Adaptive vibration control using synchronous demodulation with machine tool controller motor commutation

DOEpatents

Hopkins, David James [Livermore, CA

2008-05-13

A control system and method for actively reducing vibration in a spindle housing caused by unbalance forces on a rotating spindle, by measuring the force-induced spindle-housing motion, determining control signals based on synchronous demodulation, and provide compensation for the measured displacement to cancel or otherwise reduce or attenuate the vibration. In particular, the synchronous demodulation technique is performed to recover a measured spindle housing displacement signal related only to the rotation of a machine tool spindle, and consequently rejects measured displacement not related to spindle motion or synchronous to a cycle of revolution. Furthermore, the controller actuates at least one voice-coil (VC) motor, to cancel the original force-induced motion, and adapts the magnitude of voice coil signal until this measured displacement signal is brought to a null. In order to adjust the signal to a null, it must have the correct phase relative to the spindle angle. The feedback phase signal is used to adjust a common (to both outputs) commutation offset register (offset relative to spindle encoder angle) to force the feedback phase signal output to a null. Once both of these feedback signals are null, the system is compensating properly for the spindle-induced motion.

Feedback regulated induction heater for a flowing fluid

DOEpatents

Migliori, Albert; Swift, Gregory W.

1985-01-01

A regulated induction heater for heating a stream of flowing fluid to a predetermined desired temperature. The heater includes a radiofrequency induction coil which surrounds a glass tube through which the fluid flows. A heating element consisting of a bundle of approximately 200 stainless steel capillary tubes located within the glass tube couples the output of the induction coil to the fluid. The temperature of the fluid downstream from the heating element is sensed with a platinum resistance thermometer, the output of which is applied to an adjustable proportional and integral feedback control circuit which regulates the power applied to the induction coil. The heater regulates the fluid temperature to within 0.005.degree. C. at a flow rate of 50 cm.sup.3 /second with a response time of less than 0.1 second, and can accommodate changes in heat load up to 1500 watts.

Feedback regulated induction heater for a flowing fluid

DOEpatents

Migliori, A.; Swift, G.W.

1984-06-13

A regulated induction heater for heating a stream of flowing fluid to a predetermined desired temperature. The heater includes a radiofrequency induction coil which surrounds a glass tube through which the fluid flows. A heating element consisting of a bundle of approximately 200 stainless steel capillary tubes located within the glass tube couples the output of the induction coil to the fluid. The temperature of the fluid downstream from the heating element is sensed with a platinum resistance thermometer, the output of which is applied to an adjustable porportional and integral feedback control circuit which regulates the power applied to the induction coil. The heater regulates the fluid temperature to within 0.005/sup 0/C at a flow rate of 50 cm/sup 3//sec with a response time of less than 0.1 second, and can accommodate changes in heat load up to 1500 watts.

Improvement of wireless power transmission efficiency of implantable subcutaneous devices by closed magnetic circuit mechanism.

PubMed

Jo, Sung-Eun; Joung, Sanghoon; Suh, Jun-Kyo Francis; Kim, Yong-Jun

2012-09-01

Induction coils were fabricated based on flexible printed circuit board for inductive transcutaneous power transmission. The coil had closed magnetic circuit (CMC) structure consisting of inner and outer magnetic core. The power transmission efficiency of the fabricated device was measured in the air and in vivo condition. It was confirmed that the CMC coil had higher transmission efficiency than typical air-core coil. The power transmission efficiency during a misalignment between primary coil and implanted secondary coil was also evaluated. The decrease of mutual inductance between the two coils caused by the misalignment led to a low efficiency of the inductive link. Therefore, it is important to properly align the primary coil and implanted secondary coil for effective power transmission. To align the coils, a feedback coil was proposed. This was integrated on the backside of the primary coil and enabled the detection of a misalignment of the primary and secondary coils. As a result of using the feedback coil, the primary and secondary coils could be aligned without knowledge of the position of the implanted secondary coil.

Subranging scheme for SQUID sensors

NASA Technical Reports Server (NTRS)

Penanen, Konstantin I. (Inventor)

2008-01-01

A readout scheme for measuring the output from a SQUID-based sensor-array using an improved subranging architecture that includes multiple resolution channels (such as a coarse resolution channel and a fine resolution channel). The scheme employs a flux sensing circuit with a sensing coil connected in series to multiple input coils, each input coil being coupled to a corresponding SQUID detection circuit having a high-resolution SQUID device with independent linearizing feedback. A two-resolution configuration (course and fine) is illustrated with a primary SQUID detection circuit for generating a fine readout, and a secondary SQUID detection circuit for generating a course readout, both having feedback current coupled to the respective SQUID devices via feedback/modulation coils. The primary and secondary SQUID detection circuits function and derive independent feedback. Thus, the SQUID devices may be monitored independently of each other (and read simultaneously) to dramatically increase slew rates and dynamic range.

An active homopolar magnetic bearing with high temperature superconductor (HTS) coils and ferromagnetic cores

NASA Technical Reports Server (NTRS)

Brown, G. V.; Dirusso, E.; Provenza, A. J.

1995-01-01

A proof-of-feasibility demonstration showed that high temperature superconductor (HTS) coils can be used in a high-load, active magnetic bearing in liquid nitrogen. A homopolar radial bearing with commercially wound HTS (Bi 2223) bias and control coils produced over 200 lb (890 N) radial load capacity (measured non-rotating) and supported a shaft to 14000 rpm. The goal was to show that HTS coils can operate stably with ferromagnetic cores in a feedback controlled system at a current density similar to that in Cu in liquid nitrogen. Design compromises permitted use of circular coils with rectangular cross section. Conductor improvements will eventually permit coil shape optimization, higher current density and higher bearing load capacity. The bias coil, wound with non-twisted, multifilament HTS conductor, required negligible power to carry its direct current. The control coils were wound with monofilament HTS sheathed in Ag. These dissipated negligible power for direct current (i.e. for steady radial load components). When an alternating current (AC) was added, the AC component dissipated power which increased rapidly with frequency and quadratically with AC amplitude. In fact at frequencies above about 2 hz, the effective resistance of the control coil conductor actually exceeds that of the silver which is in electrical parallel with the oxide superconductor. This is at least qualitatively understandable in the context of a Bean-type model of flux and current penetration into a Type II superconductor. Fortunately the dynamic currents required for bearing stability are of small amplitude. These results show that while twisted multifilament conductor is not needed for stable levitation, twisted multifilaments will be required to reduce control power for sizable dynamic loads, such as those due to unbalance.

Control of twisted and coiled polymer actuator with anti-windup compensator

NASA Astrophysics Data System (ADS)

Suzuki, Motoya; Kamamichi, Norihiro

2018-07-01

A twisted and coiled polymer actuator (TCPA) is a novel soft actuator. It is fabricated by twisting nylon thread or fishing line. It can be thermally activated and has remarkable properties such as high power/mass ratio and large deformation. By applying conductive nylon fibers to the actuator, it can be electrically driven by Joule heating. However, if a controller of the actuator is designed without considering an input saturation, the control performance may be descended by windup phenomena. In this paper, to solve this problem, a feedback control with an anti-windup compensator is applied. The validity of the applied method is investigated through numerical simulations and experiments.

Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olofsson, K. E. J.; Choi, W.; Humphreys, D. A.

A basic nonlinear electromechanical model is developed for the interaction between a pre-existing near-saturated tearing-mode, a conducting wall, active coils internal to the wall, and active coils external to the wall. The tearing-mode is represented by a perturbed helical surface current and its island has a small but finite moment of inertia. The model is shown to have several properties that are qualitatively consistent with the experimental observations of mode-wall and mode-coil interactions. The main purpose of the model is to guide the design of a phase control system for locked modes (LMs) in tokamaks. Such a phase controller maymore » become an important component in integrated disruption avoidance systems. A realistic feedback controller for the LM phase is designed and tested for the electromechanical model. The results indicate that a simple fixed-gain controller can perform phase control of LMs with a range of sizes, and at arbitrary misalignment relative to a realistically dimensioned background error field. Finally, the basic model is expected to be a useful minimal dynamical system representation also for other aspects of mode-wall-coil interactions.« less

Electromechanical modelling and design for phase control of locked modes in the DIII-D tokamak

DOE PAGES

Olofsson, K. E. J.; Choi, W.; Humphreys, D. A.; ...

2016-02-05

A basic nonlinear electromechanical model is developed for the interaction between a pre-existing near-saturated tearing-mode, a conducting wall, active coils internal to the wall, and active coils external to the wall. The tearing-mode is represented by a perturbed helical surface current and its island has a small but finite moment of inertia. The model is shown to have several properties that are qualitatively consistent with the experimental observations of mode-wall and mode-coil interactions. The main purpose of the model is to guide the design of a phase control system for locked modes (LMs) in tokamaks. Such a phase controller maymore » become an important component in integrated disruption avoidance systems. A realistic feedback controller for the LM phase is designed and tested for the electromechanical model. The results indicate that a simple fixed-gain controller can perform phase control of LMs with a range of sizes, and at arbitrary misalignment relative to a realistically dimensioned background error field. Finally, the basic model is expected to be a useful minimal dynamical system representation also for other aspects of mode-wall-coil interactions.« less

Construction and Operation of an Internal Coil Device, RT-1, with a High-Temperature Superconductor

NASA Astrophysics Data System (ADS)

Ogawa, Yuichi; Yoshida, Zensho; Morikawa, Junji; Saito, Haruhiko; Watanabe, Sho; Yano, Yoshihisa; Mizumaki, Shoichi; Tosaka, Taizo

An internal coil device called Ring Trap-1 (RT-1) has been constructed to explore an innovative concept for a high-beta plasma based on a new relaxation theory. A high-temperature superconductor (HTS) Bi-2223 tape is employed for the internal coil of RT-1. The coil is cooled to 20 K with helium gas supplied by G-M refrigerators, and charged to a magnetomotive force of 250 kA using an external power supply. For these cooling and charging methods, we have developed several innovative techniques such as a demountable transfer tube system, persistent current switch, detachable electrode, and others. In addition, we have paid much attention to the deterioration of the HTS tape during the fabrication of the internal coil. As a result, we have demonstrated that the decay of the persistent current of the internal coil is ˜1% during 8 h. The internal coil is lifted with a levitation coil located at the upper region of the vacuum vessel. The coil position monitored with laser sensors is feedback controlled through the regulation of the levitation coil current. Stable levitation for a few hours has been demonstrated for various plasma experiments.

New MHD feedback control schemes using the MARTe framework in RFX-mod

NASA Astrophysics Data System (ADS)

Piron, Chiara; Manduchi, Gabriele; Marrelli, Lionello; Piovesan, Paolo; Zanca, Paolo

2013-10-01

Real-time feedback control of MHD instabilities is a topic of major interest in magnetic thermonuclear fusion, since it allows to optimize a device performance even beyond its stability bounds. The stability properties of different magnetic configurations are important test benches for real-time control systems. RFX-mod, a Reversed Field Pinch experiment that can also operate as a tokamak, is a well suited device to investigate this topic. It is equipped with a sophisticated magnetic feedback system that controls MHD instabilities and error fields by means of 192 active coils and a corresponding grid of sensors. In addition, the RFX-mod control system has recently gained new potentialities thanks to the introduction of the MARTe framework and of a new CPU architecture. These capabilities allow to study new feedback algorithms relevant to both RFP and tokamak operation and to contribute to the debate on the optimal feedback strategy. This work focuses on the design of new feedback schemes. For this purpose new magnetic sensors have been explored, together with new algorithms that refine the de-aliasing computation of the radial sideband harmonics. The comparison of different sensor and feedback strategy performance is described in both RFP and tokamak experiments.

Position control system for use with micromechanical actuators

DOEpatents

Guckel, Henry; Stiers, Eric W.

2000-01-01

A positioning system adapted for use with micromechanical actuators provides feedback control of the position of the movable element of the actuator utilizing a low Q sensing coil. The effective inductance of the sensing coil changes with position of the movable element to change the frequency of oscillation of a variable oscillator. The output of the variable oscillator is compared in a phase detector to a reference oscillator signal. The phase detector provides a pulsed output having a pulse duty cycle related to the phase or frequency difference between the oscillator signals. The output of the phase detector is provided to a drive coil which applies a magnetic force to the movable element which balances the force of a spring. The movable element can be displaced to a new position by changing the frequency of the reference oscillator.

Resonant magnetic perturbation effect on tearing mode dynamics

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Olofsson, K. E. J.; Brunsell, P. R.; Drake, J. R.

2010-03-01

The effect of a resonant magnetic perturbation (RMP) on the tearing mode (TM) dynamics is experimentally studied in the EXTRAP T2R device. EXTRAP T2R is equipped with a set of sensor coils and active coils connected by a digital controller allowing a feedback control of the magnetic instabilities. The recently upgraded feedback algorithm allows the suppression of all the error field harmonics but keeping a selected harmonic to the desired amplitude, therefore opening the possibility of a clear study of the RMP effect on the corresponding TM. The paper shows that the RMP produces two typical effects: (1) a weak oscillation in the TM amplitude and a modulation in the TM velocity or (2) a strong modulation in the TM amplitude and phase jumps. Moreover, the locking mechanism of a TM to a RMP is studied in detail. It is shown that before the locking, the TM dynamics is characterized by velocity modulation followed by phase jumps. Experimental results are reasonably explained by simulations obtained with a model.

On-coil multiple channel transmit system based on class-D amplification and pre-amplification with current amplitude feedback

PubMed Central

Gudino, N.; Heilman, J.A; Riffe, M. J.; Heid, O.; Vester, M.; Griswold, M.A.

2016-01-01

A complete high-efficiency transmit amplifier unit designed to be implemented in on-coil transmit arrays is presented. High power capability, low power dissipation, scalability and cost minimization were some of the requirements imposed to the design. The system is composed of a current mode class-D (CMCD) amplifier output stage and a voltage mode class-D (VMCD) preamplification stage. The amplitude information of the radio frequency pulse was added through a customized step-down DC-DC converter with current amplitude feedback that connects to the CMCD stage. Benchtop measurements and imaging experiments were carried out to analyze system performance. Direct control of B1 was possible and its load sensitivity was reduced to less than 10% variation from unloaded to full loaded condition. When using the amplifiers in an array configuration, isolation above 20 dB was achieved between neighboring coils by the amplifier decoupling method. High output current operation of the transmitter was proved on the benchtop through output power measurements and in a 1.5 T scanner through flip angle quantification. Finally, single and multiple channel excitations with the new hardware were demonstrated by receiving signal with the body coil of the scanner. PMID:22890962

On-coil multiple channel transmit system based on class-D amplification and pre-amplification with current amplitude feedback.

PubMed

Gudino, Natalia; Heilman, Jeremiah A; Riffe, Matthew J; Heid, Oliver; Vester, Markus; Griswold, Mark A

2013-07-01

A complete high-efficiency transmit amplifier unit designed to be implemented in on-coil transmit arrays is presented. High power capability, low power dissipation, scalability, and cost minimization were some of the requirements imposed to the design. The system is composed of a current mode class-D amplifier output stage and a voltage mode class-D preamplification stage. The amplitude information of the radio frequency pulse was added through a customized step-down DC-DC converter with current amplitude feedback that connects to the current mode class-D stage. Benchtop measurements and imaging experiments were carried out to analyze system performance. Direct control of B1 was possible and its load sensitivity was reduced to less than 10% variation from unloaded to full loaded condition. When using the amplifiers in an array configuration, isolation above 20 dB was achieved between neighboring coils by the amplifier decoupling method. High output current operation of the transmitter was proved on the benchtop through output power measurements and in a 1.5T scanner through flip angle quantification. Finally, single and multiple channel excitations with the new hardware were demonstrated by receiving signal with the body coil of the scanner. Copyright © 2012 Wiley Periodicals, Inc.

Spherical Harmonic Inductive Detection Coils and their use In Dynamic Pre-emphasis for Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Edler, Karl T.

The issue of eddy currents induced by the rapid switching of magnetic field gradients is a long-standing problem in magnetic resonance imaging. A new method for dealing with this problem is presented whereby spatial harmonic components of the magnetic field are continuously sensed, through their temporal rates of change, and corrected. In this way, the effects of the eddy currents on multiple spatial harmonic components of the magnetic field can be detected and corrections applied during the rise time of the gradients. Sensing the temporal changes in each spatial harmonic is made possible with specially designed detection coils. However to make the design of these coils possible, general relationships between the spatial harmonics of the field, scalar potential, and vector potential are found within the quasi-static approximation. These relationships allow the vector potential to be found from the field -- an inverse curl operation -- and may be of use beyond the specific problem of detection coil design. Using the detection coils as sensors, methods are developed for designing a negative feedback system to control the eddy current effects and optimizing that system with respect to image noise and distortion. The design methods are successfully tested in a series of proof-of-principle experiments which lead to a discussion of how to incorporate similar designs into an operational MRI. Keywords: magnetic resonance imaging, eddy currents, dynamic shimming, negative feedback, quasi-static fields, vector potential, inverse curl

Loss-of-Control-Inhibitor Systems for Aircraft

NASA Technical Reports Server (NTRS)

AHarrah, Ralph C.

2007-01-01

Systems to provide improved tactile feedback to aircraft pilots are being developed to help the pilots maintain harmony between their control actions and the positions of aircraft control surfaces, thereby helping to prevent loss of control. A system of this type, denoted a loss-of-control-inhibitor system (LOCIS) can be implemented as a relatively simple addition to almost any pre-existing flight-control system. The LOCIS concept offers at least a partial solution to the problem of (1) keeping a pilot aware of the state of the control system and the aircraft and (2) maintaining sufficient control under conditions that, as described below, have been known to lead to loss of control. Current commercial aircraft exhibit uneven responses of primary flight-control surfaces to aggressive pilot control commands, leading to deterioration of pilots ability to control their aircraft. In severe cases, this phenomenon can result in loss of control and consequent loss of aircraft. For an older aircraft equipped with a purely mechanical control system, the loss of harmony between a pilot s command action and the control- surface response can be attributed to compliance in the control system (caused, for example, by stretching of control cables, flexing of push rods, or servo-valve distortion). In a newer aircraft equipped with a fly-by-wire control system, the major contributions to loss of harmony between the pilot and the control surfaces are delays attributable to computer cycle time, control shaping, filtering, aliasing, servo-valve distortion, and actuator rate limiting. In addition, a fly-by-wire control system provides no tactile feedback that would enable the pilot to sense such features of the control state as surface flutter, surface jam, position limiting, actuator rate limiting, and control limiting imposed by the aircraft operational envelope. Hence, for example, when a pilot is involved in aggressive closed-loop maneuvering, as when encountering a wake-vortex upset on final landing approach, the control-surface delay can lead to loss of control. Aggressive piloting can be triggered and exacerbated by control-system anomalies, which the pilot cannot diagnose because of the lack of symptoms caused by the absence of feedback through the controls. The purpose served by a LOCIS is to counteract these adverse effects by providing real-time feedback that notifies the pilot that the aircraft is tending to lag the pilot s commands. A LOCIS (see figure) includes cockpit control input-position sensors, control-surface output-position sensors, variable dampers (for example, shock absorbers containing magneto-rheological fluids such that the damping forces can be varied within times of the order of milliseconds by varying applied magnetic fields) attached to the cockpit control levers, electromagnet coils to apply the magnetic fields, and feedback control circuits to drive the electromagnet coils. The feedback control gains are chosen so that the current applied to each electromagnet coil results in a damping force that increases in a suitable nonlinear manner (e.g., exponentially) with the difference between the actual and commanded positions of the affected control surface. The increasing damping force both alerts the pilot to the onset of a potentially dangerous situation and resists the pilot s effort to command a control surface to change position at an excessive rate

Linear motor drive system for continuous-path closed-loop position control of an object

DOEpatents

Barkman, William E.

1980-01-01

A precision numerical controlled servo-positioning system is provided for continuous closed-loop position control of a machine slide or platform driven by a linear-induction motor. The system utilizes filtered velocity feedback to provide system stability required to operate with a system gain of 100 inches/minute/0.001 inch of following error. The filtered velocity feedback signal is derived from the position output signals of a laser interferometer utilized to monitor the movement of the slide. Air-bearing slides mounted to a stable support are utilized to minimize friction and small irregularities in the slideway which would tend to introduce positioning errors. A microprocessor is programmed to read command and feedback information and converts this information into the system following error signal. This error signal is summed with the negative filtered velocity feedback signal at the input of a servo amplifier whose output serves as the drive power signal to the linear motor position control coil.

Vector magnetometer design study: Analysis of a triaxial fluxgate sensor design demonstrates that all MAGSAT Vector Magnetometer specifications can be met

NASA Technical Reports Server (NTRS)

Adams, D. F.; Hartmann, U. G.; Lazarow, L. L.; Maloy, J. O.; Mohler, G. W.

1976-01-01

The design of the vector magnetometer selected for analysis is capable of exceeding the required accuracy of 5 gamma per vector field component. The principal elements that assure this performance level are very low power dissipation triaxial feedback coils surrounding ring core flux-gates and temperature control of the critical components of two-loop feedback electronics. An analysis of the calibration problem points to the need for improved test facilities.

Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod

DOE PAGES

Okabayashi, M.; Zanca, P.; Strait, E. J.; ...

2016-11-25

Disruptions caused by tearing modes (TMs) are considered to be one of the most critical roadblocks to achieving reliable, steady-state operation of tokamak fusion reactors. We have demonstrated a promising scheme to avoid mode locking by utilizing the electro-magnetic (EM) torque produced with 3D coils that are available in many tokamaks. In this scheme, the EM torque is delivered to the modes by a toroidal phase shift between the externally applied field and the excited TM fields, compensating for the mode momentum loss through the interaction with the resistive wall and uncorrected error fields. Fine control of torque balance ismore » provided by a feedback scheme. We have explored this approach in two widely different devices and plasma conditions: DIII-D and RFX-mod operated in tokamak mode. In DIII-D, the plasma target was high β N in a non-circular divertor tokamak. We define β N as β N = β/(I p /aB t) (%Tm/MA), where β, I p, a, B t are the total stored plasma pressure normalized by the magnetic pressure, plasma current, plasma minor radius and toroidal magnetic field at the plasma center, respectively. The RFX-mod plasma was ohmically-heated with ultra-low safety factor in a circular limiter discharge with active feedback coils outside the thick resistive shell. The DIII-D and RFX-mod experiments showed remarkable consistency with theoretical predictions of torque balance. The application to ignition-oriented devices such as the International Thermonuclear Experimental Reactor (ITER) would expand the horizon of its operational regime. Finally, the internal 3D coil set currently under consideration for edge localized mode suppression in ITER would be well suited for this purpose.« less

Avoidance of tearing mode locking with electro-magnetic torque introduced by feedback-based mode rotation control in DIII-D and RFX-mod

NASA Astrophysics Data System (ADS)

Okabayashi, M.; Zanca, P.; Strait, E. J.; Garofalo, A. M.; Hanson, J. M.; In, Y.; La Haye, R. J.; Marrelli, L.; Martin, P.; Paccagnella, R.; Paz-Soldan, C.; Piovesan, P.; Piron, C.; Piron, L.; Shiraki, D.; Volpe, F. A.; DIII-D, The; RFX-mod Teams

2017-01-01

Disruptions caused by tearing modes (TMs) are considered to be one of the most critical roadblocks to achieving reliable, steady-state operation of tokamak fusion reactors. Here we have demonstrated a promising scheme to avoid mode locking by utilizing the electro-magnetic (EM) torque produced with 3D coils that are available in many tokamaks. In this scheme, the EM torque is delivered to the modes by a toroidal phase shift between the externally applied field and the excited TM fields, compensating for the mode momentum loss through the interaction with the resistive wall and uncorrected error fields. Fine control of torque balance is provided by a feedback scheme. We have explored this approach in two widely different devices and plasma conditions: DIII-D and RFX-mod operated in tokamak mode. In DIII-D, the plasma target was high β N in a non-circular divertor tokamak. Here β N is defined as β N  =  β/(I p /aB t) (%Tm/MA), where β, I p, a, B t are the total stored plasma pressure normalized by the magnetic pressure, plasma current, plasma minor radius and toroidal magnetic field at the plasma center, respectively. The RFX-mod plasma was ohmically-heated with ultra-low safety factor in a circular limiter discharge with active feedback coils outside the thick resistive shell. The DIII-D and RFX-mod experiments showed remarkable consistency with theoretical predictions of torque balance. The application to ignition-oriented devices such as the International Thermonuclear Experimental Reactor (ITER) would expand the horizon of its operational regime. The internal 3D coil set currently under consideration for edge localized mode suppression in ITER would be well suited for this purpose.

Partial Arc Curvilinear Direct Drive Servomotor

NASA Technical Reports Server (NTRS)

Sun, Xiuhong (Inventor)

2014-01-01

A partial arc servomotor assembly having a curvilinear U-channel with two parallel rare earth permanent magnet plates facing each other and a pivoted ironless three phase coil armature winding moves between the plates. An encoder read head is fixed to a mounting plate above the coil armature winding and a curvilinear encoder scale is curved to be co-axis with the curvilinear U-channel permanent magnet track formed by the permanent magnet plates. Driven by a set of miniaturized power electronics devices closely looped with a positioning feedback encoder, the angular position and velocity of the pivoted payload is programmable and precisely controlled.

Underwater (UW) Unexploded Ordnance (UXO) Multi-Sensor Data Base (MSDB) Collection

DTIC Science & Technology

2009-07-01

11 FIGURE 6 RTG SENSOR. FOUR SENSOR TRIADS ARE SHOWN, EACH WITH A 3-AXIS FLUXGATE MAGNETOMETER ...used by RTG to measure the gradients. Each triad includes a 3-axis fluxgate magnetometer and a set of feedback coils. The outputs of three triad...each with a 3-axis fluxgate magnetometer (internal, not clearly visible) and a set of 3 feedback coils. The upper triad 3-axis magnetometer

Displacement control of an antagonistic-type twisted and coiled polymer actuator

NASA Astrophysics Data System (ADS)

Suzuki, Motoya; Kamamichi, Norihiro

2018-03-01

A novel artificial muscle actuator referred to as a twisted and coiled polymer actuator can be easily fabricated by commercially available nylon fibers. It can be thermally activated and has remarkable properties such as large deformation and flexibility. The actuator uses conductive nylon fibers and can be activated by Joule heating and is easily controlled electrically. However, asymmetric response characteristics due to a speed difference in heating-cooling are a problem. In the case of actuation in air, the cooling speed depends on the external temperature, and is slower than the heating speed. To solve these problems, we apply an antagonistic structure. The validity of the applied method is investigated through numerical simulations and experiments. The response characteristics of the PID feedback control and the 2-DOF control of the displacement are investigated.

Co-located haptic and 3D graphic interface for medical simulations.

PubMed

Berkelman, Peter; Miyasaka, Muneaki; Bozlee, Sebastian

2013-01-01

We describe a system which provides high-fidelity haptic feedback in the same physical location as a 3D graphical display, in order to enable realistic physical interaction with virtual anatomical tissue during modelled procedures such as needle driving, palpation, and other interventions performed using handheld instruments. The haptic feedback is produced by the interaction between an array of coils located behind a thin flat LCD screen, and permanent magnets embedded in the instrument held by the user. The coil and magnet configuration permits arbitrary forces and torques to be generated on the instrument in real time according to the dynamics of the simulated tissue by activating the coils in combination. A rigid-body motion tracker provides position and orientation feedback of the handheld instrument to the computer simulation, and the 3D display is produced using LCD shutter glasses and a head-tracking system for the user.

Feedback-Driven Mode Rotation Control by Electro-Magnetic Torque

NASA Astrophysics Data System (ADS)

Okabayashi, M.; Strait, E. J.; Garofalo, A. M.; La Haye, R. J.; in, Y.; Hanson, J. M.; Shiraki, D.; Volpe, F.

2013-10-01

The recent experimental discovery of feedback-driven mode rotation control, supported by modeling, opens new approaches for avoidance of locked tearing modes that otherwise lead to disruptions. This approach is an application of electro-magnetic (EM) torque using 3D fields, routinely maximized through a simple feedback system. In DIII-D, it is observed that a feedback-applied radial field can be synchronized in phase with the poloidal field component of a large amplitude tearing mode, producing the maximum EM torque input. The mode frequency can be maintained in the 10 Hz to 100 Hz range in a well controlled manner, sustaining the discharges. Presently, in the ITER internal coils designed for edge localized mode (ELM) control can only be varied at few Hz, yet, well below the inverse wall time constant. Hence, ELM control system could in principle be used for this feedback-driven mode control in various ways. For instance, the locking of MHD modes can be avoided during the controlled shut down of multi hundreds Mega Joule EM stored energy in case of emergency. Feedback could also be useful to minimize mechanical resonances at the disruption events by forcing the MHD frequency away from dangerous ranges. Work supported by the US DOE under DE-AC02-09CH11466, DE-FC-02-04ER54698, DE-FG02-08ER85195, and DE-FG02-04ER54761.

Compact atmospheric pressure plasma self-resonant drive circuits

NASA Astrophysics Data System (ADS)

Law, V. J.; Anghel, S. D.

2012-02-01

This paper reports on compact solid-state self-resonant drive circuits that are specifically designed to drive an atmospheric pressure plasma jet and a parallel-plate dielectric barrier discharge of small volume (0.5 cm3). The atmospheric pressure plasma (APP) device can be operated with helium, argon or a mixture of both. Equivalent electrical models of the self-resonant drive circuits and discharge are developed and used to estimate the plasma impedance, plasma power density, current density or electron number density of three APP devices. These parameters and the kinetic gas temperature are dependent on the self-resonant frequency of the APP device. For a fixed switching frequency and APP device geometry, the plasma parameters are controlled by adjusting the dc voltage at the primary coil and the gas flow rate. The resonant frequency is controlled by the selection of the switching power transistor and means of step-up voltage transformation (ferrite core, flyback transformer, or Tesla coil). The flyback transformer operates in the tens of kHz, the ferrite core in the hundreds of kHz and Tesla coil in the MHz range. Embedded within this work is the principle of frequency pulling which is exemplified in the flyback transformer circuit that utilizes a pickup coil for feedback control of the switching frequency.

