NASA Astrophysics Data System (ADS)
Maity, Narottam; Barik, S. P.; Chaudhuri, P. K.
2016-09-01
In this paper, plane wave propagation in a rotating anisotropic material of general nature under the action of a magnetic field of constant magnitude has been investigated. The material is supposed to be porous in nature and contains voids. Following the concept of [Cowin S. C. and Nunziato, J. W. [1983] “Linear elastic materials with voids,” J. Elasticity 13, 125-147.] the governing equations of motion have been written in tensor notation taking account of rotation, magnetic field effect and presence of voids in the medium and the possibility of plane wave propagation has been examined. A number of particular cases have been derived from our general results to match with previously obtained results in this area. Effects of various parameters on the velocity of wave propagation have been presented graphically.
Rotating plane Couette flow at high rotation number
NASA Astrophysics Data System (ADS)
Suryadi, A.; Tillmark, N.; Alfredsson, P. H.
2012-11-01
Flow structures in the rotating plane Couette flow facility at KTH (described in Tsukahara, et al. J. Fluid Mech. vol. 648) have been studied at high rotation numbers. The test section is 20 mm wide with a length of 1500 mm in the streamwise (x) and 360 mm in the spanwise (z) directions and can be rotated in the spanwise direction up to angular velocities of Ωz ~ 0 . 6 rad/s. The flow is characterised by: (1) the Reynolds number Re based on the test section's half-width (h) and half of the velocity difference between the moving walls, (2) the rotation number Ω = 2Ωzh2 / ν . For low rotation numbers the primary instability consists of streamwise-oriented roll cells, but Tsukahara, et al. showed the secondary instability in the form of wavy streamwise oriented roll-cells at Re = 100 and Ω = 3 - 12 , whereas for higher Ω, the flow structures again stabilize to streamwise-oriented roll cells. Here we find that at even higher Ω in the range 40 - 70 , a new type of secondary instability develops in the form of counter-rotating helical roll-cells. The structure of this instability, as well as other instabilities, are investigated by flow visualization as well as two-dimensional PIV-measurements in several xz -planes.
Are rotating planes of satellite galaxies ubiquitous?
NASA Astrophysics Data System (ADS)
Phillips, John I.; Cooper, Michael C.; Bullock, James S.; Boylan-Kolchin, Michael
2015-11-01
We compare the dynamics of satellite galaxies in the Sloan Digital Sky Survey to simple models in order to test the hypothesis that a large fraction of satellites corotate in coherent planes. We confirm the previously reported excess of corotating satellite pairs located near diametric opposition with respect to their host, but show that this signal is unlikely to be due to rotating discs (or planes) of satellites. In particular, no overabundance of corotating satellites pairs is observed within ˜20°-50° of direct opposition, as would be expected for planar distributions inclined relative to the line of sight. Instead, the excess corotation for satellite pairs within ˜10° of opposition is consistent with random noise associated with undersampling of an underlying isotropic velocity distribution. Based upon the observed dynamics of the luminous satellite population, we conclude that at most 10 per cent of isolated hosts harbour corotating satellite planes (as traced by bright satellites).
NASA Astrophysics Data System (ADS)
Brown, J. C.; Haverkorn, M.; Gaensler, B. M.; Taylor, A. R.; Bizunok, N. S.; McClure-Griffiths, N. M.; Dickey, J. M.; Green, A. J.
2007-07-01
We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253deg<=l<=356deg, |b|<=1.5deg), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requires the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius-Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms. In the best-fitting model, the magnetic field in the fourth Galactic quadrant is directed clockwise in the Sagittarius-Carina spiral arm (as viewed from the north Galactic pole), but is oriented counterclockwise in the Scutum-Crux arm. This contrasts with recent analyses of pulsar RMs alone, in which the fourth-quadrant field was presumed to be directed counterclockwise in the Sagittarius-Carina arm. Also in contrast to recent pulsar RM studies, our joint modeling of pulsar and extragalactic RMs demonstrates that large numbers of large-scale magnetic field reversals are not required to account for observations.
Comparing viewer and array mental rotations in different planes
NASA Technical Reports Server (NTRS)
Carpenter, M.; Proffitt, D. R.; Kaiser, M. K. (Principal Investigator)
2001-01-01
Participants imagined rotating either themselves or an array of objects that surrounded them. Their task was to report on the egocentric position of an item in the array following the imagined rotation. The dependent measures were response latency and number of errors committed. Past research has shown that self-rotation is easier than array rotation. However, we found that imagined egocentric rotations were as difficult to imagine as rotations of the environment when people performed imagined rotations in the midsagittal or coronal plane. The advantages of imagined self-rotations are specific to mental rotations performed in the transverse plane.
Flow field survey near the rotational plane of an advanced design propeller on a JetStar airplane
NASA Technical Reports Server (NTRS)
Walsh, K. R.
1985-01-01
An investigation was conducted to obtain upper fuselage surface static pressures and boundary layer velocity profiles below the centerline of an advanced design propeller. This investigation documents the upper fuselage velocity flow field in support of the in-flight acoustic tests conducted on a JetStar airplane. Initial results of the boundary layer survey show evidence of an unusual flow disturbance, which is attributed to the two windshield wiper assemblies on the aircraft. The assemblies were removed, eliminating the disturbances from the flow field. This report presents boundary layer velocity profiles at altitudes of 6096 and 9144 m (20,000 and 30,000 ft) and Mach numbers from 0.6 to 0.8, and it investigated the effects of windshield wiper assemblies on these profiles. Because of the unconventional velocity profiles that were obtained with the assemblies mounted, classical boundary layer parameters, such as momentum and displacement thicknesses, are not presented. The effects of flight test variables (Mach number and angles of attack and sideslip) and an advanced design propeller on boundary layer profiles - with the wiper assemblies mounted and removed - are presented.
NASA Astrophysics Data System (ADS)
Kawata, Takuya; Alfredsson, P. Henrik
2016-07-01
Plane Couette flow under spanwise, anticyclonic system rotation [rotating plane Couette flow (RPCF)] is studied experimentally using stereoscopic particle image velocimetry for different Reynolds and rotation numbers in the fully turbulent regime. Similar to the laminar regime, the turbulent flow in RPCF is characterized by roll cells, however both instantaneous snapshots of the velocity field and space correlations show that the roll cell structure varies with the rotation number. All three velocity components are measured and both the mean flow and all four nonzero Reynolds stresses are obtained across the central parts of the channel. This also allows us to determine the wall shear stress from the viscous stress and the Reynolds stress in the center of the channel, and for low rotation rates the wall shear stress increases with increasing rotation rate as expected. The results show that zero absolute vorticity is established in the central parts of the channel of turbulent RPCF for high enough rotation rates, but also that the mean velocity profile for certain parameter ranges shows an S shape giving rise to a negative velocity gradient in the center of the channel. We find that from an analysis of the Reynolds stress transport equation using the present data there is a transport of the Reynolds shear stress towards the center of the channel, which may then result in a negative mean velocity gradient there.
Apodised aperture using rotation of plane of polarization
Simmons, W.W.; Leppelmeier, G.W.; Johnson, B.C.
1975-09-01
An apodised aperture based on the rotation of plane of polarization producing desirable characteristics on a transmitted light beam such as beam profiling in high flux laser amplifier chains is described. The apodised aperture is made with a lossless element by using one or more polarizers and/or analyzers and magneto-optical Faraday means for selectively rotating the plane of polarized radiation over the cross section to effect the desired apodisation. (auth)
Transitions in turbulent plane Couette flow with rotation
NASA Astrophysics Data System (ADS)
Salewski, Matthew; Eckhardt, Bruno
2012-11-01
The interplay of shearing and rotational forces in fluids significantly affects the transport properties of turbulent fluids such as the heat flux in rotating convection and the angular momentum flux in a fluid annulus between differentially rotating cylinders. A numerical investigation was undertaken to study the role of these forces using plane Couette flow subject to rotation about an axis perpendicular to both wall-normal and streamwise directions. Using a set of progressively increasing Reynolds numbers (650 <= Re <= 5200), our primary findings show the momentum transport for a given Re is a smooth but non-monotonic function of inverse Rossby number (1 / Ro). For lower turbulent Reynolds numbers, Re <= 1300 , a peak in momentum transport occurs at 1 / Ro = 0 . 2 ; this peak is 50% higher than the non-rotating (1 / Ro = 0) flux and is attributed to the turbulent Taylor vortices. However, as the shear is increased to Re = 5200 , a second stronger peak emerges at 1 / Ro = 0 . 03 . The flux at the second peak is nearly 20% larger than the non-rotating flux compared to the Taylor vortex peak which is now only 16% larger. This finding contributes to the understanding of the torque maximum found in the high-turbulence Taylor-Couette experiments in Maryland, USA and Twente, NL. Funded by the German Research Foundation (DFG), Project FOR-1182.
Clocking Surface Reaction by In-Plane Product Rotation.
Anggara, Kelvin; Huang, Kai; Leung, Lydie; Chatterjee, Avisek; Cheng, Fang; Polanyi, John C
2016-06-15
Electron-induced reaction of physisorbed meta-diiodobenzene (mDIB) on Cu(110) at 4.6 K was studied by Scanning Tunneling Microscopy and molecular dynamics theory. Single-electron dissociation of the first C-I bond led to in-plane rotation of an iodophenyl (IPh) intermediate, whose motion could be treated as a "clock" of the reaction dynamics. Alternative reaction mechanisms, successive and concerted, were observed giving different product distributions. In the successive mechanism, two electrons successively broke single C-I bonds; the first C-I bond breaking yielded IPh that rotated directionally by three different angles, with the second C-I bond breaking giving chemisorbed I atoms (#2) at three preferred locations corresponding to the C-I bond alignments in the prior rotated IPh configurations. In the concerted mechanism a single electron broke two C-I bonds, giving two chemisorbed I atoms; significantly these were found at angles corresponding to the C-I bond direction for unrotated mDIB. Molecular dynamics accounted for the difference in reaction outcomes between the successive and the concerted mechanisms in terms of the time required for the IPh to rotate in-plane; in successive reaction the time delay between first and second C-I bond-breaking events allowed the IPh to rotate, whereas in concerted reaction the computed delay between excitation and reaction (∼1 ps) was too short for molecular rotation before the second C-I bond broke. The dependence of the extent of motion at a surface on the delay between first and second bond breaking suggested a novel means to "clock" sub-picosecond dynamics by imaging the products arising from varying time delays between impacting pairs of electrons.
Rotating superconductor magnet for producing rotating lobed magnetic field lines
Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.
1978-01-01
This invention provides a rotating superconductor magnet for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet.
Shingyoji, C; Katada, J; Takahashi, K; Gibbons, I R
1991-02-01
When the head of a sea-urchin sperm is held in the tip of a micropipette and vibrated laterally, the flagellum beats in phase with the imposed vibration. Rotation of the plane of pipette vibration around the head axis induces a corresponding rotation of the plane of beating, in both live and reactivated sperm. Detailed analysis of the waveforms occurring at different stages of this rotation shows that the characteristic asymmetry of the flagellar bending waves rotates along with the plane of beat. The positions of small polystyrene beads attached as markers on the axonemes of demembranated sperm flagella appear unaffected by the rotation of the beat plane and asymmetry. The imposed rotation of the waveform is thus the result of a rotation of the coordinated pattern of sliding among the doublet tubules of the axoneme, and is not accompanied by a twisting of the whole axonemal structure. These data indicate that neither the plane of flagellar beat nor the direction of beat asymmetry is tightly dependent upon a structural or chemical specialization of particular members of the nine outer doublet microtubules, but that both are the result of some regulatory structure that can be forced to rotate relative to the outer structure of the axoneme.
Split-field pupil plane determination apparatus
Salmon, Joseph T.
1996-01-01
A split-field pupil plane determination apparatus (10) having a wedge assembly (16) with a first glass wedge (18) and a second glass wedge (20) positioned to divide a laser beam (12) into a first laser beam half (22) and a second laser beam half (24) which diverge away from the wedge assembly (16). A wire mask (26) is positioned immediately after the wedge assembly (16) in the path of the laser beam halves (22, 24) such that a shadow thereof is cast as a first shadow half (30) and a second shadow half (32) at the input to a relay telescope (14). The relay telescope (14) causes the laser beam halves (22, 24) to converge such that the first shadow half (30) of the wire mask (26) is aligned with the second shadow half (32) at any subsequent pupil plane (34).
Fraunhofer plane analysis of particle field holograms.
Ewan, B C
1980-04-15
Using the recently developed Fraunhofer plane particle size analyzer, comparisons have been made between direct and holographically recorded particle field measurements. The usefulness of the combination is discussed in terms of the considerable time factor gain in hologram analysis and the improvement in time resolution of the instrument to that of pulsed lasers. The time resolution is demonstrated by the observation of the time development of the particle size distribution associated with a fuel injector during and after the few milliseconds of nozzle opening.
Turbulent statistics and flow structures in spanwise-rotating turbulent plane Couette flows
NASA Astrophysics Data System (ADS)
Gai, Jie; Xia, Zhenhua; Cai, Qingdong; Chen, Shiyi
2016-09-01
A series of direct numerical simulations of spanwise-rotating turbulent plane Couette flows at a Reynolds number of 1300 with rotation numbers Ro between 0 and 0.9 is carried out to investigate the effects of anticyclonic rotation on turbulent statistics and flow structures. Several typical turbulent statistics are presented, including the mean shear rate at the centerline, the wall-friction Reynolds number, and volume-averaged kinetic energies with respect to the secondary flow field, turbulent field, and total fluctuation field. Our results show that the rotation changes these quantities in different manners. Volume-averaged balance equations for kinetic energy are analyzed and it turns out that the interaction term acts as a kinetic energy bridge that transfers energy from the secondary flow to the turbulent fluctuations. Several typical flow regimes are identified based on the correlation functions across the whole channel and flow visualizations. The two-dimensional roll cells are observed at weak rotation Ro=0.01 , where alternant clustering of vortices appears. Three-dimensional roll cells emerge around Ro≈0.02 , where the clustering of vortices shows the meandering and bifurcating behavior. For moderate rotation 0.07 ≲Ro≲0.36 , well-organized structures are observed, where the herringbonelike vortices are clustered between streaks from the top view of three-dimensional flow visualization and form annuluses. More importantly, the vortices are rather confined to one side of the walls when Ro≤0.02 and are inclined from the bottom to upper walls when Ro≥0.07 .
Detecting an in-plane rotation of magnetization in GdFeCo films
NASA Astrophysics Data System (ADS)
Hoveyda, Farzaneh; Smadici, Serban
It is often important to distinguish between magnetization reversal by coherent rotation in different planes and domain wall motion. Magnetization curves were measured at different temperatures with magneto-optical Kerr Effect in longitudinal (L-MOKE) and polar (P-MOKE) geometries on sputter-deposited GdxFeyCo1 - x - y (GFC) films of variable thickness. Depending on the probed region, the L-MOKE signal measured with decreasing external field Hext was found to be lower than the signal observed with increasing Hext (negative remanence magnetization). We show that this is due to a contribution to the signal of M⊥ , the magnetization component perpendicular to the scattering plane. This identifies the type of reversal in these GFC films as in-plane coherent rotation of magnetization. M⊥ is also proportional to the torque. Azimuthal measurements on Co2FeAl samples showed a regular variation of the MOKE signal, in one possible application of these observations to torque measurements. Work supported by the University of Louisville Research Foundation.
Flow Transitions in a Rotating Magnetic Field
NASA Technical Reports Server (NTRS)
Volz, M. P.; Mazuruk, K.
1996-01-01
Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.
NASA Astrophysics Data System (ADS)
Tatar, Kourosh; Gren, Per
2016-05-01
A method for estimating the in-plane vibrations of a rotating spindle using out-of-plane laser vibrometry measurements is described. This method enables the possibility to obtain the two orthogonal radial vibration components of a rotating spindle. The method uses the fact that the laser vibrometer signal is a total surface velocity of the measurement point in the laser direction. Measurements are conducted on a rotating milling machine spindle. The spindle is excited in a controlled manner by an active magnetic bearing and the response is measured by laser vibrometer in one of the two orthogonal directions and inductive displacement sensors in two orthogonal directions simultaneously. The work shows how the laser vibrometry crosstalk can be used for resolving the in-plane vibration component, that is the vibrations in the laser vibrometer cross direction. The result is compared to independent measurement signals from the displacement sensors. The measurement method can be used for vibration measurements on rotating parts, for example, where there is lack of space for orthogonal measurements.
Rotational Analysis of Phase Plane Curves: Complex and Pure Imaginary Eigenvalues
ERIC Educational Resources Information Center
Murray, Russell H.
2005-01-01
Although the phase plane can be plotted and analyzed using an appropriate software package, the author found it worthwhile to engage the students with the theorem and the two proofs. The theorem is a powerful tool that provides insight into the rotational behavior of the phase plane diagram in a simple way: just check the signs of c and [alpha].…
RoboPol: optical polarization-plane rotations and flaring activity in blazars
NASA Astrophysics Data System (ADS)
Blinov, D.; Pavlidou, V.; Papadakis, I. E.; Hovatta, T.; Pearson, T. J.; Liodakis, I.; Panopoulou, G. V.; Angelakis, E.; Baloković, M.; Das, H.; Khodade, P.; Kiehlmann, S.; King, O. G.; Kus, A.; Kylafis, N.; Mahabal, A.; Marecki, A.; Modi, D.; Myserlis, I.; Paleologou, E.; Papamastorakis, I.; Pazderska, B.; Pazderski, E.; Rajarshi, C.; Ramaprakash, A.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Zensus, J. A.
2016-04-01
We present measurements of rotations of the optical polarization of blazars during the second year of operation of RoboPol, a monitoring programme of an unbiased sample of gamma-ray bright blazars specially designed for effective detection of such events, and we analyse the large set of rotation events discovered in two years of observation. We investigate patterns of variability in the polarization parameters and total flux density during the rotation events and compare them to the behaviour in a non-rotating state. We have searched for possible correlations between average parameters of the polarization-plane rotations and average parameters of polarization, with the following results: (1) there is no statistical association of the rotations with contemporaneous optical flares; (2) the average fractional polarization during the rotations tends to be lower than that in a non-rotating state; (3) the average fractional polarization during rotations is correlated with the rotation rate of the polarization plane in the jet rest frame; (4) it is likely that distributions of amplitudes and durations of the rotations have physical upper bounds, so arbitrarily long rotations are not realized in nature.
NASA Astrophysics Data System (ADS)
Gouesbet, G.; Wang, J. J.; Han, Y. P.; G. Grehan
2010-09-01
This paper is the fourth of a series devoted to the transformation of beam shape coefficients through rotations of coordinate systems. These coefficients are required to express electromagnetic fields of laser beams in expanded forms, for instance for use in some generalized Lorenz-Mie theories. The main result of Part I has been the theorem of transformation of beam shape coefficients under rotations. Part II dealt with the special case of on-axis axisymmetric beams. Part III dealt with other special cases, namely when the Euler angles specifying the rotation are given some special values. The present Part IV studies another special case, namely the one of plane waves viewed as special on-axis axisymmetric beams, and can therefore be viewed as a special case of Part II. Unexpectedly, it is found that, in general, although plane waves are fairly trivial, their expansions require using non trivial beam shape coefficients, exactly as required when dealing with arbitrary shaped beams.
In-plane rotation of the doubly coupled photonic crystal nanobeam cavities
NASA Astrophysics Data System (ADS)
Lin, Tong; Tian, Feng; Zhang, Wei; Zou, Yongchao; Chau, Fook Siong; Deng, Jie; Zhou, Guangya
2016-05-01
In this letter, a nano-electro-mechanical-systems (NEMS) mechanism is proposed to drive the in-plane rotation of the doubly coupled photonic crystal (PhC) nanobeam cavities. The corresponding interactions between optical resonances and rotations are investigated. This is the first in-plane rotational tuning of the PhC cavities, which benefits from the flexible design of NEMS actuators. In experiments, more than 18 linewidths of the third order TE even mode corresponding to 0.037 mrad of the shrinking angle between the two nanobeam cavities are demonstrated; this study provides one more mechanical degree of freedom for the practical optomechanical interactions.
NASA Astrophysics Data System (ADS)
Basu, Rajratan; Kinnamon, Daniel; Skaggs, Nicole; Womack, James
2016-05-01
The in-plane switching (IPS) for a nematic liquid crystal (LC) was found to be considerably faster when the LC was doped with dilute concentrations of monolayer graphene flakes. Additional studies revealed that the presence of graphene reduced the rotational viscosity of the LC, permitting the nematic director to respond quicker in IPS mode on turning the electric field on. The studies were carried out with several graphene concentrations in the LC, and the experimental results coherently suggest that there exists an optimal concentration of graphene, allowing a reduction in the IPS response time and rotational viscosity in the LC. Above this optimal graphene concentration, the rotational viscosity was found to increase, and consequently, the LC no longer switched faster in IPS mode. The presence of graphene suspension was also found to decrease the LC's pretilt angle significantly due to the π-π electron stacking between the LC molecules and graphene flakes. To understand the π-π stacking interaction, the anchoring mechanism of the LC on a CVD grown monolayer graphene film on copper substrate was studied by reflected crossed polarized microscopy. Optical microphotographs revealed that the LC alignment direction depended on monolayer graphene's hexagonal crystal structure and its orientation.
Rotationally Vibrating Electric-Field Mill
NASA Technical Reports Server (NTRS)
Kirkham, Harold
2008-01-01
A proposed instrument for measuring a static electric field would be based partly on a conventional rotating-split-cylinder or rotating-split-sphere electric-field mill. However, the design of the proposed instrument would overcome the difficulty, encountered in conventional rotational field mills, of transferring measurement signals and power via either electrical or fiber-optic rotary couplings that must be aligned and installed in conjunction with rotary bearings. Instead of being made to rotate in one direction at a steady speed as in a conventional rotational field mill, a split-cylinder or split-sphere electrode assembly in the proposed instrument would be set into rotational vibration like that of a metronome. The rotational vibration, synchronized with appropriate rapid electronic switching of electrical connections between electric-current-measuring circuitry and the split-cylinder or split-sphere electrodes, would result in an electrical measurement effect equivalent to that of a conventional rotational field mill. A version of the proposed instrument is described.
A New Rotation Phenomena of Cells Induced by Homegeneous Electric Field
NASA Astrophysics Data System (ADS)
Hatakeyama, Toyomasa; Yagi, Hiroshi
1990-05-01
When at least two plant protoplasts are located close to each other under homogeneous electric field, almost all of the cells rotate in the vicinity of its frequency of 10 kHz and specific cells in the vicinity of 10 MHz. The first rotation occurs in the plane constituted by the connecting line between two cells and the applied electric field line. This angular velocity increases with the square of the field strength. On the other hand, the second rotation or new rotation occurs in any plane and its angular velocity complicatedly depends on the field strength. Furthermore, when two cells are arranged in such a way that their connecting line is parallel to the applied field, the second rotation occurs but the first does not. The distinctive feature of the second rotation can be explained by the anisotropic dielectric in the cell due to the shape of its vacuole.
Rhomboid prism pair for rotating the plane of parallel light beams
NASA Technical Reports Server (NTRS)
Orloff, K. L. (Inventor); Yanagita, H.
1982-01-01
An optical system is described for rotating the plane defined by a pair of parallel light beams. In one embodiment a single pair of rhomboid prisms have their respective input faces disposed to receive the respective input beams. Each prism is rotated about an axis of revolution coaxial with each of the respective input beams by means of a suitable motor and gear arrangement to cause the plane of the parallel output beams to be rotated relative to the plane of the input beams. In a second embodiment, two pairs of rhomboid prisms are provided. In a first angular orientation of the output beams, the prisms merely decrease the lateral displacement of the output beams in order to keep in the same plane as the input beams. In a second angular orientation of the prisms, the input faces of the second pair of prisms are brought into coincidence with the input beams for rotating the plane of the output beams by a substantial angle such as 90 deg.
Instability of a thin film flowing on a rotating horizontal or inclined plane.
Dávalos-Orozco, L A; Busse, F H
2002-02-01
In this paper the instability of a thin fluid film flowing under the effects of gravity, Coriolis, and centrifugal forces is investigated. It is supposed that the film flows far from the axis of rotation on a plane which may be horizontal or inclined with respect to the horizontal. In the former case, the flow is only driven by the centrifugal force while in the latter case, the flow is driven by the components of centrifugal force and gravity along the plane. This case may also be considered as the flow down a rotating cone but far from the apex. The stabilizing influence of rotation on the film flow increases with the rotation rate. Up to a certain critical rate of rotation, the film flowing down the rotating inclined plane (or cone) is more stable than the flow on the horizontal rotating plane while above this rate of rotation the situation is reversed. The instability above the critical rate is associated with a finite wave number in contrast to the vanishing wave number of the instability below the critical rate. The possibility of Ekman layer instabilities is also investigated. An equation describing the nonlinear evolution of surface waves is also obtained. Moreover, this equation is simplified for the case in which the amplitudes are very small. An equation including dissipation as well as dispersion is derived whose solutions may possess solitary waves, as in the case of similar equations considered in the literature. These solutions are likely to correspond to the solitary spiral waves observed in experiments.
Symmetry breaking in spin spirals and skyrmions by in-plane and canted magnetic fields
NASA Astrophysics Data System (ADS)
Schmidt, L.; Hagemeister, J.; Hsu, P.-J.; Kubetzka, A.; von Bergmann, K.; Wiesendanger, R.
2016-07-01
The influence of in-plane and canted magnetic fields on spin spirals and skyrmions in atomic bilayer islands of palladium and iron on an Ir(111) substrate is investigated by scanning tunneling microscopy at low temperatures. It is shown that the spin spiral propagation direction is determined by the island’s border which can be explained by equilibrium state calculations on a triangular lattice. We find a different response of spin spirals to in-plane magnetic fields for a propagation direction parallel to the applied field as compared to perpendicular, which originates from their cycloidal nature. As a result, the spin spiral propagation direction may be reorientated by in-plane fields. Furthermore, it is demonstrated that also skyrmions are distorted in canted fields which allows to determine the sense of magnetization rotation as enforced by the interfacial Dzyaloshinskii–Moriya interaction.
Hip rotation angle is associated with frontal plane knee joint mechanics during running.
Sakaguchi, Masanori; Shimizu, Norifumi; Yanai, Toshimasa; Stefanyshyn, Darren J; Kawakami, Yasuo
2015-02-01
Inability to control lower extremity segments in the frontal and transverse planes resulting in large knee abduction angle and increased internal knee abduction impulse has been associated with patellofemoral pain (PFP). However, the influence of hip rotation angles on frontal plane knee joint kinematics and kinetics remains unclear. The purpose of this study was to explore how hip rotation angles are related to frontal plane knee joint kinematics and kinetics during running. Seventy runners participated in this study. Three-dimensional marker positions and ground reaction forces were recorded with an 8-camera motion analysis system and a force plate while subjects ran along a 25-m runway at a speed of 4m/s. Knee abduction, hip rotation and toe-out angles, frontal plane lever arm at the knee, internal knee abduction moment and impulse, ground reaction forces and the medio-lateral distance from the ankle joint center to the center of pressure (AJC-CoP) were quantified. The findings of this study indicate that greater hip external rotation angles were associated with greater toe-out angles, longer AJC-CoP distances, smaller internal knee abduction impulses with shorter frontal plane lever arms and greater knee abduction angles. Thus, there appears to exist a conflict between kinematic and kinetic risk factors of PFP, and hip external rotation angle may be a key factor to control frontal plane knee joint kinematics and kinetics. These results may help provide an appropriate manipulation and/or intervention on running style to reduce the risk of PFP.
Free-form lens for rectangular illumination with the target plane rotating at a certain angle.
Liu, Dianhong; Zhang, Xiaohui; Chen, Chen
2015-11-01
We have proposed a method for rectangular illumination in a (u, v) coordinate system with high collection efficiency and favorable uniformity. In our proposed approach, with the target plane rotating at a certain angle around the z axis, one of the diagonals on the rectangular target plane moves to the coordinate axis; then, we partition the light source and target plane into grids. The intersection points of the grids are in one-to-one correspondence from the source to the target plane. This improved method will avoid the one-to-many correspondence topological relationship in the traditional (u, v) mapping method; uniformity of the illuminance pattern will be promoted. Based on this method, lenses are designed for rectangular target plane illumination; uniformity over 0.83 and efficiency of about 0.92 are obtained with a 1 mm×1 mm LED Lambertian source. PMID:26560910
Plane-wave decomposition of spatially random fields.
Nguyen, Tan H; Majeed, Hassaan; Popescu, Gabriel
2015-04-01
We investigate the uniqueness of the plane-wave decomposition of temporally deterministic, spatially random fields. Specifically, we consider the decomposition of spatially ergodic and, thus, statistically homogeneous fields. We show that when the spatial power spectrum is injective, the plane waves are the only possible coherent modes. Furthermore, the randomness of such fields originates in the spatial spectral phase, i.e., the phase associated with the coefficients of each plane wave in the expansion. By contrast, the spectral amplitude is deterministic and is specified by the spatial power spectrum. We end with a discussion showing how the results can be translated in full to the time domain.
Pohit, M; Sharma, J
2015-05-10
Image recognition in the presence of both rotation and translation is a longstanding problem in correlation pattern recognition. Use of log polar transform gives a solution to this problem, but at a cost of losing the vital phase information from the image. The main objective of this paper is to develop an algorithm based on Fourier slice theorem for measuring the simultaneous rotation and translation of an object in a 2D plane. The algorithm is applicable for any arbitrary object shift for full 180° rotation.
Rotating copper plasmoid in external magnetic field
Pandey, Pramod K.; Thareja, Raj K.
2013-02-15
Effect of nonuniform magnetic field on the expanding copper plasmoid in helium and argon gases using optical emission spectroscopy and fast imaging is presented. We report a peculiar oscillatory rotation of plasmoid in magnetic field and argon ambient. The temporal variation and appearance of the dip in the electron temperature show a direct evidence of the threading and expulsion of the magnetic field lines from the plasmoid. Rayleigh Taylor instability produced at the interface separating magnetic field and plasma is discussed.
Verification of theoretically computed spectra for a point rotating in a vertical plane
Powell, D.C.; Connell, J.R.; George, R.L.
1985-03-01
A theoretical model is modified and tested that produces the power spectrum of the alongwind component of turbulence as experienced by a point rotating in a vertical plane perpendicular to the mean wind direction. The ability to generate such a power spectrum, independent of measurement, is important in wind turbine design and testing. The radius of the circle of rotation, its height above the ground, and the rate of rotation are typical for those for a MOD-OA wind turbine. Verification of this model is attempted by comparing two sets of variances that correspond to individual harmonic bands of spectra of turbulence in the rotational frame. One set of variances is calculated by integrating the theoretically generated rotational spectra; the other is calculated by integrating rotational spectra from real data analysis. The theoretical spectrum is generated by Fourier transformation of an autocorrelation function taken from von Karman and modified for the rotational frame. The autocorrelation is based on dimensionless parameters, each of which incorporates both atmospheric and wind turbine parameters. The real data time series are formed by sampling around the circle of anemometers of the Vertical Plane Array at the former MOD-OA site at Clayton, New Mexico.
Route to Topological Superconductivity via Magnetic Field Rotation
Loder, Florian; Kampf, Arno P.; Kopp, Thilo
2015-01-01
The verification of topological superconductivity has become a major experimental challenge. Apart from the very few spin-triplet superconductors with p-wave pairing symmetry, another candidate system is a conventional, two-dimensional (2D) s-wave superconductor in a magnetic field with a sufficiently strong Rashba spin-orbit coupling. Typically, the required magnetic field to convert the superconductor into a topologically non-trivial state is however by far larger than the upper critical field Hc2, which excludes its realization. In this article, we argue that this problem can be overcome by rotating the magnetic field into the superconducting plane. We explore the character of the superconducting state upon changing the strength and the orientation of the magnetic field and show that a topological state, established for a sufficiently strong out-of-plane magnetic field, indeed extends to an in-plane field orientation. We present a three-band model applicable to the superconducting interface between LaAlO3 and SrTiO3, which should fulfil the necessary conditions to realize a topological superconductor. PMID:26477669
The orthogonal planes split of quaternions and its relation to quaternion geometry of rotations
NASA Astrophysics Data System (ADS)
Hitzer, Eckhard
2015-04-01
Recently the general orthogonal planes split with respect to any two pure unit quaternions f,g ∈ H, f2 = g2 = -1, including the case f = g, has proved extremely useful for the construction and geometric interpretation of general classes of double-kernel quaternion Fourier transformations (QFT) [7]. Applications include color image processing, where the orthogonal planes split with f = g = the grayline, naturally splits a pure quaternionic three-dimensional color signal into luminance and chrominance components. Yet it is found independently in the quaternion geometry of rotations [3], that the pure quaternion units f, g and the analysis planes, which they define, play a key role in the geometry of rotations, and the geometrical interpretation of integrals related to the spherical Radon transform of probability density functions of unit quaternions, as relevant for texture analysis in crystallography. In our contribution we further investigate these connections.
Matsushima, Kyoji
2008-07-01
Rotational transformation based on coordinate rotation in Fourier space is a useful technique for simulating wave field propagation between nonparallel planes. This technique is characterized by fast computation because the transformation only requires executing a fast Fourier transform twice and a single interpolation. It is proved that the formula of the rotational transformation mathematically satisfies the Helmholtz equation. Moreover, to verify the formulation and its usefulness in wave optics, it is also demonstrated that the transformation makes it possible to reconstruct an image on arbitrarily tilted planes from a wave field captured experimentally by using digital holography.
Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki
2014-01-21
A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.
Pumping of water through carbon nanotubes by rotating electric field and rotating magnetic field
NASA Astrophysics Data System (ADS)
Li, Xiao-Peng; Kong, Gao-Pan; Zhang, Xing; He, Guo-Wei
2013-09-01
Using molecular dynamics simulations, we demonstrate pumping of water through a carbon nanotube by applying the combination of a rotating electric field and a rotating magnetic field. The driving force is a Lorentz force generated from the motion of charges in the magnetic field, and the motion is caused by the rotation of the electric field. We find that there exits a linear relationship between the average pumping velocity v and magnetic field strength B, which can be used to control the flux of the continuous unidirectional water flow. This approach is expected to be used in liquid circulation without a pressure gradient.
Jou, D.; Sciacca, M.; Mongiovi, M. S.
2008-07-01
An equation previously proposed to describe the evolution of vortex-line density in rotating counterflow turbulent tangles in superfluid helium [Phys. Rev B 69, 094513 (2004)] is generalized to incorporate nonvanishing barycentric velocity and velocity gradients. Our generalization is compared with an analogous approach proposed by Lipniacki [Eur. J. Mech. B Fluids 25, 435 (2006)], and with experimental results by Swanson et al. [Phys. Rev. Lett. 50, 190 (1983)] in rotating counterflow, and it is used to evaluate the vortex density in plane Couette and Poiseuille flows of superfluid helium.
AC electric field induced dipole-based on-chip 3D cell rotation.
Benhal, Prateek; Chase, J Geoffrey; Gaynor, Paul; Oback, Björn; Wang, Wenhui
2014-08-01
The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.
A technique for calculating optimal Hohmann transfers with simultaneous plane and node rotations
NASA Astrophysics Data System (ADS)
Rogers, Christopher F.
This analysis presents eight nonlinear coupled equations whose solution provides sufficient information to characterize an optimal Hohmann transfer with simultaneous plane and node rotations. It also presents auxiliary equations which help provide other information of interest. The derivations utilize spherical geometry but otherwise deal very directly with the transfer geometry and thereby remain conceptually simple. The assumptions include initial and final circular orbits and impulsive burns. Numerical results illustrate the technique.
Dirac semimetal thin films in in-plane magnetic fields
Siu, Zhuo Bin; Jalil, Mansoor B. A.; Tan, Seng Ghee
2016-01-01
In this work we study the effects of in-plane magnetic fields on thin films of the Dirac Semimetal (DSM) Na3Bi where one of the in-plane directions is perpendicular to the k-separation between the two Weyl nodes that exist for each spin orientation. We show numerically that the states localized near the surfaces of these thin films are related to the Fermi arc states in semi-infinite slabs. Due to the anisotropy between the two in-plane directions, the application of a magnetic field along these directions have differing effects. A field parallel to the k space separation between the Weyl nodes leads to a broadening of the surface state band and the formation of an energy plateau, while a perpendicular field shifts the energy where the hole and particle bands meet upwards, and sharpens the tips of the bands. We illustrate the effects of these changes to the dispersion relation by studying the transmission from a source segment without a magnetic field to a drain segment with a field, with the field and interface at various in-plane directions. PMID:27721387
Dirac semimetal thin films in in-plane magnetic fields
NASA Astrophysics Data System (ADS)
Siu, Zhuo Bin; Jalil, Mansoor B. A.; Tan, Seng Ghee
2016-10-01
In this work we study the effects of in-plane magnetic fields on thin films of the Dirac Semimetal (DSM) Na3Bi where one of the in-plane directions is perpendicular to the k-separation between the two Weyl nodes that exist for each spin orientation. We show numerically that the states localized near the surfaces of these thin films are related to the Fermi arc states in semi-infinite slabs. Due to the anisotropy between the two in-plane directions, the application of a magnetic field along these directions have differing effects. A field parallel to the k space separation between the Weyl nodes leads to a broadening of the surface state band and the formation of an energy plateau, while a perpendicular field shifts the energy where the hole and particle bands meet upwards, and sharpens the tips of the bands. We illustrate the effects of these changes to the dispersion relation by studying the transmission from a source segment without a magnetic field to a drain segment with a field, with the field and interface at various in-plane directions.
Legant, Wesley R; Choi, Colin K; Miller, Jordan S; Shao, Lin; Gao, Liang; Betzig, Eric; Chen, Christopher S
2013-01-15
Recent methods have revealed that cells on planar substrates exert both shear (in-plane) and normal (out-of-plane) tractions against the extracellular matrix (ECM). However, the location and origin of the normal tractions with respect to the adhesive and cytoskeletal elements of cells have not been elucidated. We developed a high-spatiotemporal-resolution, multidimensional (2.5D) traction force microscopy to measure and model the full 3D nature of cellular forces on planar 2D surfaces. We show that shear tractions are centered under elongated focal adhesions whereas upward and downward normal tractions are detected on distal (toward the cell edge) and proximal (toward the cell body) ends of adhesions, respectively. Together, these forces produce significant rotational moments about focal adhesions in both protruding and retracting peripheral regions. Temporal 2.5D traction force microscopy analysis of migrating and spreading cells shows that these rotational moments are highly dynamic, propagating outward with the leading edge of the cell. Finally, we developed a finite element model to examine how rotational moments could be generated about focal adhesions in a thin lamella. Our model suggests that rotational moments can be generated largely via shear lag transfer to the underlying ECM from actomyosin contractility applied at the intracellular surface of a rigid adhesion of finite thickness. Together, these data demonstrate and probe the origin of a previously unappreciated multidimensional stress profile associated with adhesions and highlight the importance of new approaches to characterize cellular forces. PMID:23277584
NASA Astrophysics Data System (ADS)
Jiang, Xue; Cheng, JianChun; Liang, Bin
2015-05-01
The field rotator is a fascinating device capable to rotate the wave front by a certain angle, which can be regarded as a special kind of illusion. We have theoretically designed and experimentally realized an acoustic field rotator by exploiting acoustic metamaterials with extremely anisotropic parameters. A nearly perfect agreement is observed between the numerical simulation and experimental results. We have also studied the acoustic property of the acoustic rotator, and investigated how various structural parameters affect the performances of such devices, including the operating frequency range and rotation angle, which are of particularly significance for the application. The inspection of the operating frequency range shows the device can work within a considerably broad band as long as the effective medium approximation is valid. The influence of the configuration of the metamaterial unit has also been investigated, illustrating the increase of anisotropy of metamaterial helps to enhance the rotator effect, which can be conveniently attained by elongating each rectangle inserted to the units. Furthermore, we have analyzed the underlying physics to gain a deep insight to the rotation mechanism, and discussed the application of such devices for non-plane wave and the potential of extending the scheme to three-dimensional cases. The realization of acoustic field rotator has opened up a new avenue for the versatile manipulations on acoustic waves and our findings are of significance to their design and characterization, which may pave the way for the practical application of such devices.
NMR in rotating magnetic fields: Magic angle field spinning
Sakellariou, D.; Meriles, C.; Martin, R.; Pines, A.
2004-09-10
Magic angle sample spinning has been one of the cornerstones in high-resolution solid state NMR. Spinning frequencies nowadays have increased by at least one order of magnitude over the ones used in the first experiments and the technique has gained tremendous popularity. It is currently a routine procedure in solid-state NMR, high-resolution liquid-state NMR and solid-state MRI. The technique enhances the spectral resolution by averaging away rank 2 anisotropic spin interactions thereby producing isotropic-like spectra with resolved chemical shifts and scalar couplings. Andrew proposed that it should be possible to induce similar effects in a static sample if the direction of the magnetic field is varied, e.g., magic-angle rotation of the B0 field (B0-MAS) and this has been recently demonstrated using electromagnetic field rotation. Here we discuss on the possibilities to perform field rotation using alternative hardware, together with spectroscopic methods to recover isotropic resolution even in cases where the field is not rotating at the magic angle. Extension to higher magnetic fields would be beneficial in situations where the physical manipulation of the sample is inconvenient or impossible. Such situations occur often in materials or biomedical samples where ''ex-situ'' NMR spectroscopy and imaging analysis is needed.
A New Model to Produce Sagittal Plane Rotational Induced Diffuse Axonal Injuries
Davidsson, Johan; Risling, Marten
2011-01-01
A new in vivo animal model that produces diffuse brain injuries in sagittal plane rearward rotational acceleration has been developed. In this model, the skull of an anesthetized adult rat is tightly secured to a rotating bar. During trauma, the bar is impacted by a striker that causes the bar and the animal head to rotate rearward; the acceleration phase last 0.4 ms and is followed by a rotation at constant speed and a gentle deceleration when the bar makes contact with a padded stop. The total head angle change is less than 30°. By adjusting the air pressure in the rifle used to accelerate the striker, resulting rotational acceleration between 0.3 and 2.1 Mrad/s2 can be produced. Numerous combinations of trauma levels, post-trauma survival times, brain and serum retrieval, and tissue preparation techniques were adopted to characterize this new model. The trauma caused subdural bleedings in animals exposed to severe trauma. Staining brain tissue with β-Amyloid Precursor Protein antibodies and FD Neurosilver that detect degenerating axons revealed wide spread axonal injuries (AI) in the corpus callosum, the border between the corpus callosum and cortex and in tracts in the brain stem. The observed AIs were apparent only when the rotational acceleration level was moderate and above. On the contrary, only limited signs of contusion injuries were observed following trauma. Macrophage invasions, glial fibrillary acidic protein redistribution or hypertrophy, and blood brain barrier (BBB) changes were unusual. S100 serum analyses indicate that blood vessel and glia cell injuries occur following moderate levels of trauma despite the absence of obvious BBB injuries. We conclude that this rotational trauma model is capable of producing graded axonal injury, is repeatable and produces limited other types of traumatic brain injuries and as such is useful in the study of injury biomechanics, diagnostics, and treatment strategies following diffuse axonal injury. PMID
Asymmetric error field interaction with rotating conducting walls
Paz-Soldan, C.; Brookhart, M. I.; Hegna, C. C.; Forest, C. B.
2012-07-15
The interaction of error fields with a system of differentially rotating conducting walls is studied analytically and compared to experimental data. Wall rotation causes eddy currents to persist indefinitely, attenuating and rotating the original error field. Superposition of error fields from external coils and plasma currents are found to break the symmetry in wall rotation direction. The vacuum and plasma eigenmodes are modified by wall rotation, with the error field penetration time decreased and the kink instability stabilized, respectively. Wall rotation is also predicted to reduce error field amplification by the marginally stable plasma.
Brotman, David; Zhang, Ziheng; Sampath, Smita
2013-05-01
Noninvasive quantification of regional left ventricular rotation may improve understanding of cardiac function. Current methods used to quantify rotation typically acquire data on a set of prescribed short-axis slices, neglecting effects due to through-plane myocardial motion. We combine principles of slice-following tagged imaging with harmonic phase analysis methods to account for through-plane motion in regional rotation measurements. We compare rotation and torsion measurements obtained using our method to those obtained from imaging datasets acquired without slice-following. Our results in normal volunteers demonstrate differences in the general trends of average and regional rotation-time plots in midbasal slices and the rotation versus circumferential strain loops. We observe substantial errors in measured peak average rotation of the order of 58% for basal slices (due to change in the pattern of the curve), -6.6% for midventricular slices, and -8.5% for apical slices; and an average error in base-to-apex torsion of 19% when through-plane motion is not considered. This study concludes that due to an inherent base-to-apex gradient in rotation that exists in the left ventricular, accounting for through-plane motion is critical to the accuracy of left ventricular rotation quantification.
One-dimensional analysis of plane and radial thin film flows including solid-body rotation
NASA Technical Reports Server (NTRS)
Thomas, S.; Hankey, W.; Faghri, A.; Swanson, T.
1989-01-01
The flow of a thin liquid film with a free surface along a horizontal plate which emanates from a pressurized vessel is examined by integrating the equations of motion across the thin liquid layer and discretizing the integrated equations using finite difference techniques. The effects of 0-g and solid-body rotation will be discussed. The two cases of interest are plane flow and radial flow. In plane flow, the liquid is considered to be flowing along a channel with no change in the width of the channel, whereas in radial flow the liquid spreads out radially over a disk, so that the area changes along the radius. It is desired to determine the height of the liquid film at any location along the plate of disk, so that the heat transfer from the plate or disk can be found. The possibility that the flow could encounter a hydraulic jump is accounted for.
In-plane trapping and manipulation of ZnO nanowires by a hybrid plasmonic field
NASA Astrophysics Data System (ADS)
Zhang, Lichao; Dou, Xiujie; Min, Changjun; Zhang, Yuquan; Du, Luping; Xie, Zhenwei; Shen, Junfeng; Zeng, Yujia; Yuan, Xiaocong
2016-05-01
In general, when a semiconductor nanowire is trapped by conventional laser beam tweezers, it tends to be aligned with the trapping beam axis rather than confined in the horizontal plane, and this limits the application of these nanowires in many in-plane nanoscale optoelectronic devices. In this work, we achieve the in-plane trapping and manipulation of a single ZnO nanowire by a hybrid plasmonic tweezer system on a flat metal surface. The gap between the nanowire and the metallic substrate leads to an enhanced gradient force caused by deep subwavelength optical energy confinement. As a result, the nanowire can be securely trapped in-plane at the center of the excited surface plasmon polariton field, and can also be dynamically moved and rotated by varying the position and polarization direction of the incident laser beam, which cannot be performed using conventional optical tweezers. The theoretical results show that the focused plasmonic field induces a strong in-plane trapping force and a high rotational torque on the nanowire, while the focused optical field produces a vertical trapping force to produce the upright alignment of the nanowire; this is in good agreement with the experimental results. Finally, some typical ZnO nanowire structures are built based on this technique, which thus further confirms the potential of this method for precise manipulation of components during the production of nanoelectronic and nanophotonic devices.In general, when a semiconductor nanowire is trapped by conventional laser beam tweezers, it tends to be aligned with the trapping beam axis rather than confined in the horizontal plane, and this limits the application of these nanowires in many in-plane nanoscale optoelectronic devices. In this work, we achieve the in-plane trapping and manipulation of a single ZnO nanowire by a hybrid plasmonic tweezer system on a flat metal surface. The gap between the nanowire and the metallic substrate leads to an enhanced gradient force
Interference effects in angular streaking with a rotating terahertz field
NASA Astrophysics Data System (ADS)
Kazansky, A. K.; Bozhevolnov, A. V.; Sazhina, I. P.; Kabachnik, N. M.
2016-01-01
A method of angular streaking with a rotating terahertz electric field for photoelectrons produced by femtosecond extreme ultraviolet pulses is suggested and theoretically analyzed. The method can be used for free electron laser (FEL) pulse characterization on a shot-to-shot basis. It is shown that in related measurements an interesting phenomenon appears: formation of very bright and sharp features in the angular resolved electron spectra measured in the plane perpendicular to the collinear beam direction. These features are similar to the conventional caustics in the wave propagation. The caustics are accompanied by a well-developed interference structure. The intensity distribution along the caustic is determined by the envelope of the FEL pulse.
NASA Astrophysics Data System (ADS)
Drerup, B.; Hierholzer, E.
1986-07-01
Radiological assessment and follow-up control of scoliosis, i.e. of a lateral and rotational deviation of the spine, is performed mainly by single plane radiographs. Additional information may be gained from these radiographs by introducing a parametrized vertebral model. By analyzing the radiographic contours according to this model, axial rotation can be determined for any position and orientation of the vertebra. In addition to rotation several other data are determined for each vertebra, such as the tilting angle and the two-dimensional coordinates of the centre. By handling the data as a function of the vertebral location in spine, characteristic curves are generated. In order to find simple shape parameters for these characteristics, a smooth curve has to be fitted to the data points by a least squares approximation. This problem may be solved by a Fourier decomposition of the spinal curves. It appears, that the Fourier coefficients (amplitudes and phases) and some derived shape parameters lend themselves to a medical interpretation, which is consistent with the existing classification of the scoliotic spine.
NASA Astrophysics Data System (ADS)
Bijarnia, R.; Singh, B.
2016-05-01
The paper is concerned with the propagation of plane waves in a transversely isotropic two temperature generalized thermoelastic solid half-space with voids and rotation. The governing equations are modified in the context of Lord and Shulman theory of generalized thermoelasticity and solved to show the existence of four plane waves in the x - z plane. Reflection of these plane waves from thermally insulated stress free surface is also studied to obtain a system of four non-homogeneous equations. For numerical computations of speed and reflection coefficients, a particular material is modelled as transversely isotropic generalized thermoelastic solid half-space. The speeds of plane waves are computed against the angle of propagation to observe the effects of two temperature and rotation. Reflection coefficients of various reflected waves are also computed against the angle of incidence to observe the effects of various parameters.
Electropumping of water with rotating electric fields
NASA Astrophysics Data System (ADS)
De Luca, Sergio; Todd, B. D.; Hansen, J. S.; Daivis, Peter J.
2013-04-01
Pumping of fluids confined to nanometer dimension spaces is a technically challenging yet vitally important technological application with far reaching consequences for lab-on-a-chip devices, biomimetic nanoscale reactors, nanoscale filtration devices and the like. All current pumping mechanisms require some sort of direct intrusion into the nanofluidic system, and involve mechanical or electronic components. In this paper, we present the first nonequilibrium molecular dynamics results to demonstrate that non-intrusive electropumping of liquid water on the nanoscale can be performed by subtly exploiting the coupling of spin angular momentum to linear streaming momentum. A spatially uniform rotating electric field is applied to water molecules, which couples to their permanent electric dipole moments. The resulting molecular rotational momentum is converted into linear streaming momentum of the fluid. By selectively tuning the degree of hydrophobicity of the solid walls one can generate a net unidirectional flow. Our results for the linear streaming and angular velocities of the confined water are in general agreement with the extended hydrodynamical theory for this process, though also suggest refinements to the theory are required. These numerical experiments confirm that this new concept for pumping of polar nanofluids can be employed under laboratory conditions, opening up significant new technological possibilities.
Numerical Study of Flow Motion and Patterns Driven by a Rotating Permanent Helical Magnetic Field
NASA Astrophysics Data System (ADS)
Yang, Wenzhi; Wang, Xiaodong; Wang, Bo; Baltaretu, Florin; Etay, Jacqueline; Fautrelle, Yves
2016-10-01
Liquid metal magnetohydrodynamic flow driven by a rotating permanent helical magnetic field in a cylindrical container is numerically studied. A three-dimensional numerical simulation provides insight into the visualization of the physical fields, including the magnetic field, the Lorentz force density, and the flow structures, especially the flow patterns in the meridional plane. Because the screen parameter is sufficiently small, the model is decoupled into electromagnetic and hydrodynamic components. Two flow patterns in the meridional plane, i.e., the global flow and the secondary flow, are discovered and the impact of several system parameters on their transition is investigated. Finally, a verifying model is used for comparison with the previous experiment.
Numerical Study of Flow Motion and Patterns Driven by a Rotating Permanent Helical Magnetic Field
NASA Astrophysics Data System (ADS)
Yang, Wenzhi; Wang, Xiaodong; Wang, Bo; Baltaretu, Florin; Etay, Jacqueline; Fautrelle, Yves
2016-08-01
Liquid metal magnetohydrodynamic flow driven by a rotating permanent helical magnetic field in a cylindrical container is numerically studied. A three-dimensional numerical simulation provides insight into the visualization of the physical fields, including the magnetic field, the Lorentz force density, and the flow structures, especially the flow patterns in the meridional plane. Because the screen parameter is sufficiently small, the model is decoupled into electromagnetic and hydrodynamic components. Two flow patterns in the meridional plane, i.e., the global flow and the secondary flow, are discovered and the impact of several system parameters on their transition is investigated. Finally, a verifying model is used for comparison with the previous experiment.
Detection of cracks under cladding using magneto-optic imaging and rotating in-plane magnetization
NASA Astrophysics Data System (ADS)
Fitzpatrick, Gerald L.; Skaugset, Richard L.; Thome, David K.; Shih, William C.
1996-11-01
Conventional nondestructive inspection (NDI) of steel components, using magnetic particle, flux-leakage or near surface ultrasonic methods, is rendered difficult by the presence of protective coatings such as paint or stainless- steel cladding. Thick-section nuclear reactor pressure vessels (RPVs), having as-welded cladding up to 0.25 inches thick are a case in point. Here, magnetic particle techniques do not work and ultrasonic techniques are difficult to apply because of cladding roughens and variable elastic properties in the cladding and the weld interface. An NDI technique that is essentially unaffected by standard thicknesses of protective coatings would be a major advance. Magneto-optic imaging is one such technique. While conventional magneto-optic/eddy current imagers (MOIs) are a proven technology in the NDI of nonferromagnetic conductors, they do not possess a self-contained method for magnetizing steel. The purpose of this work was to develop methods for producing rotating, in-plane magnetization and then combine this technology with magneto-optic imaging to produce a self-contained instrument capable of real-time imaging of cracks in steel through protective coatings. We successfully demonstrated rotating in-plane magnetization using special 'quadrature' magnetic-yokes designed to accommodate both flat and cylindrical steel surfaces. The yokes were attached one at a time, to an MOI of reduced size, and the combined system was placed on a sample of the appropriate curvature containing cracks. A two-channel power amplifier was used to drive the yoke coils in quadrature. The resulting crack images were found to be much less sensitive to liftoff than conventional magnetic particle or flux-leakage NDI. In particular, cracks in steel were successfully imaged through 0.125 inches of stainless-steel cladding, making it likely that images of cracks in steel under even thicker cladding should be possible after further development of the technology. Unlike
Magnetism and rotation in relativistic field theory
NASA Astrophysics Data System (ADS)
Mameda, Kazuya; Yamamoto, Arata
2016-09-01
We investigate the analogy between magnetism and rotation in relativistic theory. In nonrelativistic theory, the exact correspondence between magnetism and rotation is established in the presence of an external trapping potential. Based on this, we analyze relativistic rotation under external trapping potentials. A Landau-like quantization is obtained by considering an energy-dependent potential.
Caustics in a field negatively refracted at a plane interface.
Shendeleva, M L
2008-03-01
An electromagnetic field radiated by a line source situated near a plane interface between a medium with positive refractive index and a medium with negative refractive index is considered by using the geometrical optics approach. Rays and wave fronts of the refracted field are constructed using Fermat's principle. It is shown that the negatively refracted rays intersecting in pairs create 2-fold caustics that meet at a cusp point. The cusp of the caustic is directed towards the interface for |n| > 1 and away from the interface for |n| < 1, where n is the relative refractive index. It is also shown that wave fronts of the refracted field propagate towards the interface, in the direction from negative to positive optical path lengths. PMID:18331494
Radiation of Electron in the Field of Plane Light Wave
Zelinsky, A.; Drebot, I.V.; Grigorev, Yu.N.; Zvonareva, O.D.; Tatchyn, R.; /SLAC
2006-02-24
Results of integration of a Lorentz equation for a relativistic electron moving in the field of running, plane, linear polarized electromagnetic wave are presented in the paper. It is shown that electron velocities in the field of the wave are almost periodic functions of time. For calculations of angular spectrum of electron radiation intensity expansion of the electromagnetic field in a wave zone into generalized Fourier series was used. Expressions for the radiation intensity spectrum are presented in the paper. Derived results are illustrated for electron and laser beam parameters of NSC KIPT X-ray generator NESTOR. It is shown that for low intensity of the interacting electromagnetic wave the results of energy and angular spectrum calculations in the frame of classical electrodynamics completely coincide with calculation results produced using quantum electrodynamics. Simultaneously, derived expressions give possibilities to investigate dependence of energy and angular Compton radiation spectrum on phase of interaction and the interacting wave intensity.
NASA Astrophysics Data System (ADS)
Mohan, N. Krishna; Rastogi, Pramod
2002-04-01
A new real-time phase-shifting readout system is developed for quantitative evaluation of full-field correlation fringes obtained by means of Fourier filtering in speckle photography. The proposed method, which uses photorefractive crystals as the recording medium, is capable of mapping the whole-field displacement data from the recorded phase-shifted fringe patterns. Experimental results are presented on a diffuse surface subjected to rotation in its own plane.
NASA Astrophysics Data System (ADS)
Wu, Chen; Ran, Shihao; Le, Henry H.; Singh, Manmohan; Larina, Irina V.; Mayerich, David; Dickinson, Mary E.; Larin, Kirill V.
2016-03-01
The mouse is a common model for studying developmental diseases. Different optical techniques have been developed to investigate mouse embryos, but each has its own set of limitations and restrictions. In this study, we imaged the same E9.5 mouse embryo with rotational imaging Optical Coherence Tomography (RI-OCT) and Selective Plane Illumination Microscopy (SPIM), and compared the two techniques. Results demonstrate that both methods can provide images with micrometer-scale spatial resolution. The RI-OCT technique was developed to increase imaging depth of OCT by performing traditional OCT imaging at multiple sides and co-registering the images. In SPIM, optical sectioning is achieved by illuminating the sample with a sheet of light. In this study, the images acquired from both techniques are compared with each other to evaluate the benefits and drawbacks of each technique for embryonic imaging. Since 3D stacks can be obtained by SPIM from different angles by rotating the sample, it might be possible to build a hybrid setup of two imaging modalities to combine the advantages of each technique.
Slowly rotating scalar field wormholes: The second order approximation
Kashargin, P. E.; Sushkov, S. V.
2008-09-15
We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second-order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the nonrotating one, and the null energy condition violation in the rotating wormhole spacetime is weaker than that in the nonrotating one.
Rotational Doppler Effect and Barnett Field in Spinning NMR
NASA Astrophysics Data System (ADS)
Chudo, Hiroyuki; Harii, Kazuya; Matsuo, Mamoru; Ieda, Jun'ichi; Ono, Masao; Maekawa, Sadamichi; Saitoh, Eiji
2015-04-01
We report the observation of the rotational Doppler effect using nuclear magnetic resonance (NMR). We have developed a coil-spinning technique that enables measurements by rotating a detector and fixing a sample. We found that the rotational Doppler effect gives rise to NMR frequency shifts equal to the rotation frequency. We formulate the rotational Doppler effect and the Barnett field using a vector model for the nuclear magnetic moment. This formulation reveals that, with just the sample rotating, both effects cancel each other, thereby explaining the absence of an NMR frequency shift in conventional sample-spinning NMR measurements.
Magnetic field structure evolution in rotating magnetic field plasmas
Petrov, Yuri; Yang Xiaokang; Huang, T.-S.
2008-07-15
A study of magnetic field structure evolution during 40-ms plasma discharge has been performed in a new device with 80 cm long/40 cm diameter cylindrical chamber, in which a plasma current I{sub p}{approx_equal}2 kA was driven and sustained by a rotating magnetic field. The main focus of the experiments is on how the changes in externally applied magnetic field affect the current profile and magnetic field in plasma. During plasma discharge, a pulse current was briefly fed to a magnetic coil located at the midplane (middle coil). The magnetic field in cross section of plasma was scanned with pickup probes. Two regimes were studied: without and with an external toroidal field (TF) produced by axial I{sub z} current. With a relatively small current (I{sub m} {<=} 600 A) in the middle coil, the plasma current is boosted up to 5 kA. The magnetic flux surfaces become extended along the axial Z direction, sometimes with the formation of doublet shape plasma. The regime without TF appears to be less stable, presumably due to the reversal of plasma current in central area of plasma column.
Curved Focal Plane Wide Field of View Telescope Design
NASA Astrophysics Data System (ADS)
Grayson, Timothy P.
2002-12-01
Ground-based surveillance of deep space has traditionally been the purview of optical telescope systems. Unlike their imaging counterparts, space surveillance telescopes emphasize wide field of view (FOV) over resolution, permitted the most rapid survey of the entire sky. At the same time there is a constant push to detect ever fainter objects, such as small pieces of space debris or small, distant asteroids. Unfortunately increased sensitivity requires very large aperture diameters, which when combined with the requirement for wide FOV results in very fast f/# telescopes. How far this set of requirements can be expanded is typically limited by large, complex, and costly corrector optics to flatten the wavefront. An alternative approach is to design the telescope to a curved focal plane. This is an approach that was once taken with film, but it has not been feasible with electronic focal plane arrays (FPA). A major break-through in FPA design may open up a new range of telescope design options. A new array fabrication technique now provides the ability to produce FPAs with a specified degree of curvature while preserving required electro-optical characteristics. This paper presents a design for a new space surveillance telescope utilizing these curved FPAs.
