WorldWideScience

Sample records for magnetically controlled circumstellar

  1. A Rigidly Rotating Magnetosphere Model for the Circumstellar Environments of Magnetic OB Stars

    Science.gov (United States)

    Townsend, R.; Owocki, S.; Groote, D.

    2005-11-01

    We report on a new model for the circumstellar environments of rotating, magnetic hot stars. This model predicts the channeling of wind plasma into a corotating magnetosphere, where -- supported against gravity by centrifugal forces -- it can steadily accumulate over time. We apply the model to the B2p star σ Ori E, demonstrating that it can simultaneously reproduce the spectroscopic, photometric and magnetic variations exhibited by the star.

  2. Disruption of circumstellar discs by large-scale stellar magnetic fields

    Science.gov (United States)

    ud-Doula, Asif; Owocki, Stanley P.; Kee, Nathaniel Dylan

    2018-05-01

    Spectropolarimetric surveys reveal that 8-10% of OBA stars harbor large-scale magnetic fields, but thus far no such fields have been detected in any classical Be stars. Motivated by this, we present here MHD simulations for how a pre-existing Keplerian disc - like that inferred to form from decretion of material from rapidly rotating Be stars - can be disrupted by a rotation-aligned stellar dipole field. For characteristic stellar and disc parameters of a near-critically rotating B2e star, we find that a polar surface field strength of just 10 G can significantly disrupt the disc, while a field of 100 G, near the observational upper limit inferred for most Be stars, completely destroys the disc over just a few days. Our parameter study shows that the efficacy of this magnetic disruption of a disc scales with the characteristic plasma beta (defined as the ratio between thermal and magnetic pressure) in the disc, but is surprisingly insensitive to other variations, e.g. in stellar rotation speed, or the mass loss rate of the star's radiatively driven wind. The disc disruption seen here for even a modest field strength suggests that the presumed formation of such Be discs by decretion of material from the star would likely be strongly inhibited by such fields; this provides an attractive explanation for why no large-scale fields are detected from such Be stars.

  3. Controlling magnetic field profiles

    International Nuclear Information System (INIS)

    Freeman, J.R.

    1979-04-01

    A method for designing solenoid magnets with controlled field profiles is discussed. The method, originated by D.B. Montgomery, minimizes both the field errors and the power consumption. An NOS time-sharing computer program for the CDC-6600, entitled MAGCOR, was constructed to provide an interactive magnet design capability. Results obtained during the design of magnets for a radial line electron accelerator are presented. 9 figures

  4. TMX magnet control system

    International Nuclear Information System (INIS)

    Goerz, D.A.

    1978-01-01

    A control system utilizing a microcomputer has been developed that controls the power supplies driving the Tandem Mirror Experiment (TMX) magnet set and monitors magnet coil operation. The magnet set consists of 18 magnet coils that are driven by 26 dc power supplies. There are two possible modes of operation with this system: a pulse mode where the coils are pulsed on for several seconds with a dc power consumption of 16 MW; and a continuous mode where the coils can run steady state at 10 percent of maximum current ratings. The processor has been given an active control role and serves as an interface between the operator and electronic circuitry that controls the magnet power supplies. This microcomputer also collects and processes data from many analog singal monitors in the coil circuits and numerous status signals from the supplies. Placing the microcomputer in an active control role has yielded a compact, cost effective system that simplifies the magnet system operation and has proven to be very reliable. This paper will describe the TMX magnet control sytem and discuss its development

  5. Optimal magnetic attitude control

    DEFF Research Database (Denmark)

    Wisniewski, Rafal; Markley, F.L.

    1999-01-01

    because control torques can only be generated perpendicular to the local geomagnetic field vector. This has been a serious obstacle for using magnetorquer based control for three-axis stabilization of a low earth orbit satellite. The problem of controlling the spacecraft attitude using only magnetic...

  6. Magnetic spectrometer control system

    International Nuclear Information System (INIS)

    Lecca, L.A.; Di Paolo, Hugo; Fernandez Niello, Jorge O.; Marti, Guillermo V; Pacheco, Alberto J.; Ramirez, Marcelo

    2003-01-01

    The design and implementation of a new computerized control system for the several devices of the magnetic spectrometer at TANDAR Laboratory is described. This system, as a main difference from the preexisting one, is compatible with almost any operating systems of wide spread use available in PC. This allows on-line measurement and control of all signals from any terminal of a computer network. (author)

  7. Tracing Planets in Circumstellar Discs

    Directory of Open Access Journals (Sweden)

    Uribe Ana L.

    2013-04-01

    Full Text Available Planets are assumed to form in circumstellar discs around young stellar objects. The additional gravitational potential of a planet perturbs the disc and leads to characteristic structures, i.e. spiral waves and gaps, in the disc density profile. We perform a large-scale parameter study on the observability of these planet-induced structures in circumstellar discs in the (submm wavelength range for the Atacama Large (SubMillimeter Array (ALMA. On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disc-planet models we calculate the disc temperature structure and (submm images of these systems. These are used to derive simulated ALMA maps. Because appropriate objects are frequent in the Taurus-Auriga region, we focus on a distance of 140 pc and a declination of ≈ 20°. The explored range of star-disc-planet configurations consists of six hydrodynamical simulations (including magnetic fields and different planet masses, nine disc sizes with outer radii ranging from 9 AU to 225 AU, 15 total disc masses in the range between 2.67·10-7 M⊙ and 4.10·10-2 M⊙, six different central stars and two different grain size distributions, resulting in 10 000 disc models. At almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disc structures induced by planet-disc interaction or the influence of magnetic fields in the wavelength range between 0.4...2.0 mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, within the range of typical masses of protoplane tary discs (0.1 M⊙...0.001 M⊙ the disc mass has a minor impact on the observability. At the distance of 140 pc it is possible to resolve discs down to 2.67·10-6 M⊙ and trace gaps in discs with 2.67·10-4 M⊙ with a signal-to-noise ratio greater than three. In general, it is more likely to trace planet-induced gaps in magneto-hydrodynamical disc models, because gaps are wider in the presence of

  8. CONFIRMATION OF CIRCUMSTELLAR PHOSPHINE

    Energy Technology Data Exchange (ETDEWEB)

    Agúndez, M.; Cernicharo, J. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco (Spain); Decin, L. [Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, NL-1098 Amsterdam (Netherlands); Encrenaz, P. [LERMA, Observatoire de Paris, 61 Av. de l' Observatoire, F-75014 Paris (France); Teyssier, D. [European Space Astronomy Centre, Urb. Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid (Spain)

    2014-08-01

    Phosphine (PH{sub 3}) was tentatively identified a few years ago in the carbon star envelopes IRC +10216 and CRL 2688 from observations of an emission line at 266.9 GHz attributable to the J = 1-0 rotational transition. We report the detection of the J = 2-1 rotational transition of PH{sub 3} in IRC +10216 using the HIFI instrument on board Herschel, which definitively confirms the identification of PH{sub 3}. Radiative transfer calculations indicate that infrared pumping in excited vibrational states plays an important role in the excitation of PH{sub 3} in the envelope of IRC +10216, and that the observed lines are consistent with phosphine being formed anywhere between the star and 100 R {sub *} from the star, with an abundance of 10{sup –8} relative to H{sub 2}. The detection of PH{sub 3} challenges chemical models, none of which offer a satisfactory formation scenario. Although PH{sub 3} holds just 2% of the total available phosphorus in IRC +10216, it is, together with HCP, one of the major gas phase carriers of phosphorus in the inner circumstellar layers, suggesting that it could also be an important phosphorus species in other astronomical environments. This is the first unambiguous detection of PH{sub 3} outside the solar system, and is a further step toward a better understanding of the chemistry of phosphorus in space.

  9. Nonlinear control of magnetic signatures

    Science.gov (United States)

    Niemoczynski, Bogdan

    Magnetic properties of ferrite structures are known to cause fluctuations in Earth's magnetic field around the object. These fluctuations are known as the object's magnetic signature and are unique based on the object's geometry and material. It is a common practice to neutralize magnetic signatures periodically after certain time intervals, however there is a growing interest to develop real time degaussing systems for various applications. Development of real time degaussing system is a challenging problem because of magnetic hysteresis and difficulties in measurement or estimation of near-field flux data. The goal of this research is to develop a real time feedback control system that can be used to minimize magnetic signatures for ferrite structures. Experimental work on controlling the magnetic signature of a cylindrical steel shell structure with a magnetic disturbance provided evidence that the control process substantially increased the interior magnetic flux. This means near field estimation using interior sensor data is likely to be inaccurate. Follow up numerical work for rectangular and cylindrical cross sections investigated variations in shell wall flux density under a variety of ambient excitation and applied disturbances. Results showed magnetic disturbances could corrupt interior sensor data and magnetic shielding due to the shell walls makes the interior very sensitive to noise. The magnetic flux inside the shell wall showed little variation due to inner disturbances and its high base value makes it less susceptible to noise. This research proceeds to describe a nonlinear controller to use the shell wall data as an input. A nonlinear plant model of magnetics is developed using a constant tau to represent domain rotation lag and a gain function k to describe the magnetic hysteresis curve for the shell wall. The model is justified by producing hysteresis curves for multiple materials, matching experimental data using a particle swarm algorithm, and

  10. Magnetically controlled permeability membranes

    KAUST Repository

    Kosel, Jurgen

    2013-10-31

    A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

  11. Magnetically controlled permeability membranes

    KAUST Repository

    Kosel, Jü rgen; Khashab, Niveen M.; Zaher, Amir

    2013-01-01

    A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

  12. MAGNETISM CONTROLS – CLIMATE

    OpenAIRE

    Thomas T. S. Watson

    2017-01-01

    It is physically impossible for the miniscule gas, Carbon Dioxide with an Atomic Weight of 44, to influence the Earth’s orbital position in space. The knowledge of magnetism has always been a wonder of the ancient world ever since it was realized that a lodestone pointed in the same direction. In modern times, particularly since 2014 when NASA determined that the face of the Moon has a positive magnetic charge, towards the Earth, it is now perfectly clear why the Moon oscillates continuously ...

  13. Superconductivity : Controlling magnetism

    NARCIS (Netherlands)

    Golubov, Alexandre Avraamovitch; Kupriyanov, Mikhail Yu.

    Manipulation of the magnetic state in spin valve structures by superconductivity has now been achieved, opening a new route for the development of ultra-fast cryogenic memories. Spintronics is a rapidly developing field that allows insight into fundamental spin-dependent physical properties and the

  14. Magnetization control in multifunctional heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Althammer, M.; Gross, R.; Goennenwein, S.T.B. [Walther-Meissner-Institut, Garching (Germany); Bihler, C.; Brandt, M.S. [Walter Schottky Institut, Garching (Germany); Schoch, W.; Limmer, W. [Institut fuer Halbleiterphysik, Ulm (Germany)

    2009-07-01

    The functionality of magnetoelectronic devices depends on the efficiency and scalabilty of magnetization control schemes. We here discuss the voltage control of magnetization orientation via the magnetoelastic channel in ferromagnetic semiconductor/piezoelectric actuator hybrid structures. The hybrids consist of a thin Ga{sub 0.955}Mn{sub 0.045}As film cemented onto a piezoelectric actuator. Using anisotropic magnetoresistance techniques, we have quantitatively determined the magnetic anisotropy within the plane of the Ga{sub 0.955}Mn{sub 0.045}As films. Exploiting the substantial changes of the magnetic anisotropy in Ga{sub 0.955}Mn{sub 0.045}As as a function of temperature T, different ratios between the magnetoelastic and the magnetocrystalline anisotropies can be realized in one and the same sample. At T=5 K the magnetoelastic anisotropy term is only a small contribution to the total anisotropy, so that only the coercive fields are slightly modified as a function of the control voltage. For T=50 K the magnetoelastic contribution dominates the magnetic anisotropy which allows to achieve a voltage control of the magnetization orientation by about 70 {sup circle}.

  15. Ring magnet firing angle control

    International Nuclear Information System (INIS)

    Knott, M.J.; Lewis, L.G.; Rabe, H.H.

    1975-01-01

    A device is provided for controlling the firing angles of thyratrons (rectifiers) in a ring magnet power supply. A phase lock loop develops a smooth ac signal of frequency equal to and in phase with the frequency of the voltage wave developed by the main generator of the power supply. A counter that counts from zero to a particular number each cycle of the main generator voltage wave is synchronized with the smooth AC signal of the phase lock loop. Gates compare the number in the counter with predetermined desired firing angles for each thyratron and with coincidence the proper thyratron is fired at the predetermined firing angle

  16. NMR magnetic field controller for pulsed nuclear magnetic resonance experiments

    International Nuclear Information System (INIS)

    Scheler, G.; Anacker, M.

    1975-01-01

    A nuclear magnetic resonance controller for magnetic fields, which can also be used for pulsed NMR investigations, is described. A longtime stability of 10 -7 is achieved. The control signal is generated by a modified time sharing circuit with resonance at the first side band of the 2 H signal. An exact calibration of the magnetic field is achieved by the variation of the H 1 - or of the time-sharing frequency. (author)

  17. The composition of circumstellar and interstellar dust

    NARCIS (Netherlands)

    Tielens, AGGM; Woodward, CE; Biscay, MD; Shull, JM

    2001-01-01

    A large number of solid dust components have been identified through analysis of stardust recovered from meteorites, and analysis of IR observations of circumstellar shells and the interstellar medium. These include graphite, hydrogenated amorphous carbon, diamond, PAHs, silicon-, iron-, and

  18. Circumstellar Disks and Outflows in Turbulent Molecular Cloud Cores: Possible Formation Mechanism for Misaligned Systems

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Tomoaki [Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160 (Japan); Machida, Masahiro N. [Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581 (Japan); Inutsuka, Shu-ichiro, E-mail: matsu@hosei.ac.jp [Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan)

    2017-04-10

    We investigate the formation of circumstellar disks and outflows subsequent to the collapse of molecular cloud cores with the magnetic field and turbulence. Numerical simulations are performed by using an adaptive mesh refinement to follow the evolution up to ∼1000 years after the formation of a protostar. In the simulations, circumstellar disks are formed around the protostars; those in magnetized models are considerably smaller than those in nonmagnetized models, but their size increases with time. The models with stronger magnetic fields tend to produce smaller disks. During evolution in the magnetized models, the mass ratios of a disk to a protostar is approximately constant at ∼1%–10%. The circumstellar disks are aligned according to their angular momentum, and the outflows accelerate along the magnetic field on the 10–100 au scale; this produces a disk that is misaligned with the outflow. The outflows are classified into two types: a magnetocentrifugal wind and a spiral flow. In the latter, because of the geometry, the axis of rotation is misaligned with the magnetic field. The magnetic field has an internal structure in the cloud cores, which also causes misalignment between the outflows and the magnetic field on the scale of the cloud core. The distribution of the angular momentum vectors in a core also has a non-monotonic internal structure. This should create a time-dependent accretion of angular momenta onto the circumstellar disk. Therefore, the circumstellar disks are expected to change their orientation as well as their sizes in the long-term evolutions.

  19. Controllable manipulation of superconductivity using magnetic vortices

    International Nuclear Information System (INIS)

    Villegas, J E; Schuller, Ivan K

    2011-01-01

    The magneto-transport of a superconducting/ferromagnetic hybrid structure, consisting of a superconducting thin film in contact with an array of magnetic nanodots in the so-called 'magnetic vortex state', exhibits interesting properties. For certain magnetic states, the stray magnetic field from the vortex array is intense enough to drive the superconducting film into the normal state. In this fashion, the normal-to-superconducting phase transition can be controlled by the magnetic history. The strong coupling between superconducting and magnetic subsystems allows characteristically ferromagnetic properties, such as hysteresis and remanence, to be dramatically transferred into the transport properties of the superconductor.

  20. Application of magnetic sensors in automation control

    Energy Technology Data Exchange (ETDEWEB)

    Hou Chunhong [AMETEK Inc., Paoli, PA 19301 (United States); Qian Zhenghong, E-mail: zqian@hdu.edu.cn [Center For Integrated Spintronic Devices (CISD), Hangzhou Dianzi University, Hangzhou, ZJ 310018 (China)

    2011-01-01

    Controls in automation need speed and position feedback. The feedback device is often referred to as encoder. Feedback technology includes mechanical, optical, and magnetic, etc. All advance with new inventions and discoveries. Magnetic sensing as a feedback technology offers certain advantages over other technologies like optical one. With new discoveries like GMR (Giant Magneto-Resistance), TMR (Tunneling Magneto-Resistance) becoming feasible for commercialization, more and more applications will be using advanced magnetic sensors in automation. This paper offers a general review on encoder and applications of magnetic sensors in automation control.

  1. Magnetic switch for reactor control rod

    International Nuclear Information System (INIS)

    Germer, J.H.

    1986-01-01

    This patent describes a control rod system for a nuclear reactor utilizing an electromagnetic grapple mechanism for holding and releasing a control rod, the improvement comprising a magnetic reed switch assembly having a Curie-point magnetic shunt and responsive to reactor coolant temperature for short circuiting the electromagnetic grapple mechanism causing release of the control rod when the coolant temperature reaches the Curie-point of the magnetic shunt. The magnetic reed switch assembly includes a: a permanent magnet, a pair of magnetic pole pieces located at and in contact with opposite ends of the permanent magnet, the Curie-point magnetic shunt being positioned adjacent the permanent magnet and in contact with the pair of magnetic pole pieces, and a reed switch positioned intermediate the pole pieces and provided with a pair of ferromagnetic reeds, a nonmagnetic enclosure around the reeds, a first of the reeds being secured at one end to a first of the pair of pole pieces, a second of the reeds having one end extending into and secured to a hollow member positioned in and extending through a second of the pair of pole pieces, the one end of the second of the reeds secured to a condector adapted to be connected to the electromagnetic grapple mechanism

  2. White dwarf atmospheres and circumstellar environments

    CERN Document Server

    Hoard, Donald W

    2012-01-01

    Written by selected astronomers at the forefront of their fields, this timely and novel book compiles the latest results from research on white dwarf stars, complementing existing literature by focusing on fascinating new developments in our understanding of the atmospheric and circumstellar environments of these stellar remnants. Complete with a thorough refresher on the observational characteristics and physical basis for white dwarf classification, this is a must-have resource for researchers interested in the late stages of stellar evolution, circumstellar dust and nebulae, and the future

  3. The Circumstellar Environment of VY CMa

    Science.gov (United States)

    Smith, N.; Humphreys, R. M.; Krautter, J.; Gehrz, R. D.; Davidson, K.; Jones, T. J.; Hubrig, S.

    1999-05-01

    VY Canis Majoris is one of the most luminous known M supergiants. It is near the upper liminosity limit for cool stars on the HR Diagram. The optical star is partially obscured by its own circumstellar material. We present preliminary results of recent HST/WFPC2 optical imaging, and ground-based near-IR and mid-IR imaging of VY CMa and its circumstellar environment. We compare these results with previously obtained images of the related, but more evolved object IRC+10420 and discuss implications for their possible evolutionary and mass loss histories.

  4. The vectorial control of magnetization by light.

    Science.gov (United States)

    Kanda, Natsuki; Higuchi, Takuya; Shimizu, Hirokatsu; Konishi, Kuniaki; Yoshioka, Kosuke; Kuwata-Gonokami, Makoto

    2011-06-21

    Application of coherent light-matter interactions has recently been extended to the ultrafast control of magnetization. An important but unrealized technique is the manipulation of magnetization vector motion to make it follow an arbitrarily designed multidimensional trajectory. Here we demonstrate a full manipulation of two-dimensional magnetic oscillations in antiferromagnetic NiO with a pair of polarization-twisted femtosecond laser pulses. We employ Raman-type nonlinear optical processes, wherein magnetic oscillations are impulsively induced with a controlled initial phase. Their azimuthal angle follows well-defined selection rules that have been determined by the symmetries of the materials. We emphasize that the temporal variation of the laser-pulse polarization angle enables us to control the phase and amplitude of the two degenerate modes, independently. These results lead to a new concept of the vectorial control of magnetization by light.

  5. Programming the control of magnetic field measurements

    International Nuclear Information System (INIS)

    David, L.

    1998-01-01

    This paper gives a short review concerning the new NMR probe measurement control system. Then it presents the new program 'CYCLOCHAMP' attached to the magnetic field measurement which also allows to cycle the magnetic field inside the cyclotrons and to equilibrate it among the SSC sectors. (authors)

  6. On circumstellar molecules in the Pleiades.

    Science.gov (United States)

    Hobbs, L. M.

    1972-01-01

    Consideration of both old and new observations of the interstellar 4232-A line of CH(+) for the brightest members of the Pleiades. These observations suggest that the molecules are circumstellar in some sense, perhaps resembling in this respect the micron-sized grains inferred to be present in this region.

  7. Novel magnetic controlled plasma sputtering method

    International Nuclear Information System (INIS)

    Axelevich, A.; Rabinovich, E.; Golan, G.

    1996-01-01

    A novel method to improve thin film vacuum sputtering is presented. This method is capable of controlling the sputtering plasma via an external set of magnets, in a similar fashion to the tetrode sputtering method. The main advantage of the Magnetic Controlled Plasma Sputtering (MCPS) is its ability to independently control all deposition parameters without any interference or cross-talk. Deposition rate, using the MCPS, is found to be almost twice the rate of triode and tetrode sputtering techniques. Experimental results using the MCPS to deposit Ni layers are described. It was demonstrated that using the MCPS method the ion beam intensity at the target is a result of the interaction of a homogeneous external magnetic field and the controlling magnetic fields. The MCPS method was therefore found to be beneficial for the production of pure stoichiometric thin solid films with high reproducibility. This method could be used for the production of compound thin films as well. (authors)

  8. Transformable ferroelectric control of dynamic magnetic permeability

    Science.gov (United States)

    Jiang, Changjun; Jia, Chenglong; Wang, Fenglong; Zhou, Cai; Xue, Desheng

    2018-02-01

    Magnetic permeability, which measures the response of a material to an applied magnetic field, is crucial to the performance of magnetic devices and related technologies. Its dynamic value is usually a complex number with real and imaginary parts that describe, respectively, how much magnetic power can be stored and lost in the material. Control of permeability is therefore closely related to energy redistribution within a magnetic system or energy exchange between magnetic and other degrees of freedom via certain spin-dependent interactions. To avoid a high power consumption, direct manipulation of the permeability with an electric field through magnetoelectric coupling leads to high efficiency and simple operation, but remains a big challenge in both the fundamental physics and material science. Here we report unambiguous evidence of ferroelectric control of dynamic magnetic permeability in a Co /Pb (Mg1/3Nb2/3) 0.7Ti0.3O3 (Co/PMN-PT) heterostructure, in which the ferroelectric PMN-PT acts as an energy source for the ferromagnetic Co film via an interfacial linear magnetoelectric interaction. The electric field tuning of the magnitude and line shape of the permeability offers a highly localized means of controlling magnetization with ultralow power consumption. Additionally, the emergence of negative permeability promises a new way of realizing functional nanoscale metamaterials with adjustable refraction index.

  9. Strain-controlled nonvolatile magnetization switching

    Science.gov (United States)

    Geprägs, S.; Brandlmaier, A.; Brandt, M. S.; Gross, R.; Goennenwein, S. T. B.

    2014-11-01

    We investigate different approaches towards a nonvolatile switching of the remanent magnetization in single-crystalline ferromagnets at room temperature via elastic strain using ferromagnetic thin film/piezoelectric actuator hybrids. The piezoelectric actuator induces a voltage-controllable strain along different crystalline directions of the ferromagnetic thin film, resulting in modifications of its magnetization by converse magnetoelastic effects. We quantify the magnetization changes in the hybrids via ferromagnetic resonance spectroscopy and superconducting quantum interference device magnetometry. These measurements demonstrate a significant strain-induced change of the magnetization, limited by an inefficient strain transfer and domain formation in the particular system studied. To overcome these obstacles, we address practicable engineering concepts and use a model to demonstrate that a strain-controlled, nonvolatile magnetization switching should be possible in appropriately engineered ferromagnetic/piezoelectric actuator hybrids.

  10. Thermally and magnetically controlled superconducting rectifiers

    International Nuclear Information System (INIS)

    Mulder, G.B.J.; TenKate, H.H.J.; Krooshoop, H.J.G.; Van de Klundert, L.J.M.

    1989-01-01

    The switches of a superconducting rectifier can be controlled either magnetically or thermally. The main purpose of this paper is to point out the differences between both methods of switching and discuss the consequences for the operation of the rectifier. The discussion is illustrated by the experimental results of a rectifier which was tested with magnetically as well as thermally controlled switches. It has an input current of 30 A, an output current of more than 1 kA and an operating frequency of a few Hertz. A superconducting magnet connected to this rectifier can be energized at a rate exceeding 1 MJ/hour and an efficiency of about 97%

  11. Magnetization reversal in nucleation controlled magnets. I. Theory

    International Nuclear Information System (INIS)

    Ramesh, R.; Srikrishna, K.

    1988-01-01

    A statistical model, based upon earlier models of Brown [J. Appl. Phys. 33, 3022 (1962)] and McIntyre [J. Phys. D 3, 1430 (1970)] has been developed to examine the magnetization reversal of domain-wall nucleation controlled permanent magnets such as sintered Fe-Nd-B and SmCo 5 . Using a Poisson distribution of the defects on the surface of the grains, a ''weakest link statistics'' type model has been developed. The model has been used to calculate hysteresis loops for sintered Fe-Nd-B-type polycrystalline magnets. It is shown that the intrinsic coercivity measured for a bulk magnet should vary inversely as the logarithm of the surface area of the grain. The effect of demagnetizing field has been incorporated by a mean-field-type approximation, to calculate the overall nucleation field from the intrinsic coercivity. The hysteresis loops theoretically calculated are in excellent agreement with the overall form of those experimentally determined for similar nucleation controlled magnets. The model also predicts that for an inhomogeneous grain size distribution, such as a bimodal distribution, kinks will be observed in the second quadrant of the hysteresis loops

  12. Automatic plasma control in magnetic traps

    International Nuclear Information System (INIS)

    Samojlenko, Y.; Chuyanov, V.

    1984-01-01

    Hot plasma is essentially in thermodynamic non-steady state. Automatic plasma control basically means monitoring deviations from steady state and producing a suitable magnetic or electric field which brings the plasma back to its original state. Briefly described are two systems of automatic plasma control: control with a magnetic field using a negative impedance circuit, and control using an electric field. It appears that systems of automatic plasma stabilization will be an indispensable component of the fusion reactor and its possibilities will in many ways determine the reactor economy. (Ha)

  13. Overview of magnetic control in ITER

    Energy Technology Data Exchange (ETDEWEB)

    Zabeo, L., E-mail: luca.zabeo@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance (France); Ambrosino, G., E-mail: ambrosin@unina.it [CREATE/Universitá di Napoli Federico II, Dip. Ingegneria Elettrica e delle Tecnologie dell’informazione, Naples (Italy); Cavinato, M., E-mail: mario.cavinato@f4e.europa.eu [Fusion for Energy (F4E), Josep Pla 2, Torres Diagonal Litoral - B3, 08019 Barcelona (Spain); Gribov, Y., E-mail: yuri.gribov@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance (France); Kavin, A., E-mail: kavina@sintez.niiefa.spb.su [D.V. Efremov Scientific Research Institute, 196641 St. Petersburg (Russian Federation); Lukash, V., E-mail: lukash@nfi.kiae.ru [Kurchatov Institute, Moscow (Russian Federation); Mattei, M., E-mail: massimiliano.mattei@unina2.it [CREATE/Seconda Universitá di Napoli, Dip. Ingegneria Industriale e dell’informazione, Naples (Italy); Pironti, A., E-mail: pironti@unina.it [CREATE/Seconda Universitá di Napoli, Dip. Ingegneria Industriale e dell’informazione, Naples (Italy); Snipes, J.A., E-mail: joseph.snipes@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance (France); Vayakis, G., E-mail: george.vayakis@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance (France); Winter, A., E-mail: axel.winter@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 St. Paul Lez Durance (France)

    2014-05-15

    ITER is targeting Q = 10 with 500 MW of fusion power. To meet this target, the plasma needs to be controlled and shaped for a period of hundreds of seconds, avoiding contact with internal components, and acting against instabilities that could result in the loss of control of the plasma and in its disruptive termination. Axisymmetric magnetic control is a well-understood area being the basic control for any tokamak device. ITER adds more stringent constraints to the control primarily due to machine protection and engineering limits. The limits on the actuators by means of the maximum current and voltage at the coils and the few hundred ms time response of the vacuum vessel requires optimization of the control strategies and the validation of the capabilities of the machine in controlling the designed scenarios. Scenarios have been optimized with realistic control strategies able to guarantee robust control against plasma behavior and engineering limits due to recent changes in the ITER design. Technological issues such as performance changes associated with the optimization of the final design of the central solenoid, control of fast transitions like H to L mode to avoid plasma-wall contact, and optimization of the plasma ramp-down have been modeled to demonstrate the successful operability of ITER and compatibility with the latest refinements in the magnetic system design. Validation and optimization of the scenarios refining the operational space available for ITER and associated control strategies will be proposed. The present capabilities of magnetic control will be assessed and the remaining critical aspects that still need to be refined will be presented. The paper will also demonstrate the capabilities of the diagnostic system for magnetic control as a basic element for control. In fact, the noisy environment (affecting primarily vertical stability), the non-axisymmetric elements in the machine structure (affecting the accuracy of the identification of the

  14. Passive axial magnetic bearing with Halbach magnetized array in magnetically suspended control moment gyro application

    International Nuclear Information System (INIS)

    Sun Jinji; Ren Yuan; Fang Jiancheng

    2011-01-01

    The paper presents a special configuration of passive axial magnetic bearing with segmented Halbach magnetized array in magnetically suspended control moment gyro (MSCMG). Peculiarity of presented passive axial magnetic bearing is its ability to provide angular stiffness so that it can produce gyro moment when it is used in MSCMG. The MSCMG with this passive axial magnetic bearing can efficiently reduce the power loss when it supplies gyro moment compared with the five degrees of freedom (5-DOF) MSCMG. The characteristics of the suspension force and stiffness of the passive axial magnetic bearing are studied using finite element method (FEM). The performance of the presented passive axial magnetic bearing with Halbach magnetized array is verified by a prototyped MSCMG. - Research highlights: → Passive axial magnetic bearing is used to provide angular stiffness. → Passive axial magnetic bearing is based on repulsion. → Layers Halbach magnetized array realizes higher stiffness per bearing volume. → Passive axial magnetic bearing can provide gyro moment in CMG. → Power loss of MSCMG with PMB does not increase when it provides gyro moment.

  15. Feedforward Control of Magnetically Levitated Planar Actuators

    OpenAIRE

    Bloemers, T.; Proimadis, I.; Kasemsinsup, Y.; Tóth, R.

    2018-01-01

    The present report summarizes the work conducted during the internship on Feedforward Control of the Magnetic Levitation Setup. Different feedforward strategies, specifically tailored for this setup, are developed and reviewed. These feedforward methods explicitly take the intrinsic position-dependent behavior of the magnetic levitation setup into account. Additionally, closed-loop stability of the given setup is assessed. All investigations are carried out under the rigid-body assumption of ...

  16. Meltable magnetic biocomposites for controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Müller, R., E-mail: robert.mueller@ipht-jena.de [Leibniz Institute of Photonic Technology (IPHT), P.O.B. 100239, Jena, D-07702 Germany (Germany); Zhou, M. [Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich Schiller University of Jena, Humboldtstrasse 10, Jena, D-07743 Germany (Germany); Dellith, A. [Leibniz Institute of Photonic Technology (IPHT), P.O.B. 100239, Jena, D-07702 Germany (Germany); Liebert, T.; Heinze, T. [Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich Schiller University of Jena, Humboldtstrasse 10, Jena, D-07743 Germany (Germany)

    2017-06-01

    New biocompatible composites with adjustable melting point in the range of 30–140 °C, consisting of magnetite nanoparticles embedded into a matrix of meltable dextran fatty acid ester are presented which can be softened under an induced alternating magnetic field (AMF). The chosen thermoplastic magnetic composites have a melting range close to human body temperature and can be easily shaped into disk or coating film under melting. The composite disks were loaded with green fluorescent protein (GFP) as a model protein. Controlled release of the protein was realized with high frequent alternating magnetic field of 20 kA/m at 400 kHz. These results showed that under an AMF the release of GFP from magnetic composite was accelerated compared to the control sample without exposure to AMF. Furthermore a texturing of particles in the polymer matrix by a static magnetic field was investigated. - Highlights: • Thermoplastic biocomposite are prepared from dextran ester and magnetite particles. • The composite can be heated by an AC magnetic field above the melting temperature. • In molten state texturing of particles is possible and improves the heating ability. • The biopolymer could be used as a remote controlled matrix for protein release.

  17. Fullerenes and fulleranes in circumstellar envelopes

    International Nuclear Information System (INIS)

    Zhang, Yong; Kwok, Sun; Sadjadi, SeyedAbdolreza

    2016-01-01

    Three decades of search have recently led to convincing discoveries of cosmic fullerenes. The presence of C_6_0 and C"+ _6_0 in both circumstellar and interstellar environments suggests that these molecules and their derivatives can be efficiently formed in circumstellar envelopes and survive in harsh conditions. Detailed analysis of the infrared bands from fullerenes and their connections with the local properties can provide valuable information on the physical conditions and chemical processes that occurred in the late stages of stellar evolution. The identification of C"+ _6_0 as the carrier of four diffuse interstellar bands (DIBs) suggests that fullerene- related compounds are abundant in interstellar space and are essential for resolving the DIB mystery. Experiments have revealed a high hydrogenation rate when C_6_0 is exposed to atomic hydrogen, motivating the attempt to search for cosmic fulleranes. In this paper, we present a short review of current knowledge of cosmic fullerenes and fulleranes and briefly discuss the implications on circumstellar chemistry. (paper)

  18. Voltage control of magnetism in multiferroic heterostructures.

    Science.gov (United States)

    Liu, Ming; Sun, Nian X

    2014-02-28

    Electrical tuning of magnetism is of great fundamental and technical importance for fast, compact and ultra-low power electronic devices. Multiferroics, simultaneously exhibiting ferroelectricity and ferromagnetism, have attracted much interest owing to the capability of controlling magnetism by an electric field through magnetoelectric (ME) coupling. In particular, strong strain-mediated ME interaction observed in layered multiferroic heterostructures makes it practically possible for realizing electrically reconfigurable microwave devices, ultra-low power electronics and magnetoelectric random access memories (MERAMs). In this review, we demonstrate this remarkable E-field manipulation of magnetism in various multiferroic composite systems, aiming at the creation of novel compact, lightweight, energy-efficient and tunable electronic and microwave devices. First of all, tunable microwave devices are demonstrated based on ferrite/ferroelectric and magnetic-metal/ferroelectric composites, showing giant ferromagnetic resonance (FMR) tunability with narrow FMR linewidth. Then, E-field manipulation of magnetoresistance in multiferroic anisotropic magnetoresistance and giant magnetoresistance devices for achieving low-power electronic devices is discussed. Finally, E-field control of exchange-bias and deterministic magnetization switching is demonstrated in exchange-coupled antiferromagnetic/ferromagnetic/ferroelectric multiferroic hetero-structures at room temperature, indicating an important step towards MERAMs. In addition, recent progress in electrically non-volatile tuning of magnetic states is also presented. These tunable multiferroic heterostructures and devices provide great opportunities for next-generation reconfigurable radio frequency/microwave communication systems and radars, spintronics, sensors and memories.

  19. Control of permanent magnet synchronous motors

    CERN Document Server

    Vaez-Zadeh, Sadegh

    2018-01-01

    This is the first comprehensive, coherent, and up-to-date book devoted solely to the control of permanent magnet synchronous (PMS) motors, as the fastest growing AC motor. It covers a deep and detailed presentation of major PMS motor modeling and control methods. The readers can find rich materials on the fundamentals of PMS motor control in addition to new motor control methods, which have mainly been developed in the last two decades, including recent advancements in the field in a systematic manner. These include extensive modeling of PMS motors and a full range of vector control and direct torque control schemes, in addition to predictive control, deadbeat control, and combined control methods. All major sensorless control and parameter estimation methods are also studied. The book covers about 10 machine models in various reference frames and 70 control and estimation schemes with sufficient analytical and implementation details including about 200 original figures. A great emphasis is placed on energy-s...

  20. Controlled fabrication of luminescent and magnetic nanocomposites

    Science.gov (United States)

    Ma, Yingxin; Zhong, Yucheng; Fan, Jing; Huang, Weiren

    2018-03-01

    Luminescent and magnetic multifunctional nanocomposite is in high demand and widely used in many scales, such as drug delivery, bioseparation, chemical/biosensors, and so on. Although lots of strategies have been successfully developed for the demand of multifunctional nanocomposites, it is not easy to prepare multifunctional nanocomposites by using a simple method, and satisfy all kinds of demands simultaneously. In this work, via a facile and versatile method, luminescent nanocrystals and magnetic nanoparticles were successfully synthesized through self-assembly under vigorous stirring and ultrasonic treatment. These multifunctional nanocomposites are not only water stable but also find wide application such as magnetic separation and concentration with a series of moderate speed, multicolor fluorescence at different emission wavelength, high efficiency of the excitation and emission, and so on. By changing different kinds of luminescent nanocrystals and controlling the amount of luminescent and magnetic nanoparticles, a train of multifunctional nanocomposites was successfully fabricated via a versatile and robust method.

  1. Electrically Controllable Magnetism in Twisted Bilayer Graphene.

    Science.gov (United States)

    Gonzalez-Arraga, Luis A; Lado, J L; Guinea, Francisco; San-Jose, Pablo

    2017-09-08

    Twisted graphene bilayers develop highly localized states around AA-stacked regions for small twist angles. We show that interaction effects may induce either an antiferromagnetic or a ferromagnetic (FM) polarization of said regions, depending on the electrical bias between layers. Remarkably, FM-polarized AA regions under bias develop spiral magnetic ordering, with a relative 120° misalignment between neighboring regions due to a frustrated antiferromagnetic exchange. This remarkable spiral magnetism emerges naturally without the need of spin-orbit coupling, and competes with the more conventional lattice-antiferromagnetic instability, which interestingly develops at smaller bias under weaker interactions than in monolayer graphene, due to Fermi velocity suppression. This rich and electrically controllable magnetism could turn twisted bilayer graphene into an ideal system to study frustrated magnetism in two dimensions.

  2. Flow-controlled magnetic particle manipulation

    Science.gov (United States)

    Grate, Jay W [West Richland, WA; Bruckner-Lea, Cynthia J [Richland, WA; Holman, David A [Las Vegas, NV

    2011-02-22

    Inventive methods and apparatus are useful for collecting magnetic materials in one or more magnetic fields and resuspending the particles into a dispersion medium, and optionally repeating collection/resuspension one or more times in the same or a different medium, by controlling the direction and rate of fluid flow through a fluid flow path. The methods provide for contacting derivatized particles with test samples and reagents, removal of excess reagent, washing of magnetic material, and resuspension for analysis, among other uses. The methods are applicable to a wide variety of chemical and biological materials that are susceptible to magnetic labeling, including, for example, cells, viruses, oligonucleotides, proteins, hormones, receptor-ligand complexes, environmental contaminants and the like.

  3. Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization

    International Nuclear Information System (INIS)

    Ida, Tetsuya; Watasaki, Masahiro; Kimura, Yosuke; Miki, Motohiro; Izumi, Mitsuru

    2010-01-01

    For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

  4. Magnetic particle separation using controllable magnetic force switches

    International Nuclear Information System (INIS)

    Wei Zunghang; Lee, C.-P.; Lai, M.-F.

    2010-01-01

    Magnetic particle separation is very important in biomedical applications. In this study, a magnetic particle microseparator is proposed that uses micro magnets to produce open/closed magnetic flux for switching on/off the separation. When all magnets are magnetized in the same direction, the magnetic force switch for separation is on; almost all magnetic particles are trapped in the channel side walls and the separation rate can reach 95%. When the magnetization directions of adjacent magnets are opposite, the magnetic force switch for separation is off, and most magnetic particles pass through the microchannel without being trapped. For the separation of multi-sized magnetic particles, the proposed microseparator is numerically demonstrated to have high separation rate.

  5. Millimeter wave studies of circumstellar chemistry

    Science.gov (United States)

    Tenenbaum, Emily Dale

    2010-06-01

    Millimeter wave studies of molecules in circumstellar envelopes and a planetary nebula have been conducted. Using the Submillimeter Telescope (SMT) of the Arizona Radio Observatory (ARO) on Mt. Graham, a comparative spectral survey from 215-285 GHz was carried out of the carbon-rich asymptotic giant branch star IRC +10216 and the oxygen-rich supergiant VY Canis Majoris. A total of 858 emission lines were observed in both objects, arising from 40 different molecules. In VY Canis Majoris, AlO, AlOH, and PO were detected for the first time in interstellar space. In IRC +10216, PH3 was detected for the first time beyond the solar system, and C3O, and CH2NH were found for the first time in a circumstellar envelope. Additionally, in the evolved planetary nebula, the Helix, H2CO, C2H, and cyclic-C3H2 were observed using the SMT and the Kitt Peak 12 m telescopes. The presence of these three molecules in the Helix suggests that relatively complex chemistry occurs in planetary nebulae, despite the harsh ultraviolet field. Overall, the research on molecules in circumstellar and planetary nebulae furthers our understanding of the nature of the material that is fed back into the interstellar medium from evolved stars. Besides telescope work, laboratory research was also conducted -- the rotational spectrum of ZnCl was measured and its bond length and rotational constants were determined. Lastly, in partial fulfillment of a graduate certificate in entrepreneurial chemistry, the commercial applications of terahertz spectroscopy were explored through literature research.

  6. Evidence for circumstellar obscuration of OB stars

    International Nuclear Information System (INIS)

    Bohannan, B.

    1975-01-01

    Reddish found a strong increase of color excess with increasing stellar luminosity: here referred to as the Reddish Effect: in ten young galactic clusters and associations. New photometric and spectroscopic observations drawn from the literature are combined with data used by Reddish to reconsider the color excess versus intrinsic magnitude diagrams of the same ten stellar groups. The reality of the Effect is questioned in all but one of the systems; this was accomplished by identifying possible foreground stars and by recognizing some of the brightest stars as supergiants, then applying correct intrinsic color indices. After careful reanalysis, the one stellar group to retain an indication of the Reddish Effect is Cygnus OB2. No correlation of reddening with luminosity was found for five additional very young stellar groups in the southern hemisphere; these groups should exhibit the Effect if it is a natural consequence of stellar evolution. Reddish ascribed the correlation to massive circumstellar remnants of material from which the stars formed. However, a peculiar dispersion in color excess could also be attributed to patchy dust within the stellar group. In several stellar systems previously identified as displaying the Reddish Effect, a correlation of observed color excess with dust and gas concentrations is noted on Palomar Sky Survey prints. If present, circumstellar dust clouds should []anifest their existence in modes other than a correlation of color excess with luminosity. The following possibilities are considered and all show negative results: correlation of color excess with spectral type; correlation of reddening slope E/subU//sub -//subB//E/subB//sub -//subV/ with spectral type; observable infrared excess. The preceding astrophysical arguments strongly imply that circumstellar dust remnants from stellar formation do not remain around stars during their main-sequence lifetimes. (auth)

  7. Gravitational Instabilities in Circumstellar Disks

    Science.gov (United States)

    Kratter, Kaitlin; Lodato, Giuseppe

    2016-09-01

    Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review, we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. We emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. In the next part of our review, we focus on the astrophysical consequences of the instability. We show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, Md/M*≥0.1. They will develop quasi-stable spiral arms that process infall from the background cloud. Although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. In this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. In some cases the instability may lead to fragmentation into bound companions. These companions are more likely to be brown dwarfs or stars than planetary mass objects. Finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular

  8. Neural control of magnetic suspension systems

    Science.gov (United States)

    Gray, W. Steven

    1993-01-01

    The purpose of this research program is to design, build and test (in cooperation with NASA personnel from the NASA Langley Research Center) neural controllers for two different small air-gap magnetic suspension systems. The general objective of the program is to study neural network architectures for the purpose of control in an experimental setting and to demonstrate the feasibility of the concept. The specific objectives of the research program are: (1) to demonstrate through simulation and experimentation the feasibility of using neural controllers to stabilize a nonlinear magnetic suspension system; (2) to investigate through simulation and experimentation the performance of neural controllers designs under various types of parametric and nonparametric uncertainty; (3) to investigate through simulation and experimentation various types of neural architectures for real-time control with respect to performance and complexity; and (4) to benchmark in an experimental setting the performance of neural controllers against other types of existing linear and nonlinear compensator designs. To date, the first one-dimensional, small air-gap magnetic suspension system has been built, tested and delivered to the NASA Langley Research Center. The device is currently being stabilized with a digital linear phase-lead controller. The neural controller hardware is under construction. Two different neural network paradigms are under consideration, one based on hidden layer feedforward networks trained via back propagation and one based on using Gaussian radial basis functions trained by analytical methods related to stability conditions. Some advanced nonlinear control algorithms using feedback linearization and sliding mode control are in simulation studies.

  9. Sensorless Control of Permanent Magnet Synchronous Machines

    DEFF Research Database (Denmark)

    Matzen, Torben N.

    Permanent magnet machines, with either surface mounted or embedded magnets on the rotor, are becoming more common due to the key advantages of higher energy conversion efficiency and higher torque density compared to the classical induction machine. Besides energy efficiency the permanent magnet...... the synchronous machine requires knowledge of the rotor shaft position due to the synchronous and undamped nature of the machine. The rotor position may be measured using a mechanical sensor, but the sensor reduces reliability and adds cost to the system and for this reason sensorless control methods started...... are dependent on the phase currents and rotor position. Based on the flux linkages the differential inductances are determined and used to establish the inductance saliency in terms of ratio and orientation. The orientation and its dependence on the current and rotor position are used to analyse the behaviour...

  10. Small Satellite Passive Magnetic Attitude Control

    Science.gov (United States)

    Gerhardt, David T.

    Passive Magnetic Attitude Control (PMAC) is capable of aligning a satellite within 5 degrees of the local magnetic field at low resource cost, making it ideal for a small satellite. However, simulation attempts to date have not been able to predict the attitude dynamics at a level sufficient for mission design. Also, some satellites have suffered from degraded performance due to an incomplete understanding of PMAC system design. This dissertation alleviates these issues by discussing the design, inputs, and validation of PMAC systems for small satellites. Design rules for a PMAC system are defined using the Colorado Student Space Weather Experiment (CSSWE) CubeSat as an example. A Multiplicative Extended Kalman Filter (MEKF) is defined for the attitude determination of a PMAC satellite without a rate gyro. After on-orbit calibration of the off-the-shelf magnetometer and photodiodes and an on-orbit fit to the satellite magnetic moment, the MEKF regularly achieves a three sigma attitude uncertainty of 4 degrees or less. CSSWE is found to settle to the magnetic field in seven days, verifying its attitude design requirement. A Helmholtz cage is constructed and used to characterize the CSSWE bar magnet and hysteresis rods both individually and in the flight configuration. Fitted parameters which govern the magnetic material behavior are used as input to a PMAC dynamics simulation. All components of this simulation are described and defined. Simulation-based dynamics analysis shows that certain initial conditions result in abnormally decreased settling times; these cases may be identified by their dynamic response. The simulation output is compared to the MEKF output; the true dynamics are well modeled and the predicted settling time is found to possess a 20 percent error, a significant improvement over prior simulation.

  11. Magnetic field control of fluorescent polymer nanorods

    International Nuclear Information System (INIS)

    Kim, Taehyung; He, Le; Bardeen, Christopher J; Morales, Jason R; Beyermann, W P

    2011-01-01

    Nanoscale objects that combine high luminescence output with a magnetic response may be useful for probing local environments or manipulating objects on small scales. Ideally, these two properties would not interfere with each other. In this paper, we show that a fluorescent polymer host material can be doped with high concentrations of 20–30 nm diameter magnetic γ-Fe 2 O 3 particles and then formed into 200 nm diameter nanorods using porous anodic alumina oxide templates. Two different polymer hosts are used: the conjugated polymer polydioctylfluorene and also polystyrene doped with the fluorescent dye Lumogen Red. Fluorescence decay measurements show that 14% by weight loading of the γ-Fe 2 O 3 nanoparticles quenches the fluorescence of the polydioctylfluorene by approximately 33%, but the polystyrene/Lumogen Red fluorescence is almost unaffected. The three-dimensional orientation of both types of nanorods can be precisely controlled by the application of a moderate strength (∼0.1 T) external field with sub-second response times. Transmission electron microscope images reveal that the nanoparticles cluster in the polymer matrix, and these clusters may serve both to prevent fluorescence quenching and to generate the magnetic moment that rotates in response to the applied magnetic field.

  12. Magnetic nuclear core restraint and control

    International Nuclear Information System (INIS)

    Cooper, M.H.

    1979-01-01

    A lateral restraint and control system for a nuclear reactor core adaptable to provide an inherent decrease of core reactivity in response to abnormally high reactor coolant fluid temperatures. An electromagnet is associated with structure for radially compressing the core during normal reactor conditions. A portion of the structures forming a magnetic circuit are composed of ferromagnetic material having a curie temperature corresponding to a selected coolant fluid temperature. Upon a selected signal, or inherently upon a preselected rise in coolant temperature, the magnetic force is decreased a given amount sufficient to relieve the compression force so as to allow core radial expansion. The expanded core configuration provides a decreased reactivity, tending to shut down the nuclear reaction

  13. Magnetic nuclear core restraint and control

    International Nuclear Information System (INIS)

    Cooper, M.H.

    1979-01-01

    A lateral restraint and control systemm for a nuclear reactor core provides an inherent decrease of core reactivity in response to abnormally high reactor coolant fluid temperatures. An electromagnet is associated with structure for radially compressing the core during normal reactor conditions. A portion of the structures forming a magnetic circuit is composed of ferromagnetic material having a curie temperature corresponding to a selected coolant fluid temperature. Upon a selected signal, or inherently upon a preselected rise in coolant temperature, the magnetic force is decreased by an amount sufficient to relieve the compression force so as to allow core radial expansion. The expanded core configuration provides a decreased reactivity, tending to shut down the nuclear reaction

  14. Magnetic nuclear core restraint and control

    International Nuclear Information System (INIS)

    Cooper, M.H.

    1978-01-01

    Disclosed is a lateral restraint and control system for a nuclear reactor core adaptable to provide an inherent decrease of core reactivity in response to abnormally high reactor coolant fluid temperatures. An electromagnet is associated with structure for radially compressing the core during normal reactor conditions. A portion of the structures forming a magnetic circuit are composed of ferromagnetic material having a curie temperature corresponding to a selected coolant fluid temperature. Upon a selected signal, or inherently upon a preselected rise in coolant temperature, the magnetic force is decreased a given amount sufficient to relieve the compression force so as to allow core radial expansion. The expanded core configuration provides a decreased reactivity, tending to shut down the nuclear reaction

  15. Thermal control for the MFTF magnet

    International Nuclear Information System (INIS)

    Vansant, J.H.; Russ, R.M.

    1980-01-01

    The external dimensions of the Yin-Yang magnet of the Mirror Fusion Test Facility will be 7.8 by 8.5 by 8.5 m, and it will weigh approximately 300 tons. More than 8000 liters of circulating liquid helium will be required to maintain the nearly 50 km of superconductor at below 5.0 K while the latter carries almost 6000 A in a magnetic field of up to nearly 7.7 T. This paper describes several features of the thermal control plans for the Yin-Yang: (1) the proposed cooldown and warmup schedules for the MFTF and the procedure for regenerating external cooling surfaces (2) the design of an external quench resistor based on an estimate of the superconductor's maximum temperature and (3) the use of a computer model of liquid helium circulation in choosing pipe size for the liquid helium lines

  16. Magnetic control of dipolaritons in quantum dots

    International Nuclear Information System (INIS)

    Rojas-Arias, J S; Vinck-Posada, H; Rodríguez, B A

    2016-01-01

    Dipolaritons are quasiparticles that arise in coupled quantum wells embedded in a microcavity, they are a superposition of a photon, a direct exciton and an indirect exciton. We propose the existence of dipolaritons in a system of two coupled quantum dots inside a microcavity in direct analogy with the quantum well case and find that, despite some similarities, dipolaritons in quantum dots have different properties and can lead to true dark polariton states. We use a finite system theory to study the effects of the magnetic field on the system, including the emission, and find that it can be used as a control parameter of the properties of excitons and dipolaritons, and the overall magnetic behaviour of the structure. (paper)

  17. Magnetic molecularly imprinted polymer for aspirin recognition and controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Kan Xianwen; Geng Zhirong; Zhao Yao; Wang Zhilin; Zhu Junjie [State Key Laboratory of Coordination Chemistry, MOE Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 22 Hankou Road, Nanjing 210093 (China)], E-mail: wangzl@nju.edu.cn, E-mail: jjzhu@nju.edu.cn

    2009-04-22

    Core-shell structural magnetic molecularly imprinted polymers (magnetic MIPs) with combined properties of molecular recognition and controlled release were prepared and characterized. Magnetic MIPs were synthesized by the co-polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) around aspirin (ASP) at the surface of double-bond-functionalized Fe{sub 3}O{sub 4} nanoparticles in chloroform. The obtained spherical magnetic MIPs with diameters of about 500 nm had obvious superparamagnetism and could be separated quickly by an external magnetic field. Binding experiments were carried out to evaluate the properties of magnetic MIPs and magnetic non-molecularly imprinted polymers (magnetic NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity and selectivity to ASP. Moreover, release profiles and release rate of ASP from the ASP-loaded magnetic MIPs indicated that the magnetic MIPs also had potential applications in drug controlled release.

  18. Magnetic molecularly imprinted polymer for aspirin recognition and controlled release

    International Nuclear Information System (INIS)

    Kan Xianwen; Geng Zhirong; Zhao Yao; Wang Zhilin; Zhu Junjie

    2009-01-01

    Core-shell structural magnetic molecularly imprinted polymers (magnetic MIPs) with combined properties of molecular recognition and controlled release were prepared and characterized. Magnetic MIPs were synthesized by the co-polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) around aspirin (ASP) at the surface of double-bond-functionalized Fe 3 O 4 nanoparticles in chloroform. The obtained spherical magnetic MIPs with diameters of about 500 nm had obvious superparamagnetism and could be separated quickly by an external magnetic field. Binding experiments were carried out to evaluate the properties of magnetic MIPs and magnetic non-molecularly imprinted polymers (magnetic NIPs). The results demonstrated that the magnetic MIPs had high adsorption capacity and selectivity to ASP. Moreover, release profiles and release rate of ASP from the ASP-loaded magnetic MIPs indicated that the magnetic MIPs also had potential applications in drug controlled release.

  19. Composite grains: Application to circumstellar dust

    Directory of Open Access Journals (Sweden)

    D. B. Vaidya

    2011-09-01

    Full Text Available Using the discrete dipole approximation (DDA we calculate the absorption efficiency of the composite grain, made up of a host silicate spheroid and inclusions of graphite, in the spectral region 5.0-25.0μm. We study the absorption as a function of the voulume fraction of the inclusions. In particular, we study the variation in the 10.0μm and 18.0μm emission features with the volume fraction of the inclusions. Using the extinction efficiencies, of the composite grains we calculate the infrared fluxes at several dust temperatures and compare the model curves with the observed infrared emission curves (IRAS-LRS, obtained for circumstellar dust shells around oxygen rich M-type stars.

  20. Hybrid supercapacitors for reversible control of magnetism.

    Science.gov (United States)

    Molinari, Alan; Leufke, Philipp M; Reitz, Christian; Dasgupta, Subho; Witte, Ralf; Kruk, Robert; Hahn, Horst

    2017-05-10

    Electric field tuning of magnetism is one of the most intensely pursued research topics of recent times aiming at the development of new-generation low-power spintronics and microelectronics. However, a reversible magnetoelectric effect with an on/off ratio suitable for easy and precise device operation is yet to be achieved. Here we propose a novel route to robustly tune magnetism via the charging/discharging processes of hybrid supercapacitors, which involve electrostatic (electric-double-layer capacitance) and electrochemical (pseudocapacitance) doping. We use both charging mechanisms-occurring at the La 0.74 Sr 0.26 MnO 3 /ionic liquid interface to control the balance between ferromagnetic and non-ferromagnetic phases of La 1-x Sr x MnO 3 to an unprecedented extent. A magnetic modulation of up to ≈33% is reached above room temperature when applying an external potential of only about 2.0 V. Our case study intends to draw attention to new, reversible physico-chemical phenomena in the rather unexplored area of magnetoelectric supercapacitors.

  1. Laser controlled magnetism in hydrogenated fullerene films

    International Nuclear Information System (INIS)

    Makarova, Tatiana L.; Shelankov, Andrei L.; Kvyatkovskii, Oleg E.; Zakharova, Irina B.; Buga, Sergei G.; Volkov, Aleksandr P.

    2011-01-01

    Room temperature ferromagnetic-like behavior in fullerene photopolymerized films treated with monatomic hydrogen is reported. The hydrogen treatment controllably varies the paramagnetic spin concentration and laser induced polymerization transforms the paramagnetic phase to a ferromagnetic-like one. Excess laser irradiation destroys magnetic ordering, presumably due to structural changes, which was continuously monitored by Raman spectroscopy. We suggest an interpretation of the data based on first-principles density-functional spin-unrestricted calculations which show that the excess spin from mono-atomic hydrogen is delocalized within the host fullerene and the laser-induced polymerization promotes spin exchange interaction and spin alignment in the polymerized phase.

  2. Experiments with a magnetically controlled pendulum

    International Nuclear Information System (INIS)

    Kraftmakher, Yaakov

    2007-01-01

    A magnetically controlled pendulum is used for observing free and forced oscillations, including nonlinear oscillations and chaotic motion. A data-acquisition system stores the data and displays time series of the oscillations and related phase plane plots, Poincare maps, Fourier spectra and histograms. The decay constant of the pendulum can be modified by positive or negative feedback. The apparatus, except for the data-acquisition system, is extremely simple and low cost, and can be assembled in a short time. The wide possibilities of varying the parameters of the pendulum make the experiments suitable for student projects

  3. Magnetization Controlled Superconductivity in a Film with Magnetic Dots

    International Nuclear Information System (INIS)

    Lyuksyutov, I.F.; Pokrovsky, V.; Pokrovsky, V.

    1998-01-01

    We consider a superconducting film with a magnetic dots array (MDA) placed upon it. Magnetic moments of the dots are normal to the film and strong enough to create vortices in the superconducting film. Magnetic interaction between dots is negligible. Zero-field cooling leads to random magnetization of the MDA well above the superconducting temperature. With this cooling, the film is in a resistive state below the (expected) superconducting transition. Paradoxically, when field cooled, the film with MDA can be superconducting. copyright 1998 The American Physical Society

  4. Circumstellar Disk Lifetimes In Numerous Galactic Young Stellar Clusters

    Science.gov (United States)

    Richert, A. J. W.; Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Broos, P. S.; Povich, M. S.; Bate, M. R.; Garmire, G. P.