Coil End Parts Development Using BEND and Design for MQXF by LARP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, Miao; Ambrosio, G.; Bermudez, S. Izquierdo

2016-09-06

End parts are critical components for saddle-shaped coils. They have a structural function where the cables are deformed in order to cross over the magnet aperture. Based on the previous design of the US LARP program for 90 mm aperture quadrupoles (TQ/LQ) and 120 mm aperture quadrupoles (HQ/LHQ) using BEND, the coil ends of the low-β quadruples (MQXF) for the HiLumi LHC upgrade were developed. This paper shows the design of the MQXF coil ends, the analysis of the coil ends during the coil fabrication, the autopsy analysis of the coil ends and the feedback to BEND parameters.

Detection of Membrane Puncture with Haptic Feedback using a Tip-Force Sensing Needle.

PubMed

Elayaperumal, Santhi; Bae, Jung Hwa; Daniel, Bruce L; Cutkosky, Mark R

2014-09-01

This paper presents calibration and user test results of a 3-D tip-force sensing needle with haptic feedback. The needle is a modified MRI-compatible biopsy needle with embedded fiber Bragg grating (FBG) sensors for strain detection. After calibration, the needle is interrogated at 2 kHz, and dynamic forces are displayed remotely with a voice coil actuator. The needle is tested in a single-axis master/slave system, with the voice coil haptic display at the master, and the needle at the slave end. Tissue phantoms with embedded membranes were used to determine the ability of the tip-force sensors to provide real-time haptic feedback as compared to external sensors at the needle base during needle insertion via the master/slave system. Subjects were able to determine the position of the embedded membranes with significantly better accuracy using FBG tip feedback than with base feedback using a commercial force/torque sensor (p = 0.045) or with no added haptic feedback (p = 0.0024).

Detection of Membrane Puncture with Haptic Feedback using a Tip-Force Sensing Needle

PubMed Central

Elayaperumal, Santhi; Bae, Jung Hwa; Daniel, Bruce L.; Cutkosky, Mark R.

2015-01-01

This paper presents calibration and user test results of a 3-D tip-force sensing needle with haptic feedback. The needle is a modified MRI-compatible biopsy needle with embedded fiber Bragg grating (FBG) sensors for strain detection. After calibration, the needle is interrogated at 2 kHz, and dynamic forces are displayed remotely with a voice coil actuator. The needle is tested in a single-axis master/slave system, with the voice coil haptic display at the master, and the needle at the slave end. Tissue phantoms with embedded membranes were used to determine the ability of the tip-force sensors to provide real-time haptic feedback as compared to external sensors at the needle base during needle insertion via the master/slave system. Subjects were able to determine the position of the embedded membranes with significantly better accuracy using FBG tip feedback than with base feedback using a commercial force/torque sensor (p = 0.045) or with no added haptic feedback (p = 0.0024). PMID:26509101

Analytical design equations for self-tuned Class-E power amplifier.

PubMed

Hu, Zhe; Troyk, Philip

2011-01-01

For many emerging neural prosthesis designs that are powered by inductive coupling, their small physical size requires large current in the extracorporeal transmitter coil, and the Class-E power amplifier topology is often used for the transmitter design. Tuning of Class-E circuits for efficient operation is difficult and a self-tuned circuit can facilitate the tuning. The coil current is sensed and used to tune the switching of the transistor switch in the Class-E circuit in order to maintain its high-efficiency operation. Although mathematically complex, the analysis and design procedure for the self-tuned Class-E circuit can be simplified due to the current feedback control, which makes the phase angle between the switching pulse and the coil current predetermined. In this paper explicit analytical design equations are derived and a detailed design procedure is presented and compared with the conventional Class-E design approaches.

Magnetoresistive flux focusing eddy current flaw detection

NASA Technical Reports Server (NTRS)

Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor); Namkung, Min (Inventor)

2005-01-01

A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

Magnetoresistive Flux Focusing Eddy Current Flaw Detection

NASA Technical Reports Server (NTRS)

Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

2005-01-01

A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil s longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multi-layer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

Feedforward and feedback control of locked mode phase and rotation in DIII-D with application to modulated ECCD experiments

NASA Astrophysics Data System (ADS)

Choi, W.; La Haye, R. J.; Lanctot, M. J.; Olofsson, K. E. J.; Strait, E. J.; Sweeney, R.; Volpe, F. A.; The DIII-D Team

2018-03-01

The toroidal phase and rotation of otherwise locked magnetic islands of toroidal mode number n  =  1 are controlled in the DIII-D tokamak by means of applied magnetic perturbations of n  =  1. Pre-emptive perturbations were applied in feedforward to ‘catch’ the mode as it slowed down and entrain it to the rotating field before complete locking, thus avoiding the associated major confinement degradation. Additionally, for the first time, the phase of the perturbation was optimized in real-time, in feedback with magnetic measurements, in order for the mode’s phase to closely match a prescribed phase, as a function of time. Experimental results confirm the capability to hold the mode in a given fixed-phase or to rotate it at up to 20 Hz with good uniformity. The control-coil currents utilized in the experiments agree with the requirements estimated by an electromechanical model. Moreover, controlled rotation at 20 Hz was combined with electron cyclotron current drive (ECCD) modulated at the same frequency. This is simpler than regulating the ECCD modulation in feedback with spontaneous mode rotation, and enables repetitive, reproducible ECCD deposition at or near the island O-point, X-point and locations in between, for careful studies of how this affects the island stability. Current drive was found to be radially misaligned relative to the island, and resulting growth and shrinkage of islands matched expectations of the modified Rutherford equation for some discharges presented here. Finally, simulations predict the as designed ITER 3D coils can entrain a small island at sub-10 Hz frequencies.

Deep Flaw Detection with Giant Magnetoresistive (GMR) Based Self-Nulling Probe

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Namkung, Min

2004-01-01

In this paper a design modification to the Very-Low Frequency GMR Based Self-Nulling Probe has been presented to enable improved signal to noise ratio for deeply buried flaws. The design change consists of incorporating a feedback coil in the center of the flux focusing lens. The use of the feedback coil enables cancellation of the leakage fields in the center of the probe and biasing of the GMR sensor to a location of high magnetic field sensitivity. The effect of the feedback on the probe output was examined, and experimental results for deep flaw detection were presented. The experimental results show that the modified probe is capable of clearly identifying flaws up to 1 cm deep in aluminum alloy structures.

Integrated Plasma Control for Alternative Plasma Shape on EAST

NASA Astrophysics Data System (ADS)

Xiao, Bingjia

2017-10-01

To support long pulse plasma operation in high performance, a set of plasma control algorithms such as PEFIT real-time equilibrium reconstruction, radiation feedback, Beta and loop voltage feedback and quasi-snowflake shape f control have been implemented on EAST Plasma Control system (PCS) which was adapted from DIII-D PCS. PEFIT is a parallelized version of EFIT by using GPU with highest computation acceleration ratio up to 100 with respect to EFIT. It demonstrated high performance both in DIII-D data analysis and in the real-time shape control on EAST plasma either in normal or quasi-snowflake shape. Loop voltage has been successfully controlled by Low Hybrid Wave (LHW) while the plasma current is maintained by poloidal field coil set. Beta control has been also demonstrated by using LHW and it will be extended to other heating sources because the PCS interface is ready. Radiation feedback control has been achieved by Neon seeding by Super-Sonic Molecular Beam Injection (SMBI). For the plasma operation in quasi-snowflake, we have reached 20 s ELMy free high confinement non-inductive discharges with betap 2, H98 1.1 and plasma current 250 kA. EAST orals.

Low noise charge ramp electrometer

DOEpatents

Morgan, John P.; Piper, Thomas C.

1992-01-01

An electrometer capable of measuring small currents without the use of a feedback resistor which tends to contribute a large noise factor to the measured data. The electrometer eliminates the feedback resistor through the use of a feedback capacitor located across the electrometer amplifier. The signal from the electrometer amplifier is transferred to a electrometer buffer amplifier which serves to transfer the signal to several receptors. If the electrometer amplifier is approaching saturation, the buffer amplifier signals a reset discriminator which energizes a coil whose magnetic field closes a magnetic relay switch which in turn resets or zeros the feedback capacitor. In turn, a reset complete discriminator restarts the measurement process when the electrometer amplifier approaches its initial condition. The buffer amplifier also transmits the voltage signal from the electrometer amplifier to a voltage-to-frequency converter. The signals from the voltage-to-frequency converter are counted over a fixed period of time and the information is relayed to a data processor. The timing and sequencing of the small current measuring system is under the control of a sequence control logic unit.

Low noise charge ramp electrometer

DOEpatents

Morgan, J.P.; Piper, T.C.

1992-10-06

An electrometer capable of measuring small currents without the use of a feedback resistor which tends to contribute a large noise factor to the measured data. The electrometer eliminates the feedback resistor through the use of a feedback capacitor located across the electrometer amplifier. The signal from the electrometer amplifier is transferred to a electrometer buffer amplifier which serves to transfer the signal to several receptors. If the electrometer amplifier is approaching saturation, the buffer amplifier signals a reset discriminator which energizes a coil whose magnetic field closes a magnetic relay switch which in turn resets or zeros the feedback capacitor. In turn, a reset complete discriminator restarts the measurement process when the electrometer amplifier approaches its initial condition. The buffer amplifier also transmits the voltage signal from the electrometer amplifier to a voltage-to-frequency converter. The signals from the voltage-to-frequency converter are counted over a fixed period of time and the information is relayed to a data processor. The timing and sequencing of the small current measuring system is under the control of a sequence control logic unit. 2 figs.

Experimental validation of coil phase parametrisation on ASDEX Upgrade, and extension to ITER

NASA Astrophysics Data System (ADS)

Ryan, D. A.; Liu, Y. Q.; Kirk, A.; Suttrop, W.; Dudson, B.; Dunne, M.; Willensdorfer, M.; the ASDEX Upgrade team; the EUROfusion MST1 team

2018-06-01

It has been previously demonstrated in Li et al (2016 Nucl. Fusion 56 126007) that the optimum upper/lower coil phase shift ΔΦopt for alignment of RMP coils for ELM mitigation depends sensitively on q 95, and other equilibrium plasma parameters. Therefore, ΔΦopt is expected to vary widely during the current ramp of ITER plasmas, with negative implications for ELM mitigation during this period. A previously derived and numerically benchmarked parametrisation of the coil phase for optimal ELM mitigation on ASDEX Upgrade (Ryan et al 2017 Plasma Phys. Control. Fusion 59 024005) is validated against experimental measurements of ΔΦopt, made by observing the changes to the ELM frequency as the coil phase is scanned. It is shown that the parametrisation may predict the optimal coil phase to within 32° of the experimental measurement for n = 2 applied perturbations. It is explained that this agreement is sufficient to ensure that the ELM mitigation is not compromised by poor coil alignment. It is also found that the phase which maximises ELM mitigation is shifted from the phase which maximizes density pump-out, in contrast to theoretical expectations that ELM mitigation and density pump out have the same ΔΦ ul dependence. A time lag between the ELM frequency response and density response to the RMP is suggested as the cause. The method for numerically deriving the parametrisation is repeated for the ITER coil set, using the baseline scenario as a reference equilibrium, and the parametrisation coefficients given for future use in a feedback coil alignment system. The relative merits of square or sinusoidal toroidal current waveforms for ELM mitigation are briefly discussed.

Real-time feedback for spatiotemporal field stabilization in MR systems.

PubMed

Duerst, Yolanda; Wilm, Bertram J; Dietrich, Benjamin E; Vannesjo, S Johanna; Barmet, Christoph; Schmid, Thomas; Brunner, David O; Pruessmann, Klaas P

2015-02-01

MR imaging and spectroscopy require a highly stable, uniform background field. The field stability is typically limited by hardware imperfections, external perturbations, or field fluctuations of physiological origin. The purpose of the present work is to address these issues by introducing spatiotemporal field stabilization based on real-time sensing and feedback control. An array of NMR field probes is used to sense the field evolution in a whole-body MR system concurrently with regular system operation. The field observations serve as inputs to a proportional-integral controller that governs correction currents in gradient and higher-order shim coils such as to keep the field stable in a volume of interest. The feedback system was successfully set up, currently reaching a minimum latency of 20 ms. Its utility is first demonstrated by countering thermal field drift during an EPI protocol. It is then used to address respiratory field fluctuations in a T2 *-weighted brain exam, resulting in substantially improved image quality. Feedback field control is an effective means of eliminating dynamic field distortions in MR systems. Third-order spatial control at an update time of 100 ms has proven sufficient to largely eliminate thermal and breathing effects in brain imaging at 7 Tesla. © 2014 Wiley Periodicals, Inc.

MHD control experiments in the Extrap T2R Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Marrelli, L.; Bolzonella, T.; Brunsell, P.; Cecconello, M.; Drake, J.; Franz, P.; Gregoratto, D.; Manduchi, G.; Martin, P.; Ortolani, S.; Paccagnella, R.; Piovesan, P.; Spizzo, G.; Yadikin, D.; Zanca, P.

2004-11-01

We report here on MHD active control experiments performed in the Extrap T2R device, which has been recently equipped with a set of 32 feedback controlled saddle coils couples. Experiments aiming at selectively exciting a resonant resistive instability in order to actively induce Quasi Single Helicity states will be presented. Open loop experiments have in fact shown that a spectrum with one dominant mode can be excited in a high aspect ratio device like T2R. In addition, evidences of controlled braking of tearing modes, which spontaneously rotate in T2R, have been gathered, allowing the determination of a threshold for mode wall locking. Different feedback control schemes have been implemented. In particular, mode suppression schemes proved successful in delaying resistive wall modes growth and in increasing the discharge duration: this suggests a hybrid mode control scenario, in which RWM are suppressed and QSH is induced. Radiation imaging and internal magnetic field reconstructions performed with the ORBIT code will be presented.

Plasma Braking Due to External Magnetic Perturbations

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Olofsson, Kejo; Brunsell, P. R.; Khan, M. W. M.; Drake, J. R.

2010-11-01

The RFP EXTRAP T2R is equipped with a comprehensive active feedback system (128 active saddle coils in the full-coverage array) and active control of both resonant and non-resonant MHD modes has been demonstrated. The feedback algorithms, based on modern control methodology such as reference mode tracking (both amplitude and phase), are a useful tool to improve the ``state of the art'' of the MHD mode control. But this tool can be used also to improve the understanding and the characterization of other phenomena such as the ELM mitigation with a resonant magnetic perturbation or the plasma viscosity. The present work studies plasma and mode braking due to static RMPs. Results show that a static RMP produces a global braking of the flow profile. The study of the effect of RMPs characterized by different helicities will also give information on the plasma viscosity profile. Experimental results are finally compared to theoretical models.

Clinical Application of Insertion Force Sensor System for Coil Embolization of Intracranial Aneurysms.

PubMed

Matsubara, Noriaki; Miyachi, Shigeru; Izumi, Takashi; Yamada, Hiroyuki; Marui, Naoki; Ota, Keisuke; Tajima, Hayato; Shintai, Kazunori; Ito, Masashi; Imai, Tasuku; Nishihori, Masahiro; Wakabayashi, Toshihiko

2017-09-01

In endovascular embolization for intracranial aneurysms, it is important to properly control the coil insertion force. However, the force can only be subjectively detected by the subtle feedback experienced by neurointerventionists at their fingertips. The authors envisioned a system that would objectively sense and quantify that force. In this article, coil insertion force was measured in cases of intracranial aneurysm using this sensor, and its actual clinical application was investigated. The sensor consists of a hemostatic valve (Y-connector). A little flexure was intentionally added in the device, and it creates a bend in the delivery wire. The sensor measures the change in the position of the bent wire depending on the insertion force and translates it into a force value. Using this, embolization was performed for 10 unruptured intracranial aneurysms. The sensor adequately recorded the force, and it reflected the operators' usual clinical experience. The presence of the sensor did not affect the procedures. The sensor enabled the operators to objectively note and evaluate the insertion force and better cooperative handling was possible. Additionally, other members of the intervention team shared the information. Force records demonstrated the characteristic patterns according to every stage of coiling (framing, filling, and finishing). The force sensor system adequately measured coil insertion force in intracranial aneurysm coil embolization procedures. The safety of this sensor was demonstrated in clinical application for the limited number of patients. This system is useful adjunct for assisting during coil embolization for an intracranial aneurysm. Copyright © 2017 Elsevier Inc. All rights reserved.

High precision locating control system based on VCM for Talbot lithography

NASA Astrophysics Data System (ADS)

Yao, Jingwei; Zhao, Lixin; Deng, Qian; Hu, Song

2016-10-01

Aiming at the high precision and efficiency requirements of Z-direction locating in Talbot lithography, a control system based on Voice Coil Motor (VCM) was designed. In this paper, we built a math model of VCM and its moving characteristic was analyzed. A double-closed loop control strategy including position loop and current loop were accomplished. The current loop was implemented by driver, in order to achieve the rapid follow of the system current. The position loop was completed by the digital signal processor (DSP) and the position feedback was achieved by high precision linear scales. Feed forward control and position feedback Proportion Integration Differentiation (PID) control were applied in order to compensate for dynamic lag and improve the response speed of the system. And the high precision and efficiency of the system were verified by simulation and experiments. The results demonstrated that the performance of Z-direction gantry was obviously improved, having high precision, quick responses, strong real-time and easily to expend for higher precision.

Resistive wall mode feedback control in EXTRAP T2R with improved steady-state error and transient response

NASA Astrophysics Data System (ADS)

Brunsell, P. R.; Olofsson, K. E. J.; Frassinetti, L.; Drake, J. R.

2007-10-01

Experiments in the EXTRAP T2R reversed field pinch [P. R. Brunsell, H. Bergsåker, M. Cecconello et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] on feedback control of m =1 resistive wall modes (RWMs) are compared with simulations using the cylindrical linear magnetohydrodynamic model, including the dynamics of the active coils and power amplifiers. Stabilization of the main RWMs (n=-11,-10,-9,-8,+5,+6) is shown using modest loop gains of the order G ˜1. However, other marginally unstable RWMs (n=-2,-1,+1,+2) driven by external field errors are only partially canceled at these gains. The experimental system stability limit is confirmed by simulations showing that the latency of the digital controller ˜50μs is degrading the system gain margin. The transient response is improved with a proportional-plus-derivative controller, and steady-state error is improved with a proportional-plus-integral controller. Suppression of all modes is obtained at high gain G ˜10 using a proportional-plus-integral-plus-derivative controller.

Analysis, design, and testing of a low cost, direct force command linear proof mass actuator for structural control

NASA Technical Reports Server (NTRS)

Slater, G. L.; Shelley, Stuart; Jacobson, Mark

1993-01-01

In this paper, the design, analysis, and test of a low cost, linear proof mass actuator for vibration control is presented. The actuator is based on a linear induction coil from a large computer disk drive. Such disk drives are readily available and provide the linear actuator, current feedback amplifier, and power supply for a highly effective, yet inexpensive, experimental laboratory actuator. The device is implemented as a force command input system, and the performance is virtually the same as other, more sophisticated, linear proof mass systems.

Shape memory polymer (SMP) gripper with a release sensing system

DOEpatents

Maitland, Duncan J.; Lee, Abraham P.; Schumann, Daniel L.; Silva, Luiz Da

2000-01-01

A system for releasing a target material, such as an embolic coil from an SMP located at the end of a catheter utilizing an optical arrangement for releasing the material. The system includes a laser, laser driver, display panel, photodetector, fiber optics coupler, fiber optics and connectors, a catheter, and an SMP-based gripper, and includes a release sensing and feedback arrangement. The SMP-based gripper is heated via laser light through an optic fiber causing the gripper to release a target material (e.g., embolic coil for therapeutic treatment of aneurysms). Various embodiments are provided for coupling the laser light into the SMP, which includes specific positioning of the coils, removal of the fiber cladding adjacent the coil, a metal coating on the SMP, doping the SMP with a gradient absorbing dye, tapering the fiber optic end, coating the SMP with low refractive index material, and locating an insert between the fiber optic and the coil.

Sensitivity Enhancement of an Inductively Coupled Local Detector Using a HEMT-based Current Amplifier

PubMed Central

Qian, Chunqi; Duan, Qi; Dodd, Steve; Koretsky, Alan; Murphy-Boesch, Joe

2015-01-01

Purpose To improve the signal transmission efficiency and sensitivity of a local detection coil that is weakly inductively coupled to a larger receive coil. Methods The resonant detection coil is connected in parallel with the gate of a HEMT transistor without impedance matching. When the drain of the transistor is capacitively shunted to ground, current amplification occurs in the resonator by feedback that transforms a capacitive impedance on the transistor’s source to a negative resistance on its gate. Results High resolution images were obtained from a mouse brain using a small, 11 mm diameter surface coil that was inductively coupled to a commercial, phased array chest coil. Although the power consumption of the amplifier was only 88 µW, 14 dB gain was obtained with excellent noise performance. Conclusion An integrated current amplifier based on a High Electron Mobility Transistor (HEMT) can enhance the sensitivity of inductively coupled local detectors when weakly coupled. This amplifier enables efficient signal transmission between customized user coils and commercial clinical coils, without the need for a specialized signal interface. PMID:26192998

Extending a Lippmann style seismometer's dynamic range by using a non-linear feedback circuit

NASA Astrophysics Data System (ADS)

Romeo, Giovanni; Spinelli, Giuseppe

2013-04-01

A Lippmann style seismometer uses a single-coil velocity-feedback method in order to extend toward lower frequencies a geophone's frequency response. Strong seismic signals may saturate the electronics, sometimes producing a characteristic whale-shaped recording. Adding a non linear feedback in the electronic circuit may avoid saturation, allowing the strong-motion use of the seismometer without affecting the usual performance. We show results from both simulations and experiments, using a Teledyne Geotech s13 as a mechanical part.

Prostate Ultrasound

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Multi-turn transmit coil to increase b1 efficiency in current source amplification.

PubMed

Gudino, N; Griswold, M A

2013-04-01

A multi-turn transmit surface coil design was presented to improve B1 efficiency when used with current source amplification. Three different coil designs driven by an on-coil current-mode class-D amplifier with current envelope feedback were tested on the benchtop and through imaging in a 1.5 T scanner. Case temperature of the power field-effect transistor at the amplifier output stage was measured to evaluate heat dissipation for the different current levels and coil configurations. In addition, a lower power rated device was tested to exploit the potential gain in B1 obtained with the multi-turn coil. As shown both on the benchtop and in a 1.5 T scanner, B1 was increased by almost 3-fold without increasing heat dissipation on the power device at the amplifier's output using a multi-turn surface coil. Similar gain was obtained when connecting a lower power rated field-effect transistor to the multi-turn coil. In addition to reduce heat dissipation per B1 in the device, higher B1 per current efficiency allows the use of field-effect transistors with lower current ratings and lower port capacitances, which could improve the overall performance of the on-coil current source transmit system. Copyright © 2013 Wiley Periodicals, Inc.

Multi-turn transmit coil to increase B1 efficiency in current source amplification

PubMed Central

Gudino, N.; Griswold, M.A.

2013-01-01

Purpose A multi-turn transmit surface coil design was presented to improve B1 efficiency when used with current source amplification. Methods Three different coil designs driven by an on-coil current-mode class-D (CMCD) amplifier with current envelope feedback were tested on the benchtop and through imaging in a 1.5 T scanner. Case temperature of the power field-effect transistor (FET) at the amplifier output stage was measured to evaluate heat dissipation for the different current levels and coil configurations. In addition, a lower power rated device was tested to exploit the potential gain in B1 obtained with the multi-turn coil. Results As shown both on the benchtop and in a 1.5 T scanner, B1 was increased by almost three-fold without increasing heat dissipation on the power device at the amplifier's output using a multi-turn surface coil. Similar gain was obtained when connecting a lower power rated FET to the multi-turn coil. Conclusion In addition to reduce heat dissipation per B1 in the device, higher B1 per current efficiency allows the use of FETs with lower current ratings and lower port capacitances which could improve the overall performance of the on-coil current source transmit system. PMID:23401060

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okabayashi, M.; Zanca, P.; Strait, E. J.

Disruptions caused by tearing modes (TMs) are considered to be one of the most critical roadblocks to achieving reliable, steady-state operation of tokamak fusion reactors. We have demonstrated a promising scheme to avoid mode locking by utilizing the electro-magnetic (EM) torque produced with 3D coils that are available in many tokamaks. In this scheme, the EM torque is delivered to the modes by a toroidal phase shift between the externally applied field and the excited TM fields, compensating for the mode momentum loss through the interaction with the resistive wall and uncorrected error fields. Fine control of torque balance ismore » provided by a feedback scheme. We have explored this approach in two widely different devices and plasma conditions: DIII-D and RFX-mod operated in tokamak mode. In DIII-D, the plasma target was high β N in a non-circular divertor tokamak. We define β N as β N = β/(I p /aB t) (%Tm/MA), where β, I p, a, B t are the total stored plasma pressure normalized by the magnetic pressure, plasma current, plasma minor radius and toroidal magnetic field at the plasma center, respectively. The RFX-mod plasma was ohmically-heated with ultra-low safety factor in a circular limiter discharge with active feedback coils outside the thick resistive shell. The DIII-D and RFX-mod experiments showed remarkable consistency with theoretical predictions of torque balance. The application to ignition-oriented devices such as the International Thermonuclear Experimental Reactor (ITER) would expand the horizon of its operational regime. Finally, the internal 3D coil set currently under consideration for edge localized mode suppression in ITER would be well suited for this purpose.« less

Oscillatory magnetic tweezers based on ferromagnetic beads and simple coaxial coils

NASA Astrophysics Data System (ADS)

Trepat, Xavier; Grabulosa, Mireia; Buscemi, Lara; Rico, Fèlix; Fabry, Ben; Fredberg, Jeffrey J.; Farré, Ramon

2003-09-01

We report the design and validation of simple magnetic tweezers for oscillating ferromagnetic beads in the piconewton and nanometer scales. The system is based on a single pair of coaxial coils operating in two sequential modes: permanent magnetization of the beads through a large and brief pulse of magnetic field and generation of magnetic gradients to produce uniaxial oscillatory forces. By using this two step method, the magnetic moment of the beads remains constant during measurements. Therefore, the applied force can be computed and varies linearly with the driving signal. No feedback control is required to produce well defined force oscillations over a wide bandwidth. The design of the coils was optimized to obtain high magnetic fields (280 mT) and gradients (2 T/m) with high homogeneity (5% variation) within the sample. The magnetic tweezers were implemented in an inverted optical microscope with a videomicroscopy-based multiparticle tracking system. The apparatus was validated with 4.5 μm magnetite beads obtaining forces up to ˜2 pN and subnanometer resolution. The applicability of the device includes microrheology of biopolymer and cell cytoplasm, molecular mechanics, and mechanotransduction in living cells.

Loudspeakers: Modeling and control

NASA Astrophysics Data System (ADS)

Al-Ali, Khalid Mohammad

This thesis documented a comprehensive study of loudspeaker modeling and control. A lumped-parameter model for a voice-coil loudspeaker in a vented enclosure was presented that derived from a consideration of physical principles. In addition, a low-frequency (20 Hz to 100 Hz), feedback control method designed to improve the nonlinear performance of the loudspeaker and a suitable performance measure for use in design and evaluation were proposed. Data from experiments performed on a variety of actual loudspeakers confirmed the practicality of the theory developed in this work. The lumped-parameter loudspeaker model, although simple, captured much of the nonlinear behavior of the loudspeaker. In addition, the model formulation allowed a straightforward application of modern control system methods and lent itself well to modern parametric identification techniques. The nonlinear performance of the loudspeaker system was evaluated using a suitable distortion measure that was proposed and compared with other distortion measures currently used in practice. Furthermore, the linearizing effect of feedback using a linear controller (both static and dynamic) was studied on a class of nonlinear systems. The results illustrated that the distortion reduction was potentially significant and a useful upper bound on the closed-loop distortion was found based on the sensitivity function of the system's linearization. A feedback scheme based on robust control theory was chosen for application to the loudspeaker system. Using the pressure output of the loudspeaker system for feedback, the technique offered significant advantages over those previously attempted. Illustrative examples were presented that proved the applicability of the theory developed in this dissertation to a variety of loudspeaker systems. The examples included a vented loudspeaker model and actual loudspeakers enclosed in both vented and sealed configurations. In each example, predictable and measurable distortion reduction at the output of the closed-loop system was recorded.

A Role of Base Plate Jerk Feedback Scheme for Suppression of the Self Vibration in a Pneumatic Positioning Stage

NASA Astrophysics Data System (ADS)

Wali, Mohebullah; Nakamura, Yukinori; Wakui, Shinji

In this study, a positioning stage is considered, which is actuated by four pneumatic cylinders and vertically supported by four coil-type spring isolators. Previously, we realized the base plate jerk feedback (BPJFB) to be analogues to a Master-Slave system which can synchronize the motion of the stage as a Slave to the motion of the base plate as a Master. However, in the case of real positioning, the stage had slightly self oscillation with higher frequency due to the higher gains set to the outer feedback loop controller besides its oscillation due to the natural vibration of the base plate. The self oscillation of stage was misunderstood to be the natural vibration of base plate due to the reaction force. However, according to the experimental results, the BPJFB scheme was able to control both of the mentioned vibrations. Suppression of the self vibration of stage is an interesting phenomenon, which should be experimentally investigated. Therefore, the current study focuses on the suppression of the self vibration of stage by using the BPJFB scheme. The experimental results show that besides operating as a Master-Slave synchronizing system, the PBJFB scheme is able to increase the damping ratio and stiffness of stage against its self vibration. This newly recognized phenomenon contributes to further increase the proportional gain of the outer feedback loop controller. As a result, the positioning speed and stability can be improved.

