Energy Technology Data Exchange (ETDEWEB)
Tarachand, R.K.; Singh, N.I.
1988-07-01
Considering the axially symmetric Einstein-Rosen metric, the problem of massive scalar field interactions in the presence of perfect fluid distribution has been studied, and it has been observed that there cannot exist any solution for the coupled massive scalar field and perfect fluid distribution for the metric. The problem reduces to the finding of interactions between zero-mass scalar field and stiff fluid.
On the equivalence of approximate stationary axially symmetric solutions of Einstein field equations
Boshkayev, Kuantay; Toktarbay, Saken; Zhami, Bakytzhan
2015-01-01
We study stationary axially symmetric solutions of the Einstein vacuum field equations that can be used to describe the gravitational field of astrophysical compact objects in the limiting case of slow rotation and slight deformation. We derive explicitly the exterior Sedrakyan-Chubaryan approximate solution, and express it in analytical form, which makes it practical in the context of astrophysical applications. In the limiting case of vanishing angular momentum, the solution reduces to the well-known Schwarzschild solution in vacuum. We demonstrate that the new solution is equivalent to the exterior Hartle-Thorne solution. We establish the mathematical equivalence between the Sedrakyan-Chubaryan, Fock-Abdildin and Hartle-Thorne formalisms.
Non-Abelian fields in AdS$_4$ spacetime: axially symmetric, composite configurations
Kichakova, Olga; Radu, Eugen; Shnir, Yasha
2014-01-01
We construct new finite energy regular solutions in Einstein-Yang-Mills-SU(2) theory. They are static, axially symmetric and approach at infinity the anti-de Sitter spacetime background. These configurations are characterized by a pair of integers $(m, n)$, where $m$ is related to the polar angle and $n$ to the azimuthal angle, being related to the known flat space monopole-antimonopole chains and vortex rings. Generically, they describe composite configurations with several individual components, possesing a nonzero magnetic charge, even in the absence of a Higgs field. Such Yang-Mills configurations exist already in the probe limit, the AdS geometry supplying the attractive force needed to balance the repulsive force of Yang-Mills gauge interactions. The gravitating solutions are constructed by numerically solving the elliptic Einstein-DeTurck--Yang-Mills equations. The variation of the gravitational coupling constant $\\alpha$ reveals the existence of two branches of gravitating solutions which bifurcate at...
Thermophoresis of Axially Symmetric Bodies
2007-11-02
Sweden Abstract. Thermophoresis of axially symmetric bodies is investigated to first order in the Knudsen-mimber, Kn. The study is made in the limit...derived. Asymptotic solutions are studied. INTRODUCTION Thermophoresis as a phenomenon has been known for a long time, and several authors have approached
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.
Magnetic Field, Force, and Inductance Computations for an Axially Symmetric Solenoid
Lane, John E.; Youngquist, Robert C.; Immer, Christopher D.; Simpson, James C.
2001-01-01
The pumping of liquid oxygen (LOX) by magnetic fields (B field), using an array of electromagnets, is a current topic of research and development at Kennedy Space Center, FL. Oxygen is paramagnetic so that LOX, like a ferrofluid, can be forced in the direction of a B field gradient. It is well known that liquid oxygen has a sufficient magnetic susceptibility that a strong magnetic gradient can lift it in the earth's gravitational field. It has been proposed that this phenomenon can be utilized in transporting (i.e., pumping) LOX not only on earth, but on Mars and in the weightlessness of space. In order to design and evaluate such a magnetic pumping system, it is essential to compute the magnetic and force fields, as well as inductance, of various types of electromagnets (solenoids). In this application, it is assumed that the solenoids are air wrapped, and that the current is essentially time independent.
Spin-orbit qubits of rare-earth-metal ions in axially symmetric crystal fields.
Bertaina, S; Shim, J H; Gambarelli, S; Malkin, B Z; Barbara, B
2009-11-27
Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several micros) and the Rabi frequency Omega(R) is anisotropic. Here, we present a study of the variations of Omega(R)(H(0)) with the magnitude and direction of the static magnetic field H(0) for the odd 167Er isotope in a single crystal CaWO(4):Er(3+). The hyperfine interactions split the Omega(R)(H(0)) curve into eight different curves which are fitted numerically and described analytically. These "spin-orbit qubits" should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.
Axially Symmetric Post-Newtonian Stellar Systems
Directory of Open Access Journals (Sweden)
Camilo Akímushkin
2010-06-01
Full Text Available We introduce a method to obtain self-consistent, axially symmetric disklike stellar models in the first post-Newtonian (1PN approximation. By using in the field equations of the 1PN approximation a distribution function (DF corresponding to a Newtonian model, two fundamental equations determining the 1PN corrections are obtained. The rotation curves of the corrected models differs from the classical ones and the corrections are clearly appreciable with values of the mass and radius of a typical galaxy. On the other hand, the relativistic mass correction can be ignored for all models. Resumen. Presentamos un método para obtener modelos estelares discoidales, axialmente simétricos, auto-consistentes en la primera aproximación post-Newtoniana (1PN. Usando en las ecuaciones de campo de la aproximación 1PN una función de distribución conocida (DF que corresponde a un modelo Newtoniano, se obtienen dos ecuaciones fundamentales para determinar las correcciones 1PN. Las curvas de rotación de los modelos corregidos difieren de las clásicas y las correcciones son claramente apreciables con los valores de la masa y el radio de una galaxia típica. Por otro lado, la corrección relativista de la masa se puede ignorar para todos los modelos.
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
On Stationary Axially Symmetric Solutions in Brans-Dicke Theory
Kirezli, Pınar
2015-01-01
Stationary axially symmetric Brans-Dicke-Maxwell solutions are re-examined in the framework of the Brans-Dicke theory. We see that, employing a particular parametrization of the standard axially symmetric metric simplifies the procedure of obtaining the Ernst equations for axially symmetric electro-vacuum space-times for this theory. This analysis also permit us to construct a two parameter extension in both Jordan and Einstein frames of an old solution generating technique frequently used to construct axially symmetric solutions for Brans-Dicke theory from a seed solution of General Relativity. As applications of this technique, several known and new solutions are constructed including a general axially symmetric BD-Maxwell solution of Plebanski-Demianski with vanishing cosmological constant, i.e. the Kinnersley solution and general magnetized Kerr-Newman type solutions. Some physical properties and circular motion of test particles for a particular subclass of Kinnersley solution, i.e. Kerr-Newman-NUT type ...
The geometrical theory of diffraction for axially symmetric reflectors
DEFF Research Database (Denmark)
Rusch, W.; Sørensen, O.
1975-01-01
The geometrical theory of diffraction (GTD) (cf. [1], for example) may be applied advantageously to many axially symmetric reflector antenna geometries. The material in this communication presents analytical, computational, and experimental results for commonly encountered reflector geometries...
Axially symmetric volume constrained anisotropic mean curvature flow
Palmer, Bennett
2011-01-01
We study the long time existence theory for a non local flow associated to a free boundary problem for a trapped non liquid drop. The drop has free boundary components on two horizontal plates and its free energy is anisotropic and axially symmetric. For axially symmetric initial surfaces with sufficiently large volume, we show that the flow exists for all time. Numerical simulations of the curvature flow are presented.
An axially symmetric solution of metric-affine gravity
Vlachynsky, E J; Obukhov, Yu N; Hehl, F W
1996-01-01
We present an exact stationary {\\it axially symmetric} vacuum solution of metric-affine gravity (MAG) which generalises the recently reported spherically symmetric solution. Besides the metric, it carries nonmetricity and torsion as post-Riemannian geometrical structures. The parameters of the solution are interpreted as mass and angular momentum and as dilation, shear and spin charges.
Aissani, Sarra; Guendouz, Laouès; Marande, Pierre-Louis; Canet, Daniel
2015-01-01
As demonstrated before, the application of a weak static B0 magnetic field (less than 10 G) may produce definite effects on the ¹⁴N Quadrupole Resonance line when the electric field gradient tensor at the nitrogen nucleus level is of axial symmetry. Here, we address more precisely the problem of the relative orientation of the two magnetic fields (the static field and the radio-frequency field of the pure NQR experiment). For a field of 6G, the evolution of the signal intensity, as a function of this relative orientation, is in very good agreement with the theoretical predictions. There is in particular an intensity loss by a factor of three when going from the parallel configuration to the perpendicular configuration. By contrast, when dealing with a very weak magnetic field (as the earth field, around 0.5 G), this effect drops to ca. 1.5 in the case Hexamethylenetetramine (HMT).This is explained by the fact that the Zeeman shift (due to the very weak magnetic field) becomes comparable to the natural line-width. The latter can therefore be determined by accounting for this competition. Still in the case of HMT, the estimated natural line-width is half the observed line-width. The extra broadening is thus attributed to earth magnetic field. The latter constitutes therefore the main cause of the difference between the natural transverse relaxation time (T₂) and the transverse relaxation time derived from the observed line-width (T₂(⁎)).
Axially and spherically symmetric solitons in warm plasma
Dvornikov, Maxim
2010-01-01
We study the existence of stable axially and spherically symmetric plasma structures on the basis of the new nonlinear Schrodinger equation (NLSE) accounting for nonlocal electron nonlinearities. The numerical solutions of NLSE having the form of spatial solitions are obtained and their stability is analyzed. We discuss the possible application of the obtained results to the theoretical description of natural plasmoids in the atmosphere.
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.
Characterization of axially-symmetric magnetic elds
AUTHOR|(CDS)2087237; Buzio, Marco
In solenoids for particle accelerators, the magnetic field is usually mapped by means of 3D Hall-sensing systems through a burdensome and costly procedure. A further problem arises from a coherent treatment between the beam physics requirements, the qualification of numerical models, the design and manufacturing of the magnet, and the magnetic measurements. For example, when the magnet is misaligned with respect to the longitudinal direction of the mapper, the fringe field shows spurious components. A method was therefore developed for measuring the magnetic field of axisymmetric magnets by exploiting their inherent symmetry. The method yields a measurement of the magnetic flux linked with a pair of sensing coils as a function of their longitudinal position. An induction transducer, sensitive to the longitudinal and radial components of the solenoid under test, has been designed and constructed. A transport system moves the transducer along the magnet axis, covering the full length of the magnet and including...
Wave Propagation through Axially Symmetric Dielectric Shells.
1981-06-01
1-8 2..2 Sc lr .o en i.. . . . . ..........eo oe e .eoe. o. eeeeo. oo....... 2 1 1.2 Baekground: Analytical Methods Based on Flat Sheet Appr oatei...Fields Near a Radome Consist of Constituent Waves. 1-2 - -t . -__-_-_-_-_-_-_..._._._._._._. 1.2 BACKGROUND: ANALYTICAL METHODS BASED ON FLAT SHEET...2.4.2. So A2 ikR x (4 ) = (K-1) E feik Cos2 dado dz (2-100) x 2 R2 o where = (aa - ap cos - zz’) R - 1 (2-101) and -11 = [6 (a+6p)-6 (a-6p)-a 1. (2
Axially symmetric pseudo-Newtonian hydrodynamics code
Kim, Jinho; Choptuik, Matthew William; Lee, Hyung Mok
2012-01-01
We develop a numerical hydrodynamics code using a pseudo-Newtonian formulation that uses the weak field approximation for the geometry, and a generalized source term for the Poisson equation that takes into account relativistic effects. The code was designed to treat moderately relativistic systems such as rapidly rotating neutron stars. The hydrodynamic equations are solved using a finite volume method with High Resolution Shock Capturing (HRSC) techniques. We implement several different slope limiters for second order reconstruction schemes and also investigate higher order reconstructions. We use the method of lines (MoL) to convert the mixed spatial-time partial differential equations into ordinary differential equations (ODEs) that depend only on time. These ODEs are solved using 2nd and 3rd order Runge-Kutta methods. The Poisson equation for the gravitational potential is solved with a multigrid method. In order to confirm the validity of our code, we carry out four different tests including one and two...
Dynamics and statics of flexible axially symmetric shallow shells
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...
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.
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.
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...
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.
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.
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.
The Axially Symmetric Ejecta of Supernova 1987A
Wang, L; Höflich, P; Khokhlov, A; Baade, D; Branch, D; Challis, P M; Filippenko, A V; Fransson, C; Garnavich, P M; Kirshner, R P; Lundqvist, P; McCray, R; Panagia, N; Pun, C S J; Phillips, M M; Sonneborn, G; Suntzeff, N B
2002-01-01
Extensive early observations proved that the ejecta of supernova 1987A (SN 1987A) are aspherical. Fifteen years after the supernova explosion, the Hubble Space Telescope has resolved the rapidly expanding ejecta. The late-time images and spectroscopy provide a geometrical picture that is consistent with early observations and suggests a highly structured, axially symmetric geometry. We present here a new synthesis of the old and new data. We show that the Bochum event, presumably a clump of $^{56}$Ni, and the late-time image, the locus of excitation by $^{44}$Ti, are most naturally accounted for by sharing a common position angle of about 14\\degree, the same as the mystery spot and early speckle data on the ejecta, and that they are both oriented along the axis of the inner circumstellar ring at 45\\degree to the plane of the sky. We also demonstrate that the polarization represents a prolate geometry with the same position angle and axis as the early speckle data and the late-time image and hence that the geo...
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.
Sarma, Debojit; Patgiri, Mahadev
2016-01-01
We present an axially symmetric, asymptotically flat empty space solution of the Einstein field equations containing a naked singularity. The spacetime is regular everywhere except on the symmetry axis where it possess a true curvature singularity. The spacetime is of type D in the Petrov classification scheme and is locally isometric to the metrics of case IV in the Kinnersley classification of type D vacuum metrics. Additionally, the spacetime also shows the evolution of closed timelike curves (CTCs) from an initial hypersurface free from CTCs.
Revised NASA axially symmetric ring model for coupled-cavity traveling-wave tubes
Wilson, Jeffrey D.
1987-01-01
A versatile large-signal, two-dimensional computer program is used by NASA to model coupled-cavity travelling-wave tubes (TWTs). In this model, the electron beam is divided into a series of disks, each of which is further divided into axially symmetric rings which can expand and contract. The trajectories of the electron rings and the radiofrequency (RF) fields are determined from the calculated axial and radial space-charge, RF, and magnetic forces as the rings pass through a sequence of cavities. By varying electrical and geometric properties of individual cavities, the model is capable of simulating severs, velocity tapers, and voltage jumps. The calculated electron ring trajectories can be used in designing magnetic focusing and multidepressed collectors. The details of using the program are presented, and results are compared with experimental data.
Qualitative behavior of axial-symmetric solutions of elliptic free boundary problems
Directory of Open Access Journals (Sweden)
Andrew F. Acker
1997-01-01
Full Text Available axial-symmetric solutions and qualitative geometric properties of the free boundary are compared to those of the fixed boundary for the axial and radial directions. Counterexamples obtained previously by the first author show that our results cannot hold in the same generality as those for similar free boundary problems in R^2.
Axially symmetric anisotropic string cosmological models in Saez-Ballester theory of gravitation
Kanakavalli, T.; Rao, G. Ananda; Reddy, D. R. K.
2017-02-01
Field equations of a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) are derived with the help of a spatially homogeneous axially symmetric anisotropic Bianchi type metric in the presence of cosmic string source. To obtain determinate solutions of the field equations we have used the fact that the scalar expansion is proportional to shear scalar and the equations of state which correspond to geometric, Takabayasi and massive strings. It is found that geometric and massive strings do not coexist with the Saez-Ballester Scalar field. However, Takabayasi string which survives has been determined. Also, physical discussion of the dynamical parameters of the model is presented.
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.
The space-time outside a source of gravitational radiation: the axially symmetric null fluid
Energy Technology Data Exchange (ETDEWEB)
Herrera, L. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Universidad de Salamanca, Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain); Di Prisco, A. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Ospino, J. [Universidad de Salamanca, Departamento de Matematica Aplicada and Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain)
2016-11-15
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 space-times. 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. (orig.)
EBQ code: transport of space-charge beams in axially symmetric devices
Energy Technology Data Exchange (ETDEWEB)
Paul, A.C.
1982-11-01
Such general-purpose space charge codes as EGUN, BATES, WOLF, and TRANSPORT do not gracefully accommodate the simulation of relativistic space-charged beams propagating a long distance in axially symmetric devices where a high degree of cancellation has occurred between the self-magnetic and self-electric forces of the beam. The EBQ code was written specifically to follow high current beam particles where space charge is important in long distance flight in axially symmetric machines possessing external electric and magnetic field. EBQ simultaneously tracks all trajectories so as to allow procedures for charge deposition based on inter-ray separations. The orbits are treated in Cartesian geometry (position and momentum) with z as the independent variable. Poisson's equation is solved in cylindrical geometry on an orthogonal rectangular mesh. EBQ can also handle problems involving multiple ion species where the space charge from each must be included. Such problems arise in the design of ion sources where different charge and mass states are present.
Babourova, O V; Kudlaev, P E
2016-01-01
On the basis of the Poincare-Weyl gauge theory of gravitation, a new conformal Weyl-Dirac theory of gravitation is proposed, which is a gravitational theory in Cartan-Weyl spacetime with the Dirac scalar field representing the dark matter model. A static approximate axially symmetric solution of the field equations in vacuum is obtained. On the base of this solution in the Newtonian approximation one considers the problem of rotation velocities in spiral components of galaxies.
Acoustic horizons for axially and spherically symmetric fluid flow
Cadoni, M
2006-01-01
We investigate the formation of acoustic horizons for an inviscid fluid moving in a pipe in the case of stationary and axi-symmetric flow. We show that, differently from what is generally believed, the acoustic horizon forms in correspondence of either a local minimum or maximum of the flux tube cross-section. Similarly, the external potential is required to have either a maximum or a minimum at the horizon, so that the external force has to vanish there. Choosing a power-law equation of state for the fluid, $P\\propto \\rho^{n}$, we solve the equations of the fluid dynamics and show that the two possibilities are realized respectively for $n>-1$ and $n<-1$. These results are extended also to the case of spherically symmetric flow.
Microscopic derivation of nuclear rotation-vibration model, axially symmetric case
Gulshani, Parviz
2015-01-01
We derive from first principles the successful phenomenological hydrodynamic model of Bohr-Davydov-Faessler-Greiner for rotation-vibration motion of an axially symmetric deformed nucleus. The derivation is not limited to small oscillation amplitude, and provides microscopic expressions for the interaction operators among the rotation, vibration, and intrinsic motions, for the moment of inertia, vibration mass, and for the deformation variables. The method uses canonical transformations to collective co-ordinates, followed by a constrained variational method, with the associated constraints imposed on the wavefunction rather than on the particle co-ordinates. The approach yields three self-consistent, time-reversal invariant, cranking-type Schrodinger equations for the rotation-vibration and intrinsic motions, and a self-consistency equation. For deformed harmonic oscillator mean-field potentials, these equations are solved in closed forms for the energies, moments of inertia, quadrupole moments and transition...
White matter biomarkers from fast protocols using axially symmetric diffusion kurtosis imaging
Hansen, Brian; Shemesh, Noam; Lund, Torben E; Sangill, Ryan; Østergaard, Leif; Jespersen, Sune N
2016-01-01
White matter tract integrity (WMTI) can be used to characterize tissue microstructure in areas with axisymmetric fiber bundles. Several WMTI biomarkers have now been validated against microscopy and provided promising results in studies of brain development and aging, as well as in a number of brain disorders. In a clinical setting, however, the diffusion kurtosis imaging (DKI) protocol utilized as part of WMTI imaging may be prohibitively long. Consequently, the diagnostic value of the WMTI parameters is rarely explored outside of dedicated animal studies and clinical studies of slowly progressing diseases. Here, we evaluate WMTI based on recently introduced axially symmetric DKI which has lower data demand than conventional DKI. We compare WMTI parameters derived from conventional DKI to those from axially symmetric DKI and to parameters calculated analytically from the axially symmetric tensors. We also assess the effect of the imposed symmetry on the kurtosis fractional anisotropy (KFA). We employ numeric...
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.
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.
Resolving optical illumination distributions along an axially symmetric photodetecting fiber.
Sorin, Fabien; Lestoquoy, Guillaume; Danto, Sylvain; Joannopoulos, John D; Fink, Yoel
2010-11-08
Photodetecting fibers of arbitrary length with internal metal, semiconductor and insulator domains have recently been demonstrated. These semiconductor devices exhibit a continuous translational symmetry which presents challenges to the extraction of spatially resolved information. Here, we overcome this seemingly fundamental limitation and achieve the detection and spatial localization of a single incident optical beam at sub-centimeter resolution, along a one-meter fiber section. Using an approach that breaks the axial symmetry through the constuction of a convex electrical potential along the fiber axis, we demonstrate the full reconstruction of an arbitrary rectangular optical wave profile. Finally, the localization of up to three points of illumination simultaneously incident on a photodetecting fiber is achieved.
Existence of axially symmetric solutions in SU(2)-Yang-Mills and related theories
Hannibal, L; Hannibal, Ludger; Ossietzky, Carl von
1999-01-01
It is shown that the static axially symmetric solutions of SU(2) Einstein-Yang-Mills-Dilaton theory constructed by Kleihaus and Kunz are gauge-equivalent to two-parameter families of embedded abelian solutions, characterized by mass and magnetic dipole moment. The existence of other particle-like solutions is excluded.
Axially symmetric equations for differential pulsar rotation with superfluid entrainment
Antonelli, M.; Pizzochero, P. M.
2017-01-01
In this article we present an analytical two-component model for pulsar rotational dynamics. Under the assumption of axial symmetry, implemented by a paraxial array of straight vortices that thread the entire neutron superfluid, we are able to project exactly the 3D hydrodynamical problem to a 1D cylindrical one. In the presence of density-dependent entrainment the superfluid rotation is non-columnar: we circumvent this by using an auxiliary dynamical variable directly related to the areal density of vortices. The main result is a system of differential equations that take consistently into account the stratified spherical structure of the star, the dynamical effects of non-uniform entrainment, the differential rotation of the superfluid component and its coupling to the normal crust. These equations represent a mathematical framework in which to test quantitatively the macroscopic consequences of the presence of a stable vortex array, a working hypothesis widely used in glitch models. Even without solving the equations explicitly, we are able to draw some general quantitative conclusions; in particular, we show that the reservoir of angular momentum (corresponding to recent values of the pinning forces) is enough to reproduce the largest glitch observed in the Vela pulsar, provided its mass is not too large.
The Einstein field equations for cylindrically symmetric elastic configurations
Energy Technology Data Exchange (ETDEWEB)
Brito, I; Vaz, E G L R [Departamento de Matematica e Aplicacoes, Universidade do Minho, 4800-058 Guimaraes (Portugal); Carot, J, E-mail: ireneb@math.uminho.pt, E-mail: jcarot@uib.cat, E-mail: evaz@math.uminho.pt [Departament de Fisica, Universitat de les Illes Balears, Cra Valdemossa pk 7.5, E-07122 Palma (Spain)
2011-09-22
In the context of relativistic elasticity it is interesting to study axially symmetric space-times due to their significance in modeling neutron stars and other astrophysical systems of interest. To approach this problem, here, a particular class of these space-times is considered. A cylindrically symmetric elastic space-time configuration is studied, where the material metric is taken to be flat. The components of the energy-momentum tensor for elastic matter are written in terms of the invariants of the strain tensor, here chosen to be the eigenvalues of the pulled-back material metric. The Einstein field equations are presented and a condition confirming the existence of a constitutive function is obtained. This condition leads to special cases, in one of which a new system for the metric functions and an expression for the constitutive function are deduced. The new system depends on a particular function, which builds up the constitutive equation.
Fields, Strings, Matrices and Symmetric Products
Dijkgraaf, R.
1999-01-01
In these notes we review the role played by the quantum mechanics and sigma models of symmetric product spaces in the light-cone quantization of quantum field theories, string theory and matrix theory. Lectures given at the Institute for Theoretical Physics, UC Santa Barbara, January 1998 and the Spring School on String Theory and Mathematics, Harvard University, May 1998.
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.
Replica symmetric spin glass field theory
Energy Technology Data Exchange (ETDEWEB)
Temesvari, T. [Research Group for Theoretical Physics of the Hungarian Academy of Sciences, Eoetvoes University, Pazmany Peter setany 1/A, H-1117 Budapest (Hungary)]. E-mail: temtam@helios.elte.hu
2007-06-18
A new powerful method to test the stability of the replica symmetric spin glass phase is proposed by introducing a replicon generator function g(v). Exact symmetry arguments are used to prove that its extremum is proportional to the inverse spin glass susceptibility. By the idea of independent droplet excitations a scaling form for g(v) can be derived, whereas it can be exactly computed in the mean field Sherrington-Kirkpatrick model. It is shown by a first order perturbative treatment that the replica symmetric phase is unstable down to dimensions d < or approx. 6, and the mean field scaling function proves to be very robust. Although replica symmetry breaking is escalating for decreasing dimensionality, a mechanism caused by the infrared divergent replicon propagator may destroy the mean field picture at some low enough dimension.
Replica symmetric spin glass field theory
Temesvári, T.
2007-06-01
A new powerful method to test the stability of the replica symmetric spin glass phase is proposed by introducing a replicon generator function g(v). Exact symmetry arguments are used to prove that its extremum is proportional to the inverse spin glass susceptibility. By the idea of independent droplet excitations a scaling form for g(v) can be derived, whereas it can be exactly computed in the mean field Sherrington-Kirkpatrick model. It is shown by a first order perturbative treatment that the replica symmetric phase is unstable down to dimensions d≲6, and the mean field scaling function proves to be very robust. Although replica symmetry breaking is escalating for decreasing dimensionality, a mechanism caused by the infrared divergent replicon propagator may destroy the mean field picture at some low enough dimension.
FINITE ELEMENT FOR STRESS-STRAIN STATE MODELING OF TWO-LAYERED AXIALLY SYMMETRIC SHELLS
Directory of Open Access Journals (Sweden)
K. S. Kurochka
2015-07-01
Full Text Available Subject of Research. Computation of composite material designs requires application of numerical methods. The finiteelement method usage is connected with surface approximation problems. Application of volumetric and laminar elements leads to systems with large sizes and a great amount of computation. The objective of this paper is to present an equivalent two-layer mathematical model for evaluation of displacements and stresses of cross-ply laminated cone shells subjected to uniformly distributed load. An axially symmetric element for shell problems is described. Method. Axially symmetric finite element is proposed to be applied in calculations with use of correlation for the inner work of each layer separately. It gives the possibility to take into account geometric and physical nonlinearities and non-uniformity in the layers of the shell. Discrete mathematical model is created on the base of the finite-element method with the use of possible motions principle and Kirchhoff–Love assumptions. Hermite element is chosen as a finite one. Cone shell deflection is considered as the quantity sought for. Main Results. One-layered and two-layered cone shells have been considered for proposed mathematical model verification with known analytical and numerical analytical solutions, respectively. The axial displacements of the two-layered cone are measured with an error not exceeding 5.4 % for the number of finite elements equal to 30. The proposed mathematical model requires fewer nodes to define the finite element meshing of the system and much less computation time. Thereby time for finding solution decreases considerably. Practical Relevance. Proposed model is applicable for computation of multilayered designs under axially symmetric loads: composite high-pressure bottles, cylinder shaped fiberglass pipes, reservoirs for explosives and flammable materials, oil and gas storage tanks.
New classes of bi-axially symmetric solutions to four-dimensional Vasiliev higher spin gravity
Sundell, Per
2016-01-01
We present new infinite-dimensional spaces of bi-axially symmetric asymptotically anti-de Sitter solutions to four-dimensional Vasiliev higher spin gravity, obtained by modifications of the Ansatz used in arXiv:1107.1217, which gave rise to a Type-D solution space. The current Ansatz is based on internal semigroup algebras (without identity) generated by exponentials formed out of the bi-axial symmetry generators. After having switched on the vacuum gauge function, the resulting generalized Weyl tensor is given by the sum of two generalized Petrov type-D tensors, and the twistor space connections are smooth in twistor space over finite regions of spacetime. We provide evidence for that the linearized twistor space connection can be brought to Vasiliev gauge.
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
Energy Technology Data Exchange (ETDEWEB)
Sharif, M. [University of the Punjab, Department of Mathematics, Lahore (Pakistan); Manzoor, Rubab [University of Management and Technology, Department of Mathematics, Lahore (Pakistan)
2016-06-15
This paper investigates the dynamics of an axial reflection symmetric model in self-interacting Brans-Dicke gravity for anisotropic fluid. We formulate hydrodynamical equations and discuss oscillations using a time-dependent perturbation for both spin-dependent and spin-independent cases. The expressions of the frequency, the total energy density, and the equation of motion of the oscillating model are obtained. We study the instability of the 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 Γ = 1, collapses for Γ > 1, and becomes unstable for 0 < Γ < 1. (orig.)
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 $0<\\Gamma<1$.
Experimental Modeling of the Electron Beam Focusing Regimesin the Axially-Symmetric Systems
Directory of Open Access Journals (Sweden)
I.V. Barsuk
2014-04-01
Full Text Available The paper describes the results of the experimental research of the volt-ampere characteristics of the three-electrode electron gun. Such systems are widely used in the electron-ray devices meant for getting visible image on the screen, and in microwave devices, such as TWT, BWT, as well. On the basis of the experimental results practical recommendations of how to choose the optimal voltage regimes on the focusing electrodes were made, which allows to form paraxial axially-symmetric beams with the diameter in crossover about 0.05-0.5 mm and beam current up to 30 mA.
Stability Analysis of Restricted Axial Symmetric Collapse in $f(R)$ Gravity
Sharif, M
2014-01-01
In this paper, we analyze stability regions of a non-static restricted class of axially symmetric spacetime with anisotropic matter distribution. We develop dynamical as well as collapse equations within the framework of proposed perturbation technique for $f(R)=R+{\\epsilon}R^2$ model and explore dynamical instabilities at Newtonian and post-Newtonian regimes. It is concluded that radial profile of physical parameters like pressure anisotropy, energy density and higher curvature terms of the $f(R)$ model affect the instability ranges.
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.
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.
Herrera, L; Ibañez, J; Ospino, J
2014-01-01
We carry out a general study on the collapse of axially (and reflection) symmetric sources in the context of general relativity. All basic equations and concepts required to perform such a general study are deployed. These equations are written down for a general anisotropic dissipative fluid. The proposed approach allows for analytical studies as well as for numerical applications. A causal transport equation derived from the Israel-Stewart theory is applied, to discuss some thermodynamic aspects of the problem. A set of scalar functions (the structure scalars) derived from the orthogonal splitting of the Riemann tensor are calculated and their role in the dynamics of the source is clearly exhibited. The characterization of the gravitational radiation emitted by the source is discussed.
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.
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...
Earliest stages of the nonequilibrium in axially symmetric, self-gravitating, dissipative fluids
Herrera, L.; Di Prisco, A.; Ospino, J.; Carot, J.
2016-09-01
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 nonequilibrium 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 toward a dissipative regime begins with a nonvanishing 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 will occur at later times. Finally, the decreasing of the effective inertial mass density, associated to thermal effects, is clearly illustrated.
Kleihaus, B; Kunz, Jutta
1999-01-01
In [hep-th/9907222] Hannibal claims to exclude the existence of particle-like static axially symmetric non-abelian solutions in SU(2) Einstein-Yang-Mills-dilaton theory. His argument is based on the asymptotic behaviour of such solutions. Here we disprove his claim by giving explicitly the asymptotic form of non-abelian solutions with winding number n=2.
Onthe static and spherically symmetric gravitational field
Gottlieb, Ioan; Maftei, Gheorghe; Mociutchi, Cleopatra
Starting from a generalization of Einstein 's theory of gravitation, proposed by one of the authors (Cleopatra Mociutchi), the authors study a particular spherical symmetric case. Among other one obtain the compatibility conditions for the existence of the static and spherically symmetruic gravitational filed in the case of extended Einstein equation.
Axisymmetric field generation within an ambient axial field
Darah, A. A.; Sarson, G. R.
2007-01-01
The generation of magnetic field in a homogeneous, electrically conducting fluid - as required for the dynamo generation of the fields of many astrophysical bodies - is normally a threshold process; the dynamo mechanism, applicable to such bodies in unmagnetised environments, requires motions of sufficient strength to overcome the innate magnetic diffusion. In the presence of an ambient field, however, the critical nature of the field generation process is relaxed. Motions can distort and amplify the ambient field for all amplitudes of flow. For motions with appropriate geometries, an internal `dynamo-like' field of appreciable strength can be generated, even for relatively weak flows. At least a minority of planets, moons and other bodies exist within significant external astrophysical fields. For these bodies, the ambient field problem is more relevant than the classical dynamo problem, yet it remains relatively little studied. In this paper we consider the effect of an axial ambient field on a spherical mean-field α2 ω dynamo model, through nonlinear calculations with α-quenching feedback. Ambient fields of varying strengths, and both stationary and oscillatory in time, are imposed. Particular focus is placed on the effects of these fields on the equatorial symmetry and the time dependence of the preferred solutions.
On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams
Energy Technology Data Exchange (ETDEWEB)
Li, Zenghai; Zhou, Feng; Vlieks, Arnold; Adolphsen, Chris; /SLAC
2011-06-23
The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun being jointly designed with LLNL, and X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.
Open-Axial-Field Magnet at ISR intersection I8
1979-01-01
This axial field spectrometer left the central collision region unobstructed in order to ease analysis of secondary particles emitted at large angle. The ISR circulating beams were passing through a hole in the magnet poles.
Nashed, Gamal Gergess Lamee
2007-01-01
An exact charged solution with axial symmetry is obtained in the teleparallel equivalent of general relativity (TEGR). The associated metric has the structure function $G(\\xi)=1-{\\xi}^2-2mA{\\xi}^3-q^2A^2{\\xi}^4$. The fourth order nature of the structure function can make calculations cumbersome. Using a coordinate transformation we get a tetrad whose metric has the structure function in a factorisable form $(1-{\\xi}^2)(1+r_{+}A\\xi)(1+r_{-}A\\xi)$ with $r_{\\pm}$ as the horizons of Reissner-Nordstr$\\ddot{o}$m space-time. This new form has the advantage that its roots are now trivial to write down. Then, we study the singularities of this space-time. Using another coordinate transformation, we obtain a tetrad field. Its associated metric yields the Reissner-Nordstr$\\ddot{o}$m black hole. In Calculating the energy content of this tetrad field using the gravitational energy-momentum, we find that the resulting form depends on the radial coordinate! Using the regularized expression of the gravitational energy-moment...
The Topology of Symmetric Tensor Fields
Levin, Yingmei; Batra, Rajesh; Hesselink, Lambertus; Levy, Yuval
1997-01-01
Combinatorial topology, also known as "rubber sheet geometry", has extensive applications in geometry and analysis, many of which result from connections with the theory of differential equations. A link between topology and differential equations is vector fields. Recent developments in scientific visualization have shown that vector fields also play an important role in the analysis of second-order tensor fields. A second-order tensor field can be transformed into its eigensystem, namely, eigenvalues and their associated eigenvectors without loss of information content. Eigenvectors behave in a similar fashion to ordinary vectors with even simpler topological structures due to their sign indeterminacy. Incorporating information about eigenvectors and eigenvalues in a display technique known as hyperstreamlines reveals the structure of a tensor field. The simplify and often complex tensor field and to capture its important features, the tensor is decomposed into an isotopic tensor and a deviator. A tensor field and its deviator share the same set of eigenvectors, and therefore they have a similar topological structure. A a deviator determines the properties of a tensor field, while the isotopic part provides a uniform bias. Degenerate points are basic constituents of tensor fields. In 2-D tensor fields, there are only two types of degenerate points; while in 3-D, the degenerate points can be characterized in a Q'-R' plane. Compressible and incompressible flows share similar topological feature due to the similarity of their deviators. In the case of the deformation tensor, the singularities of its deviator represent the area of vortex core in the field. In turbulent flows, the similarities and differences of the topology of the deformation and the Reynolds stress tensors reveal that the basic addie-viscosity assuptions have their validity in turbulence modeling under certain conditions.
Bistability between equatorial and axial dipoles during magnetic field reversals
Gissinger, Christophe; Schrinner, Martin; Dormy, Emmanuel
2012-01-01
Numerical simulations of the geodynamo in presence of an heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m = 0 axial dipolar field is replaced by an hemispherical magnetic field, dominated by an oscillating m = 1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of the Earth's dynamo.
Bistability between equatorial and axial dipoles during magnetic field reversals.