    2018-04-01

    Photometric detections of dust circumstellar disks around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disk longevity, starting with Haisch, Lada & Lada (2001), use star samples from PMS clusters but do not consider datasets with homogeneous photometric sensitivities and/or ages placed on a uniform timescale. Here we conduct the largest study to date of the longevity of inner dust disks using X-ray and 1-8 {μ m} infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t ≤ 5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disk-free objects, we impose similar stellar mass sensitivity limits for disk-bearing and disk-free YSOs while extending the analysis to stellar masses as low as M ˜ 0.1 M⊙. We find that the disk longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disk fraction of 100% at zero age, the inferred disk half-life changes significantly, from t1/2 ˜ 1.3 - 2 Myr to t1/2 ˜ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disk fraction varies with stellar mass within the first few Myr of life for stars with masses <2 M⊙, but our samples may not be complete for more massive stars. The effects of initial disk fraction and star-forming environment are also explored.

  5. THE MORPHOLOGY OF IRC+10420's CIRCUMSTELLAR EJECTA

    International Nuclear Information System (INIS)

    Tiffany, Chelsea; Humphreys, Roberta M.; Jones, Terry J.; Davidson, Kris

    2010-01-01

    Images of the circumstellar ejecta associated with the post-red supergiant IRC+10420 show a complex ejecta with visual evidence for episodic mass loss. In this paper, we describe the transverse motions of numerous knots, arcs, and condensations in the inner ejecta measured from second epoch Hubble Space Telescope/WFPC2 images. When combined with the radial motions for several of the features, the total space motion and direction of the outflows show that they were ejected at different times, in different directions, and presumably from separate regions on the surface of the star. These discrete structures in the ejecta are kinematically distinct from the general expansion of the nebula and their motions are dominated by their transverse velocities. They are apparently all moving within a few degrees of the plane of the sky. We are thus viewing IRC+10420 nearly pole-on and looking nearly directly down onto its equatorial plane. We also discuss the role of surface activity and magnetic fields on IRC+10420's recent mass-loss history.

  6. Innovative Digitally Controlled Particle Accelerator Magnet Power Supply

    DEFF Research Database (Denmark)

    Nielsen, Rasmus Ørndrup; Bidoggia, Benoit; Maheshwari, Ram Krishan

    2013-01-01

    Particle accelerator magnet power supplies needs to be extremely precise. A new and innovative power supply for particle accelerator magnets is proposed. The topologies for the input and the output converter are shown and the control architecture is described.......Particle accelerator magnet power supplies needs to be extremely precise. A new and innovative power supply for particle accelerator magnets is proposed. The topologies for the input and the output converter are shown and the control architecture is described....

  7. Magnetic Configuration Control of ITER Plasmas

    International Nuclear Information System (INIS)

    Albanese, R.; Artaserse, G.; Mattei, M.; Ambrosino, G.; Crisanti, F.; Tommasi, G. de; Fresa, R.; Portone, A.; Sartori, F.; Villone, F.

    2006-01-01

    The aim of this paper is to review the capability of the ITER Poloidal Field (PF) system of controlling the broad range of plasma configurations presently forecasted during ITER operation. The attention is focused on the axi-symmetric aspects of plasma magnetic configuration control since they pose the greatest challenges in terms of control power and they have the largest impact on machine capital cost. The paper is broadly divided in two main sections devoted, respectively, to open loop (feed-forward) and closed loop (feedback) control. In the first part of the study the PF system is assessed with respect to the initiation, ramp-up, sustained burn, ramp-down phases of the main plasma inductive scenario. The limiter-to-divertor configuration transition phase is considered in detail with the aim of assessing the PF capability to form an X-point at the lowest possible current and, therefore, to relax the thermal load on the limiter surfaces. Moreover, during the sustained burn it is important to control plasmas with a broad range of current density profiles. In the second part of the study the plasma vertical feedback control requirements are assessed in details, in particular for the high elongation configurations achievable during the early limiter-to-X point transition phase. Non-rigid plasma displacement models are used to assess the control system voltage and current requirements of different radial field control circuits obtained, for example, by connecting the outermost PF coils, some CS coils, coils sub-sections etc. At last, the main 3D effects of the vessel ports are modeled and their impact of vertical stabilization evaluated. (author)

  8. Magnetic Detachment and Plume Control in Escaping Magnetized Plasma

    International Nuclear Information System (INIS)

    Schmit, P.F.; Fisch, N.J.

    2008-01-01

    The model of two-fluid, axisymmetric, ambipolar magnetized plasma detachment from thruster guide fields is extended to include plasmas with non-zero injection angular velocity profiles. Certain plasma injection angular velocity profiles are shown to narrow the plasma plume, thereby increasing exhaust efficiency. As an example, we consider a magnetic guide field arising from a simple current ring and demonstrate plasma injection schemes that more than double the fraction of useful exhaust aperture area, more than halve the exhaust plume angle, and enhance magnetized plasma detachment

  9. Magnetic configuration control of ITER plasmas

    International Nuclear Information System (INIS)

    Albanese, R.; Mattei, M.; Portone, A.; Ambrosino, G.; Artaserse, G.; Crisanti, F.; De Tommasi, G.; Fresa, R.; Sartori, F.; Villone, F.

    2007-01-01

    The aim of this paper is to present some new tools used to review the capability of the ITER Poloidal Field (PF) system in controlling the broad range of plasma configurations presently forecasted during ITER operation. The attention is focused on the axi-symmetric aspects of plasma magnetic configuration control since they pose the greatest challenges in terms of control power and they have the largest impact on machine capital cost. Some preliminary results obtained during ongoing activities in collaboration between ENEA/CREATE and EFDA are presented. The paper is divided in two main parts devoted, respectively, to the presentation of a procedure for the PF current optimisation during the scenario, and of a software environment for the study of the PF system capabilities using the plasma linearized response. The proposed PF current optimisation procedure is then used to assess Scenario 2 design, also taking into account the presence of axisymmetric eddy currents and possible variations of poloidal beta and internal inductance. The numerical linear model based tool derived from the JET oriented eXtreme Shape Controller (XSC) tools is finally used to obtain results on the strike point sweeping in ITER

  10. Power supply control units for APS ring magnets

    International Nuclear Information System (INIS)

    Despe, O.D.

    1990-01-01

    The APS storage ring (1104 meters) is divided into 40 sectors. Each sector has 38 magnet coils in five magnet bases. Every alternate sector has an additional quadrupole magnet for skew correction. AR the main dipole magnets, two in each sector are connected in series and fed from one power supply unit. A base is controlled by one power supply control unit (PSCU). Each PSCU is connected to the host computer via a local area network (LAN). This note discusses the hardware configuration of the typical power supply control system used by the APS magnets and the software commands supported by the PSCU

  11. Design of digital logic control for accelerator magnet power supply

    International Nuclear Information System (INIS)

    Long Fengli; Hu Wei; Cheng Jian

    2008-01-01

    For the accelerator magnet power supply, usually the Programmable Logic Controller (PLC) is used to server as the controller for logic protection and control. Along with the development of modern accelerator technology, it is a trend to use fully-digital control to the magnet power supply. It is possible to integrate the logic control part into the digital control component of the power supply, for example, the Field Programmable Gate Array (FPGA). The paper introduces to different methods which are designed for the logic protection and control for accelerator magnet power supplies with the FPGA as the control component. (authors)

  12. CIRCUMSTELLAR DEBRIS DISKS: DIAGNOSING THE UNSEEN PERTURBER

    Energy Technology Data Exchange (ETDEWEB)

    Nesvold, Erika R. [Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Rd., Washington, DC 20015 (United States); Naoz, Smadar; Vican, Laura [Department of Physics and Astronomy, UCLA, 475 Portola Plaza, Los Angeles, CA 90095 (United States); Farr, Will M. [School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT (United Kingdom)

    2016-07-20

    The first indication of the presence of a circumstellar debris disk is usually the detection of excess infrared emission from the population of small dust grains orbiting the star. This dust is short-lived, requiring continual replenishment, and indicating that the disk must be excited by an unseen perturber. Previous theoretical studies have demonstrated that an eccentric planet orbiting interior to the disk will stir the larger bodies in the belt and produce dust via interparticle collisions. However, motivated by recent observations, we explore another possible mechanism for heating a debris disk: a stellar-mass perturber orbiting exterior to and inclined to the disk and exciting the disk particles’ eccentricities and inclinations via the Kozai–Lidov mechanism. We explore the consequences of an exterior perturber on the evolution of a debris disk using secular analysis and collisional N -body simulations. We demonstrate that a Kozai–Lidov excited disk can generate a dust disk via collisions and we compare the results of the Kozai–Lidov excited disk with a simulated disk perturbed by an interior eccentric planet. Finally, we propose two observational tests of a dust disk that can distinguish whether the dust was produced by an exterior brown dwarf or stellar companion or an interior eccentric planet.

  13. CIRCUMSTELLAR SHELL FORMATION IN SYMBIOTIC RECURRENT NOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Kevin; Bildsten, Lars [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)

    2012-12-20

    We present models of spherically symmetric recurrent nova shells interacting with circumstellar material (CSM) in a symbiotic system composed of a red giant (RG) expelling a wind and a white dwarf accreting from this material. Recurrent nova eruptions periodically eject material at high velocities ({approx}> 10{sup 3} km s{sup -1}) into the RG wind profile, creating a decelerating shock wave as CSM is swept up. High CSM densities cause the shocked wind and ejecta to have very short cooling times of days to weeks. Thus, the late-time evolution of the shell is determined by momentum conservation instead of energy conservation. We compute and show evolutionary tracks of shell deceleration, as well as post-shock structure. After sweeping up all the RG wind, the shell coasts at a velocity {approx}100 km s{sup -1}, depending on system parameters. These velocities are similar to those measured in blueshifted CSM from the symbiotic nova RS Oph, as well as a few Type Ia supernovae that show evidence of CSM, such as 2006X, 2007le, and PTF 11kx. Supernovae occurring in such systems may not show CSM interaction until the inner nova shell gets hit by the supernova ejecta, days to months after the explosion.

  14. Circumstellar disks around binary stars in Taurus

    International Nuclear Information System (INIS)

    Akeson, R. L.; Jensen, E. L. N.

    2014-01-01

    We have conducted a survey of 17 wide (>100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and 10 secondaries, with disk masses as low as 10 –4 M ☉ . We compare the properties of our sample to the population of known disks in Taurus and find that the disks from this binary sample match the scaling between stellar mass and millimeter flux of F mm ∝M ∗ 1.5--2.0 to within the scatter found in previous studies. We also compare the properties of the primaries to those of the secondaries and find that the secondary/primary stellar and disk mass ratios are not correlated; in three systems, the circumsecondary disk is more massive than the circumprimary disk, counter to some theoretical predictions.

  15. Circumstellar disks around binary stars in Taurus

    Energy Technology Data Exchange (ETDEWEB)

    Akeson, R. L. [NASA Exoplanet Science Institute, IPAC/Caltech, Pasadena, CA 91125 (United States); Jensen, E. L. N. [Swarthmore College, Department of Physics and Astronomy, Swarthmore, PA 19081 (United States)

    2014-03-20

    We have conducted a survey of 17 wide (>100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and 10 secondaries, with disk masses as low as 10{sup –4} M {sub ☉}. We compare the properties of our sample to the population of known disks in Taurus and find that the disks from this binary sample match the scaling between stellar mass and millimeter flux of F{sub mm}∝M{sub ∗}{sup 1.5--2.0} to within the scatter found in previous studies. We also compare the properties of the primaries to those of the secondaries and find that the secondary/primary stellar and disk mass ratios are not correlated; in three systems, the circumsecondary disk is more massive than the circumprimary disk, counter to some theoretical predictions.

  16. Magnetic agglomeration method for size control in the synthesis of magnetic nanoparticles

    Science.gov (United States)

    Huber, Dale L [Albuquerque, NM

    2011-07-05

    A method for controlling the size of chemically synthesized magnetic nanoparticles that employs magnetic interaction between particles to control particle size and does not rely on conventional kinetic control of the reaction to control particle size. The particles are caused to reversibly agglomerate and precipitate from solution; the size at which this occurs can be well controlled to provide a very narrow particle size distribution. The size of particles is controllable by the size of the surfactant employed in the process; controlling the size of the surfactant allows magnetic control of the agglomeration and precipitation processes. Agglomeration is used to effectively stop particle growth to provide a very narrow range of particle sizes.

  17. Sensorless V/f Control of Permanent Magnet Synchronous Motors

    OpenAIRE

    Montesinos-Miracle, Daniel; Perera, P. D. Chandana; Galceran-Arellano, Samuel; Blaabjerg, Frede

    2010-01-01

    V/f control strategy for permanent magnet synchronous motors can be useful for HVAC applications, where not high performance is required. Permanent magnet synchronous motors have efficiency advantages over the induction motor. But open loop V/f control is not stable in the whole frequency range. As demonstrated, the V/f control strategy becomes

  18. Feedback control for magnetic island suppression in tokamaks

    NARCIS (Netherlands)

    Hennen, B.A.

    2011-01-01

    A real-time feedback control system has been developed that finds, tracks, suppresses and/or stabilizes resistive magnetic instabilities in a nuclear fusion plasma. In a tokamak, magnetic fields confine a fusion plasma in a topology of toroidally nested magnetic surfaces. The power produced by the

  19. Geometric Control Over the Motion of Magnetic Domain Walls

    International Nuclear Information System (INIS)

    N.A. Sinitsyn; V.V. Dobrovitski; S. urazhdin; Avadh Saxena

    2008-01-01

    We propose a method that enables a precise control of magnetic patterns and relies only on the fundamental properties of the wire as well as on the choice of the path in the controlled parameter space but not on the rate of motion along this path. Possible experimental realizations of this mechanism are discussed. In particular, we show that the domain walls in magnetic nanowires can be translated by rotation of the magnetic easy axis or by applying pulses of magnetic field directed transverse to the magnetic easy axis

  20. Control of Spin Wave Dynamics in Spatially Twisted Magnetic Structures

    Science.gov (United States)

    2017-06-27

    control the spin wave dynamics of magnetic structures twisted spatially, we prepared the exchange-coupled films with the hard magnetic L10-FePt and...information writing of magnetic storage and spintronic applications. Introduction and Objective: Recent rapid progress in the research field of nano...scaled bilayer elements is also an important aim of this project. Approach/Method: The exchange-coupled films with the hard magnetic L10-FePt and

  1. Circumstellar Gas in Young Planetary Debris Disks

    Science.gov (United States)

    Roberge, A.

    Circumstellar (CS) disks orbiting young stars fall into two categories: primordial disks, composed of unprocessed interstellar dust and gas, and debris disks, produced by the destruction of solid planetary bodies. In the first class, the most abundant gas is H_2; in the second, it appears that the H_2 gas has disappeared, possibly through incorporation into gas giant planets. The lifetime of H_2 gas in a CS disk is therefore of great importance, as it dictates the timescale for the formation of giant planets. FUSE observations of H_2 in CS disk systems have shown that FUV absorption spectroscopy may sensitively probe for small amounts of gas along the line of sight to the star. Most importantly, the FUSE non-detection of H_2 gas in the Beta Pictoris disk suggests that the primordial gas lifetime is less than about 12 Myr, and that gas giant planets must form very quickly. However, this suggestion is based on one system, and needs to be tested in additional systems with a range of ages, especially since there are indications that age is not the only factor in the evolution of a CS disk. We propose for FUSE observations of 3 additional debris disk systems, Fomalhaut, HD3003, and HD2884. Fomalhaut is an intermediate age debris disk, one of the Fabulous Four CS disks first discovered in 1984. The other two disks are younger, with ages similar to that of Beta Pic. All three stars are brighter in the FUV than Beta Pic, permitting us to sensitively probe for traces of H_2 gas. We will also measure the amount of secondary atomic gas produced from planetary bodies in these disks, in an effort to understand the entire evolution of CS gas in young planetary systems.

  2. Direct Model Reference Adaptive Control for a Magnetic Bearing

    Energy Technology Data Exchange (ETDEWEB)

    Durling, Mike [Rensselaer Polytechnic Inst., Troy, NY (United States)

    1999-11-01

    A Direct Model Reference Adaptive Controller (DMRAC) is applied to a magnetic bearing test stand. The bearing of interest is the MBC 500 Magnetic Bearing System manufactured by Magnetic Moments, LLC. The bearing model is presented in state space form and the system transfer function is measured directly using a closed-loop swept sine technique. Next, the bearing models are used to design a phase-lead controller, notch filter and then a DMRAC. The controllers are tuned in simulations and finally are implemented using a combination of MATLAB, SIMULINK and dSPACE. The results show a successful implementation of a DMRAC on the magnetic bearing hardware.

  3. Energy-Based Controller Design of Stochastic Magnetic Levitation System

    Directory of Open Access Journals (Sweden)

    Weiwei Sun

    2017-01-01

    Full Text Available This paper investigates the control problem of magnetic levitation system, in which velocity feedback signal is influenced by stochastic disturbance. Firstly, single-degree-freedom magnetic levitation is regarded as an energy-transform action device. From the view of energy-balance relation, the magnetic levitation system is transformed into port-controlled Hamiltonian system model. Next, based on the Hamiltonian structure, the control law of magnetic levitation system is designed by applying Lyapunov theory. Finally, the simulation verifies the correctness of the proposed results.

  4. Controlling vortex chirality and polarity by geometry in magnetic nanodots

    OpenAIRE

    Agramunt Puig, Sebastià

    2014-01-01

    The independent control of both vortex chirality and polarity is a significant challenge in magnetic devices based on nano-sized magnetic vortex structures. By micromagnetic simulations here, we show that in soft ferromagnetic nanodots with an adequate modulated thickness, the desired combination of chirality and polarity can be achieved just by changing the direction of the in-plane applied magnetic field. Despite the complex behavior, the vortex chirality and polarity control can be summari...

  5. Bi-magnetic microwires: a novel family of materials with controlled magnetic behavior

    International Nuclear Information System (INIS)

    Pirota, K.R.; Provencio, M.; Garcia, K.L.; Escobar-Galindo, R.; Mendoza Zelis, P.; Hernandez-Velez, M.; Vazquez, M.

    2005-01-01

    A novel technique involving combined sputtering and electroplating procedures has been recently developed to deposit metallic (magnetic or not) nano and microlayer tubes onto glass-coated amorphous magnetic microwires to enable the tailoring of their magnetic behavior. Here, after introducing the general aspects of that technique, we present the latest results on a new family of two-phase magnetic samples: bi-magnetic multilayer microwires. They consist of a magnetically soft nucleus (typically a Fe or Co base amorphous microwire, coated by Pyrex layer) onto which a 30 nm thick Au layer is first sputtered followed by the electroplating of a harder microlayer, namely Co x Ni (1- x ) layer, with x controlled by the current density during electrodeposition whose micrometric thickness is also controlled by plating time. The hysteresis loops present a two-step reversal process typical of two-phase magnetic material. The magnetization reversal of the soft nucleus and the harder layer takes place at around 1 Oe and up to about 200 Oe, respectively. The presence of sputtered and electroplated layers induces significant stresses in the soft magnetic nucleus that modify its magnetization easy axis. This technique allowing us the tailoring of the magnetic behavior of multilayer magnetic microwires opens new possibilities for applying these novel materials as sensing elements in various devices

  6. Efficient Fuzzy Logic Controller for Magnetic Levitation Systems

    African Journals Online (AJOL)

    Akorede

    ABSTRACT: Magnetic levitation is a system of suspending a body or a complete system against gravity. Suspending a system ... disturbance signal was applied to the input of the control system. Fuzzy ..... Automatic Control System, fifth edition.

  7. GEOCHEMICAL CONTROLS ON NUCLEAR MAGNETIC RESONANCE MEASUREMENTS

    International Nuclear Information System (INIS)

    Knight, Rosemary

    2008-01-01

    Proton nuclear magnetic resonance (NMR) is used in the Earth Sciences as a means of obtaining information about the molecular-scale environment of fluids in porous geological materials. Laboratory experiments were conducted to advance our fundamental understanding of the link between the NMR response and the geochemical properties of geological materials. In the first part of this research project, we studied the impact of both the surface-area-to-volume ratio (S/V) of the pore space and the surface relaxivity on the NMR response of fluids in sand-clay mixtures. This study highlighted the way in which these two parameters control our ability to use NMR measurements to detect and quantify fluid saturation in multiphase saturated systems. The second part of the project was designed to explore the way in which the mineralogic form of iron, as opposed to simply the concentration of iron, affects the surface relaxation rate and, more generally, the NMR response of porous materials. We found that the magnitude of the surface relaxation rate was different for the various iron-oxide minerals because of changes in both the surface-area-to-volume ratio of the pore space, and the surface relaxivity. Of particular significance from this study was the finding of an anomalously large surface relaxivity of magnetite compared to that of the other iron minerals. Differences in the NMR response of iron minerals were seen in column experiments during the reaction of ferrihydrite-coated quartz sand with aqueous Fe(II) solutions to form goethite, lepidocrocite and magnetite; indicating the potential use of NMR as a means of monitoring geochemical reactions. The final part of the research project investigated the impact of heterogeneity, at the pore-scale, on the NMR response. This work highlighted the way in which the geochemistry, by controlling the surface relaxivity, has a significant impact on the link between NMR data and the microgeometry of the pore space.

  8. Laboratory Studies Of Circumstellar Carbonaceous Grain Formation

    Science.gov (United States)

    Contreras, Cesar; Sciamma-O'Brien, Ella; Salama, Farid

    2014-06-01

    The study of the formation processes of dust is essential to understand the budget of extraterrestrial organic molecules. Although dust with all its components plays an important role in the evolution of interstellar (IS) chemistry and in the formation of organic molecules, little is known on the formation processes of carbonaceous dust. We report the progress that was recently achieved in this domain using NASA Ames’ COSmIC facility (Contreras & Salama 2013, ApJS, 208, 6). PAHs are important chemical building blocks of IS dust. They are detected in IDPs and in meteoritic samples. Additionally, observational, laboratory, and theoretical studies have shown that PAHs are an important, ubiquitous component of the ISM. The formation of PAHs from smaller molecules has not been extensively studied. Therefore, we have performed laboratory experiments to study the dynamic processes of carbon grain formation, starting from the smallest hydrocarbon molecules into the formation of larger PAH and further into nanograins. Studies of IS dust analogs formed from a variety of PAH and hydrocarbon precursors as well as species that include the atoms O, N, and S, have recently been performed in our laboratory using the COSmIC facility to provide conditions that simulate IS and circumstellar environments. The species formed in the COSmiC chamber through a pulsed discharge nozzle plasma source are detected and characterized with a cavity ringdown spectrometer coupled to a time-of-flight mass spectrometer, thus providing both spectroscopic and ion mass information in-situ. Analysis of solid soot particles was also conducted using scanning electron microscopy at the UCSC/NASA Ames’ MACS facility. The SEM analysis of the deposition of soot from methane and acetylene precursors seeded in argon plasmas provide examples on the types of nanoparticles and micrograins that are produced in these gas mixtures under our experimental conditions. From these measurements, we derive information on

  9. DC Control Effort Minimized for Magnetic-Bearing-Supported Shaft

    Science.gov (United States)

    Brown, Gerald V.

    2001-01-01

    A magnetic-bearing-supported shaft may have a number of concentricity and alignment problems. One of these involves the relationship of the position sensors, the centerline of the backup bearings, and the magnetic center of the magnetic bearings. For magnetic bearings with permanent magnet biasing, the average control current for a given control axis that is not bearing the shaft weight will be minimized if the shaft is centered, on average over a revolution, at the magnetic center of the bearings. That position may not yield zero sensor output or center the shaft in the backup bearing clearance. The desired shaft position that gives zero average current can be achieved if a simple additional term is added to the control law. Suppose that the instantaneous control currents from each bearing are available from measurements and can be input into the control computer. If each control current is integrated with a very small rate of accumulation and the result is added to the control output, the shaft will gradually move to a position where the control current averages to zero over many revolutions. This will occur regardless of any offsets of the position sensor inputs. At that position, the average control effort is minimized in comparison to other possible locations of the shaft. Nonlinearities of the magnetic bearing are minimized at that location as well.

  10. A ferrofluid based artificial tactile sensor with magnetic field control

    Energy Technology Data Exchange (ETDEWEB)

    Volkova, T.I., E-mail: tatiana.volkova@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Böhm, V., E-mail: valter.boehm@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Naletova, V.A., E-mail: naletova@imec.msu.ru [Faculty of Mechanics and Mathematics, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Kaufhold, T., E-mail: tobias.kaufhold@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Becker, F., E-mail: felix.becker@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Zeidis, I., E-mail: igor.zeidis@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany); Zimmermann, K., E-mail: klaus.zimmermann@tu-ilmenau.de [Technical Mechanics Group, Faculty of Mechanical Engineering, Technische Universität Ilmenau, Ilmenau D-98684 (Germany)

    2017-06-01

    The paper deals with a tactile sensor inspired by biological hairs of mammals. The working principle is based on the effect of the magnetic force exerted on a paramagnetic body submerged into a ferrofluid volume under the influence of a nonuniform magnetic field. The deflection of the sensor's rod caused by external mechanical stimuli may be unambiguously identified by the distortion of the magnetic field, which occurs due to the motion of the attached body in the ferrofluid. The magnetic force acting on the body is evaluated experimentally and theoretically for the nonuniform magnetic field of a permanent magnet. The controlled oscillations of the rod are realised by applying a nonuniform magnetic field of periodically altering direction. - Highlights: • A design approach of a tactile sensor inspired by special mammalian hairs is presented. • The working principle is based on magnetic properties of a ferrofluid in magnetic fields. • The magnetic force acting on a body submerged into a ferrofluid volume is evaluated. • External mechanical stimuli may be identified by the distortion of the magnetic field. • The controlled whisking-like oscillations of the sensor's rod are realised experimentally.

  11. A ferrofluid based artificial tactile sensor with magnetic field control

    International Nuclear Information System (INIS)

    Volkova, T.I.; Böhm, V.; Naletova, V.A.; Kaufhold, T.; Becker, F.; Zeidis, I.; Zimmermann, K.

    2017-01-01

    The paper deals with a tactile sensor inspired by biological hairs of mammals. The working principle is based on the effect of the magnetic force exerted on a paramagnetic body submerged into a ferrofluid volume under the influence of a nonuniform magnetic field. The deflection of the sensor's rod caused by external mechanical stimuli may be unambiguously identified by the distortion of the magnetic field, which occurs due to the motion of the attached body in the ferrofluid. The magnetic force acting on the body is evaluated experimentally and theoretically for the nonuniform magnetic field of a permanent magnet. The controlled oscillations of the rod are realised by applying a nonuniform magnetic field of periodically altering direction. - Highlights: • A design approach of a tactile sensor inspired by special mammalian hairs is presented. • The working principle is based on magnetic properties of a ferrofluid in magnetic fields. • The magnetic force acting on a body submerged into a ferrofluid volume is evaluated. • External mechanical stimuli may be identified by the distortion of the magnetic field. • The controlled whisking-like oscillations of the sensor's rod are realised experimentally.

  12. Physical processes in circumstellar disks around young stars

    CERN Document Server

    2011-01-01

    Circumstellar disks are vast expanses of dust that form around new stars in the earliest stages of their birth. Predicted by astronomers as early as the eighteenth century, they weren't observed until the late twentieth century, when interstellar imaging technology enabled us to see nascent stars hundreds of light years away. Since then, circumstellar disks have become an area of intense study among astrophysicists, largely because they are thought to be the forerunners of planetary systems like our own-the possible birthplaces of planets.            This volume brings

  13. Magnetic fish-robot based on multi-motion control of a flexible magnetic actuator.

    Science.gov (United States)

    Kim, Sung Hoon; Shin, Kyoosik; Hashi, Shuichiro; Ishiyama, Kazushi

    2012-09-01

    This paper presents a biologically inspired fish-robot driven by a single flexible magnetic actuator with a rotating magnetic field in a three-axis Helmholtz coil. Generally, magnetic fish-robots are powered by alternating and gradient magnetic fields, which provide a single motion such as bending the fish-robot's fins. On the other hand, a flexible magnetic actuator driven by an external rotating magnetic field can create several gaits such as the bending vibration, the twisting vibration, and their combination. Most magnetic fish-like micro-robots do not have pectoral fins on the side and are simply propelled by the tail fin. The proposed robot can swim and perform a variety of maneuvers with the addition of pectoral fins and control of the magnetic torque direction. In this paper, we find that the robot's dynamic actuation correlates with the magnetic actuator and the rotating magnetic field. The proposed robot is also equipped with new features, such as a total of six degrees of freedom, a new control method that stabilizes posture, three-dimensional swimming, a new velocity control, and new turning abilities.

  14. Magnetic fish-robot based on multi-motion control of a flexible magnetic actuator

    International Nuclear Information System (INIS)

    Kim, Sung Hoon; Hashi, Shuichiro; Ishiyama, Kazushi; Shin, Kyoosik

    2012-01-01

    This paper presents a biologically inspired fish-robot driven by a single flexible magnetic actuator with a rotating magnetic field in a three-axis Helmholtz coil. Generally, magnetic fish-robots are powered by alternating and gradient magnetic fields, which provide a single motion such as bending the fish-robot's fins. On the other hand, a flexible magnetic actuator driven by an external rotating magnetic field can create several gaits such as the bending vibration, the twisting vibration, and their combination. Most magnetic fish-like micro-robots do not have pectoral fins on the side and are simply propelled by the tail fin. The proposed robot can swim and perform a variety of maneuvers with the addition of pectoral fins and control of the magnetic torque direction. In this paper, we find that the robot's dynamic actuation correlates with the magnetic actuator and the rotating magnetic field. The proposed robot is also equipped with new features, such as a total of six degrees of freedom, a new control method that stabilizes posture, three-dimensional swimming, a new velocity control, and new turning abilities. (paper)

  15. Pose control of the chain composed of magnetic particles using external uniform and gradient magnetic fields

    International Nuclear Information System (INIS)

    Zhou, J. F.; Shao, C. L.; Gu, B. Q.

    2016-01-01

    Magnetic particles (MPs) are known to respond to a magnetic field and can be moved by magnetic force, which make them good carriers in bioengineering and pharmaceutical engineering. In this paper, a pose control method for the straight chain composed of MPs is proposed, and the chain with one pose can be moved to another position with another pose using alternately employed uniform and gradient magnetic fields. Based on computer simulations, it is revealed that in the uniform magnetic field, the MPs form a straight chain with the same separation space along the field lines, and once the uniform magnetic field rotates, the chain also rotates with the field. In the gradient magnetic field, the MPs move toward the higher field so that the translation of the chain can be realized. The simulation results indicate that while the uniform magnetic field is rotating, there exists certain hysteresis between the chain and the field, and the chain is not straight anymore. So the uniform magnetic field should rest at the target angle for a period to make the chain fully relax to be straight. For nanoMP, its magnetic moment directly determines the gradient magnetic force which is much smaller than the dipole–dipole force among MPs. Therefore, the translation of the chain is much more time-consuming than rotation. To enlarge the translational velocity, it is suggested to increase the size of MPs or the magnetic field gradient

  16. Magnetic leviation. ; Challenge for control design in mechatronics

    Energy Technology Data Exchange (ETDEWEB)

    Bleuler, H.

    1992-12-01

    The purpose of this paper is to show that development of active magnetic bearing is far from being under closed circumstanses. In this paper, magnetic levitation is classified and it is shown that the industrially applied magnetic levitation is a typical mechatronics system. Control problems for active magnetic bearings are then presented. It is introduced that there are several very interesting control issues to be solved and the potential for industrial applications is vast. Among the application areas, clean-room and vacuum handling, precision optics, scanning, machining, and turbo machines are described. In addition, is introduced the emerging of new fields of research, such as micro-scale active magnetic bearings, in which a project has been started. Furthermore, status of other current research is provided, which includes identification and control methods and the position sensorless bearing. 9 refs., 5 figs.

  17. Design and control of a superconducting permanent magnet synchronous motor

    International Nuclear Information System (INIS)

    Jiang, Y; Pei, R; Hong, Z; Song, J; Fang, F; Coombs, T A

    2007-01-01

    This paper gives a detailed description of the design of a superconducting permanent magnet synchronous motor. The parameters of the motor have been identified, and the torque equation has been stated. A direct torque control algorithm is introduced and applied to a traditional permanent magnet synchronous motor and the superconducting permanent magnet synchronous motor described in this paper. The motor performance shows that the direct torque control algorithm provides excellent control to the superconducting motor, and guarantees that the magnitude of the operational armature currents is smaller than the value of the critical current of the superconducting tape used for stator winding

  18. Design and control of a superconducting permanent magnet synchronous motor

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Y [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Pei, R [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Hong, Z [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom); Song, J [Huazhong University of Science of Technology, Wuhan 430074 (China); Fang, F [Huazhong University of Science of Technology, Wuhan 430074 (China); Coombs, T A [Cambridge University Engineering Department, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)

    2007-07-15

    This paper gives a detailed description of the design of a superconducting permanent magnet synchronous motor. The parameters of the motor have been identified, and the torque equation has been stated. A direct torque control algorithm is introduced and applied to a traditional permanent magnet synchronous motor and the superconducting permanent magnet synchronous motor described in this paper. The motor performance shows that the direct torque control algorithm provides excellent control to the superconducting motor, and guarantees that the magnitude of the operational armature currents is smaller than the value of the critical current of the superconducting tape used for stator winding.

  19. Study on a magnetic spiral-type wireless capsule endoscope controlled by rotational external permanent magnet

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Bo, E-mail: yebo@hubu.edu.cn [School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074 (China); School of Computer Science and Information Engineering, HuBei University, Wuhan 430062 (China); Zhang, Wei [Department of Mechanical Engineering, Hubei University of Automotive Technology, Shiyan 442002 (China); Sun, Zhen-jun [School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074 (China); Guo, Lin [School of Computer Science and Information Engineering, HuBei University, Wuhan 430062 (China); Deng, Chao [School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074 (China); Chen, Ya-qi [Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 (China); Zhang, Hong-hai [School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074 (China); Liu, Sheng [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China)

    2015-12-01

    In this paper, the authors propose rotating an external permanent magnet (EPM) to manipulate the synchronous rotation of a magnetic spiral-type wireless capsule endoscope (WCE), and the synchronous rotation of the WCE is converted to its translational motion in intestinal tract. In order to preliminarily verify the feasibility of this method, a handheld actuator (HA) controlled by micro controller unit, a magnetic spiral-type WCE and a bracket were fabricated, theoretical analysis and simulations about the control distance of this method were performed, and in ex-vivo tests were examined in porcine small intestine to verify the control distance and control performances of this method. It was demonstrated that this method showed good performances in controlling the translational motion of the magnetic spiral-type WCE, and this method has great potential to be used in clinical application. - Highlights: • A new magnetic control method for spiral-type wireless capsule endoscope is proposed. • Wireless capsule endoscope rotates synchronously with external permanent magnet. • The method controls the wireless capsule endoscope well in porcine small intestine. • Long control distance makes the method may be used in future medical application. • Experimental setup has great advantages: high cost performance and easy operation.

  20. Controlling chaos in the permanent magnet synchronous motor

    International Nuclear Information System (INIS)

    Zribi, Mohamed; Oteafy, Ahmed; Smaoui, Nejib

    2009-01-01

    The Permanent Magnet Synchronous Motor (PMSM) is known to exhibit chaotic behavior under certain conditions. This paper proposes to use an instantaneous Lyapunov exponent control algorithm to control the PMSM. One of the objectives of the control approach is to bring order to the PMSM and to drive it to any user-defined desired state. Simulation results under different operating conditions indicate that the proposed control scheme works well. Moreover, the proposed Lyapunov exponent control scheme is able to induce chaos on the permanent magnet synchronous motor. Simulation results show the effectiveness of the proposed control scheme in chaotifing the response of the motor.

  1. Voltage control of magnetic monopoles in artificial spin ice

    Science.gov (United States)

    Chavez, Andres C.; Barra, Anthony; Carman, Gregory P.

    2018-06-01

    Current research on artificial spin ice (ASI) systems has revealed unique hysteretic memory effects and mobile quasi-particle monopoles controlled by externally applied magnetic fields. Here, we numerically demonstrate a strain-mediated multiferroic approach to locally control the ASI monopoles. The magnetization of individual lattice elements is controlled by applying voltage pulses to the piezoelectric layer resulting in strain-induced magnetic precession timed for 180° reorientation. The model demonstrates localized voltage control to move the magnetic monopoles across lattice sites, in CoFeB, Ni, and FeGa based ASI’s. The switching is achieved at frequencies near ferromagnetic resonance and requires energies below 620 aJ. The results demonstrate that ASI monopoles can be efficiently and locally controlled with a strain-mediated multiferroic approach.

  2. The interaction of Type Ia supernovae with their circumstellar medium

    NARCIS (Netherlands)

    Chiotellis, A.

    2013-01-01

    This thesis is focused on the study of a specific class of supernovae, named Type Ia (or thermonuclear) supernovae. In particular, we attempt to gain information about their origin through the study of the interaction of these supernovae with circumstellar structures that have been shaped by their

  3. Herschel/HIFI deepens the circumstellar NH3 enigma

    NARCIS (Netherlands)

    Menten, K. M.; Wyrowski, F.; Alcolea, J.; De Beck, E.; Decin, L.; Marston, A. P.; Bujarrabal, V.; Cernicharo, J.; Dominik, C.; Justtanont, K.; de Koter, A.; Melnick, G.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Schmidt, M.; Schoier, F. L.; Szczerba, R.; Teyssier, D.; Waters, L. B. F. M.; Edwards, K.; Olberg, M.; Phillips, T. G.; Morris, P.; Salez, M.; Caux, E.

    2010-01-01

    Context. Circumstellar envelopes (CSEs) of a variety of evolved stars have been found to contain ammonia (NH3) in amounts that exceed predictions from conventional chemical models by many orders of magnitude. Aims. The observations reported here were performed in order to better constrain the NH3

  4. Variable circumstellar obscuration of the carbon star R Fornacis

    International Nuclear Information System (INIS)

    Feast, M.W.; Whitelock, P.A.; Catchpole, R.M.; Roberts, G.; Overbeek, M.D.

    1984-01-01

    In 1983 the carbon Mira-type variable R For became unusually faint in the visible and infrared. This is interpreted as a change in circumstellar obscuration. For absorption by graphite spheres the required particle radius is 0.15 μm. (author)

  5. Fault tolerant homopolar magnetic bearings with flux invariant control

    International Nuclear Information System (INIS)

    Na, Uhn Joo

    2006-01-01

    The theory for a novel fault-tolerant 4-active-pole homopolar magnetic bearing is developed. If any one coil of the four coils in the bearing actuator fail, the remaining three coil currents change via an optimal distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. The homopolar magnetic bearing thus provides unaltered magnetic forces without any loss of the bearing load capacity even if any one coil suddenly fails. Numerical examples are provided to illustrate the novel fault-tolerant, 4-active pole homopolar magnetic bearings

  6. Magnetic sensorless control experiment without drift problem on HT-7

    International Nuclear Information System (INIS)

    Nakamura, K.; Luo, J.R.; Wang, H.Z.; Ji, Z.S.; Wang, H.; Wang, F.; Qi, N.; Sato, K.N.; Hanada, K.; Sakamoto, M.; Idei, H.; Hasegawa, M.; Iyomasa, A.; Kawasaki, S.; Nakashima, H.; Higashijima, A.

    2006-01-01

    Magnetic sensorless control experiments of the plasma horizontal position have been carried out in the superconducting tokamak HT-7. Previously the horizontal position was calculated from the vertical field coil current and voltage without using signals of magnetic sensors like magnetic coils and flux loops placed near the plasma. The calculations are made focusing on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem of integrator of magnetic sensors. Two kinds of experiments were carried out, to keep the position constant and swing the position in a triangular waveform

  7. Iron saturation control in RHIC dipole magnets

    International Nuclear Information System (INIS)

    Thompson, P.A.; Gupta, R.C.; Kahn, S.A.; Hahn, H.; Morgan, G.H.; Wanderer, P.J.; Willen, E.

    1991-01-01

    The Relativistic Heavy Ion Collider (RHIC) will require 360 dipoles of 80 mm bore. This paper discusses the field perturbations produced by the saturation of the yoke iron. Changes have been made to the yoke to reduce these perturbations, in particular, decapole -4 . Measurements and calculations for 6 series of dipole magnets are presented. 2 refs., 2 figs., 1 tab

  8. Magnetic particle clutch controls servo system

    Science.gov (United States)

    Fow, P. B.

    1973-01-01

    Magnetic clutches provide alternative means of driving low-power rate or positioning servo systems. They may be used over wide variety of input speed ranges and weigh comparatively little. Power drain is good with overall motor/clutch efficiency greater than 50 percent, and gain of clutch is close to linear, following hysteresis curve of core and rotor material.

  9. Discrete Current Control Strategy of Permanent Magnet Synchronous Motors

    Directory of Open Access Journals (Sweden)

    Yan Dong

    2013-01-01

    Full Text Available A control strategy of permanent magnet synchronous motors (PMSMs, which is different from the traditional vector control (VC and direct torque control (DTC, is proposed. Firstly, the circular rotating magnetic field is analyzed on the simplified model and discredited into stepping magnetic field. The stepping magnetomotive force will drive the rotor to run as the stepping motor. Secondly, the stator current orientation is used to build the control model instead of rotor flux orientation. Then, the discrete current control strategy is set and adopted in positioning control. Three methods of the strategy are simulated in computer and tested on the experiment platform of PMSM. The control precision is also verified through the experiment.

  10. Experimental Study on Position Control System Using Encoderless Magnetic Motion

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hong Youn; Heo, Hoon [Korea Univ., Seoul (Korea, Republic of); Yun, Young Min; Shim, Ho Keun; Kwon, Young Mok [TPC Mechatronics, Daejeon (Korea, Republic of)

    2016-01-15

    A position control system composed of the PMLSM(Permanent Magnet Linear Synchronous Motor), unlike conventional linear permanent magnet synchronous motor is fixed to the permanent magnet moving coil rails (permanent magnet = stator, coil = mover), the coil is fixed, moving the permanent magnet, we propose a position control system (permanent magnet = mover, coil = stator) structure. Position is measured not using conventional encoder or resolver but by adopting vector control method using 2 hall sensors generating rectangular signal. This method estimate the velocity and position of mover by using the quadruple of two hall sensor signal instead of encoder signal. Vector control of PMLSM using 2 hall sensor generating rectangular wave is proved to control the system stable and efficiently through simulation. Also hardware experiment reveals that the position control performance is measured within the range of 30-50μ in the accuracy of 10-20μ, which is improved twice to the conventional method. The proposed method exhibits its economical efficiency and practical usefulness. The vector control technique using two hall sensors can be installed in narrow place, accordingly it can be implemented on the system where the conventional encoder or resolver cannot operate.

  11. The position control of a capsule filled with magnetic fluid

    International Nuclear Information System (INIS)

    Rhee, E.J.; Park, M.K.; Yamane, R.; Oshima, S.

    2002-01-01

    In this paper, in order to establish the technique of a nozzle-flapper system of a servo valve using magnetic fluid in hydraulic system, a governing equation regarding the levitation of a capsule filled with magnetic fluid is formulated. Using PID control, an experiment for the position control of a capsule was performed. The experimental results were compared with the simulation results found by the governing equation

  12. The design, magnetization and control of a superconducting permanent magnet synchronous motor

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Y; Pei, R; Xian, W; Hong, Z; Coombs, T A [Engineering Department, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)], E-mail: yj222@cam.ac.uk

    2008-06-15

    This paper describes in detail the method of magnetization of a superconducting permanent magnet synchronous motor. The rotor of the motor consists of 60 superconducting pucks, which are magnetized by two additional copper windings. The pulse field magnetization (PFM) method is considered and the resulted distribution of the magnetizing flux linkage from the rotor is not a perfect sine wave in the air gap, which leads to a large torque ripple and harmonics of the stator currents. In order to suppress the torque ripple, an iterative learning control (ILC) algorithm is used in addition to the former field-oriented control method. The results show the ILC algorithm can largely reduce the torque ripple.

  13. Efficient fuzzy logic controller for magnetic levitation systems | Shu ...

    African Journals Online (AJOL)

    In this paper magnetic levitation controller using fuzzy logic is proposed. The proposed Fuzzy logic controller (FLC) is designed, and developed using triangular membership function with 7×7 rules. The system model was implemented in MATLAB/SIMULINK and the system responses to Fuzzy controller with different input ...

  14. Nonlinear chaos control in a permanent magnet reluctance machine

    International Nuclear Information System (INIS)

    Harb, Ahmad M.

    2004-01-01

    The dynamics of a permanent magnet synchronous machine (PMSM) is analyzed. The study shows that under certain conditions the PMSM is experiencing chaotic behavior. To control these unwanted chaotic oscillations, a nonlinear controller based on the backstepping nonlinear control theory is designed. The objective of the designed control is to stabilize the output chaotic trajectory by forcing it to the nearest constant solution in the basin of attraction. The result is compared with a nonlinear sliding mode controller. The designed controller that based on backstepping nonlinear control was able to eliminate the chaotic oscillations. Also the study shows that the designed controller is mush better than the sliding mode control

  15. APPLICATION OF NONLINEAR PID CONTROLLER IN SUPERCONDUCTING MAGNETIC ENERGY STORAGE

    OpenAIRE

    PENG, Xiaotao; CHENG, Shijie

    2011-01-01

    As a new control strategy, Nonlinear PID(NLPID) controller has been introduced in the power system successfully. The controller is free of planting model foundation in the design procedure and realized simply. In this paper, a nonlinear PID controller used for superconducting magnetic energy storage (SMES) unit connected to a power system is proposed. Purpose of designing such controller is to improve the stability of the power system in a relatively wide operation range. The design procedure...

  16. Design and simulation of permanent magnet synchronous motor control system

    Science.gov (United States)

    Li, Li; Liu, Yongqiu

    2018-06-01

    In recent years, with the development of power electronics, microelectronics, new motor control theory and rare earth permanent magnet materials, permanent magnet synchronous motors have been rapidly applied. Permanent magnet synchronous motors have the advantages of small size, low loss and high efficiency. Today, energy conservation and environmental protection are increasingly valued. It is very necessary to study them. Permanent magnet synchronous motor control system has a wide range of application prospects in the fields of electric vehicles, ships and other transportation. Using the simulation function of MATLAB/SIMULINK, a modular design structure was used to simulate the whole system model of speed loop adjustment, current PI modulation, SVPWM (Space Vector Pulse Width Module) wave generation and double closed loop. The results show that this control method has good robustness, and this method can improve the design efficiency and shorten the system design time. In this article, the analysis of the control principle of modern permanent magnet synchronous motor and the various processes of MATLAB simulation application will be analyzed in detail. The basic theory, basic method and application technology of the permanent magnet synchronous motor control system are systematically introduced.

  17. Electrically Controllable Spontaneous Magnetism in Nanoscale Mixed Phase Multiferroics

    Energy Technology Data Exchange (ETDEWEB)

    He, Q.; Chu, Y. H.; Heron, J. T.; Yang, S. Y.; Wang, C. H.; Kuo, C. Y.; Lin, H. J.; Yu, P.; Liang, C. W.; Zeches, R. J.; Chen, C. T.; Arenholz, E.; Scholl, A.; Ramesh, R.

    2010-08-02

    The emergence of enhanced spontaneous magnetic moments in self-assembled, epitaxial nanostructures of tetragonal (T-phase) and rhombohedral phases (R-phase) of the multiferroic BiFeO{sub 3} system is demonstrated. X-ray magnetic circular dichroism based photoemission electron microscopy (PEEM) was applied to investigate the local nature of this magnetism. We find that the spontaneous magnetization of the R-phase is significantly enhanced above the canted antiferromagnetic moment in the bulk phase, as a consequence of a piezomagnetic coupling to the adjacent T-phase and the epitaxial constraint. Reversible electric field control and manipulation of this magnetic moment at room temperature is shown using a combination of piezoresponse force microscopy and PEEM studies.

  18. Magnetic light cloaking control in the marine planktonic copepod Sapphirina

    Science.gov (United States)

    Kashiwagi, H.; Mizukawa, Y.; Iwasaka, M.; Ohtsuka, S.

    2017-05-01

    We investigated the light cloaking behavior of the marine planktonic copepod Sapphirina under a magnetic field. Optical interferences in the multi-laminated guanine crystal layer beneath the dorsal body surface create a brilliant structural color, which can be almost entirely removed by changing the light reflection. In the investigation, we immersed segments of Sapphirina in seawater contained in an optical chamber. When the derived Sapphirina segments were attached to the container surface, they were inert to magnetic fields up to 300 mT. However, when the back plate segments were attached to the substrate at a point, with most of the plate floating in the seawater, the plate rotated oppositely to the applied magnetic field. In addition, the brilliant parts of the Sapphirina back plate rotated backward and forward by changing the magnetic field directions. Our experiment suggests a new model of an optical micro-electro-mechanical system that is controllable by magnetic fields.

  19. Surface Magnetism of Cobalt Nanoislands Controlled by Atomic Hydrogen.

    Science.gov (United States)

    Park, Jewook; Park, Changwon; Yoon, Mina; Li, An-Ping

    2017-01-11

    Controlling the spin states of the surface and interface is key to spintronic applications of magnetic materials. Here, we report the evolution of surface magnetism of Co nanoislands on Cu(111) upon hydrogen adsorption and desorption with the hope of realizing reversible control of spin-dependent tunneling. Spin-polarized scanning tunneling microscopy reveals three types of hydrogen-induced surface superstructures, 1H-(2 × 2), 2H-(2 × 2), and 6H-(3 × 3), with increasing H coverage. The prominent magnetic surface states of Co, while being preserved at low H coverage, become suppressed as the H coverage level increases, which can then be recovered by H desorption. First-principles calculations reveal the origin of the observed magnetic surface states by capturing the asymmetry between the spin-polarized surface states and identify the role of hydrogen in controlling the magnetic states. Our study offers new insights into the chemical control of magnetism in low-dimensional systems.

  20. Magnetic tunnel structures: Transport properties controlled by bias, magnetic field, and microwave and optical radiation

    International Nuclear Information System (INIS)

    Volkov, N.V.; Eremin, E.V.; Tarasov, A.S.; Rautskii, M.V.; Varnakov, S.N.; Ovchinnikov, S.G.; Patrin, G.S.

    2012-01-01

    Different phenomena that give rise to a spin-polarized current in some systems with magnetic tunnel junctions are considered. In a manganite-based magnetic tunnel structure in CIP geometry, the effect of current-channel switching was observed, which causes bias-driven magnetoresistance, rf rectification, and the photoelectric effect. The second system under study, ferromagnetic/insulator/semiconductor, exhibits the features of the transport properties in CIP geometry that are also related to the current-channel switching effect. The described properties can be controlled by a bias, a magnetic field, and optical radiation. At last, the third system under consideration is a cooperative assembly of magnetic tunnel junctions. This system exhibits tunnel magnetoresistance and the magnetic-field-driven microwave detection effect.

  1. A New Torque Control System of Permanent Magnet Synchronous Motor

    Directory of Open Access Journals (Sweden)

    Evstratov Andrey

    2017-01-01

    Full Text Available The article describes a new approach to control of permanent magnet synchronous motor drive based on the analysis of the electromechanical transformation. The proposed control system provides quick response and low ripple of the motor torque and flux. To synthesis this control system, the authors put the electromagnetic torque and the modulus of stator flux vector as controlled values and use the Lyapunov’s second method. In addition, the stator voltage constriction and ability of low-pass filtration are taken into account. The investigation of the proposed control system has carried out with the simulation and the experimental research which have confirmed that the proposed control system correspond to all above-mentioned control tasks and the permanent magnet synchronous motor controlled under this system may be recommended to use in robotics.

  2. Controlling the flux dynamics in superconductors by nanostructured magnetic arrays

    Science.gov (United States)

    Kapra, Andrey

    In this thesis we investigate theoretically how the critical current jc of nano-engineered mesoscopic superconducting film can be improved and how one can control the dynamics of the magnetic flux, e.g., the transition from flux-pinned to flux-flow regime, using arrays of magnetic nanostructures. In particularly we investigate: (1) Vortex transport phenomena in superconductors with deposited ferromagnetic structures on top, and the influence of the sample geometry on the critical parameters and on the vortex configurations. Changing geometry of the magnetic bars and magnetization of the bars will affect the critical current jc of the superconducting film. Such nanostructured ferromagnets strongly alter the vortex structure in its neighborhood. The influence of geometry, position and magnetization of the ferromagnet (single bar or regular lattice of the bars) on the critical parameters of the superconductor is investigated. (2) Effect of flux confinement in narrow superconducting channels with zigzag-shaped banks: the flux motion is confined in the transverse (perpendicular) direction of a diamond-cell-shape channel. The matching effect for the magnetic flux is found in the system relevantless of boundary condition. We discuss the dynamics of vortices in the samples and vortex pattern formation in the channel. We show how the inclusion of higher-Tc superconductor into the sample can lead to enhanced properties of the system. By adding an external driving force, we study the vortex dynamics. The different dynamic regimes are discussed. They allowed an effective control of magnetic flux in superconductors.

  3. Design, implementation and control of a magnetic levitation device

    Science.gov (United States)

    Shameli, Ehsan

    Magnetic levitation technology has shown a great deal of promise for micromanipulation tasks. Due to the lack of mechanical contact, magnetic levitation systems are free of problems caused by friction, wear, sealing and lubrication. These advantages have made magnetic levitation systems a great candidate for clean room applications. In this thesis, a new large gap magnetic levitation system is designed, developed and successfully tested. The system is capable of levitating a 6.5(gr) permanent magnet in 3D space with an air gap of approximately 50(cm) with the traveling range of 20x20x30 mm3. The overall positioning accuracy of the system is 60mum. With the aid of finite elements method, an optimal geometry for the magnetic stator is proposed. Also, an energy optimization approach is utilized in the design of the electromagnets. In order to facilitate the design of various controllers for the system, a mathematical model of the magnetic force experienced by the levitated object is obtained. The dynamic magnetic force model is determined experimentally using frequency response system identification. The response of the system components including the power amplifiers, and position measurement system are also considered in the development of the force model. The force model is then employed in the controller design for the magnetic levitation device. Through a modular approach, the controller design for the 3D positioning system is started with the controller design for the vertical direction, i.e. z, and then followed by the controller design in the horizontal directions, i.e. x and y. For the vertical direction, several controllers such as PID, feed forward and feedback linearization are designed and their performances are compared. Also a control command conditioning method is introduced as a solution to increase the control performance and the results of the proposed controller are compared with the other designs. Experimental results showed that for the magnetic

  4. Magnetic Control in Crystal Growth from a Melt

    Science.gov (United States)

    Huang, Yue

    Control of bulk melt crystal growth techniques is desirable for producing semiconductors with the highest purity and ternary alloys with tunable electrical properties. Because these molten materials are electrically conducting, external magnetic fields are often employed to regulate the flow in the melt. However, complicated by the coupled flow, thermal, electromagnetic and chemical physics, such magnetic control is typically empirical or even an educated guess. Two magnetic flow control mechanisms: flow damping by steady magnetic fields, and flow stirring by alternating magnetic fields, are investigated numerically. Magnetic damping during optically-heated float-zone crystal growth is modeled using a spectral collocation method. The Marangoni convection at the free melt-gas interface is suppressed when exposed to a steady axial magnetic field, measured by the Hartmann number Ha. As a result, detrimental flow instabilities are suppressed, and an almost quiescent region forms in the interior, ideal for single crystal growth. Using normal mode linear stability analyses, dominant flow instabilities are determined in a range applicable to experiments (up to Ha = 300 for Pr = 0.02, and up to Ha = 500 for Pr = 0.001). The hydrodynamic nature of the instability for small Prandtl number Pr liquid bridges is confirmed by energy analyses. Magnetic stirring is modeled for melt crystal growth in an ampule exposed to a transverse rotating magnetic field. Decoupled from the flow field at small magnetic Reynolds number, the electromagnetic field is first solved via finite element analysis. The flow field is then solved using the spectral element method. At low to moderate AC frequencies (up to a few kHz), the electromagnetic body force is dominant in the azimuthal direction, which stirs a steady axisymmetric flow primarily in the azimuthal direction. A weaker secondary flow develops in the meridional plane. However, at high AC frequencies (on the order of 10 kHz and higher), only

  5. Geochemical Controls on Nuclear Magnetic Resonance Measurements

    International Nuclear Information System (INIS)

    Knight, Rosemary; Prasad, Manika; Keating, Kristina

    2003-01-01

    OAK-B135 Our research objectives are to determine, through an extensive set of laboratory experiments, the effect of the specific mineralogic form of iron and the effect of the distribution of iron on proton nuclear magnetic resonance (NMR) relaxation mechanisms. In the first nine months of this project, we have refined the experimental procedures to be used in the acquisition of the laboratory NMR data; have ordered, and conducted preliminary measurements on, the sand samples to be used in the experimental work; and have revised and completed the theoretical model to use in this project. Over the next year, our focus will be on completing the first phase of the experimental work where the form and distribution of the iron in the sands in varied

  6. The chemistry of molecular anions in circumstellar sources

    Energy Technology Data Exchange (ETDEWEB)

    Agúndez, Marcelino [LUTH, Observatoire de Paris-Meudon, 5 Place Jules Janssen, 92190 Meudon (France); Cernicharo, José [Departamento de Astrofísica, CAB, CSIC-INTA, Ctra. de Torrejón a Ajalvir km 4, 28850 Madrid (Spain); Guélin, Michel [Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d' Héres (France)

    2015-01-22

    The detection of negatively charged molecules in the interstellar and circumstellar medium in the past four years has been one of the most impacting surprises in the area of molecular astrophysics. It has motivated the interest of astronomers, physicists, and chemists on the study of the spectroscopy, chemical kinetics, and prevalence of molecular anions in the different astronomical regions. Up to six different molecular anions have been discovered in space to date, the last one being the small ion CN{sup −}, which has been observed in the envelope of the carbon star IRC +10216 and which contrary to the other larger anions is not formed by electron attachment to CN, but through reactions of large carbon anions with nitrogen atoms. Here we briefly review the current status of our knowledge of the chemistry of molecular anions in space, with particular emphasis on the circumstellar source IRC +10216, which to date is the astronomical source harboring the largest variety of anions.

  7. CIRCUMSTELLAR SHELLS IN ABSORPTION IN TYPE Ia SUPERNOVAE

    International Nuclear Information System (INIS)

    Borkowski, Kazimierz J.; Blondin, John M.; Reynolds, Stephen P.

    2009-01-01

    Progenitors of Type Ia supernovae (SNe) have been predicted to modify their ambient circumstellar (CSM) and interstellar environments through the action of their powerful winds. While there is X-ray and optical evidence for circumstellar interaction in several remnants of Type Ia SNe, widespread evidence for such interaction in Type Ia SNe themselves has been lacking. We consider prospects for the detection of CSM shells that have been predicted to be common around Type Ia SNe. Such shells are most easily detected in Na I absorption lines. Variable (declining) absorption is expected to occur soon after the explosion, primarily during the SN rise time, for shells located within ∼1-10 pc of a SN. The distance of the shell from the SN can be determined by measuring the timescale for line variability.

  8. Method of plasma impurity control without magnetic divertor

    International Nuclear Information System (INIS)

    Schivell, J.F.

