Determining the orientation and spin period of TOPEX/Poseidon satellite by a photometric method

Science.gov (United States)

Kudak, V. I.; Epishev, V. P.; Perig, V. M.; Neybauer, I. F.

2017-07-01

We present the results of photometric observations of the TOPEX/Poseidon satellite performed during 2008-2016. The satellite become space debris after a failure in January, 2006, in a low Earth orbit. In the Laboratory of Space Research of Uzhhorod National University 73 light curves of the spacecraft were obtained. Standardization of photometric light curves is briefly explained. We have calculated the color indices of reflecting surfaces and the spin rate change. The general tendency of the latter is described by an exponential decay function. The satellite spin periods based on 126 light curves (including 53 light curves from the MMT-9 project operating since 2014) were taken into account. In 2016 the period of its own rotation reached its minimum of 10.6 s. A method to derive the direction of the spin axis of an artificial satellite and the angles of the light scattered by its surface has been developed in the Laboratory of Space Research of Uzhhorod National University. We briefly describe the "Orientation" program used for these purposes. The orientation of the TOPEX/Poseidon satellite in mid-2016 is given. The angle of precession β = 45°-50° and period of precession P pr = 141.5 s have been defined. The reasons for the identified nature of the satellite's own rotation have been found. They amount to the perturbation caused by a deviation of the Earth gravity field from a central-symmetric shape and the presence of moving parts on the satellite.

Paving the Way for Small Satellite Access to Orbit: Cyclops' Deployment of SpinSat, the Largest Satellite Ever Deployed from the International Space Station

Science.gov (United States)

Hershey, Matthew P.; Newswander, Daniel R.; Smith, James P.; Lamb, Craig R.; Ballard, Perry G.

2015-01-01

The Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS), known as "Cyclops" to the International Space Station (ISS) community, successfully deployed the largest satellite ever (SpinSat) from the ISS on November 28, 2014. Cyclops, a collaboration between the NASA ISS Program, NASA Johnson Space Center Engineering, and Department of Defense Space Test Program (DoD STP) communities, is a dedicated 10-100 kg class ISS small satellite deployment system. This paper will showcase the successful deployment of SpinSat from the ISS. It will also outline the concept of operations, interfaces, requirements, and processes for satellites to utilize the Cyclops satellite deployment system.

Higher-order Zeeman and spin terms in the electron paramagnetic resonance spin Hamiltonian; their description in irreducible form using Cartesian, tesseral spherical tensor and Stevens' operator expressions

International Nuclear Information System (INIS)

McGavin, Dennis G; Tennant, W Craighead

2009-01-01

In setting up a spin Hamiltonian (SH) to study high-spin Zeeman and high-spin nuclear and/or electronic interactions in electron paramagnetic resonance (EPR) experiments, it is argued that a maximally reduced SH (MRSH) framed in tesseral combinations of spherical tensor operators is necessary. Then, the SH contains only those terms that are necessary and sufficient to describe the particular spin system. The paper proceeds then to obtain interrelationships between the parameters of the MRSH and those of alternative SHs expressed in Cartesian tensor and Stevens operator-equivalent forms. The examples taken, initially, are those of Cartesian and Stevens' expressions for high-spin Zeeman terms of dimension BS 3 and BS 5 . Starting from the well-known decomposition of the general Cartesian tensor of second rank to three irreducible tensors of ranks 0, 1 and 2, the decomposition of Cartesian tensors of ranks 4 and 6 are treated similarly. Next, following a generalization of the tesseral spherical tensor equations, the interrelationships amongst the parameters of the three kinds of expressions, as derived from equivalent SHs, are determined and detailed tables, including all redundancy equations, set out. In each of these cases the lowest symmetry, 1-bar Laue class, is assumed and then examples of relationships for specific higher symmetries derived therefrom. The validity of a spin Hamiltonian containing mixtures of terms from the three expressions is considered in some detail for several specific symmetries, including again the lowest symmetry. Finally, we address the application of some of the relationships derived here to seldom-observed low-symmetry effects in EPR spectra, when high-spin electronic and nuclear interactions are present.

Analysis of the partially filled viscous ring damper. [application as nutation damper for spinning satellite

Science.gov (United States)

Alfriend, K. T.

1973-01-01

A ring partially filled with a viscous fluid has been analyzed as a nutation damper for a spinning satellite. The fluid has been modelled as a rigid slug of finite length moving in a tube and resisted by a linear viscous force. It is shown that there are two distinct modes of motion, called the spin synchronous mode and the nutation synchronous mode. Time constants for each mode are obtained for both the symmetric and asymmetric satellite. The effects of a stop in the tube and an offset of the ring from the spin axis are also investigated. An analysis of test results is also given including a determination of the effect of gravity on the time constants in the two modes.

Drag on a Satellite Moving across a Spherical Galaxy: Tidal and Frictional Forces in Short-lived Encounters

Science.gov (United States)

Colpi, Monica; Pallavicini, Andrea

1998-07-01

The drag force on a satellite of mass M moving with speed V in the gravitational field of a spherically symmetric background of stars is computed. During the encounter, the stars are subject to a time-dependent force that alters their equilibrium. The resulting distortion in the stellar density field acts back to produce a force FΔ that decelerates the satellite. This force is computed using a perturbative technique known as linear response theory. In this paper, we extend the formalism of linear response to derive the correct expression for the back-reaction force FΔ that applies when the stellar system is described by an equilibrium one-particle distribution function. FΔ is expressed in terms of a suitable correlation function that couples the satellite dynamics to the unperturbed dynamics of the stars. At time t, the force depends upon the whole history of the composite system. In the formalism, we account for the shift of the stellar center of mass resulting from linear momentum conservation. The self-gravity of the response is neglected since it contributes to a higher order in the perturbation. Linear response theory applies also to the case of a satellite orbiting outside the spherical galaxy. The case of a satellite moving on a straight line, at high speed relative to the stellar dispersion velocity, is explored. We find that the satellite during its passage raises (1) global tides in the stellar distribution and (2) a wake, i.e., an overdense region behind its trail. If the satellite motion is external to the galaxy, it suffers a dissipative force that is not exclusively acting along V but acquires a component along R, the position vector relative to the center of the spherical galaxy. We derive the analytical expression of the force in the impulse approximation. In penetrating short-lived encounters, the satellite moves across the stellar distribution and the transient wake excited in the density field is responsible for most of the deceleration. We

Optical neural network system for pose determination of spinning satellites

Science.gov (United States)

Lee, Andrew; Casasent, David

1990-01-01

An optical neural network architecture and algorithm based on a Hopfield optimization network are presented for multitarget tracking. This tracker utilizes a neuron for every possible target track, and a quadratic energy function of neural activities which is minimized using gradient descent neural evolution. The neural net tracker is demonstrated as part of a system for determining position and orientation (pose) of spinning satellites with respect to a robotic spacecraft. The input to the system is time sequence video from a single camera. Novelty detection and filtering are utilized to locate and segment novel regions from the input images. The neural net multitarget tracker determines the correspondences (or tracks) of the novel regions as a function of time, and hence the paths of object (satellite) parts. The path traced out by a given part or region is approximately elliptical in image space, and the position, shape and orientation of the ellipse are functions of the satellite geometry and its pose. Having a geometric model of the satellite, and the elliptical path of a part in image space, the three-dimensional pose of the satellite is determined. Digital simulation results using this algorithm are presented for various satellite poses and lighting conditions.

Spherical Pendulum, Actions, and Spin

NARCIS (Netherlands)

Richter, Peter H.; Dullin, Holger R.; Waalkens, Holger; Wiersig, Jan

1996-01-01

The classical and quantum mechanics of a spherical pendulum are worked out, including the dynamics of a suspending frame with moment of inertia θ. The presence of two separatrices in the bifurcation diagram of the energy-momentum mapping has its mathematical expression in the hyperelliptic nature of

Observation of ESR spin flip satellite lines of trapped hydrogen atoms in solid H2 at 4.2 K

International Nuclear Information System (INIS)

Miyazaki, Tetsuo; Iwata, Nobuchika; Fueki, Kenji; Hase, Hirotomo

1990-01-01

ESR spectra of H atoms, produced in γ-irradiated solid H 2 , were studied at 4.2 K. Two main lines of the ESR spectra of H atoms that are separated by about 500 G accompanied two weak satellite lines. Both satellite lines and main lines decrease with the same decay rate. In the D 2 -H 2 mixtures, the satellite-line intensity depends upon the number of matrix protons. The spacing of the satellites from the main lines is equal to that of the NMR proton resonance frequency. It was concluded that the satellite lines were not ascribable to paired atoms but to spin flip lines due to an interaction of H atoms with matrix protons. The analysis of the spin flip lines and the main lines suggests that H atoms in solid H 2 are trapped in the substitutional site

Theoretical description of spin-selective reactions of radical pairs diffusing in spherical 2D and 3D microreactors

International Nuclear Information System (INIS)

Ivanov, Konstantin L.; Lukzen, Nikita N.; Sadovsky, Vladimir M.

2015-01-01

In this work, we treat spin-selective recombination of a geminate radical pair (RP) in a spherical “microreactor,” i.e., of a RP confined in a micelle, vesicle, or liposome. We consider the microreactor model proposed earlier, in which one of the radicals is located at the center of the micelle and the other one undergoes three-dimensional diffusion inside the micelle. In addition, we suggest a two-dimensional model, in which one of the radicals is located at the “pole” of the sphere, while the other one diffuses on the spherical surface. For this model, we have obtained a general analytical expression for the RP recombination yield in terms of the free Green function of two-dimensional diffusion motion. In turn, this Green function is expressed via the Legendre functions and thus takes account of diffusion over a restricted spherical surface and its curvature. The obtained expression allows one to calculate the RP recombination efficiency at an arbitrary magnetic field strength. We performed a comparison of the two models taking the same geometric parameters (i.e., the microreactor radius and the closest approach distance of the radicals), chemical reactivity, magnetic interactions in the RP and diffusion coefficient. Significant difference between the predictions of the two models is found, which is thus originating solely from the dimensionality effect: for different dimensionality of space, the statistics of diffusional contacts of radicals becomes different altering the reaction yield. We have calculated the magnetic field dependence of the RP reaction yield and chemically induced dynamic nuclear polarization of the reaction products at different sizes of the microreactor, exchange interaction, and spin relaxation rates. Interestingly, due to the intricate interplay of diffusional contacts of reactants and spin dynamics, the dependence of the reaction yield on the microreactor radius is non-monotonous. Our results are of importance for (i) interpreting

Inversion of the Earth spherical albedo from radiation-pressure

Science.gov (United States)

Wilkman, Olli; Herranen, Joonas; Näränen, Jyri; Virtanen, Jenni; Koivula, Hannu; Poutanen, Markku; Penttilä, Antti; Gritsevich, Maria; Muinonen, Karri

2017-04-01

We are studying the retrieval of the spherical albedo and net radiation of the Earth from the perturbations caused by the planet's radiation on the dynamics of its satellites. The spherical or Bond albedo gives the ratio of the fluxes incident on and scattered by the planet. The net radiation represents the net heat input into the planet's climate system and drives changes in its atmospheric, surface, and ocean temperatures. The ultimate aim of the study is inverting the problem and estimating the Earth albedo based on observations of satellites, simultaneously improving the space-geodetic positioning accuracy. Here we investigate the effect of the spherical albedo on satellite orbits with the help of a simplified model. We simulate the propagation of satellite orbits using a new simulation software. The simulation contains the main perturbing forces on medium and high Earth orbits, used by, e.g., navigation satellites, including the radiation pressure of reflected sunlight from the Earth. An arbitrary satellite shape model can be used, and the rotation of the satellite is modeled. In this first study, we use a box-wing satellite model with a simple surface BRDF. We also assume a diffusely reflecting Earth with a single global albedo value. We vary the Earth albedo and search for systematic effects on different orbits. Thereafter, we estimate the dependence of the albedo accuracy on the satellite positioning and timing data available. We show that the inversion of the spherical albedo with reasonable accuracy is feasible from the current space-geodetic measurements.

Tilted wheel satellite attitude control with air-bearing table experimental results

Science.gov (United States)

Inumoh, Lawrence O.; Forshaw, Jason L.; Horri, Nadjim M.

2015-12-01

Gyroscopic actuators for satellite control have attracted significant research interest over the years, but their viability for the control of small satellites has only recently started to become clear. Research on variable speed gyroscopic actuators has long been focused on single gimbal actuators; double gimbal actuators typically operate at constant wheel spin rate and allow tilt angle ranges far larger than the ranges needed to operate most satellite missions. This research examines a tilted wheel, a newly proposed type of inertial actuator that can generate torques in all three principal axes of a rigid satellite using a spinning wheel and a double tilt mechanism. The tilt mechanism tilts the angular momentum vector about two axes providing two degree of freedom control, while variation of the wheel speed provides the third. The equations of motion of the system lead to a singularity-free system during nominal operation avoiding the need for complex steering logic. This paper describes the hardware design of the tilted wheel and the experimental setup behind both standalone and spherical air-bearing tables used to test it. Experimental results from the air bearing table are provided with the results depicting the high performance capabilities of the proposed actuator in torque generation.

Pressure ionization of dense plasmas in spherical ion-cell model with spin-orbit interactions

International Nuclear Information System (INIS)

Ishikawa, K.; Blenski, T.; Takahashi, H.; Iguchi, T.; Nakazawa, M.

1996-01-01

We study the continuity of pressure of dense plasmas in pressure ionization in case where spin-orbit interactions are taken into account in calculations. Pressure is calculated using a stress-tensor pressure formula in the relativistically-corrected self-consistent field spherical ion-cell model (average-atom model). It appears that calculated pressure and electronic density distribution change continuously in pressure ionization if we take narrow shape resonances into account properly. This observation stresses the need of a coherent description of bound and free electrons. We also compare the results by the stress-tensor pressure formula with those by other pressure formulas. It appears that different pressure formulas give rather discrepant results in some cases. copyright 1996 American Institute of Physics

Numerical evolutions of fields on the 2-sphere using a spectral method based on spin-weighted spherical harmonics

International Nuclear Information System (INIS)

Beyer, Florian; Daszuta, Boris; Frauendiener, Jörg; Whale, Ben

2014-01-01

Many applications in science call for the numerical simulation of systems on manifolds with spherical topology. Through the use of integer spin-weighted spherical harmonics, we present a method which allows for the implementation of arbitrary tensorial evolution equations. Our method combines two numerical techniques that were originally developed with different applications in mind. The first is Huffenberger and Wandelt’s spectral decomposition algorithm to perform the mapping from physical to spectral space. The second is the application of Luscombe and Luban’s method, to convert numerically divergent linear recursions into stable nonlinear recursions, to the calculation of reduced Wigner d-functions. We give a detailed discussion of the theory and numerical implementation of our algorithm. The properties of our method are investigated by solving the scalar and vectorial advection equation on the sphere, as well as the 2 + 1 Maxwell equations on a deformed sphere. (paper)

Electron spin resonance study of a-Cr2O3 and Cr2O3·nH2O quasi-spherical nanoparticles

CSIR Research Space (South Africa)

Khamlich, S

2011-12-01

Full Text Available The quasi-spherical nanoparticles of hydrated Cr2O3 · nH2O, and crystalline -Cr2O3, have been synthesized by reduction of the first row (3d) transition metal complex of K2Cr2O7. The temperaturedependence of electron spin resonance (ESR) spectrum...

A pseudospectral matrix method for time-dependent tensor fields on a spherical shell

International Nuclear Information System (INIS)

Brügmann, Bernd

2013-01-01

We construct a pseudospectral method for the solution of time-dependent, non-linear partial differential equations on a three-dimensional spherical shell. The problem we address is the treatment of tensor fields on the sphere. As a test case we consider the evolution of a single black hole in numerical general relativity. A natural strategy would be the expansion in tensor spherical harmonics in spherical coordinates. Instead, we consider the simpler and potentially more efficient possibility of a double Fourier expansion on the sphere for tensors in Cartesian coordinates. As usual for the double Fourier method, we employ a filter to address time-step limitations and certain stability issues. We find that a tensor filter based on spin-weighted spherical harmonics is successful, while two simplified, non-spin-weighted filters do not lead to stable evolutions. The derivatives and the filter are implemented by matrix multiplication for efficiency. A key technical point is the construction of a matrix multiplication method for the spin-weighted spherical harmonic filter. As example for the efficient parallelization of the double Fourier, spin-weighted filter method we discuss an implementation on a GPU, which achieves a speed-up of up to a factor of 20 compared to a single core CPU implementation

Exactly solvable spin–glass models with ferromagnetic couplings: The spherical multi-p-spin model in a self-induced field

International Nuclear Information System (INIS)

Crisanti, Andrea; Leuzzi, Luca

2013-01-01

We report some results on the quenched disordered Spherical multi-p-Spin Model in presence of ferromagnetic couplings. In particular, we present the phase diagrams of some representative cases that schematically describe, in the mean-field approximation, the behavior of most known transitions in glassy materials, including dynamic arrest in super-cooled liquids, amorphous–amorphous transitions and spin–glass transitions. A simplified notation is introduced in order to compute systems properties in terms of an effective, self-induced, field encoding the whole ferromagnetic information

Modelling the Earth's Main Magnetic Field by the spinning Astrid-2 satellite

DEFF Research Database (Denmark)

Merayo, Jose Maria Garcia; Jørgensen, Peter Siegbjørn; Risbo, T.

1999-01-01

and therefore the mapping of the Earth's magnetic field may be possible. The spinning of the spacecraft about a certain axis makes the stabilisation in space possible. This fact and the well distributed data over the globe makes the magnetic data well suited for the estimation of the magnetic field model......The Swedish micro-satellite Astrid-2 was successfully launched into a near polar orbit last December 98. Despite the fact that its primary mission was the research of Auroral phenomena, the magnetic instrumentation has been designed to accomplish high resolution vector field magnetic measurements...... at the spacecraft altitude (circa 1000km). Several methods for field modelling are presented in this paper with the assumption that the direction of the spin axis is nearly constant. In any case the orientation of the magnetometer is to bedetermined simultaneously with the instrument calibration and main field...

Towards a Prototype of a Spherical Tippe Top

Directory of Open Access Journals (Sweden)

M. C. Ciocci

2012-01-01

Full Text Available Among spinning objects, the tippe top exhibits one of the most bizarre and counterintuitive behaviours. The commercially available tippe tops basically consist of a section of a sphere with a rod. After spinning on its rounded body, the top flips over and continues spinning on the stem. The commonly used simplified mathematical model for the tippe top is a sphere whose mass distribution is axially but not spherically symmetric, spinning on a flat surface subject to a small friction force that is due to sliding. Three main different dynamical behaviours are distinguished: tipping, nontipping, hanging, that is, the top rises but converges to an intermediate state instead of rising all the way to the vertical state. Subclasses according to the stability of relative equilibria can further be distinguished. Our concern is the degree of confidence in the mathematical model predictions, we applied 3D printing and rapid prototyping to manufacture a “3-in-1 toy” that could catch the three main characteristics defining the three main groups in the classification of spherical tippe tops as mentioned above. We propose three designs. This “toy” is suitable to validate the mathematical model qualitatively and quantitatively.

The spherical limit of the n-vector model and correlation inequaljties

International Nuclear Information System (INIS)

Angelescu, N.; Bundaru, M.; Costache, G.

1978-08-01

The asymptotics of the state of the n-vector model with a finite number of spins in the spherical limit is studied. Besides rederiving the limit free energy, corresponding to a generalized spherical model (with ''spherical constraint'' at every site), we obtain also the limit of the correlation functions, which allow a precise definition of the state of the latter model. Correlation inequalities are proved for ferromagnetic interactions in the asymptotic regime. In particular, it is shown that the generalized spherical model fulfills the expected Griffiths' type inequalities, differing in this respect from the spherical model with overall constraint. (author)

Spin flip statistics and spin wave interference patterns in Ising ferromagnetic films: A Monte Carlo study.

Science.gov (United States)

Acharyya, Muktish

2017-07-01

The spin wave interference is studied in two dimensional Ising ferromagnet driven by two coherent spherical magnetic field waves by Monte Carlo simulation. The spin waves are found to propagate and interfere according to the classic rule of interference pattern generated by two point sources. The interference pattern of spin wave is observed in one boundary of the lattice. The interference pattern is detected and studied by spin flip statistics at high and low temperatures. The destructive interference is manifested as the large number of spin flips and vice versa.

Theory of satellite geodesy applications of satellites to geodesy

CERN Document Server

Kaula, William M

2000-01-01

The main purpose of this classic text is to demonstrate how Newtonian gravitational theory and Euclidean geometry can be used and developed in the earth's environment. The second is to collect and explain some of the mathematical techniques developed for measuring the earth by satellite.Book chapters include discussions of the earth's gravitational field, with special emphasis on spherical harmonies and the potential of the ellipsoid; matrices and orbital geometry; elliptic motion, linear perturbations, resonance, and other aspects of satellite orbit dynamics; the geometry of satellite obser

Spherical gyroscopic moment stabilizer for attitude control of microsatellites

Science.gov (United States)

Keshtkar, Sajjad; Moreno, Jaime A.; Kojima, Hirohisa; Uchiyama, Kenji; Nohmi, Masahiro; Takaya, Keisuke

2018-02-01

This paper presents a new and improved concept of recently proposed two-degrees of freedom spherical stabilizer for triaxial orientation of microsatellites. The analytical analysis of the advantages of the proposed mechanism over the existing inertial attitude control devices are introduced. The extended equations of motion of the stabilizing satellite including the spherical gyroscope, for control law design and numerical simulations, are studied in detail. A new control algorithm based on continuous high-order sliding mode algorithms, for managing the torque produced by the stabilizer and therefore the attitude control of the satellite in the presence of perturbations/uncertainties, is presented. Some numerical simulations are carried out to prove the performance of the proposed mechanism and control laws.

Solar Array Power Conditioning for a Spinning Satellite

Science.gov (United States)

De Luca, Antonio; Chirulli, Giovanni

2008-09-01

The conditioning of the output power from a solar array can mainly be achieved by the adoption of DET or MPPT based architecture. There are several factors that can orientate the choice of the system designer towards one solution or the other; some of them maybe inherent to the mission derived requirements (Illumination levels, EMC cleanliness, etc.), others come directly from a careful assessment of performances and losses of both power conditioner and solar array.Definition of the criteria on which basis the final choice is justified is important as they have to guarantee a clear determination of the available versus the required power in all those mission conditions identifiable as design drivers for the overall satellite system both in terms of mass and costs.Such criteria cannot just be simple theoretical enunciations of principles; nor the meticulous definition of them on a case by case basis for different types of missions as neither option gives a guarantee of being conclusive.The aim of this paper is then to suggest assessment steps and guidelines that can be considered generically valid for any mission case, starting from the exposition of the trade off activity performed in order to choose the power conditioning solution for a spinning satellite having unregulated power bus architecture. Calculations and numerical simulations have been made in order to establish the needed solar array surface in case of adoption of a DET or MPPT solution, taking into account temperature and illumination levels on the solar cells, as well as power losses and inefficiencies from the solar generator to the main power bus, in different mission phases. Particular attention has been taken in order to correctly evaluate the thermal effects on the rest of the spacecraft as function of the adopted power system regulation.

The tensor part of the Skyrme energy density functional. I. Spherical nuclei

Energy Technology Data Exchange (ETDEWEB)

Lesinski, T.; Meyer, J. [Universite de Lyon, F-69003 Lyon (France)]|[Institut de Physique Nucleaire de Lyon, CNRS/IN2P3, Universite Lyon 1, F-69622 Villeurbanne (France); Bender, M. [DSM/DAPNIA/SPhN, CEA Saclay, F-91191 Gif-sur-Yvette Cedex (France)]|[Universite Bordeaux, CNRS/IN2P3, Centre d' Etudes Nucleaires de Bordeaux Gradignan, UMR5797, Chemin du Solarium, BP120, F-33175 Gradignan (France); Bennaceur, K. [Universite de Lyon, F-69003 Lyon (France)]|[Institut de Physique Nucleaire de Lyon, CNRS/IN2P3, Universite Lyon 1, F-69622 Villeurbanne (France)]|[DSM/DAPNIA/SPhN, CEA Saclay, F-91191 Gif-sur-Yvette Cedex (France); Duguet, T. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

2007-04-15

We perform a systematic study of the impact of the J-vector{sup 2} tensor term in the Skyrme energy functional on properties of spherical nuclei. In the Skyrme energy functional, the tensor terms originate both from zero-range central and tensor forces. We build a set of 36 parameterizations which cover a wide range of the parameter space of the isoscalar and isovector tensor term coupling constants with a fit protocol very similar to that of the successful SLy parameterizations. We analyze the impact of the tensor terms on a large variety of observables in spherical mean-field calculations, such as the spin-orbit splittings and single-particle spectra of doubly-magic nuclei, the evolution of spin-orbit splittings along chains of semi-magic nuclei, mass residuals of spherical nuclei, and known anomalies of radii. The major findings of our study are (i) tensor terms should not be added perturbatively to existing parameterizations, a complete refit of the entire parameter set is imperative. (ii) The free variation of the tensor terms does not lower the {chi}{sup 2} within a standard Skyrme energy functional. (iii) For certain regions of the parameter space of their coupling constants, the tensor terms lead to instabilities of the spherical shell structure, or even the coexistence of two configurations with different spherical shell structure. (iv) The standard spin-orbit interaction does not scale properly with the principal quantum number, such that single-particle states with one or several nodes have too large spin-orbit splittings, while those of node-less intruder levels are tentatively too small. Tensor terms with realistic coupling constants cannot cure this problem. (v) Positive values of the coupling constants of proton-neutron and like-particle tensor terms allow for a qualitative description of the evolution of spin-orbit splittings in chains of Ca, Ni and Sn isotopes. (vi) For the same values of the tensor term coupling constants, however, the overall

Three Dimensional Spherical Display Systems and McIDAS: Tools for Science, Education and Outreach

Science.gov (United States)

Kohrs, R.; Mooney, M. E.

2010-12-01

The Space Science and Engineering Center (SSEC) and Cooperative Institute for Meteorological Satellite Studies (CIMSS) at the University of Wisconsin are now using a 3D spherical display system and their Man computer Data Access System (McIDAS)-X and McIDAS-V as outreach tools to demonstrate how scientists and forecasters utilize satellite imagery to monitor weather and climate. Our outreach program displays orbits and data coverage of geostationary and polar satellites and demonstrates how each is beneficial for the remote sensing of Earth. Global composites of visible, infrared and water vapor images illustrate how satellite instruments collect data from different bands of the electromagnetic spectrum to monitor global weather patterns 24 hours a day. Captivating animations on spherical display systems are proving to be much more intuitive than traditional 2D displays, enabling audiences to view satellites orbiting above real-time weather systems circulating the entire globe. Complimenting the 3D spherical display system are the UNIX-based McIDAS-X and Java-based McIDAS-V software packages. McIDAS is used to composite the real-time global satellite data and create other weather related derived products. Client and server techniques used by these software packages provide the opportunity to continually update the real-time content on our globe. The enhanced functionality of McIDAS-V extends our outreach program by allowing in-depth interactive 4-dimensional views of the imagery previously viewed on the 3D spherical display system. An important goal of our outreach program is the promotion of remote sensing research and technology at SSEC and CIMSS. The 3D spherical display system has quickly become a popular tool to convey societal benefits of these endeavors. Audiences of all ages instinctively relate to recent weather events which keeps them engaged in spherical display presentations. McIDAS facilitates further exploration of the science behind the weather

GHRSST Level 2P Atlantic Regional Skin Sea Surface Temperature from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on the Meteosat Second Generation (MSG-2) satellite (GDS version 1)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Meteosat Second Generation (MSG) satellites are spin stabilized geostationary satellites operated by the European Organization for the Exploitation of...

GHRSST Level 2P Atlantic Regional Skin Sea Surface Temperature from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on the Meteosat Second Generation (MSG-1) satellite (GDS version 1)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Meteosat Second Generation (MSG) satellites are spin stabilized geostationary satellites operated by the European Organization for the Exploitation of...

GHRSST Level 2P Atlantic Regional Skin Sea Surface Temperature from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on the Meteosat Second Generation (MSG-3) satellite (GDS version 2)

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The Meteosat Second Generation (MSG-3) satellites are spin stabilized geostationary satellites operated by the European Organization for the Exploitation of...

The nuclear deformation versus spin-flip like excitations and the suppression of the 2νββ amplitude

International Nuclear Information System (INIS)

Raduta, A.A.; Delion, D.S.; Faessler, Amand

1997-01-01

We were the first who investigated the influence of spin-flip and non-spin-flip configuration on the separation of the transition amplitude of the Gamow-Teller double beta decay. A realistic Hamiltonian and a projected spherical single particle basis is considered, while the effects are generated by three antagonistic sources: spin-flip, non-spin-flip like excitation and nuclear deformation. Moreover, by a smooth variation of a deformation parameter one could bridge the spherical and deformed pictures. Although our application is not aimed at describing the experimental situation we chose as input data those corresponding to the transition 82 Se → 82 Kr. For near spherical case there are two resonances in M GT , one having a spin-flip structure and identified as GT resonance and one of non-spin-flip structure, placed at low energy. For large deformation and vanishing g pp coupling constant there are two resonances of spin-flip and non-spin-flip natures (ΔI = 1 and 0, respectively) and located at the same energy, what indicates that the deformation acts against the separation of this resonances. In conclusion, our calculation showed that the mechanism of M GT suppression is different for spherical and deformed nuclei. In both cases approaching the critical value of g pp where the RPA breaks down, a lot of strength is accumulated in lowest RPA state and, while in the spherical case this has a non spin-flip nature, in the deformed case the state is a mixture of both types of configurations

Spin-Stabilized Spacecrafts: Analytical Attitude Propagation Using Magnetic Torques

Directory of Open Access Journals (Sweden)

Roberta Veloso Garcia

2009-01-01

Full Text Available An analytical approach for spin-stabilized satellites attitude propagation is presented, considering the influence of the residual magnetic torque and eddy currents torque. It is assumed two approaches to examine the influence of external torques acting during the motion of the satellite, with the Earth's magnetic field described by the quadripole model. In the first approach is included only the residual magnetic torque in the motion equations, with the satellites in circular or elliptical orbit. In the second approach only the eddy currents torque is analyzed, with the satellite in circular orbit. The inclusion of these torques on the dynamic equations of spin stabilized satellites yields the conditions to derive an analytical solution. The solutions show that residual torque does not affect the spin velocity magnitude, contributing only for the precession and the drift of the spacecraft's spin axis and the eddy currents torque causes an exponential decay of the angular velocity magnitude. Numerical simulations performed with data of the Brazilian Satellites (SCD1 and SCD2 show the period that analytical solution can be used to the attitude propagation, within the dispersion range of the attitude determination system performance of Satellite Control Center of Brazil National Research Institute.

Comment on 'Spherical 2+p spin-glass model: An analytically solvable model with a glass-to-glass transition'

International Nuclear Information System (INIS)

Krakoviack, V.

2007-01-01

Guided by old results on simple mode-coupling models displaying glass-glass transitions, we demonstrate, through a crude analysis of the solution with one step of replica symmetry breaking (1RSB) derived by Crisanti and Leuzzi for the spherical s+p mean-field spin glass [Phys. Rev. B 73, 014412 (2006)], that the phase behavior of these systems is not yet fully understood when s and p are well separated. First, there seems to be a possibility of glass-glass transition scenarios in these systems. Second, we find clear indications that the 1RSB solution cannot be correct in the full glassy phase. Therefore, while the proposed analysis is clearly naive and probably inexact, it definitely calls for a reassessment of the physics of these systems, with the promise of potentially interesting developments in the theory of disordered and complex systems

Using satellite technology (global positioning system) to teach the spherical polar coordinate system

International Nuclear Information System (INIS)

O'Brien, William P Jr

2003-01-01

Students discover the equivalence between plausible geographic variables (co-latitude and longitude) of the Earth and less-familiar geometric variables (polar and azimuthal angles) of spherical polar coordinates by collecting and analysing positional data recorded during field exercises with a handheld global positioning system (GPS) receiver. This pedagogical approach to teaching spherical geometry, based on field experience rather than classroom theory, uses GPS technology to capture the curiosity of contemporary students, technical or otherwise, who might not normally find the topic of the spherical polar coordinate system comprehensible, relevant or interesting

Early-type Galaxy Spin Evolution in the Horizon-AGN Simulation

Science.gov (United States)

Choi, Hoseung; Yi, Sukyoung K.; Dubois, Yohan; Kimm, Taysun; Devriendt, Julien. E. G.; Pichon, Christophe

2018-04-01

Using the Horizon-AGN simulation data, we study the relative role of mergers and environmental effects in shaping the spin of early-type galaxies (ETGs) after z ≃ 1. We follow the spin evolution of 10,037 color-selected ETGs more massive than {10}10 {M}ȯ that are divided into four groups: cluster centrals (3%), cluster satellites (33%), group centrals (5%), and field ETGs (59%). We find a strong mass dependence of the slow rotator fraction, f SR, and the mean spin of massive ETGs. Although we do not find a clear environmental dependence of f SR, a weak trend is seen in the mean value of the spin parameter driven by the satellite ETGs as they gradually lose their spin as their environment becomes denser. Galaxy mergers appear to be the main cause of total spin changes in 94% of the central ETGs of halos with {M}vir}> {10}12.5 {M}ȯ , but only 22% of satellite and field ETGs. We find that non-merger-induced tidal perturbations better correlate with the galaxy spin down in satellite ETGs than in mergers. Given that the majority of ETGs are not central in dense environments, we conclude that non-merger tidal perturbation effects played a key role in the spin evolution of ETGs observed in the local (z < 1) universe.

The Bach equations in spin-coefficient form

Science.gov (United States)

Forbes, Hamish

2018-06-01

Conformal gravity theories are defined by field equations that determine only the conformal structure of the spacetime manifold. The Bach equations represent an early example of such a theory, we present them here in component form in terms of spin- and boost-weighted spin-coefficients using the compacted spin-coefficient formalism. These equations can be used as an efficient alternative to the standard tensor form. As a simple application we solve the Bach equations for pp-wave and static spherically symmetric spacetimes.

Towards linearization of atmospheric radiative transfer in spherical geometry

International Nuclear Information System (INIS)

Walter, Holger H.; Landgraf, Jochen

2005-01-01

We present a general approach for the linearization of radiative transfer in a spherical planetary atmosphere. The approach is based on the forward-adjoint perturbation theory. In the first part we develop the theoretical background for a linearization of radiative transfer in spherical geometry. Using an operator formulation of radiative transfer allows one to derive the linearization principles in a universally valid notation. The application of the derived principles is demonstrated for a radiative transfer problem in simplified spherical geometry in the second part of this paper. Here, we calculate the derivatives of the radiance at the top of the atmosphere with respect to the absorption properties of a trace gas species in the case of a nadir-viewing satellite instrument

Proton spin structure in the rest frame

International Nuclear Information System (INIS)

Zavada, P.

1997-01-01

It is shown that the quark-parton model in the standard infinite momentum approach overestimates the proton spin structure function g 1 (x) in comparison with the approach taking consistently into account the internal motion of quarks described by a spherical phase space in the proton rest frame. Particularly, it is shown the first moment of the spin structure function in the latter approach, assuming only the valence quarks contribution to the proton spin, does not contradict the experimental data. copyright 1997 The American Physical Society

A more realistic estimate of the variances and systematic errors in spherical harmonic geomagnetic field models

DEFF Research Database (Denmark)

Lowes, F.J.; Olsen, Nils

2004-01-01

Most modern spherical harmonic geomagnetic models based on satellite data include estimates of the variances of the spherical harmonic coefficients of the model; these estimates are based on the geometry of the data and the fitting functions, and on the magnitude of the residuals. However...

Some properties of the statistical models of the spherical Friedman world

International Nuclear Information System (INIS)

Rumyantseva, E.N.

1981-01-01

Considered are some properties of the statistical model of the spherical Friedman world filled with quantum gas of massless particles the spin of which can be equal to 0, 1/2, 1. Obtained are approximate expressions for a number of particles of Fermi- and Bose-gas and for the radius of the world taking into account mainly the dependence on the spin. The dependence of the number of particles on the radius of the world and temperature of the gas is illustrated [ru

High spin states and the competition of spherical and strongly deformed shapes in the A = 70 to 80 region

International Nuclear Information System (INIS)

Hamilton, J.H.; Ramayya, A.V.; Piercey, R.B.

1982-01-01

A wide variety of collective band structures are seen in Ge to Sr nuclei to make this an important new testing ground for nuclear models. These include bands built on coexisting and competing near-spherical and deformed shapes, γ vibrational bands and multiple positive and negative parity bands. Ground state bands in Ge and Kr but not 78 80 Sr are crossed at the 8 + to 12 + levels. Gaps in the Nilsson levels for both N and Z = 38 at large deformation lead to large ground state deformation in Kr and Sr around N = 38. The crossing of rotation aligned bands based on (g/sub 9/2/) 2 configuration are correlated with the ground state deformations. A second high spin crossing is seen in 74 Kr. Measured g factors in 68 Ge yield a two-quasineutron structure for the 8 2 + state. 30 references

Spherical model for superfluidity in a restricted geometry

International Nuclear Information System (INIS)

Fishman, S.; Ziman, T.A.L.

1982-01-01

The spherical model is solved on a hypercubic lattice in d dimensions, each bond of which is decorated with l spins. The thermodynamic functions and the helicity modulus, analogous to a superfluid density, are calculated. We find that at least two spherical fields are required for the model to exhibit low-temperature properties that can approximate reasonably those of O(n) models. The heuristic prediction that the critical temperature behaves as T/sub c/(l)approx.(l+1) -1 is checked for the model and found to hold quite accurately even for small l(> or approx. =2). The helicity modulus and magnetization of the two-constraint spherical model are found to scale approximately with the critical temperature, but the relation between them is more complex than in the undecorated model. This relation is used to check heuristic arguments concerning the helicity modulus at low temperatures. We comment on the relevance to physical systems, in particular, the problem of boson condensation in a restricted geometry

Microscopic Stern-Gerlach effect and spin-orbit pendulum

International Nuclear Information System (INIS)

Rozmej, P.; Arvieu, R.

1996-01-01

The motion of a particle with spin in spherical harmonic oscillator potential with spin-orbit interaction is discussed. The attention is focused on the spatial motion of wave packets. The particular case of wave packets moving along the circular orbits for which the most transparent and pedagogical description is possible is considered. The splitting of the wave packets into two components moving differently along classical orbits reflects a strong analogy with the Stern-Gerlach experiment. The periodic transfer of average angular momentum between spin and orbital subspaces accompanying this time evolution is called the spin-orbit pendulum. (author). 6 refs, 3 figs

Spontaneous spin-polarization and phase transition in the relativistic approach

International Nuclear Information System (INIS)

Maruyama, Tomoyuki; Tatsumi, Toshitaka

2001-01-01

We study the spin-polarization mechanism in the highly dense nuclear matter with the relativistic mean-field approach. In the relativistic Hartree-Fock framework we find that there are two kinds of spin-spin interaction channels, which are the axial-vector and tensor exchange ones. If each interaction is strong and different sign, the system loses the spherical symmetry and holds the spin-polarization in the high-density region. When the axial-vector interaction is negative enough, the system holds ferromagnetism. (author)

Model expressions for the spin-orbit interaction and phonon-mediated spin dynamics in quantum dots

Science.gov (United States)

Vaughan, M. P.; Rorison, J. M.

2018-01-01

Model expressions for the spin-orbit interaction in a quantum dot are obtained. The resulting form does not neglect cubic terms and allows for a generalized structural inversion asymmetry. We also obtain analytical expressions for the coupling between states for the electron-phonon interaction and use these to derive spin-relaxation rates, which are found to be qualitatively similar to those derived elsewhere in the literature. We find that, due to the inclusion of cubic terms, the Dresselhaus contribution to the ground state spin relaxation disappears for spherical dots. A comparison with previous theory and existing experimental results shows good agreement thereby presenting a clear analytical formalism for future developments. Comparative calculations for potential materials are presented.

Spherical cap modelling of Orsted magnetic field vectors over southern Africa

CSIR Research Space (South Africa)

Kotze, PB

2001-01-01

Full Text Available Vector magnetic field observations by the Orsted satellite during geomagnetic quiet conditions around January 1, 2000, have been employed to derive a spherical cap harmonic model (Haines, 1985) over the southern African region between 10 degrees...

Structure of high-spin states in A {approx} 60 region

Energy Technology Data Exchange (ETDEWEB)

Nakada, Hitoshi [Chiba Univ. (Japan); Furutaka, K; Hatsukawa, Y [and others

1998-03-01

High-spin states in the proton-rich Cu-Zn nuclei are investigated by the experiments at JAERI. New levels and {gamma}-rays are identified by the particle-{gamma}-{gamma} coincidence, and J{sup P} assignments are made via the DCO ratio analysis. Yrast sequences are observed up to J {approx} 18 for {sup 62}Zn, and {sup 64}Zn, J {approx} 27/2 for {sup 61}Cu and J {approx} 23/2 for {sup 63}Cu. Though we cannot settle new J{sup P} values for {sup 61,63}Zn, their yrast sequence is also extended. In {sup 64}Zn, a doublet of {gamma}-rays is discovered at 1315 keV, clarifying the similarity in the level scheme between {sup 62}Zn and {sup 64}Zn. We reproduce the yrast levels by a shell-model calculation, by which structure of the high-spin states is further studied. A parity change in the yrast sequence is established, in which the unique-parity orbit 0g{sub 9/2} plays an essential role; one nucleon excitation to g{sub 9/2} gains high angular momentum with low seniority, at the cost of the single-parity energy. Second parity-change is also suggested by the calculation. Such parity change seems characteristic to spherical or nearly spherical nuclei. In {sup 61}Cu, concentration of the {gamma}-ray intensity is observed. This happens because a stretched 3-quasiparticle configuration including 0g{sub 9/2} is relatively stable, similarly to some isomers. Thus, by studying the structure of the high-spin states of the A {approx} 60 nuclei, we have clarified the role of unique-parity orbit in high-spin states, which may be generic to spherical and nearly spherical nuclei. (J.P.N.)

A small satellite design for deep space network testing and training

Science.gov (United States)

Mcwilliams, Dennis; Slatton, Clint; Norman, Cassidy; Araiza, Joe; Jones, Jason; Tedesco, Mark; Wortman, Michael; Opiela, John; Lett, Pat; Clavenna, Michael

1993-01-01

With the continuing exploration of the Solar System and the reemphasis on Earth focused missions, the need for faster data transmission rates has grown. Ka-band could allow a higher data delivery rate over the current X-band, however the adverse effects of the Earth's atmosphere on Ka are as yet unknown. The Deep Space Network and Jet Propulsion Lab have proposed to launch a small satellite that would simultaneously transmit X and Ka signals to test the viability of switching to Ka-band. The Mockingbird Design Team at the University of Texas at Austin applied small satellite design principles to achieve this objective. The Mockingbird design, named BATSAT, incorporates simple, low-cost systems designed for university production and testing. The BATSAT satellite is a 0.64 m diameter, spherical panel led satellite, mounted with solar cells and omni-directional antennae. The antennae configuration negates the need for active attitude control or spin stabilization. The space-frame truss structure was designed for 11 g launch loads while allowing for easy construction and solar-panel mounting. The communication system transmits at 1 mW by carrying the required Ka and X-band transmitters, as well as an S band transmitter used for DSN training. The power system provides the 8.6 W maximum power requirements via silicon solar arrays and nickel-cadmium batteries. The BATSAT satellite will be lofted into an 1163 km, 70 deg orbit by the Pegasus launch system. This orbit fulfills DSN dish slew rate requirements while keeping the satellite out of the heaviest regions of the Van Allen radiation belts. Each of the three DSN stations capable of receiving Ka-band (Goldstone, Canberra, and Madrid) will have an average of 85 minutes of view-time per day over the satellites ten year design life. Mockingbird Designs hopes that its small satellite design will not only be applicable to this specific mission scenario, but that it could easily be modified for instrument capability for

A small satellite design for deep space network testing and training

Science.gov (United States)

McWilliams, Dennis; Slatton, Clint; Norman, Cassidy; Araiza, Joe; Jones, Jason; Tedesco, Mark; Wortman, Michael; Opiela, John; Lett, Pat; Clavenna, Michael

1993-05-01

With the continuing exploration of the Solar System and the reemphasis on Earth focused missions, the need for faster data transmission rates has grown. Ka-band could allow a higher data delivery rate over the current X-band, however the adverse effects of the Earth's atmosphere on Ka are as yet unknown. The Deep Space Network and Jet Propulsion Lab have proposed to launch a small satellite that would simultaneously transmit X and Ka signals to test the viability of switching to Ka-band. The Mockingbird Design Team at the University of Texas at Austin applied small satellite design principles to achieve this objective. The Mockingbird design, named BATSAT, incorporates simple, low-cost systems designed for university production and testing. The BATSAT satellite is a 0.64 m diameter, spherical panel led satellite, mounted with solar cells and omni-directional antennae. The antennae configuration negates the need for active attitude control or spin stabilization. The space-frame truss structure was designed for 11 g launch loads while allowing for easy construction and solar-panel mounting. The communication system transmits at 1 mW by carrying the required Ka and X-band transmitters, as well as an S band transmitter used for DSN training. The power system provides the 8.6 W maximum power requirements via silicon solar arrays and nickel-cadmium batteries. The BATSAT satellite will be lofted into an 1163 km, 70 deg orbit by the Pegasus launch system. This orbit fulfills DSN dish slew rate requirements while keeping the satellite out of the heaviest regions of the Van Allen radiation belts. Each of the three DSN stations capable of receiving Ka-band (Goldstone, Canberra, and Madrid) will have an average of 85 minutes of view-time per day over the satellites ten year design life. Mockingbird Designs hopes that its small satellite design will not only be applicable to this specific mission scenario, but that it could easily be modified for instrument capability for

The pseudo-spin orbit interaction and the normal spin orbit interaction

International Nuclear Information System (INIS)

Sugawara-Tanabe, K.

1999-01-01

We found the hidden symmetry of the pseudo-spin approximation which is inherent in the Dirac equation both for the spherical potential and for deformed potential with axially symmetric shape. We found two kinds of conditions for both cases, i.e., the exact conditions and the approximate condition for the pseudo-spin symmetry. The former condition is not always satisfied by the real nuclei, but the latter condition is realistic and applicable to the real nuclei. We found that the LS coupling scheme is restored not only for the parity doublet states by also for the other levels at superdeformation because of strong quadrupole field. The contribution from the unique-parity level to the E1 transition becomes non-negligible order in superdeformation. (author)

Spin-exchange and spin-destruction rates for the 3He-Na system

International Nuclear Information System (INIS)

Borel, P.I.; Soegaard, L.V.; Svendsen, W.E.; Andersen, N.

2003-01-01

Optically pumped Na is used as a spin-exchange partner to polarize 3 He. Polarizations around 20% have routinely been achieved in sealed spherical glass cells containing 3 He, N 2 , and a few droplets of Na. An optical technique has been developed to determine the Na- 3 He spin-exchange rate coefficient. By monitoring the Na spin relaxation ''in the dark,'' the average Na-Na spin-destruction cross section at 330 degree sign C is estimated to be around 5x10 -19 cm 2 . This value is 2-5 (15-30) times smaller than the previously reported values for the K-K (Rb-Rb) spin-relaxation cross section. In the temperature range 310-355 degree sign C the spin-exchange rate coefficient is found to be (6.1±0.6)x10 -20 cm 3 /s with no detectable temperature dependence. This value is in good agreement with a previous theoretical estimate reported by Walker and it is only slightly lower than the corresponding Rb- 3 He spin-exchange rate coefficient. The total Na- 3 He spin-destruction rate coefficient is, within errors, found to be the same as the Na- 3 He spin-exchange rate coefficient, thereby indicating that the maximum possible photon efficiency may approach unity for the Na- 3 He system. A technique, in which a charge-coupled device camera is used to take images of faint unquenched fluorescence light, has been utilized to allow for an instantaneous determination of the sodium number densities during the rate coefficient measurements

Spin Wave Theory of Strongly Anisotropic Magnets

DEFF Research Database (Denmark)

Lindgård, Per-Anker

1977-01-01

A strong anisotropy gives rise to a non-spherical precession of the spins with different amplitudes in the x and y directions. The highly anharmonic exchange interaction thereby becomes effectively anisotropic. The possibility of detecting a genuine two-ion anisotropy is discussed, and comments...

