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Sample records for active magnetic bearings

  1. Active Magnetic BearingsMagnetic Forces

    Kjølhede, Klaus

    2006-01-01

    the work is the characterization of magnetic forces by using two experimental different experimental approaches. Such approaches are investigated and described in details. A special test rig is designed where the 4 poles - AMB is able to generate forces up to 1900 N. The high precision......Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model...... characterization of the magnetic forces are led by using different experimental tests: (I) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor; (II) by measuring the input...

  2. Active Magnetic BearingsMagnetic Forces

    Kjølhede, Klaus

    2006-01-01

    Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model...... the work is the characterization of magnetic forces by using two experimental different experimental approaches. Such approaches are investigated and described in details. A special test rig is designed where the 4 poles - AMB is able to generate forces up to 1900 N. The high precision...... characterization of the magnetic forces are led by using different experimental tests: (I) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor; (II) by measuring the input...

  3. Active magnetic bearing-supported rotor with misaligned cageless backup bearings: A dropdown event simulation model

    Halminen, Oskari; Kärkkäinen, Antti; Sopanen, Jussi; Mikkola, Aki

    2015-01-01

    Active magnetic bearings (AMB) offer considerable benefits compared to regular mechanical bearings. On the other hand, they require backup bearings to avoid damage resulting from a failure in the component itself, or in the power or control system. During a rotor-bearing contact event - when the magnetic field has disappeared and the rotor drops on the backup bearings - the structure of the backup bearings has an impact on the dynamic actions of the rotor. In this paper, the dynamics of an active magnetic bearing-supported rotor during contact with backup bearings is studied with a simulation model. Modeling of the backup bearings is done using a comprehensive cageless ball bearing model. The elasticity of the rotor is described using the finite element method (FEM) and the degrees of freedom (DOF) of the system are reduced using component mode synthesis. Verification of the misaligned cageless backup bearings model is done by comparing the simulation results against the measurement results. The verified model with misaligned cageless backup bearings is found to correspond to the features of a real system.

  4. Active magnetic bearings used as exciters for rolling element bearing outer race defect diagnosis.

    Xu, Yuanping; Di, Long; Zhou, Jin; Jin, Chaowu; Guo, Qintao

    2016-03-01

    The active health monitoring of rotordynamic systems in the presence of bearing outer race defect is considered in this paper. The shaft is assumed to be supported by conventional mechanical bearings and an active magnetic bearing (AMB) is used in the mid of the shaft location as an exciter to apply electromagnetic force to the system. We investigate a nonlinear bearing-pedestal system model with the outer race defect under the electromagnetic force. The nonlinear differential equations are integrated using the fourth-order Runge-Kutta algorithm. The simulation and experimental results show that the characteristic signal of outer race incipient defect is significantly amplified under the electromagnetic force through the AMBs, which is helpful to improve the diagnosis accuracy of rolling element bearing׳s incipient outer race defect. PMID:26803551

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

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

  6. The development of an axial active magnetic bearing / R. Gouws

    Gouws, Rupert

    2004-01-01

    In this dissertation, the author presents the operation and development of active magnetic bearings (AMBs) , with specific focus on axial M s . The project objective is the development of an axial AMB system. The electromagnetic design, inductive sensor design, dSpace controller model design and actuating amplifier design are aspects discussed in this dissertation. The physical model constitutes two electromagnets positioned above and beneath a 2 kg steel disc with an air gap o...

  7. Condition monitoring of active magnetic bearing systems / Rupert Gouws

    Gouws, Rupert

    2007-01-01

    In this thesis, the author contextualises condition monitoring of active magnetic bearing (AMB) systems and proposes the real-time condition monitoring of AMB systems. Three real-time fault detection, diagnosis, correction and identification schemes for vibration forces on the rotor of a rotational AMB system are proposed. Two AMB systems were used to conduct this research. The one was a fully suspended 250 kW water cooling AMB pump from which historical fault data was obtained and the oth...

  8. Fault Diagnosis in a Centrifugal Pump Using Active Magnetic Bearings

    Nordmann Rainer; Aenis Martin

    2004-01-01

    The number of rotors running in active magnetic bearings (AMBs) has increased over the last few years. These systems offer a great variety of advantages compared to conventional systems. The aim of this article is to use the AMBs together with a developed built-in software for identification, fault detection, and diagnosis in a centrifugal pump. A single-stage pump representing the turbomachines is investigated. During full operation of the pump, the AMBs are used as actuators to generate def...

  9. Experimental Contribution to High Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    Kjølhede, Klaus; Santos, Ilmar

    Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model vali...... with respect to the instantaneous measured force obtained from the strain gauges signals)...... magnetic forces is conducted using different experimental tests: (a) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor, (b) by measuring the input current and bearing...

  10. Experimental Contribution to High Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    Kjølhede, Klaus; Santos, Ilmar

    2006-01-01

    Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model vali...... with respect to the instantaneous measured force obtained from the strain gauges signals)...... magnetic forces is conducted using different experimental tests: (a) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor, (b) by measuring the input current and bearing...

  11. THE EXPERIMENTAL TESTING OF AN ACTIVE MAGNETIC BEARING/ROTOR SYSTEM UNDERGOING BASE EXCITATION

    Clements, Joshua Ryan

    2000-01-01

    Active Magnetic Bearings (AMB) are a relatively recent innovation in bearing technology. Unlike conventional bearings, which rely on mechanical forces originating from fluid films or physical contact to support bearing loads, AMB systems utilize magnetic fields to levitate and support a shaft in an air-gap within the bearing stator. This design has many benefits over conventional bearings. The potential capabilities that AMB systems offer are allowing this new technology to be considered f...

  12. R+D works for the further development of high temperature reactors. (1) Captive bearing experiments for active magnetic bearings. (2) Captive bearing test for HTR blowers

    When using active magnetic bearings as blower shaft bearings, blower motors and bearings must be protected against mechanical damage in case of faults (example: total electrical supply failure due to the supply cables breaking). So-called captive bearings are provided, in order to be able to shut the blowers down safely in such faults. These captive bearings are roller bearings which are additionally fitted in the area of the blower shaft bearings, to prevent mechanical contact between the blower rotor and stator. As there was little experience available for the given boundary conditions, such as - speed, - acceleration, - bearing load, - bearing dimensions, - ambient conditions, appropriate development and tests had to be carried out. It was important to determine suitable captive bearings and the necessary ambient conditions, which will make it possible to support the failures of the magnetic bearings to be expected in 40 years' operation of the reactor without damage and to meet the requirements of the captive bearings. (orig./GL)

  13. Developments in the field of active magnetic bearings at EDF

    The studies carried out by EDF concerning the evaluation of the active magnetic bearing technology for their possible application to rotating machinery in electrical plants, and especially the 900 MW ''CP2'' turbogenerators which appear to have very little damping and vibrate noticeably during transients. Using a 4 tons test bench, the good quality of simulation applied to both permanent and transient conditions have been verified. Then, using a 10 tons test bench, the dimensioning concerns of the CP2 application were more precisely evaluated. It has been especially demonstrated that the accessible levels of force and damping were compatible with the application constraints. In a final 30 tons project, some innovative technological components have been used and the benefits from an optimization of the design of the magnetic parameters were determined. Specifications for a full-scale implementation have been therefore defined to enable the manufacturer to make a commercial offer. After a disappointing analysis of the offer, CP2 computations and studies were stopped but subsidiary studies were conducted: estimation of the damage risk under alternative bending of the CP2 rotors during their lifetime, prospective analysis of other possible applications of active magnetic bearings in power plants, development of a new vibratory test method through electromagnetic excitation. 5 figs., 6 refs

  14. Failure Mode and Effect Analysis of Active Magnetic Bearings

    K.P. Lijesh

    2016-03-01

    Full Text Available In the present research work Failure Mode and Effect Analysis (FMEA of an Active Magnetic Bearing (AMB has been presented. Various possible failures modes of AMBs and the corresponding effects of those failures on performance of AMBs have been identified. The identified failure modes of AMBs will facilitate designer to incorporate necessary design features that would prevent the occurrence of the failure. The severity, occurrence and detection of the failures modes are determined based on a rating scale of 1 to 5 to quantify the Risk Priority Number (RPN of the failure modes. The methods to eliminate or reduce the high-risk-failure modes are proposed.

  15. Active magnetic bearings: As applied to centrifugal pumps

    Nelik, Lev; Cooper, Paul; Jones, Graham; Galecki, Dennis; Pinckney, Frank; Kirk, Gordon

    1992-01-01

    Application of magnetic bearings to boiler feed pumps presents various attractive features, such as longer bearing life, lower maintenance costs, and improved operability through control of the rotordynamics. Magnetic bearings were fitted to an eight-stage, 600 hp boiler feed pump, which generates 2600 ft of heat at 680 gpm and 3560 rpm. In addition to the varied and severe operating environment in steady state operation of this pump in a power plant, it is also subjected to transient loads during frequent starts and stops. These loads can now be measured by the in-built instrumentation of the magnetic bearings. Following site installation, a follow-up bearing tune-up was performed, and pump transient response testing was conducted. The bearing response was completely satisfactory, ensuring trouble-free pump operation even in the range of reduced load. The experience gained so far through design and testing proves feasibility of magnetic bearings for boiler feed pumps, which sets the stage for application of even higher energy centrifugal pumps equipped with magnetic bearings.

  16. The thermodynamic properties of a new type catcher bearing used in active magnetic bearings system

    Normally a rotor levitated by active magnetic bearings (AMBs) system would rotate without contacting with any stator component, but the possibility still remains that the supporting force might lose temporarily or permanently, thus requiring the Catcher bearings (CBs) to provide backup protection in case of the failure of AMBs. A new type CB with two separate rolling element bearing series could have the speed distribution between the inner race and intermediate race according to certain ratio, in which the speed of each roller element bearing decreases with the limit speed of the whole CB increasing, offering high capability to sustain its initial rotation speed. Based on the theory of heat transfer, tribology, and rotor dynamics, this paper analyzes the thermal structure of double-decker catcher bearing (DDCB) and single-decker catcher bearing (SDCB), respectively. Through this structure, the thermal resistances and equations of heat transfer can be obtained. Then we calculate the friction heat and temperature distribution in the various CBs upon rotor's dropping on SDCB or DDCB, followed by the discussion on the CBs temperature rise's effects on lubrication conditions and rotor dynamics parameters. Finally various experiments are carried out to measure the temperature rise of different CBs. The results obtained validate the theoretical analysis and also provide main methods to reduce heat generation. Using DDCB is proved to be effective to reduce the temperature rise. - Highlights: • The DDCB is a more suitable catcher bearing for AMBs. • Compared to SDCB, using DDCB, the temperature rise can decrease in the same states. • A lower viscosity of lubricant may induce a lower temperature rise. • The inner raceway temperature of the first layer bearing is the highest. • Reducing the unbalance mass of the rotor is a method to decrease the temperature rise

  17. Experimental Contribution to High-Precision Characterization of Magnetic Forces in Active Magnetic Bearings

    Kjølhede, Klaus; Santos, Ilmar

    2007-01-01

    Parameter identification procedures and model validation are major steps toward intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model valid...... normalized with respect to the instantaneous measured force obtained from the strain gauges signals)....... the magnetic forces is conducted using different experimental tests: (i) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor (ii) by measuring the input current and...

  18. Optimization of active magnetic bearings for automotive flywheel energy storage systems based on soft magnetic materials

    Wegleiter H.

    2013-01-01

    Full Text Available For active magnetically suspended rotors in mobile flywheel energy storage systems the lowest possible weight, smallest size and a low price is required. Since the flywheel is operated in vacuum and very little heat can be dissipated from the rotor, the bearing’s magnetic losses have to be as minimal as well. This paper compares the design and optimization of homopolar radial active magnetic bearings with 3 different types of laminated steel. The first type is a standard transformer steel, the second one is high flux cobalt steel and the third one is high flux cobalt steel with high tensile strength.

  19. Control of Active Axial Magnetic Bearings for Flywheel-based Energy Storage System

    Morís Gómez, Juan

    2014-01-01

    This thesis deals with the design and implementation of the control system for a Flywheel-based Energy Storage System (FESS) with active magnetic bearings. The thesis focuses on the construction of realistic model of the system according to experimental tests. The simulation model will be used to control the thrust magnetic bearings in order to withstand the flywheel in levitation.

  20. TRANSIENT TEMPERATURE FIELD IN ACTIVE THRUST MAGNETIC BEARING

    Sun Shouqun; Geng Haipeng; Guo Keqian

    2005-01-01

    A transient temperature field model in a thrust magnetic bearing is built in which the heat resources come mainly from the eddy-current loss of solid cores and the copper loss of coils. The transient temperature field, system temperature rise and the thermo-equilibrium state during the rotor starting-up are calculated considering only the copper loss and the eddy-current loss. The numerical results indicate that the temperatures in coils and in magnets rise rapidly, their thermo-equilibrium states are formed within a short time. The temperatures in a thrust-disk and in a rotor rise slowly, their thermo-equilibrium states are formed after a long period time. The temperatures of the thrust-disk and the rotor are far higher than the temperatures of coils and/or magnets after the thermo-equilibrium state has come into being.

  1. Passive magnetic bearing configurations

    Post, Richard F.

    2011-01-25

    A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

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

    Yoon, Se Young; Allaire, Paul E

    2013-01-01

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

  3. Active Magnetic Bearings used as an Actuator for Rotor Health Monitoring in Conjunction with Conventional Support Bearings

    Bash, Travis Joel

    2005-01-01

    This thesis describes the test rig and results from a project expanding the field of rotor health monitoring by using Active Magnetic Bearings (AMBs) as actuators for applying a variety of known force inputs to a spinning. Similar to modal analysis and other nondestructive evaluation (NDE) techniques which apply input signals to static structures in order to monitor responses; this approach allows for the measurement of both input and output response in a rotating system for evaluation. How...

  4. Design and implement for control system of active magnetic bearings based on DSP

    Cao, Jie; Cao, Lihong

    2005-12-01

    Magnetic-bearings, which support shafts with magnetic levitation rather than mechanical contact, have been in industrial use for decades. Recent technological developments, especially in digital processing and control, have made magnetic bearings a more-robust and cost-effective design solution than ever. The dynamic characteristic of electromagnetic bearing depends upon adopted controller; the active control can makes the electromagnetic bearings to realize complex control and special control. With the development of signal processing technology and modern control theory, the main parts of the control system are the digital signal-processing (DSP) electronics, a power supply, and amplifiers. An Active Magnetic Bearing (AMB) controller is mainly discussed in the paper, which is to be solved to realize this flexible control by hardware design based on DSP using TMS320C32 processor. It is proved by experiment that this kind of controller can optimize for this system, improve its stability and also have a very important referential value on the further study of AMB system.

  5. Magnetic bearing momentum wheels with magnetic gimballing capability for 3-axis active attitude control and energy storage

    Sindlinger, R. S.

    1977-01-01

    Magnetic bearings used for the suspension of momentum wheels provide conclusive advantages: the low friction torques and the absence of abrasion allow the realization of lightweight high speed wheels with high angular momentum and energy storage capacity and virtually unlimited lifetime. The use of actively controlled bearings provides a magnetic gimballing capability by applying the external signals to the two servo loops controlling the rotational degrees of freedom. Thus, an attitude control system can be realized by using only one rotating mass for 3-axis active satellite stabilization.

  6. Active control of surge in centrifugal compressors using magnetic thrust bearing actuation

    Sanadgol, Dorsa

    This research presents a new method for active surge control in centrifugal compressors with unshrouded impellers using a magnetic thrust bearing to modulate the impeller tip clearance. Magnetic bearings offer the potential for active control of flow instabilities. This capability is highly dependent on the sensitivity of the compressor characteristics to blade tip clearance. If the position of the shaft can be actuated with sufficient authority and speed, the induced pressure modulation makes control of surge promising. The active nature of the magnetic bearing system makes the real-time static and dynamic positioning of the rotor and therefore modulation of the impeller tip clearance possible. A theoretical model is first established that describes the sensitivity of the centrifugal compressor characteristic curve to tip clearance variations induced by axial motion of the rotor. Results from simulation of the nonlinear model for a single stage high-speed centrifugal compressor show that using the proposed control method, mass flow and pressure oscillations associated with compressor surge are quickly suppressed with acceptable tip clearance excursions, typically less than 20% of the available clearance. It is shown that it is possible to produce adequate axial excursions in the clearance between the impeller blades and the adjacent stationary shroud using a magnetic thrust bearing with practical levels of drive voltage. This surge control method would allow centrifugal compressors to reliably and safely operate with a wider range than is currently done in the field. The principal advantage of the proposed approach over conventional surge control methods lies in that, in machines already equipped with magnetic bearing, the method can potentially be implemented by simply modifying controller software. This dispenses with the need to introduce additional hardware, permitting adaptation of existing machinery at virtually no cost. In addition, since the controller is

  7. Computer aided design of digital controller for radial active magnetic bearings

    Cai, Zhong; Shen, Zupei; Zhang, Zuming; Zhao, Hongbin

    1992-01-01

    A five degree of freedom Active Magnetic Bearing (AMB) system is developed which is controlled by digital controllers. The model of the radial AMB system is linearized and the state equation is derived. Based on the state variables feedback theory, digital controllers are designed. The performance of the controllers are evaluated according to experimental results. The Computer Aided Design (CAD) method is used to design controllers for magnetic bearings. The controllers are implemented with a digital signal processing (DSP) system. The control algorithms are realized with real-time programs. It is very easy to change the controller by changing or modifying the programs. In order to identify the dynamic parameters of the controlled magnetic system, a special experiment was carried out. Also, the online Recursive Least Squares (RLS) parameter identification method is studied. It can be realized with the digital controllers. Online parameter identification is essential for the realization of an adaptive controller.

  8. Impact of frequency switching on the efficiency of a fully suspended active magnetic bearing system

    Gouws, Rupert

    2012-01-01

    Due to the rising energy (and electricity) cost it is essential that an active magnetic bearing (AMB) system is operated as efficiently as possible. Frequency switching caused by an external source can cause an AMB system to operate at a higher than expected energy level and lower than expected efficiency. The purpose of this paper is therefore to investigate the impact of frequency switching (caused by an external source) on the efficiency of a fully suspended AMB system. The shaft of the fu...

  9. A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

    Du Rand, Carel P.; George van Schoor; Niemann, Andries C.

    2013-01-01

    Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance the...

  10. Modeling and flat control law for a fine pointing system based on semi active magnetic bearings

    Mahout, Vincent; Prats Menéndez, Xavier; Mignot, Jean

    2002-01-01

    In this paper aspects of non linear systems and flat control are studied for a specific application of a satellite fine pointing breadboard based on semi active magnetic bearings actuators. Authors propose a complete 6 degrees of freedom mechanical model which describes the system dynamics. A completely non linear and unstable system is obtained leading to implement non linear control laws. A combination of flat control, which ensures trajectory tracking and path plann...

  11. Adaptive control of an active magnetic bearing flywheel system using neural networks / Angelique Combrinck

    Combrinck, Angelique

    2010-01-01

    The School of Electrical, Electronic and Computer Engineering at the North-West University in Potchefstroom has established an active magnetic bearing (AMB) research group called McTronX. This group provides extensive knowledge and experience in the theory and application of AMBs. By making use of the expertise contained within McTronX and the rest of the control engineering community, an adaptive controller for an AMB flywheel system is implemented. The adaptive controller is ...

  12. Magnetostatic analysis of a rotor system supported by radial active magnetic bearings

    Ferfecki P.

    2009-01-01

    The development and the design of a radial active magnetic bearing (AMB) reflects a complex process of the multidisciplinary rotor dynamics, electromagnetism and automatic control analysis. Modelling is performed by application of the physical laws from different areas, e.g. Newton's laws of motion and Maxwell's equations. The new approach in the numerical modelling of radial AMB and design methodology allowing automatic generation of primary dimensions of the radial AMB is proposed. Instead ...

  13. Test and Theory of Electrodynamic Bearings Coupled to Active Magnetic Dampers

    Tonoli, Andrea; Girardello Detoni, Joaquim; Impinna, Fabrizio; Amati, Nicola

    2014-01-01

    Electrodynamic bearings (EDBs) are passive magnetic bearings that exploit the interaction between eddy currents developed in a rotating conductor and a static magnetic field to generate forces. Similar to other types of magnetic suspensions, EDBs provide contactless support, thus avoiding problems with lubrication, friction and wear. Electrodynamic bearings have also drawbacks such as the difficulty in insuring a stable levitation in a wide speed range. The paper presents a solution where the...

  14. Identifying parameters in active magnetic bearing system using LFT formulation and Youla factorization

    Lauridsen, Jonas; Sekunda, André Krabdrup; Santos, Ilmar;

    2015-01-01

    In this paper, a method for identifying uncertain parameters in a rotordynamic system composed of a flexible rotating shaft, rigid discs and two radial active magnetic bearings is presented. Shaft and disc dynamics are mathematically described using a Finite Element (FE) model while magnetic...... of the system matrix A of the full FE model while it is represented as several elements spread over multiple rows and columns of the system matrix of the reduced model. The parametric uncertainty, for both the full and reduced FE model, is represented using Linear Fractional Transformation (LFT). In...

  15. RESEARCH ON CONTROL OF FLYWHEEL SUSPENDED BY ACTIVE MAGNETIC BEARING SYSTEM WITH SIGNIFICANT GYROSCOPIC EFFECTS

    Zhang Kai; Zhao Lei; Zhao Hongbin

    2004-01-01

    Traditional PID controllers are no longer suitable for magnetic-bearing-supported high-speed flywheels with significant gyroscopic effects.Because gyroscopic effects greatly influence the stability of the flywheel rotor,especially at high rotational speeds.Velocity cross feedback and displacement cross feedback are used to overcome harmful effects of nutation and precession modes, and stabilize the rotor at high rotational speeds.Theoretical analysis is given to show their effects.A control platform based on RTLinux and a PC is built to control the active magnetic bearing (AMB) system, and relevant results are reported.Using velocity cross feedback and displacement cross feedback in a closed loop control system, the flywheel successfully runs at over 20 000 r/min.

  16. Development of a satellite flywheel family operating on one active axis magnetic bearings

    Poubeau, P. C.

    1977-01-01

    Since the samarium-cobalt magnets were available at industrial level, new possibilities appeared in the area of magnetic bearings with the radial passive centering and axial control of the rotor position. Magnetic bearings of this type on which a wide effort was made towards the optimization for satellite flywheel applications are described. Also, the momentum and reaction wheels were considered. This work was extended to the kinetic storage of energy for satellites.

  17. Vibration characterization of an active magnetic bearing supported rotor / J. Bean

    Bean, Jaco

    2011-01-01

    The McTronX Research group at the Potchefstroom campus of the North-West University, aims to establish a knowledge base on active magnetic bearing (AMB) systems. Up to date, the group has established a firm knowledge base on various topics related to AMB systems. A recent focus was the design and development of a high speed AMB supported rotor system called the rotor delevitation system (RDS) to analyse rotor drops. During the testing phase of the RDS, the machine exhibited vibrations, of whi...

  18. Active magnetic bearing control loop modeling for a finite element rotordynamics code

    Genta, Giancarlo; Delprete, Cristiana; Carabelli, Stefano

    1994-01-01

    A mathematical model of an active electromagnetic bearing which includes the actuator, the sensor and the control system is developed and implemented in a specialized finite element code for rotordynamic analysis. The element formulation and its incorporation in the model of the machine are described in detail. A solution procedure, based on a modal approach in which the number of retained modes is controlled by the user, is then shown together with other procedures for computing the steady-state response to both static and unbalance forces. An example of application shows the numerical results obtained on a model of an electric motor suspended on a five active-axis magnetic suspension. The comparison of some of these results with the experimental characteristics of the actual system shows the ability of the present model to predict its performance.

  19. Active magnetic bearing control loop modeling for a finite element rotordynamics code

    Genta, Giancarlo; Delprete, Cristiana; Carabelli, Stefano

    1994-05-01

    A mathematical model of an active electromagnetic bearing which includes the actuator, the sensor and the control system is developed and implemented in a specialized finite element code for rotordynamic analysis. The element formulation and its incorporation in the model of the machine are described in detail. A solution procedure, based on a modal approach in which the number of retained modes is controlled by the user, is then shown together with other procedures for computing the steady-state response to both static and unbalance forces. An example of application shows the numerical results obtained on a model of an electric motor suspended on a five active-axis magnetic suspension. The comparison of some of these results with the experimental characteristics of the actual system shows the ability of the present model to predict its performance.

  20. State of the art of control for magnetic levitation and magnetic bearing and control theory. Active control seigyo riron oyo no saisentan

    Nonami, K. (Chiba University, Chiba (Japan). Faculty of Engineering)

    1993-04-10

    From the viewpoint of control theory which was made known mainly through the papers presented in the international active magnetic bearing conference, survey was made of the latest state of active magnetic levitation and bearing system technology. The active magnetic bearing control system is applied to turbo-molecular pumps. They are analog PID-controlled rigid rotor pumps. Many of them are commonly characterized by five-axis controlled suction type active magnetic bearing. For heightening its performance, a further progress is being made in the following items of R and D: Transition from analog control to digital control using the digital signal processor. Transition from PID-controlled stabilization control to advanced control applying the modern control theory, robust control theory, learning control theory, and disturbance compensation control and other system designs. Active magnetic bearing control system with flexible rotors passing through the high order elastic mode. Active magnetic sensorless bearing by which the control is made by assuming the rotor displacement by the observer theory from the electric current in exciting coil. 37 refs., 11 figs.

  1. Intelligent H2/H∞ Robust Control of an Active Magnetic Bearings System

    Safanah M.Raafat

    2015-06-01

    Full Text Available Robust controller design requires a proper definition of uncertainty bounds. These uncertainty bounds are commonly selected randomly and conservatively for certain stability, without regard for controller performance. This issue becomes critically important for multivariable systems with high nonlinearities, as in Active Magnetic Bearings (AMB System. Flexibility and advanced learning abilities of intelligent techniques make them appealing for uncertainty estimation. The aim of this paper is to describe the development of robust H2/H∞ controller for AMB based on intelligent estimation of uncertainty bounds using Adaptive Neuro Fuzzy Inference System (ANFIS. Simulation results reveal that the robust controller design objectives of wide bandwidth and improved performance are satisfied for a wide range of frequency variations. It can be concluded that the intelligent uncertainty weighting functions can precisely compensate for the effects of modelling errors and nonlinearities in the system.

  2. Accurate Wavelet Neural Network for Efficient Controlling of an Active Magnetic Bearing System

    Youssef Harkouss

    2010-01-01

    Full Text Available Problem statement: The synthesis of a command by the neural network has an excellent advantage over the classical one such as PID. This study presented a fast and accurate Wavelet Neural Network (WNN approach for efficient controlling of an Active Magnetic Bearing (AMB system. Approach: The proposed approach combined neural network with the wavelet theory. Wavelet theory may be exploited in deriving a good initialization for the neural network and thus improved convergence of the learning algorithm. Results: We tested two control systems based on three types of neural controllers: Multiplayer Perceptron (MLP controller, RBF Neural Network (RBFNN controller and WNN controller. The simulation results show that the proposed WNN controller provides better performance comparing with standard PID controller, MLP and RBFNN controllers. Conclusion: The proposed WNN approach was shown to be useful in controlling nonlinear dynamic mechanical system, such as the AMB system used in this study.

  3. Theoretical and Experimental Investigation of Force Estimation Errors Using Active Magnetic Bearings with Embedded Hall Sensors

    Voigt, Andreas Jauernik; Santos, Ilmar

    2012-01-01

    of AMBs by embedding Hall sensors instead of mounting these directly on the pole surfaces, force estimation errors are investigated both numerically and experimentally. A linearized version of the conventionally applied quadratic correspondence between measured Hall voltage and applied AMB force is......This paper gives an original theoretical and experimental contribution to the issue of reducing force estimation errors, which arise when applying Active Magnetic Bearings (AMBs) with pole embedded Hall sensors for force quantification purposes. Motivated by the prospect of increasing the usability...... for pole embedded and pole surface mounted Hall sensors. It is shown that in a given range of bias currents and rotor offsets, pole embedded and surface mounted Hall sensors perform equally well for the four pole heteropolar flux-split radial AMB under investigation. Furthermore, frequency dependence...

  4. Development of active magnetic bearings and ferrofluid seals toward oil free sodium pumps

    Sreedhar, B.K., E-mail: bksd@igcar.gov.in; Kumar, R. Nirmal; Sharma, Prashant; Ruhela, Shivprakash; Philip, John; Sundarraj, S.I.; Chakraborty, N.; Mohana, M.; Sharma, Vijay; Padmakumar, G.; Nashine, B.K.; Rajan, K.K.

    2013-12-15

    Sodium centrifugal pumps employ conventional oil cooled bearings and mechanical seals to support the rotor assembly outside sodium and to seal the cover gas from the atmosphere. Although engineered safety features are incorporated in the design and detailed operational procedures formulated to ensure that no oil contamination of sodium can occur, there have been incidents of oil ingress into sodium. A design variant that eliminates the need for oil in top bearings and seals is therefore a promising option. This paper discusses the work in progress to develop a magnetic bearing and ferrofluid seal combination that can achieve this purpose.

  5. Development of active magnetic bearings and ferrofluid seals toward oil free sodium pumps

    Sodium centrifugal pumps employ conventional oil cooled bearings and mechanical seals to support the rotor assembly outside sodium and to seal the cover gas from the atmosphere. Although engineered safety features are incorporated in the design and detailed operational procedures formulated to ensure that no oil contamination of sodium can occur, there have been incidents of oil ingress into sodium. A design variant that eliminates the need for oil in top bearings and seals is therefore a promising option. This paper discusses the work in progress to develop a magnetic bearing and ferrofluid seal combination that can achieve this purpose

  6. Determination of Q-function optimum grid applied on active magnetic bearing control task

    Březina, Tomáš; Krejsa, Jiří

    Brno: VUT, 2003, s. 55-56. ISBN 80-214-2312-9. [Mechatronics, robotics and biomechanics 2003. Hrotovice (CZ), 24.03.2003-27.03.2003] R&D Projects: GA ČR GA101/00/1471 Institutional research plan: CEZ:AV0Z2076919 Keywords : control * magnetic bearing Subject RIV: BC - Control Systems Theory

  7. Magnetostatic analysis of a rotor system supported by radial active magnetic bearings

    Ferfecki P.

    2009-06-01

    Full Text Available The development and the design of a radial active magnetic bearing (AMB reflects a complex process of the multidisciplinary rotor dynamics, electromagnetism and automatic control analysis. Modelling is performed by application of the physical laws from different areas, e.g. Newton's laws of motion and Maxwell's equations. The new approach in the numerical modelling of radial AMB and design methodology allowing automatic generation of primary dimensions of the radial AMB is proposed. Instead of the common way of computation of electromagnetic forces by linearizing at the centre position of the rotor with respect to rotor displacement and coil current, the finite element computation of electromagnetic forces is used. The heteropolar radial AMB consisting of eight pole shoes was designed by means of the built up algorithms for rotor system with two discs fixed on the cantilever shaft. A study of the influence of the nonlinear magnetization characteristics of a rotor and stator material on the equilibrium position of a rotor system is carried out. The performed numerical study shows that results obtained from the analytical nonlinear relation for electromagnetic forces can be considerably different from forces computed with magnetostatic finite element analysis.

  8. Characteristic analysis of rotor dynamics and experiments of active magnetic bearing for HTR-10GT

    A 10 MW high-temperature gas-cooled reactor (HTR-10) was constructed by the Institute of Nuclear and New Energy Technology (INET) at Tsinghua University of China. The helium turbine and generator system of 10 MW high-temperature gas-cooled reactor (HTR-10GT) is the second phase for the HTR-10 project. It is to set up a direct helium cycle to replace the current steam cycle. The active magnetic bearing (AMB) instead of ordinary mechanical bearing was chosen to support the rotor in the HTR-10GT. This rotor is vertically mounted to hold the turbine machine, compressors and the power generator together. The rotor's length is 7 m, its weight is about 1500 kg and the rotating speed is 15,000 rpm. The structure of the rotor is so complicated that dynamic analysis of the rotor becomes difficult. One of the challenging problems is to exceed natural frequencies with enough stability and safety during reactor start up, power change and shutdown. The dynamic analysis of the rotor is the base for the design of control system. It is important for the rotor to exceed critical speeds. Some kinds of softwares and methods, such as MSC.Marc, Ansys, and the transfer matrix method (TMM), are compared to fully analyze rotor dynamics characteristic in this paper. The modal analysis has been done for the HTR-10GT rotor. MSC.Marc was finally selected to analyze the vibration mode and the natural frequency of the rotor. The effects of AMB stiffness on the critical speeds of the rotor were studied. The design characteristics of the AMB control system for the HTR-10GT were studied and the related experiment to exceed natural frequencies was introduced. The experimental results demonstrate the system functions and validate the control scheme, which will be used in the HTR-10GT project

  9. Characteristic analysis of rotor dynamics and experiments of active magnetic bearing for HTR-10GT

    A 10 MW high-temperature gas-cooled reactor (HTR-10) was constructed by the Institute of Nuclear and New Energy Technology (INET) at Tsinghua University of China. The helium turbine and generator system of 10 MW high temperature gas-cooled reactor (HTR-10GT) is the second phase for the HTR-10 project. It is to set up a direct helium cycle to replace the current steam cycle. The active magnetic bearing (AMB) instead of ordinary mechanical bearing was chosen to support the rotor in the HTR-10GT. This rotor is vertically mounted to hold the turbine machine, compressors and the power generator together. The rotor's length is 7 m, its weight is about 1500 kg and the rotating speed is 15000 r/min. The structure of the rotor is so complicated that dynamic analysis of the rotor becomes difficult. One of the challenging problems is to exceed natural frequencies with enough stability and safety during reactor start up, power change and shutdown. The dynamic analysis of the rotor is the base for the design of control system. It is important for the rotor to exceed critical speeds. Some kinds of software and methods, such as MSC.Marc, Ansys, and the Transfer Matrix Method, are compared to fully analyze rotor dynamics characteristic in this paper. The modal analysis has been done for the HTR-10GT rotor. MSC.Marc was finally selected to analyze the vibration mode and the natural frequency of the rotor. The effects of AMB stiffness on the critical speeds of the rotor were studied. The design characteristics of the AMB control system for the HTR-10GT were studied and the related experiment to exceed natural frequencies was introduced. The experimental results demonstrate the system functions and validate the control scheme, which will be used in the HTR-10GT project. (authors)

  10. Variable Parameters PD Control and Stability of a High Rate Rigid Rotor-Journal Active Magnetic Bearing System

    LUO Kai

    2005-01-01

    Stability is a key problem that means whether a high rate rotor-active magnetic bearings system works reliably or not. Aiming at a bearings system described with nonlinear equations, this paper built a linear model according to the system behavior. Considering realization of the control system and behavior of a high rate rotor system (magnetic force is far smaller than input force produced by mass eccentricity) this paper proposes a design method of variable parameters PD control algorithm that can be used universally. The control system was simplified and a mass of adjusting work of control parameters was reduced. Analysis and simulation indicated that the bearings system could get a wider stable region of harmonic motion, and proved that the algorithm is robust and advanced. The control system can be realized because the winding electric currents are positive. The method is convenient for operation and can easily be used for engineering practice.

  11. A self-sensing active magnetic bearing based on a direct current measurement approach.

    Niemann, Andries C; van Schoor, George; du Rand, Carel P

    2013-01-01

    Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM) approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs) modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A) experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator. PMID:24030681

  12. A Self-Sensing Active Magnetic Bearing Based on a Direct Current Measurement Approach

    Carel P. du Rand

    2013-09-01

    Full Text Available Active magnetic bearings (AMBs have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator.

  13. Optimal Control and H∞ Output Feedback Design Options for Active Magnetic Bearing Spindle Position Regulation

    Yifei Yang

    2013-07-01

    Full Text Available For the demand of high speed and high accuracy, the use of active magnetic bearing (AMB plays a key role in various industries such as clean rooms, compressors and satellites due to their contactless nature. In this research, two other control options for high speed machine were designed based on the optimal output feedback and H∞ output feedback control methods to improve the radical and axial position regulation of AMB. The output feedback control gain matrix with the minimum performance index is obtained by solving the Riccati equation and fed back to the system in order to achieve the system’s performance. The above designed controllers can efficiently regulate the radial and axial directions position deviation of for AMB systems. Simulations for the two control methods were carried out using Matlab and Simulink for AMB system models. Results show that the H∞ output feedback controller has a better position deviation control performance over the optimal output feedback under condition of decreasing the disturbance of reaction. Finally, simulations results demonstrate that the H∞ Output Feedback is effective.

  14. Nonlinear Control of Magnetic Bearings

    Khac Duc Do; Dang Hoe Nguyen; Thanh Binh Nguyen

    2010-01-01

    In this paper, recent results controling nonlinear systems with output tracking error constraints are applied to the design of new tracking controllers for magnetic bearings. The proposed controllers can force the rotor to track a bounded and sufficiently smooth refer-ence trajectory asymptotically and guarantee non-contactedness be-tween the rotor and the stator of the magnetic bearings. Simulation results are included to illustrate the effectiveness of the proposed con-trollers.

  15. Thin film superconductor magnetic bearings

    Weinberger, Bernard R.

    1995-12-26

    A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

  16. The development on-line monitoring system of active magnetic bearings for HTR-10GT

    High Temperature Gas-cooled Reactor (HTR) is recognized as an advanced type of reactor incorporating many design enhancements such as inherent safety features, fuel cycle flexibility, highly fuel utilization, highly efficient electricity generation and process heat application. The research and development of HTR started at the middle of the 1970's, and came to be a part of the Chinese High Technology Program in 1986. A plan to build a 10 MW High Temperature Gas-cooled Reactor (HTR-10) was approved by the State Science and Technology Commission in 1990, and in 1995 the construction was initiated at the Institute of Nuclear Energy Technology (INET), Tsinghua University. The full power 10 MW operation for 72 hours have reached in 2003, and have been checked and accepted by the State Science and Technology Commission. In order to advance the HTR-10 performance, the project of the Helium Gas Turbine Generator for the HTR-10 was authorized by the State Science and Technology Commission, and stared in 2003. In this project, active magnetic bearings (AMBs) are chosen to support the generator rotor and the turbocompressor rotor in the power conversion unit because of their numerous advantages over the conventional bearings. In order to detect how the AMB system works in operation and make diagnosis whether the system behaves normally or not, the monitoring system based on the virtual instruments is designed to monitor the working conditions of the PCU, and to ensure its normal operation. This monitoring system consists of the industry personal computer (PC), the data acquisition system, the measurement transmitters and the LabVIEW system platform. It is located at the PCU control room, and communicates with the master control room by Controller Area Net (CAN). The development is divided into the following three steps: First, a data acquisition platform to collect and acquire all the necessary and useful data from the operation of the AMB system is developed. Second, the

  17. Passive axial stabilization of a magnetic radial bearing by superconductors

    Marinescu, M.; Marinescu, N. (Ing.-Buro f. Magnettechnik, Mailander Str.19, D-6000 Frankfurt/M. 70 (DE)); Tenbrink, J.; Krauth, H. (Vacuumschmelze GmbH, Gruner Weg 37, D-6450 Hanau (DE))

    1989-09-01

    Contactless bearings for high-speed operation can be constructed using passive magnet systems, which inherently need a second, active bearing for their stabilization. Completely passive bearings only can be obtained using diamagnetic materials. This study deals with the axial stabilization of magnetic radial bearings using a permanent magnet/superconductor system. Using finite element calculation procedures it is shown that axial forces of up 3000 N and stiffnesses of up to 400 N/mm may be achieved.

  18. 主动电磁轴承系统的动力学性能分析%Analysis on Dynamic Performance for Active Magnetic Bearing-Rotor System

    严慧燕; 汪希平; 朱礼进; 张直明; 万金贵

    2001-01-01

    In the application of active magnetic bearings (AMB), one of the key problems to be solved is the safety and stability in the sense of rotor dynamics. The project related to the present paper deals with the method for analyzing bearing rotor systems with high rotation speed and specially supported by active magnetic bearings, and studies its rotor dynamics performance, including calculation of the natural frequencies with their distribution characteristics, and the critical speeds of the system. One of the targets of this project is to formulate a theory and method valid for the analysis of the dynamic performance of the active magnetic bearing-rotor system by combining the traditional theory and method of rotor dynamics with the analytical theory and design method based on modern control theory of the AMB system.

  19. Unbalanced Magnetic Pull Effect on Stiffness Models of Active Magnetic Bearing due to Rotor Eccentricity in Brushless DC Motor Using Finite Element Method

    Bangcheng Han

    2013-01-01

    Full Text Available We firstly report on an investigation into the unbalanced magnetic pull (UMP effect on the static stiffness models of radial active magnetic bearing (RAMB in brushless DC motor (BDCM in no-loaded and loaded conditions using the finite element method (FEM. The influences of the UMP on the force-control current, force-position, current stiffness, and position stiffness of RAMB are clarified in BDCM with 100 kW rated power. We found the position stiffness to be more susceptible to UMP. The primary source of UMP is the permanent magnets of BDCM. In addition, the performance of RAMB is affected by the UMP ripples during motor commutation and also periodically affected by the angular position of rotor. The characteristic curves of RAMB force versus control current (or rotor position and angular position of rotor affected by the UMP are given. The method is useful in design and optimization of RAMB in magnetically suspended BDCMs.

  20. Controller Design and Validation of Radial Active Magnetic Bearing Systems Considering Dynamical Changes Due To Rotational Speeds

    If a rotor possesses a high gyroscopic coupling or the running speed is high, the dynamical changes in the rotor become prominent. When active magnetic bearings are used to support such rotors, it is necessary for the bearing controller to take these dynamical changes into consideration. Independent-axis controllers, which are the most commonly used, modulate the bearing force solely based on the sensor output of the same axis. However, this type of controller has difficulties in overcoming the dynamical changes. On the other hand, mixed-axis controllers transform the sensor output into components corresponding to the vibrational modes. A separate controller can then be designed for each vibrational mode. In this way, the controller can be designed based on the dynamics of the rotor. In this paper, we describe a design process for a mixed-axis controller that uses a detailed mathematical model of the system. The performance of the controller is evaluated based on the ISO sensitivity requirements and unbalance response, while considering the change in the system dynamics due to the running speed

  1. Hydrodynamic Effects on Modeling and Control of a High Temperature Active Magnetic Bearing Pump with a Canned Rotor

    Melin, Alexander M [ORNL; Kisner, Roger A [ORNL; Fugate, David L [ORNL; Holcomb, David Eugene [ORNL

    2015-01-01

    Embedding instrumentation and control Embedding instrumentation and control (I\\&C) at the component level in nuclear power plants can improve component performance, lifetime, and resilience by optimizing operation, reducing the constraints on physical design, and providing on-board prognostics and diagnostics. However, the extreme environments that many nuclear power plant components operate in makes embedding instrumentation and control at the component level difficult. Successfully utilizing embedded I\\&C requires developing a deep understanding of the system's dynamics and using that knowledge to overcome material and physical limitations imposed by the environment. In this paper, we will develop a coupled dynamic model of a high temperature (700 $^\\circ$C) canned rotor pump that incorporates rotordynamics, hydrodynamics, and active magnetic bearing dynamics. Then we will compare two control design methods, one that uses a simplified decoupled model of the system and another that utilizes the full coupled system model. It will be seen that utilizing all the available knowledge of the system dynamics in the controller design yield an order of magnitude improvement in the magnitude of the magnetic bearing response to disturbances at the same level of control effort, a large reduction in the settling time of the system, and a smoother control action.

  2. Preliminary modal analysis and structure design of an HTR-10 PCU rotor with an active magnetic bearing

    A 10 MW high-temperature gas-cooled reactor (HTR-10) was constructed by INET at Tsinghua University of China. The second phase of the HTR-10 project is to set up a direct helium cycle to replace the current steam cycle. An Active Magnetic Bearing (AMB) was chosen to support the rotor. This rotor is vertically mounted to hold the turbine machine, compressors and the power generator together. The rotor's length is 7 m, its weight is about 1000 kg and the rotating speed is 15,000 r/min. One of the challenging problems is to exceed natural frequencies with enough stability and safety during reactor start up, power change and shutdown. Some kinds of FEM software and methods, such as MSC.Marc, Ansys, and the Transfer Matrix Method, are compared to fully analyze rotor dynamics characteristic. The modal analysis and preliminary structure design have been done for the HTR-10 phase II rotor. MSC.Marc was finally selected to analyze the vibration mode and the natural frequency of the rotor. The effects of AMB stiffness on the critical speeds of the rotor were studied. These results offer the basis for design of the AMB control system, and also provide research data for large magnetic bearings. (author)

  3. Sensorless Control of Axial Magnetic Bearings

    Atsumo, Daichi; Yoshida, Toshiya; Ohniwa, Katsumi

    This paper describes a sensorless control method of axial active magnetic bearings (AMBs). At high frequencies, inductance of the axial electromagnets is hardly dependent on the airgap because of the eddy current effects of the non-laminated core. Therefore the carrier frequency should be 3 kHz below to improve the sensitivity to the airgap. In the experiment, Sensorless controll of the axial AMBs have been achieved.

  4. Technical design and principle test of active magnetic bearings for the turbine compressor of HTR-10GT

    Shi Lei, E-mail: shlinet@tsinghua.edu.cn [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China); Yu Suyuan; Yang Guojun; Shi Zhengang; Xu Yang [Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084 (China)

    2012-10-15

    The 10 MW high temperature gas-cooled test reactor coupled with gas-turbine circle (HTR-10GT) has been carried out by the Institute of Nuclear and New Energy Technology (INET) of Tsinghua University in China since year 2002. In the power convention unit (PCU) of the HTR-10GT, the contact-free and no-lubricating active magnetic bearings (AMB) are adopted to support the vertical high-speed turbine machine shaft, because of their numerous advantages over the conventional oil mechanical bearings under the special reactor operating conditions. Based on the previous studies and small tests of the AMBs, the final engineering design of the AMBs for the HTR-10GT turbine compressor rotor has been finished recently. This paper firstly introduces the design principle and technical futures of the AMBs. Then the main structure, as well as the key dimensions and parameters of the different AMB components are illustrated in detail. Besides, the rotor dynamic analysis is conducted to provide the mathematic model for the unbalance attenuation with high performance control system design in order to smoothly pass across the first two bending critical speeds before reaching the rated speed of 15,000 rpm. Furthermore, a small AMB flexible test system in compliance with the dynamic similarity principle of the helium turbine compressor rotor of the HTR-10GT, has been set up to validate the advanced control algorithms and accumulate design and operation experiences for the next full scale experiment in the near future.

  5. Technical design and principle test of active magnetic bearings for the turbine compressor of HTR-10GT

    The 10 MW high temperature gas-cooled test reactor coupled with gas-turbine circle (HTR-10GT) has been carried out by the Institute of Nuclear and New Energy Technology (INET) of Tsinghua University in China since year 2002. In the power convention unit (PCU) of the HTR-10GT, the contact-free and no-lubricating active magnetic bearings (AMB) are adopted to support the vertical high-speed turbine machine shaft, because of their numerous advantages over the conventional oil mechanical bearings under the special reactor operating conditions. Based on the previous studies and small tests of the AMBs, the final engineering design of the AMBs for the HTR-10GT turbine compressor rotor has been finished recently. This paper firstly introduces the design principle and technical futures of the AMBs. Then the main structure, as well as the key dimensions and parameters of the different AMB components are illustrated in detail. Besides, the rotor dynamic analysis is conducted to provide the mathematic model for the unbalance attenuation with high performance control system design in order to smoothly pass across the first two bending critical speeds before reaching the rated speed of 15,000 rpm. Furthermore, a small AMB flexible test system in compliance with the dynamic similarity principle of the helium turbine compressor rotor of the HTR-10GT, has been set up to validate the advanced control algorithms and accumulate design and operation experiences for the next full scale experiment in the near future.

  6. Modal Tilt/Translate Control and Stability of a Rigid Rotor with Gyroscopics on Active Magnetic Bearings

    Timothy Dimond

    2012-01-01

    Full Text Available Most industrial rotors supported in active magnetic bearings (AMBs are operated well below the first bending critical speed. Also, they are usually controlled using proportional, integral and derivative controllers, which are set up as modally uncoupled parallel and tilt rotor axes. Gyroscopic effects create mode splitting and a speed-dependent plant. Two AMBs with four axes of control must simultaneously control and stabilize the rotor/AMB system. Various analyses have been published considering this problem for different rotor/AMB configurations. There has not been a fully dimensionless analysis of these rigid rotor AMB systems. This paper will perform this analysis with a modal PD controller in terms of translation mode and tilt mode dimensionless eigenvalues and eigenvectors. The number of independent system parameters is significantly reduced. Dimensionless PD controller gains, the ratio of rotor polar to transverse moments of inertia and a dimensionless speed ratio are used to evaluate a fully general system stability rigid rotor analysis. An objective of this work is to quantify the effects of gyroscopics on rigid rotor AMB systems. These gyroscopic forces reduce the system stability margin. The paper is also intended to help provide a common framework for communication between rotating machinery designers and controls engineers

  7. High performance magnetic bearings suitable for noise cancellation in permanent magnet motor driven pumps

    Conventional pumps having external drive motors experience problems due to bearing noise. In addition failure of bearings and seals can lead to limited operational reliability and impaired integrity of these pumps. Pumps using DC brushless motors and magnetic bearings offer means of overcoming these problems. A design of a pump having a DC brushless motor and magnetic bearings with a potential for Naval applications in ships and submarines is discussed. In this paper attention is given to the selection of the magnetic bearings suitable for achieving active noise cancellation

  8. Design, construction, and testing of a five active axes magnetic bearing system

    Delprete, Cristiana; Genta, Giancarlo; Carabelli, Stefano

    1994-05-01

    A high speed electric spindle based on active electromagnetic suspension technology has been designed, built, and tested. The main goal of the research work was the construction of a highly modular unit which can be used for teaching and research purposes. The design of the electromechanical components and of the control unit is described in detail, together with the characterization tests performed on the various subsystems. A description of the preliminary tests on the unit, conducted at speeds not in excess of the first deformation critical speed of the rotor, concludes the work.

  9. Design, construction, and testing of a five active axes magnetic bearing system

    Delprete, Cristiana; Genta, Giancarlo; Carabelli, Stefano

    1994-01-01

    A high speed electric spindle based on active electromagnetic suspension technology has been designed, built, and tested. The main goal of the research work was the construction of a highly modular unit which can be used for teaching and research purposes. The design of the electromechanical components and of the control unit is described in detail, together with the characterization tests performed on the various subsystems. A description of the preliminary tests on the unit, conducted at speeds not in excess of the first deformation critical speed of the rotor, concludes the work.

  10. Passive Magnetic Bearing With Ferrofluid Stabilization

    Jansen, Ralph; DiRusso, Eliseo

    1996-01-01

    A new class of magnetic bearings is shown to exist analytically and is demonstrated experimentally. The class of magnetic bearings utilize a ferrofluid/solid magnet interaction to stabilize the axial degree of freedom of a permanent magnet radial bearing. Twenty six permanent magnet bearing designs and twenty two ferrofluid stabilizer designs are evaluated. Two types of radial bearing designs are tested to determine their force and stiffness utilizing two methods. The first method is based on the use of frequency measurements to determine stiffness by utilizing an analytical model. The second method consisted of loading the system and measuring displacement in order to measure stiffness. Two ferrofluid stabilizers are tested and force displacement curves are measured. Two experimental test fixtures are designed and constructed in order to conduct the stiffness testing. Polynomial models of the data are generated and used to design the bearing prototype. The prototype was constructed and tested and shown to be stable. Further testing shows the possibility of using this technology for vibration isolation. The project successfully demonstrated the viability of the passive magnetic bearing with ferrofluid stabilization both experimentally and analytically.

  11. A CAD approach to magnetic bearing design

    Jeyaseelan, M.; Anand, D. K.; Kirk, J. A.

    1988-01-01

    A design methodology has been developed at the Magnetic Bearing Research Laboratory for designing magnetic bearings using a CAD approach. This is used in the algorithm of an interactive design software package. The package is a design tool developed to enable the designer to simulate the entire process of design and analysis of the system. Its capabilities include interactive input/modification of geometry, finding any possible saturation at critical sections of the system, and the design and analysis of a control system that stabilizes and maintains magnetic suspension.

  12. Using Magnetic Bearing Orbit Information to Maximize Centrifugal Compressor Efficiency at Off-Design Conditions

    Thornton, W. Turner; Brasz, Joost J.

    2014-01-01

    Active magnetic bearings used on oil-free centrifugal refrigeration compressors have lower stiffness than conventional oil-lubricated journal or rolling element bearings. The lower stiffness of these bearings makes them sensitive to internal flow instabilities that are precursors of rotating stall or compressor surge. At operating conditions far away from surge the internal flow is very stable and the magnetic bearings keep the shaft centered, resulting in a minimal bearing orbit. The interna...

  13. Flywheel energy storage with superconductor magnetic bearings

    Weinberger, Bernard R.; Lynds, Jr., Lahmer; Hull, John R.

    1993-01-01

    A flywheel having superconductor bearings has a lower drag to lift ratio that translates to an improvement of a factor of ten in the rotational decay rate. The lower drag results from the lower dissipation of melt-processed YBCO, improved uniformity of the permanent magnet portion of the bearings, operation in a different range of vacuum pressure from that taught by the art, and greater separation distance from the rotating members of conductive materials.

  14. AN INVESTIGATION OF MAGNETIC BEARING SYSTEMS

    Gürcan SAMTAŞ

    2007-02-01

    Full Text Available The magnetic bearing consists of levitating a shaft so that it is free to rotate about its axis. The magnetic bearing has the advantages of being very quiet work and very cleanliness because there is no mechanical friction or lubricants. The shaft has two permanent magnets attached to it. These two magnets determine a straight line rotation axis of the rotor shaft. The magnets are radially levitated and centered within a cavity by a passive permanent magnetic field in the adding stator housing assembly. The levitation and centering of the shaft axially is stabilized by a closed loop electronic servo circuit that regulates an electromagnetic field in the stator housing that pushes and pulls on the shaft magnets. The rotor weight can be between one gram and forty five thousand, four hundred grams. In 1985, the first magnetic bearing was developed that it had used to applications of gas turbines and other compressors. In these days, they can be used by many applications which are Medical, Transportation, Machine and Tools Industry, Aerospace, Vacuum and Clean room Environments... etc.

  15. Magnetic bearings for free-piston Stirling engines

    Curwen, P. W.; Fleming, D. P.; Rao, D. K.; Wilson, D. S.

    1992-08-01

    The feasibility and efficacy of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery currently being developed for long-term space missions are assessed. The study was performed for a 50-kWe Reference Stirling Space Power Converter (RSSPC) which currently uses hydrostatic gas bearings to support the reciprocating displacer and power piston assemblies. Active magnetic bearings of the attractive electromagnetic type are feasible for the RSSPC power piston. Magnetic support of the displacer assembly would require unacceptable changes to the design of the current RSSPC. However, magnetic suspension of both displacer and power piston is feasible for a relative-displacer version of the RSSPC. Magnetic suspension of the RSSPC power piston can potentially increase overall efficiency by 0.5 to 1 percent (0.1 to 0.3 efficiency points). Magnetic bearings will also overcome several operational concerns associated with hydrostatic gas bearing systems. These advantages, however, are accompanied by a 5 percent increase in specific mass of the RSSPC.

  16. Weak and strong nonlinearities in magnetic bearings

    Půst, Ladislav

    2004-01-01

    Roč. 39, č. 7 (2004), s. 779-795. ISSN 0094-114X R&D Projects: GA ČR GA101/00/1471; GA AV ČR IBS2076301 Institutional research plan: CEZ:AV0Z2076919 Keywords : weak nonlinearitiy * strong nonlinearity * magnetics bearings Subject RIV: BI - Acoustics Impact factor: 0.605, year: 2004

  17. MAGNETIC FLUID BEARINGS OF MINING EQUIPMENT

    I. Gorlov

    2012-01-01

    Full Text Available The paper considers a problem pertaining to selection friction pair materials for plain bearings of mining equipment which are lubricated with  nano-dispersed magnetic oil. Methodology for equipment tests, technology for obtaining new anti-friction materials (polymer, ceramic, amorphous and investigation results are presented in the paper.

  18. Dynamic interaction between rotor and axially-magnetized passive magnetic bearing considering magnetic eccentricity

    Enemark, Søren; Santos, Ilmar

    2014-01-01

    Passive magnetic bearings are known due to the excellent characteristics in terms of friction and no requirement of additional energy sources to work. However, passive magnetic bearings do not provide damping, are not stable and, depending on their design, may also introduce magnetic eccentricity....... Such magnetic eccentricities are generated by discrepancies in magnet fabrication. In this framework the main focus of the work is the theoretical as well as experimental investigation of the nonlinear dynamics of a rotor-bearing system with strong emphasis on the magnetic eccentricities and non......-linear stiffness. In this investigation passive magnetic bearings using axially- aligned neodymium cylinder magnets are investigated. The cylinder magnets are axially magnetised for rotor as well as bearings. Compared to bearings with radial magnetisation, the magnetic stiffness of axially-aligned bearings is...