Integrated Orbit and Attitude Control for a Nanosatellite with Power Constraints

NASA Technical Reports Server (NTRS)

Naasz, Bo; Hall, Christopher; Berry, Matthew; Hy-Young, Kim

2003-01-01

Small satellites tend to be power-limited, so that actuators used to control the orbit and attitude must compete with each other as well as with other subsystems for limited electrical power. The Virginia Tech nanosatellite project, HokieSat, must use its limited power resources to operate pulsed-plasma thrusters for orbit control and magnetic torque coils for attitude control, while also providing power to a GPS receiver, a crosslink transceiver, and other subsystems. The orbit and attitude control strategies were developed independently. The attitude control system is based on an application of Linear Quadratic Regulator (LQR) to an averaged system of equations, whereas the orbit control is based on orbit element feedback. In this paper we describe the strategy for integrating these two control systems and present simulation results to verify the strategy.

New type of eddy current sensor for large-displacement test

NASA Astrophysics Data System (ADS)

Pan, Haifeng; Zhu, Huizhong; Fu, Zhibin; Xu, Yuzheng; Feng, Guanping

2001-09-01

In this paper a new type of large displacement eddy current sensor is developed to overcome the three main disadvantages of the traditional eddy current senor. For a traditional sensor, the measurement range is limited and less than one half of the diameter of the measuring coil. The output is high sensitivity to the changes of the target material and the cable length connected between the probe and the preamplifier. When the material or the cable length changed, it is necessary to readjust the preamplifier. The probe of the new eddy current sensor has three coaxial measuring coils, one is an exciting coil and the other two are receiving coils. The diameter of measuring coils is (Phi) 11 mm. The measurement range of this sensor is 40mm and almost four times of the diameter of the coil. The form of differential input and feedback amplification is used in signal amplifier. Thus the effect of the common modules, such as the changes of the target material and the cable length, can be counteracted well.

[An implantable micro-device using wireless power transmission for measuring aortic aneurysm sac pressure].

PubMed

Guo, Xudong; Ge, Bin; Wang, Wenxing

2013-08-01

In order to detect endoleaks after endovascular aneurysm repair (EVAR), we developed an implantable micro-device based on wireless power transmission to measure aortic aneurysm sac pressure. The implantable micro-device is composed of a miniature wireless pressure sensor, an energy transmitting coil, a data recorder and a data processing platform. Power transmission without interconnecting wires is performed by a transmitting coil and a receiving coil. The coupling efficiency of wireless power transmission depends on the coupling coefficient between the transmitting coil and the receiving coil. With theoretical analysis and experimental study, we optimized the geometry of the receiving coil to increase the coupling coefficient. In order to keep efficiency balance and satisfy the maximizing conditions, we designed a closed loop power transmission circuit, including a receiving voltage feedback module based on wireless communication. The closed loop improved the stability and reliability of transmission energy. The prototype of the micro-device has been developed and the experiment has been performed. The experiments showed that the micro-device was feasible and valid. For normal operation, the distance between the transmitting coil and the receiving coil is smaller than 8cm. Besides, the distance between the micro-device and the data recorder is within 50cm.

A programmable broadband low frequency active vibration isolation system for atom interferometry.

PubMed

Tang, Biao; Zhou, Lin; Xiong, Zongyuan; Wang, Jin; Zhan, Mingsheng

2014-09-01

Vibration isolation at low frequency is important for some precision measurement experiments that use atom interferometry. To decrease the vibrational noise caused by the reflecting mirror of Raman beams in atom interferometry, we designed and demonstrated a compact stable active low frequency vibration isolation system. In this system, a digital control subsystem is used to process and feedback the vibration measured by a seismometer. A voice coil actuator is used to control and cancel the motion of a commercial passive vibration isolation platform. With the help of field programmable gate array-based control subsystem, the vibration isolation system performed flexibly and accurately. When the feedback is on, the intrinsic resonance frequency of the system will change from 0.8 Hz to about 0.015 Hz. The vertical vibration (0.01-10 Hz) measured by the in-loop seismometer is reduced by an additional factor of up to 500 on the basis of a passive vibration isolation platform, and we have proved the performance by adding an additional seismometer as well as applying it in the atom interferometry experiment.

Radiofrequency multielectrode catheter ablation in the atrium.

PubMed

Panescu, D; Fleischman, S D; Whayne, J G; Swanson, D K; Mirotznik, M S; McRury, I; Haines, D E

1999-04-01

We developed a temperature-controlled radiofrequency (RF) system which can ablate by delivering energy to up to six 12.5 mm long coil electrodes simultaneously. Temperature feedback was obtained from temperature sensors placed at each end of coil electrodes, in diametrically opposite positions. The coil electrodes were connected in parallel, via a set of electronic switches, to a 150 W 500 kHz temperature-controlled RF generator. Temperatures measured at all user-selected coil electrodes were processed by a microcontroller which sent the maximum value to the temperature input of the generator. The generator adjusted the delivered power to regulate the temperature at its input within a 5 degrees C interval about a user-defined set point. The microcontroller also activated the corresponding electronic switches so that temperatures at all selected electrodes were controlled within a 5 degrees C interval with respect to each other. Physical aspects of tissue heating were first analysed using finite element models and current density measurements. Results from these analyses also constituted design input. The performance of this system was studied in vitro and in vivo. In vitro, at set temperatures of 70 degrees C, 85% of the lesions were contiguous. All lesions created at set temperatures of 80 and 90 degrees C were contiguous. The lesion length increased almost linearly with the number of electrodes. Power requirements to reach a set temperature were larger as more electrodes were driven by the generator. The system impedance decreased as more electrodes were connected in the ablation circuit and reached a low of 45.5 ohms with five coil electrodes in the circuit. In vivo, right atrial lesions were created in eight mongrel canines. The power needed to reach 70 degrees C set temperature varied between 15 and 114 W. The system impedance was 105+/-16 ohms, with one coil electrode in the circuit, and dropped to 75+/-12 ohms when two coil electrodes were simultaneously powered. The length and the width of the lesion set varied between 17.6+/-6.1 and 59.2+/-11.7 mm and 5.9+/-0.7 and 7.1+/-1.2 mm respectively. No sudden impedance rises occurred and 75% of the lesions were contiguous. From the set of contiguous lesions, 90% were potentially therapeutic as they were transmural and extended over the entire target region. The average total procedure and fluoroscopy times were 83.4 and 5.9 min respectively. We concluded that the system can safely perform long and contiguous lesions in canine right atria.

Mechatronic design of haptic forceps for robotic surgery.

PubMed

Rizun, P; Gunn, D; Cox, B; Sutherland, G

2006-12-01

Haptic feedback increases operator performance and comfort during telerobotic manipulation. Feedback of grasping pressure is critical in many microsurgical tasks, yet no haptic interface for surgical tools is commercially available. Literature on the psychophysics of touch was reviewed to define the spectrum of human touch perception and the fidelity requirements of an ideal haptic interface. Mechanical design and control literature was reviewed to translate the psychophysical requirements to engineering specification. High-fidelity haptic forceps were then developed through an iterative process between engineering and surgery. The forceps are a modular device that integrate with a haptic hand controller to add force feedback for tool actuation in telerobotic or virtual surgery. Their overall length is 153 mm and their mass is 125 g. A contact-free voice coil actuator generates force feedback at frequencies up to 800 Hz. Maximum force output is 6 N (2N continuous) and the force resolution is 4 mN. The forceps employ a contact-free magnetic position sensor as well as micro-machined accelerometers to measure opening/closing acceleration. Position resolution is 0.6 microm with 1.3 microm RMS noise. The forceps can simulate stiffness greater than 20N/mm or impedances smaller than 15 g with no noticeable haptic artifacts or friction. As telerobotic surgery evolves, haptics will play an increasingly important role. Copyright 2006 John Wiley & Sons, Ltd.

Improved Audio Reproduction System

NASA Technical Reports Server (NTRS)

Chang, C. S.

1972-01-01

Circuitry utilizing electrical feedback of instantaneous speaker coil velocity compensates for loudspeaker resonance, transient peaks and frequency drop-off so that sounds of widely varying frequencies and amplitudes can be reproduced accurately from high fidelity recordings of any variety.

A Mechanical Coil Insertion System for Endovascular Coil Embolization of Intracranial Aneurysms

PubMed Central

Haraguchi, K.; Miyachi, S.; Matsubara, N.; Nagano, Y.; Yamada, H.; Marui, N.; Sano, A.; Fujimoto, H.; Izumi, T.; Yamanouchi, T.; Asai, T.; Wakabayashi, T.

2013-01-01

Summary Like other fields of medicine, robotics and mechanization might be introduced into endovascular coil embolization of intracranial aneurysms for effective treatment. We have already reported that coil insertion force could be smaller and more stable when the coil delivery wire is driven mechanically at a constant speed. Another background is the difficulty in synchronizing operators' minds and hands when two operators control the microcatheter and the coil respectively. We have therefore developed a mechanical coil insertion system enabling a single operator to insert coils at a fixed speed while controlling the microcatheter. Using our new system, the operator manipulated the microcatheter with both hands and drove the coil using foot switches simultaneously. A delivery wire force sensor previously reported was used concurrently, allowing the operator to detect excessive stress on the wire. In vitro coil embolization was performed using three methods: simple mechanical advance of the coil; simple mechanical advance of the coil with microcatheter control; and driving (forward and backward) of the coil using foot switches in addition to microcatheter control. The system worked without any problems, and did not interfere with any procedures. In experimental coil embolization, delivery wire control using the foot switches as well as microcatheter manipulation helped to achieve successful insertion of coils. This system could offer the possibility of developing safer and more efficient coil embolization. Although we aim at total mechanization and automation of procedures in the future, microcatheter manipulation and synchronized delivery wire control are still indispensable using this system. PMID:23693038

Design and performance evaluation of a master controller for endovascular catheterization.

PubMed

Guo, Jin; Guo, Shuxiang; Tamiya, Takashi; Hirata, Hideyuki; Ishihara, Hidenori

2016-01-01

It is difficult to manipulate a flexible catheter to target a position within a patient's complicated and delicate vessels. However, few researchers focused on the controller designs with much consideration of the natural catheter manipulation skills obtained from manual catheterization. Also, the existing catheter motion measurement methods probably lead to the difficulties in designing the force feedback device. Additionally, the commercially available systems are too expensive which makes them cost prohibitive to most hospitals. This paper presents a simple and cost-effective master controller for endovascular catheterization that can allow the interventionalists to apply the conventional pull, push and twist of the catheter used in current practice. A catheter-sensing unit (used to measure the motion of the catheter) and a force feedback unit (used to provide a sense of resistance force) are both presented. A camera was used to allow a contactless measurement avoiding additional friction, and the force feedback in the axial direction was provided by the magnetic force generated between the permanent magnets and the powered coil. Performance evaluation of the controller was evaluated by first conducting comparison experiments to quantify the accuracy of the catheter-sensing unit, and then conducting several experiments to evaluate the force feedback unit. From the experimental results, the minimum and the maximum errors of translational displacement were 0.003 mm (0.01 %) and 0.425 mm (1.06 %), respectively. The average error was 0.113 mm (0.28 %). In terms of rotational angles, the minimum and the maximum errors were 0.39°(0.33 %) and 7.2°(6 %), respectively. The average error was 3.61°(3.01 %). The force resolution was approximately 25 mN and a maximum current of 3A generated an approximately 1.5 N force. Based on analysis of requirements and state-of-the-art computer-assisted and robot-assisted training systems for endovascular catheterization, a new master controller with force feedback interface was proposed to maintain the natural endovascular catheterization skills of the interventionalists.

Sensitivity Enhancement of an Inductively Coupled Local Detector Using a HEMT-Based Current Amplifier.

PubMed

Qian, Chunqi; Duan, Qi; Dodd, Steve; Koretsky, Alan; Murphy-Boesch, Joe

2016-06-01

To improve the signal transmission efficiency and sensitivity of a local detection coil that is weakly inductively coupled to a larger receive coil. The resonant detection coil is connected in parallel with the gate of a high electron mobility transistor (HEMT) transistor without impedance matching. When the drain of the transistor is capacitively shunted to ground, current amplification occurs in the resonator by feedback that transforms a capacitive impedance on the transistor's source to a negative resistance on its gate. High resolution images were obtained from a mouse brain using a small, 11 mm diameter surface coil that was inductively coupled to a commercial, phased array chest coil. Although the power consumption of the amplifier was only 88 μW, 14 dB gain was obtained with excellent noise performance. An integrated current amplifier based on a HEMT can enhance the sensitivity of inductively coupled local detectors when weakly coupled. This amplifier enables efficient signal transmission between customized user coils and commercial clinical coils, without the need for a specialized signal interface. Magn Reson Med 75:2573-2578, 2016. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. Published 2015 This article is a U.S. Government work and is in the public domain in the USA.

Fabrication of First 4-m Coils for the LARP MQXFA Quadrupole and Assembly in Mirror Structure

DOE PAGES

Holik, Eddie Frank; Ambrosio, Giorgio; Anerella, Michael; ...

2017-01-23

The US LHC Accelerator Research Program is constructing prototype interaction region quadrupoles as part of the US in-kind contribution to the Hi-Lumi LHC project. The low-beta MQXFA Q1/Q3 coils have a 4-m length and a 150 mm bore. The design is first validated on short, one meter models (MQXFS) developed as part of the longstanding Nb3Sn quadrupole R&D by LARP in collaboration with CERN. In parallel, facilities and tooling are being developed and refined at BNL, LBNL, and FNAL to enable long coil production, assembly, and cold testing. Long length scale-up is based on the experience from the LARP 90more » mm aperture (TQ-LQ) and 120 mm aperture (HQ and Long HQ) programs. A 4-m long MQXF practice coil was fabricated, water jet cut and analyzed to verify procedures, parts, and tooling. In parallel, the first complete prototype coil (QXFP01a) was fabricated and assembled in a long magnetic mirror, MQXFPM1, to provide early feedback on coil design and fabrication following the successful experience of previous LARP mirror tests.« less

Overview of C-2W Field-Reversed Configuration Experimental Program

NASA Astrophysics Data System (ADS)

Gota, H.; Binderbauer, M. W.; Tajima, T.; Putvinski, S.; Tuszewski, M.; Dettrick, S.; Korepanov, S.; Romero, J.; Smirnov, A.; Song, Y.; Thompson, M. C.; van Drie, A.; Yang, X.; Ivanov, A. A.; TAE Team

2017-10-01

Tri Alpha Energy's research has been devoted to producing a high temperature, stable, long-lived field-reversed configuration (FRC) plasma state by neutral-beam injection (NBI) and edge biasing/control. C-2U experiments have demonstrated drastic improvements in particle and energy confinement properties of FRC's, and the plasma performance obtained via 10 MW NBI has achieved plasma sustainment of up to 5 ms and plasma (diamagnetism) lifetimes of 10 + ms. The emerging confinement scaling, whereby electron energy confinement time is proportional to a positive power of the electron temperature, is very attractive for higher energy plasma confinement; accordingly, verification of the observed Te scaling law will be a key future research objective. The new experimental device, C-2W (now also called ``Norman''), has the following key subsystem upgrades from C-2U: (i) higher injected power, optimum energies, and extended pulse duration of the NBI system; (ii) installation of inner divertors with upgraded edge-biasing systems; (iii) fast external equilibrium/mirror-coil current ramp-up capability; and (iv) installation of trim/saddle coils for active feedback control of the FRC plasma. This paper will review highlights of the C-2W program.

Toroidal plasma response based ELM control coil design for EU DEMO

NASA Astrophysics Data System (ADS)

Zhou, Lina; Liu, Yueqiang; Wenninger, Ronald; Liu, Yue; Wang, Shuo; Yang, Xu

2018-07-01

Magnetic coil design study is carried out, for the purpose of mitigating or suppressing the edge localized modes (ELMs) in a EU DEMO reference scenario. The coil design, including both the coil geometry and the coil current requirement, is based on criteria derived from the linear, full toroidal plasma response computed by the MARS-F code (Liu et al 2000 Phys. Plasma 7 3681). With a single midplane row of coils, a coil size covering about 30°–50° poloidal angle of the torus is found to be optimal for ELM control using the n  >  2 resonant magnetic perturbation (RMP) field (n is the toroidal mode number). For off-midplane coils, the coils’ poloidal location, as well as the relative toroidal phase (coil phasing) between the upper and lower rows of coils, also sensitively affects the ELM control according to the specified criteria. Assuming that the optimal coil phasing can always be straightforwardly implemented, following a simple analytic model derived from toroidal computations, it is better to place the two off-midplane rows of coils near the midplane, in order to maximize the resonant field amplitude and to have larger effects on ELMs. With the same coil current, the ex-vessel coils can be made as effective as the in-vessel coils, at the expense of increasing the ex-vessel coils’ size. This is however possible only for low-n (n  =  1–3) RMP fields. With these low-n fields, and assuming 300 kAt maximal coil current, the computed plasma displacement near the X-point can meet the 10 mm level, which we use as the conservative indicator for achieving ELM mitigation in EU DEMO. The risk of partial control coil failure in EU DEMO is also assessed based on toroidal modeling, indicating that the large n  =  1 sideband due to coil failure may need to be corrected, if the nominal n  >  1 coil configurations are used for ELM control in EU DEMO.

Auxiliary coil controls temperature of RF induction heater

NASA Technical Reports Server (NTRS)

1966-01-01

Auxiliary coil controls the temperature of an RF induction furnace that is powered by a relatively unstable RF generator. Manual or servoed adjustments of the relative position of the auxiliary coil, which is placed in close proximity to the RF coil, changes the looseness of the RF coil and hence the corresponding heating effect of its RF field.

Magnetic propulsion of a magnetic device using three square-Helmholtz coils and a square-Maxwell coil.

PubMed

Ha, Yong H; Han, Byung H; Lee, Soo Y

2010-02-01

We introduce a square coil system for remote magnetic navigation of a magnetic device without any physical movements of the coils. We used three square-Helmholtz coils and a square-Maxwell coil for magnetic propulsion of a small magnet along the desired path. All the square coils are mountable on a cubic frame that has an opening to accommodate a living subject. The square-Helmholtz coils control the magnetic propulsion direction by generating uniform magnetic field along the desired direction while the square-Maxwell coil controls the propulsion force by generating magnetic gradient field. We performed magnetic propulsion experiments with a down-scaled coil set and a three-channel coil driver. Experimental results demonstrate that we can use the square coil set for magnetic navigation of a magnetic device without any physical movements of the coils.

Enhanced control of a flexure-jointed micromanipulation system using a vision-based servoing approach

NASA Astrophysics Data System (ADS)

Chuthai, T.; Cole, M. O. T.; Wongratanaphisan, T.; Puangmali, P.

2018-01-01

This paper describes a high-precision motion control implementation for a flexure-jointed micromanipulator. A desktop experimental motion platform has been created based on a 3RUU parallel kinematic mechanism, driven by rotary voice coil actuators. The three arms supporting the platform have rigid links with compact flexure joints as integrated parts and are made by single-process 3D printing. The mechanism overall size is approximately 250x250x100 mm. The workspace is relatively large for a flexure-jointed mechanism, being approximately 20x20x6 mm. A servo-control implementation based on pseudo-rigid-body models (PRBM) of kinematic behavior combined with nonlinear-PID control has been developed. This is shown to achieve fast response with good noise-rejection and platform stability. However, large errors in absolute positioning occur due to deficiencies in the PRBM kinematics, which cannot accurately capture flexure compliance behavior. To overcome this problem, visual servoing is employed, where a digital microscopy system is used to directly measure the platform position by image processing. By adopting nonlinear PID feedback of measured angles for the actuated joints as inner control loops, combined with auxiliary feedback of vision-based measurements, the absolute positioning error can be eliminated. With controller gain tuning, fast dynamic response and low residual vibration of the end platform can be achieved with absolute positioning accuracy within ±1 micron.

Electromagnetic diagnostic system for the Keda Torus eXperiment

NASA Astrophysics Data System (ADS)

Tu, Cui; Liu, Adi; Li, Zichao; Tan, Mingsheng; Luo, Bing; You, Wei; Li, Chenguang; Bai, Wei; Fu, Chenshuo; Huang, Fangcheng; Xiao, Bingjia; Shen, Biao; Shi, Tonghui; Chen, Dalong; Mao, Wenzhe; Li, Hong; Xie, Jinglin; Lan, Tao; Ding, Weixing; Xiao, Chijin; Liu, Wandong

2017-09-01

A system for electromagnetic measurements was designed and installed on the Keda Torus eXperiment (KTX) reversed field pinch device last year. Although the unique double-C structure of the KTX, which allows the machine to be opened easily without disassembling the poloidal field windings, makes the convenient replacement and modification of the internal inductive coils possible, it can present difficulties in the design of flux coils and magnetic probes at the two vertical gaps. Moreover, the KTX has a composite shell consisting of a 6 mm stainless steel vacuum chamber and a 1.5 mm copper shell, which results in limited space for the installation of saddle sensors. Therefore, the double-C structure and composite shell should be considered, especially during the design and installation of the electromagnetic diagnostic system (EDS). The inner surface of the vacuum vessel includes two types of probes. One type is for the measurement of the global plasma parameters, and the other type is for studying the local behavior of the plasma and operating the new saddle coils. In addition, the probes on the outer surface of the composite shell are used for measurements of eddy currents. Finally, saddle sensors for radial field measurements for feedback control were installed between the conducting shell and the vacuum vessel. The entire system includes approximately 1100 magnetic probes, 14 flux coils, 4 ×26 ×2 saddle sensors, and 16 Rogowski coils. Considering the large number of probes and limited space available in the vacuum vessel, the miniaturization of the probes and optimization of the probe distribution are necessary. In addition, accurate calibration and careful mounting of the probes are also required. The frequency response of the designed magnetic probes is up to 200 kHz, and the resolution is 1 G. The EDS, being spherical and of high precision, is one of the most basic and effective diagnostic tools of the KTX and meets the demands imposed by requirements on basic machine operating information and future studies.

Position control of twisted and coiled polymer actuator using a controlled fan for cooling

NASA Astrophysics Data System (ADS)

Takagi, Kentaro; Arakawa, Takeshi; Takeda, Jun; Masuya, Ken; Tahara, Kenji; Asaka, Kinji

2017-04-01

Recently, artificial muscles made of fishing lines or sewing threads, namely twisted and coiled polymer actuators (TCPAs), have been proposed by Haines et al. A TCPA contracts by applying heat and returns to its initial length by cooling. A TCPA can be driven by voltage if the TCPA is plated by metal or if conductive wire such as nichrome is wound around it. Compared with the conventional electroactive polymers, advantages of TCPAs are low cost, simple structure, large actuation strain, and large force. However, a big disadvantage of TCPAs is slow response due to heat transfer. The problem becomes apparent during cooling, although the response of heating can be improved by feedback control. This paper proposes a control method of switching heating and cooling. In the proposed method, a TCPA is cooled by an electric cooling fan. When the TCPA is heating, the cooling fan is stopped. In a previous report, the response speed can be improved by keeping cooling fan always on; however, unnecessary energy consumption is required even during heating. In the proposed method, energy consumption during heating does not increase and the response speed can be improved using fan only during cooling. The proposed control law is as follows. Firstly, the desired control input is determined by PI-D control with respect to the length of the actuator. Then, the control inputs to the heater and to the cooling fan are switched according to the sign of the PI-D controller output. The effectiveness of the proposed control method is demonstrated by comparing the cases with and without the cooling fan in the experiments.

Quench monitoring and control system and method of operating same

DOEpatents

Ryan, David Thomas; Laskaris, Evangelos Trifon; Huang, Xianrui

2006-05-30

A rotating machine comprising a superconductive coil and a temperature sensor operable to provide a signal representative of superconductive coil temperature. The rotating machine may comprise a control system communicatively coupled to the temperature sensor. The control system may be operable to reduce electric current in the superconductive coil when a signal representative of a defined superconducting coil temperature is received from the temperature sensor.

Further Experiments with a Loudspeaker

ERIC Educational Resources Information Center

Kraftmakher, Yaakov

2010-01-01

A common moving-coil (dynamic) loudspeaker is a device very suitable for teaching the general features of oscillating systems. As an addition to a previous paper (Kraftmakher 2009), this paper includes the following topics: (i) a new design of the optical sensor for measuring the cone oscillations; (ii) positive feedback and self-excited…

Coiled-coil protein composition of 22 proteomes--differences and common themes in subcellular infrastructure and traffic control.

PubMed

Rose, Annkatrin; Schraegle, Shannon J; Stahlberg, Eric A; Meier, Iris

2005-11-16

Long alpha-helical coiled-coil proteins are involved in diverse organizational and regulatory processes in eukaryotic cells. They provide cables and networks in the cyto- and nucleoskeleton, molecular scaffolds that organize membrane systems and tissues, motors, levers, rotating arms, and possibly springs. Mutations in long coiled-coil proteins have been implemented in a growing number of human diseases. Using the coiled-coil prediction program MultiCoil, we have previously identified all long coiled-coil proteins from the model plant Arabidopsis thaliana and have established a searchable Arabidopsis coiled-coil protein database. Here, we have identified all proteins with long coiled-coil domains from 21 additional fully sequenced genomes. Because regions predicted to form coiled-coils interfere with sequence homology determination, we have developed a sequence comparison and clustering strategy based on masking predicted coiled-coil domains. Comparing and grouping all long coiled-coil proteins from 22 genomes, the kingdom-specificity of coiled-coil protein families was determined. At the same time, a number of proteins with unknown function could be grouped with already characterized proteins from other organisms. MultiCoil predicts proteins with extended coiled-coil domains (more than 250 amino acids) to be largely absent from bacterial genomes, but present in archaea and eukaryotes. The structural maintenance of chromosomes proteins and their relatives are the only long coiled-coil protein family clearly conserved throughout all kingdoms, indicating their ancient nature. Motor proteins, membrane tethering and vesicle transport proteins are the dominant eukaryote-specific long coiled-coil proteins, suggesting that coiled-coil proteins have gained functions in the increasingly complex processes of subcellular infrastructure maintenance and trafficking control of the eukaryotic cell.

Coiled-coil protein composition of 22 proteomes – differences and common themes in subcellular infrastructure and traffic control

PubMed Central

Rose, Annkatrin; Schraegle, Shannon J; Stahlberg, Eric A; Meier, Iris

2005-01-01

Background Long alpha-helical coiled-coil proteins are involved in diverse organizational and regulatory processes in eukaryotic cells. They provide cables and networks in the cyto- and nucleoskeleton, molecular scaffolds that organize membrane systems and tissues, motors, levers, rotating arms, and possibly springs. Mutations in long coiled-coil proteins have been implemented in a growing number of human diseases. Using the coiled-coil prediction program MultiCoil, we have previously identified all long coiled-coil proteins from the model plant Arabidopsis thaliana and have established a searchable Arabidopsis coiled-coil protein database. Results Here, we have identified all proteins with long coiled-coil domains from 21 additional fully sequenced genomes. Because regions predicted to form coiled-coils interfere with sequence homology determination, we have developed a sequence comparison and clustering strategy based on masking predicted coiled-coil domains. Comparing and grouping all long coiled-coil proteins from 22 genomes, the kingdom-specificity of coiled-coil protein families was determined. At the same time, a number of proteins with unknown function could be grouped with already characterized proteins from other organisms. Conclusion MultiCoil predicts proteins with extended coiled-coil domains (more than 250 amino acids) to be largely absent from bacterial genomes, but present in archaea and eukaryotes. The structural maintenance of chromosomes proteins and their relatives are the only long coiled-coil protein family clearly conserved throughout all kingdoms, indicating their ancient nature. Motor proteins, membrane tethering and vesicle transport proteins are the dominant eukaryote-specific long coiled-coil proteins, suggesting that coiled-coil proteins have gained functions in the increasingly complex processes of subcellular infrastructure maintenance and trafficking control of the eukaryotic cell. PMID:16288662

The nature of thrombosis induced by platinum and tungsten coils in saccular aneurysms.

PubMed

Byrne, J V; Hope, J K; Hubbard, N; Morris, J H

1997-01-01

To compare the efficacy and biocompatability of electrolytic and mechanically detachable embolization coils of two metal types. Experimental saccular aneurysms in pigs were used to assess embolization induced by platinum or tungsten coils. Longitudinal angiographic and histologic studies were performed on treated and untreated (control) aneurysms to compare thrombosis and cellular responses after embolization with electrolytically detachable platinum coils and with mechanically detached tungsten coils. Fewer tungsten than platinum coils were needed to induce thrombosis. The inflammatory response within the aneurysmal lumen was more florid in embolized aneurysms than in control aneurysms. No difference was found in the timing or extent of accumulation of eosinophils, lymphocytes, or polymorphs between the two coils used. Giant cell responses were more marked in treated aneurysms; tungsten coils more than platinum coils. The amount of collagen and fibrosis present increased over the study period and was similar in treated and control aneurysms. The coil type influenced the initial cellular response but had little effect on the rate or degree to which blood clot within the aneurysm was replaced by fibrous tissue.

