Axially symmetric static sources of gravitational field
Hernandez-Pastora, J L; Martin, J
2016-01-01
A general procedure to find static and axially symmetric, interior solutions to the Einstein equations is presented. All the so obtained solutions, verify the energy conditions for a wide range of values of the parameters, and match smoothly to some exterior solution of the Weyl family, thereby representing globally regular models describing non spherical sources of gravitational field. In the spherically symmetric limit, all our models converge to the well known incompressible perfect fluid solution.The key stone of our approach is based on an ansatz allowing to define the interior metric in terms of the exterior metric functions evaluated at the boundary source. Some particular sources are obtained, and the physical variables of the energy-momentum tensor are calculated explicitly, as well as the geometry of the source in terms of the relativistic multipole moments. The total mass of different configurations is also calculated, it is shown to be equal to the monopole of the exterior solution.
SUPERFISH 1 program for calculation of electromagnetic fields of axially-symmetric resonators
International Nuclear Information System (INIS)
The possibilities, structure and guidance to use the package of the SUPERFISH 1 programs computing the eigenfrequencies and fields of axial-symmetric resonators. The package has been designed to be applied at the ICL 1906A computer. The characteristic time of computing one frequency and corresponding fields is 20 s with the frequency being computed to an accuracy of 10-3. The computation time is independent of the complexity of the resonator geometry
On Axially Symmetric Space-Times Admitting Homothetic Vector Fields in Lyra's Geometry
Gad, Ragab M
2016-01-01
This paper investigates axially symmetric space-times which admit a homothetic vector field based on Lyra's geometry. The cases when the displacement vector is function of $t$ and when it is constant are studied. In the context of this geometry, we find and classify the solutions of the Einstein's field equations (EFE) for the space-time under consideration which display a homothetic symmetry.
Frame dragging, vorticity and electromagnetic fields in axially symmetric stationary spacetimes
Energy Technology Data Exchange (ETDEWEB)
Herrera, L [Escuela de Fisica, Universidad Central de Venezuela, Caracas, Venezuela (Venezuela); Gonzalez, G A [Escuela de Fisica, Universidad Industrial de Santander, AA 678, Bucaramanga (Colombia); Pachon, L A [Escuela de Fisica, Universidad Industrial de Santander, AA 678, Bucaramanga (Colombia); Laboratorio de AstronomIa y Fisica Teorica (LAFT), Departamento de Fisica, Facultad de Ciencias, La Universidad del Zulia, Maracaibo, 4004 (Venezuela); Rueda, J A [Escuela de Fisica, Universidad Industrial de Santander, AA 678, Bucaramanga (Colombia)
2006-04-07
We present a general study about the relation between the vorticity tensor and the Poynting vector of the electromagnetic field for axially symmetric stationary electrovacuum metrics. The obtained expressions allow us to understand the role of the Poynting vector in the dragging of inertial frames. The particular case of the rotating massive charged magnetic dipole is analysed in detail. In addition, the electric and magnetic parts of the Weyl tensor are calculated and the link between the latter and the vorticity is established. Then we show that, in the vacuum case, the necessary and sufficient condition for the vanishing of the magnetic part is that the spacetime be static.
Effect of an Electric Field on Transfer Processes in Axially Symmetric Magnetic Traps
International Nuclear Information System (INIS)
By solving the kinetic equation in the drift approximation, expressions are derived for the particle flux and energy density across a strong magnetic field in axially symmetric systems of the Levitron or Tokamak type. In addition to the longitudinal accelerating electric field, which is responsible for creating the longitudinal current, account is taken of the presence of a quasistatic electric field directed along the minor radius and resulting from ambipolarity of dispersion. Both the case of very low collision frequencies (lower than the characteristic frequency of the azimuthal motion of the ''blocked'' particles) and that of intermediate and high collision frequencies are considered. It is shown that, if either the thermal velocity of the particles or the ratio of the poloidal magnetic field to the longitudinal magnetic field is fairly large (so that the mean longitudinal velocity of the toroidally ''blocked'' particles is much less than the azimuthal variations of their longitudinal velocity), then allowance for the radial electric field corresponds to allowance in the flux expressions for corrections of the next higher (i.e. fourth) order with respect to the smallness parameter used. In the opposite limiting case, allowance for the radial electric field becomes very important: in the region of very low and very high collision frequencies it leads to a substantial change in the functional dependence of the dispersion and heat conduction coefficients on the plasma and magnetic field parameters, while in the region of intermediate collision frequencies it leads to corrections proportional to the square of the ratio of the Larmor radius in the poloidal magnetic field to the characteristic dimension of the plasma inhomogeneity. In conclusion, the author discusses the question of determining a self-consistent radial electric field within the framework of a theory which takes into account only the lowest order with respect to the Larmor radius. (author)
International Nuclear Information System (INIS)
The authors investigate a stationary model of a rotating, axially symmetric pole-on magnetosphere in MHD force balance. In this model both the planet's rotational and dipole axes are aligned with the magnetotail axis, which is the axis of symmetry in a cylindrical (r, φ, z) coordinate system. On the sunward side, the magnetosphere is closed by an appropriate image dipole. Inside the magnetospheric cavity they assume isotropic thermal plasma pressure. They assume further that, in general, planetary rotation leads to differentially rotating magnetotail field lines causing field-aligned Birkeland currents and a corresponding toroidal magnetic Bφ component which leads to twisted magnetotail field lines. They calculate the deformation of magnetotail field lines under the influence of both thermal plasma pressure and centrifugal forces. They present linear (analytic) solutions to the Grad-Shafranov equation which include the centrifugal force term. In the linear model, two free physical parameters, k and ω, measure the plasma thermal pressure and the ratio between plasma rotational and thermal energy densities, respectively. Low ω and high k values indicate the plasma-dominated case. Conversely, low k and high ω values indicate the rotation-dominated case. One limiting case, k = ω = 0., generates a simple vacuum magnetic field of a dipole confined within the magnetospheric cavity. The nonrotational magnetosphere with hot thermal plasma leads to a field configuration without a toroidal Bφ component and without field-aligned Birkeland currents. The other extreme, namely, a rapidly rotating magnetosphere with cold plasma, leads to a configuration in which the plasma must be confined within a thin disk in a plane where the radial magnetic field component Br vanishes locally
Axially symmetric rotating traversable wormholes
Kuhfittig, P K F
2003-01-01
This paper generalizes the static and spherically symmetric traversable wormhole geometry to a rotating axially symmetric one with a time-dependent angular velocity by means of an exact solution. It was found that the violation of the weak energy condition, although unavoidable, is considerably less severe than in the static spherically symmetric case. The radial tidal constraint is more easily met due to the rotation. Similar improvements are seen in one of the lateral tidal constraints. The magnitude of the angular velocity may have little effect on the weak energy condition violation for an axially symmetric wormhole. For a spherically symmetric one, however, the violation becomes less severe with increasing angular velocity. The time rate of change of the angular velocity, on the other hand, was found to have no effect at all. Finally, the angular velocity must depend only on the radial coordinate, confirming an earlier result.
Effective quantum number for axially symmetric problems
Trunov, N. N.
2014-01-01
We generalize the universal effective quantum number introduced earlier for centrally symmetric problems. The proposed number determines the semiclassical quantization condition for axially symmetric potentials.
Li Chao Long; Lu Jian Qin
2003-01-01
A program for calculating intense pulsed beams transport in axial-symmetrical electrostatic fields is designed. The program can calculate beam optical systems consisting of the following elements: drift spaces, three-cylinder einzel lenses, three-diaphragm einzel lenses, electrostatic accelerating tubes, as well as two-cylinder lenses. In the calculations, the effective fields of each lens are divided into several small intervals, and each interval is treated as a uniform accelerating field, each dividing point is considered as a thin lens, and iterations are used to get self-consistent solutions. Iteration procedures are incorporated in the codes to get self-consistent solutions
Institute of Scientific and Technical Information of China (English)
Jianqin Lü; Xiaosong Zhao
2008-01-01
Nonlinear transport of intense continuous beam in the axial-symmetric electrostatic fields is analyzed with the Lie algebraic method.The K-V particle distribution is adopted in the analysis. The results obtained can be used in the calculations of the intense continuous beam dynamics in the beam optical systems consisting of drift spaces, electrostatic lenses, and DC electrostatic accelerating tubes. A com-puter code has been designed for practical simulations. To meet the needs of accurate calculation, all the elements are divided into many small segments, the electric fields in each segment are regarded as uniform fields, and the dividing points are treated as thin lenses. Iter-ation procedures are adopted in the code to obtain self-consistent solutions. The code can be used to design low energy dc beam transport systems, electrostatic accelerators, and ion implantation machines.
Axial Symmetric Solutions to Einstein's Field Equations for Deformed Neutron Stars
Zubairi, Omair; Weber, Fridolin
2016-03-01
Traditional models of neutron stars are constructed under of assumption that they are perfect spheres. This is not correct, however, if the matter inside of neutron stars is described by an non-isotropic model for the equation of state. Examples of such stars are magnetars and neutron stars that would contain color-superconducting quark matter. In this work, we derive the stellar structure equations which describe the properties of non-isotropic neutron stars. The equations are solved numerically in two dimensions. We calculate stellar properties such as masses and radii along with pressure and density profiles and investigate any changes from conventional spherically symmetric neutron stars. This work was supported through the National Science Foundation under Grants PHYS-1411708 and DUE-1259951. Additional computing resources were provided by the CSRC at SDSU and the Department of Sciences at Wentworth Institute of Technology.
Axially symmetric Lorentzian wormholes in general relativity
International Nuclear Information System (INIS)
The field equations of Einstein's theory of general relativity, being local, do not fix the global structure of space-time. They admit topologically non-trivial solutions, including spatially closed universes and the amazing possibility of shortcuts for travel between distant regions in space and time - so-called Lorentzian wormholes. The aim of this thesis is to (mathematically) construct space-times which contain traversal wormholes connecting arbitrary distant regions of an asymptotically flat or asymptotically de Sitter universe. Since the wormhole mouths appear as two separate masses in the exterior space, space-time can at best be axially symmetric. We eliminate the non-staticity caused by the gravitational attraction of the mouths by anchoring them by strings held at infinity or, alternatively, by electric repulsion. The space-times are obtained by surgically grafting together well-known solutions of Einstein's equations along timelike hypersurfaces. This surgery naturally concentrates a non-zero stress-energy tensor on the boundary between the two space-times which can be investigated by using the standard thin shell formalism. It turns out that, when using charged black holes, the provided constructions are possible without violation of any of the energy conditions. In general, observers living in the axially symmetric, asymptotically flat (respectively asymptotically de Sitter) region axe able to send causal signals through the topologically non-trivial region. However, the wormhole space-times contain closed timelike curves. Because of this explicit violation of global hyperbolicity these models do not serve as counterexamples to known topological censorship theorems. (author)
Axially symmetric SU(3) gravitating skyrmions
Energy Technology Data Exchange (ETDEWEB)
Ioannidou, Theodora [Maths Division, School of Technology, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)]. E-mail: ti3@auth.gr; Kleihaus, Burkhard [Institut fuer Physik, Universitaet Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany)]. E-mail: kleihaus@theorie.physik.uni-oldenburg.de; Zakrzewski, Wojtek [Department of Mathematical Sciences, University of Durham, Durham DH1 3LE (United Kingdom)]. E-mail: w.j.zakrzewski@durham.ac.uk
2004-10-21
Axially symmetric gravitating multi-skyrmion configurations are obtained using the harmonic map ansatz introduced in [J. Math. Phys. 40 (1999) 6353]. In particular, the effect of gravity on the energy and baryon densities of the SU(3) non-gravitating multi-skyrmion configurations is studied in detail.
Axially symmetric SU(3) Gravitating Skyrmions
Ioannidou, T A; Zakrzewski, W J; Ioannidou, Theodora; Kleihaus, Burkhard; Zakrzewski, Wojtek
2004-01-01
Axially symmetric gravitating multi-skyrmion configurations are obtained using the harmonic map ansatz introduced in [1]. In particular, the effect of gravity on the energy and baryon densities of the SU(3) non-gravitating multi-skyrmion configurations is studied in detail.
Axially symmetric SU(3) gravitating skyrmions
International Nuclear Information System (INIS)
Axially symmetric gravitating multi-skyrmion configurations are obtained using the harmonic map ansatz introduced in [J. Math. Phys. 40 (1999) 6353]. In particular, the effect of gravity on the energy and baryon densities of the SU(3) non-gravitating multi-skyrmion configurations is studied in detail
Polarization converters based on axially symmetric twisted nematic liquid crystal.
Ko, Shih-Wei; Ting, Chi-Lun; Fuh, Andy Y-G; Lin, Tsung-Hsien
2010-02-15
An axially symmetric twisted nematic liquid crystal (ASTNLC) device, based on axially symmetric photoalignment, was demonstrated. Such an ASTNLC device can convert axial (azimuthal) to azimuthal (axial) polarization. The optical properties of the ASTNLC device are analyzed and found to agree with simulation results. The ASTNLC device with a specific device can be adopted as an arbitrary axial symmetric polarization converter or waveplate for axially, azimuthally or vertically polarized light. A design for converting linear polarized light to axially symmetric circular polarized light is also demonstrated. PMID:20389369
On the axially symmetric equilibrium of a magnetically confined plasma
International Nuclear Information System (INIS)
The axially symmetric equilibrium of a magnetically confined plasma is reconsidered, with the special purpose of studying high-beta schemes with a purely poloidal magnetic field. A number of special solutions of the pressure and magnetic flux functions are shown to exist, the obtained results may form starting-points in a further analysis of physically relevant configurations. (Auth.)
Exact Axially Symmetric Solution in f(T) Gravity Theory
2014-01-01
A general tetrad field with sixteen unknown functions is applied to the field equations of f(T) gravity theory. An analytic vacuum solution is derived with two constants of integration and an angle Φ that depends on the angle coordinate ϕ and radial coordinate r . The tetrad field of this solution is axially symmetric and the scalar torsion vanishes. We calculate the associated metric of the derived solution and show that it represents Kerr spacetime. Finally, we show that the derived solutio...
Directory of Open Access Journals (Sweden)
Krneta Aleksandra J.
2016-01-01
Full Text Available The paper presents a new method for the analysis of wire antennas with axial symmetry. Truncated cones have been applied to precisely model antenna geometry, while the exact kernel of the electric field integral equation has been used for computation. Accuracy and efficiency of the method has been further increased by the use of higher order basis functions for current expansion, and by selecting integration methods based on singularity cancelation techniques for the calculation of potential and impedance integrals. The method has been applied to the analysis of a typical dipole antenna, thick dipole antenna and a coaxial line. The obtained results verify the high accuracy of the method. [Projekat Ministarstva nauke Republike Srbije, br. TR-32005
Acoustic horizons in axially symmetric relativistic accretion
Abraham, H; Das, T K; Abraham, Hrvoje; Bilic, Neven; Das, Tapas K.
2006-01-01
Transonic accretion onto astrophysical objects is a unique example of analogue black hole realized in nature. In the framework of acoustic geometry we study axially symmetric accretion and wind of a rotating astrophysical black hole or of a neutron star assuming isentropic flow of a fluid described by a polytropic equation of state. In particular we analyze the causal structure of multitransonic configurations with two sonic points and a shock. Retarded and advanced null curves clearly demonstrate the presence of the acoustic black hole at regular sonic points and of the white hole at the shock. We calculate the analogue surface gravity and the Hawking temperature for the inner and the outer acoustic horizons.
Axially-symmetric Neutron stars: Implication of rapid rotation
Sharma, B K
2009-01-01
Models of relativistic rotating neutron star composed of hyperon rich matter is constructed in the framework of an effective field theory in the mean-field approach. The gross properties of compact star is calculated at both static and the mass-shedding limit in the axially symmetric basis. The effect of appearance and abundance of hyperons on equation of state of dense matter and stellar properties is lineated with particular emphasis on the underlying nuclear interactions. We find that the models can explain fast rotations, which supports the existence of millisecond pulsars. An important offshoot of the present investigation is that, irrespective of the model parameters and interaction taken, the star seems to sustain faster rotations (an increase in rotational frequency up to $\\approx$ 50%) without any further deformation.
STED microscopy based on axially symmetric polarized vortex beams
Zhehai, Zhou; Lianqing, Zhu
2016-03-01
A stimulated emission depletion (STED) microscopy scheme using axially symmetric polarized vortex beams is proposed based on unique focusing properties of such kinds of beams. The concept of axially symmetric polarized vortex beams is first introduced, and the basic principle about the scheme is described. Simulation results for several typical beams are then shown, including radially polarized vortex beams, azimuthally polarized vortex beams, and high-order axially symmetric polarized vortex beams. The results indicate that sharper doughnut spots and thus higher resolutions can be achieved, showing more flexibility than previous schemes based on flexible modulation of both phase and polarization for incident beams. Project supported by the National Natural Science Foundation of China (Grant Nos. 61108047 and 61475021), the Natural Science Foundation of Beijing, China (Grant No. 4152015), the Program for New Century Excellent Talents in Universities of China (Grant No. NCET-13-0667), and the Top Young Talents Support Program of Beijing, China (Grant No. CIT&TCD201404113).
Resonances in axially symmetric dielectric objects
Helsing, Johan
2016-01-01
A high-order convergent and robust numerical solver is constructed and used to find complex eigenwavenumbers and electromagnetic eigenfields of dielectric objects with axial symmetry. The solver is based on Fourier--Nystr\\"om discretization of M\\"uller's combined integral equations for the transmission problem and can be applied to demanding resonance problems at microwave, terahertz, and optical wavelengths. High achievable accuracy, even at very high wavenumbers, makes the solver ideal for benchmarking and for assessing the performance of general purpose commercial software.
On the generation techniques of axially symmetric stationary metrics
Indian Academy of Sciences (India)
S Chaudhuri
2002-03-01
In the present paper, a relationship between the method of Gutsunaev–Manko and the soliton technique (for two-soliton solutions) of Belinskii–Zakharov, for generating solutions of axially symmetric stationary space-times in general relativity is discussed.
Fully Characterizing Axially Symmetric Szekeres Models With Three Data Sets
Célérier, Marie-Noëlle; Singh, Tejinder P
2012-01-01
Inhomogeneous exact solutions of General Relativity with zero cosmological constant have been used in the literature to challenge the \\Lambda CDM model. From one patch Lema\\^itre-Tolman-Bondi (LTB) models to axially symmetric quasi-spherical Szekeres (QSS) Swiss-cheese models, some of them are able to reproduce to a good accuracy the cosmological data. It has been shown in the literature that a zero-\\Lambda -LTB model with a central observer can be fully determined by two data sets. We demonstrate that an axially symmetric zero-\\Lambda -QSS model with an observer located at the origin can be fully reconstructed from three data sets, number counts, luminosity distance and redshift drift. This is a first step towards a future demonstration involving five data sets and the most general Szekeres model.
Dynamics and statics of flexible axially symmetric shallow shells
Awrejcewicz, J.; Krysko, V. A.; I. V. Kravtsova
2006-01-01
In this work, we propose the method for the investigation of stochastic vibrations of deterministic mechanical systems represented by axially symmetric spherical shells. These structure members are widely used as sensitive elements of pressure measuring devices in various branches of measuring and control industry, machine design, and so forth. The proposed method can be easily extended for the investigation of shallow spherical shells, goffer-type membranes, and so on. T...
Killing tensors in stationary and axially symmetric space-times
Vollmer, Andreas
2016-01-01
We discuss the existence of Killing tensors for certain (physically motivated) stationary and axially symmetric vacuum space-times. We show nonexistence of a nontrivial Killing tensor for a Tomimatsu-Sato metric (up to valence 7), for a C-metric (up to valence 9) and for a Zipoy-Voorhees metric (up to valence 11). The results are obtained by mathematically completely rigorous, nontrivial computer algebra computations with a huge number of equations involved in the problem.
Mathematical Model of Induction Heating Processes in Axial Symmetric Inductor-Detail Systems
Directory of Open Access Journals (Sweden)
Maik Streblau
2014-05-01
Full Text Available The wide variety of models for analysis of processes in the inductor-detail systems makes it necessary to summarize them. This is a difficult task because of the variety of inductor-detail system configurations. This paper aims to present a multi physics mathematical model for complex analysis of electromagnetic and thermal fields in axial symmetric systems inductor-detail.
Conformal vector fields in symmetric and conformal symmetric spaces
Directory of Open Access Journals (Sweden)
Ramesh Sharma
1989-03-01
Full Text Available Consequences of the existence of conformal vector fields in (locally symmetric and conformal symmetric spaces, have been obtained. An attempt has been made for a physical interpretation of the consequences in the framework of general relativity.
Axial-symmetrical domain structures in ferrite-garnet films
International Nuclear Information System (INIS)
Applying the improved technique of double ultrahigh-speed photography one studied occurrence and progress of domain structure upon magnetization of a small section of (BiLaTm)3(FeGa)5O12 ferrite-garnet film prior to saturation. The radial deformation affecting the specimen on the magnetized coil side was determined to break single-axis anisotropy resulting in occurrence of axial-oriented band domain structure inside the magnetized range. That structure period reduced with growth of the pulse field amplitude. Band axial-oriented domain structure is formed under the effect of the magnetostatic axisymmetric field
Conformally symmetric massive discrete fields
De Souza, M M
2000-01-01
Conformal symmetry is taken as an attribute of theories of massless fields in manifolds with specific dimensionalities. This paper shows that this is not an absolute truth; it is a consequence of the mathematical representation used for the physical interactions. It introduces a new kind of representation where the propagation of massive (invariant mass) and massless interactions are unifiedly described by a single conformally symmetric Green's function. Sources and fields are treated at a same footing, symmetrically, as discrete fields - the fields in this new representation - fields defined with support on straight lines embedded in a (3+1)-Minkowski manifold. The discrete field turns out to be a point in phase space. It is finite everywhere. With a finite number of degrees of freedom it does not share the well known problems faced by the standard continuous formalism which can be retrieved from the discrete one by an integration over a hypersurface. The passage from discrete to continuous fields illuminate...
Axially Symmetric Bianchi Type-I Bulk-Viscous Cosmological Models with Time-Dependent and
Indian Academy of Sciences (India)
Nawsad Ali
2013-09-01
The present study deals with spatially homogeneous and anisotropic axially symmetric Bianchi type-I cosmological model with time variable cosmological term in the presence of bulk viscous fluid. The Einstein’s field equations are solved explicitly by time varying deceleration parameter . Consequences of the four cases of phenomenological decay of have been discussed which are consistent with observations. Physical and kinematical parameters of the models are discussed.
Three-dimensional equilibria in axially symmetric tokamaks.
Garabedian, Paul R
2006-12-19
The NSTAB and TRAN computer codes have been developed to study equilibrium, stability, and transport in fusion plasmas with three-dimensional (3D) geometry. The numerical method that is applied calculates islands in tokamaks like the Doublet III-D at General Atomic and the International Thermonuclear Experimental Reactor. When bifurcated 3D solutions are used in Monte Carlo computations of the energy confinement time, a realistic simulation of transport is obtained. The significance of finding many 3D magnetohydrodynamic equilibria in axially symmetric tokamaks needs attention because their cumulative effect may contribute to the prompt loss of alpha particles or to crashes and disruptions that are observed. The 3D theory predicts good performance for stellarators. PMID:17159158
Stationary axially symmetric relativistic thin discs with nonzero radial pressure
International Nuclear Information System (INIS)
A detailed analysis of the surface energy-momentum (SEMT) tensor of stationary axially symmetric relativistic thin discs with nonzero radial pressure is presented. The physical content of the SEMT is analysed and expressions for the velocity vector, energy density, principal stresses and heat flow are obtained. We also present the counter-rotating model interpretation for these discs by considering the SEMT as the superposition of two counter-rotating perfect fluids. We analyse the possibility of counter-rotation along geodesics as well as counter-rotation with equal and opposite tangential velocities, and explicit expressions for the velocities are obtained in both the cases. By assuming a given choice for the counter-rotating velocities, explicit expressions for the energy densities and pressures of the counter-rotating fluids are then obtained. Some simple thin disc models obtained from the Kerr solution are also presented. (paper)
Skyrme RPA for spherical and axially symmetric nuclei
Repko, Anton; Nesterenko, V O; Reinhard, P -G
2015-01-01
Random Phase Approximation (RPA) is the basic method for calculation of excited states of nuclei over the Hartree-Fock ground state, suitable also for energy density functionals (EDF or DFT). We developed a convenient formalism for expressing densities and currents in a form of reduced matrix elements, which allows fast calculation of spectra for spherical nuclei. All terms of Skyrme functional were taken into account, so it is possible to calculate electric, magnetic and vortical/toroidal/compression transitions and strength functions of any multipolarity. Time-odd (spin) terms in Skyrme functional become important for magnetic M1 and isovector toroidal E1 transitions. It was also found that transition currents in pygmy region (low-lying part of E1 resonance) exhibit isoscalar toroidal flow, so the previously assumed picture of neutron-skin vibration is not the only mechanism present in pygmy transitions. RPA calculations with heavy axially-symmetric nuclei now become feasible on ordinary PC. Detailed formul...
Evolution of Axially Symmetric Anisotropic Sources in $f(R,T)$ Gravity
Zubair, M
2015-01-01
We discuss the dynamical analysis in $f(R,T)$ gravity (where $R$ is Ricci scalar and $T$ is trace of energy momentum tensor) for gravitating sources carrying axial symmetry. The self gravitating system is taken to be anisotropic and line element describes axially symmetric geometry avoiding rotation about symmetry axis and meridional motions (zero vorticity case). The modified field equations for axial symmetry in $f(R,T)$ theory are formulated, together with the dynamical equations. Linearly perturbed dynamical equations lead to the evolution equation carrying adiabatic index $\\Gamma$ that defines impact of non-minimal matter to geometry coupling on range of instability for Newtonian (N) and post-Newtonian (pN) approximations.
Evolution of axially symmetric anisotropic sources in f(R, T) gravity
Energy Technology Data Exchange (ETDEWEB)
Zubair, M. [COMSATS Institute of Information Technology, Department of Mathematics, Lahore (Pakistan); Noureen, Ifra [University of Management and Technology, Department of Mathematics, Lahore (Pakistan)
2015-06-15
We discuss the dynamical analysis in f(R, T) gravity (where R is the Ricci scalar and T is the trace of the energy momentum tensor) for gravitating sources carrying axial symmetry. The self-gravitating system is taken to be anisotropic and the line element describes an axially symmetric geometry avoiding rotation about the symmetry axis and meridional motions (zero vorticity case). The modified field equations for axial symmetry in f(R, T) theory are formulated, together with the dynamical equations. Linearly perturbed dynamical equations lead to the evolution equation carrying the adiabatic index Γ, which defines the impact of a non-minimal matter to geometry coupling on the range of instability for Newtonian and post-Newtonian approximations. (orig.)
Conformally symmetric massive discrete fields
Energy Technology Data Exchange (ETDEWEB)
Souza, Manoelito M. de
2001-04-01
Conformal symmetry is taken as an attribute of theories of massless fields in manifolds with specific dimensions. This paper shows that this is not an absolute truth; it is a consequence of the mathematical representation used for the physical interactions. It introduces a new kind of representation where the propagation of massive (invariant mass) and mass-less interactions are unifiedly described by a single conformally symmetric Green's function. Sources and fields are treated at a same footing, symmetrically, as discrete fields - the fields in this new representation - fields defined with support on straight lines embedded in a (3+1) - Minkowski manifold. The discrete field turns out to be a point in phase space. It is finite everywhere. With a finite number of degrees of freedom it does not share the well known problems faced by the standard continuous formalism which can be retrieved from the discrete one by an integration over a hypersurface. The passage from discrete to continuous fields illuminates the physical meaning and origins of their properties and problems. The price for having massive discrete field with conformal symmetry is of hiding its mass and timelike velocity behind its non-constant proper-time. (author)
Build Axial Gradient Field by Using Axial Magnetized Permanent Rings
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Axial magnetic field produced by an axial magnetized permanent ring was studied. For two permanent rings, if they are magnetized in the same directions, a nearly uniform axial field can be produced. If they are magnetized in opposite direction,an axial gradient magnetic field can be generated, with the field range changing from -B0 to B0. A permanent magnet with a high axial gradient field was fabricated, the measured results agree with the PANDIRA calculation very well. For wider usage,it is desirable for the field gradient to be changed. Some methods to produce the variable gradient field are presented. These kinds of axial gradient magnetic field can also be used as a beam focusing for linear accelerator if the periodic field can be produced along the beam trajectory. The axial magnetic field is something like a solenoid, large stray field will leak to the outside environment if no method is taken to control them. In this paper, one method is illustrated to shield off the outside leakage field.
Spherically symmetric scalar field collapse
Indian Academy of Sciences (India)
Koyel Ganguly; Narayan Banerjee
2013-03-01
It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for ( + 3) < 0. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons formed before the formation of singularity. The singularities formed are shell focussing in nature. The density of the scalar field distribution is seen to diverge at singularity. The Ricci scalar also diverges at the singularity. The interior spherically symmetric metric is matched with exterior Vaidya metric at the hypersurface and the appropriate junction conditions are obtained.
Dynamics and statics of flexible axially symmetric shallow shells
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available In this work, we propose the method for the investigation of stochastic vibrations of deterministic mechanical systems represented by axially symmetric spherical shells. These structure members are widely used as sensitive elements of pressure measuring devices in various branches of measuring and control industry, machine design, and so forth. The proposed method can be easily extended for the investigation of shallow spherical shells, goffer-type membranes, and so on. The so-called charts of control parameters for a shell subjected to a transversal uniformly distributed and local harmonic loading force and resistance moment are constructed. The scenarios of the transition of vibration of shallow-type system into chaotic state are investigated with the use of the theory of differential equations and the theory of nonlinear dynamics. The method of the control of chaotic vibrations of flexible spherical shells subjected to a transversal harmonic load through a synchronized action of either harmonic resistance moment or force is proposed, illustrated, and discussed.
Decreasing "circumference" for increasing "radius" in axially symmetric gravitating systems
Lubo, M
2001-01-01
Apart from the flat space with an angular deficit, Einstein general relativity possesses another cylindrically symmetric solution. Because this configuration displays circles whose "circumferences" tend to zero when their "radius" go to infinity, it has not received much attention in the past. We propose a geometric interpretation of this feature and find that it implies field boundary conditions different from the ones found in the literature if one considers a source consisting of the scalar and the vector fields of a U(1) system . To obtain a non increasing energy density the gauge symmetry must be unbroken . For the Higgs potential this is achieved only with a vanishing vacuum expectation value but then the solution has a null scalar field. A non trivial scalar behaviour is exhibited for a potential of sixth order. The trajectories of test particles in this geometry are studied, its causal structure discussed. We find that this bosonic background can support a normalizable fermionic condensate but not suc...
View of the Axial Field Spectrometer
1980-01-01
The Axial Field Spectrometer, with the vertical uranium/scintillator calorimeter and the central drift chamber retracted for service. One coil of the Open Axial Field Magnet is just visible to the right.
Symmetry-adapted digital modeling I. Axial symmetric proteins.
Janner, A
2016-05-01
Considered are axial symmetric proteins exemplified by the octameric mitochondrial creatine kinase, the Pyr RNA-binding attenuation protein, the D-aminopeptidase and the cyclophilin A-cyclosporin complex, with tetragonal (422), trigonal (32), pentagonal (52) and pentagonal (52) point-group symmetry, respectively. One starts from the protein enclosing form, which is characterized by vertices at points of a lattice (the form lattice) whose dimension depends on the point group. This allows the indexing of Cα's at extreme radial positions. The indexing is extended to additional residues on the basis of a finer lattice, the digital modeling lattice Λ, which includes the form lattice as a sublattice. This leads to a coarse-grained description of the protein. In the crystallographic point-group case, the planar indices are obtained from a projection of atomic positions along the rotation axis, taken as the z axis. The planar indices of a Cα are then those of the nearest projected lattice point. In the non-crystallographic case, low indices are an additional requirement. The coarse-grained bead follows from the condition imposed on the residues selected to have a z coordinate within a band of value δ above and below the height of lattice points. The choice of δ permits a variation of the coarse-grained bead model. For example, the value δ = 0.5 leads to a fine-grained indexing of the full set of residues, whereas with δ = 0.25 one gets a coarse-grained model which includes only about half of these residues. Within this procedure, the indexing of the Cα only depends on the choice of the digital modeling lattice and not on the value of δ. The characteristics which distinguish the present approach from other coarse-grained models of proteins on lattices are summarized at the end. PMID:27126107
Computation of the viscous supersonic flow over symmetrical and asymmetrical external axial corners
Kutler, P.; Pulliam, T. H.; Vigneron, Y. C.
1978-01-01
The primary objective of the reported investigation is the computational verification of the experimental results obtained by Salas and Daywitt (1978). Two existing computer codes were used to compute the supersonic flow field surrounding the external axial corner. For the inviscid and turbulent flow results, the unsteady, three-dimensional implicit code of Pulliam and Steger (1978) was used. For the laminar flow results, the unsteady two-dimensional explicit procedure of Vigneron et al. (1977) was employed. Inviscid solutions for a symmetric configuration with a rounded corner resulted in either single or triple surface crossflow stagnation point flows, depending on the corner radius. Numerical results obtained for the same symmetric configuration tested experimentally show the crossflow in the vicinity of the corner to be away from the corner and thus in agreement with the experimental oil flow results.
Anomalies in PT-Symmetric Quantum Field Theory
Milton, Kimball A.
2003-01-01
It is shown that a version of PT-symmetric electrodynamics based on an axial-vector current coupling massless fermions to the photon possesses anomalies and so is rendered nonrenormalizable. An alternative theory is proposed based on the conventional vector current constructed from massive Dirac fields, but in which the PT transformation properties of electromagnetic fields are reversed. Such a theory seems to possess many attractive features.
The spacetime outside a source of gravitational radiation: The axially symmetric null fluid
Herrera, L; Ospino, J
2016-01-01
We carry out a study of the exterior of an axially and reflection symmetric source of gravitational radiation. The exterior of such a source is filled with a null fluid produced by the dissipative processes inherent to the emission of gravitational radiation, thereby representing a generalization of the Vaidya metric for axially and reflection symmetric spacetimes. The role of the vorticity, and its relationship with the presence of gravitational radiation is put in evidence. The spherically symmetric case (Vaidya) is, asymptotically, recovered within the context of the $1+3$ formalism.
Bach, Rudolf; Weyl, Hermann
2012-03-01
This is the English translation of the third of a series of 3 papers by Hermann Weyl (the third one jointly with Rudolf Bach), first published in 1917-1922, in which the authors derived and discussed the now-famous Weyl two-body static axially symmetric vacuum solution of Einstein's equations. The English translations of the other two papers are published alongside this one. The papers have been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Gernot Neugebauer, David Petroff and Bahram Mashhoon, and by a brief biography of R. Bach, written by H. Goenner.
Gapless excitations of axially symmetric vortices in systems with tensorial order parameter
International Nuclear Information System (INIS)
We extend the results of previous work on vortices in systems with tensorial order parameters. Specifically, we focus our attention on systems with a Ginzburg–Landau free energy with a global U(1)P×SO(3)S×SO(3)L symmetry in the phase, spin and orbital degrees of freedom. We consider axially symmetric vortices appearing on the spin–orbit locked SO(3)S+L vacuum. We determine the conditions required on the Ginzburg–Landau parameters to allow for an axially symmetric vortex with off diagonal elements in the order parameter to appear. The collective coordinates of the axial symmetric vortices are determined. These collective coordinates are then quantized using the time dependent Ginzburg–Landau free energy to determine the number of gapless modes propagating along the vortex
Impact of Extended Starobinsky Model on Evolution of Anisotropic Axially Symmetric Sources
Noureen, Ifra
2014-01-01
We study the implications of $R^n$ extension of Starobinsky model on dynamical instability of axially symmetric gravitating body. The matter distribution is considered to be anisotropic for which modified field equations are formed in context of $f(R)$ gravity. In order to achieve the collapse equation, we make use of the dynamical equations, extracted from linearly perturbed contracted Bianchi identities. The collapse equation carries adiabatic index $\\Gamma$ in terms of usual and dark source components, defining the range of stability/insatbility in Newtonian (N) and post-Newtonian (pN) eras. It is found that supersymmetric supergravity $f(R)$ model represents the more practical substitute of higher order curvature corrections.
A magnetic liquid deformable mirror for high stroke and low order axially symmetrical aberrations
Brousseau, D; Parent, J; Ruel, H J; Borra, Ermanno F.; Brousseau, Denis; Parent, Jocelyn; Ruel, Hubert-Jean
2006-01-01
We present a new class of magnetically shaped deformable liquid mirrors made of a magnetic liquid (ferrofluid). Deformable liquid mirrors offer advantages with respect to deformable solid mirrors: large deformations, low costs and the possibility of very large mirrors with added aberration control. They have some disadvantages (e.g. slower response time). We made and tested a deformable mirror, producing axially symmetrical wavefront aberrations by applying electric currents to 5 concentric coils made of copper wire wound on aluminum cylinders. Each of these coils generates a magnetic field which combines to deform the surface of a ferrofluid to the desired shape. We have carried out laboratory tests on a 5 cm diameter prototype mirror and demonstrated defocus as well as Seidel and Zernike spherical aberrations having amplitudes up to 20 microns, which was the limiting measurable amplitude of our equipment
International Nuclear Information System (INIS)
In this paper, the ratio of the mass coefficients for the γ-vibrational and rotational motion for the well deformed axially symmetric nuclei is calculated. Calculations are performed based on the cranking model approach. The results obtained show that the microscopic model based on the Woods–Saxon nuclear mean field potential and the pairing forces with a constant strength coefficient qualitatively explain the existing experimental data on the ratio of the mass coefficients. (author)
Modular coils and finite-β operation of a quasi-axially symmetric tokamak
International Nuclear Information System (INIS)
Quasi-axially symmetric tokamaks (QA tokamaks) are an extension of the conventional tokamak concept. In these devices the magnetic field strength is independent of the generalized toroidal magnetic co-ordinate even though the cross-sectional shape changes. An optimized plasma equilibrium belonging to the class of QA tokamaks has been proposed by Nuehrenberg. It features the small aspect ratio of a tokamak while allowing part of the rotational transform to be generated by the external field. In this article, two particular aspects of the viability of QA tokamaks are explored, namely the feasibility of modular coils and the possibility of maintaining quasi-axial symmetry in the free-boundary equilibria obtained with the coils found. A set of easily feasible modular coils for the configuration is presented. It was designed using the extended version of the NESCOIL code (MERKEL, P., Nucl. Fusion 27 (1987) 867). Using this coil system, free-boundary calculations of the plasma equilibrium were carried out using the NEMEC code (HIRSHMAN, S.P., VAN RIJ, W.I., MERKEL, P., Comput. Phys. Commun. 43 (1986) 143). It is observed that the effects of finite β and net toroidal plasma current can be compensated for with good precision by applying a vertical magnetic field and by separately adjusting the currents of the modular coils. A set of fully three dimensional (3-D) auxiliary coils is proposed to exert control on the rotational transform in the plasma. Deterioration of the quasi-axial symmetry induced by the auxiliary coils can be avoided by adequate adjustment of the currents in the primary coils. Finally, the neoclassical transport properties of the configuration are examined. It is observed that optimization with respect to confinement of the alpha particles can be maintained at operation with finite toroidal current if the aforementioned corrective measures are used. In this case, the neoclassical behaviour is shown to be very similar to that of a conventional tokamak
Axially Symmetric Shear-free Fluids in $f(R,T)$ Gravity
Noureen, Ifra
2016-01-01
In this work we have discussed the implications of shear-free condition on axially symmetric anisotropic gravitating objects in $f(R,T)$ theory. Restricted axial symmetry ignoring rotation and reflection enteries is taken into account for establishment of instability range. Implementation of linear perturbation on constitutive modified dynamical equations yield evolution equation. This equation associates adiabatic index $\\Gamma$ with material and dark source components defining stable and unstable regions in Newtonian (N) and post-Newtonian (pN) approximations.
Axially symmetric static sources: A general framework and some analytical solutions
Herrera, L.; Di Prisco, A.; J. Ibañez; Ospino, J.
2013-01-01
We provide all basic equations and concepts required to carry out a general study on axially symmetric static sources. The Einstein equations and the conservation equations are written down for a general anisotropic static fluid endowed with axial symmetry. The structure scalars are calculated and the inhomogeneity factors are identified. Finally some exact analytical solutions were found. One of these solutions describes an incompressible spheroid with isotropic pressure and becomes the well...
On the extension of axially symmetric volume flow and mean curvature flow
Kandanaarachchi, Sevvandi
2013-01-01
We investigate conditions of singularity formation of mean curvature flow and volume preserving mean curvature flow in an axially symmetric setting. We prove that no singularities can develop during a finite time interval, if the mean curvature is bounded within that time interval on the entire surface. We prove this for volume preserving mean curvature flow as well as for mean curvature flow.
Axially symmetric solutions for rotating charged perfect fluid with vanishing Lorentz force
International Nuclear Information System (INIS)
The problem of rotating charged perfect fluid in general relativity theory is considered under the assumption that the Lorentz force, acting on the charges, vanishes. For the cylindrically symmetric case the problem is reduced to a second-order non-linear differential equation. In the axially symmetric case three new solutions are obtained. Two of them describe fluids with constant pressure, while the third one describes fluid with non-constant pressure. These three solutions admit the same four-parameter group of isometries. Geometrical, hydrodynamic and electromagnetic properties of the new solutions are studied
A Volume-Weighting Cloud-in-Cell Model for Particle Simulation of Axially Symmetric Plasmas
Institute of Scientific and Technical Information of China (English)
李永东; 何锋; 刘纯亮
2005-01-01
A volume-weighting cloud-in-cell (VW-CIC) model is developed to implement the particle-in-cell (PIC) simulation in axially symmetric systems. This model gives a first-order accuracy in the cylindrical system, and it is incorporated into a PIC code. A planar diode with a finite-radius circular emitter is simulated with the code. The simulation results show that the VW-CIC model has a better accuracy and a lower noise than the conventional area-weighting cloud-in-cell (AW-CIC) model, especially on those points near the axis. The two-dimensional (2-D) space-charge-limited current density obtained from VW-CIC model is in better agreement with Lau's analytical result. This model is more suitable for 2.5-D PIC simulation of axially symmetric plasmas.
A microscopic derivation of nuclear collective rotation-vibration model, axially symmetric case
Gulshani, Parviz
2015-01-01
We derive a microscopic version of the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for collective rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitude. The nuclear Schrodinger equation is canonically transformed the to collective co-ordinates, which is then linearized using a constrained variational method. The associated constraints are imposed on the wavefunction rather than on th...
A critical regularity condition on the angular velocity of axially symmetric Navier-Stokes equations
Zhang, Qi S.
2015-01-01
Let $v$ be the velocity of Leray-Hopf solutions to the axially symmetric three-dimensional Navier-Stokes equations. It is shown that $v$ is regular if the angular velocity $v_\\theta$ satisfies an integral condition which is critical under the standard scaling. This condition allows functions satisfying \\[ |v_\\theta(x, t)| \\le \\frac{C}{r |\\ln r|^{2+\\epsilon}}, \\quad r
On a selection rule for electric transitions in axially-symmetric nuclei
International Nuclear Information System (INIS)
We consider many-body E-l transition matrix-elements between two nuclear states of different axially-symmetric deformations characterised by two different (mutually non-orthogonal) sets of single-particle wave-functions. Yet, when varying the deformations of the initial, final, or both these states one notices abrupt changes in the form of vanishing and possibly reappearance of the transition matrix elements calculated between the corresponding Slater determinants. The mechanism is explained in terms of the conservation of the |m| quantum number (absolute value of the projection of individual-nucleonic angular-momenta); consequences for the more general calculations of this type also without axial symmetry are discussed. (author)
A cylindrical shell with an axial crack under skew-symmetric loading.
Yuceoglu, U.; Erdogan, F.
1973-01-01
The skew-symmetric problem for a cylindrical shell containing an axial crack is considered. It is assumed that the material has a special orthotropy - namely, that the shear modulus may be evaluated from the measured Young's moduli and Poisson ratios and is not an independent material constant. The problem is solved within the confines of an eighth-order linearized shallow shell theory. As numerical examples, the torsion of an isotropic cylinder and that of a specially orthotropic cylinder (titanium) are considered. The membrane and bending components of the stress intensity factor are calculated and are given as functions of a dimensionless shell parameter. In the torsion problem for the axially cracked cylinder the bending effects appear to be much more significant than that found for the circumferentially cracked cylindrical shell. Also, as the shell parameter increases, unlike the results found in the pressurized shell, the bending stresses around crack ends do not change sign.
Dynamics of Axial Symmetric System in Self-Interacting Brans-Dicke Gravity
Sharif, M
2016-01-01
This paper investigates dynamics of axial reflection symmetric model in self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate hydrodynamical equations and discuss oscillations using time-dependent perturbation for both spin as well as spin-independent cases. The expressions of frequency, total energy density and equation of motion of oscillating model are obtained. We study instability of oscillating models in weak approximations. It is found that the oscillations and stability of the model depend upon the dark energy source along with anisotropy and reflection effects. We conclude that the axial reflection system remains stable for stiffness parameter $\\Gamma=1$, collapses for $\\Gamma>1$ and becomes unstable for $0<\\Gamma<1$.
Calculating the hydraulic characteristics of a plane axially symmetrical feeding collector
International Nuclear Information System (INIS)
Two-dimensional equations of liquid flow in a reactor plane cylindrical axially symmetrical feeding collector without and in the presence of friction and volume resistance are analyzed. The analytical solutions for some particular cases of spiral flow (hyperbolic spiral, logarithmic spiral, Archimedean spiral) are obtained. It is shown that the type of flow is determined by the effective Reynolds number and effective coefficient of volume hydraulic resistance. Non-uniformity in coolant feeding when hydraulic resistance increasing descreases at first and then changing the sign increases in absolute value
Chae, Dongho; Weng, Shangkun
2015-01-01
In this paper we study Liouville properties of smooth steady axially symmetric solutions of the Navier-Stokes equations. First, we provide another version of the Liouville theorem of \\cite{kpr15} in the case of zero swirl, where we replaced the Dirichlet integrability condition by mild decay conditions. Then we prove some Liouville theorems under the assumption $\\|\\f{u_r}{r}{\\bf 1}_{\\{u_r< -\\f 1r\\}}\\|_{L^{3/2}(\\mbR^3)}< C_{\\sharp}$ where $C_{\\sharp}$ is a universal constant to be specified. I...
Axially symmetric polarization converter made of patterned liquid crystal quarter wave plate.
Fan, Fan; Du, Tao; Srivastava, Abhishek Kumar; Lu, Wang; Chigrinov, Vladimir; Kwok, Hoi Sing
2012-10-01
We present a method to fabricate a radially and azimuthally polarized light converter by deploying a patterned liquid crystal (LC) quarter-wave plates (QWP). The patterned QWP has been fabricated by providing the axially symmetric alignment to the LC layer by mean of photo-alignment. When the left handed circularly (LHC) or right handed circularly (RHC) polarized light passes through these patterned QWPs, the emergent light becomes radially or azimuthally polarized. Moreover, the proposed polarization converters are characterized by the fast response time, thus could find application in various fast photonic devices. PMID:23188267
Off-axis reflecting telescope with axially-symmetric optical property and its applications
Chang, Seunghyuk
2006-06-01
The basic concept and fundamental result of a recently developed geometric aberration theory for classical off-axis reflecting telescopes and imaging systems are presented. It is shown that a classical off-axis reflecting telescope can be designed to have practically axially-symmetric optical property by eliminating the dominant aberration (linear astigmatism) caused by the asymmetric geometry. A simple closed-form equation for elimination of linear astigmatism is presented. Also, to show how the developed aberration theory can be applied to current and future telescopes, several off-axis reflecting telescopes and imaging systems are designed and analyzed.
An axially symmetric gamma-ray backscatter system for DuMond spectrometry
International Nuclear Information System (INIS)
An axially symmetric spectrometer is described which evolved from a program of measuring Compton profiles with unusually high geometric efficiency. When fitted with a large-volume Ge detector for combined X-ray and γ-ray spectrometry, such as the 51 mm diameter LO-AX detector from EG and G, it allows Compton profiles to be measured at counting rates in excess of 20000 cps. The axially symmetric configuration is also suited to high-efficiency analyses of thick targets by both XRF and Rayleigh/Compton (R/C) ratios. The same spectra permit a competitive binary-system analysis based on the shape of the Compton profile. Both this new analysis, which we call DuMond spectrometry, and R/C analysis are applied to studies of osteoporosis in the calcaneus with promising results. The combination of high intrinsic and geometric detection efficiency makes it practical to use very weak sources (≅ 100 MBq) and unusually low, localized doses (≅ 1 μGy) per reading. (orig.)
