WorldWideScience

Sample records for circulation generated magnetic

  1. Ocean circulation generated magnetic signals

    DEFF Research Database (Denmark)

    Manoj, C.; Kuvshinov, A.; Maus, S.;

    2006-01-01

    Conducting ocean water, as it flows through the Earth's magnetic field, generates secondary electric and magnetic fields. An assessment of the ocean-generated magnetic fields and their detectability may be of importance for geomagnetism and oceanography. Motivated by the clear identification...... of ocean tidal signatures in the CHAMP magnetic field data we estimate the ocean magnetic signals of steady flow using a global 3-D EM numerical solution. The required velocity data are from the ECCO ocean circulation experiment and alternatively from the OCCAM model for higher resolution. We assume...... of the magnetic field, as compared to the ECCO simulation. Besides the expected signatures of the global circulation patterns, we find significant seasonal variability of ocean magnetic signals in the Indian and Western Pacific Oceans. Compared to seasonal variation, interannual variations produce weaker signals....

  2. Lightweight Magnetic Cooler With a Reversible Circulator

    Science.gov (United States)

    Chen, Weibo; McCormick, John

    2011-01-01

    A design of a highly efficient and lightweight space magnetic cooler has been developed that can continuously provide remote/distributed cooling at temperatures in the range of 2 K with a heat sink at about 15 K. The innovative design uses a cryogenic circulator that enables the cooler to operate at a high cycle frequency to achieve a large cooling capacity. The ability to provide remote/distributed cooling not only allows flexible integration with a payload and spacecraft, but also reduces the mass of the magnetic shields needed. The active magnetic regenerative refrigerator (AMRR) system is shown in the figure. This design mainly consists of two identical magnetic regenerators surrounded by their superconducting magnets and a reversible circulator. Each regenerator also has a heat exchanger at its warm end to reject the magnetization heat to the heat sink, and the two regenerators share a cold-end heat exchanger to absorb heat from a cooling target. The circulator controls the flow direction, which cycles in concert with the magnetic fields, to facilitate heat transfer. Helium enters the hot end of the demagnetized column, is cooled by the refrigerant, and passes into the cold-end heat exchanger to absorb heat. The helium then enters the cold end of the magnetized column, absorbing heat from the refrigerant, and enters the hot-end heat exchanger to reject the magnetization heat. The efficient heat transfer in the AMRR allows the system to operate at a relatively short cycle period to achieve a large cooling power. The key mechanical components in the magnetic cooler are the reversible circulator and the magnetic regenerators. The circulator uses non-contacting, self-acting gas bearings and clearance seals to achieve long life and vibration- free operation. There are no valves or mechanical wear in this circulator, so the reliability is predicted to be very high. The magnetic regenerator employs a structured bed configuration. The core consists of a stack of thin

  3. Design and development of permanent magnet based composite magnet system for biasing of high power ferrite circulator

    International Nuclear Information System (INIS)

    The high power ferrite circulators (505 MHz and 650 MHz) which are being indigenously develop for RF system of Indus-2 and Proton Linac. A composite magnet system is required to provide stable and tunable magnetic field for biasing of high power ferrite circulator to operate in below/above resonance mode. The biasing static magnetic field is an important parameter for optimization of operating state of high power ferrite circulator. The permanent magnet based H-type composite magnet system with variable gap has been designed using Opera 3D to generate tunable magnetic field of 0.22 T ± 0.025 T in the pole gap of 35 mm over 182 mm pole diameter. This magnet system is developed using the combination of strontium ferrite permanent magnet disks (200 mm dia x 25 mm thick) and excitation coils (pole coils). The required magnetic field in the pole gap produced by permanent magnets and the fine tuning of the magnetic field is achieved by varying the DC current through excitation coils. Magnet yoke plates and pole pieces fabricated from low carbon steel whereas pole coils made from enameled copper wire. Magnetic field measurements of this magnet system has been carried out using Hall probe based three axis magnet measurement bench. The operating points of permanent magnet have been calculated from the measured magnetic field results. A detailed 3D magnetic field simulation, magnet development and magnetic field measurement results of permanent magnet based composite magnet system wilI be discussed in this paper. (author)

  4. Dynamic switching of the spin circulation in tapered magnetic nanodisks

    Science.gov (United States)

    Uhlíř, V.; Urbánek, M.; Hladík, L.; Spousta, J.; Im, M.-Y.; Fischer, P.; Eibagi, N.; Kan, J. J.; Fullerton, E. E.; Šikola, T.

    2013-05-01

    Magnetic vortices are characterized by the sense of in-plane magnetization circulation and by the polarity of the vortex core. With each having two possible states, there are four possible stable magnetization configurations that can be utilized for a multibit memory cell. Dynamic control of vortex core polarity has been demonstrated using both alternating and pulsed magnetic fields and currents. Here, we show controlled dynamic switching of spin circulation in vortices using nanosecond field pulses by imaging the process with full-field soft X-ray transmission microscopy. The dynamic reversal process is controlled by far-from-equilibrium gyrotropic precession of the vortex core, and the reversal is achieved at significantly reduced field amplitudes when compared with static switching. We further show that both the field pulse amplitude and duration required for efficient circulation reversal can be controlled by appropriate selection of the disk geometry.

  5. Distributed generation induction and permanent magnet generators

    CERN Document Server

    Lai, L

    2007-01-01

    Distributed power generation is a technology that could help to enable efficient, renewable energy production both in the developed and developing world. It includes all use of small electric power generators, whether located on the utility system, at the site of a utility customer, or at an isolated site not connected to the power grid. Induction generators (IGs) are the cheapest and most commonly used technology, compatible with renewable energy resources. Permanent magnet (PM) generators have traditionally been avoided due to high fabrication costs; however, compared with IGs they are more reliable and productive. Distributed Generation thoroughly examines the principles, possibilities and limitations of creating energy with both IGs and PM generators. It takes an electrical engineering approach in the analysis and testing of these generators, and includes diagrams and extensive case study examples o better demonstrate how the integration of energy sources can be accomplished. The book also provides the ...

  6. [Magnetic field numerical calculation and analysis for magnetic coupling of centrifugal blood pump for extracorporeal circulation].

    Science.gov (United States)

    Hu, Zhaoyan; Lu, Lijun; Zhang, Tianyi; Chen, Zhenglong; Zhang, Tao

    2013-12-01

    This paper mainly studies the driving system of centrifugal blood pump for extracorporeal circulation, with the core being disc magnetic coupling. Structure parameters of disc magnetic coupling are related to the ability of transferring magnetic torque. Therefore, it is necessary to carry out disc magnetic coupling permanent magnet pole number (n), air gap length (L(g)), permanent magnet thickness (L(m)), permanent magnet body inside diameter (R(i)) and outside diameter (R(o)), etc. thoroughly. This paper adopts the three-dimensional static magnetic field edge element method of Ansys for numerical calculation, and analyses the relations of magnetic coupling each parameter to transmission magnetic torque. It provides a good theory basis and calculation method for further optimization of the disc magnetic coupling.

  7. Magnetic Field Generation in Stars

    CERN Document Server

    Ferrario, Lilia; Zrake, Jonathan

    2015-01-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a ...

  8. Primordial Generation of Magnetic Fields

    CERN Document Server

    Pandey, Arun Kumar

    2015-01-01

    We reexamine generation of the primordial magnetic fields, at temperature $T>80$TeV, by applying a consistent kinetic theory framework which is suitably modified to take the quantum anomaly into account. The modified kinetic equation can reproduce the known quantum field theoretic results upto the leading orders. We show that our results qualitatively matches with the earlier results obtained using heuristic arguments. The modified kinetic theory can give the instabilities responsible for generation of the magnetic field due to chiral imbalance in two distinct regimes: a) when the collisions play a dominant role and b) when the primordial plasma can be regarded as collisionless. We argue that the instability developing in the collisional regime can dominate over the instability in the collisionless regime.

  9. Forced circulation type steam generator simulation code: HT4

    International Nuclear Information System (INIS)

    The purpose of this code is a understanding of dynamic characteristics of the steam generator, which is a component of High-temperature Heat Transfer Components Test Unit. This unit is a number 4th test section of Helium Engineering Demonstration Loop (HENDEL). Features of this report are as follows, modeling of the steam generator, a basic relationship for the continuity equation, numerical analysis techniques of a non-linear simultaneous equation and computer graphics output techniques. Forced circulation type steam generator with strait tubes and horizontal cut baffles, applied in this code, have be designed at the Over All System Design of the VHTRex. The code is for use with JAERI's digital computer FACOM M200. About 1.5 sec required for each time step reiteration, then about 40 sec cpu time required for a standard problem. (author)

  10. PERMANENT-MAGNET INDUCTION GENERATORS: AN OVERVIEW

    Directory of Open Access Journals (Sweden)

    K. S. S. RAMAKRISHNAN

    2011-06-01

    Full Text Available The advantage of using a permanent-magnet induction generator (PMIG instead of a conventional induction generator is its ability to suppress inrush current during system linking when synchronous input is performed. Induction machines excited with permanent-magnet (PM are called permanent-magnet induction generators. This paper presents an exhaustive survey of the literature discussing the classification of permanent-magnet machines, process of permanent-magnet excitation and voltage build-up, modelling, steady-state and performance analysis of the permanent-magnet induction generators.

  11. Tiny magnetic wireless pump: Fabrication of magnetic impeller and magnetic wireless manipulation for blood circulation in legs

    Science.gov (United States)

    Kim, Sung Hoon; Yu, Chang Ho; Ishiyama, K.

    2015-05-01

    This paper introduces a wireless pump that uses magnetic wireless manipulation to pump blood in the legs. A compact size and sufficient hydrodynamic performance were the most important requirements. Because the bonded magnet technique allows for a complex shape and various magnetization orientations, we fabricated a magnetic impeller from magnetic SmFeN powder. The impellers demonstrated a magnetic moment of 2772.64 emu and coercive force of 7.55 kOe. Using the impeller, we developed a tiny blood pump with a diameter of 22 mm and height of 6 mm. The pump allows for a maximum flow rate of 2.7 l/min and maximum pump head of approximately 170 mm Hg at a rotating speed of 6000 rpm. This level of hydrodynamic performance is sufficient to circulate blood in the legs. In this paper, we present the magnetic properties of the magnetic impeller and the hydrodynamic performance with wireless operation.

  12. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  13. A linear magnetic motor and generator

    Science.gov (United States)

    Studer, P. A.

    1980-01-01

    In linear magnetic motor and generator suitable for remote and hostile environments, magnetic forces drive reciprocating shaft along its axis. Actuator shaft is located in center of cylindrical body and may be supported by either contacting or noncontacting bearings. When device operates as bidirectional motor, drive coil selectively adds and subtracts magnetic flux to and from flux paths, producing forces that drive actuator along axis. When actuator is driven by external reciprocating engine, device becomes ac generator.

  14. Ensemble simulations of the magnetic field induced by global ocean circulation: Estimating the uncertainty

    Science.gov (United States)

    Irrgang, Christopher; Saynisch, Jan; Thomas, Maik

    2016-03-01

    The modeling of the ocean global circulation induced magnetic field is affected by various uncertainties that originate from errors in the input data and from the model itself. The amount of aggregated uncertainties and their effect on the modeling of electromagnetic induction in the ocean is unknown. For many applications, however, the knowledge of uncertainties in the modeling is essential. To investigate the uncertainty in the modeling of motional induction at the sea surface, simulation experiments are performed on the basis of different error scenarios and error covariance matrices. For these error scenarios, ensembles of an ocean general circulation model and an electromagnetic induction model are generated. This ensemble-based approach allows to estimate both the spatial distribution and temporal variation of the uncertainty in the ocean-induced magnetic field. The largest uncertainty in the ocean-induced magnetic field occurs in the area of the Antarctic Circumpolar Current. Local maxima reach values of up to 0.7 nT. The estimated global annual mean uncertainty in the ocean-induced magnetic field ranges from 0.1 to 0.4 nT. The relative amount of uncertainty reaches up to 30% of the signal strength with largest values in regions in the northern hemisphere. The major source of uncertainty is found to be introduced by wind stress from the atmospheric forcing of the ocean model. In addition, the temporal evolution of the uncertainty in the induced magnetic field shows distinct seasonal variations. Specific regions are identified which are robust with respect to the introduced uncertainties.

  15. Effects of Magnetic Flux Circulation on Radiation Belt and Ring Current Populations

    Science.gov (United States)

    Mitchell, E. J.; Fok, M. H.

    2011-12-01

    The orientation of the interplanetary magnetic field (IMF) determines the location of the dayside merging line and the magnetic flux circulation patterns. Magnetic flux circulation determines the amount of energy which enters the magnetosphere and ionosphere. We use the Lyon-Fedder-Mobarry (LFM) global Magneto-Hydro-Dynamic (MHD) code to simulate both idealized and real solar wind cases. We use several satellites to validate the LFM simulation results for the real solar wind case studies. With these cases, we examine the magnetic flux circulation under differing IMF orientations. We also use the Comprehensive Ring Current Model (CRCM) and Radiation Belt Environment (RBE) model to examine the inner magnetospheric response to the orientation of the IMF. We will present the different magnetic flux circulation patterns and the resulting effects on the radiation belt and ring current population.

  16. Linear magnetic motor/generator. [to generate electric energy using magnetic flux for spacecraft power supply

    Science.gov (United States)

    Studer, P. A. (Inventor)

    1982-01-01

    A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.

  17. Magnet Free Generators - 3rd Generation Wind Turbine Generators

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Mijatovic, Nenad; Henriksen, Matthew Lee

    2013-01-01

    This paper presents an introduction to superconducting wind turbine generators, which are often referred to as 3rd generation wind turbine generators. Advantages and challenges of superconducting generators are presented with particular focus on possible weight and efficiency improvements. A...

  18. Generation of nuclear magnetic resonance images

    International Nuclear Information System (INIS)

    Two generation techniques of nuclear magnetic resonance images, the retro-projection and the direct transformation method are studied these techniques are based on the acquisition of NMR signals which phases and frequency components are codified in space by application of magnetic field gradients. The construction of magnet coils is discussed, in particular a suitable magnet geometry with polar pieces and air gap. The obtention of image contrast by T1 and T2 relaxation times reconstructed from generated signals using sequences such as spin-echo, inversion-recovery and stimulated echo, is discussed. The mathematical formalism of matrix solution for Bloch equations is also presented. (M.C.K.)

  19. Coolant rate distribution in horizontal steam generator under natural circulation

    Energy Technology Data Exchange (ETDEWEB)

    Blagovechtchenski, A.; Leontieva, V.; Mitrioukhin, A. [St. Petersburg State Technical Univ. (Russian Federation)

    1997-12-31

    In the presentation the major factors determining the conditions of NCC (Natural Coolant Circulation) in the primary circuit and in particular conditions of coolant rate distribution on the horizontal tubes of PGV-1000 in NPP with VVER-1000 under NCC are considered. 5 refs.

  20. Magnetic flux generator for balanced membrane loudspeaker

    DEFF Research Database (Denmark)

    Rehder, Jörg; Rombach, Pirmin; Hansen, Ole

    2002-01-01

    This paper reports the development of a magnetic flux generator with an application in a hearing aid loudspeaker produced in microsystem technology (MST). The technology plans for two different designs for the magnetic flux generator utilizing a softmagnetic substrate or electroplated NiCoFe as c......CoFe as core material are presented and the production and characterization of four different mono- and double-layer planar coil types are reported....

  1. Sunquake Generation by Coronal Magnetic Restructuring

    Science.gov (United States)

    Russell, A. J. B.; Mooney, M.; Leake, J. E.; Hudson, H. S.

    2015-12-01

    Solar flares and coronal mass ejections are powered by major restructurings of the coronal magnetic field, which appear to strongly perturb the magnetic field in the photosphere as well. Could the associated Lorentz forces generate sunquakes, as suggested by Hudson et al. 2008? Here, we present the first MHD simulations of sunquake generation by magnetic field perturbations, and explore the details of this mechanism. The downgoing magnetic field change is modelled as an Alfven wave, which propagates into the lower atmosphere. When it reaches the vicinity of the beta=1 layer (where the Alfven and sound speeds are equal), non-linear coupling excites a downgoing acoustic wave, which we interpret as a sunquake. The amplitude of the acoustic wave increases nonlinearly with the amplitude of the magnetic perturbation, reaching a limit where around 35% of the injected Poynting flux is transferred to the seismic wave - enough energy to match sunquake observations.

  2. Miniaturized Air-Driven Planar Magnetic Generators

    Directory of Open Access Journals (Sweden)

    Jingjing Zhao

    2015-10-01

    Full Text Available This paper presents the design, analysis, fabrication and testing of two miniaturized air-driven planar magnetic generators. In order to reduce the magnetic resistance torque, Generator 1 establishes a static magnetic field by consisting a multilayer planar coil as the stator and two multi-pole permanent-magnet (PM rotors on both sides of the coil. To further decrease the starting torque and save more space, Generator 2 adopts the multilayer planar coil as the rotor and the multi-pole PMs as the stator, eliminating the casing without compromising the magnetic structure or output performance. The prototypes were tested gathering energy from wind which can work at a low wind speed of 1~2 m/s. Prototype of Generator 1 is with a volume of 2.61 cm3 and its normalized voltage reaches 485 mV/krpm. Prototype of Generator 2 has a volume of 0.92 cm3 and a normalized voltage as high as 538 mV/krpm. Additionally, output voltage can be estimated at better than 96% accuracy by the theoretical model developed in this paper. The two micro generators are capable of producing substantial electricity with little volume to serve as compact power conversion devices.

  3. The solar surface circulation velocity, Joy's Law and the changing solar surface magnetic field

    Science.gov (United States)

    Ulrich, R. K.; Li, J.

    2012-12-01

    The dissipation and regeneration of magnetic fields during the approximately 11-year cycle of activity is only partially understood. The 38-year record of digital observations recorded and reduced as part of the Mt. Wilson Observatory (MWO) program of synoptic observations allows a new perspective on these processes. Two central ingredients in the magnetic field evolution are 1) the winding up of field lines due to differential rotation which generates a toroidal field from a poloidal field (called the omega effect); and 2) the generation of a poloidal field from a toroidal field due to the twisting of the field lines in a rising flux-tube due presumably to the Coriolis force (called the alpha effect). The twisting causes the trailing field of a sunspot group to be closer to the pole so that as the group ages and falls apart, meridional circulation brings both trailing and leading fields toward the pole but the poleward displacement of the trailing field causes it to become dominant and reverse the polarity of the polar fields. A recent analysis of the MWO magnetograms has allowed an objective determination of the sunspot group twist as described by Joy's Law. This magnetic field twist data is compared to episodes of polar field reversal that can be identified on the concatenated synoptic charts known as supersynoptic charts. This comparison permits a quantative characterization of the role of the alpha effect in the solar cycle. The synoptic program at MWO has beneted from support by NASA, NSF and ONR over many years. The long record of magnetic eld data would not have been possible without support from these agencies. Continuing observations depend on current support which comes from NSF through grant AGS-0958779, and NASA through grants NNX09AB12G and HMI subcontract 16165880.

  4. Analysis on Non-Uniform Flow in Steam Generator During Steady State Natural Circulation Cooling

    OpenAIRE

    Susyadi; T. Yonomoto

    2007-01-01

    Investigation on non uniform flow behavior among U-tube in steam generator during natural circulation cooling has been conducted using RELAP5. The investigation is performed by modeling the steam generator into multi channel models, i.e. 9-tubes model. Two situations are implemented, high pressure and low pressure cases. Using partial model, the calculation simulates situation similar to the natural circulation test performed in LSTF. The imposed boundary conditions are flow rate, quality, pr...

  5. Sunquake Generation by Coronal Magnetic Restructuring

    CERN Document Server

    Russell, Alexander J B; Leake, James E; Hudson, Hugh S

    2016-01-01

    Sunquakes are the surface signatures of acoustic waves in the Sun's interior that are produced by some but not all flares and coronal mass ejections (CMEs). This letter explores a mechanism for sunquake generation by the magnetic field changes that occur during flares and CMEs, using MHD simulations with a semiempirical FAL-C atmosphere to demonstrate the generation of acoustic waves in the interior in response to changing magnetic tilt in the corona. We find that Alfv\\'en-sound resonance combined with the ponderomotive force produces acoustic waves in the interior with sufficient energy to match sunquake observations when the magnetic field angle changes by the order of 10 degrees in a region where the coronal field strength is a few hundred gauss or more. The most energetic sunquakes are produced when the coronal field is strong, while the variation of magnetic field strength with height and the timescale of the tilt change are of secondary importance.

  6. Application of Magnetic Force Generator in Cementation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The paper introduces a new behavior of the heat treatment technique that is cementation with magnetic force generator (MFHS). The result shows that due to the strong magnetic field action of MFHS on seep means, the energy and activity of active atom are increased, which accelerates interface activating and atoms diffusing, forms action of speed-up seeping. This technique features are Iow in energy consuming, and high in seeping efficiency.

  7. Magnetic Field Analysis of a Permanent-Magnet Induction Generator

    Science.gov (United States)

    Tsuda, Toshihiro; Fukami, Tadashi; Kanamaru, Yasunori; Miyamoto, Toshio

    The permanent-magnet induction generator (PMIG) is a new type of induction machine that has a permanent-magnet rotor inside a squirrel-cage rotor. In this paper, a new technique for the magnetic field analysis of the PMIG is proposed. The proposed technique is based on the PMIG's equivalent circuit and the two-dimensional finite-element analysis (2D-FEA). To execute the 2D-FEA, the phasors of primary and secondary currents are calculated from the equivalent circuit, and the input data for the 2D-FEA is found by converting these phasors into the space vectors. As a result, the internal magnetic fields of the PMIG can be easily analyzed without complicated calculations.

  8. Induction MHD generator using alternating magnetic field

    International Nuclear Information System (INIS)

    The induction MHD generator using an alternating magnetic field is proposed. The characteristics of the machine are analyzed theoretically and also compared with those of the induction MHD generator using a traveling magnetic field. Following conclusions are obtained for the fundamental characteristics of the present machine: (1) This type of the machine is possibly operated not only as the generator but also as the pump or as the damper. (2) The optimum condition for the maximum generator efficiency exists among the relations of the frequency, the fluid velocity and the inner core radius because of the eddy current loss due to an alternating magnetic field. (3) The power ratio of the reactive power of the machine to the gross output power can be reduced to a much smaller value than that of the traveling wave MHD generator. Therefore, even in the case of the working fluid with a relative low electrical conductivity such as two-phase liquid metal flow with high void fraction, the acceptable power ratio can be expected. (4) For the working fluid with higher electrical conductivity the skin effect is also able to be reduced to the acceptable level in the present machine, while it is a serious problem in the traveling wave MHD generator. (author)

  9. Engineering, Manufacture and Preliminary Testing of the ITER Toroidal Field (TF) Magnet Helium Cold Circulator

    Science.gov (United States)

    Rista, P. E. C.; Shull, J.; Sargent, S.

    2015-12-01

    The ITER cryodistribution system provides the supercritical Helium (SHe) forced flow cooling to the magnet system using cold circulators. The cold circulators are located in each of five separate auxiliary cold boxes planned for use in the facility. Barber-Nichols Inc. has been awarded a contract from ITER-India for engineering, manufacture and testing of the Toroidal Field (TF) Magnet Helium Cold Circulator. The cold circulator will be extensively tested at Barber-Nichols’ facility prior to delivery for qualification testing at the Japan Atomic Energy Agency's (JAEA) test facility at Naka, Japan. The TF Cold Circulator integrates features and technical requirements which Barber-Nichols has utilized when supplying helium cold circulators worldwide over a period of 35 years. Features include a vacuum-jacketed hermetically sealed design with a very low helium leak rate, a heat shield for use with both nitrogen & helium cold sources, a broad operating range with a guaranteed isentropic efficiency over 70%, and impeller design features for high efficiency. The cold circulator will be designed to meet MTBM of 17,500 hours and MTBF of 36,000 hours. Vibration and speed monitoring are integrated into a compact package on the rotating assembly with operation and health monitoring in a multi-drop PROFIBUS communication environment using an electrical cabinet with critical features and full local and network PLC interface and control. For the testing in Japan and eventual installation in Europe, the cold circulator must be certified to the Japanese High Pressure Gas Safety Act (JHPGSA) and CE marked in compliance with the European Pressure Equipment Directive (PED) including Essential Safety Requirements (ESR). The test methodology utilized at Barber-Nichols’ facility and the resulting test data, validating the high efficiency of the TF Cold Circulator across a broad operating range, are important features of this paper.

  10. Analysis of CHAMP scalar magnetic data to identify ocean circulation signals

    DEFF Research Database (Denmark)

    Manoj, C.; Maus, S.; Kuvshinov, Alexei;

    Unlike tidal ocean signals, the magnetic signal of ocean circulation has not yet been identified in satellite magnetic data. In particular, the steady signal of mean ocean flow is indistinguishable from time invariant crustal signals. One option, therefore, is to predict the seasonal and annual...... signals at satellite altitude. We predict annual variation amplitudes in the scalar anomaly of the order of 0.3 nT. We compare these predictions with the particularly quiet CHAMP night-time scalar data, subtracting core, mantle, crustal, ocean tidal, and magnetospheric contributions to the field...... variations in the ocean flow signal from ocean circulation models and compare them with the corresponding variations in satellite magnetic residuals. We used the 11 year ECCO-1 simulation data to derive the ocean transport. A 3D EM induction code in its low frequency limit, was used to simulate the magnetic...

  11. Synchronous Generator Model with Nonlinear Magnetic Circuit

    Directory of Open Access Journals (Sweden)

    Dariusz Spałek

    2013-12-01

    Full Text Available A synchronous generator with voltage controller is a system whose work describes the ordinary differential equation set for the equivalent circuits. For the nonlinear magnetic circuit of a synchronous generator (stator and rotor saturation the differential set is nonlinear. The solution of such a problem needs to develop the appropriate model for numerical simulations of the generator. First of all, the generator model type e.g. (1,1,(2,2, (3,3 or other should be chosen. Furthermore, the equivalent parameters for the model of synchronous generator should be chosen. The nonlinearity of magnetic circuit leads to changes of some equivalent parameters and additional numerical computations. There is a numerical program developed in C++ for simulations of transients in order to investigate their sensitivity to generator nonlinearity (saturation effect and equivalent parameters values. The described program (available at www.elektr.polsl.pl/dspalek/ enables to decide whether the nonlinearity for d/q axis should be taken into account and which equivalent parameter are of high importance. Subsequently, the presented model leads to conclusions on which parameters should influence significantly synchronous generator work in a power system.

  12. Magnetic-resonance velocity mapping of the central circulation

    DEFF Research Database (Denmark)

    Søndergaard, Lise

    1994-01-01

    In magnetic-resonance (MR) velocity mapping there exists a linear relationship between the velocity and signal in each element of a tomographic image. The technique can be used for quantitative measurements of linear velocities (m s-1) and flow rates (1 min-1). By using cinematographic images...... the flow profile during the cardiac cycle can be determined. This allows quantification of forward flow, regurgitant volume and regurgitant fraction in cases of heart-valve insufficiency. In valvular stenosis the transvalvular pressure gradient and valve area can be determined. Magnetic-resonance velocity...... mapping may also provide information about diastolic function of left ventricular function. Together with other MR imaging techniques, velocity mapping gives an accurate assessment of the severity of aortic dissection. Recent studies indicate that MR velocity mapping provides quantification of renal blood...

  13. The Fontan circulation and the liver : A magnetic resonance diffusion-weighted imaging study

    NARCIS (Netherlands)

    Wolff, Djoeke; van Melle, Joost P.; Dijkstra, Hildebrand; Bartelds, Beatrijs; Willems, Tineke P.; Hillege, Hans; van den Berg, Aad P.; Ebels, Tjark; Sijens, Paul E.; Berger, Rolf M. F.

    2016-01-01

    Background: Patients with a Fontan circulation tend to develop liver fibrosis, liver cirrhosis and even hepatocellular carcinoma. The aim of this study is to use the magnetic resonance technique diffusing-weighted imaging (DWI) for detecting liver fibrosis/cirrhosis in Fontan patients and to establi

  14. Magnetic field generation by intermittent convection

    CERN Document Server

    Chertovskih, R; Chimanski, E V

    2016-01-01

    Magnetic field generation by convective flows in transition to weak turbulence is studied numerically. By fixing the Prandtl number at P=0.3 and varying the Rayleigh number (Ra) as a control parameter in three-dimensional Rayleigh-Benard convection of an electrically conducting fluid, a recently reported route to hyperchaos involving quasiperiodic regimes, crises and chaotic intermittent attractors is followed, and the critical magnetic Prandtl number ($P_m^c$) for dynamo action is determined as a function of Ra. A mechanism for the onset of on-off intermittency in the magnetic energy is described, the most beneficial convective regimes for dynamo action are identified, and how intermittency affects the dependence of $P_m^c$ on Ra is discussed.

  15. SEED BANKS FOR MAGNETIC FLUX COMPRESSION GENERATORS

    Energy Technology Data Exchange (ETDEWEB)

    Fulkerson, E S

    2008-05-14

    In recent years the Lawrence Livermore National Laboratory (LLNL) has been conducting experiments that require pulsed high currents to be delivered into inductive loads. The loads fall into two categories (1) pulsed high field magnets and (2) the input stage of Magnetic Flux Compression Generators (MFCG). Three capacitor banks of increasing energy storage and controls sophistication have been designed and constructed to drive these loads. One bank was developed for the magnet driving application (20kV {approx} 30kJ maximum stored energy.) Two banks where constructed as MFCG seed banks (12kV {approx} 43kJ and 26kV {approx} 450kJ). This paper will describe the design of each bank including switching, controls, circuit protection and safety.

  16. Vortex flow generated by a magnetic stirrer

    OpenAIRE

    Halasz, G; Gyure, B.; Janosi, I. M.; Szabo, K. G.; Tel, T.

    2007-01-01

    We investigate the flow generated by a magnetic stirrer in cylindrical containers by optical observations, PIV measurements and particle and dye tracking methods. The tangential flow is that of an ideal vortex outside of a core, but inside downwelling occur with a strong jet in the very middle. In the core region dye patterns remain visible over minutes indicating a pure stirring and mixing property in this region. The results of quantitative measurements can be described by simple formulas i...

  17. Harmonic generation in magnetized quantum plasma

    Science.gov (United States)

    Kumar, Punit; Singh, Shiv; Singh, Abhisek Kumar

    2016-05-01

    A study of second harmonic generation by propagation of a linearly polarized electromagnetic wave through homogeneous high density quantum plasma in the presence of transverse magnetic field. The nonlinear current density and dispersion relations for the fundamental and second harmonic frequencies have been obtained using the recently developed quantum hydrodynamic (QHD) model. The effect of quantum Bohm potential, Fermi pressure and the electron spin have been taken into account. The second harmonic is found to be less dispersed than the first.

  18. Generation and manipulation of magnetic droplets

    OpenAIRE

    Alhetlani, E; A. Iles; Pamme, N; 2nd Micro and Nano Flows Conference (MNF2009)

    2009-01-01

    This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications. The continuous flow generation and downstream manipulation of magnetic dr...

  19. Study of the circulation theory of the cooling system in vertical evaporative cooling generator

    Institute of Scientific and Technical Information of China (English)

    YU; Shunzhou; CAI; Jing; GUO; Chaohong

    2006-01-01

    The article briefly states the current development of evaporative cooling generator and its advantages comparing with generators of traditional cooling. Vertical evaporative cooling generator, which adopts Close-Loop-Self-Cycle with no-pump and free convection boil in the hollow stator bar, is one of the great developments in generator design. This article emphasizes the importance of cooling system in generator; expatiates the circulation theory in two aspects, energy and flow; and analyzes the essential reason,motivity and stability of Close-Loop-Self-Cycle. The article points out that the motivity of the circulation is the heat absorbed by coolant. After absorbing heat the coolant will have the ability of doing work because of the phase change. In another words, it is the buoyancy causing by density difference leads to the Close-Loop-Self-Cycle. This conclusion is validated by experimental data.

  20. Application of PDCA circulation in quality control for production of steam generator pipe

    International Nuclear Information System (INIS)

    PDCA Circulation (Plan, Do, Check, Action) is applied in quality-control management during the welding process of Titanium alloy steam generator pipe. The weld defects is controlled effectively and the ratio of certified weld rose steadily, which achieve its target (90%). Experiments and engineering application show that, if the process-control could be carried out according to the PDCA circulation, activity which affect quality could be ensured to be controlled effectively without being omitted, and finally, steadily and dependable manufacture techniques could be formed so that the quality of products can be improved perpetually. (authors)

  1. Vortex flow generated by a magnetic stirrer

    CERN Document Server

    Halász, G; Jánosi, I M; Szabó, K G; Tél, T

    2007-01-01

    We investigate the flow generated by a magnetic stirrer in cylindrical containers by optical observations, PIV measurements and particle and dye tracking methods. The tangential flow is that of an ideal vortex outside of a core, but inside downwelling occur with a strong jet in the very middle. In the core region dye patterns remain visible over minutes indicating a pure stirring and mixing property in this region. The results of quantitative measurements can be described by simple formulas in the investigated region of the stirring bar's rotation frequency. The tangential flow turns out to be dynamically similar to that of big atmospheric vortices like dust devils and tornadoes.

  2. Vortex flow generated by a magnetic stirrer

    Science.gov (United States)

    Halász, Gábor; Gyüre, Balázs; Jánosi, Imre M.; Szabó, K. Gábor; Tél, Tamás

    2007-12-01

    We investigate the flow generated by a magnetic stirrer in cylindrical containers by optical observations, particle image velocimetry measurements, and particle and dye tracking methods. The tangential flow is that of an ideal vortex outside a core, but inside downwelling occurs with a strong jet in the very middle. In the core region dye patterns remain visible over minutes indicating inefficient mixing in this region. The results of quantitative measurements can be described by simple relations that depend on the stirring bar's rotation frequency. The tangential flow is similar to that of large atmospheric vortices such as dust devils and tornadoes.

  3. Magnetic trapping with simultaneous photoacoustic detection of molecularly targeted rare circulating tumor cells

    Science.gov (United States)

    Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan M.; Hu, Xiaoge; Gao, Xiaohu; O'Donnell, Matthew

    2013-03-01

    Photoacoustic (PA) imaging has been widely used in molecular imaging to detect diseased cells by targeting them with nanoparticle-based contrast agents. However, the sensitivity and specificity are easily degraded because contrast agent signals can be masked by the background. Magnetomotive photoacoustic imaging uses a new type of multifunctional composite particle combining an optically absorptive gold nanorod core and magnetic nanospheres, which can potentially accumulate and concentrate targeted cells while simultaneously enhancing their specific contrast compared to background signals. In this study, HeLa cells molecularly targeted using nanocomposites with folic acid mimicking targeted rare circulating tumor cells (CTCs) were circulated at a 6 ml/min flow rate for trapping and imaging studies. Preliminary results show that the cells accumulate rapidly in the presence of an externally applied magnetic field produced by a dual magnet system. The sensitivity of the current system can reach up to 1 cell/ml in clear water. By manipulating the trapped cells magnetically, the specificity of detecting cells in highly absorptive ink solution can be enhanced with 16.98 dB background suppression by applying motion filtering on PA signals to remove unwanted background signals insensitive to the magnetic field. The results appear promising for future preclinical studies on a small animal model and ultimate clinical detection of rare CTCs in the vasculature.

  4. High Magnetic Field Generator of Sub-Microsecond Duration

    Directory of Open Access Journals (Sweden)

    Audrius Grainys

    2012-04-01

    Full Text Available The article describes the possibility of generating a micro and sub-microsecond magnetic impulse reaching 1–10 T, investigates various configurations of microcoils and discusses the principal circuit of a magnetic field impulse generator of microsecond duration. The transient processes of current, temperature and magnetic field are calculated applying the finite element method.Article in Lithuanian

  5. A study of natural circulation in the evaporator of a horizontal-tube heat recovery steam generator

    Science.gov (United States)

    Roslyakov, P. V.; Pleshanov, K. A.; Sterkhov, K. V.

    2014-07-01

    Results obtained from investigations of stable natural circulation in an intricate circulation circuit with a horizontal layout of the tubes of evaporating surface having a negative useful head are presented. The possibility of making a shift from using multiple forced circulation organized by means of a circulation pump to natural circulation in vertical heat recovery steam generator is estimated. Criteria for characterizing the performance reliability and efficiency of a horizontal evaporator with negative useful head are proposed. The influence of various design solutions on circulation robustness is considered. With due regard of the optimal parameters, the most efficient and least costly methods are proposed for achieving more stable circulation in a vertical heat recovery steam generator when a shift is made from multiple forced to natural circulation. A procedure for calculating the circulation parameters and an algorithm for checking evaporator performance reliability are developed, and recommendations for the design of heat recovery steam generator, nonheated parts of natural circulation circuit, and evaporating surface are suggested.

  6. Effective hydrogen generation and resource circulation based on sulfur cycle system

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Hideyuki; Mabuchi, Takashi; Hayashi, Tsugumi; Yokoyama, Shun; Tohji, Kazuyuki [Graduate School of Environmental Studies, Tohoku University 6-6-20, Aramaki, Aoba-ku, Sendai, 980-8579 (Japan)

    2013-12-10

    For the effective hydrogen generation from H{sub 2}S, it should be compatible that the increscent of the photocatalytic (or electrochemical) activities and the development of effective utilization method of by-products (poly sulfide ion). In this study, “system integration” to construct the sulfur cycle system, which is compatible with the increscent of the hydrogen and or electron energy generation ratio and resource circulation, is investigated. Photocatalytic hydrogen generation rate can be enhanced by using stratified photocatalysts. Photo excited electron can be transpired to electrode to convert the electron energy to hydrogen energy. Poly sulfide ion as the by-products can be transferred into elemental sulfur and/or industrial materials such as rubber. Moreover, elemental sulfur can be transferred into H{sub 2}S which is the original materials for hydrogen generation. By using this “system integration”, the sulfur cycle system for the new energy generation can be constructed.

  7. The role of atmospheric radiation in the generation and maintenance of circulations of different scales

    International Nuclear Information System (INIS)

    It is well known that the radiation budget of the atmosphere is an important component of the earth's climate system. On shorter time scales, radiative transfer affects the evolution of atmospheric circulation, principally through interaction with cloud and storm systems, and destabilizes the atmosphere continuously. This destabilization is important for subsequent development of clouds and storm systems. The clouds and storm systems feed back to the radiation budget, as clouds significantly alter both shortwave and longwave radiative transfer. It is important to understand the role that radiative transfer plays in the evolution of these circulation systems to accurately quantify the radiation budget. The results presented here are from modeling studies designed to isolate the effect of radiative transfer on the generation of circulation systems of different spatial and temporal scales. Two different numerical weather prediction models were used and will be described briefly in the next section. Following that, the radiative transfer model that was used with both circulation models will be described. Finally, results from the modeling studies will be presented, and conclusions and future research efforts will be discussed

  8. Generation of Density Perturbations by Primordial Magnetic Fields

    OpenAIRE

    Kim, Eun-Jin; Olinto, Angela; Rosner, Robert

    1994-01-01

    We study the generation and evolution of density perturbations and peculiar velocities due to primordial magnetic fields. We assume that a random magnetic field was present before recombination and follow the field's effect on the baryon fluid starting at recombination. We find that magnetic fields generate growing density perturbations on length scales larger than the magnetic Jeans length, $\\lambda_B$, and damped oscillations for scales smaller than $\\lambda_B$. For small wavenumbers $k$ (l...

  9. Natural circulation steam generator model for optimal steam generator water level control

    International Nuclear Information System (INIS)

    Several authors have cited the control of steam generator water level as an important problem in the operation of pressurized water reactor plants. In this paper problems associated with steam generator water level control are identified, and advantages of modern estimation and control theory in dealing with these problems are discussed. A new state variable steam generator model and preliminary verification results using data from the loss of fluid test (LOFT) plant are also presented

  10. A Novel Open-winding Permanent Magnetic Starter-generator

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In order to overcome the difficulties of voltage regulation, narrow speed range and low power factor of the traditional permanent magnetic generator applied in the vehicles, a novel open-winding permanent magnetic starter-generator (see Fig.l) is used to widen the speed range and improve the efficiency in the generation mode.

  11. Design of CHWHG Type Low Frequency Magnetic Fields Generator

    Directory of Open Access Journals (Sweden)

    Bo Cheng

    2007-01-01

    Full Text Available Highly considering the invariability of magnetic field strength in the Magnetic Field Generators, which used to stimulate rat's nerve cell, surely improve the stimulation performance outcome. A new technique to get an invariable magnetic field strength within Magnetic Field Generator has been proposed, Furthermore it had implemented on microcontroller-based system providing an Alternating Magnetic Field Generator (AMFG with a high performance. The performance of the system is evaluated using two different methods. The results show that the errors are well and acceptable.

  12. Evolution of Primordial Magnetic Fields: From Generation Till Today

    CERN Document Server

    Kahniashvili, Tina; Tevzadze, Alexander G

    2015-01-01

    In this presentation we summarize our previous results concerning the evolution of primordial magnetic fields with and without helicity during the expansion of the Universe. We address different magnetogenesis scenarios such as inflation, electroweak and QCD phase transitions magnetogenesis. A high Reynolds number in the early Universe ensures strong coupling between magnetic field and fluid motions. After generation the subsequent dynamics of the magnetic field is governed by decaying hydromagnetic turbulence. We claim that primordial magnetic fields can be considered as a seeds for observed magnetic fields in galaxies and clusters. Magnetic field strength bounds obtained in our analysis are consistent with the upper and lower limits of extragalactic magnetic fields.

  13. Analysis on Non-Uniform Flow in Steam Generator During Steady State Natural Circulation Cooling

    Directory of Open Access Journals (Sweden)

    Susyadi

    2007-07-01

    Full Text Available Investigation on non uniform flow behavior among U-tube in steam generator during natural circulation cooling has been conducted using RELAP5. The investigation is performed by modeling the steam generator into multi channel models, i.e. 9-tubes model. Two situations are implemented, high pressure and low pressure cases. Using partial model, the calculation simulates situation similar to the natural circulation test performed in LSTF. The imposed boundary conditions are flow rate, quality, pressure of the primary side, feed water temperature, steam generator liquid level, and pressure in the secondary side. Calculation result shows that simulation using model with nine tubes is capable to capture important non-uniform phenomena such as reverse flow, fill-and-dump, and stagnant vertical stratification. As a result of appropriate simulation of non uniform flow, the calculated steam generator outlet flow in the primary loop is stable as observed in the experiments. The results also clearly indicate the importance of simulation of non-uniform flow in predicting both the flow stability and heat transfer between the primary and secondary side. In addition, the history of transient plays important role on the selection of the flow distribution among tubes. © 2007 Atom Indonesia. All rights reserved

  14. Generation of Alfven Waves by Magnetic Reconnection

    OpenAIRE

    Kigure, Hiromitsu; Takahashi, Kunio; Shibata, Kazunari; Yokoyama, Takaaki; Nozawa, Satoshi

    2010-01-01

    In this paper, results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, guide field. The angle theta between magnetic field lines in two half regions is a key parameter in our simulations whereas the initial distribution of the plasma is assumed to be simple; density and pressure are uniform except for the current s...

  15. U-Tube steam generator modeling for natural circulation and pot-boiling modes

    International Nuclear Information System (INIS)

    A general steam generator model is developed to account for various modes such as natural circulation and pot-boiling modes which can be occurred during transients. The present model can describe not only the swell and shrink phenomena, occurred by any small change in steam flowrates and feedwater flowrates but also natural circulation, pot-boiling, and tube uncovery modes which occur in sequence during the loss of feedwater transient if auxiliary feedwater is not followed by. The void fraction concept is used instead of the quality concept to simulate counter-current flow which takes place in the pot-boiling mode after the natural circulation mode stops. The present model is based on a one-dimensional three-region model to realistically describe the swell and shrink phenomena; downcomer, tube bundle, and steam dome regions. Both of the downcomer water level and two-phase level can be predicted during the pot-boiling mode. To verify the present model in the pot-boiling mode, a simple experiment is done and simulated by the present code. It is shown that the simulated results are relatively in good agreement with the experimental data

  16. Correlation of Steam Generator Mixing Parameters for Severe Accident Hot-Leg Natural Circulation

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Yehong; Guentay, Salih [Paul Scherrer Institut, Villigen PSI, CH-5232 (Switzerland)

    2008-07-01

    Steam generator inlet plenum mixing phenomenon with hot-leg counter-current natural circulation during a PWR station blackout severe accident is one of the important processes governing which component will fail first as a result of thermal challenge from the circulating gas with high temperature and pressure. Since steam generator tube failure represents bypass release of fission product from the reactor to environment, study of inlet plenum mixing parameters is important to risk analysis. Probability distribution functions of individual mixing parameter should be obtained from experiments or calculated by analysis. In order to perform sensitivity studies of the synergetic effects of all mixing parameters on the severe accident-induced steam generator tube failure, the distribution and correlation of these mixing parameters must be known to remove undue conservatism in thermal-hydraulic calculations. This paper discusses physical laws governing three mixing parameters in a steady state and setups the correlation among these mixing parameters. The correlation is then applied to obtain the distribution of one of the mixing parameters that has not been given in the previous CFD analysis. Using the distributions and considering the inter-dependence of the three mixing parameters, three sensitivity cases enveloping the mixing parameter uncertainties are recommended for the plant analysis. (authors)

  17. Magnetic Helicity Generation from the Cosmic Axion Field

    CERN Document Server

    Campanelli, L

    2005-01-01

    The coupling between a primordial magnetic field and the cosmic axion field generates a helical component of the magnetic field around the time in which the axion starts to oscillate. If the energy density of the seed magnetic field is comparable to the energy density of the universe at that time, then the resulting magnetic helicity is about |H_B| \\simeq (10^{-20} G)^2 kpc and remains constant after its generation. As a corollary, we find that the standard properties of the oscillating axion remain unchanged even in the presence of very strong magnetic fields.

  18. Giga-Gauss scale quasistatic magnetic field generation with laser

    CERN Document Server

    Korneev, Philipp; Tikhonchuk, Vladimir

    2014-01-01

    A simple setup for the generation of ultra-intense quasistatic magnetic fields is proposed and analysed. Estimations and numerical Particle-In-Cell calculations show that magnetic fields of gigagauss scale may be generated with conventional powerful relativistic lasers interacting with the appropriate targets of a special geometry. The setup may be useful for a wide range of applications, from laboratory astrophysics to magnetized ICF schemes.

  19. Generation of coherent radiation by magnetization reversal in graphene

    OpenAIRE

    Yukalov, V. I.; Henner, V. K.; Belozerova, T. S.

    2016-01-01

    Local magnetic moments can be created in graphene by incorporating different defects. The possibility of regulating dynamics of magnetization in graphene, by employing the Purcell effect, is analyzed. The role of the system parameters in magnetization reversal is studied. The characteristics of such a reversal can be varied in a wide range, which can be used for various applications in spintronics. It is shown that fast magnetization reversal generates coherent radiation.

  20. Strong magnetic field generation in laser plasma

    International Nuclear Information System (INIS)

    An attempt has been made to solve the magnetic field evolution equation by using Green function and taking convective, diffusion and nabla n x nabla T as a dominant source term. The maximum magnetic field is obtained to be an order of megagauss. (author). 14 refs, 1 fig

  1. Carrier molecules and extraction of circulating tumor DNA for next generation sequencing in colorectal cancer.

    Science.gov (United States)

    Beránek, Martin; Sirák, Igor; Vošmik, Milan; Petera, Jiří; Drastíková, Monika; Palička, Vladimír

    2016-01-01

    The aims of the study were: i) to compare circulating tumor DNA (ctDNA) yields obtained by different manual extraction procedures, ii) to evaluate the addition of various carrier molecules into the plasma to improve ctDNA extraction recovery, and iii) to use next generation sequencing (NGS) technology to analyze KRAS, BRAF, and NRAS somatic mutations in ctDNA from patients with metastatic colorectal cancer. Venous blood was obtained from patients who suffered from metastatic colorectal carcinoma. For plasma ctDNA extraction, the following carriers were tested: carrier RNA, polyadenylic acid, glycogen, linear acrylamide, yeast tRNA, salmon sperm DNA, and herring sperm DNA. Each extract was characterized by quantitative real-time PCR and next generation sequencing. The addition of polyadenylic acid had a significant positive effect on the amount of ctDNA eluted. The sequencing data revealed five cases of ctDNA mutated in KRAS and one patient with a BRAF mutation. An agreement of 86% was found between tumor tissues and ctDNA. Testing somatic mutations in ctDNA seems to be a promising tool to monitor dynamically changing genotypes of tumor cells circulating in the body. The optimized process of ctDNA extraction should help to obtain more reliable sequencing data in patients with metastatic colorectal cancer. PMID:27526306

  2. Next generation IR magnets for hadron colliders

    CERN Document Server

    Gupta, R; Cozzolino, J P; Escallier, J; Ganetis, G; Harrison, M; Wanderer, P J

    2003-01-01

    Brookhaven National Laboratory (BNL) is developing "React & Wind" designs and technology for building long high field accelerator magnets. This paper presents the R&D program for interaction region (IR) magnets made with "Rutherford" cable for the luminosity upgrade of the Large Hadron Collider (LHC). This paper will introduce a few new end design concepts that make the bend radius of the cable in the end independent of the coil aperture. These designs are suitable for building magnets with "React & Wind" technology. (6 refs).

  3. Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.

    Science.gov (United States)

    Danieli, E; Perlo, J; Blümich, B; Casanova, F

    2013-05-01

    Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays. PMID:23683185

  4. Highly Stable and Finely Tuned Magnetic Fields Generated by Permanent Magnet Assemblies

    Science.gov (United States)

    Danieli, E.; Perlo, J.; Blümich, B.; Casanova, F.

    2013-05-01

    Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

  5. Design of Pulsed Strong Magnetic Fields Generator and Preliminary Application

    Institute of Scientific and Technical Information of China (English)

    WEN Jun; QU Xue-min; WANG Xi-gang; LONG Kai-ping

    2015-01-01

    Objective: This paper aims to designing a pulsed strong magnetic fields generator. Methods: A large value capacitor was used to store electric energy, coil was used for producing magnetic fields, main control, circuit control charge, sampling, discharge, etc. Results: The generator provided a pulsed magnetic field with the ampli-tude of intensity from 0.1-2 T and variable time interval of pulse from 4 s-1 min. It was not only to be operated easily but also performed reliably. Conclusion:The generator will be applied in special clinical diagnosis, therapy and other fields.

  6. Exhaust circulation into dry gas desulfurization process to prevent carbon deposition in an Oxy-fuel IGCC power generation

    International Nuclear Information System (INIS)

    Highlights: • Power plant with semi-closed gas turbine and O2–CO2 coal gasifier was studied. • We adopt dry gas sulfur removal process to establish the system. • The exhaust gas circulation remarkably prevented carbon deposition. • Efficiency loss for exhaust gas circulation is quite small. • Appropriate operating condition of sulfur removal process is revealed. - Abstract: Semi-closed cycle operation of gas turbine fueled by oxygen–CO2 blown coal gasification provides efficient power generation with CO2 separation feature by excluding pre-combustion type CO2 capture that usually brings large efficiency loss. The plant efficiency at transmission end is estimated as 44% at lower heating value (LHV) providing compressed CO2 with concentration of 93 vol%. This power generation system will solve the contradiction between economical resource utilization and reduction of CO2 emission from coal-fired power plant. The system requires appropriate sulfur reduction process to protect gas turbine from corrosion and environment from sulfur emission. We adopt dry gas sulfur removal process to establish the system where apprehension about the detrimental carbon deposition from coal gas. The effect of circulation of a portion of exhaust gas to the process on the retardation of carbon deposition was examined at various gas compositions. The circulation remarkably prevented carbon deposition in the sulfur removal sorbent. The impact of the circulation on the thermal efficiency is smaller than the other auxiliary power consumption. Thus, the circulation is appropriate operation for the power generation

  7. Flow distribution calculation of parallel inverted U-tubes in steam generator under natural circulation

    International Nuclear Information System (INIS)

    For natural circulation, it is shown that reverse flow occurs in inverted U-tubes of steam generator (SG). The flow and heat transfer characteristics in inverted U-tubes were analyzed, the principle of the reverse flow was gotten, and the flow distribution program was established. The flow distribution of the parallel inverted U-tubes in one type of SG was calculated using the program, the calculation results were compared with experimental data, and the validity of the program was verified. The change of the parallel U-tubes' parameters with the pressure drop was also calculated and studied by using the program. The results show that reverse flow occurs in the short tubes and the net mass flow rate and the heat transfer rate in the primary side are lowered down step by step, which has great influence on the reactor safety. (authors)

  8. Precise numerical estimation of the magnetic field generated around recombination

    Science.gov (United States)

    Fidler, Christian; Pettinari, Guido; Pitrou, Cyril

    2016-05-01

    We investigate the generation of magnetic fields from nonlinear effects around recombination. As tight-coupling is gradually lost when approaching z ≃1100 , the velocity difference between photons and baryons starts to increase, leading to an increasing Compton drag of the photons on the electrons. The protons are then forced to follow the electrons due to the electric field created by the charge displacement; the same field, following Maxwell's laws, eventually induces a magnetic field on cosmological scales. Since scalar perturbations do not generate any magnetic field as they are curl-free, one has to resort to second-order perturbation theory to compute the magnetic field generated by this effect. We reinvestigate this problem numerically using the powerful second-order Boltzmann code SONG. We show that: (i) all previous studies do not have a high enough angular resolution to reach a precise and consistent estimation of the magnetic field spectrum; (ii) the magnetic field is generated up to z ≃10 ; (iii) it is in practice impossible to compute the magnetic field with a Boltzmann code for scales smaller than 1 Mpc. Finally we confirm that for scales of a few Mpc, this magnetic field is of order 2 ×10-29 G , many orders of magnitude smaller than what is currently observed on intergalactic scales.

  9. Active screening of magnetic field near power stations generator buses

    Directory of Open Access Journals (Sweden)

    B.I. Kuznetsov

    2013-12-01

    Full Text Available An experimental study technique for a prototyping system of active screening of power-frequency magnetic field distortions near power station generator buses via controllable magnetic field sources is presented. Results of experimental research on a proto-typing active screening system with different control algorithms are given.

  10. Performance Evaluation of a Permanent-Magnet Induction Generator

    Science.gov (United States)

    Fukami, Tadashi; Yokoi, Masahiro; Kanamaru, Yasunori; Miyamoto, Toshio

    A permanent-magnet induction generator (PMIG) is a special induction machine self-excited from the inside of the squirrel-cage rotor by a permanent-magnet rotor (PM rotor). In order to evaluate the practical value of the PMIG, its steady-state performance is analyzed theoretically and experimentally. As a result, it was found that the PMIG exhibits good power factor and efficiency compared to a general-purpose induction generator (GPIG) of the same size.

  11. Electron holography of magnetic field generated by a magnetic recording head.

    Science.gov (United States)

    Goto, Takayuki; Jeong, Jong Seok; Xia, Weixing; Akase, Zentaro; Shindo, Daisuke; Hirata, Kei

    2013-06-01

    The magnetic field generated by a magnetic recording head is evaluated using electron holography. A magnetic recording head, which is connected to an electric current source, is set on the specimen holder of a transmission electron microscope. Reconstructed phase images of the region around the magnetic pole show the change in the magnetic field distribution corresponding to the electric current applied to the coil of the head. A simulation of the magnetic field, which is conducted using the finite element method, reveals good agreement with the experimental observations.

  12. Observation of a Turbulence-Generated Large Scale Magnetic Field

    CERN Document Server

    Spence, E J; Kendrick, R D; Nornberg, M D

    2006-01-01

    A uniform magnetic field is applied to a spherical, turbulent flow of liquid sodium. An induced magnetic dipole moment is measured which cannot be generated by the interaction of the axisymmetric mean flow with the applied field, indicating the presence of a turbulent electromotive force. It is shown that the induced dipole moment should vanish for any axisymmetric laminar flow. Also observed is the production of toroidal magnetic field from applied poloidal magnetic field (the omega-effect). Its potential role in the production of the induced dipole is discussed.

  13. GENERATOR VIBRATION FAULT DIAGNOSIS METHOD BASED ON ROTOR VIBRATION AND STATOR WINDING PARALLEL BRANCHES CIRCULATING CURRENT CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    Wan Shuting; Li Heming; Li Yonggang; Tang Guiji

    2005-01-01

    Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.

  14. Explanatory analysis of the relationship between atmospheric circulation and occurrence of flood generating events in a coastal city

    DEFF Research Database (Denmark)

    Åström, Helena Lisa Alexandra; Sunyer Pinya, Maria Antonia; Madsen, H.;

    2016-01-01

    The aim of this study is to enhance the understanding of the occurrence of flood generating events in urban areas by analyzing the relationship between large-scale atmospheric circulation and extreme precipitation events, extreme sea water level events and their simultaneous occurrence......, respectively. To describe the atmospheric circulation we used the Lamb circulation type (LCT) classification and re-grouped it into Lamb circulation classes (LCC). The daily LCCs/LCTs were connected with rare precipitation and water level events in Aarhus, a Danish coastal city. Westerly and cyclonic LCCs (W......, C, SW, and NW) showed a significantly high occurrence of extreme precipitation. Similarly, for extreme water level events westerly LCCs (W and SW) showed a significantly high occurrence. Significantly low occurrence of extreme precipitation and water level events was obtained in easterly LCCs (NE, E...

