buena correlación entre las temperaturas medidas mediante la inserción de termopares y aquellas predichas por el modelo una vez que se modificó la conductividad térmica del acero en el intervalo mixto de fases. La predicción de las transformaciones de fase se confirmó a través del análisis metalográfico.
Perfect transfer of arbitrary states in quantum spin networks
International Nuclear Information System (INIS)
Christandl, Matthias; Kay, Alastair; Datta, Nilanjana; Dorlas, Tony C.; Ekert, Artur; Landahl, Andrew J.
2005-01-01
We propose a class of qubit networks that admit perfect state transfer of any two-dimensional quantum state in a fixed period of time. We further show that such networks can distribute arbitrary entangled states between two distant parties, and can, by using such systems in parallel, transmit the higher-dimensional systems states across the network. Unlike many other schemes for quantum computation and communication, these networks do not require qubit couplings to be switched on and off. When restricted to N-qubit spin networks of identical qubit couplings, we show that 2 log 3 N is the maximal perfect communication distance for hypercube geometries. Moreover, if one allows fixed but different couplings between the qubits then perfect state transfer can be achieved over arbitrarily long distances in a linear chain. This paper expands and extends the work done by Christandl et al., Phys. Rev. Lett. 92, 187902 (2004)
[INVITED] Coherent perfect absorption of electromagnetic wave in subwavelength structures
Yan, Chao; Pu, Mingbo; Luo, Jun; Huang, Yijia; Li, Xiong; Ma, Xiaoliang; Luo, Xiangang
2018-05-01
Electromagnetic (EM) absorption is a common process by which the EM energy is transformed into other kinds of energy in the absorber, for example heat. Perfect absorption of EM with structures at subwavelength scale is important for many practical applications, such as stealth technology, thermal control and sensing. Coherent perfect absorption arises from the interplay of interference and absorption, which can be interpreted as a time-reversed process of lasing or EM emitting. It provides a promising way for complete absorption in both nanophotonics and electromagnetics. In this review, we discuss basic principles and properties of a coherent perfect absorber (CPA). Various subwavelength structures including thin films, metamaterials and waveguide-based structures to realize CPAs are compared. We also discuss the potential applications of CPAs.
Whole genome association mapping by incompatibilities and local perfect phylogenies
DEFF Research Database (Denmark)
Mailund, Thomas; Besenbacher, Søren; Schierup, Mikkel Heide
2006-01-01
around each marker that is compatible with a single phylogenetic tree. This perfect phylogenetic tree is treated as a decision tree for determining disease status, and scored by its accuracy as a decision tree. The rationale for this is that the perfect phylogeny near a disease affecting mutation should...... a fast method for accurate localisation of disease causing variants in high density case-control association mapping experiments with large numbers of cases and controls. The method searches for significant clustering of case chromosomes in the "perfect" phylogenetic tree defined by the largest region...... provide more information about the affected/unaffected classification than random trees. If regions of compatibility contain few markers, due to e.g. large marker spacing, the algorithm can allow the inclusion of incompatibility markers in order to enlarge the regions prior to estimating their phylogeny...
Dual band metamaterial perfect absorber based on Mie resonances
Energy Technology Data Exchange (ETDEWEB)
Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhou, Ji, E-mail: zhouji@tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Bi, Ke [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Zhao, Qian [State Key Lab of Tribology, Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084 (China)
2016-08-08
We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric “atom” with simple structure. Two absorption bands with simulated absorptivity of 99% and 96%, experimental absorptivity of 97% and 94% at 8.45 and 11.97 GHz were achieved due to the simultaneous magnetic and electric resonances in dielectric “atom” and copper plate. Mie resonances of dielectric “atom” provide a simple way to design metamaterial perfect absorbers with high symmetry.
Perfect lensing with phase-conjugating surfaces: toward practical realization
International Nuclear Information System (INIS)
Maslovski, Stanislav; Tretyakov, Sergei
2012-01-01
It is theoretically known that a pair of phase-conjugating surfaces can function as a perfect lens, focusing propagating waves and enhancing evanescent waves. However, the known experimental approaches based on thin sheets of nonlinear materials cannot fully realize the required phase conjugation boundary condition. In this paper, we show that the ideal phase-conjugating surface is, in principle, physically realizable and investigate the necessary properties of nonlinear and nonreciprocal particles which can be used to build a perfect lens system. The physical principle of the lens operation is discussed in detail and directions of possible experimental realizations are outlined. (paper)
Hydrogen can be used as a perfect fuel
International Nuclear Information System (INIS)
Aydin, E.
2005-01-01
At present, hydrogen is one of the new and clean energy production sources. Hydrogen is the perfect partner for electricity, and together they create an integrated energy system based on distributed power generation and use. Hydrogen and electricity are interchangeable using a fuel cell (to convert hydrogen to electricity) or an electrolyzer (for converting electricity to hydrogen). A regenerative fuel cell works either way, converting hydrogen to electricity and vice versa. Hydrogen and electricity are both energy carriers because, unlike naturally occurring hydrocarbon fuels, they must both be produced using a primary energy source. In this study, it will be discussed whether hydrogen is perfect fuel or not
International Nuclear Information System (INIS)
Anon.
1991-01-01
Fluids engineering has played an important role in many applications, from ancient flood control to the design of high-speed compact turbomachinery. New applications of fluids engineering, such as in high-technology materials processing, biotechnology, and advanced combustion systems, have kept up unwaining interest in the subject. More accurate and sophisticated computational and measurement techniques are also constantly being developed and refined. On a more fundamental level, nonlinear dynamics and chaotic behavior of fluid flow are no longer an intellectual curiosity and fluid engineers are increasingly interested in finding practical applications for these emerging sciences. Applications of fluid technology to new areas, as well as the need to improve the design and to enhance the flexibility and reliability of flow-related machines and devices will continue to spur interest in fluids engineering. The objectives of the present seminar were: to exchange current information on arts, science, and technology of fluids engineering; to promote scientific cooperation between the fluids engineering communities of both nations, and to provide an opportunity for the participants and their colleagues to explore possible joint research programs in topics of high priority and mutual interest to both countries. The Seminar provided an excellent forum for reviewing the current state and future needs of fluids engineering for the two nations. With the Seminar ear-marking the first formal scientific exchange between Korea and the United States in the area of fluids engineering, the scope was deliberately left broad and general
Cosmology with moving bimetric fluids
Energy Technology Data Exchange (ETDEWEB)
García-García, Carlos; Maroto, Antonio L.; Martín-Moruno, Prado, E-mail: cargar08@ucm.es, E-mail: maroto@ucm.es, E-mail: pradomm@ucm.es [Departamento de Física Teórica I, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
2016-12-01
We study cosmological implications of bigravity and massive gravity solutions with non-simultaneously diagonal metrics by considering the generalized Gordon and Kerr-Schild ansatzes. The scenario that we obtain is equivalent to that of General Relativity with additional non-comoving perfect fluids. We show that the most general ghost-free bimetric theory generates three kinds of effective fluids whose equations of state are fixed by a function of the ansatz. Different choices of such function allow to reproduce the behaviour of different dark fluids. In particular, the Gordon ansatz is suitable for the description of various kinds of slowly-moving fluids, whereas the Kerr-Schild one is shown to describe a null dark energy component. The motion of those dark fluids with respect to the CMB is shown to generate, in turn, a relative motion of baryonic matter with respect to radition which contributes to the CMB anisotropies. CMB dipole observations are able to set stringent limits on the dark sector described by the effective bimetric fluid.
Perfect fluid Bianchi Type-I cosmological models with time varying G ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 70; Issue 4 ... Research Articles Volume 70 Issue 4 April 2008 pp 565-574 ... Department of Mathematical Sciences, A.P.S. University, Rewa 486 003, India; Department of Mathematics, Govt. ... Proceedings of the International Workshop/Conference on Computational ...
Charged perfect fluid tori in strong central gravitational and dipolar magnetic fields
Czech Academy of Sciences Publication Activity Database
Kovář, J.; Slaný, P.; Cremaschini, C.; Stuchlík, Z.; Karas, Vladimír; Trova, Audrey
2016-01-01
Roč. 93, June (2016), 124055/1-124055/20 ISSN 1550-7998 R&D Projects: GA ČR GB14-37086G; GA MŠk(CZ) LH14049 Grant - others:GA ČR(CZ) GP14-07753P Institutional support: RVO:67985815 Keywords : black holes * accretion discscretion discs Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.643, year: 2014
From many body wee partons dynamics to perfect fluid: a standard model for heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Venugopalan, R.
2010-07-22
We discuss a standard model of heavy ion collisions that has emerged both from experimental results of the RHIC program and associated theoretical developments. We comment briefly on the impact of early results of the LHC program on this picture. We consider how this standard model of heavy ion collisions could be solidified or falsified in future experiments at RHIC, the LHC and a future Electro-Ion Collider.
Hypersurface-homogeneous Universe filled with perfect fluid in f(R ...
Indian Academy of Sciences (India)
2016-11-02
Nov 2, 2016 ... the existence of dark energy and dark matter, several modified theories of gravitation have been proposed as alternative to Einstein's theory. By modifying the geometrical part of Einstein–Hilbert action of general relativity, we obtain the modified gravity. Modified gravity is of great importance because it can ...
Some invariant solutions for non-conformal perfect fluid plates in 5 ...
Indian Academy of Sciences (India)
six solutions so obtained, three are in implicit form while the remaining three could be expressed explicitly. Each solution describes an .... function F whose solutions can be obtained in the following manners: Case (I). On inserting the value of ...
Energy Technology Data Exchange (ETDEWEB)
Mirzadzhanzade, A Kh; Dedusanko, G Ya; Dinaburg, L S; Markov, Yu M; Rasizade, Ya N; Rozov, V N; Sherstnev, N M
1979-08-30
A drilling fluid is suggested for separating the drilling and plugging fluids which contains as the base increased solution of polyacrylamide and additive. In order to increase the viscoelastic properties of the liquid with simultaneous decrease in the periods of its fabrication, the solution contains as an additive dry bentonite clay. In cases of the use of a buffer fluid under conditions of negative temperatures, it is necessary to add to it table salt or ethylene glycol.
Diagnostic evaluation of rolling behavior in ball bearings by ultrasonic technique
International Nuclear Information System (INIS)
Wakabayashi, T
2012-01-01
Failures of machines having rotating parts are mostly caused by damage to bearings and there exist increasing demands for detecting damaged bearings at an early stage. However, conventional diagnostic methods, such as measuring temperature and observing vibration, have found difficulties in performing the early detection, so that more advanced diagnosis is necessary. This study therefore applies an ultrasonic technique as an advanced diagnostic method to bearing life tests. Ultrasonic wave pulses (UWP) emitted from a piezoelectric UWP generator can partially reflect from the interfaces of contact zones within the housing and the bearing with regard to the different acoustic impedance between a solid-to-solid contact and a contact dominated by some fluid layers. Hence, the intensity of the resultant UWP echoes can be determined by the real contact area formed at the interfaces. The experimental results of UWP echoes under the different operating conditions have demonstrated that the time intervals between peaks of UWP echoes varied in accordance with the movement of rolling balls and the lubricating phenomena in bearings. This behavior has further suggested the possibility of the early detection of abnormalities in ball bearings by using the variation in UWP echoes.
Perfect Worlds : Utopian Fiction in China and the West
Fokkema, Douwe
2011-01-01
Perfect Worlds biedt een uitgebreide historische analyse van utopische verhalen in de Chinese en Euro-Amerikaanse traditie. Aan bod komen onder meer de kritiek van Thomas More op Plato, de Europese oriëntalistische speurtocht naar utopieën in China en Chinese schrijvers die hun confucianistische
Perfect Worlds : Utopian Fiction in China and the West
Fokkema, Douwe
2011-01-01
Perfect Worlds biedt een uitgebreide historische analyse van utopische verhalen in de Chinese en Euro-Amerikaanse traditie. Verschillende hoofdstukken gaan onder meer in op de kritiek van Thomas More op Plato, de Europese oriëntalistische speurtocht naar utopieën in China, Dostoevsky’s reactie op
Hyper-Achievement, Perfection, and College Student Resilience
Eells, Gregory T.
2017-01-01
Over the past decade, there has been considerable attention given to college students' experience of pressure to pursue perfection through hyper-achievement and the psychological and emotional toll this process takes on them. The popular press has highlighted this phenomenon and raised specific questions about some of the related consequences like…
Cognitive Learning Styles: Can You Engineer a "Perfect" Match?
Khuzzan, Sharifah Mazlina Syed; Goulding, Jack Steven
2016-01-01
Education and training is widely acknowledged as being one of the key factors for leveraging organisational success. However, it is equally acknowledged that skills development and the acquisition of learning through managed cognitive approaches has yet to provide a "perfect" match. Whilst it is argued that an ideal learning scenario…
The Perfect Storm--Genetic Engineering, Science, and Ethics
Rollin, Bernard E.
2014-01-01
Uncertainty about ethics has been a major factor in societal rejection of biotechnology. Six factors help create a societal "perfect storm" regarding ethics and biotechnology: Social demand for ethical discussion; societal scientific illiteracy; poor social understanding of ethics; a "Gresham's Law for Ethics;" Scientific…
The Perfect Storm—Genetic Engineering, Science, and Ethics
Rollin, Bernard E.
2014-02-01
Uncertainty about ethics has been a major factor in societal rejection of biotechnology. Six factors help create a societal "perfect storm" regarding ethics and biotechnology: Social demand for ethical discussion; societal scientific illiteracy; poor social understanding of ethics; a "Gresham's Law for Ethics;" Scientific Ideology; vested interests dominating ethical discussion. How this can be remedied is discussed.
Overemphasis on Perfectly Competitive Markets in Microeconomics Principles Textbooks
Hill, Roderick; Myatt, Anthony
2007-01-01
Microeconomic principles courses focus on perfectly competitive markets far more than other market structures. The authors examine five possible reasons for this but find none of them sufficiently compelling. They conclude that textbook authors should place more emphasis on how economists select appropriate models and test models' predictions…
A short note on nearly perfect maps of locales | Razafindrakoto ...
African Journals Online (AJOL)
We characterise compact locales in terms of nearly perfect maps. We show in particular that these maps are the natural pointfree version of Bourbaki's proper maps - when defined via any ultrafillter - and that they extend Herrlich's notion of nearly closed sublocales [10]. Mathematics Subject Classication (2010): 06A15, ...