    1977-06-01

    A method is proposed for controlling impurity generation in a tokomak by skimming and pumping the scrape-off. This method avoids many of the complications of a magnetic divertor, such as specially configured magnetic fields, toroidal symmetry, and inefficient use of toroidal field volume. Estimates are given for operating parameters. Impurity reductions of as much as a factor of 10 should be achievable. The necessary high-capacity pump would employ either titanium gettering or cryocondensation

  9. Molten metal feed system controlled with a traveling magnetic field

    International Nuclear Information System (INIS)

    Praeg, W.F.

    1991-01-01

    This patent describes a continuous metal casting system in which the feed of molten metal controlled by means of a linear induction motor capable of producing a magnetic traveling wave in a duct that connects a reservoir of molten metal to a caster. The linear induction motor produces a traveling magnetic wave in the duct in opposition to the pressure exerted by the head of molten metal in the reservoir

  10. Electric-field control of magnetic domain-wall velocity in ultrathin cobalt with perpendicular magnetization.

    Science.gov (United States)

    Chiba, D; Kawaguchi, M; Fukami, S; Ishiwata, N; Shimamura, K; Kobayashi, K; Ono, T

    2012-06-06

    Controlling the displacement of a magnetic domain wall is potentially useful for information processing in magnetic non-volatile memories and logic devices. A magnetic domain wall can be moved by applying an external magnetic field and/or electric current, and its velocity depends on their magnitudes. Here we show that the applying an electric field can change the velocity of a magnetic domain wall significantly. A field-effect device, consisting of a top-gate electrode, a dielectric insulator layer, and a wire-shaped ferromagnetic Co/Pt thin layer with perpendicular anisotropy, was used to observe it in a finite magnetic field. We found that the application of the electric fields in the range of ± 2-3 MV cm(-1) can change the magnetic domain wall velocity in its creep regime (10(6)-10(3) m s(-1)) by more than an order of magnitude. This significant change is due to electrical modulation of the energy barrier for the magnetic domain wall motion.

  11. Nonlinear control of permanent magnet synchronous motor driving a ...

    African Journals Online (AJOL)

    This paper presents a non-linear control of permanent magnet synchronous motor (PMSM) fed by a PWM voltage source inverter. To improve the performance of this control technique, the input-output linearization technique is proposed for a system driving a mechanical load with two masses. In order to ensure a steady ...

  12. Digital control of wind tunnel magnetic suspension and balance systems

    Science.gov (United States)

    Britcher, Colin P.; Goodyer, Michael J.; Eskins, Jonathan; Parker, David; Halford, Robert J.

    1987-01-01

    Digital controllers are being developed for wind tunnel magnetic suspension and balance systems, which in turn permit wind tunnel testing of aircraft models free from support interference. Hardware and software features of two existing digital control systems are reviewed. Some aspects of model position sensing and system calibration are also discussed.

  13. Design of magnetic flux concentrator of permancent magnet for control rod position indicator of SMART CEDM

    International Nuclear Information System (INIS)

    Yoo, J. Y.; Kim, J. H.; Hur, H.; Kim, J. I.

    2002-01-01

    The reliability and accuracy of the information on control rod position are very important to the reactor safety and the design of the core protection system. A survey on the RSPT(Reed Switch Position Transmitter) type control rod position indication system and its actual implementation in the exiting nuclear power plants in Korea was performed first. The control rod position indicator having the high performance for SMART was developed on the basis of RSPT technology identified through the survey. The arrangement of permanent magnet and reed switches is the most important procedure in the design of control rod position indication. In this study, the magnetic flux concentrator of permanent magnet is introduced and the calculation method for effective flux area for reed switch is presented

  14. Voltage Control of Rare-Earth Magnetic Moments at the Magnetic-Insulator-Metal Interface

    Science.gov (United States)

    Leon, Alejandro O.; Cahaya, Adam B.; Bauer, Gerrit E. W.

    2018-01-01

    The large spin-orbit interaction in the lanthanides implies a strong coupling between their internal charge and spin degrees of freedom. We formulate the coupling between the voltage and the local magnetic moments of rare-earth atoms with a partially filled 4 f shell at the interface between an insulator and a metal. The rare-earth-mediated torques allow the power-efficient control of spintronic devices by electric-field-induced ferromagnetic resonance and magnetization switching.

  15. Observations of Circumstellar Thermochemical Equilibrium: The Case of Phosphorus

    Science.gov (United States)

    Milam, Stefanie N.; Charnley, Steven B.

    2011-01-01

    We will present observations of phosphorus-bearing species in circumstellar envelopes, including carbon- and oxygen-rich shells 1. New models of thermochemical equilibrium chemistry have been developed to interpret, and constrained by these data. These calculations will also be presented and compared to the numerous P-bearing species already observed in evolved stars. Predictions for other viable species will be made for observations with Herschel and ALMA.

  16. Circumstellar X-ray Emission from SN1978K

    Science.gov (United States)

    Schlegel, Eric M.; Colbert, E.; Petre, R.

    1995-02-01

    We present the X-ray light curve in the 0.2 2.4 keV band based on fiveROSAT observations of SN1978K in NGC 1313. The X-ray emission is believed to arise from the interaction of the reverse shock and the expanding debris from the supernova. The reverse shock becomes established after the outgoing shock runs into circumstellar matter.

  17. Method and device for thermal control of biological and chemical reactions using magnetic particles or magnetic beads and variable magnetic fields

    OpenAIRE

    Zilch, C.; Gerdes, W.; Bauer, J.; Holschuh, K.

    2009-01-01

    The invention relates to a method for the thermal control of at least one temperature-dependent enzymatic reaction in the presence of magnetic particles, particularly nanoparticles, or magnetic beads, in vitro by heating the magnetic beads or magnetic particles to at least one defined target temperature using alternating magnetic fields. The thermally controllable enzymatic reaction carried out with the method according to the invention is preferably a PCR reaction or another reaction for elo...

  18. Ultraviolet extinction in M-supergiant circumstellar envelopes

    International Nuclear Information System (INIS)

    Buss, R.H. Jr.; Snow, T.P. Jr.

    1986-01-01

    Using International Ultraviolet (IUS) archival low-dispersion spectra, ultraviolet spectral extinctions were derived for the circumstellar envelopes of two M supergiants: HD 60414 and HD 213310. The observed stellar systems belong to a class of widely-separated spectroscopic binaries that are called VV Cephei stars. The total extinction was calculated by dividing the reddened fluxes with unreddened comparison fluxes of similar stars (g B2.5 for HD 213310 and a normalized s+B3 for HD 60414) from the reference atlas. After substracting the interstellar extinctions, which were estimated from the E(B-V) reddening of nearby stars, the resultant circumstellar extinctions were normalized at about 3.5 inverse microns. Not only is the 2175 A extinction bump absent in the circumstellar extinctions, but the far-ultraviolet extinction rise is also absent. The rather flat, ultraviolet extinction curves were interpreted as signatures of a population of noncarbonaceous, oxygen-rich grains with diameters larger than the longest observed wavelength

  19. Edge localized modes control by resonant magnetic perturbations

    International Nuclear Information System (INIS)

    Nardon, E.

    2007-10-01

    The present work is dedicated to one of the most promising methods of control of the ELMs (Edge Localized Modes), based on a system of coils producing Resonant Magnetic Perturbations (RMPs). Our main objectives are, on the one hand, to improve the physical understanding of the mechanisms at play, and on the other hand to propose a concrete design of ELMs control coils for ITER. In order to calculate and analyze the magnetic perturbations produced by a given set of coils, we have developed the ERGOS code. The first ERGOS calculation was for the DIII-D ELMs control coils, the I-coils. It showed that they produce magnetic islands chains which overlap at the edge of the plasma, resulting in the ergodization of the magnetic field. We have then used ERGOS for the modelling of the experiments on ELMs control using the error field correction coils at JET and MAST. In the case of JET, we have shown the existence of a correlation between the mitigation of the ELMs and the ergodization of the magnetic field at the edge, in agreement with the DIII-D result. In order to design the ELMs control coils for ITER we have used ERGOS intensively, taking the case of the DIII-D I-coils as a reference. Three candidate designs came out, which we presented at the ITER Design Review, in 2007. Recently, the ITER management decided to provide a budget for building ELMs control coils, the design of which remains to be chosen between two of the three options that we proposed. Finally, in order to understand better the non-linear magnetohydrodynamics phenomena taking place in ELMs control by RMPs, we performed numerical simulations, in particular with the JOREK code for a DIII-D case. The simulations reveal the existence of convection cells induced at the edge by the magnetic perturbations, and the possible screening of the RMPs in presence of rotation

  20. Plasma automatic control in magnetic traps

    International Nuclear Information System (INIS)

    Samojlenko, Yu.I.; Chuyanov, V.A.

    1983-01-01

    Principles of constructing the systems providing a plasma equilibrium and stability in thermonuctear devices are laid down. Operation of the servo system to maintain a plasma equilibrium is described using the tokamak plasma filament as an example. Operation of the system to suppress a flute instability is also described. This system measures electric disturbances on the plasma body surface and controls charge distribution on external electrodes. It is pointed out that systems of automatic control of plasma equilibrium and stability become an essential element of a future thermonuclear reactor and the system potentialities would much determine the reactor economic efficiency

  1. Real time control of the SSC string magnets

    International Nuclear Information System (INIS)

    Calvo, O.; Flora, R.; MacPherson, M.

    1987-01-01

    The system described in this paper, called SECAR, was designed to control the excitation of a test string of magnets for the proposed Superconducting Super Collider (SSC) and will be used to upgrade the present Tevatron Excitation, Control and Regulation (TECAR) hardware and software. It resides in a VME orate and is controlled by a 68020/68881 based CPU running the application software under a real time operating system named VRTX

  2. ATLAS magnet common cryogenic, vacuum, electrical and control systems

    CERN Document Server

    Miele, P; Delruelle, N; Geich-Gimbel, C; Haug, F; Olesen, G; Pengo, R; Sbrissa, E; Tyrvainen, H; ten Kate, H H J

    2004-01-01

    The superconducting Magnet System for the ATLAS detector at the LHC at CERN comprises a Barrel Toroid, two End Cap Toroids and a Central Solenoid with overall dimensions of 20 m diameter by 26 m length and a stored energy of 1.6 GJ. Common proximity cryogenic and electrical systems for the toroids are implemented. The Cryogenic System provides the cooling power for the 3 toroid magnets considered as a single cold mass (600 tons) and for the CS. The 21 kA toroid and the 8 kA solenoid electrical circuits comprise both a switch-mode power supply, two circuit breakers, water cooled bus bars, He cooled current leads and the diode resistor ramp-down unit. The Vacuum System consists of a group of primary rotary pumps and sets of high vacuum diffusion pumps connected to each individual cryostat. The Magnet Safety System guarantees the magnet protection and human safety through slow and fast dump treatment. The Magnet Control System ensures control, regulation and monitoring of the operation of the magnets. The update...

  3. Studies of Young, Star-forming Circumstellar Disks

    Science.gov (United States)

    Bae, Jaehan

    2017-08-01

    Disks of gas and dust around forming stars - circumstellar disks - last only a few million years. This is a very small fraction of the entire lifetime of Sun-like stars, several billion years. Nevertheless, by the time circumstellar disks dissipate stars complete building up their masses, giant planets finish accreting gas, and terrestrial bodies are nearly fully grown and ready for their final assembly to become planets. Understanding the evolution of circumstellar disks are thus crucial in many contexts. Using numerical simulations as the primary tool, my thesis has focused on the studies of various physical processes that can occur throughout the lifetime of circumstellar disks, from their formation to dispersal. Chapters 2, 3, and 4 emphasize the importance of early evolution, during which time a forming star-disk system obtains mass from its natal cloud: the infall phase. In Chapter 2 and 3, I have modeled episodic outbursts of accretion in protostellar systems resulting from disk instabilities - gravitational instability and magnetorotational instability. I showed that outbursts occur preferentially during the infall phase, because the mass addition provides more favorable conditions for gravitational instability to initiate the outburst cycle, and that forming stars build up a significant fraction of their masses through repeated short-lived, episodic outbursts. The infall phase can also be important for the formation of planets. Recent ALMA observations revealed sets of bright and dark rings in circumstellar disks of young, forming stars, potentially indicating early formation of planets. In Chapter 4, I showed that infall streams can create radial pressure bumps near the outer edge of the mass landing on the disk, from which vortices can form, collecting solid particles very efficiently to make initial seeds of planets. The next three chapters highlight the role of planets in setting the observational appearance and the evolution of circumstellar disks

  4. Multimodal chemo-magnetic control of self-propelling microbots

    Science.gov (United States)

    Singh, Amit Kumar; Dey, Krishna Kanti; Chattopadhyay, Arun; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar

    2014-01-01

    We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ~25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of the force-field required to arrest the chemotactic migration. The influence of the coupled internal and external fields could halt, steer or reverse the direction the motor inside a microchannel, rotate the motor around a target, and deliver the motor to a cluster of cells. This study showcases a multimodal chemical-magnetic field regulated migration of micro-machines for sensing, transport, and delivery inside a fluidic environment.We report a controlled migration of an iron nanoparticle (FeNP) coated polymer micromotor. The otherwise diffusive motion of the motor was meticulously directed through an in situ pH-gradient and an external magnetic field. The self-propulsion owing to the asymmetric catalytic decomposition of peroxide fuel was directed through a pH gradient imposed across the motor-surface, while the magnetic field induced an external control on the movement and the speed of the motor. Interestingly, the sole influence of the pH gradient could move the motor as high as ~25 body lengths per second, which was further magnified by the external assistance from the magnetic field. Applying a magnetic field against the pH directed motion helped in the quantitative experimental estimation of

  5. Electric control of magnetism in low-dimensional magnets on ferroelectric surfaces

    Directory of Open Access Journals (Sweden)

    Dorj Odkhuu

    2017-05-01

    Full Text Available Employing first-principles electronic structure calculations, we have studied the electric field controls of magnetism and magnetic anisotropy energy (MAE of the Fe adatoms on ferroelectric BaTiO3 and PbTiO3 surfaces. Remarkably, those effects exhibit dependence of the level of coverage as well as adsorption site of Fe atoms. While the magnitude of MAE is shown tunable by ferroelectric polarization in the full coverage of Fe monolayer, the direction of magnetization undergoes a transition from perpendicular to in-plane for the half or lower coverages. This magnetization reorientation is mainly ascribed to the site-dependent Fe d–O p hybridization, as a consequence of the formation of FeTiO2 layer at the surface.

  6. Linearized models for a new magnetic control in MAST

    Energy Technology Data Exchange (ETDEWEB)

    Artaserse, G., E-mail: giovanni.artaserse@enea.it [Associazione Euratom-ENEA sulla Fusione, Via Enrico Fermi 45, I-00044 Frascati (RM) (Italy); Maviglia, F.; Albanese, R. [Associazione Euratom-ENEA-CREATE sulla Fusione, Via Claudio 21, I-80125 Napoli (Italy); McArdle, G.J.; Pangione, L. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB (United Kingdom)

    2013-10-15

    Highlights: ► We applied linearized models for a new magnetic control on MAST tokamak. ► A suite of procedures, conceived to be machine independent, have been used. ► We carried out model-based simulations, taking into account eddy currents effects. ► Comparison with the EFIT flux maps and the experimental magnetic signals are shown. ► A current driven model for the dynamic simulations of the experimental data have been performed. -- Abstract: The aim of this work is to provide reliable linearized models for the design and assessment of a new magnetic control system for MAST (Mega Ampère Spherical Tokamak) using rtEFIT, which can easily be exported to MAST Upgrade. Linearized models for magnetic control have been obtained using the 2D axisymmetric finite element code CREATE L. MAST linearized models include equivalent 2D axisymmetric schematization of poloidal field (PF) coils, vacuum vessel, and other conducting structures. A plasmaless and a double null configuration have been chosen as benchmark cases for the comparison with experimental data and EFIT reconstructions. Good agreement has been found with the EFIT flux map and the experimental signals coming from magnetic probes with only few mismatches probably due to broken sensors. A suite of procedures (equipped with a user friendly interface to be run even remotely) to provide linearized models for magnetic control is now available on the MAST linux machines. A new current driven model has been used to obtain a state space model having the PF coil currents as inputs. Dynamic simulations of experimental data have been carried out using linearized models, including modelling of the effects of the passive structures, showing a fair agreement. The modelling activity has been useful also to reproduce accurately the interaction between plasma current and radial position control loops.

  7. Linearized models for a new magnetic control in MAST

    International Nuclear Information System (INIS)

    Artaserse, G.; Maviglia, F.; Albanese, R.; McArdle, G.J.; Pangione, L.

    2013-01-01

    Highlights: ► We applied linearized models for a new magnetic control on MAST tokamak. ► A suite of procedures, conceived to be machine independent, have been used. ► We carried out model-based simulations, taking into account eddy currents effects. ► Comparison with the EFIT flux maps and the experimental magnetic signals are shown. ► A current driven model for the dynamic simulations of the experimental data have been performed. -- Abstract: The aim of this work is to provide reliable linearized models for the design and assessment of a new magnetic control system for MAST (Mega Ampère Spherical Tokamak) using rtEFIT, which can easily be exported to MAST Upgrade. Linearized models for magnetic control have been obtained using the 2D axisymmetric finite element code CREATE L. MAST linearized models include equivalent 2D axisymmetric schematization of poloidal field (PF) coils, vacuum vessel, and other conducting structures. A plasmaless and a double null configuration have been chosen as benchmark cases for the comparison with experimental data and EFIT reconstructions. Good agreement has been found with the EFIT flux map and the experimental signals coming from magnetic probes with only few mismatches probably due to broken sensors. A suite of procedures (equipped with a user friendly interface to be run even remotely) to provide linearized models for magnetic control is now available on the MAST linux machines. A new current driven model has been used to obtain a state space model having the PF coil currents as inputs. Dynamic simulations of experimental data have been carried out using linearized models, including modelling of the effects of the passive structures, showing a fair agreement. The modelling activity has been useful also to reproduce accurately the interaction between plasma current and radial position control loops

  8. Sliding Mode Attitude Control for Magnetic Actuated Satellite

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    1998-01-01

    control torques can only be generated perpendicular to the local geomagnetic field vector. This has been a serious obstacle for using magnetorquer based control for three-axis attitude control. This paper deals with three-axis stabilization of a low earth orbit satellite. The problem of controlling...... the spacecraft attitude using only magnetic torquing is realized in the form of the sliding mode control. A three dimensional sliding manifold is proposed, and it is shown that the satellite motion on the sliding manifold is asymptotically stable...

  9. Graphene levitation and orientation control using a magnetic field

    Science.gov (United States)

    Niu, Chao; Lin, Feng; Wang, Zhiming M.; Bao, Jiming; Hu, Jonathan

    2018-01-01

    This paper studies graphene levitation and orientation control using a magnetic field. The torques in all three spatial directions induced by diamagnetic forces are used to predict stable conditions for different shapes of millimeter-sized graphite plates. We find that graphite plates, in regular polygon shapes with an even number of sides, will be levitated in a stable manner above four interleaved permanent magnets. In addition, the orientation of micrometer-sized graphene flakes near a permanent magnet is studied in both air and liquid environments. Using these analyses, we are able to simulate optical transmission and reflection on a writing board and thereby reveal potential applications using this technology for display screens. Understanding the control of graphene flake orientation will lead to the discovery of future applications using graphene flakes.

  10. The need for control of magnetic parameters for energy efficient performance of magnetic tunnel junctions

    Science.gov (United States)

    Farhat, I. A. H.; Gale, E.; Alpha, C.; Isakovic, A. F.

    2017-07-01

    Optimizing energy performance of Magnetic Tunnel Junctions (MTJs) is the key for embedding Spin Transfer Torque-Random Access Memory (STT-RAM) in low power circuits. Due to the complex interdependencies of the parameters and variables of the device operating energy, it is important to analyse parameters with most effective control of MTJ power. The impact of threshold current density, Jco , on the energy and the impact of HK on Jco are studied analytically, following the expressions that stem from Landau-Lifshitz-Gilbert-Slonczewski (LLGS-STT) model. In addition, the impact of other magnetic material parameters, such as Ms , and geometric parameters such as tfree and λ is discussed. Device modelling study was conducted to analyse the impact at the circuit level. Nano-magnetism simulation based on NMAGTM package was conducted to analyse the impact of controlling HK on the switching dynamics of the film.

  11. Focused-ion-beam induced interfacial intermixing of magnetic bilayers for nanoscale control of magnetic properties

    International Nuclear Information System (INIS)

    Burn, D M; Atkinson, D; Hase, T P A

    2014-01-01

    Modification of the magnetic properties in a thin-film ferromagnetic/non-magnetic bilayer system by low-dose focused ion-beam (FIB) induced intermixing is demonstrated. The highly localized capability of FIB may be used to locally control magnetic behaviour at the nanoscale. The magnetic, electronic and structural properties of NiFe/Au bilayers were investigated as a function of the interfacial structure that was actively modified using focused Ga + ion irradiation. Experimental work used MOKE, SQUID, XMCD as well as magnetoresistance measurements to determine the magnetic behavior and grazing incidence x-ray reflectivity to elucidate the interfacial structure. Interfacial intermixing, induced by low-dose irradiation, is shown to lead to complex changes in the magnetic behavior that are associated with monotonic structural evolution of the interface. This behavior may be explained by changes in the local atomic environment within the interface region resulting in a combination of processes including the loss of moment on Ni and Fe, an induced moment on Au and modifications to the spin-orbit coupling between Au and NiFe. (paper)

  12. Decoupling Suspension Controller Based on Magnetic Flux Feedback

    Directory of Open Access Journals (Sweden)

    Wenqing Zhang

    2013-01-01

    Full Text Available The suspension module control system model has been established based on MIMO (multiple input and multiple output state feedback linearization. We have completed decoupling between double suspension points, and the new decoupling method has been applied to CMS04 magnetic suspension vehicle in national mid-low-speed maglev experiment field of Tangshan city in China. Double suspension system model is very accurate for investigating stability property of maglev control system. When magnetic flux signal is taken back to the suspension control system, the suspension module’s antijamming capacity for resisting suspension load variety has been proved. Also, the external force interference has been enhanced. As a result, the robustness and stability properties of double-electromagnet suspension control system have been enhanced.

  13. Decoupling suspension controller based on magnetic flux feedback.

    Science.gov (United States)

    Zhang, Wenqing; Li, Jie; Zhang, Kun; Cui, Peng

    2013-01-01

    The suspension module control system model has been established based on MIMO (multiple input and multiple output) state feedback linearization. We have completed decoupling between double suspension points, and the new decoupling method has been applied to CMS04 magnetic suspension vehicle in national mid-low-speed maglev experiment field of Tangshan city in China. Double suspension system model is very accurate for investigating stability property of maglev control system. When magnetic flux signal is taken back to the suspension control system, the suspension module's antijamming capacity for resisting suspension load variety has been proved. Also, the external force interference has been enhanced. As a result, the robustness and stability properties of double-electromagnet suspension control system have been enhanced.

  14. Voltage control of a magnetic switching field for magnetic tunnel junctions with low resistance and perpendicular magnetic anisotropy

    Science.gov (United States)

    Tezuka, N.; Oikawa, S.; Matsuura, M.; Sugimoto, S.; Nishimura, K.; Irisawa, T.; Nagamine, Y.; Tsunekawa, K.

    2018-05-01

    The authors investigated the voltage control of a magnetic anisotropy field for perpendicular-magnetic tunnel junctions (p-MTJs) with low and high resistance-area (RA) products and for synthetic antiferromagnetic free and pinned layers. It was found that the sample with low RA products was more sensitive to the applied bias voltage than the sample with high RA products. The bias voltage effect was less pronounced for our sample with the synthetic antiferromagnetic layer for high RA products compared to the MTJs with single free and pinned layers.

  15. A differential-delay control for ramped magnet current

    Energy Technology Data Exchange (ETDEWEB)

    Murray, J. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Electrical Engineering; Olsen, R. [Brookhaven National Lab., Upton, NY (United States)

    1992-11-01

    A differential-delay control system has been designed and implemented for the main dipole magnet power supply of the booster ring at the National Synchrotron Light Source at Brookhaven National Lab. The control algorithm was implemented on a floating-point digital signal processor; in tests, the use of digital signal-processing techniques gave a factor of ten improvement in the tracking response time, together with a modest improvement in tracking accuracy.

  16. A differential-delay control for ramped magnet current

    Energy Technology Data Exchange (ETDEWEB)

    Murray, J. (State Univ. of New York, Stony Brook, NY (United States). Dept. of Electrical Engineering); Olsen, R. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    A differential-delay control system has been designed and implemented for the main dipole magnet power supply of the booster ring at the National Synchrotron Light Source at Brookhaven National Lab. The control algorithm was implemented on a floating-point digital signal processor; in tests, the use of digital signal-processing techniques gave a factor of ten improvement in the tracking response time, together with a modest improvement in tracking accuracy.

  17. Improvement of open-type magnetically shielded room composed of magnetic square cylinders by controlling flux path

    International Nuclear Information System (INIS)

    Hirosato, S.; Yamazaki, K.; Tsuruta, T.; Haraguchi, Y.; Kosaka, M.; Gao, Y.; Muramatsu, K.; Kobayashi, K.

    2011-01-01

    We have developed an open-type magnetically shielded room composed of magnetic square cylinders that has been used for an actual MRI in a hospital. To improve shielding performance, we propose here a method to control the path of the magnetic flux in the wall composed of the magnetic square cylinders by changing the magnetic permeability in each direction of the square cylinders spatially. First, we discuss a method to control the magnetic permeability in each direction of the square cylinders independently by inserting slits without changing the outside dimensions of the square cylinders, by using 3-D magnetic field analysis. Then, the effectiveness of the design of controlling the flux pass was shown by magnetic field analysis and experiments. (author)

  18. Synthesis of thermosensitive magnetic nanocarrier for controlled sorafenib delivery

    Energy Technology Data Exchange (ETDEWEB)

    Heidarinasab, Amir [Department of Chemical Engineering, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Ahmad Panahi, Homayon [Department of Chemistry, Central Tehran Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Faramarzi, Mehdi, E-mail: faramarzi.iaug@gmail.com [Department of Chemical Engineering, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Farjadian, Fatemeh [Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Shiraz University of Medical Sciences, Shiraz (Iran, Islamic Republic of)

    2016-10-01

    Allyl glycidyl ether/N-isopropylacrylamide-grafted magnetic nanoparticles were prepared using silica-coated magnetic nanoparticles as a substrate for radical copolymerization of allyl glycidyl ether and N-isopropylacrylamide. Chitosan was coupled with the prepared nanoparticles by opening the epoxy ring of the allyl glycidyl ether. The thermosensitive magnetic nanocarrier (TSMNC) obtained can be applied as a potent drug carrier. The TSMNC structure was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, vibrating sample magnetometer, and elemental analysis. Its morphology and size were investigated using field emission scanning electron microscopy, transmission electron microscopy and dynamic light scattering. The feasibility of employing the TSMNC for adsorption and in vitro controlled release of the chemotherapeutic agent sorafenib was tested. The effect of the adsorption parameters of pH, temperature, and loading time of sorafenib onto TSMNC was evaluated. The adsorption data was fitted to the Langmuir and Freundlich isotherms and the relevant parameters derived. The drug release profile indicated that 88% of the adsorbed drug was released within 35 h at 45 °C and drug release was Fickian diffusion-controlled. The results confirmed that the TSMNC has a high adsorption capacity at low temperature and good controlled release in a slow rate at a high temperature and could be developed for further application as a drug nanocarrier. - Graphical abstract: Magnetic nanoparticles were functionalized with chitosan and N-isopropylacrylamide. It was evaluated for sorafenib (SFB) adsorption and tested as a controlled-release system in response to changes in temperature. The TSMNC showed superparamagnetic properties with a high adsorption capacity and desirable controlled release at below and above LCST. Display Omitted - Highlights: • A TSMNC was synthesized for controlled

  19. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  20. Mid-IR Observations of Mira Circumstellar Environment

    OpenAIRE

    Marengo, Massimo; Karovska, Margarita; Fazio, Giovanni G.; Hora, Joseph L.; Hoffmann, William F.; Dayal, Aditya; Deutsch, Lynne K.

    2001-01-01

    This paper presents results from high-angular resolution mid-IR imaging of the Mira AB circumbinary environment using the MIRAC3 camera at the NASA Infrared Telescope Facility (IRTF). We resolved the dusty circumstellar envelope at 9.8, 11.7 and 18 micron around Mira A (o Ceti), and measured the size of the extended emission. Strong deviations from spherical symmetry are detected in the images of Mira AB system, including possible dust clumps in the direction of the companion (Mira B). These ...

  1. Light-scattering models applied to circumstellar dust properties

    International Nuclear Information System (INIS)

    Koehler, Melanie; Mann, Ingrid

    2004-01-01

    Radiation pressure force, Poynting-Robertson effect, and collisions are important to determine the size distribution of dust in circumstellar debris disks with the two former parameters depending on the light-scattering properties of grains. We here present Mie and discrete-dipole approximation (DDA) calculations to describe the optical properties of dust particles around β Pictoris, Vega, and Fomalhaut in order to study the influence of the radiation pressure force. We find that the differences between Mie and DDA calculations are lower than 30% for all porosities. Therefore, Mie calculations can be used to determine the cut-off limits which contribute to the size distribution for the different systems

  2. Control of forced vibrations of mechanical structures by an electromagnetic controller with a permanent magnet

    DEFF Research Database (Denmark)

    Stein, George Juraj; Darula, Radoslav; Sorokin, Sergey

    2012-01-01

    A theoretical analysis of an electromagnetic vibration controller is presented. The analyzed device consists of a pot-type iron core with a coil and a permanent magnet as a source of constant magnetic flux. The magnetic circuit is closed by a yoke, excited by an external harmonic mechanical force....... The so generated magnetic flux variation induces alternating voltage in the electric circuit, which is dissipated in a shunt resistor. The induced current driven through the coil generates magnetic force, which damps the excitation force and changes the damped natural frequency of the oscillatory system....... Due to the hysteretic effects in the magnetic material the internal losses influence the overall system’s performance. A mathematical model of the force balance in the oscillatory system is derived in a simplified, linearised form. The electric as well as mechanical system is modelled using lumped...

  3. Magnetic Field Equivalent Current Analysis-Based Radial Force Control for Bearingless Permanent Magnet Synchronous Motors

    Directory of Open Access Journals (Sweden)

    Huangqiu Zhu

    2015-05-01

    Full Text Available Bearingless permanent magnet synchronous motors (BPMSMs, with all advantages of permanent magnet motors (PMSMs and magnetic bearings, have become an important research direction in the bearingless motor field. To realize a stable suspension for the BPMSM, accurate decoupling control between the electromagnetic torque and radial suspension force is indispensable. In this paper, a concise and reliable analysis method based on a magnetic field equivalent current is presented. By this analysis method, the operation principle is analyzed theoretically, and the necessary conditions to produce a stable radial suspension force are confirmed. In addition, mathematical models of the torque and radial suspension force are established which is verified by the finite element analysis (FEA software ANSYS. Finally, an experimental prototype of a 2-4 poles surface-mounted BPMSM is tested with the customized control strategy. The simulation and experimental results have shown that the motor has good rotation and suspension performance, and validated the accuracy of the proposed analysis method and the feasibility of the control strategy.

  4. Nanomodified heat-accumulating materials controlled by a magnetic field

    Science.gov (United States)

    Shchegolkov, Alexander; Shchegolkov, Alexey; Dyachkova, Tatyana; Bodin, Nikolay; Semenov, Alexander

    2017-11-01

    The paper presents studies of nanomodified heat-accumulating materials controlled by a magnetic field. In order to obtain controlled heat-accumulating materials, synthetic motor oil CASTROL 0W30, ferromagnetic particles, CNTs and paraffin were used. Mechanically activated carbon nanotubes with ferromagnetic particles were used for the nanomodification of paraffin. Mechanoactivation ensured the production of ferromagnetic particles with an average particle size of 5 µm. Using an extrusion plant, a mixture of CNTs and ferromagnetic particles was introduced into the paraffin. Further, the nanomodified paraffin in a granular form was introduced into synthetic oil. To conduct experimental studies, a contactless method for measuring temperature was used. The thermal contact control with the help of the obtained nanomodified material is possible with a magnetic induction of 1250 mT, and a heat flux of about 74 kW/m2 is provided at the same time.

  5. Control of Permanent Magnet Synchronous Generator for large wind turbines

    DEFF Research Database (Denmark)

    Busca, Cristian; Stan, Ana-Irina; Stanciu, Tiberiu

    2010-01-01

    Direct Torque Control (DTC) and Field Oriented Control (FOC) are the most dominant control strategies used in generators for wind turbines. In this paper both control methods were implemented on a Permanent Magnet Synchronous Generator (PMSG). The variable speed wind turbine with full scale power...... converter topology was chosen for design. Parameters from a 2 MW wind turbine were used for system modeling. All the components of the wind turbine system (WTS), except the DC-link and the grid site converter were implemented in MATLAB/Simulink. The pitch controller was used to limit the output power...... produced by the turbine. DTC and FOC strategies, using SVM were used to control the generator rotor speed. The performance of the two control strategies were compared after different tests have been carried out....

  6. Quantum control of topological defects in magnetic systems

    Science.gov (United States)

    Takei, So; Mohseni, Masoud

    2018-02-01

    Energy-efficient classical information processing and storage based on topological defects in magnetic systems have been studied over the past decade. In this work, we introduce a class of macroscopic quantum devices in which a quantum state is stored in a topological defect of a magnetic insulator. We propose noninvasive methods to coherently control and read out the quantum state using ac magnetic fields and magnetic force microscopy, respectively. This macroscopic quantum spintronic device realizes the magnetic analog of the three-level rf-SQUID qubit and is built fully out of electrical insulators with no mobile electrons, thus eliminating decoherence due to the coupling of the quantum variable to an electronic continuum and energy dissipation due to Joule heating. For a domain wall size of 10-100 nm and reasonable material parameters, we estimate qubit operating temperatures in the range of 0.1-1 K, a decoherence time of about 0.01-1 μ s , and the number of Rabi flops within the coherence time scale in the range of 102-104 .

  7. Controlling the competing magnetic anisotropy energies in FineMET amorphous thin films with ultra-soft magnetic properties

    Directory of Open Access Journals (Sweden)

    Ansar Masood

    2017-05-01

    Full Text Available Thickness dependent competing magnetic anisotropy energies were investigated to explore the global magnetic behaviours of FineMET amorphous thin films. A dominant perpendicular magnetization component in the as-deposited state of thinner films was observed due to high magnetoelastic anisotropy energy which arises from stresses induced at the substrate-film interface. This perpendicular magnetization component decreases with increasing film thickness. Thermal annealing at elevated temperature revealed a significant influence on the magnetization state of the FineMET thin films and controlled annealing steps leads to ultra-soft magnetic properties, making these thin films alloys ideal for a wide range of applications.

  8. Fuzzy adaptive speed control of a permanent magnet synchronous motor

    Science.gov (United States)

    Choi, Han Ho; Jung, Jin-Woo; Kim, Rae-Young

    2012-05-01

    A fuzzy adaptive speed controller is proposed for a permanent magnet synchronous motor (PMSM). The proposed fuzzy adaptive speed regulator is insensitive to model parameter and load torque variations because it does not need any accurate knowledge about the motor parameter and load torque values. The stability of the proposed control system is also proven. The proposed adaptive speed regulator system is implemented by using a TMS320F28335 floating point DSP. Simulation and experimental results are presented to verify the effectiveness of the proposed fuzzy adaptive speed controller under uncertainties such as motor parameter and load torque variations using a prototype PMSM drive system.

  9. Stability and Bifurcation in Magnetic Flux Feedback Maglev Control System

    Directory of Open Access Journals (Sweden)

    Wen-Qing Zhang

    2013-01-01

    Full Text Available Nonlinear properties of magnetic flux feedback control system have been investigated mainly in this paper. We analyzed the influence of magnetic flux feedback control system on control property by time delay and interfering signal of acceleration. First of all, we have established maglev nonlinear model based on magnetic flux feedback and then discussed hopf bifurcation’s condition caused by the acceleration’s time delay. The critical value of delayed time is obtained. It is proved that the period solution exists in maglev control system and the stable condition has been got. We obtained the characteristic values by employing center manifold reduction theory and normal form method, which represent separately the direction of hopf bifurcation, the stability of the period solution, and the period of the period motion. Subsequently, we discussed the influence maglev system on stability of by acceleration’s interfering signal and obtained the stable domain of interfering signal. Some experiments have been done on CMS04 maglev vehicle of National University of Defense Technology (NUDT in Tangshan city. The results of experiments demonstrate that viewpoints of this paper are correct and scientific. When time lag reaches the critical value, maglev system will produce a supercritical hopf bifurcation which may cause unstable period motion.

  10. A One-Axis-Controlled Magnetic Bearing and Its Performance

    Science.gov (United States)

    Li, Lichuan; Shinshi, Tadahiko; Kuroki, Jiro; Shimokohbe, Akira

    Magnetic bearings (MBs) are complex machines in which sensors and controllers must be used to stabilize the rotor. A standard MB requires active control of five motion axes, imposing significant complexity and high cost. In this paper we report a very simple MB and its experimental testing. In this MB, the rotor is stabilized by active control of only one motion axis. The other four motion axes are passively stabilized by permanent magnets and appropriate magnetic circuit design. In rotor radial translational motion, which is passively stabilized, a resonant frequency of 205Hz is achieved for a rotor mass of 11.5×10-3kg. This MB features virtually zero control current and zero rotor iron loss (hysteresis and eddy current losses). Although the rotational speed and accuracy are limited by the resonance of passively stabilized axes, the MB is still suitable for applications where cost is critical but performance is not, such as cooling fans and auxiliary support for aerodynamic bearings.

  11. Circumstellar Material on and off the Main Sequence

    Science.gov (United States)

    Steele, Amy; Debes, John H.; Deming, Drake

    2017-06-01

    There is evidence of circumstellar material around main sequence, giant, and white dwarf stars that originates from the small-body population of planetary systems. These bodies tell us something about the chemistry and evolution of protoplanetary disks and the planetary systems they form. What happens to this material as its host star evolves off the main sequence, and how does that inform our understanding of the typical chemistry of rocky bodies in planetary systems? In this talk, I will discuss the composition(s) of circumstellar material on and off the main sequence to begin to answer the question, “Is Earth normal?” In particular, I look at three types of debris disks to understand the typical chemistry of planetary systems—young debris disks, debris disks around giant stars, and dust around white dwarfs. I will review the current understanding on how to infer dust composition for each class of disk, and present new work on constraining dust composition from infrared excesses around main sequence and giant stars. Finally, dusty and polluted white dwarfs hold a unique key to our understanding of the composition of rocky bodies around other stars. In particular, I will discuss WD1145+017, which has a transiting, disintegrating planetesimal. I will review what we know about this system through high speed photometry and spectroscopy and present new work on understanding the complex interplay of physics that creates white dwarf pollution from the disintegration of rocky bodies.

  12. Are young supernova remnants interacting with circumstellar gas

    International Nuclear Information System (INIS)

    Chevalier, R.A.

    1982-01-01

    The young remnants of galactic Type I supernovae (SN 1006, SN 1572, and SN 1604) appear to be interacting with moderately dense gas (n/sub O/> or =0.1 cm -3 ). If the gas in the ambient interstellar medium, the observations suggest that gas of this density is fairly pervasive. If the gas is circumstellar, there are important implications for the progenitors of Type I supernovae. A plausible density distribution for circumstellar gas is rhoinfinityr -2 . The expansion of a supernova into such a medium is examined and is compared with expansion into a uniform medium. The two cases can be distinguished on the basis of their density profiles and their rates of expansion. Currently available data factor the hypothesis of expansion in a uniform medium for all three Type I remnants; the evidence is the strongest for SN 1572 and the weakest for SN 1604. Further X-ray and radio observations of the galactic remnants and of extragalactic Type I supernovae should serve to test this hypothesis

  13. A circumstellar molecular gas structure associated with the massive young star Cepheus A-HW 2

    Science.gov (United States)

    Torrelles, Jose M.; Rodriguez, Luis F.; Canto, Jorge; Ho, Paul T. P.

    1993-01-01

    We report the detection via VLA-D observations of ammonia of a circumstellar high-density molecular gas structure toward the massive young star related to the object Cepheus A-HW 2, a firm candidate for the powering source of the high-velocity molecular outflow in the region. We suggest that the circumstellar molecular gas structure could be related to the circumstellar disk previously suggested from infrared, H2O, and OH maser observations. We consider as a plausible scenario that the double radio continuum source of HW 2 could represent the ionized inner part of the circumstellar disk, in the same way as proposed to explain the double radio source in L1551. The observed motions in the circumstellar molecular gas can be produced by bound motions (e.g., infall or rotation) around a central mass of about 10-20 solar masses (B0.5 V star or earlier).

  14. Magnetic Trapping and Coherent Control of Laser-Cooled Molecules

    Science.gov (United States)

    Williams, H. J.; Caldwell, L.; Fitch, N. J.; Truppe, S.; Rodewald, J.; Hinds, E. A.; Sauer, B. E.; Tarbutt, M. R.

    2018-04-01

    We demonstrate coherent microwave control of the rotational, hyperfine, and Zeeman states of ultracold CaF molecules, and the magnetic trapping of these molecules in a single, selectable quantum state. We trap about 5 ×103 molecules for almost 2 s at a temperature of 70 (8 ) μ K and a density of 1.2 ×105 cm-3. We measure the state-specific loss rate due to collisions with background helium.

  15. Continuous control of spin polarization using a magnetic field

    Science.gov (United States)

    Gifford, J. A.; Zhao, G. J.; Li, B. C.; Tracy, Brian D.; Zhang, J.; Kim, D. R.; Smith, David J.; Chen, T. Y.

    2016-05-01

    The giant magnetoresistance (GMR) of a point contact between a Co/Cu multilayer and a superconductor tip varies for different bias voltage. Direct measurement of spin polarization by Andreev reflection spectroscopy reveals that the GMR change is due to a change in spin polarization. This work demonstrates that the GMR structure can be utilized as a spin source and that the spin polarization can be continuously controlled by using an external magnetic field.

  16. Continuous control of spin polarization using a magnetic field

    International Nuclear Information System (INIS)

    Gifford, J. A.; Zhao, G. J.; Li, B. C.; Tracy, Brian D.; Zhang, J.; Kim, D. R.; Smith, David J.; Chen, T. Y.

    2016-01-01

    The giant magnetoresistance (GMR) of a point contact between a Co/Cu multilayer and a superconductor tip varies for different bias voltage. Direct measurement of spin polarization by Andreev reflection spectroscopy reveals that the GMR change is due to a change in spin polarization. This work demonstrates that the GMR structure can be utilized as a spin source and that the spin polarization can be continuously controlled by using an external magnetic field.

  17. Continuous control of spin polarization using a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Gifford, J. A.; Zhao, G. J.; Li, B. C.; Tracy, Brian D.; Zhang, J.; Kim, D. R.; Smith, David J.; Chen, T. Y., E-mail: tingyong.chen@asu.edu [Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)

    2016-05-23

    The giant magnetoresistance (GMR) of a point contact between a Co/Cu multilayer and a superconductor tip varies for different bias voltage. Direct measurement of spin polarization by Andreev reflection spectroscopy reveals that the GMR change is due to a change in spin polarization. This work demonstrates that the GMR structure can be utilized as a spin source and that the spin polarization can be continuously controlled by using an external magnetic field.

  18. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  19. Control of the superconducting magnet power supply for SECRAL

    International Nuclear Information System (INIS)

    Zhou Wenxiong; Wang Yanyu; Zhou Detai; Lu Wang; Feng Yucheng; Su Jianjun

    2014-01-01

    The control of the superconducting magnet power supply (SMPS) is very important for Superconducting Electron Cyclotron Resonance Ion source with Advanced design in Lanzhou (SECRAL). In order to improve the safety and the reliability of the SMPS, a remote control system was designed and implemented. There are four power supplies needed to be controlled with suitable strategy to avoid the quench of the superconducting magnet. These four power supplies are used to supply four superconducting solenoids. Because the value and the changing rates of the current for these four solenoids are different, the power supplies must be operated synchronously to keep the current of the solenoids balanced. In this paper, we provide a detailed description for the control strategy of the four power supplies and the architecture of the hardware and the software. A serial switch is used for protocol conversion between TCP/IP and RS232 in firmware. And the software is implemented using VC++. The system can operate the four power supplies automatically after it is triggered. With the help of the control system, operation of the SMPS gets easier and safer. (authors)

  20. A New Concept of Controller for Accelerators' Magnet Power Supplies

    Science.gov (United States)

    Visintini, Roberto; Cleva, Stefano; Cautero, Marco; Ciesla, Tomasz

    2016-04-01

    The complexity of a particle accelerator implies the remote control of very large numbers of devices, with many different typologies, either distributed along the accelerator or concentrated in locations, often far away from each other. Local and global control systems handle the devices through dedicated communication channels and interfaces. Each controlled device is practically a “smart node” performing a specific task. In addition, very often, those tasks are managed in real-time mode. The performances required to the control interface has an influence on the cost of the distributed nodes as well as on their hardware and software implementation. In large facilities (e.g. CERN) the “smart nodes” derive from specific in-house developments. Alternatively, it is possible to find on the market commercial devices, whose performances (and prices) are spread over a broad range, and spanning from proprietary design (customizable to the user's needs) to open source/design. In this paper, we will describe some applications of smart nodes in the particle accelerators field, with special focus on the power supplies for magnets. In modern accelerators, in fact, magnets and their associated power supplies constitute systems distributed along the accelerator itself, and strongly interfaced with the remote control system as well as with more specific (and often more demanding) orbit/trajectory feedback systems. We will give examples of actual systems, installed and operational on two light sources, Elettra and FERMI, located in the Elettra Research Center in Trieste, Italy.

  1. The magnetic field of molecular clouds

    Science.gov (United States)

    Padoan, P.

    2018-01-01

    The magnetic field of molecular clouds (MCs) plays an important role in the process of star formation: it determines the statistical properties of supersonic turbulence that controls the fragmentation of MCs, controls the angular momentum transport during the protostellar collapse, and affects the stability of circumstellar disks. In this work, we focus on the problem of the determination of the magnetic field strength. We review the idea that the MC turbulence is super-Alfvénic, and we argue that MCs are bound to be born super-Alfvénic. We show that this scenario is supported by results from a recent simulation of supernova-driven turbulence on a scale of 250 pc, where the turbulent cascade is resolved on a wide range of scales, including the interior of MCs.

  2. Roles of superconducting magnetic bearings and active magnetic bearings in attitude control and energy storage flywheel

    International Nuclear Information System (INIS)

    Tang Jiqiang; Fang Jiancheng; Ge, Shuzhi Sam

    2012-01-01

    Compared with conventional energy storage flywheel, the rotor of attitude control and energy storage flywheel (ACESF) used in space not only has high speed, but also is required to have precise and stable direction. For the presented superconducting magnetic bearing (SMB) and active magnetic bearing (AMB) suspended ACESF, the rotor model including gyroscopic couples is established originally by taking the properties of SMB and AMB into account, the forces of SMB and AMB are simplified by linearization within their own neighbors of equilibrium points. For the high-speed rigid discal rotor with large inertia, the negative effect of gyroscopic effect of rotor is prominent, the radial translation and tilting movement of rotor suspended by only SMB, SMB with equivalent PMB, or SMB together with PD controlled AMB are researched individually. These analysis results proved originally that SMB together with AMB can make the rotor be stable and make the radial amplitude of the vibration of rotor be small while the translation of rotor suspended by only SMB or SMB and PM is not stable and the amplitude of this vibration is large. For the stability of the high-speed rotor in superconducting ACESF, the AMB can suppress the nutation and precession of rotor effectively by cross-feedback control based on the separated PD type control or by other modern control methods.

  3. Molten metal feed system controlled with a traveling magnetic field

    Science.gov (United States)

    Praeg, Walter F.

    1991-01-01

    A continuous metal casting system in which the feed of molten metal is controlled by means of a linear induction motor capable of producing a magnetic traveling wave in a duct that connects a reservoir of molten metal to a caster. The linear induction motor produces a traveling magnetic wave in the duct in opposition to the pressure exerted by the head of molten metal in the reservoir so that p.sub.c =p.sub.g -p.sub.m where p.sub.c is the desired pressure in the caster, p.sub.g is the gravitational pressure in the duct exerted by the force of the head of molten metal in the reservoir, and p.sub.m is the electromagnetic pressure exerted by the force of the magnetic field traveling wave produced by the linear induction motor. The invention also includes feedback loops to the linear induction motor to control the casting pressure in response to measured characteristics of the metal being cast.

  4. Magneto-Ionic Control of Interfacial Magnetic Anisotorpy

    Science.gov (United States)

    Bauer, Uwe; Emori, Satoru; Beach, Geoffrey

    2014-03-01

    Voltage control of magnetism could bring about revolutionary new spintronic memory and logic devices. Here, we examine domain wall (DW) dynamics in ultrathin Co films and nanowires under the influence of a voltage applied across a gadolinium oxide gate dielectric that simultaneously acts as an oxygen ion conductor. We investigate two electrode configurations, one with a continuous gate dielectric and the other with a patterned gate dielectric which exhibits an open oxide edge right underneath the electrode perimeter. We demonstrate that the open oxide edge acts as a fast diffusion path for oxygen ions and allows voltage-induced switching of magnetic anisotropy at the nanoscale by modulating interfacial chemistry rather than charge density. At room temperature this effect is limited to the vicinity of the open oxide edge, but at a temperature of 100°C it allows complete control over magnetic anisotropy across the whole electrode area, due to higher oxygen ion mobility at elevated temperature. We then harness this novel ``magneto-ionic'' effect to create unprecedentedly strong voltage-induced anisotropy modifications of 3000 fJ/Vm and create electrically programmable DW traps with pinning strengths of 650 Oe, enough to bring to a standstill DWs travelling at speeds of at least 20 m/s. This work is supported by the National Science Foundation through grant ECCS-1128439.

  5. Fabrication and magnetic control of alginate-based rolling microrobots

    Directory of Open Access Journals (Sweden)

    Jamel Ali

    2016-12-01

    Full Text Available Advances in microrobotics for biological applications are often limited due to their complex manufacturing processes, which often utilize cytotoxic materials, as well as limitations in the ability to manipulate these small devices wirelessly. In an effort to overcome these challenges, we investigated a facile method for generating biocompatible hydrogel based robots that are capable of being manipulated using an externally generated magnetic field. Here, we experimentally demonstrate the fabrication and autonomous control of loaded-alginate microspheres, which we term artificial cells. In order to generate these microparticles, we employed a centrifuge-based method in which microspheres were rapidly ejected from a nozzle tip. Specifically, we used two mixtures of sodium alginate; one containing iron oxide nanoparticles and the other containing mammalian cells. This mixture was loaded into a needle that was fixed on top of a microtube containing calcium chloride, and then briefly centrifuged to generate hundreds of Janus microspheres. The fabricated microparticles were then magnetically actuated with a rotating magnetic field, generated using electromagnetic coils, prompting the particles to roll across a glass substrate. Also, using vision-based feedback control, a single artificial cell was manipulated to autonomously move in a programmed pattern.

  6. Infrared observations of circumstellar ammonia in OH/IR supergiants

    Science.gov (United States)

    Mclaren, R. A.; Betz, A. L.

    1980-01-01

    Ammonia has been detected in the circumstellar envelopes of VY Canis Majoris, VX Sagittarii, and IRC +10420 by means of several absorption lines in the nu-2 vibration-rotation band near 950 kaysers. The line profiles are well resolved (0.2 km/sec resolution) and show the gas being accelerated to terminal expansion velocities near 30 km/sec. The observations reveal a method for determining the position of the central star on VLBI maps of OH maser emission to an accuracy of approximately 0.2 arcsec. A firm lower limit of 2 x 10 to the 15th/sq cm is obtained for the NH3 column density in VY Canis Majoris.

  7. Infrared observations of circumstellar ammonia in OH/IR supergiants

    International Nuclear Information System (INIS)

    McLaren, R.A.; Betz, A.L.

    1980-01-01

    Ammonia has been detected in the circumstellar envelopes of VY Canis Majoris, VX Sagittarii, and IRC+10420 by means of several absorption lines in the ν 2 vibration-rotation band near 950 cm -1 . The line profiles are well resolved (0.2 km s -1 resolution) and show the gas being accelerated to terminal expansion velocities near 30 km s -1 . The observations reveal a method for determining the position of the central star on VLBI maps of OH maser emission to an accuracy of approx.0''.2. A firm lower limit of 2 x 10 15 cm -2 is obtained for the NH 3 column density in VY Canis Majoris

  8. Astrobiological Effects of Stellar Radiation in Circumstellar Environments

    Science.gov (United States)

    Cuntz, Manfred; Gurdemir, Levent; Guinan, Edward F.; Kurucz, Robert L.

    2006-10-01

    The centerpiece of all life on Earth is carbon-based biochemistry. Previous scientific research has suggested that biochemistry based on carbon may also play a decisive role in extraterrestrial life forms, i.e., alien life outside of Earth, if existent. In the following, we explore if carbon-based macromolecules (such as DNA) in the environments of stars other than the Sun are able to survive the effects of energetic stellar radiation, such as UV-C in the wavelength band between 200 and 290 nm. We focus on main-sequence stars akin to the Sun, but of hotter (F-type stars) and cooler (K- and M-type stars) surface temperature. Emphasis is placed on investigating the radiative environment in stellar habitable zones (HZs). Stellar habitable zones have an important relevance in astrobiology because they constitute circumstellar regions in which a planet of suitable size can have surface temperatures for water to exist in liquid form.

  9. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  10. Antimagnets: controlling magnetic fields with superconductor-metamaterial hybrids

    International Nuclear Information System (INIS)

    Sanchez, Alvaro; Navau, Carles; Prat-Camps, Jordi; Chen Duxing

    2011-01-01

    Magnetism is very important in various areas of science and technology, ranging from magnetic recording through energy generation to trapping cold atoms. Physicists have managed to master magnetism-to create and manipulate magnetic fields-almost at will. Surprisingly, there is at least one property that has been elusive until now: how to 'switch off' the magnetic interaction of a magnetic material with existing magnetic fields without modifying them. Here we introduce the antimagnet, a design that conceals the magnetic response of a given volume from its exterior, without altering the external magnetic fields, in some respects analogous to recent theoretical proposals for cloaking electromagnetic waves with metamaterials. However, unlike these devices, which require extreme material properties, our device is feasible and needs only two kinds of available materials: superconductors and isotropic magnetic materials. Antimagnets may have applications in magnetic-based medical techniques such as magnetic resonance imaging or in reducing the magnetic signature of vessels or planes.

  11. Plasma edge control by chaotic magnetic field structures. Book of abstracts

    International Nuclear Information System (INIS)

    2013-01-01

    The following topics were dealt with: Formation of stochastic magnetic layers and plasma response to external, non-axisymmetric magnetic perturbations, energy and particle transport in stochastic magnetic fields and 3D equilibria, application of resonant magnetic perturbations for ELM control and implications for ITER, transport and exhaust in helical and island divertors. (HSI)

  12. Study at radio wavelengths of circumstellar envelopes around red giants

    International Nuclear Information System (INIS)

    Do Thi Hoai

    2015-01-01

    The thesis studies mass losing AGB stars and their circumstellar environments, with focus on the development of stellar outflows and their interaction with the surrounding medium. It uses emission from two tracers: carbon monoxide (CO), through its rotational lines in the millimeter range, probes the inner regions of the circumstellar shells out to photodissociation distances, while atomic hydrogen (HI, 21 cm) is better suited to the study of the external regions. The high spectral and spatial resolutions achieved in radio observations allow for a detailed exploration of the kinematics of the relatively slow outflows of red giants. After having introduced the subject, I discuss the case of an S-type star (RS Cnc) that has been observed in CO with the IRAM telescopes, as well as in HI with the VLA, concentrating on the modelling of the spatially resolved CO line profiles and illustrating the complementarity between HI and CO. Results of the CO modelling of other AGB stars observed at IRAM (EP Aqr, XHer and RXBoo) and of a post-AGB star observed with ALMA, the Red Rectangle, are also presented. The formation of the HI line profile in various cases of mass losing AGB stars, in particular YCVn for which a model is presented, is studied next, exploring several effects that might explain the lack of detected emission from stars with high mass loss rates. Similarities between the bipolar outflows of the AGB stars that have been studied, all having mass loss rates in the region of 10"-"7 solar masses per year and displaying nearly spherical morphologies are discussed together with the information on the gas temperature obtained from the simultaneous observation of two CO lines. (author)

  13. Circumstellar grain extinction properties of recently discovered post AGB stars

    International Nuclear Information System (INIS)

    Buss, R.H. Jr.; Lamers, H.J.G.L.M.; Snow, T.P. Jr.

    1989-01-01

    The circumstellar grains of two hot evolved post asymptotic giant branch (post AGB) stars, HD 89353 and HD 213985 were examined. From ultraviolet spectra, energy balance of the flux, and Kurucz models, the extinction around 2175 A was derived. With visual spectra, an attempt was made to detect 6614 A diffuse band absorption arising from the circumstellar grains so that we could examine the relationship of these features to the infrared features. For both stars, we did not detect any diffuse band absorption at 6614 A, implying the carrier of this diffuse band is not the carrier of the unidentified infrared features not of the 2175 A bump. The linear ultraviolet extinction of the carbon-rich star HD 89353 was determined to continue across the 2175 A region with no sign of the bump; for HD 213985 it was found to be the reverse: a strong, wide bump in the mid-ultraviolet. The 213985 bump was found to be positioned at 2340 A, longward of its usual position in the interstellar medium. Since HD 213985 was determined to have excess carbon, the bump probably arises from a carbonaceous grain. Thus, in view of the ultraviolet and infrared properties of the two post AGB stars, ubiquitous interstellar infrared emission features do not seem to be associated with the 2175 A bump. Instead, the infrared features seem related to the linear ultraviolet extinction component: hydrocarbon grains of radius less than 300 A are present with the linear HD 89353 extinction; amorphous anhydrous carbonaceous grains of radius less than 50 A might cause the shifted ultraviolet extinction bump of HD 213985

  14. Fuzzy self-learning control for magnetic servo system

    Science.gov (United States)

    Tarn, J. H.; Kuo, L. T.; Juang, K. Y.; Lin, C. E.

    1994-01-01

    It is known that an effective control system is the key condition for successful implementation of high-performance magnetic servo systems. Major issues to design such control systems are nonlinearity; unmodeled dynamics, such as secondary effects for copper resistance, stray fields, and saturation; and that disturbance rejection for the load effect reacts directly on the servo system without transmission elements. One typical approach to design control systems under these conditions is a special type of nonlinear feedback called gain scheduling. It accommodates linear regulators whose parameters are changed as a function of operating conditions in a preprogrammed way. In this paper, an on-line learning fuzzy control strategy is proposed. To inherit the wealth of linear control design, the relations between linear feedback and fuzzy logic controllers have been established. The exercise of engineering axioms of linear control design is thus transformed into tuning of appropriate fuzzy parameters. Furthermore, fuzzy logic control brings the domain of candidate control laws from linear into nonlinear, and brings new prospects into design of the local controllers. On the other hand, a self-learning scheme is utilized to automatically tune the fuzzy rule base. It is based on network learning infrastructure; statistical approximation to assign credit; animal learning method to update the reinforcement map with a fast learning rate; and temporal difference predictive scheme to optimize the control laws. Different from supervised and statistical unsupervised learning schemes, the proposed method learns on-line from past experience and information from the process and forms a rule base of an FLC system from randomly assigned initial control rules.