Atomic states and collisional relaxation in plasma polarization spectroscopy: axially symmetric case
International Nuclear Information System (INIS)
An ensemble of atoms (or ions) is described in terms of the density matrix, and two quantities, population and alignment, are assigned to each atomic level for axially symmetric plasma environment. Collisional relaxation is treated semiclassically as transitions between vectors in the Liouville space and interpreted as elastic or inelastic transitions among the population and the alignment of the levels. A spatially anisotropic velocity distribution of perturbers is expanded in terms of Legendre polynomials, and rate coefficients are defined for the transitions. A set of rate equations are constructed for the system of populations and another set for that of alignments. In the case of an isotropic Maxwellian distribution of perturbers the former reduces to the conventional collisional-radiative model describing the ionizing plasma component of populations. As an example, berylliumlike oxygen in an anisotropic plasma environment is treated by this method. (author)
The most general axially symmetric electrovac spacetime admitting separable equations of motion
International Nuclear Information System (INIS)
We obtain the most general solution of the Einstein electro-vacuum equation for the stationary axially symmetric spacetime in which the Hamilton-Jacobi and Klein-Gordon equations are separable. The most remarkable feature of the solution is its invariance under the duality transformation involving mass and NUT parameter, and the radial and angle coordinates. It is the general solution for a rotating (gravitational dyon) particle which is endowed with both gravitoelectric and gravitomagnetic charges, and a duality transformation exists from one to the other. It also happens to be a transform of the Kerr-NUT solution. Like the Kerr family, it is also possible to make this solution radiating which asymptotically conforms to the Vaidya null radiation
The axial symmetric vibrations of cylindrical shell, filled by the flowing Gas-Liquid mixture
Directory of Open Access Journals (Sweden)
Grigoryan Sh.H.
2011-09-01
Full Text Available The problem of axial symmetric self–vibrations of the infinite long shell, filled by flowing gas bubbles of large and small sizes in fluid mixture is considered. The subsonic and supersonic regimes of the mixture flow are discussed. For vibration frequencies of the system under consideration are shown that shell frequencies with big bubbles–liquids mixture exceed the frequencies of system of with small gas bubbles–liquid mixture. In subsonic regime increasing of shell thickness brings to increasing of shell frequencies, as in case of shell with pure fluid. In subsonic regime the frequencies are increasing with decreasing of the flowing velocity, on the contrary, brings to decreasing of frequencies, similar to the case of shell with the pure fluid.
Sirenko, Kostyantyn
2011-01-01
An accurate and efficient finite-difference time-domain (FDTD) method for characterizing transient waves interactions on axially symmetric structures is presented. The method achieves its accuracy and efficiency by employing localized and/or fast Fourier transform (FFT) accelerated exact absorbing conditions (EACs). The paper details the derivation of the EACs, discusses their implementation and discretization in an FDTD method, and proposes utilization of a blocked-FFT based algorithm for accelerating the computation of temporal convolutions present in nonlocal EACs. The proposed method allows transient analyses to be carried for long time intervals without any loss of accuracy and provides reliable numerical data pertinent to physical processes under resonant conditions. This renders the method highly useful in characterization of high-Q microwave radiators and energy compressors. Numerical results that demonstrate the accuracy and efficiency of the method are presented.
Report on the Dynamical Evolution of an Axially Symmetric Quasar Model
Indian Academy of Sciences (India)
N. J. Papadopoulos; N. D. Caranicolas
2006-12-01
The role of the angular momentum in the regular or chaotic character of motion in an axially symmetric quasar model is examined. It is found that, for a given value of the critical angular momentum , there are two values of the mass of the nucleus for which transition from regular to chaotic motion occurs. The [-] relationship shows a linear dependence for the time independent model and an exponential dependence for the evolving model. Both cases are explained using theoretical arguments together with some numerical evidence. The evolution of the orbits is studied, as mass is transported from the disk to the nucleus. The results are compared with the outcomes derived for galactic models with massive nuclei.
Earliest stages of the non-equilibrium in axially symmetric, self-gravitating, dissipative fluids
Herrera, L; Ospino, J; Carot, J
2016-01-01
We report a study on axially and reflection symmetric dissipative fluids, just after its departure from hydrostatic and thermal equilibrium, at the smallest time scale at which the first signs of dynamic evolution appear. Such a time scale is smaller than the thermal relaxation time, the thermal adjustment time and the hydrostatic time. It is obtained that the onset of non--equilibrium will critically depend on a single function directly related to the time derivative of the vorticity. Among all fluid variables (at the time scale under consideration), only the tetrad component of the anisotropic tensor in the subspace orthogonal to the four--velocity and the Killing vector of axial symmetry, shows signs of dynamic evolution. Also, the first step towards a dissipative regime begins with a non--vanishing time derivative of the heat flux component along the meridional direction. The magnetic part of the Weyl tensor vanishes (not so its time derivative), indicating that the emission of gravitational radiation wil...
Lin, C.-C.; Huang, T.-C.; Chu, C.-C.; Hsiao, Vincent K. S.
2016-07-01
We demonstrate an optically switchable half-wave plate (HWP) composed of a photoaligned and axially symmetric liquid crystal (ASLC) film containing two azobenzene derivatives, methyl red (MR) and 4-butyl-4‧-methoxyazobenzene (BMAB). MR is responsible for photoalignment, and BMAB is used for optical tuning and switching the state of polarization (SOP) of probe beam (633 nm He-Ne laser) passing through the MR/BMAB doped ASLC film. The photoaligned ASLC film is first fabricated using a line-shaped laser beam (532 nm) exposure applied on a rotating LC sample. The fabricated ASLC film can passively change the linearly polarized light. Under UV light exposure, the formation of cis-BMAB (bend-like shape) within the film disrupts the LC molecules, switches the LC orientation, and further changes the SOP of the probe beam. Under laser irradiation (532 nm), the formation of trans-BMAB (rod-like shape) reverts the LC orientation back and simultaneously generates cis-MR, helping anchor the LC in the previously photoaligned orientation. The photoaligned MR/BMAB-doped LC HWP can change the linear SOP under alternating UV and visible light exposure.
Fluid-structure interaction in axially symmetric models of abdominal aortic aneurysms.
Fraser, K H; Li, M-X; Lee, W T; Easson, W J; Hoskins, P R
2009-02-01
Abdominal aortic aneurysm disease progression is probably influenced by tissue stresses and blood flow conditions and so accurate estimation of these will increase understanding of the disease and may lead to improved clinical practice. In this work the blood flow and tissue stresses in axially symmetric aneurysms are calculated using a complete fluid-structure interaction as a benchmark for calculating the error introduced by simpler calculations: rigid walled for the blood flow, homogeneous pressure for the tissue stress, as well as one-way-coupled interactions. The error in the peak von Mises stress in a homogeneous pressure calculation compared with a fluid-structure interaction calculation was less than 3.5 per cent for aneurysm diameters up to 7 cm. The error in the mean wall shear stress, in a rigid-walled calculation compared with a fluid-structure interaction calculation, varied from 30 per cent to 60 per cent with increasing aneurysm diameter. These results suggest that incorporation of the fluid-structure interaction is unnecessary for purely mechanical modelling, with the aim of evaluating the current rupture probability. However, for more complex biological modelling, perhaps with the aim of predicting the progress of the disease, where accurate estimation of the wall shear stress is essential, some form of fluid-structure interaction is necessary. PMID:19278197
Conformal operators from spinor fields - I: Symmetric tensor case
International Nuclear Information System (INIS)
The full system of conformal symmetric traceless tensor operators with minimal twist constructed from generalized free massless spinor fields is given. A series of symmetric tensor operators with higher twist and the simplest antisymmetric tensor operators are given as examples for further study. (author)
Snap-through of the system for a shallow axially symmetric bimetallic shell using non-linear theory
Kosel, Tadej; Batista, Milan; Jakomin, Marko; Kosel, Franc
2015-01-01
The paper deals with the stresses, strains and buckling conditions in thin, axially symmetric, shallow, bimetallic shells. Based on third-order theory, which takes into account the equilibrium state of the forces and moments that are acting on the deformed system, the paper presents a model with a mathematical description of the geometry of the system, the stresses, the thermoelastic strains and the displacements. The mathematical formulation is based on the theory of large displacements. As ...
Effects of external axial magnetic field on fast electron propagation
International Nuclear Information System (INIS)
A scheme employing an external axial magnetic field is proposed to diagnose the intrinsic divergence of laser-generated fast electron beams, and this is studied numerically with hybrid simulations. The maximum beam radius of fast electrons increases with the initial divergence and decreases with the amplitude of the axial magnetic field. It is indicated that the intrinsic divergence of fast electrons can be inferred from measurements of the beam radius at different depth under the axial field. The proposed scheme here may be useful for future fast ignition experiments and in other applications of laser-generated fast electron beams.
Natural flat observer fields in spherically symmetric space-times
International Nuclear Information System (INIS)
An observer field in a space-time is a time-like unit vector field. It is natural if the integral curves (field lines) are geodesic and the perpendicular three-plane field is integrable (giving normal space slices). We prove that a natural observer field determines a coherent notion of time: a coordinate that is constant on the perpendicular space slices and whose difference between two space-slices is the proper time along any field line.A natural observer field is flat if the normal space slices are metrically flat. For static spherically symmetric space-times we find a necessary and sufficient condition for possession of a spherically symmetric natural flat observer field. In this case, which includes the Schwarzschild and the Kottler space-times, there is in fact a dual pair of spherically symmetric natural flat observer fields. One of these observer fields is expanding and the other contracting and it is natural to describe the expanding field as the ‘escape’ field and the dual contracting field as the ‘capture’ field.Observer fields are useful for understanding redshift and the fields described here are used in a possible explanation of redshift explored in [8]. (paper)
Static scalar field solutions in symmetric gravity
Hossenfelder, S.
2016-09-01
We study an extension of general relativity with a second metric and an exchange symmetry between the two metrics. Such an extension might help to address some of the outstanding problems with general relativity, for example the smallness of the cosmological constant. We here derive a family of exact solutions for this theory. In this two-parameter family of solutions the gravitational field is sourced by a time-independent massless scalar field. We find that the only limit in which the scalar field entirely vanishes is flat space. The regular Schwarzschild-solution is left with a scalar field hidden in the second metric’s sector.
Nuclear Axial Currents in Chiral Effective Field Theory
Baroni, A.; Girlanda, L.; Pastore, S.; Schiavilla, R.; Viviani, M
2015-01-01
Two-nucleon axial charge and current operators are derived in chiral effective field theory up to one loop. The derivation is based on time-ordered perturbation theory, and accounts for cancellations between the contributions of irreducible diagrams and the contributions due to non-static corrections from energy denominators of reducible diagrams. Ultraviolet divergencies associated with the loop corrections are isolated in dimensional regularization. The resulting axial current is finite and...
A wide low-mass binary model for the origin of axially symmetric non-thermal radio sources
International Nuclear Information System (INIS)
An accreting binary model has been proposed by recent workers to account for the origin of the axially symmetric non-thermal radio sources. The authors show that the only type of binary system that can produce the observed structural properties, is a relatively wide neutron star binary, in which the companion of the neutron star is a low-mass giant. Binaries of this type are expected to resemble closely the eight brightest galactic bulge X-ray sources as well as the progenitors of the two wide radio pulsar binaries. (U.K.)
Massive totally symmetric fields in AdS(d)
Metsaev, R R
2004-01-01
Free totally symmetric arbitrary spin massive bosonic and fermionic fields propagating in AdS(d) are investigated. Using the light cone formulation of relativistic dynamics we study bosonic and fermionic fields on an equal footing. Light-cone gauge actions for such fields are constructed. Interrelation between the lowest eigenvalue of the energy operator and standard mass parameter for arbitrary type of symmetry massive field is derived.
Axial symmetric rotation of a partially immersed body in a liquid with a surfactant layer
Indian Academy of Sciences (India)
Sunil Datta; Nidhi Pandya
2001-08-01
This paper gives a simple integral formula to evaluate the torque on a slowly rotating symmetric body partially immersed in a viscous liquid covered by an adsorbed surface ﬁlm. Besides the results known earlier, new results have also been derived for small values of the surface shear viscosity parameter . It is seen that the effect of in all cases is to increase the torque.
View of the Axial Field Spectrometer (R807)
1980-01-01
In this view of the Axial Field Spectrometer at I8, the vertical uranium/scintillator hadron calorimeter (just left of centre) is retracted to give access to the cylindrical central drift chamber. The yellow iron structure served as a filter to identify muons, with MWPCs and the array of Cherenkov counters to the right.
Energy of Gravitational Field of Static Spherically Symmetric Neutron Stars
Institute of Scientific and Technical Information of China (English)
WENDe-Hua; CHENWei; WANGXian-Ju; AIBao-Quan; LIUGuo-Tao; LIULiang-Gang
2003-01-01
By using the Einstein-Tolman expression of the energy-momentum pseudo-tensor, the energy density of the gravitational field of the static spherically symmetric neutron stars is calculated in the Cartesian coordinate system.It is exciting that the energy density of gravitational field is positive and rational The xmmerical results of the energy density of gravitational field of neutron stars are calculated. For neutron stars with M=2M, the ratio of the energy density of gravitational field to the energy density of pure matters would be up to 0.54 at the surface.
The gravitational field energy density for symmetrical and asymmetrical systems
Sosnovskiy, R
2006-01-01
The relativistic theory of gravitation has the considerable difficulties by description of the gravitational field energy. Pseudotensor t00 in the some cases cannot be interpreted as energy density of the gravitational field. In [1] the approach was proposed, which allow to express the energy density of such a field through the components of a metric tensor. This approach based on the consideration of the isothermal compression of the layer consisted of the incoherent matter. It was employ to the cylindrically and spherically symmetrical static gravitational field. In presented paper the approach is developed.
Energy of Gravitational Field of Static Spherically Symmetric Neutron Stars
Institute of Scientific and Technical Information of China (English)
WEN De-Hua; CHEN Wei; WANG Xian-Ju; AI Bao-Quan; LIU Guo-Tao; LIU Liang-Gang
2003-01-01
By using the Einstein-Tolman expression of the energy-momentum pseudo-tensor, the energy density ofthe gravitational field of the static spherically symmetric neutron stars is calculated in the Cartesian coordinate system.It is exciting that the energy density of gravitational field is positive and rational. The numerical results ot the energydensity of gravitational field of neutron stars are calculated. For neutron stars with M = 2M , the ratio of the energydensity of gravitational field to the energy density of pure matters would be up to 0.54 at the surface.
Coupled dilaton and electromagnetic field in cylindrically symmetric spacetime
Indian Academy of Sciences (India)
A Banerjee; S Chatterjee; Tanwi Ghosh
2000-03-01
An exact solution is obtained for coupled dilaton and electromagnetic ﬁeld in a cylindrically symmetric spacetime where an axial magnetic ﬁeld as well as a radial electric ﬁeld both are present. Depending on the choice of the arbitrary constants our solution reduces either to dilatonic gravity with pure electric ﬁeld or to that with pure magnetic ﬁeld. In the ﬁrst case we have a curvature singularity at a ﬁnite distance from the axis indicating the existence of the boundary of a charged cylinder which may represent the source of the electric ﬁeld. For the second case we have a singularity on the axis. When the dilaton ﬁeld is absent the electromagnetic ﬁeld disappears in both the cases. Whereas the contrary is not true. It is further shown that light rays except for those proceeding in the radial direction are either trapped or escape to inﬁnity depending on the magnitudes of certain constant parameters as well as on the nature of the electromagnetic ﬁeld. Nature of circular geodesics is also studied in the presence of dilaton ﬁeld in the cylindrically symmetric spacetime.
Institute of Scientific and Technical Information of China (English)
Liu Yu-Min; Yu Zhong-Yuan
2009-01-01
Calculations of electronic structures about the semiconductor quantum dot and the semiconductor quantum ring are presented in this paper. To reduce the calculation costs, for the quantum dot and the quantum ring, their simplified axially symmetric shapes are utilized in our analysis. The energy dependent effective mass is taken into account in solving the Schrodinger equations in the single band effective mass approximation. The calculated results show that the energy dependent effective mass should be considered only for relatively small volume quantum dots or small quantum rings. For large size quantum materials, both the energy dependent effective mass and the parabolic effective mass can give the same results. The energy states and the effective masses of the quantum dot and the quantum ring as a function of geometric parameters are also discussed in detail.
Romano, Marcello
2008-08-01
New exact analytic solutions are introduced for the rotational motion of a rigid body having two equal principal moments of inertia and subjected to an external torque which is constant in magnitude. In particular, the solutions are obtained for the following cases: (1) Torque parallel to the symmetry axis and arbitrary initial angular velocity; (2) Torque perpendicular to the symmetry axis and such that the torque is rotating at a constant rate about the symmetry axis, and arbitrary initial angular velocity; (3) Torque and initial angular velocity perpendicular to the symmetry axis, with the torque being fixed with the body. In addition to the solutions for these three forced cases, an original solution is introduced for the case of torque-free motion, which is simpler than the classical solution as regards its derivation and uses the rotation matrix in order to describe the body orientation. This paper builds upon the recently discovered exact solution for the motion of a rigid body with a spherical ellipsoid of inertia. In particular, by following Hestenes’ theory, the rotational motion of an axially symmetric rigid body is seen at any instant in time as the combination of the motion of a “virtual” spherical body with respect to the inertial frame and the motion of the axially symmetric body with respect to this “virtual” body. The kinematic solutions are presented in terms of the rotation matrix. The newly found exact analytic solutions are valid for any motion time length and rotation amplitude. The present paper adds further elements to the small set of special cases for which an exact solution of the rotational motion of a rigid body exists.
Constrained field theories on spherically symmetric spacetimes with horizons
Fernandes, Karan; Lahiri, Amitabha
2016-01-01
We apply the Dirac-Bergmann algorithm for the analysis of constraints to gauge theories defined on spherically symmetric black hole backgrounds. As a concrete example, we consider the Maxwell field on a black hole background, and determine the role of the horizon contributions on the dynamics of the theory. We find that the constraints are modified on such spacetimes through the presence of additional contributions from the horizon.
Energy Technology Data Exchange (ETDEWEB)
Andersson, P., E-mail: peter.andersson@physics.uu.se; Andersson-Sunden, E.; Sjöstrand, H.; Jacobsson-Svärd, S. [Department of Physics and Astronomy, Division of Applied Nuclear Physics, Uppsala University, Lägerhyddsgatan 1, 751 20 Uppsala (Sweden)
2014-08-01
In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm{sup −1}, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful
International Nuclear Information System (INIS)
In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the time-averaged void distribution in these loops. Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed. In this article, three axially symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm, and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper. Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020, and 0.022 cm−1, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful
Plane symmetric cosmological model of interacting fields in general relativity
International Nuclear Information System (INIS)
We have obtained plane symmetric cosmological model in the presence of linearly coupled massless scalar field and source free electromagnetic field with stiff or Zel'dovich fluid p = ρ and disordered radiation ρ = 3p. It is interesting to note that the models turn out to be identical at T → 0 and T →∞. Generally models are expanding, shearing and non-rotating. We observe that they do not approach isotropy for large value of time T. Also, some physical and geometric properties of the models are discussed. (authors)
Axial field permanent magnet DC motor with powder iron armature
Sharkh, Suleiman M.A.; Mohammad, Mohammad T.
2007-01-01
The paper describes a double-gap axial field permanent magnet (PM) dc motor whose double-layer armature wave winding is constructed of copper strips. It investigates the performance of two machines using powder iron and lamination steel materials as armature teeth. Tests are conducted to evaluate the motor torque and speed curves as well as their efficiency under different loads. Finite element analysis (FEA) and equivalent circuit models are used to determine the levels of the magnetic satur...
Vacuum arc under axial magnetic fields: experimental and simulation research
International Nuclear Information System (INIS)
Axial magnetic field (AMF) technology is a most important control method of vacuum arc, particularly for high-current vacuum arcs in vacuum interrupters. In this paper, a review of the state of current research on vacuum arcs under AMF is presented. The major aspects of vacuum arc in an AMF such as arc voltage, the motion of cathode spots, and anode activities are discussed, and the most recent progress both of experimental and simulation research is presented. (topical review)
Overview of the Axial Field Spectrometer in the ISR tunnel
1980-01-01
A view of the Axial Field Spectrometer – the last large experiment at the ISR. The horizontal top and vertical outer arrays of the uranium-scintillator hadron calorimeter are clear to be seen, with the blue cylindrical pole piece of the magnet just visible. The pipes that are visible in front of the pole piece are cryogenic feed pipes for the superconducting low-beta quadrupoles.
International Nuclear Information System (INIS)
2.5D relativistic electromagnetic PIC code for simulation of the beam interaction with plasma in axial-symmetric geometry was developed. Accurate charge weighting scheme and difference schemes near the system axis were introduced. Simulation tests of electromagnetic wave interaction with inhomogeneous plasma were carried out.
DEFF Research Database (Denmark)
Angioni, C.; Carraro, L.; Dannert, T.;
2007-01-01
Experimental observations on core particle and impurity transport from the Axial Symmetric Divertor Experiment Upgrade [O. Gruber, H.-S. Bosch, S. Gunter , Nucl Fusion 39, 1321 (1999)] and the Joint European Torus [J. Pamela, E. R. Solano, and JET EFDA Contributors, Nucl. Fusion 43, 1540 (2003...
Toroidal linear force-free magnetic fields with axial symmetry
Vandas, M.; Romashets, E.
2016-01-01
Aims: Interplanetary magnetic flux ropes are often described as linear force-free fields. To account for their curvature, toroidal configurations must be used. The aim is to find an analytic description of a linear force-free magnetic field of the toroidal geometry in which the cross section of flux ropes can be controlled. Methods: The solution is found as a superposition of fields given by linear force-free cylinders tangential to a generating toroid. The cylindrical field is expressed in a series of terms that are not all cylindrically symmetric. Results: We found the general form of a toroidal linear force-free magnetic field. The field is azimuthally symmetric with respect to the torus axis. It depends on a set of coefficients that enables controlling the flux rope shape (cross section) to some extent. By varying the coefficients, flux ropes with circular and elliptic cross sections were constructed. Numerical comparison suggests that the simple analytic formula for calculating the helicity in toroidal flux ropes of the circular cross section can be used for flux ropes with elliptic cross sections if the minor radius in the formula is set to the geometric mean of the semi-axes of the elliptic cross section.
Investigation of the space charge axial oscillations in the cross fields
International Nuclear Information System (INIS)
The space charge oscillations are prominent in the performance of the cross fields devices Two main types of oscillations are known: radially-symmetrical oscillations (RSO) and running wave oscillations (RWO). Alongside with the RSO and RWO the space charge oscillations along the magnetic field B are possible in the cross field systems. The possibility of axial electron movement is indicated by some authors. The exis- tance of the space charge cooperative oscillations along the magnetic field (axial oscillations-AO) in M-type amplifier has shown from analysis of the end current high-frequency modulation. In order to find out AO regularities the further investigations in the various systems with the cross fields are necessary. In the present work AO were studied in the magnetron diode (MD) with the smooth anode (20mm in diameter) and cold CuBeAl alloy cathode (13mm in diameter). The pressure in the diode changed from 10-6 to 10-4 Torr. MD starting was accomplished with auxiliary starting thermo-cathode located not far from the end of the basic cathode. (Auth.)
International Nuclear Information System (INIS)
Martinelli and Morini have used an analytical method for calculating values and distribution of the magnetic field in superconducting magnets. Using Fourier series the magnetic field is determined by carrying out a series expansion of the current density distribution of the system of coils. This Fourier method can be modified to include axial iron to a far greater accuracy (for finite permeability) by incorporating the image series approach of Caldwell and Zisserman. Also an exact solution can be obtained for the case of infinite permeability. A comparison of the results derived from the expansion of Martinelli and Morini with the exact solution of Caldwell and Zisserman shows excellent agreement for the iron-free case but the accuracy deteriorates as the permeability μ/sub z/ increases. The exact solution should be used for infinite permeability and also gives satisfactory results for permeability μ/sub z/ >100. A symmetric geometry is used throughout the communication for simplicity of presentation
Optical design for amateur reflecting telescopes based on tilted axial-symmetrical planoidal mirror
Chuprakov, Sergey A.
2012-09-01
Two-mirrors aplanatic optical design for amateur telescopes up to 0.5m class is described. The optical system is low cost, easy for adjusting, fast and large field of view can be used for visual and astrophotography. The method for calculation of baffles for straight light protection is described. The optical performances and sample shots for the builted device are presented. Keywords: two-mirrors system, all-reflecting schmidt system, aplanatic system, protection from straight light, baffles, obscuration, wide-field, telescopes for amateurs.
An offset-fed reflector antenna with an axially symmetric main reflector
Chang, D.-C.; Rusch, W. V. T.
1984-11-01
A design method for an offset-fed, dual reflector antenna (Cassegrain type or Gregorian type) system with an axisymmetric main reflector is presented. Geometrical optics (GO) and the geometrical theory of diffraction (GTD) are used to find the surface-current density on the main reflector. A modified Jacobi-Bessel series (JBS) method is used to find the far-field pattern for the physical optics (PO) integral. In the defocused mode of operation, a new technique is developed to find the reflection point on the subreflector corresponding to the defocused feed and a general field point on the main reflector. Two sample systems are designed.
Mechanism of Fast Axially--Symmetric Reversal of Magnetic Vortex Core
Pylypovskyi, Oleksandr V.; Sheka, Denis D.; Kravchuk, Volodymyr P.; Gaididei, Yuri; Mertens, Franz G.
2012-01-01
The magnetic vortex core in a nanodot can be switched by an alternating transversal magnetic field. We propose a simple collective coordinate model which describes comprehensive vortex core dynamics, including resonant behavior, weakly nonlinear regimes, and reversal dynamics. A chaotic dynamics of the vortex polarity is predicted. All analytical results were confirmed by micromagnetic simulations.
Experimental studies of axial magnetic fields generated in ultrashort-pulse laser-plasma interaction
Institute of Scientific and Technical Information of China (English)
李玉同; 张杰; 陈黎明; 赵理曾; 夏江帆; 魏志义; 江文勉
2000-01-01
The quasistatic axial magnetic fields in plasmas produced by ultrashort laser pulses were measured by measuring the Faraday rotation angle of the backscattered emission. The spatial distribution of the axial magnetic field was obtained with a peak value as high as 170 Tesla. Theory suggests that the axial magnetic field is generated by dynamo effect in laser-plasma interaction.
International Nuclear Information System (INIS)
A theory is presented for current collection by electrostatic probes in a collisionless, Maxwellian plasma containing a uniform magnetic field B, where the probes are spheroids or finite cylinders whose axis of symmetry is aligned with B, or disks perpendicular to B. The theory yields upper-bound and adiabatic-limit currents for the attracted particle species. For the repelled species, it yields upper and lower bounds. This work is an extension of existing theory for spherical probes by Rubinstein and Laframboise
Feature Surfaces in Symmetric Tensor Fields Based on Eigenvalue Manifold.
Palacios, Jonathan; Yeh, Harry; Wang, Wenping; Zhang, Yue; Laramee, Robert S; Sharma, Ritesh; Schultz, Thomas; Zhang, Eugene
2016-03-01
Three-dimensional symmetric tensor fields have a wide range of applications in solid and fluid mechanics. Recent advances in the (topological) analysis of 3D symmetric tensor fields focus on degenerate tensors which form curves. In this paper, we introduce a number of feature surfaces, such as neutral surfaces and traceless surfaces, into tensor field analysis, based on the notion of eigenvalue manifold. Neutral surfaces are the boundary between linear tensors and planar tensors, and the traceless surfaces are the boundary between tensors of positive traces and those of negative traces. Degenerate curves, neutral surfaces, and traceless surfaces together form a partition of the eigenvalue manifold, which provides a more complete tensor field analysis than degenerate curves alone. We also extract and visualize the isosurfaces of tensor modes, tensor isotropy, and tensor magnitude, which we have found useful for domain applications in fluid and solid mechanics. Extracting neutral and traceless surfaces using the Marching Tetrahedra method can cause the loss of geometric and topological details, which can lead to false physical interpretation. To robustly extract neutral surfaces and traceless surfaces, we develop a polynomial description of them which enables us to borrow techniques from algebraic surface extraction, a topic well-researched by the computer-aided design (CAD) community as well as the algebraic geometry community. In addition, we adapt the surface extraction technique, called A-patches, to improve the speed of finding degenerate curves. Finally, we apply our analysis to data from solid and fluid mechanics as well as scalar field analysis. PMID:26441450
Flow field interference characteristic of axial ring wing configuration
Qi, Duo; Jinfu, Feng; Jiaqiang, Zhang; Yongli, Li
2016-01-01
To analyze the air flow interference between upper and lower wings in axial ring wing configuration, NASA SC(2)-1006 supercritical airfoil is chosen as the basic airfoil. Flow field around the double-wing structure with different relative distances between upper and lower wings is numerically simulated, using SST turbulence model, and the numerical conclusion about the influence of relative distance D/L on the aerodynamic performance is drawn. It is shown that, at the speed Ma = 0.8, reflect...
Self Tuning Scalar Fields in Spherically Symmetric Spacetimes
Appleby, Stephen
2015-01-01
We search for self tuning solutions to the Einstein-scalar field equations for the simplest class of `Fab-Four' models with constant potentials. We first review the conditions under which self tuning occurs in a cosmological spacetime, and by introducing a small modification to the original theory - introducing the second and third Galileon terms - show how one can obtain de Sitter states where the expansion rate is independent of the vacuum energy. We then consider whether the same self tuning mechanism can persist in a spherically symmetric inhomogeneous spacetime. We show that there are no asymptotically flat solutions to the field equations in which the vacuum energy is screened, other than the trivial one (Minkowski space). We then consider the possibility of constructing Schwarzschild de Sitter spacetimes for the modified Fab Four plus Galileon theory. We argue that the only model that can successfully screen the vacuum energy in both an FLRW and Schwarzschild de Sitter spacetime is one containing `John...
Numerical relativity for D dimensional axially symmetric space-times: formalism and code tests
Zilhao, Miguel; Sperhake, Ulrich; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Nerozzi, Andrea
2010-01-01
The numerical evolution of Einstein's field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modelling black hole production in TeV gravity scenarios, analysis of the stability of exact solutions and tests of Cosmic Censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D\\ge 5, or SO(D-3) for D\\ge 6. Performing a dimensional reduction on a (D-4)-sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN) formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions an...
Analysis of brushless DC generator incorporating an axial field coil
Energy Technology Data Exchange (ETDEWEB)
Moradi, Hassan, E-mail: H_moradi@sbu.ac.i [Department of Electrical and Computer Engineering, Shahid Beheshti University, GC, Tehran (Iran, Islamic Republic of); Afjei, E. [Department of Electrical and Computer Engineering, Shahid Beheshti University, GC, Tehran (Iran, Islamic Republic of)
2011-07-15
Highlights: {yields} Magnetic analysis and experiment of a three-phase field assisted BLDC generator. {yields} Confirm the accuracy of the predicted flux-linkage by 2-D FE analysis. {yields} Confirm the accuracy of the FE analysis results by coupling the FE and BE method. {yields} Control the output voltage to a desired level by control the amplitude of the I{sub f}. {yields} Compatible with any application that requires variable speed operation. -- Abstract: This paper describes the magnetic analysis and experiment of a three-phase field assisted brushless DC (BLDC) generator. Unlike conventional BLDC generators, the permanent magnet is replaced with an assisted field winding. The stator and rotor are constructed with two dependent magnetically sets, in which each stator set includes nine salient poles with coil windings, and the rotor comprises of six salient poles. Other pole combinations also are possible. This construction is similar to a homopolar inductor alternator. The DC current in the assisted field winding produces axial flux which makes the rotor magnetically polarized at its ends. The magnetic field flows axially through the rotor shaft and closes through the stator teeth and the machine housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. In the numerical analysis, 2-D finite element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.), to confirm the accuracy of the predicted flux-linkage characteristics, whereas in the experimental study, a prototype BLDC generator was constructed for verifying the actual performance. Furthermore, the evaluation method based on a hybrid numerical method coupling the finite element (FE) analysis and boundary element (BE) method, has been carried out to confirm the accuracy of the 2-D FE analysis simulation results. It provides not only confirmations of the investigation in results
Analysis of brushless DC generator incorporating an axial field coil
International Nuclear Information System (INIS)
Highlights: → Magnetic analysis and experiment of a three-phase field assisted BLDC generator. → Confirm the accuracy of the predicted flux-linkage by 2-D FE analysis. → Confirm the accuracy of the FE analysis results by coupling the FE and BE method. → Control the output voltage to a desired level by control the amplitude of the If. → Compatible with any application that requires variable speed operation. -- Abstract: This paper describes the magnetic analysis and experiment of a three-phase field assisted brushless DC (BLDC) generator. Unlike conventional BLDC generators, the permanent magnet is replaced with an assisted field winding. The stator and rotor are constructed with two dependent magnetically sets, in which each stator set includes nine salient poles with coil windings, and the rotor comprises of six salient poles. Other pole combinations also are possible. This construction is similar to a homopolar inductor alternator. The DC current in the assisted field winding produces axial flux which makes the rotor magnetically polarized at its ends. The magnetic field flows axially through the rotor shaft and closes through the stator teeth and the machine housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. In the numerical analysis, 2-D finite element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.), to confirm the accuracy of the predicted flux-linkage characteristics, whereas in the experimental study, a prototype BLDC generator was constructed for verifying the actual performance. Furthermore, the evaluation method based on a hybrid numerical method coupling the finite element (FE) analysis and boundary element (BE) method, has been carried out to confirm the accuracy of the 2-D FE analysis simulation results. It provides not only confirmations of the investigation in results but also exact illustration for
Ion pump using cylindrically symmetric spindle magnetic field
International Nuclear Information System (INIS)
For all accelerators and many research and industries, excellent vacuum conditions are required and the highest possible pumping rates are necessary. For most applications the standard ion sputtering pump (ISP) meets these requirements and is optimal for financial point of view also. The physical principle of the ISP is well known and many companies manufacture variety of ISP. Most of them use dipole magnetic field produced by permanent magnet and electric dipole field between the electrodes in which tenuous plasma is created because of interaction of between the relatively fast electrons slow residual gas atoms. Performance of an ISP depends basically on the electron cloud density in between the titanium electrodes but in the available present configurations no consideration has been given to electron confinement which needs a mirror magnetic field. If this is incorporated it will make a robust ISP surely; furthermore, the requirement of constant feeding of high voltage to electrodes for supplying sufficient number of electrons will be reduced too. A study has been performed to create sufficient rotationally symmetric spindle magnetic field (SMF) with inherent presence of magnetic mirror effect to electron motion to confine them for longer time for enhancing the density of electron cloud between the electrodes. It will lessen the electric power feeding the electrodes and lengthen their life-time. Construction of further compact and robust ISP is envisaged herein. The field simulation using the commercially available permanent magnet together with simulation of electron motion in such field will be presented and discussed in the paper.
Ion pump using cylindrically symmetric spindle magnetic field
Rashid, M. H.
2012-11-01
For all accelerators and many research and industries, excellent vacuum conditions are required and the highest possible pumping rates are necessary. For most applications the standard ion sputtering pump (ISP) meets these requirements and is optimal for financial point of view also. The physical principle of the ISP is well known and many companies manufacture variety of ISP. Most of them use dipole magnetic field produced by permanent magnet and electric dipole field between the electrodes in which tenuous plasma is created because of interaction of between the relatively fast electrons slow residual gas atoms. Performance of an ISP depends basically on the electron cloud density in between the titanium electrodes but in the available present configurations no consideration has been given to electron confinement which needs a mirror magnetic field. If this is incorporated it will make a robust ISP surely; furthermore, the requirement of constant feeding of high voltage to electrodes for supplying sufficient number of electrons will be reduced too. A study has been performed to create sufficient rotationally symmetric spindle magnetic field (SMF) with inherent presence of magnetic mirror effect to electron motion to confine them for longer time for enhancing the density of electron cloud between the electrodes. It will lessen the electric power feeding the electrodes and lengthen their life-time. Construction of further compact and robust ISP is envisaged herein. The field simulation using the commercially available permanent magnet together with simulation of electron motion in such field will be presented and discussed in the paper.
Numerical relativity for D dimensional axially symmetric space-times: Formalism and code tests
International Nuclear Information System (INIS)
The numerical evolution of Einstein's field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modeling black hole production in TeV gravity scenarios, to analysis of the stability of exact solutions, and to tests of cosmic censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D≥5, or SO(D-3) for D≥6. Performing a dimensional reduction on a (D-4) sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata, and Nakamura formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions and a procedure to match them to our 3+1 dimensional evolution equations is given. We have implemented our framework by adapting the Lean code and perform a variety of simulations of nonspinning black hole space-times. Specifically, we present a modified moving puncture gauge, which facilitates long-term stable simulations in D=5. We further demonstrate the internal consistency of the code by studying convergence and comparing numerical versus analytic results in the case of geodesic slicing for D=5, 6.
Numerical relativity for D dimensional axially symmetric space-times: Formalism and code tests
Zilhão, Miguel; Witek, Helvi; Sperhake, Ulrich; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Nerozzi, Andrea
2010-04-01
The numerical evolution of Einstein’s field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modeling black hole production in TeV gravity scenarios, to analysis of the stability of exact solutions, and to tests of cosmic censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D≥5, or SO(D-3) for D≥6. Performing a dimensional reduction on a (D-4) sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata, and Nakamura formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions and a procedure to match them to our 3+1 dimensional evolution equations is given. We have implemented our framework by adapting the Lean code and perform a variety of simulations of nonspinning black hole space-times. Specifically, we present a modified moving puncture gauge, which facilitates long-term stable simulations in D=5. We further demonstrate the internal consistency of the code by studying convergence and comparing numerical versus analytic results in the case of geodesic slicing for D=5, 6.
International Nuclear Information System (INIS)
Collisional heating of an inhomogeneous plasma cylinder with the help of magnetic pumping by axial-asymmetrical alternating fields, passing along a constant magnetic field with the phase velocity ω/K11 exceeding or of the order of sound velocity Vsub(s), has been considered. The heating rate is found for a low-pressure magnetized plasma. It is the same by the order of magnitude as the rate of heating by axial-symmetrical fields. In the case of the acoustic resonance (ω approximately K11 Vsub(s)) the energy absorption rate increases by a factor of 1/ωtausub(i)>>1, provided the resonance occurs in a narrow layer, and by a factor of 1/(ωtausub(i))2, provided the resonance occurs in the whole volume of plasma (tausub(i)sup(-1) is the frequency of ion-ion collisions)
Albin, Michael; de, William; Horrocks, W., Jr.; Liotta, Frank J.
1982-01-01
The Eu(III) complex of the octadentate macrocyclic ligand, 1,4,7,10-tetraazacyclododecane-N,N',N'',N''' -tetraacetate, DOTA, has been examined by luminescence excitation, emission, and lifetime spectroscopy using pulsed dye laser techniques. The results confirm the expected axially symmetric nature of the major component in solution and reveal that 1.2 ± 0.4 water molecules arc coordinatcd to the Eu(III) ion in the complex.
Arc Behaviours in Vacuum Interrupters with Axial Magnetic Field Electrodes
Institute of Scientific and Technical Information of China (English)
WANG Zhongyi; ZHENG Yuesheng; LIU Zhiyuan; CHENG Shaoyong
2008-01-01
To improve the limiting current interruption capability and minimizing vacuum interrupter with axial magnetic field (AMF) electrodes,it is significant to investigate the vacuum arc behaviours between the contacts.AMF distributions of the slot type electrodes were studied by both numerical analysis and experiments. Furthermore,the behaviours of vacuum arcs for different parameters of the slot type AMF electrodes were investigated by using high-speed CCD camera.The influences of gap distance,contact diameter and phase shift time between AMF and arc current on the vacuum arc were investigated.The results provide a reference for research and development of vacuum interrupters with slot type or other types of AMF electrode.
High temperature superconducting axial field magnetic coupler: realization and test
Belguerras, L.; Mezani, S.; Lubin, T.; Lévêque, J.; Rezzoug, A.
2015-09-01
Contactless torque transmission through a large airgap is required in some industrial applications in which hermetic isolation is necessary. This torque transmission usually uses magnetic couplers, whose dimension strongly depends on the airgap flux density. The use of high temperature superconducting (HTS) coils to create a strong magnetic field may constitute a solution to reduce the size of the coupler. It is also possible to use this coupler to replace a torque tube in transmitting the torque produced by a HTS motor to its load. This paper presents the detailed construction and tests of an axial field HTS magnetic coupler. Pancake coils have been manufactured from BSCCO tape and used in one rotor of the coupler. The second rotor is mainly composed of NdFeB permanent magnets. Several tests have been carried out showing that the constructed coupler is working properly. A 3D finite element (FE) model of the studied coupler has been developed. Airgap magnetic field and torque measurements have been carried out and compared to the FE results. It has been shown that the measured and the computed quantities are in satisfactory agreement.
Axial Magnetic Field Effect on Taylor-Couette Flow
Directory of Open Access Journals (Sweden)
Sofiane ABERKANE
2015-01-01
Full Text Available This study is interested in the effect of an axial magnetic field imposed on incompressible flow of electrically conductive fluid between two horizontal coaxial cylinders. The imposed magnetic field is assumed uniform and constant. The effect of heat generation due to viscous dissipation is also taken into account. The inner and outer cylinders are maintained at different uniform temperatures. The movement of the fluid is due to rotation of the cylinder with a constant speed. An exact solution of the equations governing the flow was obtained in the form of Bessel functions. A finite difference implicit scheme was used in the numerical solution. The velocity and temperature distributions were obtained with and without the magnetic field. The results show that for different values of the Hartmann number, the velocity between the two cylinders decreases as the Hartmann number increases. Also, it is found that by increasing the Hartmann number, the average Nusselt number decreases. On the other hand, the Hartmann number does not affect the temperature.
Generalized plane gravitational waves of non-symmetric unified field theories in plane symmetry
Bhoyar, Sanjiv R.; Ajit Deshmukh
2012-01-01
In this paper we investigated the plane wave solutions of both the weak and strong non-symmetric unified field equations of Einstein and Bonner in a generalized plane symmetric space-time in the sense of Taub [Ann. Math. 53, 472 (1951)] for plane gravitational waves. We show that the plane wave solutions of Einstein and Bonner field equations exist in plane symmetry.
Institute of Scientific and Technical Information of China (English)
陈光
2001-01-01
The static spherically symmetric solution of Einstein gravity coupled to electromagnetic and scalar fields is obtained under the consideration of the self-gravitational interaction of the electromagnetic and scalar fields, which is singularityfree and stable.
International Nuclear Information System (INIS)
Geometrical coefficients for the interpretation of angular correlations (or distributions) of γ-rays from aligned nuclei, perturbed by axially symmetric quadrupole interactions, are presented for nuclear spins 41/2≤I≤40. The coefficients SnNk1k2, which enter into the time dependence of the aligned effects for single-crystals sources, are tabulated for k1=2,4; k2=2,4 and N=1,2,3,4. Also tabulated are the coefficients Skn for polycrystalline sources with k=1,2,3,4. (author)
International Nuclear Information System (INIS)
Geometrical coefficients for the interpretation of angular correlations (or distribution) of γ rays from polarized nuclei perturbed by axially symmetric quadrupole interactions are presented for nuclear spins I much-lt 40. The coefficients SnNk1k2, which enter into the time dependence of the polarization effects for single-crystal sources, are tabulated for k1 = 1, 3; k2 = 2, 4; and N =1,2,3. Also tabulated are the coefficients ak1k2N for the analysis of γ-ray distributions from aligned as well as from polarized nuclei
Energy Technology Data Exchange (ETDEWEB)
Wakayama, Toshitaka, E-mail: wakayama@saitama-med.ac.jp; Yonemura, Motoki [School of Biomedical Engineering, Saitama Medical University, Yamane 1397-1, Hidaka, Saitama 350-1241 (Japan); Oikawa, Hiroki; Sasanuma, Atsushi; Arai, Goki; Fujii, Yusuke [Department of Electrical and Electronic Engineering, Faculty of Engineering, Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi 321-8585 (Japan); Dinh, Thanh-Hung; Otani, Yukitoshi [Center for Optical Research & Education (CORE), Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi 321-8585 (Japan); Higashiguchi, Takeshi, E-mail: higashi@cc.utsunomiya-u.ac.jp [Department of Electrical and Electronic Engineering, Faculty of Engineering, Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi 321-8585 (Japan); Center for Optical Research & Education (CORE), Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi 321-8585 (Japan); Sakaue, Kazuyuki, E-mail: kazuyuki.sakaue@aoni.waseda.jp [Waseda Institute for Advanced Study, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Washio, Masakazu [Research Institute for Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Miura, Taisuke, E-mail: miura@fzu.cz [HiLASE Centre, Institute of Physics CAS, Za radnicí 828, 252 41, Dolní Břežany (Czech Republic); Takahashi, Akihiko [Department of Health Sciences, Faculty of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Fukuoka 812-8582 (Japan); Nakamura, Daisuke; Okada, Tatsuo [Graduate School of Information Sciences and Electrical Engineering, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395 (Japan)
2015-08-24
We demonstrated the generation of the intense radially polarized mid-infrared optical vortex at a wavelength of 10.6 μm by use of a passive axially symmetric zinc selenide (ZnSe) waveplate with high energy pulse throughput. The phase of the radially polarized optical vortex with the degree of polarization of 0.95 was spirally distributed in regard to the angle. The converted laser beam energy of about 2.6 mJ per pulse was obtained at the input pulse energy of 4.9 mJ, corresponding to the energy conversion efficiency of 56%.
International Nuclear Information System (INIS)
We demonstrated the generation of the intense radially polarized mid-infrared optical vortex at a wavelength of 10.6 μm by use of a passive axially symmetric zinc selenide (ZnSe) waveplate with high energy pulse throughput. The phase of the radially polarized optical vortex with the degree of polarization of 0.95 was spirally distributed in regard to the angle. The converted laser beam energy of about 2.6 mJ per pulse was obtained at the input pulse energy of 4.9 mJ, corresponding to the energy conversion efficiency of 56%
Ordinary versus PT-symmetric $\\phi^3$ quantum field theory
Bender, Carl M.; Branchina, V.; Messina, Emanuele
2012-01-01
A quantum-mechanical theory is PT-symmetric if it is described by a Hamiltonian that commutes with PT, where the operator P performs space reflection and the operator T performs time reversal. A PT-symmetric Hamiltonian often has a parametric region of unbroken PT symmetry in which the energy eigenvalues are all real. There may also be a region of broken PT symmetry in which some of the eigenvalues are complex. These regions are separated by a phase transition that has been repeatedly observe...
Spherically-symmetric gravitational fields in the metric-affine gauge theory of gravitation
Minkevich, A. V.; Vasilevski, Yu. G.
2003-01-01
Geometric structure of spherically-symmetric space-time in metric-affine gauge theory of gravity is studied. Restrictions on curvature tensor and Bianchi identities are obtained. By using certain simple gravitational Lagrangian the solution of gravitational equations for vacuum spherically-symmetric gravitational field is obtained.
Survey results for oblique field magnetic flux leakage survey in comparison to axial field
Energy Technology Data Exchange (ETDEWEB)
Simek, James [T.D. Williamson, Inc., Tulsa, OK (United States)
2012-07-01
Pipeline operators worldwide have implemented integrity management programs in an effort to improve operation and maintenance efficiency along with continued safe operation of pipeline systems. Several types of monitoring and data collection activities are incorporated into these programs, with in line inspection (ILI) tools providing data for detection and quantification of features that may impact the integrity of the pipeline system. Magnetic flux leakage (MFL) ILI tools are among the most widely used in pipeline systems. Primarily used for metal loss detection and quantification, these tools are extremely robust, performing successfully in the harsh environments found in operating pipelines, with the majority of MFL tools in service today relying upon axially oriented magnetic fields. For feature classes whose principal axis is aligned parallel to the pipe axis, the use of an axially applied magnetic field may quite often result in decreased performance due to difficulties in detection and sizing. Through the use of fields applied either perpendicular or in an oblique direction to the principal axis, the magnetic leakage levels generated at feature locations are increased, providing usable signal levels. When used concurrently with an axially oriented magnetizer, an obliquely applied magnetic field may provide the ability to detect, quantify, or otherwise aid in discrimination of volumetric versus non-volumetric features. Providing the ability to collect both of these data sets in a single survey would allow operators to minimize the number of surveys required to address all categories of metal loss features that may be present within pipeline systems. This paper will discuss some of the variables that affect detection and sizing of metal loss zones with respect to the applied field direction, including graphs and tables to quantify the effects of angular displacement for specific feature shapes. Several classes of features have been chosen for evaluation
Axial distribution of absorbed doses in fast neutron field at the RB reactor
International Nuclear Information System (INIS)
The coupled fast thermal system CFTS at the RB reactor is created for obtaining fast neutron fields. The axial distribution of fast neutron flux density in its second configuration (CFTS-2) is measured. The axial distribution of absorbed doses is computed on the basis of mentioned experimental results. At the end these experimental and computed results are given. (Author)
Axial shock wave heating of reversed-field theta-pinch plasmas
International Nuclear Information System (INIS)
Reversed-field theta pinches are known to contract rapidly in the axial direction soon after the radial implosion. Under certain conditions the axial implosion can be quite strong. A model is described which simulates both the radial and axial implosions. Among the important features included are realistic plasma density profiles, and current-driven anomalous transport. Given input parameters such as initial fill pressure, bias magnetic field, coil size, applied voltage (or electric field) and compression magnetic field, the model predicts the final plasma temperature, density, radial and axial dimensions, trapped magnetic flux and fraction of particles trapped within the separatrix. The results indicate very strong axial shock heating for high bias field, which leads to temperatures up to several times that predicted for simple field-free plasmas. The model is applied to parameters charcteristic of two recent experiments, and several features of the calculated results are shown to be consistent with experimental observations. It is also applied to a fusion reactor scale plasma: as a result of strong axial shock heating, the model predicts that fusion ignition (e.g., a temperature of 8 keV) can be achieved without resort to large electric field or large magnetic compression
Principal parametric resonance of axially accelerating rectangular thin plate in magnetic field
Institute of Scientific and Technical Information of China (English)
胡宇达; 张金志
2013-01-01
Nonlinear parametric vibration and stability is investigated for an axially accelerating rectangular thin plate subjected to parametric excitations resulting from the axial time-varying tension and axial time-varying speed in the magnetic field. Consid-ering geometric nonlinearity, based on the expressions of total kinetic energy, potential energy, and electromagnetic force, the nonlinear magneto-elastic vibration equations of axially moving rectangular thin plate are derived by using the Hamilton principle. Based on displacement mode hypothesis, by using the Galerkin method, the nonlinear para-metric oscillation equation of the axially moving rectangular thin plate with four simply supported edges in the transverse magnetic field is obtained. The nonlinear principal parametric resonance amplitude-frequency equation is further derived by means of the multiple-scale method. The stability of the steady-state solution is also discussed, and the critical condition of stability is determined. As numerical examples for an axially moving rectangular thin plate, the influences of the detuning parameter, axial speed, axial tension, and magnetic induction intensity on the principal parametric resonance behavior are investigated.