Indefinite and Continuative Interpretations of the English Present Perfect
Directory of Open Access Journals (Sweden)
Katarina Dea Žetko
2005-06-01
Full Text Available The objective of our paper is to demonstrate that the English present perfect is not by inherent meaning either indefinite or continuative. Notions like indefinite and continuative are contextdependent interpretations of whole constructions and their broader context. However, continuative interpretation can also be triggered by certain adverbials, negative constructions and verbs in the progressive form. But, even these factors do not always guarantee continuative interpretations. Construction, continuative meaning can be cancelled by the context in a broader sense, this fact being a proof that this meaning is merely an implicature. We will demonstrate how different factors interact and trigger either indefinite or continuative interpretations which are not inherent in the present perfect itself. Our paper will attempt to provide sufficient evidence that there is no indefinite/continuative distinction in the English present perfect, the inherent meaning or function of the present perfect is merely to locate the situation somewhere within a period that starts before the time of utterance and leads up to it.
Robust Secure Authentication and Data Storage with Perfect Secrecy
Directory of Open Access Journals (Sweden)
Sebastian Baur
2018-04-01
Full Text Available We consider an authentication process that makes use of biometric data or the output of a physical unclonable function (PUF, respectively, from an information theoretical point of view. We analyse different definitions of achievability for the authentication model. For the secrecy of the key generated for authentication, these definitions differ in their requirements. In the first work on PUF based authentication, weak secrecy has been used and the corresponding capacity regions have been characterized. The disadvantages of weak secrecy are well known. The ultimate performance criteria for the key are perfect secrecy together with uniform distribution of the key. We derive the corresponding capacity region. We show that, for perfect secrecy and uniform distribution of the key, we can achieve the same rates as for weak secrecy together with a weaker requirement on the distribution of the key. In the classical works on PUF based authentication, it is assumed that the source statistics are known perfectly. This requirement is rarely met in applications. That is why the model is generalized to a compound model, taking into account source uncertainty. We also derive the capacity region for the compound model requiring perfect secrecy. Additionally, we consider results for secure storage using a biometric or PUF source that follow directly from the results for authentication. We also generalize known results for this problem by weakening the assumption concerning the distribution of the data that shall be stored. This allows us to combine source compression and secure storage.
The periphrastic perfect of Old Persian revisited (slides) [Dataset
Bavant, M.J.J.
2011-01-01
The voice of the periphrastic perfect of Old Persian has long been a controversial issue. This document is a slide set to present the matter. It illustrates the contents of an article on the same theme: "Retour sur le parfait périphrastique du vieux perse".
Unity and Duality in Barack Obama's "A More Perfect Union"
Terrill, Robert E.
2009-01-01
Faced with a racialized political crisis that threatened to derail his campaign to become the first African American president of the United States, Barack Obama delivered a speech on race titled "A More Perfect Union." He begins by portraying himself as an embodiment of double consciousness, but then invites his audience to share his…
A linear construction of perfect secret sharing schemes
Dijk, van M.; Santis, De A.
1995-01-01
In this paper, we generalize the vector space construction due to Brickell [5]. This generalization, introduced by Bertilsson [1], leads to perfect secret sharing schemes with rational information rates in which the secret can be computed efficiently by each qualified group. A one to one
Tie-breaking in games of perfect information
DEFF Research Database (Denmark)
Tranæs, Torben
1998-01-01
The paper suggests that ties in an extensive form game have strategic implications if they represent credible threats or promises. We consider a subset of subgame-perfect Nash equilibria obtained by breaking ties according to their strategic implications, and show that the subset is nonempty for ...
Perfect 2-colorings of the generalized Petersen graph
Indian Academy of Sciences (India)
It is obvious that GP(n, k) is a 3-regular connected graph. DEFINITION 2.2 ... vertex of color i, the number of its neighbors of color j is equal to aij . ... By the given conditions, we can see that a parameter matrix of a perfect 2-coloring of. GP(n, k) ...
An improved perfectly matched layer for the eigenmode expansion technique
DEFF Research Database (Denmark)
Gregersen, Niels; Mørk, Jesper
2008-01-01
be suppressed by introducing a perfectly matched layer (PML) using e.g. complex coordinate stretching of the cylinder radius. However, the traditional PML suffers from an artificial field divergence limiting its usefulness. We show that the choice of a constant cylinder radius leads to mode profiles...
An improved perfectly matched layer in the eigenmode expansion technique
DEFF Research Database (Denmark)
Gregersen, Niels; Mørk, Jesper
2008-01-01
When employing the eigenmode expansion technique (EET), parasitic reflections at the boundary of the computational domain can be suppressed by introducing a perfectly matched layer (PML). However, the traditional PML, suffers from an artificial field divergence limiting its usefulness. We propose...
Perfect Power Prototype for Illinois Institute of Technology
Energy Technology Data Exchange (ETDEWEB)
Shahidehpour, Mohammad [Illinois Inst. Of Technology, Chicago, IL (United States)
2014-09-30
Starting in October 2008, Illinois Institute of Technology (IIT), in collaboration with over 20 participating members, led an extensive effort to develop, demonstrate, promote, and commercialize a microgrid system and offer supporting technologies that will achieve Perfect Power at the main campus of IIT. A Perfect Power system, as defined by the Galvin Electricity Initiative (GEI), is a system that cannot fail to meet the electric needs of the individual end-user. The Principle Investigator of this Perfect Power project was Dr. Mohammad Shahidehpour, Director of the Robert W. Galvin Center for Electricity Innovation at IIT. There were six overall objectives of the Perfect Power project: (1) Demonstrate the higher reliability introduced by the microgrid system at IIT; (2) Demonstrate the economics of microgrid operations; (3) Allow for a decrease of fifty percent (50%) of grid electricity load; (4) Create a permanent twenty percent (20%) decrease in peak load from 2007 level; (5) Defer planned substation through load reduction; (6) Offer a distribution system design that can be replicated in urban communities.
Generalized magneto-thermoviscoelasticity in a perfectly conducting ...
Indian Academy of Sciences (India)
on the theory of generalized thermoelastic diffusion with one relaxation time. ... cavity is taken to be traction free and subjected to both heating and external constant ... problems on wave propagation in a linear viscoelas- ... Let us consider a perfect electric conductor medium ... The energy equation in the context of general-.
The coefficient of restitution of pressurized balls: a mechanistic model
Georgallas, Alex; Landry, Gaëtan
2016-01-01
Pressurized, inflated balls used in professional sports are regulated so that their behaviour upon impact can be anticipated and allow the game to have its distinctive character. However, the dynamics governing the impacts of such balls, even on stationary hard surfaces, can be extremely complex. The energy transformations, which arise from the compression of the gas within the ball and from the shear forces associated with the deformation of the wall, are examined in this paper. We develop a simple mechanistic model of the dependence of the coefficient of restitution, e, upon both the gauge pressure, P_G, of the gas and the shear modulus, G, of the wall. The model is validated using the results from a simple series of experiments using three different sports balls. The fits to the data are extremely good for P_G > 25 kPa and consistent values are obtained for the value of G for the wall material. As far as the authors can tell, this simple, mechanistic model of the pressure dependence of the coefficient of restitution is the first in the literature. *%K Coefficient of Restitution, Dynamics, Inflated Balls, Pressure, Impact Model
Suppressing Heavy Metal Leaching through Ball Milling of Fly Ash
Directory of Open Access Journals (Sweden)
Zhiliang Chen
2016-07-01
Full Text Available Ball milling is investigated as a method of reducing the leaching concentration (often termed stablilization of heavy metals in municipal solid waste incineration (MSWI fly ash. Three heavy metals (Cu, Cr, Pb loose much of their solubility in leachate by treating fly ash in a planetary ball mill, in which collisions between balls and fly ash drive various physical processes, as well as chemical reactions. The efficiency of stabilization is evaluated by analysing heavy metals in the leachable fraction from treated fly ash. Ball milling reduces the leaching concentration of Cu, Cr, and Pb, and water washing effectively promotes stabilization efficiency by removing soluble salts. Size distribution and morphology of particles were analysed by laser particle diameter analysis and scanning electron microscopy. X-ray diffraction analysis reveals significant reduction of the crystallinity of fly ash by milling. Fly ash particles can be activated through this ball milling, leading to a significant decrease in particle size, a rise in its BET-surface, and turning basic crystals therein into amorphous structures. The dissolution rate of acid buffering materials present in activated particles is enhanced, resulting in a rising pH value of the leachate, reducing the leaching out of some heavy metals.
The goalkeeper influence on ball possession effectiveness in futsal
Directory of Open Access Journals (Sweden)
Vicente-Vila Pedro
2016-06-01
Full Text Available The aim of this study was to identify which variables were the best predictors of success in futsal ball possession when controlling for space and task related indicators, situational variables and the participation of the goalkeeper as a regular field player or not (5 vs. 4 or 4 vs. 4. The sample consisted of 326 situations of ball possession corresponding to 31 matches played by a team from the Spanish Futsal League during the 2010–2011, 2011–2012 and 2012–2013 seasons. Multidimensional qualitative data obtained from 10 ordered categorical variables were used. Data were analysed using chi-square analysis and multiple logistic regression analysis. Overall, the highest ball possession effectiveness was achieved when the goalkeeper participated as a regular field player (p<0.01, the duration of the ball possession was less than 10 s (p<0.01, the ball possession ended in the penalty area (p<0.01 and the defensive pressure was low (p<0.01. The information obtained on the relative effectiveness of offensive playing tactics can be used to improve team’s goal-scoring and goal preventing abilities.
The Imperfect Fluid behind Kinetic Gravity Braiding
Pujolas, Oriol; Vikman, Alexander
2011-01-01
We present a standard hydrodynamical description for non-canonical scalar field theories with kinetic gravity braiding. In particular, this picture applies to the simplest galileons and k-essence. The fluid variables not only have a clear physical meaning but also drastically simplify the analysis of the system. The fluid carries charges corresponding to shifts in field space. This shift-charge current contains a spatial part responsible for diffusion of the charges. Moreover, in the incompressible limit, the equation of motion becomes the standard diffusion equation. The fluid is indeed imperfect because the energy flows neither along the field gradient nor along the shift current. The fluid has zero vorticity and is not dissipative: there is no entropy production, the energy-momentum is exactly conserved, the temperature vanishes and there is no shear viscosity. Still, in an expansion around a perfect fluid one can identify terms which correct the pressure in the manner of bulk viscosity. We close by formul...
Effect of soccer shoe upper on ball behaviour in curve kicks
Ishii, Hideyuki; Sakurai, Yoshihisa; Maruyama, Takeo
2014-08-01
New soccer shoes have been developed by considering various concepts related to kicking, such as curving a soccer ball. However, the effects of shoes on ball behaviour remain unclear. In this study, by using a finite element simulation, we investigated the factors that affect ball behaviour immediately after impact in a curve kick. Five experienced male university soccer players performed one curve kick. We developed a finite element model of the foot and ball and evaluated the validity of the model by comparing the finite element results for the ball behaviour immediately after impact with the experimental results. The launch angle, ball velocity, and ball rotation in the finite element analysis were all in general agreement with the experimental results. Using the validated finite element model, we simulated the ball behaviour. The simulation results indicated that the larger the foot velocity immediately before impact, the larger the ball velocity and ball rotation. Furthermore, the Young's modulus of the shoe upper and the coefficient of friction between the shoe upper and the ball had little effect on the launch angle, ball velocity, and ball rotation. The results of this study suggest that the shoe upper does not significantly influence ball behaviour.
Effect of Ball Weight on Speed, Accuracy, and Mechanics in Cricket Fast Bowling
Directory of Open Access Journals (Sweden)
Katharine L. Wickington
2017-02-01
Full Text Available The aims of this study were: (1 to quantify the acute effects of ball weight on ball release speed, accuracy, and mechanics in cricket fast bowling; and (2 to test whether a period of sustained training with underweight and overweight balls is effective in increasing a player’s ball release speed. Ten well-trained adult male cricket players performed maximum-effort deliveries using balls ranging in weight from 46% to 137% of the standard ball weight (156 g. A radar gun, bowling target, and 2D video analysis were used to obtain measures of ball speed, accuracy, and mechanics. The participants were assigned to either an intervention group, who trained with underweight and overweight balls, or to a control group, who trained with standard-weight balls. We found that ball speed decreased at a rate of about 1.1 m/s per 100 g increase in ball weight. Accuracy and bowling mechanics were not adversely affected by changes in ball weight. There was evidence that training with underweight and overweight balls might have produced a practically meaningful increase in bowling speed (>1.5 m/s in some players without compromising accuracy or increasing their risk of injury through inducing poor bowling mechanics. In cricket fast bowling, a wide range of ball weight might be necessary to produce an effective modified-implement training program.
Fluid mechanics of heart valves.
Yoganathan, Ajit P; He, Zhaoming; Casey Jones, S
2004-01-01
Valvular heart disease is a life-threatening disease that afflicts millions of people worldwide and leads to approximately 250,000 valve repairs and/or replacements each year. Malfunction of a native valve impairs its efficient fluid mechanic/hemodynamic performance. Artificial heart valves have been used since 1960 to replace diseased native valves and have saved millions of lives. Unfortunately, despite four decades of use, these devices are less than ideal and lead to many complications. Many of these complications/problems are directly related to the fluid mechanics associated with the various mechanical and bioprosthetic valve designs. This review focuses on the state-of-the-art experimental and computational fluid mechanics of native and prosthetic heart valves in current clinical use. The fluid dynamic performance characteristics of caged-ball, tilting-disc, bileaflet mechanical valves and porcine and pericardial stented and nonstented bioprostheic valves are reviewed. Other issues related to heart valve performance, such as biomaterials, solid mechanics, tissue mechanics, and durability, are not addressed in this review.
International Nuclear Information System (INIS)
Kan, K.K.
1983-01-01
The relationship of nuclear internal flow and collective inertia, the difference of this flow from that of a classical fluid, and the approach of this flow to rigid flow in independent-particle model rotation are elucidated by reviewing the theory of Schroedinger fluid and its implications for collective vibration and rotation. (author)
DEFF Research Database (Denmark)
Dohn, Anders; Garza-Villarreal, Eduardo A.; Heaton, Pamela
2012-01-01
Perfect pitch, also known as absolute pitch (AP), refers to the rare ability to identify or produce a musical tone correctly without the benefit of an external reference. AP is often considered to reflect musical giftedness, but it has also been associated with certain disabilities due to increas...