  15. Fuzzy Impulsive Control of Permanent Magnet Synchronous Motors

    International Nuclear Information System (INIS)

    Dong, Li; Shi-Long, Wang; Xiao-Hong, Zhang; Dan, Yang; Hui, Wang

    2008-01-01

    The permanent magnet synchronous motors (PMSMs) may experience chaotic behaviours with systemic parameters falling into a certain area or under certain working conditions, which threaten the secure and stable operation of motor-driven. Hence, it is important to study the methods of controlling or suppressing chaos in PMSMs. In this work, the Takagi–Sugeno (T-S) fuzzy impulsive control model for PMSMs is established via the T-S modelling methodology and impulsive technology. Based on the new model, the control conditions of asymptotical stability and exponential stability for PMSMs have been derived by the Lyapunov method. Finally, an illustrated example is also given to show the effectiveness of the obtained results

  16. Global modelling of magnetic island control in tokamaks

    International Nuclear Information System (INIS)

    Fevrier, Olivier

    2016-01-01

    Magneto-Hydro-Dynamic (MHD) instabilities are susceptible to develop within a tokamak plasma. These instabilities manifest themselves as magnetic islands which reduce the plasma confinement. The islands can however be controlled by driving current inside them. In this thesis, we consider the modeling of the magnetic islands and their control using first principle approaches, which rely on a global MHD description of the plasma. We have detailed the inclusion a RF-driven current like source term in an MHD code, which requires special care to be given to the modeling of the current density evolution. The implementation has been benchmarked against the asymptotic models, allowing us to retrieve the influence of parameters such as deposition width or misalignment with respect to the island width and position. Beyond these aspects, we have evidenced new effects, linked to the 3D nature of the current deposition. We have observed a flip instability in which an island, reduced by the ECCD, brutally inverse its phase so that its X-Point faces the current deposition, allowing the mode the grow further. We then moved on to the topic of the best suitable control strategies for the control of the island. We have implemented in XTOR a control system that mimics the experimental ones and adapt the current deposition in function of a preset strategy. Nonlinear MHD simulations have been carried out using different control schemes, allowing us to quantify the gain to expect from each of these methods depending on the characteristics of the current deposition. (author) [fr

  17. Impulsive control of permanent magnet synchronous motors with parameters uncertainties

    International Nuclear Information System (INIS)

    Li Dong; Zhang Xiaohong; Wang Shilong; Yan Dan; Wang Hui

    2008-01-01

    The permanent magnet synchronous motors (PMSMs) may have chaotic behaviours for the uncertain values of parameters or under certain working conditions, which threatens the secure and stable operation of motor-driven. It is important to study methods of controlling or suppressing chaos in PMSMs. In this paper, robust stabilities of PMSM with parameter uncertainties are investigated. After the uncertain matrices which represent the variable system parameters are formulated through matrix analysis, a novel asymptotical stability criterion is established. Some illustrated examples are also given to show the effectiveness of the obtained results

  18. Controlling Magnetism of a Complex Metallic System Using Atomic Individualism

    Science.gov (United States)

    Mudryk, Y.; Paudyal, D.; Pecharsky, V. K.; Gschneidner, K. A., Jr.; Misra, S.; Miller, G. J.

    2010-08-01

    When the complexity of a metallic compound reaches a certain level, a specific location in the structure may be critically responsible for a given fundamental property of a material while other locations may not play as much of a role in determining such a property. The first-principles theory has pinpointed a critical location in the framework of a complex intermetallic compound—Gd5Ge4—that resulted in a controlled alteration of the magnetism of this compound using precise chemical tools.

  19. Use of electro-magnetic damping for vibration control

    DEFF Research Database (Denmark)

    Stein, George Juraj; Darula, Radoslav; Sorokin, Sergey

    2012-01-01

    to introduce additional electromagnetic damping into vibrating mechanical system. The hysteretic losses and eddy currents are included in the model, to take into account more realistic dynamic behaviour of the system. The mathematical model of the controller is derived using lumped parameter approach......Vibration of machines is an unwanted phenomenon, and it is usually of interest to eliminate it. There are various means to be used in order to reach the goal, where the utilization of the electromagnet augmented by an external shunt circuit is analyzed in the paper. The magnetic force is used...

  20. A fuzzy control technique for a magnetically levitated system

    Energy Technology Data Exchange (ETDEWEB)

    Lo Verso, G [C.N.R., Ce.Ri.S.E.P., Palermo (Italy); Trapanese, M [Dipt. di Ingegneria Elettrica, Univ. di Palermo (Italy)

    1996-12-31

    This paper presents the results of some analytical and numerical investigations on a control approach for magnetically leviated systems. This approach is based on fuzzy logic. It has been widely demonstrated that traditional control systems consent to maintain a stiff control on the air gap length. However, the traditional approaches could cause at very high speed, a vertical acceleration of the vehicle cabin larger than the maximum value currently allowed by the ISO standard. It is aim of this work to investigate the possibilities that a fuzzy controller offer in order to solve this problem. In order set up the controller, every mechanical degree of freedom is modelled in terms of some linguistic variables. These linguistic variables are described by several fuzzy sets. It must be noted that, doing so, the disturbances can be described in terms of fuzzy sets, too. A single-mass-model of the vehicle is considered in the paper. The features of the controller are numerically simulated under several types of disturbances and they are compared with a traditional control approach. It is shown how some parameters (especially the vertical acceleration) improve their behaviour. (orig.)

  1. Force analysis of magnetic bearings with power-saving controls

    International Nuclear Information System (INIS)

    Johnson, D.; Brown, G.V.; Inman, D.J.

    1992-01-01

    Most magnetic bearing control schemes use a bias current with a superimposed control current to linearize the relationship between the control current and the force it delivers. For most operating conditions, the existence of the bias current requires more power than alternative methods that do not use conventional bias. Two such methods are examined which diminish or eliminate bias current. In the typical bias control scheme it is found that for a harmonic control force command into a voltage limited transconductance amplifier, the desired force output is obtained only up to certain combinations of force amplitude and frequency. Above these values, the force amplitude is reduced and a phase lag occurs. The power saving alternative control schemes typically exhibit such deficiencies at even lower command frequencies and amplitudes. To assess the severity of these effects, a time history analysis of the force output is performed for the bias method and the alternative methods. Results of the analysis show that the alternative approaches may be viable. The various control methods examined were mathematically modeled using nondimensionalized variables to facilitate comparison of the various methods

  2. Method and apparatus for control of a magnetic structure

    Science.gov (United States)

    Challenger, Michael P.; Valla, Arthur S.

    1996-06-18

    A method and apparatus for independently adjusting the spacing between opposing magnet arrays in charged particle based light sources. Adjustment mechanisms between each of the magnet arrays and the supporting structure allow the gap between the two magnet arrays to be independently adjusted. In addition, spherical bearings in the linkages to the magnet arrays permit the transverse angular orientation of the magnet arrays to also be adjusted. The opposing magnet arrays can be supported above the ground by the structural support.

  3. Design of permanent magnet synchronous motor speed loop controller based on sliding mode control algorithm

    Science.gov (United States)

    Qiang, Jiang; Meng-wei, Liao; Ming-jie, Luo

    2018-03-01

    Abstract.The control performance of Permanent Magnet Synchronous Motor will be affected by the fluctuation or changes of mechanical parameters when PMSM is applied as driving motor in actual electric vehicle,and external disturbance would influence control robustness.To improve control dynamic quality and robustness of PMSM speed control system, a new second order integral sliding mode control algorithm is introduced into PMSM vector control.The simulation results show that, compared with the traditional PID control,the modified control scheme optimized has better control precision and dynamic response ability and perform better with a stronger robustness facing external disturbance,it can effectively solve the traditional sliding mode variable structure control chattering problems as well.

  4. The application of moving average control charts for evaluating magnetic field quality on an individual magnet basis

    International Nuclear Information System (INIS)

    Pollock, D.A.; Gunst, R.F.; Schucany, W.R.

    1994-01-01

    SSC Collider Dipole Magnet field quality specifications define limits of variation for the population mean (Systematic) and standard deviation (RMS deviation) of allowed and unallowed multipole coefficients generated by the full collection of dipole magnets throughout the Collider operating cycle. A fundamental Quality Control issue is how to determine the acceptability of individual magnets during production, in other words taken one at a time and compared to the population parameters. Provided that the normal distribution assumptions hold, the random variation of multipoles for individual magnets may be evaluated by comparing the measured results to ± 3 x RMS tolerance, centered on the design nominal. To evaluate the local and cumulative systematic variation of the magnets against the distribution tolerance, individual magnet results need to be combined with others that come before it. This paper demonstrates a Statistical Quality Control method (the Unweighted Moving Average control chart) to evaluate individual magnet performance and process stability against population tolerances. The DESY/HERA Dipole cold skew quadrupole measurements for magnets in production order are used to evaluate non-stationarity of the mean over time for the cumulative set of magnets, as well as for a moving sample

  5. New magnetic real time shape control for MAST

    Energy Technology Data Exchange (ETDEWEB)

    Pangione, L., E-mail: luigi.pangione@ccfe.ac.uk [EURATOM/CCFE Fusion Association – Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); McArdle, G.; Storrs, J. [EURATOM/CCFE Fusion Association – Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom)

    2013-10-15

    Highlights: ► New magnetic shape control system has been implemented. ► It has been intensively tested in a simulation environment. ► A tool chain to produce LTI model and simulate its behaviour has been implemented. ► Experimental results are shown. -- Abstract: The Mega Ampere Spherical Tokamak (MAST) real time plasma position controller is based on an optical linear camera placed on the mid plane of the vessel. This solution has the advantage of being a direct observation of the D{sub α} emissions coming from the interaction between the boundary of the plasma and neutral gas, but, on the other hand, it restricts the control to the outer radius of the plasma only. A complete chain of tools has been set up to implement, test and simulate a new real time magnetic plasma shape controller based on the rtEFIT code. The complete working path consists of three elements: a linear static relationship between control parameters and current demands, a linear state space model needed to represent the plasma dynamic response in closed loop simulations, and the possibility to run simulations inside the Plasma Control System (PCS). The linear relationship has been calculated using the FIESTA code, which is developed using Matlab at CCFE. The linear state space model was generated using the CREATE-L code developed by the CREATE Consortium. It has already been successfully used to model JET, FTU and TCV tokamaks. Using this working path many simulations have been carried out allowing fine tuning of the control gains before the real experiment. The simulation testing includes the plasma shape control law as implemented in PCS itself, so intensive debugging has been possible prior to operation. Successful control using rtEFIT was established in the second dedicated experiment during the MAST 2011–12 campaign. This work is a stepping stone towards divertor control which is ultimately intended for application to the super-X divertor in the MAST Upgrade experiment.

  6. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  7. Research on single-chip microcomputer controlled rotating magnetic field mineralization model

    Science.gov (United States)

    Li, Yang; Qi, Yulin; Yang, Junxiao; Li, Na

    2017-08-01

    As one of the method of selecting ore, the magnetic separation method has the advantages of stable operation, simple process flow, high beneficiation efficiency and no chemical environment pollution. But the existing magnetic separator are more mechanical, the operation is not flexible, and can not change the magnetic field parameters according to the precision of the ore needed. Based on the existing magnetic separator is mechanical, the rotating magnetic field can be used for single chip microcomputer control as the research object, design and trial a rotating magnetic field processing prototype, and through the single-chip PWM pulse output to control the rotation of the magnetic field strength and rotating magnetic field speed. This method of using pure software to generate PWM pulse to control rotary magnetic field beneficiation, with higher flexibility, accuracy and lower cost, can give full play to the performance of single-chip.

  8. Control of Internal Transport Barriers in Magnetically Confined Fusion Plasmas

    Science.gov (United States)

    Panta, Soma; Newman, David; Sanchez, Raul; Terry, Paul

    2016-10-01

    In magnetic confinement fusion devices the best performance often involves some sort of transport barriers to reduce the energy and particle flow from core to edge. Those barriers create gradients in the temperature and density profiles. If gradients in the profiles are too steep that can lead to instabilities and the system collapses. Control of these barriers is therefore an important challenge for fusion devices (burning plasmas). In this work we focus on the dynamics of internal transport barriers. Using a simple 7 field transport model, extensively used for barrier dynamics and control studies, we explore the use of RF heating to control the local gradients and therefore the growth rates and shearing rates for barrier initiation and control in self-heated fusion plasmas. Ion channel barriers can be formed in self-heated plasmas with some NBI heating but electron channel barriers are very sensitive. They can be formed in self-heated plasmas with additional auxiliary heating i.e. NBI and radio-frequency(RF). Using RF heating on both electrons and ions at proper locations, electron channel barriers along with ion channel barriers can be formed and removed demonstrating a control technique. Investigating the role of pellet injection in controlling the barriers is our next goal. Work supported by DOE Grant DE-FG02-04ER54741.

  9. The chemistry in circumstellar envelopes of evolved stars: following the origin of the elements to the origin of life.

    Science.gov (United States)

    Ziurys, Lucy M

    2006-08-15

    Mass loss from evolved stars results in the formation of unusual chemical laboratories: circumstellar envelopes. Such envelopes are found around carbon- and oxygen-rich asymptotic giant branch stars and red supergiants. As the gaseous material of the envelope flows from the star, the resulting temperature and density gradients create a complex chemical environment involving hot, thermodynamically controlled synthesis, molecule "freeze-out," shock-initiated reactions, and photochemistry governed by radical mechanisms. In the circumstellar envelope of the carbon-rich star IRC+10216, >50 different chemical compounds have been identified, including such exotic species as C(8)H, C(3)S, SiC(3), and AlNC. The chemistry here is dominated by molecules containing long carbon chains, silicon, and metals such as magnesium, sodium, and aluminum, which makes it quite distinct from that found in molecular clouds. The molecular composition of the oxygen-rich counterparts is not nearly as well explored, although recent studies of VY Canis Majoris have resulted in the identification of HCO(+), SO(2), and even NaCl in this object, suggesting chemical complexity here as well. As these envelopes evolve into planetary nebulae with a hot, exposed central star, synthesis of molecular ions becomes important, as indicated by studies of NGC 7027. Numerous species such as HCO(+), HCN, and CCH are found in old planetary nebulae such as the Helix. This "survivor" molecular material may be linked to the variety of compounds found recently in diffuse clouds. Organic molecules in dense interstellar clouds may ultimately be traced back to carbon-rich fragments originally formed in circumstellar shells.

  10. Controlled trapping and detection of magnetic particles by a magnetic microactuator and a giant magnetoresistance (GMR) sensor

    KAUST Repository

    Giouroudi, Ioanna; Gooneratne, Chinthaka Pasan; Kokkinis, Georgios

    2014-01-01

    This paper presents the design and testing of an integrated micro-chip for the controlled trapping and detection of magnetic particles (MPs). A unique magnetic micro-actuator consisting of square-shaped conductors is used to manipulate the MPs

  11. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  12. Controlling magnetic and electric dipole modes in hollow silicon nanocylinders.

    Science.gov (United States)

    van de Haar, Marie Anne; van de Groep, Jorik; Brenny, Benjamin J M; Polman, Albert

    2016-02-08

    We propose a dielectric nanoresonator geometry consisting of hollow dielectric nanocylinders which support geometrical resonances. We fabricate such hollow Si particles with an outer diameter of 108-251 nm on a Si substrate, and determine their resonant modes with cathodo-luminescence (CL) spectroscopy and optical dark-field (DF) scattering measurements. The scattering behavior is numerically investigated in a systematic fashion as a function of wavelength and particle geometry. We find that the additional design parameter as a result of the introduction of a center gap can be used to control the relative spectral spacing of the resonant modes, which will enable additional control over the angular radiation pattern of the scatterers. Furthermore, the gap offers direct access to the enhanced magnetic dipole modal field in the center of the particle.

  13. Single axis control of ball position in magnetic levitation system using fuzzy logic control

    Science.gov (United States)

    Sahoo, Narayan; Tripathy, Ashis; Sharma, Priyaranjan

    2018-03-01

    This paper presents the design and real time implementation of Fuzzy logic control(FLC) for the control of the position of a ferromagnetic ball by manipulating the current flowing in an electromagnet that changes the magnetic field acting on the ball. This system is highly nonlinear and open loop unstable. Many un-measurable disturbances are also acting on the system, making the control of it highly complex but interesting for any researcher in control system domain. First the system is modelled using the fundamental laws, which gives a nonlinear equation. The nonlinear model is then linearized at an operating point. Fuzzy logic controller is designed after studying the system in closed loop under PID control action. The controller is then implemented in real time using Simulink real time environment. The controller is tuned manually to get a stable and robust performance. The set point tracking performance of FLC and PID controllers were compared and analyzed.

  14. Study on control method of running velocity for the permanent magnet-HTSC hybrid magnetically levitated conveyance system

    International Nuclear Information System (INIS)

    Nishio, R.; Ikeda, M.; Sasaki, R.; Ohashi, S.

    2011-01-01

    The hybrid magnetically levitated carrying system is developed. Control method of running velocity of the carrier is studied. Running velocity is controlled by current of the propulsion coils. Propulsion characteristcs are improved. We have developed the magnetically levitated carrying system. In this system, pinning force of high temperature bulk super conductor (HTSC) is used for the levitation and guidance. Four HTSCs are installed on the carrier. The magnetic rail is set on the ground, and flux from the magnetic rail is pinned by HTSCs. To increase levitation force, repulsive force of the permanent magnet is used. The hybrid levitation system is composed. The permanent magnet is installed under the load stage of the carrier. Repulsive force by the permanent magnet between the load stage on the carrier and the magnetic rail on the ground is used to support the load weight. Levitation and guidance one by pinning effect of the YBaCuO HTSC in the carrier is used to levitate the carrier body. The load stage is separated from the carrier flame and can move freely for vertical direction levitation. For the propulsion system, electromagnet is installed on the surface of the magnetic rail. In this paper, control method of running velocity of the carrier is studied. Propulsion force is given as follows; Air core copper coils are installed on the magnetic rail. Interaction between current of these coils and permanent magnets on the carrier generates propulsion force. Running velocity is controlled by current of the propulsion coils. It is also changed by position of the carrier and the load weight. From the results, stability of the propulsion system is given, and propulsion characteristics are improved.

  15. Study on control method of running velocity for the permanent magnet-HTSC hybrid magnetically levitated conveyance system

    Energy Technology Data Exchange (ETDEWEB)

    Nishio, R.; Ikeda, M.; Sasaki, R. [Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan); Ohashi, S., E-mail: ohashi@kansai-u.ac.jp [Kansai University, 3-3-35 Yamate-cho, Suita, Osaka 564-8680 (Japan)

    2011-11-15

    The hybrid magnetically levitated carrying system is developed. Control method of running velocity of the carrier is studied. Running velocity is controlled by current of the propulsion coils. Propulsion characteristcs are improved. We have developed the magnetically levitated carrying system. In this system, pinning force of high temperature bulk super conductor (HTSC) is used for the levitation and guidance. Four HTSCs are installed on the carrier. The magnetic rail is set on the ground, and flux from the magnetic rail is pinned by HTSCs. To increase levitation force, repulsive force of the permanent magnet is used. The hybrid levitation system is composed. The permanent magnet is installed under the load stage of the carrier. Repulsive force by the permanent magnet between the load stage on the carrier and the magnetic rail on the ground is used to support the load weight. Levitation and guidance one by pinning effect of the YBaCuO HTSC in the carrier is used to levitate the carrier body. The load stage is separated from the carrier flame and can move freely for vertical direction levitation. For the propulsion system, electromagnet is installed on the surface of the magnetic rail. In this paper, control method of running velocity of the carrier is studied. Propulsion force is given as follows; Air core copper coils are installed on the magnetic rail. Interaction between current of these coils and permanent magnets on the carrier generates propulsion force. Running velocity is controlled by current of the propulsion coils. It is also changed by position of the carrier and the load weight. From the results, stability of the propulsion system is given, and propulsion characteristics are improved.

  16. Circumstellar matter and the nature of the SN1987A progenitor star

    International Nuclear Information System (INIS)

    Chevalier, R.A.; Fransson, C.

    1987-01-01

    The radio observations of the supernova SN1987A can be interpreted in terms of its interaction with circumstellar matter. The early turn-on of the radio emission implies a relatively low density circumstellar medium. The optical properties of the supernova imply that the progenitor star had a smaller radius than that of a typical type II supernova progenitor. The mass loss properties are consistent with this hypothesis. The authors predict the thermal X-ray luminosity of the supernova, and note that it is below the current upper limit. A bright infrared dust echo is not expected. Weak ultraviolet emission lines from circumstellar gas may be visible. Although the circumstellar density is low, it is possible that the progenitor star did lose a substantial fraction of its mass prior to the supernova explosion. (author)

  17. Neural networks based three-axis satellite attitude control using only magnetic torquers

    International Nuclear Information System (INIS)

    Sivaprakash, N.; Shanmugam, J.; Natarajan, P.

    2005-01-01

    Full text: Magnetic control is a favorable way to stabilize small satellites. Often, the hardware is simple and lightweight, and does not degrade or change mass over time. However, a magnetic control system does have some disadvantages and limitations. The control, which is in the form of magnetic moment, can only be applied perpendicular to the local magnetic field. In addition, there is uncertainty in the Earth magnetic field models due to the complicated dynamic nature of the field. Also, the magnetic hardware and the spacecraft can interact, causing both to behave in undesirable ways. To overcome these limitations some intelligence is incorporated in the controller. In this paper, control laws are developed to stabilize spacecraft on Three axes. The motivation for this project is ANUSAT, which is a micro-satellite under development at Anna University in collaboration with ISRO. This control could be carried out solely with satellite's magnetometer measurements and its position in orbit. The magnetic dipole moment for control is: M = K p (B o - B r ) + K d (dB o /dt - dB r /dt) Where B o is the measured magnetic field, B r is the reference magnetic field, and K p and K d are the control position and rate gains respectively. The value of the controller gains are selected by the Intelligent Neural Network System in the feedback path. Control laws are numerically tested to show that the magnetic control system works within resolution limits

  18. Circumstellar ammonia in oxygen-rich evolved stars

    Science.gov (United States)

    Wong, K. T.; Menten, K. M.; Kamiński, T.; Wyrowski, F.; Lacy, J. H.; Greathouse, T. K.

    2018-04-01

    Context. The circumstellar ammonia (NH3) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH3 abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. Aims: We would like to characterise the spatial distribution and excitation of NH3 in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420. Methods: We observed NH3 emission from the ground state in the inversion transitions near 1.3 cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH3 rovibrational absorption lines in the ν2 band near 10.5 μm with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). We also attempted to search for the rotational transition within the excited vibrational state (v2 = 1) near 2 mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH3 in the CSEs of these targets. Results: We detected NH3 inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH3 is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH3 abundance relative to molecular hydrogen is generally of the order of 10-7, which is a few times lower than previous estimates that were made without considering radiative

  19. Control of magnetism in dilute magnetic semiconductor (Ga,Mn)As films by surface decoration of molecules

    Science.gov (United States)

    Wang, Hailong; Wang, Xiaolei; Xiong, Peng; Zhao, Jianhua

    2016-03-01

    The responses of magnetic moments to external stimuli such as magnetic-field, heat, light and electric-field have been utilized to manipulate the magnetism in magnetic semiconductors, with many of the novel ideas applied even to ferromagnetic metals. Here, we review a new experimental development on the control of magnetism in (Ga,Mn)As thin films by surface decoration of organic molecules: Molecules deposited on the surface of (Ga,Mn)As thin films are shown to be capable of significantly modulating their saturation magnetization and Curie temperature. These phenomena are shown to originate from the carrier-mediated ferromagnetism in (Ga,Mn)As and the surface molecules acting as acceptors or donors depending on their highest occupied molecular orbitals, resembling the charge transfer mechanism in a pn junction in which the equilibrium state is reached on the alignment of Fermi levels.

  20. Control of magnetism in dilute magnetic semiconductor (Ga,MnAs films by surface decoration of molecules

    Directory of Open Access Journals (Sweden)

    Hailong eWang

    2016-03-01

    Full Text Available The responses of magnetic moments to external stimuli such as magnetic-field, heat, light and electric-field have been utilized to manipulate the magnetism in magnetic semiconductors, with many of the novel ideas applied even to ferromagnetic metals. Here, we review a new experimental development on the control of magnetism in (Ga,MnAs thin films by surface decoration of organic molecules: Molecules deposited on the surface of (Ga,MnAs thin films are shown to be capable of significantly modulating their saturation magnetization and Curie temperature. These phenomena are shown to originate from the carrier-mediated ferromagnetism in (Ga,MnAs and the surface molecules acting as acceptors or donors depending on their highest occupied molecular orbitals, resembling the charge transfer mechanism in a pn junction in which the equilibrium state is reached on the alignment of Fermi levels.

  1. Physics responsible for heating efficiency and self-controlled temperature rise of magnetic nanoparticles in magnetic hyperthermia therapy.

    Science.gov (United States)

    Shaterabadi, Zhila; Nabiyouni, Gholamreza; Soleymani, Meysam

    2018-03-01

    Magnetic nanoparticles as heat-generating nanosources in hyperthermia treatment are still faced with many drawbacks for achieving sufficient clinical potential. In this context, increase in heating ability of magnetic nanoparticles in a biologically safe alternating magnetic field and also approach to a precise control on temperature rise are two challenging subjects so that a significant part of researchers' efforts has been devoted to them. Since a deep understanding of Physics concepts of heat generation by magnetic nanoparticles is essential to develop hyperthermia as a cancer treatment with non-adverse side effects, this review focuses on different mechanisms responsible for heat dissipation in a radio frequency magnetic field. Moreover, particular attention is given to ferrite-based nanoparticles because of their suitability in radio frequency magnetic fields. Also, the key role of Curie temperature in suppressing undesired temperature rise is highlighted. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Control of ITBs in Magnetically Confined Burning Plasmas

    Science.gov (United States)

    Panta, S. R.; Newman, D. E.; Terry, P. W.; Sanchez, R.

    2017-10-01

    In the magnetically confined burning plasma devices (in this case Tokamaks), internal transport barriers (ITBs) are those regimes in which the turbulence is suppressed by the E X B velocity shear, reducing the turbulent transport. This often occurs at a critical gradient in the profiles. The change in the transport then modifies the density and temperature profiles feeding back on the system. These transport barriers have to be controlled both to form them for improved confinement and remove them to both prevent global instabilities and to remove the ash and unnecessary impurities in the device. In this work we focus on pellet injection and modulated RF heating as a way to trigger and control the ITBs. These have an immediate consequence on density and temperature and hence pressure profiles acting as a control knob. For example, depending upon pellet size and its radial position of injection, it either helps to form or strengthen the barrier or to get rid of ITBs in the different transport channels of the burning plasmas. This transport model is then used to investigate the control and dynamics of the transport barriers in burning plasmas using pellets and RF addition to the NBI power and alpha power.

  3. Position feedback control of a nonmagnetic body levitated in magnetic fluid

    International Nuclear Information System (INIS)

    Lee, J H; Nam, Y J; Park, M K; Yamane, R

    2009-01-01

    This paper is concerned with the position feedback control of a magnetic fluid actuator which is characterized by the passive levitation of a nonmagnetic body immersed in a magnetic fluid under magnetic fields. First of all, the magnetic fluid actuator is designed based on the ferrohydrostatic relation. After manufacturing the actuator, its static and dynamic characteristics are investigated experimentally. With the aid of the dynamic governing relation obtained experimentally and the proportional-derivative controller, the position tracking control of the actuator is carried out both theoretically and experimentally. As a result, the applicability of the proposed magnetic fluid actuator to various engineering devices is verified.

  4. Fuzzy Adaptive Model Following Speed Control for Vector Controlled Permanent Magnet Synchronous Motor

    Directory of Open Access Journals (Sweden)

    Baghdad BELABES

    2008-12-01

    Full Text Available In this paper a hybrid controller combining a linear model following controller (LMFC and fuzzy logic control (FLC for speed vector controlled permanent magnet synchronous motor (PMSM is described on this study. The FLC is introduced at the adaptive mechanism level. First, an LMFC system is designed to allow the plant states to be controlled to follow the states produced by a reference model. In the nominal conditions, the model following is perfect and the adaptive mechanism based on the fuzzy logic is idle. Secondly, when parameter variations or external disturbances occur, an augmented signal will be generated by FLC mechanism to preserve the desired model following control performance. The effectiveness and robustness of the proposed controller is demonstrated by some simulation results.

  5. Rapid disappearance of a warm, dusty circumstellar disk.

    Science.gov (United States)

    Melis, Carl; Zuckerman, B; Rhee, Joseph H; Song, Inseok; Murphy, Simon J; Bessell, Michael S

    2012-07-04

    Stars form with gaseous and dusty circumstellar envelopes, which rapidly settle into disks that eventually give rise to planetary systems. Understanding the process by which these disks evolve is paramount in developing an accurate theory of planet formation that can account for the variety of planetary systems discovered so far. The formation of Earth-like planets through collisional accumulation of rocky objects within a disk has mainly been explored in theoretical and computational work in which post-collision ejecta evolution typically is ignored, although recent work has considered the fate of such material. Here we report observations of a young, Sun-like star (TYC 8241 2652 1) where infrared flux from post-collisional ejecta has decreased drastically, by a factor of about 30, over a period of less than two years. The star seems to have gone from hosting substantial quantities of dusty ejecta, in a region analogous to where the rocky planets orbit in the Solar System, to retaining at most a meagre amount of cooler dust. Such a phase of rapid ejecta evolution has not been previously predicted or observed, and no currently available physical model satisfactorily explains the observations.

  6. Formation of polycyclic aromatic hydrocarbons in circumstellar envelopes

    International Nuclear Information System (INIS)

    Frenklach, M.; Feigelson, E.D.

    1989-01-01

    Production of polycyclic aromatic hydrocarbons in carbon-rich circumstellar envelopes was investigated using a kinetic approach. A detailed chemical reaction mechanism of gas-phase PAH formation and growth, containing approximately 100 reactions of 40 species, was numerically solved under the physical conditions expected in cool stellar winds. The chemistry is based on studies of soot production in hydrocarbon pyrolysis and combustion. Several first-ring and second-ring cyclization processes were considered. A linear lumping algorithm was used to describe PAH growth beyond the second aromatic ring. PAH production using this mechanism was examined with respect to a grid of idealized constant velocity stellar winds as well as several published astrophysical models. The basic result is that the onset of PAH production in the interstellar envelopes is predicted to occur within the temperature interval of 1100 to 900 K. The absolute amounts of the PAHs formed, however, are very sensitive to a number of parameters, both chemical and astrophysical, whose values are not accurately known. Astrophysically meaningful quantities of PAHs require particularly dense and slow stellar winds and high initial acetylene abundance. It is suggested that most of the PAHs may be produced in a relatively small fraction of carbon-rich red giants. 87 refs

  7. A WISE survey of circumstellar disks in Taurus

    International Nuclear Information System (INIS)

    Esplin, T. L.; Luhman, K. L.; Mamajek, E. E.

    2014-01-01

    We have compiled photometry at 3.4, 4.6, 12, and 22 μm from the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) for all known members of the Taurus complex of dark clouds. Using these data and photometry from the Spitzer Space Telescope, we have identified members with infrared excess emission from circumstellar disks and have estimated the evolutionary stages of the detected disks, which include 31 new full disks and 16 new candidate transitional, evolved, evolved transitional, and debris disks. We have also used the WISE All-Sky Source Catalog to search for new disk-bearing members of Taurus based on their red infrared colors. Through optical and near-infrared spectroscopy, we have confirmed 26 new members with spectral types of M1-M7. The census of disk-bearing stars in Taurus should now be largely complete for spectral types earlier than ∼M8 (M ≳ 0.03 M ☉ ).

  8. A WISE survey of circumstellar disks in Taurus

    Energy Technology Data Exchange (ETDEWEB)

    Esplin, T. L.; Luhman, K. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Mamajek, E. E., E-mail: taran.esplin@psu.edu [Department of Physics and Astronomy, The University of Rochester, Rochester, NY 14627 (United States)

    2014-04-01

    We have compiled photometry at 3.4, 4.6, 12, and 22 μm from the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) for all known members of the Taurus complex of dark clouds. Using these data and photometry from the Spitzer Space Telescope, we have identified members with infrared excess emission from circumstellar disks and have estimated the evolutionary stages of the detected disks, which include 31 new full disks and 16 new candidate transitional, evolved, evolved transitional, and debris disks. We have also used the WISE All-Sky Source Catalog to search for new disk-bearing members of Taurus based on their red infrared colors. Through optical and near-infrared spectroscopy, we have confirmed 26 new members with spectral types of M1-M7. The census of disk-bearing stars in Taurus should now be largely complete for spectral types earlier than ∼M8 (M ≳ 0.03 M {sub ☉}).

  9. RY Geminorum: an Algol binary with moderate circumstellar emission

    International Nuclear Information System (INIS)

    Hall, D.S.; Eaton, J.A.; Wilson, J.W.; Stuhlinger, T.

    1982-01-01

    RY Gem was observed extensively on the UBV system at two observatories over a period of 13 years. One new time of minimum, JD (Hel.) 2,444,215.490+-0.001 is derived, and a revised ephemeris for epochs since 1950: JD (Hel.)=2,439,732.6328+9sup(d).300567n is presented. Analyses carried out for both the Russell model and the Roche model give consistent values for the geometrical elements of the system: rsub(h)=r 1 =0.093+-0.001, rsub(c)=r 2 =0.2285+-0.0008, i=83 deg.5+-0 deg.2. For any reasonable value of the mass of the hotter component, the system consists of an early A-type star only slightly (Osup(m).5) above the main sequence and a cooler component having the surface temperature and gravity of a K1,3-K4,5 star. The most likely absolute dimensions of the components are M 1 =2.0+-03Msub(sun), R 1 =2.3+-0.1Rsub(sun) and M 2 =0.31+-0.06Msub(sun), R 2 =5.6+-0.2Rsub(sun). The effects of ring emission, which were removed from the observations before they were analyzed, seem to be typical of circumstellar emission in many other long-period Algol systems. (author)

  10. Young Stellar Variability of GM Cephei by Circumstellar Dust Clumps

    Science.gov (United States)

    Huang, Po-Chieh; Chen, Wen-Ping; Hu, Chia-Ling; Burkhonov, Otabek; Ehgamberdiev, Shuhrat; Liu, Jinzhong; Naito, Hiroyuki; Pakstiene, Erika; Qvam, Jan Kare Trandem; Rätz, Stefanie; Semkov, Evgeni

    2018-04-01

    UX Orionis stars are a sub-type of Herbig Ae/be or T Tauri stars exhibiting sporadic extinction of stellar light due to circumstellar dust obscuration. GM Cep is such an UX Orionis star in the young (∼ 4 Myr) open cluster Trumpler 37 at ∼ 900 pc, showing a prominent infrared access, H-alpha emission, and flare activity. Our multi-color photometric monitoring from 2009 to 2016 showed (i) sporadic brightening on a time scale of days due to young stellar accretion, (ii) cyclic, but not strictly periodical, occultation events, each lasting for a couple months, with a probable recurrence time of about two years, (iii) normal dust reddening as the star became redder when dimmer, (iv) the unusual "blueing" phenomena near the brightness minima, during which the star appeared bluer when dimmer, and (v) a noticeable polarization, from 3 to 9 percent in g', r', and i' -bands. The occultation events may be caused by dust clumps, signifying the density inhomogeneity in a young stellar disk from grain coagulation to planetesimal formation. The level of polarization was anti-correlated with the brightness in the bright state, when the dust clump backscattered stellar light. We discussed two potential hypotheses: orbiting dust clumps versus dust clumps along a spiral arm structure.

  11. ALIGNMENT OF PROTOSTARS AND CIRCUMSTELLAR DISKS DURING THE EMBEDDED PHASE

    International Nuclear Information System (INIS)

    Spalding, Christopher; Batygin, Konstantin; Adams, Fred C.

    2014-01-01

    Star formation proceeds via the collapse of a molecular cloud core over multiple dynamical timescales. Turbulence within cores results in a spatially non-uniform angular momentum of the cloud, causing a stochastic variation in the orientation of the disk forming from the collapsing material. In the absence of star-disk angular momentum coupling, such disk-tilting would provide a natural mechanism for the production of primordial spin-orbit misalignments in the resulting planetary systems. However, owing to high accretion rates in the embedded phase of star formation, the inner edge of the circumstellar disk extends down to the stellar surface, resulting in efficient gravitational and accretional angular momentum transfer between the star and the disk. Here, we demonstrate that the resulting gravitational coupling is sufficient to suppress any significant star-disk misalignment, with accretion playing a secondary role. The joint tilting of the star-disk system leads to a stochastic wandering of star-aligned bipolar outflows. Such wandering widens the effective opening angle of stellar outflows, allowing for more efficient clearing of the remainder of the protostar's gaseous envelope. Accordingly, the processes described in this work provide an additional mechanism responsible for sculpting the stellar initial mass function

  12. Macroscopic Magnetization Control by Symmetry Breaking of Photoinduced Spin Reorientation with Intense Terahertz Magnetic Near Field

    Science.gov (United States)

    Kurihara, Takayuki; Watanabe, Hiroshi; Nakajima, Makoto; Karube, Shutaro; Oto, Kenichi; Otani, YoshiChika; Suemoto, Tohru

    2018-03-01

    We exploit an intense terahertz magnetic near field combined with femtosecond laser excitation to break the symmetry of photoinduced spin reorientation paths in ErFeO3 . We succeed in aligning macroscopic magnetization reaching up to 80% of total magnetization in the sample to selectable orientations by adjusting the time delay between terahertz and optical pump pulses. The spin dynamics are well reproduced by equations of motion, including time-dependent magnetic potential. We show that the direction of the generated magnetization is determined by the transient direction of spin tilting and the magnetic field at the moment of photoexcitation.

  13. Research on magnetorheological damper suspension with permanent magnet and magnetic valve based on developed FOA-optimal control algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Ping; Gao, Hong [Anhui Polytechnic University, Wuhu (China); Niu, Limin [Anhui University of Technology, Maanshan (China)

    2017-07-15

    Due to the fail safe problem, it was difficult for the existing Magnetorheological damper (MD) to be widely applied in automotive suspensions. Therefore, permanent magnets and magnetic valves were introduced to existing MDs so that fail safe problem could be solved by the magnets and damping force could be adjusted easily by the magnetic valve. Thus, a new Magnetorheological damper with permanent magnet and magnetic valve (MDPMMV) was developed and MDPMMV suspension was studied. First of all, mechanical structure of existing magnetorheological damper applied in automobile suspensions was redesigned, comprising a permanent magnet and a magnetic valve. In addition, prediction model of damping force was built based on electromagnetics theory and Bingham model. Experimental research was onducted on the newly designed damper and goodness of fit between experiment results and simulated ones by models was high. On this basis, a quarter suspension model was built. Then, fruit Fly optimization algorithm (FOA)-optimal control algorithm suitable for automobile suspension was designed based on developing normal FOA. Finally, simulation experiments and bench tests with input surface of pulse road and B road were carried out and the results indicated that working erformance of MDPMMV suspension based on FOA-optimal control algorithm was good.

  14. Magnetic graphene enabled tunable microwave absorber via thermal control

    Science.gov (United States)

    Quan, L.; Qin, F. X.; Li, Y. H.; Estevez, D.; Fu, G. J.; Wang, H.; Peng, H.-X.

    2018-06-01

    By synthesizing nitrogen-doped graphene (NG) via a facile thermal annealing method, a fine control of the amount and location of doped nitrogen as well as the oxygen-containing functional groups is achieved with varying annealing temperature. The favorable magnetic properties have been achieved for N-doped rGO samples obtained at two temperatures of all NG samples, i.e., 500 °C and 900 °C with saturation magnetization of 0.63 emu g‑1 and 0.67 emu g‑1 at 2 K, respectively. This is attributed to the optimized competition of the N-doping and reduction process at 500 °C and the dominated reduction process at 900 °C. NG obtained at 300 °C affords the best overall absorbing performance: when the absorber thickness is 3.0 mm, the maximum absorption was ‑24.6 dB at 8.51 GHz, and the absorption bandwidth was 4.89 GHz (7.55–12.44 GHz) below ‑10 dB. It owes its large absorbing intensity to the good impedance match and significant dielectric loss. The broad absorption bandwidth benefits from local fluctuations of dielectric responses contributed by competing mechanisms. Despite the significant contribution from materials loss to the absorption, the one quarter-wavelength model is found to be responsible for the reflection loss peak positions. Of particular significance is that an appropriate set of electromagnetic parameters associated with reasonable reduction is readily accessible by convenient control of annealing temperature to modulate the microwave absorbing features of graphene. Thus, NG prepared by thermal annealing promises to be a highly efficient microwave absorbent.

  15. Controlling laser-induced magnetization reversal dynamics in a rare-earth iron garnet across the magnetization compensation point

    Science.gov (United States)

    Deb, Marwan; Molho, Pierre; Barbara, Bernard; Bigot, Jean-Yves

    2018-04-01

    In this work we explore the ultrafast magnetization dynamics induced by femtosecond laser pulses in a doped film of gadolinium iron garnet over a broad temperature range including the magnetization compensation point TM. By exciting the phonon-assisted 6S→4G and 6S→4P electronic d -d transitions simultaneously by one- and two-photon absorption processes, we find out that the transfer of heat energy from the lattice to the spin has, at a temperature slightly below TM, a large influence on the magnetization dynamics. In particular, we show that the speed and the amplitude of the magnetization dynamics can be strongly increased when increasing either the external magnetic field or the laser energy density. The obtained results are explained by a magnetization reversal process across TM. Furthermore, we find that the dynamics has unusual characteristics which can be understood by considering the weak spin-phonon coupling in magnetic garnets. These results open new perspectives for controlling the magnetic state of magnetic dielectrics using an ultrashort optically induced heat pulse.

  16. Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories

    KAUST Repository

    Ivanov, Yurii P.; Chuvilin, Andrey; Lopatin, Sergei; Kosel, Jü rgen

    2016-01-01

    Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.

  17. Modulated Magnetic Nanowires for Controlling Domain Wall Motion: Toward 3D Magnetic Memories

    KAUST Repository

    Ivanov, Yurii P.

    2016-05-03

    Cylindrical magnetic nanowires are attractive materials for next generation data storage devices owing to the theoretically achievable high domain wall velocity and their efficient fabrication in highly dense arrays. In order to obtain control over domain wall motion, reliable and well-defined pinning sites are required. Here, we show that modulated nanowires consisting of alternating nickel and cobalt sections facilitate efficient domain wall pinning at the interfaces of those sections. By combining electron holography with micromagnetic simulations, the pinning effect can be explained by the interaction of the stray fields generated at the interface and the domain wall. Utilizing a modified differential phase contrast imaging, we visualized the pinned domain wall with a high resolution, revealing its three-dimensional vortex structure with the previously predicted Bloch point at its center. These findings suggest the potential of modulated nanowires for the development of high-density, three-dimensional data storage devices. © 2016 American Chemical Society.

  18. Magneto-transport and optical control of magnetization in organic systems: From polymers to molecule-based magnets

    Science.gov (United States)

    Bozdag, Kadriye Deniz

    Organic systems can be synthesized to have various impressive properties such as room temperature magnetism, electrical conductivity as high as conventional metals and magnetic field dependent transport. In this dissertation, we report comprehensive experimental studies in two different classes of organic systems, V-Cr Prussian blue molecule-based magnets and polyaniline nanofiber networks. The first system, V-Cr Prussian blue magnets, belongs to a family of cyano-bridged bi-metallic compounds which display a broad range of interesting photoinduced magnetic properties. A notable example for optically controllable molecule-based magnets is Co-Fe Prussian blue magnet (Tc ˜ 12 K), which exhibits light-induced changes in between magnetic states together with glassy behavior. In this dissertation, the first reports of reversible photoinduced magnetic phenomena in V-Cr Prussian blue analogs and the analysis of its AC and DC magnetization behavior are presented. Optical excitation of V-Cr Prussian blue, one of the few room temperature molecule-based magnets, with UV light (lambda = 350 nm) suppresses magnetization, whereas subsequent excitation with green light (lambda = 514 nm) increases magnetization. The partial recovery effect of green light is observed only when the sample is previously UV-irradiated. Moreover the photoinduced state has a long lifetime at low temperatures (tau > 106 s at T = 10 K) indicating that V-Cr Prussian blue reaches a hidden metastable state upon illumination with UV light. The effects of optical excitation are maintained up to 200 K and completely erased when the sample is warmed above 250 K. Results of detailed magnetic studies and the likely microscopic mechanisms for the photo illumination effects on magnetic properties are discussed. The second organic system, polyaniline nanofiber networks, was synthesized via dilute polymerization and studied at low and high electric and magnetic fields for temperatures 2 K--250 K for their magneto

  19. Enhanced Energy Density in Permanent Magnets using Controlled High Magnetic Field during Processing

    Energy Technology Data Exchange (ETDEWEB)

    Carter, William G [ORNL; Rios, Orlando [ORNL; Constantinides, Steven [ORNL

    2016-05-05

    This ORNL Manufacturing Demonstraction Facility (MDF) technical collaboration focused on the use of high magnetic field processing (>2Tesla) using energy efficient large bore superconducting magnet technology and high frequency electromagnetics to improve magnet performance and reduce the energy budget associated with Alnico thermal processing. Alnico, alloys containing Al, Ni, Co and Fe, represent a class of functional nanostructured alloys, and show the greatest potential for supplementing or replacing commercial Nd-based rare-earth alloy magnets.

  20. Magnetic control of potential microrobotic drug delivery systems: nanoparticles, magnetotactic bacteria and self-propelled microjets

    NARCIS (Netherlands)

    Khalil, I.S.M.; Magdanz, V.; Sanchez, Stefan; Sanchez, S.; Schmidt, O.G.; Abelmann, Leon; Misra, Sarthak

    2013-01-01

    Development of targeted drug delivery systems using magnetic microrobots increases the therapeutic indices of drugs. These systems have to be incorporated with precise motion controllers. We demonstrate closed-loop motion control of microrobots under the influence of controlled magnetic fields.

  1. Two-Dimensional Fuzzy Sliding Mode Control of a Field-Sensed Magnetic Suspension System

    Directory of Open Access Journals (Sweden)

    Jen-Hsing Li

    2014-01-01

    Full Text Available This paper presents the two-dimensional fuzzy sliding mode control of a field-sensed magnetic suspension system. The fuzzy rules include both the sliding manifold and its derivative. The fuzzy sliding mode control has advantages of the sliding mode control and the fuzzy control rules are minimized. Magnetic suspension systems are nonlinear and inherently unstable systems. The two-dimensional fuzzy sliding mode control can stabilize the nonlinear systems globally and attenuate chatter effectively. It is adequate to be applied to magnetic suspension systems. New design circuits of magnetic suspension systems are proposed in this paper. ARM Cortex-M3 microcontroller is utilized as a digital controller. The implemented driver, sensor, and control circuits are simpler, more inexpensive, and effective. This apparatus is satisfactory for engineering education. In the hands-on experiments, the proposed control scheme markedly improves performances of the field-sensed magnetic suspension system.

  2. Speed Control Design of Permanent Magnet Synchronous Motor using TakagiSugeno Fuzzy Logic Control

    Directory of Open Access Journals (Sweden)

    Ahmad Asri Abd Samat

    2017-12-01

    Full Text Available This paper proposes a speed control design of Permanent Magnet Synchronous Motor (PMSM using Field Oriented Control (FOC. The focus is to design a speed control using Takagi — Sugeno Fuzzy Logic Control (T-S FLS. These systems will replace the conventional method which is proportional-integral (PI. The objective of this paper is to study the T—S Fuzzy Inference System (FIS speed regulator and acceleration observer for PMSM. The scope of study basically is to design and analyse the Takagi Sugeno FLC and the PMSM. This paper also will describe the methodology and process of modelling the PMSM including data analysis. The simulation work is implemented in Matlab-Simulink to verify the control method. The effectiveness of this proposed control method was confirmed through various range of speed and torque variation.

  3. Specifications, quality control, manufacturing, and testing of accelerator magnets

    CERN Document Server

    Einfeld, D

    2010-01-01

    The performance of the magnets plays an important role in the functioning of an accelerator. Most of the magnets are designed at the accelerator laboratory and built by industry. The link between the laboratory and the manufacturer is the contract containing the Technical Specifications of the magnets. For an overview of the contents of the Technical Specifications, the specifications for the magnets of ALBA (bending, quadrupole, and sextupole) are described in this paper. The basic rules of magnet design are reviewed in Appendix A.

  4. Closed loop control of the induction heating process using miniature magnetic sensors

    Science.gov (United States)

    Bentley, Anthony E.; Kelley, John Bruce; Zutavern, Fred J.

    2003-05-20

    A method and system for providing real-time, closed-loop control of the induction hardening process. A miniature magnetic sensor located near the outer surface of the workpiece measures changes in the surface magnetic field caused by changes in the magnetic properties of the workpiece as it heats up during induction heating (or cools down during quenching). A passive miniature magnetic sensor detects a distinct magnetic spike that appears when the saturation field, B.sub.sat, of the workpiece has been exceeded. This distinct magnetic spike disappears when the workpiece's surface temperature exceeds its Curie temperature, due to the sudden decrease in its magnetic permeability. Alternatively, an active magnetic sensor can measure changes in the resonance response of the monitor coil when the excitation coil is linearly swept over 0-10 MHz, due to changes in the magnetic permeability and electrical resistivity of the workpiece as its temperature increases (or decreases).

  5. Controllable transport of a skyrmion in a ferromagnetic narrow channel with voltage-controlled magnetic anisotropy

    Science.gov (United States)

    Wang, Junlin; Xia, Jing; Zhang, Xichao; Zhao, G. P.; Ye, Lei; Wu, Jing; Xu, Yongbing; Zhao, Weisheng; Zou, Zhigang; Zhou, Yan

    2018-05-01

    Magnetic skyrmions have potential applications in next-generation spintronic devices with ultralow energy consumption. In this work, the current-driven skyrmion motion in a narrow ferromagnetic nanotrack with voltage-controlled magnetic anisotropy (VCMA) is studied numerically. By utilizing the VCMA effect, the transport of skyrmion can be unidirectional in the nanotrack, leading to a one-way information channel. The trajectory of the skyrmion can also be modulated by periodically located VCMA gates, which protects the skyrmion from destruction by touching the track edge. In addition, the location of the skyrmion can be controlled by adjusting the driving pulse length in the presence of the VCMA effect. Our results provide guidelines for practical realization of the skyrmion-based information channel, diode, and skyrmion-based electronic devices such as racetrack memory.

  6. Network-targeted cerebellar transcranial magnetic stimulation improves attentional control

    Science.gov (United States)

    Esterman, Michael; Thai, Michelle; Okabe, Hidefusa; DeGutis, Joseph; Saad, Elyana; Laganiere, Simon E.; Halko, Mark A.

    2018-01-01

    Developing non-invasive brain stimulation interventions to improve attentional control is extremely relevant to a variety of neurologic and psychiatric populations, yet few studies have identified reliable biomarkers that can be readily modified to improve attentional control. One potential biomarker of attention is functional connectivity in the core cortical network supporting attention - the dorsal attention network (DAN). We used a network-targeted cerebellar transcranial magnetic stimulation (TMS) procedure, intended to enhance cortical functional connectivity in the DAN. Specifically, in healthy young adults we administered intermittent theta burst TMS (iTBS) to the midline cerebellar node of the DAN and, as a control, the right cerebellar node of the default mode network (DMN). These cerebellar targets were localized using individual resting-state fMRI scans. Participants completed assessments of both sustained (gradual onset continuous performance task, gradCPT) and transient attentional control (attentional blink) immediately before and after stimulation, in two sessions (cerebellar DAN and DMN). Following cerebellar DAN stimulation, participants had significantly fewer attentional lapses (lower commission error rates) on the gradCPT. In contrast, stimulation to the cerebellar DMN did not affect gradCPT performance. Further, in the DAN condition, individuals with worse baseline gradCPT performance showed the greatest enhancement in gradCPT performance. These results suggest that temporarily increasing functional connectivity in the DAN via network-targeted cerebellar stimulation can enhance sustained attention, particularly in those with poor baseline performance. With regard to transient attention, TMS stimulation improved attentional blink performance across both stimulation sites, suggesting increasing functional connectivity in both networks can enhance this aspect of attention. These findings have important implications for intervention applications

  7. Multi-function magnetic jack control drive mechanism

    International Nuclear Information System (INIS)

    Bollinger, L.R.; Crawford, D.C.

    1986-01-01

    A multi-function magnetic jack control drive mechanism is described for controlling a nuclear reactor comprising: an elongate pressure housing; closely-spaced drive rods located in the pressure housing, the drive rod being connected to a reactor rod which is insertable in a reactor core; electrochemical stationary latch means which are selectively actuatable for holding a respective one of the drive rods stationary with respect to the pressure housing, the plurality of stationary latch means including at least one coil located about the pressure housing; longitudinally spaced electromechanical movable latch means, individually associated with one of the drive rods and each including a base for the drive rod associated therewith, for, when actuated, holding the associated drive rod stationary with respect to the base associated therewith, the movable latch means including an associated coil located about the pressure housing; and longitudinally spaced electromechanical lift means, individually associated with the base, for, when actuated, moving an associated base longitudinally along the pressure housing from a first position to a second position to thereby enable movement of one or more of the other drive rods longitudinally independently of the other drive rods in response to sequential and repeated operation of the electromechanical means, the lift means including an associated coil located about the pressure housing

  8. Discovery of a Circumstellar Disk in the Lagoon Nebula

    Science.gov (United States)

    1997-04-01

    Circumstellar disks of gas and dust play a crucial role in the formation of stars and planets. Until now, high-resolution images of such disks around young stars within the Orion Nebula obtained with the Hubble Space Telescope (HST) constituted the most direct proof of their existence. Now, another circumstellar disk has been detected around a star in the Lagoon Nebula - also known as Messier 8 (M8) , a giant complex of interstellar gas and dust with many young stars in the southern constellation of Sagittarius and four times more distant than the Orion Nebula. The observations were carried out by an international team of scientists led by Bringfried Stecklum (Thüringer Landessternwarte, Tautenburg, Germany) [1] who used telescopes located at the ESO La Silla observatory and also observations from the HST archive. These new results are paving the road towards exciting research programmes on star formation which will become possible with the ESO Very Large Telescope. The harsh environment of circumstellar disks The existence of circumstellar disks has been inferred from indirect measurements of young stellar objects, such as the spectral energy distribution, the analysis of the profiles of individual spectral lines and measurements of the polarisation of the emitted light [2]. Impressive images of such disks in the Orion Nebula, known as proplyds (PROto-PLanetarY DiskS), have been obtained by the HST during the recent years. They have confirmed the interpretation of previous ground-based emission-line observations and mapping by radio telescopes. Moreover, they demonstrated that those disks which are located close to hot and massive stars are subject to heating caused by the intense radiation from these stars. Subsequently, the disks evaporate releasing neutral gas which streams off. During this process, shock fronts (regions with increased density) with tails of ionised gas result at a certain distance between the disk and the hot star. These objects appear on

  9. ALMA OBSERVATIONS OF HD 141569’s CIRCUMSTELLAR DISK

    Energy Technology Data Exchange (ETDEWEB)

    White, J. A.; Boley, A. C. [Department of Physics and Astronomy, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Hughes, A. M.; Flaherty, K. M. [Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States); Ford, E. [Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802-2111 (United States); Wilner, D.; Payne, M. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Corder, S., E-mail: jawhite@astro.ubc.ca [North American ALMA Science Center, National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903 (United States)

    2016-09-20

    We present ALMA band 7 (345 GHz) continuum and {sup 12}CO( J = 3-2) observations of the circumstellar disk surrounding HD 141569. At an age of about 5 Myr, the disk has a complex morphology that may be best interpreted as a nascent debris system with gas. Our 870 μ m ALMA continuum observations resolve a dust disk out to approximately 56 au from the star (assuming a distance of 116 pc) with 0.″38 resolution and 0.07 mJy beam{sup −1} sensitivity. We measure a continuum flux density for this inner material of 3.8 ± 0.4 mJy (including calibration uncertainties). The {sup 12}CO(3-2) gas is resolved kinematically and spatially from about 30 to 210 au. The integrated {sup 12}CO(3-2) line flux density is 15.7 ± 1.6 Jy km s{sup −1}. We estimate the mass of the millimeter debris and {sup 12}CO(3-2) gas to be ≳0.04 M {sub ⊕} and ∼2 × 10{sup −3} M {sub ⊕}, respectively. If the millimeter grains are part of a collisional cascade, then we infer that the inner disk (<50 au) has ∼160 M {sub ⊕} contained within objects less than 50 km in radius, depending on the planetesimal size distribution and density assumptions. Markov Chain Monte Carlo modeling of the system reveals a disk morphology with an inclination of 53.°4 centered around an M = 2.39 M {sub ⊙} host star ( M sin( i ) = 1.92 M {sub ⊙}). We discuss whether the gas in HD 141569's disk may be second generation. If it is, the system can be used to study the clearing stages of planet formation.

  10. Electrical control of 2D magnetism in bilayer CrI 3.

    Science.gov (United States)

    Huang, Bevin; Clark, Genevieve; Klein, Dahlia R; MacNeill, David; Navarro-Moratalla, Efrén; Seyler, Kyle L; Wilson, Nathan; McGuire, Michael A; Cobden, David H; Xiao, Di; Yao, Wang; Jarillo-Herrero, Pablo; Xu, Xiaodong

    2018-04-23

    Controlling magnetism via electric fields addresses fundamental questions of magnetic phenomena and phase transitions 1-3 , and enables the development of electrically coupled spintronic devices, such as voltage-controlled magnetic memories with low operation energy 4-6 . Previous studies on dilute magnetic semiconductors such as (Ga,Mn)As and (In,Mn)Sb have demonstrated large modulations of the Curie temperatures and coercive fields by altering the magnetic anisotropy and exchange interaction 2,4,7-9 . Owing to their unique magnetic properties 10-14 , the recently reported two-dimensional magnets provide a new system for studying these features 15-19 . For instance, a bilayer of chromium triiodide (CrI 3 ) behaves as a layered antiferromagnet with a magnetic field-driven metamagnetic transition 15,16 . Here, we demonstrate electrostatic gate control of magnetism in CrI 3 bilayers, probed by magneto-optical Kerr effect (MOKE) microscopy. At fixed magnetic fields near the metamagnetic transition, we realize voltage-controlled switching between antiferromagnetic and ferromagnetic states. At zero magnetic field, we demonstrate a time-reversal pair of layered antiferromagnetic states that exhibit spin-layer locking, leading to a linear dependence of their MOKE signals on gate voltage with opposite slopes. Our results allow for the exploration of new magnetoelectric phenomena and van der Waals spintronics based on 2D materials.