The nuclear deformation versus the spin-flip like excitations and the suppression of the 2 νββ decay amplitude

International Nuclear Information System (INIS)

Raduta, A. A.; Delion, D. S.; Faessler, A.

1998-01-01

The suppression mechanism of the Gamow-Teller double beta decay amplitude M GT is studied using a many body Hamiltonian which describes a composite system of protons and neutrons moving in a projected spherical single particle basis. Alike nucleons interact through pairing, while protons and neutrons by a separable dipole-dipole force both in the particle-hole (ph) and particle-particle (pp) channels. The spin-flip and non-spin-flip components of the QRPA phonons have different contributions to the M GT value. The relative magnitudes and phases depend on both the strength of the particle-particle interaction (g pp ) and nuclear deformation. The deformation yields a fragmentation of the M GT value on one hand and washes out the separation of states of pure spin-flip and non spin-flip structures. Due to this effect, M GT has only one fragmented resonance structure in the low part of the spectrum. The mechanism of M GT suppression is different for spherical and deformed nuclei. While for spherical situation the resonances of pure spin-flip and non spin-flip character are separated in energy, for deformed case the two resonances coincide. In both cases, approaching the critical value of g pp , where the Random Phase Approximation (RPA) breaks down, a lot of strength is accumulated in the lowest RPA state. The difference is that, while in the spherical case this has a non spin-flip nature, in the deformed case the state is a mixture of both types of configurations. (authors)

A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

Energy Technology Data Exchange (ETDEWEB)

Song, Xuerui; Zhang, Jian; Feng, Fupan; Wang, Junfeng; Zhang, Wenlong; Lou, Liren; Zhu, Wei; Wang, Guanzhong, E-mail: gzwang@ustc.edu.cn [Hefei National Laboratory for Physical Science at Microscale, and Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026 (China)

2014-04-15

We investigated the influence of spins on surface of nanodiamonds (NDs) to the longitudinal relaxation time (T{sub 1}) and transverse relaxation time (T{sub 2}) of nitrogen vacancy (NV) centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T{sub 1} and T{sub 2}, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T{sub 1} of NV center inside is highly dependent to the surface spins of the NDs. However, for the T{sub 2} of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T{sub 1} of an NV center in NDs is more sensitive to the change of the surface spin density than T{sub 2}.

A statistical correlation investigation for the role of surface spins to the spin relaxation of nitrogen vacancy centers

Directory of Open Access Journals (Sweden)

Xuerui Song

2014-04-01

Full Text Available We investigated the influence of spins on surface of nanodiamonds (NDs to the longitudinal relaxation time (T1 and transverse relaxation time (T2 of nitrogen vacancy (NV centers in ND. A spherical model of the NDs was suggested to account for the experimental results of T1 and T2, and the density of surface spins was roughly estimated based on the statistical analysis of experimental results of 72 NDs containing a single NV center. For NDs studied here, the T1 of NV center inside is highly dependent to the surface spins of the NDs. However, for the T2 of NV center, intrinsic contributions must be much pronounced than that by surface spins. In other words, T1 of an NV center in NDs is more sensitive to the change of the surface spin density than T2.

Instability of ultra-spinning black holes

International Nuclear Information System (INIS)

Emparan, Roberto; Myers, Robert C.

2003-01-01

It has long been known that, in higher-dimensional general relativity, there are black hole solutions with an arbitrarily large angular momentum for a fixed mass. We examine the geometry of the event horizon of such ultra-spinning black holes and argue that these solutions become unstable at large enough rotation. Hence we find that higher-dimensional general relativity imposes an effective 'Kerr-bound' on spinning black holes through a dynamical decay mechanism. Our results also give indications of the existence of new stationary black holes with 'rippled' horizons of spherical topology. We consider various scenarios for the possible decay of ultra-spinning black holes, and finally discuss the implications of our results for black holes in braneworld scenarios. (author)

Satellite Orbital Precessions Caused by the Octupolar Mass Moment ...

Indian Academy of Sciences (India)

Abstract. I consider a satellite moving around a non-spherical body of mass M and equatorial radius R, and calculate its orbital precessions caused by the body's octupolar mass moment J4. I consider only the effects averaged over one orbital period T of the satellite. I give exact for- mulas, not restricted to any special values ...

Relative tracking control of constellation satellites considering inter-satellite link

Science.gov (United States)

Fakoor, M.; Amozegary, F.; Bakhtiari, M.; Daneshjou, K.

2017-11-01

In this article, two main issues related to the large-scale relative motion of satellites in the constellation are investigated to establish the Inter Satellite Link (ISL) which means the dynamic and control problems. In the section related to dynamic problems, a detailed and effective analytical solution is initially provided for the problem of satellite relative motion considering perturbations. The direct geometric method utilizing spherical coordinates is employed to achieve this solution. The evaluation of simulation shows that the solution obtained from the geometric method calculates the relative motion of the satellite with high accuracy. Thus, the proposed analytical solution will be applicable and effective. In the section related to control problems, the relative tracking control system between two satellites will be designed in order to establish a communication link between the satellites utilizing analytical solution for relative motion of satellites with respect to the reference trajectory. Sliding mode control approach is employed to develop the relative tracking control system for body to body and payload to payload tracking control. Efficiency of sliding mode control approach is compared with PID and LQR controllers. Two types of payload to payload tracking control considering with and without payload degree of freedom are designed and suitable one for practical ISL applications is introduced. Also, Fuzzy controller is utilized to eliminate the control input in the sliding mode controller.

Dirac equation of spin particles and tunneling radiation from a Kinnersly black hole

Energy Technology Data Exchange (ETDEWEB)

Li, Guo-Ping; Zu, Xiao-Tao [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Feng, Zhong-Wen [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); China West Normal University, College of Physics and Space Science, Nanchong (China); Li, Hui-Ling [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Shenyang Normal University, College of Physics Science and Technology, Shenyang (China)

2017-04-15

In curved space-time, the Hamilton-Jacobi equation is a semi-classical particle equation of motion, which plays an important role in the research of black hole physics. In this paper, starting from the Dirac equation of spin 1/2 fermions and the Rarita-Schwinger equation of spin 3/2 fermions, respectively, we derive a Hamilton-Jacobi equation for the non-stationary spherically symmetric gravitational field background. Furthermore, the quantum tunneling of a charged spherically symmetric Kinnersly black hole is investigated by using the Hamilton-Jacobi equation. The result shows that the Hamilton-Jacobi equation is helpful to understand the thermodynamic properties and the radiation characteristics of a black hole. (orig.)

Spherical null geodesics of rotating Kerr black holes

International Nuclear Information System (INIS)

Hod, Shahar

2013-01-01

The non-equatorial spherical null geodesics of rotating Kerr black holes are studied analytically. Unlike the extensively studied equatorial circular orbits whose radii are known analytically, no closed-form formula exists in the literature for the radii of generic (non-equatorial) spherical geodesics. We provide here an approximate formula for the radii r ph (a/M;cosi) of these spherical null geodesics, where a/M is the dimensionless angular momentum of the black hole and cos i is an effective inclination angle (with respect to the black-hole equatorial plane) of the orbit. It is well-known that the equatorial circular geodesics of the Kerr spacetime (the prograde and the retrograde orbits with cosi=±1) are characterized by a monotonic dependence of their radii r ph (a/M;cosi=±1) on the dimensionless spin-parameter a/M of the black hole. We use here our novel analytical formula to reveal that this well-known property of the equatorial circular geodesics is actually not a generic property of the Kerr spacetime. In particular, we find that counter-rotating spherical null orbits in the range (3√(3)−√(59))/4≲cosi ph (a/M;cosi=const) on the dimensionless rotation-parameter a/M of the black hole. Furthermore, it is shown that spherical photon orbits of rapidly-rotating black holes are characterized by a critical inclination angle, cosi=√(4/7), above which the coordinate radii of the orbits approach the black-hole radius in the extremal limit. We prove that this critical inclination angle signals a transition in the physical properties of the spherical null geodesics: in particular, it separates orbits which are characterized by finite proper distances to the black-hole horizon from orbits which are characterized by infinite proper distances to the horizon.

Spherical neutron polarimetry applied to spin-echo and time-of-flight spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Lelievre-Berna, E., E-mail: lelievre@ill.e [Institut Laue Langevin (ILL), 6 rue Jules Horowitz, 38042 Grenoble Cedex 9 (France); Bentley, P.; Bourgeat-Lami, E.; Thomas, M. [Institut Laue Langevin (ILL), 6 rue Jules Horowitz, 38042 Grenoble Cedex 9 (France); Pappas, C. [Helmholtz Centre Berlin for Materials and Energy (HCB), Glienickerstr. 100, 14109 Berlin (Germany); Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Kischnik, R.; Moskvin, E. [Helmholtz Centre Berlin for Materials and Energy (HCB), Glienickerstr. 100, 14109 Berlin (Germany)

2009-09-01

The changes in direction of the neutron spin that take place on scattering by a magnetic interaction vector are highly dependent on their relative directions. In some circumstances, without zero-field polarimeter, it is impossible to distinguish between a simple depolarisation and a rotation of the polarisation vector. Motivated by the investigation of chiral magnetic fluctuations, we have implemented the third-generation zero-field polarimeter Cryopad on the neutron spin-echo spectrometer SPAN at the Helmholtz Centre Berlin (HCB). We present the method and the limitations of this novel technique that is now available on IN15 at the ILL. The huge progress accomplished with {sup 3}He neutron spin filters/flippers are going to facilitate the exploitation of polarised beams at spallation sources. Zero-field polarimeters like Cryopad are used routinely at several steady-state sources but their design would be inefficient at a pulse source. We have investigated the possibility to implement a zero-field polarimeter on a time-of-flight spectrometer. We propose a design that would lead to a better efficiency and present the finite element calculations.

A simple application of the Newman-Penrose spin coefficient formalism

International Nuclear Information System (INIS)

Davis, T.M.

1976-01-01

As a simple application of the Newman-Penrose spin coefficient formalism, useful for beginners, the vacuum symmetry (Schwarzschild) solution is found. The calculations also show that all spherically symmetric metrics are Petrov type D. (author)

Numerical experiments with rubble piles : equilibrium shapes and spins

NARCIS (Netherlands)

Richardson, Derek C.; Elankumaran, Pradeep; Sanderson, Robyn E.

2005-01-01

We present numerical experiments investigating the shape and spin limits of self-gravitating "perfect" rubble piles that consist of identical, smooth, rigid, spherical particles with configurable normal coefficient of restitution and no sliding friction. Such constructs are currently employed in a

Quadrupole moments of high spin states in the trans lead region

International Nuclear Information System (INIS)

Neyens, G.; Hardeman, F.; Nouwen, R.; S'heeren, G.; Van Den Bergh, M.; Cousement, R.

1990-01-01

The last few years, a lot of attention has been paid to the trans lead region. A reason for this has to be found in the fact that 208 Pb is a double magic core: both its proton and neutron shell are closed. This means that all nuclei in the lead region can be described well by the shell model, using a spherical 208 Pb core (spherical symmetric potential) and some valence particles or holes around it. The question is whether this model is also correct for high spin states. In this region, isomers with high angular momenta can only be created by alignment of all the spins of the valence particles and holes. And in some cases, alignment is not enough: core excitations are necessary to build up the large spin value of the isomeric state (e.g. the 63/2-isomer in 211 Rn. This means that a neutron pair from the closed N = 126 shell is broken up and one or both neutrons are excited to a level with higher energy and spin. The alignment of the valence-particle-spins causes an increase of the interactions between the valence particles (holes) on one hand, and between the valence particles (holes) and the hard core on the other hand. The latter interaction can cause a deformation of the core. The two interactions are taken into account in two different models: The SERI model (Spherical shell model with Empirical Residual Interactions) and the DIPM (Deformed Independent Particle Model). This paper reports that the effect of alignment of the spins of the valence particles in an isomeric state has been taken into account in the shell model by using residual interactions between the valence particles. These interactions are introduced in the theory in an empirical way or are calculated. Another model, the DIPM, takes into account the effect of alignment in a natural way: it starts from a deformed core (e.g. an axial symmetric potential) in which the valence particles are moving independently from each other)

Higher spin black holes with soft hair

Energy Technology Data Exchange (ETDEWEB)

Grumiller, Daniel [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Pérez, Alfredo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile); Prohazka, Stefan [Institute for Theoretical Physics, TU Wien,Wiedner Hauptstrasse 8-10/136, Vienna, A-1040 (Austria); Tempo, David; Troncoso, Ricardo [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile)

2016-10-21

We construct a new set of boundary conditions for higher spin gravity, inspired by a recent “soft Heisenberg hair”-proposal for General Relativity on three-dimensional Anti-de Sitter space. The asymptotic symmetry algebra consists of a set of affine û(1) current algebras. Its associated canonical charges generate higher spin soft hair. We focus first on the spin-3 case and then extend some of our main results to spin-N, many of which resemble the spin-2 results: the generators of the asymptotic W{sub 3} algebra naturally emerge from composite operators of the û(1) charges through a twisted Sugawara construction; our boundary conditions ensure regularity of the Euclidean solutions space independently of the values of the charges; solutions, which we call “higher spin black flowers”, are stationary but not necessarily spherically symmetric. Finally, we derive the entropy of higher spin black flowers, and find that for the branch that is continuously connected to the BTZ black hole, it depends only on the affine purely gravitational zero modes. Using our map to W-algebra currents we recover well-known expressions for higher spin entropy. We also address higher spin black flowers in the metric formalism and achieve full consistency with previous results.

Determination of the K*(1800) spin parity

Energy Technology Data Exchange (ETDEWEB)

Brandenburg, G W; Carnegie, R K; Cashmore, R J; Davier, M; Dunwoodie, W M; Lasinski, T A; Leith, D W.G.S.; Matthews, J A.J.; Walden, P; Williams, S H [Stanford Linear Accelerator Center, Calif. (USA)

1976-02-16

A spherical harmonic moment analysis of the reactions K/sup -/p..-->..K/sup -/..pi../sup +/n and K/sup +/p..-->..K/sup +/..pi../sup -/..delta../sup + +/ at 13 GeV/c demonstrates the existence of a broad K* state with mass in the vicinity of 1800 MeV and spin parity 3/sup -/.

Spin foam models of matter coupled to gravity

International Nuclear Information System (INIS)

Mikovic, A

2002-01-01

We construct a class of spin foam models describing matter coupled to gravity, such that the gravitational sector is described by the unitary irreducible representations of the appropriate symmetry group, while the matter sector is described by the finite-dimensional irreducible representations of that group. The corresponding spin foam amplitudes in the four-dimensional gravity case are expressed in terms of the spin network amplitudes for pentagrams with additional external and internal matter edges. We also give a quantum field theory formulation of the model, where the matter degrees of freedom are described by spin network fields carrying the indices from the appropriate group representation. In the non-topological Lorentzian gravity case, we argue that the matter representations should be appropriate SO(3) or SO(2) representations contained in a given Lorentz matter representation, depending on whether one wants to describe a massive or a massless matter field. The corresponding spin network amplitudes are given as multiple integrals of propagators which are matrix spherical functions

Satellite NMR in Cu doped with transition impurities

International Nuclear Information System (INIS)

Slichter, C.P.

1979-01-01

Measurements were made of the conduction electron spin magnetization density, M/sub sigma/(R vector) near iron group atoms (Sc through Ni) in Cu. M/sub sigma/(R vector) produces an additional effective local field which shifts the NMR frequency of nearby shells of Cu nuclei relative to Cu nuclei far from all impurities. Resonances of nearby shells appear as weak satellites to the strong resonance of distant Cu nuclei (the main line). M/sub sigma/(R vector) at a given site is proportional through know constants to the splitting of the satellite from the main line. The shell was identified giving rise to the satellite in many cases by use of single crystals. A good approximation M/sub sigma/(R vector) is proportional to the spin susceptibility chi/sub s/ of the impurity. For CuCr we find a large temperature independent chi/sub s/, in contrast to CuMn and CuFe. The results lead to a picture of the electronic structure of Cr, Mn, and Fe along the lines of Schrieffer and Hirst as ions with integral numbers of d-electrons, possessing crystal field and spin-orbit couplings

Worldwide complete spherical Bouguer and isostatic anomaly maps

Science.gov (United States)

Bonvalot, S.; Balmino, G.; Briais, A.; Peyrefitte, A.; Vales, N.; Biancale, R.; Gabalda, G.; Reinquin, F.

2011-12-01

We present here a set of digital maps of the Earth's gravity anomalies (surface "free air", Bouguer and isostatic), computed at Bureau Gravimetric International (BGI) as a contribution to the Global Geodetic Observing Systems (GGOS) and to the global geophysical maps published by the Commission for the Geological Map of the World (CGMW). The free air and Bouguer anomaly concept is extensively used in geophysical interpretation to investigate the density distributions in the Earth's interior. Complete Bouguer anomalies (including terrain effects) are usually computed at regional scales by integrating the gravity attraction of topography elements over and beyond a given area (under planar or spherical approximations). Here, we developed and applied a worldwide spherical approach aimed to provide a set of homogeneous and high resolution gravity anomaly maps and grids computed at the Earth's surface, taking into account a realistic Earth model and reconciling geophysical and geodetic definitions of gravity anomalies. This first version (1.0) has been computed by spherical harmonics analysis / synthesis of the Earth's topography-bathymetry up to degree 10800. The detailed theory of the spherical harmonics approach is given in Balmino et al., (Journal of Geodesy, submitted). The Bouguer and terrain corrections have thus been computed in spherical geometry at 1'x1' resolution using the ETOPO1 topography/bathymetry, ice surface and bedrock models from the NOAA (National Oceanic and Atmospheric Administration) and taking into account precise characteristics (boundaries and densities) of major lakes, inner seas, polar caps and of land areas below sea level. Isostatic corrections have been computed according to the Airy Heiskanen model in spherical geometry for a constant depth of compensation of 30km. The gravity information given here is provided by the Earth Geopotential Model (EGM2008), developed at degree 2160 by the National Geospatial Intelligence Agency (NGA) (Pavlis

ON THE EQUILIBRIUM FIGURE OF CLOSE-IN PLANETS AND SATELLITES

Energy Technology Data Exchange (ETDEWEB)

Correia, Alexandre C. M. [Departamento de Fisica, I3N, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro (Portugal); Rodriguez, Adrian [Insituto de Astronomia, Geofisica e Ciencias Atmosfericas, IAG-USP, Rua do Matao 1226, 05508-090 Sao Paulo (Brazil)

2013-04-20

Many exoplanets have been observed close to their parent stars with orbital periods of a few days. As for the major satellites of the Jovian planets, the figure of these planets is expected to be strongly shaped by tidal forces. However, contrary to solar system satellites, exoplanets may present high values for the obliquity and eccentricity due to planetary perturbations, and may also be captured in spin-orbit resonances different from the synchronous one. Here we give a general formulation of the equilibrium figure of those bodies that makes no particular assumption on the spin and/or orbital configurations. The gravity field coefficients computed here are well suited for describing the figure evolution of a body whose spin and orbit undergo substantial variations in time.

Nuclear structure of 94,95Mo at high spins

International Nuclear Information System (INIS)

Kharraja, B.; Ghugre, S.S.; Garg, U.; Janssens, R.V.; Carpenter, M.P.; Crowell, B.; Khoo, T.L.; Lauritsen, T.; Nisius, D.; Reviol, W.; Mueller, W.F.; Riedinger, L.L.; Kaczarowski, R.

1998-01-01

The high-spin level structures of 94,95 Mo (N=52,53) have been investigated via the 65 Cu( 36 S, αp2n) 94 Mo and 65 Cu( 36 S, αpn) 95 Mo reactions at 142 MeV. The level schemes have been extended up to spin J∼19ℎ and excitation energies E x ∼12 MeV. Spherical shell-model calculations have been performed and compared with the experimental energy levels. The level structure of 94 Mo exhibits a single-particle nature and the higher-angular-momentum states are dominated by the excitation of a g 9/2 neutron across the N=50 shell gap. The level sequences observed in 95 Mo have been interpreted on the basis of the spherical shell model and weak coupling of a d 5/2 or a g 7/2 neutron to the 94 Mo core. copyright 1998 The American Physical Society

Stationary bound-state massive scalar field configurations supported by spherically symmetric compact reflecting stars

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Academic College, Jerusalem (Israel)

2017-12-15

It has recently been demonstrated that asymptotically flat neutral reflecting stars are characterized by an intriguing no-hair property. In particular, it has been proved that these horizonless compact objects cannot support spatially regular static matter configurations made of scalar (spin-0) fields, vector (spin-1) fields and tensor (spin-2) fields. In the present paper we shall explicitly prove that spherically symmetric compact reflecting stars can support stationary (rather than static) bound-state massive scalar fields in their exterior spacetime regions. To this end, we solve analytically the Klein-Gordon wave equation for a linearized scalar field of mass μ and proper frequency ω in the curved background of a spherically symmetric compact reflecting star of mass M and radius R{sub s}. It is proved that the regime of existence of these stationary composed star-field configurations is characterized by the simple inequalities 1 - 2M/R{sub s} < (ω/μ){sup 2} < 1. Interestingly, in the regime M/R{sub s} << 1 of weakly self-gravitating stars we derive a remarkably compact analytical equation for the discrete spectrum {ω(M,R_s, μ)}{sup n=∞}{sub n=1} of resonant oscillation frequencies which characterize the stationary composed compact-reflecting-star-linearized-massive-scalar-field configurations. Finally, we verify the accuracy of the analytically derived resonance formula of the composed star-field configurations with direct numerical computations. (orig.)

Photon Pressure Force on Space Debris TOPEX/Poseidon Measured by Satellite Laser Ranging

Science.gov (United States)

Kucharski, D.; Kirchner, G.; Bennett, J. C.; Lachut, M.; Sośnica, K.; Koshkin, N.; Shakun, L.; Koidl, F.; Steindorfer, M.; Wang, P.; Fan, C.; Han, X.; Grunwaldt, L.; Wilkinson, M.; Rodríguez, J.; Bianco, G.; Vespe, F.; Catalán, M.; Salmins, K.; del Pino, J. R.; Lim, H.-C.; Park, E.; Moore, C.; Lejba, P.; Suchodolski, T.

2017-10-01

The (TOPography EXperiment) TOPEX/Poseidon (T/P) altimetry mission operated for 13 years before the satellite was decommissioned in January 2006, becoming a large space debris object at an altitude of 1,340 km. Since the end of the mission, the interaction of T/P with the space environment has driven the satellite's spin dynamics. Satellite laser ranging (SLR) measurements collected from June 2014 to October 2016 allow for the satellite spin axis orientation to be determined with an accuracy of 1.7°. The spin axis coincides with the platform yaw axis (formerly pointing in the nadir direction) about which the body rotates in a counterclockwise direction. The combined photometric and SLR data collected over the 11 year time span indicates that T/P has continuously gained rotational energy at an average rate of 2.87 J/d and spins with a period of 10.73 s as of 19 October 2016. The satellite attitude model shows a variation of the cross-sectional area in the Sun direction between 8.2 m2 and 34 m2. The direct solar radiation pressure is the main factor responsible for the spin-up of the body, and the exerted photon force varies from 65 μN to 228 μN around the mean value of 138.6 μN. Including realistic surface force modeling in orbit propagation algorithms will improve the prediction accuracy, giving better conjunction warnings for scenarios like the recent close approach reported by the ILRS Space Debris Study Group—an approximate 400 m flyby between T/P and Jason-2 on 20 June 2017.

A study of the effect of non-spherical dust particles on Geostationary Environment Monitoring Spectrometer (GEMS) aerosol optical properties retrievals

Science.gov (United States)

Go, S.; Kim, J.; KIM, M.; Choi, M.; Lim, H.

2017-12-01

Non-spherical assumption of particle shape has been used to replace the spherical assumption in the Geostationary Environment Monitoring Spectrometer (GEMS) aerosol optical properties retrievals for dust particles. GEMS aerosol retrieval algorithms are based on optimal estimation method to provide aerosol optical depth (AOD), single scattering albedo (SSA) at 443nm, and aerosol loading height (ALH) simultaneously as products. Considering computing time efficiency, the algorithm takes Look-Up Table (LUT) approach using Vector Linearized Discrete Ordinate Radiative Transfer code (VLIDORT), and aerosol optical properties for three aerosol types of absorbing fine aerosol (BC), dust and non-absorbing aerosol (NA) are integrated from AERONET inversion data, and fed into the LUT calculation. In this study, by applying the present algorithm to OMI top-of the atmosphere normalized radiance, retrieved AOD, SSA with both spherical and non-spherical assumptions have been compared to the surface AERONET observations at East Asia sites for 3 years from 2005 to 2007 to evaluate and quantify the effect of non-spherical dust particles on the satellite aerosol retrievals. The root-mean-square error (RMSE) in the satellite retrieved AOD have been slightly reduced as a result of adopting the non-spherical assumption in the GEMS aerosol retrieval algorithm. For SSA, algorithm tested with spheroid models on dust particle shows promising results for the improved SSA. In terms of ALH, the results are qualitatively compared with CALIOP products, and shows consistent variation. This result suggests the importance of taking into account the effects of non-sphericity in the retrieval of dust particles from GEMS measurements.

High spin structure of nuclei near N = 50 shell gap and search for high-spin isomers using time stamped data

International Nuclear Information System (INIS)

Saha, S.; Palit, R.; Trivedi, T.; Sethi, J.; Joshi, P.K.; Naidu, B.S.; Donthi, R.; Jadhav, S.; Nanal, V.; Pillay, R.G.; Jain, H.C.; Kumar, S.; Biswas, D.C.; Mukherjee, G.; Saha, S.

2011-01-01

Information on the high-spin states of nuclei promises to provide stringent test of the interaction of the Hamiltonian used in the calculation due to smaller basis space for high J-values. It is reported in a recent shell model review that no interaction is optimized for the region of interest around N = 50 and Z = 40 shell closure. The detailed spectroscopic information of the medium and high spin states in these nuclei is required to understand the shape transition between spherical and deformed shapes at N =60 as the higher orbitals are filled. Structure of isomers near shell closure carries important information of, for example, the extent of core excitation. In the present work, the spectroscopic study of the high spin states of 89 Zr isotope have been discussed

High spin states in 143Sm

International Nuclear Information System (INIS)

Raut, R.; Ganguly, S.; Kshetri, R.; Mukherjee, G.; Mukherjee, A.; Banerjee, P.; Saha Sarkar, M.; Bhattacharya, S.; Goswami, A.; Bhattacharjee, T.; Basu, S.K.; Mukhopadhyaya, S.; Krishichayan; Chakraborty, A.; Gangopadhyay, G.

2004-01-01

Large amount of experimental data has been obtained in the recent past on several Nd (Z=60) and Pm (Z=61) isotopes near N=82 shell closure which exhibits an irregular yrast sequence, typical of a non-spherical shape at low spins. The nucleus 143 Sm (Z=62) with a single neutron hole in the N=82 closed shell was investigated as a part of this proposed study

Phase-space spinor amplitudes for spin-1/2 systems

International Nuclear Information System (INIS)

Watson, P.; Bracken, A. J.

2011-01-01

The concept of phase-space amplitudes for systems with continuous degrees of freedom is generalized to finite-dimensional spin systems. Complex amplitudes are obtained on both a sphere and a finite lattice, in each case enabling a more fundamental description of pure spin states than that previously given by Wigner functions. In each case the Wigner function can be expressed as the star product of the amplitude and its conjugate, so providing a generalized Born interpretation of amplitudes that emphasizes their more fundamental status. The ordinary product of the amplitude and its conjugate produces a (generalized) spin Husimi function. The case of spin-(1/2) is treated in detail, and it is shown that phase-space amplitudes on the sphere transform correctly as spinors under rotations, despite their expression in terms of spherical harmonics. Spin amplitudes on a lattice are also found to transform as spinors. Applications are given to the phase space description of state superposition, and to the evolution in phase space of the state of a spin-(1/2) magnetic dipole in a time-dependent magnetic field.

Precise measurement of magnetic field gradients from free spin precession signals of He-3 and Xe-129 magnetometers

NARCIS (Netherlands)

Allmendinger, Fabian; Blümler, Peter; Doll, Michael; Grasdijk, Oliver; Heil, Werner; Jungmann, Klaus; Karpuk, Sergej; Krause, Hans-Joachim; Offenhäuser, Andreas; Repetto, Maricel; Schmidt, Ulrich; Sobolev, Yuri; Tullney, Kathlyne; Willmann, Lorenz; Zimmer, Stefan

2017-01-01

We report on precise measurements of magnetic field gradients extracted from transverse relaxation rates of precessing spin samples. The experimental approach is based on the free precession of gaseous, nuclear spin polarized He-3 and (12)9Xe atoms in a spherical cell inside a magnetic guiding field

High spin states in the f-p shell

International Nuclear Information System (INIS)

Delaunay, J.

1975-01-01

The high spin states (HSS) in Fe, Co, Ni (Z=26,27,28) isotopes exhibit features characteristics of soft or transition nuclei, 56 Fe being as well deformed prolate nucleus and the Ni isotopes often throught of as spherical. The methodology used to identify these HSS is the so called DCO (directional correlation of oriented nuclei) or ratio method which, by combining the angular distribution data plus one point of a triple γ-γ correlation in an asymmetric geometry, gives result that is found equivalent to a complete angular correlation to assign spin and mixing ratios. Some results collected with this methodology are presented [fr

Impact of spin-orbit density dependent potential in heavy ion reactions forming Se nuclei

Energy Technology Data Exchange (ETDEWEB)

Rajni; Sharma, Ishita; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India); Jain, Deepika [Mata Gujri College, Department of Physics, Fatehgarh Sahib (India)

2017-10-15

The Skyrme energy density formalism is employed to explore the effect of spin-orbit interaction potential by considering a two nucleon transfer process via various entrance channels such as {sup 23}Na + {sup 49}V, {sup 25}Mg + {sup 47}Ti, {sup 27}Al + {sup 45}Sc, {sup 29}Si + {sup 43}Ca and {sup 31}P + {sup 41}K, all forming the same compound system {sup 72}Se*, using both spherical as well as quadrupole deformed (β{sub 2}) nuclei. For spherical nuclei, the spin-orbit density part V{sub J} of nuclear potential remains unaffected with the transfer of two nucleons from the target to the projectile, however, show notable variation in magnitude after inclusion of deformation effects. Likewise, deformations play an important role in the spin-orbit density independent part V{sub P}, as the fusion pocket start appears, which otherwise diminish for the spherical nuclei. Further, the effect of an increase in the N/Z ratio of Se is explored on V{sub J} as well as V{sub P} and results are compared with transfer channels. In addition to this, the role of double spin-orbit parameters (W{sub 0} and W{sub 0}{sup '}) with relative contribution of the isoscalar and isovector parts of spin-orbit strength is explored in view of SkI2, SkI3 and SkI4 Skyrme forces. Beside this, the decay path of {sup 72}Se* nucleus formed in {sup 27}Al + {sup 45}Sc reaction is investigated within the framework of dynamical cluster decay model (DCM), where the nuclear proximity potential is obtained by both Skyrme energy density formalism (SEDF) and proximity pocket formula. The fusion hindrance in the {sup 27}Al + {sup 45}Sc reaction is also addressed via the barrier lowering parameter ΔV{sub B}. Finally, the contribution of spin-orbit density dependent interaction potential is estimated for the {sup 27}Al + {sup 45}Sc reaction using single (W{sub 0} or W{sub 0}{sup '}) and double spin-orbit parameters (W{sub 0} and W{sub 0}{sup '}). (orig.)

Spherical grating spectrometers

Science.gov (United States)

O'Donoghue, Darragh; Clemens, J. Christopher

2014-07-01

We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

Theory of quasi-spherical accretion in X-ray pulsars

Science.gov (United States)

Shakura, N.; Postnov, K.; Kochetkova, A.; Hjalmarsdotter, L.

2012-02-01

A theoretical model for quasi-spherical subsonic accretion on to slowly rotating magnetized neutron stars is constructed. In this model, the accreting matter subsonically settles down on to the rotating magnetosphere forming an extended quasi-static shell. This shell mediates the angular momentum removal from the rotating neutron star magnetosphere during spin-down episodes by large-scale convective motions. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere. The settling regime of accretion can be realized for moderate accretion rates ? g s-1. At higher accretion rates, a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of the spin-up/spin-down rates (the angular rotation frequency derivative ?, and ? near the torque reversal) of X-ray pulsars with known orbital periods, it is possible to determine the main dimensionless parameters of the model, as well as to estimate the magnetic field of the neutron star. We illustrate the model by determining these parameters for three wind-fed X-ray pulsars GX 301-2, Vela X-1 and GX 1+4. The model explains both the spin-up/spin-down of the pulsar frequency on large time-scales and the irregular short-term frequency fluctuations, which can correlate or anticorrelate with the X-ray flux fluctuations in different systems. It is shown that in real pulsars an almost iso-angular-momentum rotation law with ω˜ 1/R2, due to strongly anisotropic radial turbulent motions sustained by large-scale convection, is preferred.

Satellite Control Laboratory

DEFF Research Database (Denmark)

Wisniewski, Rafal; Bak, Thomas

2001-01-01

The Satellite Laboratory at the Department of Control Engineering of Aalborg University (SatLab) is a dynamic motion facility designed for analysis and test of micro spacecraft. A unique feature of the laboratory is that it provides a completely gravity-free environment. A test spacecraft......-axis magnetometer, three piezoelectric gyros, and four reaction wheels in a tetrahedron configuration. The operation of the spacecraft is fully autonomous. The data flow between the transducers and the onboard computer placed physically outside the satellite is provided by a radio link. The purpose...... can be implemented in the laboratory, e.g. three-axis attitude control, slew manoeuvres, spins stabilization using magnetic actuation and/or reaction wheels. The spacecraft attitude can be determined applying magnetometer measurements....

Excited eigenmodes in magnetic vortex states of soft magnetic half-spheres and spherical caps

Energy Technology Data Exchange (ETDEWEB)

Yoo, Myoung-Woo; Lee, Jae-Hyeok; Kim, Sang-Koog, E-mail: sangkoog@snu.ac.kr [National Creative Research Initiative Center for Spin Dynamics and Spin-Wave Devices, Nanospinics Laboratory, Research Institute of Advanced Materials, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of)

2014-12-14

We studied the magnetization dynamics of excitation modes in special geometrical confinements of soft magnetic half-spheres and spherical caps in magnetic vortex states using finite-element micromagnetic numerical calculations. We found additional fine features of the zeroth- and first-order gyrotropic modes and asymmetric m = +1 and m = −1 azimuthal spin-wave modes, which detailed information is unobtainable from two-dimensional mesh-cell based numerical calculations. Moreover, we examined the perpendicular bias field dependence of the excited eigenmodes, which data provide for an efficient means of control over the excited modes. Such numerical calculations offer additional details or new underlying physics on dynamic features in arbitrary-shape magnetic nano-elements such as half-spheres and spherical caps in magnetic vortex states.

Measurements of plasma density fluctuations and electric wave fields using spherical electrostatic probes

International Nuclear Information System (INIS)

Eriksson, A.I.; Bostroem, R.

1995-04-01

Spherical electrostatic probes are in wide use for the measurements of electric fields and plasma density. This report concentrates on the measurements of fluctuations of these quantities rather than background values. Potential problems with the technique include the influence of density fluctuations on electric field measurements and vice versa, effects of varying satellite potential, and non-linear rectification in the probe and satellite sheaths. To study the actual importance of these and other possible effects, we simulate the response of the probe-satellite system to various wave phenomena in the plasma by applying approximate analytical as well as numerical methods. We use a set of non-linear probe equations, based on probe characteristics experimentally obtained in space, and therefore essentially independent of any specific probe theory. This approach is very useful since the probe theory for magnetized plasmas is incomplete. 47 refs

Measurement of the depolarization of the reaction 27Al(p vector,p vector.)27Al for the study of the spin-spin potential

International Nuclear Information System (INIS)

Loeh, H.

1981-01-01

For the study of the spin-spin interaction in the optical potential the depolarisation in the elastic scattering of polarized protons was measured. The double-scattering experiments were performed in the angular range 40 0 -110 0 at an incident energy of 10.35 MeV at the Erlangen QD-magnetic spectrometer. The determination of the optical model parameters independent from the spin-spin potentials was performed by the fitting of these to the observables and sigmasup(di). These were obtained from a measurement of the angular distribution of the analyzing power and the differential cross section in the 4π-scattering chamber for the reaction 27 Al(p vector,p 0 ) at the same energy. The compound contributions present at this energy, which can also influence the depolarization, were regarded by the calculation of the compound-elastic non-spin-flip respectively spin-flip subcross sections by means of the formalism of Hofmann, Richert, Tepel and Weidenmueller. Because the target nucleus 27 Al possesses in the ground state a spin I=5/2, also the possible quadrupole spin flip had to be included. This was performed by coupled-channel calculations. The respecting compound contributions and quadrupole effects corrected depolarization data could by used for the study of the spin-spin potentials by means of DWBA calculations. As result it was shown that for the description of the experimental data a spherical spin-spin potential of the strength Vsub(SS)=1.5+-0.3 MeV had to be assumed. (orig.) [de

Development and control of a three-axis satellite simulator for the bifocal relay mirror initiative

OpenAIRE

Chernesky, Vincent S.

2001-01-01

The Three Axis Satellite Simulator (TASS) is a 4-foot diameter octagonal platform supported on a spherical air bearing. The platform hosts several satellite subsystems, including rate gyros, reaction wheels, thrusters, sun sensors, and an onboard control computer. This free-floating design allows for realistic emulation of satellite attitude dynamics in a laboratory environment. The bifocal relay mirror spacecraft system is composed of two optically coupled telescopes used to redirect the las...

Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.

Science.gov (United States)

Vaara, Juha; Hanni, Matti; Jokisaari, Jukka

2013-03-14

Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation.

Spherical neutron generator

Science.gov (United States)

Leung, Ka-Ngo

2006-11-21

A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.

Low energy spin excitations in chromium metal

International Nuclear Information System (INIS)

Pynn, R.; Azuah, R.T.; Stirling, W.G.

1997-01-01

Neutron scattering experiments with full polarization analysis have been performed with a single crystal of chromium to study the low-energy spin fluctuations in the transverse spin density wave (TSDW) state. A number of remarkable results have been found. Inelastic scattering observed close to the TSDW satellite positions at (1 ± δ,0,0) does not behave as expected for magnon scattering. In particular, the scattering corresponds to almost equally strong magnetization fluctuations both parallel and perpendicular to the ordered moments of the TSDW phase. As the Neel temperature is approached from below, scattering at the commensurate wavevector (1,0,0) increases in intensity as a result of critical scattering at silent satellites (1,0, ± δ) being included within the spectrometer resolution function. This effect, first observed by Sternlieb et al, does not account for all of the inelastic scattering around the (1,0,0) position, however, Rather, there are further collective excitations, apparently emanating from the TSDW satellites, which correspond to magnetic fluctuations parallel to the ordered TSDW moments. These branches have a group velocity that is close to that of (1,0,0) longitudinal acoustic (LA) phonons, but assigning their origin to magneto-elastic scattering raises other unanswered questions

High-spin {gamma}-ray spectroscopy of {sup 124}Ba, {sup 124}Xe and {sup 125}Xe

Energy Technology Data Exchange (ETDEWEB)

Al-Khatib, Ali

2008-08-18

Rotational spectra had been observed for the first time in excited atomic nuclei in 1938. This observation was attributed to the deviation from spherical shape. In quantum mechanics, when a perfectly spherical system rotates, it appears identical when it is viewed from any direction and no point of reference exists to which the change in position can be identified. Therefore, rotation cannot be defined for spherical nuclei. If the shape deviates from spherical symmetry, the nucleus can rotate and rotational spectra are observed. Many nucleons contribute to the rotation which is referred to as collective excitation. Depending on the mass region, nuclei have different deformations and, therefore, different shapes. Many nuclei show larger deformation with increasing excitation energy. Transitional nuclei between spherical and strongly deformed regions of the nuclear chart are usually soft with respect to deformation changes. In the mass region around A{proportional_to}125, which is the subject of this thesis, nuclei are predicted to be soft with respect to deformation. Rotational motion leads to Coriolis-induced alignments of high-j nucleons, which are in this mass region predominantly protons and neutrons from the h{sub 11/2} unique-parity intruder subshells. The proton Fermi level lies in the lower part of the h{sub 11/2} subshell which favours prolate shape whereas the neutron Fermi level lies in the upper part of the h{sub 11/2} subshell which favours oblate shape. According to the opposite shape-driving forces of protons and neutrons, shape co-existence is expected and the interplay between the h{sub 11/2} proton and neutron orbitals is of great interest for spectroscopic investigations. In addition, superdeformation has been established in this mass region. An interesting observation in this mass region is that nuclei undergo a shape-change from collective prolate to non-collective oblate states at high spins. In this spin range the transitions within the

Satellite-Based Sunshine Duration for Europe

Directory of Open Access Journals (Sweden)

Bodo Ahrens

2013-06-01

Full Text Available In this study, two different methods were applied to derive daily and monthly sunshine duration based on high-resolution satellite products provided by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT Satellite Application Facility on Climate Monitoring using data from Meteosat Second Generation (MSG SEVIRI (Spinning Enhanced Visible and Infrared Imager. The satellite products were either hourly cloud type or hourly surface incoming direct radiation. The satellite sunshine duration estimates were not found to be significantly different using the native 15-minute temporal resolution of SEVIRI. The satellite-based sunshine duration products give additional spatial information over the European continent compared with equivalent in situ-based products. An evaluation of the satellite sunshine duration by product intercomparison and against station measurements was carried out to determine their accuracy. The satellite data were found to be within ±1 h/day compared to high-quality Baseline Surface Radiation Network or surface synoptic observations (SYNOP station measurements. The satellite-based products differ more over the oceans than over land, mainly because of the treatment of fractional clouds in the cloud type-based sunshine duration product. This paper presents the methods used to derive the satellite sunshine duration products and the performance of the different retrievals. The main benefits and disadvantages compared to station-based products are also discussed.

The equilibrium of rubble-pile satellites: The Darwin and Roche ellipsoids for gravitationally held granular aggregates

Science.gov (United States)

Sharma, Ishan

2009-04-01

Many new small moons of the giant planets have been discovered recently. In parallel, satellites of several asteroids, e.g., Ida, have been found. Strikingly, a majority of these new-found planetary moons are estimated to have very low densities, which, along with their hypothesized accretionary origins, suggests a rubble internal structure. This, coupled to the fact that many asteroids are also thought to be particle aggregates held together principally by self-gravity, motivates the present investigation into the possible ellipsoidal shapes that a rubble-pile satellite may achieve as it orbits an aspherical primary. Conversely, knowledge of the shape will constrain the granular aggregate's orbit—the closer it gets to a primary, both primary's tidal effect and the satellite's spin are greater. We will assume that the primary body is sufficiently massive so as not to be influenced by the satellite. However, we will incorporate the primary's possible ellipsoidal shape, e.g., flattening at its poles in the case of a planet, and the proloidal shape of asteroids. In this, the present investigation is an extension of the first classical Darwin problem to granular aggregates. General equations defining an ellipsoidal rubble pile's equilibrium about an ellipsoidal primary are developed. They are then utilized to scrutinize the possible granular nature of small inner moons of the giant planets. It is found that most satellites satisfy constraints necessary to exist as equilibrated granular aggregates. Objects like Naiad, Metis and Adrastea appear to violate these limits, but in doing so, provide clues to their internal density and/or structure. We also recover the Roche limit for a granular satellite of a spherical primary, and employ it to study the martian satellites, Phobos and Deimos, as well as to make contact with earlier work of Davidsson [Davidsson, B., 2001. Icarus 149, 375-383]. The satellite's interior will be modeled as a rigid-plastic, cohesion-less material

Induction studies with satellite data

DEFF Research Database (Denmark)

Olsen, Nils

1999-01-01

The natural variations of the Earth's magnetic field of periods spanning from milliseconds to decades can be used to infer the conductivity-depth profile of the Earth's interior. Satellites provide a good spatial coverage of magnetic measurements, and forthcoming missions will probably allow...... for observations lasting several years, which helps to reduce the statistical error of the estimated response functions. Two methods are used to study the electrical conductivity of the Earth's mantle in the period range from hours to months. In the first, known as the potential method, a spherical harmonic...... days, this difference probably is not caused purely by differences in mantle conductivity (for which one would expect less difference for the longer periods). Further studies with data from recently launched and future satellites are needed....

Measurement of the depolarization of the reaction 27Al (p vector, p vector.) 27Al for the study of the spin-spin potential

International Nuclear Information System (INIS)

Loeh, H.

1981-01-01

For the study of the spin-spin interactions in the optical potential the depolarization in the elastic scattering of polarized protons was measured. The double-scattering experiments were performed in the angular range 40 0 -110 0 at an incident energy of 10.35 MeV at the Erlangen QD magnetic spectrometer. The determination of the optical model parameters independent from the spin-spin potentials resulted by the fit of those to the observables and sigmasup(di). These were obtained from a measurement of the angular distribution of the analyzing power and the differential cross section in the 4π-scattering chamber for the reaction 27 Al (p vector,psub(o)) at the same energy. The compound contributions present at this energy, which can also influence the depolarization, were regarded by the calculation of the compound-elastic non-spin-flip respectively spin-flip subcross sections by means of the formalism of Hofmann, Richard, Tepel, and Weidenmueller. Because of the target nucleus 27 Al posesses in the ground state a spin I=5/2 also the possible quadrupole spin flip had to be included in the analysis. This was performed by coupled channel calculations. The depolarization data corrected according to compound contributions and quadrupole effects could now be applied to the study of the spin-spin potentials by means of DWBA calculations. As result it turned out that for the description of the experimental data a spherical spin-spin potential of the strength Vsub(SS)=1.5+-0.3 MeV had to be assumed. For the addition of a tensor term however no necessity resulted. (orig.) [de

Internal and external potential-field estimation from regional vector data at varying satellite altitude

Science.gov (United States)

Plattner, Alain; Simons, Frederik J.

2017-10-01

When modelling satellite data to recover a global planetary magnetic or gravitational potential field, the method of choice remains their analysis in terms of spherical harmonics. When only regional data are available, or when data quality varies strongly with geographic location, the inversion problem becomes severely ill-posed. In those cases, adopting explicitly local methods is to be preferred over adapting global ones (e.g. by regularization). Here, we develop the theory behind a procedure to invert for planetary potential fields from vector observations collected within a spatially bounded region at varying satellite altitude. Our method relies on the construction of spatiospectrally localized bases of functions that mitigate the noise amplification caused by downward continuation (from the satellite altitude to the source) while balancing the conflicting demands for spatial concentration and spectral limitation. The `altitude-cognizant' gradient vector Slepian functions (AC-GVSF) enjoy a noise tolerance under downward continuation that is much improved relative to the `classical' gradient vector Slepian functions (CL-GVSF), which do not factor satellite altitude into their construction. Furthermore, venturing beyond the realm of their first application, published in a preceding paper, in the present article we extend the theory to being able to handle both internal and external potential-field estimation. Solving simultaneously for internal and external fields under the limitation of regional data availability reduces internal-field artefacts introduced by downward-continuing unmodelled external fields, as we show with numerical examples. We explain our solution strategies on the basis of analytic expressions for the behaviour of the estimation bias and variance of models for which signal and noise are uncorrelated, (essentially) space- and band-limited, and spectrally (almost) white. The AC-GVSF are optimal linear combinations of vector spherical harmonics

Effective one-body potential of DFT plus correlated kinetic energy density for two-electron spherical model atoms

International Nuclear Information System (INIS)

March, N.H.; Ludena, Eduardo V.