  19. Novel High Temperature Magnetic Bearings for Space Vehicle Systems Project

    National Aeronautics and Space Administration — Previous high temperature magnetic bearings employed electromagnets only. The work proposed in this SBIR program seeks to utilize High Temperature Permanent Magnets...

  20. Novel High Temperature Magnetic Bearings for Space Vehicle Systems Project

    National Aeronautics and Space Administration — Previous high temperature magnetic bearings employed only electromagnets. The work proposed in this SBIR program seeks to utilize High Temperature Permanent Magnets...

  1. Permanent magnet design for high-speed superconducting bearings

    Hull, J.R.; Uherka, K.L.; Abdoud, R.G.

    1996-09-10

    A high temperature superconducting bearing including a permanent magnet rotor levitated by a high temperature superconducting structure is disclosed. The rotor preferably includes one or more concentric permanent magnet rings coupled to permanent magnet ring structures having substantially triangular and quadrangular cross-sections. Both alternating and single direction polarity magnet structures can be used in the bearing. 9 figs.

  2. Dynamic modelling and response characteristics of a magnetic bearing rotor system with auxiliary bearings

    Free, April M.; Flowers, George T.; Trent, Victor S.

    1995-01-01

    Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied.

  3. Dynamic modelling and response characteristics of a magnetic bearing rotor system including auxiliary bearings

    Free, April M.; Flowers, George T.; Trent, Victor S.

    1993-01-01

    Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed.

  4. Analysis of Beat Vibration for Active Magnetic Bearing System%主动磁悬浮轴承系统拍振现象分析

    高辉; 徐龙祥

    2011-01-01

    Vibration analysis plays an important role in the research of active magnetic bearing(AMB) system. However, the established system mathematical models which combine the controller with the dynamic response are relatively few. The vibration equations of radial AMB subsystems are built on the basis of the stress analysis of high speed rotor system, referring the influences of the frequency characteristics of adopted incomplete differential PID controller on the generalized magnetic bearing dynamic stiffness and rotor dynamic unbalance response. The vibration modes existing in AMB system can be obtained by solving the vibration equations. One is free vibration because of the inherent frequency, and the other is harmonic vibration due to unbalanced excitation response. And the produced beat vibration phenomenon is explained when the two kinds of vibration frequency are similar. Through adjusting the control current, the generalized dynamic stiffness of magnetic bearings and as well as the inherent frequency of the system can be changed, thus resulting in the weakening of beat vibration. Simulation and experimental results can verify the "beat vibration" phenomenon and the damping effect after changing the active control. The mechanical model can provide the simulation platform for the research of vibration compensation algorithm of AMB system.%振动分析是研究主动磁悬浮轴承(Active magnetic bearings,AMB)系统的一个重要部分,但是目前结合控制器以及动态不平衡响应建立的系统数学模型相对较少.通过对高速主动磁悬浮轴承转子系统受力分析,参考所使用的不完全微分PID控制器的频率特性对AMB广义动刚度的影响以及对转子动态不平衡激励响应的影响,建立径向子系统的力学振动方程.通过此振动方程的解,得出AMB系统存在的振动形式.一种是由于系统固有频率存在而产生的自由振动,另一种是由于不平衡响应存在而产生的简谐振动,并

  5. Development of bearings and a damper based on magnetically controllable fluids

    Guldbakke, J. M.; Hesselbach, J.

    2006-09-01

    This paper presents two different kinds of magnetically controllable fluid bearings and a new magnetorheological fluid damper based upon open porous metallic foams. For the bearings, it will distinguish between a magnetohydrostatic bearing and a hydrostatic bearing with a magnetically controllable fluid. The magnetohydrostatic bearings get their load bearing capacity from the magnetohydrostatic pressure that is generated by the gradient of the magnetic field along a fluid surface. With such magnetohydrostatic bearings a specific load up to 1.6 N cm2 can be reached. To support heavier loads hydrostatic bearings with magnetically controllable fluids can be used. This bearing concept makes it possible to achieve a constant bearing gap even if the load of the bearing changes. For this purpose the fluids are used as a hydraulic medium. Due to the magnetically controlled rheological behaviour of the fluid the bearing gap remains constant. The great advantage of this closed loop system compared to that of common hydrostatic bearings using valves is the quicker response to payload changes. The reason for that is that the active element (i.e. the fluid) acts directly inside the bearing gap and not outside like in the case of valves. The foam damper developed uses the fluid to produce controllable damping forces. The open porous foam is directly placed in the active volume of the damper. By moving the foam piston the magnetically controllable fluid is pressed through the pores. The flow in the pores can be controlled by changing the fluid viscosity by applying a magnetic field. With this damper structure it is possible to reach higher damping forces whilst featuring a small design space.

  6. Modeling of Hybrid Permanent Magnetic-Gas Bearings

    Morosi, Stefano; Santos, Ilmar

    2009-01-01

    Modern turbomachinery applications require nowadays ever-growing rotational speeds and high degree of reliability. It then becomes natural to focus the attention of the research to contact-free bearings elements. The present alternatives focus on gas lubricated journal bearings or magnetic bearings....... In the present paper both the technologies are combined with the aim of developing a new kind of hybrid permanent magnetic - gas bearing. This new kind of machine is intended to exploit the benefits of the two technologies while minimizing their drawbacks. The poor start-up and low speed operation...... performance of the gas bearing is balanced by the properties of the passive magnetic one. At high speeds the dynamic characteristics of the gas bearing are improved by offsetting the stator ring of the permanent magnetic bearing. Furthermore this design shows a kind of redundancy, which offers soft failure...

  7. 风力发电机用同极型磁悬浮轴承的支承性能%Supporting characteristics of the homopolar active magnetic bearing for wind power generator

    谢振宇; 王晓; 周红凯

    2013-01-01

    The setup of vertical axis wind power generator rotor system is built. The homopolar radial active magnetic bearing and the axial active magnetic bearing with the function of suspension and brake synchronously are designed and manufactured. The main design process and configuration parameters are presented. Stability ranges of the control parameters of the active magnetic bearings are tested, the mode frequencies and modal damps of the system are obtained by experimental modal analysis, and the brake function of the axial active magnetic bearing is verified. The results show that the first critical speed of the system is far above the operating rotation speed, there is no resonance when the system is in motion. On the other hand, the axial active magnetic bearing can meet the brake demand and reduce the size and cost of the system.%建立了垂直轴风力发电机转子系统装置,设计制作了同极型径向磁悬浮轴承和具有悬浮与刹车功能的轴向磁悬浮轴承,给出了该装置的主要设计过程和结构参数.测试了磁悬浮轴承控制参数的稳定区域,采用试验模态分析方法获取了系统的模态频率和模态阻尼,并验证了轴向磁悬浮轴承的刹车功能.结果表明,系统的第一阶临界转速远高于最大工作转速,系统在运行时不会出现共振;另外,轴向磁悬浮轴承可以满足刹车制动要求,有利于减小系统的体积和成本.

  8. Toxicity of Magnetic Albumin Microspheres Bearing Adriamycin

    2000-01-01

    Magnetic albumin microspheres bearing adriamycin (ADM-MAM) is a novel chemotherapeutic compound with site-specific drug delivery characteristics. The acute and subacute toxic tests of the compound, local irritating test and anaphylactic test were performed on mice and guinea pigs. The results showed there was no macroscopically and microscopically direct cytotoxic injuries of the compound to the animal organs or to the cells. The LD50 value of the compound was higher than that of the single used adriamycin, indicating that the compound was less toxic than the single adriamycin and quite safe in its therapeutic dosage. Furthermore, there was also no side effects or toxic reactions to be observed on clinical patients with advanced carcinoma or gastric cancer.

  9. Analysis of Permanent Magnets Bearings in Flywheel Rotor Designs

    Prince Owusu-Ansah

    2016-04-01

    Full Text Available This paper discusses analysis of permanent magnet bearing in flywheel rotor designs. This work focuses on the advantages of using permanent magnets in flywheel rotor design as compared to that of the convectional mode of levitating the rotor position. The use of permanent magnet in magnetic bearing design to generate the steady state position of the magnetic field results in less variation of the force exerted on the rotor when it deviates from the nominal position than when an electrical coil is used for the same purpose. Theresults of the analysis shows that the magnetic bearing dynamics as well as its load carryingcapacity improves when the rotor is offset from its central position. The use of permanent magnet compared to current-carrying coils results in smaller overall size of magnetic bearing leading to a more compact system design resulting in improved rotordynamic performance

  10. Suppression of Base Excitation of Rotors on Magnetic Bearings

    Steven Marx; C. Nataraj

    2007-01-01

    This paper deals with rotor systems that suffer harmonic base excitation when supported on magnetic bearings. Magnetic bearings using conventional control techniques perform poorly in such situations mainly due to their highly nonlinear characteristics. The compensation method presented here is a novel optimal control procedure with a combination of conventional, proportional, and differential feedback control. A four-degree-of-freedom model is used for the rotor system, and the bearings are ...

  11. Early-stage fault isolation based on frequency response fitted by small-size samples for cryogenic cold compressors with active magnetic bearings.

    Arpaia, Pasquale; De Vito, Luca; Girone, Mario; Pezzetti, Marco

    2016-01-01

    A model-based method for fault detection and early-stage isolation, applicable when unfaulty conditions can be identified only by a reduced number of trials (even only one), is presented. The basic idea is to model analytically the uncertainty of the unfaulty frequency response and express the fault condition in terms of the noise power variance. A preliminary fault isolation is carried out by sensitivity analysis in order to identify the most influencing model parameters and assess their influence on the estimated noise. Then, during maintenance tests, the noise power is checked to detect the faulty condition. This technique is conceived to check the quality of a critical component in an experimental installation (fault detection and early-stage isolation), as well as to detect its faulty dynamic behaviors over a long horizon maintenance test campaign (condition monitoring). The method was applied to four cold compressors with active magnetic bearings at CERN by proving to be able to detect an actual faulty condition in one of such compressors. PMID:26827354

  12. Performances Comparison for a Rotating Shaft Suspended by 4-Axis Radial Active Magnetic Bearings via -Synthesis, Loop-Shaping Design, and Sub(∞with Uncertainties

    G. Barbaraci

    2011-01-01

    Full Text Available The control systems applied on active magnetic bearing are several. A perfect levitation is characterized by maintaining the operating point condition that is characterized by the center of stator coincident with the geometric center of shaft. The first controller implemented for this purpose is PID controller that is characterized by an algorithm that leads the amplifier to produce control current until the operating point condition is not reached, this is obtained by an integration operator. The effect of an integrator is essential but not necessary for a centered levitation for example in the robust control characterized by a dynamic model depended on plant of system so that it depends on angular speed as LQR controller does. In LQR there is not integrator so there is not a perfectly centered section of shaft with center of stator. On contrary PID controller does not depend on angular speed and it can be easily implemented according some simple rules. Predictive control is another interesting controller characterized by a multiple controller operating in different condition in order to get the minimum of cost function, but also in this case the angular speed is introduce for the same reason discussed before.

  13. Biodegradation reduces magnetization in oil bearing rocks: magnetization results of a combined chemical and magnetic study

    Emmerton, S.; Muxworthy, A. R.; Sephton, M. A.; Williams, W.

    2012-12-01

    A relationship between hydrocarbons and their magnetic signatures has been alluded to for decades but this is the first study to combine geochemical and magnetic data. We report an extended study that identifies a definitive connection between magnetic mineralogy and biodegradation within oil-bearing rocks. Samples from Colombia, Canada Indonesia and the UK were collected and magnetically characterized. A negative linear regression in log space between magnetic susceptibility and the percentage of extractable organic matter was observed for individual reservoirs. To determine if this relationship is due to the activity of bacteria or migration of the oil, the percentage of oil components; aliphatic, aromatics, polars and resins and the biodegradation state of the samples were compared to the magnetic susceptibility and magnetic mineralogy of the samples. Geochemical biomarker data revealed that all oil samples were derived from mature type-II kerogen, which was deposited in oxygen-poor environments allowing for an investigation into biodegradation variations. Biodegradation is the decrease of oil quality through the conversion of aliphatic hydrocarbons to polar constituents mainly through the activity of bacteria. A distinct decrease in magnetic susceptibility was correlated to decreasing oil quality (loss of aliphatic hydrocarbons, more biodegraded), which cannot be rejected at 99% confidence. Further magnetic characterization revealed that the high quality, low biodegradation oils from Colombia have a higher magnetic susceptibility (10-3-10-4 m3kg-1) and are dominated by pseudo-single domain grains of magnetite. The lower quality oils i.e., the UK, Canadian and Indonesian samples, displayed decreased magnetic susceptibility (10-5-10-6 m3kg-1) and pseudo-single domain to multidomain grains of magnetite and hematite. Magnetite and pyrrhotite framboidal material were found in all but the Canadian samples. Therefore, with decreasing oil quality there is a progressive

  14. THE EDDY LOSSES OF A MAGNETIC THRUST BEARING

    徐华; 王艳

    2004-01-01

    Accurate calculations of losses associated with the operation of magnetic bearings are particularly important for high speed applications where the rotor losses are expected to be large and for some particular applications where even low power losses will be critical. Power losses in the magnetic thrust bearing is often neglected, but if there is misaligned in the rotor and bearing, the magnetic field in the thrust bearing is no longer axisymmetric one, or the dynamic control current in the winding is time dependent one, eddy currents are caused to flow inside the conducting material, then the power losses are very important for magnetic bearing design. This paper presents an analytical model of a thrust magnetic bearing, and the magnetic fields, forces and losses of thrust magnetic bearing are calculated. In the calculations the frequency of dynamic control current is up to 1000Hz, rotating speed is from 60rpm to 1200rpm, and the non-linearity of material is also taken into consideration. The results shows that if the magnetic field is not saturation, the eddy losses is proportional to dynamic control current frequency and a square function of dynamic control current, and also 5/2 power function of shaft's speed.

  15. Hybrid Superconducting Magnetic Bearing (HSMB) for high-load devices

    Lifting capacities greater than 41 N/cm(exp 2) (60 psi) at 77 K have been achieved with a new type of levitation (hybrid) using a combination of permanent magnets and high quality melt-mixtured YBa2Cu3O(7-delta) (YBCO). The key concept of the hybrid superconducting magnetic bearing (HSMB) is the use of strong magnetic repulsion and attraction from permanent magnets for high levitation or suspension forces in conjunction with a superconductor's flux pinning characteristics to counteract the inherent instabilities in a system consisting of magnets only. To illustrate this concept, radial and axial forces between magnet/superconductor, magnet/magnet, and magnet/superconductor/magnet, were measured and compared for the thrust bearing configuration

  16. Approach to Synchronization Control of Magnetic Bearings Using Fuzzy Logic

    Yang, Li-Farn

    1996-01-01

    This paper presents a fuzzy-logic approach to the synthesis of synchronization control for magnetically suspended rotor system. The synchronization control enables a whirling rotor to undergo synchronous motion along the magnetic bearing axes; thereby avoiding the gyroscopic effect that degrade the stability of rotor systems when spinning at high speed. The control system features a fuzzy controller acting on the magnetic bearing device, in which the fuzzy inference system trained through fuzzy rules to minimize the differential errors between four bearing axes so that an error along one bearing axis can affect the overall control loop for the motion synchronization. Numerical simulations of synchronization control for the magnetically suspended rotor system are presented to show the effectiveness of the present approach.

  17. Modeling and Development of RMD Configuration Magnetic Bearing

    K.P. Lijesh

    2015-06-01

    Full Text Available The low load carrying capacity of Passive Magnetic Bearings (PMBs has restricted their use in many industrial applications. The Rotation Magnetized Direction (RMD configuration has emerged as a strong and viable method that is able to substantially enhance the load carrying capacity of passive magnetic bearings. It consists of both radially and axially polarized passive magnets. But the physical realization of a radially polarized magnet is difficult to achieve. In the present work, a RMD structure consisting of aluminum ring and cubical shaped magnets is proposed by developing the radially polarized magnets required for RMD structure. A theoretical model is derived by simulating the cuboid magnets in form of sector magnets by developing equivalent surface area. An experimental setup was designed and developed to conduct experimental verification. The theoretical model is validated by conducting experiments on RMD configuration magnetic bearing and axially magnetized full ring bearing. The comparison of the load carrying capacity by different configuration is performed and results are presented.

  18. Dynamic analysis of a magnetic bearing system with flux control

    Knight, Josiah; Walsh, Thomas; Virgin, Lawrence

    1994-01-01

    Using measured values of two-dimensional forces in a magnetic actuator, equations of motion for an active magnetic bearing are presented. The presence of geometric coupling between coordinate directions causes the equations of motion to be nonlinear. Two methods are used to examine the unbalance response of the system: simulation by direct integration in time; and determination of approximate steady state solutions by harmonic balance. For relatively large values of the derivative control coefficient, the system behaves in an essentially linear manner, but for lower values of this parameter, or for higher values of the coupling coefficient, the response shows a split of amplitudes in the two principal directions. This bifurcation is sensitive to initial conditions. The harmonic balance solution shows that the separation of amplitudes actually corresponds to a change in stability of multiple coexisting solutions.

  19. Rotor Vibration Reduction via Active Hybrid Bearings

    Nicoletti, Rodrigo; Santos, Ilmar

    2002-01-01

    The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... orifices machined in the bearing pads, one can alter the machine dynamic characteristics, thus enhancing its operational range. A mathematical model of the rotor-bearing system, as well as of the hydraulic system, is presented. Numerical results of the system frequency response show good agreement with...

  20. On-line parameter estimation of a magnetic bearing

    Delpoux, Romain; Floquet, Thierry

    2011-01-01

    This article presents a parameter estimation algorithm for a magnetic bearing. Such process have strongly nonlinear dynamics andare inherently unstable systems. A simplified model of the magnetic bearing is developed in order to be able to estimate certain parameters. These parameters are difficult to measure, and may slightly vary over time. The expression of the estimates is written as a function of integrals of the inputs and outputs of the system. The experiments show a fast and robust on...

  1. An Integrated Magnetic Circuit Model and Finite Element Model Approach to Magnetic Bearing Design

    Provenza, Andrew J.; Kenny, Andrew; Palazzolo, Alan B.

    2003-01-01

    A code for designing magnetic bearings is described. The code generates curves from magnetic circuit equations relating important bearing performance parameters. Bearing parameters selected from the curves by a designer to meet the requirements of a particular application are input directly by the code into a three-dimensional finite element analysis preprocessor. This means that a three-dimensional computer model of the bearing being developed is immediately available for viewing. The finite element model solution can be used to show areas of magnetic saturation and make more accurate predictions of the bearing load capacity, current stiffness, position stiffness, and inductance than the magnetic circuit equations did at the start of the design process. In summary, the code combines one-dimensional and three-dimensional modeling methods for designing magnetic bearings.

  2. Magnetic bearings: A key technology for advanced rocket engines?

    Girault, J. PH.

    1992-01-01

    For several years, active magnetic bearings (AMB) have demonstrated their capabilities in many fields, from industrial compressors to control wheel suspension for spacecraft. Despite this broad area, no significant advance has been observed in rocket propulsion turbomachinery, where size, efficiency, and cost are crucial design criteria. To this respect, Societe Europeenne de Propulsion (SEP) had funded for several years significant efforts to delineate the advantages and drawbacks of AMB applied to rocket propulsion systems. Objectives of this work, relative technological basis, and improvements are described and illustrated by advanced turbopump layouts. Profiting from the advantages of compact design in cryogenic environments, the designs show considerable improvements in engine life, performances, and reliability. However, these conclusions should still be tempered by high recurrent costs, mainly due to the space-rated electronics. Development work focused on this point and evolution of electronics show the possibility to decrease production costs by an order of magnitude.

  3. CONTROL SYSTEM OF MAGNETIC BEARINGS BASED ON LINEAR QUADRATIC METHOD OF OPTIMAL CONTROL STRATEGY

    Zhu Huangqiu

    2005-01-01

    A state equation for radical 4-degree-of-freedom active magnetic bearings is built, and the approach on how to use linear quadratic method of optical control theory to design a centralized and decentralized parameters control system is introduced, and also Matlab language is used to simulate and analyze. The simulation results have proved that the differences are small between centralized parameters and decentralized parameters control system. The conclusions of experiments have shown that decentralized controllers designed from optimal state feedback theory meet the requirements of active magnetic bearing system. The vibration amplitude of the rotor is about 20 μm when the speed of the rotor runs between 0 to 60 000 r/min. This method may be used in the study and design of controllers of magnetic bearings.

  4. Sudden venting test of an emergency bearing for the magnet bearing type compound molecular pump

    The vacuum evacuation system for nuclear fusion reactors bears the role of exhausting hydrogen isotopes in large quantity together with helium continuously for long hours, and as the high vacuum pumps for this purpose, the mechanical pumps which can do continuous evacuation and decrease the quantity of staying radioactive tritium, such as turbo molecular pumps and compound molecular pumps, are promising. Because of the compatibility with tritium, oil lubrication is not desirable, accordingly, the pumps with ceramic rotating vanes and magnetic bearings are demanded. As a part of the development of a magnetic bearing type mechanical pump which can be used for nuclear fusion reactors, the compound molecular pump, in which emergency bearings were incorporated, was made for trial, and the test of sudden air intrusion was carried out, as the results, various knowledges were obtained. The constitution of the testing setup, and the test results are reported. When air was injected at the pressure rise of 3.3x104 Pa/s from exhaust port side, after about 2.5 s, the maximum lift of 4.2x103 N arose. When air was injected at the pressure rise of 2.7x105 Pa/s from the suction part side, after about 0.4s, the maximum lift of 6.9x103 N arose. In the air injection alternately from the suction port and exhaust port sides, the emergency bearings functioned normally in 10 times of the test. (K.I.)

  5. Development of a dc motor with virtually zero powered magnetic bearing

    1971-01-01

    The development of magnetic bearings for use in direct current electric motors is discussed. The characteristics of the magnets used in the construction of the bearings are described. A magnetic bearing using steel armoring on permanent magnets was selected for performance tests. The specifications of the motor are presented. The test equipment used in the evaluation is described.

  6. A spindle running on a five axes magnetic suspension based on conical bearings

    Carabelli, S.; Delprete, C.; Genta, G.; Moretto, I.

    1995-12-31

    The study and design of a small electric high-speed spindle based on two conical active magnetic bearings are described. The machine has been designed to simulate the rotor of a small turbo-compressor for the air conditioning unit of a small high performance aircraft. The two radial-axial bearings are controlled by a conventional five-axes decentralized compensator. The electromechanical components have been optimized for lightness and low cost. The unit here described constitutes an experimental rig for future studies in the field of magnetic suspension systems for high speed, small size rotating machinery.

  7. Rotational characteristics in the resonance state of the HTSC-permanent magnet hybrid magnetic bearing

    The hybrid magnetic bearing has been developed. In the hybrid system, effect of the pinning force becomes smaller. Influence of the vibration and the gradient angle in the resonance state is large. The resonance frequency becomes small in the hybrid bearing system. The hybrid magnetic bearing using permanent magnets and the high-Tc bulk superconductor (HTSC) has been developed. Repulsive force of the permanent magnet is introduced to increase the load weight of the magnetic bearing. Effect of the hybrid system has been shown. In this paper, influence of the hybrid system on the dynamic characteristics of the rotor is studied. The rotational characteristics in the mechanical resonance state are studied, and the equivalent magnetic spring coefficient is estimated from the experimental results of the load weight. The resonance frequency is measured by the rotation experiments. The rotor achieves stable levitation even in the resonance state. In the hybrid system, effect of the pinning force becomes smaller than that of the lateral force generated by the repulsive force between the two permanent magnets at the smaller air gap. Thus influence of the lateral vibration and the gradient angle in the resonance state becomes larger at a smaller air gap. The equivalent magnetic spring coefficient becomes also small, and the resonance frequency becomes small in the hybrid bearing system.

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

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

    2011-05-01

    In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD. PMID:21595710

  9. Electrostatic stabilizer for a passive magnetic bearing system

    Post, Richard F.

    2015-11-24

    Electrostatic stabilizers are provided for passive bearing systems composed of annular magnets having a net positive stiffness against radial displacements and that have a negative stiffness for vertical displacements, resulting in a vertical instability. Further embodiments are shown of a radial electrostatic stabilizer geometry (using circuitry similar to that employed in the vertical stabilizer). This version is suitable for stabilizing radial (lateral) displacements of a rotor that is levitated by annular permanent magnets that are stable against vertical displacements but are unstable against radial displacements.

  10. STUDY ON CATASTROPHIC MECHANISM FOR ROTOR DROP TRANSIENT VIBRATION FOLLOWING MAGNETIC BEARING FAILURE

    方之楚

    2002-01-01

    The nonlinear and transient vibration of a rotor, which dropped onto back-up bearings when its active magnetic bearings were out of order, was investigated. After strictly deriving its equations of motion and performing numerical simulations, the timehistories of rotating speed of the dropping rotor, and normal force at the rubbing contact point as well as the frequency spectrum of the vibration displacement of back-up bearings are fully analyzed. It is found that the strong and unsteady forced bending vibration of the unbalanced and damped rotor decelerating through its first bending vibtation of the unbalanced and damped rotor decelerating through its first critical speed as well as chattering at high frequencies caused by the nonlinearity at the rubbing contact point between the journal and back-up bearings may lead to the catastrophic damage of the system.

  11. Stability Limits of a PD Controller for a Flywheel Supported on Rigid Rotor and Magnetic Bearings

    Kascak, Albert F.; Brown, Gerald V.; Jansen, Ralph H.; Dever, TImothy P.

    2006-01-01

    Active magnetic bearings are used to provide a long-life, low-loss suspension of a high-speed flywheel rotor. This paper describes a modeling effort used to understand the stability boundaries of the PD controller used to control the active magnetic bearings on a high speed test rig. Limits of stability are described in terms of allowable stiffness and damping values which result in stable levitation of the nonrotating rig. Small signal stability limits for the system is defined as a nongrowth in vibration amplitude of a small disturbance. A simple mass-force model was analyzed. The force resulting from the magnetic bearing was linearized to include negative displacement stiffness and a current stiffness. The current stiffness was then used in a PD controller. The phase lag of the control loop was modeled by a simple time delay. The stability limits and the associated vibration frequencies were measured and compared to the theoretical values. The results show a region on stiffness versus damping plot that have the same qualitative tendencies as experimental measurements. The resulting stability model was then extended to a flywheel system. The rotor dynamics of the flywheel was modeled using a rigid rotor supported on magnetic bearings. The equations of motion were written for the center of mass and a small angle linearization of the rotations about the center of mass. The stability limits and the associated vibration frequencies were found as a function of nondimensional magnetic bearing stiffness and damping and nondimensional parameters of flywheel speed and time delay.

  12. Bear

    2005-01-01

    The famous physicist made for his scholars this riddle. A fellow encountered a bear in a wasteland. There was nobody else there. Both were frightened and ran away. Fellow to the north, bear to the west. Suddenly the fellow stopped, aimed his gun to the south and shot the bear. What colour was the bear?

  13. Fully Suspended, Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig With Forced Excitation

    Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Montague, Gerald; Duffy, Kirsten; Mehmed, Oral; Johnson, Dexter; Jansen, Ralph

    2004-01-01

    The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig, a significant advancement in the Dynamic Spin Rig (DSR), is used to perform vibration tests of turbomachinery blades and components under rotating and nonrotating conditions in a vacuum. The rig has as its critical components three magnetic bearings: two heteropolar radial active magnetic bearings and a magnetic thrust bearing. The bearing configuration allows full vertical rotor magnetic suspension along with a feed-forward control feature, which will enable the excitation of various natural blade modes in bladed disk test articles. The theoretical, mechanical, electrical, and electronic aspects of the rig are discussed. Also presented are the forced-excitation results of a fully levitated, rotating and nonrotating, unbladed rotor and a fully levitated, rotating and nonrotating, bladed rotor in which a pair of blades was arranged 180 degrees apart from each other. These tests include the bounce mode excitation of the rotor in which the rotor was excited at the blade natural frequency of 144 Hz. The rotor natural mode frequency of 355 Hz was discerned from the plot of acceleration versus frequency. For nonrotating blades, a blade-tip excitation amplitude of approximately 100 g/A was achieved at the first-bending critical (approximately 144 Hz) and at the first-torsional and second-bending blade modes. A blade-tip displacement of 70 mils was achieved at the first-bending critical by exciting the blades at a forced-excitation phase angle of 908 relative to the vertical plane containing the blades while simultaneously rotating the shaft at 3000 rpm.

  14. Preparation of Myeloid Derived Suppressor Cells (MDSC) from Naive and Pancreatic Tumor-bearing Mice using Flow Cytometry and Automated Magnetic Activated Cell Sorting (AutoMACS)

    Nelson, Nadine; Szekeres, Karoly; Cooper, Denise; Ghansah, Tomar

    2012-01-01

    MDSC are a heterogeneous population of immature macrophages, dendritic cells and granulocytes that accumulate in lymphoid organs in pathological conditions including parasitic infection, inflammation, traumatic stress, graft-versus-host disease, diabetes and cancer1-7. In mice, MDSC express Mac-1 (CD11b) and Gr-1 (Ly6G and Ly6C) surface antigens7. It is important to note that MDSC are well studied in various tumor-bearing hosts where they are significantly expanded and suppress anti-tumor imm...

  15. Development of magnetic bearing system for a new third-generation blood pump.

    Lee, Jung Joo; Ahn, Chi Bum; Choi, Jaesoon; Park, Jun Woo; Song, Seung-Joon; Sun, Kyung

    2011-11-01

    A magnetic bearing system is a crucial component in a third-generation blood pump, particularly when we consider aspects such as system durability and blood compatibility. Many factors such as efficiency, occupying volume, hemodynamic stability in the flow path, mechanical stability, and stiffness need to be considered for the use of a magnetic bearing system in a third-generation blood pump, and a number of studies have been conducted to develop novel magnetic bearing design for better handling of these factors. In this study, we developed and evaluated a new magnetic bearing system having a motor for a new third-generation blood pump. This magnetic bearing system consists of a magnetic levitation compartment and a brushless direct current (BLDC) motor compartment. The active-control degree of freedom is one; this control is used for controlling the levitation in the axial direction. The levitation in the radial direction has a passive magnetic levitation structure. In order to improve the system efficiency, we separated the magnetic circuit for axial levitation by using a magnetic circuit for motor drive. Each magnetic circuit in the bearing system was designed to have a minimum gap by placing mechanical parts, such as the impeller blades, outside the circuit. A custom-designed noncontact gap sensor was used for minimizing the system volume. We fabricated an experimental prototype of the proposed magnetic bearing system and evaluated its performance by a control system using the Matlab xPC Target system. The noncontact gap sensor was an eddy current gap sensor with an outer diameter of 2.38 mm, thickness of 0.88 mm, and resolution of 5 µm. The BLDC motor compartment was designed to have an outer diameter of 20 mm, length of 28.75 mm, and power of 4.5 W. It exhibited a torque of 8.6 mNm at 5000 rpm. The entire bearing system, including the motor and the sensor, had an outer diameter of 22 mm and a length of 97 mm. The prototype exhibited sufficient levitation

  16. Stability of multi orifice active tilting-pad journal bearings

    Haugaard, Asger M.; Santos, Ilmar

    2010-01-01

    The stability properties of actively lubricated tilting-pad journal bearings are investigated theoretically. The bearing preload factor and control system gains are varied, and stable and unstable regions are identified. It is seen, that the control system influences bearing stability, and that the...... nature and magnitude of this influence depends on the rotor mass, preload factor and rotational speed. Furthermore, it is shown that assuming the bearing pads to be rigid can produce a substantial error. A rigid pad model will overpredict the stable range of the bearing, thus it may lead to failure if...

  17. Influence of backup bearings and support structure dynamics on the behavior of rotors with active supports

    Flowers, George T.

    1995-01-01

    Progress made in the current year is listed, and the following papers are included in the appendix: Steady-State Dynamic Behavior of an Auxiliary Bearing Supported Rotor System; Dynamic Behavior of a Magnetic Bearing Supported Jet Engine Rotor with Auxiliary Bearings; Dynamic Modelling and Response Characteristics of a Magnetic Bearing Rotor System with Auxiliary Bearings; and Synchronous Dynamics of a Coupled Shaft/Bearing/Housing System with Auxiliary Support from a Clearance Bearing: Analysis and Experiment.

  18. Experimental investigations of active air bearings

    Santos, Ilmar; Morosi, Stefano

    2012-01-01

    greatest challenges in a high-speed gas bearing design. A great deal of research is devoted to attack such issues, where most propose passive designs such as compliant foil bearings, tilting pad and flexure pivot gas bearings. These solutions proved to be effective in improving static and dynamic......Along with traditional oil lubrication, increasing demand for high-speed applications has renewed attention to gas bearings technology. Traditional aerostatic and aerodynamic gas lubrication has been widely used in a variety of applications, ranging from high-speed spindles to micro and meso......-scale turbomachinery. The present paper deals with experimental rotordynamic testing of a flexible rotor supported by hybrid aerostaticaerodynamic gas journal bearing equipped with an electronic radial air injection system. From a rotordynamic point of view there are two phenomena that limit the widespread of...

  19. An Air Bearing Rotating Coil Magnetic Measurement System

    Gottschalk, Stephen C; Taylor, David J; Thayer, William

    2005-01-01

    This paper describes a rotating coil magnetic measurement system supported on air bearings. The design is optimized for measurements of 0.1micron magnetic centerline changes on long, small aperture quadrupoles. Graphite impregnated epoxy resin is used for the coil holder and coil winding forms. Coil holder diameter is 11 mm with a length between supports of 750mm. A pair of coils is used to permit quadrupole bucking during centerline measurements. Coil length is 616mm, inner radius 1.82mm, outer radius 4.74mm. The key features of the mechanical system are simplicity; air bearings for accurate, repeatable measurements without needing warm up time and a vibration isolated stand that uses a steel-topped Newport optical table with air suspension. Coil rotation is achieved by a low noise servo motor controlled by a standalone Ethernet servo board running custom servo software. Coil calibration procedures that correct wire placement errors, tests for mechanical resonances, and other system checks will also be discu...

  20. Mechanical Characteristics of a Thrust Magnetic Bearing%推力轴承的力学特性

    2000-01-01

    Static and dynamic mechanical characteristics of a thrustmagnetic bearing are studied owing to the inclination of the runner disk. The application refers to a thrust magnetic bearing for a turbo-expander/compressor. The static tilt of the runner disk has remarkable influence on the mechanical characteristics of thrust magnetic bearing, it can change the static load distribution between two radial magnetic bearings and will exert violent coupling effect among a thrust magnetic bearing and two radial magnetic bearings. Such a finding can be used for the coupled electromechanical dynamics analysis of rotor system equipped with magnetic bearings.

  1. Optimization of a Hybrid Magnetic Bearing for a Magnetically Levitated Blood Pump via 3-D FEA

    Cheng, Shanbao; Olles, Mark W.; Burger, Aaron F.; Steven W Day

    2011-01-01

    In order to improve the performance of a magnetically levitated (maglev) axial flow blood pump, three-dimensional (3-D) finite element analysis (FEA) was used to optimize the design of a hybrid magnetic bearing (HMB). Radial, axial, and current stiffness of multiple design variations of the HMB were calculated using a 3-D FEA package and verified by experimental results. As compared with the original design, the optimized HMB had twice the axial stiffness with the resulting increase of negati...

  2. Local Attitudes towards Bear Management after Illegal Feeding and Problem Bear Activity

    David Fraser

    2013-09-01

    Full Text Available The “pot bears” received international media attention in 2010 after police discovered the intentional feeding of over 20 black bears during the investigation of an alleged marijuana-growing operation in Christina Lake, British Columbia, Canada. A two-phase random digit dialing survey of the community was conducted in 2011 to understand local perspectives on bear policy and management, before and after a summer of problem bear activity and government interventions. Of the 159 households surveyed in February 2011, most had neutral or positive attitudes towards bears in general, and supported the initial decision to feed the food-conditioned bears until the autumn hibernation. In contrast to wildlife experts however, most participants supported relocating the problem bears, or allowing them to remain in the area, ahead of killing; in part this arose from notions of fairness despite the acknowledged problems of relocation. Most locals were aware of the years of feeding but did not report it, evidently failing to see it as a serious form of harm, even after many bears had been killed. This underscores the importance of preventive action on wildlife feeding and the need to narrow the gap between public and expert opinion on the likely effects of relocation versus killing.

  3. The role of superconductivity in magnetic bearings for high-load applications

    Downer, James; Eisenhaure, David

    1993-01-01

    Slewing of large payloads will require control torque and angular momentum storage capacities that are large in comparison to the capabilities of available control moment gyros (CMG's). SatCon Technology Corporation is currently designing a CMG which may be employed as a slew actuator for large spacecraft or other payloads. The slew actuator employs a type of magnetic bearing which may be used in high load applications. The magnetic bearing is also used to fully gimbal the suspended rotor of the slew actuator. The use of magnetic bearings in angular momentum exchange actuators has the primary advantage that physical contact between the rotor and stator is eliminated. This leads to greatly extended life, increased reliability, and reduced vibrations. Several actuators operating on magnetic bearings have been demonstrated in previous research efforts. These were sized for use in small satellites. For conventional magnetic bearings, which employ magnetic cores, high torsional loading may require that the magnetic structure be excessively massive. An alternative magnetic bearing design which employs a superconducting coil and eliminates conventional magnetic structures is discussed. The baseline approach is to replace the field coil of a conventional magnetic bearing with the superconducting coil.

  4. Computational Analysis of Static and Dynamic Behaviour of Magnetic Suspensions and Magnetic Bearings

    Britcher, Colin P. (Editor); Groom, Nelson J.

    1996-01-01

    Static modelling of magnetic bearings is often carried out using magnetic circuit theory. This theory cannot easily include nonlinear effects such as magnetic saturation or the fringing of flux in air-gaps. Modern computational tools are able to accurately model complex magnetic bearing geometries, provided some care is exercised. In magnetic suspension applications, the magnetic fields are highly three-dimensional and require computational tools for the solution of most problems of interest. The dynamics of a magnetic bearing or magnetic suspension system can be strongly affected by eddy currents. Eddy currents are present whenever a time-varying magnetic flux penetrates a conducting medium. The direction of flow of the eddy current is such as to reduce the rate-of-change of flux. Analytic solutions for eddy currents are available for some simplified geometries, but complex geometries must be solved by computation. It is only in recent years that such computations have been considered truly practical. At NASA Langley Research Center, state-of-the-art finite-element computer codes, 'OPERA', 'TOSCA' and 'ELEKTRA' have recently been installed and applied to the magnetostatic and eddy current problems. This paper reviews results of theoretical analyses which suggest general forms of mathematical models for eddy currents, together with computational results. A simplified circuit-based eddy current model proposed appears to predict the observed trends in the case of large eddy current circuits in conducting non-magnetic material. A much more difficult case is seen to be that of eddy currents in magnetic material, or in non-magnetic material at higher frequencies, due to the lower skin depths. Even here, the dissipative behavior has been shown to yield at least somewhat to linear modelling. Magnetostatic and eddy current computations have been carried out relating to the Annular Suspension and Pointing System, a prototype for a space payload pointing and vibration

  5. Experimental Grey Box Model Identification of an Active Gas Bearing

    Theisen, Lukas Roy Svane; Pierart Vásquez, Fabián Gonzalo; Niemann, Hans Henrik;

    2014-01-01

    Gas bearings have inherent dynamics that gives rise to low damping and potential instability at certain rotational speeds. Required damping and stabilization properties can be achieved by active ow control if bearing parameters are known. This paper deals with identifacation of parameters in a...... dynamic model of an active gas bearing and subsequent control loop design. A grey box model is determined based on experiments where piezo actuated valves are used to perturb the journal and hence excite the rotor-bearing system. Such modelling from actuator to output is shown to effciently support...... controller design, in contrast to impact models that focus on resonance dynamics. The identified model is able to accurately reproduce the lateral dynamics of the rotor-bearing system in a desired operating range, in this case around the first two natural frequencies. The identified models are validated and...

  6. Performance of a continuous flow ventricular assist device: magnetic bearing design, construction, and testing.

    Allaire, P; Hilton, E; Baloh, M; Maslen, E; Bearnson, G; Noh, D; Khanwilkar, P; Olsen, D

    1998-06-01

    A new centrifugal continuous flow ventricular assist device, the CFVAD III, which is fully magnetic bearing suspended, has been developed. It has only one moving part (the impeller), has no contact (magnetic suspension), is compact, and has minimal heating. A centrifugal impeller of 2 inch outer diameter is driven by a permanent magnet brushless DC motor. This paper discusses the design, construction, testing, and performance of the magnetic bearings in the unit. The magnetic suspension consists of an inlet side magnetic bearing and an outlet side magnetic bearing, each divided into 8 pole segments to control axial and radial displacements as well as angular displacements. The magnetic actuators are composed of several different materials to minimize size and weight while having sufficient load capacity to support the forces on the impeller. Flux levels in the range of 0.1 T are employed in the magnetic bearings. Self sensing electronic circuits (without physical sensors) are employed to determine the impellar position and provide the feedback control signal needed for the magnetic bearing control loops. The sensors provide position sensitivity of approximately 0.025 mm. A decentralized 5 axis controller has been developed using modal control techniques. Proportional integral derivative controls are used for each axis to levitate the magnetically supported impeller. PMID:9650668

  7. Schemes for applying active lubrication to main engine bearings

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    The work presented here is a theoretical study that describes two different schemes for the oil injection system in actively lubricated main engine bearings. The use of active lubrication in journal bearings helps to enhance the hydrodynamic fluid film by increasing the fluid film thickness and...... orifices circumferentially located around the bearing surface. The pressure distribution of the hydrodynamic fluid film in journal bearings is governed by the Reynolds equation, which is modified to accommodate the dynamics of active lubrication, and which can be numerically solved using finite...... consequently reducing viscous friction losses and vibrations. One refers to active lubrication when conventional hydrodynamic lubrication is combined with dynamically modified hydrostatic lubrication. In this case, the hydrostatic lubrication is modified by injecting oil at controllable pressures, through...

  8. Development of superconducting magnetic bearing with superconducting coil and bulk superconductor for flywheel energy storage system

    Highlights: •We have proposed superconducting (SC) magnetic bearings using SC coil and bulks. •We manufactured a small scale test device based on our concept. •The device levitated a rotor without mechanical contact. •The rotor was rotated contactless over 2000 rpm. •We have demonstrated our SC magnetic bearing feasibility using the device. -- Abstract: We have been developing superconducting magnetic bearing for flywheel energy storage system to be applied to the railway system. The bearing consists of a superconducting coil as a stator and bulk superconductors as a rotor. A flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs). We have manufactured a small scale device equipped with the SMB. The flywheel was rotated contactless over 2000 rpm which was a frequency between its rigid body mode and elastic mode. The feasibility of this SMB structure was demonstrated

  9. Research on analytical model and design formulas of permanent magnetic bearings based on Halbach array with arbitrary segmented magnetized angle

    Wang, Nianxian; Wang, Dongxiong; Chen, Kuisheng; Wu, Huachun

    2016-07-01

    The bearing capacity of permanent magnetic bearings can be improved efficiently by using the Halbach array magnetization. However, the research on analytical model of Halbach array PMBs with arbitrary segmented magnetized angle has not been developed. The application of Halbach array PMBs has been limited by the absence of the analytical model and design formulas. In this research, the Halbach array PMBs with arbitrary segmented magnetized angle has been studied. The magnetization model of bearings is established. The magnetic field distribution model of the permanent magnet array is established by using the scalar magnetic potential model. On the basis of this, the bearing force model and the bearing stiffness model of the PMBs are established based on the virtual displacement method. The influence of the pair of magnetic rings in one cycle and the structure parameters of PMBs on the maximal bearing capacity and support stiffness characteristics are studied. The reference factors for the design process of PMBs have been given. Finally, the theoretical model and the conclusions are verified by the finite element analysis.

  10. Research of Digital Power Amplifier Simulation for High-power Blower with Active Magnetic Bearing%大功率磁悬浮鼓风机数字功放的仿真研究

    于文涛; 刘淑琴

    2011-01-01

    High-power blower with active magnetic bearing (AMB) has advantages of small, high speed, high reliability, low noise, it uses three-level digital switching power amplifier base on field programmable gate array (FPGA). Using Matlab/Simulink power system blackset library to complete the model of half-bridge circuit and current sensing circuit, simulate the FPGA internal data processing by embedded M-function modules.The simulation and experimental results verify the correctness of this method of modeling.It provides a new accurate method for simulation of digital circuit power amplifier.%大功率磁悬浮轴承鼓风机具有体积小、转速高、可靠性高、噪音低等优点,其功率放大器采用基于现场可编程门阵列(FPGA)的三电平PWM数字功放,应用Matlab/Simulink中基于电力系统模块集库,完成数字功放电路中的半桥电路和电流采样电路的建模,通过植入M函数文件内嵌功能模块模拟了FPGA内部的数据处理流程.仿真与实验结果验证了该建模方法的正确性,为数字电路功放的仿真提供了新的准确方法.

  11. 三相交流主动磁轴承参数设计与特性分析%Parameter Design and Characteristic Analysis for Three-Phase AC Active Magnetic Bearing

    诸德宏; 程新; 朱熀秋

    2009-01-01

    A mathematical model of the suspension forces is established for three-phase inverter-fed AC radial magnetic bearings. According to the requirement the suspension forces, parameters of an experimental prototype are calculated. The magnetic field and suspension forces of the rotor are verified using Ansoft. Nonlinearity of the suspension forces and the coupling characteristics of the movement between two degrees of freedom around the balance position are calculated and analyzed. The results show that the mechanical configuration and magnetic circuits of the magnetic bearing are correct, and the suspension magnetic forces satisfy the design requirement. Suspension forces have good linearity and symmetry around the balance position, and the movement of two degrees of freedom around balance position has no coupling.%建立了一种三相逆变器驱动的交流主动磁轴承的悬浮力数学模型,根据实验样机悬浮磁力的要求,给出了实验样机参数计算过程.利用Ansoft对该结构磁轴承的磁场和转子受力情况进行仿真验算,并对磁轴承悬浮力非线性和转子在平衡位置附近的运动耦合性进行了计算分析.研究结果表明:这种磁轴承机械和磁路结构合理,悬浮磁力满足设计要求,悬浮力在平衡位置附近具有较好的线性和对称性,二自由度运动几乎没有耦合.

  12. PARAMETER DESIGN AND FINITE ELEMENT ANALYSIS FOR RADIALAXIAL ACTIVE MAGNETIC BEARING WITH SHARING BIASED CURRENT%径向一轴向共用偏磁电流的主动磁轴承结构参数设计与有限元分析

    诸德宏; 卢立户; 刘海娟; 程新; 王鹏

    2011-01-01

    The configuration and working principle of a novel radial-axial active magnetic bearing with sharing biased magnetic current were introduced. The flux path was calculated by using the equivalent magnetic circuit, and the mathematical models of suspension forces were deduced. According to design desire of the suspension forces, the experiment prototype of the novel magnetic bearing was designed . The experiment prototype of the novel magnetic bearing' s flux path is analyzed by finite element Ansoft software. The results of theory analysis and finite element analysis have shown that the mechanical configuration and magnetic circuits of the magnetic bearing are reasonable, and the suspension forces are satisfied design desire, and the movement and magnetic circuits among 3 degrees of freedom around the balanceable position have almost no coupling, and using independent PID(proportion integration differentiation) control among 3 degrees of freedom for this novel magnetic bearing and greatly simplifying the control system.%介绍一种新型径向一轴向共用偏磁电流的主动磁轴承的基本结构和工作机理,用等效磁路法对该磁轴承的磁路进行计算,得到悬浮力数学模型;根据悬浮力要求设计实验样机参数,利用有限元Ansoft软件对磁轴承样机的磁路进行有限元分析.理论研究和有限元分析结果表明,该磁轴承机械和磁路结构合理,悬浮力满足设计要求,各自由度在平衡位置附近运动,与磁路没有耦合,对各自由度可采用分散的PID(proportion integration differentiation)对其进行控制,大大简化控制系统.

  13. Design and implementation of an active rectangular aerostatic thrust bearing stage with electromagnetic actuators

    MAO JunHong; LI LiChuan

    2009-01-01

    The design and implementation of an active rectangular aerostaUc thrust bearing stage with electro-magnetic actuators are presented. The stage is fundamentally precise and simple since the out-of-plane degree-of-freedoms (DOF) of a thrust air bearing are closed-loop controlled by electromagnetic actua-tors. The design is one-moving-part with mechanical symmetry, and a commercially available air bear-ing is rigidly attached to the table. The actuators are four independent coils mounted to the guiding surface of the table with iron cores, which are directly machined on the table. A bench level prototype system is developed and out-of-plane axes decoupled models of the system are derived. A control al-gorithm synthesized by arbitrarily placing closed-loop poles according to the model with air bearing dynamics neglected is implemented by C programming language running on the DOS platform. The stage is capable of vertical direction precision micro-positioning and guiding 3-DOF plane motions without limiting the working range of plane motions. Positioning accuracy of the stage no longer de-pends upon design and manufacturing of an air bearing, while passive preload of the stage for a flat film aerostatic thrust bearing is eliminated.

  14. A magnetic bearing based on eddy-current repulsion

    Nikolajsen, J. L.

    1987-01-01

    This paper describes a new type of electromagnetic bearing, called the Eddy-Current Bearing, which works by repulsion between fixed AC-electromagnets and a conducting rotor. The following advantages are expected: inherent stability, higher load carrying capacity than DC-electromagnetic bearings, simultaneous radial, angular and thrust support, motoring and generating capability, and backup mode of operation in case of primary power failure. A prototype is under construction.

  15. A permanent-magnet rotor for a high-temperature superconducting bearing

    Mulcahy, T.M.; Hull, J.R.; Uherka, K.L. [Argonne National Lab., IL (United States); Abboud, R.G. [Commonwealth Research Corp., Chicago, IL (United States); Wise, J.H.; Carnegie, D.W. [Pennsylvania State Univ., University Park, PA (United States). Engineering Science

    1995-07-01

    Design, fabrication, and performance, of a 1/3-m dia., 10-kg flywheel rotor with only one bearing is discussed. To achieve low-loss energy storage, the rotor`s segmented-ring permanent-magnet (PM) is optimized for levitation and circumferential homogeneity. The magnet`s carbon composite bands enable practical energy storage.

  16. PRINCIPLES AND PARAMETER DESIGN FOR AC-DC THREE-DEGREE FREEDOM HYBRID MAGNETIC BEARINGS

    ZHU Huangqiu; XIE Zhiyi; ZHU Dehong

    2006-01-01

    To simplify the mechanical structure, decrease the overall system size of the 3-degree freedom axial-radial magnetic bearings and reduce the manufacturing costs as well as operating costs,an innovated AC-DC 3-degree freedom hybrid magnetic bearing is proposed, which is driven by a DC amplifier in axial direction and a 3-phase power converter in radial directions respectively, and the axial and radial bias magnetic fluxes are provided with a common radial polarized permanent magnet ring. The principle producing magnetic suspension forces is introduced. By using equivalent magnetic circuit method, the calculation formulas of magnetic suspension forces and the mathematics models of the system are deduced. Nonlinearities of suspension forces and cross coupling between different degree freedoms are studied further by calculating the suspension forces at different displacements and control currents to validate the feasibility of the mathematics model. Then based on the mathematics models of the bearing, a control method of this novel bearing is designed. Lastly, the methods on parameter design and calculations of the bearing are presented, and an applicable prototype is simulated to analyze the magnetic path by using finite element analysis. The theory analysis and simulation results have shown that this magnetic bearing incorporates the merits of 3-phase AC drive, permanent magnet flux biased and axial-radial combined control, and reduces overall system size and has higher efficiency and lower cost. This innovated magnetic bearing has a wide application in super-speed and super-precision numerical control machine tools, bearingless motors, high-speed flywheels, satellites, etc.

  17. A novel permanent magnetic bearing and its anti-wear effect in impeller total artificial heart

    2003-01-01

    A novel permanent magnetic bearing has been developed, which consists of two magnetic rings with different dimensions in the same direction of axial magnetization, located concentrically. Because of the effect of magnetic field, the magnetic rings keep a distance axially from each other. If the distance between the two rings changes, a rehabilitation force is produced to return to the original position. When this distance decreases, a repelling force will be generated; its component in axial direction can be used as a magnetic spring and its radial component can function as a bearing. With this novel permanent magnetic bearing, an impeller total artificial heart (TAH) is designed, manufactured and tested. The rotation is driven radially. On the left and right sides of the rotor magnets, two small magnetic rings are fixed onto the rotor, coupling with two big magnetic rings on both sides of the motor coil, to form the magnetic bearings. Hereby the bearings are used for wear reduction rather than rotor levitation. That means the magnetic bearings counteract the attractive force between the motor coil iron and rotor magnets so as to reduce the friction between the motor stator and rotor. At the left and right ends of the rotor, two impellers with the same width but different diameters are mounted. Thus the device has only one moving part-rotor; both the left pump and the right pump eject the blood synchronically; the volume equilibrium of both pumps can be achieved automatically without need of control. The device weighing 250 g has a length of 60 mm and a diameter of 40 mm at its largest point, and can produce a blood flow up to 150 mm Hg and 6 L/min from left pump, 50 mm Hg and 6 L/min from right pump, at rotating speed of 4000 r/min of the motor. The consumed power is under 10 W.

  18. Pneumatic locking device for magnetic bearing reaction wheel

    Privat, Michel; da Costa, Arlindo

    2003-09-01

    Due to the launch vibration environment, the use of locking device is necessary for large or heavy mechanisms. This remark is true in particular for the inertial actuators like magnetic bearing reaction wheels. These actuators have a rotor that is in magnetic levitation without any contact with the stator. Locking device is mandatory to maintain the rotor during the launch vibrations. To avoid contact between rotor and stator during the functional phase, the link created by the locking device must be completely released. This article presents a pneumatic locking device with pyrotechnical sub-systems that have been realised by "ALCATEL Space Industries" for the reaction wheels development in the frame of a CNES satellites family. The first paragraph presents the wheel functioning and briefly describes the Electro-mechanical components of the reaction wheel. The second paragraph describes a device based on a metallic bellows ring. A nitrogen pressure in the ring allows pushing the rotor against the stator. The rotor release is obtained by drilling the system tubing with a pyrotechnic valve. The third point describes the qualification tests and the resulting data. Some functional tests are made in warm and cold case with the locking device in order to improve some mechanical characteristics including the locking effort generated and the leakage rate. Launch vibrations and thermal tests have been realised and the good functioning of the mechanism is proven. At the end of these tests, the qualification has been pronounced. The device is now implemented within the reaction wheel. This equipment should flight in 2004. The next paragraph presents the works realised under CNES Research and Technology contract. The objectives were the characterisation of metallic bellows and some technological studies to improve the knowledge of the mechanical and functional characteristics of these elements. The first study was to create a Finite Element model of a bellow in order to

  19. Development of an Anti-Vibration Controller for Magnetic Bearing Cooling Systems Project

    National Aeronautics and Space Administration — This proposal outlines a program to develop a vibration-free reverse-Brayton cycle cooling system using specially-tuned magnetic bearings. Such a system is critical...

  20. Method for obtaining large levitation pressure in superconducting magnetic bearings

    Hull, John R.

    1996-01-01

    A method and apparatus for compressing magnetic flux to achieve high levitation pressures. Magnetic flux produced by a magnetic flux source travels through a gap between two high temperature superconducting material structures. The gap has a varying cross-sectional area to compress the magnetic flux, providing an increased magnetic field and correspondingly increased levitation force in the gap.

  1. A Novel Integrated Structure with a Radial Displacement Sensor and a Permanent Magnet Biased Radial Magnetic Bearing

    Jinji Sun

    2014-01-01

    Full Text Available In this paper, a novel integrated structure is proposed in order to reduce the axial length of the high speed of a magnetically suspended motor (HSMSM to ensure the maximum speed, which combines radial displacement sensor probes and the permanent magnet biased radial magnetic bearing in HSMSM. The sensor probes are integrated in the magnetic bearing, and the sensor preamplifiers are placed in the control system of the HSMSM, separate from the sensor probes. The proposed integrated structure can save space in HSMSMs, improve the working frequency, reduce the influence of temperature on the sensor circuit, and improve the stability of HSMSMs.