Flow field determination at axial pump impeller tip section
International Nuclear Information System (INIS)
In most applications the principal limitation on the performance of an axial-flow pump is its cavitation-free operating range, characterized by the nett positive suction head (NPSH). The adverse effects of cavitation are not restricted to impaired performance; noise and vibration levels tend to increase and mechanical integrity of components can be jeopardised, sometimes severely. Cavitation may occur in the inlet region or, in some instances, in the stator blades; however the most usual source of cavitation occurrence is the impeller blading, specifically the tip section
Seiberg Witten Map and the Axial Anomaly in Noncommutative Field Theory
Banerjee, Rabin; Ghosh, Subir
2001-01-01
Using the point-splitting regularisation, we calculate the axial anomaly in an arbitrary even dimensional Non-Commutative (NC) field theory. Our result is (star) gauge invariant in its {\\it unintegrated} form, to the leading order in the NC parameter. Exploiting the Seiberg Witten map, this result gets transformed to the familiar Adler-Bell-Jackiw anomaly in ordinary space-time. Furthermore, using this map, we derive an expression for the unintegrated axial anomaly for constant fields in NC s...
Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures
Tian, Xiaorui; Sun, Mengtao
2015-01-01
Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of...
The Influence of the Axial Magnetic Field Upon-the Coaxial Plasma Gun Parameters
International Nuclear Information System (INIS)
This study concerns with the influence of an applied axial magnetic field upon the electrical parameters of a coaxial plasma gun device. The experimental results are investigated with 0.5 KJ plasma gun device operated with argon gas at a pressure of 3.5 Torr. An axial time independent magnetic field with intensity of 550 G is introduced along the plasma current sheath axial region, within the annular space between the two coaxial electrodes. From the measurements of the discharge current I(t) and the voltage V(t), the electrical discharge parameters of the plasma gun device and the plasma current sheath implosion velocity are estimated, in normal mode of plasma gun operation and in the mode of presence external axial magnetic field. A comparison between these two modes is studied
Dyons in presence of gravitation and symmetrized field equations
International Nuclear Information System (INIS)
Combined theory of gravitation and electromagnetism associated with particles carrying electric and magnetic charges has been established from an invariant action principle. Corresponding field equations, equation of motion and Einstein Maxwell's equations are obtained in unique and consistent way. It is shown that weak field approximation of slowly moving particle in gravitational field leads the symmetry between electromagnetic and linear gravitational fields. Postulation of the existence of gravimagnetic monopole leads structural symmetry between generalized electromagnetic and gravielectromagnetic fields. Corresponding quantization conditions and angular momentum are also analysed. (author)
International Nuclear Information System (INIS)
Methodology for 3-D calculation analysis of nuclear reactor cell with axial symmetry and finite mesh step is described. This methodology is based on the axial leakage calculation analysis method that has been developed for nuclear reactor with closed lattice like VVER-type. The trial functions that are used at full core level of nuclear reactor calculation analysis are defined. Analytical solutions of two-group diffusion equation with 'symmetrical' and 'cross' boundary conditions are given. Two-group cell characteristics that are matrixes of boundary values of these functions have been calculated. Calculated values of these matrixes have been analyzed in dependence on the step mesh along Z(axis) value. These results show that if step mesh along Z-axis is enough small then diagonal elements are closed to initial diffusion parameters of the cell and not diagonal elements that are corrections caused by curvature of neutron flux can be neglected. But in contrary, if step mesh is more than diffusion length then these corrections are essential and they should be taken into account at full core calculation analysis level. These methodology can be used in full core nuclear reactor calculation with Surface Value System with finite step mesh along Z-axis. (authors)
The gravitational field energy density for symmetrical and asymmetrical systems
Sosnovskiy, Roald
2006-01-01
The relativistic theory of gravitation has the considerable difficulties by description of the gravitational field energy. Pseudotensor t00 in the some cases cannot be interpreted as energy density of the gravitational field. In [1] the approach was proposed, which allow to express the energy density of such a field through the components of a metric tensor. This approach based on the consideration of the isothermal compression of the layer consisted of the incoherent matter. It was employ to...
Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures.
Tian, Xiaorui; Fang, Yurui; Sun, Mengtao
2015-01-01
Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule. PMID:26621558
Research on an Axial Magnetic-Field-Modulated Brushless Double Rotor Machine
Bin Yu; Chengde Tong; Zhiyi Song; Jingang Bai; Ping Zheng
2013-01-01
Double rotor machine, an electronic continuously variable transmission, has great potential in application of hybrid electric vehicles (HEVs), wind power and marine propulsion. In this paper, an axial magnetic-field-modulated brushless double rotor machine (MFM-BDRM), which can realize the speed decoupling between the shaft of the modulating ring rotor and that of the permanent magnet rotor is proposed. Without brushes and slip rings, the axial MFM-BDRM offers significant advantages such as e...
Spherically symmetric static solutions of source free SU(2) gauge field equations
International Nuclear Information System (INIS)
The complete set of solutions of spherically symmetric static SU(2) gauge field equations without sources and with boundary conditions corresponding to localized energy is investigated. The nontrivial solutions corresponding to the variety of all possible field configurations are discussed. Numerical result are given. (author)
Axial acoustic radiation force on a sphere in Gaussian field
International Nuclear Information System (INIS)
Based on the finite series method, the acoustical radiation force resulting from a Gaussian beam incident on a spherical object is investigated analytically. When the position of the particles deviating from the center of the beam, the Gaussian beam is expanded as a spherical function at the center of the particles and the expanded coefficients of the Gaussian beam is calculated. The analytical expression of the acoustic radiation force on spherical particles deviating from the Gaussian beam center is deduced. The acoustic radiation force affected by the acoustic frequency and the offset distance from the Gaussian beam center is investigated. Results have been presented for Gaussian beams with different wavelengths and it has been shown that the interaction of a Gaussian beam with a sphere can result in attractive axial force under specific operational conditions. Results indicate the capability of manipulating and separating spherical spheres based on their mechanical and acoustical properties, the results provided here may provide a theoretical basis for development of single-beam acoustical tweezers
Rotation of the vector velocity field in a symmetric sunspot
Czech Academy of Sciences Publication Activity Database
Klvaňa, Miroslav; Bumba, Václav
Noordwijk : ESA Publication Division, 2002 - (Sawaya-Lacoste, H.), s. 135-138 [Solar Cycle and Space Weather Euroconference /2./. Vico Equense (IT), 24.09.2001-29.09.2001] R&D Projects: GA ČR GA205/01/0658; GA AV ČR IAA3003903 Institutional research plan: CEZ:AV0Z1003909 Keywords : sun * vector velocity * field Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Motion of relativistic particles in axially symmetric and perturbed magnetic fields in a tokamak
de Rover, M.; Cardozo, N. J. L.; Montvai, A.
1996-01-01
An extensive comparison is given between an analytical theory for the computations of particle orbits of relativistic runaway electrons [M. de Rover et al., Phys. Plasmas 3, 4468 (1996)], and numerical simulations. A new numerical scheme is used for the computer simulations of guiding center orbits.
Rahaman, Anisur
2016-01-01
The generalized version of a lower dimensional model where vector and axial vector interaction get mixed up with different weight is considered. The bosonized version of which does not posses the local gauge symmetry. An attempt has been made here to construct BRST invariant reformulation of this model using Batalin Fradlin and Vilkovisky formalism. It is found that the extra field needed to make it gauge invariant turns into Wess-Zumino scalar with appropriate choice of gauge fixing. An application of finite field dependent BRST and anti-BRST transformation is also made here in order to show the transmutation between the BRST symmetric and the usual non-symmetric version of the model.
Modeling of a poloidally symmetric toroidal field divertor in a reversed--field-pinch plasma machine
International Nuclear Information System (INIS)
Magnetic divertors have been shown to be successful in minimizing plasma-wall interactions and in leading to high confinement regimes in Tokamaks. This leads to the hope that similar benefits may occur in an Reversed-Field-Pinch (RPF) fitted with a divertor. Previous experiments using divertors in a RFP have used a poloidal field divertor configuration such as is used in Tokamaks. This study investigates another approach; namely a toroidal field divertor. In this study a simple model of a poloidally symmetric toroidal field divertor is developed and used in a study of stochastic effects due to the divertor and in a 3-D magnetohydrodynamic (MHD) code to study the response of the plasma to the large poloidal m = 0 perturbations caused by the divertor coils. It is found that the topology of the RFP-divertor system is much more complex than had been expected. Stochasticity is enhanced in the outer edge region of the plasma because of this geometrical complexity. The way of the RFP reaches an equilibrium in this complex system is investigated with the 3-D relaxation code, DEBS (authored by Dalton Schnack). This code showed that the divertor will not hinder the formation of a reversed toroidal field in the plasma, and that the dynamics of its formation is altered when toroidal effects are considered. The plasma develops flows and currents in the throat of the divertor in response to the vacuum-like divertor fields. These flows and currents help to restore the force free character of the plasma
From $\\mathcal{PT}$ -symmetric quantum mechanics to conformal field theory
Indian Academy of Sciences (India)
Patrick Dorey; Clare Dunning; Roberto Tateo
2009-08-01
One of the simplest examples of a $\\mathcal{PT}$-symmetric quantum system is the scaling Yang–Lee model, a quantum field theory with cubic interaction and purely imaginary coupling. We give a historical review of some facts about this model in ≤ 2 dimensions, from its original definition in connection with phase transitions in the Ising model and its relevance to polymer physics, to the role it has played in studies of integrable quantum field theory and $\\mathcal{PT}$-symmetric quantum mechanics. We also discuss some more general results on $\\mathcal{PT}$-symmetric quantum mechanics and the ODE/IM correspondence, and mention applications to magnetic systems and cold atom physics.
Directory of Open Access Journals (Sweden)
Girishwar Nath
1970-10-01
Full Text Available A closed form solution of the Navier-Stokes equations has been obtained in the case of steady axisymmetric flow of an incompressible electrically conducting viscous fluid between two concentric rotating cylinders composed of an insulating material under the influence of radial magnetic field. It has been found that the velocity components are less than those of the classical hydrodynamic case. In the presence of the magnetic field, the tangential velocity becomes fully developed in a smaller axial distance than in the absence of the magnetic field. For small Reynolds number, the fully developed tangential velocity is achieved in a small axial distance, but it requires greater axial distance for large Reynolds number.
Axial-field permanent magnet motors for electric vehicles
Campbell, P.
1981-01-01
The modelling of an anisotropic alnico magnet for the purpose of field computation involves assigning a value for the material's permeability in the transverse direction. This is generally based upon the preferred direction properties, being all that are easily available. By analyzing the rotation of intrinsic magnetization due to the self demagnetizing field, it is shown that the common assumptions relating the transverse to the preferred direction are not accurate. Transverse magnetization characteristics are needed, and these are given for Alnico 5, 5-7, and 8 magnets, yielding appropriate permeability values.
Institute of Scientific and Technical Information of China (English)
Gamal G.L. Nashed
2011-01-01
A theory of (4+1)-dimensional gravity is developed on the basis of the teleparallel theory equivalent to general relativity.The fundamental gravitational field variables are the five-dimensional vector fields (pentad),defined globally on a manifold M,and gravity is attributed to the torsion.The Lagrangian density is quadratic in the torsion tensor.We then give the exact five-dimensional solution.The solution is a generalization of the familiar Schwarzschild and Kerr solutions of the four-dimensional teleparallel equivalent of general relativity.We also use the definition of the gravitational energy to calculate the energy and the spatial momentum.
Nongeocentric axial dipole field behavior during the Mono Lake excursion
Negrini, Robert M.; McCuan, Daniel T.; Horton, Robert A.; Lopez, James D.; Cassata, William S.; Channell, James E. T.; Verosub, Kenneth L.; Knott, Jeffrey R.; Coe, Robert S.; Liddicoat, Joseph C.; Lund, Steven P.; Benson, Larry V.; Sarna-Wojcicki, Andrei M.
2014-04-01
A new record of the Mono Lake excursion (MLE) is reported from the Summer Lake Basin of Oregon, USA. Sediment magnetic properties indicate magnetite as the magnetization carrier and imply suitability of the sediments as accurate recorders of the magnetic field including relative paleointensity (RPI) variations. The magnitudes and phases of the declination, inclination, and RPI components of the new record correlate well with other coeval but lower resolution records from western North America including records from the Wilson Creek Formation exposed around Mono Lake. The virtual geomagnetic pole (VGP) path of the new record is similar to that from another high-resolution record of the MLE from Ocean Drilling Program (ODP) Site 919 in the Irminger Basin between Iceland and Greenland but different from the VGP path for the Laschamp excursion (LE), including that found lower in the ODP-919 core. Thus, the prominent excursion recorded at Mono Lake, California, is not the LE but rather one that is several thousands of years younger. The MLE VGP path contains clusters, the locations of which coincide with nonaxial dipole features found in the Holocene geomagnetic field. The clusters are occupied in the same time progression by VGPs from Summer Lake and the Irminger Basin, but the phase of occupation is offset, a behavior that suggests time-transgressive decay and return of the principal field components at the beginning and end of the MLE, respectively, leaving the nonaxial dipole features associated with the clusters dominant during the excursion.
A New Semi-Symmetric Uniﬁed Field Theory of the Classical Fields of Gravity and Electromagnetism
Directory of Open Access Journals (Sweden)
Suhendro I.
2007-10-01
Full Text Available We attempt to present a classical theoretical framework in which the gravitational and electromagnetic fields are unified as intrinsic geometric objects in the space-time manifold. For this purpose, we first present the preliminary geometric considerations dealing with the metric differential geometry of Cartan connections. The unified field theory is then developed as an extension of the general theory of relativity based on a semi- symmetric Cartan connection which is meant to be as close as possible structurally to the symmetric connection of the Einstein-Riemann space-time.
Pradhan, Anirudh; Yadav, A K
2007-01-01
A plane-symmetric inhomogeneous cosmological model of perfect fluid distribution with electro-magnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. $F_{12}$ is the non-vanishing component of electromagnetic field tensor. To get a deterministic solution, we assume the free gravitational field is Petrov type-II non-degenerate. The behaviour of the electro-magnetic field tensor together with some physical aspects of the model are also discussed.
Axial magnetic field generation by intense circularly polarized laser pulses in underdense plasmas
International Nuclear Information System (INIS)
Axial magnetic field generation by intense circularly polarized laser beams in underdense plasmas has been studied with three-dimensional particle-in-cell simulations and by means of theoretical analysis. Comparisons between analytical models and simulation results have identified an inverse Faraday effect as the main mechanism of the magnetic field generation in inhomogeneous plasmas. The source of azimuthal nonlinear currents and of the axial magnetic field depends on the transverse inhomogeneities of the electron density and laser intensity. The fields reach a maximum strength of several tens of megagauss for laser pulses undergoing relativistic self-focusing and channeling in moderately relativistic regime. Ultrarelativistic laser conditions inhibit magnetic field generation by directly reducing a source term and by generating fully evacuated plasma channels.
International Nuclear Information System (INIS)
The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev et al., Phys. Plasmas 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.
Parallax error in long-axial field-of-view PET scanners—a simulation study
Schmall, Jeffrey P.; Karp, Joel S.; Werner, Matt; Surti, Suleman
2016-07-01
There is a growing interest in the design and construction of a PET scanner with a very long axial extent. One critical design challenge is the impact of the long axial extent on the scanner spatial resolution properties. In this work, we characterize the effect of parallax error in PET system designs having an axial field-of-view (FOV) of 198 cm (total-body PET scanner) using fully-3D Monte Carlo simulations. Two different scintillation materials were studied: LSO and LaBr3. The crystal size in both cases was 4 × 4 × 20 mm3. Several different depth-of-interaction (DOI) encoding techniques were investigated to characterize the improvement in spatial resolution when using a DOI capable detector. To measure spatial resolution we simulated point sources in a warm background in the center of the imaging FOV, where the effects of axial parallax are largest, and at several positions radially offset from the center. Using a line-of-response based ordered-subset expectation maximization reconstruction algorithm we found that the axial resolution in an LSO scanner degrades from 4.8 mm to 5.7 mm (full width at half max) at the center of the imaging FOV when extending the axial acceptance angle (α) from ±12° (corresponding to an axial FOV of 18 cm) to the maximum of ±67°—a similar result was obtained with LaBr3, in which the axial resolution degraded from 5.3 mm to 6.1 mm. For comparison we also measured the degradation due to radial parallax error in the transverse imaging FOV; the transverse resolution, averaging radial and tangential directions, of an LSO scanner was degraded from 4.9 mm to 7.7 mm, for a measurement at the center of the scanner compared to a measurement with a radial offset of 23 cm. Simulations of a DOI detector design improved the spatial resolution in all dimensions. The axial resolution in the LSO-based scanner, with α = ± 67°, was improved from 5.7 mm to 5.0 mm by
International Nuclear Information System (INIS)
The spinning particle is studied, interacting in a supersymmetric and gauge invariant way with anti-symmetric non-abelian tensor fields. A quantum theory is presented. The Witten index is calculated for the corresponding Dirac operator and it is concluded that the anti- symmetric non-abelian tensor fields do not give any contribution to it. (author). 7 refs
Anti-symmetric tensor matter fields and non-linear σ-model
International Nuclear Information System (INIS)
The equivalence between rank-2 anti-symmetric tensor fields, considered as gauge potentials, and torsionless non-linear σ-models suggests us to study the possibility of coupling tensorial matter with Yang-Mills fields, thorough the gauging of the isometries of the target space. We show that this coupling is actually possible; however the matter appears no longer as an elementary field, but rather as a composite one, expressed in terms of the bosonic degrees of freedom of the σ-model. A possible phenomenological application is presented that describes the interactions among vector mesons in terms of the geometrical properties of the target manifold. Also, spin-2 meson resonances may naturally be accommodated whenever the σ-model's target manifold is non-symmetric. (author)
International Nuclear Information System (INIS)
The design of rf accelerating structures nowadays is largely based on mesh-codes that solve for fields and eigenfrequencies in arbitrarily shaped cavities. The most developed codes deal with structures of cylindrical symmetry. However, no program is available that can solve for fields with azimuthal variation in cavities with dielectric and/or permeable insertions. Here we describe a discretization method using an 'orthogonal triangular double grid'. The special mesh and the FIT-discretization enable the treatment of cavities and waveguides with arbitrary material insertions and combines the features of SUPERFISH (triangular mesh, rotationally symmetric fields) and URMEL (rectangular mesh but fields with or without azimuthal variation). (orig.)
International Nuclear Information System (INIS)
The design of rf accelerating structures nowadays is largely based on mesh codes that solve for fields and eigenfrequencies in arbitrarily shaped cavities. The most developed codes deal with structures of cylindrical symmetry. However, no program is available that can solve for fields with azimuthal variation in cavities with dielectric and/or permeable insertions. Here we describe a discretization method using an 'orthogonal triangular double grid'. The special mesh and the FIT discretization allow the treatment of cavities and waveguides with arbitrary material insertions and combines the features of SUPERFISH (triangular mesh, rotationally symmetric fields) and URMEL (rectangular mesh but fields with or without azimuthal variation). (author)
Spherically Symmetric Solutions of the Einstein-Bach Equations and a Consistent Spin-2 Field Theory
International Nuclear Information System (INIS)
We briefly present a relationship between General Relativity coupled to certain spin-0 and spin-2 field theories and higher derivatives metric theories of gravity. In a special case, described by the Einstein-Bach equations, the spin-0 field drops out from the theory and we obtain a consistent spin-two field theory interacting gravitationally, which overcomes a well known inconsistency of the theory for a linear spin-two field coupled to the Einstein's gravity. Then we discuss basic properties of static spherically symmetric solutions of the Einstein-Bach equations. (author)
Resonant slow extraction in synchrotrons by using anti-symmetric sextupole fields
Zou, Ye; Yang, Jianquan
2016-01-01
This paper proposes a novel method for resonant slow extraction in synchrotrons by using special anti-symmetric sextupole fields, which can be produced by a special magnet structure. The method has the potential in applications demanding for very stable slow extraction from synchrotrons. Our studies show that the slow extraction at the half-integer resonance by using anti-symmetric sextupole field has some advantages compared to the normal sextupole field, and the latter is widely used in the slow extraction method. One of them is that it can work at a more distant tune from the resonance, so that it can reduce significantly the intensity variation of the extracted beam which is mainly caused by the ripples of magnet power supplies. The studies by both the Hamiltonian theory and numerical simulations show that the stable region at the proximity of the half-integer resonance by anti-symmetric sextupole field is much smaller and flatter than the one by standard sextupole field at the third-order resonance. By g...
The Influence of the Axial Magnetic Field Upon- the Coaxial Plasma Gun Parameters
International Nuclear Information System (INIS)
This study concerns with the influence of an applied axial magnetic field upon the electrical parameters and on the brightness (luminance) of argon plasma. The brightness was measured by with a photomultiplier type of IP28 RCA. The experimental results are investigated with plasma gun device operated with argon gas at a pressure of 3.5 Torr. An axial time independent magnetic field with intensity of 550 G is introduced along the plasma current sheath axial region, within the annular space between the two coaxial electrodes. From the measurements of the discharge current I(t) and the voltage V(t), the electrical discharge parameters of the plasma gun device and the plasma current sheath implosion velocity are estimated, in normal mode of plasma gun operation and in the mode of presence external axial magnetic field. A comparison between these two modes is studied. It was found that the thickness of skin-layer δ about 0.01 cm and the wavelength λ, of the perturbation about 1.3 cm i.e. the instability has been satisfied. The growth rate γ of the instability about 106 sec-1. (author)
Energy Technology Data Exchange (ETDEWEB)
Hamann, F., E-mail: franck.hamann@cea.fr; Combis, P.; Videau, L. [CEA, DAM, DIF, F-91297 Arpajon (France)
2015-08-15
The one-dimensional magnetohydrodynamics of a plasma cylindrical liner is addressed in the case of a two components magnetic field. The azimuthal component is responsible for the implosion of the liner and the axial field is compressed inside the liner. A complete set of analytical profiles for the magnetic field components, the density, and the local velocity are proposed at the scale of the liner thickness. Numerical simulations are also presented to test the validity of the analytical formulas.
International Nuclear Information System (INIS)
The one-dimensional magnetohydrodynamics of a plasma cylindrical liner is addressed in the case of a two components magnetic field. The azimuthal component is responsible for the implosion of the liner and the axial field is compressed inside the liner. A complete set of analytical profiles for the magnetic field components, the density, and the local velocity are proposed at the scale of the liner thickness. Numerical simulations are also presented to test the validity of the analytical formulas
Effective field calculations of the energy spectrum of the PT-symmetric (-x4) potential
Shalaby, Abouzeid M.
2009-03-01
In this work, we show that the traditional effective field approach can be applied to the PT-symmetric wrong sign (-x4) quartic potential. The importance of this work lies in the possibility of its extension to the more important PT-symmetric quantum field theory while the other approaches which use complex contours are not willing to be applicable. We calculated the effective potential of the massless -x4 theory as well as the full spectrum of the theory. Although the calculations are carried out up to first order in the coupling, the predicted spectrum is very close to the exact one taken from other works. The most important result of this work is that the effective potential obtained, which is equivalent to the Gaussian effective potential, is bounded from below while the classical potential is bounded from above. This explains the stability of the vacuum of the theory. The obtained quasiparticle Hamiltonian is non-Hermitian but PT symmetric and we showed that the calculation of the metric operator can go perturbatively. In fact, the calculation of the metric operator can be done even for higher dimensions (quantum field theory) which, up until now, cannot be calculated in the other approaches either perturbatively or in a closed form due to the possible appearance of field radicals. Moreover, we argued that the effective theory is perturbative for the whole range of the coupling constant and the perturbation series is expected to converge rapidly (the effective coupling geff=(1)/(6)).
Effective field calculations of the energy spectrum of the PT-symmetric (-x4) potential
International Nuclear Information System (INIS)
In this work, we show that the traditional effective field approach can be applied to the PT-symmetric wrong sign (-x4) quartic potential. The importance of this work lies in the possibility of its extension to the more important PT-symmetric quantum field theory while the other approaches which use complex contours are not willing to be applicable. We calculated the effective potential of the massless -x4 theory as well as the full spectrum of the theory. Although the calculations are carried out up to first order in the coupling, the predicted spectrum is very close to the exact one taken from other works. The most important result of this work is that the effective potential obtained, which is equivalent to the Gaussian effective potential, is bounded from below while the classical potential is bounded from above. This explains the stability of the vacuum of the theory. The obtained quasiparticle Hamiltonian is non-Hermitian but PT symmetric and we showed that the calculation of the metric operator can go perturbatively. In fact, the calculation of the metric operator can be done even for higher dimensions (quantum field theory) which, up until now, cannot be calculated in the other approaches either perturbatively or in a closed form due to the possible appearance of field radicals. Moreover, we argued that the effective theory is perturbative for the whole range of the coupling constant and the perturbation series is expected to converge rapidly (the effective coupling geff=(1/6)).
Ma, Hui; Wang, Jianhua; Liu, Zhiyuan; Geng, Yingsan; Wang, Zhenxing; Yan, Jing
2016-06-01
The objective of this work is to reveal the effects of an axial magnetic field (AMF) on the vacuum arc characteristics between transverse magnetic field (TMF) contacts. These vacuum arc characteristics include the vacuum arcing behavior and the arc voltage waveform. In the experiments, an external AMF was applied to a pair of TMF contacts. The external AMF flux density BAMF can be adjusted from 0 to 110 mT. The arc current in the tests varied over a range from 0 to 20 kA rms at 45 Hz. The contact material was CuCr25 (25% Cr). A high-speed charge-coupled device video camera was used to record the vacuum arc evolution. The experimental results show that the application of the AMF effectively reduces the TMF arc voltage noise component and reduces the formation of liquid metal drops between the contacts. The diffuse arc duration increases linearly with increasing AMF flux density, but it also decreases linearly with increasing arc current under application of the external AMF. The results also indicate that the diffuse arc duration before the current zero is usually more than 1 ms under the condition that the value of the AMF per kiloampere is more than 2.0 mT/kA. Finally, under application of the AMF, the arc column of the TMF contacts may constrict and remain in the center region without transverse rotation. Therefore, the combined TMF-AMF contacts should be designed such that they guarantee that the AMF is not so strong as to oppose transverse rotation of the arc column.
Axial preloading of a 20 TESLA prototype of a single turn Tokamak toroidal field coil
International Nuclear Information System (INIS)
An axial preloading system has been designed and built as part of the 0.06 scale prototype toroidal field (TF) magnet for the IGNITEX experiment. In the prototype TF coil, as in the full size IGNITEX tokamak, the peak stresses in the inner leg during discharge are made more isotropic (hence the von Mises stress intensity is lowered) through axial preloading. Although preliminary (nonpreloaded) tests of the TF magnet should produce fields as high as 15 T, preloading will permit demonstration of the high (20 T) on-axis magnetic field to be achieved in the IGNITEX device. The preloading system for the prototype is a hydraulic press capable of a load of 580 tons. The press is designed with a short stroke which takes the press from a condition of noncontact to full preloading. During the magnet's pulse and subsequent thermal growth, the hydraulic system of the press maintains the preload force
Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field
Energy Technology Data Exchange (ETDEWEB)
Oikawa, Kohei, E-mail: oikawa@ecei.tohoku.ac.jp; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)
2014-02-15
Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ∼350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ∼10{sup 19} m{sup −3} near the source exit and ∼10{sup 18} m{sup −3} near the magnetic filter can be obtained, which are higher than those with the solenoids.
Partially conserved axial-vector current and model chiral field theories in nuclear physics
International Nuclear Information System (INIS)
We comment on the relation between the two standard approaches to chiral symmetry--namely, the current algebra/partially conserved axial-vector current approach and the chiral Lagrangian method--in a manner intended to clarify recent and probable future applications of this symmetry in nuclear physics. Specifically, we show that in explicit chiral field theories the canonical πN scattering amplitude does not have the famed ''Adler zero'' unless partial conservation of axial-vector current holds as an operator equation. This implies that there are a number of familiar chiral models in which the ''Adler self-consistency'' condition does not apply to the canonical pion field. Among the problems of current interest for which our remarks are relevant are the studies of the pion-nucleus optical potential, pion condensation, and the attempts to formulate a model field theory having both reasonable nuclear saturation and good low energy pion phenomenology
Energy Technology Data Exchange (ETDEWEB)
Kostov, K.G.; Nikolov, N.A. (Department of General Physics, Sofia University, Sofia 1126 (Bulgaria))
1994-04-01
The operation of a virtual cathode oscillator (vircator) with strong axial magnetic field has been experimentally studied. Depending on the cathode--anode gap and cathode diameter, the operating voltage varies from 200 kV up to 480 kV with 2--7 kA diode current. Microwave emission is produced by the oscillating virtual cathode. The central microwave frequency follows the beam plasma frequency. It varies by 11.5 GHz up to 22 GHz, depending on the current density. The oscillation frequency does not depend on the guide magnetic field magnitude. A maximal output power of 15[plus minus]5 MW in asymmetric transverse magnetic (TM) modes is achieved by the axially extracted vircator. Variation of the magnetic field intensity in a range of 0--40 kG has an insignificant effect upon the emitted microwave power. An electron beam power to microwave power conversion efficiency of approximately 1% is obtained.
International Nuclear Information System (INIS)
The operation of a virtual cathode oscillator (vircator) with strong axial magnetic field has been experimentally studied. Depending on the cathode--anode gap and cathode diameter, the operating voltage varies from 200 kV up to 480 kV with 2--7 kA diode current. Microwave emission is produced by the oscillating virtual cathode. The central microwave frequency follows the beam plasma frequency. It varies by 11.5 GHz up to 22 GHz, depending on the current density. The oscillation frequency does not depend on the guide magnetic field magnitude. A maximal output power of 15±5 MW in asymmetric transverse magnetic (TM) modes is achieved by the axially extracted vircator. Variation of the magnetic field intensity in a range of 0--40 kG has an insignificant effect upon the emitted microwave power. An electron beam power to microwave power conversion efficiency of approximately 1% is obtained
Effect of axial magnetic field on axicon laser-induced electron acceleration
Kant, Niti; Rajput, Jyoti; Giri, Pankaj; Singh, Arvinder
2016-03-01
Radially polarized axicon Gaussian laser-induced electron acceleration has been studied under the influence of axial magnetic field. Employing an axicon is a significant method to generate a focused and diffraction free radially polarized laser beam. We have investigated direct electron acceleration in vacuum by employing a relativistic single particle simulation. It is observed that the net electron energy gain from the axicon Gaussian radially polarized laser beam can be enhanced under the influence of time varying axial magnetic field. This additional effect of the magnetic field reveals the fact that multi GeV energy gain can be achieved without the use of petawatt power lasers. Effect of laser initial intensity, initial spot size, initial phase, pulse duration and initial energy are taken into consideration for efficient electron acceleration up to GeV energies.
Batista, Milan; Jakomin, Marko; Kosel, Franc; Kosel, Tadej
2006-01-01
The paper deals with the stresses, strains and buckling conditions in thin, axially symmetric, shallow, bimetallic shells. Based on third-order theory, which takes into account the equilibrium state of the forces and moments that are acting on the deformed system, the paper presents a model with a mathematical description of the geometry of the system, the stresses, the thermoelastic strains and the displacements. The mathematical formulation is based on the theory of large displacements. As ...
Experimental investigation of axial plasma injection into a magnetic dipole field
DEFF Research Database (Denmark)
Jensen, Vagn Orla
1968-01-01
A high-density helium plasma, accelerated from a conical pinch, is injected axially into a magnetic dipole field. Magnetic probe measurements show that, near the axis, a compression of the field is super-imposed on the standard diamagnetic depression. The compression starts downstream and moves...... towards the injector. Simultaneously with the compression, an increase in the electron temperature and reflection of a small amount of plasma are seen. The amount of plasma transmitted through the dipole field is found to be nearly independent of the field strength....
Spherically symmetric fields in Rosen's bimetric theories of gravitation
Energy Technology Data Exchange (ETDEWEB)
Israelit, M. (University of Haifa, School of Education of the Kibbutz Movement, Oranim, P.O. Kiryat Tivon, Israel)
1981-07-01
By means of bimetric Killing vectors two spherically symmetric fields are investigated: (i) the time-dependent one in Rosen's flat-background bimetric theory; and (ii) the energy-preserving in Rosen's cosmological-background bimetric theory with k = 1. In the first case a wave behavior of the field is present. In the second case a time evolution is obtained for fields, created by insular systems of constant energy. These phenomena are typical for bimetric theories of gravitation.
Influence of axial self-magnetic field component on arcing behavior of spiral-shaped contacts
International Nuclear Information System (INIS)
The transverse magnetic field (TMF) contact design is commonly used in vacuum interrupters. When arcing occurs between the TMF contacts, the contact structure can create a self-induced magnetic field that drives the arc to move and rotate on the contact, and thus local overheating and severe erosion can be avoided. However, TMF contacts could also create an axial self-magnetic component, and the influence of this component on the arc behavior has not been considered to date. In this paper, five different types of Cu-Cr spiral-shaped TMF contacts with three different structures are investigated in a demountable vacuum chamber that contains a high-speed charge-coupled device video camera. It was found that the contact structure greatly influenced the arc behavior, especially in terms of arc rotation and the effective contact area, while contacts with the same slot structure but different diameters showed similar arc behavior and arc motion. The magnetic field distribution and the Lorentz force of each of the three different contact structures are simulated, and the axial self-magnetic field was first taken into consideration for investigation of the TMF contact design. It was found that contact designs that have higher axial self-magnetic field components tend to have arc columns with larger diameters and show poorer arc motion and rotation performance in the experiments
Influence of axial self-magnetic field component on arcing behavior of spiral-shaped contacts
Energy Technology Data Exchange (ETDEWEB)
Feng, Dingyu; Xiu, Shixin, E-mail: xsx@mail.xjtu.edu.cn; Wang, Yi; Liu, Gang [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China); Zhang, Yali; Bi, Dongli [Shaanxi Baoguang Vacuum Electric Device Co., Ltd., 53 Xibao Road, Baoji 721006 (China)
2015-10-15
The transverse magnetic field (TMF) contact design is commonly used in vacuum interrupters. When arcing occurs between the TMF contacts, the contact structure can create a self-induced magnetic field that drives the arc to move and rotate on the contact, and thus local overheating and severe erosion can be avoided. However, TMF contacts could also create an axial self-magnetic component, and the influence of this component on the arc behavior has not been considered to date. In this paper, five different types of Cu-Cr spiral-shaped TMF contacts with three different structures are investigated in a demountable vacuum chamber that contains a high-speed charge-coupled device video camera. It was found that the contact structure greatly influenced the arc behavior, especially in terms of arc rotation and the effective contact area, while contacts with the same slot structure but different diameters showed similar arc behavior and arc motion. The magnetic field distribution and the Lorentz force of each of the three different contact structures are simulated, and the axial self-magnetic field was first taken into consideration for investigation of the TMF contact design. It was found that contact designs that have higher axial self-magnetic field components tend to have arc columns with larger diameters and show poorer arc motion and rotation performance in the experiments.
Simulation of an Axial Vircator
Tikhomirov, V V
2013-01-01
An algorithm of particle-in-cell simulations is described and tested to aid further the actual design of simple vircators working on axially symmetric modes. The methods of correction of the numerical solution, have been chosen and jointly tested, allow the stable simulation of the fast nonlinear multiflow dynamics of virtual cathode formation and evolution, as well as the fields generated by the virtual cathode. The selected combination of the correction methods can be straightforwardly generalized to the case of axially nonsymmetric modes, while the parameters of these correction methods can be widely used to improve an agreement between the simulation predictions and the experimental data.
Axial electric wake field inside the induction gap exited by the intense electron beam
Institute of Scientific and Technical Information of China (English)
ZHANG Kai-Zhi; ZHANG Huang; LONG Ji-Dong; YANG Guo-Jun; HE Xiao-Zhong; WANG Hua-Cen
2008-01-01
While an intense electron beam passes through the accelerating gaps of a linear induction accelerator,a strong wake field will be excited.In this paper a relatively simple model is established based on the interaction between the transverse magnetic wake field and the electron beam,and the numerical calculation in succession generates a magnetic wake field distribution along the accelerator and along the beam pulse as well.The axial electric wake field is derived based on the relation between field components of a resonant mode.According to some principles in existence,the influence of this field on the high voltage properties of the induction gap is analyzed.The Dragon-I accelerator is taken as an example,and its maximum electric wake field is about 17 kV/cm,which means the effect of the wake field is noticeable.
Klein-Gordon equations for toroidal hydromagnetic waves in an axi-symmetric field
Directory of Open Access Journals (Sweden)
J. F. McKenzie
2010-03-01
Full Text Available In this paper we develop the hydromagnetic wave equations for toroidal Alfvén waves in a background axi-symmetric magnetic field. In the case where spatial variations are directed along the ambient magnetic field direction, the equations can be cast in a Klein-Gordon form in which the adiabatic-geometric amplitude factor of the perturbations varies as √ρL^{5}sin^{5}θ along a magnetic field line (where θ is colatitude and L the L-shell number and the cut-off frequency, associated with the Klein-Gordon form, displays an astonishing variation with distance along a field line (see Eqs. 35 and 37 of the text, in the case of a dipole magnetic field. We compute the eigenvalues and eigenfunctions for the Earth's dipole field which are relevant to geomagnetic pulsations.
Analysis of the axial electric field in a plasma-loaded-helix travelling wave tube
Institute of Scientific and Technical Information of China (English)
Xie Hong-Quan; Liu Pu-Kun
2006-01-01
A helix type slow wave structure filled with plasma is immersed in a strong longitudinal magnetic field. Taking into account the effect of the plasma and the dielectric, the system is separated radially into three regions. By means of the sheath model and Maxwell equation, the distribution of the electromagnetic field is established. Using the boundary conditions of each region, the dispersion relation of the slow wave structure is derived. The trend of change for the radial profile of the axial electric field is analysed respectively in different plasma densities, plasma column radius and dielectric constant by numerical computation. Some useful results are obtained on the basis of the discussion.
International Nuclear Information System (INIS)
We investigate three model field theories: a minimally coupled charged scalar field together with gravity and electromagnetism, a minimally coupled SO(3) Yang-Mills field and gravity, and the Callan-Coleman-Jackiw scalar field. We restrict ourselves to spherically symmetric configurations; the corresponding dimensional reduction leads to an action functional on a two-dimensional spacetime which contains a metric, a neutral scalar, a charged scalar, and an electromagnetic field. The action is written in the second-order, covariant and gauge-invariant form. We generalize the definition of the future and past apparent horizon so that it will not be visible from the future and past null infinity, respectively, and will form a nontimelike surface, both also in the case of the Callan-Coleman-Jackiw model. We prove an inequality relating the surface area and the charges of the apparent horizon. We study the boundary conditions for the fields at the horizon, at the regular center, and at infinity. Finally, we speculate on the existence of static spherically symmetric solutions, where a black hole is surrounded by a matter shell; in two-dimensional spacetime, this looks like a kink
Chiral extrapolation of nucleon axial charge $g_A$ in effective field theory
Li, Hongna
2016-01-01
The extrapolation of nucleon axial charge $g_A$ is investigated within the framework of heavy baryon chiral effective field theory. The intermediate octet and decuplet baryons are included in the one loop calculation. Finite range regularization is applied to improve the convergence in the quark-mass expansion. The lattice data from three different groups are used for the extrapolation. At physical pion mass, the extrapolated $g_A$ are all smaller than the experimental value.
Simulation of an Axial Vircator
Tikhomirov, V. V.; Siahlo, S. E.
2013-01-01
An algorithm of particle-in-cell simulations is described and tested to aid further the actual design of simple vircators working on axially symmetric modes. The methods of correction of the numerical solution, have been chosen and jointly tested, allow the stable simulation of the fast nonlinear multiflow dynamics of virtual cathode formation and evolution, as well as the fields generated by the virtual cathode. The selected combination of the correction methods can be straightforwardly gene...
Majumdar-Papapetrou class of nonstatic cylindrically symmetric Brans-Dicke-Maxwell fields
International Nuclear Information System (INIS)
Relations have been obtained between certain components of the metric and the electromagnetic potentials for source-free Brans-Dicke-Maxwell fields described by a nonstatic cylindrically symmetric Einstein-Rosen metric. These are important, in the sense that they generate a class of solutions that in a way can be said to belong to the class generated by similar relations obtained by Majumdar (Phys. Rev.; 72: 390 (1947)) and Papapetrou (Proc. R. Ir. Acad. Sect. A.; 51: 191 (1947)) for generalized static Einstein-Maxwell fields. The relations have further been used to reduce the B-D Maxwell equations to B-D vacuum equations and vice versa. (author)
International Nuclear Information System (INIS)
The existence of the Hawking radiation of the black hole surely affected the space-time. In this paper, using the result which is obtained by the thermodynamics method and applying the semiclassical Einstein equation when the radiation field is existent, it was obtained the static spherically symmetric metric of a Schwarzschild black hole (SBH) surrounded by the radiation field. Using this metric, it was found that the relation between the radiation energy density and the radius pressure is in accordance with the relation of the space-time
Numerical study of arc plasmas and weld pools for GTAW with applied axial magnetic fields
International Nuclear Information System (INIS)
A 3D numerical model containing the welding arc and the weld pool for gas tungsten arc welding (GTAW) with applied axial magnetic fields is established. The model is validated by comparing the calculated arc temperature with the measured ones. The influence of the magnetic field on the welding process is studied by changing the magnetic inductions, from 0 T to 0.06 T. For welding arcs, a radial spread is discovered, and a reverse flow appears over the anode. The distribution of temperature, heat flux, current density and pressure on the anode surface becomes double-peaked, while the voltage distributes in a double-valley type. For weld pools, the fluid flow cycle brings about a wide and shallow pool. In the circumferential direction, the fluid in the centre areas rotates in an opposite direction to that in the outer regions; in the axial direction, the fluid flows upwards at the centre while downwards in the edge area of the weld pool. All the driving forces including the surface tension, the shear stress from the arc plasma, the electromagnetic force and the buoyancy force that influence the fluid flow are analysed to explain these phenomena. The mechanism of how the applied axial magnetic field regulates the GTAW process is thus clarified. (paper)
Nonlinear Spinor Field Equations in Gravitational Theory: Spherical Symmetric Soliton-Like Solutions
Directory of Open Access Journals (Sweden)
V. Adanhounme
2012-09-01
Full Text Available This paper deals with an extension of a previous work [Gravitation & Cosmology, Vol. 4, 1998, pp 107-113] to exact spherical symmetric solutions to the spinor field equations with nonlinear terms which are arbitrary functions of S=ψψ, taking into account their own gravitational field. Equations with power and polynomial nonlinearities are studied in detail. It is shown that the initial set of the Einstein and spinor field equations with a power nonlinearity has regular solutions with spinor field localized energy and charge densities. The total energy and charge are finite. Besides, exact solutions, including soliton-like solutions, to the spinor field equations are also obtained in flat space-time.
Plasma flow crisis and limiting electron temperature in a vacuum arc and in axial magnetic field
International Nuclear Information System (INIS)
One studied possibility of supersonic motion of cathode plasma in a weak-current vacuum arc placed in axial magnetic field. Increase of electron temperature is shown to result inevitably in reduction of plasma speed up to sonic speed, that is, flow crisis. One derived dependence of the boundary length of plasma stationary flow on magnetic field. The maximum attainable electron temperature of plasma was determined to be governed by ion initial energy and to be equal to the triple value of electron temperature within cathode spot range
Axial anomaly of QED in a strong magnetic field and noncommutative anomaly
Sadooghi, N.; Salim, A. Jafari
2006-01-01
The Adler-Bell-Jackiw (ABJ) anomaly of a 3+1 dimensional QED is calculated in the presence of a strong magnetic field. It is shown that in the regime with the lowest Landau level (LLL) dominance a dimensional reduction from D=4 to D=2 dimensions occurs in the longitudinal sector of the low energy effective field theory. In the chiral limit, the resulting anomaly is therefore comparable with the axial anomaly of a two dimensional massless Schwinger model. It is further shown that the U(1) axia...
Effect of axial magnetic field on a 2.45 GHz permanent magnet ECR ion source
Energy Technology Data Exchange (ETDEWEB)
Nakamura, T., E-mail: tsubasa@oshima-k.ac.jp; Wada, H.; Furuse, M. [National Institute of Technology, Oshima College, 1091-1 Komatsu, Suouoshima, Oshima, Yamaguchi 742-2193 (Japan); Asaji, T. [National Institute of Technology, Toyama College, 13 Hongo, Toyama 939-8630 (Japan)
2016-02-15
Herein, we conduct a fundamental study to improve the generation efficiency of a multi-charged ion source using argon. A magnetic field of our electron cyclotron resonance ion source is composed of a permanent magnet and a solenoid coil. Thereby, the axial magnetic field in the chamber can be tuned. Using the solenoid coil, we varied the magnetic field strength in the plasma chamber and measured the ion beam current extracted at the electrode. We observed an approximately three times increase in the Ar{sup 4+} ion beam current when the magnetic field on the extractor-electrode side of the chamber was weakened. From our results, we can confirm that the multi-charged ion beam current changes depending on magnetic field intensity in the plasma chamber.
On static spherical symmetric solutions of the Bach-Einstein gravitational field equations
International Nuclear Information System (INIS)
For field equations of 4th order, following from a Lagrangian 'Ricci scalar plus Weyl scalar', it is shown (using methods of non-standard analysis) that in a neighbourhood of Minkowski space there do not exist regular static spherically symmetric solutions. With that (besides the known local expansions about r = 0 and r = infinite resp.) for the first time a global statement on the existence of such solutions is given. Finally, this result will be discussed in connection with Einstein's particle programme. (author)
Role(s) of anti-symmetrical background field in string theory
International Nuclear Information System (INIS)
In the first chapter (titled: non-commutative D-branes), we show that the B anti-symmetrical background fields can be embedded in the non-commutativity of branes and can distort gauge theories that branes convey. We know how to describe this transformation in the Abelian case thanks to the Kontsevic quantification formula. Moreover this formula combined to the Seiberg-Witter transformation allows one to compute more rapidly the explicit terms. For the non-Abelian case the situation is less clear. In the chapter 2 (titled: non-Abelian M5-branes), we have tackled the issue of the fields of a packet of N M5-branes. The direct approach based on a 6 dimensional super-symmetric multiplets has led to a stunning dead end, we have not been able to reproduce the expected anomaly in N3. We have presented in a unified manner different gauge theories. We have shown that we can get a number of freedom degrees in the magnitude order of N3 from computations based on geometrical configurations of M2 membranes. In the chapter 3 (titled: systematizing mirror symmetry) we have shown that if the presence of a non-trivial Neveu-Schwarz flux constrains the compactification manifold geometry to shift from the Calabi-Yau case, we can yet specify a mirror symmetry that mixes geometry and background fields. (A.C.)
Generation of a symmetric magnetic field by thermal convection in a plane rotating layer
Zheligovsky, V
2010-01-01
We investigate numerically magnetic field generation by thermal convection with square periodicity cells in a rotating horizontal layer of electrically-conducting fluid with stress-free electrically perfectly conducting boundaries for Rayleigh numbers in the interval 5100\\le R\\le 5800. Dynamos of three kinds, apparently not encountered before, are presented: 1) Steady and time-periodic regimes, where the flow and magnetic field are symmetric about a vertical axis. In regimes with this symmetry, the global alpha-effect is insignificant, and the complex structure of the system of amplitude equations controlling weakly nonlinear stability of the system to perturbations with large spatial and temporal scales suggests that the perturbations are likely to exhibit uncommon complex patterns of behaviour, to be studied in the future work. 2) Periodic in time regimes, where magnetic field is always concentrated in the interior of the convective layer, in contrast to the behaviour first observed by St Pierre (1993) and ...