2004-01-01

For three model problems concerning two-electron spin-compensated ground states with spherical density, the third-order linear homogeneous differential equation constructed for the determination of ρ(r) is used here in conjunction with the von Weizsacker functional to characterize the one-body potential of density functional theory (DFT). Correlated von Weizsacker-type terms are compared to the exact DFT functional

Spherical sampling

CERN Document Server

Freeden, Willi; Schreiner, Michael

2018-01-01

This book presents, in a consistent and unified overview, results and developments in the field of today´s spherical sampling, particularly arising in mathematical geosciences. Although the book often refers to original contributions, the authors made them accessible to (graduate) students and scientists not only from mathematics but also from geosciences and geoengineering. Building a library of topics in spherical sampling theory it shows how advances in this theory lead to new discoveries in mathematical, geodetic, geophysical as well as other scientific branches like neuro-medicine. A must-to-read for everybody working in the area of spherical sampling.

High spin spectroscopy of 34Cl

International Nuclear Information System (INIS)

Bisoi, Abhijit; Ray, S.; Kshetri, R.; Goswami, A.; Saha Sarkar, M.; Pramanik, D.; Sarkar, S.; Nag, S.; Selva Kumar, K.; Singh, P.; Saha, S.; Sethi, J.; Trivedi, T.; Naidu, B.S.; Donthi, R.; Nanal, V.; Palit, R.

2011-01-01

Spectroscopic information for 34 Cl is of interest for understanding the large 33 S abundance observed in nova. This nucleus has been extensively studied using proton, light ions and alpha beams but there are few experiments where heavy ions were used. In the present work, heavy ion beams are used to extract spectroscopic data for high spin states above ∼ 5 MeV, important for astrophysical scenario. Spherical shell model calculations have been done to interpret the experimental data. Several options of truncation adopted have provided useful insight into the sd - fp cross-shell calculations

Earth Reflected Solar Radiation Incident upon an Arbitrarily Oriented Spinning Flat Plate

Science.gov (United States)

Cunningham, Fred G.

1963-01-01

A general derivation is given for the earth reflected solar radiation input to a flat plate--a solar cell paddle, for example--which is spinning about an axis coincident with the axis of symmetry of the satellite to which it is affixed. The resulting equations are written for the general case so that arbitrary orientations of the spin axis with respect to the earth-satellite line and arbitrary orientations of the normal to the plate with respect to the spin axis can be treated. No attempt is made to perform the resulting integrations because of the complexity of the equations; nor is there any attempt to delineate the integration limits for the general case. However, the equations governing these limits are given. The appendixes contain: the results, in graphical form, of two representative examples; the general computer program for the calculation is given in Fortran notation; and the results of a calculation of the distribution of albedo energy on the proposed Echo II satellite. The value of the mean solar constant used is 1.395 times 10 (sup 4) ergs per centimeters-squared per second; the mean albedo of the earth is assumed to be 0.34; and the earth is assumed to be a diffuse reflector.

About mechanisms of tetonic activity of the satellites

Science.gov (United States)

Barkin, Yu. V.

2003-04-01

ABOUT MECHANISMS OF TECTONIC ACTIVITY OF THE SATELLITES Yu.V. Barkin Sternberg Astronomical Institute, Moscow, Russia, barkin@sai.msu.ru Due to attraction of the central planet and others external bodies satellite is subjected by tidal and non-tidal deformations. Elastic energy is changed in dependence from mutual position and motion of celestial bodies and as result the tensional state of satellite and its tectonic (endogenous) activity also is changed. Satellites of the planets have the definite shell’s structure and due to own rotation these shells are characterized by different oblatenesses. Gravitational interaction of the satellite and its mother planet generates big additional mechanical forces (and moments) between the neighboring non-spherical shells of the satellite (mantle, core and crust). These forces and moments are cyclic functions of time, which are changed in the different time-scales. They generate corresponding cyclic perturbations of the tensional state of the shells, their deformations, small relative transnational displacements and slow rotation of the shells and others. In geological period of time it leads to a fundamental tectonic reconstruction of the body. Definite contribution to discussed phenomena are caused by classical tidal mechanism. of planet-satellite interaction. But in this report we discuss in first the new mechanisms of endogenous activity of celestial bodies. They are connected with differential gravitational attraction of non-spherical satellite shells by the external celestial bodies which leads: 1) to small relative rotation (nutations) of the shells; 2) to small relative translational motions of the shells (displacements of their center of mass); 3) to relative displacements and rotations of the shells due to eccentricity of their center of mass positions; 4) to viscous elastic deformations of the shells and oth. (Barkin, 2001). For higher evaluations of the power of satellite endogenous activities were obtained

Ocean tides for satellite geodesy

Science.gov (United States)

Dickman, S. R.

1990-01-01

Spherical harmonic tidal solutions have been obtained at the frequencies of the 32 largest luni-solar tides using prior theory of the author. That theory was developed for turbulent, nonglobal, self-gravitating, and loading oceans possessing realistic bathymetry and linearized bottom friction; the oceans satisfy no-flow boundary conditions at coastlines. In this theory the eddy viscosity and bottom drag coefficients are treated as spatially uniform. Comparison of the predicted degree-2 components of the Mf, P1, and M2 tides with those from numerical and satellite-based tide models allows the ocean friction parameters to be estimated at long and short periods. Using the 32 tide solutions, the frequency dependence of tidal admittance is investigated, and the validity of sideband tide models used in satellite orbit analysis is examined. The implications of admittance variability for oceanic resonances are also explored.

On the spin period distribution in Be/X-ray binaries

Energy Technology Data Exchange (ETDEWEB)

Cheng, Z.-Q.; Shao, Y.; Li, X.-D., E-mail: lixd@nju.edu.cn [Department of Astronomy, Nanjing University, Nanjing 210093 (China)

2014-05-10

There is a remarkable correlation between the spin periods of the accreting neutron stars (NSs) in Be/X-ray binaries (BeXBs) and their orbital periods. Recently, Knigge et al. showed that the distribution of the spin periods contains two distinct subpopulations peaked at ∼10 s and ∼200 s, respectively, and suggested that they may be related to two types of supernovae for the formation of the NSs, i.e., core-collapse and electron-capture supernovae. Here we propose that the bimodal spin period distribution is likely to be ascribed to different accretion modes of the NSs in BeXBs. When the NS tends to capture material from the warped, outer part of the Be star disk and experiences giant outbursts, a radiatively cooling dominated disk is formed around the NS, which spins up the NS and is responsible for the short-period subpopulation. In BeXBs that are dominated by normal outbursts or are persistent, the accretion flow is advection-dominated or quasi-spherical. The spin-up process is accordingly inefficient, leading to longer periods of the neuron stars. The potential relation between the subpopulations and the supernova mechanism is also discussed.

Impurity with two electrons in the spherical quantum dot with Unite confinement potential

International Nuclear Information System (INIS)

Baghdasaryan, D A; Ghaltaghchyan, H Ts; Kazaryan, E M; Sarkisyan, H A

2016-01-01

Two-electron states in a spherical QD with the hydrogenic impurity located in the center and with a finite height confinement potential barrier are investigated. The effective mass mismatch have been taken into account. The dependence of ground state energy and Coulomb electron-electron interaction energy correction on the QD size is studied. The problem of the state exchange time control in QD is discussed, taking into account the spins of the electrons in the Russell-Saunders approximation. The effect of quantum emission has been shown. (paper)

Spherical Bessel transform via exponential sum approximation of spherical Bessel function

Science.gov (United States)

Ikeno, Hidekazu

2018-02-01

A new algorithm for numerical evaluation of spherical Bessel transform is proposed in this paper. In this method, the spherical Bessel function is approximately represented as an exponential sum with complex parameters. This is obtained by expressing an integral representation of spherical Bessel function in complex plane, and discretizing contour integrals along steepest descent paths and a contour path parallel to real axis using numerical quadrature rule with the double-exponential transformation. The number of terms in the expression is reduced using the modified balanced truncation method. The residual part of integrand is also expanded by exponential functions using Prony-like method. The spherical Bessel transform can be evaluated analytically on arbitrary points in half-open interval.

Synthesis and characterization of uniform silica nanoparticles on nickel substrate by spin coating and sol-gel method

Science.gov (United States)

Ngoc Thi Le, Hien; Jeong, Hae Kyung

2014-01-01

Spin coating and sol-gel methods are proposed for the preparation of silica nanoparticles on a nickel substrate using silicon tetrachloride, 2-methoxyethanol, and four different types of alkaline solutions. The effects of the type of alkaline solution, concentration of silica solution, and speed of spin coating on the properties of silica nanoparticles are investigated systematically. Uniform spherical shape of silica nanoparticles on Ni with the smallest size are obtained with sodium carbonate among the alkaline solutions after stirring at 70 °C for 6 h and spin-coating at 7000 rpm. Physical and electrochemical properties of the silica particles are investigated.

THEORY OF MUM FOR METAL SPHERICAL ROTOR WITH CONTACTLESS SUSPENSION

Institute of Scientific and Technical Information of China (English)

He Xiaoxia; Gao Zhongyu; Wang Yongliang

2004-01-01

Based on the motion equations of an unbalanced spherical rotor with contactless suspension,three methods of MUM (mass unbalance measurement) are put forward to measure the total mass unbalance,radical mass unbalance and radical mass unbalance of the rotor.Total mass unbalance is obtained when the unbalanced rotor plays as a simple pendulum in static situation.The pendulant period and pendulant midpoint indicate magnitude and direction of total mass unbalance of the rotor respectively.Analysis of the motion equations by using the averaging method yields that the rotor will do a special side oscillation when an auxiliary system makes the rotor spin about its pole axis which is orientating toward the local vertical.The radical mass unbalance can be obtained by building a proper displacement sensor to sense the amplitude of the side oscillation.Necessary analysis of the motion equations also shows that when the rotor spins at a small angular velocity and the rotary axis is perpendicular to the vertical,the pole axis of the rotor will precess slowly about the vertical by virtue of the axial mass unbalance.The axial mass unbalance can be estimated from the time history of the spin vector of the rotor.Finally,measurement precision of the three methods is compared and how the external torque affects the measurement precision for the three methods are examined.

Uniqueness of flat spherically symmetric spacelike hypersurfaces admitted by spherically symmetric static spacetimes

Science.gov (United States)

Beig, Robert; Siddiqui, Azad A.

2007-11-01

It is known that spherically symmetric static spacetimes admit a foliation by flat hypersurfaces. Such foliations have explicitly been constructed for some spacetimes, using different approaches, but none of them have proved or even discussed the uniqueness of these foliations. The issue of uniqueness becomes more important due to suitability of flat foliations for studying black hole physics. Here, flat spherically symmetric spacelike hypersurfaces are obtained by a direct method. It is found that spherically symmetric static spacetimes admit flat spherically symmetric hypersurfaces, and that these hypersurfaces are unique up to translation under the timelike Killing vector. This result guarantees the uniqueness of flat spherically symmetric foliations for such spacetimes.

Combined Geometric and Neural Network Approach to Generic Fault Diagnosis in Satellite Actuators and Sensors

DEFF Research Database (Denmark)

Baldi, P.; Blanke, Mogens; Castaldi, P.

2016-01-01

This paper presents a novel scheme for diagnosis of faults affecting the sensors measuring the satellite attitude, body angular velocity and flywheel spin rates as well as defects related to the control torques provided by satellite reaction wheels. A nonlinear geometric design is used to avoid t...

Effect of deformation and orientation on spin orbit density dependent nuclear potential

Science.gov (United States)

Mittal, Rajni; Kumar, Raj; Sharma, Manoj K.

2017-11-01

Role of deformation and orientation is investigated on spin-orbit density dependent part VJ of nuclear potential (VN=VP+VJ) obtained within semi-classical Thomas Fermi approach of Skyrme energy density formalism. Calculations are performed for 24-54Si+30Si reactions, with spherical target 30Si and projectiles 24-54Si having prolate and oblate shapes. The quadrupole deformation β2 is varying within range of 0.023 ≤ β2 ≤0.531 for prolate and -0.242 ≤ β2 ≤ -0.592 for oblate projectiles. The spin-orbit dependent potential gets influenced significantly with inclusion of deformation and orientation effect. The spin-orbit barrier and position gets significantly influenced by both the sign and magnitude of β2-deformation. Si-nuclei with β220. The possible role of spin-orbit potential on barrier characteristics such as barrier height, barrier curvature and on the fusion pocket is also probed. In reference to prolate and oblate systems, the angular dependence of spin-orbit potential is further studied on fusion cross-sections.

Magnetic fluctuations and correlations in MnSi : Evidence for a chiral skyrmion spin liquid phase

NARCIS (Netherlands)

Pappas, C.; Lelièvre-Berna, E.; Bentley, P.; Falus, P.; Fouquet, P.; Farago, B.

2011-01-01

We present a comprehensive analysis of high-resolution neutron scattering data involving neutron spin echo spectroscopy and spherical polarimetry, which confirm the first-order nature of the helical transition in MnSi. The experiments reveal the existence of a totally chiral dynamic phase in a very

First results of spherical GEMs

CERN Document Server

Pinto, Serge Duarte; Brock, Ian; Croci, Gabriele; David, Eric; de Oliveira, Rui; Ropelewski, Leszek; van Stenis, Miranda; Taureg, Hans; Villa, Marco

2010-01-01

We developed a method to make GEM foils with a spherical geometry. Tests of this procedure and with the resulting spherical GEMs are presented. Together with a spherical drift electrode, a spherical conversion gap can be formed. This eliminates the parallax error for detection of x-rays, neutrons or UV photons when a gaseous converter is used. This parallax error limits the spatial resolution at wide scattering angles. Besides spherical GEMs, we have developed curved spacers to maintain accurate spacing, and a conical field cage to prevent edge distortion of the radial drift field up to the limit of the angular acceptance of the detector. With these components first tests are done in a setup with a spherical entrance window but a planar readout structure; results will be presented and discussed. A flat readout structure poses difficulties, however. Therefore we will show advanced plans to make a prototype of an entirely spherical double-GEM detector, including a spherical 2D readout structure. This detector w...

A new approach to design of quasi-isotropic antenna systems for satellite applications

DEFF Research Database (Denmark)

Schjær-Jacobsen, Hans; Hansen, J.E.

1976-01-01

The new approach considered takes into account the maximum error of the quasi-isotropic radiation pattern relative to the ideal pattern. A design example involving a spherical satellite with quarter wave monopoles is used to demonstrate the effectiveness of the new approach. An investigation...

Shape and spin of asteroid 967 Helionape

Science.gov (United States)

Apostolovska, G.; Kostov, A.; Donchev, Z.; Bebekovska, E. Vchkova; Kuzmanovska, O.

2018-04-01

Knowledge of the spin and shape parameters of the asteroids is very important for understanding of the conditions during the creation of our planetary system and formation of asteroid populations. The main belt asteroid and Flora family member 967 Helionape was observed during five apparitions. The observations were made at the Bulgarian National Astronomical Observatory (BNAO) Rozhen, since March 2006 to March 2016. Lihtcurve inversion method (Kaasalainen et al. (2001)), applied on 12 relative lightcurves obtained at various geometric conditions of the asteroid, reveals the spin vector, the sense of rotation and the preliminary shape model of the asteroid. Our aim is to contribute in increasing the set of asteroids with known spin and shape parameters. This could be done with dense lightcurves, obtained during small number of apparitions, in combination with sparse data produced by photometric asteroid surveys such as the Gaia satellite (Hanush (2011)).

Evolution of the spherical clusters

International Nuclear Information System (INIS)

Surdin, V.G.

1978-01-01

The possible processes of the Galaxy spherical clusters formation and evolution are described on a popular level. The orbits of spherical cluster motion and their spatial velocities are determined. Given are the distrbutions of spherical cluster stars according to their velocities and the observed distribution of spherical clusters in the area of the Galaxy slow evolution. The dissipation and dynamic friction processes destructing clusters with the mass less than 10 4 of solar mass and bringing about the reduction of clusters in the Galaxy are considered. The paradox of forming mainly X-ray sources in spherical clusters is explained. The schematic image of possible ways of forming X-ray sources in spherical clusters is given

Fundamentals of spherical array processing

CERN Document Server

Rafaely, Boaz

2015-01-01

This book provides a comprehensive introduction to the theory and practice of spherical microphone arrays. It is written for graduate students, researchers and engineers who work with spherical microphone arrays in a wide range of applications.   The first two chapters provide the reader with the necessary mathematical and physical background, including an introduction to the spherical Fourier transform and the formulation of plane-wave sound fields in the spherical harmonic domain. The third chapter covers the theory of spatial sampling, employed when selecting the positions of microphones to sample sound pressure functions in space. Subsequent chapters present various spherical array configurations, including the popular rigid-sphere-based configuration. Beamforming (spatial filtering) in the spherical harmonics domain, including axis-symmetric beamforming, and the performance measures of directivity index and white noise gain are introduced, and a range of optimal beamformers for spherical arrays, includi...

Effect of Annealing Temperature and Spin Coating Speed on Mn-Doped ZnS Nanocrystals Thin Film by Spin Coating

Directory of Open Access Journals (Sweden)

Noor Azie Azura Mohd Arif

2017-01-01

Full Text Available ZnS:Mn nanocrystals thin film was fabricated at 300°C and 500°C via the spin coating method. Its sol-gel was spin coated for 20 s at 3000 rpm and 4000 rpm with metal tape being used to mold the shape of the thin film. A different combination of these parameters was used to investigate their influences on the fabrication of the film. Optical and structural characterizations have been performed. Optical characterization was analyzed using UV-visible spectroscopy and photoluminescence spectrophotometer while the structural and compositional analysis of films was measured via field emission scanning electron microscopy and energy dispersive X-ray. From UV-vis spectra, the wavelength of the ZnS:Mn was 250 nm and the band gap was within the range 4.43 eV–4.60 eV. In room temperature PL spectra, there were two emission peaks centered at 460 nm and 590 nm. Under higher annealing temperature and higher speed used in spin coating, an increase of 0.05 eV was observed. It was concluded that the spin coating process is able to synthesize high quality spherical ZnS:Mn nanocrystals. This conventional process can replace other high technology methods due to its synthesis cost.

Caught in the rhythm. I. How satellites settle into a plane around their central galaxy

Science.gov (United States)

Welker, C.; Dubois, Y.; Pichon, C.; Devriendt, J.; Chisari, N. E.

2018-05-01

galaxies relative to their closest filament follows the opposite trend: their tendency to align with them dominates at large distances from the central galaxy, and fades away in its vicinity. In that redshift range, we find hints that massive red centrals with a spin perpendicular to their filament also have corotating satellites well aligned with both the galactic plane and the filament. On the other hand, lower-mass blue centrals with a spin parallel to their filament have satellites flowing straight along this filament, and hence orthogonally to their galactic plane. The orbit of these satellites is then progressively bent towards a better alignment with the galactic plane as they penetrate the central region of their host halo. Conclusions: The kinematics previously described are consistent with satellite infall and spin build-up via quasi-polar flows, followed by a re-orientation of the spin of massive red galaxies through mergers.

Spherical CNNs

OpenAIRE

Cohen, Taco S.; Geiger, Mario; Koehler, Jonas; Welling, Max

2018-01-01

Convolutional Neural Networks (CNNs) have become the method of choice for learning problems involving 2D planar images. However, a number of problems of recent interest have created a demand for models that can analyze spherical images. Examples include omnidirectional vision for drones, robots, and autonomous cars, molecular regression problems, and global weather and climate modelling. A naive application of convolutional networks to a planar projection of the spherical signal is destined t...

Rapid response flood detection using the MSG geostationary satellite

DEFF Research Database (Denmark)

Proud, Simon Richard; Fensholt, Rasmus; Rasmussen, Laura Vang

2011-01-01

A novel technique for the detection of flooded land using satellite data is presented. This new method takes advantage of the high temporal resolution of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) aboard the Meteosat Second Generation (MSG) series of satellites to derive several p...... of data gathered during the 2009 flooding events in West Africa shows that the presented method can detect floods of comparable size to the SEVIRI pixel resolution on a short timescale, making it a valuable tool for large scale flood mapping....

DC cancellation as a method of generating a t2-response and of solving the radial position error in a concentric free-falling two-sphere equivalence-principle experiment in a drag-free satellite

International Nuclear Information System (INIS)

Lange, Benjamin

2010-01-01

This paper presents a new method for doing a free-fall equivalence-principle (EP) experiment in a satellite at ambient temperature which solves two problems that have previously blocked this approach. By using large masses to change the gravity gradient at the proof masses, the orbit dynamics of a drag-free satellite may be changed in such a way that the experiment can mimic a free-fall experiment in a constant gravitational field on the earth. An experiment using a sphere surrounded by a spherical shell both completely unsupported and free falling has previously been impractical because (1) it is not possible to distinguish between a small EP violation and a slight difference in the semi-major axes of the orbits of the two proof masses and (2) the position difference in the orbit due to an EP violation only grows as t whereas the largest disturbance grows as t 3/2 . Furthermore, it has not been known how to independently measure the positions of a shell and a solid sphere with sufficient accuracy. The measurement problem can be solved by using a two-color transcollimator (see the main text), and since the radial-position-error and t-response problems arise from the earth's gravity gradient and not from its gravity field, one solution is to modify the earth's gravity gradient with local masses fixed in the satellite. Since the gravity gradient at the surface of a sphere, for example, depends only on its density, the gravity gradients of laboratory masses and of the earth unlike their fields are of the same order of magnitude. In a drag-free satellite spinning perpendicular to the orbit plane, two fixed spherical masses whose connecting line parallels the satellite spin axis can generate a dc gravity gradient at test masses located between them which cancels the combined gravity gradient of the earth and differential centrifugal force. With perfect cancellation, the position-error problem vanishes and the response grows as t 2 along a line which always points toward

THE SHORT ROTATION PERIOD OF HI’IAKA, HAUMEA’S LARGEST SATELLITE

Energy Technology Data Exchange (ETDEWEB)

Hastings, Danielle M.; Margot, Jean-Luc [University of California, Los Angeles, Department of Earth, Planetary, and Space Sciences, 595 Charles Young Drive East, Los Angeles, CA 90095 (United States); Ragozzine, Darin [Florida Institute of Technology, Department of Physics and Space Sciences, 150 West University Boulevard, Melbourne, FL 32901 (United States); Fabrycky, Daniel C. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Burkhart, Luke D.; Holman, Matthew [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Fuentes, Cesar [Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Santiago (Chile); Brown, Michael E., E-mail: dhastings@g.ucla.edu [California Institute of Technology, Division of Geological and Planetary Sciences, MC 150-21, Pasadena, CA 91125 (United States)

2016-12-01

Hi’iaka is the larger outer satellite of the dwarf planet Haumea. Using relative photometry from the Hubble Space Telescope and Magellan and a phase dispersion minimization analysis, we have identified the rotation period of Hi’iaka to be ∼9.8 hr (double peaked). This is ∼120 times faster than its orbital period, creating new questions about the formation of this system and possible tidal evolution. The rapid rotation suggests that Hi’iaka could have a significant obliquity and spin precession that could be visible in light curves within a few years. We then turn to an investigation of what we learn about the (currently unclear) formation of the Haumea system and family based on this unexpectedly rapid rotation rate. We explore the importance of the initial semimajor axis and rotation period in tidal evolution theory and find that they strongly influence the time required to despin to synchronous rotation, relevant to understanding a wide variety of satellite and binary systems. We find that despinning tides do not necessarily lead to synchronous spin periods for Hi’iaka, even if it formed near the Roche limit. Therefore, the short rotation period of Hi’iaka does not rule out significant tidal evolution. Hi’iaka’s spin period is also consistent with formation near its current location and spin-up due to Haumea-centric impactors.

Preparation and Optical Properties of Spherical Inverse Opals by Liquid Phase Deposition Using Spherical Colloidal Crystals

International Nuclear Information System (INIS)

Aoi, Y; Tominaga, T

2013-01-01

Titanium dioxide (TiO 2 ) inverse opals in spherical shape were prepared by liquid phase deposition (LPD) using spherical colloidal crystals as templates. Spherical colloidal crystals were produced by ink-jet drying technique. Aqueous emulsion droplets that contain polystyrene latex particles were ejected into air and dried. Closely packed colloidal crystals with spherical shape were obtained. The obtained spherical colloidal crystals were used as templates for the LPD. The templates were dispersed in the deposition solution of the LPD, i.e. a mixed solution of ammonium hexafluorotitanate and boric acid and reacted for 4 h at 30 °C. After the LPD process, the interstitial spaces of the spherical colloidal crystals were completely filled with titanium oxide. Subsequent heat treatment resulted in removal of templates and spherical titanium dioxide inverse opals. The spherical shape of the template was retained. SEM observations indicated that the periodic ordered voids were surrounded by titanium dioxide. The optical reflectance spectra indicated that the optical properties of the spherical titanium dioxide inverse opals were due to Bragg diffractions from the ordered structure. Filling in the voids of the inverse opals with different solvents caused remarkable changes in the reflectance peak.

Friction factor for water flow through packed beds of spherical and non-spherical particles

Directory of Open Access Journals (Sweden)

Kaluđerović-Radoičić Tatjana

2017-01-01

Full Text Available The aim of this work was the experimental evaluation of different friction factor correlations for water flow through packed beds of spherical and non-spherical particles at ambient temperature. The experiments were performed by measuring the pressure drop across the bed. Packed beds made of monosized glass spherical particles of seven different diameters were used, as well as beds made of 16 fractions of quartz filtration sand obtained by sieving (polydisperse non-spherical particles. The range of bed voidages was 0.359–0.486, while the range of bed particle Reynolds numbers was from 0.3 to 286 for spherical particles and from 0.1 to 50 for non-spherical particles. The obtained results were compared using a number of available literature correlations. In order to improve the correlation results for spherical particles, a new simple equation was proposed in the form of Ergun’s equation, with modified coefficients. The new correlation had a mean absolute deviation between experimental and calculated values of pressure drop of 9.04%. For non-spherical quartz filtration sand particles the best fit was obtained using Ergun’s equation, with a mean absolute deviation of 10.36%. Surface-volume diameter (dSV necessary for correlating the data for filtration sand particles was calculated based on correlations for dV = f(dm and Ψ = f(dm. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172022

The third post-Newtonian gravitational wave polarizations and associated spherical harmonic modes for inspiralling compact binaries in quasi-circular orbits

International Nuclear Information System (INIS)

Blanchet, Luc; Faye, Guillaume; Iyer, Bala R; Sinha, Siddhartha

2008-01-01

The gravitational waveform (GWF) generated by inspiralling compact binaries moving in quasi-circular orbits is computed at the third post-Newtonian (3PN) approximation to general relativity. Our motivation is two-fold: (i) to provide accurate templates for the data analysis of gravitational wave inspiral signals in laser interferometric detectors; (ii) to provide the associated spin-weighted spherical harmonic decomposition to facilitate comparison and match of the high post-Newtonian prediction for the inspiral waveform to the numerically-generated waveforms for the merger and ringdown. This extension of the GWF by half a PN order (with respect to previous work at 2.5PN order) is based on the algorithm of the multipolar post-Minkowskian formalism, and mandates the computation of the relations between the radiative, canonical and source multipole moments for general sources at 3PN order. We also obtain the 3PN extension of the source multipole moments in the case of compact binaries, and compute the contributions of hereditary terms (tails, tails-of-tails and memory integrals) up to 3PN order. The end results are given for both the complete plus and cross polarizations and the separate spin-weighted spherical harmonic modes

Progress in octahedral spherical hohlraum study

Directory of Open Access Journals (Sweden)

Ke Lan

2016-01-01

Full Text Available In this paper, we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study. From our theoretical study, the octahedral spherical hohlraums with 6 Laser Entrance Holes (LEHs of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7. In addition, the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology. We studied the laser arrangement and constraints of the octahedral spherical hohlraums, and gave a design on the laser arrangement for ignition octahedral hohlraums. As a result, the injection angle of laser beams of 50°–60° was proposed as the optimum candidate range for the octahedral spherical hohlraums. We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields, in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport. We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums, the rugby hohlraums and the cylindrical hohlraums, and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive. Up till to now, we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG laser facilities, including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums, spherical hohlraum energetics on the SGIII prototype laser facility, and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.

High spin spectroscopy of near spherical nuclei: Role of intruder orbitals

Energy Technology Data Exchange (ETDEWEB)

Bhattacharyya, S.; Bhattacharjee, T.; Mukherjee, G. [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata - 700064 (India); Chanda, S. [Fakir Chand College, Diamond Herbour, West Bengal (India); Banerjee, D.; Das, S. K.; Guin, R. [Radiochemistry Division, Variable Energy Cyclotron Centre, BARC, Kolkata - 700064 (India); Gupta, S. Das [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata - 700064, India and Saha Institute of Nuclear Physics, Kolkata-700064 (India); Pai, H. [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata - 700064, India and Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany)

2014-08-14

High spin states of nuclei in the vicinity of neutron shell closure N = 82 and proton shell closure Z = 82 have been studied using the Clovere Ge detectors of Indian National Gamma Array. The shape driving effects of proton and neutron unique parity intruder orbitals for the structure of nuclei around the above shell closures have been investigated using light and heavy ion beams. Lifetime measurements of excited states in {sup 139}Pr have been done using pulsed-beam-γ coincidence technique. The prompt spectroscopy of {sup 207}Rn has been extended beyond the 181μs 13/2{sup +} isomer. Neutron-rich nuclei around {sup 132}Sn have been produced from proton induced fission of {sup 235}U and lifetime measurement of low-lying states of odd-odd {sup 132}I have been performed from offline decay.

Transverse spin and transverse momentum in scattering of plane waves

OpenAIRE

Saha, Sudipta; Singh, Ankit K.; Ray, Subir K.; Banerjee, Ayan; Gupta, Subhasish Dutta; Ghosh, Nirmalya

2016-01-01

We study the near field to the far field evolution of spin angular momentum (SAM) density and the Poynting vector of the scattered waves from spherical scatterers. The results show that at the near field, the SAM density and the Poynting vector are dominated by their transverse components. While the former (transverse SAM) is independent of the helicity of the incident circular polarization state, the latter (transverse Poynting vector) depends upon the polarization state. It is further demon...

Spectral Gap Estimates in Mean Field Spin Glasses

Science.gov (United States)

Ben Arous, Gérard; Jagannath, Aukosh

2018-05-01

We show that mixing for local, reversible dynamics of mean field spin glasses is exponentially slow in the low temperature regime. We introduce a notion of free energy barriers for the overlap, and prove that their existence imply that the spectral gap is exponentially small, and thus that mixing is exponentially slow. We then exhibit sufficient conditions on the equilibrium Gibbs measure which guarantee the existence of these barriers, using the notion of replicon eigenvalue and 2D Guerra Talagrand bounds. We show how these sufficient conditions cover large classes of Ising spin models for reversible nearest-neighbor dynamics and spherical models for Langevin dynamics. Finally, in the case of Ising spins, Panchenko's recent rigorous calculation (Panchenko in Ann Probab 46(2):865-896, 2018) of the free energy for a system of "two real replica" enables us to prove a quenched LDP for the overlap distribution, which gives us a wider criterion for slow mixing directly related to the Franz-Parisi-Virasoro approach (Franz et al. in J Phys I 2(10):1869-1880, 1992; Kurchan et al. J Phys I 3(8):1819-1838, 1993). This condition holds in a wider range of temperatures.

High-Spin States in Odd-Odd N=Z {sup 46}V

Energy Technology Data Exchange (ETDEWEB)

O' Leary, C.D.; Bentley, M.A.; Appelbe, D.E.; Bark, R.A.; Cullen, D.M.; Erturk, S.; Maj. A.; Sheikh, J.A.; Warner, D.D.

1999-12-31

High-spin states up to the F{sub 7/2}-shell band termination at J{pi}=15+ have been observed for the first time in the odd-odd N=Z=23 nucleous {sup 46}V. The new level scheme has two separate structures corresponding to spherical and prolate shapes. A rotational band has very similar energies to the yrast sequence in {sup 46}Ti and is therefore assumed to be a T=1 configuration.

Spin-spin interactions of electrons and also of nucleons create atomic molecular and nuclear structures

International Nuclear Information System (INIS)

Kaliambos, L.A.

2008-01-01

Fundamental interactions of spinning electrons at an interelectron separation less than 578.8 fm yield attractive electromagnetic forces with S = 0 creating vibrations under a motional emf. They explain the indistinguishability of electrons and give a vibration energy able for calculating the ground-state energies of many-electron atoms without using any perturbative approximation. Such forces create two-electron orbitals able to account for the exclusion principal and the mechanism of covalent bonds. In the outer subshells of atoms the penetrating orbitals interact also as pair-pair systems and deform drastically the probability densities of the quantum mechanical electron clouds. Such a dynamics of deformation removes the degeneracy and leads to the deviation from the shell scheme. However in the interior of atoms the large nuclear charge leads to a spherically symmetric potential with non-interacting pairs for creating shells of degenerate states giving an accurate explanation of the X-ray lines. On the other hand, considerable charge distributions in nucleons as multiples of 2e/3 and - e/3 determined by the magnetic moments, interact for creating the nuclear structure with p-n bonds. Such spin-spin interactions show that the dominant concept of the untisymmetric wave function for fermions is inapplicable not only in the simple p-n, p-p, and n-n systems but also in the LS coupling of atoms in which the electrons interact from different quantum states giving either S = 0 or S = l. (author)

Synthetic Landau Levels and Spinor Vortex Matter on a Haldane Spherical Surface with a Magnetic Monopole.

Science.gov (United States)

Zhou, Xiang-Fa; Wu, Congjun; Guo, Guang-Can; Wang, Ruquan; Pu, Han; Zhou, Zheng-Wei

2018-03-30

We present a flexible scheme to realize exact flat Landau levels on curved spherical geometry in a system of spinful cold atoms. This is achieved by applying the Floquet engineering of a magnetic quadrupole field to create a synthetic monopole field in real space. The system can be exactly mapped to the electron-monopole system on a sphere, thus realizing Haldane's spherical geometry for fractional quantum Hall physics. This method works for either bosons or fermions. We investigate the ground-state vortex pattern for an s-wave interacting atomic condensate by mapping this system to the classical Thompson's problem. The distortion and stability of the vortex pattern are further studied in the presence of dipolar interaction. Our scheme is compatible with the current experimental setup, and may serve as a promising route of investigating quantum Hall physics and exotic spinor vortex matter on curved space.

High-spin states in the A=39 mirror nuclei 39Ca and 39K

International Nuclear Information System (INIS)

Andersson, T.; Rudolph, D.; Fahlander, C.; Eberth, J.; Thomas, H.G.; Haslip, D.; Svensson, C.E.; Waddington, J.C.; LaFosse, D.R.; Sarantites, D.G.; Weintraub, W.; Wilson, J.N.; Brown, B.A.

1999-01-01

High-spin states of the mass A=39 mirror pair 39 K and 39 Ca were investigated via the fusion-evaporation reaction 28 Si+ 16 O at 125 MeV beam energy. The gammasphere array in conjunction with the 4π charged-particle detector array microball and neutron detectors was used to detect γ rays in coincidence with evaporated light particles. The results of the first high-spin study of the T z =-1/2 nucleus 39 Ca are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d 3/2 -1f 7/2 configuration space. (orig.)

Are Nanoparticles Spherical or Quasi-Spherical?

Science.gov (United States)

Sokolov, Stanislav V; Batchelor-McAuley, Christopher; Tschulik, Kristina; Fletcher, Stephen; Compton, Richard G

2015-07-20

The geometry of quasi-spherical nanoparticles is investigated. The combination of SEM imaging and electrochemical nano-impact experiments is demonstrated to allow sizing and characterization of the geometry of single silver nanoparticles. © 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Spin-resolved x-ray photoemission studies of ferromagnetic metals

International Nuclear Information System (INIS)

Klebanoff, L.E.

1996-01-01

Recent spin-resolved x-ray photoelectron spectroscopy (SRXPS) studies of ferromagnetic metals are reviewed. SRXPS studies of metallic Fe, Co, Co 66 Fe 4 Ni 1 B 14 Si 15 , and Ni demonstrate that core-level photoemission, and the itinerant electron response to core-hole creation, are highly spin-dependent. The exchange splitting of the Fe 2p 3/2 level is found to be 0.48±0.05 eV. Lifetime broadening results for the Fe 2p 3/2 N↑ (majority spin) and N↓ (minority spin) components indicate conservation of spin in core-hole filling processes involving the valence band. SRXPS study of the Fe 2p 3/2 peak asymmetry α reveals a dependence of electron endash hole excitation on the spin of the core hole. Spin analysis of the Fe 3s XPS line shape shows it to be a three-component spectrum, rather than the two-component line shape assumed previously. A photon energy dependence of one of the Fe 3s components explains disagreement among previous Fe 3s XPS results. Comparisons of SRXPS from Co metal and Co 66 Fe 4 Ni 1 B 14 Si 15 directly demonstrate the effect of a reduced atomic magnetic moment on the spin dependence of core-level XPS. The behavior of lifetime broadenings for the N↑ and N↓ Co 2p 3/2 components show that the reduced Co magnetic moment found in the Co 66 Fe 4 Ni 1 B 14 Si 15 amorphous glass is due to the transfer of ↑-spin valence electron density to the ↓-spin valence band upon glass formation. SRXPS also allows investigation of spin-dependent core-hole screening processes and satellite production, as demonstrated in SRXPS studies of ferromagnetic Ni. Future directions of SRXPS are also explored. copyright 1996 American Vacuum Society

Polarimetry on dense samples of spin-polarized 3He by magnetostatic detection

International Nuclear Information System (INIS)

Wilms, E.; Ebert, M.; Heil, W.; Surkau, R.

1997-01-01

A very sensitive low-field fluxgate magnetometer is used to detect the static magnetic field produced by dense samples of spin-polarized 3 He gas contained in spherical glass cells at pressures around several bars. The 3 He nuclear polarization can be extracted with high precision ΔP/P<1% by utilizing magnetostatic detection in combination with adiabatic fast-passage spin reversal. The polarization losses can be kept well below 0.1% thus making this type of polarimetry almost non-destructive. More simply even, P can be measured with reduced accuracy by the change of field when the cell is removed from the fluxgate. In this case the accuracy is limited to about 10% due to the uncertainties about the susceptibilities of the cell walls. (orig.)

Crystal shape-dependent magnetic susceptibility and Curie law crossover in the spin ices Dy2Ti2O7 and Ho2Ti2O7

International Nuclear Information System (INIS)

Bovo, L; Bramwell, S T; Jaubert, L D C; Holdsworth, P C W

2013-01-01

We present an experimental determination of the isothermal magnetic susceptibility of the spin ice materials Dy 2 Ti 2 O 7 and Ho 2 Ti 2 O 7 in the temperature range 1.8–300 K. The use of spherical crystals has allowed accurate correction for demagnetizing fields and allowed the true bulk isothermal susceptibility χ T (T) to be estimated. This has been compared against a theoretical expression based on a Husimi tree approximation to the spin ice model. Agreement between experiment and theory is excellent at T > 10 K, but systematic deviations occur below that temperature. Our results largely resolve an apparent disagreement between neutron scattering and bulk measurements that has been previously noted. They also show that the use of non-spherical crystals in magnetization studies of spin ice may introduce very significant systematic errors, although we note some interesting—and possibly new—systematics concerning the demagnetizing factor in cuboidal samples. Finally, our results show how experimental susceptibility measurements on spin ices may be used to extract the characteristic energy scale of the system and the corresponding chemical potential for emergent magnetic monopoles. (paper)

Earth's lithospheric magnetic field determined to spherical harmonic degree 90 from CHAMP satellite measurements

DEFF Research Database (Denmark)

Maus, S.; Rother, M.; Hemant, K.

2006-01-01

of the lithospheric field down to an altitude of about 50 km at lower latitudes, with reduced accuracy in the polar regions. Crustal features come out significantly sharper than in previous models. In particular, bands of magnetic anomalies along subduction zones become visible by satellite for the first time....

Spherical sila- and germa-homoaromaticity.

Science.gov (United States)

Chen, Zhongfang; Hirsch, Andreas; Nagase, Shigeru; Thiel, Walter; Schleyer, Paul von Ragué

2003-12-17

Guided by the 2(N + 1)2 electron-counting rule for spherical aromatic molecules, we have designed various spherical sila- and germa-homoaromatic systems rich in group 14 elements. Their aromaticity is revealed by density-functional computations of their structures and the nucleus-independent chemical shifts (NICS). Besides the formerly used endohedral inclusion strategy, spherical homoaromaticity is another way to stabilize silicon and germanium clusters.

Entangled spins and ghost-spins

Directory of Open Access Journals (Sweden)

Dileep P. Jatkar

2017-09-01

Full Text Available We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves, the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

2D Spin-Dependent Diffraction of Electrons From Periodical Chains of Nanomagnets

Directory of Open Access Journals (Sweden)

Teshome Senbeta

2012-03-01

Full Text Available The scattering of the unpolarized beams of electrons by nanomagnets in the vicinity of some scattering angles leads to complete spin polarized electrons. This result is obtained with the help of the perturbation theory. The dipole-dipole interaction between the magnetic moment of the nanomagnet and the magnetic moment of electron is treated as perturbation. This interaction is not spherically symmetric. Rather it depends on the electron spin variables. It in turn results in spinor character of the scattering amplitudes. Due to the smallness of the magnetic interactions, the scattering length of this process is very small to be proved experimentally. To enhance the relevant scattering lengths, we considered the diffraction of unpolarized beams of electrons by linear chains of nanomagnets. By tuning the distance between the scatterers it is possible to obtain the diffraction maximum of the scattered electrons at scattering angles which corresponds to complete spin polarization of electrons. It is shown that the total differential scattering length is proportional to N2 (N is a number of scatterers. Even small number of nanomagnets in the chain helps to obtain experimentally visible enhancement of spin polarization of the scattered electrons.

Spin Current Noise of the Spin Seebeck Effect and Spin Pumping

Science.gov (United States)

Matsuo, M.; Ohnuma, Y.; Kato, T.; Maekawa, S.

2018-01-01

We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal-metal-(NM-)ferromagnet(FM) bilayer system. Starting with a simple ferromagnet-insulator-(FI-)NM interface model with both spin-conserving and non-spin-conserving processes, we derive general expressions of the spin current and the spin-current noise at the interface within second-order perturbation of the FI-NM coupling strength, and estimate them for a yttrium-iron-garnet-platinum interface. We show that the spin-current noise can be used to determine the effective spin carried by a magnon modified by the non-spin-conserving process at the interface. In addition, we show that it provides information on the effective spin of a magnon, heating at the interface under spin pumping, and spin Hall angle of the NM.

Attitude Estimation Based on the Spherical Simplex Transformation Modified Unscented Kalman Filter

Directory of Open Access Journals (Sweden)

Jianwei Zhao

2014-01-01

Full Text Available An antenna attitude estimation algorithm is proposed to improve the antenna pointing accuracy for the satellite communication on-the-move. The extrapolated angular acceleration is adopted to improve the performance of the time response. The states of the system are modified according to the modification rules. The spherical simplex transformation unscented Kalman filter is used to improve the precision of the estimated attitude and decrease the calculation of the unscented Kalman filter. The experiment results show that the proposed algorithm can improve the instantaneity of the estimated attitude and the precision of the antenna pointing, which meets the requirement of the antenna pointing.

Dielectric resonance in ErFeO3 in the region of spin reorientation

International Nuclear Information System (INIS)

Dan'shin, N.K.; Kovtun, N.M.; Sdvizhkov, M.A.

1984-01-01

In the region of spin reorientation in ErFeO 3 in the millimetre wave range a dielectric resonance has been found - excitation of electromaqnetic field natural oscillations in spherical samples. The fregurncies of dielectric resonance in samples from ErFeO 3 possess strong independence of temperature and magnetic field in the vicinity of the spin reorientation for account of a strong growth in the magnetic susceptibility. The frequencies change most considerably in the region of low-temperature spin reorientation related to antiferromagnetic rare earth ordering. Strong anisotropy of magnetic susceptibility cases various temperature and field dependences of the dielectric resonance frequencies at different orientations of the exciting electromagnetic field relative to the crystal axes. It is shown that the method of dielectric resonance permits to determine with high accuracy the temperatures of spontaneous - and crystal fields of induced phase transformations. The crystal dielectric permittivity and magnetic permeability dispersion are determined

Spherical tokamak development in Brazil

Energy Technology Data Exchange (ETDEWEB)

Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma] (and others)

2003-07-01

The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

Spherical tokamak development in Brazil

International Nuclear Information System (INIS)

Ludwig, Gerson Otto; Bosco, Edson Del; Ferreira, Julio Guimaraes

2003-01-01

The general characteristics of spherical tokamaks, or spherical tori, with a brief view of work in this area already performed or in progress at several institutions worldwide are described. The paper presents also the steps in the development of the ETE (Experiment Tokamak spheric) project, its research program, technical characteristics and operating conditions as of December, 2002 a the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

Geometrical spin symmetry and spin

International Nuclear Information System (INIS)

Pestov, I. B.

2011-01-01

Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.

The YORP effect on the GOES 8 and GOES 10 satellites: A case study

Science.gov (United States)

Albuja, Antonella A.; Scheeres, Daniel J.; Cognion, Rita L.; Ryan, William; Ryan, Eileen V.

2018-01-01

The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect is a proposed explanation for the observed rotation behavior of inactive satellites in Earth orbit. This paper further explores the YORP effect for highly asymmetric inactive satellites. Satellite models are developed to represent the GOES 8 and GOES 10 satellites, both of which are currently inactive in geosynchronous Earth orbit (GEO). A simple satellite model for the GOES 8 satellite is used to analyze the short period variations of the angular velocity and obliquity as a result of the YORP effect. A more complex model for the rotational dynamics of the GOES 8 and GOES 10 satellites are developed to probe their sensitivity and to match observed spin periods and states of these satellites. The simulated rotation periods are compared to observations for both satellites. The comparison between YORP theory and observed rotation rates for both satellites show that the YORP effect could be the cause for the observed rotational behavior. The YORP model also predicts a novel state for the GOES 8 satellite, namely that it could periodically fall into a tumbling rotation state. Recent observations of this satellite are consistent with this prediction.

Magnetic structure of the swedenborgite CaBa (Co3Fe ) O7 derived by unpolarized neutron diffraction and spherical neutron polarimetry

Science.gov (United States)

Qureshi, N.; Díaz, M. T. Fernández; Chapon, L. C.; Senyshyn, A.; Schweika, W.; Valldor, M.

2018-02-01

We present a study that combines polarized and unpolarized neutrons to derive the magnetic structure of the swedenborgite compound CaBa (Co3Fe ) O7. Integrated intensities from a standard neutron diffraction experiment and polarization matrices from spherical neutron polarimetry have been simultaneously analyzed revealing a complex order, which differs from the usual spin configurations on a kagome lattice. We find that the magnetic structure is well described by a combination of two one-dimensional representations corresponding to the magnetic superspace symmetry P 21' , and it consists of spins rotating around an axis close to the [110] direction. Due to the propagation vector q =(1/3 00 ) , this modulation has cycloidal and helicoidal character rendering this system a potential multiferroic. The resulting spin configuration can be mapped onto the classical √{3 }×√{3 } structure of a kagome lattice, and it indicates an important interplay between the kagome and the triangular layers of the crystal structure.

Interrelation between the isoscalar octupole phonon and the proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei

International Nuclear Information System (INIS)

Smirnova, N.A.; Van Isacker, P.; Smirnova, N.A; Pietralla, N.; Yale Univ., New Haven, CT; Mizusaki, T.