  2. Dynamical analysis of a flywheel-superconducting bearing with a moving magnet support

    A lateral stiffness improvement approach based on a moving magnet support is developed to reduce the vibration of a flywheel rotor-high temperature superconductor (HTS) bearing. A flywheel rotor levitated with an HTS bearing is modelled and then analysed with a moving stator magnet placed above the rotor. A dynamic support principle is introduced based on moving the stator magnet in anti-phase with the rotor displacement for small variations. A complete dynamical equation of the flywheel rotor is derived including gyroscopic and imbalance effects. The simulation results showed that the dynamic support of the flywheel rotor with additional stator magnet movements decreases the vibration of the flywheel rotor considerably

  3. Detail vibration analysis of magnetic bearing helium fan in high temperature reactor

    Since the pure helium environment inside the reactor, active magnetic bearing (AMB) is considered to be the best for the helium fan supported. Using AMB in such an important place, the coming problem must be solved is to know the detail rotor dynamics and vibration issue of it while the rotor length has been increased and the bearing stiffness been decreased. As most of conventional mechanical machine, this issue has to be well studied during the design stage. If the helium fan could run on 10% away from the critical speed, the risk of unexpected vibration will be well avoided, and it can fit for all the requirements as well. Better understanding of the vibration character of the helium fan rotor can help the engineer to optimum their design, not only for the rotor, but also for the active magnetic bearing. In this paper, several analyses, including modal shape, eigenfrequency, force response and gyroscopic effect influence of this helium fan rotor are processed by finite element method. On the finite element model, the helium fan is assumed to be an equal mass and equal diameter flywheel, and the elastic levitation of AMB is assumed as spring. Through some other reasonable simplifications, and some boundary condition assumptions, the analysis is processed well, and the results show the preliminary design helium fan suspended by AMB could safety run under the operating speed, even considering the gyroscopic effect. This analysis also makes us know this helium fan rotor better than before. The finite element analysis is finished by software ANSYS 8.0. (authors)

  4. Mycosynthesis of silver nanoparticles bearing antibacterial activity.

    Azmath, Pasha; Baker, Syed; Rakshith, Devaraju; Satish, Sreedharamurthy

    2016-03-01

    Mycosynthesis of silver nanoparticles was achieved by endophytic Colletotrichum sp. ALF2-6 inhabiting Andrographis paniculata. Well dispersed nanoparticles were characterized using UV-Visible spectrometry with maximum absorption conferring at 420 nm. FTIR analysis revealed possible biomolecules reducing the metal salt and stabilization of nanoparticles. XRD analysis depicted the diffraction intensities exhibiting between 20 and 80 °C at 2theta angle thus conferring the crystalline nature of nanoparticles. Morphological characteristic using TEM revealed the polydispersity of nanoparticles with size ranging from 20 to 50 nm. Synthesized nanoparticles exhibited bactericidal activity against selected human pathogens. Nanoparticles mode of action was carried out to reveal DNA damage activity. Thus the present investigation reports facile fabrication of silver nanoparticles from endophytic fungi. PMID:27013906

  5. Design and parameter estimation of hybrid magnetic bearings for blood pump applications

    Lim, Tau Meng; Zhang, Dongsheng; Yang, Juanjuan; Cheng, Shanbao; Low, Sze Hsien; Chua, Leok Poh; Wu, Xiaowei

    2009-10-01

    This paper discusses the design and parameter estimation of the dynamics characteristics of a high-speed hybrid magnetic bearings (HMBs) system for axial flow blood pump applications. The rotor/impeller of the pump is driven by a three-phase permanent magnet (PM) brushless and sensorless DC motor. It is levitated by two HMBs at both ends in five-degree-of-freedom with proportional-integral-derivative (PID) controllers; among which four radial directions are actively controlled and one axial direction is passively controlled. Test results show that the rotor can be stably supported to speeds of 14,000 rpm. The frequency domain parameter estimation technique with statistical analysis is adopted to validate the stiffness and damping coefficients of the HMBs system. A specially designed test rig facilitated the estimation of the bearing's coefficients in air—in both the radial and axial directions. The radial stiffness of the HMBs is compared to the Ansoft's Maxwell 2D/3D finite element magnetostatic results. Experimental estimation showed that the dynamics characteristics of the HMBs system are dominated by the frequency-dependent stiffness coefficients. The actuator gain was also successfully calibrated and may potentially extend the parameter estimation technique developed in the study of identification and monitoring of the pump's dynamics properties under normal operating conditions with fluid.

  6. Active Vibration Reduction Of Rigid Rotor Supported By Journal Bearings

    Ondrouch, Jan; Ferfecki, Petr; Poruba, Z.

    Gliwice: Politechnika Slaska, 2009, s. 85-90. ISBN 978-83-60102-52-7. [International Seminar of Applied Mechanics /13./. Wisla (PL), 29.05.2009-31.05.2009] Institutional research plan: CEZ:AV0Z20760514 Keywords : rotor system * hydrodynamic bearing * active vibration reduction Subject RIV: JR - Other Machinery

  7. Pressure instability of magnetic susceptibility of pyrrhotite bearing rocks from the KTB borehole

    Kapička, Aleš; Hoffmann, V.; Petrovský, Eduard

    2003-01-01

    Roč. 47, č. 2 (2003), s. 381-391. ISSN 0039-3169 Institutional research plan: CEZ:AV0Z3012916 Keywords : magnetic susceptibility * pressure treatment * pyrrhotite -bearing rocks Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.426, year: 2003

  8. Dynamic behavior of a magnetic bearing supported jet engine rotor with auxiliary bearings

    Flowers, George T.; Xie, Huajun; Sinha, S. C.

    1995-01-01

    This paper presents a study of the dynamic behavior of a rotor system supported by auxiliary bearings. The steady-state behavior of a simulation model based upon a production jet engine is explored over a wide range of operating conditions for varying rotor imbalance, support stiffness, and damping. Interesting dynamical phenomena, such as chaos, subharmonic responses, and double-valued responses, are presented and discussed.

  9. 3Dwheel: 3-axis low-noise, high-bandwidth attitude actuation from a single momentum wheel using magnetic bearings.

    Seddon, Jon; Pechev, Alexandre

    2009-01-01

    This paper proposes a new concept for attitude actuation for small satellites that uses active magnetic bearings to support and tilt a spinning rotor to provide 3-axis attitude control of the satellite using a single actuator. A controlled 3D motion in the spinning rotor provides a conventional torque output about the momentum axis and a gyroscopic torque output about any direction in the plane normal to the spinning axis. Therefore, a single tilting momentum-wheel can generate torque along t...

  10. Mechanical characterization of journal superconducting magnetic bearings: stiffness, hysteresis and force relaxation

    Superconducting magnetic bearings (SMBs) can provide stable levitation without direct contact between them and a magnetic source (typically a permanent magnet). In this context, superconducting magnetic levitation provides a new tool for mechanical engineers to design non-contact mechanisms solving the tribological problems associated with contact at very low temperatures. In the last years, different mechanisms have been proposed taking advantage of superconducting magnetic levitation. Flywheels, conveyors or mechanisms for high-precision positioning. In this work the mechanical stiffness of a journal SMBs have been experimentally studied. Both radial and axial stiffness have been considered. The influence of the size and shape of the permanent magnets (PM), the size and shape of the HTS, the polarization and poles configuration of PMs of the journal SMB have been studied experimentally. Additionally, in this work hysteresis behavior and force relaxation are considered because they are essential for mechanical engineer when designing bearings that hold levitating axles.

  11. Research on a novel high stiffness axial passive magnetic bearing for DGMSCMG

    Sun, Jinji; Wang, Chun'e.; Le, Yun

    2016-08-01

    To increase the displacement stiffness and decrease power loss of double gimbals magnetically suspended control momentum gyro (DGMSCMG), this paper researches a new structure of axial passive magnetic bearing (APMB). Different from the existing APMB, the proposed APMB is composed of segmented permanent magnets and magnetic rings. The displacement stiffness and angular stiffness expressions are derived by equivalent magnetic circuit method and infinitesimal method based on the end magnetic flux. The relationships are analyzed between stiffness and structure parameters such as length of air gap, length of permanent magnet, height of permanent magnet and end length of magnetic ring. Besides, the axial displacement stiffness measurement method of the APMB is proposed, and it verified the correctness of proposed theoretical method. The DGMSCMG prototype is manufactured and the slow-down characteristic experiment is carried out, and the experimental result reflects the low power loss feature of the APMB.

  12. A hydrodynamically suspended, magnetically sealed mechanically noncontact axial flow blood pump: design of a hydrodynamic bearing.

    Mitamura, Yoshinori; Kido, Kazuyuki; Yano, Tetsuya; Sakota, Daisuke; Yambe, Tomoyuki; Sekine, Kazumitsu; OKamoto, Eiji

    2007-03-01

    To overcome the drive shaft seal and bearing problem in rotary blood pumps, a hydrodynamic bearing, a magnetic fluid seal, and a brushless direct current (DC) motor were employed in an axial flow pump. This enabled contact-free rotation of the impeller without material wear. The axial flow pump consisted of a brushless DC motor, an impeller, and a guide vane. The motor rotor was directly connected to the impeller by a motor shaft. A hydrodynamic bearing was installed on the motor shaft. The motor and the hydrodynamic bearing were housed in a cylindrical casing and were waterproofed by a magnetic fluid seal, a mechanically noncontact seal. Impeller shaft displacement was measured using a laser sensor. Axial and radial displacements of the shaft were only a few micrometers for motor speed up to 8500 rpm. The shaft did not make contact with the bearing housing. A flow of 5 L/min was obtained at 8000 rpm at a pressure difference of 100 mm Hg. In conclusion, the axial flow blood pump consisting of a hydrodynamic bearing, a magnetic fluid seal, and a brushless DC motor provided contact-free rotation of the impeller without material wear. PMID:17343698

  13. Active Vibration Control of Rotor-Bearing Systems

    Blanco-Ortega, Andres; Silva-Navaro, Gerardo; Beltran-Carbajal, Francisco; Vela-Valdes, Luis Gerardo

    2010-01-01

    The active vibration control of a Jeffcott-like rotor through dynamic stiffness control and acceleration scheduling is addressed. The control approach consists of a servomechanism able to move one of the supporting bearings in such a way that the effective rotor length is controlled. As a consequence, the rotor stiffness and natural frequency are modified according to an off-line and smooth trajectory planning of the rotor speed/acceleration in order to reduce the unbalance response when pass...

  14. A flywheel energy storage system with permanent magnet bearing; Ein Schwungrad-Energiespeicher mit permanentmagnetischer Lagerung

    Kolk, M.

    1997-12-01

    It is the major objective of the work reported to expand the applications of radially passive permanent magnet bearings for rotors with increased mass and moment of inertia, and to show that partially passive magnetic bearings can be used for systems with high-capacity motors and generators. The following main aspects are discussed and explained: The fundamental principles and applications of flywheels; applicable magnetic bearing systems and their components; dynamic properties of a magnetically suspended rotor; design of the motor/generator unit of a flywheel system; the entire design of the prototype system developed and its essential components; safety aspects of the flywheel; power losses and power output; current applications and possible further applications of magnetically suspended flywheels; results and applications of permanent magnet bearings. (orig./CB) [Deutsch] Ein wesentliches Ziel dieser Arbeit ist, den Einsatzbereich fuer radial passive permanentmagnetische Lager fuer Rotoren mit groesserer Masse und groesserem Traegheitsmoment zu erweitern und zu zeigen, dass partiell passive Magnetlager sich auch fuer grosse Motor- und Generatorleistungen eignen. Auf folgende Schwerpunkte wird eingegangen: die Technik und die Verwendung von Schwungraedern, verschiedene Arten der Magnetlagerung und deren Komponenten, Dynamik eines magnetgelagerten Rotors, Auslegung des Motor/Generators eines Schwungradsystems, Gesamtaufbau des realisierten Prototypen und seine wesentlichen Baugruppen, Sicherheitsaspekte des Schwungrades, Verluste und Leistungsabgabe, Anwendungen und Erweiterungen des magnetgelagerten Schwungrades, Ergebnisse und Einsatzmoeglichkeiten permanentmagnetischer Lager. (orig./GL)

  15. DESIGN AND APPLICATION OF MAGNETIC BEARING SUSPENSION SYSTEM IN A THREE PHASE INDUCTION MOTOR

    Osman GÜRDAL

    1998-03-01

    Full Text Available The current popularity of suspension and levitation stems no doubt the possibilities in high-speed ground transportation schemes. Although these are both challenging and exciting, there is considerable scope for application of suspension techniques to achieving frictionless bearing. The requirement in this case is often for close tolerances, low power consumption, small airgaps and ingeneral, compactness. Thus, magnetic suspension using DC electromagnets schemes have received more attention than the other techniques of repulsion levitation. Proposed prototype system consists of a conventional stator and its rotor without iron core, set of electromagnets for suspension of rotor shaft and set of compensation circuits feedbacked by optical-transducers. Prototyped system is aimed as a laboratory demonstration tool so there is no challenging to exceed the speeds of 1500 rev/min that is the speed of motor with mechanical bearings. Magnetic bearing suspension system provides a high impact visual demonstration of many principles in undergraduate educational programs in electrical education, e.g., electromagnetic design, PD controlled compensation of a unstable control system and power amplifier design. The system is capable of giving a good comparison between mechanical and magnetic bearing up to speeds 350 rev/min. Power losses without load show about 15% reduction with magnetic bearing. The noise of the motor is also decreased to a low level.

  16. Effect of the repulsive force in the HTSC-permanent magnet hybrid bearing system

    Magnetic levitation using the pinning force of the YBaCuO high-Tc bulk superconductor (HTSC) materials has an advantage to achieve stable levitation without control. To increase levitation force, the HTSC-permanent magnet hybrid magnetic bearing system is introduced. A circular shaped three phase Nd-Fe-B permanent magnet is installed on the rotor, and HTSC bulk superconductor is set on the stator. The additional permanent magnet is installed under the HTSC. Repulsive force of the permanent magnet is used for levitation, and pinning force between the HTSC and permanent magnet is used for guidance force of the bearing. In this system, relationship between permanent magnet and the HTSC is important. When repulsive force of the permanent magnet is large, pinning force of superconductor is used to keep the rotor position. As a result, stability for the lateral direction is decreased with hybrid system. For levitation force, effect of the hybrid system is not observed with column HTSC. Compared with the ring HTSC results, the following thing is considered. Because there is no space that flux of one permanent magnet acts on the other one with the column HTSC configuration, interaction between two permanent magnets becomes small.

  17. A feasibility assessment of magnetic bearings for free-piston Stirling space power converters

    This report describes work performed by Mechanical Technology Incorporated (MTI) under NASA Contract NAS3-26061, open-quotes A Feasibility Assessment of Magnetic Bearings for Free-Piston Stirling Space Engines.close quotes The work was performed over the period from July 1990 through August 1991. The objective of the effort was to assess the feasibility and efficacy of applying magnetic bearings to free-piston Stirling-cycle power conversion machinery of the type currently being evaluated for possible use in future long-term space missions

  18. Centrifugally activated bearing for high-speed rotating machinery

    Post, Richard F.

    1994-01-01

    A centrifugally activated bearing is disclosed. The bearing includes an annular member that extends laterally and radially from a central axis. A rotating member that rotates about the central axis relative to the annular member is also included. The rotating member has an interior chamber that surrounds the central axis and in which the annular member is suspended. Furthermore, the interior chamber has a concave shape for retaining a lubricant therein while the rotating member is at rest and for retaining a lubricant therein while the rotating member is rotating. The concave shape is such that while the rotating member is rotating a centrifugal force causes a lubricant to be forced away from the central axis to form a cylindrical surface having an axis collinear with the central axis. This centrifugally displaced lubricant provides restoring forces to counteract lateral displacement during operation.

  19. Parameter estimation and actuator characteristics of hybrid magnetic bearings for axial flow blood pump applications.

    Lim, Tau Meng; Cheng, Shanbao; Chua, Leok Poh

    2009-07-01

    Axial flow blood pumps are generally smaller as compared to centrifugal pumps. This is very beneficial because they can provide better anatomical fit in the chest cavity, as well as lower the risk of infection. This article discusses the design, levitated responses, and parameter estimation of the dynamic characteristics of a compact hybrid magnetic bearing (HMB) system for axial flow blood pump applications. The rotor/impeller of the pump is driven by a three-phase permanent magnet brushless and sensorless motor. It is levitated by two HMBs at both ends in five degree of freedom with proportional-integral-derivative controllers, among which four radial directions are actively controlled and one axial direction is passively controlled. The frequency domain parameter estimation technique with statistical analysis is adopted to validate the stiffness and damping coefficients of the HMB system. A specially designed test rig facilitated the estimation of the bearing's coefficients in air-in both the radial and axial directions. Experimental estimation showed that the dynamic characteristics of the HMB system are dominated by the frequency-dependent stiffness coefficients. By injecting a multifrequency excitation force signal onto the rotor through the HMBs, it is noticed in the experimental results the maximum displacement linear operating range is 20% of the static eccentricity with respect to the rotor and stator gap clearance. The actuator gain was also successfully calibrated and may potentially extend the parameter estimation technique developed in the study of identification and monitoring of the pump's dynamic properties under normal operating conditions with fluid. PMID:19566728

  20. Effect of Active Mineral on Load-Bearing Autoclaved Aerocrete

    彭苏萍; 王立刚

    2001-01-01

    Influence of ultrafine active mineral (DK mineral) on mechanical property of fly ash based load-bearing aerocrete was analyzed. The result shows that the addition of DK mineral in a suitable amount can enhance obviously the compressive strength of aerocrete. According to the SEM-EDS and X-ray diffraction analyses, the crystal shapes of hydration products are well developed and interlocked for samples containing DK mineral. Its microstructure is denser than that of the samples without DK mineral. Having a good activation, the DK mineral makes both the type and the quantity of hydrated products be obviously superior to that of the contrast sample.

  1. Improvement of the rotational characteristics in the HTSC-permanent magnet hybrid bearing using ring shaped magnet

    Highlights: •We have developed the HTS-permanent magnet hybrid bearing system. •Three dimensional numerical analysis is undertaken to get the effective hybrid configuration. •Repulsive force and pinning force are combined effectively. •The hybrid system shows better levitation characteristics than the non-hybrid one. •In the mechanical resonance state, vibration of the rotor in the hybrid system is small. -- Abstract: We have developed the hybrid magnetic bearing using permanent magnets and the high-Tc bulk superconductor (HTSC). Pinning force of the HTSC is used for the levitation and the guidance. Repulsive force of the permanent magnets is introduced to increase the load weight of the magnetic bearing. In this system, the stator side permanent magnet has the ring type structure so that both pinning force and repulsive force are used effectively. In this paper, influence of the hybrid system on dynamic characteristics of the rotor is studied. The rotor which is supported by the hybrid magnetic bearing is rotated. Then, vibration and the gradient angle of the rotor are measured until the rotor reaches to the end of the resonance state. Three dimensional numerical analysis of the flux which penetrates on the surface of the HTSC is undertaken. The relation between the dynamic characteristics and the flux is considered, and that of the hybrid system is compared with the non-hybrid one. In the hybrid system, the flux is changed by the influences of the stator side permanent magnet. Vibration and the gradient angle of the hybrid system are shown to be smaller than that of the non-hybrid one

  2. Improvement of the rotational characteristics in the HTSC-permanent magnet hybrid bearing using ring shaped magnet

    Emoto, Kozo; Sugiyama, Ryo; Takagi, Shogo; Ohashi, Shunsuke, E-mail: k145676@kansai-u.ac.jp

    2013-11-15

    Highlights: •We have developed the HTS-permanent magnet hybrid bearing system. •Three dimensional numerical analysis is undertaken to get the effective hybrid configuration. •Repulsive force and pinning force are combined effectively. •The hybrid system shows better levitation characteristics than the non-hybrid one. •In the mechanical resonance state, vibration of the rotor in the hybrid system is small. -- Abstract: We have developed the hybrid magnetic bearing using permanent magnets and the high-T{sub c} bulk superconductor (HTSC). Pinning force of the HTSC is used for the levitation and the guidance. Repulsive force of the permanent magnets is introduced to increase the load weight of the magnetic bearing. In this system, the stator side permanent magnet has the ring type structure so that both pinning force and repulsive force are used effectively. In this paper, influence of the hybrid system on dynamic characteristics of the rotor is studied. The rotor which is supported by the hybrid magnetic bearing is rotated. Then, vibration and the gradient angle of the rotor are measured until the rotor reaches to the end of the resonance state. Three dimensional numerical analysis of the flux which penetrates on the surface of the HTSC is undertaken. The relation between the dynamic characteristics and the flux is considered, and that of the hybrid system is compared with the non-hybrid one. In the hybrid system, the flux is changed by the influences of the stator side permanent magnet. Vibration and the gradient angle of the hybrid system are shown to be smaller than that of the non-hybrid one.

  3. GA-BASED PID NEURAL NETVVORK CONTROL FOR MAGNETIC BEARING SYSTEMS

    LI Guodong; ZHANG Qingchun; LIANG Yingchun

    2007-01-01

    In order to overcome the system non-linearity and uncertainty inherent in magnetic bearing systems, a GA(genetic algorithm)-based PID neural network controller is designed and trained to emulate the operation of a complete system (magnetic beating, controller, and power amplifiers).The feasibility of using a neural network to control nonlinear magnetic beating systems with unknown dynamics is demonstrated. The key concept of the control scheme is to use GA to evaluate the candidate solutions (chromosomes), increase the generalization ability of PID neural network and avoid suffering from the local minima problem in network learning due to the use of gradient descent learning method. The simulation results show that the proposed architecture provides well robust performance and better reinforcement learning capability in controlling magnetic bearing systems.

  4. Optimization of the Superconducting Linear Magnetic Bearing of a Maglev Vehicle

    Quéval, Loïc; Sotelo, Guilherme G.; Kharmiz, Yassin; Dias, Daniel H. N.; Sass, Felipe; Zermeño, Víctor M. R; Gottkehaskamp, Raimund

    2015-01-01

    Considering the need for cost/performance prediction and optimization of superconducting maglev vehicles, we develop and validate here a 3D finite element model to simulate superconducting linear magnetic bearings. Then we reduce the 3D model to a 2D model in order to decrease the computing time. This allows us to perform in a reasonable time a stochastic optimization considering the superconductor properties and the vehicle operation. We look for the permanent magnet guideway geometry that m...

  5. Passive magnetic bearing in the 3rd generation miniature axial flow pump-the valvo pump 2.

    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

  6. A new eddy current model for magnetic bearing control system design

    Feeley, Joseph J.; Ahlstrom, Daniel J.

    1992-01-01

    This paper describes a new VLSI-based controller for the implementation of a Linear-Quadratic-Gaussian (LQG) theory-based control system. Use of the controller is demonstrated by design of a controller for a magnetic bearing and its performance is evaluated by computer simulation.

  7. Stellar magnetic activity

    The stellar emission in the chromospheric Ca II H+K lines is compared with the coronal soft X-ray emission, measuring the effects of non-radiative heating in the outer atmosphere at temperatures differing two orders of magnitude. The comparison of stellar flux densities in Ca II H+K and X-rays is extended to fluxes from the transition-region and the high-temperature chromosphere. The stellar magnetic field is probably generated in the differentially rotating convective envelope. The relation between rotation rate and the stellar level of activity measured in chromospheric, transition-region, and coronal radiative diagnostics is discovered. X-ray observations of the binary λ Andromedae are discussed. The departure of M-type dwarfs from the main relations, and the implications for the structure of the chromospheres of these stars are discussed. Variations of the average surface flux densities of the Sun during the 11-year activity cycle agree with flux-flux relations derived for other cool stars, suggesting that the interpretation of the stellar relations may be furthered by studying the solar analogue in more detail. (Auth.)

  8. Ambient-Temperature Passive Magnetic Bearings for Flywheel Energy Storage Systems

    Bender, D.; Post, R.

    2000-05-26

    Based on prior work at the Lawrence Livermore National Laboratory ambient-temperature passive magnetic bearings are being adapted for use in high-power flywheel energy storage systems developed at the Trinity Flywheel Power company. En route to this goal specialized test stands have been built and computer codes have been written to aid in the development of the component parts of these bearing systems. The Livermore passive magnetic bearing system involves three types of elements, as follows: (1) Axially symmetric levitation elements, energized by permanent magnets., (2) electrodynamic ''stabilizers'' employing axially symmetric arrays of permanent magnet bars (''Halbach arrays'') on the rotating system, interacting with specially wound electrically shorted stator circuits, and, (3) eddy-current-type vibration dampers, employing axially symmetric rotating pole assemblies interacting with stationary metallic discs. The theory of the Livermore passive magnetic bearing concept describes specific quantitative stability criteria. The satisfaction of these criteria will insure that, when rotating above a low critical speed, a bearing system made up of the three elements described above will be dynamically stable. That is, it will not only be stable for small displacements from equilibrium (''Earnshaw-stable''), but will also be stable against whirl-type instabilities of the types that can arise from displacement-dependent drag forces, or from mechanical-hysteritic losses that may occur in the rotor. Our design problem thus becomes one of calculating and/or measuring the relevant stiffnesses and drag coefficients of the various elements and comparing our results with the theory so as to assure that the cited stability criteria are satisfied.

  9. 径向磁轴承的力学特性%Mechanical Characteristics of Radial Magnetic Bearing

    张钢; 虞烈; 谢友柏

    2001-01-01

    This paper is based on the example of a radial magnetic bearing possessed of eight-pole, and derives the calculation formulas of static and dynamic mechanical characteristics of the bearing, in which the shape and curvature of surface, eccentricity and tilt of the journal are taken into account. Variations of the static and dynamic characteristics of the radial magnetic bearing versus static tilt parameters of journal are discussed. The outcomes show that the static tilt of the journal has influence on the mechanical characteristics of radial magnetic bearing, and change the static load capacity between two radial magnetic bearings and exert coupling effect between them. To study the dynamics of a practical rotor-magnetic bearing system, at least six stiffness coefficients in each radial magnetic bearing must be considered in ideal case, and twelve stiffness coefficients must be considered in general case of tilting journal. Such a find can be used for the coupled electromechanical dynamics analysis of rotor system equipped with magnetic bearings.

  10. 径向磁轴承的力学特性%Mechanical Characteristics of Radial Magnetic Bearing

    张钢; 虞烈; 谢友柏

    2000-01-01

    This paper is based on the example of a radial magnetic bearing possessed of eight-pole, and derives the calculation formulas of static and dynamic mechanical characteristics of the bearing, in which the shape and curvature of surface, eccentricity and tilt of the journal are taken into account. Variations of the static and dynamic characteristics of the radial magnetic bearing versus static tilt parameters of journal are discussed. The outcomes show that the static tilt of the journal has influence on the mechanical characteristics of radial magnetic bearing, and change the static load capacity between two radial magnetic bearings and exert coupling effect between them. To study the dynamics of a practical rotor-magnetic bearing system, at least six stiffness coefficients in each radial magnetic bearing must be considered in ideal case, and twelve stiffness coefficients must be considered in general case of tilting journal. Such a find can be used for the coupled electromechanical dynamics analysis of rotor system equipped with magnetic bearings.

  11. Energy efficiency high speed drives with magnetic bearings; Energieeffizienz durch schnell drehende, magnetgelagerte Antriebe

    Kroll, Matthias [LEViTEC GmbH, Lahnau (Germany)

    2011-07-01

    In modern purification plans the contamination of the wastewater are biologically removed by supplying oxygen. The clarifier is ventilated by compressors around the clock and approximately 60% of the total energy consumption is used for that. It enables a great opportunity for saving energy. This contribution shows that the use of magnetic centrifugal compressors with high-speed drives leads to significant reduction of energy consumption. In addition, the drive is, due to contact free the magnetic bearings, practically wear- and maintenance-free. By the use of integrated sensors in the magnetic bearings a continuous monitoring of the compressor is implemented. Consequently this drive concept provides not only more efficiency and less energy consumption, but also leads to a higher plant availability. (orig.)

  12. A Method for stability analysis of magnetic bearings : Basic stability criteria

    Shayak, B

    2016-01-01

    In this work I outline a general procedure for dynamic modeling and stability analysis of a magnetic bearing, which is a rotating shaft confined inside a chamber through electromagnetic forces alone. I consider the simplest type of self-propelled bearing, namely a permanent magnet synchronous motor and an induction motor rotor freely suspended inside the corresponding stator, and having no eccentricity-fedback control algorithm. Writing Euler's equations for the rotor mechanics and Maxwell's equations for the electromagnetic field leads to a systematic technique for analysing the dynamics of the complete system. Physical arguments indicate that that two essential components for rotor confinement are a spatial gradient in the stator magnetic field and a torque angle lying in the second quadrant. These predictions are confirmed through the linear stability analysis. The direct practical utility of the results is mitigated by the presence of a repeated eigenvalue in the linearized equations. Despite this limitat...

  13. Development and characterization of magnetic HTS bearings for a 400 kW synchronous HTS motor

    Promising results of static and dynamic investigations on various journal type test bearings encouraged us to develop a scaled-up HTS bearing, able to carry the HTS rotor of a 400 kW superconducting motor. The stator, a YBCO hollow cylinder of 203 mm inner diameter and 250 mm length, is cooled by liquid nitrogen. Permanent magnet rings with a diameter of 200 mm were mounted on a shaft with alternating polarity. Characterization of the bearing capacity was performed with three different YBCO stators at temperatures between 66 and 86 K in a test set-up. A significant influence of the temperature was found. At a stator temperature of 72 K and a rotation frequency of 25 Hz (corresponding to nominal motor speed) a radial bearing force of 2700 N was measured for the shaft at centre position. Under rotation of the shaft the bearing capacity is reduced. At present our results range within the highest radial bearing capacities reported world-wide

  14. Radial Forces in a Centrifugal Compressor; Experimental Investigation by Using Magnetic Bearings and Static Pressure Distribution

    Arttu REUNANEN; Jaakko LARJOLA

    2005-01-01

    The volute of a centrifugal compressor causes a non-uniform pressure distribution which leads to a radial force on the impeller. This force was measured using magnetic bearings. In addition, the radial force was estimated using the static pressure distribution measured at the impeller outlet. The impeller force was found to be the highest at choke, the lowest at the design flow and moderate at stall. The radial force determined from the pressure measurements was only slightly different from the force obtained from the bearing measurements. The rotational speed was seen to affect the force to some extent.

  15. Experimental treatment of breast cancer-bearing BALB/c mice by artemisinin and transferrin-loaded magnetic nanoliposomes

    Amir Gharib

    2015-01-01

    Full Text Available Background: The combination of artemisinin and transferrin exhibits versatile anticancer activities. In previous, we successfully prepared artemisinin and transferrin-loaded magnetic nanoliposomes and evaluated their anti-proliferative activity against MCF-7 and MDA-MB-231 cell lines in vitro. In this study, we investigate the in vivo anti-breast cancer activity of artemisinin and transferrin-loaded magnetic nanoliposome against breast transplanted tumors in BALB/c mice model. Materials and Methods: Artemisinin and transferrin-loaded magnetic nanoliposomes were prepared and characterized for some physiochemical properties. Pieces of tumor tissue from the breast cancer-bearing BALB/c mice were transplanted subcutaneously to the syngeneic female BALB/c mice. In the presence of the external magnet that placed at the breast tumor site, the tissue distribution and tumor-suppressing effects of prepared nanoliposomes on tumor growth was evaluated. Results: The prepared nanoliposomes have fine spherical shape, rough surface, nano-sized diameter and magnetic properties. At 2 h after treatment, the intravenous administration of artemisinin and transferrin-loaded magnetic nanoliposomes followed using the magnetic field approximately produced 10- and 5.5-fold higher levels of artemisinin and transferrin in the tumors, respectively, compared with free artemisinin and transferrin. Moreover, in the presence of an external magnetic field, the prepared nanoliposomes could significantly induce apoptosis in the mice breast cancer cells as well as could reduce tumor volume in tumorized mice at 15 days after treatment. Conclusion: The data suggested that the artemisinin and transferrin-loaded magnetic nanoliposomes would be a good choice for the breast tumor-targeted therapy, due to its high targeting efficiency.

  16. Local Attitudes towards Bear Management after Illegal Feeding and Problem Bear Activity

    David Fraser; Sara Dubois

    2013-01-01

    Simple Summary The “pot bears” received international media attention in 2010 after police discovered the intentional feeding of black bears during the investigation of an alleged marijuana-growing operation in Christina Lake, British Columbia. Residents of this small community were surveyed by phone twice over the following year, before and after government actions. This study aimed to understand local attitudes on how these bears should be managed and whether they differed from existing bea...

  17. A contribution on the investigation of the dynamic behavior of rotating shafts with a Hybrid Magnetic Bearing Concept (HMBC) for blower application

    Within a subproject of the RAPHAEL-Program, which was part of the 6th EURATOM Framework Program supervised by the European Commission, it was investigated whether the use of a Hybrid Magnetic Bearing Concept (HMBC) will be beneficial for a blower application. Within the RAPHAEL program, the subproject 'Component Development' is dealing with R and D of components of High Temperature Reactor Technology (HTR), where a major focus is on safety- and reliability-related issues. That implies special requirements for the support of high speed rotating shafts in HTR-Applications that only can be satisfied by using Active Magnetic Bearings (AMB). Regarding safety and competitiveness, AMBs are considered to be key components for the support of rotating HTR-components due to their technical features. AMBs are characterized by an electromagnetic actuator that is generating the bearing force depending on the clearance between stator and rotor, in which the rotor is levitated. Therefore an active control of the coil current is necessary. Furthermore, Touch Down Bearings (TDB) are needed to avoid damages in case of an emergency shut down or in case of energy supply losses. This contribution provides an internal insight on the advantages of a Hybrid Magnetic Bearing Concept that is characterized by a completely Active Magnetic Bearing-supported vertical arranged rotor and an additional permanent magnetic radial orientated bearing. One benefit of the HMBC is an additional radial guidance of the shaft that may reduce the loads while dropping into the Touch Down Bearings e.g. in case of energy supply losses of the AMBs. Reduced loads on the TDBs will increase their life cycle and the availability of the AMB supported component. The scope of this R and D-Project, which will be described more detailed in this contribution, includes: the analytical modeling and simulation of the dynamic behavior of the Hybrid Magnetic Bearing System; the modification of the completely AMB-supported test

  18. A contribution on the investigation of the dynamic behaviour of rotating shafts with a hybrid magnetic bearing concept (HMBC) for blower application - HTR2008-58045

    Within a sub-project of the RAPHAEL-Program, which is part of the 6. EURATOM Framework Program supervised by the European Commission it was investigated whether the use of a Hybrid Magnetic Bearing Concept (HMBC) will be beneficial for a blower application. As in the RAPHAEL program the sub-project 'Component Development' deals with R and D on components of High Temperature Reactor Technology (HTR), a major focus is on safety- and reliability-related issues. That implies special requirements for the support of high speed rotating shafts in HTR-Applications that only can be satisfied by using Active Magnetic Bearings (AMB). Regarding safety and competitiveness, AMBs are considered key components for the support of rotating HTR-components due to their technical features. AMBs are characterized by an electromagnetic actuator that is generating the bearing force depending on the clearance between stator and rotor, in which the rotor is levitated. Therefore an active control of the coil current is necessary. Furthermore, Touch Down Bearings (TDB) are needed to avoid damages in case of an emergency shut down or in case of energy supply losses. This contribution provides an internal insight on the advantages of a Hybrid Magnetic Bearing Concept that is characterized by a completely Active Magnetic Bearing-supported vertical arranged rotor and an additional permanent magnetic Radial Bearing. One benefit of the HMBC is an additional radial guidance of the shaft that may reduce the loads while dropping into the Touch Down Bearings e.g. in case of energy supply losses of the AMBs. Reduced loads on the TDBs will increase their life cycle and the availability of the AMB supported component. The Scope of this R and D-Project, which will be described more detailed in this contribution, includes the analytical modeling and simulation of the dynamic behavior of the Hybrid Magnetic Bearing System, the modification of the completely AMB supported test facility FLP500 with a radial

  19. Influence of magnetic non-uniformity existing in a rigid rotor supported by a superconducting magnetic bearing on its whirling

    Superconducting magnetic bearings (SMBs) have a significant feature over conventional bearings in terms of supporting a shaft without physical contact while attaining its stability without control. In their large-scale rotary applications, magnetization distribution of a rotor in the circumferential direction can be non-uniform and it would be better to know influence of such circumferential magnetic non-uniformity existing in a rotor on its dynamics, especially on its behaviors in the vicinity of the critical speed. In this study, further developing our previous research, we improved our analytical model so that we can adjust several different degrees of magnetic non-uniformity by arranging multiple magnetization vectors and investigated its influence. First, we simulated dynamical behavior of the system by numerical calculations and their results show that, with increasing the degree of magnetic non-uniformity, the whirling amplitude of the system, together with the difference of the amplitudes in the orthogonal directions in the whirling plane, get larger. Further, the rotational frequency at which the whirling amplitude takes its peak gets lower, which is caused by nonlinearity of the electromagnetic force. We carried out experiments and verified our numerical predicions.

  20. MATLAB WEB SERVER AND ITS APPLICATION IN REMOTE COLLABORATIVE DESIGN OF MAGNETIC BEARING SYSTEMS

    2001-01-01

    Acclimatizing itself to the development of network,Math Works Inc constructed a MATLAB Web Server environment by dint of which one can browse the calculation and plots of MATLAB through Internet directly.The installation and use of the environment is introduced.A code established on the platform of MATLAB,which deals with the modal analysis of magnetic bearing system(MBS) supporting rotors of five degrees of freedom and considering the coupling of thrust bearing with radical bearings is modified to work in the environment.The purpose is to realize a remote call of the code by users through Internet for the performance analysis of the system.Such an application is very important to the concurrent design of MBS and for the utilization of distributive knowledge acquisition resources in collaborative design.The work on modification and realization is described and the results are discussed.

  1. Activity estimation in radioimmunotherapy using magnetic nanoparticles

    Rajabi, Hossein; Johari Daha, Fariba

    2015-01-01

    Objective Estimation of activity accumulated in tumor and organs is very important in predicting the response of radiopharmaceuticals treatment. In this study, we synthesized 177Lutetium (177Lu)-trastuzumab-iron oxide nanoparticles as a double radiopharmaceutical agent for treatment and better estimation of organ activity in a new way by magnetic resonance imaging (MRI). Methods 177Lu-trastuzumab-iron oxide nanoparticles were synthesized and all the quality control tests such as labeling yield, nanoparticle size determination, stability in buffer and blood serum up to 4 d, immunoreactivity and biodistribution in normal mice were determined. In mice bearing breast tumor, liver and tumor activities were calculated with three methods: single photon emission computed tomography (SPECT), MRI and organ extraction, which were compared with each other. Results The good results of quality control tests (labeling yield: 61%±2%, mean nanoparticle hydrodynamic size: 41±15 nm, stability in buffer: 86%±5%, stability in blood serum: 80%±3%, immunoreactivity: 80%±2%) indicated that 177Lu-trastuzumab-iron oxide nanoparticles could be used as a double radiopharmaceutical agent in mice bearing tumor. Results showed that 177Lu-trastuzumab-iron oxide nanoparticles with MRI had the ability to measure organ activities more accurate than SPECT. Conclusions Co-conjugating radiopharmaceutical to MRI contrast agents such as iron oxide nanoparticles may be a good way for better dosimetry in nuclear medicine treatment. PMID:25937783

  2. Paleomagnetism and environmental magnetism of GLAD800 sediment cores from Bear Lake, Utah and Idaho

    Heil, C.W., Jr.; King, J.W.; Rosenbaum, J.G.; Reynolds, R.L.; Colman, Steven M.

    2009-01-01

    A ???220,000-year record recovered in a 120-m-long sediment core from Bear Lake, Utah and Idaho, provides an opportunity to reconstruct climate change in the Great Basin and compare it with global climate records. Paleomagnetic data exhibit a geomagnetic feature that possibly occurred during the Laschamp excursion (ca. 40 ka). Although the feature does not exhibit excursional behavior (???40?? departure from the expected value), it might provide an additional age constraint for the sequence. Temporal changes in salinity, which are likely related to changes in freshwater input (mainly through the Bear River) or evaporation, are indicated by variations in mineral magnetic properties. These changes are represented by intervals with preserved detrital Fe-oxide minerals and with varying degrees of diagenetic alteration, including sulfidization. On the basis of these changes, the Bear Lake sequence is divided into seven mineral magnetic zones. The differing magnetic mineralogies among these zones reflect changes in deposition, preservation, and formation of magnetic phases related to factors such as lake level, river input, and water chemistry. The occurrence of greigite and pyrite in the lake sediments corresponds to periods of higher salinity. Pyrite is most abundant in intervals of highest salinity, suggesting that the extent of sulfidization is limited by the availability of SO42-. During MIS 2 (zone II), Bear Lake transgressed to capture the Bear River, resulting in deposition of glacially derived hematite-rich detritus from the Uinta Mountains. Millennial-scale variations in the hematite content of Bear Lake sediments during the last glacial maximum (zone II) resemble Dansgaard-Oeschger (D-O) oscillations and Heinrich events (within dating uncertainties), suggesting that the influence of millennial-scale climate oscillations can extend beyond the North Atlantic and influence climate of the Great Basin. The magnetic mineralogy of zones IV-VII (MIS 5, 6, and 7

  3. An active magnetic regenerator device

    2015-01-01

    A rotating active magnetic regenerator (AMR) device comprising two or more regenerator beds, a magnet arrangement and a valve arrangement. The valve arrangement comprises a plurality of valve elements arranged substantially immovably with respect to the regenerator beds along a rotational direction...

  4. Preliminary study on rotor dynamics of magnetic bearing for 10MW high temperature gas-cooled reactor

    The finite element method and MSC. Marc software are applied to analyze the rotor modal of magnetic bearings for power conversion unit (PCU) of 10 MW high temperature gas-cooled reactor (HTR-10). The effects of the magnetic bearings sustaining stiffness on the rotor natural frequencies were studied. Results show that the natural frequencies may be adjusted by changing the sustaining stiffness and rotor material. It is very important for the magnetic bearing to pass two order bending natural frequencies and design control system

  5. Nonlinear dynamic behaviour of a rotor-foundation system coupled through passive magnetic bearings with magnetic anisotropy - Theory and experiment

    Enemark, Søren; Santos, Ilmar F.

    2016-01-01

    the frequency domain by the methods of Finite Difference and pseudo-arclength continuation. The theoretical findings are validated against experiments carried out using a dedicated test-rig and a special device for characterisation of the magnetic anisotropy.The characterisation of the magnetic...... and nonlinear cross-coupling between the two orthogonal directions, especially during counter-phase motion between shaft and bearings. The clear nonlinear behaviour is facilitated by the lack of damping resulting in relatively large vibrations. The overall nonlinear dynamic behaviour is well captured...

  6. DESIGN AND APPLICATION OF MAGNETIC BEARING SUSPENSION SYSTEM IN A THREE PHASE INDUCTION MOTOR

    Osman GÜRDAL; Yusuf ÖNER

    1998-01-01

    The current popularity of suspension and levitation stems no doubt the possibilities in high-speed ground transportation schemes. Although these are both challenging and exciting, there is considerable scope for application of suspension techniques to achieving frictionless bearing. The requirement in this case is often for close tolerances, low power consumption, small airgaps and ingeneral, compactness. Thus, magnetic suspension using DC electromagnets schemes have received more attention t...

  7. Multiple stabilities analysis in a magnetic bearing system with time delays

    A kind of magnetic bearing system with time delay is considered. Firstly, multiple stabilities of the model is investigated. According to the analysis results, the bifurcation diagram is drawn in the appropriate parameter plane. Then the center manifold reduction and normal form computation for simple zero singularity are performed and detailed bifurcation analysis are carried out. Finally, some numerical simulations are presented to illustrate the results found

  8. Study on alkali leaching of a complicated uranium-bearing magnetic concentrate

    Alkali leaching of a complicated uranium-bearing magnetic concentrate was studied. The research results showed that the uranium recovery from the concentrate leaching increased with destruction and dissolution of organic matters. It is suitable and feasible to treat the magnetic concentrate by a two-stage alkali leaching process including pre-leaching, and it is beneficial to treat the obtained product solution in the subsequent operations. It is extremely possible that the residual uranium in the leached residue is closely associated with hard-to-open davidite. So it is not reasonable economically to continue intensifying the conditions to treat the concentrate

  9. Sliding Mode Output Feedback Control of a Flexible Rotor Supported by Magnetic Bearings

    A. S. Lewis

    2001-01-01

    Full Text Available A new sliding mode feedback algorithm is applied to control the vibration of a flexible rotor supported by magnetic bearings. It is assumed that the number of states is greater than the number of sensors. A mathematical model of the rotor]magnetic bearing system is presented in terms of partial differential equations. These equations are then discretized into a finite number of ordinary differential equations through Galerkin’s method. The sliding mode control law is designed to be robust to rotor unbalance and transient disturbances. A boundary layer is introduced around each sliding hyperplane to eliminate the chattering phenomenon. The results from numerical simulations are presented that not only corroborate the validity of the proposed controller, but also show the effects of various control parameters as a function of the angular speed of the rotor. In addition, results are presented that indicate how the current required by the magnetic bearings is affected by control parameters and the angular speed of the rotor.

  10. Performance of an active electric bearing for rotary micromotors

    An electric bearing used to support a micromachined rotor of variable-capacitance motors was designed and tested in order to study the characteristics of this frictionless bearing. Electrostatic suspension of a ring-shaped rotor in five degrees of freedom is required to eliminate the mechanical bearing and thus the friction and wear between the rotor and the substrate. Bulk microfabrication-based glass/silicon/glass bonding is chosen for this device, allowing the fabrication of large area sense capacitors and rotor, which make the device potentially suitable for the development of an electrostatically suspended micromachined gyroscope. The device and its basic operating principle are described, as well as the dynamics of the rotor and basic design considerations of the electric bearing system. A theoretical relationship to relate the characteristics of a classical lag–lead compensator to the stiffness properties of the electric bearing is developed to explain the experimental bearing measurements. The experimental results of closed-loop frequency response, suspension stiffness and drive voltage effects are presented and discussed for the bearing operated initially in the atmospheric environment. The performance of a tri-axial electrostatic accelerometer has also been experimentally investigated on the prototype of the electric bearing system

  11. Performance Testing of a Magnetically Suspended Double Gimbal Control Moment Gyro Based on the Single Axis Air Bearing Table

    2012-01-01

    Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG), a magnetically suspended DGCMG (MSDGCMG) is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing of a MSDGCMG independently developed by Beihang University, based on the single axis air bearing table. In this paper, taking into sufficient consideration to the moving-gimbal effects and the res...

  12. Feasibility of Applying Active Lubrication to Dynamically Loaded Fluid Film Bearings

    Estupinan, Edgar Alberto; Santos, Ilmar

    2009-01-01

    The feasibility of modifying the dynamics of the thin fluid films of dynamically loaded journal bearings, using different strategies of active lubrication is studied in this work. A significant reduction in the vibration levels, wear and power friction losses, is expected. Particularly, the focus...... of this study is on the analysis of main crankshaft bearings, where the conventional hydrodynamic lubrication is modified by injecting oil at actively controllable pressures, through orifices circumferentially located along the bearing surface....

  13. 磁悬浮轴承-转子系统非线性行为的控制%Control of Nonlinear Behaviors of an Active Magnetic Bearing - Rotor System

    孙保苍; 梁荣生; 陈威

    2011-01-01

    利用状态反馈法,对磁悬浮轴承-转子系统的振动进行控制.通过理论推导,证明在原点附近,可近似地将受控系统分解为两个渐近稳定的子系统之和.借助数值仿真对转子受控前后的运动响应进行分析,以验证该控制方案的有效性.通过比较发现,提出的状态反馈控制方案不但能控制转子的周期运动,而且对该系统的概周期运动和混沌运动也能进行有效控制.%In this paper, the nonlinear dynamical behaviors of an active magnetic beating-rotor system are investigated.In order to control the vibration of the system, a state feedback method is adopted.It is theoretically proved that the controlled system can be approximately divided into two asymptotically stable subsystems near the origin.Based on this conclusion, kinematic responses to both controlled and uncontrolled systems are analyzed by numerical simulations to verify the validity of the control scheme.Mutual comparison of the results of both systems reveals that the state feedback control scheme presented here can effectively control not only periodic vibrations, but also quasi-periodic and chaotic vibrations.

  14. From Hybrid to Actively-Controlled Gas Lubricated Bearings – Theory and Experiment

    Morosi, Stefano

    bearings, tilting pad and flexure pivot gas bearings. These solutions proved to be effective in improving static and dynamic properties of the bearings, however issues related to the manufacturing and accuracy of predictions has so far limited their applications. Another drawback is that passive bearings...... determined by the appearance of subsynchronous whirl instability. In fact, postponing the onset speed of instability poses one of the greatest challenges in high-speed gas bearing design. A great deal of research is devoted to attack such issues, where most propose passive designs such as compliant foil...... offer a low degree of robustness, meaning that an accurate optimization is necessary for each application. Another way of improving gas bearings operation performance is by using active control systems, transforming conventional gas bearings in an electro-mechanical machine component. In this framework...

  15. Linear and Nonlinear Analysis of Magnetic Bearing Bandwidth Due to Eddy Current Limitations

    Kenny, Andrew; Palazzolo, Alan

    2000-01-01

    Finite element analysis was used to study the bandwidth of alloy hyperco50a and silicon iron laminated rotors and stators in magnetic bearings. A three dimensional model was made of a heteropolar bearing in which all the flux circulated in the plane of the rotor and stator laminate. A three dimensional model of a plate similar to the region of a pole near the gap was also studied with a very fine mesh. Nonlinear time transient solutions for the net flux carried by the plate were compared to steady state time harmonic solutions. Both linear and quasi-nonlinear steady state time harmonic solutions were calculated and compared. The finite element solutions for power loss and flux bandwidth were compared to those determined from classical analytical solutions to Maxwell's equations.

  16. Control system design for flexible rotors supported by actively lubricated bearings

    Nicoletti, Rodrigo; Santos, Ilmar

    2008-01-01

    and keeping the lengths of the two eigenvalues constant in the real-imaginary plane. The methodology is applied to an industrial gas compressor supported by active tilting-pad journal bearings. The unbalance response functions and mode shapes of the flexible rotor with and without active control are...... displacement and velocity of the shaft at the bearing positions....

  17. Magnetic mineralogy analyses on greigite-bearing sediments with inconsistent magnetic polarity (Adana Basin, Southern Turkey)

    Lucifora, S.; Cifelli, F.; Mattei, M.; Cosentino, D.; Sagnotti, L.; Roberts, A.

    2012-04-01

    A paleomagnetic study has been carried out, in the framework of the VAMP (Vertical Anatolian Movement Project) project, on 4 stratigraphic sections and 1 site from the Adana basin in the southern margin of the Anatolian Plateau. About 300 standard cylindrical samples have been analysed for paleomagnetism and rock magnetism. All the sections have been deposited in the upper Messinian"lago-mare" post-evaporitic event, which occurred in the Mediterranean basin, during the reverse polarity Chron C3r. Paleomagnetic results, presented in this work, are in contrast with these data, showing both normal and reverse polarities along the sections. Standard magnetic mineralogy investigations, integrated with SEM analyses and FORC diagrams, show that magnetite and ferrimagnetic iron sulphides (greigite) are the main magnetic carriers. Moreover, we find an interesting correlation between the magnetic mineralogy of the sediments and the magnetic polarities, being magnetite the magnetic carrier in the normal polarity samples and greigite in the reverse ones. Reversal and fold tests demonstrate that normal polarity samples have been subjected to a pervasive magnetic overprint and acquired their remanent magnetization after bedding tilt. Whereas samples with a reverse polarity acquired their remanent magnetization before bedding tilt, but after syn-sedimentary soft deformation. This work is proposed as a contribution aimed to improve the understanding of the relationship between the magnetic mineralogy and the remagnetization phenomena in order to avoid misinterpretation of magnetostratigraphic and paleomagnetic data.

  18. Elastohydrodynamics Applied to Active Tilting-Pad Journal Bearings

    Haugaard, Martin Asger; Santos, Ilmar

    2010-01-01

    The static and dynamic properties of tilting-pad journal bearings with controllable radial oil injection are investigated theoretically. The tilting pads are modeled as flexible structures and their behavior is described using a three-dimensional finite element framework and linear elasticity. The...... dynamically perturbed and subsequently condensed to a 2 X 2 system, keeping only the lateral motion of the rotor. As expected, bearing dynamic coefficients are heavily influenced by the control parameters and pad compliance....

  19. Cryogenic magnetic bearing scanning mechanism design for the SPICA/SAFARI Fourier transform spectrometer

    van den Dool, Teun C.; Hamelinck, Roger F. M. M.; Kruizinga, Bob; Gielesen, Wim L. M.; Braam, Ben C.; Nijenhuis, Jan R.; Loix, Nicolas; Luyckx, Stanislas; van Loon, Dennis; Kooijman, Peter Paul; Swinyard, Bruce M.

    2010-07-01

    TNO, together with its partners Micromega and SRON, have designed a cryogenic scanning mechanism for use in the SAFARI Fourier Transform Spectrometer (FTS) on board of the SPICA mission. The optics of the FTS scanning mechanism (FTSM) consists of two back-to-back cat's-eyes. The optics are mounted on a central "back-bone" tube which houses all the important mechatronic parts: the magnetic bearing linear guiding system, a magnetic linear motor serving as the OPD actuator, internal metrology with nanometer resolution, and a launch lock. A magnetic bearing is employed to enable a large scanning stroke in a small volume. It supports the optics in a free-floating way with no friction, or other non-linearities, enabling sub-nanometer accuracy within a single stage with a stroke of -4 mm to +31.5 mm. Because the FTSM will be used at cryogenic temperatures of 4 Kelvin, the main structure and optics are all constructed from 6061 Aluminum. The overall outside dimensions of the FTSM are: 393 x 130 x 125 mm, and the mass is 2.2 kg.

  20. Stability and bifurcation analysis in a magnetic bearing system with time delays

    A kind of magnetic bearing system with time delay is considered. Firstly, linear stability of the model is investigated by analyzing the distribution of the roots of the associated characteristic equation. According to the analysis results, the bifurcation diagram is drawn in the appropriate parameter plane. It is found that the Ho pf bifurcation occurs when the delay passes through a sequence of critical values. Then the explicit algorithm for determining the direction of the Ho pf bifurcations and the stability of the bifurcating periodic solutions are derived, using the theory of normal form and center manifold. Finally, some numerical simulations are carried out to illustrate the results found

  1. Effect of unbalanced magnetic pull and hydraulic seal force on the vibration of large rotor-bearing systems

    Song, Z.; Guo, P.; Liu, Y.

    2014-03-01

    The influence of unbalanced magnetic pull (UMP) and hydraulic seal force on the vibration of large rotor-bearing systems is studied. The UMP caused by rotor eccentricity imposes important effects on rotating machinery, especially for large generators such as water turbine generator sets, because these machines operate above their first critical speed in some instances and are supported by oil film bearings. A magnetic stiffness matrix for studying the effects of the UMP is proposed. The magnetic stiffness matrix can be generated by decomposing the expression of air gap magnetic field energy. Two vibration models are constructed using the Lagrange equation. The difference between the two models lies in the boundary support condition: one has rigid support and the other has elastic bearing support. The influence of the magnetic stiffness and elastic support on the critical speed of the rotor is studied using Lyapunov nonlinear vibration stability theory. The vibration amplitude of the rotor is calculated, taking the magnetic stiffness and horizontal centrifugal force into account. The unbalanced hydraulic seal force is produced because of the asymmetry of seal clearance. This imbalance is one of the factors that causes self-excited vibration in rotating machinery, and is as important as the UMP for large water turbine generator sets. The rotor-bearing system is supported by an oil film journal bearing, whose characteristic also impose considerable influence on vibration. On the basis of the above-mentioned conditions, a three-dimensional finite element model of the rotating system that includes the oil film journal bearing is constructed. The effect of the UMP and unbalanced hydraulic seal force is considered in the construction, and studied in relation to the magnetic parameters, seal parameters, journal bearing stiffness, and outer diameter of the rotating machine critical speed. Conclusions may benefit the dynamic design and optimized operation of large rotating

  2. Effect of unbalanced magnetic pull and hydraulic seal force on the vibration of large rotor-bearing systems

    The influence of unbalanced magnetic pull (UMP) and hydraulic seal force on the vibration of large rotor-bearing systems is studied. The UMP caused by rotor eccentricity imposes important effects on rotating machinery, especially for large generators such as water turbine generator sets, because these machines operate above their first critical speed in some instances and are supported by oil film bearings. A magnetic stiffness matrix for studying the effects of the UMP is proposed. The magnetic stiffness matrix can be generated by decomposing the expression of air gap magnetic field energy. Two vibration models are constructed using the Lagrange equation. The difference between the two models lies in the boundary support condition: one has rigid support and the other has elastic bearing support. The influence of the magnetic stiffness and elastic support on the critical speed of the rotor is studied using Lyapunov nonlinear vibration stability theory. The vibration amplitude of the rotor is calculated, taking the magnetic stiffness and horizontal centrifugal force into account. The unbalanced hydraulic seal force is produced because of the asymmetry of seal clearance. This imbalance is one of the factors that causes self-excited vibration in rotating machinery, and is as important as the UMP for large water turbine generator sets. The rotor-bearing system is supported by an oil film journal bearing, whose characteristic also impose considerable influence on vibration. On the basis of the above-mentioned conditions, a three-dimensional finite element model of the rotating system that includes the oil film journal bearing is constructed. The effect of the UMP and unbalanced hydraulic seal force is considered in the construction, and studied in relation to the magnetic parameters, seal parameters, journal bearing stiffness, and outer diameter of the rotating machine critical speed. Conclusions may benefit the dynamic design and optimized operation of large rotating

  3. Radial forces analysis and rotational speed test of radial permanent magnetic bearing for horizontal axis wind turbine applications

    Kriswanto, Jamari

    2016-04-01

    Permanent magnet bearings (PMB) are contact free bearings which utilize the forces generated by the magnets. PMB in this work is a type of radial PMB, which functions as the radial bearings of the Horizontal Axis Wind Turbine (HAWT) rotor shaft. Radial PMB should have a greater radial force than the radial force HAWT rotor shaft (bearing load). This paper presents a modeling and experiments to calculate the radial force of the radial PMB. This paper also presents rotational speed test of the radial PMB compared to conventional bearings for HAWT applications. Modeling using COMSOL Multiphysics 4.3b with the magnetic fields physics models. Experiments were conducted by measuring the displacement of the rotor to the stator for a given load variation. Results of the two methods showed that the large displacement then the radial force would be greater. Radial forces of radial PMB is greater than radial forces of HAWT rotor shaft. The rotational speed test results of HAWT that used radial PMB produced higher rotary than conventional bearings with an average increase of 87.4%. Increasing rotational speed occured because radial PMB had no friction. HAWT that used radial PMB rotated at very low wind speeds are 1.4 m/s with a torque of 0.043 Nm, while the HAWT which uses conventional bearing started rotating at a wind speed of 4.4 m/s and required higher torque of 0.104 N.