  11. Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

    Science.gov (United States)

    Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.

    2016-03-01

    Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

  12. Controlling interactions between highly magnetic atoms with Feshbach resonances.

    Science.gov (United States)

    Kotochigova, Svetlana

    2014-09-01

    This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.

  13. Grand-design Spiral Arms in a Young Forming Circumstellar Disk

    Energy Technology Data Exchange (ETDEWEB)

    Tomida, Kengo; Lin, Chia Hui [Department of Earth and Space Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Machida, Masahiro N. [Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Hosokawa, Takashi [Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Sakurai, Yuya, E-mail: tomida@vega.ess.sci.osaka-u.ac.jp [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan)

    2017-01-20

    We study formation and long-term evolution of a circumstellar disk in a collapsing molecular cloud core using a resistive magnetohydrodynamic simulation. While the formed circumstellar disk is initially small, it grows as accretion continues, and its radius becomes as large as 200 au toward the end of the Class-I phase. A pair of grand-design spiral arms form due to gravitational instability in the disk, and they transfer angular momentum in the highly resistive disk. Although the spiral arms disappear in a few rotations as expected in a classical theory, new spiral arms form recurrently as the disk, soon becoming unstable again by gas accretion. Such recurrent spiral arms persist throughout the Class-0 and I phases. We then perform synthetic observations and compare our model with a recent high-resolution observation of a young stellar object Elias 2–27, whose circumstellar disk has grand-design spiral arms. We find good agreement between our theoretical model and the observation. Our model suggests that the grand-design spiral arms around Elias 2–27 are consistent with material arms formed by gravitational instability. If such spiral arms commonly exist in young circumstellar disks, it implies that young circumstellar disks are considerably massive and gravitational instability is the key process of angular momentum transport.

  14. Grand-design Spiral Arms in a Young Forming Circumstellar Disk

    International Nuclear Information System (INIS)

    Tomida, Kengo; Lin, Chia Hui; Machida, Masahiro N.; Hosokawa, Takashi; Sakurai, Yuya

    2017-01-01

    We study formation and long-term evolution of a circumstellar disk in a collapsing molecular cloud core using a resistive magnetohydrodynamic simulation. While the formed circumstellar disk is initially small, it grows as accretion continues, and its radius becomes as large as 200 au toward the end of the Class-I phase. A pair of grand-design spiral arms form due to gravitational instability in the disk, and they transfer angular momentum in the highly resistive disk. Although the spiral arms disappear in a few rotations as expected in a classical theory, new spiral arms form recurrently as the disk, soon becoming unstable again by gas accretion. Such recurrent spiral arms persist throughout the Class-0 and I phases. We then perform synthetic observations and compare our model with a recent high-resolution observation of a young stellar object Elias 2–27, whose circumstellar disk has grand-design spiral arms. We find good agreement between our theoretical model and the observation. Our model suggests that the grand-design spiral arms around Elias 2–27 are consistent with material arms formed by gravitational instability. If such spiral arms commonly exist in young circumstellar disks, it implies that young circumstellar disks are considerably massive and gravitational instability is the key process of angular momentum transport.

  15. The friction control of magnetic fluid in the Couette flow

    Energy Technology Data Exchange (ETDEWEB)

    Labkovich, O.N., E-mail: olji@tut.by; Reks, A.G.; Chernobai, V.A.

    2017-06-01

    In the work characteristic areas of magnetic fluid flow are experimentally determined in the gap between the cylinders: the area of strong dipole-dipole interaction between magnetite particles 041,2. For areas with high flow losses in viscous friction is shown the possibility of reducing the introduction of magnetic fluid of carbon nanotubes and creating a rotating magnetic field. - Highlights: • Typical areas of magnetic fluid flow are determined in the gap. • Influence of dipole-dipole interaction of magnetite particles on the viscous friction. • Features of Taylor vortex flow.

  16. Voltage-driven magnetization control in topological insulator/magnetic insulator heterostructures

    Directory of Open Access Journals (Sweden)

    Michael E. Flatté

    2017-05-01

    Full Text Available A major barrier to the development of spin-based electronics is the transition from current-driven spin torque, or magnetic-field-driven magnetization reversal, to a more scalable voltage-driven magnetization reversal. To achieve this, multiferroic materials appear attractive, however the effects in current materials occur at very large voltages or at low temperatures. Here the potential of a new class of hybrid multiferroic materials is described, consisting of a topological insulator adjacent to a magnetic insulator, for which an applied electric field reorients the magnetization. As these materials lack conducting states at the chemical potential in their bulk, no dissipative charge currents flow in the bulk. Surface states at the interface, if present, produce effects similar to surface recombination currents in bipolar devices, but can be passivated using magnetic doping. Even without conducting states at the chemical potential, for a topological insulator there is a finite spin Hall conductivity provided by filled bands below the chemical potential. Spin accumulation at the interface with the magnetic insulator provides a torque on the magnetization. Properly timed voltage pulses can thus reorient the magnetic moment with only the flow of charge current required in the leads to establish the voltage. If the topological insulator is sufficiently thick the resulting low capacitance requires little charge current.

  17. Automatic generation control with thyristor controlled series compensator including superconducting magnetic energy storage units

    Directory of Open Access Journals (Sweden)

    Saroj Padhan

    2014-09-01

    Full Text Available In the present work, an attempt has been made to understand the dynamic performance of Automatic Generation Control (AGC of multi-area multi-units thermal–thermal power system with the consideration of Reheat turbine, Generation Rate Constraint (GRC and Time delay. Initially, the gains of the fuzzy PID controller are optimized using Differential Evolution (DE algorithm. The superiority of DE is demonstrated by comparing the results with Genetic Algorithm (GA. After that performance of Thyristor Controlled Series Compensator (TCSC has been investigated. Further, a TCSC is placed in the tie-line and Superconducting Magnetic Energy Storage (SMES units are considered in both areas. Finally, sensitivity analysis is performed by varying the system parameters and operating load conditions from their nominal values. It is observed that the optimum gains of the proposed controller need not be reset even if the system is subjected to wide variation in loading condition and system parameters.

  18. Preparation of ring-shaped composite bonded magnets with continuously controlled anisotropy distribution for internal space

    International Nuclear Information System (INIS)

    Yamashita, F; Yamada, O; Ohya, S; Kobayashi, O; Nakano, M; Fukunaga, H

    2010-01-01

    We have already reported an advanced method for producing a radially-anisotropic rare earth composite bonded magnet with continuously controlled direction of anisotropy. The magnet has been applied to an inner rotor as a practical usage. In this study, the outstanding preparation method was adopted into the preparation of a magnet applied for an outer rotor. An optimized condition of extrusion and compaction at an elevated temperature could be obtained. In addition, a low pressure configuration to the ring-shaped magnet from plural preformed magnets was carried out, which had specific distribution of magnetic anisotropy for internal space for a small motor, by using self recoverability based on the viscous deformation without an alignment field. No deterioration of magnetic properties was detected through the process even if those magnets were miniaturized. Resultantly, the (BH) max of a ring-shaped magnet with the continuously controlled direction of magnetic anisotropy attained the value of 186 kJ/m 3 , and we obtained sine-wave magnetic anisotropy distribution, even if those magnets were miniaturized.

  19. Magnetism Control by Doping in LaAlO3/SrTiO3 Heterointerfaces.

    Science.gov (United States)

    Yan, Hong; Zhang, Zhaoting; Wang, Shuanhu; Wei, Xiangyang; Chen, Changle; Jin, Kexin

    2018-04-25

    Magnetic two-dimensional electron gases at the oxide interfaces are always one of the key issues in spintronics, giving rise to intriguing magnetotransport properties. However, reports about magnetic two-dimensional electron gases remain elusive. Here, we obtain the magnetic order of LaAlO 3 /SrTiO 3 systems by introducing magnetic dopants at the La site. The transport properties with a characteristic of metallic behavior at the interfaces are investigated. More significantly, magnetic-doped samples exhibit obvious magnetic hysteresis loops and the mobility is enhanced. Meanwhile, the photoresponsive experiments are realized by irradiating all samples with a 360 nm light. Compared to magnetism, the effects of dopants on photoresponsive and relaxation properties are negligible because the behavior originates from SrTiO 3 substrates. This work paves a way for revealing and better controlling the magnetic properties of oxide heterointerfaces.

  20. Repetitive transcranial magnetic stimulator with controllable pulse parameters

    Science.gov (United States)

    Peterchev, Angel V.; Murphy, David L.; Lisanby, Sarah H.

    2011-06-01

    The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10-310 µs and positive/negative phase amplitude ratio of 1-56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

  1. Controllable magnetic thermal rectification in a SMM dimmer with the Dzyaloshinskii-Moriya interaction

    Science.gov (United States)

    Xu, Ai-Hua; Liu, Juan; Luo, Bo

    2016-10-01

    Using the quantum master equation, we studied the thermally driven magnonic spin current in a single-molecule magnet (SMM) dimer with the Dzyaloshinskii-Moriya interaction (DMI). Due to the asymmetric DMI, one can observe the thermal rectifying effect in the case of the spatial symmetry coupling with the thermal reservoirs. The properties of the thermal rectification can be controlled by tuning the angle and intensity of the magnetic field. Specially, when the DM vector and magnetic field point at the specific angles, the thermal rectifying effect disappears. And this phenomenon does not depend on the intensities of DMI and magnetic field, the temperature bias and the magnetic anisotropies of the SMM.

  2. Threshold heating temperature for magnetic hyperthermia: Controlling the heat exchange with the blocking temperature of magnetic nanoparticles

    Science.gov (United States)

    Pimentel, B.; Caraballo-Vivas, R. J.; Checca, N. R.; Zverev, V. I.; Salakhova, R. T.; Makarova, L. A.; Pyatakov, A. P.; Perov, N. S.; Tishin, A. M.; Shtil, A. A.; Rossi, A. L.; Reis, M. S.

    2018-04-01

    La0.75Sr0.25MnO3 nanoparticles with average diameter close to 20.9 nm were synthesized using a sol-gel method. Measurements showed that the heating process stops at the blocking temperaturesignificantly below the Curie temperature. Measurements of Specific Absorption Rate (SAR) as a function of AC magnetic field revealed a superquadratic power law, indicating that, in addition to usual Néel and Brown relaxation, the hysteresis also plays an important role in the mechanism of heating. The ability to control the threshold heating temperature, a low remanent magnetization and a low field needed to achieve the magnetic saturation are the advantages of this material for therapeutic magnetic hyperthermia.

  3. Magnets

    International Nuclear Information System (INIS)

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  4. Wireless Magnetic-Based Closed-Loop Control of Self-Propelled Microjets

    Science.gov (United States)

    Khalil, Islam S. M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Misra, Sarthak

    2014-01-01

    In this study, we demonstrate closed-loop motion control of self-propelled microjets under the influence of external magnetic fields. We control the orientation of the microjets using external magnetic torque, whereas the linear motion towards a reference position is accomplished by the thrust and pulling magnetic forces generated by the ejecting oxygen bubbles and field gradients, respectively. The magnetic dipole moment of the microjets is characterized using the U-turn technique, and its average is calculated to be 1.310−10 A.m2 at magnetic field and linear velocity of 2 mT and 100 µm/s, respectively. The characterized magnetic dipole moment is used in the realization of the magnetic force-current map of the microjets. This map in turn is used for the design of a closed-loop control system that does not depend on the exact dynamical model of the microjets and the accurate knowledge of the parameters of the magnetic system. The motion control characteristics in the transient- and steady-states depend on the concentration of the surrounding fluid (hydrogen peroxide solution) and the strength of the applied magnetic field. Our control system allows us to position microjets at an average velocity of 115 m/s, and within an average region-of-convergence of 365 m. PMID:24505244

  5. Super-twisting sliding mode control of torque and flux in permanent magnet synchronous machine drives

    DEFF Research Database (Denmark)

    Lascu, Christian; Boldea, Ion; Blaabjerg, Frede

    2013-01-01

    This paper investigates a permanent magnet synchronous motor drive controlled by a second-order variable structure control technique, known as the super-twisting sliding modes (STSM) control. The STSM controller is designed as a direct torque and flux controller and it works in the stator flux...

  6. Fixed-Time Stability Analysis of Permanent Magnet Synchronous Motors with Novel Adaptive Control

    Directory of Open Access Journals (Sweden)

    Maoxing Liu

    2017-01-01

    Full Text Available We firstly investigate the fixed-time stability analysis of uncertain permanent magnet synchronous motors with novel control. Compared with finite-time stability where the convergence rate relies on the initial permanent magnet synchronous motors state, the settling time of fixed-time stability can be adjusted to desired values regardless of initial conditions. Novel adaptive stability control strategy for the permanent magnet synchronous motors is proposed, with which we can stabilize permanent magnet synchronous motors within fixed time based on the Lyapunov stability theory. Finally, some simulation and comparison results are given to illustrate the validity of the theoretical results.

  7. Periodical plasma structures controlled by external magnetic field

    Science.gov (United States)

    Schweigert, I. V.; Keidar, M.

    2017-06-01

    The characteristics of two-dimensional periodical structures in a magnetized plasma are studied using kinetic simulations. Ridges (i.e. spikes in electron and ion density) are formed and became more pronounced with an increase of magnetic field incidence angle in the plasma volume in the cylindrical chamber. These ridges are shifted relative to each other, which results in the formation of a two-dimensional double-layer structure. Depending on Larmor radius and Debye length up to 19 potential steps appear across the oblique magnetic field. The electrical current gathered into the channels is associated with the electron and ion density ridges.

  8. Heat transfer control in a plane magnetic fluid layer with a free surface

    International Nuclear Information System (INIS)

    Bashtovoi, V.G.; Pogirnitskaya, S.G.; Reks, A.G.

    1993-01-01

    The heat transfer mechanisms that are specific to a magnetic liquid have been already investigated extensively. The high sensitivity of the free magnetic liquid surface to the external magnetic field introduces a new feature into the heat transfer process. In the present work, the authors have investigated the possibility of controlling the heat transfer through the phenomenon of magnetic liquid surface instability in a uniform magnetic field. The conditions for heat transfer through a chamber, partially filled with a magnetic liquid, are governed by the characteristics of the free liquid surface and by its stability and development in the supercritical magnetic fields. The authors consider a model two-dimensional problem of heat transfer through a two-layer medium consisting of horizontally situated immiscible layers of magnetic and nonmagnetic liquids with given thermal conductivities. In the absence of an external magnetic field, the interface of the liquids represents a plane surface. In fields which exceed the critical magnitude, the interface is deformed along the wave. As the field intensity is increased, the amplitude of interface distortion becomes larger. The two-dimensional shape of the free magnetic liquid surface may be realized experimentally using two plane layers of magnetic and nonmagnetic liquids in a uniform magnetic field tangent to the interface of the component layers. 7 refs., 9 figs

  9. Pelvic Static Magnetic Stimulation to Control Urinary Incontinence in Older Women: A Randomized Controlled Trial

    Science.gov (United States)

    Wallis, Marianne C.; Davies, Elizabeth A.; Thalib, Lukman; Griffiths, Susan

    2012-01-01

    Objectives To determine the efficacy of non-invasive static magnetic stimulation (SMS) of the pelvic floor compared to placebo in the treatment of women aged 60 years and over with urinary incontinence for 6 months or more. Subjects and Methods A single-blinded randomized, placebo-controlled, parallel-group trial. Subjects were excluded if they had an implanted electronic device, had experienced a symptomatic urinary tract infection, or had commenced pharmacotherapy for the same in the previous 4 weeks, or if they were booked for pelvic floor or gynecological surgery within the next 3 months. Once written consent was obtained, subjects were randomly assigned to the active SMS group (n=50) or the placebo group (n=51). Treatment was an undergarment incorporating 15 static magnets of 800–1200 Gauss anterior, posterior, and inferior to the pelvis for at least 12 hours a day for 3 months. Placebo was the same protocol with inert metal disks replacing the magnets. Primary outcome measure was cessation of incontinence as measured by a 24-hour pad test. Secondary outcomes were frequency and severity of symptoms as measured by the Bristol Female Lower Urinary Tract Symptoms questionnaire (BFLUTS-SF), the Incontinence Severity Index, a Bothersomeness Visual Analog scale, and a 24-hour bladder diary. Data were collected at baseline and 12 weeks later. Results There were no statistically significant differences between groups in any of the outcome measures from baseline to 12 weeks. Initial evidence of subjective improvement in the treatment group compared to the placebo group was not sustained with sensitivity analysis. Conclusion This study found no evidence that static magnets cure or decrease the symptoms of urinary incontinence. Additional work into the basic physics of the product and garment design is recommended prior to further clinical trials research. PMID:21817123

  10. Periodical plasma structures controlled by external magnetic field

    Science.gov (United States)

    Schweigert, I. V.; Keidar, M.

    2017-11-01

    The plasma of Hall thruster type in external magnetic field is studied in 2D3V kinetic simulations using PIC MCC method. The periodical structure with maxima of electron and ion densities is formed and becomes more pronounced with increase of magnetic field incidence angle in the plasma. These ridges of electron and ion densities are aligned with the magnetic field vector and shifted relative each other. This leads to formation of two-dimensional double-layers structure in cylindrical plasma chamber. Depending on Larmor radius and Debye length up to nineteen potential steps appear across the oblique magnetic field. The electrical current gathered on the wall is associated with the electron and ion density ridges.

  11. Introduction to the controlled nuclear fusion (magnetic containment systems)

    International Nuclear Information System (INIS)

    Cabrera, J.A.; Guasp, J.; Martin, R.

    1975-01-01

    The magnetic containment systems, their more important features, and their potentiality to became thermonuclear reactors is described. The work is based upon the first part of a set of lectures dedicated to Plasma and Fusion Physics. (author)

  12. Micromagnetic analysis of geometrically controlled current-driven magnetization switching

    Directory of Open Access Journals (Sweden)

    O. Alejos

    2017-05-01

    Full Text Available The magnetization dynamics induced by current pulses in a pair of two “S-shaped” ferromagnetic elements, each one consisting on two oppositely tilted tapered spikes at the ends of a straight section, is theoretically studied by means of micromagnetic simulations. Our results indicate that the magnetization reversal is triggered by thermal activation, which assists the current-induced domain nucleation and the propagation of domain walls. The detailed analysis of the magnetization dynamics reveals that the magnetization switching is only achieved when a single domain wall is nucleated in the correct corner of the element. In agreement with recent experimental studies, the switching is purely dictated by the shape, being independent of the current polarity. The statistical study points out that successful switching is only achieved within a narrow range of the current pulse amplitudes.

  13. Summary on Sensorless permanent magnet Brushless DC Motor Control Strategies

    Directory of Open Access Journals (Sweden)

    Li Hai Xia

    2016-01-01

    Full Text Available This paper aims at discussing the development process and application of permanent magnet brushless DC motor. By referring to the related literatures, this thesis gives an overview of several common non-position sensor detection technologies, analyzing their strengths and weaknesses as well as a number of new and improved methods in practical applications. Besides, The application situation of the electric door with sensorless permanent magnet brushless DC motor was illustrated.

  14. Design of a control card for remote operation of the magnet power supply of microtron

    International Nuclear Information System (INIS)

    Khan, A.M.; Hanumaiah, B.; Ganesh; Siddappa, K.

    2003-01-01

    Full text: In this paper we report on a control card developed for remote operation of the magnet power supply of the Microtron. We have used a microcontroller, an ADC, a DAC and some circuit components to make the microcontroller perform the control operations according to the in built program. The value of the parameter to be controlled (i.e. the magnetic field) is given by the main program in the PC kept away from the system. When the user wants to use the magnet power supply system operate the microtron, he will switch ON the system and feed a particular value of the parameter (i.e. magnetic field in Gauss). This value is passed on to the control program in the microcontroller. With this value and the read back value obtained from the sensor the control card activates its control circuitary to maintain the system at the defined parameter value

  15. Reversible control of magnetic interactions by electric field in a single-phase material.

    Science.gov (United States)

    Ryan, P J; Kim, J-W; Birol, T; Thompson, P; Lee, J-H; Ke, X; Normile, P S; Karapetrova, E; Schiffer, P; Brown, S D; Fennie, C J; Schlom, D G

    2013-01-01

    Intrinsic magnetoelectric coupling describes the interaction between magnetic and electric polarization through an inherent microscopic mechanism in a single-phase material. This phenomenon has the potential to control the magnetic state of a material with an electric field, an enticing prospect for device engineering. Here, we demonstrate 'giant' magnetoelectric cross-field control in a tetravalent titanate film. In bulk form, EuTiO(3), is antiferromagnetic. However, both anti and ferromagnetic interactions coexist between different nearest europium neighbours. In thin epitaxial films, strain was used to alter the relative strength of the magnetic exchange constants. We not only show that moderate biaxial compression precipitates local magnetic competition, but also demonstrate that the application of an electric field at this strain condition switches the magnetic ground state. Using first-principles density functional theory, we resolve the underlying microscopic mechanism resulting in G-type magnetic order and illustrate how it is responsible for the 'giant' magnetoelectric effect.

  16. Graphene as a flexible template for controlling magnetic interactions between metal atoms.

    Science.gov (United States)

    Lee, Sungwoo; Kim, Dongwook; Robertson, Alex W; Yoon, Euijoon; Hong, Suklyun; Ihm, Jisoon; Yu, Jaejun; Warner, Jamie H; Lee, Gun-Do

    2017-03-01

    Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value. At the critical strain, a carbon atom can enter between the two Fe atoms and blocks the interaction between relevant orbitals of Fe atoms to quench the magnetic moment. The control of interactions between doped atoms by exploiting the mechanical flexibility of graphene is a unique approach to manipulating the magnetic properties and opens up new opportunities for mechanical-magnetic 2D device systems.

  17. Magnetic actuator for the control and mixing of magnetic bead-based reactions on-chip.

    Science.gov (United States)

    Berenguel-Alonso, Miguel; Granados, Xavier; Faraudo, Jordi; Alonso-Chamarro, Julián; Puyol, Mar

    2014-10-01

    While magnetic bead (MB)-based bioassays have been implemented in integrated devices, their handling on-chip is normally either not optimal--i.e. only trapping is achieved, with aggregation of the beads--or requires complex actuator systems. Herein, we describe a simple and low-cost magnetic actuator to trap and move MBs within a microfluidic chamber in order to enhance the mixing of a MB-based reaction. The magnetic actuator consists of a CD-shaped plastic unit with an arrangement of embedded magnets which, when rotating, generate the mixing. The magnetic actuator has been used to enhance the amplification reaction of an enzyme-linked fluorescence immunoassay to detect Escherichia coli O157:H7 whole cells, an enterohemorrhagic strain, which have caused several outbreaks in food and water samples. A 2.7-fold sensitivity enhancement was attained with a detection limit of 603 colony-forming units (CFU) /mL, when employing the magnetic actuator.

  18. Single axis controlled hybrid magnetic bearing for left ventricular assist device: hybrid core and closed magnetic circuit.

    Science.gov (United States)

    da Silva, Isaias; Horikawa, Oswaldo; Cardoso, Jose R; Camargo, Fernando A; Andrade, Aron J P; Bock, Eduardo G P

    2011-05-01

    In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  19. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    International Nuclear Information System (INIS)

    Kim, S.B.; Uwani, Y.; Joo, J.H.; Kawamoto, R.; Jo, Y.S.

    2011-01-01

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  20. Composite bonded magnets with controlled anisotropy directions prepared by viscous deformation technique

    International Nuclear Information System (INIS)

    Yamashita, Fumitoshi; Kawamura, Kiyomi; Okada, Yukihiro; Murakami, Hiroshi; Ogushi, Masaki; Nakano, Masaki; Fukunaga, Hirotoshi

    2007-01-01

    When a radially anisotropic rare earth bonded magnet for a rotor with a high (BH) max value is magnetized multi-polarly, its flux distributes rectangularly and increases a cogging torque. In order to overcome this difficulty, we newly developed highly dense Sm 2 Fe 17 N 3 and Nd 2 Fe 14 B-based composite bonded magnets with continuously controlled anisotropy directions by using a viscous deformation technique

  1. NEW METHODS AND FACILITIES OF MAGNETIC CONTROL OF THE MECHANICAL CHARACTERISTICS OF ARTICLES

    Directory of Open Access Journals (Sweden)

    V. F. Matjuk

    2004-01-01

    Full Text Available There are given the results of development in the State scientific university ''Institute of applied physics of the National Academy of Sciences of Belarus” of the facilities for magnetic control of the steels mechanical characteristics - coercimeter KIPF-1, impulse magnetic analyzers IMA- 4M, IMA-5B, impulse magnetic installations IMPOK-IB and facilities of their metrological support. The information about the scale of , using IS given.

  2. DSP Based Direct Torque Control of Permanent Magnet Synchronous Motor (PMSM) using Space Vector Modulation (DTC-SVM)

    DEFF Research Database (Denmark)

    Swierczynski, Dariusz; Kazmierkowski, Marian P.; Blaabjerg, Frede

    2002-01-01

    DSP Based Direct Torque Control of Permanent Magnet Synchronous Motor (PMSM) using Space Vector Modulation (DTC-SVM)......DSP Based Direct Torque Control of Permanent Magnet Synchronous Motor (PMSM) using Space Vector Modulation (DTC-SVM)...

  3. Electric-field control of magnetism via strain transfer across ferromagnetic/ferroelectric interfaces.

    Science.gov (United States)

    Taniyama, Tomoyasu

    2015-12-23

    By taking advantage of the coupling between magnetism and ferroelectricity, ferromagnetic (FM)/ferroelectric (FE) multiferroic interfaces play a pivotal role in manipulating magnetism by electric fields. Integrating the multiferroic heterostructures into spintronic devices significantly reduces energy dissipation from Joule heating because only an electric field is required to switch the magnetic element. New concepts of storage and processing of information thus can be envisioned when the electric-field control of magnetism is a viable alternative to the traditional current based means of controlling magnetism. This article reviews some salient aspects of the electric-field effects on magnetism, providing a short overview of the mechanisms of magneto-electric (ME) coupling at the FM/FE interfaces. A particular emphasis is placed on the ME effect via interfacial magneto-elastic coupling arising from strain transfer from the FE to FM layer. Recent results that demonstrate the electric-field control of magnetic anisotropy, magnetic order, magnetic domain wall motion, and etc are described. Obstacles that need to be overcome are also discussed for making this a reality for future device applications.

  4. Electric-field control of magnetism via strain transfer across ferromagnetic/ferroelectric interfaces

    International Nuclear Information System (INIS)

    Taniyama, Tomoyasu

    2015-01-01

    By taking advantage of the coupling between magnetism and ferroelectricity, ferromagnetic (FM)/ferroelectric (FE) multiferroic interfaces play a pivotal role in manipulating magnetism by electric fields. Integrating the multiferroic heterostructures into spintronic devices significantly reduces energy dissipation from Joule heating because only an electric field is required to switch the magnetic element. New concepts of storage and processing of information thus can be envisioned when the electric-field control of magnetism is a viable alternative to the traditional current based means of controlling magnetism. This article reviews some salient aspects of the electric-field effects on magnetism, providing a short overview of the mechanisms of magneto-electric (ME) coupling at the FM/FE interfaces. A particular emphasis is placed on the ME effect via interfacial magneto-elastic coupling arising from strain transfer from the FE to FM layer. Recent results that demonstrate the electric-field control of magnetic anisotropy, magnetic order, magnetic domain wall motion, and etc are described. Obstacles that need to be overcome are also discussed for making this a reality for future device applications. (topical review)

  5. Superconducting spin valves controlled by spiral re-orientation in B20-family magnets

    Science.gov (United States)

    Pugach, N. G.; Safonchik, M.; Champel, T.; Zhitomirsky, M. E.; Lähderanta, E.; Eschrig, M.; Lacroix, C.

    2017-10-01

    We propose a superconducting spin-triplet valve, which consists of a superconductor and an itinerant magnetic material, with the magnet showing an intrinsic non-collinear order characterized by a wave vector that may be aligned in a few equivalent preferred directions under the control of a weak external magnetic field. Re-orienting the spiral direction allows one to controllably modify long-range spin-triplet superconducting correlations, leading to spin-valve switching behavior. Our results indicate that the spin-valve effect may be noticeable. This bilayer may be used as a magnetic memory element for cryogenic nanoelectronics. It has the following advantages in comparison to superconducting spin valves proposed previously: (i) it contains only one magnetic layer, which may be more easily fabricated and controlled; (ii) its ground states are separated by a potential barrier, which solves the "half-select" problem of the addressed switch of memory elements.

  6. Evaluation of environmental control technologies for magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    1978-08-01

    The peripheral magnetic fields of several energy-related technologies are calculated, and shielding options are studied for three field intensities as possible exposure levels: 200 G, 10 G, and 0.3 G. Seven fusion reactor designs are studied. For a 200-G field level, shielding is not required. For the 10- and 0.3-G levels, land is the most economical shielding method, with shield coils an acceptable alternative at 0.3 G. Nonnuclear technologies studied are superconducting magnetic energy storage, magnetohydrodynamic (MHD) electric generators, magnetically levitated vehicles, superconducting ac generators, and underground transmission lines. Superconducting ac generators and underground transmission lines require no shielding. The superconducting magnetic energy storage coil requires no shielding for 200 G. Both a shield coil and land are needed to meet 10 G or 0.3 G. The MHD generator needs no shielding to 200 G and 10 G. Land is the most economical means of meeting the 0.3 G level. Most of the magnetically levitated vehicles require no shielding to 200 G. The field on-board can be reduced from 200 to 25 G, depending upon the vehicle design, with shield coils. The use of iron, or another permeable material, is necessary to reduce the field to 10 G or 0.3 G. However, iron introduces too much added weight to allow efficient operation.

  7. Dynamically controlled energy dissipation for fast magnetic vortex switching

    Science.gov (United States)

    Badea, R.; Berezovsky, J.

    2017-09-01

    Manipulation of vortex states in magnetic media provides new routes towards information storage and processing technology. The typical slow relaxation times (˜100 ns) of magnetic vortex dynamics may present an obstacle to the realization of these applications. Here, we investigate how a vortex state in a ferromagnetic microdisk can be manipulated in a way that translates the vortex core while enhancing energy dissipation to rapidly damp the vortex dynamics. We use time-resolved differential magneto-optical Kerr effect microscopy to measure the motion of the vortex core in response to applied magnetic fields. We first map out how the vortex core becomes sequentially trapped by pinning sites as it translates across the disk. After applying a fast magnetic field step to translate the vortex from one pinning site to another, we observe long-lived dynamics of the vortex as it settles to the new equilibrium. We then demonstrate how the addition of a short (<10 ns) magnetic field pulse can induce additional energy dissipation, strongly damping the long-lived dynamics. A model of the vortex dynamics using the Thiele equation of motion explains the mechanism behind this effect.

  8. Magnetically actuated and controlled colloidal sphere-pair swimmer

    International Nuclear Information System (INIS)

    Ran, Sijie; Guez, Allon; Friedman, Gary

    2016-01-01

    Magnetically actuated swimming of microscopic objects has been attracting attention partly due to its promising applications in the bio-medical field and partly due to interesting physics of swimming in general. While colloidal particles that are free to move in fluid can be an attractive swimming system due it its simplicity and ability to assemble in situ , stability of their dynamics and the possibility of stable swimming behavior in periodically varying magnetic fields has not been considered. Dynamic behavior of two magnetically interacting colloidal particles subjected to rotating magnetic field of switching frequency is analyzed here and is shown to result in stable swimming without any stabilizing feedback. A new mechanism of swimming that relies only on rotations of the particles themselves and of the particle pair axis is found to dominate the swimming dynamics of the colloidal particle pair. Simulation results and analytical arguments demonstrate that this swimming strategy compares favorably to dragging the particles with an external magnetic force when colloidal particle sizes are reduced. (paper)

  9. Control system for magnet power supplies for Novosibirsk free electron laser

    International Nuclear Information System (INIS)

    Velikanov, Y.M.; Veremeenko, V.F.; Vinokurov, N.A.; Galt, A.A.; Dovzhenko, B.A.; Kozak, V.R.; Kuper, E.A.; Medvedev, L.E.; Medvedko, A.S.; Serednyakov, S.S.

    2012-01-01

    A high-power free electron laser (FEL) based on the accelerator-recuperator principle is being built in Budker Institute (Russia). The magnetic system of the FEL is an important part of the installation. It consists of many magnetic elements of different types: bending magnets, quadrupole lenses and correctors. The windings of all these elements are fed from DC current power supplies. The power supply control system based on embedded intelligent controllers with the CAN-BUS interface is considered in detail. The control software structure and capabilities are described. Besides, the software tools for power supply diagnostics are described

  10. Study on the Electronic Magnetic Field Oriented Control Based on D-axis Current

    Directory of Open Access Journals (Sweden)

    Hongyu Feng

    2014-07-01

    Full Text Available In order to improve the magnetic field orientation accuracy and system performance, the electronic field oriented control has been a hot research field of the induction motor speed control. Although the vector control of AC machines has many excellent properties, the researchers have been attempting to simplify the calculating steps and the structure of the control system to improve the accuracy of filed-oriented and the performance of AC machine drives. Based on the analysis of the conventional induction motor magnetic field oriented control, this paper puts forward a novel method of stator magnetic field orientation control. By analytical methods, the given current of d-axis can be calculated directly, and the stator flux can be controlled precisely. This method has a fast flux and torque response, and the control performance is unaffected by the rotor parameters.

  11. Control of hole localization in magnetic semiconductors by axial strain

    Science.gov (United States)

    Raebiger, Hannes; Bae, Soungmin; Echeverría-Arrondo, Carlos; Ayuela, Andrés

    2018-02-01

    Mn and Fe-doped GaN are widely studied prototype systems for hole-mediated magnetic semiconductors. The nature of the hole states around the Mn and Fe impurities, however, remains under debate. Our self-interaction corrected density-functional calculations show that the charge neutral Mn 0 and positively charged Fe+ impurities have symmetry-broken d5+h ground states, in which the hole is trapped by one of the surrounding N atoms in a small polaron state. We further show that both systems also have a variety of other d5+h configurations, including symmetric, delocalized states, which may be stabilized by axial strain. This finding opens a pathway to promote long-range hole-mediated magnetic interactions by strain engineering and clarifies why highly strained thin-films samples often exhibit anomalous magnetic properties.

  12. Controlling the induced anisotropy in soft magnetic films for high-frequency applications

    NARCIS (Netherlands)

    Chezan, A.R.; Craus, C.B.; Chechenin, N.G.; Vystavel, T.; Hosson, J.Th.M. De; Niesen, L.; Boerma, D.O.

    Nanocrystalline soft magnetic Fe–Zr–N films were successfully deposited by dc magnetron reactive sputtering. The nitrogen content was controlled by varying the Ar/N2 ratio and/or the substrate temperature. The films have saturation magnetization and induced uniaxial anisotropy values in the range

  13. Motion behaviour of magneto-sensitive elastomers controlled by an external magnetic field for sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Volkova, T.I., E-mail: tatiana.volkova@tu-ilmenau.de [Technische Universität Ilmenau, Faculty of Mechanical Engineering, Technical Mechanics Group, D-98693 Ilmenau (Germany); Böhm, V., E-mail: valter.boehm@tu-ilmenau.de [Technische Universität Ilmenau, Faculty of Mechanical Engineering, Technical Mechanics Group, D-98693 Ilmenau (Germany); Kaufhold, T., E-mail: tobias.kaufhold@tu-ilmenau.de [Technische Universität Ilmenau, Faculty of Mechanical Engineering, Technical Mechanics Group, D-98693 Ilmenau (Germany); Popp, J., E-mail: jana.popp@tu-ilmenau.de [Technische Universität Ilmenau, Faculty of Mechanical Engineering, Technical Mechanics Group, D-98693 Ilmenau (Germany); Becker, F., E-mail: felix.becker@tu-ilmenau.de [Technische Universität Ilmenau, Faculty of Mechanical Engineering, Technical Mechanics Group, D-98693 Ilmenau (Germany); Borin, D.Yu., E-mail: dmitry.borin@tu-dresden.de [Technische Universität Dresden, Magnetofluiddynamics, Measuring and Automation Technology, D-01062 Dresden (Germany); Stepanov, G.V., E-mail: gstepanov@mail.ru [State Institute of Chemistry and Technology of Organoelement Compounds, 105118 Moscow (Russian Federation); Zimmermann, K., E-mail: klaus.zimmermann@tu-ilmenau.de [Technische Universität Ilmenau, Faculty of Mechanical Engineering, Technical Mechanics Group, D-98693 Ilmenau (Germany)

    2017-06-01

    The development of sensor systems with a complex adaptive regulation of the operating sensitivity and behaviour is an actual scientific and technical challenge. Smart materials like magneto-sensitive elastomers (MSE) are seen as one potential solution for this problem, since their mechanical properties may be controlled by external magnetic fields. The present paper deals with the investigation of elastic and damping properties of MSE containing magnetically soft particles under the influence of a uniform magnetic field. Based on the measurement of the first eigenfrequency of free bending vibrations of a fixed beam, the effective Young's modulus is evaluated theoretically and also numerically using Finite Element Method. It is shown that this parameter, as well as the first eigenfrequency of the beam, increases monotonically with the magnitude of the applied magnetic field. The results are aimed to develop an acceleration sensor with adaptive magnetically controllable sensitivity range for the detection of external mechanical stimuli of the environment. - Highlights: • The motion behaviour of magneto-sensitive elastomers (MSE) with magnetically soft particles is investigated. • The first eigenfrequency of free bending vibrations of an MSE beam can be controlled by a uniform magnetic field. • Based on the experimental results, the effective Young's modulus of the system is evaluated theoretically and numerically. • The Young's modulus increases monotonically with the magnitude of the applied magnetic field. • The controlled mechanical compliance of MSE may be used for development of sensor systems with adaptive sensitivity range.

  14. Radiation control in fusion plasmas by magnetic confinement

    International Nuclear Information System (INIS)

    Dachicourt, R.

    2012-10-01

    The present work addresses two important issues for the industrial use of fusion: plasma radiation control, as a part of the more general power handling issue, and high density tokamak operation. These two issues will be most critical in the demonstration reactor, called DEMO, intermediate step between ITER and a future commercial reactor. For DEMO, the need to radiate a large fraction of the power so as to limit the peak power load on the divertor will be a key constraint. High confinement will have to be combined with high radiated power fraction, and the required level of plasma purity. The main achievement of this thesis is to have shown experimental evidence of the existence of a stable plasma regime meeting the most critical requirements of a DEMO scenario: an electron density up to 40% above the Greenwald value, together with a fraction of radiated power close to 80%, with a good energy confinement and limited dilution. The plasma is additionally heated with ion cyclotron waves in a central electron heating scenario, featuring alpha particle heating. The original observations reported in this work bring highly valuable new pieces of information both to the physics of the tokamak edge layer and to the construction of an 'integrated operational scenario' required to successfully operate fusion devices. In the way for getting high density plasmas, the new observations involve the following topics. First, the formation of a poloidal asymmetry in the edge electron density profile, with a maximum density located close to toroidal pumped limiter. This asymmetry occurs inside the separatrix, with a constant plasma pressure on magnetic surfaces. Secondly, a correlative decrease of the electron temperature in the same edge region. Thirdly, the excellent coupling capabilities of the ICRH waves, up to a central line averaged electron density of 1.4 times the Greenwald density. Fourthly, a poloidally asymmetric edge radiation region, providing the dissipation of 80% of

  15. Models for the circumstellar medium of long gamma-ray burst progenitor candidates

    NARCIS (Netherlands)

    Marle, A.J. van

    2006-01-01

    Long gamma-ray bursts are highly energetic events that are thought to occur when certain massive stars, that end their lives as Wolf-Rayet stars, collapse at the end of their evolution. We present models of the circumstellar medium around those massive stars that are thought to be possible

  16. Magnetic structures synthesized by controlled oxidative etching: Structural characterization and magnetic behavior

    Directory of Open Access Journals (Sweden)

    Álvaro de Jesús Ruíz-Baltazar

    Full Text Available A facile strategy for the fabrication Fe3O4 nanostructures at room temperature and with well-defined morphology is proposed. In this methodology, the iron precursors were reduced by sodium borohydride. Subsequently an oxidative etching process promotes the formation of Fe2O3 nanostructures. Magnetic measurements revealed a well-defined superparamagnetic behavior for the material. The Zero-Field-Cooled (ZFC and Field-Cooled (FC magnetization curves reveals that critical and blocking temperature were 24 and 350 °C respectively. The Fe3O4 nanostructures were characterized using aberration-corrected (Cs scanning transmission electron microscopy (STEM and energy dispersive spectroscopy (EDS. Additionally, Raman spectra support the Fe3O4 presence and corroborate the efficiency of the synthesis process to obtain magnetite. Keywords: Chemical synthesis, Fe3O4 nanoparticles, Structural characterization, Magnetic properties

  17. Externally controlled local magnetic field in a conducting mesoscopic ring coupled to a quantum wire

    International Nuclear Information System (INIS)

    Maiti, Santanu K.

    2015-01-01

    In the present work, the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designing spin-based quantum devices is also analyzed

  18. Piezo-voltage control of magnetization orientation in a ferromagnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Althammer, M.; Brandlmaier, A.; Gepraegs, S.; Opel, M.; Gross, R. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching (Germany); Bihler, C.; Brandt, M.S. [Walter Schottky Institut, Technische Universitaet Muenchen, 85748 Garching (Germany); Schoch, W.; Limmer, W. [Institut fuer Halbleiterphysik, Universitaet Ulm, 89069 Ulm (Germany); Goennenwein, S.T.B.

    2008-06-15

    The possibility to control magnetic properties via electrical fields is investigated in a piezoelectric actuator/ferromagnetic semiconductor thin film hybrid structure. Using anisotropic magnetoresistance techniques, the magnetic anisotropy and the magnetization orientation within the plane of the ferromagnetic film are measured quantitatively. The experiments reveal that the application of an electrical field to the piezoelectric actuator allows to continuously and reversibly rotate the magnetization orientation in the ferromagnet by about 70 . (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Simulation Research of Magnetic Constriction Effect and Controlling by Axial Magnetic Field of Vacuum Arc

    Institute of Scientific and Technical Information of China (English)

    王立军; 贾申利; 史宗谦; 荣命哲

    2005-01-01

    Based on magnetohydrodynamic (MHD) model of vacuum arc, the computer simulation of vacuum arc was carried out in this paper. In the MHD model, mass conservation equation,momentum conservation equations, energy conservation equations, generalized ohm's law and Maxwell equation were considered. MHD equations were calculated by numerical method, and the distribution of vacuum arc plasma parameters and current density were obtained. Simulation results showed that the magnetic constriction effect of vacuum arc is primarily caused by the Hall effect. In addition, the inhibition of axial magnetic field (AMF) on constriction of vacuum arc was calculated and analyzed.

  20. 3D simulation of accelerator conventional magnets with end pole defined by an analytical approach controlling multipoles and magnetic length

    CERN Document Server

    Delferrière, O; Duperrier, R

    2000-01-01

    During the design of a magnet, people generally pay particular attention to get the largest transverse section with small contribution of undesirable multipoles, and the 2D cross-section is adjusted in that way with a good accuracy. But the poles are often cut with sharp ends in the beam direction. Otherwise, in order to minimize the stray field to avoid interaction with other elements on the beam lines and corner saturation, it is common to define a simple 45 degrees chamber. The such truncated poles will create an amount of multipoles that could exceed the magnet required tolerances. The magnetic length is also affected by the way that the truncation is done. We propose in this paper a handy analytical model that allows both to control integrated focusing forces and magnetic lengths for each type of conventional magnets (dipole, quadrupole, sextupole). The different end pole profiles are simulated with the 3D-program TOSCA for the dipole and the quadrupole cases. To estimate a possible damaging of optical q...

  1. Magnetic-gun igniter for controlled thermonuclear fusion

    International Nuclear Information System (INIS)

    Garwin, R.L.; Muller, R.A.; Richter, B.

    1979-01-01

    A conceptual design for the magnetic gun is given in order to show that the various parameters required turn out to be reasonable (in an engineering sense). An engineering design will necessarily turn out to be far more complex; the purpose of the following calculations is merely to show that the basic idea looks sufficiently good to warrant further work

  2. Magnetogenetics: Remote Control of Cellular Signaling with Magnetic Fields

    Science.gov (United States)

    Sauer, Jeremy P.

    Means for temporally regulating gene expression and cellular activity are invaluable for elucidating the underlying physiological processes and have therapeutic implications. Here we report the development of a system for remote regulation of gene expression by low frequency radiowaves (RF) or by a static magnetic field. We accomplished this by first adding iron oxide nanoparticles - either exogenously or as genetically encoded ferritin/ferric oxyhydroxide particle. These particles have been designed with affinity to the plasma membrane ion channel Transient Receptor Potential Vanilloid 1 (TRPV1) by a conjugated antibody. Application of a magnetic field stimulates the particle to gate the ion channel and this, in turn, initiates calcium-dependent transgene expression. We first demonstrated in vitro that TRPV1 can be actuated to cause calcium flux into the cell by directly applying a localized magnetic field. In mice expressing these genetically encoded components, application of external magnetic field caused remote stimulation of insulin transgene expression and significantly lowered blood glucose. In addition, we are investigating mechanisms by which iron oxide nanoparticles can absorb RF, and transduce this energy to cause channel opening. This robust, repeatable method for remote cellular regulation in vivo may ultimately have applications in basic science, as well as in technology and therapeutics.

  3. Hydrophobic Drug-Loaded PEGylated Magnetic Liposomes for Drug-Controlled Release

    Science.gov (United States)

    Hardiansyah, Andri; Yang, Ming-Chien; Liu, Ting-Yu; Kuo, Chih-Yu; Huang, Li-Ying; Chan, Tzu-Yi

    2017-05-01

    Less targeted and limited solubility of hydrophobic-based drug are one of the serious obstacles in drug delivery system. Thus, new strategies to enhance the solubility of hydrophobic drug and controlled release behaviors would be developed. Herein, curcumin, a model of hydrophobic drug, has been loaded into PEGylated magnetic liposomes as a drug carrier platform for drug controlled release system. Inductive magnetic heating (hyperthermia)-stimulated drug release, in vitro cellular cytotoxicity assay of curcumin-loaded PEGylated magnetic liposomes and cellular internalization-induced by magnetic guidance would be investigated. The resultant of drug carriers could disperse homogeneously in aqueous solution, showing a superparamagnetic characteristic and could inductive magnetic heating with external high-frequency magnetic field (HFMF). In vitro curcumin release studies confirmed that the drug carriers exhibited no significant release at 37 °C, whereas exhibited rapid releasing at 45 °C. However, it would display enormous (three times higher) curcumin releasing under the HFMF exposure, compared with that without HFMF exposure at 45 °C. In vitro cytotoxicity test shows that curcumin-loaded PEGylated magnetic liposomes could efficiently kill MCF-7 cells in parallel with increasing curcumin concentration. Fluorescence microscopy observed that these drug carriers could internalize efficiently into the cellular compartment of MCF-7 cells. Thus, it would be anticipated that the novel hydrophobic drug-loaded PEGylated magnetic liposomes in combination with inductive magnetic heating are promising to apply in the combination of chemotherapy and thermotherapy for cancer therapy.

  4. Effect of strain on voltage-controlled magnetism in BiFeO₃-based heterostructures.

    Science.gov (United States)

    Wang, J J; Hu, J M; Yang, T N; Feng, M; Zhang, J X; Chen, L Q; Nan, C W

    2014-04-01

    Voltage-modulated magnetism in magnetic/BiFeO3 heterostructures can be driven by a combination of the intrinsic ferroelectric-antiferromagnetic coupling in BiFeO3 and the antiferromagnetic-ferromagnetic exchange interaction across the heterointerface. However, ferroelectric BiFeO3 film is also ferroelastic, thus it is possible to generate voltage-induced strain in BiFeO3 that could be applied onto the magnetic layer across the heterointerface and modulate magnetism through magnetoelastic coupling. Here, we investigated, using phase-field simulations, the role of strain in voltage-controlled magnetism for these BiFeO3-based heterostructures. It is predicted, under certain condition, coexistence of strain and exchange interaction will result in a pure voltage-driven 180° magnetization reversal in BiFeO3-based heterostructures.

  5. Effect of strain on voltage-controlled magnetism in BiFeO3-based heterostructures

    Science.gov (United States)

    Wang, J. J.; Hu, J. M.; Yang, T. N.; Feng, M.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    Voltage-modulated magnetism in magnetic/BiFeO3 heterostructures can be driven by a combination of the intrinsic ferroelectric-antiferromagnetic coupling in BiFeO3 and the antiferromagnetic-ferromagnetic exchange interaction across the heterointerface. However, ferroelectric BiFeO3 film is also ferroelastic, thus it is possible to generate voltage-induced strain in BiFeO3 that could be applied onto the magnetic layer across the heterointerface and modulate magnetism through magnetoelastic coupling. Here, we investigated, using phase-field simulations, the role of strain in voltage-controlled magnetism for these BiFeO3-based heterostructures. It is predicted, under certain condition, coexistence of strain and exchange interaction will result in a pure voltage-driven 180° magnetization reversal in BiFeO3-based heterostructures. PMID:24686503

  6. Encapsulation of methotrexate loaded magnetic microcapsules for magnetic drug targeting and controlled drug release

    Energy Technology Data Exchange (ETDEWEB)

    Chakkarapani, Prabu [Department of Pharmaceutical Technology & Centre for Excellence in Nanobio Translational Research, Anna University, Bharathidasan Institute of Technology Campus, Tiruchirappalli 620024, Tamil Nadu (India); Subbiah, Latha, E-mail: lathasuba2010@gmail.com [Department of Pharmaceutical Technology & Centre for Excellence in Nanobio Translational Research, Anna University, Bharathidasan Institute of Technology Campus, Tiruchirappalli 620024, Tamil Nadu (India); Palanisamy, Selvamani; Bibiana, Arputha [Department of Pharmaceutical Technology & Centre for Excellence in Nanobio Translational Research, Anna University, Bharathidasan Institute of Technology Campus, Tiruchirappalli 620024, Tamil Nadu (India); Ahrentorp, Fredrik; Jonasson, Christian; Johansson, Christer [Acreo Swedish ICT AB, Arvid Hedvalls backe 4, SE-411 33 Göteborg (Sweden)

    2015-04-15

    We report on the development and evaluation of methotrexate magnetic microcapsules (MMC) for targeted rheumatoid arthritis therapy. Methotrexate was loaded into CaCO{sub 3}-PSS (poly (sodium 4-styrenesulfonate)) doped microparticles that were coated successively with poly (allylamine hydrochloride) and poly (sodium 4-styrenesulfonate) by layer-by-layer technique. Ferrofluid was incorporated between the polyelectrolyte layers. CaCO{sub 3}-PSS core was etched by incubation with EDTA yielding spherical MMC. The MMC were evaluated for various physicochemical, pharmaceutical parameters and magnetic properties. Surface morphology, crystallinity, particle size, zeta potential, encapsulation efficiency, loading capacity, drug release pattern, release kinetics and AC susceptibility studies revealed spherical particles of ~3 µm size were obtained with a net zeta potential of +24.5 mV, 56% encapsulation and 18.6% drug loading capacity, 96% of cumulative drug release obeyed Hixson-Crowell model release kinetics. Drug excipient interaction, surface area, thermal and storage stability studies for the prepared MMC was also evaluated. The developed MMC offer a promising mode of targeted and sustained release drug delivery for rheumatoid arthritis therapy. - Highlights: • Development of methotrexate magnetic microcapsules (MMC) by layer-by-layer method. • Characterization of physicochemical, pharmaceutical and magnetic properties of MMC. • Multiple layers of alternative polyelectrolytes prolongs methotrexate release time. • MMC is capable for targeted and sustained release rheumatoid arthritis therapy.

  7. Impact of magnetic saturation on the input-output linearising tracking control of an induction motor

    DEFF Research Database (Denmark)

    Dolinar, Drago; Ljusev, Petar; Stumberger, Gorazd

    2004-01-01

    This paper deals with the tracking control design of an induction motor, based on input-output linearization with magnetic saturation included. Magnetic saturation is represented by the nonlinear magnetizing curve of the iron core and is used in the control design, the observer of state variables......, and in the load torque estimator. An input-output linearising control is used to achieve better tracking performances of the drive. It is based on the mixed ”stator current - rotor flux linkage” induction motor model with magnetic saturation considered in the stationary reference frame. Experimental results show...... that the proposed input-output linearising tracking control with the included saturation behaves considerably better than the one without saturation, and that it introduces smaller position and speed errors, and better motor stiffness on account of the increased computational complexity....

  8. Oxygen-enabled control of Dzyaloshinskii-Moriya Interaction in ultra-thin magnetic films

    KAUST Repository

    Belabbes, Abderrezak; Bihlmayer, Gustav; Blü gel, Stefan; Manchon, Aurelien

    2016-01-01

    ferromagnets, resulting in spin spirals and nanoskyrmion lattices. Here, using relativistic first-principles calculations, we demonstrate that the magnitude and sign of DMI can be entirely controlled by tuning the oxygen coverage of the magnetic film, therefore

  9. The circumstellar environment of evolved stars as traced by molecules and dust. The diagnostic power of Herschel

    Science.gov (United States)

    Lombaert, Robin

    2013-12-01

    Low-to-intermediate mass stars end their life on the asymptotic giant branch (AGB), an evolutionary phase in which the star sheds most of its mantle into the circumstellar environment through a stellar wind. This stellar wind expands at relatively low velocities and enriches the interstellar medium with elements newly made in the stellar interior. The physical processes controlling the gas and dust chemistry in the outflow, as well as the driving mechanism of the wind itself, are poorly understood and constitute the broader context of this thesis work. In a first chapter, we consider the thermodynamics of the high-density wind of the oxygen-rich star oh, using observations obtained with the PACS instrument onboard the Herschel Space Telescope. Being one of the most abundant molecules, water vapor can be dominant in the energy balance of the inner wind of these types of stars, but to date, its cooling contribution is poorly understood. We aim to improve the constraints on water properties by careful combination of both dust and gas radiative-transfer models. This unified treatment is needed due to the high sensitivity of water excitation to dust properties. A combination of three types of diagnostics reveals a positive radial gradient of the dust-to-gas ratio in oh. The second chapter deals with the dust chemistry of carbon-rich winds. The 30-mic dust emission feature is commonly identified as due to magnesium sulfide (MgS). However, the lack of short-wavelength measurements of the optical properties of this dust species prohibits the determination of the temperature profile of MgS, and hence its feature strength and shape, questioning whether this species is responsible for the 30-mic feature. By considering the very optically thick wind of the extreme carbon star LL Peg, this problem can be circumvented because in this case the short-wavelength optical properties are not important for the radial temperature distribution. We attribute the 30-mic feature to MgS, but

  10. Magnetic field control of 90°, 180°, and 360° domain wall resistance

    Science.gov (United States)

    Majidi, Roya

    2012-10-01

    In the present work, we have compared the resistance of the 90°, 180°, and 360° domain walls in the presence of external magnetic field. The calculations are based on the Boltzmann transport equation within the relaxation time approximation. One-dimensional Néel-type domain walls between two domains whose magnetization differs by angle of 90°, 180°, and 360° are considered. The results indicate that the resistance of the 360° DW is more considerable than that of the 90° and 180° DWs. It is also found that the domain wall resistance can be controlled by applying transverse magnetic field. Increasing the strength of the external magnetic field enhances the domain wall resistance. In providing spintronic devices based on magnetic nanomaterials, considering and controlling the effect of domain wall on resistivity are essential.

  11. Magnetic suspension motorized spindle-cutting system dynamics analysis and vibration control review

    Directory of Open Access Journals (Sweden)

    Xiaoli QIAO

    2016-10-01

    Full Text Available The performance of high-speed spindle directly determines the development of high-end machine tools. The cutting system's dynamic characteristics and vibration control effect are inseparable with the performance of the spindle,which influence each other, synergistic effect together the cutting efficiency, the surface quality of the workpiece and tool life in machining process. So, the review status on magnetic suspension motorized spindle, magnetic suspension bearing-flexible rotor system dynamics modeling theory and status of active control technology of flexible magnetic suspension motorized spindle rotor vibration are studied, and the problems which present in the magnetic suspension flexible motorized spindle rotor systems are refined, and the development trend of magnetic levitation motorized spindle and the application prospect is forecasted.

  12. All-electric-controlled spin current switching in single-molecule magnet-tunnel junctions

    Science.gov (United States)

    Zhang, Zheng-Zhong; Shen, Rui; Sheng, Li; Wang, Rui-Qiang; Wang, Bai-Gen; Xing, Ding-Yu

    2011-04-01

    A single-molecule magnet (SMM) coupled to two normal metallic electrodes can both switch spin-up and spin-down electronic currents within two different windows of SMM gate voltage. Such spin current switching in the SMM tunnel junction arises from spin-selected single electron resonant tunneling via the lowest unoccupied molecular orbit of the SMM. Since it is not magnetically controlled but all-electrically controlled, the proposed spin current switching effect may have potential applications in future spintronics.

  13. Magnetically controlled multifrequency invisibility cloak with a single shell of ferrite material

    Science.gov (United States)

    Wang, Xiaohua; Liu, Youwen

    2015-02-01

    A magnetically controlled multifrequency invisibility cloak with a single shell of the isotropic and homogeneous ferrite material has been investigated based on the scattering cancellation method from the Mie scattering theory. The analytical and simulated results have demonstrated that such this shell can drastically reduce the total scattering cross-section of this cloaking system at multiple frequencies. These multiple cloaking frequencies of this shell can be externally controlled since the magnetic permeability of ferrites is well tuned by the applied magnetic field. This may provide a potential way to design a tunable multifrequency invisibility cloak with considerable flexibility.

  14. Magnetic sensorless control of plasma position and shape in a tokamak

    International Nuclear Information System (INIS)

    Nakamura, K.; Luo, J.R.; Wang, H.Z.

    2005-01-01

    Magnetic sensorless sensing and control experiments of the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The sensing is made focusing on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem of integrator of magnetic sensors. Two kinds of control experiments were carried out, to keep the position constant and swing the position in a triangular waveform. And magnetic sensorless sensing of plasma shape is discussed. (author)

  15. Precise Localization and Control of Catalytic Janus Micromotors using Weak Magnetic Fields

    NARCIS (Netherlands)

    Khalil, Islam S. M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Misra, Sarthak

    2015-01-01

    We experimentally demonstrate the precise localization of spherical Pt-Silica Janus micromotors (diameter 5 mu m) under the influence of controlled magnetic fields. First, we control the motion of the Janus micromotors in two-dimensional (2D) space. The control system achieves precise localization

  16. Magnetic-field control of low-pressure diffuse discharges

    International Nuclear Information System (INIS)

    Cooper, J.R.