Acoustic monitoring of a ball sinking in vibrated granular sediments
van den Wildenberg, Siet; Léopoldès, Julien; Tourin, Arnaud; Jia, Xiaoping
2017-06-01
We develop an ultrasound probing to investigate the dynamics of a high density ball sinking in 3D opaque dense granular suspensions under horizontal weak vibrations. We show that the motion of the ball in these horizontally vibrated glass bead packings saturated by water is consistent with the frictional rheology. The extracted stress-strain relation evidences an evolution of flow behaviour from frictional creep to inertial regimes. Our main finding is that weak external vibration primarily affects the yield stress and controls the depth of sinking via vibration-induced sliding at the grain contact. Also, we observe that the extracted rheological parameters depend on the size of the probing ball, suggesting thus a non-local rheology.
Durability Tests of Ball Valve Prototype with Flowmeter Operation
Rogula, J.; Romanik, G.
2018-02-01
The results of the investigation of the prototypical ball valve are presented in this article. The innovation of the tested valve is a ball with a built-in measuring orifice. The valve has been subjected to durability tests. Leakage under three temperatures: ambient, -30°C and +100°C was analyzed. Sealing elements of the valve were tested for roughness and deviation of shape before and after the cycles of operation. Ball valve operation means cycles of open/close. It was planned to perform 1000 cycles at each temperature condition accordingly. Tests of the valve were performed under gas pressure equal to 10 MPa. The research was carried out under the Operational Program "Intelligent Development" (POIR 01.01.01-00-0013 / 15 "Development of devices for measurement of media flow on industrial trunk-lines".
Geometric modeling in the problem of ball bearing accuracy
Glukhov, V. I.; Pushkarev, V. V.; Khomchenko, V. G.
2017-06-01
The manufacturing quality of ball bearings is an urgent problem for machine-building industry. The aim of the research is to improve the geometric specifications accuracy of bearings based on evidence-based systematic approach and the method of adequate size, location and form deviations modeling of the rings and assembled ball bearings. The present work addressed the problem of bearing geometric specifications identification and the study of these specifications. The deviation from symmetric planar of rings and bearings assembly and mounting width are among these specifications. A systematic approach to geometric specifications values and ball bearings tolerances normalization in coordinate systems will improve the quality of bearings by optimizing and minimizing the number of specifications. The introduction of systematic approach to the international standards on rolling bearings is a guarantee of a significant increase in accuracy of bearings and the quality of products where they are applied.
A Case of Lung Lesions Induced by a soccer Ball
Directory of Open Access Journals (Sweden)
Masaaki Takemoto
2013-01-01
Full Text Available An 18-year-old youth soccer forward received a direct hit from a kicked soccer ball on the anterior right chest when the goal keeper kicked the ball from a distance of 1 meter. Immediately following the hit, the subject experienced dypnea, chest pain and had a cough, with several milliliters of hemoptysis. His symptoms subsided after 20 minutes of rest. However, he still felt mild discomfort and was taken to our department for evaluation. On examination, all vital signs were normal. A computed tomography scan of the chest was obtained, and revealed a small area of opacification in the right lung field suggesting a pulmonary contusion or traumatic lung edema. Ten days after the initial injury, he was cleared for full participation. We herein reported the first case of a lung lesion induced by a soccer ball. Conservative treatment resulted in a favorable outcome.
Geometrical origin of chaoticity in the bouncing ball billiard
International Nuclear Information System (INIS)
Mátyás, L.; Barna, I.F.
2011-01-01
Highlights: ► We study the possible separation of neighouring trajectories in the bouncing ball billiard. ► In a certain interval of frequencies semianalitical evaluations are possible. ► One may find a lower bound for the maximal Lyapunov exponent in case of a resonance. - Abstract: We present a study of the chaotic behaviour of the bouncing ball billiard. The work is realised on the purpose of finding at least certain causes of separation of the neighbouring trajectories. Having in view the geometrical construction of the system, we report a clear origin of chaoticity of the bouncing ball billiard. By this we claim that in case when the floor is made of arc of circles – in a certain interval of frequencies – one can give semi-analytical estimates on chaotic behaviour.
Stimulated leaks found with SmartBall tool
Energy Technology Data Exchange (ETDEWEB)
Anon.
2011-05-15
Pure Technologies has developed a SmartBall leak detection tool which can be used in oil and gas pipelines. This tool contains acoustic sensors which listen for leaks and other problems in pipelines. Pig tracking units are used to track the tool along with receivers positioned on the pipe. With these technologies, SmartBall is able to detect small leaks that conventional methods would not detect and to assess their location accurately. Two runs on a Petrobras pipeline in Brazil highlighted the effectiveness of this technology, detecting three simulated leaks as small as 240mL/min. In addition, this system can give an estimation of the leak rate and traverse non piggable pipelines. Software is then used to analyze data and generate a report giving the size and location of the leaks identified. SmartBall is a technology capable of detecting small leaks and locating them in all sorts of oil and gas pipelines.
Study on the luminous characteristics of a natural ball lightning
Wang, Hao; Yuan, Ping; Cen, Jianyong; Liu, Guorong
2018-02-01
According to the optical images of the whole process of a natural ball lightning recorded by two slit-less spectrographs in the Qinghai plateau of China, the simulated observation experiment on the luminous intensity of the spherical light source was carried out. The luminous intensity and the optical power of the natural ball lightning in the wavelength range of 400-690 nm were estimated based on the experimental data and the Lambert-Beer Law. The results show that the maximum luminous intensity was about 1.24 × 105 cd in the initial stage of the natural ball lightning, and the maximum luminous intensity and the maximum optical power in most time of its life were about 5.9 × 104 cd and 4.2 × 103 W, respectively.
Validation of single ball rolling contact fatigue machine dynamics
Energy Technology Data Exchange (ETDEWEB)
Allison, Bryan [SKF Aeroengine, Falconer (United States)
2017-01-15
Single ball test machines are a common method for accelerated rolling contact fatigue testing of bearing materials. Historically, it has always been assumed that the force applied by the retaining bars is negligible, without any data to support this claim. In this study, strain gauges were placed on the retaining bars to determine the load experienced by the retaining bars. This value was then compared to the applied load. It was found that a load of approximately 4 N was transferred to the retainer by the test ball during steady state operation, when a 8385 N load was applied to the ball via the rings. A simulation of the system was also created and successfully predicted the expected loads with reasonable accuracy. This information, as well as the technique of strain gauging the retaining bars, may be useful in the development of similar testing machinery.
Simulating fullerene ball bearings of ultra-low friction
International Nuclear Information System (INIS)
Li Xiaoyan; Yang Wei
2007-01-01
We report the direct molecular dynamics simulations for molecular ball bearings composed of fullerene molecules (C 60 and C 20 ) and multi-walled carbon nanotubes. The comparison of friction levels indicates that fullerene ball bearings have extremely low friction (with minimal frictional forces of 5.283 x 10 -7 and 6.768 x 10 -7 nN/atom for C 60 and C 20 bearings) and energy dissipation (lowest dissipation per cycle of 0.013 and 0.016 meV/atom for C 60 and C 20 bearings). A single fullerene inside the ball bearings exhibits various motion statuses of mixed translation and rotation. The influences of the shaft's distortion on the long-ranged potential energy and normal force are discussed. The phonic dissipation mechanism leads to a non-monotonic function between the friction and the load rate for the molecular bearings
Czech Academy of Sciences Publication Activity Database
Dimitrova, Miglena; Popov, Tsv.K.; Adámek, Jiří; Kovačič, J.; Ivanova, P.; Hasan, E.; López-Bruna, D.; Seidl, Jakub; Vondráček, Petr; Dejarnac, Renaud; Stöckel, Jan; Imríšek, Martin; Pánek, Radomír
2017-01-01
Roč. 59, č. 12 (2017), č. článku 125001. ISSN 0741-3335 R&D Projects: GA ČR(CZ) GA15-10723S; GA MŠk(CZ) LM2015045 Institutional support: RVO:61389021 Keywords : Plasma potential * electron temperature * bi-Maxwellian EEDF * ball-pen probe * Langmuir probe * COMPASS tokamak * last closed flux surface Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.392, year: 2016
Conceptual design of ball-screw type control element drive mechanism
Energy Technology Data Exchange (ETDEWEB)
Kim, Ji Ho; Kim, Jong In; Huh, Hyung [Korea Atomic Energy Research Institute, Taejon (Korea)
1999-10-01
In this report, the design features of ball-screw type CEDM with fine-step movement capability are described. The contents of this report are as follows: -Review of Design Requirements for Ball-screw type CEDM -System Description for Ball-screw type CEDM -Design of Ball Bearing and Ball-screw Assembly -Detail Design of Rotary Step Motor -Detail Design of Angular Position Indicator -Materials. The Ball-screw type CEDM described in this report is to be utilized as the starting point for design development of CEDM for SMART. 11 refs., 43 figs., 3 tabs. (Author)
Combination of minimum enclosing balls classifier with SVM in coal-rock recognition
Song, QingJun; Jiang, HaiYan; Song, Qinghui; Zhao, XieGuang; Wu, Xiaoxuan
2017-01-01
Top-coal caving technology is a productive and efficient method in modern mechanized coal mining, the study of coal-rock recognition is key to realizing automation in comprehensive mechanized coal mining. In this paper we propose a new discriminant analysis framework for coal-rock recognition. In the framework, a data acquisition model with vibration and acoustic signals is designed and the caving dataset with 10 feature variables and three classes is got. And the perfect combination of feature variables can be automatically decided by using the multi-class F-score (MF-Score) feature selection. In terms of nonlinear mapping in real-world optimization problem, an effective minimum enclosing ball (MEB) algorithm plus Support vector machine (SVM) is proposed for rapid detection of coal-rock in the caving process. In particular, we illustrate how to construct MEB-SVM classifier in coal-rock recognition which exhibit inherently complex distribution data. The proposed method is examined on UCI data sets and the caving dataset, and compared with some new excellent SVM classifiers. We conduct experiments with accuracy and Friedman test for comparison of more classifiers over multiple on the UCI data sets. Experimental results demonstrate that the proposed algorithm has good robustness and generalization ability. The results of experiments on the caving dataset show the better performance which leads to a promising feature selection and multi-class recognition in coal-rock recognition. PMID:28937987
Combination of minimum enclosing balls classifier with SVM in coal-rock recognition.
Song, QingJun; Jiang, HaiYan; Song, Qinghui; Zhao, XieGuang; Wu, Xiaoxuan
2017-01-01
Top-coal caving technology is a productive and efficient method in modern mechanized coal mining, the study of coal-rock recognition is key to realizing automation in comprehensive mechanized coal mining. In this paper we propose a new discriminant analysis framework for coal-rock recognition. In the framework, a data acquisition model with vibration and acoustic signals is designed and the caving dataset with 10 feature variables and three classes is got. And the perfect combination of feature variables can be automatically decided by using the multi-class F-score (MF-Score) feature selection. In terms of nonlinear mapping in real-world optimization problem, an effective minimum enclosing ball (MEB) algorithm plus Support vector machine (SVM) is proposed for rapid detection of coal-rock in the caving process. In particular, we illustrate how to construct MEB-SVM classifier in coal-rock recognition which exhibit inherently complex distribution data. The proposed method is examined on UCI data sets and the caving dataset, and compared with some new excellent SVM classifiers. We conduct experiments with accuracy and Friedman test for comparison of more classifiers over multiple on the UCI data sets. Experimental results demonstrate that the proposed algorithm has good robustness and generalization ability. The results of experiments on the caving dataset show the better performance which leads to a promising feature selection and multi-class recognition in coal-rock recognition.
Combination of minimum enclosing balls classifier with SVM in coal-rock recognition.
Directory of Open Access Journals (Sweden)
QingJun Song
Full Text Available Top-coal caving technology is a productive and efficient method in modern mechanized coal mining, the study of coal-rock recognition is key to realizing automation in comprehensive mechanized coal mining. In this paper we propose a new discriminant analysis framework for coal-rock recognition. In the framework, a data acquisition model with vibration and acoustic signals is designed and the caving dataset with 10 feature variables and three classes is got. And the perfect combination of feature variables can be automatically decided by using the multi-class F-score (MF-Score feature selection. In terms of nonlinear mapping in real-world optimization problem, an effective minimum enclosing ball (MEB algorithm plus Support vector machine (SVM is proposed for rapid detection of coal-rock in the caving process. In particular, we illustrate how to construct MEB-SVM classifier in coal-rock recognition which exhibit inherently complex distribution data. The proposed method is examined on UCI data sets and the caving dataset, and compared with some new excellent SVM classifiers. We conduct experiments with accuracy and Friedman test for comparison of more classifiers over multiple on the UCI data sets. Experimental results demonstrate that the proposed algorithm has good robustness and generalization ability. The results of experiments on the caving dataset show the better performance which leads to a promising feature selection and multi-class recognition in coal-rock recognition.
A self-similar magnetohydrodynamic model for ball lightnings
International Nuclear Information System (INIS)
Tsui, K. H.
2006-01-01
Ball lightning is modeled by magnetohydrodynamic (MHD) equations in two-dimensional spherical geometry with azimuthal symmetry. Dynamic evolutions in the radial direction are described by the self-similar evolution function y(t). The plasma pressure, mass density, and magnetic fields are solved in terms of the radial label η. This model gives spherical MHD plasmoids with axisymmetric force-free magnetic field, and spherically symmetric plasma pressure and mass density, which self-consistently determine the polytropic index γ. The spatially oscillating nature of the radial and meridional field structures indicate embedded regions of closed field lines. These regions are named secondary plasmoids, whereas the overall self-similar spherical structure is named the primary plasmoid. According to this model, the time evolution function allows the primary plasmoid expand outward in two modes. The corresponding ejection of the embedded secondary plasmoids results in ball lightning offering an answer as how they come into being. The first is an accelerated expanding mode. This mode appears to fit plasmoids ejected from thundercloud tops with acceleration to ionosphere seen in high altitude atmospheric observations of sprites and blue jets. It also appears to account for midair high-speed ball lightning overtaking airplanes, and ground level high-speed energetic ball lightning. The second is a decelerated expanding mode, and it appears to be compatible to slowly moving ball lightning seen near ground level. The inverse of this second mode corresponds to an accelerated inward collapse, which could bring ball lightning to an end sometimes with a cracking sound
The Energy Cost of Running with the Ball in Soccer.