  4. Influence of Back-Up Bearings and Support Structure Dynamics on the Behavior of Rotors With Active Supports

    Flowers, George T.

    1996-01-01

    This report presents a synopsis of the research work. Specific accomplishments are itemized below: (1) Experimental facilities have been developed. This includes a magnetic bearing test rig and an auxiliary bearing test rig. In addition, components have been designed, constructed, and tested for use with a rotordynamics test rig located at NASA Lewis Research Center. (2) A study of the rotordynamics of an auxiliary bearing supported T-501 engine model was performed. (3) An experimental/simulation study of auxiliary bearing rotordynamics has been performed. (4) A rotordynamical model for a magnetic bearing supported rotor system, including auxiliary bearing effects has been developed and simulation studies performed.(5) A finite element model for a foil bearing has been developed and studies of a rotor supported by foil bearings have been performed. (6) Two students affiliated with this project have graduated with M.S. degrees.

  5. Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet

    Oka, T., E-mail: okat@eng.niigata-u.ac.jp [Niigata University, 8050 Ikarashi-Ninocho, Nishi-ku, Niigata 950-2181 (Japan); Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M. [Niigata University, 8050 Ikarashi-Ninocho, Nishi-ku, Niigata 950-2181 (Japan); Tsujimura, M. [Aichi Giken Co., 50-1 Takeshita, Hitotugi-cho, Kariya, Aichi 448-0003 (Japan); Yokoyama, K. [Ashikaga Institute of Technology, 268-1 Ohmae-cho, Ashikaga, Tochigi 326-8558 (Japan)

    2014-01-15

    Highlights: ► The magnetic separation for Ni compounds was conducted by HTS bulk magnet. ► The coarse Ni-sulfate crystals were formed from the Ni-phosphite precipitates. ► Ni-sulfate crystals was separated from the mixture of Ni-sulfate and Ni-phosphite compounds. -- Abstract: The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45 T at 35 K in the static magnetic field of 5 T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow.

  6. Summer declines in activity and body temperature offer polar bears limited energy savings

    Whiteman, J.P.; Harlow, H.J.; Durner, George M.; Anderson-Sprecher, R.; Albeke, Shannon E.; Regehr, Eric V.; Amstrup, Steven C.; Ben-David, M.

    2015-01-01

    Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of “ice” bears in summer is unknown, “shore” bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation.

  7. Animal physiology. Summer declines in activity and body temperature offer polar bears limited energy savings.

    Whiteman, J P; Harlow, H J; Durner, G M; Anderson-Sprecher, R; Albeke, S E; Regehr, E V; Amstrup, S C; Ben-David, M

    2015-07-17

    Polar bears (Ursus maritimus) summer on the sea ice or, where it melts, on shore. Although the physiology of "ice" bears in summer is unknown, "shore" bears purportedly minimize energy losses by entering a hibernation-like state when deprived of food. Such a strategy could partially compensate for the loss of on-ice foraging opportunities caused by climate change. However, here we report gradual, moderate declines in activity and body temperature of both shore and ice bears in summer, resembling energy expenditures typical of fasting, nonhibernating mammals. Also, we found that to avoid unsustainable heat loss while swimming, bears employed unusual heterothermy of the body core. Thus, although well adapted to seasonal ice melt, polar bears appear susceptible to deleterious declines in body condition during the lengthening period of summer food deprivation. PMID:26185248

  8. Solar activity monitoring and forecasting capabilities at Big Bear Solar Observatory

    P. T. Gallagher

    Full Text Available The availability of full-disk, high-resolution Ha images from Big Bear Solar Observatory (USA, Kanzelhöhe Solar Observatory (Austria, and Yunnan Astronomical Observatory (China allows for the continual monitoring of solar activity with unprecedented spatial and temporal resolution. Typically, this Global Ha Network (GHN provides almost uninterrupted Ha images with a cadence of 1 min and an image scale of 1'' per pixel. 

    Every hour, GHN images are transferred to the web-based BBSO Active Region Monitor (ARM; www.bbso.njit.edu/arm, which includes the most recent EUV, continuum, and magnetogram data from the Solar and Heliospheric Observatory, together with magnetograms from the Global Oscillation Network Group. ARM also includes a variety of active region properties from the National Oceanic and Atmospheric Administration’s Space Environment Center, such as up-to-date active region positions, GOES 5-min X-ray data, and flare identification. Stokes I, V, Q, and U images are available from the recently operational BBSO Digital Vector Magnetograph and the Vector Magnetograph at the Huairou Solar Observing Station of Beijing Observatory. Vector magnetograms provide complete information on the photospheric magnetic field, and allow for magnetic flux gradients, electric currents, and shear forces to be calculated: these measurements are extremely sensitive to conditions resulting in flaring activity. Furthermore, we have developed a Flare Prediction System which estimates the probability for each region to produce C-, M-, or X-class flares based on nearly eight years of NOAA data from cycle 22. This, in addition to BBSO’s daily solar activity reports, has proven a useful resource for activity forecasting.

    Key words. Solar physics, astronomy and astrophysics (flares and mass ejections; instruments and techniques

  9. Modeling and Analysis of Coupling Performance of Dynamic Stiffness Models for a Novel Combined Radial-Axial Hybrid Magnetic Bearing

    Bangcheng Han

    2014-01-01

    Full Text Available The combined radial-axial magnetic bearing (CRAMB with permanent magnet creating bias flux can reduce the size, cost, and mass and save energy of the magnetic bearing. The CRAMB have three-degree-of-freedom control ability, so its structure and magnetic circuits are more complicated compared to those of the axial magnetic bearing (AMB or radial magnetic bearing (RMB. And the eddy currents have a fundamental impact on the dynamic performance of the CRAMB. The dynamic stiffness model and its cross coupling problems between different degrees of freedom affected for the CRAMB are proposed in this paper. The dynamic current stiffness and the dynamic displacement stiffness models of the CRAMB are deduced by using the method of equivalent magnetic circuit including eddy current effect, but the dynamic current stiffness of the RMB unit is approximately equal to its static current stiffness. The analytical results of an example show that the bandwidth of the dynamic current stiffness of the AMB unit and the dynamic displacement stiffness of the CRAMB is affected by the time-varying control currents or air gap, respectively. And the dynamic current stiffness and the dynamic displacement stiffness between the AMB unit and the RMB unit are decoupled due to few coupling coefficients.

  10. Authigenesis of magnetic minerals in gas hydrate-bearing sediments in the Nankai Trough, offshore Japan

    Kars, Myriam; Kodama, Kazuto

    2015-03-01

    Gas hydrate occurrence is one of the possible mechanisms invoked for iron sulfide formation. A high-resolution rock magnetic study was conducted in IODP Expedition 316 Hole C0008C located in the Megasplay Fault Zone of the Nankai Trough, offshore Japan. In this particular zone, no bottom simulating reflectors (BSR), indicating the base of the gas hydrate stability field, have been identified. Two hundred and eighteen Pleistocene samples were collected from 70 to 110 m CSF in order to document the changes in the concentration, grain size, and rock magnetic parameters of magnetic minerals, through the gas hydrate-bearing horizons. Two different populations of magnetic grains are recognized in the pseudosingle domain range. Three types of magnetic mineral assemblages are identified: iron oxides (magnetite), ferrimagnetic iron sulfides (greigite and pyrrhotite), and their mixture. Greigite and pyrrhotite are authigenic and constitute six layers, called IS1-IS6. IS1, IS3, IS4, and IS6 are associated with pore water anomalies, suggesting the occurrence of gas hydrates and anoxic conditions. IS2 and IS5 are probable gas hydrates horizons, although there is no independent data to confirm it. The remaining intervals are mainly composed of detrital iron oxides and paramagnetic iron sulfides. Two scenarios based on different diagenetic stages are proposed to explain the variations in the magnetic properties and mineralogy over the studied interval. The results suggest that rock magnetism appears useful to better constrain the gas hydrate distribution in Hole C0008C, and counterbalances the low resolution of pore water analyses and the absence of a BSR.

  11. Linear and Non-Linear Control Techniques Applied to Actively Lubricated Journal Bearings

    Nicoletti, Rodrigo; Santos, Ilmar

    2003-01-01

    The main objectives of actively lubricated bearings are the simultaneous reduction of wear and vibration between rotating and stationary machinery parts. For reducing wear and dissipating vibration energy until certain limits, one can count with the conventional hydrodynamic lubrication. For...... further reduction of shaft vibrations one can count with the active lubrication action, which is based on injecting pressurised oil into the bearing gap through orifices machined in the bearing sliding surface. The design and efficiency of some linear (PD, PI and PID) and non-linear controllers, applied...... to a tilting-pad journal bearing, are analysed and discussed. Important conclusions about the application of integral controllers, responsible for changing the rotor-bearing equilibrium position and consequently the "passive" oil film damping coefficients, are achieved. Numerical results show an...

  12. Three Types of Active Lubrication Systems for the Main Bearings of Reciprocating Machines

    Santos, Ilmar; Pulido, E. E.

    2010-01-01

    In the paper the authors investigate three different schemes for the realization of the controllable oil injection system to be couple to the main engine bearings. The use of active lubrication in fluid film bearings helps to enhance the hydrodynamic fluid film by increasing the fluid film...... engine, where the conventional lubrication of the main bearing is modified by applying radial oil injection. The performance of such a hybrid bearing is compared to an equivalent conventional lubricated bearing in terms of the maximum fluid film pressures, minimum fluid film thicknesses and reduction of...... thickness and consequently reducing viscous friction losses and vibrations. One refers to active lubrication when conventional hydrodynamic lubrication is combined with dynamically modified hydrostatic lubrication. In this case, the hydrostatic lubrication is modified by injecting oil at controllable...

  13. Program for tests on magnetic bearing suspended rotor dynamics for gas turbine high temperature reactor (GTHTR300)

    A program for test on rotor dynamics was planned for the turbo-machine of the Gas Turbine High Temperature Reactor (GTHTR300). The rotor system of the turbo-machine consists of a turbo-compressor rotor and a generator rotor connected with a flexible coupling, each suspended with two radial magnetic bearings. The rotors, which are flexible rotors, pass over the critical speeds of bending mode. The magnetic bearing is required to have a high load capacity, about 10 times larger than any built thus far to support a flexible rotor. In the rotor design, the standard limit of the vibration amplitude of 75 μm at the rated rotational speed of 3,600 rpm was fulfilled by optimizing the stiffness of the magnetic bearings. A test apparatus was designed to verify the design of the magnetic bearing suspended turbo-machine rotor of the GTHTR300. The test apparatus is composed of 1/3-scale test rotors, which are connected with a flexible coupling and driven by a variable speed motor. The test magnetic bearing was designed within the state-of-the-art technology to have a load capacity about 1/10 of that of the actual one. The test rotors were designed to closely simulate the critical speeds and vibration modes of the actual ones. This paper shows the test apparatus and the test plan for the magnetic bearing suspended rotor system. The present study is entrusted from the Ministry of Education, Culture, Sports, Science and Technology of Japan. (author)

  14. Analysis on Dynamic Performance for Active Magnetic Bearing—Rotor System

    YANHui-yan; WANGXi-ping; 等

    2001-01-01

    In the application of active magnetic bearings(AMB),one of the key problems to be solved is the safety and stabiltiy in the sense of rotor dynamics,The project related to the present paper deals with the method for analyzing bearing rotor systems with high rotation speed and specially supported by active magnetic bearings,and studies its rotor dynamics performance,including calculation of the natural frequencies with their distribution characteristics,and the critical speeds of the system.one of the targets of this project is to formulate a theory and method valid for the analysis of the dynamic performance of the active magntic bearing-rotor systemby combining the traditional theory and method of rotor dynamics with the analytical theory and design method based on modern control theory of the AMB system.

  15. Low- and high-temperature magnetic properties of iron-bearing particles of combustion origin

    Kim, W.; Doh, S. J.; Yu, Y.; Moon, J. W.

    2012-04-01

    Magnetic particulates in the urban atmosphere are often observed in the forms of spherules and aggregates derived from iron impurities in fossil fuels upon combustion. Recently, magnetic properties of various atmospheric samples gather a scientific interest as economic and rapid proxies in the pollution studies based on their strong linkage to heavy metals and/or volatile organic carbons. Here we present low- and high-temperature magnetic properties of iron-bearing spherules and aggregates separated from the dry-deposit of aerosols and vehicle exhaust emission, respectively. Spherical particles behave like magnetite with the domain state of pseudo-single-domain even for larger than 10 μm in diameter. This probably involves the growth of magnetite branching small particles with a dendritic texture. For the aggregates containing abundant sulfur, only a magnetite signal can be found in low-temperature but both pyrrhotite and magnetite signals occur in high-temperature. Such discrepancy indicates that aggregates of magnetite-like particles with non-monoclinic pyrrhotite due to the absence of low-temperature transition in remanence at around 30 - 35 K.

  16. Tilting-Pad Journal Bearings with Active Lubrication Applied as Calibrated Shakers: Theory and Experiment

    Cerda Varela, Alejandro Javier; Santos, Ilmar

    2014-01-01

    In recent years, a continuous research effort has transformed the conventional tilting-pad journal bearing into a mechatronic machine element. The addition of electromechanical elements provides the possibility of generating controllable forces over the rotor as a function of a suitable control...... dependent calibration function, i.e. the transfer function between control signal and force over the rotor. This work presents a theoretical model of the calibration function for a tilting-pad journal bearing with active lubrication. The bearing generates controllable forces by injecting pressurized oil...... signal. Such forces can be applied in order to perform parameter identification procedures in-situ, which enables evaluation of the mechanical condition of the machine in a non-invasive way. The usage of a controllable bearing as a calibrated shaker requires obtaining the bearing specific frequency...

  17. Sensorless Speed Control of a Permanent Magnet Type Axial Gap Self Bearing Motor

    Nguyen, Dich Quang; Ueno, Satoshi

    The goal of this paper is use the Luenberger observer to research a new capability of controlling the axial gap self bearing motor, in which an analytical and experimental evaluation of a sensorless speed vector control of a permanent magnet type axial gap self bearing motor is presented. Rotor speed and position are estimated by using a state observer, not by using any shaft mounted position sensor as encoder or resolver etc. The approach is based on the estimation of the motor back-EMF (or induced voltage) through a Luenberger observer with help of measured stator currents and reference voltages. In order to achieve an accurate estimation of the rotor speed and position in all operating range, adaptive gain of observer controller is proposed. Furthermore, due to the change of air gap at the practical experiment, a compensation procedure also assures the system working stably at any axial position of rotor. The experiment is implemented based on dSpace1104 with two three-phase inverters. Results confirm that axial force and rotating torque can be controlled independently and motor can get the good performance in steady state at the average and high speed range.

  18. 5th workshop 'Magnetic bearings'. Proceedings; 5. Workshop Magnetlagertechnik. Tagungsband

    Gaertner, S.; Rottenbach, T. (comps.)

    2001-07-01

    The workshop investigated the state of the art of magnetic bearings and their applications. It was attended by experts from industry, research institutions and universities who took the chance to exchange their experience and keep abreast of new developments. The proceedings volume contains all papers presented at the meeting, in chronological order. [German] Der Workshop stellt sich zur Aufgabe, sowohl die Fortschritte in Forschung und Entwicklung in der Magnetlagertechnik aufzuzeigen als auch den Stand der Technik an speziellen Anwendungen darzustellen. Die Veranstaltung versteht sich als Forum fuer Forscher und Anwender aus der Industrie, industriellen Forschungseinrichtungen sowie Universitaeten und Hochschulen. Daher steht der Erfahrungsaustausch zwischen Entwicklern, Herstellern und Betreibern im Mittelpunkt. Interessierte Fachleute aus Wissenschaft und Industrie haben hier die Moeglichkeit, sich ueber die Grundlagen, Einsatzmoeglichkeiten und Anwendungsgebiete der Magnetlagertechnologie zu informieren. Im vorliegenden Tagungsband sind die von den Autoren eingereichten Beitraege in der Reihenfolge des Tagungsprogramms wiedergegeben. (orig.)

  19. Actively lubricated bearings applied as calibrated shakers to aid parameter identification in rotordynamics

    Santos, Ilmar; Cerda Varela, Alejandro Javier

    2013-01-01

    -invasive perturbation forces, or in other words, as a "calibrated shaker", to perform in-situ rotordynamic tests. The main original contributions of this paper are three: a) the experimental characterization of the active fluid film forces generated in an actively-lubricated tilting-pad journal bearing in the frequency......The servo valve input signal and the radial injection pressure are the two main parameters responsible for dynamically modifying the journal oil film pressure and generating active fluid film forces in controllable fluid film bearings. Such fluid film forces, resulting from a strong coupling...... domain and the application of such a controllable bearing as a calibrated shaker aiming at determining the frequency response function (FRF) of rotordynamic systems; b) experimental quantification of the influence of the supply pressure and servo valve input signal on the FRF of rotor-journal bearing...

  20. Linear and Non-Linear Control Techniques Applied to Actively Lubricated Journal Bearings

    Nicoletti, Rodrigo; Santos, Ilmar

    2003-01-01

    The main objectives of actively lubricated bearings are the simultaneous reduction of wear and vibration between rotating and stationary machinery parts. For reducing wear and dissipating vibration energy until certain limits, one can count with the conventional hydrodynamic lubrication....... For further reduction of shaft vibrations one can count with the active lubrication action, which is based on injecting pressurised oil into the bearing gap through orifices machined in the bearing sliding surface. The design and efficiency of some linear (PD, PI and PID) and non-linear controllers, applied...... vibration reduction of unbalance response of a rigid rotor, where the PD and the non-linear P controllers show better performance for the frequency range of study (0 to 80 Hz). The feasibility of eliminating rotor-bearing instabilities (phenomena of whirl) by using active lubrication is also investigated...

  1. Rotational Remanent Magnetization (RRM) to Identify Pyrrhotite in Natural Iron-Sulfide-Bearing Samples

    Slotznick, S. P.; Kirschvink, J. L.; Fischer, W. W.; Webb, S. M.

    2014-12-01

    Pyrrhotite has been known for several decades to have anomalous demagnetization behavior when using tumbling AF techniques. This was quantified by Thomson (1990) to show that pyrrhotite can acquire rotational remanent magnetization (RRM) similar to the more intensely-studied iron sulfide, greigite. Use of RRM as an identification tool in natural samples has not become standard practice, perhaps due to the decrease in use of tumbling AF techniques. However, using the 2G SQuID magnetometer with in-line AF/ARM coils and RAPID automated protocols (Kirschvink et al. 2008), one can easily produce and measure RRM. This method of measuring RRM has been used to identify greigite (Suzuki et al. 2006), but not pyrrhotite. We present room temperature RRM measurements for samples spinning from -20 to +20 rev/sec, perpendicular to peak AF fields of 90mT (at 950 Hz) in iron-sulfide-bearing shales, argillites, and carbonates throughout Earth History (Miocene, Cretaceous, Mesoproterozoic, Late Archean). Presence of pyrrhotite was confirmed using AF demagnetization of NRM (GRM), IRM acquisition/AF demagnetization (Cisowski plots), Kappabridge thermal susceptibility, ultra-high resolution scanning SQuID microscopy (UHRSSM), and/or X-ray absorption near edge spectroscopy (XANES)/multiple energy X-ray fluorescence (XRF) imaging. Although the total absence of pyrrhotite cannot be proven, the same techniques were applied to rocks that do not gain RRM easily to identify their iron sulfides and ferromagnetic minerals, and no magnetic iron sulfides were found. The RRM signal for pyrrhotite is distinct from that of greigite, suggesting it could be used as a tool for distinguishing these magnetic iron sulfides from each other. Further work on room temperature RRM could define a unique non-destructive rock magnetic test for pyrrhotite.

  2. Test equipment for a flywheel energy storage system using a magnetic bearing composed of superconducting coils and superconducting bulks

    Ogata, M.; Matsue, H.; Yamashita, T.; Hasegawa, H.; Nagashima, K.; Maeda, T.; Matsuoka, T.; Mukoyama, S.; Shimizu, H.; Horiuchi, S.

    2016-05-01

    Energy storage systems are necessary for renewable energy sources such as solar power in order to stabilize their output power, which fluctuates widely depending on the weather. Since ‘flywheel energy storage systems’ (FWSSs) do not use chemical reactions, they do not deteriorate due to charge or discharge. This is an advantage of FWSSs in applications for renewable energy plants. A conventional FWSS has capacity limitation because of the mechanical bearings used to support the flywheel. Therefore, we have designed a superconducting magnetic bearing composed of a superconducting coil stator and a superconducting bulk rotor in order to solve this problem, and have experimentally manufactured a large scale FWSS with a capacity of 100 kWh and an output power of 300 kW. The superconducting magnetic bearing can levitate 4 tons and enables the flywheel to rotate smoothly. A performance confirmation test will be started soon. An overview of the superconducting FWSS is presented in this paper.

  3. Magnetic polarity ages of the fossil-bearing strata at the Si hetun section, West Liaoning:A preliminary result

    2001-01-01

    Rock-magnetic and palaeomagnetic studies have been carried out on the interval of famous fossil-bearing sedimentary rocks and its overlying basalts and underlying basalts at the Sihetun section, West Liaoning Province. Normal polarity was obtained for the sedimentary interval and the underlying basalts, while reversed polarity was found in the overlying basalts. Taking account of the new 40Ar/39Ar ages (Swisher et al., 1999), we classified the fossil-bearing sedimentary interval into the Barremian M3n zone (Early Cretaceous age). Several abnormal horizons on magnetic properties, probably corresponding to the tuffs,were observed in the fossil-bearing sedimentary interval.This implies that the massive bio-extinction may link to dramatic environmental changes that were caused by voleanic eruptions.``

  4. Magnetization behavior of RE123 bulk magnets bearing twin seed-crystals in pulsed field magnetization processes

    Oka, T.; Miyazaki, T.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Langer, M.

    2016-02-01

    Melt-textured Y-Ba-Cu-O high temperature superconducting bulk magnets were fabricated by the cold seeding method with using single or twin-seed crystals composed of Nd-Ba-Cu-O thin films on MgO substrates. The behavior of the magnetic flux penetration into anisotropic-grown bulk magnets thus fabricated was precisely evaluated during and after the pulsed field magnetization operated at 35 K. These seed crystals were put on the top surfaces of the precursors to grow large grains during the melt-processes. Although we know the magnetic flux motion is restricted by the enhanced pinning effect in temperature ranges lower than 77 K, we observed that flux invasion occurred at applied fields of 3.3 T when the twin seeds were used. This is definitely lower than those of 3.7 T when the single-seeds were employed. This means that the magnetic fluxes are capable of invading into twin-seeded bulk magnets more easily than single-seeded ones. The twin seeds form the different grain growth regions, the narrow-GSR (growth sector region) and wide-GSR, according to the different grain growth directions which are parallel and normal to the rows of seed crystals, respectively. The invading flux measurements revealed that the magnetic flux invades the sample from the wide-GSR prior to the narrow-GSR. It suggests that such anisotropic grain growth leads to different distributions of pinning centers, variations of J c values, and the formation of preferential paths for the invading magnetic fluxes. Using lower applied fields definitely contributed to lowering the heat generation during the PFM process, which, in turn, led to enhanced trapped magnetic fluxes.

  5. Exploring integral controllers in actively-lubricated tilting-pad journal bearings

    Salazar, Jorge Andrés González; Santos, Ilmar

    2015-01-01

    Active tilting-pad journal bearings with radial oil injection combine good stability properties of conventional tilting-pad journal bearings with the capability of improving their dynamic properties even more by control techniques. The main contribution of this work is the experimental...... investigation of integral controllers for feedback-controlled lubrication with the aim of: a) presetting the static journal center and consequently exploring the changes of bearing dynamic properties; b) obtaining an integral controller capable of re-positioning the static journal eccentricity for matching...... equilibria under conventional hydrodynamic and feedback-controlled lubrication regimes. A novel application is proposed, that tries to build non-invasive perturbation forces and uses the active fluid film forces of the bearing as a calibrated shaker....

  6. Textured bearing surface in artificial joints to reduce macrophage activation

    Nakanishi, Yoshitaka; Nishi, Naoki; Chikaura, Hiroto; Nakashima, Yuta; Miura, Hiromasa; Higaki, Hidehiko; Mizuta, Hiroshi; Iwamoto, Yukihide; Fujiwara, Yukio; Komohara, Yoshihiro; Takeya, Motohiro

    2015-12-01

    Micro slurry-jet erosion has been proposed as a precision machining technique for the bearing surfaces of artificial joints in order to reduce the total amount of polyethylene wear and to enlarge the size of the wear debris. The micro slurry-jet erosion method is a wet blasting technique which uses alumina particles as the abrasive medium along with compressed air and water to create an ideal surface. Pin-on-disc wear tests with multidirectional sliding motion on the textured surface of a \\text{Co}-\\text{Cr}-\\text{Mo} alloy counterface for polyethylene resulted in both a reduction of wear as well as enlargement of the polyethylene debris size. In this study, primary human peripheral blood mononuclear phagocytes were incubated with the debris, and it was elucidated that the wear debris generated on the textured surface regulated secretion of the proinflammatory cytokines IL-6 and TNF-α, indicating a reduction in the induced tissue reaction and joint loosening.

  7. Synthesis of New Thiazole Derivatives Bearing A Sulfonamide Moiety Of Expected Anticancer And Radiosensitizing Activities

    In a search for new cytotoxic agents with improved antitumor activity and selectivity, some new pyrano thiazole and thiazolopyranopyrimidine derivatives bearing sulfonamide moiety were synthesized. The newly synthesized compounds were evaluated for their antitumor activity alone and in combination with γ-irradiation. These new compounds were docked inside the active site of carbonic anhydrase II to predict their mechanism of action.

  8. Diffusion in active magnetic colloids

    Properties of active colloids of circle swimmers are reviewed. As a particular example of active magnetic colloids the magnetotactic bacteria under the action of a rotating magnetic field is considered. The relation for a diffusion coefficient due to the random switching of the direction of rotation of their rotary motors is derived on the basis of the master equation. The obtained relation is confirmed by the direct numerical simulation of random trajectory of a magnetotactic bacterium under the action of the Poisson type internal noise due to the random switching of rotary motors. The results obtained are in qualitative and quantitative agreement with the available experimental results and allow one to determine the characteristic time between the switching events of a rotary motor of the bacterium. - Highlights: • Magnetotactic bacteria in a rotating field behaves as circle swimmers. • Diffusion coefficient of these swimmers due to the random switching of rotary motors is calculated. • Results are in good qualitative and quantitative agreement with available experimental results

  9. Linear and non-linear control techniques applied to actively lubricated journal bearings

    Nicoletti, R.; Santos, I. F.

    2003-03-01

    The main objectives of actively lubricated bearings are the simultaneous reduction of wear and vibration between rotating and stationary machinery parts. For reducing wear and dissipating vibration energy until certain limits, one can use the conventional hydrodynamic lubrication. For further reduction of shaft vibrations one can use the active lubrication action, which is based on injecting pressurized oil into the bearing gap through orifices machined in the bearing sliding surface. The design and efficiency of some linear (PD, PI and PID) and a non-linear controller, applied to a tilting-pad journal bearing, are analysed and discussed. Important conclusions about the application of integral controllers, responsible for changing the rotor-bearing equilibrium position and consequently the "passive" oil film damping coefficients, are achieved. Numerical results show an effective vibration reduction of unbalance response of a rigid rotor, where the PD and the non-linear P controllers show better performance for the frequency range of study (0-80 Hz). The feasibility of eliminating rotor-bearing instabilities (phenomena of whirl) by using active lubrication is also investigated, illustrating clearly one of its most promising applications.

  10. Study on the controllability for active magnetic bearings

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

  11. Magnetic Helicity Injection in Solar Active Regions

    Hong-Qi Zhang

    2006-01-01

    We present the evolution of magnetic field and its relationship with magnetic (current) helicity in solar active regions from a series of photospheric vector magnetograms obtained by Huairou Solar Observing Station, longitudinal magnetograms by MDI of SOHO and white light images of TRACE. The photospheric current helicity density is a quantity reflecting the local twisted magnetic field and is related to the remaining magnetic helicity in the photosphere, even if the mean current helicity density brings the general chiral property in a layer of solar active regions. As new magnetic flux emerges in active regions, changes of photospheric current helicity density with the injection of magnetic helicity into the corona from the subatmosphere can be detected, including changes in sign caused by the injection of magnetic helicity of opposite sign. Because the injection rate of magnetic helicity and photospheric current helicity density have different means in the solar atmosphere,the injected magnetic helicity is probably not proportional to the current helicity density remaining in the photosphere. The evidence is that rotation of sunspots does not synchronize exactly with the twist of photospheric transverse magnetic field in some active regions (such as, delta active regions). They represent different aspects of magnetic chirality. A combined analysis of the observational magnetic helicity parameters actually provides a relative complete picture of magnetic helicity and its transfer in the solar atmosphere.

  12. Development and characterization of magnetic iron oxide nanoparticles with a cisplatin-bearing polymer coating for targeted drug delivery

    Unterweger, Harald; Tietze, Rainer; Janko, Christina; Zaloga, Jan; Lyer, Stefan; Dürr, Stephan; Taccardi, Nicola; Goudouri, Ourania-Menti; Hoppe, Alexander; Eberbeck, Dietmar; Schubert, Dirk W; Boccaccini, Aldo R; Alexiou, Christoph

    2014-01-01

    A highly selective and efficient cancer therapy can be achieved using magnetically directed superparamagnetic iron oxide nanoparticles (SPIONs) bearing a sufficient amount of the therapeutic agent. In this project, SPIONs with a dextran and cisplatin-bearing hyaluronic acid coating were successfully synthesized as a novel cisplatin drug delivery system. Transmission electron microscopy images as well as X-ray diffraction analysis showed that the individual magnetite particles were around 4.5 nm in size and monocrystalline. The small crystallite sizes led to the superparamagnetic behavior of the particles, which was exemplified in their magnetization curves, acquired using superconducting quantum interference device measurements. Hyaluronic acid was bound to the initially dextran-coated SPIONs by esterification. The resulting amide bond linkage was verified using Fourier transform infrared spectroscopy. The additional polymer layer increased the vehicle size from 22 nm to 56 nm, with a hyaluronic acid to dextran to magnetite weight ratio of 51:29:20. A maximum payload of 330 μg cisplatin/mL nanoparticle suspension was achieved, thus the particle size was further increased to around 77 nm with a zeta potential of −45 mV. No signs of particle precipitation were observed over a period of at least 8 weeks. Analysis of drug-release kinetics using the dialysis tube method revealed that these were driven by inverse ligand substitution and diffusion through the polymer shell as well as enzymatic degradation of hyaluronic acid. The biological activity of the particles was investigated in a nonadherent Jurkat cell line using flow cytometry. Further, cell viability and proliferation was examined in an adherent PC-3 cell line using xCELLigence analysis. Both tests demonstrated that particles without cisplatin were biocompatible with these cells, whereas particles with the drug induced apoptosis in a dose-dependent manner, with secondary necrosis after prolonged incubation

  13. Connection between active longitudes and magnetic helicity

    Brandenburg, A

    2005-01-01

    A two-dimensional mean field dynamo model is solved where magnetic helicity conservation is fully included. The model has a negative radial velocity gradient giving rise to equatorward migration of magnetic activity patterns. In addition the model develops longitudinal variability with activity patches travelling in longitude. These patches may be associated with active longitudes.

  14. Compensation of Cross-Coupling Stiffness and Increase of Direct Damping in Multirecess Journal Bearings using Active Hybrid Lubrication

    Santos, Ilmar; Watanabe, F.Y.

    2004-01-01

    Fluid film forces are generated in hydrostatic journal bearings by two types of lubrication mechanisms: the hydrostatic lubrication in the bearing recesses and hydrodynamic lubrication in the bearing lands, when operating in rotation. The combination of both lubrication mechanisms leads to hybrid...... journal bearings (HJB). When part of hydrostatic pressure is also dynamically modified by means of hydraulic control systems, one refers to the active lubrication. The main contribution of the present theoretical work is to show that it is possible to reduce cross-coupling stiffness and increase the...... direct damping coefficients by means of the active lubrication, what leads to rotor-bearing systems with larger threshold of stability....

  15. Tunable reflector with active magnetic metamaterials.

    Deng, Tianwei; Huang, Ruifeng; Tang, Ming-Chun; Tan, Peng Khiang

    2014-03-24

    We placed active magnetic metamaterials on metallic surface to implement a tunable reflector with excellent agile performance. By incorporating active elements into the unit cells of the magnetic metamaterial, this active magnetic metamaterial can be tuned to switch function of the reflector among a perfect absorber, a perfect reflector and a gain reflector. This brings about DC control lines to electrically tune the active magnetic metamaterial with positive loss, zero loss and even negative loss. The design, analytical and numerical simulation methods, and experimental results of the tunable reflector are presented. PMID:24663977

  16. Demagnetizing fields in active magnetic regenerators

    Nielsen, Kaspar Kirstein; Bahl, Christian R.H.; Smith, Anders

    2014-01-01

    A magnetic material in an externally applied magnetic field will in general experience a spatially varying internal magnetic field due to demagnetizing effects. When the performance of active magnetic regenerators (AMRs) is evaluated using numerical models the internal field is often assumed to be...... is in general both a function of the overall shape of the regenerator and its morphology (packed particles, parallel plates etc.) as well as the magnetization of the material. Due to the pronounced temperature dependence of the magnetization near the Curie temperature, the demagnetization field is...

  17. Modeling and Development of a Magnetic Bearing Controller for a High Speed Flywheel System

    Dever, Timothy P.; Brown, Gerald V.; Duffy, Kirsten P.; Jansen, Ralph H.

    2005-01-01

    This paper describes a modeling effort used to develop an improved type of magnetic bearing controller, called a modal controller, for use on high speed flywheel systems. The controller design is based on models of the flywheel system, is designed to directly control the natural dynamics of the spinning rotor, and is generic enough to be readily adapted to future flywheel systems. Modeling and development are described for two key controller subsystems: the modal controller subsystem, which allows direct control over the rotor rigid body modes, and the bending mode compensation subsystem, which tracks, and prevents interference from, the rotor bending modes during flywheel operation. Integration of modeling results into the final controller is described and data taken on the NASA Glenn D1 flywheel module during high speed operation are presented and discussed. The improved modal controller described in this paper has been successfully developed and implemented and has been used for regular hands-free operation of the D1 flywheel module up to its maximum operating speed of 60,000 RPM.

  18. Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System

    Nicoletti, Rodrigo; Santos, Ilmar

    2005-01-01

    In the present paper the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted...... active lubricated tilting-pad bearing. By applying a simple proportional controller it is possible to reach 30% reduction of the resonance peak associated with the first rigid body mode shape of the system. One of the most important consequences of such a vibration reduction in rotating machines is the...

  19. Superconducting magnet activities at CEN Saclay

    The activities in superconducting magnets at DPhPE/Saclay spread over a wide range from DC magnets mainly for particle and nuclear physics and also for other fields of research, pulsed magnets for particle accelerators and for a controlled fusion tokamak machine. The superconducting magnets designed during recent years involve a variety of conductor types, winding schemes, materials and cooling modes, including the use of superfluid helium. (author)

  20. Pumps for cryogenic liquids with superconducting magnetic bearings. Final report; Pumpen fuer kryogene Fluessigkeiten mit supraleitenden Magnetlagern. Abschlussbericht

    Gerlach, G.; Fuchs, G.; Sorber, J.; Brosche, H.; Richter, M.; Frenzel, C.

    2000-07-01

    A liquid nitrogen pump with contactless superconducting magnetic bearings was to be developed on the basis of an available motor with superconducting bearings. Contactless superconducting magnetic bearings require practically no servicing. A high demand for pumps for cryogenic liquids is expected with the impending use of hydrogen as an energy source. The pumping of liquid nitrogen was demonstrated successfully with the new test aggregate. The maximum pumped volume was 17 l/min at a lift of 0.5 m and 6 l/min at a lift of 1 m. In all, 15 hours of operation were registered in the superconducting state of the bearing, which included 2 hours of uninterrupted pump operation. The higher speed range for which magnetic bearings are optimally suited was not reached. Operation at higher frequencies was impossible either because of stronger resonance amplituees or because the power system was too weak. [German] Ziel des Vorhabens war die Entwicklung einer Pumpe fuer fluessigen Stickstoff mit beruehrungslosen supraleitenden Magnetlagern auf der Basis eines vorhandenen supraleitend gelagerten Motors. Die beruehrungslose supraleitende Magnetlager sind praktisch wartungsfrei. Ein Bedarf an Pumpen fuer kryogene Fluessigkeiten entsteht insbesondere durch den in naher Zukunft zu erwartenden Einsatz von Wasserstoff als Energietraeger. Mit dem entworfenen Aggregat wurde das Pumpen von Fluessigstickstoff erfolgreich demonstriert. Der Foerderstrom betrug bei 0,5m Foerderhoehe maximal 17 l/min; beim 1m Foerderhoehe wurden maximal 6 l/min gemessen. Es wurden insgesamt ca. 15 Betriebsstunden in supraleitenden Zustand des Lagers, darunter 2 Stunden ununterbrochener Pumpbetrieb registriert. Der hoehere Drehzahlbereich, fuer den das Magnetlager eigentlich paedestiniert ist, konnte nicht erreicht werden. Ein Betrieb bei hoeheren (Ist-)Frequenzen war nicht moeglich, entweder durch staerkere Resonanzausschlaege oder durch einen zu schwachen Antrieb. (orig.)

  1. Active lubrication applied to radial gas journal bearings. Part 2: Modelling improvement and experimental validation

    Pierart, Fabián G.; Santos, Ilmar F.

    2016-01-01

    Actively-controlled lubrication techniques are applied to radial gas bearings aiming at enhancing one of their most critical drawbacks, their lack of damping. A model-based control design approach is presented using simple feedback control laws, i.e. proportional controllers. The design approach...... combines three main domains: tribology, dynamics and control. The Reynolds equation with radial injection, including piezoelectrically controlled jet, describes the non-linear interaction between bearing surface and rotating shaft. Dynamics of the flexible shaft and rotating parts are modelled aid by...... finite element method and the global model is used as control design tool. Active lubrication allows for significant increase in damping factor of the rotor-bearing system. Very good agreement between theory and experiment is obtained, supporting the multi-physic design tool developed....

  2. Actively lubricated bearings applied as calibrated shakers to aid parameter identification in rotordynamics

    Santos, Ilmar; Cerda Varela, Alejandro Javier

    2013-01-01

    between hydrodynamic, hydrostatic and controllable lubrication regimes, can be used either to control or to excite rotor lateral vibrations. An accurate characterization of the active oil film forces is of fundamental importance to elucidate the feasibility of applying the active lubrication as non......-invasive perturbation forces, or in other words, as a "calibrated shaker", to perform in-situ rotordynamic tests. The main original contributions of this paper are three: a) the experimental characterization of the active fluid film forces generated in an actively-lubricated tilting-pad journal bearing in the frequency...... systems; c) experimental indication of how small such active fluid film forces (perturbation forces) should be, in order to perturb the rotor-journal bearing system without significantly changing its dynamic characteristics. To validate the experimental procedure and results obtained via actively-lubricated...

  3. Thermally activated magnetization reversal in magnetic tunnel junctions

    Zhou Guang-Hong; Wang Yin-Gang; Qi Xian-Jin; Li Zi-Quan; Chen Jian-Kang

    2009-01-01

    In this paper, the magnetization reversal of the ferromagnetic layers in the lrMn/CoFe/AlOx/CoFe magnetic tunnel junction has been investigated using bulk magnetometry. The films exhibit very complex magnetization processes and reversal mechanism. Thermal activation phenomena such as the training effect, the asymmetry of reversal, the loop broadening and the decrease of exchange field while holding the film at negative saturation have been observed on the hysteresis loops of the pinned ferromagnetic layer while not on those of the free ferromagnetic layer. The thermal activation phenomena observed can be explained by the model of two energy barrier distributions with different time constants.

  4. Water-soluble ruthenium complexes bearing activity against protozoan parasites.

    Sarniguet, Cynthia; Toloza, Jeannette; Cipriani, Micaella; Lapier, Michel; Vieites, Marisol; Toledano-Magaña, Yanis; García-Ramos, Juan Carlos; Ruiz-Azuara, Lena; Moreno, Virtudes; Maya, Juan Diego; Azar, Claudio Olea; Gambino, Dinorah; Otero, Lucía

    2014-06-01

    Parasitic illnesses are major causes of human disease and misery worldwide. Among them, both amebiasis and Chagas disease, caused by the protozoan parasites, Entamoeba histolytica and Trypanosoma cruzi, are responsible for thousands of annual deaths. The lack of safe and effective chemotherapy and/or the appearance of current drug resistance make the development of novel pharmacological tools for their treatment relevant. In this sense, within the framework of the medicinal inorganic chemistry, metal-based drugs appear to be a good alternative to find a pharmacological answer to parasitic diseases. In this work, novel ruthenium complexes [RuCl2(HL)(HPTA)2]Cl2 with HL=bioactive 5-nitrofuryl containing thiosemicarbazones and PTA=1,3,5-triaza-7-phosphaadamantane have been synthesized and fully characterized. PTA was included as co-ligand in order to modulate complexes aqueous solubility. In fact, obtained complexes were water soluble. Their activity against T. cruzi and E. histolytica was evaluated in vitro. [RuCl2(HL4)(HPTA)2]Cl2 complex, with HL4=N-phenyl-5-nitrofuryl-thiosemicarbazone, was the most active compound against both parasites. In particular, it showed an excellent activity against E. histolytica (half maximal inhibitory concentration (IC50)=5.2 μM), even higher than that of the reference drug metronidazole. In addition, this complex turns out to be selective for E. histolytica (selectivity index (SI)>38). The potential mechanism of antiparasitic action of the obtained ruthenium complexes could involve oxidative stress for both parasites. Additionally, complexes could interact with DNA as second potential target by an intercalative-like mode. Obtained results could be considered a contribution in the search for metal compounds that could be active against multiple parasites. PMID:24740394

  5. The Magnetic Free Energy in Active Regions

    Metcalf, Thomas R.; Mickey, Donald L.; LaBonte, Barry J.

    2001-01-01

    The magnetic field permeating the solar atmosphere governs much of the structure, morphology, brightness, and dynamics observed on the Sun. The magnetic field, especially in active regions, is thought to provide the power for energetic events in the solar corona, such as solar flares and Coronal Mass Ejections (CME) and is believed to energize the hot coronal plasma seen in extreme ultraviolet or X-rays. The question remains what specific aspect of the magnetic flux governs the observed variability. To directly understand the role of the magnetic field in energizing the solar corona, it is necessary to measure the free magnetic energy available in active regions. The grant now expiring has demonstrated a new and valuable technique for observing the magnetic free energy in active regions as a function of time.

  6. Feasibility of Influencing the Dynamic Fluid Film Coefficients of a Multirecess Journal Bearing by means of Active Hybrid Lubrication

    Santos, Ilmar; Watanabe, F. Y.

    2003-01-01

    The main objective of this research project is the investigation of multirecess hydrostatic journal bearings with active hybrid (hydrostatic and hydrodynamic) lubrication. This paper gives a theoretical contribution to the modeling of this kind of bearing, combining computational fluid dynamics a...... significant modifications of active hybrid forces, which can be useful while reducing vibration and stabilizing rotating machines.......The main objective of this research project is the investigation of multirecess hydrostatic journal bearings with active hybrid (hydrostatic and hydrodynamic) lubrication. This paper gives a theoretical contribution to the modeling of this kind of bearing, combining computational fluid dynamics and...

  7. Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System

    Nicoletti, Rodrigo; Santos, Ilmar

    2004-01-01

    In the present paper, the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted...... lubricated tilting-pad bearing. By applying a simple proportional controller, it is possible to reach 30% reduction of the resonance peak associated with the first rigid body mode shape of the system. One of the most important consequences of such a vibration reduction in rotating machines is the feasibility...

  8. Experimental Identification of Dynamic Coefficients of Tilting-Pad Bearings with Active Lubrication

    Salazar, Jorge Andrés González; Cerda Varela, Alejandro Javier; Santos, Ilmar

    supply unit, b) servovalves, c) radial injection nozzles, d) displacement sensors and e) well-tuned digital controllers which turn the bearing static and dynamic properties controllable. A scaled-down industrial rotor, composed by a flexible rotor supported by a four rocker LBP tilting-pad journal......This article presents the experimental identification of the equivalent dynamic coefficients of an activelylubricated bearing under different lubrication regimes, namely: passive (no injection flow), hybrid (constant injection flow) and feedback-controlled (variable injection flow) lubrication. The...... bearing featuring active lubrication under light load conditions, is used for such a goal. The experimental identification is performed in the frequency domain by means of the measured FRFs and a finite element model of the rotor. The comparison between results under the different lubrication regimes...

  9. Development and characterization of magnetic iron oxide nanoparticles with a cisplatin-bearing polymer coating for targeted drug delivery

    Unterweger H

    2014-08-01

    Full Text Available Harald Unterweger,1 Rainer Tietze,1 Christina Janko,1 Jan Zaloga,1 Stefan Lyer,1 Stephan Dürr,1 Nicola Taccardi,2 Ourania-Menti Goudouri,3 Alexander Hoppe,3 Dietmar Eberbeck,4 Dirk W Schubert,5 Aldo R Boccaccini,3 Christoph Alexiou1 1ENT Department, Section of Experimental Oncology and Nanomedicine (SEON, Else Kroener-Fresenius-Stiftung-Professorship, University Hospital Erlangen, 2Chair of Chemical Engineering I (Reaction Engineering, 3Institute of Biomaterials, Department of Materials Science and Engineering, University Erlangen-Nuremberg, Erlangen, 4Physikalisch-Technische Bundesanstalt, Berlin, 5Institute of Polymer Materials, Department of Materials Science and Engineering, University Erlangen-Nuremberg, Erlangen, Germany Abstract: A highly selective and efficient cancer therapy can be achieved using magnetically directed superparamagnetic iron oxide nanoparticles (SPIONs bearing a sufficient amount of the therapeutic agent. In this project, SPIONs with a dextran and cisplatin-bearing hyaluronic acid coating were successfully synthesized as a novel cisplatin drug delivery system. Transmission electron microscopy images as well as X-ray diffraction analysis showed that the individual magnetite particles were around 4.5 nm in size and monocrystalline. The small crystallite sizes led to the superparamagnetic behavior of the particles, which was exemplified in their magnetization curves, acquired using superconducting quantum interference device measurements. Hyaluronic acid was bound to the initially dextran-coated SPIONs by esterification. The resulting amide bond linkage was verified using Fourier transform infrared spectroscopy. The additional polymer layer increased the vehicle size from 22 nm to 56 nm, with a hyaluronic acid to dextran to magnetite weight ratio of 51:29:20. A maximum payload of 330 µg cisplatin/mL nanoparticle suspension was achieved, thus the particle size was further increased to around 77 nm with a zeta

  10. Absolute alpha activity measurements of some plants growing in monazite bearing soils in Sri Lanka

    Mahawatte, P.; Hewamanna, R. (Colombo Univ. (Sri Lanka). Radioisotope Centre)

    1991-01-01

    Deposits of monazite bearing soils occur along the Southwest, West and East Coasts of Sri Lanka. High levels of gamma activity in some plant species growing in the West Coast have been reported. The high levels were due to the presence of the daughter nuclides of {sup 232}Th, most of which are alpha emitters. Absolute alpha activity measurements of ash samples of some plants growing in monazite bearing soils were carried out using the alpha sensitive polymeric nuclear track detector CR-39. The values ranged from 60-1900 mBq/g and were in good agreement with the values obtained from conventional scintillation counting method. The activity concentration of {sup 228}Th in the ash samples was also calculated by measuring the activity concentration of emanated thoron trapped inside a glass bottle with the use of a CR-39 track detector. (author).

  11. Absolute alpha activity measurements of some plants growing in monazite bearing soils in Sri Lanka

    Deposits of monazite bearing soils occur along the Southwest, West and East Coasts of Sri Lanka. High levels of gamma activity in some plant species growing in the West Coast have been reported. The high levels were due to the presence of the daughter nuclides of 232Th, most of which are alpha emitters. Absolute alpha activity measurements of ash samples of some plants growing in monazite bearing soils were carried out using the alpha sensitive polymeric nuclear track detector CR-39. The values ranged from 60-1900 mBq/g and were in good agreement with the values obtained from conventional scintillation counting method. The activity concentration of 228Th in the ash samples was also calculated by measuring the activity concentration of emanated thoron trapped inside a glass bottle with the use of a CR-39 track detector. (author)

  12. Rock magnetic characterization of ferrimagnetic iron sulfides in gas hydrate-bearing marine sediments at Site C0008, Nankai Trough, Pacific Ocean, off-coast Japan

    Kars, Myriam; Kodama, Kazuto

    2015-07-01

    A high-resolution rock magnetic study was carried out in Integrated Ocean Drilling Program (IODP) Expedition 316 Hole C0008A located in the Megasplay Fault Zone of the Nankai Trough, SW offshore Japan, in order to document changes in magnetic properties throughout gas hydrate-bearing horizons. A total of 169 Pleistocene discrete samples were collected from ~110 to 153 m core depth below sea floor (CSF), and their magnetic minerals concentration, grain size, composition, and rock magnetic parameters were estimated. Results showed the presence of iron oxides ((titano)-magnetite), iron sulfides (greigite and pyrrhotite), and their mixture, among which single-domain greigite is the most major magnetic mineral present in the samples. Two horizons containing ferrimagnetic iron sulfides (114.5-127.5 and 129.5-150 m CSF) covering almost the entire studied interval were identified, both associated with slight local pore water anomalies, suggesting occurrence of gas hydrates and anoxic conditions. These results are different from the neighboring Hole C0008C (215 m away from Hole C0008A) where four pore water anomalies and six iron sulfide-rich intervals were identified for the same time slice. Comparison of the lithology, physical properties, and geochemical data of the two boreholes at Site C0008 suggests that a combination of processes (e.g., availability of reactive iron, microbial activity) is responsible for such laterally varying distribution of the ferrimagnetic iron sulfides.

  13. Bifurcations and intermittent magnetic activity

    The sequence of equilibria of two-dimensional reduced magnetohydrodynamics has been studied as a function of the tearing mode stability parameter Δ'. After a symmetry-breaking bifurcation occurring at Δ' ∼ 0, which originates a state with a small magnetic island, the system undergoes a second bifurcation, of tangent type, at Δ' ∼ 1. Above this value, no stationary solutions with small islands exist. The system rapidly develops an island of macroscopic size. This general property is proposed as a basic ingredient of the intermittent events observed in magnetically confined plasmas. (author)

  14. Bifurcations and intermittent magnetic activity

    Tebaldi, C.; Ottaviani, M.; Porcelli, F. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking

    1996-04-01

    The sequence of equilibria of two-dimensional reduced magnetohydrodynamics has been studied as a function of the tearing mode stability parameter {Delta}`. After a symmetry-breaking bifurcation occurring at {Delta}` {approx} 0, which originates a state with a small magnetic island, the system undergoes a second bifurcation, of tangent type, at {Delta}` {approx} 1. Above this value, no stationary solutions with small islands exist. The system rapidly develops an island of macroscopic size. This general property is proposed as a basic ingredient of the intermittent events observed in magnetically confined plasmas. (author).

  15. Maintenance Free Bearings

    S. M. Muzakkir & Harish Hirani

    2015-01-01

    In the present research work the need of a Maintenance Free Bearings (MFB) is established. The paper presents preliminary friction calculations to highlight the ways to achieve maintenance free bearings. The existing technologies of well established maintenance free bearings are described. The hybridization of bearing technologies to achieve low cost maintenance free bearings has been exemplified. Finally a combination of passive magnetic repulsion and hydrodynamics ha...

  16. Inconsistent magnetic polarities in magnetite- and greigite-bearing sediments: Understanding complex magnetizations in the late Messinian in the Adana Basin (southern Turkey)

    Lucifora, Stella; Cifelli, Francesca; Mattei, Massimo; Sagnotti, Leonardo; Cosentino, Domenico; Roberts, Andrew P.

    2012-10-01

    We present paleomagnetic, rock magnetic and scanning electron microscope data from three upper Messinian stratigraphic sections from the Adana Basin (southern Turkey). The collected samples are from fine-grained units, which were deposited during the Messinian Salinity Crisis (within subchron C3r). Paleomagnetic results reveal an inconsistent polarity record, related to a mixture of magnetite and greigite that hinders determination of a reliable magnetostratigraphy. Three classes of samples are recognized on the basis of paleomagnetic results. The first is characterized by a single magnetization component, with normal polarity, that is stable up to 530-580°C and is carried by magnetite. The second is characterized by a single magnetization component, with reversed polarity, that is stable up to 330-420°C. This magnetization is due to greigite, which developed after formation of slumps and before tectonic tilting of the studied successions. The third is characterized by reversed polarity, which is stable up to 530-580°C. We interpret this component as a primary magnetization carried by fine-grained and magnetically stable detrital magnetite. Results indicate that in the Adana Basin the assumption that a primary magnetization is carried by magnetite, and a magnetic overprint carried by greigite, does not hold because a late magnetic overprint has also been found for magnetite-bearing samples. Our data illustrate the complexity of magnetostratigraphic reconstructions in successions characterized by variable mixtures of magnetic minerals with different magnetic stability that formed at different stages. We demonstrate the need to perform detailed magnetic mineralogy analyses when conducting magnetostratigraphic studies of clay-rich sediments from marine or lacustrine environments.

  17. Observational Study of Solar Magnetic Active Phenomena

    Hongqi Zhang

    2006-06-01

    The electric current separated into two parts reflected the quantative properties of heterogeneity and chirality of magnetic field, and defined them as the shear and twist components of current. We analyze the basic configuration and evolution of superactive region NOAA 6580-6619-6659. It is found that the contribution of the twist component of current cannot be reflected in the normal analysis of the magnetic shear and gradient of the active regions. The observational evidence of kink magnetic ropes generated from the subatmosphere cannot be found completely in some super delta active regions.

  18. Active vibration control of a rotor-bearing system based on dynamic stiffness

    Andrés Blanco Ortega; Francisco Beltrán Carbajal; Gerardo Silva Navarro; Marco Antonio Oliver Salazar

    2010-01-01

    This paper presents an active vibration control scheme to reduce unbalance induced synchronous vibration in rotorbearing systems supported on two ball bearings, one of which can be automatically moved to control the effective rotor length and, as an immediate consequence, the rotor stiffness. This dynamic stiffness control scheme, based on frequency analysis, speed control and acceleration scheduling, is used to avoid resonant vibration of a rotor system when it passes (runup or coast down) t...

  19. Myocardial enzyme activities of black bears and comparison with those of human beings

    HOU Wan-ru; LUO Fei-li; HU Zhi-ping

    2005-01-01

    According to the principle of enzyme reaction rate, healthy pent black bears' myocardial enzyme activity is assayed by visual colorimetry and compared with that of healthy human beings. The determination at 37℃ and the statistic analysis of the experimental data work out the following findings. For male black bears, the average CK activity is 163.20U/L, the confidence interval of its expected value (127.70 to 198.70)U/L, and the coefficient of variation 39.2%; the average CK-MB activity 21.62U/L, the confidential interval (17.72 to 25.51)U/L, and the coefficient of variation 34.26%; the average LDH activity 604.20U/L, the confidence interval (524.56 to 683.83)U/L, and the coefficient of variation 23.80%; the average HBDH activity 516.70U/L, the confidence interval (453.06 to 580.34)U/L, and the coefficient of variation 22.24%; the average GOT activity 69.70U/L, the confidence interval (60.21 to 79.19)U/L, and the coefficient of variation 24.59%. For female black bears, the average CK activity is 145.50U/L, the confidence interval (114.59 to 176.21)U/L, and the coefficient of variation 38.27%; the average CK-MB activity 18.84U/L, the confidence interval (14.64 to 23.04)U/L, and the coefficient of variation 40.34%; the average LDH activity 563.70U/L, the confidence interval (473.80 to 652.60)U/L, and the coefficient of variation 28.80%; the average of HBDH activity 475.50U/L, the confidence interval (412.10 to 538.40)U/L, and the coefficient of variation 24.07%; the average of GOT activity is 62.37U/L, the confidential interval (52.54 to 72.20)U/L, and the coefficient of variation 28.46%. The male black bear's average myocardium enzyme activities are slightly higher than those of the female. But the statistical results indicate that the difference is not significant.