2000-01-01

The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2 + 1 state. We apply the proton-neutron version of the Interacting Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin symmetric dynamical symmetry limits of the model, namely the vibrational and the γ-unstable ones, are considered. We derived analytical formulae for excitation energies as well as B(E1), B(M1), B(E2), and B(E3) values for a number of transitions between low-lying states. The model well reproduces many known transition strengths in the near spherical nuclei 142 Ce and 94 Mo. (authors)

Interrelation between the isoscalar octupole phonon and the proton-neutron mixed-symmetry quadrupole phonon in near-spherical nuclei

Energy Technology Data Exchange (ETDEWEB)

Smirnova, N.A.; Van Isacker, P. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France); Smirnova, N.A [Paris-11 Univ., 91 - Orsay (France). Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse]|[Institute for Nuclear Physics, Moscow State University (Russian Federation); Pietralla, N. [Institut fur Kernphysik, Universitat zu Koln (Germany)]|[Yale Univ., New Haven, CT (United States). Wright Nuclear Structure Lab; Mizusaki, T. [Tokyo Univ. (Japan). Dept. of Physics

2000-07-01

The interrelation between the octupole phonon and the low-lying proton-neutron mixed-symmetry quadrupole in near-spherical nuclei is investigated. The one-phonon states decay by collective E3 and E2 transitions to the ground state and by relatively strong E1 and M1 transitions to the isoscalar 2{sup +}{sub 1} state. We apply the proton-neutron version of the Interacting Boson Model including quadrupole and octupole bosons (sdf-IBM-2). Two F-spin symmetric dynamical symmetry limits of the model, namely the vibrational and the {gamma}-unstable ones, are considered. We derived analytical formulae for excitation energies as well as B(E1), B(M1), B(E2), and B(E3) values for a number of transitions between low-lying states. The model well reproduces many known transition strengths in the near spherical nuclei {sup 142}Ce and {sup 94}Mo. (authors)

Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction

KAUST Repository

Ortiz Pauyac, Christian

2016-06-19

In the present thesis we introduce the reader to the field of spintronics and explore new phenomena, such as spin transfer torques, spin filtering, and three types of spin-orbit torques, Rashba, spin Hall, and spin swapping, which have emerged very recently and are promising candidates for a new generation of memory devices in computer technology. A general overview of these phenomena is presented in Chap. 1. In Chap. 2 we study spin transfer torques in tunnel junctions in the presence of spin filtering. In Chap. 3 we discuss the Rashba torque in ferromagnetic films, and in Chap. 4 we study spin Hall effect and spin swapping in ferromagnetic films, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives are summarized in Chap. 5.

A coordinated two-satellite study of energetic electron precipitation events

International Nuclear Information System (INIS)

Imhof, W.L.; Nakano, G.H.; Gaines, E.E.; Reagan, J.B.

1975-01-01

A new technique for studying the spatial/temporal variations of energetic electron precipitation events is investigated. Data are presented in which precipitating electrons were measured simultaneously on two coordinated polar-orbiting satellites and the bremsstrahlung produced by the electrons precipitating into the atmosphere was observed from one of the satellites. Two electron spectrometers measuring the intensities and energy spectra of electrons of >130 keV were located on the oriented satellite 1971-089A (altitude, approx. =800 km), whereas a single similar spectrometer measuring electrons of >160 keV was located on the spinning low-altitude (approx.750 km) satellite 1972-076B. The X rays of >50 keV were measured with a 50-cm 3 germanium spectrometer placed on the 1972-076B satellite. With the coordinated data a study is made of events in which large fluctuations were observed in the precipitating energetic electron intensities. In the examples presented the satellite X ray data alone demonstrate that the spatially integrated electron influx was constant in time, and when the X ray data are combined with the direct electron measurements from the two satellites, the resulting data suggest that the major features in the flux profiles were primarily spatial in nature. The combination of X ray and electron measurements from two satellites is shown to provide an important method for studying and attempting to resolve spatial and temporal effects

Differential saturation study of radial and angular modulation mechanisms of electron spin--lattice relaxation for trapped hydrogen atoms in sulfuric acid glasses. [X radiation

Energy Technology Data Exchange (ETDEWEB)

Plonka, A; Kevan, L

1976-11-01

A differential ESR saturation study of allowed transitions and forbidden proton spin-flip satellite transitions for trapped hydrogen atoms in sulfuric acid glasses indicates that angular modulation dominates the spin-lattice relaxation mechanisms and suggests that the modulation arises from motion of the H atom.

Spin-polarized spin excitation spectroscopy

International Nuclear Information System (INIS)

Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J

2010-01-01

We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.

Classical emergence of intrinsic spin-orbit interaction of light at the nanoscale

Science.gov (United States)

Vázquez-Lozano, J. Enrique; Martínez, Alejandro

2018-03-01

Traditionally, in macroscopic geometrical optics intrinsic polarization and spatial degrees of freedom of light can be treated independently. However, at the subwavelength scale these properties appear to be coupled together, giving rise to the spin-orbit interaction (SOI) of light. In this work we address theoretically the classical emergence of the optical SOI at the nanoscale. By means of a full-vector analysis involving spherical vector waves we show that the spin-orbit factorizability condition, accounting for the mutual influence between the amplitude (spin) and phase (orbit), is fulfilled only in the far-field limit. On the other side, in the near-field region, an additional relative phase introduces an extra term that hinders the factorization and reveals an intricate dynamical behavior according to the SOI regime. As a result, we find a suitable theoretical framework able to capture analytically the main features of intrinsic SOI of light. Besides allowing for a better understanding into the mechanism leading to its classical emergence at the nanoscale, our approach may be useful to design experimental setups that enhance the response of SOI-based effects.

A method of inversion of satellite magnetic anomaly data

Science.gov (United States)

Mayhew, M. A.

1977-01-01

A method of finding a first approximation to a crustal magnetization distribution from inversion of satellite magnetic anomaly data is described. Magnetization is expressed as a Fourier Series in a segment of spherical shell. Input to this procedure is an equivalent source representation of the observed anomaly field. Instability of the inversion occurs when high frequency noise is present in the input data, or when the series is carried to an excessively high wave number. Preliminary results are given for the United States and adjacent areas.

Assessing the Impact of Earth Radiation Pressure Acceleration on Low-Earth Orbit Satellites

Science.gov (United States)

Vielberg, Kristin; Forootan, Ehsan; Lück, Christina; Kusche, Jürgen; Börger, Klaus

2017-04-01

The orbits of satellites are influenced by several external forces. The main non-gravitational forces besides thermospheric drag, acting on the surface of satellites, are accelerations due to the Earth and Solar Radiation Pres- sure (SRP and ERP, respectively). The sun radiates visible and infrared light reaching the satellite directly, which causes the SRP. Earth also emits and reflects the sunlight back into space, where it acts on satellites. This is known as ERP acceleration. The influence of ERP increases with decreasing distance to the Earth, and for low-earth orbit (LEO) satellites ERP must be taken into account in orbit and gravity computations. Estimating acceler- ations requires knowledge about energy emitted from the Earth, which can be derived from satellite remote sensing data, and also by considering the shape and surface material of a satellite. In this sensitivity study, we assess ERP accelerations based on different input albedo and emission fields and their modelling for the satellite missions Challenging Mini-Satellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE). As input fields, monthly 1°x1° products of Clouds and the Earth's Radiant En- ergy System (CERES), L3 are considered. Albedo and emission models are generated as latitude-dependent, as well as in terms of spherical harmonics. The impact of different albedo and emission models as well as the macro model and the altitude of satellites on ERP accelerations will be discussed.

The spherical harmonics method, II (application to problems with plane and spherical symmetry)

Energy Technology Data Exchange (ETDEWEB)

Mark, C

1958-12-15

The application of the spherical harmonic method to problems with plane or spherical symmetry is discussed in detail. The numerical results of some applications already made are included to indicate the degree of convergence obtained. Formulae for dealing with distributions of isotropic sources are developed. Tables useful in applying the method are given in Section 11. (author)

SASKTRAN: A spherical geometry radiative transfer code for efficient estimation of limb scattered sunlight

International Nuclear Information System (INIS)

Bourassa, A.E.; Degenstein, D.A.; Llewellyn, E.J.

2008-01-01

The inversion of satellite-based observations of limb scattered sunlight for the retrieval of constituent species requires an efficient and accurate modelling of the measurement. We present the development of the SASKTRAN radiative transfer model for the prediction of limb scatter measurements at optical wavelengths by method of successive orders along rays traced in a spherical atmosphere. The component of the signal due to the first two scattering events of the solar beam is accounted for directly along rays traced in the three-dimensional geometry. Simplifying assumptions in successive scattering orders provide computational optimizations without severely compromising the accuracy of the solution. SASKTRAN is designed for the analysis of measurements from the OSIRIS instrument and the implementation of the algorithm is efficient such that the code is suitable for the inversion of OSIRIS profiles on desktop computers. SASKTRAN total limb radiance profiles generally compare better with Monte-Carlo reference models over a large range of solar conditions than the approximate spherical and plane-parallel models typically used for inversions

High-spin, multiparticle isomers in 121,123Sb

International Nuclear Information System (INIS)

Jones, G. A.; Walker, P. M.; Podolyak, Zs.; Cullen, I. J.; Garnsworthy, A. B.; Liu, Z.; Thompson, N. J.; Williams, S. J.; Zhu, S.; Carpenter, M. P.; Janssens, R. V. F.; Khoo, T. L.; Seweryniak, D.; Carroll, J. J.; Chakrawarthy, R. S.; Hackman, G.; Chowdhury, P.; Dracoulis, G. D.; Lane, G. J.; Kondev, F. G.

2008-01-01

Isomers in near-spherical Z=51, antimony isotopes are reported here for the first time using fusion-fission reactions between 27 Al and a pulsed 178 Hf beam of energy, 1150 MeV. γ rays were observed from the decay of isomeric states with half-lives, T 1/2 =200(30) and 52(3)μs, and angular momenta I=((25/2)) and I π =(23/2) + , in 121,123 Sb, respectively. These states are proposed to correspond to ν(h (11/2) ) 2 configurations, coupled to an odd d (5/2) or g (7/2) proton. Nanosecond isomers were also identified at I π =(19/2) - [T 1/2 =8.5(5) ns] in 121 Sb and I π =((15/2) - ) [T 1/2 =37(4) ns] in 123 Sb. Information on spins and parities of states in these nuclei was obtained using a combination of angular correlation and intensity-balance measurements. The configurations of states in these nuclei are discussed using a combination of spin/energy systematics and shell-model calculations for neighboring tin isotones and antimony isotopes

Spin current and spin transfer torque in ferromagnet/superconductor spin valves

Science.gov (United States)

Moen, Evan; Valls, Oriol T.

2018-05-01

Using fully self-consistent methods, we study spin transport in fabricable spin valve systems consisting of two magnetic layers, a superconducting layer, and a spacer normal layer between the ferromagnets. Our methods ensure that the proper relations between spin current gradients and spin transfer torques are satisfied. We present results as a function of geometrical parameters, interfacial barrier values, misalignment angle between the ferromagnets, and bias voltage. Our main results are for the spin current and spin accumulation as functions of position within the spin valve structure. We see precession of the spin current about the exchange fields within the ferromagnets, and penetration of the spin current into the superconductor for biases greater than the critical bias, defined in the text. The spin accumulation exhibits oscillating behavior in the normal metal, with a strong dependence on the physical parameters both as to the structure and formation of the peaks. We also study the bias dependence of the spatially averaged spin transfer torque and spin accumulation. We examine the critical-bias effect of these quantities, and their dependence on the physical parameters. Our results are predictive of the outcome of future experiments, as they take into account imperfect interfaces and a realistic geometry.

Fault Diagnosis for Satellite Sensors and Actuators using Nonlinear Geometric Approach and Adaptive Observers

DEFF Research Database (Denmark)

Baldi, P.; Blanke, Mogens; Castaldi, P.

2018-01-01

This paper presents a novel scheme for diagnosis of faults affecting sensors that measure the satellite attitude, body angular velocity, flywheel spin rates, and defects in control torques from reaction wheel motors. The proposed methodology uses adaptive observers to provide fault estimates that...

Satellite Control Laboratory

DEFF Research Database (Denmark)

Wisniewski, Rafal; Bak, Thomas

2001-01-01

The Satellite Laboratory at the Department of Control Engineering of Aalborg University (SatLab) is a dynamic motion facility designed for analysis and test of micro spacecraft. A unique feature of the laboratory is that it provides a completely gravity-free environment. A test spacecraft...... of the laboratory is to conduct dynamic tests of the control and attitude determination algorithms during nominal operation and in abnormal conditions. Further it is intended to use SatLab for validation of various algorithms for fault detection, accommodation and supervisory control. Different mission objectives...... can be implemented in the laboratory, e.g. three-axis attitude control, slew manoeuvres, spins stabilization using magnetic actuation and/or reaction wheels. The spacecraft attitude can be determined applying magnetometer measurements...

Polarimetry on dense samples of spin-polarized {sup 3}He by magnetostatic detection

Energy Technology Data Exchange (ETDEWEB)

Wilms, E.; Ebert, M.; Heil, W.; Surkau, R. [Mainz Univ. (Germany). Inst. fuer Physik

1997-12-21

A very sensitive low-field fluxgate magnetometer is used to detect the static magnetic field produced by dense samples of spin-polarized {sup 3}He gas contained in spherical glass cells at pressures around several bars. The {sup 3}He nuclear polarization can be extracted with high precision {Delta}P/P<1% by utilizing magnetostatic detection in combination with adiabatic fast-passage spin reversal. The polarization losses can be kept well below 0.1% thus making this type of polarimetry almost non-destructive. More simply even, P can be measured with reduced accuracy by the change of field when the cell is removed from the fluxgate. In this case the accuracy is limited to about 10% due to the uncertainties about the susceptibilities of the cell walls. (orig.). 29 refs.

High resolution satellite imagery : from spies to pipeline management

Energy Technology Data Exchange (ETDEWEB)

Adam, S. [Canadian Geomatic Solutions Ltd., Calgary, AB (Canada); Farrell, M. [TransCanada Transmission, Calgary, AB (Canada)

2000-07-01

The launch of Space Imaging's IKONOS satellite in September 1999 has opened the door for corridor applications. The technology has been successfully implemented by TransCanada PipeLines in mapping over 1500 km of their mainline. IKONOS is the world's first commercial high resolution satellite which collects data at 1-meter black/white and 4-meter multi-spectral. Its use is regulated by the U.S. government. It is the best source of high resolution satellite image data. Other sources include the Indian Space Agency's IRS-1 C/D satellite and the Russian SPIN-2 which provides less reliable coverage. In addition, two more high resolution satellites may be launched this year to provide imagery every day of the year. IKONOS scenes as narrow as 5 km can be purchased. TransCanada conducted a pilot study to determine if high resolution satellite imagery is as effective as ortho-photos for identifying population structures within a buffer of TransCanada's east line right-of-way. The study examined three unique segments where residential, commercial, industrial and public features were compared. It was determined that IKONOS imagery is as good as digital ortho-photos for updating structures from low to very high density areas. The satellite imagery was also logistically easier than ortho-photos to acquire. This will be even more evident when the IKONOS image archives begins to grow. 4 tabs., 3 figs.

Testing the gravitational interaction in the field of the Earth via satellite laser ranging and the Laser Ranged Satellites Experiment (LARASE)

International Nuclear Information System (INIS)

Lucchesi, D M; Peron, R; Visco, M; Anselmo, L; Pardini, C; Bassan, M; Pucacco, G

2015-01-01

In this work, the Laser Ranged Satellites Experiment (LARASE) is presented. This is a research program that aims to perform new refined tests and measurements of gravitation in the field of the Earth in the weak field and slow motion (WFSM) limit of general relativity (GR). For this objective we use the free available data relative to geodetic passive satellite lasers tracked from a network of ground stations by means of the satellite laser ranging (SLR) technique. After a brief introduction to GR and its WFSM limit, which aims to contextualize the physical background of the tests and measurements that LARASE will carry out, we focus on the current limits of validation of GR and on current constraints on the alternative theories of gravity that have been obtained with the precise SLR measurements of the two LAGEOS satellites performed so far. Afterward, we present the scientific goals of LARASE in terms of upcoming measurements and tests of relativistic physics. Finally, we introduce our activities and we give a number of new results regarding the improvements to the modelling of both gravitational and non-gravitational perturbations to the orbit of the satellites. These activities are a needed prerequisite to improve the forthcoming new measurements of gravitation. An innovation with respect to the past is the specialization of the models to the LARES satellite, especially for what concerns the modelling of its spin evolution, the neutral drag perturbation and the impact of Earth's solid tides on the satellite orbit. (paper)

Semi-analytical study of the rotational motion stability of artificial satellites using quaternions

International Nuclear Information System (INIS)

Dos Santos, Josué C; Zanardi, Maria Cecília; Matos, Nicholas

2013-01-01

This study at aims performing the stability analysis of the rotational motion to artificial satellites using quaternions to describe the satellite attitude (orientation on the space). In the system of rotational motion equations, which is composed by four kinematic equations of the quaternions and by the three Euler equations in terms of the rotational spin components. The influence of the gravity gradient and the direct solar radiation pressure torques have been considered. Equilibrium points were obtained through numerical simulations using the softwares Matlab and Octave, which are then analyzed by the Routh-Hurwitz Stability Criterion

Combined Geometric and Neural Network Approach to Generic Fault Diagnosis in Satellite Reaction Wheels

DEFF Research Database (Denmark)

Baldi, P.; Blanke, Mogens; Castaldi, P.

2015-01-01

This paper suggests a novel diagnosis scheme for detection, isolation and estimation of faults affecting satellite reaction wheels. Both spin rate measurements and actuation torque defects are dealt with. The proposed system consists of a fault detection and isolation module composed by a bank of...

Computation of higher spherical harmonics moments of the angular flux for neutron transport problems in spherical geometry

International Nuclear Information System (INIS)

Sahni, D.C.; Sharma, A.

2000-01-01

The integral form of one-speed, spherically symmetric neutron transport equation with isotropic scattering is considered. Two standard problems are solved using normal mode expansion technique. The expansion coefficients are obtained by solving their singular integral equations. It is shown that these expansion coefficients provide a representation of all spherical harmonics moments of the angular flux as a superposition of Bessel functions. It is seen that large errors occur in the computation of higher moments unless we take certain precautions. The reasons for this phenomenon are explained. They throw some light on the failure of spherical harmonics method in treating spherical geometry problems as observed by Aronsson

World Gravity Map: a set of global complete spherical Bouguer and isostatic anomaly maps and grids

Science.gov (United States)

Bonvalot, S.; Balmino, G.; Briais, A.; Kuhn, M.; Peyrefitte, A.; Vales, N.; Biancale, R.; Gabalda, G.; Reinquin, F.

2012-04-01

We present here a set of digital maps of the Earth's gravity anomalies (surface free air, Bouguer and isostatic), computed at Bureau Gravimetric International (BGI) as a contribution to the Global Geodetic Observing Systems (GGOS) and to the global geophysical maps published by the Commission for the Geological Map of the World (CGMW) with support of UNESCO and other institutions. The Bouguer anomaly concept is extensively used in geophysical interpretation to investigate the density distributions in the Earth's interior. Complete Bouguer anomalies (including terrain effects) are usually computed at regional scales by integrating the gravity attraction of topography elements over and beyond a given area (under planar or spherical approximations). Here, we developed and applied a worldwide spherical approach aimed to provide a set of homogeneous and high resolution gravity anomaly maps and grids computed at the Earth's surface, taking into account a realistic Earth model and reconciling geophysical and geodetic definitions of gravity anomalies. This first version (1.0) has been computed by spherical harmonics analysis / synthesis of the Earth's topography-bathymetry up to degree 10800. The detailed theory of the spherical harmonics approach is given in Balmino et al., (Journal of Geodesy, 2011). The Bouguer and terrain corrections have thus been computed in spherical geometry at 1'x1' resolution using the ETOPO1 topography/bathymetry, ice surface and bedrock models from the NOAA (National Oceanic and Atmospheric Administration) and taking into account precise characteristics (boundaries and densities) of major lakes, inner seas, polar caps and of land areas below sea level. Isostatic corrections have been computed according to the Airy-Heiskanen model in spherical geometry for a constant depth of compensation of 30km. The gravity information given here is provided by the Earth Geopotential Model (EGM2008), developed at degree 2160 by the National Geospatial

Non-Existence of Black Hole Solutionsfor a Spherically Symmetric, Static Einstein-Dirac-Maxwell System

Science.gov (United States)

Finster, Felix; Smoller, Joel; Yau, Shing-Tung

We consider for j=1/2, 3/2,... a spherically symmetric, static system of (2j+1) Dirac particles, each having total angular momentum j. The Dirac particles interact via a classical gravitational and electromagnetic field. The Einstein-Dirac-Maxwell equations for this system are derived. It is shown that, under weak regularity conditions on the form of the horizon, the only black hole solutions of the EDM equations are the Reissner-Nordstrom solutions. In other words, the spinors must vanish identically. Applied to the gravitational collapse of a "cloud" of spin-1/2-particles to a black hole, our result indicates that the Dirac particles must eventually disappear inside the event horizon.

Statistical Mechanics of Thin Spherical Shells

Directory of Open Access Journals (Sweden)

Andrej Košmrlj

2017-01-01

Full Text Available We explore how thermal fluctuations affect the mechanics of thin amorphous spherical shells. In flat membranes with a shear modulus, thermal fluctuations increase the bending rigidity and reduce the in-plane elastic moduli in a scale-dependent fashion. This is still true for spherical shells. However, the additional coupling between the shell curvature, the local in-plane stretching modes, and the local out-of-plane undulations leads to novel phenomena. In spherical shells, thermal fluctuations produce a radius-dependent negative effective surface tension, equivalent to applying an inward external pressure. By adapting renormalization group calculations to allow for a spherical background curvature, we show that while small spherical shells are stable, sufficiently large shells are crushed by this thermally generated “pressure.” Such shells can be stabilized by an outward osmotic pressure, but the effective shell size grows nonlinearly with increasing outward pressure, with the same universal power-law exponent that characterizes the response of fluctuating flat membranes to a uniform tension.

Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation.

Science.gov (United States)

Dumez, Jean-Nicolas; Håkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T; Roy, Soumya Singha; Brown, Richard C D; Pileio, Giuseppe; Levitt, Malcolm H

2015-01-28

Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T1. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in (13)CH3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.

Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation

International Nuclear Information System (INIS)

Dumez, Jean-Nicolas; Håkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T.; Roy, Soumya Singha; Brown, Richard C. D.; Pileio, Giuseppe; Levitt, Malcolm H.

2015-01-01

Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T 1 . Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in 13 CH 3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states

Spherical Tensor Calculus for Local Adaptive Filtering

Science.gov (United States)

Reisert, Marco; Burkhardt, Hans

In 3D image processing tensors play an important role. While rank-1 and rank-2 tensors are well understood and commonly used, higher rank tensors are rare. This is probably due to their cumbersome rotation behavior which prevents a computationally efficient use. In this chapter we want to introduce the notion of a spherical tensor which is based on the irreducible representations of the 3D rotation group. In fact, any ordinary cartesian tensor can be decomposed into a sum of spherical tensors, while each spherical tensor has a quite simple rotation behavior. We introduce so called tensorial harmonics that provide an orthogonal basis for spherical tensor fields of any rank. It is just a generalization of the well known spherical harmonics. Additionally we propose a spherical derivative which connects spherical tensor fields of different degree by differentiation. Based on the proposed theory we present two applications. We propose an efficient algorithm for dense tensor voting in 3D, which makes use of tensorial harmonics decomposition of the tensor-valued voting field. In this way it is possible to perform tensor voting by linear-combinations of convolutions in an efficient way. Secondly, we propose an anisotropic smoothing filter that uses a local shape and orientation adaptive filter kernel which can be computed efficiently by the use spherical derivatives.

Spin current evolution in the separated spin-up and spin-down quantum hydrodynamics

International Nuclear Information System (INIS)

Trukhanova, Mariya Iv.

2015-01-01

We have developed a method of quantum hydrodynamics (QHD) that describes particles with spin-up and with spin-down in separate. We have derived the equation of the spin current evolution as a part of the set of the quantum hydrodynamics equations that treat particles with different projection of spin on the preferable direction as two different species. We have studied orthogonal propagation of waves in the external magnetic field and determined the contribution of quantum corrections due to the Bohm potential and to magnetization energy of particles with different projections of spin in the spin-current wave dispersion. We have analyzed the limits of weak and strong magnetic fields. - Highlights: • We derive the spin current equation for particles with different projection of spin. • We predict the contribution of Bohm potential to the dynamics of spin current. • We derive the spin-current wave in the system of spin-polarized particles. • We study the propagation of spin-acoustic wave in magnetized dielectrics.

Single-step linking transition from superdeformed to spherical states in {sup 143}Eu

Energy Technology Data Exchange (ETDEWEB)

Atac, A.; Axelsson, A.; Persson, J. [Uppsala Univ. (Sweden)] [and others

1996-12-31

A discrete {gamma}-ray transition which connects the second lowest SD state with a normally deformed one in {sup 143}Eu has been discovered. It has an energy of 3360.6 keV and carries 3.2 % of the full intensity of the SD band. It feeds into a nearly spherical state which is above the I = 35/2{sup +}, E=4947 keV level. The exact placement of the single-step link could, however, not be established due to the especially complicated level scheme in the region of interest. The angular correlation study favours a stretched dipole character for the 3360.6 keV transition. The single-step link agrees well with the previously determined two-step links, both with respect to energy and spin.

Muonium spin exchange in spin-polarized media: Spin-flip and -nonflip collisions

International Nuclear Information System (INIS)

Senba, M.

1994-01-01

The transverse relaxation of the muon spin in muonium due to electron spin exchange with a polarized spin-1/2 medium is investigated. Stochastic calculations, which assume that spin exchange is a Poisson process, are carried out for the case where the electron spin polarization of the medium is on the same axis as the applied field. Two precession signals of muonium observed in intermediate fields (B>30 G) are shown to have different relaxation rates which depend on the polarization of the medium. Furthermore, the precession frequencies are shifted by an amount which depends on the spin-nonflip rate. From the two relaxation rates and the frequency shift in intermediate fields, one can determine (i) the encounter rate of muonium and the paramagnetic species, (ii) the polarization of the medium, and most importantly (iii) the quantum-mechanical phase shift (and its sign) associated with the potential energy difference between electron singlet and triplet encounters. Effects of spin-nonflip collisions on spin dynamics are discussed for non-Poisson as well as Poisson processes. In unpolarized media, the time evolution of the muon spin in muonium is not influenced by spin-nonflip collisions, if the collision process is Poissonian. This seemingly obvious statement is not true anymore in non-Poissonian processes, i.e., it is necessary to specify both spin-flip and spin-nonflip rates to fully characterize spin dynamics

Hydrologically induced orientation variations of a tri-axial Earth's principal axes based on satellite-gravimetric and hydrological models

Directory of Open Access Journals (Sweden)

Shen Wenbin

2013-05-01

Full Text Available The Earth is a tri-axial body, with unequal principal inertia moments, A, B and C. The corresponding principal axes a, b and c are determined by the mass distribution of the Earth, and their orientations vary with the mass redistribution. In this study, the hydrologically induced variations are estimated on the basis of satellite gravimetric data, including those from satellite laser ranging (SLR and gravity recovery and climate experiment (GRACE, and hydrological models from global land data assimilation system (GLDAS. The longitude variations of a and b are mainly related to the variations of the spherical harmonic coefficients C¯22 and S¯22, which have been estimated to be consisting annual variations of about 1. 6 arc seconds and 1. 8 arc seconds, respectively, from gravity data. This result is confirmed by land surface water storage provided by the GLDAS model. If the atmospheric and oceanic signals are removed from the spherical harmonic coefficients C¯21 and S¯21, the agreement of the orientation series for c becomes poor, possibly due to the inaccurate background models used in pre-processing of the satellite gravimetric data. Determination of the orientation variations may provide a better understanding of various phenomena in the study of the rotation of a tri-axial Earth.

Modeling mantle convection in the spherical annulus

Science.gov (United States)

Hernlund, John W.; Tackley, Paul J.

2008-12-01

Most methods for modeling mantle convection in a two-dimensional (2D) circular annular domain suffer from innate shortcomings in their ability to capture several characteristics of the spherical shell geometry of planetary mantles. While methods such as rescaling the inner and outer radius to reduce anomalous effects in a 2D polar cylindrical coordinate system have been introduced and widely implemented, such fixes may have other drawbacks that adversely affect the outcome of some kinds of mantle convection studies. Here we propose a new approach that we term the "spherical annulus," which is a 2D slice that bisects the spherical shell and is quantitatively formulated at the equator of a spherical polar coordinate system after neglecting terms in the governing equations related to variations in latitude. Spherical scaling is retained in this approximation since the Jacobian function remains proportional to the square of the radius. We present example calculations to show that the behavior of convection in the spherical annulus compares favorably against calculations performed in other 2D annular domains when measured relative to those in a fully three-dimensional (3D) spherical shell.

Neutron spin quantum precession using multilayer spin splitters and a phase-spin echo interferometer

International Nuclear Information System (INIS)

Ebisawa, Toru; Tasaki, Seiji; Kawai, Takeshi; Hino, Masahiro; Akiyoshi, Tsunekazu; Achiwa, Norio; Otake, Yoshie; Funahashi, Haruhiko.

1996-01-01

Neutron spin quantum precession by multilayer spin splitter has been demonstrated using a new spin interferometer. The multilayer spin splitter consists of a magnetic multilayer mirror on top, followed by a gap layer and a non magnetic multilayer mirror which are evaporated on a silicon substrate. Using the multilayer spin splitter, a polarized neutron wave in a magnetic field perpendicular to the polarization is split into two spin eigenstates with a phase shift in the direction of the magnetic field. The spin quantum precession is equal to the phase shift, which depends on the effective thickness of the gap layer. The demonstration experiments verify the multilayer spin splitter as a neutron spin precession device as well as the coherent superposition principle of the two spin eigenstates. We have developed a new phase-spin echo interferometer using the multilayer spin splitters. We present successful performance tests of the multilayer spin splitter and the phase-spin echo interferometer. (author)

Spherical spacelike geometries in static spherically symmetric spacetimes: Generalized Painlevè–Gullstrand coordinates, foliation, and embedding

Energy Technology Data Exchange (ETDEWEB)

Akbar, M.M., E-mail: akbar@utdallas.edu

2017-06-10

It is well known that static spherically symmetric spacetimes can admit foliations by flat spacelike hypersurfaces, which are best described in terms of the Painlevè–Gullstrand coordinates. The uniqueness and existence of such foliations were addressed earlier. In this paper, we prove, purely geometrically, that any possible foliation of a static spherically symmetric spacetime by an arbitrary codimension-one spherical spacelike geometry, up to time translation and rotation, is unique, and we find the algebraic condition under which it exists. This leads us to what can be considered as the most natural generalization of the Painlevè–Gullstrand coordinate system for static spherically symmetric metrics, which, in turn, makes it easy to derive generic conclusions on foliation and to study specific cases as well as to easily reproduce previously obtained generalizations as special cases. In particular, we note that the existence of foliation by flat hypersurfaces guarantees the existence of foliation by hypersurfaces whose Ricci curvature tensor is everywhere non-positive (constant negative curvature is a special case). The study of uniqueness and the existence concurrently solves the question of embeddability of a spherical spacelike geometry in one-dimensional higher static spherically symmetric spacetimes, and this produces known and new results geometrically, without having to go through the momentum and Hamiltonian constraints.

Spiral CT manifestations of spherical pneumonia

International Nuclear Information System (INIS)

Li Xiaohong; Yang Hongwei; Xu Chunmin; Qin Xiu

2008-01-01

Objective: To explore the Spiral CT manifestations and differential diagnosis of spherical pneumonia. Methods: 18 cases of spherical pneumonia and 20 cases of peripheral pulmonary carcinoma were selected, both of them were confirmed by clinic and/or pathology. The SCT findings of both groups were compared retrospectively. Results: Main spiral CT findings of spherical pneumonia were showed as followings: square or triangular lesions adjacent to pleura; with irregular shape, blurry, slightly lobulated margin, sometimes with halo sign. Small inflammatory patches and intensified vascular markings around the lesions were seen. Lesions became smaller or vanished after short-term anti-inflammatory treatment. Conclusion: Spherical pneumonia showed some characteristics on Spiral CT scan, which are helpful in diagnosis and differential diagnosis of this disease. (authors)

Non-conformal contact mechanical characteristic analysis on spherical components

Energy Technology Data Exchange (ETDEWEB)

Zhen-zhi, G.; Bin, H.; Zheng-ming, G.; Feng-mei, Y.; Jin, Q [The 2. Artillery Engineering Univ., Xi' an (China)

2017-03-15

Non-conformal spherical-contact mechanical problems is a three-dimensional coordination or similar to the coordination spherical contact. Due to the complexity of the problem of spherical-contact and difficulties of solving higher-order partial differential equations, problems of three-dimensional coordination or similar to the coordination spherical-contact is still no exact analytical method for solving. It is based on three-dimensional taper model is proposed a model based on the contour surface of the spherical contact and concluded of the formula of the contact pressure and constructed of finite element model by contact pressure distribution under the non-conformal spherical. The results shows spherical contact model can reflect non-conformal spherical-contacting mechanical problems more than taper-contacting model, and apply for the actual project.

Origin of the Local Group satellite planes

Science.gov (United States)

Banik, Indranil; O'Ryan, David; Zhao, Hongsheng

2018-04-01

We attempt to understand the planes of satellite galaxies orbiting the Milky Way (MW) and M31 in the context of Modified Newtonian Dynamics (MOND), which implies a close MW-M31 flyby occurred ≈8 Gyr ago. Using the timing argument, we obtain MW-M31 trajectories consistent with cosmological initial conditions and present observations. We adjust the present M31 proper motion within its uncertainty in order to simulate a range of orbital geometries and closest approach distances. Treating the MW and M31 as point masses, we follow the trajectories of surrounding test particle disks, thereby mapping out the tidal debris distribution. Around each galaxy, the resulting tidal debris tends to cluster around a particular orbital pole. We find some models in which these preferred spin vectors align fairly well with those of the corresponding observed satellite planes. The radial distributions of material in the simulated satellite planes are similar to what we observe. Around the MW, our best-fitting model yields a significant fraction (0.22) of counter-rotating material, perhaps explaining why Sculptor counter-rotates within the MW satellite plane. In contrast, our model yields no counter-rotating material around M31. This is testable with proper motions of M31 satellites. In our best model, the MW disk is thickened by the flyby 7.65 Gyr ago to a root mean square height of 0.75 kpc. This is similar to the observed age and thickness of the Galactic thick disk. Thus, the MW thick disk may have formed together with the MW and M31 satellite planes during a past MW-M31 flyby.

Spin drift and spin diffusion currents in semiconductors

Energy Technology Data Exchange (ETDEWEB)

Idrish Miah, M [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia)], E-mail: m.miah@griffith.edu.au

2008-09-15

On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

Spin drift and spin diffusion currents in semiconductors

Directory of Open Access Journals (Sweden)

M Idrish Miah

2008-01-01

Full Text Available On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

Spin drift and spin diffusion currents in semiconductors

International Nuclear Information System (INIS)

Idrish Miah, M

2008-01-01

On the basis of a spin drift-diffusion model, we show how the spin current is composed and find that spin drift and spin diffusion contribute additively to the spin current, where the spin diffusion current decreases with electric field while the spin drift current increases, demonstrating that the extension of the spin diffusion length by a strong field does not result in a significant increase in spin current in semiconductors owing to the competing effect of the electric field on diffusion. We also find that there is a spin drift-diffusion crossover field for a process in which the drift and diffusion contribute equally to the spin current, which suggests a possible method of identifying whether the process for a given electric field is in the spin drift or spin diffusion regime. Spin drift-diffusion crossover fields for GaAs are calculated and are found to be quite small. We derive the relations between intrinsic spin diffusion length and the spin drift-diffusion crossover field of a semiconductor for different electron statistical regimes. The findings resulting from this investigation might be important for semiconductor spintronics.

Scaling of a fast spherical discharge

Energy Technology Data Exchange (ETDEWEB)

Antsiferov, P. S., E-mail: Ants@isan.troitsk.ru; Dorokhin, L. A. [Russian Academy of Sciences, Institute of Spectroscopy (Russian Federation)

2017-02-15

The influence of the discharge cavity dimensions on the properties of the spherical plasma formed in a fast discharge was studied experimentally. The passage of a current pulse with an amplitude of 30–40 kA and a rise rate of ~10{sup 12} A/s (a fast discharge) through a spherical ceramic (Al{sub 2}O{sub 3}) cavity with an inner diameter of 11 mm filled with argon at a pressure of 80 Pa results in the formation of a 1- to 2-mm-diameter spherical plasma with an electron temperature of several tens of electronvolts and a density of 10{sup 18}–10{sup 19} cm{sup –3}. It is shown that an increase in the inner diameter of the discharge cavity from 11 to 21 mm leads to the fourfold increase in the formation time of the spherical plasma and a decrease in the average ion charge. A decrease in the cavity diameter to 7 mm makes the spherical plasma unstable.

Spherical aberrations of human astigmatic corneas.

Science.gov (United States)

Zhao, Huawei; Dai, Guang-Ming; Chen, Li; Weeber, Henk A; Piers, Patricia A

2011-11-01

To evaluate whether the average spherical aberration of human astigmatic corneas is statistically equivalent to human nonastigmatic corneas. Spherical aberrations of 445 astigmatic corneas prior to laser vision correction were retrospectively investigated to determine Zernike coefficients for central corneal areas 6 mm in diameter using CTView (Sarver and Associates). Data were divided into groups according to cylinder power (0.01 to 0.25 diopters [D], 0.26 to 0.75 D, 0.76 to 1.06 D, 1.07 to 1.53 D, 1.54 to 2.00 D, and >2.00 D) and according to age by decade. Spherical aberrations were correlated with age and astigmatic power among groups and the entire population. Statistical analyses were conducted, and P.05 for all tested groups). Mean spherical aberration of astigmatic corneas was not correlated significantly with cylinder power or age (P>.05). Spherical aberrations are similar to those of nonastigmatic corneas, permitting the use of these additional data in the design of aspheric toric intra-ocular lenses. Copyright 2011, SLACK Incorporated.

Touchless attitude correction for satellite with constant magnetic moment

Science.gov (United States)

Ao, Hou-jun; Yang, Le-ping; Zhu, Yan-wei; Zhang, Yuan-wen; Huang, Huan

2017-09-01

Rescue of satellite with attitude fault is of great value. Satellite with improper injection attitude may lose contact with ground as the antenna points to the wrong direction, or encounter energy problems as solar arrays are not facing the sun. Improper uploaded command may set the attitude out of control, exemplified by Japanese Hitomi spacecraft. In engineering practice, traditional physical contact approaches have been applied, yet with a potential risk of collision and a lack of versatility since the mechanical systems are mission-specific. This paper puts forward a touchless attitude correction approach, in which three satellites are considered, one having constant dipole and two having magnetic coils to control attitude of the first. Particular correction configurations are designed and analyzed to maintain the target's orbit during the attitude correction process. A reference coordinate system is introduced to simplify the control process and avoid the singular value problem of Euler angles. Based on the spherical triangle basic relations, the accurate varying geomagnetic field is considered in the attitude dynamic mode. Sliding mode control method is utilized to design the correction law. Finally, numerical simulation is conducted to verify the theoretical derivation. It can be safely concluded that the no-contact attitude correction approach for the satellite with uniaxial constant magnetic moment is feasible and potentially applicable to on-orbit operations.

Spherical grating based x-ray Talbot interferometry

Energy Technology Data Exchange (ETDEWEB)

Cong, Wenxiang, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu; Xi, Yan, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu; Wang, Ge, E-mail: congw@rpi.edu, E-mail: xiy2@rpi.edu, E-mail: wangg6@rpi.edu [Biomedical Imaging Center, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2015-11-15

Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and

Spherical grating based x-ray Talbot interferometry

International Nuclear Information System (INIS)

Cong, Wenxiang; Xi, Yan; Wang, Ge

2015-01-01

Purpose: Grating interferometry is a state-of-the-art x-ray imaging approach, which can acquire information on x-ray attenuation, phase shift, and small-angle scattering simultaneously. Phase-contrast imaging and dark-field imaging are very sensitive to microstructural variation and offers superior contrast resolution for biological soft tissues. However, a common x-ray tube is a point-like source. As a result, the popular planar grating imaging configuration seriously restricts the flux of photons and decreases the visibility of signals, yielding a limited field of view. The purpose of this study is to extend the planar x-ray grating imaging theory and methods to a spherical grating scheme for a wider range of preclinical and clinical applications. Methods: A spherical grating matches the wave front of a point x-ray source very well, allowing the perpendicular incidence of x-rays on the grating to achieve a higher visibility over a larger field of view than the planer grating counterpart. A theoretical analysis of the Talbot effect for spherical grating imaging is proposed to establish a basic foundation for x-ray spherical gratings interferometry. An efficient method of spherical grating imaging is also presented to extract attenuation, differential phase, and dark-field images in the x-ray spherical grating interferometer. Results: Talbot self-imaging with spherical gratings is analyzed based on the Rayleigh–Sommerfeld diffraction formula, featuring a periodic angular distribution in a polar coordinate system. The Talbot distance is derived to reveal the Talbot self-imaging pattern. Numerical simulation results show the self-imaging phenomenon of a spherical grating interferometer, which is in agreement with the theoretical prediction. Conclusions: X-ray Talbot interferometry with spherical gratings has a significant practical promise. Relative to planar grating imaging, spherical grating based x-ray Talbot interferometry has a larger field of view and

Spin Polarization Oscillations without Spin Precession: Spin-Orbit Entangled Resonances in Quasi-One-Dimensional Spin Transport

Directory of Open Access Journals (Sweden)

D. H. Berman

2014-03-01

Full Text Available Resonant behavior involving spin-orbit entangled states occurs for spin transport along a narrow channel defined in a two-dimensional electron gas, including an apparent rapid relaxation of the spin polarization for special values of the channel width and applied magnetic field (so-called ballistic spin resonance. A fully quantum-mechanical theory for transport using multiple subbands of the one-dimensional system provides the dependence of the spin density on the applied magnetic field and channel width and position along the channel. We show how the spatially nonoscillating part of the spin density vanishes when the Zeeman energy matches the subband energy splittings. The resonance phenomenon persists in the presence of disorder.

Effect of spin rotation coupling on spin transport

International Nuclear Information System (INIS)

Chowdhury, Debashree; Basu, B.

2013-01-01

We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k → ⋅p → perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k → ⋅p → framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied

Effect of spin rotation coupling on spin transport

Energy Technology Data Exchange (ETDEWEB)

Chowdhury, Debashree, E-mail: debashreephys@gmail.com; Basu, B., E-mail: sribbasu@gmail.com

2013-12-15

We have studied the spin rotation coupling (SRC) as an ingredient to explain different spin-related issues. This special kind of coupling can play the role of a Dresselhaus like coupling in certain conditions. Consequently, one can control the spin splitting, induced by the Dresselhaus like term, which is unusual in a semiconductor heterostructure. Within this framework, we also study the renormalization of the spin-dependent electric field and spin current due to the k{sup →}⋅p{sup →} perturbation, by taking into account the interband mixing in the rotating system. In this paper we predict the enhancement of the spin-dependent electric field resulting from the renormalized spin rotation coupling. The renormalization factor of the spin electric field is different from that of the SRC or Zeeman coupling. The effect of renormalized SRC on spin current and Berry curvature is also studied. Interestingly, in the presence of this SRC-induced SOC it is possible to describe spin splitting as well as spin galvanic effect in semiconductors. -- Highlights: •Studied effect of spin rotation coupling on the spin electric field, spin current and Berry curvature. •In the k{sup →}⋅p{sup →} framework we study the renormalization of spin electric field and spin current. •For an inertial system we have discussed the spin splitting. •Expression for the Berry phase in the inertial system is discussed. •The inertial spin galvanic effect is studied.

Part I: Spin wave dynamics in YIG spheres

International Nuclear Information System (INIS)

Anon.

1987-01-01

An experimental study is made of the interactions between spin wave modes excited in a sphere of yttrium iron garnet by pumping the Suhl subsidiary absorption with microwaves. The dynamical behavior of the magnetization is observed under high resolution by varying the dc field and microwave pump power. Varied behavior is found: (1) onset of the Suhl instability by excitation of a single spin wave mode; (2) when two or more modes are excited, interactions lead to auto-oscillations displaying period-doubling to chaos; (3) quasiperiodicity, locking, and chaos occur when three or more modes are excited; (4) abrupt transition to wide band power spectra (i.e., turbulence), with hysteresis; (5) irregular relaxation oscillations and aperiodic spiking behavior. A theoretical model is developed using the plane wave approximation obtaining the lowest order nonlinear interaction terms between the excited modes. Extension of this analysis to the true spherical spin-modes is discussed. Bifurcation behavior is examined, and dynamical behavior is numerically computed and compared to the experimental data. A theory is developed regarding the nature of the experimentally observed relaxation oscillations and spiking behavior based on the interaction of ''weak'' and ''strong'' modes, and this is demonstrated in the numerical simulations for two modes. Quasiperiodicity is shown to occur in the numerical study when at least 3 modes are excited with appropriate parameter values. A possible mechanism for generating microwave subharmonics at half of the pumping frequency is discussed. 57 refs., 25 figs., 5 tabs

The nuclear deformation versus the spin-flip like excitations and the suppression of the 2νββ decay amplitude

International Nuclear Information System (INIS)

Raduta, A.A.; Delion, D.S.; Faessler, A.

1997-01-01

The suppression mechanism of the Gamow-Teller double beta decay amplitude M GT is studied using a many body Hamiltonian which describes a composite system of protons and neutrons moving in a projected spherical single particle basis. Alike nucleons interact through pairing while protons and neutrons by a separable dipole-dipole force both in the particle-hole (ph) and particle-particle (pp) channels. The spin-flip and non-spin-flip components of the QRPA phonons have a differents contribution to the M GT values. The relative magnitudes and phases depend both on the strength of the particle-particle interaction (g pp ) and on the nuclear deformation. The deformation yields a fragmentation of the M GT value on one hand and washes out the separation of states of pure spin-flip and non-spin-flip structures. Due to this effect M GT has only one fragmented resonance structure in the low part of the spectrum. (orig.)

ELSA- The European Levitated Spherical Actruator

Science.gov (United States)

Ruiz, M.; Serin, J.; Telteu-Nedelcu, D.; De La Vallee Poussin, H.; Onillon, E.; Rossini, L.

2014-08-01

The reaction sphere is a magnetic bearing spherical actuator consisting of a permanent magnet spherical rotor that can be accelerated in any direction. It consists of an 8-pole permanent magnet spherical rotor that is magnetically levitated and can be accelerated about any axis by a 20-pole stator with electromagnets. The spherical actuator is proposed as a potential alternative to traditional momentum exchange devices such as reaction wheels (RWs) or control moment gyroscopes (CMGs). This new actuator provides several benefits such as reduced mass and power supply allocated to the attitude and navigation unit, performance gain, and improved reliability due to the absence of mechanical bearings. The paper presents the work done on the levitated spherical actuator and more precisely the electrical drive including its control unit and power parts. An elegant breadboard is currently being manufactured within the frame of an FP7 project. This project also comprises a feasibility study to show the feasibility of integrating such a system on a flight platform and to identify all the challenges to be solved in terms of technology or components to be developed.