  15. Experimental verification of the horizontal steam generator boil-off transfer degradation at natural circulation

    Energy Technology Data Exchange (ETDEWEB)

    Hyvaerinen, J. [Finnish Centre for Radiation and Nuclear Safety, Helsinki (Finland); Kouhia, J. [VTT Energy, Lappeenranta (Finland)

    1997-12-31

    The presentation summarises the highlights of experimental results obtained for VVER type horizontal steam generator heat transfer, primary side flow pattern, and mixing in the hot collector during secondary side boil-off with primary at single-phase natural circulation. The experiments were performed using the PACTEL facility with Large Diameter (LD) steam generator models, with collector instrumentation designed specifically for these tests. The key findings are as follows: (1) the primary to secondary heat transfer degrades as the secondary water inventory is depleted, following closely the wetted tube area; (2) a circulatory flow pattern exists in the tube bundle, resulting in reversed flow (from cold to the hot collector) in the lower part of the tube bundle, and continuous flow through the upper part, including the tubes that have already dried out; and (3) mixing of the hot leg flow entering the hot collector and reversed, cold, tube flow remains confined within the collector itself, extending only a row or two above the elevation at which tube flow reversal has taken place. 6 refs.

  16. Research program of natural circulation steam generator design of national 1000 MWe PWR

    International Nuclear Information System (INIS)

    A concept design of natural circulation steam generator for the national 1000MWe PWR of the Chinese National Nuclear Program has been proposed and a relevant research program to validate the efficiency and/or effectiveness of some new design assemblies and/or components has been completed. There are three salient features in the steam generator design. Firstly, steam separation equipment was improved and carryover moisture was further reduced to below 0.1%. Secondly, the water level at the secondary side being elevated, secondary side water volume was expanded to satisfy the EPRI-URD requirements of LFB20. Finally, an inactive device, sludge collector was incorporated to enhance the secondary sludge control. The validation research program consists of two parts; cold state screening test, hot state validation test and corresponding computational analysis, and cold state test and corresponding computational analysis of sludge collector design. The validation tests were completed in 2001. Three sets of steam separator were selected from cold screening tests for hot validation. The hot test showed the most important parameters, outlet carryover, of all three sets were under 0.1%. The best case was only 0.0018%. The sludge collector showed a collection efficiency of over 50%

  17. Microwave generation for magnetic fusion energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Antonsen, T.M. Jr.; Destler, W.W.; Granatstein, V.L.; Levush, B.

    1992-01-01

    This progress report encompasses work on two separate projects, both related to developing sources for electron cyclotron resonance heating of magnetic fusion plasmas. The report is therefore divided into two parts as follows: Free electron laser with small period wigglers; and theory and modeling of high frequency, high power gryotron operation. Task A is experimental and eventually aims at developing continuously tunable, cw sources for ECRH with power per unit as high as 5 megawatts. Task B provides gryotron theory and modeling in support of the gryotron development programs at MIT and Varian.

  18. Motor-Generator powering the PS (Proton Synchrotron) main magnets

    CERN Multimedia

    1983-01-01

    This motor-generator,30 MW peak, 1500 r.p.m.,pulsed power supply for the PS main magnet replaced in 1968 the initial 3000 r.p.m. motor-generator-flywheel set which had served from the PS start-up in 1959 until end 1967. See also photo 8302337 and its abstract.

  19. Trapping and dynamic manipulation of polystyrene beads mimicking circulating tumor cells using targeted magnetic/photoacoustic contrast agents

    Science.gov (United States)

    Wei, Chen-Wei; Xia, Jinjun; Hu, Xiaoge; Gao, Xiaohu; O’Donnell, Matthew

    2012-01-01

    Abstract. Results on magnetically trapping and manipulating micro-scale beads circulating in a flow field mimicking metastatic cancer cells in human peripheral vessels are presented. Composite contrast agents combining magneto-sensitive nanospheres and highly optical absorptive gold nanorods were conjugated to micro-scale polystyrene beads. To efficiently trap the targeted objects in a fast stream, a dual magnet system consisting of two flat magnets to magnetize (polarize) the contrast agent and an array of cone magnets producing a sharp gradient field to trap the magnetized contrast agent was designed and constructed. A water-ink solution with an optical absorption coefficient of 10  cm−1 was used to mimic the optical absorption of blood. Magnetomotive photoacoustic imaging helped visualize bead trapping, dynamic manipulation of trapped beads in a flow field, and the subtraction of stationary background signals insensitive to the magnetic field. The results show that trafficking micro-scale objects can be effectively trapped in a stream with a flow rate up to 12  ml/min and the background can be significantly (greater than 15 dB) suppressed. It makes the proposed method very promising for sensitive detection of rare circulating tumor cells within high flow vessels with a highly absorptive optical background. PMID:23223993

  20. Trapping and dynamic manipulation of polystyrene beads mimicking circulating tumor cells using targeted magnetic/photoacoustic contrast agents

    Science.gov (United States)

    Wei, Chen-Wei; Xia, Jinjun; Pelivanov, Ivan; Hu, Xiaoge; Gao, Xiaohu; O'Donnell, Matthew

    2012-10-01

    Results on magnetically trapping and manipulating micro-scale beads circulating in a flow field mimicking metastatic cancer cells in human peripheral vessels are presented. Composite contrast agents combining magneto-sensitive nanospheres and highly optical absorptive gold nanorods were conjugated to micro-scale polystyrene beads. To efficiently trap the targeted objects in a fast stream, a dual magnet system consisting of two flat magnets to magnetize (polarize) the contrast agent and an array of cone magnets producing a sharp gradient field to trap the magnetized contrast agent was designed and constructed. A water-ink solution with an optical absorption coefficient of 10 cm-1 was used to mimic the optical absorption of blood. Magnetomotive photoacoustic imaging helped visualize bead trapping, dynamic manipulation of trapped beads in a flow field, and the subtraction of stationary background signals insensitive to the magnetic field. The results show that trafficking micro-scale objects can be effectively trapped in a stream with a flow rate up to 12 ml/min and the background can be significantly (greater than 15 dB) suppressed. It makes the proposed method very promising for sensitive detection of rare circulating tumor cells within high flow vessels with a highly absorptive optical background.

  1. Glutathione production using magnetic fields generated by magnets

    Directory of Open Access Journals (Sweden)

    Lucielen Oliveira dos Santos

    2012-12-01

    Full Text Available The objective of this work was to study the production of GSH by Saccharomyces cerevisiae ATCC 7754 in a fermentor (5 L using a cell recycle system with magnets. The fermentation conditions were 20°C, 500 rpm, 5% (v/v of inoculum, pHinitial 5, 1.1 vvm aeration and total fermentation time of 72 h. The time of application of MF ranged from 24, 48 or 72 h. In comparison to the control experiment, the best results were obtained with 72 h of application of MF. The cell concentration reached 19.5 g/L and GSH concentration was 271.9 mg/L that corresponded to an increase of 2.63 and 32.1% compared to the control experiment, respectively.

  2. Microwave generation for magnetic fusion energy applications

    International Nuclear Information System (INIS)

    This progress report encompasses work on three separate projects, all related to developing sources for electron cyclotron resonance heating of magnetic fusion plasmas. The report is therefore divided into three parts as follows: free electron lasers with small period wigglers; theory and modeling of high frequency, high power gyrotron operation; and depressed collectors for energy recovery in gyrotrons. Task A is experimental and eventually aims at developing CW sources for ECRH at frequencies as high as 600 GHz. Task B provides gyrotron theory and modeling in support of the gyrotron development programs at MIT and Varian. Task C was phased out in the current contract year but recent publications are included in this report in order to create a permanent record for the use of future researchers with interest in the topic of increasing gyrotron efficiency through the use of depressed collectors

  3. 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...... 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....

  4. The evolution of primordial magnetic fields since their generation

    Science.gov (United States)

    Kahniashvili, Tina; Brandenburg, Axel; Tevzadze, Alexander G.

    2016-10-01

    We study the evolution of primordial magnetic fields in an expanding cosmic plasma. For this purpose we present a comprehensive theoretical model to consider the evolution of MHD turbulence that can be used over a wide range of physical conditions, including cosmological and astrophysical applications. We model different types of decaying cosmic MHD turbulence in the expanding Universe and characterize the large-scale magnetic fields in such a medium. Direct numerical simulations of freely decaying MHD turbulence are performed for different magnetogenesis scenarios: magnetic fields generated during cosmic inflation as well as electroweak and QCD phase transitions in the early Universe. Magnetic fields and fluid motions are strongly coupled due to the high Reynolds number in the early Universe. Hence, we abandon the simple adiabatic dilution model to estimate magnetic field amplitudes in the expanding Universe and include turbulent mixing effects on the large-scale magnetic field evolution. Numerical simulations have been carried out for non-helical and helical magnetic field configurations. The numerical results show the possibility of inverse transfer of energy in magnetically dominated non-helical MHD turbulence. On the other hand, decay properties of helical turbulence depend on whether the turbulent magnetic field is in a weakly or a fully helical state. Our results show that primordial magnetic fields can be considered as a seed for the observed large-scale magnetic fields in galaxies and clusters. Bounds on the magnetic field strength are obtained and are consistent with the upper and lower limits set by observations of extragalactic magnetic fields.

  5. Modeling HEDLA magnetic field generation experiments on laser facilities

    International Nuclear Information System (INIS)

    The Flash Center is engaged in a collaboration to simulate laser driven experiments aimed at understanding the generation and amplification of cosmological magnetic fields using the FLASH code. In these experiments a laser illuminates a solid plastic or graphite target launching an asymmetric blast wave into a chamber which contains either Helium or Argon at milli-bar pressures. Induction coils placed several centimeters away from the target detect large scale magnetic fields on the order of tens to hundreds of Gauss. The time dependence of the magnetic field is consistent with generation via the Biermann battery mechanism near the blast wave. Attempts to perform simulations of these experiments using the FLASH code have uncovered previously unreported numerical difficulties in modeling the Biermann battery mechanism near shock waves which can lead to the production of large non-physical magnetic fields. We report on these difficulties and offer a potential solution. (authors)

  6. Mutational analysis of single circulating tumor cells by next generation sequencing in metastatic breast cancer

    Science.gov (United States)

    Galardi, Francesca; Pestrin, Marta; Gabellini, Stefano; Simi, Lisa; Mancini, Irene; Vannucchi, Alessandro Maria; Pazzagli, Mario; Di Leo, Angelo; Pinzani, Pamela

    2016-01-01

    Circulating Tumor Cells (CTCs) represent a “liquid biopsy” of the tumor potentially allowing real-time monitoring of cancer biology and therapies in individual patients. The purpose of the study was to explore the applicability of a protocol for the molecular characterization of single CTCs by Next Generation Sequencing (NGS) in order to investigate cell heterogeneity and provide a tool for a personalized medicine approach. CTCs were enriched and enumerated by CellSearch in blood from four metastatic breast cancer patients and singularly isolated by DEPArray. Upon whole genome amplification 3–5 single CTCs per patient were analyzed by NGS for 50 cancer-related genes. We found 51 sequence variants in 25 genes. We observed inter- and intra-patient heterogeneity in the mutational status of CTCs. The highest number of somatic deleterious mutations was found in the gene TP53, whose mutation is associated with adverse prognosis in breast cancer. The discordance between the mutational status of the primary tumor and CTCs observed in 3 patients suggests that, in advanced stages of cancer, CTC characteristics are more closely linked to the dynamic modifications of the disease status. In one patient the mutational profiles of CTCs before and during treatment shared only few sequence variants. This study supports the applicability of a non-invasive approach based on the liquid biopsy in metastatic breast cancer patients which, in perspective, should allow investigating the clonal evolution of the tumor for the development of new therapeutic strategies in precision medicine. PMID:27034166

  7. Scaling modeling analysis of flow instability in U-tubes of steam generator under natural circulation

    International Nuclear Information System (INIS)

    Highlights: • The flow instability criterion (critical Reynolds number) in U-tubes of SG is derived. • The flow and heat transfer in the plenums and pipes and U-tubes are modeled. • A set of scaling modeling criteria are obtained by the integral analogy method. • The scaling modeling conditions in the SG primary side are given. - Abstract: It is found that under the natural circulation condition the reverse flow occurs in the U-tubes of steam generator (SG), which has large influence on the reactor safety. Though the reverse flow in SG is thought as the Ledinegg-type flow instability that is dominated by the flow resistance and gravitation pressure drop, it has not been studied well. Because of the complexity of the problem and the limitation of research conditions, it is a good way to perform the numerical simulation based on the scaling model. In the present work, based on one-dimensional N–S equations, the flow instability in U-tubes is investigated and the flow instability criterion (critical Reynolds number) is derived. The flow and heat transfer in the plenums and pipes are modeled by three-dimensional conservation equations. Using the integral analogy method, a set of scaling modeling criteria are also obtained, and the scaling modeling conditions in the stream generator primary side are given by the similar second theorem. The applicability of these conditions is discussed. The results can be used as the basic of the numerical simulation of the flow instability in U-tubes of SG

  8. Magnetic flux generation and transport in cool stars

    CERN Document Server

    Işık, Emre; Schüssler, Manfred

    2011-01-01

    The Sun and other cool stars harbouring outer convection zones manifest magnetic activity in their atmospheres. The connection between this activity and the properties of a deep-seated dynamo generating the magnetic flux is not well understood. By employing physical models, we study the spatial and temporal characteristics of the observable surface field for various stellar parameters. We combine models for magnetic flux generation, buoyancy instability, and transport, which encompass the entire convection zone. The model components are: (1) a thin-layer alpha-Omega dynamo at the base of the convection zone; (2) buoyancy instabilities and the rise of flux tubes through the convection zone in 3D, which provides a physically consistent determination of emergence latitudes and tilt angles; and (3) horizontal flux transport at the surface. For solar-type stars and rotation periods longer than about 10 days, the latitudinal dynamo waves generated by the deep-seated alpha-Omega dynamo are faithfully reflected by th...

  9. Analysis and Design of Hybrid Excitation Permanent Magnet Synchronous Generators

    Institute of Scientific and Technical Information of China (English)

    JIN Wan-bing; ZHANG Dong; AN Zhong-liang; TAN Ren-yuan

    2006-01-01

    On the basis of a conventional permanent magnet (PM) synchronous generator's construction,a novel kind of Hybrid Excitation Permanent Magnet Synchronous Generator (HEPMSG) is introduced by inserting exciting winding in the stator or rotor.Firstly,the construction of HEPMSG is improved with the addition of PM excitation on the ferromagnetic pole,and its working principle and design method are studied in detail.Then,an appropriate exciting current control system is presented considering the characteristics of HEPMSG.Finally,a prototype is made,and test results confirm the analysis and design.

  10. Fetal circulation in left-sided congenital heart disease measured by cardiovascular magnetic resonance: a case–control study

    OpenAIRE

    Al Nafisi, Bahiyah; van Amerom, Joshua FP; Forsey, Jonathan; Jaeggi, Edgar; Grosse-Wortmann, Lars; Yoo, Shi-Joon; Macgowan, Christopher K; Seed, Mike

    2013-01-01

    Background The distribution of blood flow in fetuses with congenital heart disease (CHD) is likely to influence fetal growth, organ development, and postnatal outcome, but has previously been difficult to study. We present the first measurements of the distribution of the fetal circulation in left-sided CHD made using phase contrast cardiac magnetic resonance (CMR). Methods Twenty-two fetuses with suspected left-sided CHD and twelve normal controls underwent fetal CMR and echocardiography at ...

  11. Gravitational radiation generated by cosmological phase transition magnetic fields

    International Nuclear Information System (INIS)

    We study gravitational waves generated by the cosmological magnetic fields induced via bubble collisions during the electroweak (EW) and QCD phase transitions. The magnetic field generation mechanisms considered here are based on the use of the fundamental EW minimal supersymmetric and QCD Lagrangians. The gravitational waves spectrum is computed using a magnetohydrodynamic turbulence model. We find that the gravitational wave spectrum amplitude generated by the EW phase transition peaks at a frequency of approximately 1-2 mHz, and is of the order of 10-20-10-21; thus this signal is possibly detectable by the Laser Interferometer Space Antenna (LISA). The gravitational waves generated during the QCD phase transition, however, are outside the LISA sensitivity bands.

  12. Optical magnetic flux generation in superconductor

    Indian Academy of Sciences (India)

    Masayoshi Tonouchi

    2002-05-01

    The generation of the magnetic flux quanta inside the superconductors is studied as a new effect to destroy superconductivity using femtosecond (fs) laser. The vortices are successfully generated in the YBa2Cu3O7- thin film striplines by the fs laser. It is revealed that the vortex distribution in the strip reflects the fs laser beam profile.

  13. Design and Analysis of Tubular Permanent Magnet Linear Wave Generator

    Directory of Open Access Journals (Sweden)

    Jikai Si

    2014-01-01

    Full Text Available Due to the lack of mature design program for the tubular permanent magnet linear wave generator (TPMLWG and poor sinusoidal characteristics of the air gap flux density for the traditional surface-mounted TPMLWG, a design method and a new secondary structure of TPMLWG are proposed. An equivalent mathematical model of TPMLWG is established to adopt the transformation relationship between the linear velocity of permanent magnet rotary generator and the operating speed of TPMLWG, to determine the structure parameters of the TPMLWG. The new secondary structure of the TPMLWG contains surface-mounted permanent magnets and the interior permanent magnets, which form a series-parallel hybrid magnetic circuit, and their reasonable structure parameters are designed to get the optimum pole-arc coefficient. The electromagnetic field and temperature field of TPMLWG are analyzed using finite element method. It can be included that the sinusoidal characteristics of air gap flux density of the new secondary structure TPMLWG are improved, the cogging force as well as mechanical vibration is reduced in the process of operation, and the stable temperature rise of generator meets the design requirements when adopting the new secondary structure of the TPMLWG.

  14. Dynamic Analysis of Permanent Magnet Synchronous Generator with Power Electronics

    Directory of Open Access Journals (Sweden)

    OZCIRA, S.

    2010-05-01

    Full Text Available Permanent magnet DC motor-generators (PMDC, PMSG have been widely used in industrial and energy sectors recently. Power control of these systems can be achieved by controlling the output voltage. In this study, PMDC-PMSG systems are mathematically modeled and simulated in MATLAB and Simulink software. Then the results are discussed. A low power permanent magnet synchronous generator is driven by a permanent magnet DC motor and the output voltage is controlled by a frequency cycle-converter. The output of a half-wave uncontrolled rectifier is applied to an SPWM inverter and the power is supplied to a 300V, 50Hz load. The load which is connected to an LC filter is modeled by state-space equations. LC filter is utilized in order to suppress the voltage oscillations at the inverter output.

  15. Laser-generated magnetic fields in quasi-hohlraum geometries

    Science.gov (United States)

    Pollock, Bradley; Turnbull, David; Ross, Steven; Hazi, Andrew; Ralph, Joseph; Lepape, Sebastian; Froula, Dustin; Haberberger, Dan; Moody, John

    2014-10-01

    Laser-generated magnetic fields of 10--40 T have been produced with 100--4000 J laser drives at Omega EP and Titan. The fields are generated using the technique described by Daido et al. [Phys. Rev. Lett. 56, 846 (1986)], which works by directing a laser through a hole in one plate to strike a second plate. Hot electrons generated in the laser-produced plasma on the second plate collect on the first plate. A strap connects the two plates allowing a current of 10 s of kA to flow and generate a solenoidal magnetic field. The magnetic field is characterized using Faraday rotation, b-dot probes, and proton radiography. Further experiments to study the effect of the magnetic field on hohlraum performance are currently scheduled for Omega. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA-27344.

  16. Generation of zonal flows in rotating fluids and magnetized plasmas

    DEFF Research Database (Denmark)

    Juul Rasmussen, J.; Garcia, O.E.; Naulin, V.;

    2006-01-01

    The spontaneous generation of large-scale flows by the rectification of small-scale turbulent fluctuations is of great importance both in geophysical flows and in magnetically confined plasmas. These flows regulate the turbulence and may set up effective transport barriers. In the present...

  17. Multilayer magnetic circuit for millimeter scale MEMS air turbine generator

    International Nuclear Information System (INIS)

    The multilayer magnetic circuit for the millimeter scale MEMS (Micro Electrical Mechanical System) air turbine generator is proposed in this paper. The dimensions of the fabricated air turbine generator were 3.6 mm, 3.4 mm and 3.5 mm, length, width and height, respectively. The air turbine was fabricated by the MEMS technology. Multilayer magnetic circuits were fabricated by the green sheet process. The achieved output voltage and output power of the generator were 6.2mV and 1.92μVA respectively. Moreover, the optimization of the ceramic magnetic circuit for the generator was performed to improve the output power. In this experiment, the horseshoe shape circuit and step-wise shape circuit were compared on the output power by the spindle machine. When two kinds magnetic circuit were compared, the output power of the step-wise shape circuit was higher than that of the horseshoe shape circuit. The output voltage and the output power of the step-wise shape circuit were 28mV and 1.53 mVA when load resistance of 0.512 Ω was connected

  18. Optimization of Multibrid Permanent-Magnet Wind Generator Systems

    DEFF Research Database (Denmark)

    Chen, Zhe; Li, H.; Polinder, H.

    2009-01-01

    This paper investigates the cost-effective ranges of gearbox ratios and power ratings of multibrid permanent-magnet (PM) wind generator systems by using a design optimization method. First, the analytical model of a multibrid wind turbine concept consisting of a single-stage gearbox and a three...

  19. Generation of Whistler Wave by a Rotating Magnetic Field Source

    Science.gov (United States)

    Karavaev, A.; Papadopoulos, K.; Shao, X.; Sharma, A. S.; Gigliotti, A.; Gekelman, W.; Pribyl, P.; Vincena, S.

    2008-12-01

    The interaction of Rotating Magnetic Fields (RMF) with plasmas is a fundamental plasma physics problem with implications to fusion related Field-Reversed Configurations (FRC), space propulsion, astronaut protection from cosmic rays in long interstellar travel, control of the energetic population in the radiation belts and near zone processes in pulsar magnetospheres. In this paper we report recent experiments on the generation of whistler waves with a new type RMF-based antenna. The experiments were conducted on UCLA's Large Plasma Device (LAPD). The Rotating Magnetic Field (RMF) is created using poly-phased loop antennas. A number of parameter combinations, e.g. plasma density, background magnetic field, and driving current, were used. It was found that RMF created by a two phase-delayed loop antenna drives significant currents along the ambient magnetic field. The measured amplitude of induced wave field was proportional to the square-root of the plasma density. The spatial decay rate for the wave perturbation across the background magnetic field was found to scale with the plasma skin depth. A small amplitude second harmonic was also measured. The paper will also present analytic and simulation results that account for the experimental results; in particular, the scaling of the induced magnetic field as a function of the RMF and plasma parameters and the spatial decay rate of magnetic field. Applications of RMF as an efficient radiation source of plasma waves in space plasmas will be discussed. This work was sponsored by ONR MURI Grant 5-28828

  20. Steam condensation and liquid hold-up in steam generator U-tubes during oscillatory natural circulation

    International Nuclear Information System (INIS)

    In many accident scenarios, natural circulation is an important heat transport mechanism for long-term cooling of light water reactors. In the event of a small pipe break, with subsequent loss of primary cooling fluid loss-of-coolant accident (LOCA), or under abnormal operating conditions, early tripping of the main coolant pumps can be actuated. Primary fluid flow will then progress from forced to natural convection. Understanding of the flow regimes and heat-removal mechanisms in the steam generators during the entire transient is of primary importance to safety analysis. Flow oscillations during two-phase natural circulation experiments for pressurized water reactors (PWRs) with inverted U-tube steam generators occur at high pressure and at a primary inventory range between two-phase circulation and reflex heat removal. This paper deals with the oscillatory flow behavior that was observed in the LOBI-MOD2 facility during the transition period between two-phase natural circulation and reflex condensation

  1. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    International Nuclear Information System (INIS)

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed

  2. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Energy Technology Data Exchange (ETDEWEB)

    Bouda, N. R., E-mail: nybouda@iastate.edu; Pritchard, J.; Weber, R. J.; Mina, M. [Department of Electrical and Computer engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2015-05-07

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  3. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Science.gov (United States)

    Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-01

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  4. FORMING CAPABILITIES OF A PULSE MAGNETIC FIELD GENERATOR

    Directory of Open Access Journals (Sweden)

    A. A. Petkov

    2015-04-01

    Full Text Available Purpose. Determination of areas ratio of the parameters of the discharge circuit elements of the generator, which ensure the formation of magnetic field pulses of different shapes. Methodology. Numerical simulation using dimensionless variables that determine the nature of the transition process in the discharge circuit of the generator, and use the procedure for determining the pulse points of meeting the conditions of extremum and the transition through zero. Results. Obtained a description of the formation of the three specific areas of waveforms: oscillatory weakly damped oscillatory strongly damped and unipolar pulse with a monotonic rise and fall values. A relation to the choice of parameters of elements of the discharge circuit of the generator, which formed unipolar pulses with a monotonic rise and fall values. Originality. A completed and extended database that implements the mapping of the formal description of the pulse shape with a description of areas ratio parameters for high-voltage pulse discharge circuit test units, with respect to the pulses of current flowing in the formation of the magnetic field. Practical value. The relations obtained allow to select the parameters of the discharge circuit elements of the generator designed to generate test pulses of magnetic field.

  5. Relativistic Scott correction in self-generated magnetic fields

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, Søren; Solovej, Jan Philip

    2012-01-01

    We consider a large neutral molecule with total nuclear charge $Z$ in a model with self-generated classical magnetic field and where the kinetic energy of the electrons is treated relativistically. To ensure stability, we assume that $Z \\alpha .../3}$ and it is unchanged by including the self-generated magnetic field. We prove the first correction term to this energy, the so-called Scott correction of the form $S(\\alpha Z) Z^2$. The current paper extends the result of \\cite{SSS} on the Scott correction for relativistic molecules to include a self-generated...... constant. We are interested in the ground state energy in the simultaneous limit $Z \\rightarrow \\infty$, $\\alpha \\rightarrow 0$ such that $\\kappa=Z \\alpha$ is fixed. The leading term in the energy asymptotics is independent of $\\kappa$, it is given by the Thomas-Fermi energy of order $Z^{7...

  6. Computational Models for Creating Homogeneous Magnetic Field Generation Systems

    Directory of Open Access Journals (Sweden)

    Gerlys M. Villalobos-Fontalvo

    2013-11-01

    Full Text Available It is increasingly common to use magnetic fields at the cellular level to assess their interaction with biological tissues. The stimulation is usually done with Helmholtz coils which generate a uniform magnetic field in the center of the system. However, assessing cellular behavior with different magnetic field characteristics can be a long and expensive process. For this, it can be used computational models to previously estimate the cellular behavior due to variety of field characteristics prior to in-vitro stimulation in a laboratory. In this paper, we present a methodology for the development of three computational models of homogeneous magnetic field generation systems for possible application in cell stimulation. The models were developed in the Ansys Workbench environment and it was evaluated the magnetic flux density behavior at different configurations. The results were validated with theoretical calculations from the Biot-Savart law. Validated models will be coupled to Ansys APDL environment in order to assess the harmonic response of the system.

  7. Spin transfer torque generated magnetic droplet solitons (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Chung, S. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Mohseni, S. M. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden); Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Sani, S. R. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden); Iacocca, E.; Dumas, R. K.; Pogoryelov, Ye. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Anh Nguyen, T. N. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Laboratory for Nanotechnology (LNT), Vietnam National University - Ho Chi Minh City (VNU-HCM), Ho Chi Minh City (Viet Nam); Muduli, P. K. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Eklund, A. [Devices and Circuits, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Hoefer, M. [Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Åkerman, J., E-mail: johan.akerman@physics.gu.se [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden)

    2014-05-07

    We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90°, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy.

  8. EFFECTIVE SHIELDING OF UNIDIRECTIONAL CURRENT GENERATED MAGNETIC FIELDS

    Institute of Scientific and Technical Information of China (English)

    徐霖; 傅正财; 杜亚平

    2002-01-01

    This paper presented an effective shielding design of magnetic fields generated by unidirectional current.Theoretical formulas and numerical computation software based on boundary element method (BEM) are employed to evaluate the shielding effectiveness (SE) of cylindrical shell. It is shown that ungrounded or one-end-grounded metal shell is ineffective for such magnetic fields. SE can be obtained by connecting the two ends of the conducting shell with low impedance connector, or alternatively, grounding the two ends. The experimental results also support these conclusions.

  9. Second Harmonic Generation from Co Magnetic Thin Films

    Institute of Scientific and Technical Information of China (English)

    卢永雄; 叶骏; 金庆原

    2003-01-01

    The magnetization-induced second harmonic generation (MSHG) in the sputtered and epitaxial-grown Co thin films was studied. The magnetic contrast of the MSHG intensity could be clearly distinguished for the cobalt films prepared by both the methods, but the signal measured in air for sputtered films was not smoother than that for the in-situ measurement of epitaxial films. Compared with the magneto-optical Kerr effect, the MSHG shows some new behaviour indicating that more information could be obtained if these two methods are combined. The MSHG reveals a giant nonlinear Kerr rotation in orders of magnitude larger than its linear one.

  10. An investigation of electromagnetic rig-generated strong magnetic fields

    OpenAIRE

    Ekreem, Nasser B.

    2009-01-01

    In this thesis, two alternative solenoid designs are presented: 'Air-core' coil design and 'C-shape' coil design. The coils were designed to be capable of generating strong and static magnetic fields in various samples of magnetic materials. In the case of the first design, the sample would be placed in the central air space. In the second design, the sample would be placed in part of the 'jaws' of the 'C' shape. It was intended that the rig would be used to measure the magnetostriction strai...

  11. 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.

  12. Generation of scale invariant magnetic fields in bouncing universes

    Science.gov (United States)

    Sriramkumar, L.; Atmjeet, Kumar; Jain, Rajeev Kumar

    2015-09-01

    We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic field can arise before the bounce for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape after the bounce. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the e-Script N-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and evaluate the spectra of the electric and magnetic fields at a suitable time after the bounce. As one could have intuitively expected, though the complete spectra depend on the details of the bounce, we find that, under the original conditions, scale invariant spectra of the magnetic fields do arise for wavenumbers much smaller than the scale associated with the bounce. We also show that magnetic fields which correspond to observed strengths today can be generated for specific values of the parameters. But, we find that, at the bounce, the backreaction due to the electromagnetic modes that have been generated can be significantly large calling into question the viability of the model. We briefly discuss the implications of our results.

  13. Dark matter and generation of galactic magnetic fields

    CERN Document Server

    Berezhiani, Zurab; Tkachev, I I

    2013-01-01

    A mechanism for creation of galactic and intergalactic magnetic fields at a recent cosmological epoch is proposed. We show that in rotating protogalaxies circular electric currents are generated by the interactions of free electrons with dark matter particles while the impact of such interactions on galactic protons is considerably weaker. Light dark matter particles can be efficient for generation of such currents if these particles have some long range interactions. In particular, millicharged warm dark matter particles or light mirror particles with the photon kinetic mixing to the usual matter are considered. The induced currents may be strong enough to create the observed magnetic fields on the galaxy scales without need for a strong dynamo amplification. On the other hand, the angular momentum transfer from the rotating gas to dark matter component could change the dark matter profile and formation of cusps at galactic centers would be inhibited. We also discuss how the global motion of the ionized gas ...

  14. FUZZY FAULT DETECTION FOR PERMANENT MAGNET SYNCHRONOUS GENERATOR

    Directory of Open Access Journals (Sweden)

    N. Selvaganesan

    2011-07-01

    Full Text Available Faults in engineering systems are difficult to avoid and may result in serious consequences. Effective fault detection and diagnosis can improve system reliability and avoid expensive maintenance. In this paper fuzzy system based fault detection scheme for permanent magnet synchronous generator is proposed. The sequence current components like positive and negative sequence currents are used as fault indicators and given as inputs to fuzzy fault detector. Also, the fuzzy inference system is created and rule base is evaluated, relating the sequence current component to the type of faults. These rules are fired for specific changes in sequence current component and the faults are detected. The feasibility of the proposed scheme for permanent magnet synchronous generator is demonstrated for different types of fault under various operating conditions using MATLAB/Simulink.

  15. Classification of three-generation models on magnetized orbifolds

    CERN Document Server

    Abe, Tomo-hiro; Kobayashi, Tatsuo; Miura, Takashi; Nishiwaki, Kenji; Sakamoto, Makoto; Tatsuta, Yoshiyuki

    2015-01-01

    We classify the combinations of parameters which lead three generations of quarks and leptons in the framework of magnetized twisted orbifolds on $T^2/Z_2$, $T^2/Z_3$, $T^2/Z_4$ and $T^2/Z_6$ with allowing nonzero discretized Wilson line phases and Scherk-Schwarz phases. We also analyze two actual examples with nonzero phases leading to one-pair Higgs and five-pair Higgses and discuss the difference from the results without nonzero phases studied previously.

  16. Tokamak with in situ magnetohydrodynamic generation of toroidal magnetic field

    Science.gov (United States)

    Schaffer, Michael J.

    1986-01-01

    A tokamak apparatus includes an electrically conductive metal pressure vessel for defining a chamber and confining liquid therein. A liner disposed within said chamber defines a toroidal space within the liner and confines gas therein. The metal vessel provides an electrically conductive path linking the toroidal space. Liquid metal is forced outwardly through the chamber outside of the toroidal space to generate electric current in the conductive path and thereby generate a toroidal magnetic field within the toroidal space. Toroidal plasma is developed within the toroidal space about the major axis thereof.

  17. Precise Thermometry for Next Generation LHC Superconducting Magnet Prototypes

    CERN Document Server

    Datskov, V; Bottura, L; Perez, J C; Borgnolutti, F; Jenninger, B; Ryan, P

    2013-01-01

    The next generation of LHC superconducting magnets is very challenging and must operate in harsh conditions: high radiation doses in a range between 10 and 50 MGy, high voltage environment of 1 to 5 kV during the quench, dynamic high magnetic field up to 12 T, dynamic temperature range 1.8 K to 300 K in 0.6 sec. For magnet performance and long term reliability it is important to study dynamic thermal effects, such as the heat flux through the magnet structure, or measuring hot spot in conductors during a magnet quench with high sampling rates above 200 Hz. Available on the market cryogenic temperature sensors comparison is given. An analytical model for special electrically insulating thermal anchor (Kapton pad) with high voltage insulation is described. A set of instrumentation is proposed for fast monitoring of thermal processes during normal operation, quenches and failure situations. This paper presents the technology applicable for mounting temperature sensors on high voltage superconducting (SC) cables....

  18. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, Nathaniel J

    2014-01-08

    I. Grant Objective The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereasthefficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  19. Controlling the magnetic field distribution on the micrometer scale and generation of magnetic bead patterns for microfluidic applications.

    Science.gov (United States)

    Yu, Xu; Feng, Xuan; Hu, Jun; Zhang, Zhi-Ling; Pang, Dai-Wen

    2011-04-19

    As is well known, controlling the local magnetic field distribution on the micrometer scale in a microfluidic chip is significant and has many applications in bioanalysis based on magnetic beads. However, it is a challenge to tailor the magnetic field introduced by external permanent magnets or electromagnets on the micrometer scale. Here, we demonstrated a simple approach to controlling the local magnetic field distribution on the micrometer scale in a microfluidic chip by nickel patterns encapsulated in a thin poly(dimethylsiloxane) (PDMS) film under the fluid channel. With the precisely controlled magnetic field, magnetic bead patterns were convenient to generate. Moreover, two kinds of fluorescent magnetic beads were patterned in the microfluidic channel, which demonstrated that it was possible to generate different functional magnetic bead patterns in situ, and could be used for the detection of multiple targets. In addition, this method was applied to generate cancer cell patterns.

  20. Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath

    Science.gov (United States)

    Kato, Yoshiaki; Steiner, Oskar; Hansteen, Viggo; Gudiksen, Boris; Wedemeyer, Sven; Carlsson, Mats

    2016-08-01

    Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab “pump” the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in the chromosphere and higher tends to oscillate with a period of ν ≈ 4 mHz. We conclude that this process of “magnetic pumping” is a most plausible mechanism for the direct generation of longitudinal chromospheric and coronal compressive waves within magnetic flux concentrations, and it may provide an important heat source in the chromosphere. It may also be responsible for certain types of dynamic fibrils.

  1. FLASH magnetohydrodynamic simulations of shock-generated magnetic field experiments

    Science.gov (United States)

    Tzeferacos, P.; Fatenejad, M.; Flocke, N.; Gregori, G.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Scopatz, A.; Weide, K.

    2012-12-01

    We report the results of benchmark FLASH magnetohydrodynamic (MHD) simulations of experiments conducted by the University of Oxford High Energy Density Laboratory Astrophysics group and its collaborators at the Laboratoire pour l'Utilisation des Lasers Intenses (LULI). In these experiments, a long-pulse laser illuminates a target in a chamber filled with Argon gas, producing shock waves that generate magnetic fields via the Biermann battery mechanism. We first outline the implementation of 2D cylindrical geometry in the unsplit MHD solver in FLASH and present results of verification tests. We then describe the results of benchmark 2D cylindrical MHD simulations of the LULI experiments using FLASH that explore the impact of external fields along with the possibility of magnetic field amplification by turbulence that is associated with the shock waves and that is induced by a grid placed in the gas-filled chamber.

  2. Investigation on factors affecting reverse flow in inverted U-tubes of steam generator under natural circulation

    International Nuclear Information System (INIS)

    For natural circulation, it is shown that reverse flow occurs in the inverted U-tubes of steam generator (SG) at certain low power levels. A flow model based on one-dimensional Oberbeck-Boussinesq equation was formulated to analyze this phenomenon. Two SGs of different scales were calculated. The results show that the reverse flow phenomenon occurs easily in the shorter U-tubes in small SG. but the phenomenon occurs easily in the longer U-tubes in large SG. The inlet temperature has great influence on the occurrence of reverse flow. (authors)

  3. Magnetic field generation in fully convective rotating spheres

    CERN Document Server

    Dobler, W; Brandenburg, A

    2004-01-01

    Magnetohydrodynamic simulations of fully convective, rotating spheres with volume heating near the center and cooling at the surface are presented. The dynamo-generated magnetic field saturates at equipartition field strength near the surface. In the interior, the field is dominated by small-scale structures, but outside the sphere by the global scale. Azimuthal averages of the field reveal a large-scale field of smaller amplitude also inside the star. The internal angular velocity shows some tendency to be constant along cylinders and is ``anti-solar'' (fastest at the poles and slowest at the equator).

  4. Magnetic field generation during intense laser channelling in underdense plasma

    Science.gov (United States)

    Smyth, A. G.; Sarri, G.; Vranic, M.; Amano, Y.; Doria, D.; Guillaume, E.; Habara, H.; Heathcote, R.; Hicks, G.; Najmudin, Z.; Nakamura, H.; Norreys, P. A.; Kar, S.; Silva, L. O.; Tanaka, K. A.; Vieira, J.; Borghesi, M.

    2016-06-01

    Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.

  5. Design of High Performance Permanent-Magnet Synchronous Wind Generators

    Directory of Open Access Journals (Sweden)

    Chun-Yu Hsiao

    2014-11-01

    Full Text Available This paper is devoted to the analysis and design of high performance permanent-magnet synchronous wind generators (PSWGs. A systematic and sequential methodology for the design of PMSGs is proposed with a high performance wind generator as a design model. Aiming at high induced voltage, low harmonic distortion as well as high generator efficiency, optimal generator parameters such as pole-arc to pole-pitch ratio and stator-slot-shoes dimension, etc. are determined with the proposed technique using Maxwell 2-D, Matlab software and the Taguchi method. The proposed double three-phase and six-phase winding configurations, which consist of six windings in the stator, can provide evenly distributed current for versatile applications regarding the voltage and current demands for practical consideration. Specifically, windings are connected in series to increase the output voltage at low wind speed, and in parallel during high wind speed to generate electricity even when either one winding fails, thereby enhancing the reliability as well. A PMSG is designed and implemented based on the proposed method. When the simulation is performed with a 6 Ω load, the output power for the double three-phase winding and six-phase winding are correspondingly 10.64 and 11.13 kW. In addition, 24 Ω load experiments show that the efficiencies of double three-phase winding and six-phase winding are 96.56% and 98.54%, respectively, verifying the proposed high performance operation.

  6. Generation of Alfvenic Waves and Turbulence in Magnetic Reconnection Jets

    Science.gov (United States)

    Hoshino, M.

    2014-12-01

    The magneto-hydro-dynamic (MHD) linear stability for the plasma sheet with a localized bulk plasma flow parallel to the neutral sheet is investigated. We find three different unstable modes propagating parallel to the anti-parallel magnetic field line, and we call them as "streaming tearing'', "streaming sausage'', and "streaming kink'' mode. The streaming tearing and sausage modes have the tearing mode-like structure with symmetric density fluctuation to the neutral sheet, and the streaming kink mode has the asymmetric fluctuation. The growth rate of the streaming tearing mode decreases with increasing the magnetic Reynolds number, while those of the streaming sausage and kink modes do not strongly depend on the Reynolds number. The wavelengths of these unstable modes are of the order of the thickness of plasma sheet, which behavior is almost same as the standard tearing mode with no bulk flow. Roughly speaking the growth rates of three modes become faster than the standard tearing mode. The situation of the plasma sheet with the bulk flow can be realized in the reconnection exhaust with the Alfvenic reconnection jet, and the unstable modes may be regarded as one of the generation processes of Alfvenic turbulence in the plasma sheet during magnetic reconnection.

  7. Design of a Ferrite Permanent Magnet Rotor for a Wind Power Generator

    OpenAIRE

    Eklund, Petter

    2013-01-01

    Due to the insecurity of the supply of raw materials needed for neodymium-iron-boron magnets, typically used in permanent magnet generators, the use of ferrite magnets as an alternative was investigated. The investigation was conducted by attempting to redesign a generator that previously used neodymium-iron-boron magnets for use with ferrite magnets. The major part of the redesign was to find an alternate rotor design with an electromagnetic design adapted to the characteristics of the ferri...

  8. A hybrid fuzzy logic and extreme learning machine for improving efficiency of circulating water systems in power generation plant

    Science.gov (United States)

    Aziz, Nur Liyana Afiqah Abdul; Siah Yap, Keem; Afif Bunyamin, Muhammad

    2013-06-01

    This paper presents a new approach of the fault detection for improving efficiency of circulating water system (CWS) in a power generation plant using a hybrid Fuzzy Logic System (FLS) and Extreme Learning Machine (ELM) neural network. The FLS is a mathematical tool for calculating the uncertainties where precision and significance are applied in the real world. It is based on natural language which has the ability of "computing the word". The ELM is an extremely fast learning algorithm for neural network that can completed the training cycle in a very short time. By combining the FLS and ELM, new hybrid model, i.e., FLS-ELM is developed. The applicability of this proposed hybrid model is validated in fault detection in CWS which may help to improve overall efficiency of power generation plant, hence, consuming less natural recourses and producing less pollutions.

  9. Magnetic Simulation and Analysis of Radial Flux Permanent Magnet Generator using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Pudji Irasari

    2012-07-01

    Full Text Available This paper discusses magnetic simulation and analysis of radial flux permanent magnet generator (PMG using finite element method (FEM by utilizing open source software FEMM 4.2. The specification of generator is 25 V, 28 A, 3 phase, 300 rpm. The analyzed magnetic flux was in the air gap, stator teeth and slots to find out the distribusian pattern and its fluctuation. The simulations were conducted in no-load and nominal load (28 A conditions. Furthermore the maximum flux density of simulation (Bg(sim was used to calculate phase voltage Eph to find out the magnitude of generated electromotive force (EMF. The calculation results were presented as voltage vs. rotation graph in no-load condition and voltage vs. current graph in nominal load condition. Both graphs were validated with Eph of experiment result (Eph(exp and Eph that the value of Bg obtained from analytical calculation (Eph(calc. The final results showed that in no-load condition, Eph graph with Bg(sim (Eph(sim was close to Eph(exp and Eph(calc. The error rate with respect to the experiment was 6,9%. In nominal load condition, Eph(sim graph almost coincides with Eph(calc. graph, with the voltage drop of both was 0,441 V. Both graphs however were far different from Eph(exp graph, which has 9 V of voltage drop. The overall results demonstrated that magnetic distribution pattern presented by FEM was very helpful to avoid magnetic flux accumulation in a particular segment. Besides Bg(sim facilitated to predict the value of Eph.

  10. Giga-Gauss scale quasistatic magnetic field generation in an 'escargot' target

    CERN Document Server

    Korneev, Ph; Tikhonchuk, V

    2014-01-01

    A simple setup for the generation of ultra-intense quasistatic magnetic fields, based on the generation of electron currents with a predefined geometry in a curved 'escargot' target, is proposed and analysed. Particle-In-Cell simulations and qualitative estimates show that giga-Gauss scale magnetic fields may be achieved with existent laser facilities. The described mechanism of the strong magnetic field generation may be useful in a wide range of applications, from laboratory astrophysics to magnetized ICF schemes.

  11. POWER GENERATION USING MEGNETOHYDRODYNAMIC GENERATOR WITH A CIRCULATION FLOW DRIVEN BY SOLAR-HEAT-INDUCED NATURAL CONVECTION

    Science.gov (United States)

    The project team has theoretically studied the mechanism of magnetohydrodynamic generator, the coupling of heat transfer and buoyancy-driven free convection, and radiation heat transfer. A number of ideas for the projects have been brainstormed in the team. The underline physi...

  12. Delaunay mesh generation for an unstructured-grid ocean general circulation model

    OpenAIRE

    Legrand, S.; Legat, V.; E. Deleersnijder

    2000-01-01

    An incremental method is presented to generate automatically boundary-fitted Delaunay triangulations of the global ocean. The method takes into account Earth curvature and allows local mesh refinement in order to resolve topological or dynamical features like midocean ridges or western boundary currents. Crucial issues like the nodes insertion process, the boundary integrity problem or the creation of inner nodes are explained. Finally, the quality of generated triangulations is discussed.

  13. Concentrated Windings in Compact Permanent Magnet Synchronous Generators: Managing Efficiency

    Directory of Open Access Journals (Sweden)

    Olivier Barré

    2016-01-01

    Full Text Available In electric power generation, customers want generators with high efficiency. Nowadays, modern turbo-generators have efficiencies greater than 98%. Although this amount should not be obtained for all kind of machines, efficiency will remain one of the main parameters for customer choice. Efficiency is also linked to the life of the machine: the higher the efficiency is, the longer the machine’s lifetime. During the past decade, new forms of energy production have appeared and generators have been developed to fit well into this market. For example, wind generators evolved towards permanent magnet generators having high polarity and running at low speed. Nevertheless, their structure is not fixed. An industrial company has built a prototype of such a generator which uses fractional-slot concentrated-windings (FSCW. This kind of winding is not the structure used by default in such electrical machines. Another field of interest is in autonomous generators which can be used on boats. Even if everyone has in mind large merchant ships, we must not forget smaller ships, such as fishing boats and short-range cruise ships, which spend the most of their time near the coast. This kind of ship does nothave large areas for installing the electric generation or the electric propulsion. It is the reason why, in this article, we focus on the efficiency of machines using fractional-slot concentrated-windings. In many publications which compare performances between distributed and concentrated windings, the result is almost the same. The efficiency of FSCW is not as high as the efficiency associated to the machines which are using distributed windings. Design methods have to be redrawn to integrate, as soon as possible, the loss mitigation in order to provide the best efficiency in power conversion. The following discussion, step by step, introduces the loss mitigation in every part of a machine using FSCW. To close the discussion, a design is produced and it

  14. Design considerations for permanent magnet direct drive generators for wind energy applications

    NARCIS (Netherlands)

    Jassal, A.K.; Polinder, H.; Damen, M.E.C.; Versteegh, K.

    2012-01-01

    Permanent Magnet Direct Drive (PMDD) generators offer very high force density, high efficiency and low number of components. Due to these advantages, PMDD generators are getting popular in the wind energy industry especially for offshore application. Presence of permanent magnets gives magnetic fiel

  15. The use of mirror image symmetry in coil winding, applications and advantages in magnetic field generation

    International Nuclear Information System (INIS)

    In this paper, an improved method of winding inductors, transformers and motors is discovered. This invention greatly enhances the ability to generate magnetic fields with a given amount of wire. This invention may be as fundamental to the use of magnetic fields as was Nikola Tesla's use of rotating magnetic fields for the generation of alternating current

  16. Mercury's thermal history and the generation of its magnetic field

    International Nuclear Information System (INIS)

    Thermal history of Mercury's interior is examined using the model of Stevenson et al. (1983), extended to include the effects of tidal heating in Mercury's solid inner core. The implications of Mercury's thermal history for the source of the planet's magnetic field are discussed. It is shown that the major results of this model are similar to the results obtained with the Stevenson et al. model, except for the addition of inner-core tidal dissipation. It is concluded that the extended model properly characterizes Mercury's internal structure and thermal history, and that the criteria for dynamo generation are not properly satisfied. Alternative explanations, including the possibility of a weak thermoelectric dynamo, are examined

  17. Magnetic-Field Generation by Randomly Forced Shearing Waves

    CERN Document Server

    Schekochihin, A A; Kleeorin, N; Lesur, G; Mallet, A; McWilliams, J C; Rogachevskii, I; Yousef, T A

    2008-01-01

    A rigorous theory for the generation of a large-scale magnetic field by random nonhelically forced motions of a conducting fluid combined with a linear shear is presented in the analytically tractable limit of Rm << Re << 1. This is a minimal proof-of-concept calculation aiming to put the shear dynamo, a new effect recently reported in a number of numerical experiments, on a firm physical and analytical footing. Numerically observed scalings of the wavenumber and growth rate of the fastest growing mode, previously not understood, are derived analytically. The simplicity of the model suggests that shear dynamo may be a generic property of shear flows -- with ubiquitous relevance to astrophysical systems.

  18. Generation of scale invariant magnetic fields in bouncing universes

    CERN Document Server

    Sriramkumar, L; Jain, Rajeev Kumar

    2015-01-01

    We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic fields can arise {\\it before the bounce} for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape {\\it after the bounce}. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the ${\\rm e}$-${\\cal N}$-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and eva...

  19. Design and analysis of permanent magnet moving coil type generator used in a micro-CHP generation system

    Science.gov (United States)

    Oros Pop, Susana Teodora; Berinde, Ioan; Vadan, Ioan

    2015-12-01

    This paper presents the design and analysis of a permanent magnet moving coil type generator driven by a free piston Stirling engine. This assemble free piston Stirling engine - permanent magnet moving coil type generator will be used in a combined heat and power (CHP) system for producing heat and power in residential area. The design procedure for moving coil type linear generator starts from the rated power imposed and finally uses the Faraday law of induction. The magneto-static magnetic field generated by permanent magnets is analyzed by means of Reluctance method and Finite Element Method in order to evaluate the magnetic flux density in the air gap, which is a design data imposed in the design stage, and the results are compared.

  20. [Lung cancer molecular testing, what role for Next Generation Sequencing and circulating tumor DNA].

    Science.gov (United States)

    Pécuchet, Nicolas; Legras, Antoine; Laurent-Puig, Pierre; Blons, Hélène

    2016-01-01

    Molecular screening has become a standard of care for patients with advanced cancers and impacts on how to treat a patient. Advances in genomic technologies with the development of high throughput sequencing methods will certainly improve the possibilities to access a more accurate molecular diagnosis and to go beyond the identification of validated targets as a large number of genes can be screened for actionable changes. Moreover, accurate high throughput testing may help tumor classification in terms of prognosis and drug sensitivity. Finally, it will be possible to assess tumor heterogeneity and changes in molecular profiles during follow-up using ultra-deep sequencing technologies and circulating tumor DNA characterization. The accumulation of somatic ADN alterations is considered as the main contributing factor in carcinogenesis. The alterations can occur at different levels: mutation, copy number variations or gene translocations resulting in altered expression of the corresponding genes or impaired protein functions. Genes involved are mainly tumor suppressors, oncogenes or ADN repair genes whose modifications in tumors will impinge cell fate and proliferation from tumor initiation to metastasis. The entire genome of various tumor types, have now been sequenced. In lung cancer, the average number of mutations is very high with more than 8.9 mutations/Mb (Network TCGAR, 2014) that is to say more than 10,000 mutations/genome. These alterations need to be classified, indeed, some are true drivers that directly impact proliferation and some are passenger mutations linked to genetic instability. The development of targeted therapies relies on the identification of oncogenic drivers. The identification of genotype-phenotype associations as in the case of EGFR-TKI (Epidermal growth factor receptor-tyrosine kinase inhibitor) and EGFR mutations in lung cancer led to the restriction of drugs to patients for which tumor genotype predicts efficacy. Tumor

  1. [Lung cancer molecular testing, what role for Next Generation Sequencing and circulating tumor DNA].

    Science.gov (United States)

    Pécuchet, Nicolas; Legras, Antoine; Laurent-Puig, Pierre; Blons, Hélène

    2016-01-01

    Molecular screening has become a standard of care for patients with advanced cancers and impacts on how to treat a patient. Advances in genomic technologies with the development of high throughput sequencing methods will certainly improve the possibilities to access a more accurate molecular diagnosis and to go beyond the identification of validated targets as a large number of genes can be screened for actionable changes. Moreover, accurate high throughput testing may help tumor classification in terms of prognosis and drug sensitivity. Finally, it will be possible to assess tumor heterogeneity and changes in molecular profiles during follow-up using ultra-deep sequencing technologies and circulating tumor DNA characterization. The accumulation of somatic ADN alterations is considered as the main contributing factor in carcinogenesis. The alterations can occur at different levels: mutation, copy number variations or gene translocations resulting in altered expression of the corresponding genes or impaired protein functions. Genes involved are mainly tumor suppressors, oncogenes or ADN repair genes whose modifications in tumors will impinge cell fate and proliferation from tumor initiation to metastasis. The entire genome of various tumor types, have now been sequenced. In lung cancer, the average number of mutations is very high with more than 8.9 mutations/Mb (Network TCGAR, 2014) that is to say more than 10,000 mutations/genome. These alterations need to be classified, indeed, some are true drivers that directly impact proliferation and some are passenger mutations linked to genetic instability. The development of targeted therapies relies on the identification of oncogenic drivers. The identification of genotype-phenotype associations as in the case of EGFR-TKI (Epidermal growth factor receptor-tyrosine kinase inhibitor) and EGFR mutations in lung cancer led to the restriction of drugs to patients for which tumor genotype predicts efficacy. Tumor

  2. Coolant stratification and its thermohydrodynamic specificity under natural circulation in horizontal steam generator collectors

    Energy Technology Data Exchange (ETDEWEB)

    Blagovechtchenski, A.; Leontieva, V.; Mitriukhin, A. [Saint-Petersburg Technical Univ. (Russian Federation)

    1997-12-31

    The experiments and the test facilities for the study of the stratification phenomenon in the hot plenum of reactor and the upper parts of the steam generator collectors in a nuclear power plant are described. The aim of the experiments was to define the conditions of the stratification initiation, to study the temperature field in the upper part, the definition of the characteristics in the stratification layer, and also to study the factors which cause the intensity of the stagnant volume cooling.

  3. Innovative Method Using Magnetic Particle Tracking to Measure Solids Circulation in a Spouted Bed

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, Ms. Emily [Waynesburg University; Halow, John [Waynesburg University; Daw, C Stuart [ORNL

    2010-01-01

    We describe an innovative method for measuring particle motion inside spouted fluidized beds. The method uses a magnetic tracer particle, which follows the bulk particle flow and is continuously tracked by multiple magnetic field detectors located outside the bed. We analyze signals from the detectors to determine the tracer position at each instant in time. From statistical analysis of the tracer trajectory, characteristic measures of the bulk particle flow, such as the average recirculation frequency, can be determined as a function of operating conditions. For experiments with a range of particle sizes and densities in a 3.9-cm-diameter spouted bed, we find that average solids recirculation rates correlate with excess velocity (superficial minus minimum spouting velocity), particle density, and bed depth.

  4. Innovative method using magnetic particle tracking to measure solids circulation in a spouted fluidized bed

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, Ms. Emily [Waynesburg University; Halow, John [Waynesburg University; Daw, C Stuart [ORNL

    2009-01-01

    We describe an innovative method for measuring particle motion inside spouted fluidized beds. The method uses a magnetic tracer particle, which follows the bulk particle flow and is continuously tracked by multiple magnetic field detectors located outside the bed. We analyze signals from the detectors to determine the tracer position at each instant in time. From statistical analysis of the tracer trajectory, characteristic measures of the bulk particle flow, such as the average recirculation frequency, can be determined as a function of operating conditions. For experiments with a range of particle sizes and densities in a 3.9-cm-diameter spouted bed, we find that average solids recirculation rates correlate with excess velocity (superficial minus minimum spouting velocity), particle density, and bed depth.

  5. The study, design and testing of a linear oscillating generator with moving permanent magnets

    Directory of Open Access Journals (Sweden)

    Teodora Susana Oros (Pop

    2015-12-01

    Full Text Available This paper presents a study, design and testing of a Linear Oscillating Generator. There are presented the main steps of the magnetic and electric calculations for a permanent magnet linear alternator of fixed coil and moving magnets type. Finally it has been shown the comparative analysis between the linear oscillating generator with moving permanent magnets in no load operation and load operation.