Gissinger, Christophe; Petitdemange, Ludovic; Schrinner, Martin; Dormy, Emmanuel
2012-06-08
Numerical simulations of the geodynamo in the presence of heterogeneous heating are presented. We study the dynamics and the structure of the magnetic field when the equatorial symmetry of the flow is broken. If the symmetry breaking is sufficiently strong, the m=0 axial dipolar field is replaced by a hemispherical magnetic field, dominated by an oscillating m=1 magnetic field. Moreover, for moderate symmetry breaking, a bistability between the axial and the equatorial dipole is observed. In this bistable regime, the axial magnetic field exhibits chaotic switches of its polarity, involving the equatorial dipole during the transition period. This new scenario for magnetic field reversals is discussed within the framework of Earth's dynamo.
Ivanovski, S. L.; Zakharov, V. V.; Della Corte, V.; Crifo, J.-F.; Rotundi, A.; Fulle, M.
2017-01-01
In-situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. For the interpretations of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of the Stardust mission and analysis of samples of interplanetary dust have shown that these particles are highly aspherical, which should be taken into account in any credible model. The aim of the present work is to study the dynamics of ellipsoidal shape particles with various aspect ratios introduced in a spherically symmetric expanding gas flow and to reveal the possible differences in dynamics between spherical and aspherical particles. Their translational and rotational motion under influence of the gravity and of the aerodynamic force and torque is numerically integrated in a wide range of physical parameters values including those of comet 67P/Churyumov-Gerasimenko. The main distinctions of the dynamics of spherical and ellipsoidal particles are discussed. The aerodynamic characteristics of the ellipsoidal particles, and examples of their translational and rotational motion in the postulated gas flow are presented.
Schwartz, Benjamin L.; Yin, Ziying; Magin, Richard L.
2016-09-01
Cylindrical homogenous phantoms for magnetic resonance (MR) elastography in biomedical research provide one way to validate an imaging systems performance, but the simplified geometry and boundary conditions can cloak complexity arising at tissue interfaces. In an effort to develop a more realistic gel tissue phantom for MRE, we have constructed a heterogenous gel phantom (a sphere centrally embedded in a cylinder). The actuation comes from the phantom container, with the mechanical waves propagating toward the center, focusing the energy and thus allowing for the visualization of high-frequency waves that would otherwise be damped. The phantom was imaged and its stiffness determined using a 9.4 T horizontal MRI with a custom build piezo-elastic MRE actuator. The phantom was vibrated at three frequencies, 250, 500, and 750 Hz. The resulting shear wave images were first used to reconstruct material stiffness maps for thin (1 mm) axial slices at each frequency, from which the complex shear moduli μ were estimated, and then compared with forward modeling using a recently developed theoretical model which took μ as inputs. The overall accuracy of the measurement process was assessed by comparing theory with experiment for selected values of the shear modulus (real and imaginary parts). Close agreement is shown between the experimentally obtained and theoretically predicted wave fields.
Gallo, Emanuel
2015-01-01
In this article we extend a recent theorem proven by Hod (Phys. Lett. B, {\\bf 727}, 345--348, 2013) to $n$-dimensional Einstein and Einstein-Gauss-Bonnet theories, which gives an upper bound for the photon sphere radii of spherically symmetric black holes. As applications of these results we give a universal upper bound for the real part of quasinormal modes in the WKB limit and a universal lower bound for the position of the first relativistic image in the strong lensing regime produced by these type of black holes. For the axially-symmetric case, we also make some general comments (independent of the underlying gravitational theory) on the relation between circular null geodesics and the fastest way to circle a black hole.
The Topology of Three-Dimensional Symmetric Tensor Fields
Lavin, Yingmei; Levy, Yuval; Hesselink, Lambertus
1994-01-01
We study the topology of 3-D symmetric tensor fields. The goal is to represent their complex structure by a simple set of carefully chosen points and lines analogous to vector field topology. The basic constituents of tensor topology are the degenerate points, or points where eigenvalues are equal to each other. First, we introduce a new method for locating 3-D degenerate points. We then extract the topological skeletons of the eigenvector fields and use them for a compact, comprehensive description of the tensor field. Finally, we demonstrate the use of tensor field topology for the interpretation of the two-force Boussinesq problem.
Nam-Il, Kim; Moon-Young, Kim
2005-06-01
An improved numerical method to exactly evaluate the dynamic element stiffness matrix is proposed for the spatially coupled free vibration analysis of non-symmetric thin-walled curved beams subjected to uniform axial force. For this purpose, firstly equations of motion, boundary conditions and force-deformation relations are rigorously derived from the total potential energy for a curved beam element. Next systems of linear algebraic equations with non-symmetric matrices are constructed by introducing 14 displacement parameters and transforming the fourth-order simultaneous differential equations into the first-order simultaneous equations. And then explicit expressions for displacement parameters are numerically evaluated via eigensolutions and the exact 14×14 element stiffness matrix is determined using force-deformation relations. In order to demonstrate the validity and the accuracy of this study, the spatially coupled natural frequencies of non-symmetric thin-walled curved beams subjected to uniform compressive and tensile forces are evaluated and compared with analytical and finite element solutions using Hermitian curved beam elements or ABAQUS's shell element. In addition, some results by the parametric study are reported.
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.
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.
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.
Constrained field theories on spherically symmetric spacetimes with horizons
Fernandes, Karan; Lahiri, Amitabha; Ghosh, Suman
2017-02-01
We apply the Dirac-Bergmann algorithm for the analysis of constraints to gauge theories defined on spherically symmetric black hole backgrounds. We find that the constraints for a given theory are modified on such spacetimes through the presence of additional contributions from the horizon. 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.
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.
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.
Yamaoka, Kiwamu
2007-04-15
This paper consists of two parts on reversing-pulse electric birefringence (RPEB) signal patterns. The first is the theoretical formulation of two axially symmetric models coexisting in equilibrium in solution. The present RPEB theory is based on the original Tinoco-Yamaoka theory with classical electric dipole moments, which was recently modified and extended by Yamaoka, Sasai, and Kohno to include various electric and optical parameters and most importantly the ion-fluctuation dipole moment (1/2) along the longitudinal direction of axially symmetric molecules. The theory contains the electric polarizability anisotropy Deltaalpha', which can be either positive or negative in relation to the shape of components. The overall signal can be expressed as the sum of the fractions of two components in proportions to the coefficient F(1) or F(2) (=1-F(1)). The second part is the simulation of theoretical RPEB curves for the two-component system with various sets of electric and hydrodynamic parameters for hypothetical but interesting cases. In consideration of the decay behavior, calculated decay curves were compared with experimentally conceivable signals, classifying them into three categories according to cases: F(1)>1, 0signal in buildup and reverse transients reveals the mechanism of field orientation and electro-optic properties of molecules in solution. The ratio q=/ktDeltaalpha(') is the crucial factor that controls the pattern of RPEB signals. If q value of one component is positive and the other is negative, the simulated RPEB curves are characterized by three cases: q>0, q0 or qsignals. If -1signal patterns appears.
Andersson, P.; Andersson-Sunden, E.; Sjöstrand, H.; Jacobsson-Svärd, S.
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-1, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication
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.
Kleihaus, B
1999-01-01
We point out that the statements in [hep-th/9903063] concerning the regularity of static axially symmetric solutions in Yang-Mills-dilaton (YMD) [1] and Einstein-Yang-Mills(-dilaton) (EYMD) theory [2,3] are incorrect, and that the non-singular local gauge potential of the YMD solutions [4] is twice differentiable.
Revisiting the quantum scalar field in spherically symmetric quantum gravity
Borja, Enrique F; Strobel, Eckhard
2012-01-01
We extend previous results in spherically symmetric gravitational systems coupled with a massless scalar field within the loop quantum gravity framework. As starting point, we take the Schwarzschild spacetime. The results presented here rely on the uniform discretization method. We are able to minimize the associated discrete master constraint using a variational method. The trial state for the vacuum consists of a direct product of a Fock vacuum for the matter part and a Gaussian centered around the classical Schwarzschild solution. This paper follows the line of research presented by Gambini, Pullin and Rastgoo and a comparison between their result and the one given in this work is made.
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.
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...
Deflection of Rotating Symmetric Molecules by Inhomogeneous Fields
Gershnabel, Erez
2011-01-01
We consider deflection of rotating symmetric molecules by inhomogeneous optical and static electric fields, compare results with the case of linear molecules, and find new singularities in the distribution of the scattering angle. Scattering of the prolate/oblate molecules is analyzed in detail, and it is shown that the process can be efficiently controlled by means of short and strong femtosecond laser pulses. In particular, the angular dispersion of the deflected molecules may be dramatically reduced by laser-induced molecular pre-alignment. We first study the problem by using a simple classical model, and then find similar results by means of more sophisticated methods, including the formalism of adiabatic invariants and direct numerical simulation of the Euler-Lagrange equations of motion. The suggested control scheme opens new ways for many applications involving molecular focusing, guiding, and trapping by optical and static fields.
Collimation of laser-produced plasmas using axial magnetic field
Energy Technology Data Exchange (ETDEWEB)
Roy, Amitava; Harilal, Sivanandan S.; Hassan, Syed M.; Endo, Akira; Mocek, Tomas; Hassanein, A.
2015-06-01
We investigated the expansion dynamics of laser-produced plasmas expanding into an axial magnetic field. Plasmas were generated by focusing 1.064 µm Nd:YAG laser pulses onto a planar tin target in vacuum and allowed to expand into a 0.5 T magnetic-filed where field lines were aligned along the plume expansion direction. Gated images employing intensified CCD showed focusing of the plasma plume, which were also compared with results obtained using particle-in-cell modelling methods. The estimated density and temperature of the plasma plumes employing emission spectroscopy revealed significant changes in the presence and absence of the 0.5T magnetic field. In the presence of the field, the electron temperature is increased with distance from the target, while the density showed opposite effects.
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
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.
Revisiting the quantum scalar field in spherically symmetric quantum gravity
Borja, Enrique F.; Garay, Iñaki; Strobel, Eckhard
2012-07-01
We extend previous results in spherically symmetric gravitational systems coupled with a massless scalar field within the loop quantum gravity framework. As a starting point, we take the Schwarzschild spacetime. The results presented here rely on the uniform discretization method. We are able to minimize the associated discrete master constraint using a variational method. The trial state for the vacuum consists of a direct product of a Fock vacuum for the matter part and a Gaussian centered around the classical Schwarzschild solution. This paper follows the line of research presented by Gambini et al (2009 Class. Quantum Grav. 26 215011 (arXiv:0906.1774v1)) and a comparison between their result and the one given in this work is made.
Mass Structure of Axial Vector Types of Leptons and Fields
Sharafiddinov, Rasulkhozha S
2011-01-01
A classification of currents with respect to C-operation admits the existence of C-noninvariant types of Dirac fermions. Among them one can meet an electroweakly charged C-antisymmetrical leptons, the mass of which includes the electric and weak components responsible for the existence of their anapole charge, charge radius and electric dipole moment. Such connections can constitute the paraleptons of axial-vector currents, for example, at the interactions with field of spinless nuclei of true neutrality. We derive the united equations which relate the structural parts of mass to anapole, charge radius and electric dipole of any truly neutral lepton in the framework of flavour symmetry. Thereby, they establish the C-odd nature of leptons and fields at the level of constancy law of the size implied from the multiplication of a weak mass of C-antisymmetrical lepton by its electric mass. Therefore, all leptons of C-antisymmetricality regardless of the difference in masses of an axial-vector character, have the s...
Zwick, Susanne; Schaub, Christian; Haist, Tobias; Osten, Wolfgang
2010-09-13
We introduce a new kind of light field to improve and simplify the trapping process of axially displaced particles. To this end we employ a light field with an axially expanded intensity distribution, which at the same time enables stable axial trapping. We present simulations of the axial intensity distribution of the novel trapping field and first experimental results, which demonstrate the improvement of the reliability of the axial trapping process. The method can be used to automate trapping of particles that are located outside of the focal plane of the microscope.
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.
Effect of an axially-symmetric cyclonic vortex on the sea surface temperature in the Gulf of Mexico
Energy Technology Data Exchange (ETDEWEB)
Villanueva, E.E.; Mendoza, V.M.; Adem, J. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)]. E-mail: eevu@atmosfera.unam.mx
2006-04-15
A model for the mixed layer of the Gulf of Mexico has been used to determine the effect that an idealized cyclonic vortex has in the sea surface temperature. The model consists of the equations of conservation of thermal energy and this of balance between mechanical energy and thermal energy, last based on the Kraus-Turner theory; both equations are vertically integrated in the mixed layer. As atmospheric forcing, we prescribe the surface wind associated with an axially-symmetric cyclonic vortex characterized by two parameters: the maximum tangential velocity and the radius at which that velocity is reached. The values of these two parameters, which depend on the position of the vortex, correspond to two cases: hurricane Hilda, which crossed the central part of the Gulf of Mexico between September 29 and October 3, 1964 and hurricane Gilbert whose trajectory between 11 and 17 September, 1988 crossed the Caribbean Sea, the Yucatan Peninsula and the southwest Gulf of Mexico. The results show that a cyclonic vortex with such characteristics, produce during its passage by the sea vertical turbulent water transport through the thermocline (entrainment) that is able to cool down the mixed layer in several degrees and increases the thermocline depth in several meters, in agreement with the observations. [Spanish] Se aplica un modelo de capa de mezcla para el Golfo de Mexico con el objeto de determinar el efecto de un vortice ciclonico idealizado sobre la temperatura de la superficie del mar. El modelo consiste basicamente de dos ecuaciones, la de conservacion de energia termica y la de balance entre energia mecanica y energia termica, esta ultima derivada de la teoria de Kraus-Turner; ambas ecuaciones son verticalmente integradas y acopladas en la capa de mezcla. Como forzamiento atmosferico sobre la superficie del mar se prescribe el viento asociado a un vortice ciclonico axialmente simetrico caracterizado por dos parametros: la velocidad tangencial maxima y el radio al
Magnetic field uniformity of the practical tri-axial Helmholtz coils systems.
Beiranvand, R
2014-05-01
In this paper, effects of the assembly misalignments and the manufacturing mismatches on the magnetic field uniformity of a practical tri-axial Helmholtz coils system have been modeled mathematically. These undesired effects regularly occur in any practical tri-axial Helmholtz coils system. To confirm the mathematical calculations, a tri-axial Helmholtz coils system has been constructed and the uniformity of its magnetic field has been measured under different conditions. The experimental results are in good agreement with the mathematical analyses.
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.
Subjected to Axial Compressive Load and Transverse Magnetic Field
Directory of Open Access Journals (Sweden)
Mei-Feng Liu
2010-01-01
Full Text Available The interactive behaviors between transverse magnetic fields and axial loads of a magnetoelastic (ME beam subjected to general boundary conditions are investigated. In particular, the instability criterion for the magneto-mechanical buckling problem is intricately discussed based on the structure characteristics and the initial conditions. The equation of motion for the proposed physical model is introduced according to the Hamilton's principle, and the stability criterion is obtained by using the method of multiple scales implemented on both spatial and time domains. Eventually a so-called Schrodinger equation with cubic nonlinearity (NLS can be generated by suitably changing the variables; as a result, the stable criterion for the magnetoelastic beam can be acquired after dissecting the nonlinear Schrodinger equation and requiring the imaginary part of the time domain solution to be vanished. Stability criterion curve for the dispersion equation of the ME beam is firstly depicted in order to reveal the magnificent influence of the structure characteristic itself, followed by the instability constraint due to the variation of initial conditions and the observation locations. The results indicate that the prior one actually denotes a parabola, whereas the latter one is sometimes a diamond-like or ellipse-like region spotting along the prior one.
Matthiesen, D. H.; Wargo, M. J.; Motakef, S.; Carlson, D. J.; Nakos, J. S.
1987-01-01
Ga-doped germanium was grown in a vertical Bridgman-Stockbarger system with melt stabilization by axial magnetic fields of 30 kG. It was found that radial segregation of gallium is negligible and that the initial transient of axial macro-segregation is in apparent compliance with the theory of diffusion controlled plane front solidification.
Generalized plane gravitational waves of non-symmetric unified field theories in plane symmetry
Directory of Open Access Journals (Sweden)
Sanjiv R. Bhoyar
2012-12-01
Full Text Available 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.
Nakawaki, Y
2000-01-01
It is shown that ghost fields are indispensable in deriving well-defined antiderivatives in pure space-like axial gauge quantizations of gauge fields. To avoid inessential complications we confine ourselves to noninteracting abelian fields and incorporate their quantizations as a continuous deformation of those in light-cone gauge. We attain this by constructing an axial gauge formulation in auxiliary coordinates $x^{\\mu}= (x^+,x^-,x^1,x^2)$, where $x^+=x^0{\\rm sin}{\\theta}+x^3{\\rm cos}{\\theta}, x^-=x^0{\\rm cos}{\\theta}-x^3{\\rm sin}{\\theta}$ and $x^+$ and $A_-=A^0{\\rm cos} {\\theta}+A^3{\\rm sin}{\\theta}=0$ are taken as the evolution parameter and the gauge fixing condition, respectively. We introduce $x^-$-independent residual gauge fields as ghost fields and accomodate them to the Hamiltonian formalism by applying McCartor and Robertson's method. As a result, we obtain conserved translational generators $P_{\\mu}$, which retain ghost degrees of freedom integrated over the hyperplane $x^-=$ constant. They enabl...
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.
Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field
Sellers, C. C.; Walker, John S.; Szofran, Frank R.; Motakef, Shariar
2000-01-01
This paper treats a liquid-metal flow inside an electrically insulating cylinder with electrically conducting solids above and below the liquid region. There is a uniform axial magnetic field, and there is an electric current through the liquid and both solids. Since the lower liquid-solid interface is concave into the solid and since the liquid is a better electrical conductor than the adjacent solid, the electric current is locally concentrated near the centerline. The return to a uniform current distribution involves a radial electric current which interacts with the axial magnetic field to drive an azimuthal flow. The axial variation of the centrifugal force due to the azimuthal velocity drives a meridional circulation with radial and axial velocities. This problem models the effects of Peltier marking during the vertical Bridgman growth of semiconductor crystals with an externally applied magnetic field, where the meridional circulation due to the Peltier Current may produce important mixing in the molten semiconductor.
Noether symmetric classical and quantum scalar field cosmology
Vakili, Babak
2011-01-01
We study the evolution of a two dimensional minisuperspace cosmological model in classical and quantum levels by the Noether symmetry approach. The phase space variables turn out to correspond to the scale factor of a Friedmann-Robertson-Walker (FRW) model and a scalar field with which the action of the model is augmented. It is shown that the minisuperspace of such a model is a two dimensional manifold with vanishing Ricci scalar. We present a coordinate transformation which cast the corresponding minisuper metric to a Minkowskian or Euclidean one according to the choices of an ordinary or phantom model for the scalar field. Then, the Noether symmetry of such a cosmological model is investigated by utilizing the behavior of the corresponding Lagrangian under the infinitesimal generators of the desired symmetry. We explicitly calculate the form of the scalar field potential functions for which such symmetries exist. For these potential functions, the exact classical and quantum solutions in the cases where th...
BRST symmetric gaugeon formalism for Yang-Mills fields
Koseki, M; Endo, R
1995-01-01
Yokoyama's gaugeon formalism is knwon to admit q-number gauge transformation. We introduce BRST symmetries into the formalism for the Yang-Mills gauge field. Owing to the BRST symmetry, Yokoyama's physical subsidiary conditions are replaced by a single condition of the Kugo-Ojima type. Our physical subsidiary condition is invariant under the q-number gauge transformation. Thus, our physical subspace is gauge invariant.
Three-dimensional model and simulation of vacuum arcs under axial magnetic fields
Wang, Lijun; Jia, Shenli; Zhou, Xin; Wang, Haijing; Shi, Zongqian
2012-01-01
In this paper, a three-dimensional (3d) magneto-hydro-dynamic (MHD) model of axial magnetic field vacuum arcs (AMFVAs) is established. Based on this model, AMFVAs are simulated and analyzed. Three-dimensional spatial distributions of many important plasma parameters and electric characteristics in AMFVAs can be obtained, such as ion number density, ion temperature, electron temperature, plasma pressure, current densities along different directions (x, y, and z), ion velocities along different directions, electric fields strength along different directions, and so on. Simulation results show that there exist significant spiral-shaped rotational phenomena in the AMFVAs, this kind of rotational phenomenon also can be verified by the many related experiments (AMFVAs photographs, especially for stronger AMF strength). For current simulation results of AMFVAs, the maximal rotational velocity at anode side is about 1100 m/s. Radial electric field is increased from arc center to arc edge; axial electric field is decreased from cathode side to anode side. Radial electric field at arc edge can be larger than axial electric field. Azimuthal electric field in most regions is much smaller than radial and axial electric field, but it can reach about 1.19 kV/m. Radial magnetic field is the smallest one compared with other components, it reaches to maximum value at the position near to anode, it can influence arc characteristics.
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.
Energy Technology Data Exchange (ETDEWEB)
Fiedler, B.; Schimming, R.
1983-01-01
The fourth order field equations proposed by TREDER with a linear combination of BACH's tensor and EINSTEIN's tensor on the left-hand side admit static centrally symmetric solutions which are analytical and non-flat in some neighborhood of the centre of symmetry.
Resonant slow extraction in synchrotrons using anti-symmetric sextupole fields
Zou, Ye; Tang, Jingyu; Yang, Jianquan
2016-09-01
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 potential in applications demanding very stable slow extraction from synchrotrons. Our studies show that slow extraction at the half-integer resonance by using an anti-symmetric sextupole field has some advantages compared to the standard sextupole field, which is widely used in the slow extraction method. One advantage 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. Studies by both the Hamiltonian theory and numerical simulations show that the stable region near 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. The particles outside the region will be driven out in two possible directions in quite a short transit time but with spiral steps similar to the third-order resonant extraction. By gradually increasing the field strength, the beam can be extracted with intensity more homogeneous than by the usual third-order resonant method, because of both smaller intensity variation and spike in the beginning spill. With the same field strength and tune distance to the resonance, the change in the stable region area due to the working point variation in the case of the anti-symmetric sextupole is about 1/14 of the one for the standard sextupole. Detailed studies including beam dynamic behaviors near other resonances, expression of the field in polynomial expansion, influence of 2-D field error, half-integer stop-band, and resonant slow extraction using a quadrupole field are also presented.
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.
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.
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.
Uniform Core Field in Symmetrical Planar Waveguides and Circular Fibers with Nonlinear Claddings
Institute of Scientific and Technical Information of China (English)
庞霖; 严瑛白; 金国藩; 邬敏贤; 郭履容; 陈波
2001-01-01
It is known that no uniform electric field profile exists in a planar linear waveguide. The uniform core field can be shown to exist in symmetrical planar waveguides and circular fibers with nonlinear claddings. Theoretical analysis and numerical calculations are carried out to show that when the modal index equals to the core refractive-index, the core field becomes uniform at an appropriate optical power. Analysis for a step-index circular fiber with nonlinear cladding have also shown that the core field becomes uniform under similar conditions. The occurrence of a uniform field in a waveguide core may believe to have promising applications in waveguide, optoelectronic and photonic devices.
CFD Numerical Simulation of the Complex Turbulent Flow Field in an Axial-Flow Water Pump
Directory of Open Access Journals (Sweden)
Wan-You Li
2014-09-01
Full Text Available Further optimal design of an axial-flow water pump calls for a thorough recognition of the characteristics of the complex turbulent flow field in the pump, which is however extremely difficult to be measured using the up-to-date experimental techniques. In this study, a numerical simulation procedure based on computational fluid dynamics (CFD was elaborated in order to obtain the fully three-dimensional unsteady turbulent flow field in an axial-flow water pump. The shear stress transport (SST k-ω model was employed in the CFD calculation to study the unsteady internal flow of the axial-flow pump. Upon the numerical simulation results, the characteristics of the velocity field and pressure field inside the impeller region were discussed in detail. The established model procedure in this study may provide guidance to the numerical simulations of turbomachines during the design phase or the investigation of flow and pressure field characteristics and performance. The presented information can be of reference value in further optimal design of the axial-flow pump.
Cold atmospheric plasma jet in an axial DC electric field
Lin, Li; Keidar, Michael
2016-08-01
Cold atmospheric plasma (CAP) jet is currently intensively investigated as a tool for new and potentially transformative cancer treatment modality. However, there are still many unknowns about the jet behavior that requires attention. In this paper, a helium CAP jet is tested in an electrostatic field generated by a copper ring. Using Rayleigh microwave scattering method, some delays of the electron density peaks for different ring potentials are observed. Meanwhile, a similar phenomenon associated with the bullet velocity is found. Chemical species distribution along the jet is analyzed based on the jet optical emission spectra. The spectra indicate that a lower ring potential, i.e., lower DC background electric field, can increase the amount of excited N2, N2+, He, and O in the region before the ring, but can decrease the amount of excited NO and HO almost along the entire jet. Combining all the results above, we discovered that an extra DC potential mainly affects the temporal plasma jet properties. Also, it is possible to manipulate the chemical compositions of the jet using a ring with certain electric potentials.
Numerical simulation of a helical shape electric arc in the external axial magnetic field
Urusov, R. M.; Urusova, I. R.
2016-10-01
Within the frameworks of non-stationary three-dimensional mathematical model, in approximation of a partial local thermodynamic equilibrium, a numerical calculation was made of characteristics of DC electric arc burning in a cylindrical channel in the uniform external axial magnetic field. The method of numerical simulation of the arc of helical shape in a uniform external axial magnetic field was proposed. This method consists in that that in the computational algorithm, a "scheme" analog of fluctuations for electrons temperature is supplemented. The "scheme" analogue of fluctuations increases a weak numerical asymmetry of electrons temperature distribution, which occurs randomly in the course of computing. This asymmetry can be "picked up" by the external magnetic field that continues to increase up to a certain value, which is sufficient for the formation of helical structure of the arc column. In the absence of fluctuations in the computational algorithm, the arc column in the external axial magnetic field maintains cylindrical axial symmetry, and a helical form of the arc is not observed.
Drift-diffusion model of normal glow discharge in an axial magnetic field
Surzhikov, S. T.
2016-12-01
A two-dimensional axisymmetrical computing model is formulated with using of which the mathematical modeling of the normal glow discharge in molecular hydrogen is fulfilled in an axial magnetic field with the induction B = 0.1 T in the pressure range p = 1.25-5 Torr and the current-source electromotive force E = 1-3 kV.
Scalar Field Model of Dark Energy In the Double Complex Symmetric Gravitational Theory
Institute of Scientific and Technical Information of China (English)
SHAO Ying; GUI Yuan-Xing; WANG Wei
2006-01-01
The scalar field model of dark energy is established in the double complex symmetric gravitational theory. The universe we live in is taken as the real part of double complex space M4C(J). The two cases of scalar field (ordinary and phantom scalar field) are discussed in a unified way. Not only can the double Friedmann equations be obtained, but also the equation of state for dark energy, potential V(φ) and scalar field φ can be expressed. Hence, a new method is proposed to study dark energy and the evolution of the universe.
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...
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
Families of particles with different masses in PT-symmetric quantum field theory.
Bender, Carl M; Klevansky, S P
2010-07-16
An elementary field-theoretic mechanism is proposed that allows one Lagrangian to describe a family of particles having different masses but otherwise similar physical properties. The mechanism relies on the observation that the Dyson-Schwinger equations derived from a Lagrangian can have many different but equally valid solutions. Nonunique solutions to the Dyson-Schwinger equations arise when the functional integral for the Green's functions of the quantum field theory converges in different pairs of Stokes' wedges in complex-field space, and the solutions are physically viable if the pairs of Stokes' wedges are PT symmetric.
Zhang, Ran; Zhang, Tengfei; Xu, Lu; Han, Fangfang; Zhao, Yun; Ni, Zhonghai
2017-01-01
A new series of short axially symmetrically (4a and 4b) and asymmetrically (4c and 4d) 1,3,6,8-tetrasubstituted pyrene-based compounds with two phenyl moieties and two diphenylamine units on the pyrene core were designed and synthesized based on stepwise synthetic strategy. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. The structures of 4a and 4b were determined by single-crystal X-ray diffraction analysis, indicating that the compounds are twisted by the peripheral substituents and the intermolecular π-π interactions have been efficiently interrupted. The four compounds exhibit high absolute fluorescence quantum yields (VF) in dichloromethane (83.31-88.45%) and moderate VFs in film states (20.78-38.68%). In addition, compounds 4a and 4b display relatively higher absolute VFs than those of 4c and 4d in film states. All the compounds exhibit high thermal stability with decomposition temperatures above 358 °C and the values of 4c and 4d are higher than 4a and 4b. Compounds 4a and 4b can form morphologically stable amorphous thin films with Tg values of 146 °C and 149 °C, respectively. However, there are no obvious Tg observed in compounds 4c and 4d. Electroluminescent devices using 4a and 4b as doped emission layer show promising device performance with low turn-on voltage (3.0 V), maximum brightness around 15100 cd/m2 and 16100 cd/m2, maximum luminance efficiency of 12.4 cd/A and 13.6 cd/A and maximum external quantum efficiency of 5.34% and 5.63%, respectively.
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.
Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field.
Oikawa, Kohei; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira
2014-02-01
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(19) m(-3) near the source exit and ∼10(18) m(-3) near the magnetic filter can be obtained, which are higher than those with the solenoids.
Proterozoic low orbital obliquity and axial-dipolar geomagnetic field from evaporite palaeolatitudes
Evans, David A. D.
2006-11-01
Palaeomagnetism of climatically sensitive sedimentary rock types, such as glacial deposits and evaporites, can test the uniformitarianism of ancient geomagnetic fields and palaeoclimate zones. Proterozoic glacial deposits laid down in near-equatorial palaeomagnetic latitudes can be explained by `snowball Earth' episodes, high orbital obliquity or markedly non-uniformitarian geomagnetic fields. Here I present a global palaeomagnetic compilation of the Earth's entire basin-scale evaporite record. Magnetic inclinations are consistent with low orbital obliquity and a geocentric-axial-dipole magnetic field for most of the past two billion years, and the snowball Earth hypothesis accordingly remains the most viable model for low-latitude Proterozoic ice ages. Efforts to reconstruct Proterozoic supercontinents are strengthened by this demonstration of a consistently axial and dipolar geomagnetic reference frame, which itself implies stability of geodynamo processes on billion-year timescales.
Evans, David A D
2006-11-02
Palaeomagnetism of climatically sensitive sedimentary rock types, such as glacial deposits and evaporites, can test the uniformitarianism of ancient geomagnetic fields and palaeoclimate zones. Proterozoic glacial deposits laid down in near-equatorial palaeomagnetic latitudes can be explained by 'snowball Earth' episodes, high orbital obliquity or markedly non-uniformitarian geomagnetic fields. Here I present a global palaeomagnetic compilation of the Earth's entire basin-scale evaporite record. Magnetic inclinations are consistent with low orbital obliquity and a geocentric-axial-dipole magnetic field for most of the past two billion years, and the snowball Earth hypothesis accordingly remains the most viable model for low-latitude Proterozoic ice ages. Efforts to reconstruct Proterozoic supercontinents are strengthened by this demonstration of a consistently axial and dipolar geomagnetic reference frame, which itself implies stability of geodynamo processes on billion-year timescales.
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.
Yuan, Jian-Hui; Chen, Ni; Mo, Hua; Zhang, Yan; Zhang, Zhi-Hai
2015-12-01
A detailed investigation of the second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells under the influence of applied electric field by using the compact-density-matrix approach and the finite difference method. The results show that the second-harmonic generation susceptibility obtained in two cases can reach the magnitude of 10-4 m/V, which depend dramatically on the applied electric field and the structural parameters. Finally, the resonant peak and its corresponding to the resonant energy are also taken into account.
Liu, Y; Koashi, M; Imoto, N; Liu, Yu-xi; Miranowicz, Adam; Koashi, Masato; Imoto, Nobuyuki
2002-01-01
The entanglement of excitonic states in a system of $N$ spatially separated semiconductor microcrystallites is investigated. The interaction among the different microcrystallites is mediated by a single-mode cavity field. It is found that the symmetric sharing of the entanglement (measured by the concurrence) between any pair of the excitonic state with $N$ qubits defined by the number states (vacuum and a single-exciton states) or the coherent states (odd and even coherent states) can be prepared by the cavity field for this system.
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.
Kaplan, Alex; Carmon, Tal; Kozlov, Maxim; Cohen, Oren; Bartal, Guy; Schwefel, Harald G L
2013-01-01
We present an optical mode solver for a whispering gallery resonator coupled to an adjacent arbitrary shaped nano-particle that breaks the axial symmetry of the resonator. Such a hybrid resonator-nanoparticle is similar to what was recently used for bio-detection and for field enhancement. We demonstrate our solver by parametrically studying a toroid-nanoplasmonic device and get the optimal nano-plasmonic size for maximal enhancement. We investigate cases near a plasmonic resonance as well as far from a plasmonic resonance. Unlike common plasmons that typically benefit from working near their resonance, here working far from plasmonic resonance provides comparable performance. This is because the plasmonic resonance enhancement is accompanied by cavity quality degradation through plasmonic absorption.
Energy Technology Data Exchange (ETDEWEB)
Papadichev, V.A. [Lebedev Physical Institute, Moscow (Russian Federation)
1995-12-31
Various types of undulators with or without axial magnetic field are used in FELs. Supplementary beam focusing can be applied by wedging, inclining or profiling pole faces of plan undulators or superposing external focusing magnetic fields in addition to undulator own focusing. Space-charge forces influence significantly particle motion in high-current, low-energy electron beams. Finally, one can use simultaneously two or more different undulators for some specific purpose: more efficient and selective higher harmonics generation, changing polarization types and direction, gain enhancement in double-period undulator etc. All these cases can be treated by solving the generalized equations of transverse orbital motion in a linear approximation, which is widely used for orbit calculation, gives sufficient accuracy for practical purposes and allows to consider many variants and optimize the chosen one. The undulator field is described as a field of two plane undulators with mutually orthogonal fields and an arbitrary axial (phase) shift between them. Various values of the phase shift correspond to right- or left-handed helical undulators, plane undulator of different polarization etc. The general formulae are reduced to forms that allow easier examination of particular cases: planar or helical undulator combined with axial magnetic field or without it, gyroresonance, limiting beam current, polarization etc.
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.
Numerical Solution of Flow Field Diagnosis Dproblem in Multistage Axial Compressors
Institute of Scientific and Technical Information of China (English)
Z.C.Zhang; J.Liu; 等
1995-01-01
A mathematical model is developed for the flow field diagnosis problem in multistage axial compressors.In view of the ill-posedness of the diagnostic problem,an effective measure is adopted to transfer the diagnostic problem into a variational problem which is solved by a regularization method.Two numerical results demonstrate the rationality of the flow diagnosis problem and the effectiveness of the computational method。
Modelling of the Noise Spectra of Axial Flow Fans in a Free Field
Wu, S. F.; Su, S. G.; Shah, H. S.
1997-03-01
This paper presents a semi-empirical formula for predicting the noise spectra of axial flow fans in a free field. The basic assumption made in deriving this formula is that sound radiation from an axial flow fan in a free field is primarily due to the fluctuating pressure exerted on the fan blade surface. This fluctuating pressure is correlated to the lift force per unit length acting on the fan blade, and is subsequently approximated by pressure pulses that decay both in space and time. Accordingly, the radiated acoustic pressure is expressed in terms of superposition of contributions from these pressure pulses, and the line spectrum is obtained by taking a Fourier series expansion. To simulate the narrow and broad band sound spectra, a normal distribution-like shape function is designed which divides the frequency into consecutive bands centered at the blade passage frequency and its harmonics. The amplitude of this shape function at the center frequency of each band is unity but decays exponentially. The decay rate decreases with an increase in the number of bands. Thus, at high frequencies the narrow bands merge to form broad band-like spectra. The noise spectra thus obtained are compared with the measured ones from four different types of axial flow fans running under various conditions, and a favorable agreement in each case is obtained.
Field test of classical symmetric encryption with continuous variables quantum key distribution.
Jouguet, Paul; Kunz-Jacques, Sébastien; Debuisschert, Thierry; Fossier, Simon; Diamanti, Eleni; Alléaume, Romain; Tualle-Brouri, Rosa; Grangier, Philippe; Leverrier, Anthony; Pache, Philippe; Painchault, Philippe
2012-06-18
We report on the design and performance of a point-to-point classical symmetric encryption link with fast key renewal provided by a Continuous Variable Quantum Key Distribution (CVQKD) system. Our system was operational and able to encrypt point-to-point communications during more than six months, from the end of July 2010 until the beginning of February 2011. This field test was the first demonstration of the reliability of a CVQKD system over a long period of time in a server room environment. This strengthens the potential of CVQKD for information technology security infrastructure deployments.