  20. Design, synthesis and antiproliferative activities of diaryl urea derivatives bearing N-acylhydrazone moiety

    Bei Zhang; Yan Fang Zhao; Xin Zhai; Wei Jie Fan; Jun Ling Ren; Chun Fu Wu; Ping Gong

    2012-01-01

    A new series of diaryl urea derivatives bearing N-acylhydrazone moiety were designed and synthesized.All the target compounds were evaluated for their antiproliferative activities against human leukemia cell line (HL-60),human lung adenocarcinoma epithelial cell hne (A549) and human breast cancer cell line (MDA-MB-231) in vitro by standard MTT assay.The pharmacological results indicated that some compounds exhibited promising antitumor activities.Compound lj showed the most potent antiproliferative activity against the tested three cell lines with IC50 values of 0.13 μmol/L,0.7 μ mol/L and 0.5 μmol/L,respectively.

  1. Detecting grizzly bear use of ungulate carcasses using global positioning system telemetry and activity data.

    Ebinger, Michael R; Haroldson, Mark A; van Manen, Frank T; Costello, Cecily M; Bjornlie, Daniel D; Thompson, Daniel J; Gunther, Kerry A; Fortin, Jennifer K; Teisberg, Justin E; Pils, Shannon R; White, P J; Cain, Steven L; Cross, Paul C

    2016-07-01

    Global positioning system (GPS) wildlife collars have revolutionized wildlife research. Studies of predation by free-ranging carnivores have particularly benefited from the application of location clustering algorithms to determine when and where predation events occur. These studies have changed our understanding of large carnivore behavior, but the gains have concentrated on obligate carnivores. Facultative carnivores, such as grizzly/brown bears (Ursus arctos), exhibit a variety of behaviors that can lead to the formation of GPS clusters. We combined clustering techniques with field site investigations of grizzly bear GPS locations (n = 732 site investigations; 2004-2011) to produce 174 GPS clusters where documented behavior was partitioned into five classes (large-biomass carcass, small-biomass carcass, old carcass, non-carcass activity, and resting). We used multinomial logistic regression to predict the probability of clusters belonging to each class. Two cross-validation methods-leaving out individual clusters, or leaving out individual bears-showed that correct prediction of bear visitation to large-biomass carcasses was 78-88 %, whereas the false-positive rate was 18-24 %. As a case study, we applied our predictive model to a GPS data set of 266 bear-years in the Greater Yellowstone Ecosystem (2002-2011) and examined trends in carcass visitation during fall hyperphagia (September-October). We identified 1997 spatial GPS clusters, of which 347 were predicted to be large-biomass carcasses. We used the clustered data to develop a carcass visitation index, which varied annually, but more than doubled during the study period. Our study demonstrates the effectiveness and utility of identifying GPS clusters associated with carcass visitation by a facultative carnivore. PMID:26971522

  2. Low-temperature magnetic properties of iron-bearing sulfides and their contribution to magnetism of cometary bodies

    Kohout, Tomáš; Kosterov, A.; Haloda, J.; Týcová, P.; Zbořil, R.

    2010-01-01

    Roč. 208, č. 2 (2010), s. 955-962. ISSN 0019-1035 R&D Projects: GA AV ČR KJB300130903 Institutional research plan: CEZ:AV0Z30130516 Keywords : sulfide * magnetism * comets * Rosetta * magnetic fields * meteorites Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.813, year: 2010

  3. Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System

    Nicoletti, Rodrigo; Santos, Ilmar

    In the present paper, the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted...... into the model by using two different approaches: (a) linearized active oil film forces and the assumption that the hydrodynamic forces and the active hydraulic forces can be decoupled; (b) equivalent dynamic coefficients of the active oil film and the solution of the modified Reynolds' equation for...... the active lubrication. The second approach based on the equivalent dynamic coefficients leads to more accurate results since it includes the frequency dependence of the active hydraulic forces. Theoretical and experimental results reveal the feasibility of reducing resonance peaks by using the active...

  4. Rock magnetism of greigite bearing sediments from the Dead Sea, Israel

    Ute Frank; Norbert Nowaczyk; Jörg F.W. Negendank

    2007-01-01

    Laminated evaporitic sediments from the Dead Sea, Israel, were subjected to detailed rock magnetic investigations including the analysis of laboratory induced magnetizations and high temperature runs of the saturation magnetization. Ti-magnetite and greigite were identified as the main magnetic carrier minerals. The variations in concentration, grain size and coercitivity depended parameters reflect the varying amount of greigite with respect to Ti-magnetite. Samples with a high greigite conc...

  5. Environmental contaminants activate human and polar bear (Ursus maritimus) pregnane X receptors (PXR, NR1I2) differently

    Lille-Langøy, Roger, E-mail: Roger.lille-langoy@bio.uib.no [University of Bergen, Department of Biology, P.O. Box 7803, N-5020 Bergen (Norway); Goldstone, Jared V. [Woods Hole Oceanographic Institution, 266 Woods Hole Road, 02543-1050 Woods Hole, MA (United States); Rusten, Marte [University of Bergen, Department of Molecular Biology, P.O. Box 7803, N-5020 Bergen (Norway); Milnes, Matthew R. [Mars Hill University, 100 Athletic Street, Box 6671, Mars Hill, 28754 NC (United States); Male, Rune [University of Bergen, Department of Molecular Biology, P.O. Box 7803, N-5020 Bergen (Norway); Stegeman, John J. [Woods Hole Oceanographic Institution, 266 Woods Hole Road, 02543-1050 Woods Hole, MA (United States); Blumberg, Bruce [University of California, Irvine, 92697 CA (United States); Goksøyr, Anders [University of Bergen, Department of Biology, P.O. Box 7803, N-5020 Bergen (Norway)

    2015-04-01

    Background: Many persistent organic pollutants (POPs) accumulate readily in polar bears because of their position as apex predators in Arctic food webs. The pregnane X receptor (PXR, formally NR1I2, here proposed to be named promiscuous xenobiotic receptor) is a xenobiotic sensor that is directly involved in metabolizing pathways of a wide range of environmental contaminants. Objectives: In the present study, we comparably assess the ability of 51 selected pharmaceuticals, pesticides and emerging contaminants to activate PXRs from polar bears and humans using an in vitro luciferase reporter gene assay. Results: We found that polar bear PXR is activated by a wide range of our test compounds (68%) but has a slightly more narrow ligand specificity than human PXR that was activated by 86% of the 51 test compounds. The majority of the agonists identified (70%) produces a stronger induction of the reporter gene via human PXR than via polar bear PXR, however with some notable and environmentally relevant exceptions. Conclusions: Due to the observed differences in activation of polar bear and human PXRs, exposure of each species to environmental agents is likely to induce biotransformation differently in the two species. Bioinformatics analyses and structural modeling studies suggest that amino acids that are not part of the ligand-binding domain and do not interact with the ligand can modulate receptor activation. - Highlights: • Comparative study of ligand activation of human and polar bear PXRs. • Polar bear PXR is a promiscuous ligand-activated nuclear receptor but less so than human PXR. • Environmental contaminants activate human and polar bear PXRs differently. • Expression and ligand promiscuity indicate that PXR is a xenosensor in polar bears.

  6. Environmental contaminants activate human and polar bear (Ursus maritimus) pregnane X receptors (PXR, NR1I2) differently

    Background: Many persistent organic pollutants (POPs) accumulate readily in polar bears because of their position as apex predators in Arctic food webs. The pregnane X receptor (PXR, formally NR1I2, here proposed to be named promiscuous xenobiotic receptor) is a xenobiotic sensor that is directly involved in metabolizing pathways of a wide range of environmental contaminants. Objectives: In the present study, we comparably assess the ability of 51 selected pharmaceuticals, pesticides and emerging contaminants to activate PXRs from polar bears and humans using an in vitro luciferase reporter gene assay. Results: We found that polar bear PXR is activated by a wide range of our test compounds (68%) but has a slightly more narrow ligand specificity than human PXR that was activated by 86% of the 51 test compounds. The majority of the agonists identified (70%) produces a stronger induction of the reporter gene via human PXR than via polar bear PXR, however with some notable and environmentally relevant exceptions. Conclusions: Due to the observed differences in activation of polar bear and human PXRs, exposure of each species to environmental agents is likely to induce biotransformation differently in the two species. Bioinformatics analyses and structural modeling studies suggest that amino acids that are not part of the ligand-binding domain and do not interact with the ligand can modulate receptor activation. - Highlights: • Comparative study of ligand activation of human and polar bear PXRs. • Polar bear PXR is a promiscuous ligand-activated nuclear receptor but less so than human PXR. • Environmental contaminants activate human and polar bear PXRs differently. • Expression and ligand promiscuity indicate that PXR is a xenosensor in polar bears

  7. The effects of automated scatter feeders on captive grizzly bear activity budgets.

    Andrews, Nathan L P; Ha, James C

    2014-01-01

    Although captive bears are popular zoo attractions, they are known to exhibit high levels of repetitive behaviors (RBs). These behaviors have also made them particularly popular subjects for welfare research. To date, most research on ursid welfare has focused on various feeding methods that seek to increase time spent searching for, extracting, or consuming food. Prior research indicates an average of a 50% reduction in RBs when attempts are successful and, roughly, a 50% success rate across studies. This research focused on decreasing time spent in an RB while increasing the time spent active by increasing time spent searching for, extracting, and consuming food. The utility of timed, automated scatter feeders was examined for use with captive grizzly bears (Ursis arctos horribilis). Findings include a significant decrease in time spent in RB and a significant increase in time spent active while the feeders were in use. Further, the bears exhibited a wider range of behaviors and a greater use of their enclosure. PMID:24467390

  8. Polar bear hepatic cytochrome P450: Immunochemical quantitation, EROD/PROD activity and organochlorines

    Letcher, R.J.; Norstrom, R.J. [Carleton Univ., Ottawa, Ontario (Canada). Centre for Analytical and Environmental Chemistry]|[Environment Canada, Ottawa, Ontario (Canada). Canadian Wildlife Service

    1994-12-31

    Polar bears (Ursus maritimus) are an ubiquitous mammal atop the arctic marine food chain and bioaccumulate lipophilic environmental contaminants. Antibodies prepared against purified rat liver cytochrome P450-1 Al, -1 A2, -2Bl and -3Al enzymes have been found to cross-react with structurally-related orthologues present in the hepatic microsomes of wild polar bears, immunochemically determined levels of P450-1 A and -2B proteins in polar bear liver relative to liver of untreated rats suggested enzyme induction, probably as a result of exposure to xenobiotic contaminants. Optical density quantitation of the most immunochemically responsive isozymes P450-I Al, -IA2 and -2Bi to polygonal rabbit anti-rat P450-IA/IA2 sera and -2BI antibodies in hepatic microsomes of 13 adult male polar bars from the Resolute Bay area of the Canadian Arctic is presented. Correlations with EROD and PROD catalytic activities and levels of organochlorines, such as polychlorinated biphenyls (PCBs), 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (p,p-DDE) and their methyl sulfone (MeSO2-) metabolites are made to determine if compound-specific enzyme induction linkages exist. Inter-species immunochemical quantitation of isozymic P450 cytochromes can serve as an indicator of exposure to biologically active contaminant.

  9. Experimental treatment of breast cancer-bearing BALB/c mice by artemisinin and transferrin-loaded magnetic nanoliposomes

    Amir Gharib; Zohreh Faezizadeh; Seyed Ali Reza Mesbah-Namin; Ramin Saravani

    2015-01-01

    Background: The combination of artemisinin and transferrin exhibits versatile anticancer activities. In previous, we successfully prepared artemisinin and transferrin-loaded magnetic nanoliposomes and evaluated their anti-proliferative activity against MCF-7 and MDA-MB-231 cell lines in vitro. In this study, we investigate the in vivo anti-breast cancer activity of artemisinin and transferrin-loaded magnetic nanoliposome against breast transplanted tumors in BALB/c mice model. Materials and M...

  10. Performance of a Ferrofluid Based Rough Parallel Plate Slider Bearing: A Comparison of Three Magnetic Fluid Flow Models

    Jimit R. Patel

    2016-01-01

    Full Text Available Efforts have been made to present a comparison of all the three magnetic fluid flow models (Neuringer-Rosensweig model, Shliomis model, and Jenkins model so far as the performance of a magnetic fluid based parallel plate rough slider bearing is concerned. The stochastic model of Christensen and Tonder is adopted for the evaluation of effect of transverse surface roughness. The stochastically averaged Reynolds-type equation is solved with suitable boundary conditions to obtain the pressure distribution resulting in the calculation of load carrying capacity. The graphical results establish that for a bearing’s long life period the Shliomis model may be employed for higher loads. However, for lower to moderate loads, the Neuringer-Rosensweig model may be deployed.

  11. International program activities in magnetic fusion energy

    The following areas of our international activities in magnetic fusion are briefly described: (1) policy; (2) background; (3) strategy; (4) strategic considerations and concerns; (5) domestic program inplications, and (6) implementation. The current US activities are reviewed. Some of our present program needs are outlined

  12. Doppler-free magnetic optical activity

    Giraud-Cotton, S.; Kaftandjian, V.P.; Talin, B.

    1980-01-01

    The theory of Doppler-free magnetic optical activity associated with a single absorption line is presented. The transmission of tunable laser light, linearly polarized, through a dilute gaseous medium along a steady magnetic field is studied in the presence of a second counterpropagating saturating laser. The third order non linear susceptibility is calculated for a two-level system exhibiting a normal Zeeman effect, with arbitrary J values.

  13. The Relationship between Magnetic Gradient and Magnetic Shear in Five Super Active Regions Producing Great Flares

    Hai-Min Wang; Hui Song; Ju Jing; Vasyl Yurchyshyn; Yuan-Yong Deng; Hong-Qi Zhang; David Falconer; Jing Li

    2006-01-01

    We study the magnetic structure of five well-known active regions that produced great flares (X5 or larger). The six flares under investigation are the X12 flare on 1991 June 9in AR 6659, the X5.7 flare on 2000 July 14 in AR 9077, the X5.6 flare on 2001 April 6 in AR 9415, the X5.3 flare on 2001 August 25 in AR 9591, the X17 flare on 2003 October 28 and the X10 flare on 2003 October 29, both in AR 10486. The last five events had corresponding LASCO observations and were all associated with Halo CMEs. We analyzed vector magnetograms from Big Bear Solar Observatory, Huairou Solar Observing Station, Marshall Space Flight Center and Mees Solar Observatory. In particular, we studied the magnetic gradient derived from line-of-sight magnetograms and magnetic shear derived from vector magnetograms, and found an apparent correlation between these two parameters at a level of about 90%. We found that the magnetic gradient could be a better proxy than the shear for predicting where a major flare might occur: all six flares occurred in neutral lines with maximum gradient. The mean gradient of the flaring neutral lines ranges from 0.14 to 0.50 G km-1, 2.3to 8 times the average value for all the neutral lines in the active regions. If we use magnetic shear as the proxy, the flaring neutral line in at least one, possibly two, of the six events would be mis-identified.

  14. Performance Testing of a Magnetically Suspended Double Gimbal Control Moment Gyro Based on the Single Axis Air Bearing Table

    Jiancheng Fang

    2012-07-01

    Full Text Available Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG, a magnetically suspended DGCMG (MSDGCMG is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing of a MSDGCMG independently developed by Beihang University, based on the single axis air bearing table. In this paper, taking into sufficient consideration to the moving-gimbal effects and the response bandwidth limit of the gimbal, a special MSDGCMG steering law is proposed subject to the limits of gimbal angle rate and angle acceleration. Finally, multiple experiments are carried out, with different MSDGCMG angular momenta as well as different desired attitude angles. The experimental results indicate that the MSDGCMG has a good gimbal angle rate and output torque tracking capabilities, and that the attitude stability with MSDGCMG as actuator is superior to 10−3°/s. The MSDGCMG performance testing in this paper, carried out under moving-base condition, will offer a technique base for the future research and application of MSDGCMGs.

  15. Performance testing of a magnetically suspended double gimbal control moment gyro based on the single axis air bearing table.

    Cui, Peiling; Zhang, Huijuan; Yan, Ning; Fang, Jiancheng

    2012-01-01

    Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG), a magnetically suspended DGCMG (MSDGCMG) is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing of a MSDGCMG independently developed by Beihang University, based on the single axis air bearing table. In this paper, taking into sufficient consideration to the moving-gimbal effects and the response bandwidth limit of the gimbal, a special MSDGCMG steering law is proposed subject to the limits of gimbal angle rate and angle acceleration. Finally, multiple experiments are carried out, with different MSDGCMG angular momenta as well as different desired attitude angles. The experimental results indicate that the MSDGCMG has a good gimbal angle rate and output torque tracking capabilities, and that the attitude stability with MSDGCMG as actuator is superior to 10(-3)°/s. The MSDGCMG performance testing in this paper, carried out under moving-base condition, will offer a technique base for the future research and application of MSDGCMGs. PMID:23012536

  16. Separation of lanthanides and actinides using magnetic silica particles bearing covalently attached tetra-CMPO-calix[4]arenes.

    Böhmer, Volker; Dozol, Jean-François; Grüttner, Cordula; Liger, Karine; Matthews, Susan E; Rudershausen, Sandra; Saadioui, Mohamed; Wang, Pingshan

    2004-08-21

    Calix[4]arene tetraethers in the cone conformation bearing four -NH-CO-CH2-P(O)Ph2 (= CMPO) residues on their wide rim and one, two or four omega-amino alkyl residues of various lengths at the narrow rim were synthesized. Reaction with dichlorotriazinyl (DCT) functionalized magnetic particles led to complete coverage of the available surface by covalently linked CMPO-calix[4]arenes in all cases. Magnetically assisted removal of Eu(iii) and Am(iii) from acidic solutions was distinctly more efficient with these particles in comparison to analogous particles bearing the same amount of analogous single-chain CMPO-functions. The best result, an increase of the extraction efficiency by a factor of 140-160, was obtained for attachment via two propyl spacers. The selectivity Am/Eu was in the range of 1.9-2.8. No decrease of the extraction ability was observed, when the particles were repeatedly used, after simple back extraction with water. PMID:15305214

  17. Linking Microbial Activity with Arsenic Fate during Cow Dung Disposal of Arsenic-Bearing Wastes

    Clancy, T. M.; Reddy, R.; Tan, J.; Hayes, K. F.; Raskin, L.

    2014-12-01

    To address widespread arsenic contamination of drinking water sources numerous technologies have been developed to remove arsenic. All technologies result in the production of an arsenic-bearing waste that must be evaluated and disposed in a manner to limit the potential for environmental release and human exposure. One disposal option that is commonly recommended for areas without access to landfills is the mixing of arsenic-bearing wastes with cow dung. These recommendations are made based on the ability of microorganisms to create volatile arsenic species (including mono-, di-, and tri-methylarsine gases) to be diluted in the atmosphere. However, most studies of environmental microbial communities have found only a small fraction (wastes produced during drinking water treatment in West Bengal, India. Arsenic in gaseous, aqueous, and solid phases was measured. Consistent with previous reports, less than 0.02% of the total arsenic present was volatilized. A much higher amount (~5%) of the total arsenic was mobilized into the liquid phase. Through the application of molecular tools, including 16S rRNA sequencing and quantification of gene transcripts involved in methanogenesis, this study links microbial community activity with arsenic fate in potential disposal environments. These results illustrate that disposal of arsenic-bearing wastes by mixing with cow dung does not achieve its end goal of promoting arsenic volatilization but rather appears to increase arsenic mobilization in the aqueous phase, raising concerns with this approach.

  18. Cluster magnetic fields from active galactic nuclei

    Sutter, P M; Yang, H -Y

    2009-01-01

    Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several sub-resolution approaches that link the estimated accretion rate as measured on the simulation mesh to the accretion rate onto the central black hole and the resulting feedback. We examine the effects of magnetized outflows on the accretion history of the black hole and discuss the ability of these models to magnetize the cluster medium.

  19. Black and Brown Bear Activity at Selected Coastal Sites in Glacier Bay National Park and Preserve, Alaska: A Preliminary Assessment Using Noninvasive Procedures

    Partridge, Steve; Smith, Tom; Lewis, Tania

    2009-01-01

    A number of efforts in recent years have sought to predict bear activity in various habitats to minimize human disturbance and bear/human conflicts. Alaskan coastal areas provide important foraging areas for bears (Ursus americanus and U. arctos), particularly following den emergence when there may be no snow-free foraging alternatives. Additionally, coastal areas provide important food items for bears throughout the year. Glacier Bay National Park and Preserve (GLBA) in southeastern Alaska has extensive coastal habitats, and the National Park Service (NPS) has been long interested in learning more about the use of these coastal habitats by bears because these same habitats receive extensive human use by park visitors, especially kayaking recreationists. This study provides insight regarding the nature and intensity of bear activity at selected coastal sites within GLBA. We achieved a clearer understanding of bear/habitat relationships within GLBA by analyzing bear activity data collected with remote cameras, bear sign mapping, scat collections, and genetic analysis of bear hair. Although we could not quantify actual levels of bear activity at study sites, agreement among measures of activity (for example, sign counts, DNA analysis, and video record) lends support to our qualitative site assessments. This work suggests that habitat evaluation, bear sign mapping, and periodic scat counts can provide a useful index of bear activity for sites of interest.

  20. Inertia Wheel on Low-Noise Active Magnetic Suspension

    Carabelli, S.; Genta, G.; Silvagni, M.; Tonoli, A.

    2002-01-01

    Magnetic bearings are particularly suited for space applications for a number of reasons: - they are ideally suited for vacuum applications; - the lack of lubrication and wear enhances the reliability and guaranties a long maintenance-free operation - the low drag torque decreases power consumption and reduces the torque exerted on the stator of the machine. - the possibility of insulating actively the spacecraft from the excitation due to unbalance of the rotating system In the case of reaction wheels, a well designed magnetic suspension allows high speed operation with a very low power consumption and vibration level. Conversely, microgravity (and possibly vacuum) operation is an advantage for magnetic bearings. The absence of static forces allows to operate with low current levels, thus reducing electrical noise and allowing to reach even lower vibration levels than in Earth applications of magnetic bearings. Active magnetic bearings (AMB) allow to adapt the working characteristics of the system to the operating needs: it is possible to use the actuators to lock the system during launch (absence of grabbers) and to stiffen the suspension when the spacecraft is accelerated (impulsive phases), while working in conditions optimised for microgravity when this is needed. Magnetic suspension systems designed for microgravity environment cannot be correctly tested on the ground. Testing in ground conditions results in the need of grossly overdesigning the levitation device; furthermore, in some cases ground testing is completely impossible, if not by introducing devices which compensate for the Earth gravitational field. If the compensation for the gravitational force is supplied by the same actuators used for microgravity operation, the actuators and the power amplifiers must be overdesigned and in some cases the suspension can be altogether impossible. They work in conditions which are much different from nominal ones and, above all, it is impossible to reach the

  1. Bearing structures

    A hydrostatic bearing for the lower end of the vertical shaft of a sodium pump comprises a support shell encircling the shaft and a bush located between the shell and shaft. Liquid sodium is fed from the pump outlet to the bush/shaft and bush/shell interfaces to provide hydrostatic support. The bush outer surface and the shell inner surface are of complementary part-spherical shape and the bush floats relative to the shaft so that the bush can align itself with the shaft axis. Monitoring of the relative rotational speed of the bush with respect to the shaft (such rotation being induced by the viscous drag forces present) is also performed for the purposes of detecting abnormal operation of the bearing or partial seizure, at least one magnet is rotatable with the bush, and a magnetic sensor provides an output having a frequency related to the speed of the bush. (author)

  2. Quantum mechanical first principles calculations of the electronic and magnetic structure of Fe-bearing rock-forming silicates

    The focus of this thesis is the study of the electronic and magnetic structure of three representatives of the main Fe-bearing rock-forming silicates: Fe2+2Si2O6, almandine Fe2+3Al2(SiO4)3 and andradite Ca3Fe3+2(SiO4)3. For this purpose the quantum mechanical first principles electronic structure calculations are performed by the most efficient DFT method in the local spin-density approximation for calculating spectroscopic data: the spin-polarized self consistent charge X[alpha] method. These minerals have attracted significant attention due to their abundance in the Earth's crust and mantle, and because crystallised silicates are main components of cosmic dust which is the most abundant raw material in the Universe. The specific feature and strength of these investigations consist in the theoretical characterization of these complex systems based on experimental results. This means that, on one hand, experimental spectroscopic and crystallographic data are being used to judge the reliability of the calculations, whereas, on the other hand, experimental data are interpreted and explained by the theoretical results. This work is divided into seven main parts. Chapter 1 is the introduction to the thesis. Chapter 2 describes the theoretical bases, ideas, approximations and advantages of the SCC- X[alpha] method and basics of the art of cluster construction. Chapter 3 considers physical bases of absorption and Moessbauer spectroscopy, crystal field theory, evaluation of the main spectroscopic values within the frames of the SCC- X[alpha] method and magnetic interaction between atoms. In addition, tetragonally, trigonally and angularly distorted octahedral sites with various degrees of the distortions are calculated and analyzed. The electronic and magnetic structures of orthoferrosilite, almandine and andradite are described in Chapters 4, 5 and 6, respectively. In the case of orthoferrosilite the magnetic interactions between the iron spins within the ribbons and

  3. Anticancer activity of Jasminum angustifolium Linn against Ehrlich ascites carcinoma cells bearing mice

    Pradeep Rajkumar

    2012-06-01

    Full Text Available Objective: Present investigations were carried out for evaluation of antitumor and in vitro antioxidant activity of ethanol and aqueous extracts of Jasminum angustifolium Linn. Methods: For its antitumor activity, Ehrlich ascites carcinoma (EAC induced swiss albino mice were used and were divided into five group with 6 animal each.The antitumor effect was assessed using viable tumour cell count, packed cell volume, body weight, mean survival time and percentage increase in life span. Apart from that, hematological and liver enzyme studies were noticed upon the ethanol and aqueous extracts of Jasminum angustifolium Linn administered at 500 mg/kg per day for 14 days, after 24 hours of tumor inoculation. Results: Treatment with extracts significantly restored the altered parameters to normal when compared to cancer control group. Conclusion: The results suggest that ethanol extract of Jasminum angustifolium Linn possess significant antitumor effects in EAC tumour bearing mice. [J Exp Integr Med 2012; 2(3.000: 271-275

  4. A multifunctional magnetic nanocarrier bearing fluorescent dye for targeted drug delivery by enhanced two-photon triggered release

    Banerjee, Shashwat S; Chen, D-H [Department of Chemical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)], E-mail: chendh@mail.ncku.edu.tw

    2009-05-06

    We report a novel nanoformulation for targeted drug delivery which utilizes nanophotonics through the fusion of nanotechnology with biomedical application. The approach involves an energy-transferring magnetic nanoscopic co-assembly fabricated of rhodamine B (RDB) fluorescent dye grafted gum arabic modified Fe{sub 3}O{sub 4} magnetic nanoparticle and photosensitive linker by which dexamethasone drug is conjugated to the magnetic nano-assembly. The advantage offered by this nanoformulation is the indirect photo-triggered-on-demand drug release by efficient up-converting energy of the near-IR (NIR) light to higher energy and intraparticle energy transfer from the dye grafted magnetic nanoparticle to the linker for drug release by cleavage. The synthesized nanoparticles were found to be of ultra-small size (13.33 nm) and are monodispersed in an aqueous suspension. Dexamethasone (Dexa) drug conjugated to RDB-GAMNP by photosensitive linker showed appreciable release of Dexa by photo-triggered response on exposure to radiation having a wavelength in the NIR region whereas no detectable release was observed in the dark. Photo-triggered response for the nanoformulation not bearing the rhodamine B dye was drastically less as less Dexa was released on exposure to NIR radiation which suggest that the photo-cleavage of linker and release of Dexa mainly originated from the indirect excitation through the uphill energy conversions based on donor-acceptor model FRET. The promising pathway of nanophotonics for the on-demand release of the drug makes this nanocarrier very promising for applications in nanomedicine.

  5. Inertially stabilized line-of-sight control system using a magnetic bearing with vernier gimbaling capacity

    Lin, Zhuchong; Liu, Kun

    2014-11-01

    Line of sight stabilization and control system is widely used in pointing and stabilizing the line of sight of optical sensors. Multi-axis gimbals configurations are commonly used for isolating disturbance from the angular motion of the base where the stabilization platform is mounted. However, in the case of large payload, nonlinear friction and the bandwidth limit of the servo loop can greatly diminish the performance of the whole system. Magnetic actuators, because of their high force per mass capability and non-friction characteristic, are promising means of achieving high-accuracy stabilization. Nevertheless, the gap between magnetic actuators and the payload is very small, which limits the slewing range of the line of sight as well as the angular motion range of the base that can be isolated. A novel two-stage stabilization configuration is developed, which combines multi-axis gimbals configuration and magnetic actuators as well as both of their advantages. At the first stage, a multi-axis gimbals configuration is adopted to isolate the large angular motion of the base while at the second stage magnetic actuators are utilized to perform high-accuracy stabilization. A so-called "stabilizing inside and tracking outside" scheme is carried out to perform two-stage stabilization control. The advantage of this configuration compared with conventional configuration is analyzed through analytical method. Finally, the effectiveness of the design is investigated through simulation studies.

  6. A novel Planar Magnetic Bearing and Motor Configuration applied in a Positioning Stage

    Molenaar, A.

    2000-01-01

    This thesis presents the design and implementation of a fully contactless high precision magnetically suspended position stage with large planar stroke. This stage is the first which is suitable for practical application in vacuum. The underlying electromechanical working principles, modelling and a

  7. Pressure-induced changes in magnetic susceptibility and its anisotropy of pyrrhotite bearing rocks

    Kapička, Aleš; Petrovský, Eduard; Hoffmann, V.

    Sb4 (1999), s. 81-82. ISSN 0534-0403. [Textures and physical properties of rocks. Göttingen, 13.10.1999-16.10.1999] R&D Projects: GA AV ČR KSK1012601 Subject RIV: DE - Earth Magnetism, Geodesy, Geography

  8. Low-temperature magnetic properties of iron-bearing minerals and their contribution to magnetism of cometary bodies

    Kohout, Tomáš; Kosterov, A.; Čuda, J.; Haloda, J.; Halodová, P.; Zbořil, R.

    Helsinki: University of Helsinki, 2014 - (Muinonen, K.; Penttilä, A.; Granvik, M.; Virkki, A.; Fedorets, G.; Wilkman, O.; Kohout, T.). s. 300-300 ISBN 978-952-10-8962-6. [Asteroids, Comets, Meteors. 30.06.2014-04.07.2014, Helsinki] Institutional support: RVO:67985831 Keywords : comet * magnetism * sulfides * troilite * daubreelite * chromite * alabandite Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics http://www.helsinki.fi/acm2014/pdf-material/Day-3/Session-1/Room-3/KOHOUT-F54C.pdf

  9. Stability and coupling dynamic behavior of nonlinear journal active electromagnetic bearing rotor system

    2008-01-01

    The stability and coupling dynamic behavior of a journal active electromagnetic bearing rotor system are analyzed.The gyroscopic effect is considered in the rotor model.The system equations are formulated by combining equations for rotor motion and decentralized proportional integral differential (PID) controllers.A method combining the predictor-corrector mechanism and the Netwon-Raphson method is presented to calculate the critical speed at the corresponding Hopf bifurcation point of the system.For periodic motions,a continuation method combining the predictor-corrector mechanism and shooting method is presented.Non-linear unbalanced periodic motions and their stability margins are obtained using the shooting method and established continuation method for periodic motions.With the change of control parameters,the system local stability and bifurcation behaviors are obtained using the Floquet theory.The numerical examples show that the schemes not only significantly save computing cost,but also have high precision.

  10. Synthesis, Characterization, and Antifungal Activity of Phenylpyrrole-Substituted Tetramic Acids Bearing Carbonates.

    Xu, Wen-Qin; Chen, Min; Wang, Kun-Yao; Ren, Zheng-Jiao; Lu, Ai-Min; Yang, Chun-Long

    2016-01-01

    For the aim of discovering new fungicide, a series of phenylpyrrole-substituted tetramic acid derivatives bearing carbonates 6a-q were designed and synthesized via 4-(2,4-dioxopyrrolidin-3-ylidene)-4-(phenylamino)butanoic acids 4a-k and the cyclized products 1',3,4,5'-tetrahydro-[2,3'-bipyrrolylidene]-2',4',5(1H)-triones 5a-k. The compounds were characterized using IR, ¹H- and (13)C-NMR spectroscopy, mass spectrometry (EI-MS), and elemental analysis. The structure of 6b was confirmed by X-ray diffraction crystallography. The title compounds 6a-q were bioassayed in vitro against the phytopathogenic fungi Fusarium graminearum, Botrytis cinerea and Rhizoctonia solani at a concentration of 100 μg/mL, respectively. Most compounds displayed good inhibitory activity. PMID:27007370

  11. Recent Activities in Magnetic Separation in Sweden

    Wang, Yanmin; Forssberg, Eric

    1995-01-01

    This paper describes some industrial applications of magnetic separation in Swedish mineral industry. Recent studies on magnetic treatment of minerals in Sweden are also presented. These studies involve selectivity of wet magnetic separation, wet magnetic recovery of mineral fines and ultrafines, sulphide processing by magnetic means, as well as dry magnetic purification of industrial minerals.

  12. Magnetization and geochemistry of greigite-bearing Cretaceous strata, North Slope Basin, Alaska

    Reynolds, R.L.; Tuttle, M.L.; Rice, C.A.; Fishman, N.S.; Karachewski, J.A.; Sherman, David M.

    1994-01-01

    Greigite is ubiquitous in marine mudstone of the Seabee Formation, and it dominates the magnetic properties of the Seabee. The Seabee rocks fill an ancient submarine canyon cut into marine, transitional, and nonmarine sandstone, siltstone, and mudstone beds of the undifferentiated Ninuluk and Seabee Formations. Different geochemical signatures in the Seabee Formation and undifferentiated Ninuluk and Seabee rocks indicate different origins of their greigite and associated iron disulfide minerals. In the Seabee, greigite and pyrite formed during early diagenesis via bacterial sulfate reduction utilizing indigenous sulfate and organic carbon. -Authors

  13. Rod-like Schiff Base Magnetic Liquid Crystals Bearing Organic Radical

    ZHENG, Min-Yan; AN, Zhong-Wei

    2006-01-01

    4 novel rod-like Schiff base magnetic liquid crystals have been prepared in which trans-bicyclohexyl or trans-cyclohexyl phenyl and biphenyl carboxylic acid phenol ester mesogenic cores with n-propyl and n-pentyl substituents were terminated by 4-amino-TEMPO (TEMPO=2,2,6,6-tetramethylpiperidine-l-oxyl). Of these compounds the silk-like and schlieren textures were found from 4c and 4d by POM (Polarizing Optical Microscope).DSC (Differential Scanning Calorimeter) measurements show that the mesophase exists from 4-6 ℃. EPR spectra reveal their paramagnetic properties.

  14. Magnetic activity of planet-hosting stars

    Poppenhaeger, Katja

    2011-05-01

    Magnetic activity in cool stars is a widely observed phenomenon, however it is still far from being understood. How fundamental stellar parameters like mass and rotational period quantitatively cause a stellar magnetic field which manifests itself in features such as spots, flares and high-energy coronal emission is a lively area of research in solar and stellar astrophysics. Especially for planet-hosting stars, stellar activity profiles are very interesting as exoplanets are affected by high-energy radiation, both at the time of planet formation as well as during the further lifetime of a star-planet system. In extreme cases, the atmosphere of a planet very close to its host star can be strongly heated by the stellar X-ray and EUV emission and finally escape the planet's gravitational attraction, so that the atmosphere of the planet evaporates over time. Theoretically, planets can also affect their host star's magnetic activity. In analogy to processes in binary stars which lead to enhanced - both overall and periodically varying - activity levels, also giant planets might influence the stellar activity by tidal or magnetic interaction processes, however on a weaker level than in binaries. Some indications for such interactions exist from chromospheric measurements in stars with Hot Jupiters. In this thesis I investigate the magnetic activity of planet-hosting stars and especially possible effects from star-planet interactions with an emphasis on stellar coronae in X-rays. I tested a complete sample of all known planet-hosting stars within 30 pc distance from the Sun for correlations of stellar X-ray properties with planetary parameters. A significant correlation exists between the stellar X-ray luminosity and the product of planetary mass and inverse semimajor axis. However, this could be traced back to a selection effect introduced by planetary detection methods. For stars in the solar neighborhood, planets are mainly detected by radial velocity shifts in the

  15. Design of multi-input multi-output controller for magnetic bearing which suspends helium gas-turbine generator rotor for high temperature gas cooled reactor

    A design of a MIMO controller, which links magnetic forces of multiple magnetic bearings by feedback of multiple measurement values of vibration of a rotor, was proposed for the radial magnetic bearings for the generator rotor of helium gas turbine with a power output of 300 MWe. The generator rotor is a flexible rotor, which passes over the forth critical speed. A controller transfer function was derived at the forth critical speed, in which the bending vibration mode is similar to the one which is excited by unbalance mass to reduce a modeling error. A 1404-dimensional un-symmetric coefficient matrix of equation of state for the rotating rotor affected by Jayro effect was reduced by a modal decomposition using Schur decomposition to reduce a reduction error. The numerical results showed that unbalance response of rotor was 53 and 80 μmp-p, respectively, well below the allowable limits both at the rated and critical speeds. (author)

  16. Bear feeding activity at alpine insect aggregation sites in the Yellowstone ecosystem

    Mattson, David J.; Gillin, Colin M.; Benson, Scott A.; Knight, Richard R.

    1991-01-01

    Bears (Ursidae) were observed from fixed-wing aircraft on or near alpine talus in the Shoshone National Forest between 15 June and 15 September in 1981–1989. Bears fed on insect aggregations at 6 known and 12 suspected alpine talus sites, disproportionately more at elevations > 3350 m, on slopes > 30°, and on south- and west-facing aspects. While at these sites, bears almost exclusively ate invertebrates, typically army cutworm moths (Euxoa auxiliaris). Subadult grizzly bears (Ursus arctos horribilis) appeared to be underrepresented at the sites, and proportionate representation of adult females with young appeared to decrease between 15 June and 15 September. Overall, observations of bears at these sites increased between 1981 and 1989. We suggest that alpine insect aggregations are an important food source for bears in the Shoshone National Forest, especially in the absence of high-quality foraging alternatives in July and August of most years.

  17. Magnetic activity in accretion disc boundary layers

    Armitage, Philip J.

    2002-03-01

    We use three-dimensional magnetohydrodynamic simulations to study the structure of the boundary layer between an accretion disc and a non-rotating, unmagnetized star. Under the assumption that cooling is efficient, we obtain a narrow but highly variable transition region in which the radial velocity is only a small fraction of the sound speed. A large fraction of the energy dissipation occurs in high-density gas adjacent to the hydrostatic stellar envelope, and may therefore be reprocessed and largely hidden from view of the observer. As suggested by Pringle, the magnetic field energy in the boundary layer is strongly amplified by shear, and exceeds that in the disc by an order of magnitude. These fields may play a role in generating the magnetic activity, X-ray emission and outflows in disc systems where the accretion rate is high enough to overwhelm the stellar magnetosphere.

  18. Experimental Studies with an Active Magnetic Regenerating Refrigerator

    Eriksen, Dan; Engelbrecht, Kurt; Bahl, Christian;

    2015-01-01

    Experimental results for an active magnetic regenerator (AMR) are presented. The focus is on whether or not it pays off to partly substitute soft magnetic material with non-magnetic insulation in a flux-conducting core in the magnet system. Such a substitution reduces losses due to heat conductio...

  19. Photospheric Magnetic Free Energy Density of Solar Active Regions

    Zhang, Hongqi

    2016-01-01

    We present the photospheric energy density of magnetic fields in two solar active regions inferred from observational vector magnetograms, and compare it with the possible different defined energy parameters of magnetic fields in the photosphere. We analyze the magnetic fields in active region NOAA 6580-6619-6659 and 11158. It is noticed that the quantity 1/4pi Bn.Bp is an important energy parameter that reflects the contribution of magnetic shear on the difference between the potential magnetic field (Bp) and non-potential one (Bn), and also the contribution to the free magnetic energy near the magnetic neutral lines in the active regions. It is found that the photospheric mean magnetic energy density changes obviously before the powerful solar flares in the active region NOAA 11158, it is consistent with the change of magnetic fields in the lower atmosphere with flares.

  20. Active lubrication applied to radial gas journal bearings. Part 1: Modeling

    Morosi, Stefano; Santos, Ilmar

    2011-01-01

    regulating radial injection of lubricant through the means of piezoelectric actuators mounted on the back of the bearing sleeves. A feedback law is used to couple the dynamic of a simplified rotor-bearing system with the pneumatic and dynamic characteristics of a piezoelectric actuated valve system. Selected...

  1. Xenoestrogenic and dioxin-like activity in blood of East Greenland polar bears (Ursus maritimus)

    Erdmann, Simon Erik; Dietz, Rune; Sonne, Christian;

    2013-01-01

    induced ER response. Positive correlations were found in subadult bears between XER and several POP biomarkers. XER and XERcomp correlated positively to each other. A total of 91% of the polar bear blood extracts elicited agonistic AhR transactivity. The AhR-TCDD equivalent (AhR-TEQ) median levels were...

  2. Longitudinal fecal hormone analysis for monitoring reproductive activity in the female polar bear (Ursus maritimus).

    Stoops, M A; MacKinnon, K M; Roth, T L

    2012-12-01

    The objective was to identify suitable enzyme immunoassays to monitor gonadal and placental function in the female polar bear. Immunoreactive progesterone, progesterone metabolite (PdG), estrogen, and androgen metabolite (T) concentrations were measured in fecal samples collected over 24 mo from captive female bears (N = 20). Whereas fecal extracts produced displacement curves parallel to the standard curve for each respective steroid, T and PdG more accurately reflected reproductive events. Concentrations of fecal T increased (P < 0.05) during the breeding season, and brief spikes were associated with estrus and mating. A postovulatory increase in PdG was not always detected, but sustained baseline T after mating appeared consistent with ovulation. Parturient bears excreted higher PdG concentrations (P < 0.05) during expected time of embryo implantation in Fall, and a late gestational rise in fecal T occurred 30 days prepartum. Many nonparturient bears also had a PdG rise in the Fall, suggesting they experienced either pregnancy loss or a pseudopregnancy. Differentiating pregnant and pseudopregnant states was not achieved using fecal PdG alone, but when combined with fecal T, comprehensive diagnoses could be made. Nonparturient bears demonstrated elevated (P < 0.05) fecal T during summer months, whereas parturient bears did not. In summary, noninvasive hormone monitoring techniques were established for the female polar bear. Although this study was directed at facilitating management and breeding efforts of captive polar bears, the methods could be applied to studies of reproductive function in wild populations. PMID:23040062

  3. Active-Controlled Fluid Film Based on Wave-Bearing Technology

    Dimofte, Florin; Hendricks, Robert C.

    2011-01-01

    It has been known since 1967 that the steady-state and dynamic performance, including the stability of a wave bearing, are highly dependent on the wave amplitude. A wave-bearing profile can be readily obtained by elastically distorting the stationary bearing sleeve surface. The force that distorts the elastic sleeve surface could be an applied force or pressure. The magnitude and response of the distorting force would be defined by the relation between the bearing surface stiffness and the bearing pressure, or load, in a feedback loop controller. Using such devices as piezoelectric or other electromechanical elements, one could step control or fully control the bearing. The selection between these systems depends on the manner in which the distortion forces are applied, the running speed, and the reaction time of the feedback loop. With these techniques, both liquid- (oil-) or gas- (air-) lubricated wave bearings could be controlled. This report gives some examples of the dependency of the bearing's performance on the wave amplitude. The analysis also was proven experimentally.

  4. Establishing a definition of polar bear (Ursus maritimus) health: a guide to research and management activities.

    Patyk, Kelly A; Duncan, Colleen; Nol, Pauline; Sonne, Christian; Laidre, Kristin; Obbard, Martyn; Wiig, Øystein; Aars, Jon; Regehr, Eric; Gustafson, Lori L; Atwood, Todd

    2015-05-01

    The meaning of health for wildlife and perspectives on how to assess and measure health, are not well characterized. For wildlife at risk, such as some polar bear (Ursus maritimus) subpopulations, establishing comprehensive monitoring programs that include health status is an emerging need. Environmental changes, especially loss of sea ice habitat, have raised concern about polar bear health. Effective and consistent monitoring of polar bear health requires an unambiguous definition of health. We used the Delphi method of soliciting and interpreting expert knowledge to propose a working definition of polar bear health and to identify current concerns regarding health, challenges in measuring health, and important metrics for monitoring health. The expert opinion elicited through the exercise agreed that polar bear health is defined by characteristics and knowledge at the individual, population, and ecosystem level. The most important threats identified were in decreasing order: climate change, increased nutritional stress, chronic physiological stress, harvest management, increased exposure to contaminants, increased frequency of human interaction, diseases and parasites, and increased exposure to competitors. Fifteen metrics were identified to monitor polar bear health. Of these, indicators of body condition, disease and parasite exposure, contaminant exposure, and reproductive success were ranked as most important. We suggest that a cumulative effects approach to research and monitoring will improve the ability to assess the biological, ecological, and social determinants of polar bear health and provide measurable objectives for conservation goals and priorities and to evaluate progress. PMID:25679818

  5. Synthesis and evaluation of radiolabeled, folic acid-PEG conjugated, amino silane coated magnetic nanoparticles in tumor bearing Balb/C mice

    Razjouyan Javad

    2015-07-01

    Full Text Available To design a potent agent for positron emission tomography/magnetic resonance imaging (PET/MRI imaging and targeted magnetic hyperthermia-radioisotope cancer therapy radiolabeled surface modified superparamagnetic iron oxide nanoparticles (SPIONs were used as nanocarriers. Folic acid was conjugated for increasing selective cellular binding and internalization through receptor-mediated endocytosis. SPIONs were synthesized by the thermal decomposition of tris (acetylacetonato iron (III to achieve narrow and uniform nanoparticles. To increase the biocompatibility of SPIONs, they were coated with (3-aminopropyl triethoxysilane (APTES, and then conjugated with synthesized folic acid-polyethylene glycol (FA-PEG through amine group of (3-aminopropyl triethoxysilane. Finally, the particles were labeled with 64Cu (t1/2 = 12.7 h using 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid mono (N-hydroxy succinimide ester DOTA-NHS chelator. After the characterization of SPIONs, their cellular internalization was evaluated in folate receptor (FR overexpressing KB (established from a HeLa cell contamination and mouse fibroblast cell (MFB lines. Eventually, active and passive targeting effects of complex were assessed in KB tumor-bearing Balb/C mice through biodistribution studies. Synthesized bare SPIONs had low toxicity effect on healthy cells, but surface modification increased their biocompatibility. Moreover, KB cells viability was reduced when using folate conjugated SPIONs due to FR-mediated endocytosis, while having little effect on healthy cells (MFB. Moreover, this radiotracer had tolerable in vivo characteristics and tumor uptake. In the receptor blocked case, tumor uptake was decreased, indicating FR-specific uptake in tumor tissue while enhanced permeability and retention effect was major mechanism for tumor uptake.

  6. Xenoestrogenic and dioxin-like activity in blood of East Greenland polar bears (Ursus maritimus)

    Erdmann, Simon Erik; Dietz, Rune; Sonne, Christian;

    2013-01-01

    The aims of the project were to (i) extract the lipophilic persistent organic pollutants (POPs) from the blood of 99 East Greenland polar bears and assess the combined mixture effect on the estrogen receptor (ER) and the aryl hydrocarbon receptor (AhR) mediated transactivity; (ii) To evaluate...... whether the receptor transactivities were associated with selected POP markers, and (iii) compare the receptor transactivities in polar bears with earlier studies on Greenlandic Inuit. Lipophilic POPs were extracted using a combination of solid-phase extraction (SPE) and high performance liquid...... induced ER response. Positive correlations were found in subadult bears between XER and several POP biomarkers. XER and XERcomp correlated positively to each other. A total of 91% of the polar bear blood extracts elicited agonistic AhR transactivity. The AhR-TCDD equivalent (AhR-TEQ) median levels were...

  7. Antitumor effect of vitamin D-binding protein-derived macrophage activating factor on Ehrlich ascites tumor-bearing mice.

    Koga, Y; Naraparaju, V R; Yamamoto, N

    1999-01-01

    Cancerous cells secrete alpha-N-acetylgalactosaminidase (NaGalase) into the blood stream, resulting in deglycosylation of serum vitamin D3-binding protein (known as Gc protein), which is a precursor for macrophage activating factor (MAF). Incubation of Gc protein with immobilized beta-galactosidase and sialidase generates the most potent macrophage activating factor (designated GcMAF). Administration of GcMAF to cancer-bearing hosts can bypass the inactivated MAF precursor and act directly on macrophages for efficient activation. Therapeutic effects of GcMAF on Ehrlich ascites tumor-bearing mice were assessed by survival time and serum NaGalase activity, because serum NaGalase activity was proportional to tumor burden. A single administration of GcMAF (100 pg/mouse) to eight mice on the same day after transplantation of the tumor (5 x 10(5) cells) showed a mean survival time of 21 +/- 3 days for seven mice, with one mouse surviving more than 60 days, whereas tumor-bearing controls had a mean survival time of 13 +/- 2 days. Six of the eight mice that received two GcMAF administrations, at Day 0 and Day 4 after transplantation, survived up to 31 +/- 4 days whereas, the remaining two mice survived for more than 60 days. Further, six of the eight mice that received three GcMAF administrations with 4-day intervals showed an extended survival of at least 60 days, and serum NaGalase levels were as low as those of control mice throughout the survival period. The cure with subthreshold GcMAF-treatments (administered once or twice) of tumor-bearing mice appeared to be a consequence of sustained macrophage activation by inflammation resulting from the macrophage-mediated tumoricidal process. Therefore, a protracted macrophage activation induced by a few administrations of minute amounts of GcMAF eradicated the murine ascites tumor. PMID:9893164

  8. Magnetic Pump Axial Force Balance Method based on the Magnetic Bearing%基于永磁悬推力轴承的磁力泵轴向力平衡方法

    周龙德; 杨国来

    2013-01-01

    针对磁力泵在运行过程中产生的轴向力平衡问题,通过对磁力泵轴向力的分析,提出了采用永磁悬浮推力轴承来替代普通推力轴承的方法,彻底解决了磁力泵工作现场推力轴承磨损与破裂的问题,实现了磁力泵无接触传动,降低了噪声和功率损失,提高了磁力泵的工作效率和使用寿命.%Focused on the problem of the axial force balance in the operation process of the magnetic pump and based on the magnetic pump axial force analysis,the way that using the permanent magnetic suspension thrust bearing to replace the traditional thrust bearing was proposed,which completely solves the problem that thrust bearing wear and fracture in the magnetic pump working site,realizing the magnetic pump non-contact transmission,noise reducing,power loss,and improves the pump efficiency and service life.

  9. Deciphering Solar Magnetic Activity: On Grand Minima in Solar Activity

    McIntosh, Scott W

    2015-01-01

    The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magnetism, perhaps even indicators of a significant downward trend, over recent decades. Are we entering a minimum in solar activity that is deeper and longer than a typical solar minimum, a "grand minimum"? How could we tell if we are? What is a grand minimum and how does the Sun recover? These are very pertinent questions for modern civilization. In this paper we present a hypothetical demonstration of entry and exit from grand minimum conditions based on a recent analysis of solar features over the past 20 years and their p...

  10. A Model of Mercury's Magnetospheric Magnetic Field with Dependence on Magnetic Activity

    Korth, H.; Tsyganenko, N. A.; Johnson, C. L.; Philpott, L. C.; Anderson, B. J.; Solomon, S. C.; McNutt, R. L., Jr.

    2015-12-01

    Accurate knowledge of Mercury's magnetospheric magnetic field is required to characterize the planet's internal field and the structure of the magnetosphere. We present the first model of Mercury's magnetospheric magnetic field that includes a dependence on magnetic activity. The model consists of individual modules for magnetic fields of internal origin, approximated by a dipole of magnitude 190 nT RM3, where RM is Mercury's radius, offset northward by 479 km along the spin axis, and of external origin resulting from currents flowing on the magnetopause boundary and in the cross-tail current sheet. The magnetic field is confined within a magnetopause shape derived from Magnetometer observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft and dependent on magnetic activity. The cross-tail current is prescribed having a disk shape near the planet and extending into a sheet at larger distances. The magnitude of the tail current, which also depends on magnetic activity, is fit to minimize the root-mean-square residual between the model magnetic field and the field within the magnetosphere observed by MESSENGER. The model was fit separately for magnetic field observations within distinct levels of magnetic activity. Linear fits of model parameters versus magnetic activity allows continuous scaling of the model to magnetic activity. The magnetic field contribution from each module is shielded individually by a scalar potential function, which was fit to minimize the root-mean-square normal magnetic field component at the magnetopause. The resulting model reproduces the dependence of the magnetospheric size and tail current intensity on magnetic activity, and allows more accurate characterization of the internal field.

  11. Mixed-mu superconducting bearings

    Hull, John R.; Mulcahy, Thomas M.

    1998-01-01

    A mixed-mu superconducting bearing including a ferrite structure disposed for rotation adjacent a stationary superconductor material structure and a stationary permanent magnet structure. The ferrite structure is levitated by said stationary permanent magnet structure.

  12. AUGMENTATION OF IMMUNE FUNCTIONS AND AUTOLOGOUS TUMOR-KILLING ACTIVITY BY KAPPA-SELENOCARRAGEENAN IN MICE BEARING SARCOMA 180

    Wei Hulai; Jia Zhengping; Zhao Huishun

    1998-01-01

    Objective: To study the enhancement of the immune functions and autologous tumor-killing (ATK) activity by kappa-selenocarrageenan (KSC) in mice bearing sarcoma 180. Methods: To measure the effects of KSC and/or Cyclophosphamide (Cy) on natural killer (NK) activity,lymphokine-activated killer (LAK) activity, the production of interleukin-2 (IL-2), ATK activity and the growth of sarcoma 180 (S180). Results: KSC promoted NK activity, LAK activity and ATK activity in vivo, increased IL-2 production at 40 mg/kg/d×9d. It also enhanced the antitumor action of Cy (20 mg/kg/d×9d) and offset the inhibition of Cy on immunocopetent cells. The ATK activity in splenocytes of S180-bearing mice could be induced and increased by recombinant interleukin-2 (rIL-2) in vitro. Conclusion: KSC has an up- regulating effect on the immune functions and ATK activity in tumorbearing mice. It can be used as a biological response modifier (BRM) in cancer biotherapy.

  13. An active antenna for ELF magnetic fields

    Sutton, John F.; Spaniol, Craig

    1994-01-01

    The work of Nikola Tesla, especially that directed toward world-wide electrical energy distribution via excitation of the earth-ionosphere cavity resonances, has stimulated interest in the study of these resonances. Not only are they important for their potential use in the transmission of intelligence and electrical power, they are important because they are an integral part of our natural environment. This paper describes the design of a sensitive, untuned, low noise active antenna which is uniquely suited to modern earth-ionosphere cavity resonance measurements employing fast-Fourier transform techniques for near-real-time data analysis. It capitalizes on a little known field-antenna interaction mechanism. Recently, the authors made preliminary measurements of the magnetic fields in the earth-ionosphere cavity. During the course of this study, the problem of designing an optimized ELF magnetic field sensor presented itself. The sensor would have to be small, light weight (for portable use), and capable of detecting the 5-50 Hz picoTesla-level signals generated by the natural excitations of the earth-ionosphere cavity resonances. A review of the literature revealed that past researchers had employed very large search coils, both tuned and untuned. Hill and Bostick, for example, used coils of 30,000 turns wound on high permeability cores of 1.83 m length, weighing 40 kg. Tuned coils are unsuitable for modern fast-Fourier transform data analysis techniques which require a broad spectrum input. 'Untuned' coils connected to high input impedance voltage amplifiers exhibit resonant responses at the resonant frequency determined by the coil inductance and the coil distributed winding capacitance. Also, considered as antennas, they have effective areas equal only to their geometrical areas.

  14. Magnetic activity at Mars - Mars Surface Magnetic Observatory

    Vennerstrøm, Susanne; Menvielle, M.; Merayo, José M.G.;

    2012-01-01

    , and use this to provide an estimate of the expected magnetic disturbances at the Martian surface. Far from crustal anomaly regions the expected magnetic disturbances originating from currents associated with the induced magnetosphere are very weak at the day-side, but most likely larger on the night...... around medium intensity radial anomalies in the equatorial region appear to derive from local current loops or vortices around cusp-like radial fields, acting to partly cancel the crustal field. The radial perturbation is further found to depend on upstream solar wind dynamic pressure. We define a...

  15. Tumor inhibitory activity of methanolic and ethyl acetate soluble extracts of Thuja occidentalis L. on mice bearing Ehrlich ascites carcinoma.