    1986-01-01

    Application of a magnetic field in a direction transverse to the electric field in a diffuse discharge can have a strong effect on the transport parameters in the discharge medium and on the external characteristics of the discharge as a whole. Deviations in these transport parameters were investigated in this work by means of Monte Carlo calculations, and the electrical characteristics of the total discharge were observed experimentally. Results of the theoretical investigation show that, in attaching gas mixtures, both the ionization and attachment-rate coefficients in the positive column of the discharge are changed such that the combined effect results in an increase in resistivity. Experimentally, it is seen that application of a crossed magnetic field to an abnormal glow discharge in attaching gases in a certain parameter range causes the discharge voltage to increase significantly. The effect seems to be most strongly influenced by processes in the cathode-fall region

  17. Sodium ordering and the control of magnetism in sodium cobaltate

    International Nuclear Information System (INIS)

    Morris, D.J.P.; Roger, M.; Tennant, D.A.; Goff, J.P.; Gutmann, M.J.; Hoffmann, J.-U.; Prabhakaran, D.; Shannon, N.; Lake, B.; Deen, P.P.

    2007-01-01

    The long-range three-dimensional ordering of Na + ions was studied in a sample of composition Na 0.75 CoO 2 using single-crystal neutron diffraction. Large-scale numerical simulations reveal the ordering principle for this system, the formation of multi-vacancy charged droplets then order long range, and the structure factors from these defect clusters are in good agreement with the observed neutron diffraction intensities. The electrostatic potential is found to be the dominant factor in determining the sodium ordering and its associated distortion field. The superstructures induce a periodic potential in the CoO 2 , giving potential wells that are larger than the single-particle hopping frequency and so able to localize holes. The results readily explain many of the observed electrical and magnetic properties, including the three dimensionality of the magnetic excitations

  18. Precise position control of a helical magnetic robot in pulsatile flow using the rotating frequency of the external magnetic field

    Directory of Open Access Journals (Sweden)

    Jongyul Kim

    2017-05-01

    Full Text Available We propose a position control method for a helical magnetic robot (HMR that uses the rotating frequency of the external rotating magnetic field (ERMF to minimize the position fluctuation of the HMR caused by pulsatile flow in human blood vessels. We prototyped the HMR and conducted several experiments in pseudo blood vessel environments with a peristaltic pump. We experimentally obtained the relation between the flow rate and the rotating frequency of the ERMF required to make the HMR stationary in a given pulsatile flow. Then we approximated the pulsatile flow by Fourier series and applied the required ERMF rotating frequency to the HMR in real time. Our proposed position control method drastically reduced the position fluctuation of the HMR under pulsatile flow.

  19. Size-controlled magnetic nanoparticles with lecithin for biomedical applications

    Science.gov (United States)

    Park, S. I.; Kim, J. H.; Kim, C. G.; Kim, C. O.

    2007-05-01

    Lecithin-adsorbed magnetic nanoparticles were prepared by three-step process that the thermal decomposition was combined with ultrasonication. Experimental parameters were three items—molar ratio between Fe(CO) 5 and oleic acid, keeping time at decomposition temperature and lecithin concentration. As the molar ratio between Fe(CO) 5 and oleic acid, and keeping time at decomposition temperature increased, the particle size increased. However, the change of lecithin concentration did not show the remarkable particle size variation.

  20. Size-controlled magnetic nanoparticles with lecithin for biomedical applications

    International Nuclear Information System (INIS)

    Park, S.I.; Kim, J.H.; Kim, C.G.; Kim, C.O.

    2007-01-01

    Lecithin-adsorbed magnetic nanoparticles were prepared by three-step process that the thermal decomposition was combined with ultrasonication. Experimental parameters were three items-molar ratio between Fe(CO) 5 and oleic acid, keeping time at decomposition temperature and lecithin concentration. As the molar ratio between Fe(CO) 5 and oleic acid, and keeping time at decomposition temperature increased, the particle size increased. However, the change of lecithin concentration did not show the remarkable particle size variation

  1. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Directory of Open Access Journals (Sweden)

    Sumeet Kumar

    2015-02-01

    Full Text Available In the present study, monodispersed CeO2 nanoparticles (NPs of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD, field emission scanning electron microscope (FE-SEM, high resolution transmission electron microscopy (HR-TEM, ultra-violet visible (UV-VIS spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms, coercivity (Hc and retentivity (Mr are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.

  2. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  3. Magnetic-field-controlled negative differential conductance in scanning tunneling spectroscopy of graphene npn junction resonators

    Science.gov (United States)

    Li, Si-Yu; Liu, Haiwen; Qiao, Jia-Bin; Jiang, Hua; He, Lin

    2018-03-01

    Negative differential conductance (NDC), characterized by the decreasing current with increasing voltage, has attracted continuous attention for its various novel applications. The NDC typically exists in a certain range of bias voltages for a selected system and controlling the regions of NDC in curves of current versus voltage (I -V ) is experimentally challenging. Here, we demonstrate a magnetic-field-controlled NDC in scanning tunneling spectroscopy of graphene npn junction resonators. The magnetic field not only can switch on and off the NDC, but also can continuously tune the regions of the NDC in the I -V curves. In the graphene npn junction resonators, magnetic fields generate sharp and pronounced Landau-level peaks with the help of the Klein tunneling of massless Dirac fermions. A tip of scanning tunneling microscope induces a relatively shift of the Landau levels in graphene beneath the tip. Tunneling between the misaligned Landau levels results in the magnetic-field-controlled NDC.

  4. Design of a temperature measurement and feedback control system based on an improved magnetic nanoparticle thermometer

    Science.gov (United States)

    Du, Zhongzhou; Sun, Yi; Liu, Jie; Su, Rijian; Yang, Ming; Li, Nana; Gan, Yong; Ye, Na

    2018-04-01

    Magnetic fluid hyperthermia, as a novel cancer treatment, requires precise temperature control at 315 K-319 K (42 °C-46 °C). However, the traditional temperature measurement method cannot obtain the real-time temperature in vivo, resulting in a lack of temperature feedback during the heating process. In this study, the feasibility of temperature measurement and feedback control using magnetic nanoparticles is proposed and demonstrated. This technique could be applied in hyperthermia. Specifically, the triangular-wave temperature measurement method is improved by reconstructing the original magnetization response of magnetic nanoparticles based on a digital phase-sensitive detection algorithm. The standard deviation of the temperature in the magnetic nanoparticle thermometer is about 0.1256 K. In experiments, the temperature fluctuation of the temperature measurement and feedback control system using magnetic nanoparticles is less than 0.5 K at the expected temperature of 315 K. This shows the feasibility of the temperature measurement method for temperature control. The method provides a new solution for temperature measurement and feedback control in hyperthermia.

  5. Magnetic control of potential microrobotic drug delivery systems: nanoparticles, magnetotactic bacteria and self-propelled microjets.

    Science.gov (United States)

    Khalil, Islam S M; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G; Abelmann, Leon; Misra, Sarthak

    2013-01-01

    Development of targeted drug delivery systems using magnetic microrobots increases the therapeutic indices of drugs. These systems have to be incorporated with precise motion controllers. We demonstrate closed-loop motion control of microrobots under the influence of controlled magnetic fields. Point-to-point motion control of a cluster of iron oxide nanoparticles (diameter of 250 nm) is achieved by pulling the cluster towards a reference position using magnetic field gradients. Magnetotactic bacterium (MTB) is controlled by orienting the magnetic fields towards a reference position. MTB with membrane length of 5 µm moves towards the reference position using the propulsion force generated by its flagella. Similarly, self-propelled microjet with length of 50 µm is controlled by directing the microjet towards a reference position by external magnetic torque. The microjet moves along the field lines using the thrust force generated by the ejecting oxygen bubbles from one of its ends. Our control system positions the cluster of nanoparticles, an MTB and a microjet at an average velocity of 190 µm/s, 28 µm/s, 90 µm/s and within an average region-of-convergence of 132 µm, 40 µm, 235 µm, respectively.

  6. Control of the radial electric field shear by modification of the magnetic field configuration in LHD

    International Nuclear Information System (INIS)

    Ida, K.; Yoshinuma, M.; Yokoyama, M.

    2005-01-01

    Control of the radial electric field, E γ , is considered to be important in helical plasmas, because the radial electric field and its shear are expected to reduce neoclassical and anomalous transport, respectively. In general, the radial electric field can be controlled by changing the collisionality, and positive or negative electric field have been obtained by decreasing or increasing the electron density, respectively. Although the sign of the radial electric field can be controlled by changing the collisionality, modification of the magnetic field is required to achieve further control of the radial electric field, especially producing a strong radial electric field shear. In the Large Helical Device (LHD) the radial electric field profiles are shown to be controlled by the modification of the magnetic field by 1) changing the radial profile of the helical ripples, ε h , 2) creating a magnetic island with an external perturbation field coil and 3) changing the local island divertor coil current. (author)

  7. Control of the radial electric field shear by modification of the magnetic field configuration in LHD

    International Nuclear Information System (INIS)

    Ida, K.; Yoshinuma, M.; Yokoyama, M.

    2005-01-01

    Control of the radial electric field, E r , is considered to be important in helical plasmas, because the radial electric field and its shear are expected to reduce neoclassical and anomalous transport, respectively. In general, the radial electric field can be controlled by changing the collisionality, and positive or negative electric fields have been obtained by decreasing or increasing the electron density, respectively. Although the sign of the radial electric field can be controlled by changing the collisionality, modification of the magnetic field is required to achieve further control of the radial electric field, especially to produce a strong radial electric field shear. In the Large Helical Device (LHD) the radial electric field profiles are shown to be controlled by the modification of the magnetic field by (1) changing the radial profile of the effective helical ripples, ε h (2) creating a magnetic island with an external perturbation field coil and (3) changing the local island divertor coil current

  8. Control of Surge in Centrifugal Compressors by Active Magnetic Bearings Theory and Implementation

    CERN Document Server

    Yoon, Se Young; Allaire, Paul E

    2013-01-01

    Control of Surge in Centrifugal Compressors by Active Magnetic Bearings sets out the fundamentals of integrating the active magnetic bearing (AMB) rotor suspension technology in compressor systems, and describes how this relatively new bearing technology can be employed in the active control of compressor surge. The authors provide a self-contained and comprehensive review of rotordynamics and the fundamentals of the AMB technology. The active stabilization of compressor surge employing AMBs in a machine is fully explored, from the modeling of the instability and the design of feedback controllers, to the implementation and experimental testing of the control algorithms in a specially-constructed, industrial-size centrifugal compression system. The results of these tests demonstrate the great potential of the new surge control method developed in this text. This book will be useful for engineers in industries that involve turbocompressors and magnetic bearings, as well as for researchers and graduate students...

  9. Edge localized modes control by resonant magnetic perturbations; Controle des instabilites de bord par perturbations magnetiques resonantes

    Energy Technology Data Exchange (ETDEWEB)

    Nardon, E

    2007-10-15

    The present work is dedicated to one of the most promising methods of control of the ELMs (Edge Localized Modes), based on a system of coils producing Resonant Magnetic Perturbations (RMPs). Our main objectives are, on the one hand, to improve the physical understanding of the mechanisms at play, and on the other hand to propose a concrete design of ELMs control coils for ITER. In order to calculate and analyze the magnetic perturbations produced by a given set of coils, we have developed the ERGOS code. The first ERGOS calculation was for the DIII-D ELMs control coils, the I-coils. It showed that they produce magnetic islands chains which overlap at the edge of the plasma, resulting in the ergodization of the magnetic field. We have then used ERGOS for the modelling of the experiments on ELMs control using the error field correction coils at JET and MAST. In the case of JET, we have shown the existence of a correlation between the mitigation of the ELMs and the ergodization of the magnetic field at the edge, in agreement with the DIII-D result. In order to design the ELMs control coils for ITER we have used ERGOS intensively, taking the case of the DIII-D I-coils as a reference. Three candidate designs came out, which we presented at the ITER Design Review, in 2007. Recently, the ITER management decided to provide a budget for building ELMs control coils, the design of which remains to be chosen between two of the three options that we proposed. Finally, in order to understand better the non-linear magnetohydrodynamics phenomena taking place in ELMs control by RMPs, we performed numerical simulations, in particular with the JOREK code for a DIII-D case. The simulations reveal the existence of convection cells induced at the edge by the magnetic perturbations, and the possible screening of the RMPs in presence of rotation.

  10. Interstellar Chemistry Special Feature: The chemistry in circumstellar envelopes of evolved stars: Following the origin of the elements to the origin of life

    Science.gov (United States)

    Ziurys, Lucy M.

    2006-08-01

    Mass loss from evolved stars results in the formation of unusual chemical laboratories: circumstellar envelopes. Such envelopes are found around carbon- and oxygen-rich asymptotic giant branch stars and red supergiants. As the gaseous material of the envelope flows from the star, the resulting temperature and density gradients create a complex chemical environment involving hot, thermodynamically controlled synthesis, molecule "freeze-out," shock-initiated reactions, and photochemistry governed by radical mechanisms. In the circumstellar envelope of the carbon-rich star IRC+10216, >50 different chemical compounds have been identified, including such exotic species as C8H, C3S, SiC3, and AlNC. The chemistry here is dominated by molecules containing long carbon chains, silicon, and metals such as magnesium, sodium, and aluminum, which makes it quite distinct from that found in molecular clouds. The molecular composition of the oxygen-rich counterparts is not nearly as well explored, although recent studies of VY Canis Majoris have resulted in the identification of HCO+, SO2, and even NaCl in this object, suggesting chemical complexity here as well. As these envelopes evolve into planetary nebulae with a hot, exposed central star, synthesis of molecular ions becomes important, as indicated by studies of NGC 7027. Numerous species such as HCO+, HCN, and CCH are found in old planetary nebulae such as the Helix. This "survivor" molecular material may be linked to the variety of compounds found recently in diffuse clouds. Organic molecules in dense interstellar clouds may ultimately be traced back to carbon-rich fragments originally formed in circumstellar shells.

  11. Magnetic methods for nondestructive control of residual stresses

    International Nuclear Information System (INIS)

    Suarez, J.C.; Cruz, C.; Alarcon, H.; Ledo, J.L.

    1993-01-01

    In this work, magnetic methods being used at present to determine the TR in ferromagnetic materials are introduced, comparing them with similar technic, based in the application of Strain gauges, DRX and ultrasonic. The technical requirements needed to perform TR measurements, based on the magnetoelastic effect (MEA) and the measuring of Barkhausen noise (BNA) are analyzed. Finally, it is showed the development obtained by CEADEN in the use of these two techniques and the perspectives of their introduction in the country, using national equipment

  12. Permanent magnet brushless DC motor drives and controls

    CERN Document Server

    Xia, Chang-liang

    2012-01-01

    An advanced introduction to the simulation and hardware implementation of BLDC motor drives A thorough reference on the simulation and hardware implementation of BLDC motor drives, this book covers recent advances in the control of BLDC motor drives, including intelligent control, sensorless control, torque ripple reduction and hardware implementation. With the guidance of the expert author team, readers will understand the principle, modelling, design and control of BLDC motor drives. The advanced control methods and new achievements of BLDC motor drives, of interest to more a

  13. Independent control of the vortex chirality and polarity in a pair of magnetic nanodots

    Energy Technology Data Exchange (ETDEWEB)

    Li, Junqin; Wang, Yong, E-mail: wangyong@sinap.ac.cn; Cao, Jiefeng; Meng, Xiangyu; Zhu, Fangyuan; Wu, Yanqing; Tai, Renzhong

    2017-08-01

    Independent control of the vortex chirality and polarity is realized by changing the in-plane magnetic field direction in nanodot pair through Object Oriented Micromagnetic Framework (OOMMF) simulation. The two magnetic circles are close to each other and have magnetic interaction. The two circles always have the same polarity and opposite chirality at every remanent state. There are totally four predictable magnetic states in the nanodot pair which can be obtained in the remanent state relaxed from the saturation state along all possible directions. An explanation on the formation of vortex states is given by vortex dynamics. The vortex states are stable in large out-of-plane magnetic field which is in a direction opposite to the vortex polarity. The geometry of the nanodot pair gives a way to easily realize a vortex state with specific polarity and chirality.

  14. Method for providing slip energy control in permanent magnet electrical machines

    Science.gov (United States)

    Hsu, John S.

    2006-11-14

    An electric machine (40) has a stator (43), a permanent magnet rotor (38) with permanent magnets (39) and a magnetic coupling uncluttered rotor (46) for inducing a slip energy current in secondary coils (47). A dc flux can be produced in the uncluttered rotor when the secondary coils are fed with dc currents. The magnetic coupling uncluttered rotor (46) has magnetic brushes (A, B, C, D) which couple flux in through the rotor (46) to the secondary coils (47c, 47d) without inducing a current in the rotor (46) and without coupling a stator rotational energy component to the secondary coils (47c, 47d). The machine can be operated as a motor or a generator in multi-phase or single-phase embodiments and is applicable to the hybrid electric vehicle. A method of providing a slip energy controller is also disclosed.

  15. Pressure control valve using proportional electro-magnetic solenoid actuator

    International Nuclear Information System (INIS)

    Yun, So Nam; Ham, Young Bog; Park, Pyoung Won

    2006-01-01

    This paper presents an experimental characteristics of electro-hydraulic proportional pressure control valve. In this study, poppet and valve body which are assembled into the proportional solenoid were designed and manufactured. The constant force characteristics of proportional solenoid actuator in the control region should be independent of the plunger position in order to be used to control the valve position in the fluid flow control system. The stroke-force characteristics of the proportional solenoid actuator is determined by the shape (or parameters) of the control cone. In this paper, steady state and transient characteristics of the solenoid actuator for electro-hydraulic proportional valve are analyzed using finite element method and it is confirmed that the proportional solenoid actuator has a constant attraction force in the control region independently on the stroke position. The effects of the parameters such as control cone length, thickness and taper length are also discussed

  16. Electric Field Controlled Magnetism in BiFeO3/Ferromagnet Films

    Science.gov (United States)

    Holcomb, M. B.; Chu, Y. H.; Martin, L. W.; Gajek, M.; Seidel, J.; Ramesh, R.; Scholl, A.; Fraile-Rodriguez, A.

    2008-03-01

    Electric field control of magnetism is a hot technological topic at the moment due to its potential to revolutionize today's devices. Magnetoelectric materials, those having both electric and magnetic order and the potential for coupling between the two, are a promising avenue to approach electric control. BiFeO3, both a ferroelectric and an antiferromagnet, is the only single phase room temperature magnetoelectric that is currently known. In addition to other possibilities, its multiferroic nature has potential in the very active field of exchange bias, where an antiferromagnetic thin film pins the magnetic direction of an adjoining ferromagnetic layer. Since this antiferromagnet is electrically tunable, this coupling could allow electric-field control of the ferromagnetic magnetization. Direction determination of antiferromagnetic domains in BFO has recently been shown using linear and circular dichroism studies. Recently, this technique has been extended to look at the magnetic domains of a ferromagnetic grown on top of BFO. The clear magnetic changes induced by application of electric fields reveal the possibility of electric control.

  17. Modeling and simulation of permanent magnet synchronous motor based on neural network control strategy

    Science.gov (United States)

    Luo, Bingyang; Chi, Shangjie; Fang, Man; Li, Mengchao

    2017-03-01

    Permanent magnet synchronous motor is used widely in industry, the performance requirements wouldn't be met by adopting traditional PID control in some of the occasions with high requirements. In this paper, a hybrid control strategy - nonlinear neural network PID and traditional PID parallel control are adopted. The high stability and reliability of traditional PID was combined with the strong adaptive ability and robustness of neural network. The permanent magnet synchronous motor will get better control performance when switch different working modes according to different controlled object conditions. As the results showed, the speed response adopting the composite control strategy in this paper was faster than the single control strategy. And in the case of sudden disturbance, the recovery time adopting the composite control strategy designed in this paper was shorter, the recovery ability and the robustness were stronger.

  18. Controlled trapping and detection of magnetic particles by a magnetic microactuator and a giant magnetoresistance (GMR) sensor

    KAUST Repository

    Giouroudi, Ioanna

    2014-04-01

    This paper presents the design and testing of an integrated micro-chip for the controlled trapping and detection of magnetic particles (MPs). A unique magnetic micro-actuator consisting of square-shaped conductors is used to manipulate the MPs towards a giant magnetoresistance (GMR) sensing element which rapidly detects the majority of MPs trapped around the square-shaped conductors. The ability to precisely transport a small number of MPs in a controlled manner over long distances by magnetic forces enables the rapid concentration of a majority of MPs to the sensing zone for detection. This is especially important in low concentration samples. The conductors are designed in such a manner so as to increase the capture efficiency as well as the precision and speed of transportation. By switching current to different conductors, MPs can be manipulated and immobilized on the innermost conductor where the GMR sensor is located. This technique rapidly guides the MPs towards the sensing zone. Secondly, for optimum measurement capability with high spatial resolution the GMR sensor is fabricated directly underneath and all along the innermost conductor to detect the stray fields originating from the MPs. Finally, a microfluidic channel is fabricated on top of this micro-chip. Experiments inside the microchannel were carried out and the MPs were successfully trapped at the sensing area. © (2014) Trans Tech Publications.

  19. Control Of DC 30V/15A Power Supply Using AT89C Micro controller By Look-Up Table Method For Magnetization System Application

    International Nuclear Information System (INIS)

    Abdillah, Arieko; Hermanto, Lingga; Manaf, Azwar

    2003-01-01

    Experiment of Control System Dc current based on micro controller Atm el AT89C52 has been done. Micro controller controls the transistors that will be activate. These transistors will allow the DC current passed trough to produce a homogeneous of magnetic field. This system produce DC current from 1,8 A to 12 A that produce the magnetic field measures from 23 mT to 325 mT. All manner of data using look-up table method. Micro controller and power supply circuit were isolated by optocoupler. This system can be used as first prototypes of control system of magnetic field for magnetize purpose

  20. The magnet power control system for the tandem mirror experiment-upgrade

    International Nuclear Information System (INIS)

    Bell, H.H.

    1983-01-01

    This paper describes the desktop computer/CAMAC based system that controls the power source for the Tandem Mirror Experiment-Upgrade (TMX-U) magnet power system. Presently it contains 42 dc rectifier power supplies connected to 24 magnet coils arranged in 17 circuits. During each shot, the system delivers 22.6 MW dc to the magnets for about 3 s. The system is presently being changed to add six power supplies, two solenoidal throttle coils, and two reverse C-coils. When complete, the delivered power will increase to 36.9 MW. The closed-loop control system usually provides current (and thus, magnetic field) that is within 1% of the requested current. Achieving this accuracy required using grounding, shielding, and isolation methods to reduce noise and related problems

  1. Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

    Science.gov (United States)

    Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Ishii, Yui; Mori, Shigeo

    2016-12-01

    We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La 0.7 Sr 0.3 MnO 3 (LSMO) and Nd 0.5 Sr 0.5 MnO 3 , in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  2. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  3. Magnetic dipole moment estimation and compensation for an accurate attitude control in nano-satellite missions

    Science.gov (United States)

    Inamori, Takaya; Sako, Nobutada; Nakasuka, Shinichi

    2011-06-01

    Nano-satellites provide space access to broader range of satellite developers and attract interests as an application of the space developments. These days several new nano-satellite missions are proposed with sophisticated objectives such as remote-sensing and observation of astronomical objects. In these advanced missions, some nano-satellites must meet strict attitude requirements for obtaining scientific data or images. For LEO nano-satellite, a magnetic attitude disturbance dominates over other environmental disturbances as a result of small moment of inertia, and this effect should be cancelled for a precise attitude control. This research focuses on how to cancel the magnetic disturbance in orbit. This paper presents a unique method to estimate and compensate the residual magnetic moment, which interacts with the geomagnetic field and causes the magnetic disturbance. An extended Kalman filter is used to estimate the magnetic disturbance. For more practical considerations of the magnetic disturbance compensation, this method has been examined in the PRISM (Pico-satellite for Remote-sensing and Innovative Space Missions). This method will be also used for a nano-astrometry satellite mission. This paper concludes that use of the magnetic disturbance estimation and compensation are useful for nano-satellites missions which require a high accurate attitude control.

  4. Oxygen-enabled control of Dzyaloshinskii-Moriya Interaction in ultra-thin magnetic films

    KAUST Repository

    Belabbes, Abderrezak

    2016-04-22

    The search for chiral magnetic textures in systems lacking spatial inversion symmetry has attracted a massive amount of interest in the recent years with the real space observation of novel exotic magnetic phases such as skyrmions lattices, but also domain walls and spin spirals with a defined chirality. The electrical control of these textures offers thrilling perspectives in terms of fast and robust ultrahigh density data manipulation. A powerful ingredient commonly used to stabilize chiral magnetic states is the so-called Dzyaloshinskii-Moriya interaction (DMI) arising from spin-orbit coupling in inversion asymmetric magnets. Such a large antisymmetric exchange has been obtained at interfaces between heavy metals and transition metal ferromagnets, resulting in spin spirals and nanoskyrmion lattices. Here, using relativistic first-principles calculations, we demonstrate that the magnitude and sign of DMI can be entirely controlled by tuning the oxygen coverage of the magnetic film, therefore enabling the smart design of chiral magnetism in ultra-thin films. We anticipate that these results extend to other electronegative ions and suggest the possibility of electrical tuning of exotic magnetic phases.

  5. Mechanical control of magnetism in oxygen deficient perovskite SrTiO3.

    Science.gov (United States)

    Zhang, Yajun; Wang, Jie; Sahoo, M P K; Shimada, Takahiro; Kitamura, Takayuki

    2015-10-28

    Mechanical control of magnetism in perovskite oxides is an important and promising approach in spintronics. Based on the first-principles calculations, we demonstrate that a negative pressure leads to a great enhancement of magnetic moment in deficient SrTiO3 with oxygen vacancies, whereas a positive pressure results in the gradual disappearance of magnetism. Spin charge density, Bader charge analysis and electronic density of states successfully elucidate the origin and underlying physics of the enhancement and disappearance of magnetism. It is found that the split electronic states of dz(2), dyz and dzx in the 3d orbitals of Ti atoms remarkably contribute to the occupancy of majority spin states under negative pressure, which induces a large magnetic moment. Under positive pressure, however, the equal occupancy of both majority and minority t2g and eg states leads to the disappearance of magnetization. In addition, both negative and positive pressures can largely lower the vacancy formation enthalpy, suggesting that the oxygen vacancy is preferable with pressure. Our findings may provide a mechanism to achieve the pressure control of magnetization in nonmagnetic perovskite oxides.

  6. Speed Sensorless Control of Permanent Magnet Synchronous Motors in Mine Electric Locomotive Drive

    Directory of Open Access Journals (Sweden)

    Yudong LI

    2014-04-01

    Full Text Available This paper presents a novel sensorless control method of permanent magnet synchronous motors a low speed based on a high-frequency voltage signal injection. The approach superimposes a persistent HF voltage signal into the estimated d-axis to get the rotor position error angle-related signal by detecting the corresponding voltage response and current response. Then the rotor position and motor speed are obtained. Theoretical analysis and simulation results demonstrate that the approach can achieve sensorless control of permanent magnet synchronous motors at zero and low speed, ensure good dynamic and static performances, and achieve effective control when applied to servo system. Finally, a test prototype system which used a digital signal processor and space vector pulse width modulation technology has been developed. Experimental results show that the system has better static, the effectiveness and dynamic performance of the adaptive test signals in a sensorless controlled surface-mounted permanent magnet synchronous machines.

  7. Input-output linearizing tracking control of induction machine with the included magnetic saturation

    DEFF Research Database (Denmark)

    Dolinar, Drago; Ljusev, Petar; Stumberger, Gorazd

    2003-01-01

    The tracking control design of an induction motor, based on input-output linearisation with magnetic saturation included is addressed. The magnetic saturation is represented by a nonlinear magnetising curve for the iron core and is used in the control, the observer of the state variables......, and in the load torque estimator. An input-output linearising control is used to achieve better tracking performances. It is based on the mixed 'stator current - rotor flux linkage' induction motor model with magnetic saturation considered in the stationary reference frame. Experimental results show...... that the proposed input-output linearising tracking control with saturation included behaves considerably better than the one without saturation, and that it introduces smaller position and speed errors, and better motor stiffness on account of the increased computational complexity....

  8. Arrangement of permanent magnet and reed switches for control rod position indicator of SMART CEDM

    International Nuclear Information System (INIS)

    Yoo, J. Y.; Kim, J. I.; Kim, J. H.; Hur, H.; Jang, M. H.

    2001-01-01

    The reliability and accuracy of the information on control rod position are very important to the reactor safety and the design of the core protection system. A survey on the RSPT(Reed Switch Position Transmitter) type control rod position indication system and its actual implementation in the exiting nuclear power plants in Korea was performed first. The control rod position indicator having the high performance for SMART was developed on the basis of RSPT technology identified through the survey. The arrangement of permanent magnet and reed switches is the most important procedure in the design of control rod position indication. In this study, the characteristics of permanent magnet and reed switches are introduced and the calculation method for arrangement of permanent magnet and reed switch is presented

  9. Multi-Objective PID-Controller Tuning for a Magnetic Levitation System using NSGA-II

    DEFF Research Database (Denmark)

    Pedersen, Gerulf K. M.; Yang, Zhenyu

    2006-01-01

    This paper investigates the issue of PID-controller parameter tuning for a magnetic levitation system using the non-dominated sorting genetic algorithm (NSGA-II). The magnetic levitation system is inherently unstable and the PID-controller parameters are hard to find using conventional methods....... Based on four different performance measures, derived from the step response of the levitation system, the algorithm is used to find a set of non-dominated parameters for a PID-controller that can stabilize the system and minimize the performance measures....

  10. Magnetic state controllable critical temperature in epitaxial Ho/Nb bilayers

    Directory of Open Access Journals (Sweden)

    Yuanzhou Gu

    2014-04-01

    Full Text Available We study the magnetic properties of Ho thin films with different crystallinity (either epitaxial or non-epitaxial and investigate their proximity effects with Nb thin films. Magnetic measurements show that epitaxial Ho has large anisotropy in two different crystal directions in contrast to non-epitaxial Ho. Transport measurements show that the superconducting transition temperature (Tc of Nb thin films can be significantly suppressed at zero field by epitaxial Ho compared with non-epitaxial Ho. We also demonstrate a direct control over Tc by changing the magnetic states of the epitaxial Ho layer, and attribute the strong proximity effects to exchange interaction.

  11. Control over Janus micromotors by the strength of a magnetic field

    Science.gov (United States)

    Baraban, Larysa; Makarov, Denys; Schmidt, Oliver G.; Cuniberti, Gianaurelio; Leiderer, Paul; Erbe, Artur

    2013-01-01

    For transportation of molecules or biological cells using artificial motors, the control over their motion, i.e. direction and speed of transfer, is important. Here, we demonstrate that modification of the velocity and orientation of a magnetic Janus particle can be efficiently controlled by tuning the strength of an applied homogeneous magnetic field. Interestingly, by keeping the same orientation of the magnetic field but changing its magnitude not only the velocity of capped particles can be altered but even their direction of motion can be reversed. We put forth a simple qualitative model, which allows us to explain this intriguing observation.For transportation of molecules or biological cells using artificial motors, the control over their motion, i.e. direction and speed of transfer, is important. Here, we demonstrate that modification of the velocity and orientation of a magnetic Janus particle can be efficiently controlled by tuning the strength of an applied homogeneous magnetic field. Interestingly, by keeping the same orientation of the magnetic field but changing its magnitude not only the velocity of capped particles can be altered but even their direction of motion can be reversed. We put forth a simple qualitative model, which allows us to explain this intriguing observation. Electronic supplementary information (ESI) available: Videos (1-3) describe the behavior of the magnetic Janus micromotors at different magnetic fields applied. The magnetic field is always applied along the positive direction of the y-axis. All the movies are recorded at the same frame rate of 21 images per second. Experiments were performed at 30 wt% of hydrogen peroxide in aqueous solution. Video 1 shows the motion of the Janus micromotors when a small magnetic field is applied (B = 0.2 mT). The particle is propelled in the direction ``opposite to the cap'' with a velocity of about 6 μm s-1. Video 2 displays the motion of the same Janus bead when an intermediately strong

  12. CIRCUMSTELLAR MAGNETITE FROM THE LAP 031117 CO3.0 CHONDRITE

    Energy Technology Data Exchange (ETDEWEB)

    Zega, Thomas J. [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721-0092 (United States); Haenecour, Pierre; Floss, Christine [Laboratory for Space Sciences and Physics Department, Washington University, One Brookings Drive, Campus Box 1105, St. Louis, MO 63130 (United States); Stroud, Rhonda M., E-mail: tzega@lpl.arizona.edu [Materials Science and Technology Division, Code 6366, Naval Research Laboratory, 4555 Overlook Ave, SW Washington, DC 20375 (United States)

    2015-07-20

    We report the first microstructural confirmation of circumstellar magnetite, identified in a petrographic thin section of the LaPaz Icefield 031117 CO3.0 chondrite. The O-isotopic composition of the grain indicates an origin in a low-mass (∼2.2 M{sub ⊙}), approximately solar metallicity red/asymptotic giant branch (RGB/AGB) star undergoing first dredge-up. The magnetite is a single crystal measuring 750 × 670 nm, is free of defects, and is stoichiometric Fe{sub 3}O{sub 4}. We hypothesize that the magnetite formed via oxidation of previously condensed Fe dust within the circumstellar envelope of its progenitor star. Using an empirically derived rate constant for this reaction, we calculate that such oxidation could have occurred over timescales ranging from approximately ∼9000–500,000 years. This timescale is within the lifetime of estimates for dust condensation within RGB/AGB stars.

  13. Direct torque control via feedback linearization for permanent magnet synchronous motor drives

    DEFF Research Database (Denmark)

    Lascu, Cristian; Boldea, Ion; Blaabjerg, Frede

    2012-01-01

    The paper describes a direct torque controlled (DTC) permanent magnet synchronous motor (PMSM) drive that employs feedback linearization and uses sliding-mode and linear controllers. We introduce a new feedback linearization approach that yields a decoupled linear PMSM model with two state...

  14. One-phase dual converter for two quadrant power control of superconducting magnets

    International Nuclear Information System (INIS)

    Ehsani, M.; Kustom, R.I.; Boom, R.W.

    1985-01-01

    This paper presents the results of theoretical and experimental development of a new dc-ac-dc converter for superconducting magnet power supplies. The basic operating principles of the circuit are described followed by a theoretical treatment of the dynamics and control of the system. The successful results of the first experimental operation and control of such a circuit are presented and discussed

  15. Adaptive Sliding Mode Control of Chaos in Permanent Magnet Synchronous Motor via Fuzzy Neural Networks

    Directory of Open Access Journals (Sweden)

    Tat-Bao-Thien Nguyen

    2014-01-01

    Full Text Available In this paper, based on fuzzy neural networks, we develop an adaptive sliding mode controller for chaos suppression and tracking control in a chaotic permanent magnet synchronous motor (PMSM drive system. The proposed controller consists of two parts. The first is an adaptive sliding mode controller which employs a fuzzy neural network to estimate the unknown nonlinear models for constructing the sliding mode controller. The second is a compensational controller which adaptively compensates estimation errors. For stability analysis, the Lyapunov synthesis approach is used to ensure the stability of controlled systems. Finally, simulation results are provided to verify the validity and superiority of the proposed method.

  16. Heterodyne spatial interferometry of circumstellar dust shells at a wavelength of 11 microns

    International Nuclear Information System (INIS)

    Sutton, E.C.

    1979-01-01

    The spatial distribution of the 11 micron thermal emission from circumstellar dust envelopes has been studied using an infrared heterodyne interferometer. Circumstellar dust envelopes often exist around cool, late-type stars. These envelopes radiate strongly at 11 microns, particularly if they are composed of silicate grains, which have a strong emission feature near this wavelength. By measuring the spatial distribution of this dust emission it is possible to probe the temperatures and densities of the circumstellar material and thereby to gain an understanding of the structures of circumstellar envelopes. Among the sources which have been observed with this interferometer are α Orionis, o Ceti, VY Canis Majoris, and IRC + 10216. The 11 micron brightness distributions of these objects all have spatially extended dust-emission components which are resolved in these measurements. The dust envelopes of α Orionis and o Ceti are optically thin, having optical depths at 11 microns of 0.02 and 0.04, respectively. In addition, variations are seen in the 11 micron brightness distribution of o Ceti which correlate with the stellar variability. These variations primarily represent changes in the relative amount of spatially compact photospheric emission and spatially extended dust emission. The source VY Canis Majoris, on the other had, has a dust envelope which is optically thick at 11 microns. The dust envelope of IRC + 10216, although optically thick at visible wavelengths, does not seem to be optically thick at 11 microns since there is a spatially compact component of the 11 micron brightness distribution which presumably represents emission from the central star

  17. Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science

    OpenAIRE

    Kuchner, Marc J.; Silverberg, Steven M.; Bans, Alissa S.; Bhattacharjee, Shambo; Kenyon, Scott J.; Debes, John H.; Currie, Thayne; Garcia, Luciano; Jung, Dawoon; Lintott, Chris; McElwain, Michael; Padgett, Deborah L.; Rebull, Luisa M.; Wisniewski, John P.; Nesvold, Erika

    2016-01-01

    The Disk Detective citizen science project aims to find new stars with 22 μm excess emission from circumstellar dust using data from NASA's Wide-field Infrared Survey Explorer (WISE) mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false positives (galaxies, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectr...

  18. Surface-Chemistry-Mediated Control of Individual Magnetic Helical Microswimmers in a Swarm.

    Science.gov (United States)

    Wang, Xiaopu; Hu, Chengzhi; Schurz, Lukas; De Marco, Carmela; Chen, Xiangzhong; Pané, Salvador; Nelson, Bradley J

    2018-05-31

    Magnetic helical microswimmers, also known as artificial bacterial flagella (ABFs), perform 3D navigation in various liquids under low-strength rotating magnetic fields by converting rotational motion to translational motion. ABFs have been widely studied as carriers for targeted delivery and release of drugs and cells. For in vivo/ in vitro therapeutic applications, control over individual groups of swimmers within a swarm is necessary for several biomedical applications such as drug delivery or small-scale surgery. In this work, we present the selective control of individual swimmers in a swarm of geometrically and magnetically identical ABFs by modifying their surface chemistry. We confirm experimentally and analytically that the forward/rotational velocity ratio of ABFs is independent of their surface coatings when the swimmers are operated below their step-out frequency (the frequency requiring the entire available magnetic torque to maintain synchronous rotation). We also show that ABFs with hydrophobic surfaces exhibit larger step-out frequencies and higher maximum forward velocities compared to their hydrophilic counterparts. Thus, selective control of a group of swimmers within a swarm of ABFs can be achieved by operating the selected ABFs at a frequency that is below their step-out frequencies but higher than the step-out frequencies of unselected ABFs. The feasibility of this method is investigated in water and in biologically relevant solutions. Selective control is also demonstrated inside a Y-shaped microfluidic channel. Our results present a systematic approach for realizing selective control within a swarm of magnetic helical microswimmers.

  19. Design of a 2-DOF Control and Disturbance Estimator for a Magnetic Levitation System

    Directory of Open Access Journals (Sweden)

    A. Pati

    2017-02-01

    Full Text Available This work proposes a systematic two-degree freedom control scheme to improve the reference input tracking and load disturbance rejection for an unstable magnetic levitation system. The proposed control strategy is a two-step design process. Firstly, a proportional derivative controller is introduced purposely to get the desired set-point response of the magnetic levitation system and then, an integral square error (ISE performance specification is used for designing a set-point tracking controller. Secondly, a disturbance estimator is designed using the desired closed loop complimentary sensitivity function for the rejection of load disturbances. This leads to the decoupling of the nominal set-point response from the load disturbance response similar to an open loop control manner. Thus, it is convenient to optimize both controllers simultaneously as well as separately. The effectiveness of the proposed control strategy is validated through simulation.

  20. Imparting magnetic dipole heterogeneity to internalized iron oxide nanoparticles for microorganism swarm control

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Paul Seung Soo, E-mail: psk25@drexel.edu [Drexel University, Department of Mechanical Engineering and Mechanics (United States); Becker, Aaron, E-mail: aaron.becker@childrens.harvard.edu [Harvard University, Department of Cardiovascular Surgery (United States); Ou, Yan, E-mail: ouy2@rpi.edu; Julius, Anak Agung, E-mail: agung@rpi.edu [Rensselaer Polytechnic Institute, Department of Electrical, Computer, and Systems Engineering (United States); Kim, Min Jun, E-mail: mkim@coe.drexel.edu [Drexel University, Department of Mechanical Engineering and Mechanics (United States)

    2015-03-15

    Tetrahymena pyriformis is a single cell eukaryote that can be modified to respond to magnetic fields, a response called magnetotaxis. Naturally, this microorganism cannot respond to magnetic fields, but after modification using iron oxide nanoparticles, cells are magnetized and exhibit a constant magnetic dipole strength. In experiments, a rotating field is applied to cells using a two-dimensional approximate Helmholtz coil system. Using rotating magnetic fields, we characterize discrete cells’ swarm swimming which is affected by several factors. The behavior of the cells under these fields is explained in detail. After the field is removed, relatively straight swimming is observed. We also generate increased heterogeneity within a population of cells to improve controllability of a swarm, which is explored in a cell model. By exploiting this straight swimming behavior, we propose a method to control discrete cells utilizing a single global magnetic input. Successful implementation of this swarm control method would enable teams of microrobots to perform a variety of in vitro microscale tasks impossible for single microrobots, such as pushing objects or simultaneous micromanipulation of discrete entities.

  1. Imparting magnetic dipole heterogeneity to internalized iron oxide nanoparticles for microorganism swarm control

    International Nuclear Information System (INIS)

    Kim, Paul Seung Soo; Becker, Aaron; Ou, Yan; Julius, Anak Agung; Kim, Min Jun

    2015-01-01

    Tetrahymena pyriformis is a single cell eukaryote that can be modified to respond to magnetic fields, a response called magnetotaxis. Naturally, this microorganism cannot respond to magnetic fields, but after modification using iron oxide nanoparticles, cells are magnetized and exhibit a constant magnetic dipole strength. In experiments, a rotating field is applied to cells using a two-dimensional approximate Helmholtz coil system. Using rotating magnetic fields, we characterize discrete cells’ swarm swimming which is affected by several factors. The behavior of the cells under these fields is explained in detail. After the field is removed, relatively straight swimming is observed. We also generate increased heterogeneity within a population of cells to improve controllability of a swarm, which is explored in a cell model. By exploiting this straight swimming behavior, we propose a method to control discrete cells utilizing a single global magnetic input. Successful implementation of this swarm control method would enable teams of microrobots to perform a variety of in vitro microscale tasks impossible for single microrobots, such as pushing objects or simultaneous micromanipulation of discrete entities

  2. Study on the controllability for active magnetic bearings

    International Nuclear Information System (INIS)

    Jiang, Z F; Wu, H C; Lu, H; Li, C R

    2005-01-01

    One of the main challenges in AMB is its controllability which means it is difficult to get a stable spindle and controller. To solve this problem, some methods have been developed previously, but the value of the controllability of AMB was not calculated. The subject of our study is to develop a new method and find a mathematical model that aims to research the controllability of AMB, the status at passing through levitation process, running, a critical speed and achieve high-speed rotation. The stiffness and damping of AMB, which changes randomly along with the rotor running, are determined by the controller system. How to get the relationship between the stiffness and damping with dynamic coefficients of rotor-AMB system is a key problem to get an optimization controller. In this paper, a mathematical model of the relationship is established. Stiffness and damping of AMB can change if the parameter of controller modulated. Based on rotor dynamics theory, the dynamic characteristics of rotors such as critical speeds, system stability and unbalanced excitation are analyzed. Computer simulations are carried out and the effectiveness of the presented procedure is investigated

  3. High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk around UX Tau A

    Science.gov (United States)

    Serabyn, G.; Grady, C. A.; Currie, T.

    2012-01-01

    We present H-band polarimetric imagery of UX Tau A taken with HiCIAO/AO188 on the Subaru Telescope. UX Tau A has been classified as a pre-transitional disk object, with a gap structure separating its inner and outer disks. Our imagery taken with the 0.15" (21 AU) radius coronagraphic mask has revealed a strongly polarized circumstellar disk surrounding UX Tau A which extends to 120 AU, at a spatial resolution of 0.1" (14 AU). It is inclined by 46 degrees plus or minus 2 degrees as the west side is nearest. Although SED modeling and sub-millimeter imagery suggested the presence of a gap in the disk, with the inner edge of the outer disk estimated to be located at 25 - 30 AU, we detect no evidence of a gap at the limit of our inner working angle (23AU) at the near-infrared wavelength. We attribute the observed strong polarization (up to 66 %) to light scattering by dust grains in the disk. However, neither polarization models of the circumstellar disk based on Rayleigh scattering nor Mie scattering approximations were consistent with the observed azimuthal profile of the polarization degrees of the disk. Instead, a geometric optics model of the disk with nonspherical grains with the radii of 30 micrometers is consistent with the observed profile. We suggest that the dust grains have experienced frequent collisional coagulations and have grown in the circumstellar disk of UX Tau A.

  4. Constraints on Circumstellar Dust Grain Sizes from High Spatial Resolution Observations in the Thermal Infrared

    Science.gov (United States)

    Bloemhof, E. E.; Danen, R. M.; Gwinn, C. R.

    1996-01-01

    We describe how high spatial resolution imaging of circumstellar dust at a wavelength of about 10 micron, combined with knowledge of the source spectral energy distribution, can yield useful information about the sizes of the individual dust grains responsible for the infrared emission. Much can be learned even when only upper limits to source size are available. In parallel with high-resolution single-telescope imaging that may resolve the more extended mid-infrared sources, we plan to apply these less direct techniques to interpretation of future observations from two-element optical interferometers, where quite general arguments may be made despite only crude imaging capability. Results to date indicate a tendency for circumstellar grain sizes to be rather large compared to the Mathis-Rumpl-Nordsieck size distribution traditionally thought to characterize dust in the general interstellar medium. This may mean that processing of grains after their initial formation and ejection from circumstellar atmospheres adjusts their size distribution to the ISM curve; further mid-infrared observations of grains in various environments would help to confirm this conjecture.

  5. Magnetic induction of hyperthermia by a modified self-learning fuzzy temperature controller

    Science.gov (United States)

    Wang, Wei-Cheng; Tai, Cheng-Chi

    2017-07-01

    The aim of this study involved developing a temperature controller for magnetic induction hyperthermia (MIH). A closed-loop controller was applied to track a reference model to guarantee a desired temperature response. The MIH system generated an alternating magnetic field to heat a high magnetic permeability material. This wireless induction heating had few side effects when it was extensively applied to cancer treatment. The effects of hyperthermia strongly depend on the precise control of temperature. However, during the treatment process, the control performance is degraded due to severe perturbations and parameter variations. In this study, a modified self-learning fuzzy logic controller (SLFLC) with a gain tuning mechanism was implemented to obtain high control performance in a wide range of treatment situations. This implementation was performed by appropriately altering the output scaling factor of a fuzzy inverse model to adjust the control rules. In this study, the proposed SLFLC was compared to the classical self-tuning fuzzy logic controller and fuzzy model reference learning control. Additionally, the proposed SLFLC was verified by conducting in vitro experiments with porcine liver. The experimental results indicated that the proposed controller showed greater robustness and excellent adaptability with respect to the temperature control of the MIH system.

  6. Power and reactive power simultaneous control by 0.5 MJ superconducting magnet energy storage

    International Nuclear Information System (INIS)

    Ise, Toshifumi; Tsuji, Kiichiro; Murakami, Yoshishige

    1984-01-01

    Superconducting magnet energy storage (SMES) is expected to be widely applied to the pulsed sources for fusion reactor research and to the energy storage substituting for pumping-up power stations, because of its fast energy storing and discharging and very high efficiency. Some results have been obtained so far. In this paper, however, the simultaneous control of power and reactive power is considered for an energy storage composed of two sets of thyristorized power conversion system and superconducting magnets in series connection, and a direct digital control system is described on the principle, design and configuration including the compensator, and on the experiment using the 0.5 MJ superconducting magnet energy storage installed in the Superconduction Engineering Experiment Center, Osaka University. The results obtained are as follows: (1) P control priority mode and Q control priority mode (in which power and reactive power control has priority, respectively) were proposed as the countermeasures when the simultaneous control of power and reactive power became impossible; (2) the design method was established, by which power and reactive power control loops can independently be designed as a result of simulation; (3) the achievement of the simultaneous control of power and reactive power was confirmed by using P-control priority mode and Q-control priority mode, in the experiment using the control system designed by simulation. The validity of simulation model was also confirmed by actual response waveforms. (Wakatsuki, Y.)

  7. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  8. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  9. Control of light scattering by nanoparticles with optically-induced magnetic responses

    International Nuclear Information System (INIS)

    Liu Wei; Miroshnichenko, Andrey E.; Kivshar, Yuri S.

    2014-01-01

    Conventional approaches to control and shape the scattering patterns of light generated by different nanostructures are mostly based on engineering of their electric response due to the fact that most metallic nanostructures support only electric resonances in the optical frequency range. Recently, fuelled by the fast development in the fields of metamaterials and plasmonics, artificial optically-induced magnetic responses have been demonstrated for various nanostructures. This kind of response can be employed to provide an extra degree of freedom for the efficient control and shaping of the scattering patterns of nanoparticles and nanoantennas. Here we review the recent progress in this research direction of nanoparticle scattering shaping and control through the interference of both electric and optically-induced magnetic responses. We discuss the magnetic resonances supported by various structures in different spectral regimes, and then summarize the original results on the scattering shaping involving both electric and magnetic responses, based on the interference of both spectrally separated (with different resonant wavelengths) and overlapped dipoles (with the same resonant wavelength), and also other higher-order modes. Finally, we discuss the scattering control utilizing Fano resonances associated with the magnetic responses. (topical review - plasmonics and metamaterials)

  10. Orientation-controlled synthesis and magnetism of single crystalline Co nanowires

    International Nuclear Information System (INIS)

    Huang, Gui-Fang; Huang, Wei-Qing; Wang, Ling-Ling; Zou, B.S.; Pan, Anlian

    2012-01-01

    Orientation control and the magnetic properties of single crystalline Co nanowires fabricated by electrodeposition have been systematically investigated. It is found that the orientation of Co nanowires can be effectively controlled by varying either the current density or the pore diameter of AAO templates. Lower current density or small diameter is favorable for forming the (1 0 0) texture, while higher current values or larger diameter leads to the emergence and enhancement of (1 1 0) texture of Co nanowires. The mechanism for the manipulated growth characterization is discussed in detail. The orientation of Co nanowires has a significant influence on the magnetic properties, resulting from the competition between the magneto-crystalline and shape anisotropy of Co nanowires. This work offers a simple method to manipulate the orientation and magnetic properties of nanowires for future applications. - Highlights: ► Single crystalline Co nanowires have successfully been grown by DC electrodeposition. ► Orientation controlling and its effect on magnetism of Co nanowires were investigated. ► The orientation of Co nanowires can be effectively controlled by varying current density. ► The crystalline orientation of Co nanowires has significant influence on the magnetic properties.

  11. Modulation of magnetic coercivity in Ni thin films by reversible control of strain

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Wen-Chin, E-mail: wclin@ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Huang, Chia-Wei; Ting, Yi-Chieh; Lo, Fang-Yuh [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Chern, Ming-Yau [Department of Physics, National Taiwan University, Taipei 106, Taiwan (China)

    2015-05-01

    In this study, we demonstrated the magnetoelectric control of magnetic thin films. (111)-textured Pd/Ni/Pd thin films were prepared on mica/lead zirconium titanate (PZT) substrates for the investigation. The reversible modulation of magnetic coercivity in Ni films was observed through the electric-voltage-controlled strain variation from the PZT substrate. For 14 nm Ni film, the applied electric field of ±350 V/m led to ±0.5% strain variation of PZT, which was transferred to ±0.4% strain variation of Pd/Ni/Pd thin films on mica, and resulted in ∓17 Oe (∓5% of the preliminary magnetic coercivity). The reversible modulation of magnetic coercivity is supposed to be caused by the voltage-controlled strain through the magneto-elastic effect. - Highlights: • The magnetoelectric control of the magnetic coercivity of Pd/Ni/Pd thin films was demonstrated. • The ±0.4% strain variation of 14 nm Ni thin films resulted in ±17 Oe change of H{sub c}. • The reversible modulation of H{sub c} is supposed to be caused by the magneto-elastic effect.

  12. Nonlinear Control of an Active Magnetic Bearing System Achieved Using a Fuzzy Control with Radial Basis Function Neural Network

    Directory of Open Access Journals (Sweden)

    Seng-Chi Chen

    2014-01-01

    Full Text Available Studies on active magnetic bearing (AMB systems are increasing in popularity and practical applications. Magnetic bearings cause less noise, friction, and vibration than the conventional mechanical bearings; however, the control of AMB systems requires further investigation. The magnetic force has a highly nonlinear relation to the control current and the air gap. This paper proposes an intelligent control method for positioning an AMB system that uses a neural fuzzy controller (NFC. The mathematical model of an AMB system comprises identification followed by collection of information from this system. A fuzzy logic controller (FLC, the parameters of which are adjusted using a radial basis function neural network (RBFNN, is applied to the unbalanced vibration in an AMB system. The AMB system exhibited a satisfactory control performance, with low overshoot, and produced improved transient and steady-state responses under various operating conditions. The NFC has been verified on a prototype AMB system. The proposed controller can be feasibly applied to AMB systems exposed to various external disturbances; demonstrating the effectiveness of the NFC with self-learning and self-improving capacities is proven.

  13. Optimal fuzzy logic-based PID controller for load-frequency control including superconducting magnetic energy storage units

    International Nuclear Information System (INIS)

    Pothiya, Saravuth; Ngamroo, Issarachai

    2008-01-01

    This paper proposes a new optimal fuzzy logic-based-proportional-integral-derivative (FLPID) controller for load frequency control (LFC) including superconducting magnetic energy storage (SMES) units. Conventionally, the membership functions and control rules of fuzzy logic control are obtained by trial and error method or experiences of designers. To overcome this problem, the multiple tabu search (MTS) algorithm is applied to simultaneously tune PID gains, membership functions and control rules of FLPID controller to minimize frequency deviations of the system against load disturbances. The MTS algorithm introduces additional techniques for improvement of search process such as initialization, adaptive search, multiple searches, crossover and restarting process. Simulation results explicitly show that the performance of the optimum FLPID controller is superior to the conventional PID controller and the non-optimum FLPID controller in terms of the overshoot, settling time and robustness against variations of system parameters

  14. Speed control of switched reluctance motors taking into account mutual inductances and magnetic saturation effects

    Energy Technology Data Exchange (ETDEWEB)

    Alrifai, M., E-mail: alrifm@eng.kuniv.edu.k [Electrical Engineering Department, College of Engineering and Petroleum, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait); Zribi, M.; Rayan, M. [Electrical Engineering Department, College of Engineering and Petroleum, Kuwait University, P.O. Box 5969, Safat 13060 (Kuwait); Krishnan, R. [Center for Rapid Transit Systems, Electrical and Computer Engineering Department, Virginia Tech University, 461 Durham Hall, Blacksburg, VA 24061-011 (United States)

    2010-06-15

    This paper deals with the speed control of switched reluctance motor (SRM) drives taking into account the effects of the mutual inductances between two adjacent phases and the effects of the magnetic saturation of the core. To overcome the problems commonly associated with single-phase excitation, a nonlinear SRM model, which is suitable for two-phase excitation and which takes into account the effects of mutual inductances between two adjacent phases and the magnetic saturation effects, is considered in the design of the proposed controllers. A feedback linearization control scheme and a sliding mode control scheme are designed for this motor drive. The proposed controllers guarantee the convergence of the phase currents and the rotor speed of the motor to their desired values. Simulation results indicate that the proposed controllers work well and that they are robust to changes in the parameters of the system and to changes in the load torque.

  15. Speed control of switched reluctance motors taking into account mutual inductances and magnetic saturation effects

    International Nuclear Information System (INIS)

    Alrifai, M.; Zribi, M.; Rayan, M.; Krishnan, R.

    2010-01-01

    This paper deals with the speed control of switched reluctance motor (SRM) drives taking into account the effects of the mutual inductances between two adjacent phases and the effects of the magnetic saturation of the core. To overcome the problems commonly associated with single-phase excitation, a nonlinear SRM model, which is suitable for two-phase excitation and which takes into account the effects of mutual inductances between two adjacent phases and the magnetic saturation effects, is considered in the design of the proposed controllers. A feedback linearization control scheme and a sliding mode control scheme are designed for this motor drive. The proposed controllers guarantee the convergence of the phase currents and the rotor speed of the motor to their desired values. Simulation results indicate that the proposed controllers work well and that they are robust to changes in the parameters of the system and to changes in the load torque.

  16. Implementation of advanced feedback control algorithms for controlled resonant magnetic perturbation physics studies on EXTRAP T2R

    International Nuclear Information System (INIS)

    Frassinetti, L.; Olofsson, K.E.J.; Brunsell, P.R.; Drake, J.R.

    2011-01-01

    The EXTRAP T2R feedback system (active coils, sensor coils and controller) is used to study and develop new tools for advanced control of the MHD instabilities in fusion plasmas. New feedback algorithms developed in EXTRAP T2R reversed-field pinch allow flexible and independent control of each magnetic harmonic. Methods developed in control theory and applied to EXTRAP T2R allow a closed-loop identification of the machine plant and of the resistive wall modes growth rates. The plant identification is the starting point for the development of output-tracking algorithms which enable the generation of external magnetic perturbations. These algorithms will then be used to study the effect of a resonant magnetic perturbation (RMP) on the tearing mode (TM) dynamics. It will be shown that the stationary RMP can induce oscillations in the amplitude and jumps in the phase of the rotating TM. It will be shown that the RMP strongly affects the magnetic island position.

  17. Implementation of advanced feedback control algorithms for controlled resonant magnetic perturbation physics studies on EXTRAP T2R

    Science.gov (United States)

    Frassinetti, L.; Olofsson, K. E. J.; Brunsell, P. R.; Drake, J. R.

    2011-06-01

    The EXTRAP T2R feedback system (active coils, sensor coils and controller) is used to study and develop new tools for advanced control of the MHD instabilities in fusion plasmas. New feedback algorithms developed in EXTRAP T2R reversed-field pinch allow flexible and independent control of each magnetic harmonic. Methods developed in control theory and applied to EXTRAP T2R allow a closed-loop identification of the machine plant and of the resistive wall modes growth rates. The plant identification is the starting point for the development of output-tracking algorithms which enable the generation of external magnetic perturbations. These algorithms will then be used to study the effect of a resonant magnetic perturbation (RMP) on the tearing mode (TM) dynamics. It will be shown that the stationary RMP can induce oscillations in the amplitude and jumps in the phase of the rotating TM. It will be shown that the RMP strongly affects the magnetic island position.