  6. Magnetic field generation by short ultraintense laser pulse in underdense plasmas

    International Nuclear Information System (INIS)

    The theory of magnetic field generation due to the interaction of short relativistic laser pulses with underdense plasmas has been developed. The magnetic field is generated due to the inverse Faraday effect occurring with a circularly polarized laser pulse. The spatial distribution of the magnetic field is investigated. It is shown that the magnetic field magnitude depends on the relationship between the laser beam radius and the plasma skin-depth. (Author)

  7. Magnetic Field Effect on Natural Convection Flow with Internal Heat Generation using Fast  –  Method

    Directory of Open Access Journals (Sweden)

    M.A. Taghikhani

    2015-01-01

    Full Text Available The magnetic field effect on laminar natural convection flow is investigated in a filled enclosure with internal heat generation using two-dimensional numerical simulation. The enclosure is heated by a uniform volumetric heat density and walls have constant temperature. A fixed magnetic field is applied to the enclosure. The dimensionless governing equations are solved numerically for the stream function, vorticity and temperature using finite difference method for various Rayleigh (Ra and Hartmann (Ha numbers in MATLAB software. The stream function equation is solved using fast Poisson's equation solver on a rectangular grid (POICALC function in MATLAB, voricity and temperature equations are solved using red-black Gauss-Seidel and bi-conjugate gradient stabilized (BiCGSTAB methods respectively. The results show that the strength of the magnetic field has significant effects on the flow and temperature fields. For the square cavity, the maximum temperature reduces with increasing Ra number. It is also observed that at low Ra number, location of the maximum temperature is at the centre of the cavity and it shifts upwards with increase in Ra number. Circulation inside the enclosure and therefore the convection becomes stronger as the Ra number increases while the magnetic field suppresses the convective flow and the heat transfer rate. The ratio of the Lorentz force to the buoyancy force (Ha2/Ra is as an index to compare the contribution of natural convection and magnetic field strength on heat transfer.

  8. Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse

    CERN Document Server

    von der Pahlen, J Graf

    2014-01-01

    The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed $X$-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the $X$-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar struct...

  9. Novel circulating peptide biomarkers for esophageal squamous cell carcinoma revealed by a magnetic bead-based MALDI-TOFMS assay.

    Science.gov (United States)

    Jia, Kun; Li, Wei; Wang, Feng; Qu, Haixia; Qiao, Yuanyuan; Zhou, Lanping; Sun, Yulin; Ma, Qingwei; Zhao, Xiaohang

    2016-04-26

    Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant neoplasms worldwide. Patients are often diagnosed at advanced stages with poor prognosis due to the absence of obvious early symptoms. Here, we applied a high-throughput serum peptidome analysis to identify circulating peptide markers of ESCC. Weak cationic exchange magnetic beads coupled to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used for two-stage proteotypic peptide profiling in complex serum samples collected from 477 cancer patients and healthy controls. We established a genetic algorithm model containing three significantly differentially expressed peptides at 1,925.5, 2,950.6 and 5,900.0 Da with a sensitivity and specificity of 97.00% and 95.92% in the training set and 97.03% and 100.00% in the validation set, respectively. The model's diagnostic capability was significantly better than SCC-Ag and Cyfra 21-1, especially for early stage ESCC, with an achieved sensitivity of 96.94%. Subsequently, these peptides were identified as fragments of AHSG, TSP1 and FGA by linear ion trap-orbitrap hybrid tandem mass spectrometry. Notably, increased tissue and serum levels of TSP1 in ESCC were verified and correlated with disease progression. In addition, tissue TSP1 was an independent poor prognostic factor in ESCC. In conclusion, the newly established circulating peptide panel and identified proteins could serve as potential biomarkers for the early detection and diagnosis of ESCC. Nevertheless, a larger cohort will be required for further unequivocal validation of their clinical application. PMID:26993605

  10. Generation of a large-scale barotropic circulation in rotating convection

    Science.gov (United States)

    Rubio, Antonio; Julien, Keith; Weiss, Jeffrey

    2012-11-01

    We recently reported on the existence of a slow-growing large scale barotropic mode in DNS of rotating Rayleigh-Benard convection using the non-hydrostatic balanced geostrophic equations (NHBGE) (Julien et al. 2012). Such large scale modes had been previously observed as an inverse cascade in stable layer quasi-geostophic dynamics or via instability mechanisms of thermal Rossby waves occuring in presence of sloping endwalls (i.e quasi-geostrophic beta-convection). In this talk we report on the early time history of this large scale mode and discuss the generating physical mechanism as a ``symmetry-breaking'' forcing function of the barotropic vorticity equation. Impacts of the large scale barotropic mode on the smaller scale baroclinic components of the flow are detailed with a specific emphasis on the changing nature of the heat transport as the barotropic mode evolves. This work was supported by the National Science Foundation under FRG grants DMS-0855010 and DMS-0854841. Computational resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS).

  11. Generation of free convection due to changes of the local circulation system

    Directory of Open Access Journals (Sweden)

    T. Foken

    2009-11-01

    Full Text Available Eddy-covariance and Sodar/RASS experimental measurement data of the COPS (Convective and Orographically-induced Precipitation Study field campaign 2007 are used to investigate the generation of near-ground free convection conditions (FCCs in the Kinzig valley, Black Forest, Southwest Germany. The measured high-quality turbulent flux data revealed that FCCs are initiated near the ground in situations where moderate to high buoyancy fluxes and a simultaneously occurring drop of the wind speed were present. The minimum in wind speed – observable by the Sodar measurements through the whole vertical extension of the valley atmosphere – is the consequence of a thermally-induced valley wind system, which changes its wind direction from down to up-valley winds in the morning hours. Buoyancy then dominates over shear within the production of turbulence kinetic energy near the ground. These situations are detected by the stability parameter (ratio of the measurement height to the Obukhov length when the level of free convection, which starts above the Obukhov length, drops below that of the sonic anemometer. An analysis of the scales of turbulent motions during FCCs using wavelet transform shows the occurrence of large-scale turbulence structures. Regarding the entire COPS measurement period, FCCs in the morning hours occur on about 50% of all days. Enhanced surface fluxes of latent and sensible heat are found on these days.

  12. Generating buoyant magnetic flux ropes in solar-like convective dynamos

    CERN Document Server

    Nelson, Nicholas J

    2014-01-01

    Our Sun exhibits strong convective dynamo action which results in magnetic flux bundles emerging through the stellar surface as magnetic spots. Global-scale dynamo action is believed to generate large-scale magnetic structures in the deep solar interior through the interplay of convection, rotation, and shear. Portions of these large-scale magnetic structures are then believed to rise through the convective layer, forming magnetic loops which then pierce the photosphere as sunspot pairs. Previous global simulations of 3D MHD convection in rotating spherical shells have demonstrated mechanisms whereby large-scale magnetic wreaths can be generated in the bulk of the convection zone. Our recent simulations have achieved sufficiently high levels of turbulence to permit portions of these wreaths to become magnetically buoyant and rise through the simulated convective layer through a combination of magnetic buoyancy and advection by convective giant cells. These buoyant magnetic loops are created in the bulk of the...

  13. High magnetic field generation for laser-plasma experiments

    International Nuclear Information System (INIS)

    An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system supplying 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented

  14. A 3 T magnetic field generator using melt-processed bulk superconductors as trapped field magnets and its applications

    International Nuclear Information System (INIS)

    An intense magnetic field generator yielding 3.15 T in the open space between the magnetic poles has been constructed by using a pair of melt-processed bulk superconductors as trapped field magnets. The field was measured in a 2 mm gap between the magnetic poles set face-to-face after the pulsed-field magnetization 'IMRA' method. This field generator is composed of Sm-based 123 compounds, vacuum pumps, pulsed-field coils and GM refrigerators with compressors. The system can be used in various applications. We investigated, for instance, the application to a high gradient magnetic separation system. It was found that the alpha hematite fine particles mixed in the flowing water was completely removed by this technique which was operated in the field of 1.7 T in the gap of 20 mm

  15. Experimental studies of axial magnetic fields generated in ultrashort-pulse laser-plasma interaction

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The quasistatic axial magnetic fields in plasmas produced by ultrashort laser pulses were measured by measuring the Faraday rotation angle of the backscattered emission. The spatial distribution of the axial magnetic field was obtained with a peak value as high as 170 Tesla. Theory suggests that the axial magnetic field is generated by dynamo effect in laser-plasma interaction.

  16. Design of a Permanent Magnet Synchronous Generator for a Vertical Axis Wind Turbine

    OpenAIRE

    Madani, Nima

    2011-01-01

    Different types of permanent magnet generators for wind power application have been subject of research during last two decades. In this thesis different topologies of electrical generators have been investigated for small scale vertical axis wind turbine application. A two stage induction generator is proposed as a alternative solution with respect to the cost of such a system. However, a biggest emphasis in the report has been put on the design of Permanent Magnet Synchronous Generator (PMS...

  17. Melatonin rhythm onset in the adult siberian hamster: influence of photoperiod but not 60-Hz magnetic field exposure on melatonin content in the pineal gland and in circulation.

    Science.gov (United States)

    Yellon, S M; Truong, H N

    1998-02-01

    To determine the relationship between pineal melatonin production and its appearance in circulation, the rising phase of the pineal and serum melatonin rhythm was studied in the adult Siberian hamster. Melatonin concentrations increased in the pineal gland and in serum at 1.50 and 1.75 h, respectively, relative to lights off in long days (16 h of light/day) and at 2.00 and 2.75 h, respectively, in short days (10 h of light/day). Thus, a photoperiod-dependent melatonin rise in circulation lagged production by the pineal gland by 0.50 h--a delay of 0.75 h in short-day hamsters versus 0.25 h in long-day hamsters. Following initiation of this rise, concentrations that were typical of the nighttime peak were achieved within 2 h of melatonin rhythm onset, regardless of photoperiod. To determine whether clock control of the rising phase of the melatonin rhythm, in the absence of photoperiod cues, may be disrupted by perturbations in the ambient magnetic field, hamsters in constant darkness were acutely exposed to a 1-Gauss, 60-Hz magnetic field for 15 min or were daily exposed to this treatment for 14 or 21 days. Neither the melatonin rise in pineal content or circulation during subjective night was affected by acute or chronic magnetic field exposures; testes regression similarly occurred in sham and daily magnetic field-exposed hamsters in constant darkness. These findings indicate that magnetic field exposures are unlikely to serve as a zeitgeber for the circadian mechanism that controls onset of the melatonin rhythm; rather, photoperiod is a predominant cue that may differentially regulate the rising phase of melatonin production in the pineal gland and concentration in circulation.

  18. Self-generation mechanisms of intense magnetic fields in laser produced plasmas on solid targets

    International Nuclear Information System (INIS)

    Mechanisms of magnetic field self-generation in laser produced plasma are presented. Magnetic field generation due to the thermoelectric sources (Vnsub(e) x VTsub(e)), resonance absorption, ponderomotive forces, some kind of instabilities (modulational, Weibel, Rayleigh-Taylor instabilities) is considered. Estimates or scaling laws for parameters typical for current experiments are given. (author)

  19. The Generation of Magnetic Field by Transverse Plasmons in Laser-Produced Plasma

    Institute of Scientific and Technical Information of China (English)

    LIU Shan-qiu; LI Xiao-qing

    2000-01-01

    In this paper, it is studied that a quasi-steady magnetic field could be generated in laser-producde plasmas with high-frequency electromagnetic radiation through wave-wave and wave-partide interactions in the vicinity of critical point. The behavior of self-generated magnetic field can be described by nonlinear coupling equatiom.

  20. The role of current loop in harmonic generation from magnetic metamaterials in two polarizations

    CERN Document Server

    Sajedian, Iman; Zakery, Abdolnasser; Rho, Junsuk

    2016-01-01

    In this paper, we investigate the role of the current loop in the generation of second and third harmonic signals from magnetic metamaterials. We will show that the fact that the current loop in the magnetic resonance acts as a source for nonlinear effects and it consists of two orthogonal parts, leads to the generation of two harmonic signals in two orthogonal polarizations.

  1. Improved cost of energy comparison of permanent magnet generators for large offshore wind turbines

    NARCIS (Netherlands)

    Hart, K.; McDonald, A.; Polinder, H.; Corr, E.; Carroll, J.

    2014-01-01

    This paper investigates geared and direct-drive permanent magnet generators for a typical offshore wind turbine, providing a detailed comparison of various wind turbine drivetrain configurations in order to minimise the Cost of Energy. The permanent magnet generator topologies considered include a d

  2. Circulating Glutamate and Taurine Levels Are Associated with the Generation of Reactive Oxygen Species in Paroxysmal Atrial Fibrillation

    Directory of Open Access Journals (Sweden)

    Shintaro Takano

    2016-01-01

    Full Text Available Atrial fibrillation (AF is the most common cardiac arrhythmia, but its proarrhythmic mechanism remains to be elucidated. Glutamate (Glu and taurine (Tau are present in the myocardium at substantially higher concentrations than in the plasma, suggesting their active role in myocardium. Here, we tested the hypothesis that the metabolism of Glu and Tau is altered in association with the generation of reactive oxygen species (ROS in patients with AF. Fifty patients with paroxysmal AF and 50 control subjects without a history of AF were consecutively enrolled. Circulating Glu and Tau levels were measured and correlations between Glu/Tau and ROS levels were examined. Glu/Tau content was significantly higher in patients with AF versus controls (Glu: 79.2±23.9 versus 60.5±25.2 nmol/L; Tau: 78.8±19.8 versus 68.5±20.8 nmol/L; mean ± standard deviation (SD, p<0.001 for both. Glu/Tau levels also showed an independent association with AF by multiple logistic regression analysis. Glu and Tau levels both showed significant positive associations with plasma hydroperoxide concentrations. These data suggest a novel pathophysiological role of Glu and Tau in association with ROS production in paroxysmal AF, providing new insights into the elevated amino acid content in cardiac disease.

  3. Convectively Generated Gravity Waves In The Tropical Stratosphere: Case Studies And Importance For The Circulation Of The Middle Atmosphere

    Science.gov (United States)

    Pfister, Leonhard; Chan, Kwoklong R.; Gary, Bruce; Singh, Hanwant B. (Technical Monitor)

    1995-01-01

    The advent of high altitude aircraft measurements in the stratosphere over tropical convective systems has made it possible to observe the mesoscale disturbances in the temperature field that these systems excite. Such measurements show that these disturbances have horizontal scales comparable to those of the underlying anvils (about 50-100 km) with peak to peak theta surface variations of about 300-400 meters. Moreover, correlative wind measurements from the tropical phase of the Stratosphere-Troposphere Exchange Project (STEP) clearly show that these disturbances are gravity waves. We present two case studies of anvil-scale gravity waves over convective systems. Using steady and time-dependent linear models of gravity wave propagation in the stratosphere, we show: (1) that the underlying convective systems are indeed the source of the observed phenomena; and (2) that their generating mechanism can be crudely represented as flow over a time-dependent mountain. We will then discuss the effects gravity waves of the observed amplitudes have on the circulation of the middle atmosphere, particularly the quasi-biennial, and semiannual oscillations.

  4. Analysis on background magnetic field to generate eddy current by pulsed gradient of permanent-magnet MRI

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper the analytical expressions for the magnetic field H and induction B in iron-pole plates generated by MRI gradient coil are given using line-current and the multilayer dielectric plate model with the mirror-image method.Eddy current emanates from the magnetic flux in the iron-pole plates.In order to fully suppress the eddy current,this magnetic flux should be fully eliminated.The research results indicate the magnetic permeability of the resist-eddy plate must be bigger than that of magnetic pole material,i.e.pure iron,and that the resist-eddy plate should be thick enough to be far away from its magnetic saturation.

  5. A plasma generator utilizing the high intensity ASTROMAG magnets

    Science.gov (United States)

    Sullivan, James D.; Post, R. S.; Lane, B. G.; Tarrh, J. M.

    1986-01-01

    The magnet configuration for the proposed particle astrophysics magnet facility (ASTROMAG) on the space station includes a cusp magnetic field with an intensity of a few tesla. With these large magnets (or others) located in the outer ionosphere, many quite interesting and unique plasma physics experiments become possible. First there are studies utilizing the magnet alone to examine the supersonic, sub-Alfvenic interaction with the ambient medium; the scale length for the magnet perturbation is approx. 20 m. The magnetic field geometry when combined with the Earth's and their relative motion will give rise to a host of plasma phenomena: ring nulls, x-points, ion-acoustic and lower-hybrid shocks, electron heating (possible shuttle glow without a surface) launching of Alfvenwaves, etc. Second, active experiments are possible for a controlled study of fundamental plasma phenomena. A controlled variable species plasma can be made by using an RF ion source; use of two soft iron rings placed about the line cusp would give an adequate resonance zone (ECH or ICH) and a confining volume suitable for gas efficiency. The emanating plasma can be used to study free expansion of plasma along and across field lines (polar wind), plasma flows around the space platform, turbulent mixing in the wake region, long wavelength spectrum of convecting modes, plasma-dust interactions, etc.

  6. Dynamo-generated magnetic fields in fast rotating single giants

    CERN Document Server

    Konstantinova-Antova, Renada; Schröder, Klaus-Peter; Petit, Pascal

    2009-01-01

    Red giants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. Using the spectro-polarimeter NARVAL of the Telescope Bernard Lyot (TBL), Pic du Midi, France and the LSD technique, we began a survey of magnetic fields in single G-K-M giants. Early results include 6 MF-detections with fast rotating giants, and for the first time a magnetic field was detected directly in an evolved M-giant: EK Boo. Our results could be explained in the terms of $\\alpha$--$\\omega$ dynamo operating in these giants.

  7. Dynamo-generated magnetic fields in fast rotating single giants

    OpenAIRE

    Konstantinova-Antova, Renada; Aurière, Michel; Schröder, Klaus-Peter; Petit, Pascal

    2009-01-01

    Red giants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. Using the spectro-polarimeter NARVAL of the Telescope Bernard Lyot (TBL), Pic du Midi, France and the LSD technique, we began a survey of magnetic fields in single G-K-M giants. Early results include 6 MF-detections with fast rotating giants, and for the first time a magnetic field was detected directly in an evolved M-giant: EK Boo. Our results could be explained in the terms of $\\alpha$--$\\o...

  8. Comparison of the breadth and complexity of bovine viral diarrhea (BVDV) populations circulating in 34 persistently infected cattle generated in one outbreak.

    Science.gov (United States)

    Ridpath, J F; Bayles, D O; Neill, J D; Falkenberg, S M; Bauermann, F V; Holler, L; Braun, L J; Young, D B; Kane, S E; Chase, C C L

    2015-11-01

    Exposure to bovine viral diarrhea viruses (BVDV) results in acute and persistent infections. Persistent infections result from in utero exposure during the first trimester of gestation. Clinical presentation, in persistently infected cattle (PI), is highly variable. The reasons for this variation is largely unknown. The BVDV circulating in PI exist as quasispecies (swarms of individual viruses). An outbreak resulting in 34 PI cattle presented an opportunity to compare a large number of PI׳s. Methods were developed to compare the circulating viral populations within PI animals. It was found that PI animals generated in the same outbreak carry circulating viral populations that differ widely in size and diversity. Further, it was demonstrated that variation in PI viral populations could be used as a quantifiable phenotype. This observation makes it possible to test the correlation of this phenotype to other phenotypes such as growth rate, congenital defects, viral shed and cytokine expression.

  9. Buoyant Magnetic Loops Generated by Global Convective Dynamo Action

    CERN Document Server

    Nelson, Nicholas J; Brun, A Sacha; Miesch, Mark S; Toomre, Juri

    2012-01-01

    Our global 3D simulations of convection and dynamo action in a Sun-like star reveal that persistent wreaths of strong magnetism can be built within the bulk of the convention zone. Here we examine the characteristics of buoyant magnetic structures that are self-consistently created by dynamo action and turbulent convective motions in a simulation with solar stratification but rotating at three times the current solar rate. These buoyant loops originate within sections of the magnetic wreaths in which turbulent flows amplify the fields to much larger values than is possible through laminar processes. These amplified portions can rise through the convective layer by a combination of magnetic buoyancy and advection by convective giant cells, forming buoyant loops. We measure statistical trends in the polarity, twist, and tilt of these loops. Loops are shown to preferentially arise in longitudinal patches somewhat reminiscent of active longitudes in the Sun, although broader in extent. We show that the strength o...

  10. Consistent generation of magnetic fields in axion inflation models

    CERN Document Server

    Fujita, Tomohiro; Tada, Yuichiro; Takeda, Naoyuki; Tashiro, Hiroyuki

    2015-01-01

    There has been a growing evidence for the existence of magnetic fields in the extra-galactic regions, while the attempt to associate their origin with the inflationary epoch alone has been found extremely challenging. We therefore take into account the consistent post-inflationary evolution of the magnetic fields that are originated from vacuum fluctuations during inflation. In the model of our interest, the electromagnetic (EM) field is coupled to a pseudo-scalar inflaton $\\phi$ through the characteristic term $\\phi F\\tilde F$, breaking the conformal invariance. This interaction dynamically breaks the parity and enables a continuous production of only one of the polarization states of the EM field through tachyonic instability. The produced magnetic fields are thus helical. We find that the dominant contribution to the observed magnetic fields in this model comes from the modes that leave the horizon near the end of inflation, further enhanced by the tachyonic instability right after the end of inflation. Th...

  11. Magnetic flux concentrations from dynamo-generated fields

    CERN Document Server

    Jabbari, Sarah; Losada, Illa R; Kleeorin, Nathan; Rogachevskii, Igor

    2014-01-01

    The mean-field theory of magnetized stellar convection gives rise to the two possibility of distinct instabilities: the large-scale dynamo instability, operating in the bulk of the convection zone, and a negative effective magnetic pressure instability (NEMPI) operating in the strongly stratified surface layers. The latter might be important in connection with magnetic spot formation, but the growth rate of NEMPI is suppressed with increasing rotation rates, although recent direct numerical simulations (DNS) have shown a subsequent increase in the growth rate. We examine quantitatively whether this increase in the growth rate of NEMPI can be explained by an alpha squared mean-field dynamo, and whether both NEMPI and the dynamo instability can operate at the same time. We use both DNS and mean-field simulations (MFS) to solve the underlying equations numerically either with or without an imposed horizontal field. We use the test-field method to compute relevant dynamo coefficients. DNS show that magnetic flux ...

  12. Study of second-generation high-temperature superconducting magnets: the self-field screening effect

    International Nuclear Information System (INIS)

    Second-generation high-temperature superconductors (2G HTS) have high current density in very high magnetic fields. They are good candidates for high field magnets, especially when the magnetic field exceeds the critical fields of low-temperature superconductors. However, the thin and flat geometry of these conductors allows persistent screening currents (or shielding currents) to flow in the conductors. The screening currents caused by the ramping of applied current to the coil is identified as the self-field screening effect. The screening-current-induced magnetic field changes the magnetic field distribution of the magnet, and it also generates drift. This paper employs both experimental and numerical methods to study the mechanism of self-field screening currents for 2G HTS magnets. A 2G HTS magnet was constructed and tested, and a finite element model was built based on the magnet. The comparison between calculation and measurement is presented with detailed analysis. Current distributions inside the HTS magnet are calculated to illustrate the effects of screening. The screening-current-induced magnetic field is quantified by comparing the magnetic field distribution with a baseline copper model. The model is also used to explain the mechanism of the current sweep strategy, which can be used to effectively eliminate screening currents. (paper)

  13. Collisionless Shocks -- Magnetic Field Generation and Particle Acceleration

    OpenAIRE

    Frederiksen, J. Trier; Hededal, C. B.; Haugboelle, T.; Nordlund, A.

    2003-01-01

    We present numerical results from plasma particle simulations of collisionless shocks and ultra-relativistic counter-streaming plasmas. We demonstrate how the field-particle interactions lead to particle acceleration behind the shock-front. Further, we demonstrate how ultra relativistic counter-streaming plasmas create large scale patchy magnetic field structures and that these field structures propagate down-stream of the shock front. These results may help explain the origin of the magnetic...

  14. Formation of magnetic minerals at hydrocarbon-generation conditions

    OpenAIRE

    Abubakar, R.; Muxworthy, A. R.; Sephton, M.A.; Southern, P.; Watson, J. S.; Fraser, A.J.; Almeida, T.P.

    2015-01-01

    In this paper, we report the pyrolysis and formation of magnetic minerals in three source rock samples from the Wessex Basin in Dorset, southern England. The experimental conditions in the laboratory recreated the catagenesis environment of oil source rocks. Magnetic analysis of both the heated and the unheated samples at room temperature and at very low-temperatures (5 K), coupled with transmission electron-microscopy imaging and X-ray analysis, revealed the formation of nanometre-sized (...

  15. Comparison of Megawatt-Class Permanent Magnet Wind Turbine Generator Concepts

    DEFF Research Database (Denmark)

    Henriksen, Matthew Lee; Jensen, Bogi Bech

    2012-01-01

    This paper begins by investigating which permanent magnet synchronous generators are being used in wind turbines today. These are broken into three classes based on the ratio of speed between the blades and the generator. Four example gearbox/generator combinations are demonstrated to explore...

  16. Observation of magnetic field generation via the Weibel instability in interpenetrating plasma flows

    CERN Document Server

    Huntington, C M; Ross, J S; Zylstra, A B; Drake, R P; Froula, D H; Gregori, G; Kugland, N L; Kuranz, C C; Levy, M C; Li, C K; Meinecke, J; Morita, T; Petrasso, R; Plechaty, C; Remington, B A; Ryutov, D D; Sakawa, Y; Spitkovsky, A; Takabe, H; Park, H -S

    2013-01-01

    As the ejecta from supernovae or other energetic astrophysical events stream through the interstellar media, this plasma is shaped by instabilities that generate electric and magnetic fields. Among these instabilities, the Weibel filamentation instability plays a particularly important role, as it can generate significant magnetic fields in an initially un-magnetized medium. It is theorized that these Weibel fields are responsible for the observed gamma-ray burst light curve, particle acceleration in shock waves, and for providing seed fields for larger-scale cosmological magnetic structures. While the presence of these instability-generated fields has been inferred from astrophysical observation and predicted in simulation, observation in experiments is challenging. Here we report direct observation of well-organized, large-amplitude, filamentary magnetic fields associated with the Weibel instability in a scaled laboratory experiment. The experimental images, captured with proton radiography, are shown to be...

  17. Generation of Primordial Magnetic Fields on Linear Over-density Scales

    CERN Document Server

    Naoz, Smadar

    2013-01-01

    Magnetic fields appear to be present in all galaxies and galaxy clusters. Recent measurements indicate that a weak magnetic field may be present even in the smooth low density intergalactic medium. One explanation for these observations is that a seed magnetic field was generated by some unknown mechanism early in the life of the Universe, and was later amplified by various dynamos in nonlinear objects like galaxies and clusters. We show that a primordial magnetic field is expected to be generated in the early Universe on purely linear scales through vorticity induced by scale-dependent temperature fluctuations or equivalently, a spatially varying speed of sound of the gas. Residual free electrons left over after recombination tap into this vorticity to generate magnetic field via the Biermann battery process. Although the battery operates even in the absence of any relative velocity between dark matter and gas at the time of recombination, the presence of such a relative velocity modifies the predicted spati...

  18. A two-phase spherical electric machine for generating rotating uniform magnetic fields

    OpenAIRE

    Lawler, Clinton T.

    2007-01-01

    This thesis describes the design and construction of a novel two-phase spherical electric machine that generates rotating uniform magnetic fields, known as a fluxball machine. Alternative methods for producing uniform magnetic fields with air-cored solenoidal magnets are discussed and evaluated. Analytical and numerical models of these alternatives are described and compared. The design details of material selection, slot geometry, and mechanical connections are described for the fluxball mac...

  19. Life cycle assessment of electric power generation by wind turbines containing rare earth magnets

    OpenAIRE

    Venås, Christoffer

    2015-01-01

    Direct-drive permanent magnet generator (DD-PMG) wind turbines are becoming a larger part of the growing offshore wind turbine market. The strong permanent magnets used, the NdFeB magnets, contains neodymium metal. The neodymium metal is a rare earth element (REE), and there are large environmental concerns regarding the mining and processing of the REEs. The research within the field is scarce. Consequently, there is a lack of knowledge of the environmental consequences of a shift away from ...

  20. Controlled and spontaneous magnetic field generation in a gun-driven spheromak

    OpenAIRE

    WOODRUFF, S; Cohen, B. I.; Hooper, E.B.; McLean, H. S.; Stallard, B. W.; Hill, D. N.; Holcomb, C. T.; Romero-Talamás, 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 (delta B/B similar to 1% on the midplane edge) yields T-e profiles peaked at > 200 eV. Trends indic...

  1. Second order semiclassics with self-generated magnetic fields

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, Søren; Solovej, Jan Philip

    2012-01-01

    $ effectively determines the strength of the field. We consider the weak field regime with $\\beta h^{2}\\ge {const}>0$, where $h$ is the semiclassical parameter. For smooth potentials we prove that the semiclassical asymptotics of the total energy is given by the non-magnetic Weyl term to leading order...

  2. Dynamical quark mass generation in a strong external magnetic field

    CERN Document Server

    Mueller, Niklas; Fischer, Christian S

    2014-01-01

    We investigate the effect of a strong magnetic field on dynamical chiral symmetry breaking in quenched and unquenched QCD. To this end we apply the Ritus formalism to the coupled set of (truncated) Dyson-Schwinger equations for the quark and gluon propagator under the presence of an external constant Abelian magnetic field. We work with an approximation that is trustworthy for large fields eH > \\Lambda_{QCD}^2 but is not restricted to the lowest Landau level. We confirm the linear rise of the quark condensate with large external field previously found in other studies and observe the transition to the asymptotic power law at extremely large fields. We furthermore quantify the validity of the lowest Landau level approximation and find substantial quantitative differences to the full calculation even at very large fields. We discuss unquenching effects in the strong field propagators, condensate and the magnetic polarization of the vacuum. We find a significant weakening of magnetic catalysis caused by the back...

  3. Construction of Epidermal Growth Factor Receptor Peptide Magnetic Nanovesicles with Lipid Bilayers for Enhanced Capture of Liver Cancer Circulating Tumor Cells.

    Science.gov (United States)

    Ding, Jian; Wang, Kai; Tang, Wen-Jie; Li, Dan; Wei, You-Zhen; Lu, Ying; Li, Zong-Hai; Liang, Xiao-Fei

    2016-09-20

    Highly effective targeted tumor recognition via vectors is crucial for cancer detection. In contrast to antibodies and proteins, peptides are direct targeting ligands with a low molecular weight. In the present study, a peptide magnetic nanovector platform containing a lipid bilayer was designed using a peptide amphiphile (PA) as a skeleton material in a controlled manner without surface modification. Fluorescein isothiocyanate-labeled epidermal growth factor receptor (EGFR) peptide nanoparticles (NPs) could specifically bind to EGFR-positive liver tumor cells. EGFR peptide magnetic vesicles (EPMVs) could efficiently recognize and separate hepatoma carcinoma cells from cell solutions and treated blood samples (ratio of magnetic EPMVs versus anti-EpCAM NPs: 3.5 ± 0.29). Analysis of the circulating tumor cell (CTC) count in blood samples from 32 patients with liver cancer showed that EPMVs could be effectively applied for CTC capture. Thus, this nanoscale, targeted cargo-packaging technology may be useful for designing cancer diagnostic systems.

  4. Axial magnetic field generation by intense circularly polarized laser pulses in underdense plasmas

    International Nuclear Information System (INIS)

    Axial magnetic field generation by intense circularly polarized laser beams in underdense plasmas has been studied with three-dimensional particle-in-cell simulations and by means of theoretical analysis. Comparisons between analytical models and simulation results have identified an inverse Faraday effect as the main mechanism of the magnetic field generation in inhomogeneous plasmas. The source of azimuthal nonlinear currents and of the axial magnetic field depends on the transverse inhomogeneities of the electron density and laser intensity. The fields reach a maximum strength of several tens of megagauss for laser pulses undergoing relativistic self-focusing and channeling in moderately relativistic regime. Ultrarelativistic laser conditions inhibit magnetic field generation by directly reducing a source term and by generating fully evacuated plasma channels.

  5. Design and Finite Element Analysis of a Novel Transverse Flux Permanent Magnet Disk Generator

    DEFF Research Database (Denmark)

    Hosseini, Seyedmohsen; Moghani, Javad Shokrollahi; Ershad, Nima Farrokhzad;

    2011-01-01

    This paper presents a novel structure of a transverse flux permanent magnet disk generator. The proposed disk shape structure simplifies prototyping by using simple laminated steel sheets in comparison with previous transverse flux structures that employ bent laminations and soft magnetic...

  6. Characteristic Analysis and Trial Manufacture of Permanent-Magnetic Type Linear Generator

    Science.gov (United States)

    Takahara, Kenji; Ohsaki, Shingo; Itoh, Yuzo; Ohyama, Kazuhiro; Kawaguchi, Hideki

    This paper describes design and trial manufacture of the linear generator, which can convert any mechanical vibration of an automobile to electric energy. A mover, which includes permanent magnets, is linearly driven through a stator, by vibrations. Nd Fe-B magnets in the mover are placed as same magnetic poles face mutually, in order to make the change of magnetic flux in the coils of the stator. The coils are placed in the stator with same intervals of magnets. The coils are wound for the reverse to the next coil and they are connected series all. A magnetic material case covers the stator makes the magnetic flax is extended through the case and decrease canceling the flux in the coils of the stator. Numerical simulations calculated distribution of the magnetic field, electromotive force and driven power of the mover in order to determine the size of the linear generator. The linear generator and an experimental apparatus were produced on the basis of the simulation, and its performance was tested by experiments. The produced linear generator was confirmed to be useful as an onboard auxiliary power supply.

  7. Blowing jets as a circulation flow control to enhancement the lift of wing or generated power of wind turbine

    Directory of Open Access Journals (Sweden)

    Alexandru DUMITRACHE

    2014-06-01

    Full Text Available The goal of this paper is to provide a numerical flow analysis based on RANS equations in two directions: the study of augmented high-lift system for a cross-section airfoil of a wing up to transonic regime and the circulation control implemented by tangentially blowing jet over a highly curved surface due to Coanda effect on a rotor blade for a wind turbine. This study were analyzed the performance, sensitivities and limitations of the circulation control method based on blowing jet for a fixed wing as well as for a rotating wing. Directions of future research are identified and discussed.

  8. Low power wind energy conversion system based on variable speed permanent magnet synchronous generators

    OpenAIRE

    Carranza Castillo, Oscar; Garcerá Sanfeliú, Gabriel; Figueres Amorós, Emilio; GONZÁLEZ MORALES, LUIS GERARDO

    2014-01-01

    This paper presents a low power wind energy conversion system (WECS) based on a permanent magnet synchronous generator and a high power factor (PF) rectifier. To achieve a high PF at the generator side, a power processing scheme based on a diode rectifier and a boost DC-DC converter working in discontinuous conduction mode is proposed. The proposed generator control structure is based on three cascaded control loops that regulate the generator current, the turbine speed and the amount of powe...

  9. Chromospheric and Coronal Wave Generation in a Magnetic Flux Sheath

    CERN Document Server

    Kato, Yoshiaki; Hansteen, Viggo; Gudiksen, Boris; Wedemeyer, Sven; Carlsson, Mats

    2016-01-01

    Using radiation magnetohydrodynamic simulations of the solar atmospheric layers from the upper convection zone to the lower corona, we investigate the self-consistent excitation of slow magneto-acoustic body waves (slow modes) in a magnetic flux concentration. We find that the convective downdrafts in the close surroundings of a two-dimensional flux slab "pump" the plasma inside it in the downward direction. This action produces a downflow inside the flux slab, which encompasses ever higher layers, causing an upwardly propagating rarefaction wave. The slow mode, excited by the adiabatic compression of the downflow near the optical surface, travels along the magnetic field in the upward direction at the tube speed. It develops into a shock wave at chromospheric heights, where it dissipates, lifts the transition region, and produces an offspring in the form of a compressive wave that propagates further into the corona. In the wake of downflows and propagating shock waves, the atmosphere inside the flux slab in ...

  10. Magnetic field dependence of singlet oxygen generation by nanoporous silicon

    OpenAIRE

    Amonkosolpan, Jamaree; Aliev, Gazi N; Wolverson, Daniel; Snow, Paul A; Davies, James John

    2014-01-01

    Energy transfer from photoexcited excitons localized in silicon nanoparticles to adsorbed oxygen molecules excites them to the reactive singlet spin state. This process has been studied experimentally as a function of nanoparticle size and applied external magnetic field as a test of the accepted understanding of this process in terms of the exchange coupling between the nano-Si exciton and the adsorbed O2 molecules.

  11. Increased Efficiency of a Permanent Magnet Synchronous Generator through Optimization of NdFeB Magnet Arrays

    Science.gov (United States)

    Khazdozian, Helena; Hadimani, Ravi; Jiles, David

    2014-03-01

    The United States is currently dependent on fossil fuels for the majority of its energy needs, which has many negative consequences such as climate change. Wind turbines present a viable alternative, with the highest energy return on investment among even fossil fuel generation. Traditional commercial wind turbines use an induction generator for energy conversion. However, induction generators require a gearbox to increase the rotational speed of the drive shaft. These gearboxes increase the overall cost of the wind turbine and account for about 35 percent of reported wind turbine failures. Direct drive permanent magnet synchronous generators (PMSGs) offer an alternative to induction generators which eliminate the need for a gearbox. Yet, PMSGs can be more expensive than induction generators at large power output due to their size and weight. To increase the efficiency of PMSGs, the geometry and configuration of NdFeB permanent magnets were investigated using finite element techniques. The optimized design of the PMSG increases flux density and minimizes cogging torque with NdFeB permanent magnets of a reduced volume. These factors serve to increase the efficiency and reduce the overall cost of the PMSG. This work is supported by a National Science Foundation IGERT fellowship and the Barbara and James Palmer Endowment at the Department of Electrical and Computer Engineering of Iowa State University.

  12. Two-dimensional model of intrinsic magnetic flux losses in helical flux compression generators

    CERN Document Server

    Haurylavets, V V

    2012-01-01

    Helical Flux Compression Generators (HFCG) are used for generation of mega-amper current and high magnetic fields. We propose the two dimensional HFCG filament model based on the new description of the stator and armature contact point. The model developed enables one to quantitatively describe the intrinsic magnetic flux losses and predict the results of experiments with various types of HFCGs. We present the effective resistance calculations based on the non-linear magnetic diffusion effect describing HFCG performance under the strong conductor heating by currents.

  13. Generation of a cold, intense relativistic electron beam using a magnetized foilless diode

    International Nuclear Information System (INIS)

    An annular electron beam with less than 30 mrad of angular velocity spread, a radius of 1 cm, and a current density exceeding 0.4 MA/cm2 has been generated with a magnetized foilless diode. The diode current loss is limited to less than a few percent by careful design of the tapered transition region connecting a self-magnetically insulated vacuum transmission line to the externally magnetized foilless diode. Details of the transition section design and operating characteristics of the electron beam generator are given

  14. Lagrange-Maxwell equation and magnetic saturation parametric resonance of generator set

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Lagrange-Maxwell's equation is extended firstly. With the theory of electromechanical analytical dynamics, the magnetic complement energy in air gap of generator is acquired. The torsional vibration differential equations with periodic coefficients of rotor shafting of generator which is in the state of magnetic saturation are established.It is shown that the magnetic saturation may cause double frequency electromagnetic moment. By means of the averaging method, the first approximate solution and corresponding solution of the primary parametric resonance is obtained. The characteristics and laws of the primary parametric resonance excited by the electromagnetism are analyzed and some of new phenomena are revealed.

  15. Multifold Enhancement of Third-Harmonic Generation in Dielectric Nanoparticles Driven by Magnetic Fano Resonances.

    Science.gov (United States)

    Shorokhov, Alexander S; Melik-Gaykazyan, Elizaveta V; Smirnova, Daria A; Hopkins, Ben; Chong, Katie E; Choi, Duk-Yong; Shcherbakov, Maxim R; Miroshnichenko, Andrey E; Neshev, Dragomir N; Fedyanin, Andrey A; Kivshar, Yuri S

    2016-08-10

    Strong Mie-type magnetic dipole resonances in all-dielectric nanostructures provide novel opportunities for enhancing nonlinear effects at the nanoscale due to the intense electric and magnetic fields trapped within the individual nanoparticles. Here we study third-harmonic generation from quadrumers of silicon nanodisks supporting high-quality collective modes associated with the magnetic Fano resonance. We observe nontrivial wavelength and angular dependencies of the generated harmonic signal featuring a multifold enhancement of the nonlinear response in oligomeric systems. PMID:27403664

  16. Surface-electrode trap with an integrated permanent magnet for generating a magnetic-field gradient at trapped ions

    CERN Document Server

    Kawai, Yuji; Noguchi, Atsushi; Urabe, Shinji; Tanaka, Utako

    2016-01-01

    We report on a surface-electrode trap with SmCo magnets arranged in a quadrupole configuration underneath the trap electrode. Because the distance between the magnets and the trapped ions can be as little as several hundred micrometers, a large magnetic field is produced without any heat management. The magnetic-field gradient was measured using the Zeeman splitting of a single trapped $^{40}$Ca$^+$ ion at several positions, and a field gradient of 36 T/m was obtained. Such a field gradient is useful for the generation of a state-dependent force, which is important for quantum simulation and/or quantum gate operation using radio-frequency or microwave radiation.

  17. Research on Operation Principle and Control of Novel Hybrid Excitation Bearingless Permanent Magnet Generator

    Directory of Open Access Journals (Sweden)

    Huangqiu Zhu

    2016-08-01

    Full Text Available Under the condition of load changing, the magnetic field of traditional permanent magnet generators (PMG is hard to be adjusted, and the mechanical bearings are significantly worn. To overcome the drawbacks above, a novel hybrid excitation bearingless permanent magnet generator (HEBPMG is proposed in this paper, which has integrated the merits of hybrid excitation permanent magnet generators and magnetic bearings. Firstly, the structure and winding configuration of the HEBPMG are introduced, and then the principles of radial suspension and power generation are presented. The suspension principle as well as power generation principle is analyzed in this paper. Then, the flux linkage and induced voltage equations are derived, and the accurate mathematical model of radial suspension force is built based on the Maxwell tensor method. Subsequently, by means of the finite element analysis software-ANSYS Maxwell, the corresponding electromagnetic characteristics are analyzed to verify the correctness of the mentioned models. In addition, a compensation control strategy based on flux-linkage observation is proposed to solve the problems of unstable suspension force and generating voltage under variable load condition in this paper. Meanwhile, the corresponding control system is constructed and its feasibility is validated by simulation results. Finally, an experimental prototype of a 2.2 kW HEBPMG is tested. Experimental researches show that the HEBPMG can operate steadily under variable load condition and possess good suspension performance and power generation quality.

  18. Effect of Magnetic Field on Entropy Generation in a Microchannel Heat Sink with Offset Fan Shaped

    Directory of Open Access Journals (Sweden)

    Mohammad Nasiri

    2015-12-01

    Full Text Available In this study, convection flow in microchannel heat sink with offset fan-shaped reentrant cavities in sidewall filled with Fe3O4-water is numerically investigated. The effects of changing some parameters such as Reynolds number and magnetic field are considered. The nanofluid flow is laminar, steady and incompressible, while the thermo-physical properties of nanoparticles were assumed constant. A finite volume method and two phase mixture models were used to simulate the flow. The obtained results show that the frictional entropy generation increases as Reynolds number increases, while a reverse trend is observed for thermal entropy generation. By applying a non-uniform magnetic field, the entropy generation due to heat transfer decreases at first and then increases. When using the uniform magnetic field, the frictional entropy generation and thermal entropy generation is negligible. For all studied cases, the total entropy generation decreases using non-uniform magnetic fields. The results indicate that by increasing the magnetic field power, the total entropy generation decreases.

  19. Role of particle masses in the magnetic field generation driven by the parity violating interaction

    Science.gov (United States)

    Dvornikov, Maxim

    2016-09-01

    Recently the new model for the generation of strong large scale magnetic fields in neutron stars, driven by the parity violating interaction, was proposed. In this model, the magnetic field instability results from the modification of the chiral magnetic effect in presence of the electroweak interaction between ultrarelativistic electrons and nucleons. In the present work we study how a nonzero mass of charged particles, which are degenerate relativistic electrons and nonrelativistic protons, influences the generation of the magnetic field in frames of this approach. For this purpose we calculate the induced electric current of these charged particles, electroweakly interacting with background neutrons and an external magnetic field, exactly accounting for the particle mass. This current is calculated by two methods: using the exact solution of the Dirac equation for a charged particle in external fields and computing the polarization operator of a photon in matter composed of background neutrons. We show that the induced current is vanishing in both approaches leading to the zero contribution of massive particles to the generated magnetic field. We discuss the implication of our results for the problem of the magnetic field generation in compact stars.

  20. Generation of strong magnetic fields in dense quark matter driven by the electroweak interaction of quarks

    CERN Document Server

    Dvornikov, Maxim

    2016-01-01

    We study the generation of strong large scale magnetic fields in dense quark matter. The magnetic field growth is owing to the magnetic field instability driven by the electroweak interaction of quarks. We discuss the situation when the chiral symmetry is unbroken in the degenerate quark matter. In this case we predict the amplification of the seed magnetic field $10^{12}\\,\\text{G}$ to the strengths $(10^{14}-10^{15})\\,\\text{G}$. In our analysis we use the typical parameters of the quark matter in the core of a hybrid star or in a quark star. We also discuss the application of the obtained results to describe the magnetic fields generation in magnetars.

  1. A coupled model of magnetic flux generation and transport in stars

    CERN Document Server

    Işık, Emre; Schüssler, Manfred; 10.1002/asna.200710865

    2011-01-01

    We present a combined model for magnetic field generation and transport in cool stars with outer convection zones. The mean toroidal magnetic field, which is generated by a cyclic thin-layer alpha-omega dynamo at the bottom of the convection zone is taken to determine the emergence probability of magnetic flux tubes in the photosphere. Following the nonlinear rise of the unstable thin flux tubes, emergence latitudes and tilt angles of bipolar magnetic regions are determined. These quantities are put into a surface flux transport model, which simulates the surface evolution of magnetic flux under the effects of large-scale flows and turbulent diffusion. First results are discussed for the case of the Sun and for more rapidly rotating solar-type stars.

  2. Role of particle masses in the magnetic field generation driven by the parity violating interaction

    CERN Document Server

    Dvornikov, Maxim

    2016-01-01

    Recently the new model for the generation of strong large scale magnetic fields in neutron stars, driven by the parity violating interaction, was proposed. In this model, the magnetic field instability results from the modification of the chiral magnetic effect in presence of the electroweak interaction between ultrarelativistic electrons and nucleons. In the present work we study how a nonzero mass of charged particles, which are degenerate relativistic electrons and nonrelativistic protons, influences the generation of the magnetic field in frames of this approach. For this purpose we calculate the induced electric current of these charged particles, electroweakly interacting with background neutrons and an external magnetic field, exactly accounting for the particle mass. This current is calculated by two methods: using the exact solution of the Dirac equation for a charged particle in external fields and computing the polarization operator of a photon in matter composed of background neutrons. We show tha...

  3. Preliminary Results of Performance Measurements on a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    Science.gov (United States)

    Polzin, K. A.; Raitses, Y.; Merino, E.; Fisch, N. J.

    2008-01-01

    The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic configurations. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying a higher thrust efficiency. Preliminary thruster performance measurements on this configuration were obtained over a power range of 100-250 W. The thrust levels over this power range were 3.5-6.5 mN, with anode efficiencies and specific impulses spanning 14-19% and 875- 1425 s, respectively. The magnetic field in the thruster was lower for the thrust measurements than the plasma probe measurements due to heating and weakening of the permanent magnets, reducing the maximum field strength from 2 kG to roughly 750-800 G. The discharge current levels observed during thrust stand testing were anomalously high compared to those levels measured in previous experiments with this thruster.

  4. Differences in generation of magnetic storms driven by magnetic clouds, ejecta, sheath region before ICME and CIR

    Science.gov (United States)

    Nikolaeva, Nadezhda; Yermolaev, Yuri; Lodkina, Irina

    2016-07-01

    We investigate the efficiency of main phase storm generation by different solar wind (SW) streams when using 12 functions coupling (FC) various interplanetary parameters with magnetospheric state. By using our Catalog of Solar Wind Phenomena [Yermolaev et al., 2009] created on the basis of the OMNI database for 1976-2000, we selected the magnetic storms with Dst ≤ -50 nT for which interplanetary sources were following: MC (10 storms); Ejecta (31 storms); Sheath (21 storms); CIRs (31magnetic storms). To compare the interplanetary drivers we estimate an efficiency of magnetic storm generation by type of solar wind stream with using 12 coupling functions. We obtained that in average Sheath has more large efficiency of the magnetic storm generation and MC has more low efficiency in agreement with our previous results which show that by using a modification of formula by Burton et al. [1975] for connection of interplanetary conditions with Dst and Dst* indices the efficiency of storm generation by Sheath and CIR was ~50% higher than generation by ICME [Nikolaeva et al., 2013; 2015]. The most part of FCs has sufficiently high correlation coefficients. In particular the highest values of coefficients (~ 0.5 up to 0.63) are observed for Sheath- driven storms. In a small part of FCs with low coefficients it is necessary to increase the number of magnetic storms to increase the statistical significance of results. The reliability of the obtained data and possible reasons of divergences for various FCs and various SW types require further researches. The authors are grateful for the opportunity to use the OMNI database. This work was supported by the Russian Foundation for Basic Research, project 16-02-00125, and by Program of Presidium of the Russian Academy of Sciences. References: Nikolaeva, N. S., Y. I. Yermolaev, and I. G. Lodkina (2013), Modeling of Dst-index temporal profile on the main phase of the magnetic storms generated by different types of solar wind, Cosmic

  5. Impact of magnetic field parameters and iron oxide nanoparticle properties on heat generation for use in magnetic hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Shah, Rhythm R. [Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, AL (United States); Davis, Todd P.; Glover, Amanda L.; Nikles, David E. [Department of Chemistry, The University of Alabama, Tuscaloosa, AL (United States); Brazel, Christopher S., E-mail: cbrazel@eng.ua.edu [Department of Chemical and Biological Engineering, The University of Alabama, Tuscaloosa, AL (United States)

    2015-08-01

    Heating of nanoparticles (NPs) using an AC magnetic field depends on several factors, and optimization of these parameters can improve the efficiency of heat generation for effective cancer therapy while administering a low NP treatment dose. This study investigated magnetic field strength and frequency, NP size, NP concentration, and solution viscosity as important parameters that impact the heating efficiency of iron oxide NPs with magnetite (Fe{sub 3}O{sub 4}) and maghemite (γ-Fe{sub 2}O{sub 3}) crystal structures. Heating efficiencies were determined for each experimental setting, with specific absorption rates (SARs) ranging from 3.7 to 325.9 W/g Fe. Magnetic heating was conducted on iron oxide NPs synthesized in our laboratories (with average core sizes of 8, 11, 13, and 18 nm), as well as commercially-available iron oxides (with average core sizes of 8, 9, and 16 nm). The experimental magnetic coil system made it possible to isolate the effect of magnetic field parameters and independently study the effect on heat generation. The highest SAR values were found for the 18 nm synthesized particles and the maghemite nanopowder. Magnetic field strengths were applied in the range of 15.1–47.7 kA/m, with field frequencies ranging from 123 to 430 kHz. The best heating was observed for the highest field strengths and frequencies tested, with results following trends predicted by the Rosensweig equation. An increase in solution viscosity led to lower heating rates in nanoparticle solutions, which can have significant implications for the application of magnetic fluid hyperthermia in vivo. - Highlights: • Heating was tested in seven iron oxide nanoparticles for different magnetic fields. • Confirms an optimal nanoparticle size for heating that agrees with the literature. • Verifies Rosenweig's equation to predict the effect of field frequency on heating. • Reports reduced heating in high viscosity environments.

  6. Studies of HED Plasmas with Self-Generated Magnetic Field

    Energy Technology Data Exchange (ETDEWEB)

    Medvedev, Mikhail [Univ. of Kansas, Lawrence, KS (United States)

    2016-02-08

    High-amplitude sub-Larmor-scale electromagnetic turbulence is ubiquitous in high-energy density environments, such as laboratory plasmas produced by high-intensity lasers, e.g., NIF, Omega-EP, Trident, and others, and in astrophysical and space plasmas, e.g., at high-Mach-number collisionless shocks in weakly magnetized plasmas upstream regions of quasi-parallel shocks, sites of magnetic reconnection and others. Studies of plasmas and turbulence in these environments are important for fusion energy sciences and the inertial confinement concept, in particular, as well as to numerous astrophysical systems such as gamma-ray bursts, supernovae blast waves, jets of quasars and active galactic nuclei, shocks in the interplanetary medium, solar flares and many more. Such turbulence can be of various origin and thus have rather different properties, from being purely magnetic (Weibel) turbulence to various types of electromagnetic turbulence (for example, whistler wave turbulence or turbulence produced by filamentation or Weibel-type streaming instability), to purely electrostatic Langmuir turbulence. In this project we use analytical and numerical tools to study the transport, radiative, and magneto-optical properties of plasmas with sub-Larmor-scale turbulence. We discovered the connection of transport/diffusion properties to certain spectral benchmark features of (jitter) radiation produced by the plasma and radiation propagation through it. All regimes, from the relativistic to non-relativistic, were thoroughly investigated and predictions were made for laboratory plasmas and astrophysical plasmas. Thus, all the tasks outlined in the proposal were fully and successfully accomplished.

  7. Magnetic Field Generation and Zonal Flows in the Gas Giants

    Science.gov (United States)

    Duarte, L.; Wicht, J.; Gastine, T.

    2013-12-01

    The surface dynamics of Jupiter and Saturn is dominated by a banded system of fierce zonal winds. The depth of these winds remains unclear but they are thought to be confined to the very outer envelopes where hydrogen remains molecular and the electrical conductivity is negligible. The dynamo responsible for the dipole dominated magnetic fields of both Gas Giants, on the other hand, likely operates in the deeper interior where hydrogen assumes a metallic state. We present numerical simulations that attempt to model both the zonal winds and the interior dynamo action in an integrated approach. Using the anelastic version of the MHD code MagIC, we explore the effects of density stratification and radial electrical conductivity variations. The electrical conductivity is assumed to remain constant in the thicker inner metallic region and decays exponentially towards the outer boundary throughout the molecular envelope. Our results show that the combination of stronger density stratification (Δρ≈55) and a weaker conducting outer layer is essential for reconciling dipole dominated dynamo action and a fierce equatorial zonal jet. Previous simulations with homogeneous electrical conductivity show that both are mutually exclusive, with solutions either having strong zonal winds and multipolar magnetic fields or weak zonal winds and dipole dominated magnetic fields. The particular setup explored here allows the equatorial jet to remain confined to the weaker conducting region where is does not interfere with the deeper seated dynamo action. The equatorial jet can afford to remain geostrophic and reaches throughout the whole shell. This is not an option for the additional mid to higher latitude jets, however. In dipole dominated dynamo solutions, appropriate for the Gas Giants, zonal flows remain very faint in the deeper dynamo region but increase in amplitude in the weakly conducting outer layer in some of our simulations. This suggests that the mid to high latitude jets

  8. Precise Measurement of a Magnetic Field Generated by the Electromagnetic Flux Compression Technique

    CERN Document Server

    Nakamura, D; Matsuda, Y H; Takeyama, S

    2013-01-01

    The precision of the values of a magnetic field generated by electromagnetic flux compression was investigated in ultra-high magnetic fields of up to 700 T. In an attempt to calibrate the magnetic field measured by pickup coils, precise Faraday rotation (FR) measurements were conducted on optical (quartz and crown) glasses. A discernible "turn-around" phenomenon was observed in the FR signal as well as the pickup coils before the end of a liner implosion. We found that the magnetic field measured by pickup coils should be corrected by taking into account the high-frequency response of the signal transmission line. Near the peak magnetic field, however, the pickup coils failed to provide reliable values, leaving the FR measurement as the only method to precisely measure an extremely high magnetic fields.

  9. The role of rotation on the evolution of dynamo generated magnetic fields in Super Earths

    CERN Document Server

    Zuluaga, Jorge I

    2011-01-01

    Planetary magnetic fields could have a role on the evolution of planetary atmospheres and the required conditions for the emergence and evolution of life (habitability). After briefly review the current efforts to study the evolution of dynamo generated magnetic fields in massive earth-like rocky planets (Super Earths), we take the results from thermal evolution models and updated scaling laws for convection driven magnetodynamos to predict the evolution of the local Rossby number, the basic indicator of core magnetic field geometry and regime. We study the dependence of this property on planetary mass and rotation rate. Previous works have paid Attention only to the evolution of dipolar dominant core magnetic fields assuming rapid rotating planets. Here we extend these results including consistently the effects of rotation on the evolution of planetary magnetic field properties and obtain global constraints to the existence of intense protective magnetic fields in rapidly and slowly rotating Super Earths. We...

  10. Effects on cerebral circulation of decimeter wave therapy and variable magnetic field in patients with hemiparesis of vascular and traumatic origin

    Energy Technology Data Exchange (ETDEWEB)

    Strelkova, N.I.; Gavrilkov, A.T.; Dyuzhilova, N.F.; Strel' tsova, Ye.N.