Piras, Alessandro; Raffi, Milena; Atmatzidis, Charalampos; Merni, Franco; Di Michele, Rocco
2017-11-01
Running with the ball is a soccer-specific activity frequently used by players during match play and training drills. Nevertheless, the energy cost (EC) of on-grass running with the ball has not yet been determined. The purpose of this study was therefore to assess the EC of constant-speed running with the ball, and to compare it with the EC of normal running. Eight amateur soccer players performed two 6- min runs at 10 km/h on artificial turf, respectively with and without the ball. EC was measured with indirect calorimetry and, furthermore, estimated with a method based on players' accelerations measured with a GPS receiver. The EC measured with indirect calorimetry was higher in running with the ball (4.60±0.42 J/kg/m) than in normal running (4.19±0.33 J/kg/m), with a very likely moderate difference between conditions. Instead, a likely small difference was observed between conditions for EC estimated from GPS data (4.87±0.07 vs. 4.83±0.08 J/kg/m). This study sheds light on the energy expenditure of playing soccer, providing relevant data about the EC of a typical soccer-specific activity. These findings may be a reference for coaches to precisely determine the training load in drills with the ball, such as soccer-specific circuits or small-sided games. © Georg Thieme Verlag KG Stuttgart · New York.
International Nuclear Information System (INIS)
Powell, R.L.; Mondy, L.A.; Stoker, G.G.; Milliken, W.J.; Graham, A.L.
1989-01-01
With falling ball rheometry, we have measured the apparent relative viscosity of suspensions of large, neutrally buoyant, rigid rods in a viscous Newtonian fluid, while approximately maintaining the rods in a randomly oriented configuration. A new technique for measuring the time of flight of a ball between two positions is used. This computerized technique, based upon an eddy current detector, enables us to determine the position of a metallic (nonmagnetic) ball falling through an opaque suspension, with high accuracy (less than 1.5% error). The rods for the suspensions had a nominal aspect ratio of 10 and experiments were carried out at a single volume fraction, 0.05. Two populations of rods were used to having nominal diameters of 1.5875 mm and 3.175 mm. To within the errors of these experiments, suspensions from both populations had the same relative viscosity, with the overall average being 1.457. This viscosity was significantly different from that of a similar suspension (volume fraction=0.05) of rods of nominal aspect ratio 20 and it agreed well with theoretical results for the viscosity of a dilute suspension of randomly oriented rods
A power recirculating test rig for ball screw endurance tests
Directory of Open Access Journals (Sweden)
Giberti Hermes
2016-01-01
Full Text Available A conceptual design of an innovative test rig for endurance tests of ball screws is presented in this paper. The test rig layout is based on the power recirculating principle and it also allows to overtake the main critical issues of the ball screw endurance tests. Among these there are the high power required to make the test, the lengthy duration of the same and the high loads between the screw and the frame that holds it. The article describes the test rig designed scheme, the kinematic expedients to be adopted in order to obtain the required performance and functionality and the sizing procedure to choose the actuation system.
Note: A 1-m Foucault pendulum rolling on a ball
Salva, H. R.; Benavides, R. E.; Venturino, J. A.; Cuscueta, D. J.; Ghilarducci, A. A.
2013-10-01
We have built a short Foucault pendulum of 1-m length. The aim of this work was to increase the sensitivity to elliptical trajectories from other longer pendula. The design was a semi-rigid pendulum that rolls over a small ball. The measurements of the movements (azimuth and elliptical trajectory) were done by an optical method. The resulting pendulum works in a medium satisfactory way due to problems of the correct choice of the mass of the bob together with the diameter of the supporting ball. It is also important to keep the rolling surface very clean.
Ball Bearing Stiffnesses- A New Approach Offering Analytical Expressions
Guay, Pascal; Frikha, Ahmed
2015-09-01
Space mechanisms use preloaded ball bearings in order to withstand the severe vibrations during launch.The launch strength requires the calculation of the bearing stiffness, but this calculation is complex. Nowadays, there is no analytical expression that gives the stiffness of a bearing. Stiffness is computed using an iterative algorithm such as Newton-Raphson, to solve the nonlinear system of equations.This paper aims at offering a simplified analytical approach, based on the assumption that the contact angle is constant. This approach gives analytical formulas of the stiffness of preloaded ball bearing.
Ball lightning dynamics and stability at moderate ion densities
International Nuclear Information System (INIS)
Morrow, R
2017-01-01
A general mechanism is presented for the dynamics and structure of ball lightning and for the maintenance of the ball lightning structure for several seconds. Results are obtained using a spherical geometry for air at atmospheric pressure, by solving the continuity equations for electrons, positive ions and negative ions coupled with Poisson’s equation. A lightning strike can generate conditions in the lightning channel with a majority of positive nitrogen ions, and a minority of negative oxygen ions and electrons. The calculations are initiated with electrons included; however, at the moderate ion densities chosen the electrons are rapidly lost to form negative ions, and after 1 µ s their influence on the ion dynamics is negligible. Further development after 1 µ s is followed using a simpler set of equations involving only positive ions and negative ions, but including ion diffusion. The space-charge electric field generated by the majority positive ions drives them from the centre of the distribution and drives the minority negative ions and electrons towards the centre of the distribution. In the central region the positive and negative ion distributions eventually overlap exactly and their space-charge fields cancel resulting in zero electric field, and the plasma ball formed is quite stable for a number of seconds. The formation of such plasma balls is not critically dependent on the initial diameter of the ion distributions, or the initial density of minority negative ions. The ion densities decrease relatively slowly due to mutual neutralization of positive and negative ions. The radiation from this neutralization process involving positive nitrogen ions and negative oxygen ions is not sufficient to account for the reported luminosity of ball lightning and some other source of luminosity is shown to be required; the plasma ball model used could readily incorporate other ions in order to account for the luminosity and range of colours reported for ball
Study of Complexities in Bouncing Ball Dynamical System
Directory of Open Access Journals (Sweden)
Lal Mohan SAHA
2016-04-01
Full Text Available Evolutionary motions in a bouncing ball system consisting of a ball having a free fall in the Earth’s gravitational field have been studied systematically. Because of nonlinear form of the equations of motion, evolutions show chaos for certain set of parameters for certain initial conditions. Bifurcation diagram has been drawn to study regular and chaotic behavior. Numerical calculations have been performed to calculate Lyapunov exponents, topological entropies and correlation dimension as measures of complexity. Numerical results are shown through interesting graphics.
Ball milling of chalcopyrite: Moessbauer spectroscopy and XRD studies
International Nuclear Information System (INIS)
Pollak, H.; Fernandes, M.; Levendis, D.; Schonig, L.
1999-01-01
The aim of this project is to study the behavior of chalcopyrite under ball milling for extended periods in order to determine how it's decompose or transform. Tests were done with chalcopyrite mixed with iron and zinc with and without surfactant. The use of surfactants has various effects such as avoiding oxidation and clustering of the fine particles. In all case magnetic chalcopyrite is transformed into a paramagnetic component showing a disordered structure, thus revealing that Cu atoms have replaced Fe atoms. In the case of ball milling in air, chalcopyrite is decomposed with the lost of iron, while in milling under surfactants, iron enters into the chalcopyrite structure. (author)
Charge, mass and energy measured in the Plastic Ball
International Nuclear Information System (INIS)
Gustafsson, H.A.; Gutbrod, H.H.; Kolb, B.
1984-01-01
In relativistic nuclear collisions the multiplicity of charged particles reflects the violence of the reaction and, presumably, the impact parameter. Furthermore, the total transverse energy in a collision might be a signature of compression. Both quantities are global features that can be measured in the Plastic Ball. The total mass in an event in light charge fragments can be detected (with assumptions made in certain kinematic regions) through particle identification. In addition, the neutron detection efficiency is quite high because of the large thickness of the plastic scintillator in the Plastic Ball. Here the authors present several global quantities for the reaction of 400 MeV/nucleon Nb + Nb
Relativistic fluid dynamics with spin
Florkowski, Wojciech; Friman, Bengt; Jaiswal, Amaresh; Speranza, Enrico
2018-04-01
Using the conservation laws for charge, energy, momentum, and angular momentum, we derive hydrodynamic equations for the charge density, local temperature, and fluid velocity, as well as for the polarization tensor, starting from local equilibrium distribution functions for particles and antiparticles with spin 1/2. The resulting set of differential equations extends the standard picture of perfect-fluid hydrodynamics with a conserved entropy current in a minimal way. This framework can be used in space-time analyses of the evolution of spin and polarization in various physical systems including high-energy nuclear collisions. We demonstrate that a stationary vortex, which exhibits vorticity-spin alignment, corresponds to a special solution of the spin-hydrodynamical equations.
Lipidomics by Supercritical Fluid Chromatography
Directory of Open Access Journals (Sweden)
Laurent Laboureur
2015-06-01
Full Text Available This review enlightens the role of supercritical fluid chromatography (SFC in the field of lipid analysis. SFC has been popular in the late 1980s and 1990s before almost disappearing due to the commercial success of liquid chromatography (LC. It is only 20 years later that a regain of interest appeared when new commercial instruments were introduced. As SFC is fully compatible with the injection of extracts in pure organic solvent, this technique is perfectly suitable for lipid analysis and can be coupled with either highly universal (UV or evaporative light scattering or highly specific (mass spectrometry detection methods. A short history of the use of supercritical fluids as mobile phase for the separation oflipids will be introduced first. Then, the advantages and drawbacks of SFC are discussed for each class of lipids (fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides defined by the LIPID MAPS consortium.
Lipidomics by Supercritical Fluid Chromatography
Laboureur, Laurent; Ollero, Mario; Touboul, David
2015-01-01
This review enlightens the role of supercritical fluid chromatography (SFC) in the field of lipid analysis. SFC has been popular in the late 1980s and 1990s before almost disappearing due to the commercial success of liquid chromatography (LC). It is only 20 years later that a regain of interest appeared when new commercial instruments were introduced. As SFC is fully compatible with the injection of extracts in pure organic solvent, this technique is perfectly suitable for lipid analysis and can be coupled with either highly universal (UV or evaporative light scattering) or highly specific (mass spectrometry) detection methods. A short history of the use of supercritical fluids as mobile phase for the separation oflipids will be introduced first. Then, the advantages and drawbacks of SFC are discussed for each class of lipids (fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, prenols, polyketides) defined by the LIPID MAPS consortium. PMID:26090714
DEFF Research Database (Denmark)
Shyroki, Dzmitry; Lavrinenko, Andrei
2007-01-01
A complex-coordinate method known under the guise of the perfectly matched layer (PML) method for treating unbounded domains in computational electrodynamics is related to similar techniques in fluid dynamics and classical quantum theory. It may also find use in electronic-structure finite......-difference simulations. Straightforward transfer of the PML formulation to other fields does not seem feasible, however, since it is a unique feature of electrodynamics - the natural invariance - that allows analytic trick of complex coordinate scaling to be represented as pure modification of local material parameters...
Perfect quantum multiple-unicast network coding protocol
Li, Dan-Dan; Gao, Fei; Qin, Su-Juan; Wen, Qiao-Yan
2018-01-01
In order to realize long-distance and large-scale quantum communication, it is natural to utilize quantum repeater. For a general quantum multiple-unicast network, it is still puzzling how to complete communication tasks perfectly with less resources such as registers. In this paper, we solve this problem. By applying quantum repeaters to multiple-unicast communication problem, we give encoding-decoding schemes for source nodes, internal ones and target ones, respectively. Source-target nodes share EPR pairs by using our encoding-decoding schemes over quantum multiple-unicast network. Furthermore, quantum communication can be accomplished perfectly via teleportation. Compared with existed schemes, our schemes can reduce resource consumption and realize long-distance transmission of quantum information.
Perfect commuting-operator strategies for linear system games
Cleve, Richard; Liu, Li; Slofstra, William
2017-01-01
Linear system games are a generalization of Mermin's magic square game introduced by Cleve and Mittal. They show that perfect strategies for linear system games in the tensor-product model of entanglement correspond to finite-dimensional operator solutions of a certain set of non-commutative equations. We investigate linear system games in the commuting-operator model of entanglement, where Alice and Bob's measurement operators act on a joint Hilbert space, and Alice's operators must commute with Bob's operators. We show that perfect strategies in this model correspond to possibly infinite-dimensional operator solutions of the non-commutative equations. The proof is based around a finitely presented group associated with the linear system which arises from the non-commutative equations.
Novel beam bunching methods by perfect crystals and electromagnetic means
International Nuclear Information System (INIS)
Rauch, H.
1985-01-01
The use of perfect crystals for installing new neutron small-angle scattering cameras provides advantages for measurements in the small Q-range and for real-time experiments. A neutron resonator is proposed which is based on the combination of perfect crystal back-reflections in Zeman energy splitting. The neutron magnetic resonance system in combination with gated crystals can act as a pumping unit for neutrons and as a new pulse-shaping unit. It is shown how travelling magnetic waves can act as powerful neutron bunching units. The achievable velocity changes are around 5 m/s and, therefore, by a factor of 100 larger than in the case of neutron magnetic resonance systems. The advantage of expanding potentials for focusing neutrons from a source with a long pulse duration becomes obvious. Real gain factors higher than 10 are expected for properly designed systems. (author)
Tunable enhanced optical absorption of graphene using plasmonic perfect absorbers
Energy Technology Data Exchange (ETDEWEB)
Cai, Yijun [Institute of Optoelectronic Technology, Department of Electronic Engineering, Xiamen University, Xiamen 361005 (China); Institute of Electromagnetics and Acoustics, Department of Electronic Science, Xiamen University, Xiamen 361005 (China); Zhu, Jinfeng, E-mail: nanoantenna@hotmail.com [Institute of Electromagnetics and Acoustics, Department of Electronic Science, Xiamen University, Xiamen 361005 (China); Liu, Qing Huo [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States)
2015-01-26
Enhancement and manipulation of light absorption in graphene is a significant issue for applications of graphene-based optoelectronic devices. In order to achieve this purpose in the visible region, we demonstrate a design of a graphene optical absorber inspired by metal-dielectric-metal metamaterial for perfect absorption of electromagnetic waves. The optical absorbance ratios of single and three atomic layer graphene are enhanced up to 37.5% and 64.8%, respectively. The graphene absorber shows polarization-dependence and tolerates a wide range of incident angles. Furthermore, the peak position and bandwidth of graphene absorption spectra are tunable in a wide wavelength range through a specific structural configuration. These results imply that graphene in combination with plasmonic perfect absorbers have a promising potential for developing advanced nanophotonic devices.
A quantitative comparison of corrective and perfective maintenance
Henry, Joel; Cain, James
1994-01-01
This paper presents a quantitative comparison of corrective and perfective software maintenance activities. The comparison utilizes basic data collected throughout the maintenance process. The data collected are extensive and allow the impact of both types of maintenance to be quantitatively evaluated and compared. Basic statistical techniques test relationships between and among process and product data. The results show interesting similarities and important differences in both process and product characteristics.
The perfect family: decision making in biparental care.