Spherical Torus Center Stack Design

International Nuclear Information System (INIS)

C. Neumeyer; P. Heitzenroeder; C. Kessel; M. Ono; M. Peng; J. Schmidt; R. Woolley; I. Zatz

2002-01-01

The low aspect ratio spherical torus (ST) configuration requires that the center stack design be optimized within a limited available space, using materials within their established allowables. This paper presents center stack design methods developed by the National Spherical Torus Experiment (NSTX) Project Team during the initial design of NSTX, and more recently for studies of a possible next-step ST (NSST) device

Spherical Demons: Fast Surface Registration

Science.gov (United States)

Yeo, B.T. Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

2009-01-01

We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast – registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces. PMID:18979813

Proca stars: Gravitating Bose–Einstein condensates of massive spin 1 particles

Directory of Open Access Journals (Sweden)

Richard Brito

2016-01-01

Full Text Available We establish that massive complex Abelian vector fields (mass μ can form gravitating solitons, when minimally coupled to Einstein's gravity. Such Proca stars (PSs have a stationary, everywhere regular and asymptotically flat geometry. The Proca field, however, possesses a harmonic time dependence (frequency w, realizing Wheeler's concept of geons for an Abelian spin 1 field. We obtain PSs with both a spherically symmetric (static and an axially symmetric (stationary line element. The latter form a countable number of families labelled by an integer m∈Z+. PSs, like (scalar boson stars, carry a conserved Noether charge, and are akin to the latter in many ways. In particular, both types of stars exist for a limited range of frequencies and there is a maximal ADM mass, Mmax, attained for an intermediate frequency. For spherically symmetric PSs (rotating PSs with m=1,2,3, Mmax≃1.058MPl2/μ (Mmax≃1.568,2.337,3.247MPl2/μ, slightly larger values than those for (mini-boson stars. We establish perturbative stability for a subset of solutions in the spherical case and anticipate a similar conclusion for fundamental modes in the rotating case. The discovery of PSs opens many avenues of research, reconsidering five decades of work on (scalar boson stars, in particular as possible dark matter candidates.

Toroidal high-spin isomers in the nucleus 304120

Science.gov (United States)

Staszczak, A.; Wong, Cheuk-Yin; Kosior, A.

2017-05-01

Background: Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis with I =Iz . The toroidal high-K isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. Purpose: We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus 120304184. Method: Our method consists of three steps: First, we use the deformation-constrained Skyrme-Hartree-Fock-Bogoliubov approach to search for the nuclear density distributions with toroidal shapes. Next, using these toroidal distributions as starting configurations, we apply an additional cranking constraint of a large angular momentum I =Iz about the symmetry z axis and search for the energy minima of the system as a function of the deformation. In the last step, if a local energy minimum with I =Iz is found, we perform at this point the cranked symmetry- and deformation-unconstrained Skyrme-Hartree-Fock calculations to locate a stable toroidal high-spin isomeric state in free convergence. Results: We have theoretically located two toroidal high-spin isomeric states of 120304184 with an angular momentum I =Iz=81 ℏ (proton 2p-2h, neutron 4p-4h excitation) and I =Iz=208 ℏ (proton 5p-5h, neutron 8p-8h) at the quadrupole moment deformations Q20=-297.7 b and Q20=-300.8 b with energies 79.2 and 101.6 MeV above the spherical ground state, respectively. The nuclear density distributions of the toroidal high-spin isomers 120304184(Iz=81 ℏ and 208 ℏ ) have the maximum density close to the nuclear matter density, 0.16 fm-3, and a torus major to minor radius aspect ratio R /d =3.25 . Conclusions: We demonstrate that aligned angular momenta of Iz=81 ℏ and 208 ℏ arising from

Spin Hall and spin swapping torques in diffusive ferromagnets

KAUST Repository

Pauyac, C. O.

2017-12-08

A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.

Spin Hall and spin swapping torques in diffusive ferromagnets

KAUST Repository

Pauyac, C. O.; Chshiev, M.; Manchon, Aurelien; Nikolaev, S. A.

2017-01-01

A complete set of the generalized drift-diffusion equations for a coupled charge and spin dynamics in ferromagnets in the presence of extrinsic spin-orbit coupling is derived from the quantum kinetic approach, covering major transport phenomena, such as the spin and anomalous Hall effects, spin swapping, spin precession and relaxation processes. We argue that the spin swapping effect in ferromagnets is enhanced due to spin polarization, while the overall spin texture induced by the interplay of spin-orbital and spin precessional effects displays a complex spatial dependence that can be exploited to generate torques and nucleate/propagate domain walls in centrosymmetric geometries without use of external polarizers, as opposed to the conventional understanding of spin-orbit mediated torques.

Generalized moment analysis of magnetic field correlations for accumulations of spherical and cylindrical magnetic pertubers

Directory of Open Access Journals (Sweden)

Felix Tobias Kurz

2016-12-01

Full Text Available In biological tissue, an accumulation of similarly shaped objects with a susceptibility difference to the surrounding tissue generates a local distortion of the external magnetic field in magnetic resonance imaging. It induces stochastic field fluctuations that characteristically influence proton spin diffusion in the vicinity of these magnetic perturbers. The magnetic field correlation that is associated with such local magnetic field inhomogeneities can be expressed in the form of a dynamic frequency autocorrelation function that is related to the time evolution of the measured magnetization. Here, an eigenfunction expansion for two simple magnetic perturber shapes, that of spheres and cylinders, is considered for restricted spin diffusion in a simple model geometry. Then, the concept of generalized moment analysis, an approximation technique that is applied in the study of (non-reactive processes that involve Brownian motion, allows to provide analytical expressions for the correlation function for different exponential decay forms. Results for the biexponential decay for both spherical and cylindrical magnetized objects are derived and compared with the frequently used (less accurate monoexponential decay forms. They are in asymptotic agreement with the numerically exact value of the correlation function for long and short times.

Spin-orbit and spin-lattice coupling

International Nuclear Information System (INIS)

Bauer, Gerrit E.W.; Ziman, Timothy; Mori, Michiyasu

2014-01-01

We pursued theoretical research on the coupling of electron spins in the condensed matter to the lattice as mediated by the spin-orbit interaction with special focus on the spin and anomalous Hall effects. (author)

Second rank direction cosine spherical tensor operators and the nuclear electric quadrupole hyperfine structure Hamiltonian of rotating molecules

Science.gov (United States)

di Lauro, C.

2018-03-01

Transformations of vector or tensor properties from a space-fixed to a molecule-fixed axis system are often required in the study of rotating molecules. Spherical components λμ,ν of a first rank irreducible tensor can be obtained from the direction cosines between the two axis systems, and a second rank tensor with spherical components λμ,ν(2) can be built from the direct product λ × λ. It is shown that the treatment of the interaction between molecular rotation and the electric quadrupole of a nucleus is greatly simplified, if the coefficients in the axis-system transformation of the gradient of the electric field of the outer charges at the coupled nucleus are arranged as spherical components λμ,ν(2). Then the reduced matrix elements of the field gradient operators in a symmetric top eigenfunction basis, including their dependence on the molecule-fixed z-angular momentum component k, can be determined from the knowledge of those of λ(2) . The hyperfine structure Hamiltonian Hq is expressed as the sum of terms characterized each by a value of the molecule-fixed index ν, whose matrix elements obey the rule Δk = ν. Some of these terms may vanish because of molecular symmetry, and the specific cases of linear and symmetric top molecules, orthorhombic molecules, and molecules with symmetry lower than orthorhombic are considered. Each ν-term consists of a contraction of the rotational tensor λ(2) and the nuclear quadrupole tensor in the space-fixed frame, and its matrix elements in the rotation-nuclear spin coupled representation can be determined by the standard spherical tensor methods.

Collective pairing states and non-unitary representations of the quasi-spin group

International Nuclear Information System (INIS)

Lorazo, B.

1975-01-01

Some months ago, a parameter-dependent (psub(i))-quasi-spin group was presented by the author. The interest for considering such a group was partly suggested by the possibility of describing, with a reasonable accuracy, the ground state of even spherical nuclei with one closed shell by a n-pair wave function [Σsub(i)psub(i)Ssub(+)sup(i)] sup(n)/0> depending upon the real parameters psub(i) (the operators Ssub(+)sup(i) are the one-orbit quasi-spin operators). It was stated that the formalism would provide the exact mathematical framework to discuss the generalized seniority quantum number. The relevance of this point of view has been vigorously questioned. For the author of the present paper, the arguments given are based on misinterpretation of some unconventional and possibly ambiguous aspects of the work. Proof is given below that group theoretical considerations can effectively be used in place of standard commutator techniques. (Auth.)

The prediction of spherical aberration with schematic eyes.

Science.gov (United States)

Liou, H L; Brennan, N A

1996-07-01

Many model eyes have been proposed; they differ in optical characteristics and therefore have different aberrations and image quality. In predicting the visual performance of the eye, we are most concerned with the central foveal vision. Spherical aberration is the only on-axis monochromatic aberration and can be used as a criterion to assess the degree of resemblance of eye models to the human eye. We reviewed and compiled experimental values of the spherical aberration of the eye, calculated the spherical aberration of several different categories of model eyes and compared the calculated results to the experimental data. Results show an over-estimation of spherical aberration by all models, the finite schematic eyes predicting values of spherical aberration closest to the experimental data. Current model eyes do not predict the average experimental values of the spherical aberration of the eye. A new model eye satisfying this assessment criterion is required for investigations of the visual performance of the eye.

Measurement of Turbulence Modulation by Non-Spherical Particles

DEFF Research Database (Denmark)

Mandø, Matthias; Rosendahl, Lasse

2010-01-01

The change in the turbulence intensity of an air jet resulting from the addition of particles to the flow is measured using Laser Doppler Anemometry. Three distinct shapes are considered: the prolate spheroid, the disk and the sphere. Measurements of the carrier phase and particle phase velocities...... at the centerline of the jet are carried out for mass loadings of 0.5, 1, 1.6 and particle sizes 880μm, 1350μm, 1820μm for spherical particles. For each non-spherical shape only a single size and loading are considered. The turbulence modulation of the carrier phase is found to highly dependent on the turbulence......, the particle mass flow and the integral length scale of the flow. The expression developed on basis of spherical particles only is applied on the data for the non-spherical particles. The results suggest that non-spherical particles attenuate the carrier phase turbulence significantly more than spherical...

Spin rotation after a spin-independent scattering. Spin properties of an electron gas in a solid

International Nuclear Information System (INIS)

Zayets, V.

2014-01-01

It is shown that spin direction of an electron may not be conserved after a spin-independent scattering. The spin rotations occur due to a quantum-mechanical fact that when a quantum state is occupied by two electrons of opposite spins, the total spin of the state is zero and the spin direction of each electron cannot be determined. It is shown that it is possible to divide all conduction electrons into two group distinguished by their time-reversal symmetry. In the first group the electron spins are all directed in one direction. In the second group there are electrons of all spin directions. The number of electrons in each group is conserved after a spin-independent scattering. This makes it convenient to use these groups for the description of the magnetic properties of conduction electrons. The energy distribution of spins, the Pauli paramagnetism and the spin distribution in the ferromagnetic metals are described within the presented model. The effects of spin torque and spin-torque current are described. The origin of spin-transfer torque is explained within the presented model

The MEDUSA electron and ion spectrometer and the PIA ultraviolet photometers on Astrid-2

Directory of Open Access Journals (Sweden)

O. Norberg

2001-06-01

Full Text Available The miniature electron and ion spectrometer MEDUSA on Astrid-2 consists of two "top-hat"-type spherical electrostatic analyzers, sharing a common top-hat. Fast energy sweeps (16 electron sweeps and 8 ion sweeps per second allow for very high temporal resolution measurements of a two-dimensional slice of the particle distribution function. The energy range covered, is in the case of electrons, 4 eV to 22 keV and, in the case of ions, 2 eV to 12 keV. MEDUSA is mounted with its aperture close to the spin plane of Astrid-2, which allows for good pitch-angle coverage when the local magnetic field is in the satellite spin plane. The PIA-1/2 spin-scanning ultraviolet photometers measure auroral emissions. Using the spacecraft spin and orbital motion, it is possible to create two-dimensional images from the data. Spin-scanning photometers, such as PIA, are low-cost, low mass alternatives to auroral imagers, but place constraints on the satellite attitude. Data from MEDUSA are used to study processes in the auroral region, in particular, electrodynamics of aurora and "black aurora". MEDUSA is also a technological development, paving the way for highly capable, miniaturized particle spectrometers.Key words. Ionosphere (instruments and techniques – Magnetospheric physics (auroral phenomena; instruments and techniques

Spin injection and spin accumulation in all-metal mesoscopic spin valves

NARCIS (Netherlands)

Jedema, FJ; Nijboer, MS; Filip, AT; van Wees, BJ

2003-01-01

We study the electrical injection and detection of spin accumulation in lateral ferromagnetic-metal-nonmagnetic-metal-ferromagnetic-metal (F/N/F) spin valve devices with transparent interfaces. Different ferromagnetic metals, Permalloy (Py), cobalt (Co), and nickel (Ni), are used as electrical spin

The susceptibilities in the spin-S Ising model

International Nuclear Information System (INIS)

Ainane, A.; Saber, M.

1995-08-01

The susceptibilities of the spin-S Ising model are evaluated using the effective field theory introduced by Tucker et al. for studying general spin-S Ising model. The susceptibilities are studied for all spin values from S = 1/2 to S = 5/2. (author). 12 refs, 4 figs

Maui Space Surveillance System Satellite Categorization Laboratory

Science.gov (United States)

Deiotte, R.; Guyote, M.; Kelecy, T.; Hall, D.; Africano, J.; Kervin, P.

The MSSS satellite categorization laboratory is a fusion of robotics and digital imaging processes that aims to decompose satellite photometric characteristics and behavior in a controlled setting. By combining a robot, light source and camera to acquire non-resolved images of a model satellite, detailed photometric analyses can be performed to extract relevant information about shape features, elemental makeup, and ultimately attitude and function. Using the laboratory setting a detailed analysis can be done on any type of material or design and the results cataloged in a database that will facilitate object identification by "curve-fitting" individual elements in the basis set to observational data that might otherwise be unidentifiable. Currently the laboratory has created, an ST-Robotics five degree of freedom robotic arm, collimated light source and non-focused Apogee camera have all been integrated into a MATLAB based software package that facilitates automatic data acquisition and analysis. Efforts to date have been aimed at construction of the lab as well as validation and verification of simple geometric objects. Simple tests on spheres, cubes and simple satellites show promising results that could lead to a much better understanding of non-resolvable space object characteristics. This paper presents a description of the laboratory configuration and validation test results with emphasis on the non-resolved photometric characteristics for a variety of object shapes, spin dynamics and orientations. The future vision, utility and benefits of the laboratory to the SSA community as a whole are also discussed.

Control of electron spin decoherence in nuclear spin baths

Science.gov (United States)

Liu, Ren-Bao

2011-03-01

Nuclear spin baths are a main mechanism of decoherence of spin qubits in solid-state systems, such as quantum dots and nitrogen-vacancy (NV) centers of diamond. The decoherence results from entanglement between the electron and nuclear spins, established by quantum evolution of the bath conditioned on the electron spin state. When the electron spin is flipped, the conditional bath evolution is manipulated. Such manipulation of bath through control of the electron spin not only leads to preservation of the center spin coherence but also demonstrates quantum nature of the bath. In an NV center system, the electron spin effectively interacts with hundreds of 13 C nuclear spins. Under repeated flip control (dynamical decoupling), the electron spin coherence can be preserved for a long time (> 1 ms) . Thereforesomecharacteristicoscillations , duetocouplingtoabonded 13 C nuclear spin pair (a dimer), are imprinted on the electron spin coherence profile, which are very sensitive to the position and orientation of the dimer. With such finger-print oscillations, a dimer can be uniquely identified. Thus, we propose magnetometry with single-nucleus sensitivity and atomic resolution, using NV center spin coherence to identify single molecules. Through the center spin coherence, we could also explore the many-body physics in an interacting spin bath. The information of elementary excitations and many-body correlations can be extracted from the center spin coherence under many-pulse dynamical decoupling control. Another application of the preserved spin coherence is identifying quantumness of a spin bath through the back-action of the electron spin to the bath. We show that the multiple transition of an NV center in a nuclear spin bath can have longer coherence time than the single transition does, when the classical noises due to inhomogeneous broadening is removed by spin echo. This counter-intuitive result unambiguously demonstrates the quantumness of the nuclear spin bath

The ETE spherical Tokamak project. IAEA report

Energy Technology Data Exchange (ETDEWEB)

Ludwig, Gerson Otto; Del Bosco, E.; Berni, L.A.; Ferreira, J.G.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Barroso, J.J.; Castro, P.J.; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma]. E-mail: ludwig@plasma.inpe.br

2002-07-01

This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the historical development of the ETE (Spherical Tokamak Experiment) project, its research program, technical characteristics and operating conditions as of October, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

Spherical solitons in Earth’S mesosphere plasma

International Nuclear Information System (INIS)

Annou, K.; Annou, R.

2016-01-01

Soliton formation in Earth’s mesosphere plasma is described. Nonlinear acoustic waves in plasmas with two-temperature ions and a variable dust charge where transverse perturbation is dealt with are studied in bounded spherical geometry. Using the perturbation method, a spherical Kadomtsev–Petviashvili equation that describes dust acoustic waves is derived. It is found that the parameters taken into account have significant effects on the properties of nonlinear waves in spherical geometry

Broadband VHF observations for lightning impulses from a small satellite SOHLA-1 (Maido 1)

Science.gov (United States)

Morimoto, T.; Kikuchi, H.; Ushio, T.; Kawasaki, Z.; Hidekazu, H.; Aoki, T.

2009-12-01

Lightning Research Group of Osaka University (LRG-OU) has been developing VHF Broadband Digital Interferometer (DITF) to image precise lightning channels and monitor lightning activity widely. The feature of broadband DITF is its ultrawide bandwidth (from 25MHz to 100MHz) and implicit redundancy for estimating VHF source location. LRG-OU considers an application of the broadband DITF to the spaceborne measurement system and joins the SOHLA (Space Oriented Higashi-Osaka Leading Associate) satellite project. The SOHLA satellite project represents a technology transfer program to expand the range of the space development community in Japan. The objective is to get SMEs (Small and Medium sized manufacturing Enterprises) involved in small space projects and new space technologies. Under the cooperative agreement, JAXA (Japan Aerospace Exploration Agency) intends to contribute to socio-economic development by returning its R&D results to society, and SOHLA tries to revitalize the local economy through the commercialization of versatile small satellites. According to the agreement, JAXA provides SOHLA its technical information on small satellites and other technical assistance for the development of the small satellites, SOHLA-1. The prime objective of the SOHLA-1 program is to realize low-cost and short term development of a microsatellite which utilizes the components and bus technologies of JAXA’s MicroLabSat. SOHLA-1 is a spin-stabilized microsatellite of MicroLabSat heritage (about 50 kg). The spin axis is fixed to inertial reference frame. The spin axis (z-axis) lies in the plane containing the solar direction and the normal to the orbital plane. LRG-OU takes responsibility for a science mission of SOHLA-1. To examine the feasibility of the DITF receiving VHF lightning impulses in space, LRG-OU proposes the BMW (Broadband Measurement of Waveform for VHF Lightning Impulses). BMW consists of a single pair of an antenna, a band-pass filter, an amplifier, and an

Magnetocaloric effect in quantum spin-s chains

Directory of Open Access Journals (Sweden)

A. Honecker

2009-01-01

Full Text Available We compute the entropy of antiferromagnetic quantum spin-s chains in an external magnetic field using exact diagonalization and Quantum Monte Carlo simulations. The magnetocaloric effect, i. e., temperature variations during adiabatic field changes, can be derived from the isentropes. First, we focus on the example of the spin-s=1 chain and show that one can cool by closing the Haldane gap with a magnetic field. We then move to quantum spin-s chains and demonstrate linear scaling with s close to the saturation field. In passing, we propose a new method to compute many low-lying excited states using the Lanczos recursion.

Graphene spin diode: Strain-modulated spin rectification

Energy Technology Data Exchange (ETDEWEB)

Wang, Yunhua; Wang, B., E-mail: stslyl@mail.sysu.edu.cn, E-mail: wangbiao@mail.sysu.edu.cn [Sino-French Institute of Nuclear Engineering and Technology, School of Physics and Engineering, State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-sen University, Guangzhou 510275 (China); Liu, Yulan, E-mail: stslyl@mail.sysu.edu.cn, E-mail: wangbiao@mail.sysu.edu.cn [School of Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

2014-08-04

Strain effects on spin transport in a ferromagnetic/strained/normal graphene junction are explored theoretically. It is shown that the spin-resolved Fermi energy range can be controlled by the armchair direction strain because the strain-induced pseudomagnetic field suppresses the current. The spin rectification effect for the bias reversal occurs because of a combination of ferromagnetic exchange splitting and the broken spatial symmetry of the junction. In addition, the spin rectification performance can be tuned remarkably by manipulation of the strains. In view of this strain-modulated spin rectification effect, we propose that the graphene-based ferromagnetic/strained/normal junction can be used as a tunable spin diode.

Spin Torques in Systems with Spin Filtering and Spin Orbit Interaction

KAUST Repository

Ortiz Pauyac, Christian

2016-01-01

filtering. In Chap. 3 we discuss the Rashba torque in ferromagnetic films, and in Chap. 4 we study spin Hall effect and spin swapping in ferromagnetic films, exploring the nature of spin-orbit torques based on these mechanisms. Conclusions and perspectives

Drones, quasi-spin or iso-spin. A comparison of many-body techniques for general spin

International Nuclear Information System (INIS)

McKenzie, B.J.; Stedman, G.E.

1976-01-01

For an effective-spin system with 2S + 1 levels there are a number of possible mappings of spin onto pseudo-fermion operators. The relative merits of three of these methods are investigated by calculating to second order the dispersion relation for coupled spin-phonon modes in crystals containing S = 1 effective spin impurities. It is found that the drone formalism quickly becomes intractable at higher spin values, as does the related quasi-spin formalism developed in contrast with the iso-spin (or Abrinkosov projection) formalism. (author)

Spin-current emission governed by nonlinear spin dynamics.

Science.gov (United States)

Tashiro, Takaharu; Matsuura, Saki; Nomura, Akiyo; Watanabe, Shun; Kang, Keehoon; Sirringhaus, Henning; Ando, Kazuya

2015-10-16

Coupling between conduction electrons and localized magnetization is responsible for a variety of phenomena in spintronic devices. This coupling enables to generate spin currents from dynamical magnetization. Due to the nonlinearity of magnetization dynamics, the spin-current emission through the dynamical spin-exchange coupling offers a route for nonlinear generation of spin currents. Here, we demonstrate spin-current emission governed by nonlinear magnetization dynamics in a metal/magnetic insulator bilayer. The spin-current emission from the magnetic insulator is probed by the inverse spin Hall effect, which demonstrates nontrivial temperature and excitation power dependences of the voltage generation. The experimental results reveal that nonlinear magnetization dynamics and enhanced spin-current emission due to magnon scatterings are triggered by decreasing temperature. This result illustrates the crucial role of the nonlinear magnon interactions in the spin-current emission driven by dynamical magnetization, or nonequilibrium magnons, from magnetic insulators.

Laplacian eigenmodes for spherical spaces

International Nuclear Information System (INIS)

Lachieze-Rey, M; Caillerie, S

2005-01-01

The possibility that our space is multi-rather than singly-connected has gained renewed interest after the discovery of the low power for the first multipoles of the CMB by WMAP. To test the possibility that our space is a multi-connected spherical space, it is necessary to know the eigenmodes of such spaces. Except for lens and prism space, and to some extent for dodecahedral space, this remains an open problem. Here we derive the eigenmodes of all spherical spaces. For dodecahedral space, the demonstration is much shorter, and the calculation method much simpler than before. We also apply our method to tetrahedric, octahedric and icosahedric spaces. This completes the knowledge of eigenmodes for spherical spaces, and opens the door to new observational tests of the cosmic topology. The vector space V k of the eigenfunctions of the Laplacian on the 3-sphere S 3 , corresponding to the same eigenvalue λ k = -k(k + 2), has dimension (k + 1) 2 . We show that the Wigner functions provide a basis for such a space. Using the properties of the latter, we express the behaviour of a general function of V k under an arbitrary rotation G of SO(4). This offers the possibility of selecting those functions of V k which remain invariant under G. Specifying G to be a generator of the holonomy group of a spherical space X, we give the expression of the vector space V x k of the eigenfunctions of X. We provide a method to calculate the eigenmodes up to an arbitrary order. As an illustration, we give the first modes for the spherical spaces mentioned

Spin Funneling for Enhanced Spin Injection into Ferromagnets

Science.gov (United States)

Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

2016-07-01

It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.

SPIN–SPIN COUPLING IN THE SOLAR SYSTEM

International Nuclear Information System (INIS)

Batygin, Konstantin; Morbidelli, Alessandro

2015-01-01

The richness of dynamical behavior exhibited by the rotational states of various solar system objects has driven significant advances in the theoretical understanding of their evolutionary histories. An important factor that determines whether a given object is prone to exhibiting non-trivial rotational evolution is the extent to which such an object can maintain a permanent aspheroidal shape, meaning that exotic behavior is far more common among the small body populations of the solar system. Gravitationally bound binary objects constitute a substantial fraction of asteroidal and TNO populations, comprising systems of triaxial satellites that orbit permanently deformed central bodies. In this work, we explore the rotational evolution of such systems with specific emphasis on quadrupole–quadrupole interactions, and show that for closely orbiting, highly deformed objects, both prograde and retrograde spin–spin resonances naturally arise. Subsequently, we derive capture probabilities for leading order commensurabilities and apply our results to the illustrative examples of (87) Sylvia and (216) Kleopatra asteroid systems. Cumulatively, our results suggest that spin–spin coupling may be consequential for highly elongated, tightly orbiting binary objects

SPIN–SPIN COUPLING IN THE SOLAR SYSTEM

Energy Technology Data Exchange (ETDEWEB)

Batygin, Konstantin [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Morbidelli, Alessandro, E-mail: kbatygin@gps.caltech.edu [Departement Lagrange, Observatoire de la Côte d’Azur, F-06304 Nice (France)

2015-09-10

The richness of dynamical behavior exhibited by the rotational states of various solar system objects has driven significant advances in the theoretical understanding of their evolutionary histories. An important factor that determines whether a given object is prone to exhibiting non-trivial rotational evolution is the extent to which such an object can maintain a permanent aspheroidal shape, meaning that exotic behavior is far more common among the small body populations of the solar system. Gravitationally bound binary objects constitute a substantial fraction of asteroidal and TNO populations, comprising systems of triaxial satellites that orbit permanently deformed central bodies. In this work, we explore the rotational evolution of such systems with specific emphasis on quadrupole–quadrupole interactions, and show that for closely orbiting, highly deformed objects, both prograde and retrograde spin–spin resonances naturally arise. Subsequently, we derive capture probabilities for leading order commensurabilities and apply our results to the illustrative examples of (87) Sylvia and (216) Kleopatra asteroid systems. Cumulatively, our results suggest that spin–spin coupling may be consequential for highly elongated, tightly orbiting binary objects.

Low-Q Electrically Small Spherical Magnetic Dipole Antennas

DEFF Research Database (Denmark)

Kim, Oleksiy S.

2010-01-01

Three novel electrically small antenna configurations radiating a TE10 spherical mode corresponding to a magnetic dipole are presented and investigated: multiarm spherical helix (MSH) antenna, spherical split ring resonator (S-SRR) antenna, and spherical split ring (SSR) antenna. All three antennas...... are self-resonant, with the input resistance tuned to 50 ohms by an excitation curved dipole/monopole. A prototype of the SSR antenna has been fabricated and measured, yielding results that are consistent with the numerical simulations. Radiation quality factors (Q) of these electrically small antennas (in...

FY 2006 Miniature Spherical Retroreflectors Final Report

Energy Technology Data Exchange (ETDEWEB)

Anheier, Norman C.; Bernacki, Bruce E.; Krishnaswami, Kannan

2006-12-28

Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniature spherical retroreflectors using the unique optical and material properties of chalcogenide glass to reduce both performance limiting spherical aberrations. The optimized optical performance will provide efficient signal retroreflection that enables a broad range of remote detection scenarios for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications. Miniature spherical retroreflectors can be developed to aid in the detection of signatures of nuclear proliferation or other chemical vapor or radiation signatures. Miniature spherical retroreflectors are not only well suited to traditional LIDAR methods for chemical plume detection and identification, but could enable remote detection of difficult semi-volatile chemical materials or low level radiation sources.

Spin nematics next to spin singlets

Science.gov (United States)

Yokoyama, Yuto; Hotta, Chisa

2018-05-01

We provide a route to generate nematic order in a spin-1/2 system. Unlike the well-known magnon-binding mechanism, our spin nematics requires neither the frustration effect nor spin polarization in a high field or in the vicinity of a ferromagnet, but instead appears next to the spin singlet phase. We start from a state consisting of a quantum spin-1/2 singlet dimer placed on each site of a triangular lattice, and show that interdimer ring exchange interactions efficiently dope the SU(2) triplets that itinerate and interact, easily driving a stable singlet state to either Bose-Einstein condensates or a triplet crystal, some hosting a spin nematic order. A variety of roles the ring exchange serves includes the generation of a bilinear-biquadratic interaction between nearby triplets, which is responsible for the emergent nematic order separated from the singlet phase by a first-order transition.

Spin distribution of evaporation residues formed in complete and incomplete fusion in 16O+154Sm system

Science.gov (United States)

Singh, D.; Linda, Sneha B.; Giri, Pankaj K.; Mahato, Amritraj; Tripathi, R.; Kumar, Harish; Afzal Ansari, M.; Sathik, N. P. M.; Ali, Rahbar; Kumar, Rakesh; Muralithar, S.; Singh, R. P.

2017-11-01

Spin distributions for several evaporation residues populated in the 16O+154Sm system have been measured at projectile energy ≈ 6.2 MeV/A by using the charged particle-γ-coincidence technique. The measured spin distributions of the evaporation residues populated through incomplete fusion associated with 'fast' α and 2α-emission channels are found to be entirely different from fusion-evaporation channels. It is observed that the mean input angular momentum for the evaporation residues formed in incomplete fusion channel is relatively higher than that observed for evaporation residues in complete fusion channels. The feeding intensity profile of evaporation residues populated through complete fusion and incomplete fusion have also been studied. The incomplete fusion channels are found to have narrow range feeding only for high spin states, while complete fusion channels are strongly fed over a broad spin range and widely populated. Comparison of present results with earlier data suggests that the mean input angular momentum values are relatively smaller for spherical target than that of deformed target using the same projectile and incident energy highlighting the role of target deformation in incomplete fusion dynamics.

Spin distribution of evaporation residues formed in complete and incomplete fusion in 16O+154Sm system

Directory of Open Access Journals (Sweden)

D. Singh

2017-11-01

Full Text Available Spin distributions for several evaporation residues populated in the 16O+154Sm system have been measured at projectile energy ≈ 6.2 MeV/A by using the charged particle–γ-coincidence technique. The measured spin distributions of the evaporation residues populated through incomplete fusion associated with ‘fast’ α and 2α-emission channels are found to be entirely different from fusion–evaporation channels. It is observed that the mean input angular momentum for the evaporation residues formed in incomplete fusion channel is relatively higher than that observed for evaporation residues in complete fusion channels. The feeding intensity profile of evaporation residues populated through complete fusion and incomplete fusion have also been studied. The incomplete fusion channels are found to have narrow range feeding only for high spin states, while complete fusion channels are strongly fed over a broad spin range and widely populated. Comparison of present results with earlier data suggests that the mean input angular momentum values are relatively smaller for spherical target than that of deformed target using the same projectile and incident energy highlighting the role of target deformation in incomplete fusion dynamics.

Effect of Ionosphere on Geostationary Communication Satellite Signals

Science.gov (United States)

Erdem, Esra; Arikan, Feza; Gulgonul, Senol

2016-07-01

Geostationary orbit (GEO) communications satellites allow radio, television, and telephone transmissions to be sent live anywhere in the world. They are extremely important in daily life and also for military applications. Since, satellite communication is an expensive technology addressing crowd of people, it is critical to improve the performance of this technology. GEO satellites are at 35,786 kilometres from Earth's surface situated directly over the equator. A satellite in a geostationary orbit (GEO) appears to stand still in the sky, in a fixed position with respect to an observer on the earth, because the satellite's orbital period is the same as the rotation rate of the Earth. The advantage of this orbit is that ground antennas can be fixed to point towards to satellite without their having to track the satellite's motion. Radio frequency ranges used in satellite communications are C, X, Ku, Ka and even EHG and V-band. Satellite signals are disturbed by atmospheric effects on the path between the satellite and the receiver antenna. These effects are mostly rain, cloud and gaseous attenuation. It is expected that ionosphere has a minor effect on the satellite signals when the ionosphere is quiet. But there are anomalies and perturbations on the structure of ionosphere with respect to geomagnetic field and solar activity and these conditions may cause further affects on the satellite signals. In this study IONOLAB-RAY algorithm is adopted to examine the effect of ionosphere on satellite signals. IONOLAB-RAY is developed to calculate propagation path and characteristics of high frequency signals. The algorithm does not have any frequency limitation and models the plasmasphere up to 20,200 km altitude, so that propagation between a GEO satellite and antenna on Earth can be simulated. The algorithm models inhomogeneous, anisotropic and time dependent structure of the ionosphere with a 3-D spherical grid geometry and calculates physical parameters of the

A spherical Taylor-Couette dynamo

Science.gov (United States)

Marcotte, Florence; Gissinger, Christophe

2016-04-01

We present a new scenario for magnetic field amplification in the planetary interiors where an electrically conducting fluid is confined in a differentially rotating, spherical shell (spherical Couette flow) with thin aspect-ratio. When the angular momentum sufficiently decreases outwards, a primary hydrodynamic instability is widely known to develop in the equatorial region, characterized by pairs of counter-rotating, axisymmetric toroidal vortices (Taylor vortices) similar to those observed in cylindrical Couette flow. We characterize the subcritical dynamo bifurcation due to this spherical Taylor-Couette flow and study its evolution as the flow successively breaks into wavy and turbulent Taylor vortices for increasing Reynolds number. We show that the critical magnetic Reynolds number seems to reach a constant value as the Reynolds number is gradually increased. The role of global rotation on the dynamo threshold and the implications for planetary interiors are finally discussed.

Spherical tokamak development in Brazil

International Nuclear Information System (INIS)

Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J.; Barbosa, L.F.W.; Patire Junior, H.; The high-power microwave sources group

2003-01-01

This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

Miniaturization of Spherical Magnetodielectric Antennas

DEFF Research Database (Denmark)

Hansen, Troels Vejle

; Arbitrary order of the spherical wave, arbitrary radius of the spherical antenna, as well as arbitrarily large core permeability and/or permittivity, given an inversely proportional frequency variation of the imaginary part(s) and an arbitrary dispersion of the real part(s) - thus describing both lossless...... with a magnetic loss tangent of 1 and relative permeability of 300 yield Q/e equal 65% of the Chu lower bound, with a simultaneous e of 71%....

Spherical tokamak development in Brazil

Energy Technology Data Exchange (ETDEWEB)

Ludwig, G.O.; Del Bosco, E.; Ferreira, J.G.; Berni, L.A.; Oliveira, R.M.; Andrade, M.C.R.; Shibata, C.S.; Ueda, M.; Barroso, J.J.; Castro, P.J. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Lab. Associado de Plasma; Barbosa, L.F.W. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil). Faculdade de Engenharia, Arquitetura e Urbanismo; Patire Junior, H. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil). Div. de Mecanica Espacial e Controle; The high-power microwave sources group

2003-12-01

This paper describes the general characteristics of spherical tokamaks, or spherical tori, with a brief overview of work in this area already performed or in progress at several institutions worldwide. The paper presents also the steps in the development of the ETE (Experimento Tokamak Esferico) project, its research program, technical characteristics and operating conditions as of December, 2002 at the Associated Plasma Laboratory (LAP) of the National Space Research Institute (INPE) in Brazil. (author)

Spectral combination of spherical gravitational curvature boundary-value problems

Science.gov (United States)

PitoÅák, Martin; Eshagh, Mehdi; Šprlák, Michal; Tenzer, Robert; Novák, Pavel

2018-04-01

Four solutions of the spherical gravitational curvature boundary-value problems can be exploited for the determination of the Earth's gravitational potential. In this article we discuss the combination of simulated satellite gravitational curvatures, i.e., components of the third-order gravitational tensor, by merging these solutions using the spectral combination method. For this purpose, integral estimators of biased- and unbiased-types are derived. In numerical studies, we investigate the performance of the developed mathematical models for the gravitational field modelling in the area of Central Europe based on simulated satellite measurements. Firstly, we verify the correctness of the integral estimators for the spectral downward continuation by a closed-loop test. Estimated errors of the combined solution are about eight orders smaller than those from the individual solutions. Secondly, we perform a numerical experiment by considering the Gaussian noise with the standard deviation of 6.5× 10-17 m-1s-2 in the input data at the satellite altitude of 250 km above the mean Earth sphere. This value of standard deviation is equivalent to a signal-to-noise ratio of 10. Superior results with respect to the global geopotential model TIM-r5 are obtained by the spectral downward continuation of the vertical-vertical-vertical component with the standard deviation of 2.104 m2s-2, but the root mean square error is the largest and reaches 9.734 m2s-2. Using the spectral combination of all gravitational curvatures the root mean square error is more than 400 times smaller but the standard deviation reaches 17.234 m2s-2. The combination of more components decreases the root mean square error of the corresponding solutions while the standard deviations of the combined solutions do not improve as compared to the solution from the vertical-vertical-vertical component. The presented method represents a weight mean in the spectral domain that minimizes the root mean square error

Non magnetic neutron spin quantum precession using multilayer spin splitter and a phase-spin echo interferometer

Energy Technology Data Exchange (ETDEWEB)

Ebisawa, T.; Tasaki, S.; Kawai, T.; Akiyoshi, T. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Achiwa, N.; Hino, M.; Otake, Y.; Funahashi, H.

1996-08-01

The authors have developed cold neutron optics and interferometry using multilayer mirrors. The advantages of the multilayer mirrors are their applicability to long wavelength neutrons and a great variety of the mirror performance. The idea of the present spin interferometry is based on nonmagnetic neutron spin quantum precession using multilayer spin splitters. The equation for polarized neutrons means that the polarized neutrons are equivalent to the coherent superposition of two parallel spin eigenstates. The structure and principle of a multilayer spin splitter are explained, and the nonmagnetic gap layer of the multilayer spin splitter gives rise to neutron spin quantum precession. The performance test of the multilayer spin splitter were made with a new spin interferometer, which is analogous optically to a spin echo system with vertical precession field. The spin interferometers were installed at Kyoto University research reactor and the JRR-3. The testing method and the results are reported. The performance tests on a new phase-spin echo interferometer are described, and its applications to the development of a high resolution spin echo system and a Jamin type cold neutron interferometer are proposed. (K.I.)

Unified treatment of complete orthonormal sets for wave functions, and Slater orbitals of particles with arbitrary spin in coordinate, momentum and four-dimensional spaces

International Nuclear Information System (INIS)

Guseinov, I.I.

2007-01-01

The new analytical relations of complete orthonormal sets for the tensor wave functions and the tensor Slater orbitals of particles with arbitrary spin in coordinate, momentum and four-dimensional spaces are derived using the properties of tensor spherical harmonics and complete orthonormal scalar basis sets of ψ α -exponential type orbitals, φ α -momentum space orbitals and z α -hyperspherical harmonics introduced by the author for particles with spin s=0, where the α=1,0,-1,-2,.... All of the tensor wave functions obtained are complete without the inclusion of the continuum and, therefore, their group of transformations is the four-dimensional rotation group O(4). The analytical formulas in coordinate space are also derived for the overlap integrals over tensor Slater orbitals with the same screening constant. We notice that the new idea presented in this work is the combination of tensor spherical harmonics of rank s with complete orthonormal scalar sets for radial parts of ψ α -, φ α - and z α -orbitals, where s=1/2,1,3/2,2,...

Spin current through quantum-dot spin valves

International Nuclear Information System (INIS)

Wang, J; Xing, D Y

2006-01-01

We report a theoretical study of the influence of the Coulomb interaction on the equilibrium spin current in a quantum-dot spin valve, in which the quantum dot described by the Anderson impurity model is coupled to two ferromagnetic leads with noncollinear magnetizations. In the Kondo regime, electrons transmit through the quantum dot via higher-order virtual processes, in which the spin of either lead electrons or a localized electron on the quantum dot may reverse. It is found that the magnitude of the spin current decreases with increasing Coulomb interactions due to spin flip effects on the dot. However, the spatial direction of the spin current remains unchanged; it is determined only by the exchange coupling between two noncollinear magnetizations

Turbulence Modulation by Non-Spherical Particles

DEFF Research Database (Denmark)

Mandø, Matthias

This study deals with the interaction between turbulence and non-spherical particles and represents an extension of the modeling framework for particleladen flows. The effect of turbulence on particles is commonly referred to as turbulent dispersion while the effect of particles on the carrier....... This study encompass an outlook on existing work, an experimental study, development of a numerical model and a case study advancing the modeling techniques for pulverized coal combustion to deal with larger non-spherical biomass particles. Firstly, existing knowledge concerning the motion of non......-spherical particles and turbulence modulation are outlined. A complete description of the motion of non-spherical particles is still lacking. However, evidence suggests that the equation of motion for a sphere only represent an asymptotical value for a more general, but yet unformulated, description of the motion...

Transformation of Real Spherical Harmonics under Rotations

Science.gov (United States)

Romanowski, Z.; Krukowski, St.; Jalbout, A. F.

2008-08-01

The algorithm rotating the real spherical harmonics is presented. The convenient and ready to use formulae for l = 0, 1, 2, 3 are listed. The rotation in R3 space is determined by the rotation axis and the rotation angle; the Euler angles are not used. The proposed algorithm consists of three steps. (i) Express the real spherical harmonics as the linear combination of canonical polynomials. (ii) Rotate the canonical polynomials. (iii) Express the rotated canonical polynomials as the linear combination of real spherical harmonics. Since the three step procedure can be treated as a superposition of rotations, the searched rotation matrix for real spherical harmonics is a product of three matrices. The explicit formulae of matrix elements are given for l = 0, 1, 2, 3, what corresponds to s, p, d, f atomic orbitals.

Compound nucleus effects in spin-spin cross sections

International Nuclear Information System (INIS)

Thompson, W.J.

1976-01-01

By comparison with recent data, it is shown that spin-spin cross sections for low-energy neutrons may be dominated by a simple compound-elastic level-density effect, independent of spin-spin terms in the nucleon-nucleus optical-model potential. (Auth.)

A method that reveals the multi-level ultrametric tree hidden in p -spin-glass-like systems

International Nuclear Information System (INIS)

Baviera, R; Virasoro, M A

2015-01-01

In the study of disordered models like spin glasses the key object of interest is the rugged energy hypersurface defined in configuration space. The statistical mechanics calculation of the Gibbs–Boltzmann partition function gives the information necessary to understand the equilibrium behavior of the system as a function of the temperature but is not enough if we are interested in the more general aspects of the hypersurface: it does not give us, for instance, the different degrees of ruggedness at different scales. In the context of the replica symmetry breaking (RSB) approach we discuss here a rather simple extension that can provide a much more detailed picture. The attractiveness of the method relies on the fact that it is conceptually transparent and the additional calculations are rather straightforward. We think that this approach reveals an ultrametric organisation with many levels in models like p-spin glasses when we include saddle points. In this first paper we present detailed calculations for the spherical p-spin glass model where we discover that the corresponding decreasing Parisi function q(x) codes this hidden ultrametric organisation. (paper)

TEST BED FOR THE SIMULATION OF MAGNETIC FIELD MEASUREMENTS OF LOW EARTH ORBIT SATELLITES

Directory of Open Access Journals (Sweden)

Alberto Gallina

2018-03-01

Full Text Available The paper presents a test bed designed to simulate magnetic environment experienced by a spacecraft on low Earth orbit. It consists of a spherical air bearing located inside a Helmholtz cage. The spherical air bearing is used for simulating microgravity conditions of orbiting bodies while the Helmholtz cage generates a controllable magnetic field resembling the one surrounding a satellite during its motion. Dedicated computer software is used to initially calculate the magnetic field on an established orbit. The magnetic field data is then translated into current values and transmitted to programmable power supplies energizing the cage. The magnetic field within the cage is finally measured by a test article mounted on the air bearing. The paper provides a description of the test bed and the test article design. An experimental test proves the good performance of the entire system.

Evaluation of spacecraft technology programs (effects on communication satellite business ventures), volume 1

Science.gov (United States)

Greenburg, J. S.; Gaelick, C.; Kaplan, M.; Fishman, J.; Hopkins, C.

1985-01-01

Commercial organizations as well as government agencies invest in spacecraft (S/C) technology programs that are aimed at increasing the performance of communications satellites. The value of these programs must be measured in terms of their impacts on the financial performane of the business ventures that may ultimately utilize the communications satellites. An economic evaluation and planning capability was developed and used to assess the impact of NASA on-orbit propulsion and space power programs on typical fixed satellite service (FSS) and direct broadcast service (DBS) communications satellite business ventures. Typical FSS and DBS spin and three-axis stabilized spacecraft were configured in the absence of NASA technology programs. These spacecraft were reconfigured taking into account the anticipated results of NASA specified on-orbit propulsion and space power programs. In general, the NASA technology programs resulted in spacecraft with increased capability. The developed methodology for assessing the value of spacecraft technology programs in terms of their impact on the financial performance of communication satellite business ventures is described. Results of the assessment of NASA specified on-orbit propulsion and space power technology programs are presented for typical FSS and DBS business ventures.

Dynamics of a spherical minority game

International Nuclear Information System (INIS)

Galla, T; Coolen, A C C; Sherrington, D

2003-01-01

We present an exact dynamical solution of a spherical version of the batch minority game (MG) with random external information. The control parameters in this model are the ratio of the number of possible values for the public information over the number of agents, and the radius of the spherical constraint on the microscopic degrees of freedom. We find a phase diagram with three phases: two without anomalous response (an oscillating versus a frozen state) and a further frozen phase with divergent integrated response. In contrast to standard MG versions, we can also calculate the volatility exactly. Our study reveals similarities between the spherical and the conventional MG, but also intriguing differences. Numerical simulations confirm our analytical results

Investigation of spherical and concentric mechanism of compound droplets

Directory of Open Access Journals (Sweden)

Meifang Liu

2016-07-01

Full Text Available Polymer shells with high sphericity and uniform wall thickness are always needed in the inertial confined fusion (ICF experiments. Driven by the need to control the shape of water-in-oil (W1/O compound droplets, the effects of the density matching level, the interfacial tension and the rotation speed of the continuing fluid field on the sphericity and wall thickness uniformity of the resulting polymer shells were investigated and the spherical and concentric mechanisms were also discussed. The centering of W1/O compound droplets, the location and movement of W1/O compound droplets in the external phase (W2 were significantly affected by the density matching level of the key stage and the rotation speed of the continuing fluid field. Therefore, by optimizing the density matching level and rotation speed, the batch yield of polystyrene (PS shells with high sphericity and uniform wall thickness increased. Moreover, the sphericity also increased by raising the oil/water (O/W2 interfacial tension, which drove a droplet to be spherical. The experimental results show that the spherical driving force is from the interfacial tension affected by the two relative phases, while the concentric driving force, as a resultant force, is not only affected by the three phases, but also by the continuing fluid field. The understanding of spherical and concentric mechanism can provide some guidance for preparing polymer shells with high sphericity and uniform wall thickness.

New bands and spin-parity assignments in 111Ru

International Nuclear Information System (INIS)

Urban, W.; Rzaca-Urban, T.; Droste, C.; Rohozinski, S.G.; Durell, J.L.; Phillips, W.R.; Smith, A.G.; Varley, B.J.; Schulz, N.; Ahmad, I.; Pinston, J.A.

2004-01-01

The 111 Ru nucleus, populated in the spontaneous fission of 248 Cm has been studied by means of prompt gamma spectroscopy using the EUROGAM2 array. Spin and parity assignments, based on angular correlations, linear polarization, and conversion coefficient measurements differ from those available in the literature. New bands are reported, which incorporate γ transitions seen previously but not placed in the scheme of 111 Ru or placed incorrectly. The bands are interpreted as neutron excitations into subshells originating predominantly from the h 11/2 , g 7/2 and s 1/2 spherical orbitals. The s 1/2 band, strongly mixed with the d 3/2 , d 5/2 and g 7/2 configurations, is observed for the first time in this region. (orig.)