Coherent control for the spherical symmetric box potential in short and intensive XUV laser fields
Barna, I F
2007-01-01
Coherent control calculations are presented for a spherically symmetric box potential for non-resonant two photon transition probabilities. With the help of a genetic algorithm (GA) the population of the excited states are maximized and minimized. The external driving field is a superposition of three intensive extreme ultraviolet (XUV) linearly polarized laser pulses with different frequencies in the femtosecond duration range. We solved the quantum mechanical problem within the dipole approximation. Our investigation clearly shows that the dynamics of the electron current has a strong correlation with the optimized and neutralizing pulse shape.
Non-Hermitian ${\\cal PT}$-symmetric relativistic quantum theory in an intensive magnetic field
Rodionov, V N
2016-01-01
We develop relativistic non-Hermitian quantum theory and its application to neutrino physics in a strong magnetic field. It is well known, that one of the fundamental postulates of quantum theory is the requirement of Hermiticity of physical parameters. This condition not only guarantees the reality of the eigenvalues of Hamiltonian operators, but also implies the preservation of the probabilities of the considered quantum processes. However as it was shown relatively recently (Bender, Boettcher 1998), Hermiticity is a sufficient but it is not a necessary condition. It turned out that among non-Hermitian Hamiltonians it is possible to allocate a number of such which have real energy spectra and can ensure the development of systems over time with preserving unitarity. This type of Hamiltonians includes so-called parity-time (${\\cal PT}$) symmetric models which is already used in various fields of modern physics. The most developed in this respect are models, which used in the field of ${\\cal PT}$-symmetric op...
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.
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...
Duality for symmetric second rank tensors. II. The linearized gravitational field
Casini, H; Urrutia, L F; Urrutia, Luis F.
2003-01-01
The construction of dual theories for linearized gravity in four dimensions is considered. Our approach is based on the parent Lagrangian method previously developed for the massive spin-two case, but now considered for the zero mass case. This leads to a dual theory described in terms of a rank two symmetric tensor, analogous to the usual gravitational field, and an auxiliary antisymmetric field. This theory has an enlarged gauge symmetry, but with an adequate partial gauge fixing it can be reduced to a gauge symmetry similar to the standard one of linearized gravitation. We present examples illustrating the general procedure and the physical interpretation of the dual fields. The zero mass case of the massive theory dual to the massive spin-two theory is also examined, but we show that it only contains a spin-zero excitation.
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 ...
Generation of families of spectra in PT-symmetric quantum mechanics and scalar bosonic field theory.
Schmidt, Steffen; Klevansky, S P
2013-04-28
This paper explains the systematics of the generation of families of spectra for the -symmetric quantum-mechanical Hamiltonians H=p(2)+x(2)(ix)(ε), H=p(2)+(x(2))(δ) and H=p(2)-(x(2))(μ). In addition, it contrasts the results obtained with those found for a bosonic scalar field theory, in particular in one dimension, highlighting the similarities to and differences from the quantum-mechanical case. It is shown that the number of families of spectra can be deduced from the number of non-contiguous pairs of Stokes wedges that display PT symmetry. To do so, simple arguments that use the Wentzel-Kramers-Brillouin approximation are used, and these imply that the eigenvalues are real. However, definitive results are in most cases presently only obtainable numerically, and not all eigenvalues in each family may be real. Within the approximations used, it is illustrated that the difference between the quantum-mechanical and the field-theoretical cases lies in the number of accessible regions in which the eigenfunctions decay exponentially. This paper reviews and implements well-known techniques in complex analysis and PT-symmetric quantum theory.
Hydrodynamic Analysis of the Flow Field Induced by a Symmetrical Suction Elbow at the Pump Inlet
Muntean, S.; Bosioc, A. I.; Drăghici, I.; Anton, L. E.
2016-11-01
The paper investigates the hydrodynamic field generated by the symmetrical suction elbow at the pump impeller inlet. The full three-dimensional turbulent numerical investigation of the flow in the symmetrical suction elbow is performed using FLUENT then the flow non-uniformity generated by it is numerically computed. The numerical results on the annular cross section are qualitatively and quantitatively validated against LDV data. A good agreement between numerical results and experimental data is obtained on this cross section located downstream to the suction elbow and upstream to the pump impeller. The hydrodynamic flow structure with four vortices is identified plotting the vorticity field. The largest values of the vorticity magnitude are identified in the center of both vortices located behind the shaft. The vortex core location is plotted on four annular cross sections located along to the cylindrical part between the suction elbow and the pump inlet. Also, the three-dimensional distribution of the vortex core filaments is visualized and extracted. The shapes of vortex core filaments located behind the pump shaft agree well with its visualization performed on the test rig. As a result, the three-dimensional complex geometry of the suction elbow and the pump shaft are identified as the main sources of the flow non-uniformity at the pump inlet.
Institute of Scientific and Technical Information of China (English)
盛丽娜; 宋明涛
2007-01-01
In an axially symmetric magnetic field, charged particles move along the axis and rotate around the axis at the same time. Accordingly, the transverse motion can be decomposed into two parts, the focusing movement and the rotation of the meridian plane, and the 4-dimensional transfer matrix can be expressed as the product of a focusing matrix and two rotation matrices. The overall transfer matrix is re-derived in this article with the rotation matrices and the focusing matrix. Then the corresponding sigma matrix is given to further estimate the beam emittance extracted from electron cyclotron resonance ion source. The second moment of the beam distribution function is discussed in detail.%带电粒子在轴对称磁场中一边沿着对称轴向前运动,一边绕对称轴旋转.所以横向运动可以分解为两部分:聚焦运动和子午面的旋转.因此,4维横向传输矩阵可以表示为聚焦矩阵和旋转矩阵的乘积.用旋转矩阵和聚焦矩阵重新推导了总的传输矩阵.然后给出了相应的相椭圆系数矩阵来进一步估算从ECR离子源引出束流的发射度.详细地讨论了束流分布函数的二次矩.
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,...
Symmetric dynamic behaviour of a superconducting proximity array with respect to field reversal
Lankhorst, M.; Poccia, N.
2017-01-01
As the complexity of strongly correlated systems and high temperature superconductors increases, so does also the essential complexity of defects found in these materials and the complexity of the supercurrent pathways. It can be therefore convenient to realize a solid-state system with regular supercurrent pathways and without the disguising effects of disorder in order to capture the essential characteristics of a collective dynamics. Using a square array of superconducting islands placed on a normal metal, we observe a state in which magnetic field-induced vortices are frozen in the dimples of the egg crate potential by their strong repulsion interaction. In this system a dynamic vortex Mott insulator transition has been previously observed. In this work, we will show the symmetric dynamic behaviour with respect to field reversal and we will compare it with the asymmetric behaviour observed at the dynamic vortex Mott transition.
Chang, Lei; Li, Qingchong; Zhang, Huijie; Li, Yinghong; Wu, Yun; Zhang, Bailing; Zhuang, Zhong
2016-08-01
The effect of the radial density configuration in terms of width, edge gradient and volume gradient on the wave field and energy flow in an axially uniform helicon plasma is studied in detail. A three-parameter function is employed to describe the density, covering uniform, parabolic, linear and Gaussian profiles. It finds that the fraction of power deposition near the plasma edge increases with density width and edge gradient, and decays in exponential and “bump-on-tail” profiles, respectively, away from the surface. The existence of a positive second-order derivative in the volume density configuration promotes the power deposition near the plasma core, which to our best knowledge has not been pointed out before. The transverse structures of wave field and current density remain almost the same during the variation of density width and gradient, confirming the robustness of the m=1 mode observed previously. However, the structure of the electric wave field changes significantly from a uniform density configuration, for which the coupling between the Trivelpiece-Gould (TG) mode and the helicon mode is very strong, to non-uniform ones. The energy flow in the cross section of helicon plasma is presented for the first time, and behaves sensitive to the density width and edge gradient but insensitive to the volume gradient. Interestingly, the radial distribution of power deposition resembles the radial profile of the axial component of current density, suggesting the control of the power deposition profile in the experiment by particularly designing the antenna geometry to excite a required axial current distribution. supported by National Natural Science Foundation of China (No. 11405271)
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°.
Energy Technology Data Exchange (ETDEWEB)
Fradin, C.
1998-07-01
The prediction of flow structure and performances of an axial transonic compressor requires accurate solvers. Taking into account the complex flow patterns, it is important to validate codes by comparing it with experimental results. It is well understood that the availability of experimental data is fundamentally important for the improvement of the solvers. An axial transonic compressor has been fitted in the ERECA test facility of ONERA. The rotor of this compressor is isolated from stators. This experimental configuration allows to obtain a steady flow into the relative frame linked to the rotor. Due to this fact, experimental tests became easier because the basic phenomena are not hidden by mutual interactions rotor-stator. Measurements have been made in a test section far upstream the rotor, to provide the inlet conditions in the computation domain. Non intrusive and fast response measurement techniques allow to obtain the detailed flow structure in several test sections located in the rotor and far downstream it. All tests were carried out at four operating conditions of the compressor. Results provide good test cases for numerical prediction methods using three-dimensional Navier-Stokes solvers. (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.
A Simple Method of FLow Field DIagnosis in Multistage Axial Flow Compressors
Institute of Scientific and Technical Information of China (English)
JieLiu; DajunYe
1994-01-01
The calculating method of flow field diagnosis in multistage axial compressors is presented in this paper.The distributions of loss and deviation angle of every blade row,and blockage factors are evalusted using tested total temperature and total pressure at inlet and outlet of compressor,as well as the endwall static pressures.One operating Mode of a two-stage fan is presented comparing results from the diagnostic method with measurements,and the results have demonstrated the important effects of diagnostic method.
Chiral extrapolation of nucleon axial charge gA in effective field theory
Li, Hong-na; Wang, P.
2016-12-01
The extrapolation of nucleon axial charge gA 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 gA are all smaller than the experimental value. Supported by National Natural Science Foundation of China (11475186) and Sino-German CRC 110 (NSFC 11621131001)
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.
Institute of Scientific and Technical Information of China (English)
问建; 张割
2012-01-01
A helical antenna with a cuiving reflection cavity was designed based on symmetrical pitch angle axial mode helical antenna with a parasitic helix to improve radiation performance of axial mode helical antennas. Its radiation properties was simulated with the software HFSS. The contrast result come from the simulation of several helical antennas shows that the helical antenna can effectively improve the power gain coefficient of axial mode helical antenna. Its circular polarizable consistency is good. The method is simple and efficient for improving radiation performance of axial mode helical antennas.%为了改善轴向模螺旋天线的辐射特性,在带有寄生螺旋的均匀升角轴向模螺旋天线基础上,设计了一种带有曲反射面背腔的螺旋天线,并用HFSS软件对天线的辐射特性进行了仿真分析.通过对比几种不同形式的螺旋天线的仿真结果,证明了该种螺旋天线可以有效地提高轴向模螺旋天线增益系数,圆极化一致性良好,是一种提高轴向模螺旋天线性能的有效方法.
High-rate axial-field ionization chamber for particle identification of Radioactive beams
Desouza, Romualdo; Vadas, Justin; Singh, Varinderjit; Visser, G.; Alexander, A.; Hudan, S.; Huston, J.; Wiggins, B.; Chbihi, A.; Famiano, M.; Bischak, M.
2017-01-01
The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. The detector is optimized for use with low-energy radioactive beams (<) 5 MeV/A. 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 rise-time of 60 to 70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate while providing a time resolution of 6 to 8 ns. Tests with an α source establish the detector energy resolution as 8 % for an energy deposit of 3.5 MeV. Beam tests indicate that the detector is an effective tool for the characterization of low-energy radioactive beams at beam intensities up to 3 x 105 ions/s. Supported by the U.S. DOE under Award # DE-FG02-88ER-40404 and the NSF under Grant No. 1342962.
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...
Kr II and Xe II axial velocity distribution functions in a cross-field ion source
Lejeune, A.; Bourgeois, G.; Mazouffre, S.
2012-07-01
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.
Optimization of the recovery efficiency in an axial HGMF cell with bounded flow field
Badescu, V.; Murariu, V.; Rotariu, O.; Rezlescu, N.
1996-09-01
This work presents a method to optimize the recovery efficiency of fine paramagnetic particles from a liquid suspension in an axial HGMF cell. The cell has the flow field bounded by a circular cylindrical wall. It has only one ferromagnetic wire mounted outside the flow field, parallel with its axis and in `paramagnetic capture mode'. The optimization criterion was deduced from the analysis of the particles' trajectories inside the magnetic active space. It is based on the relationship between the geometrical 0022-3727/29/9/042/img1 and operational 0022-3727/29/9/042/img2 parameters for which the filtration efficiency is 100%. The work also presents some experimental data which are in good agreement with theoretical results.
Electron states in quantum rings with structural distortions under axial or in-plane magnetic fields
Energy Technology Data Exchange (ETDEWEB)
Planelles, J [Departament de Quimica Fisica i Analitica, Universitat Jaume I, Box 224, E-12080 Castello (Spain); Rajadell, F [Departament de Quimica Fisica i Analitica, Universitat Jaume I, Box 224, E-12080 Castello (Spain); Climente, J I [Departament de Quimica Fisica i Analitica, Universitat Jaume I, Box 224, E-12080 Castello (Spain)
2007-09-19
A comprehensive study of anisotropic quantum rings, QRs, subject to axial and in-plane magnetic field, both aligned and transverse to the anisotropy direction, is carried out. Elliptical QRs for a wide range of eccentricity values and also perfectly circular QRs including one or more barriers disturbing the QR current are considered. These models mimic anisotropic geometry deformations and mass diffusion occurring in the QR fabrication process. Symmetry considerations and simplified analytical models supply physical insight into the obtained numerical results. Our study demonstrates that, except for unusual extremely large eccentricities, QR geometry deformations only appreciably influence a few low-lying states, while the effect of barriers disturbing the QR current is stronger and affects all studied states to a similar extent. We also show that the response of the electron states to in-plane magnetic fields provides accurate information on the structural anisotropy.
Mukherjee, P; Hazra, L N
2014-02-01
Pupil plane filtering by radial Walsh filters is a convenient technique for tailoring the axial intensity distribution near the focal plane of a rotationally symmetric imaging system. Radial Walsh filters, derived from radial Walsh functions, form a set of orthogonal phase filters that take on values either 0 or π phase, corresponding to +1 or -1 values of the radial Walsh functions over prespecified annular regions of the circular filter. Order of these filters is given by the number of zero-crossings, or equivalently phase transitions within the domain over which the set is defined. In general, radial Walsh filters are binary phase zone plates, each of them demonstrating distinct focusing characteristics. The set of radial Walsh filters can be classified into distinct groups, where the members of each group possess self-similar structures. Self-similarity can also be observed in the corresponding axial intensity distributions. These observations provide valuable clues in tackling the inverse problem of synthesis of phase filter in accordance with prespecified axial intensity distributions. This paper reports our observations on self-similarity in radial Walsh filters of various orders and corresponding axial intensity distributions.
On global regular solutions to magnetohydrodynamics in axi-symmetric domains
Nowakowski, Bernard; Zajączkowski, Wojciech M.
2016-12-01
We consider mhd equations in three-dimensional axially symmetric domains under the Navier boundary conditions for both velocity and magnetic fields. We prove the existence of global, regular axi-symmetric solutions and examine their stability in the class of general solutions to the mhd system. As a consequence, we show the existence of global, regular solutions to the mhd system which are close in suitable norms to axi-symmetric solutions.
Experimental Investigation of the Flow Field in a Multistage Axial Flow Compressor
Directory of Open Access Journals (Sweden)
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.
Advanced axial field D.C. motor development for electric passenger vehicle
Jones, W. J.
1982-01-01
A wound-field axial-flux dc motor was developed for an electric vehicle drive system. The motor is essentially an axial-flux version of the classical Gramme-ring winding motor, but the active conductors are recessed into slots cut into the two opposite faces of the laminated tape-wound core ring. Three motors were built and tested in the program. The second (functional) model was a six-pole machine which weighed 88.5 kg. It developed 16.9 km (33.0 hp), and a max speed of 4800 rpm. Full load efficiency was 92% and predicted SAE D-cycle efficiency was 88%. The last engineering) model was a 4-pole machine with compoles, allowing a weight reduction to 45 kg (100 lbs.) while addressing some manufacturability problems. The engineering model was rated at 13.2 kw (17.6 hp) at 3000 rpm, with a peak power of 19.8 km (26.4 hp) and a max speed of 7200 rpm. Initial test results on this motor showed poor commutation and efficiency; the program was terminated without resolution of these problems.
Institute of Scientific and Technical Information of China (English)
张睿; 王德; 徐琴; 姜佳俊; 施敏
2012-01-01
Chiral C2-symmetric N-heterocyclic carbene （NHC） palladium diaquo complex 5b prepared from （S）-BINAM was found to be a fairly effective catalyst for the enantioselective asymmetric fluorination of oxindoles to give the corresponding products in moderate enantioselectivities along with good to excellent yields.
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.
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
Axial anomaly effects in finite isospin $\\chi$PT in a magnetic field
Adhikari, Prabal
2015-01-01
In this paper, we consider finite isospin chiral perturbation theory including the effects of the axial anomaly (through the Wess-Zumino-Witten term) in a strong magnetic field. We firstly prove that in a strong external magnetic field ($H_{\\rm ext}$) or more precisely the Schwinger limit, where photon back-reactions are suppressed, only neutral pions can condense and the condensation of charged pions is forbidden. Secondly, we find that the $\\pi^{0}$ domain wall is an example of a phase that can exist in a strong magnetic field and suggest the existence of a new phase transition line from the normal vacuum state to the $\\pi^{0}$ domain wall state. This phase transition exists for non-zero pion masses if the baryon chemical potential exceeds a critical value $16\\pi f_{\\pi}^{2}m_{\\pi}/eH_{\\rm ext}$. The phase transition line persists away from the Schwinger limit when the photons can back-react to the external magnetic field.
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…
Study of Magnetic Field Behavior at Lower Pressure of Neon in the Axial Phase of INTI Plasma Focus
Directory of Open Access Journals (Sweden)
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.
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.
Axial Myopia Is Associated with Visual Field Prognosis of Primary Open-Angle Glaucoma.
Directory of Open Access Journals (Sweden)
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.
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.
Rozgacheva, I K
2016-01-01
A precise solution of the general relativity equations for centrally symmetric distribution of a pseudoscalar field with U(1) symmetry is presented. It is found that energy density of the field is restricted in the symmetry center and falls with radial distance at a much slower rate than in numerical simulations of dark matter haloes. This result can solve the cusp problem for galaxies and the problem of rotation curves for galaxy exteriors.
The flow field investigations of no load conditions in axial flow fixed-blade turbine
Yang, J.; Gao, L.; Wang, Z. W.; Zhou, X. Z.; Xu, H. X.
2014-03-01
During the start-up process, the strong instabilities happened at no load operation in a low head axial flow fixed-blade turbine, with strong pressure pulsation and vibration. The rated speed can not reach until guide vane opening to some extent, and stable operation could not be maintained under the rated speed at some head, which had a negative impact on the grid-connected operation of the unit. In order to find the reason of this phenomenon, the unsteady flow field of the whole flow passage at no load conditions was carried out to analyze the detailed fluid field characteristics including the pressure pulsation and force imposed on the runner under three typical heads. The main hydraulic cause of no load conditions instability was described. It is recommended that the power station should try to reduce the no-load running time and go into the high load operation as soon as possible when connected to grid at the rated head. Following the recommendations, the plant operation practice proved the unstable degree of the unit was reduced greatly during start up and connect to the power grid.
Design method and magnetic field analysis of axial-magnetized permanent magnet micromotor
Institute of Scientific and Technical Information of China (English)
YANG Jiewei; WU Yihui; JIA Hongguang; ZHANG Ping; WANG Shurong
2007-01-01
To investigate the impact of size on its performance in designing an axial-magnetized permanent magnet micromotor,the finite element method is adopted to simulate the magnetic field of the dual rotor motor,and the flux density wave form distributed in the airgap is obtained.The influence of the external dimensions,pole numbers and magnet thicknesses of the rotor,and the airgap distances on the flux density,are analyzed and analytical results are given.With the increase of the airgap distance,the flux density under more poles reduces more quickly than under fewer poles.With the increase of the magnet thickness,the flux density is a rising curve,and after the magnet thickness attains a certain point,the flux density is almost a constant.While reducing the diameter of the rotor,the decrease of the flux density slows down as magnet thickness is reduced.To avoid having a seriously distorted waveform,the distance between inner and outer radii of the rotor must be larger than 1.5 millimeter.Results of the magnetic field analysis can guide a microminiaturization of the motor.Moreover,the results are analyzed theoretically and the simulated values are almost consistent with the experimental values.
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.
Institute of Scientific and Technical Information of China (English)
孟凡英; 吕晓军
2014-01-01
针对农业灌溉中对轴流泵性能的要求，为了更深入的研究该轴流泵的性能特性，研究了NACA0006对称翼型导叶的轴流泵性能，利用计算流体动力学软件Fluent ，采用RNG k-ε湍流模型和SIMPLEC算法对该轴流泵进行数值模拟。通过对其进行数值计算和对比分析表明，设计工况下的数据值不仅与 Fluent软件模拟的数据值相对误差为1．9％，并且应用Fluent软件模拟计算得到泵的性能曲线与性能实验的结果吻合较好，证明了在轴流泵导叶设计中，NACA0006翼型不仅结构简单、适用性良好，而且取得了更高的效率。%For the requirements of axial flow pump performance in agricultural irrigation ,in order to research the characteristics of axial-flow pump further ,the performance of axial guide vane by NACA 0006 symmetrical air-foil flow pump was studied .Through the computational fluid dynamics software of Fluent and RNG k -εtur-bulent model and SIMPLEC algorithm ,the axial flow pump was simulated .The numerical calculation and com-parative analysis showed that relative error of data was 1 .9% with data stimulated by Fluent software under design condition ,and the performance curve and experiment results simulated by application of Fluent software were in good agreement .It proved that the design of flow pump in axial guide vane ,NACA0006 airfoil had sim-ple structure and good applicability ,and it could achieve higher efficiency .
Kool, Th.W.; Bollegraaf, B.
2010-01-01
Numerical and analytical methods are used to investigate the calculation of the zero field splitting |2D| and g(perp) parameters in EPR for octahedrally surrounded d3 spin systems (S = 3/2) in strong and moderate axial crystal fields (|D|>=h{\
Institute of Scientific and Technical Information of China (English)
BAO Ai-Dong; YAO Hai-Bo; WU Shi-Shu
2009-01-01
A topological way to distinguish divergences of the Abelian axial-vector current in quantum field theory is proposed. By usirg the properties of the Atiyah-Singer index theorem, the non-trivial Jacobian factor of the integration measure in the path-integral formulation of the theory is connected with the topological properties of the gauge field. The singularity of the fermion current related to the topological character can be correctly examined in a gauge background.
Energy Technology Data Exchange (ETDEWEB)
Arani, A. Ghorbanpour, E-mail: aghorban@kashanu.ac.ir [Faculty of Mechanical Engineering University of Kashan, Kashan (Iran, Islamic Republic of); Institute of Nanoscience & Nanotechnology, University of Kashan, Kashan (Iran, Islamic Republic of); Haghparast, E.; BabaAkbar Zarei, H. [Faculty of Mechanical Engineering University of Kashan, Kashan (Iran, Islamic Republic of)
2016-08-15
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.
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.
Symmetric Powers of Symmetric Bilinear Forms
Institute of Scientific and Technical Information of China (English)
Se(a)n McGarraghy
2005-01-01
We study symmetric powers of classes of symmetric bilinear forms in the Witt-Grothendieck ring of a field of characteristic not equal to 2, and derive their basic properties and compute their classical invariants. We relate these to earlier results on exterior powers of such forms.
Neutral beam excitation of Alfven continua in the madison symmetric torus reversed field pinch
Koliner, Jonathan Jay
Alfven continua and Alfven eigenmodes (AEs) have been generated for reversed-field pinch (RFP) plasma equilibria in Madison Symmetric Torus (MST). Data gathered from the extensive suite of diagnostics on MST was used to generate equilibria using MSTFIT and VMEC. Three dimensional equilibria for spontaneous helical states were generated using the equilibrium reconstruction code V3FIT. The reduced-MHD codes AE3D and STELLGAP were run on all generated equilibria to calculate the continua and AEs. All continuum solutions contain a toroidicity-induced Alfven gap at 200-400 kHz, within which AE solutions appear by coupling of m=0,1 at medium n. The first observation of beam-driven instabilities on the RFP was performed using MST magnetics during neutral beam injection (NBI). Spatially coherent bursts with n=5,m=1 were observed in plasmas with edge safety factor q_a=0. The bursts oscillate at 65 kHz, and reach maximum amplitude and decay away within 100 mus. These bursts persist for the duration of NBI. Secondary n=-1 and n=4 bursts are coupled in time, reaching maximum amplitude with 50 mus after the n=5 peak amplitude. While the n=5 bursts scale weakly with the electron density n_e and strongly with the beam velocity v_beam, the n=4 bursts scale with the Alfven speed v_A. The burst frequencies are well below those of the calculated AEs and the modes are driven even with v_ beam plasmas. In reversed plasmas, the temporally changing q profile changes the burst resonances, bringing n=6 into resonance halfway through the sawtooth cycle. The n=5 mode switches from its frequency in non-reversed plasmas to a higher frequency at the end of the sawtooth cycle. In deeply reversed plasmas, the bursts are weaker and display chirping behavior as the plasma reversal increases. During the transition to a helical state, the bursts increase in frequency as q on-axis changes, altering the parallel wavenumber k_||. When the helical state is established, the bursts terminate.
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.
Institute of Scientific and Technical Information of China (English)
薛航; 陈徐屹; 张小英
2014-01-01
The study on the cooling structure of vectoring nozzle is very essential for developing the vectoring propulsion technology in aero-engine .To study the cooling technology of the heat shield on the axial-symmetric vectoring nozzle with 20° deflection ,the heat balance equation based on heat transfer of nozzle has been devel-oped and solved with Newton-Rafael method to give wall temperature .Heat transfer of film cooling is computed with empirical formula of cooling effectiveness .And radiative heating from the gas is computed with net radia-tion analysis method in an enclosure .To verify the computation method ,wall temperature of a certain axial-symmetric nozzle in after burning condition is computed and compared with the results of reference .Study shows that the heat shield plays a good cooling part for convergent part of nozzle with film cooling reducing its temperature remarkably .Compared with convergent part of nozzle which is protected by the heat shield ,tem-perature of the divergent section of nozzle is much higher and needs further cooling .%航空发动机矢量喷管的冷却结构设计是研究矢量推进技术应用的关键问题之一。针对某偏转20°轴对称矢量喷管隔热屏采用的十种气膜冷却结构，建立基于壁面传热的热平衡方程，采用牛顿-拉斐尔森迭代法得出十种冷却结构下壁面及隔热屏的温度。其中气膜冷却采用有效温比经验公式计算，燃气辐射采用封闭腔净辐射分析法计算，并把本文计算的壁温与文献结果进行对比分析。结果表明：隔热屏对喷管收敛段有很好的冷却作用，采用气膜冷却可显著降低其温度；相对于受隔热屏保护的收敛段而言，喷管扩张段的受热形势较为严峻，温度更高，其冷却有待加强。
Gair, S.; Eastham, J. F.; Canova, A.
1996-04-01
The article reports on a study of the effects of slot closure in axial-field permanent magnet brushless machines by a two-dimensional finite element method (2D FEM) of analysis. The closure of the slots is made by using soft magnetic powder wedge material. Parameter values and machine performance for the open and closed slot configuration are computed. In order to test the 2D FEM model, calculated results are compared with measurements and favorable agreement is shown.
Sidabras, Jason W.; Richie, James E.; Hyde, James S.
2017-01-01
In continuous-wave (CW) Electron Paramagnetic Resonance (EPR) a low-frequency time-harmonic magnetic field, called field modulation, is applied parallel to the static magnetic field and incident on the sample. Varying amplitude of the field modulation incident on the sample has consequences on spectral line-shape and line-height over the axis of the sample. Here we present a method of coupling magnetic field into the cavity using slots perpendicular to the sample axis where the slot depths are designed in such a way to produce an axially uniform magnetic field along the sample. Previous literature typically assumes a uniform cross-section and axial excitation due to the wavelength of the field modulation being much larger than the cavity. Through numerical analysis and insights obtained from the eigenfunction expansion of dyadic Green's functions, it is shown that evanescent standing-wave modes with complex cross-sections are formed within the cavity. From this analysis, a W-band (94 GHz) cylindrical cavity is designed where modulation slots are optimized to present a uniform 100 kHz field modulation over the length of the sample.
Relaxation of 2+1 dimensional classical O(2) symmetric scalar fields
Borsanyi, S; Borsanyi, Sz.; Szep, Zs.
2001-01-01
Real time thermalization and relaxation phenomena are studied in the low energy density phase of the 2+1 dimensional classical O(2) symmetric scalar theory by solving numerically its dynamics. The near-equilibrium decay rate of on-shell waves and the power law governing the large time asymptotics of the off-shell relaxation agree with the analytic results based on linear response theory. The realisation of the Mermin-Wagner theorem is also studied in the final equilibrium ensemble.
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...
Energy Technology Data Exchange (ETDEWEB)
Kousaka, Hiroyuki; Ono, Kouichi [Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)
2003-05-01
The electromagnetic fields and plasma parameters have been studied in an azimuthally symmetric surface wave-excited plasma (SWP) source, by using a two-dimensional numerical analysis based on the finite-difference time-domain (FDTD) approximation to Maxwell's equations self-consistently coupled with a fluid model for plasma evolution. The FDTD/fluid hybrid simulation was performed for different gas pressures in Ar and different microwave powers at 2.45 GHz, showing that the surface waves (SWs) occur along the plasma-dielectric interfaces to sustain overdense plasmas. The numerical results indicated that the electromagnetic SWs consist of two different waves, Wave-1 and Wave-2, having relatively shorter and longer wavelengths. The Wave-1 was seen to fade away with increasing pressure and increasing power, while the Wave-2 remained relatively unchanged over the range of pressure and power investigated. The numerical results revealed that the Wave-1 propagates as backward SWs whose phase velocity and group velocity point in the opposite directions. In contrast, the Wave-2 appeared to form standing waves, being ascribed to a superposition of forward SWs whose phase and group velocities point in the same direction. The fadeaway of the Wave-1 or backward SWs at increased pressures and increased powers was seen with the damping rate increasing in the axial direction, being related to the increased plasma electron densities. A comparison with the conventional FDTD simulation indicated that such fine structure of the electromagnetic fields of SWs is not observed in the FDTD simulation with spatially uniform and time-independent plasma distributions; thus, the FDTD/fluid hybrid model should be employed in simulating the electromagnetic fields and plasma parameters in SWPs with high accuracy.
Xia, Ying; Wang, Shiyu; Sun, Wenjia; Xiu, Jie
2017-01-01
The electromagnetically induced parametric vibration of the symmetrical three-phase induction stator is examined. While it can be analyzed by an approximate analytical or numerical method, more accurate and simple analytical method is desirable. This work proposes a new method based on the field-synchronous coordinates. A mechanical-electromagnetic coupling model is developed under this frame such that a time-invariant governing equation with gyroscopic term can be developed. With the general vibration theory, the eigenvalue is formulated; the transition curves between the stable and unstable regions, and response are all determined as closed-form expressions of basic mechanical-electromagnetic parameters. The dependence of these parameters on the instability behaviors is demonstrated. The results imply that the divergence and flutter instabilities can occur even for symmetrical motors with balanced, constant amplitude and sinusoidal voltage. To verify the analytical predictions, this work also builds up a time-variant model of the same system under the conventional inertial frame. The Floquét theory is employed to predict the parametric instability and the numerical integration is used to obtain the parametric response. The parametric instability and response are both well compared against those under the field-synchronous coordinates. The proposed field-synchronous coordinates allows a quick estimation on the electromagnetically induced vibration. The convenience offered by the body-fixed coordinates is discussed across various fields.
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 (high voltage gain (~6) and ultralow static power dissipation (high-performance high-density logic circuit using a low-temperature fabrication process, which makes it suitable for flexible electronics.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 (high voltage gain (~6) and ultralow static power dissipation (high-performance high-density logic circuit using a low-temperature fabrication process, which makes it suitable for flexible electronics. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01040g
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.
Institute of Scientific and Technical Information of China (English)
S. Saviz; E. Lashani; Farzin M. Aghamir
2012-01-01
A theory for the two-stream free-electron laser (TSFEL) with a helical wiggler and an axial guide magnetic field is developed.In the analysis,the effects of self-fields are taken into account.An analysis of the two-stream steady-state electron trajectories is given by solving the equation of motion.Numerical calculations show that there are seven groups of orbits in the presence of self-fields instead of two groups reported in the absence of self-fields.The stability of the trajectories is studied numerically.
Nuclear axial current operators to fourth order in chiral effective field theory
Krebs, H; Epelbaum, E.; Meißner, U.-G
2016-01-01
We present the complete derivation of the nuclear axial charge and current operators as well as the pseudoscalar operators to fourth order in the chiral expansion relative to the dominant one-body contribution using the method of unitary transformation. We demonstrate that the unitary ambiguity in the resulting operators can be eliminated by the requirement of renormalizability and by matching of the pion-pole contributions to the nuclear forces. We give expressions for the renormalized singl...
On the Intimate Connection Between Mass Scales and Their Relations in Symmetric Quantum Field Theory
Gobira, S R
2003-01-01
We illustrate the importance of mass scales and their relation in the specific case of the linear sigma model within the context of its one loop Ward identities. In the calculation it becomes apparent the delicate and essential connection between divergent and finite parts of amplitudes. Most importantly, the examples shows how to use mass scales identities which are absolutely necessary to manipulate graphs involving several masses in a way as to show its equivalence to others involving different (than the previous) masses. Finally we show that in the context of the Implicitly Regularization all infinite parts can and should be written in terms of a single scale which is the renormalization group scale. This facilitates, e.g., obtaining symmetric counterterms and immediately lead to the proper definition of Renormalization Group Constants.
McLeman, James A; Bingham, Robert
2012-01-01
The precise process by which dark filamentary clouds collapse to form stars is a subject of intense debate. In this paper we consider a cylindrical distribution of plasma with both axial and azimuthal magnetic field and examine the resulting gravitational stability. The azimuthal magnetic field is created from an electric current in the plasma and is found to be dictated by Ampere's law. We model this system by using the magnetohydrodynamic (MHD) equation to derive a new virial theorem. We can reduce it to the virial theorem due to Chandrasekhar and Fermi (1953) if we remove the azimuthal magnetic field, as this will represent the case which they have considered. This new virial theorem gives us a fresh insight into the stability of the system. We also derive from this new virial theorem the case where there is only an azimuthal magnetic field. Our generalised stability condition allows for a possible electric current within realistic astronomical values.
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.
Cho, Chahee Peter
1995-01-01
Until recently, brush dc motors have been the dominant drive system because they provide easily controlled motor speed over a wide range, rapid acceleration and deceleration, convenient control of position, and lower product cost. Despite these capabilities, the brush dc motor configuration does not satisfy the design requirements for the U.S. Navy's underwater propulsion applications. Technical advances in rare-earth permanent magnet materials, in high-power semiconductor transistor technology, and in various rotor position-sensing devices have made using brushless permanent magnet motors a viable alternative. This research investigates brushless permanent magnet motor technology, studying the merits of dual-air gap, axial -field, brushless, permanent magnet motor configuration in terms of power density, efficiency, and noise/vibration levels. Because the design objectives for underwater motor applications include high-power density, high-performance, and low-noise/vibration, the traditional, simplified equivalent circuit analysis methods to assist in meeting these goals were inadequate. This study presents the development and verification of detailed finite element analysis (FEA) models and lumped parameter circuit models that can calculate back electromotive force waveforms, inductance, cogging torque, energized torque, and eddy current power losses. It is the first thorough quantification of dual air-gap, axial -field, brushless, permanent magnet motor parameters and performance characteristics. The new methodology introduced in this research not only facilitates the design process of an axial field, brushless, permanent magnet motor but reinforces the idea that the high-power density, high-efficiency, and low-noise/vibration motor is attainable.
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.
Nuclear axial current operators to fourth order in chiral effective field theory
Krebs, H; Meißner, U -G
2016-01-01
We present the complete derivation of the nuclear axial charge and current operators as well as the pseudoscalar operators to fourth order in the chiral expansion relative to the dominant one-body contribution using the method of unitary transformation. We demonstrate that the unitary ambiguity in the resulting operators can be eliminated by the requirement of renormalizability and by matching of the pion-pole contributions to the nuclear forces. We give expressions for the renormalized single-, two- and three-nucleon contributions to the charge and current operators and pseudoscalar operators including the relevant relativistic corrections. We also verify explicitly the validity of the continuity equation.