Akçay, Erol; Roughgarden, Joan
2009-10-13
Previous theoretical work on parental decisions in biparental care has emphasized the role of the conflict between evolutionary interests of parents in these decisions. A prominent prediction from this work is that parents should compensate for decreases in each other's effort, but only partially so. However, experimental tests that manipulate parents and measure their responses fail to confirm this prediction. At the same time, the process of parental decision making has remained unexplored theoretically. We develop a model to address the discrepancy between experiments and the theoretical prediction, and explore how assuming different decision making processes changes the prediction from the theory. We assume that parents make decisions in behavioral time. They have a fixed time budget, and allocate it between two parental tasks: provisioning the offspring and defending the nest. The proximate determinant of the allocation decisions are parents' behavioral objectives. We assume both parents aim to maximize the offspring production from the nest. Experimental manipulations change the shape of the nest production function. We consider two different scenarios for how parents make decisions: one where parents communicate with each other and act together (the perfect family), and one where they do not communicate, and act independently (the almost perfect family). The perfect family model is able to generate all the types of responses seen in experimental studies. The kind of response predicted depends on the nest production function, i.e. how parents' allocations affect offspring production, and the type of experimental manipulation. In particular, we find that complementarity of parents' allocations promotes matching responses. In contrast, the relative responses do not depend on the type of manipulation in the almost perfect family model. These results highlight the importance of the interaction between nest production function and how parents make decisions
Quality strategies implemented within the tourism agency Perfect Tour
Directory of Open Access Journals (Sweden)
Madar, A.
2012-01-01
Full Text Available The paper presents the quality strategies adopted by the tourism agency Perfect Tour. The most important advantages of the Romanian agency in comparison with its competitors are: the focus on high quality services, cooperation with other international agencies, entering new fields like medical tourism and sole representative of Disneyland Paris. The strategies adopted explain the good financial results even in the period of crisis.
A psychogenic dystonia perfect responsive to antidepressant treatment.
Volkan Solmaz; Durdane Aksoy; Betul Cevik; Semiha Gulsum Kurt; Elmas Pekdas; Sema inanir
2014-01-01
After ruling out of organic causes, movement disorders are named as psychogenic movement disorders, it can mimic perfectly Organic movement disorders, but with a good history, clinical observations and detailed examination is very helpful in the diagnosis of this disease. In here we will present a 15 years old male patient, he was complaining of urinary incontinence at night, emerging dystonic posture especially in crowded environments, eating, and during activities that require attention, fo...
Perfect independent sets with respect to infinitely many relations
Czech Academy of Sciences Publication Activity Database
Doležal, Martin; Kubiś, Wieslaw
2016-01-01
Roč. 55, č. 7 (2016), s. 847-856 ISSN 0933-5846 R&D Projects: GA ČR(CZ) GA14-07880S Institutional support: RVO:67985840 Keywords : perfect clique * free subgroup * open relation Subject RIV: BA - General Mathematics Impact factor: 0.394, year: 2016 http://link.springer.com/article/10.1007%2Fs00153-016-0498-3
Comment on ``Perfect imaging with positive refraction in three dimensions''
Merlin, R.
2010-11-01
Leonhardt and Philbin [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.81.011804 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.
Comment on ''Perfect imaging with positive refraction in three dimensions''
International Nuclear Information System (INIS)
Merlin, R.
2010-01-01
Leonhardt and Philbin [Phys. Rev. A 81, 011804(R) (2010)] have recently constructed a mathematical proof that the Maxwell's fish-eye lens provides perfect imaging of electromagnetic waves without negative refraction. In this comment, we argue that the unlimited resolution is an artifact of having introduced an unphysical drain at the position of the geometrical image. The correct solution gives focusing consistent with the standard diffraction limit.
Overlapped illusion optics: a perfect lens brings a brighter feature
Energy Technology Data Exchange (ETDEWEB)
Xu Yadong; Gao Lei; Chen Huanyang [School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006 (China); Du Shengwang, E-mail: kenyon@ust.hk [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)
2011-02-15
In this paper, we show that a perfect lens can be employed to make multiple objects appear like only one object in the far field, leading to a new concept in illusion optics. Numerical simulations have been performed to verify the functionalities for both passive and active objects. The conceptual device can be utilized to enhance the illumination brightness for both incoherent and coherent systems.
Overlapped illusion optics: a perfect lens brings a brighter feature
International Nuclear Information System (INIS)
Xu Yadong; Gao Lei; Chen Huanyang; Du Shengwang
2011-01-01
In this paper, we show that a perfect lens can be employed to make multiple objects appear like only one object in the far field, leading to a new concept in illusion optics. Numerical simulations have been performed to verify the functionalities for both passive and active objects. The conceptual device can be utilized to enhance the illumination brightness for both incoherent and coherent systems.
The perfect family: decision making in biparental care.
Directory of Open Access Journals (Sweden)
Erol Akçay
Full Text Available Previous theoretical work on parental decisions in biparental care has emphasized the role of the conflict between evolutionary interests of parents in these decisions. A prominent prediction from this work is that parents should compensate for decreases in each other's effort, but only partially so. However, experimental tests that manipulate parents and measure their responses fail to confirm this prediction. At the same time, the process of parental decision making has remained unexplored theoretically. We develop a model to address the discrepancy between experiments and the theoretical prediction, and explore how assuming different decision making processes changes the prediction from the theory.We assume that parents make decisions in behavioral time. They have a fixed time budget, and allocate it between two parental tasks: provisioning the offspring and defending the nest. The proximate determinant of the allocation decisions are parents' behavioral objectives. We assume both parents aim to maximize the offspring production from the nest. Experimental manipulations change the shape of the nest production function. We consider two different scenarios for how parents make decisions: one where parents communicate with each other and act together (the perfect family, and one where they do not communicate, and act independently (the almost perfect family.The perfect family model is able to generate all the types of responses seen in experimental studies. The kind of response predicted depends on the nest production function, i.e. how parents' allocations affect offspring production, and the type of experimental manipulation. In particular, we find that complementarity of parents' allocations promotes matching responses. In contrast, the relative responses do not depend on the type of manipulation in the almost perfect family model. These results highlight the importance of the interaction between nest production function and how parents make
A not-so-short description of the PERFECT platform
International Nuclear Information System (INIS)
Bugat, S.; Zeghadi, A.; Adjanor, G.
2010-01-01
This article describes the building of the so-called 'PERFECT platform', which main issue was to allow the development of the PERFECT end-products dedicated to the prediction of the degradation of material properties due to irradiation. First, the general principles used to build the platform are detailed. Such principles guided the choices of preferential development language, architecture, and operating system. The architecture of the platform is then described. It allows an easy development of the end-products, and a 'black-box' integration of the codes developed during the project. Each end-product can be seen as a sequence of modules, each module representing a physical phenomenon in time and space. The platform is very flexible, so that different methodologies can be tested and compared inside an end-product. The second part is devoted to the description of a classical PERFECT study, defined thanks to the graphical user interface developed in the project. Focus is made in particular on how a selection of modules is done, how the input data can be entered, and how the study execution is fully controlled by the user. A final description of the post-processing facilities on the results is exposed.
Bernard, Peter S
2015-01-01
This book presents a focused, readable account of the principal physical and mathematical ideas at the heart of fluid dynamics. Graduate students in engineering, applied math, and physics who are taking their first graduate course in fluids will find this book invaluable in providing the background in physics and mathematics necessary to pursue advanced study. The book includes a detailed derivation of the Navier-Stokes and energy equations, followed by many examples of their use in studying the dynamics of fluid flows. Modern tensor analysis is used to simplify the mathematical derivations, thus allowing a clearer view of the physics. Peter Bernard also covers the motivation behind many fundamental concepts such as Bernoulli's equation and the stream function. Many exercises are designed with a view toward using MATLAB or its equivalent to simplify and extend the analysis of fluid motion including developing flow simulations based on techniques described in the book.
Effect of panel shape of soccer ball on its flight characteristics
Hong, Sungchan; Asai, Takeshi
2014-05-01
Soccer balls are typically constructed from 32 pentagonal and hexagonal panels. Recently, however, newer balls named Cafusa, Teamgeist 2, and Jabulani were respectively produced from 32, 14, and 8 panels with shapes and designs dramatically different from those of conventional balls. The newest type of ball, named Brazuca, was produced from six panels and will be used in the 2014 FIFA World Cup in Brazil. There have, however, been few studies on the aerodynamic properties of balls constructed from different numbers and shapes of panels. Hence, we used wind tunnel tests and a kick-robot to examine the relationship between the panel shape and orientation of modern soccer balls and their aerodynamic and flight characteristics. We observed a correlation between the wind tunnel test results and the actual ball trajectories, and also clarified how the panel characteristics affected the flight of the ball, which enabled prediction of the trajectory.
Noninvasive medical management of fungus ball uropathy in a premature infant.
Alkalay, A L; Srugo, I; Blifeld, C; Komaiko, M S; Pomerance, J J
1991-09-01
Unilateral renal obstruction secondary to fungus balls is described in a premature infant. Noninvasive medical management, which included amphotericin B and 5-flucytosine therapy and forced diuresis, resulted in disappearance of fungus balls and resolution of the obstruction.
Generalized isoperimetric inequalities for extrinsic balls in minimal submanifolds
DEFF Research Database (Denmark)
Markvorsen, Steen; Palmer, Vicente
2002-01-01
The volume of an extrinsic ball in a minimal submanifold has a well defined lower bound when the ambient manifold has an upper bound on its sectional curvatures, see e.g. [2] and [10]. When this upper bound is non-positive, the second named author has shown an isoperimetric inequality for such do...
Thump, ring: the sound of a bouncing ball
Energy Technology Data Exchange (ETDEWEB)
Katz, J I, E-mail: katz@wuphys.wustl.ed [Department of Physics and McDonnell Center for the Space Sciences, Washington University, St Louis, MO 63130 (United States)
2010-07-15
A basketball bounced on a stiff surface produces a characteristic loud thump, followed by a high-pitched ringing. Describing the ball as an inextensible but flexible membrane containing compressed air, I formulate an approximate theory of the generation of these sounds and predict their amplitudes and waveforms.
Thump, ring: the sound of a bouncing ball
International Nuclear Information System (INIS)
Katz, J I
2010-01-01
A basketball bounced on a stiff surface produces a characteristic loud thump, followed by a high-pitched ringing. Describing the ball as an inextensible but flexible membrane containing compressed air, I formulate an approximate theory of the generation of these sounds and predict their amplitudes and waveforms.
High-Energy Ball-Milling of Alloys and Compounds
International Nuclear Information System (INIS)
Le Caer, G.; Delcroix, P.; Begin-Colin, S.; Ziller, T.
2002-01-01
After outlining some characteristics of high-energy ball-milling, we discuss selected examples of phase transformation and of alloy synthesis which focus on deviations from archetypal behaviours and throw light on the milling mechanisms. Some contributions of Moessbauer spectrometry to the characterization of ground materials are described.
Reduced graphene oxide synthesis by high energy ball milling
Energy Technology Data Exchange (ETDEWEB)
Mondal, O. [Department of Physics, M.U.C Women' s College, Burdwan 713104 (India); Mitra, S. [MLS Prof' s Unit, Indian Association for the Cultivation of Science, Kolkata 700032 (India); Pal, M. [CSIR-Central Glass and Ceramic Research Institute, Kolkata 700032 (India); Datta, A. [University School of Basic and Applied Science (USBAS), Guru Gobind Singh Indraprastha University, New Delhi 110075 (India); Dhara, S. [Surface and Nanoscience Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Chakravorty, D., E-mail: mlsdc@iacs.res.in [MLS Prof' s Unit, Indian Association for the Cultivation of Science, Kolkata 700032 (India)
2015-07-01
Graphene oxide is transformed to reduced graphene oxide by high energy ball milling in inert atmosphere. The process of ball milling introduces defects and removes oxygen functional groups, thereby creating the possibility of fine tuning the band gap of all intermediate stages of the structural evolution. A limit of the backbone sp{sup 2} network structure has been found which should be able to accommodate defects, before amorphization sets in. The amorphization of graphene oxide is achieved rather quickly in comparison to that of graphite. From thermogravimetric and differential scanning calorimetric analysis along with Fourier transform infrared (FTIR) and Raman spectroscopic studies, it is found that the number of oxygen-containing groups decreases at a faster rate than that of aromatic double bonds with increasing ball milling time with a maximum limit of 3 h. Several characterization techniques (FTIR, Raman, UV–Visible and X-ray photoelectron spectroscopy) have confirmed that the material synthesized is, indeed, reduced graphene oxide. - Highlights: • Graphene oxide is transformed to reduced graphene oxide by high energy ball milling in inert atmosphere. • Fine tuning the band gap by introducing defects and removing oxygen functional groups. • Introduction of excess defects leads to amorphization. • Photoluminescence has been observed in the UV-blue region.
Results from the crystal ball detector at SPEAR
International Nuclear Information System (INIS)
Bloom, E.D.
1979-11-01
The Crystal Ball detector is a device particularly suited to the measurement of photons with energies lower than 1 GeV. The detector has as its principal component a 16 radiation length thick, highly segmented shell of NaI(Tl) surrounding cylindrical, proportional, and magnetostrictive spark chambers. The main Ball and various elements of the central chambers cover 94% of 4π sr. Segmented endcap NaI(Tl) detectors of 20 radiation lengths behind magneto strictive spark chambers supplement the main Ball. The Ball and endcaps close the solid angle for charged particle and photon detection to 98% of 4π sr. In addition, detectors of interspersed iron and proportional tubes provide for μ-π separation over 15% of 4π sr, about theta/sub CM/ = 90 0 . In this report preliminary results are presented from the data obtained. In particular, QED at E/sub CM/ = 6.5 GeV, R/sub hadron/ and related inclusive distributions, eta branching fractions at J/psi and psi'', and a detailed study of the psionium system are discussed
Fuzzy controller for better tennis ball robot | Nguyen | Journal of ...
African Journals Online (AJOL)
This paper aims at designing a tennis ball robot as a training facility for tennis players. The robot is built with fuzzy controller which provides proper techniques for the players to gain practical experience as well as technical skills; thus, it can effectively serve the community and train athletes in the high-performance sport.