    Archana M Navale

    2014-06-01

    Full Text Available Thuja occidentalis (Cupressaceae is an ornamental plant of European origin. It has been used in folk medicine for the treatment of cancer. Mice bearing Ehrlich Ascites Carcinoma (EAC mice were treated with methanolic extract (165 mg/kg, ethyl acetate soluble fraction (30 mg/kg and combination of both extracts of TO. Inhibition of tumor growth, increase in survival time of animal with treatment, and hematological parameters were determined. Both methanolic and ethyl acetate soluble fractions of TO exerted tumor growth inhibitory activity in mice bearing EAC. Combination treatment of two extracts showed more pronounced effect. In conclusion, Methanolic and ethyl acetate soluble extracts of TO exhibit anticancer activity against Ehrlich ascites carcinoma in mice. Thus, it has anticancer potential and should be further evaluated in higher models.

  16. Xenoestrogenic and dioxin-like activity in blood of East Greenland polar bears (Ursus maritimus).

    Erdmann, Simon E; Dietz, Rune; Sonne, Christian; Bechshøft, Thea Ø; Vorkamp, Katrin; Letcher, Robert J; Long, Manhai; Bonefeld-Jørgensen, Eva C

    2013-07-01

    The aims of the project were to (i) extract the lipophilic persistent organic pollutants (POPs) from the blood of 99 East Greenland polar bears and assess the combined mixture effect on the estrogen receptor (ER) and the aryl hydrocarbon receptor (AhR) mediated transactivity; (ii) To evaluate whether the receptor transactivities were associated with selected POP markers, and (iii) compare the receptor transactivities in polar bears with earlier studies on Greenlandic Inuit. Lipophilic POPs were extracted using a combination of solid-phase extraction (SPE) and high performance liquid chromatography (HPLC). ER mediated transactivity was determined using the ER luciferase reporter MVLN cell assay. The extracts were tested alone (XER) and together with 17β-estradiol (E2) as a physiological mimic (XERcomp). Dioxins and dioxin-like (DL) compounds were extracted by a combination of SPE and the Supelco Dioxin Prep System®. AhR mediated dioxin-like transactivity was determined using the AhR luciferase reporter Hepa 1.12cR cell assay. Agonistic ER transactivity was elicited by 19% of the samples, and a further increased E2 induced ER response was found for 52%, whereas 17% antagonized the E2 induced ER response. Positive correlations were found in subadult bears between XER and several POP biomarkers. XER and XERcomp correlated positively to each other. A total of 91% of the polar bear blood extracts elicited agonistic AhR transactivity. The AhR-TCDD equivalent (AhR-TEQ) median levels were higher among adult bears compared to subadult bears, but not significantly. PMID:23648332

  17. Evaluation of the Effectiveness of an Active Magnetic Damper (AMD) in Damping Subsynchronous Vibrations in a Flexible Rotor

    Mendoza, Hector

    2000-01-01

    Subsynchronous vibrations such as those caused by rotor instability represent one of the most harrowing scenarios of rotor vibration. They are related to a great diversity of destabilizing forces and some of them are not well understood yet. Therefore, special attention must be paid to this type of vibration. Active Magnetic Bearings (AMBs) monitor the position of the shaft and change the dynamics of the system accordingly to keep the rotor in a desired position, offering the possibility of...

  18. Pulse-driven magnetoimpedance sensor detection of cardiac magnetic activity.

    Shinsuke Nakayama

    Full Text Available This study sought to establish a convenient method for detecting biomagnetic activity in the heart. Electrical activity of the heart simultaneously induces a magnetic field. Detection of this magnetic activity will enable non-contact, noninvasive evaluation to be made. We improved the sensitivity of a pulse-driven magnetoimpedance (PMI sensor, which is used as an electric compass in mobile phones and as a motion sensor of the operation handle in computer games, toward a pico-Tesla (pT level, and measured magnetic fields on the surface of the thoracic wall in humans. The changes in magnetic field detected by this sensor synchronized with the electric activity of the electrocardiogram (ECG. The shape of the magnetic wave was largely altered by shifting the sensor position within 20 mm in parallel and/or perpendicular to the thoracic wall. The magnetic activity was maximal in the 4th intercostals near the center of the sterna. Furthermore, averaging the magnetic activity at 15 mm in the distance between the thoracic wall and the sensor demonstrated magnetic waves mimicking the P wave and QRS complex. The present study shows the application of PMI sensor in detecting cardiac magnetic activity in several healthy subjects, and suggests future applications of this technology in medicine and biology.

  19. Applications of magnetically active fibre reinforced composites

    Etches, Julie; Bond, Ian; Mellor, Philip

    2005-05-01

    As the application of fibre reinforced polymer composites (FRP) becomes more widespread there is a desire to add functionality beyond that of simple mechanical properties in order to facilitate the development of 'smart' materials. For example, the functionality being discussed in this paper is the imparting of significant magnetic properties to a FRP. This can take the form of soft magnetic performance for use in electrical machines or hard magnetic performance for novel forms of sensing or power generation. It has been demonstrated that by using hollow glass fibres as a reinforcement, magnetic material can be introduced into these fibres without significant effects on the structural behaviour of the FRP. The current studies have included the assessment of such a magnetic FRP in a variety of applications. The addition of hard magnetic materials, e.g. magnetite and barium ferrite, has been achieved through the use of nanopowders and the resulting FRP has been assessed for morphing structures applications. The magnitude of magnetic performance that can be currently achieved is controlled by the availability of suitable magnetic materials in fine powder form and the volume of magnetic material which can be incorporated within the fibres.

  20. Magnetic activity of surface plasmon resonance using dielectric magnetic materials fabricated on quartz glass substrate

    Narushima, Kazuki; Ashizawa, Yoshito; Brachwitz, Kerstin; Hochmuth, Holger; Lorenz, Michael; Grundmann, Marius; Nakagawa, Katsuji

    2016-07-01

    The magnetic activity of surface plasmons in Au/MFe2O4 (M = Ni, Co, and Zn) polycrystalline bilayer films fabricated on a quartz glass substrate was studied for future magnetic sensor applications using surface plasmon resonance. The excitation of surface plasmons and their magnetic activity were observed in all investigated Au/MFe2O4 films. The magnetic activity of surface plasmons of the polycrystalline Au/NiFe2O4 film was larger than those of the other polycrystalline Au/MFe2O4 films, the epitaxial NiFe2O4 film, and metallic films. The large magnetic activity of surface plasmons of the polycrystalline film is controlled by manipulating surface plasmon excitation conditions and magnetic properties.

  1. ANTI-OXIDANT ACTIVITY OF MORINDA CITRIFOLIA ON LYMPHOMA-BEARING MICE

    Anitha, T.; S. Mohandass

    2006-01-01

    Oral treatment with 50 mg Kg-1 day-1 of crude methanol extract of Morinda citrifolia leaves for 14 days significantly increased the anti-oxidant enzymes, like catalase, glutathione peroxidase (GSHPx) and superoxide dismutase (SOD), and anti-oxidants like glutathione (GSH) and ascorbic acid decreased in lymphoma-bearing mice.

  2. Model-Based Control Design for Flexible Rotors Supported by Active Gas Bearings - Theory & Experiment

    Pierart Vásquez, Fabián Gonzalo

    , abundant and clean. Nevertheless, this technology has important drawbacks: the low viscosity of the lubricant results in a low load carrying capacity and gas bearings also presents low damping properties, which often lead to a reduced stability range and make dangerous running close to, or across the...

  3. Perspectives for uranium-bearing waste reprocessing from former mining and milling activity in Tajikistan

    The possibility for uranium-bearing waste reprocessing from uranium tailings Map 1-9, Chkalovsk city is investigated. Optimal process (temperature, ph medium, time) technological parameters are determined, allowing producing yellow cake (U3O8) from waste with low uranium content. Basic process flow diagram for uranium industry waste reprocessing is proposed.

  4. ACTIVE VIBRATION REDUCTION OF RIGID ROTOR BY KINEMATIC EXCITATION OF BUSHES OF JOURNAL BEARINGS

    Ondrouch, Jan; Ferfecki, Petr; Poruba, Z.

    2009-01-01

    Roč. 49, č. 2 (2009), s. 107-110. ISSN 0543-5846 Institutional research plan: CEZ:AV0Z20760514 Keywords : bearing * controller * rotor system * vibration reduction Subject RIV: JR - Other Machinery Impact factor: 0.439, year: 2009

  5. A magnetically active microfluidic device for chemiluminescence bioassays

    Zheng, Yi; Zhao, Shulin; Liu, Yi-Ming

    2011-01-01

    Highly active horseradish peroxidase functionalized magnetic nanoparticles were prepared and packed into a microfluidic channel, producing an in-line bioreactor that enabled a sensitive chemiluminescence assay of H2O2. The proposed magnetically active microfluidic device proved useful for chemiluminescence assays of biomedically interesting compounds.

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

    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.

  7. Magnetic history of solar active regions

    An attempt was made to use recent magnetic observations to trace the history of a typical solar active region from birth to death. By comparing the short-term motions to the long-term spreading, it is demonstrated that the decay process is dominated, over periods ranging from days to months, by a random walk of field lines, with a diffusion constant of roughly 200 to 400 km2/sec. While the interaction between diffusion and differential rotation dictates the geometric pattern of the decaying region, the actual quantity of surviving flux appears to be less, and its ultimate annihilation more thorough, than would have been expected. This probably indicates a continued subsurface coupling between opposite polarity features. In addition, the long-range agreement between theory and observation is considerably improved by postulating the existence, in the middle latitudes of each hemisphere, of a systematic, poleward-moving meridional flow of about 3 m/sec. The outlook for being able to make continued progress towards the understanding of basic solar phenomena by further efforts in this direction is promising

  8. Design, synthesis, and self-assembly of optically active perylenetetracarboxylic diimide bearing two peripheral chiral binaphthyl moieties

    An optically active perylenetetracarboxylic diimide (PTCDI) bearing two optically active binaphthyl moieties has been designed and synthesized. The self-assembly properties of these novel PTCDI derivatives in DMF/H2O were systematically investigated by electronic absorption, circular dichroism (CD) spectra, IR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) technique. Observation of CD signal in the whole absorption region of PTCDI chromophore, indicates effective chiral information transfer from the chiral binaphthyl units to the central PTCDI chromophore at molecular level. The intermolecular π–π interaction between PTCDI rings together with the additionally formed hydrogen bonds between the crown ether moieties of (S)-1 and additional water molecules and the chiral discrimination of periphery chiral side chains induces further intensified asymmetrical perturbation of the chiral binaphthyl units to the central PTCDI chromophore during the self-assembly process, resulting in the formation of right-handed helical arrangement of corresponding molecules in a stack of PTCDI chromophores in aggregates. In addition, the formed nanostructures were revealed to show good semiconducting properties. - Graphical abstract: An optically active perylenetetracarboxylic diimide bearing two optically active binaphthyl moieties has been prepared. Self-assembly properties of this novel PTCDI derivative in DMF/H2O were systematically investigated. Experimental results indicate the effective chiral information transfer and expression at molecular and intermolecular level. Highlights: ► An optically active perylenetetracarboxylic diimide bearing two optically active binaphthyl moieties has been prepared. ► Self-assembly properties of this novel PTCDI derivative in DMF/H2O were systematically investigated. ► Experimental results indicate the effective chiral information transfer and expression at molecular

  9. The Limit of Free Magnetic Energy in Active Regions

    Moore, Ron; Falconer, David; Sterling, Alphonse

    2012-01-01

    By measuring from active-region magnetograms a proxy of the free energy in the active region fs magnetic field, it has been found previously that (1) there is an abrupt upper limit to the free energy the field can hold that increases with the amount of magnetic field in the active region, the active region fs magnetic flux content, and (2) the free energy is usually near its limit when the field explodes in a CME/flare eruption. That is, explosive active regions are concentrated in a main-sequence path bordering the free-energy ]limit line in (flux content, free-energy proxy) phase space. Here, from measurement of Marshall Space Flight Center vector magnetograms, we find the magnetic condition that underlies the free ]energy limit and the accompanying main sequence of explosive active regions. Using a suitable free ]energy proxy measured from vector magnetograms of 44 active regions, we find that (1) in active regions at and near their free ]energy limit, the ratio of magnetic-shear free energy to the non ]free magnetic energy the potential field would have is approximately 1 in the core field, the field rooted along the neutral line, and (2) this ratio is progressively less in active regions progressively farther below their free ]energy limit. This shows that most active regions in which this core-field energy ratio is much less than 1 cannot be triggered to explode; as this ratio approaches 1, most active regions become capable of exploding; and when this ratio is 1 or greater, most active regions are compelled to explode. From these results we surmise the magnetic condition that determines the free ]energy limit is the ratio of the free magnetic energy to the non-free energy the active region fs field would have were it completely relaxed to its potential ]field configuration, and that this ratio is approximately 1 at the free-energy limit and in the main sequence of explosive active regions.

  10. Specific characteristics of mining activity in the area of occurrence of water-bearing rocks

    kola Jaromír

    2002-01-01

    Underground coal mining in water-bearing rocks has its specific features which have to be considered during early development, driving and coal faces operations and liquidation works connected with coal mines enclosure.In more details is described mining working preparation, mining complex installation and longwall face production.After many miscarriages it was necessary to eliminate difficult mine geological conditions influence by using mine drainage both from the surface and from undergrou...

  11. Light-Activated Magnetic Compass in Birds

    Solov'yov, Ilia; Greiner, Walter

    2013-01-01

    Migrating birds fly thousand miles without having a map, or a GPS unit. But they may carry their own sensitive navigational tool, which allows them "see" the Earth’s magnetic field. Here we review the important physical and chemical constraints on a possible compass sensor and discuss the suggest......Migrating birds fly thousand miles without having a map, or a GPS unit. But they may carry their own sensitive navigational tool, which allows them "see" the Earth’s magnetic field. Here we review the important physical and chemical constraints on a possible compass sensor and discuss...... the suggestion that radical pairs in a photoreceptor cryptochrome might provide a biological realization for a magnetic compass. Finally, we review the current evidence supporting a role for radical pair reactions in the magnetic compass of birds....

  12. Pulse-Driven Magnetoimpedance Sensor Detection of Cardiac Magnetic Activity

    Nakayama, Shinsuke; Sawamura, Kenta; Mohri, Kaneo; Uchiyama, Tsuyoshi

    2011-01-01

    This study sought to establish a convenient method for detecting biomagnetic activity in the heart. Electrical activity of the heart simultaneously induces a magnetic field. Detection of this magnetic activity will enable non-contact, noninvasive evaluation to be made. We improved the sensitivity of a pulse-driven magnetoimpedance (PMI) sensor, which is used as an electric compass in mobile phones and as a motion sensor of the operation handle in computer games, toward a pico-Tesla (pT) level...

  13. Novel magnetic nanoparticles coated by benzene- and β-cyclodextrin-bearing dextran, and the sorption of polycyclic aromatic hydrocarbon

    Cho, Eunae; Tahir, Muhammad Nazir; Min Choi, Jae;

    2015-01-01

    mono-6-O-deoxy-monoazido β-cyclodextrin. Characterization was then carried out by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometry. Using the developed magnetic nanoparticles, the...... significant. Furthermore, the polysaccharide derivative-coated magnetic adsorbents could be recovered by an external magnet for reuse....

  14. Structural Design and Simulation Analysis of Five Freedom Degree Magnetic Bearings Electric Spindle%五自由度磁悬浮电主轴的结构设计与仿真

    陈瑞; 刘贤兴

    2011-01-01

    Based on the traditional structure of five freedom degree magnetic bearings electric spindle, the two parts of five freedom degree magnetic bearings electric spindle were introduced, which were three freedom degree permanent magnet bias mixed magnetic bearings and two freedom degree magnetic bearings asynchronous motor. Firstly, the prototype of five freedom degree magnetic bearings electric spindle was designed, and then the magnetic force and levitation force by electromagnetic analysis software Asoft/Maxwell was analyzed, thus verifying the structure and parameter rationality of the prototype. Finally, the simulation model of control system in Matlab/Simulink was constructed and some related simulation was did, which lays foundation for establishing the control system of the magnetic bearings electric spindle.%在传统五自由度磁悬浮电主轴结构的基础上,提出了一种由永磁偏置三自由度混合磁轴承和二自由度磁悬浮异步电机构成的五自由度磁悬浮电主轴结构.设计了五自由度磁悬浮电主轴的试验样机,通过电磁场分析软件Asoft/Maxwell分析了样机的磁场和悬浮力,验证了所设计样机结构和参数的合理性.在MATLAB/Simulink环境下构建了控制系统的仿真模型,进行了相关的仿真研究,为磁悬浮电主轴数字控制系统的建立奠定了基础.

  15. Magnetically Responsive Activated Carbons for Bio - and Environmental Applications

    Šafařík, Ivo; Horská, Kateřina; Popisková, K.; Šafaříková, Miroslava

    2012-01-01

    Roč. 4, č. 3 (2012), s. 346-352. ISSN 2035-1755 R&D Projects: GA ČR(CZ) GAP503/11/2263; GA MŠk LH12190 Institutional support: RVO:67179843 Keywords : Activated Carbon * Magnetic Modification * Magnetic Separation Subject RIV: EH - Ecology, Behaviour

  16. 基于在线动平衡的磁轴承参数辨识%Parameter identification for magnetic bearing based on online dynamic balancing

    侯二永; 刘昆

    2013-01-01

    针对磁悬浮刚性转子系统,提出了一种基于在线动平衡的磁轴承参数辨识方法。采用已知大小和相位的不平衡质量作为激振源,根据动平衡仪测得的转子不平衡响应,求得磁轴承位移刚度和电流刚度。利用某型磁悬浮控制力矩陀螺对该方法进行了实验验证,得到了一定转速范围内的磁轴承位移刚度和电流刚度,证明了该方法的正确性和实用性。实验结果表明,外转子型磁轴承位移刚度和电流刚度随转速的增加而下降明显。%Based on online dynamic balancing,a novel parameter identification method is proposed for magnetic suspending rigid rotor system. Two unbalancing masses with given magnitude and phase were added to the rotor and used as a vibration exciter.The displacement stiffness and current stiffness were identified from the unbalancing response detected by the balancing monitor.The proposed method was experimentally validated with a magnetic suspending control moment gyroscope,and the displacement stiffness and current stiffness of its magnetic bearings were obtained within a certain rotational speed interval,which demonstrates the correctness and feasibility of the method.The experimental results show that the displacement stiffness and current stiffness decrease notably with the rotational speed increased for an outer rotor magnetic bearing.

  17. cis-Nitenpyram Analogues Bearing Acyloxy Segments Anchored on the Tetrahydropyrimidine Ring: Synthesis,Insecticidal Activities and Molecular Docking Studies

    SUN Chuan-wen; WU Ying; CHEN Yan-xia; NAN Shi-bin; ZHANG Wang-geng

    2013-01-01

    A series of novel cis-nitenpyram analogues bearing acyloxy segments anchored on the tetrahydropyrimidine ring was designed and synthesized.Preliminary bioassays indicate that all the nitenpyram analogues 3a—3n exhibit good insecticidal activities against Nilaparvata lugens and Aphis medicaginis at 100 mg/L,while analogue 3k affords the best activity in vitro and the lethal concentration 50(LC50) values(0.187,0.214 mg/L) are close to that of nitenpyram.The structure activity relationships(SARs) suggest that their insecticidal potency is influenced by the species of acyloxy segments.The docking results reveal that analogue 3k forms stronger hydrogen-bonding with the nAChR,which explain the structure activity relationships(SARs) observed in vitro and imply that the strategies of our designed nitenpyram analogues are feasible.

  18. Synthesis and Biological Evaluation of a Valinomycin Analog Bearing a Pentafluorophenyl Active Ester Moiety.

    D'Accolti, Lucia; Denora, Nunzio; La Piana, Gianluigi; Marzulli, Domenico; Siwy, Zuzanna S; Fusco, Caterina; Annese, Cosimo

    2015-12-18

    A valuable analog of the K(+)-ionophore valinomycin (1), bearing a pentafluorophenyl ester moiety, has been obtained by selective reaction between the tertiary hydroxyl moiety of analog 2 (available from valinomycin hydroxylation) and the isocyanate group of pentafluorophenyl N-carbonyl glycinate (3) catalyzed by bis(N,N-dimethylformamide)dichlorodioxomolybdenum(VI). LC-HRMS studies show that analog 4 undergoes easy derivatization under mild conditions by reaction with OH- and NH2-containing compounds. Mitochondrial depolarization assays suggest that 4 acts as a K(+)-ionophore, provided that the glycine carboxyl group is appropriately masked. PMID:26566090

  19. 磁悬浮轴承转子位移自检测方法%Self-sensing Methods of Rotor Displacement for Magnetic Bearings

    金婕; 朱熀秋

    2014-01-01

    磁悬浮轴承转子位移传感器检测的速度和精度,对磁悬浮轴承位移闭环控制的精度具有重要影响。论文指出了磁悬浮轴承转子传统的位移传感器检测方法的不足,分析了参数估计法,状态估计等几种目前主要的磁悬浮轴承自检测技术的基本原理,性能和适用范围,最后,对磁悬浮轴承位移自检测技术的发展趋势做了进一步阐述。%The speed and accuracy of rotor displacement sensor for magnetic bearings have important impact on the precision of closed-loop control for magnetic bearings.The article pointed out the drawbacks of the traditional displacement sensors.The principles, performances and applicable ranges of parameter estima-tion, state estimation and other main self-sensing technologies were analyzed.Finally, the development trend and prospect of self-sensing technology were further formulated.

  20. Journal bearing

    Menke, John R.; Boeker, Gilbert F.

    1976-05-11

    1. An improved journal bearing comprising in combination a non-rotatable cylindrical bearing member having a first bearing surface, a rotatable cylindrical bearing member having a confronting second bearing surface having a plurality of bearing elements, a source of lubricant adjacent said bearing elements for supplying lubricant thereto, each bearing element consisting of a pair of elongated relatively shallowly depressed surfaces lying in a cylindrical surface co-axial with the non-depressed surface and diverging from one another in the direction of rotation and obliquely arranged with respect to the axis of rotation of said rotatable member to cause a flow of lubricant longitudinally along said depressed surfaces from their distal ends toward their proximal ends as said bearing members are rotated relative to one another, each depressed surface subtending a radial angle of less than 360.degree., and means for rotating said rotatable bearing member to cause the lubricant to flow across and along said depressed surfaces, the flow of lubricant being impeded by the non-depressed portions of said second bearing surface to cause an increase in the lubricant pressure.

  1. Magnetism and Electricity Activity "Attracts" Student Interest

    Roman, Harry T.

    2010-01-01

    Electricity and magnetism are intimately linked, this relationship forming the basis of the modern electric utility system and the generation of bulk electrical energy. There is rich literature from which to teach students the basics, but nothing drives the point home like having them learn from firsthand experience--and that is what this…

  2. The influence of the magnetic field on the performance of an active magnetic regenerator (AMR)

    Bjørk, Rasmus; Engelbrecht, Kurt

    2011-01-01

    The influence of the time variation of the magnetic field, termed the magnetic field profile, on the performance of a magnetocaloric refrigeration device using the active magnetic regeneration (AMR) cycle is studied for a number of process parameters for both a parallel plate and packed bed...... regenerator using a numerical model. The cooling curve of the AMR is shown to be almost linear far from the Curie temperature of the magnetocaloric material. It is shown that a magnetic field profile that is 10% of the cycle time out of sync with the flow profile leads to a drop in both the maximum...

  3. Stellar magnetic activity – Star-Planet Interactions

    Poppenhaeger, K.

    2015-01-01

    Full Text Available Stellar magnetic activity is an important factor in the formation and evolution of exoplanets. Magnetic phenomena like stellar flares, coronal mass ejections, and high-energy emission affect the exoplanetary atmosphere and its mass loss over time. One major question is whether the magnetic evolution of exoplanet host stars is the same as for stars without planets; tidal and magnetic interactions of a star and its close-in planets may play a role in this. Stellar magnetic activity also shapes our ability to detect exoplanets with different methods in the first place, and therefore we need to understand it properly to derive an accurate estimate of the existing exoplanet population. I will review recent theoretical and observational results, as well as outline some avenues for future progress.

  4. Tests of an Induced Activity Monitor in a magnetic environment

    Pangallo, M; Perrot, Anne Laure; Vincke, H; CERN. Geneva. TS Department

    2005-01-01

    The Induced Activity Monitors (IAM) dedicated to measure the gamma ambient dose equivalent rate (due to the photons from the activated materials) will be installed inside the LHC accelerator and in the experimental caverns. Some of these IAM detectors (plastic ionization chambers) will be located in areas were magnetic fields will be present. Therefore the response of such radiation detectors in a magnetic field environment has been experimentally and theoretically studied and the results are reported in this note. The tests were performed at CERN in the CMS H2 experimental area with conventional and superconductor magnets. The response of the IAM was studied for different orientations of its chamber with respect to the magnetic field lines and for different magnetic field intensities up to 3T. Moreover, FLUKA Monte Carlo Simulations were performed to fully understand the physical effects responsible for the various measurement results. The conclusions of this study will permit to choose the proper orientatio...

  5. Contribution of Italy to the activities on intercomparison of analysis methods for seismically isolated nuclear structures: Finite element analysis of lead rubber bearings

    This paper presents a summary of the results of nonlinear Finite Element (FE) analyses carried out by ENEL-Ricerca, Hydraulic and Structural Centre and ENEA-ERG-SIEC-SISM, on Lead Rubber Bearings (LRBs). Activities were carried out in the framework of the four years' Coordinated Research Programme (CRP) of the International Atomic Energy Agency (IAEA) on Intercomparison of Analysis Methods for Seismically Isolated Nuclear Structures. The bearing Finite Element Models (FEMs) are validated through comparisons of the numerical results with experimental test data. The reliability of FEMs for simulating the behaviour of rubber bearings is presented and discussed. (author)

  6. Magnetic Levitation Technique for Active Vibration Control

    Hoque, Emdadul; Mizuno, Takeshi

    2010-01-01

    A zero-power controlled magnetic levitation system has been presented in this chapter. The unique characteristic of the zero-power control system is that it can generate negative stiffness with zero control current in the steady-state which is realized in this chapter. The detail characteristics of the levitation system are investigated. Moreover, two major contributions, the stiffness adjustment and nonlinear compensation of the suspension system have been introduced elaborately. Often, ther...

  7. Magnetic structure of an activated filament in a flaring active region

    Sasso, C; Solanki, S K

    2013-01-01

    While the magnetic field in quiescent prominences has been widely investigated, less is known about the field in activated prominences. We introduce observational results on the magnetic field structure of an activated filament in a flaring active region. We study, in particular, its magnetic structure and line-of-sight flows during its early activated phase, shortly before it displays signs of rotation. We invert the Stokes profiles of the chromospheric He I 10830 A triplet and the photospheric Si I 10827 A line observed in this filament by the VTT on Tenerife. Using these inversion results we present and interpret the first maps of velocity and magnetic field obtained in an activated filament, both in the photosphere and the chromosphere. Up to 5 different magnetic components are found in the chromospheric layers of the filament, while outside the filament a single component is sufficient to reproduce the observations. Magnetic components displaying an upflow are preferentially located towards the centre of...

  8. Blood Pump Having a Magnetically Suspended Rotor

    Antaki, James F. (Inventor); Paden, Bradley (Inventor); Burgreen, Gregory (Inventor); Groom, Nelson J. (Inventor)

    2002-01-01

    A blood pump preferably has a magnetically suspended rotor that rotates within a housing. The rotor may rotate about a stator disposed within the housing. Radial magnetic bearings may be defined within the stator and the rotor in order to suspend the rotor. The radial magnetic bearings may be passive magnetic bearings that include permanent magnets disposed within the stator and the rotor or active magnetic bearings. The pump may further include an axial magnetic bearing that may be either a passive or an active magnetic bearing. A motor that drives the rotor may be disposed within the housing in order to more easily dissipate heat generated by the motor. A primary flow path is defined between the rotor and the stator, and a secondary flow path is defined between the stator and the rotor. Preferably, a substantial majority of blood passes through the primary flow path. The secondary flow path is large enough so that it provides adequate flushing of the secondary flow path while being small enough to permit efficient operation of the radial magnet bearings across the secondary flow path.

  9. Deciphering Solar Magnetic Activity: On Grand Minima in Solar Activity

    Scott William Mcintosh; Leamon, Robert J.

    2015-01-01

    The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magne...

  10. Deciphering solar magnetic activity: on grand minima in solar activity

    Mcintosh, Scott W.; Leamon, Robert J.

    2015-01-01

    The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magne...

  11. 外加磁场对磁流体润滑油膜轴承的影响∗%Effects on Magnetic-fluid-lubricated Oil-film Bearings by Magnetic Field

    张亚南; 王建梅; 张笑天; 张艳娟

    2015-01-01

    In order to study the distribution of magnetic field in the magnetic⁃fluid⁃lubricate d oil⁃film bearings,three dif⁃ferent forms of the external magnetic field was exerted through the application of permanent magnet,toroidal solenoid and Helmholtz coils.Two⁃dimensional solid finite element model of magnetic field was established and analyzed to study the magnetic field distribution of three different models.The magnetic field distribution in oil film district for different models was compared.The results show that the magnetic field is different for three different models,it is mainly distributed in per⁃manent magnets,the oil film,bearing pedestal and roll part near the magnet for the permanent magnets model,mainly in the oil film,bearing pedestal and roll part near the magnet for toroidal solenoid model,and mainly in the coil and the end of the oil film for Helmholtz coils model.The magnetic field distribution of the three different models in oil film district has an end effect and presents uneven distribution along the axial,which is small in the middle and large at ends.The magnetic field distribution in oil film district is uniform along the radial direction for the permanent magnet model and toroidal solenoid model, but not uniform for the Helmholtz coils model.%为了研究磁流体润滑油膜轴承内磁场的分布情况,分别通过永磁铁、螺线管及亥姆赫兹线圈对其施加3种不同形式的外磁场。通过磁场二维实体有限元模型的数值仿真,分析在3种模型下磁流体润滑油膜轴承的磁场分布特性,并比较磁场在油膜区的分布情况。结果表明,永磁铁模型的磁场主要分布在永磁铁、油膜、轴承座以及靠近磁铁的轧辊部分,螺线管模型的磁场主要分布在油膜、轴承座以及靠近磁铁的轧辊部分,亥姆霍兹线圈模型的磁场主要分布在线圈以及油膜的端部;3种模型在油膜区磁场分布沿轴向均呈现中间小、两端

  12. 外加磁场对磁流体润滑油膜轴承的影响∗%Effects on Magnetic-fluid-lubricated Oil-film Bearings by Magnetic Field

    张亚南; 王建梅; 张笑天; 张艳娟

    2015-01-01

    为了研究磁流体润滑油膜轴承内磁场的分布情况,分别通过永磁铁、螺线管及亥姆赫兹线圈对其施加3种不同形式的外磁场。通过磁场二维实体有限元模型的数值仿真,分析在3种模型下磁流体润滑油膜轴承的磁场分布特性,并比较磁场在油膜区的分布情况。结果表明,永磁铁模型的磁场主要分布在永磁铁、油膜、轴承座以及靠近磁铁的轧辊部分,螺线管模型的磁场主要分布在油膜、轴承座以及靠近磁铁的轧辊部分,亥姆霍兹线圈模型的磁场主要分布在线圈以及油膜的端部;3种模型在油膜区磁场分布沿轴向均呈现中间小、两端大的不均匀现象,且具有端部效应;永磁铁模型和螺线管模型在油膜区磁场沿径向分布均匀,亥姆霍兹线圈模型沿径向分布不均匀。%In order to study the distribution of magnetic field in the magnetic⁃fluid⁃lubricate d oil⁃film bearings,three dif⁃ferent forms of the external magnetic field was exerted through the application of permanent magnet,toroidal solenoid and Helmholtz coils.Two⁃dimensional solid finite element model of magnetic field was established and analyzed to study the magnetic field distribution of three different models.The magnetic field distribution in oil film district for different models was compared.The results show that the magnetic field is different for three different models,it is mainly distributed in per⁃manent magnets,the oil film,bearing pedestal and roll part near the magnet for the permanent magnets model,mainly in the oil film,bearing pedestal and roll part near the magnet for toroidal solenoid model,and mainly in the coil and the end of the oil film for Helmholtz coils model.The magnetic field distribution of the three different models in oil film district has an end effect and presents uneven distribution along the axial,which is small in the middle and large at ends.The magnetic field

  13. Highly active antibody-modified magnetic polyelectrolyte capsules.

    Valdepérez, Daniel; Del Pino, Pablo; Sánchez, Lourdes; Parak, Wolfgang J; Pelaz, Beatriz

    2016-07-15

    Polyelectrolyte hollow capsules are versatile platforms typically used for encapsulation of a wide variety of macromolecules in their cavity. The polymer shell of these capsules as composed by alternating layers of oppositely charged polyelectrolytes also allows for adding additional functionalities. The properties of the shell can be for example engineered by trapping different nanoparticles in-between the shell layers and/or by attaching bioactive molecules such as antibodies to the outermost layer. Herein, iron oxide NPs were inmobilized into the shell of polyelectrolyte capsules and the outermost layer of the shell was covalently modified with anti peroxidase antibodies. These capsules act as prototype model system, aiming to obtain a microstructure with the potential capability to specifically recognize and separate macromolecules. Due to the magnetic nanoparticles in the capsule shell, the capsules together with the attached target might be extracted by magnetic field gradients. Here we verified this approach by extracting horseradish peroxidase from a solution through magnetic separation with capsules bearing antibodies against horseradish peroxidase. The bioactivity of the capsules and the high degree of specific antibody functionalization were confirmed and quantified through an enzymatic reaction mediated by the extracted horseradish peroxidase. PMID:27089014

  14. Superconducting bearings for flywheel applications

    Abrahamsen, A.B.

    2001-01-01

    A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings in flywheels.

  15. Superconducting bearings for flywheel applications

    Abrahamsen, A.B.

    2001-01-01

    A literature study on the application of superconducting bearings in energy storage flywheel systems. The physics of magnetic levitation and superconductors are presented in the first part of the report, followed by a discussion of the literature found onthe applications of superconducting bearings...

  16. The connection between stellar activity cycles and magnetic field topology

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Folsom, C. P.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Waite, I. A.

    2016-08-01

    Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. On the Sun, polarity reversals are a feature of its activity cycle. In this paper, we examine the magnetic properties of stars with existing chromospherically determined cycle periods. Previous authors have suggested that cycle periods lie on multiple branches, either in the cycle period-Rossby number plane or the cycle period-rotation period plane. We find some evidence that stars along the active branch show significant average toroidal fields that exhibit large temporal variations while stars exclusively on the inactive branch remain dominantly poloidal throughout their entire cycle. This lends credence to the idea that different shear layers are in operation along each branch. There is also evidence that the short magnetic polarity switches observed on some stars are characteristic of the inactive branch while the longer chromospherically determined periods are characteristic of the active branch. This may explain the discrepancy between the magnetic and chromospheric cycle periods found on some stars. These results represent a first attempt at linking global magnetic field properties obtained form ZDI and activity cycles.

  17. A superconducting thrust-bearing system for an energy storage flywheel

    Coombs, T.A.; Cansiz, A.; Campbell, A.M. [IRC in Superconductivity, Cambridge (United Kingdom)

    2002-05-01

    We have constructed a bearing system for an energy storage flywheel. This bearing system uses a combination of permanent magnets and superconductors in an arrangement commonly termed as an Evershed bearing. In an Evershed system there are in fact two bearings which act in concert. In our system we have one bearing constructed entirely out of permanent magnets acting in attraction. This system bears the weight of the flywheel (43.6 kg) but would not, on its own, be stable. Stability is provided by a superconducting bearing which is formed by the interaction between the magnetic field of a permanent magnet sited on the rotor and superconductors on the stator. This overall arrangement is stable over a range of levitation heights and has been tested at rotation speeds of up to around 12 Hz (the maximum speed is dictated by the drive system not the bearing system). There is a sharp resonance peaking at between 2 and 3 Hz and spin down tests indicate that the equivalent coefficient of friction is of the order of 10{sup -5}. The rate of change of velocity is, however, not constant so the drag is clearly not solely frictional. The position of the resonance is dictated by the stiffness of the bearing relative to the mass of the flywheel but the amplitude of the resonance is dictated by the variation in magnitude of the magnetic field of the permanent magnets. Large magnets are (at present) fabricated in sections and this leads to a highly inhomogeneous field. The field has been smoothed by using a combination of iron which acts passively and copper which provides magnetic shielding due to the generation of eddy currents and therefore acts as an 'active' component. Calculations based on the spin down tests indicate that the resultant variation in field is of the order of 3% and measurements are being carried out to confirm this. (author)

  18. Rotor dynamic behaviour of a high-speed oil-free motor compressor with a rigid coupling supported on four radial magnetic bearings

    Schmied, J.; Pradetto, J. C.

    1994-01-01

    The combination of a high-speed motor, dry gas seals, and magnetic bearings realized in this unit facilitates the elimination of oil. The motor is coupled with a quill shaft to the compressor. This yields higher natural frequencies of the rotor than with the use of a diaphragm coupling and helps to maintain a sufficient margin of the maximum speed to the frequency of the second compressor bending mode. However, the controller of each bearing then has to take the combined modes of both machines into account. The requirements for the controller to ensure stability and sufficient damping of all critical speeds are designed and compared with the implemented controller. The calculated closed loop behavior was confirmed experimentally, except the stability of some higher modes due to slight frequency deviations of the rotor model to the actual rotor. The influence of a mechanical damper as a device to provide additional damping to high models is demonstrated theoretically. After all, it was not necessary to install the damper, since all modes cold be stabilized by the controller.

  19. Whirling Dervish Dynamos: Magnetic Activity in CV Secondaries

    Saar, Steven

    2003-07-01

    The mass-losing secondary stars of cataclysmic variables {CVs} are the most rapidly rotating cool dwarfs observable. Other rapid rotators show a maximal, "saturated" level of magnetic activity {e.g., X-ray emission}, but there are hints from contact binaries and young clusters that activity may be suppressed at the highest rotation rates. CV secondaries are thus important probes of magnetic dynamos at rotational extremes. Implications for CV evolution {e.g., the ``period gap", accretion variability} may also be profound. Unfortunately, study of CV secondaries is hampered by pesky accretion-related phenomena and reflection effects. As a result, little systematic work has been done. To explore activity in these stars, we therefore propose to study far-UV spectra of AM Her-type systems {which have no accretion disks} in deep photometric minima in which accretion is shut off. Magnetic-related emission from the secondary will be separated {in velocity} from residual accretion emission by observations near quadratures. Lower chromospheric irradiation due to the white dwarf primary will be removed by modeling, yielding the true level of magnetic activity on the secondary. We will compare the results to other dMe stars and draw implications for magnetic dynamos and activity at rotational extremes, and for CV evolution and behavior.

  20. Synchronous suspension control study for magnetic bearing rotor displacement%磁悬浮轴承的转子位移同步悬浮控制研究

    王军; 曾励

    2011-01-01

    提出一种对磁悬浮轴承进行转子位移同步悬浮控制的策略,建立了位移同步悬浮控制系统的控制模型,基于状态重构机理实现转子位移同步,按状态空间法设计状态同步矩阵和系统闭环状态反馈矩阵,并对所设计系统进行了仿真分析.%Put forward a control strategy that displacement of the magnetic suspension bearing' s rotor synchronized suspension. The model of the displacement synchronization suspension control system was structured. Based on principles of state reconstruction, achieve displacement synchronization of the rotor. By state space method, designed state synchronization matrix and system' s closed state feedback matrix and analyzed the result of this system simulation.

  1. Adsorption of Imidacloprid on Powdered Activated Carbon and Magnetic Activated Carbon

    Zahoor, M.; Mahramanlioglu, M.

    2011-01-01

    The adsorptive characteristics of imidacloprid on magnetic activated carbon (MAC12) in comparison to powdered activated carbon (PAC) were investigated. Adsorption of imidacloprid onto powdered activated carbon and magnetic activated carbon was studied as a function of time, initial imidacloprid concentration, temperature and pH. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models for both carbons were used to describe the kinetic data. The adsorption equilibrium data we...

  2. Magnetic flare model of quasars and active galactic nuclei

    As a model of quasars and active galactic nuclei, we present the magnetic flare model which clarifies the connection between the primary energy source and the non-thermal phenomena. The behavior of the magnetic field generated in the accretion disk around a massive black hole is investigated in terms of the αω-dynamo and the magnetic buoyancy. The magnetic field is responsible not only for the angular momentum transfer but also for the vertical energy transfer owing to the magnetic buoyancy. Magnetic energy thus transferred should be released in the coronal region above the disk surface through its flare-like reconnection as in the solar flare. We expect that it will produce a variety of non-thermal activities characteristic to quasars and active galactic nuclei. We argue that the following scenario is compatible with various observations: A flare generates the relativistic shock behind which electrons are heated up to the relativistic energy. Subsequently, they produce X and γ rays by the inverse Compton scattering of low energy photons as well as emit from radio up to soft X photons by the synchrotron radiation. (author)

  3. Investigation of magnetic active core sizes and hydrodynamic diameters of a magnetically fractionated ferrofluid

    In this work we address the question which relates between the size of the magnetically active core of magnetic nanoparticles (MNPs) and the size of the overall particle in the solution (the so-called hydrodynamic diameter dhyd) exists. For this purpose we use two methods of examination that can deliver conclusions about the properties of MNP which are not accessible with normal microscopy. On the one hand, we use temperature dependent magnetorelaxation (TMRX) method, which enables direct access to the energy barrier distribution and by using additional hysteresis loop measurements can provide details about the size of the magnetically active cores. On the other hand, to determine the size of the overall particle in the solution, we use the magnetooptical relaxation of ferrofluids (MORFF) method, where the stimulation is done magnetically while the reading of the relaxation signal, however, is done optically. As a basis for the examinations in this work we use a ferrofluid that was developed for medicinal purposes and which has been fractioned magnetically to obtain differently sized fractions of MNPs. The two values obtained through these methods for each fraction shows the success in fractioning the original solution. Therefore, one can conclude a direct correlation between the size of the magnetically active core and the size of the complete particle in the solution from the experimental results. To calculate the size of the magnetically active core we found a temperature dependent anisotropy constant which was taken into account for the calculations. Furthermore, we found relaxation signals at 18 K for all fractions in these TMRX measurements, which have their origin in other magnetic effects than the Néel relaxation.

  4. Model-based Process Monitoring and Control of Micro-milling using Active Magnetic Bearings

    Blom, R.S.

    2011-01-01

    The process of micro-milling is a promising technology for the fabrication of micro-parts with arbitrary 3D features in a wide range of materials. However, as a result of the reduced dimensions, the susceptibility of the process for machine tool errors and vibrations is higher, having adverse effects on accuracy and surface quality of the resulting workpieces. Furthermore, the production time and the efficiency of the process suffer from low material removal rates and excessive tool wear and ...

  5. Model-based Process Monitoring and Control of Micro-milling using Active Magnetic Bearings

    Blom, R.S.

    2011-01-01

    The process of micro-milling is a promising technology for the fabrication of micro-parts with arbitrary 3D features in a wide range of materials. However, as a result of the reduced dimensions, the susceptibility of the process for machine tool errors and vibrations is higher, having adverse effect

  6. Microwave assisted synthesis of novel 4h-chromene derivatives bearing phenoxypyrazole and their antimicrobial activity assess

    Sangani Chetan B.

    2012-01-01

    Full Text Available A new series of 4H-chromene derivatives 4(a-p bearing 5-phenoxypyrazole nucleus has been synthesized under microwave irradiation by reaction of 5-phenoxypyrazole-4-carbaldehyde 1(a-h, malononitrile 2 and compounds (Cyclohexanedione, Dimedon 3(a-b in presence of NaOH as basic catalyst. All the compounds were screened against three Gram positive bacteria (Streptococcus pneumoniae, Clostridium tetani, Bacillus subtilis, three Gram negative bacteria (Salmonella typhi, Vibrio cholerae, Escherichia coli and two fungi (Aspergillus fumigatus, Candida albicans using broth microdilution MIC (Minimum Inhibitory Concentration method. Upon study of antimicrobial screening, it has been observed that, majority of the compounds were found to be active against Clostridium tetani and Bacillus subtilis as well as against Candida albicans as compared to standard drugs.

  7. Influence of eddy effect to the parameter design and optimized design for magnetic bearing%涡流效应对磁轴承参数设计的影响及优化设计

    张维煜; 朱熀秋

    2012-01-01

    The movement state is significantly different from that of resting and suspended state for the solid rotor under the condition of rotating, due to the large additional magnetic field produced by eddy currents in the rotor. Therefore, the accuracy of parameter design for magnetic bearing based on quiescent point is not high, and the eddy current effect on the parameters of the design must be considered. In this paper, the changes of the key parameters in the parameter design affected by the eddy current effect were estimated, and the simulation results of magnetic flux densities were compared with those obtained from experimental measurements. An agreement was found between the finite element model (FEM) results and experimental observations. On this basis, an optimization scheme was also proposed, and the optimization simulation results with finite element analysis software show that the design method is reasonable and design result is accurate. So this scheme makes the parameters design accurate and close to the actual operation. Therefore, analyzing the influence of eddy effect to the parameter design for a three-phase AC active magnetic bearing and providing accurate and very simple optimization scheme are important references for the parameters design of active magnetic bearing with solid rotor.%实心结构的转子旋转时,产生的附加磁场(涡流场)会使转子的运动状态显著不同于静止悬浮,可见依赖于静态工作点的磁轴承参数设计精确性不高,因此需要考虑涡流效应对参数设计的影响.利用有限元仿真软件估算了磁轴承设计中的关键参数受涡流效应影响的变化情况,并通过对比气隙磁通密度的实测值与有限元仿真值,验证了所建立有限元模型的正确性.在此基础上还提出了一种优化方案,并通过优化实例的仿真结果验证了该设计方法的合理性和设计结果的正确性.因此,分析涡流效应对交流主动磁轴承参数设计的影

  8. Measurements of flux pumping activation of trapped field magnets

    Weinstein, Roy; Parks, Drew; Sawh, Ravi-Persad [Texas Center for Superconductivity, 202 Houston Science Center, University of Houston, Houston, TX 77204-5002 (United States); Davey, Kent [Physics Department, 617 Science and Research Building I, University of Houston, Houston, TX 77204-5005 (United States)

    2010-11-15

    Large grains of high temperature superconducting (HTS) material can be utilized as trapped field magnets (TFMs). Persistent currents are set up in the HTS when it is cooled in a magnetic field, or exposed to a magnetic field after cooling. TFMs have been improved over the past two decades by the efforts of a large number of worldwide research groups. However, applications using TFMs have lagged, in part due to the problem of high fields needed for activation. We describe herein experiments designed to observe the behaviour of TFM activation using repeated applications of low fields (called 'pumping'). Significant partial activation is obtained using a non-uniform pumping field (e.g., a small permanent magnet) which is higher in the centre of the HTS than at the periphery. Cooling in zero field followed by pumping with such a field results in trapping the full applied field, in comparison to half of the applied field being trapped by cooling in zero field followed by application of a uniform field. We find that for partial activation by cooling in a field and subsequent activation by pumping, the resulting fields are additive. We also conclude that for activation by fluxoid pumping, creep assists the process.

  9. Functional magnetic resonance imaging of higher brain activity

    Functional magnetic resonance images (fMRIs) exhibit small differences in the magnetic resonance signal intensity in positions corresponding to focal areas of brain activation. These signal are caused by variation in the oxygenation state of the venous vasculature. Using this non-invasive and dynamic method, it is possible to localize functional brain activation, in vivo, in normal individuals, with an accuracy of millimeters and a temporal resolution of seconds. Though a series of technical difficulties remain, fMRI is increasingly becoming a key method for visualizing the working brain, and uncovering the topographical organization of the human brain, and understanding the relationship between brain and the mind

  10. 基于磁路分析的轴向混合磁轴承径向承载力解析计算%Calculation of Radial Electromagnetic Force of Axial Hybrid Magnetic Bearing Based on Magnetic Circuit Analysis

    张云鹏; 刘淑琴; 李红伟; 范友鹏

    2012-01-01

    研究轴向混合磁轴承实现五自由度悬浮时,需要计算径向承载力与磁轴承结构参数以及永磁体参数之间的关系。为了解决轴向混合磁轴承缺乏径向承载力解析数学模型的问题,该文在分析轴向混合磁轴承磁路以及各部分磁导的基础上,结合稀土永磁体的工作特性,用虚位移法得出了轴向混合磁轴承的径向承载力解析数学模型。模型表明,在小径向位移时,该型的混合磁轴承径向承载力随着径向位移增加而增加,近似线性关系,径向承载力和刚度随轴向气隙增大而减小;磁轴承径向承载力随永磁体的有效长度增加呈现先增大后趋近饱和。利用有限元方法对径向承载力进行仿真计算,仿真结果与模型计算结果基本吻合。%In studying axial hybrid magnetic bearing (HMB) for suspension in five degree of freedom (DOF), the relationship between radial electromagnetic force and magnetic bearing structural parameters and permanent magnet parameters should be calculated. In order to overcome the lack of analytical calculation model for radial electromagnet force of axial HMB, based on magnetic circuit analysis and calculation of magnetic conductance for each parts, the analytical calculation model for radial electromagnet force of axial HMB is proposed in this paper. The analytical formulation of radial electromagnetic force is derived by using virtual displacement method and demagnetization characteristics of the rare earth permanent magnet. It is found that the radial electromagnetic force increases with the radial displacement increasing approximately in linear relationship, and the radial force and stiffness decreases with the axial gap increasing. The radial electromagnetic force increased and then saturated with increasing permanent magnet effective length. The model of axial HMB is simulated by finite-element method software and the simulation results are basically in

  11. Boswellic acids synergize antitumor activity and protect against the cardiotoxicity of doxorubicin in mice bearing Ehrlich's carcinoma.

    Ali, Shimaa A; Zaitone, Sawsan A; Moustafa, Yasser M

    2015-08-01

    This study aimed to test whether boswellic acids add to the antitumor effects of doxorubicin against solid tumors of Ehrlich's ascites carcinoma (EAC) grown in mice, and to investigate the protective effects of boswellic acids against doxorubicin-induced cardiotoxicity. Sixty-four female Swiss albino mice bearing EAC solid tumors were distributed among 8 groups as follows: group 1, EAC control group; group 2, doxorubicin treatment group [mice were injected with doxorubicin (6 mg·(kg body mass)(-1)·week(-1)) for 3 weeks]; groups 3-5, these mice were treated with boswellic acids (125, 250, or 500 mg·kg(-1)·day(-1)), respectively; groups 6-8, these mice were treated with a combination of doxorubicin and boswellic acids (125, 250, or 500 mg·kg(-1)·day(-1)), respectively, for 3 weeks. The results indicated that boswellic acids synergized the antitumor activity of doxorubicin. Doxorubicin-treated mice showed elevated serum activities of lactate dehydrogenase and creatine kinase isoenzyme MB as well as cardiac malondialdehyde. Further, decreases in cardiac levels of reduced glutathione, superoxide dismutase, and catalase activities were observed. These effects were accompanied by an increase in cardiac expression of caspase 3. Thus, treatment with boswellic acids attenuated doxorubicin-evoked disturbances in the above-mentioned parameters, highlighting antioxidant and antiapoptotic activities. Therefore, boswellic acids could be potential candidates for ameliorating the cardiotoxicity of doxorubicin. PMID:26230640

  12. Simulation of magnetic active polymers for versatile microfluidic devices

    Gusenbauer, Markus; Fischbacher, Johann; Reichel, Franz; Exl, Lukas; Bance, Simon; Kataeva, Nadezhda; Binder, Claudia; Brückl, Hubert; Schrefl, Thomas

    2013-01-01

    We propose to use a compound of magnetic nanoparticles (20-100 nm) embedded in a flexible polymer (Polydimethylsiloxane PDMS) to filter circulating tumor cells (CTCs). The analysis of CTCs is an emerging tool for cancer biology research and clinical cancer management including the detection, diagnosis and monitoring of cancer. The combination of experiments and simulations lead to a versatile microfluidic lab-on-chip device. Simulations are essential to understand the influence of the embedded nanoparticles in the elastic PDMS when applying a magnetic gradient field. It combines finite element calculations of the polymer, magnetic simulations of the embedded nanoparticles and the fluid dynamic calculations of blood plasma and blood cells. With the use of magnetic active polymers a wide range of tunable microfluidic structures can be created. The method can help to increase the yield of needed isolated CTCs.

  13. Development of an active magnetic regenerator for space applications

    Chen, Weibo

    2014-07-01

    This paper discusses the design of a micromachined regenerator in an Active Magnetic Regenerative Refrigeration (AMRR) system for space applications. The AMRR system is designed to provide continuous remote/distributed cooling at about 2 K and reject heat at temperatures of about 15 K. This paper first discusses the general thermal and fluid performance requirements for an AMRR regenerator, a unique structured bed configuration that enables the regenerator to meet these requirements, and its thermal and fluid performance based on numerical analyses. The paper then discusses the general design consideration for the magnetic field driving the regenerator for optimal thermal performance, and the analysis processes to optimize the variation rate of the magnetic field in an actual superconducting magnet during the isothermal processes of the AMRR cycle to enhance the performance of an actual regenerator. The paper finally presents the thermal performance of the regenerator from such iterative design optimization processes.

  14. Superconductor bearings, flywheels and transportation

    Werfel, F. N.; Floegel-Delor, U.; Rothfeld, R.; Riedel, T.; Goebel, B.; Wippich, D.; Schirrmeister, P.

    2012-01-01

    This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS-FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

  15. Superconductor bearings, flywheels and transportation

    This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

  16. Paclitaxel-induced macrophage activities in the tumor-bearing host: immunologic implications and therapeutic applications

    Mullins, David Warren

    1998-01-01

    Tumors induce immune dysfunction through the production of soluble factors that subvert macrophage (Mf) function to favor tumor growth. Previous studies suggested that tumor-induced immune cell dysfunction may be reversible through regimens that disrupt tumor cell suppressor mechanisms and concurrently promote tumoricidal activities. Because the antineoplastic agent paclitaxel (TAXOL) activates Mf function, we studied mechanisms of paclitaxel-mediated cytotoxic and immunostimulatory respons...

  17. The effects of habitat and human activity on daybed selection in brown bears

    Huusko, Jari

    2012-01-01

    The non-lethal effects of predation, i.e. predation risk, can significantly affect the prey population by inducing changes in behavior to reduce the risk of predation. Vigilance, hiding, and fleeing are common responses in order to lower predation risk while changes in habitat selection, habitat use, and changes in activity patterns are more severe changes and can profoundly affect prey fitness. Prey may begin to avoid habitats frequented by predators and may begin to reduce their activity du...

  18. The influence of the magnetic field on the performance of an active magnetic regenerator (AMR)

    Bjørk, R

    2014-01-01

    The influence of the time variation of the magnetic field, termed the magnetic field profile, on the performance of a magnetocaloric refrigeration device using the active magnetic regeneration (AMR) cycle is studied for a number of process parameters for both a parallel plate and packed bed regenerator using a numerical model. The cooling curve of the AMR is shown to be almost linear far from the Curie temperature of the magnetocaloric material. It is shown that a magnetic field profile that is 10% of the cycle time out of sync with the flow profile leads to a drop in both the maximum temperature span and the maximum cooling capacity of 20-40\\% for both parallel plate and packed bed regenerators. The maximum cooling capacity is shown to depend very weakly on the ramp rate of the magnetic field. Reducing the temporal width of the high field portion of the magnetic field profile by 10% leads to a drop in maximum temperature span and maximum cooling capacity of 5-20%. An increase of the magnetic field from 1 T t...

  19. Antitumor activity and systemic effects of PVM/MA-shelled selol nanocapsules in lung adenocarcinoma-bearing mice

    de Souza, Ludmilla Regina; Alexandre Muehlmann, Luis; Carneiro Matos, Lívia; Simón-Vázquez, Rosana; Guerreiro Marques Lacava, Zulmira; Maurício Batista De-Paula, Alfredo; Mosiniewicz-Szablewska, Ewa; Suchocki, Piotr; César Morais, Paulo; González-Fernández, África; Nair Báo, Sônia; Bentes Azevedo, Ricardo

    2015-12-01

    Selol is a semi-synthetic compound containing selenite that is effective against cancerous cells and safer for clinical applications in comparison with other inorganic forms of selenite. Recently, we have developed a formulation of poly(methyl vinyl ether-co-maleic anhydride)-shelled selol nanocapsules (SPN), which reduced the proliferative activity of lung adenocarcinoma cells and presented little deleterious effects on normal cells in in vitro studies. In this study, we report on the antitumor activity and systemic effects induced by this formulation in chemically induced lung adenocarcinoma-bearing mice. The in vivo antitumor activity of the SPN was verified by macroscopic quantification, immunohistochemistry and morphological analyses. Toxicity analyses were performed by evaluations of the kidney, liver, and spleen; analyses of hemogram and plasma levels of alanine aminotransferase, aspartate transaminase, urea, and creatinine; and DNA fragmentation and cell cycle activity of the bone marrow cells. Furthermore, we investigated the potential of the SPN formulation to cause hemolysis, activate the complement system, provoke an inflammatory response and change the conformation of the plasma proteins. Our results showed that the SPN reduced the area of the surface tumor nodules but not the total number of tumor nodules. The biochemical and hematological findings were suggestive of the low systemic toxicity of the SPN formulation. The surface properties of the selol nanocapsules point to characteristics that are consistent with the treatment of the tumors in vivo: low hemolytic activity, weak inflammatory reaction with no activation of the complement system, and mild or absent conformational changes of the plasma proteins. In conclusion, this report suggests that the SPN formulation investigated herein exhibits anti-tumoral effects against lung adenocarcinoma in vivo and is associated with low systemic toxicity and high biocompatibility.