Stress field rotation or block rotation: An example from the Lake Mead fault system
NASA Technical Reports Server (NTRS)
Ron, Hagai; Nur, Amos; Aydin, Atilla
1990-01-01
The Coulomb criterion, as applied by Anderson (1951), has been widely used as the basis for inferring paleostresses from in situ fault slip data, assuming that faults are optimally oriented relative to the tectonic stress direction. Consequently if stress direction is fixed during deformation so must be the faults. Freund (1974) has shown that faults, when arranged in sets, must generally rotate as they slip. Nur et al., (1986) showed how sufficiently large rotations require the development of new sets of faults which are more favorably oriented to the principal direction of stress. This leads to the appearance of multiple fault sets in which older faults are offset by younger ones, both having the same sense of slip. Consequently correct paleostress analysis must include the possible effect of fault and material rotation, in addition to stress field rotation. The combined effects of stress field rotation and material rotation were investigated in the Lake Meade Fault System (LMFS) especially in the Hoover Dam area. Fault inversion results imply an apparent 60 degrees clockwise (CW) rotation of the stress field since mid-Miocene time. In contrast structural data from the rest of the Great Basin suggest only a 30 degrees CW stress field rotation. By incorporating paleomagnetic and seismic evidence, the 30 degrees discrepancy can be neatly resolved. Based on paleomagnetic declination anomalies, it is inferred that slip on NW trending right lateral faults caused a local 30 degrees counter-clockwise (CCW) rotation of blocks and faults in the Lake Mead area. Consequently the inferred 60 degrees CW rotation of the stress field in the LMFS consists of an actual 30 degrees CW rotation of the stress field (as for the entire Great Basin) plus a local 30 degrees CCW material rotation of the LMFS fault blocks.
Propagation speed of rotation signals for field lines undergoing magnetic reconnection
Lapenta, Giovanni; Goldman, Martin; Newman, David; Markidis, Stefano
2013-10-15
Reconnection is associated with two bending of the magnetic field lines. Considering the usual plane of a 2D reconnection simulation, the first bending is in-plane and produces the needed topological changes by bringing oppositely directed filed lines in proximity. The second is typical of fast reconnection and is out of plane, leading to the formation of the Hall magnetic field. This second rotation has recently been observed to proceed at superAlfvénic speeds and to carry substantial energy fluxes (Shay et al., Phys. Rev. Lett. 107, 065001 (2011)). We revisit these rotations with a new diagnostics based on dispersing a multitude of virtual probes into a kinetic simulation, akin the approach of multi spacecraft missions. The results of the new diagnostics are compared with the theory of characteristics applied to the two fluid model. The comparison of virtual probes and the method of characteristics confirm the findings relative to the out of plane rotation and uncover the existence of two families of characteristics. Both are observed in the simulation. The early stage of reconnection develops on the slower compressional branch and the later faster phase develops on the faster torsional branch. The superAlfvénic signal is only relevant in the second phase.
Stensdotter, Ann-Katrin; Dinhoff Pedersen, Morten; Meisingset, Ingebrigt; Vasseljen, Ottar; Stavdahl, Øyvind
2016-05-01
This study repeats the experimental protocol for investigation of head stabilization in healthy humans, described by Keshner and Peterson (1995) but with a modification of the analysis. Head movements were considered with respect to the room instead of relative to the trunk. The aim was to investigate the approximate contribution of reflex and voluntary control across perturbing frequencies and conditions with modulation of visual information and mental attention and discuss the resulting outcome while comparing methods. Seventeen healthy individuals were asked to keep the head steady in space while subjected to pseudorandom rotational perturbations in the horizontal plane, firmly seated on an actuated chair. Both methods confirmed the results for gain in previous studies showing fair ability to keep the head steady in space below 1 Hz with vision. Compensation deteriorated when vision was removed and worsened further with addition of a mental task. Between 1 and 2 Hz, unity gain occurred between head and trunk movements, whereas above 2 Hz the head moved more than the trunk. For phase angles, the original method demonstrated a phase split occurring from ~1 Hz, a purely mathematical artifact that caused subjects with virtually identical movements to appear as significantly different. This artifact was eliminated by analyzing the head-room relative to trunk-room rather than head-trunk relative to trunk-room angles, thus preventing potentially erroneous interpretations of the results. PMID:27225623
Phase Diagram of a 2-D Plane Rotator Model with Integer and Half-Integer Vortices
NASA Astrophysics Data System (ADS)
de Souza, Adauto J. F.; Landau, D. P.
1996-03-01
A two-dimensional plane rotator spin model is simulated by employing the single cluster embeding Monte Carlo technique and the re-weighting histogram analysis. The system is described by the Hamiltonian^1 \\cal H = -J1 sum_< i,j > Si \\cdot Sj - J2 sum_< i,j > ( Si \\cdot Sj )^2. In adition to the familiar integer vortices, this model possesses half-integer vortex excitations as well. The system exhibits three low-temperature phases which may be identified by the behavior of suitably defined two-point correlation functions. The half- and integer-vortex densities as a function of temperature are calculated for several values of the parameter α = J_2/J_1. The phase boundaries are determined and the nature of the phase transitions is investigated. Research supported in part by the CNPq and the NSF. Permanent address: Departmento de Física e Matemática, Universidade Federal Rural de Pernambuco, 52171-900, Recife, Pernambuco, Brazil ^1 D.H. Lee and G. Grinstein Phys. Rev. Lett. \\underline55, 541, (1985)
Theoretical study of alignment dynamics of magnetic oblate spheroids in rotating magnetic fields
NASA Astrophysics Data System (ADS)
Tan, Mingyang; Song, Han; Dhagat, Pallavi; Jander, Albrecht; Walker, Travis W.
2016-06-01
Magnetic composites containing anisotropic magnetic particles can achieve properties not possible in corresponding bulk or thin films of the magnetic material. In this work, we discuss how planar magnetic anisotropy may be achieved in a composite by aligning disk-shaped particles in an in-plane rotating magnetic field. Previous efforts have reported a simple model of aligning particles in a high-frequency rotating magnetic field. However, no complete analytic solution was proposed. Here, we provide a full analytic solution that describes the alignment dynamics of microdisks in a rotating field that covers the entire frequency range. We also provide simplified solutions at both high-frequency and low-frequency limits through asymptotic expansions for easy implementation into industrial settings. The analytic solution is confirmed by numerical simulation and shows agreement with experiments.
Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane
NASA Technical Reports Server (NTRS)
Pant, Bharat B. (Inventor); Wan, Hong (Inventor)
2001-01-01
A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.
Single-Plane Magnetically Focused Elongated Small Field Proton Beams.
McAuley, Grant A; Slater, James M; Wroe, Andrew J
2015-08-01
We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams.
Ibata, Rodrigo A.; Martin, Nicolas F.; Ibata, Neil G.; Lewis, Geraint F.; Conn, Anthony; Elahi, Pascal; Arias, Veronica; Fernando, Nuwanthika
2014-03-20
In a recent contribution, Bahl and Baumgardt investigated the incidence of planar alignments of satellite galaxies in the Millennium-II simulation and concluded that vast, thin planes of dwarf galaxies, similar to that observed in the Andromeda galaxy (M31), occur frequently by chance in Λ-cold dark matter cosmology. However, their analysis did not capture the essential fact that the observed alignment is simultaneously radially extended, yet thin, and kinematically unusual. With the caveat that the Millennium-II simulation may not have sufficient mass resolution to identify confidently simulacra of low-luminosity dwarf galaxies, we re-examine that simulation for planar structures, using the same method as employed by Ibata et al. on the real M31 satellites. We find that 0.04% of host galaxies display satellite alignments that are at least as extreme as the observations, when we consider their extent, thickness, and number of members rotating in the same sense. We further investigate the angular momentum properties of the co-planar satellites, and find that the median of the specific angular momentum derived from the line-of-sight velocities in the real M31 structure (1.3 × 10{sup 4} km s{sup –1} kpc) is very high compared to systems drawn from the simulations. This analysis confirms that it is highly unlikely that the observed structure around the Andromeda galaxy is due to a chance occurrence. Interestingly, the few extreme systems that are similar to M31 arise from the accretion of a massive sub-halo with its own spatially concentrated entourage of orphan satellites.
NASA Astrophysics Data System (ADS)
Ibata, Rodrigo A.; Ibata, Neil G.; Lewis, Geraint F.; Martin, Nicolas F.; Conn, Anthony; Elahi, Pascal; Arias, Veronica; Fernando, Nuwanthika
2014-03-01
In a recent contribution, Bahl & Baumgardt investigated the incidence of planar alignments of satellite galaxies in the Millennium-II simulation and concluded that vast, thin planes of dwarf galaxies, similar to that observed in the Andromeda galaxy (M31), occur frequently by chance in Λ-cold dark matter cosmology. However, their analysis did not capture the essential fact that the observed alignment is simultaneously radially extended, yet thin, and kinematically unusual. With the caveat that the Millennium-II simulation may not have sufficient mass resolution to identify confidently simulacra of low-luminosity dwarf galaxies, we re-examine that simulation for planar structures, using the same method as employed by Ibata et al. on the real M31 satellites. We find that 0.04% of host galaxies display satellite alignments that are at least as extreme as the observations, when we consider their extent, thickness, and number of members rotating in the same sense. We further investigate the angular momentum properties of the co-planar satellites, and find that the median of the specific angular momentum derived from the line-of-sight velocities in the real M31 structure (1.3 × 104 km s-1 kpc) is very high compared to systems drawn from the simulations. This analysis confirms that it is highly unlikely that the observed structure around the Andromeda galaxy is due to a chance occurrence. Interestingly, the few extreme systems that are similar to M31 arise from the accretion of a massive sub-halo with its own spatially concentrated entourage of orphan satellites.
Optical polarization plane rotation for the blazar PG 1553+113
NASA Astrophysics Data System (ADS)
Blinov, D.; Casadi, C.
2016-09-01
We report about RoboPol observations of the ongoing rotation of the optical polarization angle for the blazar PG 1553+113 (RA=15h55m43s; Dec=+11d11m24s). The rotation began around August, 19. So far the total amplitude of the rotation is ~130 degrees with an average rate of ~8 deg/day.
van den Hoorn, W; Bruijn, S M; Meijer, O G; Hodges, P W; van Dieën, J H
2012-01-10
This study investigated whether people with low back pain (LBP) reduce variability of movement between the pelvis and thorax (trunk) in the transverse plane during gait at different speeds compared to healthy controls. Thirteen people with chronic LBP and twelve healthy controls walked on a treadmill at speeds from 0.5 to 1.72 m/s, with increments of 0.11 m/s. Step-to-step variability of the trunk, pelvis, and thorax rotations were calculated. Step-to-step deviations of pelvis and thorax rotations from the average pattern (residual rotations) were correlated to each other, and the linear regression coefficients between these deviations calculated. Spectral analysis was used to determine the frequencies of the residual rotations, to infer the relation of reduced trunk variability to trunk stiffness and/or damping. Variability of trunk motion (thorax relative to pelvis) was lower (P=0.02), covariance between the residual rotations of pelvis and thorax motions was higher (P=0.03), and the linear regression coefficients were closer to 1 (P=0.05) in the LBP group. Most power of segmental residual rotations was below stride frequency (~1 Hz). In this frequency range, trunk residual rotations had less power than pelvis or thorax residual rotations. These data show that people with LBP had lower variability of trunk rotations, as a result of the coupling of deviations of residual rotations in one segment to deviations of a similar shape (correlation) and amplitude (regression coefficient) in the other segment. These results support the argument that people with LBP adopt a protective movement strategy, possibly by increased trunk stiffness.
NASA Astrophysics Data System (ADS)
Sereno, M.; Lupone, S.; Debiossac, M.; Kalashnyk, N.; Roncin, P.
2016-09-01
A procedure to measure the residual tilt angle τ between a flat surface and the azimuthal rotation axis of the sample holder is described. When the incidence angle θ and readout of the azimuthal angle ϕ are controlled by motors, an active compensation mechanism can be implemented to reduce the effect of the tilt angle during azimuthal motion. After this correction, the effective angle of incidence is kept fixed, and only a small residual oscillation of the scattering plane remains.
Theory and application of plane elliptic multipoles for static magnetic fields
NASA Astrophysics Data System (ADS)
Schnizer, P.; Schnizer, B.; Akishin, P.; Fischer, E.
2009-08-01
Standard textbooks on beam dynamics study the impact of the magnetic field quality on the beam using field representations based on circular multipoles. Iron dominated magnets, however, typically provide a good field region with a non-circular aspect ratio (i.e. an ellipse whose axis a is significantly larger than the axis b); a boundary not ideal for circular multipoles. The development of superconductors, originally driven to reach fields above ≈2 T, allows using them today in completely different fields: iron dominated DC magnets, to save the energy for coil powering as well as repeatedly fast ramped magnets. The cold mass of magnets, housed in common cryostats sectors, makes it tedious to implement additional correction magnets at a later stage, as it requires to warm up the sections where the magnets should be installed as well as unwelding the cryostat. Thus the field homogeneity of the magnets and its influence on the beam has to be thoroughly studied during the project planning phase. Elliptic multipoles, a new type of field expansion for static or quasi-static (here magnetic) two-dimensional fields, are proposed and investigated, which are particular solutions of the potential equation in plane elliptic coordinates obtained by the method of separation. The proper subsets of these particular solutions appropriate for representing static real or complex fields regular within an ellipse are identified. Formulas are given for computing expansion coefficients from given fields. The advantage of this new approach is that the expansion is valid, convergent and accurate in a larger domain, namely in an ellipse circumscribed to the reference circle of the common circular multipoles in polar coordinates. Formulas are derived for calculating the circular multipoles from the elliptical ones. The effectiveness of the approach was tested on many different magnet designs and is illustrated here on the dipole design chosen for the core synchrotron (SIS 100) of the FAIR
New Limits on Extragalactic Magnetic Fields from Rotation Measures.
Pshirkov, M S; Tinyakov, P G; Urban, F R
2016-05-13
We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields. PMID:27232014
New Limits on Extragalactic Magnetic Fields from Rotation Measures.
Pshirkov, M S; Tinyakov, P G; Urban, F R
2016-05-13
We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields.
New Limits on Extragalactic Magnetic Fields from Rotation Measures
NASA Astrophysics Data System (ADS)
Pshirkov, M. S.; Tinyakov, P. G.; Urban, F. R.
2016-05-01
We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2 σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields.
Rothschild, Freda; Bishop, Alexis I; Kitchen, Marcus J; Paganin, David M
2014-03-24
The Cornu spiral is, in essence, the image resulting from an Argand-plane map associated with monochromatic complex scalar plane waves diffracting from an infinite edge. Argand-plane maps can be useful in the analysis of more general optical fields. We experimentally study particular features of Argand-plane mappings known as "vorticity singularities" that are associated with mapping continuous single-valued complex scalar speckle fields to the Argand plane. Vorticity singularities possess a hierarchy of Argand-plane catastrophes including the fold, cusp and elliptic umbilic. We also confirm their connection to vortices in two-dimensional complex scalar waves. The study of vorticity singularities may also have implications for higher-dimensional fields such as coherence functions and multi-component fields such as vector and spinor fields. PMID:24663998
Electric-field-induced rotation of Brownian metal nanowires.
Arcenegui, Juan J; García-Sánchez, Pablo; Morgan, Hywel; Ramos, Antonio
2013-09-01
We describe the physical mechanism responsible for the rotation of Brownian metal nanowires suspended in an electrolyte exposed to a rotating electric field. The electric field interacts with the induced charge in the electrical double layer at the metal-electrolyte interface, causing rotation due to the torque on the induced dipole and to the induced-charge electro-osmotic flow around the particle. Experiments demonstrate that the primary driving mechanism is the former of these two. Our analysis contrasts with previous work describing the electrical manipulation of metallic particles with electric fields, which neglected the electrical double layer. Theoretical values for the rotation speed are calculated and good agreement with experiments is found.
David, D.; Bar, I.; Rosenwaks, S. )
1993-11-11
The [mu]-v, v-J, and [mu]-v-J vector correlations of the OH fragments from the photodissociation at 193 nm of the 3[sub 03] in-plane rotational state of the fundamental symmetric stretch of water, H[sub 2]O (1,0,0), are probed by Doppler polarization spectroscopy. The observed correlations are close to the limiting values expected for an idealized orientation (with minimal influence of the parent rotation) where the transition dipole moment of the parent is parallel to the fragment angular momentum and perpendicular to its velocity. This is the first time that these correlations are measured for the photodissociation of an initially prepared, vibrationally excited molecule in a specific rotational state. 23 refs., 2 figs., 1 tab.
Novel rotating field probe for inspection of tubes
Xin, J.; Tarkleson, E.; Lei, N.; Udpa, L.; Udpa, S. S.
2012-05-17
Inspection of steam generator tubes in nuclear power plants is extremely critical for safe operation of the power plant. In the nuclear industry, steam generator tube inspection using eddy current techniques has evolved over the years from a single bobbin coil, to rotating probe coil (RPC) and array probe, in an attempt to improve the speed and reliability of inspection. The RPC probe offers the accurate spatial resolution but involves complex mechanical rotation. This paper presents a novel design of eddy current probes based on rotating fields produced by three identical coils excited by a balanced three-phase supply. The sensor thereby achieves rotating probe functionality by electronic means and eliminates the need for mechanical rotation. The field generated by the probe is largely radial that result in induced currents that flow circularly around the radial axis and rotating around the tube at a synchronous speed effectively producing induced eddy currents that are multidirectional. The probe will consequently be sensitive to cracks of all orientations in the tube wall. The finite element model (FEM) results of the rotating fields and induced currents are presented. A prototype probe is being built to validate simulation results.
Tatalias, M; Bockisch, C J; Bertolini, G; Straumann, D; Palla, A
2011-03-01
Estimation of subjective whole-body tilt in stationary roll positions after rapid rotations shows hysteresis. We asked whether this phenomenon is also present during continuous quasi-static whole-body rotation and whether gravitational cues are a major contributing factor. Using a motorized turntable, 8 healthy subjects were rotated continuously about the earth-horizontal naso-occipital axis (earth-vertical roll plane) and the earth-vertical naso-occipital axis (earth-horizontal roll plane). In both planes, three full constant velocity rotations (2°/s) were completed in clockwise and counterclockwise directions (acceleration = 0.05°/s(2), velocity plateau reached after 40 s). Subjects adjusted a visual line along the perceived longitudinal body axis (pLBA) every 2 s. pLBA deviation from the longitudinal body axis was plotted as a function of whole-body roll position, and a sine function was fitted. At identical whole-body earth-vertical roll plane positions, pLBA differed depending on whether the position was reached by a rotation from upright or by passing through upside down. After the first 360° rotation, pLBA at upright whole-body position deviated significantly in the direction of rotation relative to pLBA prior to rotation initiation. This deviation remained unchanged after subsequent full rotations. In contrast, earth-horizontal roll plane rotations resulted in similar pLBA before and after each rotation cycle. We conclude that the deviation of pLBA in the direction of rotation during quasi-static earth-vertical roll plane rotations reflects static antihysteresis and might be a consequence of the known static hysteresis of ocular counterroll: a visual line that is perceived that earth-vertical is expected to be antihysteretic, if ocular torsion is hysteretic.
Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS2
NASA Astrophysics Data System (ADS)
Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados del Águila, Andrés; Ballottin, Mariana V.; Christianen, Peter C. M.; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf
2016-08-01
We control the linear polarization of emission from the coherently emitting K+ and K- valleys (valley coherence) in monolayer WS2 with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τc=260 fs .
Surface chirality induced by rotational electrodeposition in magnetic fields
Mogi, Iwao; Morimoto, Ryoichi; Aogaki, Ryoichi; Watanabe, Kazuo
2013-01-01
The surfaces of minerals could serve important catalytic roles in the prebiotic syntheses of organic molecules, such as amino acids. Thus, the surface chirality is responsible for the asymmetric syntheses of biomolecules. Here, we show induction of the surface chirality of copper metal film by electrodeposition via electrochemical cell rotation in magnetic fields. Such copper film electrodes exhibit chiral behaviour in the electrochemical reaction of alanine enantiomers, and the rotating direction allows control of the chiral sign. These findings are discussed in connection with the asymmetric influence of the system rotation on the magnetohydrodynamic micro-vortices around the electrode surfaces. PMID:23999254
Perception of combined translation and rotation in the horizontal plane in humans.
Crane, Benjamin T
2016-09-01
Thresholds and biases of human motion perception were determined for yaw rotation and sway (left-right) and surge (fore-aft) translation, independently and in combination. Stimuli were 1 Hz sinusoid in acceleration with a peak velocity of 14°/s or cm/s. Test stimuli were adjusted based on prior responses, whereas the distracting stimulus was constant. Seventeen human subjects between the ages of 20 and 83 completed the experiments and were divided into 2 groups: younger and older than 50. Both sway and surge translation thresholds significantly increased when combined with yaw rotation. Rotation thresholds were not significantly increased by the presence of translation. The presence of a yaw distractor significantly biased perception of sway translation, such that during 14°/s leftward rotation, the point of subjective equality (PSE) occurred with sway of 3.2 ± 0.7 (mean ± SE) cm/s to the right. Likewise, during 14°/s rightward motion, the PSE was with sway of 2.9 ± 0.7 cm/s to the left. A sway distractor did not bias rotation perception. When subjects were asked to report the direction of translation while varying the axis of yaw rotation, the PSE at which translation was equally likely to be perceived in either direction was 29 ± 11 cm anterior to the midline. These results demonstrated that rotation biased translation perception, such that it is minimized when rotating about an axis anterior to the head. Since the combination of translation and rotation during ambulation is consistent with an axis anterior to the head, this may reflect a mechanism by which movements outside the pattern that occurs during ambulation are perceived.
NASA Astrophysics Data System (ADS)
Zhou, Xiang-Fa; Zhou, Zheng-Wei; Wu, Congjun; Guo, Guang-Can
2015-03-01
We consider the ground-state properties of the two-component spin-orbit-coupled ultracold bosons subject to a rotationally symmetric in-plane gradient magnetic field. In the noninteracting case, the ground state supports giant vortices carrying large angular momenta without rotating the trap. The vorticity is highly tunable by varying the amplitudes and orientations of the magnetic field. Interactions drive the system from a giant-vortex state to various configurations of vortex lattice states along a ring. Vortices exhibit ellipse-shaped envelopes with the major and minor axes determined by the spin-orbit coupling and healing lengths, respectively. Phase diagrams of vortex lattice configurations are constructed and their stabilities are analyzed.
Investigations of Magnetically Enhanced RIE Reactors with Rotating Magnetic Fields
NASA Astrophysics Data System (ADS)
Babaeva, Natalia Yu.; Kushner, Mark J.
2008-10-01
In Magnetically Enhanced Reactive Ion Etching (MERIE) reactors, a magnetic field parallel to the substrate enables higher plasma densities and control of ion energy distributions. Since it is difficult to make the B-field uniform across the wafer, the B-field is often azimuthally rotated at a few Hz to average out non-uniformities. The rotation is slow enough that the plasma is in quasi-equilibrium with the instantaneous B-field. For the pressures (10's mTorr or less) and B-fields (10's - 100's G) of interest, electrons are magnetized whereas ions are usually not. The orientation and intersection of the B-field with the wafer are important, as intersecting field lines provide a low resistance path for electron current to the substrate. We report on a modeling study of plasma properties in MERIE reactors having rotating B-fields by investigating a series of quasi-steady states of B-field profiles. To resolve side-to-side variations, computations are performed in Cartesian coordinates. The model, nonPDPSIM, was improved with full tensor conductivities in the fluid portions of the code and v x B forces in the kinetic portions. Results are discussed while varying the orientation and strength of the B-field for electropositive (argon) and electronegative (Ar/CxFy, Ar/Cl2) gas mixtures.
Magnetic Field Rotations at Kinetic Scales in the Solar Wind
NASA Astrophysics Data System (ADS)
Chen, Christopher; Matteini, Lorenzo; Burgess, David; Horbury, Timothy
2015-04-01
The distribution of spatial angle changes in the solar wind magnetic field is usually attributed to a mixture of turbulence and other structures. Recent results have suggested that in the MHD inertial range this distribution may be scale invariant, generated by the turbulence, and consist mainly of field rotations. Here, we examine the distribution of magnetic field rotations in the smaller scale kinetic range (from ion to electron scales), where the turbulence is thought to be dissipated, using combined fluxgate/search-coil magnetometer data from Cluster. The degree of self-similarity is measured and the spatial distribution of the fluctuations at different scales is compared. At ion scales, the energy in angle rotations larger than α drops exponentially with α with e-folding ~10°, and at electron scales with e-folding
Magnetic field induced by elliptical instability in a rotating spheroid
NASA Astrophysics Data System (ADS)
Lacaze, L.; Herreman, W.; Le Bars, M.; Le Dizès, S.; Le Gal, P.
2006-10-01
The tidal or the elliptical instability of the rotating fluid flows is generated by the resonant interaction of the inertial waves. In a slightly elliptically deformed rotating sphere, the most unstable linear mode is called the spin-over mode, and is a solid body rotation versus an axis aligned with the maximum strain direction. In the non-viscous case, this instability corresponds to the median moment of the inertial instability of the solid rotating bodies. This analogy is furthermore illustrated by an elliptical top experiment, which shows the expected inviscid heteroclinic behaviour. In geophysics, the elliptical instability may appear in the molten liquid cores of the rotating planets, which are slightly deformed by the tidal gravitational effects of the close bodies. It may then participate in the general outer core dynamics and possibly the geodynamo process. In this context, Kerswell and Malkus (Kerswell, R.R. and Malkus, W.V.R., Tidal instability as the source for Io's magnetic signature. Geophys. Res. Lett., 1998, 25, 603 606) showed that the puzzling magnetic field of the Jovian satellite Io may indeed be induced by the elliptically unstable motions of its liquid core that deflect the Jupiter's magnetic field. Our magnetohydrodynamics (MHD) experiment is a toy-experiment of this geophysical situation and demonstrates for the first time the possibility of an induction of a magnetic field by the flow motions due to the elliptical instability. A full analytical calculation of the magnetic dipole induced by the spin-over is presented. Finally, exponential growths of this induced magnetic field in a slightly deformed rotating sphere filled with galinstan liquid metal are measured for different rotating rates. Their growth rates compare well with the theoretical predictions in the limit of a vanishing Lorentz force.
Aberration influenced generation of rotating two-lobe light fields
NASA Astrophysics Data System (ADS)
Kotova, S. P.; Losevsky, N. N.; Prokopova, D. V.; Samagin, S. A.; Volostnikov, V. G.; Vorontsov, E. N.
2016-08-01
The influence of aberrations on light fields with a rotating intensity distribution is considered. Light fields were generated with the phase masks developed using the theory of spiral beam optics. The effects of basic aberrations, such as spherical aberration, astigmatism and coma are studied. The experimental implementation of the fields was achieved with the assistance of a liquid crystal spatial light modulator HOLOEYE HEO-1080P, operating in reflection mode. The results of mathematical modelling and experiments have been qualitatively compared.
JET ROTATION DRIVEN BY MAGNETOHYDRODYNAMIC SHOCKS IN HELICAL MAGNETIC FIELDS
Fendt, Christian
2011-08-10
In this paper, we present a detailed numerical investigation of the hypothesis that a rotation of astrophysical jets can be caused by magnetohydrodynamic (MHD) shocks in a helical magnetic field. Shock compression of the helical magnetic field results in a toroidal Lorentz force component that will accelerate the jet material in the toroidal direction. This process transforms magnetic angular momentum (magnetic stress) carried along the jet into kinetic angular momentum (rotation). The mechanism proposed here only works in a helical magnetic field configuration. We demonstrate the feasibility of this mechanism by axisymmetric MHD simulations in 1.5 and 2.5 dimensions using the PLUTO code. In our setup, the jet is injected into the ambient gas with zero kinetic angular momentum (no rotation). We apply different dynamical parameters for jet propagation such as the jet internal Alfven Mach number and fast magnetosonic Mach number, the density contrast of the jet to the ambient medium, and the external sonic Mach number of the jet. The mechanism we suggest should work for a variety of jet applications, e.g., protostellar or extragalactic jets, and internal jet shocks (jet knots) or external shocks between the jet and the ambient gas (entrainment). For typical parameter values for protostellar jets, the numerically derived rotation feature looks consistent with the observations, i.e., rotational velocities of 0.1%-1% of the jet bulk velocity.
NASA Astrophysics Data System (ADS)
Bekeraité, S.; Walcher, C. J.; Falcón-Barroso, J.; Garcia Lorenzo, B.; Lyubenova, M.; Sánchez, S. F.; Spekkens, K.; van de Ven, G.; Wisotzki, L.; Ziegler, B.; Aguerri, J. A. L.; Barrera-Ballesteros, J.; Bland-Hawthorn, J.; Catalán-Torrecilla, C.; García-Benito, R.
2016-10-01
We measured the distribution in absolute magnitude - circular velocity space for a well-defined sample of 199 rotating galaxies of the Calar Alto Legacy Integral Field Area Survey (CALIFA) using their stellar kinematics. Our aim in this analysis is to avoid subjective selection criteria and to take volume and large-scale structure factors into account. Using stellar velocity fields instead of gas emission line kinematics allows including rapidly rotating early-type galaxies. Our initial sample contains 277 galaxies with available stellar velocity fields and growth curve r-band photometry. After rejecting 51 velocity fields that could not be modelled because of the low number of bins, foreground contamination, or significant interaction, we performed Markov chain Monte Carlo modelling of the velocity fields, from which we obtained the rotation curve and kinematic parameters and their realistic uncertainties. We performed an extinction correction and calculated the circular velocity vcirc accounting for the pressure support of a given galaxy. The resulting galaxy distribution on the Mr-vcirc plane was then modelled as a mixture of two distinct populations, allowing robust and reproducible rejection of outliers, a significant fraction of which are slow rotators. The selection effects are understood well enough that we were able to correct for the incompleteness of the sample. The 199 galaxies were weighted by volume and large-scale structure factors, which enabled us to fit a volume-corrected Tully-Fisher relation (TFR). More importantly, we also provide the volume-corrected distribution of galaxies in the Mr-vcirc plane, which can be compared with cosmological simulations. The joint distribution of the luminosity and circular velocity space densities, representative over the range of -20 > Mr > -22 mag, can place more stringent constraints on the galaxy formation and evolution scenarios than linear TFR fit parameters or the luminosity function alone. Galaxies main
Rotational Sweepback of Magnetic Field Lines in Geometrical Models of Pulsar Radio Emission
NASA Technical Reports Server (NTRS)
Dyks, J.; Harding, Alice K.
2004-01-01
We study the rotational distortions of the vacuum dipole magnetic field in the context of geometrical models of the radio emission from pulsars. We find that at low altitudes the rotation deflects the local direction of the magnetic field by at most an angle of the order of r(sup 2 sub n), where r(sub n) = r/R(sub lc), r is the radial distance and R(sub lc) is the light cylinder radius. To the lowest (i.e. second) order in r(sub n) this distortion is symmetrical with respect to the plane containing the dipole axis and the rotation axis ((Omega, mu) plane). The lowest order distortion which is asymmetrical with respect to the (Omega, mu) plane is third order in r(sub n). These results confirm the common assumption that the rotational sweepback has negligible effect on the position angle (PA) curve. We show, however, that the influence of the sweep back on the outer boundary of the open field line region (open volume) is a much larger effect, of the order of r(sup 1/2 sub n). The open volume is shifted backwards with respect to the rotation direction by an angle delta(sub o nu) approx. 0.2 sin alpha r(sup 1/2 sub n) where alpha is the dipole inclination with respect to the rotation axis. The associated phase shift of the pulse profile Delta phi(sub o nu) approx. 0.2 r(sup 1/2 sub n) can easily exceed the shift due to combined effects of aberration and propagation time delays (approx. 2r(sub n)). This strongly affects the misalignment of the center of the PA curve and the center of the pulse profile, thereby modifying the delay radius relation. Contrary to intuition, the effect of sweepback dominates over other effects when emission occurs at low altitudes. For r(sub n) < or approx. 3 x 10(exp -3) the shift becomes negative, i.e. the center of the position angle curve precedes the profile center. With the sweepback effect included, the modified delay-radius relation predicts larger emission radii and is in much better agreement with the other methods of determining r
ON THE ROTATION OF THE MAGNETIC FIELD ACROSS THE HELIOPAUSE
Opher, M.; Drake, J. F.
2013-12-01
Based on the difference between the orientation of the interstellar and the solar magnetic fields, there was an expectation by the community that the magnetic field direction will rotate dramatically across the heliopause (HP). Recently, the Voyager team concluded that Voyager 1 (V1) crossed into interstellar space last year. The question is then why there was no significant rotation in the direction of the magnetic field across the HP. Here we present simulations that reveal that strong rotations in the direction of the magnetic field at the HP at the location of V1 (and Voyager 2) are not expected. The solar magnetic field strongly affects the drapping of the interstellar magnetic field (B {sub ISM}) around the HP. B {sub ISM} twists as it approaches the HP and acquires a strong T component (East-West). The strong increase in the T component occurs where the interstellar flow stagnates in front of the HP. At this same location the N component B{sub N} is significantly reduced. Above and below, the neighboring B {sub ISM} lines also twist into the T direction. This behavior occurs for a wide range of orientations of B {sub ISM}. The angle δ = asin (B{sub N} /B) is small (around 10°-20°), as seen in the observations. Only after some significant distance outside the HP is the direction of the interstellar field distinguishably different from that of the Parker spiral.
Rotation of the optical polarization plane for the blazar 4C +38.41
NASA Astrophysics Data System (ADS)
Panopoulou, G. V.; Maragkakis, G. M.; Xexakis, K.
2016-08-01
We report on the ongoing rotation of the optical polarization angle (R-band) seen in the monitored blazar 4C +38.41 (RA=16:35:15.5, DEC=38:08:05, J2000) as recorded within the framework of the RoboPol program.
Simultaneous Generalizations of the Theorems of Ceva and Menelaus for Field Planes
ERIC Educational Resources Information Center
Houston, Kelly B.; Powers, Robert C.
2009-01-01
In 1992, Klamkin and Liu proved a very general result in the Extended Euclidean Plane that contains the theorems of Ceva and Menelaus as special cases. In this article, we extend the Klamkin and Liu result to projective planes "PG"(2, F) where F is a field. (Contains 2 figures.)
Mao, S. A.; McClure-Griffiths, N. M.; Gaensler, B. M.; Brown, J. C.; Van Eck, C. L.; Stil, J. M.; Taylor, A. R.; Haverkorn, M.; Kronberg, P. P.; Shukurov, A.
2012-08-10
We present a study of the Milky Way disk and halo magnetic field, determined from observations of Faraday rotation measure (RM) toward 641 polarized extragalactic radio sources in the Galactic longitude range 100 Degree-Sign -117 Degree-Sign , within 30 Degree-Sign of the Galactic plane. For |b| < 15 Degree-Sign , we observe a symmetric RM distribution about the Galactic plane. This is consistent with a disk field in the Perseus arm of even parity across the Galactic mid-plane. In the range 15 Degree-Sign < |b| < 30 Degree-Sign , we find median RMs of -15 {+-} 4 rad m{sup -2} and -62 {+-} 5 rad m{sup -2} in the northern and southern Galactic hemispheres, respectively. If the RM distribution is a signature of the large-scale field parallel to the Galactic plane, then this suggests that the halo magnetic field toward the outer Galaxy does not reverse direction across the mid-plane. The variation of RM as a function of Galactic latitude in this longitude range is such that RMs become more negative at larger |b|. This is consistent with an azimuthal magnetic field of strength 2 {mu}G (7 {mu}G) at a height 0.8-2 kpc above (below) the Galactic plane between the local and the Perseus spiral arm. We propose that the Milky Way could possess spiral-like halo magnetic fields similar to those observed in M51.
Rotational stability of a long field-reversed configuration
NASA Astrophysics Data System (ADS)
Barnes, D. C.; Steinhauer, L. C.
2014-02-01
Rotationally driven modes of long systems with dominantly axial magnetic field are considered. We apply the incompressible model and order axial wavenumber small. A recently developed gyro-viscous model is incorporated. A one-dimensional equilibrium is assumed, but radial profiles are arbitrary. The dominant toroidal (azimuthal) mode numbers ℓ =1 and ℓ =2 modes are examined for a variety of non-reversed (B) and reversed profiles. Previous results for both systems with rigid rotor equilibria are reproduced. New results are obtained by incorporation of finite axial wavenumber and by relaxing the assumption of rigid electron and ion rotation. It is shown that the frequently troublesome ℓ =2 field reversed configuration (FRC) mode is not strongly affected by ion kinetic effects (in contrast to non-reversed cases) and is likely stabilized experimentally only by finite length effects. It is also shown that the ℓ =1 wobble mode has a complicated behavior and is affected by a variety of configuration and profile effects. The rotationally driven ℓ =1 wobble is completely stabilized by strong rotational shear, which is anticipated to be active in high performance FRC experiments. Thus, observed wobble modes in these systems are likely not driven by rotation alone.
NASA Astrophysics Data System (ADS)
Pinkerton I., S. F.; Rhodes, E. J., Jr.; Bogart, R. S.; Orr, M.; Martin, G.; Spinella, A.
2013-12-01
Time series of full-disk Dopplergrams were acquired at the 60-Foot Solar tower of the Mount Wilson Observatory every year between 1987 and 2009. The 60-Foot Tower was designed by George Ellery Hale to provide an image plane that did not rotate throughout each observing day. However, preliminary analyses of a portion of this archive, carried out in 2007, suggested that the focal plane of the Tower might actually be rotating slowly. If confirmed, such an instrumental rotation would suggest that the alignment of the optics has changed slightly over the years since 1907. This possible rotation of the image plane was uncovered through the computation of subsurface flow maps using the ring-diagram method of local helioseismology. Some of the initial MWO flow maps appeared to show evidence for a so-called “washing machine” effect similar to the pattern that was seen in the initial GONG flow maps. We have been working to confirm the early estimates of the focal plane rotation. The purpose of this paper is to report on the status of this endeavor as well as explore the ramifications of a rotating image plane on our anticipated meridional and zonal flow results.
NASA Astrophysics Data System (ADS)
Afanasyev, Y. D.; Rhines, P. B.; Lindahl, E. G.
2009-12-01
An optical method of altimetric imaging velocimetry (AIV) for measuring the slope of the surface elevation in the rotating fluid with free surface is described. This method allows one to obtain the major dynamical fields in the fluid layer including velocity, vorticity and surface elevation. When used in combination with the Optical Thickness method the AIV can be used to render the full dynamical characteristics of a two-layer flow. Both methods allow one to achieve very high spatial resolution by rendering a velocity vector in each pixel of the image. An example of the two-layer source-driven flow on a γ-plane (also called polar β-plane) is offered to demonstrate the application of these methods. This “β-plume’ is a gyre-like response to a point source of fluid, including intense jets, eddies and Rossby waves.
NASA Astrophysics Data System (ADS)
Mao, Yijun; Xu, Chen; Qi, Datong
2015-02-01
A vector aeroacoustics method is developed to analyze the acoustic energy flow path from the rotating source. In this method, the instantaneous and time-averaged active acoustic intensity vectors are evaluated from the time-domain and frequency-domain acoustic pressure and acoustic velocity formulations, respectively. With the above method, the acoustic intensity vectors and the acoustic energy streamlines are visualized to investigate the propagation feature of the noise radiated from the monopole and dipole point sources and the rotor in subsonic rotation. The result reveals that a portion of the acoustic energy spirals many circles before moving towards the far field, and another portion of the acoustic energy firstly flows inward along the radial direction and then propagates along the axial direction. Further, an acoustic black hole exists in the plane of source rotation, from which the acoustic energy cannot escape once the acoustic energy flows into it. Moreover, by visualizing the acoustic intensity field around the rotating sources, the acoustic-absorption performance of the acoustic liner built in the casing and centerbody is discussed.
Inequivalence of quantum field theories on noncommutative spacetimes: Moyal versus Wick-Voros planes
Balachandran, A. P.; Ibort, A.; Marmo, G.; Martone, M.
2010-04-15
In this paper, we further develop the analysis started in an earlier paper on the inequivalence of certain quantum field theories on noncommutative spacetimes constructed using twisted fields. The issue is of physical importance. Thus it is well known that the commutation relations among spacetime coordinates, which define a noncommutative spacetime, do not constrain the deformation induced on the algebra of functions uniquely. Such deformations are all mathematically equivalent in a very precise sense. Here we show how this freedom at the level of deformations of the algebra of functions can fail on the quantum field theory side. In particular, quantum field theory on the Wick-Voros and Moyal planes are shown to be inequivalent in a few different ways. Thus quantum field theory calculations on these planes will lead to different physics even though the classical theories are equivalent. This result is reminiscent of chiral anomaly in gauge theories and has obvious physical consequences. The construction of quantum field theories on the Wick-Voros plane has new features not encountered for quantum field theories on the Moyal plane. In fact it seems impossible to construct a quantum field theory on the Wick-Voros plane which satisfies all the properties needed of field theories on noncommutative spaces. The Moyal twist seems to have unique features which make it a preferred choice for the construction of a quantum field theory on a noncommutative spacetime.
NASA Astrophysics Data System (ADS)
DeBock, M. F. M.; Classen, I. G. J.; Busch, C.; Jaspers, R. J. E.; Koslowski, H. R.; Unterberg, B.; TEXTOR Team
2008-01-01
For fusion reactors, based on the principle of magnetic confinement, it is important to avoid so-called magnetic islands or tearing modes. They reduce confinement and can be the cause of major disruptions. One class of magnetic islands is that of the perturbation field driven modes. This perturbation field can, for example, be the intrinsic error field. Theoretical work predicts a strong relationship between plasma rotation and the excitation of perturbation field modes. Experimentally, the theory on mode excitation and plasma rotation has been confirmed on several tokamaks. In those experiments, however, the control over the plasma rotation velocity and direction, and over the externally applied perturbation field was limited. In this paper experiments are presented that were carried out at the TEXTOR tokamak. Two tangential neutral beam injectors and a set of helical perturbation coils, called the dynamic ergodic divertor (DED), provide control over both the plasma rotation and the external perturbation field in TEXTOR. This made it possible to set up a series of experiments to test the theory on mode excitation and plasma rotation in detail. The perturbation field induced by the DED not only excites magnetic islands, it also sets up a layer near the plasma boundary where the magnetic field is stochastic. It will be shown that this stochastic field alters both the rotational response of the plasma on the perturbation field and the threshold for mode excitation. It therefore has to be included in an extended theory on mode excitation.
Abe, K.; Hasegawa, T.
2010-03-15
Quantum-mechanical analysis of ion motion in a rotating-radio-frequency (rrf) trap or in a Penning trap with a quadrupole rotating field is carried out. Rrf traps were introduced by Hasegawa and Bollinger [Phys. Rev. A 72, 043404 (2005)]. The classical motion of a single ion in this trap is described by only trigonometric functions, whereas in the conventional linear radio-frequency (rf) traps it is by the Mathieu functions. Because of the simple classical motion in the rrf trap, it is expected that the quantum-mechanical analysis of the rrf traps is also simple compared to that of the linear rf traps. The analysis of Penning traps with a quadrupole rotating field is also possible in a way similar to the rrf traps. As a result, the Hamiltonian in these traps is the same as the two-dimensional harmonic oscillator, and energy levels and wave functions are derived as exact results. In these traps, it is found that one of the vibrational modes in the rotating frame can have negative energy levels, which means that the zero-quantum-number state (''ground'' state) is the highest energy state.
NMR system and method having a permanent magnet providing a rotating magnetic field
Schlueter, Ross D [Berkeley, CA; Budinger, Thomas F [Berkeley, CA
2009-05-19
Disclosed herein are systems and methods for generating a rotating magnetic field. The rotating magnetic field can be used to obtain rotating-field NMR spectra, such as magic angle spinning spectra, without having to physically rotate the sample. This result allows magic angle spinning NMR to be conducted on biological samples such as live animals, including humans.
Generation of Whistler Wave by a Rotating Magnetic Field Source
NASA Astrophysics Data System (ADS)
Karavaev, A.; Papadopoulos, K.; Shao, X.; Sharma, A. S.; Gigliotti, A.; Gekelman, W.; Pribyl, P.; Vincena, S.
2008-12-01
The interaction of Rotating Magnetic Fields (RMF) with plasmas is a fundamental plasma physics problem with implications to fusion related Field-Reversed Configurations (FRC), space propulsion, astronaut protection from cosmic rays in long interstellar travel, control of the energetic population in the radiation belts and near zone processes in pulsar magnetospheres. In this paper we report recent experiments on the generation of whistler waves with a new type RMF-based antenna. The experiments were conducted on UCLA's Large Plasma Device (LAPD). The Rotating Magnetic Field (RMF) is created using poly-phased loop antennas. A number of parameter combinations, e.g. plasma density, background magnetic field, and driving current, were used. It was found that RMF created by a two phase-delayed loop antenna drives significant currents along the ambient magnetic field. The measured amplitude of induced wave field was proportional to the square-root of the plasma density. The spatial decay rate for the wave perturbation across the background magnetic field was found to scale with the plasma skin depth. A small amplitude second harmonic was also measured. The paper will also present analytic and simulation results that account for the experimental results; in particular, the scaling of the induced magnetic field as a function of the RMF and plasma parameters and the spatial decay rate of magnetic field. Applications of RMF as an efficient radiation source of plasma waves in space plasmas will be discussed. This work was sponsored by ONR MURI Grant 5-28828
NASA Astrophysics Data System (ADS)
Singh, Madan; Kumar, Arvind; Singh, Kehar
2008-03-01
In the present paper, we describe multiplexing in optical encryption of two-dimensional images, by using apertures and rotation of one of the constituent phase diffusers of a sandwich phase diffuser in the Fourier plane. The sandwich phase diffuser is made with two random constituent phase-diffusing surfaces sandwiched together. The apertures of different sizes and shapes are made with the help of 'paint brush' software. Simulation results are presented showing the effects of size, shape, and orientation of the apertures on the decrypted images obtained via multiplexing techniques. In addition to the results of using aperture systems in encryption and decryption, the results of rotation of one of the constituent phase diffusers in decryption are analyzed and used in multiplexing. Due to the use of aperture systems and the rotation of the constituent phase diffuser, the multiplexing capability of the system in encryption is enhanced along with the enhanced security due to using a sandwich diffuser. To evaluate the reliability of the technique, mean square error between the decrypted and the original image has been calculated.
Dynamics of Magnetotactic Bacteria in a Rotating Magnetic Field
Ērglis, Kaspars; Wen, Qi; Ose, Velta; Zeltins, Andris; Sharipo, Anatolijs; Janmey, Paul A.; Cēbers, Andrejs
2007-01-01
The dynamics of the motile magnetotactic bacterium Magnetospirillum gryphiswaldense in a rotating magnetic field is investigated experimentally and analyzed by a theoretical model. These elongated bacteria are propelled by single flagella at each bacterial end and contain a magnetic filament formed by a linear assembly of ∼40 ferromagnetic nanoparticles. The movements of the bacteria in suspension are analyzed by consideration of the orientation of their magnetic dipoles in the field, the hydrodynamic resistance of the bacteria, and the propulsive force of the flagella. Several novel features found in experiments include a velocity reversal during motion in the rotating field and an interesting diffusive wandering of the trajectory curvature centers. A new method to measure the magnetic moment of an individual bacterium is proposed based on the theory developed. PMID:17526564
Separation of chiral particles in a rotating electric field
NASA Astrophysics Data System (ADS)
Doi, M.; Makino, M.
2016-09-01
When a particle having a permanent dipole is placed in a rotating electric field in a fluid, it will migrate along the direction of the angular vector of the field. The average velocity of the particle is calculated based on a Brownian motion framework that accounts for the translation-rotation coupling. An explicit expression is given for the average velocity of the particle as a function of the hydrodynamic mobility tensors and the frequency of the field. The expression indicates that the chiral particle and its mirror-image particle move in opposite direction (which accounts for the right/left molecular separation in racemic solutions), and that the migration velocity has a peak at a certain frequency determined by the geometry of the particle. Calculations are made for a twisted ribbon particle and the relation between the migration velocity and the structure of the twisted ribbon particle is discussed.
Biomechanical Comparison of 3 Ankle Braces With and Without Free Rotation in the Sagittal Plane
Alfuth, Martin; Klein, Dieter; Koch, Raphael; Rosenbaum, Dieter
2014-01-01
Context: Various designs of braces including hinged and nonhinged models are used to provide external support of the ankle. Hinged ankle braces supposedly allow almost free dorsiflexion and plantar flexion of the foot in the sagittal plane. It is unclear, however, whether this additional degree of freedom affects the stabilizing effect of the brace in the other planes of motion. Objective: To investigate the dynamic and passive stabilizing effects of 3 ankle braces, 2 hinged models that provide free plantar flexion–dorsiflexion in the sagittal plane and 1 ankle brace without a hinge. Design: Crossover study. Setting: University Movement Analysis Laboratory. Patients or Other Participants: Seventeen healthy volunteers (5 women, 12 men; age = 25.4 ± 4.8 years; height = 180.3 ± 6.5 cm; body mass = 75.5 ± 10.4 kg). Intervention(s): We dynamically induced foot inversion on a tilting platform and passively induced foot movements in 6 directions via a custom-built apparatus in 3 brace conditions and a control condition (no brace). Main Outcome Measure(s): Maximum inversion was determined dynamically using an in-shoe electrogoniometer. Passively induced maximal joint angles were measured using a torque and angle sensor. We analyzed differences among the 4 ankle-brace conditions (3 braces, 1 control) for each of the dependent variables with Friedman and post hoc tests (P < .05). Results: Each ankle brace restricted dynamic foot-inversion movements on the tilting platform as compared with the control condition, whereas only the 2 hinged ankle braces differed from each other, with greater movement restriction caused by the Ankle X model. Passive foot inversion was reduced with all ankle braces. Passive plantar flexion was greater in the hinged models as compared with the nonhinged brace. Conclusions: All ankle braces showed stabilizing effects against dynamic and passive foot inversion. Differences between the hinged braces and the nonhinged brace did not appear to be
Cheng, Yu; Muroski, Megan E; Petit, Dorothée C M C; Mansell, Rhodri; Vemulkar, Tarun; Morshed, Ramin A; Han, Yu; Balyasnikova, Irina V; Horbinski, Craig M; Huang, Xinlei; Zhang, Lingjiao; Cowburn, Russell P; Lesniak, Maciej S
2016-02-10
Magnetic particles that can be precisely controlled under a magnetic field and transduce energy from the applied field open the way for innovative cancer treatment. Although these particles represent an area of active development for drug delivery and magnetic hyperthermia, the in vivo anti-tumor effect under a low-frequency magnetic field using magnetic particles has not yet been demonstrated. To-date, induced cancer cell death via the oscillation of nanoparticles under a low-frequency magnetic field has only been observed in vitro. In this report, we demonstrate the successful use of spin-vortex, disk-shaped permalloy magnetic particles in a low-frequency, rotating magnetic field for the in vitro and in vivo destruction of glioma cells. The internalized nanomagnets align themselves to the plane of the rotating magnetic field, creating a strong mechanical force which damages the cancer cell structure inducing programmed cell death. In vivo, the magnetic field treatment successfully reduces brain tumor size and increases the survival rate of mice bearing intracranial glioma xenografts, without adverse side effects. This study demonstrates a novel approach of controlling magnetic particles for treating malignant glioma that should be applicable to treat a wide range of cancers. PMID:26708022
Cheng, Yu; Muroski, Megan E; Petit, Dorothée C M C; Mansell, Rhodri; Vemulkar, Tarun; Morshed, Ramin A; Han, Yu; Balyasnikova, Irina V; Horbinski, Craig M; Huang, Xinlei; Zhang, Lingjiao; Cowburn, Russell P; Lesniak, Maciej S
2016-02-10
Magnetic particles that can be precisely controlled under a magnetic field and transduce energy from the applied field open the way for innovative cancer treatment. Although these particles represent an area of active development for drug delivery and magnetic hyperthermia, the in vivo anti-tumor effect under a low-frequency magnetic field using magnetic particles has not yet been demonstrated. To-date, induced cancer cell death via the oscillation of nanoparticles under a low-frequency magnetic field has only been observed in vitro. In this report, we demonstrate the successful use of spin-vortex, disk-shaped permalloy magnetic particles in a low-frequency, rotating magnetic field for the in vitro and in vivo destruction of glioma cells. The internalized nanomagnets align themselves to the plane of the rotating magnetic field, creating a strong mechanical force which damages the cancer cell structure inducing programmed cell death. In vivo, the magnetic field treatment successfully reduces brain tumor size and increases the survival rate of mice bearing intracranial glioma xenografts, without adverse side effects. This study demonstrates a novel approach of controlling magnetic particles for treating malignant glioma that should be applicable to treat a wide range of cancers.
Vision and Wide-Field Imagers with Curved Focal Planes
NASA Astrophysics Data System (ADS)
Arianpour, Ashkan
This dissertation provides details regarding the implementation of curved-focal surface fiber coupled imaging for medical and wide-field applications. An optomechanical fluid-filled eye model with visual acuity better than 20/20 vision was design and characterized. A wearable telescopic contact lens was worn on the optomechanical eye model and the performance characterized. Measurements of the contact lens surfaces were modeled to quantify the impact of contact lens fabrication on end-result resolution. Separately, the limitations of the field of view in fiber coupled monocentric imaging are analyzed. This dissertation describes a novel technique to address this based on conformal micro-optics. The design, simulation, and fabrication of an embossed surface relief micro-prism that increases the field of view are demonstrated.
Analytical model for electromagnetic cascades in rotating electric field
Nerush, E. N.; Bashmakov, V. F.; Kostyukov, I. Yu.
2011-08-15
Electromagnetic cascades attract a lot of attention as an important quantum electrodynamics effect that will reveal itself in various electromagnetic field configurations at ultrahigh intensities. We study cascade dynamics in rotating electric field analytically and numerically. The kinetic equations for the electron-positron plasma and gamma-quanta are formulated. The scaling laws are derived and analyzed. For the cascades arising far above the threshold the dependence of the cascade parameters on the field frequency is derived. The spectra of high-energy cascade particles are calculated. The analytical results are verified by numerical simulations.
Specific heat of twisted bilayer graphene: Engineering phonons by atomic plane rotations
Nika, Denis L.; Cocemasov, Alexandr I.; Balandin, Alexander A.
2014-07-21
We have studied the phonon specific heat in single-layer, bilayer, and twisted bilayer graphene. The calculations were performed using the Born-von Karman model of lattice dynamics for intralayer atomic interactions and spherically symmetric interatomic potential for interlayer interactions. We found that at temperature T < 15 K, specific heat varies with temperature as T{sup n}, where n = 1 for graphene, n = 1.6 for bilayer graphene, and n = 1.3 for the twisted bilayer graphene. The phonon specific heat reveals an intriguing dependence on the twist angle in bilayer graphene, which is particularly pronounced at low temperature. The results suggest a possibility of phonon engineering of thermal properties of layered materials by twisting the atomic planes.
Microscopic observation of magnetic bacteria in the magnetic field of a rotating permanent magnet
NASA Astrophysics Data System (ADS)
Smid, Pieter; Shcherbakov, Valeriy; Petersen, Nikolai
2015-09-01
Magnetotactic bacteria are ubiquitous and can be found in both freshwater and marine environments. Due to intracellular chains of magnetic single domain particles, they behave like swimming compass needles. In external magnetic fields like the Earth's magnetic field, a torque is acting on the chain. This will cause the bacterium to be rotated and aligned with the external field. The swimming direction of magnetotactic bacteria can be controlled with external magnetic fields, which makes it convenient to study them under a light microscope. Usually, a special set of coils arranged around a light microscope is used to control the swimming magnetotactic bacteria. Here, we present a simple mechanical system with a permanent magnet, which produces a rotating magnetic field of nearly constant amplitude in the focal plane of a light microscope. The device is placed beside the light microscope and easily adaptable to almost any microscope and thus convenient for field experiments. To describe the trajectories qualitatively, a theoretical model of the trajectories is presented. This device can be used to control the swimming direction of magnetotactic bacteria and also for studying their magnetic and hydrodynamic properties.
Microscopic observation of magnetic bacteria in the magnetic field of a rotating permanent magnet.
Smid, Pieter; Shcherbakov, Valeriy; Petersen, Nikolai
2015-09-01
Magnetotactic bacteria are ubiquitous and can be found in both freshwater and marine environments. Due to intracellular chains of magnetic single domain particles, they behave like swimming compass needles. In external magnetic fields like the Earth's magnetic field, a torque is acting on the chain. This will cause the bacterium to be rotated and aligned with the external field. The swimming direction of magnetotactic bacteria can be controlled with external magnetic fields, which makes it convenient to study them under a light microscope. Usually, a special set of coils arranged around a light microscope is used to control the swimming magnetotactic bacteria. Here, we present a simple mechanical system with a permanent magnet, which produces a rotating magnetic field of nearly constant amplitude in the focal plane of a light microscope. The device is placed beside the light microscope and easily adaptable to almost any microscope and thus convenient for field experiments. To describe the trajectories qualitatively, a theoretical model of the trajectories is presented. This device can be used to control the swimming direction of magnetotactic bacteria and also for studying their magnetic and hydrodynamic properties. PMID:26429479
Propagation of rotational field correlation through atmospheric turbulence.
Nairat, Mazen; Voelz, David
2014-04-01
A general formulation is presented that describes the propagation of the rotational field correlation of an optical beam through atmospheric turbulence. The associated influence on the orbital angular momentum (OAM) of a single photon is described analytically. The analysis predicts the probability of change in the OAM state due to the process of propagating through turbulence. The probability of a change in an OAM state depends on the Fresnel number and on the ratio of the beam diameter to the Fried parameter.
Approximate quantitative relationships for rotating magnetic field current drive
NASA Astrophysics Data System (ADS)
Hugrass, W. N.; Ohnishi, M.
1999-08-01
A simplified model for the rotating magnetic field (RMF) current drive in an infinitely long cylindrical plasma is used to obtain approximate relationships between the fluid flow velocities, collisionality and degree of nonlinearity. These approximate relationships provide simple quantitative estimates for the basic conditions required for the RMF current drive technique to be applied successfully. In particular, the condition required for the motion of the ion fluid not to be flux-preserving, is evaluated quantitatively for the first time.
Computation of Bound Orbits in the Plane of a Galaxy with a Flat Rotation Curve
ERIC Educational Resources Information Center
Bacon, M. E.; Sharrar, Amber
2010-01-01
A standard topic in an advanced undergraduate classical mechanics course is the determination of the orbits in a gravitational field. In the present paper we report on the calculation of bound orbits in the gravitational field of a spiral galaxy. Calculations such as these could serve to focus attention on an area of cutting edge astrophysics and…
Flux buildup in FRCs using rotating magnetic fields
NASA Astrophysics Data System (ADS)
Hoffman, Alan L.
1999-11-01
FRCs have a purely diamagnetic current with a line density magnitude I' = Δ B/μo just sufficient to reverse the external confinement field. This results in an average electron rotational velocity ωr ≈ j_e/ner. A rotating magnetic field (RMF) causes the electrons to oscillate along the axial field lines and creates an azimuthal EMF equal to
OBLIQUELY ROTATING PULSARS: SCREENING OF THE INDUCTIVE ELECTRIC FIELD
Melrose, D. B.; Yuen Rai
2012-02-01
Pulsar electrodynamics has been built up by taking ingredients from two models, the vacuum-dipole model, which ignores the magnetosphere but includes the inductive electric field due to the obliquely rotating magnetic dipole, and the corotating-magnetosphere model, which neglects the vacuum inductive electric field and assumes a corotating magnetosphere. We argue that the inductive field can be neglected only if it is screened by a current, J{sub sc}, which we calculate for a rigidly rotating magnetosphere. Screening of the parallel component of the inductive field can be effective, but the perpendicular component cannot be screened in a pulsar magnetosphere. The incompletely screened inductive electric field has not been included in any model for a pulsar magnetosphere, and taking it into account has important implications. One effect is that it implies that the magnetosphere cannot be corotating, and we suggest that drift relative to corotation offers a natural explanation for the drifting of subpulses. A second effect is that this screening of the parallel inductive electric field must break down in the outer magnetosphere, and this offers a natural explanation for the acceleration of the electrons that produce pulsed gamma-ray emission.
Investigations on the Incompletely Developed Plane Diagonal-Tension Field
NASA Technical Reports Server (NTRS)
Kuhn, Paul
1940-01-01
This report presents the results of an investigation on the incompletely developed diagonal-tension field. Actual diagonal-tension beams work in an intermediate stage between pure shear and pure diagonal tension; the theory developed by wagner for diagonal tension is not directly applicable. The first part of the paper reviews the most essential items of the theory of pure diagonal tension as well as previous attempts to formulate a theory of incomplete diagonal tension. The second part of the paper describes strain measurement made by the N. A. C. A. to obtain the necessary coefficients for the proposed theory. The third part of the paper discusses the stress analysis of diagonal-tension beams by means of the proposed theory.
Intensity modulated arc therapy (IMAT) with centrally blocked rotational fields.
Cotrutz, C; Kappas, C; Webb, S
2000-08-01
A new technique for intensity-modulated beam (IMB) delivery that combines the features of intensity modulated arc therapy (IMAT) with the use of 'classical blocks' is proposed. The role of the blocks is to realize the high-gradient modulation of the intensity profile corresponding to the region to be protected within the body contour, while the MLC leaves or the secondary collimator defines the rest of the field and delivers intensity-modulated multiple rotational segments. The centrally blocked radiation fields are applied sequentially, in several rotations. Each rotation of the gantry is responsible for delivering one segment of the optimal intensity profile. The new IMAT technique is applied for a treatment geometry represented by an annular target volume centrally located within a circular body contour. The annulus encompasses a circular critical structure, which is to be protected. The beam opening and corresponding weight of each segment are determined in two ways. The first method applies a linear optimization algorithm to precalculated centrally blocked radial dose profiles. These radial profiles are calculated for a set of beam openings, ranging from the largest field that covers the whole planning target volume (PTV) to the smallest, which is 1 cm larger than the width of the central block. The optimization is subjected to dose homogeneity constraints imposed on a linear combination of these profiles and finally delivers the dimensions and weights of the rotational beams to be used in combination. The second method decomposes into several subfields the fluence profile of a rotational beam known to deliver a constant dose level to PTV. This fluence profile is determined by using the analytical method proposed by Brahme for the case of the annular PTV and the concentric organ at risk (OAR). The proper segmentation of this intensity profile provides the field sizes and corresponding weights of the subfields to be used in combination. Both methods show that
Multiple-plane particle image velocimetry using a light-field camera.