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.
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\\).
Pura, Jose Luis; Anaya, Julián; Souto, Jorge; Carmelo Prieto, Ángel; Rodríguez, Andrés; Rodríguez, Tomás; Jiménez, Juan
2016-11-01
We present a phenomenon concerning electromagnetic enhancement at the heterojunction region of axially heterostructured Si/SiGe nanowires when the nanowire is illuminated by a focused laser beam. The local electric field is sensed by micro Raman spectroscopy, which allows the enhancement of the Raman signal arising from the heterojunction region to be revealed; the Raman signal per unit volume increases at least ten times with respect to the homogeneous Si and SiGe nanowire segments. In order to explore the physical meaning of this phenomenon, a three-dimensional solution of the Maxwell equations of the interaction between the focused laser beam and the nanowire was carried out by finite element methods. A local enhancement of the electric field at the heterojunction was deduced. However, the magnitude of the electromagnetic field enhancement only approaches the experimental one when the free carriers are considered, showing enhanced absorption at the carrier depleted heterojunction region. The existence of this effect promises a way of improving photon harvesting using axially heterostructured semiconductor nanowires.
Lakshminarayana, B.; Zhang, J.; Murthy, K. N. S.
1987-01-01
Detailed measurement of the flow field in the tip region of a compressor rotor was carried out using a Laser Doppler Velocimeter (LDV) and a Kiel probe at two different tip clearance heights. At both clearance sizes, the relative stagnation pressure and the axial and tangential components of relative velocities were measured upstream, inside the passage and downstream of the rotor, up to about 20 percent of the blade span from the annulus wall. The velocities, outlet angles, losses, momentum thickness, and force defect thickness are compared for the two clearances. A detailed interpretation of the effect of tip clearance on the flow field is given. There are substantial differences in flow field, on momentum thickness, and performance as the clearance is varied. The losses increase linearly within the passage and their values increase in direct proportion to tip clearance height. No discernable vortex (discrete) is observed downstream of the rotor.
Axially Symmetric Post-Newtonian Stellar Systems
Directory of Open Access Journals (Sweden)
Camilo Akímushkin
2010-01-01
Full Text Available Presentamos un método para obtener modelos estelares discoidales, axialmente simétricos, auto-consistentes en la primera aproximación post-Newtoniana (1PN. Usando en las ecuaciones de campo de la aproximación 1PN una función de distribución conocida (DF que corresponde a un modelo Newtoniano, se obtienen dos ecuaciones fundamentales para determinar las correcciones 1PN. Las curvas de rotación de los modelos corregidos difieren de las clásicas y las correcciones son claramente apreciables con los valores de la masa y el radio de una galaxia típica. Por otro lado, la corrección relativista de la masa se puede ignorar para todos los modelos.
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 ...
Quantization of massive scalar fields over axis symmetric space-time backgrounds
Piedra, O P F; Oca, Alejandro Cabo Montes de; Piedra, Owen Pavel Fernandez
2007-01-01
The renormalized mean value of the quantum Lagrangian and the Energy-Momentum tensor for scalar fields coupled to an arbitrary gravitational field configuration are analytically evaluated in the Schwinger-DeWitt approximation, up to second order in the inverse mass value. The cylindrical symmetry situation is considered. The results furnish the starting point for investigating iterative solutions of the back-reaction problem related with the quantization of cylindrical scalar field configurations. Due to the homogeneity of the equations of motion of the Klein-Gordon field, the general results are also valid for performing the quantization over either vanishing or non-vanishing mean field configurations. As an application, compact analytical expressions are derived here for the quantum mean Lagrangian and Energy-Momentum tensor in the particular background given by the Black-String space-time.
Zheng, Chun-Yang; Zhu, Shao-Ping; He, Xian-Tu
2002-07-01
The quasi-static magnetic fields created in the interaction of relativistic laser pulses with under-dense plasmas have been investigated by three-dimensional particle-in-cell simulation. The relativistic ponderomotive force can drive an intense electron current in the laser propagation direction, which is responsible for the generation of a helical magnetic field. The axial magnetic field results from a difference beat of wave-wave, which drives a solenoidal current. In particular, the physical significance of the kinetic model for the generation of the axial magnetic field is discussed.
Awe, Thomas
2013-10-01
Magnetically driven implosions provide an energy-rich platform for inertial confinement fusion. The magnetized liner inertial fusion concept (MagLIF, Slutz et al., Phys. Plasmas 17, 056303 (2010)) uses a pulsed-power-driven metallic liner to compress and inertially confine preheated and premagnetized fusion fuel. The fuel is premagnetized with a uniform axial seed field Bz , 0 of 10 to 30 T, which is then compressed by the liner to nearly 1000 T. In the fuel, the ultra-high field reduces thermal conduction and enhances alpha-particle heating. Preheating the fuel to 100-300 eV eases requirements on liner-convergence; nonetheless, convergence ratios at stagnation of 20 or more may be necessary. The ability to maintain liner stability and uniformity through stagnation may ultimately determine the success of the MagLIF concept. The integrity of magnetically imploded liners is compromised both by electrode instabilities and by the magneto-Rayleigh Taylor (MRT) instability. Electrode instabilities form local perturbations that can mix liner material into the fuel prior to bulk compression. Recent experiments on the Z facility have shown that this instability is mitigated when the liner's ends implode onto a nylon ``cushion,'' which impedes local perturbation growth. Other recent experiments have, for the first time, studied the implosion dynamics of premagnetized (Bz , 0 > 0) MagLIF-type liners. When seeded with a 7 or 10 T axial field, these liners developed 3D-helix-like surface instabilities; such instabilities starkly contrast with the azimuthally-correlated MRT instabilities that have been consistently observed in many earlier unmagnetized (Bz , 0 = 0 T) experiments. Quite unexpectedly, the helical structure persisted throughout the implosion, even though the azimuthal drive field greatly exceeded the expected axial field at the liner surface for all but the earliest stages of the experiment. Thus far, no self-consistent model has reproduced this fundamentally 3D
Directory of Open Access Journals (Sweden)
Teresa D'Aprile
2000-11-01
Full Text Available In this paper we study the existence of concentrated solutions of the nonlinear field equation $$ -h^{2}Delta v+V(xv-h^{p}Delta_{p}v+ W'(v=0,, $$ where $v:{mathbb R}^{N}o{mathbb R}^{N+1}$, $Ngeq 3$, $p>N$, the potential $V$ is positive and radial, and $W$ is an appropriate singular function satisfying a suitable symmetric property. Provided that $h$ is sufficiently small, we are able to find solutions with a certain spherical symmetry which exhibit a concentration behaviour near a circle centered at zero as $ho 0^{+}$. Such solutions are obtained as critical points for the associated energy functional; the proofs of the results are variational and the arguments rely on topological tools. Furthermore a penalization-type method is developed for the identification of the desired solutions.
Wei, Qin; Yu, Fan; Jin, Fang; Shuo, Li; Guoguo, Li; Gang, Lv
2012-04-01
A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device's characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations.
Wei, Qin; Yu, Fan; Jin, Fang; Shuo, Li; Guoguo, Li; Gang, Lv
2012-04-01
A new high temperature superconductor axial-flux coreless maglev motor (HTS AFIM) is proposed, of which the primary windings are made of HTS tapes and the secondary is a non-magnetic conductor. The main works of this paper are the magnetic-field computation and characteristics analysis of HTS AFIM. For the first one, the reduction of magnetic fields near outer and inner radius of the HTS AFIM is solved by introducing the sub-loop electro-magnetic model along the radial position. For the second one, the AC losses of HTS coils are calculated. The relationships between the device's characteristics and device parameters are presented, and the results indicate that under certain frequency and current levitation device can output enough lift force. The conclusions are verified by finite element calculations.
Dutta, Sourav; Panja, Madan Mohan; Chakraborty, Subenoy
2016-06-01
Non-minimally coupled scalar field cosmology has been studied in this work within the framework of Einstein gravity. In the background of homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime non-minimally coupled scalar field having self-interacting potential is taken as the source of the matter content. The constraint of imposing Noether symmetry on the Lagrangian of the system not only determines the infinitesimal generator (the symmetry vector) but also the coupling function and the self-interacting potential for the scalar field. By choosing appropriately a point transformation in the augmented space, one of the transformed variables is cyclic for the Lagrangian. Finally, using constants of motion, the solutions are analyzed.
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.
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.
Auluck, S K H
2014-01-01
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 ...
Harko, T.; Mak, M. K.
2005-10-01
A class of exact solutions of the gravitational field equations in the vacuum on the brane are obtained by assuming the existence of a conformal Killing vector field, with non-static and non-central symmetry. In this case, the general solution of the field equations can be obtained in a parametric form in terms of the Bessel functions. The behavior of the basic physical parameters describing the non-local effects generated by the gravitational field of the bulk (dark radiation and dark pressure) is also considered in detail, and the equation of state satisfied at infinity by these quantities is derived. As a physical application of the obtained solutions we consider the behavior of the angular velocity of a test particle moving in a stable circular orbit. The tangential velocity of the particle is a monotonically increasing function of the radial distance and, in the limit of large values of the radial coordinate, tends to a constant value, which is independent on the parameters describing the model. Therefore, a brane geometry admitting a one-parameter group of conformal motions may provide an explanation for the dynamics of the neutral hydrogen clouds at large distances from the galactic center, which is usually explained by postulating the existence of the dark matter.
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。
Tan, Mingsheng; Stone, Douglas R.; Triana, Joseph C.; Almagri, Abdulgader F.; Fiksel, Gennady; Ding, Weixing; Sarff, John S.; McCollam, Karsten J.; Li, Hong; Liu, Wandong
2017-02-01
A 40-channel capacitive probe has been developed to measure the electrostatic fluctuations associated with the tearing modes deep into Madison Symmetric Torus (MST) reversed field pinch plasma. The capacitive probe measures the ac component of the plasma potential via the voltage induced on stainless steel electrodes capacitively coupled with the plasma through a thin annular layer of boron nitride (BN) dielectric (also serves as the particle shield). When bombarded by the plasma electrons, BN provides a sufficiently large secondary electron emission for the induced voltage to be very close to the plasma potential. The probe consists of four stalks each with ten cylindrical capacitors that are radially separated by 1.5 cm. The four stalks are arranged on a 1.3 cm square grid so that at each radial position, there are four electrodes forming a square grid. Every two adjacent radial sets of four electrodes form a cube. The fluctuating electric field can be calculated by the gradient of the plasma potential fluctuations at the eight corners of the cube. The probe can be inserted up to 15 cm (r/a = 0.7) into the plasma. The capacitive probe has a frequency bandwidth from 13 Hz to 100 kHz, amplifier-circuit limit, sufficient for studying the tearing modes (5-30 kHz) in the MST reversed-field pinch.
Favre, Mario; Wyndham, Edmund; Veloso, Felipe; Bhuyan, Heman; Reyes, Sebastian; Ruiz, Hugo Marcelo; Caballero-Bendixsen, Luis Sebastian
2016-10-01
We present further detailed studies of the dynamics and plasma properties of a laser produced Carbon plasma expanding in a static axial magnetic field. The laser plasmas are produced in vacuum, 1 .10-6 Torr, using a graphite target, with a Nd:YAG laser, 3.5 ns, 340 mJ at 1.06 μm, focused at 2 .109 W/cm2, and propagate in static magnetic fields of maximum value 0.2 T. 15 ns time and spaced resolved OES is used to investigate plasma composition. 50 ns time resolved plasma imaging is used to visualize the plasma dynamics. A mm size B-dot probe is used, in combination with a Faraday cup, to characterize the interaction between the expanding plasma and the magnetic field. As a result of time and space correlated measurements, unique features of the laser plasma dynamics in the presence of the magnetic field are identified, which highlight the confinement effects of the static magnetic field Funded by project FONDECYT 1141119.
Quantum transport of the semiconductor pump: Due to an axial external field
Energy Technology Data Exchange (ETDEWEB)
Xiao, Yun-Chang, E-mail: phyxiaofan@163.com [College of Electrical and Information Engineering, Hunan University of Arts and Science, Changde 415000 (China); Wang, Ri-Xing, E-mail: wangrixing@sina.com [College of Electrical and Information Engineering, Hunan University of Arts and Science, Changde 415000 (China); Deng, Wei-Ying, E-mail: weiyindeng@gmail.com [Department of Physics, South China University of Technology, Guangzhou 510640 (China)
2014-09-15
Parametric semiconductor pump modulated by the external field is investigated. The pump center attaching to two normal leads is driven by the potentials formed in the interfaces. With the Floquet scattering matrix method, the pumped currents modulated by the parameters are studied. Results reveal that the charge and spin currents pumped from the system can be strengthen by the external field besides the potentials. Directed spin currents can be pumped more strongly than the charge currents, and even the pure spin currents can be achieved in some external field couplings to the pump parameters.
QED effective action for an O(2)xO(3) symmetric field in the full mass range
Ahmadiniaz, N; Raya, A; Schubert, C
2013-01-01
An interesting class of background field configurations in QED are the O(2)xO(3) symmetric fields. Those backgrounds have some instanton-like properties and yield a one-loop effective action that is highly nontrivial but amenable to numerical calculation, for both scalar and spinor QED. Here we use the recently developed "partial-wave-cutoff method" for a numerical analysis of both effective actions in the full mass range. In particular, at large mass we are able to match the asymptotic behavior of the physically renormalized effective action against the leading two mass levels of the inverse mass (or heat kernel) expansion. At small mass we obtain good numerical results even in the massless case for the appropriately (unphysically) renormalized effective action after the removal of the chiral anomaly term through a small radial cutoff factor. In particular, we show that the effective action after this removal remains finite in the massless limit, which also provides indirect support for M. Fry's hypothesis t...
Daggolu, Parthiv; Ryu, Jae Woo; Galyukov, Alex; Kondratyev, Alexey
2016-10-01
With the use of 300 mm silicon wafers for industrial semiconductor device manufacturing, the Czochralski (Cz) crystal growth process has to be optimized to achieve higher quality and productivity. Numerical studies based on 2D global thermal models combined with 3D simulation of melt convection are widely used today to save time and money in the process development. Melt convection in large scale Cz Si growth is controlled by a CUSP or transversal magnetic field (MF) to suppress the melt turbulence. MF can be optimized to meet necessary characteristics of the growing crystal, in terms of point defects, as MF affects the melt/crystal interface geometry and allows adjustment of the pulling rate. Among the different knobs associated with the CUSP magnetic field, the nature of its configuration, going from symmetric to asymmetric, is also reported to be an important tool for the control of crystallization front. Using a 3D unsteady model of the CGSim software, we have studied these effects and compared with several experimental results. In addition, physical mechanisms behind these observations are explored through a detailed modeling analysis of the effect of an asymmetric CUSP MF on convection features governing the heat transport in the silicon melt.
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...
Symmetric structure of field algebra of G-spin models determined by a normal subgroup
Energy Technology Data Exchange (ETDEWEB)
Xin, Qiaoling, E-mail: xinqiaoling0923@163.com; Jiang, Lining, E-mail: jianglining@bit.edu.cn [School of Mathematics and Statistics, Beijing Institute of Technology, Beijing 100081 (China)
2014-09-15
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 F{sub H} of the field algebra F of G-spin models, so that F{sub H} is a D(H; G)-module algebra, whereas F is not. Then the observable algebra A{sub (H,G)} is obtained as the D(H; G)-invariant subalgebra of F{sub H}, and there exists a unique C*-representation of D(H; G) such that D(H; G) and A{sub (H,G)} are commutants with each other.
Global confinement in the MST (Madison Symmetric Torus) reversed field pinch
Energy Technology Data Exchange (ETDEWEB)
Almagri, A.; Assadi, S.; Beckstead, J.; Chartas, G.; Cudzinovic, M.; Den Hartog, D.; Dexter, R.; Hokin, S.; Holly, D.; Klevans, E.; Nebel, R.; Prager, S.; Rempel, T.; Sarff, J.; Scime, E.; Shen, W.; Spragins, C.; Sprott, C.; Starr, G.; Stoneking, M.; Veerasingam, R.; Watts, C.
1990-10-01
Global confinement measured in the first six months of MST full design operation is summarized. Central electron temperature and enhancement of resistivity over the Z = 1 Spitzer value are similar to other RFP experiments for the same value of I/N. As in several other RFP experiments, energy confinement time and poloidal beta are found to decrease with increasing plasma current, with maximum values of {tau}{sub E} {approximately} 1 ms and {beta}{sub p} {approximately} 10%. Particle transport may be approximated with a diffusion coefficient D {approximately} 40 m{sup 2}/s for a discharge studied with a 1-d particle-neutral code. A more elaborate code, incorporating heat and impurity transport, indicates an increase of Z{sub eff} with I/N. This code also reveals that the toroidal magnetic field decays resistively between discrete dynamo events, at the rate given by the measured global resistivity. Edge suprathermal electrons are observed as on other RFPs, with temperatures comparable to the central electron temperature and carrying a current density at least 15% of the total measured with an insertable magnetic coil array. Radial magnetic profiles measured with this array may be matched with a Modified Polynomial Function Model equilibrium for a value of {beta}{sub p} which is a factor of two larger than measured, but which is required due to the large values of {Theta} for a given F found in MST discharges ({Theta} = 1.85 at F= {minus}0.15). 15 refs., 14 figs.
Directory of Open Access Journals (Sweden)
Dipankar Chatterjee
2016-01-01
Full Text Available A quasi two-dimensional numerical study is performed to analyze the thermo-magneto-convective transport of liquid metal around a square cylinder in a square duct subjected to a strong externally imposed axial magnetic field. The channel bottom wall is considered heated while the top wall is maintained at the free stream temperature keeping the cylinder adiabatic. The Reynolds and Hartmann numbers are kept in the range and . The flow dynamics in the aforementioned range of parameters reveals the existence of four different regimes out of which the first three ones are similar to the classical non-MHD 2-D cylinder wakes while the fourth one is characterized by the vortices evolved from the duct side walls due to the boundary layer separation which strongly disturbs the Kármán vortex street. The flow dynamics and heat transfer rate from the heated channel wall are observed to depend on the imposed magnetic field strength. With increasing magnetic field, the flow becomes stabilized resulting in a degradation in the forced convection heat transfer. A special case at a very high Reynolds number with Ha = 2160 is also considered to show the development of a Kelvin–Helmholtz-type instability that substantially affects the heat transfer rate.
Andreev, O.; Kobzev, A.; Kolesnikov, Yu.; Thess, A.
Flows around obstacles are among the most common problems encountered in the fluid mechanics literature, and cylindrical obstacles definitely received the most extensive attention. The reason for this is that this relatively simple geometry already encompasses most of the important physical effects likely to play a role in flow around more complicated obstacles. This means that understanding the cylinder problem provides relevant insight on a wide variety of problem ranging from aerodynamics, with the flow around a wing or a vehicle, to pollutant dispersion around building, flows in turbines … When the working fluid conducts electricity additional effects are involved. In particular, the presence of a magnetic field tends to homogenise the flow in the direction of the magnetic field lines which leads to strong alterations of the flow patterns known from the classical nonconducting case. This configuration is also a very generic one as Magnetohydrodynamic flows around obstacle also occur in a wide variety of applications: for instance, the space vehicle re-entry problem features the flow of a conducting plasma around an obstacle: [1] and [2] have shown that it could be influenced by a strong magnetic field in order to reduce heat transfer. The cooling blanket of the future nuclear fusion reactor ITER soon to be built in France, features a complex flow of liquid metal in a very high magnetic field (typically 10 T), in which the occurrence of obstacles cannot be avoided.
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).
DEFF Research Database (Denmark)
Witting, Nanna; Andersen, Linda K; Vissing, John
2016-01-01
musculature involvement in the majority of myopathies in which paraspinal musculature was examined. Even in diseases named after a certain pattern of non-axial muscle affection, such as facioscapulohumeral and limb girdle muscular dystrophies, affection of the axial musculature was often severe and early...
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.
Directory of Open Access Journals (Sweden)
Pengfei Sun
2014-01-01
Full Text Available The non-contact magnetostrictive sensor (MsS has been widely used in the guided wave testing of pipes, cables, and so on. However, it has a disadvantage of low excitation efficiency. A new method for enhancing the excitation efficiency of the non-contact MsS for pipe inspection using guided waves, by adjusting the axial length of the excitation magnetic field, is proposed. A special transmitter structure, in which two copper rings are added beside the transmitter coil, is used to adjust the axial length at the expense of weakening the excitation magnetic field. An equivalent vibration model is presented to analyze the influence of the axial length variation. The final result is investigated by experiments. Results show that the excitation efficiency of the non-contact MsS is enhanced in the whole inspection frequency range of the L(0,2 mode if the axial length is adjusted to a certain value. Moreover that certain axial length is the same for pipes of different sizes but made of the same material.
THERMAL STRESS FIELD WHEN CRACK ARREST IN AN AXIAL SYMMETRY METAL DIE USING ELECTROMAGNETIC HEATING
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
In order to solve the thermal stress field around crack tip in metal die when crack prevention using electromagnetic heating, a metal die with a half-embedded round crack was selected as the study object. The complex function method was used as a basis for the theoretical model of the space crack prevention in metal dies using electromagnetic heating. The crack arrest was accomplished by a pulse current discharge through the inner and outer. The theoretical analysis results show that the temperature around the crack tip rises instantly above the melting point of the metal. Small welded joints are formed at a small sphere near the crack tip inside the metal die by metal melting as a result of the heat concentration effect when the current pulse discharged. The thermal compressive stress field appears around the crack tip at the moment. The research results show that the crack prevention using electromagnetic heating can decrease the stress concentration and forms a compressive stress area around the crack tip, and also prevents the main crack from propagating further, and the goal of crack preventing can be reached.
Reactive control of subsonic axial fan noise in a duct.
Liu, Y; Choy, Y S; Huang, L; Cheng, L
2014-10-01
Suppressing the ducted fan noise at low frequencies without varying the flow capacity is still a technical challenge. This study examines a conceived device consisting of two tensioned membranes backed with cavities housing the axial fan for suppression of the sound radiation from the axial fan directly. The noise suppression is achieved by destructive interference between the sound fields from the axial fan of a dipole nature and sound radiation from the membrane via vibroacoustics coupling. A two-dimensional model with the flow effect is presented which allows the performance of the device to be explored analytically. The air flow influences the symmetrical behavior and excites the odd in vacuo mode response of the membrane due to kinematic coupling. Such an asymmetrical effect can be compromised with off-center alignment of the axial fan. Tension plays an important role to sustain the performance to revoke the deformation of the membrane during the axial fan operation. With the design of four appropriately tensioned membranes covered by a cylindrical cavity, the first and second blade passage frequencies of the axial fan can be reduced by at least 20 dB. The satisfactory agreement between experiment and theory demonstrates that its feasibility is practical.
(FIELD) SYMMETRIZATION SELECTION RULES
Energy Technology Data Exchange (ETDEWEB)
P. PAGE
2000-08-01
QCD and QED exhibit an infinite set of three-point Green's functions that contain only OZI rule violating contributions, and (for QCD) are subleading in the large N{sub c} expansion. We prove that the QCD amplitude for a neutral hybrid {l_brace}1,3,5. . .{r_brace}{+-} exotic current to create {eta}{pi}{sup 0} only comes from OZI rule violating contributions under certain conditions, and is subleading in N{sub c}.
Awad, Mervat El-Sayed
1988-10-01
A special perturbation technique of Encke type associated with the Kustaanheimo-Stiefel (KS) regularized variables is developed for satellite motions in the earth's gravitational field with axial symmetry. Its computational algorithm is of recursive nature and could be applied to any perturbed conic motion, whatever the number of the zonal harmonic coefficients may be. Applications of the algorithm are also included.
Field scale simulation of axial hydrokinetic turbines in a natural marine environment
Chawdhary, Saurabh; Angelidis, Dionysios; Shen, Lian; Sotiropoulos, Fotis
2016-11-01
Commercialization of marine and hydrokinetic (MHK) energy technologies is still in the development stage. Existing technologies need fundamental research to enable efficient energy extraction from identified MHK sites. We propose a large eddy simulation (LES)-based framework to investigate the site-specific flow dynamics past MHK arrays in a real-life marine environment. To this end, we use advanced computational tools developed at the Saint Anthony Falls Laboratory (SAFL) to resolve the vast range of scales present in the flow. The new generation unstructured Cartesian flow solver, coupled with a sharp interface immersed boundary method for 3D incompressible flows, is used to numerically investigate New York City's East River, where an array of MHK turbines is to be deployed as part of the Roosevelt Island Tidal Energy (RITE) Project. Multi-resolution simulations on locally refined grids are used to simulate the flow in a section of the East River with detailed river bathymetry and inset turbines at field scale. The results are analyzed in terms of the wake recovery, overall wake dynamics, and the power produced by the turbines. These results will help develop design guidelines for the site-specific turbine array configuration. This work was supported by NSF Grant IIP-1318201.
Institute of Scientific and Technical Information of China (English)
Reza Khazaeinezhad; Mahdi Esmaeilzadeh
2012-01-01
Electron acceleration in the inverse free electron laser (IFEL) with a helical wiggler in the presence of ion-channel guiding and axial magnetic field is investigated in this article.The effects of tapering wiggler amplitude and axial magnetic field are calculated for the electron acceleration.In free electron lasers,electron beams lose energy through radiation while in IFEL electron beams gain energy from the laser.The equation of electron motion and the equation of energy exchange between a single electron and electromagnetic waves are derived and then solved numerically using the fourth order Runge-Kutta method.The tapering effects of a wiggler magnetic field on electron acceleration are investigated and the results show that the electron acceleration increases in the case of a tapered wiggler magnetic field with a proper taper constant.
Palaniappan, D.
2009-04-01
An exact solution for a magnetostatic boundary value problem involving two fused (overlapping) spheres placed in a field generated by an axial magnetic point dipole is constructed based on the image method. The basic idea is illustrated for two unequal superconducting spheres intersecting with a vertex angle π /2 and the analytical solution for the scalar magnetic potential satisfying the Neumann boundary condition at the surface is derived. The image solution for a dipole-twin-sphere configuration consists of three image dipoles—one inside each sphere and the third inside a pseudo-/virtual sphere—all located at the respective inverse points inside the superconducting two-sphere assembly. The levitation force acting on the two-sphere superconducting surface is also calculated for the overlapping geometry. These exact results can be used as a benchmark for testing numerical algorithms for overlapping spherical superconductors. Our simple approach also offers clues for solving the Neumann boundary value problem for vertex angles π /n, n is an integer, and other related superconducting geometries.
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.
Vasiljević, Gorazd
2014-01-01
This BSc thesis deals with certain topics from graph theory. When we talk about studying graphs, we usually mean studying their structure and their structural properties. By doing that, we are often interested in automorphisms of a graph (symmetries), which are permutations of its vertex set, preserving adjacency. There exist graphs, which are symmetric enough, so that automorhism group acts transitively on their vertex set. This means that for any pair of vertices of the graph, there is an a...
Matyjasek, Jerzy
2016-10-01
In this paper, using the general Schwinger-DeWitt approach, we construct the approximate stress-energy tensor of the quantized massive scalar field with arbitrary curvature coupling in D =4 and D =5 classical spacetimes of the electrically charged static black holes with the cosmological constant. Depending on the sign of the cosmological constant we consider both spherically symmetric and topological spacetimes with the special emphasis put on the extremal and ultraextremal configurations. Moreover, we analyze the geometries of the closest vicinity of the degenerate horizons, which topologically are the product of the maximally symmetric subspaces. We solve the semiclassical Einstein field equations for such product spacetimes. Since the transformation k →-k and f''→-f'' leaves the equations unchanged, where k is the curvature of the (D -2 )-dimensional subspace and f'' is the second derivative of the metric potential at the degenerate horizon, it suffices to consider only the spherically symmetric case. It is shown that in four and five dimensions there are forbidden sectors of the parameter space.
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...
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.
Evaluation of the performance and flow in an axial compressor
Waddell, J. L.
1982-10-01
An experimental evaluation of the axial compressor test rig with one stage of symmetric blading was conducted to determine its suitability for studies of tip clearance effects. Measurements were made of performance parameters and internal flow fields. The configuration tested was found to be unsuitable due to poor flow from the inlet guide vanes, particularly near the tip region. Secondary flows and flaws in construction of the guide vanes were suggested as probable causes. Recommendations were made for a program to resolve the problem.
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.
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.
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.
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.
Velikovich, A. L.; Giuliani, J. L.; Clark, R. W.; Mikitchuk, D.; Kroupp, E.; Maron, Y.; Fisher, A.; Schmit, P. F.
2014-10-01
Recent progress in developing the MagLIF approach to pulsed-power driven inertial confinement fusion has stimulated the interest in observation and mitigation of the magnetic Rayleigh-Taylor instability (MRTI) of liners and Z-pinches imploded in an axial magnetic field. Theoretical analysis of these issues is particularly important because direct numerical simulation of the MRTI development is challenging due to intrinsically 3D helical structure of the fastest-growing modes. We review the analytical small-amplitude theory of the MRTI perturbation development and the weakly nonlinear theory of MRTI mode interaction, emphasizing basic physics, opportunity for 3D code verification against exact analytical solutions, and stabilization criteria. The theory is compared to the experimental results obtained at Weizmann Institute with gas-puff Z pinches and on the Z facility at Sandia with solid liners imploded in an axial magnetic field. Work supported by the US DOE/NNSA, and by the US-Israel Binational Science Foundation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
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...
Plane symmetric cosmological models
Yadav, Anil Kumar; Ray, Saibal; Mallick, A
2016-01-01
In this work, we perform the Lie symmetry analysis on the Einstein-Maxwell field equations in plane symmetric spacetime. Here Lie point symmetries and optimal system of one dimensional subalgebras are determined. The similarity reductions and exact solutions are obtained in connection to the evolution of universe. The present study deals with the electromagnetic energy of inhomogeneous universe where $F_{12}$ is the non-vanishing component of electromagnetic field tensor. To get a deterministic solution, it is assumed that the free gravitational field is Petrov type-II non-degenerate. The electromagnetic field tensor $F_{12}$ is found to be positive and increasing function of time. As a special case, to validate the solution set, we discuss some physical and geometric properties of a specific sub-model.
Study of axial magnetic effect
Energy Technology Data Exchange (ETDEWEB)
Braguta, Victor [IHEP, Protvino, Moscow region, 142284 Russia ITEP, B. Cheremushkinskaya street 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Chernodub, M. N. [CNRS, Laboratoire de Mathématiques et Physique Théorique, Université François-Rabelais Tours, Fédération Denis Poisson, Parc de Grandmont, 37200 Tours, France Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium); School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Goy, V. A. [School of Natural Sciences, Far Eastern Federal University, Sukhanova street 8, Vladivostok, 690950 (Russian Federation); Landsteiner, K. [Instituto de Física Teórica UAM/CSIC, C/ Nicolás Cabrera 13-15, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Molochkov, A. V. [School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Ulybyshev, M. [ITEP, B. Cheremushkinskaya street 25, Moscow, 117218 Russia Institute for Theoretical Problems of Microphysics, Moscow State University, Moscow, 119899 (Russian Federation)
2016-01-22
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 T{sup 2} behavior at high temperatures. We find, however, that energy flow is about one order of magnitude lower compared to a theoretical prediction.
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.
Hill, Craig; Sotiropoulos, Fotis; Guala, Michele
2014-11-01
Natural channels ideal for hydrokinetic turbine installations present complex environments containing asymmetric flow, regions of high shear and turbulent eddies that impact turbine performance. To understand the impacts caused by variable topography, baseline conditions in a laboratory flume are compared to turbine performance, flow characteristics, and channel topography measurements from two additional experiments with small-scale and large-scale bathymetric features. Both aligned and staggered multi-turbine configurations were investigated. Small-scale axial-flow rotors attached to miniature DC motors provided measurements of turbine performance and response to i) complex topographic features and ii) flow features induced by upstream turbines. Discussion will focus on optimal streamwise and lateral spacing for axial-flow devices, turbine-topography interactions within arrays and inter-array flow-field measurements. Primary focus will center on results from turbines separated by a streamwise distance of 7dT. Additionally, results indicate possible control strategies for turbines installed in complex natural environments. This work was supported by NSF PFI Grant IIP-1318201, CAREER: Geophysical Flow Control (NSF).
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.
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...
Plasma Control in Symmetric Mirror Machines
Horton, W.; Rowan, W. L.; Alvarado, Igor; Fu, X. R.; Beklemishev, A. D.
2014-10-01
Plasma confinement in the symmetric rotating mirror plasma at the Budker Institute shows enhanced confinement with high electron temperatures with end plates biasing. Improved confinement is achieved by biasing end plate cells in the expansion tanks so as to achieve an inward pointing radial electric field. The negative potential well produces vortex plasma rotation similar to that in the negative potential well of Ohmic heated tokamaks. This plasma state has similarity with the lower turbulence level regimes documented in the Helimak where negative biasing of the end plates produces an inward radial electric field. To understand this vortex confinement we carry out 3D simulations with nonlinear partial differential equations for the electric potential and density in plasmas with an axially localized region of unfavorable and favorable magnetic curvature. The simulations show that the plasma density rapidly adjusts to be higher in the region of favorable curvature regions and remains relatively well confined while rapidly rotating. The results support the concept of using plasma-biasing electrodes in large expander tanks to achieve enhanced mirror plasma confinement. Supported by US-DoE grant to UT, LANL and the Budker Institute for Nuclear Physics.
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...
Surti, S; Karp, J S
2015-07-07
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
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
Maraghechi, Behrouz
2004-01-01
A relativistic theory for Raman backscattering in the beam frame of electrons is presented and is used to find the growth rate of a free-electron laser (FEL), in the Raman regime. A one dimensional helical wiggler and an axial magnetic field are considered. The effects of static self-electric and self-magnetic fields, induced by the steady-state charge density and currents of the non-neutral electron beam, are taken into account to find the steady-state trajectories. The wiggler effects on the linear dispersion relations of the space-charge wave and radiation are included in the analysis. A numerical computation is conducted to compare the growth rate of the excited waves with nonrelativistic treatment. It was found that self-field effects increase the growth rate in the group II orbits and decrease it in the group I orbits. However, the wiggler effects on growth rate are stronger and increase the growth rate on both group I and group II orbits. The discontinuity, due to the cyclotron resonance with the radia...
Suder, K. L.; Hathaway, M. D.; Okiishi, T. H.; Strazisar, A. J.; Adamczyk, J. J.
1987-01-01
This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.
Suder, K. L.; Strazisar, A. J.; Adamczyk, J. J.; Hathaway, M. D.; Okiishi, T. H.
1987-01-01
This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within highspeed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctutions, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.
Energy Technology Data Exchange (ETDEWEB)
Rohdenburg, M.; Saathoff, H.
2002-07-01
Research of TU Brunswick University showed that the performance of single-stage axial blowers is influenced significantly by 3D loss while profile loss is insignificant. Calculation methods should take account of this fact. A characteristic field calculation method was therefore developed based on practical measurements and on a method presented in an earlier publication. New correlations for side wall boundary layer parameters for single-stage axial blowers could be established by this method. This provides a modified characteristic field method and new correlations for calculating characteristic fields with rotor adjustment angles of {+-}15 already in the design stage. The research project was concluded successfully. (orig.) [German] An der TU-Braunschweig in juengerer Zeit durchgefuehrte Forschungsarbeiten zeigen, dass das Betriebsverhalten von einstufigen Ventilatoren axialer Bauart erheblich von den 3D-Verlusten gepraegt wird, die Profilverluste dagegen nur eine kleine Rolle spielen. Ein Kennfeld-Nachrechnungsverfahren sollte daher neben den Profilgrenzschichten (2D-Verluste) auch die Naben- und Gehaeusegrenzschichten (3D-Verluste) in korrekter Weise beruecksichtigen. Zu dessen Entwicklung wurden Grenzschichtkenngroessen der Naben- und Gehaeusegrenzschichten von drei Versuchsventilatoren an einer Reihe von ausgewaehlten Betriebspunkten ermittelt. Bei den Messungen handelte es sich um Sonden- und Hitzdrahtmessungen in den Zu- und Nachlaeufen der Beschaufelungen und um Druckverteilungsmessungen im Gehaeusebereich oberhalb des Rotors; bei ebenfalls noetigen Berechnungen der Geschwindigkeitsverteilungen handelte es sich um einfache Rechnungen mit Hilfe der Gleichgewichtsbedingung. Das Kennlinienberechnungsverfahren wurde in Anlehnung an ein vorhandenes Verfahren aus der Literatur entwickelt. Aus den im Vorhaben gewonnenen Messergebnissen konnten neue Korrelationen der Seitenwandgrenzschichtparameter fuer einstufige Axialventilatoren abgeleitet werden. Damit steht
Jiang, Haiyong
2016-04-11
We present an automatic algorithm for symmetrizing facade layouts. Our method symmetrizes a given facade layout while minimally modifying the original layout. Based on the principles of symmetry in urban design, we formulate the problem of facade layout symmetrization as an optimization problem. Our system further enhances the regularity of the final layout by redistributing and aligning boxes in the layout. We demonstrate that the proposed solution can generate symmetric facade layouts efficiently. © 2015 IEEE.