Field Equations and Radial Solutions in a Noncommutative Spherically Symmetric Geometry
Directory of Open Access Journals (Sweden)
Aref Yazdani
2014-01-01
Full Text Available We study a noncommutative theory of gravity in the framework of torsional spacetime. This theory is based on a Lagrangian obtained by applying the technique of dimensional reduction of noncommutative gauge theory and that the yielded diffeomorphism invariant field theory can be made equivalent to a teleparallel formulation of gravity. Field equations are derived in the framework of teleparallel gravity through Weitzenbock geometry. We solve these field equations by considering a mass that is distributed spherically symmetrically in a stationary static spacetime in order to obtain a noncommutative line element. This new line element interestingly reaffirms the coherent state theory for a noncommutative Schwarzschild black hole. For the first time, we derive the Newtonian gravitational force equation in the commutative relativity framework, and this result could provide the possibility to investigate examples in various topics in quantum and ordinary theories of gravity.
Field Equations and Radial Solution in a Noncommutative Spherically Symmetric Geometry
Yazdani, Aref
2014-01-01
We study a noncommutative theory of gravity in the framework of torsional spacetime. This theory is based on a Lagrangian obtained by applying the technique of dimensional reduction of noncommutative gauge theory and that the yielded diffeomorphism invariant field theory can be made equivalent to a teleparallel formulation of gravity. Field equations are derived in the framework of teleparallel gravity through Weitzenbock geometry. We solve these field equations by considering a mass that is distributed spherically symmetrically in a stationary static spacetime in order to obtain a noncommutative line element.This new line element interestingly reaffirms the coherent state theory for a noncommutative Schwarzschild black hole. For the first time, we derive the Newtonian gravitational force equation in the commutative relativity framework, and this result could provide the possibility to investigate examples in various topics in quantum and ordinary theories of gravity.
Field Equations and Radial Solutions in a Noncommutative Spherically Symmetric Geometry
International Nuclear Information System (INIS)
We study a noncommutative theory of gravity in the framework of torsional spacetime. This theory is based on a Lagrangian obtained by applying the technique of dimensional reduction of noncommutative gauge theory and that the yielded diffeomorphism invariant field theory can be made equivalent to a teleparallel formulation of gravity. Field equations are derived in the framework of teleparallel gravity through Weitzenbock geometry. We solve these field equations by considering a mass that is distributed spherically symmetrically in a stationary static spacetime in order to obtain a noncommutative line element. This new line element interestingly reaffirms the coherent state theory for a noncommutative Schwarzschild black hole. For the first time, we derive the Newtonian gravitational force equation in the commutative relativity framework, and this result could provide the possibility to investigate examples in various topics in quantum and ordinary theories of gravity
Shaw, D J; Barrow, John D.; Shaw, Douglas J.
2006-01-01
We apply the method of matched asymptotic expansions to analyse whether cosmological variations in physical `constants' and scalar fields are detectable, locally, on the surface of local gravitationally bound systems such as planets and stars, or inside virialised systems like galaxies and clusters. We assume spherical symmetry and derive a sufficient condition for the local time variation of the scalar fields that drive varying constants to track the cosmological one. We calculate under number of specific examples in detail by matching the Schwarzschild spacetime to spherically symmetric inhomogeneous Tolman-Bondi metrics in an intermediate region by rigorously construction matched asymptotic expansions on cosmological and local astronomical scales which overlap in an intermediate domain. We conclude that, independent of the details of the scalar-field theory describing the varying 'constant', the condition for cosmological variations to be measured locally is almost always satisfied in physically realistic ...
Gorbatenko, M V; Popov, E Yu
2015-01-01
The domain of wave functions and effective potentials of the Dirac and Klein-Gordon equations for quantum-mechanical particles in static centrally symmetric gravitational fields are analyzed by taking into account the Hilbert causality condition. For all the explored metrics, assuming existence of event horizons, the conditions of a "fall" of a particle to the appropriate event horizons are implemented. The exclusion is one of the solutions for the Reissner-Nordstroem extreme field with the single event horizon. In this case, while fulfilling the condition found by V.I.Dokuchaev, Yu.N.Yeroshenko, the normalization integral is convergent and the wave functions become zero on the event horizon. This corresponds to the Hilbert causality condition. In our paper, due to the analysis of the effective potential for the Reissner-Nordstroem extreme field with real radial wave functions of the Dirac equation, the impossibility is demonstrated for the bound stationary state existence of quantum-mechanical particles, wit...
Axial behaviors of a theta pinch plasma with an antiparallel trapped magnetic field
International Nuclear Information System (INIS)
Fundamental plasma behavior has been almost revealed for theta pinch method in the researches for realizing controlled fusion reactions. Interest is also being taken in the axial behavior of plasma under such condition that the direction of the line of magnetic force confined in a pinched plasma column is reversed in relation to external magnetic field. The authors examined the axial behavior of linear theta pinch plasma with a high speed camera using the image converter tube RCA-4449A and the magnetic probe, and succeeded in photographing the details of plasma shape and its change with time. The experimental results and examinations are described in detail with the outline of experimental apparatuses, and summarized as follows. Area waves in compressional wave mode were observed during a second half cycle of discharge current, and the measured value of their propagation speed coincided with the calculated value. Collision of area waves at the center of the coil did not give the effect to annihilate the antiparallel field. Antiparalllel field arrangement, in which the location of zero magnetic field exists in pinch plasma, presents interesting problems such as heating and the stability in torus system in addition to the phenomena of area waves. The study with toroidal pinch will be a future research subject. (Wakatsuki, Y.)
International Nuclear Information System (INIS)
Dose distributions for 4 MV X rays for symmetrical and offset fields using tapered multi-leaf collimators were measured with a computer controlled dosimeter system and analysis of the obtained data was carried out. Off-center axis ratios (OCR) for square and rectangular fields were different in the region of low dose. The equation for the correction was shown. OCR's for offset fields were almost the same as those for symmetrical fields when the field widths were less than about 10 cm and the depths were greater than about 6 cm. (author)
Growth rate enhancement of free-electron laser by two consecutive wigglers with axial magnetic field
Indian Academy of Sciences (India)
A Hasanbeigi; A Farhadian; E Khademi Bidhendi
2014-06-01
The operative mechanism for a free-electron laser (FEL) with two consecutive helical wigglers having opposite circular polarization in the presence of an axial magnetic field is proposed and analysed. With the help of fluid theory, a tenth-degree polynomial dispersion equation for electromagnetic and space-charge waves is derived. The results are used to illustrate and discuss the dependence of growth rate on different system parameters. Finally, it is shown that for the same system parameters the growth rate of the proposed structure is more than the growth rate of instability in a conventional FEL.
Distribution of Cathode Spots in Vacuum Arc Under Nonuniform Axial Magnetic Fields
Institute of Scientific and Technical Information of China (English)
SHI Zong-qian; JIA Shen-li; WANG Li-jun; LI Xing-wen; WANG Zheng
2007-01-01
Recent results on the distribution of vacuum arc cathode spots (CSs) in nonuniform axial magnetic field (AMF) are presented.Based on previous studies,we deem that two contrary influences of AMF,inward effect and outward effect,are attributed to CSs distribution.With this notion,we have analyzed the controlling effectiveness of nonuniform AMF on CSs distribution. Experiments were conducted in a detachable vacuum chamber with iron-style AMF electrodes.Images of vacuum arc column and the distribution of CSs were photographed with a high-speed charge coupled device (CCD) camera. Experimental results agreed well with the theoretical analysis.
Institute of Scientific and Technical Information of China (English)
王立军; 贾申利; 史宗谦; 荣命哲
2005-01-01
Based on magnetohydrodynamic (MHD) model of vacuum arc, the computer simulation of vacuum arc was carried out in this paper. In the MHD model, mass conservation equation,momentum conservation equations, energy conservation equations, generalized ohm's law and Maxwell equation were considered. MHD equations were calculated by numerical method, and the distribution of vacuum arc plasma parameters and current density were obtained. Simulation results showed that the magnetic constriction effect of vacuum arc is primarily caused by the Hall effect. In addition, the inhibition of axial magnetic field (AMF) on constriction of vacuum arc was calculated and analyzed.
International Nuclear Information System (INIS)
We study the linear analysis of electrohydrodynamic capillary instability of the interface between two viscous, incompressible and electrically conducting fluids in a fully saturated porous medium, when the phases are enclosed between two horizontal cylindrical surfaces coaxial with the interface and, when there is mass and heat transfer across the interface. The fluids are subjected to a constant electric field in the axial direction. Here, we use an irrotational theory in which the motion and pressure are irrotational and the viscosity enters through the jump in the viscous normal stress in the normal stress balance at the interface. A quadratic dispersion relation that accounts for the growth of axisymmetric waves is obtained and stability criterion is given in terms of a critical value of wave number as well as electric field. It is observed that heat transfer has stabilizing effect on the stability of the considered system while medium porosity destabilizes the interface. The axial electric field has dual effect on the stability analysis
Stefani, F; Stefani, Frank; Gerbeth, Gunter
2004-01-01
Using a mean-field dynamo model with a spherically symmetric helical turbulence parameter alpha which is dynamically quenched and disturbed by additional noise, the basic features of geomagnetic polarity reversals are shown to be generic consequences of the dynamo action in the vicinity of exceptional points of the spectrum. This simple paradigmatic model yields long periods of constant polarity which are interrupted by self-accelerating field decays leading to asymmetric polarity reversals. It shows the recently discovered bimodal field distribution, and it gives a natural explanation of the correlation between polarity persistence time and field strength. In addition, we find typical features of coherence resonance in the dependence of the persistence time on the noise.
Ghotra, Harjit Singh; Kant, Niti
2016-05-01
Electron injected in the path of a circularly polarized Gaussian laser beam under the influence of an external axial magnetic field is shown to be accelerated with a several GeV of energy in vacuum. A small angle of injection δ with 0 ∘ propagation of laser pulse is suggested for better trapping of electron in laser field and stronger betatron resonance under the influence of axial magnetic field. Such an optimized electron injection with axial magnetic field maximizes the acceleration gradient and electron energy gain with low electron scattering.
Ghotra, Harjit Singh; Kant, Niti
2016-05-01
Electron injected in the path of a circularly polarized Gaussian laser beam under the influence of an external axial magnetic field is shown to be accelerated with a several GeV of energy in vacuum. A small angle of injection δ with 0 ∘ < δ < 20 ∘ for a sideway injection of electron about the axis of propagation of laser pulse is suggested for better trapping of electron in laser field and stronger betatron resonance under the influence of axial magnetic field. Such an optimized electron injection with axial magnetic field maximizes the acceleration gradient and electron energy gain with low electron scattering.
Magnetohydrodynamic stability of cylindrical liquid bridges under a uniform axial magnetic field
Nicolás, J. A.
1992-11-01
The effect of a uniform axial magnetic field on the stability of cylindrical liquid bridges of negligible viscosity and resistivity is examined in this paper, in the limit case when magnetic forces dominate inertia forces. The analysis yields the bifurcation curve and the growth factor in the neighborhood of the stability limit points as a function of two dimensionless parameters: Λ, the slenderness of the bridge and M, a nondimensional quantity proportional to the magnetic field. It is found that bridges of any slenderness can be stabilized by magnetic fields when M≳1/√2. The results are compared to those existing for capillary liquid jets, showing that the stability curves coincide and that the stabilizing effects are greater for liquid bridges than for infinite columns.
Dilaton minimally coupled to 2 + 1 Einstein Maxwell fields; stationary cyclic symmetric black holes
Garcia-Diaz, A A
2014-01-01
Using the Schwarzschild coordinate frame for a static cyclic symmetric metric in 2 + 1 Einstein gravity coupled to a electric Maxwell field and a dilaton logarithmically depending on the radial coordinate in the presence of an exponential potential the general solution of the Einstein Maxwell dilaton equations is derived and it is identified with the Chan Mann charged dilaton solution. Via a general SL(2;R) transformation, applied on the obtained charged dilaton metric, a family of stationary dilaton solutions has been generated; these solutions possess five parameters: dilaton and cosmological constants , charge, momentum, and mass for some values of them. All the exhibited solutions have been characterized by their quasi-local energy, mass, and momentum through their series expansions at spatial infinity. The structural functions determining these solutions increase as the radial coordinate does, hence they do not exhibit an dS AdS behavior at infinity Moreover, the algebraic structure of the Maxwell field,...
Kevrekidis, P. G.
2014-01-01
In a recent publication [5 Galley, Phys. Rev. Lett. 110, 174301 (2013), 10.1103/PhysRevLett.110.174301], Galley proposed an initial value problem formulation of Hamilton's principle that enables consideration of dissipative systems. Here we explore this formulation at the level of field theories with infinite degrees of freedom. In particular, we illustrate that it affords a previously unwarranted and appealing as well as broadly relevant possibility, namely, to generalize the popular collective coordinate or variational method to open systems, i.e., nonconservative ones. To showcase the relevance or validity of the method we explore two case examples from the timely area of PT-symmetric variants of field theories, in this case for a sine-Gordon and for a ϕ4 model.
International Nuclear Information System (INIS)
The work presented in this thesis concerns the magnetic fields generated in laser produced plasma. A summary of the theoretical and experimental studies concerning the toroidal magnetic fields and realised by different groups of research is presented. Then, we present our original contribution on the generation of axial magnetic fields by the dynamo effect. The experimental work for the detection of magnetic field is based on the Faraday rotation and Zeeman effects. The experimental diagrams are detailed and discussed. The experimental results are presented and compared to the theory. Finaly, we present some consequences of the generation of the axial magnetic fields in laser produced plasma as a discussion of the thermal conductivity
Converging Cylindrical Shock Waves in a Nonideal Gas With an Axial Magnetic Field
Directory of Open Access Journals (Sweden)
J. P. Vishwakarma
2006-11-01
Full Text Available This paper analyses the propagation of converging cylindrical shock waves in a nonidealgas, in the presence of an axial magnetic field. Chester-Chisnell-Whitham’s method has beenemployed to determine the shock velocity and the other flow-variables just behind the shockin the cases, when (i the gas is weakly ionised before and behind the shock front, (ii the gasis strongly ionised before and behind the shock front, and (iii nonionised gas undergoes intenseionisation as a result of the passage of the shock. The effects of the nonidealness of the gas,the conductivity of the gas, and the axial magnetic field have been investigated. It is found thatin the case (i, an increase in the value of parameter ( characterising the nonidealness of thegas accelerates the convergence of the shock. In the case (ii, the shock speed and pressurebehind the shock increase very fast as the axis is approached; and this increase occurs earlierif the strength of the initial magnetic field is increased. In the case (iii, for smaller values of theinitial magnetic field, the shock speed, and pressure behind the shock decrease very fast afterattaining a maximum; and for higher values of the initial magnetic field, the tendency of decreaseappears from the beginning. This shows that the magnetic field has damping effect on the shockpropagation. In the case (iii, it was also found that the growth of the shock in the initial phaseand decay in the last phase were faster when it was converging in a nonideal gas in comparisonwith that in a perfect gas. Further, it has been shown that the gas-ionising nature of the shockhas damping effect on its convergence.
International Nuclear Information System (INIS)
The storage pumps are equipped with various types of inlet casings. The flow nonuniformity is generated by the suction elbows being ingested by the impeller leading to unsteady phenomena and worse cavitational behaviour. A symmetrical suction elbow model corresponding to the double flux storage pump was manufactured and installed on the test rig in order to assess the flow field at the pump inlet. The experimental investigations are performed for 9 discharge values from 0.5 to 1.3 of nominal discharge. LDV measurements are performed on the annular section of the pump inlet in order to quantify the flow non-uniformity generated by the symmetrical suction elbow. Both axial and circumferential velocity components are simultaneously measured on the half plane (180°) of the annular inlet section along to 19 survey axis with 62 points on each. The flow field on the next half plane is determined tacking into account the symmetry. As a result, the flow map on the pump inlet annular section is reconstructed revealing a significant variation of the circumferential velocity component. The absolute flow angle is computed showing a significant variation of ±38°
ǎghici, I., Dr; Muntean, S.; Bosioc, A. I.; Anton, L. E.
2014-03-01
The storage pumps are equipped with various types of inlet casings. The flow nonuniformity is generated by the suction elbows being ingested by the impeller leading to unsteady phenomena and worse cavitational behaviour. A symmetrical suction elbow model corresponding to the double flux storage pump was manufactured and installed on the test rig in order to assess the flow field at the pump inlet. The experimental investigations are performed for 9 discharge values from 0.5 to 1.3 of nominal discharge. LDV measurements are performed on the annular section of the pump inlet in order to quantify the flow non-uniformity generated by the symmetrical suction elbow. Both axial and circumferential velocity components are simultaneously measured on the half plane (180°) of the annular inlet section along to 19 survey axis with 62 points on each. The flow field on the next half plane is determined tacking into account the symmetry. As a result, the flow map on the pump inlet annular section is reconstructed revealing a significant variation of the circumferential velocity component. The absolute flow angle is computed showing a significant variation of ±38°.
High-rate axial-field ionization chamber for particle identification of radioactive beams
Vadas, J; Visser, G; Alexander, A; Hudan, S; Huston, J; Wiggins, B B; Chbihi, A; Famiano, M; Bischak, M M; deSouza, R T
2016-01-01
The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV/A) the detector presents only three 0.5 $\\mu$m/cm$^2$ foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate. Tests with an $\\alpha$ source establish the detector energy resolution as $\\sim$8 $\\%$ for an energy deposit of $\\sim$3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A $^{39}$K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3 x 10$^5$ ions/s the energy resolution has degraded to 14% with a pileup of 12%. The go...
The effect of residual axial gravity on the stability of liquid columns subjected to electric fields
Gonzalez, Heliodoro; Castellanos, Antonio
1993-04-01
The stability criterion for almost cylindrical dielectric liquid bridges subjected to axial electric fields in the presence of residual axial gravity is obtained. In its absence, a perfectly cylindrical equilibrium solution is allowed for all values of the relevant parameters, which are the slenderness of the liquid bridge, the electrical Bond number and the relative permittivity between the outer and inner media. This basic solution is unstable beyond a critical slenderness which varies with the electrical parameters (Gonzalez et al. 1989). The destabilization takes place axisymmetrically. The inclusion of the gravitational Bond number as a new, small parameter may be treated by means of the Liapunov-Schmidt Method, a well-known projection technique that gives the local bifurcation diagram relating the admissible equilibrium amplitudes for the liquid bridge and the aforementioned parameters. As in the absence of applied electric field, the gravitational Bond number breaks the pitchfork diagram into two isolated branches of axisymmetric equilibrium solutions. The stable one has a turning point whose location determines the new stability criterion. Quantitative results are presented after solving the resulting set of linear recursive problems by means of the method of lines.
Numerical analysis of branched cracks in bi-axial stress fields
International Nuclear Information System (INIS)
The stress corrosion cracks as seen for example in PWR steam generator tubing made of Inconel 600 are usually found to be of highly irregular kinked and branched shapes. Numerical analysis of kinked and branched cracks in bi-axial plane stress fields using methods such as finite or boundary element method may provide useful and cost effective solutions. However, accurate analysis of complex shaped cracks requires very fine meshes and, consequently, excessively high computational efforts. This paper discusses some possible strategies of numerical modeling of kinked and branched cracks in general bi-axial stress field using the general-purpose finite element code ABAQUS. The strategies discussed include J-integral and stress intensity factor solutions with different mesh densities. The accuracy of the numerical results obtained is compared with reference solutions from the literature. The main result of the paper is an optimal numerical strategy, which maximizes the accuracy of the result at as low computational efforts as feasible. The selected optimal strategy is expected to be used in the future simulations of large networks of inter-granular stress corrosion cracks at the grain-size scale using incomplete random tessellation.(author)
Kr II and Xe II axial velocity distribution functions in a cross-field ion source
International Nuclear Information System (INIS)
Laser induced fluorescence measurements were carried out in a cross-field ion source to examine the behaviour of the axial ion velocity distribution functions (VDFs) in the expanding plasma. In the present paper, we focus on the axial VDFs of Kr II and Xe II ions. We examine the contourplots in a 1D-phase space (x,vx) representation in front of the exhaust channel and along the centerline of the ion source. The main ion beam, whose momentum corresponds to the ions that are accelerated through the whole potential drop, is observed. A secondary structure reveals the ions coming from the opposite side of the channel. We show that the formation of the neutralized ion flow is governed by the annular geometry. The assumption of a collisionless shock or a double layer due to supersonic beam interaction is not necessary. A non-negligible fraction of slow ions originates in local ionization or charge-exchange collision events between ions of the expanding plasma and atoms of the background residual gas. Slow ions that are produced near the centerline in the vicinity of the exit plane are accelerated toward the source body with a negative velocity leading to a high sputtering of front face. On the contrary, the ions that are produced in the vicinity of the channel exit plane are partially accelerated by the extended electric field.
Axial magnetic field extraction type microwave ion source with a permanent magnet
International Nuclear Information System (INIS)
A new type of microwave ion source in which a permanent magnet generates an axially directed magnetic field needed for the electron cyclotron resonance was developed. The electron cyclotron resonance produces a high density plasma in the ion source. A mA-order ion beam can be extracted. Compared with usual microwave ion sources, this source has a distinguished feature in that the axially directed magnetic field is formed by use of a permanent magnet. Shape of magnetic force lines near the ion extraction aperture was carefully investigated. The extracted ion current as a function of the ion extraction voltage was measured. The experimental data are in good agreement with the theoretical line. The ion source can be heated up to 500 deg C, and extraction of the alkaline metal ions is possible. The extracted ion current for various elements are shown in the table. The current density normalized by the proton was 350-650 mA/cm2 which was nearly equal to the upper limit of the extractable positive ion current density. The plasma density was estimated and was 2 - 3 x 1012 cm-3. The mass spectrum of a Cesium ion beam was obtained. A negligible amount of impurities was observed. The emittance diagram of the extracted ion beam was measured. The result shows that a low emittance and high brightness ion source is constructed. (Kato, T.)
Spherically symmetric scalar field collapse an example of the spacetime problem of time
Romano, J D
1995-01-01
A canonical formalism for spherical symmetry, originally developed by Kucha\\v{r} to describe vacuum Schwarzschild black holes, is extended to include a spherically symmetric, massless, scalar field source. By introducing the ADM mass as a canonical coordinate on phase space, one finds that the super-Hamiltonian and supermomentum constraints for the coupled system simplify considerably. Yet, despite this simplification, it is difficult to find a functional time formalism for the theory. First, the configuration variable that played the role of time for the vacuum theory is no longer a spacetime scalar once spherically symmetric matter is coupled to gravity. Second, although it is possible to perform a canonical transformation to a new set of variables in terms of which the super-Hamiltonian and supermomentum constraints can be solved, the new time variable also fails to be a spacetime scalar. As such, our solutions suffer from the so-called {\\it spacetime problem of time}. A candidate for a time variable that ...
Misra, A
2000-01-01
The axial-gauge boson propagator contains 1/(n.k)^p-type singularities. These singularities have generally been treated by inventing prescriptions for them. We propose an alternative procedere for treating these singularities in the path-integral formalism using the known way of treating the 1/k^{2n}-type singularities in Lorentz-type gauges. For this purpose we use a finite field-dependent BRS transformation that inerpolates between the Lorentz and axial-type gauges. We arrive at the \\epsilon-dependent tree propagator in axial-type gauges.
High confinement plasmas in the Madison Symmetric Torus reversed-field pinch
International Nuclear Information System (INIS)
Reduction of core-resonant m=1 magnetic fluctuations and improved confinement in the Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch have been routinely achieved through control of the surface poloidal electric field, but it is now known that the achieved confinement has been limited in part by edge-resonant m=0 magnetic fluctuations. Now, through refined poloidal electric field control, plus control of the toroidal electric field, it is possible to reduce simultaneously the m=0 and m=1 fluctuations. This has allowed confinement of high-energy runaway electrons, possibly indicative of flux-surface restoration in the usually stochastic plasma core. The electron temperature profile steepens in the outer region of the plasma, and the central electron temperature increases substantially, reaching nearly 1.3 keV at high toroidal plasma current (500 kA). At low current (200 kA), the total beta reaches 15% with an estimated energy confinement time of 10 ms, a tenfold increase over the standard value which for the first time substantially exceeds the constant-beta confinement scaling that has characterized most reversed-field-pinch plasmas
Erices, Cristián; Martínez, Cristián
2015-08-01
The general stationary cylindrically symmetric solution of Einstein-massless scalar field system with a nonpositive cosmological constant is presented. It is shown that the general solution is characterized by four integration constants. Two of these essential parameters have a local meaning and characterize the gravitational field strength. The other two have a topological origin, as they define an improper coordinate transformation that provides the stationary solution from the static one. The Petrov scheme is considered to explore the effects of the scalar field on the algebraic classification of the solutions. In general, these spacetimes are of type I. However, the presence of the scalar field allows us to find a nonvacuum type O solution and a wider family of type D spacetimes, in comparison with the vacuum case. The mass and angular momentum of the solution are computed using the Regge-Teitelboim method in the case of a negative cosmological constant. In absence of a cosmological constant, the curvature singularities in the vacuum solutions can be removed by including a phantom scalar field, yielding nontrivial locally homogeneous spacetimes. These spacetimes are of particular interest, as they have all their curvature invariants constant.
Near-Field Characterization of Radial and Axial Blast Waves From a Cylindrical Explosive Charge
McNesby, Kevin; Homan, Barrie
This paper uses experiment (high speed imaging) and simulation (ALE-3D) to investigate radial and axial blast waves produced by uncased, cylindrical charges of TNT (trinitrotoluene). Recently there has been work reported on predicting secondary blast waves in the explosive mid-field (approximately 1 meter from charge center of mass) for cylindrical charges of RDX (trimethylenetrinitramine)/binder formulations. The work we will present seeks to provide complementary information in the explosive near-field, including the approach to chemical ``freeze out'', for end-detonated, right circular cylinders of TNT. Additionally, this work attempts to retrieve state variables (temperature, pressure, velocities) from high-definition images of the explosive event. Keywords: cylindrical charges, blast, shock waves
Yunqiang Liu; Jiuping Xu; Shize Wang; Bin Qi
2013-01-01
The axial stress and deformation of high temperature high pressure deviated gas wells are studied. A new model is multiple nonlinear equation systems by comprehensive consideration of axial load of tubular string, internal and external fluid pressure, normal pressure between the tubular and well wall, and friction and viscous friction of fluid flowing. The varied temperature and pressure fields were researched by the coupled differential equations concerning mass, momentum, and energy equatio...
Intensity-modulated radiation therapy: overlapping co-axial modulated fields
Energy Technology Data Exchange (ETDEWEB)
Metcalfe, P [Centre for Medical Radiation Physics, University of Wollongong, NSW (Australia); Tangboonduangjit, P [Centre for Medical Radiation Physics, University of Wollongong, NSW (Australia); White, P [Nepean Cancer Care Centre, Sydney, NSW (Australia)
2004-08-21
The Varian multi-leaf collimator has a 14.5 cm leaf extension limit from each carriage. This means the target volumes in the head and neck region are sometimes too wide for standard width-modulated fields to provide adequate dose coverage. A solution is to set up asymmetric co-axial overlapping fields. This protects the MLC carriage while in return the MLC provides modulated dose blending in the field overlap region. Planar dose maps for coincident fields from the Pinnacle radiotherapy treatment planning system are compared with planar dose maps reconstructed from radiographic film and electronic portal images. The film and portal images show small leaf-jaw matchlines at each field overlap border. Linear profiles taken across each image show that the observed leaf-jaw matchlines from the accelerator images are not accounted for by the treatment planning system. Dose difference between film reconstructed electronic portal images and planning system are about 2.5 cGy in a modulated field at d{sub max}. While the magnitude of the dose differences are small improved round end leaf modelling combined with a finer dose calculation grid may minimize the discrepancy between calculated and delivered dose.
Simulations of the lower-hybrid antenna in the Madison Symmetric Torus reversed-field pinch
International Nuclear Information System (INIS)
Due to constraints inherent to a reversed-field pinch plasma configuration, an unusual launch structure—the interdigital line—was used for lower-hybrid current-drive experiments in the Madison Symmetric Torus. The antenna design and performance were analyzed using an array of codes (including RANT3D/AORSA1D-H, Microwave Studio and VORPAL). It was found that the voltage phasing was not the intended one. As a result, the parallel-wavenumber spectrum of the launched wave peaks at a value lower than desired, making the accessibility marginal. Further simulations demonstrated that the error can largely be corrected by either lowering the antenna operating frequency or shortening the length of the resonators. (paper)
International Nuclear Information System (INIS)
Determination of the plasma potential in the core of the Madison Symmetric Torus (MST) Reversed Field Pinch (RFP) is one of the primary purposes of the MST Heavy Ion Beam Probe (HIBP). In particular, the relationship between the equilibrium electric field and plasma rotation and transport will be investigated. Preliminary measurements inside the core indicate that the plasma potential Φp is positive and in the range of 0.5 kV to 2.5 kV for standard discharges (including the range of observed potentials and possible errors). This is the first such measurement in the core of an RFP with moderate temperature and density. Because an RFP magnetic field is produced by plasma currents, initial experiments have emphasized finding Φp at locations known to be in the core of standard discharges, even though the magnetic field and, thus, the locations themselves are not fully known. The sensitivity of the beam ion orbits to the current profile is being exploited by using the HIBP signals to provide a constraint on the magnetic equilibrium model and thereby help determine the current profile. A simple density scaling experiment has been performed showing a significant decrease in Φp with increasing density. The intriguing, though preliminary results from this and other experiments point to a significant role for Φp measurements in an RFP. (author)
Research on an Axial Magnetic-Field-Modulated Brushless Double Rotor Machine
Directory of Open Access Journals (Sweden)
Bin Yu
2013-09-01
Full Text Available Double rotor machine, an electronic continuously variable transmission, has great potential in application of hybrid electric vehicles (HEVs, wind power and marine propulsion. In this paper, an axial magnetic-field-modulated brushless double rotor machine (MFM-BDRM, which can realize the speed decoupling between the shaft of the modulating ring rotor and that of the permanent magnet rotor is proposed. Without brushes and slip rings, the axial MFM-BDRM offers significant advantages such as excellent reliability and high efficiency. Since the number of pole pairs of the stator is not equal to that of the permanent magnet rotor, which differs from the traditional permanent magnet synchronous machine, the operating principle of the MFM-BDRM is deduced. The relations of corresponding speed and toque transmission are analytically discussed. The cogging toque characteristics, especially the order of the cogging torque are mathematically formulated. Matching principle of the number of pole pairs of the stator, that of the permanent magnet rotor and the number of ferromagnetic pole pieces is inferred since it affects MFM-BDRM’s performance greatly, especially in the respect of the cogging torque and electromagnetic torque ripple. The above analyses are assessed with the three-dimensional (3D finite-element method (FEM.
Experimental Investigation of the Flow Field in a Multistage Axial Flow Compressor
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B. Lakshminarayana
1996-01-01
Full Text Available The nature of the flow field in a three stage axial flow compressor, including a detailed survey at the exit of an embedded stator as well as the overall performance of the compressor is presented and interpreted in this paper. The measurements include area traverse of a miniature five hole probe (1.07 mm dia downstream of stator 2, radial traverses of a miniature five hole probe at the inlet, downstream of stator 3 and at the exit of the compressor at various circumferential locations, area traverse of a low response thermocouple probe downstream of stator 2, radial traverses of a single sensor hot-wire probe at the inlet, and casing static pressure measurements at various circumferential and axial locations across the compressor at the peak efficiency operating point. Mean velocity, pressure and total temperature contours as well as secondary flow contours at the exit of the stator 2 are reported and interpreted. Secondary flow contours show the migration of fluid particles toward the core of the low pressure regions located near the suction side casing endwall corner.
Static, spherically symmetric solutions with a scalar field in Rastall gravity
Bronnikov, K A; Piattella, O F; Santos, E C
2016-01-01
Rastall's theory belongs to the class of non-conservative theories of gravity. In vacuum, the only non-trivial static, spherically symmetric solution is the Schwarzschild one, except in a very special case. When a canonical scalar field is coupled to the gravity sector in this theory, new exact solutions appear for some values of the Rastall parameter $a$. Some of these solutions describe the same space-time geometry as the recently found solutions in the $k$-essence theory with a power function for the kinetic term of the scalar field. There is a large class of solutions (in particular, those describing wormholes and regular black holes) whose geometry coincides with that of solutions of GR coupled to scalar fields with nontrivial self-interaction potentials; the form of these potentials, however, depends on the Rastall parameter $a$. We also note that all solutions of GR with a zero trace of the energy-momentum tensor, including black-hole and wormhole ones, may be re-interpreted as solutions of Rastall's t...
Casimir effect of the electromagnetic field in D-dimensional spherically symmetric cavities
International Nuclear Information System (INIS)
Eigenmodes of the electromagnetic field with perfectly conducting or infinitely permeable conditions on the boundary of a D-dimensional spherically symmetric cavity is derived explicitly. It is shown that there are (D-2) polarizations for TE modes and one polarization for TM modes, giving rise to a total of (D-1) polarizations. In case of a D-dimensional ball, the eigenfrequencies of the electromagnetic field with perfectly conducting boundary condition coincides with the eigenfrequencies of gauge 1-forms with relative boundary condition; whereas the eigenfrequencies of the electromagnetic field with infinitely permeable boundary condition coincides with the eigenfrequencies of gauge 1-forms with absolute boundary condition. Casimir energies of single and concentric spherical shells in D-dimensions are computed. The Casimir energy of concentric spherical shells can be written as a sum of the single spherical shell contributions and an interacting term, and the latter is free of divergence. The interacting term always gives rise to an attractive force between the two spherical shells. Its leading term is the Casimir force acting between two parallel plates of the same area, as expected by proximity force approximation.
The Axial Double Probe and Fields Signal Processing for the MMS Mission
Ergun, R. E.; Tucker, S.; Westfall, J.; Goodrich, K. A.; Malaspina, D. M.; Summers, D.; Wallace, J.; Karlsson, M.; Mack, J.; Brennan, N.; Pyke, B.; Withnell, P.; Torbert, R.; Macri, J.; Rau, D.; Dors, I.; Needell, J.; Lindqvist, P.-A.; Olsson, G.; Cully, C. M.
2016-03-01
The Axial Double Probe (ADP) instrument measures the DC to ˜100 kHz electric field along the spin axis of the Magnetospheric Multiscale (MMS) spacecraft (Burch et al., Space Sci. Rev., 2014, this issue), completing the vector electric field when combined with the spin plane double probes (SDP) (Torbert et al., Space Sci. Rev., 2014, this issue, Lindqvist et al., Space Sci. Rev., 2014, this issue). Two cylindrical sensors are separated by over 30 m tip-to-tip, the longest baseline on an axial DC electric field ever attempted in space. The ADP on each of the spacecraft consists of two identical, 12.67 m graphite coilable booms with second, smaller 2.25 m booms mounted on their ends. A significant effort was carried out to assure that the potential field of the MMS spacecraft acts equally on the two sensors and that photo- and secondary electron currents do not vary over the spacecraft spin. The ADP on MMS is expected to measure DC electric field with a precision of ˜1 mV/m, a resolution of ˜25 μV/m, and a range of ˜±1 V/m in most of the plasma environments MMS will encounter. The Digital Signal Processing (DSP) units on the MMS spacecraft are designed to perform analog conditioning, analog-to-digital (A/D) conversion, and digital processing on the ADP, SDP, and search coil magnetometer (SCM) (Le Contel et al., Space Sci. Rev., 2014, this issue) signals. The DSP units include digital filters, spectral processing, a high-speed burst memory, a solitary structure detector, and data compression. The DSP uses precision analog processing with, in most cases, >100 dB in dynamic range, better that -80 dB common mode rejection in electric field ( E) signal processing, and better that -80 dB cross talk between the E and SCM ( B) signals. The A/D conversion is at 16 bits with ˜1/4 LSB accuracy and ˜1 LSB noise. The digital signal processing is powerful and highly flexible allowing for maximum scientific return under a limited telemetry volume. The ADP and DSP are
Alebastrov, Y A
2016-01-01
Attention is drawn to the mathematical equality of rights of symmetrical constituents derived affinorr of a vector field in relation to its antisymmetric constituents. In this regard, raises the question not only of equitable accounting, but and mainly question of the real existence of fields, represented by these constituents. In particular, we conclude that the classical electromagnetic field at any point of space\\,-\\,time accompanied, in the General case, independent {\\em physical} field, defined symmetrical derived affinor of 4-potential of classical electrodynamics. Discussed, within the framework of the Bogolyubov and Shirkov axiomatic, a theory of real vector field, clearly and equitably taking into account the symmetric derived affinors this field and found a number of important distinguishing features this model. Despite accounting explicitly gauge-noninvariant constituents, the proposed theory has specialized gauge invariance, which provides, in particular, conservation of electric current. In this ...
String loops in the field of braneworld spherically symmetric black holes and naked sigularities
Stuchlík, Z
2013-01-01
We study motion of current-carrying string loops in the field of braneworld spherically symmetric black holes and naked singularities. The spacetime is described by the RN geometry with tidal charge b reflecting the non-local tidal effects coming from the external dimension; both positive and negative values of the spacetime parameter b are considered. We restrict attention to the axisymmetric motion of string loops when the motion can be fully governed by an appropriately defined effective potential related to the energy and angular momentum of the string loops. In dependence on these two constants of the motion, the string loops can be captured, trapped, or can escape to infinity. In close vicinity of stable equilibrium points at the centre of trapped states the motion is regular. We describe how it is transformed to chaotic motion with growing energy of the string loop. In the field of naked singularities the trapped states located off the equatorial plane of the system exist and trajectories unable to cro...
Stability of Reflection Symmetric Collapsing Structures
Sharif, M
2015-01-01
In this paper, we explore instability regions of non-static axial reflection symmetric spacetime with anisotropic source in the interior. We impose linear perturbation on the Einstein field equations and dynamical equations to establish the collapse equation. The effects of different physical factors like energy density and anisotropic stresses on the instability regions are studied under Newtonian and post-Newtonian limits. We conclude that stiffness parameter has a significant role in this analysis while the reflection terms increase instability ranges of non-static axial collapse.
Dynamics of multiple viscoelastic carbon nanotube based nanocomposites with axial magnetic field
International Nuclear Information System (INIS)
Nanocomposites and magnetic field effects on nanostructures have received great attention in recent years. A large amount of research work was focused on developing the proper theoretical framework for describing many physical effects appearing in structures on nanoscale level. Great step in this direction was successful application of nonlocal continuum field theory of Eringen. In the present paper, the free transverse vibration analysis is carried out for the system composed of multiple single walled carbon nanotubes (MSWCNT) embedded in a polymer matrix and under the influence of an axial magnetic field. Equivalent nonlocal model of MSWCNT is adopted as viscoelastically coupled multi-nanobeam system (MNBS) under the influence of longitudinal magnetic field. Governing equations of motion are derived using the Newton second low and nonlocal Rayleigh beam theory, which take into account small-scale effects, the effect of nanobeam angular acceleration, internal damping and Maxwell relation. Explicit expressions for complex natural frequency are derived based on the method of separation of variables and trigonometric method for the “Clamped-Chain” system. In addition, an analytical method is proposed in order to obtain asymptotic damped natural frequency and the critical damping ratio, which are independent of boundary conditions and a number of nanobeams in MNBS. The validity of obtained results is confirmed by comparing the results obtained for complex frequencies via trigonometric method with the results obtained by using numerical methods. The influence of the longitudinal magnetic field on the free vibration response of viscoelastically coupled MNBS is discussed in detail. In addition, numerical results are presented to point out the effects of the nonlocal parameter, internal damping, and parameters of viscoelastic medium on complex natural frequencies of the system. The results demonstrate the efficiency of the suggested methodology to find the closed form
Free electron laser experiment in resonant helical and axial magnetic fields
International Nuclear Information System (INIS)
The authors report on an intermediate energy, long pulse free electron laser (FEL). The experiment is designed to investigate cyclotron resonance effects in FELs. The power source is a Marx generator which produces a repeatable, flat accelerating voltage pulse. The thermionic electron gun operates immersed in a shaped magnetic field. The perpendicular energy of the emitted electrons is estimated to be less than one percent of their total energy. The beam propagates in a two meter long drift tube, guided by a uniform axial magnetic field that can be varied between 0.7 and 7.0 kG. The wiggler fields are generated by a bifilar helical winding. An adjustable, adiabatic entrance profile is produced by staggering the wiggler termination windings. The system has been designed to that under normal operating conditions, the emitted radiation propagates in the lowest mode of the cylindrical drift tube. The authors have observed microwave power levels of over 10 KW at approximately 10 GHz. Spectra observed with an X-band waveguide dispersive line show that most of the power is concentrated in a narrow peak (Δf/f<0.1). Preliminary results indicate that the output frequency increases with beam energy
Flow Fields with Vortex in a Small Semi-open Axial Fan
Institute of Scientific and Technical Information of China (English)
Norimasa. Shiomi; Yoichi Kinoue; Ying zi Jin; Toshiaki Setoguchi; Kenji Kaneko
2009-01-01
In order to clarify the effect of tip clearance (TC) size on fan performance and the flow field at rotor outlet in a small semi-open axial fan, the experimental investigation was carried out. The tip diameter of test fan rotor was 180mm and test TC sizes were 1 mm (TC=1 mm) and 4mm (TC=4mm). Fan characteristics tests were carried out for two cases of TC size and three-dimensional velocity fields at rotor outlet were measured using a single slant hot-wire probe at four flow-rate conditions. As a result, it was found that the pressure -flow-rate characteristics curves for two cases showed almost the same tendency. However, the ensemble averaged velocity profiles along radial measurement stations of TC=4mm largely changed compared with that of TC=1mm in cases of small flow-rate condition. From the phase-locked averaging results, it was also found that the vortex existed in the rotor outlet flow field of high flow-rate condition for each TC case. Compared with the vortices for TC=1mm and TC=4mm, the vortex for TC=4mm was stronger than that for TC=1mm.
String loops in the field of braneworld spherically symmetric black holes and naked singularities
International Nuclear Information System (INIS)
We study motion of current-carrying string loops in the field of braneworld spherically symmetric black holes and naked singularities. The spacetime is described by the Reissner-Nordström geometry with tidal charge b reflecting the non-local tidal effects coming from the external dimension; both positive and negative values of the spacetime parameter b are considered. We restrict attention to the axisymmetric motion of string loops when the motion can be fully governed by an appropriately defined effective potential related to the energy and angular momentum of the string loops. In dependence on these two constants of the motion, the string loops can be captured, trapped, or can escape to infinity. In close vicinity of stable equilibrium points at the centre of trapped states the motion is regular. We describe how it is transformed to chaotic motion with growing energy of the string loop. In the field of naked singularities the trapped states located off the equatorial plane of the system exist and trajectories unable to cross the equatorial plane occur, contrary to the trajectories in the field of black holes where crossing the equatorial plane is always admitted. We concentrate our attention to the so called transmutation effect when the string loops are accelerated in the deep gravitational field near the black hole or naked singularity by transforming the oscillatory energy to the energy of the transitional motion. We demonstrate that the influence of the tidal charge can be substantial especially in the naked singularity spacetimes with b > 1 where the acceleration to ultrarelativistic velocities with Lorentz factor γ ∼ 100 can be reached, being more than one order higher in comparison with those obtained in the black hole spacetimes
Axial Myopia Is Associated with Visual Field Prognosis of Primary Open-Angle Glaucoma.
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Chen Qiu
Full Text Available To identify whether myopia was associated with the visual field (VF progression of primary open-angle glaucoma (POAG.A total of 270 eyes of 270 POAG followed up for more than 3 years with ≥9 reliable VFs by Octopus perimetry were retrospectively reviewed. Myopia was divided into: mild myopia (-2.99 diopter [D], 0, moderate myopia (-5.99, 3.00 D, marked myopia (-9.00, -6.00 D and non-myopia (0 D or more. An annual change in the mean defect (MD slope >0.22 dB/y and 0.30 dB/y was defined as fast progression, respectively. Logistic regression was performed to determine prognostic factors for VF progression.For the cutoff threshold at 0.22 dB/y, logistic regression showed that vertical cup-to-disk ratio (VCDR; p = 0.004 and the extent of myopia (p = 0.002 were statistically significant. When logistic regression was repeated after excluding the extent of myopia, axial length (AL; p = 0.008, odds ratio [OR] = 0.796 reached significance, as did VCDR (p = 0.001. Compared to eyes with AL≤23 mm, the OR values were 0.334 (p = 0.059, 0.309 (p = 0.044, 0.266 (p = 0.019, 0.260 (p = 0.018, respectively, for 23 26 mm. The significance of vertical cup-to-disk ratio of (p = 0.004 and the extent of myopia (p = 0.008 did not change for the cutoff threshold at 0.30dB/y.VCDR and myopia were associated with VF prognosis of POAG. Axial myopia may be a protective factor against VF progression.
Study of Magnetic Field Behavior at Lower Pressure of Neon in the Axial Phase of INTI Plasma Focus
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K.K.A. Devi
2014-03-01
Full Text Available The magnetic field distribution substantially affects mechanisms for the generation of radiation in Z-pinches. Investigation of the axial component of the magnetic field is one of the important problems in plasma focus studies. The designed magnetic probe is intended to use for the study of current sheet in INTI plasma focus device with energy of about 3.3 kJ. The measurements of the azimuthal component of the magnetic field on the INTI Plasma Focus operated at neon pressures below 1 Torr was carried out using a custom built calibrated magnetic probe. The probe was tested for neon gas under the various lower pressures (i.e., 0.1, 0.3, 0.5 and 0.7, 1, 2, 3, 5 torr etc.. It is observed that the time response of the designed probe is sufficient for the rise time of the magnetic field associated with the current in the axial phase. We also note that the small size of the designed probe is well suited to sense the magnetic field without perturbing the plasma unduly. The probe designed and constructed is also suitable to carryout measurements to obtain axial distributions of trajectory, average axial velocity and magnetic field of the current sheath at a certain radial distances along the axis of the tube.
de Brito, P. E.; Nazareno, H. N.
2007-01-01
In the present work we treat the problem of a particle in a uniform magnetic field along the symmetric gauge, so chosen since the wavefunctions present the required cylindrical symmetry. It is our understanding that by means of this work we can make a contribution to the teaching of the present subject, as well as encourage students to use…
Tomographic imaging of resistive mode dynamics in the Madison Symmetric Torus reversed-field pinch
International Nuclear Information System (INIS)
A detailed study of the dynamics and magnetic topological effects of resistive-tearing modes is presented for different operational regimes in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. Soft-x-ray tomography and magnetic measurements, along with numerical reconstruction of magnetic-field lines with the ORBIT code [R. B. White and M. S. Chance, Phys. Fluids 27, 2455 (1984)], have been employed. Magnetic-mode dynamics has been investigated in standard plasmas during the transition to the quasi-single helicity state, in which a single mode dominates the mode spectrum. Single helical soft-x-ray structures are studied with tomography in these cases. These structures are associated with magnetic islands, indicating that helical flux surfaces appear in the plasma. Mode dynamics has also been examined during auxiliary inductive current drive, the goal of which is to reduce the tearing-mode amplitudes. In this case the phenomenology of the soft-x-ray structures appearing in the plasma is more complex. In fact, when a quasi-single helicity spectrum occurs, a single island bigger than in the standard case is usually found. On the other hand, when all modes decrease, two helical soft-x-ray structures are observed, with the same helicity as the two innermost resonant modes. This constitutes the first direct evidence of magnetic-chaos reduction during auxiliary inductive current drive, which is responsible for the achievement of the best confinement in the reversed-field pinch configuration up to now
Non-linear effects in the post-Newtonian approximation of a spherically symmetric field
Energy Technology Data Exchange (ETDEWEB)
Gambi, J.M.; Zamorano, P. [Madrid Univ. Carlos 3, Madrid (Spain). Dept. de Matematicas; Romero, P.; Garcia del Pino, M.L. [Madrid Univ. Complutense, Madrid (Spain). Dept. de Astronomia y Geodesia
2000-02-01
Conditions for the compatibility of the exterior metric of a spherically symmetric object with the field equations for the empty space and equations of motion and of trajectories for test particles, written in polar Gaussian and Fermi coordinates, are obtained to show that, although their explicit exact solutions cannot be derived in these coordinates, the post-Newtonian limits of these solutions can, nevertheless, be obtained. With these limits, it is next shown that the cited post-Newtonian equations do not fit into the standard post-Newtonian approximation either. It is then shown that these coordinates can, nevertheless, be included in a more general formalism together with the usual post-Newtonian (standard, harmonic, Painleve and isotropic) coordinates so that their respective equations of motion may be compared to each other and, finally, it is demonstrated that the only non-linear term taken in the Christoffel symbols with these usual coordinates in the standard post-Newtonian equations of motion to explain some known perturbations is not needed when polar Gaussian or Fermi coordinates are used to explain also those perturbations. In fact, it is demonstrated that these are the only coordinates for which that term becomes zero.