Skupsch, Christoph; Brücker, Christoph
2013-01-28
Planar velocity fields in flows are determined simultaneously on parallel measurement planes by means of an in-house manufactured light-field camera. The planes are defined by illuminating light sheets with constant spacing. Particle positions are reconstructed from a single 2D recording taken by a CMOS-camera equipped with a high-quality doublet lens array. The fast refocusing algorithm is based on synthetic-aperture particle image velocimetry (SAPIV). The reconstruction quality is tested via ray-tracing of synthetically generated particle fields. The introduced single-camera SAPIV is applied to a convective flow within a measurement volume of 30 x 30 x 50 mm³.
Extracting full-field dynamic strain response of a rotating wind turbine using photogrammetry
NASA Astrophysics Data System (ADS)
Baqersad, Javad; Poozesh, Peyman; Niezrecki, Christopher; Avitabile, Peter
2015-04-01
Health monitoring of wind turbines is typically performed using conventional sensors (e.g. strain-gages and accelerometers) that are usually mounted to the nacelle or gearbox. Although many wind turbines stop operating due to blade failures, there are typically few to no sensor mounted on the blades. Placing sensors on the rotating parts of the structure is a challenge due to the wiring and data transmission constraints. Within the current work, an approach to monitor full-field dynamic response of rotating structures (e.g. wind turbine blades or helicopter rotors) is developed and experimentally verified. A wind turbine rotor was used as the test structure and was mounted to a block and horizontally placed on the ground. A pair of bearings connected to the rotor shaft allowed the turbine to freely spin along the shaft. Several optical targets were mounted to the blades and a pair of high-speed cameras was used to monitor the dynamics of the spinning turbine. Displacements of the targets during rotation were measured using three-dimensional point tracking. The point tracking technique measured both rigid body displacement and flexible deformation of the blades at target locations. While the structure is rotating, only flap displacements of optical targets (displacements out of the rotation plane) were used in strain prediction process. The measured displacements were expanded and applied to the finite element model of the turbine to extract full-field dynamic strain on the structure. The proposed approach enabled the prediction of dynamic response on the outer surface as well as within the inner points of the structure where no other sensor could be easily mounted. In order to validate the proposed approach, the predicted strain was compared to strain measured at four locations on the spinning blades using a wireless strain-gage system.
Transient and quasisteady behavior with rotating magnetic field current drive
NASA Astrophysics Data System (ADS)
Steinhauer, Loren C.
2001-07-01
The time-dependent behavior of rotating magnetic field (RMF) current drive is investigated using a two-fluid model. The important new factor is the addition of transverse ion mobility in contrast to rigid-ion models of the past. The equations simplify conveniently, allowing the behavior on each surface (r=const) to be isolated, which permits a quadrature solution for the ion fluid rotation. A rapid transient phase leads to quasisteady behavior that evolves on the relatively slow diffusion timescale. The fast transient timescale is set by the ion inertia. Unless there is an ion momentum source to balance the electron drag on the ion fluid, there is no quasisteady current drive effect. Collisions with neutrals offer such a momentum source in some experiments, notably rotamaks and the Star Thrust Experiment. Other sources of ion momentum are essential for RMF current drive in hotter, fusion-relevant plasmas. The properties of the quasisteady state are found, including the self-consistent ion fluid rotation rate and radial electric field, and RMF corrections on the pressure balance.
Kelly, Brian P; Zufelt, Nephi A; Sander, Elizabeth J; DiAngelo, Denis J
2013-04-26
The center of rotation (CoR) has become an increasingly used metric for biomechanical evaluation of spinal joints however traditional methods of determination remain prone to high degrees of uncertainty. The objective was to use a novel robotic testing protocol to investigate the effects of placement of fixed CoRs in the cervical spine. Human cadaveric C4-C5 (n=3) and C6-C7 (n=5) motion segment units (MSU) were rotated in flexion-extension to limits of 2.5 N m bending or 225 N resultant force about three points in a disc plane (A1, C1, P1) located at 25%, 50% and 75% along the length of the midline of the intervertebral disc respectively in the sagittal view, and three points (A2, C2, P2) in a sub-adjacent plane 5mm below the disc plane. Significant differences in range of rotation occurred between CoRs within the same plane but not between the same points in different planes (e.g. A1-A2). In flexion and extension axial forces at posterior points of rotation (P1, P2) were significantly different from those at anterior and central points. Shear forces were significantly different between points within the same plane except for the disc plane in extension, and between the same points in different planes in flexion and extension. The results indicate that the native cervical MSU is highly sensitive to the CoR location in terms of mechanics and range of motion, and that the CoR location likely varies between flexion and extension. The methodology developed has potential for application towards investigation of optimal CoR locations and in-vitro evaluations of the effects of implantable instrumentation.
Rotating sample magnetometer for cryogenic temperatures and high magnetic fields.
Eisterer, M; Hengstberger, F; Voutsinas, C S; Hörhager, N; Sorta, S; Hecher, J; Weber, H W
2011-06-01
We report on the design and implementation of a rotating sample magnetometer (RSM) operating in the variable temperature insert (VTI) of a cryostat equipped with a high-field magnet. The limited space and the cryogenic temperatures impose the most critical design parameters: the small bore size of the magnet requires a very compact pick-up coil system and the low temperatures demand a very careful design of the bearings. Despite these difficulties the RSM achieves excellent resolution at high magnetic field sweep rates, exceeding that of a typical vibrating sample magnetometer by about a factor of ten. In addition the gas-flow cryostat and the high-field superconducting magnet provide a temperature and magnetic field range unprecedented for this type of magnetometer.
Taylor, Jane; Boutong, Sara; Brett, Sarah; Louis, Amal; Heppenstall, James; Morton, Allison C.; Gunn, Julian P.
2015-01-01
Objectives To investigate the value of rotational coronary angiography (RoCA) in the context of percutaneous coronary intervention (PCI) planning. Background As a diagnostic tool, RoCA is associated with decreased patient irradiation and contrast use compared with conventional coronary angiography (CA) and provides superior appreciation of three‐dimensional anatomy. However, its value in PCI remains unknown. Methods We studied stable coronary artery disease assessment and PCI planning by interventional cardiologists. Patients underwent either RoCA or conventional CA pre‐PCI for planning. These were compared with the referral CA (all conventional) in terms of quantitative lesion assessment and operator confidence. An independent panel reanalyzed all parameters. Results Six operators performed 127 procedures (60 RoCA, 60 conventional CA, and 7 crossed‐over) and assessed 212 lesions. RoCA was associated with a reduction in the number of lesions judged to involve a bifurcation (23 vs. 30 lesions, P < 0.05) and a reduction in the assessment of vessel caliber (2.8 vs. 3.0 mm, P < 0.05). RoCA improved confidence assessing lesion length (P = 0.01), percentage stenosis (P = 0.02), tortuosity (P < 0.04), and proximity to a bifurcation (P = 0.03), particularly in left coronary artery cases. X‐ray dose, contrast agent volume, and procedure duration were not significantly different. Conclusions Compared with conventional CA, RoCA augments quantitative lesion assessment, enhances confidence in the assessment of coronary artery disease and the precise details of the proposed procedure, but does not affect X‐ray dose, contrast agent volume, or procedure duration. © 2015 Wiley Periodicals, Inc. PMID:26012725
Benedetti, G.A.
1996-03-01
The coupled equations of motion for a circular ring or circular ring segment are developed for the case where the ring is rotating about an axis in its plane and subjected to an angular velocity as well as an angular acceleration. Coupling results from bending in and out of the plane of the ring as well as from extension and torsion of the ring. These equations are then applied to special cases to determine the coupled equations of motion for a ring, beam and cable rotating at a constant angular speed. Coupled equations of motion for a non-rotating circular ring or circular ring segment are developed for the cases of extensional motion and inextensional motion. These equations are subsequently linearized and uncoupled for extensional and inextensional motion in the plane of the ring as well as for uncoupled motion out of the plane of the ring. The critical angular speed for lateral dynamic instability is determined for a rotating circular shaft which supports several rotating circular ring segments.
Geodesics in the field of a rotating deformed gravitational source
NASA Astrophysics Data System (ADS)
Boshkayev, K. A.; Quevedo, H.; Abutalip, M. S.; Kalymova, Zh. A.; Suleymanova, Sh. S.
2016-01-01
We investigate equatorial geodesics in the gravitational field of a rotating and deformed source described by the approximate Hartle-Thorne metric. In the case of massive particles, we derive within the same approximation analytic expressions for the orbital angular velocity, the specific angular momentum and energy, and the radii of marginally stable and marginally bound circular orbits. Moreover, we calculate the orbital angular velocity and the radius of lightlike circular geodesics. We study numerically the frame dragging effect and the influence of the quadrupolar deformation of the source on the motion of test particles. We show that the effects originating from the rotation can be balanced by the effects due to the oblateness of the source.
Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A
2016-01-01
Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms. PMID:27350295
Pan, Y.; Nikitin, A. M.; Araizi, G. K.; Huang, Y. K.; Matsushita, Y.; Naka, T.; de Visser, A.
2016-01-01
Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms. PMID:27350295
Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A
2016-01-01
Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.
NASA Astrophysics Data System (ADS)
Pan, Y.; Nikitin, A. M.; Araizi, G. K.; Huang, Y. K.; Matsushita, Y.; Naka, T.; de Visser, A.
2016-06-01
Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.
Stoschus, H.; Schmitz, O.; Frerichs, H.; Unterberg, B.; Abdullaev, S. S.; Clever, M.; Coenen, J. W.; Kruezi, U.; Schega, D.; Samm, U.; Jakubowski, M. W.
2010-06-15
Measurements of the plasma edge electron density n{sub e} and temperature T{sub e} fields during application of a fast rotating, resonant magnetic perturbation (RMP) field show a characteristic modulation of both, n{sub e} and T{sub e} coherent to the rotation frequency of the RMP field. A phase delay PHI between the n{sub e}(t) and T{sub e}(t) waveforms is observed and it is demonstrated that this phase delay PHI is a function of the radius with PHI(r) depending on the relative rotation of the RMP field and the toroidal plasma rotation. This provides for the first time direct experimental evidence for a rotation dependent damping of the external RMP field in the edge layer of a resistive high-temperature plasma which breaks down at low rotation and high resonant field amplitudes.
NASA Astrophysics Data System (ADS)
Luo, Feilong; Goolaup, Sarjoosing; Li, Sihua; Lim, Gerard Joseph; Tan, Funan; Engel, Christian; Zhang, Senfu; Ma, Fusheng; Zhou, Tiejun; Lew, Wen Siang
2016-08-01
In this work, we present an efficient method for characterizing the spin orbit torque field-like term in an in-plane magnetized system using the harmonic measurement technique. This method does not require a priori knowledge of the planar and anomalous hall resistances and is insensitive to non-uniformity in magnetization, as opposed to the conventional harmonic technique. We theoretically and experimentally demonstrate that the field-like term in the Ta/Co/Pt film stack with in-plane magnetic anisotropy can be obtained by an in-plane transverse field sweep as expected, and magnetization non-uniformity is prevented by the application of fixed magnetic field. The experimental results are in agreement with the analytical calculations.
Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS_{2}.
Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados Del Águila, Andrés; Ballottin, Mariana V; Christianen, Peter C M; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf
2016-08-12
We control the linear polarization of emission from the coherently emitting K^{+} and K^{-} valleys (valley coherence) in monolayer WS_{2} with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τ_{c}=260 fs. PMID:27563997
Three-dimensional magnetized and rotating hot plasma equilibrium in a gravitational field
NASA Astrophysics Data System (ADS)
Catto, Peter J.; Krasheninnikov, Sergei I.; Pusztai, Istvan
2015-11-01
We present analytic and numerical solutions for three-dimensional magnetized axisymmetric equilibria confining rotating hot plasma in a gravitational field. Our solution to the full Shafranov-Grad equation can exhibit strong equatorial plane localization of the plasma density and current, resulting in disk equilibria for the plasma density. We find that a toriodal magnetic field is sometimes necessary to find a equilibrium in the presence of gravity for many cases of interest. Work supported by the US Department of Energy grants DE-FG02-91ER-54109 at MIT and DE-FG02-04ER54739 at UCSD & by an International Career Grant from Vetenskapsrådet.
Two charges on plane in a magnetic field: III. He{sup +} ion
Escobar-Ruiz, M.A.
2014-12-15
The He{sup +} ion on a plane subject to a constant magnetic field B perpendicular to the plane is considered taking into account the finite nuclear mass. Factorization of eigenfunctions permits to reduce the four-dimensional problem to three-dimensional one. The ground state energy of the composite system is calculated in a wide range of magnetic fields from B=0.01 up to B=100a.u. and center-of-mass Pseudomomentum K from 0 to 1000 a.u. using a variational approach. The accuracy of calculations for B=0.1a.u. is cross-checked in Lagrange-mesh method and not less than five significant figures are reproduced in energy. Similarly to the case of moving neutral system on the plane a phenomenon of a sharp change of energy behavior as a function of K for a certain critical K{sub c} but a fixed magnetic field occurs.
The temperature field around a spherical ridge or trough in a plane
Fransaer, J.; Roos, J.R. )
1992-05-01
An analytical solution, which describes the temperature field around a single spherical particle partly embedded in a plane or around a trough making an arbitrary contact angle with a plane, is presented here. The temperature distributions for three cases are studied: the temperature distribution around a conducting bowl or trough, the temperature distribution around a non-conducting bowl or trough present in a conducting plane, and the temperature profile around a conducting bowl or trough conducting heat toward a sink at infinity. The normalized heat flux distribution on the plane and particle is presented. The various incremental resistances caused by a single and a dilute planar random array of truncated spherical particles are also derived.
Rotational and magnetic field instabilities in neutron stars
Kokkotas, Kostas D.
2014-01-14
In this short review we present recent results on the dynamics of neutron stars and their magnetic fields. We discuss the progress that has been made, during the last 5 years, in understanding the rotational instabilities with emphasis to the one due to the f-mode, the possibility of using gravitational wave detection in constraining the parameters of neutron stars and revealing the equation of state as well as the detectability of gravitational waves produced during the unstable phase of a neutron star’s life. In addition we discuss the dynamics of extremely strong magnetic fields observed in a class of neutron stars (magnetars). Magnetic fields of that strength are responsible for highly energetic phenomena (giant flares) and we demonstrate that the analysis of the emitted electromagnetic radiation can lead in constraining the parameters of neutron stars. Furthermore, we present our results from the study of such violent phenomena in association with the emission of gravitational radiation.
Semiconductor Crystal Growth in Static and Rotating Magnetic fields
NASA Technical Reports Server (NTRS)
Volz, Martin
2004-01-01
Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a
How good a clock is rotation? The stellar rotation-mass-age relationship for old field stars
Epstein, Courtney R.; Pinsonneault, Marc H. E-mail: pinsono@astronomy.ohio-state.edu
2014-01-10
The rotation-mass-age relationship offers a promising avenue for measuring the ages of field stars, assuming the attendant uncertainties to this technique can be well characterized. We model stellar angular momentum evolution starting with a rotation distribution from open cluster M37. Our predicted rotation-mass-age relationship shows significant zero-point offsets compared to an alternative angular momentum loss law and published gyrochronology relations. Systematic errors at the 30% level are permitted by current data, highlighting the need for empirical guidance. We identify two fundamental sources of uncertainty that limit the precision of rotation-based ages and quantify their impact. Stars are born with a range of rotation rates, which leads to an age range at fixed rotation period. We find that the inherent ambiguity from the initial conditions is important for all young stars, and remains large for old stars below 0.6 M {sub ☉}. Latitudinal surface differential rotation also introduces a minimum uncertainty into rotation period measurements and, by extension, rotation-based ages. Both models and the data from binary star systems 61 Cyg and α Cen demonstrate that latitudinal differential rotation is the limiting factor for rotation-based age precision among old field stars, inducing uncertainties at the ∼2 Gyr level. We also examine the relationship between variability amplitude, rotation period, and age. Existing ground-based surveys can detect field populations with ages as old as 1-2 Gyr, while space missions can detect stars as old as the Galactic disk. In comparison with other techniques for measuring the ages of lower main sequence stars, including geometric parallax and asteroseismology, rotation-based ages have the potential to be the most precise chronometer for 0.6-1.0 M {sub ☉} stars.
Rotating and binary relativistic stars with magnetic field
NASA Astrophysics Data System (ADS)
Markakis, Charalampos
We develop a geometrical treatment of general relativistic magnetohydrodynamics for perfectly conducting fluids in Einstein--Maxwell--Euler spacetimes. The theory is applied to describe a neutron star that is rotating or is orbiting a black hole or another neutron star. Under the hypotheses of stationarity and axisymmetry, we obtain the equations governing magnetohydrodynamic equilibria of rotating neutron stars with poloidal, toroidal or mixed magnetic fields. Under the hypothesis of an approximate helical symmetry, we obtain the first law of thermodynamics governing magnetized equilibria of double neutron star or black hole - neutron star systems in close circular orbits. The first law is written as a relation between the change in the asymptotic Noether charge deltaQ and the changes in the area and electric charge of black holes, and in the vorticity, baryon rest mass, entropy, charge and magnetic flux of the magnetofluid. In an attempt to provide a better theoretical understanding of the methods used to construct models of isolated rotating stars and corotating or irrotational binaries and their unexplained convergence properties, we analytically examine the behavior of different iterative schemes near a static solution. We find the spectrum of the linearized iteration operator and show for self-consistent field methods that iterative instability corresponds to unstable modes of this operator. On the other hand, we show that the success of iteratively stable methods is due to (quasi-)nilpotency of this operator. Finally, we examine the integrability of motion of test particles in a stationary axisymmetric gravitational field. We use a direct approach to seek nontrivial constants of motion polynomial in the momenta---in addition to energy and angular momentum about the symmetry axis. We establish the existence and uniqueness of quadratic constants and the nonexistence of quartic constants for stationary axisymmetric Newtonian potentials with equatorial symmetry
Dynamics of Crowd Behaviors: From Complex Plane to Quantum Random Fields
NASA Astrophysics Data System (ADS)
Ivancevic, Vladimir G.; Reid, Darryn J.
2015-11-01
The following sections are included: * Complex Plane Dynamics of Crowds and Groups * Introduction * Complex-Valued Dynamics of Crowd and Group Behaviors * Kähler Geometry of Crowd and Group Dynamics * Computer Simulations of Crowds and Croups Dynamics * Braids of Agents' Behaviors in the Complex Plane * Hilbert-Space Control of Crowds and Groups Dynamics * Quantum Random Fields: A Unique Framework for Simulation, Optimization, Control and Learning * Introduction * Adaptive Quantum Oscillator * Optimization and Learning on Banach and Hilbert Spaces * Appendix * Complex-Valued Image Processing * Linear Integral Equations * Riemann-Liouville Fractional Calculus * Rigorous Geometric Quantization * Supervised Machine-Learning Methods * First-Order Logic and Quantum Random Fields
Chandrasekhar's Relation and Stellar Rotation in the Kepler Field
NASA Astrophysics Data System (ADS)
Silva, J. R. P.; Soares, B. B.; de Freitas, D. B.
2014-11-01
According to the statistical law of large numbers, the expected mean of identically distributed random variables of a sample tends toward the actual mean as the sample increases. Under this law, it is possible to test the Chandrasekhar's relation (CR), langVrang = (π/4)-1langVsin irang, using a large amount of Vsin i and V data from different samples of similar stars. In this context, we conducted a statistical test to check the consistency of the CR in the Kepler field. In order to achieve this, we use three large samples of V obtained from Kepler rotation periods and a homogeneous control sample of Vsin i to overcome the scarcity of Vsin i data for stars in the Kepler field. We used the bootstrap-resampling method to estimate the mean rotations (langVrang and langVsin irang) and their corresponding confidence intervals for the stars segregated by effective temperature. Then, we compared the estimated means to check the consistency of CR, and analyzed the influence of the uncertainties in radii measurements, and possible selection effects. We found that the CR with langsin irang = π/4 is consistent with the behavior of the langVrang as a function of langVsin irang for stars from the Kepler field as there is a very good agreement between such a relation and the data.
Chandrasekhar's relation and stellar rotation in the Kepler field
Silva, J. R. P.; Soares, B. B.; De Freitas, D. B. E-mail: brauliosoares@uern.br
2014-11-20
According to the statistical law of large numbers, the expected mean of identically distributed random variables of a sample tends toward the actual mean as the sample increases. Under this law, it is possible to test the Chandrasekhar's relation (CR), (V) = (π/4){sup –1}(Vsin i), using a large amount of Vsin i and V data from different samples of similar stars. In this context, we conducted a statistical test to check the consistency of the CR in the Kepler field. In order to achieve this, we use three large samples of V obtained from Kepler rotation periods and a homogeneous control sample of Vsin i to overcome the scarcity of Vsin i data for stars in the Kepler field. We used the bootstrap-resampling method to estimate the mean rotations ((V) and (Vsin i)) and their corresponding confidence intervals for the stars segregated by effective temperature. Then, we compared the estimated means to check the consistency of CR, and analyzed the influence of the uncertainties in radii measurements, and possible selection effects. We found that the CR with (sin i) = π/4 is consistent with the behavior of the (V) as a function of (Vsin i) for stars from the Kepler field as there is a very good agreement between such a relation and the data.
Spin in stationary gravitational fields and rotating frames
Obukhov, Yuri N.; Silenko, Alexander J.; Teryaev, Oleg V.
2010-03-24
A spin motion of particles in stationary spacetimes is investigated in the framework of the classical gravity and relativistic quantum mechanics. We bring the Dirac equation for relativistic particles in nonstatic spacetimes to the Hamiltonian form and perform the Foldy-Wouthuysen transformation. We show the importance of the choice of tetrads for description of spin dynamics in the classical gravity. We derive classical and quantum mechanical equations of motion of the spin for relativistic particles in stationary gravitational fields and rotating frames and establish the full agreement between the classical and quantum mechanical approaches.
Comparison of potential field solutions for Carrington Rotation 2144
NASA Astrophysics Data System (ADS)
Hayashi, Keiji; Yang, Shangbin; Deng, Yuagyong
2016-02-01
We examined differences among the coronal magnetic field structures derived with the potential field source surface (PFSS) model for Carrington Rotation 2144, from 21 November to 19 December 2013. We used the synoptic maps of solar photospheric magnetic field from four observatories, the Huairou Solar Observing Station (HSOS), Global Oscillation Network Group (GONG), Helioseismic Magnetic Imager (HMI), and Wilcox Solar Observatory (WSO). We tested two smoothing methods, Gaussian and boxcar averaging, and correction of unbalanced net magnetic flux. The solutions of three-dimensional coronal magnetic field are significantly different each other. An open-field region derived with HSOS data agrees best with the corresponding coronal hole observed by Solar Dynamics Observatories/Atmospheric Imaging Assembly, while HMI data yielded best agreements with the near-Earth OMNI database. The GONG data overall gave agreements as good as the HMI. The PFSS calculations using WSO data were least sensitive to the choices we examined in this work. Differences in PFSS solutions using different choices and parameters in smoothing imply that the photospheric magnetic field distributions with size of several degrees at midlatitude and low-latitude regions can be decisive, at least, in the examined period. To better determine the global solar corona, therefore, further evaluation of influences from compact bipolar magnetic field is needed.
NASA Astrophysics Data System (ADS)
Liu, Xianguo; Wing Or, Siu; Ming Leung, Chung; Ho, S. L.
2013-05-01
Magnetite (Fe3O4) nanoflakes with widths of 100-200 nm and thicknesses of 10-80 nm were prepared by a hydrothermal synthesis method. Fe3O4 nanoflake composites with and without magnetic field-induced rotational orientation of flake planes of Fe3O4 nanoflakes in paraffin binder were fabricated using 35 wt. % Fe3O4 nanoflakes. The rotationally oriented composite showed higher permeability and resonance frequency than the nonoriented one, and its value of (μ0-1)fr reached 214.8 GHz and exceeded the Snoek's limit. Considering a uniform and a random distribution of flake planes of Fe3O4 nanoflakes in the oriented and nonoriented composites, respectively, the complex permeability of both composites was calculated using the Landau-Lifshitz-Gilbert equation and the Bruggeman's effective medium theory in the 2-18 GHz microwave frequency range.
Crystal-oriented tungsten-bronze type ceramics prepared by a rotating magnetic field
NASA Astrophysics Data System (ADS)
Tanaka, S.; Doshida, Y.; Shimizu, H.; Furushima, R.; Uematsu, K.
2011-03-01
Forming and sintering of c-axis-oriented Sr2NaNb5O15 (SNN) ceramics were examined. Particle-oriented SNN was fabricated by using a rotating high magnetic field and subsequent sintering without magnetic field. SNN ceramics are tungsten-bronze-type ferroelectric materials with a tetragonal crystal system. The diamagnetic susceptibilities of the c-axis are smaller than that of the a- and b-axis (χc < χa,b < 0). SNN powder was prepared by conventional solid-state reaction. The synthesized powder was mixed with distilled water and a dispersant by using ball milling to give a slurry with solid loading of 30 vol%. The slurry was poured into a plastic mold and this was placed in a 10Tesla magnetic field in a superconducting magnet. The mold was rotated at 30 rpm while the slurry dried at room temperature. The resulting powder compact with a columnar shape was heated at 5 K/min to 1473 K, held for 6 h, and then heated at 1525 K for 2 h to prevent exaggerated grain growth. XRD patterns showed that c-axis-oriented SNN polycrystalline ceramics were produced in the presence of the rotating magnetic field. In XRD patterns viewed from the top surface of the sintered specimens, peaks from the c-planes of the crystal, such as 001 and 002, were very strong. Diffraction peaks which were very strong in the ceramics, such as 320 and 410, were absent in the specimen. Oriented microstructure was developed well by sintering. Grain-growth along to c-axis was observed in the SNN ceramics heated at 1525 K.
Transient effects in rotating magnetic field current drive*
NASA Astrophysics Data System (ADS)
Steinhauer, Loren
2000-10-01
The time-dependent behavior of rotating magnetic field (RMF) current drive is investigated using a two-fluid model. The time and radius dependence separates so that the time-dependent behavior can be found by quadrature. This leads to the prediction of transient behavior leading rapidly to a quasi-steady state that evolves on a diffusion timescale. During the transient phase the ions and electrons spin up together. The timescale of the transient phase is set by the ion inertia in balance with ion-electron friction. Unless there is an additional ion momentum source to balance the resistive friction with the electrons, the quasi-steady state has no current drive effect. Collisions with neutrals is a momentum source in some experiments, notably rotamaks and the STX experiment at the University of Washington. Other sources of ion momentum will be needed for effective RMF current drive in hotter, fusion-relevant plasmas. The properties of the quasi-steady state are found, including the self-consistent ion rotation rate and radial electric field, and RMF corrections on the pressure balance. *This research is supported by USDOE grant DE-FG0398ER54480.
Links between surface magnetic fields, abundances, and surface rotation in clusters and in the field
NASA Astrophysics Data System (ADS)
Przybilla, Norbert
2015-01-01
Theory predicts that hydrodynamical instabilities transport angular momentum and chemical elements in rotating massive stars. An interplay of rotation and a magnetic field affects these transport processes. The complexity of the problem imposes that a comprehensive description cannot be developed on theoretical grounds alone, progress in the understanding of the evolution of massive stars has to be guided by observations. The challenge lies both in the derivation of accurate and precise observational constraints as well as in the extraction of the relevant information for identifying possible correlations - like between surface magnetic fields, abundances, and surface rotation - from a multivariate function of the many parameters involved. I review the most important steps recently made based on detailed studies of massive stars both in the field and in clusters towards finding such links that ultimately may guide the further development of the models.
Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field
NASA Technical Reports Server (NTRS)
Volz, M. P.; Schweizer, M.; Cobb, S. D.; Walker, J. S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)
2002-01-01
A series of (100)-oriented gallium-doped germanium crystals have been grown by the Bridgman method and under the influence of a rotating magnetic field (RMF). The RMF has a marked affect on the interface shape, changing it from concave to nearly flat. The onset of time-dependent flow instabilities occurs when the critical magnetic Taylor number is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. The critical magnetic Taylor number is a sensitive function of the aspect ratio and, as the crystal grows under a constant applied magnetic field, the induced striations change from nonperiodic to periodic, undergo a period-doubling transition, and then cease to exist. Also, by pulsing the RMF on and off, it is shown that intentional interface demarcations can be introduced.
NASA Astrophysics Data System (ADS)
Read, P. L.; Jacoby, T. N. L.; Rogberg, P. H. T.; Wordsworth, R. D.; Yamazaki, Y. H.; Miki-Yamazaki, K.; Young, R. M. B.; Sommeria, J.; Didelle, H.; Viboud, S.
2015-08-01
A series of rotating, thermal convection experiments were carried out on the Coriolis platform in Grenoble, France, to investigate the formation and energetics of systems of zonal jets through nonlinear eddy/wave-zonal flow interactions on a topographic β-plane. The latter was produced by a combination of a rigid, conically sloping bottom and the rotational deformation of the free upper surface. Convection was driven by a system of electrical heaters laid under the (thermally conducting) sloping bottom and led to the production of intense, convective vortices. These were observed to grow in size as each experiment proceeded and led to the development of weak but clear azimuthal jet-like flows, with a radial scale that varied according to the rotation speed of the platform. Detailed analyses reveal that the kinetic energy-weighted radial wavenumber of the zonal jets, kJy, scales quite closely either with the Rhines wavenumber as kJy ≃ 2(βT/2urms)1/2, where urms is the rms total or eddy velocity and βT is the vorticity gradient produced by the sloping topography, or the anisotropy wavenumber as k J y ≃ 1 . 25 ( βT 3 / ɛ ) 1 / 5 , where ɛ is the upscale turbulent energy transfer rate. Jets are primarily produced by the direct quasi-linear action of horizontal Reynolds stresses produced by trains of topographic Rossby waves. The nonlinear production rate of zonal kinetic energy is found to be strongly unsteady, however, with fluctuations of order 10-100 times the amplitude of the mean production rate for all cases considered. The time scale of such fluctuations is found to scale consistently with either an inertial time scale, τ p ˜ 1 . / √{ u r m s β T } , or the Ekman spin-down time scale. Kinetic energy spectra show some evidence for a k-5/3 inertial subrange in the isotropic component, suggestive of a classical Kolmogorov-Batchelor-Kraichnan upscale energy cascade and a steeper spectrum in the zonal mean flow, though not as steep as k-5, as
Lin, Hwai-Ting; Ko, Hsing-Tsen; Lee, Kung-Che; Chen, Ying-Cheng; Wang, Dean-Chuan
2015-05-01
[Purpose] This study aimed to investigate the effect of shoulder positions and speeds on internal and external rotation torque of college baseball players and age-matched non-players. [Subjects] Twenty first-level collegiate baseball players and 19 college students were recruited. [Methods] A dynamometer system was used to evaluate the shoulder rotation strength in sitting postures. Three testing positions, namely shoulder abduction of 45°, 70°, and 90° in the scapular plane, were combined with three testing speeds at 60°/s, 120°/s, and 210°/s. [Results] The maximum external and internal rotation torques both occurred at shoulder abduction of 70°. However, only external rotation torque was affected by the speed, with the peak value observed at 60°/s. The internal rotation torque of baseball players was larger than that of the control group under all testing conditions, but the external rotation did not show any difference. The ratio of external to internal rotation torque changed with the testing positions and speeds in both groups. The ratio in the control group was greater than that in the player group. [Conclusion] The shoulder position could affect the rotational strength, and the baseball players could strengthen their external rotators for better performance and injury prevention.
Transport properties of bilayer graphene in a strong in-plane magnetic field
NASA Astrophysics Data System (ADS)
Van der Donck, M.; Peeters, F. M.; Van Duppen, B.
2016-03-01
A strong in-plane magnetic field drastically alters the low-energy spectrum of bilayer graphene by separating the parabolic energy dispersion into two linear Dirac cones. The effect of this dramatic change on the transport properties strongly depends on the orientation of the in-plane magnetic field with respect to the propagation direction of the charge carriers and the angle at which they impinge on the electrostatic potentials. For magnetic fields oriented parallel to the potential boundaries an additional propagating mode that results from the splitting into Dirac cones enhances the transmission probability for charge carriers tunneling through the potentials and increases the corresponding conductance. Our results show that the chiral suppression of transmission at normal incidence, reminiscent of bilayer graphene's 2 π Berry phase, is turned into a chiral enhancement when the magnetic field increases, thus indicating a transition from a bilayer to a monolayer-like system at normal incidence. Further, we find that the typical transmission resonances stemming from confinement in a potential barrier are shifted to higher energy and are eventually transformed into antiresonances with increasing magnetic field. For magnetic fields oriented perpendicular to the potential boundaries we find a very pronounced transition from a bilayer system to two separated monolayer-like systems with Klein tunneling emerging at certain incident angles symmetric around 0, which also leaves a signature in the conductance. For both orientations of the magnetic field, the transmission probability is still correctly described by pseudospin conservation. Finally, to motivate the large in-plane magnetic field, we show that its energy spectrum can be mimicked by specific lattice deformations such as a relative shift of one of the layers. With this equivalence we introduce the notion of an in-plane pseudomagnetic field.
Vector-based plane-wave spectrum method for the propagation of cylindrical electromagnetic fields.
Shi, S; Prather, D W
1999-11-01
We present a vector-based plane-wave spectrum (VPWS) method for efficient propagation of cylindrical electromagnetic fields. In comparison with electromagnetic propagation integrals, the VPWS method significantly reduces time of propagation. Numerical results that illustrate the utility of this method are presented.
The unique effect of in-plane anisotropic strain in the magnetization control by electric field
NASA Astrophysics Data System (ADS)
Zhao, Y. Y.; Wang, J.; Hu, F. X.; Liu, Y.; Kuang, H.; Wu, R. R.; Sun, J. R.; Shen, B. G.
2016-05-01
The electric field control of magnetization in both (100)- and (011)-Pr0.7Sr0.3MnO3/Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PSMO/PMN-PT) heterostructures were investigated. It was found that the in-plane isotropic strain induced by electric field only slightly reduces the magnetization at low temperature in (100)-PSMO/PMN-PT film. On the other hand, for (011)-PSMO/PMN-PT film, the in-plane anisotropic strain results in in-plane anisotropic, nonvolatile change of magnetization at low-temperature. The magnetization, remanence and coercivity along in-plane [100] direction are suppressed by the electric field while the ones along [01-1] direction are enhanced, which is ascribed to the extra effective magnetic anisotropy induced by the electric field via anisotropic piezostrains. More interestingly, such anisotropic modulation behaviors are nonvolatile, demonstrating a memory effect.
NASA Astrophysics Data System (ADS)
Tamaki, Tamotsu; Umezaki, Eisaku; Yamagata, Masatsune; Inoue, Shun-ichi
1984-10-01
For the therapy of diseases of spinal deformity such as scoliosis, the data of 3-dimensional and correct spinal configuration are needed. Authors developed the system of spinal configuration analysis using bi-plane X-ray photogrammetry which is strong aid for this subject. The idea of correction angle of rotation of vertebra is introduced for this system. Calculated result under this idea has the clinical meaning because the correction angle is the angle which should be corrected on the treatment such as operation or wearing the equipment. Method of 30° oblique projection which gives the apparent X-ray image and eases the measurement of the anatomically characteristic points is presented. The anatomically characteristic bony points whose images should be measured on a- or b-film are of four points. These are centers of upper and lower end plates of each vertebra the center is calculated from two points which are most distant each other on the contour of vertebral end plate ), the lower end points of root of right and left pedicles. Some clinical applications and the effectiveness of this system are presented.
Wong, Anson L. K.; Rickards, Cory
2014-01-01
Purpose/Background: Hip external rotator (ER) and internal rotator (IR) muscle weakness is theorized to be associated with lower extremity injury in athletes including knee ligament tears and patellofemoral pain. Previous studies investigating hip musculature strength have utilized various sagittal plane hip positions for testing. The relationship between results at these different positions is unknown. Methods: Eighty healthy, pain‐free young adults participated in the study: 40 female, mean age 22.90 (± 2.32) years, and 40 male, mean age 23.50 (± 2.15) years. Peak isometric torque of bilateral hip ER and IR were tested at 90° and 0° of hip flexion with an instrumented dynamometer. Peak muscle forces were calculated. Peak forces were normalized by body mass. Mean normalized force was calculated for dominant and non‐dominant limbs for ER and IR in both positions. Male and female data were analyzed separately with paired t‐tests (2‐tailed). Reference values for average muscle force and torque were calculated for dominant and non‐dominant limbs for both hip positions. Results: Hip IR normalized peak force was greater at 90° compared to 0° flexion position bilaterally in both genders (p < .01). Hip ER normalized peak force was greater at 90° compared to 0° flexion in dominant limbs of both genders and in non‐dominant limbs of males (p < .01). Non‐dominant hip ER normalized force in females was greater at 90° versus 0° flexion; however, it was not significant (p = .092). Post hoc analysis of normalized average force (average over 5‐second contraction) yielded similar results. Conclusion: Clinicians and researchers should use consistent positioning for testing of hip ER and IR strength. This will improve certainty of determining if a patient’s strength has changed or if differences between groups are present. Reference values reported will be useful in order to determine if weakness is present and to set goals, particularly in cases of
Reducing ferrite tuner power loss by bias field rotation
Smythe, W.R.
1983-08-01
It has been suggested that ferrite tuners for rf cavities with the magnetic bias field perpendicular to the rf magnetic field would have greatly reduced rf losses. Recent measurements at Los Alamos National Laboratory appear to confirm this effect. A simple model proposed here allows the calculation of tuning characteristics for a variety of bias schemes. The model shows that the perpendicular bias scheme mentioned above requires very much larger bias levels than does the parallel bias scheme in order to achieve the same tuning range with a particular ferrite tuner. However, further investigation with the model has led to the discovery that the use of perpendicular bias at low frequency and parallel bias at high frequency requires only a modest increase in the bias field. In effect, the ferrite is kept highly magnetized, reducing ferrite losses, and is tuned primarily by rotating the bias field direction with respect to the rf field direction. The resulting reduction in dissipation can significantly reduce the amount of ferrite required per cavity.
Quantitative measurement of in-plane acoustic field components using surface-mounted fiber sensors
NASA Technical Reports Server (NTRS)
Claus, Richard O.; Dhawan, Rajat R.; Gunther, Michael F.; Murphy, Kent A.
1993-01-01
Extrinsic Fabry-Perot interferometric sensors have been used to obtain calibrated, quantitative measurements of the in-plane displacement components associated with the propagation of ultrasonic elastic stress waves on the surfaces of solids. The frequency response of the sensor is determined by the internal spacing between the two reflecting fiber endface surfaces which form the Fabry-Perot cavity, a distance which is easily controlled during fabrication. With knowledge of the material properties of the solid, the out-of-plane displacement component of the wave may also be determined, giving full field data.
Characterization of rf-SSET in both in-plane and perpendicular magnetic fields
NASA Astrophysics Data System (ADS)
Tang, Chunyang; Yang, Zhen; Yuan, Mingyun; Rimberg, A. J.; Savage, D. E.; Eriksson, M. A.; Rimberg Team; Eriksson Collaboration
2013-03-01
Previous success in coupling an aluminum radio-frequency superconducting single electron transistor (rf-SSET) to quantum dots (QDs) has demonstrated use of the rf-SSET as an ultra-sensitive and fast charge sensor. Since a magnetic field is usually necessary for quantum dot qubit manipulation, it is important to understand the effect of magnetic fields, either in-plane or perpendicular, on the performance of any charge sensor near the QDs. Here we report characterization of rf-SSETs in both in-plane and perpendicular magnetic fields. The rf-SSET works well in an in-plane fields up to 1 Tesla at a temperature of 30 mK. At 0.3K, in a perpendicular field generated by a stripline located 700 nm away, the rf-SSET charge sensitivity even shows improvement for up to 2.1 mA current through the stripline (corresponding roughly to a field of 6 Gauss). This work was supported by NSA, LPS and ARO
NASA Astrophysics Data System (ADS)
Pshirkov, M. S.; Tinyakov, P. G.; Kronberg, P. P.; Newton-McGee, K. J.
2011-09-01
We made use of the two latest sets of rotation measures (RMs) of extragalactic radio sources, namely the NRAO VLA Sky Survey rotation measures catalog and a compilation by Kronberg and Newton-McGee, to infer the global structure of the Galactic magnetic field (GMF). We have checked that these two data sets are mutually consistent. Given the existence of clear patterns in the all-sky RM distributions we considered GMF models consisting of two components: disk (spiral or ring) and halo. The parameters of these components were determined by fitting different model field geometries to the observed RMs. We found that the model consisting of a symmetric (with respect to the Galactic plane) spiral disk and antisymmetric halo fits the data best and reproduces the observed distribution of RMs over the sky very well. We confirm that ring disk models are disfavored. Our results favor small pitch angles around ~ - 5° and an increased vertical scale of electron distribution, in agreement with some recent studies. Based on our fits, we select two benchmark models suitable for studies of cosmic ray propagation, including cosmic rays at ultrahigh energies.
Simulation studies of FRC with rotating magnetic field current drive
NASA Astrophysics Data System (ADS)
Belova, E. V.; Davidson, R. C.
2007-11-01
The HYM code has been modified to include the effects of rotating magnetic field (RMF) current drive. Initial 3D two-fluid and hybrid simulations have been performed for even-parity RMF and different plasma parameters. Simulations show that the RMF pushes the plasma radially inward, resulting in a reduced plasma density outside the separatrix. Lower plasma density and larger RMF amplitudes result in faster RMF field penetration, in agreement with previous studies [R. Milroy, Phys. Plasmas 8, 2804 (2001)]. Effects of the applied RMF field on particle confinement have been studied using 3D test particle simulations. Simulations of stationary RMFs show that for relatively large ion Larmor radius (S^*<20), there is very little difference between even- and odd-parity RMFs in terms of the ion losses. The rate of particle losses is larger in larger FRCs, and increases with the RMF amplitude. In contrast, high-frequency RMF can reduce ion losses provided φrmfφci, and the RMF is of even-parity. The improved particle confinement is related to ponderomotive forces due to the rapidly oscillating, inhomogeneous electromagnetic field. It is also found that high-frequency, odd-parity RMFs force particles away from the midplane toward the FRC ends.
Plasma Compression using Rotating Electric Fields - the Strong Drive Regime
Danielson, J. R.; Surko, C. M.
2006-10-18
The rotating wall technique has proven to be an excellent method to create high-density, single-component plasmas in Penning-Malmberg traps. It has become useful, and sometimes critical, for applications such as antihydrogen production and the tailoring of ion crystals and positron beams. Azimuthally phased rf fields apply a torque that injects angular momentum and produces radial plasma compression as it spins the plasma up. Recently, we discovered a new 'strong-drive' regime in which plasmas can be compressed until the E x B rotation frequency, fE (where fE {proportional_to} n, the plasma density) approaches the applied frequency, fRW. We review here highlights of a recently published study of this regime [Danielson, et al., Phys. Plasmas 13, 055706 (2006)]. Good compression is achieved over a broad range of RW frequencies without the need to tune to a plasma mode. Setting the plasma density can be done simply and reliably by tuning fRW. Characteristics of this strong-drive regime and the resulting high-density steady states are discussed.
Domain wall depinning from notches using combined in- and out-of-plane magnetic fields
NASA Astrophysics Data System (ADS)
Goertz, Jelle J. W.; Ziemys, Grazvydas; Eichwald, Irina; Becherer, Markus; Swagten, Henk J. M.; Breitkreutz-v. Gamm, Stephan
2016-05-01
Controlled domain wall motion and pinning in nanowires with perpendicular magnetic anisotropy are of great importance in modern magnetic memory and logic devices. Here, we investigate by experiment the DW pinning and depinning from a notch in a magnetic nanowire, under the influence of combined in- and out-of-plane magnetic fields. In our experiment, the perpendicular magnetization of the Co/Pt nanowires is tilted with the help of sub-μs in-plane field pulses generated by an on-chip coil. Consequently, the energy density of the DW is decreased and the depinning field of the notch is reduced. A theoretical model is applied and compared to the measurement results. The DW depinning mechanism and the DW type are further investigated by micromagnetic simulations.
Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field
NASA Technical Reports Server (NTRS)
Volz, M. P.; Szofran, F. R.; Cobb, S. D.; Schweizer, M.; Walker, J. S.
2005-01-01
A series of (100)-oriented gallium-doped germanium crystals has been grown by the vertical Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow instabilities occur when the critical magnetic Taylor number (Tm(sup c)) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. Tm(sup c) decreases as the aspect ratio of the melt increases, and approaches the theoretical limit expected for an infinite cylinder. Intentional interface demarcations are introduced by pulsing the RMF on and off The RMF has a marked affect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased.
Bridgman Growth of Germanium Crystals in a Rotating Magnetic Field
NASA Technical Reports Server (NTRS)
Volz, M. P.; Walker, J. S.; Schweizer, M.; Cobb, S. D.; Szofran, F. R.
2004-01-01
A series of (100)-oriented gallium-doped germanium crystals have been grown by the Bridgman method and under the influence of a rotating magnetic field (RMF). Time-dependent flow instabilities occur when the critical magnetic Taylor number (Tm(sup c) is exceeded, and this can be observed by noting the appearance of striations in the grown crystals. The experimental data indicate that Tm(sup c) increases as the aspect ratio of the melt decreases. Modeling calculations predicting Tm(sup c) as a function of aspect ratio are in reasonable agreement with the experimental data. The RMF has a marked affect on the interface shape, changing it from concave to nearly flat as the RMF strength is increased. Also, by pulsing the RMF on and off, it is shown that intentional interface demarcations can be introduced.
Rotating dipole and quadrupole field for a multiple cathode system
Chang, X.; Ben-Zvi, I.; Kewisch, J.; Litvinenko, V.; Meng, W.; Pikin, A.; Ptitsyn, V.; Rao, T.; Sheehy, B.; Skarita, J.; Wang, E.; Wu, Q.; Xin, T.
2011-03-28
A multiple cathode system has been designed to provide the high average current polarized electron bunches for the future electron-ion collider eRHIC [1]. One of the key research topics in this design is the technique to generate a combined dipole and quadrupole rotating field at high frequency (700 kHz). This type of field is necessary for combining bunches from different cathodes to the same axis with minimum emittance growth. Our simulations and the prototype test results to achieve this will be presented. The future eRHIC project, next upgrade of EHIC, will be the first electron-heavy ion collider in the world. For polarized-electron and polarized proton collisions, it requires a polarized electron source with high average current ({approx}50 mA), short bunch ({approx}3 mm), emittance of about 20 {micro}m and energy spread of {approx}1% at 10 MeV. The state-of-art polarized electron cathode can generate average current of about more than 1 mA, but much less than 50 mA. The current is limited by the quantum efficiency, lifetime, space charge and ultra-high vacuum requirement of the polarized cathode. A possible approach to achieve the 50 mA beam is to employ multiple cathodes, such as 20 cathodes, and combine the multiple bunched beams from cathodes to the same axis. We name it as 'Gatling gun' because its operations bear similarity to a multi-barrel Gatling gun. The electron spin direction is not affected by electric field but will follow to the direction of the magnetic bending. This requires that, to preserve the spin polarization from cathode, the fixed bending field after the solenoid and the rotating bending field in combiner must be either a pair of electric bendings or a pair of magnetic bendings. We choose the scheme with a pair of magnetic bendings because it is much easier than the scheme with a pair of electric bendings at our 200 keV electron energy level.
The TCS Rotating Magnetic Field FRC Current-Drive Experiment
Hoffman, Alan J.; Guo, Houyang Y.; Slough, John T.; Tobin, Stephen J.; Schrank, Louis S.; Reass, William A.; Wurden, Glen A.
2002-03-15
Field-reversed configurations (FRCs) have extremely attractive reactor attributes because of their singly connected geometry. They have been created in theta-pinch devices, but being compact toroids and lacking a center hole, their toroidal current cannot be sustained by transformer action as in other toroidal configurations. A new device, the Translation, Confinement, and Sustainment (TCS) facility has been constructed to use rotating magnetic fields (RMFs) to build up and sustain the flux of hot FRCs formed by the normal theta-pinch method. RMF formation and sustainment of similar, but cold, pure poloidal field configurations have been demonstrated in devices called rotamaks, and RMF formation, but not sustainment, has been achieved in a smaller FRC facility called the Star Thrust Experiment (STX). Initial formation and sustainment have now been achieved in TCS, albeit still with cold (T{sub e} {approx} 50 eV) plasmas. Both the formation and final steady-state conditions are found to agree with newly developed analytic and numerical models for RMF flux buildup and sustainment inside a standard cylindrical flux conserver. The required plasma conditions (mainly resistivity but also density) can now be determined for the planned hot FRC, RMF flux buildup experiments and for eventual reactor conditions.
Rotation of solar magnetic fields for the current solar cycle 24
Shi, X. J.; Xie, J. L.
2014-11-01
The rotation of solar magnetic fields for the current solar cycle 24 is investigated through a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields during Carrington rotation numbers 2076-2146 (2008 October to 2014 January). The sidereal rotation rates of positive and negative magnetic fields at some latitudes are shown, and it can be found that the positive (negative) fields generally rotate faster than the negative (positive) fields in the southern (northern) hemisphere at low latitudes. The mean rotation profiles of total, positive, and negative magnetic fields between ±60° latitudes in the time interval are also obtained. It should be noted that both of the mean rotation profiles of the positive and negative magnetic fields, as well as the mean rotation profile of the total magnetic field, exhibit a quasi-rigid rotation at latitudes above about 55°. The mean rotation rates of the positive (negative) polarity reach their maximum values at about 9°(6)° latitude in the southern (northern) hemisphere. The mean rotation profile of the total magnetic field displays an obvious north-south asymmetry, where the rotation seems to be more differential in the northern hemisphere. The latitude variation in the rotation rate differences between positive and negative magnetic fields is further studied, and it is found that magnetic fields with the same polarity as the leading sunspots at a given hemisphere rotate faster than those with the opposite polarity, except for the zones around 52° latitude of the southern hemisphere and around 35° latitude of the northern hemisphere. The implication of these results is discussed. It is clear that the obtained results can provide some observational constraints on the theoretical research of the mechanisms of differential rotation and solar cycle.
NASA Technical Reports Server (NTRS)
Giveona, Amir; Shaklan, Stuart; Kern, Brian; Noecker, Charley; Kendrick, Steve; Wallace, Kent
2012-01-01
In a setup similar to the self coherent camera, we have added a set of pinholes in the diffraction ring of the Lyot plane in a high-contrast stellar Lyot coronagraph. We describe a novel complex electric field reconstruction from image plane intensity measurements consisting of light in the coronagraph's dark hole interfering with light from the pinholes. The image plane field is modified by letting light through one pinhole at a time. In addition to estimation of the field at the science camera, this method allows for self-calibration of the probes by letting light through the pinholes in various permutations while blocking the main Lyot opening. We present results of estimation and calibration from the High Contrast Imaging Testbed along with a comparison to the pair-wise deformable mirror diversity based estimation technique. Tests are carried out in narrow-band light and over a composite 10% bandpass.
Physical states and properties of barium titanate films in a plane electric field
NASA Astrophysics Data System (ADS)
Shirokov, V. B.; Kalinchuk, V. V.; Shakhovoi, R. A.; Yuzyuk, Yu. I.
2016-07-01
The influence of a plane electric field on the phase states of barium titanate thin films under the conditions of forced deformation has been studied. The field dependence of a complete set of material constants has been taken in the region of the c-phase, where polarization losses are absent. The material constants are calculated using equations of the piezoelectric effect derived by linearizing the nonlinear equations of state from the phenomenological; theory for barium titanate. It has been shown that there is a critical value of the field at which the electromechanical coupling coefficient reaches a maximum.
Spin-torque diode with tunable sensitivity and bandwidth by out-of-plane magnetic field
NASA Astrophysics Data System (ADS)
Li, X.; Zheng, C.; Zhou, Y.; Kubota, H.; Yuasa, S.; Pong, Philip W. T.
2016-06-01
Spin-torque diodes based on nanosized magnetic tunnel junctions are novel microwave detectors with high sensitivity and wide frequency bandwidth. While previous reports mainly focus on improving the sensitivity, the approaches to extend the bandwidth are limited. This work experimentally demonstrates that through optimizing the orientation of the external magnetic field, wide bandwidth can be achieved while maintaining high sensitivity. The mechanism of the frequency- and sensitivity-tuning is investigated through analyzing the dependence of resonant frequency and DC voltage on the magnitude and the tilt angle of hard-plane magnetic field. The frequency dependence is qualitatively explicated by Kittel's ferromagnetic resonance model. The asymmetric resonant frequency at positive and negative magnetic field is verified by the numerical simulation considering the in-plane anisotropy. The DC voltage dependence is interpreted through evaluating the misalignment angle between the magnetization of the free layer and the reference layer. The tunability of the detector performance by the magnetic field angle is evaluated through characterizing the sensitivity and bandwidth under 3D magnetic field. The frequency bandwidth up to 9.8 GHz or maximum sensitivity up to 154 mV/mW (after impedance mismatch correction) can be achieved by tuning the angle of the applied magnetic field. The results show that the bandwidth and sensitivity can be controlled and adjusted through optimizing the orientation of the magnetic field for various applications and requirements.
NASA Astrophysics Data System (ADS)
Guo, H. Y.; Hoffman, A. L.; Milroy, R. D.
2007-11-01
Greatly reduced recycling and impurity ingestion in the Translation, Confinement, and Sustainment—Upgrade (TCSU) device has allowed much higher plasma temperatures to be achieved in the field reversed configurations (FRC) under rotating magnetic field (RMF) formation and sustainment. The hotter plasmas have higher magnetic fields and much higher diamagnetic electron rotation rates so that the important ratio of average electron rotation frequency to RMF frequency, called ζ, approaches unity, for the first time, in TCSU. A large fraction of the RMF power is absorbed by an as yet unexplained (anomalous) mechanism directly proportional to the square of the RMF magnitude. It becomes of relatively lesser significance as the FRC current increases, and simple resistive heating begins to dominate, but the anomalous absorption is useful for initial plasma heating. Measurements of total absorbed power, and comparisons of applied RMF torque to torque on the electrons due to electron-ion friction under high-ζ operation, over a range of temperatures and fields, have allowed the separation of the classical Ohmic and anomalous heating to be inferred, and cross-field plasma resistivities to be calculated.
Faraday rotation due to quadratic gravitation
NASA Astrophysics Data System (ADS)
Chen, Yihan; Liu, Liping; Tian, Wen-Xiu
2011-01-01
The linearized field equations of quadratic gravitation in stationary space-time are written in quasi-Maxwell form. The rotation of the polarization plane for an electromagnetic wave propagating in the gravito-electromagnetic field caused by a rotating gravitational lens is discussed. The influences of the Yukawa potential in quadratic gravitation on the gravitational Faraday rotation are investigated.
NASA Astrophysics Data System (ADS)
Schmidt, C. H.; Laitinen, T. A.; Eibert, T. F.
2011-10-01
Near-field measurement and transformation techniques are widely applied to characterize radiation patterns of antennas. Spherical and cylindrical near-field measurements have been researched extensively and various techniques with different probe compensation capabilities and complexities exist. Among those techniques applicable for (almost) arbitrary probes, the crucial computational efficiency has been achieved through the use of Fast Fourier Transform based preprocessing of the measurement data. It is shown in this paper that the Fast Fourier Transform based preprocessing can also be utilized in conjunction with the plane wave based fully probe-corrected near-field far-field transformation with low numerical complexity. The collection of probe signals is split into smaller subsets for individual orthogonal azimuthal Fourier modes by an Inverse Fast Fourier Transform. These smaller subsets can be transformed to the far field very efficiently with full probe correction. The technique presented in this paper is applicable for arbitrary "body of revolution" antenna measurement grids, including the important cases of cylindrical and spherical measurement grids. The "body of revolution" grids are rotationally symmetric around the z-axis and the probe signals must be available equidistantly in ϕ.
Zhang, Xiao-Zheng; Thomas, Jean-Hugh; Bi, Chuan-Xing; Pascal, Jean-Claude
2012-10-01
A time-domain plane wave superposition method is proposed to reconstruct nonstationary sound fields. In this method, the sound field is expressed as a superposition of time convolutions between the estimated time-wavenumber spectrum of the sound pressure on a virtual source plane and the time-domain propagation kernel at each wavenumber. By discretizing the time convolutions directly, the reconstruction can be carried out iteratively in the time domain, thus providing the advantage of continuously reconstructing time-dependent pressure signals. In the reconstruction process, the Tikhonov regularization is introduced at each time step to obtain a relevant estimate of the time-wavenumber spectrum on the virtual source plane. Because the double infinite integral of the two-dimensional spatial Fourier transform is discretized directly in the wavenumber domain in the proposed method, it does not need to perform the two-dimensional spatial fast Fourier transform that is generally used in time domain holography and real-time near-field acoustic holography, and therefore it avoids some errors associated with the two-dimensional spatial fast Fourier transform in theory and makes possible to use an irregular microphone array. The feasibility of the proposed method is demonstrated by numerical simulations and an experiment with two speakers.
Tools and Setups for Experiments with AC and Rotating Magnetic Fields
ERIC Educational Resources Information Center
Ponikvar, D.
2010-01-01
A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several…
Resistivity scaling of rotating magnetic field current drive in FRCs
NASA Astrophysics Data System (ADS)
Hoffman, A. L.; Guo, H. Y.; Milroy, R. D.; Pietrzyk, Z. A.
2003-10-01
Rotating magnetic fields (RMFs) have been used to both form and sustain low density, prolate FRCs in the translation confinement and sustainment (TCS) facility. The two most important factors governing performance are the plasma resistivity, which sets the maximum density for which toroidal current can be maintained, and the energy loss rate, which sets the plasma temperature. The plasma resistivity has been determined by carefully measuring the amount of RMF power absorbed by the FRC. When the ratio of RMF magnitude, Bohgr, to external poloidal confinement field, Be, is high, this resistivity is very adversely affected by the RMF drive process. However, when Bohgr/Be falls below about 0.3, the resistivity returns to values typical of non-driven FRCs. The observed scaling leads to a density dependence of ne ~ Bohgr/rsohgr1/2 where rs is the FRC separatrix radius and ohgr is the RMF frequency. Since the FRC contains little or no toroidal field, Be is proportional to (neTt)1/2 where Tt = Te + Ti is the sum of the electron and ion temperatures. In the present experiments, except for the initial start-up phase where Tt can exceed 100 eV, the plasma temperature is limited to about 40 eV by high oxygen impurity levels. Thus, low Bohgr/Be, low resistivity operation was only realized by operating at low values of Bohgr. The RMF drive sustains particles as well as flux, and resistive input powers can be in the MW range at higher values of Bohgr, so that high temperature, steady-state operation should be possible once impurity levels are reduced. Changes are being made to the present 'O-ring' sealed, quartz chambered TCS to provide bakable metal walls and wall conditioning as in other quasi-steady fusion facilities.
Rotational Evolution and Magnetic Field of AP Stars
NASA Astrophysics Data System (ADS)
Xiaojun, C.; Matsuura, O. T.
1990-11-01
RESUMO. Prop6e- se qLie 0 campo de estrelas Ap pode ser 9cr ado pelo mecanismo de na base clo envelope c 0 fl V C C t V 0, C t r a ri S p 0 r t a d C) p a r a a S LI p e r f C 1 e p e I a Instabllidade de boiament 0 na ase de Haya hi. Campos cibservados permit em est imar uma perda de momento durante a ase pr -Seque%nC:ia P r ri C: p a I a ci ni p a t V C I C: C) m a s C) b s e r V a nT C 5. E S t r C I a S A normals, que ro t a ao , ria0 most ram camp Os :os superficia; importantes e isto pode ac:oriteaer C LIma protoestrela evolue para Sequencia Principal em passar pela fase de Hayashi. ABSTRACT: It 5 proposed that the ma9netic field o Ap stars may be enerated by the dynamo at the base of the convective envelope, arid transported to the surface b y t h C i ri s t a b iii t y C) f b LI 0 y a n c y i n t h C H a y a s hi p h a s e. Observed surface ma9netic fields allow to estimate a 1055 of an9ular momentum during the pre-Main Sequence phase compatible with the observations. apidIy rotating normal A stars do not shciw important surface magnetic fields and this may occur if a protostar evcilves to Main Sequence skipping the Hayashi phase. Key words: HYDROMAGNETICS - STARS-PECULIAR A
Wide-field Monitoring of the Galactic Plane in the K- and the H-band
NASA Astrophysics Data System (ADS)
Yanagisawa, K.; Nakada, Y.; Izumiura, H.; Watanabe, E.; Shimizu, Y.; Okada, N.; Okita, K.; Norimoto, K.; Okata, T.; Koyano, H.; Yoshida, M.
The Okayama Astrophysical Observatory of NAOJ started the monitoring program of mass-losing AGB stars using an imaging camera named Okayama Astrophysical Observatory Wide Field Camera. The fast optics yields a field of view of 1¡ß1 deg2 and the pixel resolution of 2 arcsec at the focus of the 91-cm telescope. A HAWAII2 array will be installed inside the camera reaching the limiting magnitude of K=13 with a 45-s exposure. In 2003 the monitoring will start covering the Galactic plane from l=0 to 270 deg every three weeks.
Orientational dynamics of a ferronematic liquid crystal in a rotating magnetic field
Boychuk, A. N. Zakhlevnykh, A. N.; Makarov, D. V.
2015-09-15
The behavior of the orientational structure of a ferronematic in a rotating uniform magnetic field is investigated using the continual theory. The time-dependent system of equations describing the dynamics of the ferronematic is derived. The dependences of the angles of rotation of the director and of the magnetization of the ferronematic on the velocity of field rotation are determined for various values of the material parameters. Two regimes (synchronous and asynchronous) of rotation of the ferronematic structure are detected. In the synchronous regime, the director rotates with the frequency of the magnetic field and a constant phase delay. The asynchronous regime is characterized by a time-dependent phase delay. The dependence of the critical angular velocity of magnetic field rotation, which determines the boundary between the synchronous and asynchronous regimes, on the magnetic field strength is derived.