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.
Chambler, A F; Chapman-Sheath, P J; Pearse, M F; Hollingdale, J
1997-10-01
Chronic recurrent multifocal osteomyelitis is often confused with symmetrical Brodie's abscess as it has a similar pathogenesis. We report an otherwise healthy 17-year-old boy presenting with a true symmetrical Brodie's abscess. We conclude that a symmetrical Brodie's abscess presenting in an otherwise healthy patient is a separate clinical condition with a different management protocol.
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.
Effects of a Kind of Non-smooth Blade on the Unsteady Flow Field at the Exit of an Axial Fan
Institute of Scientific and Technical Information of China (English)
Hongwei MA; Jibo GUO
2008-01-01
An experimental investigation of effects of a kind of streamwise-grooved blade on the unsteady flow field at an exit of an axial-flow fan was performed. The flow field at 25% chord downstream from the trailing edge at hub was measured using a fast-response five-hole pressure probe at different mass-flow conditions. The unsteady flow of the grooved blades was compared with that of the smooth blades. The measurement results indicate that: (1)the grooved blades restrain the velocity fluctuation and the pressure fluctuation by modulating the blade boundary layers, which contributes to the flow loss reduction in the hub region and in the rotor wake region at the design condition; (2) the atream-wise grooves play an important role in restraining the radial migration in the blade boundary layer and abating the tip flow mixing, which contributes to the flow loss reduction in the tip region at the design condition; (3) at the near stall condition, the grooved surface can not reduce the flow loss, even increase the loss nearby when the separation happens in the blade boundary layer.
Effects of a kind of non-smooth blade on the unsteady flow field at the exit of an axial fan
Hongwei, Ma; Jibo, Guo
2008-03-01
An experimental investigation of effects of a kind of streamwise-grooved blade on the unsteady flow field at an exit of an axial-flow fan was performed. The flow field at 25% chord downstream from the trailing edge at hub was measured using a fast-response five-hole pressure probe at different mass-flow conditions. The unsteady flow of the grooved blades was compared with that of the smooth blades. The measurement results indicate that: (1) the grooved blades restrain the velocity fluctuation and the pressure fluctuation by modulating the blade boundary layers, which contributes to the flow loss reduction in the hub region and in the rotor wake region at the design condition; (2) the stream-wise grooves play an important role in restraining the radial migration in the blade boundary layer and abating the tip flow mixing, which contributes to the flow loss reduction in the tip region at the design condition; (3) at the near stall condition, the grooved surface can not reduce the flow loss, even in-crease the loss nearby when the separation happens in the blade boundary layer.
Particle-vortex symmetric liquid
Mulligan, Michael
2017-01-01
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 by Breznay et al. [Proc. Natl. Acad. Sci. USA 113, 280 (2016), 10.1073/pnas.1522435113] to exhibit particle-vortex symmetric electrical response, and the nearby metallic phase discovered earlier by Mason and Kapitulnik [Phys. Rev. Lett. 82, 5341 (1999), 10.1103/PhysRevLett.82.5341] 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 a (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 require the introduction of disorder; rather, it results when the Dirac fermions exhibit vanishing Hall effect. The theory predicts approximately equal (diagonal) thermopower and Nernst signal with a deviation parameterized by the measured electrical Hall response at the symmetric point.
Chen, Kan; Liu, Xiang; Matsuki, Takayuki
2015-01-01
Inspired by the abundant experimental observation of axial vector states, we study whether the observed axial vector states can be categorized into the conventional axial vector meson family. In this paper we carry out analysis based on the mass spectra and two-body Okubo-Zweig-Iizuka-allowed decays. Besides testing the possible axial vector meson assignments, we also predict abundant information for their decays and the properties of some missing axial vector mesons, which are valuable to further experimental exploration of the observed and predicted axial vector mesons.
Wave Propagation through Axially-Symmetric Dielectric Shells.
1980-02-01
estimating the amplitude and phase of guided waves excited on finite dielectric slabs by incident plane waves. The procedure is based onj the moment...8217 ’ " ] cos2 ,0 dado dz, (4-69) x2 2 where = (ao - ap’ cos0 -zz’) (4-70) and [...1 [6 (+6p)-6 (a-6p)-a -1 . (4-71) After doing the integrals, we have
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...
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.
Convection in axially symmetric accretion discs with microscopic transport coefficients
Malanchev, K. L.; Postnov, K. A.; Shakura, N. I.
2017-01-01
The vertical structure of stationary thin accretion discs is calculated from the energy balance equation with heat generation due to microscopic ion viscosity η and electron heat conductivity κ, 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 dependence of the viscosity coefficient on temperature is assumed. A polytropic-like structure in this case is found for Thomson scattering-dominated opacity.
Refractive index determination in axially symmetric oprtically inhomogeneous media
Ionescu-Pallas, Nicholas; Vlad, Valentin I.; Bociort, Florian
The focussing method from transversally light, put forward by Dietrich Marcuse in view of determining the refractive index profile (RIP) in optical fibers and fiber performs, is revised. A more rigorous derivation of the Marcuse formula is given, establishing the conditions of its validity and a simplified version is initially proposed, able to avoid the systematic errors in the processing of light intensity data.
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.
Minimum Ballistic Factor Problem of Slender Axial Symmetric Missiles
Directory of Open Access Journals (Sweden)
V. B. Tawakley
1979-01-01
Full Text Available The problem of determining the geometry of slender, axisymmetric missiles of minimum ballistic factor in hypersonic flow has been solved via the calculus of variations under the assumptions that the flow is Newtonian and the surface averaged skin-friction coefficient is constant. The study has been made for conditions of given length and diameter, given diameter and surfacearea, and given surface area and length. The earlier investigations/sup 8/ where only regular shapes were determined has been extended to cover those class of bodies which consist of regular shapes followed or preceded by zero slope shapes.
Quéva, Julien
2015-01-01
This article investigates the properties of a set of conformally invariant equations on conformally flat Einstein spacetimes. These equations are shown to be gauge invariant if $d=4$. We provide a conformally invariant gauge condition to that equation which generalizes in a simple manner, on those spacetimes, the Eastwood-Singer gauge condition. A byproduct of this conformally invariant gauge fixing equation is an alternate proof of Branson's factorization formula of GJMS operators on Einstein manifolds for $d=4$. A field strength $F$ is built upon the field $A$, its properties are worked out in details.
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.
Lu, Bing-Nan; Zhao, En-Guang; Zhou, Shan-Gui
2013-01-01
We have developed multi-dimensional constrained covariant density functional theories (MDC-CDFT) for finite nuclei in which the shape degrees of freedom \\beta_{\\lambda\\mu} with even \\mu, e.g., \\beta_{20}, \\beta_{22}, \\beta_{30}, \\beta_{32}, \\beta_{40}, etc., can be described simultaneously. The functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. For the pp channel, either the BCS approach or the Bogoliubov transformation is implemented. The MDC-CDFTs with the BCS approach for the pairing (in the following labelled as MDC-RMF models with RMF standing for "relativistic mean field") have been applied to investigate multi-dimensional potential energy surfaces and the non-axial octupole $Y_{32}$-correlations in N=150 isotones. In this contribution we present briefly the formalism of MDC-RMF models and some results from these models. The potential energy surfaces with and without triaxial deformatio...
Hathaway, M. D.; Suder, K. L.; Strazisar, A. J.; Adamczyk, J. J.; Okiishi, T. H.
1987-01-01
Unsteady velocity field measurements made within the stator row of a transonic axial-flow fan are presented. Measurements were obtained at midspan for two different stator blade rows using a laser anemometer. The first stator row consists of double circular-arc airfoils with a solidity of 1.68. The second features controlled-diffusion airfoils with a solidity of 0.85. Both were tested at design-speed peak efficiency conditions. In addition, the controlled-diffusion stator was also tested at near stall conditions. The procedures developed here are used to identify the rotor wake generated and unresolved unsteadiness from the velocity measurements (rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and unresolved unsteadiness refers to all remaining unsteadiness which contributes to the spread in the distribution of velocities such as vortex shedding, turbulence, etc.). Auto and cross correlations of these unsteady velocity fluctuations are presented to show their relative magnitude and spatial distributions. Amplification and attenuation of both rotor wake generated and unresolved unsteadiness are shown to occur within the stator blade passage.
Hathaway, M. D.; Suder, K. L.; Okiishi, T. H.; Strazisar, A. J.; Adamczyk, J. J.
1987-01-01
Unsteady velocity field measurements made within the stator row of a transonic axial-flow fan are presented. Measurements were obtained at midspan for two different stator blade rows using a laser anemometer. The first stator row consists of double circular-arc airfoils with a solidity of 1.68. The second features controlled-diffusion airfoils with a solidity of 0.85. Both were tested at design-speed peak efficiency conditions. In addition, the controlled-diffusion stator was also tested at near stall conditions. The procedures developed here are used to identify the rotor wake generated and unresolved unsteadiness from the velocity measurements (rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and unresolved unsteadiness refers to all remaining unsteadiness which contributes to the spread in the distribution of velocities such as vortex shedding, turbulence, etc.). Auto and cross correlations of these unsteady velocity fluctuations are presented to show their relative magnitude and spatial distributions. Amplification and attenuation of both rotor wake generated and unresolved unsteadiness are shown to occur within the stator blade passage.
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.
MEASUREMENT AND VISUALIZATION OF FLOW FIELD IN AXIAL FLOW FAN%在轴流风扇中的流场测量和显示
Institute of Scientific and Technical Information of China (English)
葛宁
2000-01-01
介绍了利用激光多普勒测速仪(LDA)和激光片光流场显示技术在一轴流风扇转子叶尖附近流场测量得到的结果.试验结果表明,转子叶尖处的通道涡并不是叶尖间隙流卷起造成的,而是由于端壁附面层受到叶尖间隙流的横向冲击后从机匣壁面上脱落形成的.%An experimental investigation associated with the basic fluid mechanics in an axial flow fan is described in this paper. The flow field in the tip region has been studied by laser Doppler anemometer (LDA) and flow visualization technique. Some experimental data and images are interpreted to understand the complex interactions between the annulus wall boundary layer and the leakage flow. It shows that the vortex inside the blade passage is produced by the separation of annulus wall boundary layer rather than the rolling up of leakage flow.
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...
Relativistic RPA in axial symmetry
Arteaga, D Pena; 10.1103/PhysRevC.77.034317
2009-01-01
Covariant density functional theory, in the framework of self-consistent Relativistic Mean Field (RMF) and Relativistic Random Phase approximation (RPA), is for the first time applied to axially deformed nuclei. The fully self-consistent RMF+RRPA equations are posed for the case of axial symmetry and non-linear energy functionals, and solved with the help of a new parallel code. Formal properties of RPA theory are studied and special care is taken in order to validate the proper decoupling of spurious modes and their influence on the physical response. Sample applications to the magnetic and electric dipole transitions in $^{20}$Ne are presented and analyzed.
Canteaut, Anne; Videau, Marion
2005-01-01
http://www.ieee.org/; We present an extensive study of symmetric Boolean functions, especially of their cryptographic properties. Our main result establishes the link between the periodicity of the simplified value vector of a symmetric Boolean function and its degree. Besides the reduction of the amount of memory required for representing a symmetric function, this property has some consequences from a cryptographic point of view. For instance, it leads to a new general bound on the order of...
DÍaz, R.; Rivas, M.
2010-01-01
In order to study Boolean algebras in the category of vector spaces we introduce a prop whose algebras in set are Boolean algebras. A probabilistic logical interpretation for linear Boolean algebras is provided. An advantage of defining Boolean algebras in the linear category is that we are able to study its symmetric powers. We give explicit formulae for products in symmetric and cyclic Boolean algebras of various dimensions and formulate symmetric forms of the inclusion-exclusion principle.
Axial symmetry and conformal Killing vectors
Mars, M; Mars, Marc; Senovilla, Jose M.M.
1993-01-01
Axisymmetric spacetimes with a conformal symmetry are studied and it is shown that, if there is no further conformal symmetry, the axial Killing vector and the conformal Killing vector must commute. As a direct consequence, in conformally stationary and axisymmetric spacetimes, no restriction is made by assuming that the axial symmetry and the conformal timelike symmetry commute. Furthermore, we prove that in axisymmetric spacetimes with another symmetry (such as stationary and axisymmetric or cylindrically symmetric spacetimes) and a conformal symmetry, the commutator of the axial Killing vector with the two others mush vanish or else the symmetry is larger than that originally considered. The results are completely general and do not depend on Einstein's equations or any particular matter content.
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...
Modelling larval transport in a axial convergence front
Robins, P.
2010-12-01
Marine larvae exhibit different vertical swimming behaviours, synchronised by factors such as tidal currents and daylight, in order to aid retention near the parent populations and hence promote production, avoid predation, or to stimulate digestion. This paper explores two types of larval migration in an estuarine axial convergent front which is an important circulatory mechanism in many coastal regions where larvae are concentrated. A parallelised, three-dimensional, ocean model was applied to an idealised estuarine channel which was parameterised from observations of an axial convergent front which occurs in the Conwy Estuary, U.K. (Nunes and Simpson, 1985). The model successfully simulates the bilateral cross-sectional recirculation of an axial convergent front, which has been attributed to lateral density gradients established by the interaction of the lateral shear of the longitudinal currents with the axial salinity gradients. On the flood tide, there is surface axial convergence whereas on the ebb tide, there is (weaker) surface divergence. Further simulations with increased/decreased tidal velocities and with stronger/weaker axial salinity gradients are planned so that the effects of a changing climate on the secondary flow can be understood. Three-dimensional Lagrangian Particle Tracking Models (PTMs) have been developed which use the simulated velocity fields to track larvae in the estuarine channel. The PTMs take into account the vertical migrations of two shellfish species that are commonly found in the Conwy Estuary: (i) tidal migration of the common shore crab (Carcinus maenas) and (ii), diel (daily) migration of the Great scallop (Pecten maximus). These migration behaviours are perhaps the most widespread amongst shellfish larvae and have been compared with passive (drifting) particles in order to assess their relative importance in terms of larval transport. Preliminary results suggest that the net along-estuary dispersal over a typical larval
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.
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.
Inverse Symmetric Inflationary Attractors
Odintsov, S D
2016-01-01
We present a class of inflationary potentials which are invariant under a special symmetry, which depends on the parameters of the models. As we show, in certain limiting cases, the inverse symmetric potentials are qualitatively similar to the $\\alpha$-attractors models, since the resulting observational indices are identical. However, there are some quantitative differences which we discuss in some detail. As we show, some inverse symmetric models always yield results compatible with observations, but this strongly depends on the asymptotic form of the potential at large $e$-folding numbers. In fact when the limiting functional form is identical to the one corresponding to the $\\alpha$-attractors models, the compatibility with the observations is guaranteed. Also we find the relation of the inverse symmetric models with the Starobinsky model and we highlight the differences. In addition, an alternative inverse symmetric model is studied and as we show, not all the inverse symmetric models are viable. Moreove...
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
Energy Technology Data Exchange (ETDEWEB)
Tipler, F.J.
1977-08-01
Causally symmetric spacetimes are spacetimes with J/sup +/(S) isometric to J/sup -/(S) for some set S. We discuss certain properties of these spacetimes, showing for example that, if S is a maximal Cauchy surface with matter everywhere on S, then the spacetime has singularities in both J/sup +/(S) and J/sup -/(S). We also consider totally vicious spacetimes, a class of causally symmetric spacetimes for which I/sup +/(p) =I/sup -/(p) = M for any point p in M. Two different notions of stability in general relativity are discussed, using various types of causally symmetric spacetimes as starting points for perturbations.
Energy Technology Data Exchange (ETDEWEB)
Davies, C.L.; Maslen, E.N.
1983-12-21
A procedure for solving the few-particle Schroedinger equation exactly is applied to a model system consisting of two identical particles and a massive third particle. The type of interaction potential is not specified except that it should not diverge more rapidly than r/sup -2/ at the particle positions. Allowable interactions include the Coulomb and the harmonic oscillator potentials. The principles are illustrated by reference to the spatially symmetric states of the system.
Dunajewski, Adam; Dusza, Jacek J.; Rosado Muñoz, Alfredo
2014-11-01
The article presents a proposal for the description of human gait as a periodic and symmetric process. Firstly, the data for researches was obtained in the Laboratory of Group SATI in the School of Engineering of University of Valencia. Then, the periodical model - Mean Double Step (MDS) was made. Finally, on the basis of MDS, the symmetrical models - Left Mean Double Step and Right Mean Double Step (LMDS and RMDS) could be created. The method of various functional extensions was used. Symmetrical gait models can be used to calculate the coefficients of asymmetry at any time or phase of the gait. In this way it is possible to create asymmetry, function which better describes human gait dysfunction. The paper also describes an algorithm for calculating symmetric models, and shows exemplary results based on the experimental data.
Periodicity effects of axial waves in elastic compound rods
DEFF Research Database (Denmark)
Nielsen, R. B.; Sorokin, S. V.
2015-01-01
Floquet analysis is applied to the Bernoulli-Euler model for axial waves in a periodic rod. Explicit asymptotic formulae for the stop band borders are given and the topology of the stop band pattern is explained. Eigenfrequencies of the symmetric unit cell are determined by the Phase-closure Prin...
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...
Time-Symmetric Approach to Gravity
Chu, S Y
1998-01-01
Quantization of the time symmetric system of interacting strings requires that gravity, just as electromagnetism in Wheeler-Feynman's time symmetric electro- dynamics, also be an "adjunct field" instead of an independent entity. The "adjunct field" emerges, at a scale large compared to that of the strings, as a "statistic" that summarizes how the string positions in the underlying space- time are "compactified" into those in Minkowski space. We are able to show, WITHOUT adding a scalar curvature term to the string action, that the "adjunct gravitational field" satisfies Einstein's equation with no cosmological term.
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.
Bender, Carl M.
2015-07-01
The average quantum physicist on the street would say that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under combined matrix transposition and complex conjugation) in order to guarantee that the energy eigenvalues are real and that time evolution is unitary. However, the Hamiltonian H = p2 + ix3, which is obviously not Dirac Hermitian, has a positive real discrete spectrum and generates unitary time evolution, and thus it defines a fully consistent and physical quantum theory. Evidently, the axiom of Dirac Hermiticity is too restrictive. While H = p2 + ix3 is not Dirac Hermitian, it is PT symmetric; that is, invariant under combined parity P (space reflection) and time reversal T. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics is extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past few years, some of these properties have been verified in laboratory experiments. A particularly interesting PT-symmetric Hamiltonian is H = p2 - x4, which contains an upside-down potential. This potential is discussed in detail, and it is explained in intuitive as well as in rigorous terms why the energy levels of this potential are real, positive, and discrete. Applications of PT-symmetry in quantum field theory are also discussed.
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.
Notari, Alessio; Tywoniuk, Konrad
2016-12-01
We analyze in detail the background cosmological evolution of a scalar field coupled to a massless abelian gauge field through an axial term phi/fγ F ~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 ρR, which can lead to inflation without the need of a flat potential. We analyze the system, for momenta k smaller than the cutoff fγ, including the backreaction numerically. We consider the evolution from a given static initial condition and explicitly show that, if fγ is smaller than the field excursion phi0 by about a factor of at least Script O (20), there is a friction effect which turns on before 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 perturbations, scalars and tensors. Such oscillations have a period of 4-5 efolds and an amplitude which is typically less than a few percent and decreases linearly with fγ. We also stress that the curvature perturbation on uniform density slices should be sensitive to slow-roll parameters related to ρR rather than dot phi2/2 and we discuss the existence of friction terms acting on the perturbations, although we postpone a calculation of the power spectrum and of non-gaussianity to future work and we simply define and compute suitable slow roll parameters. Finally we stress that this scenario may be realized in the axion case, if the coupling 1/fγ to U(1) (photons) is much larger than the coupling 1/fG to non-abelian gauge fields (gluons), since the latter sets the range of the potential and therefore the maximal allowed phi0~ fG.
Adamczyk, John J.
1996-01-01
The role of unsteady flow processes in establishing the performance of axial flow turbomachinery was investigated. The development of the flow model, as defined by the time average flow equations associated with the passage of the blade row embedded in a multistage configuration, is presented. The mechanisms for unsteady momentum and energy transport is outlined. The modeling of the unsteady momentum and energy transport are discussed. The procedure for simulating unsteady multistage turbomachinery flows is described.
Directory of Open Access Journals (Sweden)
Margaret Tzaphlidou
2004-01-01
Full Text Available 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.
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
Brachat, Jerome; Mourrain, Bernard; Tsigaridas, Elias
2009-01-01
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 total degree d as a sum of powers of linear forms (Waring's problem), incidence properties on secant varieties of the Veronese Variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester's approach from the dual point of view. Exploiting this duality, we propose necessary and sufficient conditions for the existence of such a decomposition of a given rank, using the properties of Hankel (and quasi-Hankel) matrices, derived from multivariate polynomials and normal form computations. This leads to the resolution of polynomial equations of small degree in non-generic cases. We propose a new algorithm for symmetric tensor decomposition, based on th...
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...
Multiparty Symmetric Sum Types
DEFF Research Database (Denmark)
Nielsen, Lasse; Yoshida, Nobuko; Honda, Kohei
2010-01-01
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...... with 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...
Immanant Conversion on Symmetric Matrices
Directory of Open Access Journals (Sweden)
Purificação Coelho M.
2014-01-01
Full Text Available Letr Σn(C denote the space of all n χ n symmetric matrices over the complex field C. The main objective of this paper is to prove that the maps Φ : Σn(C -> Σn (C satisfying for any fixed irre- ducible characters X, X' -SC the condition dx(A +aB = dχ·(Φ(Α + αΦ(Β for all matrices A,В ε Σ„(С and all scalars a ε C are automatically linear and bijective. As a corollary of the above result we characterize all such maps Φ acting on ΣИ(С.
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.
Institute of Scientific and Technical Information of China (English)
孟康; 陈旺生; 梅丹
2012-01-01
针对现有蝶阀存在易磨损、使用寿命短等问题,研制出一种对称多叶片式耐磨风量调节阀。利用标准κ-ε模型对该阀的流场进行了数值模拟,并与蝶阀进行了对比研究,结果表明,该阀流场分布比较均匀,无偏流现象,阀体边壁处流体速度较小,结构合理,具有较好的耐磨性能。%To solve the problems of current butterfly valves such as easiness of wearing and short service lifespan etc.,a kind of symmetric multi-vane wear-resistant air flow regulating valve was developed.The standard κ-ε model was applied to carry out the numerical simulation of the flow field,and then the simulation results was compared with that of the butterfly valve.The simulation results showed that the flow field of the symmetric multi-vane wear-resistant air flow regulating valve was distributed uniformly without flow deviation,and the flow velocity at the valve wall was low;the structure and the wear-resistance performance of the new valve were excellent.
Kononets, Yu. V.
2016-12-01
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.
Distributed Searchable Symmetric Encryption
Bösch, Christoph; Peter, Andreas; Leenders, Bram; Lim, Hoon Wei; Tang, Qiang; Wang, Huaxiong; Hartel, Pieter; Jonker, Willem
2014-01-01
Searchable Symmetric Encryption (SSE) allows a client to store encrypted data on a storage provider in such a way, that the client is able to search and retrieve the data selectively without the storage provider learning the contents of the data or the words being searched for. Practical SSE schemes
Symmetric Spaces in Supergravity
Ferrara, Sergio
2008-01-01
We exploit the relation among irreducible Riemannian globally symmetric spaces (IRGS) and supergravity theories in 3, 4 and 5 space-time dimensions. IRGS appear as scalar manifolds of the theories, as well as moduli spaces of the various classes of solutions to the classical extremal black hole Attractor Equations. Relations with Jordan algebras of degree three and four are also outlined.
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.
Generating functions for symmetric and shifted symmetric functions
Jing, Naihuan; Rozhkovskaya, Natasha
2016-01-01
We describe generating functions for several important families of classical symmetric functions and shifted Schur functions. The approach is originated from vertex operator realization of symmetric functions and offers a unified method to treat various families of symmetric functions and their shifted analogues.
EQUIFOCAL HYPERSURFACES IN SYMMETRIC SPACES
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This note investigates the multiplicity problem of principal curvatures of equifocal hyper surfaces in simply connected rank 1 symmetric spaces. Using Clifford representation theory, and the author also constructs infinitely many equifocal hypersurfaces in the symmetric spaces.
Faults Analysis of the Axial Magnetic Field Switched Reluctance Drive System%轴向磁场开关磁阻电机系统的故障分析∗
Institute of Scientific and Technical Information of China (English)
李洋; 王德明; 张广明; 梅磊
2014-01-01
The structure of an axial magnetic field switched reluctance motor was briefly introduced, and the winding faults and power converter were analyzed. The fault of power converter frequently occurs in the axial magnetic field switched reluctance drive system and the winding is the weakest part of the motor. The mechanism of these two faults was illustrated, and the conception of fault tolerant control method of switched reluctance motor was put forward.%介绍了轴向磁场开关磁阻电机的结构，对功率变换器的故障和电机本体的绕组故障进行分析。功率变换器是开关磁阻电机系统中发生故障比较频繁的环节之一，电机的绕组是开关磁阻电机本体上最薄弱的部分。详细说明了这两类故障的发生机理，并提出开关磁阻电机容错控制方法的构想。
Chen, Yan; Feng, Huijuan; Ma, Jiayao; Peng, Rui; You, Zhong
2016-06-01
The traditional waterbomb origami, produced from a pattern consisting of a series of vertices where six creases meet, is one of the most widely used origami patterns. From a rigid origami viewpoint, it generally has multiple degrees of freedom, but when the pattern is folded symmetrically, the mobility reduces to one. This paper presents a thorough kinematic investigation on symmetric folding of the waterbomb pattern. It has been found that the pattern can have two folding paths under certain circumstance. Moreover, the pattern can be used to fold thick panels. Not only do the additional constraints imposed to fold the thick panels lead to single degree of freedom folding, but the folding process is also kinematically equivalent to the origami of zero-thickness sheets. The findings pave the way for the pattern being readily used to fold deployable structures ranging from flat roofs to large solar panels.
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 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
Symmetrization Selection Rules, 1
Page, P R
1996-01-01
We introduce a category of strong and electromagnetic interaction selection rules for the two-body connected decay and production of exotic J^{PC} = 0^{+-}, 1^{-+}, 2^{+-}, 3^{-+}, ... hybrid and four-quark mesons. The rules arise from symmetrization in states in addition to Bose symmetry and CP invariance. Examples include various decays to \\eta'\\eta, \\eta\\pi, \\eta'\\pi and four-quark interpretations of a 1^{-+} signal.
Symmetrization Selection Rules, 2
Page, P R
1996-01-01
We introduce strong interaction selection rules for the two-body decay and production of hybrid and conventional mesons coupling to two S-wave hybrid or conventional mesons. The rules arise from symmetrization in states in the limit of non-relativistically moving quarks. The conditions under which hybrid coupling to S-wave states is suppressed are determined by the rules, and the nature of their breaking is indicated.
The experimental study of acoustic field in an asymmetric borehole
Institute of Scientific and Technical Information of China (English)
LINWeijun; ZHANGChengyu; ZHANGHailan; WANGXiuming
2003-01-01
The acoustic field in an asymmetric borehole was investigated by recording and comparing the waveforms with different offset in both axial symmetric borehole and axial asymmetric borehole. The two-dimensional spectrum in wave-number and frequency domain was also calculated and compared with the result of numeric simulation with 2.5-D finite difference method, and a consistent result was obtained. This work provides an accurate verification of our investigation of asymmetric borehole with 2.5-D finite difference method.
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.
Exterior Powers of Symmetric Bilinear Forms
Institute of Scientific and Technical Information of China (English)
Seán McGarraghy
2002-01-01
We study exterior powers of classes of symmetric bilinear forms in the Witt-Grothendieck ring of a field of characteristic not equal to 2, and derive their basic properties. The exterior powers are used to obtain annihilating polynomials for quadratic forms in the Witt ring.
Institute of Scientific and Technical Information of China (English)
李淼; 徐建博
2012-01-01
复合域乘法运算是对称密码算法中的基本运算和重要模块,因操作复杂且计算时间长,其实现性能在很大程度上制约着对称密码算法的运算速度.文章研究了对称密码算法中的复合域乘法运算特点及实现原理,设计了以GF(28)为基域,扩展到GF((28)k)(k=1,2,3,4)域上的复合域乘法可重构架构,通过配置能够灵活高效地实现GF(28)、GF((28)2)、GF((28)3)、GF((28)4)域上的有限域乘法操作.同时结合处理器的指令设计方法,设计了通用的复合域乘法操作及配置指令,能够极大的提高对称密码算法中复合域乘法运算的处理效率.最后文章对复合域乘法可重构架构进行了模拟与验证,在0.18μm CMOS工艺标准单元库下进行逻辑综合以及布局布线,并对综合结果进行了性能评估.结果表明,文章提出的复合域乘法可重构架构及相应的专用指令,在灵活性的前提下提供了较高的执行效率,具有较高的实用价值.% The composite field multiplication is a basic operation and important module in symmetric cipher algorithms. Due to complicated operation and long computation time, the performance of composite field multiplication restricts the computing speed of symmetric cipher algorithms to a large extent. In this paper, the operating characteristics and realization principle of composite field multiplication have been researched, and a reconfigurable architecture of composite field multiplication on GF(28) basic field and extend to GF((28)k)(k=1,2,3,4) extension field has been presented. By configuration, this architecture can implement finite field multiplication operation on GF(28), GF((28)2), GF((28)3) and GF((28)4) flexibly and efficiently. In the meanwhile, combined with instruction design method of general-purpose processors, general composite field multiplication operation and configuration instructions have been designed, which can greatly improve the processing
Altered Axial Skeletal Development
The axial skeleton is routinely examined in standard developmental toxicity bioassays and has proven to be sensitive to a wide variety of chemical agents. Dysmorphogenesis in the skull, vertebral column and ribs has been described in both human populations and in laboratory anima...
Flow Field Characteristics Analysis of Axial Flow Pump Based on CFD%基于 CFD的轴流泵流场特性分析
Institute of Scientific and Technical Information of China (English)
曹婷; 郑源
2014-01-01
For more further research on axial-flow pump,learning pump running under different conditions and to further emphasizing the impor-tance of optimal conditions running,combined with a model pump data in South-to-North Water Transfer Project,the model pump were numerically simulated by using CFD software Fluent with multiple reference system coordinates were chosen and based on the S-A turbulence model. Axial flow pump hydraulic performance under different conditions were estimated by calculating,the external characteristic curve were drawn. Compared with the experimental result,they were approximate,showing the simulation’s accuracy. The pressure and velocity distribution of blade and guide vanes were analyzed based on the result of the numerical simulation. Some laws of blade and guide vanes’flow pattern under different conditions were showed,the bland pressure was increased in the radial. The magnitude of relative velocity presented cylindrical surface distribution increased from hub to rim. The pressure of Guide vanes was presented as zonal distribution and water flowed out along the axial finally.%为更深入研究轴流泵，了解不同工况下轴流泵的运行状态，进一步强调最优工况运行的重要性，结合南水北调工程中某泵站模型的数据，采用流体力学软件Fluent，在多重参考坐标系下，选用S-A湍流模型对模型泵进行数值模拟。通过计算，对不同工况下的轴流泵水力性能进行了预估，绘制了轴流泵的特性曲线，与试验值进行比较，吻合较好，说明了数值模拟的准确性。根据数值计算结果，分析了轴流泵叶轮叶片和导叶叶片表面的速度及压力分布，揭示了叶片和导叶表面流态和压力的分布规律：叶片压力径向递增，相对速度由轮毂到轮缘逐渐加快，按圆柱面分布，导叶表面压力呈带状分布，水流最终从导叶出口沿轴向流出。
Radiative corrections in symmetrized classical electrodynamics
Van Meter JR; Kerman; Chen; Hartemann
2000-12-01
The physics of radiation reaction for a point charge is discussed within the context of classical electrodynamics. The fundamental equations of classical electrodynamics are first symmetrized to include magnetic charges: a double four-potential formalism is introduced, in terms of which the field tensor and its dual are employed to symmetrize Maxwell's equations and the Lorentz force equation in covariant form. Within this framework, the symmetrized Dirac-Lorentz equation is derived, including radiation reaction (self-force) for a particle possessing both electric and magnetic charge. The connection with electromagnetic duality is outlined, and an in-depth discussion of nonlocal four-momentum conservation for the wave-particle system is given.
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Density functional theory (DFT) calculations were carried out to investigate the organic field effect transistor (OFET) performance of the symmetrical metal-free tetrakis (1,2,5-thiadiazole) porphyrazine (S4)PzH2 and tetrakis (1,4-diamyloxybenzene) (A4)PzH2 as well as the low-symmetry metal-free porphy- razine with annulated 1,2,5-thiadiazole and 1,4-diamyloxybenzene groups in the ratio 2:2 (cis) and 1:3, that is, (cis-S2A2)PzH2 and (SA3)PzH2, (S = 1,2,5-thiadiazole ring, A = annulated 1,4-diamyloxy-benzene ring, Pz = porphyrazine) in terms of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy, ionization energy (IE), electron affinity (EA), and their reorganization energy (λ) during the charge-transport process. On the basis of Marcus electron transfer theory, electronic couplings (V) and field effect transistor (FET) properties for the four compounds with known crystal structure have been calculated. The electron transfer mobility (μ -) is revealed to be 0.056 cm2·V-1·s-1 for (S4)PzH2. The hole transfer mobility (μ+) is 0.075, 0.098, and 8.20 cm2·V-1·s-1 for (cis-S2A2)PzH2, (SA3)PzH2, and (A4)PzH2, respectively. The present work represents the theoretical effort towards understanding the OFET properties of symmetrical and unsymmetrical porphyrazine derivatives with annulated 1,2,5-thiadiazole and 1,4-diamyloxybenzene.
Symmetric Tensor Decomposition
DEFF Research Database (Denmark)
Brachat, Jerome; Comon, Pierre; Mourrain, Bernard;
2010-01-01
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 total degree d as a sum of powers of linear forms (Waring’s problem), incidence properties on secant varieties of the Veronese variety and the representation of linear forms as a linear combination of evaluations at distinct points. Then we reformulate Sylvester’s approach from the dual point of view...
Symmetrically Constrained Compositions
Beck, Matthias; Lee, Sunyoung; Savage, Carla D
2009-01-01
Given integers $a_1, a_2, ..., a_n$, with $a_1 + a_2 + ... + a_n \\geq 1$, a symmetrically constrained composition $\\lambda_1 + lambda_2 + ... + lambda_n = M$ of $M$ into $n$ nonnegative parts is one that satisfies each of the the $n!$ constraints ${\\sum_{i=1}^n a_i \\lambda_{\\pi(i)} \\geq 0 : \\pi \\in S_n}$. We show how to compute the generating function of these compositions, combining methods from partition theory, permutation statistics, and lattice-point enumeration.
Numerical Simulation and Flow Behaviors of Taylor Flow in Co-Axial Rotating Cylinder
Directory of Open Access Journals (Sweden)
Sheng Chung Tzeng
2014-04-01
Full Text Available This work uses the incense as the trace of flow to perform flow visualization of Taylor-Couette flow. The test section was made of a rotational inner cylinder and a stationary outer cylinder. Two modes of inner cylinder were employed. One had a smooth wall, and the other had an annular ribbed wall. Clear and complete Taylor vortices were investigated in both smooth and ribbed wall of co-axial rotating cylinder. Besides, a steady-state, axis-symmetrical numerical model was provided to simulate the present flow field. The Taylor vortices could be also successfully predicted. However, the assumption of steady-state flow might reduce some flow perturbations, resulting in an over-predicted critical Taylor number. A transient simulation is suggested to be performed in the future.
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.
Sirsi, Swarnamala; Hegde, Subramanya
2011-01-01
Quantum computation on qubits can be carried out by an operation generated by a Hamiltonian such as application of a pulse as in NMR, NQR. Quantum circuits form an integral part of quan- tum computation. We investigate the nonlocal operations generated by a given Hamiltonian. We construct and study the properties of perfect entanglers, that is, the two-qubit operations that can generate maximally entangled states from some suitably chosen initial separable states in terms of their entangling power. Our work addresses the problem of analyzing the quantum evolution in the special case of two qubit symmetric states. Such a symmetric space can be considered to be spanned by the angular momentum states {|j = 1,m>;m = +1, 0,-1}. Our technique relies on the decomposition of a Hamiltonian in terms of newly defined Hermitian operators Mk's (k= 0.....8) which are constructed out of angular momentum operators Jx, Jy, Jz. These operators constitute a linearly independent set of traceless matrices (except for M0). Further...