Optical spin generation/detection and spin transport lifetimes

International Nuclear Information System (INIS)

Miah, M. Idrish

2011-01-01

We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.

Optical spin generation/detection and spin transport lifetimes

Energy Technology Data Exchange (ETDEWEB)

Miah, M. Idrish, E-mail: m.miah@griffith.edu.au [Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)

2011-02-25

We generate electron spins in semiconductors by optical pumping. The detection of them is also performed by optical technique using time-resolved pump-probe photoluminescence polarization measurements in the presence of an external magnetic field perpendicular to the generated spin. The spin polarization in dependences of the pulse length, pump-probe delay and external magnetic field is studied. From the dependence of spin-polarization on the delay of the probe, the electronic spin transport lifetimes and the spin relaxation frequencies as a function of the strength of the magnetic field are estimated. The results are discussed based on hyperfine effects for interacting electrons.

How Spherical Is a Cube (Gravitationally)?

Science.gov (United States)

Sanny, Jeff; Smith, David

2015-01-01

An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center. By integrating over ring elements of a spherical shell, we show that the…

Spherical cows in dark matter indirect detection

Energy Technology Data Exchange (ETDEWEB)

Bernal, Nicolás [Centro de Investigaciones, Universidad Antonio Nariño, Cra 3 Este # 47A-15, Bogotá (Colombia); Necib, Lina; Slatyer, Tracy R., E-mail: nicolas.bernal@uan.edu.co, E-mail: lnecib@mit.edu, E-mail: tslatyer@mit.edu [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2016-12-01

Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated well outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.

Angular dependence of spin-orbit spin-transfer torques

KAUST Repository

Lee, Ki-Seung

2015-04-06

In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.

Angular dependence of spin-orbit spin-transfer torques

KAUST Repository

Lee, Ki-Seung; Go, Dongwook; Manchon, Aurelien; Haney, Paul M.; Stiles, M. D.; Lee, Hyun-Woo; Lee, Kyung-Jin

2015-01-01

In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.

On the spin-axis dynamics of a Moonless Earth

Energy Technology Data Exchange (ETDEWEB)

Li, Gongjie; Batygin, Konstantin, E-mail: gli@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, The Institute for Theory and Computation, 60 Garden Street, Cambridge, MA 02138 (United States)

2014-07-20

The variation of a planet's obliquity is influenced by the existence of satellites with a high mass ratio. For instance, Earth's obliquity is stabilized by the Moon and would undergo chaotic variations in the Moon's absence. In turn, such variations can lead to large-scale changes in the atmospheric circulation, rendering spin-axis dynamics a central issue for understanding climate. The relevant quantity for dynamically forced climate change is the rate of chaotic diffusion. Accordingly, here we re-examine the spin-axis evolution of a Moonless Earth within the context of a simplified perturbative framework. We present analytical estimates of the characteristic Lyapunov coefficient as well as the chaotic diffusion rate and demonstrate that even in absence of the Moon, the stochastic change in Earth's obliquity is sufficiently slow to not preclude long-term habitability. Our calculations are consistent with published numerical experiments and illustrate the putative system's underlying dynamical structure in a simple and intuitive manner.

Satellites

International Nuclear Information System (INIS)

Burns, J.A.; Matthews, M.S.

1986-01-01

The present work is based on a conference: Natural Satellites, Colloquium 77 of the IAU, held at Cornell University from July 5 to 9, 1983. Attention is given to the background and origins of satellites, protosatellite swarms, the tectonics of icy satellites, the physical characteristics of satellite surfaces, and the interactions of planetary magnetospheres with icy satellite surfaces. Other topics include the surface composition of natural satellites, the cratering of planetary satellites, the moon, Io, and Europa. Consideration is also given to Ganymede and Callisto, the satellites of Saturn, small satellites, satellites of Uranus and Neptune, and the Pluto-Charon system

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

Energy Technology Data Exchange (ETDEWEB)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

2015-05-07

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

Science.gov (United States)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

2015-05-01

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

International Nuclear Information System (INIS)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

2015-01-01

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems

Noise in tunneling spin current across coupled quantum spin chains

Science.gov (United States)

Aftergood, Joshua; Takei, So

2018-01-01

We theoretically study the spin current and its dc noise generated between two spin-1 /2 spin chains weakly coupled at a single site in the presence of an over-population of spin excitations and a temperature elevation in one subsystem relative to the other, and we compare the corresponding transport quantities across two weakly coupled magnetic insulators hosting magnons. In the spin chain scenario, we find that applying a temperature bias exclusively leads to a vanishing spin current and a concomitant divergence in the spin Fano factor, defined as the spin current noise-to-signal ratio. This divergence is shown to have an exact analogy to the physics of electron scattering between fractional quantum Hall edge states and not to arise in the magnon scenario. We also reveal a suppression in the spin current noise that exclusively arises in the spin chain scenario due to the fermion nature of the spin-1/2 operators. We discuss how the spin Fano factor may be extracted experimentally via the inverse spin Hall effect used extensively in spintronics.

When measured spin polarization is not spin polarization

International Nuclear Information System (INIS)

Dowben, P A; Wu Ning; Binek, Christian

2011-01-01

Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO 2 and Cr 2 O 3 illustrate some of the complications which hinders comparisons of spin polarization values. (viewpoint)

Magnetic Nanostructures Spin Dynamics and Spin Transport

CERN Document Server

Farle, Michael

2013-01-01

Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.

Definition of multipath/RFI experiments for orbital testing with a small applications technology satellite

Science.gov (United States)

Birch, J. N.; French, R. H.

1972-01-01

An investigation was made to define experiments for collection of RFI and multipath data for application to a synchronous relay satellite/low orbiting satellite configuration. A survey of analytical models of the multipath signal was conducted. Data has been gathered concerning the existing RFI and other noise sources in various bands at VHF and UHF. Additionally, designs are presented for equipment to combat the effects of RFI and multipath: an adaptive delta mod voice system, a forward error control coder/decoder, a PN transmission system, and a wideband FM system. The performance of these systems was then evaluated. Techniques are discussed for measuring multipath and RFI. Finally, recommended data collection experiments are presented. An extensive tabulation is included of theoretical predictions of the amount of signal reflected from a rough, spherical earth.

New high spin states and isomers in the {sup 208}Pb and {sup 207}Pb nuclei

Energy Technology Data Exchange (ETDEWEB)

Broda, R.; Wrzesinski, J.; Pawlat, T. [and others

1996-12-31

The two most prominent examples of the heavy doubly closed shell (DCS) nuclei, {sup 208}Pb and {sup 132}Sn, are not accessible by conventional heavy-ion fusion processes populating high-spin states. This experimental difficulty obscured for a long time the investigation of yrast high-spin states in both DCS and neighboring nuclei and consequently restricted the study of the shell model in its most attractive regions. Recent technical development of multidetector gamma arrays opened new ways to exploit more complex nuclear processes which populate the nuclei of interest with suitable yields for gamma spectroscopy and involve population of moderately high spin states. This new possibility extended the range of accessible spin values and is a promising way to reach new yrast states. Some of these states are expected to be of high configurational purity and can be a source of important shell model parameters which possibly can be used later to check the validity of the spherical shell model description at yet higher spin and higher excitation energy. The nuclei in the closest vicinity of {sup 132}Sn are produced in spontaneous fission and states with spin values up to I=14 can be reached in fission gamma spectroscopy studies with the presently achieved sensitivity of gamma arrays. New results on yrast states in the {sup 134}Te and {sup 135}I nuclei populated in fission of the {sup 248}Cm presented at this conference illustrate such application of the resolving power offered by modern gamma techniques.

Spin Relaxation and Manipulation in Spin-orbit Qubits

Science.gov (United States)

Borhani, Massoud; Hu, Xuedong

2012-02-01

We derive a generalized form of the Electric Dipole Spin Resonance (EDSR) Hamiltonian in the presence of the spin-orbit interaction for single spins in an elliptic quantum dot (QD) subject to an arbitrary (in both direction and magnitude) applied magnetic field. We predict a nonlinear behavior of the Rabi frequency as a function of the magnetic field for sufficiently large Zeeman energies, and present a microscopic expression for the anisotropic electron g-tensor. Similarly, an EDSR Hamiltonian is devised for two spins confined in a double quantum dot (DQD). Finally, we calculate two-electron-spin relaxation rates due to phonon emission, for both in-plane and perpendicular magnetic fields. Our results have immediate applications to current EDSR experiments on nanowire QDs, g-factor optimization of confined carriers, and spin decay measurements in DQD spin-orbit qubits.

Nonlinear spin current generation in noncentrosymmetric spin-orbit coupled systems

Science.gov (United States)

Hamamoto, Keita; Ezawa, Motohiko; Kim, Kun Woo; Morimoto, Takahiro; Nagaosa, Naoto

2017-06-01

Spin current plays a central role in spintronics. In particular, finding more efficient ways to generate spin current has been an important issue and has been studied actively. For example, representative methods of spin-current generation include spin-polarized current injections from ferromagnetic metals, the spin Hall effect, and the spin battery. Here, we theoretically propose a mechanism of spin-current generation based on nonlinear phenomena. By using Boltzmann transport theory, we show that a simple application of the electric field E induces spin current proportional to E2 in noncentrosymmetric spin-orbit coupled systems. We demonstrate that the nonlinear spin current of the proposed mechanism is supported in the surface state of three-dimensional topological insulators and two-dimensional semiconductors with the Rashba and/or Dresselhaus interaction. In the latter case, the angular dependence of the nonlinear spin current can be manipulated by the direction of the electric field and by the ratio of the Rashba and Dresselhaus interactions. We find that the magnitude of the spin current largely exceeds those in the previous methods for a reasonable magnitude of the electric field. Furthermore, we show that application of ac electric fields (e.g., terahertz light) leads to the rectifying effect of the spin current, where dc spin current is generated. These findings will pave a route to manipulate the spin current in noncentrosymmetric crystals.

Spin temperature concept verified by optical magnetometry of nuclear spins

Science.gov (United States)

Vladimirova, M.; Cronenberger, S.; Scalbert, D.; Ryzhov, I. I.; Zapasskii, V. S.; Kozlov, G. G.; Lemaître, A.; Kavokin, K. V.

2018-01-01

We develop a method of nonperturbative optical control over adiabatic remagnetization of the nuclear spin system and apply it to verify the spin temperature concept in GaAs microcavities. The nuclear spin system is shown to exactly follow the predictions of the spin temperature theory, despite the quadrupole interaction that was earlier reported to disrupt nuclear spin thermalization. These findings open a way for the deep cooling of nuclear spins in semiconductor structures, with the prospect of realizing nuclear spin-ordered states for high-fidelity spin-photon interfaces.

Theory and applications of spherical microphone array processing

CERN Document Server

Jarrett, Daniel P; Naylor, Patrick A

2017-01-01

This book presents the signal processing algorithms that have been developed to process the signals acquired by a spherical microphone array. Spherical microphone arrays can be used to capture the sound field in three dimensions and have received significant interest from researchers and audio engineers. Algorithms for spherical array processing are different to corresponding algorithms already known in the literature of linear and planar arrays because the spherical geometry can be exploited to great beneficial effect. The authors aim to advance the field of spherical array processing by helping those new to the field to study it efficiently and from a single source, as well as by offering a way for more experienced researchers and engineers to consolidate their understanding, adding either or both of breadth and depth. The level of the presentation corresponds to graduate studies at MSc and PhD level. This book begins with a presentation of some of the essential mathematical and physical theory relevant to ...

Spin-Mechatronics

Science.gov (United States)

Matsuo, Mamoru; Saitoh, Eiji; Maekawa, Sadamichi

2017-01-01

We investigate the interconversion phenomena between spin and mechanical angular momentum in moving objects. In particular, the recent results on spin manipulation and spin-current generation by mechanical motion are examined. In accelerating systems, spin-dependent gauge fields emerge, which enable the conversion from mechanical angular momentum into spins. Such a spin-mechanical effect is predicted by quantum theory in a non-inertial frame. Experiments which confirm the effect, i.e., the resonance frequency shift in nuclear magnetic resonance, the stray field measurement of rotating metals, and electric voltage generation in liquid metals, are discussed.

Electron spin and nuclear spin manipulation in semiconductor nanosystems

International Nuclear Information System (INIS)

Hirayama, Yoshiro; Yusa, Go; Sasaki, Satoshi

2006-01-01

Manipulations of electron spin and nuclear spin have been studied in AlGaAs/GaAs semiconductor nanosystems. Non-local manipulation of electron spins has been realized by using the correlation effect between localized and mobile electron spins in a quantum dot- quantum wire coupled system. Interaction between electron and nuclear spins was exploited to achieve a coherent control of nuclear spins in a semiconductor point contact device. Using this device, we have demonstrated a fully coherent manipulation of any two states among the four spin levels of Ga and As nuclei. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Bulk electron spin polarization generated by the spin Hall current

OpenAIRE

Korenev, V. L.

2005-01-01

It is shown that the spin Hall current generates a non-equilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known equilibrium polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

Bulk electron spin polarization generated by the spin Hall current

Science.gov (United States)

Korenev, V. L.

2006-07-01

It is shown that the spin Hall current generates a nonequilibrium spin polarization in the interior of crystals with reduced symmetry in a way that is drastically different from the previously well-known “equilibrium” polarization during the spin relaxation process. The steady state spin polarization value does not depend on the strength of spin-orbit interaction offering possibility to generate relatively high spin polarization even in the case of weak spin-orbit coupling.

Non-Spherical Gravitational Collapse of Strange Quark Matter

Institute of Scientific and Technical Information of China (English)

Zade S S; Patil K D; Mulkalwar P N

2008-01-01

We study the non-spherical gravitational collapse of the strange quark null fluid.The interesting feature which emerges is that the non-spherical collapse of charged strange quark matter leads to a naked singularity whereas the gravitational collapse of neutral quark matter proceeds to form a black hole.We extend the earlier work of Harko and Cheng[Phys.Lett.A 266 (2000) 249]to the non-spherical case.

On the phase diagram of non-spherical nanoparticles

CERN Document Server

Wautelet, M; Hecq, M

2003-01-01

The phase diagram of nanoparticles is known to be a function of their size. In the literature, this is generally demonstrated for cases where their shape is spherical. Here, it is shown theoretically that the phase diagram of non-spherical particles may be calculated from the spherical case, at the same surface area/volume ratio, both with and without surface segregation, provided the surface tension is considered to be isotropic.

Measurement of quasi-static and low frequency electric fields on the Viking satellite

International Nuclear Information System (INIS)

Block, L.P.; Faelthammar, C.G.; Lindqvist, P.A.; Marklund, G.T.; Mozer, F.S.; Pedersen, A.

1987-03-01

The instrument for measurement of quasi-static and low frequency (dc and slow varying) electric fields on the Viking satellite is described. The instrument uses three spherical probe pairs to measure the full three-dimensional electric field vector with 18.75 ms time resolution. The probes are kept near plasma potential by means of a controllable bias current. A guard covering part of the booms is biased to a negative voltage to prevent photoelectrons escaping from the probes from reaching the satellite body. Current-voltage sweeps are performed to determine the plasma density and temperature and to select the optimal bias current. The bias currents to the probes and the voltage offset on the guards as well as the current-voltage sweeps are controlled by an on-board microprocessor which can be programmed from the ground and allows great flexibility. (authors)

Spherical proton emitters

International Nuclear Information System (INIS)

Berg, S.; Semmes, P.B.; Nazarewicz, W.

1997-01-01

Various theoretical approaches to proton emission from spherical nuclei are investigated, and it is found that all the methods employed give very similar results. The calculated decay widths are found to be qualitatively insensitive to the parameters of the proton-nucleus potential, i.e., changing the potential parameters over a fairly large range typically changes the decay width by no more than a factor of ∼3. Proton half-lives of observed heavy proton emitters are, in general, well reproduced by spherical calculations with the spectroscopic factors calculated in the independent quasiparticle approximation. The quantitative agreement with experimental data obtained in our study requires that the parameters of the proton-nucleus potential be chosen carefully. It also suggests that deformed proton emitters will provide invaluable spectroscopic information on the angular momentum decomposition of single-proton orbitals in deformed nuclei. copyright 1997 The American Physical Society

Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei; Pearson, John E.; Hoffmann, Axel [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Vlaminck, Vincent [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Colegio de Ciencias e Ingenería, Universidad San Fransciso de Quito, Quito (Ecuador); Divan, Ralu [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States); Bader, Samuel D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)

2013-12-09

The spin diffusion length of Pt at room temperature and at 8 K is experimentally determined via spin pumping and spin Hall effect in permalloy/Pt bilayers. Voltages generated during excitation of ferromagnetic resonance from the inverse spin Hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Varying the Pt layer thickness gives rise to an evolution of the voltage line shape due to the superposition of the above two effects. By studying the ratio of the two voltage components with the Pt layer thickness, the spin diffusion length of Pt can be directly extracted. We obtain a spin diffusion length of ∼1.2 nm at room temperature and ∼1.6 nm at 8 K.

Mismatch and misalignment: dark haloes and satellites of disc galaxies

Science.gov (United States)

Deason, A. J.; McCarthy, I. G.; Font, A. S.; Evans, N. W.; Frenk, C. S.; Belokurov, V.; Libeskind, N. I.; Crain, R. A.; Theuns, T.

2011-08-01

We study the phase-space distribution of satellite galaxies associated with late-type galaxies in the GIMIC suite of simulations. GIMIC consists of resimulations of five cosmologically representative regions from the Millennium Simulation, which have higher resolution and incorporate baryonic physics. Whilst the disc of the galaxy is well aligned with the inner regions (r˜ 0.1r200) of the dark matter halo, both in shape and angular momentum, there can be substantial misalignments at larger radii (r˜r200). Misalignments of >45° are seen in ˜30 per cent of our sample. We find that the satellite population aligns with the shape (and angular momentum) of the outer dark matter halo. However, the alignment with the galaxy is weak owing to the mismatch between the disc and dark matter halo. Roughly 20 per cent of the satellite systems with 10 bright galaxies within r200 exhibit a polar spatial alignment with respect to the galaxy - an orientation reminiscent of the classical satellites of the Milky Way. We find that a small fraction (˜10 per cent) of satellite systems show evidence for rotational support which we attribute to group infall. There is a bias towards satellites on prograde orbits relative to the spin of the dark matter halo (and to a lesser extent with the angular momentum of the disc). This preference towards co-rotation is stronger in the inner regions of the halo where the most massive satellites accreted at relatively early times are located. We attribute the anisotropic spatial distribution and angular momentum bias of the satellites at z= 0 to their directional accretion along the major axes of the dark matter halo. The satellite galaxies have been accreted relatively recently compared to the dark matter mass and have experienced less phase-mixing and relaxation - the memory of their accretion history can remain intact to z= 0. Understanding the phase-space distribution of the z= 0 satellite population is key for studies that estimate the host halo

Medium-spin levels and the character of the 20.4 ns 13/2+ isomer in 145Gd

International Nuclear Information System (INIS)

Pakkanen, A.; Muhonen, J.; Piiparinen, M.

1981-06-01

Levels of the N = 81 nucleus 145 Gd have been investigated by in-beam γ-ray and conversion electron spectroscopy with the 144 Sm( 3 He,2n) reaction. Fourteen new low- and medium-spin states between 1.0 and 2.4 MeV excitation, the known yrast levels up to spin (21/2) + , five other high-spin non-yrast states and a new 20.4 ns (13/2) + isomer at 2200.2 keV in 145 Gd have been observed. The isomer decays via a fast 927.3 keV E3 transition with B(E3) = 48 +- 7 W.u. Another weaker decay branch is a mixed, strongly hindered E1+M2+E3 transition to the νhsub(11/2)sup(-1) state. We propose an octupole νfsub(7/2)jsub(0)sup(-2)x3 - main configuration for the isomer, analogous to the 997 keV (13/2) + isomer in 147 Gd. The levels of 145 Gd are discussed on the basis of the spherical shell model. (author)

M2 ocean tide parameters and the deceleration of the moon's mean longitude from satellite orbit data

Science.gov (United States)

Felsentreger, T. L.; Marsh, J. G.; Williamson, R. G.

1979-01-01

An estimation is made of the principal long-period spherical harmonic parameters in the representation of the M2 ocean tide from the orbital histories of the three satellites 1967-92A, Starlette, and GEOS 3. The data used are primarily the evolution of the orbital inclinations of the satellites in conjunction with the longitude of the ascending node from GEOS 3. Analysis procedure and analytic formulation, as well as ocean tidal parameter estimation and deceleration of the lunar mean longitude are outlined. The credibility of the M2 ocean tide solution is further enhanced by the close accord between the computed value for the deceleration of the lunar mean longitude and other recently reported estimates. It is evident from the results presented that studies of close earth satellite orbits are able to provide important information about the tidal forces acting on the earth.

Investigation of the feasibility of an analytical method of accounting for the effects of atmospheric drag on satellite motion

Science.gov (United States)

Bozeman, Robert E.

1987-01-01

An analytic technique for accounting for the joint effects of Earth oblateness and atmospheric drag on close-Earth satellites is investigated. The technique is analytic in the sense that explicit solutions to the Lagrange planetary equations are given; consequently, no numerical integrations are required in the solution process. The atmospheric density in the technique described is represented by a rotating spherical exponential model with superposed effects of the oblate atmosphere and the diurnal variations. A computer program implementing the process is discussed and sample output is compared with output from program NSEP (Numerical Satellite Ephemeris Program). NSEP uses a numerical integration technique to account for atmospheric drag effects.

Recent Progress on Spherical Torus Research

Energy Technology Data Exchange (ETDEWEB)

Ono, Masayuki [PPPL; Kaita, Robert [PPPL

2014-01-01

The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ~ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ~ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of attractive fusion energy power source. Since the start of the two megaampere class ST facilities in 2000, National Spherical Torus Experiment (NSTX) in the US and Mega Ampere Spherical Tokamak (MAST) in UK, active ST research has been conducted worldwide. More than sixteen ST research facilities operating during this period have achieved remarkable advances in all of fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

Elastic interaction between surface and spherical pore

International Nuclear Information System (INIS)

Ganeev, G.Z.; Kadyrzhanov, K.K.; Kislitsyn, S.B.; Turkebaev, T.Eh.

2000-01-01

The energy of elastic interaction of a gas-filled spherical cavity with a boundary of an elastic isotropic half-space is determined. The elastic field of a system of a spherical cavity - boundary is represented as an expansion in series of potential functions. The factors of expansions are determined by boundary conditions on a free surface of an elastic half-space and on a spherical surface of a cavity with pressure of gas P. Function of a Tresca-Miesesa on a surface of elastic surface is defined additionally with purpose creep condition determination caused by gas pressure in the cavity. (author)

Studies of spherical inertial-electrostatic confinement

International Nuclear Information System (INIS)

Miley, G.H.

1992-01-01

Theoretical and experimental results from studies of Spherical Inertial-Electrostatic Confinement (SIEC) are presented. This principle of IEC involves the confinement by multiple potential wells created by ion injection into a spherical device containing biased grids. A semitransparent cathode accelerates ions, generating a spherical ion-beam flow which converges at the center of the spherical volume, creating a space charge (potential well) region. An electron flow is created by the core (virtual anode) region, forming in turn a virtual cathode. Ions trapped inside this well oscillate back and forth until they fuse or degrade in energy. Such multiple wells with virtual anodes and cathodes, have been called ''Poissors'' following the original work by Farnsworth and by Hirsch. Fusion within the core occurs by reactions between non-Maxwellian beam-beam type ions. This has the potential for achieving a high power density and also for burning both D-T and advanced fuels. If successful, such a device would be attractive for a variety of high power density applications, e.g., space power or as a neutron source based on D-D or D-T operation. Simulations of recent SIEC experiments have been carried out using the XL-code, to solve Poisson's equation, self-consistently with the collisionless Vlasov equation in spherical geometry for several current species and grid parameters. The potential profile predictions are reasonably consistent with experimental results. Potential well measurements used a collimated proton detector. Results indicate that an ∼ 15-kV virtual anode, at least one centimeter in radius, was formed in a spherical device with a cathode potential of 30 kV using an ion current of ∼ 30 mA. Analysis indicates D + densities on the order of 10 9 cm -3 , and D 2 + densities on the order of 10 10 cm -3 . Steady-state D-D neutron emission of about 10 6 n/sec is observed

Muon spin relaxation measurements of spin-correlation decay in spin-glass AgMn

Energy Technology Data Exchange (ETDEWEB)

Heffner, R.H.; Cooke, D.W.; Leon, M.; Schillaci, M.E. (Los Alamos National Lab., NM (USA)); MacLaughlin, D.E.; Gupta, L.C. (California Univ., Riverside (USA))

1984-01-01

The field (H) dependence of the muon longitudinal spin-lattice relaxation rate well below the spin glass temperature in AgMn is found to obey an algebraic form given by (H)sup(..gamma..-1), with ..gamma.. = 0.54 +- 0.05. This suggests that Mn spin correlations decay with time as tsup(-..gamma..), in agreement with mean field theories of spin-glass dynamics which yield ..gamma..

Systematic Calibration for a Backpacked Spherical Photogrammetry Imaging System

Science.gov (United States)

Rau, J. Y.; Su, B. W.; Hsiao, K. W.; Jhan, J. P.

2016-06-01

A spherical camera can observe the environment for almost 720 degrees' field of view in one shoot, which is useful for augmented reality, environment documentation, or mobile mapping applications. This paper aims to develop a spherical photogrammetry imaging system for the purpose of 3D measurement through a backpacked mobile mapping system (MMS). The used equipment contains a Ladybug-5 spherical camera, a tactical grade positioning and orientation system (POS), i.e. SPAN-CPT, and an odometer, etc. This research aims to directly apply photogrammetric space intersection technique for 3D mapping from a spherical image stereo-pair. For this purpose, several systematic calibration procedures are required, including lens distortion calibration, relative orientation calibration, boresight calibration for direct georeferencing, and spherical image calibration. The lens distortion is serious on the ladybug-5 camera's original 6 images. Meanwhile, for spherical image mosaicking from these original 6 images, we propose the use of their relative orientation and correct their lens distortion at the same time. However, the constructed spherical image still contains systematic error, which will reduce the 3D measurement accuracy. Later for direct georeferencing purpose, we need to establish a ground control field for boresight/lever-arm calibration. Then, we can apply the calibrated parameters to obtain the exterior orientation parameters (EOPs) of all spherical images. In the end, the 3D positioning accuracy after space intersection will be evaluated, including EOPs obtained by structure from motion method.

Spin manipulation and relaxation in spin-orbit qubits

Science.gov (United States)

Borhani, Massoud; Hu, Xuedong

2012-03-01

We derive a generalized form of the electric dipole spin resonance (EDSR) Hamiltonian in the presence of the spin-orbit interaction for single spins in an elliptic quantum dot (QD) subject to an arbitrary (in both direction and magnitude) applied magnetic field. We predict a nonlinear behavior of the Rabi frequency as a function of the magnetic field for sufficiently large Zeeman energies, and present a microscopic expression for the anisotropic electron g tensor. Similarly, an EDSR Hamiltonian is devised for two spins confined in a double quantum dot (DQD), where coherent Rabi oscillations between the singlet and triplet states are induced by jittering the inter-dot distance at the resonance frequency. Finally, we calculate two-electron-spin relaxation rates due to phonon emission, for both in-plane and perpendicular magnetic fields. Our results have immediate applications to current EDSR experiments on nanowire QDs, g-factor optimization of confined carriers, and spin decay measurements in DQD spin-orbit qubits.

Spin transfer torque with spin diffusion in magnetic tunnel junctions

KAUST Repository

Manchon, Aurelien

2012-08-09

Spin transport in magnetic tunnel junctions in the presence of spin diffusion is considered theoretically. Combining ballistic tunneling across the barrier and diffusive transport in the electrodes, we solve the spin dynamics equation in the metallic layers. We show that spin diffusion mixes the transverse spin current components and dramatically modifies the bias dependence of the effective spin transfer torque. This leads to a significant linear bias dependence of the out-of-plane torque, as well as a nonconventional thickness dependence of both spin torque components.

Muon spin relaxation measurements of spin-correlation decay in spin-glass AgMn

International Nuclear Information System (INIS)

Heffner, R.H.; Cooke, D.W.; Leon, M.; Schillaci, M.E.; MacLaughlin, D.E.; Gupta, L.C.

1984-01-01

The field (H) dependence of the muon longitudinal spin-lattice relaxation rate well below the spin glass temperature in AgMn is found to obey an algebraic form given by (H)sup(γ-1), with γ = 0.54 +- 0.05. This suggests that Mn spin correlations decay with time as tsup(-γ), in agreement with mean field theories of spin-glass dynamics which yield γ < approx. 0.5. Near the glass temperature the agreement between the data and theory is not as good. (Auth.)

Spherical Dunkl-monogenics and a factorization of the Dunkl-Laplacian

International Nuclear Information System (INIS)

Fei Minggang; Cerejeiras, Paula; Kaehler, Uwe

2010-01-01

In this paper, we consider and study a factorization of the Dunkl-Laplacian in terms of spherical coordinates. This allows for the construction of a direct sum decomposition of spherical Dunkl-harmonics. By explicit representation in spherical coordinates of Dunkl-harmonics, one obtains explicit projection operators from Dunkl-harmonics to inner (resp. outer) Dunkl-monogenics. Concrete examples of spherical Dunkl-monogenics will be given at the end.

IMPROVING THE MODEL OF EMISSION FROM SPINNING DUST: EFFECTS OF GRAIN WOBBLING AND TRANSIENT SPIN-UP

International Nuclear Information System (INIS)

Hoang, Thiem; Lazarian, A.; Draine, B. T.

2010-01-01

Observations continue to support the interpretation of the anomalous microwave foreground as electric dipole radiation from spinning dust grains as proposed by Draine and Lazarian. In this paper, we present a refinement of the original model by improving the treatment of a number of physical effects. First, we consider a disk-like grain rotating with angular velocity at an arbitrary angle with respect to the grain symmetry axis (i.e., grain wobbling) and derive the rotational damping and excitation coefficients arising from infrared emission, plasma-grain interactions, and electric dipole emission. The angular velocity distribution and the electric dipole emission spectrum for disk-like grains is calculated using the Langevin equation, for cases both with and without fast internal relaxation. Our results show that for fast internal relaxation, the peak emissivity of spinning dust, compared to earlier studies, increases by a factor of ∼2 for the warm neutral medium (WNM), the warm ionized medium (WIM), the cold neutral medium (CNM), and the photodissociation region, and by a factor ∼4 for reflection nebulae. The frequency at the emission peak also increases by factors ∼1.4 to ∼2 for these media. Without internal relaxation, the increase of emissivity is comparable, but the emission spectrum is more extended to higher frequency. The increased emission results from the non-sphericity of grain shape and from the anisotropy in damping and excitation along directions parallel and perpendicular to the grain symmetry axis. Second, we provide a detailed numerical study including transient spin-up of grains by single-ion collisions. The range of grain size in which single-ion collisions are important is identified. The impulses broaden the emission spectrum and increase the peak emissivity for the CNM, WNM, and WIM, although the increases are not as large as those due to the grain wobbling. In addition, we present an improved treatment of rotational excitation and

Fabrication of an eyeball-like spherical micro-lens array using extrusion for optical fiber coupling

International Nuclear Information System (INIS)

Shen, S C; Huang, J C; Pan, C T; Chao, C H; Liu, K H

2009-01-01

Batch fabrication of an eyeball-like spherical micro-lens array (ESMA) not only can reduce micro assembly cost, but also can replace conventional ball lenses or costly gradient refractive index without sacrificing performance. Compared to the conventional half-spherical micro-lenses, the ESMA is an eyeball-like spherical lens which can focus light in all directions, thus providing application flexibility for optical purposes. The current ESMA is made of photoresist SU-8 using the extrusion process instead of the traditional thermal reflow process. For the process of an ESMA, this research develops a new process at ambient temperature by spin-coating SU-8 on a surface of a silicon wafer which serves as an extrusion plate and extruding it through a nozzle to form an ESMA. This nozzle consists of a nozzle orifice and nozzle cavity. The nozzle orifice is defined and made of SU-8 photoresist using ultra-violet lithography, which exhibits good mechanical property. The fabrication process of a nozzle cavity employs bulk micromachining to fabricate the cavities. Next, viscous SU-8 spun on the extrusion plate is extruded through the nozzle orifice to form an ESMA. Based on the effect of surface tension, by varying the amount of SU-8 on the plate extruded through different nozzle orifices, various diameters of ESMA can be fabricated. In this paper, a 4 × 4 ESMA with a numerical aperture of about 0.38 and diameters ranging from 60 to 550 µm is fabricated. Optical measurements indicate a diameter variance within 3% and the maximum coupling efficiency is approximately 62% when the single mode fiber is placed at a distance of 10 µm from the ESMA. The research has proved that the extrusion fabrication process of an ESMA is capable of enhancing the coupling efficiency

Spin-orbit mediated control of spin qubits

DEFF Research Database (Denmark)

Flindt, Christian; Sørensen, A.S; Flensberg, Karsten

2006-01-01

We propose to use the spin-orbit interaction as a means to control electron spins in quantum dots, enabling both single-qubit and two-qubit operations. Very fast single-qubit operations may be achieved by temporarily displacing the electrons. For two-qubit operations the coupling mechanism is bas...... on a combination of the spin-orbit coupling and the mutual long-ranged Coulomb interaction. Compared to existing schemes using the exchange coupling, the spin-orbit induced coupling is less sensitive to random electrical fluctuations in the electrodes defining the quantum dots....

Spinning particle approach to higher spin field theory

International Nuclear Information System (INIS)

Corradini, Olindo

2011-01-01

We shortly review on the connection between higher-spin gauge field theories and supersymmetric spinning particle models. In such approach the higher spin equations of motion are linked to the first-class constraint algebra associated with the quantization of particle models. Here we consider a class of spinning particle models characterized by local O(N)-extended supersymmetry since these models are known to provide an alternative approach to the geometric formulation of higher spin field theory. We describe the canonical quantization of the models in curved target space and discuss the obstructions that appear in presence of an arbitrarily curved background. We then point out the special role that conformally flat spaces appear to have in such models and present a derivation of the higher-spin curvatures for maximally symmetric spaces.

Shot noise of spin current and spin transfer torque

Science.gov (United States)

Yu, Yunjin; Zhan, Hongxin; Wan, Langhui; Wang, Bin; Wei, Yadong; Sun, Qingfeng; Wang, Jian

2013-04-01

We report the theoretical investigation of the shot noise of the spin current (Sσ) and the spin transfer torque (Sτ) for non-collinear spin polarized transport in a spin-valve device which consists of a normal scattering region connected by two ferromagnetic electrodes (MNM system). Our theory was developed using the non-equilibrium Green’s function method, and general nonlinear Sσ - V and Sτ - V relations were derived as a function of the angle θ between the magnetizations of two leads. We have applied our theory to a quantum dot system with a resonant level coupled with two ferromagnetic electrodes. It was found that, for the MNM system, the auto-correlation of the spin current is enough to characterize the fluctuation of the spin current. For a system with three ferromagnetic layers, however, both auto-correlation and cross-correlation of the spin current are needed to characterize the noise of the spin current. For a quantum dot with a resonant level, the derivative of spin torque with respect to bias voltage is proportional to sinθ when the system is far away from resonance. When the system is near resonance, the spin transfer torque becomes a non-sinusoidal function of θ. The derivative of the noise of the spin transfer torque with respect to the bias voltage Nτ behaves differently when the system is near or far away from resonance. Specifically, the differential shot noise of the spin transfer torque Nτ is a concave function of θ near resonance while it becomes a convex function of θ far away from resonance. For certain bias voltages, the period Nτ(θ) becomes π instead of 2π. For small θ, it was found that the differential shot noise of the spin transfer torque is very sensitive to the bias voltage and the other system parameters.

Preparation of spherical particles by vibrating orifice technique

Science.gov (United States)

Shibata, Shuichi; Tomizawa, Atsushi; Yoshikawa, Hidemi; Yano, Tetsuji; Yamane, Masayuki

2000-05-01

Preparation of micrometer-sized spherical particles containing Rhodamine 6G (R6G) has been investigated for the spherical cavity micro-laser. Using phenyl triethoxy silane (PTES) as a starting material, R6G-doped monodisperse spherical particles were prepared by the vibrating orifice technique. Processing consists of two major processes: (1) Hydrolysis and polymerization of PTES and (2) Droplet formation from PTES oligomers by vibrating orifice technique. A cylindrical liquid jet passing through the orifice of 10 and 20 micrometers in diameter breaks up into equal- sized droplets by mechanical vibration. Alcohol solvent of these droplets was evaporated during flying with carrier gas and subsequently solidified in ammonium water trap. For making smooth surface and god shaped particles, control of molecular weight of PTES oligomer was essential. R6G-doped hybrid spherical particles of 4 to 10 micrometers size of cavity structure were successfully obtained. The spherical particles were pumped by a second harmonic pulse of Q- switched Nd:YAG laser and laser emission peaks were observed at wavelengths which correspond to the resonance modes.

Spherical rhenium metal powder

International Nuclear Information System (INIS)

Leonhardt, T.; Moore, N.; Hamister, M.

2001-01-01

The development of a high-density, spherical rhenium powder (SReP) possessing excellent flow characteristics has enabled the use of advanced processing techniques for the manufacture of rhenium components. The techniques that were investigated were vacuum plasma spraying (VPS), direct-hot isostatic pressing (D-HIP), and various other traditional powder metallurgy processing methods of forming rhenium powder into near-net shaped components. The principal disadvantages of standard rhenium metal powder (RMP) for advanced consolidation applications include: poor flow characteristics; high oxygen content; and low and varying packing densities. SReP will lower costs, reduce processing times, and improve yields when manufacturing powder metallurgy rhenium components. The results of the powder characterization of spherical rhenium powder and the consolidation of the SReP are further discussed. (author)

Spin precession and spin Hall effect in monolayer graphene/Pt nanostructures

Science.gov (United States)

Savero Torres, W.; Sierra, J. F.; Benítez, L. A.; Bonell, F.; Costache, M. V.; Valenzuela, S. O.

2017-12-01

Spin Hall effects have surged as promising phenomena for spin logics operations without ferromagnets. However, the magnitude of the detected electric signals at room temperature in metallic systems has been so far underwhelming. Here, we demonstrate a two-order of magnitude enhancement of the signal in monolayer graphene/Pt devices when compared to their fully metallic counterparts. The enhancement stems in part from efficient spin injection and the large spin resistance of graphene but we also observe 100% spin absorption in Pt and find an unusually large effective spin Hall angle of up to 0.15. The large spin-to-charge conversion allows us to characterise spin precession in graphene under the presence of a magnetic field. Furthermore, by developing an analytical model based on the 1D diffusive spin-transport, we demonstrate that the effective spin-relaxation time in graphene can be accurately determined using the (inverse) spin Hall effect as a means of detection. This is a necessary step to gather full understanding of the consequences of spin absorption in spin Hall devices, which is known to suppress effective spin lifetimes in both metallic and graphene systems.

Muon spin-relaxation measurements of spin-correlation decay in spin-glass AgMn

International Nuclear Information System (INIS)

Heffner, R.H.; Cooke, D.W.; Leon, M.; Schillaci, M.E.; MacLaughlin, D.E.; Gupta, L.C.

1983-01-01

The field (H) dependence of the muon longitudinal spin-lattice relaxation rate well below the spin-glass temperature in AgMn is found to obey an algebraic form given by (H)/sup nu-1/, with nu = 0.54 +- 0.05. This suggests that Mn spin correlations decay with time as t - /sup nu/, in agreement with mean field theories of spin-glass dynamics which yield nu less than or equal to 0.5. Near the glass temperature the agreement between the data and theory is not as good

Spin-chirality decoupling in Heisenberg spin glasses and related systems

OpenAIRE

Kawamura, Hikaru

2006-01-01

Recent studies on the spin and the chirality orderings of the three-dimensional Heisenberg spin glass and related systems are reviewed with particular emphasis on the possible spin-chirality decoupling phenomena. Chirality scenario of real spin-glass transition and its experimental consequence on the ordering of Heisenberg-like spin glasses are discussed.

Spin current

CERN Document Server

Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

2012-01-01

In a new branch of physics and technology called spin-electronics or spintronics, the flow of electrical charge (usual current) as well as the flow of electron spin, the so-called 'spin current', are manipulated and controlled together. This book provides an introduction and guide to the new physics and application of spin current.

Spin current

CERN Document Server

Valenzuela, Sergio O; Saitoh, Eiji; Kimura, Takashi

2017-01-01

Since the discovery of the giant magnetoresistance effect in magnetic multilayers in 1988, a new branch of physics and technology, called spin-electronics or spintronics, has emerged, where the flow of electrical charge as well as the flow of electron spin, the so-called “spin current,” are manipulated and controlled together. The physics of magnetism and the application of spin current have progressed in tandem with the nanofabrication technology of magnets and the engineering of interfaces and thin films. This book aims to provide an introduction and guide to the new physics and applications of spin current, with an emphasis on the interaction between spin and charge currents in magnetic nanostructures.

Effects of x-ray and neutron irradiation on spherical colonies

International Nuclear Information System (INIS)

Aramaki, Ryoji

1980-01-01

Responses of in vitro cultured mammalian cells in spherical colonies to 200 kVp x-rays and D-T neutrons were studied using reproductive capacity as a criterion for survival. Cell lines used were FM3A, L5 and Chinese hamster V79. The spherical colonies exposed to x-rays exhibited two-component survival curves. All cells used were more radio-resistant in spherical colonies than in single cell suspensions. It was suggested that this difference in response was attributable to the presence of hypoxic cells in spherical colonies. Dose-modifying Factor (DMF), the ratios of D 0 of the second slopes of the curves for spherical colonies to those for single cells, were 1.6 for FM3A, 1.8 for L5, and 1.7 for Chinese hamster V79. The hypoxic cell fractions in spherical colonies for FM3A, L5, and Chinese hamster V79, were 0.1, 0.6 and 0.4, respectively, resulting in variations in cell survival in spherical colonies following x-radiation. No significant difference was observed between responses of spherical colonies and single cell suspensions to D-T neutrons. FM3A and Chinese hamster V79 showed two-component survival curves when irradiated with neutrons at 37 0 C, but not at 25 0 C. The repair of potentially lethal and sub-lethal damage was also investigated using FM3A in spherical colonies. No detectable repair of potentially lethal damage was observed for x-rays and D-T neutrons. The effect of neutron fractionation was considerably smaller for spherical colonies as compared to single cells. (author)

Nuclear spin noise in the central spin model

Science.gov (United States)

Fröhling, Nina; Anders, Frithjof B.; Glazov, Mikhail

2018-05-01

We study theoretically the fluctuations of the nuclear spins in quantum dots employing the central spin model which accounts for the hyperfine interaction of the nuclei with the electron spin. These fluctuations are calculated both with an analytical approach using homogeneous hyperfine couplings (box model) and with a numerical simulation using a distribution of hyperfine coupling constants. The approaches are in good agreement. The box model serves as a benchmark with low computational cost that explains the basic features of the nuclear spin noise well. We also demonstrate that the nuclear spin noise spectra comprise a two-peak structure centered at the nuclear Zeeman frequency in high magnetic fields with the shape of the spectrum controlled by the distribution of the hyperfine constants. This allows for direct access to this distribution function through nuclear spin noise spectroscopy.

Entanglement entropy in random quantum spin-S chains

International Nuclear Information System (INIS)

Saguia, A.; Boechat, B.; Continentino, M. A.; Sarandy, M. S.

2007-01-01

We discuss the scaling of entanglement entropy in the random singlet phase (RSP) of disordered quantum magnetic chains of general spin S. Through an analysis of the general structure of the RSP, we show that the entanglement entropy scales logarithmically with the size of a block, and we provide a closed expression for this scaling. This result is applicable for arbitrary quantum spin chains in the RSP, being dependent only on the magnitude S of the spin. Remarkably, the logarithmic scaling holds for the disordered chain even if the pure chain with no disorder does not exhibit conformal invariance, as is the case for Heisenberg integer-spin chains. Our conclusions are supported by explicit evaluations of the entanglement entropy for random spin-1 and spin-3/2 chains using an asymptotically exact real-space renormalization group approach

Competing Spin Liquids and Hidden Spin-Nematic Order in Spin Ice with Frustrated Transverse Exchange

Directory of Open Access Journals (Sweden)

Mathieu Taillefumier

2017-12-01

Full Text Available Frustration in magnetic interactions can give rise to disordered ground states with subtle and beautiful properties. The spin ices Ho_{2}Ti_{2}O_{7} and Dy_{2}Ti_{2}O_{7} exemplify this phenomenon, displaying a classical spin-liquid state, with fractionalized magnetic-monopole excitations. Recently, there has been great interest in closely related “quantum spin-ice” materials, following the realization that anisotropic exchange interactions could convert spin ice into a massively entangled, quantum spin liquid, where magnetic monopoles become the charges of an emergent quantum electrodynamics. Here we show that even the simplest model of a quantum spin ice, the XXZ model on the pyrochlore lattice, can realize a still-richer scenario. Using a combination of classical Monte Carlo simulation, semiclassical molecular-dynamics simulation, and analytic field theory, we explore the properties of this model for frustrated transverse exchange. We find not one, but three competing forms of spin liquid, as well as a phase with hidden, spin-nematic order. We explore the experimental signatures of each of these different states, making explicit predictions for inelastic neutron scattering. These results show an intriguing similarity to experiments on a range of pyrochlore oxides.

Spherical convolutions and their application in molecular modelling

DEFF Research Database (Denmark)

Boomsma, Wouter; Frellsen, Jes

2017-01-01

Convolutional neural networks are increasingly used outside the domain of image analysis, in particular in various areas of the natural sciences concerned with spatial data. Such networks often work out-of-the box, and in some cases entire model architectures from image analysis can be carried over...... to other problem domains almost unaltered. Unfortunately, this convenience does not trivially extend to data in non-euclidean spaces, such as spherical data. In this paper, we introduce two strategies for conducting convolutions on the sphere, using either a spherical-polar grid or a grid based...... of spherical convolutions in the context of molecular modelling, by considering structural environments within proteins. We show that the models are capable of learning non-trivial functions in these molecular environments, and that our spherical convolutions generally outperform standard 3D convolutions...

Watermarking on 3D mesh based on spherical wavelet transform.

Science.gov (United States)

Jin, Jian-Qiu; Dai, Min-Ya; Bao, Hu-Jun; Peng, Qun-Sheng

2004-03-01

In this paper we propose a robust watermarking algorithm for 3D mesh. The algorithm is based on spherical wavelet transform. Our basic idea is to decompose the original mesh into a series of details at different scales by using spherical wavelet transform; the watermark is then embedded into the different levels of details. The embedding process includes: global sphere parameterization, spherical uniform sampling, spherical wavelet forward transform, embedding watermark, spherical wavelet inverse transform, and at last resampling the mesh watermarked to recover the topological connectivity of the original model. Experiments showed that our algorithm can improve the capacity of the watermark and the robustness of watermarking against attacks.

Separating inverse spin Hall voltage and spin rectification voltage by inverting spin injection direction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wenxu, E-mail: xwzhang@uestc.edu.cn; Peng, Bin; Han, Fangbin; Wang, Qiuru; Zhang, Wanli [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Soh, Wee Tee; Ong, Chong Kim [Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore)

2016-03-07

We develop a method for universally resolving the important issue of separating the inverse spin Hall effect (ISHE) from the spin rectification effect (SRE) signal. This method is based on the consideration that the two effects depend on the spin injection direction: The ISHE is an odd function of the spin injection direction while the SRE is independent on it. Thus, the inversion of the spin injection direction changes the ISHE voltage signal, while the SRE voltage remains. It applies generally to analyzing the different voltage contributions without fitting them to special line shapes. This fast and simple method can be used in a wide frequency range and has the flexibility of sample preparation.