  20. The anisotropy of magnetic susceptibility of uniaxial superparamagnetic particles: Consequences for its interpretation in magnetite and maghemite bearing rocks

    Lanci, Luca; Zanella, Elena

    2016-01-01

    A simple model that provides a quantitative description of the magnetic susceptibility of superparamagnetic to stable single-domain uniaxial magnetic particles can be built in the framework of the theory of stochastic resonance. This model expands that of Mullins and Tile (1973) for superparamagnetic grains by considering the dependence of superparamagnetic susceptibility on the particle orientation and thus describes the anisotropy of magnetic susceptibility (AMS) of ensembles of superparamagnetic as well as single-domain particles. The theory predicts that on the contrary of stable single domain, the maximum anisotropy of superparamagnetic particles is parallel to their easy axis and shows that the AMS of ensembles of uniaxial particle is strongly dependent on the distribution of particle grain size, coercivity, measurement temperature, and frequency. It also explains why the inverse AMS pattern expected for stable single-domain particles is rarely observed in natural samples. We use examples of well-characterized obsidian specimens to show that, as predicted by the theory, in the presence of significant superparamagnetic contributions, the maximum susceptibility axis of AMS is directed along the preferential direction of particles easy axis.

  1. Measuring starspots on magnetically active stars with the VLTI

    Wittkowski, M; Hubrig, S; Posselt, B; Von der Lühe, O

    2002-01-01

    We present feasibility studies to directly image stellar surface features, which are caused by magnetic activity, with the Very Large Telescope Interferometer (VLTI). We concentrate on late type magnetically active stars, for which the distribution of starspots on the surface has been inferred from photometric and spectroscopic imaging analysis. The study of the surface spot evolution during consecutive rotation cycles will allow first direct measurements (apart from the Sun) of differential rotation which is the central ingredient of magnetic dynamo processes. The VLTI will provide baselines of up to 200 m, and two scientific instruments for interferometric studies at near- and mid-infrared wavelengths. Imaging capabilities will be made possible by closure-phase techniques. We conclude that a realistically modeled cool surface spot can be detected on stars with angular diameters exceeding ~2 mas using the VLTI with the first generation instrument AMBER. The spot parameters can then be derived with reasonable...

  2. Stellar Magnetic Dynamos and Activity Cycles

    Wright, Nicholas J

    2013-01-01

    Using a new uniform sample of 824 solar and late-type stars with measured X-ray luminosities and rotation periods we have studied the relationship between rotation and stellar activity that is believed to be a probe of the underlying stellar dynamo. Using an unbiased subset of the sample we calculate the power law slope of the unsaturated regime of the activity -- rotation relationship as $L_X/L_{bol}\\propto Ro^\\beta$, where $\\beta=-2.70\\pm0.13$. This is inconsistent with the canonical $\\beta = -2$ slope to a confidence of 5$\\sigma$ and argues for an interface-type dynamo. We map out three regimes of coronal emission as a function of stellar mass and age, using the empirical saturation threshold and theoretical super-saturation thresholds. We find that the empirical saturation timescale is well correlated with the time at which stars transition from the rapidly rotating convective sequence to the slowly rotating interface sequence in stellar spin-down models. This may be hinting at fundamental changes in the ...

  3. Next generation of HTS magnetic application: HTS bulk and coil interaction

    The next generation of HTS magnetic bearings (SMB) will operate at magnetic field excitation higher than permanent magnets (> 1.0 T). The new bearing type is capable to support heavy -load rotors of more than one ton mass. Using FEM we calculate the interaction of HTS bulk and 2G coil to achieve higher magnetic flux excitation and flux gradients of HTS bearings at temperatures of 50 – 60 K. The new total HTS bearing type multiplies the present 10 -15 N/cm2 force density obtained with PM's by a factor of 5 and passes the force properties of active magnetic bearings (AMB). HTS coil excitation is capable to increases the levitation forces to more than the present 10 kN level and reduces relative cooling and material effort per load. We design a magnetic bearing for HTS bulk -coil excitation.

  4. Enhanced anti-tumor activity and reduced toxicity by combination andrographolide and bleomycin in ascitic tumor-bearing mice.

    Guo, Huizhen; Zhang, Zhenbiao; Su, Zuqing; Sun, Chaoyue; Zhang, Xie; Zhao, Xiaoning; Lai, Xiaoping; Su, Ziren; Li, Yucui; Zhan, Janis Yaxian

    2016-04-01

    Bleomycin (BLM) is an effective anti-carcinogen. With the main detrimental effects of inducing pulmonary fibrosis on patients, its clinical use is limited. Developing agents that enhance the efficacy and attenuate the side effects of cancer chemotherapy are critical. Andrographolide (Andro), an active diterpenoid labdane component extracted from Andrographis panicula, is generally prescribed for treatment of inflammatory associated diseases. The study showed that BLM combined with Andro was significantly more effective than BLM alone on inhibiting the tumor growth, arresting the cell cycle at G0/G1 phase, promoting the capase-3 and capase-8 activity to induce cancer cell apoptosis. The underlying mechanisms may be related to the transcriptional regulation of P53/P21/Cyclin pathways. Moreover, BLM induced pulmonary fibrosis in tumor-bearing mice, but BLM combined with Andro dramatically alleviated the lesion in pulmonary fibrosis by activating the SOD, suppressing MDA and HYP production, in the meanwhile attenuating the IL-1β, TNF- α, IL-6 and TGF-β1 level. These mechanisms were associated with its effect on inhibition of protein expression of TGF-β, α-SMA, p-Smad2/3, enhanced expression of Smad7. Thus, it demonstrated that Andro might be a potential adjuvant therapeutic agent for BLM. PMID:26874212

  5. New aminoporphyrins bearing urea derivative substituents: synthesis, characterization, antibacterial and antifungal activity

    Gholamreza Karimipour

    2015-06-01

    Full Text Available This work studied the synthesis of 5,10,15-tris(4-aminophenyl-20-(N,N-dialkyl/diaryl-N-phenylurea porphyrins (P1-P4 with alkyl or aryl groups of Ph, iPr, Et and Me, respectively and also the preparation of their manganese (III and cobalt (II complexes (MnP and CoP. The P1-P4 ligands were characterized by different spectroscopic techniques (1H NMR, FTIR, UV-Vis and elemental analysis, and metalated with Mn and Co acetate salts. The antibacterial and antifungal activities of these compounds in vitro were investigated by agar-disc diffusion method against Escherichia coli (-, Pseudomonas aeruginosa (-, Staphylococcus aureus(+, Bacillus subtilis (+ and Aspergillus oryzae and Candida albicans. Results showed that antibacterial and antifungal activity of the test samples increased with increase of their concentrations and the highest activity was obtained when the concentration of porphyrin compounds was 100 µg/mL. The activity for the porphyrin ligands depended on the nature of the urea derivative substituents and increased in the order P1 > P2 > P3 >P4, which was consistent with the order of their liposolubility. MnP and CoP complexes exhibited much higher antibacterial and antifungal activity than P1-P4ligands. Further, the growth inhibitory effects of these compounds was generally in the order CoP complexes > MnP complexes > P1-P4 ligands. Among these porphyrin compounds, CoP1displayed the highest antibacterial and antifungal activity, especially with a concentration of 100 µg/mL, against all the four tested bacteria and two fungi, and therefore it could be potential to be used as drug.

  6. Barbiturate bearing aroylhydrazine derivatives: Synthesis, NMR investigations, single crystal X-ray studies and biological activity

    Giziroglu, Emrah; Sarikurkcu, Cengiz; Aygün, Muhittin; Basbulbul, Gamze; Soyleyici, H. Can; Firinci, Erkan; Kirkan, Bulent; Alkis, Ayse; Saylica, Tayfur; Biyik, Halil

    2016-03-01

    A series of barbituric acid aroylhydrazine derivatives have been prepared from their corresponding 1,3-dimethyl-5-acetyl barbituric acid and aroylhydrazines. All compounds have been fully characterized by using FT-IR, multinuclear NMR (1H, 13C) and Mass (MS) spectrometry. We also describe the X-ray crystal structure of 3a, which crystallizes in the monoclinic P21/n space group. The crystal structure is stabilized with infinite linear chains of dimeric units. Furthermore, all compounds were investigated for their tyrosinase inhibition, antioxidative and antimicrobial activies. The results from biological activity assays have shown that all of compounds have excellent antioxidant, significant tyrosinase inhibition and moderate antimicrobial activity.

  7. Tensile and impact behaviour of BATMAN II steels, Ti-bearing reduced activation martensitic alloys

    Filacchioni, G.; Casagrande, E.; De Angelis, U.; De Santis, G.; Ferrara, D.; Pilloni, L.

    Two series of Reduced Activation Ferrous alloys (RAF) have been produced and studied by Casaccia's Laboratories. These martensitic alloys are named BATMAN steels. They are among the few presently developed RAF materials to exploit Ti as a carbide forming and grain size stabilizing element instead of Ta. In this work their mechanical properties are illustrated.

  8. Experimental results for a novel rotary active magnetic regenerator

    Engelbrecht, Kurt; Eriksen, Dan; Bahl, Christian; Bjørk, Rasmus; Geyti, Jørgen; Lozano, Jaime; Nielsen, Kaspar Kirstein; Saxild, Finn B.; Smith, Anders; Pryds, Nini

    2012-01-01

    Active magnetic regenerator (AMR) refrigerators represent an alternative to vapor compression technology and have great potential in realizing cooling devices with high efficiency, which are highly desirable for a broad range of applications. The technology relies on the magnetocaloric effect in a...

  9. Magnetic helicity and energy spectra of a solar active region

    Zhang, Hongqi; Sokoloff, D D

    2013-01-01

    We compute magnetic helicity and energy spectra of the solar active region NOAA 11158 during 11-15 February 2011 at 20 degr southern heliographic latitude using observational photospheric vector magnetograms. We adopt the isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field. The sign of magnetic helicity turns out to be predominantly positive at all wavenumbers. This sign is consistent with what is theoretically expected for the southern hemisphere. The relative magnetic helicity is around 8% and strongest at intermediate wavenumbers of k ~ 0.4 Mm^{-1}, corresponding to a scale of 2 pi/k ~ 16 Mm. The same sign and a somewhat smaller value is also found for the relative current helicity evaluated in real space based on the vertical components of magnetic field and current density. The current helicity spectrum is estimated from the magnetic helicity spectrum and its modulus shows a k^{-5/3} spectrum at large wavenumbers. A similar power law is also obtained for...

  10. Dynamics of an active magnetic particle in a rotating magnetic field.

    Cēbers, A; Ozols, M

    2006-02-01

    The motion of an active (self-propelling) particle with a permanent magnetic moment under the action of a rotating magnetic field is considered. We show that below a critical frequency of the external field the trajectory of a particle is a circle. For frequencies slightly above the critical point the particle moves on an approximately circular trajectory and from time to time jumps to another region of space. Symmetry of the particle trajectory depends on the commensurability of the field period and the period of the orientational motion of the particle. We also show how our results can be used to study the properties of naturally occurring active magnetic particles, so-called magnetotactic bacteria. PMID:16605340

  11. Blood Pump Bearing System

    Aber, Gregory S. (Inventor)

    2000-01-01

    An apparatus is provided for a blood pump bearing system within a pump housing to support long-term highspeed rotation of a rotor with an impeller blade having a plurality of individual magnets disposed thereon to provide a small radial air gap between the magnets and a stator of less than 0.025 inches. The bearing system may be mounted within a flow straightener, diffuser, or other pump element to support the shaft of a pump rotor. The bearing system includes a zirconia shaft having a radiused end. The radiused end has a first radius selected to be about three times greater than the radius of the zirconia shaft. The radiused end of the zirconia shaft engages a flat sapphire endstone. Due to the relative hardness of these materials a flat is quickly produced during break-in on the zirconia radiused end of precisely the size necessary to support thrust loads whereupon wear substantially ceases. Due to the selection of the first radius, the change in shaft end-play during pump break-in is limited to a total desired end-play of less than about 0.010 inches. Radial loads are supported by an olive hole ring jewel that makes near line contact around the circumference of the Ir shaft to support big speed rotation with little friction. The width of olive hole ring jewel is small to allow heat to conduct through to thereby prevent heat build-up in the bearing. A void defined by the bearing elements may fill with blood that then coagulates within the void. The coagulated blood is then conformed to the shape of the bearing surfaces.

  12. Edge Adapted Wavelets, Solar Magnetic Activity, and Climate Change

    Johnson, Robert W

    2009-01-01

    The continuous wavelet transform is adapted to account for signal truncation through renormalization and by modifying the shape of the analyzing window. Comparison is made of the instant and integrated wavelet power with previous algorithms. The edge adapted and renormalized admissible wavelet transforms are used to estimate the level of solar magnetic activity from the sunspot record. The solar activity is compared to Oerlemans' temperature reconstruction and to the Central England Temperatu...

  13. Vibration Reduction System Using Magnetic Suspension Technology

    Spychała Jarosław

    2015-01-01

    Full Text Available The article presents considerations concerning the construction of vibration reduction system using magnetic suspension technology. Presents the results of simulation, numerical and experimental the bearingless electric motor, for which successfully used this type of solution. Positive results of research and testing have become the basis for the development of the concept of building this type of active vibration reduction system , at the same time acting as a support for a technical object, which is a jet engine. Bearing failures are manifested by loss or distortion of their mass, which leads to a total destruction of the roller bearing, and thus reflected in the security. The article presents the concept of building active magnetic suspension to eliminate the bearing system of classical rolling bearing and replace it with magnetic bearing.

  14. Why the White Bear is Still There: Electrophysiological Evidence for Ironic Semantic Activation during Thought Suppression

    Giuliano, Ryan J.; Wicha, Nicole Y. Y.

    2010-01-01

    Much research has focused on the paradoxical effects of thought suppression, leading to the viewpoint that increases in unwanted thoughts are due to an ironic monitoring process which increases the activation of the very thoughts one is trying to rid from consciousness. However, it remains unclear from behavioral findings whether suppressed thoughts become more accessible during the act of suppression. In the current study, event-related potentials were recorded while participants suppressed ...

  15. FY-97 operations of the pilot-scale glass melter to vitrify simulated ICPP high activity sodium-bearing waste

    A 3.5 liter refractory-lined joule-heated glass melter was built to test the applicability of electric melting to vitrify simulated high activity waste (HAW). The HAW streams result from dissolution and separation of Idaho Chemical Processing Plant (ICPP) calcines and/or radioactive liquid waste. Pilot scale melter operations will establish selection criteria needed to evaluate the application of joule heating to immobilize ICPP high activity waste streams. The melter was fabricated with K-3 refractory walls and Inconel 690 electrodes. It is designed to be continuously operated at 1,150 C with a maximum glass output rate of 10 lbs/hr. The first set of tests were completed using surrogate HAW-sodium bearing waste (SBW). The melter operated for 57 hours and was shut down due to excessive melt temperatures resulting in low glass viscosity (< 30 Poise). Due to the high melt temperature and low viscosity the molten glass breached the melt chamber. The melter has been dismantled and examined to identify required process improvement areas and successes of the first melter run. The melter has been redesigned and is currently being fabricated for the second run, which is scheduled to begin in December 1997

  16. Preclinical evaluation of somatostatin analogs bearing two macrocyclic chelators for high specific activity labeling with radiometals

    Radiometallated analogues of the regulatory peptide somatostatin are of interest in the in vivo localization and targeted radiotherapy of somatostatin receptor-overexpressing tumors. An important aspect of their use in vivo is a fast and efficient labeling (complexation) protocol for radiometals along with a high specific activity. We describe in this manuscript synthetic methods for the coupling of two chelators (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid = DOTA) to the bioactive peptide [Tyr3,Thr8]-octreotide (TATE) in order to increase the specific activity (radioactivity in Bq per mole peptide). The full chelator-linker-peptide conjugate was assembled on solid support using standard Fmoc chemistry. Two DOTA-chelators were linked to the peptide using lysine or N,N'-bis(3-aminopropyl)-glycine (Apg); in addition, pentasarcosine (Sar5) was used as a spacer between the chelators and the peptide to probe its influence on biology and pharmacology. Complexation rates with In3+ and Y3+ salts and the corresponding radiometals were high, the bis-DOTA-derivatives showed higher complexation rates and gave higher specific activity than DOTA-TATE. Pharmacological and biological data of the complexed molecules did not show significant differences if compared to the parent peptide [111/natIn-DOTA]-TATE except for [(111/natIn-DOTA)2-Apg]-TATE which showed a lower binding affinity and rate of internalization into tumor cells. The biodistribution of [(111/natIn-DOTA)-Lys(111/natIn-DOTA)]-TATE in the rat tumor model (AR4-2J) showed a high and specific (as shown by a blocking experiment) tracer uptake in somatostatin receptor-positive tissue but a lower tumor uptake compared to [111/natIn-DOTA]-TATE. (orig.)

  17. Solar Magnetism and the Activity Telescope at HSOS

    Hong-Qi Zhang; Ya-Nan Wang; Qi-Qian Hu; Jun-Sun Xue; Hai-Tian Lu; Hou-Kun Ni; Han-Liang Chen; Xiao-Jun Zhou; Qing-Sheng Zhu; Lü-Jun Yuan; Yong Zhu; Dong-Guang Wang; Yuan-Yong Deng; Ke-Liang Hu; Jiang-Tao Su; Jia-Ben Lin; Gang-Hua Lin; Shi-Mo Yang; Wei-Jun Mao

    2007-01-01

    A new solar telescope system is described, which has been operating at Huairou Solar Observing Station (HSOS), National Astronomical Observatories, Chinese Academy of Sciences (CAS), since the end of 2005. This instrument, the Solar Magnetism and Activity Telescope (SMAT), comprises two telescopes which respectively make measurements of full solar disk vector magnetic field and Hα observation. The core of the full solar disk video vector magnetograph is a birefringent filter with 0.1(A) bandpass, installed in the tele-centric optical system of the telescope. We present some preliminary observational results of the full solar disk vector magnetograms and Hα filtergrams obtained with this telescope system.

  18. Development and active demonstration of acid digestion of burnable plutonium bearing solid wastes

    The investigations were focused on the active demonstration of the process in a technical scale plant by treatment of 790 kg of waste which contained about 7 kg of plutonium. Complete oxidation of the waste material is achieved within 15 min in sulfuric acid (kept under oxidizing condition by nitric acid) at 250 deg C. At 250 deg C with permanent stirring a rate of plutonium oxide to plutonium sulfate conversion of up to 99.9% is obtained within 8 hours. The waste oxidation product, besides offgas, is a residue of 320 g per kg waste digested. Precipitation of plutonium is achieved with an efficiency of 88% using cetylpyridinium nitrate. Active process demonstration was performed in a plant of 10 kg capacity per daily run from March 1983 until June 1985. The average waste throughput achieved was 4.1 kg waste per run (maximum 10.4 kg). The plutonium decontamination factors were 1010 for the cleaned offgas and 106 for the liquid secondary waste. Tantalum as a potential construction material for the digester does not exhibit specific corrosion; its surface corrosion is 0.1 mm per annum at the maximum

  19. Numerical analysis of a reciprocating active magnetic regenerator

    A time-dependent, two-dimensional mathematical model of a configuration system for magnetic refrigeration has been developed, based on a reciprocating active magnetic regenerator operating at room temperature. The model's geometry is made of parallel plates of magnetocaloric material separated by microchannels. Through the microchannels, the flow of a heat transfer fluid has also been simulated. Water has been used as heat transfer fluid and as magnetocaloric material we have used the benchmark material gadolinium. The heat transfer inside the regenerator and the fluid flow are modelled separately and the magnetocaloric effect is taken into account by the inclusion of a variable source term in the energy equation. The model simulates the steps of the active magnetic regenerative refrigeration cycle and evaluates the performance in terms of cooling load, COP, temperature span and pressure drop for the parallel-plate configuration. The model has been validated by comparing the numerical results with the results obtained from an experimental device made by a partner. This parametric study allows us to identify the most important characteristics that have a significant influence on the thermal behaviour of the active magnetic regenerator. Several simulation results are discussed and some optimal solutions are presented. - Highlights: • We have developed a 2D model of an active magnetic regenerator. • The MCE is included as a source term with data from experimental measurements. • A validation of the model with experimental data is included. • We analysed the temperature span, the cooling power, the COP and the pressure drop of the system

  20. Synthesis, characterization and antiamoebic activity of chalcones bearing N-substituted ethanamine tail.

    Leeza Zaidi, Saadia; Mittal, Sonam; Rajala, Maitreyi S; Avecilla, Fernando; Husain, Mohammad; Azam, Amir

    2015-06-15

    A series of chalcones (4-21) possessing N-substituted ethanamine were synthesized by the aldol condensation reaction of 1-(4-(2-substituted ethoxy)phenyl)ethanones with different aldehydes preceded by the reaction of 2-chloro N-substituted ethanamine hydrochloride and 4-hydroxy acetophenone. The structure of all the synthesized compounds was elucidated by various spectral and X-ray diffraction studies. The compounds were screened against HM1: IMSS strain of Entamoeba histolytica and cytotoxicity was performed on A549 (non-small cell lung cancer cell line) cells by MTT assay. Out of eighteen compounds twelve showed better activity then the standard drug metronidazole. The compound 9, 14 and 19 showed good cell viability, hence were least toxic. PMID:26021707

  1. Chromospheric magnetic fields of an active region filament

    Xu, Z.; Solanki, S.; Lagg, A.

    2012-06-01

    Vector magnetic fields of an active region filament are co-spatially and co-temporally mapped in photosphere and upper chromosphere, by using spectro-polarimetric observations made by Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). A Zeeman-based ME inversion is performed on the full Stokes vectors of both the photospheric Si I 1082.7 nm and the chromospheric He I 1083.0 nm lines. We found that the strong magnetic fields, with the field strength of 600 - 800 G in the He I line formation height, are not uncommon among AR filaments. But such strong magnetic field is not always found in AR filaments.

  2. Numerical Modeling of Multi-Material Active Magnetic Regeneration

    Nielsen, Kaspar Kirstein; Engelbrecht, Kurt; Bahl, Christian Robert Haffenden;

    2009-01-01

    Magnetic refrigeration is a potentially environmentally-friendly alternative to vapour compression technology that is presented in this paper. The magnetocaloric effect in two magnetocaloric compounds in the La(Fe,Co,Si)13 series is presented in terms of their adiabatic temperature change and the...... specific heat as a function of temperature at constant magnetic field. A 2.5-dimensional numerical model of an active magnetic regenerative (AMR) refrigerator device is presented. The experimental AMR located at Risø DTU has been equipped with a parallel-plate based regenerator made of the two materials....... Experimental zero heat-load temperature spans are presented for different operating conditions and the results are compared to predictions of the numerical model. It is concluded that the model reproduces the experimental tendencies and when including thermal parasitic losses to ambient and the predictions...

  3. Magnetic field structures in active compact radio sources

    The analysis of simultaneous multifrequency linear polarimetry data between 1.4 GHz and 90 GHz for about 20 active, compact radio sources at six epochs from 1977 December 10 1980 July is presented. In addition, monthly 8 Ghz polarization data on the same sources were examined. The general polarization characteristics of these sources can be well described in terms of magnetic fields which are largely turbulent and slightly anisotropic. The magnetic field symmetry axes are generally aligned with the source structural axes on the milli-arcsecond scale (OJ 287 is a notable exception.) Monte Carlo calculations indicate that observed polarization variations and in particular rotator polarization events can be produced in this model as a consequence of random walks generated through evolution of the turbulent magnetic field. 43 references

  4. Inconsistent magnetic polarities in magnetite-and greigite-bearing sediments: Understanding complex magnetizations in the late Messinian in the Adana Basin (southern Turkey)

    Lucifora, S.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, IT-00146 Rome, Italy; Cifelli, F.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, IT-00146 Rome, Italy; Mattei, M.; Dipartimento di Scienze Geologiche, Universita` di Roma TRE, Rome; Sagnotti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cosentino, D.; Dipartimento di Scienze Geologiche, Universita` 'Roma Tre', Rome, Italy; Roberts, A. P.; Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia

    2012-01-01

    We present paleomagnetic, rock magnetic and scanning electron microscope data from three upper Messinian stratigraphic sections from the Adana Basin (southern Turkey). The collected samples are from fine-grained units, which were deposited during the Messinian Salinity Crisis (within subchron C3r). Paleomagnetic results reveal an inconsistent polarity record, related to a mixture of magnetite and greigite that hinders determination of a reliable magnetostratigraphy. Three classes of samples a...

  5. Factors affecting date of implantation, parturition, and den entry estimated from activity and body temperature in free-ranging brown bears.

    Andrea Friebe

    Full Text Available Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12, the mean date of parturition was 26 January (SD = 12, and the mean duration of the gestation period was 56 days (SD = 2. The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.

  6. The Magnetic Classification of Solar Active Regions 1992 - 2015

    Jaeggli, Sarah A.; Norton, Aimee A.

    2016-01-01

    The purpose of this letter is to address a blind-spot in our knowledge of solar active region statistics. To the best of our knowledge there are no published results showing the variation of the Mount Wilson magnetic classifications as a function of solar cycle based on modern observations. We show statistics for all active regions reported in the daily Solar Region Summary from 1992 January 1 to 2015 December 31. We find that the $\\alpha$ and $\\beta$ class active regions (including all sub-g...

  7. Synthesis and catalytic activity of metallo-organic complexes bearing 5-amino 2-ethylpyridine -2-carboximidate

    LUO MEI; XU JIA; ZHANG JING CHENG

    2016-06-01

    A series of copper, cobalt, nickel and manganese complexes were synthesized and characterized. Reaction of 5-amino-2-cyanopyridine with $ MCl_{2}$·x$H_{2}O$ (M: $Cu^{2+}$, $Co^{2+}$, $Ni^{2+}$, $Mn^{2+})$ in anhydrous ethanol resulted in the formation of four complexes $[NH_{2}EtPyCuCl_{2}(CH_{3}OH)].H_{2}O 1$, $[(NH_{2}EtPyHCl)_{3}Co]$$(Cl)_{3}.3H_{2}O 2$, $[(NH_{2}EtPy)_{2}$ 2$(H_{2}O)Ni]$ $(Cl_{2})$ 3, and $[(NH_{2}EtPy)_{2}$ 2$(H_{2}O)$ Mn]$(Cl_{2})$ 4 $[NH_{2} EtPy=5-amino-oethylpyridine-2-carboximidate], respectively. The structures of these compounds were determined by X-raydiffraction, NMR and IR spectroscopy, and elemental analysis. Each complex was then used as a catalyst in the Henry reaction, and its catalytic activity was determined by 1H NMR. Good catalytic effects were achieved (69–87%).

  8. FINE MAGNETIC FEATURES AND CHIRALITY IN SOLAR ACTIVE REGION NOAA 10930

    In this paper, we present fine magnetic features near the magnetic inversion line in the solar active region NOAA 10930. The high-resolution vector magnetograms obtained by Hinode allow detailed analyses around magnetic fibrils in the active region. The analyses are based on the fact that the electric current density can be divided into two components: the shear component caused by the magnetic inhomogeneity and the twist component caused by the magnetic field twist. The relationships between magnetic field, electric current density, and its two components are examined. It is found that the individual magnetic fibrils are dominated by the current density component caused by the magnetic inhomogeneity, while the large-scale magnetic region is generally dominated by the electric current component associated with the magnetic twist. The microstructure of the magnetic field in the solar atmosphere is far from the force-free field. The current mainly flows around the magnetic flux fibrils in the active regions.

  9. Towards age/rotation/magnetic activity relation with seismology

    Mathur Savita

    2015-01-01

    Full Text Available The knowledge of stellar ages directly impacts the characterization of a planetary system as it puts strong constraints on the moment when the system was born. Unfortunately, the determination of precise stellar ages is a very difficult task. Different methods can be used to do so (based on isochrones or chemical element abundances but they usually provide large uncertainties. During its evolution a star goes through processes leading to loss of angular momentum but also changes in its magnetic activity. Building rotation, magnetic, age relations would be an asset to infer stellar ages model independently. Several attempts to build empirical relations between rotation and age (namely gyrochronology were made with a focus on cluster stars where the age determination is easier and for young stars on the main sequence. For field stars, we can now take advantage of high-precision photometric observations where we can perform asteroseismic analyses to improve the accuracy of stellar ages. Furthermore, the variability in the light curves allow us to put strong constraints on the stellar rotation and magnetic activity. By combining these precise measurements, we are on the way of understanding and improving relations between magnetic activity, rotation, and age, in particular at different stages of stellar evolution. I will review the status on gyrochronology relationships based on observations of young cluster stars. Then I will focus on solar-like stars and describe the inferences on stellar ages, rotation, and magnetism that can be provided by high-quality photometric observations such as the ones of the Kepler mission, in particular through asteroseismic analyses.

  10. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  11. Magnetic-electronic pressure studies of natural iron-bearing minerals and materials using 57Fe Moessbauer spectroscopy in a diamond anvil cell

    The possibility of measuring 57Fe Moessbauer spectra of natural isotopic abundance materials at variable high pressures and cryogenic temperatures in a diamond anvil cell (DAC) on a timescale comparable to conventional Moessbauer spectroscopy (MS) is described. This is exemplified by satisfactory spectra obtained for an ilmenite (FeTiO3) sample (absorber) in ∼12 h at temperatures where the sample is paramagnetic and in 20-30 h below spin-ordering temperature of ∼60 K where resonance intensity is reduced due to magnetically split spectral components. A commercially available 57Co(Rh) point source of 14.4 keV resonant radiation and a Kr-CO2 proportional counter have both been used. Sufficiently high count-rates are obtained by using both the 14.4 keV resonant γ-ray and associated 1.8 keV escape peak events. To optimise the resonance effect, careful attention has been paid to minimize non-resonant radiation within the discriminator window set to select the 14.4 keV resonant radiation. This has been achieved by setting an appropriate source-DAC-detector geometry (i.e., solid angle) to reduce scattering events off components of the DAC to a minimum. By using conventional commercially available Moessbauer apparatus, magnetic-electronic properties of iron-bearing minerals and materials with an iron content greater than ∼20% may be investigated to pressures in excess of 10 GPa encompassing many minerals of the earth's interior

  12. Ruthenium-based olefin metathesis catalysts bearing pH-responsive ligands: External control of catalyst solubility and activity

    Balof, Shawna Lynn

    2011-12-01

    Sixteen novel, Ru-based olefin metathesis catalysts bearing pH responsive ligands were synthesized. The pH-responsive groups employed with these catalysts included dimethylamino (NMe2) modified NHC ligands as well as N-donor dimethylaminopyridine (DMAP) and 3-(o-pyridyl)propylidene ligands. These pH-responsive ligands provided the means by which the solubility and/or activity profiles of the catalysts produced could be controlled via acid addition. The main goal of this dissertation was to design catalyst systems capable of performing ring opening metathesis (ROMP) and ring closing metathesis (RCM) reactions in both organic and aqueous media. In an effort to quickly gain access to new catalyst structures, a template synthesis for functionalized NHC ligand precursors was designed, in addition to other strategies, to obtain ligand precursors with ancillary NMe2 groups. Kinetic studies for the catalysts produced from these precursors showed external control of catalyst solubility was afforded via protonation of the NMe2 groups of their NHC ligands. Additionally, this protonation afforded external control of catalyst propagation rates for several catalysts. This is the first known independent external control for the propagation rates of ROMP catalysts. The incorporation of pH-responsive N-donor ligands into catalyst structures also provided the means for the external control of metathesis activity, as the protonation of these ligands resulted in an increased initiation rate based on their fast and irreversible dissociation from the metal center. The enhanced external control makes these catalysts applicable to a wide range of applications, some of which have been explored by us and/or through collaboration. Three of the catalysts designed showed remarkable metathesis activity in aqueous media. These catalysts displayed comparable RCM activity in aqueous media to a class of water-soluble catalysts reported by Grubbs et al., considered to be the most active catalyst for

  13. Hydrodynamic bearings

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  14. Exploring the efficiency potential for an active magnetic regenerator

    Eriksen, Dan; Engelbrecht, Kurt; Haffenden Bahl, Christian Robert;

    2016-01-01

    A novel rotary state of the art active magnetic regenerator refrigeration prototype was used in an experimental investigation with special focus on efficiency. Based on an applied cooling load, measured shaft power, and pumping power applied to the active magnetic regenerator, a maximum second......-law efficiency of 18% was obtained at a cooling load of 81.5 W, resulting in a temperature span of 15.5 K and a coefficient of performance of 3.6. A loss analysis is given, based on measured pumping power and shaft power together with theoretically estimated regenerator presssure drop. It is shown that......, especially for the pressure drop, significant improvements can be made to the machine. However, a large part of the losses may be attributed to regenerator irreversibilities. Considering these unchanged, an estimated upper limit to the second-law efficiency of 30% is given by eliminating parasitic losses and...

  15. Design and performance study of the active magnetic refrigerator for room-temperature application

    Zheng, Z.G.; Yu, H.Y.; Zhong, X.C.; Zeng, D.C.; Liu, Z.W. [School of Materials Science and Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640 (China)

    2009-01-15

    A room-temperature magnetic refrigerator, consisting of permanent magnet, active magnetic refrigeration (AMR) cycle bed, pumps, hydraulic circuit, active magnetic double regenerator cycle (AM2RC) and control subsystems, has been designed. The magnetic field is supplied by NdFeB permanent magnets. The AMR bed made by stainless steel 304 encloses gadolinium particles as the magnetic working substance. Each part of the refrigerator is controlled by the programmable controller. The different standard heat exchangers are employed to expel heat. The cycle performance of this self-designed facility is analyzed using Langevin theory. The results provide useful data for future design and development of room-temperature magnetic refrigeration. (author)

  16. Repetitive transcranial magnetic stimulation activates specific regions in rat brain

    Ji, Ru-Rong; Schlaepfer, Thomas E.; Aizenman, Carlos D.; Epstein, Charles M.; Qiu, Dike; Huang, Justin C.; Rupp, Fabio

    1998-01-01

    Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive technique to induce electric currents in the brain. Although rTMS is being evaluated as a possible alternative to electroconvulsive therapy for the treatment of refractory depression, little is known about the pattern of activation induced in the brain by rTMS. We have compared immediate early gene expression in rat brain after rTMS and electroconvulsive stimulation, a well-established animal model for electroconvulsive ther...

  17. On the filament motion in magnetic field of active regions

    The study of filament motion in magnetic field of active regions is fulfiled. Filament movement can possibly be presented as a drift in the crossed fields, but there exist fast movements that cannot be described as a drift. For very fast motion, with acceleration greater than that of free fall, it is sometimes necessary to assume, that the motion is carried out due to the filament's own electric current. A model, describing filament motion data, given by Mouradian M. is presented

  18. On the Magnetic Field Strength of Active Region Filaments

    Kuckein, C; Pillet, V Martinez; Casini, R; Sainz, R Manso; Shimizu, T

    2009-01-01

    We study the vector magnetic field of a filament observed over a compact Active Region Neutral Line. Spectropolarimetric data acquired with TIP-II (VTT, Tenerife, Spain) of the 10830 \\AA spectral region provide full Stokes vectors which were analyzed using three different methods: magnetograph analysis, Milne-Eddington inversions and PCA-based atomic polarization inversions. The inferred magnetic field strengths in the filament are of the order of 600 - 700 G by all these three methods. Longitudinal fields are found in the range of 100 - 200 G whereas the transverse components become dominant, with fields as large as 500 - 600 G. We find strong transverse fields near the Neutral Line also at photospheric levels. Our analysis indicates that strong (higher than 500 G, but below kG) transverse magnetic fields are present in Active Region filaments. This corresponds to the highest field strengths reliably measured in these structures. The profiles of the Helium 10830 \\AA lines observed in this Active Region filam...

  19. Edge Adapted Wavelets, Solar Magnetic Activity, and Climate Change

    Johnson, Robert W

    2009-01-01

    The continuous wavelet transform is adapted to account for signal truncation through renormalization and by modifying the shape of the analyzing window. Comparison is made of the instant and integrated wavelet power with previous algorithms. The edge adapted and renormalized admissible wavelet transforms are used to estimate the level of solar magnetic activity from the sunspot record. The solar activity is compared to Oerlemans' temperature reconstruction and to the Central England Temperature record. A correlation is seen for years between 1610 and 1990, followed by a strong deviation as the recently observed temperature increases.

  20. MAGNETIC ACTIVITY CYCLES IN THE EXOPLANET HOST STAR {epsilon} ERIDANI

    Metcalfe, T. S.; Mathur, S. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Buccino, A. P.; Mauas, P. J. D.; Petrucci, R. [Instituto de Astronomia y Fisica del Espacio (CONICET), C.C. 67 Sucursal 28, C1428EHA-Buenos Aires (Argentina); Brown, B. P. [Department of Astronomy and Center for Magnetic Self-Organization, University of Wisconsin, Madison, WI 53706-1582 (United States); Soderblom, D. R. [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Henry, T. J. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302 (United States); Hall, J. C. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Basu, S. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)

    2013-02-01

    The active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 {+-} 0.03 years and 12.7 {+-} 0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called 'active' and 'inactive' sequences as proposed by Boehm-Vitense. Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.

  1. Tooling Converts Stock Bearings To Custom Bearings

    Fleenor, E. N., Jr.

    1983-01-01

    Technique for reworking stock bearings saves time and produces helicopter-rotor bearings ground more precisely. Split tapered ring at one end of threaded bolt expands to hold inside of inner race bearing assembly; nut, at other end of bolt, adjusts amount of spring tension. Piece of hardware grasps bearing firmly without interfering with grinding operation. Operation produces bearing of higher quality than commercially available bearings.

  2. Active split-ring metamaterial slabs for magnetic resonance imaging

    Lopez, Marcos A; Freire, Manuel J; Behr, Volker C; Jakob, Peter M; Marques, Ricardo

    2011-01-01

    In this work, it is analyzed the ability of split-ring metamaterial slabs with zero/high permeability to reject/confine the radiofrequency magnetic field in magnetic resonance imaging systems. Using an homogenization procedure, split-ring slabs have been designed and fabricated to work in a 1.5T system. Active elements consisting of pairs of crossed diodes are inserted in the split-rings. With these elements, the permeability of the slabs can be automatically switched between a unity value when interacting with the strong excitation field of the transmitting body coil, and zero or high values when interacting with the weak field produced by protons in tissue. Experiments are shown for different configurations where these slabs can help to locally increase the signal-to-noise-ratio.

  3. Numerical modeling and analysis of the active magnetic regenerator

    Nielsen, Kaspar Kirstein

    In this thesis the active magnetic regenerator (AMR) is analyzed using various numerical tools and experimental devices. A 2-dimensional transient numerical model of the AMR is developed and implemented and it is used to investigate the in uence of a range of parameters on the performance of the...... investigated using the numerical AMR model. The results show indeed that the performance may be enhanced signicantly and it may thus be concluded that the performance of the AMR is dependent on a vast number of parameters (material composition, magnetic eld source, regenerator geometry, regenerator eciency...... AMR. The model simulates a regenerator made of parallel plates. The operating parameters, such as uid ow rates, thermal utilization, magnetocaloric properties etc. are varied as are geometric properties such as plate and channel thickness, regenerator length and porosity. In this way the performance...

  4. Towards age/rotation/magnetic activity relation with seismology

    Mathur, Savita

    2015-01-01

    The knowledge of stellar ages directly impacts the characterization of a planetary system as it puts strong constraints on the moment when the system was born. Unfortunately, the determination of precise stellar ages is a very difficult task. Different methods can be used to do so (based on isochrones or chemical element abundances) but they usually provide large uncertainties. During its evolution a star goes through processes leading to loss of angular momentum but also changes in its magnetic activity. Building rotation, magnetic, age relations would be an asset to infer stellar ages model independently. Several attempts to build empirical relations between rotation and age (namely gyrochronology) were made with a focus on cluster stars where the age determination is easier and for young stars on the main sequence. For field stars, we can now take advantage of high-precision photometric observations where we can perform asteroseismic analyses to improve the accuracy of stellar ages. Furthermore, the variab...

  5. Optimisation Of An Integrated Planar Magnetic For Active Antenna Panels

    Strixner, E.; Godzik, S.; Drechsler, E., , Dr.

    2011-10-01

    The envisaged German Space Missions HRWS and TerraSAR-X follow-on have triggered the development of a new generation of low voltage DC power supplies for active antennas at Astrium GmbH. The basic approachis tointegrate all power, digital, RF electronics and RF radiators required for one antenna tile into one common unit. Due to the high number of electronic boxes needed for one antenna it is essential to optimise cost, volume, efficiency and weight. The development of an integrated planar magnetic for power conversion is one contribution to this overall optimisation process. The focus of this presentation is the development of an integrated planar magnetic used for a half-bridge forward converter with secondary side synchronous current doubler. The converter is supplied from a 100 V power bus and delivers a total average output power of 280W for the drain supply of the pulsed RF power stages.

  6. Activation of sweeping magnets in Tevatron II standardized target piles

    As designs of the primary targeting schemes for the new Tevatron II slow spill beams progress, it is becoming clear that a standardized form for these schemes is emerging. The general form consists of a production target (usually about 30 cm of beryllium having a diameter from 0.64 to 1.27 cm) followed by from one to three of the new Tevatron II H frame magnets recently developed by D. Eartly. These magnets sweep the unused primary proton beam onto a massive steel beam dump containing a core of material capable of dispersing the energy of the beam along with a hole for transmitting the secondary beam desired at experimental targets. Typical primary proton intensities at such production targets are planned to be in the range of 3 x 1012 to 5 x 1012 protons per spill. If one assumes such operation during a run of 4000 hours per year, 60 spills per hour, the integrated beam is seen to be approximately 1 x 1018 per year targetted at a rate of 7/0 x 1010 protons/sec during the run. It is clear, from experience, that such beam intensities require that the water used to cool the beam dump must be in a closed loop system both to protect personnel during operations from the external radiation exposure rate due to short lived radionuclides (e.g., 11C and 7Be) and to protect against release of significant activities of tritium into surface waters. It is not certain that a closed loop system is required for the sweeping magnets. This TM reports on a calculation designed to evaluate this potential problem, the expected dose rates external to such magnets, and the total activity which will be contained in them and the target

  7. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    Sikora, Marek [Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw (Poland); Begelman, Mitchell C., E-mail: sikora@camk.edu.pl, E-mail: mitch@jila.colorado.edu [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309 (United States)

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  8. Optimization of magnetic powdered activated carbon for aqueous Hg(II) removal and magnetic recovery.

    Faulconer, Emily K; von Reitzenstein, Natalia V Hoogesteijn; Mazyck, David W

    2012-01-15

    Activated carbon is known to adsorb aqueous Hg(II). MPAC (magnetic powdered activated carbon) has the potential to remove aqueous Hg to less than 0.2 μg/L while being magnetically recoverable. Magnetic recapture allows simple sorbent separation from the waste stream while an isolated waste potentially allows for mercury recycling. MPAC Hg-removal performance is verified by mercury mass balance, calculated by quantifying adsorbed, volatilized, and residual aqueous mercury. The batch reactor contained a sealed mercury-carbon contact chamber with mixing and constant N(2) (g) headspace flow to an oxidizing trap. Mercury adsorption was performed using spiked ultrapure water (100 μg/L Hg). Mercury concentrations were obtained using EPA method 245.1 and cold vapor atomic absorption spectroscopy. MPAC synthesis was optimized for Hg removal and sorbent recovery according to the variables: C:Fe, thermal oxidation temperature and time. The 3:1 C:Fe preserved most of the original sorbent surface area. As indicated by XRD patterns, thermal oxidation reduced the amorphous characteristic of the iron oxides but did not improve sorbent recovery and damaged porosity at higher oxidation temperatures. Therefore, the optimal synthesis variables, 3:1 C:Fe mass ratio without thermal oxidation, which can achieve 92.5% (± 8.3%) sorbent recovery and 96.3% (± 9%) Hg removal. The mass balance has been closed to within approximately ± 15%. PMID:22104766

  9. Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

    Wappel, Julia

    2016-01-28

    A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations.

  10. Simple activation by acid of latent Ru-NHC-based metathesis initiators bearing 8-quinolinolate co-ligands

    Wappel, Julia; Fischer, Roland C; Cavallo, Luigi; Slugovc, Christian

    2016-01-01

    Summary A straightforward synthesis utilizing the ring-opening metathesis polymerization (ROMP) reaction is described for acid-triggered N,O-chelating ruthenium-based pre-catalysts bearing one or two 8-quinolinolate ligands. The innovative pre-catalysts were tested regarding their behavior in ROMP and especially for their use in the synthesis of poly(dicyclopentadiene) (pDCPD). Bearing either the common phosphine leaving ligand in the first and second Grubbs olefin metathesis catalysts, or the Ru–O bond cleavage for the next Hoveyda-type catalysts, this work is a step forward towards the control of polymer functionalization and living or switchable polymerizations. PMID:26877818

  11. Optimization of magnetic powdered activated carbon for aqueous Hg(II) removal and magnetic recovery

    Faulconer, Emily K., E-mail: emily.faulconer@yahoo.com [Department of Environmental Engineering Sciences, University of Florida, 217 Black Hall, P.O. Box 116450, Gainesville, FL 32611-645 (United States); Hoogesteijn von Reitzenstein, Natalia V.; Mazyck, David W. [Department of Environmental Engineering Sciences, University of Florida, 217 Black Hall, P.O. Box 116450, Gainesville, FL 32611-645 (United States)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer Thermal oxidation of MPAC decreased the amorphous characteristic of iron oxides. Black-Right-Pointing-Pointer Thermal oxidation did not influence magnetic recovery or Hg removal performance. Black-Right-Pointing-Pointer At all thermal oxidation temperatures, the 3:1 MPAC achieved the highest Hg removal. - Abstract: Activated carbon is known to adsorb aqueous Hg(II). MPAC (magnetic powdered activated carbon) has the potential to remove aqueous Hg to less than 0.2 {mu}g/L while being magnetically recoverable. Magnetic recapture allows simple sorbent separation from the waste stream while an isolated waste potentially allows for mercury recycling. MPAC Hg-removal performance is verified by mercury mass balance, calculated by quantifying adsorbed, volatilized, and residual aqueous mercury. The batch reactor contained a sealed mercury-carbon contact chamber with mixing and constant N{sub 2} (g) headspace flow to an oxidizing trap. Mercury adsorption was performed using spiked ultrapure water (100 {mu}g/L Hg). Mercury concentrations were obtained using EPA method 245.1 and cold vapor atomic absorption spectroscopy. MPAC synthesis was optimized for Hg removal and sorbent recovery according to the variables: C:Fe, thermal oxidation temperature and time. The 3:1 C:Fe preserved most of the original sorbent surface area. As indicated by XRD patterns, thermal oxidation reduced the amorphous characteristic of the iron oxides but did not improve sorbent recovery and damaged porosity at higher oxidation temperatures. Therefore, the optimal synthesis variables, 3:1 C:Fe mass ratio without thermal oxidation, which can achieve 92.5% ({+-}8.3%) sorbent recovery and 96.3% ({+-}9%) Hg removal. The mass balance has been closed to within approximately {+-}15%.

  12. Control of active liquid crystals with a magnetic field.

    Guillamat, Pau; Ignés-Mullol, Jordi; Sagués, Francesc

    2016-05-17

    Living cells sense the mechanical features of their environment and adapt to it by actively remodeling their peripheral network of filamentary proteins, known as cortical cytoskeleton. By mimicking this principle, we demonstrate an effective control strategy for a microtubule-based active nematic in contact with a hydrophobic thermotropic liquid crystal. By using well-established protocols for the orientation of liquid crystals with a uniform magnetic field, and through the mediation of anisotropic shear stresses, the active nematic reversibly self-assembles with aligned flows and textures that feature orientational order at the millimeter scale. The turbulent flow, characteristic of active nematics, is in this way regularized into a laminar flow with periodic velocity oscillations. Once patterned, the microtubule assembly reveals its intrinsic length and time scales, which we correlate with the activity of motor proteins, as predicted by existing theories of active nematics. The demonstrated commanding strategy should be compatible with other viable active biomaterials at interfaces, and we envision its use to probe the mechanics of the intracellular matrix. PMID:27140604

  13. Evolution of the Magnetic Field Distribution of Active Regions

    Dacie, Sally; van Driel-Gesztelyi, Lidia; Long, David; Baker, Deb; Janvier, Miho; Yardley, Stephanie; Pérez-Suárez, David

    2016-01-01

    Aims. Although the temporal evolution of active regions (ARs) is relatively well understood, the processes involved continue to be the subject of investigation. We study how the magnetic field of a series of ARs evolves with time to better characterise how ARs emerge and disperse. Methods. We examine the temporal variation in the magnetic field distribution of 37 emerging ARs. A kernel density estimation plot of the field distribution was created on a log-log scale for each AR at each time step. We found that the central portion of the distribution is typically linear and its slope was used to characterise the evolution of the magnetic field. Results. The slopes were seen to evolve with time, becoming less steep as the fragmented emerging flux coalesces. The slopes reached a maximum value of ~ -1.5 just before the time of maximum flux before becoming steeper during the decay phase towards the quiet Sun value of ~ -3. This behaviour differs significantly from a classical diffusion model, which produces a slope...

  14. Photocatalytically active titanium dioxide nanopowders: Synthesis, photoactivity and magnetic separation

    Two approaches were used to obtain nanocrystalline titanium dioxide (TiO2) photocatalyst powders. Firstly, low-temperature synthesis method and secondly liquid flame spraying. The structural properties of the produced powders were determined with X-ray diffraction, transmission electron microscopy and nitrogen adsorption tests. The photocatalytic properties of the powders were studied with methylene blue (MB) discoloration tests. After discolorations tests, TiO2 was coagulated with magnetite particles using FeCl3·6 H2O at a fixed pH value. Magnetic separation of coagulated TiO2 and magnetite was carried out by a permanent magnet. The obtained results showed that the particle size of the powders synthesized at low-temperature was very small and the specific surface area high. The phase content of the powder was also shown to depend greatly on the acidity of the synthesis solution. Powder synthesized by liquid flame spraying was mixture of anatase and rutile phases with essentially larger particle size and lower specific surface area than those of low-temperature synthesized powders. The MB discoloration test showed that photocatalytic activity depends on the phase structure as well as the specific surface area of the synthesized TiO2 powder. The magnetic separation of TiO2–magnetite coagulate from solution proved to be efficient around pH:8

  15. Solar activity, magnetic storms and their effects on biological systems

    Full text: In the present time much attention is spent on the electromagnetic waves, solar radiation and magnetic storms on biological systems, including on person. However, there are few publications describing the mechanism of these influences on human. First of all it is necessary to point out that electromagnetic waves, the flow of particles in space and magnetic storms, acting on person human-all is connected with biophysical processes. So approach to influence of these factors on organism follows the processes of influence of these waves on bio system. Magnetic storms are phenomena continuously connected with solar activity. Investigation of cosmic space has intensified the practical importance of the problem of interaction with natural factors of external ambience. Much attention deserves the cosmic radiation, geomagnetic field, elements of climate and weathers. However the mechanism of bio tropic action of these factors is not enough studied. Beginning XXI century was already signified the successes in investigation of Mars. The Space shuttles 'Spirit' and 'Opportunity' successfully have carried out some work on examining and finding of water on Mars. A flight of person to Mars is being considered. One of the important mechanisms of influence on human organism is, in our opinion, the rising of the resonance at coincidence of frequencies and their more important factor is a phenomena of electromagnetic induction and forming the radicals in the organism

  16. Effects of flow balancing on active magnetic regenerator performance

    Eriksen, Dan; Engelbrecht, Kurt; Bahl, Christian;

    2016-01-01

    Experiments with a recently constructed rotary multi-bed active magnetic regnenerator (AMR) prototype have revealed strong impacts on the temperature span from variations in the resistances of the flow channels carrying heat transfer fluid in and out of the regenerator beds. In this paper we show...... through numerical modeling how unbalanced flow in the beds decreases the cooling power and COP for a dual bed device. Furthermore, it is shown how resistance variations in multi-bed devices give rise to unbalanced flow in the individual beds and how this decreases cooling powers and COPs of the machines...

  17. Dimensionless numerical model for simulation of active magnetic regenerator refrigerator

    Sarlah, A.; Poredos, A. [Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, SI-1000 Ljubljana (Slovenia)

    2010-09-15

    In order to obtain a better reliability, consistency and accuracy of results obtained with a numerical simulation of an AMRR (active magnetic regenerator refrigerator), a dimensionless numerical model was developed, which can equally be used for determination of regenerator's heat transfer coefficient and simulation of passive heat regenerators or AMRR operation. Regenerator's heat transfer coefficient {alpha}{sub f}, is a crucial input parameter in the simulation of AMRR operation and has a primal effect on the outcome of a solution. This paper deals with a derived dimensionless model and discusses errors involved when using different models for heat transfer coefficient and AMRR operation simulation. (author)

  18. Improved modelling of a parallel plate active magnetic regenerator

    Engelbrecht, Kurt; Tušek, J.; Nielsen, Kaspar Kirstein;

    2013-01-01

    Much of the active magnetic regenerator (AMR) modelling presented in the literature considers only the solid and fluid domains of the regenerator and ignores other physical effects that have been shown to be important, such as demagnetizing fields in the regenerator, parasitic heat losses and fluid...... flow maldistribution in the regenerator. This paper studies the effects of these loss mechanisms and compares theoretical results with experimental results obtained on an experimental AMR device. Three parallel plate regenerators were tested, each having different demagnetizing field characteristics...

  19. Three-axis active magnetic attitude control asymptotical study

    Ovchinnikov, M. Yu.; Roldugin, D. S.; Penkov, V. I.

    2015-05-01

    Active magnetic attitude control system providing given inertial attitude is considered. Control algorithm is constructed on the basis of a planar motion model. It decreases attitude discrepancy. Alternative approach is based on the PD-controller design. System behavior is analyzed for specific motion cases and sometimes for specific inertia tensor (axisymmetrical satellite) using averaging technique. Overall satellite angular motion is covered. Necessary attitude is found to be accessible for some control parameters. Stability is proven and optimal algorithm parameters are obtained. Floquet-based analysis is performed to verify and broaden analytical results.

  20. Photometric magnetic-activity metrics tested with the Sun: Application to Kepler M dwarfs

    Mathur, S; Garcia, R A; Ceillier, T

    2014-01-01

    The Kepler mission has been providing high-quality photometric data leading to many breakthroughs in the exoplanet search and in stellar physics. Stellar magnetic activity results from the interaction between rotation, convection, and magnetic field. Constraining these processes is important if we want to better understand stellar magnetic activity. Using the Sun, we want to test a magnetic activity index based on the analysis of the photo- metric response and then apply it to a sample of M dwarfs observed by Kepler. We estimate a global stellar magnetic activity index by measuring the standard deviation of the whole time series, Sph. Because stellar variability can be related to convection, pulsations, or magnetism, we need to ensure that this index mostly takes into account magnetic effects. We define another stellar magnetic activity index as the average of the standard deviation of shorter subseries which lengths are determined by the rotation period of the star. This way we can ensure that the measured p...

  1. The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches

    Bobra, Monica G; Hoeksema, J Todd; Turmon, Michael J; Liu, Yang; Hayashi, Keiji; Barnes, Graham; Leka, K D

    2014-01-01

    A new data product from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) called Space-weather HMI Active Region Patches (SHARPs) is now available. SDO/HMI is the first space-based instrument to map the full-disk photospheric vector magnetic field with high cadence and continuity. The SHARP data series provide maps in patches that encompass automatically tracked magnetic concentrations for their entire lifetime; map quantities include the photospheric vector magnetic field and its uncertainty, along with Doppler velocity, continuum intensity, and line-of-sight magnetic field. Furthermore, keywords in the SHARP data series provide several parameters that concisely characterize the magnetic-field distribution and its deviation from a potential-field configuration. These indices may be useful for active-region event forecasting and for identifying regions of interest. The indices are calculated per patch and are available on a twelve-minute cadence. Quick-look data are avail...

  2. Magnetic bearing optical delay line

    Dool, T.C. van den; Kamphues, F.G.; Fouss, B.; Henrioulle, K.; Hogenhuis, H.

    2004-01-01

    TNO TPD, in close cooperation with Micromega-Dynamics and Dutch Space, has developed an advanced Optical Delay Line (ODL) for use in PRIMA, GENIE and other ground based interferometers. The delay line design is modular and flexible, which makes scaling for other applications a relatively easy task.