Crystal Structure of the CLOCK Transactivation Domain Exon19 in Complex with a Repressor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Zhiqiang; Su, Lijing; Pei, Jimin

In the canonical clock model, CLOCK:BMAL1-mediated transcriptional activation is feedback regulated by its repressors CRY and PER and, in association with other coregulators, ultimately generates oscillatory gene expression patterns. How CLOCK:BMAL1 interacts with coregulator(s) is not well understood. Here we report the crystal structures of the mouse CLOCK transactivating domain Exon19 in complex with CIPC, a potent circadian repressor that functions independently of CRY and PER. The Exon19:CIPC complex adopts a three-helical coiled-coil bundle conformation containing two Exon19 helices and one CIPC. Unique to Exon19:CIPC, three highly conserved polar residues, Asn341 of CIPC and Gln544 of the two Exon19 helices,more » are located at the mid-section of the coiled-coil bundle interior and form hydrogen bonds with each other. Combining results from protein database search, sequence analysis, and mutagenesis studies, we discovered for the first time that CLOCK Exon19:CIPC interaction is a conserved transcription regulatory mechanism among mammals, fish, flies, and other invertebrates.« less

MRI-guided Therapeutic Ultrasound : In vitro Validation of a New MR Compatible, Phased Array, Contact Endorectal Ultrasound Transducer with Active Feedback Control of Temperature Evolution

NASA Astrophysics Data System (ADS)

Salomir, Rares; Rata, Mihaela; Lafon, Cyril; Melodelima, David; Chapelon, Jean-Yves; Mathias, Adrien; Cotton, François; Bonmartin, Alain; Cathignol, Dominique

2006-05-01

Contact application of high intensity ultrasound was demonstrated to be suitable for thermal ablation of sectorial tumours of the digestive duct. Experimental validation of a new MR compatible ultrasonic device is described here, dedicated to the minimal invasive therapy of localized colorectal cancer. This is a cylindrical 1D 64-element phased array transducer of 14 mm diameter and 25 mm height (Imasonic, France) allowing electronic rotation of the acoustic beam. Operating frequency ranges from 3.5 to 4.0 MHz and up to 5 effective electrical watts per element are available. A plane wave is reconstructed by simultaneous excitation of eigth adjacent elements with an appropriate phase law. Driving electronics operates outside the Faraday cage of the scanner and provides fast switching capabilities. Excellent passive and active compatibility with the MRI data acquisition has been demonstrated. In addition, feasibility of active temperature control has been demonstrated based on real-time data export out of the MR scanner and a PID feedback algorithm. Further studies will address the in-vivo validation and the integration of a miniature NMR coil for increased SNR in the near field.

Analysis and decoupling control of a permanent magnet spherical actuator.

PubMed

Zhang, Liang; Chen, Weihai; Liu, Jingmeng; Wu, Xingming

2013-12-01

This paper presents the analysis and decoupling control of a spherical actuator, which is capable of performing three degree-of-freedom motion in one joint. The proposed actuator consists of a rotor with multiple PM (Permanent Magnet) poles in a circle and a stator with circumferential coils in three layers. Based on this actuator design, a decoupling control approach is developed. Unlike existing control methods that each coil is responsible for both the spinning and tilting motion, the proposed control strategy specifies the function of each coil. Specifically, the spinning motion is governed by the middle layer coils with a step control approach; while the tilting motion is regulated by upper and lower coils with a computed torque control method. Experiments have been conducted on the prototype to verify the validity of the design procedure, and the experimental results demonstrate the effectiveness of the analysis and control strategy.

Online tuning of impedance matching circuit for long pulse inductively coupled plasma source operation—An alternate approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudhir, Dass; Bandyopadhyay, M., E-mail: mainak@ter-india.org; Chakraborty, A.

2014-01-15

Impedance matching circuit between radio frequency (RF) generator and the plasma load, placed between them, determines the RF power transfer from RF generator to the plasma load. The impedance of plasma load depends on the plasma parameters through skin depth and plasma conductivity or resistivity. Therefore, for long pulse operation of inductively coupled plasmas, particularly for high power (∼100 kW or more) where plasma load condition may vary due to different reasons (e.g., pressure, power, and thermal), online tuning of impedance matching circuit is necessary through feedback. In fusion grade ion source operation, such online methodology through feedback is notmore » present but offline remote tuning by adjusting the matching circuit capacitors and tuning the driving frequency of the RF generator between the ion source operation pulses is envisaged. The present model is an approach for remote impedance tuning methodology for long pulse operation and corresponding online impedance matching algorithm based on RF coil antenna current measurement or coil antenna calorimetric measurement may be useful in this regard.« less

Modeling of Feedback Stabilization of External MHD Modes in Toroidal Geometry

NASA Astrophysics Data System (ADS)

Chu, M. S.; Chance, M. S.; Okabayashi, M.

2000-10-01

The intelligent shell feedback scheme(C.M. Bishop, Plasma Phys. Contr. Nucl. Fusion 31), 1179 (1989). seeks to utilize external coils to suppress the unstable MHD modes slowed down by the resistive shell. We present a new formulation and numerical results of the interaction between the plasma and its outside vacuum region, with complete plasma response and the inclusion of a resistive vessel in general toroidal geometry. This is achieved by using the Green's function technique, which is a generalization of that previously used for the VACUUM(M.S. Chance, Phys. Plasmas 4), 2161 (1997). code and coupled with the ideal MHD code GATO. The effectiveness of different realizations of the intelligent shell concept is gauged by their ability to minimize the available free energy to drive the MHD mode. Computations indicate poloidal coverage of 30% of the total resistive wall surface area and 6 or 7 segments of ``intelligent coil'' arrays superimposed on the resistive wall will allow recovery of up to 90% the effectiveness of the ideal shell in stabilizing the ideal external kink.

A precision analogue integrator system for heavy current measurement in MFDC resistance spot welding

NASA Astrophysics Data System (ADS)

Xia, Yu-Jun; Zhang, Zhong-Dian; Xia, Zhen-Xin; Zhu, Shi-Liang; Zhang, Rui

2016-02-01

In order to control and monitor the quality of middle frequency direct current (MFDC) resistance spot welding (RSW), precision measurement of the welding current up to 100 kA is required, for which Rogowski coils are the only viable current transducers at present. Thus, a highly accurate analogue integrator is the key to restoring the converted signals collected from the Rogowski coils. Previous studies emphasised that the integration drift is a major factor that influences the performance of analogue integrators, but capacitive leakage error also has a significant impact on the result, especially in long-time pulse integration. In this article, new methods of measuring and compensating capacitive leakage error are proposed to fabricate a precision analogue integrator system for MFDC RSW. A voltage holding test is carried out to measure the integration error caused by capacitive leakage, and an original integrator with a feedback adder is designed to compensate capacitive leakage error in real time. The experimental results and statistical analysis show that the new analogue integrator system could constrain both drift and capacitive leakage error, of which the effect is robust to different voltage levels of output signals. The total integration error is limited within  ±0.09 mV s-1 0.005% s-1 or full scale at a 95% confidence level, which makes it possible to achieve the precision measurement of the welding current of MFDC RSW with Rogowski coils of 0.1% accuracy class.

Measurement of Diffusion in Entangled Rod-Coil Triblock Copolymers

NASA Astrophysics Data System (ADS)

Olsen, B. D.; Wang, M.

2012-02-01

Although rod-coil block copolymers have attracted increasing attention for functional nanomaterials, their dynamics relevant to self-assembly and processing have not been widely investigated. Because the rod and coil blocks have different reptation behavior and persistence lengths, the mechanism by which block copolymers will diffuse is unclear. In order to understand the effect of the rigid block on reptation, tracer diffusion of a coil-rod-coil block copolymer through an entangled coil polymer matrix was experimentally measured. A monodisperse, high molecular weight coil-rod-coil triblock was synthesized using artificial protein engineering to prepare the helical rod and bioconjugaiton of poly(ethylene glycol) coils to produce the final triblock. Diffusion measurements were performed using Forced Rayleigh scattering (FRS), at varying ratios of the rod length to entanglement length, where genetic engineering is used to control the protein rod length and the polymer matrix concentration controls the entanglement length. As compared to PEO homopolymer tracers, the coil-rod-coil triblocks show markedly slower diffusion, suggesting that the mismatch between rod and coil reptation mechanisms results in hindered diffusion of these molecules in the entangled state.

Satellite Attitude Control Utilizing the Earth's Magnetic Field

NASA Technical Reports Server (NTRS)

White, John S.; Shigemoto, Fred H.; Bourquin, Kent

1961-01-01

A study was conducted to determine the feasibility of a satellite attitude fine-control system using the interaction of the earth's magnetic field with current-carrying coils to produce torque. The approximate intensity of the earth's magnetic field was determined as a function of the satellite coordinates. Components of the magnetic field were found to vary essentially sinusoidally at approximately twice orbital frequency. Amplitude and distortion of the sinusoidal components were a function of satellite orbit. Two systems for two-axis attitude control evolved from this study, one using three coils and the other using two coils. The torques developed by the two systems differ only when the component of magnetic field along the tracking line is zero. For this case the two-coil system develops no torque whereas the three-coil system develops some effective torque which allows partial control. The equations which describe the three-coil system are complex in comparison to those of the two-coil system and require the measurement of all three components of the magnetic field as compared with only one for the two-coil case. Intermittent three-axis torquing can also be achieved. This torquing can be used for coarse attitude control, or for dumping the stored momentum of inertia reaction wheels. Such a system has the advantage of requiring no fuel aboard the satellite. For any of these magnetic torquing schemes the power required to produce the magnetic moment and the weight of the coil seem reasonable.

Position feedback system for volume holographic storage media

DOEpatents

Hays, Nathan J [San Francisco, CA; Henson, James A [Morgan Hill, CA; Carpenter, Christopher M [Sunnyvale, CA; Akin, Jr William R. [Morgan Hill, CA; Ehrlich, Richard M [Saratoga, CA; Beazley, Lance D [San Jose, CA

1998-07-07

A method of holographic recording in a photorefractive medium wherein stored holograms may be retrieved with maximum signal-to noise ratio (SNR) is disclosed. A plurality of servo blocks containing position feedback information is recorded in the crystal and made non-erasable by heating the crystal. The servo blocks are recorded at specific increments, either angular or frequency, depending whether wavelength or angular multiplexing is applied, and each servo block is defined by one of five patterns. Data pages are then recorded at positions or wavelengths enabling each data page to be subsequently reconstructed with servo patterns which provide position feedback information. The method of recording data pages and servo blocks is consistent with conventional practices. In addition, the recording system also includes components (e.g. voice coil motor) which respond to position feedback information and adjust the angular position of the reference angle of a reference beam to maximize SNR by reducing crosstalk, thereby improving storage capacity.

Fail-Safe Magnetic Bearing Controller Demonstrated Successfully

NASA Technical Reports Server (NTRS)

Choi, Benjamin B.; Provenza, Andrew J.

2001-01-01

The Structural Mechanics and Dynamics Branch has successfully demonstrated a fail-safe controller for the Fault-Tolerant Magnetic Bearing rig at the NASA Glenn Research Center. The rotor is supported by two 8-pole redundant radial bearings, and coil failing situations are simulated by manually shutting down their control current commands from the controller cockpit. The effectiveness of the controller was demonstrated when only two active coils from each radial bearing could be used (that is, 14 coils failed). These remaining two coils still levitated the rotor and spun it without losing stability or desired position up to the maximum allowable speed of 20,000 rpm.

Control of power to an inductively heated part

DOEpatents

Adkins, Douglas R.; Frost, Charles A.; Kahle, Philip M.; Kelley, J. Bruce; Stanton, Suzanne L.

1997-01-01

A process for induction hardening a part to a desired depth with an AC signal applied to the part from a closely coupled induction coil includes measuring the voltage of the AC signal at the coil and the current passing through the coil; and controlling the depth of hardening of the part from the measured voltage and current. The control system determines parameters of the part that are functions of applied voltage and current to the induction coil, and uses a neural network to control the application of the AC signal based on the detected functions for each part.

Control of power to an inductively heated part

DOEpatents

Adkins, D.R.; Frost, C.A.; Kahle, P.M.; Kelley, J.B.; Stanton, S.L.

1997-05-20

A process for induction hardening a part to a desired depth with an AC signal applied to the part from a closely coupled induction coil includes measuring the voltage of the AC signal at the coil and the current passing through the coil; and controlling the depth of hardening of the part from the measured voltage and current. The control system determines parameters of the part that are functions of applied voltage and current to the induction coil, and uses a neural network to control the application of the AC signal based on the detected functions for each part. 6 figs.

First Trial of Real-time Poloidal Beta Control in KSTAR

NASA Astrophysics Data System (ADS)

Han, Hyunsun; Hahn, S. H.; Bak, J. G.; Walker, M. L.; Woo, M. H.; Kim, J. S.; Kim, Y. J.; Bae, Y. S.; KSTAR Team

2014-10-01

Sustaining the plasma in a stable and a high performance condition is one of the important control issues for future steady state tokamaks. In the 2014 KSTAR campaign, we have developed a real-time poloidal beta (βp) control technique and carried out preliminary experiments to identify its feasibility. In the control system, the βp is calculated in real time using the measured diamagnetic loop signal (DLM03) with coil pickup corrections, and compared with the target value leading to the change of the neutral beam (NB) heating power using a feedback PID control algorithm. To match the required power of NB which is operated with constant voltage, the duty cycles of the modulation were adjusted as the ratio of the required power to the maximum achievable one. This paper will present the overall procedures of the βp control, the βp estimation process implemented in the plasma control system, and the analysis on the preliminary experimental results. This work is supported by the KSTAR research project funded by the Ministry of Science, ICT & Future Planning of Korea.

Optimal Control Design using an H(sub 2) Method for the Glovebox Integrated Microgravity Isolation Technology (G-Limit)

NASA Technical Reports Server (NTRS)

Calhoun, Philip C.; Hampton, R. David

2002-01-01

The acceleration environment on the International Space Station (ISS) will likely exceed the requirements of many micro-gravity experiments. The Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) is being built by the NASA Marshall Space Flight Center to attenuate the nominal acceleration environment and provide some isolation for microgravity science experiments. G-LIMIT uses Lorentz (voice-coil) magnetic actuators to isolate a platform for mounting science payloads from the nominal acceleration environment. The system utilizes payload acceleration, relative position, and relative orientation measurements in a feedback controller to accomplish the vibration isolation task. The controller provides current commands to six magnetic actuators, producing the required experiment isolation from the ISS acceleration environment. This paper presents the development of a candidate control law to meet the acceleration attenuation requirements for the g-LIMIT experiment platform. The controller design is developed using linear optimal control techniques for frequency-weighted H(sub 2) norms. Comparison of the performance and robustness to plant uncertainty for this control design approach is included in the discussion.

Frequency Weighted H2 Control Design for the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT)

NASA Technical Reports Server (NTRS)

Calhoun, Philip C.; Hampton, R. David

2004-01-01

The acceleration environment on the International Space Station (ISS) exceeds the requirements of many microgravity experiments. The Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) has been built by the NASA Marshall Space Flight Center to attenuate the nominal acceleration environment and provide some isolation for microgravity science experiments. The g-LIMIT uses Lorentz (voice-coil) magnetic actuators to isolate a platform, for mounting science payloads, from the nominal acceleration environment. The system utilizes payload-acceleration, relative-position, and relative-orientation measurements in a feedback controller to accomplish the vibration isolation task. The controller provides current commands to six magnetic actuators, producing the required experiment isolation from the ISS acceleration environment. The present work documents the development of a candidate control law to meet the acceleration attenuation requirements for the g-LIMIT experiment platform. The controller design is developed using linear optimal control techniques for frequency-weighted H2 norms. Comparison of performance and robustness to plant uncertainty for this control design approach is included in the discussion. System performance is demonstrated in the presence of plant modeling error.

Optimal Control Design Using an H2 Method for the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT)

NASA Technical Reports Server (NTRS)

Calhoun, Phillip C.; Hampton, R. David; Whorton, Mark S.

2001-01-01

The acceleration environment on the International Space Station (ISS) will likely exceed the requirements of many micro-gravity experiments. The Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) is being built by the NASA Marshall Space Flight Center to attenuate the nominal acceleration environment and provide some isolation for micro-gravity science experiments. G-LIMIT uses Lorentz (voice-coil) magnetic actuators to isolate a platform for mounting science payloads from the nominal acceleration environment. The system utilizes payload acceleration, relative position, and relative orientation measurements in a feedback controller to accomplish the vibration isolation task. The controller provides current command to six magnetic actuators, producing the required experiment isolation from the ISS acceleration environment. This paper presents the development of a candidate control law to meet the acceleration attenuation requirements for the g-LIMIT experiment platform. The controller design is developed using linear optimal control techniques for both frequency-weighted H(sub 2) and H(sub infinity) norms. Comparison of the performance and robustness to plant uncertainty for these two optimal control design approaches are included in the discussion.

Superconducting Coil Winding Machine Control System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nogiec, J. M.; Kotelnikov, S.; Makulski, A.

The Spirex coil winding machine is used at Fermilab to build coils for superconducting magnets. Recently this ma-chine was equipped with a new control system, which al-lows operation from both a computer and a portable remote control unit. This control system is distributed between three layers, implemented on a PC, real-time target, and FPGA, providing respectively HMI, operational logic and direct controls. The system controls motion of all mechan-ical components and regulates the cable tension. Safety is ensured by a failsafe, redundant system.

A superconducting large-angle magnetic suspension

NASA Technical Reports Server (NTRS)

Downer, James R.; Anastas, George V., Jr.; Bushko, Dariusz A.; Flynn, Frederick J.; Goldie, James H.; Gondhalekar, Vijay; Hawkey, Timothy J.; Hockney, Richard L.; Torti, Richard P.

1992-01-01

SatCon Technology Corporation has completed a Small Business Innovation Research (SBIR) Phase 2 program to develop a Superconducting Large-Angle Magnetic Suspension (LAMS) for the NASA Langley Research Center. The Superconducting LAMS was a hardware demonstration of the control technology required to develop an advanced momentum exchange effector. The Phase 2 research was directed toward the demonstration for the key technology required for the advanced concept CMG, the controller. The Phase 2 hardware consists of a superconducting solenoid ('source coils') suspended within an array of nonsuperconducting coils ('control coils'), a five-degree-of-freedom positioning sensing system, switching power amplifiers, and a digital control system. The results demonstrated the feasibility of suspending the source coil. Gimballing (pointing the axis of the source coil) was demonstrated over a limited range. With further development of the rotation sensing system, enhanced angular freedom should be possible.

A superconducting large-angle magnetic suspension

NASA Astrophysics Data System (ADS)

Downer, James R.; Anastas, George V., Jr.; Bushko, Dariusz A.; Flynn, Frederick J.; Goldie, James H.; Gondhalekar, Vijay; Hawkey, Timothy J.; Hockney, Richard L.; Torti, Richard P.

1992-12-01

SatCon Technology Corporation has completed a Small Business Innovation Research (SBIR) Phase 2 program to develop a Superconducting Large-Angle Magnetic Suspension (LAMS) for the NASA Langley Research Center. The Superconducting LAMS was a hardware demonstration of the control technology required to develop an advanced momentum exchange effector. The Phase 2 research was directed toward the demonstration for the key technology required for the advanced concept CMG, the controller. The Phase 2 hardware consists of a superconducting solenoid ('source coils') suspended within an array of nonsuperconducting coils ('control coils'), a five-degree-of-freedom positioning sensing system, switching power amplifiers, and a digital control system. The results demonstrated the feasibility of suspending the source coil. Gimballing (pointing the axis of the source coil) was demonstrated over a limited range. With further development of the rotation sensing system, enhanced angular freedom should be possible.

Feedforward and feedback control of locked mode phase and rotation in DIII-D with application to modulated ECCD experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, W.; La Haye, R. J.; Lanctot, M. J.

The toroidal phase and rotation of otherwise locked magnetic islands of toroidal mode number n=1 are controlled in the DIII-D tokamak by means of applied magnetic perturbations of n=1. Pre-emptive perturbations were applied in feedforward to "catch" the mode as it slowed down and entrain it to the rotating field before complete locking, thus avoiding the associated major confinement degradation. Additionally, for the first time, the phase of the perturbation was optimized in real-time, in feedback with magnetic measurements, in order for the mode’s phase to closely match a prescribed phase, as a function of time. Experimental results confirm themore » capability to hold the mode in a given fixed-phase or to rotate it at up to 20 Hz with good uniformity. The controlcoil currents utilized in the experiments agree with the requirements estimated by an electromechanical model. Moreover, controlled rotation at 20 Hz was combined with Electron Cyclotron Current Drive (ECCD) modulated at the same frequency. This is simpler than regulating the ECCD modulation in feedback with spontaneous mode rotation, and enables repetitive, reproducible ECCD deposition at or near the island O-point, X-point and locations in between, for careful studies of how this affects the island stability. Current drive was found to be radially misaligned relative to the island, and resulting growth and shrinkage of islands matched expectations of the Modified Rutherford Equation for some discharges presented here. Finally, simulations predict the as designed ITER 3D coils can entrain a small island at sub-10 Hz frequencies.« less

Feedforward and feedback control of locked mode phase and rotation in DIII-D with application to modulated ECCD experiments

DOE PAGES

Choi, W.; La Haye, R. J.; Lanctot, M. J.; ...

2018-02-05

The toroidal phase and rotation of otherwise locked magnetic islands of toroidal mode number n=1 are controlled in the DIII-D tokamak by means of applied magnetic perturbations of n=1. Pre-emptive perturbations were applied in feedforward to "catch" the mode as it slowed down and entrain it to the rotating field before complete locking, thus avoiding the associated major confinement degradation. Additionally, for the first time, the phase of the perturbation was optimized in real-time, in feedback with magnetic measurements, in order for the mode’s phase to closely match a prescribed phase, as a function of time. Experimental results confirm themore » capability to hold the mode in a given fixed-phase or to rotate it at up to 20 Hz with good uniformity. The controlcoil currents utilized in the experiments agree with the requirements estimated by an electromechanical model. Moreover, controlled rotation at 20 Hz was combined with Electron Cyclotron Current Drive (ECCD) modulated at the same frequency. This is simpler than regulating the ECCD modulation in feedback with spontaneous mode rotation, and enables repetitive, reproducible ECCD deposition at or near the island O-point, X-point and locations in between, for careful studies of how this affects the island stability. Current drive was found to be radially misaligned relative to the island, and resulting growth and shrinkage of islands matched expectations of the Modified Rutherford Equation for some discharges presented here. Finally, simulations predict the as designed ITER 3D coils can entrain a small island at sub-10 Hz frequencies.« less

Kinetic studies on strand displacement in de novo designed parallel heterodimeric coiled coils.

PubMed

Groth, Mike C; Rink, W Mathis; Meyer, Nils F; Thomas, Franziska

2018-05-14

Among the protein folding motifs, which are accessible by de novo design, the parallel heterodimeric coiled coil is most frequently used in bioinspired applications and chemical biology in general. This is due to the straightforward sequence-to-structure relationships, which it has in common with all coiled-coil motifs, and the heterospecificity, which allows control of association. Whereas much focus was laid on designing orthogonal coiled coils, systematic studies on controlling association, for instance by strand displacement, are rare. As a contribution to the design of dynamic coiled-coil-based systems, we studied the strand-displacement mechanism in obligate heterodimeric coiled coils to investigate the suitability of the dissociation constants ( K D ) as parameters for the prediction of the outcome of strand-displacement reactions. We use two sets of heterodimeric coiled coils, the previously reported N-A x B y and the newly characterized C-A x B y . Both comprise K D values in the μM to sub-nM regime. Strand displacement is explored by CD titration and a FRET-based kinetic assay and is proved to be an equilibrium reaction with half-lifes from a few seconds up to minutes. We could fit the displacement data by a competitive binding model, giving rate constants and overall affinities of the underlying association and dissociation reactions. The overall affinities correlate well with the ratios of K D values determined by CD-thermal denaturation experiments and, hence, support the dissociative mechanism of strand displacement in heterodimeric coiled coils. From the results of more than 100 different displacement reactions we are able to classify three categories of overall affinities, which allow for easy prediction of the equilibrium of strand displacement in two competing heterodimeric coiled coils.

DOE Office of Scientific and Technical Information (OSTI.GOV)

X. Zhao, S. Ramakrishnan, J. Lawson, C.Neumeyer, R. Marsala, H. Schneider, Engineering Operations

NSTX at Princeton Plasma Physics Laboratory (PPPL) requires sophisticated plasma positioning control system for stable plasma operation. TF magnetic coils and PF magnetic coils provide electromagnetic fields to position and shape the plasma vertically and horizontally respectively. NSTX utilizes twenty six coil power supplies to establish and initiate electromagnetic fields through the coil system for plasma control. A power protection and interlock system is utilized to detect power system faults and protect the TF coils and PF coils against excessive electromechanical forces, overheating, and over current. Upon detecting any fault condition the power system is restricted, and it is eithermore » prevented from initializing or suppressed to de-energize coil power during pulsing. Power fault status is immediately reported to the computer system. This paper describes the design and operation of NSTX's protection and interlocking system and possible future expansion.« less

Results of coil closure of patent ductus arteriosus using a tapered tip catheter for enhanced control.

PubMed

Devanagondi, Rajiv; Latson, Larry; Bradley-Skelton, Sharon; Prieto, Lourdes

2016-08-01

This article describes the efficacy and embolization rates of coil delivery via modified vertebral catheter (MVC) for patent ductus arteriosus (PDA) closure. Various techniques have been devised to enhance coil control and prevent embolization during PDA closure. Since 1995, they have delivered coils via tapered vertebral catheters for improved coil control. Catheterization reports, angiograms, and echocardiograms were reviewed for patients with PDA occlusion via MVC from 2001 to 2014. Residual shunting was determined by angiography and echocardiogram within 24 hr post-procedure. Procedural success was defined as ≤ trivial angiographic and echocardiographic shunt, and no aortic nor LPA obstruction, after final coil delivery. About 125 coil occlusions were attempted in 103 patients. Minimal PDA diameter was 2 (0.6-6) mm. Four coils were removed with a snare/bioptome due to aortic/LPA obstruction following release. Seven were malpositioned while still held by the MVC of which three embolized while attempting withdrawal. Five embolized after full release from the MVC. The embolization rate was 6.4%. Embolizations were more likely in PDAs ≥ 2.5 mm (P < 0.05). Ultimately, 98/103 PDAs were occluded using the MVC. No patient had greater trivial residual shunt or aortic/LPA obstruction for an overall success rate of 95%. For PDAs < 2.5 mm the success rate was 97%. Coil delivery via MVC was safe and effective for small PDAs. While fully controlled release and retrieval devices are now available for PDA closure with lower embolization rates, coil occlusion by MVC should still be considered for small PDAs, especially in resource limited regions. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Kinetic studies on strand displacement in de novo designed parallel heterodimeric coiled coils† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc05342h

PubMed Central

Groth, Mike C.; Rink, W. Mathis; Meyer, Nils F.

2018-01-01

Among the protein folding motifs, which are accessible by de novo design, the parallel heterodimeric coiled coil is most frequently used in bioinspired applications and chemical biology in general. This is due to the straightforward sequence-to-structure relationships, which it has in common with all coiled-coil motifs, and the heterospecificity, which allows control of association. Whereas much focus was laid on designing orthogonal coiled coils, systematic studies on controlling association, for instance by strand displacement, are rare. As a contribution to the design of dynamic coiled-coil-based systems, we studied the strand-displacement mechanism in obligate heterodimeric coiled coils to investigate the suitability of the dissociation constants (KD) as parameters for the prediction of the outcome of strand-displacement reactions. We use two sets of heterodimeric coiled coils, the previously reported N-AxBy and the newly characterized C-AxBy. Both comprise KD values in the μM to sub-nM regime. Strand displacement is explored by CD titration and a FRET-based kinetic assay and is proved to be an equilibrium reaction with half-lifes from a few seconds up to minutes. We could fit the displacement data by a competitive binding model, giving rate constants and overall affinities of the underlying association and dissociation reactions. The overall affinities correlate well with the ratios of KD values determined by CD-thermal denaturation experiments and, hence, support the dissociative mechanism of strand displacement in heterodimeric coiled coils. From the results of more than 100 different displacement reactions we are able to classify three categories of overall affinities, which allow for easy prediction of the equilibrium of strand displacement in two competing heterodimeric coiled coils. PMID:29780562

Actuator with built-in viscous damping for isolation and structural control

NASA Astrophysics Data System (ADS)

Hyde, T. Tupper; Anderson, Eric H.

1994-05-01

This paper describes the development and experimental application of an actuator with built-in viscous damping. An existing passive damper was modified for use as a novel actuation device for isolation and structural control. The device functions by using the same fluid for viscous damping and as a hydraulic lever for a voice coil actuator. Applications for such an actuator include structural control and active isolation. Lumped parameter models capturing structural and fluid effects are presented. Component tests of free stroke, blocked force, and passive complex stiffness are used to update the assumed model parameters. The structural damping effectiveness of the new actuator is shown to be that of a regular D-strut passively and that of a piezoelectric strut with load cell feedback actively in a complex testbed structure. Open and closed loop results are presented for a force isolation application showing an 8 dB passive and 20 dB active improvement over an undamped mount. An optimized design for a future experimental testbed is developed.

A wide-band fiber optic frequency distribution system employing thermally controlled phase compensation

NASA Technical Reports Server (NTRS)

Johnson, Dean; Calhoun, Malcolm; Sydnor, Richard; Lutes, George

1993-01-01

An active wide-band fiber optic frequency distribution system employing a thermally controlled phase compensator to stabilize phase variations induced by environmental temperature changes is described. The distribution system utilizes bidirectional dual wavelength transmission to provide optical feedback of induced phase variations of 100 MHz signals propagating along the distribution cable. The phase compensation considered differs from earlier narrow-band phase compensation designs in that it uses a thermally controlled fiber delay coil rather than a VCO or phase modulation to compensate for induced phase variations. Two advantages of the wide-band system over earlier designs are (1) that it provides phase compensation for all transmitted frequencies, and (2) the compensation is applied after the optical interface rather than electronically ahead of it as in earlier schemes. Experimental results on the first prototype shows that the thermal stabilizer reduces phase variations and Allan deviation by a factor of forty over an equivalent uncompensated fiber optic distribution system.

Double layer field shaping systems for toroidal plasmas

DOEpatents

Ohyabu, Nobuyoshi

1982-01-01

Methods and apparatus for plasma generation, confinement and control such as Tokamak plasma systems are described having a two layer field shaping coil system comprising an inner coil layer close to the plasma and an outer coil layer to minimize the current in the inner coil layer.