    1981-08-01

    Both the artherosclerotic process in the case of cerebrovascular accident and cerebral trauma lead to impairment of cerebral hemodynamics, blood and spinal fluid circulation, macroscopic and microscopic disturbances. Electromagnetic waves in the decimeter range (decimeter waves - DMW) and a variable magnetic field (VMF) were used to treat these processes. Treatment was delivered directly to the region of the cerebral lesion, on the basis of the penetrating capacity of DMW and VMF to a relatively great depth (7 to 9 and 4 to 7 cm, respectively). Results of these treatments are discussed.

  11. Microwave generation for magnetic fusion energy applications, Task A

    International Nuclear Information System (INIS)

    This report details progress over the past year in the research program ''Free Electron Lasers with Short Period Wigglers.'' The work is performed jointly by the laboratory for Plasma Research and the Electrical Engineering Department of the University of Maryland and is funded by the US Department of Energy Office of Fusion Energy. The goal of the work is the development of an electron cyclotron resonance heating (ECRH) scheme for magnetic fusion plasmas such as the Compact Ignition Tokamak (CIT). Our approach is the development of a free electron laser using a sheet electron beam and a short period wiggler magnet. The specific requirements for the heating method include 10 to 30 MW of average power with pulse durations of several seconds to CW at a frequency near 300 GHz (∼600 GHz) in the case of second harmonic (ECRH). Compatible with the experimental nature of the program, radiation frequency flexibility of 30% total bandwidth and 5% rapid dynamic (approx-lt 10 ms) bandwidth is desirable. As the source will eventually be applied to a reactor, priority is placed upon high system efficiency and reliability. Use of established technologies is encouraged where possible

  12. Design, Prototyping, and Analysis of a Novel Modular Permanent Magnet Transverse Flux Disk Generator

    DEFF Research Database (Denmark)

    Hosseini, Seyedmohsen; Moghani, Javad Shokrollahi; Ershad, Nima Farrokhzad;

    2011-01-01

    This paper presents the design, prototyping, and analysis of a novel modular transverse flux permanent magnet disk generator. The disk-shaped structure simplifies the construction procedure by using laminated steel sheets. To reduce output harmonics, the excitation of the generator is done......, a prototype has been constructed and tested. The experimental results are in good agreement with simulation results....

  13. On the Influence of Weak Magnetic and Electric Fields on the Fluctuations of Ionic Electric Currents in Blood Circulation

    CERN Document Server

    Kanokov, Zakirjon; Nasirov, Avazbek K

    2009-01-01

    An analysis of a variety of existing experimental data leads to the conclusion on the existence of a resonance mechanism allowing weak magnetic fields to affect biological processes. These fields may either be static magnetic fields comparable in magnitude with the magnetic field of the earth or weak ultra-low frequency time-dependent fields. So far, a generally accepted theoretical model allowing one to understand the effect of magnetic and electric fields on biological processes is not available. By this reason, it is not clear which characteristics of the fields, like magnetic and electric field strength, frequency of change of the field, shape of the electromagnetic wave, the duration of the magnetic or electric influence or some particular combination of them, are responsible for the biological effect. In the present analysis it is shown that external time-independent magnetic fields may cause a resonance amplification of ionic electric currents in biological tissues and, in particular, in the vasculatur...

  14. Study of magnetic field expansion using a plasma generator for space radiation active protection

    Institute of Scientific and Technical Information of China (English)

    JIA Xiang-Hong; JIA Shao-Xia; XU Feng; BAI Yan-Qiang; WAN Jun; LIU Hong-Tao; JIANG Rui

    2013-01-01

    There are many active protecting methods including Electrostatic Fields,Confined Magnetic Field,Unconfined Magnetic Field and Plasma Shielding etc.for defending the high-energy solar particle events (SPE) and Galactic Cosmic Rays (GCR) in deep space exploration.The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far.The magnetic field expansion caused by plasma can improve its protective efficiency of space particles.One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric.A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency (RF) power supply of 13.56 MHz,which exits from both sides of the magnet and makes the magnetic field expand on one side.The discharging belts phenomenon is similar to the Earth's radiation belt,but the mechanism has yet to be understood.A magnetic probe is used to measure the magnetic field expansion distributions,and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.

  15. Modeling of Self-Excited Isolated Permanent Magnet Induction Generator Using Iterative Numerical Method

    Directory of Open Access Journals (Sweden)

    Mohamed Mostafa R.

    2016-01-01

    Full Text Available Self-Excited Permanent Magnet Induction Generator (PMIG is commonly used in wind energy generation systems. The difficulty of Self-Excited Permanent Magnet Induction Generator (SEPMIG modeling is the circuit parameters of the generator vary at each load conditions due to the a change in the frequency and stator voltage. The paper introduces a new modeling for SEPMIG using Gauss-sidle relaxation method. The SEPMIG characteristics using the proposed method are studied at different load conditions according to the wind speed variation, load impedance changes and different shunted capacitor values. The system modeling is investigated due to the magnetizing current variation, the efficiency variation, the power variation and power factor variation. The proposed modeling system satisfies high degree of simplicity and accuracy.

  16. Gut reaction by heartless shrimps: experimental evidence for the role of the gut in generating circulation before cardiac ontogeny.

    Science.gov (United States)

    Spicer, John I

    2006-12-22

    Before the appearance of a functional heart in many invertebrate species, the assumption was that general body movements provide circulatory function. Consequently, I investigated the frequency of gut movements in the brine shrimp, Artemia franciscana, immediately post-hatch to the point when a functional heart appeared. Prior to cardiac ontogeny, movements of internal musculature and gut provided pre-cardiac circulatory currents with the rate of gut movements increasing when swimming limbs were impeded. There was also some evidence that gut movements were responsive to low oxygen, indicating a possible regulatory function for the gut in early circulation. Overall, this suggests that general body movements are not always adequate to provide internal circulation in small, heartless individuals. PMID:17148293

  17. Performance of a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    Science.gov (United States)

    Polzin, Kurt A.; Raitses, Yevgeny; Fisch, Nathaniel J.

    2008-01-01

    While Hall thrusters can operate at high efficiency at kW power levels, it is difficult to construct one that operates over a broad envelope down to 100W while maintaining an efficiency of 45- 55%. Scaling to low power while holding the main dimensionless parameters constant requires a decrease in the thruster channel size and an increase in the magnetic field strength. Increasing the magnetic field becomes technically challenging since the field can saturate the miniaturized inner components of the magnetic circuit and scaling down the magnetic circuit leaves very little room for magnetic pole pieces and heat shields. An alternative approach is to employ a cylindrical Hall thruster (CHT) geometry. Laboratory model CHTs have operated at power levels ranging from the order of 50 Watts up to 1 kW. These thrusters exhibit performance characteristics which are comparable to conventional, annular Hall thrusters of similar size. Compared to the annular Hall thruster, the CHT has a lower insulator surface area to discharge chamber volume ratio. Consequently, there is the potential for reduced wall losses in the channel of a CHT, and any reduction in wall losses should translate into lower channel heating rates and reduced erosion. This makes the CHT geometry promising for low-power applications. Recently, a CHT that uses permanent magnets to produce the magnetic field topology was tested. This thruster has the promise of reduced power consumption over previous CHT iterations that employed electromagnets. Data are presented for two purposes: to expose the effect different controllable parameters have on the discharge and to summarize performance measurements (thrust, Isp, efficiency) obtained using a thrust stand. These data are used to gain insight into the thruster's operation and to allow for quantitative comparisons between the permanent magnet CHT and the electromagnet CHT.

  18. Impact of magnetic field parameters and iron oxide nanoparticle properties on heat generation for use in magnetic hyperthermia

    Science.gov (United States)

    Shah, Rhythm R.; Davis, Todd P.; Glover, Amanda L.; Nikles, David E.; Brazel, Christopher S.

    2015-08-01

    Heating of nanoparticles (NPs) using an AC magnetic field depends on several factors, and optimization of these parameters can improve the efficiency of heat generation for effective cancer therapy while administering a low NP treatment dose. This study investigated magnetic field strength and frequency, NP size, NP concentration, and solution viscosity as important parameters that impact the heating efficiency of iron oxide NPs with magnetite (Fe3O4) and maghemite (γ-Fe2O3) crystal structures. Heating efficiencies were determined for each experimental setting, with specific absorption rates (SARs) ranging from 3.7 to 325.9 W/g Fe. Magnetic heating was conducted on iron oxide NPs synthesized in our laboratories (with average core sizes of 8, 11, 13, and 18 nm), as well as commercially-available iron oxides (with average core sizes of 8, 9, and 16 nm). The experimental magnetic coil system made it possible to isolate the effect of magnetic field parameters and independently study the effect on heat generation. The highest SAR values were found for the 18 nm synthesized particles and the maghemite nanopowder. Magnetic field strengths were applied in the range of 15.1-47.7 kA/m, with field frequencies ranging from 123 to 430 kHz. The best heating was observed for the highest field strengths and frequencies tested, with results following trends predicted by the Rosensweig equation. An increase in solution viscosity led to lower heating rates in nanoparticle solutions, which can have significant implications for the application of magnetic fluid hyperthermia in vivo.

  19. A precise numerical estimation of the magnetic field generated around recombination

    CERN Document Server

    Fidler, Christian; Pitrou, Cyril

    2015-01-01

    We investigate the generation of magnetic fields from non-linear effects around recombination. As tight-coupling is gradually lost when approaching $z\\simeq 1100$, the velocity difference between photons and baryons starts to increase, leading to an increasing Compton drag of the photons on the electrons. The protons are then forced to follow the electrons due to the electric field created by the charge displacement; the same field, following Maxwell's laws, eventually induces a magnetic field on cosmological scales. Since scalar perturbations do not generate any magnetic field as they are curl-free, one has to resort to second-order perturbation theory to compute the magnetic field generated by this effect. We reinvestigate this problem numerically using the powerful second-order Boltzmann code SONG. We show that: i) all previous studies do not have a high enough angular resolution to reach a precise and consistent estimation of the magnetic field spectrum; ii) the magnetic field is generated up to $z\\simeq ...

  20. Investigation on magnetoacoustic signal generation with magnetic induction and its application to electrical conductivity reconstruction.

    Science.gov (United States)

    Ma, Qingyu; He, Bin

    2007-08-21

    A theoretical study on the magnetoacoustic signal generation with magnetic induction and its applications to electrical conductivity reconstruction is conducted. An object with a concentric cylindrical geometry is located in a static magnetic field and a pulsed magnetic field. Driven by Lorentz force generated by the static magnetic field, the magnetically induced eddy current produces acoustic vibration and the propagated sound wave is received by a transducer around the object to reconstruct the corresponding electrical conductivity distribution of the object. A theory on the magnetoacoustic waveform generation for a circular symmetric model is provided as a forward problem. The explicit formulae and quantitative algorithm for the electrical conductivity reconstruction are then presented as an inverse problem. Computer simulations were conducted to test the proposed theory and assess the performance of the inverse algorithms for a multi-layer cylindrical model. The present simulation results confirm the validity of the proposed theory and suggest the feasibility of reconstructing electrical conductivity distribution based on the proposed theory on the magnetoacoustic signal generation with magnetic induction.

  1. Direct Driven Permanent Magnet Synchronous Generators with Diode Rectifiers for Use in Offshore Wind Turbines

    OpenAIRE

    Reigstad, Tor Inge

    2007-01-01

    This work is focused on direct-driven permanent magnets synchronous generators (PMSG) with diode rectifiers for use in offshore wind turbines. Reactive compensation of the generator, power losses and control of the generator are studied. Configurations for power transmission to onshore point of common connection are also considered. Costs, power losses, reliability and interface with the PMSG are discussed. The purpose of the laboratory tests and simulations are to learn how a PMSG with dio...

  2. Circulating AMH reflects ovarian morphology by magnetic resonance imaging and 3D ultrasound in 121 healthy girls

    DEFF Research Database (Denmark)

    Hagen, Casper P; Mouritsen, Annette; Mieritz, Mikkel G;

    2015-01-01

    CONTEXT: In adult women, Anti-Müllerian hormone (AMH) is produced by small growing follicles, and circulating levels of AMH reflect the number of antral follicles as well as primordial follicles. Whether AMH reflects follicle numbers in healthy girls remains to be elucidated. OBJECTIVE: This study...

  3. Generation of Seed Magnetic Field around First Stars: the Biermann Battery Effect

    CERN Document Server

    Doi, Kentaro

    2011-01-01

    We investigate generation processes of magnetic fields around first stars. Since the first stars are expected to form anisotropic ionization fronts in the surrounding clumpy media, magnetic fields are generated by effects of radiation force as well as the Biermann battery effect. We have calculated the amplitude of magnetic field generated by the effects of radiation force around the first stars in the preceding paper, in which the Biermann battery effects are not taken into account.In this paper, we calculate the generation of magnetic fields by the Biermann battery effect as well as the effects of radiation force, utilizing the radiation hydrodynamics simulations. As a result, we find that the generated magnetic field strengths are ~ 10^{-19}G-10^{-17}G at ~ 100pc-1kpc scale mainly by the Biermann battery, which is an order of magnitude larger than the results of our previous study. We also find that this result is insensitive to various physical parameters including the mass of the source star, distance be...

  4. Evanescent magnetic field effects on entropy generation at the onset of natural convection

    Indian Academy of Sciences (India)

    Mourad Magherbi; Atef El Jery; Nejib Hidouri; Ammar Ben Brahim

    2010-04-01

    This paper numerically investigates the effect of an externally evanescent magnetic field on total entropy generation in a fluid enclosed in a square cavity by using a control volume finite element method to solve the conservation equations at Prandtl number of 0·71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for, fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number varying from 104 to 105. The effects of the Hartman number and the magnetic field inclination angle on the evolution of total entropy generation throughout the transient regime were investigated. Results show that the application of evanescent magnetic field not only suppresses the fluctuation of the total entropy generation in the transient state, but also reduces the gap for magnetic field relaxation time less than 1/10.

  5. Accurate Modeling of a Transverse Flux Permanent Magnet Generator Using 3D Finite Element Analysis

    DEFF Research Database (Denmark)

    Hosseini, Seyedmohsen; Moghani, Javad Shokrollahi; Jensen, Bogi Bech

    2011-01-01

    This paper presents an accurate modeling method that is applied to a single-sided outer-rotor transverse flux permanent magnet generator. The inductances and the induced electromotive force for a typical generator are calculated using the magnetostatic three-dimensional finite element method. A new...... method is then proposed that reveals the behavior of the generator under any load. Finally, torque calculations are carried out using three dimensional finite element analyses. It is shown that although in the single-phase generator the cogging torque is very high, this can be improved significantly by...... combining three single-phase modules into a three-phase generator....

  6. A novel HTS SMES application in combination with a permanent magnet synchronous generator type wind power generation system

    Science.gov (United States)

    Kim, G. H.; Kim, A. R.; Kim, S.; Park, M.; Yu, I. K.; Seong, K. C.; Won, Y. J.

    2011-11-01

    Superconducting magnetic energy storage (SMES) system is a DC current driven device and can be utilized to improve power quality particularly in connection with renewable energy sources due to higher efficiency and faster response than other devices. This paper suggests a novel connection topology of SMES which can smoothen the output power flow of the wind power generation system (WPGS). The structure of the proposed system is cost-effective because it reduces a power converter in comparison with a conventional application of SMES. One more advantage of SMES in the proposed system is to improve the capability of low voltage ride through (LVRT) for the permanent magnet synchronous generator (PMSG) type WPGS. The proposed system including a SMES has been modeled and analyzed by a PSCAD/EMTDC. The simulation results show the effectiveness of the novel SMES application strategy to not only mitigate the output power of the PMSG but also improve the capability of LVRT for PMSG type WPGS.

  7. Probing latitudinal variations of the solar magnetic field in cycles 21-23 by Parker's Two-Layer Dynamo Model with meridional circulation

    Science.gov (United States)

    Popova, E.; Zharkova, V.; Zharkov, S.

    2013-11-01

    Principle component analysis (PCA) of the solar background magnetic field (SBMF) measured from Wilcox Solar Observatory (WSO) magnetograms revealed the following principal components (PCs) in latitudes: two main symmetric components, which are the same for all cycles 21-23, and three pairs of asymmetric components, which are unique for each cycle. These SBMF variations are assumed to be those of poloidal magnetic field travelling slightly off-phase from pole to pole while crossing the equator. They are assumed to be caused by a joint action of dipole and quadruple magnetic sources in the Sun. In the current paper, we make the first attempt to interpret these latitudinal variations in the surface magnetic field with Parker's two-layer dynamo model. The latitudinal distributions of such waves are simulated for cycles 21-23 by the modified Parker's dynamo model taking into account both α and ω effects operating simultaneously in the two (upper and lower) layers of the solar convective zone (SCZ) and having opposite directions of meridional circulation. The simulations are carried out for both dipole and quadruple magnetic sources with the dynamo parameters specifically selected to provide the curves fitting closely the PCs derived from SBMF variations in cycles 21-23. The simulations are optimised for matching the positions of maximums in latitude, the number of equator crossings and the phase difference between the two dynamo waves operating in the two layers. The dominant pair of PCs present in each cycle is found to be fully asymmetric with respect to the magnetic poles and produced by a magnetic dipole. This pair is found to account for the two main dynamo waves operating between the two magnetic poles. There are also three further pairs of waves unique to each cycle and associated with multiple magnetic sources in the Sun. For the odd cycle 21 the simulated poloidal field fits the observed PCs, only if they are produced by magnetic sources with a quadruple

  8. Analysis of the Magnetic Field Effect on Entropy Generation at Thermosolutal Convection in a Square Cavity

    Directory of Open Access Journals (Sweden)

    Ammar Ben Brahim

    2011-05-01

    Full Text Available Thermosolutal convection in a square cavity filled with air and submitted to an inclined magnetic field is investigated numerically. The cavity is heated and cooled along the active walls with a mass gradient whereas the two other walls of the cavity are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined in transient state for laminar flow by solving numerically the continuity, momentum energy and mass balance equations, using a Control Volume Finite—Element Method. The structure of the studied flows depends on four dimensionless parameters which are the Grashof number, the buoyancy ratio, the Hartman number and the inclination angle. The results show that the magnetic field parameter has a retarding effect on the flow in the cavity and this lead to a decrease of entropy generation, Temperature and concentration decrease with increasing value of the magnetic field parameter.

  9. Theoretical study of self generation of magnetic field due to laser plasma interaction

    International Nuclear Information System (INIS)

    Self generated high order magnetic field in the corona of Inertial Confinement Fusion Plasma plays a very important role in the design of fusion target because of its strong influence on the transport of thermal flux from the critical density region to the ablation layer. A theoretical study of the generation of megagauss magnetic field study has been presented. Out of number of causes, in this paper we have studied the role of pressure and temperatures gradient inside the fuel pellet to estimate the magnitude of the magnetic field produced. The intense pressure and temperature gradients inside the plasma caused by the lasers intensity (I > 1019 Wcm-2) short pulse (t⁓1 ps) giving rise to the Magnetic field. (author)

  10. Magnetic field seed generation in plasmas around charged and rotating black holes

    International Nuclear Information System (INIS)

    Previous work by the authors introduced the possibility of generating seed magnetic fields by spacetime curvature and applied it in the vicinity of a Schwarzschild black hole. It was pointed out that it would be worthwhile to consider the effect in other background geometries and particularly in the vicinity of a rotating black hole, which is generically to be expected, astrophysically. In this paper that suggestion is followed up and we calculate generated magnetic field seed due to Reissner–Nördstrom and Kerr spacetimes. The conditions for the drive for the seed of a magnetic field is obtained for charged black holes, finding that in the horizon the drive vanishes. Also, the ψN-force produced by the Kerr black hole is obtained and its relation with the magnetic field seed is discussed, producing a more effective drive. (paper)

  11. Simulations of Magnetic Field Generation in Laser-Produced Blast Waves

    Science.gov (United States)

    Lamb, D.; Fatenejad, M.; Gregori, G.; Miniati, F.; Park, H.-S.; Remington, B.; Ravasio, A.; Koenig, M.; Murphy, C. D.

    2011-10-01

    Magnetic fields are ubiquitous in the Universe. The origin of these fields and process by which they are amplified are not fully understood, although amplification is thought to involve turbulence. Experiments being conducted at medium-scale laser facilities (such as the LULI laser the Janus laser) can investigate the self-generation of magnetic fields under conditions that resemble astrophysical shocks. In these experiments, two 527 nm, 1.5 ns long laser beams are focused onto a 500 μm diameter graphite rod producing an explosion and asymmetric blast wave into a Helium filled chamber. A variety of diagnostics measure the velocity, electron density, and show that a large scale magnetic field is produced. We report preliminary hydrodynamic and MHD simulations using FLASH of a simplified version of the experiment. The results provide insights into the origin and generation of the magnetic field. This work was partially supported by the US DOE, the European Research Council, and Laserlab Europe.

  12. Generation and measurement of multi megagauss fields in inertial magnets

    Indian Academy of Sciences (India)

    N Nalini; T C Kaushik; S C Gupta

    2010-10-01

    We present here the development of a facility to generate high (multi megagauss) magnetic field of 4 to 5 s rise time, using inertial magnets. The facility includes a low inductance, high current capacitor bank (280 kJ/40 kV) and an inertial magnet, which is a copper disk machined to have a keyhole in it. As the high current from the capacitor bank is discharged through the copper disk, a high magnetic field is produced along its axis, before it is destroyed by the combined effect of the dynamic loading and skin effect. A maximum peak magnetic field of 257 T is realized, when the magnet with 3·6 mm inner diameter, 35 mm outer diameter and 5 mm length, is powered by the capacitor bank charged to 28 kV (134 kJ). The transient magnetic field is measured using a B dot probe with an error of ±25 T. The probe in most of high field shots (> 200 T) got destroyed before recording the peak field and the trailing edge of the magnetic field. Experimental evidence of enhancement of the probe survival for longer time in copper disks using spatial non-uniform conductivity with 1 mm thick SS brazed to the inner wall of the inertial magnet is also reported.

  13. Initial results on high enthalpy plasma generation in a magnetized coaxial source

    International Nuclear Information System (INIS)

    Initial investigation on high enthalpy plasma stream generation in the North Carolina State University Coaxial Plasma Source (CPS) facility is presented. Tenuous, yet high enthalpy, flows are produced from this Magnetized Coaxial plasma Gun (MCG) which allow laboratory study of plasma streams with a wide variety of applications. The applicability includes, but is not limited to, advanced thrusters for electric space propulsion, astrophysical jets and critical ionization phenomena, magnetic fusion compact toroid devices and tokamak fueling, large scale plasma etching and deposition, etc

  14. Magnetic field generation from Self-Consistent collective neutrino-plasma interactions

    Energy Technology Data Exchange (ETDEWEB)

    Brizard, A.J.; Murayama H.; Wurtele, J.S.

    1999-11-24

    A new Lagrangian formalism for self-consistent collective neutrino-plasma interactions is presented in which each neutrino species is described as a classical ideal fluid. The neutrino-plasma fluid equations are derived from a covariant relativistic variational principle in which finite-temperature effects are retained. This new formalism is then used to investigate the generation of magnetic fields and the production of magnetic helicity as a result of collective neutrino-plasma interactions.

  15. Quasistatic Magnetic Field Generation by an Intense Ultrashort Laser Pulse in Underdense Plasma

    Institute of Scientific and Technical Information of China (English)

    ZHENG Chun-Yang; ZHU Shao-Ping; HE Xian-Tu

    2000-01-01

    The quasistatic magnetic field created in the interaction of intense ultrashort laser pulses with underdense plasmas has been investigated by two-dimensional particle simulation. The relativistic ponderomotive force and plasma wave excited in self-modulation processes can drive intense electron current mainly in the propagation direction.As a result, an azimuthal, multi-mega Gauss order quasi-static magnetic field can be generated around the laserbeam.

  16. The magnetic field generated by an electron bound in angular-momentum eigenstates

    CERN Document Server

    Ayuel, K

    1999-01-01

    The magnetic field generated by an electron bound in a spherically symmetric potential is calculated for eigenstates of the orbital and total angular momentum. General expressions are presented for the current density in such states and the magnetic field is calculated through the vector potential, which is obtained from the current density by direct integration. The method is applied to the hydrogen atom, for which we reproduce and extend known results.

  17. Generation of Vortex Beams with Strong Longitudinally Polarized Magnetic Field by Using a Metasurface

    CERN Document Server

    Veysi, Mehdi; Capolino, Filippo

    2014-01-01

    A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analytical results. Both a high magnetic-to-electric-field contrast ratio and a magnetic field enhancement are achieved. We also investigate the metasurface physical constraints to convert a linearly polarized beam into an azimuthally E- polarized beam and characterize the performance of magnetic field enhancement and electric field suppression of a realistic metasurface. These findings are potentially useful for novel optical spectroscopy related to magnetic dipolar transitions and for optical manipulation of particles with sp...

  18. Second harmonic generation with plasmonic metasurfaces: direct comparison of electric and magnetic resonances

    CERN Document Server

    Chandrasekar, Rohith; Lagutchev, Alexei; Shalaev, Vladimir M; Ciraci, Cristian; Smith, David R; Kildishev, Alexander V

    2015-01-01

    Plasmonic resonances in metallic nanostructures have been shown to drastically enhance local electromagnetic fields, and thereby increase the efficiency of nonlinear optical phenomena, such as second harmonic generation (SHG). While it has been experimentally observed that enhanced fields can significantly boost SHG, to date it proved difficult to probe electrical and magnetic resonances in one and the same nanostructure. This however is necessary to directly compare relative contributions of electrical and magnetic components of SHG enhancement. In this paper we report an experimental study of a metasurface capable of providing electrical and magnetic resonant SHG enhancement for TM polarization. Our metasurface could be engineered such that the peak frequencies of electrical and magnetic resonances could be adjusted independently. We used this feature to distinguish their relative contributions. Experimentally it was observed that the magnetic resonance provides only 50% as much enhancement to SHG as compar...

  19. An optimal design of coreless direct-drive axial flux permanent magnet generator for wind turbine

    Science.gov (United States)

    Ahmed, D.; Ahmad, A.

    2013-06-01

    Different types of generators are currently being used in wind power technology. The commonly used are induction generator (IG), doubly-fed induction generator (DFIG), electrically excited synchronous generator (EESG) and permanent magnet synchronous generator (PMSG). However, the use of PMSG is rapidly increasing because of advantages such as higher power density, better controllability and higher reliability. This paper presents an innovative design of a low-speed modular, direct-drive axial flux permanent magnet (AFPM) generator with coreless stator and rotor for a wind turbine power generation system that is developed using mathematical and analytical methods. This innovative design is implemented in MATLAB / Simulink environment using dynamic modelling techniques. The main focus of this research is to improve efficiency of the wind power generation system by investigating electromagnetic and structural features of AFPM generator during its operation in wind turbine. The design is validated by comparing its performance with standard models of existing wind power generators. The comparison results demonstrate that the proposed model for the wind power generator exhibits number of advantages such as improved efficiency with variable speed operation, higher energy yield, lighter weight and better wind power utilization.

  20. An optimal design of coreless direct-drive axial flux permanent magnet generator for wind turbine

    International Nuclear Information System (INIS)

    Different types of generators are currently being used in wind power technology. The commonly used are induction generator (IG), doubly-fed induction generator (DFIG), electrically excited synchronous generator (EESG) and permanent magnet synchronous generator (PMSG). However, the use of PMSG is rapidly increasing because of advantages such as higher power density, better controllability and higher reliability. This paper presents an innovative design of a low-speed modular, direct-drive axial flux permanent magnet (AFPM) generator with coreless stator and rotor for a wind turbine power generation system that is developed using mathematical and analytical methods. This innovative design is implemented in MATLAB / Simulink environment using dynamic modelling techniques. The main focus of this research is to improve efficiency of the wind power generation system by investigating electromagnetic and structural features of AFPM generator during its operation in wind turbine. The design is validated by comparing its performance with standard models of existing wind power generators. The comparison results demonstrate that the proposed model for the wind power generator exhibits number of advantages such as improved efficiency with variable speed operation, higher energy yield, lighter weight and better wind power utilization.

  1. Effect of transverse magnetic field on generation of electron beam in gas diode

    International Nuclear Information System (INIS)

    One studied experimentally the effect of the transverse magnetic field (0.08 and 0.016 T) on the generation of an electron beam within a gas diode. At U=25 kV gas diode voltage and helium low pressure (45 Torr) the transverse magnetic field is shown to affect the beam current amplitude outside the foil and on its foil cross section distribution. Under the increased pressure values and at generation of an ultra short-time avalanche electron beam (UAEB) in helium, nitrogen and in air the transverse magnetic field is shown to affect negligibly the UAEB amplitude and duration outside the foil. At the generator voltage equal to hundreds of kilovolts a portion of the escaping electrons was found to arrive to the gas diode lateral walls including those from the discharge plasma in the vicinity of a cathode

  2. Generation of a spin-polarized electron beam by multipole magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Ebrahim, E-mail: ekarimi@uottawa.ca [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Grillo, Vincenzo [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Boyd, Robert W. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Institute of Optics, University of Rochester, Rochester, NY 14627 (United States); Santamato, Enrico [Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, 80126 Napoli (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Napoli (Italy)

    2014-03-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin–magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of this analysis could prove useful in the design of an improved electron microscope. - Highlights: • Theory of generating spin-polarized electron beams. • Interacting electron vortex beams with space-variant magnetic fields. • Bohr–Pauli impossibility of generating spin-polarized free electrons.

  3. Encouragement of Enzyme Reaction Utilizing Heat Generation from Ferromagnetic Particles Subjected to an AC Magnetic Field.

    Science.gov (United States)

    Suzuki, Masashi; Aki, Atsushi; Mizuki, Toru; Maekawa, Toru; Usami, Ron; Morimoto, Hisao

    2015-01-01

    We propose a method of activating an enzyme utilizing heat generation from ferromagnetic particles under an ac magnetic field. We immobilize α-amylase on the surface of ferromagnetic particles and analyze its activity. We find that when α-amylase/ferromagnetic particle hybrids, that is, ferromagnetic particles, on which α-amylase molecules are immobilized, are subjected to an ac magnetic field, the particles generate heat and as a result, α-amylase on the particles is heated up and activated. We next prepare a solution, in which α-amylase/ferromagnetic particle hybrids and free, nonimmobilized chitinase are dispersed, and analyze their activities. We find that when the solution is subjected to an ac magnetic field, the activity of α-amylase immobilized on the particles increases, whereas that of free chitinase hardly changes; in other words, only α-amylase immobilized on the particles is selectively activated due to heat generation from the particles.

  4. Encouragement of Enzyme Reaction Utilizing Heat Generation from Ferromagnetic Particles Subjected to an AC Magnetic Field.

    Directory of Open Access Journals (Sweden)

    Masashi Suzuki

    Full Text Available We propose a method of activating an enzyme utilizing heat generation from ferromagnetic particles under an ac magnetic field. We immobilize α-amylase on the surface of ferromagnetic particles and analyze its activity. We find that when α-amylase/ferromagnetic particle hybrids, that is, ferromagnetic particles, on which α-amylase molecules are immobilized, are subjected to an ac magnetic field, the particles generate heat and as a result, α-amylase on the particles is heated up and activated. We next prepare a solution, in which α-amylase/ferromagnetic particle hybrids and free, nonimmobilized chitinase are dispersed, and analyze their activities. We find that when the solution is subjected to an ac magnetic field, the activity of α-amylase immobilized on the particles increases, whereas that of free chitinase hardly changes; in other words, only α-amylase immobilized on the particles is selectively activated due to heat generation from the particles.

  5. Reduction of Cogging Torque in Dual Rotor Permanent Magnet Generator for Direct Coupled Wind Energy Systems

    Directory of Open Access Journals (Sweden)

    Sivachandran Paulsamy

    2014-01-01

    Full Text Available In wind energy systems employing permanent magnet generator, there is an imperative need to reduce the cogging torque for smooth and reliable cut in operation. In a permanent magnet generator, cogging torque is produced due to interaction of the rotor magnets with slots and teeth of the stator. This paper is a result of an ongoing research work that deals with various methods to reduce cogging torque in dual rotor radial flux permanent magnet generator (DRFPMG for direct coupled stand alone wind energy systems (SAWES. Three methods were applied to reduce the cogging torque in DRFPMG. The methods were changing slot opening width, changing magnet pole arc width and shifting of slot openings. A combination of these three methods was applied to reduce the cogging torque to a level suitable for direct coupled SAWES. Both determination and reduction of cogging torque were carried out by finite element analysis (FEA using MagNet Software. The cogging torque of DRFPMG has been reduced without major change in induced emf. A prototype of 1 kW, 120 rpm DRFPMG was fabricated and tested to validate the simulation results. The test results have good agreement with the simulation predictions.

  6. Fiber Bragg Grating Sensor as Valuable Technological Platform for New Generation of Superconducting Magnets

    CERN Document Server

    Chiuchiolo, A; Cusano, A; Bajko, M; Perez, J C; Bajas, H; Viret, P; Giordano, M; Breglio, G

    2014-01-01

    New generation of superconducting magnets for high energy applications designed, manufactured and tested at the European Organization for Nuclear Research (CERN) require the implementation of reliable sensors able to monitor the mechanical stresses affecting the winding from fabrication to operation in magnetic field of 13 T. This work deals with the embedding of Fiber Bragg Grating sensors in a short model Nb3Sn dipole magnet in order to monitor the strain developed in the coil during the cool down to 1.9 K, the powering up to 15.8 kA and the warm up, offering perspectives for the replacement of standard strain gauges.

  7. Impact of continuous particle injection on generation and decay of the magnetic field in collisionless shocks

    Science.gov (United States)

    Garasev, Mikhail; Derishev, Evgeny

    2016-09-01

    We present numerical simulations of the magnetic field turbulence in a collisionless electron-positron plasma with continuous injection of new pairs, which maintains the anisotropy in the particle distribution over a long time. With these simulations, we follow the evolution of a small (and, therefore, uniform) region in the fluid comoving frame to model the generation and decay of the magnetic field in shocks. The upstream is modified by two-photon pair production due to self-absorption of the shock's high-energy radiation. We find that the overall picture of the magnetic field build-up is consistent with the development of Weibel instability. However, the long-term injection of anisotropic pairs in the upstream leads to the formation of large-scale structures in the magnetic field, while small-scale structures are almost absent. We find that being amplified at the shock front, this magnetic field mostly preserves its large spatial scale and then slowly decays in the downstream on a time-scale approximately equal to the duration of the injection phase. The observed decay of the magnetic field is in exceptionally good agreement with predictions of the so-called phase mixing model. The generation of a long-lived magnetic field in relativistic collisionless shocks with an injection-modified upstream explains how they can efficiently produce the synchrotron radiation in gamma-ray bursts.

  8. On the theory of magnetic field generation by relativistically strong laser radiation

    International Nuclear Information System (INIS)

    The authors consider the interaction of subpicosecond relativistically strong short laser pulses with an underdense cold unmagnetized electron plasma. It is shown that the strong plasma inhomogeneity caused by laser pulses results in the generation of a low frequency (quasistatic) magnetic field. Since the electron density distribution is determined completely by the pump wave intensity, the generated magnetic field is negligibly small for nonrelativistic laser pulses but increases rapidly in the ultrarelativistic case. Due to the possibility of electron cavitation (complete expulsion of electrons from the central region) for narrow and intense beams, the increase in the generated magnetic field slows down as the beam intensity is increased. The structure of the magnetic field closely resembles that of the field produced by a solenoid; the field is maximum and uniform in the cavitation region, then it falls, changes polarity and vanishes. In extremely dense plasmas, highly intense laser pulses in the self-channeling regime can generate magnetic fields ∼ 100 Mg and greater

  9. Fetal Circulation

    Science.gov (United States)

    ... Pressure High Blood Pressure Tools & Resources Stroke More Fetal Circulation Updated:Jul 8,2016 click to enlarge The ... fetal heart. These two bypass pathways in the fetal circulation make it possible for most fetuses to survive ...

  10. Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

    Science.gov (United States)

    Schmitter, E. D.

    2010-02-01

    Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate the charge density and the velocity field and in this way lead to electric and magnetic field oscillations in the 0.5-20-Hz range that can be monitored from a distance of several kilometers.

  11. Generation of large-scale magnetic fields from inflation in teleparallelism

    CERN Document Server

    Bamba, Kazuharu; Luo, Ling-Wei

    2012-01-01

    We explore the generation of large-scale magnetic fields from inflation in teleparallelism, in which the gravitational theory is described by the torsion scalar instead of the scalar curvature in general relativity. In particular, we examine the case that the conformal invariance of the electromagnetic field during inflation is broken by a non-minimal gravitational coupling between the torsion scalar and the electromagnetic field. It is shown that for a power-law type coupling, the magnetic field on 1Mpc scale with its strength of $\\sim 10^{-9}$G at the present time can be generated.

  12. Generation of large-scale magnetic fields from inflation in teleparallelism

    Energy Technology Data Exchange (ETDEWEB)

    Bamba, Kazuharu [Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Geng, Chao-Qiang; Luo, Ling-Wei, E-mail: bamba@kmi.nagoya-u.ac.jp, E-mail: geng@phys.nthu.edu.tw, E-mail: d9622508@oz.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 300, Taiwan (China)

    2012-10-01

    We explore the generation of large-scale magnetic fields from inflation in teleparallelism, in which the gravitational theory is described by the torsion scalar instead of the scalar curvature in general relativity. In particular, we examine the case that the conformal invariance of the electromagnetic field during inflation is broken by a non-minimal gravitational coupling between the torsion scalar and the electromagnetic field. It is shown that for a power-law type coupling, the magnetic field on 1 Mpc scale with its strength of ∼ 10{sup −9} G at the present time can be generated.

  13. Reducing costs of wind power with a gearless permanent-magnet generator

    International Nuclear Information System (INIS)

    This article examines a disc-type axial-field permanent magnet generator (PMG) utilizing the latest generation of permanent magnet material, namely Nd15B8Fe77. A frequency converter (FC) is needed to keep the system synchronized with the grid. It also offers a possibility to use variable speed. The main advantages of this novel system compared to the conventional one are a higher overall efficiency, better reliability, reduced weight and diminished need for maintenance, all contributing to the cost-reduction of wind power. (author)

  14. Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

    Directory of Open Access Journals (Sweden)

    E. D. Schmitter

    2010-02-01

    Full Text Available Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate the charge density and the velocity field and in this way lead to electric and magnetic field oscillations in the 0.5–20-Hz range that can be monitored from a distance of several kilometers.

  15. Multipolar third-harmonic generation driven by optically-induced magnetic resonances

    CERN Document Server

    Smirnova, Daria A; Smirnov, Lev A; Kivshar, Yuri S

    2016-01-01

    We analyze the third-harmonic generation from high-index dielectric nanoparticles and discuss the basic features and multipolar nature of the parametrically generated electromagnetic fields near the Mie-type optical resonances in silicon particles. By combining both analytical and numerical methods, we study the nonlinear scattering from simple nanoparticle geometries such as spheres and disks driven by the magnetic dipole resonance. We reveal the approaches for manipulating and directing the resonantly enhanced nonlinear emission with subwavelength all-dielectric structures that can be of a particular interest for a design of nonlinear optical antennas and engineering the magnetic optical nonlinear response at nanoscale.

  16. Reducing costs of wind power with a gearless permanent-magnet generator

    Energy Technology Data Exchange (ETDEWEB)

    Vihriaelae, H.; Peraelae, R.; Soederlund, L.; Eriksson, J.T. [Tampere Univ. of Technology (Finland). Lab. of Electricity and Magnetism

    1995-12-31

    This article examines a disc-type axial-field permanent magnet generator (PMG) utilizing the latest generation of permanent magnet material, namely Nd{sub 15}B{sub 8}Fe{sub 77}. A frequency converter (FC) is needed to keep the system synchronized with the grid. It also offers a possibility to use variable speed. The main advantages of this novel system compared to the conventional one are a higher overall efficiency, better reliability, reduced weight and diminished need for maintenance, all contributing to the cost-reduction of wind power. (author)

  17. Waves in plasmas generated by a rotating magnetic field and implications to radiation belts

    Science.gov (United States)

    Karavaev, Alexey V.

    The interaction of rotating magnetic fields (RMF) with magnetized plasmas is a fundamental plasma physics problem with implications to a wide range of areas, including laboratory and space plasma physics. Despite the importance of the topic the basic physics of the phenomenon remains unexplored. An important application of a RMF is its potential use as an efficient radiation source of low frequency waves in space plasmas, including whistler and shear Alfvéen waves (SAW) for controlled remediation of energetic particles in the Earth's radiation belts. In this dissertation the RMF waves generated in magnetized plasma are studied using numerical simulations with a semi-analytical three-dimensional magneto-hydrodynamic (MHD) model and experiments on the generation of whistler and magnetohydrodynamic waves conducted in UCLA's Large Plasma Device. Comparisons of the simulation results with the experimental measurements, namely, measured spatiotemporal wave structures, dispersion relation with finite transverse wave number, wave amplitude dependence on plasma and RMF source parameters, show good agreement in both the whistler and MHD wave regimes. In both the experiments and the 3D MHD simulations a RMF source was found to be very efficient in the generation of MHD and whistler waves with arbitrary polarizations. The RMF source drives significant field aligned plasma currents confined by the ambient magnetic field for both the whistler and MHD wave regimes, resulting in efficient transport of wave energy along the ambient magnetic field. The efficient transfer of the wave energy results in slow decay rates of the wave amplitude along the ambient magnetic field. The circular polarization of the waves generated by the RMF source, slow amplitude decay rate along the ambient magnetic field and nonzero transverse wave number determined by the RMF source size lead to nonlocal gradients of the wave magnetic field in the direction perpendicular to the ambient magnetic field. A

  18. Theory and experimental show up of axial magnetic fields self-generated in dense laser-produced plasmas

    International Nuclear Information System (INIS)

    The work presented in this thesis concerns the magnetic fields generated in laser produced plasma. A summary of the theoretical and experimental studies concerning the toroidal magnetic fields and realised by different groups of research is presented. Then, we present our original contribution on the generation of axial magnetic fields by the dynamo effect. The experimental work for the detection of magnetic field is based on the Faraday rotation and Zeeman effects. The experimental diagrams are detailed and discussed. The experimental results are presented and compared to the theory. Finaly, we present some consequences of the generation of the axial magnetic fields in laser produced plasma as a discussion of the thermal conductivity

  19. A highly efficient method for second and third harmonic generation from magnetic metamaterials

    CERN Document Server

    Sajedian, Iman; Zakery, Abdolnasser; Rho, Junsuk

    2016-01-01

    Second and third harmonic signals have been usually generated by using nonlinear crystals, but that method suffers from the low efficiency in small thicknesses. Metamaterials can be used to generate harmonic signals in small thicknesses. Here, we introduce a new method for amplifying second and third harmonic generation from magnetic metamaterials. We show that by using a grating structure under the metamaterial, the grating and the metamaterial form a resonator, and amplify the resonant behavior of the metamaterial. Therefore, we can generate second and third harmonic signals with high efficiency from this metamaterial-based nonlinear media.

  20. Detonation driven induction generators with parallel and antiparallel external and induced magnetic fields

    International Nuclear Information System (INIS)

    Based on Maxwell's equations, the electric current and voltage pulses induced in explosion driven induction generators (R/sub m/ = μ0sigmavL>>1) with plane electrodes and homogeneous external magnetic field B0 are calculated analytically for two plasma shock flows, (i) the jet flow with shock speed v(t) = v0, t> or =0, and (ii) the plane detonation flow with shock speed v(t) = (2/3)(E0/rho0)/sup 1/3/t/sup -1/3/, t> or =0. The external load circuit with resistance R0 and inductance L0 is connected either (I) to the downstream ends or (II) to the flow entrance ends of the electrodes so that the magnetic self-field B(t) of the generated current I(t) is (I) parallel and (II) antiparallel to the transverse external field B0. In both generator models I and II, the jet flow produces large current and voltage pulses, whereas the detonation flow generates considerably smaller and shorter current and voltage pulses. In all cases, the magnetic self-field B(t) of the generated current I(t) is of the order-of-magnitude of B0, but the generator with electrode wiring I (positive superposition of B and B0) produces considerably more power and energy than the generator with electrode wiring II (negative superposition of B and B0)

  1. 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...

  2. Generation of electromagnetic emission during the injection of dense supersonic plasma flows into arched magnetic field

    Science.gov (United States)

    Viktorov, Mikhail; Golubev, Sergey; Mansfeld, Dmitry; Vodopyanov, Alexander

    2016-04-01

    Interaction of dense supersonic plasma flows with an inhomogeneous arched magnetic field is one of the key problems in near-Earth and space plasma physics. It can influence on the energetic electron population formation in magnetosphere of the Earth, movement of plasma flows in magnetospheres of planets, energy release during magnetic reconnection, generation of electromagnetic radiation and particle precipitation during solar flares eruption. Laboratory study of this interaction is of big interest to determine the physical mechanisms of processes in space plasmas and their detailed investigation under reproducible conditions. In this work a new experimental approach is suggested to study interaction of supersonic (ion Mach number up to 2.7) dense (up to 1015 cm‑3) plasma flows with inhomogeneous magnetic field (an arched magnetic trap with a field strength up to 3.3 T) which opens wide opportunities to model space plasma processes in laboratory conditions. Fully ionized plasma flows with density from 1013 cm‑3 to 1015 cm‑3 are created by plasma generator on the basis of pulsed vacuum arc discharge. Then plasma is injected in an arched open magnetic trap along or across magnetic field lines. The filling of the arched magnetic trap with dense plasma and further magnetic field lines break by dense plasma flow were experimentally demonstrated. The process of plasma deceleration during the injection of plasma flow across the magnetic field lines was experimentally demonstrated. Pulsed plasma microwave emission at the electron cyclotron frequency range was observed. It was shown that frequency spectrum of plasma emission is determined by position of deceleration region in the magnetic field of the magnetic arc, and is affected by plasma density. Frequency spectrum shifts to higher frequencies with increasing of arc current (plasma density) because the deceleration region of plasma flow moves into higher magnetic field. The observed emission can be related to the

  3. Design Optimization and Site Matching of Direct-Drive Permanent Magnet Wind Generator Systems

    DEFF Research Database (Denmark)

    Li, H.; Chen, Zhe

    2009-01-01

    generator systems, the combinations of five rated rotor speeds in the range of 10-30 rpm and nine power ratings from 100 kW to 10 MW, are optimally designed, respectively. The optimum results are compared graphically in terms of the generator design indexes. Next, according to the design principle......This paper investigates the possible site matching of the direct-drive wind turbine concepts based on the electromagnetic design optimization of permanent magnet (PM) generator systems. Firstly, the analytical models of a three-phase radial-flux PM generator with a back-to-back power converter...... are presented. The optimum design models of direct-drive PM wind generation system are developed with an improved genetic algorithm, and a 500-kW direct-drive PM generator for the minimal generator active material cost is compared to demonstrate the effectiveness of the design optimization. Forty-five PM...

  4. Generation of a North/South Magnetic Field Component from Variations in the Photospheric Magnetic Field

    Science.gov (United States)

    Ulrich, Roger K.; Tran, Tham

    2016-04-01

    We address the problem of calculating the transverse magnetic field in the solar wind outside of the hypothetical sphere that is called the source surface where the solar wind originates. This calculation must overcome a widely used fundamental assumption about the source surface - the field is normally required to be purely radial at the source surface. Our model rests on the fact that a change in the radial field strength at the source surface is a change in the field line density. Surrounding field lines must move laterally to accommodate this field line density change. As the outward wind velocity drags field lines past the source surface, this lateral component of motion produces a tilt, implying there is a transverse component to the field. An analytic method of calculating the lateral translation speed of the field lines is developed. We apply the technique to an interval of approximately two Carrington rotations at the beginning of 2011 using 2-h averages of data from the Helioseismic Magnetic Imager instrument onboard the Solar Dynamics Observatory spacecraft. We find that the value of the transverse magnetic field is dominated on a global scale by the effects of high-latitude concentrations of field lines that are buffeted by supergranular motions.

  5. Electrical characteristics of an MHD generator with a transversally shaped configuration of magnetic induction

    International Nuclear Information System (INIS)

    Electrical characteristics of a Faraday-type MHD generator with a transversally shaped field configuration (SFC) of magnetic induction were investigated experimentally by using shock heated plasma. The magnetic induction was sharply reduced near electrodes in order to minimize the electrical losses caused by the Hall effect and the conductivity nonuniformity in the boundary layer. The performance of the proposed generator was experimentally compared with that of the conventional type with a uniform field configuration. It was shown that the apparent conductivity, the output power, and the internal resistance were markedly improved in the SFC design, namely, by a factor of from about 1.5 to 2.0. The experimental characteristics agreed qualitatively with results of three-dimensional computer simulations. A possible arrangement of the superconducting coil for the generation of the SFC for a full-scale MHD generator channel was also proposed

  6. Identification of some additional loss components in high-power low-voltage permanent magnet generators

    Energy Technology Data Exchange (ETDEWEB)

    Hamalainen, H.

    2013-11-01

    Permanent magnet generators (PMG) represent the cutting edge technology in modern wind mills. The efficiency remains high (over 90%) at partial loads. To improve the machine efficiency even further, every aspect of machine losses has to be analyzed. Additional losses are often given as a certain percentage without providing any detailed information about the actual calculation process; meanwhile, there are many design-dependent losses that have an effect on the total amount of additional losses and that have to be taken into consideration. Additional losses are most often eddy current losses in different parts of the machine. These losses are usually difficult to calculate in the design process. In this doctoral thesis, some additional losses are identified and modeled. Further, suggestions on how to minimize the losses are given. Iron losses can differ significantly between the measured no-load values and the loss values under load. In addition, with embedded magnet rotors, the quadrature-axis armature reaction adds losses to the stator iron by manipulating the harmonic content of the flux. It was, therefore, re-evaluated that in salient pole machines, to minimize the losses and the loss difference between the no-load and load operation, the flux density has to be kept below 1.5 T in the stator yoke, which is the traditional guideline for machine designers. Eddy current losses may occur in the end-winding area and in the support structure of the machine, that is, in the finger plate and the clamping ring. With construction steel, these losses account for 0.08% of the input power of the machine. These losses can be reduced almost to zero by using nonmagnetic stainless steel. In addition, the machine housing may be subjected to eddy current losses if the flux density exceeds 1.5 T in the stator yoke. Winding losses can rise rapidly when high frequencies and 10-15 mm high conductors are used. In general, minimizing the winding losses is simple. For example, it can be

  7. Performance impvovement of MHD generator by transversely shaped distribution of magnetic induction

    International Nuclear Information System (INIS)

    Effect of transversely shaped configuration of the applied magnetic induction upon the output performance of MHD generators was investigated. About 30% increase in the output power density was found even in the case of relatively small size of an oil-fired MHD channel with the magnetic induction of 2.65 Tesla. With increasing the magnetic induction over 4 Tesla, the power saturation characteristic appearing under the uniform magnetic field configuration was completely eliminated by employing the proposed transversely shaped magnetic field configuration. At the load matching condition, the output power density for the case of coal-fired commercial size MHD generators was improved by a factor of 200% under the assumed diffuse mode. About 100% power increase was obtained even when light load conditions were used in order to keep the maximum local current density below the critical value of the current density for avoiding the onset of transverse arcing. Also, no power saturation characteristics against the magnetic induction appeared even in such an above mentioned forced diffuse conduction mode. Preliminary experiments were performed using A-N2-K plasma and exhibited encouraging results for the present proposal

  8. Parametric Harmonic Generation as a Probe of Unconstrained Spin Magnetization Precession in the Shallow Barrier Limit.

    Science.gov (United States)

    Capua, Amir; Rettner, Charles; Parkin, Stuart S P

    2016-01-29

    We study the parametric excitation of high orders of magnetization precession in ultrathin films having perpendicular magnetic anisotropy. We observe that for a given driving field amplitude the harmonic generation can be increased by lowering the barrier with the application of an in-plane magnetic field in the manner of the Smit-Beljers effect. In this effect, the magnetic stiffness is reduced not by lowering the magnitude of the magnetic field upon which the spins precess, but rather by effectively releasing the field's "anchoring" point. This results in a shallow energy barrier where the electrons' spin is locally unconstrained. While the observation is unveiled in the form of nonlinear high harmonic generation, we believe that the physics whereby the barrier is suppressed by an external magnetic field may apply to other phenomena associated with ultrathin films. In these cases, such unconstrained motion may serve as a sensitive probe of the torques associated with proximate spin currents. Moreover, our approach may be used as a model system for the study of phase transitions in the field of nonlinear dynamics. PMID:26871356

  9. Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

    OpenAIRE

    E. D. Schmitter

    2010-01-01

    Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound ...

  10. Observation of magnetic field generation via the Weibel instability in interpenetrating plasma flows

    Energy Technology Data Exchange (ETDEWEB)

    Huntington, C. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Fiuza, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ross, J. S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zylstra, A. B. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Drake, R. P. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic, and Space Sciences; Froula, D. H. [Univ. of Rochester, NY (United States). Physics Dept. and Lab. for Laser Energetics; Gregori, G. [Univ. of Oxford (United Kingdom). Dept. of Physics; Kugland, N. L. [Lam Research Corp., Fremont, CA (United States); Kuranz, C. C. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Atmospheric, Oceanic, and Space Sciences; Levy, M. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Li, C. K. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Meinecke, J. [Univ. of Oxford (United Kingdom). Dept. of Physics; Morita, T. [Osaka Univ. (Japan). Inst. of Laser Engineering; Petrasso, R. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Plechaty, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Remington, B. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ryutov, D. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sakawa, Y. [Osaka Univ. (Japan). Inst. of Laser Engineering; Spitkovsky, A. [Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences; Takabe, H. [Osaka Univ. (Japan). Inst. of Laser Engineering; Park, H.-S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-01-19

    Collisionless shocks can be produced as a result of strong magnetic fields in a plasma flow, and therefore are common in many astrophysical systems. The Weibel instability is one candidate mechanism for the generation of su fficiently strong fields to create a collisionless shock. Despite their crucial role in astrophysical systems, observation of the magnetic fields produced by Weibel instabilities in experiments has been challenging. Using a proton probe to directly image electromagnetic fields, we present evidence of Weibel-generated magnetic fields that grow in opposing, initially unmagnetized plasma flows from laser-driven laboratory experiments. Three-dimensional particle-in-cell simulations reveal that the instability effi ciently extracts energy from the plasma flows, and that the self-generated magnetic energy reaches a few percent of the total energy in the system. Furthermore, this result demonstrates an experimental platform suitable for the investigation of a wide range of astrophysical phenomena, including collisionless shock formation in supernova remnants, large-scale magnetic field amplification, and the radiation signature from gamma-ray bursts.

  11. Wide operation frequency band magnetostrictive vibration power generator using nonlinear spring constant by permanent magnet

    Science.gov (United States)

    Furumachi, S.; Ueno, T.

    2016-04-01

    We study magnetostrictive vibration based power generator using iron-gallium alloy (Galfenol). The generator is advantages over conventional, such as piezoelectric material in the point of high efficiency highly robust and low electrical impedance. Generally, the generator exhibits maximum power when its resonant frequency matches the frequency of ambient vibration. In other words, the mismatch of these frequencies results in significant decrease of the output. One solution is making the spring characteristics nonlinear using magnetic force, which distorts the resonant peak toward higher or lower frequency side. In this paper, vibrational generator consisting of Galfenol plate of 6 by 0.5 by 13 mm wound with coil and U shape-frame accompanied with plates and pair of permanent magnets was investigated. The experimental results show that lean of resonant peak appears attributed on the non-linear spring characteristics, and half bandwidth with magnets is 1.2 times larger than that without. It was also demonstrated that the addition of proof mass is effective to increase the sensitivity but also the bandwidth. The generator with generating power of sub mW order is useful for power source of wireless heath monitoring for bridge and factory machine.

  12. Coordinated Low Voltage Ride through strategies for Permanent Magnet Direct Drive Synchronous Generators

    Directory of Open Access Journals (Sweden)

    Zhang Ge

    2016-01-01

    Full Text Available By analyzing the mechanism of the low voltage ride through on the permanent magnet direct drive synchronous wind power generating units, this paper proposes a coordinated control strategy for permanent magnet synchronous generator. In order to avoid over speed operation of the generation units, over voltage on DC capacitor and over current on convert, the improved pitch angle control and inverter control are used. When the grid voltage drops, the captured wind power is cut down by the variable pitch system, which limits the speed of the generator, the generator side converter keeps the DC capacitor voltage stabile; and the grid side converter provides reactive power to the grid to help the grid voltage recover. The control strategy does not require any additional hardware equipment, with existing control means, the unit will be able to realize low voltage ride through. Finally, based on Matlab/Simulink to build permanent magnet direct drive wind power generation system, the simulation results verify the correctness and effectiveness of the control strategy.

  13. [Changes in prostatic circulation in response to laser therapy and magnetic therapy in patients with benign prostatic hyperplasia].