Institute of Scientific and Technical Information of China (English)
Weibin Chen; Qiwen Zhan
2007-01-01
Plasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM)probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D)finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, taper angle of the probe, and the metal film thickness. The tolerance of the alignment angle is investigated. Probe designs with different metal coatings and their enhancement performance are studied as well. The nanometric spot size at the tip apex and high field enhancement of the apertureless NSOM probe have important potential application in semiconductor metrology.
The Symmetricity of Normal Modes in Symmetric Complexes
Song, Guang
2016-01-01
In this work, we look at the symmetry of normal modes in symmetric structures, particularly structures with cyclic symmetry. We show that normal modes of symmetric structures have different levels of symmetry, or symmetricity. One novel theoretical result of this work is that, for a ring structure with $m$ subunits, the symmetricity of the normal modes falls into $m$ groups of equal size, with normal modes in each group having the same symmetricity. The normal modes in each group can be computed separately, using a much smaller amount of memory and time (up to $m^3$ less), thus making it applicable to larger complexes. We show that normal modes with perfect symmetry or anti-symmetry have no degeneracy while the rest of the modes have a degeneracy of two. We show also how symmetry in normal modes correlates with symmetry in structure. While a broken symmetry in structure generally leads to a loss of symmetricity in symmetric normal modes, the symmetricity of some symmetric normal modes is preserved even when s...
Convexity and symmetrization in relativistic theories
Ruggeri, T.
1990-09-01
There is a strong motivation for the desire to have symmetric hyperbolic field equations in thermodynamics, because they guarantee well-posedness of Cauchy problems. A generic quasi-linear first order system of balance laws — in the non-relativistic case — can be shown to be symmetric hyperbolic, if the entropy density is concave with respect to the variables. In relativistic thermodynamics this is not so. This paper shows that there exists a scalar quantity in relativistic thermodynamics whose concavity guarantees a symmetric hyperbolic system. But that quantity — we call it —bar h — is not the entropy, although it is closely related to it. It is formed by contracting the entropy flux vector — ha with a privileged time-like congruencebar ξ _α . It is also shown that the convexity of h plus the requirement that all speeds be smaller than the speed of light c provide symmetric hyperbolic field equations for all choices of the direction of time. At this level of generality the physical meaning of —h is unknown. However, in many circumstances it is equal to the entropy. This is so, of course, in the non-relativistic limit but also in the non-dissipative relativistic fluid and even in relativistic extended thermodynamics for a non-degenerate gas.
Asymptotic solutions for the case of nearly symmetric gravitational lens systems
Wertz, O.; Pelgrims, V.; Surdej, J.
2012-08-01
Gravitational lensing provides a powerful tool to determine the Hubble parameter H0 from the measurement of the time delay Δt between two lensed images of a background variable source. Nevertheless, knowledge of the deflector mass distribution constitutes a hurdle. We propose in the present work interesting solutions for the case of nearly symmetric gravitational lens systems. For the case of a small misalignment between the source, the deflector and the observer, we first consider power-law (ɛ) axially symmetric models for which we derive an analytical relation between the amplification ratio and source position which is independent of the power-law slope ɛ. According to this relation, we deduce an expression for H0 also irrespective of the value ɛ. Secondly, we consider the power-law axially symmetric lens models with an external large-scale gravitational field, the shear γ, resulting in the so-called ɛ-γ models, for which we deduce simple first-order equations linking the model parameters and the lensed image positions, the latter being observable quantities. We also deduce simple relations between H0 and observables quantities only. From these equations, we may estimate the value of the Hubble parameter in a robust way. Nevertheless, comparison between the ɛ-γ and singular isothermal ellipsoid (SIE) models leads to the conclusion that these models remain most often distinct. Therefore, even for the case of a small misalignment, use of the first-order equations and precise astrometric measurements of the positions of the lensed images with respect to the centre of the deflector enables one to discriminate between these two families of models. Finally, we confront the models with numerical simulations to evaluate the intrinsic error of the first-order expressions used when deriving the model parameters under the assumption of a quasi-alignment between the source, the deflector and the observer. From these same simulations, we estimate for the case of the
Energy Technology Data Exchange (ETDEWEB)
Assadi, S.
1994-01-01
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.
Investigation of Aluminum-Copper Tube Hydroforming with Axial Feeding
Parto D., M.; Seyedkashi, S. M. H.; Liaghat, Gh.; Naeini, H. Moslemi; Panahizadeh R., V.
2011-01-01
Hydroforming of a two-layered Aluminum-Copper tube is investigated numerically and experimentally. Pressure is applied through a nonlinear path along with symmetrical axial feeding. ABAQUS/Explicit commercial code is used for finite element simulation of the process. ASTM C11000 Copper alloy is used as inner layer and ASTM AA1050A Aluminum alloy is used as outer layer. The simulation results show that the part can be successfully formed under internal pressure of 40 MPa with 8 mm axial displacement. Stress distributions on both inner and outer tubes are compared and maximum thinning on their wall is also discussed. Different friction conditions are applied on the process using different coefficients of friction and their effects are investigated on thinning percentage of inner and outer tubes and also on axial feeding. It is observed that finite element results are in good agreement with experimental results.
Axial super-resolution evanescent wave tomography
Pendharker, Sarang; Shende, Swapnali; Newman, Ward; Ogg, Stephen; Nazemifard, Neda; Jacob, Zubin
2016-12-01
Optical tomographic reconstruction of a 3D nanoscale specimen is hindered by the axial diffraction limit, which is 2-3 times worse than the focal plane resolution. We propose and experimentally demonstrate an axial super-resolution evanescent wave tomography (AxSET) method that enables the use of regular evanescent wave microscopes like Total Internal Reflection Fluorescence Microscope (TIRF) beyond surface imaging, and achieve tomographic reconstruction with axial super-resolution. Our proposed method based on Fourier reconstruction achieves axial super-resolution by extracting information from multiple sets of three-dimensional fluorescence images when the sample is illuminated by an evanescent wave. We propose a procedure to extract super-resolution features from the incremental penetration of an evanescent wave and support our theory by 1D (along the optical axis) and 3D simulations. We validate our claims by experimentally demonstrating tomographic reconstruction of microtubules in HeLa cells with an axial resolution of $\\sim$130 nm. Our method does not require any additional optical components or sample preparation. The proposed method can be combined with focal plane super-resolution techniques like STORM and can also be adapted for THz and microwave near-field tomography.
Axial super-resolution evanescent wave tomography.
Pendharker, Sarang; Shende, Swapnali; Newman, Ward; Ogg, Stephen; Nazemifard, Neda; Jacob, Zubin
2016-12-01
Optical tomographic reconstruction of a three-dimensional (3D) nanoscale specimen is hindered by the axial diffraction limit, which is 2-3 times worse than the focal plane resolution. We propose and experimentally demonstrate an axial super-resolution evanescent wave tomography method that enables the use of regular evanescent wave microscopes like the total internal reflection fluorescence microscope beyond surface imaging and achieve a tomographic reconstruction with axial super-resolution. Our proposed method based on Fourier reconstruction achieves axial super-resolution by extracting information from multiple sets of 3D fluorescence images when the sample is illuminated by an evanescent wave. We propose a procedure to extract super-resolution features from the incremental penetration of an evanescent wave and support our theory by one-dimensional (along the optical axis) and 3D simulations. We validate our claims by experimentally demonstrating tomographic reconstruction of microtubules in HeLa cells with an axial resolution of ∼130 nm. Our method does not require any additional optical components or sample preparation. The proposed method can be combined with focal plane super-resolution techniques like stochastic optical reconstruction microscopy and can also be adapted for THz and microwave near-field tomography.
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.
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.
2003-01-01
We study the anisotropic Heisenberg (XYZ) spin-1/2 chain placed in a magnetic field pointing along the x-axis. We use bosonization and a renormalization group analysis to show that the model has a non-trivial fixed point at a certain value of the XY anisotropy a and the magnetic field h. Hence, there is a line of critical points in the (a,h) plane on which the system is gapless, even though the Hamiltonian has no continuous symmetry. The quantum critical line corresponds to a spin-flop transi...
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.
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.
轴流泵水力模型内部流场数值模拟%Numerical simulation of internal flow field in hydraulic model of axial-flow pump
Institute of Scientific and Technical Information of China (English)
齐学义; 汪玮华; 郝连松
2012-01-01
Based on the Reynolds time-averaged Navier-Stokes equations with turbulence mode, by using SIMPLEC algorithm to make pressure-velocity coupling, and by using the implicit different format with second-order accuracy, the stationary 3-D turbulent flow in axial-flow pump was numerically simulated and the velocity vectors, static pressure contours, and other flow informations were obtained. The simulation result showed that the flow field distribution and flow form were better in general in design condition, but a local low pressure area occurred at the inlet of impeller blade back near the wheel rim and the load on the outer wall of guide vane was large, indicating that it would be necessary to improve the axial-flow pump model and pump performance.%基于Reynolds时均N-S方程,采用标准k-ε湍流模型,压力、速度耦合使用SIMPLEC算法,离散采用具有二阶精度的隐式格式差分,对轴流泵过流部件内部流场进行三维定常湍流数值模拟,得到泵内流动的速度和压力矢量分布图,以及其他一些流动的信息.数值模拟结果表明,设计工况下的流场分布和流态总体较好,但叶轮叶片背面进口靠近轮缘处出现局部低压,导叶外壁区域负荷大,说明该轴流泵水力模型还有进一步改进和对其性能进一步提高的必要.
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.
Topological states in partially-PT-symmetric azimuthal potentials
Kartashov, Yaroslav V; Torner, Lluis
2015-01-01
We introduce partially-parity-time-symmetric (pPT-symmetric) azimuthal potentials composed from individual PT-symmetric cells located on a ring, where two azimuthal directions are nonequivalent in a sense that in such potentials excitations carrying topological dislo-cations exhibit different dynamics for different directions of energy circulation in the initial field distribution. Such non-conservative ratchet-like structures support rich families of stable vortex solitons in cubic nonlinear media, whose properties depend on the sign of the topological charge due to the nonequivalence of azimuthal directions. In contrast, oppositely charged vortex solitons remain equivalent in similar fully PT-symmetric potentials. The vortex solitons in the pPT- and PT-symmetric potentials are shown to feature qualitatively different internal current distributions, which are described by different discrete rotation symmetries of the intensity profiles.
Parallel Symmetric Eigenvalue Problem Solvers
2015-05-01
Plemmons G. Golub and A. Sameh. High-speed computing : scientific appli- cations and algorithm design. University of Illinois Press, Champaign, Illinois , 1988...16. SECURITY CLASSIFICATION OF: Sparse symmetric eigenvalue problems arise in many computational science and engineering applications such as...Eigenvalue Problem Solvers Report Title Sparse symmetric eigenvalue problems arise in many computational science and engineering applications such as
Representation of Fuzzy Symmetric Relations
1986-03-19
Std Z39-18 REPRESENTATION OF FUZZY SYMMETRIC RELATIONS L. Valverde Dept. de Matematiques i Estadistica Universitat Politecnica de Catalunya Avda...REPRESENTATION OF FUZZY SYMMETRIC RELATIONS L. "Valverde* Dept. de Matematiques i Estadistica Universitat Politecnica de Catalunya Avda. Diagonal, 649
Zhang, Peng; Tang, Ming; Gao, Feng; Zhu, Benpeng; Fu, Songnian; Ouyang, Jun; Shum, Perry Ping; Liu, Deming
2014-08-11
We report a highly sensitive fiber-optic sensor based on two cascaded intrinsic fiber Fabry-Perot interferometers (IFFPIs). The cascaded IFFPIs have different free spectral ranges (FSRs) and are formed by a short section of hollow core photonic crystal fiber sandwiched by two single mode fibers. With the superposition of reflective spectrum with different FSRs, the Vernier effect will be generated in the proposed sensor and we found that the strain sensitivity of the proposed sensor can be improved from 1.6 pm/με for a single IFFPI sensor to 47.14 pm/με by employing the Vernier effect. The sensor embed with a metglas ribbon can be also used to measure the magnetic field according to the similar principle. The sensitivity of the magnetic field measurement is achieved to be 71.57 pm/Oe that is significantly larger than the 2.5 pm/Oe for a single IFFPI sensor.
2013-05-01
McNeill , S. R. Determination of Displacements Using an Improved Digital Image Correlation Method. Computer Vision August 1983. 13 12. Bruck, H. A... McNeill , S. R.; Russell, S. S.; Sutton, M. A. Use of Digital Image Correlation for Determination of Displacements and Strains. Non-Destructive...Evaluation for Aerospace Requirements, 1989. 13. Sutton, M. A.; McNeill , S. R.; Helm, J. D.; Schreier, H. Full-field Non-Contacting Measurement of
Institute of Scientific and Technical Information of China (English)
Hongwei MA; Baihe LI
2008-01-01
This paper presents a numerical investigation of effects of axial non-uniform tip clearances on the aerodynamic performance of a transonic axial compressor rotor (NASA Rotor 37). The three-dimensional steady flow field within the rotor passage was simulated with the datum tip clearance of 0.356 mm at the design wheel speed of 17188.7 rpm. The simulation results are well consistent with the measurement results, which verified the numeri-cal method. Then the three-dimensional steady flow field within the rotor passage was simulated respectively with different axial non-uniform tip clearances. The calculation results showed that optimal axial non-uniform tip clearances could improve the compressor performance, while the efficiency and the pressure ratio of the com-pressor were increased. The flow mechanism is that the axial non-uniform tip clearance can weaken the tip leak-age vortex, blow down low-energy fluids in boundary layers and reduce both flow blockage and tip loss.
Shear-free axial model in massive Brans-Dicke gravity
Sharif, M.; Manzoor, Rubab
2017-01-01
This paper explores the influences of dark energy on the shear-free axially symmetric evolution by considering self-interacting Brans-Dicke gravity as a dark energy candidate. We describe energy source of the model and derive all the effective dynamical variables as well as effective structure scalars. It is found that scalar field is one of the sources of anisotropy and dissipation. The resulting effective structure scalars help to study the dynamics associated with dark energy in any axial configuration. In order to investigate shear-free evolution, we formulate a set of governing equations along with heat transport equation. We discuss consequences of shear-free condition upon different SBD fluid models like dissipative non-geodesic and geodesic models. For dissipative non-geodesic case, the rotational distribution turns out to be the necessary and sufficient condition for radiating model. The dissipation depends upon inhomogeneous expansion. The geodesic model is found to be irrotational and non-radiating. The non-dissipative geodesic model leads to FRW model for positive values of the expansion parameter.
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.
Xing, Hui; Dong, Xianglei; Wu, Hongjing; Hao, Guanhua; Wang, Jianyuan; Chen, Changle; Jin, Kexin
2016-05-01
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.
Gauge-symmetric approach to effective lagrangians: The η' meson from QCD
Damgaard, P. H.; Nielsen, H. B.; Sollacher, R.
1994-02-01
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.
Maximally Symmetric Spacetimes emerging from thermodynamic fluctuations
Bravetti, A; Quevedo, H
2015-01-01
In this work we prove that the maximally symmetric vacuum solutions of General Relativity emerge from the geometric structure of statistical mechanics and thermodynamic fluctuation theory. To present our argument, we begin by showing that the pseudo-Riemannian structure of the Thermodynamic Phase Space is a solution to the vacuum Einstein-Gauss-Bonnet theory of gravity with a cosmological constant. Then, we use the geometry of equilibrium thermodynamics to demonstrate that the maximally symmetric vacuum solutions of Einstein's Field Equations -- Minkowski, de-Sitter and Anti-de-Sitter spacetimes -- correspond to thermodynamic fluctuations. Moreover, we argue that these might be the only possible solutions that can be derived in this manner. Thus, the results presented here are the first concrete examples of spacetimes effectively emerging from the thermodynamic limit over an unspecified microscopic theory without any further assumptions.
Representations of the infinite symmetric group
Borodin, Alexei
2016-01-01
Representation theory of big groups is an important and quickly developing part of modern mathematics, giving rise to a variety of important applications in probability and mathematical physics. This book provides the first concise and self-contained introduction to the theory on the simplest yet very nontrivial example of the infinite symmetric group, focusing on its deep connections to probability, mathematical physics, and algebraic combinatorics. Following a discussion of the classical Thoma's theorem which describes the characters of the infinite symmetric group, the authors describe explicit constructions of an important class of representations, including both the irreducible and generalized ones. Complete with detailed proofs, as well as numerous examples and exercises which help to summarize recent developments in the field, this book will enable graduates to enhance their understanding of the topic, while also aiding lecturers and researchers in related areas.
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.
Influence of Transverse Shear on an Axial Crack in a Cylindrical Shell
DEFF Research Database (Denmark)
Krenk, Steen
1978-01-01
An axial crack in a cylindrical shell is investigated by use of a 10th order shell theory, which accounts for transverse shear deformations as well as a special kind of orthotropy. The symmetric problem is formulated in terms of two coupled singular integral equations, which are solved numerically...
Nonlinear waves in $\\cal PT$-symmetric systems
Konotop, Vladimir V.; Yang, Jianke; Zezyulin, Dmitry A.
2016-01-01
Recent progress on nonlinear properties of parity-time ($\\cal PT$-) symmetric systems is comprehensively reviewed in this article. $\\cal PT$ symmetry started out in non-Hermitian quantum mechanics, where complex potentials obeying $\\cal PT$ symmetry could exhibit all-real spectra. This concept later spread out to optics, Bose-Einstein condensates, electronic circuits, and many other physical fields, where a judicious balancing of gain and loss constitutes a $\\cal PT$-symmetric system. The nat...
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 the frequencydomain simulations of resonant modes in a circular-cylinder cavity with perfectly conducting walls, a shielded uniaxial anisotropic dielectric cylinder, and an open dielectric sphere for which, after proper implementation of the perfectly matched layer boundary conditions, the radiation quality factor...
Exact Spherically Symmetric Solutions in Massive Gravity
Berezhiani, Z; Nesti, F; Pilo, L
2008-01-01
A phase of massive gravity free from pathologies can be obtained by coupling the metric to an additional spin-two field. We study the gravitational field produced by a static spherically symmetric body, by finding the exact solution that generalizes the Schwarzschild metric to the case of massive gravity. Besides the usual 1/r term, the main effects of the new spin-two field are a shift of the total mass of the body and the presence of a new power-like term, with sizes determined by the mass and the shape (the radius) of the source. These modifications, being source dependent, give rise to a dynamical violation of the Strong Equivalence Principle. Depending on the details of the coupling of the new field, the power-like term may dominate at large distances or even in the ultraviolet. The effect persists also when the dynamics of the extra field is decoupled.
Extended symmetrical classical electrodynamics.
Fedorov, A V; Kalashnikov, E G
2008-03-01
In this paper, we discuss a modification of classical electrodynamics in which "ordinary" point charges are absent. The modified equations contain additional terms describing the induced charges and currents. The densities of the induced charges and currents depend on the vector k and the vectors of the electromagnetic field, E and B . It is shown that the vectors E and B can be defined in terms of two four-potentials and the components of k are the components of a four-tensor of the third rank. The Lagrangian of the modified electrodynamics is defined. The conditions are derived at which only one four-potential determines the behavior of the electromagnetic field. It is also shown that static modified electrodynamics can describe the electromagnetic field in the inner region of an electric monopole. In the outer region of the electric monopole the electric field is governed by the Maxwell equations. It follows from boundary conditions at the interface between the inner and outer regions of the monopole that the vector k has a discrete spectrum. The electric and magnetic fields, energy, and angular momentum of the monopole are found for different eigenvalues of k .
Schwarz, J H; Schwarz, John H.; Sen, Ashoke
1994-01-01
It is frequently useful to construct dual descriptions of theories containing antisymmetric tensor fields by introducing a new potential whose curl gives the dual field strength, thereby interchanging field equations with Bianchi identities. We describe a general procedure for constructing actions containing both potentials at the same time, such that the dual relationship of the field strengths arises as an equation of motion. The price for doing this is the sacrifice of manifest Lorentz invariance or general coordinate invariance, though both symmetries can be realized nonetheless. There are various examples of global symmetries that have been realized as symmetries of field equations but not actions. These can be elevated to symmetries of the action by our method. The main example that we focus on is the low-energy effective action description of the heterotic string theory compactified on a six-torus to four dimensions. We show that the SL(2,R) symmetry, whose SL(2,Z) subgroup has been conjectured to be a...
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.
Faryad, Muhammad; Lakhtakia, Akhlesh
2017-02-01
Mathematical statements of the Huygens principle relate the electric and magnetic field phasors at an arbitrary location in a source-free region enclosed by a surface to the tangential components of the electric and magnetic field phasors over that surface, via the dyadic Green functions applicable to the linear homogeneous medium occupying that region. We have mathematically formulated the Huygens principle for the electric and magnetic field phasors when the permittivity and permeability dyadics of the medium are symmetric, the symmetric parts of the two magnetoelectric dyadics of the medium are negative of each other, and both magnetoelectric dyadics also contain anti-symmetric terms. We have also formulated the Huygens principle for the electric (resp. magnetic) field phasor in a medium whose permittivity (resp. permeability) is scalar, the permeability (resp. permittivity) is symmetric, the symmetric parts of the two magnetoelectric dyadics reduce to dissimilar scalars, and anti-symmetric parts of the two magnetoelectric dyadics are identical.
Directory of Open Access Journals (Sweden)
Tara L Alvarez
2014-06-01
Full Text Available Convergence insufficiency (CI is a prevalent binocular vision disorder with symptoms that include double/blurred vision, eyestrain, and headaches when engaged in reading or other near work. Randomized clinical trials support that Office-Based Vergence and Accommodative Therapy with home reinforcement leads to a sustained reduction in patient symptoms. However, the underlying neurophysiological basis for treatment is unknown. Functional activity and vergence eye movements were quantified from seven binocularly normal controls (BNC and four CI patients before and after 18 hours of vergence training. An fMRI conventional block design of sustained fixation versus vergence eye movements stimulated activity in the frontal eye fields (FEF, the posterior parietal cortex (PPC and the cerebellar vermis (CV. Comparing the CI patients’ baseline measurements to the post vergence training data sets with a paired t-test revealed the following: 1 the percent change in the BOLD signal in the FEF, PPC and CV significantly increased (p<0.02, 2 the peak velocity from 4° symmetrical convergence step responses increased (p<0.01 and 3 patient symptoms assessed using the CI Symptom Survey (CISS improved (p<0.05. CI patient measurements after vergence training were more similar to levels observed within BNC. A regression analysis revealed the peak velocity from BNC and CI subjects before and after vergence training was significantly correlated to the percent BOLD signal change within the FEF, PPC and CV (r=0.6;p<0.05. Results have clinical implications for understanding the behavioral and neurophysiological changes after vergence training in patients with CI, which may lead to the sustained reduction in visual symptoms.
Research on a Novel Axial Field Disk Type Switched Reluctance Motor%新型轴向磁场盘式开关磁阻电机的研究
Institute of Scientific and Technical Information of China (English)
梅营; 潘再平
2011-01-01
提出了一种新型的采用三相6/4极结构的轴向磁场盘式开关磁阻电机,与前人研究较多的单相盘式开关磁阻电机相比,定、转子结构更加简单,加工成本更低,便于调速控制,且克服了单相电机不能自起动的缺陷.使用Ansoft公司的Maxwell 3D软件进行了三维有限元仿真分析,并制作实验样机,验证了电机的性能.%This paper proposed a novel axial field disk type switched reluctance motor ( AFSRM ), which has both the merit of SRM such as simple and robust structure, easy to control and the merit of disk machine such as short shaft, high torque/inertia rate. Comparing with the single phase AFSRM fully researched before, the novel AFSRM has simpler rotor and stator structure, and lower manufacturing cost. Since the novel AFSRM has 6/4 poles, it avoided the weakness of single phase AFSRM, inability to self start-up. In this paper, three-dimensional field and torque analysis of the novel AFSRM were carried out using Maxwell 3D, a 3D finite-element analysis (FEA) software. In addition, a prototype of novel AFSRM was made to validate the design and test the performance.
Distal symmetrical polyneuropathy: definition for clinical research.
England, J D; Gronseth, G S; Franklin, G; Miller, R G; Asbury, A K; Carter, G T; Cohen, J A; Fisher, M A; Howard, J F; Kinsella, L J; Latov, N; Lewis, R A; Low, P A; Sumner, A J
2005-01-01
The objective of this report was to develop a case definition of "distal symmetrical polyneuropathy" to standardize and facilitate clinical research and epidemiological studies. A formalized consensus process was employed to reach agreement after a systematic review and classification of evidence from the literature. The literature indicates that symptoms alone have relatively poor diagnostic accuracy in predicting the presence of polyneuropathy; signs are better predictors of polyneuropathy than symptoms; and single abnormalities on examination are less sensitive than multiple abnormalities in predicting the presence of polyneuropathy. The combination of neuropathic symptoms, signs, and electrodiagnostic findings provides the most accurate diagnosis of distal symmetrical polyneuropathy. A set of case definitions was rank ordered by likelihood of disease. The highest likelihood of polyneuropathy (useful for clinical trials) occurs with a combination of multiple symptoms, multiple signs, and abnormal electrodiagnostic studies. A modest likelihood of polyneuropathy (useful for field or epidemiological studies) occurs with a combination of multiple symptoms and multiple signs when the results of electrodiagnostic studies are not available. A lower likelihood of polyneuropathy occurs when electrodiagnostic studies and signs are discordant. For research purposes, the best approach for defining distal symmetrical polyneuropathy is a set of case definitions rank ordered by estimated likelihood of disease. The inclusion of this formalized case definition in clinical and epidemiological research studies will ensure greater consistency of case selection.
Yasmin, Safia; Rahaman, Anisur
2016-12-01
A (1+1) dimensional model where vector and axial vector interaction get mixed up with different weight is considered with a generalized masslike term for gauge field. Through Poincaré algebra it has been made confirm that only a Lorentz covariant masslike term leads to a physically sensible theory as long as the number of constraints in the phase space is two. With that admissible masslike term, phase space structure of this model with proper identification of physical canonical pair has been determined using Diracs' scheme of quantization of constrained system. The bosonized version of the model remains gauge non-invariant to start with. Therefore, with the inclusion of appropriate Wess-Zumino term it is made gauge symmetric. An alternative quantization has been carried out over this gauge symmetric version to determine the phase space structure in this situation. To establish that the Wess-Zumino fields allocates themselves in the un-physical sector of the theory an attempts has been made to get back the usual theory from the gauge symmetric theory of the extended phase-space without hampering any physical principle. It has been found that the role of gauge fixing is crucial for this transmutation.
PT-symmetric deformations of integrable models.
Fring, Andreas
2013-04-28
We review recent results on new physical models constructed as PT-symmetrical deformations or extensions of different types of integrable models. We present non-Hermitian versions of quantum spin chains, multi-particle systems of Calogero-Moser-Sutherland type and nonlinear integrable field equations of Korteweg-de Vries type. The quantum spin chain discussed is related to the first example in the series of the non-unitary models of minimal conformal field theories. For the Calogero-Moser-Sutherland models, we provide three alternative deformations: a complex extension for models related to all types of Coxeter/Weyl groups; models describing the evolution of poles in constrained real-valued field equations of nonlinear integrable systems; and genuine deformations based on antilinearly invariant deformed root systems. Deformations of complex nonlinear integrable field equations of Korteweg-de Vries type are studied with regard to different kinds of PT-symmetrical scenarios. A reduction to simple complex quantum mechanical models currently under discussion is presented.
Pseudo-Z symmetric space-times
Energy Technology Data Exchange (ETDEWEB)
Mantica, Carlo Alberto, E-mail: carloalberto.mantica@libero.it [Physics Department, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Suh, Young Jin, E-mail: yjsuh@knu.ac.kr [Department of Mathematics, Kyungpook National University, Taegu 702-701 (Korea, Republic of)
2014-04-15
In this paper, we investigate Pseudo-Z symmetric space-time manifolds. First, we deal with elementary properties showing that the associated form A{sub k} is closed: in the case the Ricci tensor results to be Weyl compatible. This notion was recently introduced by one of the present authors. The consequences of the Weyl compatibility on the magnetic part of the Weyl tensor are pointed out. This determines the Petrov types of such space times. Finally, we investigate some interesting properties of (PZS){sub 4} space-time; in particular, we take into consideration perfect fluid and scalar field space-time, and interesting properties are pointed out, including the Petrov classification. In the case of scalar field space-time, it is shown that the scalar field satisfies a generalized eikonal equation. Further, it is shown that the integral curves of the gradient field are geodesics. A classical method to find a general integral is presented.
Tunable axial potentials for atom chip waveguides
Stickney, James A; Imhof, Eric; Kroese, Bethany R; Crow, Jonathon A R; Olson, Spencer E; Squires, Matthew B
2014-01-01
We present a method for generating algebraically precise magnetic potentials along the axis of a cold atom waveguide near the surface of an atom chip. With a single chip design consisting of several wire pairs, various axial potentials can be created, including double wells, triple wells, and pure harmonic traps with suppression of higher order terms. We characterize the error along a harmonic trap between the expected algebraic form and magnetic field simulations and find excel- lent agreement, particularly at small displacements from the trap center. Finally, we demonstrate experimental control over the bottom fields of an asymmetric double well potential.
Direct optical nanoscopy with axially localized detection
Bourg, N; Dupuis, G; Barroca, T; Bon, P; Lécart, S; Fort, E; Lévêque-Fort, S
2014-01-01
Evanescent light excitation is widely used in super-resolution fluorescence microscopy to confine light and reduce background noise. Herein we propose a method of exploiting evanescent light in the context of emission. When a fluorophore is located in close proximity to a medium with a higher refractive index, its near-field component is converted into light that propagates beyond the critical angle. This so-called Supercritical Angle Fluorescence (SAF) can be captured using a hig-NA objective and used to determine the axial position of the fluorophore with nanometer precision. We introduce a new technique for 3D nanoscopy that combines direct STochastic Optical Reconstruction Microscopy (dSTORM) imaging with dedicated detection of SAF emission. We demonstrate that our approach of a Direct Optical Nanoscopy with Axially Localized Detection (DONALD) yields a typical isotropic 3D localization precision of 20 nm.
Institute of Scientific and Technical Information of China (English)
王保伟; 许根慧; 孙洪伟
2001-01-01
利用电场作用通过交流和直流等离子体在低温、常压和低功率下催化反应将甲烷直接转化为碳二烃(乙烷、乙烯、乙炔)。考察了在对称电场作用下催化剂的催化性能。实验结果表明，在交流电场作用下，碳二烃选择性差别不大；甲烷转化率的大小顺序为：MnO2/Al2O3＞Ni/Al2O3＞MoO—Al2O3＞Ni/NaY＞Pd/ZSM-5＞Ni/H4Mg2Si3O4＞Ni/ZSM-5＞Co/ZSM-5＞无催化剂：在直流电场作用下，碳二烃选择性差别也不大(除Ni/NaY外)，甲烷转化率的大小顺序为：Ni/Al2O3＞Ni/HaMg2Si3O4＞Ni/ZSM-5＞Co/ZSM-5＞MnO2/Al2O3＞MoO3/Al2O3＞Ni/NaY＞无催化剂＞Pd/ZSM-5。%Low-power catalytic conversion of methane to C2 hydrocarbons(ethane, ethCene and acetylene) through AC or DC plasma catalysis reactionsin symmetric electrical field was studied under low temperature andatmospheric pressure. The function of catalyst was tested. The appropriate condition was: voltage 90 V～1l0 V (power 15 W～20 W DC); voltage 20 V～40 V (AC). The appropriate inlet flow of methane was 45 mL/min～80mL/min under AC and DC field. The selectivity to C2 hydrocarbons was above 95%.
Analytical approach to quasiperiodic beam Coulomb field modeling
Rubtsova, I. D.
2016-09-01
The paper is devoted to modeling of space charge field of quasiperiodic axial- symmetric beam. Particle beam is simulated by charged disks. Two analytical Coulomb field expressions are presented, namely, Fourier-Bessel series and trigonometric polynomial. Both expressions permit the integral representation. It provides the possibility of integro-differential beam dynamics description. Consequently, when beam dynamics optimization problem is considered, it is possible to derive the analytical formula for quality functional gradient and to apply directed optimization methods. In addition, the paper presents the method of testing of space charge simulation code.
Critical exact solutions for self-gravitating Dirac fields
Cianci, Roberto; Vignolo, Stefano
2016-01-01
We consider the Einstein-Dirac field equations describing a self-gravitating massive neutrino, looking for axially-symmetric exact solutions; in the search of general solutions, we find some that are specific and which have critical features, such as the fact that the space-time curvature turns out to be flat and the spinor field gives rise to a vanishing bi-linear scalar $\\overline{\\psi}\\psi=0$ with non-vanishing bi-linear pseudo-scalar $i\\overline{\\psi}\\gamma^5\\psi\
Harmonic analysis on symmetric spaces
Terras, Audrey
This text explores the geometry and analysis of higher rank analogues of the symmetric spaces introduced in volume one. To illuminate both the parallels and differences of the higher rank theory, the space of positive matrices is treated in a manner mirroring that of the upper-half space in volume one. This concrete example furnishes motivation for the general theory of noncompact symmetric spaces, which is outlined in the final chapter. The book emphasizes motivation and comprehensibility, concrete examples and explicit computations (by pen and paper, and by computer), history, and, above all, applications in mathematics, statistics, physics, and engineering. The second edition includes new sections on Donald St. P. Richards’s central limit theorem for O(n)-invariant random variables on the symmetric space of GL(n, R), on random matrix theory, and on advances in the theory of automorphic forms on arithmetic groups.
Application of the wavelet transforms on axial strain calculation in ultrasound elastography
Institute of Scientific and Technical Information of China (English)
LUO Jianwen; BAI Jing; SHAO Jinhua
2006-01-01
In ultrasound elastography, the axial strain distribution within biological tissues is calculated as the numerical derivative (differentiation) of the estimated axial displacement field. Unfortunately, the numerical derivative is unstable because it can greatly amplify the noises, especially at high frequencies. This work focuses on the axial strain calculation from the estimated axial displacements using wavelet transforms (WTs), including continuous wavelet transforms (CWTs) and discrete wavelet transforms (DWTs). The feasibility of the WT-based method using the quadratic spline function is verified by computer simulations and some phantom data. Results indicate that the WT-based method can effectively reduce the noise amplification in axial strain calculation.
Effects of Magnetic Field Topology on Secondary Neutron Spectra in MagLIF
Appelbe, Brian; Chittenden, Jeremy
2015-11-01
Ignition in Magneto-Inertial Fusion schemes requires both inertial and magnetic confinement of the fuel and charged fusion products. Recent theoretical and experimental work has demonstrated the confinement of charged fusion products by magnetic fields in Magnetized Liner Inertial Fusion (MagLIF) experiments. This confinement can be inferred from the ratio of secondary to primary neutron yields and the shape of secondary neutron spectra. In this work we investigate the effects of magnetic field topology on the shape of secondary neutron spectra. The MagLIF design has a cylindrical geometry and includes both axial and azimuthal magnetic fields. The azimuthal field is initially in the liner surrounding the fuel but instability growth may cause it to penetrate into the fuel. Charged fusion products (such as tritons or alpha particles) that are isotropically emitted and then confined by an axial field will flow parallel and anti-parallel to the field with equal intensities. In the case of tritons, this motion results in a secondary neutron spectrum emitted in the axial direction that is symmetric. However, in an azimuthal field such particles exhibit singular orbits and there is a net ion drift along the axis. This ion drift can cause the secondary neutron spectrum to be asymmetric. We examine the effects on the spectrum shape of confinement by a combination of axial and azimuthal fields.
Directory of Open Access Journals (Sweden)
Shi-Wei Lo
2011-01-01
Full Text Available The moving bullet out of a rifle barrel is propelled by a fired explosive charge. Subsequently, a disturbed muzzle blast wave is initiated which lasts several milliseconds. In this study, axially symmetric, unsteady, Large Eddy Simulation (LES, and Ffowcs Williams and Hawkins (FWH equations were solved by the implicit-time formulation. For the spatial discretization, second order upwind scheme was employed. In addition, dynamic mesh model was used to where the ballistic domain changed with time due to the motion of bullet. Results obtained for muzzle flow field and for noise recorded were compared with those obtained from experimental data; these two batches of results were in agreement. Five cases of gunshot including one model of an unsuppressed rifle and four models of suppressors were simulated. Besides, serial images of species distributions and velocity vectors-pressure contours in suppressors and near muzzle field were displayed. The sound pressure levels (dB in far field that were post-processed by the fast Fourier transform (FFT were compared. The proposed physical model and the numerical simulations used in the present work are expected to be extended to solve other shooting weapon problems with three-dimensional and complex geometries.