Hildreth, Owen J; Rykaczewski, Konrad; Fedorov, Andrei G; Wong, Ching P
2013-02-01
Metal-assisted Chemical Etching of silicon has recently emerged as a powerful technique to fabricate 1D, 2D, and 3D nanostructures in silicon with high feature fidelity. This work demonstrates that out-of-plane rotational catalysts utilizing polymer pinning structures can be designed with excellent control over rotation angle. A plastic deformation model was developed establishing that the catalyst is driven into the silicon substrate with a minimum pressure differential across the catalyst thickness of 0.4-0.6 MPa. Force-displacement curves were gathered between an Au tip and Si or SiO(2) substrates under acidic conditions to show that Derjaguin and Landau, Verwey and Overbeek (DLVO) based forces are capable of providing restorative forces on the order of 0.2-0.3 nN with a calculated 11-18 MPa pressure differential across the catalyst. This work illustrates that out-of-plane rotational structures can be designed with controllable rotation and also suggests a new model for the driving force for catalyst motion based on DLVO theory. This process enables the facile fabrication of vertically aligned thin-film metallic structures and scalloped nanostructures in silicon for applications in 3D micro/nano-electromechanical systems, photonic devices, nanofluidics, etc.
3-D explosions: a meditation on rotation (and magnetic fields)
NASA Astrophysics Data System (ADS)
Wheeler, J. C.
This is the text of an introduction to a workshop on asymmetric explosions held in Austin in June, 2003. The great progress in supernova research over thirty-odd years is briefly reviewed. The context in which the meeting was called is then summarized. The theoretical success of the intrinsically multidimensional delayed detonation paradigm in explaining the nature of Type Ia supernovae coupled with new techniques of observations in the near IR and with spectropolarimetry promise great advances in understanding binary progenitors, the explosion physics, and the ever more accurate application to cosmology. Spectropolarimetry has also revealed the strongly asymmetric nature of core collapse and given valuable perspectives on the supernova - gamma-ray burst connection. The capability of the magneto-rotational instability to rapidly create strong toroidal magnetic fields in the core collapse ambiance is outlined. This physics may be the precursor to driving MHD jets that play a role in asymmetric supernovae. Welcome to the brave new world of three-dimensional explosions!
Kiapour, Ata M.; Kiapour, Ali; Goel, Vijay K.; Quatman, Carmen E.; Wordeman, Samuel C.; Hewett, Timothy E.; Demetropoulos, Contantine K.
2015-01-01
Despite general agreement on the effects of knee valgus and internal tibial rotation on anterior cruciate (ACL) loading, compelling debate persists on the interrelationship between these rotations and how they contribute to the multi-planar ACL injury mechanism. This study investigates coupling between knee valgus and internal tibial rotation and their effects on ACL strain as a quantifiable measure of injury risk. Nineteen instrumented cadaveric legs were imaged and tested under a range of knee valgus and internal tibial torques. Posterior tibial slope and the medial tibial depth, along with changes in tibiofemoral kinematics and ACL strain, were quantified. Valgus torque significantly increased knee valgus rotation and ACL strain (p<0.02), yet generated minimal coupled internal tibial rotation (p=0.537). Applied internal tibial torque significantly increased internal tibial rotation and ACL strain and generated significant coupled knee valgus rotation (p<0.001 for all comparisons). Similar knee valgus rotations (7.3° vs 7.4°) and ACL strain levels (4.4% vs 4.9%) were observed under 50 N-m of valgus and 20 N-m of internal tibial torques, respectively. Coupled knee valgus rotation under 20 N-m of internal tibial torque was significantly correlated with internal tibial rotation, lateral and medial tibial slopes, and medial tibial depth (R2>0.30; p<0.020). These findings demonstrate uni-directional coupling between knee valgus and internal tibial rotation in a cadaveric model. Although both knee valgus and internal tibial torques contribute to increased ACL strain, knee valgus rotation has the ultimate impact on ACL strain regardless of loading mode. PMID:26070647
Kiapour, Ata M; Kiapour, Ali; Goel, Vijay K; Quatman, Carmen E; Wordeman, Samuel C; Hewett, Timothy E; Demetropoulos, Constantine K
2015-07-16
Despite general agreement on the effects of knee valgus and internal tibial rotation on anterior cruciate ligament (ACL) loading, compelling debate persists on the interrelationship between these rotations and how they contribute to the multi-planar ACL injury mechanism. This study investigates coupling between knee valgus and internal tibial rotation and their effects on ACL strain as a quantifiable measure of injury risk. Nineteen instrumented cadaveric legs were imaged and tested under a range of knee valgus and internal tibial torques. Posterior tibial slope and the medial tibial depth, along with changes in tibiofemoral kinematics and ACL strain, were quantified. Valgus torque significantly increased knee valgus rotation and ACL strain (p<0.020), yet generated minimal coupled internal tibial rotation (p=0.537). Applied internal tibial torque significantly increased internal tibial rotation and ACL strain and generated significant coupled knee valgus rotation (p<0.001 for all comparisons). Similar knee valgus rotations (7.3° vs 7.4°) and ACL strain levels (4.4% vs 4.9%) were observed under 50 Nm of valgus and 20 Nm of internal tibial torques, respectively. Coupled knee valgus rotation under 20 Nm of internal tibial torque was significantly correlated with internal tibial rotation, lateral and medial tibial slopes, and medial tibial depth (R(2)>0.30; p<0.020). These findings demonstrate uni-directional coupling between knee valgus and internal tibial rotation in a cadaveric model. Although both knee valgus and internal tibial torques contribute to increased ACL strain, knee valgus rotation has the ultimate impact on ACL strain regardless of loading mode.
Laboratory and field testing of commercial rotational seismometers
Nigbor, R.L.; Evans, J.R.; Hutt, C.R.
2009-01-01
There are a small number of commercially available sensors to measure rotational motion in the frequency and amplitude ranges appropriate for earthquake motions on the ground and in structures. However, the performance of these rotational seismometers has not been rigorously and independently tested and characterized for earthquake monitoring purposes as is done for translational strong- and weak-motion seismometers. Quantities such as sensitivity, frequency response, resolution, and linearity are needed for the understanding of recorded rotational data. To address this need, we, with assistance from colleagues in the United States and Taiwan, have been developing performance test methodologies and equipment for rotational seismometers. In this article the performance testing methodologies are applied to samples of a commonly used commercial rotational seismometer, the eentec model R-1. Several examples were obtained for various test sequences in 2006, 2007, and 2008. Performance testing of these sensors consisted of measuring: (1) sensitivity and frequency response; (2) clip level; (3) self noise and resolution; and (4) cross-axis sensitivity, both rotational and translational. These sensor-specific results will assist in understanding the performance envelope of the R-1 rotational seismometer, and the test methodologies can be applied to other rotational seismometers.
NASA Astrophysics Data System (ADS)
Mori, Hiroshi; Asahara, Yousuke
1996-03-01
We analyze the linearity and modulation depth of ac magnetic-field sensors or current sensors, using a ferrimagnetic or ferromagnetic film as the Faraday rotator and employing the detection of only the zeroth-order optical diffraction component from the rotator. It is theoretically shown that for this class of sensor the condition of a constant modulation depth and that of a constant ratio error give an identical series of curves for the relationship between Faraday rotation angle greater than or equals V and polarizer/analyzer relative angle Phi . We give some numerical examples to demonstrate the usefulness of the result with reference to a rare-earth iron garnet film as the rotator.
Calculation of the electric field resulting from human body rotation in a magnetic field
NASA Astrophysics Data System (ADS)
Cobos Sánchez, Clemente; Glover, Paul; Power, Henry; Bowtell, Richard
2012-08-01
A number of recent studies have shown that the electric field and current density induced in the human body by movement in and around magnetic resonance imaging installations can exceed regulatory levels. Although it is possible to measure the induced electric fields at the surface of the body, it is usually more convenient to use numerical models to predict likely exposure under well-defined movement conditions. Whilst the accuracy of these models is not in doubt, this paper shows that modelling of particular rotational movements should be treated with care. In particular, we show that v × B rather than -(v · ∇)A should be used as the driving term in potential-based modelling of induced fields. Although for translational motion the two driving terms are equivalent, specific examples of rotational rigid-body motion are given where incorrect results are obtained when -(v · ∇)A is employed. In addition, we show that it is important to take into account the space charge which can be generated by rotations and we also consider particular cases where neglecting the space charge generates erroneous results. Along with analytic calculations based on simple models, boundary-element-based numerical calculations are used to illustrate these findings.
Uniform rotating field network structure to efficiently package a magnetic bubble domain memory
NASA Technical Reports Server (NTRS)
Wolfshagen, Ronald G. (Inventor); Ypma, John E. (Inventor); Murray, Glen W. (Inventor); Chen, Thomas T. (Inventor)
1978-01-01
A unique and compact open coil rotating magnetic field network structure to efficiently package an array of bubble domain devices is disclosed. The field network has a configuration which effectively enables selected bubble domain devices from the array to be driven in a vertical magnetic field and in an independent and uniform horizontal rotating magnetic field. The field network is suitably adapted to minimize undesirable inductance effects, improve capabilities of heat dissipation, and facilitate repair or replacement of a bubble device.
Rotational shear near the solar surface as a probe for subphotospheric magnetic fields
NASA Astrophysics Data System (ADS)
Kitchatinov, L. L.
2016-05-01
Helioseismology revealed an increase in the rotation rate with depth just beneath the solar surface. The relative magnitude of the radial shear is almost constant with latitude. This rotational state can be interpreted as a consequence of two conditions characteristic of the near-surface convection: the smallness of convective turnover time in comparison with the rotation period and absence of a horizontal preferred direction of convection anisotropy. The latter condition is violated in the presence of a magnetic field. This raises the question of whether the subphotospheric fields can be probed with measurements of near-surface rotational shear. The shear is shown to be weakly sensitive to magnetic fields but can serve as a probe for sufficiently strong fields of the order of one kilogauss. It is suggested that the radial differential rotation in extended convective envelopes of red giants is of the same origin as the near-surface rotational shear of the Sun.
Szkudlarek, Krzesimir; Sypek, Maciej; Cywiński, Grzegorz; Suszek, Jarosław; Zagrajek, Przemysław; Feduniewicz-Żmuda, Anna; Yahniuk, Ivan; Yatsunenko, Sergey; Nowakowska-Siwińska, Anna; Coquillat, Dominique; But, Dmytro B; Rachoń, Martyna; Węgrzyńska, Karolina; Skierbiszewski, Czesław; Knap, Wojciech
2016-09-01
We present the concept, the fabrication processes and the experimental results for materials and optics that can be used for terahertz field-effect transistor detector focal plane arrays. More specifically, we propose 3D printed arrays of a new type - diffractive multi-zone lenses of which the performance is superior to that of previously used mono-zone diffractive or refractive elements and evaluate them with GaN/AlGaN field-effect transistor terahertz detectors. Experiments performed in the 300-GHz atmospheric window show that the lens arrays offer both a good efficiency and good uniformity, and may improve the signal-to-noise ratio of the terahertz field-effect transistor detectors by more than one order of magnitude. In practice, we tested 3 × 12 lens linear arrays with printed circuit board THz detector arrays used in postal security scanners and observed significant signal-to-noise improvements. Our results clearly show that the proposed technology provides a way to produce cost-effective, reproducible, flat optics for large-size field-effect transistor THz-detector focal plane arrays.
Model for the growth of electrodeposited ferromagnetic aggregates under an in-plane magnetic field.
Cronemberger, C; Sampaio, L C; Guimarães, A P; Molho, P
2010-02-01
The quasi-two-dimensional deposition of ferromagnetic materials by electrochemical process under the influence of a magnetic field applied in the plane of the growth leads to a surprising symmetry breaking in the dendritic structures found. The reasons for these features are still not completely understood. The original dense circular envelope becomes rectangular, as well as the sparse figures have their shapes elongated. This paper reports the results of a diffusion-limited aggregation (DLA) -like simulation. The model proposed here, a modification of the original DLA model, can deal with ferromagnetic particles under the influence of an electric field and the dipolar interactions between particles, submitted to an applied magnetic field in the plane of growth of such structures. The results were produced varying the applied magnetic field and the magnetic moment of the particles and show that the balance between these interactions is an important mechanisms that can be responsible for the changes in shape of the aggregates observed in the experiments. PMID:20365564
Model for the growth of electrodeposited ferromagnetic aggregates under an in-plane magnetic field
NASA Astrophysics Data System (ADS)
Cronemberger, C.; Sampaio, L. C.; Guimarães, A. P.; Molho, P.
2010-02-01
The quasi-two-dimensional deposition of ferromagnetic materials by electrochemical process under the influence of a magnetic field applied in the plane of the growth leads to a surprising symmetry breaking in the dendritic structures found. The reasons for these features are still not completely understood. The original dense circular envelope becomes rectangular, as well as the sparse figures have their shapes elongated. This paper reports the results of a diffusion-limited aggregation (DLA) -like simulation. The model proposed here, a modification of the original DLA model, can deal with ferromagnetic particles under the influence of an electric field and the dipolar interactions between particles, submitted to an applied magnetic field in the plane of growth of such structures. The results were produced varying the applied magnetic field and the magnetic moment of the particles and show that the balance between these interactions is an important mechanisms that can be responsible for the changes in shape of the aggregates observed in the experiments.
Szkudlarek, Krzesimir; Sypek, Maciej; Cywiński, Grzegorz; Suszek, Jarosław; Zagrajek, Przemysław; Feduniewicz-Żmuda, Anna; Yahniuk, Ivan; Yatsunenko, Sergey; Nowakowska-Siwińska, Anna; Coquillat, Dominique; But, Dmytro B; Rachoń, Martyna; Węgrzyńska, Karolina; Skierbiszewski, Czesław; Knap, Wojciech
2016-09-01
We present the concept, the fabrication processes and the experimental results for materials and optics that can be used for terahertz field-effect transistor detector focal plane arrays. More specifically, we propose 3D printed arrays of a new type - diffractive multi-zone lenses of which the performance is superior to that of previously used mono-zone diffractive or refractive elements and evaluate them with GaN/AlGaN field-effect transistor terahertz detectors. Experiments performed in the 300-GHz atmospheric window show that the lens arrays offer both a good efficiency and good uniformity, and may improve the signal-to-noise ratio of the terahertz field-effect transistor detectors by more than one order of magnitude. In practice, we tested 3 × 12 lens linear arrays with printed circuit board THz detector arrays used in postal security scanners and observed significant signal-to-noise improvements. Our results clearly show that the proposed technology provides a way to produce cost-effective, reproducible, flat optics for large-size field-effect transistor THz-detector focal plane arrays. PMID:27607620
NASA Astrophysics Data System (ADS)
Thakur, R. C.; Rana, G. C.
2013-06-01
In this paper, we investigate the effect of a vertical magnetic field on thermal instability of an Oldroydian visco-elastic rotating fluid in a porous medium. By applying the normal mode analysis method, the dispersion relation governing the effects of rotation, magnetic field and medium permeability is derived and solved analytically and numerically. For the case of stationary convection, the Oldroydian viscoelastic fluid behaves like an ordinary Newtonian fluid and it is observed that rotation has a stabilizing effect while the magnetic field and medium permeability have a stabilizing/destabilizing effect under certain conditions on thermal instability of the Oldroydian viscoelastic fluid in a porous medium. The oscillatory modes are introduced due to the presence of rotation, the magnetic field and gravity field. It is also observed that the `principle of exchange of stability' is invalid in the presence of rotation and the magnetic field.
Teodorescu, C.; Young, W. C.; Swan, G. W. S.; Ellis, R. F.; Hassam, A. B.; Romero-Talamas, C. A.
2010-08-20
Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic ExB rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.
E-field extraction from Hx- and Hy- near field values by using plane wave spectrum method
NASA Astrophysics Data System (ADS)
Ravelo, B.; Riah, Z.; Baudry, D.; Mazari, B.
2011-01-01
This paper deals with a technique for calculating the 3D E-field components knowing only the two components (Hx and Hy) of the H-field in near-zone. The originality of the under study technique lies on the possibility to take into account the evanescent wave influences. The presented E-field extraction process is based on the exploitation of the Maxwell-Ampere relation combined with the plane wave spectrum (PWS) method. The efficiency of the proposed technique is evidenced by comparing the E-field deduced from H-field and the own E-field radiated by the association of electrical- and also magnetic- elementary dipoles in different configurations by using Matlab text programming environment. In addition, as a concrete demonstrator, the concept was also validated with the computation of EM-wave radiated by an open-end microstrip transmission line. As result of comparison, very good agreement between the exact E-field and that one extracted from the H-field was realized by considering the near-field scanned at the height, z = 5 mm and 8 mm above the under test structure at the operating frequency, f = 1 GHz. The presented technique can simplify the difficulties about the E-near-field measurement in EMC applications.
NASA Technical Reports Server (NTRS)
Pearson, J. C.; Pickett, Herbert M.; Sastry, K. V. L. N.
2000-01-01
C2H5CN (Propionitrile or ethyl cyanide) is a well known interstellar species abundantly observed in hot cores during the onset of star formation. The onset of star formation generally results in elevated temperature, which thermally populates may low lying vibrational states such as the 206/cm in-plane bend and the 212/cm first excited torsional state in C2H5CN. Unfortunately, these two states are strongly coupled through a complex series of torsion-vibration-rotation interactions, which dominate the spectrum. In order to understand the details of these interactions and develop models capable of predicting unmeasured transitions for astronomical observations in C2H5CN and similar molecules, several thousand rotational transitions in the lowest excited in-plane bend and first excited torsional state have been recorded, assigned and analyzed. The analysis reveals very strong a- and b-type Coriolis interactions and a number of other smaller interactions and has a number of important implications for other C3V torsion-rotation-vibration systems. The relative importance and the physical origins of the coupling among the rotational, vibrational and torsional motions will be presented along with a full spectroscopic analysis and supporting astronomical observations.
NASA Astrophysics Data System (ADS)
Dong, Dong; Zou, Xu-Bo; Guo, Guang-Can
2015-07-01
We studied the system of pure Rashba spin-orbit coupled Bose gas with an in-plane magnetic field. Based on the mean field theory, we obtained the zero temperature phase diagram of the system which exhibits three phases, plane wave (PW) phase, striped wave (SW) phase, and zero momentum (ZM) phase. It was shown that with a growing in-plane field, both SW and ZM phases will eventually turn into the PW phase. Furthermore, we adopted the Bogoliubov theory to study the excitation spectrum as well as the sound speed. Project supported by the National Natural Science Foundation of China (Grant No. 10774088).
NASA Astrophysics Data System (ADS)
Sobolewski, P.; Krzyścin, J. W.; Jarosławski, J.; Stebel, K.
2008-01-01
Erythemaly weighted UV and total UVA irradiance measured at the ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research; 69° N, 16° E) in June 2007 by two Kipp & Zonen UV broadband meters type, UV-S-AE-T, are examined. One unit is movable and mounted to rotating vertical plane, and the other is permanently fixed horizontally. The UV broadband meters measure simultaneously to allow the comparison of UV irradiances on vertical and horizontal plane. The entire range of relative exposure variations during clear-sky conditions over ALOMAR is examined using STAR and Radonic1 model (developed at the Meteorological Institute, Munich) for various action spectra (erythema, UVA, and vitamin D3). It seems that multiplication of the daily mean dose from a standard broadband meter placed horizontally by 0.5 gives reasonable estimation of the daily mean exposure on a vertical plane randomly oriented towards Sun. The extreme value and daily variability of relative exposure are the highest for UVA, next for UVB, then for vitamin D3 weighed UV irradiance. The minima of relative exposure (~0.20-0.30) are almost the same for all weighting functions. Specific cloud configuration could lead to significant enhancement of UV relative exposure of rotating plane being the most pronounced when biometer is in shadow. A statistical model is proposed, that it is able to simulate vitamin D3 weighted UV irradiances on vertical surface using explanatory variables: erythemal and total UVA irradiance from standard (horizontal) observations by Kipp & Zonen dual band biometer, the orientation of vertical plane, solar zenith angle, and column amount of total ozone. Statistical model will allow to reconstruct (or monitor) vitamin D3 weighted UV irradiances using available past (or actual) data.
A discussion of Bl conservation on a two dimensional magnetic field plane in watt balances
NASA Astrophysics Data System (ADS)
Li, Shisong; Zhao, Wei; Huang, Songling
2016-05-01
The watt balance is an experiment being pursued in national metrology institutes for precision determination of the Planck constant h. In watt balances, the 1/r magnetic field, expected to generate a geometrical factor Bl independent to any coil horizontal displacement, can be created by a strict two dimensional, symmetric (horizontal r and vertical z) construction of the magnet system. In this paper, we present an analytical understanding of magnetic field distribution when the r symmetry of the magnet is broken and the establishment of the Bl conservation is shown. By using either Gauss’s law on magnetism with monopoles or conformal transformations, we extend the Bl conservation to arbitrary two dimensional magnetic planes where the vertical magnetic field component equals zero. The generalized Bl conservation allows a relaxed physical alignment criteria for watt balance magnet systems.
Non-minimally coupled scalar field cosmology on the phase plane
Hrycyna, Orest; Szydlowski, Marek E-mail: uoszydlo@cyf-kr.edu.pl
2009-04-15
In this publication we investigate dynamics of a flat FRW cosmological model with a non-minimally coupled scalar field with the coupling term {xi}R{psi}{sup 2} in the scalar field action. The quadratic potential function V({psi}) {proportional_to} {psi}{sup 2} is assumed. All the evolutional paths are visualized and classified in the phase plane, at which the parameter of non-minimal coupling {xi} plays the role of a control parameter. The fragility of global dynamics with respect to changes of the coupling constant is studied in details. We find that the future big rip singularity appearing in the phantom scalar field cosmological models can be avoided due to non-minimal coupling constant effects. We have shown the existence of a finite scale factor singular point (future or past) where the Hubble function as well as its first cosmological time derivative diverge.
On the smoothness of electric fields near plane gratings of cylindrical conductors
Judd, D.L.
1995-02-01
The electric field near an infinite plane grating of equally spaced round rods at the same potential, forming the boundary of a uniform field, is determined analytically to good accuracy by conformal transformations and evaluated numerically. This contribution, which has a frankly pedagogical flavor, to the Klaus Halbach Festschrift is offered to honor his displayed mastery of conformal techniques. Although the numerical work and the form of its presentation are new, the transformation used is not original. However, to locate its antecedents in an archival journal it was necessary to seek out a paper published in 1923 (close to the year of his birth, and of mine), in a place obscure to modern physicists, so the authors efforts cannot be said to replicate recent published work. A new insight is obtained in the form of a simple estimate of departures from field uniformity at all distances from rods of any size.
NASA Astrophysics Data System (ADS)
Kikuchi, Y.; de Bock, M. F. M.; Finken, K. H.; Jakubowski, M.; Jaspers, R.; Koslowski, H. R.; Kraemer-Flecken, A.; Lehnen, M.; Liang, Y.; Matsunaga, G.; Reiser, D.; Wolf, R. C.; Zimmermann, O.
2006-08-01
The magnetic field penetration process into a magnetized plasma is of basic interest both for plasma physics and astrophysics. In this context special measurements on the field penetration and field amplification are performed by a Hall probe on the dynamic ergodic divertor (DED) on the TEXTOR tokamak and the data are interpreted by a two-fluid plasma model. It is observed that the growth of the forced magnetic reconnection by the rotating DED field is accompanied by a change of the plasma fluid rotation. The differential rotation frequency between the DED field and the plasma plays an important role in the process of the excitation of tearing modes. The momentum input from the rotating DED field to the plasma is interpreted by both a ponderomotive force at the rational surface and a radial electric field modified by an edge ergodization.
Quantum tunneling from scalar fields in rotating black strings
NASA Astrophysics Data System (ADS)
Gohar, H.; Saifullah, K.
2013-08-01
Using the Hamilton-Jacobi method of quantum tunneling and complex path integration, we study Hawking radiation of scalar particles from rotating black strings. We discuss tunneling of both charged and uncharged scalar particles from the event horizons. For this purpose, we use the Klein-Gordon equation and find the tunneling probability of outgoing scalar particles. The procedure gives Hawking temperature for rotating charged black strings as well.
Guo, H.Y.; Hoffman, A.L.; Steinhauer, L.C.
2005-06-15
Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF B{sub {omega}} to external confinement field B{sub e}. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but vacuum calculations with full RMF penetration showed that very low values of B{sub {omega}}/B{sub e} would still be required to provide field-line closure. Recent comparisons of symmetric and antisymmetric RMF drive on the translation, confinement, and sustainment (TCS) facility [A. L. Hoffman, H. Y. Guo, J. T. Slough et al., Fusion Sci. Technol. 41, 92 (2002)] have shown strong improvements in the basic confinement properties of the FRCs when using antisymmetric drive, even with ratios of B{sub {omega}}/B{sub e} as high as 0.3. This is due to normal standard operation with only partial penetration of the RMF beyond the FRC separatrix. The uniform transverse RMF in vacuum is shielded by the conducting plasma, resulting in a mostly azimuthal field near the FRC separatrix with a very small radial component. Simple numerical calculations using analytical solutions for the partially penetrated antisymmetric RMF, superimposed on Grad-Shafranov solutions for the poloidal FRC fields, show good field-line closure for the TCS experimental conditions. The antisymmetric arrangement also leads to more efficient current drive and improved stabilization of rotational modes.
Force on a heated sphere in a horizontal plane acoustic standing wave field
NASA Technical Reports Server (NTRS)
Leung, E. W.; Wang, T. G.
1985-01-01
The force on a heated sphere in a horizontal plane acoustic standing wave field is the subject of this investigation. The heated sphere produces a thermal gradient in the resonance chamber. The force on the sphere in a direction perpendicular to that of gravity is measured. This force is enhanced in the region near the pressure node, and is weakened in the region near the pressure antinode. Measurements of the force on a heated sphere with sound pressure levels between 148 and 156 dB are presented.
Stable oscillation in spin torque oscillator excited by a small in-plane magnetic field
Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Ito, Takahiro; Utsumi, Yasuhiro
2015-08-07
Theoretical conditions to excite self-oscillation in a spin torque oscillator consisting of a perpendicularly magnetized free layer and an in-plane magnetized pinned layer are investigated by analytically solving the Landau-Lifshitz-Gilbert equation. The analytical relation between the current and oscillation frequency is derived. It is found that a large amplitude oscillation can be excited by applying a small field pointing to the direction anti-parallel to the magnetization of the pinned layer. The validity of the analytical results is confirmed by comparing with numerical simulation, showing good agreement especially in a low current region.
New method to determine proton trajectories in the equatorial plane of a dipole magnetic field.
Ioanoviciu, Damaschin
2015-01-01
A parametric description of proton trajectories in the equatorial plane of Earth's dipole magnetic field has been derived. The exact expression of the angular coordinate contains an integral to be performed numerically. The radial coordinate results from the initial conditions by basic mathematical operations and by using trigonometric functions. With the approximate angular coordinate formula, applicable for a wide variety of cases of protons trapped in Earth's radiation belts, no numerical integration is needed. The results of exact and approximate expressions were compared for a specific case and small differences were found.
NASA Technical Reports Server (NTRS)
Plummer, E. W.; Bell, A. E.
1972-01-01
Total energy distributions of field emitted electrons from the tungsten (110) and (100) planes as a function of coverage by hydrogen and deuterium have been recorded utilizing a spherical deflection energy analyzer. The elastic tunneling resonance spectrum gives a plot of the 'local density of states' in the adsorbate. The inelastic tunneling spectrum reveals those discrete excitation energies available in the adsorbate-substrate complex. These spectroscopic data have been used to infer the chemical nature of the binding states which have been observed in the flash desorption spectrum of hydrogen from tungsten.
The Effect of a Rotating Magnetic Field on Flow Stability During Crystal Growth
NASA Technical Reports Server (NTRS)
Volz, Martin P.; Mazuruk, K.
2000-01-01
The effect of a rotating magnetic field on the stability of flow in crystal growth configurations has been experimentally modeled using liquid gallium contained in a finite cylinder and heated from below. Several distinct flow regions were determined as a function of the Rayleigh and Hartmann numbers. At low values of the Rayleigh and Hartmann numbers, a region of stationary flow exists. As the rotating magnetic field is increased, the critical Rayleigh number bounding the stationary flow region can increase by a factor of 10. However, the rotating magnetic field itself induces an instability at a critical value of the Hartmann number independent of the Rayleigh number. In the stationary flow region, the rotating magnetic field can induce fluid motion with velocities several orders of magnitude larger than typical semiconductor crystal growth velocities. Thus, a rotating magnetic field can be used to achieve the benefits of forced convection without triggering deleterious instabilities.
High-quality InN films on MgO (100) substrates: The key role of 30° in-plane rotation
Compeán García, V. D.; López Luna, E.; Rodríguez, A. G.; Vidal, M. A.; Orozco Hinostroza, I. E.; Escobosa Echavarría, A.
2014-05-12
High crystalline layers of InN were grown on MgO(100) substrates by gas source molecular beam epitaxy. Good quality films were obtained by means of an in-plane rotation process induced by the annealing of an InN buffer layer to minimize the misfit between InN and MgO. In situ reflection high-energy electron diffraction showed linear streaky patterns along the [011{sup ¯}0] azimuth and a superimposed diffraction along the [112{sup ¯}0] azimuth, which correspond to a 30° α-InN film rotation. This rotation reduces the mismatch at the MgO/InN interface from 19.5% to less than 3.5%, increasing the structural quality, which was analyzed by high-resolution X-ray diffraction and Raman spectroscopy. Only the (0002) c plane diffraction of α-InN was observed and was centered at 2θ = 31.4°. Raman spectroscopy showed two modes corresponding to the hexagonal phase: E1(LO) at 591 cm{sup −1} and E2(high) at 488 cm{sup −1}. Hall effect measurements showed a carrier density of 9 × 10{sup 18} cm{sup −3} and an electron Hall mobility of 340 cm{sup 2}/(V s) for a film thickness of 140 nm.
Flow field and thermal characteristics induced by a rotationally oscillating heated flat plate
NASA Astrophysics Data System (ADS)
Koffi, Moise
The objective of this dissertation is the study the flow and heat transfer in the vicinity of a rectangular flat heated plate of subject to rotational oscillations. Of interest is the effect of the flow field on the thermal characteristics of the plate's surface. A constant heat flux is applied to both sides while the plate is rotated about a fixed edge at a frequency of 2 rad/s in an infinite domain at atmospheric pressure. A computational simulation of the flow with FLUENT reveals a hooked-shape vortex tube around the free edges of the plate, which is confirmed by the flow visualization with smoke particles. During the flapping cycle, vortices form and grow progressively on one face while they shed from the opposite, until they are completely detached from both surfaces at stroke reversal. A data acquisition system uses a numerical computing and programming software (MATLAB) to track the surface temperature recorded by J- type thermocouples at desired locations on the plate. Both experimental and computational results agree with local surface temperature profiles characterized by a transient unsteady periodic variation followed by a steady periodic phase. These characteristics are symmetrical about the median plane of the plate, which is normal to its axis of rotation. The cooling rate of the surface, proportional to the frequency of rotation, depends on the angular position of the plate and the spatial location on the plate's surface. However, the highest heat transfer coefficient is recorded at free edges, especially in the corners swept by strong tip vortices shedding in two orthogonal directions. Conclusions of the present study are used to explain the role of ear flapping in the metabolic heat regulation of large mammals such as elephants. Flow visualization and surface temperature measurements of full size rigid and flexible elephant ear-shape models were carried out. Results indicate improved interaction between the shedding vortex and the model's boundary
Luminescence of double quantum wells subject to in-plane magnetic fields
NASA Astrophysics Data System (ADS)
Orlita, M.; Grill, R.; Hlídek, P.; Zvára, M.; Döhler, G. H.; Malzer, S.; Byszewski, M.
2005-10-01
We report on photoluminescence (PL) measurements of a symmetric GaAs/AlGaAs double quantum well (DQW) in high magnetic fields. For this study, a selectively contacted p-δn-DQW-δn-p structure was chosen, allowing an independent tuning of the electron density in the DQW and thus a creation of a two-dimensional electron gas. Our attention was focused on phenomena in in-plane magnetic fields, where the field-induced depopulation of the antibonding subband observable in the PL spectra as a so-called N -type kink was predicted by Huang and Lyo (HL) [Phys. Rev. B 59, 7600 (1999)]. Whereas the equivalent behavior has been observed several times in the electric transport measurements and a proper theoretical description has been found, to the best of our knowledge, no PL experiment in a direct comparison with the theoretical model developed by HL has ever been published. We carried out a self-consistent calculation based on their model and achieved a good agreement with our experimental results. Additionally, the influence of the excitonic interaction on the PL spectra, not taken into account by HL, is also discussed. This enables us to explain small deviations from the HL theory. The interpretation of the in-plane magnetic field measurements is supported by the experiment with the magnetic field in the perpendicular orientation that allows a sufficiently accurate estimation of the electron density in the DQW. Distinctive renormalization effects of DQW subbands at various electron densities are also observed and discussed.
NASA Astrophysics Data System (ADS)
Hildreth, Owen J.; Rykaczewski, Konrad; Fedorov, Andrei G.; Wong, Ching P.
2013-01-01
Metal-assisted Chemical Etching of silicon has recently emerged as a powerful technique to fabricate 1D, 2D, and 3D nanostructures in silicon with high feature fidelity. This work demonstrates that out-of-plane rotational catalysts utilizing polymer pinning structures can be designed with excellent control over rotation angle. A plastic deformation model was developed establishing that the catalyst is driven into the silicon substrate with a minimum pressure differential across the catalyst thickness of 0.4-0.6 MPa. Force-displacement curves were gathered between an Au tip and Si or SiO2 substrates under acidic conditions to show that Derjaguin and Landau, Verwey and Overbeek (DLVO) based forces are capable of providing restorative forces on the order of 0.2-0.3 nN with a calculated 11-18 MPa pressure differential across the catalyst. This work illustrates that out-of-plane rotational structures can be designed with controllable rotation and also suggests a new model for the driving force for catalyst motion based on DLVO theory. This process enables the facile fabrication of vertically aligned thin-film metallic structures and scalloped nanostructures in silicon for applications in 3D micro/nano-electromechanical systems, photonic devices, nanofluidics, etc.Metal-assisted Chemical Etching of silicon has recently emerged as a powerful technique to fabricate 1D, 2D, and 3D nanostructures in silicon with high feature fidelity. This work demonstrates that out-of-plane rotational catalysts utilizing polymer pinning structures can be designed with excellent control over rotation angle. A plastic deformation model was developed establishing that the catalyst is driven into the silicon substrate with a minimum pressure differential across the catalyst thickness of 0.4-0.6 MPa. Force-displacement curves were gathered between an Au tip and Si or SiO2 substrates under acidic conditions to show that Derjaguin and Landau, Verwey and Overbeek (DLVO) based forces are capable of
THE ROTATION PROFILE OF SOLAR MAGNETIC FIELDS BETWEEN {+-}60 Degree-Sign LATITUDES
Shi, X. J.; Xie, J. L.
2013-08-10
Through a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields from Carrington Rotation Nos. 1625 to 2129 (from 1975 February to 2012 October), the sidereal rotation rates of solar magnetic fields between {+-}60 Degree-Sign latitudes are investigated. It seems that the temporal variation of rotation rates should be related to the solar cycle phase. The rotation profile of magnetic fields is obtained: the sidereal rotation rates decrease from the equator to mid-latitude and reach their minimum values of about 13.16 deg day{sup -1} (13.17 deg day{sup -1}) at 53 Degree-Sign (54 Degree-Sign ) latitude in the northern (southern) hemisphere, then increase toward higher latitudes. This rotation profile is different from the differential rotation law obtained by Snodgrass from a cross-correlation analysis of daily magnetograms, in which the rotation rates show a steep decrease from the equator to the poles. However, it is much closer to the quasi-rigid rotation law derived by Stenflo from an auto-correlation analysis of daily magnetograms. Some possible interpretations are discussed for the resulting rotation profile.
Influence of field size on a PTW type 23342 plane-parallel ionization chamber's response
Austerlitz, C.; Villar, H.P.; Santos, M.A.P.
2004-12-01
The response of a PTW type 23342 plane-parallel ionization chamber, both in air and in phantom, was evaluated for x-ray tube potentials between 30 and 100 kV and radiation field diameters ranging from 30 to 70 mm. The experiments were performed with a calibrated Pantak x-ray machine and made use of the same set of x-ray qualities adopted by the PTB primary laboratory for the calibration of such chambers. A Plexiglas registered phantom (1.18 g cm{sup -3}) 110 mm long, 110 mm wide, and 80 mm deep was used for phantom measurements. X-ray qualities were characterized by using 99.99% pure aluminum filters. On the basis of the IAEA's TRS 398, the article discusses the dependence of the plane-parallel ionization chamber readings with field size in air and in phantom, its implication with regard to clinical dosimetry, cross-calibration, and dissemination of calibration factors.
Truncation planes from a dilute pyroclastic density current: field data and analogue experiments.
NASA Astrophysics Data System (ADS)
Douillet, Guilhem Amin; Gegg, Lukas; Mato, Celia; Kueppers, Ulrich; Dingwell, Donald B.
2016-04-01
Pyroclastic density currents (PDCs) are a catastrophic transport mode of ground hugging gas-particle mixtures associated with explosive volcanic eruptions. The extremely high sedimentation rates and turbulence levels of these particulate density currents can freeze and preserve dynamic phenomena that happen but are not recorded in other sedimentary environments. Several intriguing and unanticipated features have been identified in outcrops and reproduced via analogue experiments, with the potential to change our views on morphodynamics and particle motion. Three types of small-scale (ca. 10 cm) erosion structures were observed on the stoss side of dune bedforms in the field: 1) vertical erosion planes covered with stoss-aggrading, vertical lamination, 2) overturned laminations at the preserved limit of erosion planes and 3) loss of stratification at erosion planes. These features are interpreted to indicate rapidly evolving velocities, undeveloped boundary layers, and a diffuse zone rather than a sharp border defining the flow-bed interface. Most experimental work on particle motion and erosion from the literature has been accomplished under constant conditions and with planar particle beds. Here, in order to reproduce the field observations, short-lived air-jets generated with a compressor-gun were shot into stratified beds of coarse particles (300 μm) of low density (1000 kg/m3). These "eroding jets" were filmed with a high speed camera and the deposits were sectioned after the experiments. The three natural types of erosion characteristics were experimentally generated. Vertical erosion planes are produced by small-scale, relatively sustained jets. Overturned laminations are due to a fluidization-like behavior at the erosion front of short-lived, strong jets, demonstrating that the fluid's velocity profile penetrates into the deposit. Loss of lamination seems related to the nature of erosion onset in packages. Rather than providing simple answers, the dataset
Chatterjee, I; Gandhi, O P; Hagmann, M J; Riazi, A
1980-01-01
The exposure of humans to electromagnetic near fields has not been sufficiently emphasized by researcher. We have used the plane-wave-spectrum approach to evaluate the electromagnetic field and determine the energy deposited in a lossy, homogeneous, semi-infinite slab placed in the near field of a source leaking radiation. Values of the fields and absorbed energy in the target are obtained by vector summation of the contributions of all the plane waves into which the prescribed field is decomposed. Use of a fast Fourier transform algorithm contributes to the high efficiency of the computations. The numerical results show that, for field distributions that are nearly constant over a physical extent of at least a free-space wavelength, the energy coupled into the target is approximately equal to the resulting from plane-wave exposed.
Chatterjee, I.; Gandhi, O.P.; Hagmann, M.J.; Riazi, A.
1980-01-01
The exposure of humans to electromagnetic near fields has not been sufficiently emphasized by researcher. We have used the plane-wave-spectrum approach to evaluate the electromagnetic field and determine the energy deposited in a lossy, homogeneous, semi-infinite slab placed in the near field of a source leaking radiation. Values of the fields and absorbed energy in the target are obtained by vector summation of the contributions of all the plane waves into which the prescribed field is decomposed. Use of a fast Fourier transform algorithm contributes to the high efficiency of the computations. The numerical results show that, for field distributions that are nearly constant over a physical extent of at least a free-space wavelength, the energy coupled into the target is approximately equal to the resulting from plane-wave exposed.
Mizuki, Toru; Sawai, Miyuki; Nagaoka, Yutaka; Morimoto, Hisao; Maekawa, Toru
2013-01-01
We immobilize hydrolases such as lipase and chitinase on superparamagnetic particles, which are subjected to a rotational magnetic field, and measure the activities of the enzymes. We find that the activities of lipase and chitinase increase in the rotational magnetic field compared to those in the absence of a magnetic field and reach maximum at certain frequencies. The present methodology may well be utilized for the design and development of efficient micro reactors and micro total analysis systems (μ-TASs). PMID:23799111
Apparatus and method for generating a magnetic field by rotation of a charge holding object
Gerald, II, Rex E.; Vukovic, Lela; Rathke, Jerome W.
2009-10-13
A device and a method for the production of a magnetic field using a Charge Holding Object that is mechanically rotated. In a preferred embodiment, a Charge Holding Object surrounding a sample rotates and subjects the sample to one or more magnetic fields. The one or more magnetic fields are used by NMR Electronics connected to an NMR Conductor positioned within the Charge Holding Object to perform NMR analysis of the sample.
The sound field of a rotating monopole in a plug flow
NASA Astrophysics Data System (ADS)
Belyaev, I. V.
2016-07-01
A theoretical study is performed on the sound field generated by a rotating point monopole in a jet flow, the mixing layer of which is simulated by a velocity discontinuity. Its sound in the far field is compared to the sound field generated by a rotating monopole in a uniform flow in the absence of a velocity discontinuity, which makes it possible to estimate the size of the sound refraction effect.
NASA Astrophysics Data System (ADS)
Zhao, Qiang
2016-02-01
Motivated by recent experiments carried out by Spielman's group at NIST, we study the vortex formation in a rotating Bose-Einstein condensate in synthetic magnetic field confined in a harmonic potential combined with an optical lattice. We obtain numerical solutions of the two-dimensional Gross-Pitaevskii equation and compare the vortex formation by synthetic magnetic field method with those by rotating frame method. We conclude that a large angular momentum indeed can be created in the presence of the optical lattice. However, it is still more difficult to rotate the condensate by the synthetic magnetic field than by the rotating frame even if the optical lattice is added, and the chemical potential and energy remain almost unchanged by increasing rotational frequency.
Frame-dragging effects on magnetic fields near a rotating black hole
NASA Astrophysics Data System (ADS)
Karas, V.; Kopáček, O.; Kunneriath, D.
2012-07-01
We discuss the role of general relativity frame dragging acting on magnetic field lines near a rotating (Kerr) black hole. Near ergosphere the magnetic structure becomes strongly influenced and magnetic null points can develop. We consider aligned magnetic fields as well as fields inclined with respect to the rotation axis, and the two cases are shown to behave in profoundly different ways. Further, we construct surfaces of equal values of local electric and magnetic intensities, which have not yet been discussed in the full generality of a boosted rotating black hole.
Near-field coupling model between PCB and grounded transmission line based on plane wave spectrum
NASA Astrophysics Data System (ADS)
Leseigneur, Christelle; Baudry, David; Ravelo, Blaise; Louis, Anne
2013-10-01
This article presents an explicit model of electromagnetic (EM) coupling between electronic circuits and metallic wire placed above the ground plane. The model is based on the interaction between the EM near-field (NF) that has been treated with plane wave spectrum (PWS) and the Taylor model. The routine process illustrating the methodology is addressed is this article. The practicability of the model developed was upheld with different analytical and real demonstrators. First, the NF coupling between a straight transmission line (TL) and 1 GHz Wilkinson power divider (PWD) designed and implemented in planar technology was provided. Subsequently, simulations with a powerful commercial tool and measurements from 0.2 GHz to 2 GHz revealed a good agreement between the coupling voltages from the proposed model. As a second proof of concept, a printed circuit board incorporating a 40 MHz RF oscillator was placed 5 mm above the grounded TL. Once again, coupling voltages matched measurements were observed with magnitude relative difference lower than 5 dB. The hereby model presents huge benefits not only in terms of flexibility in the design process but it can also be run with very less computation time compared to the existing standard simulators. The model can be potentially a good candidate for investigating complex systems EMC engineering.
Scaling of plane-wave functions in statistically optimized near-field acoustic holography.
Hald, Jørgen
2014-11-01
Statistically Optimized Near-field Acoustic Holography (SONAH) is a Patch Holography method, meaning that it can be applied in cases where the measurement area covers only part of the source surface. The method performs projections directly in the spatial domain, avoiding the use of spatial discrete Fourier transforms and the associated errors. First, an inverse problem is solved using regularization. For each calculation point a multiplication must then be performed with two transfer vectors--one to get the sound pressure and the other to get the particle velocity. Considering SONAH based on sound pressure measurements, existing derivations consider only pressure reconstruction when setting up the inverse problem, so the evanescent wave amplification associated with the calculation of particle velocity is not taken into account in the regularized solution of the inverse problem. The present paper introduces a scaling of the applied plane wave functions that takes the amplification into account, and it is shown that the previously published virtual source-plane retraction has almost the same effect. The effectiveness of the different solutions is verified through a set of simulated measurements. PMID:25373969
In situ biaxial rotation at low-temperatures in high magnetic fields
Selby, N. S.; Crawford, M.; Tracy, L.; Reno, J. L.; Pan, W.
2014-09-15
We report the design, construction, and characterization of a biaxial sample rotation stage for use in a cryogenic system for orientation-dependent studies of anisotropic electronic transport phenomena at low temperatures and high magnetic fields. Our apparatus allows for continuous rotation of a sample about two axes, both independently and simultaneously.
Rotation of the photospheric magnetic fields: A north-south asymmetry
NASA Technical Reports Server (NTRS)
Antonucci, E.; Hoeksema, J. T.; Scherrer, P. H.
1989-01-01
During most of solar cycle 21 the large-scale photospheric field rotated more rapidly in the Northern Hemisphere than in the southern. The large-scale northern field rotated with a 26.9 day period (synodic), was centered at 15 degress N, and covered a latitude zone about 24 degrees wide. The large-scale southern field rotated with a periodicity of 28.1 days, was centered at 26 degrees S, and covered a latitude zone about 32 degrees wide. Our analysis showed rotational power at only a few discrete latitudes and frequencies in each hemisphere. The center of each peak lies near the sunspot differential rotation curve. The largest scale field contributes to the configuration of the coronal and interplanetary magnetic field (IMF). The strength of the first harmonic of the northern field suggests that this structure may be related to the 4-sector pattern observed in the IMF polarity. The southern field had much lower power at the first harmonic of the solar rotation rate and so would contribute only to a 2-sector structure in the IMF. These results were discovered in Fourier analysis of photospheric synoptic charts obtained at the Wilcox Solar Observatory from 1976 to 1986 and confirmed in higher resolution maps from the National Solar Observatory. Mt. Wilson magnetic field measurements from solar cycle 20 show a similar north-south asymmetry.
Simulation Studies of Field-Reversed Configurations with Rotating Magnetic Field Current Drive
NASA Astrophysics Data System (ADS)
Belova, E. V.; Davidson, R. C.
2008-11-01
Results of 3D kinetic simulations of rotating magnetic field (RMF) current drive in field-reversed configuration (FRC) are presented. Self-consistent hybrid simulations have been performed using the HYM code for even- and odd-parity RMF and different FRC parameters and RMF frequencies. Simulations show that the RMF pushes the plasma radially inward, resulting in a reduced plasma density outside separatrix. Lower plasma density and larger RMF amplitudes result in faster RMF field penetration, in agreement with previous two-fluid studies. Generation of axisymmetric toroidal magnetic field during the RMF current drive has been observed. Numerical study of the effects of the applied RMF field on particle confinement shows that the rate of particle losses increases for RMF frequency close to the ion cyclotron frequency. It is also shown that high-frequency even-parity RMF reduces ion losses when it is fully penetrated. It is also found that fully-penetrated, odd-parity RMF forces particles away from the midplane toward the FRC ends. The observed changes in particle confinement are related to ponderomotive forces. Partially penetrated RMF results in mostly radial ponderomotive forces which improve particle confinement in both cases.
Jalali, Mahdi; Sedghi, Tohid; Shafei, Shahin
2014-01-01
A novel configuration of a printed monopole antenna with a very compact size for satisfying WLAN operations at the 5.2/5.8 GHz and also for X-band operations at the 10 GHz has been proposed. The antenna includes a simple square-shaped patch as the radiator, the rotated U-shaped conductor back plane element with embedded strip on it, and the partial rectangular ground surface. By using the rotated U-shaped conductor-backed plane with proper values, good impedance matching and improvement in bandwidth can be achieved, at the lower and upper bands. The impedance bandwidth for S11 < -10 dB is about 1.15 GHz for 5 GHz band and 5.3 GHz for X-band. The measured peak gains are about 1.9 dBi at WLAN-band and 4.2 dBi at X-band. The experimental results represent that the realized antenna with good omnidirectional radiation characteristics, enough impedance bandwidth, and reasonable gains can be appropriate for various applications of the future developed technologies and handheld devices. PMID:24711732
NASA Astrophysics Data System (ADS)
Popkov, A. F.; Kulagin, N. E.; Soloviov, S. V.; Sukmanova, K. S.; Gareeva, Z. V.; Zvezdin, A. K.
2015-10-01
The room temperature multiferroic BiFeO3, by far the most studied experimentally, exhibits outstanding ferroelectric properties with a cycloidal magnetic order in the bulk and many unexpected advantages for possible applications in spintronics, sensor techniques, and photovoltaics. To consider ferroelectric and magnetic phase transitions in multiferroic BiFeO3 under electric field, we suggest the Ginsburg-Landau-like approach based on the symmetry and P -ω -L coupling, where the order parameters are: P is the electric polarization, ω is the axial vector of antidistorsion (describing a rotation of the oxygen octahedrons), and L is the antiferromagnetic vector. The theoretical model is consistent with experiment and ab initio calculations data. We give the complete set of numerical coefficients of the model and explore the behavior of P and ω vectors in strong electric field. The proposed approach is particularly promising for the analysis of magnetoelectric phenomena whose length scale is significantly larger than the length of the cell used in ab initio calculations. The considered cycloid problem is the clear example of such a system. Electric field-induced transformations of cycloid are exemplified on an epitaxial BiFeO3 film grown on the (001)-oriented substrate. We show that the jump of vectors P and ω in the field E =6 MV/m is accompanied by a jump of a cycloid spin rotation plane. This effect is of particular interest for spintronics and nanoelectronics.
In-plane tunnelling field-effect transistor integrated on Silicon
Fina, Ignasi; Apachitei, Geanina; Preziosi, Daniele; Deniz, Hakan; Kriegner, Dominik; Marti, Xavier; Alexe, Marin
2015-01-01
Silicon has persevered as the primary substrate of microelectronics during last decades. During last years, it has been gradually embracing the integration of ferroelectricity and ferromagnetism. The successful incorporation of these two functionalities to silicon has delivered the desired non-volatility via charge-effects and giant magneto-resistance. On the other hand, there has been a numerous demonstrations of the so-called magnetoelectric effect (coupling between ferroelectric and ferromagnetic order) using nearly-perfect heterostructures. However, the scrutiny of the ingredients that lead to magnetoelectric coupling, namely magnetic moment and a conducting channel, does not necessarily require structural perfection. In this work, we circumvent the stringent requirements for epilayers while preserving the magnetoelectric functionality in a silicon-integrated device. Additionally, we have identified an in-plane tunnelling mechanism which responds to a vertical electric field. This genuine electroresistance effect is distinct from known resistive-switching or tunnel electro resistance. PMID:26403693
A study of the round jet/plane wall flow field
NASA Technical Reports Server (NTRS)
Foss, J. F.; Kleis, S. J.
1971-01-01
Impingement angles, between the axisymmetric jet axis and the plane wall, from zero to 15 degrees have been examined for nozzle heights of 0.75, 1.0, 1.5 and 2.0 diameters and for: (1) a fully developed pipe flow, and (2) a relatively uniform exit velocity condition. Velocity measurements have been used to define isotach contours and to determine mass, momentum and energy flux values for the near field (within five diameters) of the jet. Surface pressure measurements have been used to define surface pressure forces and jet centerline trajectories. The geometric and flow conditions examined and the interpretation of the results have been motivated by the externally blown flap STOL aircraft application.
In-plane tunnelling field-effect transistor integrated on Silicon.
Fina, Ignasi; Apachitei, Geanina; Preziosi, Daniele; Deniz, Hakan; Kriegner, Dominik; Marti, Xavier; Alexe, Marin
2015-01-01
Silicon has persevered as the primary substrate of microelectronics during last decades. During last years, it has been gradually embracing the integration of ferroelectricity and ferromagnetism. The successful incorporation of these two functionalities to silicon has delivered the desired non-volatility via charge-effects and giant magneto-resistance. On the other hand, there has been a numerous demonstrations of the so-called magnetoelectric effect (coupling between ferroelectric and ferromagnetic order) using nearly-perfect heterostructures. However, the scrutiny of the ingredients that lead to magnetoelectric coupling, namely magnetic moment and a conducting channel, does not necessarily require structural perfection. In this work, we circumvent the stringent requirements for epilayers while preserving the magnetoelectric functionality in a silicon-integrated device. Additionally, we have identified an in-plane tunnelling mechanism which responds to a vertical electric field. This genuine electroresistance effect is distinct from known resistive-switching or tunnel electro resistance. PMID:26403693
Hall, Maclin S.; Jackson, Theodore G.; Knerr, Christopher
1998-02-17
An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like. In addition to velocity measurements of ultrasonic signals in the plane of the web in the MD and CD, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web.
Hall, M.S.; Jackson, T.G.; Knerr, C.
1998-02-17
An improved system for measuring the velocity of ultrasonic signals within the plane of moving web-like materials, such as paper, paperboard and the like. In addition to velocity measurements of ultrasonic signals in the plane of the web in the MD and CD, one embodiment of the system in accordance with the present invention is also adapted to provide on-line indication of the polar specific stiffness of the moving web. In another embodiment of the invention, the velocity of ultrasonic signals in the plane of the web are measured by way of a plurality of ultrasonic transducers carried by synchronously driven wheels or cylinders, thus eliminating undue transducer wear due to any speed differences between the transducers and the web. In order to provide relatively constant contact force between the transducers and the webs, the transducers are mounted in a sensor housings which include a spring for biasing the transducer radially outwardly. The sensor housings are adapted to be easily and conveniently mounted to the carrier to provide a relatively constant contact force between the transducers and the moving web. 37 figs.
NASA Technical Reports Server (NTRS)
Sims, William Herbert, III (Inventor); Martin, James Joseph (Inventor); Lewis, Raymond A. (Inventor)
2003-01-01
A containment apparatus for containing a cloud of charged particles comprises a cylindrical vacuum chamber having a longitudinal axis. Within the vacuum chamber is a containment region. A magnetic field is aligned with the longitudinal axis of the vacuum chamber. The magnetic field is time invariant and uniform in strength over the containment region. An electric field is also aligned with the longitudinal axis of the vacuum chamber and the magnetic field. The electric field is time invariant, and forms a potential well over the containment region. One or more means are disposed around the cloud of particles for inducing a rotating electric field internal to the vacuum chamber. The rotating electric field imparts energy to the charged particles within the containment region and compress the cloud of particles. The means disposed around the outer surface of the vacuum chamber for inducing a rotating electric field are four or more segments forming a segmented ring, the segments conforming to the outer surface of the vacuum chamber. Each of the segments is energized by a separate alternating voltage. The sum of the voltages imposed on each segment establishes the rotating field. When four segments form a ring, the rotating field is obtained by a signal generator applying a sinusoidal signal phase delayed by 90,180 and 270 degrees in sequence to the four segments.
Faraday Rotation Measure Gradients from a Helical Magnetic Field in 3C273
Zavala, Robert T.; Taylor, G.B.; /NRAO, Socorro /KIPAC, Menlo Park
2005-06-06
Using high frequency (12-22 GHz) VLBA observations we confirm the existence of a Faraday rotation measure gradient of {approx}500 rad m{sup -2} mas{sup -1} transverse to the jet axis in the quasar 3C273. The gradient is seen in two epochs spaced roughly six months apart. This stable transverse rotation measure gradient is expected if a helical magnetic field wraps around the jet. The overall order to the magnetic field in the inner projected 40 parsecs is consistent with a helical field. However, we find an unexpected increase in fractional polarization along the edges of the source, contrary to expectations. This high fractional polarization rules out internal Faraday rotation, but is not readily explained by a helical field. After correcting for the rotation measure, the intrinsic magnetic field direction in the jet of 3C273 changes from parallel to nearly perpendicular to the projected jet motion at two locations. If a helical magnetic field causes the observed rotation measure gradient then the synchrotron emitting electrons must be separate from the helical field region. The presence or absence of transverse rotation measure gradients in other sources is also discussed.
DARK MATTER, MAGNETIC FIELDS, AND THE ROTATION CURVE OF THE MILKY WAY
Ruiz-Granados, B.; Battaner, E.; Florido, E.; Calvo, J.; Rubino-Martin, J. A.
2012-08-20
The study of the disk rotation curve of our Galaxy at large distances provides an interesting scenario for us to test whether magnetic fields should be considered as a non-negligible dynamical ingredient. By assuming a bulge, an exponential disk for the stellar and gaseous distributions, and a dark halo and disk magnetic fields, we fit the rotation velocity of the Milky Way. In general, when the magnetic contribution is added to the dynamics, a better description of the rotation curve is obtained. Our main conclusion is that magnetic fields should be taken into account for the Milky Way dynamics. Azimuthal magnetic field strengths of B{sub {phi}} {approx} 2 {mu}G at distances of {approx}2 R{sub 0}(16 kpc) are able to explain the rise-up for the rotation curve in the outer disk.
The Rotational Spectrum and Anharmonic Force Field of Chlorine Dioxide, OClO
NASA Technical Reports Server (NTRS)
Muller, Holger S. P.; Sorensen, G.; Birk, Manfred; Friedl, Randy R.
1997-01-01
The ground state rotational and quartic centrifugal distortion constants, their vibrational changes, and the sextic centrifugal distortion constants were used in a calculation of the quartic force field together with data from infrared studies.
NASA Astrophysics Data System (ADS)
Haldar, Samadyuti
2016-04-01
The stability of thin electrically conducting viscoelastic fluid film flowing down on a non-conducting inclined plane in the presence of electromagnetic field is investigated under induction-free approximation. Surface evolution equation is derived by long-wave expansion method. The stabilizing role of Hartman number M (magnetic field) and the destabilizing role of the viscoelastic property {\\varGamma} and the electric parameter E on such fluid film are established through the linear stability analysis of the surface evolution equation. Investigation shows that at small values of Hartman number ( M), the influence of electric parameter ( E) on the viscoelastic parameter {(\\varGamma)} is insignificant, while for large values of M, E introduces more destabilizing effect at low values of {\\varGamma} than that at high values of {\\varGamma }. An interesting result also perceived from our analysis is that the stabilizing effect of Hartman number ( M) is decreasing with the increase of the values of {\\varGamma} and E, even it gives destabilizing effect after a certain high value of the electric field depending on the high value of {\\varGamma}. The weakly nonlinear study reveals that the increase of {\\varGamma} decreases the explosive and subcritical unstable zones but increases the supercritical stable zone keeping the unconditional zone almost constant.
Mechanical design of mounts for IGRINS focal plane arrays and field flattening lenses
NASA Astrophysics Data System (ADS)
Oh, Jae Sok; Park, Chan; Cha, Sang-Mok; Yuk, In-Soo; Kim, Kang-Min; Chun, Moo-Young; Ko, Kyeongyeon; Oh, Heeyeong; Jeong, Ueejeong; Nah, Jakyoung; Lee, Hanshin; Pavel, Michael; Jaffe, Daniel T.
2014-07-01
IGRINS, the Immersion GRating INfrared Spectrometer, is a near-infrared wide-band high-resolution spectrograph jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS employs three HAWAII-2RG focal plane array (FPA) detectors. The mechanical mounts for these detectors and for the final (field-flattening) lens in the optical train serve a critical function in the overall instrument design: Optically, they permit the only positional compensation in the otherwise "build to print" design. Thermally, they permit setting and control of the detector operating temperature independently of the cryostat bench. We present the design and fabrication of the mechanical mount as a single module. The detector mount includes the array housing, housing for the SIDECAR ASIC, a field flattener lens holder, and a support base. The detector and ASIC housing will be kept at 65 K and the support base at 130 K. G10 supports thermally isolate the detector and ASIC housing from the support base. The field flattening lens holder attaches directly to the FPA array housing and holds the lens with a six-point kinematic mount. Fine adjustment features permit changes in axial position and in yaw and pitch angles. We optimized the structural stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis. Based on the computer simulation, the designed detector mount meets the optical and thermal requirements very well.
NASA Astrophysics Data System (ADS)
Merkel, K.; Nagaraj, M.; Kocot, A.; Kohlmeier, A.; Mehl, G. H.; Vij, J. K.
2012-03-01
Biaxiality in the nematic phase for a liquid crystalline tetrapode made up of organo-siloxanes mesogens is investigated using polarized infrared spectroscopy. An ordering of the minor director for the homeotropically aligned sample is found to depend on the amplitude of the in-plane electric field. On increasing the in-plane electric field, the minor director, lying initially along the rubbing direction, rotates to the direction of the applied field. The scalar order parameters of the second rank tensor are found to depend significantly on the strength of the electric field. A most significant increase is found in the nematic order parameter and in the parameter that characterizes the phase biaxiality.