Second harmonic generation of off axial vortex beam in the case of walk-off effect
Chen, Shunyi; Ding, Panfeng; Pu, Jixiong
2016-07-01
Process of off axial vortex beam propagating in negative uniaxial crystal is investigated in this work. Firstly, we get the formulae of the normalized electric field and calculate the location of vortices for second harmonic beam in two type of phase matching. Then, numerical analysis verifies that the intensity distribution and location of vortices of the first order original vortex beam depend on the walk-off angle and off axial magnitude. It is shown that, in type I phase matching, the distribution of vortices is symmetrical about the horizontal axis, the separation distance increases as the off axial magnitude increases or the off axial magnitude deceases. However, in type II phase matching, the vortices are symmetrical along with some vertical axis, and increase of the walk-off angle or off axial magnitude leads to larger separation distance. Finally, the case of high order original off axial vortex beam is also investigated.
Bubnov, Andrey; Gubina, Nadezda; Zhukovsky, Vladimir
2016-05-01
We study vacuum polarization effects in the model of Dirac fermions with additional interaction of an anomalous magnetic moment with an external magnetic field and fermion interaction with an axial-vector condensate. The proper time method is used to calculate the one-loop vacuum corrections with consideration for different configurations of the characteristic parameters of these interactions.
International Nuclear Information System (INIS)
The sensitivity characteristics of Positron Emission Tomography (PET) systems with wide Axial Field of View (AFOV) was studied by MonteCarlo simulations complemented by an approximate analytical model, aiming at full-body human PET systems with AFOV in the order of 200 cm. Simulations were based on the GEANT4 package and followed closely the NEMA NU-2 1994 norm. The sensitivity, dominated by the solid angle, grows strongly with the AFOV and with the axial acceptance angle, while the scatter fraction is almost independent from the geometry
Solving outside-axial-field-of-view scatter correction problem in PET via digital experimentation
Andreyev, Andriy; Zhu, Yang-Ming; Ye, Jinghan; Song, Xiyun; Hu, Zhiqiang
2016-03-01
Unaccounted scatter impact from unknown outside-axial-field-of-view (outside-AFOV) activity in PET is an important degrading factor for image quality and quantitation. Resource consuming and unpopular way to account for the outside- AFOV activity is to perform an additional PET/CT scan of adjacent regions. In this work we investigate a solution to the outside-AFOV scatter problem without performing a PET/CT scan of the adjacent regions. The main motivation for the proposed method is that the measured random corrected prompt (RCP) sinogram in the background region surrounding the measured object contains only scattered events, originating from both inside- and outside-AFOV activity. In this method, the scatter correction simulation searches through many randomly-chosen outside-AFOV activity estimates along with known inside-AFOV activity, generating a plethora of scatter distribution sinograms. This digital experimentation iterates until a decent match is found between a simulated scatter sinogram (that include supposed outside-AFOV activity) and the measured RCP sinogram in the background region. The combined scatter impact from inside- and outside-AFOV activity can then be used for scatter correction during final image reconstruction phase. Preliminary results using measured phantom data indicate successful phantom length estimate with the method, and, therefore, accurate outside-AFOV scatter estimate.
Optical signatures of dissolved organic matter from the Endeavour and Axial vent fields
Stubbins, A.; Butterfield, D.; Rossel, P. E.; Dittmar, T.
2011-12-01
Recent studies have revealed that hydrothermal systems in the deep ocean are both sources and processors of dissolved organic matter (DOM). Sub-floor stores of fossil organic carbon may be exported to the deep ocean directly adding fossil C to the deep ocean dissolved organic carbon (DOC) pool and altering its apparent age. Fossil methane and carbon dioxide are also exported from vents. These C sources can then be utilized by chemotrophs and later enter the DOM pool as fossil DOC. Finally, when deep ocean waters are entrained into vent systems, the resultant heating may alter the chemical and optical properties of the DOM in these deep ocean waters. Dissolved organic matter (DOM) samples were collected from vents ranging in temperature from 10 to over 300 degrees centigrade across the Endeavour and Axial fields along the Juan de Fuca ridge. Elevated DOC and protein-like fluorescence reveal the vents to fuel the chemotrophic production of organic matter either in the adjacent water column or local sediments. High DOC and increased humic-like fluorescence in the hottest vent fluids, suggests the thermal degradation of DOM either from buried fossil sources or the entrainment of local waters enriched in DOC due to chemotrophic productivity. Natural and radio-carbon analyses are underway and will provide further insight into the ultimate source of this colored, fluorescent hydrothermal DOM.
Barrios, Nahuel; Pullin, Jorge
2015-01-01
We consider a massive scalar field living on the recently found exact quantum space-time corresponding to vacuum spherically symmetric loop quantum gravity. The discreteness of the quantum space time naturally regularizes the scalar field, eliminating divergences. However, the resulting finite theory depends on the details of the micro physics. We argue that such dependence can be eliminated through a finite renormalization and discuss its nature. This is an example of how quantum field theories on quantum space times deal with the issues of divergences in quantum field theories.
Ghaffari, A.
1971-01-01
Investigation of two cases of integrability of a second-order differential equation describing the projection of an axisymmetric satellite orbit on to a plane perpendicular to the rotation axis. It is demonstrated that for these two cases the integration can be carried out either by quadratures or reduced to a first-order differential equation. Analytical and physical properties are expressed, and it is shown that the equation can be derived from the classical plane eikonal equation of geometric optics.
Axial anomaly in the presence of the Aharonov-Bohm gauge field
International Nuclear Information System (INIS)
The axial anomaly for Euclidean Dirac fermions in the presence of a background Aharonov-Bohm gauge potential was computed. The non-perturbative result depends on the self-adjoint extensions of the Dirac operator. The role of the quantum mechanical parameters involved in the expression for the axial anomaly is discussed. A derivation of the effective action by means of the stereographic projection is also considered. (authors). 14 refs
Arani, A. Ghorbanpour; Haghparast, E.; BabaAkbar Zarei, H.
2016-08-01
In the present research, vibration and instability of axially moving single-layered graphene sheet (SLGS) subjected to magnetic field is investigated. Orthotropic visco-Pasternak foundation is developed to consider the influences of orthotropy angle, damping coefficient, normal and shear modulus. Third order shear deformation theory (TSDT) is utilized due to its accuracy of polynomial functions than other plate theories. Motion equations are obtained by means of Hamilton's principle and solved analytically. Influences of various parameters such as axially moving speed, magnetic field, orthotropic viscoelastic surrounding medium, thickness and aspect ratio of SLGS on the vibration characteristics of moving system are discussed in details. The results indicated that the critical speed of moving SLGS is strongly dependent on the moving speed. Therefore, the critical speed of moving SLGS can be improved by applying magnetic field. The results of this investigation can be used in design and manufacturing of marine vessels in nanoscale.
International Nuclear Information System (INIS)
Absract: After suitable annealing under a tensile stress, Fe73.5Cu1Nb3Si13.5B9 amorphous wire becomes the nano-structured material together with a transverse anisotropy field Hk=-3.2 kA/m. Its circular permeability, μ=μ'-jμ'', was determined from the measurements of the impedance, as a function of the frequency (f=333-33,333 Hz) and amplitude (IAC=0.1-100 mA) of AC current and the axially applied DC field (H=0-89 kA/m). We found that the circular technical magnetization of this sample carried out by the spontaneous domain nucleation process. The influences of the AC current frequency and the axial DC field on the circular magnetization have been studied
Ring, P; Lalazissis, G A
1997-01-01
A Fortran program for the calculation of the ground state properties of axially deformed even-even nuclei in the relativistic framework is presented. In this relativistic mean field (RMF) approach a set of coupled differential equations namely the Dirac equation with potential terms for the nucleons and the Glein-Gordon type equations with sources for the meson and the electromagnetic fields are to be solved self-consistently. The well tested basis expansion method is used for this purpose. Accordingly a set of harmonic oscillator basis generated by an axially deformed potential are used in the expansion. The solution gives the nucleon spinors, the fields and level occupancies, which are used in the calculation of the ground state properties.
Wang, Huapei; Kent, Dennis V; Rochette, Pierre
2015-12-01
The geomagnetic field is predominantly dipolar today, and high-fidelity paleomagnetic mean directions from all over the globe strongly support the geocentric axial dipole (GAD) hypothesis for the past few million years. However, the bulk of paleointensity data fails to coincide with the axial dipole prediction of a factor-of-2 equator-to-pole increase in mean field strength, leaving the core dynamo process an enigma. Here, we obtain a multidomain-corrected Pliocene-Pleistocene average paleointensity of 21.6 ± 11.0 µT recorded by 27 lava flows from the Galapagos Archipelago near the Equator. Our new result in conjunction with a published comprehensive study of single-domain-behaved paleointensities from Antarctica (33.4 ± 13.9 µT) that also correspond to GAD directions suggests that the overall average paleomagnetic field over the past few million years has indeed been dominantly dipolar in intensity yet only ∼ 60% of the present-day field strength, with a long-term average virtual axial dipole magnetic moment of the Earth of only 4.9 ± 2.4 × 10(22) A ⋅ m(2). PMID:26598664
Directory of Open Access Journals (Sweden)
N Akbar
2016-01-01
Full Text Available The instinct system of cilia motion with magnetic field and slip for Jeffrey fluid model in a symmetric channel is examined. The problem of two-dimensional fluid motion in a symmetric channel with ciliated walls is considered. The structures of ciliary motion are stubborn by the sovereignty of viscid possessions above inertial properties by the long-wavelength and low Reynolds approximation. Exact solutions for the longitudinal pressure gradient, temperature and velocities are obtained. The pressure gradient and volume flow rate for different values of the flow parameters are also discussed. The flow property for the Jeffrey fluid is presented graphically as a function of the cilia and metachronal wave velocity.
Institute of Scientific and Technical Information of China (English)
ZHANG Hong-Bao; CAO Zhou-Jian; GAO Chong-Shou
2004-01-01
Si-Jie Gao has recently investigated Hawking radiation from spherically symmetrical gravitational collapse to an extremal R-N black hole for a real scalar field. Especially he estimated the upper bound for the expected number of particles in any wave packet belonging to Hout spontaneously produced from the state |0＞in, which confirms the traditional belief that extremal black holes do not radiate particles. Making some modifications, we demonstrate that the analysis can go through for a charged scalar field.
Ghaffarnejad, Hossein
2014-01-01
We use two dimensional analogue of Einstein-Hilbert gravity minimally coupled with a mass-less, charge-less quantum scalar matter field. The matter field propagates on spherically symmetric four dimensional curved space time which in two dimensional analogue its 2-sphere part is described by a dilaton scalar field. We seek renormaized expectation value of stress tensor operator of the spherical quantum scalar field. Hadamard renormalization prescription is applied in this article leading to non-free trace anomaly of covariantly conserved nonsingular stress tensor. Its covariantly conservation condition demands to input a variable cosmological parameter. With this variable cosmological parameter the derived trace anomaly will be correspond with results of the works presented in Refs. [5, 6, 7, 8, 14, 15, 16] where the zeta function regularization method is used and trace anomaly is obtained in terms of Ricci scalar of corresponding two dimensional metric and derivatives of the dilaton field. Also we obtain dif...
An Unbroken Axial Vector Current Conservation Law
Sharafiddinov, Rasulkhozha S
2015-01-01
The mass, energy and momentum of the neutrino of a true flavor have an axial-vector nature. As a consequence, the left-handed truly neutral neutrino in an axial-vector field of emission can be converted into a right-handed one and vice versa. This predicts the unidenticality of masses, energies and momenta of neutrinos of the different components. Recognizing such a difference in masses, energies, momenta and accepting that the left-handed axial-vector neutrino and the right-handed antineutrino of true neutrality refer to long-lived C-odd leptons, and the right-handed truly neutral neutrino and the left-handed axial-vector antineutrino are of short-lived fermions of C-oddity, we would write a new CP-even Dirac equation taking into account the flavor symmetrical axial-vector mass, energy and momentum matrices. Their presence explains the spontaneous mirror symmetry violation, confirming that an axial-vector current conservation law has never violated. They reflect the availability of a mirror Minkowski space i...
International Nuclear Information System (INIS)
The axial buckling behavior of magnetically affected current-carrying nanowires is studied accounting for the surface energy effect. Using Euler–Bernoulli beam theory, the Lorentz force on the nanowire is determined and the governing equations are established. By application of the Galerkin approach and assumed mode method, the critical axial compressive load of the nanostructure is evaluated in the cases of simply supported and fully clamped ends. The effects of surface energy, electric current, strength of the magnetic field, slenderness ratio, and nanowire’s radius on the axial buckling loads are comprehensively discussed. The obtained results reveal that both the electric current and exerted magnetic field endanger the axial stability of the nanowire. For high levels of electric current or magnetic field strength, the surface effect becomes significant in the axial buckling performance of the nanostructure. (paper)
Eriksson, Stefanie; Lasič, Samo; Nilsson, Markus; Westin, Carl-Fredrik; Topgaard, Daniel
2015-01-01
We introduce a nuclear magnetic resonance method for quantifying the shape of axially symmetric microscopic diffusion tensors in terms of a new diffusion anisotropy metric, DΔ, which has unique values for oblate, spherical, and prolate tensor shapes. The pulse sequence includes a series of equal-amplitude magnetic field gradient pulse pairs, the directions of which are tailored to give an axially symmetric diffusion-encoding tensor b with variable anisotropy bΔ. Averaging of data acquired for...
van, Ngoc Huynh; Lee, Jae-Hyun; Whang, Dongmok; Kang, Dae Joon
2016-06-01
We have successfully synthesized axially doped p- and n-type regions on a single Si nanowire (NW). Diodes and complementary metal-oxide-semiconductor (CMOS) inverter devices using single axial p- and n-channel Si NW field-effect transistors (FETs) were fabricated. We show that the threshold voltages of both p- and n-channel Si NW FETs can be lowered to nearly zero by effectively controlling the doping concentration. Because of the high performance of the p- and n-type Si NW channel FETs, especially with regard to the low threshold voltage, the fabricated NW CMOS inverters have a low operating voltage (DOI: 10.1039/c6nr01040g
International Nuclear Information System (INIS)
In this paper, the generation of high-quality and high-energy micro electron beam in vacuum by a chirped Gaussian laser pulse in the presence of an axial magnetic field is numerically investigated. The features of energy and angular spectra, emittances, and position distribution of electron beam are compared in two cases, i.e., in the presence and absence of an external magnetic field. The electron beam is accelerated with higher energy and qualified in spatial distribution in the presence of the magnetic field. The presence of an axial magnetic field improves electron beam spatial quality as well as its gained energy through keeping the electron motion parallel to the direction of propagation for longer distances. It has been found that a 64 μm electron bunch with about MeV initial energy becomes a 20 μm electron beam with high energy of the order of GeV, after interacting with a laser pulse in the presence of an external magnetic field
Energy Technology Data Exchange (ETDEWEB)
Akou, H., E-mail: h.akou@nit.ac.ir; Hamedi, M. [Department of Physics, Faculty of Basic Science, Babol University of Technology, Babol 47148-71167 (Iran, Islamic Republic of)
2015-10-15
In this paper, the generation of high-quality and high-energy micro electron beam in vacuum by a chirped Gaussian laser pulse in the presence of an axial magnetic field is numerically investigated. The features of energy and angular spectra, emittances, and position distribution of electron beam are compared in two cases, i.e., in the presence and absence of an external magnetic field. The electron beam is accelerated with higher energy and qualified in spatial distribution in the presence of the magnetic field. The presence of an axial magnetic field improves electron beam spatial quality as well as its gained energy through keeping the electron motion parallel to the direction of propagation for longer distances. It has been found that a 64 μm electron bunch with about MeV initial energy becomes a 20 μm electron beam with high energy of the order of GeV, after interacting with a laser pulse in the presence of an external magnetic field.
Divergence theorem for symmetric (0,2)-tensor fields on a semi-Riemannian manifold with boundary
International Nuclear Information System (INIS)
We prove in this paper a divergence theorem for symmetric (0,2)-tensors on a semi-Riemannian manifold with boundary. As a consequence we establish the complete divergence theorem on a semi-Riemannian manifold with any kinds of smooth boundaries. This result contains the previous attempts to write this theorem on a semi-Riemannian manifold as Unal results. A vanishing theorem for gradient timelike Killing vector fields on Einstein semi-Riemannian manifolds is obtained. As a tool, an induced volume form is defined for a degenerate boundary by using a star like operator that we define on degenerate submanifolds. (author)
Directory of Open Access Journals (Sweden)
Tamer Dawod
2015-01-01
Full Text Available Purpose: This work investigated the accuracy of prowess treatment planning system (TPS in dose calculation in a homogenous phantom for symmetric and asymmetric field sizes using collapse cone convolution / superposition algorithm (CCCS. Methods: The measurements were carried out at source-to-surface distance (SSD set to 100 cm for 6 and 10 MV photon beams. Data for a full set of measurements for symmetric fields and asymmetric fields, including inplane and crossplane profiles at various depths and percentage depth doses (PDDs were obtained during measurements on the linear accelerator.Results: The results showed that the asymmetric collimation dose lead to significant errors (up to approximately 7% in dose calculations if changes in primary beam intensity and beam quality. It is obvious that the most difference in the isodose curves was found in buildup and the penumbra regions. Conclusion: The results showed that the dose calculation using Prowess TPS based on CCCS algorithm is generally in excellent agreement with measurements.
Full mass range analysis of the QED effective action for an O(2)xO(3) symmetric field
Ahmadiniaz, Naser; Raya, Alfredo; Schubert, Christian
2013-01-01
An interesting class of background field configurations in quantum electrodynamics (QED) are the O(2)xO(3) symmetric fields, originally introduced by S.L. Adler in 1972. Those backgrounds have some instanton-like properties and yield a one-loop effective action that is highly nontrivial, but amenable to numerical calculation. Here, we use the recently developed "partial-wave-cutoff method" for a full mass range numerical analysis of the effective action for the "standard" O(2)xO(3) symmetric field, modified by a radial suppression factor. At large mass, we are able to match the asymptotics of the physically renormalized effective action against the leading two mass levels of the inverse mass expansion. For small masses, with a suitable choice of the renormalization scheme we obtain stable numerical results even in the massless limit. We analyze the N - point functions in this background and show that, even in the absence of the radial suppression factor, the two-point contribution to the effective action is t...
Hong, S. H.; Wilhelm, H. E.
1978-01-01
An electrical discharge between two ring electrodes embedded in the mantle of a cylindrical chamber is considered, in which the plasma in the anode and cathode regions rotates in opposite directions under the influence of an external axial magnetic field. The associated boundary-value problem for the coupled partial differential equations describing the azimuthal velocity and radial current-density fields is solved in closed form. The velocity, current density, induced magnetic induction, and electric fields are presented for typical Hartmann numbers, magnetic Reynolds numbers, and geometry parameters. The discharge is shown to produce anodic and cathodic plasma sections rotating at speeds of the order 1,000,000 cm/sec for conventional magnetic field intensities. Possible application of the magnetoactive discharge as a plasma centrifuge for isotope separation is discussed.
Strains and axial outflows in the field of a rotating black hole
Bini, Donato; Geralico, Andrea
2014-01-01
We study the behaviour of an initially spherical bunch of accelerated particles emitted along trajectories parallel to the symmetry axis of a rotating black hole. We find that, under suitable conditions, curvature and inertial strains compete to model the shape of axial outflows of matter contributing to generate jet-like structures. This is of course a purely kinematical effect which does not account by itself for physical processes underlying the formation of jets. In our analysis a crucial role is played by a property of the electric and magnetic part of the Weyl tensor to be Lorentz-invariant boosting along the axis of symmetry in Kerr spacetime.
Institute of Scientific and Technical Information of China (English)
张华; 施卫东; 陈斌; 曹卫东; 张启华
2014-01-01
Axial flow pump is a kind of typical pumps with rotor-stator interaction, thus the measurement of the flow field between impeller and guide vane would facilitate the study of the internal rotor-stator interaction mechanism. Through a structural modifi-cation of a traditional axial flow pump, the requirements of particle image velocimetry (PIV) measurement are met. Under the condition of opt.0.8Q , the axial vortex is identified between impeller hub and guide vane hub, which is developed into the main flow and to affect the movement when the relative positions of impeller and guide vane at different flow rates are the same. Besides, the development and the dissipation of the tip leakage and the passage vortex in impeller passages are mainly responsible for the difference of the flow field close to the outer rim. As the flow rate decreases, the distribution of the meridional velocities at the impeller outlet becomes more non-uniform and the radial velocity component keeps increasing. The PIV measurement results under the condition of opt.1.0Q indicate that the flow separation and the trailing vortex at the trailing edge of a blade are likely to result in a velocity sudden change in this area, which would dramatically destroy the continuity of the flow field. Moreover, the radial direction of the flow between impeller and guide vane on the measurement plane does not always point from hub to rim. For a certain position, the direction is just from rim to hub, as is affected by the location of the intersection line of the shooting section and the impeller blade on the impeller as well as the angle between the intersection line and the rotating shaft.
Jing, C.; Chang, C.; Gold, S. H.; Konecny, R.; Antipov, S.; Schoessow, P.; Kanareykin, A.; Gai, W.
2013-11-01
Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications.
Energy Technology Data Exchange (ETDEWEB)
Jing, C.; Konecny, R.; Antipov, S. [Euclid Techlabs, LLC, 5900 Harper Rd., Solon, Ohio 44139 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chang, C. [Science and Technology on High Power Microwave Laboratory, Xi' an City 710024 (China); Institute of Energy, Tsinghua University, Beijing 100084 (China); Gold, S. H. [Naval Research Laboratory, Plasma Physics Division, Washington, DC 20375 (United States); Schoessow, P.; Kanareykin, A. [Euclid Techlabs, LLC, 5900 Harper Rd., Solon, Ohio 44139 (United States); Gai, W. [High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2013-11-18
Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications.
Energy Technology Data Exchange (ETDEWEB)
Mayhall, D J; Stein, W; Gronberg, J B
2006-05-15
We have performed preliminary computer-based, transient, magnetostatic calculations of the eddy-current power loss in rotating titanium-alloy and aluminum wheels and wheel rims in the predominantly axially-directed, steady magnetic fields of two small, solenoidal coils. These calculations have been undertaken to assess the eddy-current power loss in various possible International Linear Collider (ILC) positron target wheels. They have also been done to validate the simulation code module against known results published in the literature. The commercially available software package used in these calculations is the Maxwell 3D, Version 10, Transient Module from the Ansoft Corporation.
Propagation of Axially Symmetric Detonation Waves
Energy Technology Data Exchange (ETDEWEB)
Druce, R L; Roeske, F; Souers, P C; Tarver, C M; Chow, C T S; Lee, R S; McGuire, E M; Overturf, G E; Vitello, P A
2002-06-26
We have studied the non-ideal propagation of detonation waves in LX-10 and in the insensitive explosive TATB. Explosively-driven, 5.8-mm-diameter, 0.125-mm-thick aluminum flyer plates were used to initiate 38-mm-diameter, hemispherical samples of LX-10 pressed to a density of 1.86 g/cm{sup 3} and of TATB at a density of 1.80 g/cm{sup 3}. The TATB powder was a grade called ultrafine (UFTATB), having an arithmetic mean particle diameter of about 8-10 {micro}m and a specific surface area of about 4.5 m{sup 2}/g. Using PMMA as a transducer, output pressure was measured at 5 discrete points on the booster using a Fabry-Perot velocimeter. Breakout time was measured on a line across the booster with a streak camera. Each of the experimental geometries was calculated using the Ignition and Growth Reactive Flow Model, the JWL++ Model and the Programmed Burn Model. Boosters at both ambient and cold (-20 C and -54 C) temperatures have been experimentally and computationally studied. A comparison of experimental and modeling results is presented.
Newtonian limit of axially symmetric spacetimes
International Nuclear Information System (INIS)
We illustrate how Ehlers' formal mathematical definition of the Newtonian limit requires additional information to successfully determine the Newtonian limit. This information can be obtained through the physical arguments of Cooperstock's definition. We show that Ehlers' formalism is equivalent to Cooperstock's derivation of the Newtonian limit when the physical arguments are included in the former definition
Santos-Oliván, Daniel; Sopuerta, Carlos F.
2016-05-01
We present a new hybrid Cauchy-characteristic evolution scheme that is particularly suited to study gravitational collapse in spherically symmetric asymptotically (global) anti-de Sitter (AdS) spacetimes. The Cauchy evolution allows us to track the scalar field through the different round trips to the AdS boundary, while the characteristic method can bring us very close to the point of formation of an apparent horizon. We describe all the details of the method, including the transition between the two evolution schemes and the details of the numerical implementation for the case of massless scalar fields. We use this scheme to provide more numerical evidence for a recent conjecture on the power law scaling of the apparent horizon mass resulting from the collapse of subcritical configurations. We also compute the critical exponents and echoing periods for a number of critical points and confirm the expectation that their values should be the same as in the asymptotically flat case.
International Nuclear Information System (INIS)
The problem of motion under more general (not necessarily axisymmetric) fields was touched in a few occasions, mainly in the search of integrable cases. In we have studied the problem of motion of a heavy magnetized gyrostat carrying electric charges and acted upon by uniform electric and magnetic fields in addition to gravity. The equilibrium positions of the gyrostat have been found. The stability analysis was performed for some positions of equilibrium when the body is dynamically symmetric and the gyrostatic moment is directed along the axis of symmetry. In this work we study the stability for all the equilibrium positions under no restriction on the moments of inertia and the gyrostatic moment. (author)
Lush, David C
2016-01-01
It is investigated whether the Planck-Einstein relation between the energy and frequency of light quanta, and the de Broglie wavelength of matter can be wholly or partially explained as consequences of the relativistic Doppler shift of electromagnetic fields caused by oscillating electric dipoles within the elementary particles constituting light and matter, and their electromagnetic interaction with similarly constituted particles. Assuming the oscillation is at the zitterbewegung frequency of the Dirac electron theory, the photon energy is found to be approximately half the value expected according to the Planck-Einstein relation. The relativistically Doppler shifted time-symmetric electromagnetic field due to the particle is found to have a superluminal phase velocity equal to that of the de Broglie matter wave, a group velocity equal to the particle velocity, and a wavelength of \\(h/p\\).
An Unbroken Axial-Vector Current Conservation Law
Sharafiddinov, Rasulkhozha S.
2016-04-01
The mass, energy and momentum of the neutrino of a true flavor have an axial-vector nature. As a consequence, the left-handed truly neutral neutrino in an axial-vector field of emission can be converted into a right-handed one and vice versa. This predicts the unidenticality of masses, energies and momenta of neutrinos of the different components. Recognizing such a difference in masses, energies, momenta and accepting that the left-handed axial-vector neutrino and the right-handed antineutrino of true neutrality refer to long-lived C-odd leptons, and the right-handed truly neutral neutrino and the left-handed axial-vector antineutrino are of short-lived fermions of C-oddity, we would write a new CP-even Dirac equation taking into account the flavor symmetrical axial-vector mass, energy and momentum matrices. Their presence explains the spontaneous mirror symmetry violation, confirming that an axial-vector current conservation law has never violated. They reflect the availability of a mirror Minkowski space in which a neutrino is characterized by left as well as by right space-time coordinates. Therefore, it is not surprising that whatever the main purposes experiments about a quasielastic axial-vector mass say in favor of an axial-vector mirror Minkowski space-time.
Primordial magnetic fields of non-minimal photon-torsion axial coupling origin
de Andrade, Garcia
2010-01-01
Dynamo action is shown to be induced from homogeneous non-minimal photon-torsion axial coupling in the quantum electrodynamics (QED) framework in Riemann flat spacetime contortion decays. The geometrical optics in Riemann-Cartan spacetime is considering and a plane wave expansion of the electromagnetic vector potential is considered leading to a set of the equations for the ray congruence. Since we are interested mainly on the torsion effects in this first report we just consider the Riemann-flat case composed of the Minkowskian spacetime with torsion. It is also shown that in torsionic de Sitter background the vacuum polarisation does alter the propagation of individual photons, an effect which is absent in Riemannian spaces. It is shown that the cosmological torsion background inhomogeneities induce Lorentz violation and massive photon modes in this QED. Magnetic dynamos in this torsioned spacetime electrodynamics are simpler obtained in Fourier space than the cosmic ones, previously obtained by Bassett et ...
International Nuclear Information System (INIS)
New flows and instabilities are presented for a ferrofluid drop contained in glass Hele-Shaw cells with simultaneously applied in-plane clockwise rotating and DC axial uniform magnetic fields. When a ferrofluid drop is stressed by a uniform DC axial magnetic field, up to ∼250 G in 0.9-1.4 mm gap Hele-Shaw cells, the drop forms a labyrinth pattern. With subsequent application of an in-plane uniform rotating magnetic field, up to ∼100 G rms at frequency 20-40 Hz, smooth spirals form from viscous shear due to ferrofluid flow. If the rotating magnetic field is applied first, the drop is held together without a labyrinth. Gradual increase of the DC axial magnetic field, to a critical magnetic field value, results in an abrupt phase transformation from a large drop to many small discrete droplets. A preliminary minimum magnetization and surface energy analysis is presented to model the phase transformation
International Nuclear Information System (INIS)
In the calculation of monitor units and treatment times of MV photon beams the head scatter factor Sc accounts for the change in photon fluence when the collimator setting and thus the field size is changed. Sc can be measured with a narrow beam-coaxial phantom [1] as a function of the settings of the X and Y collimator blocks. Although Sc is expected to have a symmetrical nature Sc turns out to be an asymmetrical function of these settings. Elongated fields in X and Y directions can have Sc values which differ several per cent. In order to obtain sufficient accuracy usually Sc is measured for a matrix of field sizes of for instance X=2 up to 40 cm and Y=2 up to 40 cm. The reason of this asymmetry originates from the fact that the X and Y blocks are located in different planes. So the aperture - looking upstream from the measurement point to the blocks - is an asymmetrical function of the collimator setting. Our approach is to correct the asymmetry in Sc by considering Sc as a function of the corrected field dimensions either CfX and Y or X and CfY. The factor Cf has a value between 0.0 and 1.0 depending on the beam energy and the accelerator design. An iteration algorithm based on the Clarkson approach is used to calculate a best fit Cf value from Sc values of square and some elongated fields. Effectively the Sc matrix is reduced to a one dimensional function Sc(r), with r the average radius of fields with dimensions X=Cfa and Y=a or X=a and Y=Cfa. The algorithm is applied to calculate Sc of rectangular shaped fields. The accuracy of the method, based on one single - a priori - unknown, parameter Cf is well within measurement accuracy (0.5 %). Besides, a substantial reduction of the number of Sc measurements, necessary to cover the clinically used fields, is achieved this way. The method is validated for symmetrical beams with energies ranging from 6 to 25 MV of accelerators of several manufacturers and also for asymmetrical wedged fields of the 6 MV beams of a
International Nuclear Information System (INIS)
Pipe elbows were important parts frequently used in the pipelines of nuclear power, thermal power and chemical plants, and their integrity needed to be assured under seismic loads and thermal stresses considering local wall thinning or complex stress distribution due to special configuration different from straight pipe. This article investigated in details elastic-plastic stress-strain state of pipe elbow using finite element analysis and clarified there existed high bi-axial stress field at side inner surface of pipe elbow axial cracks initiated. Bi-axial stress factor was around 0.6 for sound elbow and up to 0.95 for local wall thinning at crown. Fracture strain of 1.15 was reduced to around 0.15 for bi-axial stress factor from 0.6 to 0.9. Normalized fatigue life for bi-axial stress field (0.6 - 0.8) was largely reduced to around 15, 19 and 10% of fatigue life of uni-axial state dependent on material strength level. Proposed revised universal slopes taking account of multi-axial stress factor could explain qualitatively effects of strain range, internal pressure and ratchet strain (pre-strain) on low-cycle fatigue life of pipe elbow. (T. Tanaka)
Mukherjee, Arnab; Mukherjee, Rajdip; Ankit, Kumar; Bhattacharya, Avisor; Nestler, Britta
2016-03-01
In the present work, we study morphologies arising due to competing substrate interaction, electric field, and confinement effects on a symmetric diblock copolymer. We employ a coarse-grained nonlocal Cahn-Hilliard phenomenological model taking into account the appropriate contributions of substrate interaction and electrostatic field. The proposed model couples the Ohta-Kawasaki functional with Maxwell equation of electrostatics, thus alleviating the need for any approximate solution used in previous studies. We calculate the phase diagram in electric-field-substrate strength space for different film thicknesses. In addition to identifying the presence of parallel, perpendicular, and mixed lamellae phases similar to analytical calculations, we also find a region in the phase diagram where hybrid morphologies (combination of two phases) coexist. These hybrid morphologies arise either solely due to substrate affinity and confinement or are induced due to the applied electric field. The dependence of the critical fields for transition between the various phases on substrate strength, film thickness, and dielectric contrast is discussed. Some preliminary 3D results are also presented to corroborate the presence of hybrid morphologies.
Tuning phase structures of a symmetrical diblock copolymer with a patterned electric field.
Kan, Di; He, Xuehao
2016-05-11
Electric fields can induce the orientation of the phase interfaces of block copolymers and provide a potential method to tune polymer phase structures for nanomaterial manufacture. In this work, we applied self-consistent field theory to study the self-assembly of a diblock copolymer confined between two parallel neutral substrates on which a set of electrodes was imposed to form a patterned electric field. The results showed that an alternatively distributed electric field can induce the formation of a parallel lamellar phase structure, which exists stably only in the system with selective substrates. The phase structure was proved to be sensitive to the characteristics of the electric field distribution, such as the strength of the electric field, the size and position of the electrodes, and the corresponding phase diagram was calculated in detail. The transition pathway of the phase structure from the perpendicular layered phase to the parallel layered phase was further analysed using the minimum energy path method. It is shown that the path and the active energy barrier of the phase transition depend on the electric field strength. Compound electric field patterns that can be designed to control the formation of novel and complex microphase structures were also examined. PMID:27102422
SYMMETRIC VORTICAL STRUCTURE AND ITS TOPOLOGICAL STABILITY
Institute of Scientific and Technical Information of China (English)
WANG Gang; LIANG Xin-gang; GANG Ming-li
2005-01-01
Using time-dependent compressible laminar Navier-Stokes equations with a finite volume method incorporating a third-order-accurate discretization scheme, the flow structures around a slender at certain incidences are numerical simulated and typical crossflow patterns are presented. At incidence 10°, these vortical configurations are different at dissimilar axial locations though they are symmetric. At 35°, the symmetric vortical structures still maintain over the slender, yet their interaction at afterbody is intense than that at the forebody since the two vortices have fully developed downstream. The unstable topological structure of trajectory of saddle-to-saddle points and multiple limit cycle are further discussed in topological stability theory. These structures easily produce bifurcation with perturbation. The results support the view of hydrodynamic instability of vortices flow field.
Jiang, Yu; Wang, Xianyu
2014-01-01
This paper studied the periodic orbits, manifolds and chaos in a rotating plane-symmetric potential field. It is found that the dynamical behaviour near the equilibrium point is totally decided by the structure of the submanifolds and subspaces near the equilibrium point. The non-degenerate equilibrium points are classified into twelve cases. The necessary and sufficient conditions for the linearly stable, non-resonant unstable and resonant equilibrium points are established. Furthermore, it is found that the resonant equilibrium point is a Hopf bifurcation point which leads to the chaotic motion near the resonant equilibrium point; it is found the appearing and disappearing of periodic orbit families near resonant equilibrium points with parametric variation. Besides, it is discovered that the number of periodic orbit families depends on the structure of the submanifolds. In the end, the theory developed here is applied to two particular cases, the rotating homogeneous cube and the circular restricted three-...
Jiang, Chunsheng; Liang, Renrong; Wang, Jing; Xu, Jun
2015-09-01
A carrier-based analytical drain current model for negative capacitance symmetric double-gate field effect transistors (NC-SDG FETs) is proposed by solving the differential equation of the carrier, the Pao-Sah current formulation, and the Landau-Khalatnikov equation. The carrier equation is derived from Poisson’s equation and the Boltzmann distribution law. According to the model, an amplified semiconductor surface potential and a steeper subthreshold slope could be obtained with suitable thicknesses of the ferroelectric film and insulator layer at room temperature. Results predicted by the analytical model agree well with those of the numerical simulation from a 2D simulator without any fitting parameters. The analytical model is valid for all operation regions and captures the transitions between them without any auxiliary variables or functions. This model can be used to explore the operating mechanisms of NC-SDG FETs and to optimize device performance.
International Nuclear Information System (INIS)
A carrier-based analytical drain current model for negative capacitance symmetric double-gate field effect transistors (NC-SDG FETs) is proposed by solving the differential equation of the carrier, the Pao-Sah current formulation, and the Landau–Khalatnikov equation. The carrier equation is derived from Poisson’s equation and the Boltzmann distribution law. According to the model, an amplified semiconductor surface potential and a steeper subthreshold slope could be obtained with suitable thicknesses of the ferroelectric film and insulator layer at room temperature. Results predicted by the analytical model agree well with those of the numerical simulation from a 2D simulator without any fitting parameters. The analytical model is valid for all operation regions and captures the transitions between them without any auxiliary variables or functions. This model can be used to explore the operating mechanisms of NC-SDG FETs and to optimize device performance. (paper)
International Nuclear Information System (INIS)
A compact quantum correction model for a symmetric double gate (DG) metal-oxide-semiconductor field-effect transistor (MOSFET) is investigated. The compact quantum correction model is proposed from the concepts of the threshold voltage shift (ΔVTHQM) and the gate capacitance (Cg) degradation. First of all, ΔVTHQM induced by quantum mechanical (QM) effects is modeled. The Cg degradation is then modeled by introducing the inversion layer centroid. With ΔVTHQM and the Cg degradation, the QM effects are implemented in previously reported classical model and a comparison between the proposed quantum correction model and numerical simulation results is presented. Based on the results, the proposed quantum correction model can be applicable to the compact model of DG MOSFET
Chakraborty, Pritam; Sabharwall, Piyush; Carroll, Mark C.
2016-07-01
The fracture behavior of nuclear grade graphites is strongly influenced by underlying microstructural features such as the character of filler particles, and the distribution of pores and voids. These microstructural features influence the crack nucleation and propagation behavior, resulting in quasi-brittle fracture with a tortuous crack path and significant scatter in measured bulk strength. This study uses a phase-field method to model the microstructural and multi-axial fracture in H-451, a historic variant of nuclear graphite that provides the basis for an idealized study on a legacy grade. The representative volume elements are constructed from randomly located pores with random size obtained from experimentally determined log-normal distribution. The representative volume elements are then subjected to simulated multi-axial loading, and a reasonable agreement of the resulting fracture stress with experiments is obtained. Quasi-brittle stress-strain evolution with a tortuous crack path is also observed from the simulations and is consistent with experimental results.
轴流式血泵流场CFD仿真%Flow field CFD analysis of axial flow blood pump
Institute of Scientific and Technical Information of China (English)
谢雄; 谭建平
2014-01-01
In the development of axial flow blood pump,the arterial partial flow field may produce an area with very low flow shear rate,so it is necessary to consider the non-Newtonian charac-teristics of blood fluid.In this paper,a model of axial flow blood pump was established,and flow and rotate-speed’s impacts on the inlet and outlet of the flow field in the blood pump were ana-lyzed through Computational Fluid Dynamics (CFD)simulation,as wel as the influence of the guide vane on the flow field.By the pump water experiment of the designed blood pump,its out-put flow and pressure were measured;the results show that the designed blood pump is consist-ent on the law with the simulation.%在轴流式血泵的研发过程中，动脉局部流场中可能产生流动剪切率非常低的区域，因此有必要考虑血液的非牛顿特性。建立了轴流式血泵模型，通过CFD仿真分析得到血泵转速和流量的变化对血泵出入口压力分布和速度分布的影响，并采用水和甘油（2∶1）的混合流体替代血液，对设计的血泵进行驱动实验，测量了轴流式血泵输出流量和压力参数。结果表明：所设计的血泵在规律上和仿真是相符的。
Magnetic fields produced by rotating symmetrical bodies with homogeneous surface charge density
Espejel-Morales, R.; Murguía-Romero, G.; Calles, A.; Cabrera-Bravo, E.; Morán-López, J. L.
2016-07-01
We present a numerical calculation for the stationary magnetic field produced by different rotating bodies with homogeneous and constant surface charge density. The calculation is done by superposing the magnetic field produced by a set of loops of current which mimic the magnetic field produced by belts of current defined by slices of fixed width. We consider the cases of a sphere, ellipsoids, open and closed cylinders and a combination of these in a dumbbell-like shell. We also plot their magnetic field lines using a technique that make use of the Runge–Kutta fourth-order method. Up to our knowledge, the case of closed cylinders was not calculated before. In contrast to previous results, we find that the magnetic field inside finite hollow bodies is homogeneous only in the case of a sphere. This is consequence of the fact that, for the sphere, the surface of any slice taken perpendicularly to the rotation axis, depends only on its thickness, like in the case of an infinite cylinder.
Scalar field dark energy with a minimal coupling in a spherically symmetric background
Matsumoto, Jiro
2016-01-01
Dark energy models and modified gravity theories have been actively studied and the behaviors in the solar system have been also carefully investigated in a part of the models. However, the behaviors of the scalar field in an isotropic space-time under the simple models of dark energy, e.g. quintessence model without matter coupling, have not been well investigated. One of the reason of it would be the nonlinearity of the field equation. In this paper, the theoretical analysises are carried out by using the appropriate values of the parameters and taking some limit for the field. As a result, it is shown that there is a model that can naturally pass the solar system tests and there is also a model that would not be valid.
Dynamic conductivity of symmetric three-barrier plane nanosystem in constant electric field
Directory of Open Access Journals (Sweden)
O. Voitsekhivska
2011-03-01
Full Text Available The theory of dynamic conductivity of nanosystem is developed within the model of rectangular potentials and different effective masses of electron in open three-barrier resonance-tunnel structure in a constant homogeneous electric field. The application of this theory for the improvement of operating characteristics of quantum cascade laser active region (for the experimentally investigated In0.53Ga0.47As/In0.52Al0.48As heterosystem proves that for a certain geometric design of nanosystem there exists such minimal magnitude of constant electric field intensity, at which the electromagnetic field radiation power together with the density of current flowing through the separate cascade of quantum laser becomes maximal.
Initial operation of the MST [Madison Symmetric Torus] reversed field pinch
International Nuclear Information System (INIS)
During the initial operation of the MST reversed field pinch, plasmas have been obtained with current of 500 kA and reversal duration of 28 msec. Discharges typically are initiated with a loop voltage of 150 volts and attain a loop voltage of about 20 volts at the time of peak current. Density up to 2 /times/ 1013 cm/sup /minus/3/ is obtained, and electron temperature is measured to be about 300 eV for 400 kA plasmas. The plasma parameters are improving steadily with wall conditioning and field error reduction. Sawtooth-like oscillations and magnetic fluctuations are characterized. 2 refs., 4 figs
Scalar field dark energy with a minimal coupling in a spherically symmetric background
Matsumoto, Jiro
2016-01-01
Dark energy models and modified gravity theories have been actively studied and the behaviors in the solar system have been also carefully investigated in a part of the models. However, the behaviors of the scalar field in an isotropic space-time under the simple models of dark energy, e.g. quintessence model without matter coupling, have not been well investigated. One of the reason of it would be the nonlinearity of the field equation. In this paper, the theoretical analysises are carried o...
Particles versus fields in $\\mathcal{PT}$-symmetrically deformed integrable systems
Indian Academy of Sciences (India)
Andreas Fring
2009-08-01
We review some recent results on how $\\mathcal{PT}$ symmetry, that is a simultaneous time-reversal and parity transformation, can be used to construct new integrable models. Some complex valued multi-particle systems, such as deformations of the Calogero–Moser– Sutherland models, are shown to arise naturally from real valued field equations of non-linear integrable systems. Deformations of complex non-linear integrable field equations, some of them even allowing for compacton solutions, are also investigated. The integrabilty of various systems is established by means of the Painlevé test.
Energy Technology Data Exchange (ETDEWEB)
Cohen, S.A.; Milroy, R.D.
2000-01-13
The effects on magnetic-field-line structure of adding various static transverse magnetic fields to a Solovev-equilibrium field-reversed configuration is examined. It is shown that adding fields that are anti-symmetric about the axial mid-plane maintains the closed field-line structure, while adding fields with planar or helical symmetry opens the field structure. Anti-symmetric modes also introduce pronounced shear.
Radial electrical field in non axi-symmetrical tokamak plasmas - study through doppler reflectometry
International Nuclear Information System (INIS)
Nuclear fusion research aims at producing plasmas mainly heated by fusion reactions between Tritium and Deuterium ions. This work deals with the problem of turbulent transport, which is one of the main limiting factors in the performance of tokamak operation. It is focused on the radial electric field (Er, pointing outwards/inwards from the plasma), which can generate transport barriers when its shearing rate is sufficient to cause a turbulence de-correlation. We have investigated the mechanisms causing the spontaneous generation of the radial electric field inside the last closed magnetic surface. In the Tore Supra tokamak, a Doppler reflectometer allows a quasi-direct measurement of the electric drift velocity due to Er. The effect of ripple (a periodic variation of the magnetic field between two coils, in the toroidal direction) is shown by comparing the measurements with predictions from various models, corresponding to different diffusion regimes (ripple-plateau, local trapping). In some special experimental conditions, a locally positive radial electric field has been measured inside the last closed flux surface in Tore Supra, which contrasts with the usual negative Er in this region. This suggests the presence of other non-ambipolar mechanisms. A discussion on the possible role of MHD activity and islands based on the Doppler reflectometry measurements is made. (author)
Sini, R; Kuriakose, V C
2008-01-01
Dirac equation for a general black hole metric having a cosmic string in the back ground is derived. We evaluate quasi normal mode frequencies for Schwarzschild, RN extremal, SdS and near extremal SdS black hole space times with cosmic string perturbed by a massless Dirac field, using WKB approximation.
Ma, Jie; Wen, Guang-Dong; Su, Bao-Gen; Yang, Yi-Wen; Ren, Qi-Long
2015-06-01
Current-voltage (I-V) characteristics of hydrogen DC plasma torches with different sizes in an external axial magnetic field under atmospheric pressure are reported. Three anodes with different diameters are adopted in a 50-kW torch: 25 mm, 30 mm, and 35 mm, respectively. Two different diameters of anodes, that is, 100 mm and 130 mm, are adopted in a 1-MW plasma torch. The arc voltage shows a negative trend with the increase of arc current under the operating regimes. On the contrary, arc voltage shows a positive trend as the flow rate of carrier gas increases, and a similar trend is found with increasing the external magnetic flux density. A similarity formula is constructed to correlate the experimental data of the torches mentioned above. Linear fitting shows that the Pearson correlation coefficient is 0.9958. Project supported by the Special Fund for Basic Scientific Research of Central Colleges, China (Grant No. 2012FZA4023).
Directory of Open Access Journals (Sweden)
Sharma B.R.
2010-01-01
Full Text Available The effect of a weak uniform axial magnetic field on separation of a binary mixture of incompressible viscous thermally and electrically conducting fluids flowing due to a rotating disc of uniform high suction is examined. Neglecting the induced electric field the equations governing the motion, temperature and concentration are solved in cylindrical polar coordinate by expanding the flow parameters as well as the temperature and the concentration in powers of suction parameter. The solution obtained for concentration distribution is plotted against the different axial distances from the disc for various values of non-dimensional parameters. It is found that the temperature gradient, axial magnetic field, Reynolds number, Schmidt number, Prandtl number and suction parameter effect the species separation significantly.
Senoo, Yasutoshi
1987-03-01
The flow field near the tip of compressor rotor blades is distorted by leakage through the tip clearance and the performance of the compressor is deteriorated. The literature regarding the tip clearance of compressor blades consists of computational fluid mechanics and experimental studies on the flow field and the pressure loss. Empirical equations expressing the pressure loss and the efficiency drop are varied. They relate to the lift coefficient in different ways, depending upon the ways of understanding the mechanics of pressure losses. These methods are examined and compared. Also, a brief discussion is made on the optimum value of the tip clearance.