  18. Low eddy loss axial hybrid magnetic bearing with gimballing control ability for momentum flywheel

    International Nuclear Information System (INIS)

    Tang, Jiqiang; Sun, Jinji; Fang, Jiancheng; Shuzhi Sam, Ge

    2013-01-01

    For a magnetically suspended momentum flywheel (MSMF), the spinning rotor can be tilted by a pair of the presented axial hybrid magnetic bearing (AHMB) with eight poles and rotates around the radial axes to generate a large torque to maneuver the spacecraft. To improve the control performance and gimballing control ability of the AHMB, characteristics such as magnetic suspension force, angular stiffness and tilting momentum are researched. These segmented stator poles cause the magnetic density in the thrust rotor plate to be uneven unavoidably and the rotational loss is large at high speed, but we optimized the stator poles configuration and caused the thrust rotor plate formed by bulk DT4C and laminated material to make the magnetic density in the thrust rotor plate change less and be smoother. Laminated material such as 1J50 film with a thickness of 0.1 mm can make the variation of the magnetic density in DT4C become very small and the eddy loss of it be negligible, but the stress produced in the “O” shape stacks by reeling has a bad effect on its power loss. Nanocrystalline can reduce eddy losses and is not affected by the reeling process. Based on the AHBM consisting of the stator with eight improved poles and the presented thrust rotor plate with DT4 and nanocrystalline, the rotational loss of 5-DOF magnetically suspended momentum flywheel with angular momentum of 15 N m s at 5000 rpm has reduced from 23.4 W to 3.2 W, which proved that this AHMB has low eddy loss for the gimballing control ability. - Highlights: ► Control methods of rotor driven by AHMBs and their characteristics are researched. ► Optimized stator and rotor of AHMB reduce its eddy losses greatly. ► Presented the factors affecting the eddy losses of AHMBs. ► The good performances of AHMB with low eddy loss are proved by experiments.

  19. A current controlled matrix converter for wind energy conversion systems based on permanent magnet synchronous generator

    OpenAIRE

    Naggar H. Saad; Ahmed A. El-Sattar; Mohamed I. Marei

    2016-01-01

    The main challenges of wind energy conversion systems (WECS) are to maximize the energy capture from the wind and injecting reactive power during the fault. This paper presents a current controlled matrix converter to interface Permanent Magnet Synchronous Generators (PMSG) based WECS with the grid. To achieve fast dynamic response with reduced current ripples, a hysteresis current control is utilized. The proposed control system decouples the active and reactive components of the PMSG curren...

  20. Mathematical Modelling and Predictive Control of Permanent Magnet Synchronous Motor Drives

    Czech Academy of Sciences Publication Activity Database

    Belda, Květoslav

    2013-01-01

    Roč. 2, č. 4 (2013), s. 114-120 ISSN 1805-3386 R&D Projects: GA ČR(CZ) GAP102/11/0437 Institutional support: RVO:67985556 Keywords : Permanent magnet synchronous motor * mathematical modelling * discrete predictive control * multistep explicit control law * square-root optimization Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/2014/AS/belda-0422285.pdf

  1. Control of Earth-like magnetic fields on the transformation of ferrihydrite to hematite and goethite.

    Science.gov (United States)

    Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J; Barrón, Vidal; Torrent, José; Roberts, Andrew P

    2016-07-26

    Hematite and goethite are the two most abundant iron oxides in natural environments. Their formation is controlled by multiple environmental factors; therefore, their relative concentration has been used widely to indicate climatic variations. In this study, we aimed to test whether hematite and goethite growth is influenced by ambient magnetic fields of Earth-like values. Ferrihydrite was aged at 95 °C in magnetic fields ranging from ~0 to ~100 μT. Our results indicate a large influence of the applied magnetic field on hematite and goethite growth from ferrihydrite. The synthesized products are a mixture of hematite and goethite for field intensities fields favour hematite formation by accelerating ferrimagnetic ferrihydrite aggregation. Additionally, hematite particles growing in a controlled magnetic field of ~100 μT appear to be arranged in chains, which may be reduced to magnetite keeping its original configuration, therefore, the presence of magnetic particles in chains in natural sediments cannot be used as an exclusive indicator of biogenic magnetite. Hematite vs. goethite formation in our experiments is influenced by field intensity values within the range of geomagnetic field variability. Thus, geomagnetic field intensity could be a source of variation when using iron (oxyhydr-)oxide concentrations in environmental magnetism.

  2. Adaptive PIF control for permanent magnet synchronous motors based on GPC.

    Science.gov (United States)

    Lu, Shaowu; Tang, Xiaoqi; Song, Bao

    2012-12-24

    To enhance the control performance of permanent magnet synchronous motors (PMSMs), a generalized predictive control (GPC)-based proportional integral feedforward (PIF) controller is proposed for the speed control system. In this new approach, firstly, based on the online identification of controlled model parameters, a simplified GPC law supplies the PIF controller with suitable control parameters according to the uncertainties in the operating conditions. Secondly, the speed reference curve for PMSMs is usually required to be continuous and continuously differentiable according to the general servo system design requirements, so the adaptation of the speed reference is discussed in details in this paper. Hence, the performance of the speed control system using a GPC-based PIF controller is improved for tracking some specified signals. The main motivation of this paper is the extension of GPC law to replace the traditional PI or PIF controllers in industrial applications. The efficacy and usefulness of the proposed controller are verified through experimental results.

  3. High performance current controller for particle accelerator magnets supply

    DEFF Research Database (Denmark)

    Maheshwari, Ram Krishan; Bidoggia, Benoit; Munk-Nielsen, Stig

    2013-01-01

    The electromagnets in modern particle accelerators require high performance power supply whose output is required to track the current reference with a very high accuracy (down to 50 ppm). This demands very high bandwidth controller design. A converter based on buck converter topology is used...

  4. Low Cost Sensorless Control of Permanent Magnet Motors

    DEFF Research Database (Denmark)

    Montesinos, Daniel; Galceran, Samuel; Blaabjerg, Frede

    2005-01-01

    This paper provides a review of the literature addressing sensorless operation of PM brushless machines. The methods explained are state-of-the-art of open and closed loop control strategies. The closed loop review includes those methods based on voltage and current measurements, and algebraic ma...

  5. Microwave absorption properties of carbon nanocoils coated with highly controlled magnetic materials by atomic layer deposition.

    Science.gov (United States)

    Wang, Guizhen; Gao, Zhe; Tang, Shiwei; Chen, Chaoqiu; Duan, Feifei; Zhao, Shichao; Lin, Shiwei; Feng, Yuhong; Zhou, Lei; Qin, Yong

    2012-12-21

    In this work, atomic layer deposition is applied to coat carbon nanocoils with magnetic Fe(3)O(4) or Ni. The coatings have a uniform and highly controlled thickness. The coated nanocoils with coaxial multilayer nanostructures exhibit remarkably improved microwave absorption properties compared to the pristine carbon nanocoils. The enhanced absorption ability arises from the efficient complementarity between complex permittivity and permeability, chiral morphology, and multilayer structure of the products. This method can be extended to exploit other composite materials benefiting from its convenient control of the impedance matching and combination of dielectric-magnetic multiple loss mechanisms for microwave absorption applications.

  6. Modeling and control for a magnetic levitation system based on SIMLAB platform in real time

    Directory of Open Access Journals (Sweden)

    Mundher H.A. Yaseen

    2018-03-01

    Full Text Available Magnetic Levitation system becomes a hot topic of study due to the minimum friction and low energy consumption which regards as very important issues. This paper proposed a new magnetic levitation system using real-time control simulink feature of (SIMLAB microcontroller. The control system of the maglev transportation system is verified by simulations with experimental results, and its superiority is indicated in comparison with previous literature and conventional control strategies. In addition, the proposed system was implemented under effect of three controller types which are Linear–quadratic regulator (LQR, proportional–integral–derivative controller (PID and Lead compensation. As well, the controller system performance was compared in term of three parameters Peak overshoot, Settling time and Rise time. The findings prove the agreement of simulation with experimental results obtained. Moreover, the LQR controller produced a great stability and homogeneous response than other controllers used. For experimental results, the LQR brought a 14.6%, 0.199 and 0.064 for peak overshoot, Setting time and Rise time respectively. Keywords: Magnetic levitation system, Linear Quadratic Regulator (LQR, PID control, Lead compensation

  7. Precise control of the drug kinetics by means of non-invasive magnetic drug delivery system

    International Nuclear Information System (INIS)

    Chuzawa, M.; Mishima, F.; Akiyama, Y.; Nishijima, S.

    2013-01-01

    Highlights: ► We examined the kinetics of ferromagnetic drugs by simulation. ► We tried to accumulate the magnetic drug in the target part by rotating a magnet. ► Ferromagnetic drugs were accumulated in the target part along the rotating axis. ► Ferromagnetic drugs could be swept downstream in the off-axis part. -- Abstract: In order to solve the problems of the side effects and medical lowering, has been advanced a study on the drug delivery system (DDS) to accumulate the drugs locally in the body with minimum dosage. The DDS is a system that controls the drug kinetics in the body precisely and accumulates the drug locally at the target part, keeping the drugs at high density. Among the DDS, the magnetic drug delivery system (MDDS) is the one that we studied. This is a technique to accumulate drugs by using the magnetic force as the physical driving force. Our previous researches showed the possibility of the technique of MDDS to accumulate the drugs with higher accumulation rate and locality than the traditional methods. It is necessary to apply a strong external magnetic field and a high magnetic gradient to accumulate the ferromagnetic drugs at a deep diseased part non-invasively. However, by applying a static magnetic field from one direction, the drug accumulates only at the surface of the body locates near the magnet. In this study, we tried to change the magnetic field applied by a superconducting bulk magnet with time, in order to make a constant and strong magnetic field applied in the center of the body and to accumulate the ferromagnetic drugs at the deep target part in the body. First of all, the effect of the surface treatment of the ferromagnetic drugs to prevent its absorption in the normal tissue was examined. Then, to increase the accumulation rate of the ferromagnetic drugs at the target part, the distribution of magnetic field was changed, and the optimum spatial and temporal conditions of magnetic field were examined

  8. Controlled and spontaneous magnetic field generation in a gun-driven spheromak

    International Nuclear Information System (INIS)

    Woodruff, S.; Cohen, B.I.; Hooper, E.B.; Mclean, H.S.; Stallard, B.W.; Hill, D.N.; Holcomb, C.T.; Romero-Talamas, C.; Wood, R.D.; Cone, G.; Sovinec, C.R.

    2005-01-01

    In the Sustained Spheromak Physics Experiment, SSPX [E. B. Hooper, D. Pearlstein, and D. D. Ryutov, Nucl. Fusion 39, 863 (1999)], progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1 m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations (δB/B∼1% on the midplane edge) yields T e profiles peaked at >200 eV. Trends indicate a limiting beta (β e ∼4%-6%), and so we have been motivated to increase T e by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with δB/B∼2% and large voltage fluctuations (δV∼1 kV), giving a 50% increase in current amplification, I tor /I gun . (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX (∼0.7 T along the geometric axis). By increasing the time between pulses, a quasisteady sustainment is produced (with periodic good confinement), comparing well with resistive magnetohydrodynamic simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses

  9. Controlled and Spontaneous Magnetic Field Generation in a Gun-Driven Spheromak

    International Nuclear Information System (INIS)

    Woodruff, S; Cohen, B I; Hooper, E B; McLean, H S; Stallard, B W; Hill, D N; Holcomb, C T; Romero-Talamas, C; Wood, R D; Cone, G; Sovinec, C R

    2005-04-01

    In the Sustained Spheromak Physics Experiment, SSPX, progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1-m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations ((delta)B/B∼1% on the midplane edge) yields T e profiles peaked at > 200eV. Trends indicate a limiting beta (β e ∼ 4-6%), and so we have been motivated to increase T e by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with (delta)B/B ∼2% and large voltage fluctuations ((delta)V ∼ 1kV), giving a 50% increase in current amplification, I tor /I gun . (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX (∼0.7T along the geometric axis). By increasing the time between pulses, a quasi-steady sustainment is produced (with periodic good confinement), comparing well with resistive MHD simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses

  10. Control of proliferation rate of N27 dopaminergic neurons using Transcranial Magnetic Stimulation orientation

    Science.gov (United States)

    Meng, Yiwen; Hadimani, Ravi; Anantharam, Vellareddy; Kanthasamy, Anumantha; Jiles, David

    2015-03-01

    Transcranial magnetic stimulation (TMS) has been used to investigate possible treatments for a variety of neurological disorders. However, the effect that magnetic fields have on neurons has not been well documented in the literature. We have investigated the effect of different orientation of magnetic field generated by TMS coils with a monophasic stimulator on the proliferation rate of N27 neuronal cells cultured in flasks and multi-well plates. The proliferation rate of neurons would increase by exposed horizontally adherent N27 cells to a magnetic field pointing upward through the neuronal proliferation layer compared with the control group. On the other hand, proliferation rate would decrease in cells exposed to a magnetic field pointing downward through the neuronal growth layer compared with the control group. We confirmed results obtained from the Trypan-blue and automatic cell counting methods with those from the CyQuant and MTS cell viability assays. Our findings could have important implications for the preclinical development of TMS treatments of neurological disorders and represents a new method to control the proliferation rate of neuronal cells.

  11. Controllable deposition of gadolinium doped ceria electrolyte films by magnetic-field-assisted electrostatic spray deposition

    International Nuclear Information System (INIS)

    Ksapabutr, Bussarin; Chalermkiti, Tanapol; Wongkasemjit, Sujitra; Panapoy, Manop

    2013-01-01

    This paper describes a simple and low-temperature approach to fabrication of dense and crack-free gadolinium doped ceria (GDC) thin films with controllable deposition by a magnetic-field-assisted electrostatic spray deposition technique. The influences of external permanent magnets on the deposition of GDC films were investigated. The coating area deposited using two magnets with the same pole arrangement decreased in comparison with the case of no magnets, whereas the largest deposition area was obtained in the system of the opposite poles. Analysis of as-deposited films at 450 °C indicated the formation of uniform, smooth and dense thin films with a single-phase fluorite structure. The films produced in the system using same poles were thicker, smaller in crystallite size and smoother than those fabricated under other conditions. Additionally, the GDC film deposited using the same pole arrangement showed the maximum in electrical conductivity of about 2.5 × 10 −2 S/cm at a low operating temperature of 500 °C. - Highlights: • Magnetic-field-assisted electrostatic spray allows a controllable coating. • Dense, crack-free thin films were obtained at low process temperature of 450 °C. • Control of deposition, thickness and uniformity is easy to achieve simultaneously. • Films from the same pole were thicker, smaller in crystal size and smoother. • The maximum conductivity of doped ceria film was 2.5 × 10 −2 S/cm at 500 °C

  12. Longitudinal wave function control in single quantum dots with an applied magnetic field

    Science.gov (United States)

    Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai

    2015-01-01

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018

  13. Quality control in the design, fabrication and operation of the ITER magnets

    International Nuclear Information System (INIS)

    Mitchell, N.

    2006-01-01

    The ITER magnets are a complex system involving interfaces between many advanced technologies (superconductors, forging/welding/machining of massive structures, cryogenics, composites and moulding, high voltage electrical), yet at the same time form part of the ITER 'basic machine' which is required to operate at the design parameters, broadly failure free, for the design life of the tokamak. This imposes special quality control problems for the ITER project integration by the ITER International Team (IT) through the design, fabrication and operation. The magnets are not a test bed for new technology but in spite of this must use it, successfully. There is little previous experience of such a system but full functionality is required from the start, with limited opportunity for adjustment. And, finally, costs and schedule must be contained. The procurement strategy for the machine, with magnet components being supplied 'in kind', requires particular attention to the specifications, scheduling and quality control (QC). Special issues here are the testing requirements on magnet components, especially before final installation but also at critical intermediate stages. Unnecessary or ineffective quality control procedures cause delay and high costs, and divert attention from critical items. The main points of the magnet QC programme are summarised, including the use of codes and standards, qualification, manufacturing quality assurance, commissioning and in-service inspection

  14. Longitudinal wave function control in single quantum dots with an applied magnetic field.

    Science.gov (United States)

    Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai

    2015-01-27

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.

  15. A Novel Maximum Power Point Tracking Control for Permanent Magnet Direct Drive Wind Energy Conversion Systems

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2012-05-01

    Full Text Available This paper proposes a novel optimal current given (OCG maximum power point tracking (MPPT control strategy based on the theory of power feedback and hill climb searching (HCS for a permanent magnet direct drive wind energy conversion system (WECS. The presented strategy not only has the advantages of not needing the wind speed and wind turbine characteristics of the traditional HCS method, but it also improves the stability and accuracy of MPPT by estimating the exact loss torque. The OCG MPPT control strategy is first carried out by simulation, then an experimental platform based on the dSPACE1103 controller is built and a 5.5 kW permanent magnet synchronous generator (PMSG is tested. Furthermore, the proposed method is compared experimentally with the traditional optimum tip speed ratio (TSR MPPT control. The experiments verify the effectiveness of the proposed OCG MPPT strategy and demonstrate its better performance than the traditional TSR MPPT control.

  16. Conical Magnetic Bearings Developed for Active Stall Control in Gas Turbine Engines

    Science.gov (United States)

    Trudell, Jeffrey J.; Kascak, Albert F.; Provenza, Andrew J.; Buccieri, Carl J.

    2004-01-01

    Active stall control is a current research area at the NASA Glenn Research Center that offers a great benefit in specific fuel consumption by allowing the gas turbine to operate beyond the onset of stall. Magnetic bearings are being investigated as a new method to perform active stall control. This enabling global aviation safety technology would result in improved fuel efficiency and decreased carbon dioxide emissions, as well as improve safety and reliability by eliminating oil-related delays and failures of engine components, which account for 40 percent of the commercial aircraft departure delays. Active stall control works by perturbing the flow in front of the compressor stage such that it cancels the pressure wave, which causes the compressor to go into stall. Radial magnetic bearings are able to whirl the shaft so that variations in blade tip leakage would flow upstream causing a perturbation wave that could cancel the rotating stall cell. Axial or thrust magnetic bearings cannot be used to cancel the surge mode in the compressor because they have a very low bandwidth and thus cannot modulate at a high enough frequency. Frequency response is limited because the thrust runner cannot be laminated. To improve the bandwidth of magnetic thrust bearings, researchers must use laminations to suppress the eddy currents. A conical magnetic bearing can be laminated, resulting in increased bandwidth in the axial direction. In addition, this design can produce both radial and thrust force in a single bearing, simplifying the installation. The proposed solution combines the radial and thrust bearing into one design that can be laminated--a conical magnetic bearing. The new conical magnetic bearing test rig, funded by a Glenn fiscal year 2002 Director's Discretionary Fund, was needed because none of the existing rigs has an axial degree of freedom. The rotor bearing configuration will simulate that of the main shaft on a gas turbine engine. One conical magnetic bearing

  17. 3D microwave cavity with magnetic flux control and enhanced quality factor

    Energy Technology Data Exchange (ETDEWEB)

    Reshitnyk, Yarema [The University of Queensland, School of Mathematics and Physics, St Lucia (Australia); Jerger, Markus [The University of Queensland, ARC Centre of Excellence for Engineered Quantum Systems, 4072 (Australia); Fedorov, Arkady [The University of Queensland, School of Mathematics and Physics, St Lucia (Australia); The University of Queensland, ARC Centre of Excellence for Engineered Quantum Systems, 4072 (Australia)

    2016-12-15

    Three-dimensional (3D) microwave cavities have been extensively used for coupling and interacting with superconducting quantum bits (qubits), providing a versatile platform for quantum control experiments and for realizing hybrid quantum systems. While having high quality factors (>10{sup 6}) superconducting cavities do not permit magnetic field control of qubits. In contrast, cavities made of normal metals are transparent to magnetic fields, but experience lower quality factors (∝10{sup 4}). We have created a hybrid cavity which is primarily composed of aluminium but also contains a small copper insert reaching the internal quality factor of ≅10{sup 5}, an order of magnitude improvement over all previously tested normal metal cavities. In order to demonstrate precise magnetic control, we performed spectroscopy of three superconducting qubits, where individual control of each qubit's frequency was exerted with small external wire coils. An improvement in quality factor and magnetic field control makes this 3D hybrid cavity an attractive new element for circuit quantum electrodynamics experiments. (orig.)

  18. Design and fabrication of magnetically functionalized flexible micropillar arrays for rapid and controllable microfluidic mixing

    KAUST Repository

    Zhou, BingPu; Xu, Wei; Syed, Ahad; Chau, Yeungyeung; Chen, Longqing; Chew, Basil; Yassine, Omar; Wu, Xiaoxiao; Gao, Yibo; Zhang, Jingxian; Xiao, Xiao; Kosel, Jü rgen; Zhang, Xixiang; Yao, Zhaohui; Wen, Weijia

    2015-01-01

    Magnetically functionalized PDMS-based micropillar arrays have been successfully designed, fabricated and implanted for controllable microfluidic mixing. The arrangement of PDMS micropillar arrays inside the microchannel can be flexibly controlled by an external magnetic field. As a consequence, the flow fields inside the microchannel can be regulated at will via magnetic activation conveniently. When a microchannel is implanted with such micropillar arrays, two microstreams can be mixed easily and controllably upon the simple application of an on/off magnetic signal. Mixing efficiencies based on micropillar arrays with different densities were investigated and compared. It was found that micropillar arrays with higher density (i.e. smaller pillar pitch) would render better mixing performance. Our microfluidic system is capable of generating highly reproducible results within many cycles of mixing/non-mixing conversion. We believe that the simple mixing-triggering method together with rapid and controllable mixing control will be extraordinarily valuable for various biological or chemical applications in the future. This journal is © The Royal Society of Chemistry 2015.

  19. Design and fabrication of magnetically functionalized flexible micropillar arrays for rapid and controllable microfluidic mixing

    KAUST Repository

    Zhou, BingPu

    2015-03-25

    Magnetically functionalized PDMS-based micropillar arrays have been successfully designed, fabricated and implanted for controllable microfluidic mixing. The arrangement of PDMS micropillar arrays inside the microchannel can be flexibly controlled by an external magnetic field. As a consequence, the flow fields inside the microchannel can be regulated at will via magnetic activation conveniently. When a microchannel is implanted with such micropillar arrays, two microstreams can be mixed easily and controllably upon the simple application of an on/off magnetic signal. Mixing efficiencies based on micropillar arrays with different densities were investigated and compared. It was found that micropillar arrays with higher density (i.e. smaller pillar pitch) would render better mixing performance. Our microfluidic system is capable of generating highly reproducible results within many cycles of mixing/non-mixing conversion. We believe that the simple mixing-triggering method together with rapid and controllable mixing control will be extraordinarily valuable for various biological or chemical applications in the future. This journal is © The Royal Society of Chemistry 2015.

  20. Magnetic Actuation Connector Between Extension Shaft and Armature for Bottom Mounted Control Rod Drive Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Hyung; Cho, Yeong Garp; Kim, Jong In [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    The electromagnet and armature inside the guide tube interact and produce magnetism, thus making the armature, connecting extension shaft and control rod move up and down to control the power of reactor. During the overhaul, the control absorber rod (CAR), extension shaft, and armature of BMCRDM are lifted together for closing a seal valve. But total length of CAR assembly is so long that it cannot be lifted due to exposure above the water level of pool which is strictly controlled. In addition to this, it is difficult to calibrate a position indicator and lifting force of electromagnet without armature assembly as a seal valve is closed. For this reason, it is necessary to install a disconnecting system between armature and extension shaft. Therefore, KAERI has developed magnetic actuation connector using plunger between armature and extension shaft for the bottom mounted control rod drive mechanism in research reactor. The results of a FEM and the experiments in this work lead to the following conclusions: The FEM result for the design of the magnetic actuation connector is compared with the measured lifting force of prototype production. As a result, it is shown that the lifting force of the prototype connector has a good agreement with the result of the FEM. A newly developed technique of prototype magnetic actuation connector which is designed by FEM analysis result is proposed.

  1. Magnetic Actuation Connector Between Extension Shaft and Armature for Bottom Mounted Control Rod Drive Mechanism

    International Nuclear Information System (INIS)

    Huh, Hyung; Cho, Yeong Garp; Kim, Jong In

    2013-01-01

    The electromagnet and armature inside the guide tube interact and produce magnetism, thus making the armature, connecting extension shaft and control rod move up and down to control the power of reactor. During the overhaul, the control absorber rod (CAR), extension shaft, and armature of BMCRDM are lifted together for closing a seal valve. But total length of CAR assembly is so long that it cannot be lifted due to exposure above the water level of pool which is strictly controlled. In addition to this, it is difficult to calibrate a position indicator and lifting force of electromagnet without armature assembly as a seal valve is closed. For this reason, it is necessary to install a disconnecting system between armature and extension shaft. Therefore, KAERI has developed magnetic actuation connector using plunger between armature and extension shaft for the bottom mounted control rod drive mechanism in research reactor. The results of a FEM and the experiments in this work lead to the following conclusions: The FEM result for the design of the magnetic actuation connector is compared with the measured lifting force of prototype production. As a result, it is shown that the lifting force of the prototype connector has a good agreement with the result of the FEM. A newly developed technique of prototype magnetic actuation connector which is designed by FEM analysis result is proposed

  2. Magnetic Control of Fe3O4 Nanomaterial for Fat Ablation in Microchannel

    Directory of Open Access Journals (Sweden)

    Ming Chang

    2015-11-01

    Full Text Available In this study, surface modification of iron (II, III oxide Fe3O4 nanoparticles by oleic acid (OA coating is investigated for the microablation of fat in a microchannel. The nanoparticles are synthesized by the co-precipitation method and then dispersed in organic solvent prior to mixing with the OA. The magnetization, agglomeration, and particle size distribution properties of the OA-coated Fe3O4 nanoparticles are characterized. The surface modification of the Fe3O4 nanoparticles reveals that upon injection into a microchannel, the lipophilicity of the OA coating influences the movement of the nanoparticles across an oil-phase barrier. The motion of the nanoparticles is controlled using an AC magnetic field to induce magnetic torque and a static gradient field to control linear translation. The fat microablation process in a microchannel is demonstrated using an oscillating driving field of less than 1200 Am−1.

  3. Strain-controlled magnetic domain wall propagation in hybrid piezoelectric/ferromagnetic structures.

    Science.gov (United States)

    Lei, Na; Devolder, Thibaut; Agnus, Guillaume; Aubert, Pascal; Daniel, Laurent; Kim, Joo-Von; Zhao, Weisheng; Trypiniotis, Theodossis; Cowburn, Russell P; Chappert, Claude; Ravelosona, Dafiné; Lecoeur, Philippe

    2013-01-01

    The control of magnetic order in nanoscale devices underpins many proposals for integrating spintronics concepts into conventional electronics. A key challenge lies in finding an energy-efficient means of control, as power dissipation remains an important factor limiting future miniaturization of integrated circuits. One promising approach involves magnetoelectric coupling in magnetostrictive/piezoelectric systems, where induced strains can bear directly on the magnetic anisotropy. While such processes have been demonstrated in several multiferroic heterostructures, the incorporation of such complex materials into practical geometries has been lacking. Here we demonstrate the possibility of generating sizeable anisotropy changes, through induced strains driven by applied electric fields, in hybrid piezoelectric/spin-valve nanowires. By combining magneto-optical Kerr effect and magnetoresistance measurements, we show that domain wall propagation fields can be doubled under locally applied strains. These results highlight the prospect of constructing low-power domain wall gates for magnetic logic devices.

  4. Fractional Order PID Control of Rotor Suspension by Active Magnetic Bearings

    Directory of Open Access Journals (Sweden)

    Parinya Anantachaisilp

    2017-01-01

    Full Text Available One of the key issues in control design for Active Magnetic Bearing (AMB systems is the tradeoff between the simplicity of the controller structure and the performance of the closed-loop system. To achieve this tradeoff, this paper proposes the design of a fractional order Proportional-Integral-Derivative (FOPID controller. The FOPID controller consists of only two additional parameters in comparison with a conventional PID controller. The feasibility of FOPID for AMB systems is investigated for rotor suspension in both the radial and axial directions. Tuning methods are developed based on the evolutionary algorithms for searching the optimal values of the controller parameters. The resulting FOPID controllers are then tested and compared with a conventional PID controller, as well as with some advanced controllers such as Linear Quadratic Gausian (LQG and H ∞ controllers. The comparison is made in terms of various stability and robustness specifications, as well as the dimensions of the controllers as implemented. Lastly, to validate the proposed method, experimental testing is carried out on a single-stage centrifugal compressor test rig equipped with magnetic bearings. The results show that, with a proper selection of gains and fractional orders, the performance of the resulting FOPID is similar to those of the advanced controllers.

  5. Fractional order sliding-mode control based on parameters auto-tuning for velocity control of permanent magnet synchronous motor.

    Science.gov (United States)

    Zhang, BiTao; Pi, YouGuo; Luo, Ying

    2012-09-01

    A fractional order sliding mode control (FROSMC) scheme based on parameters auto-tuning for the velocity control of permanent magnet synchronous motor (PMSM) is proposed in this paper. The control law of the proposed F(R)OSMC scheme is designed according to Lyapunov stability theorem. Based on the property of transferring energy with adjustable type in F(R)OSMC, this paper analyzes the chattering phenomenon in classic sliding mode control (SMC) is attenuated with F(R)OSMC system. A fuzzy logic inference scheme (FLIS) is utilized to obtain the gain of switching control. Simulations and experiments demonstrate that the proposed FROSMC not only achieve better control performance with smaller chatting than that with integer order sliding mode control, but also is robust to external load disturbance and parameter variations. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

  6. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  7. MAGNET

    CERN Multimedia

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  8. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  9. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  10. Reconfigurable logic via gate controlled domain wall trajectory in magnetic network structure

    Science.gov (United States)

    Murapaka, C.; Sethi, P.; Goolaup, S.; Lew, W. S.

    2016-01-01

    An all-magnetic logic scheme has the advantages of being non-volatile and energy efficient over the conventional transistor based logic devices. In this work, we present a reconfigurable magnetic logic device which is capable of performing all basic logic operations in a single device. The device exploits the deterministic trajectory of domain wall (DW) in ferromagnetic asymmetric branch structure for obtaining different output combinations. The programmability of the device is achieved by using a current-controlled magnetic gate, which generates a local Oersted field. The field generated at the magnetic gate influences the trajectory of the DW within the structure by exploiting its inherent transverse charge distribution. DW transformation from vortex to transverse configuration close to the output branch plays a pivotal role in governing the DW chirality and hence the output. By simply switching the current direction through the magnetic gate, two universal logic gate functionalities can be obtained in this device. Using magnetic force microscopy imaging and magnetoresistance measurements, all basic logic functionalities are demonstrated. PMID:26839036

  11. Magnetophoresis behaviour at low gradient magnetic field and size control of nickel single core nanobeads

    Energy Technology Data Exchange (ETDEWEB)

    Benelmekki, M., E-mail: benelmekki@fisica.uminho.p [Centro de Fisica, Universidade do Minho, Braga (Portugal); Montras, A. [Sepmag Tecnologies, Parc Tecnologic del Valles, Barcelona (Spain); Martins, A.J.; Coutinho, P.J.G. [Centro de Fisica, Universidade do Minho, Braga (Portugal); Martinez, Ll.M. [Sepmag Technologies, Atlanta, GA (United States)

    2011-08-15

    Magnetic separation of organic compounds, proteins, nucleic acids and other biomolecules, and cells from complex reaction mixtures is becoming the most suitable solution for large production in bioindustrial purification and extraction processes. Optimal magnetic properties can be achieved by the use of metals. However, they are extremely sensitive to oxidation and degradation under atmospheric conditions. In this work Ni nanoparticles are synthesised by conventional solution reduction process with the addition of a non-ionic surfactant as a surface agent. The nanoparticles were surfacted in citric acid and then coated with silica to form single core Ni nanobeads. A magnetophoresis study at different magnetic field gradients and at the different steps of synthesis route was performed using Horizontal Low Gradient Magnetic Field (HLGMF) systems. The reversible aggregation times are reduced to a few seconds, allowing a very fast separation process. - Research highlights: Monodispersed single core Ni-silica core-shell structures were prepared. Control of Ni nanoparticles size was achieved using a non-ionic surfactant. Magnetophoresis at different magnetic field gradients was monitored. Magnetophoresis at different steps of synthesis route was performed. Attractive magnetic interactions overcome electrostatic repulsions.

  12. Design of magnetic flywheel control for performance improvement of fuel cells used in vehicles

    International Nuclear Information System (INIS)

    Huang, Chung-Neng; Chen, Yui-Sung

    2017-01-01

    Because hydrogen can be extracted naturally and stored for a long time, different types of fuel cells have been developed to generate clean power, particularly for use in vehicles. However, the power demand of a running vehicle leads to unstable and irregular loading of fuel cells. This not only reduces fuel cell lifespan and efficiency but also affects driving safety when the slow output response cannot satisfy an abrupt increase in power demand. Magnetic flywheels with characteristics such as high energy density, high-speed charging ability, and low loss have been extensively used in Formula One cars. This study developed a hybrid powertrain in which a magnetic flywheel system (MFS) is integrated with the fuel cells to solve the aforementioned problems. Moreover, an auto-tuning proportional–integral–derivative (PID) controller based on the controls of a multiple adaptive neuro-fuzzy interference system and particle swarm optimization was designed for MFS control. Furthermore, MATLAB/Simulink simulations considering an FTP-75 urban driving cycle were conducted, and a variability improvement of approximately 27.3% in fuel cell output was achieved. - Highlights: • A hybrid powertrain integrating the magnetic flywheel and fuel cells is proposed. • An auto-tuning PID controller is designed for MFS control. • The MIMO-ANFIS and PSO based optimal control is realized. • A 27.3% improvement in the output variability of fuel cell is achieved under control.

  13. An infrared diagnostic for magnetism in hot stars

    Czech Academy of Sciences Publication Activity Database

    Oksala, M.E.; Grunhut, J.H.; Kraus, Michaela; Borges Fernandes, M.; Neiner, C.; Condori, C.A.H.; Condori, J.C.; Souza, C. T.

    2015-01-01

    Roč. 578, June (2015), A112/1-A112/4 ISSN 0004-6361 R&D Projects: GA ČR(CZ) GA14-21373S Institutional support: RVO:67985815 Keywords : stars * magnetic field * circumstellar matter Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  14. A modular and extensible data acquisition and control system for testing superconducting magnets

    International Nuclear Information System (INIS)

    Darryl F. Orris and Ruben H. Carcagno

    2001-01-01

    The Magnet Test Facility at Fermilab tests a variety of full-scale and model superconducting magnets for both R and D and production. As the design characteristics and test requirements of these magnets vary widely, the magnet test stand must accommodate a wide range of Data Acquisition (DAQ) and Control requirements. Such a system must provide several functions, which includes: quench detection, quench protection, power supply control, quench characterization, and slow DAQ of temperature, mechanical strain gauge, liquid helium level, etc. The system must also provide cryogenic valve control, process instrumentation monitoring, and process interlock logic associated with the test stand. A DAQ and Control system architecture that provides the functionality described above has been designed, fabricated, and put into operation. This system utilizes a modular approach that provides both extensibility and flexibility. As a result, the complexity of the hardware is minimized while remaining optimized for future expansion. The architecture of this new system is presented along with a description of the different technologies applied to each module. Commissioning and operating experience as well as plans for future expansion are discussed

  15. Torque decomposition and control in an iron core linear permanent magnet motor.

    NARCIS (Netherlands)

    Overboom, T.T.; Smeets, J.P.C.; Stassen, J.M.; Jansen, J.W.; Lomonova, E.

    2012-01-01

    Abstract—This paper concerns the decomposition and control of the torque produced by an iron core linear permanent magnet motor. The proposed method is based on the dq0-decomposition of the three-phase currents using Park’s transformation. The torque is decomposed into a reluctance component and two

  16. Experimental Investigation of Electro-chemical Processes Controlled by High Magnetic Fields.

    Czech Academy of Sciences Publication Activity Database

    Mathon, Ph.; Nouri, A.; Alemany, A.; Chopart, J.P.; Sobolík, Václav

    2006-01-01

    Roč. 42, 4 (2006) , s. 363-369 ISSN 0024-998X Institutional research plan: CEZ:AV0Z40720504 Keywords : lorentz and magnetic force * diffusion-controlled regime * electrical current Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  17. Flexible method for fabricating protein patterns on superhydrophobic platforms controlled by magnetic field.

    Science.gov (United States)

    Wang, Jian; Li, Hao; Zou, Haoyang; Wang, Chenmiao; Zhang, Hao; Mano, João F; Song, Wenlong

    2017-02-28

    Inspired by the rolling of water droplets on lotus leaves, we developed a novel, magnetic field-controlled patterning method for water-soluble proteins and other functional materials on superhydrophobic platforms. This simple method can be used to fabricate biochips and open micro-fluidic devices in a simple way.

  18. Physical property control in core/shell inorganic nanostructures for fluorescence and magnetic targeting applications

    Science.gov (United States)

    Roberts, Stephen K.

    Nanomaterials show immense promise for the future in numerous areas of application. Properties that are unique from the bulk material and are tunable allow for innovation in material design. This thesis will focus on controlling the physical properties of core/shell nanostructures to enhance the utility of the materials. The first focus is on the impact of different solvent mixtures during the shell growth phase of SILAR based core/shell quantum dot synthesis is studied. Gaining insight into the mechanism for SILAR growth of core/shell nanoparticles allows improved synthetic yields and precursor binding, providing enhanced control to synthesis of core/shell nanoparticles. The second focus of this thesis is exploring the use of magnetic nanoparticles for magnetic drug targeting for cardiovascular conditions. Magnetic targeting for drug delivery enables increased local drug concentration, while minimizing non-specific interactions. In order to be effective for magnetic targeting, it must be shown that low magnetic strength is sufficient to capture flowing nanoparticles. By demonstrating the binding of a therapeutic agent to the surface at medicinal levels, the viability for use as a nanoparticle drug delivery system is improved.

  19. High Temperature Superconducting Magnets with Active Control for Attraction Levitation Transport Applications

    Science.gov (United States)

    Jones, Harry; Jenkins, Richard G.; Goodall, Roger M.; Macleod, Colin; ElAbbar, Abdallah A.; Campbell, Archie M.

    1996-01-01

    A research program, involving 3 British universities, directed at quantifying the controllability of High Temperature Superconducting (HTS) magnets for use in attraction levitation transport systems will be described. The work includes measurement of loss mechanisms for iron cored HTS magnets which need to produce a flux density of approx. 1 tesla in the airgap between the magnet poles and a ferromagnetic rail. This flux density needs to be maintained and this is done by introducing small variations of the magnet current using a feedback loop, at frequencies up to 10 Hz to compensate for load changes, track variation etc. The test magnet assemblies constructed so far will be described and the studies and modelling of designs for a practical levitation demonstrator (using commercially obtained HTS tape) will be discussed with particular emphasis on how the field distribution and its components, e.g., the component vector normal to the broad face of the tape, can radically affect design philosophy compared to the classical electrical engineering approach. Although specifically aimed at levitation transport the controllability data obtained have implications for a much wider range of applications.

  20. Adaptive Nonsingular Terminal Sliding Model Control and Its Application to Permanent Magnet Synchronous Motor Drive System

    OpenAIRE

    Liu Yue; Zhou Shuo

    2016-01-01

    To improve the dynamic performance of permanent magnet synchronous motor(PMSM) drive system, a adaptive nonsingular terminal sliding model control((NTSMC) strategy was proposed. The proposed control strategy presents an adaptive variable-rated exponential reaching law which the L1 norm of state variables is introduced. Exponential and constant approach speed can adaptively adjust according to the state variables’ distance to the equilibrium position.The proposed scheme can shorten the reachin...

  1. Controlling chaos in permanent magnet synchronous motor based on finite-time stability theory

    International Nuclear Information System (INIS)

    Du-Qu, Wei; Bo, Zhang

    2009-01-01

    This paper reports that the performance of permanent magnet synchronous motor (PMSM) degrades due to chaos when its systemic parameters fall into a certain area. To control the undesirable chaos in PMSM, a nonlinear controller, which is simple and easy to be constructed, is presented to achieve finite-time chaos control based on the finite-time stability theory. Computer simulation results show that the proposed controller is very effective. The obtained results may help to maintain the industrial servo driven system's security operation. (general)

  2. Childhood temporal lobe epilepsy: correlation between electroencephalography and magnetic resonance spectroscopy: a case-control study.

    Science.gov (United States)

    Azab, Seham Fa; Sherief, Laila M; Saleh, Safaa H; Elshafeiy, Mona M; Siam, Ahmed G; Elsaeed, Wafaa F; Arafa, Mohamed A; Bendary, Eman A; Sherbiny, Hanan S; Elbehedy, Rabab M; Aziz, Khalid A

    2015-04-18

    The diagnosis of epilepsy should be made as early as possible to give a child the best chance for treatment success and also to decrease complications such as learning difficulties and social and behavioral problems. In this study, we aimed to assess the ability of magnetic resonance spectroscopy (MRS) in detecting the lateralization side in patients with Temporal lobe epilepsy (TLE) in correlation with EEG and MRI findings. This was a case-control study including 40 patients diagnosed (clinically and by EEG) as having temporal lobe epilepsy aged 8 to 14 years (mean, 10.4 years) and 20 healthy children with comparable age and gender as the control group. All patients were subjected to clinical examination, interictal electroencephalography and magnetic resonance imaging (MRI). Proton magnetic resonance spectroscopic examination (MRS) was performed to the patients and the controls. According to the findings of electroencephalography, our patients were classified to three groups: Group 1 included 20 patients with unitemporal (lateralized) epileptic focus, group 2 included 12 patients with bitemporal (non-lateralized) epileptic focus and group 3 included 8 patients with normal electroencephalography. Magnetic resonance spectroscopy could lateralize the epileptic focus in 19 patients in group 1, nine patients in group2 and five patients in group 3 with overall lateralization of (82.5%), while electroencephalography was able to lateralize the focus in (50%) of patients and magnetic resonance imaging detected lateralization of mesial temporal sclerosis in (57.5%) of patients. Magnetic resonance spectroscopy is a promising tool in evaluating patients with epilepsy and offers increased sensitivity to detect temporal pathology that is not obvious on structural MRI imaging.

  3. Hydrophilic magnetic nanoclusters with thermo-responsive properties and their drug controlled release

    International Nuclear Information System (INIS)

    Meerod, Siraprapa; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha

    2015-01-01

    Synthesis and drug controlled release properties of thermo-responsive magnetic nanoclusters grafted with poly(N-isopropylacrylamide) (poly(NIPAAm)) and poly(NIPAAm-co-poly(ethylene glycol) methyl ether methacrylate) (PEGMA) copolymers were described. These magnetic nanoclusters were synthesized via an in situ radical polymerization in the presence of acrylamide-grafted magnetic nanoparticles (MNPs). Poly(NIPAAm) provided thermo-responsive properties, while PEGMA played a role in good water dispersibility to the nanoclusters. The ratios of PEGMA to NIPAAm in the (co)polymerization in the presence of the MNPs were fine-tuned such that the nanoclusters with good water dispersibility, good magnetic sensitivity and thermo responsiveness were obtained. The size of the nanoclusters was in the range of 50–100 nm in diameter with about 100–200 particles/cluster. The nanoclusters were well dispersible in water at room temperature and can be suddenly agglomerated when temperature was increased beyond the lower critical solution temperature (LCST) (32 °C). The release behavior of an indomethacin model drug from the nanoclusters was also investigated. These novel magnetic nanoclusters with good dispersibility in water and reversible thermo-responsive properties might be good candidates for the targeting drug controlled release applications. - Highlights: • Nanoclusters with good water dispersibility and magnetic response were prepared. • They were grafted with thermo-responsive poly(NIPAAm) and/or poly(PEGMA). • Poly(NIPAAm) provided thermo-responsive properties to the nanoclusters. • Poly(PEGMA) provided good water dispersibilityto the nanoclusters. • Accelerated and controllable releases of a drug from the nanoclusters were shown

  4. Performance estimation of control rod position indicator due to aging of magnet

    International Nuclear Information System (INIS)

    Yu, Je Yong; Kim, Ji Ho; Huh, Hyung; Choi, Myoung Hwan; Sohn, Dong Seong

    2009-01-01

    The Control Element Drive Mechanism (CEDM) for the integral reactor is designed to raise and lower the control rod in steps of 2mm in order to satisfy the design features of the integral reactor which are the soluble boron free operation and the use of a nuclear heating for the reactor start-up. The actual position of the control rod could be achieved to sense the magnet connected to the control rod by the position indicator around the upper pressure housing of CEDM. It is sufficient that the actual position information of control rod at 20mm interval from the position indicator is used for the core safety analysis. As the magnet moves upward along the position indicator assembly from the bottom to the top in the upper pressure housing, the output voltage increases linearly step-wise at 0.2VDC increments. Between every step there are transient areas which occur by a contact closing of three reed switches which is the 2-3-2 contact closing sequence. In this paper the output voltage signal corresponding to the position of control rod was estimated on the 2-1-2 contact closing sequence due to the aging of the magnet.

  5. Bifurcation Phenomena of a Magnetic Island at a Rational Surface in a Magnetic-Shear Control Experiment

    International Nuclear Information System (INIS)

    Ida, K.; Inagaki, S.; Yoshinuma, M.; Narushima, Y.; Itoh, K.; Kobuchi, T.; Watanabe, K. Y.; Funaba, H.; Sakakibara, S.; Morisaki, T.; LHD Experimental Group

    2008-01-01

    Three states of a magnetic island are observed when the magnetic shear at the rational surface is modified using inductive current associated with the neutral beam current drive in the Large Helical Device. One state is the healed magnetic island with a zero island width. The second state is the saturated magnetic island with partial flattening of the T e profile. The third state is characterized by the global flattening of the T e profile in the core region. As the plasma assumes each of the three states consecutively through a bifurcation process a clear hysteresis in the relation between the size of the magnetic island and the magnetic shear is observed

  6. Adaptive automatic generation control with superconducting magnetic energy storage in power systems

    International Nuclear Information System (INIS)

    Tripathy, S.C.; Balasubramanian, R.; Nair, P.S.C.

    1992-01-01

    An improved automatic generation control (AGC) employing self-tuning adaptive control for both main AGC loop and superconducting magnetic energy storage (SMES) is presented in this paper. Computer simulations on a two-area interconnected power system show that the proposed adaptive control scheme is very effective in damping out oscillations caused by load disturbances and its performance is quite insensitive to controller gain parameter changes of SMES. A comprehensive comparative performance evaluation of control schemes using adaptive and non-adaptive controllers in the main AGC and in the SMES control loops is presented. The improvement in performance brought in by the adaptive scheme is particularly pronounced for load changes of random magnitude and duration. The proposed controller can be easily implemented using microprocessors

  7. Induction of biogenic magnetization and redox control by a component of the target of rapamycin complex 1 signaling pathway.

    Directory of Open Access Journals (Sweden)

    Keiji Nishida

    Full Text Available Most organisms are simply diamagnetic, while magnetotactic bacteria and migratory animals are among organisms that exploit magnetism. Biogenic magnetization not only is of fundamental interest, but also has industrial potential. However, the key factor(s that enable biogenic magnetization in coordination with other cellular functions and metabolism remain unknown. To address the requirements for induction and the application of synthetic bio-magnetism, we explored the creation of magnetism in a simple model organism. Cell magnetization was first observed by attraction towards a magnet when normally diamagnetic yeast Saccharomyces cerevisiae were grown with ferric citrate. The magnetization was further enhanced by genetic modification of iron homeostasis and introduction of ferritin. The acquired magnetizable properties enabled the cells to be attracted to a magnet, and be trapped by a magnetic column. Superconducting quantum interference device (SQUID magnetometry confirmed and quantitatively characterized the acquired paramagnetism. Electron microscopy and energy-dispersive X-ray spectroscopy showed electron-dense iron-containing aggregates within the magnetized cells. Magnetization-based screening of gene knockouts identified Tco89p, a component of TORC1 (Target of rapamycin complex 1, as important for magnetization; loss of TCO89 and treatment with rapamycin reduced magnetization in a TCO89-dependent manner. The TCO89 expression level positively correlated with magnetization, enabling inducible magnetization. Several carbon metabolism genes were also shown to affect magnetization. Redox mediators indicated that TCO89 alters the intracellular redox to an oxidized state in a dose-dependent manner. Taken together, we demonstrated that synthetic induction of magnetization is possible and that the key factors are local redox control through carbon metabolism and iron supply.

  8. A High-mass Protobinary System with Spatially Resolved Circumstellar Accretion Disks and Circumbinary Disk

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, S.; Kluska, J.; Kreplin, A.; Bate, M.; Harries, T. J.; Hone, E.; Anugu, A. [School of Physics, Astrophysics Group, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom); Hofmann, K.-H.; Weigelt, G. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Monnier, J. D. [Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); De Wit, W. J. [ESO, Alonso de Cordova 3107, Vitacura, Santiago 19 (Chile); Wittkowski, M., E-mail: skraus@astro.ex.ac.uk [ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany)

    2017-01-20

    High-mass multiples might form via fragmentation of self-gravitational disks or alternative scenarios such as disk-assisted capture. However, only a few observational constraints exist on the architecture and disk structure of high-mass protobinaries and their accretion properties. Here, we report the discovery of a close (57.9 ± 0.2 mas = 170 au) high-mass protobinary, IRAS17216-3801, where our VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image the circumstellar disks around the individual components with ∼3 mas resolution. We estimate the component masses to ∼20 and ∼18 M {sub ⊙} and find that the radial intensity profiles can be reproduced with an irradiated disk model, where the inner regions are excavated of dust, likely tracing the dust sublimation region in these disks. The circumstellar disks are strongly misaligned with respect to the binary separation vector, which indicates that the tidal forces did not have time to realign the disks, pointing toward a young dynamical age of the system. We constrain the distribution of the Br γ and CO-emitting gas using VLTI/GRAVITY spectro-interferometry and VLT/CRIRES spectro-astrometry and find that the secondary is accreting at a higher rate than the primary. VLT/NACO imaging shows L ′-band emission on (3–4)× larger scales than the binary separation, matching the expected dynamical truncation radius for the circumbinary disk. The IRAS17216-3801 system is ∼3× more massive and ∼5× more compact than other high-mass multiplies imaged at infrared wavelength and the first high-mass protobinary system where circumstellar and circumbinary dust disks could be spatially resolved. This opens exciting new opportunities for studying star–disk interactions and the role of multiplicity in high-mass star formation.

  9. Voltage-controlled spin selection in a magnetic resonant tunneling diode.

    Science.gov (United States)

    Slobodskyy, A; Gould, C; Slobodskyy, T; Becker, C R; Schmidt, G; Molenkamp, L W

    2003-06-20

    We have fabricated all II-VI semiconductor resonant tunneling diodes based on the (Zn,Mn,Be)Se material system, containing dilute magnetic material in the quantum well, and studied their current-voltage characteristics. When subjected to an external magnetic field the resulting spin splitting of the levels in the quantum well leads to a splitting of the transmission resonance into two separate peaks. This is interpreted as evidence of tunneling transport through spin polarized levels, and could be the first step towards a voltage controlled spin filter.

  10. Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on the ZnO nanorod template

    International Nuclear Information System (INIS)

    Tang Yang; Zhao Dongxu; Shen Dezhen; Zhang Jiying; Wang Xiaohua

    2009-01-01

    The ZnO nanorods were used as a template to fabricate nickel nanoclusters by electrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrode for depositing metallic and magnetic nickel nanoclusters. The growth sites of Ni nanoclusters could be controlled by adjusting the applied potential. Under -1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing the potential to be more negative the ZnO nanorods were covered by Ni nanoclusters. The magnetic properties of the electrodeposited Ni nanoclusters also evolved with the applied potentials.

  11. Controllable growth and magnetic properties of nickel nanoclusters electrodeposited on the ZnO nanorod template

    Energy Technology Data Exchange (ETDEWEB)

    Tang Yang; Zhao Dongxu; Shen Dezhen; Zhang Jiying [Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 16 East Nan-Hu Road, Open Economic Zone, Changchun 130033 (China); Wang Xiaohua, E-mail: dxzhao2000@yahoo.com.c [National Key Laboratory of High Power Semiconductor Laser, Changchun University of Science and Technology, 7089 WeiXing Road, ChangChun 130022 (China)

    2009-12-09

    The ZnO nanorods were used as a template to fabricate nickel nanoclusters by electrodeposition. The ZnO nanorod arrays act as a nano-semiconductor electrode for depositing metallic and magnetic nickel nanoclusters. The growth sites of Ni nanoclusters could be controlled by adjusting the applied potential. Under -1.15 V the Ni nanoclusters could be grown on the tips of ZnO nanorods. On increasing the potential to be more negative the ZnO nanorods were covered by Ni nanoclusters. The magnetic properties of the electrodeposited Ni nanoclusters also evolved with the applied potentials.

  12. Magnetoelectric control of valley and spin in a silicene nanoribbon modulated by the magnetic superlattices

    Energy Technology Data Exchange (ETDEWEB)

    An, Xing-Tao, E-mail: anxt@hku.hk

    2015-03-20

    The control of valley and spin degrees of freedom and the transport properties of electrons in a zigzag silicene nanoribbon modulated by the magnetic superlattices are investigated theoretically. Due to the valley–spin locking effect in silicene, the valley degree of freedom can be controlled by magnetic means. The valley or/and spin selection induced by the exchange field result in the perfect spin–valley filter and tunneling magnetoresistance effect in the double ferromagnetic barriers on the surface of the silicene nanoribbon. It is more interesting that there are valley-resolved minigaps and minibands in the zigzag silicene nanoribbon modulated by the magnetic superlattices which give rise to the periodically modulated spin (or/and valley) polarization and tunneling magnetoresistance. The results obtained may have certain practical significance in applications for future valleytronic and spintronic devices. - Highlights: • The valley can be controlled by a magnetic field in silicene. • The valley-resolved miniband transport is studied in the silicene superlattices. • There are the perfect spin–valley filter and tunneling magnetoresistance effect.

  13. Highly controllable near-surface swimming of magnetic Janus nanorods: application to payload capture and manipulation

    International Nuclear Information System (INIS)

    Mair, Lamar O; Carpenter, Jerome; Evans, Benjamin; Hall, Adam R; Shields, Adam; Superfine, Richard; Ford, Kris; Millard, Michael

    2011-01-01

    Directed manipulation of nanomaterials has significant implications in the field of nanorobotics, nanobiotechnology, microfluidics and directed assembly. With the goal of highly controllable nanomaterial manipulation in mind, we present a technique for the near-surface manoeuvering of magnetic nanorod swimmers and its application to controlled micromanipulation. We fabricate magnetic Janus nanorods and show that the magnetic rotation of these nanorods near a floor results in predictable translational motion. The nanorod plane of rotation is nearly parallel to the floor, the angle between rod tilt and floor being expressed by θ, where 0 0 0 . Orthogonal magnetic fields control in-plane motion arbitrarily. Our model for translation incorporates symmetry breaking through increased drag at the no-slip surface boundary. Using this method we demonstrate considerable rod steerability. Additionally, we approach, capture, and manipulate a polystyrene microbead as proof of principle. We attach Janus nanorods to the surfaces of cells and utilize these rods to manipulate individual cells, proving the ability to manoeuver payloads with a wide range of sizes.

  14. Radiative transfer in gray circumstellar dust envelopes: VY Canis Majoris revisited

    International Nuclear Information System (INIS)

    Schwartz, R.D.

    1975-01-01

    The circumstellar dust model for VY CMa proposed by Herbig is reinvestigated using a generalized form of Huang's theory of radiative transfer. The resultant envelope parameters and the emergent energy distribution are found to be insensitive to the choice of Eddington factor for a given envelope inner boundary temperature. Observed fluxes from 0.43 to 74 μ are incorporated into the model, and problems relating to grain emissivity for lambda>30 μ and grain survival at the indicated inner boundary temperature of 1855degreeK are discussed

  15. Gas phase chemical kinetics at high temperature of carbonaceous molecules: application to circumstellar envelopes

    Science.gov (United States)

    Biennier, L.; Gardez, A.; Saidani, G.; Georges, R.; Rowe, B.; Reddy, K. P. J.

    2011-05-01

    Circumstellar shells of evolved stars are a theater of extremely rich physical and chemical processes. More than seventy molecules of varied nature have been identified in the envelopes through their spectral fingerprints in the microwave or far infrared regions. Many of them are carbon chain molecules and radicals and a significant number are unique to the circumstellar medium. However, observational data remain scarce and more than half of the detected species have been observed in only one object, the nearby carbon star IRC + 10216. Chemical kinetic models are needed to describe the formation of molecules in evolved circumstellar outflows. Upcoming terrestrial telescopes such as ALMA will increase the spatial resolution by several orders of magnitude and provide a wealth of data. The determination of relevant laboratory kinetics data is critical to keep up with the development of the observations and of the refinement of chemical models. Today, the majority of reactions studied in the laboratory are the ones involved in combustion and concerning light hydrocarbons. Our objective is to provide the scientific community with rate coefficients of reactions between abundant species in these warm environments. Cyanopolyynes from HC_2N to HC_9N have all been detected in carbon rich circumstellar envelopes in up to 10 sources for HC_3N. Neutral-neutral reactions of the CN radical with unsaturated hydrocarbons could be a dominant route in the formation of cyanopolyynes, even at low temperatures. Our approach aims to bridge the temperature gap between resistively heated flow tubes and shock tubes. The present kinetic measurements are obtained using a new reactor combining a high enthalpy source (Moudens et al. 2011) with a flow tube and a pulsed laser photolysis and laser induced fluorescence system to probe the undergoing chemical reactions. The high enthalpy flow tube has been used to measure the rate constant of the reaction of the CN radical with propane, propene

  16. Archival Legacy Investigations of Circumstellar Environments (ALICE): Statistical assessment of point source detections

    Science.gov (United States)

    Choquet, Élodie; Pueyo, Laurent; Soummer, Rémi; Perrin, Marshall D.; Hagan, J. Brendan; Gofas-Salas, Elena; Rajan, Abhijith; Aguilar, Jonathan

    2015-09-01

    The ALICE program, for Archival Legacy Investigation of Circumstellar Environment, is currently conducting a virtual survey of about 400 stars, by re-analyzing the HST-NICMOS coronagraphic archive with advanced post-processing techniques. We present here the strategy that we adopted to identify detections and potential candidates for follow-up observations, and we give a preliminary overview of our detections. We present a statistical analysis conducted to evaluate the confidence level on these detection and the completeness of our candidate search.

  17. Direct imaging of extra-solar planetary systems with the Circumstellar Imaging Telescope (CIT)

    International Nuclear Information System (INIS)

    Terrile, R.J.

    1988-01-01

    In a joint study conducted by the Jet Propulsion Laboratory and the Perkin-Elmer Corporation it was found that an earth orbital, 1.5 meter diameter low scattered light coronagraphic telescope can achieve a broad range of scientific objectives including the direct detection of Jupiter-sized planets around the nearby stars. Recent major advances in the understanding of coronagraphic performance and in the field of super smooth mirror fabrication allow such an instrument to be designed and built within current technology. Such a project, called the Circumstellar Imaging Telescope (CIT), is currently being proposed. 10 references

  18. MAGNET

    CERN Multimedia

    Benoit Curé

    The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...

  19. MAGNET

    CERN Multimedia

    B. Curé

    During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...

  20. Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

    Science.gov (United States)

    Lingos, P. C.; Wang, J.; Perakis, I. E.