Hama, T; Aoki, T; Osuga, K; Sugiyama, S; Iwasaki, D
2012-01-01
Japanese paddy rice systems commonly adopt the rotation of vegetables, wheat and soybeans with paddy rice. Crop rotation may, however, increase the nutrient load in effluent discharged from the district because more fertilizer is applied to the rotation crops than is applied to paddy crops. We investigated a paddy-field district subject to collective crop rotation and quantified the annual nutrient load of effluent from the district in three consecutive years. The total annual exports of nitrogen and phosphorus over the investigation period ranged from 30.3 to 40.6 kg N ha(-1) and 2.62 to 3.13 kg P ha(-1). The results suggest that rotation cropping increases the effluent nutrient load because applied fertilizer is converted to nitrate, and surface runoff is increased due to the absence of shuttering boards at the field outlets.
NASA Astrophysics Data System (ADS)
Das, T.; Figueira de Morisson Faria, C.
2016-08-01
We analyze the imprint of nodal planes in high-order-harmonic spectra from aligned diatomic molecules in intense laser fields whose components exhibit orthogonal polarizations. We show that the typical suppression in the spectra associated to nodal planes is distorted, and that this distortion can be employed to map the electron's angle of return to its parent ion. This investigation is performed semianalytically at the single-molecule response and single-active orbital level, using the strong-field approximation and the steepest descent method. We show that the velocity form of the dipole operator is superior to the length form in providing information about this distortion. However, both forms introduce artifacts that are absent in the actual momentum-space wave function. Furthermore, elliptically polarized fields lead to larger distortions in comparison to two-color orthogonally polarized fields. These features are investigated in detail for O2, whose highest occupied molecular orbital provides two orthogonal nodal planes.
NASA Technical Reports Server (NTRS)
Mcaninch, G. L.; Myers, M. K.
1980-01-01
The parabolic approximation for the acoustic equations of motion is applied to the study of the sound field generated by a plane wave at or near grazing incidence to a finite impedance boundary. It is shown how this approximation accounts for effects neglected in the usual plane wave reflection analysis which, at grazing incidence, erroneously predicts complete cancellation of the incident field by the reflected field. Examples are presented which illustrate that the solution obtained by the parabolic approximation contains several of the physical phenomena known to occur in wave propagation near an absorbing boundary.
Davalos-Orozco, L. A.; Aguilar-Rosas, J. E.
1989-09-01
The Rayleigh--Taylor instability of a continuously stratified magnetofluid under a general rotation field and a vertically stratified horizontal magnetic field is investigated. The upper bound for the growth rate of the perturbation is found and corrections to that obtained by Chakraborty (Phys. Fluids /bold 25/, 743 (1982)) are given. The theory predicts the formation of rolls appearing in natural rotating convection and magnetoconvection.
NASA Technical Reports Server (NTRS)
Rahmat-Samii, Y.; Galindo-Israel, V.; Mittra, R.
1980-01-01
The planar configuration with a probe scanning a polar geometry is discussed with reference to its usefulness in the determination of a far field from near-field measurements. The accuracy of the method is verified numerically, using the concept of probe compensation as a vector deconvolution. Advantages of the Jacobi-Bessel series over the fast Fourier transforms for the plane-polar geometry are demonstrated. Finally, the far-field pattern of the Viking high gain antenna is constructed from the plane-polar near-field measured data and compared with the previously measured far-field pattern.
Stability of rotating self-gravitating filaments: effects of magnetic field
NASA Astrophysics Data System (ADS)
Sadhukhan, Shubhadeep; Mondal, Surajit; Chakraborty, Sagar
2016-07-01
We have performed systematic local linear stability analysis on a radially stratified infinite self-gravitating cylinder of rotating plasma under the influence of magnetic field. In order to render the system analytically tractable, we have focused solely on the axisymmetric modes of perturbations. Using cylindrical coordinate system, we have derived the critical linear mass density of a non-rotating filament required for gravitational collapse to ensue in the presence of azimuthal magnetic field. Moreover, for such filaments threaded by axial magnetic field, we show that the growth rates of the modes having non-zero radial wavenumber are reduced more strongly by the magnetic field than that of the modes having zero radial wavenumber. More importantly, our study contributes to the understanding of the stability property of rotating astrophysical filaments that are more often than not influenced by magnetic fields. In addition to complementing many relevant numerical studies reported the literature, our results on filaments under the influence of magnetic field generalize some of the very recent analytical works. For example, here we prove that even a weak magnetic field can play a dominant role in determining stability of the filament when the rotation time-scale is larger than the free-fall time-scale. A filamentary structure with faster rotation is, however, comparatively more stable for the same magnetic field. The results reported herein, due to strong locality assumption, are strictly valid for the modes for which one can ignore the radial variations in the density and the magnetic field profiles.
NASA Astrophysics Data System (ADS)
Milroy, Richard D.
2001-06-01
A numerical model has been used to study the effects that open field line plasma may have on the rotating magnetic field (RMF), when it is applied to a field-reversed configuration (FRC) for current drive. The model is a two-dimensional (r-θ) magnetohydrodynamic computer simulation. The RMF is found to be an extremely good particle pump, continuously sweeping plasma into the FRC from the outer region, and thus evacuating the space near the containment vessel wall. This effect can lead to a very low density near the wall, providing good thermal insulation. However, if there is a plasma source in the open field line region (such as outgassing from the containment vessel wall) capable of maintaining relatively low-density plasma, the RMF may be amplified in this region. While this effect may speed the rate of penetration, it also has a deleterious effect where excessive penetration leads to predictions of an internal structure that rotates slower than the RMF, and chaotic equilibrium.
Velas, K. M.; Milroy, R. D.
2014-01-15
A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure B{sub r}, B{sub θ}, and B{sub z} at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.
Modeling Current Drive in Space Plasma with Rotating Magnetic Field (RMF)
NASA Astrophysics Data System (ADS)
Shao, X.; Papadopoulos, K.; Joyce, G.
2006-05-01
The interaction of rotating magnetic fields with plasmas is fundamental plasma physics problem with implications to fusion related Field-Reversed Configuration (FRC) configurations, space propulsion, astronaut protection from cosmic rays in long interstellar travel, control of energetic population in the radiation belts and near zone processes in pulsar magnetospheres. Despite its importance the basic plasma physics understanding of the interaction of rotating magnetic fields with magneto-plasmas, the scaling laws that control it and the range of potential applications to space plasmas remains unexplored. In this study, we focus on studying current drive in Space Plasma with RMF rotation rates satisfying (electron gyro-frequency) > RMF rotation rate >> (ion gyro-frequency) so that ion dynamics can be neglected. The relevant physics in this regime can be described by the so-called EMHD equations. This description neglects displacement current and plasma oscillations by enforcing quasi-neutrality. An important ingredient of the description is the presence of the Hall current and retention of the electron inertia. A spherical-coordinate-based EMHD code is developed and applied to study current drive with rotating magnet in plasma with magnetic field strength B much larger than the ambient magnetic field Bo. The current will modify the B field dependence on the distance to B~1/r**n. This study will investigate the value of n and determine the resultant magnetic profile as a function of the rotating speed relatively to the particle gyro-frequencies and plasma parameters.
ROTATION RATE DIFFERENCES OF POSITIVE AND NEGATIVE SOLAR MAGNETIC FIELDS BETWEEN ±60° LATITUDES
Shi, X. J.; Xie, J. L.
2015-04-15
Based on a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields from Carrington Rotations Nos. 1625 to 2135 (from 1975 February to 2013 March), the sidereal rotation rates of the positive and negative magnetic fields in the latitude range of ±60° are obtained, and the rotation rate differences between them are investigated. The time–latitude distribution of the rate differences is shown, which looks like a butterfly diagram at the low and middle latitudes. For comparison, the time–latitude distribution of the longitudinally averaged photospheric magnetic fields is shown. We conclude that the magnetic fields having the same polarity as the leading sunspots at a given hemisphere rotate faster than those exhibiting the opposite polarity at low and middle latitudes. However, at higher latitudes, the magnetic fields having the same polarity as the leading sunspots at a given hemisphere do not always rotate faster than those with the opposite polarity. Furthermore, the relationship between the rotation rate differences and solar magnetic fields is studied through a correlation analysis. Our result shows that the correlation coefficients between them reach maximum values at 13° (14°) latitude in the northern (southern) hemisphere, and change sign at 28° latitude in both hemispheres, then reach their minimum values at 58° (53°) latitude in the northern (southern) hemisphere.
NASA Astrophysics Data System (ADS)
Kovalenko, V. M.; Byehkov, N. M.; Kisel, G. A.; Dikovskaia, N. D.
1984-03-01
Measurements have been made of pressure distributions and pulsations in a cross flow past a circular cylinder placed near a plane screen of finite length. The experiments reported here have been carried out under low turbulence conditions over a range of Reynolds numbers that includes the critical values. The boundary layer separation points and the evolution of the front critical point and other characteristic zones with the distance to the screen are determined. The components of the aerodynamic force acting on the cylinder and the Strouhal number are calculated on the basis of the predominant pulsation frequencies on the cylinder.
Sunspot rotation. II. Effects of varying the field strength and twist of an emerging flux tube
NASA Astrophysics Data System (ADS)
Sturrock, Z.; Hood, A. W.
2016-09-01
Context. Observations of flux emergence indicate that rotational velocities may develop within sunspots. However, the dependence of this rotation on sub-photospheric field strength and twist remains largely unknown. Aims: We investigate the effects of varying the initial field strength and twist of an emerging sub-photospheric magnetic flux tube on the rotation of the sunspots at the photosphere. Methods: We consider a simple model of a stratified domain with a sub-photospheric interior layer and three overlying atmospheric layers. A twisted arched flux tube is inserted in the interior and is allowed to rise into the atmosphere. To achieve this, the magnetohydrodynamic equations are solved using the Lagrangian-remap code, Lare3d. We perform a parameter study by independently varying the sub-photospheric magnetic field strength and twist. Results: Altering the initial magnetic field strength and twist of the flux tube significantly affects the tube's evolution and the rotational motions that develop at the photosphere. The rotation angle, vorticity, and current show a direct dependence on the initial field strength. We find that an increase in field strength increases the angle through which the fieldlines rotate, the length of the fieldlines extending into the atmosphere, and the magnetic energy transported to the atmosphere. This also affects the amount of residual twist in the interior. The length of the fieldlines is crucial as we predict the twist per unit length equilibrates to a lower value on longer fieldlines. No such direct dependence is found when we modify the twist of the magnetic field owing to the complex effect this has on the tension force acting on the tube. However, there is still a clear ordering in quantities such as the rotation angle, helicity, and free energy with higher initial twist cases being related to sunspots that rotate more rapidly, transporting more helicity and magnetic energy to the atmosphere.
Milroy, R. D.; Kim, C. C.; Sovinec, C. R.
2010-06-15
Three-dimensional simulations of field reversed configuration (FRC) formation and sustainment with rotating magnetic field (RMF) current drive have been performed with the NIMROD code [C. R. Sovinec et al., J. Comput. Phys. 195, 355 (2004)]. The Hall term is a zeroth order effect with strong coupling between Fourier components, and recent enhancements to the NIMROD preconditioner allow much larger time steps than was previously possible. Boundary conditions to capture the effects of a finite length RMF antenna have been added, and simulations of FRC formation from a uniform background plasma have been performed with parameters relevant to the translation, confinement, and sustainment-upgrade experiment at the University of Washington [H. Y. Guo, A. L. Hoffman, and R. D. Milroy, Phys. Plasmas 14, 112502 (2007)]. The effects of both even-parity and odd-parity antennas have been investigated, and there is no evidence of a disruptive instability for either antenna type. It has been found that RMF effects extend considerably beyond the ends of the antenna, and that a large n=0 B{sub t}heta can develop in the open-field line region, producing a back torque opposing the RMF.
NASA Astrophysics Data System (ADS)
Miller, Kenneth Elric
2001-11-01
The Star Thrust Experiment (STX) has formed and sustained the Field Reversed Configuration (FRC) with a Rotating Magnetic Field (RMF) operated at a strength of 25 G and a frequency of 350 kHz. The RMF was generated with two IGBT switched solid state power supplies capable of delivering 2 MW each. Plasmas were typically 2 m long by 0.2m in radius and consisted of fully ionized deuterium at temperatures of 60 eV and peak densities of 5 × 1018m- 3. The primary diagnostic was an extremely small 24 channel berylia jacketed internal magnetic probe that was used to make measurements as a function of time, radius, and axial position. These measurements when combined with the FRC's unique geometry and equilibrium relationships determined many other important plasma parameters. Axial confining fields of 100 G maintained a true vacuum boundary around the plasma and allowed for the study of FRC RMF equilibrium interactions. Key findings are that the RMF maintained a near zero separatrix pressure, penetrated only partially, and drove strong radial and axial flows. Issues discussed include the importance of the RMF driving an axial current distribution consistent with that of the FRC, possible benefits of varying the average beta condition, and potential RMF antenna length limits set by the tendency of driven axial flows to screen the RMF from the plasma.
Magnetostrictive behaviors of Fe-Si(001) single-crystal films under rotating magnetic fields
NASA Astrophysics Data System (ADS)
Kawai, Tetsuroh; Aida, Takuya; Ohtake, Mitsuru; Futamoto, Masaaki
2015-05-01
Magnetostrictive behaviors under rotating magnetic fields are investigated for bcc(001) single-crystal films of Fe100-x-Six(x = 0, 6, 10 at. %). The magnetostriction observation directions are along bcc[100] and bcc[110] of the films. The magnetostriction waveform varies greatly depending on the observation direction. For the observation along [100], the magnetostriction waveform of all the films is bathtub-like and the amplitude stays at almost constant even when the magnetic field is increased up to the anisotropy field. On the other hand, the waveform along [110] is triangular and the amplitude increases with increasing magnetic field up to the anisotropy field and then saturates. In addition, the waveform of Fe90Si10 film is distorted triangular when the applied magnetic fields are less than its anisotropy field. These magnetostrictive behaviors under rotating magnetic fields are well explained by employing a proposed modified coherent rotation model where the anisotropy field and the magnetization reversal field are determined by using measured magnetization curves. The results show that magnetocrystalline anisotropy plays important role on magnetostrictive behavior under rotating magnetic fields.
Brown, M. J.; Khalsa, H. S.; Nelson, M. A.; Boswell, D.
2004-01-01
As part of the larger Joint URBAN 2003 tracer field experiment performed in Oklahoma City from June 29 to July 30, 2003, a collaborative team of government and university researchers instrumented a downtown street canyon with a high density of wind sensor instrumentation (Brown et al., 2003). The goal of the Park Avenue street canyon experiment was to garner flow field information in order to better understand the transport and dispersion of tracers released in the street canyon and to test and improve the next generation of urban dispersion models. In this paper, we focus on describing the mean flow patterns that developed in the street canyon in a horizontal plane near the surface. We look at the patterns that develop over entire Intensive Operating Periods (IOP's) lasting from 6-9 hours in length, and as a function of inflow wind direction. Most prior street canyon experiments have generally focused on the vertical structure of the flow; this work contributes to the understanding of the horizontal nature of the flow.
Characterizing the feedback of magnetic field on the differential rotation of solar-like stars
NASA Astrophysics Data System (ADS)
Varela, J.; Strugarek, A.; Brun, A. S.
2016-10-01
The aim of this article is to study how the differential rotation of solar-like stars is influenced by rotation rate and mass in presence of magnetic fields generated by a convective dynamo. We use the ASH code to model the convective dynamo of solar-like stars at various rotation rates and masses, hence different effective Rossby numbers. We obtained models with either prograde (solar-like) or retrograde (anti-solar-like) differential rotation. The trends of differential rotation versus stellar rotation rate obtained for simulations including the effect of the magnetic field are weaker compared with hydro simulations (ΔΩ ∝(Ω /Ω⊙) 0.44 in the MHD case and ΔΩ ∝(Ω /Ω⊙) 0.89 in the hydro case), hence showing a better agreement with the observations. Analysis of angular momentum transport revealed that the simulations with retrograde and prograde differential rotation have opposite distribution of the viscous, turbulent Reynolds stresses and meridional circulation contributions. The thermal wind balance is achieved in the prograde cases. However, in retrograde cases Reynolds stresses are dominant for high latitudes and near the top of the convective layer. Baroclinic effects are stronger for faster rotating models.
NASA Technical Reports Server (NTRS)
Sheeley, N. R., Jr.
1981-01-01
This paper examines the effect that solar differential rotation would have on a hypothetical large-scale equatorial dipole field. The evolving large-scale field pattern is expressed as a series of non-axisymmetric moments. As time increases, power is transferred to progressively higher order moments. In the 27d rotating coordinate system, each moment undergoes a small retrograde drift which remains nearly uniform until that mode begins to fade. The synodic rotation periods of the first few moments are comparable to the observed 28.5d period of the sun's large-scale field near sunspot maximum. Differential rotation may be the source of this 28.5d period, but the eruption of new flux is necessary to keep the pattern going.
Effect of paddy-upland rotation on methanogenic archaeal community structure in paddy field soil.
Liu, Dongyan; Ishikawa, Hiroki; Nishida, Mizuhiko; Tsuchiya, Kazunari; Takahashi, Tomoki; Kimura, Makoto; Asakawa, Susumu
2015-01-01
Methanogenic archaea are strict anaerobes and demand highly reduced conditions to produce methane in paddy field soil. However, methanogenic archaea survive well under upland and aerated conditions in paddy fields and exhibit stable community. In the present study, methanogenic archaeal community was investigated in fields where paddy rice (Oryza sativa L.) under flooded conditions was rotated with soybean (Glycine max [L.] Merr.) under upland conditions at different rotation histories, by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) and real-time quantitative PCR methods targeting 16S rRNA and mcrA genes, respectively. Soil samples collected from the fields before flooding or seeding, during crop cultivation and after harvest of crops were analyzed. The abundance of the methanogenic archaeal populations decreased to about one-tenth in the rotational plots than in the consecutive paddy (control) plots. The composition of the methanogenic archaeal community also changed. Most members of the methanogenic archaea consisting of the orders Methanosarcinales, Methanocellales, Methanomicrobiales, and Methanobacteriales existed autochthonously in both the control and rotational plots, while some were strongly affected in the rotational plots, with fatal effect to some members belonging to the Methanosarcinales. This study revealed that the upland conversion for one or longer than 1 year in the rotational system affected the methanogenic archaeal community structure and was fatal to some members of methanogenic archaea in paddy field soil. PMID:25113614
NASA Astrophysics Data System (ADS)
Begley, Matthew R.; Creton, Costantino; McMeeking, Robert M.
2015-11-01
A general asymptotic plane strain crack tip stress field is constructed for linear versions of neo-Hookean materials, which spans a wide variety of special cases including incompressible Mooney elastomers, the compressible Blatz-Ko elastomer, several cases of the Ogden constitutive law and a new result for a compressible linear neo-Hookean material. The nominal stress field has dominant terms that have a square root singularity with respect to the distance of material points from the crack tip in the undeformed reference configuration. At second order, there is a uniform tension parallel to the crack. The associated displacement field in plane strain at leading order has dependence proportional to the square root of the same coordinate. The relationship between the amplitude of the crack tip singularity (a stress intensity factor) and the plane strain energy release rate is outlined for the general linear material, with simplified relationships presented for notable special cases.
Triggered star formation: Rotation, magnetic fields and outflows
NASA Astrophysics Data System (ADS)
Frank, A.; Li, S.; Blackman, E. G.
2015-12-01
Star formation can be triggered by compression from wind or supernova driven shock waves that sweep over molecular clouds. In a previous work we used Adaptive Mesh Refinement (AMR) simulation methods, including sink particles, to simulate the full collapse of a stable Bonnor-Ebert sphere subjected to a passing shock. We tracked the flow of cloud material after a star (a sink particle) had formed. For rotating clouds we observed the formation of disks which then interact with the post-shock flow. In this paper we take the next step forward in complexity, presenting first results of simulations that include a magnetized cloud. Our results show that after a disk is formed a collimated magneto-centrifugal outflow is launched. The outflow is bipolar but asymmetric, due to interactions with the shocked flow. We explore the influence of the outflows on the post-triggering collapse dynamics.
NASA Astrophysics Data System (ADS)
Grezes, C.; Rojas Rozas, A.; Ebrahimi, F.; Alzate, J. G.; Cai, X.; Katine, J. A.; Langer, J.; Ocker, B.; Khalili Amiri, P.; Wang, K. L.
2016-07-01
The effect of in-plane magnetic field on switching voltage (Vsw) and thermal stability factor (Δ) are investigated in electric-field-controlled perpendicular magnetic tunnel junctions (p-MTJs). Dwell time measurements are used to determine the voltage dependence of the energy barrier height for various in-plane magnetic fields (Hin), and gain insight into the Hin dependent energy landscape. We find that both Vsw and Δ decrease with increasing Hin, with a dominant linear dependence. The results are reproduced by calculations based on a macrospin model while accounting for the modified magnetization configuration in the presence of an external magnetic field.
Ding, Ting; Hu, Hong; Bai, Chen; Guo, Shifang; Yang, Miao; Wang, Supin; Wan, Mingxi
2016-07-01
Cavitation plays important roles in almost all high-intensity focused ultrasound (HIFU) applications. However, current two-dimensional (2D) cavitation mapping could only provide cavitation activity in one plane. This study proposed a three-dimensional (3D) ultrasound plane-by-plane active cavitation mapping (3D-UPACM) for HIFU in free field and pulsatile flow. The acquisition of channel-domain raw radio-frequency (RF) data in 3D space was performed by sequential plane-by-plane 2D ultrafast active cavitation mapping. Between two adjacent unit locations, there was a waiting time to make cavitation nuclei distribution of the liquid back to the original state. The 3D cavitation map equivalent to the one detected at one time and over the entire volume could be reconstructed by Marching Cube algorithm. Minimum variance (MV) adaptive beamforming was combined with coherence factor (CF) weighting (MVCF) or compressive sensing (CS) method (MVCS) to process the raw RF data for improved beamforming or more rapid data processing. The feasibility of 3D-UPACM was demonstrated in tap-water and a phantom vessel with pulsatile flow. The time interval between temporal evolutions of cavitation bubble cloud could be several microseconds. MVCF beamformer had a signal-to-noise ratio (SNR) at 14.17dB higher, lateral and axial resolution at 2.88times and 1.88times, respectively, which were compared with those of B-mode active cavitation mapping. MVCS beamformer had only 14.94% time penalty of that of MVCF beamformer. This 3D-UPACM technique employs the linear array of a current ultrasound diagnosis system rather than a 2D array transducer to decrease the cost of the instrument. Moreover, although the application is limited by the requirement for a gassy fluid medium or a constant supply of new cavitation nuclei that allows replenishment of nuclei between HIFU exposures, this technique may exhibit a useful tool in 3D cavitation mapping for HIFU with high speed, precision and resolution
Ding, Ting; Hu, Hong; Bai, Chen; Guo, Shifang; Yang, Miao; Wang, Supin; Wan, Mingxi
2016-07-01
Cavitation plays important roles in almost all high-intensity focused ultrasound (HIFU) applications. However, current two-dimensional (2D) cavitation mapping could only provide cavitation activity in one plane. This study proposed a three-dimensional (3D) ultrasound plane-by-plane active cavitation mapping (3D-UPACM) for HIFU in free field and pulsatile flow. The acquisition of channel-domain raw radio-frequency (RF) data in 3D space was performed by sequential plane-by-plane 2D ultrafast active cavitation mapping. Between two adjacent unit locations, there was a waiting time to make cavitation nuclei distribution of the liquid back to the original state. The 3D cavitation map equivalent to the one detected at one time and over the entire volume could be reconstructed by Marching Cube algorithm. Minimum variance (MV) adaptive beamforming was combined with coherence factor (CF) weighting (MVCF) or compressive sensing (CS) method (MVCS) to process the raw RF data for improved beamforming or more rapid data processing. The feasibility of 3D-UPACM was demonstrated in tap-water and a phantom vessel with pulsatile flow. The time interval between temporal evolutions of cavitation bubble cloud could be several microseconds. MVCF beamformer had a signal-to-noise ratio (SNR) at 14.17dB higher, lateral and axial resolution at 2.88times and 1.88times, respectively, which were compared with those of B-mode active cavitation mapping. MVCS beamformer had only 14.94% time penalty of that of MVCF beamformer. This 3D-UPACM technique employs the linear array of a current ultrasound diagnosis system rather than a 2D array transducer to decrease the cost of the instrument. Moreover, although the application is limited by the requirement for a gassy fluid medium or a constant supply of new cavitation nuclei that allows replenishment of nuclei between HIFU exposures, this technique may exhibit a useful tool in 3D cavitation mapping for HIFU with high speed, precision and resolution
A polarizing situation: Taking an in-plane perspective for next-generation near-field studies
NASA Astrophysics Data System (ADS)
Schuck, P. James; Bao, Wei; Borys, Nicholas J.
2016-04-01
By enabling the probing of light-matter interactions at the functionally relevant length scales of most materials, near-field optical imaging and spectroscopy accesses information that is unobtainable with other methods. The advent of apertureless techniques, which exploit the ultralocalized and enhanced near-fields created by sharp metallic tips or plasmonic nanoparticles, has resulted in rapid adoption of near-field approaches for studying novel materials and phenomena, with spatial resolution approaching sub-molecular levels. However, these approaches are generally limited by the dominant out-of-plane polarization response of apertureless tips, restricting the exploration and discovery of many material properties. This has led to recent design and fabrication breakthroughs in near-field tips engineered specifically for enhancing in-plane interactions with near-field light components. This mini-review provides a perspective on recent progress and emerging directions aimed at utilizing and controlling in-plane optical polarization, highlighting key application spaces where in-plane near-field tip responses have enabled recent advancements in the understanding and development of new nanostructured materials and devices.
The role of rotation in the evolution of dynamo-generated magnetic fields in Super Earths
NASA Astrophysics Data System (ADS)
Zuluaga, Jorge I.; Cuartas, Pablo A.
2012-01-01
Planetary magnetic fields could impact the evolution of planetary atmospheres and have a role in the determination of the required conditions for the emergence and evolution of life (planetary habitability). We study here the role of rotation in the evolution of dynamo-generated magnetic fields in massive Earth-like planets, Super Earths (1-10 M⊕). Using the most recent thermal evolution models of Super Earths (Gaidos, E., Conrad, C.P., Manga, M., Hernlund, J. [2010]. Astrophys. J. 718, 596-609; Tachinami, C., Senshu, H., Ida, S. [2011]. Astrophys. J. 726, 70) and updated scaling laws for convection-driven dynamos, we predict the evolution of the local Rossby number. This quantity is one of the proxies for core magnetic field regime, i.e. non-reversing dipolar, reversing dipolar and multipolar. We study the dependence of the local Rossby number and hence the core magnetic field regime on planetary mass and rotation rate. Previous works have focused only on the evolution of core magnetic fields assuming rapidly rotating planets, i.e. planets in the dipolar regime. In this work we go further, including the effects of rotation in the evolution of planetary magnetic field regime and obtaining global constraints to the existence of intense protective magnetic fields in rapidly and slowly rotating Super Earths. We find that the emergence and continued existence of a protective planetary magnetic field is not only a function of planetary mass but also depend on rotation rate. Low-mass Super Earths ( M ≲ 2 M⊕) develop intense surface magnetic fields but their lifetimes will be limited to 2-4 Gyrs for rotational periods larger than 1-4 days. On the other hand and also in the case of slowly rotating planets, more massive Super Earths ( M ≳ 2 M⊕) have weak magnetic fields but their dipoles will last longer. Finally we analyze tidally locked Super Earths inside and outside the habitable zone of GKM stars. Using the results obtained here we develop a classification of
Cantillon-Murphy, P; Wald, L L; Adalsteinsson, E; Zahn, M
2010-09-01
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, τ. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad/s. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4°C and 7°C above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B(0). Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B(0). Results are presented for the expected temperature increase in small tumors (~1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002 to 0.01 solid volume fraction) and nanoparticle radii (1 to 10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful The goal of this work is to examine, by means of analysis and simulation, the concept of interactive fluid magnetization using the dynamic behavior of superparamagnetic iron oxide nanoparticle suspensions in the MRI environment. In addition to the usual magnetic fields associated with MRI, a rotating magnetic field is applied transverse to the main B(0) field of the MRI. Additional or modified magnetic fields have been previously proposed for hyperthermia and targeted drug delivery within MRI. Analytical predictions and numerical simulations
Wald, L.L.; Adalsteinsson, E.; Zahn, M.
2010-01-01
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle’s time constant, τ. As the magnetic field frequency is increased, the nanoparticle’s magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad/s. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid’s temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4°C and 7°C above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid’s temperature in the MRI environment which is characterized by a large DC field, B0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B0. Results are presented for the expected temperature increase in small tumors (~1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002 to 0.01 solid volume fraction) and nanoparticle radii (1 to 10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful The goal of this work is to examine, by means of analysis and simulation, the concept of interactive fluid magnetization using the dynamic behavior of superparamagnetic iron oxide nanoparticle suspensions in the MRI environment. In addition to the usual magnetic fields associated with MRI, a rotating magnetic field is applied transverse to the main B0 field of the MRI. Additional or modified magnetic fields have been previously proposed for hyperthermia and targeted drug delivery within MRI. Analytical predictions and numerical simulations
NASA Astrophysics Data System (ADS)
Cantillon-Murphy, P.; Wald, L. L.; Adalsteinsson, E.; Zahn, M.
2010-09-01
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, τ. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad s -1. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4 and 7 °C above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B0. Results are presented for the expected temperature increase in small tumors ( ˜1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002-0.01 solid volume fraction) and nanoparticle radii (1-10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful the goal of this work is to examine, by means of analysis and simulation, the concept of interactive fluid magnetization using the dynamic behavior of superparamagnetic iron oxide nanoparticle suspensions in the MRI environment. In addition to the usual magnetic fields associated with MRI, a rotating magnetic field is applied transverse to the main B0 field of the MRI. Additional or modified magnetic fields have been previously proposed for hyperthermia and targeted drug delivery within MRI. Analytical predictions and numerical simulations of the
Clemente, R. A.; Gilli, M.; Farengo, R.
2008-10-15
Steady state solutions, suitable for field-reversed configurations (FRCs) sustained by rotating magnetic fields (RMFs) are obtained by properly including three-dimensional effects, in the limit of large FRC elongation, and the radial component of Ohm's law. The steady electrostatic potential, necessary to satisfy Ohm's law, is considered to be a surface function. The problem is analyzed at the midplane of the configuration and it is reduced to the solution of two coupled nonlinear differential equations for the real and imaginary parts of the phasor associated to the longitudinal component of the vector potential. Additional constraints are obtained by requesting that the steady radial current density and poloidal magnetic flux vanish at the plasma boundary which is set at the time-averaged separatrix. The results are presented in terms of the degree of synchronism of the electrons with the RMF and compared with those obtained when radial current effects are neglected. Three important differences are observed when compared with the case without radial current density. First, at low penetration of the RMF into the plasma there is a significant increase in the driven azimuthal current. Second, the RMF amplitude necessary to access the high synchronism regime, starting from low synchronism, is larger and the difference appears to increase as the separatrix to classical skin depth ratio increases. Third, the minimum RMF amplitude necessary to sustain almost full synchronism is reduced.
NASA Technical Reports Server (NTRS)
Ghosh, P.; Abramowicz, M. A.
1991-01-01
The role of the internal gravity modes in mediating the growth of nonaxisymmetric instabilities is investigated by studying the instability of stratified incompressible differentially rotating fluid cylinders to global nonaxisymmetric modes. The results indicate that, in addition to a modified version of the well-known principal branch mediated by surface modes of the system (analogous to f-modes of stars), there exist unstable branches of the dispersion relation mediated by internal gravity modes of the system (similar to the g-modes of stars). These branches arise due to the interaction between the g-modes. It is shown that the maximum growth rate on one of the new branches can sometimes equal or exceed that on the principal branch, thus modifying the principal branch.
The effect of rotating magnetic field on the microstructure of in situ TiB2/Cu composites
NASA Astrophysics Data System (ADS)
Zou, C.; Kang, H.; Li, R.; Li, M.; Wang, W.; Chen, Z.; Wang, T.
2016-03-01
Nano ceramic particulate reinforced metal matrix composites are confronted with the problem of particle aggregation emerging in the process of solidification. It sharply deteriorates the mechanical properties of the composites. In order to improve the microstructure and particle distribution, in situ TiB2/Cu composites were prepared using Ti and Cu-B master alloys in a vacuum medium frequency induction furnace equipped with a rotating magnetic field (RMF). The effect of RMF magnetic field intensity employed on the microstructure and particles distribution of the TiB2/Cu composites were investigated. The results show that with the applied RMF, TiB2 particles are homogeneously distributed in the copper matrix, which significantly improves the mechanical properties of TiB2/Cu composites. The mechanism of RMF may be ascribed to the following two aspects. On the one hand, the electromagnetic body force generated by appropriate RMF drives forced convection in the equatorial plane of composite melt during solidification. On the other hand, a secondary flow in the meridional plane is engendered by a radial pressure gradient, thus making a strong agitation in the melt. These two effects result in a homogenous dispersion of TiB2 particles in the copper matrix, and hence excellent properties of TiB2/Cu composites were obtained.
In-Plane Field Magneto-transport in a Six-fold Degenerate Si-(111) 2DEG
NASA Astrophysics Data System (ADS)
Kott, Tomasz M.; Hu, Binhui; McFarland, Robert N.; Brown, Stephen H.; Kane, Bruce E.
2011-03-01
In-plane magneto-transport is an effective tool for measuring sub-band occupancy and differentiating between effects such as the so-called ``reentrant Metal-Insulator Transition'' or a ferromagnetic to paramagnetic phase transition. Using a two-dimensional electron gas (2DEG) on high mobility (up to 100 , 000 cm2 / Vs) hydrogen terminated Si-(111) surfaces, we have studied the magneto-resistance due to in-plane magnetic fields of this six-fold degenerate system. While high perpendicular field (up to 12 T) measurements indicate field-dependent valley splitting, parallel field data helps differentiate this dependence from spin dynamics. The application of an in-plane field polarizes the 2DEG into distinct sub-bands. I will present measurements of both spin and valley sub-band polarization in parallel magnetic fields from samples of various mobility (10 , 000 - 100 , 000 cm2 / Vs) and discuss these results in the context of the broader question of field-dependent valley splitting. In a simple picture of valley splitting on Si-(111) surfaces, one would expect two valley polarization fields in addition to the spin polarization. I will discuss how this interaction-free model fits with the perpendicular field measurements, and what we can learn about the six-fold degenerate system.
NASA Astrophysics Data System (ADS)
Volpe, F. A.; Frassinetti, L.; Brunsell, P. R.; Drake, J. R.; Olofsson, K. E. J.
2013-04-01
A new non-disruptive error field (EF) assessment technique not restricted to low density and thus low beta was demonstrated at the EXTRAP-T2R reversed field pinch. Stable and marginally stable external kink modes of toroidal mode number n = 10 and n = 8, respectively, were generated, and their rotation sustained, by means of rotating magnetic perturbations of the same n. Due to finite EFs, and in spite of the applied perturbations rotating uniformly and having constant amplitude, the kink modes were observed to rotate non-uniformly and be modulated in amplitude. This behaviour was used to precisely infer the amplitude and approximately estimate the toroidal phase of the EF. A subsequent scan permitted to optimize the toroidal phase. The technique was tested against deliberately applied as well as intrinsic EFs of n = 8 and 10. Corrections equal and opposite to the estimated error fields were applied. The efficacy of the error compensation was indicated by the increased discharge duration and more uniform mode rotation in response to a uniformly rotating perturbation. The results are in good agreement with theory, and the extension to lower n, to tearing modes and to tokamaks, including ITER, is discussed.
English, Niall J; Kusalik, Peter G; Woods, Sarah A
2012-03-01
Non-equilibrium molecular dynamics simulations of R and S enantiomers of 1,1-chlorofluoroethane, both for pure liquids and racemic mixtures, have been performed at 298 K in the absence and presence of both electromagnetic (e/m) and circularly polarised electric (CP) fields of varying frequency (100-2200 GHz) and intensity (0.025-0.2 V Å(-1) (rms)). Significant non-thermal field effects were noted in the coupling of rotational and translational motion; for instance, in microwave and far-infrared (MW/IR) e/m fields, marked increases in rotational and translational diffusion vis-à-vis the zero-field case took place at 0.025-0.1 V Å(-1) (rms), with a reduction in translational diffusion vis-à-vis the zero-field case above 0.1 V Å(-1) (rms) above 100 GHz. This was due to enhanced direct coupling of rotational motion with the more intense e/m field at the ideal intrinsic rotational coupling frequency (approximately 700 GHz) leading to such rapidly oscillating rotational motion that extent of translational motion was effectively reduced. In the case of CP fields, rotational and translational diffusion was also enhanced for all intensities, particularly at approximately 700 GHz. For both MW/IR and CP fields, non-linear field effects were evident above around 0.1 V Å(-1) (rms) intensity, in terms of enhancements in translational and rotational motion. Simulation of 90-10 mol. % liquid mixtures of a Lennard-Jones solvent with R and S enantiomer-solutes in MW/IR and CP fields led to more limited promotion of rotational and translational diffusion, due primarily to increased frictional effects. For both e/m and CP fields, examination of the laboratory- and inertial-frame auto- and cross-correlation functions of velocity and angular velocity demonstrated the development of explicit coupling with the external fields at the applied frequencies, especially so in the more intense fields where nonlinear effects come into play. For racemic mixtures, elements of the laboratory
NASA Astrophysics Data System (ADS)
Sobolewski, P.; Krzyścin, J. W.; Jaroslawski, J.; Stebel, K.
2008-06-01
Erythemaly weighted UV and total UV-A irradiance measured at the ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research; 69° N, 16° E) in June 2007 by two Kipp & Zonen UV broadband meters type, UV-S-EA-T, are examined. One unit is mounted on rotating vertical plane and the other is permanently fixed horizontally. The UV broadband meters measure simultaneously to compare UV irradiances on vertical and horizontal planes. The entire range of such relative exposure variations during clear-sky and overcast conditions over ALOMAR in the period March June 2007 is examined using STAR and Radonic1 model (developed at the Meteorological Institute, University of Munich) for various action spectra: erythema, UV-A, and vitamin D3. The model and observations support that the daily means of relative exposures are quite stable, i.e., vary within the range 0.4 0.6 with the mean around 0.5 when the averaged intra-day, day-to-day, and seasonal changes of the relative erythemal exposures are considered. It seems that multiplication of the daily mean dose from a broadband meter placed horizontally by the factor of 0.5 gives reasonable estimation of the daily mean exposure on a vertically oriented receiver randomly oriented towards the Sun. The model studies during clear-sky conditions show that the extreme value and daily variability of relative exposure are the highest for UV-A, next for erythemal UV, then for vitamin D3 weighed UV irradiance. The minima of relative exposure (~0.20 0.30) are almost the same for all weighting functions. The comparison of model simulations and measurements suggests that specific cloud configuration could lead to significant enhancement of UV exposure of rotating receiver.
Plane-grating flat-field soft x-ray spectrometer
NASA Astrophysics Data System (ADS)
Hague, C. F.; Underwood, J. H.; Avila, A.; Delaunay, R.; Ringuenet, H.; Marsi, M.; Sacchi, M.
2005-02-01
We describe a soft x-ray spectrometer covering the 120-800 eV range. It is intended for resonant inelastic x-ray scattering experiments performed at third generation synchrotron radiation (SR) facilities and has been developed with SOLEIL, the future French national SR source in mind. The Hettrick-Underwood principle is at the heart of the design using a combination of varied line-spacing plane grating and spherical-mirror to provide a flat-field image. It is slitless for optimum acceptance. This means the source size determines the resolving power. A spot size of ⩽5μm is planned at SOLEIL which, according to simulations, should ensure a resolving power ⩾1000 over the whole energy range. A 1024×1024 pixel charge-coupled device (CCD) with a 13μm×13μm pixel size is used. This is an improvement on the use of microchannel-plate detectors, both as concerns efficiency and spatial resolution. Additionally spectral line curvature is avoided by the use of a horizontal focusing mirror concentrating the beam in the nondispersing direction. It allows for readout using a binning mode to reduce the intrinsically large CCD readout noise. Preliminary results taken at beamlines at Elettra (Trieste) and at BESSY (Berlin) are presented.
Flow in isothermal layers of ferrofluid by action of uniform rotating magnetic field
Kashevskii, B.E.
1986-01-01
The author attempts to determine how intense the flow of a ferrofluid in a rotating magnetic field can become owing to the temperature dependence of the properties when a nonuniform temperature field has been produced within the volume of such a fluid. It was found that in a channel with a strong temperature dependence of viscosity, a uniform rotating magnetic field is capable of effectively influencing the flow of a ferrofluid within nonisothermal layers, which may be of interest in solving problems of heat transfer.
Tools and setups for experiments with AC and rotating magnetic fields
NASA Astrophysics Data System (ADS)
Ponikvar, D.
2010-09-01
A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several experiments and describes setups and tools which are easy to obtain and work with. Free software is offered to generate the required signals by a personal computer. The experiments can be implemented in introductory physics courses on electromagnetism for undergraduates or specialized courses at high schools.
Collisionless Magnetic Reconnection and Dynamo Processes in a Spatially Rotating Magnetic Field
NASA Astrophysics Data System (ADS)
Choe, Gwangson; Lee, Junggi
2016-04-01
Spatially rotating magnetic fields have been observed in the solar wind and in the Earth's magnetopause as well as in reversed field pinch (RFP) devices. Such field configurations have a similarity with extended current layers having a spatially varying plasma pressure instead of the spatially varying guide field. It is thus expected that magnetic reconnection may take place in a rotating magnetic field no less than in an extended current layer. We have investigated the spontaneous evolution of a collisionless plasma system embedding a rotating magnetic field with a two-and-a-half-dimensional electromagnetic particle-in-cell (PIC) simulation. It is found that a magnetic-flux-reducing diffusion phase and a magnetic-flux-increasing dynamo phase are alternating with a certain period. The temperature of the system also varies with the same period, showing a similarity to sawtooth oscillations in tokamaks. We have shown that a modified theory of sawtooth oscillations can explain the periodic behavior observed in the simulation. A strong guide field distorts the current layer as was observed in laboratory experiments. This distortion is smoothed out as magnetic islands fade away by the O-line diffusion, but is soon strengthened by the growth of magnetic islands. These processes are all repeating with a fixed period. Our results suggest that a rotating magnetic field configuration continuously undergoes deformation and relaxation in a short time-scale although it might look rather steady in a long-term view.
Liu, Dun; Wang, Lijun; Wang, Zhigang; Cuschieri, Alfred
2012-10-10
Weak magnetic fields (40 and 75 mT) were used either to enhance cell membrane poration (magnetoporation) or to ablate cultured human tumor cells (magnetolysis) by polymer-coated multiwalled carbon nanotubes, which form rotating bundles on exposure to magnetic fields. Findings of this study have potential clinical applications including enhanced tumor cell poration for targeted cancer chemotherapy and mechanical ablation of tumors.
Rotational energy of the hydrogen molecular ion in a magnetic field
Maluendes, S.A.; Fernandez, F.M.; Castro, E.A.
1983-10-01
A general method which combines hypervirial relations with the Hellmann-Feynman theorem and perturbation theory is applied in order to calculate the rotational eigenvalues of the hydrogen molecular ion in a magnetic field. Analytical expressions as well as numerical results are presented for both low and high field strengths.
Harvey-Smith, L.; Madsen, G. J.; Gaensler, B. M.
2011-08-01
We present a study of the line-of-sight magnetic fields in five large-diameter Galactic H II regions. Using the Faraday rotation of background polarized radio sources, as well as dust-corrected H{alpha} surface brightness as a probe of electron density, we estimated the strength and orientation of the magnetic field along 93 individual sight lines through the H II regions. Each of the H II regions displayed a coherent magnetic field. The magnetic field strength (line-of-sight component) in the regions ranges from 2 to 6 {mu}G, which is similar to the typical magnetic field strength in the diffuse interstellar medium. We investigated the relationship between magnetic field strength and electron density in the five H II regions. The slope of magnetic field versus density in the low-density regime (0.8 cm{sup -3} < n{sub e} <30 cm{sup -3}) is very slightly above zero. We also calculated the ratio of thermal to magnetic pressure, {beta}{sub th}, for each data point, which fell in the range 1.01 < {beta}{sub th} < 25. Finally, we studied the orientation of the magnetic field in the solar neighborhood (d < 1.1 kpc) using our data from five H II regions along with existing measurements of the line-of-sight magnetic field strength from polarized pulsars whose distances have been determined from their annual parallax. We identify a net direction for the magnetic field in the solar neighborhood, but find no evidence for a preferred vertical direction of the magnetic field above or below the Galactic plane.
Chiral pumping effect induced by rotating electric fields
NASA Astrophysics Data System (ADS)
Ebihara, Shu; Fukushima, Kenji; Oka, Takashi
2016-04-01
We propose an experimental setup using 3D Dirac semimetals to access a novel phenomenon induced by the chiral anomaly. We show that the combination of a magnetic field and a circularly polarized laser induces a finite charge density with an accompanying axial current. This is because the circularly polarized laser breaks time-reversal symmetry and the Dirac point splits into two Weyl points, which results in an axial-vector field. We elucidate the appearance of the axial-vector field with the help of the Floquet theory by deriving an effective Hamiltonian for high-frequency electric fields. This anomalous charge density, i.e., the chiral pumping effect, is a phenomenon reminiscent of the chiral magnetic effect with a chiral chemical potential. We explicitly compute the pumped density and the axial-current expectation value. We also take account of coupling to the chiral magnetic effect to calculate a balanced distribution of charge and chirality in a material that behaves as a chiral battery.
New Methodology For Use in Rotating Field Nuclear MagneticResonance
Jachmann, Rebecca C.
2007-05-18
High-resolution NMR spectra of samples with anisotropicbroadening are simplified to their isotropic spectra by fast rotation ofthe sample at the magic angle 54.7 circ. This dissertation concerns thedevelopment of novel Nuclear Magnetic Resonance (NMR) methodologies basedwhich would rotate the magnetic field instead of the sample, rotatingfield NMR. It provides an over of the NMR concepts, procedures, andexperiments needed to understand the methodologies that will be used forrotating field NMR. A simple two-dimensional shimming method based onharmonic corrector rings which can provide arbitrary multiple ordershimming corrections were developed for rotating field systems, but couldbe used in shimming other systems as well. Those results demonstrate, forexample, that quadrupolar order shimming improves the linewidth by up toan order of magnitude. An additional order of magnitude reduction is inprinciple achievable by utilizing this shimming method for z-gradientcorrection and higher order xy gradients. A specialized pulse sequencefor the rotating field NMR experiment is under development. The pulsesequence allows for spinning away from the magic angle and spinningslower than the anisotropic broadening. This pulse sequence is acombination of the projected magic angle spinning (p-MAS) and magic angleturning (MAT) pulse sequences. This will be useful to rotating field NMRbecause there are limits on how fast a field can be spun and spin at themagic angle is difficult. One of the goals of this project is forrotating field NMR to be used on biological systems. The p-MAS pulsesequence was successfully tested on bovine tissue samples which suggeststhat it will be a viable methodology to use in a rotating field set up. Aside experiment on steering magnetic particle by MRI gradients was alsocarried out. Some movement was seen in these experiment, but for totalcontrol over steering further experiments would need to bedone.
New Methodology For Use in Rotating Field Nuclear MagneticResonance
Jachmann, Rebecca C.
2007-01-01
High-resolution NMR spectra of samples with anisotropicbroadening are simplified to their isotropic spectra by fast rotation ofthe sample at the magic angle 54.7 circ. This dissertation concerns thedevelopment of novel Nuclear Magnetic Resonance (NMR) methodologies basedwhich would rotate the magnetic field instead of the sample, rotatingfield NMR. It provides an over of the NMR concepts, procedures, andexperiments needed to understand the methodologies that will be used forrotating field NMR. A simple two-dimensional shimming method based onharmonic corrector rings which can provide arbitrary multiple ordershimming corrections were developed for rotating field systems, but couldbe used in shimming other systems as well. Those results demonstrate, forexample, that quadrupolar order shimming improves the linewidth by up toan order of magnitude. An additional order of magnitude reduction is inprinciple achievable by utilizing this shimming method for z-gradientcorrection and higher order xy gradients. A specialized pulse sequencefor the rotating field NMR experiment is under development. The pulsesequence allows for spinning away from the magic angle and spinningslower than the anisotropic broadening. This pulse sequence is acombination of the projected magic angle spinning (p-MAS) and magic angleturning (MAT) pulse sequences. This will be useful to rotating field NMRbecause there are limits on how fast a field can be spun and spin at themagic angle is difficult. One of the goals of this project is forrotating field NMR to be used on biological systems. The p-MAS pulsesequence was successfully tested on bovine tissue samples which suggeststhat it will be a viable methodology to use in a rotating field set up. Aside experiment on steering magnetic particle by MRI gradients was alsocarried out. Some movement was seen in these experiment, but for totalcontrol over steering further experiments would need to bedone.
Robust full-field measurement considering rotation using digital image correlation
NASA Astrophysics Data System (ADS)
Wu, Rong; Qian, Hao; Zhang, Dongsheng
2016-10-01
Digital image correlation (DIC) has been widely accepted as a method for displacement and strain measurement and is applied in a variety of engineering fields. Most DIC algorithms encounter errors in measuring the deformation in conditions that involve rotation since they are designed without considering rotation of the deformed object. In this paper, a robust and automated DIC method capable of determining full-field displacement and strain components with random rotations has been presented. The algorithm starts with the determination of the initial position of the seed point in the integer-pixel domain. An approximate rotational angle between the reference and the deformed subset is estimated using an automated feature matching technology. A two-step Newton-Raphson algorithm has been developed for optimizing a suite of variables including displacement, strain and the rotational angle to achieve subpixel accuracy. A reliable propagation scheme, which enables rapid determination of the initial guess for full-field analysis is also proposed. Results from numerical simulations are used to validate the feasibility of the proposed DIC method. An application to 3-point bending with large deflection shows that the algorithm can be employed to measure displacement or strain parameters of the deformed object with arbitrary angles of rotation.
Poloidal rotation in tokamaks with large electric field gradients
Hinton, F.L.; Kim, Y.
1995-01-01
The ion poloidal flow velocity near the plasma edge in a tokamak has been calculated by extending neoclassical theory to include orbit squeezing, which is the reduction of the ion banana widths due to radial electric field shear. The pressure gradient-driven ion parallel flow is reduced by orbit squeezing, and then no longer cancels the diamagnetic flow in its contribution to poloidal flow. This allows the poloidal flow velocity to be a significant fraction of the ion diamagnetic velocity, which can be much larger than the standard neoclassical value (proportional to the ion temperature gradient). Equations for determining the poloidal flow and radial electric field profiles self-consistently are given. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Choi, Tae-Hoon; Woo, Jae-Hyeon; Choi, Yeongyu; Yoon, Tae-Hoon
2016-09-01
We investigated the two-dimensional (2-D) confinement effect of liquid crystals (LCs) on the switching of vertically aligned LCs by an in-plane electric field. When an in-plane field is applied to a vertical alignment (VA) cell, virtual walls are built at the center of the interdigitated electrodes and at the middle of the gaps between them. The LC molecules are confined not only by the two substrates but also by the virtual walls so that the turn-off time of a VA cell driven by an in-plane field is dependent on the pitch of the interdigitated electrodes as well as the cell gap. Therefore, the turn-off time of a VA cell driven by an in-plane field can be reduced simply by decreasing the pitch of the interdigitated electrodes as a result of the enhanced anchoring provided by the virtual walls. The experimental results showed good agreement with a simple model based on the 2-D confinement effect of LCs.
Choi, Tae-Hoon; Woo, Jae-Hyeon; Choi, Yeongyu; Yoon, Tae-Hoon
2016-09-01
We investigated the two-dimensional (2-D) confinement effect of liquid crystals (LCs) on the switching of vertically aligned LCs by an in-plane electric field. When an in-plane field is applied to a vertical alignment (VA) cell, virtual walls are built at the center of the interdigitated electrodes and at the middle of the gaps between them. The LC molecules are confined not only by the two substrates but also by the virtual walls so that the turn-off time of a VA cell driven by an in-plane field is dependent on the pitch of the interdigitated electrodes as well as the cell gap. Therefore, the turn-off time of a VA cell driven by an in-plane field can be reduced simply by decreasing the pitch of the interdigitated electrodes as a result of the enhanced anchoring provided by the virtual walls. The experimental results showed good agreement with a simple model based on the 2-D confinement effect of LCs. PMID:27607702
NASA Technical Reports Server (NTRS)
Lichtenstein, B. R.; Sonett, C. P.
1979-01-01
The paper shows that the experimentally observed close alignment of magnetic field minimum variance direction with the average magnetic field for Alfven waves in the solar wind is consistent with theoretically predicted properties of plane large amplitude Alfven waves in the MHD approximation. The theoretical properties of these Alfven waves constrain the time averaged magnetic field to cluster around the direction of minimum variance, which is aligned with the wave normal. Thus, spacecraft magnetometer observations in the solar wind of minimum variance directions strongly peaked about the average magnetic field direction are consistent with plane large amplitude Alfven waves which have wave normals aligned with the directions of minimum variance. This does not imply that geometrical hydromagnetic calculations for Alfven wave propagation direction in the solar wind are incorrect, but there is a discrepancy between geometrical hydromagnetics theory and observations that IMF minimum variance directions tend to be aligned with the ideal Parker spiral instead of the radial direction.
Oz, E.; Myers, C. E.; Edwards, M. R.; Berlinger, B.; Brooks, A.; Cohen, S. A.
2011-01-05
The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RMFo) current drive and plasma heating system to form and sustain high-Β plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RMFo from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (τfc) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with (τfc > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 103 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.
Absorption of massless scalar field by rotating black holes
NASA Astrophysics Data System (ADS)
Leite, Luiz C. S.; Crispino, Luís C. B.; de Oliveira, Ednilton S.; Macedo, Caio F. B.; Dolan, Sam R.
2016-07-01
We compute the absorption cross-section of the Kerr black holes (BH) for the massless scalar field, and present a selection of numerical results, to complement the results of Ref.[C. F. B. Macedo, L. C. S. Leite, E. S. Oliveria, S. R. Dolan and L. C. B. Crispino, Phys. Rev. D 88 (2013) 064033.] We show that, in the high-frequency regime, the cross-section approaches the geodesic capture cross-section. We split the absorption cross-section into corotating and counterrotating contributions, and we show that the counterrotating contribution exceeds the corotating one.
Rigid-body rotation of an electron cloud in divergent magnetic fields
Fruchtman, A.; Gueroult, R.; Fisch, N. J.
2013-07-10
For a given voltage across a divergent poloidal magnetic field, two electric potential distributions, each supported by a rigid-rotor electron cloud rotating with a different frequency, are found analytically. The two rotation frequencies correspond to the slow and fast rotation frequencies known in uniform plasma. Due to the centrifugal force, the equipotential surfaces, that correspond to the two electric potential distributions, diverge more than the magnetic surfaces do, the equipotential surfaces in the fast mode diverge largely in particular. The departure of the equipotential surfaces from the magnetic field surfaces may have a significant focusing effect on the ions accelerated by the electric field. Furthermore, the focusing effect could be important for laboratory plasma accelerators as well as for collimation of astrophysical jets.
NASA Astrophysics Data System (ADS)
Dhiman, Joginder Singh; Sharma, Rajni
2016-03-01
The self-gravitating instability of an infinitely extending axisymmetric cylinder of viscoelastic medium permeated with non uniform magnetic field and rotation is studied for both the strongly coupled plasma (SCP) and weakly coupled plasma (WCP). The non uniform magnetic field and rotation are considered to act along the axial direction of the cylinder. The normal mode method of perturbations is applied to obtain the dispersion relation. The condition for the onset of gravitational instability has been derived from the dispersion relation under both strongly and weakly coupling limits. It is found that the Jeans criterion for gravitational collapse gets modified due to the presence of shear and bulk viscosities for the SCP, however, the magnetic field and rotation whether uniform or non uniform has no effect on the Jeans criterion of an infinitely extending axisymmetric cylinder of a self-gravitating viscoelastic medium.
Rigid-body rotation of an electron cloud in divergent magnetic fields
Fruchtman, A.; Gueroult, R.; Fisch, N. J.
2013-07-10
For a given voltage across a divergent poloidal magnetic field, two electric potential distributions, each supported by a rigid-rotor electron cloud rotating with a different frequency, are found analytically. The two rotation frequencies correspond to the slow and fast rotation frequencies known in uniform plasma. Due to the centrifugal force, the equipotential surfaces, that correspond to the two electric potential distributions, diverge more than the magnetic surfaces do, the equipotential surfaces in the fast mode diverge largely in particular. The departure of the equipotential surfaces from the magnetic field surfaces may have a significant focusing effect on the ions acceleratedmore » by the electric field. Furthermore, the focusing effect could be important for laboratory plasma accelerators as well as for collimation of astrophysical jets.« less
Model for B1 Imaging in MRI Using the Rotating RF Field
Weber, Ewald; Crozier, Stuart
2014-01-01
Conventionally, magnetic resonance imaging (MRI) is performed by pulsing gradient coils, which invariably leads to strong acoustic noise, patient safety concerns due to induced currents, and costly power/space requirements. This modeling study investigates a new silent, gradient coil-free MR imaging method, in which a radiofrequency (RF) coil and its nonuniform field (B 1 +) are mechanically rotated about the patient. The advantage of the rotating B 1 + field is that, for the first time, it provides a large number of degrees of freedom to aid a successful B 1 + image encoding process. The mathematical modeling was performed using flip angle modulation as part of a finite-difference-based Bloch equation solver. Preliminary results suggest that representative MR images with intensity deviations of <5% from the original image can be obtained using rotating RF field approach. This method may open up new avenues towards anatomical and functional imaging in medicine. PMID:24963336
On the dissipation of the rotation energy of dust grains in interstellar magnetic fields
NASA Astrophysics Data System (ADS)
Papoular, R.
2016-04-01
A new mechanism is described, analysed and visualized, for the dissipation of suprathermal rotation energy of molecules in magnetic fields, a necessary condition for their alignment. It relies upon the Lorentz force perturbing the motion of every atom of the structure, as each is known to carry its own net electric charge because of spatial fluctuations in electron density. If the molecule is large enough that the frequency of its lowest frequency phonon lies near or below the rotation frequency, then the rotation couples with the molecular normal modes and energy flows from the former to the latter. The rate of this exchange is very fast, and the vibrational energy is radiated away in the IR at a still faster rate, which completes the removal of rotation energy. The energy decay rate scales like the field intensity, the initial angular velocity, the number of atoms in the grain and the inverse of the moment of inertia. It does not depend on the susceptibility. Here, the focus is on carbon-rich molecules which are diamagnetic. The same process must occur if the molecule is paramagnetic or bathes in an electric field instead. A semi-empirical method of chemical modelling was used extensively to illustrate and quantify these concepts as applied to a hydrocarbon molecule. The motion of a rotating molecule in a field was monitored in time so as to reveal the energy transfer and visualize the evolution of its orientation towards the stable configuration.
Numerical Simulation of Non-Rotating and Rotating Coolant Channel Flow Fields. Part 1
NASA Technical Reports Server (NTRS)
Rigby, David L.
2000-01-01
Future generations of ultra high bypass-ratio jet engines will require far higher pressure ratios and operating temperatures than those of current engines. For the foreseeable future, engine materials will not be able to withstand the high temperatures without some form of cooling. In particular the turbine blades, which are under high thermal as well as mechanical loads, must be cooled. Cooling of turbine blades is achieved by bleeding air from the compressor stage of the engine through complicated internal passages in the turbine blades (internal cooling, including jet-impingement cooling) and by bleeding small amounts of air into the boundary layer of the external flow through small discrete holes on the surface of the blade (film cooling and transpiration cooling). The cooling must be done using a minimum amount of air or any increases in efficiency gained through higher operating temperature will be lost due to added load on the compressor stage. Turbine cooling schemes have traditionally been based on extensive empirical data bases, quasi-one-dimensional computational fluid dynamics (CFD) analysis, and trial and error. With improved capabilities of CFD, these traditional methods can be augmented by full three-dimensional simulations of the coolant flow to predict in detail the heat transfer and metal temperatures. Several aspects of turbine coolant flows make such application of CFD difficult, thus a highly effective CFD methodology must be used. First, high resolution of the flow field is required to attain the needed accuracy for heat transfer predictions, making highly efficient flow solvers essential for such computations. Second, the geometries of the flow passages are complicated but must be modeled accurately in order to capture all important details of the flow. This makes grid generation and grid quality important issues. Finally, since coolant flows are turbulent and separated the effects of turbulence must be modeled with a low Reynolds number
Magnetic-field-induced rotation of light with orbital angular momentum
Shi, Shuai; Ding, Dong-Sheng Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen
2015-06-29
Light carrying orbital angular momentum (OAM) has attractive applications in the fields of precise optical measurements and high capacity optical communications. We study the rotation of a light beam propagating in warm {sup 87}Rb atomic vapor using a method based on magnetic-field-induced circular birefringence. The dependence of the rotation angle on the magnetic field makes it appropriate for weak magnetic field measurements. We quote a detailed theoretical description that agrees well with the experimental observations. The experiment shown here provides a method to measure the magnetic field intensity precisely and expands the application of OAM-carrying light. This technique has advantage in measurement of magnetic field weaker than 0.5 G, and the precision we achieved is 0.8 mG.
Stress field in the Northern Rhine area, Central Europe, from earthquake fault plane solutions
NASA Astrophysics Data System (ADS)
Hinzen, Klaus-G.