International Nuclear Information System (INIS)
Full text: We review the conceptual foundation of Yang-Mills gauge field theories. On these gauge theories the Standard Model (SM) are constructed. The fundamental postulates and their immediate consequence of the SM are formulated. The SM is a Yang-Mills type gauge field theory basically dictated by the Generalized Gauge Principle (GGP). According to this principle all fundamental forces of nature such as strong, electroweak, gravitational are mediated by an exchange of the Yang-Mills gauge fields corresponding gauge group. The SM is constructed by extension of the global non-Abelian SU(3)xSU(2)xU(1) symmetry to the local SU(3)xSU(2)xU(1) symmetry under which the Lagrangian of the SM invariant. This full symmetry has to be broken by Higgs mechanism down to the Electroweak gauge symmetry. The concept of fundamental particles does not exist. To Look for not Fundamental Particles but Fundamental symmetries. By searching of more general theory it is natural to search first of all Global symmetries and then to learn consequences connected with the localization of the global symmetries like wise of SM. The SM is renormalizable and therefor potentially consist at all energy scales. The SM in principle can describe the properties of the Universe beginning at 10-43 sec. after BIG BANG. A SM of the BIG BANG Particle physics provides one of the few windows of the high energy world beyond SM which is consistent with SM and Cosmology. All the fundamental particles of the SM such as quarks, leptons and weak intermediate vector-gauge Bosons except one Higgs boson H0 have been discovered and there masses and spins have been determined. The SM is stunning. Until now, no cracks have been found. There is no experiment that contradicts the SM. Moreover there is nothing observed beyond the SM. The SM works better and better. We proposed to construct colour singular nuclear forces theory based on Quantum Chromodynamics (QCD). As well Theological aspects of the BIG BANG
Symmetric structure of field algebra of G-spin models determined by a normal subgroup
International Nuclear Information System (INIS)
Let G be a finite group and H a normal subgroup. D(H; G) is the crossed product of C(H) and CG which is only a subalgebra of D(G), the double algebra of G. One can construct a C*-subalgebra FH of the field algebra F of G-spin models, so that FH is a D(H; G)-module algebra, whereas F is not. Then the observable algebra A(H,G) is obtained as the D(H; G)-invariant subalgebra of FH, and there exists a unique C*-representation of D(H; G) such that D(H; G) and A(H,G) are commutants with each other
Santos-Oliván, Daniel
2016-01-01
We present a new hybrid Cauchy-characteristic evolution method that is particularly suited for the study of gravitational collapse in spherically-symmetric asymptotically (global) Anti-de Sitter (AdS) spacetimes. The Cauchy evolution allows us to track the scalar field through the different bounces off the AdS boundary while the characteristic method can bring us very close to the point of formation of an apparent horizon. Here, we describe all the details of the method, including the transition between the two evolution schemes and the details of the numerical implementation for the case of massless scalar fields. We use this scheme to provide more numerical evidence for a recent conjecture on the power-law scaling of the apparent horizon mass resulting from the collapse of subcritical configurations. We also compute the critical exponents and echoing periods for a number of critical points and confirm the expectation that their values should be the same as in the asymptotically-flat case.
Two-dimensional inflow-wind solution of black hole accretion with an evenly symmetric magnetic field
Mosallanezhad, Amin; Yuan, Feng
2015-01-01
We solve the two-dimensional magnetohydrodynamic (MHD) equations of black hole accretion with the presence of magnetic field. The field includes a turbulent component, whose role is represented by the viscosity, and a large-scale ordered component. The latter is further assumed to be evenly symmetric with the equatorial plane. The equations are solved in the $r-\\theta$ plane of a spherical coordinate by assuming time-steady and radially self-similar. An inflow-wind solution is found. Around the equatorial plane, the gas is inflowing; while above and below the equatorial plane at a certain critical $\\theta$ angle, $\\theta\\sim 47^{\\circ}$, the inflow changes its direction of radial motion and becomes wind. The driving forces are analyzed and found to be the centrifugal force and the gradient of gas and magnetic pressure. The properties of wind are also calculated. The specific angular momentum of wind is found to be significantly larger than that of inflow, thus wind can transfer angular momentum outward. These...
Munaretto, S.; Chapman, B. E.; Nornberg, M. D.; Boguski, J.; DuBois, A. M.; Almagri, A. F.; Sarff, J. S.
2016-05-01
The orientation of 3D equilibria in the Madison Symmetric Torus (MST) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch can now be controlled with a resonant magnetic perturbation (RMP). Absent the RMP, the orientation of the stationary 3D equilibrium varies from shot to shot in a semi-random manner, making its diagnosis difficult. Produced with a poloidal array of saddle coils at the vertical insulated cut in MST's thick conducting shell, an m = 1 RMP with an amplitude br/B ˜ 10% forces the 3D structure into any desired orientation relative to MST's diagnostics. This control has led to improved diagnosis, revealing enhancements in both the central electron temperature and density. With sufficient amplitude, the RMP also inhibits the generation of high-energy (>20 keV) electrons, which otherwise emerge due to a reduction in magnetic stochasticity in the core. Field line tracing reveals that the RMP reintroduces stochasticity to the core. A m = 3 RMP of similar amplitude has little effect on the magnetic topology or the high-energy electrons.
Turbulent convection in a horizontal duct with strong axial magnetic field
Zhang, Xuan; Zikanov, Oleg
2014-11-01
Convection in a horizontal duct with one heated wall is studied computationally. The work is motivated by the concept of a blanket for fusion reactors, according to which liquid metal slowly flows in toroidal ducts aligned with the main component of the magnetic field. We first assume that the magnetic field is sufficiently strong for the flow to be purely two-dimensional and analyze chaotic flow regimes at very high Grashof numbers. Furthermore, three-dimensional perturbations are considered and the relation between the length of the duct and the critical Hartmann number, below which the flow becomes three-dimensional, is determined. Financial support was provided by the US NSF (Grant CBET 1232851).
International Nuclear Information System (INIS)
The Wolfenstein parametrization is extended to the quark masses in the deep ultraviolet, and an algorithm to derive symmetric textures which are compatible with existing data is developed. It is found that there are only five such textures
Axial Myopia Is Associated with Visual Field Prognosis of Primary Open-Angle Glaucoma
Qiu, Chen; Qian, Shaohong; Sun, Xinghuai; Zhou, Chuandi; Meng, Fanrong
2015-01-01
Purpose To identify whether myopia was associated with the visual field (VF) progression of primary open-angle glaucoma (POAG). Methods A total of 270 eyes of 270 POAG followed up for more than 3 years with ≥9 reliable VFs by Octopus perimetry were retrospectively reviewed. Myopia was divided into: mild myopia (-2.99 diopter [D], 0), moderate myopia (-5.99, 3.00 D), marked myopia (-9.00, -6.00 D) and non-myopia (0 D or more). An annual change in the mean defect (MD) slope >0.22 dB/y and 0.30 ...
International Nuclear Information System (INIS)
The power deposition of neutral beam injection (NBI) on translated field-reversed configuration (FRC) plasma has been investigated. A certain level of electron heating effect was observed in the slowly decaying phase of the decompressed FRC, leading to a hollow electron temperature profile. Numerical calculation of beam trajectories has shown that about 50% of the injected NB power is absorbed by the plasma electron inside the separatrix with a hollow deposition profile similar to the observed electron temperature profile. The estimated absorbed NB power of 120 kW will be enough to bring the change in electron temperature, since the electron conduction and radiation loss was estimated to be ∼100 kW
International Nuclear Information System (INIS)
It has been suggested that magnetically trapped particles play a role in the asymmetry-induced radial transport observed in the Occidental non-neutral plasma trap. This magnetic trapping would occur due to a small increase (β≡δB/B≅0.4%) in magnetic field at the center of our solenoid and would keep low velocity particles confined to the ends of the trap. To test this suggestion, three coils of additional windings have been added to the trap solenoid thus allowing adjustment of the axial field variation δB. The effect of these adjustments on typical radial flux resonances is investigated. Making B as uniform as possible reduces β by a factor of 5.9, but this produces little change in the transport. Varying β over the broader range from -8.5% to 9.5% gives variations of 20%-90% in the magnitude, peak frequency, and width of the flux resonances, but these variations do not match the predictions of a simple model of trapped particle transport based on isotropic particle distributions
Li, Jingqi
2011-09-01
The diode characteristics of carbon nanotube field-effect transistors (CNTFETs) with symmetric source and drain contacts have been experimentally found at zero gate voltage (Li J. et al., Appl. Phys. Lett., 92 (2008) 133111). We calculate this characteristic using a semiclassical method based on Schottky barrier transistor mechanism. The influences of metal work function, the diameter of the carbon nanotubes and the dielectric thickness on the rectification behavior have been studied. The calculation results show that the metal with a higher work function results in a better diode characteristics for a p-type CNTFET. For single-walled carbon nanotubes (SWNTs) with different band gaps, both forward current and reverse current increase with decreasing band gap, but the ratio of forward current to reverse current decreases with decreasing band gap. This result is well consistent with the experimental observations reported previously. The simulation of the dielectric thickness effect indicates that the thinner the dielectric layer, the better the rectification behavior. The CNTFETs without a bottom gate could not show the diode characteristics, which is consistent with the reported experimental observation. © 2011 Europhysics Letters Association.
Batkovich, D. V.; Chetyrkin, K. G.; Kompaniets, M. V.
2016-05-01
We report on a completely analytical calculation of the field anomalous dimension γφ and the critical exponent η for the O (n)-symmetric φ4 model at the record six loop level. We successfully compare our result for γφ with n = 1 with the predictions based on the method of the Borel resummation combined with a conformal mapping (Kazakov et al., 1979 [40]). Predictions for seven loop contribution to the field anomalous dimensions are given.
Gd-123 bulk field pole magnets cooled with condensed neon for axial-gap type synchronous motor
International Nuclear Information System (INIS)
We have conducted to develop an axial-gap type synchronous propulsion motor with Gd-bulk HTS field pole magnets. It has been established on the fundamental technology upon the liquid nitrogen cooling. In the present study, we aimed an output improvement of the motor by the magnetic flux density enhancement of the bulk HTS, in a word, the trapped magnetic flux density on the HTS bulk. The output of the motor depends on the physics of the motor, the magnetic flux density, and the electric current density flowing through the armature. We have employed a condensed neon with a helium GM refrigerator. The bulk HTS placed on the rotor disk inside the motor frame was successfully cooled down with circulating condensed neon. The temperature at the bulk HTS surface reached 38 K. Upon magnetization, we developed controlled magnetic field density distribution coil (CMDC) composed of a couple of pulsed copper armature coil. In the magnetization procedure, with decreasing magnetization temperature, minute by minute, after Sander and Kamijyo that the step cooling magnetization method was used. In addition, the CMDC coil has enabled to control the applied flux distribution. Three parameters as the temperature, the applied magnetic field, and the effective applied flux density distribution were changed within eight times pulsed magnetizations in total. Up to 4th pulsed magnetization, we kept (1st step) high temperature, and subsequent pulsed magnetizations were done at low temperature. As a result, the highest maximum trapped magnetic flux density was reached 1.31 T, about 2.5 times compared to the value obtained upon cooling with liquid nitrogen. Consequently, the output of the motor has been enhanced to 25 kW from 10 kW taken in the previous operation
Energy Technology Data Exchange (ETDEWEB)
Wang, Lijun, E-mail: lijunwang@mail.xjtu.edu.cn; Deng, Jie; Wang, Haijing; Jia, Shenli; Qin, Kang; Shi, Zongqian [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an 710049 (China)
2015-10-15
In this research, drawing vacuum arc (VA) experiments were conducted using composite contacts under currents ranging from 5 kA to 20 kA root mean square (rms). The new type of contact comprised an axial magnetic field (AMF) configuration and a transverse magnetic field (TMF) configuration. The TMF plate was in the center, surrounded by the AMF plate. The contact generated both AMFs and TMFs simultaneously. VA appearances and arc voltages were recorded, and the VA was modeled as a conductor for electromagnetic force analysis in ANSYS software. The results showed that the coaxiality of operating mechanisms significantly influenced arc behavior just as the arc was ignited. When arc brightness did not increase after ignition, there was a voltage drop accompanied with diffusion of the VA. As to VA development, when an arc was ignited on an AMF plate, it spread on the plate and rotated. Over time the arc current increased, the constricting arc forms, and the arc column rotated on the TMF plate under the action of Ampere's force. With regard to the influence of a magnetic field on a VA at different stages, in the initial drawing arc stage the TMF was dominant, and the arc started to rotate under the action of Ampere's force. Afterwards, the AMF was dominant, with a steadily burning arc. As for contact melting, in the initial arcing period, a contracted short arc caused severe melting and erosion of the contact plate. When the ignition spot or root was close to the slot of plate, the electromagnetic force pushed the arc toward slot and contact edge, resulting in local erosion of the slot region.
Wang, Lijun; Deng, Jie; Wang, Haijing; Jia, Shenli; Qin, Kang; Shi, Zongqian
2015-10-01
In this research, drawing vacuum arc (VA) experiments were conducted using composite contacts under currents ranging from 5 kA to 20 kA root mean square (rms). The new type of contact comprised an axial magnetic field (AMF) configuration and a transverse magnetic field (TMF) configuration. The TMF plate was in the center, surrounded by the AMF plate. The contact generated both AMFs and TMFs simultaneously. VA appearances and arc voltages were recorded, and the VA was modeled as a conductor for electromagnetic force analysis in ANSYS software. The results showed that the coaxiality of operating mechanisms significantly influenced arc behavior just as the arc was ignited. When arc brightness did not increase after ignition, there was a voltage drop accompanied with diffusion of the VA. As to VA development, when an arc was ignited on an AMF plate, it spread on the plate and rotated. Over time the arc current increased, the constricting arc forms, and the arc column rotated on the TMF plate under the action of Ampere's force. With regard to the influence of a magnetic field on a VA at different stages, in the initial drawing arc stage the TMF was dominant, and the arc started to rotate under the action of Ampere's force. Afterwards, the AMF was dominant, with a steadily burning arc. As for contact melting, in the initial arcing period, a contracted short arc caused severe melting and erosion of the contact plate. When the ignition spot or root was close to the slot of plate, the electromagnetic force pushed the arc toward slot and contact edge, resulting in local erosion of the slot region.
International Nuclear Information System (INIS)
In this research, drawing vacuum arc (VA) experiments were conducted using composite contacts under currents ranging from 5 kA to 20 kA root mean square (rms). The new type of contact comprised an axial magnetic field (AMF) configuration and a transverse magnetic field (TMF) configuration. The TMF plate was in the center, surrounded by the AMF plate. The contact generated both AMFs and TMFs simultaneously. VA appearances and arc voltages were recorded, and the VA was modeled as a conductor for electromagnetic force analysis in ANSYS software. The results showed that the coaxiality of operating mechanisms significantly influenced arc behavior just as the arc was ignited. When arc brightness did not increase after ignition, there was a voltage drop accompanied with diffusion of the VA. As to VA development, when an arc was ignited on an AMF plate, it spread on the plate and rotated. Over time the arc current increased, the constricting arc forms, and the arc column rotated on the TMF plate under the action of Ampere's force. With regard to the influence of a magnetic field on a VA at different stages, in the initial drawing arc stage the TMF was dominant, and the arc started to rotate under the action of Ampere's force. Afterwards, the AMF was dominant, with a steadily burning arc. As for contact melting, in the initial arcing period, a contracted short arc caused severe melting and erosion of the contact plate. When the ignition spot or root was close to the slot of plate, the electromagnetic force pushed the arc toward slot and contact edge, resulting in local erosion of the slot region
International Nuclear Information System (INIS)
Electron bunch acceleration by a laser pulse having Gaussian radial and temporal profiles of intensity has been studied numerically in a static helical magnetic wiggler in vacuum. The main electron bunch parameters for simulations are 10 MeV initial energy with 0.1% longitudinal energy spread, 1 mm mrad rms transverse emittance, and 3x1012 cm-3 density. It is shown that the radial Gaussian profile can decrease the acceleration gradient compared with that of the plane-wave approximation due to the reduction of electron-pulse interaction area. In order to collimate electron bunch and overcome the decreasing of the acceleration gradient, an external axial magnetic field is used. The importance of the electron initial phase with respect to laser pulse is considered, and some appropriate values are found. Finally, acceleration of a femtosecond (fs) microbunch with an optimum appropriate initial phase is considered, which leads to a nearly monoenergetic microbunch and an acceleration gradient of about ≅0.2 GeV/m
Liu, Yunqiang; Xu, Jiuping; Wang, Shize; Qi, Bin
2013-01-01
The axial stress and deformation of high temperature high pressure deviated gas wells are studied. A new model is multiple nonlinear equation systems by comprehensive consideration of axial load of tubular string, internal and external fluid pressure, normal pressure between the tubular and well wall, and friction and viscous friction of fluid flowing. The varied temperature and pressure fields were researched by the coupled differential equations concerning mass, momentum, and energy equations instead of traditional methods. The axial load, the normal pressure, the friction, and four deformation lengths of tubular string are got ten by means of the dimensionless iterative interpolation algorithm. The basic data of the X Well, 1300 meters deep, are used for case history calculations. The results and some useful conclusions can provide technical reliability in the process of designing well testing in oil or gas wells. PMID:24163623
Directory of Open Access Journals (Sweden)
Yunqiang Liu
2013-01-01
Full Text Available The axial stress and deformation of high temperature high pressure deviated gas wells are studied. A new model is multiple nonlinear equation systems by comprehensive consideration of axial load of tubular string, internal and external fluid pressure, normal pressure between the tubular and well wall, and friction and viscous friction of fluid flowing. The varied temperature and pressure fields were researched by the coupled differential equations concerning mass, momentum, and energy equations instead of traditional methods. The axial load, the normal pressure, the friction, and four deformation lengths of tubular string are got ten by means of the dimensionless iterative interpolation algorithm. The basic data of the X Well, 1300 meters deep, are used for case history calculations. The results and some useful conclusions can provide technical reliability in the process of designing well testing in oil or gas wells.
Caratori Tontini, Fabio; Crone, Timothy J.; Ronde, Cornel E. J.; Fornari, Daniel J.; Kinsey, James C.; Mittelstaedt, Eric; Tivey, Maurice
2016-06-01
High-resolution geophysical data have been collected using the Autonomous Underwater Vehicle (AUV) Sentry over the ASHES (Axial Seamount Hydrothermal Emission Study) high-temperature (~348°C) vent field at Axial Seamount, on the Juan de Fuca Ridge. Multiple surveys were performed on a 3-D grid at different altitudes above the seafloor, providing an unprecedented view of magnetic data resolution as a function of altitude above the seafloor. Magnetic data derived near the seafloor show that the ASHES field is characterized by a zone of low magnetization, which can be explained by hydrothermal alteration of the host volcanic rocks. Surface manifestations of hydrothermal activity at the ASHES vent field are likely controlled by a combination of local faults and fractures and different lava morphologies near the seafloor. Three-dimensional inversion of the magnetic data provides evidence of a vertical, pipe-like upflow zone of the hydrothermal fluids with a vertical extent of ~100 m.
Institute of Scientific and Technical Information of China (English)
郑春阳; 朱少平; 贺贤土
2002-01-01
The quasi-static magnetic fields created in the interaction of relativistic laser pulses with under-dense plasmashave been investigated by three-dimensional particle-in-cell simulation. The relativistic ponderomotive force candrive an intense electron current in the laser propagation direction, which is responsible for the generation ofa helical magnetic field. The axial magnetic field results from a difference beat of wave-wave, which drives asolenoidal current. In particular, the physical significance of the kinetic model for the generation of the axialmagnetic field is discussed.
Multiple broken symmetries in striped La2 -xBaxCuO4 detected by the field-symmetric Nernst effect
Soumyanarayanan, Anjan; Tee, X. Y.; Ito, T.; Ushiyama, T.; Tomioka, Y.; Panagopoulos, C.
2016-02-01
We report a thermoelectric investigation of the stripe and superconducting phases of the cuprate La2 -xBaxCuO4 near x =1 /8 . We vary the doping and the magnetic field to identify features in the field-symmetric Nernst effect consistent with the reports of time-reversal symmetry breaking above the superconducting Tc. Crucially, we further detect a field-invariant peak at the stripe charge order temperature, TCO. Our observations suggest the onset of a nontrivial charge ordered phase at TCO, and the subsequent presence of spontaneously generated vortices before the emergence of bulk superconductivity.
International Nuclear Information System (INIS)
Direct measurement of axial magnetic field in the PF-1000 dense plasma focus (DPF), and its reported correlation with neutron emission, call for a fresh look at previous reports of existence of axial magnetic field component in the DPF from other laboratories, and associated data suggesting toroidal directionality of fast ions participating in fusion reactions, with a view to understand the underlying physics. In this context, recent work dealing with application of the hyperbolic conservation law formalism to the DPF is extended in this paper to a curvilinear coordinate system, which reflects the shape of the DPF current sheath. Locally unidirectional shock propagation in this coordinate system enables construction of a system of 7 one-dimensional hyperbolic conservation law equations with geometric source terms, taking into account all the components of magnetic field and flow velocity. Rankine-Hugoniot jump conditions for this system lead to expressions for the axial magnetic field and three components of fluid velocity having high ion kinetic energy
Ultraviolet and infrared aspects of the axial anomaly. I
International Nuclear Information System (INIS)
The paper is the first part of a brief review of some perturbative aspects of the Adler-Bell-Jackiw axial anomaly, described in terms of ultraviolet and infrared behavior of the famous VVA triangle graph. Apart from a general overview of the diversified role played by the anomaly in quantum field theory and particle physics, an elementary introduction is presented to the subject of the anomaly, comprehensible to an uninitiated reader with only a basic background in quantum field theory. The ultraviolet aspects of the anomaly are stressed and the topics covered are the following: vector and axial-vector Ward identities for the VVA triangle graph; the anomaly and several ways to derive it, namely the symmetric momentum cut-off and shifting the integration variables in linearly divergent integrals; the Adler-Rosenberg argument; the Pauli-Villars method; and dimensional regularization. (author) 2 figs., 34 refs
Badescu, V.; Murariu, V.; Rotariu, O.; Rezlescu, N.
1996-01-01
The theory of magnetic particles′ capture on a HGMF-axial magnetic filter cell with bounded flow field is presented. The equations of particle motion for both potential and laminar flow are obtained. By analytical solving of these equations, the trajectories of particles are established. The flow velocity of the fluid suspension for the case of potential flow is set equal with the velocity averaged across the tube section for the laminar flow. Thus, it is possible to make a comparison between...
Shen, Yu; Ren, Zhongming; Li, Xi; Ren, Weili; Xi, Yan
2011-12-01
Effect of a low axial magnetic field on the growth behavior of the primary Al 2Cu phase in the Al-40 wt% Cu hypereutectic alloy during directional solidification at a low growth speed has been investigated experimentally. The results show that the application of a low magnetic field (≤1 T) causes the primary Al 2Cu phase to become deformed and irregular opposed to the well developed strip-like primary phase in the absence of the field. The deformation of the primary phase is maximum when a 0.5 T magnetic field is applied. Moreover, it has been found that the magnetic field promotes a transition of the primary phase morphology from faceted growth to irregular cellular structure and makes the primary phase spacing decrease with the increase of the magnetic field intensity. From the macroscopic scale, the magnetic field causes the occurrence of a considerable radial macrosegregation. These experimental results may be attributed to the effects of thermoelectric magnetic force (TEMF) in the solid and thermoelectromagnetic convection (TEMC) in the liquid. Further, the model of these effects is presented and evaluated numerically. The results indicate that the numerical magnitude of the TEMF during directional solidification under a 0.5 T low axial magnetic field can be of the order of 10 3 N/m 3. The force causes TEMC at different scales to modify the distribution of solute at the interface and should be responsible for the deformation, fracture and deflection of the primary phase.
Energy Technology Data Exchange (ETDEWEB)
Baisanov, O.A. [Military Institute of Air Defense Forces, Aktobe (Kazakhstan); Doskeyev, G.A.; Doskeyev, T.G. [Aktobe State University named after K. Zhubanov, Aktobe (Kazakhstan); Spivak-Lavrov, I.F., E-mail: spivakif@rambler.ru [Aktobe State University named after K. Zhubanov, Aktobe (Kazakhstan)
2011-07-21
The exact differential equations defining deviations of the paths of charged particles from the axial trajectory are derived in curvilinear coordinates. These equations are in a form suited for carrying out relativistically correct numerical calculations of the dynamics of charged particle beams.
International Nuclear Information System (INIS)
The exact differential equations defining deviations of the paths of charged particles from the axial trajectory are derived in curvilinear coordinates. These equations are in a form suited for carrying out relativistically correct numerical calculations of the dynamics of charged particle beams.
Stability analysis of restricted non-static axial symmetry
Energy Technology Data Exchange (ETDEWEB)
Sharif, M.; Bhatti, M. Zaeem Ul Haq, E-mail: msharif.math@pu.edu.pk, E-mail: mzaeem.math@gmail.com [Department of Mathematics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590 (Pakistan)
2013-11-01
This paper aims to investigate the instability of very restricted class of non-static axially symmetric spacetime with anisotropic matter configuration. The perturbation scheme is established for the Einstein field equations and conservation laws. The instability range in the Newtonian and post-Newtonian regions are explored by constructing the collapse equation in this scenario. It is found that the adiabatic index plays an important role in the stability analysis which depends upon the physical parameters i.e., energy density and anisotropic pressure of the fluid distribution.
Stability analysis of restricted non-static axial symmetry
International Nuclear Information System (INIS)
This paper aims to investigate the instability of very restricted class of non-static axially symmetric spacetime with anisotropic matter configuration. The perturbation scheme is established for the Einstein field equations and conservation laws. The instability range in the Newtonian and post-Newtonian regions are explored by constructing the collapse equation in this scenario. It is found that the adiabatic index plays an important role in the stability analysis which depends upon the physical parameters i.e., energy density and anisotropic pressure of the fluid distribution
International Nuclear Information System (INIS)
For the temperature fields in rod clads of experimental assemblies a good agreement have been got with use of prior calculations by subchannel code COBRA-IV-I, from results of which an additional information about δt/δX3 distribution was taken. The method of definition the local fields of velocity, turbulent kinetic energy, temperature and eddy diffusivities for one-phase axial stabilized fluids in arbitrary formed rod bundle assemblies with invariable upward geometry was developed. According to this model the AGURA code was worked out to calculate local thermal hydraulic problems in combination with temperature fields in fuel rods and constructive elements of fuel assemblies. The method does not use any prior geometric scales and is based only on invariant local flow parameters: turbulent kinetic energy, velocity field deformation tensor and specific work of inner friction. Verification of this method by available experimental data showed a good agreement of calculation data and findings of velocity and t.k.e. fields, when the secondary flows have not a substantial influence to a balance of axial momentum and turbulent kinetic energy. (author)
Exact solution of the one-dimensional super-symmetric t-J model with unparallel boundary fields
Zhang, Xin; Yang, Wen-Li; Shi, Kangjie; Wang, Yupeng
2013-01-01
The exact solution of the one-dimensional super-symmetric t-J model under generic integrable boundary conditions is obtained via the Bethe ansatz methods. With the coordinate Bethe ansatz, the corresponding R-matrix and K-matrices are derived for the second eigenvalue problem associated with spin degrees of freedom. It is found that the second eigenvalue problem can be transformed to that of the transfer matrix of the inhomogeneous XXX spin chain, which allows us to obtain the spectrum of the Hamiltonian and the associated Bethe ansatz equations by the off-diagonal Bethe ansatz method.
Ghanem, Sari; Häfner, Dietrich
2016-01-01
We prove uniform decay estimates in the entire exterior of the Schwarzschild black hole for gauge invariant norms on the Yang-Mills fields valued in the Lie algebra associated to the Lie group $SU(2)$. We assume that the initial data are spherically symmetric satisfying a certain Ansatz, and have small energy, which eliminates the stationary solutions which do not decay. We first prove a Morawetz type estimate that is stronger than the one assumed in previous work by the first author, without...
Energy Technology Data Exchange (ETDEWEB)
Fidanza, St
2003-11-15
In the first chapter (titled: non-commutative D-branes), we show that the B anti-symmetrical background fields can be embedded in the non-commutativity of branes and can distort gauge theories that branes convey. We know how to describe this transformation in the Abelian case thanks to the Kontsevic quantification formula. Moreover this formula combined to the Seiberg-Witter transformation allows one to compute more rapidly the explicit terms. For the non-Abelian case the situation is less clear. In the chapter 2 (titled: non-Abelian M5-branes), we have tackled the issue of the fields of a packet of N M5-branes. The direct approach based on a 6 dimensional super-symmetric multiplets has led to a stunning dead end, we have not been able to reproduce the expected anomaly in N{sup 3}. We have presented in a unified manner different gauge theories. We have shown that we can get a number of freedom degrees in the magnitude order of N{sup 3} from computations based on geometrical configurations of M2 membranes. In the chapter 3 (titled: systematizing mirror symmetry) we have shown that if the presence of a non-trivial Neveu-Schwarz flux constrains the compactification manifold geometry to shift from the Calabi-Yau case, we can yet specify a mirror symmetry that mixes geometry and background fields. (A.C.)
Indian Academy of Sciences (India)
Kunle Adegoke; Helmut Büttner
2010-02-01
We have investigated the one-dimensional spin-1/2 axial next-nearest-neighbour Ising (ANNNI) model in two orthogonal magnetic fields at zero temperature. There are four different possible ground state configurations for the ANNNI model in a longitudinal field, in the thermodynamic limit. The inclusion of a transverse field introduces quantum fluctuations which destroy the existing spin order along certain critical lines. The effects of the fluctuations in three of the four ordered regions were investigated using the finite-size scaling technique. The phase boundaries of the ANNNI model in two orthogonal magnetic fields were thus determined numerically. For certain limits of the Hamiltonian we compared the obtained results with the existing literature and our results were in good agreement with the results in the existing literature.
On the Reduction of Vector and Axial-Vector Fields in a Meson Effective Action at O(p4)
International Nuclear Information System (INIS)
Starting from an effective NJL-type quark interaction we have derived an effective meson action for the pseudoscalar sector. The vector and axial-vector degrees of freedom have been integrated out, applying the static equations of motion. As the results we have found a (reduced) pseudoscalar meson Lagrangian of the Gasser-Leutwyler type with modified structure coefficients Li. This method has been also used to construct the reduced weak and electromagnetic-weak currents. The application of the reduced Lagrangian and currents has been considered in physical processes. 36 refs., 1 fig., 1 tab
Institute of Scientific and Technical Information of China (English)
RONG Li; NIE Zuo-ren; ZUO Tie-yong
2006-01-01
A coupled thermal-mechanical model of the rotary swaging of pure magnesium was developed using the general finite-element software program MSC/Marc to visualize the effect of axial feeding velocity on the rotary swaging process. The radial displacement occurring in one pulse impact increases in proportion to axial feeding velocity (vax). When the other processing parameters are fixed, the surface roughness of the swaged bar increases with vax and is in parabolic relation with vax. There exists a minimum velocity vax, min below which the decrease of vax will no longer improve the surface roughness. Under the technological conditions of this simulation, when the finial diameter d=6.6 mm, vax, min=1.82 m/min, and when d=7.0 mm, vax, min=1.83 m/min. If Ra=3.2 is required for the end product, then vax, max=6.02 m/min is gotten for d=6.6 mm and vax, max=7.05 m/min for d=7.0mm. The increase of vax has no notable influence on strain distribution along radial direction. The errors between the experimental and simulated height of the spiral spine-like ridges are below 8.0%.
Nowak, Paweł Mateusz; Woźniakiewicz, Michał; Kościelniak, Paweł
2015-12-01
It is commonly accepted that the modern CE instruments equipped with efficient cooling system enable accurate determination of electrophoretic or electroosmotic mobilities. It is also often assumed that velocity of migration in a given buffer is constant throughout the capillary length. It is simultaneously neglected that the noncooled parts of capillary produce extensive Joule heating leading to an axial electric field distortion, which contributes to a difference between the effective and nominal electric field potentials and between velocities in the cooled and noncooled parts of capillary. This simplification introduces systematic errors, which so far were however not investigated experimentally. There was also no method proposed for their elimination. We show a simple and fast method allowing for estimation and elimination of these errors that is based on combination of a long-end and short-end injections. We use it to study the effects caused by variation of temperature, electric field, capillary length, and pH. PMID:26383237
International Nuclear Information System (INIS)
This report is a continuation of the thesis [23], devoted to the onset of necking plastic instabilities during tension tests on metallic plates bi-axially loaded in their plane. We are also interested here in compression tests, and in the development of antisymmetric defects with respect to the median plane of the plate. As in the thesis, we search for the dominant mode, i.e. the most unstable pair of wavelengths (λ1, λ2) in the loading plane. An approximate analytical formulation for the growth rate is proposed, especially for plane-strain tests in the absence of viscous effects, and for static tests in tension in the x1 and x2 loading directions. In that latter case, we retrieve published results [14][15]. For plane-strain tests, we show that infinitely dense networks of shear bands inclined at 45 deg. with respect to the loading direction instantaneously occur when heat softening prevails over work-hardening. (author)
Institute of Scientific and Technical Information of China (English)
Zhang Cun-Xi; Nie Yi-Hang; Liang Jiu-Qing
2008-01-01
We have investigated theoretically the field-driven electron-transport through a double-quantum-well semiconductor-heterostructure with spin-orbit coupling. The numerical results demonstrate that the transmission spectra are divided into two sets due to the bound-state level-splitting and each set contains two asymmetric resonance peaks which may be selectively suppressed by changing the difference in phase between two driving fields. When the phase difference changes from O to π, the dip of asymmetric resonance shifts from one side of resonance peak to the other side and the asymmetric Fano resonance degenerates into the symmetric Breit-Wigner resonance at a critical value of phase difference. Within a given range of incident electron energy, the spin polarization of transmission current is completely governed by the phase difference which may be used to realize the tunable spin filtering.
Salmi, Marie S.; Johnson, H. Paul; Tivey, Maurice A.; Hutnak, Michael
2014-09-01
A systematic heat flow survey using thermal blankets within the Endeavour segment of the Juan de Fuca Ridge axial valley provides quantitative estimates of the magnitude and distribution of conductive heat flow at a mid-ocean ridge, with the goal of testing current models of hydrothermal circulation present within newly formed oceanic crust. Thermal blankets were deployed covering an area of 700 by 450 m in the Raven Hydrothermal vent field area located 400 m north of the Main Endeavour hydrothermal field. A total of 176 successful blanket deployment sites measured heat flow values that ranged from 0 to 31 W m-2. Approximately 53% of the sites recorded values lower than 100 mW m-2, suggesting large areas of seawater recharge and advective extraction of lithospheric heat. High heat flow values were concentrated around relatively small "hot spots." Integration of heat flow values over the Raven survey area gives an estimate of conductive heat output of 0.3 MW, an average of 0.95 W m-2, over the survey area. Fluid circulation cell dimensions and scaling equations allow calculation of a Rayleigh number of approximately 700 in Layer 2A. The close proximity of high and low heat flow areas, coupled with previous estimates of surficial seafloor permeability, argues for the presence of small-scale hydrothermal fluid circulation cells within the high-porosity uppermost crustal layer of the axial seafloor.
Kurniawan, Candra
2012-01-01
Photonic crystal is a dielectric material which has a refractive index or permittivity which vary periodically, thus preventing the propagation of light with specific frequency and direction. The frequency range is called a photonic bandgap (PBG). If the structure of photonic crystals is modified by taking one line of rod in a photonic crystal is obtained a waveguide. Giving structures with symmetrical defects around the waveguide channel with the parameters given occurs coupling between the waveguide and cavity. Coupling indicates transfer part or all of the EM field depends on the frequency of EM field in the photonic crystal. Green tensor method can be used to calculate the total electric field in a 2D photonic crystal. With the aid of MATLAB programs can be shown to the powerful visualization calculation of the total electrical field in 2D photonic crystals. Based on analysis of the literature and the bandgap graphic and the field energy in the defects show that effective frequency which produces maximum ...
Study of axial magnetic effect
International Nuclear Information System (INIS)
The Axial Magnetic Effect manifests itself as an equilibrium energy flow of massless fermions induced by the axial (chiral) magnetic field. Here we study the Axial Magnetic Effect in the quenched SU(2) lattice gauge theory with massless overlap fermions at finite temperature. We numerically observe that in the low-temperature hadron phase the effect is absent due to the quark confinement. In the high-temperature deconfinement phase the energy flow is an increasing function of the temperature which reaches the predicted asymptotic T2 behavior at high temperatures. We find, however, that energy flow is about one order of magnitude lower compared to a theoretical prediction
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this article, the low pressure axial flow fan with circumferential skewed rotor blade, including the radial blade, the forward-skewed blade and the backward-skewed blade, was studied with experimental methods. The aerodynamic performance of the rotors was measured. At the design condition at outlet of the rotors, detailed flow measurements were performed with a five-hole probe and a Hot-Wire Anemometer (HWA). The results show that compared to the radial rotor, the forward-skewed rotor demonstrates a wider Stable Operating Range (SOR), is able to reduce the total pressure loss in the hub region and make main loading of blade accumulating in the mid-span region. There is a wider wake in the upper mid-span region of the forward-skewed rotor. Compared to the radial rotor, in the backward-skewed rotor there is higher total pressure loss near the hub and shroud regions and lower loss in the mid-span region. In addition, the velocity deficit in the wake is lower at mid-span of the backward-skewed rotor than the forward-skewed rotor.
International Nuclear Information System (INIS)
We investigate the question of whether and how the configuration space of the reduced system is restricted by the Hamiltonian constraint in the sense of Ashtekar and Horowitz. We deal with the model spherically symmetric system which has been defined and studied in the preceding papers of this series. We find restrictions of the asymptotical configuration space which seem to forbid the evaporation of black holes. Another consequence of the restrictions is that the relevant part of any spacetime with collapse can be foliated by Cauchy hypersurfaces so that the canonical formalism is applicable without problems. We show that singular apparent horizons can form, and that they are visible from the future null infinity, if the configuration space is not restricted. However, we are not able to construct the quantum field so that the results remain formal
International Nuclear Information System (INIS)
Full text: We present the design and first realization of short-wavelength (λ = 4.53 μm), single mode emitting quantum cascade lasers in a master oscillator power amplifier configuration. Watt-level peak optical output power is demonstrated for typical non-tapered 4 μm wide and 5.25 mm long (DFB: 1.25 mm, FP: 4 mm) devices. Far field measurements prove a symmetric, single-transverse-mode emission in TM00-mode with typical divergences of 25° in and 27° perpendicular to the growth direction. We demonstrate single mode tuning over a range of 7.9 cm-1 for temperatures between 263 K and 313 K and also single mode emission for different driving currents and varied pulse-lengths between 25 ns and 100 ns. The side mode suppression ratio is measured to be higher than 20 dB. (author)
Ghanem, Sari
2016-01-01
We prove uniform decay estimates in the entire exterior of the Schwarzschild black hole for gauge invariant norms on the Yang-Mills fields valued in the Lie algebra associated to the Lie group $SU(2)$. We assume that the initial data are spherically symmetric satisfying a certain Ansatz, and have small energy, which eliminates the stationary solutions which do not decay. We first prove a Morawetz type estimate that is stronger than the one assumed in previous work by the first author, without passing through the scalar wave equation on the Yang-Mills curvature, using the Yang-Mills equations directly. This allows one by then to adapt the proof constructed in this previous work to show local energy decay and uniform decay of the $L^{\\infty}$ norm of the middle components in the entire exterior of the Schwarzschild black hole, including the event horizon.
Kumar, Varun; Kumar, Manoj; Shakher, Chandra
2015-08-01
In this paper, digital holographic interferometry (DHI) is implemented to investigate the effect of upward decreasing gradient magnetic field on the temperature and temperature profile of diffusion flame created by butane torch burner. In the experiment double exposure digital holographic interferometry is used to calculate the temperature distribution inside the flame. First a digital hologram is recorded in the absence of flame and second hologram is recorded in the presence of flame. Phases in two different states of air (i.e. in absence of flame and presence of flame) are reconstructed individually by numerical method. The phase difference map is obtained by subtracting the reconstructed phase of air in presence and absence of flame. Refractive index inside the flame is obtained from the axi-symmetric phase difference data using the Abel inversion integral. Temperature distribution inside the flame is calculated from the refractive index data using Lorentz - Lorentz equation. Experiment is conducted on a diffusion flame created by butane torch burner in the absence of magnetic field and in presence of upward decreasing gradient magnetic field. Experimental investigations reveal that the maximum temperature inside the flame increases under the influence of upward decreasing magnetic field.
Inducing chaos by breaking axial symmetry in a black hole magnetosphere
Energy Technology Data Exchange (ETDEWEB)
Kopáček, O.; Karas, V., E-mail: kopacek@ig.cas.cz [Astronomical Institute, Academy of Sciences, Boční II, CZ-141 31 Prague (Czech Republic)
2014-06-01
While the motion of particles near a rotating, electrically neutral (Kerr), and charged (Kerr-Newman) black hole is always strictly regular, a perturbation in the gravitational or the electromagnetic field generally leads to chaos. The transition from regular to chaotic dynamics is relatively gradual if the system preserves axial symmetry, whereas non-axisymmetry induces chaos more efficiently. Here we study the development of chaos in an oblique (electro-vacuum) magnetosphere of a magnetized black hole. Besides the strong gravity of the massive source represented by the Kerr metric, we consider the presence of a weak, ordered, large-scale magnetic field. An axially symmetric model consisting of a rotating black hole embedded in an aligned magnetic field is generalized by allowing an oblique direction of the field having a general inclination with respect to the rotation axis of the system. The inclination of the field acts as an additional perturbation to the motion of charged particles as it breaks the axial symmetry of the system and cancels the related integral of motion. The axial component of angular momentum is no longer conserved and the resulting system thus has three degrees of freedom. Our primary concern within this contribution is to find out how sensitive the system of bound particles is to the inclination of the field. We employ the method of the maximal Lyapunov exponent to distinguish between regular and chaotic orbits and to quantify their chaoticity. We find that even a small misalignment induces chaotic motion.
The role of multipolar magnetic fields in pulsar magnetospheres
Asséo, E; Asseo, Estelle; Khechinashvili, David
2002-01-01
We explore the role of complex multipolar magnetic fields in determining physical processes near the surface of rotation powered pulsars. We model the actual magnetic field as the sum of global dipolar and star-centered multipolar fields. In configurations involving axially symmetric and uniform multipolar fields, 'neutral points' and 'neutral lines' exist close to the stellar surface. Also, the curvature radii of magnetic field lines near the stellar surface can never be smaller than the stellar radius, even for very high order multipoles. Consequently, such configurations are unable to provide an efficient pair creation process above pulsar polar caps, necessary for plasma mechanisms of generation of pulsar radiation. In configurations involving axially symmetric and non-uniform multipoles, the periphery of the pulsar polar cap becomes fragmented into symmetrically distributed narrow sub-regions where curvature radii of complex magnetic field lines are less than the radius of the star. The pair production p...
Directory of Open Access Journals (Sweden)
Fahad Abbasi
2016-01-01
Full Text Available This article addresses the peristaltic transport of Eyring-Prandtl fluid in an inclined asymmetric channel. Heat and mass transfer phenomena along with Soret and Dufour effects is analyzed. Effects of inclined magnetic field and Joule heating are also discussed. Long wavelength approximation is adopted. Numerical computations for flow quantities of interest are analyzed. It is found that the parabolic velocity profile tends to shift from center of the channel towards the channel walls in the case of opposing flow. Velocity and temperature decrease whereas concentration increases by increasing the non-Newtonian parameter. Further the dependence of magnetic field on the angle is quite significant
Rodionov, V N
2014-01-01
The modified Dirac-Pauli equations, which is entered by means of ${\\gamma_5}$-mass extension of Hamiltonian operators, are considered. We also take into account the interaction of fermions with the intensive homogenous magnetic field focusing attention on (g-2) gyromagnetic factor of particles with spin $1/2$. Without the use of perturbation theory in the external field the exact energy spectra are deduced with regard to spin effects of fermions. We discuss the possible proposals of experimental measuring of properties of new particles which arising in this model.
Rodionov, V. N.
2015-11-01
The modified Dirac-Pauli equations, which is entered by means of γ 5-mass extension of Hamiltonian operators, are considered. We also take into account the interaction of fermions with the intensive homogenous magnetic field focusing attention on (g-2) gyromagnetic factor of particles with spin 1/2. Without the use of perturbation theory in the external field the exact energy spectra are deduced with regard to spin effects of fermions. We discuss the possible proposals of experimental measuring of properties of new particles which arising in this model.
Energy Technology Data Exchange (ETDEWEB)
Flohr, Michael [Physikalisches Institut der Universitaet Bonn, Nussallee 12, 53115 Bonn (Germany)], E-mail: flohr@th.physik.uni-bonn.de; Voelskow, Julia [Physikalisches Institut der Universitaet Bonn, Nussallee 12, 53115 Bonn (Germany)], E-mail: voelskow@th.physik.uni-bonn.de
2008-04-01
The Virasoro field associated to b, c ghost systems with arbitrary integer spin {lambda} on an n-sheeted branched covering of the Riemann sphere is deformed. This leads to reducible but indecomposable representations, if the new Virasoro field acts on the space of states, enlarged by taking the tensor product over the different sheets of the surface. For {lambda}=1, proven LCFT structures are made explicit through this deformation. In the other cases, the existence of Jordan cells is ruled out in favour of a novel kind of indecomposable representations.
Particle-vortex symmetric liquid
Mulligan, Michael
2016-01-01
We introduce an effective theory with manifest particle-vortex symmetry for disordered thin films undergoing a magnetic field-tuned superconductor-insulator transition. The theory may enable one to access both the critical properties of the strong-disorder limit, which has recently been confirmed [Breznay et al., PNAS 113, 280 (2016)] to exhibit particle-vortex symmetric electrical response, and the metallic phase discovered earlier [Mason and Kapitulnik, Phys. Rev. Lett. 82, 5341 (1999)] in less disordered samples. Within the effective theory, the Cooper-pair and field-induced vortex degrees of freedom are simultaneously incorporated into an electrically-neutral Dirac fermion minimally coupled to an (emergent) Chern-Simons gauge field. A derivation of the theory follows upon mapping the superconductor-insulator transition to the integer quantum Hall plateau transition and the subsequent use of Son's particle-hole symmetric composite Fermi liquid. Remarkably, particle-vortex symmetric response does not requir...
Mass Effect on Axial Charge Dynamics
Guo, Er-dong
2016-01-01
We studied effect of finite quark mass on the dynamics of axial charge using the D3/D7 model in holography. The mass term in axial anomaly equation affects both the fluctuation (generation) and dissipation of axial charge. We studied the dependence of the effect on quark mass and external magnetic field. For axial charge generation, we calculated the mass diffusion rate, which characterizes the helicity flipping rate. The rate is a non-monotonous function of mass and can be significantly enhanced by the magnetic field. The diffusive behavior is also related to a divergent susceptibility of axial charge. For axial charge dissipation, we found that in the long time limit, the mass term dissipates all the charge effectively generated by parallel electric and magnetic fields. The result is consistent with a relaxation time approximation. The rate of dissipation through mass term is a monotonous increasing function of both quark mass and magnetic field.
Surti, S.; Karp, J. S.
2015-07-01
Current generation of commercial time-of-flight (TOF) PET scanners utilize 20-25 mm thick LSO or LYSO crystals and have an axial FOV (AFOV) in the range of 16-22 mm. Longer AFOV scanners would provide increased intrinsic sensitivity and require fewer bed positions for whole-body imaging. Recent simulation work has investigated the sensitivity gains that can be achieved with these long AFOV scanners, and has motivated new areas of investigation such as imaging with a very low dose of injected activity as well as providing whole-body dynamic imaging capability in one bed position. In this simulation work we model a 72 cm long scanner and prioritize the detector design choices in terms of timing resolution, crystal size (spatial resolution), crystal thickness (detector sensitivity), and depth-of-interaction (DOI) measurement capability. The generated list data are reconstructed with a list-mode OSEM algorithm using a Gaussian TOF kernel that depends on the timing resolution and blob basis functions for regularization. We use lesion phantoms and clinically relevant metrics for lesion detectability and contrast measurement. The scan time was fixed at 10 min for imaging a 100 cm long object assuming a 50% overlap between adjacent bed positions. Results show that a 72 cm long scanner can provide a factor of ten reduction in injected activity compared to an identical 18 cm long scanner to get equivalent lesion detectability. While improved timing resolution leads to further gains, using 3 mm (as opposed to 4 mm) wide crystals does not show any significant benefits for lesion detectability. A detector providing 2-level DOI information with equal crystal thickness also does not show significant gains. Finally, a 15 mm thick crystal leads to lower lesion detectability than a 20 mm thick crystal when keeping all other detector parameters (crystal width, timing resolution, and DOI capability) the same. However, improved timing performance with 15
International Nuclear Information System (INIS)
Current generation of commercial time-of-flight (TOF) PET scanners utilize 20–25 mm thick LSO or LYSO crystals and have an axial FOV (AFOV) in the range of 16–22 mm. Longer AFOV scanners would provide increased intrinsic sensitivity and require fewer bed positions for whole-body imaging. Recent simulation work has investigated the sensitivity gains that can be achieved with these long AFOV scanners, and has motivated new areas of investigation such as imaging with a very low dose of injected activity as well as providing whole-body dynamic imaging capability in one bed position. In this simulation work we model a 72 cm long scanner and prioritize the detector design choices in terms of timing resolution, crystal size (spatial resolution), crystal thickness (detector sensitivity), and depth-of-interaction (DOI) measurement capability. The generated list data are reconstructed with a list-mode OSEM algorithm using a Gaussian TOF kernel that depends on the timing resolution and blob basis functions for regularization. We use lesion phantoms and clinically relevant metrics for lesion detectability and contrast measurement. The scan time was fixed at 10 min for imaging a 100 cm long object assuming a 50% overlap between adjacent bed positions. Results show that a 72 cm long scanner can provide a factor of ten reduction in injected activity compared to an identical 18 cm long scanner to get equivalent lesion detectability. While improved timing resolution leads to further gains, using 3 mm (as opposed to 4 mm) wide crystals does not show any significant benefits for lesion detectability. A detector providing 2-level DOI information with equal crystal thickness also does not show significant gains. Finally, a 15 mm thick crystal leads to lower lesion detectability than a 20 mm thick crystal when keeping all other detector parameters (crystal width, timing resolution, and DOI capability) the same. However, improved timing performance with 15
International Nuclear Information System (INIS)
The Madison Symmetric Torus (MST) is the newest and largest reversed field pinch presently in operation. It incorporates a number of design features that set it apart from other pinches, including the use of the conducting shell as both a vacuum vessel and single-turn toroidal field coil. Specially insulated voltage gaps are exposed to the plasma. Magnetic field errors at these gaps as well as at the various diagnostic and pumping ports are minimized through a variety of techniques. The physics goals of MST include study of the effect of large plasma size on confinement and the investigation, in detail, of RFP turbulence, dynamo and transport. Details of the design and initial operation of the device are presented
R., Sini; Varghese, Nijo; Kuriakose, V. C.