Diagnostics for real-time plasma control in PBX-M

NASA Astrophysics Data System (ADS)

Kaita, R.; Batha, S.; Bell, R. E.; Bernabei, S.; Hatcher, R.; Kozub, T.; Kugel, H.; Levinton, F.; Okabayashi, M.; Sesnic, S.; von Goeler, S.; Zolfaghari, A.; PBX-M Group

1995-01-01

An important issue for future tokamaks is real-time plasma control for the avoidance of magnetohydrodynamic instabilities and other applications that require detailed plasma profile and fluctuation data. Although measurements from diagnostics providing this information require significantly more processing than magnetic flux data, recent advancements could make them practical for adjusting operational settings for plasma heating and current drive systems as well as field coil currents. On the Princeton Beta Experiment-Modification (PBX-M), the lower hybrid current drive phasing can be varied during a plasma shot using digitally programmable ferrite phase shifters, and neural beam functions can be fully computer controlled. PBX-M diagnostics that may be used for control purposes include motional Stark-effect polarimetry for magnetic field pitch angle profiles, soft x-ray arrays for plasma position control and the separation of βp from li, hard x-ray detectors for energetic electron distributions, a multichannel electron cyclotron emission radiometer for ballooning mode identification, and passive plate eddy current monitors for kink stabilization. We will describe the present status of these systems on PBX-M, and discuss their suitability for feedback applications.

Experimental study of a self-powered and sensing MR-damper-based vibration control system

NASA Astrophysics Data System (ADS)

Sapiński, Bogdan

2011-10-01

The paper deals with a semi-active vibration control system based on a magnetorheological (MR) damper. The study outlines the model and the structure of the system, and describes its experimental investigation. The conceptual design of this system involves harvesting energy from structural vibrations using an energy extractor based on an electromagnetic transduction mechanism (Faraday's law). The system consists of an electromagnetic induction device (EMI) prototype and an MR damper of RD-1005 series manufactured by Lord Corporation. The energy extracted is applied to control the damping characteristics of the MR damper. The model of the system was used to prove that the proposed vibration control system is feasible. The system was realized in the semi-active control strategy with energy recovery and examined through experiments in the cases where the control coil of the MR damper was voltage-supplied directly from the EMI or voltage-supplied via the rectifier, or supplied with a current control system with two feedback loops. The external loop used the sky-hook algorithm whilst the internal loop used the algorithm switching the photorelay, at the output from the rectifier. Experimental results of the proposed vibration control system were compared with those obtained for the passive system (MR damper is off-state) and for the system with an external power source (conventional system) when the control coil of the MR damper was supplied by a DC power supply and analogue voltage amplifier or a DC power supply and a photorelay. It was demonstrated that the system is able to power-supply the MR damper and can adjust itself to structural vibrations. It was also found that, since the signal of induced voltage from the EMI agrees well with that of the relative velocity signal across the damper, the device can act as a 'velocity-sign' sensor.

High performance advanced tokamak regimes in DIII-D for next-step experiments

NASA Astrophysics Data System (ADS)

Greenfield, C. M.; Murakami, M.; Ferron, J. R.; Wade, M. R.; Luce, T. C.; Petty, C. C.; Menard, J. E.; Petrie, T. W.; Allen, S. L.; Burrell, K. H.; Casper, T. A.; DeBoo, J. C.; Doyle, E. J.; Garofalo, A. M.; Gorelov, I. A.; Groebner, R. J.; Hobirk, J.; Hyatt, A. W.; Jayakumar, R. J.; Kessel, C. E.; La Haye, R. J.; Jackson, G. L.; Lohr, J.; Makowski, M. A.; Pinsker, R. I.; Politzer, P. A.; Prater, R.; Strait, E. J.; Taylor, T. S.; West, W. P.; DIII-D Team

2004-05-01

Advanced Tokamak (AT) research in DIII-D [K. H. Burrell for the DIII-D Team, in Proceedings of the 19th Fusion Energy Conference, Lyon, France, 2002 (International Atomic Energy Agency, Vienna, 2002) published on CD-ROM] seeks to provide a scientific basis for steady-state high performance operation in future devices. These regimes require high toroidal beta to maximize fusion output and poloidal beta to maximize the self-driven bootstrap current. Achieving these conditions requires integrated, simultaneous control of the current and pressure profiles, and active magnetohydrodynamic stability control. The building blocks for AT operation are in hand. Resistive wall mode stabilization via plasma rotation and active feedback with nonaxisymmetric coils allows routine operation above the no-wall beta limit. Neoclassical tearing modes are stabilized by active feedback control of localized electron cyclotron current drive (ECCD). Plasma shaping and profile control provide further improvements. Under these conditions, bootstrap supplies most of the current. Steady-state operation requires replacing the remaining Ohmic current, mostly located near the half radius, with noninductive external sources. In DIII-D this current is provided by ECCD, and nearly stationary AT discharges have been sustained with little remaining Ohmic current. Fast wave current drive is being developed to control the central magnetic shear. Density control, with divertor cryopumps, of AT discharges with edge localized moding H-mode edges facilitates high current drive efficiency at reactor relevant collisionalities. A sophisticated plasma control system allows integrated control of these elements. Close coupling between modeling and experiment is key to understanding the separate elements, their complex nonlinear interactions, and their integration into self-consistent high performance scenarios. Progress on this development, and its implications for next-step devices, will be illustrated by results of recent experiment and simulation efforts.

Reduction of characteristic RL time for fast, efficient magnetic levitation

NASA Astrophysics Data System (ADS)

Li, Yuqing; Feng, Guosheng; Wang, Xiaofeng; Wu, Jizhou; Ma, Jie; Xiao, Liantuan; Jia, Suotang

2017-09-01

We demonstrate the reduction of characteristic time in resistor-inductor (RL) circuit for fast, efficient magnetic levitation according to Kirchhoff's circuit laws. The loading time is reduced by a factor of ˜4 when a high-power resistor is added in series with the coils. By using the controllable output voltage of power supply and voltage of feedback circuit, the loading time is further reduced by ˜ 3 times. The overshoot loading in advance of the scheduled magnetic field gradient is equivalent to continuously adding a resistor without heating. The magnetic field gradient with the reduced loading time is used to form the upward magnetic force against to the gravity of the cooled Cs atoms, and we obtain an effectively levitated loading of the Cs atoms to a crossed optical dipole trap.

Control of critical coupling in a coiled coaxial cable resonator.

PubMed

Huang, Jie; Wei, Tao; Wang, Tao; Fan, Jun; Xiao, Hai

2014-05-01

This paper reports a coiled coaxial cable resonator fabricated by cutting a slot in a spring-like coiled coaxial cable to produce a periodic perturbation. Electromagnetic coupling between two neighboring slots was observed. By manipulating the number of slots, critical coupling of the coiled coaxial cable resonator can be well controlled. An ultrahigh signal-to-noise ratio (over 50 dB) at the resonant frequency band was experimentally achieved from a coiled coaxial cable resonator with 38 turns. A theoretic model is developed to understand the device physics. The proposed device can be potentially used as a high quality and flexibly designed band-stop filter or a sensor in structural health monitoring.

Development of a simple MR-compatible vibrotactile stimulator using a planar-coil-type actuator.

PubMed

Kim, Hyung-Sik; Choi, Mi-Hyun; Chung, Yoon-Gi; Kim, Sung-Phil; Jun, Jae-Hoon; Park, Jang-Yeon; Yi, Jeong-Han; Park, Jong-Rak; Lim, Dae-Woon; Chung, Soon-Cheol

2013-06-01

For this study, we developed a magnetic resonance (MR)-compatible vibrotactile stimulator using a planar-coil-type actuator. The newly developed vibrotactile stimulator consists of three units: control unit, drive unit, and planar-coil-type actuator. The control unit controls frequency, intensity, time, and channel, and transfers the stimulation signals to the drive unit. The drive unit operates the planar-coil-type actuator in response to commands from the control unit. The planar-coil-type actuator, which uses a planar coil instead of conventional electric wire, generates vibrating stimulation through interaction of the current of the planar coil with the static magnetic field of the MR scanner. Even though the developed tactile stimulating system is small, simple, and inexpensive, it has a wide range of stimulation frequencies (20 ~ 400 Hz, at 40 levels) and stimulation intensities (0 ~ 7 V, at 256 levels). The stimulation intensity does not change due to frequency changes. Since the transient response time is a few microseconds, the stimulation time can be controlled on a scale of microseconds. In addition, this actuator has the advantages of providing highly repeatable stimulation, being durable, being able to assume various shapes, and having an adjustable contact area with the skin. The new stimulator operated stably in an MR environment without affecting the MR images. Using functional magnetic resonance imaging, we observed the brain activation changes resulting from stimulation frequency and intensity changes.

Innovations in compact stellarator coil design

NASA Astrophysics Data System (ADS)

Pomphrey, N.; Berry, L.; Boozer, A.; Brooks, A.; Hatcher, R. E.; Hirshman, S. P.; Ku, L.-P.; Miner, W. H.; Mynick, H. E.; Reiersen, W.; Strickler, D. J.; Valanju, P. M.

2001-03-01

Experimental devices for the study of the physics of high beta (β gtrsim 4%), low aspect ratio (A lesssim 4.5) stellarator plasmas require coils that will produce plasmas satisfying a set of physics goals, provide experimental flexibility and be practical to construct. In the course of designing a flexible coil set for the National Compact Stellarator Experiment, several innovations have been made that may be useful in future stellarator design efforts. These include: the use of singular value decomposition methods for obtaining families of smooth current potentials on distant coil winding surfaces from which low current density solutions may be identified; the use of a control matrix method for identifying which few of the many detailed elements of a stellarator boundary must be targeted if a coil set is to provide fields to control the essential physics of the plasma; the use of a genetic algorithm for choosing an optimal set of discrete coils from a continuum of potential contours; the evaluation of alternate coil topologies for balancing the trade-off between physics objectives and engineering constraints; the development of a new coil optimization code for designing modular coils and the identification of a `natural' basis for describing current sheet distributions.

Energy landscapes of a mechanical prion and their implications for the molecular mechanism of long-term memory.

PubMed

Chen, Mingchen; Zheng, Weihua; Wolynes, Peter G

2016-05-03

Aplysia cytoplasmic polyadenylation element binding (CPEB) protein, a translational regulator that recruits mRNAs and facilitates translation, has been shown to be a key component in the formation of long-term memory. Experimental data show that CPEB exists in at least a low-molecular weight coiled-coil oligomeric form and an amyloid fiber form involving the Q-rich domain (CPEB-Q). Using a coarse-grained energy landscape model, we predict the structures of the low-molecular weight oligomeric form and the dynamics of their transitions to the β-form. Up to the decamer, the oligomeric structures are predicted to be coiled coils. Free energy profiles confirm that the coiled coil is the most stable form for dimers and trimers. The structural transition from α to β is shown to be concentration dependent, with the transition barrier decreasing with increased concentration. We observe that a mechanical pulling force can facilitate the α-helix to β-sheet (α-to-β) transition by lowering the free energy barrier between the two forms. Interactome analysis of the CPEB protein suggests that its interactions with the cytoskeleton could provide the necessary mechanical force. We propose that, by exerting mechanical forces on CPEB oligomers, an active cytoskeleton can facilitate fiber formation. This mechanical catalysis makes possible a positive feedback loop that would help localize the formation of CPEB fibers to active synapse areas and mark those synapses for forming a long-term memory after the prion form is established. The functional role of the CPEB helical oligomers in this mechanism carries with it implications for targeting such species in neurodegenerative diseases.

Robust SMES controller design for stabilization of inter-area oscillation considering coil size and system uncertainties

NASA Astrophysics Data System (ADS)

Ngamroo, Issarachai

2010-12-01

It is well known that the superconducting magnetic energy storage (SMES) is able to quickly exchange active and reactive power with the power system. The SMES is expected to be the smart storage device for power system stabilization. Although the stabilizing effect of SMES is significant, the SMES is quite costly. Particularly, the superconducting magnetic coil size which is the essence of the SMES, must be carefully selected. On the other hand, various generation and load changes, unpredictable network structure, etc., cause system uncertainties. The power controller of SMES which is designed without considering such uncertainties, may not tolerate and loses stabilizing effect. To overcome these problems, this paper proposes the new design of robust SMES controller taking coil size and system uncertainties into account. The structure of the active and reactive power controllers is the 1st-order lead-lag compensator. No need for the exact mathematical representation, system uncertainties are modeled by the inverse input multiplicative perturbation. Without the difficulty of the trade-off of damping performance and robustness, the optimization problem of control parameters is formulated. The particle swarm optimization is used for solving the optimal parameters at each coil size automatically. Based on the normalized integral square error index and the consideration of coil current constraint, the robust SMES with the smallest coil size which still provides the satisfactory stabilizing effect, can be achieved. Simulation studies in the two-area four-machine interconnected power system show the superior robustness of the proposed robust SMES with the smallest coil size under various operating conditions over the non-robust SMES with large coil size.

Numerical simulations on active shielding methods comparison and wrapped angle optimization for gradient coil design in MRI with enhanced shielding effect

NASA Astrophysics Data System (ADS)

Wang, Yaohui; Xin, Xuegang; Guo, Lei; Chen, Zhifeng; Liu, Feng

2018-05-01

The switching of a gradient coil current in magnetic resonance imaging will induce an eddy current in the surrounding conducting structures while the secondary magnetic field produced by the eddy current is harmful for the imaging. To minimize the eddy current effects, the stray field shielding in the gradient coil design is usually realized by minimizing the magnetic fields on the cryostat surface or the secondary magnetic fields over the imaging region. In this work, we explicitly compared these two active shielding design methods. Both the stray field and eddy current on the cryostat inner surface were quantitatively discussed by setting the stray field constraint with an ultra-low maximum intensity of 2 G and setting the secondary field constraint with an extreme small shielding ratio of 0.000 001. The investigation revealed that the secondary magnetic field control strategy can produce coils with a better performance. However, the former (minimizing the magnetic fields) is preferable when designing a gradient coil with an ultra-low eddy current that can also strictly control the stray field leakage at the edge of the cryostat inner surface. A wrapped-edge gradient coil design scheme was then optimized for a more effective control of the stray fields. The numerical simulation on the wrapped-edge coil design shows that the optimized wrapping angles for the x and z coils in terms of our coil dimensions are 40° and 90°, respectively.

Understanding Peptide Oligomeric State in Langmuir Monolayers of Amphiphilic 3-Helix Bundle-Forming Peptide-PEG Conjugates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lund, Reidar; Ang, JooChuan; Shu, Jessica Y.

Coiled-coil peptide-polymer conjugates are an emerging class of biomaterials. Fundamental understanding of the coiled-coil oligomeric state and assembly process of these hybrid building blocks is necessary to exert control over their assembly into well-defined structures. Here in this paper, we studied the effect of peptide structure and PEGylation on the self-assembly process and oligomeric state of a Langmuir monolayer of amphiphilic coiled-coil peptide-polymer conjugates using X-ray reflectivity (XR) and grazing-incidence X-ray diffraction (GIXD). Our results show that the oligomeric state of PEGylated amphiphiles based on 3-helix bundle-forming peptide is surface pressure dependent, a mixture of dimers and trimers was formedmore » at intermediate surface pressure but transitions into trimers completely upon increasing surface pressure. Moreover, the interhelical distance within the coiled-coil bundle of 3-helix peptide-PEG conjugate amphiphiles was not perturbed under high surface pressure. Present studies provide valuable insights into the self-assembly process of hybrid peptide-polymer conjugates and guidance to develop biomaterials with controlled multivalency of ligand presentation.« less

Understanding Peptide Oligomeric State in Langmuir Monolayers of Amphiphilic 3-Helix Bundle-Forming Peptide-PEG Conjugates

DOE PAGES

Lund, Reidar; Ang, JooChuan; Shu, Jessica Y.; ...

2016-10-26

Coiled-coil peptide-polymer conjugates are an emerging class of biomaterials. Fundamental understanding of the coiled-coil oligomeric state and assembly process of these hybrid building blocks is necessary to exert control over their assembly into well-defined structures. Here in this paper, we studied the effect of peptide structure and PEGylation on the self-assembly process and oligomeric state of a Langmuir monolayer of amphiphilic coiled-coil peptide-polymer conjugates using X-ray reflectivity (XR) and grazing-incidence X-ray diffraction (GIXD). Our results show that the oligomeric state of PEGylated amphiphiles based on 3-helix bundle-forming peptide is surface pressure dependent, a mixture of dimers and trimers was formedmore » at intermediate surface pressure but transitions into trimers completely upon increasing surface pressure. Moreover, the interhelical distance within the coiled-coil bundle of 3-helix peptide-PEG conjugate amphiphiles was not perturbed under high surface pressure. Present studies provide valuable insights into the self-assembly process of hybrid peptide-polymer conjugates and guidance to develop biomaterials with controlled multivalency of ligand presentation.« less

Analysis of TMT primary mirror control-structure interaction

NASA Astrophysics Data System (ADS)

MacMynowski, Douglas G.; Thompson, Peter M.; Sirota, Mark J.

2008-07-01

The primary mirror control system (M1CS) keeps the 492 segments of the Thirty Meter Telescope primary mirror aligned in the presence of disturbances. A global position control loop uses feedback from inter-segment edge sensors to three actuators behind each segment that control segment piston, tip and tilt. If soft force actuators are used (e.g. voice-coil), then in addition to the global position loop there will be a local servo loop to provide stiffness. While the M1 control system at Keck compensates only for slow disturbances such as gravity and thermal variations, the M1CS for TMT will need to provide some compensation for higher frequency wind disturbances in order to meet stringent error budget targets. An analysis of expected high-wavenumber wind forces on M1 suggests that a 1Hz control bandwidth is required for the global feedback of segment edge-sensorbased position information in order to minimize high spatial frequency segment response for both seeing-limited and adaptive optics performance. A much higher bandwidth is required from the local servo loop to provide adequate stiffness to wind or acoustic disturbances. A related paper presents the control designs for the local actuator servo loops. The disturbance rejection requirements would not be difficult to achieve for a single segment, but the structural coupling between segments mounted on a flexible mirror cell results in controlstructure interaction (CSI) that limits the achievable bandwidth. Using a combination of simplified modeling to build intuition and the full telescope finite element model for verification, we present designs and analysis for both the local servo loop and global loop demonstrating sufficient bandwidth and resulting wind-disturbance rejection despite the presence of CSI.

Integrated Scenario Modeling of NSTX Advanced Plasma Configurations

NASA Astrophysics Data System (ADS)

Kessel, Charles; Synakowski, Edward

2003-10-01

The Spherical Torus will provide an attractive fusion energy source if it can demonstrate the following major features: high elongation and triangularity, 100% non-inductive current with a credible path to high bootstrap fractions, non-solenoidal startup and current rampup, high beta with stabilization of RWM instabilities, and sufficiently high energy confinement. NSTX has specific experimental milestones to examine these features, and integrated scenario modeling is helping to understand how these configurations might be produced and what tools are needed to access this operating space. Simulations with the Tokamak Simulation Code (TSC), CURRAY, and JSOLVER/BALMSC/PEST2 have identified fully non-inductively sustained, high beta plasmas that rely on strong plasma shaping accomplished with a PF coil modification, off-axis current drive from Electron Bernstein Waves (EBW), flexible on-axis heating and CD from High Harmonic Fast Wave (HHFW) and Neutral Beam Injection (NBI), and density control. Ideal MHD stability shows that with wall stabilization through plasma rotation and/or RWM feedback coils, a beta of 40% is achievable, with 100% non-inductive current sustained for 4 current diffusion times. Experimental data and theory are combined to produce a best extrapolation to these regimes, which is continuously improved as the discharges approach these parameters, and theoretical/computational methods expand. Further investigations and development for integrated scenario modeling on NSTX is discussed.

Passive radiative cooling of a HTS coil for attitude orbit control in micro-spacecraft

NASA Astrophysics Data System (ADS)

Inamori, Takaya; Ozaki, Naoya; Saisutjarit, Phongsatorn; Ohsaki, Hiroyuki

2015-02-01

This paper proposes a novel radiative cooling system for a high temperature superconducting (HTS) coil for an attitude orbit control system in nano- and micro-spacecraft missions. These days, nano-spacecraft (1-10 kg) and micro-spacecraft (10-100 kg) provide space access to a broader range of spacecraft developers and attract interest as space development applications. In planetary and high earth orbits, most previous standard-size spacecraft used thrusters for their attitude and orbit control, which are not available for nano- and micro-spacecraft missions because of the strict power consumption, space, and weight constraints. This paper considers orbit and attitude control methods that use a superconducting coil, which interacts with on-orbit space plasmas and creates a propulsion force. Because these spacecraft cannot use an active cooling system for the superconducting coil because of their mass and power consumption constraints, this paper proposes the utilization of a passive radiative cooling system, in which the superconducting coil is thermally connected to the 3 K cosmic background radiation of deep space, insulated from the heat generation using magnetic holders, and shielded from the sun. With this proposed cooling system, the HTS coil is cooled to 60 K in interplanetary orbits. Because the system does not use refrigerators for its cooling system, the spacecraft can achieve an HTS coil with low power consumption, small mass, and low cost.

Obtaining changes in calibration-coil to seismometer output constants using sine waves

USGS Publications Warehouse

Ringler, Adam T.; Hutt, Charles R.; Gee, Lind S.; Sandoval, Leo D.; Wilson, David C.

2013-01-01

The midband sensitivity of a broadband seismometer is one of the most commonly used parameters from station metadata. Thus, it is critical for station operators to robustly estimate this quantity with a high degree of accuracy. We develop an in situ method for estimating changes in sensitivity using sine‐wave calibrations, assuming the calibration coil and its drive are stable over time and temperature. This approach has been used in the past for passive instruments (e.g., geophones) but has not been applied, to our knowledge, to derive sensitivities of modern force‐feedback broadband seismometers. We are able to detect changes in sensitivity to well within 1%, and our method is capable of detecting these sensitivity changes using any frequency of sine calibration within the passband of the instrument.

Multiphase soft switched DC/DC converter and active control technique for fuel cell ripple current elimination

DOEpatents

Lai, Jih-Sheng; Liu, Changrong; Ridenour, Amy

2009-04-14

DC/DC converter has a transformer having primary coils connected to an input side and secondary coils connected to an output side. Each primary coil connects a full-bridge circuit comprising two switches on two legs, the primary coil being connected between the switches on each leg, each full-bridge circuit being connected in parallel wherein each leg is disposed parallel to one another, and the secondary coils connected to a rectifying circuit. An outer loop control circuit that reduces ripple in a voltage reference has a first resistor connected in series with a second resistor connected in series with a first capacitor which are connected in parallel with a second capacitor. An inner loop control circuit that reduces ripple in a current reference has a third resistor connected in series with a fourth resistor connected in series with a third capacitor which are connected in parallel with a fourth capacitor.

Campaign for Levitation in LDX

NASA Astrophysics Data System (ADS)

Garnier, D. T.; Hansen, A. K.; Mauel, M. E.; Ortiz, E. E.; Boxer, A. C.; Ellsworth, J. L.; Karim, I.; Kesner, J.; Michael, P. C.; Zhukovsky, A.

2006-10-01

In the past year, preparations have been made for the first flight of the Levitated Dipole Experiment (LDX). LDX, which consists of a 560 kg superconducting coil floating within a 5 m diameter vacuum chamber, is designed to study fusion relevant plasmas confined in a dipole magnetic field. During the spring, a high temperature superconducting levitation coil was integrated into the LDX facility. Testing was undertaken to verify the thermal performance of the coil under expected levitation conditions. In addition, a real-time operating system digital control system was developed that will be used for the levitation control. In July, plasma experiments were conducted with all superconducting magnets in operation. While still supported, roughly 75% of the weight of the floating coil was magnetically lifted by the levitation coil above. A series of plasma experiments were conducted with the same magnetic geometry as will be the case during levitation. During August, the second generation launcher system will be installed. The launcher, which retracts beyond the plasma's last closed field lines during operation, is designed to safely catch the floating coil following an unexpected loss of control. After this installation, levitation experiments will commence.

Magnetic Catheter Manipulation in the Interventional MRI Environment

PubMed Central

Wilson, Mark W.; Martin, Alastair B.; Lillaney, Prasheel; Losey, Aaron D.; Yee, Erin J.; Bernhardt, Anthony; Malba, Vincent; Evans, Lee; Sincic, Ryan; Saeed, Maythem; Arenson, Ronald L.; Hetts, Steven W.

2013-01-01

Purpose To evaluate deflection capability of a prototype endovascular catheter, which is remotely magnetically steerable, for use in the interventional MRI environment. Materials and Methods Copper coils were mounted on the tips of commercially available 2.3 – 3.0 Fr microcatheters. The coils were fabricated in a novel manner by plasma vapor deposition of a copper layer followed by laser lithography of the layer into coils. Orthogonal helical (solenoid) and saddle-shaped (Helmholtz) coils were mounted on a single catheter tip. Microcatheters were tested in water bath phantoms in a 1.5T clinical MRI scanner, with variable simultaneous currents applied to the coils. Catheter tip deflection was imaged in the axial plane utilizing a “real-time” steady-state free precession (SSFP) MRI sequence. Degree of deflection and catheter tip orientation were measured for each current application. Results The catheter tip was clearly visible in the longitudinal and axial planes. Magnetic field artifacts were visible when the orthogonal coils at the catheter tip were energized. Variable amounts of current applied to a single coil demonstrated consistent catheter deflection in all water bath experiments. Changing current polarity reversed the observed direction of deflection, whereas current applied to two different coils resulted in deflection represented by the composite vector of individual coil activations. Microcatheter navigation through the vascular phantom was successful through control of applied current to one or more coils. Conclusion Controlled catheter deflection is possible with laser lithographed multi-axis coil tipped catheters in the MRI environment. PMID:23707097

Molecular basis of coiled-coil oligomerization-state specificity.

PubMed

Ciani, Barbara; Bjelic, Saša; Honnappa, Srinivas; Jawhari, Hatim; Jaussi, Rolf; Payapilly, Aishwarya; Jowitt, Thomas; Steinmetz, Michel O; Kammerer, Richard A

2010-11-16

Coiled coils are extensively and successfully used nowadays to rationally design multistranded structures for applications, including basic research, biotechnology, nanotechnology, materials science, and medicine. The wide range of applications as well as the important functions these structures play in almost all biological processes highlight the need for a detailed understanding of the factors that control coiled-coil folding and oligomerization. Here, we address the important and unresolved question why the presence of particular oligomerization-state determinants within a coiled coil does frequently not correlate with its topology. We found an unexpected, general link between coiled-coil oligomerization-state specificity and trigger sequences, elements that are indispensable for coiled-coil formation. By using the archetype coiled-coil domain of the yeast transcriptional activator GCN4 as a model system, we show that well-established trimer-specific oligomerization-state determinants switch the peptide's topology from a dimer to a trimer only when inserted into the trigger sequence. We successfully confirmed our results in two other, unrelated coiled-coil dimers, ATF1 and cortexillin-1. We furthermore show that multiple topology determinants can coexist in the same trigger sequence, revealing a delicate balance of the resulting oligomerization state by position-dependent forces. Our experimental results should significantly improve the prediction of the oligomerization state of coiled coils. They therefore should have major implications for the rational design of coiled coils and consequently many applications using these popular oligomerization domains.

Dim star fringe stabilization demonstration using pathlength feed-forward on the SIM testbed 3 (STB3)

NASA Astrophysics Data System (ADS)

Goullioud, Renaud; Alvarez-Salazar, Oscar S.; Nemati, Bijan

2003-02-01

Future space-based optical interferometers such as the Space Interferometer Mission require fringe stabilization to the level of nanometers in order to produce astrometric data at the micro-arc-second level. Even the best attitude control system available to date will not be able to stabilize the attitude of a several thousand pound spacecraft to a few milli-arc-seconds. Active pathlength control is usually implemented to compensate for attitude drift of the spacecraft. This issue has been addressed in previous experiments while tracking bright stars. In the case of dim stars, as the sensor bandwidth falls below one hertz, feedback control will not provide sufficient rejection. However, stabilization of the fringes from a dim-star down to the nanometer level can be done open loop using information from additional interferometers looking at bright guide stars. The STB3 testbed developed at the Jet Propulsion Laboratory features three optical interferometers sharing a common baseline, dynamically representative to the SIM interferometer. An artificial star feeding the interferometers is installed on a separate optics bench. Voice coils are used to simulate the attitude motion of the spacecraft by moving the entire bench. Data measured on STB3 show that fringe motion of a dim star due to spacecraft attitude changes can be attenuated by 80 dB at 0.1Hz without feedback control, using only information from two guide stars. This paper describes the STB3 setup, the pathlength feed-forward architecture, implementation issues and data collected with the system.

A household randomized, controlled trial of the efficacy of 0.03% transfluthrin coils alone and in combination with long-lasting insecticidal nets on the incidence of Plasmodium falciparum and Plasmodium vivax malaria in Western Yunnan Province, China.