    Science.gov (United States)

    2005-01-01

    The results of preoperative preparation were analysed in 59 patients with prostatic benign hyperplasia (PBH) subjected to TUR. Treatment outcomes were assessed by transrectal ultrasound (color Doppler mapping) in two groups of patients. Group 1 received combined therapy including transrectal laser radiation of the prostate, group 2--transrectal magnetotherapy. The analysis showed that laser radiation reduced insignificantly the size of the prostate and adenomatous node, improved microcirculation and circulation in the prostate. This resulted in relief of inflammation and reduction of the number of postoperative inflammatory complications. Transrectal magnetotherapy has a positive effect on vascularization and hemodynamics of the prostate, local immunity, contamination of the tissues with pathogenic flora. PMID:16419474

  14. Simplified theory of nonuniform electrical conduction for an open cycle MHD generator with shaped magnetic induction

    International Nuclear Information System (INIS)

    Simplified formulae were derived for the approximate evaluation of electrical performances of an MHD generator with nonuniform equilibrium plasma. In order to clarify the effectiveness of the properly shaped nonuniform magnetic induction of the type B varies as nsub(e), the transverse component Bsub(y) was included in the formulation of the theory. It was shown that the terminal characteristics of the generator, such as the internal resistance, the motional emf, the current and the output power could be improved significantly under the shaped Bsub(z) varies as nsub(e) type of applied magnetic induction for wide ranges of electrode- and insulator wall temperatures, channel sizes and averaged intensities of the magnetic induction. (author)

  15. Self-generated magnetic fields in blast-wave driven Rayleigh-Taylor experiments

    Science.gov (United States)

    Flaig, Markus; Plewa, Tomasz

    2015-12-01

    We study the effect of self-generated magnetic fields in two-dimensional computer models of blast-wave driven high-energy density Rayleigh-Taylor instability (RTI) experiments. Previous works [1,2] suggested that such fields have the potential to influence the RTI morphology and mixing. When neglecting the friction force between electrons and ions, we do indeed find that dynamically important (β≲103) magnetic fields are generated. However, in the more realistic case where the friction force is accounted for, the resulting fields are much weaker, β≳105 , and can no longer influence the dynamics of the system. Although we find no evidence for dynamically important magnetic fields being created in the two-dimensional case studied here, the situation might be different in a three-dimensional setup, which will be addressed in a future study.

  16. Thermal Analysis on Radial Flux Permanent Magnet Generator (PMG using Finite Element Method

    Directory of Open Access Journals (Sweden)

    Hilman Syaeful A Syaeful A

    2011-05-01

    Full Text Available The main source of heat in the permanent magnet generator (PMG is the total losses which f come from winding losses, core losses and rotational losses. Total heat arising from such these losses must be properly distributed and maintained so as not to exceed the maximum allowable temperature to prevent damage to insulation on the winding and demagnetization on the permanent magnet machines. In this research, we consider thermal analysis which is occurred on the radial flux PMG by using finite element method to determine the extent to which the heat generated can be properly distributed. The simulation results show that there are no points of heat concentration or hot spot. The simulation maximum temperatures of the permanent magnet and the winding are 39.1oC and 72.5oC respectively while the experimental maximum temperature of the winding is 62oC.

  17. Magnetic moment generation from non-minimal couplings in a scenario with Lorentz-symmetry violation

    Energy Technology Data Exchange (ETDEWEB)

    Belich, H. [Universidade Federal do Espirito Santo (UFES), Departamento de Fisica e Quimica, Vitoria, ES (Brazil); Universidade de Brasilia, International Center for Condensed Matter Physics, CP 04513, Brasilia, DF (Brazil); Grupo de Fisica Teorica Jose Leite Lopes, CP 91933, Petropolis, RJ (Brazil); Colatto, L.P. [CEFET-RJ UnED-Petropolis, Petropolis, RJ (Brazil); Grupo de Fisica Teorica Jose Leite Lopes, CP 91933, Petropolis, RJ (Brazil); Costa-Soares, T. [Universidade Federal de Juiz de Fora (UFJF), Colegio Tecnico Universitario, Juiz de Fora, MG (Brazil); Grupo de Fisica Teorica Jose Leite Lopes, CP 91933, Petropolis, RJ (Brazil); Helayel-Neto, J.A. [CBPF-Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, RJ (Brazil); Grupo de Fisica Teorica Jose Leite Lopes, CP 91933, Petropolis, RJ (Brazil); Orlando, M.T.D. [Universidade Federal do Espirito Santo (UFES), Departamento de Fisica e Quimica, Vitoria, ES (Brazil); Grupo de Fisica Teorica Jose Leite Lopes, CP 91933, Petropolis, RJ (Brazil)

    2009-07-15

    This paper deals with situations that illustrate how the violation of Lorentz symmetry in the gauge sector may contribute to magnetic moment generation of massive neutral particles with spin-1/(2) and spin-1. The procedure we adopt here is based on Relativistic Quantum Mechanics. We work out the non-relativistic regime that follows from the wave equation corresponding to a certain particle coupled to an external electromagnetic field and a background that accounts for the Lorentz-symmetry violation, and we thereby read off the magnetic dipole moment operator for the particle under consideration. We keep track of the parameters that govern the non-minimal electromagnetic coupling and the breaking of Lorentz symmetry in the expressions we get for the magnetic moments in the different cases we contemplate. Our claim is that the tiny magnetic dipole moment of truly-elementary neutral particles might signal Lorentz-symmetry violation. (orig.)

  18. Adiabatically twisting a magnetic molecule to generate pure spin currents in graphene

    International Nuclear Information System (INIS)

    The spin–orbit effect in graphene is too muted to have any observable significance with respect to its application in spintronics. However, graphene technology is too valuable to be rendered impotent to spin transport. In this communication we look at the effect of adiabatically twisting a single-molecule magnet embedded in a graphene monolayer. Surprisingly, we see that pure spin currents (zero charge current) can be generated from the system via quantum pumping. In addition we also see that spin-selective current can be pumped from the system. The pure spin current seen is quite resilient to temperature while disorder has a limited effect. Furthermore, the direction of these spin-pumped currents can be easily and exclusively controlled by the magnetization of the single-molecule magnet, with disorder having no effect on the magnetization control of the pumped spin currents. (paper)

  19. Generation of ULF waves by electric or magnetic dipoles. [propagation from earth surface to ionosphere

    Science.gov (United States)

    Harker, K. J.

    1975-01-01

    The generation of ULF waves by ground-based magnetic and electric dipoles is studied with a simplified model consisting of three adjoining homogeneous regions representing the groud, the vacuum (free space) region, and the ionosphere. The system is assumed to be immersed in a homogeneous magnetic field with an arbitrary tilt angle. By the use of Fourier techniques and the method of stationary phase, analytic expressions are obtained for the field strength of the compressional Alfven waves in the ionosphere. Expressions are also obtained for the strength of the torsional Alfven wave in the ionosphere and the ULF magnetic field at ground level. Numerical results are obtained for the compressional Alfven-wave field strength in the ionosphere with a nonvertical geomagnetic field and for the ULF magnetic field at ground level for a vertical geomagnetic field.

  20. A novel HTS SMES application in combination with a permanent magnet synchronous generator type wind power generation system

    Energy Technology Data Exchange (ETDEWEB)

    Kim, G.H.; Kim, A.R.; Kim, S. [Changwon National University, 9 Sarim-dong, Changwon 641-773 (Korea, Republic of); Park, M., E-mail: paku@changwon.ac.kr [Changwon National University, 9 Sarim-dong, Changwon 641-773 (Korea, Republic of); Yu, I.K. [Changwon National University, 9 Sarim-dong, Changwon 641-773 (Korea, Republic of); Seong, K.C. [Superconducting Device and Cryogenics Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Won, Y.J. [Korea Electric Power Corporation, Changwon 641-241 (Korea, Republic of)

    2011-11-15

    A novel connection topology of SMES is proposed in this paper. Structure of the proposed system is cost-effective because it reduces a converter. The proposed system smoothens output power of wind power generation system. Advantage of the system is to improve the low voltage ride through capability. Superconducting magnetic energy storage (SMES) system is a DC current driven device and can be utilized to improve power quality particularly in connection with renewable energy sources due to higher efficiency and faster response than other devices. This paper suggests a novel connection topology of SMES which can smoothen the output power flow of the wind power generation system (WPGS). The structure of the proposed system is cost-effective because it reduces a power converter in comparison with a conventional application of SMES. One more advantage of SMES in the proposed system is to improve the capability of low voltage ride through (LVRT) for the permanent magnet synchronous generator (PMSG) type WPGS. The proposed system including a SMES has been modeled and analyzed by a PSCAD/EMTDC. The simulation results show the effectiveness of the novel SMES application strategy to not only mitigate the output power of the PMSG but also improve the capability of LVRT for PMSG type WPGS.

  1. A novel HTS SMES application in combination with a permanent magnet synchronous generator type wind power generation system

    International Nuclear Information System (INIS)

    A novel connection topology of SMES is proposed in this paper. Structure of the proposed system is cost-effective because it reduces a converter. The proposed system smoothens output power of wind power generation system. Advantage of the system is to improve the low voltage ride through capability. Superconducting magnetic energy storage (SMES) system is a DC current driven device and can be utilized to improve power quality particularly in connection with renewable energy sources due to higher efficiency and faster response than other devices. This paper suggests a novel connection topology of SMES which can smoothen the output power flow of the wind power generation system (WPGS). The structure of the proposed system is cost-effective because it reduces a power converter in comparison with a conventional application of SMES. One more advantage of SMES in the proposed system is to improve the capability of low voltage ride through (LVRT) for the permanent magnet synchronous generator (PMSG) type WPGS. The proposed system including a SMES has been modeled and analyzed by a PSCAD/EMTDC. The simulation results show the effectiveness of the novel SMES application strategy to not only mitigate the output power of the PMSG but also improve the capability of LVRT for PMSG type WPGS.

  2. 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...

  3. Low Voltage Ride-Through of Variable Speed Wind Turbines with Permanent Magnet Synchronous Generator

    DEFF Research Database (Denmark)

    Hu, Weihao; Chen, Zhe; Wang, Yue;

    2009-01-01

    This paper presents a simulation model of a MW-level variable speed wind turbine with a permanent magnet synchronous generator (PMSG) and a full-scale converter developed in the simulation tool of PSCAD/EMTDC. The low voltage ride-through (LVRT) capability of the wind turbine is investigated. A new...... speed wind turbines with PMSG....

  4. Tsunami-generated magnetic fields may constrain focal mechanisms of earthquakes.

    Science.gov (United States)

    Kawashima, Issei; Toh, Hiroaki

    2016-01-01

    A geomagnetic observatory named SFEMS is being operated on the deep seafloor in the northwest Pacific since August, 2001. SFEMS is capable of measuring both scalar and vector geomagnetic fields as well as the seafloor instrument's precise attitudes, which makes it a powerful tool in detecting the so-called oceanic dynamo effect. It was found that SFEMS captured clear magnetic signals generated by the giant tsunamis of the 2011 Tohoku Earthquake even for an epicentral distance of larger than 1500 km. Here we report estimates of the focal mechanism of a closer tsunamigenic earthquake in January, 2007 on the seaward slope of the Kuril Trench using tsunami-generated variations in the observed downward magnetic component. Three-dimensional solutions of the tsunami-generated magnetic components were calculated by a new numerical code based on non-uniform thin-sheet approximation and particle motions of seawater using the linear Boussinesq approximation. As a result, a southeast dipping fault alone reproduced the dispersive nature of the downward magnetic component, while any northwest dipping faults could not. This implies that the tsunami-generated electromagnetic fields are useful for determination of focal mechanisms of tsunamigenic earthquakes, since fault dips are one of the most difficult source parameters to estimate even in modern seismology. PMID:27353343

  5. Experimental studies of the pressures generated by a liquid oxygen slug in a magnetic field

    Science.gov (United States)

    Boulware, Jeffrey C.; Ban, Heng; Jensen, Scott; Wassom, Steve

    2010-07-01

    The strong paramagnetic susceptibility of liquid oxygen (LOX) has established it as a good candidate for a cryogenic magnetic fluid system. While its properties have been known for several decades, a fundamental understanding of the behavior of LOX in a magnetically controlled fluid system is needed for the development of a suitable space application that can operate reliably and efficiently. This study conducted quantitative experiments on the dynamics of a LOX slug in a tube when subjected to electrically-induced magnetic fields within a solenoid. The experiments used a quartz tube with an inner diameter of 1.9 mm and LOX slugs of 0.6, 1.3, 1.9, 2.5, and 3.2 mm length at various initial positions relative to the solenoid. The pressures generated by the motion of the LOX slug under the magnetic force were recorded to characterize the pressure differential generated and the breakdown of the slug. The highest attainable pressure differential was found to be 1.45 kPa, which correlated well to theoretical predictions once the analysis accounted for the resistance heating of the solenoid. The noted differences between experimental results and theory could also be attributed to impeded slug motion from shear and mass forces. Within the workable pressure range, however, an optimal slug length was found which appropriately balances the pressure, shear, and magnetic forces in the system. This paper presents the experimental data on the dynamics and the maximum pressure differential generated by a LOX slug in a magnetic field and discusses the viability of LOX in a magnetic fluid management system intended for space applications.

  6. New generation of cryogen free advanced superconducting magnets for neutron scattering experiments

    Science.gov (United States)

    Kirichek, O.; Brown, J.; Adroja, D. T.; Manuel, P.; Kouzmenko, G.; Bewley, R. I.; Wotherspoon, R.

    2012-12-01

    Recent advances in superconducting technology and cryocooler refrigeration have resulted in a new generation of advanced superconducting magnets for neutron beam applications. These magnets have outstanding parameters such as high homogeneity and stability at highest magnetic fields possible, a reasonably small stray field, low neutron scattering background and larger exposure to neutron detectors. At the same time the pulse tube refrigeration technology provides a complete re-condensing regime which allows to minimise the requirements for cryogens without introducing additional noise and mechanical vibrations. The magnets can be used with dilution refrigerator insert which expands the temperature range from 20mK to 300K. Here we are going to present design, test results and the operational data of the 14T magnet for neutron diffraction and the 9T wide angle chopper magnet for neutron spectroscopy developed by Oxford Instruments in collaboration with ISIS neutron source. First scientific results obtained from the neutron scattering experiments with these magnets are also going to be discussed.

  7. Can Impact-generated Plasmas be Responsible for Magnetization on Moon?

    Science.gov (United States)

    Oran, Rona; Shprits, Yuri; Weiss, Benjamin

    2016-04-01

    Although the Moon presently does not have a core dynamo magnetic field, spacecraft measurements have revealed the presence of remanent magnetization in the lunar crust. The source of the crustal magnetic anomalies remains uncertain. A key question is whether the crustal magnetization is a record of ancient intrinsic fields, or whether they were created by external fields. In the latter case, an ancient dynamo field is not needed in order to explain the anomalies. This carries broad implications to our understanding of the Moon's thermal history and current internal structure. Furthermore, the lunar crustal field serves as a test case for understanding magnetization of other solar system bodies, such as Mars, Mercury, and asteroids. Strong anomalies were identified at the antipodes of young large impact craters, which has led to the theory that meteor impacts may be responsible for the magnetization of the crust. In this picture ionized vapor clouds, generated by the impacts, interact and compress the surrounding solar wind. These transient field amplifications would subsequently be recorded by heated or shocked lunar rocks. Although this hypothesis has been studied for several decades using hydrodynamic and impact simulations, all simulations thus far did not include the magnetic field, and magnetic field amplification was only estimated from general geometric arguments. To address this gap, we coducted the first magnetohydrodynamic simulations of this process. We systematically explore the role of magnetic field reconnection, variable solar wind conditions, friction between the vapor and molten ejecta, and the finite resistivity of the lunar mantle and crust. Our preliminary results show that vapor expansion and magnetic field reconnection would cause large amounts of solar wind magnetic flux to be removed, leading to only moderate field amplification at the antipodes, several orders of magnitude below the required value. We propose that the compression of the

  8. MODELING AND STUDY OF HYDROELECTRIC GENERATING SETS OF SMALL HYDRO POWER PLANTS WITH FREQUENCY-CONTROLLED PERMANENT MAGNET SYNCHRONOUS GENERATORS

    Directory of Open Access Journals (Sweden)

    R. I. Mustafayev

    2016-01-01

    Full Text Available Currently, the hydroelectric generating sets of small HPPs with Pelton turbines employ as their generating units conventional synchronous generators with electromagnetic excitation. To deal with the torque pulsatile behaviour, they generally install a supplementary flywheel on the system shaft that levels the pulsations. The Pelton turbine power output is adjusted by the needle changing water flow in the nozzle, whose advancement modifies the nozzle area and eventually – the flow. They limit the needle full stroke time to 20–40 sec. since quick shutting the nozzle for swift water flow reduction may result in pressure surges. For quick power adjustment so-called deflectors are employed, whose task is retraction of water jets from the Pelton turbine buckets. Thus, the mechanical method of power output regulation requires agreement between the needle stroke inside the turbine nozzles and the deflector. The paper offers employing frequency-controlled synchronous machines with permanent magnets qua generating units for the hydroelectric generating sets of small HPPs with Pelton turbines. The developed computer model reveals that this provides a higher level of adjustability towards rapid-changing loads in the grid. Furthermore, this will replace the power output mechanical control involving the valuable deflector drive and the turbine nozzle needles with electrical revolution rate and power output regulation by a frequency converter located in the generator stator circuit. Via frequency start, the controllable synchronous machine ensures stable operation of the hydroelectric generating set with negligibly small amount of water (energy carrier. Finally, in complete absence of water, the frequency-relay start facilitates shifting the generator operation to the synchronous capacitor mode, which the system operating parameter fluctograms obtained through computer modeling prove. 

  9. Generation of a North/South Magnetic Field Component from Variations in the Photospheric Magnetic Field

    CERN Document Server

    Ulrich, Roger K

    2016-01-01

    We address the problem of calculating the transverse magnetic field in the solar wind outside of the hypothetical sphere called the source surface where the solar wind originates. This calculation must overcome a widely used fundamental assumption about the source surface -- the field is normally required to purely radial at the source surface. Our model rests on the fact that a change in the radial field strength at the source surface is a change in the field line density. Surrounding field lines must move laterally in order to accommodate this field line density change. As the outward wind velocity drags field lines past the source surface this lateral component of motion produces a tilt implying there is a transverse component to the field. An analytic method of calculating the lateral translation speed of the field lines is developed. We apply the technique to an interval of approximately two Carrington rotations at the beginning of 2011 using 2-h averages of data from the Helioseismic Magnetic Imager ins...

  10. Demonstration of variable speed permanent magnet generator at small, low-head hydro site

    Energy Technology Data Exchange (ETDEWEB)

    Brown Kinloch, David [Shaker Landing Hydro Associates, Inc., Louisville, KY (United States)

    2015-12-18

    Small hydro developers face a limited set of bad choices when choosing a generator for a small low-head hydro site. Direct drive synchronous generators are expensive and technically complex to install. Simpler induction generators are higher speed, requiring a speed increaser, which results in inefficiencies and maintenance problems. In addition, both induction and synchronous generators turn at a fixed speed, causing the turbine to run off its peak efficiency curve whenever the available head is different than the designed optimum head.The solution to these problems is the variable speed Permanent Magnet Generators (PMG). At the Weisenberger Mill in Midway, KY, a variable speed Permanent Magnet Generator has been installed and demonstrated. This new PMG system replaced an existing induction generator that had a HTD belt drive speed increaser system. Data was taken from the old generator before it was removed and compared to data collected after the PMG system was installed. The new variable speed PMG system is calculated to produce over 96% more energy than the old induction generator system during an average year. This significant increase was primarily due to the PMG generator operating at the correct speed at the maximum head, and the ability for the PMG generator to reduce its speed to lower optimum speeds as the stream flow increased and the net head decreased.This demonstration showed the importance of being able to adjust the speed of fixed blade turbines. All fixed blade turbines with varying net heads could achieve higher efficiencies if the speed can be matched to the optimum speed as the head changes. In addition, this demonstration showed that there are many potential efficiencies that could be realized with variable speed technology at hydro sites where mismatched turbine and generator speeds result in lower power output, even at maximum head. Funding for this project came from the US Dept. of Energy, through Award Number DE-EE0005429.

  11. Generation of spin polarization in graphene by the spin-orbit interaction and a magnetic barrier

    Science.gov (United States)

    Zhang, Qingtian; Chan, K. S.; Lin, Zijing

    2014-10-01

    We study the generation of spin polarization in monolayer graphene in the presence of Rashba spin-orbit interaction (SOI) and a ferromagnetic (FM) stripe. It is shown that Rashba SOI alone can generate an in-plane (x-y plane) spin polarization, but a FM stripe with magnetization parallel to the current direction cannot generate any spin polarization. A combination of the Rashba SOI and the magnetic field of a FM stripe can increase the spin polarization to a value close to 100%, and the polarization components can be found along the x, y and z directions. The attainment of highly spin polarized current using the Rashba SOI and FM effect could have useful applications in the development of graphene spintronics.

  12. Stability Augmentation of Wind Farm using Variable Speed Permanent Magnet Synchronous Generator

    Science.gov (United States)

    Rosyadi, Marwan; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

    This paper presents a new control strategy of variable speed permanent magnet wind generator for stability augmentation of wind farm including fixed speed wind turbine with Induction Generator (IG). A new control scheme is developed for two levels back-to-back converters of Permanent Magnet Synchronous Generator (PMSG), by which both active and reactive powers delivered to the grid can be controlled easily. To avoid the converter damage, the DC link protection controller is also proposed in order to protect the dc link circuit during fault condition. To evaluate the control capability of the proposed controllers, simulations are performed on two model systems composed of wind farms connected to an infinite bus. From transient and steady state analyses by using PSCAD/EMTDC, it is concluded that the proposed control scheme is very effective to improve the stability of wind farm for severe network disturbance and randomly fluctuating wind speed.

  13. Entropy generation during fluid flow in a channel under the effect of transverse magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Damseh, R.A.; Al-Odat, M.Q. [Al-Huson University College, Al-Balqa Applied University, Mechanical Engineering Department, P.O.B (50), Irbid (Jordan); Al-Nimr, M.A. [Jordan University of Science and Technology, Mechanical Engineering Department, Irbid (Jordan)

    2008-06-15

    Entropy generation due to fluid flow and heat transfer inside a horizontal channel made of two parallel plates under the effect of transverse magnetic field is numerically investigated. The flow is assumed to be steady, laminar, hydro-dynamically and thermally fully developed of electrically conducting fluid. Both horizontal walls are maintained at constant temperatures higher than that of the fluid. The governing equations in Cartesian coordinate are solved by an implicit finite difference technique. After the flow field and the temperature distributions are obtained, the entropy generation profiles are computed and presented graphically. The factors, which were found to affect the problem under consideration are the magnetic parameter, Eckert number, Prandtl number, and the temperature parameter ({theta}{sub {infinity}}). It was found that, entropy generation increased as all parameters involved in the present problem increased. (orig.)

  14. The generation of magnetic fields by the Biermann battery and the interplay with the Weibel instability

    CERN Document Server

    Schoeffler, K M; Fonseca, R A; Silva, L O

    2015-01-01

    An investigation of magnetic fields generated in an expanding bubble of plasma with misaligned temperature and density gradients (driving the Biermann battery mechanism) is performed. With gradient scales $L$, large-scale magnetic fields are generated by the Biermann battery mechanism with plasma $\\beta \\sim 1$, as long as $L$ is comparable to the ion inertial length $d_i$. For larger system sizes, $L/d_e > 100$ (where $d_e$ is the electron inertial length), the Weibel instability generates magnetic fields of similar magnitude but with wavenumber $k d_e \\sim 0.2$. In both cases, the growth and saturation of these fields have a weak dependence on mass ratio $m_i/m_e$, indicating electron mediated physics. A scan in system size is performed at $m_i/m_e = 2000$, showing agreement with previous results with $m_i/m_e = 25$. In addition, the instability found at large system sizes is quantitatively demonstrated to be the Weibel instability. Furthermore, magnetic and electric energy spectra at scales below the elect...

  15. Relationships between atmospheric circulation indices and rainfall in Northern Algeria and comparison of observed and RCM-generated rainfall

    Science.gov (United States)

    Taibi, S.; Meddi, M.; Mahé, G.; Assani, A.

    2015-09-01

    This work aims, as a first step, to analyze rainfall variability in Northern Algeria, in particular extreme events, during the period from 1940 to 2010. Analysis of annual rainfall shows that stations in the northwest record a significant decrease in rainfall since the 1970s. Frequencies of rainy days for each percentile (5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th) and each rainfall interval class (1-5, 5-10, 10-20, 20-50, and ≥50 mm) do not show a significant change in the evolution of daily rainfall. The Tenes station is the only one to show a significant decrease in the frequency of rainy days up to the 75th percentile and for the 10-20-mm interval class. There is no significant change in the temporal evolution of extreme events in the 90th, 95th, and 99th percentiles. The relationships between rainfall variability and general atmospheric circulation indices for interannual and extreme event variability are moderately influenced by the El Niño-Southern Oscillation and Mediterranean Oscillation. Significant correlations are observed between the Southern Oscillation Index and annual rainfall in the northwestern part of the study area, which is likely linked with the decrease in rainfall in this region. Seasonal rainfall in Northern Algeria is affected by the Mediterranean Oscillation and North Atlantic Oscillation in the west. The ENSEMBLES regional climate models (RCMs) are assessed using the bias method to test their ability to reproduce rainfall variability at different time scales. The Centre National de Recherches Météorologiques (CNRM), Czech Hydrometeorological Institute (CHMI), Eidgenössische Technische Hochschule Zürich (ETHZ), and Forschungszentrum Geesthacht (GKSS) models yield the least biased results.

  16. Study on the Fault-Tolerance Concept of the Five-Phase Permanent Magnet Synchronous Generator

    Directory of Open Access Journals (Sweden)

    LIVADARU, L.

    2014-05-01

    Full Text Available In this paper an investigation on the fault tolerance capability of the five-phase permanent magnet synchronous generator is presented. The electric machine, which has lap stator winding and surface permanent magnets, has been designed for islanded-use purposes. The study takes into consideration the open-circuit type faults. It was analyzed the operation under healthy, one-phase open-circuited and two-phase open-circuited (adjacent and non-adjacent conditions respectively. The results derive from FEM-based simulations and experimental tests.

  17. LETTER TO THE EDITOR: Magnetic islands and spontaneous generation of zonal flows

    Science.gov (United States)

    Grasso, D.; Margheriti, L.; Porcelli, F.; Tebaldi, C.

    2006-09-01

    A study of saturated magnetic island equilibria on the basis of the resistive magneto-hydro-dynamic model is presented. A bifurcation in the sequence of equilibria is found as the ratio of the width of the current layer in the initial (non-reconnected) configuration over the island periodicity length reaches a critical threshold. Below this threshold, spontaneous generation of zonal flows occurs. This result is suggestive of a possible evolution of current sheets in magnetically confined plasmas and may be relevant to the understanding of the suppression of drift-wave turbulence and the formation of internal transport barriers in tokamak experiments.

  18. Bifurcation analysis in a vortex flow generated by an oscillatory magnetic obstacle

    DEFF Research Database (Denmark)

    Beltrán, A.; Ramos, E.; Cuevas, S.;

    2010-01-01

    A numerical simulation and a theoretical model of the two-dimensional flow produced by the harmonic oscillation of a localized magnetic field (magnetic obstacle) in a quiescent viscous, electrically conducting fluid are presented. Nonuniform Lorentz forces produced by induced currents interacting...... of rotation twice per cycle. The transformation of the flow field present in the first part of the cycle into the pattern displayed in the second half occurs via the generation of hyperbolic and elliptic critical points. The numerical solution of the flow indicates that for low frequencies (v.e. Re-omega = 1...

  19. Generation of low-frequency electric and magnetic fields during large- scale chemical and nuclear explosions

    Energy Technology Data Exchange (ETDEWEB)

    Adushkin, V.V. [Academy of Sciences, Moscow (Russian Federation). Inst. for Dynamics of the Geospheres; Dubinya, V.A.; Karaseva, V.A.; Soloviev, S.P.; Surkov, V.V. [Lawrence Livermore National Lab., CA (United States)

    1995-06-01

    We discuss the main parameters of the electric field in the surface layer of the atmosphere and the results of the investigations of the natural electric field variations. Experimental investigations of the electromagnetic field for explosions in air are presented. Electromagnetic signals generated by underground nuclear and chemical explosions are discussed and explosions for 1976--1991 are listed. Long term anomalies of the earth`s electromagnetic field in the vicinity of underground explosions were also investigated. Study of the phenomenon of the irreversible shock magnetization showed that in the zone nearest to the explosion the quasistatic magnetic field decreases in inverse proportion to the distance.

  20. Modeling and analysis of solar wind generated contributions to the near-Earth magnetic field

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Moretto, T.; Rastatter, L.;

    2006-01-01

    Solar wind generated magnetic disturbances are currently one of the major obstacles for improving the accuracy in the determination of the magnetic field due to sources internal to the Earth. In the present study a global MHD model of solar wind magnetosphere interaction is used to obtain...... of identifying the most important aspects of the solar wind disturbances in an internal field modeling context. The contribution from the distant magnetospheric currents is found to consist of two, mainly opposing, contributions from respectively the dayside magnetopause currents and the cross-tail current...

  1. Impact of continuous particle injection on generation and decay of the magnetic field in collisionless shocks

    CERN Document Server

    Garasev, Mikhail

    2016-01-01

    We present numerical simulations of the magnetic field turbulence in collisionless electron-positron plasma with continuous injection of new pairs, which maintains anisotropy in the particle distribution over long time. With these simulations we model generation and decay of the magnetic field in shocks, where the upstream is modified by two-photon pair production due to self-absorption of the shock's high-energy radiation. We find that the overall picture of magnetic field build-up is consistent with development of Weibel instability. However, the long-term injection of anisotropic pairs in the upstream leads to formation of large-scale structures in the magnetic field, while the small-scale structures are almost absent. Furthermore, we find that being amplified at the shock front this magnetic field mostly preserves its large spatial scale and then slowly decays in the downstream on a timescale approximately equal to duration of the injection phase. We observe that the decay of the magnetic field is in exce...

  2. TRANSIENT STABILITY ANALYSIS OF PERMANENT MAGNET SYNCHRONOUS GENERATOR WITH TWO LEVEL CONVERTER INVERTER

    Directory of Open Access Journals (Sweden)

    KRISHNA KUMARI.T

    2013-04-01

    Full Text Available Wind energy plays a prominent role in the generation of power from renewable sources. Generation by permanent magnet synchronous generator (PMSG is recently been popular. But the major concern in using this generator is that the voltage and the power generated are variable due to the intermittent nature of wind energy. Because of the wide use of PMSG the study of the transient stability analysis is very important. In this paper the performance study of PMSG is done by using suitable control strategies to develop a constant voltage and power. The transient stability analysis is also carried out by simulating both the symmetrical and the unsymmetrical faults as network disturbances. This is demonstrated using MATLAB simulations.

  3. Design of direct-driven permanent-magnet generators for wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Grauers, A. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Electric Power Engineering

    1996-12-01

    This thesis presents an investigation of how a direct-driven wind turbine generator should be designed and how small and efficient such a generator will be. Advantages and disadvantages of various types of direct-driven wind turbine generators are discussed, and a radial-flux permanent magnet generator connected to a forced commutated rectifier is chosen for a detailed theoretical investigation. Further, a design method is developed for the electromagnetic part of the chosen generator type. The generator is optimized with a simplified cost function which, besides including the cost of the active generator parts and the cost of the structure, also includes the cost of the average losses. Therefore, a method to calculate the average losses is derived. The design method is used to investigate the optimization of a 500 kW generator, and the size, efficiency and active weight of optimized generators from 30 kW to 3 MW are presented. A result of the investigation is that the outer diameters of the direct-driven generators are only slightly larger than the width of conventional wind energy converter nacelles. A comparison of average efficiency shows that direct-driven generators, including the losses in the frequency converters, are more efficient than conventional wind energy converter trains. Compared with other direct-driven generators, the proposed generator type is small, mainly because of the forced commutated rectifier and because the generator is not required to produce a pull-out torque higher than the rated torque. 34 refs, 44 figs, 20 tabs

  4. Nearshore circulation

    NARCIS (Netherlands)

    Battjes, J.A.; Sobey, R.J.; Stive, M.J.F.

    1990-01-01

    Shelf circulation is driven primarily by wind- and tide-induced forces. It is laterally only weakly constrained so that the geostrophic (Coriolis) acceleration is manifest in the response. Nearshore circulation on the other hand is dominated by wave-induced forces associated with shallow-water. wave

  5. External Magnetic Field Reduction Techniques for the Advanced Stirling Radioisotope Generator

    Science.gov (United States)

    Niedra, Janis M.; Geng, Steven M.

    2013-01-01

    Linear alternators coupled to high efficiency Stirling engines are strong candidates for thermal-to-electric power conversion in space. However, the magnetic field emissions, both AC and DC, of these permanent magnet excited alternators can interfere with sensitive instrumentation onboard a spacecraft. Effective methods to mitigate the AC and DC electromagnetic interference (EMI) from solenoidal type linear alternators (like that used in the Advanced Stirling Convertor) have been developed for potential use in the Advanced Stirling Radioisotope Generator. The methods developed avoid the complexity and extra mass inherent in data extraction from multiple sensors or the use of shielding. This paper discusses these methods, and also provides experimental data obtained during breadboard testing of both AC and DC external magnetic field devices.

  6. Generation of a symmetric magnetic field by thermal convection in a plane rotating layer

    CERN Document Server

    Zheligovsky, V

    2010-01-01

    We investigate numerically magnetic field generation by thermal convection with square periodicity cells in a rotating horizontal layer of electrically-conducting fluid with stress-free electrically perfectly conducting boundaries for Rayleigh numbers in the interval 5100\\le R\\le 5800. Dynamos of three kinds, apparently not encountered before, are presented: 1) Steady and time-periodic regimes, where the flow and magnetic field are symmetric about a vertical axis. In regimes with this symmetry, the global alpha-effect is insignificant, and the complex structure of the system of amplitude equations controlling weakly nonlinear stability of the system to perturbations with large spatial and temporal scales suggests that the perturbations are likely to exhibit uncommon complex patterns of behaviour, to be studied in the future work. 2) Periodic in time regimes, where magnetic field is always concentrated in the interior of the convective layer, in contrast to the behaviour first observed by St Pierre (1993) and ...

  7. Astrophysics of magnetically collimated jets generated from laser-produced plasmas.

    Science.gov (United States)

    Ciardi, A; Vinci, T; Fuchs, J; Albertazzi, B; Riconda, C; Pépin, H; Portugall, O

    2013-01-11

    The generation of astrophysically relevant jets, from magnetically collimated, laser-produced plasmas, is investigated through three-dimensional, magnetohydrodynamic simulations. We show that for laser intensities I∼10(12)-10(14) W cm(-2), a magnetic field in excess of ∼0.1  MG, can collimate the plasma plume into a prolate cavity bounded by a shock envelope with a standing conical shock at its tip, which recollimates the flow into a supermagnetosonic jet beam. This mechanism is equivalent to astrophysical models of hydrodynamic inertial collimation, where an isotropic wind is focused into a jet by a confining circumstellar toruslike envelope. The results suggest an alternative mechanism for a large-scale magnetic field to produce jets from wide-angle winds.

  8. Second-harmonic generation in asymmetric quantum dots in the presence of a static magnetic field

    Institute of Scientific and Technical Information of China (English)

    Li Xue-Chao; Wang An-Min; Wang Zhao-Liang; Yang Yang

    2012-01-01

    The second-harmonic generation (SHG) coefficient in an asymmetric quantum dot (QD) with a static magnetic field is theoretically investigated.Within the framework of the effective-mass approximation,we obtain the confined wave functions and energies of electrons in the QD.We also obtain the SHG coefficient by the compact-density-matrix approach and the iterative method.The numerical results for the typical GaAs/AlGaAs QD show that the SHG coefficient depends strongly on the magnitude of magnetic field,parameters of the asymmetric potential and the radius of the QD.The resonant peak shifts with the magnetic field or the radius of the QD changing.

  9. Dynamical effects of self-generated magnetic fields in cosmic ray modified shocks

    CERN Document Server

    Caprioli, Damiano; Amato, Elena; Vietri, Mario

    2008-01-01

    Recent observations of greatly amplified magnetic fields ($\\delta B/B\\sim 100$) around supernova shocks are consistent with the predictions of the non-linear theory of particle acceleration (NLT), if the field is generated upstream of the shock by cosmic ray induced streaming instability. The high acceleration efficiencies and large shock modifications predicted by NLT need however to be mitigated to confront observations, and this is usually assumed to be accomplished by some form of turbulent heating. We show here that magnetic fields with the strength inferred from observations have an important dynamical role on the shock, and imply a shock modification substantially reduced with respect to the naive unmagnetized case. The effect appears as soon as the pressure in the turbulent magnetic field becomes comparable with the pressure of the thermal gas. The relative importance of this unavoidable effect and of the poorly known turbulent heating is assessed. More specifically we conclude that even in the cases ...

  10. Flicker Study on Variable Speed Wind Turbines with Permanent Magnet Synchronous Generator

    DEFF Research Database (Denmark)

    Hu, Weihao; Chen, Zhe; Wang, Yue;

    2008-01-01

    Grid connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbines with a permanent magnet synchronous generator (PMSG) and a full-scale converter developed in the simul......Grid connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbines with a permanent magnet synchronous generator (PMSG) and a full-scale converter developed...... capacity, grid impedance angle) are analyzed. Flicker mitigation is realized by output reactive power control of the variable speed wind turbines with PMSG. Simulation results show the output reactive power control is an effective measure to mitigate the flicker during continuous operation of grid...

  11. Performance Prediction of a Stand-Alone Permanent-Magnet Induction Generator

    Science.gov (United States)

    Fukami, Tadashi; Shimizu, Bungo; Hanaoka, Ryoichi; Takata, Shinzo; Miyamoto, Toshio

    A permanent-magnet induction generator (PMIG) is a special induction machine self-excited from the inside of the squirrel-cage rotor by a permanent-magnet (PM) rotor. The PMIG can be made to operate as a stand-alone generator when the squirrel-cage rotor is driven by an external prime mover. Moreover, if the capacitors are connected across the stator terminals, adjusting their values can control the output voltage. This paper presents a method for predicting the steady-state performance of such a stand-alone PMIG theoretically. By introducing the per-unit system, a nonlinear equivalent circuit, which can include the variation of the circuit parameters, is derived. Based on this equivalent circuit, the steady-state performance is theoretically calculated, and its validity is confirmed through experiments.

  12. Terahertz generation by two cross focused Gaussian laser beams in magnetized plasma

    International Nuclear Information System (INIS)

    This paper presents a theoretical model for terahertz (THz) radiation generation by two cross-focused Gaussian laser beams in a collisionless magnetoplasma. The plasma is redistributed due to the ponderomotive nonlinearity which leads to the cross focusing of the laser beams. The focusing of the copropagating laser beams increases with increasing the externally applied static magnetic field which is perpendicular to the wave propagation direction. The nonlinear current at THz frequency arises on account of nonlinear ponderomotive force as a result of beating of the two lasers. The generated THz radiation amplitude increases significantly with increasing magnetic field. The cross focusing of two laser beams enhances the THz yield. Optimization of laser-plasma parameters gives the radiated normalized THz power of the order of 10 kW

  13. Numerical simulations of impulsively generated Alfv\\'en waves in solar magnetic arcades

    CERN Document Server

    Chmielewski, P; Musielak, Z E; Srivastava, A K

    2014-01-01

    We perform numerical simulations of impulsively generated Alfv\\'en waves in an isolated solar arcade, which is gravitationally stratified and magnetically confined. We study numerically the propagation of Alfv\\'en waves along such magnetic structure that extends from the lower chromosphere, where the waves are generated, to the solar corona, and analyze influence of the arcade size and width of the initial pulses on the wave propagation and reflection. Our model of the solar atmosphere is constructed by adopting the temperature distribution based on the semi-empirical VAL-C model and specifying the curved magnetic field lines that constitute the asymmetric magnetic arcade. The propagation and reflection of Alfv\\'en waves in this arcade is described by 2.5D magnetohydrodynamic equations that are numerically solved by the FLASH code. Our numerical simulations reveal that the Alfv\\'en wave amplitude decreases as a result of a partial reflection of Alfv\\'en waves in the solar transition region, and that the waves...

  14. Bifurcation analysis in a vortex flow generated by an oscillatory magnetic obstacle.

    Science.gov (United States)

    Beltrán, Alberto; Ramos, Eduardo; Cuevas, Sergio; Brøns, Morten

    2010-03-01

    A numerical simulation and a theoretical model of the two-dimensional flow produced by the harmonic oscillation of a localized magnetic field (magnetic obstacle) in a quiescent viscous, electrically conducting fluid are presented. Nonuniform Lorentz forces produced by induced currents interacting with the oscillating magnetic field create periodic laminar flow patterns that can be characterized by three parameters: the oscillation Reynolds number, Reomega, the Hartmann number, Ha, and the dimensionless amplitude of the magnetic obstacle oscillation, D. The analysis is restricted to oscillations of small amplitude and Ha=100. The resulting flow patterns are described and interpreted in terms of position and evolution of the critical points of the instantaneous streamlines. It is found that in most of the cycle, the flow is dominated by a pair of counter rotating vortices that switch their direction of rotation twice per cycle. The transformation of the flow field present in the first part of the cycle into the pattern displayed in the second half occurs via the generation of hyperbolic and elliptic critical points. The numerical solution of the flow indicates that for low frequencies (v.e. Reomega=1), two elliptic and two hyperbolic points are generated, while for high frequencies (v.e. Reomega=100), a more complex topology involving four elliptic and two hyperbolic points appear. The bifurcation map for critical points of the instantaneous streamline is obtained numerically and a theoretical model based on a local analysis that predicts most of the qualitative properties calculated numerically is proposed. PMID:20365856

  15. Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability

    Directory of Open Access Journals (Sweden)

    K.-I. Nishikawa

    2013-09-01

    Full Text Available We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012, the structure of the kinetic Kelvin–Helmholtz instability (KKHI of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (γj = 1.5 is larger than for a relativistic jet case (γj = 15.

  16. Generation of Vortex Beams with Strong Longitudinally Polarized Magnetic Field by Using a Metasurface

    OpenAIRE

    Veysi, Mehdi; Guclu, Caner; Capolino, Filippo

    2014-01-01

    A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analyt...

  17. Calculations of self-generated magnetic fields in parylene disc experiments

    International Nuclear Information System (INIS)

    Experiments have been planned at Livermore to measure self-generated magnetic fields using the Faraday Rotation of frequency quadrupled 1.1 μm laser light. The LASNEX code was used during the planning of these experiments and has provided valuable information in establishing the conditions under which the thermoelectric fields expected can be measured. Suspected thermoelectric fields have been inferred from experiments that have been carried out at NRL

  18. Low speed doubly salient permanent magnet generator with passive rotor for a tidal current turbine

    OpenAIRE

    HARKATI, Nacereddine; Moreau, Luc; ZAIM, El Hadi; CHARPENTIER, Jean-Frederic

    2013-01-01

    International audience; This paper presents a low speed permanent magnet generator that can be associated with a tidal turbine. This structure has a passive rotor which leads to a simple and robust structural solution. The principle of operation and an electromecanical model of this machine are presented. The use of this model is based on the accurate calculation of inductances in operating condition including saturation regime. An original method for determining these inductances is then pre...

  19. Physics of Giant ElectroMagnetic Pulse generation in short pulse laser experiments

    OpenAIRE

    Poyé, Alexandre; Hulin, Sébastien; Bailly-Grandvaux, Mathieu; Dubois, Jean-Luc; Ribolzi, Jérôme; Raffestin, Didier; Bardon, Matthieu; Lubrano-Lavaderci, Frédéric; D'Humières, Emmanuel; Santos, Joao Jorge; Nicolaï, Philippe; Tikhonchuk, Vladimir

    2015-01-01

    In this paper we describe the physical processes that lead to the generation of Giant Electro- Magnetic Pulses (GEMP) on powerful laser facilities. Our study is based on experimental mea- surements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralisation current in the target holder and the electromagnetic emission shows that the source of ...

  20. Modeling and control of a variable-speed wind turbine equipped with permanent magnet synchronous generator

    Energy Technology Data Exchange (ETDEWEB)

    Aliprantis, D.C.; Papathanassiou, S.A.; Papadopoulos, M.P.; Kladas, A.G. [Purdue University, Electrical and Computer Engineering, West Lafayette, IN (United States)

    2000-08-01

    In this paper the operation of a variable-speed, stall regulated wind turbine equipped with a permanent magnet synchronous generator (PMSG) is examined. The emphasis is placed on the analysis of the electric part of the system, i.e. the electrical generator, the power electronics converters and the control. The operational characteristics of the machine are investigated through a series of computer simulations and the speed control system is designed to maximize the power output and achieve a smooth torque and power profile. (orig.)

  1. Predictive control of a chaotic permanent magnet synchronous generator in a wind turbine system

    Science.gov (United States)

    Manal, Messadi; Adel, Mellit; Karim, Kemih; Malek, Ghanes

    2015-01-01

    This paper investigates how to address the chaos problem in a permanent magnet synchronous generator (PMSG) in a wind turbine system. Predictive control approach is proposed to suppress chaotic behavior and make operating stable; the advantage of this method is that it can only be applied to one state of the wind turbine system. The use of the genetic algorithms to estimate the optimal parameter values of the wind turbine leads to maximization of the power generation. Moreover, some simulation results are included to visualize the effectiveness and robustness of the proposed method. Project supported by the CMEP-TASSILI Project (Grant No. 14MDU920).

  2. Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip.

    Science.gov (United States)

    Ploss, Daniel; Kriesch, Arian; Pfeifer, Hannes; Banzer, Peter; Peschel, Ulf

    2014-06-01

    We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|E(azi)|2 / |E(tot)|2 ≈55% ± 5% for λ0 = 1550 nm), respectively subwavelength confined (FWHM ≈450 nm ≈λ0/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4 μm). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper. PMID:24921567

  3. Direct Depth- and Lateral- Imaging of Nanoscale Magnets Generated by Ion Impact.

    Science.gov (United States)

    Röder, Falk; Hlawacek, Gregor; Wintz, Sebastian; Hübner, René; Bischoff, Lothar; Lichte, Hannes; Potzger, Kay; Lindner, Jürgen; Fassbender, Jürgen; Bali, Rantej

    2015-01-01

    Nanomagnets form the building blocks for a variety of spin-transport, spin-wave and data storage devices. In this work we generated nanoscale magnets by exploiting the phenomenon of disorder-induced ferromagnetism; disorder was induced locally on a chemically ordered, initially non-ferromagnetic, Fe60Al40 precursor film using  nm diameter beam of Ne(+) ions at 25 keV energy. The beam of energetic ions randomized the atomic arrangement locally, leading to the formation of ferromagnetism in the ion-affected regime. The interaction of a penetrating ion with host atoms is known to be spatially inhomogeneous, raising questions on the magnetic homogeneity of nanostructures caused by ion-induced collision cascades. Direct holographic observations of the flux-lines emergent from the disorder-induced magnetic nanostructures were made in order to measure the depth- and lateral- magnetization variation at ferromagnetic/non-ferromagnetic interfaces. Our results suggest that high-resolution nanomagnets of practically any desired 2-dimensional geometry can be directly written onto selected alloy thin films using a nano-focussed ion-beam stylus, thus enabling the rapid prototyping and testing of novel magnetization configurations for their magneto-coupling and spin-wave properties. PMID:26584789

  4. Efficient generation of monoclonal antibodies against peptide in the context of MHCII using magnetic enrichment.

    Science.gov (United States)

    Spanier, Justin A; Frederick, Daniel R; Taylor, Justin J; Heffernan, James R; Kotov, Dmitri I; Martinov, Tijana; Osum, Kevin C; Ruggiero, Jenna L; Rust, Blake J; Landry, Samuel J; Jenkins, Marc K; McLachlan, James B; Fife, Brian T

    2016-01-01

    Monoclonal antibodies specific for foreign antigens, auto-antigens, allogeneic antigens and tumour neo-antigens in the context of major histocompatibility complex II (MHCII) are highly desirable as novel immunotherapeutics. However, there is no standard protocol for the efficient generation of monoclonal antibodies that recognize peptide in the context of MHCII, and only a limited number of such reagents exist. In this report, we describe an approach for the generation and screening of monoclonal antibodies specific for peptide bound to MHCII. This approach exploits the use of recombinant peptide:MHC monomers as immunogens, and subsequently relies on multimers to pre-screen and magnetically enrich the responding antigen-specific B cells before fusion and validation, thus saving significant time and reagents. Using this method, we have generated two antibodies enabling us to interrogate antigen presentation and T-cell activation. This methodology sets the standard to generate monoclonal antibodies against the peptide-MHCII complexes. PMID:27292946

  5. Enhanced magnetic energy harvesting properties of magneto-mechano-electric generator by tailored geometry

    Science.gov (United States)

    Annapureddy, Venkateswarlu; Lee, Ha Young; Yoon, Woon-Ha; Woo, Hyun-Jae; Lee, Ji-Hye; Palneedi, Haribabu; Kim, Hwee-Jong; Choi, Jong-Jin; Jeong, Dae-Yong; Yi, Sam Nyung; Ryu, Jungho

    2016-08-01

    By tailoring the truncated shape of a cantilever structured magneto-mechano-electric (MME) generator that is composed of a piezoelectric single crystal fiber composite and a magnetostrictive Ni plate, a superior output harvesting power density of over 680% was obtained as compared to a typical rectangular shaped generator. The effect of the MME generator's shape on the strain distribution induced by magnetostriction and vibration characteristics and harvesting properties were simulated by finite element analysis modeling and confirmed experimentally, respectively. The truncated shape was effective for not only utilizing a more uniform in-plane strain distribution in the active piezoelectric area but also magnifying the flexural vibration amplitude, which in turn can make the generator more powerful under tiny magnetic oscillations.

  6. Magnetic Configurations Related to the Coronal Heating and Solar Wind Generation I. Twist and Expansion Profiles of Magnetic Loops Produced by Flux Emergence

    CERN Document Server

    Lee, Hwanhee

    2014-01-01

    The generation of outflows from the Sun known as solar winds is coupled with the heating of the solar corona, and both processes are operated in magnetic structures formed on the Sun. To study the magnetic configuration responsible for these processes, we use three-dimensional magnetohydrodynamic simulations to reproduce magnetic structures via flux emergence and investigate their configurations. We focus on two key quantities characterizing a magnetic configuration: the force-free parameter alpha and the flux expansion rate fex, the former of which represents how much a magnetic field is twisted while the latter represents how sharply a magnetic field expands. We derive distributions of these quantities in an emerging flux region. Our result shows that an emerging flux region consists of outer part where a magnetic loop takes a large flux expansion rate but a small value of alpha at their photospheric footpoints, and inner part occupied by those loops where a strong electric current flows. We also investigat...

  7. A numerical model of resistive generation of intergalactic magnetic field at cosmic dawn

    CERN Document Server

    Miniati, Francesco

    2011-01-01

    Miniati and Bell (2011) proposed a mechanism for the generation of magnetic seeds that is based the finite resistivity of the low temperature IGM in the high redshift universe. In this model, cosmic-ray protons generated by the first generation of galaxies, escape into the intergalactic medium carrying an electric current that induces return currents, $j_t$, and associated electric fields, $\\vec E=\\eta\\vec j_t$ there. Because the resistivity, $\\eta$, depends on the IGM temperature, which is highly inhomogeneous due to adiabatic contraction and shocks produced by structure formation, a non-vanishing curl of the electric field exists which sustains the growth of magnetic field. In this contribution we have developed an approximate numerical model for this process by implementing the source terms of the resistive mechanism in the cosmological code CHARM. Our numerical estimates substantiate the earlier analysis in Miniati and Bell (2011) which found magnetic seeds between 10$^{-18}$ and 10$^{-16}$ Gauss througho...

  8. Comparison of the dipolar magnetic field generated by two Ising-like models

    Science.gov (United States)

    Peqini, Klaudio; Duka, Bejo

    2015-04-01

    We consider two Ising-like models named respectively the "domino" model and the Rikitake disk dynamo model. Both models are based on some collective interactions that can generate a dipolar magnetic field which reproduces the well-known features of the geomagnetic field: the reversals and secular variation (SV). The first model considers the resultant dipolar magnetic field as formed by the superposition of the magnetic fields generated by the dynamo elements called macrospins, while the second one, starting from the two-disk dynamo action, takes in consideration the collective interactions of several disk dynamo elements. We will apply two versions of each model: the short-range and the long-range coupled dynamo elements. We will study the statistical properties of the time series generated by the simulation of all models. The comparison of these results with the paleomagnetic data series and long series of SV enables us to conclude which of these Ising-like models better match with the geomagnetic field time series. Key words: geomagnetic field, domino model, Rikitake disk dynamo, dipolar moment

  9. 立式自然循环蒸汽发生器的重量优化设计%Optimal Design of Vertical Natural Circulation Steam Generator Weight

    Institute of Scientific and Technical Information of China (English)

    秦慧敏; 阎昌琪; 王建军; 王盟; 贺士晶

    2011-01-01

    蒸汽发生器(SG)是压水堆核动力装置中重量及尺寸较大的关键设备之一,且随着SG大容量、大型化的发展趋势使其重量和体积进一步增加,这给设备的运输和布置带来了困难,因此,有必要在SG设计中,在满足换热性能及安全要求的条件下,寻找设计参数的最佳组合,以减小SG重量或体积.本文建立了SG重量评价程序,并在对影响SG重量的热工参数和结构参数进行敏感性分析的基础上,采用复合形-遗传优化算法,以SG重量为目标进行了参数优化设计.优化结果显示:与原始方案相比,优化设计方案的重量减小了17.16%o,优化效果显著,并从理论上证明了优化的可能性,研究结果可为实际工程设计提供参考.%The steam generator is one of the key equipments in the PWR nuclear power plant, which has relative large weight and dimension, nowadays, it tends to using high capacity steam generators, which makes the steam generators to be heavier and larger,and it causes difficulties to the transport and arrangement of steam generators. Therefore, it is necessary to apply optimization techniques to the design of the steam generator in order to achieve the minimum weight or volume by means of finding the optimum combination of design parameters while satisfying the heat exchange requirements and safety constraints. In this work, the evaluation model and corresponding codes of a vertical natural circulation steam generator were established, and based on the sensitivity analysis of thermohydraulic parameters and structural parameters which influence steam generator weight, the optimal design of steam generator, taking the net weight as objective, was carried out using a complex-genetic algorithm. The optimal results indicate that the net weight of optimum design is 17.16%, less than original design. The result shows an obvious effect which proves the possibility of optimization and can provide reference for real engineering

  10. Cassini Observations of Plasmoid Structure and Dynamics: Implications for the Role of Magnetic Reconnection in Magnetospheric Circulation at Saturn

    Science.gov (United States)

    Jackman, C. M.; Slavin, J. A.; Cowley, S. W. H.

    2011-01-01

    We survey the Cassini magnetometer data during the deep tail orbits in 2006, and find 34 direct encounters with plasmoids. They occur as single, isolated events but also in groups of two or more plasmoids as is frequently observed at Earth . We show a case study example of three such plasmoids over three hours, where we estimate an upper limit of 5.68 GWb of flux closure, and derive a reconnection rate over this interval of 526 kV. We show the results of a superposed epoch analysis of al1 34 plasmoids indicating that, on average, plasmoids at Saturn are approix.8 min in duration and they tend toward a loop-like, as opposed to flux rope-like topology, with little or no axial core magnetic field. Our analysis shows that plasmoids at Saturn are followed by an extended interval of the post-plasmoid plasma sheet (PPPS) lasting approx.58 min. The average open magnetic flux disconnected by the continued reconnet:tion following plasmoid formation that creates the PPPS is approx.3 GWb. We calculate expected recurrence rates for plasmoids, and compare these with a derived observational recurrence rate of one plasmoid every approx.2.4 days, explaining the reasons why the spacecraft has not observed as many plasmoids as we predict will be released. We conclude that the Cassini magnetometer measurements require a combination of Vasyliunas-type closed-flux plasma sheet and Dungey-type open-flux lobe reconnection to account for the observed properties of the plasmoids and PPPS in Saturn's magnetotail.

  11. Effect of Heaving Movement on Flow Instability in U-Tubes of Marine Steam Generator under Natural Circulation

    Directory of Open Access Journals (Sweden)

    Jianli Hao

    2013-01-01

    Full Text Available Under heaving movement conditions, the single phase flow instability in U-tubes is affected by the additional force, which will influence the marine reactor operation. In the present work, one-dimensional thermal-hydraulic model in U-tubes under heaving movement conditions is established, and the critical pressure drop (CPD and critical mass flow rate (CMFR which relate to the occurrence of reverse flow in U-tubes are proposed and analyzed. The effects of the heaving period and heaving acceleration amplitude on the flow instability in U-tubes with the different length are discussed. It is shown that (1 the CPD and CMFR are obviously affected by the heaving movement, which means that the reverse flow characteristic in U-tubes will be changed; (2 the fluctuation periods of the CPD and CMFR are the same as the heaving period, but the fluctuation magnitude of them is little affected by the heaving period; (3 the relative changes of CPD and CMFR are the linear function of heaving acceleration amplitude; and (4 the U-tube length has little influence on the relative changes of CPD and CMFR compared with the heaving acceleration amplitude, which means that the heaving movement has little influence on the space distribution of reverse flow in the U-tubes of marine steam generator.

  12. Design and analysis of a plane vibration-based electromagnetic generator using a magnetic spring and ferrofluid

    Science.gov (United States)

    Wang, Siqi; Li, Decai

    2015-09-01

    This paper describes the design and characterization of a plane vibration-based electromagnetic generator that is capable of converting low-frequency vibration energy into electrical energy. A magnetic spring is formed by a magnetic attractive force between fixed and movable permanent magnets. The ferrofluid is employed on the bottom of the movable permanent magnet to suspend it and reduce the mechanical damping as a fluid lubricant. When the electromagnetic generator with a ferrofluid of 0.3 g was operated under a resonance condition, the output power reached 0.27 mW, and the power density of the electromagnetic generator was 5.68 µW/cm2. The electromagnetic generator was also used to harvest energy from human motion. The measured average load powers of the electromagnetic generator from human waist motion were 0.835 mW and 1.3 mW during walking and jogging, respectively.