2008-01-01
Dirac equation for a general black hole metric having a cosmic string is derived. The quasi-normal mode frequencies for Schwarzschild, RN extremal, SdS and near extremal SdS black hole space-times with cosmic string perturbed by a massless Dirac field are obtained using WKB approximation and found that in all these cases, decay is less in black holes having cosmic string compared to black holes with out string.
Metamorphosis of helical magnetorotational instability in the presence axial electric current
Priede, Jānis
2014-01-01
This paper presents numerical linear stability analysis of a cylindrical Taylor-Couette flow of liquid metal carrying axial electric current in a generally helical external magnetic field. Axially symmetric disturbances are considered in the inductionless approximation corresponding to zero magnetic Prandtl number. It is shown that the electric current passing through the liquid can extend the range of helical magnetorotational instability indefinitely by transforming it into a purely electromagnetic instability. Two different electromagnetic instability mechanisms are found. The first is that of the well-known Tayler instability, which is due to the interaction of the electric current with its own magnetic field. The second is a new kind of electromagnetic instability driven by the interaction of electric current with a weak collinear magnetic field.
Ortiz, Néstor
2013-01-01
A spherical dust cloud which is initially at rest and which has a monotonously decaying density profile collapses and forms a shell-focussing singularity. Provided the density profile is not too flat, meaning that its second radial derivative is negative at the center, this singularity is visible to local, and sometimes even to global observers. According to the strong cosmic censorship conjecture, such naked singularities should be unstable under generic, nonspherical perturbations of the initial data or when more realistic matter models are considered. In an attempt to gain some understanding about this stability issue, in this work we initiate the analysis of a simpler but related problem. We discuss the stability of test fields propagating in the vicinity of the Cauchy horizon associated to the naked central singularity. We first study the high-frequency limit and show that the fields undergo a blueshift as they approach the Cauchy horizon. However, in contrast to what occurs at inner horizons of black ho...
International Nuclear Information System (INIS)
Thomson scattering measurements of the central electron temperature and density during the plasma current peak have been performed on the MST Reversed Field Pinch (RFP). This Thomson scattering diagnostic was calibrated for absolute electron density measurements. These measurements of Te and ne, when combined with profile assumptions, were used to calculate estimates of energy confinement time (τE) and poloidal beta (βθ). A standard discharge with Ip ∼ 400 kA, F ∼ -0.1, and θ ∼ 1.6 typically exhibited Te ∼ 275 eV, ne ∼ 2.0 x 1013 cm-3, τE ≤ 1 ms, and βθ ≤ 8%. The results of a limited plasma current scaling study did not indicate a strong scaling of Te or τE with Ip. The Thomson scattering diagnostic was used in conjunction with a bolometer, VUV radiation monitor, and edge magnetic coils to study the loss of energy from the plasma. Results indicate that thermal transport from stochastic magnetic fields, particle loss, and radiation are important energy loss processes. The experiments done for this study included an F-scan, a paddle limiter insertion series, and an argon doping series. The plasma maintained a constant βτ during these perturbation experiments, suggesting that increases in one energy loss channel are compensated by drops in other channels and increases in input power to the plasma
SU-D-9A-04: Brain PET/CT Imaging On a Scanner with a Large Axial Field-Of-View
International Nuclear Information System (INIS)
Purpose: Large axial field-of-view (FOV) PET/CT scanners are valued for high sensitivity. Brain PET image quality may depend on the head position within the FOV. We investigated the precision of activity estimation for brain PET imaging when the brain was positioned at the end (END) and in the middle (CEN) of the FOV. The additional CT dose for the CEN position was recorded. Methods: An image quality (Jaszczak) phantom and a striatal phantom were filled with F-18 and positioned in END and CEN locations. For each phantom and each location, we acquired a ∼1-hr listmode PET, rebinned the data into 10 frames with equal number of coincidence events, and reconstructed each frame using an iterative algorithm. For the striatal phantom, END and CEN were compared by drawing on each image three regions of interest (ROI) in axially separated uniform areas. The standard deviation of the activity estimation within each ROI was averaged over the 10 images. The coefficient of variation (CV) for activity estimation was calculated at each position. Image quality was assessed by inspecting the resolution bar pattern in the Jaszczak phantom at two different head positions. Results: The CV was the lowest for ROIs near the center of the FOV. For slices near the end, not only was the CV highest, but also the resolution pattern was degraded. CTDIvol summarized in the dose report indicated that the CT dose was ∼ 10% higher for CEN as compared to END position. Conclusion: Positioning the brain in the middle of the FOV in a large FOV PET/CT scanner allows more precise measurement of tracer uptake and better image quality at the cost of increased CT dose. For the end location longer scan times may minimize image quality degradation without any additional CT dose
Davies, Ben; Sahu, Kailash C
2007-01-01
We present NAOMI/OASIS adaptive-optics assisted integral-field spectroscopy of the transitional massive hypergiant IRC +10420, an extreme mass-losing star apparently in the process of evolving from a Red Supergiant toward the Wolf-Rayet phase. To investigate the present-day mass-loss geometry of the star, we study the appearance of the line-emission from the inner wind as viewed when reflected off the surrounding nebula. We find that, contrary to previous work, there is strong evidence for wind axi-symmetry, based on the equivalent-width and velocity variations of H$\\alpha$ and Fe {\\sc ii} $\\lambda$6516. We attribute this behaviour to the appearance of the complex line-profiles when viewed from different angles. We also speculate that the Ti {\\sc ii} emission originates in the outer nebula in a region analogous to the Strontium Filament of $\\eta$ Carinae, based on the morphology of the line-emission. Finally, we suggest that the present-day axisymmetric wind of IRC +10420, combined with its continued blueward...
Vectorial versus axial goldstone bosons
International Nuclear Information System (INIS)
The Yukawa interactions of fermions with Goldstone bosons are given in closed form for an arbitrary renormalizable field theory to all orders of perturbation theory or for a general effective Lagrangian. Although the diagonal couplings are always pseudoscalar there is an important difference between spontaneously broken vector and axial-vector global symmetries. Compared to the axial case, the diagonal douplings of 'vectorial' Goldstone bosons to charged fermions are suppressed by mixing angles or appear only via radiative corrections involving gauge fields. This general result may be relevant for the problem of flavour symmetry breaking in composite models. (Author)
Origin of axial current in scyllac
International Nuclear Information System (INIS)
The origin of the axial current observed in Scyllac (a high beta stellarator experiment) is discussed. A shaped coil and/or helical winding produce rotational transform which links magnetic lines of force to the plasma column and the axial current is induced electromagnetically. This phenomenon is inherent in a pulsed high-beta stellarator. The rotational transform produced by the induced axial current is much smaller than that associated with the l = 1, 0 equilibrium fields. The effect of the axial current on the equilibrium and stability of the plasma column is thus small. It is also shown that the magnetic field shear near a plasma surface is very strong
Symmetrization of Facade Layouts
Jiang, Haiyong
2016-02-26
We present an automatic approach for symmetrizing urban facade layouts. Our method can generate a symmetric layout through minimally modifying the original input layout. Based on the principles of symmetry in urban design, we formulate facade layout symmetrization as an optimization problem. Our method further enhances the regularity of the final layout by redistributing and aligning elements in the layout. We demonstrate that the proposed solution can effectively generate symmetric facade layouts.
Institute of Scientific and Technical Information of China (English)
SHI Zongqian; LIU Zhigang; JIA Shenli; SONG Xiaochuan; WANG Lijun
2009-01-01
Effect of the axial magnetic field (AMF) on resisting the constriction of a high-current vacuum arc is studied in this paper. Two typical AMF distributions were investigated, i.e., the traditional bell-shaped AMF, and the saddle-shaped AMF. Experiments were conducted in a detachable vacuum chamber with a rms arc current in the range of 10 kA to 25 kA. The arc column was photographed by a high-speed digital camera with an exposure time of 2 microseconds. The constriction of the vacuum arc was compared by processing the images of the arc column under the two different field configurations and numerically determining the dimensions of the arc column near the electrodes. It was also confirmed that the AMF distribution had a signifcant influence on its effectiveness in resisting arc constriction, Furthermore, the AMF strength near the periphery of the arc is more influential than that at the centre of the electrodes in resisting arc constriction.
Chaotic motion in axially symmetric potentials with oblate quadrupole deformation
International Nuclear Information System (INIS)
By computing the Poincare's surfaces of section and Lyapunov exponents, we study the effect of introducing an oblate quadrupole in the dynamics associated with two generic spherical potentials of physical interest: the central monopole and the isotropic harmonic oscillator. In the former case we find saddle points in the effective potential, in contrast to the statements presented by Gueron and Letelier in [E. Gueron, P.S. Letelier, Phys. Rev. E 63 (2001) 035201]. The results we show in the second case have application in nuclear or atomic physics. In particular, we find values of oblate deformation leading to a disappearance of shell structure in the single-particle spectrum. -- Highlights: → We find chaotic motion around a monopole with oblate quadrupole deformation. → This corrects the statements introduced in [E. Gueron, P.S. Letelier, Phys. Rev. E 63 (2001) 035201]. → We present an alternative model for the potential due to an oblate deformed nuclei. → This leads to stochastic regions in the phase space of classical orbits. → It suggests that the shell structure of single-particle spectrum tends to disappear.
Chaotic motion in axially symmetric potentials with oblate quadrupole deformation
Energy Technology Data Exchange (ETDEWEB)
Letelier, Patricio S. [Departamento de Matematica Aplicada, IMECC, Universidade Estadual de Campinas, 13083-859, Campinas, SP (Brazil); Ramos-Caro, Javier, E-mail: javier@ime.unicamp.br [Departamento de Matematica Aplicada, IMECC, Universidade Estadual de Campinas, 13083-859, Campinas, SP (Brazil); Lopez-Suspes, Framsol, E-mail: framsol@gmail.com [Facultad de Telecomunicaciones, Universidad Santo Tomas and Escuela de Fisica, Universidad Industrial de Santander, Bucaramanga (Colombia)
2011-10-03
By computing the Poincare's surfaces of section and Lyapunov exponents, we study the effect of introducing an oblate quadrupole in the dynamics associated with two generic spherical potentials of physical interest: the central monopole and the isotropic harmonic oscillator. In the former case we find saddle points in the effective potential, in contrast to the statements presented by Gueron and Letelier in [E. Gueron, P.S. Letelier, Phys. Rev. E 63 (2001) 035201]. The results we show in the second case have application in nuclear or atomic physics. In particular, we find values of oblate deformation leading to a disappearance of shell structure in the single-particle spectrum. -- Highlights: → We find chaotic motion around a monopole with oblate quadrupole deformation. → This corrects the statements introduced in [E. Gueron, P.S. Letelier, Phys. Rev. E 63 (2001) 035201]. → We present an alternative model for the potential due to an oblate deformed nuclei. → This leads to stochastic regions in the phase space of classical orbits. → It suggests that the shell structure of single-particle spectrum tends to disappear.
Convection in axially symmetric accretion discs with microscopic transport coefficients
Malanchev, K L; Shakura, N I
2016-01-01
The vertical structure of stationary thin accretion discs is calculated from the energy balance equation with heat generation due to microscopic ion viscosity {\\eta} and electron heat conductivity {\\kappa}, both depending on temperature. In the optically thin discs it is found that for the heat conductivity increasing with temperature, the vertical temperature gradient exceeds the adiabatic value at some height, suggesting convective instability in the upper disc layer. There is a critical Prandtl number, Pr = 4/9, above which a Keplerian disc become fully convective. The vertical density distribution of optically thin laminar accretion discs as found from the hydrostatic equilibrium equation cannot be generally described by a polytrope but in the case of constant viscosity and heat conductivity. In the optically thick discs with radiation heat transfer, the vertical disc structure is found to be convectively stable for both absorption dominated and scattering dominated opacities, unless a very steep dependen...
Three-dimensional equilibria in axially symmetric tokamaks
Garabedian, Paul R.
2006-01-01
The NSTAB and TRAN computer codes have been developed to study equilibrium, stability, and transport in fusion plasmas with three-dimensional (3D) geometry. The numerical method that is applied calculates islands in tokamaks like the Doublet III-D at General Atomic and the International Thermonuclear Experimental Reactor. When bifurcated 3D solutions are used in Monte Carlo computations of the energy confinement time, a realistic simulation of transport is obtained. The significance of findin...
Computation of liquid drop deformation energy for axial symmetric nuclei
International Nuclear Information System (INIS)
Computation methods for deformation dependent terms of the nuclear potential energy in the Myers-Swiatecki's and Krappe-Nix's variants of the liquid-drop model are presented. Also, an extension of the Krappe-Nix integral, surface and Coulomb energies formulas in case of reflection asymmetric deformations leading to fragments with different charge-to-mass ratio is introduced. (author)
Axially symmetric equations for differential pulsar rotation with superfluid entrainment
Antonelli, Marco
2016-01-01
We propose an analytical two-components model for pulsar rotational dynamics: the aim is to reduce the 3D hydrodynamical problem to a 1D (radial) problem, using the hypothesis of negligible azimuthal inhomogeneities. The result is the construction of a computationally simple model that takes into account for the non-uniform structure of the star, entrainment effect and differential rotation of the superfluid component. For the first time all these ingredients are treated in a fully consistent way within the picture provided by our initial hypotheses. Our treatment clarifies which are the physical inputs needed to build, to current knowledge, more realistic simulations of rotating neutron stars and gives a neat description of the effect of entrainment when straight vortex lines are considered. Moreover, on this basis, we briefly introduce a new method that can be used to put a constraint to the mass of the pulsars that display very large glitches and to the relative spin up timescales.
Studying optical characteristics of an axial symmetric non stationary plasma
International Nuclear Information System (INIS)
The distribution function of arc pulsations was obtained as functions of current intensity, gas flow rate, and distance from the cathode in a plasmatron with a fixed arc length. The intensities of plasma emission were measured by the method of transverse images. As the results, the temperature distribution over the arc radius was determined and the effect of pulsations on the measurement precision was noted
Dust-filled axially symmetric universes with a cosmological constant
Aguiar, P; Aguiar, Paulo; Crawford, Paulo
2000-01-01
Following the recent recognition of a positive value for the vacuum energy density and the realization that a simple Kantowski-Sachs model might fit the classical tests of cosmology, we study the qualitative behavior of three anisotropic and homogeneous models: Kantowski-Sachs, Bianchi type-I and Bianchi type-III universes, with dust and a cosmological constant, in order to find out which are physically permitted. We find that these models undergo isotropization up to the point that the observations will not be able to distinguish between them and the standard model, except for the Kantowski-Sachs model $(\\Omega_{k_{0}}0)$ with $\\Omega_{\\Lambda_{0}}$ smaller than some critical value $\\Omega_{\\Lambda_{M}}$. Even if one imposes that the Universe should be nearly isotropic since the last scattering epoch ($z\\approx 1000$), meaning that the Universe should have approximately the same Hubble parameter in all directions (considering the COBE 4-Year data), there is still a large range for the matter density paramete...
International Nuclear Information System (INIS)
We investigate the effective potential of the PT symmetric (-gφ4) field theory, perturbatively as well as non-perturbatively. For the perturbative calculations, we first use normal ordering to obtain the first order effective potential, from which the predicted vacuum condensate vanishes exponentially as G→0+, in agreement with previous calculations. For the higher orders, we employ the invariance of the bare parameters under the change of the mass scale t to fix the transformed form totally equivalent to the original theory. The form so obtained up to G3 is new and shows that all the 1PI amplitudes are perturbative for both the G>1 region. For the intermediate region, we modified the fractal self-similar resummation method to have a unique resummation formula for all G values. This unique formula is necessary, because the effective potential is the generating functional for all the one-particle irreducible (1PI) amplitudes that can be obtained via ∂nE/∂bn, and thus we can obtain an analytic calculation of the 1PI amplitudes. Again, the resummed form of the effective potential is new and interpolates the effective potential between the perturbative regions. Moreover, the resummed effective potential agrees in spirit to a previous calculation concerning bound states. (orig.)
Symmetrical extensions of graphs
International Nuclear Information System (INIS)
We study symmetrical extensions of graphs, with special emphasis on symmetrical and Aut0(Λd)-symmetrical extensions of d-dimensional grids Λd by finite graphs. These topics are of interest in group theory and graph theory and possibly also in crystallography and some branches of physics. We prove the existence of a connected locally finite graph admitting infinitely many symmetrical extensions by a fixed finite graph. On the other hand, we prove that the number of symmetrical and Aut0(Λd)-symmetrical extensions of the d-dimensional grid Λd by a finite graph is finite in several interesting cases. Moreover, for every positive integer d we construct all Aut0(Λd)-symmetrical extensions of the d-dimensional grid Λd by two-vertex graphs
Directory of Open Access Journals (Sweden)
N. Sitaram
2011-01-01
Full Text Available The flow field at the rotor exit of a low aspect ratio axial flow fan for different tip geometries and for different flow coefficients is measured in the present study. The following configurations are tested: (1 rotor without partial shroud, designated as rotor (wos, (2 rotor with partial shroud, designated as rotor (ws, and (3 rotor with perforated (perforations in the shape of discrete circular holes partial shroud, designated as rotor (wps. From steady state measurements, the performance of rotor (wps is found to be the best. Both the rotors with partial shrouds have stalled at a higher flow coefficient compared to that of rotor (wos. From periodic flow measurements, it is concluded that the low velocity region near the tip section is considerably reduced with the use of partial shrouds with perforations. The extent of this low velocity region for both rotor (wos and rotor (wps increases with decreasing flow coefficient due to increased stage loading. This core of low momentum fluid has moved inwards of the annulus and towards the pressure side as the flow coefficient decreases. The extent of the low momentum fluid is smaller for rotor (wps than that of rotor (wos at all flow coefficients.
2002-01-01
% PS201 Study of $\\bar{p}$ and $\\bar{n}$ annihilations at LEAR with OBELIX, a large acceptance and high resolution detector based on the Open Axial Field Spectrometer \\\\ \\\\OBELIX is designed to study exclusive final states of antiproton and antineutron annihilations at low energies with protons and nuclei. \\\\ \\\\The physics motivations of the experiment are:\\\\ \\\\\\begin{itemize} \\item (gg, ggg), hybrids ($ q \\bar{q} g $), multiquarks ($ q q \\bar{q} \\bar{q} $) and light mesons ($ q \\bar{q} $) produced in $ N \\bar{N} $ annihilations and study of their spectroscopy and decays. Also broad structures will be searched for by comparing identical decay modes in exclusive final states of the same type occuring from initial states with different angular momentum or isospin. \\item Study of the dynamics of $ N \\bar{N} $ interactions and of the dependence of the final and intermediate resonant states of annihilation upon the quantum numbers of the initial $ N \\bar{N} $ state (angular momentum: S and P-wave in $\\bar{p}p $ at...
Hamilton's equations for a fluid membrane: axial symmetry
International Nuclear Information System (INIS)
Consider a homogeneous fluid membrane, or vesicle, described by the Helfrich-Canham energy, quadratic in the mean curvature. When the membrane is axially symmetric, this energy can be viewed as an 'action' describing the motion of a particle; the contours of equilibrium geometries are identified with particle trajectories. A novel Hamiltonian formulation of the problem is presented which exhibits the following two features: (i) the second derivatives appearing in the action through the mean curvature are accommodated in a natural phase space and (ii) the intrinsic freedom associated with the choice of evolution parameter along the contour is preserved. As a result, the phase space involves momenta conjugate not only to the particle position but also to its velocity, and there are constraints on the phase space variables. This formulation provides the groundwork for a field theoretical generalization to arbitrary configurations, with the particle replaced by a loop in space
Notari, Alessio
2016-01-01
We analyze in detail the background cosmological evolution of a scalar field coupled to a massless abelian gauge field through an axial term $\\frac{\\phi}{f_\\gamma} F \\tilde{F}$, such as in the case of an axion. Gauge fields in this case are known to experience tachyonic growth and therefore can backreact on the background as an effective dissipation into radiation energy density $\\rho_R$, which which can lead to inflation without the need of a flat potential. We analyze the system, for momenta $k$ smaller than the cutoff $f_\\gamma$, including numerically the backreaction. We consider the evolution from a given static initial condition and explicitly show that, if $f_\\gamma$ is smaller than the field excursion $\\phi_0$ by about a factor of at least ${\\cal O} (20)$, there is a friction effect which turns on before that the field can fall down and which can then lead to a very long stage of inflation with a generic potential. In addition we find superimposed oscillations, which would get imprinted on any kind of...
Beyond axial symmetry: An improved class of models for global data
Castruccio, Stefano
2014-03-01
An important class of models for data on a spherical domain, called axially symmetric, assumes stationarity across longitudes but not across latitudes. The main aim of this work is to introduce a new and more flexible class of models by relaxing the assumption of longitudinal stationarity in the context of regularly gridded climate model output. In this investigation, two other related topics are discussed: the lack of fit of an axially symmetric parametric model compared with a non-parametric model and to longitudinally reversible processes, an important subclass of axially symmetric models.
Symmetric, coherent, Choquet capacities
Kadane, Joseph B.; Wasserman, Larry
1996-01-01
Choquet capacities are a generalization of probability measures that arise in robustness, decision theory and game theory. Many capacities that arise in robustness are symmetric or can be transformed into symmetric capacities. We characterize the extreme points of the set of upper distribution functions corresponding to coherent, symmetric Choquet capacities on [0, 1]. We also show that the set of 2-alternating capacities is a simplex and we give a Choquet representation of this set.
Particle-vortex symmetric liquid
Mulligan, Michael
2016-01-01
We introduce an effective theory with manifest particle-vortex symmetry for disordered thin films undergoing a magnetic field-tuned superconductor-insulator transition. The theory may enable one to access both the critical properties of the strong-disorder limit, which has recently been confirmed [Breznay et al., PNAS 113, 280 (2016)] to exhibit particle-vortex symmetric electrical response, and the metallic phase discovered earlier [Mason and Kapitulnik, Phys. Rev. Lett. 82, 5341 (1999)] in ...
Symmetric cryptographic protocols
Ramkumar, Mahalingam
2014-01-01
This book focuses on protocols and constructions that make good use of symmetric pseudo random functions (PRF) like block ciphers and hash functions - the building blocks for symmetric cryptography. Readers will benefit from detailed discussion of several strategies for utilizing symmetric PRFs. Coverage includes various key distribution strategies for unicast, broadcast and multicast security, and strategies for constructing efficient digests of dynamic databases using binary hash trees. • Provides detailed coverage of symmetric key protocols • Describes various applications of symmetric building blocks • Includes strategies for constructing compact and efficient digests of dynamic databases
Eriksson, Stefanie; Lasič, Samo; Nilsson, Markus; Westin, Carl-Fredrik; Topgaard, Daniel
2015-03-14
We introduce a nuclear magnetic resonance method for quantifying the shape of axially symmetric microscopic diffusion tensors in terms of a new diffusion anisotropy metric, DΔ, which has unique values for oblate, spherical, and prolate tensor shapes. The pulse sequence includes a series of equal-amplitude magnetic field gradient pulse pairs, the directions of which are tailored to give an axially symmetric diffusion-encoding tensor b with variable anisotropy bΔ. Averaging of data acquired for a range of orientations of the symmetry axis of the tensor b renders the method insensitive to the orientation distribution function of the microscopic diffusion tensors. Proof-of-principle experiments are performed on water in polydomain lyotropic liquid crystals with geometries that give rise to microscopic diffusion tensors with oblate, spherical, and prolate shapes. The method could be useful for characterizing the geometry of fluid-filled compartments in porous solids, soft matter, and biological tissues. PMID:25770532
Energy Technology Data Exchange (ETDEWEB)
Eriksson, Stefanie; Topgaard, Daniel, E-mail: daniel.topgaard@fkem1.lu.se [Division of Physical Chemistry, Department of Chemistry, Lund University, Lund (Sweden); Lasič, Samo [CR Development AB, Lund (Sweden); Nilsson, Markus [Lund University Bioimaging Center, Lund University, Lund (Sweden); Westin, Carl-Fredrik [Department of Radiology, BWH, Harvard Medical School, Boston, Massachusetts MA 02215 (United States); Department of Biomedical Engineering, Medical Informatics, Linköping University, Linköping (Sweden)
2015-03-14
We introduce a nuclear magnetic resonance method for quantifying the shape of axially symmetric microscopic diffusion tensors in terms of a new diffusion anisotropy metric, D{sub Δ}, which has unique values for oblate, spherical, and prolate tensor shapes. The pulse sequence includes a series of equal-amplitude magnetic field gradient pulse pairs, the directions of which are tailored to give an axially symmetric diffusion-encoding tensor b with variable anisotropy b{sub Δ}. Averaging of data acquired for a range of orientations of the symmetry axis of the tensor b renders the method insensitive to the orientation distribution function of the microscopic diffusion tensors. Proof-of-principle experiments are performed on water in polydomain lyotropic liquid crystals with geometries that give rise to microscopic diffusion tensors with oblate, spherical, and prolate shapes. The method could be useful for characterizing the geometry of fluid-filled compartments in porous solids, soft matter, and biological tissues.
Efficient Cartesian-grid-based modeling of rotationally symmetric bodies
DEFF Research Database (Denmark)
Shyroki, Dzmitry
2007-01-01
Axially symmetric waveguides, resonators, and scatterers of arbitrary cross section and anisotropy in the cross section can be modeled rigorously with use of 2-D Cartesian-grid based codes by means of mere redefinition of material permittivity and permeability profiles. The method is illustrated by...
Margaret Tzaphlidou; Evangelos Fotiou
2004-01-01
The axial periodicity of rat arachnoid and dura mater collagen fibrils exposed to 910 MHz for 2 h/day for 30 consecutive days was measured by means of image analysis of electron-optical data. Such measurements were compared with those from sham-exposed animals. These measurements reveal that on exposure, the intermolecular interactions during collagen fibril assembly are affected.
Axial and focal-plane diffraction catastrophe integrals
Energy Technology Data Exchange (ETDEWEB)
Berry, M V [H H Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Howls, C J [School of Mathematics, University of Southampton, Southampton, SO17 1BJ (United Kingdom)
2010-09-17
Exact expressions in terms of Bessel functions are found for some of the diffraction catastrophe integrals that decorate caustics in optics and mechanics. These are the axial and focal-plane sections of the elliptic and hyperbolic umbilic diffraction catastrophes, and symmetric elliptic and hyperbolic unfoldings of the X{sub 9} diffraction catastrophes. These representations reveal unexpected relations between the integrals.
Reciprocal and unidirectional scattering of parity-time symmetric structures.
Jin, L; Zhang, X Z; Zhang, G; Song, Z
2016-01-01
Parity-time symmetry is of great interest. The reciprocal and unidirectional features are intriguing besides the symmetry phase transition. Recently, the reciprocal transmission, unidirectional reflectionless and invisibility are intensively studied. Here, we show the reciprocal reflection/transmission in -symmetric system is closely related to the type of symmetry, that is, the axial (reflection) symmetry leads to reciprocal reflection (transmission). The results are further elucidated by studying the scattering of rhombic ring form coupled resonators with enclosed synthetic magnetic flux. The nonreciprocal phase shift induced by the magnetic flux and gain/loss break the parity and time-reversal symmetry but keep the parity-time symmetry. The reciprocal reflection (transmission) and unidirectional transmission (reflection) are found in the axial (reflection) -symmetric ring centre. The explorations of symmetry and asymmetry from symmetry may shed light on novel one-way optical devices and application of -symmetric metamaterials. PMID:26876806
Noncommutative Bessel symmetric functions
Novelli, Jean-Christophe; Thibon, Jean-Yves
2006-01-01
The consideration of tensor products of 0-Hecke algebra modules leads to natural analogs of the Bessel J-functions in the algebra of noncommutative symmetric functions. This provides a simple explanation of various combinatorial properties of Bessel functions.
A symmetrical rail accelerator
Energy Technology Data Exchange (ETDEWEB)
Igenbergs, E. (Technische Univ. Muenchen, Lehrstuhl fuer Raumfahrttechnik, Richard-Wagner-Strasse 18, 8000 Muenchen 2 (DE))
1991-01-01
This paper reports on the symmetrical rail accelerator that has four rails, which are arranged symmetrically around the bore. The opposite rails have the same polarity and the adjacent rails the opposite polarity. In this configuration the radial force acting upon the individual rails is significantly smaller than in a conventional 2-rail configuration and a plasma armature is focussed towards the axis of the barrel. Experimental results indicate a higher efficiency compared to a conventional rail accelerator.
International Nuclear Information System (INIS)
The purpose of this calculation is to develop axial profiles for estimating the axial variation in burnup of a boiling water reactor (BWR) assembly spent nuclear fuel (SNF) given the average burnup of an assembly. A discharged fuel assembly typically exhibits higher burnup in the center and lower burnup at the ends of the assembly. Criticality safety analyses taking credit for SNF burnup must account for axially varying burnup relative to calculations based on uniformly distributed assembly average burnup due to the under-burned tips. Thus, accounting for axially varying burnup in criticality analyses is also referred to as accounting for the ''end effect'' reactivity. The magnitude of the reactivity change due to ''end effect'' is dependent on the initial assembly enrichment, the assembly average burnup, and the particular axial profile characterizing the burnup distribution. The set of bounding axial profiles should incorporate multiple BWR core designs and provide statistical confidence (95 percent confidence that 95 percent of the population is bound by the profile) that end nodes are conservatively represented. The profiles should also conserve the overall burnup of the fuel assembly. More background on BWR axial profiles is provided in Attachment I
Energy Technology Data Exchange (ETDEWEB)
J. Huffer
2004-09-28
The purpose of this calculation is to develop axial profiles for estimating the axial variation in burnup of a boiling water reactor (BWR) assembly spent nuclear fuel (SNF) given the average burnup of an assembly. A discharged fuel assembly typically exhibits higher burnup in the center and lower burnup at the ends of the assembly. Criticality safety analyses taking credit for SNF burnup must account for axially varying burnup relative to calculations based on uniformly distributed assembly average burnup due to the under-burned tips. Thus, accounting for axially varying burnup in criticality analyses is also referred to as accounting for the ''end effect'' reactivity. The magnitude of the reactivity change due to ''end effect'' is dependent on the initial assembly enrichment, the assembly average burnup, and the particular axial profile characterizing the burnup distribution. The set of bounding axial profiles should incorporate multiple BWR core designs and provide statistical confidence (95 percent confidence that 95 percent of the population is bound by the profile) that end nodes are conservatively represented. The profiles should also conserve the overall burnup of the fuel assembly. More background on BWR axial profiles is provided in Attachment I.
On the cylindrically symmetric wormholes WhCR^e: The motion of test particles
Aminova, Asya V; Chumarov, Pavel I; Shemakhin, Aleksandr Yu
2016-01-01
In this article we partially implement the program outlined in the previous paper of the authors [A. V. Aminova and P. I. Chumarov, Phys. Rev. D 88, 044005 (2013)]. The program owes its origins to the following comment in paper [M. Cveti\\v{c} and D. Youm, Nucl. Phys. B, 438, 182 (1995), Addendum-ibid. 449,146 (1995)], where a class of static spherically symmetric solutions in $(4+n)$-dimensional Kaluza--Klein theory was studied: "...We suspect that the same thing [as for spherical symmetry] will happen for axially symmetric stationary configurations, but it remains to be proven". We study the radial and non-radial motion of test particles in the cylindrically symmetric wormholes found in the authors'paper of type $\\rm WhCR^e$ in 6-dimensional reduced Kaluza--Klein theory with Abelian gauge field and two dilaton fields, with particular attention to the extent to which the wormhole is traversable. In the case of non-radial motion along a hypersurface z=const we show that, as in the Kerr and Schwarzschild geomet...
Inflation in spherically symmetric inhomogeneous models
Energy Technology Data Exchange (ETDEWEB)
Stein-Schabes, J.A.
1986-11-01
Exact analytical solutions of Einstein's equations are found for a spherically symmetric inhomogeneous metric in the presence of a massless scalar field with a flat potential. The process of isotropization and homogenization is studied in detail. It is found that the time dependence of the metric becomes de Sitter for large times. Two cases are studied. The first deals with a homogeneous scalar field, while the second with a spherically symmetric inhomogeneous scalar field. In the former case the metric is of the Robertson-Walker form, while the latter is intrinsically inhomogeneous. 16 refs.
Inflation in spherically symmetric inhomogeneous models
International Nuclear Information System (INIS)
Exact analytical solutions of Einstein's equations are found for a spherically symmetric inhomogeneous metric in the presence of a massless scalar field with a flat potential. The process of isotropization and homogenization is studied in detail. It is found that the time dependence of the metric becomes de Sitter for large times. Two cases are studied. The first deals with a homogeneous scalar field, while the second with a spherically symmetric inhomogeneous scalar field. In the former case the metric is of the Robertson-Walker form, while the latter is intrinsically inhomogeneous. 16 refs
Chang, Yuan-Pin; Sartakov, Boris; Küpper, Jochen
2013-01-01
The Controlled Molecule Imaging group (CMI) at the Center for Free Electron Laser Science (CFEL) has developed the CMIstark software to calculate, view, and analyze the energy levels of adiabatic Stark energy curves of linear, symmetric top and asymmetric top molecules. The program exploits the symmetry of the Hamiltonian to generate fully labeled adiabatic Stark energy curves. CMIstark is written in Python and easily extendable, while the core numer- ical calculations make use of machine optimized BLAS and LAPACK routines. Calculated energies are stored in HDF5 files for convenient access and programs to extract ASCII data or to generate graphical plots are provided.
Signatures for axial chromodynamics
International Nuclear Information System (INIS)
Within the context of basic left-right symmetry and the hypothesis of unification of weak, electromagnetic and strong forces at a mass level approximately equal to 104-106 GeV, relatively light ''mass'' axial gluons, confined or liberated, must be postulated. The authors remark that the existence of such ''light'' axial gluons supplementing the familiar vector octet preserves the successes of QCD, both for deep inelastic processes and charmonium physics. Through the characteristic spin-spin force, generated by their exchange, they may even help resolve some of the discrepancies between vector QCD predictions and charmonium physics. The main remark of this note is that if colour is liberated, not only vector but also axial-vector gluons are produced in high-energy e-e+ experiments, e.g. at PETRA and PEP, with fairly large cross-section. Distinctive decay modes of such liberated axial gluons are noted
Thermophoretic motion of bodies with axial symmetry
International Nuclear Information System (INIS)
Thermophoresis of axially symmetric bodies is investigated to first order in the Knudsen number, K n. The study is made in the limit where the typical length of the immersed body is small compared with the mean free path. It is shown that in this case, in contrast to what is the case for spherical bodies, the arising thermal force on the body is not in general anti-parallel to the temperature gradient. It is also shown that the gas exerts a torque on the body, which in magnitude and direction depends on the body geometry. Equations of motion describing the body movement are derived. Stationary solutions are studied
Surface nanoscale axial photonics
Sumetsky, M.; Fini, J. M.
2011-01-01
Dense photonic integration promises to revolutionize optical computing and communications. However, efforts towards this goal face unacceptable attenuation of light caused by surface roughness in microscopic devices. Here we address this problem by introducing Surface Nanoscale Axial Photonics (SNAP). The SNAP platform is based on whispering gallery modes circulating around the optical fiber surface and undergoing slow axial propagation readily described by the one-dimensional Schr\\"odinger e...
Symmetric centres of braided monoidal categories
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This paper introduces the concept of‘symmetric centres' of braided monoidal categories. Let H be a Hopf algebra with bijective antipode over a field k. We address the symmetric centre of the Yetter-Drinfel'd module category HH(yD) and show that a left Yetter-Drinfel'd module M belongs to the symmetric centre of HH(yD) if and only if M is trivial. We also study the symmetric centres of categories of representations of quasitriangular Hopf algebras and give a sufficient and necessary condition for the braid of H(M) to induce the braid of (H(H)(A),(○)A,A,φ,l,r), or equivalently, the braid of (A#H(H),(○)A,A,φ,l,r), where A is a quantum commutative H-module algebra.
Counting with symmetric functions
Mendes, Anthony
2015-01-01
This monograph provides a self-contained introduction to symmetric functions and their use in enumerative combinatorics. It is the first book to explore many of the methods and results that the authors present. Numerous exercises are included throughout, along with full solutions, to illustrate concepts and also highlight many interesting mathematical ideas. The text begins by introducing fundamental combinatorial objects such as permutations and integer partitions, as well as generating functions. Symmetric functions are considered in the next chapter, with a unique emphasis on the combinatorics of the transition matrices between bases of symmetric functions. Chapter 3 uses this introductory material to describe how to find an assortment of generating functions for permutation statistics, and then these techniques are extended to find generating functions for a variety of objects in Chapter 4. The next two chapters present the Robinson-Schensted-Knuth algorithm and a method for proving Pólya’s enu...
Symmetric Tensor Decomposition
DEFF Research Database (Denmark)
Brachat, Jerome; Comon, Pierre; Mourrain, Bernard;
2010-01-01
We present an algorithm for decomposing a symmetric tensor, of dimension n and order d, as a sum of rank-1 symmetric tensors, extending the algorithm of Sylvester devised in 1886 for binary forms. We recall the correspondence between the decomposition of a homogeneous polynomial in n variables of...... polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on this characterization and on linear algebra computations with Hankel matrices. The impact of this contribution is two-fold. First it permits an efficient computation of the...... decomposition of any tensor of sub-generic rank, as opposed to widely used iterative algorithms with unproved global convergence (e.g. Alternate Least Squares or gradient descents). Second, it gives tools for understanding uniqueness conditions and for detecting the rank....
N>=2 symmetric superpolynomials
Alarie-Vézina, L; Mathieu, P
2015-01-01
The theory of symmetric functions has been extended to the case where each variable is paired with an anticommuting one. The resulting expressions, dubbed superpolynomials, provide the natural N=1 supersymmetric version of the classical bases of symmetric functions. Here we consider the case where two independent anticommuting variables are attached to each ordinary variable. The N=2 super-version of the monomial, elementary, homogeneous symmetric functions, as well as the power sums, are then constructed systematically (using an exterior-differential formalism for the multiplicative bases), these functions being now indexed by a novel type of superpartitions. Moreover, the scalar product of power sums turns out to have a natural N=2 generalization which preserves the duality between the monomial and homogeneous bases. All these results are then generalized to an arbitrary value of N. Finally, for N=2, the scalar product and the homogenous functions are shown to have a one-parameter deformation, a result that...
Ramezani, Hamidreza; Kovanis, V; Vitebskiy, I; Kottos, Tsampikos; 10.1103/PhysRevLett.109.033902
2012-01-01
We show that complex PT-symmetric photonic lattices can lead to a new class of self-imaging Talbot effects. For this to occur, we find that the input field pattern, has to respect specific periodicities which are dictated by the symmetries of the system. While at the spontaneous PT-symmetry breaking point, the image revivals occur at Talbot lengths governed by the characteristics of the passive lattice, at the exact phase it depends on the gain and loss parameter thus allowing one to control the imaging process.
Multiparty Symmetric Sum Types
DEFF Research Database (Denmark)
Nielsen, Lasse; Yoshida, Nobuko; Honda, Kohei
2010-01-01
determining how the session proceeds, the symmetric sum type represents a choice made by agreement among all the participants of a session. Such behaviour can be found in many practical systems, including collaborative workflow in healthcare systems for clinical practice guidelines (CPGs). Processes with the......This paper introduces a new theory of multiparty session types based on symmetric sum types, by which we can type non-deterministic orchestration choice behaviours. While the original branching type in session types can represent a choice made by a single participant and accepted by others...
Progressive symmetric erythrokeratoderma
Directory of Open Access Journals (Sweden)
Gharpuray Mohan
1990-01-01
Full Text Available Four patients had symmetrically distributed hyperkeratotic plaques on the trunk and extremities; The lesions in all of them had appeared during infancy, and after a brief period of progression, had remained static, All of them had no family history of similar skin lesions. They responded well to topical applications of 6% salicylic acid in 50% propylene glycol. Unusual features in these cases of progressive symmetric erythrokeratoderma were the sparing of palms and soles, involvement of the trunk and absence of erythema.
Scholl, M. A.; Ingebritsen, S. E.; Essaid, H. I.
1993-02-01
Fox (1990), in order to explain observations during the Axial Seamount Hydrothermal Emissions Study (ASHES), proposed a conceptual model for a two-phase subsea hydrothermal system in which steam controlled flow patterns by blocking liquid flow. An attempt is made here to demonstrate with a very general model that relative permeability contrasts by themselves do not cause spatial isolation of phases in steam/liquid water systems and that density segregation, independent of relative permeability effects, should not be ruled out as an explanation for the observations at the ASHES site. Fox replies that density segregation is probably not the only mechanism at work.
International Nuclear Information System (INIS)
The paper demonstrates the possibility of separating 98Mo and 100Mo isotopes by means of the electromagnetic separator in the system of axially symmetric magnetic fields with two field reversals. The advantage of the method lies in the separation of the 100M o isotope in its pure form, without being contaminated with other isotopes. Of apparent interest is the proposed here method of increasing the productive capacity of the electromagnetic technique of isotope separation.
Static black holes with axial symmetry in asymptotically AdS4 spacetime
Kichakova, Olga; Kunz, Jutta; Radu, Eugen; Shnir, Yasha
2016-02-01
The known static electrovacuum black holes in a globally AdS4 background have an event horizon which is geometrically a round sphere. In this work we argue that the situation is different in models with matter fields possessing an explicit dependence on the azimuthal angle φ , which, however, does not manifest at the level of the energy-momentum tensor. As a result, the full solutions are axially symmetric only, possessing a single (timelike) Killing vector field. Explicit examples of such static black holes are constructed in Einstein-(complex) scalar field and Einstein-Yang-Mills theories. The basic properties of these solutions are discussed, looking for generic features. For example, we notice that the horizon has an oblate spheroidal shape for solutions with a scalar field and a prolate one for black holes with Yang-Mills fields. The deviation from sphericity of the horizon geometry manifests itself in the holographic stress tensor. Finally, based on the results obtained in the probe limit, we conjecture the existence in Einstein-Maxwell theory of static black holes with axial symmetry only.
International Nuclear Information System (INIS)
A 1.6 cell photocathode S-Band gun developed by the BNL/SLAC/UCLA collaboration is now in operation at the Brookhaven Accelerator Test Facility (ATF). One of the main features of this RF gun is the symmetrization of the RF coupling iris with an identical vacuum pumping port located in the full cell. The effects of the asymmetry caused by the RF coupling iris were experimentally investigated by positioning a metallic plunger at the back wall of the vacuum port iris. The higher order modes produced were studied using electron beamlets with 8-fold symmetry. The 8-fold beamlets were produced by masking the laser beam. These experimental results indicate that the integrated electrical center and the geometrical center of the gun are within 175 microm. Which is within the laser alignment tolerance of 250 microm
Multiparty Symmetric Sum Types
Directory of Open Access Journals (Sweden)
Lasse Nielsen
2010-11-01
Full Text Available This paper introduces a new theory of multiparty session types based on symmetric sum types, by which we can type non-deterministic orchestration choice behaviours. While the original branching type in session types can represent a choice made by a single participant and accepted by others determining how the session proceeds, the symmetric sum type represents a choice made by agreement among all the participants of a session. Such behaviour can be found in many practical systems, including collaborative workflow in healthcare systems for clinical practice guidelines (CPGs. Processes using the symmetric sums can be embedded into the original branching types using conductor processes. We show that this type-driven embedding preserves typability, satisfies semantic soundness and completeness, and meets the encodability criteria adapted to the typed setting. The theory leads to an efficient implementation of a prototypical tool for CPGs which automatically translates the original CPG specifications from a representation called the Process Matrix to symmetric sum types, type checks programs and executes them.
The Axial Current in Electromagnetic Interaction
Cheoun, M K; Cheon, I T; Cheoun, Myung Ki; Cheon, Il-Tong
1998-01-01
We discussed the possibility that the charged axial currents of matter fields could be non-conserved in electromagnetic interaction at $O(e) $ order. It means that chiral symmetry is broken explicitly by electromagnetic interaction. This explicit symmetry breaking of chiral symmetry is shown to lead the mass differences between the charged and neutral particles of matter fields.
Kononets, Yu. V.
2016-07-01
The presented enhanced version of Eriksen's theorem defines an universal transform of the Foldy-Wouthuysen type and in any external static electromagnetic field (ESEMF) reveals a discrete symmetry of Dirac's equation (DE), responsible for existence of a highly influential conserved quantum number—the charge index distinguishing two branches of DE spectrum. It launches the charge-index formalism (CIF) obeying the charge-index conservation law (CICL). Via its unique ability to manipulate each spectrum branch independently, the CIF creates a perfect charge-symmetric architecture of Dirac's quantum mechanics (DQM), which resolves all the riddles of the standard DE theory (SDET). Besides the abstract CIF algebra, the paper discusses: (1) the novel accurate charge-symmetric definition of the electric-current density; (2) DE in the true-particle representation, where electrons and positrons coexist on equal footing; (3) flawless "natural" scheme of second quantization; and (4) new physical grounds for the Fermi-Dirac statistics. As a fundamental quantum law, the CICL originates from the kinetic-energy sign conservation and leads to a novel single-particle physics in strong-field situations. Prohibiting Klein's tunneling (KT) in Klein's zone via the CICL, the precise CIF algebra defines a new class of weakly singular DE solutions, strictly confined in the coordinate space and experiencing the total reflection from the potential barrier.
International Nuclear Information System (INIS)
A phase-contrast X-ray imaging system - with a 60x30 mm field of view - for biomedical observations was developed. To extend the observation field of view, the system is fitted with a skew-symmetric two-crystal X-ray interferometer. To attain the required sub-nanoradian mechanical stability between the crystal blocks for precise operation, the interferometer was mounted on two extremely rigid positioning tables (one with a sleeve bearings) and was controlled by a feedback positioning system using phase-lock interferometry. The imaging system produced a 60x30 mm interference pattern with 60% visibility using 17.7 keV monochromatic synchrotron X-rays at the Photon Factory. It was then used to perform radiographic observation (i.e., phase mapping) of rat liver vessels. These results indicate that this imaging system can be used to perform observations of large and in vivo biological samples
HEMODYNAMICS FOR ASYMMETRIC INLET AXIAL VELOCITY PROFILE IN CAROTID BIFURCATION MODEL
Institute of Scientific and Technical Information of China (English)
DING Zu-rong; LIU Bin; YANG Shuo; XIA Yan
2008-01-01
The asymmetric inlet velocity profile has been observed in phantom model using LDA and in health subjects using Magnet Resonance (MR). The effects of asymmetric inlet axial velocity profile on the flow field and the Wall Shear Stress (WSS) ofcarotid bifurcation were numerically studied herein with the TF-AHCB model. The results show that the Wall Shear Stress Gradient (WSSG) in the front part of the sinus for inward-tilting inlet axial velocity profile is nearly 2 times of that for the symmetric one in the beginning of systole, the end of systole, and diastole, respectively. The area of WSS below 5x 10.3 Pa at the outer wall of the sinus for outward-tilting inlet axial velocity profile is 1.5 times of that for the inward-tilting one during diastole of the cardiac cycle. The asymmetric inlet velocity profiles can reduce the flow velocity near the inner wall of the sinus, which has been normally considered a high velocity region. It is concluded that besides bifurcation geometry and flow waveform, the asymmetry of inlet velocity profile is probably a factor influencing atherosclerosis.
Frequency study of microwave generation in an axially extracted virtual cathode oscillator
Energy Technology Data Exchange (ETDEWEB)
Yatsuzuka, M.; Nakayama, M.; Nobuhara, S. [Himeji Inst. of Tech., Hyogo (Japan). Dept. of Electrical Engineering; Hashimoto, Y. [Kobe City Coll. of Technology, Hyogo (Japan). Dept. of Electronic Engineering; Ishihara, O. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Electrical Engineering
1996-12-31
In virtual cathode oscillators (vircators) the axial electric field, driven by either reflecting electrons between the real and virtual cathodes or oscillations of the virtual cathode, couples with axially symmetric transverse magnetic waveguide mode (TM{sub 0m}). To study this mechanism in detail the dependence of radiation frequency on cathode diameter, output waveguide diameter, and anode-cathode (A-K) gap spacing was studied experimentally in an axially-extracted vircator at Himeji Institute of Technology. The radiation frequency decreased with increasing A-K gap spacing for a constant cathode diameter. The maximum power emission was observed at the A-K gap spacing for which reflecting trapped electrons between the real and virtual cathodes determine the radiation frequency. The measurement of power density profile in the radial and azimuthal directions showed the radiation pattern of TM{sub 01} mode, in agreement with the observed frequency which satisfies the dispersion relation of TM{sub 01} mode in the circular output waveguide.