PubMed

Hill, Nigel; Zhou, Hong Ning; Wang, Piyu; Guo, Xiaofang; Carneiro, Ilona; Moore, Sarah J

2014-05-31

Mosquito coils are the most commonly used household insecticidal product in the world with sales exceeding 50 billion coils, used by two billion people worldwide annually. Despite strong evidence that coils prevent mosquito bites a systematic review concluded that there is no evidence that burning mosquito coils prevents malaria acquisition. Therefore, the current trial was designed to measure and compare prevention of malaria infection by mosquito coils or long-lasting insecticidal net (LLIN) or a combination of the two in Yunnan, China in the Greater Mekong sub-region. A four-arm single blind household-randomized design was chosen as coils emanate insecticide throughout the household. Households enrolled at baseline were randomly allocated by the lottery method to one of the four intervention arms: (i) nothing, (ii) 0.03% transfluthrin coils alone, (iii) deltamethrin long-lasting insecticide treated nets, (LLINs) alone or (iv) a combination of transfluthrin coils and deltamethrin LLINs. All household members were recruited to the study, with only those households excluded with pregnant or breastfeeding mothers, members with chest complaints or allergies or members that regularly slept away from home. The main outcome of interest was Plasmodium falciparum malaria prevalence detected by rapid diagnostic tests (RDTs) during six repeated monthly cross-sectional surveys. The secondary outcome of interest was the effect on Plasmodium vivax prevalence detected in the same way. A total of 2,052 households were recruited into the study, comprising 7,341 individuals The odds ratios of testing positive by RDT with P. falciparum or P. vivax were >75% lower for all intervention arms compared with the control arm. Coils alone provided 77% protection (95% CI: 50%-89%), LLINs provided 91% protection (95% CI: 72%-97%) and the combination of coils and LLINs provided 94% protection (95% CI: 77%-99%) against P. falciparum compared with the control arm. There was no statistically significant difference between the protective efficacies of the different interventions. This is the first robust clinical evaluation of transfluthrin mosquito coils as a means to reduce malaria and the high degree of infection prevented would indicate they represent a potentially highly effective tool, which could be integrated into larger vector control programmes. ClinicalTrials.gov Identifier: NCT00442442, March 2007.

ACCELERATOR TARGET POSITIONER AND CONTROL CIRCUIT THEREFOR

DOEpatents

Stone, K.F.; Force, R.J.; Olson, W.W.; Cagle, D.S.

1959-12-15

An apparatus is described for inserting and retracting a target material with respect to the internal beam of a charged particle accelerator and to circuitry for controlling the timing and motion of the target placement. Two drive coils are mounted on the shaft of a target holder arm and disposed within the accelerator magnetic field with one coil at right angles to the other. Control circuitry alternately connects each coil to a current source and to a varying shorting resistance whereby the coils interchangeably produce driving and braking forces which swing the target arm within a ninety degree arc. The target is thus moved into the beam and away from it at high speeds and is brought to rest after each movement without whiplash or vibration.

Wright Laboratory Research and Development Facilities Handbook

DTIC Science & Technology

1992-08-01

properties o. superconductors SPECIAL/UNIQUE CAPABILITIES: Two superconducting coils: 3-inch bore, 10 Tesla coil. 20 kilojoule repetitively pulsed coil 7 inch...bore, cryogenically cooled 14 Tesla coil INSTRUMENTATION: Computer Controlled Variable Temperature (2-400K) and Field (0-5 Tesla ) Squid Susceptometer...Variable Temperature (10-80K) and Field (0-10 Tesla ) Transport Current Measurement Apparatus RF Source Sputtering Rig, Optical Microscope, Furnaces

13. ROOM 40, LOOKING WEST FROM THE RUBENS COIL. SPINNER ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

13. ROOM 40, LOOKING WEST FROM THE RUBENS COIL. SPINNER MAGNETOMETER IS VISIBLE AT FAR LEFT, AND THE RUBENS COIL CONTROL UNIT AT FAR RIGHT. - U.S. Geological Survey, Rock Magnetics Laboratory, 345 Middlefield Road, Menlo Park, San Mateo County, CA

The force control and path planning of electromagnetic induction-based massage robot.

PubMed

Wang, Wendong; Zhang, Lei; Li, Jinzhe; Yuan, Xiaoqing; Shi, Yikai; Jiang, Qinqin; He, Lijing

2017-07-20

Massage robot is considered as an effective physiological treatment to relieve fatigue, improve blood circulation, relax muscle tone, etc. The simple massage equipment quickly spread into market due to low cost, but they are not widely accepted due to restricted massage function. Complicated structure and high cost caused difficulties for developing multi-function massage equipment. This paper presents a novel massage robot which can achieve tapping, rolling, kneading and other massage operations, and proposes an improved reciprocating path planning algorithm to improve massage effect. The number of coil turns, the coil current and the distance between massage head and yoke were chosen to investigate the influence on massage force by finite element method. The control system model of the wheeled massage robot was established, including control subsystem of the motor, path algorithm control subsystem, parameter module of the massage robot and virtual reality interface module. The improved reciprocating path planning algorithm was proposed to improve regional coverage rate and massage effect. The influence caused by coil current, the number of coil turns and the distance between massage head and yoke were simulated in Maxwell. It indicated that coil current has more important influence compared to the other two factors. The path planning simulation of the massage robot was completed in Matlab, and the results show that the improved reciprocating path planning algorithm achieved higher coverage rate than the traditional algorithm. With the analysis of simulation results, it can be concluded that the number of coil turns and the distance between the moving iron core and the yoke could be determined prior to coil current, and the force can be controllable by optimizing structure parameters of massage head and adjusting coil current. Meanwhile, it demonstrates that the proposed algorithm could effectively improve path coverage rate during massage operations, therefore the massage effect can be improved.

A Synthetic Coiled-Coil Interactome Provides Heterospecific Modules for Molecular Engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinke, Aaron W.; Grant, Robert A.; Keating, Amy E.

2010-06-21

The versatile coiled-coil protein motif is widely used to induce and control macromolecular interactions in biology and materials science. Yet the types of interaction patterns that can be constructed using known coiled coils are limited. Here we greatly expand the coiled-coil toolkit by measuring the complete pairwise interactions of 48 synthetic coiled coils and 7 human bZIP coiled coils using peptide microarrays. The resulting 55-member protein 'interactome' includes 27 pairs of interacting peptides that preferentially heteroassociate. The 27 pairs can be used in combinations to assemble sets of 3 to 6 proteins that compose networks of varying topologies. Of specialmore » interest are heterospecific peptide pairs that participate in mutually orthogonal interactions. Such pairs provide the opportunity to dimerize two separate molecular systems without undesired crosstalk. Solution and structural characterization of two such sets of orthogonal heterodimers provide details of their interaction geometries. The orthogonal pair, along with the many other network motifs discovered in our screen, provide new capabilities for synthetic biology and other applications.« less

Magnetic catheter manipulation in the interventional MR imaging environment.

PubMed

Wilson, Mark W; Martin, Alastair B; Lillaney, Prasheel; Losey, Aaron D; Yee, Erin J; Bernhardt, Anthony; Malba, Vincent; Evans, Lee; Sincic, Ryan; Saeed, Maythem; Arenson, Ronald L; Hetts, Steven W

2013-06-01

To evaluate deflection capability of a prototype endovascular catheter, which is remotely magnetically steerable, for use in the interventional magnetic resonance (MR) imaging environment. Copper coils were mounted on the tips of commercially available 2.3-3.0-F microcatheters. The coils were fabricated in a novel manner by plasma vapor deposition of a copper layer followed by laser lithography of the layer into coils. Orthogonal helical (ie, solenoid) and saddle-shaped (ie, Helmholtz) coils were mounted on a single catheter tip. Microcatheters were tested in water bath phantoms in a 1.5-T clinical MR scanner, with variable simultaneous currents applied to the coils. Catheter tip deflection was imaged in the axial plane by using a "real-time" steady-state free precession MR imaging sequence. Degree of deflection and catheter tip orientation were measured for each current application. The catheter tip was clearly visible in the longitudinal and axial planes. Magnetic field artifacts were visible when the orthogonal coils at the catheter tip were energized. Variable amounts of current applied to a single coil demonstrated consistent catheter deflection in all water bath experiments. Changing current polarity reversed the observed direction of deflection, whereas current applied to two different coils resulted in deflection represented by the composite vector of individual coil activations. Microcatheter navigation through the vascular phantom was successful through control of applied current to one or more coils. Controlled catheter deflection is possible with laser lithographed multiaxis coil-tipped catheters in the MR imaging environment. Copyright © 2013 SIR. Published by Elsevier Inc. All rights reserved.

Application of mosquito repellent coils and associated self-reported health issues in Ghana.

PubMed

Hogarh, Jonathan N; Antwi-Agyei, Philip; Obiri-Danso, Kwasi

2016-02-04

The use of mosquito coils has gained widespread patronage in malaria-endemic countries, even though it is not a recommended preventive measure for avoiding mosquitoes. Mosquito coils contain insecticides, which are expected to vaporize slowly once the coil is lit, to provide protection against the mosquito. The mosquito coil base material contains a variety of compounds capable of burning slowly to gradually release the insecticide. The mosquito coil smoke, however, is potentially a source of indoor air pollution with implications for acute respiratory infections (ARI) and other illnesses. The present study investigated the application of mosquito coils and associated self-reported health issues in Ghana. A cross-sectional study was undertaken in which questionnaires were randomly administered to 480 households across four districts in Ghana. Respondents who exclusively applied mosquito coils were grouped as test cohort, while those who did not apply any mosquito repellency method constituted a control cohort. The test group that applied mosquito coils reported malaria incidence rate of 86.3 %. The control group that did not apply any mosquito repellency method reported an incidence rate of malaria at 72.4 %. Chi square analysis suggested that the observed difference was statistically significant (x (2) = 4.25; p = 0.04). The number of respondents who reported symptoms of cough from mosquito coil application (52.6 % incidence rate) was marginally greater than their counterparts who did not apply coils (46.1 % incidence rate). It was also found that respondents with shortage of breath, which was used as a proxy for ARI, were more likely to have applied mosquito coil. The application of mosquito coils did not necessarily reduce the incidence of malaria in the study communities. It however presented a potential respiratory risk factor, which should be further investigated by critically examining exposure to particulate matter emissions from burning coils.

GPUbased, Microsecond Latency, HectoChannel MIMO Feedback Control of Magnetically Confined Plasmas

NASA Astrophysics Data System (ADS)

Rath, Nikolaus

Feedback control has become a crucial tool in the research on magnetic confinement of plasmas for achieving controlled nuclear fusion. This thesis presents a novel plasma feedback control system that, for the first time, employs a Graphics Processing Unit (GPU) for microsecond-latency, real-time control computations. This novel application area for GPU computing is opened up by a new system architecture that is optimized for low-latency computations on less than kilobyte sized data samples as they occur in typical plasma control algorithms. In contrast to traditional GPU computing approaches that target complex, high-throughput computations with massive amounts of data, the architecture presented in this thesis uses the GPU as the primary processing unit rather than as an auxiliary of the CPU, and data is transferred from A-D/D-A converters directly into GPU memory using peer-to-peer PCI Express transfers. The described design has been implemented in a new, GPU-based control system for the High-Beta Tokamak - Extended Pulse (HBT-EP) device. The system is built from commodity hardware and uses an NVIDIA GeForce GPU and D-TACQ A-D/D-A converters providing a total of 96 input and 64 output channels. The system is able to run with sampling periods down to 4 μs and latencies down to 8 μs. The GPU provides a total processing power of 1.5 x 1012 floating point operations per second. To illustrate the performance and versatility of both the general architecture and concrete implementation, a new control algorithm has been developed. The algorithm is designed for the control of multiple rotating magnetic perturbations in situations where the plasma equilibrium is not known exactly and features an adaptive system model: instead of requiring the rotation frequencies and growth rates embedded in the system model to be set a priori, the adaptive algorithm derives these parameters from the evolution of the perturbation amplitudes themselves. This results in non-linear control computations with high computational demands, but is handled easily by the GPU based system. Both digital processing latency and an arbitrary multi-pole response of amplifiers and control coils is fully taken into account for the generation of control signals. To separate sensor signals into perturbed and equilibrium components without knowledge of the equilibrium fields, a new separation method based on biorthogonal decomposition is introduced and used to derive a filter that performs the separation in real-time. The control algorithm has been implemented and tested on the new, GPU-based feedback control system of the HBT-EP tokamak. In this instance, the algorithm was set up to control four rotating n = 1 perturbations at different poloidal angles. The perturbations were treated as coupled in frequency but independent in amplitude and phase, so that the system effectively controls a helical n = 1 perturbation with unknown poloidal spectrum. Depending on the plasma's edge safety factor and rotation frequency, the control system is shown to be able to suppress the amplitude of the dominant 8 kHz mode by up to 60% or amplify the saturated amplitude by a factor of up to two. Intermediate feedback phases combine suppression and amplification with a speed up or slow down of the mode rotation frequency. Increasing feedback gain results in the excitation of an additional, slowly rotating 1.4 kHz mode without further effects on the 8 kHz mode. The feedback performance is found to exceed previous results obtained with an FPGA- and Kalman-filter based control system without requiring any tuning of system model parameters. Experimental results are compared with simulations based on a combination of the Boozer surface current model and the Fitzpatrick-Aydemir model. Within the subset of phenomena that can be represented by the model as well as determined experimentally, qualitative agreement is found.

Control of External Kink Instability

NASA Astrophysics Data System (ADS)

Navratil, Gerald

2004-11-01

A fundamental pressure and current limiting phenomenon in magnetically confined plasmas for fusion energy is the long wavelength ideal-MHD kink mode. These modes have been extensively studied in tokamak and reversed field pinch (RFP) devices. They are characterized by significant amplitude on the boundary of the confined plasma and can therefore be controlled by manipulation of the external boundary conditions. In the past ten years, the theoretically predicted stabilizing effect of a nearby conducting wall has been documented in experiments, which opens the possibility of a significant increase in maximum stable plasma pressure. While these modes are predicted to remain unstable when the stabilizing wall is resistive, their growth rates are greatly reduced from the hydrodynamic time scale to the time scale of magnetic diffusion through the resistive wall. These resistive wall slowed kink modes have been identified as limiting phenomena in tokamak (DIII-D, PBX-M, HBT-EP, JT-60U, JET, NSTX) and RFP (HBTX, Extrap, T2R) devices. The theoretical prediction of stabilization to nearly the ideal wall pressure limit by toroidal plasma rotation and/or active feedback control using coils has recently been realized experimentally. Sustained, stable operation at double the no-wall pressure limit has been achieved. Discovery of the phenomenon of resonant field amplification by marginally stable kink modes and its role in the momentum balance of rotationally stabilized plasmas has emerged as a key feature. A theoretical framework, based on an extension of the very successful treatment of the n=0 axisymmetric mode developed in the early 1990's, to understand the stabilization mechanisms and model the performance of active feedback control systems is now established. This allows design of kink control systems for burning plasma experiments like ITER.

Computational fluid dynamics (CFD) using porous media modeling predicts recurrence after coiling of cerebral aneurysms.

PubMed

Umeda, Yasuyuki; Ishida, Fujimaro; Tsuji, Masanori; Furukawa, Kazuhiro; Shiba, Masato; Yasuda, Ryuta; Toma, Naoki; Sakaida, Hiroshi; Suzuki, Hidenori

2017-01-01

This study aimed to predict recurrence after coil embolization of unruptured cerebral aneurysms with computational fluid dynamics (CFD) using porous media modeling (porous media CFD). A total of 37 unruptured cerebral aneurysms treated with coiling were analyzed using follow-up angiograms, simulated CFD prior to coiling (control CFD), and porous media CFD. Coiled aneurysms were classified into stable or recurrence groups according to follow-up angiogram findings. Morphological parameters, coil packing density, and hemodynamic variables were evaluated for their correlations with aneurysmal recurrence. We also calculated residual flow volumes (RFVs), a novel hemodynamic parameter used to quantify the residual aneurysm volume after simulated coiling, which has a mean fluid domain > 1.0 cm/s. Follow-up angiograms showed 24 aneurysms in the stable group and 13 in the recurrence group. Mann-Whitney U test demonstrated that maximum size, dome volume, neck width, neck area, and coil packing density were significantly different between the two groups (P < 0.05). Among the hemodynamic parameters, aneurysms in the recurrence group had significantly larger inflow and outflow areas in the control CFD and larger RFVs in the porous media CFD. Multivariate logistic regression analyses demonstrated that RFV was the only independently significant factor (odds ratio, 1.06; 95% confidence interval, 1.01-1.11; P = 0.016). The study findings suggest that RFV collected under porous media modeling predicts the recurrence of coiled aneurysms.

Fourier transform-infrared spectroscopy as a diagnostic tool for mosquito coil smoke inhalation toxicity in Swiss Albino mice

NASA Astrophysics Data System (ADS)

Anusha, Chidambaram; Sankar, Renu; Varunkumar, Krishnamoorthy; Sivasindhuja, Gnanasambantham; Ravikumar, Vilwanathan

2017-12-01

The goal of this study is to establish Fourier transform-infrared (FTIR) spectroscopy as a diagnostic tool for allethrin-based mosquito coil smoke inhalation induced toxicity in mice. Primarily, we confirmed mosquito coil smoke inhalation toxicity in mice via reduced the body, organ weight and major vital organ tissue morphological structure changes. Furthermore, FTIR spectra was collected from control and mosquito coil smoke inhalation (8 h per day for 30 days) mice various tissues like liver, kidney, lung, heart and brain, to investigate the functional groups and their corresponding biochemical content variations. The FTIR spectra result shown major bio macromolecules such as protein and lipid functional peaks were shifted (decreased) in the mosquito coil smoke inhalation group as compared to control. The drastic peak shift was noticed in the liver, kidney followed by lung and brain. It is therefore concluded that the FTIR spectroscopy can be a successful detection tool in mosquito coil smoke inhalation toxicity.

A super-cusp divertor configuration for tokamaks

NASA Astrophysics Data System (ADS)

Ryutov, D. D.

2015-10-01

> This study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase's cusp divertor. It turns out that the set of remote coils can indeed produce a cusp divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough control that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the cusp divertor, the resulting configuration could be called `a super-cusp'. General geometrical features of the three-null configurations produced by remote coils are described. Issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.

Regulatory coiled-coil domains promote head-to-head assemblies of AAA+ chaperones essential for tunable activity control.

PubMed

Carroni, Marta; Franke, Kamila B; Maurer, Michael; Jäger, Jasmin; Hantke, Ingo; Gloge, Felix; Linder, Daniela; Gremer, Sebastian; Turgay, Kürşad; Bukau, Bernd; Mogk, Axel

2017-11-22

Ring-forming AAA+ chaperones exert ATP-fueled substrate unfolding by threading through a central pore. This activity is potentially harmful requiring mechanisms for tight repression and substrate-specific activation. The AAA+ chaperone ClpC with the peptidase ClpP forms a bacterial protease essential to virulence and stress resistance. The adaptor MecA activates ClpC by targeting substrates and stimulating ClpC ATPase activity. We show how ClpC is repressed in its ground state by determining ClpC cryo-EM structures with and without MecA. ClpC forms large two-helical assemblies that associate via head-to-head contacts between coiled-coil middle domains (MDs). MecA converts this resting state to an active planar ring structure by binding to MD interaction sites. Loss of ClpC repression in MD mutants causes constitutive activation and severe cellular toxicity. These findings unravel an unexpected regulatory concept executed by coiled-coil MDs to tightly control AAA+ chaperone activity.

Power Supply Changes for NSTX Resistive Wall Mode Coils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramakrishnan, S S.

The National Spherical Torus Experiment (NSTX) has been designed and installed in the existing facilities at Princeton Plasma Physics Laboratory (PPPL). Most of the hardware, plant facilities, auxiliary sub-systems, and power systems originally used for the Tokamak Fusion Test Reactor (TFTR) have been used with suitable modifications to reflect NSTX needs. Prior to 2004, the NSTX power system was feeding twelve (12) circuits in the machine. In 2004 the Resistive Wall Mode (RWM) Coils were installed on the machine to correct error fields. There are six of these coils installed around the machine in the mid-plane. Since these coils needmore » fast and accurate controls, a Switching Power Amplifier (SPA) with three sub-units was procured, installed and commissioned along with other power loop components. Two RWM Coils were connected in series and fed from one SPA sub-unit. After the initial RWM campaign, operational requirements evolved such that each of the RWM coils now requires separate power and control. Hence a second SPA with three sub-units has been procured and installed. The second unit is of improved design and has the controls and power components completely isolated. The existing thyristor rectifier is used as DC Link to both of the Switching Power Amplifiers. The controls for the RWM are integrated into the overall computer control of the DC Power systems for NSTX. This paper describes the design changes in the RWM Power system for NSTX.« less

Runaway electron generation and control

NASA Astrophysics Data System (ADS)

Esposito, B.; Boncagni, L.; Buratti, P.; Carnevale, D.; Causa, F.; Gospodarczyk Martin-Solis, M., Jr.; Popovic, Z.; Agostini, M.; Apruzzese, G.; Bin, W.; Cianfarani, C.; De Angelis, R.; Granucci, G.; Grosso, A.; Maddaluno, G.; Marocco, D.; Piergotti, V.; Pensa, A.; Podda, S.; Pucella, G.; Ramogida, G.; Rocchi, G.; Riva, M.; Sibio, A.; Sozzi, C.; Tilia, B.; Tudisco, O.; Valisa, M.; FTU Team

2017-01-01

We present an overview of FTU experiments on runaway electron (RE) generation and control carried out through a comprehensive set of real-time (RT) diagnostics/control systems and newly installed RE diagnostics. An RE imaging spectrometer system detects visible and infrared synchrotron radiation. A Cherenkov probe measures RE escaping the plasma. A gamma camera provides hard x-ray radial profiles from RE bremsstrahlung interactions in the plasma. Experiments on the onset and suppression of RE show that the threshold electric field for RE generation is larger than that expected according to a purely collisional theory, but consistent with an increase due to synchrotron radiation losses. This might imply a lower density to be targeted with massive gas injection for RE suppression in ITER. Experiments on active control of disruption-generated RE have been performed through feedback on poloidal coils by implementing an RT boundary-reconstruction algorithm evaluated on magnetic moments. The results indicate that the slow plasma current ramp-down and the simultaneous reduction of the reference plasma external radius are beneficial in dissipating the RE beam energy and population, leading to reduced RE interactions with plasma facing components. RE active control is therefore suggested as a possible alternative or complementary technique to massive gas injection.

Rapid mixing of viscous liquids by electrical coiling

PubMed Central

Kong, Tiantian; Li, Jingmei; Liu, Zhou; Zhou, Zhuolong; Ng, Peter Hon Yu; Wang, Liqiu; Shum, Ho Cheung

2016-01-01

The control for the processing of precursor liquids determines whether the properties and functions of the final material product can be engineered. An inherent challenge of processing viscous liquids arises from their large resistance to deform. Here, we report on the discovery of an electric approach that can significantly contribute to address this challenge. The applied electric force can induce a straight viscous jet to coil, and the resulting coiling characteristics are governed by the electric stress. We demonstrate the promising use of electrical coiling in the rapid and efficient mixing of viscous liquids. Remarkably, the degree of mixing can be precisely adjusted by tuning the applied electric stress. Our approach of controlling the coiling electrically has important implications on applications such as dispensing and printing of resins, printing patterned surfaces and scaffolds, processing of food and generating non-woven fabrics. PMID:26860660

Eight channel transmit array volume coil using on-coil radiofrequency current sources

PubMed Central

Kurpad, Krishna N.; Boskamp, Eddy B.

2014-01-01

Background At imaging frequencies associated with high-field MRI, the combined effects of increased load-coil interaction and shortened wavelength results in degradation of circular polarization and B1 field homogeneity in the imaging volume. Radio frequency (RF) shimming is known to mitigate the problem of B1 field inhomogeneity. Transmit arrays with well decoupled transmitting elements enable accurate B1 field pattern control using simple, non-iterative algorithms. Methods An eight channel transmit array was constructed. Each channel consisted of a transmitting element driven by a dedicated on-coil RF current source. The coil current distributions of characteristic transverse electromagnetic (TEM) coil resonant modes were non-iteratively set up on each transmitting element and 3T MRI images of a mineral oil phantom were obtained. Results B1 field patterns of several linear and quadrature TEM coil resonant modes that typically occur at different resonant frequencies were replicated at 128 MHz without having to retune the transmit array. The generated B1 field patterns agreed well with simulation in most cases. Conclusions Independent control of current amplitude and phase on each transmitting element was demonstrated. The transmit array with on-coil RF current sources enables B1 field shimming in a simple and predictable manner. PMID:24834418

High frequency magnetostrictive transducers for waveguide applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daw, Joshua Earl; Taylor, Steven Cheney; Rempe, Joy Lynn

A high frequency magnetostrictive transducer includes a magnetostrictive rod or wire inserted co-axially into a driving coil, wherein the driving coil includes a coil arrangement with a plurality of small coil segments along the magnetostrictive rod or wire; wherein frequency operation of the high frequency magnetostrictive transducer is controlled by a length of the small coil segments and a material type of the magnetostrictive rod or wire. This design of the high frequency magnetostrictive transducer retains the beneficial aspects of the magnetostrictive design, while reducing its primary drawback, lower frequency operation.

A superconducting large-angle magnetic suspension

NASA Technical Reports Server (NTRS)

Downer, James; Goldie, James; Torti, Richard

1991-01-01

The component technologies were developed required for an advanced control moment gyro (CMG) type of slewing actuator for large payloads. The key component of the CMG is a large-angle magnetic suspension (LAMS). The LAMS combines the functions of the gimbal structure, torque motors, and rotor bearings of a CMG. The LAMS uses a single superconducting source coil and an array of cryoresistive control coils to produce a specific output torque more than an order of magnitude greater than conventional devices. The designed and tested LAMS system is based around an available superconducting solenoid, an array of twelve room-temperature normal control coils, and a multi-input, multi-output control system. The control laws were demonstrated for stabilizing and controlling the LAMS system.

Some Aspects of an Air-Core Single-Coil Magnetic Suspension System

NASA Technical Reports Server (NTRS)

Hamlet, Irvin L.; Kilgore, Robert A.

1966-01-01

This paper presents some of the technical aspects in the development at the Langley Research Center of an air-cove, dual-wound, single-coil, magnetic-suspension system with one-dimensional control. Overall electrical system design features and techniques are discussed in addition to the problems of control and stability. Special treatment is given to the operation of a dual-wound, high-current support coil which provides the bias fields and superimposed modulated field. Other designs features include a six-phase, solid-state power stage for modulation of the relatively large magnitude control current, and an associated six-phase trigger circuit.

Axial flow plasma shutter

DOEpatents

Krausse, George J.

1988-01-01

A shutter (36) is provided for controlling a beam, or current, of charged particles in a device such as a thyratron (10). The substrate (38) defines an aperture (60) with a gap (32) which is placeable within the current. Coils (48) are formed on the substrate (38) adjacent the aperture (60) to produce a magnetic field for trapping the charged particles in or about aperture (60). The proximity of the coils (48) to the aperture (60) enables an effective magnetic field to be generated by coils (48) having a low inductance suitable for high frequency control. The substantially monolithic structure including the substrate (38) and coils (48) enables the entire shutter assembly (36) to be effectively located with respect to the particle beam.

Performance of the Conduction-Cooled LDX Levitation Coil

NASA Astrophysics Data System (ADS)

Michael, P. C.; Schultz, J. H.; Smith, B. A.; Titus, P. H.; Radovinsky, A.; Zhukovsky, A.; Hwang, K. P.; Naumovich, G. J.; Camille, R. J.

2004-06-01

The Levitated Dipole Experiment (LDX) was developed to study plasma confinement in a dipole magnetic field. Plasma is confined in the magnetic field of a 680-kg Nb3Sn Floating Coil (F-coil) that is electromagnetically supported at the center of a 5-m diameter by 3-m tall vacuum chamber. The Levitation Coil (L-coil) is a 2800-turn, double pancake winding that supports the weight of the F-coil and controls its vertical position within the vacuum chamber. The use of high-temperature superconductor (HTS) Bi-2223 for the L-coil minimizes the electrical and cooling power needed for levitation. The L-coil winding pack and support plate are suspended within the L-coil cryostat and cooled by conduction to a single-stage cryocooler rated for 25-W heat load at approximately 20 K. The coil current leads consist of conduction-cooled copper running from room temperature to 80 K and a pair of commercially-available, 150-A HTS leads. An automatically filled liquid-nitrogen reservoir provides cooling for the coil's radiation shield and for the leads' 80-K heat stations. This paper discusses the L-coil system design and its observed cryogenic performance.

Error field optimization in DIII-D using extremum seeking control

NASA Astrophysics Data System (ADS)

Lanctot, M. J.; Olofsson, K. E. J.; Capella, M.; Humphreys, D. A.; Eidietis, N.; Hanson, J. M.; Paz-Soldan, C.; Strait, E. J.; Walker, M. L.

2016-07-01

DIII-D experiments have demonstrated a new real-time approach to tokamak error field control based on maximizing the toroidal angular momentum. This approach uses extremum seeking control theory to optimize the error field in real time without inducing instabilities. Slowly-rotating n  =  1 fields (the dither), generated by external coils, are used to perturb the angular momentum, monitored in real-time using a charge-exchange spectroscopy diagnostic. Simple signal processing of the rotation measurements extracts information about the rotation gradient with respect to the control coil currents. This information is used to converge the control coil currents to a point that maximizes the toroidal angular momentum. The technique is well-suited for multi-coil, multi-harmonic error field optimizations in disruption sensitive devices as it does not require triggering locked tearing modes or plasma current disruptions. Control simulations highlight the importance of the initial search direction on the rate of the convergence, and identify future algorithm upgrades that may allow more rapid convergence that projects to convergence times in ITER on the order of tens of seconds.

53. VIEW OF TIRRILL VOLTAGE REGULATOR LOCATED ON SOUTH WALL ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

53. VIEW OF TIRRILL VOLTAGE REGULATOR LOCATED ON SOUTH WALL OF CONTROL ROOM. THE SOLENOID COILS AT THE TOP RIGHT OF THE PHOTOGRAPH DETECT VARIATIONS IN VOLTAGE AND CURRENT. THE ARMATURES OF THESE COILS ACT ON A SPRING LOADED BEAM. MOVEMENT OF THIS BEAM INDIRECTLY CONTROL SWITCHES WHICH CAUSE RESISTANCE GRIDS TO BE SWITCHED IN OR OUT OF THE EXCITER GENERATOR FIELD COILS (SEE CT-142A-95). - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

Magnetohydrodynamic modes analysis and control of Fusion Advanced Studies Torus high-current scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villone, F.; Mastrostefano, S.; Calabrò, G.