    2015-05-01

    Femtosecond (fs) coherent control of collective order parameters is important for nonequilibrium phase dynamics in correlated materials. Here, we propose such control of ferromagnetic order based on using nonadiabatic optical manipulation of electron-hole (e -h ) photoexcitations to create fs carrier-spin pulses with controllable direction and time profile. These spin pulses are generated due to the time-reversal symmetry breaking arising from nonperturbative spin-orbit and magnetic exchange couplings of coherent photocarriers. By tuning the nonthermal populations of exchange-split, spin-orbit-coupled semiconductor band states, we can excite fs spin-orbit torques that control complex magnetization pathways between multiple magnetic memory states. We calculate the laser-induced fs magnetic anisotropy in the time domain by using density matrix equations of motion rather than the quasiequilibrium free energy. By comparing to pump-probe experiments, we identify a "sudden" out-of-plane magnetization canting displaying fs magnetic hysteresis, which agrees with switchings measured by the static Hall magnetoresistivity. This fs transverse spin-canting switches direction with magnetic state and laser frequency, which distinguishes it from the longitudinal nonlinear optical and demagnetization effects. We propose that sequences of clockwise or counterclockwise fs spin-orbit torques, photoexcited by shaping two-color laser-pulse sequences analogous to multidimensional nuclear magnetic resonance (NMR) spectroscopy, can be used to timely suppress or enhance magnetic ringing and switching rotation in magnetic memories.

  1. Application of optimal control theory to laser heating of a plasma in a solenoidal magnetic field

    International Nuclear Information System (INIS)

    Neal, R.D.

    1975-01-01

    Laser heating of a plasma column confined by a solenoidal magnetic field is studied via modern optimal control techniques. A two-temperature, constant pressure model is used for the plasma so that the temperature and density are functions of time and location along the plasma column. They are assumed to be uniform in the radial direction so that refraction of the laser beam does not occur. The laser intensity used as input to the column at one end is taken as the control variable and plasma losses are neglected. The localized behavior of the plasma heating dynamics is first studied and conventional optimal control theory applied. The distributed parameter optimal control problem is next considered with minimum time to reach a specified final ion temperature criterion as the objective. Since the laser intensity can only be directly controlled at the input end of the plasma column, a boundary control situation results. The problem is unique in that the control is the boundary value of one of the state variables. The necessary conditions are developed and the problem solved numerically for typical plasma parameters. The problem of maximizing the space-time integral of neutron production rate in the plasma is considered for a constant distributed control problem where the laser intensity is assumed fixed at maximum and the external magnetic field is taken as a control variable

  2. Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

    Directory of Open Access Journals (Sweden)

    Miaolei Zhou

    Full Text Available As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

  3. Feedforward-feedback hybrid control for magnetic shape memory alloy actuators based on the Krasnosel'skii-Pokrovskii model.

    Science.gov (United States)

    Zhou, Miaolei; Zhang, Qi; Wang, Jingyuan

    2014-01-01

    As a new type of smart material, magnetic shape memory alloy has the advantages of a fast response frequency and outstanding strain capability in the field of microdrive and microposition actuators. The hysteresis nonlinearity in magnetic shape memory alloy actuators, however, limits system performance and further application. Here we propose a feedforward-feedback hybrid control method to improve control precision and mitigate the effects of the hysteresis nonlinearity of magnetic shape memory alloy actuators. First, hysteresis nonlinearity compensation for the magnetic shape memory alloy actuator is implemented by establishing a feedforward controller which is an inverse hysteresis model based on Krasnosel'skii-Pokrovskii operator. Secondly, the paper employs the classical Proportion Integration Differentiation feedback control with feedforward control to comprise the hybrid control system, and for further enhancing the adaptive performance of the system and improving the control accuracy, the Radial Basis Function neural network self-tuning Proportion Integration Differentiation feedback control replaces the classical Proportion Integration Differentiation feedback control. Utilizing self-learning ability of the Radial Basis Function neural network obtains Jacobian information of magnetic shape memory alloy actuator for the on-line adjustment of parameters in Proportion Integration Differentiation controller. Finally, simulation results show that the hybrid control method proposed in this paper can greatly improve the control precision of magnetic shape memory alloy actuator and the maximum tracking error is reduced from 1.1% in the open-loop system to 0.43% in the hybrid control system.

  4. Active Magnetic Bearings Stiffness and Damping Identification from Frequency Characteristics of Control System

    Directory of Open Access Journals (Sweden)

    Chaowu Jin

    2016-01-01

    Full Text Available At present, the stiffness and damping identification for active magnetic bearings (AMBs are still in the stage of theoretical analysis. The theoretical analysis indicates that if the mechanical structure and system parameters are determined, AMBs stiffness and damping are only related to frequency characteristic of control system, ignoring operating condition. More importantly, few verification methods are proposed. Considering the shortcomings of the theoretical identification, this paper obtains these coefficients from the experiment by using the magnetic bearing as a sine exciter. The identification results show that AMBs stiffness and damping have a great relationship with the control system and rotating speed. Specifically, at low rotating speed, the stiffness and damping can be obtained from the rotor static suspension by adding the same excitation frequency. However, at high speed, different from the static suspension situation, the AMBs supporting coefficients are not only related to the frequency characteristics of control system, but also related to the system operating conditions.

  5. Control of magnetic vortex polarity by the phase difference between voltage signals

    Science.gov (United States)

    Cui, Huanqing; Cai, Li; Yang, Xiaokuo; Wang, Sen; Zhang, Mingliang; Li, Cheng; Feng, Chaowen

    2018-02-01

    Using micromagnetic simulations, we investigate the voltage control of magnetic vortex polarity based on a designed multiferroic heterostructure that contains two separate piezoelectric films beneath a magnetostrictive nanodisk. The results show that controllable switching of vortex polarity can be achieved by proper modulation of the phase difference between two sinusoidal voltage pulses V1 and V2, which are applied to the two separate piezoelectric films, respectively. The frequencies of V1 and V2 are set at the gyrotropic eigenfrequency fG of the nanodisk, and the vortex polarity switching is completed via the nucleation-annihilation process of the vortex-antivortex pair. Our findings provide an additional effective means for ultralow power switching of the magnetic vortex, which lays the foundation for voltage-controlled vortex random access memory.

  6. Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems

    CERN Document Server

    Wu, Zhizheng; Ben Amara, Foued

    2013-01-01

    Modeling and Control of Magnetic Fluid Deformable Mirrors for Adaptive Optics Systems presents a novel design of wavefront correctors based on magnetic fluid deformable mirrors (MFDM) as well as corresponding control algorithms. The presented wavefront correctors are characterized by their linear, dynamic response. Various mirror surface shape control algorithms are presented along with experimental evaluations of the performance of the resulting adaptive optics systems. Adaptive optics (AO) systems are used in various fields of application to enhance the performance of optical systems, such as imaging, laser, free space optical communication systems, etc. This book is intended for undergraduate and graduate students, professors, engineers, scientists and researchers working on the design of adaptive optics systems and their various emerging fields of application. Zhizheng Wu is an associate professor at Shanghai University, China. Azhar Iqbal is a research associate at the University of Toronto, Canada. Foue...

  7. TEA controllable preparation of magnetite nanoparticles (Fe3O4 NPs) with excellent magnetic properties

    Science.gov (United States)

    Han, Chengliang; Zhu, Dejie; Wu, Hanzhao; Li, Yao; Cheng, Lu; Hu, Kunhong

    2016-06-01

    A fast and controllable synthesis method for superparamagnetic magnetite nanoparticles (Fe3O4 NPs) was developed in Fe(III)-triethanolamine (TEA) solution. The phase structure, morphology and particle size of the as-synthesized samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the magnetic particles were pure Fe3O4 with mean sizes of approximately 10 nm. The used TEA has key effects on the formation of well dispersing Fe3O4 NPs. Vibrating sample magnetometer (VSM) result indicated that the as-obtained Fe3O4 NPs exhibited superparamagnetic behavior and the saturation magnetization (Ms) was about 70 emu/g, which had potential applications in magnetic science and technology.

  8. Controlled data storage for non-volatile memory cells embedded in nano magnetic logic

    Science.gov (United States)

    Riente, Fabrizio; Ziemys, Grazvydas; Mattersdorfer, Clemens; Boche, Silke; Turvani, Giovanna; Raberg, Wolfgang; Luber, Sebastian; Breitkreutz-v. Gamm, Stephan

    2017-05-01

    Among the beyond-CMOS technologies, perpendicular Nano Magnetic Logic (pNML) is a promising candidate due to its low power consumption, its non-volatility and its monolithic 3D integrability, which makes it possible to integrate memory and logic into the same device by exploiting the interaction of bi-stable nanomagnets with perpendicular magnetic anisotropy. Logic computation and signal synchronization are achieved by focus ion beam irradiation and by pinning domain walls in magnetic notches. However, in realistic circuits, the information storage and their read-out are crucial issues, often ignored in the exploration of beyond-CMOS devices. In this paper we address these issues by experimentally demonstrating a pNML memory element, whose read and write operations can be controlled by two independent pulsed currents. Our results prove the correct behavior of the proposed structure that enables high density memory embedded in the logic plane of 3D-integrated pNML circuits.

  9. Motion control of a large gap magnetic suspension system for microrobotic manipulation

    Energy Technology Data Exchange (ETDEWEB)

    Craig, David; Khamesee, Mir Behrad [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Ontario, N2L 3G1 (Canada)

    2007-06-07

    Magnetic suspension systems have shown a great deal of promise in the field of microrobotics. This paper discusses the performance of a new large gap magnetic suspension system developed by the researchers. The magnetic drive unit consists of six electromagnets attached to a soft iron pole piece and yoke. Levitation of an 11.19 g microrobot prototype is demonstrated for step, ramp and periodic input trajectories using PID control. The working envelope of the microrobot is 30 x 22 x 20 mm{sup 3}, with an RMS error on the order of 18 {mu}m in the vertical direction and 8 {mu}m in the horizontal direction. It is demonstrated that the levitated microrobot is able to track the desired trajectory precisely and that the system has potential application for micromanipulation.

  10. Magnetic-field control of quantum critical points of valence transition.

    Science.gov (United States)

    Watanabe, Shinji; Tsuruta, Atsushi; Miyake, Kazumasa; Flouquet, Jacques

    2008-06-13

    We study the mechanism of how critical end points of first-order valence transitions are controlled by a magnetic field. We show that the critical temperature is suppressed to be a quantum critical point (QCP) by a magnetic field, and unexpectedly, the QCP exhibits nonmonotonic field dependence in the ground-state phase diagram, giving rise to the emergence of metamagnetism even in the intermediate valence-crossover regime. The driving force of the field-induced QCP is clarified to be cooperative phenomena of the Zeeman and Kondo effects, which create a distinct energy scale from the Kondo temperature. This mechanism explains the peculiar magnetic response in CeIrIn(5) and the metamagnetic transition in YbXCu(4) for X=In as well as the sharp contrast between X=Ag and Cd.

  11. Electric field control of magnon-induced magnetization dynamics in multiferroics.

    Science.gov (United States)

    Risinggård, Vetle; Kulagina, Iryna; Linder, Jacob

    2016-08-24

    We consider theoretically the effect of an inhomogeneous magnetoelectric coupling on the magnon-induced dynamics of a ferromagnet. The magnon-mediated magnetoelectric torque affects both the homogeneous magnetization and magnon-driven domain wall motion. In the domains, we predict a reorientation of the magnetization, controllable by the applied electric field, which is almost an order of magnitude larger than that observed in other physical systems via the same mechanism. The applied electric field can also be used to tune the domain wall speed and direction of motion in a linear fashion, producing domain wall velocities several times the zero field velocity. These results show that multiferroic systems offer a promising arena to achieve low-dissipation magnetization rotation and domain wall motion by exciting spin-waves.

  12. Motion control of a large gap magnetic suspension system for microrobotic manipulation

    International Nuclear Information System (INIS)

    Craig, David; Khamesee, Mir Behrad

    2007-01-01

    Magnetic suspension systems have shown a great deal of promise in the field of microrobotics. This paper discusses the performance of a new large gap magnetic suspension system developed by the researchers. The magnetic drive unit consists of six electromagnets attached to a soft iron pole piece and yoke. Levitation of an 11.19 g microrobot prototype is demonstrated for step, ramp and periodic input trajectories using PID control. The working envelope of the microrobot is 30 x 22 x 20 mm 3 , with an RMS error on the order of 18 μm in the vertical direction and 8 μm in the horizontal direction. It is demonstrated that the levitated microrobot is able to track the desired trajectory precisely and that the system has potential application for micromanipulation

  13. Electrical control of memristance and magnetoresistance in oxide magnetic tunnel junctions

    KAUST Repository

    Zhang, Kun

    2015-01-01

    Electric-field control of magnetic and transport properties of magnetic tunnel junctions has promising applications in spintronics. Here, we experimentally demonstrate a reversible electrical manipulation of memristance, magnetoresistance, and exchange bias in Co/CoO–ZnO/Co magnetic tunnel junctions, which enables the realization of four nonvolatile resistance states. Moreover, greatly enhanced tunneling magnetoresistance of 68% was observed due to the enhanced spin polarization of the bottom Co/CoO interface. The ab initio calculations further indicate that the spin polarization of the Co/CoO interface is as high as 73% near the Fermi level and plenty of oxygen vacancies can induce metal–insulator transition of the CoO1−v layer. Thus, the electrical manipulation mechanism on the memristance, magnetoresistance and exchange bias can be attributed to the electric-field-driven migration of oxygen ions/vacancies between very thin CoO and ZnO layers.

  14. Electric-field controlled ferromagnetism in MnGe magnetic quantum dots

    Directory of Open Access Journals (Sweden)

    Faxian Xiu

    2011-03-01

    Full Text Available Electric-field control of ferromagnetism in magnetic semiconductors at room temperature has been actively pursued as one of the important approaches to realize practical spintronics and non-volatile logic devices. While Mn-doped III-V semiconductors were considered as potential candidates for achieving this controllability, the search for an ideal material with high Curie temperature (Tc>300 K and controllable ferromagnetism at room temperature has continued for nearly a decade. Among various dilute magnetic semiconductors (DMSs, materials derived from group IV elements such as Si and Ge are the ideal candidates for such materials due to their excellent compatibility with the conventional complementary metal-oxide-semiconductor (CMOS technology. Here, we review recent reports on the development of high-Curie temperature Mn0.05Ge0.95 quantum dots (QDs and successfully demonstrate electric-field control of ferromagnetism in the Mn0.05Ge0.95 quantum dots up to 300 K. Upon the application of gate-bias to a metal-oxide-semiconductor (MOS capacitor, the ferromagnetism of the channel layer (i.e. the Mn0.05Ge0.95 quantum dots was modulated as a function of the hole concentration. Finally, a theoretical model based upon the formation of magnetic polarons has been proposed to explain the observed field controlled ferromagnetism.

  15. Microfluidic synthesis of microfibers for magnetic-responsive controlled drug release and cell culture.

    Directory of Open Access Journals (Sweden)

    Yung-Sheng Lin

    Full Text Available This study demonstrated the fabrication of alginate microfibers using a modular microfluidic system for magnetic-responsive controlled drug release and cell culture. A novel two-dimensional fluid-focusing technique with multi-inlets and junctions was used to spatiotemporally control the continuous laminar flow of alginate solutions. The diameter of the manufactured microfibers, which ranged from 211 µm to 364 µm, could be well controlled by changing the flow rate of the continuous phase. While the model drug, diclofenac, was encapsulated into microfibers, the drug release profile exhibited the characteristic of a proper and steady release. Furthermore, the diclofenac release kinetics from the magnetic iron oxide-loaded microfibers could be controlled externally, allowing for a rapid drug release by applying a magnetic force. In addition, the successful culture of glioblastoma multiforme cells in the microfibers demonstrated a good structural integrity and environment to grow cells that could be applied in drug screening for targeting cancer cells. The proposed microfluidic system has the advantages of ease of fabrication, simplicity, and a fast and low-cost process that is capable of generating functional microfibers with the potential for biomedical applications, such as drug controlled release and cell culture.

  16. FPGA implementation of adaptive ANN controller for speed regulation of permanent magnet stepper motor drives

    Energy Technology Data Exchange (ETDEWEB)

    Hasanien, Hany M., E-mail: Hanyhasanien@ieee.or [Dept. of Elec. Power and Machines, Faculty of Eng., Ain Shams Univ., Cairo (Egypt)

    2011-02-15

    This paper presents a novel adaptive artificial neural network (ANN) controller, which applies on permanent magnet stepper motor (PMSM) for regulating its speed. The dynamic response of the PMSM with the proposed controller is studied during the starting process under the full load torque and under load disturbance. The effectiveness of the proposed adaptive ANN controller is then compared with that of the conventional PI controller. The proposed methodology solves the problem of nonlinearities and load changes of PMSM drives. The proposed controller ensures fast and accurate dynamic response with an excellent steady state performance. Matlab/Simulink tool is used for this dynamic simulation study. The main contribution of this work is the implementation of the proposed controller on field programmable gate array (FPGA) hardware to drive the stepper motor. The driver is built on FPGA Spartan-3E Starter from Xilinx. Experimental results are presented to demonstrate the validity and effectiveness of the proposed control scheme.

  17. Analysis Of The Method Of Predictive Control Applicable To Active Magnetic Suspension Systems Of Aircraft Engines

    Directory of Open Access Journals (Sweden)

    Kurnyta-Mazurek Paulina

    2015-12-01

    Full Text Available Conventional controllers are usually synthesized on the basis of already known parameters associated with the model developed for the object to be controlled. However, sometimes it proves extremely difficult or even infeasible to find out these parameters, in particular when they subject to changes during the exploitation lifetime. If so, much more sophisticated control methods have to be applied, e.g. the method of predictive control. Thus, the paper deals with application of the predictive control approach to follow-up tracking of an active magnetic suspension where the mathematical and simulation models for such a control system are disclosed with preliminary results from simulation investigations of the control system in question.

  18. FPGA implementation of adaptive ANN controller for speed regulation of permanent magnet stepper motor drives

    International Nuclear Information System (INIS)

    Hasanien, Hany M.

    2011-01-01

    This paper presents a novel adaptive artificial neural network (ANN) controller, which applies on permanent magnet stepper motor (PMSM) for regulating its speed. The dynamic response of the PMSM with the proposed controller is studied during the starting process under the full load torque and under load disturbance. The effectiveness of the proposed adaptive ANN controller is then compared with that of the conventional PI controller. The proposed methodology solves the problem of nonlinearities and load changes of PMSM drives. The proposed controller ensures fast and accurate dynamic response with an excellent steady state performance. Matlab/Simulink tool is used for this dynamic simulation study. The main contribution of this work is the implementation of the proposed controller on field programmable gate array (FPGA) hardware to drive the stepper motor. The driver is built on FPGA Spartan-3E Starter from Xilinx. Experimental results are presented to demonstrate the validity and effectiveness of the proposed control scheme.

  19. Tracking Control of a Magnetic Shape Memory Actuator Using an Inverse Preisach Model with Modified Fuzzy Sliding Mode Control

    Directory of Open Access Journals (Sweden)

    Jhih-Hong Lin

    2016-08-01

    Full Text Available Magnetic shape memory (MSM alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved.

  20. Tracking Control of a Magnetic Shape Memory Actuator Using an Inverse Preisach Model with Modified Fuzzy Sliding Mode Control.

    Science.gov (United States)

    Lin, Jhih-Hong; Chiang, Mao-Hsiung

    2016-08-25

    Magnetic shape memory (MSM) alloys are a new class of smart materials with extraordinary strains up to 12% and frequencies in the range of 1 to 2 kHz. The MSM actuator is a potential device which can achieve high performance electromagnetic actuation by using the properties of MSM alloys. However, significant non-linear hysteresis behavior is a significant barrier to control the MSM actuator. In this paper, the Preisach model was used, by capturing experiments from different input signals and output responses, to model the hysteresis of MSM actuator, and the inverse Preisach model, as a feedforward control, provided compensational signals to the MSM actuator to linearize the hysteresis non-linearity. The control strategy for path tracking combined the hysteresis compensator and the modified fuzzy sliding mode control (MFSMC) which served as a path controller. Based on the experimental results, it was verified that a tracking error in the order of micrometers was achieved.

  1. Biohydrogels with magnetic nanoparticles as crosslinker: characteristics and potential use for controlled antitumor drug-delivery.

    Science.gov (United States)

    Barbucci, Rolando; Giani, Gabriele; Fedi, Serena; Bottari, Severino; Casolaro, Mario

    2012-12-01

    Hybrid magnetic hydrogels are of interest for applications in biomedical science as controlled drug-delivery systems. We have developed a strategy to obtain novel hybrid hydrogels with magnetic nanoparticles (NPs) of CoFe(2)O(3) and Fe(3)O(4) as crosslinker agents of carboxymethylcellulose (CMC) or hyaluronic acid (HYAL) polymers and we have tested these systems for controlled doxorubicin release. The magnetic NPs are functionalized with (3-aminopropyl)trimethoxysilane (APTMS) in order to introduce amino groups on the surface. The amino coating is determined and quantified by standard Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy methods, and by cyclic voltammetry, a novel approach that permits us to look at the solution properties of the functionalized NPs. The gel formation involves the creation of an amide bond between the carboxylic groups of CMC or HYAL and the amine groups of functionalized NPs, which work as crosslinking agents of the polymer chains. The hybrid hydrogels are chemically and morphologically characterized. The rheological and the water uptake properties of the hydrogels are also investigated. Under the application of an alternating magnetic field, the CMC-HYAL hybrid hydrogel previously loaded with doxorubicin shows a drug release greater than that showed by the CMC-HYAL hydrogel crosslinked with 1,3-diaminopropane. In conclusion, the presence of magnetic NPs makes the synthesized hybrid hydrogels suitable for application as a drug-delivery system by means of alternating magnetic fields. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Passive superconductor: A viable method of controlling magnetization multipoles in the SSC dipole

    International Nuclear Information System (INIS)

    Green, M.A.

    1989-02-01

    At injection, the magnetization of the superconductor produces the dominant field error in the SSC dipole magnets. The field generated by magnetization currents in the superconductor is rich in higher symmetric multipoles (normal sextupole, normal decapole, and so on). Pieces of passive superconductor properly located within the bore of the dipole magnet can cancel the higher multipoles generated by the SSC dipole coils. The multipoles generated by the passive superconductor (predominantly sextupole and decapole) are controlled by the angular and radial location of the superconductor, the volume of superconductor, and the size of the superconducting filaments within the passive conductor. This paper will present the tolerances on each of these factors. The paper will show that multipole correction using passive superconductor is in general immune to the effects of temperature and magnetization decay due to flux creep, provided that dipole superconductor and the passive correction superconductor are properly specified. When combined with a lumped correction system, the passive superconductor can be a viable alternative to continuous correction coils within the SSC dipoles. 20 refs., 8 figs., 2 tabs

  3. Passive superconductor a viable method of controlling magnetization multipoles in the SSC dipole

    International Nuclear Information System (INIS)

    Green, M.A.

    1989-01-01

    At injection, the magnetization of the superconductor produces the dominant field error in the SSC dipole magnets. The field generated by magnetization currents in the superconductor is rich in higher symmetric multipoles (normal sextupole, normal decapole, and so on). Pieces of passive superconductor properly located within the bore of the dipole magnet can cancel the higher multipoles generated by the SSC dipole coils. The multipoles generated by the passive superconductor (predominantly sextupole and decapole) are controlled by the angular and radial location of the superconductor, the volume of superconductor, and the size of the superconducting filaments within the passive conductor. This paper will present the tolerances on each of these factors. The paper will show that multipole correction using passive superconductor is in general immune to the effects of temperature and magnetization decay due to flux creep, provided that dipole superconductor and the passive correction superconductor are properly specified. When combined with a lumped correction system, the passive superconductor can be a viable alternative to continuous correction coils within the SSC dipoles. 20 refs., 8 figs., 2 tabs

  4. Alternating Magnetic Field Controlled, Multifunctional Nano-Reservoirs: Intracellular Uptake and Improved Biocompatibility

    Directory of Open Access Journals (Sweden)

    GhoshMitra Somesree

    2009-01-01

    Full Text Available Abstract Biocompatible magnetic nanoparticles hold great therapeutic potential, but conventional particles can be toxic. Here, we report the synthesis and alternating magnetic field dependent actuation of a remotely controllable, multifunctional nano-scale system and its marked biocompatibility with mammalian cells. Monodisperse, magnetic nanospheres based on thermo-sensitive polymer network poly(ethylene glycol ethyl ether methacrylate-co-poly(ethylene glycol methyl ether methacrylate were synthesized using free radical polymerization. Synthesized nanospheres have oscillating magnetic field induced thermo-reversible behavior; exhibiting desirable characteristics comparable to the widely used poly-N-isopropylacrylamide-based systems in shrinkage plus a broader volumetric transition range. Remote heating and model drug release were characterized for different field strengths. Nanospheres containing nanoparticles up to an iron concentration of 6 mM were readily taken up by neuron-like PC12 pheochromocytoma cells and had reduced toxicity compared to other surface modified magnetic nanocarriers. Furthermore, nanosphere exposure did not inhibit the extension of cellular processes (neurite outgrowth even at high iron concentrations (6 mM, indicating minimal negative effects in cellular systems. Excellent intracellular uptake and enhanced biocompatibility coupled with the lack of deleterious effects on neurite outgrowth and prior Food and Drug Administration (FDA approval of PEG-based carriers suggest increased therapeutic potential of this system for manipulating axon regeneration following nervous system injury.

  5. Modeling and control for a magnetic levitation system based on SIMLAB platform in real time

    Science.gov (United States)

    Yaseen, Mundher H. A.; Abd, Haider J.

    2018-03-01

    Magnetic Levitation system becomes a hot topic of study due to the minimum friction and low energy consumption which regards as very important issues. This paper proposed a new magnetic levitation system using real-time control simulink feature of (SIMLAB) microcontroller. The control system of the maglev transportation system is verified by simulations with experimental results, and its superiority is indicated in comparison with previous literature and conventional control strategies. In addition, the proposed system was implemented under effect of three controller types which are Linear-quadratic regulator (LQR), proportional-integral-derivative controller (PID) and Lead compensation. As well, the controller system performance was compared in term of three parameters Peak overshoot, Settling time and Rise time. The findings prove the agreement of simulation with experimental results obtained. Moreover, the LQR controller produced a great stability and homogeneous response than other controllers used. For experimental results, the LQR brought a 14.6%, 0.199 and 0.064 for peak overshoot, Setting time and Rise time respectively.

  6. Nonlinear Speed Control of Permanent Magnet Synchronous Motor with Salient Poles

    Directory of Open Access Journals (Sweden)

    K. Kyslan

    2015-12-01

    Full Text Available This paper presents the speed control of permanent magnet synchronous motor with salient poles based on two-step linearization method. In the first step, the direct compensation of the nonlinearities in the equations of current is used. In the second step, the input-output linearization in the state space is used for the decoupling of flux and torque axis. Simulated results are compared to the field oriented vector control structure with PI controllers in order to show differences in the performance of both approaches.

  7. Control strategy for permanent magnet synchronous motor with contra-rotating rotors under unbalanced loads condition

    DEFF Research Database (Denmark)

    Cheng, Shuangyin; Luo, Derong; Huang, Shoudao

    2015-01-01

    This study presents an investigation into the control of an axial-flux permanent magnet synchronous machine (PMSM) with contra-rotating rotors fed by a single inverter, which corresponds to two PMSM connected in series. In this study, the mathematic model of the PMSM with contra-rotating rotors...... water vehicle propulsions. The control strategy is implemented on a DSP 28335 processor featured hardware platform and is tested on a 1.2 kW prototype machine. Experimental results validate the correctness of the analysis and control strategy....

  8. Power Control of Permanent Magnet Generator Based Variable Speed Wind Turbines

    DEFF Research Database (Denmark)

    Deng, Fujin; Chen, Zhe

    2009-01-01

    When the wind power accounts for a large portion of the grid, it will be required to regulate the active power and reactive power. This paper investigates a MWlevel variable speed wind turbine with a permanent magnet synchronous generator (PMSG). The power control capabilities of two kinds...... of control schemes conducted respectively on this wind turbine under two conditions, including rapid wind speed change and grids faults, are compared. The simulation study of the wind turbine system is conducted using PSCAD/EMTDC, and the results show the different power control capabilities of the two...

  9. Carbon-coated NiPt, CoPt nanoalloys: size control and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    El-Gendy, A.A. [Kirchhoff Institute for Physics, University of Heidelberg, D-69120 Heidelberg (Germany); Leibniz Institute for Solid State and Materials Research (IFW) Dresden (Germany); Hampel, S.; Leonhardt, A.; Khavrus, V.; Buechner, B. [Leibniz Institute for Solid State and Materials Research (IFW) Dresden (Germany); Klingeler, R. [Kirchhoff Institute for Physics, University of Heidelberg, D-69120 Heidelberg (Germany)

    2011-07-01

    Controlled synthesis of magnetic nanoparticles with well-defined size and composition is always a challenge in material-based nanoscience. Here, we apply the high pressure chemical vapour deposition technique (HPCVD) to obtain carbon-shielded magnetic alloy nanoparticles under control of the particle size. Carbon encapsulated NiPt, CoPt (NiPt rate at C, CoPt rate at C) nanoalloys were synthesized by means of HPCVD starting from sublimating appropriate metal-organic precursors. Structural characterization by means of high resolution transmission electron microscopy, energy dispersive X-ray analysis and X-ray diffraction indicated the formation of coated bimetallic Ni{sub x}Pt{sub 100-x} and CoxPt{sub 100-x} nanoparticles. Adjusting the sublimation temperature of the different precursors allowed tuning the core sizes with small size distribution. In addition, detailed studies of the magnetic properties are presented. AC magnetic heating studies imply the potential of the coated nanoalloys for hyperthermia therapy.

  10. Tuning dipolar magnetic interactions by controlling individual silica coating of iron oxide nanoparticles

    Science.gov (United States)

    Rivas Rojas, P. C.; Tancredi, P.; Moscoso Londoño, O.; Knobel, M.; Socolovsky, L. M.

    2018-04-01

    Single and fixed size core, core-shell nanoparticles of iron oxides coated with a silica layer of tunable thickness were prepared by chemical routes, aiming to generate a frame of study of magnetic nanoparticles with controlled dipolar interactions. The batch of iron oxides nanoparticles of 4.5 nm radii, were employed as cores for all the coated samples. The latter was obtained via thermal decomposition of organic precursors, resulting on nanoparticles covered with an organic layer that was subsequently used to promote the ligand exchange in the inverse microemulsion process, employed to coat each nanoparticle with silica. The amount of precursor and times of reaction was varied to obtain different silica shell thicknesses, ranging from 0.5 nm to 19 nm. The formation of the desired structures was corroborated by TEM and SAXS measurements, the core single-phase spinel structure was confirmed by XRD, and superparamagnetic features with gradual change related to dipolar interaction effects were obtained by the study of the applied field and temperature dependence of the magnetization. To illustrate that dipolar interactions are consistently controlled, the main magnetic properties are presented and analyzed as a function of center to center minimum distance between the magnetic cores.

  11. Sensorless interior permanent magnet synchronous motor control with rotational inertia adjustment

    Directory of Open Access Journals (Sweden)

    Yongle Mao

    2016-12-01

    Full Text Available Mechanical model is generally required in high dynamic sensorless motor control schemes for zero phase lag estimation of rotor position and speed. However, the rotational inertia uncertainty will cause dynamic estimation errors, eventually resulting in performance deterioration of the sensorless control system. Therefore, this article proposes a high dynamic performance sensorless control strategy with online adjustment of the rotational inertia. Based on a synthetic back electromotive force model, the voltage equation of interior permanent magnet synchronous motor is transformed to that of an equivalent non-salient permanent magnet synchronous motor. Then, an extended nonlinear observer is designed for interior permanent magnet synchronous motor in the stator-fixed coordinate frame, with rotor position, speed and load torque simultaneously estimated. The effect of inaccurate rotational inertia on the estimation of rotor position and speed is investigated, and a novel rotational inertia adjustment approach that employs the gradient descent algorithm is proposed to suppress the dynamic estimation errors. The effectiveness of the proposed control strategy is demonstrated by experimental tests.

  12. GA-based fuzzy reinforcement learning for control of a magnetic bearing system.

    Science.gov (United States)

    Lin, C T; Jou, C P

    2000-01-01

    This paper proposes a TD (temporal difference) and GA (genetic algorithm)-based reinforcement (TDGAR) learning method and applies it to the control of a real magnetic bearing system. The TDGAR learning scheme is a new hybrid GA, which integrates the TD prediction method and the GA to perform the reinforcement learning task. The TDGAR learning system is composed of two integrated feedforward networks. One neural network acts as a critic network to guide the learning of the other network (the action network) which determines the outputs (actions) of the TDGAR learning system. The action network can be a normal neural network or a neural fuzzy network. Using the TD prediction method, the critic network can predict the external reinforcement signal and provide a more informative internal reinforcement signal to the action network. The action network uses the GA to adapt itself according to the internal reinforcement signal. The key concept of the TDGAR learning scheme is to formulate the internal reinforcement signal as the fitness function for the GA such that the GA can evaluate the candidate solutions (chromosomes) regularly, even during periods without external feedback from the environment. This enables the GA to proceed to new generations regularly without waiting for the arrival of the external reinforcement signal. This can usually accelerate the GA learning since a reinforcement signal may only be available at a time long after a sequence of actions has occurred in the reinforcement learning problem. The proposed TDGAR learning system has been used to control an active magnetic bearing (AMB) system in practice. A systematic design procedure is developed to achieve successful integration of all the subsystems including magnetic suspension, mechanical structure, and controller training. The results show that the TDGAR learning scheme can successfully find a neural controller or a neural fuzzy controller for a self-designed magnetic bearing system.

  13. Radiative transfer in spherical circumstellar dust envelopes. III. Dust envelope models of some well known infrared stars

    International Nuclear Information System (INIS)

    Apruzese, J.P.

    1975-01-01

    The radiative transfer techniques described elsewhere by the author have been employed to construct dust envelope models of several well known infrared stars. The resulting calculations indicate that the infrared emissivity of circumstellar grains generally must be higher than that which many calculations of small nonsilicate grains yield. This conclusion is dependent to some degree on the (unknown) size of the stellar envelopes considered, but is quite firm in the case of the spatially resolved envelope of IRC+10216. Further observations of the spatial distribution of the infrared radiation from stellar envelopes will be invaluable in deciphering the properties of the circumstellar grains

  14. SiO maser emission as a density tracer of circumstellar envelopes

    Science.gov (United States)

    Stroh, Michael; Pihlstrom, Ylva; Sjouwerman, Lorant

    2018-06-01

    The circumstellar envelopes (CSEs) of evolved stars offer a method to construct a sample of point-masses along the full Galactic plane, which can be used to test models of the gravitational potential. In the CSEs of red giants, SiO maser emission is frequently observed at 43 and 86 GHz, providing line-of-sight velocities. The Bulge Asymmetries and Dynamical Evolution (BAaDE) project aims to explore the complex structure of the inner Galaxy and Galactic Bulge, by observing 43 GHz SiO at the Very Large Array and 86 GHz SiO at the Atacama Large Millimeter/submillimeter Array, with an expected final sample of about 20,000 line-of-sight velocities and positions. We observed the 43 GHz and 86 GHz transitions near-simultaneously in a subsample of the sources using the Australia Telescope Compact Array and found that on average the 43 GHz v=1 line is 1.3 times stronger than the 86 GHz v=1 line. The presence of a detectable 43 GHz v=3 line alters the statistics, consistent with the SiO masers displaying 43 GHz v=3 emission arising in a denser regime in the circumstellar shell compared to those without. Comparing our results with radiative models implies that the 43 GHz v=3 line is a tracer of density variations caused by stellar pulsations. We will discuss these results in the context of the BAaDE project.

  15. Shifting of the resonance location for planets embedded in circumstellar disks

    Science.gov (United States)

    Marzari, F.

    2018-03-01

    Context. In the early evolution of a planetary system, a pair of planets may be captured in a mean motion resonance while still embedded in their nesting circumstellar disk. Aims: The goal is to estimate the direction and amount of shift in the semimajor axis of the resonance location due to the disk gravity as a function of the gas density and mass of the planets. The stability of the resonance lock when the disk dissipates is also tested. Methods: The orbital evolution of a large number of systems is numerically integrated within a three-body problem in which the disk potential is computed as a series of expansion. This is a good approximation, at least over a limited amount of time. Results: Two different resonances are studied: the 2:1 and the 3:2. In both cases the shift is inwards, even if by a different amount, when the planets are massive and carve a gap in the disk. For super-Earths, the shift is instead outwards. Different disk densities, Σ, are considered and the resonance shift depends almost linearly on Σ. The gas dissipation leads to destabilization of a significant number of resonant systems, in particular if it is fast. Conclusions: The presence of a massive circumstellar disk may significantly affect the resonant behavior of a pair of planets by shifting the resonant location and by decreasing the size of the stability region. The disk dissipation may explain some systems found close to a resonance but not locked in it.

  16. Infrared spectrophotometry and radiative transfer in optically thick circumstellar dust envelopes

    International Nuclear Information System (INIS)

    Merrill, K.M.

    1976-01-01

    The Two-Micron Sky Survey of Neugebauer and Leighton and, more recently, the AFCRL Infrared Sky Survey of Walker and Price have detected numerous compact, isolated, bright infrared sources which are not identified with previously cataloged stars. Observations of many such objects suggest that extensive circumstellar dust envelopes modify the flux from a central source. The present investigations employ broad bandpass photometry at lambda lambda 1.65 μm to 12.5 μm and narrow bandpass spectrophotometry (Δ lambda/lambda approximately 0.015) at lambda lambda 2-4 μm and lambda lambda 8-13 μm to determine the properties of a large sample of such infrared sources. Infrared spectrophotometry can clearly differentiate between normal stars of spectral types M(''oxygen-rich'') and C (''carbon-rich'') on the basis of characteristic absorption bands arising in cool stellar atmospheres. Most of the 2 μ Sky Survey and many of the AFCRL Sky Survey sources appear to be stars of spectral types M and C which are differentiated from normal cool comparison stars only by the presence of extensive circumstellar dust envelopes. Due to the large optical depth of the envelopes, the flux from the star and from the dust cannot be simply separated. Hence solutions of radiative transfer through spherically symmetric envelopes of arbitrary optical depth were generated by a generalized computer code which employed opacities of real dust

  17. Mass loss from OH/IR stars - Models for the infrared emission of circumstellar dust shells

    Science.gov (United States)

    Justtanont, K.; Tielens, A. G. G. M.

    1992-01-01

    The IR emission of a sample of 24 OH/IR stars is modeled, and the properties of circumstellar dust and mass-loss rate of the central star are derived. It is shown that for some sources the observations of the far-IR emission is well fitted with a lambda exp -1 law, while some have a steeper index of 1.5. For a few sources, the presence of circumstellar ice grains is inferred from detailed studies of the observed 10-micron feature. Dust mass-loss rates are determined from detailed studies for all the stars in this sample. They range from 6.0 x 10 exp -10 solar mass/yr for an optically visible Mira to 2.2 x 10 exp -6 solar mass/yr for a heavily obscured OH/IR star. These dust mass-loss rates are compared to those calculated from IRAS photometry using 12-, 25-, and 60-micron fluxes. The dust mass-loss rates are also compared to gas mass-loss rates determined from OH and CO observations. For stars with tenuous shells, a dust-to-gas ratio of 0.001 is obtained.

  18. Enantiomeric separation of complex organic molecules produced from irradiation of interstellar/circumstellar ice analogs

    Science.gov (United States)

    Nuevo, M.; Meierhenrich, U. J.; D'Hendecourt, L.; Muñoz Caro, G. M.; Dartois, E.; Deboffle, D.; Thiemann, W. H.-P.; Bredehöft, J.-H.; Nahon, L.

    Irradiation of interstellar/circumstellar ice analogs by ultraviolet (UV) light followed by warm up in the laboratory leads to the formation of complex organic molecules, stable at room temperature. Hydrolysis of the room temperature residue releases amino acids, the building blocks of proteins. These amino acids exist in two different forms (L and D), but proteins encountered in living beings consist exclusively of L enantiomers. The origin of this property, called homochirality, is still unknown. Amino acids can be detected and quantified by chemical techniques such as chiral gas chromatography coupled with mass spectrometry (GC-MS). Enantiomers of chiral organics are also known to interact selectively with circularly polarized light (CPL), leading to a selective production or destruction of the final compounds. This paper describes how we settled an experiment where amino acids are formed by irradiation of interstellar/circumstellar ice analogs with ultraviolet (UV) CPL, produced by a synchrotron radiation beamline, which allowed us to quantify the effect of such polarized light on the production of amino acids. These results can be compared to the enantiomeric excesses measured in primitive meteorites such as Murchison.

  19. Arcsecond Resolution Mapping of Sulfur Dioxide Emission in the Circumstellar Envelope of VY Canis Majoris

    Science.gov (United States)

    Fu, Roger R.; Moullet, Arielle; Patel, Nimesh A.; Biersteker, John; Derose, Kimberly L.; Young, Kenneth H.

    2012-02-01

    We report Submillimeter Array observations of SO2 emission in the circumstellar envelope (CSE) of the red supergiant VY Canis Majoris, with an angular resolution of ≈1''. SO2 emission appears in three distinct outflow regions surrounding the central continuum peak emission that is spatially unresolved. No bipolar structure is noted in the sources. A fourth source of SO2 is identified as a spherical wind centered at the systemic velocity. We estimate the SO2 column density and rotational temperature assuming local thermal equilibrium (LTE) as well as perform non-LTE radiative transfer analysis using RADEX. Column densities of SO2 are found to be ~1016 cm-2 in the outflows and in the spherical wind. Comparison with existing maps of the two parent species OH and SO shows the SO2 distribution to be consistent with that of OH. The abundance ratio f_{SO_{2}}/f_{SO} is greater than unity for all radii larger than 3 × 1016 cm. SO2 is distributed in fragmented clumps compared to SO, PN, and SiS molecules. These observations lend support to specific models of circumstellar chemistry that predict f_{SO_{2}}/f_{SO}>1 and may suggest the role of localized effects such as shocks in the production of SO2 in the CSE.

  20. ARCSECOND RESOLUTION MAPPING OF SULFUR DIOXIDE EMISSION IN THE CIRCUMSTELLAR ENVELOPE OF VY CANIS MAJORIS

    International Nuclear Information System (INIS)

    Fu, Roger R.; Moullet, Arielle; Patel, Nimesh A.; Biersteker, John; Derose, Kimberly L.; Young, Kenneth H.

    2012-01-01

    We report Submillimeter Array observations of SO 2 emission in the circumstellar envelope (CSE) of the red supergiant VY Canis Majoris, with an angular resolution of ≈1''. SO 2 emission appears in three distinct outflow regions surrounding the central continuum peak emission that is spatially unresolved. No bipolar structure is noted in the sources. A fourth source of SO 2 is identified as a spherical wind centered at the systemic velocity. We estimate the SO 2 column density and rotational temperature assuming local thermal equilibrium (LTE) as well as perform non-LTE radiative transfer analysis using RADEX. Column densities of SO 2 are found to be ∼10 16 cm –2 in the outflows and in the spherical wind. Comparison with existing maps of the two parent species OH and SO shows the SO 2 distribution to be consistent with that of OH. The abundance ratio f SO 2 /f SO is greater than unity for all radii larger than 3 × 10 16 cm. SO 2 is distributed in fragmented clumps compared to SO, PN, and SiS molecules. These observations lend support to specific models of circumstellar chemistry that predict f SO 2 /f SO >1 and may suggest the role of localized effects such as shocks in the production of SO 2 in the CSE.

  1. The peculiar balmer decrement of SN 2009ip: Constraints on circumstellar geometry

    Energy Technology Data Exchange (ETDEWEB)

    Levesque, Emily M.; Stringfellow, Guy S.; Bally, John; Keeney, Brian A. [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado 389-UCB, Boulder, CO 80309 (United States); Ginsburg, Adam G., E-mail: Emily.Levesque@colorado.edu [European Southern Observatory, ESO Headquarters, Karl-Schwarzschild-Strasse 2, D-95748 Garching bei München (Germany)

    2014-01-01

    We present optical and near-IR spectroscopic observations of the luminous blue variable SN 2009ip during its remarkable photometric evolution of 2012. The spectra sample three key points in the SN 2009ip light curve, corresponding to its initial brightening in August (2012-A) and its dramatic rebrightening in early October (2012-B). Based on line fluxes and velocities measured in our spectra, we find a surprisingly low I(Hα)/I(Hβ) ratio (∼1.3-1.4) in the 2012-B spectra. Such a ratio implies either a rare Case B recombination scenario where Hα, but not Hβ, is optically thick, or an extremely high density for the circumstellar material of n{sub e} > 10{sup 13} cm{sup –3}. The Hα line intensity yields a minimum radiating surface area of ≳20,000 AU{sup 2} in Hα at the peak of SN 2009ip's photometric evolution. Combined with the nature of this object's spectral evolution in 2012, a high circumstellar density and large radiating surface area imply the presence of a thin disk geometry around the central star (and, consequently, a possible binary companion), suggesting that the observed 2012-B rebrightening of SN 2009ip can be attributed to the illumination of the disk's inner rim by fast-moving ejecta produced by the underlying events of 2012-A.

  2. THE PDS 66 CIRCUMSTELLAR DISK AS SEEN IN POLARIZED LIGHT WITH THE GEMINI PLANET IMAGER

    International Nuclear Information System (INIS)

    Wolff, Schuyler G.; Greenbaum, Alexandra Z.; Perrin, Marshall; Hines, Dean C.; Millar-Blanchaer, Maxwell A.; Nielsen, Eric L.; Wang, Jason; Dong, Ruobing; Duchêne, Gaspard; Graham, James R.; Kalas, Paul; Cardwell, Andrew; Chilcote, Jeffrey; Draper, Zachary H.; Fitzgerald, Michael P.; Hung, Li-Wei; Goodsell, Stephen J.; Grady, Carol A.; Hartung, Markus; Hibon, Pascale

    2016-01-01

    We present H- and K-band imaging polarimetry for the PDS 66 circumstellar disk obtained during the commissioning of the Gemini Planet Imager (GPI). Polarization images reveal a clear detection of the disk in to the 0.″12 inner working angle (IWA) in the H band, almost three times closer to the star than the previous Hubble Space Telescope (HST) observations with NICMOS and STIS (0.″35 effective IWA). The centro-symmetric polarization vectors confirm that the bright inner disk detection is due to circumstellar scattered light. A more diffuse disk extends to a bright outer ring centered at 80 AU. We discuss several physical mechanisms capable of producing the observed ring + gap structure. GPI data confirm enhanced scattering on the east side of the disk that is inferred to be nearer to us. We also detect a lateral asymmetry in the south possibly due to shadowing from material within the IWA. This likely corresponds to a temporally variable azimuthal asymmetry observed in HST/STIS coronagraphic imaging

  3. THE PDS 66 CIRCUMSTELLAR DISK AS SEEN IN POLARIZED LIGHT WITH THE GEMINI PLANET IMAGER

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, Schuyler G.; Greenbaum, Alexandra Z. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Perrin, Marshall; Hines, Dean C. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Millar-Blanchaer, Maxwell A. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Nielsen, Eric L. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Wang, Jason; Dong, Ruobing; Duchêne, Gaspard; Graham, James R.; Kalas, Paul [Astronomy Department, University of California, Berkeley, Berkeley, CA 94720 (United States); Cardwell, Andrew [LBT Observatory, University of Arizona, 933 N. Cherry Avenue, Room 552, Tucson, AZ 85721 (United States); Chilcote, Jeffrey [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Draper, Zachary H. [University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2 (Canada); Fitzgerald, Michael P.; Hung, Li-Wei [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Goodsell, Stephen J. [Gemini Observatory, 670 N. A’ohoku Place, Hilo, HI 96720 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Hartung, Markus; Hibon, Pascale, E-mail: swolff9@jh.edu [Gemini Observatory, Casilla 603, La Serena (Chile); and others

    2016-02-10

    We present H- and K-band imaging polarimetry for the PDS 66 circumstellar disk obtained during the commissioning of the Gemini Planet Imager (GPI). Polarization images reveal a clear detection of the disk in to the 0.″12 inner working angle (IWA) in the H band, almost three times closer to the star than the previous Hubble Space Telescope (HST) observations with NICMOS and STIS (0.″35 effective IWA). The centro-symmetric polarization vectors confirm that the bright inner disk detection is due to circumstellar scattered light. A more diffuse disk extends to a bright outer ring centered at 80 AU. We discuss several physical mechanisms capable of producing the observed ring + gap structure. GPI data confirm enhanced scattering on the east side of the disk that is inferred to be nearer to us. We also detect a lateral asymmetry in the south possibly due to shadowing from material within the IWA. This likely corresponds to a temporally variable azimuthal asymmetry observed in HST/STIS coronagraphic imaging.

  4. Mass loss of evolved massive stars: the circumstellar environment at high angular resolution

    International Nuclear Information System (INIS)

    Montarges, Miguel

    2014-01-01

    Mass loss of evolved stars is still largely mysterious, despite its importance as the main evolution engine for the chemical composition of the interstellar medium. For red supergiants (RSG), the triggering of the outflow and the mechanism of dust condensation remain unknown. Concerning red giant stars, we still do not know how their mass loss is able to form a bipolar planetary nebula. During my PhD thesis, I observed evolved stars with high angular resolution techniques. They allowed us to study the surface and the close environment of these stars, from where mass loss originates. With near-infrared interferometric observations, I characterized the water vapor and carbon monoxide envelope of the nearby RSG Betelgeuse. I also monitored a hot spot on its surface and analyzed the structure of its convection, as well as that of Antares (another very nearby supergiant) thanks to radiative hydrodynamical simulations. Diffraction-limited imaging techniques (near-infrared adaptive optics, ultraviolet space telescope) allowed me to observe the evolution of inhomogeneities in the circumstellar envelope of Betelgeuse and to discover a circumstellar disk around L2 Puppis, an asymptotic giant branch star. These multi-scale and multi-wavelength observations obtained at several epochs allowed us to monitor the evolution of the structures and to derive information on the dynamics of the stellar environment. With a wider stellar sample expected in the next few years, this observing program will allow a better understanding of the mass loss of evolved stars. (author)

  5. IDENTIFYING NEARBY, YOUNG, LATE-TYPE STARS BY MEANS OF THEIR CIRCUMSTELLAR DISKS

    International Nuclear Information System (INIS)

    Schneider, Adam; Song, Inseok; Melis, Carl; Zuckerman, B.; Bessell, Mike

    2012-01-01

    It has recently been shown that a significant fraction of late-type members of nearby, very young associations (age ∼<10 Myr) display excess emission at mid-IR wavelengths indicative of dusty circumstellar disks. We demonstrate that the detection of mid-IR excess emission can be utilized to identify new nearby, young, late-type stars including two definite new members ('TWA 33' and 'TWA 34') of the TW Hydrae Association (TWA). Both new TWA members display mid-IR excess emission in the Wide-field Infrared Survey Explorer catalog and they show proper motion and youthful spectroscopic characteristics—namely, Hα emission, strong lithium absorption, and low surface gravity features consistent with known TWA members. We also detect mid-IR excess—the first unambiguous evidence of a dusty circumstellar disk—around a previously identified UV-bright, young, accreting star (2M1337) that is a likely member of the Lower-Centaurus Crux region of the Scorpius-Centaurus Complex.

  6. Power Maximization Control of Variable Speed Wind Generation System Using Permanent Magnet Synchronous Generator

    Science.gov (United States)

    Morimoto, Shigeo; Nakamura, Tomohiko; Takeda, Yoji

    This paper proposes the sensorless output power maximization control of the wind generation system. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. The generator torque is suitably controlled according to the generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control method, where the information of wind velocity is not required. Moreover, the maximum available generated power is obtained by the optimum current vector control. The current vector of PMSG is optimally controlled according to the generator speed and the required torque in order to minimize the losses of PMSG considering the voltage and current constraints. The proposed wind power generation system can be achieved without mechanical sensors such as a wind velocity detector and a position sensor. Several experimental results show the effectiveness of the proposed control method.

  7. Magnetic field modeling and optimal operational control of a single-side axial-flux permanent magnet motor with center poles

    International Nuclear Information System (INIS)

    Liu, C.-T.; Lee, S.-C.

    2006-01-01

    A detailed approach for analyzing magnetic field distributions of a single-sided axial-flux permanent magnet motor with center poles will be provided. Based on the devised flux model, the related position-dependent torque and axial force of the motor can be systematically developed. By incorporating adequate control designs, the optimal operational performance of the motor system can be conveniently achieved. Results showed that not only the motor structure is suitable for related military and transportation applications, but also the magnetic field model can provide appropriate mathematical basis for relative operational realizations

  8. Magnetic

    Science.gov (United States)

    Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.

    2015-06-01

    The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.

  9. MAGNET

    CERN Multimedia

    Benoit Curé

    The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...

  10. MAGNET

    CERN Document Server

    B. Curé

    The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...

  11. MAGNET

    CERN Multimedia

    Benoit Curé

    2013-01-01

    Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...

  12. Versatile controllability of non-axisymmetric magnetic perturbations in KSTAR experiments

    Science.gov (United States)

    Han, Hyunsun; Jeon, Y. M.; in, Y.; Kim, J.; Yoon, S. W.; Hahn, S. H.; Ahn, H. S.; Woo, M. H.; Park, B. H.; Bak, J. G.; Kstar Team

    2015-11-01

    A newly upgraded IVCC (In-Vessel Control Coil) system equipped with four broadband power supplies, along with current connection patch panel, will be presented and discussed in terms of its capability on various KSTAR experiments. Until the last run-campaign, there were impressive experimental results on ELM(Edge Localized Mode) control experiments using the 3D magnetic field, but the non-axisymmetric field configuration could not be changed in a shot, let alone the limited number of accessible configurations. Introducing the new power supplies, such restrictions have been greatly reduced. Based on the preliminary commissioning results for 2015 KSTAR run-campaign, this new system has been confirmed to easily cope with various dynamic demands for toroidal and poloidal phases of 3D magnetic field in a shot. This enables us to diagnose the plasma response in more detail and to address the 3-D field impacts on the ELM behaviors better than ever.

  13. Ultrasound control of magnet growing rod distraction in early onset scoliosis.

    Science.gov (United States)

    Pérez Cervera, T; Lirola Criado, J F; Farrington Rueda, D M

    2016-01-01

    The growing rod technique is currently one of the most common procedures used in the management of early onset scoliosis. However, in order to preserve spine growth and control the deformity it requires frequent surgeries to distract the rods. Magnetically driven growing rods have recently been introduced with same treatment goal, but without the inconvenience of repeated surgical distractions. One of the limitations of this technical advance is an increase in radiation exposure due to the increase in distraction frequency compared to conventional growing rods. An improvement of the original technique is presented, proposing a solution to the inconvenience of multiple radiation exposure using ultrasound technology to control the distraction process of magnetically driven growing rods. Copyright © 2014 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

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

    Science.gov (United States)

    Singh, Simranjeet

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

  15. NUCLEAR-MAGNETIC MINI-RELAXOMETER FOR LIQUID AND VISCOUS MEDIA CONTROL

    Directory of Open Access Journals (Sweden)

    V. V. Davydov

    2015-01-01

    Full Text Available The paper deals with a new method for registration of nuclear magnetic resonance signal of small volume liquid and viscous media being studied (0.5 ml in a weak magnetic field (0.06 –0.08 T, and measuring of longitudinal T1 and transverse T2 relaxation constants. A new construction of NMR mini-relaxometer magnetic system is developed for registration of NMR signal. The nonuniformity of a magnetic field in a pole where registration coil is located is 0,410–3 sm–1 (the induction is В0 = 0.079 T. An electrical circuit of autodyne receiver (weak fluctuations generator has been developed with usage of low noise differential amplifier and NMR signal operating and control scheme (based on microcontroller STM32 for measuring of relaxation constants of liquid and viscous media in automatic operating mode. New technical decisions made it possible to improve relaxometer response time and dynamic range of measurements for relaxation constants T1 and T2 in comparison with small sized nuclear-magnetic spectrometer developed by the authors earlier (with accuracy characteristics conservation. The developed schemes for self-tuning of registration frequency, generating amplitude of magnetic field H1 in registration coil, and amplitude and frequency of modulating field provide measuring of T1 and T2 with error less than 0.5 % and signal to noise ratio about 1.2 in temperature range from 3 to 400 C. A new construction of mini-relaxometer reduced the weight of the device to 4 kg (with independent supply unit and increased transportability and operating convenience.

  16. Field oriented control of permanent magnet synchronous motors with time constant adaption

    International Nuclear Information System (INIS)

    Afsharnia, S.; Vahedi, A.

    2001-01-01

    In this paper, initially, we present a method for on-line identifying of Permanent Magnet Synchronous Machine electrical parameters, then these parameters will be used in the vector control structure of motors. Simulation results show the efficiency of this method to parameters identifying of machine even in the presence of saturation, variation of temperature and etc. Because of simplicity and being economic, this method can be used by electro motors constructors to identify motor parameters for different operating points

  17. Design of a Discrete Tracking Controller for a Magnetic Levitation System: A Nonlinear Rational Model Approach

    Directory of Open Access Journals (Sweden)

    Fernando Gómez-Salas

    2015-01-01

    Full Text Available This work proposes a discrete-time nonlinear rational approximate model for the unstable magnetic levitation system. Based on this model and as an application of the input-output linearization technique, a discrete-time tracking control design will be derived using the corresponding classical state space representation of the model. A simulation example illustrates the efficiency of the proposed methodology.

  18. Using magnetic levitation for non-destructive quality control of plastic parts.

    Science.gov (United States)

    Hennek, Jonathan W; Nemiroski, Alex; Subramaniam, Anand Bala; Bwambok, David K; Yang, Dian; Harburg, Daniel V; Tricard, Simon; Ellerbee, Audrey K; Whitesides, George M

    2015-03-04

    Magnetic levitation (MagLev) enables rapid and non-destructive quality control of plastic parts. The feasibility of MagLev as a method to: i) rapidly assess injection-molded plastic parts for defects during process optimization, ii) monitor the degradation of plastics after exposure to harsh environmental conditions, and iii) detect counterfeit polymers by density is demonstrated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Ferroelectric control of magnetization in BiFeO3/CoFe heterostructures.

    Science.gov (United States)

    Gajek, Martin; Martin, Lane; Heron, John; Seidel, Jan; Ramesh, Ramamoorthy

    2009-03-01

    The cross coupling between ferroic order parameters in multiferroics opens an alternative for the control of magnetism in magnetoelectric devices by purely electrical means. We first report on the exchange coupling between BiFeO3, an antiferromagnetic ferroelectric , and CoFe. We then show that the domain structure of the ferromagnet can be changed by poling the ferroelectric layer. Finally, we will discuss the implementation of our findings into possible device schemes.

  20. Magnet power supply control of the NSLS VUV and x-ray storage rings transfer lines

    International Nuclear Information System (INIS)

    Klein, J.D.; Ramamoorthy, S.; Singh, O.; Smith, J.D.

    1985-01-01

    The transfer lines for NSLS VUV and x-ray storage rings have been split. New power supplies have been incorporated with existing ones. The existing microprocessor system has been upgraded in order to control the additional functions. This system expands the input/output port of the microprocessor to an addressable serial/parallel link to each magnet power supply. The implementation of this system will be discussed