Homogenous finitary symmetric groups
Directory of Open Access Journals (Sweden)
Otto. H. Kegel
2015-03-01
Full Text Available We characterize strictly diagonal type of embeddings of finitary symmetric groups in terms of cardinality and the characteristic. Namely, we prove the following. Let kappa be an infinite cardinal. If G=underseti=1stackrelinftybigcupG i , where G i =FSym(kappan i , (H=underseti=1stackrelinftybigcupH i , where H i =Alt(kappan i , is a group of strictly diagonal type and xi=(p 1 ,p 2 ,ldots is an infinite sequence of primes, then G is isomorphic to the homogenous finitary symmetric group FSym(kappa(xi (H is isomorphic to the homogenous alternating group Alt(kappa(xi , where n 0 =1,n i =p 1 p 2 ldotsp i .
Symmetric Synchronous Collaborative Navigation
Gerosa, Luca; Giordani, Alessandra; Ronchetti, Marco
2004-01-01
Synchronous collaborative navigation is a form of social navigation where users virtually share a web browser. In this paper, we present a symmetric, proxy-based architecture where each user can take the lead and guide others in visiting web sites, without the need for a special browser or other software. We show how we have applied this scheme to a problem-solving-oriented e-learning system.
Gomez-Marin, A.; Sancho, J. M.
2004-01-01
In this paper we present a model of a symmetric Brownian motor (SBM) which changes the sign of its velocity when the temperature gradient is inverted. The velocity, external work and efficiency are studied as a function of the temperatures of the baths and other relevant parameters. The motor shows a current reversal when another parameter (a phase shift) is varied. Analytical predictions and results from numerical simulations are performed and agree very well. Generic properties of this type...
Symmetric Extended Ockham Algebras
Institute of Scientific and Technical Information of China (English)
T.S. Blyth; Jie Fang
2003-01-01
The variety eO of extended Ockham algebras consists of those algealgebra with an additional endomorphism k such that the unary operations f and k commute. Here, we consider the cO-algebras which have a property of symmetry. We show that there are thirty two non-isomorphic subdirectly irreducible symmetric extended MS-algebras and give a complete description of them.2000 Mathematics Subject Classification: 06D15, 06D30
09031 Executive Summary -- Symmetric Cryptography
Handschuh, Helena; Lucks, Stefan; Preneel, Bart; Rogaway, Phillip
2009-01-01
Research in Symmetric Cryptography is quickly evolving. The seminar was the second of its kind, the first one took place in 2007. We observe a steadily increasing interest in Symmetric Cryptography, as well as a growing practical demand for symmetric algorithms and protocols. The seminar was very successful in discussing recent results and sharing new ideas. Furthermore, it inspired the participants to consider how Symmetric Cryptography has evolved in the past, and h...
Symmetric and skew-symmetric weight functions in perturbation models of 2D interfacial cracks
Piccolroaz, A; Movchan, A B
2008-01-01
In this paper we address the vector problem of a 2D interfacial crack loaded by a general asymmetric distribution of forces acting on its faces. It is shown that the general integral formula for the evaluation of stress intensity factors, as well as high-order terms, requires both symmetric and skew-symmetric weight function matrices. The symmetric weight function matrix is obtained via the solution of a Wiener-Hopf functional equation, whereas the derivation of the skew-symmetric weight function matrix requires the construction of the corresponding full field singular solution. The weight function matrices are then used in the perturbation analysis of a crack advancing quasi-statically along the interface between two dissimilar media. A general and rigorous asymptotic procedure is developed to compute the perturbations of stress intensity factors as well as high-order terms.
Schwarzschild and Kerr Solutions of Einstein's Field Equation -- an introduction
Heinicke, Christian; .,
2015-01-01
Starting from Newton's gravitational theory, we give a general introduction into the spherically symmetric solution of Einstein's vacuum field equation, the Schwarzschild(-Droste) solution, and into one specific stationary axially symmetric solution, the Kerr solution. The Schwarzschild solution is unique and its metric can be interpreted as the exterior gravitational field of a spherically symmetric mass. The Kerr solution is only unique if the multipole moments of its mass and its angular momentum take on prescribed values. Its metric can be interpreted as the exterior gravitational field of a suitably rotating mass distribution. Both solutions describe objects exhibiting an event horizon, a frontier of no return. The corresponding notion of a black hole is explained to some extent. Eventually, we present some generalizations of the Kerr solution.
Symmetrization of binary random variables
Kagan, Abram; Mallows, Colin L.; Shepp, Larry A.; Vanderbei, Robert J.; Vardi, Yehuda
1999-01-01
A random variable [math] is called an independent symmetrizer of a given random variable [math] if (a) it is independent of [math] and (b) the distribution of [math] is symmetric about [math] . In cases where the distribution of [math] is symmetric about its mean, it is easy to see that the constant random variable [math] is a minimum-variance independent symmetrizer. Taking [math] to have the same distribution as [math] clearly produces a symmetric sum, but it may not be of minimum variance....
Boost-rotation symmetric vacuum spacetimes with spinning sources
Pravdova, A.; Pravda, V.
2001-01-01
Boost-rotation symmetric vacuum spacetimes with spinning sources which correspond to gravitational field of uniformly accelerated spinning "particles" are studied. Regularity conditions and asymptotic properties are analyzed. News functions are derived by transforming the general spinning boost-rotation symmetric vacuum metric to Bondi-Sachs coordinates.
On renormalization of axial anomaly
International Nuclear Information System (INIS)
It is shown that multiplicative renormalization of the axial singlet current results in renormalization of the axial anomaly in all orders of perturbation theory. It is a necessary condition for the Adler - Bardeen theorem being valid. 10 refs.; 2 figs
Axial compressor stability enhancement
Houghton, Timothy Oliver.
2010-01-01
Aircraft jet engines must operate in a stable manner at all times. One source of instability is compressor stall. Stall problems can be reduced by machining cavities into the compressor casing adjacent to the rotor blades. This ?casing treatment? is the focus of the present work. Two treatment configurations are tested: circumferential grooves cut into the casing above the rotor blades, and axial slots cut into the casing adjacent to the rotor blade leading edges. The performance of a single ...
Joglekar, Satish D.
2000-01-01
We summarize the work done in connecting Green's functions in a different classes of gauges and its applications to the problems in the axial gauges.The procedure adopted uses finite field-dependent BRS [FFBRS] transformations to connect axial and the Lorentz type gauges.These transformations preserve the vacuum expectation of gauge-invariant observables explicitly. We discuss the applications of these ideas to the axial gauge pole problem and to the preservation of the Wilson loop and the th...
Cassou-Nogues, Ph.; Erez, B.; Taylor, M. J.
2004-01-01
We establish comparison results between the Hasse-Witt invariants w_t(E) of a symmetric bundle E over a scheme and the invariants of one of its twists E_{\\alpha}. For general twists we describe the difference between w_t(E) and w_t(E_{\\alpha}) up to terms of degree 3. Next we consider a special kind of twist, which has been studied by A. Fr\\"ohlich. This arises from twisting by a cocycle obtained from an orthogonal representation. We show how to explicitly describe the twist for representatio...
International Nuclear Information System (INIS)
The closed-cycled refrigeration of neon by using a GM cryocooler has successfully provided a low-temperature pulsed-field magnetization at 38 K for field-pole Gd123 bulks in the testing rotating machine. Upon magnetization, a new split-type of armature coil, Controlled Magnetic field density Distribution Coil (CMDC) was employed. The CMDC has realized a control of magnetic field by choosing effective diameter of the vortex coil either 44 mm or 84 mm for the sample with 60 mm in diameter. The maximum trapped magnetic flux density reached over 1.3 T at 1.3 mm from the surface of bulk. 2.5 times larger flux was obtained for the field pole bulk in contrast to the liquid nitrogen cooling. The output of the motor was enhanced to 25 kW associated with a practical closed-cycle cooling without a liquid cryogen
The gravitation energy for a cylindrically and spherically symmetrical system
Sosnovskiy, R
2005-01-01
It has been shown that t00 component of the energy-momentum pseudotensor in the case of cylindrically symmetrical static gravitational field cannot be interpreted as energy density of the gravitation field. An approach has been suggested allows one to express the energy density of the cylindrically or spherically symmetrical static gravitation field in terms of the metric tensor components. The approach based on the consideration of the process of isothermal compression of a cylinder consisted of incoherent matter.
The gravitation energy for a cylindrically and spherically symmetrical system
Sosnovskiy, Roald
2005-01-01
It has been shown that t00 component of the energy-momentum pseudotensor in the case of cylindrically symmetrical static gravitational field cannot be interpreted as energy density of the gravitation field. An approach has been suggested allows one to express the energy density of the cylindrically or spherically symmetrical static gravitation field in terms of the metric tensor components. The approach based on the consideration of the process of isothermal compression of a cylinder consiste...
Primitive axial algebras of Jordan type
Hall, J I; Rehren, F; Shpectorov, S.
2014-01-01
An axial algebra over the field $\\mathbb F$ is a commutative algebra generated by idempotents whose adjoint action has multiplicity-free minimal polynomial. For semisimple associative algebras this leads to sums of copies of $\\mathbb F$. Here we consider the first nonassociative case, where adjoint minimal polynomials divide $(x-1)x(x-\\eta)$ for fixed $0\
Elastic stars in general relativity: IV. Axial perturbations
Karlovini, M; Karlovini, Max; Samuelsson, Lars
2007-01-01
This is the fourth paper in a series that attempt to put forward a consistent framework for modelling solid regions in neutron stars. Here we turn our attention to axial perturbations of spherically symmetric spacetimes using a gauge invariant approach due to one of us. Using the formalism developed in the first paper in the series it turns out that the matter perturbations are neatly expressible in terms of a ``metric'' tensor field depending only on the speeds of shear wave propagation along the principal directions in the solid. The results are applicable to a wide class of elastic materials and does not assume material isotropy nor quasi-Hookean behaviour. The perturbation equations are then specialised to a static background and are given by two coupled wave equations. Our formalism is thus slightly simpler than the previously existing results of Shumaker & Thorne, where an additional initial value equation needs to be solved. The simplification is mainly due to the gauge invariance of our approach a...
Symmetrization for redundant channels
Tulplue, Bhalchandra R. (Inventor); Collins, Robert E. (Inventor)
1988-01-01
A plurality of redundant channels in a system each contain a global image of all the configuration data bases in each of the channels in the system. Each global image is updated periodically from each of the other channels via cross channel data links. The global images of the local configuration data bases in each channel are separately symmetrized using a voting process to generate a system signal configuration data base which is not written into by any other routine and is available for indicating the status of the system within each channel. Equalization may be imposed on a suspect signal and a number of chances for that signal to heal itself are provided before excluding it from future votes. Reconfiguration is accomplished upon detecting a channel which is deemed invalid. A reset function is provided which permits an externally generated reset signal to permit a previously excluded channel to be reincluded within the system. The updating of global images and/or the symmetrization process may be accomplished at substantially the same time within a synchronized time frame common to all channels.
Hamilton's equations for a fluid membrane: axial symmetry
Energy Technology Data Exchange (ETDEWEB)
Capovilla, R [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apdo Postal 14-740, 07000 Mexico, DF (Mexico); Guven, J [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apdo Postal 70-543, 04510 Mexico, DF (Mexico); Rojas, E [Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico)
2005-09-23
Consider a homogeneous fluid membrane, or vesicle, described by the Helfrich-Canham energy, quadratic in the mean curvature. When the membrane is axially symmetric, this energy can be viewed as an 'action' describing the motion of a particle; the contours of equilibrium geometries are identified with particle trajectories. A novel Hamiltonian formulation of the problem is presented which exhibits the following two features: (i) the second derivatives appearing in the action through the mean curvature are accommodated in a natural phase space and (ii) the intrinsic freedom associated with the choice of evolution parameter along the contour is preserved. As a result, the phase space involves momenta conjugate not only to the particle position but also to its velocity, and there are constraints on the phase space variables. This formulation provides the groundwork for a field theoretical generalization to arbitrary configurations, with the particle replaced by a loop in space.
Detecting internally symmetric protein structures
Directory of Open Access Journals (Sweden)
Basner Jodi
2010-06-01
Full Text Available Abstract Background Many functional proteins have a symmetric structure. Most of these are multimeric complexes, which are made of non-symmetric monomers arranged in a symmetric manner. However, there are also a large number of proteins that have a symmetric structure in the monomeric state. These internally symmetric proteins are interesting objects from the point of view of their folding, function, and evolution. Most algorithms that detect the internally symmetric proteins depend on finding repeating units of similar structure and do not use the symmetry information. Results We describe a new method, called SymD, for detecting symmetric protein structures. The SymD procedure works by comparing the structure to its own copy after the copy is circularly permuted by all possible number of residues. The procedure is relatively insensitive to symmetry-breaking insertions and deletions and amplifies positive signals from symmetry. It finds 70% to 80% of the TIM barrel fold domains in the ASTRAL 40 domain database and 100% of the beta-propellers as symmetric. More globally, 10% to 15% of the proteins in the ASTRAL 40 domain database may be considered symmetric according to this procedure depending on the precise cutoff value used to measure the degree of perfection of the symmetry. Symmetrical proteins occur in all structural classes and can have a closed, circular structure, a cylindrical barrel-like structure, or an open, helical structure. Conclusions SymD is a sensitive procedure for detecting internally symmetric protein structures. Using this procedure, we estimate that 10% to 15% of the known protein domains may be considered symmetric. We also report an initial, overall view of the types of symmetries and symmetric folds that occur in the protein domain structure universe.
Fast imaging of mean, axial and radial diffusion kurtosis
DEFF Research Database (Denmark)
Hansen, Brian; Shemesh, Noam; Jespersen, Sune Nørhøj
2016-01-01
benefit from more efficient acquisition and computational methods. To meet this demand, we recently developed a method capable of estimating mean kurtosis with only 13 diffusion weighted images. This approach was later shown to provide very accurate mean kurtosis estimates and to be more efficient in...... terms of contrast to noise per unit time. However, insofar, the computation of two other critical DKI parameters, radial and axial kurtosis, has required the estimation of all 22 variables parameterizing the full DKI signal expression. Here, we present two strategies for estimating all of DKI......'s principal parameters – mean kurtosis, radial kurtosis, and axial kurtosis – using only 19 diffusion weighted images, compared to the current state-of-the-art acquisitions typically requiring about 60 images. The first approach is based on axially symmetric diffusion and kurtosis tensors, presented here for...
International Nuclear Information System (INIS)
Linear and nonlinear magnetohydrodynamic (MHD) stability of current-driven modes are studied in the MST reversed field pinch. Measured low frequency (f < 35 kHz) magnetic fluctuations are consistent with the global resistive tearing instabilities predicted by 3-D MHD simulations. At frequencies above 35 kHz, the magnetic fluctuations were detected to be localized and externally resonant. Discrete dynamo events, ''sawtooth oscillations,'' have been observed in the experimental RFP plasmas. This phenomenon causes the plasma to become unstable to m = 1 tearing modes. The modes that may be important in different phases of these oscillations are identified. These results then assist in nonlinear studies and also help to interpret the spectral broadening of the measured data during a discrete dynamo event. Three-wave nonlinear coupling of spectral Fourier modes is measured in the MST by applying bispectral analysis to magnetic fluctuations measured at the plasma edge at 64 toroidal locations and 16 poloidal locations, permitting observation of coupling over 8 poloidal and 32 toroidal modes. Comparison to bispectra predicted by resistive MHD computation indicates reasonably good agreement. However, during the crash phase of the sawtooth oscillation the nonlinear coupling is strongly enhanced, concomitant with a broadened k-spectrum. During the sawtooth formation the plasma is undergoing a pure diffusive process. The dynamo only occurs during the sawtooth crash. High frequency activity prior to a sawtooth crash is caused by nonlinear frequency (small-scale) mode coupling. Growth rate and coupling coefficients of toroidal mode spectra are calculated by statistical modeling. Temporal evolution of edge toroidal mode spectra has been predicted by transfer function analysis. The driving sources of electrostatic fields are different than for the magnetic fields. The characteristics of tearing modes can be altered by external field errors and addition of impurities to the plasma
International Nuclear Information System (INIS)
The μ-(oxo)bis[tetra-tert-butylphthalocyaninato] aluminum(III) [(tBu)4PcAl]2O films with the crystallites oriented preferably in one direction were obtained via chemical transformation of tetra-tert-butylsubstituted chloroaluminum(III) phthalocyanine (tBu)4PcAlCl film upon its annealing in magnetic field. A comparative analysis of the influence of post-deposition annealing process without and under applied magnetic field of 1 T, on the orientation and morphology of (tBu)4PcAlCl and [(tBu)4PcAl]2O films, has been carried out by the methods of UV-vis, Infrared and Raman spectroscopies, XRD as well as atomic force microscopy. The formation of [(tBu)4PcAl]2O films with elongated crystallites having preferential orientation was observed upon heating of the films in magnetic field while annealing without magnetic field under the same conditions does not demonstrate any effect on the structure and morphology of these films. The reasons of the sensitivity of this reaction to the presence of such magnetic field is discussed and studied by electronic paramagnetic resonance spectroscopy
Ma, John Z G
2010-01-01
The aurora often breaks down into elongated filaments that are aligned with the geomagnetic field. It is natural to infer from this that when important structures are found in the electrostatic fields they, too, will follow a cylindrical geometry. With ionospheric applications in mind, we have therefore studied the response of the ion distribution function and its transport properties to the sudden introduction of an electric field which increases linearly with radial distance. In this first study we have considered collision-free conditions. We have solved the attendant Boltzmann equation by tracking the ions back in time, thereby using the temporal link between the initial position and velocity of an ion and the position and velocity at an arbitrary time and place. We have obtained a complete analytical solution for the ion trajectories and the ion distribution function, in addition to the transport properties, for all values of time and space. We have found that individual ions gyrate in phase at a frequen...
Directory of Open Access Journals (Sweden)
Walt Wells
2008-01-01
Full Text Available Our objective in this paper is to solve a second order differential equation for a long, simply supported column member subjected to a lateral axial load using Heun's numerical method. We will use the solution to find the critical load at which the column member will fail due to buckling. We will calculate this load using Euler's derived analytical approach for an exact solution, as well as Euler's Numerical Method. We will then compare the three calculated values to see how much they deviate from one another. During the critical load calculation, it will be necessary to calculate the moment of inertia for the column member.
Symmetric Waveguide Orthomode Junctions
Wollack, E. J.; Grammer, W.
2003-01-01
Imaging applications at millimeter and submillimeter wavelengths demand precise characterization of the amplitude, spectrum, and polarization of the electromagnetic radiation. The use of a waveguide orthomode transducer (OMT) can help achieve these goals by increasing spectral coverage and sensitivity while reducing exit aperture size, optical spill, instrumental polarization offsets, and lending itself to integration in focal plane arrays. For these reasons, four-old symmetric OMTs are favored over a traditional quasi-optical wire grid for focal plane imaging arrays from a systems perspective. The design, fabrication, and test of OMTs realized with conventional split-block techniques for millimeter wave-bands are described. The design provides a return loss is -20 dB over a full waveguide band (40% bandwidth), and the cross-polarization and isolation are greater than -40 dB for tolerances readily achievable in practice. Prototype examples realized in WR10.0 and WR3.7 wavebands will be considered in detail.
Institute of Scientific and Technical Information of China (English)
傅育熙
1998-01-01
An alternative presentation of the π－calculus is given.This version of the π-calculus is symmetric in the sense that communications are symmetric and there is no difference between input and output prefixes.The point of the symmetric π-calculus is that it has no abstract names.The set of closed names is therefore homogeneous.The π－calculus can be fully embedded into the symmetric π-calculus.The symmetry changes the emphasis of the communication mechanism of the π-calculus and opens up possibility for further variations.
Directory of Open Access Journals (Sweden)
Giuseppe Dattoli
1996-05-01
Full Text Available q analog of bessel functions, symmetric under the interchange of q and q^ −1 are introduced. The definition is based on the generating function realized as product of symmetric q-exponential functions with appropriate arguments. Symmetric q-Bessel function are shown to satisfy various identities as well as second-order q-differential equations, which in the limit q → 1 reproduce those obeyed by the usual cylindrical Bessel functions. A brief discussion on the possible algebraic setting for symmetric q-Bessel functions is also provided.
Calculations for axial compressor blading with uniform inlet enthalpy and radial enthalpy gradient
Schlachter, W
1981-01-01
A computer program was used to calculate the radial distribution of flow parameters in an axial compressor stage designed to have a symmetrical velocity diagram at the mean radius and particular variations of reaction from hub to tip. Uniform energy addition was assumed to occur in the rotor. Both cases of uniform enthalpy and uniform radial enthalpy gradient at the entrance to the stage were considered. Advantages were found in the selection of fully symmetric blading and in the use of the i...
Institute of Scientific and Technical Information of China (English)
周泰锦; 莫亦荣
1999-01-01
The symmetry orbital-symmetry orbital tensor method is applied to the evaluation of molecular integrals (one-electron and two-electron integrals) and the symmetry-orbital-tensor and self-consistent-field (SOT-SCF) calculations. A calculation scheme is proposed to simplify the evaluation of integrals and a key equation is derived to reduce the computation efforts in SCF iterations. According to the key equation, compared with the traditional SCF method, the computation efficiencies including CPU timing and external disk (or internal memory) requirement increase in the magnitude of the square of the order of a point group. The new SOT method is expected to be useful in the theoretical calculations of large molecular systems of high point group symmetries.
Spherically symmetric charged compact stars
Energy Technology Data Exchange (ETDEWEB)
Maurya, S.K. [University of Nizwa, Department of Mathematical and Physical Sciences, College of Arts and Science, Nizwa (Oman); Gupta, Y.K. [Jaypee Institute of Information Technology University, Department of Mathematics, Noida, Uttar Pradesh (India); Ray, Saibal [Government College of Engineering and Ceramic Technology, Department of Physics, Kolkata, West Bengal (India); Chowdhury, Sourav Roy [Seth Anandaram Jaipuria College, Department of Physics, Kolkata, West Bengal (India)
2015-08-15
In this article we consider the static spherically symmetric metric of embedding class 1. When solving the Einstein-Maxwell field equations we take into account the presence of ordinary baryonic matter together with the electric charge. Specific new charged stellar models are obtained where the solutions are entirely dependent on the electromagnetic field, such that the physical parameters, like density, pressure etc. do vanish for the vanishing charge. We systematically analyze altogether the three sets of Solutions I, II, and III of the stellar models for a suitable functional relation of ν(r). However, it is observed that only the Solution I provides a physically valid and well-behaved situation, whereas the Solutions II and III are not well behaved and hence not included in the study. Thereafter it is exclusively shown that the Solution I can pass through several standard physical tests performed by us. To validate the solution set presented here a comparison has also been made with that of the compact stars, like RX J 1856 - 37, Her X - 1, PSR 1937+21, PSRJ 1614-2230, and PSRJ 0348+0432, and we have shown the feasibility of the models. (orig.)
Nonlinear electrodynamics as a symmetric hyperbolic system
Abalos, Fernando; Goulart, Érico; Reula, Oscar
2015-01-01
Nonlinear theories generalizing Maxwell's electromagnetism and arising from a Lagrangian formalism have dispersion relations in which propagation planes factor into null planes corresponding to two effective metrics which depend on the point-wise values of the electromagnetic field. These effective Lorentzian metrics share the null (generically two) directions of the electromagnetic field. We show that, the theory is symmetric hyperbolic if and only if the cones these metrics give rise to have a non-empty intersection. Namely that there exist families of symmetrizers in the sense of Geroch which are positive definite for all covectors in the interior of the cones intersection. Thus, for these theories, the initial value problem is well-posed. We illustrate the power of this approach with several nonlinear models of physical interest such as Born-Infeld, Gauss-Bonnet and Euler-Heisenberg.
Symmetric Differentiation on Time Scales
da Cruz, Artur M. C. Brito; Martins, Natalia; Delfim F. M. Torres
2012-01-01
We define a symmetric derivative on an arbitrary nonempty closed subset of the real numbers and derive some of its properties. It is shown that real-valued functions defined on time scales that are neither delta nor nabla differentiable can be symmetric differentiable.
Hah, Chunill; Hathaway, Michael; Katz, Joseph
2014-01-01
The primary focus of this paper is to investigate the effect of rotor tip gap size on how the rotor unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor at near stall operation (for example, where maximum pressure rise is obtained). A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at this flow condition with both a small and a large tip gaps. The numerically obtained flow fields at the small clearance matches fairly well with the available initial measurements obtained at the Johns Hopkins University with 3-D unsteady PIV in an index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. The numerical results are also compared with previously published measurements in a low speed single stage compressor (Maerz et al. [2002]). The current study shows that, with the smaller rotor tip gap, the tip clearance vortex moves to the leading edge plane at near stall operating condition, creating a nearly circumferentially aligned vortex that persists around the entire rotor. On the other hand, with a large tip gap, the clearance vortex stays inside the blade passage at near stall operation. With the large tip gap, flow instability and related large pressure fluctuation at the leading edge are observed in this one and a half stage compressor. Detailed examination of the unsteady flow structure in this compressor stage reveals that the flow instability is due to shed vortices near the leading edge, and not due to a three-dimensional separation vortex originating from the suction side of the blade, which is commonly referred to during a spike-type stall inception. The entire tip clearance flow is highly unsteady. Many vortex structures in the tip clearance flow, including the sheet vortex system near the casing, interact with each other. The
Symmetric Rearrangements Around Infinity with Applications to Levy Processes
Drewitz, Alexander; Sun, Rongfeng
2011-01-01
We prove a new rearrangement inequality for multiple integrals, which partly generalizes a result of Friedberg and Luttinger (1976) and can be interpreted as involving symmetric rearrangements of domains around infinity. As applications, we prove two comparison results for general Levy processes and their symmetric rearrangements. The first application concerns the survival probability of a point particle in a Poisson field of moving traps following independent Levy motions. We show that the survival probability can only increase if the point particle does not move, and the traps and the Levy motions are symmetrically rearranged. This essentially generalizes an isoperimetric inequality of Peres and Sousi (2011) for the Wiener sausage. In the second application, we show that the q-capacity of a Borel measurable set for a Levy process can only increase if the set and the Levy process are symmetrically rearranged. This result generalizes an inequality obtained by Watanabe (1983) for symmetric Levy processes.
Axial skeletal CT densitometry
International Nuclear Information System (INIS)
Since the discovery of the Roentgen ray a precise and accurate assessment of bone mineral content has been a challenge to many investigators. A number of methods have been developed but no one satisfied. Considering its technical possibilities computed tomography is very promising in determination of bone mineral content (BMC). The new modality enables BMC estimations in the axial skeletal trabecular bone. CT densitometry can be performed on a normal commercially available third generation whole body CT scanner. No dedicated device in a special clinical set-up is necessary. In this study 106 patients, most of them clinically suspected of osteoporosis, were examined. The new method CT densitometry has been evaluated. The results have been correlated to alternative BMC determination methods. (Auth.)
DNA Cryptography Based on Symmetric Key Exchange
Tausif Anwar; Abhishek Kumar; Sanchita Paul
2015-01-01
DNA cryptography is a technology of bio science to encrypt large message in compact volume. Now a day, researchers are going to research in the field of secure data transmission. Hiding the encrypted message is important part of Cryptography. Hidden message is in the form of DNA sequence, image, audio and video, which is used to prevent important data from the intruders. In this paper, a new cryptography technique is proposed using Symmetric Key Exchange, one-time pad scheme and DNA hyb...
Conformally symmetric traversable wormholes
International Nuclear Information System (INIS)
Exact solutions of traversable wormholes are found under the assumption of spherical symmetry and the existence of a nonstatic conformal symmetry, which presents a more systematic approach in searching for exact wormhole solutions. In this work, a wide variety of solutions are deduced by considering choices for the form function, a specific linear equation of state relating the energy density and the pressure anisotropy, and various phantom wormhole geometries are explored. A large class of solutions impose that the spatial distribution of the exotic matter is restricted to the throat neighborhood, with a cutoff of the stress-energy tensor at a finite junction interface, although asymptotically flat exact solutions are also found. Using the 'volume integral quantifier', it is found that the conformally symmetric phantom wormhole geometries may, in principle, be constructed by infinitesimally small amounts of averaged null energy condition violating matter. Considering the tidal acceleration traversability conditions for the phantom wormhole geometry, specific wormhole dimensions and the traversal velocity are also deduced
Weyl symmetric structure of QCD vacuum
International Nuclear Information System (INIS)
Full text: We consider Weyl symmetric structure of the classical vacuum in quantum chromodynamics. In the framework of formalism of gauge invariant Abelian projection we show that classical vacuums can be constructed in terms of Killing vector fields on the group SU(3). Consequently, homotopic classes of Killing vector fields determine the topological structure of the vacuum. In particular, the second homotopy group π2(SU(3)/U(1)·U(1)) describes all topologically non-equivalent vacuums which are classified by two topological numbers. Starting with a given Killing vector field one can construct vacuums forming a Weyl sextet representation. An interesting feature of SU(3) gauge theory is that it admits a Weyl symmetric vacuum represented by a linear superposition of the vacuums from the Weyl vacuum sextet. A non-trivial manifestation of the Weyl symmetry is demonstrated on monopole solutions. We construct a family of finite energy monopole solutions in Yang-Mills-Higgs theory which includes the Weyl monopole sextet. We conjecture that a similar Weyl symmetric vacuum structure can be realized at quantum level in quantum chromodynamics. (author)
Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin
2016-01-01
We report the results of a phase-field study of degenerate seaweed to tilted dendrite transition and their growth dynamics during directional solidification of a binary alloy. Morphological selection maps in the planes of (G, Vp) and (ε4, Vp) show that lower pulling velocity, weaker anisotropic strength and higher thermal gradient can enhance the formation of the degenerate seaweed. The tip undercooling shows oscillations in seaweed growth, but it keeps at a constant value in dendritic growth. The M-S instability on the tips and the surface tension anisotropy of the solid-liquid interface are responsible for the formation of the degenerate seaweed. It is evidenced that the place where the interfacial instability occurs determines the morphological transition. The transient transition from degenerate seaweed to tilted dendrite shows that dendrites are dynamically preferred over seaweed. For the tilted dendritic arrays with a large tilted angle, primary spacing is investigated by comparing predicted results with the classical scaling power law, and the growth direction is found to be less sensitive to the pulling velocity and the primary spacing. Furthermore, the effect of the initial interface wavelength on the morphological transition is investigated to perform the history dependence of morphological selection. PMID:27210816
Directory of Open Access Journals (Sweden)
Jian Pan
2011-12-01
Full Text Available We report experimentally that for a particular high-symmetry planar periodic arrangement of metal double-triangle nanoparticle arrays fabricated via angle resolved nanosphere lithography, both anti-symmetric and symmetric magnetic resonances can be explicitly excited at off-normal incidence. Further, we demonstrate that the underlying mechanism for the formation of these two modes is a result of direct interactions with the incident electric and magnetic fields, respectively. As a consequence, with increasing the incident angle there is a relatively small blue-shift in the transmission for the electric-field induced anti-symmetric mode, while a remarkable red-shift is observed for the magnetic-field induced symmetric mode.
International Nuclear Information System (INIS)
Quantitative determination of microstructure and nanostructure properties is essential in research, development and in control of the production process. In instruments for dimensional nanometrology the positioning stage is the key component, since the characteristics of the position acquisition and control determine directly the achievable precision of the complete system. Compact commercial positioning systems usually employ capacitive or inductive position sensors. Both technologies not only offer a resolution in the nanometre range, but also require a (periodic) calibration. To achieve traceable measurements, interferometric sensors need to be implemented into the metrology system. However, currently available commercial interferometers turned out to be too large to be installed in miniature positioning stages easily. Therefore, a new highly compact interferometer to allow for traceability and an uncertainty in the Ångstrom range was developed. One of its first applications will be the new metrological low-noise atomic force microscope at the Physikalisch-Technische Bundesanstalt. The new interferometer is based on a modified homodyne Twyman–Green interferometer concept. It uses a novel signal processing approach based on a field programmable gate array, whereby a spatial interferogram is acquired by a high-speed CMOS line sensor and transformed into its frequency spectrum through a discrete Fourier transform. The spectral representation is analyzed for its major components; the phase information bears a direct connection to the displacement of the positioning unit. Furthermore, a possible stage tilt during the scan gives rise to a shift of the peak magnitude in the frequency spectrum. In addition, the developed system proved to be easily extendable to multiple axes by superimposing multiple interferograms on a single line sensor
Axial anomaly in nonrenormalizable theories
International Nuclear Information System (INIS)
The anomaly for the axial current in nonrenormalizable theories with electromagnetic coupling is considered. The spinor electrodynamics with Pauli term is examined in detail using the Feynman graph technique and the point-splitting method. The same finite value for the axial anomaly emerges. (author)
Open String on Symmetric Product
Fuji, H; Fuji, Hiroyuki; Matsuo, Yutaka
2001-01-01
We develop some basic properties of the open string on the symmetric product which is supposed to describe the open string field theory in discrete lightcone quantization (DLCQ). After preparing the consistency conditions of the twisted boundary conditions for Annulus/M\\"obius/Klein Bottle amplitudes in generic non-abelian orbifold, we classify the most general solutions of the constraints when the discrete group is $S_N$. We calculate the corresponding orbifold amplitudes from two viewpoints -- from the boundary state formalism and from the trace over the open string Hilbert space. It is shown that the topology of the world sheet for the short string and that of the long string in general do not coincide. For example the annulus sector for the short string contains all the sectors (torus, annulus, Klein bottle, M\\"obius strip) of the long strings. The boundary/cross-cap states of the short strings are classified into three categories in terms of the long string, the ordinary boundary and the cross-cap states...
MINIMIZATION PROBLEM FOR SYMMETRIC ORTHOGONAL ANTI-SYMMETRIC MATRICES
Institute of Scientific and Technical Information of China (English)
Yuan Lei; Anping Liao; Lei Zhang
2007-01-01
By applying the generalized singular value decomposition and the canonical correlation decomposition simultaneously, we derive an analytical expression of the optimal approximate solution (X), which is both a least-squares symmetric orthogonal anti-symmetric solution of the matrix equation ATXA ＝ B and a best approximation to a given matrix X*.Moreover, a numerical algorithm for finding this optimal approximate solution is described in detail, and a numerical example is presented to show the validity of our algorithm.
Static black holes with axial symmetry in asymptotically AdS$_4$ spacetime
Kichakova, Olga; Radu, Eugen; Shnir, Yasha
2015-01-01
The known static electro-vacuum black holes in a globally AdS$_4$ background have an event horizon which is geometrically a round sphere. In this work we argue that the situation is different in models with matter fields possessing an explicit dependence on the azimuthal angle $\\varphi$, which, however, does not manifest at the level of the energy-momentum tensor. As a result, the full solutions are axially symmetric only, possessing a single (timelike) Killing vector field. Explicit examples of such static black holes are constructed in Einstein--(complex) scalar field and Einstein--Yang-Mills theories. The basic properties of these solutions are discussed, looking for generic features. For example, we notice that the horizon has an oblate spheroidal shape for solutions with a scalar field and a prolate one for black holes with Yang-Mills fields. The deviation from sphericity of the horizon geometry manifests itself in the holographic stress-tensor. Finally, based on the results obtained in the probe limit, ...
Hulot, G.; Khokhlov, A.; Johnson, C. L.
2012-12-01
It is well known that the geometry of the recent time-averaged paleomagnetic field (TAF) is very close to that of a geocentric axial dipole (GAD). Yet, numerous numerical dynamo simulations show that some departures from such a simple geometry is to be expected, not least because of the heterogeneous thermal core-mantle boundary conditions that the convecting mantle imposes on the geodynamo. Indeed, many TAF models recovered from averaging lava flow paleomagnetic directional data (the most numerous and reliable of all data) would suggest this is the case. However, assessing the significance of such minor departures from the GAD is particularly challenging, because non-linear directional data are sensitive not only to the time-averaged component of the field, but also to its time fluctuating component, known as the paleosecular variation (PSV). This means that in addition to data errors, PSV also must be taken into account when assessing any lava flow directional data based claims of departures of the TAF from the GAD. Furthermore, because of limited age information for these data , it is necessary to assess departures from the GAD by resorting to a statistical approach. We report recent progress using an approach we have suggested and further developed (Khokhlov et al., Geophysical Journal International, 2001, 2006) to test the compatibility of combined time-averaged (TAF) and paleosecular variation (PSV) field models, against any lava flow paleomagnetic database, asssuming that these TAF and PSV models are defined within the Giant Gaussian Process statistical framework. In particular we will show how sensitive statistical measures of the compatibility of a combined set of TAF and PSV models with a given directional database can be defined. These measures can be used to test published TAF and PSV models with updated 0-5 Ma lava flow paleomagnetic data sets. They also lay the groundwork for designing inverse methods better suited to seek the minimum required
Rapalino, Otto; Smirniotopoulos, James G
2016-01-01
Extra-axial brain tumors are the most common adult intracranial neoplasms and encompass a broad spectrum of pathologic subtypes. Meningiomas are the most common extra-axial brain tumor (approximately one-third of all intracranial neoplasms) and typically present as slowly growing dural-based masses. Benign meningiomas are very common, and may occasionally be difficult to differentiate from more aggressive subtypes (i.e., atypical or malignant varieties) or other dural-based masses with more aggressive biologic behavior (e.g., hemangiopericytoma or dural-based metastases). Many neoplasms that typically affect the brain parenchyma (intra-axial), such as gliomas, may also present with primary or secondary extra-axial involvement. This chapter provides a general and concise overview of the common types of extra-axial tumors and their typical imaging features. PMID:27432671
Bode, Hans R.
2009-01-01
Morphogen gradients play an important role in pattern formation during early stages of embryonic development in many bilaterians. In an adult hydra, axial patterning processes are constantly active because of the tissue dynamics in the adult. These processes include an organizer region in the head, which continuously produces and transmits two signals that are distributed in gradients down the body column. One signal sets up and maintains the head activation gradient, which is a morphogenetic gradient. This gradient confers the capacity of head formation on tissue of the body column, which takes place during bud formation, hydra's mode of asexual reproduction, as well as during head regeneration following bisection of the animal anywhere along the body column. The other signal sets up the head inhibition gradient, which prevents head formation, thereby restricting bud formation to the lower part of the body column in an adult hydra. Little is known about the molecular basis of the two gradients. In contrast, the canonical Wnt pathway plays a central role in setting up and maintaining the head organizer. PMID:20066073
The nucleon axial isoscalar coupling constant and the Bjorken sum rule
International Nuclear Information System (INIS)
The nucleon coupling constant with the axial isoscalar current entering the Bjorken sum rule for the deep inelastic scattering of polarized electrons on a polarized target is calculated in nonperturbative QCD. The result, gsub(A)sup(s) approximately 0.5, is about a factor of two smaller as compared to that of the SU(6) symmetric quark model
DNA Cryptography Based on Symmetric Key Exchange
Directory of Open Access Journals (Sweden)
Tausif Anwar
2015-06-01
Full Text Available DNA cryptography is a technology of bio science to encrypt large message in compact volume. Now a day, researchers are going to research in the field of secure data transmission. Hiding the encrypted message is important part of Cryptography. Hidden message is in the form of DNA sequence, image, audio and video, which is used to prevent important data from the intruders. In this paper, a new cryptography technique is proposed using Symmetric Key Exchange, one-time pad scheme and DNA hybridization to minimize time complexity.XOR operation with OTP DNA sequence is used as encryption technique based on DNA cryptography. Symmetric Key Exchange is presenting a secure key generation scheme. This method is very efficient in encrypting, hiding, transmitting and preventing powerful attacks.
Symmetric $q$-deformed KP hierarch
Tian, Kelei; He, Jingsong; Su, Yucai
2014-01-01
Based on the analytic property of the symmetric $q$-exponent $e_q(x)$, a new symmetric $q$-deformed Kadomtsev-Petviashvili ($q$-KP) hierarchy associated with the symmetric $q$-derivative operator $\\partial_q$ is constructed. Furthermore, the symmetric $q$-CKP hierarchy and symmetric $q$-BKP hierarchy are defined. Here we also investigate the additional symmetries of the symmetric $q$-KP hierarchy.
Niksic, T.; Vretenar, D.; Ring, P.
2006-01-01
We report the first study of restoration of rotational symmetry and fluctuations of the quadrupole deformation in the framework of relativistic mean-field models. A model is developed which uses the generator coordinate method to perform configuration mixing calculations of angular momentum projected wave functions, calculated in a relativistic point-coupling model. The geometry is restricted to axially symmetric shapes, and the intrinsic wave functions are generated from the solutions of the...
Institute of Scientific and Technical Information of China (English)
YIN Yajun; WU Jiye; YIN Jie
2008-01-01
To make the geometrical basis for soft matters with curved surfaces such as biomembranes as simple as possible, a symmetrical analytical system was developed in conventional differential geometry.The conventional second fundamental tensor is replaced by the so-called conjugate fundamental tensor.Because the differential properties of the conjugate fundamental tensor and the first fundamental tensor are symmetrical, the symmetrical analytical system including the symmetrical differential operators, symmetrical differential characteristics, and symmetrical integral theorems for tensor fields defined on curved surfaces can be constructed. From the symmetrical analytical system, the symmetrical integral theorems for mean curvature and Gauss curvature, with which the symmetrical Minkowski integral formulas are easily deduced just as special cases, can be derived. The applications of this symmetrical analytical system to biology not only display its simplicity and beauty, but also show its powers in depicting the symmetrical patterns of net-works of biomembrane nanotubes. All these symmetrical patterns in soft matters should be just the reason-able and natural results of the symmetrical analytical system.
Spherically symmetric cosmology: resource paper
Coley, A. A.; Lim, W. C.; De Leon, G.
2008-01-01
We use the 1+3 frame formalism to write down the evolution equations for spherically symmetric models as a well-posed system of first order PDEs in two variables, suitable for numerical and qualitative analysis.
Symmetrical dialogue in investor relations
Harold Hassink; Laury Bollen; Meinderd de Vries
2008-01-01
Purpose – Previous research shows that symmetrical dialogue between companies and their investors through e-mail does not match the quality of the asymmetrically provided information on investor relations websites. This paper seeks to further examine the quality of symmetrical dialogue and especially whether sender identity affects the corporate e-mail handling performance. Design/methodology/approach – A “mystery sender” approach is used to test whether companies answer similar e-mails from ...
Symmetric Gini Covariance and Correlation
Sang, Yongli; Dang, Xin; Sang, Hailin
2016-01-01
Standard Gini covariance and Gini correlation play important roles in measuring the dependence of random variables with heavy tails. However, the asymmetry brings a substantial difficulty in interpretation. In this paper, we propose a symmetric Gini-type covariance and a symmetric Gini correlation ($\\rho_g$) based on the joint rank function. The proposed correlation $\\rho_g$ is more robust than the Pearson correlation but less robust than the Kendall's $\\tau$ correlation. We establish the rel...
Generation of symmetric exponential sums
Sergeyev, Yaroslav D.
2011-01-01
In this paper, a new method for generation of infinite series of symmetric identities written for exponential sums in real numbers is proposed. Such systems have numerous applications in theory of numbers, chaos theory, algorithmic complexity, dynamic systems, etc. Properties of generated identities are studied. Relations of the introduced method for generation of symmetric exponential sums to the Morse-Hedlund sequence and to the theory of magic squares are established.
Symmetric Composite Laminate Stress Analysis
Wang, T.; Smolinski, K. F.; Gellin, S.
1985-01-01
It is demonstrated that COSMIC/NASTRAN may be used to analyze plate and shell structures made of symmetric composite laminates. Although general composite laminates cannot be analyzed using NASTRAN, the theoretical development presented herein indicates that the integrated constitutive laws of a symmetric composite laminate resemble those of a homogeneous anisotropic plate, which can be analyzed using NASTRAN. A detailed analysis procedure is presented, as well as an illustrative example.
Gauge-symmetric approach to effective lagrangians: the η' meson from QCD
International Nuclear Information System (INIS)
We present a general scheme for extracting effective degrees of freedom from an underlying fundamental lagrangian, through a series of well-defined transformations in the functional integral of the cut-off theory. This is done by introducing collective fields in a gauge-symmetric manner. Through appropriate gauge fixings of this symmetry one can remove long-distance degrees of freedom from the underlying theory, replacing them by the collective fields. Applying this technique to QCD, we set out to extract the long-distance dynamics in the pseudoscalar flavour singlet sector through a gauging (and subsequent gauge fixing) of the U(1)A flavour symmetry which is broken by the anomaly. By this series of exact transformations of a cut-off generating functional for QCD, we arrive at a theory describing the long-distance physics of a pseudoscalar flavour singlet meson coupled to the residual quark-gluon degrees of freedom. As an example we show how to derive a Witten-Veneziano-like relation between the η' mass and the topological susceptibility. The resulting effective lagrangian contains an axial vector field, which shares the relevant features with the Veneziano ghost. This field is responsible for removing the η' degree of freedom from the fundamental QCD lagrangian. (orig.)
Li, Zhi-Hui; Ma, Qiang; Cui, Junzhi
2016-06-01
The new second-order two-scale (SOTS) finite element algorithm is developed for the dynamic thermo-mechanical coupling problems in axisymmetric and spherical symmetric structures made of composite materials. The axisymmetric structure considered is periodic in both radial and axial directions and homogeneous in circumferential direction. The spherical symmetric structure is only periodic in radial direction. The dynamic thermo-mechanical coupling model is presented and the equivalent compact form is derived. Then, the cell problems, effective material coefficients and the homogenized thermo-mechanical coupling problem are obtained successively by the second-order asymptotic expansion of the temperature increment and displacement. The homogenized material obtained is manifested with the anisotropic property in the circumferential direction. The explicit expressions of the homogenized coefficients in the plane axisymmetric and spherical symmetric cases are given and both the derivation of the analytical solutions of the cell functions and the quasi-static thermoelasticity problems are discussed. Based on the SOTS method, the corresponding finite-element procedure is presented and the unconditionally stable implicit algorithm is established. Some numerical examples are solved and the mutual interaction between the temperature and displacement field is studied under the condition of structural vibration. The computational results demonstrate that the second-order asymptotic analysis finite-element algorithm is feasible and effective in simulating and predicting the dynamic thermo-mechanical behaviors of the composite materials with small periodic configurations in axisymmetric and spherical symmetric structures. This may provide a vital computational tool for analyzing composite material internal temperature distribution and structural deformation induced by the dynamic thermo-mechanical coupling response under strong aerothermodynamic environment.
Lu, Jie
2016-06-01
In this work, we report analytical results on transverse domain wall (TDW) statics and field-driven dynamics in quasi-one-dimensional biaxial nanowires under arbitrary uniform transverse magnetic fields (TMFs) based on the Landau-Lifshitz-Gilbert equation. Without axial driving fields, the static TDW should be symmetric about its center while twisted in its azimuthal angle distribution. By decoupling polar and azimuthal degrees of freedom, an approximate solution is provided which reproduces these features to a great extent. When an axial driving field is applied, the dynamical behavior of a TDW is viewed as the response of its static profile to external excitations. By means of the asymptotic expansion method, the TDW velocity in the traveling-wave mode is obtained, which provides the extent and boundary of the "velocity-enhancement" effect of TMFs on TDWs in biaxial nanowires. Finally, numerical simulations are performed and strongly support our analytics.
Institute of Scientific and Technical Information of China (English)
罗玲; 李丹; 吕晓威; 王震
2012-01-01
According to the special structure and complex electromagnetic field distribution of axial flux coreless permanent magnet synchronous generator, a 3D prototype model was established and its boundary conditions was set for solving by using electromagnetic finite element simulation software MagNet. No-load air-gap magnetic field was analyzed by using 3D static solver and no-load back-electromotive force at different speed was calculated by using 3D transient with motion solver. Finally, no-load characteristic of the prototype generator was tested. The test results show that the simulation model is reasonable and the analysis method is effective.%针对盘式无铁心永磁同步风力发电机结构的特殊性及其电磁场分布的复杂性,采用电磁场有限元分析软件MagNet对一台样机进行了3D建模；设置了求解所需的边界条件；利用静态求解器得到了磁场分布规律；通过动态求解器计算了不同转速下的空载电压,并绘制了样机的空载特性曲线；最后通过空载试验验证了仿真模型的合理性及计算方法的正确性.
FINITE ELEMENT ANALYSIS OF AXIAL FEED BAR ROLLING
Institute of Scientific and Technical Information of China (English)
C.G. Xu; G.H. Liu; G.S. Ren; Z. Shen; C.P. Ma; W. W. Ren
2007-01-01
A flexible technique of hot working of bars by axial feed rolling was introduced. The processdeformation, strain field, stress field, and temperature field of the parts are analyzed by finite elementmethod (FEM)-simulation software DEFORM-3D. The material flow rule and tool load have beeninvestigated.