2003-12-01
Fault plane solutions (FPS) from 110 earthquakes in the northern Rhine area with local magnitudes, ranging from 1.0 to 6.1, and occurring between 1976 and 2002 are determined. FPS are retrieved from P-wave first motions using a grid search approach allowing a detailed exploration of the parameter space. The influence of the 1D velocity model on take-off angles and resulting FPS is examined. All events were relocated with a recently developed minimum 1D model of the velocity structure [J. Geophys. Res. (2003)]. Rose diagrams of the orientation of P, T and B axes show a clear preference of trends of P and T axes at N292°E and N27°E, respectively. The majority of B axes trend in northerly directions. Plunges of P and T axes are mostly around 45° while most B axes are subhorizontal. The main direction of the maximum horizontal stress directly inferred from the fault plane solutions is N118°E. To calculate the orientations of the principal stress axes and the shape of the stress tensor, the inversion method of Gephard and Forsyth [J. Geophys. Res. 89 (1984) 9305] was applied to the whole data set and to several subsets of data. The subsets were formed by grouping events from various geological and tectonic areas and by grouping events into different depth ranges. The subset areas include the Lower Rhine Embayment, the Rhenish Massif, the middle Rhine area, the Neuwied Basin and the area known as the Stavelot-Venn Massif. Inversion of the entire data set shows some ambiguity between a strike-slip and extensional stress regime, with a vertical axis for the medium principal stress and a trend of N305°E and N35°E for the σ1 and σ3 axis, respectively, as the best fitting tensor. Earthquakes from the Lower Rhine Embayment and, to some degree, from the middle Rhine area indicate an extensional stress regime. In the Lower Rhine Embayment, plunge and trend of the σ1 axis are 76° and N162°E and for the σ3 axis 7° and N42°E. The best fitting solution for the area of
NASA Astrophysics Data System (ADS)
Peng, J.; Zhao, P. W.
2015-04-01
The self-consistent tilted axis cranking relativistic mean-field (TAC-RMF) theory based on a point-coupling interaction is applied to investigate the observed magnetic and antimagnetic rotations in the nucleus 110Cd . The energy spectra, the relation between the spin and the rotational frequency, the deformation parameters, and the reduced M 1 and E 2 transition probabilities are studied with the various configurations. It is found that the configuration has to be changed to reproduce the energy spectra and the relations between the spin and the rotational frequency for both the magnetic and antimagnetic rotational bands. The shears mechanism for the magnetic rotation and the two-shears-like mechanism for the antimagnetic rotation are examined by investigating the orientation of the neutron and proton angular momenta. The calculated electromagnetic transitions B (M 1 ) and B (E 2 ) are in reasonable agreement with the data, and their tendencies are coincident with the typical characteristics of the magnetic and antimagnetic rotations.
Numerical Simulation and Analysis of Flow-Field in Rotating Rectangular Passage
NASA Astrophysics Data System (ADS)
Wei, X. L.
Applying the finite volume method, the air flow field in a straight passage with a rotating coordinate system is simulated in case the passage is rotating as a whole and also the case that upper wall remaining stationary and the other 3 rotating at arbitrary speeds. The SST turbulence model and the RSM model are utilized to solve these problems respectively. For the case all walls rotating simultaneously, comparisons between the present calculation results with the test data quoted from reference literature are made. Agreements with experimental data are good. It is found that the results by the SST turbulence model are closer to the test data than those by the RSM model. The SST model is selected to calculate the case only part of walls rotating, after taking into account the amount of computation. The results show that the peak velocity of mainstream also leans to the pressure side, but the eddy is continuously formed near the pressure side and the top wall, and drifts towards the lower wall at lower rotation (100~300rpm). At higher rotation (600~2 000rpm), the peak velocity of mainstream is moved to the suction side and the lower wall, the vortices are increased in number, the distribution of velocity along the height and breadth is no longer symmetric. The current exhibits strong three-dimensional characteristics.
NASA Technical Reports Server (NTRS)
Lionello, Roberto; Linker, Jon A.; Mikic, Zoran; Riley, Pete
2006-01-01
Solar energetic particles, which are believed to originate from corotating interacting regions (CIRS) at low heliographic latitude, were observed by the Ulysses spacecraft even as it passed over the Sun's poles. One interpretation of this result is that high-latitude field lines intercepted by Ulysses connect to low-latitude CIRs at much larger heliocentric distances. The Fisk model explains the latitudinal excursion of magnetic field lines in the solar corona and heliosphere as the inevitable consequence of the interaction of a tilted dipole in a differentially rotating photosphere with rigidly rotating coronal holes. We use a time-dependent three-dimensional magnetohydrodynamic (MHD) algorithm to follow the evolution of a simple model of the solar corona in response to the differential rotation of the photospheric magnetic flux. We examine the changes of the coronal-hole boundaries, the redistribution of the line-of-sight magnetic field, and the precession of field lines in the corona. Our results confirm the basic idea of the Fisk model, that differential rotation leads to changes in the heliographic latitude of magnetic field lines. However, the latitudinal excursion of magnetic field lines in this simple "tilted dipole" model is too small to explain the Ulysses observations. Although coronal holes in our model rotate more rigidly than do photospheric features (in general agreement with observations), they do not rotate strictly rigidly as assumed by Fisk. This basic difference between our model and Fisk's will be explored in the future by considering more realistic magnetic flux distributions, as observed during Ulysses polar excursions.
NASA Astrophysics Data System (ADS)
Nagaraj, Mamatha; Merkel, K.; Vij, J. K.; Kocot, A.
2010-09-01
Biaxiality in the nematic phase has been investigated for the bent-core liquid-crystal para-heptylbenzoate diester, using polarised IR spectroscopy. Anisotropic fluctuations of the nematic director are discussed in terms of the self-assembly of the chiral conformers. The ordering of the minor director for the homeotropicaly aligned sample is found to depend on the rubbing of the substrates of the cell and the amplitude of in-plane electric field. On increasing the in-plane electric field, the rotation of the minor director in the plane of the substrate is observed with an angle of approximately 45°, where initially the minor director is shown to lie along the rubbing direction. It is also shown that on the average the long axis of the molecules is normal to the substrate with surface treatment, with and without rubbing. The electric in-plane field combined with rubbing is shown to induce biaxial order in the nematic phase of a material with negative dielectic anisotropy for the first time.
Keavney, D. J.; Cheng, X. M.; Buchanan, K. S.
2009-06-24
We report the polarity reversal of a magnetic vortex core using a nonresonant in-plane pulsed magnetic field of arbitrary waveform studied using time-resolved x-ray photoemission electron microscopy and micromagnetic simulations. The imaging and simulations show that a 5 mT pulse, higher than the critical field for nonlinear effects, effectively leads to the randomization of the vortex core polarity. The micromagnetic simulations further show that the onset of stochastic core polarity randomization does not necessarily coincide with the critical reversal field, leading to a field window for predictable core reversal.
Pogorelov, Nikolai V.; Borovikov, Sergey N.; Zank, Gary P.; Ogino, Tatsuki E-mail: snb0003@uah.edu E-mail: ogino@stelab.nagoya-u.ac.jp
2009-05-10
We investigate the effects of the 11 year solar cycle and 25 day rotation period of the Sun on the interaction of the solar wind (SW) with the local interstellar medium (LISM). Our models take into account the partially ionized character of the LISM and include momentum and energy transfer between the ionized and neutral components. We assume that the interstellar magnetic field vector belongs to the hydrogen deflection plane as discovered in the SOHO SWAN experiment. This plane is inclined at an angle of about 60 deg. toward the ecliptic plane of the Sun, as suggested in recent publications relating the local interstellar cloud properties to the radio emission observed by Voyager 1. It is assumed that the latitudinal extent of the boundary between the slow and fast SW regions, as well as the angle between the Sun's rotation and magnetic-dipole axes, are periodic functions of time, while the polarity of the interstellar magnetic field changes sign every 11 years at the solar maximum. The global variation of the SW-LISM interaction pattern, the excursions of the termination shock and the heliopause, and parameter distributions in certain directions are investigated. The analysis of the behavior of the wavy heliospheric current sheet in the supersonic SW region shows the importance of neutral atoms on its dynamics.
Activity of an enzyme immobilized on superparamagnetic particles in a rotational magnetic field
Mizuki, Toru; Watanabe, Noriyuki; Nagaoka, Yutaka; Fukushima, Tadamasa; Morimoto, Hisao; Usami, Ron; Maekawa, Toru
2010-03-19
We immobilize {alpha}-amylase extracted from Bacillus Iicheniformis on the surfaces of superparamagnetic particles and investigate the effect of a rotational magnetic field on the enzyme's activity. We find that the activity of the enzyme molecules immobilized on superparamagnetic particles increases in the rotational magnetic field and reaches maximum at a certain frequency. We clarify the effect of the cluster structures formed by the superparamagnetic particles on the activity. Enzyme reactions are enhanced even in a tiny volume of solution using the present method, which is very important for the development of efficient micro reactors and micro total analysis systems ({mu}-TAS).
Inward transport and compression of a positron plasma by a rotating electric field
Greaves; Surko
2000-08-28
Inward transport of a magnetized pure positron plasma confined in a Penning-Malmberg trap is produced by applying a rotating electric field to the plasma. Compression is observed over a broad range of frequencies. Compression factors up to 20 in central density were obtained. Positron collisions with a neutral buffer gas are used to counteract the heating due to the rotating electric field. The results have implications for a variety of applications including the production of brightness enhanced positron beams, the study of electron-positron plasmas, and antihydrogen production.
NASA Astrophysics Data System (ADS)
Lee, H. H.; Seol, J.; Ko, W. H.; Terzolo, L.; Aydemir, A. Y.; In, Y.; Ghim, Y.-c.; Lee, S. G.
2016-08-01
Effects of neoclassical toroidal viscosity (NTV) induced by intrinsic error fields and toroidal field ripple on cocurrent toroidal rotation in H-mode tokamak plasmas are investigated. It is expected that large NTV torque can be localized at the edge region through the 1/ν-regime in the vicinity of E r ˜ 0 in the cocurrent rotating H-mode plasma. Numerical simulation on toroidal rotation demonstrates that the edge localized NTV torque determined by the intrinsic error fields and toroidal field ripples in the level of most tokamaks can damp the toroidal rotation velocity over the whole region while reducing the toroidal rotation pedestal which is clearly observed in Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. It is found that the NTV torque changes the toroidal rotation gradient in the pedestal region dramatically, but the toroidal rotation profile in the core region responds rigidly without a change in the gradient. On the other hand, it shows that the NTV torque induced by the intrinsic error fields and toroidal field ripple in the level of the KSTAR tokamak, which are expected to be smaller than most tokamaks by at least one order of magnitude, is negligible in determining the toroidal rotation velocity profile. Experimental observation on the toroidal rotation change by the externally applied nonaxisymmetric magnetic fields on KSTAR also suggests that NTV torque arising from nonaxisymmetric magnetic fields can damp the toroidal rotation over the whole region while diminishing the toroidal rotation pedestal.
On the Physics of the Interaction of a Rotating Magnetic Field with a Magnetized Plasma
NASA Astrophysics Data System (ADS)
Karavaev, A. V.; Papadopoulos, K.; Shao, X.; Milikh, G.; Gekelman, W.; Gigliotti, A.; Vincena, S.
2007-12-01
The interaction of Rotating Magnetic Fields (RMF) with plasmas is a fundamental plasma physics problem with implications to fusion related Field-Reversed Configurations (FRC), space propulsion, astronaut protection from cosmic rays in long interstellar travel, control of energetic population in the radiation belts and near zone processes in pulsar magnetospheres. An important but not yet explored application of RMF is as an efficient radiation source of MHD and whistler waves in space plasmas. Despite its importance the basic plasma physics understanding of the interaction of rotating magnetic fields with magneto-plasmas, the scaling laws that control it and the range of potential applications to space plasmas remains unexplored. To zero order a magnetic field rotating at a rate w in a plasma drives plasma currents due to the difference in mass between electrons and ions. The electrons quickly come to a co-rotation with RMF, generating a differential azimuthal current whose maximum is given by Jtheta = nwr . The RMF can be generated either by a pair of polyphase coils, superconducting or else, or a rotating permanent magnet. Key questions include the depth of penetration of the field in the plasma, the spatiotemporal structure of the induced magnetic field as a function of the RMF and plasma parameters and the spatial decay rate magnetic field. Flux conservation arguments indicate that the induced field will decay slower than 1/r**2 and 2D simulation studies indicate that depending on the plasma beta it falls as 1/r**n with n smaller than 1.5. Our preliminary simulations indicate that penetration lengths exceeding 20-30 collisionless skin depths can be reached. The paper will present a combination of analytic/computational results along with preliminary experiments conducted using the Large Plasma Device (LAPD) located at UCLA that emphasize the RMF properties for generating MHD and whistler waves. This work was sponsored by ONR MURI Grant 5-28828
The Plane Wave Spectrum in Acousto-Optic Imaging of Ultrasonic Fields.
NASA Astrophysics Data System (ADS)
Mehrl, David Joseph
This thesis takes an in-depth look at two major areas of acousto-optics: Bragg diffraction imaging and Schlieren imaging. Both of these methods relate to the imaging of ultrasonic sound fields. The latter method is particularly relevant as it forms the basis for many practical signal processing schemes. A review of the angular plane wave spectrum concept is followed by an outline of a three-dimensional acousto -optic interaction formalism. This formalism forms the basis for the wave-theory analyses of Bragg diffraction and Schlieren imaging which are undertaken in later chapters. A ray tracing method, applicable to acousto-optic scattering, is also developed and justified on the basis of eikonal theory. Bragg diffraction imaging is analyzed by means of both ray tracing and wave theory methods, and the results are shown to be in mutual agreement. Also discussed are the development and results of a computer program which generates three-dimensional ray tracings that depict various Bragg diffraction imaging configurations. Experimental results are presented that support our theoretical findings. Schlieren imaging is analyzed in chapter 4. The classical Raman-Nath model (and its limitations) is first discussed. We then proceed to analyze Schlieren imaging by means of wave theory. We find that the Schlieren image of a monophonic sound field possesses an extremely large depth of focus (i.e. it is almost diffraction free). We proceed to show that the Raman-Nath interpretation can be extended to high frequency (Bragg) regimes, provided certain constraints are met. Finally, we examine wideband Schlieren imaging using optical heterodyning, which is of great practical importance in signal processing schemes. Several key results are obtained. We first present an illustrative example of a Schlieren signal processing scheme employing optical heterodyning. Although this scheme is not new per se, we present experimental results of a working experiment in which we correlate a pulse
Wick rotation for quantum field theories on degenerate Moyal space(-time)
Grosse, Harald; Lechner, Gandalf; Ludwig, Thomas; Verch, Rainer
2013-02-15
In this paper the connection between quantum field theories on flat noncommutative space(-times) in Euclidean and Lorentzian signature is studied for the case that time is still commutative. By making use of the algebraic framework of quantum field theory and an analytic continuation of the symmetry groups which are compatible with the structure of Moyal space, a general correspondence between field theories on Euclidean space satisfying a time zero condition and quantum field theories on Moyal Minkowski space is presented ('Wick rotation'). It is then shown that field theories transferred to Moyal space(-time) by Rieffel deformation and warped convolution fit into this framework, and that the processes of Wick rotation and deformation commute.
Control of rotating waves in cardiac muscle: analysis of the effect of an electric field.
Pumir, A; Plaza, F; Krinsky, V I
1994-08-22
The effect of an electric field on rotating waves in cardiac muscle is considered from a theoretical point of view. A model of excitation propagation taking into account the cellular structure of the heart is presented and studied. The application of a direct current electric field along the cardiac tissue is known to induce changes in membrane potential which decay exponentially with distance. Investigation of the model shows that the electric field induces a gradient of potential inside a cell which does not decay with distance, and results in modification of excitation propagation which extends a considerable distance from the electrodes. In two dimensions, it induces a drift of rotating waves. The effect of the electric field on propagation velocity and on rotating waves cannot be obtained in any arbitrary models of cardiac muscle. For an electric field of about 1 V cm-1 and junctional resistances of about 20 M omega, the change in velocity of propagation can be up to several percent, resulting in a drift velocity of rotating waves of the order of 1 cm s-1. To test these predictions, experiments with cardiac preparations are proposed.
Influence of IMF Rotation on the Magnetic Field Depression in the Magnetosheath: A Kinetic View
NASA Astrophysics Data System (ADS)
Tsubouchi, K.; Terasawa, T.
2001-12-01
Numerical simulations using a one-dimensional hybrid code are performed to investigate how the particle kinetic process determines the magnetosheath structure when the upstream solar wind carries the IMF rotation. It is known from the conventional MHD theory that the interaction of such an IMF disturbance with the bow shock leads to the formation of the diamagnetic structure (density enhancement and magnetic field depression) in the downstream, the edges of which correspond to the excited slow, or intermediate, shock waves. However, the downstream plasma has strong anisotropy (energy imbalance between the component parallel and perpendicular to the magnetic field) in the quasi-perpendicular shock regime; which enables the mirror instability to grow, for instance. Thus the present kinetic approach is essential for the precise understanding of the resultant magnetosheath structure. The most significant result (different from MHD view) is that the rotating magnetic field which passes through the shock rapidly modifies the directional energy distribution of ions in the downstream. Stronger energy of the perpendicular component turns to contribute to the substantial parallel heating in the field rotation. Such ion isotropization shows the net increase of the total thermal pressure which makes the reduction of the magnetic field to maintain the pressure balance. Inside this field rotation region, a large amount of particles with v∥ ~ 0 are accumulated. This process can be considered as an analogy of the physics in the mirror instability. However, the condition for the instability is immediately suppressed when particles experience the field rotation, so that the resultant structure is stably convected in the downstream. Geotail magnetosheath observation is compared to the simulation results.
Spin current pumped by a rotating magnetic field in zigzag graphene nanoribbons
NASA Astrophysics Data System (ADS)
Wang, J.; Chan, K. S.
2010-10-01
We study electron spin resonance in zigzag graphene nanoribbons by applying a rotating magnetic field on the system without any bias. By using the nonequilibrium Green's function technique, the spin-resolved pumped current is explicitly derived in a rotating reference frame. The pumped spin current density increases with the system size and the intensity of the transverse rotating magnetic field. For graphene nanoribbons with an even number of zigzag chains, there is a nonzero pumped charge current in addition to the pumped spin current owing to the broken spatial inversion symmetry of the system, but its magnitude is much smaller than the spin current. The short-ranged static disorder from either impurities or defects in the ribbon can depress the spin current greatly due to the localization effect, whereas the long-ranged disorder from charge impurities can avoid inter-valley scattering so that the spin current can survive in the strong disorder for the single-energy mode.
NASA Astrophysics Data System (ADS)
B, Gisi; S, Sakiroglu; İ, Sokmen
2016-01-01
In this work, we investigate the effects of interplay of spin-orbit interaction and in-plane magnetic fields on the electronic structure and spin texturing of parabolically confined quantum wire. Numerical results reveal that the competing effects between Rashba and Dresselhaus spin-orbit interactions and the external magnetic field lead to a complicated energy spectrum. We find that the spin texturing owing to the coupling between subbands can be modified by the strength of spin-orbit couplings as well as the magnitude and the orientation angle of the external magnetic field.
Graf von der Pahlen, J.; Tsiklauri, D.
2014-06-15
The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed X-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the X-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar structure is found to be a signature of X-point collapse, rather than tearing mode, and factors relating to potential discoveries in experimental scenarios or space-craft observations are discussed.
Photometric light curves for ten rapidly rotating stars in Alpha Persei, the Pleiades, and the field
NASA Technical Reports Server (NTRS)
Prosser, Charles F.; Schild, Rudolph E.; Stauffer, John R.; Jones, Burton F.
1993-01-01
We present the results from a photometric monitoring program of ten rapidly rotating stars observed during 1991 using the FLWO 48-in. telescope. Brightness variations for an additional six cluster stars observed with the Lick 40-in. telescope are also given. The periods and light curves for seven Alpha Persei members, two Pleiades members, and one naked T Tauri field star are reported.
Gravitomagnetic Field of the Universe and Coriolis Force on the Rotating Earth
ERIC Educational Resources Information Center
Veto, B.
2011-01-01
The Machian effect of distant masses of the universe in the frame of reference of the rotating Earth is demonstrated using the gravitomagnetic approach of general relativity. This effect appears in the form of a gravitomagnetic Lorentz force acting on moving bodies on the Earth. The gravitomagnetic field of the universe--deduced from a simple…
Non-radial oscillations of the magnetized rotating stars with purely toroidal magnetic fields
NASA Astrophysics Data System (ADS)
Asai, Hidetaka; Lee, Umin; Yoshida, Shijun
2015-06-01
We calculate non-axisymmetric oscillations of uniformly rotating polytropes magnetized with a purely toroidal magnetic field, taking account of the effects of the deformation due to the magnetic field. As for rotation, we consider only the effects of Coriolis force on the oscillation modes, ignoring those of the centrifugal force, that is, of the rotational deformation of the star. Since separation of variables is not possible for the oscillation of rotating magnetized stars, we employ finite series expansions for the perturbations using spherical harmonic functions. We calculate magnetically modified normal modes such as g-, f-, p-, r-, and inertial modes. In the lowest order, the frequency shifts produced by the magnetic field scale with the square of the characteristic Alfvén frequency. As a measure of the effects of the magnetic field, we calculate the proportionality constant for the frequency shifts for various oscillation modes. We find that the effects of the deformation are significant for high frequency modes such as f- and p-modes but unimportant for low-frequency modes such as g-, r-, and inertial modes.
All-Fiber Optical Magnetic Field Sensor Based on Faraday Rotation
Sun, L.; Jiang, S.; Marciante, J.R.
2010-06-18
An all-fiber optical magnetic field sensor with a sensitivity of 0.49 rad/T is demonstrated. It consists of a fiber Faraday rotator (56-wt.%-terbium–doped silica fiber) and a fiber polarizer (Corning SP1060 fiber).
Laboratory and field studies in rotational spectroscopy at the Jet Propulsion Laboratory
NASA Technical Reports Server (NTRS)
Drouin, Brian J.
2004-01-01
Rotational spectroscopy of atmospheric molecules has long been a hallmark of laboratory and field studies at the Jet Propulsion Laboratory. in addition to maintenance of the millimeter and submillimeter spectral line catalog, the laboratory has actively purued the challenging laboratory tasks of quantitative linewidth measurements and transient species identification.
Computational estimation of magnetically induced electric fields in a rotating head
NASA Astrophysics Data System (ADS)
Ilvonen, Sami; Laakso, Ilkka
2009-01-01
Change in a magnetic field, or similarly, movement in a strong static magnetic field induces electric fields in human tissues, which could potentially cause harmful effects. In this paper, the fields induced by different rotational movements of a head in a strong homogeneous magnetic field are computed numerically. Average field magnitudes near the retinas and inner ears are studied in order to gain insight into the causes of phosphenes and vertigo-like effects, which are associated with extremely low-frequency (ELF) magnetic fields. The induced electric fields are calculated in four different anatomically realistic head models using an efficient finite-element method (FEM) solver. The results are compared with basic restriction limits by IEEE and ICNIRP. Under rotational movement of the head, with a magnetic flux rate of change of 1 T s-1, the maximum IEEE-averaged electric field and maximum ICNIRP-averaged current density were 337 mV m-1 and 8.84 mA m-2, respectively. The limits by IEEE seem significantly stricter than those by ICNIRP. The results show that a magnetic flux rate of change of 1 T s-1 may induce electric field in the range of 50 mV m-1 near retinas, and possibly even larger values near the inner ears. These results provide information for approximating the threshold electric field values of phosphenes and vertigo-like effects.
Lee, Jun-Tae; Abid, Aamir; Cheung, Ka Ho; Sudheendra, L; Kennedy, Ian M
2012-09-01
The dynamics of superparamagnetic particles subject to competing magnetic and viscous drag forces have been examined with a uniform, stationary, external magnetic field. In this approach, competing drag and magnetic forces were created in a fluid suspension of superparamagnetic particles that was confined in a capillary tube; competing viscous drag and magnetic forces were established by rotating the tube. A critical Mason number was determined for conditions under which the rotation of the capillary prevents the formation of chains from individual particles. The statistics of chain length were investigated by image analysis while varying parameters such as the rotation speed and the viscosity of the liquid. The measurements showed that the rate of particle chain formation was decreased with increased viscosity and rotation speed ; the particle dynamics could be quantified by the same dimensionless Mason number that has been demonstrated for rotating magnetic fields. The potential for enhancement of mixing in a bioassay was assessed using a fast chemical reaction that was diffusion-limited. Reducing the Mason below the critical value, so that chains were formed in the fluid, gave rise to a modest improvement in the time to completion of the reaction. PMID:23066382
Electric Power Generation from Earth's Rotation through its Own Magnetic Field
NASA Astrophysics Data System (ADS)
Chyba, Christopher F.; Hand, Kevin P.
2016-07-01
We examine electric power generation from Earth's rotation through its own nonrotating magnetic field (that component of the field symmetric about Earth's rotation axis). There is a simple general proof that this is impossible. However, we identify a loophole in that proof and show that voltage can be continuously generated in a low-magnetic-Reynolds-number conductor rotating with Earth, provided magnetically permeable material is used to ensure curl(v ×B0)≠0 within the conductor, where B0 derives from the axially symmetric component of Earth's magnetic flux density, and v is Earth's rotation velocity at the conductor's location. We solve the relevant equations for one laboratory realization, and from this solution, we predict the voltage magnitude and sign dependence on system dimensions and orientation relative to Earth's rotation. The effect, which would be available nearly globally with no intermittency, requires testing and further examination to see if it can be scaled to practical emission-free power generation.
Chen, P; Tsay, T T
2006-09-01
Changes in population levels of Meloidogyne hapla, M. incognita, Pratylenchus coffeae, and P. penetrans were studied in 12 strawberry fields in the Dahu region of Taiwan. Ten potential rotation crops and two cultural practices were evaluated for their effect on nematode populations and influence on strawberry yield. Rotation with rice or taro and the cultural practice of flooding and bare fallowing for four months were found to reduce nematode soil populations to two or fewer nematodes per 100 ml soil. Average strawberry yields increased between 2.4% to 6.3% following taro compared to the bare fallow treatment. Corn suppressed M. incognita and M. hapla populations and resulted in an increased in strawberry yield compared to bare fallow. Other phytopathogens also present in these fields limited taro as the rotation choice for nematode management. Results of this research and economic analysis of the input requirements for various rotation crops, corn and bare fallow were recommended as the most appropriate rotation strategies for nematode management in strawberry in this region.
NASA Astrophysics Data System (ADS)
Zeng, S.; Wang, X.-X.
1999-02-01
The identification of unbalance is the crux of field balancing of dual rotors system with slightly different rotating speeds. On the basis of correlation theory, this paper explains a method called “Single Point Discrete Fourier Transformation (DFT)” to identify the unbalance. By theoretical analysis, the correlation integral time and its maximum possible error are determined. The field balancing experiment on WLZY-350 horizontal spiral centrifuge verifies its precision, reliability and applicability in practice.
Constraining the String Gauge Field by Galaxy Rotation Curves and Perihelion Precession of Planets
NASA Astrophysics Data System (ADS)
Cheung, Yeuk-Kwan E.; Xu, Feng
2013-09-01
We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as compared to the three-parameter dark matter model with the NFW profile. The average χ2 value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.
NASA Technical Reports Server (NTRS)
Ramachandran Narayanan; Mazuruk, Konstantin
1998-01-01
The use of a rotating magnetic field for stirring metallic melts has been a commonly adopted practice for a fairly long period. The elegance of the technique stems from its non-intrusive nature and the intense stirring it can produce in an electrically conducting medium. A further application of the method in recent times has been in the area of crystal growth from melts (e.g. germanium). The latter experiments have been mainly research oriented in order to understand the basic physics of the process and to establish norms for optimizing such a technique for the commercial production of crystals. When adapted for crystal growth applications, the rotating magnetic field is used to induce a slow flow or rotation in the melt which in effect significantly curtails temperature field oscillations in the melt. These oscillations are known to cause dopant striations and thereby inhomogeneities in the grown crystal that essentially degrades the crystal quality. The applied field strength is typically of the order of milli-Teslas with a frequency range between 50-400 Hz. In this investigation, we report findings from experiments that explore the feasibility of applying a rotating magnetic field to aqueous salt solutions, that are characterized by conductivities that are several orders of magnitude smaller than semi-conductor melts. The aim is to study the induced magnetic field and consequently the induced flow in such in application. Detailed flow field description obtained through non-intrusive particle displacement tracking will be reported along with an analytical assessment of the results. It is anticipated that the obtained results will facilitate in establishing a parameter range over which the technique can be applied to obtain a desired flow field distribution. This method can find applicability in the growth of crystals from aqueous solutions and give an experimenter another controllable parameter towards improving the quality of the grown crystal.
CONSTRAINING THE STRING GAUGE FIELD BY GALAXY ROTATION CURVES AND PERIHELION PRECESSION OF PLANETS
Cheung, Yeuk-Kwan E.; Xu Feng
2013-09-01
We discuss a cosmological model in which the string gauge field coupled universally to matter gives rise to an extra centripetal force and will have observable signatures on cosmological and astronomical observations. Several tests are performed using data including galaxy rotation curves of 22 spiral galaxies of varied luminosities and sizes and perihelion precessions of planets in the solar system. The rotation curves of the same group of galaxies are independently fit using a dark matter model with the generalized Navarro-Frenk-White (NFW) profile and the string model. A remarkable fit of galaxy rotation curves is achieved using the one-parameter string model as compared to the three-parameter dark matter model with the NFW profile. The average {chi}{sup 2} value of the NFW fit is 9% better than that of the string model at a price of two more free parameters. Furthermore, from the string model, we can give a dynamical explanation for the phenomenological Tully-Fisher relation. We are able to derive a relation between field strength, galaxy size, and luminosity, which can be verified with data from the 22 galaxies. To further test the hypothesis of the universal existence of the string gauge field, we apply our string model to the solar system. Constraint on the magnitude of the string field in the solar system is deduced from the current ranges for any anomalous perihelion precession of planets allowed by the latest observations. The field distribution resembles a dipole field originating from the Sun. The string field strength deduced from the solar system observations is of a similar magnitude as the field strength needed to sustain the rotational speed of the Sun inside the Milky Way. This hypothesis can be tested further by future observations with higher precision.
High-resolution, flat-field, plane-grating, f/10 spectrograph with off-axis parabolic mirrors.
Schieffer, Stephanie L; Rimington, Nathan W; Nayyar, Ved P; Schroeder, W Andreas; Longworth, James W
2007-06-01
A high-resolution, flat-field, plane-grating, f/10 spectrometer based on the novel design proposed by Gil and Simon [Appl. Opt. 22, 152 (1983)] is demonstrated. The spectrometer design employs off-axis parabolic collimation and camera mirrors in a configuration that eliminates spherical aberrations and minimizes astigmatism, coma, and field curvature in the image plane. In accordance with theoretical analysis, the performance of this spectrometer achieves a high spatial resolution over the large detection area, which is shown to be limited only by the quality of its optics and their proper alignment within the spatial resolution of a 13 microm x 13 microm pixelated CCD detector. With a 1500 lines/mm grating in first order, the measured spectral resolving power of lambda/Dlambda = 2.5(+/-0.5) x 10(4) allows the clear resolution of the violet Ar(I) doublet at 419.07 and 419.10 nm.
NASA Technical Reports Server (NTRS)
Give'on, Amir; Kern, Brian D.; Shaklan, Stuart
2011-01-01
In this paper we describe the complex electric field reconstruction from image plane intensity measurements for high contrast coronagraphic imaging. A deformable mirror (DM) surface is modied with pairs of complementary shapes to create diversity in the image plane of the science camera where the intensity of the light is measured. Along with the Electric Field Conjugation correction algorithm, this estimation method has been used in various high contrast imaging testbeds to achieve the best contrasts to date both in narrow and in broad band light. We present the basic methodology of estimation in easy to follow list of steps, present results from HCIT and raise several open quations we are confronted with using this method.
The magnetopause as a tangential discontinuity for large field rotation angles
NASA Technical Reports Server (NTRS)
Papamastorakis, I.; Paschmann, G.; Sckopke, N.; Bame, S. J.; Berchem, J.
1984-01-01
Three passes of the ISEE 1 and 2 satellites through the dayside terrestrial magnetopause are discussed where the magnetopause is identified as a tangential discontinuity. This identification is based primarily on the failure of the plasma and magnetic field data to satisfy the conditions for a rotational discontinuity. In all these cases the interplanetary magnetic field was directed strongly southward and the angles between the fields on the two sides of the magnetopause ranged between 136 deg and 170 deg. As this is precisely the field geometry thought to be most conducive for reconnection, the magnetopause would be expected to be a rotational discontinuity. The simplest explanation of this result would appear to be that the magnetic field orientation is not the only factor controlling the onset of reconnection. However, as the identification of the discontinuity applies only locally, it cannot be excluded that for the magnetic field conditions investigated here, different portions of the magnetopause can be described as tangential and rotational discontinuities simultaneously.
NASA Astrophysics Data System (ADS)
Noharet, Bertrand; Hey, Rolph; Sjoberg, Henrik J.
1998-03-01
We present in this paper a study of the influence of the target resolution and contrast on correlation filter performance. Classical filters and the Optimum filter designed by Javidi et al. for non-overlapping noise were considered and tested on a set of realistic images based on real-world non- overlapping noise realizations. We show that for the images that we have tested, there is a limit of the resolution after which classical linear filters fail to detect properly targets, while the Optimum filter still performs well. Furthermore, it was observed that for some background images and fairly low target resolutions, there are values for the target illumination that prevent the classical filter to detect the target, while again it is possible to tune the Optimum filter to make it tolerant to varying target illumination. Eventually, we propose a new composite filter for in-plane rotation tolerance based on individual optimum filters and built according to the equal correlation principle perform best for our test images.
Process e/sup -/. -->. e/sup -/(. nu. nu-bar) in the field of a circularly polarized plane wave
Skobelev, V.V.
1987-12-01
The e/sup -/..-->..e/sup -/(..nu..nu-bar) process in the field of a circularly polarized plane wave is studied in the framework of the Glashow-Weinberg-Salam model. General expressions for the probability of creation of neutrino pairs are obtained, and the case of a low-intensity wave is studied in detail. The effects of asymmetry of emission of electron and muon neutrinos are estimated, and comparison with previous results is performed.
On the control of rapidly rotating convection by an axially varying magnetic field
NASA Astrophysics Data System (ADS)
Gopinath, Venkatesh; Sreenivasan, Binod
2015-11-01
The magnetic field in rapidly rotating dynamos is spatially inhomogeneous. The axial variation of the magnetic field is of particular importance because tall columnar vortices aligned with the rotation axis form at the onset of convection. The classical picture of magnetoconvection with constant or axially varying magnetic fields is that the Rayleigh number and wavenumber at onset decrease appreciably from their non-magnetic values. Nonlinear dynamo simulations show that the axial lengthscale of the self-generated azimuthal magnetic field becomes progressively smaller as we move towards a rapidly rotating regime. With a small-scale field, however, the magnetic control of convection is different from that in previous studies with a uniform or large-scale field. This study looks at the competing viscous and magnetic mode instabilities when the Ekman number ? (ratio of viscous to Coriolis forces) is small. As the applied magnetic field strength (measured by the Elsasser number ?) increases, the critical Rayleigh number for onset of convection initially increases in a viscous branch, reaches an apex where both viscous and magnetic instabilities co-exist, and then falls in the magnetic branch. The magnetic mode of onset is notable for its dramatic suppression of convection in the bulk of the fluid layer where the field is weak. The viscous-magnetic mode transition occurs at ?, which implies that small-scale convection can exist at field strengths higher than previously thought. In spherical shell dynamos with basal heating, convection near the tangent cylinder is likely to be in the magnetic mode. The wavenumber of convection is only slightly reduced by the self-generated magnetic field at ?, in agreement with previous planetary dynamo models. The back reaction of the magnetic field on the flow is, however, visible in the difference in kinetic helicity between cyclonic and anticyclonic vortices.
Lyutyy, T V; Denisov, S I; Reva, V V; Bystrik, Yu S
2015-10-01
We study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations. PMID:26565245
NASA Astrophysics Data System (ADS)
Lyutyy, T. V.; Denisov, S. I.; Reva, V. V.; Bystrik, Yu. S.
2015-10-01
We study the deterministic and stochastic rotational dynamics of ferromagnetic nanoparticles in a precessing magnetic field. Our approach is based on the system of effective Langevin equations and on the corresponding Fokker-Planck equation. Two key characteristics of the rotational dynamics, namely the average angular frequency of precession of nanoparticles and their average magnetization, are of interest. Using the Langevin and Fokker-Planck equations, we calculate both analytically and numerically these characteristics in the deterministic and stochastic cases, determine their dependence on the model parameters, and analyze in detail the role of thermal fluctuations.
Eye torsion and the apparent horizon under head tilt and visual field rotation
NASA Technical Reports Server (NTRS)
Merker, B. H.; Held, R.
1981-01-01
Two different experimental manipulations, namely head tilt and the viewing of a visual display rotating around the line of sight, induce torsional displacements of the eyes and a tilting of the apparent horizon. The present study examines the routes by which visual (field rotation) and otolith-proprioceptive (head tilt) sources of afference influence horizon judgments. In particular, the relationship between torsional eye movements and horizon estimates is addressed. The results indicate that visual and otolith-proprioceptive information sum directly in their influence on eye torsion, but interact more complexly in horizon estimates, indicating a dissociation of their central determinants.
Fischer, Andreas; Kupsch, Christian; Gürtler, Johannes; Czarske, Jürgen
2015-09-21
Non-intrusive fast 3d measurements of volumetric velocity fields are necessary for understanding complex flows. Using high-speed cameras and spectroscopic measurement principles, where the Doppler frequency of scattered light is evaluated within the illuminated plane, each pixel allows one measurement and, thus, planar measurements with high data rates are possible. While scanning is one standard technique to add the third dimension, the volumetric data is not acquired simultaneously. In order to overcome this drawback, a high-speed light field camera is proposed for obtaining volumetric data with each single frame. The high-speed light field camera approach is applied to a Doppler global velocimeter with sinusoidal laser frequency modulation. As a result, a frequency multiplexing technique is required in addition to the plenoptic refocusing for eliminating the crosstalk between the measurement planes. However, the plenoptic refocusing is still necessary in order to achieve a large refocusing range for a high numerical aperture that minimizes the measurement uncertainty. Finally, two spatially separated measurement planes with 25×25 pixels each are simultaneously acquired with a measurement rate of 0.5 kHz with a single high-speed camera.
Antimagnetic rotation in 108,110In with tilted axis cranking relativistic mean-field approach
NASA Astrophysics Data System (ADS)
Sun, Wu-Ji; Xu, Hai-Dan; Li, Jian; Liu, Yong-Hao; Ma, Ke-Yan; Yang, Dong; Lu, Jing-Bing; Ma, Ying-Jun
2016-08-01
Based on tilted axis cranking relativistic mean-field theory within point-coupling interaction PC-PK1, the rotational structure and the characteristic features of antimagnetic rotation for ΔI = 2 bands in 108,110In are studied. Tilted axis cranking relativistic mean-field calculations reproduce the experimental energy spectrum well and are in agreement with the experimental I ∼ ω plot, although the calculated spin overestimates the experimental values. In addition, the two-shears-like mechanism in candidate antimagnetic rotation bands is clearly illustrated and the contributions from two-shears-like orbits, neutron (gd) orbits above Z = 50 shell and Z = 50, N = 50 core are investigated microscopically. The predicted B(E2), dynamic moment of inertia ℑ(2), deformation parameters β and γ, and ℑ(2)/B(E2) ratios in tilted axis cranking relativistic mean-field calculations are discussed and the characteristic features of antimagnetic rotation for the bands before and after alignment are shown. Supported by National Natural Science Foundation of China (11205068, 11205069, 11405072, 11475072, 11547308) and China Postdoctoral Science Foundation (2012M520667)
Liang, Wenfeng; Zhang, Ke; Yang, Xieliu; Liu, Lianqing; Yu, Haibo; Zhang, Weijing
2015-01-01
In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field
Zhang, Ke; Yang, Xieliu; Liu, Lianqing; Yu, Haibo; Zhang, Weijing
2015-01-01
In this paper, the translational motion and self-rotational behaviors of the Raji cells, a type of B-cell lymphoma cell, in an optically induced, non-rotational, electric field have been characterized by utilizing a digitally programmable and optically activated microfluidics chip with the assistance of an externally applied AC bias potential. The crossover frequency spectrum of the Raji cells was studied by observing the different linear translation responses of these cells to the positive and negative optically induced dielectrophoresis force generated by a projected light pattern. This digitally projected spot served as the virtual electrode to generate an axisymmetric and non-uniform electric field. Then, the membrane capacitance of the Raji cells could be directly measured. Furthermore, Raji cells under this condition also exhibited a self-rotation behavior. The repeatable and controlled self-rotation speeds of the Raji cells to the externally applied frequency and voltage were systematically investigated and characterized via computer-vision algorithms. The self-rotational speed of the Raji cells reached a maximum value at 60 kHz and demonstrated a quadratic relationship with respect to the applied voltage. Furthermore, optically projected patterns of four orthogonal electrodes were also employed as the virtual electrodes to manipulate the Raji cells. These results demonstrated that Raji cells located at the center of the four electrode pattern could not be self-rotated. Instead any Raji cells that deviated from this center area would also self-rotate. Most importantly, the Raji cells did not exhibit the self-rotational behavior after translating and rotating with respect to the center of any two adjacent electrodes. The spatial distributions of the electric field generated by the optically projected spot and the pattern of four electrodes were also modeled using a finite element numerical simulation. These simulations validated that the electric field
NASA Astrophysics Data System (ADS)
Cantillon-Murphy, P.; Wald, L. L.; Adalsteinsson, E.; Zahn, M.
2010-03-01
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle's time constant, τ. As the magnetic field frequency is increased, the nanoparticle's magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad/s. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid's temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4 and 7 degree Centigrade above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid's temperature in the MRI environment which is characterized by a large DC field, B0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B0. Results are presented for the expected temperature increase in small tumors (approximately 1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002-0.01 solid volume fraction) and nanoparticle radii (1-10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful selection of the rotating or sinusoidal field parameters (field frequency and amplitude). The work indicates that it may be feasible to combine low-field MRI with a magnetic hyperthermia system using superparamagnetic iron oxide nanoparticles.
Wald, L.L.; Adalsteinsson, E.; Zahn, M.
2009-01-01
In the presence of alternating-sinusoidal or rotating magnetic fields, magnetic nanoparticles will act to realign their magnetic moment with the applied magnetic field. The realignment is characterized by the nanoparticle’s time constant, τ. As the magnetic field frequency is increased, the nanoparticle’s magnetic moment lags the applied magnetic field at a constant angle for a given frequency, Ω, in rad/s. Associated with this misalignment is a power dissipation that increases the bulk magnetic fluid’s temperature which has been utilized as a method of magnetic nanoparticle hyperthermia, particularly suited for cancer in low-perfusion tissue (e.g., breast) where temperature increases of between 4°C and 7°C above the ambient in vivo temperature cause tumor hyperthermia. This work examines the rise in the magnetic fluid’s temperature in the MRI environment which is characterized by a large DC field, B0. Theoretical analysis and simulation is used to predict the effect of both alternating-sinusoidal and rotating magnetic fields transverse to B0. Results are presented for the expected temperature increase in small tumors (~1 cm radius) over an appropriate range of magnetic fluid concentrations (0.002 to 0.01 solid volume fraction) and nanoparticle radii (1 to 10 nm). The results indicate that significant heating can take place, even in low-field MRI systems where magnetic fluid saturation is not significant, with careful selection of the rotating or sinusoidal field parameters (field frequency and amplitude). The work indicates that it may be feasible to combine low-field MRI with a magnetic hyperthermia system using superparamagnetic iron oxide nanoparticles. PMID:20161608
NASA Astrophysics Data System (ADS)
Blackman, Eric G.; Owen, James E.
2016-05-01
Late-type main-sequence stars exhibit an X-ray to bolometric flux ratio that depends on {tilde{R}o}, the ratio of rotation period to convective turnover time, as {tilde{R}o}^{-ζ } with 2 ≤ ζ ≤ 3 for {tilde{R}o} > 0.13, but saturates with |ζ| < 0.2 for {tilde{R}o} < 0.13. Saturated stars are younger than unsaturated stars and show a broader spread of rotation rates and X-ray activity. The unsaturated stars have magnetic fields and rotation speeds that scale roughly with the square root of their age, though possibly flattening for stars older than the Sun. The connection between faster rotators, stronger fields, and higher activity has been established observationally, but a theory for the unified time-evolution of X-ray luminosity, rotation, magnetic field and mass loss that captures the above trends has been lacking. Here we derive a minimalist holistic framework for the time evolution of these quantities built from combining a Parker wind with new ingredients: (1) explicit sourcing of both the thermal energy launching the wind and the X-ray luminosity via dynamo produced magnetic fields; (2) explicit coupling of X-ray activity and mass-loss saturation to dynamo saturation (via magnetic helicity build-up and convection eddy shredding); (3) use of coronal equilibrium to determine how magnetic energy is divided into wind and X-ray contributions. For solar-type stars younger than the Sun, we infer conduction to be a subdominant power loss compared to X-rays and wind. For older stars, conduction is more important, possibly quenching the wind and reducing angular momentum loss. We focus on the time evolution for stars younger than the Sun, highlighting what is possible for further generalizations. Overall, the approach shows promise towards a unified explanation of all of the aforementioned observational trends.
Oblique Magnetic Fields and the Role of Frame Dragging near Rotating Black Hole
NASA Astrophysics Data System (ADS)
Karas, V.; Kopacek, O.; Kunneriath, D.; Hamersky, J.
2014-12-01
Magnetic null points can develop near the ergosphere boundary of a rotating black hole by the combined effects of strong gravitational field and the frame-dragging mechanism. The induced electric component does not vanish in the magnetic null and an efficient process of particle acceleration can occur in its immediate vicinity. Furthermore, the effect of imposed (weak) magnetic field can trigger an onset of chaos in the motion of electrically charged particles. The model set-up appears to be relevant for low-accretion-rate nuclei of some galaxies which exhibit episodic accretion events (such as the Milky Way's supermassive black hole) embedded in a large-scale magnetic field of external origin with respect to the central black hole. In this contribution we summarise recent results and we give an outlook for future work with the focus on the role of gravito-magnetic effects caused by rotation of the black hole.
Suppression of the n=2 rotational instability in field-reversed configurations
NASA Astrophysics Data System (ADS)
Hoffman, Alan L.; Slough, J.; Harding, Dennis G.
1983-06-01
Compact toroid plasmas formed in field-reversed theta pinches are generally destroyed after 30-50 μsec by a rotating n=2 instability. In the reported experiment, instability is controlled, and the plasma destruction is avoided in the TRX-1 theta pinch through the application of octopole magnetic fields. The decay times for loss of poloidal flux and particles are unaffected by the octopole fields. These decay times are about 100 μsec based on inferences from interferometry and excluded flux measurements. The weak, rotating elliptical disturbance (controlled n=2 mode) also made possible a novel determination of the density profile near the separatrix using single-chord interferometry. The local density gradient scale length in this region is found to be about one ion gyrodiameter.
Humoral (immunological) responses in female albino rats during rotating magnetic field exposures
NASA Astrophysics Data System (ADS)
Reid, K.; Falter, H.; Persinger, M. A.
1991-12-01
Experiments were designed to evaluate the primary and secondary humoral responses to a rotating magnetic field configuration, which is known to evoke significant biobehavioral changes. Ten days after inoculation with human serum albumin and 10 days before a booster, female rats were exposed to eigher a 0.5 Hz rotating magnetic field (RMF) or to room conditions (control). The lighting schedule was either continuous or involved a light-dark cycle (LD) of 12:12h. A third group of rats served as colony room controls. Group differences of low statistical significance were found when females were exposed to continuous lighting rather than the LD 12:12 light-dark cycle. However, the effects were considered trivial and not sufficient to explain the previously reported biobehavioral changes evoked by this field configuration.
Time-odd mean fields in covariant density functional theory: Rotating systems
Afanasjev, A. V.; Abusara, H.
2010-09-15
Time-odd mean fields (nuclear magnetism) and their impact on physical observables in rotating nuclei are studied in the framework of covariant density functional theory (CDFT). It is shown that they have profound effect on the dynamic and kinematic moments of inertia. Particle number, configuration, and rotational frequency dependencies of their impact on the moments of inertia have been analyzed in a systematic way. Nuclear magnetism can also considerably modify the band crossing features such as crossing frequencies and the properties of the kinematic and dynamic moments of inertia in the band crossing region. The impact of time-odd mean fields on the moments of inertia in the regions away from band crossing only weakly depends on the relativistic mean-field parametrization, reflecting good localization of the properties of time-odd mean fields in CDFT. The moments of inertia of normal-deformed nuclei considerably deviate from the rigid-body value. On the contrary, superdeformed and hyperdeformed nuclei have the moments of inertia which are close to rigid-body value. The structure of the currents in rotating frame, their microscopic origin, and the relations to the moments of inertia have been systematically analyzed. The phenomenon of signature separation in odd-odd nuclei, induced by time-odd mean fields, has been analyzed in detail.
Thermodynamics of charged rotating dilaton black branes with power-law Maxwell field
NASA Astrophysics Data System (ADS)
Zangeneh, M. Kord; Sheykhi, A.; Dehghani, M. H.
2015-10-01
In this paper, we construct a new class of charged rotating dilaton black brane solutions, with a complete set of rotation parameters, which is coupled to a nonlinear Maxwell field. The Lagrangian of the matter field has the form of the power-law Maxwell field. We study the causal structure of the spacetime and its physical properties in ample details. We also compute thermodynamic and conserved quantities of the spacetime, such as the temperature, entropy, mass, charge, and angular momentum. We find a Smarr-formula for the mass and verify the validity of the first law of thermodynamics on the black brane horizon. Finally, we investigate the thermal stability of solutions in both the canonical and the grand-canonical ensembles and disclose the effects of dilaton field and nonlinearity of the Maxwell field on the thermal stability of the solutions. We find that, for α ≤ 1, charged rotating black brane solutions are thermally stable independent of the values of the other parameters. For α >1, the solutions can encounter an unstable phase depending on the metric parameters.
Generation of shear Alfven waves by a rotating magnetic field source: Three-dimensional simulations
Karavaev, A. V.; Gumerov, N. A.; Papadopoulos, K.; Shao, Xi; Sharma, A. S.; Gekelman, W.; Wang, Y.; Van Compernolle, B.; Pribyl, P.; Vincena, S.
2011-03-15
The paper discusses the generation of polarized shear Alfven waves radiated from a rotating magnetic field source created via a phased orthogonal two-loop antenna. A semianalytical three-dimensional cold two-fluid magnetohydrodynamics model was developed and compared with recent experiments in the University of California, Los Angeles large plasma device. Comparison of the simulation results with the experimental measurements and the linear shear Alfven wave properties, namely, spatiotemporal wave structure, a dispersion relation with nonzero transverse wave number, the magnitude of the wave dependences on the wave frequency, show good agreement. From the simulations it was found that the energy of the Alfven wave generated by the rotating magnetic field source is distributed between the kinetic energy of ions and electrons and the electromagnetic energy of the wave as: {approx}1/2 is the energy of the electromagnetic field, {approx}1/2 is the kinetic energy of the ion fluid, and {approx}2.5% is the kinetic energy of electron fluid for the experiment. The wave magnetic field power calculated from the experimental data and using a fluid model differ by {approx}1% and is {approx}250 W for the experimental parameters. In both the experiment and the three-dimensional two-fluid magnetohydrodynamics simulations the rotating magnetic field source was found to be very efficient for generating shear Alfven waves.
HD 18078: A very slowly rotating Ap star with an unusual magnetic field structure
NASA Astrophysics Data System (ADS)
Mathys, G.; Romanyuk, I. I.; Kudryavtsev, D. O.; Landstreet, J. D.; Pyper, D. M.; Adelman, S. J.
2016-02-01
Context. The existence of a significant population of Ap stars with very long rotation periods (up to several hundred years) has progressively emerged over the past two decades. However, only lower limits of the periods are known for most of them because their variations have not yet been observed over a sufficient timebase. Aims: We determine the rotation period of the slowly rotating Ap star HD 18078 and we derive constraints on the geometrical structure of its magnetic field. Methods: We combine measurements of the mean magnetic field modulus obtained from 1990 to 1997 with determinations of the mean longitudinal magnetic field spanning the 1999-2007 time interval to derive an unambiguous value of the rotation period. We show that this value is consistent with photometric variations recorded in the Strömgren uvby photometric system between 1995 and 2004. We fit the variations of the two above-mentioned field moments with a simple model to constrain the magnetic structure. Results: The rotation period of HD 18078 is (1358 ± 12) d. The geometrical structure of its magnetic field is consistent to first order with a colinear multipole model whose axis is offset from the centre of the star. Conclusions: HD 18078 is only the fifth Ap star with a rotation period longer than 1000 d for which the exact value of that period (as opposed to a lower limit) could be determined. The strong anharmonicity of the variations of its mean longitudinal magnetic field and the shift between their extrema and those of the mean magnetic field modulus are exceptional and indicative of a very unusual magnetic structure. Based in part on observations made at Observatoire de Haute Provence (CNRS), France; at Kitt Peak National Observatory, National Optical Astronomy Observatory (NOAO Prop. ID: KP2442; PI: T. Lanz), which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation; at the Canada
Rotation in a reversed field pinch with active feedback stabilization of resistive wall modes
NASA Astrophysics Data System (ADS)
Cecconello, M.; Menmuir, S.; Brunsell, P. R.; Kuldkepp, M.
2006-09-01
Active feedback stabilization of multiple resistive wall modes (RWMs) has been successfully proven in the EXTRAP T2R reversed field pinch. One of the features of plasma discharges operated with active feedback stabilization, in addition to the prolongation of the plasma discharge, is the sustainment of the plasma rotation. Sustained rotation is observed both for the internally resonant tearing modes (TMs) and the intrinsic impurity oxygen ions. Good quantitative agreement between the toroidal rotation velocities of both is found: the toroidal rotation is characterized by an acceleration phase followed, after one wall time, by a deceleration phase that is slower than in standard discharges. The TMs and the impurity ions rotate in the same poloidal direction with also similar velocities. Poloidal and toroidal velocities have comparable amplitudes and a simple model of their radial profile reproduces the main features of the helical angular phase velocity. RWMs feedback does not qualitatively change the TMs behaviour and typical phenomena such as the dynamo and the 'slinky' are still observed. The improved sustainment of the plasma and TMs rotation occurs also when feedback only acts on internally non-resonant RWMs. This may be due to an indirect positive effect, through non-linear coupling between TMs and RWMs, of feedback on the TMs or to a reduced plasma-wall interaction affecting the plasma flow rotation. Electromagnetic torque calculations show that with active feedback stabilization the TMs amplitude remains well below the locking threshold condition for a thick shell. Finally, it is suggested that active feedback stabilization of RWMs and current profile control techniques can be employed simultaneously thus improving both the plasma duration and its confinement properties.
Out-of-Plane Computed-Tomography-Guided Biopsy Using a Magnetic-Field-Based Navigation System
Wallace, Michael J. Gupta, Sanjay; Hicks, Marshall E.
2006-02-15
The purpose of this article is to report our clinical experience with out-of-plane computed-tomography (CT)-guided biopsies using a magnetic-field-based navigation system. Between February 2002 and March 2003, 20 patients underwent CT-guided biopsy in which an adjunct magnetic-field-based navigation system was used to aid an out-of-plane biopsy approach. Eighteen patients had an underlying primary malignancy. All biopsies involved the use of a coaxial needle system in which an outer 18G guide needle was inserted to the lesion using the navigation system and an inner 22G needle was then used to obtain fine-needle aspirates. Complications and technical success were recorded. Target lesions were located in the adrenal gland (n = 7), liver (n = 6), pancreas (n = 3), lung (n = 2), retroperitoneal lymph node (n = 1), and pelvis (n = 1). The mean lesion size (maximum transverse diameter) was 26.5 mm (range: 8-70 mm) and the mean and median cranial-caudal distance, between the transaxial planes of the final needle tip location and the needle insertion site, was 40 mm (range: 18-90 mm). Needle tip positioning was successfully placed within the lesion in all 20 biopsies. A diagnosis of malignancy was obtained in 14 biopsies. Benign diagnoses were encountered in the remaining six biopsies and included a benign adrenal gland (n = 2), fibroelastic tissue (n = 1), hepocytes with steatosis (n = 2) and reactive hepatocytes (n = 1). No complications were encountered. A magnetic-field-based navigation system is an effective adjunct tool for accurate and safe biopsy of lesions that require an out-of-plane CT approach.
Liquid-metal flow through a thin-walled elbow in a plane perpendicular to a uniform magnetic field
Walker, J.S.
1986-04-01
This paper presents analytical solutions for the liquid-metal flow through two straight pipes connected by a smooth elbow with the same inside radius. The pipes and the elbow lie in a plane which is perpendicular to a uniform, applied magnetic field. The strength of the magnetic field is assumed to be sufficiently strong that inertial and viscous effects are negligible. This assumption is appropriate for the liquid-lithium flow in the blanket of a magnetic confinement fusion reactor, such as a tokamak. The pipes and the elbow have thin metal walls.
Iñarrea, J.
2013-12-04
We report on theoretical studies of a recently discovered strong radiation-induced magnetoresistance spike obtained in ultraclean two-dimensional electron systems at low temperatures. The most striking feature of this spike is that it shows up on the second harmonic of the cyclotron resonance. We apply the radiation-driven electron orbits model in the ultraclean scenario to offer a theoretical approach of this striking effect. We explain the effect of an in-plane magnetic field on the spike which consists in a vanishing effect when this field increases.
Mode- and plasma rotation in a resistive shell reversed-field pinch
NASA Astrophysics Data System (ADS)
Malmberg, J.-A.; Brzozowski, J.; Brunsell, P. R.; Cecconello, M.; Drake, J. R.
2004-02-01
Mode rotation studies in a resistive shell reversed-field pinch, EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1 (2001)] are presented. The phase relations and nonlinear coupling of the resonant modes are characterized and compared with that expected from modeling based on the hypothesis that mode dynamics can be described by a quasi stationary force balance including electromagnetic and viscous forces. Both m=0 and m=1 resonant modes are studied. The m=1 modes have rotation velocities corresponding to the plasma flow velocity (20-60 km/s) in the core region. The rotation velocity decreases towards the end of the discharge, although the plasma flow velocity does not decrease. A rotating phase locked m=1 structure is observed with a velocity of about 60 km/s. The m=0 modes accelerate throughout the discharges and reach velocities as high as 150-250 km/s. The observed m=0 phase locking is consistent with theory for certain conditions, but there are several conditions when the dynamics are not described. This is not unexpected because the assumption of quasi stationarity for the mode spectra is not fulfilled for many conditions. Localized m=0 perturbations are formed in correlation with highly transient discrete dynamo events. These perturbations form at the location of the m=1 phase locked structure, but rotate with a different velocity as they spread out in the toroidal direction.
Rayleigh-Taylor stability of a two-fluid system under a general rotation field
NASA Astrophysics Data System (ADS)
Dávalos-Orozco, L. A.
1996-01-01
In this paper we investigate the Rayleigh-Taylor instability of a two-fluid layer system under a general rotation field. Gravity is always perpendicular to the two horizontal layers and rotation has an arbitrary angle with respect to the vertical. It is found that, in an unstable situation, an increase in the non-dimensional density-difference increases the stable angular area of wave propagation, measured with respect to the horizontal component of rotation. However, it is found that the vertical component of rotation reduces not only this stable angular area but also the range in which the horizontal component stabilizes the system according to a previous study by Dávalos-Orozco ( Fluid Dyn. Res., 12: 243, 1993). This decrease in stable area occurs along with a decrease in the growth rate in the unstable region. Numerical analysis of the eigenvalue equation shows that the stable angular area disappears after the non-dimensional vertical component of rotation attains the value 0.33. Exact and approximate analytical expressions for the critical values are calculated to help to understand the physics of the numerical analysis.
Muon-Spin Rotation in Multiferroic Cu3Mo2O9 under Electric Fields
NASA Astrophysics Data System (ADS)
Kuroe, Haruhiko; Kuwahara, Hideki; Sekine, Tomoyuki; Watanabe, Isao; Raselli, Andrea-Raeto; Elender, Matthias; Biswas, Pabitra Kumar; Hase, Masashi; Oka, Kunihiko; Ito, Toshimitsu; Eisaki, Hiroshi
It has been demonstrated that the muon spin rotation measurements under electric field give helpful information about the electrically induced magnetism, e.g., the cross correlation effects in multiferroic materials. We have developed an electric-field application system up to 500V for the Dolly spectrometer at the Paul Scherrer Institute. We report the electric-field effects on the μSR spectrum in the multiferroic material Cu3Mo2O9, where a slightly canted antiferromagnetic long-range order appears together with the ferroelectricity below 8K. In the muon-spin rotation spectrum at 1.5K, two kinds of the internal magnetic fields are clearly observed as a beating oscillation. The muon-spin spectrum depends on the electric fields along the c axis of the crystal along which the spontaneous electric polarization appears. From the fitting of the spectra in time and frequency domains, it is shown that the observation of the electric-field dependence on the muon-spin spectra clearly indicates a change of the internal magnetic fields induced by the application of the external electric fields. We propose a model with one muon-stopping site which explains the observed spectra qualitatively. This model is based on the magnetic excitations in Cu3Mo2O9 obtained from the inelastic neutron-scattering experiments.
NASA Astrophysics Data System (ADS)
Matsushima, Kyoji; Schimmel, Hagen; Wyrowski, Frank
2003-09-01
A novel method for simulating field propagation is presented. The method, based on the angular spectrum of plane waves and coordinate rotation in the Fourier domain, removes geometric limitations posed by conventional propagation calculation and enables us to calculate complex amplitudes of diffracted waves on a plane not parallel to the aperture. This method can be implemented by using the fast Fourier transformation twice and a spectrum interpolation. It features computation time that is comparable with that of standard calculation methods for diffraction or propagation between parallel planes. To demonstrate the method, numerical results as well as a general formulation are reported for a single-axis rotation.