  3. Water-soluble aluminium phthalocyanine–polymer conjugates for PDT: photodynamic activities and pharmacokinetics in tumour-bearing mice

    Brasseur, N; Ouellet, R; Madeleine, C La; Lier, J E van

    1999-01-01

    The potential use of unsubstituted aluminium phthalocyanine (AlClPc) as a sensitizer for photodynamic therapy (PDT) of cancer has not been fully exploited in spite of its higher efficiency as compared to the sulphonated derivatives. This is largely due to the strong hydrophobic character of AlClPc which renders the material difficult to formulate for in vivo administration. We prepared two water-soluble derivatives of AlClPc by axial coordination of polyethyleneglycol (PEG, MW 2000) or polyvinylalcohol (PVA, MW 13 000–23 000) to the central aluminium ion. Their photodynamic activities were evaluated in vitro against the EMT-6 mouse mammary tumour cells and in vivo against the EMT-6 and the colon carcinoma Colo-26 tumours implanted intradermally in Balb/c mice. Pharmacokinetics were studied in the EMT-6 tumour-bearing mice. After 1 h incubation, the light dose required to kill 90% of cells (LD90) was at least three times less for AlClPc (Cremophor emulsion) as compared to AlPc–PEG and AlPc–PVA, while after 24 h incubation all three preparations were highly phototoxic. All three dye preparations induced complete EMT-6 tumour regression in 75–100% of animals at a low drug dose (0.25 μmol kg−1) following PDT (400 J cm−2, 650–700 nm) at 24 h pi. Complete tumour regression in the Colo-26 tumour model was obtained in 30% of mice at a dose of 2 μmol kg−1. In the non-cured animals, AlPc–PVA induced the most significant tumour growth delay. This dye showed a prolonged plasma half-life (6.8 h) as compared to AlClPc (2.6 h) and AlPc–PEG (23 min), lower retention by liver and spleen and higher tumour-to-skin and tumour-to-muscle ratios. Our data demonstrate that addition of hydrophilic axial ligands to AlPc, while modifying in vitro and in vivo kinetics, does not reduce the PDT efficiency of the parent molecule. Moreover, in the case of the polyvinylalcohol derivative, axial coordination confers advantageous pharmacokinetics to AlPc, which makes this

  4. Water-soluble aluminium phthalocyanine-polymer conjugates for PDT: photodynamic activities and pharmacokinetics in tumour-bearing mice.

    Brasseur, N; Ouellet, R; La Madeleine, C; van Lier, J E

    1999-07-01

    The potential use of unsubstituted aluminium phthalocyanine (AlClPc) as a sensitizer for photodynamic therapy (PDT) of cancer has not been fully exploited in spite of its higher efficiency as compared to the sulphonated derivatives. This is largely due to the strong hydrophobic character of AlClPc which renders the material difficult to formulate for in vivo administration. We prepared two water-soluble derivatives of AlClPc by axial coordination of polyethyleneglycol (PEG, MW 2000) or polyvinylalcohol (PVA, MW 13,000-23,000) to the central aluminium ion. Their photodynamic activities were evaluated in vitro against the EMT-6 mouse mammary tumour cells and in vivo against the EMT-6 and the colon carcinoma Colo-26 tumours implanted intradermally in Balb/c mice. Pharmacokinetics were studied in the EMT-6 tumour-bearing mice. After 1 h incubation, the light dose required to kill 90% of cells (LD90) was at least three times less for AlClPc (Cremophor emulsion) as compared to AlPc-PEG and AlPc-PVA, while after 24 h incubation all three preparations were highly phototoxic. All three dye preparations induced complete EMT-6 tumour regression in 75-100% of animals at a low drug dose (0.25 micromol kg(-1)) following PDT (400 J cm(-2), 650-700 nm) at 24 h pi. Complete tumour regression in the Colo-26 tumour model was obtained in 30% of mice at a dose of 2 micromol kg(-1). In the non-cured animals, AlPc-PVA induced the most significant tumour growth delay. This dye showed a prolonged plasma half-life (6.8 h) as compared to AlClPc (2.6 h) and AlPc-PEG (23 min), lower retention by liver and spleen and higher tumour-to-skin and tumour-to-muscle ratios. Our data demonstrate that addition of hydrophilic axial ligands to AlPc, while modifying in vitro and in vivo kinetics, does not reduce the PDT efficiency of the parent molecule. Moreover, in the case of the polyvinylalcohol derivative, axial coordination confers advantageous pharmacokinetics to AlPc, which makes this

  5. The Magnetic Classification of Solar Active Regions 1992-2015

    Jaeggli, S. A.; Norton, A. A.

    2016-03-01

    The purpose of this Letter is to address a blindspot in our knowledge of solar active region (AR) statistics. To the best of our knowledge, there are no published results showing the variation of the Mount Wilson magnetic classifications as a function of solar cycle based on modern observations. We show statistics for all ARs reported in the daily Solar Region Summary from 1992 January 1 to 2015 December 31. We find that the α and β class ARs (including all sub-groups, e.g., βγ, βδ) make up fractions of approximately 20% and 80% of the sample, respectively. This fraction is relatively constant during high levels of activity however, an increase in the α fraction to about 35% and and a decrease in the β fraction to about 65% can be seen near each solar minimum and are statistically significant at the 2σ level. Over 30% of all ARs observed during the years of solar maxima were appended with the classifications γ and/or δ, while these classifications account for only a fraction of a percent during the years near the solar minima. This variation in the AR types indicates that the formation of complex ARs may be due to the pileup of frequent emergence of magnetic flux during solar maximum, rather than the emergence of complex, monolithic flux structures.

  6. Observational evidence for enhanced magnetic activity of superflare stars.

    Karoff, Christoffer; Knudsen, Mads Faurschou; De Cat, Peter; Bonanno, Alfio; Fogtmann-Schulz, Alexandra; Fu, Jianning; Frasca, Antonio; Inceoglu, Fadil; Olsen, Jesper; Zhang, Yong; Hou, Yonghui; Wang, Yuefei; Shi, Jianrong; Zhang, Wei

    2016-01-01

    Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares. PMID:27009381

  7. The Magnetic Classification of Solar Active Regions 1992 - 2015

    Jaeggli, Sarah A

    2016-01-01

    The purpose of this letter is to address a blind-spot in our knowledge of solar active region statistics. To the best of our knowledge there are no published results showing the variation of the Mount Wilson magnetic classifications as a function of solar cycle based on modern observations. We show statistics for all active regions reported in the daily Solar Region Summary from 1992 January 1 to 2015 December 31. We find that the $\\alpha$ and $\\beta$ class active regions (including all sub-groups e.g. $\\beta\\gamma$, $\\beta\\delta$) make up fractions of approximately 20% and 80% of the sample respectively. This fraction is relatively constant during high levels of activity, however, an increase in the $\\alpha$ fraction to about 35% and and a decrease in the $\\beta$ fraction to about 65% can be seen near each solar minimum and is statistically significant at the 2-$\\sigma$ level. Over 30% of all active regions observed during the years of solar maxima were appended with the classifications $\\gamma$ and/or $\\del...

  8. Magnetic Activity Cycles in the Exoplanet Host Star epsilon Eridani

    Metcalfe, T S; Brown, B P; Mathur, S; Soderblom, D R; Henry, T J; Mauas, P J D; Petrucci, R; Hall, J C; Basu, S

    2012-01-01

    The active K2 dwarf epsilon Eri has been extensively characterized, both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3 year magnetic activity cycle in epsilon Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3 year and 13 year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3 year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95+/-0.03 years and 12.7+/-0.3 years, which by analogy with the solar case suggests a revised identification of the dynamo mechanisms that are responsible for the so-called "active" and "inactive" sequences as proposed by Bohm-V...

  9. Development on software system of structure design for radial magnetic bearing%径向磁力轴承结构设计软件系统的开发

    朱晓明

    2011-01-01

    Magnetic bearing is applying in more fields because of its many excellent characteristics. As the important base of sustaining system, the structure design of magnetic hearing requires balance among many parameters and repeated calculaton, thus add the complexity. Aiming at design process of magnetic bearing, the theoretic formula and experimental formula are deduced. Combinig parameterized programming thinking and interactive programming mode, a design software system for magnetic bearing is developed with the application of VC++6.0. The test proved the software system can complete the structure design rapidly and correctly, shorten the development period and increase the reliability.%由于磁力轴承具有多种优点,其应用越来越广泛。磁力轴承的结构设计是进行支撑系统设计的重要基础,但其设计过程需要对多个参数进行综合衡量并反复计算,增加了设计复杂度。针对磁力轴承的设计过程,推导了径向磁力轴承的理论公式和经验公式。通过参数化程序设计思想和交互式程序设计方法,利用VC++6.0设计环境,开发了轴承结构设计软件系统。通过测试证明,该软件系统能够快速准确完成轴承的结构设计,大大缩短了开发周期,增加了可靠性。

  10. Influence of concomitant infusion of thymidine and inosine on methotrexate activity in normal and P388-bearing mice

    Uitendaal, Martin P.; Schornagel, J.H.; Leyva, A.; Pinedo, H.M.

    1984-01-01

    Combinations of thymidine and inosine (ranging from 0 to 7.5 mg/hr) were co-administered during a 72-hr continuous i.v. infusion of 3 μg/hr methotrexate in normal and P388 solid tumor-bearing DBA/2 mice. Methotrexate alone was lethal to all normal mice. Inosine at 1.0–7.5 mg/hr could reverse toxicit

  11. ON MAGNETIC ACTIVITY BAND OVERLAP, INTERACTION, AND THE FORMATION OF COMPLEX SOLAR ACTIVE REGIONS

    McIntosh, Scott W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Leamon, Robert J., E-mail: mscott@hao.ucar.edu [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)

    2014-11-20

    Recent work has revealed a phenomenological picture of the how the ∼11 yr sunspot cycle of the Sun arises. The production and destruction of sunspots is a consequence of the latitudinal-temporal overlap and interaction of the toroidal magnetic flux systems that belong to the 22 yr magnetic activity cycle and are rooted deep in the Sun's convective interior. We present a conceptually simple extension of this work, presenting a hypothesis on how complex active regions can form as a direct consequence of the intra- and extra-hemispheric interaction taking place in the solar interior. Furthermore, during specific portions of the sunspot cycle, we anticipate that those complex active regions may be particularly susceptible to profoundly catastrophic breakdown, producing flares and coronal mass ejections of the most severe magnitude.

  12. MAGNET

    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...

  13. A Study of Active Rotor-Blade Vibration Control using Electro-Magnetic Actuation - Part II: Experiment

    Christensen, Rene Hardam; Santos, Ilmar

    2004-01-01

    mistuning, can easily be generated by substitution or rearranging the blades. Six sets of electro-magnetic actuators are applied to the system in order to control the blades as well as the rotor vibrations. Four sets of actuators are mounted in the rotating disc acting directly onto each one of the blades....... The remaining two sets of actuators are applied to act directly onto the hub, working as an active radial bearing controlling the rotor lateral movement. The rig is equipped with sensors measuring blade and rotor vibrations. Actuators and sensors are connected to a digital signal processor running the...... control algorithm. Measurement signals and actuator control signals from the sensors and actuators fixed in the rotating disc are transmitted to the control unit through a slip-ring device. Various measured responses of both the controlled and the non-controlled system with identical blades and with...

  14. Superconducting bearings in flywheels

    Coombs, T.A.; Campbell, A.M.; Ganney, I.; Lo, W. [Cambridge Univ. (United Kingdom). Interdisciplinary Research Centre in Superconductivity (IRC); Twardowski, T. [International Energy Systems, Chester High Road, Neston, South Wirral (United Kingdom); Dawson, B. [British Nuclear Fuels, Capenhurst, South Wirral (United Kingdom)

    1998-05-01

    Investigations are being carried out into the use of superconducting magnetic bearings to levitate energy storage flywheels. In a planned program of work, Cambridge University are aiming to produce a practical bearing system for Pirouette(TM). The Pirouette(TM) system is designed to provide 5 kWh of recoverable energy which is currently recoverable at a rate of 5 kW (future revisions will provide up to 50 kW). IES (a British Nuclear Fuels subsidiary) the owners of the Pirouette(TM) machine have supplied Cambridge with a flywheel. This flywheel weighs >40 kg and is being levitated using an Evershed-type arrangement in which the superconductor is being used to stabilize the interaction between two magnets. To date we have demonstrated stable levitation in static and low speed tests in a rig designed for low speeds of rotation in air. A second rig which is currently under construction at BNFL will run in vacuum at speeds of up to 50 (orig.) 5 refs.

  15. Superconducting bearings in flywheels

    Investigations are being carried out into the use of superconducting magnetic bearings to levitate energy storage flywheels. In a planned program of work, Cambridge University are aiming to produce a practical bearing system for Pirouette(TM). The Pirouette(TM) system is designed to provide 5 kWh of recoverable energy which is currently recoverable at a rate of 5 kW (future revisions will provide up to 50 kW). IES (a British Nuclear Fuels subsidiary) the owners of the Pirouette(TM) machine have supplied Cambridge with a flywheel. This flywheel weighs >40 kg and is being levitated using an Evershed-type arrangement in which the superconductor is being used to stabilize the interaction between two magnets. To date we have demonstrated stable levitation in static and low speed tests in a rig designed for low speeds of rotation in air. A second rig which is currently under construction at BNFL will run in vacuum at speeds of up to 50 (orig.)

  16. Superconducting-electromagnetic hybrid bearing using YBCO bulk locks for passive axial levitation

    A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90 deg. from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance. (author)

  17. 2-dimensional numerical modeling of active magnetic regeneration

    Nielsen, Kaspar Kirstein; Pryds, Nini; Smith, Anders;

    2009-01-01

    Various aspects of numerical modeling of Active Magnetic Regeneration (AMR) are presented. Using a 2-dimensional numerical model for solving the unsteady heat transfer equations for the AMR system, a range of physical effects on both idealized and non-idealized AMR are investigated. The modeled...... system represents a linear, parallel-plate based AMR. The idealized version of the model is able to predict the theoretical performance of AMR in terms of cooling power and temperature span. This is useful to a certain extent, but a model reproducing experiments to a higher degree is desirable. Therefore...... physical effects such as thermal parasitic losses have been included. Furthermore, experimentally found magnetocaloric properties are used when available, since the commonly used mean field model can be too idealized and is not always able to determine the magnetocaloric effect accurately. In the present...

  18. Property Analysis and Application of Magnetic Bearing - Hollow Shaft - Centrifugal Impeller Rotor%电磁轴承-空心轴-离心叶轮转子特性分析及应用

    邱希望; 琚亚平; 秦瑞鸿; 李振华; 张楚华

    2015-01-01

    面向高速无油节能环保型流体机械技术的实际需求,重点对某一电磁轴承-空心轴-离心叶轮转子系统的支撑刚度、临界转速和叶轮强度进行了有限元分析。研究表明:该电磁轴承的支撑刚度为813000~7317000 N/m;在设计转速下,转轴为刚性轴,可采用刚性轴的电磁轴承控制方案,离心叶轮强度满足材料要求。%Aiming at the practical requirement of high speed, oil free, energy saving and environment conservation fluid machinery technology, this paper is focused on the supporting stiffness of magnetic bearing, the critical speed of rotor system and the strength of rotating impeller based on finite element method. The results show that the stiffness of the designed magnetic bearing ranges within 813 000~7 317 000 N/m. At the design speed, the rotor system is a rigid one and the electronic- magnetic control strategy for rigid shaft can be used. The stress of the centrifugal impeller meets the requirement of material strength.

  19. Deciphering solar magnetic activity. I. On the relationship between the sunspot cycle and the evolution of small magnetic features

    Sunspots are a canonical marker of the Sun's internal magnetic field which flips polarity every ∼22 yr. The principal variation of sunspots, an ∼11 yr variation, modulates the amount of the magnetic field that pierces the solar surface and drives significant variations in our star's radiative, particulate, and eruptive output over that period. This paper presents observations from the Solar and Heliospheric Observatory and Solar Dynamics Observatory indicating that the 11 yr sunspot variation is intrinsically tied to the spatio-temporal overlap of the activity bands belonging to the 22 yr magnetic activity cycle. Using a systematic analysis of ubiquitous coronal brightpoints and the magnetic scale on which they appear to form, we show that the landmarks of sunspot cycle 23 can be explained by considering the evolution and interaction of the overlapping activity bands of the longer-scale variability.

  20. Effect of Magnetic Field on Enzyme Activities in Main Soils of Northeast China

    LIUXIAOYI; YIYANLI; 等

    1996-01-01

    Soil enzyme activities as affected by applied magnetic field were studied with three main soils (brown soil,black soil and albic soil) collected from Northeast China,Appropriate intensities of magnetic field could obviously enhance the activities of hydrogen peroxidases,invertases,amylases and phosphatases in the three soils,although the effect varied with types and water regimes of the soils.Increasing times of magnetic treatment could multiple its good effect on the activities of hydrogen peroxidases in soils.

  1. Thermal activation-induced sweep-rate dependence of magnetic switching astroid

    We examine the sweep-rate dependence of magnetic switching field, Hs, in submicron magnetic tunnel junctions where shape anisotropy is dominant. Experimental data support the use of a single-domain thermal activation model for description of activated magnetic reversal in junctions 0.2 by 0.5 μm or less in size. A scaling law is obtained for the thermal activation energy which varies as the cube of junction size. [copyright] 2001 American Institute of Physics

  2. Asymmetric magnetic disorder observed in thermally activated magnetization reversal of exchange-biased IrMn/CoFe films

    We report an asymmetry of magnetic disorder in exchange-biased IrMn(tIrMn=5–20 nm)/CoFe(50 nm) films observed by means of a Kerr microscope, capable of direct domain observation. From the correlation between the magnetization half-reversal time and applied magnetic field, we find that the magnetization switching in all the films occurs via a thermally activated reversal mechanism for both branches of hysteresis loops. Surprisingly, in the forward branch reversal where the applied magnetic field is antiparallel to the direction of exchange-bias field, degree of magnetic disorder decreases as exchange-bias field increases, which is definitely contrasted with the case of backward branch reversal. This result is likely ascribed to the fact that the local values of exchange-bias field and coercive field are oppositely fluctuating with each other in the film. - Highlights: ► Quite different “magnetic disorder” in the same structural-disordered system. ► Elucidation of magnetization reversal mechanism via direct domain observation. ► The simple model which explains the origin of asymmetric magnetic disorder.

  3. Active Portofolio Management in the Presence of Regime Switching: What Are the Benefits of Defensive Asset Allocation Strategies If the Investor Faces Bear Markets?

    Klaus Grobys

    2012-06-01

    Full Text Available This paper studies the asset allocation decision in the presence of regime switchingin stock market returns. The analysis is based on two stock indices: DJI 30 and OMX30. The two-step optimization procedure employed points towards the usage of defensiveasset allocation strategies under bear markets and ordinary index tracking strategies underbull markets. The out-of-sample experiments strengthen the performance of active strategiesthat distinguish between different regimes. Moreover, the Sharpe ratios of portfolios basedon such strategies are higher than the ones of ordinary index tracking based portfolios.

  4. Formation of Solar Delta Active Regions:Twist and Writhe of Magnetic Ropes

    Hong-Qi Zhang

    2004-01-01

    We analyze the process of formation of delta configuration in some well-known super active regions based on photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows a potential-like configuration in the solar atmosphere,the magnetic shear develops mainly near the magnetic neutral line with magnetic islands of opposite polarities, and the large-scale photospheric twisted field forming gradually later. Some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, supposed to be generated in the subatmosphere,is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and not entirely consistent with the relationship with magnetic shear in some delta active regions. (3) The proposition is that the large-scale delta active regions are formed from contribution by small-scale non-potential magnetic flux bundles generated in the subatmosphere.

  5. Activity Analyses for Solar-Type Stars Observed With Kepler. I. Proxies of Magnetic Activity

    He, Han; Yun, Duo

    2016-01-01

    Light curves of solar-type stars often show gradual fluctuations due to rotational modulation by magnetic features (starspots and faculae) on stellar surfaces. Two quantitative measures of modulated light curves are employed as the proxies of magnetic activity for solar-type stars observed with Kepler telescope. The first is named autocorrelation index $i_{AC}$, which describes the degree of periodicity of the light curve, the second is the effective fluctuation range of the light curve $R_{eff}$, which reflects the depth of rotational modulation. The two measures are complementary and depict different aspects of magnetic activities on solar-type stars. By using the two proxies $i_{AC}$ and $R_{eff}$, we analyzed activity properties of two carefully selected solar-type stars observed with Kepler (Kepler ID: 9766237 and 10864581), which have distinct rotational periods (14.7 vs. 6.0 days). We also applied the two measures to the Sun for a comparative study. The result shows that both the measures can reveal cy...

  6. Evolution of Magnetic Helicity and Energy Spectra of Solar Active Regions

    Zhang, Hongqi; Sokoloff, D D

    2015-01-01

    We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field for estimating magnetic energy and helicity spectra as well as current helicity spectra of individual active regions and the change of their spectral indices with the solar cycle. The departure of the spectral index of current helicity from 5/3 is analyzed, and it is found that it is lower than that of magnetic energy. There is no obvious relationship between the change of the normalized magnetic helicity and the integral scale of the magnetic field for individual active regions. The evolution of the spectral index reflects the development and distribution of various scales of magnetic structures in active regions. It is found that around solar maximum the magnetic energy and helicity spectra are steeper.

  7. Design, synthesis, and structure-activity relationships of novel benzothiazole derivatives bearing the ortho-hydroxy N-carbamoylhydrazone moiety as potent antitumor agents.

    Ma, Junjie; Chen, Dong; Lu, Kuan; Wang, Lihui; Han, Xiaoqi; Zhao, Yanfang; Gong, Ping

    2014-10-30

    A series of novel benzothiazole derivatives bearing the ortho-hydroxy N-carbamoylhydrazone moiety were designed and synthesized and their cytotoxic activities against five cancer cell lines (NCI-H226, SK-N-SH, HT29, MKN45, and MDA-MB-231) were screened in vitro. Most of them showed moderate to excellent activity against all the tested cell lines. Among them, compounds 15g (procaspase-3 EC50 = 1.42 μM) and 16b (procaspase-3 EC50 = 0.25 μM) exhibited excellent antitumor activity with IC50 values ranging from 0.14 μM to 0.98 μM against all cancer cell lines, which were 1.8-8.7 times more active than the first procaspase activating compound (PAC-1) (procaspase-3 EC50 = 4.08 μM). The structure-activity relationship (SAR) analyses indicated that the introduction of a lipophilic group (a benzyloxy or heteroaryloxy group) at the 4-position of the 2-hydroxy phenyl ring was beneficial to antitumor activity, and the presence of substituents containing nitrogen that are positively charged at physiological pH could also improve antitumor activity. It was also confirmed that the steric effect of the 4-position substituent of the benzyloxy group had a significant influence on cytotoxic activity. PMID:25171780

  8. Electrospun magnetic nanofibre mats – A new bondable biomaterial using remotely activated magnetic heating

    Zhong, Yi [Department of Materials Engineering, University of British Columbia, Vancouver (Canada); Key Laboratory of Science & Technology of Eco-Textile, Ministry of Education, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai (China); Leung, Victor; Yuqin Wan, Lynn [Department of Materials Engineering, University of British Columbia, Vancouver (Canada); Dutz, Silvio [Institut für Biomedizinische Technik und Informatik, Technische Universität Ilmenau (Germany); Department of Nano Biophotonics, Leibniz Institute of Photonic Technology, Jena (Germany); Ko, Frank K., E-mail: frank.ko@ubc.ca [Department of Materials Engineering, University of British Columbia, Vancouver (Canada); Häfeli, Urs O., E-mail: urs.hafeli@ubc.ca [Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver (Canada)

    2015-04-15

    A solvothermal process was adopted to produce hydrophilic magnetite (Fe{sub 3}O{sub 4}) nanoparticles which were subsequently emulsified with a chloroform/methanol (70/30 v/v) solution of poly(caprolactone) (PCL) and then electrospun into a 0.2 mm thick PCL mat. The magnetic heating of the mats at a field amplitude of 25 kA/m and frequency of 400 kHz exhibited promising efficiency for magnetic hyperthermia, with a specific absorption rate of about 40 W/g for the magnetic mat. The produced heat was used to melt the magnetic mat onto the surrounding non-magnetic polymer mat from within, without destroying the nanostructure of the non-magnetic polymer more than 0.5 mm away. Magnetic nanofibre mats might thus be useful for internal heat sealing applications, and potentially also for thermotherapy.

  9. Electrospun magnetic nanofibre mats - A new bondable biomaterial using remotely activated magnetic heating

    Zhong, Yi; Leung, Victor; Yuqin Wan, Lynn; Dutz, Silvio; Ko, Frank K.; Häfeli, Urs O.

    2015-04-01

    A solvothermal process was adopted to produce hydrophilic magnetite (Fe3O4) nanoparticles which were subsequently emulsified with a chloroform/methanol (70/30 v/v) solution of poly(caprolactone) (PCL) and then electrospun into a 0.2 mm thick PCL mat. The magnetic heating of the mats at a field amplitude of 25 kA/m and frequency of 400 kHz exhibited promising efficiency for magnetic hyperthermia, with a specific absorption rate of about 40 W/g for the magnetic mat. The produced heat was used to melt the magnetic mat onto the surrounding non-magnetic polymer mat from within, without destroying the nanostructure of the non-magnetic polymer more than 0.5 mm away. Magnetic nanofibre mats might thus be useful for internal heat sealing applications, and potentially also for thermotherapy.

  10. Electrospun magnetic nanofibre mats – A new bondable biomaterial using remotely activated magnetic heating

    A solvothermal process was adopted to produce hydrophilic magnetite (Fe3O4) nanoparticles which were subsequently emulsified with a chloroform/methanol (70/30 v/v) solution of poly(caprolactone) (PCL) and then electrospun into a 0.2 mm thick PCL mat. The magnetic heating of the mats at a field amplitude of 25 kA/m and frequency of 400 kHz exhibited promising efficiency for magnetic hyperthermia, with a specific absorption rate of about 40 W/g for the magnetic mat. The produced heat was used to melt the magnetic mat onto the surrounding non-magnetic polymer mat from within, without destroying the nanostructure of the non-magnetic polymer more than 0.5 mm away. Magnetic nanofibre mats might thus be useful for internal heat sealing applications, and potentially also for thermotherapy

  11. Modulation of cortical oscillatory activity during transcranial magnetic stimulation.

    Brignani, Debora; Manganotti, Paolo; Rossini, Paolo M; Miniussi, Carlo

    2008-05-01

    Transcranial magnetic stimulation (TMS) can transiently modulate cortical excitability, with a net effect depending on the stimulation frequency ( or =5 Hz facilitation, at least for the motor cortex). This possibility has generated interest in experiments aiming to improve deficits in clinical settings, as well as deficits in the cognitive domain. The aim of the present study was to investigate the on-line effects of low frequency (1 Hz) TMS on the EEG oscillatory activity in the healthy human brain, focusing particularly on the outcome of these modulatory effects in relation to the duration of the TMS stimulation. To this end, we used the event-related desynchronization/synchronization (ERD/ERS) approach to determine the patterns of oscillatory activity during two consecutive trains of sham and real TMS. Each train of stimulation was delivered to the left primary motor cortex (MI) of healthy subjects over a period of 10 min, while EEG rhythms were simultaneously recorded. Results indicated that TMS induced an increase in the power of brain rhythms that was related to the period of the stimulation, i.e. the synchronization of the alpha band increased with the duration of the stimulation, and this increase was inversely correlated with motor-evoked potentials (MEPs) amplitude. In conclusion, low frequency TMS over primary motor cortex induces a synchronization of the background oscillatory activity on the stimulated region. This induced modulation in brain oscillations seems to increase coherently with the duration of stimulation, suggesting that TMS effects may involve short-term modification of the neural circuitry sustaining MEPs characteristics. PMID:17557296

  12. Significance of magnetic resonance imaging for early rheumatoid arthritis activity

    E Y Pogozeva

    2009-01-01

    Full Text Available Objective. To assess possibility of magnetic resonance image (MRI application for rheu- matoid arthritis (RA activity and severity assessment.Material and methods. 100 pts with RA who fulfilled the 1987 ACR criteria with disease duration less than 12 months were included. Standard clinical examination with evaluation of tender and swollen joint counts, acute phase markers, hand and foot X-ray and hand MRI with 0,2 T Artoscan apparatus (ESAOTE Biomedica, Italy were performed.Results. MRI showed hand joint synovitis in 94,5%, erosions – in 67,3% of cases. X-ray examination revealed erosions in only 20,8% of pts. Localization of erosions revealed by X-ray and MRI coincided in 36,4% of cases and in 61,8% of pts erosions were detected only by MRI. MRI confirmed clinical conclusion about presence or absence of metacarpophalangeal and wrist joint synovitis in 64,5% and 74,5% of cases respectively. In8,2% and 21,8% MRI revealed signs of synovitis in clinically intact joints. MRI synovitis score correlated with clinical and laboratory measures of disease activity – DAS 28 (r=0,37, p=0,001, CRP(r=0,30, p=0,001, ESR (r=0,42, p=0,001, HAQ (r=0,24, p=0,001. Weak correlation was revealed between ESR and presence of erosions (r=0,29, CRP, ESR and MRI signs of bone marrow edema (r=0,27, p=0,005 and r=0,29, p=0,002 respectively. Relationship between laboratory and clinical features was weaker and referred only to CRP level and swollen joint count (p=0,05.Conclusion. MRI signs may be used as additional and independent measures of inflammatory activity (particularly synovitis score and severity of RA

  13. Harnessing microbial subsurface metal reduction activities to synthesise nanoscale cobalt ferrite with enhanced magnetic properties

    Coker, Victoria S.; Telling, Neil D.; van der Laan, Gerrit; Pattrick, Richard A.D.; Pearce, Carolyn I.; Arenholz, Elke; Tuna, Floriana; Winpenny, Richard E.P.; Lloyd, Jonathan R.

    2009-03-24

    Nanoscale ferrimagnetic particles have a diverse range of uses from directed cancer therapy and drug delivery systems to magnetic recording media and transducers. Such applications require the production of monodisperse nanoparticles with well-controlled size, composition, and magnetic properties. To fabricate these materials purely using synthetic methods is costly in both environmental and economical terms. However, metal-reducing microorganisms offer an untapped resource to produce these materials. Here, the Fe(III)-reducing bacterium Geobacter sulfurreducens is used to synthesize magnetic iron oxide nanoparticles. A combination of electron microscopy, soft X-ray spectroscopy, and magnetometry techniques was employed to show that this method of biosynthesis results in high yields of crystalline nanoparticles with a narrow size distribution and magnetic properties equal to the best chemically synthesized materials. In particular, it is demonstrated here that cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles with low temperature coercivity approaching 8 kOe and an effective anisotropy constant of {approx} 10{sup 6} erg cm{sup -3} can be manufactured through this biotechnological route. The dramatic enhancement in the magnetic properties of the nanoparticles by the introduction of high quantities of Co into the spinel structure represents a significant advance over previous biomineralization studies in this area using magnetotactic bacteria. The successful production of nanoparticulate ferrites achieved in this study at high yields could open up the way for the scaled-up industrial manufacture of nanoparticles using environmentally benign methodologies. Production of ferromagnetic nanoparticles for pioneering cancer therapy, drug delivery, chemical sensors, catalytic activity, photoconductive materials, as well as more traditional uses in data storage embodies a large area of inorganic synthesis research. In particular, the addition of transition metals other than

  14. Alloantigen-activated lymphocytes from mice bearing a spontaneous nonimmunogenic adenocarcinoma inhibit its growth in vivo by recruiting host immunoreactivity

    Nylon wool columns eluting lymphocytes from the spleen of mice bearing a clinically evident spontaneous, nonimmunogenic adenocarcinoma of recent origin (TS/A) do not display cytotoxic response, release of lymphokines, and proliferation in vitro against TS/A cells, nor do they inhibit TS/A tumor growth in a Winn-type neutralization assay in vivo. After 5-day co-culture with allogeneic spleen cells from mice differing at multiple minor histocompatibility antigens only, these lymphocytes are still noncytolytic against TS/A cells, whereas they release interferon-γ, mediate delayed-type hypersensitivity (DTH) reactions, and inhibit TS/A tumor growth in the Winn assay. In the Winn test, alloactivated lymphocytes from TS/A tumor-bearing mice are more effective than those from normal mice on a per cell basis. The induction of this TS/A tumor inhibition ability depends on the presence in the cultures of Thy-1+ lymphocytes. The presence of Lyt-2+ lymphocytes is also important, whereas that of asialo GM1+ is not. The TS/A inhibition in vivo by alloactivated lymphocytes mostly depends on Thy-1+, Lyt-2- and asialo GM- lymphocytes, even though a few Thy- cells are also very efficient tumor inhibitors. The alloactivated lymphocytes inhibit TS/A tumor growth by recruiting the radiosensitive effector mechanisms of the recipient mice required for ultimate tumor rejection. TS/A tumor rejection leaves a specific DTH and an immunologic memory resulting in rejection of a second lethal TS/A challenge in a significant number of mice

  15. The Maximum Free Magnetic Energy Allowed in a Solar Active Region

    Moore, Ronald L.; Falconer, David A.

    2009-01-01

    Two whole-active-region magnetic quantities that can be measured from a line-of-sight magnetogram are (sup L) WL(sub SG), a gauge of the total free energy in an active region's magnetic field, and sup L(sub theta), a measure of the active region's total magnetic flux. From these two quantities measured from 1865 SOHO/MDI magnetograms that tracked 44 sunspot active regions across the 0.5 R(sub Sun) central disk, together with each active region's observed production of CMEs, X flares, and M flares, Falconer et al (2009, ApJ, submitted) found that (1) active regions have a maximum attainable free magnetic energy that increases with the magnetic size (sup L) (sub theta) of the active region, (2) in (Log (sup L)WL(sub SG), Log(sup L) theta) space, CME/flare-productive active regions are concentrated in a straight-line main sequence along which the free magnetic energy is near its upper limit, and (3) X and M flares are restricted to large active regions. Here, from (a) these results, (b) the observation that even the greatest X flares produce at most only subtle changes in active region magnetograms, and (c) measurements from MSFC vector magnetograms and from MDI line-of-sight magnetograms showing that practically all sunspot active regions have nearly the same area-averaged magnetic field strength: =- theta/A approximately equal to 300 G, where theta is the active region's total photospheric flux of field stronger than 100 G and A is the area of that flux, we infer that (1) the maximum allowed ratio of an active region's free magnetic energy to its potential-field energy is 1, and (2) any one CME/flare eruption releases no more than a small fraction (less than 10%) of the active region's free magnetic energy. This work was funded by NASA's Heliophysics Division and NSF's Division of Atmospheric Sciences.

  16. Ionospheric trough observation probability dependence on the season, local time, longitude and magnetic activity level

    Probability of different ionospheric trough observation for Kosmos satellite data (about 3000 circuits) is analysed. Trough appearance probability variations with the season, longitude, local time and magnetic activity are discriminated and investigated. It is shown that trough production probability depends on the magnetic activity and background ionization. The last is determined by illumination variations and neutral wind

  17. An Index (PC) Aimed at Monitoring the (P)olar (C)ap for Magnetic Activity

    National Oceanic and Atmospheric Administration, Department of Commerce — PC is an index for magnetic activity in the (P)olar (C)ap. It is based on data from a single nearpole station, and aimed to monitor the polar cap magnetic activity...

  18. Determination of the Topology Skeleton of Magnetic Fields in a Solar Active Region

    Hui Zhao; Jing-Xiu Wang; Jun Zhang; Chi-Jie Xiao; Hai-Min Wang

    2008-01-01

    Magnetic topology has been a key to the understanding of magnetic energy re-lease mechanism. Based on observed vector magnetograms, we have determined the three-dimensional (3D) topology skeleton of the magnetic fields in the active region NOAA 10720.The skeleton consists of six 3D magnetic nulls and a network of corresponding spines, fans,and null-null lines. For the first time, we have identified a spiral magnetic null in Sun's corona.The magnetic lines of force twisted around the spine of the null, forming a 'magnetic wreath'with excess of free magnetic energy and resembling observed brightening structures at extra-ultraviolet (EUV) wavebands. We found clear evidence of topology eruptions which are re-ferred to as catastrophic changes of topology skeleton associated with a coronal mass ejection(CME) and an explosive X-ray flare. These results shed new lights on the structural complex-ity and its role in explosive magnetic activity. The concept of flux rope has been widely used in modelling explosive magnetic activity, although their observational identity is rather ob-scure or, at least, lacking of necessary details up to date. We suggest that the magnetic wreath associated with the 3D spiral null is likely an important class of the physical entity of flux ropes.

  19. Restoration of bearings

    Parker, R. J.; Zaretsky, E. V.; Hanau, H.

    1977-01-01

    Process consisting of grinding raceways to oversize but original quality condition and installing new oversize balls or bearings restores wornout ball and roller bearings to original quality, thereby doubling their operating life. Evaluations reveal process results in restoration of 90% of replaced bearings at less than 50% of new-bearing costs.

  20. Magnetic graphene oxide-polystyrene and magnetic activated carbon-polystyrene nanocomposites as sorbents for bisphenol A.

    Rekos, Kyriazis; Kampouraki, Zoi Christina; Samanidou, Victoria; Deliyanni, Eleni

    2016-04-01

    Magnetic graphene oxide-polystyrene and magnetic activated carbon-polystyrene nanocomposites as sorbents for bisphenol A. Kyriazis Rekos1, Zoi Christina Kampouraki1, Victoria Samanidou2, Eleni Deliyanni1 1 Laboratory of General and Inorganic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece 2 Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece The aim of this work was to prepare and characterize novel composites of magnetic activated carbon or magnetic graphene oxide with polystyrene (GO/PSm), through one step simple and effective route. Μagnetite nanoparticles, prepared in the laboratory, were dispersed in the presence of activated carbon (C) or graphene oxide (GO) in a polystyrene (PS) solution in dimethylformamide, at elevated temperature, for the fabrication of the magnetite-Carbon-PS (C-PSm) and magnetite- Graphene Oxide-PS (GO-PSm) hybrid-nanoparticles. For comparison, C-PS and GO-PS composites were also prepared in the same route. The nanocomposites were tested for their sorption ability for an endocrine disruptor, bisphenol A. The effect of solution pH, initial concentration, contact time and temperature were examined. The magnetic graphite oxide-polystyrene presented higher adsorption capacity (100 mg/g) than the non magnetic composites (70 mg/g), as well as than initial graphite oxide (20 mg/g). FTIR, XRD, BET, TGA, VSM and SEM were performed in order to investigate the role of the PS on the better adsorption performance of the mGO-PS nanocomposites. The characterization with these techniques revealed the possible interactions of the surface functional groups of activated carbon and/or graphite oxide with polystyrene that resulted in the better performance of the magnetic nanocomposites for bisphenol A adsorption.

  1. MAGNET

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  2. Immunotherapy of BALB/c mice bearing Ehrlich ascites tumor with vitamin D-binding protein-derived macrophage activating factor.

    Yamamoto, N; Naraparaju, V R

    1997-06-01

    Vitamin D3-binding protein (DBP; human DBP is known as Gc protein) is the precursor of macrophage activating factor (MAF). Treatment of mouse DBP with immobilized beta-galactosidase or treatment of human Gc protein with immobilized beta-galactosidase and sialidase generated a remarkably potent MAF, termed DBPMAF or GcMAF, respectively. The domain of Gc protein responsible for macrophage activation was cloned and enzymatically converted to the cloned MAF, designated CdMAF. In Ehrlich ascites tumor-bearing mice, tumor-specific serum alpha-N-acetylgalactosaminidase (NaGalase) activity increased linearly with time as the transplanted tumor cells grew in the peritoneal cavity. Therapeutic effects of DBPMAF, GcMAF, and CdMAF on mice bearing Ehrlich ascites tumor were assessed by survival time, the total tumor cell count in the peritoneal cavity, and serum NaGalase activity. Mice that received a single administration of DBPMAF or GcMAF (100 pg/mouse) on the same day after transplantation of tumor (1 x 10(5) cells) showed a mean survival time of 35 +/- 4 days, whereas tumor-bearing controls had a mean survival time of 16 +/- 2 days. When mice received the second DBPMAF or GcMAF administration at day 4, they survived more than 50 days. Mice that received two DBPMAF administrations, at days 4 and 8 after transplantation of 1 x 10(5) tumor cells, survived up to 32 +/- 4 days. At day 4 posttransplantation, the total tumor cell count in the peritoneal cavity was approximately 5 x 10(5) cells. Mice that received two DBPMAF administrations, at days 0 and 4 after transplantation of 5 x 10(5) tumor cells, also survived up to 32 +/- 4 days, while control mice that received the 5 x 10(5) ascites tumor cells only survived for 14 +/- 2 days. Four DBPMAF, GcMAF, or CdMAF administrations to mice transplanted with 5 x 10(5) Ehrlich ascites tumor cells with 4-day intervals showed an extended survival of at least 90 days and an insignificantly low serum NaGalase level between days 30 and 90

  3. Magnetic properties of the Bled El Hadba phosphate-bearing formation (Djebel Onk, Algeria): Consequences of the enrichment of the phosphate ore deposit

    Bezzi, Nacer; Aïfa, Tahar; Merabet, Djoudi; Pivan, Jean-Yves

    2008-02-01

    To improve the enrichment of the Thanetian marine phosphate ore deposit from the quarry of Bled El Hadba (Djebel Onk, Algeria) before its exploitation, we first conducted a joint study using different techniques for comparison. These studies reveal that magnetic minerals play a significant role within the matrix of the central productive unit which is squeezed between two other units. Magnetic separation procedures show that there are some positive correlations between magnetic susceptibility and grain size fraction (80-250 μm). These dolomite-rich fractions are more clearly separated. Different tools were used to characterize the magnetic minerals (X-ray, microprobe, differential scanning calorimetry, thermogravimetric and thermomagnetic analyses). They show correlations between magnetic phases and the presence of associated magnetic minerals within the matrix or included in the phosphate ore deposit. They enabled us to distinguish a series of magnetic minerals (magnetite, hematite, maghemite, goethite, ilmenite, pyrite, iron-titanium oxide and titanium oxide sulphate) and to determine that Fe and Ti are prevalent in the separated fractions, following the same variation as Mg. The phosphorous (phosphate) rate is higher in the non-magnetic material, especially in the layers that are rich in dolomitic carbonates (upper and lower units), which could be trapped within the dolomitic matrix, while Magnesium (dolomite) is more important in the magnetic fraction. The separation of phosphate elements and dolomite carbonates is effective and therefore the ore can be enriched through magnetic procedures. Comparison between products enriched by magnetic separation, flotation and calcination showed important differences, chemically, economically and technically speaking.

  4. Active removal of radioactivity in the blood circulation using biotin-bearing liposomes and avidin for rapid tumour imaging

    In order to shorten the delay between the administration of tumour-imaging agents and obtainment of scintigrams, rapid delivery of radionuclide to tumours followed by rapid clearance from the blood is required. We used liposomes with biotin bound on their surface (B-liposomes) as carriers for rapid delivery. For rapid blood clearance, we employed avidin in the expectation that the strong affinity between biotin and avidin would result in the aggregation of B-liposomes in the blood circulation, and that these aggregates would be taken up rapidly by the reticuloendothelial system, resulting in the rapid elimination of liposomes and the radionuclide encapsulated in them. When B-liposomes encapsulating gallium-67 deferoxamine were intravenously administered to mice bearing sarcoma 180, large amounts of 67Ga were delivered to tumours by 4 h after injection, though the 67Ga blood level remained high. On the other hand, administration of avidin 4 h after administration of the B-liposomes dramatically reduced the blood level so that it was only 5% of that in the non-treated group 1 h later. As a result, the tumour-to-blood ratio reached nearly 14 and 5 h after radionuclide administration, suggesting that rapid tumour-imaging will be feasible by means of this method. (orig.)

  5. A review of methods for the decontamination of alpha-bearing waste streams to very low-levels of activity

    This report reviews the processes presently available for the decontamination of alpha-bearing waste effluents. Evaporation, chemical precipitation, organic and inorganic ion exchange, solvent extraction, ultrafiltration, electrical and microbiological processes are considered in turn. Each type of process and its applications in the nuclear industry are briefly described together with the results from any recent development studies. From the information available the advantages and limitations of the process for alpha removal to low-levels (10-2-10-3 Bq/msup(l)) are assessed. It is concluded that no single process is capable of removing the actinides to these very low levels but that this level of decontamination should be achieved by the use of two or more processes either sequentially or in combination; e.g. the use of ultrafiltration or precipitation processes in combination with finely divided inorganic ion exchange materials. Processes involving a good solid-liquid separation, such as ultrafiltration appear to be the most appropriate for actinides which show a tendency to hydrolyse and form colloids. However, there is very limited information available on the removal of actinides by such processes, particularly at levels < Bq/ml. Electrical and biological processes are not yet sufficiently developed for their potential to be properly assessed. (author)

  6. Research on Attitude System of Active Magnetic Control Small Satellite

    Zhaowei, Sun; Di, Yang

    1998-01-01

    When enter orbit, small satellite often tumble as a result of disturbance. How to capture it promptly with finite magnetic torque is an important problem. Because of the coupling of dynamics and control, the small satellite control system is a nonlinear attitude control system with bounds. For high direction and steady precision, an effective method must be found. In this paper, combining with the bound conditions of magnetic torque, two methods are researched. The first is energy method. It ...

  7. Dependence of Stellar Magnetic Activity Cycles on Rotational Period in a Nonlinear Solar-type Dynamo

    Pipin, V. V.; Kosovichev, A. G.

    2016-06-01

    We study the turbulent generation of large-scale magnetic fields using nonlinear dynamo models for solar-type stars in the range of rotational periods from 14 to 30 days. Our models take into account nonlinear effects of dynamical quenching of magnetic helicity, and escape of magnetic field from the dynamo region due to magnetic buoyancy. The results show that the observed correlation between the period of rotation and the duration of activity cycles can be explained in the framework of a distributed dynamo model with a dynamical magnetic feedback acting on the turbulent generation from either magnetic buoyancy or magnetic helicity. We discuss implications of our findings for the understanding of dynamo processes operating in solar-like stars.

  8. Dependence of stellar magnetic activity cycles on rotational period in nonlinear solar-type dynamo

    Pipin, Valery

    2016-01-01

    We study turbulent generation of large-scale magnetic fields using nonlinear dynamo models for solar-type stars in the range of rotational periods from 14 to 30 days. Our models take into account non-linear effects of dynamical quenching of magnetic helicity, and escape of magnetic field from the dynamo region due to magnetic buoyancy. The results show that the observed correlation between the period of rotation and the duration of activity cycles can be explained in the framework of a distributed dynamo model with a dynamical magnetic feedback acting on the turbulent generation either from magnetic buoyancy or magnetic helicity. We discuss implications of our findings for the understanding of dynamo processes operating in solar-like stars.

  9. Differential activation of nerve fibers with magnetic stimulation in humans

    Olree Kenneth S

    2006-07-01

    Full Text Available Abstract Background Earlier observations in our lab had indicated that large, time-varying magnetic fields could elicit action potentials that travel in only one direction in at least some of the myelinated axons in peripheral nerves. The objective of this study was to collect quantitative evidence for magnetically induced unidirectional action potentials in peripheral nerves of human subjects. A magnetic coil was maneuvered to a location on the upper arm where physical effects consistent with the creation of unidirectional action potentials were observed. Electromyographic (EMG and somatosensory evoked potential (SEP recordings were then made from a total of 20 subjects during stimulation with the magnetic coil. Results The relative amplitudes of the EMG and SEP signals changed oppositely when the current direction in the magnetic coil was reversed. This effect was consistent with current direction in the coil relative to the arm for all subjects. Conclusion A differential evocation of motor and sensory fibers was demonstrated and indicates that it may be possible to induce unidirectional action potentials in myelinated peripheral nerve fibers with magnetic stimulation.

  10. Flare activity, sunspot motions, and the evolution of vector magnetic fields in Hale region 17244

    Neidig, Donald F.; Hagyard, Mona J.; Machado, Marcos E.; Smith, Jesse B., Jr.

    1986-01-01

    The magnetic and dynamical circumstances leading to the 1B/M4 flare of November 5, 1980 are studied, and a strong association is found between the buildup of magnetic shear and the onset of flare activity within the active region. The development of shear, as observed directly in vector magnetograms, is consistent in detail with the dynamical history of the active region and identifies the precise location of the optical and hard-X-ray kernels of the flare emission.

  11. Activation of tumor suppressor p53 gene expression by magnetic thymine-imprinted chitosan nanoparticles.

    Lee, Mei-Hwa; Thomas, James L; Chen, Jian-Zhou; Jan, Jeng-Shiung; Lin, Hung-Yin

    2016-02-01

    Chitosan is a natural biodegradable polysaccharide that has been used to enhance gene delivery, owing to the ease with which chitosan nanoparticles enter the nucleus of cells. To study the effects of nuclear delivery of telomeric gene sequences, which contain thymine, we formed magnetic thymine-imprinted chitosan nanoparticles (TIPs) by the precipitation of chitosan, mixed with thymine and magnetic nanoparticles (to aid in separations). The mean size of the TIPS was 116 ± 18 nm; the dissociation constant for thymine was 21.8 mg mL(-1). We then treated human hepatocellular carcinoma (HepG2) with TIPs nanoparticles bearing bound thymine or a bound telomeric DNA sequence. The expression of the tumor suppressor p53 gene increased when TIPs were applied and decreased when telomere-bound TIPs were applied. PMID:26693943

  12. The slow dissociation rate of K-1602 contributes to the enhanced inhibitory activity of this novel alkyl-aryl-bearing fluoroketolide.

    Krokidis, Marios; Bougas, Anthony; Stavropoulou, Maria; Kalpaxis, Dimitrios; Dinos, George P

    2016-04-01

    Ketolides belong to the latest generation of macrolides and are not only effective against macrolide susceptible bacterial strains but also against some macrolide resistant strains. Here we present data providing insights into the mechanism of action of K-1602, a novel alkyl-aryl-bearing fluoroketolide. According to our data, the K-1602 interacts with the ribosome as a one-step slow binding inhibitor, displaying an association rate constant equal to 0.28 × 10(4 )M(-1) s(-1) and a dissociation rate constant equal to 0.0025 min(-1). Both constants contribute to produce an overall inhibition constant Ki equal to 1.49 × 10(-8 )M, which correlates very well with the superior activity of this compound when compared with many other ketolides or fluoroketolides. PMID:25807301

  13. Pharmacokinetics and anti-tumour activity of LM985 in mice bearing transplantable adenocarcinomas of the colon.

    Double, J A; Bibby, M. C.; Loadman, P.M.

    1986-01-01

    LM985 is one of a series of compounds based on the flavone ring structure and selected for clinical trial primarily for its activity in colon 38 as part of the NCI screen. We have investigated the anti-tumour activity against three differing transplantable adenocarcinomas of the mouse colon (MAC). Single i.p. injection at maximum tolerated dose showed no activity against the ascitic tumour MAC 15A, moderate activity against subcutaneous tumours MAC 13 and MAC 15A and produced a significant gr...

  14. Thermally-Activated Magnetic Reversal Induced by a Spin-Polarized Current

    Myers, E. B.; Albert, F. J.; Saneky, J. C.; Bonet, E.; Buhrman, R. A.; Ralph, D. C.

    2002-01-01

    We have measured the statistical properties of magnetic reversal in nanomagnets driven by a spin-polarized current. Like reversal induced by a magnetic field, spin-transfer-driven reversal near room temperature exhibits the properties of thermally-activated escape over an effective barrier. However, the spin-transfer effect produces qualitatively different behaviors than an applied magnetic field. We discuss an effective current vs. field phase diagram. If the current and field are tuned so t...

  15. Anticancer activity of subfractions containing pure compounds of Chaga mushroom (Inonotus obliquus) extract in human cancer cells and in Balbc/c mice bearing Sarcoma-180 cells.

    Chung, Mi Ja; Chung, Cha-Kwon; Jeong, Yoonhwa; Ham, Seung-Shi

    2010-06-01

    The Chaga mushroom (Inonotus obliquus) has been used in folk medicine to treat cancers. However, limited information exists on the underlying anticancer effects of the major component of I. obliquusin vivo. We hypothesize that the pure compounds (3beta-hydroxy-lanosta-8,24-dien-21-al, inotodiol and lanosterol, respectively) separated from I. obliquus would inhibit tumor growth in Balbc/c mice bearing Sarcoma-180 cells (S-180) in vivo and growth of human carcinoma cells in vitro. To test this hypothesis, the growth inhibition of each subfraction isolated from I. obliquus on human carcinoma cell lines (lung carcinoma A-549 cells, stomach adenocarcinoma AGS cells, breast adenocarcinoma MCF-7 cells, and cervical adenocarcinoma HeLa cells) was tested in vitro. Then, after S-180 implantation, the mice were fed a normal chow supplemented with 0, 0.1 or 0.2 mg of subfraction 1, 2 or 3 per mouse per day. All of the subfractions isolated from I. obliquus showed significant cytotoxic activity against the selected cancer cell lines in vitro. Subfraction 1 was more active than subfraction 2 and subfraction 3 against the A549, AGS and MCF-7 cancer cell lines in vitro. In in vivo results, subfraction 1 isolated from I. obliquus at concentrations of 0.1 and 0.2 mg/mouse per day significantly decreased tumor volume by 23.96% and 33.71%, respectively, as compared with the control. Subfractions 2 and 3 also significantly inhibited tumor growth in mice bearing S-180 as compared with the control mouse tumor. Subfraction 1 isolated from I. obliquus showed greater inhibition of tumor growth than subfractions 2 and 3, which agrees well with the in vitro results. The results suggest that I. obliquus and its compounds in these subfractions isolated from I. obliquus could be used as natural anticancer ingredients in the food and/or pharmaceutical industry. PMID:20607061

  16. Optimization of superconducting tiling pattern for superconducting bearings

    Hull, John R.

    1996-01-01

    An apparatus and method for reducing magnetic field inhomogeneities which produce rotational loss mechanisms in high temperature superconducting magnetic bearings. Magnetic field inhomogeneities are reduced by dividing high temperature superconducting structures into smaller structures, and arranging the smaller structures into tiers which stagger the magnetic field maximum locations of the smaller structures.

  17. Toward Modelling Topsoil Magnetic Susceptibility for Demining Activities

    Hannam, J. A.; Dearing, J. A.

    2003-12-01

    The Landmine Monitor estimates that landmines cause up to 20,000 fatalities and casualties worldwide every year, in over 100 countries affected by landmine contamination. Although detection technologies have become more sophisticated, the metal detector still remains the most widely employed detection system in landmine affected regions. With increased use of minimum metal mines, the performance and sensitivity of metal detectors are increasingly challenged. In addition to mine constituents, depth of burial and orientation, soil properties significantly affect metal detection capabilities. Soils with high magnetic susceptibility, in particular those dominated by viscous components, interfere with the response signal in both frequency and time domain metal detection systems. Using Bosnia and Herzegovina (BiH) as a pilot region, we created an expert system to predict topsoil susceptibility from environmental information within a SOTER data base. Initially, the knowledge base is constructed from published relationships of environmental parameters and magnetic susceptibility and knowledge of experts in the field of soil magnetism. The knowledge base is underpinned by environmental conditions that are known to enhance or reduce magnetic susceptibility in topsoils. Where semi-quantitative data exists, transfer-functions are used to provide first approximations of susceptibility classes and offer a basis for a probability score for the susceptibility class. As a first approximation, susceptibility values are categorized into five continuous classes delimited by published magnetic susceptibility ranges in topsoils. The predicted susceptibility maps result in regional contrasts, delineated by the spatial scale of the environmental information. Further development of the model using a Baysean rule-based system with fuzzy boundaries is anticipated. Validation of the model is proposed using archived soil survey samples from BiH. In addition to providing essential data for

  18. The iInfluence of reinforcement function definition on properties of Q-learning based controller for active magnetic bearing

    Březina, Tomáš; Krejsa, Jiří

    Trenčianske Teplice : University of Trenčín, 2003, s. 62-65. ISBN 80-88914-92-2. [Mechatronika 2003. Trenčianske Teplice (SK), 18.06.2003-20.06.2003] Institutional research plan: CEZ:AV0Z2076919 Keywords : Q-learning * control Subject RIV: JB - Sensors, Measurment, Regulation

  19. Time scheduling of magnetic surveys in mid-latitudes with respect to forecasting geomagnetic activity

    Hejda, Pavel; Bochníček, Josef; Horáček, Josef; Nejedlá, Jaroslava

    2006-01-01

    Roč. 58, č. 6 (2006), s. 735-740. ISSN 1343-8832 R&D Projects: GA AV ČR IAA3012105 Institutional research plan: CEZ:AV0Z30120515 Keywords : magnetic surveys * repeat stations * geomagnetic activity Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.954, year: 2006

  20. Employing Magnetic Levitation to Monitor Reaction Kinetics and Measure Activation Energy

    Benz, Lauren; Cesafsky, Karen E.; Le, Tran; Park, Aileen; Malicky, David

    2012-01-01

    This article describes a simple and inexpensive undergraduate-level kinetics experiment that uses magnetic levitation to monitor the progress and determine the activation energy of a condensation reaction on a polymeric solid support. The method employs a cuvette filled with a paramagnetic solution positioned between two strong magnets. The…