Predicting brain acceleration during heading of soccer ball
Taha, Zahari; Hasnun Arif Hassan, Mohd; Azri Aris, Mohd; Anuar, Zulfika
2013-12-01
There has been a long debate whether purposeful heading could cause harm to the brain. Studies have shown that repetitive heading could lead to degeneration of brain cells, which is similarly found in patients with mild traumatic brain injury. A two-degree of freedom linear mathematical model was developed to study the impact of soccer ball to the brain during ball-to-head impact in soccer. From the model, the acceleration of the brain upon impact can be obtained. The model is a mass-spring-damper system, in which the skull is modelled as a mass and the neck is modelled as a spring-damper system. The brain is a mass with suspension characteristics that are also defined by a spring and a damper. The model was validated by experiment, in which a ball was dropped from different heights onto an instrumented dummy skull. The validation shows that the results obtained from the model are in a good agreement with the brain acceleration measured from the experiment. This findings show that a simple linear mathematical model can be useful in giving a preliminary insight on what human brain endures during a ball-to-head impact.
Kinase inhibition by the Jamaican ball moss, Tillandsia recurvata L.
Lowe, Henry I C; Watson, Charah T; Badal, Simone; Toyang, Ngeh J; Bryant, Joseph
2012-10-01
This research was undertaken in order to investigate the inhibitory potential of the Jamaican ball moss, Tillandsia recurvata against several kinases. The inhibition of these kinases has emerged as a potential solution to restoring the tight regulation of normal cellular growth, the loss of which leads to cancer cell formation. Kinase inhibition was investigated using competition binding (to the ATP sites) assays, which have been previously established and authenticated. Four hundred and fifty one kinases were tested against the Jamaican ball moss extract and a dose-response was tested on 40 kinases, which were inhibited by more than 35% compared to the control. Out of the 40 kinases, the Jamaican ball moss selectively inhibited 5 (CSNK2A2, MEK5, GAK, FLT and DRAK1) and obtained Kd(50)s were below 20 μg/ml. Since MEK5 and GAK kinases have been associated with aggressive prostate cancer, the inhibitory properties of the ball moss against them, coupled with its previously found bioactivity towards the PC-3 cell line, makes it promising in the arena of drug discovery towards prostate cancer.
Development of Stick and Ball Sports on Gateball
Directory of Open Access Journals (Sweden)
Indriyanti
2017-10-01
Full Text Available The purpose of this research is to make product design development of stick and ball sports in gateball. The approach used in this study is a method of Research and Development. The subject of this research is the Central Java on gateball club event gateball in Semarang and Yogyakarta. Experts and expert expert gateball expert in mechanical engineering. The data analysis phase the work field, and the data analysis stage include observation, observation, interviews, and documentation of the test kefektifan products, expert judgment expert expert gateball and expert mechanical engineering expert. The results of this research are stick and ball exercise for beginner players gateball gateball. The result of the validator 3 expert expert from the expert gateball and expert mechanical engineering product validation data beginning the first phase obtained a score above 73 definitions of the criteria of “good”, on the second stage of the product validation data obtained a score above the 81 criteria for “excellent”. The results of the interviews to the development of gateball players 19 stick and ball gateball can not be used to play in a match and can be used for subsequent exercises but for beginners a product development tool model stick and ball gateball “ INC. “can be used to enhance the ability of basic techniques in motion game for players, gateball.
Preliminary Studies on the Development of Meat Balls | Igene ...
African Journals Online (AJOL)
The UUFB sample was rated highest in terms of overall likeness and may economically complement some of the existing popular meat-based snacks in Nigeria. The significance of the study is discussed. @JASEM Keyterms: Meat, Meat ball, Quality, Product development. J. Appl. Sci. Environ. Manage. June, 2012, Vol.
Haemolytic toxicity due to domestic naphthalene ball exposure in a ...
African Journals Online (AJOL)
This report presents a 29year-old male, Commercial tricycle driver, Ibo by tribe, Christian and single and was admitted with fatigue , severe abdominal pain , vomiting , yellowish coloration of the eyes and passage of dark urine (cocacola colored) following the use of naphthalene ball for the purpose of repelling mosquitoes ...
International Nuclear Information System (INIS)
Eichmann, G.; Elvekjaer, F.; Steiner, F.
1977-07-01
The jets in e + e - -annihilation are identified with two back-to-back hadron-balls with a thermodynamic decay spectrum. The data are reproduced nicely by the model. The data at 7.4 GeV shows a cigar-like shape displayed in a 'jet-contour-diagram'. Predictions for PETRA and PEP energies are made. (orig.) [de
Moment of Inertia of a Ping-Pong Ball
Cao, Xian-Sheng
2012-01-01
This note describes how to theoretically calculate and experimentally measure the moment of inertia of a Ping-Pong[R] ball. The theoretical calculation results are in good agreement with the experimental measurements that can be reproduced in an introductory physics laboratory.
Precession of a Spinning Ball Rolling down an Inclined Plane
Cross, Rod
2015-01-01
A routine problem in an introductory physics course considers a rectangular block at rest on a plane inclined at angle a to the horizontal. In order for the block not to slide down the incline, the coefficient of sliding friction, µ, must be at least tan a. The situation is similar for the case of a ball rolling down an inclined plane. In order…
Brown carbon in tar balls from smoldering biomass combustion
R. K. Chakrabarty; H. Moosmuller; L.-W. A. Chen; K. Lewis; W. P. Arnott; C. Mazzoleni; M. K. Dubey; C. E. Wold; W. M. Hao; S. M. Kreidenweis
2010-01-01
We report the direct observation of laboratory production of spherical, carbonaceous particles - "tar balls" - from smoldering combustion of two commonly occurring dry mid-latitude fuels. Real-time measurements of spectrally varying absorption Angstrom coefficients (AAC) indicate that a class of light absorbing organic carbon (OC) with wavelength dependent...
Estructura temporal y gestual del kin-ball
Directory of Open Access Journals (Sweden)
Rafael Díaz Amate
2015-06-01
Full Text Available El objetivo de este estudio es analizar la estructura temporal del kin-ball y cuantificar el número de golpeos, jugadas, puntos y los tipos de contacto utilizados, en cada período y partido. Se han analizado un total de 13 partidos, correspondientes a la fase de grupos, semifinales y final del VII Campeonato de España de Kin-ball. Es un deporte caracterizado por la realización de esfuerzos interválicos de intensidad media-alta y de corta duración. Un partido de kin-ball tiene una duración media de 46 min aproximadamente, siendo el ratio tiempo de trabajo y tiempo de descanso de 1:1,51 y la duración media por punto de 12,07 s. Así, un partido de kin-ball tiene un volumen de 73 puntos con un total de 390 golpeos. Los tipos de golpeos utilizados determinan que es un deporte defensivo. Todos estos análisis ayudan a tener un mayor conocimiento de esta disciplina deportiva por parte de los entrenadores y jugadores para tener un entrenamiento más específico.
Ball Games of Native American Women of the Plains.
Pesavento, Wilma J.
The problem under investigation concerned (1) determining the ball games of Native American girls and women of the Great Plains, (2) determining the geographical spread of the games within the culture area, and (3) determining the characteristics of the various games. Data for this investigation were obtained from the 48 "Annual Reports of the…
The spectacle of the ball python (Python regius)
DEFF Research Database (Denmark)
Da Silva, Mari-Ann Otkjær; Heegaard, Steffen; Wang, Tobias
2014-01-01
A detailed morphological description of the spectacle of the ball python (Python regius) is provided. The eyes of 21 snakes were examined by light microscopy and/or transmission electron microscopy. Additionally, eyes of nine live snakes were examined using optical coherence tomography (OCT...
Drilling Fluids Using Multiwall Carbon Nanotube (MWCNT
Directory of Open Access Journals (Sweden)
Mostafa Sedaghatzadeh
2012-11-01
Full Text Available Designing drilling fluids for drilling in deep gas reservoirs and geothermal wells is a major challenge. Cooling drilling fluids and preparing stable mud with high thermal conductivity are of great concern. Drilling nanofluids, i.e. a low fraction of carbon nanotube (CNT well dispersed in mud, may enhance the mixture thermal conductivity compared to the base fluids. Thus, they are potentially useful for advanced designing high temperature and high pressure (HTHP drilling fluids. In the present study, the impacts of CNT volume fraction, ball milling time, functionalization, temperature, and dispersion quality (by means of scanning electron microscopy, SEM on the thermal and rheological properties of water-based mud are experimentally investigated. The thermal conductivities of the nano-based drilling fluid are measured with a transient hot wire method. The experimental results show that the thermal conductivity of the water-based drilling fluid is enhanced by 23.2% in the presence of 1 vol% functionalized CNT at room temperature; it increases by 31.8% by raising the mud temperature to 50 °C. Furthermore, significant improvements are seen in the rheological properties—such as yield point, filtration properties, and annular viscosity—of the CNTmodified drilling fluid compared to the base mud, which pushes forward their future development.
Ball Bearings Equipped for In Situ Lubrication on Demand
Marchetti, Mario; Jones, William R., Jr.; Pepper, Stephen V.; Jansen, Mark; Predmore, Roamer
2005-01-01
In situ systems that provide fresh lubricants to ball/race contacts on demand have been developed to prolong the operational lives of ball bearings. These systems were originally intended to be incorporated into ball bearings in mechanisms that are required to operate in outer space for years, in conditions in which lubricants tend to deteriorate and/or evaporate. These systems may also be useful for similarly prolonging bearing lifetimes on Earth. Reservoirs have been among the means used previously to resupply lubricants. Lubricant- resupply reservoirs are bulky and add complexity to bearing assemblies. In addition, such a reservoir cannot be turned on or off as needed: it supplies lubricant continuously, often leading to an excess of lubricant in the bearing. A lubricator of the present type includes a porous ring cartridge attached to the inner or the outer ring of a ball bearing (see Figure 1). Oil is stored in the porous cartridge and is released by heating the cartridge: Because the thermal expansion of the oil exceeds that of the cartridge, heating causes the ejection of some oil. A metal film can be deposited on a face of the cartridge to serve as an electrical-resistance heater. The heater can be activated in response to a measured increase in torque that signals depletion of oil from the bearing/race contacts. Because the oil has low surface tension and readily wets the bearing-ring material, it spreads over the bearing ring and eventually reaches the ball/race contacts. The Marangoni effect (a surface-tension gradient associated with a temperature gradient) is utilized to enhance the desired transfer of lubricant to the ball/race contacts during heating. For a test, a ball bearing designed for use at low speed was assembled without lubricant and equipped with a porous-ring lubricator, the resistance heater of which consumed a power of less than 1 W when triggered on by a torque-measuring device. In the test, a load of 20 lb (.89 N) was applied and the
Deinzer, R; Förster, P; Fuck, L; Herforth, A; Stiller-Winkler, R; Idel, H
1999-01-01
This study analyses the effects of academic stress on crevicular interleukin-1beta(I1-1beta) both at experimental gingivitis sites and at sites of perfect oral hygiene. I1-1beta is thought to play a predominant role in periodontal tissue destruction. 13 medical students participating in a major medical exam (exam group) and 13 medical students not participating in any exam throughout the study period (control group) volunteered for the study. In a split-mouth-design, they refrained from any oral hygiene procedures in two opposite quadrants for 21 days (experimental gingivitis) while they maintained perfect hygiene levels at the remaining sites. Crevicular fluid was sampled for further I1-1beta analysis at teeth 5 and 6 of the upper jaw at days 1, 5, 8, 11, 14, 18 and 21 of the experimental gingivitis period. Exam students showed significantly higher I1-1beta levels than controls both at experimental gingivitis sites (area under the curve, exam group: 1240.64+/-140.07; control group: 697.61+/-111.30; p=0.004) and at sites of perfect oral hygiene (exam group: 290.42+/-63.19; control group: 143.98+/-42.71; p = 0.04). These results indicate that stress might affect periodontal health by increasing local I1-1beta levels especially when oral hygiene is neglected.
'Perfectly disordered' medium as a model for the description of micro-inhomogeneous mixtures
International Nuclear Information System (INIS)
Levin, V M; Markov, M G; Alvarez-Tostado, J M
2004-01-01
The correct description of the macroscopic (overall) physical properties of micro-inhomogeneous (composite) materials by micro-mechanics methods (the self-consistent schemes, for example) requires information about the microstructure and texture of such materials. Often, such information (of shapes inhomogeneities and peculiarities of their spatial distribution) is not available. In this paper, we suggest a method of calculation of the characteristics of micro-inhomogeneous materials that could be applied to a wide class of isotropic materials. This method assumes the absence of a closed order in the material microstructure (a 'perfectly disordered' (PD) medium). We used the PD approximation to predict the effective thermo- and poroelastic, electric and thermal properties of micro-inhomogeneous media. The expressions for the effective characteristics obtained by this method are always inside of the Hashin-Shtrikman universal bounds. For a two-phase material with fluid component, the effective bulk module satisfies Gassmann's relation for fluid-filled porous media and generalizes such a relation to inhomogeneous thermoelastic and poroelastic media. A comparison of the theoretical results with available experimental data shows a satisfactory coincidence even in the case of high contrast of the component properties. The simplicity of the numerical realization of the method makes it attractive for applications in the absence of detailed information about the material's microstructure
Real-time detecting and tracking ball with OpenCV and Kinect
Osiecki, Tomasz; Jankowski, Stanislaw
2016-09-01
This paper presents a way to detect and track ball with using the OpenCV and Kinect. Object and people recognition, tracking are more and more popular topics nowadays. Described solution makes it possible to detect ball based on the range, which is set by the user and capture information about ball position in three dimensions. It can be store in the computer and use for example to display trajectory of the ball.
Visual strategies underpinning the development of visual-motor expertise when hitting a ball
Sarpeshkar, Vishnu; Abernethy, B.; Mann, D.L.
2017-01-01
It is well known that skilled batters in fast-ball sports do not align their gaze with the ball throughout ball-flight, but instead adopt a unique sequence of eye and head movements that contribute toward their skill. However, much of what we know about visual-motor behavior in hitting is based on
Solid lubricant mass contact transfer technology usage for vacuum ball bearings longevity increasing
Arzymatov, B.; Deulin, E.
2016-07-01
A contact mass transfer technological method of solid lubricant deposition on components of vacuum ball bearings is presented. Physics-mathematical model of process contact mass transfer is being considered. The experimental results of ball bearings covered with solid lubricant longevity in vacuum are presented. It is shown that solid lubricant of contact mass transfer method deposition is prospective for ball bearing longevity increasing.
Visual Illusions and the Control of Ball Placement in Goal-Directed Hitting
Caljouw, Simone R.; Van der Kamp, John; Savelsbergh, Geert J. P.