  13. Periodic magnetic domain wall pinning in an ultrathin film with perpendicular anisotropy generated by the stray magnetic field of a ferromagnetic nanodot array

    Science.gov (United States)

    Metaxas, P. J.; Zermatten, P.-J.; Jamet, J.-P.; Ferré, J.; Gaudin, G.; Rodmacq, B.; Schuhl, A.; Stamps, R. L.

    2009-03-01

    The stray magnetic field of an array of hard ferromagnetic perpendicularly magnetized [Co/Pt]4 nanodots is used to nondestructively generate a periodic pinning potential for domain walls in an underlying [Pt/Co]2/Pt layer with perpendicular anisotropy. Pinning is evidenced using magneto-optical microscopy. The magnetic field (H) dependence of the average wall velocity in the presence of the periodic pinning potential is consistent with thermally activated creep, modified only by the addition of a uniform retarding field Hret, whose magnitude depends on the relative alignment of H and the dots' magnetizations.

  14. Angular momentum transfer of Laguerre - Gaussian laser pulses and quasi-static magnetic field generation in plasma channels

    International Nuclear Information System (INIS)

    To generate a strong axial and azimuthal quasi-static magnetic field, we propose to study the interaction of Laguerre-Gaussian laser beams in a parabolic plasma channel. Our study shows that the higher-order modes with orbital angular momentum generate a stronger magnetic field in comparison to the lower-order modes of the laser beam. The contribution of the effective mass of photon on the orbital angular momentum and the polarization state of the beam are analyzed analytically and with 2D Particle in Cell (PIC) simulation. These effects have been put forwarded in analyzing the magnetic field generation. (author)

  15. Investigating the Effects of I-Shaped Cores in an Outer-Rotor Transverse Flux Permanent Magnet Generator

    DEFF Research Database (Denmark)

    Hosseini, Seyedmohsen; Moghani, Javad Shokrollahi; Jensen, Bogi Bech

    2011-01-01

    This paper deals with the effects of I-shaped cores in an outer-rotor transverse flux permanent magnet generator. Performance characteristics of a typical outer-rotor transverse flux permanent magnet generator are obtained in two cases; with and without I-shaped cores. The results show that...... the advantages and disadvantage of using I-shaped cores and emphasizes the necessity of performing a tradeoff study between using and not using I-shaped cores in practical transverse flux permanent magnet generators....

  16. The search for a 100MA RancheroS magnetic flux compression generator

    Energy Technology Data Exchange (ETDEWEB)

    Watt, Robert Gregory [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-01

    The Eulerian AMR rad-hydro-MHD code Roxane was used to investigate modifications to existing designs of the new RancheroS class of Magnetic Flux Compression Generators (FCGs) which might allow some members of this FCG family to exceed 100 MA driving a 10 nH static load. This report details the results of that study and proposes a specific generator modification which seems to satisfy both the peak current and desired risetime for the current pulse into the load. The details of the study and necessary modifications are presented. For details of the LA43S RancheroS FCG design and predictions for the first use of the generator refer to the relevant publications.

  17. The search for a 100MA RancheroS magnetic flux compression generator

    Energy Technology Data Exchange (ETDEWEB)

    Watt, Robert Gregory [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-01

    The Eulerian AMR rad-hydro-MHD code Roxane (Appendix A) was used to investigate modifications to existing designs of the new RancheroS class of Magnetic Flux Compression Generators (FCGs) which might allow some members of this FCG family to exceed 100 MA driving a 10 nH static load. This report details the results of that study and proposes a specific generator modification which seems to satisfy both the peak current and desired risetime for the current pulse into the load. The details of the study and necessary modifications will presented. For details of the LA43S RancheroS FCG design and predictions for the first use of the generator refer to Reference 1.

  18. Development of a Direct Drive Permanent Magnet Generator for Small Wind Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Chertok, Allan; Hablanian, David; McTaggart, Paul; DOE Project Officer - Keith Bennett

    2004-11-16

    In this program, TIAX performed the conceptual design and analysis of an innovative, modular, direct-drive permanent magnet generator (PMG) for use in small wind turbines that range in power rating from 25 kW to 100 kW. TIAX adapted an approach that has been successfully demonstrated in high volume consumer products such as direct-drive washing machines and portable generators. An electromagnetic model was created and the modular PMG design was compared to an illustrative non-modular design. The resulting projections show that the modular design can achieve significant reductions in size, weight, and manufacturing cost without compromising efficiency. Reducing generator size and weight can also lower the size and weight of other wind turbine components and hence their manufacturing cost.

  19. Modeling of a Permanent Magnet Linear Generator for Wave-Energy Conversion

    KAUST Repository

    Tom, Nathan

    2015-05-31

    © 2015 by ASME. This paper begins with a brief review of the equation of motion for a generic floating body with modification to incorporate the influence of a power-take-off (PTO) unit. Since the damping coefficient is considered the dominant contribution to the PTO reaction force, the optimum non time-varying values are presented for all frequencies, recovering the well-known impedance-matching principle at the resonance condition of the coupled system. The construction of a laboratory-scale permanent magnet linear generator (PMLG), developed at the University of California at Berkeley, is discussed along with the basic electromagnetic equations used to model its performance. Modeling of the PMLG begins with a lumped magnetic circuit analysis, which provides an analytical solution to predict the magnetic flux available for power conversion. The voltage generated across each phase of the stator, induced by the motion of the armature, provides an estimate for the electromagnetic damping as a function of the applied resistive load. The performance of the PMLG and the validation of the proposed analytical model is completed by a set of dry-bench tests. Results from the bench test showed good agreement with the described electromechanical model, thus providing an analytical solution that can assist in further optimization of the PMLG.

  20. Alfven Wave Generation by a Rotating Magnetic Field Source: Theory, Modeling and Experimental Results

    Science.gov (United States)

    Shao, X.; Karavaev, A. V.; Gumerov, N.; Sharma, A. S.; Papadopoulos, K.; Gekelman, W. N.; Wang, Y.; Vincena, S. T.; Pribyl, P.

    2010-12-01

    Recent experiments conducted in the Large Plasma Device (LAPD) located at UCLA demonstrated efficient excitation of whistler and shear Alfven waves by a Rotating Magnetic Field (RMF) source. We present analytical theory, computational modeling and experimental results of the shear Alfven wave excitation by RMF source created by a phased orthogonal two-loop antenna in a plasma. An analytical theory and simulations using a three-dimensional cold two-fluid model of Alfven wave excitation were developed and compared with experiments. These comparisons show good agreement on linear shear Alfven wave properties, namely, spatio-temporal wave structure, dispersion relation, and the dependence of wave magnitude on the wave frequency. From the simulations it was found that the energy of the Alfven wave generated by the rotating magnetic field source is distributed among the kinetic energies of ions and electrons and the electromagnetic energy of the wave. The wave magnetic field power calculated from the experimental data and using a fluid model agrees within 1 percent. The RMF source is thus very efficient in generating shear Alfven waves. Work supported by ONR MURI grant.

  1. Generation of zonal flow and magnetic field in the ionospheric E-layer

    Science.gov (United States)

    Kahlon, L. Z.; Kaladze, T. D.

    2015-10-01

    > We review the generation of zonal flow and magnetic field by coupled electromagnetic ultra-low-frequency waves in the Earth's ionospheric E-layer. It is shown that, under typical ionospheric E-layer conditions, different planetary low-frequency waves can couple with each other. Propagation of coupled internal-gravity-Alfvén, coupled Rossby-Khantadze and coupled Rossby-Alfvén-Khantadze waves is revealed and studied. A set of appropriate equations describing the nonlinear interaction of such waves with sheared zonal flow is derived. The conclusion on the instability of short-wavelength turbulence of such coupled waves with respect to the excitation of low-frequency and large-scale perturbation of the sheared zonal flow and sheared magnetic field is deduced. The nonlinear mechanism of the instability is based on the parametric triple interaction of finite-amplitude coupled waves leading to the inverse energy cascade towards longer wavelength. The possibility of generation of an intense mean magnetic field is shown. Obtained growth rates are discussed for each case of the considered coupled waves.

  2. Photon mass new limits from strong photon-torsion coupling generation of primordial magnetic fields

    CERN Document Server

    de Andrade, Garcia

    2011-01-01

    Recently Adelberger et al [Phys Rev Lett 98: 010402, (2007)] have placed a limit to photon mass by investigating the primordial magnetic fields. Earlier Bertolami et al [Phys Lett \\textbf{B} 455, 96(1999)] showed that massive photons in a spontaneous Lorentz breaking may generate primordial magnetic fields consistent with galactic dynamo seeds. Torsion coupling constant of order $10^{-5}$, much higher than the previously obtained by de Sabbata and Sivaram of $10^{-24}$, leads to strong amplification of magnetic field able to seed galactic dynamo at recombination era contrary to what happens in general relativistic dynamos. This results in $B\\sim{10^{-5}{\\beta}G}$ where ${\\beta}$ is the massive photon-torsion coupling. Thus in order to obtain the observed galaxy field of $B_{G}\\sim{{\\mu}G}$ one should have a coupling $\\beta\\sim{10^{-1}}$, never observed in the universe. Thus we may conclude that the weaker couplings for torsion to e.m fields shall only produce magnetic fields without dynamos starting from extr...

  3. Extracting Ocean-Generated Tidal Magnetic Signals from Swarm Data Through Satellite Gradiometry

    Science.gov (United States)

    Sabaka, Terence J.; Tyler, Robert H.; Olsen, Nils

    2016-01-01

    Ocean-generated magnetic field models of the Principal Lunar, M2, and the Larger Lunar elliptic, N2, semidiurnal tidal constituents were estimated through a "Comprehensive Inversion" of the first 20.5 months of magnetic measurements from European Space Agency's (ESA) Swarm satellite constellation mission. While the constellation provides important north-south along-track gradiometry information, it is the unique low-spacecraft pair that allows for east-west cross-track gradiometry. This latter type is crucial in delivering an M2 estimate of similar quality with that derived from over 10 years of CHAMP satellite data but over a shorter interval, at higher altitude, and during more magnetically disturbed conditions. Recovered N2 contains nonoceanic signal but is highly correlated with theoretical models in regions of maximum oceanic amplitude. Thus, satellite magnetic gradiometry may eventually enable the monitoring of ocean electrodynamic properties at temporal resolutions of 1 to 2 years, which may have important implications for the inference of ocean temperature and salinity.

  4. The Self Exitated Induction Generator with Observation Magnetizing Characteristic in The Air Gap

    Directory of Open Access Journals (Sweden)

    Ridwan Gunawan

    2015-02-01

    Full Text Available This paper discusses the Self Exitated induction Generator (SEIG by approaching the induction machine, physically and mathematically which then transformed from three-phase frame abc to-axis frame, direct axis and quadratur-axis. Based on the reactive power demand of induction machine, capacitor mounted on the stator of the induction machine then do the physical and mathematical approach of the system to obtain a state space model. Underknown relationships, magnetization reactance and magnetizing current is not linear, so do mathematical approach to the magnetization reactance equation used in the calculation. Obtained state space model and the magnetic reactance equation is simulated by Runge kutta method of fourth order. The equation of reactance, is simulated by first using the polynomial equation and second using the exponent equation. The load voltage at d axis and q axis using the polynomial laggs 640µs to the exponent equation. The polynomial voltage magnetitude is less than 0.6068 volt from the exponent voltage magnitude

  5. Efficient Generation of Jets from Magnetically Arrested Accretion on a Rapidly Spinning Black Hole

    CERN Document Server

    Tchekhovskoy, Alexander; McKinney, Jonathan C

    2011-01-01

    We describe global, 3D, time-dependent, non-radiative, general-relativistic, magnetohydrodynamic simulations of accreting black holes (BHs). The simulations are designed to transport a large amount of magnetic flux to the center, more than the BH can swallow. The excess magnetic flux remains outside the BH, impedes accretion, and leads to a magnetically arrested disc. We find powerful outflows. For a BH with spin parameter a = 0.5, the efficiency with which the accretion system generates outflowing energy in jets and winds is eta ~ 30%. For a = 0.99, we find eta ~ 140%, which means that more energy flows out of the BH than flows in. Thus, the gravitational mass of the BH decreases with time. This simulation represents an unambiguous demonstration, within an astrophysically plausible scenario, of the extraction of net energy from a spinning BH via the Penrose-Blandford-Znajek mechanism. We suggest that magnetically arrested accretion might explain observations of AGN with apparent eta ~ few x 100%.

  6. Electronic and Optical Properties of a Lens Shaped Quantum Dot under Magnetic Field: Second and Third-Harmonic Generation

    International Nuclear Information System (INIS)

    In the present work, we have studied electronic and optical properties of a lens-shaped quantum dot under an external magnetic field. For this goal, we have calculated the energy levels and wave functions using the finite element method (FEM) for different values of magnetic field. We have also studied effect of magnetic field on second harmonic generation (SHG) and third-harmonic generation (THG) in the lens-shaped quantum dot. In this regard, we have obtained an analytic expression for the SHG and THG by a compact density matrix approach and an iterative procedure. According to the obtained results, it is found that the presence of the magnetic field affects the symmetry of the system. The SHG and THG are decreased with increasing the magnetic field. The magnetic field has a great influence on the energy levels, wave functions, the SHG and THG in a lens shaped quantum dot. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  7. Dynamo generated magnetic configurations in accretion discs and the nature of quasi-periodic oscillations in accreting binary systems

    CERN Document Server

    Moss, David; Suleimanov, Valery

    2016-01-01

    Magnetic fields are important for accretion disc structure. Magnetic fields in a disc system may be transported with the accreted matter. They can be associated with either the central body and/or jet, and be fossil or dynamo excited in situ. We consider dynamo excitation of magnetic fields in accretion discs of accreting binary systems in an attempt to clarify possible configurations of dynamo generated magnetic fields. We first model the entire disc with realistic radial extent and thickness using an alpha-quenching non-linearity. We then study the simultaneous effect of feedback from the Lorentz force from the dynamo-generated field. We perform numerical simulations in the framework of a relatively simple mean-field model which allows the generation of global magnetic configurations. We explore a range of possibilities for the dynamo number, and find quadrupolar-type solutions with irregular temporal oscillations that might be compared to observed rapid luminosity fluctuations. The dipolar symmetry models ...

  8. A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator

    Directory of Open Access Journals (Sweden)

    Petter Eklund

    2014-05-01

    Full Text Available The price of rare-earth metals used in neodymium-iron-boron (NdFeB permanent magnets (PMs has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage.

  9. Biofunctionalized magnetic nanospheres-based cell sorting strategy for efficient isolation, detection and subtype analyses of heterogeneous circulating hepatocellular carcinoma cells.

    Science.gov (United States)

    Chen, Lan; Wu, Ling-Ling; Zhang, Zhi-Ling; Hu, Jiao; Tang, Man; Qi, Chu-Bo; Li, Na; Pang, Dai-Wen

    2016-11-15

    Hepatocellular carcinoma (HCC) is an awful threat to human health. Early-stage HCC may be detected by isolation of circulating tumor cells (CTCs) from peripheral blood samples, which is beneficial to the diagnosis and therapy. However, the extreme rarity and high heterogeneity of HCC CTCs have been restricting the relevant research. To achieve an efficient isolation, reliable detection and subtype analyses of heterogeneous HCC CTCs, herein, we present a cell sorting strategy based on anti-CD45 antibody-modified magnetic nanospheres. By this strategy, leukocyte depletion efficiency was up to 99.9% within 30min in mimic clinical samples, and the purity of the spiked HCC cells was improved 265-317-fold. Besides, the isolated HCC cells remained viable at 92.3% and could be directly recultured. Moreover, coupling the convenient, fast and effective cell sorting strategy with specific ICC identification via biomarkers AFP and GPC3, HCC CTCs were detectable in peripheral blood samples, showing the potential for HCC CTC detection in clinic. Notably, this immunomagnetic cell sorting strategy enabled isolating more heterogeneous HCC cells compared with the established EpCAM-based methods, and further achieved characterization of three different CTC subtypes from one clinical HCC blood sample, which may assist clinical HCC analyses such as prognosis or personalized treatment. PMID:27240010

  10. Integral equation for electrostatic waves generated by a point source in a spatially homogeneous magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Podesta, John J. [Space Science Institute, Boulder, Colorado 80301 (United States)

    2012-08-15

    The electric field generated by a time varying point charge in a three-dimensional, unbounded, spatially homogeneous plasma with a uniform background magnetic field and a uniform (static) flow velocity is studied in the electrostatic approximation which is often valid in the near field. For plasmas characterized by Maxwell distribution functions with isotropic temperatures, the linearized Vlasov-Poisson equations may be formulated in terms of an equivalent integral equation in the time domain. The kernel of the integral equation has a relatively simple mathematical form consisting of elementary functions such as exponential and trigonometric functions (sines and cosines), and contains no infinite sums of Bessel functions. Consequently, the integral equation is amenable to numerical solutions and may be useful for the study of the impulse response of magnetized plasmas and, more generally, the response to arbitrary waveforms.

  11. A New High Efficiency Multiwave Cerenkov Generator Operating at Low Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    张军; 钟辉煌; 舒挺; 杨建华

    2003-01-01

    With a resonant cavity inserted between the second slow-wave-structure section and the tapered waveguide, a new structure of the multiwave Cerenkov generator (MWCG) operating at low guiding magnetic field is proposed to produce high efficiency and high power microwave. Some features and potential advantages of the proposed device are analysed. The 2.5-dimensional particle-in-cell simulation is employed to verify the initial expectation.The results show that, with the use of an electron beam of 640kev and 8.4kA guided by the magnetic field of 0.6 T, a stable and monochromatic X-band microwave output of 4 GW in peak power is achieved, and the average efficiency is over 30%.

  12. Scott Correction for Large Atoms and Molecules in a Self-Generated Magnetic Field

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, Søren; Solovej, Jan Philip

    2012-01-01

    We consider a large neutral molecule with total nuclear charge $Z$ in non-relativistic quantum mechanics with a self-generated classical electromagnetic field. To ensure stability, we assume that $Z\\al^2\\le \\kappa_0$ for a sufficiently small $\\kappa_0$, where $\\al$ denotes the fine structure...... constant. We show that, in the simultaneous limit $Z\\to\\infty$, $\\al\\to 0$ such that $\\kappa =Z\\al^2$ is fixed, the ground state energy of the system is given by a two term expansion $c_1Z^{7/3} + c_2(\\kappa) Z^2 + o(Z^2)$. The leading term is given by the non-magnetic Thomas-Fermi theory. Our result shows...... that the magnetic field affects only the second (so-called Scott) term in the expansion....

  13. Analytical solution for the diffusion of a capacitor discharge generated magnetic field pulse in a conductor

    Science.gov (United States)

    Grants, Ilmārs; Bojarevičs, Andris; Gerbeth, Gunter

    2016-06-01

    Powerful forces arise when a pulse of a magnetic field in the order of a few tesla diffuses into a conductor. Such pulses are used in electromagnetic forming, impact welding of dissimilar materials and grain refinement of solidifying alloys. Strong magnetic field pulses are generated by the discharge current of a capacitor bank. We consider analytically the penetration of such pulse into a conducting half-space. Besides the exact solution we obtain two simple self-similar approximate solutions for two sequential stages of the initial transient. Furthermore, a general solution is provided for the external field given as a power series of time. Each term of this solution represents a self-similar function for which we obtain an explicit expression. The validity range of various approximate analytical solutions is evaluated by comparison to the exact solution.

  14. Extracting Ocean-Generated Tidal Magnetic Signals from Swarm Data through Satellite Gradiometry

    DEFF Research Database (Denmark)

    Sabaka, Terence J.; Tyler, Robert H.; Olsen, Nils

    2016-01-01

    Ocean-generated magnetic field models of the Principal Lunar, M2, and the Larger Lunar elliptic, N2, semi-diurnal tidal constituents were estimated through a “Comprehensive Inversion" of the first 20.5 months of magnetic measurements from ESA's Swarm satellite constellation mission. While the con...

  15. Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Lopatin, I. V., E-mail: lopatin@opee.hcei.tsc.ru; Akhmadeev, Yu. H.; Koval, N. N. [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, 2/3 Akademichesky Avenue, 634055 Tomsk (Russian Federation)

    2015-10-15

    The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. When the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8–12 h. Using a cathode consisting of several parallel-connected tungsten filaments ∼0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa)

  16. Passive magnetic bearing in the 3rd generation miniature axial flow pump-the valvo pump 2.

    Science.gov (United States)

    Okamoto, Eiji; Ishida, Yuya; Yano, Tetsuya; Mitamura, Yoshinori

    2015-06-01

    The new miniature axial flow pump (valvo pump 2) that is installed at the base of the ascending aorta consists of a six-phase stator, an impeller in which four neodymium magnets are incorporated, and passive magnetic bearings that suspend the impeller for axial levitation. The impeller is sustained by hydrodynamic force between the blade tip of the impeller and the inner housing of the stator. The passive magnetic bearing consists of a ring neodymium magnet and a columnar neodymium magnet. The ring neodymium magnet is set in the stationary side and the columnar neodymium magnet is incorporated in the impeller shaft. Both neodymium magnets are coaxially mounted, and the anterior and posterior passive magnetic bearings suspend the impeller by repulsion force against the hydrodynamic force that acts to move the impeller in the inflow port direction. The passive magnetic bearing was evaluated by a tensile test, and the levitation force of 8.5 N and stiffness of 2.45 N/mm was obtained. Performance of the axial flow pump was evaluated by an in vitro experiment. The passive magnetic bearing showed sufficient levitation capacity to suspend the impeller in an axial direction. In conclusion, the passive magnetic bearing is promising to be one of levitation technology for the third-generation axial flow blood pump. PMID:25407124

  17. Multi-Machine Controller Design of Permanent Magnet Wind Generators using Hamiltonian Energy Method

    Directory of Open Access Journals (Sweden)

    Bing Wang

    2013-07-01

    Full Text Available In this paper, the nonlinear control problem of permanent magnet wind generators is investigated based on Hamiltonian energy method. A nonlinear design method is proposed for the multi-machine system, such that the closed-loop system is stable simultaneously. Moreover, in the presence of disturbances, the closed-loop is finite–gain L2 stable under the action of the Hamiltonian controller. In order to illustrate the effectiveness of the proposed method, the simulations are performed which show that the gotten controller can improve the transient property and robustness of the system.  

  18. Generating vorticity and magnetic fields in plasmas in general relativity: Spacetime curvature drive

    Energy Technology Data Exchange (ETDEWEB)

    Asenjo, Felipe A.; Mahajan, Swadesh M. [Institute for Fusion Studies, University of Texas at Austin, Texas 78712 (United States); Qadir, Asghar [Centre for Advanced Mathematics and Physics, National University of Sciences and Technology, H12, Islamabad 4400 (Pakistan)

    2013-02-15

    Using the generally covariant magnetofluid formalism for a hot plasma, a spacetime curvature driven mechanism for generating seed vorticity/magnetic field is presented. The 'battery' owes its origin to the interaction between the gravity modified Lorentz factor of the fluid element and the inhomogeneous plasma thermodynamics. The general relativistic drive is evaluated for two simple cases: seed formation in a simplified model of a hot plasma accreting in stable orbits around a Schwarzschild black hole and for particles in free fall near the horizon. Some astrophysical applications are suggested.

  19. FLASH hydrodynamic simulations of experiments to explore the generation of cosmological magnetic fields

    Science.gov (United States)

    Scopatz, A.; Fatenejad, M.; Flocke, N.; Gregori, G.; Koenig, M.; Lamb, D. Q.; Lee, D.; Meinecke, J.; Ravasio, A.; Tzeferacos, P.; Weide, K.; Yurchak, R.

    2013-03-01

    We report the results of FLASH hydrodynamic simulations of the experiments conducted by the University of Oxford High Energy Density Laboratory Astrophysics group and its collaborators at the Laboratoire pour l'Utilisation de Lasers Intenses (LULI). In these experiments, a long-pulse laser illuminates a target in a chamber filled with Argon gas, producing shock waves that generate magnetic fields via the Biermann battery mechanism. The simulations show that the result of the laser illuminating the target is a series of complex hydrodynamic phenomena.

  20. Design and testing of an armature-reaction-compensated permanent magnet synchronous generator for island operation

    Energy Technology Data Exchange (ETDEWEB)

    Kamiev, K.

    2013-11-01

    At present, permanent magnet synchronous generators (PMSGs) are of great interest. Since they do not have electrical excitation losses, the highly efficient, lightweight and compact PMSGs equipped with damper windings work perfectly when connected to a network. However, in island operation, the generator (or parallel generators) alone is responsible for the building up of the network and maintaining its voltage and reactive power level. Thus, in island operation, a PMSG faces very tight constraints, which are difficult to meet, because the flux produced by the permanent magnets (PMs) is constant and the voltage of the generator cannot be controlled. Traditional electrically excited synchronous generators (EESGs) can easily meet these constraints, because the field winding current is controllable. The main drawback of the conventional EESG is the relatively high excitation loss. This doctoral thesis presents a study of an alternative solution termed as a hybrid excitation synchronous generator (HESG). HESGs are a special class of electrical machines, where the total rotor current linkage is produced by the simultaneous action of two different excitation sources: the electrical and permanent magnet (PM) excitation. An overview of the existing HESGs is given. Several HESGs are introduced and compared with the conventional EESG from technical and economic points of view. In the study, the armature-reaction-compensated permanent magnet synchronous generator with alternated current linkages (ARC-PMSG with ACL) showed a better performance than the other options. Therefore, this machine type is studied in more detail. An electromagnetic design and a thermal analysis are presented. To verify the operation principle and the electromagnetic design, a down-sized prototype of 69 kVA apparent power was built. The experimental results are demonstrated and compared with the predicted ones. A prerequisite for an ARC-PMSG with ACL is an even number of pole pairs (p = 2, 4, 6

  1. Plasma circuit breaker in a magnetic field as a high-power ion flux generator

    International Nuclear Information System (INIS)

    It is ascertained that plasma circuit breaker (PCB) in the external magnetic field of acute-anguled geometry in the mode when PCB serves as inductive storage loading is a natural magnetoizolated diode. Using PCB as an ion emitter and as a high-voltage generator it proved possible in case of full electron magnetiuzation to attain the maximum efficiency of the storage. The density of ion current evaluated by the measured energy density for 30 J/cm2 thermocouple and by the energy of 1.5 MeV constitutes 100 A/cm2. The given method of ion generation is very effective when high ion currents with a high energy are required

  2. Permanent Magnet Synchronous Generator Driven Wind Energy Conversion System Based on Parallel Active Power Filter

    Directory of Open Access Journals (Sweden)

    FERDI Brahim

    2014-05-01

    Full Text Available This paper proposes a novel application of the instantaneous P-Q theory in a wind energy conversion system (WECS. The proposed WECS is formed by permanent magnet synchronous generator (PMSG wind turbine system connected to the grid through parallel active power filter (PAPF. PAPF uses the generated wind energy to feed loads connected at the point of common coupling (PPC, compensates current harmonics and injects the excess of this energy into the grid using P-Q theory as control method. To demonstrate the feasibility and the performance of the proposed control scheme, simulation of this wind system has been realized using MATLAB/SIMULINK software. Simulation results show the accuracy and validity of the proposed control scheme for the PMSGPAPF system.

  3. A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars.

    Science.gov (United States)

    Stello, Dennis; Cantiello, Matteo; Fuller, Jim; Huber, Daniel; García, Rafael A; Bedding, Timothy R; Bildsten, Lars; Aguirre, Victor Silva

    2016-01-21

    Magnetic fields play a part in almost all stages of stellar evolution. Most low-mass stars, including the Sun, show surface fields that are generated by dynamo processes in their convective envelopes. Intermediate-mass stars do not have deep convective envelopes, although 10 per cent exhibit strong surface fields that are presumed to be residuals from the star formation process. These stars do have convective cores that might produce internal magnetic fields, and these fields might survive into later stages of stellar evolution, but information has been limited by our inability to measure the fields below the stellar surface. Here we report the strength of dipolar oscillation modes for a sample of 3,600 red giant stars. About 20 per cent of our sample show mode suppression, by strong magnetic fields in the cores, but this fraction is a strong function of mass. Strong core fields occur only in red giants heavier than 1.1 solar masses, and the occurrence rate is at least 50 per cent for intermediate-mass stars (1.6-2.0 solar masses), indicating that powerful dynamos were very common in the previously convective cores of these stars. PMID:26727160

  4. A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars.

    Science.gov (United States)

    Stello, Dennis; Cantiello, Matteo; Fuller, Jim; Huber, Daniel; García, Rafael A; Bedding, Timothy R; Bildsten, Lars; Aguirre, Victor Silva

    2016-01-21

    Magnetic fields play a part in almost all stages of stellar evolution. Most low-mass stars, including the Sun, show surface fields that are generated by dynamo processes in their convective envelopes. Intermediate-mass stars do not have deep convective envelopes, although 10 per cent exhibit strong surface fields that are presumed to be residuals from the star formation process. These stars do have convective cores that might produce internal magnetic fields, and these fields might survive into later stages of stellar evolution, but information has been limited by our inability to measure the fields below the stellar surface. Here we report the strength of dipolar oscillation modes for a sample of 3,600 red giant stars. About 20 per cent of our sample show mode suppression, by strong magnetic fields in the cores, but this fraction is a strong function of mass. Strong core fields occur only in red giants heavier than 1.1 solar masses, and the occurrence rate is at least 50 per cent for intermediate-mass stars (1.6-2.0 solar masses), indicating that powerful dynamos were very common in the previously convective cores of these stars.

  5. Numerical Simulation of Superhalo Electrons Generated by Magnetic Reconnection in the Solar Wind Source Region

    CERN Document Server

    Yang, L -P; He, J -S; Tu, C -Y; Zhang, S -H; Zhang, L; Feng, X -S

    2014-01-01

    Superhalo electrons appear to be continuously present in the interplanetary medium, even at very quiet times, with a power-law spectrum at energies above $\\sim$2 keV. Here we numerically investigate the generation of superhalo electrons by magnetic reconnection in the solar wind source region, using the MHD and test particle simulations for both single X-line reconnection and multiple X-line reconnection. We find that the direct current electric field, produced in the magnetic reconnection region, can accelerate electrons from an initial thermal energy of T $\\sim10^5$ K up to hundreds of keV. After acceleration, some of the accelerated electrons, together with the nascent solar wind flow driven by the reconnection, propagate upwards along the newly-opened magnetic field lines into the interplanetary space, while the rest move downwards into the lower atmosphere. Similar to the observed superhalo electrons at 1 AU, the flux of the upward-traveling accelerated electrons versus energy displays a power-law distri...

  6. Circulation economics

    DEFF Research Database (Denmark)

    Ingebrigtsen, Stig; Jakobsen, Ove

    2006-01-01

    presupposes a perspective integrating economic, natural and cultural values. Third, to organize the interplay between all stakeholders we introduce an arena for communicative cooperation. Originality/value - The paper concludes that circulation economics presupposes a change in paradigm, from a mechanistic...

  7. Dynamical mass generation in QED with magnetic fields: arbitrary field strength and coupling constant

    CERN Document Server

    Rojas, Eduardo; Bashir, Adnan; Raya, Alfredo

    2008-01-01

    We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics, in the presence of magnetic fields of arbitrary strength, by solving the Schwinger-Dyson equation (SDE) for the fermion self-energy in the rainbow approximation. We employ the Ritus eigenfunction formalism which provides a neat solution to the technical problem of summing over all Landau levels. It is well known that magnetic fields catalyze the generation of fermion mass m for arbitrarily small values of electromagnetic coupling \\alpha. For intense fields it is also well known that m \\propto \\sqrt eB. Our approach allows us to span all regimes of parameters \\alpha and eB. We find that m \\propto \\sqrt eB provided \\alpha is small. However, when \\alpha increases beyond the critical value \\alpha_c which marks the onslaught of dynamical fermion masses in vacuum, we find m \\propto \\Lambda, the cut-off required to regularize the ultraviolet divergences. Our method permits us to verify the results available in l...

  8. Control Loop for a Pulse Generator of a Fast Septum Magnet using DSP and Fuzzy Logic

    CERN Document Server

    Aldaz-Carroll, E; Dieperink, J H; Schröder, G; Vossenberg, Eugène B

    1997-01-01

    A prototype of a fast pulsed eddy current septum magnet for one of thebeam extraction's from the SPS towards LHC is under development. The precision of the magnetic field must be better than ±1.0 10-4 during a flat top of 30 µs. The current pulse is generated by discharging the capacitors of a LC circuit that resonates on the 1st and on the 3rd harmonic of a sine wave with a repetition rate of 15 s. The parameters of the circuit and the voltage on the capacitors must be carefully adjusted to meet the specifications. Drifts during operation must be corrected between two pulses by mechanically adjusting the inductance of the coil in the generator as well as the primary capacitor voltage. This adjustment process is automated by acquiring the current pulse waveform with sufficient time and amplitude resolution, calculating the corrections needed and applying these corrections to the hardware for the next pulse. A very cost-effective and practical solution for this adjustment process is the integration of off-th...

  9. Improvement of the combined function magnet for a highly bright x-ray generator

    International Nuclear Information System (INIS)

    A new type of the rotating anticathode X-ray generator has achieved the beam brilliance of 130 kW/mm2 (at 2.3 kW), in which the electron beam up to 60 keV and 38 mA irradiates the inner surface of a U-shaped Cu anticathode. Higher-flux electron beam is expected from simulation by optimizing the geometry of the combined function instead of fringing field of the bending magnet. In order to minimize the sizes of the X-ray source, the electron beam has been focused in a short distance by the new combined function bending magnet, of which geometrical shape was determined by simulation with the codes of Opera-3D, General Particle Tracer (GPT) and CST-STUDIO. The result of simulation clearly shows that the role of combined functions in both of the bending and the steering magnets is important to focus the beam in small sizes. FWHM sizes of the beam are predicted by simulation to be 0.45 mm (horizontal) and 0.05 mm (vertical) for a beam of 120 keV and 75 mA, of which effective brilliance is about 500 kW/mm2. High power test has just been started by using the high-voltage power supply of 120 kV and 75 mA instead of 60 kV and 100 mA for the X-ray generator. The beam focus sizes on the target will be verified in the experiments. (author)

  10. LVRT SCHEME OF WIND ENERGY SYSTEM USING PERMANENT MAGNET SYNCHRONOUS GENERATOR AND HYSTERESIS CURRENT CONTROLLER

    Directory of Open Access Journals (Sweden)

    E.RAJENDRAN

    2013-04-01

    Full Text Available In this research paper provided the information about low-voltage ride-through (LVRT scheme for the permanent magnet synchronous generator (PMSG, and wind energy conversion system. The dc-link voltage is uncomfortable by the generator side converter instead of the grid-side converter (GSC. Considering the nonlinear correlation between the generator speed (ωm and the dc-link voltage (Vdc, a dc-link Voltage controller is anticipated using a hysteresis current controller. Among all, low-voltage ride-through has been fundamental in the field, which is one of the most important challenges for wind energy conversion system. It is essential to design an included controller to protect the converter from overvoltage/overcurrent and to support the grid voltage during faults and recoveries. A unified dc-link voltage control scheme and hysteresis current controller based wind energy conversion system is proposed. The controllers for grid-side converters are coordinated to provide fault ride-through capability. The generator side is forced by space vector modulationand grid side implemented hysteresis current controller. The Grid Side Controller controls the grid active power and maximum power deliver to the grid. The ability of this control algorithm has been confirmed by simulation results.

  11. Stokes IQUV magnetic Doppler imaging of Ap stars - II. Next generation magnetic Doppler imaging of α2 CVn

    Science.gov (United States)

    Silvester, J.; Kochukhov, O.; Wade, G. A.

    2014-05-01

    We present updated magnetic field maps of the chemically peculiar B9p star α2 CVn created using a series of time-resolved observations obtained using the high-resolution spectropolarimeters ESPaDOnS and Narval. We compare these new magnetic field maps with the original magnetic Doppler imaging maps based on spectra recorded with the MuSiCoS spectropolarimeter and taken a decade earlier. These new maps are inferred from line profiles in all four Stokes parameters using the magnetic Doppler imaging code INVERS10. With the addition of new lines exhibiting Stokes IQUV signatures, we have a unique insight into how the derived magnetic surface structure may be affected by the atomic lines chosen for inversion. We report new magnetic maps of α2 CVn created using strong iron lines (directly comparable to the published MuSiCoS maps), weak iron lines and chromium lines, all of which yield a magnetic field structure roughly consistent with that obtained previously. We then derive an updated magnetic structure map for α2 CVn based on the complete sample of Fe and Cr lines, which we believe to produce a more representative model of the magnetic topology of α2 CVn. In agreement with the previous mapping, this new updated magnetic map shows a dipolar-like field which has complex sub-structure which cannot be explained by a simple low-order multipolar geometry. Our new maps show that regardless of the atomic line or species choice, the reconstructed magnetic field is consistent with that published previously, suggesting that the reconstructed field is a realistic representation of the magnetic field of α2 CVn. α2 CVn is the first Ap star for which multiple, high-resolution magnetic maps have been derived, providing important observational evidence for the stability of both the large- and small-scale magnetic field.

  12. An Impulse Induction MHD Generator Having a Magnetic Field with a Radial Component

    International Nuclear Information System (INIS)

    An impulse induction MHD generator with a cylindrical channel has been theoretically and experimentally investigated. Given certain assumptions, it is possible to write the general system of the partial differential equations, which describes the behaviour of the generator. The mean spatial values of the physical quantities are calculated under certain simplifying conditions and a system of the common differential equations is obtained. After separation the common differential equations of the third order for the velocity and the current are found. These equations are homogeneous with constant and identical coefficients. The solution of these equations is not too complicated and information about their time dependence is obtained. The expressions for the power generated and the generator efficiency are found in the usual way. The equation of the volt-ampere characteristic is also obtained and the characteristic of the generator is found not to be, in general, linear. The equations for the case of open-circuit current and short-circuit voltage are derived. These equations are the common differential equations of the second order and their solutions give the possibility of determining two of the parameters of the plasma clusters. The theoretical conclusions are verified experimentally. A plasma gun is the source of the plasma clusters. The pressure is varied over 1.4 x 10-2 to 2 x 10-1 Torr. The magnetic field is 2 x 10-2 T. The electrical conductivity and the mass of the clusters is calculated from the expressions for the open-circuit voltage and short-circuit current. The results of the theoretical and experimental calculations are in acceptable agreement. It is possible to say that the generator will operate and could, after refinement, be used for diagnostics of plasma clusters. (author)

  13. Design and Comparison of a Novel Stator Interior Permanent Magnet Generator for Direct-Drive Wind Turbines

    DEFF Research Database (Denmark)

    Zhang, Johan Xi; Chen, Zhe; Cheng, M.

    2007-01-01

    A novel stator interior permanent magnet generator (SIPMG) is presented. A modular stator design is used for convenience in manufacture and maintenance. The generator has the advantages of rugged rotor and concentrated winding design whereas the torque ripple is smaller than that produced...... by a doubly salient machine. Several low-speed multi-pole SIPMGs are designed for direct-drive wind turbines with ratings from 3 to 10 MW. Comparisons between the SIPMG and rotor-surface-mounted permanent magnet synchronous generator (PMSG) show that the SIPMGs have about 120% torque density and 78% cost per...

  14. Assessment of EGFR mutations in circulating tumor cell preparations from NSCLC patients by next generation sequencing: toward a real-time liquid biopsy for treatment.

    Directory of Open Access Journals (Sweden)

    Antonio Marchetti

    Full Text Available Assessment of EGFR mutation in non-small cell lung cancer (NSCLC patients is mandatory for optimization of pharmacologic treatment. In this respect, mutation analysis of circulating tumor cells (CTCs may be desirable since they may provide real-time information on patient's disease status.Blood samples were collected from 37 patients enrolled in the TRIGGER study, a prospective phase II multi-center trial of erlotinib treatment in advanced NSCLC patients with activating EGFR mutations in tumor tissue. 10 CTC preparations from breast cancer patients without EGFR mutations in their primary tumors and 12 blood samples from healthy subjects were analyzed as negative controls. CTC preparations, obtained by the Veridex CellSearch System, were subjected to ultra-deep next generation sequencing (NGS on the Roche 454 GS junior platform.CTCs fulfilling all Veridex criteria were present in 41% of the patients examined, ranging in number between 1 and 29. In addition to validated CTCs, potential neoplastic elements were seen in 33 cases. These included cells not fulfilling all Veridex criteria (also known as "suspicious objects" found in 5 (13% of 37 cases, and isolated or clustered large naked nuclei with irregular shape observed in 33 (89% cases. EGFR mutations were identified by NGS in CTC preparations of 31 (84% patients, corresponding to those present in matching tumor tissue. Twenty-five (96% of 26 deletions at exon 19 and 6 (55% of 11 mutations at exon 21 were detectable (P = 0.005. In 4 (13% cases, multiple EGFR mutations, suggesting CTC heterogeneity, were documented. No mutations were found in control samples.We report for the first time that the CellSearch System coupled with NGS is a very sensitive and specific diagnostic tool for EGFR mutation analysis in CTC preparations with potential clinical impact.

  15. Experimental investigation of effect of heat load on thermal performance of natural circulation steam generation system as applied to PTC-based solar system

    International Nuclear Information System (INIS)

    Highlights: • Effects of heat load on flow pattern, thermal efficiency and two phase heat transfer coefficient was analyzed. • An extended correlation equation was fitted for two flow patterns. • The critical RHP for flow transition was identified to be between 34.37 K/kW and 33.35 K/kW. - Abstract: An indoor experimental test rig of parabolic trough collector (PTC)-based natural circulation steam generation system consisting in a thermosyphon loop was presented. A series of five heat loads (0.6–1.2 kW) were applied to investigate effect of heat load on thermal performance of the system. Effect of heat load on flow pattern, thermal efficiency and two phase heat transfer coefficient was discussed, respectively. An extended correlation equation was provided for two flow patterns, which is characterized by heat pipe thermal resistance. The critical heat pipe thermal resistance for flow pattern transition was ranged from 34.37 K/kW to 33.35 K/kW. Simultaneously, thermal efficiency shows a continuous increase as heat load kept rising. The effect of backflow was found to be negligible when heat load increased to 1.1 kW. Additionally, the average two-phase heat transfer coefficient in receiver also went up with the rising of heat load for the same flow pattern. Due to the flow pattern transition, which resulted in a dryness fraction drop in receiver, a maximum heat transfer coefficient of 285.86 W/m2 K was obtained at heat load of 1.0 kW under a steam discharging pressure of 0.15 MPa

  16. Generation of an external magnetic field with the spin orientation effect in a single layer Ising nanographene

    Science.gov (United States)

    Şarlı, Numan

    2016-09-01

    In this work, the magnetic properties of the single layer Ising nanogaphene (SLING) are investigated by using Kaneyoshi approach (KA) within the effective field theory for different spin orientations of its magnetic atoms. We find that the magnetizations of the SLING has no phase transition, certain Curie temperature and distinct peak of susceptibility at Tc for the some spin orientations at the zero external magnetic field (H=0.0). Because these behaviors occur at H≠0.0, we suggest that the SLING generates an external magnetic field and behaves as an external magnetic field generator for these spin orientations. However, the SLING exhibits ferromagnetic behaviors for only one spin orientations. But, it exhibits antiferromagnetic behaviors for the others. For the AFM cases, diamagnetic susceptibility behaviors and type II superconductivity hysteresis behaviors are obtained. We hope that these results can open a door to obtain new class of single layer graphene and graphene-based magnetic field generator devices with the spin orientation effect.

  17. Convection and magnetic field generation in the interior of planets (August Love Medal Lecture)

    Science.gov (United States)

    Christensen, U. R.

    2009-04-01

    Thermal convection driven by internal energy plays a role of paramount importance in planetary bodies. Its numerical modeling has been an essential tool for understanding how the internal engine of a planet works. Solid state convection in the silicate or icy mantles is the cause of endogenic tectonic activity, volcanism and, in the case of Earth, of plate motion. It also regulates the energy budget of the entire planet, including that of its core, and controls the presence or absence of a dynamo. The complex rheology of solid minerals, effects of phase transitions, and chemical heterogeneity are important issues in mantle convection. Examples discussed here are the convection pattern in Mars and the complex morphology of subducted slabs that are observed by seismic tomography in the Earth's mantle. Internally driven convection in the deep gas envelopes of the giant planets is possibly the cause for the strong jet streams at the surfaces that give rise to their banded appearance. Modeling of the magnetohydrodynamic flow in the conducting liquid core of the Earth has been remarkably successful in reproducing the primary properties of the geomagnetic field. As an examplefor attempts to explain also secondary properties, I will discuss dynamo models that account for the thermal coupling to the mantle. The understanding of the somewhat enigmatic magnetic fields of some other planets is less advanced. Here I will show that dynamos that operate below a stable conducting layer in the upper part of the planetary core can explain the unusual magnetic field properties of Mercury and Saturn. The question what determines the strength of a dynamo-generated magnetic field has been a matter of debate. From a large set of numerical dynamo simulations that cover a fair range of control parameters, we find a rule that relates magnetic field strength to the part of the energy flux that is thermodynamically available to be transformed into other forms of energy. This rules predicts

  18. Advanced Control of Permanent Magnet Synchronous Generators for Variable Speed Wind Energy Conversion Systems

    Science.gov (United States)

    Hostettler, Jacob

    Various environmental and economic factors have lead to increased global investment in alternative energy technologies such as solar and wind power. Although methodologies for synchronous generator control are well researched, wind turbines present control systems challenges not presented by traditional generation. The varying nature of wind makes achieving synchronism with the existing electrical power grid a greater challenge. Departing from early use of induction machines, permanent magnet synchronous generators have become the focus of power systems and control systems research into wind energy systems. This is due to their self excited nature, along with their high power density. The problem of grid synchronism is alleviated through the use of high performance power electronic converters. In achievement of the optimal levels of efficiency, advanced control systems techniques oer promise over more traditional approaches. Research into sliding mode control, and linear matrix inequalities with nite time boundedness and Hinfinity performance criteria, when applied to the dynamical models of the system, demonstrate the potential of these control methodologies as future avenues for achieving higher levels of performance and eciency in wind energy.

  19. Loss measurement and analysis for the prototype generator with HTS stator and permanent magnet rotor

    Energy Technology Data Exchange (ETDEWEB)

    Song, Peng, E-mail: songp10@mails.tsinghua.edu.cn [Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084 (China); Qu, Timing, E-mail: tmqu@mail.tsinghua.edu.cn [Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084 (China); Department of Mechanical Engineering, Tsinghua University, Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084 (China); Yu, Xiaoyu [Department of Mechanical Engineering, Tsinghua University, Key Laboratory for Advanced Materials Processing Technology, Ministry of Education, Beijing 100084 (China); Li, Longnian; Gu, Chen [Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084 (China); Li, Xiaohang [Innova Superconductor Technology Co., Ltd., Beijing 100084 (China); Wang, Dewen; Hu, Boping [Beijing Zhong Ke San Huan Hi-Tech Co., Ltd., Beijing 100084 (China); Chen, Duxing [Department Fis, University Autonoma Barcelona, Barcelona 08193 (Spain); Han, Zhenghe [Applied Superconductivity Research Center, Department of Physics, Tsinghua University, Beijing 100084 (China)

    2013-11-15

    Highlights: •A novel prototype HTS generator with HTS armature windings was developed. •No-load loss and the iron loss at low temperature were measured. •The total loss at low temperature is much larger than the room temperature case. •The reason for no-load loss increment at low temperature is discussed. -- Abstract: A prototype HTS synchronous generator with a permanent magnet rotor and HTS armature windings was developed. The rated armature frequency is 10 Hz. The cryogenic Dewar is tightly surrounded outside the iron core. Both HTS coils and the iron core were cooled by using conduction cooling method. During the process of no-load running, the no-load loss power data were obtained through the torque measurement. The temperature evolution characteristics of the stator was measured by PT-100 temperature sensors. These results show that the no-load loss power at around 77 K are much larger than that at room temperature. The possible reason for the no-load loss increment is discussed. The ac loss power of one individual HTS coil used in this generator was also tested. Compared with the iron loss power, the ac loss power is rather small and could be neglected.

  20. A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

    Science.gov (United States)

    Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

    2010-03-01

    A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

  1. The effects of ion mass variation and domain size on octupolar out-of-plane magnetic field generation in collisionless magnetic reconnection

    International Nuclear Information System (INIS)

    Graf von der Pahlen and Tsiklauri [Phys. Plasmas 21, 060705 (2014)] established that the generation of octupolar out-of-plane magnetic field structure in a stressed X-point collapse is due to ion currents. The field has a central region, comprising of the well-known quadrupolar field (quadrupolar components), as well as four additional poles of reversed polarity closer to the corners of the domain (octupolar components). In this extended work, the dependence of the octupolar structure on domain size and ion mass variation is investigated. Simulations show that the strength and spatial structure of the generated octupolar magnetic field is independent of ion to electron mass ratio; thus showing that ion currents play a significant role in out-of-plane magnetic structure generation in physically realistic scenarios. Simulations of different system sizes show that the width of the octupolar structure remains the same and has a spacial extent of the order of the ion inertial length. The width of the structure thus appears to be independent on boundary condition effects. The length of the octupolar structure, however, increases for greater domain sizes, prescribed by the external system size. This was found to be a consequence of the structure of the in-plane magnetic field in the outflow region halting the particle flow and thus terminating the in-plane currents that generate the out-of-plane field. The generation of octupolar magnetic field structure is also established in a tearing-mode reconnection scenario. The differences in the generation of the octupolar field and resulting qualitative differences between X-point collapse and tearing-mode are discussed

  2. Design, Construction and Ocean Testing of Wave Energy Conversion System with Permanent Magnet Tubular Linear Generator

    Institute of Scientific and Technical Information of China (English)

    陈中显; 余海涛; 刘春元; 洪立玮

    2016-01-01

    In this paper, the design, construction and ocean testing of a wave energy conversion system are stud-ied. Based on the motion characteristics of double buoys in ocean waves, a wave energy conversion system with permanent magnet tubular linear generator(PMTLG)is proposed to convert ocean wave energy into electricity. The wave energy conversion system was installed in the Yellow Sea near Lianyungang, China. The ocean test re-sults indicate that it had dynamic and static performance, and obtained an expected amount of electricity. The calcu-lation result indicates the average output power was about 1,000,W, and the conversion efficiency from wave en-ergy into electricity was 1.4%,. In addition, the wireless data communication, mechanics and oceanography were also discussed.

  3. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers

    KAUST Repository

    Kim, J.

    2014-12-04

    The valley pseudospin is a degree of freedom that emerges in atomically thin two-dimensional transition metal dichalcogenides (MX2). The capability to manipulate it, in analogy to the control of spin in spintronics, can open up exciting opportunities. Here, we demonstrate that an ultrafast and ultrahigh valley pseudo-magnetic field can be generated by using circularly polarized femtosecond pulses to selectively control the valley degree of freedom in monolayer MX2. Using ultrafast pump-probe spectroscopy, we observed a pure and valley-selective optical Stark effect in WSe2 monolayers from the nonresonant pump, resulting in an energy splitting of more than 10 milli-electron volts between the K and K′ valley exciton transitions. Our study opens up the possibility to coherently manipulate the valley polarization for quantum information applications.

  4. Flicker Mitigation by Speed Control of Permanent Magnet Synchronous Generator Variable-Speed Wind Turbines

    DEFF Research Database (Denmark)

    Hu, Weihao; Zhang, Yunqian; Chen, Zhe;

    2013-01-01

    Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a full-scale back-to-back power converter and permanent magnet synchronous generator (PMSG......) developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated. The 3p (three times per revolution) power oscillation due to wind shear and tower shadow effects is the significant part in the flicker emission of variable speed wind turbines with PMSG during continuous...... operation. A new method of flicker mitigation by controlling the rotational speed is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the rotational speed of the PMSG. Simulation results show that damping the 3p active power...

  5. Low Voltage Ride-Through Capability Solutions for Permanent Magnet Synchronous Wind Generators

    Directory of Open Access Journals (Sweden)

    Victor F. Mendes

    2016-01-01

    Full Text Available Due to the increasing number of wind power plants, several countries have modified their grid codes to include specific requirements for the connection of this technology to the power system. One of the requirements is the ride-through fault capability (RTFC, i.e., the system capability to sustain operation during voltage sags. In this sense, the present paper intends to investigate the behavior of a full-converter wind generator with a permanent magnet synchronous machine during symmetrical and asymmetrical voltage sags. Two solutions to improve the low voltage ride-through capability (LVRT of this technology are analyzed: discharging resistors (brake chopper and resonant controllers (RCs. The design and limitations of these solutions and the others proposed in the literature are discussed. Experimental results in a 34 kW test bench, which represents a scaled prototype of a real 2 MW wind conversion system, are presented.

  6. Design and implement of the signal generator in the magnetic focused conductivity tomography system

    Institute of Scientific and Technical Information of China (English)

    FU Lin; HUANG Kama

    2007-01-01

    To improve stability and performance of the signal source and sweeping detection,as well as to extract abundant and reliable signal,the direct digital synthesis technology was employed to design the generator of the source which formed sweeping frequencies of sine wave output from 1 to 20 MHz.The planar spiral coil was connected as an amplitude modulation circuit.The same coil adopted differential architecture for signal detection and extraction.The MC1595 was utilized to compose a phase detector in which difference of phases varies with the change of frequencies.A low pass filter was designed to filter the carry waves of the sweeping source.Thereby the system gained abundant data and its stability was improved.Further,the spatial resolution of the system was enhanced.All of the above favors the use of software in the magnetic focused conductivity tomography system (MFCT) to reconstruct the image of conductivity within the human body.

  7. Jitter characteristic of series magnetic pulse compressor employed in ns trigger generator.

    Science.gov (United States)

    Lin, Jiajin; Zhang, Jiande; Yang, Jianhua; Zhang, Huibo; Qiu, Yongfeng; Yang, Xiao

    2014-05-01

    The jitter characteristic of series magnetic pulse compressor (MPC) employed in ns trigger generator was explored. The time delay of the series MPC is the sum value of the compression time in each stage. The primary voltage disturbance is the original parameter to affect the timing stability of the system. Decreasing the relative jitter of the primary voltage and the first compression time are the practical and exclusive approaches to decrease to time jitter of the series MPC. The jitter experiment was carried out on the three-stage series MPC charged with a fast step-up LC transformer. The performance data show that the delay time decreases with the increase of primary voltage. Meanwhile, the measured ratio between the time jitter and the relative jitter of the primary voltage accords with the theoretical result. PMID:24880359

  8. Generating synthetic magnetic field intermittency using a Minimal Multiscale Lagrangian Mapping approach

    Energy Technology Data Exchange (ETDEWEB)

    Subedi, P.; Chhiber, R.; Tessein, J. A.; Wan, M.; Matthaeus, W. H. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)

    2014-12-01

    The Minimal Multiscale Lagrangian Mapping procedure developed in the context of neutral fluid turbulence is a simple method for generating synthetic vector fields. Using a sequence of low-pass filtered fields, fluid particles are displaced at their rms speed for some scale-dependent time interval, and then interpolated back to a regular grid. Fields produced in this way are seen to possess certain properties of real turbulence. This paper extends the technique to plasmas by taking into account the coupling between the velocity and magnetic fields. We examine several possible applications to plasma systems. One use is as initial conditions for simulations, wherein these synthetic fields may efficiently produce a strongly intermittent cascade. The intermittency properties of the synthetic fields are also compared with those of the solar wind. Finally, studies of cosmic ray transport and modulation in the test particle approximation may benefit from improved realism in synthetic fields produced in this way.

  9. Generating Synthetic Magnetic Field Intermittency Using a Minimal Multiscale Lagrangian Mapping Approach

    Science.gov (United States)

    Subedi, P.; Chhiber, R.; Tessein, J. A.; Wan, M.; Matthaeus, W. H.

    2014-12-01

    The Minimal Multiscale Lagrangian Mapping procedure developed in the context of neutral fluid turbulence is a simple method for generating synthetic vector fields. Using a sequence of low-pass filtered fields, fluid particles are displaced at their rms speed for some scale-dependent time interval, and then interpolated back to a regular grid. Fields produced in this way are seen to possess certain properties of real turbulence. This paper extends the technique to plasmas by taking into account the coupling between the velocity and magnetic fields. We examine several possible applications to plasma systems. One use is as initial conditions for simulations, wherein these synthetic fields may efficiently produce a strongly intermittent cascade. The intermittency properties of the synthetic fields are also compared with those of the solar wind. Finally, studies of cosmic ray transport and modulation in the test particle approximation may benefit from improved realism in synthetic fields produced in this way.

  10. Generating synthetic magnetic field intermittency using a Minimal Multiscale Lagrangian Mapping approach

    International Nuclear Information System (INIS)

    The Minimal Multiscale Lagrangian Mapping procedure developed in the context of neutral fluid turbulence is a simple method for generating synthetic vector fields. Using a sequence of low-pass filtered fields, fluid particles are displaced at their rms speed for some scale-dependent time interval, and then interpolated back to a regular grid. Fields produced in this way are seen to possess certain properties of real turbulence. This paper extends the technique to plasmas by taking into account the coupling between the velocity and magnetic fields. We examine several possible applications to plasma systems. One use is as initial conditions for simulations, wherein these synthetic fields may efficiently produce a strongly intermittent cascade. The intermittency properties of the synthetic fields are also compared with those of the solar wind. Finally, studies of cosmic ray transport and modulation in the test particle approximation may benefit from improved realism in synthetic fields produced in this way.