2014-08-15

One of the main FAST (Fusion Advanced Studies Torus) goals is to have a flexible experiment capable to test tools and scenarios for safe and reliable tokamak operation, in order to support ITER and help the final DEMO design. In particular, in this paper, we focus on operation close to a possible border of stability related to low-q operation. To this purpose, a new FAST scenario has then been designed at I{sub p} = 10 MA, B{sub T} = 8.5 T, q{sub 95} ≈ 2.3. Transport simulations, carried out by using the code JETTO and the first principle transport model GLF23, indicate that, under these conditions, FASTmore » could achieve an equivalent Q ≈ 3.5. FAST will be equipped with a set of internal active coils for feedback control, which will produce magnetic perturbation with toroidal number n = 1 or n = 2. Magnetohydrodynamic (MHD) mode analysis and feedback control simulations performed with the codes MARS, MARS-F, CarMa (both assuming the presence of a perfect conductive wall and using the exact 3D resistive wall structure) show the possibility of the FAST conductive structures to stabilize n = 1 ideal modes. This leaves therefore room for active mitigation of the resistive mode (down to a characteristic time of 1 ms) for safety purposes, i.e., to avoid dangerous MHD-driven plasma disruption, when working close to the machine limits and magnetic and kinetic energy density not far from reactor values.« less

Applying graph theory to protein structures: an atlas of coiled coils.

PubMed

Heal, Jack W; Bartlett, Gail J; Wood, Christopher W; Thomson, Andrew R; Woolfson, Derek N

2018-05-02

To understand protein structure, folding and function fully and to design proteins de novo reliably, we must learn from natural protein structures that have been characterised experimentally. The number of protein structures available is large and growing exponentially, which makes this task challenging. Indeed, computational resources are becoming increasingly important for classifying and analysing this resource. Here, we use tools from graph theory to define an atlas classification scheme for automatically categorising certain protein substructures. Focusing on the α-helical coiled coils, which are ubiquitous protein-structure and protein-protein interaction motifs, we present a suite of computational resources designed for analysing these assemblies. iSOCKET enables interactive analysis of side-chain packing within proteins to identify coiled coils automatically and with considerable user control. Applying a graph theory-based atlas classification scheme to structures identified by iSOCKET gives the Atlas of Coiled Coils, a fully automated, updated overview of extant coiled coils. The utility of this approach is illustrated with the first formal classification of an emerging subclass of coiled coils called α-helical barrels. Furthermore, in the Atlas, the known coiled-coil universe is presented alongside a partial enumeration of the 'dark matter' of coiled-coil structures; i.e., those coiled-coil architectures that are theoretically possible but have not been observed to date, and thus present defined targets for protein design. iSOCKET is available as part of the open-source GitHub repository associated with this work (https://github.com/woolfson-group/isocket). This repository also contains all the data generated when classifying the protein graphs. The Atlas of Coiled Coils is available at: http://coiledcoils.chm.bris.ac.uk/atlas/app.

Computational fluid dynamics (CFD) using porous media modeling predicts recurrence after coiling of cerebral aneurysms

PubMed Central

Ishida, Fujimaro; Tsuji, Masanori; Furukawa, Kazuhiro; Shiba, Masato; Yasuda, Ryuta; Toma, Naoki; Sakaida, Hiroshi; Suzuki, Hidenori

2017-01-01

Objective This study aimed to predict recurrence after coil embolization of unruptured cerebral aneurysms with computational fluid dynamics (CFD) using porous media modeling (porous media CFD). Method A total of 37 unruptured cerebral aneurysms treated with coiling were analyzed using follow-up angiograms, simulated CFD prior to coiling (control CFD), and porous media CFD. Coiled aneurysms were classified into stable or recurrence groups according to follow-up angiogram findings. Morphological parameters, coil packing density, and hemodynamic variables were evaluated for their correlations with aneurysmal recurrence. We also calculated residual flow volumes (RFVs), a novel hemodynamic parameter used to quantify the residual aneurysm volume after simulated coiling, which has a mean fluid domain > 1.0 cm/s. Result Follow-up angiograms showed 24 aneurysms in the stable group and 13 in the recurrence group. Mann-Whitney U test demonstrated that maximum size, dome volume, neck width, neck area, and coil packing density were significantly different between the two groups (P < 0.05). Among the hemodynamic parameters, aneurysms in the recurrence group had significantly larger inflow and outflow areas in the control CFD and larger RFVs in the porous media CFD. Multivariate logistic regression analyses demonstrated that RFV was the only independently significant factor (odds ratio, 1.06; 95% confidence interval, 1.01–1.11; P = 0.016). Conclusion The study findings suggest that RFV collected under porous media modeling predicts the recurrence of coiled aneurysms. PMID:29284057

Automatic tuned MRI RF coil for multinuclear imaging of small animals at 3T.

PubMed

Muftuler, L Tugan; Gulsen, Gultekin; Sezen, Kumsal D; Nalcioglu, Orhan

2002-03-01

We have developed an MRI RF coil whose tuning can be adjusted automatically between 120 and 128 MHz for sequential spectroscopic imaging of hydrogen and fluorine nuclei at field strength 3 T. Variable capacitance (varactor) diodes were placed on each rung of an eight-leg low-pass birdcage coil to change the tuning frequency of the coil. The diode junction capacitance can be controlled by the amount of applied reverse bias voltage. Impedance matching was also done automatically by another pair of varactor diodes to obtain the maximum SNR at each frequency. The same bias voltage was applied to the tuning varactors on all rungs to avoid perturbations in the coil. A network analyzer was used to monitor matching and tuning of the coil. A Pentium PC controlled the analyzer through the GPIB bus. A code written in LABVIEW was used to communicate with the network analyzer and adjust the bias voltages of the varactors via D/A converters. Serially programmed D/A converter devices were used to apply the bias voltages to the varactors. Isolation amplifiers were used together with RF choke inductors to provide isolation between the RF coil and the DC bias lines. We acquired proton and fluorine images sequentially from a multicompartment phantom using the designed coil. Good matching and tuning were obtained at both resonance frequencies. The tuning and matching of the coil were changed from one resonance frequency to the other within 60 s. (c) 2002 Elsevier Science (USA).

49 CFR 236.730 - Coil, receiver.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Definitions § 236.730 Coil, receiver. Concentric layers of insulated wire wound around the core of a receiver of an automatic train stop, train control or cab signal device on a locomotive. ...

Design of the superconducting magnet for 9.4 Tesla whole-body magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Li, Y.; Wang, Q.; Dai, Y.; Ni, Z.; Zhu, X.; Li, L.; Zhao, B.; Chen, S.

2017-02-01

A superconducting magnet for 9.4 Tesla whole-body magnetic resonance imaging is designed and fabricated in Institute of Electrical Engineering, Chinese Academy of Sciences. In this paper, the electromagnetic design methods of the main coils and compensating coils are presented. Sensitivity analysis is performed for all superconducting coils. The design of the superconducting shimming coils is also presented and the design of electromagnetic decoupling of the Z2 coils from the main coils is introduced. Stress and strain analysis with both averaged and detailed models is performed with finite element method. A quench simulation code with anisotropic continuum model and control volume method is developed by us and is verified by experimental study. By means of the quench simulation code, the quench protection system for the 9.4 T magnet is designed for the main coils, the compensating coils and the shimming coils. The magnet cryostat design with zero helium boiling-off technology is also introduced.

Four-channel surface coil array for sequential CW-EPR image acquisition

NASA Astrophysics Data System (ADS)

Enomoto, Ayano; Emoto, Miho; Fujii, Hirotada; Hirata, Hiroshi

2013-09-01

This article describes a four-channel surface coil array to increase the area of visualization for continuous-wave electron paramagnetic resonance (CW-EPR) imaging. A 776-MHz surface coil array was constructed with four independent surface coil resonators and three kinds of switches. Control circuits for switching the resonators were also built to sequentially perform EPR image acquisition for each resonator. The resonance frequencies of the resonators were shifted using PIN diode switches to decouple the inductively coupled coils. To investigate the area of visualization with the surface coil array, three-dimensional EPR imaging was performed using a glass cell phantom filled with a solution of nitroxyl radicals. The area of visualization obtained with the surface coil array was increased approximately 3.5-fold in comparison to that with a single surface coil resonator. Furthermore, to demonstrate the applicability of this surface coil array to animal imaging, three-dimensional EPR imaging was performed in a living mouse with an exogenously injected nitroxyl radical imaging agent.

A spiral, bi-planar gradient coil design for open magnetic resonance imaging.

PubMed

Zhang, Peng; Shi, Yikai; Wang, Wendong; Wang, Yaohui

2018-01-01

To design planar gradient coil for MRI applications without discretization of continuous current density and loop-loop connection errors. In the new design method, the coil current is represented using a spiral curve function described by just a few control parameters. Using a proper parametric equation set, an ensemble of spiral contours is reshaped to satisfy the coil design requirements, such as gradient linearity, inductance and shielding. In the given case study, by using the spiral coil design, the magnetic field errors in the imaging area were reduced from 5.19% (non-spiral design) to 4.47% (spiral design) for the transverse gradient coils, and for the longitudinal gradient coil design, the magnetic field errors were reduced to 5.02% (spiral design). The numerical evaluation shows that when compared with conventional wire loop, the inductance and resistance of spiral coil was reduced by 11.55% and 8.12% for x gradient coil, respectively. A novel spiral gradient coil design for biplanar MRI systems, the new design offers better magnetic field gradients, smooth contours than the conventional connected counterpart, which improves manufacturability.

Experiments and modelling of active quasi-single helicity regime generation in a reversed field pinch

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Brunsell, P. R.; Drake, J. R.

2009-07-01

The interaction of a static resonant magnetic perturbation (RMP) with a tearing mode (TM) is becoming a relevant topic in fusion plasma physics. RMPs can be generated by active coils and then used to affect the properties of TMs and of the corresponding magnetic islands. This paper shows how the feedback system of the EXTRAP T2R reversed field pinch (RFP) can produce a RMP that affects a rotating TM and stimulate the transition to the so-called quasi-single helicity (QSH) regime, a RFP plasma state characterized by a magnetic island surrounded by low magnetic chaos. The application of the RMP can increase the QSH probability up to 10% and enlarge the size of the corresponding island. Part of the experimental results are supported by a theoretical study that models the effect of the active coils on the magnetic island.

Atomic force microscopy capable of vibration isolation with low-stiffness Z-axis actuation.

PubMed

Ito, Shingo; Schitter, Georg

2018-03-01

For high-resolution imaging without bulky external vibration isolation, this paper presents an atomic force microscope (AFM) capable of vibration isolation with its internal Z-axis (vertical) actuators moving the AFM probe. Lorentz actuators (voice coil actuators) are used for the Z-axis actuation, and flexures guiding the motion are designed to have a low stiffness between the mover and the base. The low stiffness enables a large Z-axis actuation of more than 700 µm and mechanically isolates the probe from floor vibrations at high frequencies. To reject the residual vibrations, the probe tracks the sample by using a displacement sensor for feedback control. Unlike conventional AFMs, the Z-axis actuation attains a closed-loop control bandwidth that is 35 times higher than the first mechanical resonant frequency. The closed-loop AFM system has robustness against the flexures' nonlinearity and uses the first resonance for better sample tracking. For further improvement, feedforward control with a vibration sensor is combined, and the resulting system rejects 98.4% of vibrations by turning on the controllers. The AFM system is demonstrated by successful AFM imaging in a vibrational environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Compliance and control characteristics of an additive manufactured-flexure stage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, ChaBum; Tarbutton, Joshua A.

2015-04-15

This paper presents a compliance and positioning control characteristics of additive manufactured-nanopositioning system consisted of the flexure mechanism and voice coil motor (VCM). The double compound notch type flexure stage was designed to utilize the elastic deformation of two symmetrical four-bar mechanisms to provide a millimeter-level working range. Additive manufacturing (AM) process, stereolithography, was used to fabricate the flexure stage. The AM stage was inspected by using 3D X-ray computerized tomography scanner: air-voids and shape irregularity. The compliance, open-loop resonance peak, and damping ratio of the AM stage were measured 0.317 mm/N, 80 Hz, and 0.19, respectively. The AM stagemore » was proportional-integral-derivative positioning feedback-controlled and the capacitive type sensor was used to measure the displacement. As a result, the AM flexure mechanism was successfully 25 nm positioning controlled within 500 μm range. The resonance peak was found approximately at 280 Hz in closed-loop. This research showed that the AM flexure mechanism and the VCM can provide millimeter range with high precision and can be a good alternative to an expensive metal-based flexure mechanism and piezoelectric transducer.« less

Improvements in Technique of NMR Imaging and NMR Diffusion Measurements in the Presence of Background Gradients.

NASA Astrophysics Data System (ADS)

Lian, Jianyu

In this work, modification of the cosine current distribution rf coil, PCOS, has been introduced and tested. The coil produces a very homogeneous rf magnetic field, and it is inexpensive to build and easy to tune for multiple resonance frequency. The geometrical parameters of the coil are optimized to produce the most homogeneous rf field over a large volume. To avoid rf field distortion when the coil length is comparable to a quarter wavelength, a parallel PCOS coil is proposed and discussed. For testing rf coils and correcting B _1 in NMR experiments, a simple, rugged and accurate NMR rf field mapping technique has been developed. The method has been tested and used in 1D, 2D, 3D and in vivo rf mapping experiments. The method has been proven to be very useful in the design of rf coils. To preserve the linear relation between rf output applied on an rf coil and modulating input for an rf modulating -amplifying system of NMR imaging spectrometer, a quadrature feedback loop is employed in an rf modulator with two orthogonal rf channels to correct the amplitude and phase non-linearities caused by the rf components in the rf system. The modulator is very linear over a large range and it can generate an arbitrary rf shape. A diffusion imaging sequence has been developed for measuring and imaging diffusion in the presence of background gradients. Cross terms between the diffusion sensitizing gradients and background gradients or imaging gradients can complicate diffusion measurement and make the interpretation of NMR diffusion data ambiguous, but these have been eliminated in this method. Further, the background gradients has been measured and imaged. A dipole random distribution model has been established to study background magnetic fields Delta B and background magnetic gradients G_0 produced by small particles in a sample when it is in a B_0 field. From this model, the minimum distance that a spin can approach a particle can be determined by measuring and <{bf G}_sp{0 }{2}>. From this model, the particle concentration in a sample can be determined by measuring the lineshape of a free induction decay (fid).

Nuclear reactor safety device

DOEpatents

Hutter, Ernest

1986-01-01

A safety device is disclosed for use in a nuclear reactor for axially repositioning a control rod with respect to the reactor core in the event of an upward thermal excursion. Such safety device comprises a laminated helical ribbon configured as a tube-like helical coil having contiguous helical turns with slidably abutting edges. The helical coil is disclosed as a portion of a drive member connected axially to the control rod. The laminated ribbon is formed of outer and inner laminae. The material of the outer lamina has a greater thermal coefficient of expansion than the material of the inner lamina. In the event of an upward thermal excursion, the laminated helical coil curls inwardly to a smaller diameter. Such inward curling causes the total length of the helical coil to increase by a substantial increment, so that the control rod is axially repositioned by a corresponding amount to reduce the power output of the reactor.

High-Temperature Magnetic Bearings Being Developed for Gas Turbine Engines

NASA Technical Reports Server (NTRS)

Kascak, Albert F.

1998-01-01

Magnetic bearings are the subject of a new NASA Lewis Research Center and U.S. Army thrust with significant industry participation, and cooperation with other Government agencies. The NASA/Army emphasis is on high-temperature applications for future gas turbine engines. Magnetic bearings could increase the reliability and reduce the weight of these engines by eliminating the lubrication system. They could also increase the DN (diameter of bearing times the rpm) limit on engine speed and allow active vibration cancellation systems to be used, resulting in a more efficient, "more electric" engine. Finally, the Integrated High Performance Turbine Engine Technology (IHPTET) program, a joint Department of Defense/industry program, identified a need for a high-temperature (1200 F) magnetic bearing that could be demonstrated in their Phase III engine. This magnetic bearing is similar to an electric motor. It has a laminated rotor and stator made of cobalt steel. Wound around the stator's circumference are a series of electrical wire coils which form a series of electric magnets that exert a force on the rotor. A probe senses the position of the rotor, and a feedback controller keeps it centered in the cavity. The engine rotor, bearings, and casing form a flexible structure with many modes. The bearing feedback controller, which could cause some of these modes to become unstable, could be adapted to varying flight conditions to minimize seal clearances and monitor the health of the system.

Mechanism for and method of biasing magnetic sensor

DOEpatents

Kautz, David R.

2007-12-04

A magnetic sensor package having a biasing mechanism involving a coil-generated, resistor-controlled magnetic field for providing a desired biasing effect. In a preferred illustrated embodiment, the package broadly comprises a substrate; a magnetic sensor element; a biasing mechanism, including a coil and a first resistance element; an amplification mechanism; a filter capacitor element; and an encapsulant. The sensor is positioned within the coil. A current applied to the coil produces a biasing magnetic field. The biasing magnetic field is controlled by selecting a resistance value for the first resistance element which achieves the desired biasing effect. The first resistance element preferably includes a plurality of selectable resistors, the selection of one or more of which sets the resistance value.

MAST magnetic diagnostics

NASA Astrophysics Data System (ADS)

Edlington, T.; Martin, R.; Pinfold, T.

2001-01-01

The mega-ampere spherical tokamak (MAST) experiment is a new, large, low aspect ratio device (R=0.7-0.8 m, a=0.5-0.65 m, maximum BT˜0.63 T at R=0.7 m) operating its first experimental physics campaign. Designed to study a wide variety of plasma shapes with up to 2 MA of plasma current with an aspect ratio down to 1.3, the poloidal field (PF) coils used for plasma formation, equilibrium and shaping are inside the main vacuum vessel. For plasma control and to investigate a wide range of plasma phenomena, an extensive set of magnetic diagnostics have been installed inside the vacuum vessel. More than 600 vacuum compatible, bakeable diagnostic coils are configured in a number of discrete arrays close to the plasma edge with about half the coils installed behind the graphite armour tiles covering the center column. The coil arrays measure the toroidal and poloidal variation in the equilibrium field and its high frequency fluctuating components. Internal coils also measure currents in the PF coils, plasma current, stored energy and induced currents in the mechanical support structures of the coils and graphite armour tiles. The latter measurements are particularly important when halo currents are induced following a plasma termination, for example, when the plasma becomes vertically unstable. The article describes the MAST magnetic diagnostic coil set and their calibration. The way in which coil signals are used to control the plasma equilibrium is described and data from the first MAST experimental campaign presented. These coil data are used as input to the code EFIT [L. Lao et al., Nucl. Fusion 25, 1611 (1985)], for measurement of halo currents in the vacuum vessel structure and for measurements of the structure of magnetic field fluctuations near the plasma edge.

Magnetic navigation of an untethered micro device using four stationary coils.

PubMed

Ha, Yong H; Choi, Kyung M; Han, Byung H; Cho, Min H; Lee, Soo Y

2009-01-01

We introduce a magnetic navigation of a small magnet using four stationary coils. We used a Maxwell gradient coil to get magnetic propulsion force and three Helmholtz coils to control the moving direction of the magnet in the magnetic navigation. Using a three-channel coil driver with output capacity of 320A, we performed magnetic navigation of a small NdFeB magnet with the size of 10 mm x 10 mm x 12 mm on a horizontal plane. When navigated with a slow speed of about 1 mm/s, the magnet kept track of any arbitrary navigational path. We expect the proposed magnetic navigation method can be easily incorporated into the system for human applications since it does not use any moving coils.

Charge control microcomputer device for vehicle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morishita, M.; Kouge, S.

1986-08-26

A charge control microcomputer device is described for a vehicle, comprising: an AC generator driven by an engine for generating an output current, the generator having armature coils and a field coil; a battery charged by a rectified output of the generator and generating a terminal voltage; a voltage regulator for controlling a current flowing in the field coil, to control an output voltage of the generator to a predetermined value; an engine controlling microcomputer for receiving engine parameter data from the engine, to control the operation of the engine; a charge control microcomputer for processing input data including datamore » on at least one engine parameter output from the engine controlling microcomputer, and charge system data including at least one of battery terminal voltage data, generator voltage data and generator output current data, to provide a reference voltage for the voltage regulator.« less

Levitation in the field of a nonsuperconducting coil with magnetic flux stabilization

NASA Astrophysics Data System (ADS)

Koshurnikov, E. K.

2013-09-01

A method providing the "frozen flux" conditions in a nonsuperconducting coil is suggested and demonstrated with a model. The feasibility of permanent magnet stable levitation in the field of the coil with magnetic flux stabilization and mean current control is shown. The method allows researchers to exploit permanent magnet-superconducting body interaction in physical devices, for example, to reproduce, using nonsuperconducting coils, the frozen magnetic flux conditions required for the stable levitation of the magnet over a superconducting body.

Process optimization of helium cryo plant operation for SST-1 superconducting magnet system

NASA Astrophysics Data System (ADS)

Panchal, P.; Panchal, R.; Patel, R.; Mahesuriya, G.; Sonara, D.; Srikanth G, L. N.; Garg, A.; Christian, D.; Bairagi, N.; Sharma, R.; Patel, K.; Shah, P.; Nimavat, H.; Purwar, G.; Patel, J.; Tanna, V.; Pradhan, S.

2017-02-01

Several plasma discharge campaigns have been carried out in steady state superconducting tokamak (SST-1). SST-1 has toroidal field (TF) and poloidal field (PF) superconducting magnet system (SCMS). The TF coils system is cooled to 4.5 - 4.8 K at 1.5 - 1.7 bar(a) under two phase flow condition using 1.3 kW helium cryo plant. Experience revealed that the PF coils demand higher pressure heads even at lower temperatures in comparison to TF coils because of its longer hydraulic path lengths. Thermal run away are observed within PF coils because of single common control valve for all PF coils in distribution system having non-uniform lengths. Thus it is routine practice to stop the cooling of PF path and continue only TF cooling at SCMS inlet temperature of ˜ 14 K. In order to achieve uniform cool down, different control logic is adopted to make cryo stable system. In adopted control logic, the SCMS are cooled down to 80 K at constant inlet pressure of 9 bar(a). After authorization of turbine A/B, the SCMS inlet pressure is gradually controlled by refrigeration J-T valve to achieve stable operation window for cryo system. This paper presents process optimization for cryo plant operation for SST-1 SCMS.

Hybrid Active-Passive Systems for Control of Aircraft Interior Noise

NASA Technical Reports Server (NTRS)

Fuller, Chris R.

1999-01-01

Previous work has demonstrated the large potential for hybrid active-passive systems for attenuating interior noise in aircraft fuselages. The main advantage of an active-passive system is, by utilizing the natural dynamics of the actuator system, the control actuator power and weight is markedly reduced and stability/robustness is enhanced. Three different active-passive approaches were studied in the past year. The first technique utilizes multiple tunable vibration absorbers (ATVA) for reducing narrow band sound radiated from panels and transmitted through fuselage structures. The focus is on reducing interior noise due to propeller or turbo fan harmonic excitation. Two types of tunable vibration absorbers were investigated; a solid state system based upon a piezoelectric mechanical exciter and an electromechanical system based upon a Motran shaker. Both of these systems utilize a mass-spring dynamic effect to maximize tile output force near resonance of the shaker system and so can also be used as vibration absorbers. The dynamic properties of the absorbers (i.e. resonance frequency) were modified using a feedback signal from an accelerometer mounted on the active mass, passed through a compensator and fed into the drive component of the shaker system (piezoelectric element or voice coil respectively). The feedback loop consisted of a two coefficient FIR filter, implemented on a DSP, where the input is acceleration of tile ATVA mass and the output is a force acting in parallel with the stiffness of the absorber. By separating the feedback signal into real and imaginary components, the effective natural frequency and damping of the ATVA can be altered independently. This approach gave control of the resonance frequencies while also allowing the simultaneous removal of damping from the ATVA, thus increasing the ease of controllability and effectiveness. In order to obtain a "tuned" vibration absorber the chosen resonant frequency was set to the excitation frequency. In order to minimize sound radiation a gradient descent algorithm was developed which globally adapted the resonance frequencies of multiple ATVA's while minimizing a cost based upon the radiated sound power or sound energy obtained from an array of microphones.

Control coil arrangement for a rotating machine rotor

DOEpatents

Shah, Manoj R.; Lewandowsk, Chad R.

2001-07-31

A rotating machine (e.g., a turbine, motor or generator) is provided wherein a fixed solenoid or other coil configuration is disposed adjacent to one or both ends of the active portion of the machine rotor for producing an axially directed flux in the active portion so as to provide planar axial control at single or multiple locations for rotor balance, levitation, centering, torque and thrust action. Permanent magnets can be used to produce an axial bias magnetic field. The rotor can include magnetic disks disposed in opposed, facing relation to the coil configuration.

Interaction between shock coils increased the incidence of inappropriate therapies and lead failure in implantable cardioverter defibrillator.

PubMed

El Garhy, Mohammad; Ohlow, Marc-Alexander; Lauer, Bernward

Shock coil interaction in patients with multiple implantable cardioverter defibrillator (ICD) leads is occasionally observed. We aimed to evaluate the incidence of shock coil interaction and its clinical relevance. All ICD patients (646 patients) who came to follow up control in our ICD ambulance between January 1, 2011, and December 31, 2011 in the department of cardiology in Bad Berka hospital were retrospectively evaluated in this study. All baseline demographic, clinical, and procedural characteristics and postoperative chest x ray in postero-anterior and lateral view as well as clinical and ICD follow up data were evaluated. Among 646 patients 42 had multiple ICD leads (6.5%) of whom 36 patients (5.5% of total cohort patients and 85.7% of patients with multiple ICD leads) had shock coil interaction and presented the study group (Group I). The control group (Group II) consisted of 610 patients without coil-coil interaction including patients with single shock lead (604 patients) or patients with multiple leads but without interaction between shock coils (6 patients). Inappropriate anti-tachycardia therapies and RV lead revisions were more frequent in patients with interaction between shock coils (Group I vs Group II: 27.7% and 5.7%; p = 0.049 and 30.6% vs 6.4; p = 0.0001, respectively). Interaction between shock coils may be one of possible causes of lead failure and resulted in inappropriate therapies and subsequent lead revision. Copyright © 2018 Indian Heart Rhythm Society. Production and hosting by Elsevier B.V. All rights reserved.

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

46 CFR 153.434 - Heat transfer coils within a tank.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Heat transfer coils within a tank. 153.434 Section 153... Cargo Temperature Control Systems § 153.434 Heat transfer coils within a tank. When a cargo tank... the heat transfer fluid at a pressure greater than the pressure exerted on the heating or cooling...

Reducing costs while maintaining quality in endovascular neurosurgical procedures.

PubMed

Kashlan, Osama N; Wilson, Thomas J; Chaudhary, Neeraj; Gemmete, Joseph J; Stetler, William R; Dunnick, N Reed; Thompson, B Gregory; Pandey, Aditya S

2014-11-01

As medical costs continue to rise during a time of increasing medical resource utilization, both hospitals and physicians must attempt to limit superfluous health care expenses. Neurointerventional treatment has been shown to be costly, but it is often the best treatment available for certain neuropathologies. The authors studied the effects of 3 policy changes designed to limit the costs of performing neurointerventional procedures at the University of Michigan. The authors retrospectively analyzed the costs of performing neurointerventional procedures during the 6-month periods before and after the implementation of 3 cost-saving policies: 1) the use of an alternative, more economical contrast agent, 2) standardization of coil prices through negotiation with industry representatives to receive economies of scale, and 3) institution of a feedback method to show practitioners the costs of unused products per patient procedure. The costs during the 6-month time intervals before and after implementation were also compared with costs during the most recent 6-month time period. The policy requiring use of a more economical contrast agent led to a decrease in the cost of contrast usage of $42.79 per procedure for the first 6 months after implementation, and $137.09 per procedure for the most current 6-month period, resulting in an estimated total savings of $62,924.31 for the most recent 6-month period. The standardized coil pricing system led to savings of $159.21 per coil after the policy change, and $188.07 per coil in the most recent 6-month period. This yielded total estimated savings of $76,732.56 during the most recent 6-month period. The feedback system for unused items decreased the cost of wasted products by approximately $44.36 per procedure in the 6 months directly after the policy change and by $48.20 per procedure in the most recent 6-month period, leading to total estimated savings of $22,123.80 during the most recent 6-month period. According to extrapolation over a 1-year period, the 3 policy changes decreased costs by an estimated $323,561.34. Simple cost-saving policies can lead to substantial reductions in costs of neurointerventional procedures while maintaining high levels of quality and growth of services.

Embolization of the Gastroduodenal Artery Before Selective Internal Radiotherapy: A Prospectively Randomized Trial Comparing Standard Pushable Coils with Fibered Interlock Detachable Coils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudeck, Oliver, E-mail: oliver.dudeck@med.ovgu.de; Bulla, Karsten; Wieners, Gero

2011-02-15

The purpose of this study was compare embolization of the gastroduodenal artery (GDA) using standard pushable coils with the Interlock detachable coil (IDC), a novel fibered mechanically detachable long microcoil, in patients scheduled for selective internal radiotherapy (SIRT). Fifty patients (31 male and 19 female; median age 66.6 {+-} 8.1 years) were prospectively randomized for embolization using either standard coils or IDCs. Procedure time, radiation dose, number of embolization devices, complications, and durability of vessel occlusion at follow-up angiography were recorded. The procedures differed significantly in time (14:32 {+-} 5:56 min for standard coils vs. 2:13 {+-} 1:04 min formore » IDCs; p < 0.001); radiation dose for coil deployment (2479 {+-} 1237 cGycm Superscript-Two for standard coils vs. 275 {+-} 268 cGycm Superscript-Two for IDCs; p < 0.001); and vessel occlusion (17:18 {+-} 6:39 min for standard coils vs. 11:19 {+-} 7:54 min for IDCs; p = 0.002). A mean of 6.2 {+-} 1.8 coils (n = 27) were used in the standard coil group, and 1.3 {+-} 0.9 coils (p < 0.0001) were used in the IDC group (n = 23) because additional pushable coils were required to achieve GDA occlusion in 4 patients. In 2 patients, the IDC could not be deployed through a Soft-VU catheter. One standard coil dislodged in the hepatic artery and was retrieved. Vessel reperfusion was noted in only 1 patient in the standard coil group. Controlled embolization of the GDA with fibered IDCs was achieved more rapidly than with pushable coils. However, vessel occlusion may not be obtained using a single device only, and the use of sharply angled guiding catheters hampered coil pushability.« less

Improved extraction of ePTFE and medical adhesive modified defibrillation leads from the coronary sinus and great cardiac vein.