Quantum dynamics of nuclear spins and spin relaxation in organic semiconductors

Science.gov (United States)

Mkhitaryan, V. V.; Dobrovitski, V. V.

2017-06-01

We investigate the role of the nuclear-spin quantum dynamics in hyperfine-induced spin relaxation of hopping carriers in organic semiconductors. The fast-hopping regime, when the carrier spin does not rotate much between subsequent hops, is typical for organic semiconductors possessing long spin coherence times. We consider this regime and focus on a carrier random-walk diffusion in one dimension, where the effect of the nuclear-spin dynamics is expected to be the strongest. Exact numerical simulations of spin systems with up to 25 nuclear spins are performed using the Suzuki-Trotter decomposition of the evolution operator. Larger nuclear-spin systems are modeled utilizing the spin-coherent state P -representation approach developed earlier. We find that the nuclear-spin dynamics strongly influences the carrier spin relaxation at long times. If the random walk is restricted to a small area, it leads to the quenching of carrier spin polarization at a nonzero value at long times. If the random walk is unrestricted, the carrier spin polarization acquires a long-time tail, decaying as 1 /√{t } . Based on the numerical results, we devise a simple formula describing the effect quantitatively.

Inversion of Magnetic Measurements of the CHAMP Satellite Over the Pannonian Basin

Science.gov (United States)

Kis, K. I.; Taylor, P. T.; Wittmann, G.; Toronyi, B.; Puszta, S.

2011-01-01

The Pannonian Basin is a deep intra-continental basin that formed as part of the Alpine orogeny. In order to study the nature of the crustal basement we used the long-wavelength magnetic anomalies acquired by the CHAMP satellite. The anomalies were distributed in a spherical shell, some 107,927 data recorded between January 1 and December 31 of 2008. They covered the Pannonian Basin and its vicinity. These anomaly data were interpolated into a spherical grid of 0.5 x 0.5, at the elevation of 324 km by the Gaussian weight function. The vertical gradient of these total magnetic anomalies was also computed and mapped to the surface of a sphere at 324 km elevation. The former spherical anomaly data at 425 km altitude were downward continued to 324 km. To interpret these data at the elevation of 324 km we used an inversion method. A polygonal prism forward model was used for the inversion. The minimum problem was solved numerically by the Simplex and Simulated annealing methods; a L2 norm in the case of Gaussian distribution parameters and a L1 norm was used in the case of Laplace distribution parameters. We INTERPRET THAT the magnetic anomaly WAS produced by several sources and the effect of the sable magnetization of the exsolution of hemo-ilmenite minerals in the upper crustal metamorphic rocks.

Chaotic spin exchange: is the spin non-flip rate observable?

International Nuclear Information System (INIS)

Senba, Masayoshi

1994-01-01

If spin exchange is of the Poisson nature, that is, if the time distribution of collisions obeys an exponential distribution function and the collision process is random, the muon spin depolarization is determined only by the spin flip rate regardless of the spin non-flip rate. In this work, spin exchange is discussed in the case of chaotic spin exchange, where the distribution of collision time sequences, generated by a deterministic equation, is exponential but not random (deterministic chaos). Even though this process has the same time distribution as a Poisson process, the muon polarization is affected by the spin non-flip rate. Having an exponential time distribution function is not a sufficient condition for the non-observation of the spin non-flip rate and it is essential that the process is also random. (orig.)

Vibration dependence of the tensor spin-spin and scalar spin-spin hyperfine interactions by precision measurement of hyperfine structures of 127I2 near 532 nm

International Nuclear Information System (INIS)

Hong Fenglei; Zhang Yun; Ishikawa, Jun; Onae, Atsushi; Matsumoto, Hirokazu

2002-01-01

Hyperfine structures of the R(87)33-0, R(145)37-0, and P(132)36-0 transitions of molecular iodine near 532 nm are measured by observing the heterodyne beat-note signal of two I 2 -stabilized lasers, whose frequencies are bridged by an optical frequency comb generator. The measured hyperfine splittings are fit to a four-term Hamiltonian, which includes the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions, with an accuracy of ∼720 Hz. High-accurate hyperfine constants are obtained from this fit. Vibration dependences of the tensor spin-spin and scalar spin-spin hyperfine constants are determined for molecular iodine, for the first time to our knowledge. The observed hyperfine transitions are good optical frequency references in the 532-nm region

Shot noise of spin current and spin transfer torque

International Nuclear Information System (INIS)

Yu Yunjin; Zhan Hongxin; Wan Langhui; Wang Bin; Wei Yadong; Sun Qingfeng; Wang Jian

2013-01-01

We report the theoretical investigation of the shot noise of the spin current (S σ ) and the spin transfer torque (S τ ) for non-collinear spin polarized transport in a spin-valve device which consists of a normal scattering region connected by two ferromagnetic electrodes (MNM system). Our theory was developed using the non-equilibrium Green’s function method, and general nonlinear S σ − V and S τ − V relations were derived as a function of the angle θ between the magnetizations of two leads. We have applied our theory to a quantum dot system with a resonant level coupled with two ferromagnetic electrodes. It was found that, for the MNM system, the auto-correlation of the spin current is enough to characterize the fluctuation of the spin current. For a system with three ferromagnetic layers, however, both auto-correlation and cross-correlation of the spin current are needed to characterize the noise of the spin current. For a quantum dot with a resonant level, the derivative of spin torque with respect to bias voltage is proportional to sinθ when the system is far away from resonance. When the system is near resonance, the spin transfer torque becomes a non-sinusoidal function of θ. The derivative of the noise of the spin transfer torque with respect to the bias voltage N τ behaves differently when the system is near or far away from resonance. Specifically, the differential shot noise of the spin transfer torque N τ is a concave function of θ near resonance while it becomes a convex function of θ far away from resonance. For certain bias voltages, the period N τ (θ) becomes π instead of 2π. For small θ, it was found that the differential shot noise of the spin transfer torque is very sensitive to the bias voltage and the other system parameters. (paper)

Electromagnetic cloaking in higher order spherical cloaks

Science.gov (United States)

Sidhwa, H. H.; Aiyar, R. P. R. C.; Kulkarni, S. V.

2017-06-01

The inception of transformation optics has led to the realisation of the invisibility devices for various applications, one of which is spherical cloaking. In this paper, a formulation for a higher-order spherical cloak has been proposed to reduce its physical thickness significantly by introducing a nonlinear relation between the original and transformed coordinate systems and it has been verified using the ray tracing approach. Analysis has been carried out to observe the anomalies in the variation of refractive index for higher order cloaks indicating the presence of poles in the relevant equations. Furthermore, a higher-order spherical cloak with predefined values of the material characteristics on its inner and outer surfaces has been designed for practical application.

Construction of a quartz spherical analyzer: application to high-resolution analysis of the Ni Kα emission spectrum

International Nuclear Information System (INIS)

Honnicke, Marcelo Goncalves; Cusatis, Cesar

2016-01-01

The construction and characterization of a focusing X-ray spherical analyzer based on α-quartz 44̄04 are presented. For this study, the performance of the analyzer was demonstrated by applying it to a high-resolution X-ray spectroscopy study of theKα_1_,_2emission spectrum of Ni. An analytical representation based on physical grounds was assumed to model the shape of the X-ray emission lines. Satellite structures assigned to 3dspectator hole transitions were resolved and determined as well as their relative contribution to the emission spectrum. The present results on 1s"-"13d"-"1shake probabilities support a recently proposed calculation framework based on a multi-configuration atomic model.

Spherical Nb single crystals containerlessly grown by electrostatic levitation

International Nuclear Information System (INIS)

Sung, Y.S.; Takeya, H.; Hirata, K.; Togano, K.

2003-01-01

Spherical Nb (T m =2750 K) single crystals were grown via containerless electrostatic levitation (ESL). Samples became spherical at melting in levitation and undercooled typically 300-450 K prior to nucleation. As-processed samples were still spherical without any macroscopic shape change by solidification showing a uniform dendritic surface morphology. Crystallographic {111} planes exposed in equilateral triangular shapes on the surface by preferential macroetching and spotty back-reflection Laue patterns confirm the single crystal nature of the ESL-processed Nb samples. No hysteresis in magnetization between zero field and field cooling also implies a clean defect-free condition of the spherical Nb single crystals

Higher-order spin effects in the amplitude and phase of gravitational waveforms emitted by inspiraling compact binaries: Ready-to-use gravitational waveforms

International Nuclear Information System (INIS)

Arun, K. G.; Buonanno, Alessandra; Ochsner, Evan; Faye, Guillaume

2009-01-01

We provide ready-to-use time-domain gravitational waveforms for spinning compact binaries with precession effects through 1.5 post-Newtonian (PN) order in amplitude, and compute their mode decomposition using spin-weighted -2 spherical harmonics. In the presence of precession, the gravitational-wave modes (l,m) contain harmonics originating from combinations of the orbital frequency and precession frequencies. We find that the gravitational radiation from binary systems with large mass asymmetry and large inclination angle can be distributed among several modes. For example, during the last stages of inspiral, for some maximally spinning configurations, the amplitude of the (2, 0) and (2, 1) modes can be comparable to the amplitude of the (2, 2) mode. If the mass ratio is not too extreme, the l=3 and l=4 modes are generally 1 or 2 orders of magnitude smaller than the l=2 modes. Restricting ourselves to spinning, nonprecessing compact binaries, we apply the stationary-phase approximation and derive the frequency-domain gravitational waveforms including spin-orbit and spin(1)-spin(2) effects through 1.5PN and 2PN order, respectively, in amplitude, and 2.5PN order in phase. Since spin effects in the amplitude through 2PN order affect only the first and second harmonics of the orbital phase, they do not extend the mass reach of gravitational-wave detectors. However, they can interfere with other harmonics and lower or raise the signal-to-noise ratio depending on the spin orientation. These ready-to-use waveforms could be employed in the data analysis of the spinning, inspiraling binaries as well as in comparison studies at the interface between analytical and numerical relativity.

Effect of spherical aberration on scintillations of Gaussian beams in atmospheric turbulence

International Nuclear Information System (INIS)

Ji, Xiaoling; Deng, Jinping

2014-01-01

The effect of spherical aberration on scintillations of Gaussian beams in weak, moderate and strong turbulence is studied using numerical simulation method. It is found that the effect of the negative spherical aberration on the on-axis scintillation index is quite different from that of the positive spherical aberration. In weak turbulence, the positive spherical aberration results in a decrease of the on-axis scintillation index on propagation, but the negative spherical aberration results in an increase of the on-axis scintillation index when the propagation distance is not large. In particular, in weak turbulence the negative spherical aberration may cause peaks of the on-axis scintillation index, and the peaks disappear in moderate and strong turbulence, which is explained in physics. The strong turbulence leads to less discrepancy among scintillations of Gaussian beams with and without spherical aberration. - Highlights: • In weak turbulence scintillations can be suppressed using positive spherical aberration. • In weak turbulence scintillations may be very large due to negative spherical aberration. • The effect of spherical aberration on scintillations is less with increasing of turbulence

Effect of spherical aberration on scintillations of Gaussian beams in atmospheric turbulence

Energy Technology Data Exchange (ETDEWEB)

Ji, Xiaoling, E-mail: jiXL100@163.com; Deng, Jinping

2014-07-18

The effect of spherical aberration on scintillations of Gaussian beams in weak, moderate and strong turbulence is studied using numerical simulation method. It is found that the effect of the negative spherical aberration on the on-axis scintillation index is quite different from that of the positive spherical aberration. In weak turbulence, the positive spherical aberration results in a decrease of the on-axis scintillation index on propagation, but the negative spherical aberration results in an increase of the on-axis scintillation index when the propagation distance is not large. In particular, in weak turbulence the negative spherical aberration may cause peaks of the on-axis scintillation index, and the peaks disappear in moderate and strong turbulence, which is explained in physics. The strong turbulence leads to less discrepancy among scintillations of Gaussian beams with and without spherical aberration. - Highlights: • In weak turbulence scintillations can be suppressed using positive spherical aberration. • In weak turbulence scintillations may be very large due to negative spherical aberration. • The effect of spherical aberration on scintillations is less with increasing of turbulence.

Spherical near-field scanning at the Technical University of Denmark

DEFF Research Database (Denmark)

Hansen, J. E.; Jensen, F.

1988-01-01

The early work (1969-79) on spherical near-field antenna measurements at the Technical University of Denmark (TUD) is outlined. A spherical near-field transmission formula is described and the first probe-corrected spherical near-field measurements are discussed. The TUD-ESA (European Space Agency...

SU (N ) spin-wave theory: Application to spin-orbital Mott insulators

Science.gov (United States)

Dong, Zhao-Yang; Wang, Wei; Li, Jian-Xin

2018-05-01

We present the application of the SU (N ) spin-wave theory to spin-orbital Mott insulators whose ground states exhibit magnetic orders. When taking both spin and orbital degrees of freedom into account rather than projecting Hilbert space onto the Kramers doublet, which is the lowest spin-orbital locked energy levels, the SU (N ) spin-wave theory should take the place of the SU (2 ) one due to the inevitable spin-orbital multipole exchange interactions. To implement the application, we introduce an efficient general local mean-field method, which involves all local fluctuations, and develop the SU (N ) linear spin-wave theory. Our approach is tested firstly by calculating the multipolar spin-wave spectra of the SU (4 ) antiferromagnetic model. Then, we apply it to spin-orbital Mott insulators. It is revealed that the Hund's coupling would influence the effectiveness of the isospin-1 /2 picture when the spin-orbital coupling is not large enough. We further carry out the SU (N ) spin-wave calculations of two materials, α -RuCl3 and Sr2IrO4 , and find that the magnonic and spin-orbital excitations are consistent with experiments.

Spin-inversion in nanoscale graphene sheets with a Rashba spin-orbit barrier

Directory of Open Access Journals (Sweden)

Somaieh Ahmadi

2012-03-01

Full Text Available Spin-inversion properties of an electron in nanoscale graphene sheets with a Rashba spin-orbit barrier is studied using transfer matrix method. It is found that for proper values of Rashba spin-orbit strength, perfect spin-inversion can occur in a wide range of electron incident angle near the normal incident. In this case, the graphene sheet with Rashba spin-orbit barrier can be considered as an electron spin-inverter. The efficiency of spin-inverter can increase up to a very high value by increasing the length of Rashba spin-orbit barrier. The effect of intrinsic spin-orbit interaction on electron spin inversion is then studied. It is shown that the efficiency of spin-inverter decreases slightly in the presence of intrinsic spin-orbit interaction. The present study can be used to design graphene-based spintronic devices.

Spin-pump-induced spin transport in a thermally evaporated pentacene film

Energy Technology Data Exchange (ETDEWEB)

Tani, Yasuo; Shikoh, Eiji, E-mail: shikoh@elec.eng.osaka-cu.ac.jp [Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Teki, Yoshio [Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan)

2015-12-14

We report the spin-pump-induced spin transport properties of a pentacene film prepared by thermal evaporation. In a palladium(Pd)/pentacene/Ni{sub 80}Fe{sub 20} tri-layer sample, a pure spin-current is generated in the pentacene layer by the spin-pumping of Ni{sub 80}Fe{sub 20}, which is independent of the conductance mismatch problem in spin injection. The spin current is absorbed into the Pd layer, converted into a charge current with the inverse spin-Hall effect in Pd, and detected as an electromotive force. This is clear evidence for the pure spin current at room temperature in pentacene films prepared by thermal evaporation.

Spin-Triplet Pairing Induced by Spin-Singlet Interactions in Noncentrosymmetric Superconductors

Science.gov (United States)

Matsuzaki, Tomoaki; Shimahara, Hiroshi

2017-02-01

In noncentrosymmetric superconductors, we examine the effect of the difference between the intraband and interband interactions, which becomes more important when the band splitting increases. We define the difference ΔVμ between their coupling constants, i.e., that between the intraband and interband hopping energies of intraband Cooper pairs. Here, the subscript μ of ΔVμ indicates that the interactions scatter the spin-singlet and spin-triplet pairs when μ = 0 and μ = 1,2,3, respectively. It is shown that the strong antisymmetric spin-orbit interaction reverses the target spin parity of the interaction: it converts the spin-singlet and spin-triplet interactions represented by ΔV0 and ΔVμ>0 into effective spin-triplet and spin-singlet pairing interactions, respectively. Hence, for example, triplet pairing can be induced solely by the singlet interaction ΔV0. We name the pairing symmetry of the system after that of the intraband Cooper pair wave function, but with an odd-parity phase factor excluded. The pairing symmetry must then be even, even for the triplet component, and the following results are obtained. When ΔVμ is small, the spin-triplet p-wave interactions induce spin-triplet s-wave and spin-triplet d-wave pairings in the regions where the repulsive singlet s-wave interaction is weak and strong, respectively. When ΔV0 is large, a repulsive interband spin-singlet interaction can stabilize spin-triplet pairing. When the Rashba interaction is adopted for the spin-orbit interaction, the spin-triplet pairing interactions mediated by transverse magnetic fluctuations do not contribute to triplet pairing.

Dynamical spin accumulation in large-spin magnetic molecules

Science.gov (United States)

Płomińska, Anna; Weymann, Ireneusz; Misiorny, Maciej

2018-01-01

The frequency-dependent transport through a nanodevice containing a large-spin magnetic molecule is studied theoretically in the Kondo regime. Specifically, the effect of magnetic anisotropy on dynamical spin accumulation is of primary interest. Such accumulation arises due to finite components of frequency-dependent conductance that are off diagonal in spin. Here, employing the Kubo formalism and the numerical renormalization group method, we demonstrate that the dynamical transport properties strongly depend on the relative orientation of spin moments in electrodes of the device, as well as on intrinsic parameters of the molecule. In particular, the effect of dynamical spin accumulation is found to be greatly affected by the type of magnetic anisotropy exhibited by the molecule, and it develops for frequencies corresponding to the Kondo temperature. For the parallel magnetic configuration of the device, the presence of dynamical spin accumulation is conditioned by the interplay of ferromagnetic-lead-induced exchange field and the Kondo correlations.

Hardy's argument and successive spin-s measurements

International Nuclear Information System (INIS)

Ahanj, Ali

2010-01-01

We consider a hidden-variable theoretic description of successive measurements of noncommuting spin observables on an input spin-s state. In this scenario, the hidden-variable theory leads to a Hardy-type argument that quantum predictions violate it. We show that the maximum probability of success of Hardy's argument in quantum theory is ((1/2)) 4s , which is more than in the spatial case.

Large spin current injection in nano-pillar-based lateral spin valve

Energy Technology Data Exchange (ETDEWEB)

Nomura, Tatsuya [Department of Physics, Kyushu University, 744 Motooka, Fukuoka, 819-0395 (Japan); Ohnishi, Kohei; Kimura, Takashi, E-mail: t-kimu@phys.kyushu-u.ac.jp [Department of Physics, Kyushu University, 744 Motooka, Fukuoka, 819-0395 (Japan); Research Center for Quantum Nano-Spin Sciences, Kyushu University, 744 Motooka, Fukuoka, 819-0395 (Japan)

2016-08-26

We have investigated the influence of the injection of a large pure spin current on a magnetization process of a non-locally located ferromagnetic dot in nano-pillar-based lateral spin valves. Here, we prepared two kinds of the nano-pillar-type lateral spin valve based on Py nanodots and CoFeAl nanodots fabricated on a Cu film. In the Py/Cu lateral spin valve, although any significant change of the magnetization process of the Py nanodot has not been observed at room temperature. The magnetization reversal process is found to be modified by injecting a large pure spin current at 77 K. Switching the magnetization by the nonlocal spin injection has also been demonstrated at 77 K. In the CoFeAl/Cu lateral spin valve, a room temperature spin valve signal was strongly enhanced from the Py/Cu lateral spin valve because of the highly spin-polarized CoFeAl electrodes. The room temperature nonlocal switching has been demonstrated in the CoFeAl/Cu lateral spin valve.

Spin Hall effects

Science.gov (United States)

Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

2015-10-01

Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

Spin-orbit induced electronic spin separation in semiconductor nanostructures.

Science.gov (United States)

Kohda, Makoto; Nakamura, Shuji; Nishihara, Yoshitaka; Kobayashi, Kensuke; Ono, Teruo; Ohe, Jun-ichiro; Tokura, Yasuhiro; Mineno, Taiki; Nitta, Junsaku

2012-01-01

The demonstration of quantized spin splitting by Stern and Gerlach is one of the most important experiments in modern physics. Their discovery was the precursor of recent developments in spin-based technologies. Although electrical spin separation of charged particles is fundamental in spintronics, in non-uniform magnetic fields it has been difficult to separate the spin states of charged particles due to the Lorentz force, as well as to the insufficient and uncontrollable field gradients. Here we demonstrate electronic spin separation in a semiconductor nanostructure. To avoid the Lorentz force, which is inevitably induced when an external magnetic field is applied, we utilized the effective non-uniform magnetic field which originates from the Rashba spin-orbit interaction in an InGaAs-based heterostructure. Using a Stern-Gerlach-inspired mechanism, together with a quantum point contact, we obtained field gradients of 10(8) T m(-1) resulting in a highly polarized spin current.

Spherical subsystem of galactic radiosources

Energy Technology Data Exchange (ETDEWEB)

Gorshkov, A G; Popov, M V [Moskovskij Gosudarstvennyj Univ. (USSR). Gosudarstvennyj Astronomicheskij Inst. ' ' GAISh' '

1975-05-01

The concentration of statistically complete sampling radiosources of the Ohiof scanning with plane spectra towards the Galaxy centre has been discovered. Quantitative calculations have showed that the sources form a spheric subsystem, which is close in parameters to such old formations in the Galaxy as globular clusters and the RRLsub(YR) type stars. The luminosity of the galaxy spheric subsystem object equals 10/sup 33/ erg/sec, the total number of objects being 7000. The existence of such a subsystem explains s the anomalously by low incline of statistics lgN-lgS in HF scanning PKS (..gamma..-2700Mgz) and the Michigan University scanning (..gamma..=8000Mgz) because the sources of galaxy spheric subsystem make up a considerable share in the total number of sources, especially at high frequencies (50% of sources with a flux greater than a unit of flux per 8000Mgz). It is very probable that the given subsystem consists of the representatives of one of the following class of objects: a) heat sources - the H2H regions with T=10/sup 40/K, Nsub(e)=10/sup 3/, l=1 ps b) supermass black holes with mass M/Mo approximately 10/sup 5/.

Mean-Field Studies of a Mixed Spin-3/2 and Spin-2 and a Mixed Spin-3/2 and Spin-5/2 Ising System with Different Anisotropies

International Nuclear Information System (INIS)

Wei Guozhu; Miao Hailing

2009-01-01

The magnetic properties of a mixed spin-3/2 and spin-2 and a mixed spin-3/2 and spin-5/2 Ising ferromagnetic system with different anisotropies are studied by means of mean-field theory (MFT). The dependence of the phase diagram on single-ion anisotropy strengths is studied too. In the mixed spin-3/2 and spin-2 Ising model, besides the second-order phase transition, the first order-disorder phase transition and the tricritical line are found. In the mixed spin-3/2 and spin-5/2 Ising model, there is no first-order transition and tricritical line. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Comparative Aspects of Spin-Dependent Interaction Potentials for Spin-1/2 and Spin-1 Matter Fields

Directory of Open Access Journals (Sweden)

P. C. Malta

2016-01-01

Full Text Available This paper sets out to establish a comparative study between classes of spin- and velocity-dependent potentials for spin-1/2 and spin-1 matter currents/sources in the nonrelativistic regime. Both (neutral massive scalar and vector particles are considered to mediate the interactions between (pseudo-scalar sources or (pseudo-vector currents. Though our discussion is more general, we contemplate specific cases in which our results may describe the electromagnetic interaction with a massive (Proca-type photon exchanged between two spin-1/2 or two spin-1 carriers. We highlight the similarities and peculiarities of the potentials for the two different types of charged matter and also focus our attention on the comparison between the particular aspects of two different field representations for spin-1 matter particles. We believe that our results may contribute to a further discussion of the relation between charge, spin, and extensibility of elementary particles.

Heat and spin interconversion

International Nuclear Information System (INIS)

Ohnuma, Yuichi; Matsuo, Mamoru; Maekawa, Sadamichi; Saitoh, Eeiji

2017-01-01

Spin Seebeck and spin Peltier effects, which are mutual conversion phenomena of heat and spin, are discussed on the basis of the microscopic theory. First, the spin Seebeck effect, which is the spin-current generation due to heat current, is discussed. The recent progress in research on the spin Seebeck effect are introduced. We explain the origin of the observed sign changes of the spin Seebeck effect in compensated ferromagnets. Next, the spin Peltier effect, which is the heat-current generation due to spin current, is discussed. Finally, we show that the spin Seebeck and spin Peltier effects are summarized by Onsager's reciprocal relation and derive Kelvin's relation for the spin and heat transports. (author)

Rotational Invariance of the 2d Spin - Spin Correlation Function

Science.gov (United States)

Pinson, Haru

2012-09-01

At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).

Spin-independent transparency of pure spin current at normal/ferromagnetic metal interface

Science.gov (United States)

Hao, Runrun; Zhong, Hai; Kang, Yun; Tian, Yufei; Yan, Shishen; Liu, Guolei; Han, Guangbing; Yu, Shuyun; Mei, Liangmo; Kang, Shishou

2018-03-01

The spin transparency at the normal/ferromagnetic metal (NM/FM) interface was studied in Pt/YIG/Cu/FM multilayers. The spin current generated by the spin Hall effect (SHE) in Pt flows into Cu/FM due to magnetic insulator YIG blocking charge current and transmitting spin current via the magnon current. Therefore, the nonlocal voltage induced by an inverse spin Hall effect (ISHE) in FM can be detected. With the magnetization of FM parallel or antiparallel to the spin polarization of pure spin currents ({{\\boldsymbol{σ }}}sc}), the spin-independent nonlocal voltage is induced. This indicates that the spin transparency at the Cu/FM interface is spin-independent, which demonstrates that the influence of spin-dependent electrochemical potential due to spin accumulation on the interfacial spin transparency is negligible. Furthermore, a larger spin Hall angle of Fe20Ni80 (Py) than that of Ni is obtained from the nonlocal voltage measurements. Project supported by the National Basic Research Program of China (Grant No. 2015CB921502), the National Natural Science Foundation of China (Grant Nos. 11474184 and 11627805), the 111 Project, China (Grant No. B13029), and the Fundamental Research Funds of Shandong University, China.

Rapid Prototyping of Electrically Small Spherical Wire Antennas

DEFF Research Database (Denmark)

Kim, Oleksiy S.

2014-01-01

It is shown how modern rapid prototyping technologies can be applied for quick and inexpensive, but still accurate, fabrication of electrically small wire antennas. A well known folded spherical helix antenna and a novel spherical zigzag antenna have been fabricated and tested, exhibiting...

Equilibrium spherically curved two-dimensional Lennard-Jones systems

NARCIS (Netherlands)

Voogd, J.M.; Sloot, P.M.A.; van Dantzig, R.

2005-01-01

To learn about basic aspects of nano-scale spherical molecular shells during their formation, spherically curved two-dimensional N-particle Lennard-Jones systems are simulated, studying curvature evolution paths at zero-temperature. For many N-values (N < 800) equilibrium configu- rations are traced

Stability of the spherical form of nuclei

International Nuclear Information System (INIS)

Sabry, A.A.

1976-08-01

An extension of the mass formula for a spherical nucleus in the drop model to include a largely deformed nucleus of different forms is investigated. It is found that although the spherical form is stable under small deformations from equilibrium, there exists for heavier nuclei another more favourable stable form, which can be approximated by two, or three touching prolate ellipsoids of revolution

Elastic properties of spherically anisotropic piezoelectric composites

International Nuclear Information System (INIS)

En-Bo, Wei; Guo-Qing, Gu; Ying-Ming, Poon

2010-01-01

Effective elastic properties of spherically anisotropic piezoelectric composites, whose spherically anisotropic piezoelectric inclusions are embedded in an infinite non-piezoelectric matrix, are theoretically investigated. Analytical solutions for the elastic displacements and the electric potentials under a uniform external strain are derived exactly. Taking into account of the coupling effects of elasticity, permittivity and piezoelectricity, the formula is derived for estimating the effective elastic properties based on the average field theory in the dilute limit. An elastic response mechanism is revealed, in which the effective elastic properties increase as inclusion piezoelectric properties increase and inclusion dielectric properties decrease. Moreover, a piezoelectric response mechanism, of which the effective piezoelectric response vanishes due to the symmetry of spherically anisotropic composite, is also disclosed. (condensed matter: structure, thermal and mechanical properties)

Flow and scour around spherical bodies

DEFF Research Database (Denmark)

Truelsen, Christoffer

2003-01-01

Spherical bodies placed in the marine environment may bury themselves due to the action of the waves and the current on the sediment in their immediate neighborhood. The present study addresses this topic by a numerical and an experimental investigation of the flow and scour around a spherical body...... results except in the critical flow regime. For flow around a near-wall sphere, a weak horseshoe vortex emerges as the gap ratio becomes less than or equal to 0.3. In Chapter 3, a RANS flow solver has been used to compute the bed shear stress for a near-wall sphere. The model results compare well...... 4, an experimental study on the scour around spherical bodies and self-burial in sand for steady current and waves has been carried out. The effect of the contraction of streamlines is found to be the key element in the scour process both for steady current and waves. Furthermore, it is demonstrated...

Spherical tokamak power plant design issues

International Nuclear Information System (INIS)

Hender, T.C.; Bond, A.; Edwards, J.; Karditsas, P.J.; McClements, K.G.; Mustoe, J.; Sherwood, D.V.; Voss, G.M.; Wilson, H.R.

2000-01-01

The very high β potential of the spherical tokamak has been demonstrated in the START experiment. Systems code studies show the cost of electricity from spherical tokamak power plants, operating at high β in second ballooning mode stable regime, is comparable with fossil fuels and fission. Outline engineering designs are presented based on two concepts for the central rod of the toroidal field (TF) circuit - a room temperature water cooled copper rod or a helium cooled cryogenic aluminium rod. For the copper rod case the TF return limbs are supported by the vacuum vessel, while for the aluminium rod the TF coils form an independent structure. In both cases thermohydraulic and stress calculations indicate the viability of the design. Two-dimensional neutronics calculations show the feasibility of tritium self-sufficiency without an inboard blanket. The spherical tokamak has unique maintenance possibilities based on lowering major component structures into a hot cell beneath the device and these are discussed

Integrals of products of spherical functions

International Nuclear Information System (INIS)

Veverka, O.

1975-01-01

Various branches of mathematical physics use integral formulas of the products of spherical functions. In quantum mechanics and in transport theory the integrals ∫sub((4π))dΩ vectorYsub(s)sup(t)(Ω vector)Ysub(l)sup(k)(Ω vector)Ysub(n)sup(m)(Ω vector), ∫sub(-1)sup(1)dμPsub(s)sup(t)(μ)Psub(l)sup(k)(μ)Psub(n)sup(m)(μ), ∫sub(-1)sup(1)dμPsub(s)(μ)Psub(l)(μ)Psub(n)(μ) are generally applied, where Ysub(α)sup(β)(Ω vector) are spherical harmonics, Psub(α)sup(β)(μ) are associated Legendre functions, and Psub(α)(μ) are Legendre polynomials. In the paper, the general procedure of calculating the integrals of the products of any combination of spherical functions is given. The procedure is referred to in a report on the boundary conditions for the cylindrical geometry in neutron transport theory for both the outer and inner cylindrical boundaries. (author)

Spin-lattice relaxation of individual solid-state spins

Science.gov (United States)

Norambuena, A.; Muñoz, E.; Dinani, H. T.; Jarmola, A.; Maletinsky, P.; Budker, D.; Maze, J. R.

2018-03-01

Understanding the effect of vibrations on the relaxation process of individual spins is crucial for implementing nanosystems for quantum information and quantum metrology applications. In this work, we present a theoretical microscopic model to describe the spin-lattice relaxation of individual electronic spins associated to negatively charged nitrogen-vacancy centers in diamond, although our results can be extended to other spin-boson systems. Starting from a general spin-lattice interaction Hamiltonian, we provide a detailed description and solution of the quantum master equation of an electronic spin-one system coupled to a phononic bath in thermal equilibrium. Special attention is given to the dynamics of one-phonon processes below 1 K where our results agree with recent experimental findings and analytically describe the temperature and magnetic-field scaling. At higher temperatures, linear and second-order terms in the interaction Hamiltonian are considered and the temperature scaling is discussed for acoustic and quasilocalized phonons when appropriate. Our results, in addition to confirming a T5 temperature dependence of the longitudinal relaxation rate at higher temperatures, in agreement with experimental observations, provide a theoretical background for modeling the spin-lattice relaxation at a wide range of temperatures where different temperature scalings might be expected.

Muon spin rotation and other microscopic probes of spin-glass dynamics

International Nuclear Information System (INIS)

MacLaughlin, D.E.

1980-01-01

A number of different microscopic probe techniques have been employed to investigate the onset of the spin-glass state in dilute magnetic alloys. Among these are Moessbauer-effect spectroscopy, neutron scattering, ESR of the impurity spins, host NMR and, most recently, muon spin rotation and depolarization. Spin probes yield information on the microscopic static and dynamic behavior of the impurity spins, and give insight into both the spin freezing process and the nature of low-lying excitations in the ordered state. Microscopic probe experiments in spin glasses are surveyed, and the unique advantages of muon studies are emphasized

Satellite alignment. I. Distribution of substructures and their dependence on assembly history from n-body simulations

International Nuclear Information System (INIS)

Wang, Yang Ocean; Lin, W. P.; Yu, Yu; Kang, X.; Dutton, Aaron; Macciò, Andrea V.

2014-01-01

Observations have shown that the spatial distribution of satellite galaxies is not random, but aligned with the major axes of central galaxies. This alignment is dependent on galaxy properties, such that red satellites are more strongly aligned than blue satellites. Theoretical work conducted to interpret this phenomenon has found that it is due to the non-spherical nature of dark matter halos. However, most studies overpredict the alignment signal under the assumption that the central galaxy shape follows the shape of the host halo. It is also not clear whether the color dependence of alignment is due to an assembly bias or an evolution effect. In this paper we study these problems using a cosmological N-body simulation. Subhalos are used to trace the positions of satellite galaxies. It is found that the shapes of dark matter halos are mis-aligned at different radii. If the central galaxy shares the same shape as the inner host halo, then the alignment effect is weaker and agrees with observational data. However, it predicts almost no dependence of alignment on the color of satellite galaxies, though the late accreted subhalos show stronger alignment with the outer layer of the host halo than their early accreted counterparts. We find that this is due to the limitation of pure N-body simulations where satellite galaxies without associated subhalos ('orphan galaxies') are not resolved. These orphan (mostly red) satellites often reside in the inner region of host halos and should follow the shape of the host halo in the inner region.

Quantifying Spin Hall Angles from Spin Pumping : Experiments and Theory

NARCIS (Netherlands)

Mosendz, O.; Pearson, J.E.; Fradin, F.Y.; Bauer, G.E.W.; Bader, S.D.; Hoffmann, A.

2010-01-01

Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating Ni80Fe20|normal metal (N) bilayers into a coplanar

A GOCE only gravity model GOSG01S and the validation of GOCE related satellite gravity models

Directory of Open Access Journals (Sweden)

Xinyu Xu

2017-07-01

Full Text Available We compile the GOCE-only satellite model GOSG01S complete to spherical harmonic degree of 220 using Satellite Gravity Gradiometry (SGG data and the Satellite-to-Satellite Tracking (SST observations along the GOCE orbit based on applying a least-squares analysis. The diagonal components (Vxx, Vyy, Vzz of the gravitational gradient tensor are used to form the system of observation equations with the band-pass ARMA filter. The point-wise acceleration observations (ax, ay, az along the orbit are used to form the system of observation equations up to the maximum spherical harmonic degree/order 130. The analysis of spectral accuracy characteristics of the newly derived gravitational model GOSG01S and the existing models GOTIM04S, GODIR04S, GOSPW04S and JYY_GOCE02S based on their comparison with the ultra-high degree model EIGEN-6C2 reveals a significant consistency at the spectral window approximately between 80 and 190 due to the same period SGG data used to compile these models. The GOCE related satellite gravity models GOSG01S, GOTIM05S, GODIR05S, GOTIM04S, GODIR04S, GOSPW04S, JYY_GOCE02S, EIGEN-6C2 and EGM2008 are also validated by using GPS-leveling data in China and USA. According to the truncation at degree 200, the statistic results show that all GGMs have very similar differences at GPS-leveling points in USA, and all GOCE related gravity models have better performance than EGM2008 in China. This suggests that all these models provide much more information on the gravity field than EGM2008 in areas with low terrestrial gravity coverage. And STDs of height anomaly differences in China for the selected truncation degrees show that GOCE has improved the accuracy of the global models beyond degree 90 and the accuracies of the models improve from 24 cm to 16 cm. STDs of geoid height differences in USA show that GOSG01S model has best consistency comparing with GPS-leveling data for the frequency band of the degree between 20 and 160.

Synthesis and characterization of spherical 2-diazo-4,6-dinitrophenol (DDNP)

International Nuclear Information System (INIS)

Yang Zongwei; Liu Yucun; Liu Dengcheng; Yan Liwei; Chen Ji

2010-01-01

Spherical 2-diazo-4,6-dinitrophenol (DDNP) with good flowability and controlled bulk density (0.65-0.95 g/cm 3 ) has been prepared at factory scale by the modified method using 4-methylphenol as crystal control ingredient. Results showed that the yield of product was increased by 5-10%, and the waste water was significantly decreased due to circulation use of waste water compared with traditional method. Synthesized spherical DDNP was characterized by IR, laser granularity measurement, SEM, HPLC and XRD. IR spectrum confirmed the structural features of spherical DDNP. The particle analysis revealed that the modified method could offer spherical DDNP with average particle size of 350 μm and high purity (>98.52%). The XRD peaks of spherical DDNP have similar diffraction angles as those of traditional DDNP. The DSC profile of spherical DDNP showed the exothermic decomposition in the temperature range of 161.2-188.5 deg. C. The product can be pressed at over 40 MPa without dead pressed phenomenon, and the minimum detonating charge of spherical DDNP was measured to be about 0.15 g. Furthermore, impact sensitivity test suggested that spherical DDNP is less sensitive than traditional DDNP.

A new concept of space solar power satellite

Science.gov (United States)

Li, Xun; Duan, Baoyan; Song, Liwei; Yang, Yang; Zhang, Yiqun; Wang, Dongxu

2017-07-01

Space solar power satellite (SSPS) is a tremendous energy system that collects and converts solar power to electric power in space, and then transmits the electric power to earth wirelessly. In this paper, a novel SSPS concept based on ε-near-zero (ENZ) metamaterial is proposed. A spherical condenser made of ENZ metamaterial is developed, by using the refractive property of the ENZ metamaterial sunlight can be captured and redirected to its center. To make the geometric concentration ratio of the PV array reasonable, a hemispherical one located at the center is used to collect and convert the normal-incidence sunlight to DC power, then through a phased array transmitting antenna the DC power is beamed down to the rectenna on the ground. Detailed design of the proposed concept is presented.

Spin-orbit-coupled transport and spin torque in a ferromagnetic heterostructure

KAUST Repository

Wang, Xuhui; Ortiz Pauyac, Christian; Manchon, Aurelien

2014-01-01

Ferromagnetic heterostructures provide an ideal platform to explore the nature of spin-orbit torques arising from the interplay mediated by itinerant electrons between a Rashba-type spin-orbit coupling and a ferromagnetic exchange interaction. For such a prototypic system, we develop a set of coupled diffusion equations to describe the diffusive spin dynamics and spin-orbit torques. We characterize the spin torque and its two prominent—out-of-plane and in-plane—components for a wide range of relative strength between the Rashba coupling and ferromagnetic exchange. The symmetry and angular dependence of the spin torque emerging from our simple Rashba model is in an agreement with experiments. The spin diffusion equation can be generalized to incorporate dynamic effects such as spin pumping and magnetic damping.

Spin-orbit-coupled transport and spin torque in a ferromagnetic heterostructure

KAUST Repository

Wang, Xuhui

2014-02-07

Ferromagnetic heterostructures provide an ideal platform to explore the nature of spin-orbit torques arising from the interplay mediated by itinerant electrons between a Rashba-type spin-orbit coupling and a ferromagnetic exchange interaction. For such a prototypic system, we develop a set of coupled diffusion equations to describe the diffusive spin dynamics and spin-orbit torques. We characterize the spin torque and its two prominent—out-of-plane and in-plane—components for a wide range of relative strength between the Rashba coupling and ferromagnetic exchange. The symmetry and angular dependence of the spin torque emerging from our simple Rashba model is in an agreement with experiments. The spin diffusion equation can be generalized to incorporate dynamic effects such as spin pumping and magnetic damping.

Electron-Spin Filters Would Offer Spin Polarization Greater than 1

Science.gov (United States)

Ting, David Z.

2009-01-01

A proposal has been made to develop devices that would generate spin-polarized electron currents characterized by polarization ratios having magnitudes in excess of 1. Heretofore, such devices (denoted, variously, as spin injectors, spin polarizers, and spin filters) have typically offered polarization ratios having magnitudes in the approximate range of 0.01 to 0.1. The proposed devices could be useful as efficient sources of spin-polarized electron currents for research on spintronics and development of practical spintronic devices.

Efficient micromagnetic modelling of spin-transfer torque and spin-orbit torque

Science.gov (United States)

Abert, Claas; Bruckner, Florian; Vogler, Christoph; Suess, Dieter

2018-05-01

While the spin-diffusion model is considered one of the most complete and accurate tools for the description of spin transport and spin torque, its solution in the context of dynamical micromagnetic simulations is numerically expensive. We propose a procedure to retrieve the free parameters of a simple macro-spin like spin-torque model through the spin-diffusion model. In case of spin-transfer torque the simplified model complies with the model of Slonczewski. A similar model can be established for the description of spin-orbit torque. In both cases the spin-diffusion model enables the retrieval of free model parameters from the geometry and the material parameters of the system. Since these parameters usually have to be determined phenomenologically through experiments, the proposed method combines the strength of the diffusion model to resolve material parameters and geometry with the high performance of simple torque models.

Periphony-Lattice Mixed-Order Ambisonic Scheme for Spherical Microphone Arrays

DEFF Research Database (Denmark)

Chang, Jiho; Marschall, Marton

2018-01-01

to performance that is independent of the incident direction of the sound waves. On the other hand, mixed-order ambisonic (MOA) schemes that select an appropriate subset of spherical harmonics can improve the performance for horizontal directions at the expense of other directions. This paper proposes an MOA......Most methods for sound field reconstruction and spherical beamforming with spherical microphone arrays are mathematically based on the spherical harmonics expansion. In many cases, this expansion is truncated at a certain order as in higher order ambisonics (HOA). This truncation leads...

Spin Drag and Spin-Charge Separation in Cold Fermi Gases

International Nuclear Information System (INIS)

Polini, Marco; Vignale, Giovanni

2007-01-01

Low-energy spin and charge excitations of one-dimensional interacting fermions are completely decoupled and propagate with different velocities. These modes, however, can decay due to several possible mechanisms. In this Letter we expose a new facet of spin-charge separation: not only the speeds but also the damping rates of spin and charge excitations are different. While the propagation of long-wavelength charge excitations is essentially ballistic, spin propagation is intrinsically damped and diffusive. We suggest that cold Fermi gases trapped inside a tight atomic waveguide offer the opportunity to measure the spin-drag relaxation rate that controls the broadening of a spin packet

Spherical torus, compact fusion at low field

International Nuclear Information System (INIS)

Peng, Y.K.M.

1985-02-01

A spherical torus is obtained by retaining only the indispensable components on the inboard side of a tokamak plasma, such as a cooled, normal conductor that carries current to produce a toroidal magnetic field. The resulting device features an exceptionally small aspect ratio (ranging from below 2 to about 1.3), a naturally elongated D-shaped plasma cross section, and ramp-up of the plasma current primarily by noninductive means. As a result of the favorable dependence of the tokamak plasma behavior to decreasing aspect ratio, a spherical torus is projected to have small size, high beta, and modest field. Assuming Mirnov confinement scaling, an ignition spherical torus at a field of 2 T features a major radius of 1.5 m, a minor radius of 1.0 m, a plasma current of 14 MA, comparable toroidal and poloidal field coil currents, an average beta of 24%, and a fusion power of 50 MW. At 2 T, a Q = 1 spherical torus will have a major radius of 0.8 m, a minor radius of 0.5 m, and a fusion power of a few megawatts

Spinning Them Off: Entrepreneuring Practices in Corporate Spin-Offs

Directory of Open Access Journals (Sweden)

Katja Maria Hydle

2016-01-01

Full Text Available This paper focuses on the practices between parent and child firms in corporate spinoffs. We uncover the enacted aspects of knowledge, called knowing, through theories from seven cases of incumbent-backed spin-offs and find that the management of the parent firms are highly involved in the spin-offs. The practices associated with spinning off are solving problems, involving multidisciplinary expertise and entrepreneuring management at the parent firm. We contribute to the spin-off literature by discussing the knowledge required for successfully spinning off child firms and to practice theory by empirically uncovering the practical understanding involved in the origin and perpetuation of an organization.

A modular spherical harmonics approach to the neutron transport equation

International Nuclear Information System (INIS)

Inanc, F.; Rohach, A.F.

1989-01-01

A modular nodal method was developed for solving the neutron transport equation in 2-D xy coordinates. The spherical harmonic expansion was used for approximating the second-order even-parity form of the neutron transport equation. The boundary conditions of the spherical harmonics approximation were derived in a form to have forms analogous to the partial currents in the neutron diffusion equation. Relations were developed for generating both the second-order spherical harmonic equations and the boundary conditions in an automated computational algorithm. Nodes using different orders of the spherical harmonics approximation to the transport equation were interfaced through mixed-type boundary conditions. The determination of spherical harmonic orders implemented in the nodes were determined by the scheme in an automated manner. Results of the method compared favorably to benchmark problems. (author)

Spin and tunneling dynamics in an asymmetrical double quantum dot with spin-orbit coupling: Selective spin transport device

Science.gov (United States)

Singh, Madhav K.; Jha, Pradeep K.; Bhattacherjee, Aranya B.

2017-09-01

In this article, we study the spin and tunneling dynamics as a function of magnetic field in a one-dimensional GaAs double quantum dot with both the Dresselhaus and Rashba spin-orbit coupling. In particular, we consider different spatial widths for the spin-up and spin-down electronic states. We find that the spin dynamics is a superposition of slow as well as fast Rabi oscillations. It is found that the Rashba interaction strength as well as the external magnetic field strongly modifies the slow Rabi oscillations which is particularly useful for implementing solid state selective spin transport device.

Enhanced Spin-Orbit Torque via Modulation of Spin Current Absorption

KAUST Repository

Qiu, Xuepeng

2016-11-18

The magnitude of spin-orbit torque (SOT), exerted to a ferromagnet (FM) from an adjacent heavy metal (HM), strongly depends on the amount of spin current absorbed in the FM. We exploit the large spin absorption at the Ru interface to manipulate the SOTs in HM/FM/Ru multilayers. While the FM thickness is smaller than its spin dephasing length of 1.2 nm, the top Ru layer largely boosts the absorption of spin currents into the FM layer and substantially enhances the strength of SOT acting on the FM. Spin-pumping experiments induced by ferromagnetic resonance support our conclusions that the observed increase in the SOT efficiency can be attributed to an enhancement of the spin-current absorption. A theoretical model that considers both reflected and transmitted mixing conductances at the two interfaces of FM is developed to explain the results.

Excitation of coherent propagating spin waves by pure spin currents.