NASA Astrophysics Data System (ADS)
Cirilo-Lombardo, Diego Julio
2015-06-01
The two-dimensional charge transport with parallel (in plane) magnetic field is considered from the physical and mathematical point of view. To this end, we start with the magnetic field parallel to the plane of charge transport, in sharp contrast to the configuration described by the theorems of Aharonov and Casher where the magnetic field is perpendicular. We explicitly show that the specific form of the arising equation enforces the respective field solution to fulfill the Majorana condition. Consequently, as soon any physical system is represented by this equation, the rise of fields with Majorana type behavior is immediately explained and predicted. In addition, there exists a quantized particular phase that removes the action of the vector potential producing interesting effects. Such new effects are able to explain due to the geometrical framework introduced, several phenomenological results recently obtained in the area of spintronics and quantum electronic devices. The quantum ring as spin filter is worked out in this framework and also the case of the quantum Hall effect.
Deards, C. L.; Hoffman, A. L.; Steinhauer, L. C.
2011-11-15
Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.
Magnetic field variation caused by rotational speed change in a magnetohydrodynamic dynamo.
Miyagoshi, Takehiro; Hamano, Yozo
2013-09-20
We have performed numerical magnetohydrodynamic dynamo simulations in a spherical shell with rotational speed or length-of-day (LOD) variation, which is motivated by correlations between geomagnetic field and climatic variations with ice and non-ice ages. The results show that LOD variation leads to magnetic field variation whose amplitude is considerably larger than that of LOD variation. The heat flux at the outer sphere and the zonal flow also change. The mechanism of the magnetic field variation due to LOD variation is also found. The keys are changes of dynamo activity and Joule heating.
Bose-Einstein condensates in strong electric fields: Effective gauge potentials and rotating states
Kailasvuori, J.M.; Hansson, T.H.; Kavoulakis, G.M.
2002-11-01
Magnetically trapped atoms in Bose-Einstein condensates are spin polarized. Since the magnetic field is inhomogeneous, the atoms acquire Berry phases of the Aharonov-Bohm type during adiabatic motion. In the presence of an electric field, there is an additional Aharonov-Casher effect. Taking into account the limitations on the strength of the electric fields due to the polarizability of the atoms, we investigate the extent to which these effects can be used to induce rotation in a Bose-Einstein condensate.
The rotation of photospheric magnetic fields: A random walk transport model
NASA Technical Reports Server (NTRS)
Wang, Y. -M.; Sheeley, N. R., Jr.
1994-01-01
In an earlier study of solar differential rotation, we showed that the transport of magnetic flux across latitudes acts to establish quasi-stationary patterns, therby accounting for the observed rigid rotation of the large-scale photospheric field. In that paper, the effect of supergranular convection was represented by a continuum diffusion, limiting the applicability of the calculations to large spatial scales. Here we extend the model to scales comparable to that of the supergranulation itself by replacing the diffusive transport with a discrete random walk process. Rotation curves are derived by cross-correlating the simulated photospheric field maps for a variety of time lags and spatial resolutions. When the lag between maps is relatively short less than or approximately = 15 days), the midlatitude correlation functions show two distinct components: a broad feature associated with the large-scale unipolar patterns and a narrow feature originating from small magnetic structures encompossing from one to several supergranular cells. By fitting the broad component we obtain the rigid rotation profile of the patterns, whereas by fitting the narrow component, we recover the differential rate of the photospheric plasma itself. For time lags of 1 month or greater, only the broad feature associated with the long-lived patterns remains clearly identifiable in the simulations.
NASA Astrophysics Data System (ADS)
Fang, X.; Ma, Y.
2014-12-01
Mars does not have a global intrinsic magnetic field but has localized crustal magnetic anomalies particularly in the southern hemisphere. Several studies have reported that heavy ion escape rates are highly dependent on the orientation of magnetic anomalies to the Sun, although significant uncertainty remains regarding the magnitude of the changes. Due to modeling complexity, however, all the previously published global studies were conducted based on an oversimplified steady state approximation. Very recently our team incorporated for the first time a time-dependent calculation into a global MHD model by considering the continuous rotation of the crustal field with the planet. The new non-steady-state simulations revealed a general anti-correlation of ion escape with the subsolar magnetic strength when the strongest crustal field region is on the dayside, consistent with previous findings. However, the details of how the rotation of the localized crustal field regulates global ion loss over time are still poorly understood, particularly when the strong magnetic anomalies move into the nightside. In contrast with previous global modeling work, which adopted a steady state approximation and mainly focused on the effects of external drivers (i.e., solar EUV and solar wind plasma), this study aims to improve our understanding of how the internal time-varying perturbation due to the rotation of crustal magnetic anomalies regulates the plasma interaction and ultimately affects planetary ion escape.
Zhang, Site; Asoubar, Daniel; Hellmann, Christian; Wyrowski, Frank
2016-01-20
The propagation of electromagnetic fields between non-parallel planes based on a spectrum-of-plane-wave analysis is discussed and formulations for an efficient numerical implementation are presented in detail. It is shown that with the help of interpolation techniques, the numerical implementation can be done with the standard uniform fast Fourier transform (FFT) of easy access. Different interpolation techniques are numerically examined, and it turns out that the use of cubic interpolation, together with the uniform FFT, brings both significantly increased computational efficiency and high simulation accuracy. Apart from the aspect of computational efficiency, all formulations in this work are generalized in a fully vectorial manner in comparison to previous works. PMID:26835928
Zhang, Site; Asoubar, Daniel; Hellmann, Christian; Wyrowski, Frank
2016-01-20
The propagation of electromagnetic fields between non-parallel planes based on a spectrum-of-plane-wave analysis is discussed and formulations for an efficient numerical implementation are presented in detail. It is shown that with the help of interpolation techniques, the numerical implementation can be done with the standard uniform fast Fourier transform (FFT) of easy access. Different interpolation techniques are numerically examined, and it turns out that the use of cubic interpolation, together with the uniform FFT, brings both significantly increased computational efficiency and high simulation accuracy. Apart from the aspect of computational efficiency, all formulations in this work are generalized in a fully vectorial manner in comparison to previous works.
NASA Astrophysics Data System (ADS)
Sawa, Takeyasu; Fujimoto, M.
1993-05-01
The approximate dynamo equation, which yields asymptotic solutions for the large scale bisymmetric spiral (BSS) magnetic fields rotating rigidly over a large area of the galactic disk, is derived. The vertical thickness and the dynamo strength of the gaseous disk which are necessary to generate and sustain the BSS magnetic fields is determined. The globally BSS magnetic fields which propagate over the disk as a wave without being twisted more tightly are reproduced. A poloidal field configuration is theoretically predicted in the halo around the disk, and is observed in the edge-on galaxy NGC4631. Mathematical methods for the galactic dynamo are shown to be equivalent. Those methods give different growth rates between the BSS and the axisymmetric spiral (ASS) magnetic fields in the disk. Magnetohydrodynamical excitation is discussed between the BSS magnetic fields and the two armed spiral density waves.
Effect of Transverse Magnetic Fields on Cold-Atom Nonlinear Magneto-Optical Rotation
NASA Astrophysics Data System (ADS)
Meyer, David; Kunz, Paul; Fatemi, Fredrik; Quraishi, Qudsia
2016-05-01
We investigate nonlinear magneto-optical rotation (NMOR) in cold atoms in the presence of a transverse magnetic field where alignment-to-orientation conversion (AOC) dominates. The AOC mechanism, which relies on AC-Stark shifts generated by a strong, off-resonant probe beam, significantly alters the NMOR resonance. When an additional magnetic field is present, parallel to the electric field of the light, a nested feature within this NMOR resonance manifests. Unlike similar features observed with lower optical power in warm vapors, attributed to optical pumping through nearby hyperfine levels, this feature is due solely to the AOC mechanism. Using numerical simulations, a perturbative solution, and experimental observations we characterize the feature with respect to optical power, optical polarization, magnetic field strength, and magnetic field direction. These results shed further light on the AOC mechanism common to NMOR-based experiments and we demonstrate a potential application to measure transverse DC magnetic fields and spatial gradients.
On the Rotation the Interstellar Magnetic Field Ahead of the Heliopause
NASA Astrophysics Data System (ADS)
Opher, Merav; Drake, James
Based on the difference between the orientation of the interstellar and the solar magnetic fields, there was an expectation by the community that the magnetic field direction will rotate dramatically across the heliopause (HP). Recently, the Voyager team concluded that Voyager 1 (V1) crossed into interstellar space last year. The question is then why there was no significant rotation in the direction of the magnetic field across the HP. Here we present simulations that reveal that strong rotations in the direction of the magnetic field at the HP at the location of V1 (and Voyager 2) are not expected. The solar magnetic field strongly affects the draping of the interstellar magnetic field (BISM) around the HP. BISM twists as it approaches the HP and acquires a strong T component (East-West). The strong increase in the T component occurs where the interstellar flow stagnates in front of the HP. At this same location the N component BN is significantly reduced. Above and below, the neighboring BISM lines also twist into the T direction. This behavior occurs for a wide range of orientations of BISM. The angle delta = a sin(BN /B) is small (around 10(°) -20(°) ), as seen in the observations. Only after some significant distance outside the HP is the direction of the interstellar field distinguishably different from that of the Parker spiral. In the twist region (after the HP) there is a fast variation of the angle delta/AU and then a slower one farther away as seen in the observations (Burlaga & Ness 2014). We will discuss, as well in this talk, the mechanism responsible for the twist. The same twist is seen ahead of the magnetopause, where the field in the magnetosheath (equivalent to BISM) (in cases where reconnection is small) rotates toward the direction of the magnetospheric magnetic field (equivalent to the HS magnetic field) well upstream of the magnetopause (Phan et al. 1994). The IBEX ribbon, the band of increased intensity of energetic neutral atoms at 1 ke
NASA Technical Reports Server (NTRS)
Bryant, Robert G. (Inventor); Fox, Robert L. (Inventor)
2006-01-01
An electro-active transducer includes a ferroelectric material sandwiched by first and second electrode patterns. When the device is used as an actuator, the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when voltage is applied to the electrode patterns. When the device is used as a sensor. the first and second electrode patterns are configured to introduce an electric field into the ferroelectric material when the ferroelectric material experiences deflection in a direction substantially perpendicular thereto. In each case, the electrode patterns are designed to cause the electric field to: i) originate at a region of the ferroelectric material between the first and second electrode patterns. and ii) extend radially outward from the region of the ferroelectric material (at which the electric field originates) and substantially parallel to the ferroelectric material s plane.
Arnaut, Luk R
2010-04-01
We derive an integral expression for the plane-wave expansion of the time-varying (nonstationary) random field inside a mode-stirred reverberation chamber. It is shown that this expansion is a so-called oscillatory process, whose kernel can be expressed explicitly in closed form. The effect of nonstationarity is a modulation of the spectral density of the field on a time scale that is a function of the cavity relaxation time. It is also shown how the contribution by a nonzero initial value of the field can be incorporated into the expansion. The results are extended to a special class of second-order processes, relevant to the reception of a mode-stirred reverberation field by a device under test with a first-order (relaxation-type) frequency response.
NASA Astrophysics Data System (ADS)
Arnaut, Luk R.
2010-04-01
We derive an integral expression for the plane-wave expansion of the time-varying (nonstationary) random field inside a mode-stirred reverberation chamber. It is shown that this expansion is a so-called oscillatory process, whose kernel can be expressed explicitly in closed form. The effect of nonstationarity is a modulation of the spectral density of the field on a time scale that is a function of the cavity relaxation time. It is also shown how the contribution by a nonzero initial value of the field can be incorporated into the expansion. The results are extended to a special class of second-order processes, relevant to the reception of a mode-stirred reverberation field by a device under test with a first-order (relaxation-type) frequency response.
The JCMT Plane Survey: early results from the ℓ = 30° field
NASA Astrophysics Data System (ADS)
Moore, T. J. T.; Plume, R.; Thompson, M. A.; Parsons, H.; Urquhart, J. S.; Eden, D. J.; Dempsey, J. T.; Morgan, L. K.; Thomas, H. S.; Buckle, J.; Brunt, C. M.; Butner, H.; Carretero, D.; Chrysostomou, A.; deVilliers, H. M.; Fich, M.; Hoare, M. G.; Manser, G.; Mottram, J. C.; Natario, C.; Olguin, F.; Peretto, N.; Polychroni, D.; Redman, R. O.; Rigby, A. J.; Salji, C.; Summers, L. J.; Berry, D.; Currie, M. J.; Jenness, T.; Pestalozzi, M.; Traficante, A.; Bastien, P.; diFrancesco, J.; Davis, C. J.; Evans, A.; Friberg, P.; Fuller, G. A.; Gibb, A. G.; Gibson, S.; Hill, T.; Johnstone, D.; Joncas, G.; Longmore, S. N.; Lumsden, S. L.; Martin, P. G.; Lu'o'ng, Q. Nguyê˜n.; Pineda, J. E.; Purcell, C.; Richer, J. S.; Schieven, G. H.; Shipman, R.; Spaans, M.; Taylor, A. R.; Viti, S.; Weferling, B.; White, G. J.; Zhu, M.
2015-11-01
We present early results from the JCMT (James Clerk Maxwell Telescope) Plane Survey (JPS), which has surveyed the northern inner Galactic plane between longitudes ℓ = 7° and ℓ = 63° in the 850-μm continuum with SCUBA-2 (Submm Common-User Bolometer Array 2), as part of the JCMT Legacy Survey programme. Data from the ℓ = 30° survey region, which contains the massive-star-forming regions W43 and G29.96, are analysed after approximately 40 per cent of the observations had been completed. The pixel-to-pixel noise is found to be 19 mJy beam-1 after a smooth over the beam area, and the projected equivalent noise levels in the final survey are expected to be around 10 mJy beam-1. An initial extraction of compact sources was performed using the FELLWALKER method, resulting in the detection of 1029 sources above a 5σ surface-brightness threshold. The completeness limits in these data are estimated to be around 0.2 Jy beam-1 (peak flux density) and 0.8 Jy (integrated flux density) and are therefore probably already dominated by source confusion in this relatively crowded section of the survey. The flux densities of extracted compact sources are consistent with those of matching detections in the shallower APEX (Atacama Pathfinder Experiment) Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. We analyse the virial and evolutionary state of the detected clumps in the W43 star-forming complex and find that they appear younger than the Galactic-plane average.
La Haye, R.J.
1997-02-01
The existing theoretical and experimental basis for predicting the levels of resonant static error field at different components m,n that stop plasma rotation and produce a locked mode is reviewed. For ITER ohmic discharges, the slow rotation of the very large plasma is predicted to incur a locked mode (and subsequent disastrous large magnetic islands) at a simultaneous weighted error field ({Sigma}{sub 1}{sup 3}w{sub m1}B{sup 2}{sub rm1}){sup {1/2}}/B{sub T} {ge} 1.9 x 10{sup -5}. Here the weights w{sub m1} are empirically determined from measurements on DIII-D to be w{sub 11} = 0. 2, w{sub 21} = 1.0, and w{sub 31} = 0. 8 and point out the relative importance of different error field components. This could be greatly obviated by application of counter injected neutral beams (which adds fluid flow to the natural ohmic electron drift). The addition of 5 MW of 1 MeV beams at 45{degrees} injection would increase the error field limit by a factor of 5; 13 MW would produce a factor of 10 improvement. Co-injection beams would also be effective but not as much as counter-injection as the co direction opposes the intrinsic rotation while the counter direction adds to it. A means for measuring individual PF and TF coil total axisymmetric field error to less than 1 in 10,000 is described. This would allow alignment of coils to mm accuracy and with correction coils make possible the very low levels of error field needed.
Solidification of II-VI Compounds in a Rotating Magnetic Field
NASA Technical Reports Server (NTRS)
Gillies, D. C.; Volz, M. P.; Mazuruk, K.; Motakef, S.; Dudley, M.; Matyi, R.
1999-01-01
This project is aimed at using a rotating magnetic field (RMF) to control fluid flow and transport during directional solidification of elemental and compound melts. Microgravity experiments have demonstrated that small amounts of residual acceleration of less than a micro-g can initiate and prolong fluid flow, particularly when there is a static component of the field perpendicular to the liquid solid interface. Thus a true diffusion boundary layer is not formed, and it becomes difficult to verify theories of solidification or to achieve diffusion controlled solidification. The RMF superimposes a stirring effect on an electrically conducting liquid, and with appropriate field strengths and frequencies, controlled transport of material through a liquid column can be obtained. As diffusion conditions are precluded and complete mixing conditions prevail, the technique is appropriate for traveling solvent zone or float zone growth methods in which the overall composition of the liquid can be maintained throughout the growth experiment. Crystals grown by RMF techniques in microgravity in previous, unrelated missions have shown exceptional properties. The objective of the project is two-fold, namely (1) using numerical modeling to simulate the behavior of a solvent zone with applied thermal boundary conditions and demonstrate the effects of decreasing gravity levels, or an increasing applied RMF, or both, and (2) to grow elements and II-VI compounds from traveling solvent zones both with and without applied RMFs, and to determine objectively how well the modeling predicts solidification parameters. Numerical modeling has demonstrated that, in the growth of CdTe from a tellurium solution, a rotating magnetic field can advantageously modify the shape of the liquid solid interface such that the interface is convex as seen from the liquid. Under such circumstances, the defect structure is reduced as any defects which are formed tend to grow out and not propagate. The flow
Field effect tuning of microwave Faraday rotation and isolation with large-area graphene
NASA Astrophysics Data System (ADS)
Skulason, Helgi S.; Sounas, Dimitrios L.; Mahvash, Farzaneh; Francoeur, Sebastien; Siaj, Mohamed; Caloz, Christophe; Szkopek, Thomas
2015-08-01
We have demonstrated field effect tuning of microwave frequency Faraday rotation in magnetically biased large-area graphene in a hollow circular waveguide isolator geometry. Oxidized intrinsic silicon was used as a microwave transparent back-gate for large-area graphene devices. A 26 dB modulation of isolation in the K-band was achieved with a gate voltage modulation of 10 V corresponding to a carrier density modulation of 7 × 10 11 /cm2. We have developed a simple analytical model for transmission and isolation of the structure. Field effect modulation of Faraday rotation can be extended to other two dimensional electronic systems and is anticipated to be useful for gate voltage controlled isolators, circulators, and other non-reciprocal devices.
A.S. Landsman, S.A. Cohen, A.H. Glasser
2005-11-01
Heating of figure-8 ions by odd-parity rotating magnetic fields (RMFο) applied to an elongated field-reversed configuration (FRC) is investigated. The largest energy gain occurs at resonances (s ≡ ω(sub)R/ω) of the RMFο frequency, ω(sub)R, with the figure-8 orbital frequency, ω, and is proportional to s^2 for s – even resonances and to s for s – odd resonances. The threshold for the transition from regular to stochastic orbits explains both the onset and saturation of heating. The FRC magnetic geometry lowers the threshold for heating below that in the tokamak by an order of magnitude.
Influence of light sheet separation on SPIV measurement in a large field spanwise plane
NASA Astrophysics Data System (ADS)
Foucaut, J. M.; Coudert, S.; Braud, C.; Velte, C.
2014-03-01
Stereoscopic particle image velocimetry (SPIV) is nowadays a well-established measurement technique for turbulent flows. However, the accuracy and the spatial resolution are still highly questionable in the presence of complex flow with both strong gradients and out-of-plane motions. To give guidelines for both setup and measurements of such flow configurations, a large region of overlap between two SPIV systems on the same laser light sheet is acquired in a plane normal to the streamwise direction of a high Reynolds turbulent boundary layer flow. A simple separation of the two light sheets is used to improve the accuracy of the measurements by increasing the velocity dynamic range especially. It also presents the enhancement of accuracy due to the light sheet separation for characterizing streamwise vortices (i.e. perpendicular to the sheet). The proposed technique has been demonstrated in the Laboratoire de Mécanique de Lille wind tunnel facility which has been specially designed to study fully developed turbulent boundary layers at high Reynolds numbers. The outlook is to study in detail the physics of the streamwise vortices generated from vortex generators taking advantage of the large scales of this turbulent boundary layer.
NASA Astrophysics Data System (ADS)
Bercu, V.; Martinelli, M.; Massa, C. A.; Pardi, L. A.; Rössler, E. A.; Leporini, D.
2008-08-01
Exploiting the high angular resolution of high field electron paramagnetic resonance measured at 95, 190, and 285 GHz we determine the rotational nonergodicity parameter of different probe molecules in the glass former o-terphenyl and polybutadiene in a model-independent way. Our results clearly show a characteristic change in the temperature of the nonergodicity parameter proving a rather sharp dynamic crossover in both systems, in contrast to previous results from other techniques.
Radio Frequency (RF) Trap for Confinement of Antimatter Plasmas Using Rotating Wall Electric Fields
NASA Technical Reports Server (NTRS)
Sims, William Herbert, III; Pearson, J. Boise
2004-01-01
Perturbations associated with a rotating wall electric field enable the confinement of ions for periods approaching weeks. This steady state confinement is a result of a radio frequency manipulation of the ions. Using state-of-the-art techniques it is shown that radio frequency energy can produce useable manipulation of the ion cloud (matter or antimatter) for use in containment experiments. The current research focuses on the improvement of confinement systems capable of containing and transporting antimatter.
Determining the Ocean's Role on the Variable Gravity Field and Earth Rotation
NASA Technical Reports Server (NTRS)
Ponte, Rui M.
2000-01-01
Our three year investigation, carried out over the period 18-19 Nov 2000, focused on the study of the variability in ocean angular momentum and mass signals and their relation to the Earth's variable rotation and gravity field. This final report includes a summary description of our work and a list of related publications and presentations. One thrust of the investigation was to determine and interpret the changes in the ocean mass field, as they impact on the variable gravity field and Earth rotation. In this regard, the seasonal cycle in local vertically-integrated ocean mass was analyzed using two ocean models of different complexity: (1) the simple constant-density, coarse resolution model of Ponte; and (2) the fully stratified, eddy-resolving model of Semtner and Chervin. The dynamics and thermodynamics of the seasonal variability in ocean mass were examined in detail, as well as the methodologies to calculate those changes under different model formulations. Another thrust of the investigation was to examine signals in ocean angular momentum (OAM) in relation to Earth rotation changes. A number of efforts were undertaken in this regard. Sensitivity of the oceanic excitation to different assumptions about how the ocean is forced and how it dissipates its energy was explored.
NASA Astrophysics Data System (ADS)
Heyn, Martin F.; Ivanov, Ivan B.; Kasilov, Sergei V.; Kernbichler, Winfried
2006-04-01
The interaction of rotating magnetic fields (RMFs) with a plasma is modelled in the linear approximation. A kinetic Hamiltonian model for the rf plasma conductivity is used. A radially inhomogeneous periodic cylindrical plasma with a rotational transform of the magnetic field is studied with parameters relevant to the dynamic ergodic divertor (DED) of TEXTOR. For the case of a finite electron diamagnetic velocity it is shown that the torque resulting from the RMF tends to bring the electron fluid approximately to the rest frame of this field. This result is in qualitative agreement with long mean-free path drift MHD theory. In contrast to that theory where a resonant behaviour is found at electron and ion diamagnetic frequencies, in the present kinetic analysis, the RMF frequency where the torque passes through zero is smaller than the electron diamagnetic frequency if there is an electron temperature gradient present. The relation of these results with recent experimental measurements of the DED-induced plasma rotation in TEXTOR is discussed.
Giant Faraday rotation induced by the Berry phase in bilayer graphene under strong terahertz fields
NASA Astrophysics Data System (ADS)
Yang, Fan; Xu, Xiaodong; Liu, Ren-Bao
2014-04-01
High-order terahertz (THz) sideband generation in semiconductors is a phenomenon with physics similar to that of high-order harmonic generation but in a regime of much lower frequency. Our previous paper [1] found that the electron-hole pair excited by a weak optical laser can accumulate a Berry phase along a cyclic trajectory under the driving of a strong elliptically polarized THz field. Furthermore, the Berry phase appears as the Faraday rotation angle of the emission signal under short-pulse excitation in monolayer MoS_{2}. In this paper, the theory of the Berry phase in THz extreme nonlinear optics is applied to biased bilayer graphene with Bernal stacking, which has similar Bloch band features and optical properties to monolayer MoS_{2}, such as the time-reversal related valleys and the valley contrasting optical selection rule. However, the biased bilayer graphene has much larger Berry curvature than monolayer MoS_{2}, which leads to a large Berry phase of the quantum trajectory and in turn a giant Faraday rotation of the optical emission (˜1 rad for a THz field with frequency 1 THz and strength 8 kV cm-1). This surprisingly big angle shows that the Faraday rotation can be induced more efficiently by the Berry curvature in momentum space than by the magnetic field in real space. It provides opportunities to use bilayer graphene and THz lasers for ultrafast electro-optical devices.
Cross-field electron transport induced by a rotating spoke in a cylindrical Hall thruster
Ellison, C. L.; Raitses, Y.; Fisch, N. J.
2012-01-15
Rotating spoke phenomena have been observed in a variety of Hall thruster and other E x B devices. It has been suggested that the spoke may be associated with the enhancement of the electron cross-field transport. In this paper, the current conducted across the magnetic field via a rotating spoke has been directly measured for the first time in the E x B discharge of a cylindrical Hall thruster. The spoke current was measured using a segmented anode. Synchronized measurements with a high speed camera and a four-segment anode allow observation of the current as a function of time and azimuthal position. Upwards of 50% of the total current is conducted through the spoke, which occupies a quarter of the Hall thruster channel area. To determine the transport mechanism, emissive and Langmuir probes were installed to measure fluctuating plasma potential, electron density, and temperature. A perturbed, azimuthal electric field and density are observed to oscillate in-phase with the rotating spoke. The resulting drift current is found to enhance electron transport with a magnitude equal to the spoke current to within margins of error.
Rotational dynamics of an asymmetric-top molecule in parallel electric and nonresonant laser fields
NASA Astrophysics Data System (ADS)
Omiste, Juan J.; González-Férez, Rosario
2013-09-01
We present a theoretical study of the rotational dynamics of asymmetric-top molecules in an electric field and a parallel nonresonant linearly polarized laser pulse. The time-dependent Schrödinger equation is solved within the rigid rotor approximation. Using the benzonitrile molecule as a prototype, we investigate the field-dressed dynamics for experimentally accessible field configurations and compare these results to the adiabatic predictions. We show that for an asymmetric-top molecule in parallel fields, the formation of the pendular doublets and the avoided crossings between neighboring levels are the two main sources of nonadiabatic effects. We also provide the field parameters under which the adiabatic dynamics would be achieved.
NASA Astrophysics Data System (ADS)
Morozova, Viktoriya; Ahmedov, Bobomurat; Rezzolla, Luciano
2016-07-01
We extend the Wald solution for magnetic field to a black hole that is also moving at constant velocity. In particular, we derive analytic solutions for the Maxwell equations for a rotating black hole moving at constant speed in an asymptotically uniform magnetic test field. By adopting Kerr-Schild coordinates we avoid singular behaviors at the horizon and obtain a complete description of the charge and current distributions in terms of the black-hole spin and velocity. Using this solution, we compute the energy losses expected when charged particles are accelerated along the magnetic field lines, improving previous estimates that had to cope with singular electromagnetic fields on the horizon. When used to approximate the emission from binary black holes in a uniform magnetic field, our estimates match reasonably well those from numericalrelativity calculations in the force-free approximation.
NASA Astrophysics Data System (ADS)
Innocenti, Maria Elena; Lapenta, Giovanni; Goldman, Martin; Newman, David; Markidis, Stefano
2015-04-01
In Petschek's model for magnetic reconnection, switch-off (SO) condition is achieved through back-to-back slow mode shocks (SS). No rotational discontinuity (RD) is needed, unless in specific cases detailed in [Vasyliunas 1975]. Decades of simulations with different models (MHD, Hall MHD, hybrid, PIC) have yielded contradictory results regarding the achievement of the SO condition during magnetic reconnection events. It has been recently argued that the formation of Petschek's SO-SS is inhibited by the development of the firehose instability, which provokes the flapping of the magnetic field in the reconnection exhausts (Liu et al., 2012). We report here on the formation of localized switch-off areas in simulations of collisionless magnetic reconnection in extremely large domains (hundreds of ion skin depths) for extremely long times (hundreds of inverse ion cyclotron frequency). A guide field (a magnetic field in the direction perpendicular to the reconnection plane) prevents the development of the firehose instability. The switch-off areas are marked by magnetic field line bending (in a way closely resembling the textbook description of RDs), by the formation of a nozzle-like structure in the in-plane projection of the ion and electron velocities perpendicular to the magnetic field direction and by a reduced rate of plasmoid formation. We use Rankine-Hugoniot conditions to characterize the transitions as Rotational Discontinuities and we comment on their origin. Priest, E. and Forbes, T. (2007). Magnetic reconnection. Magnetic Reconnection, by Eric Priest, Terry Forbes, Cambridge, UK: Cambridge University Press, 2007, 1. Vasyliunas V. (1975). Theoretical models of magnetic field line merging. Review of Geophysics and Space Phsyics, 1975. Liu, Y.-H., Drake, J. F., and Swisdak, M. (2012). The structure of the magnetic reconnection exhaust boundary. Physics of Plasmas (1994-present), 19(2):-.
NASA Astrophysics Data System (ADS)
Luo, Linqiang; Dao, Nam; Kittiwatanakul, Salinporn; Wolf, Stuart; Lu, Jiwei; UVa NanoStar Team
The giant magnetoresistance (GMR) effect of a pseudo spin valve made of Co90Fe10/Cu/Ni80Fe20 has been investigated, with a magnetic field applied perpendicularly tilted to the sample plane. Without using a pinning layer, the magnetic separation of the free and fixed layers is uniquely achieved by utilizing perpendicular fields due to different anisotropy energies between Ni80Fe20 and Co90Fe10. The magneto-transport measurements are carried out by Van der Pauw method in current-in-plane geometry at room temperature. By tilting the magnetic field at different angles from out-of-plane, the GMR plateau's width can be tuned. A plateau width of about 2000 Oe is observed at tilted angle 0.5o, which opens a significantly larger window for high-resistance states comparing with a plateau width of 10 Oe for in-plane fields. With the out-of-plane tilted fields, the orientation of the magnetic moments can be tuned continuously out of the sample plane, and the relative orientation between Ni80Fe20 and Co90Fe10 can also be tuned by the tilted angle, enabling us to precisely control the sample's states for current-induced spin dynamics study that is very difficult in the case of in-plane applied magnetic fields.
NASA Astrophysics Data System (ADS)
Hedan, S.; Pop, O.; Valle, V.; Cottron, M.
2006-08-01
We propose in this paper, to analyse, the evolution of out-of-plane displacement fields for a crack propagation in brittle materials. As the crack propagation is a complex process that involves the deformation mechanisms, the out-of-plane displacement measurement gives pertinent information about the 3D effects. For investigation, we use the interferometric method. The optical device includes a laser source, a Michelson interferometer and an ultra high-speed CCD camera. To take into account the crack velocity, we dispose of a maximum frame rate of 1Mfps. The experimental tests have been carried out for a SEN (Single Edge Notch) specimen of PMMA material. The crack propagation is initiated by adding a dynamic energy given by the impact of a cutter on the initial crack. The obtained interferograms are analysed with a new phase extraction method entitled MPC [6]. This analysis, which has been developed specially for dynamic studies, gives the out-of-plane displacement with an accuracy of about 10 nm.
Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars.
van Saders, Jennifer L; Ceillier, Tugdual; Metcalfe, Travis S; Aguirre, Victor Silva; Pinsonneault, Marc H; García, Rafael A; Mathur, Savita; Davies, Guy R
2016-01-14
A knowledge of stellar ages is crucial for our understanding of many astrophysical phenomena, and yet ages can be difficult to determine. As they become older, stars lose mass and angular momentum, resulting in an observed slowdown in surface rotation. The technique of 'gyrochronology' uses the rotation period of a star to calculate its age. However, stars of known age must be used for calibration, and, until recently, the approach was untested for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for old field stars whose ages have been determined with asteroseismology. The data for the cluster agree with previous period-age relations, but these relations fail to describe the asteroseismic sample. Here we report stellar evolutionary modelling, and confirm the presence of unexpectedly rapid rotation in stars that are more evolved than the Sun. We demonstrate that models that incorporate dramatically weakened magnetic braking for old stars can--unlike existing models--reproduce both the asteroseismic and the cluster data. Our findings might suggest a fundamental change in the nature of ageing stellar dynamos, with the Sun being close to the critical transition to much weaker magnetized winds. This weakened braking limits the diagnostic power of gyrochronology for those stars that are more than halfway through their main-sequence lifetimes. PMID:26727162
Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars.
van Saders, Jennifer L; Ceillier, Tugdual; Metcalfe, Travis S; Aguirre, Victor Silva; Pinsonneault, Marc H; García, Rafael A; Mathur, Savita; Davies, Guy R
2016-01-14
A knowledge of stellar ages is crucial for our understanding of many astrophysical phenomena, and yet ages can be difficult to determine. As they become older, stars lose mass and angular momentum, resulting in an observed slowdown in surface rotation. The technique of 'gyrochronology' uses the rotation period of a star to calculate its age. However, stars of known age must be used for calibration, and, until recently, the approach was untested for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for old field stars whose ages have been determined with asteroseismology. The data for the cluster agree with previous period-age relations, but these relations fail to describe the asteroseismic sample. Here we report stellar evolutionary modelling, and confirm the presence of unexpectedly rapid rotation in stars that are more evolved than the Sun. We demonstrate that models that incorporate dramatically weakened magnetic braking for old stars can--unlike existing models--reproduce both the asteroseismic and the cluster data. Our findings might suggest a fundamental change in the nature of ageing stellar dynamos, with the Sun being close to the critical transition to much weaker magnetized winds. This weakened braking limits the diagnostic power of gyrochronology for those stars that are more than halfway through their main-sequence lifetimes.
Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
NASA Astrophysics Data System (ADS)
van Saders, Jennifer L.; Ceillier, Tugdual; Metcalfe, Travis S.; Silva Aguirre, Victor; Pinsonneault, Marc H.; García, Rafael A.; Mathur, Savita; Davies, Guy R.
2016-01-01
A knowledge of stellar ages is crucial for our understanding of many astrophysical phenomena, and yet ages can be difficult to determine. As they become older, stars lose mass and angular momentum, resulting in an observed slowdown in surface rotation. The technique of ‘gyrochronology’ uses the rotation period of a star to calculate its age. However, stars of known age must be used for calibration, and, until recently, the approach was untested for old stars (older than 1 gigayear, Gyr). Rotation periods are now known for stars in an open cluster of intermediate age (NGC 6819; 2.5 Gyr old), and for old field stars whose ages have been determined with asteroseismology. The data for the cluster agree with previous period-age relations, but these relations fail to describe the asteroseismic sample. Here we report stellar evolutionary modelling, and confirm the presence of unexpectedly rapid rotation in stars that are more evolved than the Sun. We demonstrate that models that incorporate dramatically weakened magnetic braking for old stars can—unlike existing models—reproduce both the asteroseismic and the cluster data. Our findings might suggest a fundamental change in the nature of ageing stellar dynamos, with the Sun being close to the critical transition to much weaker magnetized winds. This weakened braking limits the diagnostic power of gyrochronology for those stars that are more than halfway through their main-sequence lifetimes.
NASA Astrophysics Data System (ADS)
Zhang, Xu-Dong; Fan, Bao-Chun; Gui, Ming-Yue; Pan, Zhen-Hua; Dong, Gang
2012-02-01
Gaseous detonation propagating in a toroidal chamber was numerically studied for hydrogen/oxygen/nitrogen mixtures. The numerical method used is based on the three-dimensional Euler equations with detailed finiterate chemistry. The results show that the calculated streak picture is in qualitative agreement with the picture recorded by a high speed streak camera from published literature. The three-dimensional flow field induced by a continuously rotating detonation was visualized and distinctive features of the rotating detonations were clearly depicted. Owing to the unconfined character of detonation wavelet, a deficit of detonation parameters was observed. Due to the effects of wall geometries, the strength of the outside detonation front is stronger than that of the inside portion. The detonation thus propagates with a constant circular velocity. Numerical simulation also shows three-dimensional rotating detonation structures, which display specific feature of the detonationshock combined wave. Discrete burning gas pockets are formed due to instability of the discontinuity. It is believed that the present study could give an insight into the interesting properties of the continuously rotating detonation, and is thus beneficial to the design of continuous detonation propulsion systems.
NASA Astrophysics Data System (ADS)
Orlita, M.; Byszewski, M.; Döhler, G. H.; Grill, M.; Hlídek, P.; Malzer, S.; Zvára, M.
2006-08-01
We report on photoluminescence (PL) measurements of a GaAs/AlGaAs double quantum well (DQW) in high magnetic fields. Measurements were carried out on a selectively contacted symmetric p- δn-DQW- δn-p structure, which allows a variation of the electron density in DQW by a p-n bias and simultaneously a tilting of DQW, when a p-p bias is applied. Attention was paid to phenomena in in-plane magnetic fields, theoretically studied by Huang and Lyo (HL), [Phys. Rev. B 59, (1999) 7600]. In this paper, we compare our results for both symmetric and asymmetric DQWs with the theoretical model made by HL. Whereas the spectra from a symmetric DQW fully confirmed the theoretical predictions, the results gained from DQW with an electric-field-induced asymmetry did not allow a proper study of anticipated effects. The reasons for that are discussed.
NASA Technical Reports Server (NTRS)
Mazuruk, Konstantin; Grugel, Richard N.
2003-01-01
A magnetohydrodynamic model that examines the effect of rotating an electrically conducting cylinder with a uniform external magnetic field applied orthogonal to its axis is presented. Noting a simple geometry, it can be classified as a fundamental dynamo problem. For the case of an infinitely long cylinder, an analytical solution is obtained and analyzed in detail. A semi-analytical model was developed that considers a finite cylinder. Experimental data from a spinning brass wheel in the presence of Earth's magnetic field were compared to the proposed theory and found to fit well.
Determining the Ocean's Role on the Variable Gravity Field on Earth Rotation
NASA Technical Reports Server (NTRS)
Ponte, Rui M.
1999-01-01
A number of ocean models of different complexity have been used to study changes in the oceanic mass field and angular momentum and their relation to the variable Earth rotation and gravity field. Time scales examined range from seasonal to a few days. Results point to the importance of oceanic signals in driving polar motion, in particular the Chandler and annual wobbles. Results also show that oceanic signals have a measurable impact on length-of-day variations. Various circulation features and associated mass signals, including the North Pacific subtropical gyre, the equatorial currents, and the Antarctic Circumpolar Current play a significant role in oceanic angular momentum variability.
Paramagnetic colloids in rotating fields: from chains through chaos to clusters
NASA Astrophysics Data System (ADS)
Abdi, Hamed; Soheilian, Rasam; Erb, Randall; Maloney, Craig
We present computer simulations and experiments on dilute suspensions of superparamagnetic particles subject to rotating magnetic fields. We focus on short chains of particles and their decay routes to stable structures. At low rate, the chains track the external field. At intermediate rate, the short chains break up but perform a periodic (albeit complex) motion. At sufficiently high rates, the chains generally undergo chaotic motion at short times and decay to either close-packed clusters or more dispersed colloidal ``molecules'' at long times. We show that the transition out of the chaotic states follows a first order reaction kinetics. NSF.
NASA Astrophysics Data System (ADS)
Mattei, D.; Smith, I.; Ferrari, A.; Carbillet, M.
2010-10-01
Post-processing for exoplanet detection using direct imaging requires large data cubes and/or sophisticated signal processing technics. For alt-azimuthal mounts, a projection effect called field rotation makes the potential planet rotate in a known manner on the set of images. For ground based telescopes that use extreme adaptive optics and advanced coronagraphy, technics based on field rotation are already broadly used and still under progress. In most such technics, for a given initial position of the planet the planet intensity estimate is a linear function of the set of images. However, due to field rotation the modified instrumental response applied is not shift invariant like usual linear filters. Testing all possible initial positions is therefore very time-consuming. To reduce the time process, we propose to deal with each subset of initial positions computed on a different machine using parallelization programming. In particular, the MOODS algorithm dedicated to the VLT-SPHERE instrument, that estimates jointly the light contributions of the star and the potential exoplanet, is parallelized on the Observatoire de la Cote d'Azur cluster. Different parallelization methods (OpenMP, MPI, Jobs Array) have been elaborated for the initial MOODS code and compared to each other. The one finally chosen splits the initial positions on the processors available by accounting at best for the different constraints of the cluster structure: memory, job submission queues, number of available CPUs, cluster average load. At the end, a standard set of images is satisfactorily processed in a few hours instead of a few days.
Position, rotation, and intensity invariant recognizing method
Ochoa, E.; Schils, G.F.; Sweeney, D.W.
1987-09-15
A method for recognizing the presence of a particular target in a field of view which is target position, rotation, and intensity invariant includes the preparing of a target-specific invariant filter from a combination of all eigen-modes of a pattern of the particular target. Coherent radiation from the field of view is then imaged into an optical correlator in which the invariant filter is located. The invariant filter is rotated in the frequency plane of the optical correlator in order to produce a constant-amplitude rotational response in a correlation output plane when the particular target is present in the field of view. Any constant response is thus detected in the output plane to determine whether a particular target is present in the field of view. Preferably, a temporal pattern is imaged in the output plane with a optical detector having a plurality of pixels and a correlation coefficient for each pixel is determined by accumulating the intensity and intensity-square of each pixel. The orbiting of the constant response caused by the filter rotation is also preferably eliminated either by the use of two orthogonal mirrors pivoted correspondingly to the rotation of the filter or the attaching of a refracting wedge to the filter to remove the offset angle. Detection is preferably performed of the temporal pattern in the output plane at a plurality of different angles with angular separation sufficient to decorrelate successive frames. 1 fig.
NASA Astrophysics Data System (ADS)
Chernodub, M. N.
2013-01-01
Recently, we have demonstrated that for a certain class of Casimir-type systems (“devices”) the energy of zero-point vacuum fluctuations reaches its global minimum when the device rotates about a certain axis rather than remains static. This rotational vacuum effect may lead to the emergence of permanently rotating objects provided the negative rotational energy of zero-point fluctuations cancels the positive rotational energy of the device itself. In this paper, we show that for massless electrically charged particles the rotational vacuum effect should be drastically (astronomically) enhanced in the presence of a magnetic field. As an illustration, we show that in a background of experimentally available magnetic fields the zero-point energy of massless excitations in rotating torus-shaped doped carbon nanotubes may indeed overwhelm the classical energy of rotation for certain angular frequencies so that the permanently rotating state is energetically favored. The suggested “zero-point-driven” devices—which have no internally moving parts—correspond to a perpetuum mobile of a new, fourth kind: They do not produce any work despite the fact that their equilibrium (ground) state corresponds to a permanent rotation even in the presence of an external environment. We show that our proposal is consistent with the laws of thermodynamics.
Evolution of a magnetic field in a differentially rotating radiative zone
NASA Astrophysics Data System (ADS)
Gaurat, M.; Jouve, L.; Lignières, F.; Gastine, T.
2015-08-01
Context. Recent spectropolarimetric surveys of main-sequence intermediate-mass stars have exhibited a dichotomy in the distribution of the observed magnetic field between the kG dipoles of Ap/Bp stars and the sub-Gauss magnetism of Vega and Sirius. Aims: We would like to test whether this dichotomy is linked to the stability versus instability of large-scale magnetic configurations in differentially rotating radiative zones. Methods: We computed the axisymmetric magnetic field obtained from the evolution of a dipolar field threading a differentially rotating shell. A full parameter study including various density profiles and initial and boundary conditions was performed with a 2D numerical code. We then focused on the ratio between the toroidal and poloidal components of the magnetic field and discuss the stability of the configurations dominated by the toroidal component using local stability criteria and insights from recent 3D numerical simulations. Results: The numerical results and a simple model show that the ratio between the toroidal and the poloidal magnetic fields is highest after an Alfvén crossing time of the initial poloidal field. For high density contrasts, this ratio converges towards an asymptotic value that can thus be extrapolated to realistic stellar cases. We then consider the stability of the magnetic configurations to non-axisymmetric perturbations and find that configurations dominated by the toroidal component are likely to be unstable if the shear strength is significantly higher than the poloidal Alfvén frequency. An expression for the critical poloidal field below which magnetic fields are likely to be unstable is found and is compared to the lower bound of Ap/Bp magnetic fields.
Electro-phoretic rotation and orientation of polarizable spheroidal particles in AC fields
NASA Astrophysics Data System (ADS)
Miloh, Touvia; Goldstein, Ben Weis
2015-02-01
A theoretical study is provided for determining the angular rotation rate of an ideally polarized (metallic) spheroidal particle freely suspended in a symmetric electrolyte under general alternating current ambient electric excitations. In particular, we discuss cases of electro-rotation (ROT) and electro-orientation (EOR) of such nano/micro particles incited by two orthogonal electric field components which may be out of phase. The analysis is carried under the Poisson-Nernst-Planck approximation and the "weak" field model. The analytic expressions thus obtained are valid for a conducting prolate spheroid with arbitrary eccentricity including the limiting cases of isotropic spheres and infinitely long cylindrical rods. The total dipolophoretic (DIP) angular velocity is decomposed from contributions due to dielectrophoresis (DEP) induced by the dipole-moment within the particle and by the induced-charge electrophoresis (ICEP) mechanism near the conducting surface. It is demonstrated that the explicit expressions for the DIP angular velocities reduce to the well-known ROT solution for the sphere as well as to the recently found expressions (based on slender-body approximation) for both ROT and EOR of metal nanowires [Arcenegui et al., "Electro-orientation and electrorotation of metal nanowires," Phys. Rev. E 88(6), 063018 (2013)]. Some comparisons with available experimental data are also provided for slender spheroidal geometries including a detailed discussion of DEP and ICEP effects and their relative contributions to the overall DIP rotational velocity.
Magnetic field effect on waves in a centrifuged layer of a rotating conducting viscous fluid
NASA Astrophysics Data System (ADS)
Klueva, N. V.; Sandalov, V. M.; Tkach, M. E.; Soldatov, I. N.
2015-05-01
This paper considers wave processes in a centrifuged layer of an incompressible viscous conducting fluid in an axial magnetic field in the cavity of a rapidly rotating infinite cylinder with insulating walls. Inertial modes (solutions of the linearized boundary-value problem of magnetohydrodynamics) are represented as a superposition of helical fields. Expressions for the vorticity parameters of the helical flows forming the inertial mode at a small Stewart number are given. Dispersion curves of inertial waves are constructed, and the influence of the magnetic field on the flow field is analyzed. The critical frequencies at which the lowest (surface) mode arises are determined. The spatial and temporal stability of the modes are investigated.
Nonlinear magneto-optical rotation with frequency-modulated light in the geophysical field range
NASA Astrophysics Data System (ADS)
Acosta, V.; Ledbetter, M. P.; Rochester, S. M.; Budker, D.; Jackson Kimball, D. F.; Hovde, D. C.; Gawlik, W.; Pustelny, S.; Zachorowski, J.; Yashchuk, V. V.
2006-05-01
Recent work investigating resonant nonlinear magneto-optical rotation (NMOR) related to long-lived (τrel˜1s) ground-state atomic coherences has demonstrated potential magnetometric sensitivities exceeding 10-11G/Hz for small (≲1μG ) magnetic fields. In the present work, NMOR using frequency-modulated light (FM NMOR) is studied in the regime where the longitudinal magnetic field is in the geophysical range (˜500mG) , of particular interest for many applications. In this regime a splitting of the FM NMOR resonance due to the nonlinear Zeeman effect is observed. At sufficiently high light intensities, there is also a splitting of the FM NMOR resonances due to ac Stark shifts induced by the optical field, as well as evidence of alignment-to-orientation conversion type processes. The consequences of these effects for FM-NMOR-based atomic magnetometry in the geophysical field range are considered.
VizieR Online Data Catalog: JCMT Plane Survey: l=30° field (Moore+, 2015)
NASA Astrophysics Data System (ADS)
Moore, T. J. T.; Plume, R.; Thompson, M. A.; Parsons, H.; Urquhart, J. S.; Eden, D. J.; Dempsey, J. T.; Morgan, L. K.; Thomas, H. S.; Buckle, J.; Brunt, C. M.; Butner, H.; Carretero, D.; Chrysostomou, A.; Devilliers, H. M.; Fich, M.; Hoare, M. G.; Manser, G.; Mottram, J. C.; Natario, C.; Olguin, F.; Peretto, N.; Polychroni, D.; Redman, R. O.; Rigby, A. J.; Salji, C.; Summers, L. J.; Berry, D.; Currie, M. J.; Jenness, T.; Pestalozzi, M.; Traficante, A.; Bastien, P.; Difrancesco, J.; Davis, C. J.; Evans, A.; Friberg, P.; Fuller, G. A.; Gibb, A. G.; Gibson, S.; Hill, T.; Johnstone, D.; Joncas, G.; Longmore, S. N.; Lumsden, S. L.; Martin, P. G.; Nguyen Luong, Q.; Pineda, J. E.; Purcell, C.; Richer, J. S.; Schieven, G. H.; Shipman, R.; Spaans, M.; Taylor, A. R.; Viti, S.; Weferling, B.; White, G. J.; Zhu, M.
2016-06-01
JPS uses the wide-field submm-band bolometer camera SCUBA-2 (the Submm Common-User Bolometer Array 2) in the 850um band at a spatial resolution of 14.5-arcsec. The 850um survey data presented in this paper cover the l=30° field of the JPS and were observed between 2012 June and 2013 October. The 11 tiles making up the field were observed on average three times each. A strategy of minimum elevation limits for given atmospheric opacity bands within the allocated range was adopted, in order to minimize variations in the resulting noise in each repeated tile. (1 data file).
Tokamak equilibria with non field-aligned axisymmetric divergence-free rotational flows
Tsui, K. H.; Navia, C. E.; Serbeto, A.; Shigueoka, H.
2011-07-15
Rotational ideal divergence-free magnetohydrodynamic (MHD) equations are expressed in terms of transformed variables w-vector{sub *}=({mu}{rho}){sup 1/2}v-vector and {mu}p{sub *} = ({mu}p + w{sub *}{sup 2}/2), where v-vector, p, and {rho} are plasma velocity, pressure, and mass density, respectively. With divergence-free flows, {nabla}{center_dot}v-vector=0, the plasma density {rho} does not appear in the MHD equations written in terms of w-vector{sub *} and {mu}p{sub *}. The non field-aligned rotational Grad-Shafranov equation is represented in spherical coordinates. Tokamak-like axisymmetric equilibria with v-vector perpendicular {nabla}{rho} are obtained analytically by solving for torus solutions under only three source functions.
Rapidly Rotating, X-Ray Bright Stars in the Kepler Field
NASA Astrophysics Data System (ADS)
Howell, Steve B.; Mason, Elena; Boyd, Patricia; Smith, Krista Lynne; Gelino, Dawn M.
2016-11-01
We present Kepler light curves and optical spectroscopy of twenty X-ray bright stars located in the Kepler field of view. The stars, spectral type F-K, show evidence for rapid rotation including chromospheric activity 100 times or more above the Sun at maximum and flaring behavior in their light curves. Eighteen of our objects appear to be (sub)giants and may belong to the class of FK Com variables, which are evolved rapidly spinning single stars with no excretion disk and high levels of chromospheric activity. Such stars are rare and are likely the result of W UMa binary mergers, a process believed to produce the FK Com class of variable and their descendants. The FK Com stage, including the presence of an excretion disk, is short lived but leads to longer-lived stages consisting of single, rapidly rotating evolved (sub)giants with high levels of stellar activity.
NASA Astrophysics Data System (ADS)
Liu, Yueqiang; Connor, J. W.; Cowley, S. C.; Ham, C. J.; Hastie, R. J.; Hender, T. C.
2012-10-01
A numerical study is carried out, based on a simple toroidal tokamak equilibrium, to demonstrate the radial re-distribution of the electromagnetic torque density, as a result of a rotating resistive plasma (linear) response to a static resonant magnetic perturbation field. The computed electromagnetic torque peaks at several radial locations even in the presence of a single rational surface, due to resonances between the rotating response, in the plasma frame, and both Alfvén and sound continuum waves. These peaks tend to merge together to form a rather global torque distribution, when the plasma resistivity is large. The continuum resonance induced net electromagnetic torque remains finite even in the limit of an ideal plasma.
Influence of a modulated bias field on dynamic conversion in a rotating gradient experiment
NASA Astrophysics Data System (ADS)
Nyenhuis, J. A.; Friedlaender, F. J.; Matsumoto, S.
1984-03-01
In the rotating gradient experiment, a magnetic bubble is in steady state circular motion. The modulation of the dc bias field by a small sinusoidal component, the tickle field, has been found effective in reducing the static coercivity, resulting in stable bubble motion. In this study, the influence of the tickle field on Bloch curve punch-through velocity is investigated. A bubble is circulated both in the presence and absence of the tickle field. For low amplitude tickle fields, Hzt≤0.25 Oe, the translational velocity at which punch-through occurs, ≂3.5 m/s, is the same both in the presence and absence of the tickle field. However, the minimum velocity at which a bubble can be propagated is lower in the presence of the tickle field. For larger Hzt, the punch-through velocity is reduced, with the extent of the reduction depending on the tickle field frequency. The amplitude and frequency of the tickle field affect the apparent dynamic coercivity.
NASA Astrophysics Data System (ADS)
Handoko, Djati; Quach, Duy-Truong; Lee, Sang-Hyuk; Shim, Je-Ho; Kim, Dong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Kim, Namdong; Shin, Hyun-Joon
2015-06-01
We report our investigation on the magnetic-domain structure of a Co/Pt multilayer with perpendicular magnetic anisotropy under a horizontal in-plane field by using a high-resolution scanning transmission X-ray microscope (STXM) developed at Pohang Accelerator Laboratory. The ruggedshaped striped magnetic-domain structure that was initially formed under a field cycle along the out-of-the plane magnetic easy axis was found to be stretched and elongated along the direction of the horizontal in-plane field. As the in-plane field was strengthened, the striped pattern exhibited an anisotropic domain growth with further stretching and aligning, as well as with a modification of the magnetic-domain's width.
Guzatov, D V; Gaida, L S; Afanas'ev, Anatolii A
2008-12-31
The light pressure force acting on a spherical dielectric particle in the interference field of two plane monochromatic electromagnetic waves is studied in detail for different particle radii and angles of incidence of waves. (light pressure)
Rotational polarities of sudden impulses in the magnetotail lobe
NASA Technical Reports Server (NTRS)
Kawano, H.; Yamamoto, T.; Kokubun, S.; Lepping, R. P.
1992-01-01
A sudden impulse (SI) is a sudden change in the magnetic field strength which is caused by a change in the solar wind pressure and is observed throughout the magnetosphere. In this report we have examined the rotations of the magnetic field vectors at times of SIs in the magnetotail lobe, by using IMP 6, 7, and 8 magnetometer data. The following properties have been found: (1) at the time of SI the arrowhead of the magnetic vector tends to rotate in one plane; (2) the plane of rotation tends to include the unperturbed magnetic field vector; (3) the plane of rotation tends to be aligned with the radial direction from the magnetotail axis; and (4) the magnetic vectors have a particular rotational polarity: when the plane of rotation is viewed so that the Sun is to the right of the viewed plane and the magnetotail axis is to the bottom, the arrowhead of the vector tends to rotate counterclockwise in this plane. These magnetic vector properties are consistent with those expected when part of an increase in solar wind lateral pressure squeezes the magnetotail axisymmetrically while moving tailward.
Akahori, Takuya; Gaensler, B. M.; Ryu, Dongsu E-mail: bryan.gaensler@sydney.edu.au
2014-08-01
Rotation measure (RM) grids of extragalactic radio sources have been widely used for studying cosmic magnetism. However, their potential for exploring the intergalactic magnetic field (IGMF) in filaments of galaxies is unclear, since other Faraday-rotation media such as the radio source itself, intervening galaxies, and the interstellar medium of our Galaxy are all significant contributors. We study statistical techniques for discriminating the Faraday rotation of filaments from other sources of Faraday rotation in future large-scale surveys of radio polarization. We consider a 30° × 30° field of view toward the south Galactic pole, while varying the number of sources detected in both present and future observations. We select sources located at high redshifts and toward which depolarization and optical absorption systems are not observed so as to reduce the RM contributions from the sources and intervening galaxies. It is found that a high-pass filter can satisfactorily reduce the RM contribution from the Galaxy since the angular scale of this component toward high Galactic latitudes would be much larger than that expected for the IGMF. Present observations do not yet provide a sufficient source density to be able to estimate the RM of filaments. However, from the proposed approach with forthcoming surveys, we predict significant residuals of RM that should be ascribable to filaments. The predicted structure of the IGMF down to scales of 0.°1 should be observable with data from the Square Kilometre Array, if we achieve selections of sources toward which sightlines do not contain intervening galaxies and RM errors are less than a few rad m{sup –2}.
Observations of ferrofluid flow under a uniform rotating magnetic field in a spherical cavity
NASA Astrophysics Data System (ADS)
Torres-Díaz, Isaac; Rinaldi, Carlos; Khushrushahi, Shahriar; Zahn, Markus
2012-04-01
Flow of a ferrofluid in spherical and cylindrical geometries were measured under the influence of a uniform rotating magnetic field produced by two perpendicular spherical coils, a so-called fluxball, excited by quadrature currents. Using an ultrasound velocity profile technique and a commercial oil based ferrofluid (EFH1, Ferrotec) we observed rotational flow around the z-axis. In comparison, the radial component of the flow was found to be negligible. Results show that the magnitude of the azimuthal velocity profile increases as the applied magnetic field amplitude increases. This behavior is also observed for ferrofluid in a cylindrical container placed inside the fluxball cavity and inside a two-pole stator winding. These results indicate that inhomogeneities in the magnetic field produced by slots and finite height of the stator winding used in prior experiments are not the source of previously observed flows produced by a two pole stator winding. The experiments reported here either point to the existence of non-uniform demagnetizing magnetic fields due to the finite height of the cylindrical container, the existence of couple stresses and spin viscosity in ferrofluids, or to the need to develop alternate governing and constitutive equations capable of describing the experimental observations.
NASA Astrophysics Data System (ADS)
Kang, Junmo; Jariwala, Deep; Ryder, Christopher R.; Wells, Spencer A.; Choi, Yongsuk; Hwang, Euyheon; Cho, Jeong Ho; Marks, Tobin J.; Hersam, Mark C.
2016-04-01
Black phosphorus (BP) has recently emerged as a promising narrow band gap layered semiconductor with optoelectronic properties that bridge the gap between semi-metallic graphene and wide band gap transition metal dichalcogenides such as MoS2. To date, BP field-effect transistors have utilized a lateral geometry with in-plane transport dominating device characteristics. In contrast, we present here a vertical field-effect transistor geometry based on a graphene/BP van der Waals heterostructure. The resulting device characteristics include high on-state current densities (> 1600 A/cm2) and current on/off ratios exceeding 800 at low temperature. Two distinct charge transport mechanisms are identified, which are dominant for different regimes of temperature and gate voltage. In particular, the Schottky barrier between graphene and BP determines charge transport at high temperatures and positive gate voltages, whereas tunneling dominates at low temperatures and negative gate voltages. These results elucidate out-of-plane electronic transport in BP, and thus have implications for the design and operation of BP-based van der Waals heterostructures.
NASA Astrophysics Data System (ADS)
Kacem, S.; Eichwald, O.; Ducasse, O.; Renon, N.; Yousfi, M.; Charrada, K.
2012-01-01
Streamers dynamics are characterized by the fast propagation of ionized shock waves at the nanosecond scale under very sharp space charge variations. The streamer dynamics modelling needs the solution of charged particle transport equations coupled to the elliptic Poisson's equation. The latter has to be solved at each time step of the streamers evolution in order to follow the propagation of the resulting space charge electric field. In the present paper, a full multi grid (FMG) and a multi grid (MG) methods have been adapted to solve Poisson's equation for streamer discharge simulations between asymmetric electrodes. The validity of the FMG method for the computation of the potential field is first shown by performing direct comparisons with analytic solution of the Laplacian potential in the case of a point-to-plane geometry. The efficiency of the method is also compared with the classical successive over relaxation method (SOR) and MUltifrontal massively parallel solver (MUMPS). MG method is then applied in the case of the simulation of positive streamer propagation and its efficiency is evaluated from comparisons to SOR and MUMPS methods in the chosen point-to-plane configuration. Very good agreements are obtained between the three methods for all electro-hydrodynamics characteristics of the streamer during its propagation in the inter-electrode gap. However in the case of MG method, the computational time to solve the Poisson's equation is at least 2 times faster in our simulation conditions.
Kastrup, U.; Zoback, M.L.; Deichmann, N.; Evans, Kenneth F.; Giardini, D.; Michael, A.J.
2004-01-01
This study is devoted to a systematic analysis of the state of stress of the central European Alps and northern Alpine foreland in Switzerland based on focal mechanisms of 138 earthquakes with magnitudes between 1 and 5. The most robust feature of the results is that the azimuth of the minimum compressive stress, S3, is generally well constrained for all data subsets and always lies in the NE quadrant. However, within this quadrant, the orientation of S3 changes systematically both along the structural strike of the Alpine chain and across it. The variation in stress along the mountain belt from NE to SW involves a progressive, counterclockwise rotation of S3 and is most clear in the foreland, where it amounts to 45??-50??. This pattern of rotation is compatible with the disturbance to the stress field expected from the indentation of the Adriatic Block into the central European Plate, possibly together with buoyancy forces arising from the strongly arcuate structure of the Moho to the immediate west of our study area. Across the Alps, the variation in azimuth of S3 is defined by a progressive, counterclockwise rotation of about 45?? from the foreland in the north across the Helvetic domain to the Penninic nappes in the south and is accompanied by a change from a slight predominance of strike-slip mechanisms in the foreland to a strong predominance of normal faulting in the high parts of the Alps. The observed rotation can be explained by the perturbation of the large-scale regional stress by a local uniaxial deviatoric tension with a magnitude similar to that of the regional differential stress and with an orientation perpendicular to the strike of the Alpine belt. The tensile nature and orientation of this stress is consistent with the "spreading" stress expected from lateral density changes due to a crustal root beneath the Alps. Copyright 2004 by the American Geophysical Union.
NASA Astrophysics Data System (ADS)
Morandi, P.; Brémand, F.; Doumalin, P.; Germaneau, A.; Dupré, J. C.