  11. Physics of Giant ElectroMagnetic Pulse generation in short pulse laser experiments

    CERN Document Server

    Poyé, Alexandre; Bailly-Grandvaux, Mathieu; Dubois, Jean-Luc; Ribolzi, Jérôme; Raffestin, Didier; Bardon, Matthieu; Lubrano-Lavaderci, Frédéric; D'Humières, Emmanuel; Santos, Joao Jorge; Nicolaï, Philippe; Tikhonchuk, Vladimir

    2015-01-01

    In this paper we describe the physical processes that lead to the generation of Giant Electro- Magnetic Pulses (GEMP) on powerful laser facilities. Our study is based on experimental mea- surements of both the charging of a solid target irradiated by an ultra-short, ultra-intense laser and the detection of the electromagnetic emission in the GHz domain. An unambiguous correlation between the neutralisation current in the target holder and the electromagnetic emission shows that the source of the GEMP is the remaining positive charge inside the target after the escape of fast electrons accelerated by the ultra-intense laser. A simple model for calculating this charge in the thick target case is presented. From this model and knowing the geometry of the target holder, it becomes possible to estimate the intensity and the dominant frequencies of the GEMP on any facility.

  12. Electron Cloud Generation and Trapping in a Quadrupole Magnet at the Los Alamos Proton Storage Ring

    International Nuclear Information System (INIS)

    Recent beam physics studies on the two-stream e-p instability at the LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where primary electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies using this diagnostic show that the 'prompt' electron flux striking the wall in a quadrupole is comparable to the prompt signal in the adjacent drift space. In addition, the 'swept' electron signal, obtained using the sweeping feature of the diagnostic after the beam was extracted from the ring, was larger than expected and decayed slowly with an exponential time constant of 50 to 100 (micro)s. Other measurements include the cumulative energy spectra of prompt electrons and the variation of both prompt and swept electron signals with beam intensity. Experimental results were also obtained which suggest that a good fraction of the electrons observed in the adjacent drift space for the typical beam conditions in the 2006 run cycle were seeded by electrons ejected from the quadrupole

  13. Generation of large scale magnetic fields in single-field inflation

    International Nuclear Information System (INIS)

    We consider the generation of large scale magnetic fields in slow-roll inflation. The inflaton field is described in a supergravity framework where the conformal invariance of the electromagnetic field is generically and naturally broken. For each class of inflationary scenarios, we determine the functional dependence of the gauge coupling that is consistent with the observations on the magnetic field strength at various astrophysical scales and, at the same time, avoid a back-reaction problem. Then, we study whether the required coupling functions can naturally emerge in well motivated, possibly string inspired, models. We argue that this is non-trivial and can be realized only for a restricted class of scenarios. This includes power-law inflation where the inflaton field is interpreted as a modulus. However, this scenario seems to be consistent only if the energy scale of inflation is low and the reheating stage prolonged. Another reasonable possibility appears to be small field models since no back-reaction problem is present in this case but, unfortunately, the corresponding scenario cannot be justified in a stringy framework. Finally, large field models do not lead to sensible model building

  14. Generation of excited coherent states for a charged particle in a uniform magnetic field

    International Nuclear Information System (INIS)

    We introduce excited coherent states, |β,α;nгЂ‰≔a†n|β,αгЂ‰, where n is an integer and states |β,αгЂ‰ denote the coherent states of a charged particle in a uniform magnetic field. States |β,αгЂ‰ minimize the Schrödinger-Robertson uncertainty relation while having the nonclassical properties. It has been shown that the resolution of identity condition is realized with respect to an appropriate measure on the complex plane. Some of the nonclassical features such as sub-Poissonian statistics and quadrature squeezing of these states are investigated. Our results are compared with similar Agarwal’s type photon added coherent states (PACSs) and it is shown that, while photon-counting statistics of |β,α,nгЂ‰ are the same as PACSs, their squeezing properties are different. It is also shown that for large values of |β|, while they are squeezed, they minimize the uncertainty condition. Additionally, it has been demonstrated that by changing the magnitude of the external magnetic field, Bext, the squeezing effect is transferred from one component to another. Finally, a new scheme is proposed to generate states |β,α;nгЂ‰ in cavities. 

  15. Effect of the plasma-generated magnetic field on relativistic electron transport.

    Science.gov (United States)

    Nicolaï, Ph; Feugeas, J-L; Regan, C; Olazabal-Loumé, M; Breil, J; Dubroca, B; Morreeuw, J-P; Tikhonchuk, V

    2011-07-01

    In the fast-ignition scheme, relativistic electrons transport energy from the laser deposition zone to the dense part of the target where the fusion reactions can be ignited. The magnetic fields and electron collisions play an important role in the collimation or defocusing of this electron beam. Detailed description of these effects requires large-scale kinetic calculations and is limited to short time intervals. In this paper, a reduced kinetic model of fast electron transport coupled to the radiation hydrodynamic code is presented. It opens the possibility to carry on hybrid simulations in a time scale of tens of picoseconds or more. It is shown with this code that plasma-generated magnetic fields induced by noncollinear temperature and density gradients may strongly modify electron transport in a time scale of a few picoseconds. These fields tend to defocus the electron beam, reducing the coupling efficiency to the target. This effect, that was not seen before in shorter time simulations, has to be accounted for in any ignition design using electrons as a driver. PMID:21867317

  16. Magnetic field enhancement of generation-recombination and shot noise in organic light emitting diodes

    Science.gov (United States)

    Djidjou, T. K.; Chen, Ying; Basel, Tek; Shinar, J.; Rogachev, A.

    2015-03-01

    We have studied the effect of magnetic field on noise in series of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene-based organic light emitting diodes with dominant hole injection, dominant electron injection, and balanced electron and hole injection. The noise spectra of the balanced devices revealed the generation-recombination (g-r) noise term, which we associated with bimolecular electron-hole recombination. The presence of the g-r noise term is correlated with the strong organic magnetoresistance (up to 25%) observed in the balanced devices. The noise spectra also have the shot noise contribution with the Fano factor 0.25-0.4. We found that time constant of the g-r term decreases and the magnitude of shot noise increases when magnetic field is applied. This behavior can be consistently explained within the polaron-polaron model of organic magnetoresistance. We have not found any evidence that the magnetoresistance in studied devices is affected by traps.

  17. Magnetic field enhancement of generation-recombination and shot noise in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Djidjou, T. K.; Basel, Tek; Rogachev, A. [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States); Chen, Ying; Shinar, J. [Ames Laboratory-USDOE, and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    2015-03-21

    We have studied the effect of magnetic field on noise in series of 2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene-based organic light emitting diodes with dominant hole injection, dominant electron injection, and balanced electron and hole injection. The noise spectra of the balanced devices revealed the generation-recombination (g-r) noise term, which we associated with bimolecular electron-hole recombination. The presence of the g-r noise term is correlated with the strong organic magnetoresistance (up to 25%) observed in the balanced devices. The noise spectra also have the shot noise contribution with the Fano factor 0.25–0.4. We found that time constant of the g-r term decreases and the magnitude of shot noise increases when magnetic field is applied. This behavior can be consistently explained within the polaron-polaron model of organic magnetoresistance. We have not found any evidence that the magnetoresistance in studied devices is affected by traps.

  18. Second Harmonic Generation as a Nondestructive Readout of Optical (Photo(electro)chromic and Magnetic) Memories

    Science.gov (United States)

    Aktsipetrov, O.; Fedyanin, A.; Melnikov, A.; Mishina, E.; Murzina, T.

    1998-01-01

    Optical second harmonic generation (SHG) is suggested as a nonlinear-optical nondestructive readout of (thin) film-based optical memories. Systematic studies of photoinduced, electroinduced, and magnetoinduced variations in the anisotropic SHG intensity in (i) thin solid photo(electro)chromic films of bacteriorhodopsin, (ii) photosensitive Langmuir-Blodgett films of 4-nitro-4'-N-octadecylazobenzene, and (iii) rare-earth iron garnet films show sufficient modification of their nonlinear-optical properties by these external factors. These photo-, electro- and magnetomodified nonlinear-optical properties of thin films being used for recording the information can be easily distinguished by the SHG readout. The IR fundamental radiation used for the excitation of the SHG is shown not to disturb the information recorded in photo(electro)chromic memories. For, what is to our knowledge, the first time, the surface-bulk crossterms in the SHG intensity originating from the interference of the crystalline and magnetization induced second harmonic fields are observed in magnetic iron garnet films.

  19. Stokes $IQUV$ Magnetic Doppler Imaging of Ap stars II: Next Generation Magnetic Doppler Imaging of $\\alpha^2$ CVn

    CERN Document Server

    Silvester, J; Wade, G A

    2014-01-01

    We present updated magnetic field maps of the chemically peculiar B9p star $\\alpha^2$ CVn created using a series of time resolved observations obtained using the high resolution spectropolarimeters ESPaDOnS and Narval. We compare these new magnetic field maps with the original magnetic Doppler imaging maps based on spectra recorded with the MuSiCoS spectropolarimeter and taken a decade earlier. These new maps are inferred from line profiles in all four Stokes parameters using the magnetic Doppler imaging code INVERS10. With the addition of new lines exhibiting Stokes $IQUV$ signatures we have a unique insight into how the derived magnetic surface structure may be affected by the atomic lines chosen for inversion. We report new magnetic maps of $\\alpha^2$ CVn created using strong iron lines (directly comparable to the published MuSiCoS maps), weak iron lines and chromium lines, all of which yield a magnetic field structure roughly consistent with that obtained previously. We then derive an updated magnetic str...

  20. A Novel Method to Magnetic Flux Linkage Optimization of Direct-Driven Surface-Mounted Permanent Magnet Synchronous Generator Based on Nonlinear Dynamic Analysis

    Directory of Open Access Journals (Sweden)

    Qian Xie

    2016-07-01

    Full Text Available This paper pays attention to magnetic flux linkage optimization of a direct-driven surface-mounted permanent magnet synchronous generator (D-SPMSG. A new compact representation of the D-SPMSG nonlinear dynamic differential equations to reduce system parameters is established. Furthermore, the nonlinear dynamic characteristics of new D-SPMSG equations in the process of varying magnetic flux linkage are considered, which are illustrated by Lyapunov exponent spectrums, phase orbits, Poincaré maps, time waveforms and bifurcation diagrams, and the magnetic flux linkage stable region of D-SPMSG is acquired concurrently. Based on the above modeling and analyses, a novel method of magnetic flux linkage optimization is presented. In addition, a 2 MW D-SPMSG 2D/3D model is designed by ANSYS software according to the practical design requirements. Finally, five cases of D-SPMSG models with different magnetic flux linkages are simulated by using the finite element analysis (FEA method. The nephograms of magnetic flux density are agreement with theoretical analysis, which both confirm the correctness and effectiveness of the proposed approach.

  1. Generation of a focused proton beam with a self-magnetically BΘ-insulated ion diode

    International Nuclear Information System (INIS)

    A self-magnetically BΘ -insulated ion diode was investigated and optimized at the pulsed power line KALIF (2 MV, 50 ns, 2 Ω) to produce a focused and pulsed high-intensity proton beam for generation of high-power density in matter. This diode is characterized by an azimuthal insulating magnetic field that is generated by the diode current. The beam is neutralized by electrons from the cathode vanes, so that neither a gas filled drift space nor foils are needed. The beam therefore propagates in vacuum and repeated shots are possible without changing parts. The protons had energies up to 1.8 MeV and the proton content in the ion beam was about 50%. The maximum total diode current was about 800 kA and its efficiency was as high as 70%. The beam microdivergence was determined to be 1.1 degree. The radial dependence of the proton current density was measured and is proportional to r-1.74. This result was confirmed by 2D quasistatic particle-in-cell simulations. The focus was optimized by adjusting the anode shape and the gap geometry and by decreasing the beam divergence. The FWHM diameter of the focus at a distance of 300 mm was about 10 mm and the resulting focused power density was 0.13 TW/cm2. The effect of the gap distance on focusing and impedance was investigated and it was found necessary to adjust the gap to better than 0.1 mm over the total 30-cm-diam anode to obtain the best performance. The electron loss and the corresponding erosion at the posts that hold the anode was reduced. The lifetime is now limited by the plastic anode insert to 10--15 pulses. Based on these results a ''small BΘ diode'' is suggested for which a power density increase of a factor of 3 is estimated

  2. Self focusing of laser beams and its effect in the generation of magnetic field in laser-produced plasma

    International Nuclear Information System (INIS)

    The present work deals with the generation of magnetic field in a plasma due to self focusing effects of laser beam. Spontaneously generated magnetic fields of the order of several kilogauss have been investigated and the cause for the generation of B-field has been attributed to the time dependent ponderomotive force of a self focused inhomogeneous gaussian shaped laser beam. The magnitude of the magnetic field is found to increase with self focusing effect of the laser beam. It can be shown that for high-frequency laser (viz. Nd-glass laser having the wavelength (λ) = 1.06 μm and amplitude of E-field (E00) = 3.9 x 1011 V/m), the magnitude of B-field is found to be in better agreement with the experiment. B-field varies inversely with temperature which has not been taken care in earlier reports. (author)

  3. On the possibility for laboratory simulation of generation of Alfven disturbances in magnetic tubes in the solar atmosphere

    Science.gov (United States)

    Prokopov, Pavel; Zaharov, Yuriy; Tishchenko, Vladimir; Boyarintsev, Eduard; Melehov, Aleksandr; Ponomarenko, Arnold; Posuh, Vitaliy; Shayhislamov, Ildar

    2016-03-01

    The paper deals with generation of Alfven plasma disturbances in magnetic flux tubes through exploding laser plasma in magnetized background plasma. Processes with similar effect of excitation of torsion-type waves seem to provide energy transfer from the solar photosphere to corona. The studies were carried out at experimental stand KI-1 represented a high-vacuum chamber of 1.2 m diameter, 5 m long, external magnetic field up to 500 Gs along the chamber axis, and up to 2×10^-6 Torr pressure in operating mode. Laser plasma was produced when focusing the CO2 laser pulse on a flat polyethylene target, and then the laser plasma propagated in θ-pinch background hydrogen (or helium) plasma. As a result, the magnetic flux tube of 15-20 cm radius was experimentally simulated along the chamber axis and the external magnetic field direction. Also, the plasma density distribution in the tube was measured. Alfven wave propagation along the magnetic field was registered from disturbance of the magnetic field transverse component B_ψ and field-aligned current J_z. The disturbances propagate at near-Alfven velocity of 70-90 km/s and they are of left-hand circular polarization of the transverse component of magnetic field. Presumably, Alfven wave is generated by the magnetic laminar mechanism of collisionless interaction between laser plasma cloud and background. The right-hand polarized high-frequency whistler predictor was registered which have been propagating before Alfven wave at 300 km/s velocity. The polarization direction changed with Alfven wave coming. Features of a slow magnetosonic wave as a sudden change in background plasma concentration along with simultaneous displacement of the external magnetic field were found. The disturbance propagates at ~20-30 km/s velocity, which is close to that of ion sound at low plasma beta value. From preliminary estimates, the disturbance transfers about 10 % of the original energy of laser plasma.

  4. The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo

    Science.gov (United States)

    Squire, J.; Bhattacharjee, A.

    2016-04-01

    > A novel large-scale dynamo mechanism, the magnetic shear-current effect, is discussed and explored. The effect relies on the interaction of magnetic fluctuations with a mean shear flow, meaning the saturated state of the small-scale dynamo can drive a large-scale dynamo - in some sense the inverse of dynamo quenching. The dynamo is non-helical, with the mean field coefficient zero, and is caused by the interaction between an off-diagonal component of the turbulent resistivity and the stretching of the large-scale field by shear flow. Following up on previous numerical and analytic work, this paper presents further details of the numerical evidence for the effect, as well as an heuristic description of how magnetic fluctuations can interact with shear flow to produce the required electromotive force. The pressure response of the fluid is fundamental to this mechanism, which helps explain why the magnetic effect is stronger than its kinematic cousin, and the basic idea is related to the well-known lack of turbulent resistivity quenching by magnetic fluctuations. As well as being interesting for its applications to general high Reynolds number astrophysical turbulence, where strong small-scale magnetic fluctuations are expected to be prevalent, the magnetic shear-current effect is a likely candidate for large-scale dynamo in the unstratified regions of ionized accretion disks. Evidence for this is discussed, as well as future research directions and the challenges involved with understanding details of the effect in astrophysically relevant regimes.

  5. Helium circulator design concepts for the modular high temperature gas-cooled reactor (MHTGR) plant

    International Nuclear Information System (INIS)

    Two helium circulators are featured in the Modular High-Temperature Gas-Cooled Reactor (MHTGR) power plant - (1) the main circulator, which facilitates the transfer of reactor thermal energy to the steam generator, and (2) a small shutdown cooling circulator that enables rapid cooling of the reactor system to be realized. The 3170 kW(e) main circulator has an axial flow compressor, the impeller being very similar to the unit in the Fort St. Vrain (FSV) plant. The 164 kW(e) shutdown cooling circulator, the design of which is controlled by depressurized conditions, has a radial flow compressor. Both machines are vertically oriented, have submerged electric motor drives, and embody rotors that are supported on active magnetic bearings. As outlined in this paper, both machines have been conservatively designed based on established practice. The circulators have features and characteristics that have evolved from actual plant operating experience. With a major goal of high reliability, emphasis has been placed on design simplicity, and both machines are readily accessible for inspection, repair, and replacement, if necessary. In this paper, conceptual design aspects of both machines are discussed, together with the significant technology bases. As appropriate for a plant that will see service well into the 21st century, new and emerging technologies have been factored into the design. Examples of this are the inclusion of active magnetic bearings, and an automated circulator condition monitoring system. (author). 18 refs, 20 figs, 13 tabs

  6. Design optimization of radial flux permanent magnetwind generator for highest annual energy input and lower magnet volumes

    Energy Technology Data Exchange (ETDEWEB)

    Faiz, J.; Rajabi-Sebdani, M.; Ebrahimi, B. M. (Univ. of Tehran, Tehran (Iran)); Khan, M. A. (Univ. of Cape Town, Cape Town (South Africa))

    2008-07-01

    This paper presents a multi-objective optimization method to maximize annual energy input (AEI) and minimize permanent magnet (PM) volume in use. For this purpose, the analytical model of the machine is utilized. Effects of generator specifications on the annual energy input and PM volume are then investigated. Permanent magnet synchronous generator (PMSG) parameters and dimensions are then optimized using genetic algorithm incorporated with an appropriate objective function. The results show an enhancement in PMSG performance. Finally 2D time stepping finite element method (2D TSFE) is used to verify the analytical results. Comparison of the results validates the optimization method

  7. A Multiple Z-Pinch Configuration for the Generation of High-Density, Magnetized Plasmas

    Science.gov (United States)

    Tarditi, Alfonso G.

    2015-11-01

    The z-pinch is arguably the most straightforward and economical approach for the generation and confinement of hot plasmas, with a long history of theoretical investigations and experimental developments. While most of the past studies were focused on countering the natural tendency of z-pinches to develop instabilities, this study attempts to take advantage of those unstable regimes to form a quasi-stable plasma, with higher density and temperature, possibly of interest for a fusion reactor concept. For this purpose, a configuration with four z-pinch discharges, with axis parallel to each other and symmetrically positioned, is considered. Electrodes for the generation of the discharges and magnetic coils are arranged to favor the formation of concave discharge patterns. The mutual attraction from the co-streaming discharge currents enhances this pattern, leading to bent plasma streams, all nearing towards the axis. This configuration is intended to excite and sustain a ``kink'' unstable mode for each z-pinch, eventually producing either plasmoid structures, detached from each discharge, or sustained kink patterns: both these cases appear to lead to plasmas merging in the central region. The feasibility of this approach in creating a higher density, hotter, meta-stable plasma regime is investigated computationally, addressing both the kink excitation phase and the dynamics of the converging plasma columns.

  8. Voltage Regulation Using a Permanent Magnet Synchronous Generator with a Series Compensator: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Ping; Wu, Ziping; Muljadi, Eduard; Gao, Wenzhong

    2015-08-24

    A wind power plant (WPP) is often operated at unity power factor, and the utility host where the WPP connects prefers to regulate the voltage. Although this may not be an issue in a stiff grid, the connection to a weak grid can be a problematic. This paper explores the advantages of having voltage regulation capability via reactive power control. Another issue in wind power generation is that not all turbines are able to control their reactive power due to technical reasons or contractual obligations. A synchronous condenser (SC) using a permanent magnet synchronous generator (PMSG) is proposed to provide necessary reactive power for regulating voltage at a weak grid connection. A PMSG has the advantage of higher efficiency and reliability. Because of its lack of a field winding, a PMSG is typically controlled by a full-power converter, which can be costly. In the proposed system, the reactive power of the SC is controlled by a serially connected compensator operating in a closed-loop configuration. The compensator also damps the PMSG’s tendency to oscillate. The compensator’s VA rating is only a fraction of the rating of the SC and the PMSG. In this initial investigation, the proposed scheme is shown to be effective by computer simulations.

  9. Modelling and Design of a 3 kW Permanent Magnet Synchronous Generator suitable for Variable Speed Small Wind Turbines

    Directory of Open Access Journals (Sweden)

    Acharya Parash

    2016-01-01

    Full Text Available This paper presents the modeling and design of a 3 kW Permanent Magnet Synchronous Generator (PMSG used for a variable speed wind turbine. Initially, the PMSG is modeled in the d-q reference frame. Different optimized parameters of the generator are extracted from the design and used in simulation of the PMSG. The generator output power is matched with the power of the turbine such that the generator is not either over-sized or under-sized.

  10. Use of a magnetic force exciter to vibrate a piezocomposite generating element in a small-scale windmill

    International Nuclear Information System (INIS)

    A piezocomposite generating element (PCGE) can be used to convert ambient vibrations into electrical energy that can be stored and used to power other devices. This paper introduces a design of a magnetic force exciter for a small-scale windmill that vibrates a PCGE to convert wind energy into electrical energy. A small-scale windmill was designed to be sensitive to low-speed wind in urban regions for the purpose of collecting wind energy. The magnetic force exciter consists of exciting magnets attached to the device’s input rotor and a secondary magnet fixed at the tip of the PCGE. The PCGE is fixed to a clamp that can be adjusted to slide on the windmill’s frame in order to change the gap between exciting and secondary magnets. Under an applied wind force, the input rotor rotates to create a magnetic force interaction that excites the PCGE. The deformation of the PCGE enables it to generate electric power. Experiments were performed with different numbers of exciting magnets and different gaps between the exciting and secondary magnets to determine the optimal configuration for generating the peak voltage and harvesting the maximum wind energy for the same range of wind speeds. In a battery-charging test, the charging time for a 40 mA h battery was approximately 3 h for natural wind in an urban region. The experimental results show that the prototype can harvest energy in urban regions with low wind speeds and convert the wasted wind energy into electricity for city use. (paper)

  11. Generating magnetic response and half-metallicity in GaP via dilute Ti-doping for spintronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Hardev S. [Department of Physics, Panjab University, Chandigarh 160014 (India); Kashyap, Manish K., E-mail: manishdft@gmail.com [Department of Physics, Kurukshetra University, Kurukshetra 136119, Haryana (India); Kumar, Manoj [Department of Physics, Panjab University, Chandigarh 160014 (India); Kendriya Vidyalya No. 1, Kanchrapara, 743193 West Bengal (India); Thakur, Jyoti [Department of Physics, Kurukshetra University, Kurukshetra 136119, Haryana (India); Singh, Mukhtiyar [Department of Physics, Dyanand Postgraduate College, Hisar, 125001 Haryana (India); Reshak, Ali H. [New Technologies – Research Centre, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Saini, G.S.S. [Department of Physics, Panjab University, Chandigarh 160014 (India)

    2015-11-15

    Existence of band gap in one spin channel and metallic character in other leads to interesting magnetic and optical properties of any material. These materials are capable to generate fully spin polarized current and are responsible for maximizing the efficiency of spintronic devices. The present work explores the electronic and magnetic properties of Ti-doped GaP compound with dopant concentrations; x = 0.02, 0.03 and 0.06 in order to search new Diluted Magnetic Semiconductor (DMS) compounds as spintronic materials using full potential linearized augmented plane wave plus local orbitals (FPLAPW + lo) method. The generalized gradient approximation (GGA) is used to decide exact exchange-correlation (XC) potentials. The calculated results showed that the total magnetic moment of ∼1.00 μ{sub B} gets induced after Ti-doping in GaP at all dopant concentrations, irrespective of any magnetic element present. Further, this doping also generates half-metallicity in GaP with a half-metallic (HM) gap at Fermi level (E{sub F}) in minority spin channel. The half metallicity is originated by the hybridization of Ti-d states with P–p states. This induced magnetism appeared in the systems is the result of exchange interactions between host (GaP) and Ti-atom. - Highlights: • Dilute doping of Ti in Gap is addressed to produce authenticate theoretical data. • Ti-doping generates band gap at Fermi level in minority spin channel. • Magnetism appeared is the result of exchange interactions between host (GaP) and Ti. • Magnetic moment remains constant within studied dopant concentrations.

  12. 超强永磁场处理对工业循环水电导率影响的研究%Influence of Permanent Magnetic Field Treatment on Conductivity of Industrial Circulating Water

    Institute of Scientific and Technical Information of China (English)

    李东魁; 姜丽丽; 左海滨; 谭赞林

    2011-01-01

    In this research, the developed water treatment equipment adopting permanent magnetic field was used to simulate the physical handling process of the industrial circulating water system in the laboratory. The experiment show that the magnetic field intensity, processing time and flow rate have notable impact on the conductivity of circulating water, when the circulating solution is tap water (Ca2+ concentration is less than 2.5 mmol/L), velocity is 0.6 m/s or 2.3 m/s, the conductivity of the treated solution firstly increases with the increasing of the magnetic field treatment time and then presents the multi-extremum property; when the circulating solution is calcium chloride and calcium bicarbonate mixed solution (Ca2+ concentration is greater than 2.5 mmol/L), velocity is 1.2 m/s or 2.3 m/s, the conductivity of the treated solution firstly decreases with the increasing of the magnetic treatment time and then presents the multi-extremum property. The results show that choosing the appropriate magnetic field intensity, flow rate and processing time of circulating water, the conductivity of the treated circulating water can be controlled, the hazards of the scaling in the circulating water system may be reduced.%本文利用研制的超强永磁水处理设备在实验室模拟磁场对工业循环水系统进行物理处理,实验发现:磁场强度、处理时间、水流速对循环水的电导率产生了影响;当循环水为自来水(Ca2+浓度小于2.5 mmol/L),水速为0.6和2.3 m/s时磁场处理使得循环水的电导率随处理的时间增加先上升,而后呈现多极值性增加趋势;当循环水为CaCh与Ca(HCO3)2配置溶液(Ca2+浓度大于2.5 mmol/L),水速为1.2和2.3 m/s时磁场处理使得循环水的电导率呈现随处理的时间增加先下降,而后出现多极值性增加趋势.结果表明:选择适当磁场强度、水流速度和处理时间对循环水进行磁处理,能够调控循环水的电导率,减少循环水系统结垢危害.

  13. PMG: Numerical model of a fault tolerant permanent magnet generator for high rpm applications

    Science.gov (United States)

    Bertrand, Alexandre

    The aerospace industry is confronting an increasing number of challenges these days. One can think for instance of the environmental challenges as well as the economic and social ones to name a few. These challenges have forced the industry to turn their design philosophy toward new ways of doing things. It is in this context that was born the More Electrical Aircraft (MEA) concept. This concept aims at giving a more prominent part to electrical power in the overall installed power balance aboard aircrafts (in comparison to more traditional power sources such as mechanical and hydraulic). In order to be able to support this increasing demand in electrical power, the electric power generation aboard aircrafts needed reengineering. This is one of the main reasons the More Electrical Engine (MEE) concept was born: to serve the needs of the MEA philosophy. It is precisely under the MEE concept that this project takes place. This project, realized in collaboration with Pratt & Whitney Canada (PWC), is a first attempt at the electrical modelling of this new type of electrical generator designed for aircrafts. The main objectives of this project are to understand the principles of operation of the New Architecture Electromagnetic Machine (NAEM) and to build a simplified model for EMTP-RV for steady-state simulations. This document contains the results that were obtained during the electrical modelling project of the New Architecture Electromagnetic Machine (NAEM) by the author using data from PWC. The model built by PWC using MagNet, a finite element analysis software, was used as the reference during the project. It was possible to develop an electrical model of the generator that replicate with a good accuracy the behaviour of the model of reference under steady-state operation. Some technical avenues are explored in the discussion in order to list the key improvements that will need to be done to the electrical model in future work.

  14. How doctors generate diagnostic hypotheses: a study of radiological diagnosis with functional magnetic resonance imaging.

    Directory of Open Access Journals (Sweden)

    Marcio Melo

    Full Text Available BACKGROUND: In medical practice, diagnostic hypotheses are often made by physicians in the first moments of contact with patients; sometimes even before they report their symptoms. We propose that generation of diagnostic hypotheses in this context is the result of cognitive processes subserved by brain mechanisms that are similar to those involved in naming objects or concepts in everyday life. METHODOLOGY AND PRINCIPAL FINDINGS: To test this proposal we developed an experimental paradigm with functional magnetic resonance imaging (fMRI using radiological diagnosis as a model. Twenty-five radiologists diagnosed lesions in chest X-ray images and named non-medical targets (animals embedded in chest X-ray images while being scanned in a fMRI session. Images were presented for 1.5 seconds; response times (RTs and the ensuing cortical activations were assessed. The mean response time for diagnosing lesions was 1.33 (SD ±0.14 seconds and 1.23 (SD ±0.13 seconds for naming animals. 72% of the radiologists reported cogitating differential diagnoses during trials (3.5 seconds. The overall pattern of cortical activations was remarkably similar for both types of targets. However, within the neural systems shared by both stimuli, activation was significantly greater in left inferior frontal sulcus and posterior cingulate cortex for lesions relative to animals. CONCLUSIONS: Generation of diagnostic hypotheses and differential diagnoses made through the immediate visual recognition of clinical signs can be a fast and automatic process. The co-localization of significant brain activation for lesions and animals suggests that generating diagnostic hypotheses for lesions and naming animals are served by the same neuronal systems. Nevertheless, diagnosing lesions was cognitively more demanding and associated with more activation in higher order cortical areas. These results support the hypothesis that medical diagnoses based on prompt visual recognition of

  15. Conservation of Circulation in Magnetohydrodynamics

    CERN Document Server

    Bekenstein, J D; Bekenstein, Jacob D.; Oron, Asaf

    2000-01-01

    We demonstrate, both at the Newtonian and (general) relativistic levels, theexistence of a generalization of Kelvin's circulation theorem (for pure fluids)which is applicable to perfect magnetohydrodynamics. The argument is based onthe least action principle for magnetohydrodynamic flow. Examples of the newconservation law are furnished. The new theorem should be helpful inidentifying new kinds of vortex phenomena distinct from magnetic ropes or fluidvortices.

  16. Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

    OpenAIRE

    E. D. Schmitter

    2010-01-01

    Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate ...

  17. Control of the Helicity Content of a Gun-Generated Spheromak by Incorporating a Conducting Shell into a Magnetized Coaxial Plasma Gun

    Science.gov (United States)

    Matsumoto, Tadafumi; Sekiguchi, Jun'ichi; Asai, Tomohiko

    In the formation of magnetized plasmoid by a magnetized coaxial plasma gun (MCPG), the magnetic helicity content of the generated plasmoid is one of the critical parameters. Typically, the bias coil to generate a poloidal flux is mounted either on the outer electrode or inside the inner electrode. However, most of the flux generated in the conventional method spreads even radially outside of the formation region. Thus, only a fraction of the total magnetic flux is actually exploited for helicity generation in the plasmoid. In the proposed system, the plasma gun incorporates a copper shell mounted on the outer electrode. By changing the rise time of the discharge bias coil current and the geometrical structure of the shell, the magnetic field structure and its time evolution can be controlled. The effect of the copper shell has been numerically simulated for the actual gun structure, and experimentally confirmed. This may increase the magnetic helicity content results, through increased poloidal magnetic field.

  18. Radiographic progression is associated with resolution of systemic inflammation in patients with axial spondylarthritis treated with tumor necrosis factor α inhibitors: A study of radiographic progression, inflammation on magnetic resonance imaging, and circulating biomarkers of inflammation

    DEFF Research Database (Denmark)

    Pedersen, Susanne Juhl; Sørensen, Inge Juul; Lambert, Robert G W;

    2011-01-01

    To investigate the relationship of circulating biomarkers of inflammation (C-reactive protein [CRP], interleukin-6 [IL-6], and YKL-40), angiogenesis (vascular endothelial growth factor), cartilage turnover (C-terminal crosslinking telopeptide of type II collagen [CTX-II], total aggrecan, matrix...... metalloproteinase 3 [MMP-3], and cartilage oligomeric matrix protein [COMP]), and bone turnover (CTX-I and osteocalcin) to inflammation on magnetic resonance imaging (MRI) and radiographic progression in patients with axial spondylarthritis (SpA) beginning tumor necrosis factor a (TNFa) inhibitor therapy....

  19. Helicity Balance and Steady-State Strength of the Dynamo Generated Galactic Magnetic Field

    OpenAIRE

    Kleeorin, N.; Moss, D.; Rogachevskii, I.; Sokoloff, D.

    2002-01-01

    We demonstrate that the inclusion of the helicity flux in the magnetic helicity balance in the nonlinear stage of galactic dynamo action results in a radical change in the magnetic field dynamics. The equilibrium value of the large-scale magnetic field is then approximately the equipartition level. This is in contrast to the situation without the flux of helicity, when the magnetic helicity is conserved locally, which leads to substantially subequipartition values for the equilibrium large-sc...

  20. Effect of a transverse magnetic field on the generation of electron beams in the gas-filled diode

    Science.gov (United States)

    Baksht, E. H.; Burachenko, A. G.; Erofeev, M. V.; Kostyrya, I. D.; Lomaev, M. I.; Rybka, D. V.; Tarasenko, V. F.

    2008-06-01

    The effect of a transverse magnetic field (0.080 and 0.016 T) on generation of an electron beam in the gas-filled diode is experimentally investigated. It is shown that, at voltage U = 25 kV across the diode and a low helium pressure (45 Torr), the transverse magnetic field influences the beam current amplitude behind a foil and its distribution over the foil cross section. At elevated pressures and under the conditions of ultrashort avalanche electron beam formation in helium, nitrogen, and air, the transverse magnetic field (0.080 and 0.016 T) has a minor effect on the amplitude and duration of the beam behind the foil. It is established that, when the voltage of the pulse generator reaches several hundreds of kilovolts, some runaway electrons (including the electrons from the discharge plasma near the cathode) are incident on the side walls of the diode.

  1. Experimental Investigation on Low Magnetic Field Operation of an Overmoded Slow-Wave High-Power Microwave Generator

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun; ZHONG Hui-Huang; SHU Ting; LUO Ling; WANG Yong

    2004-01-01

    @@ The experimental results of an overmoded slow-wave high-power microwave generator operated at low magnetic field are presented. The feasibility of low magnetic field operation is investigated both theoretically and experimentally based on the characteristics of the overmoded slow-wave device. The experiments were carried out at the Spark-2 accelerator. Under the condition of guiding magnetic field strength of 0.55 T, diode voltage of 474 k V,and beam current of 5.2kA, a microwave was generated with power of 510MW, mode of TM01, and frequency of 9.54 GHz. The relative half-width of the frequency spectrum is less than 1%, and the beam-to-microwave efficiency is about 21% in our experiments.

  2. Diagnosis of Short-Circuit Fault in Large-Scale Permanent-Magnet Wind Power Generator Based on CMAC

    Directory of Open Access Journals (Sweden)

    Chin-Tsung Hsieh

    2013-01-01

    Full Text Available This study proposes a method based on the cerebellar model arithmetic controller (CMAC for fault diagnosis of large-scale permanent-magnet wind power generators and compares the results with Error Back Propagation (EBP. The diagnosis is based on the short-circuit faults in permanent-magnet wind power generators, magnetic field change, and temperature change. Since CMAC is characterized by inductive ability, associative ability, quick response, and similar input signals exciting similar memories, it has an excellent effect as an intelligent fault diagnosis implement. The experimental results suggest that faults can be diagnosed effectively after only training CMAC 10 times. In comparison to training 151 times for EBP, CMAC is better than EBP in terms of training speed.

  3. On the magnetic field and the electrical potential generated by bioelectric sources in an anisotropic volume conductor

    NARCIS (Netherlands)

    Peters, M.J.; Elias, P.J.H.

    1988-01-01

    The electrical conductivity in biological tissue is often dependent on the direction of the fibres. In the paper the influence of this anisotropic nature on the electrical potential and magnetic field generated by a current dipole is studied analytically. Three different methods are discussed. The v

  4. Comparison of Wind Power Converter Reliability with Low-Speed and Medium-Speed Permanent-Magnet Synchronous Generators

    DEFF Research Database (Denmark)

    Zhou, Dao; Blaabjerg, Frede; Franke, Toke;

    2015-01-01

    , according to the lifetime power cycles, the lifespan can be calculated when operating in various wind classes. It is concluded that, although the low-speed permanent-magnet synchronous generator is able to eliminate the gearbox, the lifespan of its machine-side converter is lower than the one-stage medium...

  5. Flicker Mitigation by Speed Control of Permanent Magnet Synchronous Generator Variable-Speed Wind Turbines

    Directory of Open Access Journals (Sweden)

    Yanting Hu

    2013-07-01

    Full Text Available Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a full-scale back-to-back power converter and permanent magnet synchronous generator (PMSG developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated. The 3p (three times per revolution power oscillation due to wind shear and tower shadow effects is the significant part in the flicker emission of variable speed wind turbines with PMSG during continuous operation. A new method of flicker mitigation by controlling the rotational speed is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the rotational speed of the PMSG. Simulation results show that damping the 3p active power oscillation by using the flicker mitigation speed controller is an effective means for flicker mitigation of variable speed wind turbines with full-scale back-to-back power converters and PMSG during continuous operation.

  6. Proton magnetic resonance with parahydrogen induced polarization. Imaging strategies and continuous generation

    Energy Technology Data Exchange (ETDEWEB)

    Dechent, Jan Falk Frederik

    2012-12-17

    A major challenge in imaging is the detection of small amounts of molecules of interest. In the case of magnetic resonance imaging (MRI) their signals are typically concealed by the large background signal of e.g. the tissue of the body. This problem can be tackled by hyperpolarization which increases the NMR signals up to several orders of magnitude. However, this strategy is limited for {sup 1}H, the most widely used nucleus in NMR and MRI, because the enormous number of protons in the body screen the small amount of hyperpolarized ones. Here, I describe a method giving rise to high {sup 1}H MRI contrast for hyperpolarized molecules against a large background signal. The contrast is based on the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via parahydrogen induce polarization (PHIP) and it can easily be implemented in common pulse sequences. Hyperpolarization methods typically require expensive technical equipment (e.g. lasers or microwaves) and most techniques work only in batch mode, thus the limited lifetime of the hyperpolarization is limiting its applications. Therefore, the second part of my thesis deals with the simple and efficient generation of an hyperpolarization. These two achievements open up alternative opportunities to use the standard MRI nucleus {sup 1}H for e.g. metabolic imaging in the future.

  7. Proton magnetic resonance with parahydrogen induced polarization. Imaging strategies and continuous generation

    International Nuclear Information System (INIS)

    A major challenge in imaging is the detection of small amounts of molecules of interest. In the case of magnetic resonance imaging (MRI) their signals are typically concealed by the large background signal of e.g. the tissue of the body. This problem can be tackled by hyperpolarization which increases the NMR signals up to several orders of magnitude. However, this strategy is limited for 1H, the most widely used nucleus in NMR and MRI, because the enormous number of protons in the body screen the small amount of hyperpolarized ones. Here, I describe a method giving rise to high 1H MRI contrast for hyperpolarized molecules against a large background signal. The contrast is based on the J-coupling induced rephasing of the NMR signal of molecules hyperpolarized via parahydrogen induce polarization (PHIP) and it can easily be implemented in common pulse sequences. Hyperpolarization methods typically require expensive technical equipment (e.g. lasers or microwaves) and most techniques work only in batch mode, thus the limited lifetime of the hyperpolarization is limiting its applications. Therefore, the second part of my thesis deals with the simple and efficient generation of an hyperpolarization. These two achievements open up alternative opportunities to use the standard MRI nucleus 1H for e.g. metabolic imaging in the future.

  8. Application of magnetic, geochemical and micro-morphological methods in environmental studies of urban pollution generated by road traffic

    Energy Technology Data Exchange (ETDEWEB)

    Bucko, M.

    2012-11-01

    Road traffic is at present one of the major sources of environmental pollution in urban areas. Magnetic particles, heavy metals and other compounds generated by traffic can greatly affect ambient air quality and have direct implications for human health. The general aim of this research was to identify and characterize magnetic vehicle-derived particulates using magnetic, geochemical and micro-morphological methods. A combination of three different methods was used to discriminate sources of particular anthropogenic particles. Special emphasis was placed on the application of various collectors (roadside soil, snow, lichens and moss bags) to monitor spatial and temporal distribution of traffic pollution on roadsides. The spatial distribution of magnetic parameters of road dust accumulated in roadside soil, snow, lichens and moss bags indicates that the highest concentration of magnetic particles is in the sampling points situated closest to the road edge. The concentration of magnetic particles decreases with increasing distance from the road indicating vehicle traffic as a major source of emission. Significant differences in horizontal distribution of magnetic susceptibility were observed between soil and snow. Magnetic particles derived from road traffic deposit on soil within a few meters from the road, but on snow up to 60 m from the road. The values of magnetic susceptibility of road dust deposited near busy urban motorway are significantly higher than in the case of low traffic road. These differences are attributed to traffic volume, which is 30 times higher on motorway than on local road. Moss bags placed at the edge of urban parks situated near major roads show higher values of magnetic susceptibility than moss bags from parks located near minor routes. Enhanced concentrations of heavy metals (e.g. Fe, Mn, Zn, Cu, Cr, Ni and Co) were observed in the studied samples. This may be associated with specific sources of vehicle emissions (e.g. exhaust and non

  9. Integration of permanent magnet synchronous generator wind turbines into power grid

    Science.gov (United States)

    Abedini, Asghar

    , integrating energy storage systems with wind farms has attracted a lot of attention. These two subjects are addressed in this dissertation in detail. Permanent Magnet Synchronous Generators (PMSG) are used in variable speed wind turbines. In this thesis, the dynamic of the PMSG is investigated and a power electronic converter is designed to integrate the wind turbine to the grid. The risks of PMSG wind turbines such as low voltage ride through and short circuits, are assessed and the methods of mitigating the risks are discussed. In the second section of the thesis, various methods of smoothing wind turbine output power are explained and compared. Two novel methods of output power smoothing are analyzed: Rotor inertia and Super capacitors. The advantages and disadvantages of each method are explained and the dynamic model of each method is developed. The performance of the system is evaluated by simulating the wind turbine system in each method. The concepts of the methods of smoothing wind power can be implemented in other types of wind turbines such as Doubly Fed Induction Generator (DFIG) wind turbines.

  10. A magnetically isolated diode with Bτ-field as a generator of high-power microsecond ion beam

    International Nuclear Information System (INIS)

    The results of a study of the generation of a high-power microsecond ion beam in a planar magnetically isolated diode with external radially distributed isolating field are presented. A ring cross-section ion beam consisting mainly of H+ and C+ ions was studied. The energy range of most of the generated ions is 300-500 keV. The total energy stored in the beam extracted from the diode is 10 kJ and the generation efficiency reaches 60%. 5 refs., 4 figs

  11. A Review Paper on Modeling And Simulation of Permanent Magnet Synchronous Generator Based on Wind Energy Conversion System

    Directory of Open Access Journals (Sweden)

    Venugopal J Kante

    2014-06-01

    Full Text Available This paper present‘s a comprehensive review on study of modeling and simulation of permanent magnet synchronous generator based on wind energy conversion system, in which the basic wind energy conversion equation, wind turbine mathematical equation, wind turbine controls, and drive train, different types of drive train, are discussed, the PMSG (permanent magnet synchronous generator is introduced as construction, mathematical equation of PMSG are established in the d-q model, and different types of wind generator concept in short is discussed, configuration of different power converter‘s is proposed with modeling and simulation of PMSG based on WECS at variable speed operation and maximum power capture, various control technique for the system are discussed for both machine-side and grid-side in detail, the different types of MPPT technique is presented in this paper.

  12. System frequency support of permanent magnet synchronous generator-based wind power plant

    Science.gov (United States)

    Wu, Ziping

    With ever-increasing penetration of wind power into modern electric grids all over the world, a trending replacement of conventional synchronous generators by large wind power plants will likely result in the poor overall frequency regulation performance. On the other hand, permanent magnet synchronous generator wind Turbine System (PMSG-WTG) with full power back to back converters tends to become one of the most promising wind turbine technologies thanks to various advantages. It possesses a significant amount of kinetic energy stored in the rotating mass of turbine blades, which can be utilized to enhance the total inertia of power system. Additionally, the deloaded operation and decoupled control of active and reactive power make it possible for PMSG-WTG to provide a fast frequency regulation through full-power converter. First of all, a comprehensive and in-depth survey is conducted to analyze the motivations for incorporating the inertial response and frequency regulation of VSWT into the system frequency regulation. Besides, control classifications, fundamental control concepts and advanced control schemes implemented for auxiliary frequency support of individual WT or wind power plant are elaborated along with a comparison of the potential frequency regulation capabilities of four major types of WTs. Secondly, a Controls Advanced Research Turbine2-Permanent Magnet Synchronous Generator wind turbine (CART2-PMSG) integrated model representing the typical configuration and operation characteristics of PMSG-WT is established in Matlab/Simulink,. Meanwhile, two different rotor-side converter control schemes, including rotor speed-based control and active power-based control, are integrated into this CART2-PMSG integrated model to perform Maximum Power Point Tracking (MPPT) operation over a wide range of wind speeds, respectively. Thirdly, a novel comprehensive frequency regulation (CFR) control scheme is developed and implemented into the CART2-PMSG model based

  13. Direct optical detection of current induced spin accumulation in metals by magnetization-induced second harmonic generation

    International Nuclear Information System (INIS)

    Strong spin-orbit coupling in non-magnetic heavy metals has been shown to lead to large spin currents flowing transverse to a charge current in such a metal wire. This in turn leads to the buildup of a net spin accumulation at the lateral surfaces of the wire. Spin-orbit torque effects enable the use of the accumulated spins to exert useful magnetic torques on adjacent magnetic layers in spintronic devices. We report the direct detection of spin accumulation at the free surface of nonmagnetic metal films using magnetization-induced optical surface second harmonic generation. The technique is applied to probe the current induced surface spin accumulation in various heavy metals such as Pt, β-Ta, and Au with high sensitivity. The sensitivity of the technique enables us to measure the time dynamics on a sub-ns time scale of the spin accumulation arising from a short current pulse. The ability of optical surface second harmonic generation to probe interfaces suggests that this technique will also be useful for studying the dynamics of spin accumulation and transport across interfaces between non-magnetic and ferromagnetic materials, where spin-orbit torque effects are of considerable interest

  14. Relaxation time diagram for identifying heat generation mechanisms in magnetic fluid hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Enio, E-mail: lima@cab.cnea.gov.ar; De Biasi, Emilio; Zysler, Roberto D.; Vasquez Mansilla, Marcelo; Mojica-Pisciotti, Mary L. [Centro Atómico Bariloche/CONICET (Argentina); Torres, Teobaldo E.; Calatayud, M. Pilar; Marquina, C.; Ricardo Ibarra, M.; Goya, Gerardo F. [Universidad de Zaragoza, Instituto de Nanociencia de Aragón INA (Spain)

    2014-12-15

    We present a versatile diagram to envisage the dominant relaxation mechanism of single-domain magnetic nanoparticles (MNPs) under alternating magnetic fields, as those used in magnetic fluid hyperthermia (MFH). The diagram allows estimating the heating efficiency, measured by the Specific Power Absorption (SPA), originated in the magnetic and viscous relaxation times of single-domain MNPs for a given frequency of the ac magnetic field (AFM). The diagram has been successfully applied to different colloids, covering a wide variety of MNPs with different magnetic anisotropy and particle size, and dispersed in different viscous liquid carriers. From the general diagram, we derived a specific chart based on the Linear Response Theory in order to easily estimate the experimental condition for the optimal SPA values of most colloids currently used in MFH.

  15. A Steady State Tokamak Operation by Use of Magnetic Monopoles

    OpenAIRE

    Narihara, K.

    1991-01-01

    A steady state tokamak operation based on a magnetic monopole circuit is considered. Circulation of a chain of iron cubes which trap magnetic monopoles generates the needed loop voltage. The monopole circuit is enclosed by a series of solenoid coils in which the magnetic field is feedback controlled so that the force on the circuit balance against the mechanical friction. The driving power is supplied through the current sources of poloidal, ohmic and solenoid coils. The current drive efficie...

  16. Design, fabrication, and characterization of a solenoid system to generate magnetic field for an ECR proton source

    Indian Academy of Sciences (India)

    S K Jain; P A Naik; P R Hannurkar

    2010-08-01

    Solenoid coils with iron jacket (electromagnets) have been designed and developed for generation and confinement of the plasma produced by an electron cyclotron resonance source operating at 2450 MHz frequency. The magnetic field configurations designed using the solenoid coils are off-resonance, mirror, and flat, satisfying electron cyclotron resonance condition along the axis of the plasma chamber. 2D Poisson software was used for designing. Details of design, fabrication, and magnetic field mapping of the solenoid coils are presented in this paper.

  17. Feasibility of a magnetic suspension for second generation Gravitational Wave interferometers

    OpenAIRE

    Varvella, Monica; Calloni, Enrico; Di Fiore, Luciano; Milano, Leopoldo; Arnaud, Nicolas

    2004-01-01

    This paper deals with the use of a magnetic levitation system as a part of a multi-stage seismic attenuator for gravitational wave interferometric antennas. The proposed configuration uses permanent magnets in attraction to balance the suspended weight, plus a closed loop position control to obtain a stable levitation. The system is analyzed using a MATLAB simulation code to compute the forces exerted by extended magnets. The validity of this model has been tested by a comparison with the exp...

  18. Magnetic diagnostic of SOL-filaments generated by type I ELMs on JET and ASDEX Upgrade

    DEFF Research Database (Denmark)

    Naulin, Volker; Vianello, N.; Schrittwieser, R.;

    2011-01-01

    This contribution is focused on the magnetic signatures of type I ELM filaments. On JET a limited number of high time resolution magnetic coils were used to derive essential ELM filament parameters. The method uses forward modelling and simultaneous fitting of magnetic pickup coil signals to a...... simple model, motivated by observations. A new diagnostic in the form of a reciprocating probe with three magnetic pickup loops was developed for ASDEX Upgrade (AUG). Measurements during the passage of type-I ELM filaments determine the filaments to be in the scrape off layer (SOL) and to carry currents...

  19. Experimental study of spiral flow generator in liquid-solid horizontal circulating fluidized bed%水平液固循环流化床起旋器的实验研究

    Institute of Scientific and Technical Information of China (English)

    彭培英; 张伟; 刘燕

    2009-01-01

    An experiment was made of the particles distribution of each section of a single-loop solids circulation system in a φ29 mm×4 200 mm cold liquid-solid horizontal circulating fluidized bed test facility. The CCD image measurement and data processing system was used to study the particles distribution at different operating conditions with the spiral flow generator added.The experiment shows that the spiral pipe flow generator arranged in the liquid-solid horizontal circulating fluidized bed can effectively improve the uniform distribution of particles in a certain distance; but as the axial distance increases, the effect of the spiral flow generator weakened. There was a low non-uniform distribution as the guide vane angle and liquid flow rate increased. For the particle with the same diameter, density and initial volume add the larger the solid particles containing the greater rate of non-uniform degrees.%在φ29 mm×4 200 mm流化床装置上,利用CCD图像测量与数据处理系统在线对导流叶片式局部起旋器对水平液固循环流化床内固相颗粒分布特性的影响进行了研究.结果表明:安装局部起旋器后,颗粒分布状况在一定距离内得到明显改善;但随着轴向距离增加,起旋器作用效果减弱.随着导叶包角、液体流速的增加,颗粒固含率不均匀度减小.对于相同直径的颗粒,密度和初始加入量越大,颗粒固含率不均匀度越大.

  20. Generation of Internal-Image Functional Aptamers of Okadaic Acid via Magnetic-Bead SELEX

    Directory of Open Access Journals (Sweden)

    Chao Lin

    2015-12-01

    Full Text Available Okadaic acid (OA is produced by Dinophysis and Prorocentrum dinoflagellates and primarily accumulates in bivalves, and this toxin has harmful effects on consumers and operators. In this work, we first report the use of aptamers as novel non-toxic probes capable of binding to a monoclonal antibody against OA (OA-mAb. Aptamers that mimic the OA toxin with high affinity and selectivity were generated by the magnetic bead-assisted systematic evolution of ligands by exponential enrichment (SELEX strategy. After 12 selection rounds, cloning, sequencing and enzyme-linked immunosorbent assay (ELISA analysis, four candidate aptamers (O24, O31, O39, O40 were selected that showed high affinity and specificity for OA-mAb. The affinity constants of O24, O31, O39 and O40 were 8.3 × 108 M−1, 1.47 × 109 M−1, 1.23 × 109 M−1 and 1.05 × 109 M−1, respectively. Indirect competitive ELISA was employed to determine the internal-image function of the aptamers. The results reveal that O31 has a similar competitive function as free OA toxin, whereas the other three aptamers did not bear the necessary internal-image function. Based on the derivation of the curvilinear equation for OA/O31, the equation that defined the relationship between the OA toxin content and O31 was Y = 2.185X − 1.78. The IC50 of O31 was 3.39 ng·mL−1, which was close to the value predicted by the OA ELISA (IC50 = 4.4 ng·mL−1; the IC10 was 0.33 ng·mL−1. The above data provides strong evidence that internal-image functional aptamers could be applicable as novel probes in a non-toxic assay.

  1. pH-Based Scale Inhibition Effects Assessment and Prediction of Industrial Circulating Water After Ultra-Strong Permanent Magnetic Field Treatment%基于pH值的超强永磁场处理工业循环水阻垢效果评估与预测

    Institute of Scientific and Technical Information of China (English)

    李东魁; 左海滨; 姜丽丽; 谭赞麟

    2014-01-01

    Magnetic field treatment of industrial circulating water has the effects of scale inhibition .The ultra-strong permanent magnetic field treatment of industrial circulating water was simulated in laboratory .The relationships of the pH value of treated circulating water to magnetic field intensity ,the speed and temperature of the circulating wa-ter ,exposure time to the magnetic field ,and calcium ion concentration were analyzed .A model based on pH value of industrial circulating water treated by ultra-strong permanent magnetic field was established for assessing the effects of scale inhibition .It can provide references for quality control of circulating water treated by magnetic field and theo-retical foundation for ultra-strong permanent magnetic field application in industry .%磁场处理工业循环水具有一定的阻垢效果。在实验室利用研制的超强永磁场模拟处理工业循环水装置,研究磁场处理后循环水pH值与磁场强度、循环水速度、循环水温度、磁场处理时间、钙离子浓度等的关系,建立基于pH值的超强永磁场循环水处理阻垢效果评价模型,为研制磁场处理循环水的质量控制模型提供参考,为超强永磁场应用于工业生产实践提供必要理论基础。

  2. Control generating of bacterial magnetic nanoparticle-doxorubicin conjugates by poly-L-glutamic acid surface modification

    Energy Technology Data Exchange (ETDEWEB)

    Guo Lin [Key Laboratory of Mesoscopic Chemistry of MOE and School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093 (China); Huang Ji; Zheng Limin, E-mail: linguo@nju.edu.cn [State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093 (China)

    2011-04-29

    By using poly-L-glutamic acid (PLGA) to modify the membrane surface of bacterial magnetic nanoparticles (BMPs), (BMP)-doxorubicin conjugates (DBMP-P) could be control generated. The doxorubicin loading ratio could be raised up to 81.7% (w/w) in comparison with that of dual functional linkers. DBMP-P was characterized by transmission electron micrographs, attenuated total reflection infrared spectroscopy, magnetic properties, and dynamic light scattering. It is found that increase of the doxorubicin/PLGA modified BMP (PBMP) ratio leads to an increase of the drug loading ratio and a decrease of saturation magnetization. Besides, DBMP-P is sensitive to pH to facilitate drug release, shows enhancement of uptake by cancer cells, and is strongly cytotoxic to HePG2 and MCF-7 cells.

  3. Effects of Radiation Heat Transfer on Entropy Generation at Thermosolutal Convection in a Square Cavity Subjected to a Magnetic Field

    Directory of Open Access Journals (Sweden)

    Ammar Ben Brahim

    2011-11-01

    Full Text Available Thermosolutal convection in a square cavity filled with a binary perfect gas mixture and submitted to an oriented magnetic field taking into account the effect of radiation heat transfer is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined for laminar flow by solving numerically: The continuity, momentum energy and mass balance equations, using a Control Volume Finite-Element Method. The structure of the studied flows depends on five dimensionless parameters which are: The Grashof number, the buoyancy ratio, the Hartman number, the inclination angle of the magnetic field and the radiation parameter.