2010-01-01
When hitting, kicking, or throwing balls at targets, online control in the target area is impossible. We assumed this lack of late corrections in the target area would induce an effect of a single-winged Muller-Lyer illusion on ball placement. After extensive practice in hitting balls to different landing locations, participants (N = 9) had to hit…
Sphere interaction in bounded shear flow of Oldroyd-B fluids
Chiu, Shang-Huan; Pan, Tsorng-Whay; Glowinski, Roland
2017-11-01
It is well-known that, up to the initial sphere displacement, binary encounters of spheres in bounded shear flow of a Newtonian fluid can have either swapping or non-swapping trajectories under creeping flow conditions. The motion of dilute sphere suspensions in bounded shear flow of Oldroyd-B fluids at zero Reynolds number has been studied. The pass and return trajectories of the two ball mass centers in a two wall driven shear flow are similar to those in a Newtonian fluid; but they lose the symmetry due to the effect of elastic force arising from viscoelastic fluids. A tumbling chain of two balls (a dipole) may occur, depending on the value of the Weissenberg number and the initial vertical displacement of the ball mass center to the middle plane between two walls. The two ball tumbling motion has also been compared with that of an ellipsoid in bounded shear flow Oldroyd-B fluids. This work was supported by NSF (Grant DMS-1418308).
Hall Effect Influence on a Highly Conducting Fluid
Energy Technology Data Exchange (ETDEWEB)
Witalis, E A
1966-11-15
The properties of an incompressible perfect fluid exhibiting Hall effect is investigated in the limit of infinite electrical conductivity and mobility. The magnetic field strength and the fluid velocity are found to obey the equations B = {mu}{rho}/{sigma} x curlV and V -{mu}/({sigma}{mu}{sub 0}) x curlB (MKS units) where {rho}, {sigma} and {mu} denote mass density, conductivity and charge carrier mobility. Some physical interpretations and applications are given.
Experimental and theoretical studies of levitated quantum fluids
International Nuclear Information System (INIS)
Schmidt, J.; Halley, J.W.; Giese, C.F.
1998-01-01
We describe the opportunities for improved scientific understanding and technical manipulation of cryogenic fields, particularly molecular hydrogen, by the use of carefully designed magnetic field configurations produced with assemblies of permanent magnets. We discuss the levitation of hydrogen in order to perfect technical means for handling this and other cryogenic fluids. The development of the techniques to be explored here provide extraordinary opportunities for improved methods for handling rocket fuels and cryogenic fluids in low gravity environments
Hall Effect Influence on a Highly Conducting Fluid
International Nuclear Information System (INIS)
Witalis, E.A.
1966-11-01
The properties of an incompressible perfect fluid exhibiting Hall effect is investigated in the limit of infinite electrical conductivity and mobility. The magnetic field strength and the fluid velocity are found to obey the equations B = μρ/σ x curlV and V -μ/(σμ 0 ) x curlB (MKS units) where ρ, σ and μ denote mass density, conductivity and charge carrier mobility. Some physical interpretations and applications are given
Fluid Density and Impact Cavity Formation
Directory of Open Access Journals (Sweden)
Ga-Chun Lin
2018-01-01
Full Text Available Characteristics of the impact cavity formed when a steel ball is dropped into aqueous solutions of densities ranging from 0.98 g·cm-3 to 1.63 g·cm-3 were investigated. A high-speed camera was used to record the formation and collapse of the cavity. The results showed cavity diameter, volume, and pinch-off time are independent of fluid density, on average. There was an unexplained reduction in cavity formation for densities of 1.34 g·cm-3 and 1.45 g·cm-3.
Directory of Open Access Journals (Sweden)
Raül Sanchis Francés
2013-06-01
Full Text Available Resum: El Ball de Torrent és una moixiganga dramàtica popular escenificada a la ciutat de València i altres indrets del País Valencià des de finals del segle XVII fins a principis del segle XX. Estava organitzada per agrupacions gremials, juntes d’hospitals o clavaris de festes i protagonitzada per personatges agrupats en comparses que representaven una paròdia sobre les relacions entre les estructures de poder i les classes populars. Tot i la variabilitat segons el moment històric, es conforma com una mescla de quadres amb danses, música i jocs teatrals. El ball interacciona de diverses formes amb algunes festes valencianes i és, probablement, una de les mostres de teatre de carrer més nostrades i menys estudiades de la València Moderna. En aquest article es realitza una revisió bibliogràfica crítica i una primera anàlisi historiogràfica.Paraules clau: Ball de Torrent, Dansa i música tradicional, Teatre, Moixiganga, Festa valencianaAbstract: Ball de Torrent (Dance of Torrent is a popular dramatic masquerade staged in Valencia since the late seventeenth century to the early twentieth. It was organized by guilds, hospital managements or festival organizers. The actors were grouped in associations representing a parody on the relationships between power structures and popular classes. Despite the variability depending on the historical period, it consisted of a mixture of episodes or scenes with dance, music and theatre games. Any Festivals in Valencia are connected with the Ball de Torrent. It’s probably one of the most interesting samples of street theatre and studied under of the Modern Valencia. This paper analyses historical sources to review and critique bibliography.Keywords: Dance of Torrent, Traditional Dance and Music, Theatre, Masquerade, Feasts of Valencia
Evaluation of possible head injuries ensuing a cricket ball impact.
Mohotti, Damith; Fernando, P L N; Zaghloul, Amir
2018-05-01
The aim of this research is to study the behaviour of a human head during the event of an impact of a cricket ball. While many recent incidents were reported in relation to head injuries caused by the impact of cricket balls, there is no clear information available in the published literature about the possible threat levels and the protection level of the current protective equipment. This research investigates the effects of an impact of a cricket ball on a human head and the level of protection offered by the existing standard cricket helmet. An experimental program was carried out to measure the localised pressure caused by the impact of standard cricket balls. The balls were directed at a speed of 110 km/h on a 3D printed head model, with and without a standard cricket helmet. Numerical simulations were carried out using advanced finite element package LS-DYNA to validate the experimental results. The experimental and numerical results showed approximately a 60% reduction in the pressure on the head model when the helmet was used. Both frontal and side impact resulted in head acceleration values in the range of 225-250 g at a ball speed of 110 km/h. There was a 36% reduction observed in the peak acceleration of the brain when wearing a helmet. Furthermore, numerical simulations showed a 67% reduction in the force on the skull and a 95% reduction in the skull internal energy when introducing the helmet. (1) Upon impact, high localised pressure could cause concussion for a player without helmet. (2) When a helmet was used, the acceleration of the brain observed in the numerical results was at non-critical levels according to existing standards. (3) A significant increase in the threat levels was observed for a player without helmet, based on force, pressure, acceleration and energy criteria, which resulted in recommending the compulsory use of the cricket helmet. (4) Numerical results showed a good correlation with experimental results and hence, the
10 CFR 609.16 - Perfection of liens and preservation of collateral.
2010-01-01
... 10 Energy 4 2010-01-01 2010-01-01 false Perfection of liens and preservation of collateral. 609.16... THAT EMPLOY INNOVATIVE TECHNOLOGIES § 609.16 Perfection of liens and preservation of collateral. (a... to perfect and maintain liens, as applicable, on assets which are pledged as collateral for the...
An Infinite Family of Circulant Graphs with Perfect State Transfer in Discrete Quantum Walks
Zhan, Hanmeng
2017-01-01
We study perfect state transfer in a discrete quantum walk. In particular, we show that there are infinitely many $4$-regular circulant graphs that admit perfect state transfer between antipodal vertices. To the best of our knowledge, previously there was no infinite family of $k$-regular graphs with perfect state transfer, for any $k\\ge 3$.
Approximating perfection a mathematician's journey into the world of mechanics
Lebedev, Leonid P
2004-01-01
This is a book for those who enjoy thinking about how and why Nature can be described using mathematical tools. Approximating Perfection considers the background behind mechanics as well as the mathematical ideas that play key roles in mechanical applications. Concentrating on the models of applied mechanics, the book engages the reader in the types of nuts-and-bolts considerations that are normally avoided in formal engineering courses: how and why models remain imperfect, and the factors that motivated their development. The opening chapter reviews and reconsiders the basics of c
Extinction in finite perfect crystals: Case of a sphere
International Nuclear Information System (INIS)
Al Haddad, M.; Becker, P.
1990-01-01
The extinction factor in finite perfect crystals is calculated from pure dynamical theory. In particular, a detailed solution is proposed for a sphere, in which case the extinction factor depends on the Bragg angle θ and the parameter (R/Λ), where R is the radius of the crystal and Λ the extinction length. An approximate solution based on the Laue geometry is proposed and corrections to take care of the complex boundary conditions are presented. An expression easily usable in refinement programs is proposed that fits the exact value to better than 1%. (orig.)
Seeking perfection: a Kantian look at human genetic engineering.
Gunderson, Martin
2007-01-01
It is tempting to argue that Kantian moral philosophy justifies prohibiting both human germ-line genetic engineering and non-therapeutic genetic engineering because they fail to respect human dignity. There are, however, good reasons for resisting this temptation. In fact, Kant's moral philosophy provides reasons that support genetic engineering-even germ-line and non-therapeutic. This is true of Kant's imperfect duties to seek one's own perfection and the happiness of others. It is also true of the categorical imperative. Kant's moral philosophy does, however, provide limits to justifiable genetic engineering.
Using a quantum dot system to realize perfect state transfer
International Nuclear Information System (INIS)
Li Ji; Wu Shi-Hai; Zhang Wen-Wen; Xi Xiao-Qiang
2011-01-01
There are some disadvantages to Nikolopoulos et al.'s protocol [Nikolopoulos G M, Petrosyan D and Lambropoulos P 2004 Europhys. Lett. 65 297] where a quantum dot system is used to realize quantum communication. To overcome these disadvantages, we propose a protocol that uses a quantum dot array to construct a four-qubit spin chain to realize perfect quantum state transfer (PQST). First, we calculate the interaction relation for PQST in the spin chain. Second, we review the interaction between the quantum dots in the Heitler—London approach. Third, we present a detailed program for designing the proper parameters of a quantum dot array to realize PQST. (general)
Analysis of the Perfect Table Fuzzy Rainbow Tradeoff
Directory of Open Access Journals (Sweden)
Byoung-Il Kim
2014-01-01
Full Text Available Cryptanalytic time memory tradeoff algorithms are tools for inverting one-way functions, and they are used in practice to recover passwords that restrict access to digital documents. This work provides an accurate complexity analysis of the perfect table fuzzy rainbow tradeoff algorithm. Based on the analysis results, we show that the lesser known fuzzy rainbow tradeoff performs better than the original rainbow tradeoff, which is widely believed to be the best tradeoff algorithm. The fuzzy rainbow tradeoff can attain higher online efficiency than the rainbow tradeoff and do so at a lower precomputation cost.
Assessing Measures of Order Flow Toxicity via Perfect Trade Classification
DEFF Research Database (Denmark)
Andersen, Torben G.; Bondarenko, Oleg
. The VPIN metric involves decomposing volume into active buys and sells. We use the best-bid-offer (BBO) files from the CME Group to construct (near) perfect trade classification measures for the E-mini S&P 500 futures contract. We investigate the accuracy of the ELO Bulk Volume Classification (BVC) scheme...... systematic classification errors that are correlated with trading volume and return volatility. When controlling for trading intensity and volatility, the BVC-VPIN measure has no incremental predictive power for future volatility. We conclude that VPIN is not suitable for measuring order flow imbalances....
Artificial hairy surfaces with a nearly perfect hydrophobic response.
Hsu, Shu-Hau; Sigmund, Wolfgang M
2010-02-02
A nearly perfect hydrophobic interface by dint of mimicking hairs of arthropods was achieved for the first time. These Gamma-shape artificial hairs were made via a membrane casting technique on polypropylene substrates. This extreme hydrophobicity merely arises from microstructure modification, and no further chemical treatments are needed. The ultralow adhesion to water droplets was evaluated through video assessment, and it is believed to be attributed to the mechanical response of the artificial hairs. The principle of this fabrication technique is accessible and is expected to be compatible with large-area fabrication of superhydrophobic interfaces.
Manipulating the loss in electromagnetic cloaks for perfect wave absorption.
Argyropoulos, Christos; Kallos, Efthymios; Zhao, Yan; Hao, Yang
2009-05-11
We examine several ways to manipulate the loss in electro-magnetic cloaks, based on transformation electromagnetics. It is found that, by utilizing inherent electric and magnetic losses of metamaterials, perfect wave absorption can be achieved based on several popular designs of electromagnetic cloaks. A practical implementation of the absorber, consisting of ten discrete layers of metamaterials, is proposed. The new devices demonstrate super-absorptivity over a moderate wideband range, suitable for both microwave and optical applications. It is corroborated that the device is functional with a subwavelength thickness and, hence, advantageous compared to the conventional absorbers.
Supersymmetric dark-matter Q-balls and their interactions in matter
International Nuclear Information System (INIS)
Kusenko, Alexander; Loveridge, Lee C.; Shaposhnikov, Mikhail
2005-01-01
Supersymmetric extensions of the Standard Model contain nontopological solitons, Q-balls, which can be stable and can be a form of cosmological dark matter. Understanding the interaction of SUSY Q-balls with matter fermions is important for both astrophysical limits and laboratory searches for these dark-matter candidates. We show that a baryon scattering off a baryonic SUSY Q-ball can convert into its antiparticle with a high probability, while the baryon number of the Q-ball is increased by two units. For a SUSY Q-ball interacting with matter, this process dominates over those previously discussed in the literature
Analysis on Sealing Reliability of Bolted Joint Ball Head Component of Satellite Propulsion System
Guo, Tao; Fan, Yougao; Gao, Feng; Gu, Shixin; Wang, Wei
2018-01-01
Propulsion system is one of the important subsystems of satellite, and its performance directly affects the service life, attitude control and reliability of the satellite. The Paper analyzes the sealing principle of bolted joint ball head component of satellite propulsion system and discuss from the compatibility of hydrazine anhydrous and bolted joint ball head component, influence of ground environment on the sealing performance of bolted joint ball heads, and material failure caused by environment, showing that the sealing reliability of bolted joint ball head component is good and the influence of above three aspects on sealing of bolted joint ball head component can be ignored.
Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.;
2017-01-01
Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid
Micro-ball lens structure fabrication based on drop on demand printing the liquid mold
Energy Technology Data Exchange (ETDEWEB)
Zhu, Xiaoyang, E-mail: zhuxy1026@163.com; Zhu, Li, E-mail: zhuli@njust.edu.cn; Chen, Hejuan; Yang, Lijun; Zhang, Weiyi
2016-01-15
Graphical abstract: - Highlights: • The glycerol micro-ball droplet was introduced to be as liquid mold to fabricate micro-ball lens. • A molding process was used to fabricate the micro-ball lens and the scales of them can be controlled. • The accurate molding process is mainly attributed to the ultrahigh adhesion of the treated substrate. • The micro-ball lenses with contact angle of 120° and 150° were fabricated, analyzed and discussed. - Abstract: In this paper, we demonstrated a simple micro-ball lens array (MBLA) fabrication method using a drop-on-demand (DOD) droplet printing technique and liquid mold. The micro-ball droplet array on the hydrophobic surface is used as the liquid mold to fabricate the MBLA. The ultrahigh adhesion force between the micro-ball droplet and the substrate is ascribed to the Wenzel state of the micro-ball droplet, while the replication process with low position error is attributed to the ultrahigh adhesion force between the micro-ball droplet and the substrate and the high viscosity of the micro-ball droplet and polydimethylsiloxane (PDMS) liquid. The micro-ball lenses (MBLs) with a contact angle of 120° and 150° were fabricated and the important fabrication details were discussed. The optical performance and scanning electron microscope (SEM) data of the MBLs showed that the MBLs had high quality surface morphology and good optical performance.
Knee Angle and Stride Length in Association with Ball Speed in Youth Baseball Pitchers
Directory of Open Access Journals (Sweden)
Bart van Trigt
2018-05-01
Full Text Available The purpose of this study was to determine whether stride length and knee angle of the leading leg at foot contact, at the instant of maximal external rotation of the shoulder, and at ball release are associated with ball speed in elite youth baseball pitchers. In this study, fifty-two elite youth baseball pitchers (mean age 15.2 SD (standard deviation 1.7 years pitched ten fastballs. Data were collected with three high-speed video cameras at a frequency of 240 Hz. Stride length and knee angle of the leading leg were calculated at foot contact, maximal external rotation, and ball release. The associations between these kinematic variables and ball speed were separately determined using generalized estimating equations. Stride length as percentage of body height and knee angle at foot contact were not significantly associated with ball speed. However, knee angles at maximal external rotation and ball release were significantly associated with ball speed. Ball speed increased by 0.45 m/s (1 mph with an increase in knee extension of 18 degrees at maximal external rotation and 19.5 degrees at ball release. In conclusion, more knee extension of the leading leg at maximal external rotation and ball release is associated with higher ball speeds in elite youth baseball pitchers.
The head tracks and gaze predicts: how the world's best batters hit a ball.
Directory of Open Access Journals (Sweden)
David L Mann
Full Text Available Hitters in fast ball-sports do not align their gaze with the ball throughout ball-flight; rather, they use predictive eye movement strategies that contribute towards their level of interceptive skill. Existing studies claim that (i baseball and cricket batters cannot track the ball because it moves too quickly to be tracked by the eyes, and that consequently (ii batters do not - and possibly cannot - watch the ball at the moment they hit it. However, to date no studies have examined the gaze of truly elite batters. We examined the eye and head movements of two of the world's best cricket batters and found both claims do not apply to these batters. Remarkably, the batters coupled the rotation of their head to the movement of the ball, ensuring the ball remained in a consistent direction relative to their head. To this end, the ball could be followed if the batters simply moved their head and kept their eyes still. Instead of doing so, we show the elite batters used distinctive eye movement strategies, usually relying on two predictive saccades to anticipate (i the location of ball-bounce, and (ii the location of bat-ball contact, ensuring they could direct their gaze towards the ball as they hit it. These specific head and eye movement strategies play important functional roles in contributing towards interceptive expertise.
International Nuclear Information System (INIS)
Granger, R.A.
1985-01-01
This text offers the most comprehensive approach available to fluid mechanics. The author takes great care to insure a physical understanding of concepts grounded in applied mathematics. The presentation of theory is followed by engineering applications, helping students develop problem-solving skills from the perspective of a professional engineer. Extensive use of detailed examples reinforces the understanding of theoretical concepts
BALL KINEMATICS IN FINE POLISHING BETWEEN MISALIGNED DISKS IN CONIC OPENINGS
Directory of Open Access Journals (Sweden)
K. G. Shchetnikovich
2009-01-01
Full Text Available The paper considers ball kinematics in polishing between misaligned disks rotating with equal angular velocity; one of these disks has conic openings. Analytical dependences have been obtained for calculation of an angular velocity and ball sliding speed in the conic opening. It has been revealed that at a constant contact of a ball with elastic coating of a flat disk and absence of vibrations in the technological system an instantaneous axis of ball rotation does not change its position in the moving ball. It has been ascertained that when a ball is in contact with a flat disk having elastic coating with grooves changes in the position of ball rotation instantaneous axis have a regular character and do not depend on vibrations in the technological system.
Entanglement and the three-dimensionality of the Bloch ball
Energy Technology Data Exchange (ETDEWEB)
Masanes, Ll., E-mail: ll.masanes@gmail.com [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Müller, M. P. [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany); Pérez-García, D. [Departamento de Analisis Matematico and IMI, Universidad Complutense de Madrid, 28040 Madrid (Spain); Augusiak, R. [ICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels, Barcelona (Spain)
2014-12-15
We consider a very natural generalization of quantum theory by letting the dimension of the Bloch ball be not necessarily three. We analyze bipartite state spaces where each of the components has a d-dimensional Euclidean ball as state space. In addition to this, we impose two very natural assumptions: the continuity and reversibility of dynamics and the possibility of characterizing bipartite states by local measurements. We classify all these bipartite state spaces and prove that, except for the quantum two-qubit state space, none of them contains entangled states. Equivalently, in any of these non-quantum theories, interacting dynamics is impossible. This result reveals that “existence of entanglement” is the requirement with minimal logical content which singles out quantum theory from our family of theories.
Magnet balls stuck to the frenulum of the lip.
Kondamudi, Noah P; Ayush Gupta; Kaur, Ranbir
2014-03-01
Accidents associated with magnets as foreign bodies pose a serious threat to the health of children and adolescents. Prompt management and removal of the magnet is important to avoid life-threatening complications. Our aim was to highlight an unusual health hazard associated with magnets in children. We report on a unique case of an adolescent girl who presented with two magnet balls stuck to the frenulum of her upper lip, resulting in intense pain and discomfort. The magnets were removed painlessly by induced magnetism through metallic mosquito forceps. As children experiment with toys and products containing detachable magnetic balls, more cases will likely present to emergency departments. Increased awareness and preventive measures should be undertaken to reduce the morbidity and mortality associated with magnets. Copyright © 2014 Elsevier Inc. All rights reserved.
Synthesis of Randomly Substituted Anionic Cyclodextrins in Ball Milling
Directory of Open Access Journals (Sweden)
László Jicsinszky
2017-03-01
Full Text Available A number of influencing factors mean that the random substitution of cyclodextrins (CD in solution is difficult to reproduce. Reaction assembly in mechanochemistry reduces the number of these factors. However, lack of water can improve the reaction outcomes by minimizing the reagent’s hydrolysis. High-energy ball milling is an efficient, green and simple method for one-step reactions and usually reduces degradation and byproduct formation. Anionic CD derivatives have successfully been synthesized in the solid state, using a planetary ball mill. Comparison with solution reactions, the solvent-free conditions strongly reduced the reagent hydrolysis and resulted in products of higher degree of substitution (DS with more homogeneous DS distribution. The synthesis of anionic CD derivatives can be effectively performed under mechanochemical activation without significant changes to the substitution pattern but the DS distributions were considerably different from the products of solution syntheses.
Coefficient of restitution of sports balls: A normal drop test
International Nuclear Information System (INIS)
Haron, Adli; Ismail, K A
2012-01-01
Dynamic behaviour of bodies during impact is investigated through impact experiment, the simplest being a normal drop test. Normally, a drop test impact experiment involves measurement of kinematic data; this includes measurement of incident and rebound velocity in order to calculate a coefficient of restitution (COR). A high speed video camera is employed for measuring the kinematic data where speed is calculated from displacement of the bodies. Alternatively, sensors can be employed to measure speeds, especially for a normal impact where there is no spin of the bodies. This paper compares experimental coefficients of restitution (COR) for various sports balls, namely golf, table tennis, hockey and cricket. The energy loss in term of measured COR and effects of target plate are discussed in relation to the material and construction of these sports balls.
Sir Robert Ball: Victorian Astronomer and Lecturer par excellence
Jones, R. I. G.
2005-12-01
Between 1875 and 1910 Sir Robert Stawell Ball gave an estimated 2,500 lectures in towns and cities all over the British Isles and abroad. This paper traces his lecturing career from its beginnings in Ireland to the triumphs of the Royal Institution, and on lecture tours in the United States of America. After a period in mathematics and mechanics, he became a populariser of science, especially astronomy, and found fame and fortune among the working classes and the aristocracy. What motivated him to tireless travels is uncertain, but it might have been that it was rewarding, financially and to his reputation. Whatever his motives, contemporary accounts are clear that BallÕs lectures were extremely popular and well-received.
Coordinate transformations make perfect invisibility cloaks with arbitrary shape
International Nuclear Information System (INIS)
Yan Wei; Yan Min; Ruan Zhichao; Qiu Min
2008-01-01
By investigating wave properties at cloak boundaries, invisibility cloaks with arbitrary shape constructed by general coordinate transformations are confirmed to be perfectly invisible to the external incident wave. The differences between line transformed cloaks and point transformed cloaks are discussed. The fields in the cloak medium are found analytically to be related to the fields in the original space via coordinate transformation functions. At the exterior boundary of the cloak, it is shown that no reflection is excited even though the permittivity and permeability do not always have a perfectly matched layer form, whereas at the inner boundary, no reflection is excited either, and in particular no field can penetrate into the cloaked region. However, for the inner boundary of any line transformed cloak, the permittivity and permeability in a specific tangential direction are always required to be infinitely large. Furthermore, the field discontinuity at the inner boundary always exists; the surface current is induced to make this discontinuity self-consistent. A point transformed cloak does not experience such problems. The tangential fields at the inner boundary are all zero, implying that no field discontinuity exists
A perfectly conducting surface in electrodynamics with Lorentz symmetry breaking
Borges, L. H. C.; Barone, F. A.
2017-10-01
In this paper we consider a model which exhibits explicit Lorentz symmetry breaking due to the presence of a single background vector v^{μ } coupled to the gauge field. We investigate such a theory in the vicinity of a perfectly conducting plate for different configurations of v^{μ }. First we consider no restrictions on the components of the background vector and we treat it perturbatively up to second order. Next, we treat v^{μ } exactly for two special cases: the first one is when it has only components parallel to the plate, and the second one when it has a single component perpendicular to the plate. For all these configurations, the propagator for the gauge field and the interaction force between the plate and a point-like electric charge are computed. Surprisingly, it is shown that the image method is valid in our model and we argue that it is a non-trivial result. We show there arises a torque on the mirror with respect to its positioning in the background field when it interacts with a point-like charge. It is a new effect with no counterpart in theories with Lorentz symmetry in the presence of a perfect mirror.
A perfectly conducting surface in electrodynamics with Lorentz symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Borges, L.H.C. [UNESP, Campus de Guaratingueta, DFQ, Guaratingueta, SP (Brazil); Barone, F.A. [IFQ, Universidade Federal de Itajuba, Itajuba, MG (Brazil)
2017-10-15
In this paper we consider a model which exhibits explicit Lorentz symmetry breaking due to the presence of a single background vector v{sup μ} coupled to the gauge field. We investigate such a theory in the vicinity of a perfectly conducting plate for different configurations of v{sup μ}. First we consider no restrictions on the components of the background vector and we treat it perturbatively up to second order. Next, we treat v{sup μ} exactly for two special cases: the first one is when it has only components parallel to the plate, and the second one when it has a single component perpendicular to the plate. For all these configurations, the propagator for the gauge field and the interaction force between the plate and a point-like electric charge are computed. Surprisingly, it is shown that the image method is valid in our model and we argue that it is a non-trivial result. We show there arises a torque on the mirror with respect to its positioning in the background field when it interacts with a point-like charge. It is a new effect with no counterpart in theories with Lorentz symmetry in the presence of a perfect mirror. (orig.)
Simulation of laser radar tooling ball measurements: focus dependence
Smith, Daniel G.; Slotwinski, Anthony; Hedges, Thomas
2015-10-01
The Nikon Metrology Laser Radar system focuses a beam from a fiber to a target object and receives the light scattered from the target through the same fiber. The system can, among other things, make highly accurate measurements of the position of a tooling ball by locating the angular position of peak signal quality, which is related to the fiber coupling efficiency. This article explores the relationship between fiber coupling efficiency and focus condition.
Condition monitoring of thrust ball bearings using continuous AE
Czech Academy of Sciences Publication Activity Database
Chlada, Milan; Nohal, L.; Převorovský, Zdeněk
2016-01-01
Roč. 26, č. 2 (2016), A14-A14 ISSN 1213-3825. [Europen Conference on Acoustic Emission Testing /32./. 07.09.2016-09.09.2016, Praha] Grant - others:NETME Centre Plus - národní program udržitelnosti(CZ) LO1202 Institutional support: RVO:61388998 Keywords : continuous acoustic emission * rolling contact fatigue * thrust ball bearing * histogram of counting periods * wavelet analysis Subject RIV: BI - Acoustic s
Unexpected Expectations The Curiosities of a Mathematical Crystal Ball
Wapner, Leonard M
2012-01-01
Unexpected Expectations: The Curiosities of a Mathematical Crystal Ball explores how paradoxical challenges involving mathematical expectation often necessitate a reexamination of basic premises. The author takes you through mathematical paradoxes associated with seemingly straightforward applications of mathematical expectation and shows how these unexpected contradictions may push you to reconsider the legitimacy of the applications. The book requires only an understanding of basic algebraic operations and includes supplemental mathematical background in chapter appendices. After a history o
Development of Stick and Ball Sports on Gateball
Indriyanti; Tri Nur Harsono; Rumini
2017-01-01
The purpose of this research is to make product design development of stick and ball sports in gateball. The approach used in this study is a method of Research and Development. The subject of this research is the Central Java on gateball club event gateball in Semarang and Yogyakarta. Experts and expert expert gateball expert in mechanical engineering. The data analysis phase the work field, and the data analysis stage include observation, observation, interviews, and documentation of the te...
International Nuclear Information System (INIS)
Eichmann, G.; Elvekjaer, F.; Steiner, F.
1978-01-01
The jets in e + e - annihilation are identified with two back-to-back hadron-balls with a thermodynamic decay spectrum. The data on , s dsigma|dx, dsigma|dp, dsigma|dy and on the angular coefficient α are reproduced nicely by the model. The data at 7.4 GeV shows a cigarlike shape displayed in a ''jet-contour-diagram''. Predictions for PETRA and PEP energies are made