2014-07-01
In this paper, a new optical tomography process is presented. It has been developed for time-resolved measurement of kinematic fields in the whole volume of structure. This new process is based on the scan of the specimen by a plane laser beam submitted to a motion of rotation. Calibration and reconstruction steps have been established and are described in this document. Acquisition is achieved by illuminating successive slices in the specimen using a rotating plane laser beam and data are recorded with a single CCD camera. The recorded volumes are analyzed by Digital Volume Correlation to measure the three displacement components in the bulk. This new acquisition process is assessed by performing sub-voxel rigid body translations along the three axes. We discuss the quality of a reconstructed volume and also the measurement accuracy in terms of mean error and standard deviation through rigid body displacement tests. Results are compared with those obtained using classical Optical Scanning Tomography (OST) and using X-ray Tomography.
NASA Astrophysics Data System (ADS)
He, Wen-Yu; Su, Ying; Yang, Mudan; He, Lin
2016-06-01
In the Comment, the authors argue that due to the different symmetry properties, the comparison between the twisting and in-plane magnetic field in bilayer graphene fails. However, we do not think it addresses the main result of our work. Here from the perspective of tunable chirality and quantum transmission signature, we review the feature shared by twisting and in-plane magnetic field in bilayer graphene and show that the Comment does not contradict our main results.
Colavita, E.; Hacyan, S.
2014-03-15
We analyze the solutions of the Klein–Gordon and Dirac equations describing a charged particle in an electromagnetic plane wave combined with a magnetic field parallel to the direction of propagation of the wave. It is shown that the Klein–Gordon equation admits coherent states as solutions, while the corresponding solutions of the Dirac equation are superpositions of coherent and displaced-number states. Particular attention is paid to the resonant case in which the motion of the particle is unbounded. -- Highlights: •We study a relativistic electron in a particular electromagnetic field configuration. •New exact solutions of the Klein–Gordon and Dirac equations are obtained. •Coherent and displaced number states can describe a relativistic particle.
Fourfold symmetry in the ab-plane of the upper critical field for the high-T{sub c} cuprates
Noji, T.; Koike, Y.; Nishizaki, T.; Kobayashi, N.
1996-11-01
The authors have found clear anisotropy in the ab plane with fourfold symmetry of the resistive superconducting transition under magnetic fields for single-crystal Pb{sub 2}Sr{sub 2}Y{sub 0.62}Ca{sub 0.38}Cu{sub 3}O{sub 8}, which is regarded as anisotropy of the upper critical field Hc{sub 2}. This is not only qualitatively but also quantitatively similar to that formerly observed in La{sub 1.86}Sr{sub 0.14}CuO{sub 4}. The observed fourfold symmetry is explained as being mainly due to the anisotropy of the superconducting energy gap owing to d{sub x{sup 2}{minus}y{sup 2}} pairing. H{sub c2}, one of the bulk properties, supports d{sub x{sup 2}{minus}y{sup 2}} pairing in the high-T{sub c} superconductivity.
Dynamics of an active magnetic particle in a rotating magnetic field.
Cēbers, A; Ozols, M
2006-02-01
The motion of an active (self-propelling) particle with a permanent magnetic moment under the action of a rotating magnetic field is considered. We show that below a critical frequency of the external field the trajectory of a particle is a circle. For frequencies slightly above the critical point the particle moves on an approximately circular trajectory and from time to time jumps to another region of space. Symmetry of the particle trajectory depends on the commensurability of the field period and the period of the orientational motion of the particle. We also show how our results can be used to study the properties of naturally occurring active magnetic particles, so-called magnetotactic bacteria. PMID:16605340
Detection of radio-frequency magnetic fields using nonlinear magneto-optical rotation
NASA Astrophysics Data System (ADS)
Ledbetter, M. P.; Acosta, V. M.; Rochester, S. M.; Budker, D.; Pustelny, S.; Yashchuk, V. V.
2007-02-01
We describe a room-temperature alkali-metal atomic magnetometer for detection of small, high-frequency magnetic fields. The magnetometer operates by detecting optical rotation due to the precession of an aligned ground state in the presence of a small oscillating magnetic field. The resonance frequency of the magnetometer can be adjusted to any desired value by tuning the bias magnetic field. Based on experimentally measured signal-to-noise ratio, we demonstrate a sensitivity of 100pG/Hz (rms) in a 3.5-cm -diameter paraffin coated cell. Assuming detection at the photon shot-noise limit, we project a sensitivity as low as 25pG/Hz (rms).
Detection of radio-frequency magnetic fields using nonlinear magneto-optical rotation
Ledbetter, M. P.; Acosta, V. M.; Rochester, S. M.; Budker, D.; Pustelny, S.; Yashchuk, V. V.
2007-02-15
We describe a room-temperature alkali-metal atomic magnetometer for detection of small, high-frequency magnetic fields. The magnetometer operates by detecting optical rotation due to the precession of an aligned ground state in the presence of a small oscillating magnetic field. The resonance frequency of the magnetometer can be adjusted to any desired value by tuning the bias magnetic field. Based on experimentally measured signal-to-noise ratio, we demonstrate a sensitivity of 100 pG/{radical}(Hz) (rms) in a 3.5-cm-diameter paraffin coated cell. Assuming detection at the photon shot-noise limit, we project a sensitivity as low as 25 pG/{radical}(Hz) (rms)
Experimental investigations of the unsteady rotating flow field in a cylindrical vessel
NASA Astrophysics Data System (ADS)
Denk, V.; Dürholt, A.
1991-12-01
The rotating flow field in a cylindrical vessel — the so-called whirlpool — is widely used in food engineering as a method for separating particles out of a suspension (Cup-of-tea-method). However many of these whirlpools do not operate adequately or fail entirely. In order to solve this problem, the first step was to investigate the flow field and its time dependency which has not been sufficiently understood until now. The rotating flow in a cylindrical vessel — induced by a fluid jet during the filling period of this vessel — is slowed down by fluid friction after the closing of the inlet valve. The velocity fields to be found mainly near, and pressure distributions at the bottom of the vessel, are measured during this unsteady flow. The results, especially those which describe vortex systems, are used to improve the separation system. This paper is restricted to the hydrodynamic aspect. Therefore success in industrial applications can only be indicated.
A novel hybrid microrobot using rotational magnetic field for medical applications.
Fu, Qiang; Guo, Shuxiang; Yamauchi, Yasuhiro; Hirata, Hideyuki; Ishihara, Hidenori
2015-04-01
Magnetically actuated microrobots for such tools have potential accomplish procedures in biological and medical applications. In this paper, a novel magnetically actuated hybrid microrobot with hybrid motion driven by an electromagnetic actuation system has been proposed. An o-ring type permanent magnet is embedded in the hybrid microrobot as an actuator driven by rotational magnetic field which is generated by a 3 axes Helmholtz coils. It is composed by two motion mechanisms. One is the spiral jet motion moved by rotating its body. The other one is fin motion moved by vibrating its body. Because only one permanent magnet is used inside the hybrid microrobot, two motions can be controlled separately without any interference. The hybrid microrobot can change its two motions to realize multi-DOFs movement and flexibility motion. The verified experiments are conducted in the pipe. The experimental results indicate that the moving speed can be controlled by adjusting the magnetic field changing frequency and the direction of motion can be controlled by changing the magnetic field direction. PMID:25681973
A novel hybrid microrobot using rotational magnetic field for medical applications.
Fu, Qiang; Guo, Shuxiang; Yamauchi, Yasuhiro; Hirata, Hideyuki; Ishihara, Hidenori
2015-04-01
Magnetically actuated microrobots for such tools have potential accomplish procedures in biological and medical applications. In this paper, a novel magnetically actuated hybrid microrobot with hybrid motion driven by an electromagnetic actuation system has been proposed. An o-ring type permanent magnet is embedded in the hybrid microrobot as an actuator driven by rotational magnetic field which is generated by a 3 axes Helmholtz coils. It is composed by two motion mechanisms. One is the spiral jet motion moved by rotating its body. The other one is fin motion moved by vibrating its body. Because only one permanent magnet is used inside the hybrid microrobot, two motions can be controlled separately without any interference. The hybrid microrobot can change its two motions to realize multi-DOFs movement and flexibility motion. The verified experiments are conducted in the pipe. The experimental results indicate that the moving speed can be controlled by adjusting the magnetic field changing frequency and the direction of motion can be controlled by changing the magnetic field direction.
NASA Astrophysics Data System (ADS)
Sharma, A. S.; Karavaev, A. V.; Gumerov, N.; Shao, X.; Papadopoulos, K.; Gekelman, W.; Wang, Y.; Vincena, S.; Pribyl, P.
2010-11-01
Recent experiments conducted in the Large Plasma Device (LAPD) located at UCLA demonstrated efficient excitation of whistler and shear Alfven waves by a Rotating Magnetic Field (RMF) source. We present analytical theory, computational modeling and experimental results of the shear Alfven wave excitation by RMF source created by a phased orthogonal two-loop antenna in a plasma. An analytical theory and simulations using a three-dimensional cold two-fluid model of Alfven wave excitation were developed and compared with experiments. These comparisons show good agreement on linear shear Alfven wave properties, namely, spatio-temporal wave structure, dispersion relation, and the dependence of wave magnitude on the wave frequency. From the simulations it was found that the energy of the Alfven wave generated by the rotating magnetic field source is distributed among the kinetic energies of ions and electrons and the electromagnetic energy of the wave. The wave magnetic field power calculated from the experimental data and using a fluid model agrees within ˜1 percent. The RMF source is thus very efficient in generating shear Alfven waves. Work supported by ONR MURI grant.
NASA Astrophysics Data System (ADS)
Shao, X.; Karavaev, A. V.; Gumerov, N.; Sharma, A. S.; Papadopoulos, K.; Gekelman, W. N.; Wang, Y.; Vincena, S. T.; Pribyl, P.
2010-12-01
Recent experiments conducted in the Large Plasma Device (LAPD) located at UCLA demonstrated efficient excitation of whistler and shear Alfven waves by a Rotating Magnetic Field (RMF) source. We present analytical theory, computational modeling and experimental results of the shear Alfven wave excitation by RMF source created by a phased orthogonal two-loop antenna in a plasma. An analytical theory and simulations using a three-dimensional cold two-fluid model of Alfven wave excitation were developed and compared with experiments. These comparisons show good agreement on linear shear Alfven wave properties, namely, spatio-temporal wave structure, dispersion relation, and the dependence of wave magnitude on the wave frequency. From the simulations it was found that the energy of the Alfven wave generated by the rotating magnetic field source is distributed among the kinetic energies of ions and electrons and the electromagnetic energy of the wave. The wave magnetic field power calculated from the experimental data and using a fluid model agrees within 1 percent. The RMF source is thus very efficient in generating shear Alfven waves. Work supported by ONR MURI grant.
Determining the Ocean's Role on the Variable Gravity Field and Earth Rotation
NASA Technical Reports Server (NTRS)
Ponte, Rui M.; Frey, H. (Technical Monitor)
2000-01-01
A number of ocean models of different complexity have been used to study changes in the oceanic angular momentum (OAM) and mass fields and their relation to the variable Earth rotation and gravity field. Time scales examined range from seasonal to a few days. Results point to the importance of oceanic signals in driving polar motion, in particular the Chandler and annual wobbles. Results also show that oceanic signals have a measurable impact on length-of-day variations. Various circulation features and associated mass signals, including the North Pacific subtropical gyre, the equatorial currents, and the Antarctic Circumpolar Current play a significant role in oceanic angular momentum variability. The impact on OAM values of an optimization procedure that uses available data to constrain ocean model results was also tested for the first time. The optimization procedure yielded substantial changes, in OAM, related to adjustments in both motion and mass fields,as well as in the wind stress torques acting on the ocean. Constrained OAM values were found to yield noticeable improvements in the agreement with the observed Earth rotation parameters, particularly at the seasonal timescale.
Tsai, Wei-Yi; Huang, Jer-Shing; Huang, Chen-Bin
2014-02-12
We demonstrate selective trapping or rotation of optically isotropic dielectric microparticles by plasmonic near field in a single gold plasmonic Archimedes spiral. Depending on the handedness of circularly polarized excitation, plasmonic near fields can be selectively engineered into either a focusing spot for particle trapping or a plasmonic vortex for particle rotation. Our design provides a simple solution for subwavelength optical manipulation and may find applications in micromechanical and microfluidic systems. PMID:24392638
Naiedja, H.; Quentin, P.; Bartel, J.
2011-05-15
Making use of the Bloch density matrix technique, we derive exact analytical expressions for the density profile in Fourier space, for the current density and the so-called integrated current for fermionic systems confined by a two-dimensional harmonic oscillator, in the presence of a magnetic field or in a rotating trap of arbitrary strength. We present numerical, illustrative examples with or without magnetic field (with or without rotation).
Tsai, Wei-Yi; Huang, Jer-Shing; Huang, Chen-Bin
2014-02-12
We demonstrate selective trapping or rotation of optically isotropic dielectric microparticles by plasmonic near field in a single gold plasmonic Archimedes spiral. Depending on the handedness of circularly polarized excitation, plasmonic near fields can be selectively engineered into either a focusing spot for particle trapping or a plasmonic vortex for particle rotation. Our design provides a simple solution for subwavelength optical manipulation and may find applications in micromechanical and microfluidic systems.
Fan, Xiaolong; Zhou, Hengan; Rao, Jinwei; Zhao, Xiaobing; Zhao, Jing; Zhang, Fengzhen; Xue, Desheng
2015-01-01
Based on the electric rotating magnetoresistance method, the shape anisotropy of a Co microstrip has been systematically investigated. We find that the shape anisotropy is dependent not only on the shape itself, but also on the magnetization distribution controlled by an applied magnetic field. Together with micro-magnetic simulations, we present a visualized picture of how non-uniform magnetization affects the values and polarities of the anisotropy constants and . From the perspective of potential appliantions, our results are useful in designing and understanding the performance of micro- and nano-scale patterned ferromagnetic units and the related device properties. PMID:26563520
Chen, Rui-Pin; Chen, Zhaozhong; Chew, Khian-Hooi; Li, Pei-Gang; Yu, Zhongliang; Ding, Jianping; He, Sailing
2015-05-29
A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system.
Chen, Rui-Pin; Chen, Zhaozhong; Chew, Khian-Hooi; Li, Pei-Gang; Yu, Zhongliang; Ding, Jianping; He, Sailing
2015-01-01
A caustic vector vortex optical field is experimentally generated and demonstrated by a caustic-based approach. The desired caustic with arbitrary acceleration trajectories, as well as the structured states of polarization (SoP) and vortex orders located in different positions in the field cross-section, is generated by imposing the corresponding spatial phase function in a vector vortex optical field. Our study reveals that different spin and orbital angular momentum flux distributions (including opposite directions) in different positions in the cross-section of a caustic vector vortex optical field can be dynamically managed during propagation by intentionally choosing the initial polarization and vortex topological charges, as a result of the modulation of the caustic phase. We find that the SoP in the field cross-section rotates during propagation due to the existence of the vortex. The unique structured feature of the caustic vector vortex optical field opens the possibility of multi-manipulation of optical angular momentum fluxes and SoP, leading to more complex manipulation of the optical field scenarios. Thus this approach further expands the functionality of an optical system. PMID:26024434
NASA Astrophysics Data System (ADS)
Frassinetti, L.; Olofsson, K. E. J.; Fridström, R.; Setiadi, A. C.; Brunsell, P. R.; Volpe, F. A.; Drake, J.
2013-08-01
A new method for the estimate of the wall diffusion time of non-axisymmetric fields is developed. The method based on rotating external fields and on the measurement of the wall frequency response is developed and tested in EXTRAP T2R. The method allows the experimental estimate of the wall diffusion time for each Fourier harmonic and the estimate of the wall diffusion toroidal asymmetries. The method intrinsically considers the effects of three-dimensional structures and of the shell gaps. Far from the gaps, experimental results are in good agreement with the diffusion time estimated with a simple cylindrical model that assumes a homogeneous wall. The method is also applied with non-standard configurations of the coil array, in order to mimic tokamak-relevant settings with a partial wall coverage and active coils of large toroidal extent. The comparison with the full coverage results shows good agreement if the effects of the relevant sidebands are considered.
Babourova, O. V.; Frolov, B. N.
2010-07-15
The direct interaction of the 4-rotational (Lorentzian) gauge field with angular orbital momentum of an external field is considered. This interaction appears in a new Poincare gauge theory of gravitation, in which tetrads are not true gauge fields, but represent some functions of the translational and 4-rotational gauge fields. The given interaction leads to a new effect: the existence of an electronic orbit precession under the action of an intensive external gravitational field (gravidiamagnetic effect), and also substantiates the existence of the direct interaction of the proper angular momentum of a gyroscope with the torsion field, which theoretically can be generated by the rotational angular momentum of the planet Earth. The latter interaction can be detected by the experiment Gravity Probe B on the satellite orbit.
Torres, Ana M; Lopez, Jose J; Pueo, Basilio; Cobos, Maximo
2013-04-01
Plane-wave decomposition (PWD) methods using microphone arrays have been shown to be a very useful tool within the applied acoustics community for their multiple applications in room acoustics analysis and synthesis. While many theoretical aspects of PWD have been previously addressed in the literature, the practical advantages of the PWD method to assess the acoustic behavior of real rooms have been barely explored so far. In this paper, the PWD method is employed to analyze the sound field inside a selected set of real rooms having a well-defined purpose. To this end, a circular microphone array is used to capture and process a number of impulse responses at different spatial positions, providing angle-dependent data for both direct and reflected wavefronts. The detection of reflected plane waves is performed by means of image processing techniques applied over the raw array response data and over the PWD data, showing the usefulness of image-processing-based methods for room acoustics analysis.
Control of Meridional Flow by a Non-Uniform Rotational Magnetic Field
NASA Technical Reports Server (NTRS)
Mazuruk, Konstantin; Ramachandran, Narayanan
1999-01-01
The diffusive mass transfer of species during crystal growth in vertical ampoules is significantly affected by fluid flow in the liquid mother phase (melt). For electrically conductive melts, an elegant way of remotely inducing and controlling this flow is by utilizing a uniform rotational magnetic field (RMF) in the transverse direction. It induces an azimuthal flow which tends to homogenize the thermal and solutal fields. The rotating field also reduces the diffusion boundary layer, stabilizes temperature fluctuations, and promotes better overall crystal growth. For moderate strengths of the applied magnetic field (2-20 m Tesla) with frequencies of up to 400 Hz, the induced secondary meridional flow becomes significant. It typically consists of one roll at the bottom of the liquid column and a second roll (vortex) at the top. The flow along the centerline (ampoule axis) is directed from the growing solid (interface) towards the liquid (melt). In case of convex interfaces (e.g. in floating zone crystal growth) such flow behavior is beneficial since it suppresses diffusion at the center. However, for concave interfaces (e.g. vertical Bridgman crystal growth) such a flow tends to exacerbate the situation in making the interface shape more concave. It would be beneficial to have some control of this meridional flow- for example, a single recirculating cell with controllable direction and flow magnitude will make this technique even more attractive for crystal growth. Such flow control is a possibility if a non-uniform PNE field is utilized for this purpose. Although this idea has been proposed earlier, it has not been conclusively demonstrated so far. In this work, we derive the governing equations for the fluid dynamics for such a system and obtain solutions for a few important cases. Results from parallel experimental measurements of fluid flow in a mercury column subjected to non-uniform RMF will also be presented.
San Emeterio Alvarez, L.; Lacoste, B.; Rodmacq, B.; Sousa, R. C. Dieny, B.; Pakala, M.
2014-05-07
Field-current phase diagrams were measured on in-plane anisotropy Co{sub 60}Fe{sub 20}B{sub 20} magnetic tunnel junctions to obtain the spin transfer torque (STT) field-current switching window. These measurements were used to characterise junctions with varying free layer thicknesses from 2.5 down to 1.1 nm having a reduced effective demagnetizing field due to the perpendicular magnetic anisotropy at CoFeB/MgO interface. Diagrams were obtained with 100 ns current pulses, of either same or alternating polarity. When consecutive pulses have the same polarity, it is possible to realize the STT switching even for conditions having a low switching probability. This was evidenced in diagrams with consecutive pulses of alternating polarity, with 100% switching obtained at 4.7 MA/cm{sup 2}, compared to the lower 3.4 MA/cm{sup 2} value for same polarity pulses. Although the low level of the current density window is higher in alternating polarity diagrams, the field window in both diagrams is the same and therefore independent of the pulse polarity sequence.
Slowly rotating neutron stars in scalar-tensor theories with a massive scalar field
NASA Astrophysics Data System (ADS)
Yazadjiev, Stoytcho S.; Doneva, Daniela D.; Popchev, Dimitar
2016-04-01
In the scalar-tensor theories with a massive scalar field, the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally implies that the scalar-tensor neutron stars with a massive scalar field can have rather different structure and properties in comparison with their counterparts in the massless case and in general relativity. In the present paper, we study slowly rotating neutron stars in scalar-tensor theories with a massive gravitational scalar. Two examples of scalar-tensor theories are examined—the first example is the massive Brans-Dicke theory and the second one is a massive scalar-tensor theory indistinguishable from general relativity in the weak-field limit. In the latter case, we study the effect of the scalar field mass on the spontaneous scalarization of neutron stars. Our numerical results show that the inclusion of a mass term for the scalar field indeed changes the picture drastically compared to the massless case. It turns out that mass, radius, and moment of inertia for neutron stars in massive scalar-tensor theories can differ drastically from the pure general relativistic solutions if sufficiently large masses of the scalar field are considered.
The mean coronal magnetic field determined from Helios Faraday rotation measurements
NASA Technical Reports Server (NTRS)
Patzold, M.; Bird, M. K.; Volland, H.; Levy, G. S.; Seidel, B. L.; Stelzried, C. T.
1987-01-01
Coronal Faraday rotation of the linearly polarized carrier signals of the Helios spacecraft was recorded during the regularly occurring solar occultations over almost a complete solar cycle from 1975 to 1984. These measurements are used to determine the average strength and radial variation of the coronal magnetic field at solar minimum at solar distances from 3-10 solar radii, i.e., the range over which the complex fields at the coronal base are transformed into the interplanetary spiral. The mean coronal magnetic field in 1975-1976 was found to decrease with radial distance according to r exp-alpha, where alpha = 2.7 + or - 0.2. The mean field magnitude was 1.0 + or - 0.5 x 10 to the -5th tesla at a nominal solar distance of 5 solar radii. Possibly higher magnetic field strengths were indicated at solar maximum, but a lack of data prevented a statistical determination of the mean coronal field during this epoch.
The polarization electric field and its effects in an anisotropic rotating magnetospheric plasma
NASA Technical Reports Server (NTRS)
Huang, T. S.; Birmingham, T. J.
1992-01-01
Spatial variations of density and temperature along a magnetic field line are evaluated for a plasma undergoing adiabatic motion in a rotating magnetosphere. The effects of centrifugal and gravitational forces are accounted for, as is anisotropy in the pitch angle distribution functions of individual species. A polarization electric field is invoked to eliminate the net electric charge density resulting from the aforementioned mass dependent forces and different anisotropies. The position of maximum density in a two-component, electron-ion plasma is determined both in the absence and in the presence of the polarization effect and compared. A scale height, generalized to include anisotropies, is derived for the density fall-off. The polarization electric field is also included in the parallel guiding center equation; equilibrium points are determined and compared in both individual and average senses with the position of density maximum. Finally a transverse (to magnetic field lines) electric component is deduced as a consequence of dissimilar charge neutralization on adjacent field lines. The E x B velocity resultant from such a 'fringing' electric field is calculated and compared with the magnitude of other drifts.
The acoustic field of singing humpback whales in the vertical plane
NASA Astrophysics Data System (ADS)
Au, Whitlow W. L.; Pack, Adam A.; Lammers, Marc O.; Herman, Louis; Andrews, Kimberly; Deakos, Mark
2003-04-01
A vertical array of five hydrophones was used to measure the acoustic field of singing humpback whales. Once a singer was located, two swimmers with snorkel gear were deployed to determine the orientation of the whale and to position the boat so that the array could be deployed in front of the whale at a minimum standoff distance of 10 m. The spacing of the hydrophones was 7 m with the deepest hydrophone deployed at depth of 35 m. An 8-channel TASCAM recorder having a bandwidth of 24 kHz was used to record the hydrophone signals. The location of the singer was determined by computing the time of arrival differences between the hydrophone signals. The maximum source level varied between individual units in a song, with values between 180 and 190 dB. The acoustic field determined by considering the relative intensity of higher frequency harmonics in the signals indicate that the sounds are projected in the horizontal direction with the singer's head canted downward 45 to 60°. High-frequency harmonics extended beyond 24 kHz, suggesting that humpback whales may have an upper frequency limit of hearing as high as 24 kHz.
Eseev, M. K.; Kobets, A. G.; Meshkov, I. N.; Rudakov, A. Yu.; Yakovenko, S. L.
2013-10-15
Results from experimental studies of plasma storage in a Penning-Malmberg trap at the LEPTA facility are presented. The number of stored particles is found to increase substantially when using the so-called “rotating wall” method, in which a transverse rotating electric field generated by a cylindrical segmented electrode cut into four pairs is applied to the plasma storage region. The conditions of transverse compression of the plasma bunch under the action of the rotating field and buffer gas are studied. The optimal storage parameters are determined for these experimental conditions. Mechanisms of the action of the rotating field and buffer gas on the process of plasma storage are discussed.
Sugimoto, Norihiko
2015-12-15
Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.
NASA Astrophysics Data System (ADS)
KofroÅ, David
2016-05-01
We present the separation of the Teukolsky master equation for the test field of arbitrary spin on the background of the rotating C -metric. We also summarize and simplify some known results about Debye potentials of these fields on type D background. The equation for the Debye potential is also separated. Solving for the Debye potential of the electromagnetic field we show that on the extremely rotating C -metric no magnetic field can penetrate through the outer black hole horizon—we thus recover the Meissner effect for the C -metric.
Modeling the radio signature of the orbital parameters, rotation, and magnetic field of exoplanets
NASA Astrophysics Data System (ADS)
Hess, S. L. G.; Zarka, P.
2011-07-01
Context. Since the first extra-solar planet discovery in 1995, several hundreds of these planets have been discovered. Most are hot Jupiters, i.e. massive planets orbiting close to their star. These planets may be powerful radio emitters. Aims: We simulate the radio dynamic spectra resulting from various interaction models between an exoplanet and its parent star, i.e. exoplanet-induced stellar emission and three variants of the exoplanet's magnetospheric auroral radio emission (full auroral oval, active sector fixed in longitude, and active sector fixed in local time). Methods: We show the physical information about the system that can be drawn from radio observations, and how this can be achieved. This information includes the magnetic field strength and the rotation period of the emitting body (planet or star), the orbital period, the orbit's inclination, and the magnetic field tilt relative to the rotation axis or offset relative to the center of the planet. For most of these parameters, radio observations provide a unique means of measuring them. Results: Our results should provide the proper framework of analysis and interpretation for future detections of radio emissions from exoplanetary systems - or from magnetic white dwarf-planet or white dwarf-brown dwarf systems -, that are expected to commence soon as part of extensive programs at large radiotelescopes such as LOFAR, UTR2 or the GMRT. Our methodology can be easily adapted to simulate specific observations, once effective detection is achieved.
S. TOBIN; ET AL
2000-12-01
The experimental setup and test results for the {approximately}125 MW rotating magnetic field current drive system of the Translation, Confinement and Sustainment Experiment at the University of Washington are described. The oscillator system, constructed at Los Alamos National Laboratory, drives two tank circuits (15 kV{sub peak} potential, 8.5 kA{sub peak} maximum circulating current in each tank to date) operated 90{degree} out of phase to produce a 54 G rotating magnetic field with a frequency of 163 kHz ({omega} = 1.02{sup x} 10{sup {minus}6} s{sup {minus}1}). Programmable waveform generators control ''hot deck'' totem pole drivers that are used to control the grid of 12 Machlett 8618 magnetically beamed triode tubes. This setup allows the current to be turned on or off in less than 100 ns ({approximately}6{degree}). Both tank circuits are isolated from the current source by a 1:1 air core, transmission line transformer. Each tank circuit contains two saddle coils (combined inductance of 1.6 {micro}H) and radio frequency capacitors (580 nF). Test results are presented for three conditions: no external load, a resistive external load and a plasma load. A SPICE model of the oscillator system was created. Comparisons between this model and experimental data are given.
Giant capacitance of a plane capacitor with a two-dimensional electron gas in a magnetic field
NASA Astrophysics Data System (ADS)
Skinner, Brian; Shklovskii, B. I.
2013-01-01
If a clean two-dimensional electron gas (2DEG) with a low concentration n comprises one electrode of a plane capacitor, the resulting capacitance C can be higher than the “geometric capacitance” Cg determined by the physical separation d between electrodes. A recent paper [B. Skinner and B. I. Shklovskii, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.82.155111 82, 155111 (2010)] argued that when the effective Bohr radius aB of the 2DEG satisfies aB≪d, one can achieve C≫Cg at a low concentration nd2≪1. Here we show that even for devices with aB>d, including graphene, for which aB is effectively infinite, one also arrives at C≫Cg at low electron concentrations if there is a strong perpendicular magnetic field.
Boriskin, Artem V; Sauleau, Ronan; Nosich, Alexander I
2009-02-01
The near fields of small-size extended hemielliptic lenses made of rexolite and isotropic quartz and illuminated by E- and H-polarized plane waves are studied. Variations in the focal domain size, shape, and location are reported versus the angle of incidence of the incoming wave. The problem is solved numerically in a two-dimensional formulation. The accuracy of results is guaranteed by using a highly efficient numerical algorithm based on the combination of the Muller boundary integral equations, the method of analytical regularization, and the trigonometric Galerkin discretization scheme. The analysis fully accounts for the finite size of the lens as well as its curvature and thus can be considered as a reference solution for other electromagnetic solvers. Moreover, the trusted description of the focusing ability of a finite-size hemielliptic lens can be useful in the design of antenna receivers.
Shot noise of charge current in a quantum dot responded by rotating and oscillating magnetic fields
Zhao, Hong-Kang Zou, Wei-Ke; Chen, Qiao
2014-09-07
We have investigated the shot noise and Fano factor of the dynamic spin-polarized quantum dot under the perturbations of a rotating magnetic field (RMF), and an oscillating magnetic field (OMF) by employing the non-equilibrium Green's function approach. The shot noise is enhanced from sub-Poissonian to super-Poissonian due to the application of RMF and OMF, and it is controlled sensitively by the tilt angle θ of RMF. The magnitude of shot noise increases as the photon energy ℏω of OMF increases, and its valley eventually is reversed to peaks as the photon energy is large enough. Double-peak structure of Fano factor is exhibited as the frequency of OMF increases to cover a large regime. The Zeeman energy μ{sub 0}B{sub 0} acts as an effective gate bias to exhibit resonant behavior, and novel peak emerges associated with the applied OMF.
Waves in plasmas generated by a rotating magnetic field and implications to radiation belts
NASA Astrophysics Data System (ADS)
Karavaev, Alexey V.
The interaction of rotating magnetic fields (RMF) with magnetized plasmas is a fundamental plasma physics problem with implications to a wide range of areas, including laboratory and space plasma physics. Despite the importance of the topic the basic physics of the phenomenon remains unexplored. An important application of a RMF is its potential use as an efficient radiation source of low frequency waves in space plasmas, including whistler and shear Alfvéen waves (SAW) for controlled remediation of energetic particles in the Earth's radiation belts. In this dissertation the RMF waves generated in magnetized plasma are studied using numerical simulations with a semi-analytical three-dimensional magneto-hydrodynamic (MHD) model and experiments on the generation of whistler and magnetohydrodynamic waves conducted in UCLA's Large Plasma Device. Comparisons of the simulation results with the experimental measurements, namely, measured spatiotemporal wave structures, dispersion relation with finite transverse wave number, wave amplitude dependence on plasma and RMF source parameters, show good agreement in both the whistler and MHD wave regimes. In both the experiments and the 3D MHD simulations a RMF source was found to be very efficient in the generation of MHD and whistler waves with arbitrary polarizations. The RMF source drives significant field aligned plasma currents confined by the ambient magnetic field for both the whistler and MHD wave regimes, resulting in efficient transport of wave energy along the ambient magnetic field. The efficient transfer of the wave energy results in slow decay rates of the wave amplitude along the ambient magnetic field. The circular polarization of the waves generated by the RMF source, slow amplitude decay rate along the ambient magnetic field and nonzero transverse wave number determined by the RMF source size lead to nonlocal gradients of the wave magnetic field in the direction perpendicular to the ambient magnetic field. A
NASA Astrophysics Data System (ADS)
Chadima, Martin; Studynka, Jan
2013-04-01
Low-field magnetic susceptibility of paramagnetic and diamagnetic minerals is field-independent by definition being also field-independent in pure magnetite. On the other hand, in pyrrhotite, hematite and high-Ti titanomagnetite it may be clearly field-dependent. Consequently, the field-dependent AMS enables the magnetic fabric of the latter group of minerals to be separated from the whole-rock AMS. The methods for the determination of the field-dependent AMS consist of separate measurements of each specimen in several fields within the Rayleigh Law range and subsequent processing in which the field-independent and field-dependent AMS components are calculated. The disadvantage of this technique is that each specimen must be measured several times, which is relatively laborious and time consuming. Recently, a new 3D rotator was developed for the MFK1-FA Kappabridge, which rotates the specimen simultaneously about two axes with different velocities. The measurement is fully automated in such a way that, once the specimen is inserted into the rotator, it requires no additional manipulation to measure the full AMS tensor. Consequently, the 3D rotator enables to measure the AMS tensors in the pre-set field intensities without any operator interference. Whole procedure is controlled by newly developed Safyr5 software; once the measurements are finished, the acquired data are immediately processed and can be visualized in a standard way.
Flow of immiscible ferrofluids in a planar gap in a rotating magnetic field
Sule, Bhumika; Torres-Díaz, Isaac; Rinaldi, Carlos
2015-07-15
Analytical solutions are obtained for the steady, fully developed flow of two layers of immiscible ferrofluids of different thicknesses between two parallel plates. Interfacial linear and internal angular momentum balance relations are derived for the case when there is a ferrofluid-ferrofluid interface to obtain the translational and spin velocity profiles in the gap. As expected for the limit of low applied field amplitude, the magnitude of the translational velocity is directly proportional to the frequency of the applied magnetic field and to the square of the magnetic field amplitude. Expressions for the velocity profiles are obtained for the zero spin viscosity and non-zero spin viscosity cases and the effect of applied pressure gradient on the flows is studied. The spin velocity in both ferrofluid phases is in the direction of the rotating magnetic field, except for cases of extreme applied pressure gradients for which the fluid vorticity opposes the spin. We find that for the case of non-zero spin viscosity, flow reversals are predicted using representative ferrofluid property values and field conditions. The unique predictions of the solution with non-zero spin viscosity could be used to experimentally test the existence of couple stresses in ferrofluids and the validity of previously reported values of the so-called spin viscosity.
Flow of immiscible ferrofluids in a planar gap in a rotating magnetic field
NASA Astrophysics Data System (ADS)
Sule, Bhumika; Torres-Díaz, Isaac; Rinaldi, Carlos
2015-07-01
Analytical solutions are obtained for the steady, fully developed flow of two layers of immiscible ferrofluids of different thicknesses between two parallel plates. Interfacial linear and internal angular momentum balance relations are derived for the case when there is a ferrofluid-ferrofluid interface to obtain the translational and spin velocity profiles in the gap. As expected for the limit of low applied field amplitude, the magnitude of the translational velocity is directly proportional to the frequency of the applied magnetic field and to the square of the magnetic field amplitude. Expressions for the velocity profiles are obtained for the zero spin viscosity and non-zero spin viscosity cases and the effect of applied pressure gradient on the flows is studied. The spin velocity in both ferrofluid phases is in the direction of the rotating magnetic field, except for cases of extreme applied pressure gradients for which the fluid vorticity opposes the spin. We find that for the case of non-zero spin viscosity, flow reversals are predicted using representative ferrofluid property values and field conditions. The unique predictions of the solution with non-zero spin viscosity could be used to experimentally test the existence of couple stresses in ferrofluids and the validity of previously reported values of the so-called spin viscosity.
Manske, Maria A; Barker, Jerry L; Wong, Pei-Fong; Westlake, Wallace; Garden, Adam S; Ang, K Kian; Rosenthal, David I
2004-01-01
With a monoisocentric 3-field technique for treating head-and-neck cancer, collimator rotation may be needed for the upper lateral fields to avoid cephalad-positioned shoulders or to avoid unnecessary arytenoid irradiation while maintaining more anterior coverage. For patients with unilateral lymphadenopathy, lateral oblique-opposed boost fields can be used to encompass the primary tumor and ipsilateral lymph nodes without junctioning through gross disease. When initial collimated lateral fields are also rotated with a gantry angle to produce oblique boost fields, however, the resulting matchline with a low anterior neck (LAN) boost field is no longer nondivergent. This can be corrected by manual adjustment of collimator and gantry angles for the LAN field using 3D treatment planning software. The goal of this study was to derive mathematical formulas to simplify this process. We used a transformation matrix to define formulas that could predict the appropriate modifications to the LAN boost field. Output from the formulas was (1) visually tested within 3D treatment planning software and (2) verified using a solid water head-and-neck phantom and radiographic film dosimetry to confirm that a nondivergent matchline was obtained in several clinical scenarios. When evaluated with 3D treatment planning software, the formulas accurately predicted the appropriate gantry and collimator angles of the LAN boost field for a variety of possible beam combinations. When evaluated with film dosimetry, the formulas were shown to accurately predict the appropriate gantry and collimator angles of the LAN boost field to within the +/- 2 mm/1 degrees tolerance specifications of the linear accelerator and acceptable for routine clinical use. The presented formulas are simple and geometrically precise. They predict the necessary manipulations of the LAN boost field to maintain a geometrically precise matchline, as verified by 3D treatment planning software, phantom dosimetry, and actual
Zhu, Chuntao; Zhang, Ying; Wang, Yinan; Li, Qingchuan; Mu, Wei; Han, Xiaojun
2016-02-24
It is well-known that homogeneous electric fields can be used to generate giant unilamellar vesicles (GUVs). Herein we report an interesting phenomenon of formation of GUVs and lipid tubes simultaneously using a nonhomogeneous electric field generated by point-to-plane electrodes. The underlying mechanism was analyzed using finite element analysis. The two forces play main roles, that is, the pulling force (F) to drag GUVs into lipid tubes induced by fluid flow, and the critical force (Fc) to prevent GUVs from deforming into lipid tubes induced by electric fields. In the center area underneath the needle electrode, the GUVs were found because F is less than Fc in that region, whereas in the edge area the lipid tubes were obtained because F is larger than Fc. The diffusion coefficient of lipid in the tubes was found to be 4.45 μm(2) s(-1) using a fluorescence recovery after photobleaching (FRAP) technique. The method demonstrated here is superior to conventional GUV or lipid tube fabrication methods, and has great potential in cell mimic or hollow material fabrication using GUVs and tubes as templates. PMID:26756162
NASA Astrophysics Data System (ADS)
Kobelski, A.; Jensen, E.; Wexler, D.; Heiles, C.; Kepley, A.; Kuiper, T.; Bisi, M.
2016-04-01
The STEREO mission spacecraft recently passed through superior conjunction, providing an opportunity to probe the solar corona using radio transmissions. Strong magnetic field and dense plasma environment induce Faraday rotation of the linearly polarized fraction of the spacecraft radio carrier signal. Variations in the Faraday rotation signify changes in magnetic field components and plasma parameters, and thus can be used to gain understanding processes of the quiescent sun as well as active outbursts including coronal mass ejections. Our 2015 observing campaign resulted in a series of measurements over several months with the 100m Green Bank Telescope (GBT) to investigate the coronal Faraday rotation at various radial distances. These observations reveal notable fluctuations in the Faraday rotation of the signal in the deep corona, and should yield unique insights into coronal magnetohydrodynamics down to a 1.5 solar radius line-of-sight solar elongation.
Faraday rotation and magnetic properties of neodynium trifluoride under high magnetic field
NASA Astrophysics Data System (ADS)
Guillot, M.; Schmiedel, T.; Xu, You
1999-04-01
Faraday rotation (Fr) and magnetization (M) measurements were performed in the trifluoride of neodymium NdF3 in high continuous magnetic field (17 T below 77 K and 30 T above this temperature). The temperature range extends from 15 to 300 K (Fr) and from 1.6 to 300 K (M), respectively; the external field was applied along the (c) direction of the hexagonal structure at 633 nm wavelength. M was found to be linear versus H above 40 K; the magnetic susceptibility (χ) follows a Curie-Weiss law. At low temperature, only the lowest doublet is populated and the saturation of M is observed. Below 30 K, Fr presents a nonlinear field dependence in H higher than 7 T but remains linear in the 30-300 K range. The Verdet constant (V) was then deduced. All the data confirm a complex and unusual temperature variation of the ratio V/χ which cannot be attributed to a strong superexchange coupling between the spins of the Nd3+ ions as previously proposed; they underline a paramagnetic behavior which is influenced by crystal field effects.
Magnetostrictive behaviors of Fe-Al(001) single-crystal films under rotating magnetic fields
NASA Astrophysics Data System (ADS)
Kawai, Tetsuroh; Abe, Tatsuya; Ohtake, Mitsuru; Futamoto, Masaaki
2016-05-01
Magnetostrictive behaviors of Fe100-x - Alx(x = 0 - 30 at.%)(001) single-crystal films under rotating magnetic fields are investigated along the two different crystallographic orientations, [100] and [110]. The behaviors of Fe and Fe90Al10 films show bath-tub like waveform along [100], easy magnetization axis, and triangular waveform along [110], hard magnetization axis, with respect to their four-fold magnetic anisotropy. On the other hand, the behaviors of Fe80Al20 film are different from those of Fe or Fe90Al10 film. The output of the film along [100] shows a strong magnetic field dependence. The Fe70Al30 film shows similar magnetostrictive behaviors along both [100] and [110] reflecting its magnetic properties, which are almost same for the both directions. The growth of ordered phase (B2) in Fe80Al20 and Fe70Al30 films is considered to have affected their magnetostrictive behaviors. The Al content dependence on λ100 and λ111 values shows similar tendency to that reported for the bulk samples but the values are slightly different. The Fe90Al10(001) single-crystal film shows a large magnetostriction along [100] under a very small magnetic field of 0.02 kOe, which is comparable to the saturated one, and changes the value abruptly in relation to the angle of applied magnetic field.
Stabilization of Satellite derived Gravity Field Coefficients by Earth Rotation Parameters
NASA Astrophysics Data System (ADS)
Heiker, A.; Kutterer, H.; Müller, J.
2009-04-01
Recent gravity field missions (e.g. GRACE) provide monthly solutions for the time-variable Earth gravity field. However, the low-degree harmonic coefficients are poorly resolved, especially those of degree 2. The Earth rotation parameters (ERP), consisting of polar motion and lod, and the gravity field coefficients (GFC) of degree 2 are linked by the Euler-Liouville Equation. Thus the consideration of ERP time series helps to improve the estimates of GFC2. Due to the covariances between the GFC of degree 2 and further low-degree gravity field coefficients (up to degree 10) the residuals of the first group of coefficients has to be propagated to the second group in order to guarantee an overall consistency. Previous work has shown a significant influence of ERP on GFC up to degree 4 with the results depending on the covariances assumed a priori. This presentation shows the result of a consistent joint analysis of GRACE derived GFC and ERP in an extended Gauss-Helmert model which includes a sophisticated variance-covariance component estimation (VCCE). As the covariances of the GRACE derived GFC are largely not known, some different variance-covariance structures are assumed and estimated with the VCCE. The results are compared and discussed.
Growth of II-VI Solid Solutions in the Presence of a Rotating Magnetic Field
NASA Technical Reports Server (NTRS)
Gillies, D. C; Motakef, S.; Dudley, M.; Matyi, R.; Volz, H.
1999-01-01
The application of a rotating magnetic field (RMF)in the frequency range 60-400 Hz and field strength of the order of 2-8 mT to crystal growth has received increasing attention in recent years. To take full advantage of the control of fluid flow by the forces applied by the field, the liquid column must be electrically conducting. Also, the application of RMF to the directional solidification of a column of liquid can result in complete mixing in the resultant solid. Thus, the technique of RMF is suited to solvent zones and float zones where the composition of the liquid is more readily controlled. In the work we report on, numerical modeling has been applied to II-VI systems, particularly tellurium based traveling heater techniques (THM). Results for a spectrum of field strengths and acceleration levels will be presented. These show clearly the effects of competing buoyancy forces and electromagnetic stirring. Crystals of cadmium zinc telluride and mercury cadmium telluride have been grown terrestrially from a tellurium solvent zone. The effects of the RMF during these experiments will be demonstrated with micrographs showing etch pits, white beam x-ray synchrotron topographs and triple axis x-ray diffraction.
Radial modes of slowly rotating compact stars in the presence of magnetic field
NASA Astrophysics Data System (ADS)
Panda, N. R.; Mohanta, K. K.; Sahu, P. K.
2016-09-01
Compact stars are composed of very high-density hadron matter. When the matter is above nuclear matter density, then there is a chance of different phases of matter such as hadron matter to quark matter. There is a possible phase which, having the quark core surrounded by a mixed phase followed by hadronic matter, may be considered as a hybrid phase inside the stars called hybrid star (HS). The star which consists of only u, d and s quarks is called quark star (QS) and the star which has only hadronic matter is called neutron star (NS). For the equation of state (EOS) of hadronic matter, we have considered the Relativistic Mean Field (RMF) theory and we incorporated the effect of strong magnetic fields. For the EOS of the quark phase we use the simple MIT bag model. We have assumed Gaussian parametrization to make the density dependent for both bag pressure in quark matter and magnetic field. We have constructed the intermediate mixed phase by using the Glendenning conjecture. Eigenfrequencies of radial pulsations of slowly rotating magnetized compact stars (NS, QS, HS) are calculated in a general relativistic formalism given by Chandrasekhar and Friedman. We have studied the effect of central density on the square of the frequencies of the compact stars in the presence of zero and strong magnetic field.
NASA Astrophysics Data System (ADS)
Wang, Jing-Rong; Liu, Guo-Zhu; Zhang, Chang-Jin
2016-07-01
Angle-resolved upper critical field Hc 2 provides an efficient tool to probe the gap symmetry of unconventional superconductors. We revisit the behavior of in-plane Hc 2 in d -wave superconductors by considering both the orbital effect and Pauli paramagnetic effect. After carrying out systematic analysis, we show that the maxima of Hc 2 could be along either nodal or antinodal directions of a d -wave superconducting gap, depending on the specific values of a number of tuning parameters. This behavior is in contrast to the common belief that the maxima of in-plane Hc 2 are along the direction where the superconducting gap takes its maximal value. Therefore, identifying the precise d -wave gap symmetry through fitting experiments results of angle-resolved Hc 2 with model calculations at a fixed temperature, as widely used in previous studies, is difficult and practically unreliable. However, our extensive analysis of angle-resolved Hc 2 show that there is a critical temperature T*: in-plane Hc 2 exhibits its maxima along nodal directions at T
UBIQUITOUS ROTATING NETWORK MAGNETIC FIELDS AND EXTREME-ULTRAVIOLET CYCLONES IN THE QUIET SUN
Zhang Jun; Liu Yang E-mail: yliu@sun.stanford.edu
2011-11-01
We present Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) observations of EUV cyclones in the quiet Sun. These cyclones are rooted in the rotating network magnetic fields (RNFs). Such cyclones can last several to more than 10 hr and, at the later phase, they are found to be associated with EUV brightenings (microflares) and even EUV waves. SDO Helioseismic and Magnetic Imager (HMI) observations show a ubiquitous presence of RNFs. Using HMI line-of-sight magnetograms on 2010 July 8, we find 388 RNFs in an area of 800 x 980 arcsec{sup 2} near the disk center where no active region is present. The sense of rotation shows a weak hemisphere preference. The unsigned magnetic flux of the RNFs is about 4.0 x 10{sup 21} Mx, or 78% of the total network flux. These observational phenomena at small scale reported in this Letter are consistent with those at large scale in active regions. The ubiquitous RNFs and EUV cyclones over the quiet Sun may suggest an effective way to heat the corona.
Helioseismic Constraints on Rotation and Magnetic Fields in the Solar Core
NASA Astrophysics Data System (ADS)
Goode, Philip R.
2001-05-01
In recent years, more and more precise measurements have been made of solar oscillation frequencies and line widths. From space, the Solar and Heliospheric Observatory/Michelson Doppler Imager (MDI) data has led to much progress. From the ground, networks, like Global Oscillation Network Group (GONG), Taiwanese Oscillation Network (TON), and Birmingham Solar Oscillations Network (BiSON) have also led to much progress. The sharpened and enriched oscillation spectrum of data have been critically complemented by advances in the treatments of the opacities and the equation of state. All of this has led to a significantly more precise probing of the solar core. Here we discuss the progress made and suggest how the core may be better probed with seismic data on-hand. In particular, we review our knowledge of the rotation and structure of the core. We further argue that much may be learned about the core by exploiting the line width data from the aforementioned sources. Line-width data can be used to place sharper constraints on core properties, like the degree to which the Sun rotates on a single axis and the upper limit on magnetic fields that may be buried in the core.
PIV measurements of the velocity field in counter-rotating cylindrical Couette flow
NASA Astrophysics Data System (ADS)
van Hout, Rene; Katz, Joseph
2007-11-01
An experimental investigation using Particle Image Velocimetry (PIV) was carried out to study the latitudinal planar velocity field in air counter-rotating cylindrical Couette flow at high Reynolds numbers. The facility consisted of two concentric cylinders with a radius ratio of η=ri / ri ro . - ro= 0.55 and aspect ratio γ=L/( ro-ri )= 11.2. Measurements were done at two outer cylinder Reynolds numbers, Ro = -25,196 and -52,042 while the inner cylinder Reynolds number varied between Ri = 2,635 to 40,446. At constant Ro with increasing Ri, the mean azimuthal velocity profile became increasingly flatter over most of the annulus with a strong shear layer near the cylinder wall. The radius at which Uθ changed sign moved away from the inner cylinder. Plotted against inner wall coordinates, the azimuthal velocity profile displayed log law behavior albeit with increased values of κ and B as Ri was increased. Normalized rms values of the azimuthal fluctuating velocity component and Reynolds stresses peak near to the wall. Magnitudes increase and become more significant over the whole width of the annulus as Ri increased. Higher moments display double peaks. Holding the inner cylinder rotation speed constant while increasing the outer cylinder speed strongly influenced the radial profiles of turbulent stresses.
Force field parameters for rotation around chi torsion axis in nucleic acids.
Ode, Hirotaka; Matsuo, Yuri; Neya, Saburo; Hoshino, Tyuji
2008-11-30
To raise the accuracy of the force field for nucleic acids, several parameters were elaborated, focusing on the rotation around chi torsion axis. The reliability of molecular dynamics (MD) simulation was significantly increased by improving the torsion parameters at C8--N9--C1'--X (X = H1', C2', O4') in A, G and those at C6--N1--C1'--X in C, T, and U. In this work, we constructed small models representing the chemical structure of A, G, C, T, and U, and estimated energy profile for chi-axis rotation by executing numerous quantum mechanical (QM) calculations. The parameters were derived by discrete Fourier transformation of the calculated QM data. A comparison in energy profile between molecular mechanical (MM) calculation and QM one shows that our presently derived parameters well reproduce the energy surface of QM calculation for all the above torsion terms. Furthermore, our parameters show a good performance in MD simulations of some nucleic acids. Hence, the present refinement of parameters will enable us to perform more accurate simulations for various types of nucleic acids.
NASA Technical Reports Server (NTRS)
Kumar, Vinod; Kumar, Nagendra; Srivastava, Krishna M.; Mittal, R. C.
1993-01-01
The problem of gravitational instability of an infinite homogeneous self-gravitating medium carrying a uniform magnetic field in the presence of Hall effect has been investigated to include the effect due to rotation. The dispersion relation has been obtained. It has been found that the Jeans's criterion for the instability remains unaffected even when the effect due to rotation is considered in the presence of Hall effect carrying a uniform magnetic.
NASA Astrophysics Data System (ADS)
Lee, Jongsuh; Wang, Semyung; Pluymers, Bert; Desmet, Wim; Kindt, Peter
2015-02-01
Generally, the dynamic characteristics (natural frequency, damping, and mode shape) of a structure can be estimated by experimental modal analysis. Among these dynamic characteristics, mode shape requires multiple measurements of the structure at different positions, which increases the experimental cost and time. Recently, the Hilbert-Huang transform (HHT) method has been introduced to extract mode-shape information from a continuous measurement, which requires vibration measurements from one position to another position continuously with a non-contact sensor. In this research study, an effort has been made to estimate the mode shapes of a rolling tire with a single measurement instead of using the conventional experimental setup (i.e., measurement of the vibration of a rolling tire at multiple positions similar to the case of a non-rotating structure), which is used to estimate the dynamic behavior of a rolling tire. For this purpose, HHT, which was used in the continuous measurement of a non-rotating structure in previous research studies, has been used for the case of a rotating system in this study. Ambiguous mode combinations can occur in this rotating system, and therefore, a method to overcome this ambiguity is proposed in this study. In addition, the specific phenomenon for a rotating system is introduced, and the effect of this phenomenon with regard to the obtained results through HHT is investigated.
Lee, Jongsuh; Wang, Semyung; Pluymers, Bert; Desmet, Wim; Kindt, Peter
2015-02-01
Generally, the dynamic characteristics (natural frequency, damping, and mode shape) of a structure can be estimated by experimental modal analysis. Among these dynamic characteristics, mode shape requires multiple measurements of the structure at different positions, which increases the experimental cost and time. Recently, the Hilbert-Huang transform (HHT) method has been introduced to extract mode-shape information from a continuous measurement, which requires vibration measurements from one position to another position continuously with a non-contact sensor. In this research study, an effort has been made to estimate the mode shapes of a rolling tire with a single measurement instead of using the conventional experimental setup (i.e., measurement of the vibration of a rolling tire at multiple positions similar to the case of a non-rotating structure), which is used to estimate the dynamic behavior of a rolling tire. For this purpose, HHT, which was used in the continuous measurement of a non-rotating structure in previous research studies, has been used for the case of a rotating system in this study. Ambiguous mode combinations can occur in this rotating system, and therefore, a method to overcome this ambiguity is proposed in this study. In addition, the specific phenomenon for a rotating system is introduced, and the effect of this phenomenon with regard to the obtained results through HHT is investigated.
Mellow, Tim; Kärkkäinen, Leo
2014-03-01
An acoustic curtain is an array of microphones used for recording sound which is subsequently reproduced through an array of loudspeakers in which each loudspeaker reproduces the signal from its corresponding microphone. Here the sound originates from a point source on the axis of symmetry of the circular array. The Kirchhoff-Helmholtz integral for a plane circular curtain is solved analytically as fast-converging expansions, assuming an ideal continuous array, to speed up computations and provide insight. By reversing the time sequence of the recording (or reversing the direction of propagation of the incident wave so that the point source becomes an "ideal" point sink), the curtain becomes a time reversal mirror and the analytical solution for this is given simultaneously. In the case of an infinite planar array, it is demonstrated that either a monopole or dipole curtain will reproduce the diverging sound field of the point source on the far side. However, although the real part of the sound field of the infinite time-reversal mirror is reproduced, the imaginary part is an approximation due to the missing singularity. It is shown that the approximation may be improved by using the appropriate combination of monopole and dipole sources in the mirror.
Evolution of turbulence and in-plane vortices in the near field flow behind multi-scale planar grids
NASA Astrophysics Data System (ADS)
Gan, L.; Krogstad, P.-Å.
2016-08-01
In this experimental work, we carry out detailed two-dimensional particle image velocimetry investigations for the near field wakes behind a conventional and two multi-scale planar grids, using stitched camera fields of view. Statistical independent measurements are conducted focusing on the first few mesh distances downstream of the grid. It is found that the multiple integral length scales originated from the grids loose their importance on the turbulence development after about three mesh distances downstream, much earlier than the distance where the turbulence becomes homogeneous. The largest eddy size, represented by the integral length scales, does not show clear differences in its growth rate among the three grids after an initial development of three times the largest grid size downstream. Nevertheless, when examining individual vortex behaviours using conditional averaging and filtering processes, clear differences are found. The grids are found to have different decay rates of peak vorticity and projected vortex strengths. Despite these differences, the in-plane vorticity correlation function reveals that the mean vortex shape of all the grids shows a universal near-Gaussian pattern which does not change much as the turbulence decays.
Seo, Jooyeok; Nam, Sungho; Jeong, Jaehoon; Lee, Chulyeon; Kim, Hwajeong; Kim, Youngkyoo
2015-01-14
We report planar liquid crystal-gated-organic field-effect transistors (LC-g-OFETs) with a simple in-plane drain-source-gate electrode structure, which can be cost-effectively prepared by typical photolithography/etching processes. The LC-g-OFET devices were fabricated by forming the LC layer (4-cyano-4'-pentylbiphenyl, 5CB) on top of the channel layer (poly(3-hexylthiophene), P3HT) that was spin-coated on the patterned indium-tin oxide (ITO)-coated glass substrates. The LC-g-OFET devices showed p-type transistor characteristics, while a current saturation behavior in the output curves was achieved for the 50-150 nm-thick P3HT (channel) layers. A prospective on/off ratio (>1 × 10(3)) was obtained regardless of the P3HT thickness, whereas the resulting hole mobility (0.5-1.1 cm(2)/(V s)) at a linear regime was dependent on the P3HT thickness. The tilted ordering of 5CB at the LC-P3HT interfaces, which is induced by the gate electric field, has been proposed as a core point of working mechanism for the present LC-g-OFETs. PMID:25478816
NASA Astrophysics Data System (ADS)
Briquet, M.; Neiner, C.; Petit, P.; Leroy, B.; de Batz, B.
2016-03-01
Aims: The main-sequence B-type star ζ Cassiopeiae is known as a N-rich star with a magnetic field discovered with the Musicos spectropolarimeter. We model the magnetic field of the star by means of 82 new spectropolarimetric observations of higher precision to investigate the field strength, topology, and effect. Methods: We gathered data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL; Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from ζ Cas. We used a dipole oblique rotator model to determine the field configuration by fitting the longitudinal field measurements and by synthesizing the measured Stokes V profiles. We also made use of the Zeeman-Doppler imaging technique to map the stellar surface and to deduce the difference in rotation rate between the pole and equator. Results: ζ Cas exhibits a polar field strength Bpol of 100-150 G, which is the weakest polar field observed so far in a massive main-sequence star. Surface differential rotation is ruled out by our observations and the field of ζ Cas is strong enough to enforce rigid internal rotation in the radiative zone according to theory. Thus, the star rotates as a solid body in the envelope. Conclusions: We therefore exclude rotationally induced mixing as the cause of the surface N-enrichment. We discuss that the transport of chemicals from the core to the surface by internal gravity waves is the most plausible explanation for the nitrogen overabundance at the surface of ζ Cas. Based on observations obtained at the Télescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique (CNRS) of France.
NASA Technical Reports Server (NTRS)
Croell, Arne; Dold, P.; Kaiser, Th.; Szofran, Frank; Benz, K. W.
1999-01-01
Hear and mass transfer in float-zone processing are strongly influenced by convective flows in the zone. They are caused by buoyancy convection, thermocapillary (Marangoni) convection, or artificial sources such as rotation and radio frequency heating. Flows in conducting melts can be controlled by the use of magnetic fields, either by damping fluid motion with static fields or by generating a def@ned flow with rotating fields. The possibilities of using static and rotating magnetic fields in silicon floating-zone growth have been investigated by experiments in axial static fields up to ST and in transverse rotating magnetic fields up to 7.S mT. Static fields of a few 100 MT already suppress most striations but are detrimental to the radial segregation by introducing a coring effect. A complete suppression of dopant striations caused by time-dependent thermocapillary convection and a reduction of the coring to insignificant values, combined with a shift of the axial segregation profile towards a more diffusion-limited case, is possible with static fields ? 1T. However, under certain conditions the use of high axial magnetic fields can lead to the appearance of a new type of pronounced dopant striations, caused by thermoelec:romagnetic convection. The use of a transverse rotating magnetic field influences the microscopic segregation at quite low inductions, of the order of a few mT. The field shifts time-dependent flows and the resulting striation patterns from a broad range of low frequencies at high amplitudes to a few high frequencies at low amplitudes
A CONSTRAINT ON THE ORGANIZATION OF THE GALACTIC CENTER MAGNETIC FIELD USING FARADAY ROTATION
Law, C. J.; Brentjens, M. A.; Novak, G.
2011-04-10
We present new 6 and 20 cm Very Large Array (VLA) observations of polarized continuum emission of roughly 0.5 deg{sup 2} of the Galactic center (GC) region. The 6 cm observations detect diffuse linearly polarized emission throughout the region with a brightness of roughly 1 mJy per 15''x10'' beam. The Faraday rotation measure (RM) toward this polarized emission has structure on degree size scales and ranges from roughly +330 rad m{sup -2} east of the dynamical center (Sgr A) to-880 rad m{sup -2} west of the dynamical center. This RM structure is also seen toward several nonthermal radio filaments, which implies that they have a similar magnetic field orientation and constrains models for their origin. Modeling shows that the RM and its change with Galactic longitude are best explained by the high electron density and strong magnetic field of the GC region. Considering the emissivity of the GC plasma shows that while the absolute RM values are indirect measures of the GC magnetic field, the RM longitude structure directly traces the magnetic field in the central kiloparsec of the Galaxy. Combining this result with previous work reveals a larger RM structure covering the central {approx}2{sup 0} of the Galaxy. This RM structure is similar to that proposed by Novak and coworkers, but is shifted roughly 50 pc west of the dynamical center of the Galaxy. If this RM structure originates in the GC region, it shows that the GC magnetic field is organized on {approx}300 pc size scales. The pattern is consistent with a predominantly poloidal field geometry, pointing from south to north, that is perturbed by the motion of gas in the Galactic disk.