  4. Generation of flat-top pulsed magnetic fields with feedback control approach

    CERN Document Server

    Kohama, Yoshimitsu

    2015-01-01

    We describe the construction of a simple, compact, and cost-effective feedback system that produces flat-top field profiles in pulsed magnetic fields. This system is designed for use in conjunction with a typical capacitor-bank driven pulsed magnet, and was tested using a 60-T pulsed magnet. With the developed feedback controller, we have demonstrated flat-top magnetic fields as high as 60.64 T with an excellent field stability of +-0.005 T. The result indicates that the flat-top pulsed magnetic field produced features high field stability and an accessible field strength. These features make this system useful for improving the resolution of data with signal averaging.

  5. Self-consistent modeling of induced magnetic field in Titan's atmosphere accounting for the generation of Schumann resonance

    Science.gov (United States)

    Béghin, Christian

    2015-02-01

    This model is worked out in the frame of physical mechanisms proposed in previous studies accounting for the generation and the observation of an atypical Schumann Resonance (SR) during the descent of the Huygens Probe in the Titan's atmosphere on 14 January 2005. While Titan is staying inside the subsonic co-rotating magnetosphere of Saturn, a secondary magnetic field carrying an Extremely Low Frequency (ELF) modulation is shown to be generated through ion-acoustic instabilities of the Pedersen current sheets induced at the interface region between the impacting magnetospheric plasma and Titan's ionosphere. The stronger induced magnetic field components are focused within field-aligned arcs-like structures hanging down the current sheets, with minimum amplitude of about 0.3 nT throughout the ramside hemisphere from the ionopause down to the Moon surface, including the icy crust and its interface with a conductive water ocean. The deep penetration of the modulated magnetic field in the atmosphere is thought to be allowed thanks to the force balance between the average temporal variations of thermal and magnetic pressures within the field-aligned arcs. However, there is a first cause of diffusion of the ELF magnetic components, probably due to feeding one, or eventually several SR eigenmodes. A second leakage source is ascribed to a system of eddy-Foucault currents assumed to be induced through the buried water ocean. The amplitude spectrum distribution of the induced ELF magnetic field components inside the SR cavity is found fully consistent with the measurements of the Huygens wave-field strength. Waiting for expected future in-situ exploration of Titan's lower atmosphere and the surface, the Huygens data are the only experimental means available to date for constraining the proposed model.

  6. Sensorless Doubly-Fed Induction Generator Control Under Power System Transients and Faults: The Influence of Magnetic Saturation

    DEFF Research Database (Denmark)

    Serban, Ioan; Boldea, Ion; Blaabjerg, Frede

    2004-01-01

    The present paper investigates the influence of magnetic saturation on the rotor position and speed estimators and the machine behavior during transients and short-circuit faults for a doubly-fed induction generator (DFIG) connected to the power grid. The DFIG is considered driven by a wind turbine...... whose torque vs. generator speed at different wind speed is optimised. The DFIG is connected to the grid, at a certain initial speed, simultaneously in the stator and in the rotor for given values of active and reactive stator power references. Subsequently a sudden three-phase short......-circuit at the middle of a typical local power grid is investigated. A computer program in Matlab-Simulink package for the whole system has been developed and applied to simulate transients as described above with and without considering the magnetic saturation in the machine. It is shown by digital simulations...

  7. A Design Fuzzy Logic Controller for a Permanent Magnet Wind Generator to Enhance the Dynamic Stability of Wind Farms

    OpenAIRE

    Marwan Rosyadi; Muyeen, S.M.; Rion Takahashi; Junji Tamura

    2012-01-01

    In this paper, a design fuzzy logic controller for a variable speed permanent magnet wind generator connected to a grid system through a LC-filter is proposed. A new current control method of grid side conversion is developed by integrating the fuzzy controller, in which both active and reactive power, delivered to a power grid system, is controlled effectively. The fuzzy logic controller is designed to adjust the gain parameters of the PI controllers under any operating conditions, so that t...

  8. Non-linear control of variable-speed wind turbines with permanent magnet synchronous generators: a robust backstepping approach

    Science.gov (United States)

    Şeker, Murat; Zergeroğlu, Erkan; Tatlicioğlu, Enver

    2016-01-01

    In this study, a robust backstepping approach for the control problem of the variable-speed wind turbine with a permanent magnet synchronous generator is presented. Specifically, to overcome the negative effects of parametric uncertainties in both mechanical and electrical subsystems, a robust controller with a differentiable compensation term is proposed. The proposed methodology ensures the generator velocity tracking error to uniformly approach a small bound where practical tracking is achieved. Stability of the overall system is ensured by Lyapunov-based arguments. Comparative simulation studies with a standard proportional-integral-type controller are performed to illustrate the effectiveness, feasibility and efficiency of the proposed controller.

  9. High energy micro electron beam generation using chirped laser pulse in the presence of an axial magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Akou, H., E-mail: h.akou@nit.ac.ir; Hamedi, M. [Department of Physics, Faculty of Basic Science, Babol University of Technology, Babol 47148-71167 (Iran, Islamic Republic of)

    2015-10-15

    In this paper, the generation of high-quality and high-energy micro electron beam in vacuum by a chirped Gaussian laser pulse in the presence of an axial magnetic field is numerically investigated. The features of energy and angular spectra, emittances, and position distribution of electron beam are compared in two cases, i.e., in the presence and absence of an external magnetic field. The electron beam is accelerated with higher energy and qualified in spatial distribution in the presence of the magnetic field. The presence of an axial magnetic field improves electron beam spatial quality as well as its gained energy through keeping the electron motion parallel to the direction of propagation for longer distances. It has been found that a 64 μm electron bunch with about MeV initial energy becomes a 20 μm electron beam with high energy of the order of GeV, after interacting with a laser pulse in the presence of an external magnetic field.

  10. Electromagnetic analysis and experimental testing of a light switchwith a permanent magnet generator for energy harvesting based on three dimensional finite element model

    Science.gov (United States)

    Shin, Hyeon-Jae; Choi, Jang-Young; Kim, Il-Jung; Choi, Yeon-Suk

    2014-05-01

    This paper presents a small-size permanent magnet generator for an energy harvester. The generator is suitable for a switch, as it uses a magnetic force as the retention force and the force of motion to recognize switch operation. In addition, the induced voltages have positive or negative values depending on the switching direction. It is possible to monitor switch operation for achieving intelligent power consumption. Finally, measurements of the generated voltage are presented to reveal the effectiveness of the energy harvester.

  11. Direct Generation of Intense Compression Waves in Molten Metals by Using a High Static Magnetic Field and Their Application

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Compression waves propagating through molten metals are contributed to degassing, accelerating reaction rate,removing exclusions from molten metals and refining solidification structures during metallurgical processing of ma-terials. In the present study, two electromagnetic methods are proposed to generate intense compression wavesdirectly in liquid metals. One is the simultaneous imposition of a high frequency electrical current field and a staticmagnetic field; the other is that of a high frequency magnetic field and a static magnetic field. A mathematical modelbased on compressible fluid dynamics and electromagnetic fields theory has been developed to derive pressure distri-butions of the generated waves in a metal. It shows that the intensity of compression waves is proportional to thatof the high frequency electromagnetic force. And the frequency is the same as that of the imposed electromagneticforce. On the basis of theoretical analyses, pressure change in liquid gallium was examined by a pressure transducerunder various conditions. The observed results approximately agreed with the predictions derived from the theoreticalanalyses and calculations. Moreover, the effect of the generated waves on improvement of solidification structureswas also examined. It shows that the generated compression waves can refine solidification structures when they wereapplied to solidification process of Sn-Pb alloy. This study indicates a new method to generate compression wavesby imposing high frequency electromagnetic force locally on molten metals and this kind of compression waves canprobably overcome the difficulties when waves are excited by mechanical vibration in high temperature environments.

  12. Feasibility of a magnetic suspension for second generation Gravitational Wave interferometers

    CERN Document Server

    Varvella, M; Fiore, L D; Milano, L; Arnaud, N; Varvella, Monica; Calloni, Enrico; Fiore, Luciano Di; Milano, Leopoldo; Arnaud, Nicolas

    2004-01-01

    This paper deals with the use of a magnetic levitation system as a part of a multi-stage seismic attenuator for gravitational wave interferometric antennas. The proposed configuration uses permanent magnets in attraction to balance the suspended weight, plus a closed loop position control to obtain a stable levitation. The system is analyzed using a MATLAB simulation code to compute the forces exerted by extended magnets. The validity of this model has been tested by a comparison with the experimental data from a levitated suspension prototype.

  13. Magnetic Circuit Model of PM Motor-Generator to Predict Radial Forces

    Science.gov (United States)

    McLallin, Kerry (Technical Monitor); Kascak, Peter E.; Dever, Timothy P.; Jansen, Ralph H.

    2004-01-01

    A magnetic circuit model is developed for a PM motor for flywheel applications. A sample motor is designed and modeled. Motor configuration and selection of materials is discussed, and the choice of winding configuration is described. A magnetic circuit model is described, which includes the stator back iron, rotor yoke, permanent magnets, air gaps and the stator teeth. Iterative solution of this model yields flux linkages, back EMF, torque, power, and radial force at the rotor caused by eccentricity. Calculated radial forces are then used to determine motor negative stiffness.

  14. On the possibility of connecting a non-operating main circulation pump with three pumps in operation without preliminary coast-down of power-generating unit No. 5 in the Novovoronezh nuclear power plant

    Science.gov (United States)

    Vitkovskii, I. L.; Nikonov, S. P.; Ryasnyi, S. I.

    2014-02-01

    The subject of this paper is a transient caused by connection of a standby loop to three operating circulation pumps at the initial reactor heat rate equal to 70% of the rated value without preliminarily reducing it to 30% of the rated level as required by the safe operation regulations. Failure of the following normal operation systems is supposed: the first- and the second-type warning protection systems, all quick-acting reducing devices releasing steam into the auxiliary manifold, the electric heaters of the pressurizer, the pressurizer injection system, the primary cooling circuit fluid makeup/blow-through systems, and the blocking systems to shut down the main circulation pump after the level in the steam generator is exceeded. In addition, it is supposed that, under transient conditions, the valves of the turbine regulation system will be in the position in which they were at the moment of the initial event until generation of the signal for positive closing of the turbine stop valves. The first signal to actuate the reactor emergency protection system (EPS) is skipped. The failure of all quick-acting reducing devices releasing steam into the atmosphere is assumed. In addition to equipment failure, at the moment when the main circulation pump is connected, the operator erroneously puts in a new setting to maintain the power allowable for four pumps in operation-in the calculations it was taken equal to 104% of the rated level at most considering the accuracy of evaluating and maintaining the reactor heat rate-and the working group of the reactor protection and control system (P&CS) starts moving upward. On reaching the set power level, the automatic reactor power regulator stops operating and the P&CS elements remain in the position in which they are at the moment. Compliance with the design safety criteria for the adopted scenario of the transient is demonstrated.

  15. Prospects for Non-Rare Earth Permanent Magnets for Traction Motors and Generators

    Science.gov (United States)

    Kramer, M. J.; McCallum, R. W.; Anderson, I. A.; Constantinides, S.

    2012-07-01

    With the advent of high-flux density permanent magnets based on rare earth elements such as neodymium (Nd) in the 1980s, permanent magnet-based electric machines had a clear performance and cost advantage over induction machines when weight and size were factors such as in hybrid electric vehicles and wind turbines. However, the advantages of the permanent magnet-based electric machines may be overshadowed by supply constraints and high prices of their key constituents, rare earth elements, which have seen nearly a 10-fold increase in price in the last 5 years and the imposition of export limits by the major producing country, China, since 2010. We outline the challenges, prospects, and pitfalls for several potential alloys that could replace Nd-based permanent magnets with more abundant and less strategically important elements.

  16. Generation of a magnetic island by edge turbulence in tokamak plasmas

    Science.gov (United States)

    Poyé, A.; Agullo, O.; Muraglia, M.; Garbet, X.; Benkadda, S.; Sen, A.; Dubuit, N.

    2015-03-01

    We investigate, through extensive 3D magneto-hydro-dynamics numerical simulations, the nonlinear excitation of a large scale magnetic island and its dynamical properties due to the presence of small-scale turbulence. Turbulence is induced by a steep pressure gradient in the edge region [B. D. Scott, Plasma Phys. Controlled Fusion 49, S25 (2007)], close to the separatrix in tokamaks where there is an X-point magnetic configuration. We find that quasi-resonant localized interchange modes at the plasma edge can beat together and produce extended modes that transfer energy to the lowest order resonant surface in an inner stable zone and induce a seed magnetic island. The island width displays high frequency fluctuations that are associated with the fluctuating nature of the energy transfer process from the turbulence, while its mean size is controlled by the magnetic energy content of the turbulence.

  17. Generation of a magnetic island by edge turbulence in tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Poyé, A. [Aix-Marseille Université, CNRS, PIIM, UMR 7345, Marseille (France); Université de Bordeaux, CELIA Laboratory, Talence 33405 (France); Agullo, O.; Muraglia, M.; Benkadda, S.; Dubuit, N. [Aix-Marseille Université, CNRS, PIIM, UMR 7345, Marseille (France); France-Japan Magnetic Fusion Laboratory, LIA 336 CNRS, Marseille (France); Garbet, X. [IRFM, CEA, St-Paul-Lez-Durance 13108 (France); Sen, A. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

    2015-03-15

    We investigate, through extensive 3D magneto-hydro-dynamics numerical simulations, the nonlinear excitation of a large scale magnetic island and its dynamical properties due to the presence of small-scale turbulence. Turbulence is induced by a steep pressure gradient in the edge region [B. D. Scott, Plasma Phys. Controlled Fusion 49, S25 (2007)], close to the separatrix in tokamaks where there is an X-point magnetic configuration. We find that quasi-resonant localized interchange modes at the plasma edge can beat together and produce extended modes that transfer energy to the lowest order resonant surface in an inner stable zone and induce a seed magnetic island. The island width displays high frequency fluctuations that are associated with the fluctuating nature of the energy transfer process from the turbulence, while its mean size is controlled by the magnetic energy content of the turbulence.

  18. Microwave generation from an axially extracted virtual cathode oscillator with a guide magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kostov, K.G.; Nikolov, N.A. (Department of General Physics, Sofia University, Sofia 1126 (Bulgaria))

    1994-04-01

    The operation of a virtual cathode oscillator (vircator) with strong axial magnetic field has been experimentally studied. Depending on the cathode--anode gap and cathode diameter, the operating voltage varies from 200 kV up to 480 kV with 2--7 kA diode current. Microwave emission is produced by the oscillating virtual cathode. The central microwave frequency follows the beam plasma frequency. It varies by 11.5 GHz up to 22 GHz, depending on the current density. The oscillation frequency does not depend on the guide magnetic field magnitude. A maximal output power of 15[plus minus]5 MW in asymmetric transverse magnetic (TM) modes is achieved by the axially extracted vircator. Variation of the magnetic field intensity in a range of 0--40 kG has an insignificant effect upon the emitted microwave power. An electron beam power to microwave power conversion efficiency of approximately 1% is obtained.

  19. Microwave generation from an axially extracted virtual cathode oscillator with a guide magnetic field

    International Nuclear Information System (INIS)

    The operation of a virtual cathode oscillator (vircator) with strong axial magnetic field has been experimentally studied. Depending on the cathode--anode gap and cathode diameter, the operating voltage varies from 200 kV up to 480 kV with 2--7 kA diode current. Microwave emission is produced by the oscillating virtual cathode. The central microwave frequency follows the beam plasma frequency. It varies by 11.5 GHz up to 22 GHz, depending on the current density. The oscillation frequency does not depend on the guide magnetic field magnitude. A maximal output power of 15±5 MW in asymmetric transverse magnetic (TM) modes is achieved by the axially extracted vircator. Variation of the magnetic field intensity in a range of 0--40 kG has an insignificant effect upon the emitted microwave power. An electron beam power to microwave power conversion efficiency of approximately 1% is obtained

  20. Generation of Helical and Axial Magnetic Fields by the Relativistic Laser Pulses in Under-dense Plasma: Three-Dimensional Particle-in-Cell Simulation

    Science.gov (United States)

    Zheng, Chun-Yang; Zhu, Shao-Ping; He, Xian-Tu

    2002-07-01

    The quasi-static magnetic fields created in the interaction of relativistic laser pulses with under-dense plasmas have been investigated by three-dimensional particle-in-cell simulation. The relativistic ponderomotive force can drive an intense electron current in the laser propagation direction, which is responsible for the generation of a helical magnetic field. The axial magnetic field results from a difference beat of wave-wave, which drives a solenoidal current. In particular, the physical significance of the kinetic model for the generation of the axial magnetic field is discussed.

  1. An Anisotropic Model for Magnetostriction and Magnetization Computing for Noise Generation in Electric Devices

    OpenAIRE

    Serigne Saliou Mbengue; Nicolas Buiron; Vincent Lanfranchi

    2016-01-01

    During the manufacturing process and use of ferromagnetic sheets, operations such as rolling, cutting, and tightening induce anisotropy that changes the material’s behavior. Consequently for more accuracy in magnetization and magnetostriction calculations in electric devices such as transformers, anisotropic effects should be considered. In the following sections, we give an overview of a macroscopic model which takes into account the magnetic and magnetoelastic anisotropy of the material for...

  2. Use of superconducting shields for generating ultra-low magnetic field regions and several related experiments

    International Nuclear Information System (INIS)

    Part I of this thesis describes a technique for producing ultra-low field regions. Lead foil (0.0025'' thick and 99.9 percent pure) was used to construct cylindrical superconducting magnetic shields with bottom end caps (4'' dia. x 33'' long and 8'' dia. x 56'' long). Several shields with absolute fields below 10-8 gauss over 20'' along their axes were fabricated. The shields are pleated, folded flat and then cooled through their transition temperature (70K) by ''heat flushing,'' i.e., moving the transition temperature from bottom to top in a slow and controlled manner. Cooling a shield inside of an outer previously heat flushed one produced our lowest fields when repeated 2 to 4 times. The magnetic fields are measured using a Josephson double point contact magnetometer with a differential sensitivity of 10-9 gauss coupled to a flip coil for absolute calibration. Part II describes the investigation of residual trapped flux in small superconducting shields and of remanent magnetization in materials used in ultra-low field regions. The apparatus used for these measurements was placed inside an ultra-low field shield. Using this same apparatus the magnetic charge of a series of samples with a single-pass technique was also measured. Schwinger has suggested that the theoretical quarks of Gell-Mann's model may be magnetically charged. An experiment designed to measure the fractional electric charge of the proposed quarks have had some interesting results (further definitive experiments are now in progress). The magnetic charge of eleven samples was measured and found to be consistent with zero. The sensitivity was 1/50 g0 (g0 = h-bar c/2e, the smallest magnetic charge allowed by the Dirac theory--although other theories predict larger values for the elementary magnetic charge). The results were consistent with those from similar multipass experiments conducted by Alvarez et al

  3. Conservation of circulation in magnetohydrodynamics

    Science.gov (United States)

    Bekenstein; Oron

    2000-10-01

    We demonstrate at both the Newtonian and (general) relativistic levels the existence of a generalization of Kelvin's circulation theorem (for pure fluids) that is applicable to perfect magnetohydrodynamics. The argument is based on the least action principle for magnetohydrodynamic flow. Examples of the new conservation law are furnished. The new theorem should be helpful in identifying new kinds of vortex phenomena distinct from magnetic ropes or fluid vortices. PMID:11089118

  4. Numerical study of magnetic field on mixed convection and entropy generation of nanofluid in a trapezoidal enclosure

    Science.gov (United States)

    Aghaei, Alireza; Khorasanizadeh, Hossein; Sheikhzadeh, Ghanbarali; Abbaszadeh, Mahmoud

    2016-04-01

    The flow under influence of magnetic field is experienced in cooling electronic devices and voltage transformers, nuclear reactors, biochemistry and in physical phenomenon like geology. In this study, the effects of magnetic field on the flow field, heat transfer and entropy generation of Cu-water nanofluid mixed convection in a trapezoidal enclosure have been investigated. The top lid is cold and moving toward right or left, the bottom wall is hot and the side walls are insulated and their angle from the horizon are 15°, 30°, 45° and 60°. Simulations have been carried out for constant Grashof number of 104, Reynolds numbers of 30, 100, 300 and 1000, Hartmann numbers of 25, 50, 75 and 100 and nanoparticles volume fractions of zero up to 0.04. The finite volume method and SIMPLER algorithm have been utilized to solve the governing equations numerically. The results showed that with imposing the magnetic field and enhancing it, the nanofluid convection and the strength of flow decrease and the flow tends toward natural convection and finally toward pure conduction. For this reason, for all of the considered Reynolds numbers and volume fractions, by increasing the Hartmann number the average Nusselt number decreases. Furthermore, for any case with constant Reynolds and Hartmann numbers by increasing the volume fraction of nanoparticles the maximum stream function decreases. For all of the studied cases, entropy generation due to friction is negligible and the total entropy generation is mainly due to irreversibility associated with heat transfer and variation of the total entropy generation with Hartmann number is similar to that of the average Nusselt number. With change in lid movement direction at Reynolds number of 30 the average Nusselt number and total entropy generation are changed, but at Reynolds number of 1000 it has a negligible effect.

  5. Superconducting FCL using a combined inducted magnetic field trigger and shunt coil

    Science.gov (United States)

    Tekletsadik, Kasegn D.

    2007-10-16

    A single trigger/shunt coil is utilized for combined induced magnetic field triggering and shunt impedance. The single coil connected in parallel with the high temperature superconducting element, is designed to generate a circulating current in the parallel circuit during normal operation to aid triggering the high temperature superconducting element to quench in the event of a fault. The circulating current is generated by an induced voltage in the coil, when the system current flows through the high temperature superconducting element.

  6. Development of magnetic flux leakage technique for examination of steam generator tubes of prototype fast breeder reactor

    International Nuclear Information System (INIS)

    Highlights: • For non-destructive detection of small localized defects in SG tubes of PFBR, tandem GMR array sensors based MFL technique developed. • 3D-finite element modeling performed for optimization of magnetizing current and spacing between the magnetizing coils. • The optimized magnetizing structure with ferrite core and guides detected 0.54 mm deep OD circumferential notch, 0.56 mm deep flat bottom hole, and 1.08 mm diameter hole in the tube with a SNR better than 6 dB. • Images of notches have been obtained using the tandem GMR array sensor. • The use of MFL and remote field eddy current techniques is expected to ensure comprehensive inspection of SG tubes of PFBR. - Abstract: For non-destructive examination of small diameter (outer diameter, OD 17.2 mm) and thick walled (wall thickness, 2.3 mm) ferromagnetic Modified 9Cr–1Mo steel steam generator (SG) tubes of Prototype Fast Breeder Reactor (PFBR), this paper proposes magnetic flux leakage (MFL) technique. Three dimensional finite element (3D-FE) modeling has been performed to optimize the magnetizing unit and inter-coil spacing of bobbin coils used for axial magnetization of the tube. The performance of the technique has been evaluated experimentally by measuring the axial (Ba) component of the leakage fields from localized machined defects in SG tubes. The MFL technique has shown capability to detect and image tube outside defects with a signal-to-noise ratio (SNR) better than 6 dB. Study reveals that Inconel support plates surrounding the SG tubes do not influence the MFL signals. As the MFL technique can detect localized defects in the presence of support plates as well as sodium and the remote field eddy current technique is sensitive to distributed wall thinning, their combined use will ensure comprehensive inspection of the SG tubes

  7. Dynamical Feedback of Self-generated Magnetic Fields in Cosmic Rays Modified Shocks

    Energy Technology Data Exchange (ETDEWEB)

    Caprioli, D.; /Pisa, Scuola Normale Superiore; Blasi, P.; /Arcetri Observ. /Fermilab; Amato, E.; /Arcetri Observ.; Vietri, M.; /Pisa, Scuola Normale Superiore

    2008-07-01

    We present a semi-analytical kinetic calculation of the process of non-linear diffusive shock acceleration (NLDSA) which includes magnetic field amplification due to cosmic ray induced streaming instability, the dynamical reaction of the amplified magnetic field and the possible effects of turbulent heating. This kinetic calculation allows us to show that the net effect of the amplified magnetic field is to enhance the maximum momentum of accelerated particles while reducing the concavity of the spectra, with respect to the standard predictions of NLDSA. This is mainly due to the dynamical reaction of the amplified field on the shock, which smoothens the shock precursor. The total compression factors which are obtained for parameters typical of supernova remnants are R{sub tot} {approx} 7-10, in good agreement with the values inferred from observations. The strength of the magnetic field produced through excitation of streaming instability is found in good agreement with the values inferred for several remnants if the thickness of the X-ray rims are interpreted as due to severe synchrotron losses of high energy electrons. We also discuss the relative role of turbulent heating and magnetic dynamical reaction in smoothening the shock precursor.

  8. A magnetic reconnection mechanism for the generation of anomalous cosmic rays

    Science.gov (United States)

    Drake, James; Opher, Merav; Swisdak, Marc; Chamoun, Jacob

    The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyagers 1 and 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collisionless magnetic reconnection. Particle-in-cell simulations reveal that the current layers break up into a turbulent bath of magnetic islands that merge to release a large fraction of the energy in the sectored magnetic field. Most of the magnetic energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The dominant acceleration mechanism is through reflection in contracting islands, a first-order Fermi mechanism. Particle energy gain is regulated by the approach to the marginal firehose condition. The ACR differ-ential energy spectrum for all of the ion species takes the form of a power law with a spectral index slightly above 1.5, which is consistent with observations.

  9. 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...

  10. Diode with magnetic insulation and Br field as a generator of power microsecond ion beam

    International Nuclear Information System (INIS)

    Results of investigations into the generation of microsecond duration high-power ion beam in a plane magnetoisolated diode with an external isolating field with radial distribution are presented. The investigations are conducted using a microsecond generator operating in the regime of generating positive high-voltage ≤600 kV amplitude pulses. Ring-type cross section ion beam consisting mainly of H+ and C+ ions is studied. The energy range occupied by the major part of the ions generated makes up 300-500 keV. The complete energy store of the beam extracted from the diode makes up 10 kJ, the generation efficiency is 60%

  11. Effect of low-frequency pulsed magnetic field on heterotrophic bacteria in circulation cooling water at power plants%低频脉冲磁场对电厂循环冷却水异养菌的影响

    Institute of Scientific and Technical Information of China (English)

    薛金英; 刘智安; 武红梅; 乔波波; 周斐博

    2012-01-01

    The bactericidal experiments of low-frequency pulsed magnetic field have been carried out, aiming at two aspects: the change of variable frequency pulse magnetic field direction, and the two directions of fixed frequency and sweep frequency range. The experimental results show that the change of microbiological physiological function took place under the magnetic field effect. The variable-frequency pulsed magnetic field not only can inhibit the growth of heterotrophic bacteria in circulating cooling water, but also can stimulate the reproduction of heterotrophic bacteria. When the direction of magnetic field is parallel and perpendicular with the water flow direction, the bactericidal rate reaches more than 70%. When the direction of magnetic field is parallel with the water flow direction in the range of 11-17 kHz sweep frequency, the bactericidal rate can reach 82.64%. Therefore, the effective sweep frequency range should be determined,when low frequency pulsed magnetic field is made use of. Thus,better bactericidal effect can be obtained.%从变频脉冲磁场方向的变化以及固定频率与扫频范围两个方向进行了低频脉冲磁场的杀菌实验.实验表明微生物生理功能在磁场作用下发生改变,变频脉冲电磁场既能抑制循环水中异养菌的生长,也能刺激异养菌的繁衍;当磁场方向与水流方向平行和垂直时能达到70%以上的杀菌率,其中磁场方向与水流方向平行时在11~17 kHz频率范围内的杀菌率达到82.64%.因此利用低频脉冲磁场进行杀菌时应确定有效的扫频范围,才能达到较好的杀菌效果.

  12. Generation of zonal flow and magnetic field by finite-amplitude waves in the ionospheric E-layer

    Science.gov (United States)

    Kahlon, Laila; Kaladze, Tamaz

    2016-07-01

    We review the generation of zonal flow and magnetic field by coupled electromagnetic (EM) ULF waves in the Earth's ionospheric E layer. It is shown that under the typical ionospheric E-layer conditions different planetary low-frequency waves can couple with each other. Propagation of coupled internal-gravity-Alfvén (CIGA), coupled Rossby-Khantadze (CRK) and coupled Rossby-Alfvén-Khantadze (CRAK) waves is revealed and studied. A set of appropriate equations describing the nonlinear interaction of such waves with sheared zonal flow is derived. The conclusion on the instability of short wavelength turbulence of such coupled waves with respect to the excitation of low-frequency and large-scale perturbation of the sheared zonal flow and sheared magnetic field is deduced. The nonlinear mechanism of the instability is based on the parametric triple interaction of finite amplitude coupled waves leading to the inverse energy cascade toward the longer wavelength. The possibility of generation of the intense mean magnetic field is shown. Obtained growth rates are discussed for each case of the considered coupled waves.

  13. An Anisotropic Model for Magnetostriction and Magnetization Computing for Noise Generation in Electric Devices.

    Science.gov (United States)

    Mbengue, Serigne Saliou; Buiron, Nicolas; Lanfranchi, Vincent

    2016-01-01

    During the manufacturing process and use of ferromagnetic sheets, operations such as rolling, cutting, and tightening induce anisotropy that changes the material's behavior. Consequently for more accuracy in magnetization and magnetostriction calculations in electric devices such as transformers, anisotropic effects should be considered. In the following sections, we give an overview of a macroscopic model which takes into account the magnetic and magnetoelastic anisotropy of the material for both magnetization and magnetostriction computing. Firstly, a comparison between the model results and measurements from a Single Sheet Tester (SST) and values will be shown. Secondly, the model is integrated in a finite elements code to predict magnetostrictive deformation of an in-house test bench which is a stack of 40 sheets glued together by the Vacuum-Pressure Impregnation (VPI) method. Measurements on the test bench and Finite Elements results are presented. PMID:27092513

  14. Reorienting MHD Colliding Flows: A Shock Physics Mechanism for Generating Filaments Normal to Magnetic Fields

    CERN Document Server

    Fogerty, Erica L; Frank, Adam; Heitsch, Fabian; Pon, Andy

    2016-01-01

    We present numerical simulations of reorienting oblique shocks that form in the collision layer between magnetized colliding flows. Reorientation aligns parsec-scale post-shock filaments normal to the background magnetic field. We find that reorientation begins with pressure gradients between the collision region and the ambient medium. This drives a lateral expansion of post-shock gas, which reorients the growing filament from the outside-in (i.e. from the flow-ambient boundary, toward the colliding flows axis). The final structures of our simulations resemble polarization observations of filaments in Taurus and Serpens South, as well as the integral-shaped filament in Orion A. Given the ubiquity of colliding flows in the interstellar medium, shock reorientation may be relevant to the formation of filaments normal to magnetic fields.

  15. Vortices at the magnetic equator generated by hybrid Alfvén resonant waves

    International Nuclear Information System (INIS)

    We performed three-dimensional magnetohydrodynamic simulations of shear Alfvén waves in a full field line system with magnetosphere-ionosphere coupling and plasma non-uniformities. Feedback instability of the Alfvén resonant modes showed various nonlinear features under the field line cavities: (i) a secondary flow shear instability occurs at the magnetic equator, (ii) trapping of the ionospheric Alfvén resonant modes facilitates deformation of field-aligned current structures, and (iii) hybrid Alfvén resonant modes grow to cause vortices and magnetic oscillations around the magnetic equator. Essential features in the initial brightening of auroral arc at substorm onsets could be explained by the dynamics of Alfvén resonant modes, which are the nature of the field line system responding to a background rapid change

  16. An Anisotropic Model for Magnetostriction and Magnetization Computing for Noise Generation in Electric Devices

    Directory of Open Access Journals (Sweden)

    Serigne Saliou Mbengue

    2016-04-01

    Full Text Available During the manufacturing process and use of ferromagnetic sheets, operations such as rolling, cutting, and tightening induce anisotropy that changes the material’s behavior. Consequently for more accuracy in magnetization and magnetostriction calculations in electric devices such as transformers, anisotropic effects should be considered. In the following sections, we give an overview of a macroscopic model which takes into account the magnetic and magnetoelastic anisotropy of the material for both magnetization and magnetostriction computing. Firstly, a comparison between the model results and measurements from a Single Sheet Tester (SST and values will be shown. Secondly, the model is integrated in a finite elements code to predict magnetostrictive deformation of an in-house test bench which is a stack of 40 sheets glued together by the Vacuum-Pressure Impregnation (VPI method. Measurements on the test bench and Finite Elements results are presented.

  17. The Effect of Lower Mantle Metallization on Magnetic Field Generation in Rocky Exoplanets

    CERN Document Server

    Vilim, Ryan; Elkins-Tanton, Linda

    2013-01-01

    Recent theoretical and experimental evidence indicates that many of the materials that are thought to exist in the mantles of terrestrial exoplanets will metallize and become good conductors of electricity at mantle pressures. This allows for strong electromagnetic coupling of the core and the mantle in these planets. We use a numerical dynamo model to study the effect of a metallized lower mantle on the dynamos of terrestrial exoplanets using several inner core sizes and mantle conductivities. We find that the addition of an electrically conducting mantle results in stronger core-mantle boundary fields because of the increase in magnetic field stretching. We also find that a metallized mantle destabilizes the dynamo resulting in less dipolar, less axisymmetric poloidal magnetic fields at the core-mantle boundary. The conducting mantle efficiently screens these fields to produce weaker surface fields. We conclude that a conducting mantle will make the detection of extrasolar terrestrial magnetic fields more d...

  18. On the use of intense ion beams for generating magnetized target fusion plasma

    International Nuclear Information System (INIS)

    Magnetized Target Fusion (MTF) is a concept for creating a burning D-T plasma in a potentially inexpensive system. In essence, the concept involves ion heating on time scales short compared to ion transport times plus strong inhibition of thermal electron transport with a transverse magnetic field. The magnetic field is not intended to confine the ionic component. MTF is an intrinsically pulsed concept. A straightforward analysis of MTF indicates that D-T burning conditions can be achieved in compact plasma volumes with modest initial temperatures, through the use of pulsed power technology. In terms of size, density, temperature, and time scales, MTF occupies a position in phase space that is intermediate between steady MFE schemes and ICF. In terms of cost, it is one to two orders of magnitude less expensive than these. In this paper, the authors consider a possible method for creating the initial conditions adequate for the MTF concept through the use intense ion beam injection

  19. An Anisotropic Model for Magnetostriction and Magnetization Computing for Noise Generation in Electric Devices

    Science.gov (United States)

    Mbengue, Serigne Saliou; Buiron, Nicolas; Lanfranchi, Vincent

    2016-01-01

    During the manufacturing process and use of ferromagnetic sheets, operations such as rolling, cutting, and tightening induce anisotropy that changes the material’s behavior. Consequently for more accuracy in magnetization and magnetostriction calculations in electric devices such as transformers, anisotropic effects should be considered. In the following sections, we give an overview of a macroscopic model which takes into account the magnetic and magnetoelastic anisotropy of the material for both magnetization and magnetostriction computing. Firstly, a comparison between the model results and measurements from a Single Sheet Tester (SST) and values will be shown. Secondly, the model is integrated in a finite elements code to predict magnetostrictive deformation of an in-house test bench which is a stack of 40 sheets glued together by the Vacuum-Pressure Impregnation (VPI) method. Measurements on the test bench and Finite Elements results are presented. PMID:27092513

  20. Spherical, rolling magnet generators for passive energy harvesting from human motion

    Science.gov (United States)

    Bowers, Benjamin J.; Arnold, David P.

    2009-09-01

    In this work, non-resonant, vibrational energy harvester architectures intended for human-motion energy scavenging are researched. The basic design employs a spherical, unidirectionally magnetized permanent magnet (NdFeB) ball that is allowed to move arbitrarily in a spherical cavity wrapped with copper coil windings. As the ball rotates and translates within the cage, the time-varying magnetic flux induces a voltage in the coil according to Faraday's Law. Devices ranging from 1.5 cm3 to 4 cm3 in size were tested under human activity scenarios—held in the user's hand or placed in the user's pocket while walking (4 km h-1) and running (14.5 km h-1). These harvesters have demonstrated rms voltages ranging from ~80 mV to 700 mV and time-averaged power densities up to 0.5 mW cm-3.

  1. Vortices at the magnetic equator generated by hybrid Alfvén resonant waves

    Energy Technology Data Exchange (ETDEWEB)

    Hiraki, Yasutaka, E-mail: hiraki.yasutaka@nipr.ac.jp [National Institute of Polar Research, Midori-cho 10-3, Tachikawa, Tokyo 190-8518 (Japan)

    2015-01-15

    We performed three-dimensional magnetohydrodynamic simulations of shear Alfvén waves in a full field line system with magnetosphere-ionosphere coupling and plasma non-uniformities. Feedback instability of the Alfvén resonant modes showed various nonlinear features under the field line cavities: (i) a secondary flow shear instability occurs at the magnetic equator, (ii) trapping of the ionospheric Alfvén resonant modes facilitates deformation of field-aligned current structures, and (iii) hybrid Alfvén resonant modes grow to cause vortices and magnetic oscillations around the magnetic equator. Essential features in the initial brightening of auroral arc at substorm onsets could be explained by the dynamics of Alfvén resonant modes, which are the nature of the field line system responding to a background rapid change.

  2. Generating Long Scale-Length Plasma Jets Embedded in a Uniform, Multi-Tesla Magnetic-Field

    Science.gov (United States)

    Manuel, Mario; Kuranz, Carolyn; Rasmus, Alex; Klein, Sallee; Fein, Jeff; Belancourt, Patrick; Drake, R. P.; Pollock, Brad; Hazi, Andrew; Park, Jaebum; Williams, Jackson; Chen, Hui

    2013-10-01

    Collimated plasma jets emerge in many classes of astrophysical objects and are of great interest to explore in the laboratory. In many cases, these astrophysical jets exist within a background magnetic field where the magnetic pressure approaches the plasma pressure. Recent experiments performed at the Jupiter Laser Facility utilized a custom-designed solenoid to generate the multi-tesla fields necessary to achieve proper magnetization of the plasma. Time-gated interferometry, Schlieren imaging, and proton radiography were used to characterize jet evolution and collimation under varying degrees of magnetization. Experimental results will be presented and discussed. This work is funded by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-NA0001840, by the National Laser User Facility Program, grant number DE-NA0000850, by the Predictive Sciences Academic Alliances Program in NNSA-ASC, grant number DEFC52-08NA28616, and by NASA through Einstein Postdoctoral Fellowship grant number PF3-140111 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060.

  3. Spontaneous generation of a temperature anisotropy in a strongly coupled magnetized plasma

    CERN Document Server

    Ott, T; Hartmann, P; Donkó, Z

    2016-01-01

    A magnetic field was recently shown to enhance field-parallel heat conduction in a strongly correlated plasma whereas cross-field conduction is reduced. Here we show that in such plasmas, the magnetic field has the additional effect of inhibiting the isotropization process between field-parallel and cross-field temperature components thus leading to the emergence of strong and long-lived temperature anisotropies when the plasma is locally perturbed. An extended heat equation is shown to describe this process accurately.

  4. Periodic magnetic structures generated by spin–polarized currents in nanostripes

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, Oleksii M., E-mail: alexey@volkov.ca; Sheka, Denis D. [Taras Shevchenko National University of Kiev, 01601 Kiev (Ukraine); Kravchuk, Volodymyr P.; Gaididei, Yuri [Bogolyubov Institute for Theoretical Physics, 03680 Kiev (Ukraine); Mertens, Franz G. [Physics Institute, University of Bayreuth, 95440 Bayreuth (Germany)

    2013-11-25

    The influence of a transverse spin–polarized current on long ferromagnetic nanostripes is studied numerically. The magnetization behavior is analyzed for all range of the applied currents, up to the saturation. It is shown that the saturation current is a nonmonotonic function of the stripe width. A number of stable periodic magnetization structures are observed below the saturation. Type of the periodical structure depends on the stripe width. Besides the one–dimensional domain structure, typical for narrow wires, and the two–dimensional vortex–antivortex lattice, typical for wide films, a number of intermediate structures are observed, e.g., cross–tie and diamond state.

  5. A method for mechanical generation of radio frequency fields in nuclear magnetic resonance force microscopy

    CERN Document Server

    Wagenaar, J J T; Donkersloot, R J; Marsman, F; de Wit, M; Bossoni, L; Oosterkamp, T H

    2016-01-01

    We present an innovative method for magnetic resonance force microscopy (MRFM) with ultra-low dissipation, by using the higher modes of the mechanical detector as radio frequency (rf) source. This method allows MRFM on samples without the need to be close to an rf source. Furthermore, since rf sources require currents that give dissipation, our method enables nuclear magnetic resonance experiments at ultra-low temperatures. Removing the need for an on-chip rf source is an important step towards a MRFM which can be widely used in condensed matter physics.

  6. Chaotic signal generation in low-voltage vircator with electron source shielded from external magnetic field

    Science.gov (United States)

    Kurkin, S. A.; Hramov, A. E.; Koronovskii, A. A.

    2011-02-01

    The effect of shielding an electron source from a homogeneous external magnetic field of the drift chamber on the nonlinear dynamics of the electron beam with a virtual cathode (VC) and on the characteristics of output microwave radiation in a low-voltage vircator have been numerically simulated within the framework of a two-dimensional model. It is established that the increased degree of shielding of the electron source from the external magnetic field leads to the complication of the VC dynamics in the system and the corresponding chaotization of the output microwave radiation. Physical processes that account for the observed effect of shielding are analyzed.

  7. Topologies of velocity-field stagnation points generated by a single pair of magnets in free-surface electromagnetic experiments.

    Science.gov (United States)

    de la Cruz, J M García; Vassilicos, J C; Rossi, L

    2014-10-01

    The velocity fields generated by a static pair of magnets in free-surface electromagnetically forced flows are analyzed for different magnet attitudes, ionic currents, and brine depths. A wide range of laminar velocity fields is obtained despite the forcing simplicity. The velocity fields are classified according to their temporal mean flow topology, which strongly depends on the forcing geometry but barely on its strength, even through the bifurcation to unsteady regimes. The mean flow topology possesses a major influence on the critical Reynolds number Rec under which the steady velocity fields remain stable. The qualitative comparison of the dependence of Rec on the topology is in agreement with previous works. The unsteady configurations evidence the advection of smaller flow structures by the largest scales, commonly known as "sweeping." PMID:25375588

  8. SolCalc: A Suite for the Calculation and the Display of Magnetic Fields Generated by Solenoid Systems

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, M. L. [Fermilab

    2014-07-01

    SolCalc is a software suite that computes and displays magnetic fields generated by a three dimensional (3D) solenoid system. Examples of such systems are the Mu2e magnet system and Helical Solenoids for muon cooling systems. SolCalc was originally coded in Matlab, and later upgraded to a compiled version (called MEX) to improve solving speed. Matlab was chosen because its graphical capabilities represent an attractive feature over other computer languages. Solenoid geometries can be created using any text editor or spread sheets and can be displayed dynamically in 3D. Fields are computed from any given list of coordinates. The field distribution on the surfaces of the coils can be displayed as well. SolCalc was benchmarked against a well-known commercial software for speed and accuracy and the results compared favorably.

  9. Generation and Evolution of High-Mach Number, Laser-Driven Magnetized Collisionless Shocks in the Laboratory

    CERN Document Server

    Schaeffer, Derek; Haberberger, Dan; Fiksel, Gennady; Bhattacharjee, Amitava; Barnak, Daniel; Hu, Suxing; Germaschewski, Kai

    2016-01-01

    Shocks act to convert incoming supersonic flows to heat, and in collisionless plasmas the shock layer forms on kinetic plasma scales through collective electromagnetic effects. These collisionless shocks have been observed in many space and astrophysical systems [Smith 1975, Smith 1980, Burlaga 2008, Sulaiman 2015], and are believed to accelerate particles, including cosmic rays, to extremely high energies [Kazanas 1986, Loeb 2000, Bamba 2003, Masters 2013, Ackermann 2013]. Of particular importance are the class of high-Mach number, supercritical shocks [Balogh 2013] ($M_A\\gtrsim4$), which must reflect significant numbers of particles back into the upstream to accommodate entropy production, and in doing so seed proposed particle acceleration mechanisms [Blandford 1978, McClements 2001, Caprioli 2014, Matsumoto 2015]. Here we present the first laboratory generation of high-Mach number magnetized collisionless shocks created through the interaction of an expanding laser-driven plasma with a magnetized ambient ...

  10. The Value of Magnetic Resonance Imaging and Transcranial Doppler to Evaluate Posterior Circulation Ischemia%磁共振成像和经颅多普勒评价后循环缺血的价值

    Institute of Scientific and Technical Information of China (English)

    魏九金; 周永立

    2012-01-01

    Objective:To study the value of magnetic resonance imaging(MRI) and transcranial doppler(TCD) to evaluate posterior circulation ischemia.Methods:The retrospective analysis of clinical data of 56 cases with Posterior circulation ischemia.Results:It was found a total of 46 infarcted focuses in brain stem,Cerebellum,occipital lobe by head MRI examined.The abnormal vascular of vertebrobasilar artery by magnetic resonance angiography examined were 39 cases(69.6%) with asymmetric and various sized of bilateral vertebral arteries,10 cases(17.9%) with different degree stenosis of one side vertebral artery in initial segment,1 case with stenosis of subclavian artery.The abnormal vascular of TCD were 40 cases(71.4%) with the blood flow velocity,36 cases(64.3%)with abnormal spectrum.Conclusion:MRI and TCD could provide objective basis for clinical diagnosis of posterior circulation ischemia.MRI better than TCD.%目的:探讨磁共振成像(MRI)和经颅多普勒(TCD)评价后循环缺血的价值。方法:对56例诊断为后循环缺血患者的临床资料进行回顾性分析。结果:头颅MRI发现脑干、小脑、枕叶梗死灶共46个;椎基底动脉磁共振血管造影显示达39例(69.6%)双侧椎动脉不对称、粗细不均,10例(17.9%)一侧椎动脉起始段不同程度狭窄,1例锁骨下动脉狭窄。TCD显示血流速度异常者40例(71.4%),频谱异常36例(64.3%)。结论:MRI和TCD能给后循环缺血的诊断提供客观依据;MRI优于TCD。

  11. The effect of magnetic field on mean flow generation by rotating two-dimensional convection

    CERN Document Server

    Currie, Laura K

    2016-01-01

    Motivated by the significant interaction of convection, rotation and magnetic field in many astrophysical objects, we investigate the interplay between large-scale flows driven by rotating convection and an imposed magnetic field. We utilise a simple model in two dimensions comprised of a plane layer that is rotating about an axis inclined to gravity. It is known that this setup can result in strong mean flows; we numerically examine the effect of an imposed horizontal magnetic field on such flows. We show that increasing the field strength in general suppresses the time-dependent mean flows, but in some cases it organises them leading to stronger time-averaged flows. Further, we discuss the effect of the field on the correlations responsible for driving the flows and the competition between Reynolds and Maxwell stresses. A change in behaviour is observed when the (fluid and magnetic) Prandtl numbers are decreased. In the smaller Prandtl number regime, it is shown that significant mean flows can persist even ...

  12. Some peculiarities in the magnetic behavior of aerosol generated NiO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, Yu.G., E-mail: yurimor@dio.ru [Institute of Structural Macrokinetics and Materials Science, Chernogolovka, Moscow Region 142432 (Russian Federation); Ortega, D., E-mail: d.ponce@ucl.ac.uk [Department of Physics and Astronomy, University College London, WC1E 6BT London (United Kingdom); Davy-Faraday Research Laboratory, The Royal Institution of Great Britain, W1S 4BS London (United Kingdom); Belousova, O.V. [Institute of Structural Macrokinetics and Materials Science, Chernogolovka, Moscow Region 142432 (Russian Federation); Parkin, I.P., E-mail: i.p.parkin@ucl.ac.uk [Department of Chemistry, Materials Chemistry Centre, University College London, 20 Gordon Street, WC1H 0AJ London (United Kingdom); Kuznetsov, M.V., E-mail: maxim1968@mail.ru [Department of Chemistry, Materials Chemistry Centre, University College London, 20 Gordon Street, WC1H 0AJ London (United Kingdom)

    2013-09-25

    Highlights: •Structural and magnetic characterization of cubic-shaped aerosol NiO nanoparticles. •Procedure for subtracting an underlying diamagnetic contribution. •Correlation between specific surface area of NPs and their diamagnetic susceptibility. •Critical transition temperature associated to a hypothetical superconductive state. -- Abstract: Nickel oxide nanoparticles (NPs) 6–24 nm size have been prepared by a levitation-jet method based on metal vapor condensation in a mixture of gaseous streams of helium and air (or oxygen). Particles were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) N{sub 2} adsorption and SQUID magnetometry. It is revealed that at room-temperature (RT) the nanoparticles show a small magnetic moment and the magnetic field dependence of their susceptibility a minimum lying below the high-field values. After the appropriate subtraction of both ferromagnetic and paramagnetic components from the initial magnetization curves, the appearance of a diamagnetic contribution is observed. The possible link between the latter contribution and the occurrence of some features related to RT superconductivity in NiO NPs is discussed.

  13. A new mechanism for the generation of primordial seeds for the cosmic magnetic fields

    CERN Document Server

    Gasperini, M

    2001-01-01

    We discuss the inflationary production of magnetic seeds for the galactic dynamo through the photon-graviphoton mixing typical of extended models of local supersymmetry. An analisys of the allowed region in parameter space shows that such a mechanism is compatible with existing phenomenological bounds on the vector mass and on the mixing parameter.

  14. Transcranial magnetic stimulation-induced 'visual echoes' are generated in early visual cortex

    NARCIS (Netherlands)

    Jolij, Jacob; Lamme, Victor A. F.

    2010-01-01

    Transcranial magnetic stimulation (TMS) of the early visual areas can trigger perception of a flash of light, a so-called phosphene. Here we show that a very brief presentation of a stimulus can modulate features of a subsequent TMS-induced phosphene, to a level that participants mistake phosphenes

  15. Electricity generation from enhanced geothermal systems by oilfield produced water circulating through reservoir stimulated by staged fracturing technology for horizontal wells: A case study in Xujiaweizi area in Daqing Oilfield, China

    International Nuclear Information System (INIS)

    In this paper, the feasibility of generating electricity from EGS (enhanced geothermal systems) by oilfield produced water circulating through reservoir stimulated by staged fracturing technology for horizontal wells is investigated based on the geological data of Xujiaweizi area, located in the Daqing Oilfield, northeast China. HDR (hot dry rock) resource potential assessment is carried out by using volumetric method. Reservoir stimulation is numerically simulated based on the geological data of well YS-1 and field fracturing experience in this region. Geometric dimensions and flow conductivity of the resulting fracture are imported into the hydro-thermal model to calculate the electricity generation potential of the proposed EGS power plant. An EGS design scheme is proposed based on the simulation results. The system is also evaluated from the economic and environmental aspects. The results indicate that HDR resource in Xujiaweizi area is of great potential for development. Through the staged fracturing technology for horizontal wells, electricity generation power of the proposed EGS project can roughly meet the commercial standard. For 20 years of continuous production, power generation from the proposed EGS power plant is economic feasible. Meanwhile, significant reductions in greenhouse gas emissions can be achieved. - Highlights: • Staged fracturing technology for horizontal well is used in HDR (hot dry rock) development. • Fracturing simulations and heat production simulations are combined. • A 3 MW power plant is designed in Xujiaweizi based on the simulation results

  16. Magnetic field generation in the presence of double diffusive convection in partly stable core of mercury

    International Nuclear Information System (INIS)

    Complete text of publication follows. Some recent dynamo models for Mercury assume that the top part of the fluid core is stably stratified because of a sub-adiabatic temperature gradient at the core-mantle boundary. In these models, the dynamo is maintained by the vigorous convection in the deep parts of the core. These models have been successful in producing the observed weak large-scale magnetic field at the surface of the planet. However, they have been based on the concept of co-density, which combines the buoyancy effects of temperature and composition into a single variable and assumes equal diffusivities for the both components. To overcome this limitation, we have solved two separate transport equations to model the evolution of temperature and light constituents in the outer core. To analyse the potential effects of double diffusive convection (DDC) on Mercury's dynamo we have explored a model where the two diffusivities differ by an order of magnitude and the outer core is partly stable. The results, computed for an Ekman number of 3.0 x 10-4 and 2 wght% sulphur concentration, show a significant difference in the nature and amplitude of the magnetic fields between the DDC and co-density models. For the DDC case, we find a strong toroidal magnetic field within the stably stratified layer of the core fluid which is missing in the co-density model. Also, magnetic field at the planetary surface is about two orders of magnitude stronger in the more realistic DDC model compared to the co-density model. A weak surface magnetic field, similar to that observed at Mercury, is produced in DDC models for a very small fraction of light constituents (< 0.2 wght%). These results imply that the core of Mercury may be poor in sulphur and other light constituents.

  17. Inference of Magnetic Field in the Coronal Streamer Invoking Kink Wave Motions generated by Multiple EUV Waves

    Science.gov (United States)

    Srivastava, A. K.; Singh, Talwinder; Ofman, Leon; Dwivedi, Bhola N.

    2016-08-01

    We analyze the observations from Solar TErrestrial RElations Observatory (STEREO) of an oscillating coronal streamer. STEREO-B Extreme Ultraviolet Imaging (EUVI) temporal data on 7 March 2012 shows an evolution of two consecutive EUV waves that interact with footpoint of a coronal streamer clearly evident in the co-spatial and co-temporal STEREO-B/COR-1 observations. The waves are observed in the STEREO-B/EUVI too, and its apparent energy exchange with coronal streamer generates kink oscillations. We apply the methodology of MHD seismology of the observed waves and determine the magnetic field profile of the coronal streamer. In particular, we estimate the phase velocities of the kink wave perturbations by tracking them at different heights. We also estimate electron densities inside and outside the streamer using spherically symmetric inversion of polarized brightness images in STEREO-B/COR-1. We detect two large scale kink wave oscillations that diagnose exponentially decaying radial profiles of magnetic field in streamer up to 3 solar radii. Within the limit of observational and systematic uncertainties, we find that magnetic field of streamer varies slowly at various heights, although its nature always remains exponentially decaying with height. It is seen that during evolution of second kink motion in streamer, it increases in brightness (thus mass density), and also in areal extent slightly, which may be associated with decreased photospheric magnetic flux at footpoint of streamer. As a result, magnetic field profile produced by second kink wave is reduced within streamer compared to the one diagnosed by the first one.

  18. Effect of Magnetic Treatment on Circulating Water%强磁处理对工业循环冷却水的研究

    Institute of Scientific and Technical Information of China (English)

    姜丽丽; 左海滨; 张建良; 杨天钧; 谭赞麟

    2009-01-01

    At present the methods used are chemical treatment methods, which can cause secondary pollution or spend a lot of money, in order to prevent the emergence of cooling water pipe corrosion and scaling issues, the physical method such as magnetic treatment is used to test the effect of different magnetic intensity, the treatment time and the flow rate on the parameters such as PSI, pH and the electrical conductivity. The results show that the optimum magnetic intensity is 34 000 Gs and the lower pH value can be obtained, so that old scale falls off,and the possibility of scale formation is reduced. The cooling water of blast furnace in Shougang is magnetically treated and good results are obtained.%为了防止冷却器水管出现结垢或腐蚀问题,目前所采用的均为化学处理方法,这会造成二次污染或花费大量资金,因此采用物理方法--磁处理方法对循环冷却水测定不同磁场强度下循环水的pH值、电导率、PSI的变化情况.对比未经过磁处理的循环水,试验结果表明防垢效果最佳时的磁场强度为34 000 Gs,可以有效降低pH值,使旧垢脱落,减少循环水结垢的可能性,并用首钢高炉冷却水进行磁处理,取得了满意的效果.

  19. Optimized Permanent Magnet Generator Topologies for Direct-Drive Wind Turbines

    NARCIS (Netherlands)

    Dubois, M.R.J.

    2004-01-01

    The thesis deals with the issue of cost reduction in direct-drive generators for wind turbines. Today, the combination gearbox-medium-speed (1000-2000 rpm) induction generator largely dominates the market of MW-scale wind turbines. This is due to the lower costs of the gearbox option compared to the

  20. 不同槽型对海浪发电用永磁直线同步发电机的影响研究%Influence of Different Cogging Structure on Permanent Magnet Linear Synchronous Generator for Wave Power Generation

    Institute of Scientific and Technical Information of China (English)

    刘立宁; 田敬成; 李丹

    2012-01-01

    针对海浪发电机采用永磁直线同步发电系统会引起电机严重振动进而发生永磁体断裂的问题,基于直线电机与永磁电机理论,分析了两种槽型对海浪发电用永磁直线同步发电机的电磁力的影响,通过仿真计算确定了采用开槽结构进一步优化电机结构,使海浪发电为用永磁直线同步发电机齿槽力最小1.%Wave generator with linear permanent magnet synchronous power system will cause serious vibration and lead to permanent magnet crack. Based on the theory of linear generator and permanent magnet generator, this paper analyzes the influence of two slot-types on electromagnetic force in linear permanent magnet synchronous generator. According to simulation results, the slotted structure of generator is optimized to minimize cogging force of linear permanent magnet synchronous generator for wave power generation.