Institute of Scientific and Technical Information of China (English)
张华; 施卫东; 陈斌; 张德胜; 胡啟祥
2013-01-01
To investigate the flow field distribution at the regions of the impeller and guide vane inlet and outlet under condition of 0.8Qopt, the axial flow pump with ns=700 was selected for model scaling and structural modification, from which we could get a test bed suitable for a 2D-PIV internal flow field test. Structural modifications included: the conventional metal material was replaced with transparent organic glass material to achieve the purpose of internal visualization;the conventional conical diffuser vane was designed into cylindrical shape to reduce the complexity of optical refraction;the runner chamber was merged with a guide vane casing to form as a whole to eliminate the occlusion of the flange to an internal flow field between the region of impeller and diffuser vane;the bearing within the diffuser vane was moved backward and rib plates were installed to make the load transfer to foundation smoothly. Based on the above methods, an experiment pump section was modified successfully, and the efficiency of the experimental pump reached 73.79%, which was close to that of the prototype pump. It was indicated that less damage occurred to the original flow field with structural modification. During the PIV measurement, the shaft encoder and synchronizer were used for better synchronous effect. Meanwhile, an ideal experimental result was obtained by using organic glass hollow spheres as tracer particles, and a new calibration method. As shown in the original PIV images, the particle distribution was homogeneous with most particles appearing to be micro-exposure, which meant an ideal experiment effect. From the analysis of the experimental result, it was indicated that, owing to the effect of the tip leakage flow at the 0.8Qopt operating point, the inflow at the rim of an impeller leading edge deflects to the hub side, but the whole flow field is evenly distributed on the front section of an impeller; a clockwise vortex with an outer diameter larger than the hub
Energy Technology Data Exchange (ETDEWEB)
Tanjia, F., E-mail: tanjia.fatema@gmail.com [Dipartimento di Fisica, Universià di Napoli “Federico II” (Italy); INFN Sezione di Napoli (Italy); Fedele, R. [Dipartimento di Fisica, Universià di Napoli “Federico II” (Italy); INFN Sezione di Napoli (Italy); De Nicola, S. [Dipartimento di Fisica, Universià di Napoli “Federico II” (Italy); INFN Sezione di Napoli (Italy); CNR-SPIN, Complesso Universitario di Monte S' Angelo, Napoli (Italy); Akhter, T. [Dipartimento di Fisica, Universià di Napoli “Federico II” (Italy); INFN Sezione di Napoli (Italy); Jovanović, D. [Institute of Physics, University of Belgrade, Belgrade (Serbia)
2016-09-01
A numerical investigation on the spatiotemporal evolution of an electron beam, externally injected in a plasma in the presence of a plasma wake field, is carried out. The latter is driven by an ultra-short relativistic axially-symmetric femtosecond electron bunch. We first derive a novel Poisson-like equation for the wake potential where the driving term is the ultra-short bunch density, taking suitably into account the interplay between the sharpness and high energy of the bunch. Then, we show that a channel is formed longitudinally, through the externally injected beam while experiencing the effects of the bunch-driven plasma wake field, within the context of thermal wave model. The formation of the channel seems to be a final stage of the 3D evolution of the beam. This involves the appearance of small filaments and bubbles around the longitudinal axis. The bubbles coalesce forming a relatively stable axially-symmetric hollow beam structure. - Highlights: • A novel Poisson-like equation for the wake potential driven by the ultra-short bunch density is derived in the context of PWF theory. • The spatiotemporal evolution of another externally injected electron beam in the presence plasma wake field is numerically investigated. • A channel is formed longitudinally, through the externally injected beam while experiencing the effects of the bunch-driven plasma wake field. • A relatively stable axially symmetric hollow beam structure is formed through the evolution.
Tanjia, F; De Nicola, S; Akhter, T; Jovanovic, D
2015-01-01
A numerical investigation on the spatiotemporal evolution of an electron beam, externally injected in a plasma in the presence of a plasma wake field, is carried out. The latter is driven by an ultra-short relativistic axially-symmetric femtosecond electron bunch. We first derive a novel Poisson-like equation for the wake potential where the driving term is the ultra-short bunch density, taking suitably into account the interplay between the sharpness and high energy of the bunch. Then, we show that a channel is formed longitudinally, through the externally injected beam while experiencing the effects of the bunch-driven plasma wake field, within the context of thermal wave model. The formation of the channel seems to be a final stage of the 3D evolution of the beam. This involves the appearance of small filaments and bubbles around the longitudinal axis. The bubbles coalesce forming a relatively stable axially-symmetric hollow beam structure.
Direct optical nanoscopy with axially localized detection
Bourg, N.; Mayet, C.; Dupuis, G.; Barroca, T.; Bon, P.; Lécart, S.; Fort, E.; Lévêque-Fort, S.
2015-09-01
Evanescent light excitation is widely used in super-resolution fluorescence microscopy to confine light and reduce background noise. Here, we propose a method of exploiting evanescent light in the context of emission. When a fluorophore is located in close proximity to a medium with a higher refractive index, its near-field component is converted into light that propagates beyond the critical angle. This so-called supercritical-angle fluorescence can be captured using a high-numerical-aperture objective and used to determine the axial position of the fluorophore with nanometre precision. We introduce a new technique for three-dimensional nanoscopy that combines direct stochastic optical reconstruction microscopy (dSTORM) with dedicated detection of supercritical-angle fluorescence emission. We demonstrate that our approach of direct optical nanoscopy with axially localized detection (DONALD) typically yields an isotropic three-dimensional localization precision of 20 nm within an axial range of ∼150 nm above the coverslip.
域上2×2对称矩阵空间的加法秩保持%Additive preservers of rank on the spaces of 2 × 2 symmetric matrices over fields
Institute of Scientific and Technical Information of China (English)
张显
2004-01-01
Let F be a field and n be a positive integer. Denote the set of all n × n symmetric matrices over F by Sn(F).An operator f: Sn(F) → Sn(F) is said to be additive if f(A + B) = f(A) + f(B) for any A, B ∈ Sn(F), and is called a preserver of rank on Sn(F) if rankf(X) =rankX for every X ∈ Sn(F). When n ≥ 3, for any F the forms of the additive preservers of rank on Sn(F) have been determined by the author in [4]. Here, when F is arbitrary, the general form of all additive operators from S2(F) to itself satisfying rankf(X) =rankX for every X ∈ S2(F) \\ {xD12| x ∈ F \\ {0}} is determined. Thereby, the additive preservers of rank on S2(F) for any F are characterized.%令F是一个域,n是一个正整数.Sn(F)记F上所有n×n对称矩阵的集合.若一个算子f:Sn(F)→Sn(F)满足对任意的A,B∈Sn(F)都有f(A+B)=f(A)+f(B),则称之为加法的;若对任意的X∈Sn(F)都有rankf(X)=rankX,则称f为Sn(F)上的秩保持.当n≥3及F为任意域时,Sn(F)上的所有加法秩保持已被作者在[4]中确定.这里,对于任意的F,S2(F)上所有的满足对每个X∈S2(F)\\{xD12|x∈F\\{0}}都有rankf(X)=rankX的加法算子的一般形式被确定,由此S2(F)上的所有加法秩保持被刻划.
Spherically symmetric black-hole entropy without brick walls
Ren, Zhao; Yue-Qin, Wu; Li-Chun, Zhang
2003-11-01
Properties of the thermal radiation of black holes are discussed using a new equation of state density motivated by the generalized uncertainty relation in quantum gravity. There is no burst at the last stage of emission from a spherically symmetric black hole. When the new equation of state density is used to investigate the entropy of a bosonic field and fermionic field outside the horizon of a static spherically symmetric black hole, the divergence that appears in the brick-wall model is removed without any cutoff. The entropy proportional to the horizon area is derived from the contribution from the vicinity of the horizon.
Axial Stringy System of the Kerr Spinning Particle
Burinskii, A
2004-01-01
The structure of classical spinning particle based on the Kerr-Newman black hole (BH) solution is investigated. For large angular momentum, $|a|>>m$, the BH horizons disappear exposing a naked ringlike source which is a circular relativistic string. It was shown recently that electromagnetic excitations of this string lead to the appearance of an extra axial stringy system which consists of two half-infinite strings of opposite chirality. In this paper we consider the relation of this stringy system to the Dirac equation. We also show that the axial strings are the Witten superconducting strings and describe their structure by the Higgs field model where the Higgs condensate is used to regularize axial singularity. We argue that this axial stringy system may play the role of a classical carrier of the wave function.
Symmetrical progressive erythro-keratoderma
Directory of Open Access Journals (Sweden)
Sunil Gupta
1999-01-01
Full Text Available A 13-year-old male child had gradually progressive, bilaterall, symmetrical, erythematous hyperkeratotic plaques over knees, elbows, natal cleft, dorsa of hands and feet with palmoplantar keratoderma. High arched palate, fissured tongue and sternal depression (pectus-excavatum were unusual associations.
Axiomatizations of symmetrically weighted solutions
Kleppe, John; Reijnierse, Hans; Sudhölter, P.
2013-01-01
If the excesses of the coalitions in a transferable utility game are weighted, then we show that the arising weighted modifications of the well-known (pre)nucleolus and (pre)kernel satisfy the equal treatment property if and only if the weight system is symmetric in the sense that the weight of a su
Computationally Efficient Searchable Symmetric Encryption
Liesdonk, van Peter; Sedghi, Saeed; Doumen, Jeroen; Hartel, Pieter; Jonker, Willem; Jonker, Willem; Petkovic, Milan
2010-01-01
Searchable encryption is a technique that allows a client to store documents on a server in encrypted form. Stored documents can be retrieved selectively while revealing as little information as possible to the server. In the symmetric searchable encryption domain, the storage and the retrieval are
Shearfree Spherically Symmetric Fluid Models
Sharif, M
2013-01-01
We try to find some exact analytical models of spherically symmetric spacetime of collapsing fluid under shearfree condition. We consider two types of solutions: one is to impose a condition on the mass function while the other is to restrict the pressure. We obtain totally of five exact models, and some of them satisfy the Darmois conditions.
Institute of Scientific and Technical Information of China (English)
赵屹; 金英子; 吴文浩; 张立; 钱红玉
2012-01-01
In the paper, the authors apply theories of isolated blade design method, CFD technology, genetic algorithm, and use self-made software to optimize the hub ratio of axial flow fan. The optimization objective is fan flow. Then the authors comparatively analyze the fan internal flow field, including static characteristic, blade surface static pressure distribution and meridian plane vortex quantity distribution, etc. , to make sure the feasibility of this optimization method, and conclude the effect of hub ratio to the fan performance. The results show that the energy loss brought by vortex is reduced on fan blades and hub surface after optimization, while the vortex and energy loss on tip are increased slightly. In different flow, there are varied improvements on fan static pressure and outlet velocity after optimization. Under the rating conditions, the fan performance, static characteristic and internal flow field have good improvement.%采用孤立叶型设计法、CFD技术、遗传算法等理论,运用自编软件对某一轴流风扇轮毂比参数进行结构优化设计,优化目标为风扇流量.对比分析优化前后风扇内部流场,如风扇的静特性、叶片表面静压分布、子午面涡量分布等信息.由此验证优化方法的可行性,并总结轮毂比参数对此风扇性能的影响.结果表明:优化后风扇叶片和轮毂表面减小了因涡流带来的能量损失,但叶顶间隙处的涡流增大,能量损失略有增大；在不同流量下,优化后风扇静压有不同程度的提高；优化后风扇的出口速度均比优化前大幅提高；风扇在额定工况下性能、静特性及内部流场都得到了很好的改善.
Modelling non-symmetric collagen fibre dispersion in arterial walls.
Holzapfel, Gerhard A; Niestrawska, Justyna A; Ogden, Ray W; Reinisch, Andreas J; Schriefl, Andreas J
2015-05-06
New experimental results on collagen fibre dispersion in human arterial layers have shown that the dispersion in the tangential plane is more significant than that out of plane. A rotationally symmetric dispersion model is not able to capture this distinction. For this reason, we introduce a new non-symmetric dispersion model, based on the bivariate von Mises distribution, which is used to construct a new structure tensor. The latter is incorporated in a strain-energy function that accommodates both the mechanical and structural features of the material, extending our rotationally symmetric dispersion model (Gasser et al. 2006 J. R. Soc. Interface 3, 15-35. (doi:10.1098/rsif.2005.0073)). We provide specific ranges for the dispersion parameters and show how previous models can be deduced as special cases. We also provide explicit expressions for the stress and elasticity tensors in the Lagrangian description that are needed for a finite-element implementation. Material and structural parameters were obtained by fitting predictions of the model to experimental data obtained from human abdominal aortic adventitia. In a finite-element example, we analyse the influence of the fibre dispersion on the homogeneous biaxial mechanical response of aortic strips, and in a final example the non-homogeneous stress distribution is obtained for circumferential and axial strips under fixed extension. It has recently become apparent that this more general model is needed for describing the mechanical behaviour of a variety of fibrous tissues.
Understanding symmetrical components for power system modeling
Das, J C
2017-01-01
This book utilizes symmetrical components for analyzing unbalanced three-phase electrical systems, by applying single-phase analysis tools. The author covers two approaches for studying symmetrical components; the physical approach, avoiding many mathematical matrix algebra equations, and a mathematical approach, using matrix theory. Divided into seven sections, topics include: symmetrical components using matrix methods, fundamental concepts of symmetrical components, symmetrical components –transmission lines and cables, sequence components of rotating equipment and static load, three-phase models of transformers and conductors, unsymmetrical fault calculations, and some limitations of symmetrical components.
Xu, Qin
1987-01-01
The existence of steady, nonlinear circulations in a flow susceptible to conditionally symmetric instability is studied, treating the latent heating as an energy source which is implicitly related to the motion field. The viscous nonlinear circulations of symmetrical instability are briefly discussed, and an existence theorem for steady, nonlinear symmetric circulations with bounded rates of latent heat release is given. The uniqueness and stability of these circulations are discussed, and some physical interpretations are given.
The group theory for solving electromagnetic scattering problems with geometric symmetric structure
Institute of Scientific and Technical Information of China (English)
朱峰; 杨海川; 任朗
1997-01-01
It is a very important issue to reduce computer storage and calculation time for matrix in solving scattering field by making use of geometric and physical symmetric features of a scattering body. A general definition for the symmetric and anti-symmetric structure is given by applying the group theory in mathematics and a general method for treating the electromagnetic scattering problems with symmetry is proposed. An example for applying the theory mentioned above is also given.
Symmetric and conserved energy-momentum tensors in moving media
Ravndal, Finn
2011-01-01
A symmetric and conserved energy-momentum tensor for a scalar field in a moving medium is derived using the Gordon metric. When applied to an electromagnetic field, the method gives a similar result. This approach thus points a way out of the old Abraham-Minkowski controversy around the question about the correct energy-momentum tensor for the electromagnetic field in a material medium.
Circularly symmetric light scattering from nanoplasmonic spirals.
Trevino, Jacob; Cao, Hui; Dal Negro, Luca
2011-05-11
In this paper, we combine experimental dark-field imaging, scattering, and fluorescence spectroscopy with rigorous electrodynamics calculations in order to investigate light scattering from planar arrays of Au nanoparticles arranged in aperiodic spirals with diffuse, circularly symmetric Fourier space. In particular, by studying the three main types of Vogel's spirals fabricated by electron-beam lithography on quartz substrates, we demonstrate polarization-insensitive planar light diffraction in the visible spectral range. Moreover, by combining dark-field imaging with analytical multiparticle calculations in the framework of the generalized Mie theory, we show that plasmonic spirals support distinctive structural resonances with circular symmetry carrying orbital angular momentum. The engineering of light scattering phenomena in deterministic structures with circular Fourier space provides a novel strategy for the realization of optical devices that fully leverage on enhanced, polarization-insensitive light-matter coupling over planar surfaces, such as thin-film plasmonic solar cells, plasmonic polarization devices, and optical biosensors.
Axial Current and Noether Charge
Mahato, Prasanta
2012-01-01
A decade ago, a Lagrangian density has been proposed by the author where only the local symmetries of the Lorentz subgroup of (A)ds group is retained. This formalism has been found to produce some results encompassing that of standard Einstein-Hilbert formalism. In the present article, the conserved axial vector matter currents, constructed in some earlier paper, have been found to be a result of Noether's theorem. PACS: 04.20.Fy, 04.20.Cv, 11.40.-q Keywords: Torsion, Axial Current, Noether's Theorem
An Axial-Vector Photon in a Mirror World
Sharafiddinov, Rasulkhozha S.
2016-03-01
The unity of symmetry laws emphasizes, in the case of a mirror CP-even Dirac Lagrangian, the ideas of the left- and right-handed axial-vector photons referring to long- and short-lived bosons of true neutrality, respectively. Such a difference in lifetimes expresses the unidenticality of masses, energies and momenta of axial-vector photons of the different components. They define the unified field theory equation of C-odd particles with an integral spin. Together with a new equation of a theory of truly neutral particles with the half-integral spin, the latter reflects the availability in their nature of the second type of the local axial-vector gauge transformation responsible for origination in the Lagrangian of C-oddity of an interaction Newton component giving an axial-vector mass to all the interacting particles and fields. The mirror axial-vector mass, energy and momentum operators constitute a CP-invariant equation of quantum mechanics, confirming that each of them can individually influence on matter field. Thereby, findings suggest at the level of the mass-charge structure of gauge invariance a new equation for the C-noninvariant Lagrangian.
Luce, J.S.; Smith, L.P.
1960-11-22
A method and apparatus are given for producing coaxial arc discharges in an evacuated enclosure and within a strong, confining magnetic field. The arcs are maintained at a high potential difference. Electrons will diffuse to the more positive arc from the negative arc, and positive ions will diffuse from the more positive arc to the negative arc. Coaxial arc discharges have the advantage that ions which return to strike the positive arc discharge will lose no energy since they do not strike a solid wall or electrode. Those discharges are useful in confining an ionized plasma between the discharges, and have the advantage of preventing impurities from the walls of the enclosure from entering ihe plasma area because of the arc barrier set up bv the cylindrical outer arc.
Symmetric normalisation for intuitionistic logic
DEFF Research Database (Denmark)
Guenot, Nicolas; Straßburger, Lutz
2014-01-01
, but using a non-local rewriting. The second system is the symmetric completion of the first, as normally given in deep inference for logics with a DeMorgan duality: all inference rules have duals, as cut is dual to the identity axiom. We prove a generalisation of cut elimination, that we call symmetric...... normalisation, where all rules dual to standard ones are permuted up in the derivation. The result is a decomposition theorem having cut elimination and interpolation as corollaries.......We present two proof systems for implication-only intuitionistic logic in the calculus of structures. The first is a direct adaptation of the standard sequent calculus to the deep inference setting, and we describe a procedure for cut elimination, similar to the one from the sequent calculus...
SELF-SIMILAR SOLUTIONS OF FRACTURE DYNAMICS PROBLEMS ON AXIALLY SYMMETRY
Institute of Scientific and Technical Information of China (English)
吕念春; 程靳; 程云虹; 屈德志
2001-01-01
By the theory of complex functions, a penny-shaped crack on axially symmetric propagating problems for composite materials was studied. The general representations of the analytical solutions with arbitrary index of self-similarity were presented for fracture elastodynamics problems on axially symmetry by the ways of self-similarity under the /addershaped loads. The problerns dealt with can be transformed into Riemann-Hilbert problems and their closed analytical solutions are obtained rather simple by this method. After those analytical solutions are utilized by using the method of rotational superposition theorem in conjunction with that of Smirnov-Sobolev, the solutions of arbitrary complicated problems can be obtained.
Symmetric two-coordinate photodiode
Directory of Open Access Journals (Sweden)
Dobrovolskiy Yu. G.
2008-12-01
Full Text Available The two-coordinate photodiode is developed and explored on the longitudinal photoeffect, which allows to get the coordinate descriptions symmetric on the steepness and longitudinal resistance great exactness. It was shown, that the best type of the coordinate description is observed in the case of scanning by the optical probe on the central part of the photosensitive element. The ways of improvement of steepness and linear of its coordinate description were analyzed.
A note on obtaining symmetrical angular yield curves in MeV ion channeling
Ruan, J.; Townsend, J.; Choyke, W. J.
1987-11-01
Planar channeling effects can distort the angular yield (dip) curve measured about an axial channeling direction. Two methods for minimizing distortion due to planar channeling are discussed: 1) varying the angles θ and φ of a two-axis goniometer together during the angular scan, and 2) remounting the sample so that a scan of only θ produces an undistorted symmetric dip curve. In practice, remounting the sample is preferred in order to minimize effects due to the mechanical limitations of the goniometer.
Three-dimensional modes of a symmetric nonlinear plane waveguide
Akhmediev, N. N.; Nabiev, R. F.; Popov, Yu. M.
1989-01-01
The three-dimensional problem of a symmetric nonlinear plane waveguide, which consist of a linear medium layer surrounded by nonlinear media, is investigated. The stationary solution of this problem is a mode whose field is falling to zero at infinity in all directions perpendicular to the propagation direction. The even, odd and assymetrical solutions of the problem are obtained.
Symmetric-key cryptosystem with DNA technology
Institute of Scientific and Technical Information of China (English)
LU MingXin; LAI XueJia; XIAO GuoZhen; QIN Lei
2007-01-01
DNA cryptography is a new field which has emerged with progress in the research of DNA computing. In our study, a symmetric-key cryptosystem was designed by applying a modern DNA biotechnology, microarray, into cryptographic technologies. This is referred to as DNA symmetric-key cryptosystem (DNASC). In DNASC,both encryption and decryption keys are formed by DNA probes, while its ciphertext is embedded in a specially designed DNA chip (microarray). The security of this system is mainly rooted in difficult biology processes and problems, rather than conventional computing technology, thus it is unaffected by changes from the attack of the coming quantum computer. The encryption process is a fabrication of a specially designed DNA chip and the decryption process is the DNA hybridization.In DNASC, billions of DNA probes are hybridized and identified at the same time,thus the decryption process is conducted in a massive, parallel way. The great potential in vast parallelism computation and the extraordinary information density of DNA are displayed in DNASC to some degree.
Electroweak Baryogenesis in R-symmetric Supersymmetry
Energy Technology Data Exchange (ETDEWEB)
Fok, R.; Kribs, Graham D.; Martin, Adam; Tsai, Yuhsin
2013-03-01
We demonstrate that electroweak baryogenesis can occur in a supersymmetric model with an exact R-symmetry. The minimal R-symmetric supersymmetric model contains chiral superfields in the adjoint representation, giving Dirac gaugino masses, and an additional set of "R-partner" Higgs superfields, giving R-symmetric \\mu-terms. New superpotential couplings between the adjoints and the Higgs fields can simultaneously increase the strength of the electroweak phase transition and provide additional tree-level contributions to the lightest Higgs mass. Notably, no light stop is present in this framework, and in fact, we require both stops to be above a few TeV to provide sufficient radiative corrections to the lightest Higgs mass to bring it up to 125 GeV. Large CP-violating phases in the gaugino/higgsino sector allow us to match the baryon asymmetry of the Universe with no constraints from electric dipole moments due to R-symmetry. We briefly discuss some of the more interesting phenomenology, particularly of the of the lightest CP-odd scalar.
Axial structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Veronique Bernard; Latifa Elouadrhiri; Ulf-G Meissner
2002-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Numerical analysis of cavitation within slanted axial-flow pump
Institute of Scientific and Technical Information of China (English)
张睿; 陈红勋
2013-01-01
In this paper, the cavitating flow within a slanted axial-flow pump is numerically researched. The hydraulic and cavitation performance of the slanted axial-flow pump under different operation conditions are estimated. Compared with the experimental hydraulic performance curves, the numerical results show that the filter-based model is better than the standard k-e model to predict the parameters of hydraulic performance. In cavitation simulation, compared with the experimental results, the proposed numerical method has good predicting ability. Under different cavitation conditions, the internal cavitating flow fields within slanted axial-flow pump are investigated. Compared with flow visualization results, the major internal flow features can be effectively grasped. In order to explore the origin of the cavitation performance breakdown, the Boundary Vorticity Flux (BVF) is introduced to diagnose the cavitating flow fields. The analysis results indicate that the cavitation performance drop is relevant to the instability of cavitating flow on the blade suction surface.
Duality symmetric string and M-theory
Berman, David S.; Thompson, Daniel C.
2015-03-01
We review recent developments in duality symmetric string theory. We begin with the world-sheet doubled formalism which describes strings in an extended spacetime with extra coordinates conjugate to winding modes. This formalism is T-duality symmetric and can accommodate non-geometric T-fold backgrounds which are beyond the scope of Riemannian geometry. Vanishing of the conformal anomaly of this theory can be interpreted as a set of spacetime equations for the background fields. These equations follow from an action principle that has been dubbed Double Field Theory (DFT). We review the aspects of generalised geometry relevant for DFT. We outline recent extensions of DFT and explain how, by relaxing the so-called strong constraint with a Scherk-Schwarz ansatz, one can obtain backgrounds that simultaneously depend on both the regular and T-dual coordinates. This provides a purely geometric higher dimensional origin to gauged supergravities that arise from non-geometric compactification. We then turn to M-theory and describe recent progress in formulating an En(n) U-duality covariant description of the dynamics. We describe how spacetime may be extended to accommodate coordinates conjugate to brane wrapping modes and the construction of generalised metrics in this extended space that unite the bosonic fields of supergravity into a single object. We review the action principles for these theories and their novel gauge symmetries. We also describe how a Scherk-Schwarz reduction can be applied in the M-theory context and the resulting relationship to the embedding tensor formulation of maximal gauged supergravities.
On the integrability of PT-symmetric dimers
Pickton, J
2013-01-01
The coupled discrete linear and Kerr nonlinear Schrodinger equations with gain and loss describing transport on dimers with parity-time (PT) symmetric potentials are considered. The model is relevant among others to experiments in optical couplers and proposals on Bose-Einstein condensates in PT symmetric double-well potentials. It is shown that the models are integrable. A pendulum equation with a linear potential and a constant force for the phase-difference between the fields is obtained, which explains the presence of unbounded solutions above a critical threshold parameter.
Institute of Scientific and Technical Information of China (English)
Mohammed Ashraful Islam
2000-01-01
The analytic cosmological solutions of Einstein's field equations for a type of static metric representing plane, spherical and hyperbolic symmetric spaces are presented and their properties are discussed separately. A general type of solution is obtained which represents the plane, spherical and hyperbolic symmetric cosmological models. Its physical properties are also discussed in details.
Strong cosmic censorship for T^2-symmetric cosmological spacetimes with collisionless matter
Dafermos, M; Dafermos, Mihalis; Rendall, Alan D.
2006-01-01
We prove strong cosmic censorship for T^2-symmetric cosmological spacetimes (with spatial topology T^3 and vanishing cosmological constant Lambda) with collisionless matter. Gowdy symmetric spacetimes constitute a special case. The formulation of the conjecture is in terms of generic C^2-inextendibility of the metric. Our argument exploits a rigidity property of Cauchy horizons, inherited from Killing fields.
Singular Value Decomposition for Unitary Symmetric Matrix
Institute of Scientific and Technical Information of China (English)
ZOUHongxing; WANGDianjun; DAIQionghai; LIYanda
2003-01-01
A special architecture called unitary sym-metric matrix which embodies orthogonal, Givens, House-holder, permutation, and row (or column) symmetric ma-trices as its special cases, is proposed, and a precise corre-spondence of singular values and singular vectors between the unitary symmetric matrix and its mother matrix is de-rived. As an illustration of potential, it is shown that, for a class of unitary symmetric matrices, the singular value decomposition (SVD) using the mother matrix rather than the unitary symmetric matrix per se can save dramatically the CPU time and memory without loss of any numerical precision.
Symmetric products of mixed Hodge modules
Maxim, Laurentiu; Schuermann, Joerg
2010-01-01
Generalizing a theorem of Macdonald, we show a formula for the mixed Hodge structure on the cohomology of the symmetric products of bounded complexes of mixed Hodge modules by showing the existence of the canonical action of the symmetric group on the multiple external self-products of complexes of mixed Hodge modules. We also generalize a theorem of Hirzebruch and Zagier on the signature of the symmetric products of manifolds to the case of the symmetric products of symmetric parings on bounded complexes with constructible cohomology sheaves where the pairing is not assumed to be non-degenerate.
An Axial Vector Photon in a Mirror World
Sharafiddinov, Rasulkhozha S
2015-01-01
The unity of symmetry laws emphasizes, in the case of a mirror CP-even Dirac Lagrangian, the ideas of the left- and right-handed axial-vector photons referring to long- and short-lived bosons of true neutrality, respectively. Such a difference in lifetimes expresses the unidenticality of masses, energies and momenta of axial-vector photons of the different components. They define the unified field theory equation of C-odd particles with an integral spin. Together with a new equation of a theory of truly neutral particles with the half-integral spin, the latter reflects the availability in their nature of the second type of the local axial-vector gauge transformation responsible for origination in the Lagrangian of C-oddity of an interaction Newton component giving an axial-vector mass to all the interacting particles and fields. The mirror axial-vector mass, energy and momentum operators constitute a CP-invariant equation of quantum mechanics, confirming that each of them can individually influence on matter ...
Phase-coupled optical diode based on PT symmetric system
Gao, Yong-Pan; Cao, Cong; Zhang, Yong; Wang, Tie-Jun; Wang, Chuan
2017-01-01
Here we investigate a phase-coupled parity-time symmetric plasmonic system, and theoretically achieved the all optical on-chip plasmonic diode using the coupled mode theory. The proposed symmetrical system consists of one loss cavity and one gain cavity each coupled with the waveguide, and we find that the controllable amplification of the input field can be achieved by changing the power coupling fraction between the resonators and the waveguide. Moreover, this loss-gain symmetric system could work as a frequency comb filter, and the operation on the device could be controlled by tuning the coupling strength between the two plasmonic cavities by tuning the coupling distance between the cavities and the waveguide.
Lagrangian formulation of symmetric space sine-Gordon models
Bakas, Ioannis; Shin, H J; Park, Q Han
1996-01-01
The symmetric space sine-Gordon models arise by conformal reduction of ordinary 2-dim \\sigma-models, and they are integrable exhibiting a black-hole type metric in target space. We provide a Lagrangian formulation of these systems by considering a triplet of Lie groups F \\supset G \\supset H. We show that for every symmetric space F/G, the generalized sine-Gordon models can be derived from the G/H WZW action, plus a potential term that is algebraically specified. Thus, the symmetric space sine-Gordon models describe certain integrable perturbations of coset conformal field theories at the classical level. We also briefly discuss their vacuum structure, Backlund transformations, and soliton solutions.
Rings with involution whose symmetric elements are central
Directory of Open Access Journals (Sweden)
Taw Pin Lim
1980-01-01
Full Text Available In a ring R with involution whose symmetric elements S are central, the skew-symmetric elements K form a Lie algebra over the commutative ring S. The classification of such rings which are 2-torsion free is equivalent to the classification of Lie algebras K over S equipped with a bilinear form f that is symmetric, invariant and satisfies [[x,y],z]=f(y,zx−f(z,xy. If S is a field of char ≠2, f≠0 and dimK>1 then K is a semisimple Lie algebra if and only if f is nondegenerate. Moreover, the derived algebra K′ is either the pure quaternions over S or a direct sum of mutually orthogonal abelian Lie ideals of dim≤2.
Nonlinear waves in $\\cal PT$-symmetric systems
Konotop, Vladimir V; Zezyulin, Dmitry A
2016-01-01
Recent progress on nonlinear properties of parity-time ($\\cal PT$-) symmetric systems is comprehensively reviewed in this article. $\\cal PT$ symmetry started out in non-Hermitian quantum mechanics, where complex potentials obeying $\\cal PT$ symmetry could exhibit all-real spectra. This concept later spread out to optics, Bose-Einstein condensates, electronic circuits, and many other physical fields, where a judicious balancing of gain and loss constitutes a $\\cal PT$-symmetric system. The natural inclusion of nonlinearity into these $\\cal PT$ systems then gave rise to a wide array of new phenomena which have no counterparts in traditional dissipative systems. Examples include the existence of continuous families of nonlinear modes and integrals of motion, stabilization of nonlinear modes above $\\cal PT$-symmetry phase transition, symmetry breaking of nonlinear modes, distinctive soliton dynamics, and many others. In this article, nonlinear $\\cal PT$-symmetric systems arising from various physical disciplines ...
Dispersion of axially symmetric waves in fluid-filled cylindrical shells
DEFF Research Database (Denmark)
Bao, X.L.; Überall, H.; Raju, P. K.;
2000-01-01
, 317 (1972)]. We have extended the work of Kumar to the case of fluid-filled aluminum shells and steel shells imbedded in air. These cases demonstrate the existence of circumferential waves traveling in the filler fluid, exhibiting a certain simplicity of the dispersion curves of these waves....... This is in striking contrast to the results for double (outside and inside) loading by two fluids of comparable density, where circumferential waves in both external and internal fluids were found, their interaction causing segmentation and repulsion phenomena of their dispersion curves. The condition of standing...
Comparison between formulas of rotational band for axially symmetric deformed nuclei
Institute of Scientific and Technical Information of China (English)
WU Xi; LEI Yi-An
2008-01-01
The experimental rotational spectra of the deformed nuclei available in even-even and odd-A nuclei in the rare-earth and actinide regions are systematically analyzed with several rotational spectra formulas,including Bohr-Mottelson's I(I+l)-expansion,Harris'w2-expansion,ab and abc formulas.It is shown that the simple 2-parameter ab formula is much better than the widely used 2-parameter Bohr-Mottelson's AB formula and Harris'αβ formula.The available data of the rotational spectra of both ground-state band in even-even nuclei and one-quaasiparticle band in odd-A nuclei can be conveniently and rather accurately reproduced by ab formula and abc formula.The moment of inertia and the variation with rotational frequency of angular momentum can be satisfactorily reproduced by ab and abc formulas.
Influence of angular momentum in axially symmetric potentials with octupole deformation
Institute of Scientific and Technical Information of China (English)
JIN Hua; SUN Zhen-Wu; ZHENG Ren-Rong
2009-01-01
The chaotic classical single-particle motion in an oblate octupole deformed potential with a non-zero z-component of angular momentum Lz is investigated. The stability analysis of the trajectories shows that with increasing rotation of the system, the unstable negative curvature regions of the effective potential surface decrease, which converts the chaotic motion of the system into a regular one.
Directory of Open Access Journals (Sweden)
Khalaf A. M.
2015-04-01
Full Text Available The interacting boson model (sd-IBM1 with intrinsic coherent state is used to study the shape phase transitions from spherical U(5 to prolate deformed SU(3 shapes in Nd- Sm isotopic chains. The Hamiltonian is written in the creation and annihilation form with one and two body terms.For each nucleus a fitting procedure is adopted to get the best model parameters by fitting selected experimental energy levels, B(E2 transi- tion rates and two-neutron separation energies with the calculated ones.The U(5-SU(3 IBM potential energy surfaces (PES’s are analyzed and the critical phase transition points are identified in the space of model parameters.In Nd-Sm isotopic chains nuclei evolve from spherical to deformed shapes by increasing the boson number. The nuclei 150 Nd and 152 Sm have been found to be close to critical points.We have also studied the energy ratios and the B(E2 values for yrast band at the critical points.
A numerical study of Penrose-like inequalities in a family of axially symmetric initial data
Jaramillo, J L; Ansorg, M
2007-01-01
Our current picture of black hole gravitational collapse relies on two assumptions: i) the resulting singularity is hidden behind an event horizon -- weak cosmic censorship conjecture -- and ii) spacetime eventually settles down to a stationarity state. In this setting, it follows that the minimal area containing an apparent horizon is bound by the square of the total ADM mass (Penrose inequality conjecture). Following Dain et al. 2002, we construct numerically a family of axisymmetric initial data with one or several marginally trapped surfaces. Penrose and related geometric inequalities are discused for these data. As a by-product, it is shown how Penrose inequality can be used as a diagnosis for an apparent horizon finder numerical routine.