Science.gov (United States)

Demidov, Vladislav E; Urazhdin, Sergei; Liu, Ronghua; Divinskiy, Boris; Telegin, Andrey; Demokritov, Sergej O

2016-01-28

Utilization of pure spin currents not accompanied by the flow of electrical charge provides unprecedented opportunities for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. It was recently shown that pure spin currents can be used to excite coherent magnetization dynamics in magnetic nanostructures. However, because of the intrinsic nonlinear self-localization effects, magnetic auto-oscillations in the demonstrated devices were spatially confined, preventing their applications as sources of propagating spin waves in magnonic circuits using these waves as signal carriers. Here, we experimentally demonstrate efficient excitation and directional propagation of coherent spin waves generated by pure spin current. We show that this can be achieved by using the nonlocal spin injection mechanism, which enables flexible design of magnetic nanosystems and allows one to efficiently control their dynamic characteristics.

Electrical detection of spin current and spin relaxation in nonmagnetic semiconductors

International Nuclear Information System (INIS)

Miah, M Idrish

2008-01-01

We report an electrical method for the detection of spin current and spin relaxation in nonmagnetic semiconductors. Optically polarized spins are dragged by an electric field in GaAs. We use the anomalous Hall effect for the detection of spin current and spin relaxation. It is found that the effect depends on the electric field and doping density as well as on temperature, but not on the excitation power. A calculation for the effect is performed using the measured spin polarization by a pump-probe experiment. The results are also discussed in comparison with a quantitative evaluation of the spin lifetimes of the photogenerated electrons under drift in GaAs

Electrical detection of spin current and spin relaxation in nonmagnetic semiconductors

Energy Technology Data Exchange (ETDEWEB)

Miah, M Idrish [Nanoscale Science and Technology Centre and School of Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au

2008-09-21

We report an electrical method for the detection of spin current and spin relaxation in nonmagnetic semiconductors. Optically polarized spins are dragged by an electric field in GaAs. We use the anomalous Hall effect for the detection of spin current and spin relaxation. It is found that the effect depends on the electric field and doping density as well as on temperature, but not on the excitation power. A calculation for the effect is performed using the measured spin polarization by a pump-probe experiment. The results are also discussed in comparison with a quantitative evaluation of the spin lifetimes of the photogenerated electrons under drift in GaAs.

Spin Transport in Nondegenerate Si with a Spin MOSFET Structure at Room Temperature

Science.gov (United States)

Sasaki, Tomoyuki; Ando, Yuichiro; Kameno, Makoto; Tahara, Takayuki; Koike, Hayato; Oikawa, Tohru; Suzuki, Toshio; Shiraishi, Masashi

2014-09-01

Spin transport in nondegenerate semiconductors is expected to pave the way to the creation of spin transistors, spin logic devices, and reconfigurable logic circuits, because room-temperature (RT) spin transport in Si has already been achieved. However, RT spin transport has been limited to degenerate Si, which makes it difficult to produce spin-based signals because a gate electric field cannot be used to manipulate such signals. Here, we report the experimental demonstration of spin transport in nondegenerate Si with a spin metal-oxide-semiconductor field-effect transistor (MOSFET) structure. We successfully observe the modulation of the Hanle-type spin-precession signals, which is a characteristic spin dynamics in nondegenerate semiconductors. We obtain long spin transport of more than 20 μm and spin rotation greater than 4π at RT. We also observe gate-induced modulation of spin-transport signals at RT. The modulation of the spin diffusion length as a function of a gate voltage is successfully observed, which we attribute to the Elliott-Yafet spin relaxation mechanism. These achievements are expected to lead to the creation of practical Si-based spin MOSFETs.

Current-induced spin polarization in a spin-polarized two-dimensional electron gas with spin-orbit coupling

International Nuclear Information System (INIS)

Wang, C.M.; Pang, M.Q.; Liu, S.Y.; Lei, X.L.

2010-01-01

The current-induced spin polarization (CISP) is investigated in a combined Rashba-Dresselhaus spin-orbit-coupled two-dimensional electron gas, subjected to a homogeneous out-of-plane magnetization. It is found that, in addition to the usual collision-related in-plane parts of CISP, there are two impurity-density-free contributions, arising from intrinsic and disorder-mediated mechanisms. The intrinsic parts of spin polarization are related to the Berry curvature, analogous with the anomalous and spin Hall effects. For short-range collision, the disorder-mediated spin polarizations completely cancel the intrinsic ones and the total in-plane components of CISP equal those for systems without magnetization. However, for remote disorders, this cancellation does not occur and the total in-plane components of CISP strongly depend on the spin-orbit interaction coefficients and magnetization for both pure Rashba and combined Rashba-Dresselhaus models.

Anisotropic interactions of a single spin and dark-spin spectroscopy in diamond

Science.gov (United States)

Epstein, R. J.; Mendoza, F. M.; Kato, Y. K.; Awschalom, D. D.

2005-11-01

Experiments on single nitrogen-vacancy (N-V) centres in diamond, which include electron spin resonance, Rabi oscillations, single-shot spin readout and two-qubit operations with a nearby13C nuclear spin, show the potential of this spin system for solid-state quantum information processing. Moreover, N-V centre ensembles can have spin-coherence times exceeding 50 μs at room temperature. We have developed an angle-resolved magneto-photoluminescence microscope apparatus to investigate the anisotropic electron-spin interactions of single N-V centres at room temperature. We observe negative peaks in the photoluminescence as a function of both magnetic-field magnitude and angle that are explained by coherent spin precession and anisotropic relaxation at spin-level anti-crossings. In addition, precise field alignment unmasks the resonant coupling to neighbouring `dark' nitrogen spins, otherwise undetected by photoluminescence. These results demonstrate the capability of our spectroscopic technique for measuring small numbers of dark spins by means of a single bright spin under ambient conditions.

Direct Observation on Spin-Coating Process of PS- b -P2VP Thin Films

Energy Technology Data Exchange (ETDEWEB)

Ogawa, Hiroki; Takenaka, Mikihito; Miyazaki, Tsukasa; Fujiwara, Akihiko; Lee, Byeongdu; Shimokita, Keisuke; Nishibori, Eiji; Takata, Masaki

2016-05-10

We studied the structural development of symmetric poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) block copolymers during spin-coating using in situ grazing incidence small angle X-ray scattering (GISAXS) measurements. During the spin-coating process, after the formation of the micelles in dilute solution, the selective solvent induced two kinds of the morphological transition. Firstly, the disordered spherical micelles were transformed into a BCC lattice of spheres of which the (110) plane was oriented perpendicularly to the substrate surface. Secondly, further evaporation induced a transition from spheres on the BCC lattice into cylindrical structures. The orientation of the cylinders perpendicular to the substrate surface was induced by solvent convection perpendicular to the substrate, which occurs during rapid solvent evaporation. After this transition, vitrification of PS and P2VP prevented any further transition from cylinders to the more thermodynamically stable lamellar structures, as are generally observed as the bulk equilibrium state.

Spin-resolved electron waiting times in a quantum-dot spin valve

Science.gov (United States)

Tang, Gaomin; Xu, Fuming; Mi, Shuo; Wang, Jian

2018-04-01

We study the electronic waiting-time distributions (WTDs) in a noninteracting quantum-dot spin valve by varying spin polarization and the noncollinear angle between the magnetizations of the leads using the scattering matrix approach. Since the quantum-dot spin valve involves two channels (spin up and down) in both the incoming and outgoing channels, we study three different kinds of WTDs, which are two-channel WTD, spin-resolved single-channel WTD, and cross-channel WTD. We analyze the behaviors of WTDs in short times, correlated with the current behaviors for different spin polarizations and noncollinear angles. Cross-channel WTD reflects the correlation between two spin channels and can be used to characterize the spin-transfer torque process. We study the influence of the earlier detection on the subsequent detection from the perspective of cross-channel WTD, and define the influence degree quantity as the cumulative absolute difference between cross-channel WTDs and first-passage time distributions to quantitatively characterize the spin-flip process. We observe that influence degree versus spin-transfer torque for different noncollinear angles as well as different polarizations collapse into a single curve showing universal behaviors. This demonstrates that cross-channel WTDs can be a pathway to characterize spin correlation in spintronics system.

Spin Filters as High-Performance Spin Polarimeters

International Nuclear Information System (INIS)

Rougemaille, N.; Lampel, G.; Peretti, J.; Drouhin, H.-J.; Lassailly, Y.; Filipe, A.; Wirth, T.; Schuhl, A.

2003-01-01

A spin-dependent transport experiment in which hot electrons pass through a ferromagnetic metal / semiconductor Schottky diode has been performed. A spin-polarized free-electron beam, emitted in vacuum from a GaAs photocathode, is injected into the thin metal layer with an energy between 5 and 1000 eV above to the Fermi level. The transmitted current collected in the semiconductor substrate increases with injection energy because of secondary - electron multiplication. The spin-dependent part of the transmitted current is first constant up to about 100 eV and then increases by 4 orders of magnitude. As an immediate application, the solid-state hybrid structure studied here leads to a very efficient and compact device for spin polarization detection

Spin transport in spin filtering magnetic tunneling junctions.

Science.gov (United States)

Li, Yun; Lee, Eok Kyun

2007-11-01

Taking into account spin-orbit coupling and s-d interaction, we investigate spin transport properties of the magnetic tunneling junctions with spin filtering barrier using Landauer-Büttiker formalism implemented with the recursive algorithm to calculate the real-space Green function. We predict completely different bias dependence of negative tunnel magnetoresistance (TMR) between the systems composed of nonmagnetic electrode (NM)/ferromagnetic barrier (FB)/ferromagnet (FM) and NM/FB/FM/NM spin filtering tunnel junctions (SFTJs). Analyses of the results provide us possible ways of designing the systems which modulate the TMR in the negative magnetoresistance regime.

Effective pair potentials for spherical nanoparticles

International Nuclear Information System (INIS)

Van Zon, Ramses

2009-01-01

An effective description for rigid spherical nanoparticles in a fluid of point particles is presented. The points inside the nanoparticles and the point particles are assumed to interact via spherically symmetric additive pair potentials, while the distribution of points inside the nanoparticles is taken to be spherically symmetric and smooth. The resulting effective pair interactions between a nanoparticle and a point particle, as well as between two nanoparticles, are then given by spherically symmetric potentials. If overlap between particles is allowed, as can occur for some forms of the pair potentials, the effective potential generally has non-analytic points. It is shown that for each effective potential the expressions for different overlapping cases can be written in terms of one analytic auxiliary potential. Even when only non-overlapping situations are possible, the auxiliary potentials facilitate the formulation of the effective potentials. Effective potentials for hollow nanoparticles (appropriate e.g. for buckyballs) are also considered and shown to be related to those for solid nanoparticles. For hollow nanoparticles overlap is more physical, since this covers the case of a smaller particle embedded in a larger, hollow nanoparticle. Finally, explicit expressions are given for the effective potentials derived from basic pair potentials of power law and exponential form, as well as from the commonly used London–van der Waals, Morse, Buckingham, and Lennard-Jones potentials. The applicability of the latter is demonstrated by comparison with an atomic description of nanoparticles with an internal face centered cubic structure

Spin relaxation through Kondo scattering in Cu/Py lateral spin valves

Science.gov (United States)

Batley, J. T.; Rosaond, M. C.; Ali, M.; Linfield, E. H.; Burnell, G.; Hickey, B. J.

Within non-magnetic metals it is reasonable to expect the Elliot-Yafet mechanism to govern spin-relaxation and thus the temperature dependence of the spin diffusion length might be inversely proportional to resistivity. However, in lateral spin valves, measurements have found that at low temperatures the spin diffusion length unexpectedly decreases. We have fabricated lateral spin valves from Cu with different concentrations of magnetic impurities. Through temperature dependent charge and spin transport measurements we present clear evidence linking the presence of the Kondo effect within Cu to the suppression of the spin diffusion length below 30 K. We have calculated the spin-relaxation rate and isolated the contribution from magnetic impurities. At very low temperatures electron-electron interactions play a more prominent role in the Kondo effect. Well below the Kondo temperature a strong-coupling regime exists, where the moments become screened and the magnetic dephasing rate is reduced. We also investigate the effect of this low temperature regime (>1 K) on a pure spin current. This work shows the dominant role of Kondo scattering, even in low concentrations of order 1 ppm, within pure spin transport.

Spin polarization of tunneling current in barriers with spin-orbit coupling

International Nuclear Information System (INIS)

Fujita, T; Jalil, M B A; Tan, S G

2008-01-01

We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons

Spin polarization of tunneling current in barriers with spin-orbit coupling.

Science.gov (United States)

Fujita, T; Jalil, M B A; Tan, S G

2008-03-19

We present a general method for evaluating the maximum transmitted spin polarization and optimal spin axis for an arbitrary spin-orbit coupling (SOC) barrier system, in which the spins lie in the azimuthal plane and finite spin polarization is achieved by wavevector filtering of electrons. Besides momentum filtering, another prerequisite for finite spin polarization is asymmetric occupation or transmission probabilities of the eigenstates of the SOC Hamiltonian. This is achieved most efficiently by resonant tunneling through multiple SOC barriers. We apply our analysis to common SOC mechanisms in semiconductors: pure bulk Dresselhaus SOC, heterostructures with mixed Dresselhaus and Rashba SOC and strain-induced SOC. In particular, we find that the interplay between Dresselhaus and Rashba SOC effects can yield several advantageous features for spin filter and spin injector functions, such as increased robustness to wavevector spread of electrons.

Spin pumping and inverse spin Hall effects in heavy metal/antiferromagnet/Permalloy trilayers

Science.gov (United States)

Saglam, Hilal; Zhang, Wei; Jungfleisch, M. Benjamin; Jiang, Wanjun; Pearson, John E.; Hoffmann, Axel

Recent work shows efficient spin transfer via spin waves in insulating antiferromagnets (AFMs), suggesting that AFMs can play a more active role in the manipulation of ferromagnets. We use spin pumping and inverse spin Hall effect experiments on heavy metal (Pt and W)/AFMs/Py (Ni80Fe20) trilayer structures, to examine the possible spin transfer phenomenon in metallic AFMs, i . e . , FeMn and PdMn. Previous work has studied electronic effects of the spin transport in these materials, yielding short spin diffusion length on the order of 1 nm. However, the work did not examine whether besides diffusive spin transport by the conduction electrons, there are additional spin transport contributions from spin wave excitations. We clearly observe spin transport from the Py spin reservoir to the heavy metal layer through the sandwiched AFMs with thicknesses well above the previously measured spin diffusion lengths, indicating that spin transport by spin waves may lead to non-negligible contributions This work was supported by US DOE, OS, Materials Sciences and Engineering Division. Lithographic patterning was carried out at the CNM, which is supported by DOE, OS under Contract No. DE-AC02-06CH11357.

A model of Earth’s magnetic field derived from 2 years of Swarm satellite constellation data

DEFF Research Database (Denmark)

Olsen, Nils; Finlay, Chris; Kotsiaros, Stavros

2016-01-01

More than 2 years of magnetic field data taken by the three-satellite constellation mission Swarm are used to derive a model of Earth’s magnetic field and its time variation. This model is called SIFMplus. In addition to the magnetic field observations provided by each of the three Swarm satellites...... the North–South gradient. The SIFMplus model provides a description of the static lithospheric field that is very similar to models determined from CHAMP data, up to at least spherical harmonic degree n=75. Also the core field part of SIFMplus, with a quadratic time dependence for n≤6 and a linear time...... with the model of the core, lithospheric and large-scale magnetospheric fields, a magnetic potential that depends on quasi-dipole latitude and magnetic local time....

Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide

DEFF Research Database (Denmark)

Javadi, Alisa; Ding, Dapeng; Appel, Martin Hayhurst

2018-01-01

Access to the electron spin is at the heart of many protocols for integrated and distributed quantum-information processing [1-4]. For instance, interfacing the spin-state of an electron and a photon can be utilized to perform quantum gates between photons [2,5] or to entangle remote spin states [6......-9]. Ultimately, a quantum network of entangled spins constitutes a new paradigm in quantum optics [1]. Towards this goal, an integrated spin-photon interface would be a major leap forward. Here we demonstrate an efficient and optically programmable interface between the spin of an electron in a quantum dot...... and photons in a nanophotonic waveguide. The spin can be deterministically prepared with a fidelity of 96\\%. Subsequently the system is used to implement a "single-spin photonic switch", where the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may...

Spin symposium

Energy Technology Data Exchange (ETDEWEB)

Anon.

1989-01-15

The recent 8th International Symposium on High Energy Spin Physics at the University of Minnesota in Minneapolis, Minnesota, opened with a bang when L. Pondrom (Wisconsin), donning a hard hat borrowed from construction workers, ventured that 'spin, the notorious inessential complication of hadronic physics, is finally telling us what real QCD (quantum chromodynamics, the field theory of quarks and gluons) looks like.' He was referring to an animated discussion on the meaning of the recent spin oriented (polarized) scattering results from the European Muon Collaboration (EMC) at CERN and reported at the Symposium by R. Garnet (Liverpool) and P. Schuler (Yale) which show that the proton spin is not simply a reflection of the spins of its constituent quarks.

Method of producing spherical lithium aluminate particles

International Nuclear Information System (INIS)

Yang, L.; Medico, R.R.; Baugh, W.A.

1983-01-01

Spherical particles of lithium aluminate are formed by initially producing aluminium hydroxide spheroids, and immersing the spheroids in a lithium ion-containing solution to infuse lithium ions into the spheroids. The lithium-infused spheroids are rinsed to remove excess lithium ion from the surface, and the rinsed spheroids are soaked for a period of time in a liquid medium, dried and sintered to form lithium aluminate spherical particles. (author)

Inverse spin Hall effect by spin injection

Science.gov (United States)

Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

2007-09-01

Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

The kinematic differences between off-spin and leg-spin bowling in cricket.

Science.gov (United States)

Beach, Aaron J; Ferdinands, René E D; Sinclair, Peter J

2016-09-01

Spin bowling is generally coached using a standard technical framework, but this practice has not been based upon a comparative biomechanical analysis of leg-spin and off-spin bowling. This study analysed the three-dimensional (3D) kinematics of 23 off-spin and 20 leg-spin bowlers using a Cortex motion analysis system to identify how aspects of the respective techniques differed. A multivariate ANOVA found that certain data tended to validate some of the stated differences in the coaching literature. Off-spin bowlers had a significantly shorter stride length (p = 0.006) and spin rate (p = 0.001), but a greater release height than leg-spinners (p = 0.007). In addition, a number of other kinematic differences were identified that were not previously documented in coaching literature. These included a larger rear knee flexion (p = 0.007), faster approach speed (p < 0.001), and flexing elbow action during the arm acceleration compared with an extension action used by most of the off-spin bowlers. Off-spin and leg-spin bowlers also deviated from the standard coaching model for the shoulder alignment, front knee angle at release, and forearm mechanics. This study suggests that off-spin and leg-spin are distinct bowling techniques, supporting the development of two different coaching models in spin bowling.

Field-controlled spin current in frustrated spin chains

Directory of Open Access Journals (Sweden)

A.K. Kolezhuk

2009-01-01

Full Text Available We study states with spontaneous spin current, emerging in frustrated antiferromagnetic spin-S chains subject to a strong external magnetic field. As a numerical tool, we use a non-Abelian symmetry realization of the density matrix renormalization group. The field dependence of the order parameter and the critical exponents are presented for zigzag chains with S=1/2, 1, 3/2, and 2.

Nuclear spin content and constraints on exotic spin-dependent couplings

International Nuclear Information System (INIS)

Kimball, D F Jackson

2015-01-01

There are numerous recent and ongoing experiments employing a variety of atomic species to search for couplings of atomic spins to exotic fields. In order to meaningfully compare these experimental results, the coupling of the exotic field to the atomic spin must be interpreted in terms of the coupling to electron, proton, and neutron spins. Traditionally, constraints from atomic experiments on exotic couplings to neutron and proton spins have been derived using the single-particle Schmidt model for nuclear spin. In this model, particular atomic species are sensitive to either neutron or proton spin couplings, but not both. More recently, semi-empirical models employing nuclear magnetic moment data have been used to derive new constraints for non-valence nucleons. However, comparison of such semi-empirical models to detailed large-scale nuclear shell model calculations and analysis of known physical effects in nuclei show that existing semi-empirical models cannot reliably be used to predict the spin polarization of non-valence nucleons. The results of our re-analysis of nuclear spin content are applied to searches for exotic long-range monopole–dipole and dipole–dipole couplings of nuclei leading to significant revisions of some published constraints. (paper)

Spin injection into Pt-polymers with large spin-orbit coupling

Science.gov (United States)

Sun, Dali; McLaughlin, Ryan; Siegel, Gene; Tiwari, Ashutosh; Vardeny, Z. Valy

2014-03-01

Organic spintronics has entered a new era of devices that integrate organic light-emitting diodes (OLED) in organic spin valve (OSV) geometry (dubbed bipolar organic spin valve, or spin-OLED), for actively manipulating the device electroluminescence via the spin alignment of two ferromagnetic electrodes (Science 337, 204-209, 2012; Appl. Phys. Lett. 103, 042411, 2013). Organic semiconductors that contain heavy metal elements have been widely used as phosphorescent dopants in white-OLEDs. However such active materials are detrimental for OSV operation due to their large spin-orbit coupling (SOC) that may limit the spin diffusion length and thus spin-OLED based on organics with large SOC is a challenge. We report the successful fabrication of OSVs based on pi-conjugated polymers which contain intrachain Platinum atoms (dubbed Pt-polymers). Spin injection into the Pt-polymers is investigated by the giant magnetoresistance (GMR) effect as a function of bias voltage, temperature and polymer layer thickness. From the GMR bias voltage dependence we infer that the ``impendence mismatch'' between ferromagnetic electrodes and Pt-polymer may be suppressed due to the large SOC. Research sponsored by the NSF (Grant No. DMR-1104495) and NSF-MRSEC (DMR 1121252) at the University of Utah.

New Benchmarks from Tokamak Experiments for Theoretical Calculations of the Dielectronic Satellite Spectra of Helium-like Ions

International Nuclear Information System (INIS)

Bitter, M.; Gu, M.F.; Vainshtein, L.A.; Beiersdorfer, P.; Bertschinger, G.; Marchuk, O.; Bell, R.; LeBlanc, B.; Hill, K.W.; Johnson, D.; Roquemore, L.

2003-01-01

Dielectronic satellite spectra of helium-like argon, recorded with a high-resolution X-ray crystal spectrometer at the National Spherical Torus Experiment, were found to be inconsistent with existing predictions resulting in unacceptable values for the power balance and suggesting the unlikely existence of non-Maxwellian electron energy distributions. These problems were resolved with calculations from a new atomic code. It is now possible to perform reliable electron temperature measurements and to eliminate the uncertainties associated with determinations of non-Maxwellian distributions

Spin-polarized light-emitting diodes based on organic bipolar spin valves

Science.gov (United States)

Vardeny, Zeev Valentine; Nguyen, Tho Duc; Ehrenfreund, Eitan Avraham

2017-10-25

Spin-polarized organic light-emitting diodes are provided. Such spin-polarized organic light-emitting diodes incorporate ferromagnetic electrodes and show considerable spin-valve magneto-electroluminescence and magneto-conductivity responses, with voltage and temperature dependencies that originate from the bipolar spin-polarized space charge limited current.

Collisions of droplets on spherical particles

Science.gov (United States)

Charalampous, Georgios; Hardalupas, Yannis

2017-10-01

Head-on collisions between droplets and spherical particles are examined for water droplets in the diameter range between 170 μm and 280 μm and spherical particles in the diameter range between 500 μm and 2000 μm. The droplet velocities range between 6 m/s and 11 m/s, while the spherical particles are fixed in space. The Weber and Ohnesorge numbers and ratio of droplet to particle diameter were between 92 deposition and splashing regimes, a regime is observed in the intermediate region, where the droplet forms a stable crown, which does not breakup but propagates along the particle surface and passes around the particle. This regime is prevalent when the droplets collide on small particles. The characteristics of the collision at the onset of rim instability are also described in terms of the location of the film on the particle surface and the orientation and length of the ejected crown. Proper orthogonal decomposition identified that the first 2 modes are enough to capture the overall morphology of the crown at the splashing threshold.

QED approach to the nuclear spin-spin coupling tensor

International Nuclear Information System (INIS)

Romero, Rodolfo H.; Aucar, Gustavo A.

2002-01-01

A quantum electrodynamical approach for the calculation of the nuclear spin-spin coupling tensor of nuclear-magnetic-resonance spectroscopy is given. Quantization of radiation fields within the molecule is considered and expressions for the magnetic field in the neighborhood of a nucleus are calculated. Using a generalization of time-dependent response theory, an effective spin-spin interaction is obtained from the coupling of nuclear magnetic moments to a virtual quantized magnetic field. The energy-dependent operators obtained reduce to usual classical-field expressions at suitable limits

Realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect

Energy Technology Data Exchange (ETDEWEB)

Ling, Xiaohui [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Laboratory for spin photonics, College of Physics and Microelectronic Science, Hunan University, Changsha 410082 (China); Department of Physics and Electronic Information Science, Hengyang Normal University, Hengyang 421002 (China); Yi, Xunong [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Zhou, Xinxing; Liu, Yachao; Shu, Weixing; Wen, Shuangchun [Laboratory for spin photonics, College of Physics and Microelectronic Science, Hunan University, Changsha 410082 (China); Luo, Hailu, E-mail: hailuluo@hnu.edu.cn [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, and Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Laboratory for spin photonics, College of Physics and Microelectronic Science, Hunan University, Changsha 410082 (China)

2014-10-13

We report the realization of tunable spin-dependent splitting in intrinsic photonic spin Hall effect. By breaking the rotational symmetry of a cylindrical vector beam, the intrinsic vortex phases that the two spin components of the vector beam carries, which is similar to the geometric Pancharatnam-Berry phase, are no longer continuous in the azimuthal direction, and leads to observation of spin accumulation at the opposite edge of the beam. Due to the inherent nature of the phase and independency of light-matter interaction, the observed photonic spin Hall effect is intrinsic. Modulating the topological charge of the vector beam, the spin-dependent splitting can be enhanced and the direction of spin accumulation is switchable. Our findings may provide a possible route for generation and manipulation of spin-polarized photons, and enables spin-based photonics applications.

Spin-flip and spin orbit interactions in heavy ion systems

International Nuclear Information System (INIS)

Bybell, D.P.

1983-01-01

The role of spin orbit forces in heavy ion reactions is not completely understood. Experimental data is scarce for these systems but the data that does exist indicates a stronger spin orbit force than predicted by the folding models. The spin-flip probability of non-spin zero projectiles is one technique used for these measurements and is often taken as a direct indicator of a spin orbit interaction. This work measures the projectile spin-flip probability for three inelastic reactions; 13 C + 24 Mg, E/sub cm/ = 22.7 MeV; 13 C + 12 C, E/sub cm/ = 17.3 MeV; and 6 Li + 12 C, E/sub cm/ = 15.2 MeV, all leading to the first J/sup π/ = 2 + state of the target. The technique of particle-γ angular correlations was used for measuring the final state density matrix elements, of which the absolute value M = 1 magnetic substate population is equivalent to the spin-flip probability. The method was explored in detail and found to be sensitive to spin-flip probabilities smaller than 1%. The technique was also found to be a good indicator of the reaction mechanism involved. Nonzero and occasionally large spin-flip probabilities were observed in all systems, much larger than the folding model predictions. Information was obtained on the non-spin-flip density matrix elements. In the 13 C + 24 Mg reaction, these were found to agree with calculations when the finite size of the particle detector is included

Simple description of odd-A nuclei around the critical point of the spherical to axially deformed shape phase transition

International Nuclear Information System (INIS)

Zhang Yu; Pan Feng; Liu Yuxin; Luo Yanan; Draayer, J. P.

2011-01-01

An analytically solvable model, X(3/2j+1), is proposed to describe odd-A nuclei near the X(3) critical point. The model is constructed based on a collective core described by the X(3) critical point symmetry coupled to a spin-j particle. A detailed analysis of the spectral patterns for cases j=1/2 and j=3/2 is provided to illustrate dynamical features of the model. By comparing theory with experimental data and results of other models, it is found that the X(3/2j+1) model can be taken as a simple yet very effective scheme to describe those odd-A nuclei with an even-even core at the critical point of the spherical to axially deformed shape phase transition.

Magnetic proximity control of spin currents and giant spin accumulation in graphene

Science.gov (United States)

Singh, Simranjeet

Two dimensional (2D) materials provide a unique platform to explore the full potential of magnetic proximity driven phenomena. We will present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to the ferromagnetic-insulator (FMI) magnetization in graphene/FMI heterostructures. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. We also discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the non-local spin signals in graphene, which is due to spin relaxation by thermally-induced transverse fluctuations of the FMI magnetization. Additionally, it has been a challenge to grow a smooth, robust and pin-hole free tunnel barriers on graphene, which can withstand large current densities for efficient electrical spin injection. We have experimentally demonstrated giant spin accumulation in graphene lateral spin valves employing SrO tunnel barriers. Nonlocal spin signals, as large as 2 mV, are observed in graphene lateral spin valves at room temperature. This high spin accumulations observed using SrO tunnel barriers puts graphene on the roadmap for exploring the possibility of achieving a non-local magnetization switching due to the spin torque from electrically injected spins. Financial support from ONR (No. N00014-14-1-0350), NSF (No. DMR-1310661), and C-SPIN, one of the six SRC STARnet Centers, sponsored by MARCO and DARPA.

Non-Spherical Microcapsules for Increased Core Content Volume Delivery

Science.gov (United States)

Oliva-Buisson, Yvette J.

2014-01-01

The goal of this project was to advance microencapsulation from the standard spherical microcapsule to a non-spherical, high-aspect ratio (HAR), elongated microcapsule. This was to be accomplished by developing reproducible methods of synthesizing or fabricating robust, non-spherical, HAR microcapsules. An additional goal of this project was to develop the techniques to the point where scale-up of these methods could be examined. Additionally, this project investigated ways to apply the microencapsulation techniques developed as part of this project to self-healing formulations.

Emulating Spherical Wave Channel Models in Multi-probe Anechoic Chamber Setups

DEFF Research Database (Denmark)

Fan, Wei; Carreño, Xavier; Nielsen, Jesper Ødum

2015-01-01

to emulate spherical wave channel models in multi-probe anechoic chamber setups. In this paper, a technique based on the field synthesis principle is proposed to approximate spherical waves emitted from arbitrarily located point sources with arbitrary polarizations. Simulation results show that static......Spherical wave channel modeling has attracted huge research attention for massive multiple-input multiple-output (MIMO) and short-distance MIMO systems. Current research work in multi-probe anechoic chamber systems is limited to reproduce radio channels assuming planar wavefronts. There is a need...... spherical waves can be reproduced with a limited number of probes, and the field synthesis accuracy of spherical wave depends on the location of the source point....

Possible evidence for spin-transfer torque induced by spin-triplet supercurrent

KAUST Repository

Li, Lailai

2017-10-04

Cooper pairs in superconductors are normally spin singlet. Nevertheless, recent studies suggest that spin-triplet Cooper pairs can be created at carefully engineered superconductor-ferromagnet interfaces. If Cooper pairs are spin-polarized they would transport not only charge but also a net spin component, but without dissipation, and therefore minimize the heating effects associated with spintronic devices. Although it is now established that triplet supercurrents exist, their most interesting property - spin - is only inferred indirectly from transport measurements. In conventional spintronics, it is well known that spin currents generate spin-transfer torques that alter magnetization dynamics and switch magnetic moments. The observation of similar effects due to spin-triplet supercurrents would not only confirm the net spin of triplet pairs but also pave the way for applications of superconducting spintronics. Here, we present a possible evidence for spin-transfer torques induced by triplet supercurrents in superconductor/ferromagnet/superconductor (S/F/S) Josephson junctions. Below the superconducting transition temperature T_c, the ferromagnetic resonance (FMR) field at X-band (~ 9.0 GHz) shifts rapidly to a lower field with decreasing temperature due to the spin-transfer torques induced by triplet supercurrents. In contrast, this phenomenon is absent in ferromagnet/superconductor (F/S) bilayers and superconductor/insulator/ferromagnet/superconductor (S/I/F/S) multilayers where no supercurrents pass through the ferromagnetic layer. These experimental observations are discussed with theoretical predictions for ferromagnetic Josephson junctions with precessing magnetization.

Spin Currents and Spin Orbit Torques in Ferromagnets and Antiferromagnets

Science.gov (United States)

Hung, Yu-Ming

This thesis focuses on the interactions of spin currents and materials with magnetic order, e.g., ferromagnetic and antiferromagnetic thin films. The spin current is generated in two ways. First by spin-polarized conduction-electrons associated with the spin Hall effect in heavy metals (HMs) and, second, by exciting spin-waves in ferrimagnetic insulators using a microwave frequency magnetic field. A conduction-electron spin current can be generated by spin-orbit coupling in a heavy non-magnetic metal and transfer its spin angular momentum to a ferromagnet, providing a means of reversing the magnetization of perpendicularly magnetized ultrathin films with currents that flow in the plane of the layers. The torques on the magnetization are known as spin-orbit torques (SOT). In the first part of my thesis project I investigated and contrasted the quasistatic (slowly swept current) and pulsed current-induced switching characteristics of micrometer scale Hall crosses consisting of very thin (magnetized CoFeB layers on beta-Ta. While complete magnetization reversal occurs at a threshold current density in the quasistatic case, pulses with short duration (≤10 ns) and larger amplitude (≃10 times the quasistatic threshold current) lead to only partial magnetization reversal and domain formation. The partial reversal is associated with the limited time for reversed domain expansion during the pulse. The second part of my thesis project studies and considers applications of SOT-driven domain wall (DW) motion in a perpendicularly magnetized ultrathin ferromagnet sandwiched between a heavy metal and an oxide. My experiment results demonstrate that the DW motion can be explained by a combination of the spin Hall effect, which generates a SOT, and Dzyaloshinskii-Moriya interaction, which stabilizes chiral Neel-type DW. Based on SOT-driven DW motion and magnetic coupling between electrically isolated ferromagnetic elements, I proposed a new type of spin logic devices. I then

Inverse spin Hall effect induced by spin pumping into semiconducting ZnO

Energy Technology Data Exchange (ETDEWEB)

Lee, Jung-Chuan [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Huang, Leng-Wei [Graduate Institute of Applied Physics, National Chengchi University, Taipei 11605, Taiwan (China); Hung, Dung-Shing, E-mail: dshung@mail.mcu.edu.tw [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Department of Information and Telecommunications Engineering, Ming Chuan University, Taipei 111, Taiwan (China); Chiang, Tung-Han [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Huang, J. C. A., E-mail: jcahuang@mail.ncku.edu.tw [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Liang, Jun-Zhi [Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China); Department of Physics, Fu Jen Catholic University, Taipei 242, Taiwan (China); Lee, Shang-Fan, E-mail: leesf@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, Taipei 11529, Taiwan (China); Graduate Institute of Applied Physics, National Chengchi University, Taipei 11605, Taiwan (China)

2014-02-03

The inverse spin Hall effect (ISHE) of n-type semiconductor ZnO thin films with weak spin-orbit coupling has been observed by utilizing the spin pumping method. In the ferromagnetic resonance condition, the spin pumping driven by the dynamical exchange interaction of a permalloy film injects a pure spin current into the adjacent ZnO layer. This spin current gives rise to a DC voltage through the ISHE in the ZnO layer, and the DC voltage is proportional to the microwave excitation power. The effect is sizeable even when the spin backflow is considered.

Inverse spin Hall effect induced by spin pumping into semiconducting ZnO

International Nuclear Information System (INIS)

Lee, Jung-Chuan; Huang, Leng-Wei; Hung, Dung-Shing; Chiang, Tung-Han; Huang, J. C. A.; Liang, Jun-Zhi; Lee, Shang-Fan

2014-01-01

The inverse spin Hall effect (ISHE) of n-type semiconductor ZnO thin films with weak spin-orbit coupling has been observed by utilizing the spin pumping method. In the ferromagnetic resonance condition, the spin pumping driven by the dynamical exchange interaction of a permalloy film injects a pure spin current into the adjacent ZnO layer. This spin current gives rise to a DC voltage through the ISHE in the ZnO layer, and the DC voltage is proportional to the microwave excitation power. The effect is sizeable even when the spin backflow is considered

MISR Dark Water aerosol retrievals: operational algorithm sensitivity to particle non-sphericity

Directory of Open Access Journals (Sweden)

O. V. Kalashnikova

2013-08-01

Full Text Available The aim of this study is to theoretically investigate the sensitivity of the Multi-angle Imaging SpectroRadiometer (MISR operational (version 22 Dark Water retrieval algorithm to aerosol non-sphericity over the global oceans under actual observing conditions, accounting for current algorithm assumptions. Non-spherical (dust aerosol models, which were introduced in version 16 of the MISR aerosol product, improved the quality and coverage of retrievals in dusty regions. Due to the sensitivity of the retrieval to the presence of non-spherical aerosols, the MISR aerosol product has been successfully used to track the location and evolution of mineral dust plumes from the Sahara across the Atlantic, for example. However, the MISR global non-spherical aerosol optical depth (AOD fraction product has been found to have several climatological artifacts superimposed on valid detections of mineral dust, including high non-spherical fraction in the Southern Ocean and seasonally variable bands of high non-sphericity. In this paper we introduce a formal approach to examine the ability of the operational MISR Dark Water algorithm to distinguish among various spherical and non-spherical particles as a function of the variable MISR viewing geometry. We demonstrate the following under the criteria currently implemented: (1 Dark Water retrieval sensitivity to particle non-sphericity decreases for AOD below about 0.1 primarily due to an unnecessarily large lower bound imposed on the uncertainty in MISR observations at low light levels, and improves when this lower bound is removed; (2 Dark Water retrievals are able to distinguish between the spherical and non-spherical particles currently used for all MISR viewing geometries when the AOD exceeds 0.1; (3 the sensitivity of the MISR retrievals to aerosol non-sphericity varies in a complex way that depends on the sampling of the scattering phase function and the contribution from multiple scattering; and (4 non-sphericity

Developement of Spherical Polyurethane Beads

Institute of Scientific and Technical Information of China (English)

K. Maeda; H. Ohmori; H. Gyotoku

2005-01-01

@@ 1Results and Discussion We established a new method to produce the spherical polyurethane beads which have narrower distribution of particle size. This narrower distribution was achieved by the polyurethane prepolymer which contains ketimine as a blocked chain-extending agent. Firstly, the prepolymer is dispersed into the aqueous solution containing surfactant. Secondaly, water comes into the inside of prepolymer as oil phase. Thirdly, ketimine is hydrolyzed to amine, and amine reacts with prepolymer immediately to be polyurethane.Our spherical polyurethane beads are very suitable for automotive interior parts especially for instrument panel cover sheet producing under the slush molding method, because of good process ability, excellent durability to the sunlight and mechanical properties at low temperature. See Fig. 1 ,Fig. 2 and Fig. 3 (Page 820).

Induction-detection electron spin resonance with spin sensitivity of a few tens of spins

Energy Technology Data Exchange (ETDEWEB)

Artzi, Yaron; Twig, Ygal; Blank, Aharon [Schulich Faculty of Chemistry Technion—Israel Institute of Technology, Haifa 32000 (Israel)

2015-02-23

Electron spin resonance (ESR) is a spectroscopic method that addresses electrons in paramagnetic materials directly through their spin properties. ESR has many applications, ranging from semiconductor characterization to structural biology and even quantum computing. Although it is very powerful and informative, ESR traditionally suffers from low sensitivity, requiring many millions of spins to get a measureable signal with commercial systems using the Faraday induction-detection principle. In view of this disadvantage, significant efforts were made recently to develop alternative detection schemes based, for example, on force, optical, or electrical detection of spins, all of which can reach single electron spin sensitivity. This sensitivity, however, comes at the price of limited applicability and usefulness with regard to real scientific and technological issues facing modern ESR which are currently dealt with conventional induction-detection ESR on a daily basis. Here, we present the most sensitive experimental induction-detection ESR setup and results ever recorded that can detect the signal from just a few tens of spins. They were achieved thanks to the development of an ultra-miniature micrometer-sized microwave resonator that was operated at ∼34 GHz at cryogenic temperatures in conjunction with a unique cryogenically cooled low noise amplifier. The test sample used was isotopically enriched phosphorus-doped silicon, which is of significant relevance to spin-based quantum computing. The sensitivity was experimentally verified with the aid of a unique high-resolution ESR imaging approach. These results represent a paradigm shift with respect to the capabilities and possible applications of induction-detection-based ESR spectroscopy and imaging.

Sextupole system for the correction of spherical aberration

Science.gov (United States)

Crewe, A.V.; Kopf, D.A.

In an electron beam device in which an electron beam is developed and then focused by a lens to a particular spot, there is provided a means for eliminating spherical aberration. A sextupole electromagnetic lens is positioned between two focusing lenses. The interaction of the sextupole with the beam compensates for spherical aberration. (GHT)

Models for randomly distributed nanoscopic domains on spherical vesicles

Science.gov (United States)

Anghel, Vinicius N. P.; Bolmatov, Dima; Katsaras, John

2018-06-01

The existence of lipid domains in the plasma membrane of biological systems has proven controversial, primarily due to their nanoscopic size—a length scale difficult to interrogate with most commonly used experimental techniques. Scattering techniques have recently proven capable of studying nanoscopic lipid domains populating spherical vesicles. However, the development of analytical methods able of predicting and analyzing domain pair correlations from such experiments has not kept pace. Here, we developed models for the random distribution of monodisperse, circular nanoscopic domains averaged on the surface of a spherical vesicle. Specifically, the models take into account (i) intradomain correlations corresponding to form factors and interdomain correlations corresponding to pair distribution functions, and (ii) the analytical computation of interdomain correlations for cases of two and three domains on a spherical vesicle. In the case of more than three domains, these correlations are treated either by Monte Carlo simulations or by spherical analogs of the Ornstein-Zernike and Percus-Yevick (PY) equations. Importantly, the spherical analog of the PY equation works best in the case of nanoscopic size domains, a length scale that is mostly inaccessible by experimental approaches such as, for example, fluorescent techniques and optical microscopies. The analytical form factors and structure factors of nanoscopic domains populating a spherical vesicle provide a new and important framework for the quantitative analysis of experimental data from commonly studied phase-separated vesicles used in a wide range of biophysical studies.

Rayleigh-Taylor instability in multi-structured spherical targets

International Nuclear Information System (INIS)

Gupta, N.K.; Lawande, S.V.

1986-01-01

An eigenvalue equation for the exponential growth rate of the Rayleigh-Taylor instability is derived in spherical geometry. The free surface and jump boundary conditions are obtained from the eigenvalue equation. The eigenvalue equation is solved in the cases where the initial fluid density profile has a step function or exponential variation in space and analytical formulae for growth rate of the instability are obtained. The solutions for the step function are generalized for any number N of spherical zones forming an arbitrary fluid density profile. The results of the numerical calculations for N spherical zones are compared with the exact analytical results for exponential fluid density profile with N=10 and a good agreement is observed. The formalism is further used to study the effects of density gradients on Rayleigh-Taylor instability in spherical geometry. Also analytical formulae are presented for a particular case of N=3 and shell targets. The formalism developed here can be used to study the growth of the instability in present day multi-structured shell targets. (author)

Nuclear spin-lattice relaxation in nitroxide spin-label EPR.

Science.gov (United States)

Marsh, Derek

2016-11-01

Nuclear relaxation is a sensitive monitor of rotational dynamics in spin-label EPR. It also contributes competing saturation transfer pathways in T 1 -exchange spectroscopy, and the determination of paramagnetic relaxation enhancement in site-directed spin labelling. A survey shows that the definition of nitrogen nuclear relaxation rate W n commonly used in the CW-EPR literature for 14 N-nitroxyl spin labels is inconsistent with that currently adopted in time-resolved EPR measurements of saturation recovery. Redefinition of the normalised 14 N spin-lattice relaxation rate, b=W n /(2W e ), preserves the expressions used for CW-EPR, whilst rendering them consistent with expressions for saturation recovery rates in pulsed EPR. Furthermore, values routinely quoted for nuclear relaxation times that are deduced from EPR spectral diffusion rates in 14 N-nitroxyl spin labels do not accord with conventional analysis of spin-lattice relaxation in this three-level system. Expressions for CW-saturation EPR with the revised definitions are summarised. Data on nitrogen nuclear spin-lattice relaxation times are compiled according to the three-level scheme for 14 N-relaxation: T 1 n =1/W n . Results are compared and contrasted with those for the two-level 15 N-nitroxide system. Copyright © 2016 Elsevier Inc. All rights reserved.

JUST: Joint Upgraded Spherical Tokamak

International Nuclear Information System (INIS)

Azizov, E.A.; Dvorkin, N.Ya.; Filatov, O.G.

1997-01-01

The main goals, ideas and the programme of JUST, spherical tokamak (ST) for the plasma burn investigation, are presented. The place and prospects of JUST in thermonuclear investigations are discussed. (author)

Spin injection and detection in lateral spin valves with hybrid interfaces

Science.gov (United States)

Wang, Le; Liu, Wenyu; Ying, Hao; Chen, Luchen; Lu, Zhanjie; Han, Shuo; Chen, Shanshan; Zhao, Bing; Xu, Xiaoguang; Jiang, Yong

2018-06-01

Spin injection and detection in lateral spin valves with hybrid interfaces comprising a Co/Ag transparent contact and a Co/MgO/Ag junction (III) are investigated at room temperature in comparison with pure Co/Ag transparent contacts (I) and Co/MgO/Ag junctions (II). The measured spin-accumulation signals of a type III device are five times higher than those for type I. The extracted spin diffusion length in Ag is 180 nm for all three types of devices. The enhancement of the spin signal of the hybrid structure is mainly attributed to the increase of the interfacial spin polarization from the Co/MgO/Ag junction.

Spherical loudspeaker array for local active control of sound.

Science.gov (United States)

Rafaely, Boaz

2009-05-01

Active control of sound has been employed to reduce noise levels around listeners' head using destructive interference from noise-canceling sound sources. Recently, spherical loudspeaker arrays have been studied as multiple-channel sound sources, capable of generating sound fields with high complexity. In this paper, the potential use of a spherical loudspeaker array for local active control of sound is investigated. A theoretical analysis of the primary and secondary sound fields around a spherical sound source reveals that the natural quiet zones for the spherical source have a shell-shape. Using numerical optimization, quiet zones with other shapes are designed, showing potential for quiet zones with extents that are significantly larger than the well-known limit of a tenth of a wavelength for monopole sources. The paper presents several simulation examples showing quiet zones in various configurations.

Large spin accumulation due to spin-charge coupling across a break-junction

Science.gov (United States)

Chen, Shuhan; Zou, Han; Chui, Siu-Tat; Ji, Yi

2013-03-01

We investigate large spin signals in break-junction nonlocal spin valves (NLSV). The break-junction is a nanometer-sized vacuum tunneling gap between the spin detector and the nonmagnetic channel, formed by electro-static discharge. The spin signals can be either inverted or non-inverted and the magnitudes are much larger than those of standard NLSV. Spin signals with high percentage values (10% - 0%) have been observed. When the frequency of the a.c. modulation is varied, the absolute magnitudes of signals remain the same although the percentage values change. These observations affirm the nonlocal nature of the measurements and rule out local magnetoresistive effects. Owing to the spin-charge coupling across the break-junction, the spin accumulation in a ferromagnet splits into two terms. One term decays on the charge screening length (0.1 nm) and the other decays on the spin diffusion length (10 nm nm). The magnitude of the former is proportional to the resistance of the junction. Therefore a highly resistive break-junction leads to a large spin accumulation and thereby a large spin signal. The signs of the spin signal are determined by the relationship between spin-dependent conductivities, diffusion constants, and density of states of the ferromagnet. This work was supported by US DOE grant No. DE-FG02-07ER46374.

Spin dynamics under local gauge fields in chiral spin-orbit coupling systems