Casimir Energy in the Axial Gauge
Esposito, G; Kirsten, K; Esposito, Giampiero; Kamenshchik, Alexander Yu.; Kirsten, Klaus
2000-01-01
The zero-point energy of a conducting spherical shell is studied by imposing the axial gauge via path-integral methods, with boundary conditions on the electromagnetic potential and ghost fields. The coupled modes are then found to be the temporal and longitudinal modes for the Maxwell field. The resulting system can be decoupled by studying a fourth-order differential equation with boundary conditions on longitudinal modes and their second derivatives. The exact solution of such equation is found by using a Green-function method, and is obtained from Bessel functions and definite integrals involving Bessel functions. Complete agreement with a previous path-integral analysis in the Lorenz gauge, and with Boyer's value, is proved in detail.
Optimization of axial blowers. Optimierung von Axial-Ventilatoren
Energy Technology Data Exchange (ETDEWEB)
Bolte, W.
1992-08-01
For the optimum possible design of axial blowers, trials are evaluated in the article, which are based on the grid profile examined by N. Scholz. The computation for the pressure number and the primary degree of efficiency are shown as well as the evaluation of the effect of the Reynolds and mach number on the degree of efficiency and determination of the secondary losses. In a final example, the dimensions of a blower are computed from the data determined during the trials. (orig.).
Low-pressure reversible axial fan with straight profile blades and relatively high efficiency
2012-01-01
The paper presents the design and operating characteristics of a model of reversible axial fan with only one impeller, whose reversibility is achieved by changing the direction of rotation. The fan is designed for the purpose of providing alternating air circulation in wood dryers in order to reduce the consumption of electricity for the fan and increase energy efficiency of the entire dryer. To satisfy the reversibility of flow, the shape of the blade profile is symmetrical along the l...
Classical limits of boot-rotation symmetric spacetimes
Kofron, David
2010-01-01
Boost-rotation symmetric spacetimes are exceptional as they are the only exact asymptotically flat solutions to the Einstein equations describing spatially bounded sources ("point-like" particles, black holes) undergoing non-trivial motion ("uniform acceleration") with radiation. We construct the Newtonian limit of these spacetimes: it yields fields of uniformly accelerated sources in classical mechanics. We also study the special-relativistic limit of the charged rotating C-metric and so find accelerating electromagnetic magic field.
Supercharacters, symmetric functions in noncommuting variables, and related Hopf algebras
Aguiar, Marcelo; Benedetti, Carolina; Bergeron, Nantel; Chen, Zhi; Diaconis, Persi; Hendrickson, Anders; Hsiao, Samuel; Isaacs, I Martin; Jedwab, Andrea; Johnson, Kenneth; Karaali, Gizem; Lauve, Aaron; Le, Tung; Lewis, Stephen; Li, Huilan; Magaard, Kay; Marberg, Eric; Novelli, Jean-Christophe; Pang, Amy; Saliola, Franco; Tevlin, Lenny; Thibon, Jean-Yves; Thiem, Nathaniel; Venkateswaran, Vidya; Vinroot, C Ryan; Yan, Ning; Zabrocki, Mike
2010-01-01
We identify two seemingly disparate structures: supercharacters, a useful way of doing Fourier analysis on the group of unipotent uppertriangular matrices with coefficients in a finite field, and the ring of symmetric functions in noncommuting variables. Each is a Hopf algebra and the two are isomorphic as such. This allows developments in each to be transferred. The identification suggests a rich class of examples for the emerging field of combinatorial Hopf algebras.
Discrete Torsion and Symmetric Products
Dijkgraaf, R
1999-01-01
In this note we point out that a symmetric product orbifold CFT can be twisted by a unique nontrivial two-cocycle of the permutation group. This discrete torsion changes the spins and statistics of corresponding second-quantized string theory making it essentially ``supersymmetric.'' The long strings of even length become fermionic (or ghosts), those of odd length bosonic. The partition function and elliptic genus can be described by a sum over stringy spin structures. The usual cubic interaction vertex is odd and nilpotent, so this construction gives rise to a DLCQ string theory with a leading quartic interaction.
A charged spherically symmetric solution
Indian Academy of Sciences (India)
K Moodley; S D Maharaj; K S Govinder
2003-09-01
We ﬁnd a solution of the Einstein–Maxwell system of ﬁeld equations for a class of accelerating, expanding and shearing spherically symmetric metrics. This solution depends on a particular ansatz for the line element. The radial behaviour of the solution is fully speciﬁed while the temporal behaviour is given in terms of a quadrature. By setting the charge contribution to zero we regain an (uncharged) perfect ﬂuid solution found previously with the equation of state =+ constant, which is a generalisation of a stiff equation of state. Our class of charged shearing solutions is characterised geometrically by a conformal Killing vector.
Parallel Symmetric Eigenvalue Problem Solvers
2015-05-01
taken from a uniform distribution in [−W/2,+W/2] with some W ∈ [1, 30], meaning the Hamiltonian matrix will likely be symmetric indefinite. This W...residual vectors Rk = AYk −BYkΘk 8: Test for convergence 9: Solve the set of linear systems AVk+1 = BYk 10: end for Our test matrix A is a synthetic test...have squared the condition number of the matrix , so it is now more difficult to solve the linear systems arising at each TraceMin iteration. Again
Theory and experiment for soap-film bridge in an electric field.
Moulton, Derek E; Pelesko, John A
2008-06-01
Surface tension and electrostatic forces dominate the behavior of many micro and nano scale systems. Understanding interactions between these forces may therefore be of great utility in a number of engineering systems. We investigate one such interaction by subjecting an elastic membrane suspended between two parallel rings to an axially symmetric electric field. A model is formulated and analyzed and the effect of the field is characterized. Experimentally, the system is investigated using a soap-film bridge and a high voltage power source. Experimental observations verify the validity of the theory, in predicting both membrane profile as well as critical device length at which stability is lost.
A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates
Directory of Open Access Journals (Sweden)
Fufei Liu
2017-01-01
Full Text Available To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range.
A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates
Liu, Fufei; Dai, Yutang; Karanja, Joseph Muna; Yang, Minghong
2017-01-01
To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating) accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range. PMID:28117740
Disk-Magnetosphere Interaction and Outflows: Conical Winds and Axial Jets
Romanova, M M; Koldoba, A V; Lovelace, R V E
2009-01-01
We investigate outflows from the disk-magnetosphere boundary of rotating magnetized stars in cases where the magnetic field of a star is bunched into an X-type configuration using axisymmetric and full 3D MHD simulations. Such configuration appears if viscosity in the disk is larger than diffusivity, or if the accretion rate in the disk is enhanced. Conical outflows flow from the inner edge of the disk to a narrow shell with an opening angle 30-45 degrees. Outflows carry 0.1-0.3 of the disk mass and part of the disk's angular momentum outward. Conical outflows appear around stars of different periods, however in case of stars in the "propeller" regime, an additional - much faster component appears: an axial jet, where matter is accelerated up to very high velocities at small distances from the star by magnetic pressure force above the surface of the star. Exploratory 3D simulations show that conical outflows are symmetric about rotational axis of the disk even if magnetic dipole is significantly misaligned. C...
Axial Spondyloarthritis: An Evolving Concept
Directory of Open Access Journals (Sweden)
Nelly Ziadé
2015-07-01
Full Text Available Axial spondyloarthritis (AxSpA is the prototype of a family of inter-related yet heterogeneous diseases sharing common clinical and genetic manifestations: the spondyloarthritides (SpAs. The condition mainly affects the sacroiliac joints and axial skeleton, and has a clear classification scheme, wider epidemiological data, and distinct therapeutic guidelines when compared with other SpAs. However, the concept of AxSpA has not been immutable over time and has evolved tremendously on many levels over the past decades. This review identifies the evolution of the AxSpA concept at two levels. First, at the level of classification, the old classifications and rationales leading to the current Assessment of SpondyloArthritis international Society (ASAS classification are reviewed, and the advantages and drawbacks are discussed. Second, at the therapeutic level, current and future treatments are described and treatment strategies are discussed.
[Axial spondyloarthritis and ankylosing spondylitis].
Nordström, Dan; Kauppi, Markku
2010-01-01
Current classification criteria for ankylosing spondylitis do not allow diagnosis before radiographic changes are visible in sacroiliacal joints. The the new axial spondyloarthropathy (SpA) criteria include axial SpA without radiographic changes as well as established ankylosing spondylitis, recognizing them as a continuum of the same disease. This is of major importance as the burden of early SpA is comparable to that of later stage disease. Diagnosis relies on inflammatory MRI findings which is the most significant change compared to earlier criteria. Emerging data on the efficacy of tumor necrosis factor (TNF) alpha blocking therapies already in early but also in established disease have given new promising alternatives for treatment of this often very cumbersome disease, that rarely responds to classic DMARDs.
Self-collimated axial jets from thin accretion disks
Tirabassi, Giulio; Carlevaro, Nakia; Benini, Riccardo
2012-01-01
We show how an appropriate stationary crystalline structure of the magnetic field can induce a partial fragmentation of the accretion disk, generating an axial jet composed of hot rising plasma twisted in a funnel-like structure by the rotation of the system. The most important feature of the obtained jet is its high degree of collimation, naturally arising from the condition for its existence. The presence of non-zero dissipative effects allows the plasma ejection throughout the axial jet and the predicted values of the accretion rate are in agreement with observations.
An effective theory for QCD with an axial chemical potential
Andrianov, Alexander A; Espriu, Domenec; Planells, Xumeu
2013-01-01
We consider the low energy realization of QCD in terms of meson fields when an axial chemical potential is present; a situation that may be relevant in heavy ion collisions. We shall demonstrate that the presence of an axial charge constitutes an explicit source of parity breaking. The eigenstates of strong interactions do not have a definite parity and interactions that would otherwise be forbidden compete with the familiar ones. In this work, we first focus on scalars and pseudoscalars that are described by a generalized linear sigma model; and next, we give some hints on how the Vector Meson Dominance model describes the vector sector.
Single Rod Vibration in Axial Flow
Weichselbaum, Noah; Wang, Shengfu; Bardet, Philippe
2013-11-01
Fluid structure interaction of a single rod in axial flow is a coupled dynamical system present in many application including nuclear reactors, steam generators, and towed antenna arrays. Fluid-structure response can be quantified thanks to detailed experimental data where both structure and fluid responses are recorded. Such datum deepen understanding of the physics inherent to the system and provide high-dimensionality quantitative measurements to validate coupled structural and CFD codes with various level of complexity. In this work, single rods fixed on both ends in a concentric pipe, are subjected to an axial flow with Reynolds number based on hydraulic diameter of Re =4000. Rods of varying material stiffness and diameter are utilized in the experiment resulting in a range of dimensionless U between 0.5 and 1, where U = (ρA/EI)1/2uL. Experimental measurements of the velocity field around the rod are taken with PIV from time-resolved Nd:YLF laser and a high speed CMOS camera. Three-dimensional and temporal vibration and deflection of the rod is recorded with shadowgraphy utilizing two sets of pulsed high power LED and dedicated CMOS camera. Through integration of these two diagnostics, it is possible to reconstruct the full FSI domain providing unique validation data.
Schwarz Methods: To Symmetrize or Not to Symmetrize
Holst, Michael
2010-01-01
A preconditioning theory is presented which establishes sufficient conditions for multiplicative and additive Schwarz algorithms to yield self-adjoint positive definite preconditioners. It allows for the analysis and use of non-variational and non-convergent linear methods as preconditioners for conjugate gradient methods, and it is applied to domain decomposition and multigrid. It is illustrated why symmetrizing may be a bad idea for linear methods. It is conjectured that enforcing minimal symmetry achieves the best results when combined with conjugate gradient acceleration. Also, it is shown that absence of symmetry in the linear preconditioner is advantageous when the linear method is accelerated by using the Bi-CGstab method. Numerical examples are presented for two test problems which illustrate the theory and conjectures.
Unsteady cooperative flow type in the axial compressor
Institute of Scientific and Technical Information of China (English)
ZHENG Xinqian; ZHOU Sheng; HOU Anping; XIONG Jinsong
2005-01-01
For increasing the performance of the axial compressor, a method for realizing unsteady cooperative flow type is proposed in this paper as a critical objective in the new generation of the axial compressor design system. Unsteady excitations were utilized to trigger the transformation from the unsteady natural flow pattern into the unsteady cooperative flow pattern, resulting in increment of aerodynamic performances of axial compressor. Numerical simulations show that distinct positive effect can be obtained for the 2D cascade in a wide range of subsonic working conditions. No positive effect can be observed under the 2D supersonic working conditions and unsteady excitations have little influence on the flow field space-time structure. However, positive effect can be obtained under the 3D transsonic working conditions. In addition, engineering applications of unsteady cooperative flow type are discussed.
Development and Testing of an Axial Halbach Magnetic Bearing
Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.
2006-01-01
The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.
Golimumab for treatment of axial spondyloarthritis.
Rios Rodriguez, Valeria; Poddubnyy, Denis
2016-02-01
Axial spondyloarthritis comprises two forms: nonradiographic (nonradiographic axial spondyloarthritis) and radiographic (better known as ankylosing spondylitis), which are often considered as two stages of one disease. Historically, all currently available TNF-α inhibitors were first investigated in ankylosing spondylitis and later on in nonradiographic axial spondyloarthritis. This year, EMA has granted golimumab approval for the treatment of active nonradiographic axial spondyloarthritis based on the recently published data from the GO-AHEAD study. This article summarizes recent data on efficacy and safety of golimumab in the treatment of ankylosing spondylitis and nonradiographic axial spondyloarthritis.
Energy Technology Data Exchange (ETDEWEB)
Carolus, T.; Schneider, M.
2002-10-01
A computer program for predicting the wide-band noise spectrom of axial blower rotors from flow field variables was developed. First, a bibliographic search was carried out on current methods of noise prediction. The main input parameters of the selected methods were varied systematically in the sense of a sensitivity analysis in order to check the plausibility of the results and assess the accuracy required of the input parameters. The selected methods were implemented in a user-friendly PC program ('SIBNOISE-AX'). The methods and the computer program were tested using the example of two blowers, i.e. a low-pressure and a high-pressure axial blower. Both blowers were calculated without guide wheels as the research project focused on rotor wheel noise only. Aerodynamic and acoustic data were obtained in a standard test stand in order to provide a data base. Time-averaged flow fields in the rotor wheels were calculated using a commercial CFD code, and parameters like boundary layer thickness and relevant velocities in the blade region were derived which - in addition to simple estimates - were used as input parameters in the noise prediction methods. The results provided by the calculations differed depending on the method employed, but some methods provided results that were in good agreement with the measurements. Their accuracy was sufficient even when the input parameters were only estimated and could be improved further by using the numerically calculated flow field parameters. The research project was thus completed successfully.
Fine Spectra of Symmetric Toeplitz Operators
Directory of Open Access Journals (Sweden)
Muhammed Altun
2012-01-01
Full Text Available The fine spectra of 2-banded and 3-banded infinite Toeplitz matrices were examined by several authors. The fine spectra of n-banded triangular Toeplitz matrices and tridiagonal symmetric matrices were computed in the following papers: Altun, “On the fine spectra of triangular toeplitz operators” (2011 and Altun, “Fine spectra of tridiagonal symmetric matrices” (2011. Here, we generalize those results to the (2+1-banded symmetric Toeplitz matrix operators for arbitrary positive integer .
Axial electron channeling statistical method of site occupancy determination
Institute of Scientific and Technical Information of China (English)
YE; Jia
2001-01-01
［1］Johnson, W., Sowerby, R., Venter, R. D., Plane Strain Slip Line Fields for Metal Deformation Processes——A Source Book and Bibliography, New York: Pergamon Press, 1982.［2］Hill, R., The Mathematical Theory of Plasticity, Oxford: Oxford University Press, 1950.［3］Sokolovsky, V. V., Theory of Plasticity(in Russia), Moskow: Nat. Tech. Press, 1950.［4］Kachanov, L. M., Foundations Theory of Plasticity, London: North-Holland, 1975.［5］Shield, R. T., On the plastic flow of metal condition of axial symmetry, Proc. Roy. Soc., 1955, 233A: 267.［6］Lippmann, H., IUTAM Symposium on Metal Forming Plasticity, New York: Springer-Verlag, 1979.［7］Spencer, A. J. M., The approximate solution of certain problem of axially-symmetric plastic flow, J. Mech. Phys. Solids, 1964, 12: 231.［8］Wang, R., Xiong, Z. H., Wang, W. B., Foundation of Plasticity (in Chinese), Beijing: Science Press, 1982.［9］Collins, I. E., Dewhurst, P., A slip line field analysis of asymmetrical hot rolling, International Journal of Mechanical Science, 1975, 17: 643.［10］Collins, I. F., Slip line field analysis of forming processes in plane strain and axial symmetry, Advanced Technology of Plasticity, 1984, 11: 1074.［11］Yu, M. H., Yang, S. Y., Liu, C. Y. et al., Unified plane-strain slip line field theory system, J. Civil Engineering (in Chinese), 1997, 30(2): 14［12］Simmons, J. A., Hauser, F., Dorn, E., Mathematical Theories of Plastic Deformation Under Impulsive Loading, Berkeley-Los Angeles: University of California Press, 1962.［13］Lin, C. C., On a perturbation theory based on the method of characteristies, J. Math. Phys., 1954, 33: 117—134.［14］Hopkins, H. G., The method of characteristics and its applications to the theory of stress waver in solids, in Engineering Plasticity, Combridge: Combridge University Press, 1968, 277—315.［15］Shield, R. T., The plastic indentation of a layer by a flat punch, Quart. Appl. Math., 1955, 13: 27.［16］Haar, A., von
Symmetric functions and Hall polynomials
MacDonald, Ian Grant
1998-01-01
This reissued classic text is the acclaimed second edition of Professor Ian Macdonald's groundbreaking monograph on symmetric functions and Hall polynomials. The first edition was published in 1979, before being significantly expanded into the present edition in 1995. This text is widely regarded as the best source of information on Hall polynomials and what have come to be known as Macdonald polynomials, central to a number of key developments in mathematics and mathematical physics in the 21st century Macdonald polynomials gave rise to the subject of double affine Hecke algebras (or Cherednik algebras) important in representation theory. String theorists use Macdonald polynomials to attack the so-called AGT conjectures. Macdonald polynomials have been recently used to construct knot invariants. They are also a central tool for a theory of integrable stochastic models that have found a number of applications in probability, such as random matrices, directed polymers in random media, driven lattice gases, and...
Classification of symmetric toroidal orbifolds
Energy Technology Data Exchange (ETDEWEB)
Fischer, Maximilian; Ratz, Michael; Torrado, Jesus [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Vaudrevange, Patrick K.S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2012-09-15
We provide a complete classification of six-dimensional symmetric toroidal orbifolds which yield N{>=}1 supersymmetry in 4D for the heterotic string. Our strategy is based on a classification of crystallographic space groups in six dimensions. We find in total 520 inequivalent toroidal orbifolds, 162 of them with Abelian point groups such as Z{sub 3}, Z{sub 4}, Z{sub 6}-I etc. and 358 with non-Abelian point groups such as S{sub 3}, D{sub 4}, A{sub 4} etc. We also briefly explore the properties of some orbifolds with Abelian point groups and N=1, i.e. specify the Hodge numbers and comment on the possible mechanisms (local or non-local) of gauge symmetry breaking.
A Minimally Symmetric Higgs Boson
Low, Ian
2014-01-01
Models addressing the naturalness of a light Higgs boson typically employ symmetries, either bosonic or fermionic, to stabilize the Higgs mass. We consider a setup with the minimal amount of symmetries: four shift symmetries acting on the four components of the Higgs doublet, subject to the constraints of linearly realized SU(2)xU(1) electroweak symmetry. Up to terms that explicitly violate the shift symmetries, the effective lagrangian can be derived, irrespective of the spontaneously broken group G in the ultraviolet, and is universal in all models where the Higgs arises as a pseudo-Nambu-Goldstone boson (PNGB). Very high energy scatterings of vector bosons could provide smoking gun signals of a minimally symmetric Higgs boson.
Predicting the Coupling Properties of Axially-Textured Materials
Directory of Open Access Journals (Sweden)
María E. Fuentes-Montero
2013-10-01
Full Text Available A description of methods and computer programs for the prediction of “coupling properties” in axially-textured polycrystals is presented. Starting data are the single-crystal properties, texture and stereography. The validity and proper protocols for applying the Voigt, Reuss and Hill approximations to estimate coupling properties effective values is analyzed. Working algorithms for predicting mentioned averages are given. Bunge’s symmetrized spherical harmonics expansion of orientation distribution functions, inverse pole figures and (single and polycrystals physical properties is applied in all stages of the proposed methodology. The established mathematical route has been systematized in a working computer program. The discussion of piezoelectricity in a representative textured ferro-piezoelectric ceramic illustrates the application of the proposed methodology. Polycrystal coupling properties, predicted by the suggested route, are fairly close to experimentally measured ones.
Fast imaging of mean, axial and radial diffusion kurtosis
DEFF Research Database (Denmark)
Hansen, Brian; Shemesh, Noam; Jespersen, Sune Nørhøj
2016-01-01
Abstract Diffusion kurtosis imaging (DKI) is being increasingly reported to provide sensitive biomarkers of subtle changes in tissue microstructure. However, DKI also imposes larger data requirements than diffusion tensor imaging (DTI), hence, the widespread adaptation and exploration of DKI would...... for the first time, and referred to as axially symmetric DKI. The second approach is applicable in tissues with a priori known principal diffusion direction, and does not require fitting of any kind. The approaches are evaluated in human brain in vivo as well as in fixed rat spinal cord, and are demonstrated...... 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...
Computing symmetric colorings of the dihedral group
Zelenyuk, Yuliya
2016-06-01
A symmetry on a group G is a mapping G ∋ x ↦ gx-1 g ∈ G, where g ∈ G. A subset A ⊆ G is symmetric if it is invariant under some symmetry, that is, A = gA-1g. The notion of symmetry has interesting relations to enumerative combinatorics. A coloring is symmetric if χ(gx-1g) = χ(x) for some g ∈ G. We discuss an approach how to compute the number of symmetric r-colorings for any finite group. Using this approach we derive the formula for the number of symmetric r-colorings of the dihedral group D3.
Directory of Open Access Journals (Sweden)
A.M. Abd-Alla
2016-06-01
Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric rotating channel is studied under long wavelength and low Reynolds number assumptions are investigated. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity and shear stress on the channel walls have been computed numerically. The effects of the ratio of relaxation to retardation times, time-mean flow, rotation, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity and shear stress are discussed in detail and shown graphically. The results indicate that the effect of the ratio of relaxation to retardation times, time-mean flow, rotation, the phase angle and the gravitational field are very pronounced in the phenomena. Comparison was made with the results obtained in the asymmetric channel and symmetric channel.
Third-order aberrations of a plane symmetric optical system∗%面对称光学系统的初级波像差理论研究*
Institute of Scientific and Technical Information of China (English)
孙金霞; 潘国庆; 刘英
2013-01-01
The wave aberration theory of non-symmetrical optical systems is useful for understanding the misalignment in symmetrical systems and designing of off-axis mirror systems. A theory about the third-order aberrations for sub-aperture plane symmetric optical system is developed by using the aberration theory for full-aperture axially symmetric spherical systems. This paper proves the nodal aberration theory, namely, the points in the field with zero third-order aberration will deviate from the field center except for spherical aberration. It also reveals that the nodal aberrations arise from the transformation of the aberrations in full-aperture systems. This theory can be efficiently used in non-symmetric optical system designing process.% 非旋转轴对称光学系统波像差理论的建立有利于理解旋转轴对称光学系统的装调误差和离轴三反射光学系统等非旋转轴对称光学系统的选型设计。本文利用旋转轴对称球面光学系统的全口径初级波像差理论推导了子孔径面对称光学系统的初级波像差分布公式，证明了面对称光学系统中的节点像差理论，即除球差外的所有初级像差的零值节点偏离视场中心，而不再是视场的旋转对称函数；并首次阐述了多零值节点初级非对称像差产生的根源和变化特性。该理论可以有效指导非对称光学系统初始结构的选择和优化设计过程。
Automorphism groups of causal symmetric spaces of Cayley type and bounded symmetric domains
Institute of Scientific and Technical Information of China (English)
Soji; Kaneyuki
2005-01-01
Symmetric spaces of Cayley type are a higher dimensional analogue of a onesheeted hyperboloid in R3. They form an important class of causal symmetric spaces. To a symmetric space of Cayley type M, one can associate a bounded symmetric domain of tube type D. We determine the full causal automorphism group of M. This clarifies the relation between the causal automorphism group and the holomorphic automorphism group of D.
Institute of Scientific and Technical Information of China (English)
沙毅; 侯丽艳
2012-01-01
In order to investigate the variable-thickness performance of blade in a axial flow pump, a QY90-4.4-1.5 submersible axial flow pump with specific speed 550 and rotate velocity 2900 r/min, especially its particular impeller and guide vane has been designed on the basis of arc method and streamline method. Based on experiments with increasing in leaf thickness, the reason about the difference among curves of qv-H, qv-P, qv-tj were studied. The three-dimensional internal flow with effect of impeller blade thickness within axial flow has been numerically simulated by CFD, both the relative velocity distribution on the optimal condition and static pressure distribution on the different condition of blade surface were obtained. It can be revealed that pump performance with thin blade was improved, but the anti-cavitation was reduced. It also can be showed that the situations of flow separation, backflow and secondary flow were more serious for the thick blades, which were the main reasons for the low efficiency of pump.%为研究叶片厚度对轴流泵性能影响及其内部流场变化规律,该文采用圆弧法和流线法进行比转速550、转速2 900 r/min的QY90-4.4-1.5型潜水轴流泵水力模型设计,完成产品开发及样机型式试验.通过加厚叶轮叶片进行对比试验,阐明泵流量—扬程、流量—轴功率和流量—效率曲线产生差别的原因.采用计算流体动力学(CFD)方法进行叶片厚度对流场影响的数值计算,得到最优工况叶片表面相对速度分布和不同工况叶片表面静压分布.经过分析,阐明薄叶片总体性能优于厚叶片,但抗汽蚀性能可能劣于厚叶片.厚叶片翼型脱流、叶片进出口出现回流及二次流情况更为严重,水力损失较大,是泵效率等性能参数偏低的主要原因.
3-D Simulation of Vertical-Axial Tidal Current Turbine
Directory of Open Access Journals (Sweden)
Zhiyang Zhang
2016-12-01
Full Text Available Vertical-axial tidal current turbine is the key for the energy converter, which has the advantages of simple structure, adaptability to flow and uncomplex convection device. It has become the hot point for research and application recently. At present, the study on the hydrodynamic performance of vertical-axial tidal current turbine is almost on 2-D numerical simulation, without the consideration of 3-D effect. CFD (Computational Fluid Dynamics method and blade optimal control technique are used to improve accuracy in the prediction of tidal current turbine hydrodynamic performance. Numerical simulation of vertical-axial tidal current turbine is validated. Fixed and variable deflection angle turbine are comparatively studied to analysis the influence of 3-D effect and the character of fluid field and pressure field. The method, put the plate on the end of blade, of reduce the energy loss caused by 3-D effect is proposed. The 3-D CFD numerical model of vertical-axial tidal current turbine hydrodynamic performance in this study may provide theoretical, methodical and technical reference for the optimal design of turbine.
The Radially Symmetric Euler Equations as an Exterior Differential System
Baty, Roy; Ramsey, Scott; Schmidt, Joseph
2016-11-01
This work develops the Euler equations as an exterior differential system in radially symmetric coordinates. The Euler equations are studied for unsteady, compressible, inviscid fluids in one-dimensional, converging flow fields with a general equation of state. The basic geometrical constructions (for example, the differential forms, tangent planes, jet space, and differential ideal) used to define and analyze differential equations as systems of exterior forms are reviewed and discussed for converging flows. Application of the Frobenius theorem to the question of the existence of solutions to radially symmetric converging flows is also reviewed and discussed. The exterior differential system is further applied to derive and analyze the general family of characteristic vector fields associated with the one-dimensional inviscid flow equations.
Almost perfectly symmetric SWCNT-based CMOS devices and scaling.
Zhang, Zhiyong; Wang, Sheng; Wang, Zhenxing; Ding, Li; Pei, Tian; Hu, Zhudong; Liang, Xuelei; Chen, Qing; Li, Yan; Peng, Lian-Mao
2009-11-24
Symmetric n- and p-type field-effect transistors (FETs) have been fabricated on the same undoped single-walled carbon nanotube (SWCNT). The polarity of the FET is defined by controlled injection of electrons (n-type, via Sc electrodes) or holes (p-type, via Pd electrodes) into the SWCNT, instead of via chemically doping the SWCNT. The SWCNT-based FETs with different channel lengths show a clear trend of performance improvement for channel length scaling. Taking full advantage of the perfect symmetric band structure of the semiconductor SWCNT, a perfect SWCNT-based CMOS inverter is demonstrated, which gives a voltage gain of over 160, and for the two adjacent n- and p-type FETs fabricated on the same SWCNT, high field mobility is realized simultaneously for electrons (3000 cm(2)/V.s) and holes (3300 cm(2)/V.s).
General description of circularly symmetric Bessel beams of arbitrary order
Wang, Jia Jie; Wriedt, Thomas; Lock, James A.; Mädler, Lutz
2016-11-01
A general description of circularly symmetric Bessel beams of arbitrary order is derived in this paper. This is achieved by analyzing the relationship between different descriptions of polarized Bessel beams obtained using different approaches. It is shown that a class of circularly symmetric Davis Bessel beams derived using the Hertz vector potentials possesses the same general functional dependence as the aplanatic Bessel beams generated using the angular spectrum representation (ASR). This result bridges the gap between different descriptions of Bessel beams and leads to a general description of circularly symmetric Bessel beams, such that the Davis Bessel beams and the aplanatic Bessel beams are merely the two simplest cases of an infinite number of possible circularly symmetric Bessel beams. Additionally, magnitude profiles of the electric and magnetic fields, the energy density and the Poynting vector are displayed for Bessel beams in both paraxial and nonparaxial cases. The results presented in this paper provide a fresh perspective on the description of Bessel beams and cast some insights into the light scattering and light-matter interactions problems in practice.
Effect of BladeTip Clearance on the Internal Fluid Field in Axial-Flow Fan%叶顶间隙对轴流风机内部流场影响的研究
Institute of Scientific and Technical Information of China (English)
刘洋; 杨志刚
2013-01-01
A large axial-flow fan with different blade tip clearances were simulated in the design-condition by CFD software based on Realizable k-εturbulence model and SIMPLE algorithm. The effect of different tip clearances on the performance of the axial-flow fan and the outlet velocity and pressure were discussed. The formation of leakage flow and leakage vortex was investigated. The numerical results showed that the decline trend of the performance with tip clearance size increasing. The impact of the leakage flow on outlet velocity, total pressure, and turbulence kinetic energy was huge. The leakage vortex was formed by leakage flow entraining with main stream and it will be influenced by the tip clearance size.% 基于Realizable k-ε湍流模型和 SIMPLE 算法，对某轴流式通风机在不同叶顶间隙下进行了设计工况时的数值模拟。讨论了不同叶顶间隙大小对风机性能的影响，分析了叶轮出口截面速度、压力等参数的分布以及叶顶泄漏流和泄漏涡随间隙大小的变化情况。数值结果表明，随叶顶间隙逐渐增大，风机性能不断下降；叶轮出口截面速度、总压和湍动能大小受间隙泄漏流的影响明显；泄漏涡由泄漏流与主流发生卷吸而形成，且泄漏涡会受到间隙大小的影响。
CANONICAL EXTENSIONS OF SYMMETRIC LINEAR RELATIONS
Sandovici, Adrian; Davidson, KR; Gaspar, D; Stratila, S; Timotin, D; Vasilescu, FH
2006-01-01
The concept of canonical extension of Hermitian operators has been recently introduced by A. Kuzhel. This paper deals with a generalization of this notion to the case of symmetric linear relations. Namely, canonical regular extensions of symmetric linear relations in Hilbert spaces are studied. The
Symmetric products, permutation orbifolds and discrete torsion
Bántay, P
2000-01-01
Symmetric product orbifolds, i.e. permutation orbifolds of the full symmetric group S_{n} are considered by applying the general techniques of permutation orbifolds. Generating functions for various quantities, e.g. the torus partition functions and the Klein-bottle amplitudes are presented, as well as a simple expression for the discrete torsion coefficients.
Energy Technology Data Exchange (ETDEWEB)
Toya, Y. [Nagano National College of Technology, Nagano (Japan); Nakamura, I. [Nagoya University, Nagoya (Japan). Faculty of Engineering
1997-08-25
The present study concerns an experimental investigation of the instability of a Taylor vortex flow with two immiscible fluids. The fluids are used containing aqueous solution of glycerol and silicone oil. The experiments are made in a symmetric system and at a range of the aspect ratio approximately from 4 to 6. As results, a cell configuration is clarified by flow visualization, and through a surprising phenomenon where there are opposite directions of flow on a boundary surface between the fluids. The heights of cells are measured to clarify the instability of the vortices. The critical Reynolds number at which the primary mode is mutually bifurcated to the secondary mode and another critical Reynolds number at which the secondary mode changes to the wavy Taylor vortex flow are investigated. These results are compared with the features of the Taylor vortex flow with one fluid and are similar to those in an asymmetric system. But the phenomenon that there are two flow directions on the boundary surface has never been reported. 15 refs., 9 figs.
Inversion-symmetric topological insulators
Hughes, Taylor L.; Prodan, Emil; Bernevig, B. Andrei
2011-06-01
We analyze translationally invariant insulators with inversion symmetry that fall outside the current established classification of topological insulators. These insulators exhibit no edge or surface modes in the energy spectrum and hence they are not edge metals when the Fermi level is in the bulk gap. However, they do exhibit protected modes in the entanglement spectrum localized on the cut between two entangled regions. Their entanglement entropy cannot be made to vanish adiabatically, and hence the insulators can be called topological. There is a direct connection between the inversion eigenvalues of the Hamiltonian band structure and the midgap states in the entanglement spectrum. The classification of protected entanglement levels is given by an integer N, which is the difference between the negative inversion eigenvalues at inversion symmetric points in the Brillouin zone, taken in sets of 2. When the Hamiltonian describes a Chern insulator or a nontrivial time-reversal invariant topological insulator, the entirety of the entanglement spectrum exhibits spectral flow. If the Chern number is zero for the former, or time reversal is broken in the latter, the entanglement spectrum does not have spectral flow, but, depending on the inversion eigenvalues, can still exhibit protected midgap bands similar to impurity bands in normal semiconductors. Although spectral flow is broken (implying the absence of real edge or surface modes in the original Hamiltonian), the midgap entanglement bands cannot be adiabatically removed, and the insulator is “topological.” We analyze the linear response of these insulators and provide proofs and examples of when the inversion eigenvalues determine a nontrivial charge polarization, a quantum Hall effect, an anisotropic three-dimensional (3D) quantum Hall effect, or a magnetoelectric polarization. In one dimension, we establish a link between the product of the inversion eigenvalues of all occupied bands at all inversion
Singularity in Gravitational Collapse of Plane Symmetric Charged Vaidya Spacetime
Sharif, M
2010-01-01
We study the final outcome of gravitational collapse resulting from the plane symmetric charged Vaidya spacetime. Using the field equations, we show that the weak energy condition is always satisfied by collapsing fluid. It is found that the singularity formed is naked. The strength of singularity is also investigated by using Nolan's method. This turns out to be a strong curvature singularity in Tipler's sense and hence provides a counter example to the cosmic censorship hypothesis.
An introduction to spherically symmetric loop quantum gravity black holes
Energy Technology Data Exchange (ETDEWEB)
Gambini, Rodolfo [Instituto de Física, Facultad de Ciencias, Iguá 4-225, esq. Mataojo, 11400 Montevideo (Uruguay); Pullin, Jorge [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)
2015-03-26
We review recent developments in the treatment of spherically symmetric black holes in loop quantum gravity. In particular, we discuss an exact solution to the quantum constraints that represents a black hole and is free of singularities. We show that new observables that are not present in the classical theory arise in the quantum theory. We also discuss Hawking radiation by considering the quantization of a scalar field on the quantum spacetime.
Joglekar, Yogesh N
2010-01-01
We study the properties of a parity- and time-reversal- (PT) symmetric tight-binding chain of size N with position-dependent hopping amplitude. In contrast to the fragile PT-symmetric phase of a chain with constant hopping and imaginary impurity potentials, we show that, under very general conditions, our model is {\\it always} in the PT-symmetric phase. We numerically obtain the energy spectrum and the density of states of such a chain, and show that they are widely tunable. By studying the size-dependence of inverse participation ratios, we show that although the chain is not translationally invariant, most of its eigenstates are extended. Our results indicate that tight-binding models with non-Hermitian PT-symmetric hopping have a robust PT-symmetric phase and rich dynamics.