PubMed

Wilkoff, Bruce L; Belott, Peter H; Love, Charles J; Scheiner, Avram; Westlund, Randy; Rippy, Marian; Krishnan, Mohan; Norlander, Barry E; Steinhaus, Bruce; Emmanuel, Janson; Zeller, Peter J

2005-03-01

Permanent leads with shocking coils for defibrillation therapy are sometimes implanted in the coronary sinus (CS) and great cardiac vein (GCV). These shocking coils, as documented by pathologic examination of animal investigations, often become tightly encapsulated by fibrosis and can be very difficult to remove. One of three configurations of the Guidant model 7109 Perimeter coronary sinus shocking lead was implanted into the distal portion of the GCV of 24 sheep for up to 14 months. Group 1 had unmodified coils (control), group 2 had coils backfilled with medical adhesive (MA), and Group 3 had coils coated with expanded polytetrafluoroethylene (ePTFE). Eighteen leads, three from each group at 6 and 14 months were transvenously extracted from the left jugular vein. The remaining six animals were not subject to extraction. All animals were euthanized for pathological and microscopic examination. All six of the control, three of the MA, and one of the ePTFE leads required the use of an electrosurgical dissection sheath (EDS) for extraction. Five control, two MA, and none of the ePTFE leads had significant fibrotic attachments to the shocking coils. Significant trauma was observed at necropsy for those leads requiring the use of the EDS for extraction. Tissue ingrowth is a major impediment to the removal of defibrillation leads implanted in the CS and GCV of sheep. Reduction of tissue ingrowth by coating the shocking coils with ePTFE or by backfilling with MA facilitates transvenous lead removal with reduced tissue trauma.

Statistical Methods for Quality Control of Steel Coils Manufacturing Process using Generalized Linear Models

NASA Astrophysics Data System (ADS)

García-Díaz, J. Carlos

2009-11-01

Fault detection and diagnosis is an important problem in process engineering. Process equipments are subject to malfunctions during operation. Galvanized steel is a value added product, furnishing effective performance by combining the corrosion resistance of zinc with the strength and formability of steel. Fault detection and diagnosis is an important problem in continuous hot dip galvanizing and the increasingly stringent quality requirements in automotive industry has also demanded ongoing efforts in process control to make the process more robust. When faults occur, they change the relationship among these observed variables. This work compares different statistical regression models proposed in the literature for estimating the quality of galvanized steel coils on the basis of short time histories. Data for 26 batches were available. Five variables were selected for monitoring the process: the steel strip velocity, four bath temperatures and bath level. The entire data consisting of 48 galvanized steel coils was divided into sets. The first training data set was 25 conforming coils and the second data set was 23 nonconforming coils. Logistic regression is a modeling tool in which the dependent variable is categorical. In most applications, the dependent variable is binary. The results show that the logistic generalized linear models do provide good estimates of quality coils and can be useful for quality control in manufacturing process.

Electromagnetic attachment mechanism

NASA Technical Reports Server (NTRS)

Monford, Leo G., Jr. (Inventor)

1992-01-01

An electromagnetic attachment mechanism is disclosed for use as an end effector of a remote manipulator system. A pair of electromagnets, each with a U-shaped magnetic core with a pull-in coil and two holding coils, are mounted by a spring suspension system on a base plate of the mechanism housing with end pole pieces adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate of a grapple fixture affixed to a target object. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery backup is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary source. A centerline mounted camera and video monitor are used in cooperation with a target pattern on the reflective surface of the strike plate to effect targeting and alignment.

Analysis of switching surges generated by current interruption in an energy-storge coil

NASA Astrophysics Data System (ADS)

Chowdhuri, P.

1981-10-01

The transient voltages which are generated when the current in a large magnetic energy storage coil is interruped by a dc vacuum circuit breaker is analyzed. The effect of the various parameters in the circuit on the transient voltage is dicussed. The self inductance of the dump resistor must be minimized to control the generated transient. Contrary to general belief, a capacitor across the coil is not an effective surge suppressor. In fact, the capacitor may excite oscillations of higher magnitude. However, a capacitor, in addition to a surge suppressor, may be used to modify the frequency components of the transient voltage so that these frequency components are not coincident with the natural frequencies of the coil. Otherwise, resonant oscillations inside the coil may attain damaging magnitudes. The capacitor would also reduce the steepness of the wavefront of the transient across the coil, thus reducing the nonlinear voltage distribution inside the coil.

Robust peptide bundles designed computationally

NASA Astrophysics Data System (ADS)

Haider, Michael; Zhang, Huixi Violet; Kiick, Kristi; Saven, Jeffery; Pochan, Darrin

Peptides are ideal candidates for the design and controlled assembly of nanoscale materials due to their potential to assemble with atomistic precision as in biological systems. Unlike other work utilizing natural proteins and structural motifs, this effort is completely de novo in order to build arbitrary structures with desired size for the specific placement and separation of functional groups. We have successfully computationally designed soluble, coiled coil, peptide, tetramer bundles which are robust and stable. Using circular dichroism we demonstrated the thermal stability of these bundles as well as confirmed their alpha helical and coiled coil nature. The stability of these bundles arises from the computational design of the coiled coil interior core residues. The coiled coil tetramer was confirmed to be the dominant species by analytical ultra-centrifugation sedimentation studies. We also established how these bundles behave in solution using small angle neutron scattering. The form factor of the bundles is well represented by a cylinder model and their behavior at high concentrations is modeled using a structure factor for aggregates of the cylinders. All of these experiments support our claim that the designed coiled coil bundles were achieved in solution. NSF DMREF 1234161.

Synthesis, characterisation and applications of coiled carbon nanotubes.

PubMed

Hanus, Monica J; Harris, Andrew T

2010-04-01

Coiled carbon nanotubes are helical carbon structures formed when heptagonal and pentagonal rings are inserted into the hexagonal backbone of a 'straight' nanotube. Coiled carbon nanotubes have been reported with both regular and irregular helical structures. In this work the structure, growth mechanism(s), synthesis, properties and potential applications of coiled carbon nanotubes are reviewed. Published data suggests that coiled carbon nanotube synthesis occurs due to nonuniform extrusion of carbon from a catalyst surface. To date, coiled carbon nanotubes have been synthesised using catalyst modification techniques including: (i) the addition of S or P containing compounds during synthesis; (ii) the use of binary or ternary metal catalysts; (iii) the use of microwaves to create a local temperature gradient around individual catalyst particles and; (iv) the use of pH control during catalyst preparation. In most instances coiled carbon nanotubes are produced as a by-product; high yield and/or large-scale synthesis of coiled carbon nanotubes remains problematic. The qualitative analysis of coiled carbon nanotubes is currently hindered by the absence of specific characterisation data in the literature, e.g., oxidation profiles measured by thermogravimetric analysis and Raman spectra of pure coiled carbon nanotube samples.

Boehringer Mannheim award lecture 1995. La conference Boehringer Mannheim 1995. De novo design of alpha-helical proteins: basic research to medical applications.

PubMed

Hodges, R S

1996-01-01

The two-stranded alpha-helical coiled-coil is a universal dimerization domain used by nature in a diverse group of proteins. The simplicity of the coiled-coil structure makes it an ideal model system to use in understanding the fundamentals of protein folding and stability and in testing the principles of de novo design. The issues that must be addressed in the de novo design of coiled-coils for use in research and medical applications are (i) controlling parallel versus antiparallel orientation of the polypeptide chains, (ii) controlling the number of helical strands in the assembly (iii) maximizing stability of homodimers or heterodimers in the shortest possible chain length that may require the engineering of covalent constraints, and (iv) the ability to have selective heterodimerization without homodimerization, which requires a balancing of selectivity versus affinity of the dimerization strands. Examples of our initial inroads in using this de novo design motif in various applications include: heterodimer technology for the detection and purification of recombinant peptides and proteins; a universal dimerization domain for biosensors; a two-stage targeting and delivery system; and coiled-coils as templates for combinatorial helical libraries for basic research and drug discovery and as synthetic carrier molecules. The universality of this dimerization motif in nature suggests an endless number of possibilities for its use in de novo design, limited only by the creativity of peptide-protein engineers.

Wireless Displacement Sensing of Micromachined Spiral-Coil Actuator Using Resonant Frequency Tracking

PubMed Central

Ali, Mohamed Sultan Mohamed; AbuZaiter, Alaa; Schlosser, Colin; Bycraft, Brad; Takahata, Kenichi

2014-01-01

This paper reports a method that enables real-time displacement monitoring and control of micromachined resonant-type actuators using wireless radiofrequency (RF). The method is applied to an out-of-plane, spiral-coil microactuator based on shape-memory-alloy (SMA). The SMA spiral coil forms an inductor-capacitor resonant circuit that is excited using external RF magnetic fields to thermally actuate the coil. The actuation causes a shift in the circuit's resonance as the coil is displaced vertically, which is wirelessly monitored through an external antenna to track the displacements. Controlled actuation and displacement monitoring using the developed method is demonstrated with the microfabricated device. The device exhibits a frequency sensitivity to displacement of 10 kHz/μm or more for a full out-of-plane travel range of 466 μm and an average actuation velocity of up to 155 μm/s. The method described permits the actuator to have a self-sensing function that is passively operated, thereby eliminating the need for separate sensors and batteries on the device, thus realizing precise control while attaining a high level of miniaturization in the device. PMID:25014100

Spiral Gradient Coil Design for Use in Cylindrical MRI Systems.

PubMed

Wang, Yaohui; Xin, Xuegang; Liu, Feng; Crozier, Stuart

2018-04-01

In magnetic resonance imaging, the stream function based method is commonly used in the design of gradient coils. However, this method can be prone to errors associated with the discretization of continuous current density and wire connections. In this paper, we propose a novel gradient coil design scheme that works directly in the wire space, avoiding the system errors that may appear in the stream function approaches. Specifically, the gradient coil pattern is described with dedicated spiral functions adjusted to allow the coil to produce the required field gradients in the imaging area, minimal stray field, and other engineering terms. The performance of a designed spiral gradient coil was compared with its stream-function counterpart. The numerical evaluation shows that when compared with the conventional solution, the inductance and resistance was reduced by 20.9 and 10.5%, respectively. The overall coil performance (evaluated by the figure of merit (FoM)) was improved up to 26.5% for the x -gradient coil design; for the z-gradient coil design, the inductance and resistance were reduced by 15.1 and 6.7% respectively, and the FoM was increased by 17.7%. In addition, by directly controlling the wire distributions, the spiral gradient coil design was much sparser than conventional coils.

Manufacture and Quality Control of Insert Coil with Real ITER TF Conductor

DOE PAGES

Ozeki, H.; Isono, T.; Uno, Y.; ...

2016-03-02

JAEA successfully completed the manufacture of the toroidal field (TF) insert coil (TFIC) for a performance test of the ITER TF conductor in the final design in cooperation with Hitachi, Ltd. The TFIC is a single-layer 8.875-turn solenoid coil with 1.44-m diameter. This will be tested for 68-kA current application in a 13-T external magnetic field. TFIC was manufactured in the following order: winding of the TF conductor, lead bending, fabrication of the electrical termination, heat treatment, turn insulation, installation of the coil into the support mandrel structure, vacuum pressure impregnation (VPI), structure assembly, and instrumentation. Here in this presentation,more » manufacture process and quality control status for the TFIC manufacturing are reported.« less

The EarLens System: New Sound Transduction Methods

PubMed Central

Perkins, Rodney; Fay, Jonathan P.; Rucker, Paul; Rosen, Micha; Olson, Lisa; Puria, Sunil

2010-01-01

The hypothesis is tested that an open-canal hearing device, with a microphone in the ear canal, can be designed to provide amplification over a wide bandwidth and without acoustic feedback. In the design under consideration, a transducer consisting of a thin silicone platform with an embedded magnet is placed directly on the tympanic membrane. Sound picked up by a microphone in the ear canal, including sound-localization cues thought to be useful for speech perception in noisy environments, is processed and amplified, and then used to drive a coil near the tympanic-membrane transducer. The perception of sound results from the vibration of the transducer in response the electromagnetic field produced by the coil. Sixteen subjects (ranging from normal-hearing to moderately hearing-impaired) wore this transducer for up to a ten-month period, and were monitored for any adverse reactions. Three key functional characteristics were measured: 1) the maximum equivalent pressure output (MEPO) of the transducer; 2) the feedback gain margin (GM), which describes the maximum allowable gain before feedback occurs; and 3) the tympanic-membrane damping effect (DTM), which describes the change in hearing level due to placement of the transducer on the eardrum. Results indicate that the tympanic-membrane transducer remains in place and is well tolerated. The system can produce sufficient output to reach threshold for those with as much as 60 dBHL of hearing impairment for up to 8 kHz in 86% of the study population, and up to 11.2 kHz in 50% of the population. The feedback gain margin is on average 30 dB except at the ear canal resonance frequencies of 3 and 9 kHz, where the average was reduced to 12 dB and 23 dB respectively. The average value of DTM is close to 0 dB everywhere except in the 2–4 kHz range, where it peaks at 8 dB. A new alternative system that uses photonic energy to transmit both the signal and power to a photodiode and micro-actuator on an EarLens platform is also described. PMID:20116419

Livermore's 2004 R&D 100 Awards: Magnetically Levitated Train Takes Flight

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazi, A

2005-09-20

the 1960s, transportation industry planners have sought an energy-efficient design for a train that can glide through air at speeds up to 500 kilometers per hour. This type of train, called a magnetically levitated (maglev) train, is thought to be a viable solution to meet the nation's growing need for intercity and urban transportation networks. However, despite some promising developments, unresolved concerns with the operation and safety of maglev trains has prevented the transition from demonstration model to commercial development. Inductrack, a maglev system originally conceived by Livermore physicist Richard Post, is designed to address these issues. Post's work onmore » Inductrack began with funding from Livermore's Laboratory Directed Research and Development Program, and in 2003, the technology was licensed to General Atomics (GA) in San Diego for train and transit system applications. This year, members of the Livermore-GA team received an R&D 100 Award for Inductrack's development. Inductrack uses permanent magnets to produce the magnetic fields that levitate the train and provides economic and operational advantages over other maglev systems. It can be adapted to both high-speed and urban-speed environments. In the event of a power failure, the train slows gradually until it comes to rest on its auxiliary wheels. The maintenance requirements for Inductrack are also lower than they are for other systems, plus it has a short turning radius and is designed for quiet operation. Previous designs for maglev systems did not offer the energy efficiency or safety protections that are in the Inductrack design. Electromagnetic systems (EMS) use powered electromagnets to levitate the train. However, these systems are based on magnetic attraction rather than repulsion and thus are inherently unstable. In EMS trains, the levitation gap--the separation between the magnet pole faces and the iron rail--is only about 10 millimeters and, during operation, must be maintained to within {+-}1 millimeter. Position sensors and electronic feedback systems are required to control the magnetic current and to compensate for the inherent instability. This requirement, plus the onboard source of emergency power required to ensure operational safety during a sudden power loss, increases the complexity of EMS trains. In contrast, in electrodynamic systems (EDS), large superconducting magnet coils mounted on the sides of the train generate high-intensity magnetic field poles. Interaction of the current between the coils and the track levitates the train. At operating speeds (above a liftoff speed of about 100 kilometers per hour), the magnetic levitation force balances the weight of the car at a stable position. EDS trains do not require the feedback control systems that EMS trains use to stabilize levitation. However, the superconducting magnetic coils must be kept at temperatures of only 5 kelvins, so costly electrically powered cryogenic equipment is required. Also, passengers, especially those with pacemakers, must be shielded from the high magnetic fields generated by the superconductors.« less

Self-assembly of coiled coil peptides into nanoparticles vs 2-d plates: effects of assembly pathway

NASA Astrophysics Data System (ADS)

Kim, Kyunghee; Pochan, Darrin

Molecular solution assembly, or self-assembly, is a process by which ordered nanostructures or patterns are formed by non-covalent interactions during assembly. Biomimicry, the use of bioinspired molecules or biologically relevant materials, is an important area of self-assembly research with peptides serving a critical role as molecular tools. The morphology of peptide assemblies can be controlled by adjusting solution conditions such as the concentration of peptides, the temperature, and pH. Herein, spherical nanostructures, which have potential for creating an encapsulation system, are formed by self-assembly when coiled coil peptides are combined in solution. These peptides are homotrimeric and heterodimeric coiled-coil bundles and the homotrimer is connected with each of heterodimer through their external surfaces via disulfide bonds. The resultant covalent constructs could co-assemble into complementary trimeric hubs, respectively. The two peptide constructs are directly mixed and assembled in solution in order to produce either spherical particles or 2-d plates depending on the solution conditions and kinetic pathway of assembly. In particular, structural changes of the self-assembled peptides are explored by control of the thermal history of the assembly solution.

Control advances for achieving the ITER baseline scenario on KSTAR

NASA Astrophysics Data System (ADS)

Eidietis, N. W.; Barr, J.; Hahn, S. H.; Humphreys, D. A.; in, Y. K.; Jeon, Y. M.; Lanctot, M. J.; Mueller, D.; Walker, M. L.

2017-10-01

Control methodologies developed to enable successful production of ITER baseline scenario (IBS) plasmas on the superconducting KSTAR tokamak are presented: decoupled vertical control (DVC), real-time feedforward (rtFF) calculation, and multi-input multi-output (MIMO) X-point control. DVC provides fast vertical control with the in-vessel control coils (IVCC) while sharing slow vertical control with the poloidal field (PF) coils to avoid IVCC saturation. rtFF compensates for inaccuracies in offline PF current feedforward programming, allowing reduction or removal of integral gain (and its detrimental phase lag) from the shape controller. Finally, MIMO X-point control provides accurate positioning of the X-point despite low controllability due to the large distance between coils and plasma. Combined, these techniques enabled achievement of IBS parameters (q95 = 3.2, βN = 2) with a scaled ITER shape on KSTAR. n =2 RMP response displays a strong dependence upon this shaping. Work supported by the US DOE under Award DE-SC0010685 and the KSTAR project.

A Bearingless Switched-Reluctance Motor for High Specific Power Applications

NASA Technical Reports Server (NTRS)

Choi, Benjamin B.; Siebert, Mark

2006-01-01

A 12-8 switched-reluctance motor (SRM) is studied in bearingless (or self-levitated) operation with coil currents limited to the linear region to avoid magnetic saturation. The required motoring and levitating currents are summed and go into a single motor coil per pole to obtain the highest power output of the motor by having more space for motor coil winding. Two controllers are investigated for the bearingless SRM operation. First, a model-based controller using the radial force, which is adjusted by a factor derived from finite element analysis, is presented. Then a simple and practical observation-based controller using a PD (proportional-derivative) control algorithm is presented. Both controllers were experimentally demonstrated to 6500 rpm. This paper reports the initial efforts toward eventual self levitation of a SRM operating into strong magnetic core saturation at liquid nitrogen temperature.

ELECTRICAL COIL STRUCTURE

DOEpatents

Baker, W.R.; Hartwig, A.

1962-09-25

A compactly wound electrical coil is designed for carrying intense pulsed currents such as are characteristic of controlled thermonuclear reaction devices. A flat strip of conductor is tightly wound in a spiral with a matching flat strip of insulator. To provide for a high fluid coolant flow through the coil with minimum pumping pressure, a surface of the conductor is scored with parallel transverse grooves which form short longitudinal coolant pasaages when the conductor is wound in the spiral configuration. Owing to this construction, the coil is extremely resistant to thermal and magnetic shock from sudden high currents. (AEC)

In situ post-weld heat treatment on martensitic stainless steel turbine runners using a robotic induction heating process to control temperature distribution

NASA Astrophysics Data System (ADS)

Boudreault, E.; Hazel, B.; Côté, J.; Godin, S.

2014-03-01

A new robotic heat treatment process is developed. Using this solution it is now possible to perform local heat treatment on large steel components. Crack, cavitation and erosion repairs on turbine blades and Pelton buckets are among the applications of this technique. The proof of concept is made on a 13Cr-4Ni stainless steel designated "CA6NM". This alloy is widely used in the power industry for modern system components. Given the very tight temperature tolerance (600 to 630 °C) for post-weld heat treatment on this alloy, 13Cr-4Ni stainless steel is very well suited for demonstrating the possibilities of this process. To achieve heat treatment requirements, an induction heating system is mounted on a compact manipulator named "Scompi". This robot moves a pancake coil in order to control the temperature distribution. A simulator using thermal finite element analysis is first used for path planning. A feedback loop adjusts parameters in function of environmental conditions.

A Soft Parallel Kinematic Mechanism.

PubMed

White, Edward L; Case, Jennifer C; Kramer-Bottiglio, Rebecca

2018-02-01

In this article, we describe a novel holonomic soft robotic structure based on a parallel kinematic mechanism. The design is based on the Stewart platform, which uses six sensors and actuators to achieve full six-degree-of-freedom motion. Our design is much less complex than a traditional platform, since it replaces the 12 spherical and universal joints found in a traditional Stewart platform with a single highly deformable elastomer body and flexible actuators. This reduces the total number of parts in the system and simplifies the assembly process. Actuation is achieved through coiled-shape memory alloy actuators. State observation and feedback is accomplished through the use of capacitive elastomer strain gauges. The main structural element is an elastomer joint that provides antagonistic force. We report the response of the actuators and sensors individually, then report the response of the complete assembly. We show that the completed robotic system is able to achieve full position control, and we discuss the limitations associated with using responsive material actuators. We believe that control demonstrated on a single body in this work could be extended to chains of such bodies to create complex soft robots.

SERVOMOTOR CONTROL SYSTEM

DOEpatents

MacNeille, S.M.

1958-12-01

Control systems for automatic positioning of an electric motor operated vapor valve are described which is operable under the severe conditions existing in apparatus for electro-magnetlcally separating isotopes. In general, the system includes a rotor for turning the valve comprising two colls mounted mutually perpendicular to each other and also perpendicular to the magnetic field of the isotope separating apparatus. The coils are furnished with both a-c and d- c current by assoclate control circuitry and a position control is provided for varying the ratlo of the a-c currents in the coils and at the same time, but in an inverse manner, the ratio between the d-c currents in the coils is varied. With the present system the magnitude of the motor torque is constant for all valves of the rotor orientatlon angle.

Haptic interface of web-based training system for interventional radiology procedures

NASA Astrophysics Data System (ADS)

Ma, Xin; Lu, Yiping; Loe, KiaFock; Nowinski, Wieslaw L.

2004-05-01

The existing web-based medical training systems and surgical simulators can provide affordable and accessible medical training curriculum, but they seldom offer the trainee realistic and affordable haptic feedback. Therefore, they cannot offer the trainee a suitable practicing environment. In this paper, a haptic solution for interventional radiology (IR) procedures is proposed. System architecture of a web-based training system for IR procedures is briefly presented first. Then, the mechanical structure, the working principle and the application of a haptic device are discussed in detail. The haptic device works as an interface between the training environment and the trainees and is placed at the end user side. With the system, the user can be trained on the interventional radiology procedures - navigating catheters, inflating balloons, deploying coils and placing stents on the web and get surgical haptic feedback in real time.

Uniform magnetic fields and double-wrapped coil systems: improved techniques for the design of bioelectromagnetic experiments.

PubMed

Kirschvink, J L

1992-01-01

A common mistake in biomagnetic experimentation is the assumption that Helmholtz coils provide uniform magnetic fields; this is true only for a limited volume at their center. Substantial improvements on this design have been made during the past 140 years with systems of three, four, and five coils. Numerical comparisons of the field uniformity generated by these designs are made here, along with a table of construction details and recommendations for their use in experiments in which large volumes of uniform intensity magnetic exposures are needed. Double-wrapping, or systems of bifilar windings, can also help control for the non-magnetic effects of the electric coils used in many experiments. In this design, each coil is wrapped in parallel with two separate, adjacent strands of copper wire, rather than the single strand used normally. If currents are flowing in antiparallel directions, the magnetic fields generated by each strand will cancel and yield virtually no external magnetic field, whereas parallel currents will yield an external field. Both cases will produce similar non-magnetic effects of ohmic heating, and simple measures can reduce the small vibration and electric field differences. Control experiments can then be designed such that the only major difference between treated and untreated groups is the presence or absence of the magnetic field. Double-wrapped coils also facilitate the use of truly double-blind protocol, as the same apparatus can be used either for experimental or control groups.

GREAT-a randomized controlled trial comparing HydroSoft/HydroFrame and bare platinum coils for endovascular aneurysm treatment: procedural safety and core-lab-assessedangiographic results.

PubMed

Taschner, Christian A; Chapot, René; Costalat, Vincent; Machi, Paolo; Courthéoux, Patrick; Barreau, Xavier; Berge, Jérôme; Pierot, Laurent; Kadziolka, Kryzsztof; Jean, Betty; Blanc, Raphaël; Biondi, Alessandra; Brunel, Hervé; Gallas, Sophie; Berlis, Ansgar; Herbreteau, Denis; Berkefeld, Joachim; Urbach, Horst; El Shikh, Samer; Fiehler, Jens; Desal, Hubert; Graf, Erika; Bonafé, Alain

2016-08-01

Hybrid hydrogel-platinum coils (HydroCoil) have proven effective for endovascular aneurysm treatment. To overcome technical limitations (coil stiffness, time restriction for placement), a second generation of softer hydrogel coils has been brought to clinical practice (HydroSoft, HydroFrame). We report on procedural safety and core-lab-assessed angiographic results from an open-label multicenter randomized controlled trial. Web-based randomization occurred in 15 medical centers in France and seven in Germany between coil embolization with second-generation hydrogel coils and treatment with any bare platinum coil. Assist devices could be used as clinically required. Primary endpoint is a composite outcome including major aneurysm recurrence and poor clinical outcome at 18 months follow-up. Five hundred thirteen patients were randomized (hydrogel n = 256, bare platinum n = 257). Twenty patients were excluded for missing informed consent and nine patients for treatment related criteria. Four hundred eighty-four patients were analyzed as randomized (hydrogel n = 243, bare platinum n = 241). Two hundred eight had ruptured aneurysms (43 %). Prespecified procedural complications occurred in 58 subjects (hydrogel n = 28, bare platinum n = 30, p = 0.77). The 14-day mortality rate was 2.1 % in both arms of the study. The median calculated packing densities for aneurysms assigned to hydrogel and bare platinum were 39 and 31 % respectively (p < 0.001). No statistically significant differences were found between arms in the post procedural angiographic occlusion rate (p = 0.8). Second-generation hydrogel coils can be used in a wide spectrum of aneurysms with a risk profile equivalent to bare platinum. Packing density was significantly higher in aneurysms treated with hydrogel coils. http://www.germanctr.de , DRKS00003132.

Implementation of a transcutaneous charger for fully implantable middle ear hearing device.

PubMed

Lim, H; Yoon, Y; Lee, C; Park, I; Song, B; Cho, J

2005-01-01

A transcutaneous charger for the fully implantable middle ear hearing device (F-IMEHD), which can monitor the charging level of battery, has been designed and implemented. In order to recharge the battery of F-IMEHD, the electromagnetic coupling between primary coil at outer body and secondary coil at inner body has been used. Considering the implant condition of the F-IMEHD, the primary coil and the secondary coil have been designed. Using the resonance of LC tank circuit at each coil, transmission efficiency was increased. Since the primary and the secondary coil are magnetically coupled, the current variation of the primary coil is related with the impedance of internal resonant circuit. Using the principle mentioned above, the implanted module could transmit outward the information about charging state of battery or coupling between two coils by the changing internal impedance. As in the demonstrated results of experiment, the implemented charger has supplied the sufficient operating voltage for the implanted battery within about 10 mm distance. And also, it has been confirmed that the implanted module can transmit information outward by control of internal impedance.

Control system for a small fission reactor

DOEpatents

Burelbach, James P.; Kann, William J.; Saiveau, James G.

1986-01-01

A system for controlling the reactivity of a small fission reactor includes an elongated, flexible hollow tube in the general form of a helical coiled spring axially positioned around and outside of the reactor vessel in an annular space between the reactor vessel and a surrounding cylindrical-shaped neutron reflector. A neutron absorbing material is provided within the hollow tube with the rate of the reaction controlled by the extension and compression of the hollow tube, e.g., extension of the tube increases reactivity while its compression reduces reactivity, in varying the amount of neutron absorbing material disposed between the reactor vessel and the neutron reflector. Conventional mechanical displacement means may be employed to control the coil density of the hollow tube as desired. In another embodiment, a plurality of flexible hollow tubes each containing a neutron absorber are positioned adjacent to one another in spaced relation around the periphery of the reactor vessel and inside the outer neutron reflector with reactivity controlled by the extension and compression of all or some of the coiled hollow tubes. Yet another embodiment of the invention envisions the neutron reflector in the form of an expandable coil spring positioned in an annular space between the reactor vessel and an outer neutron absorbing structure for controlling the neutron flux reflected back into the reactor vessel.

Endovascular Catheter for Magnetic Navigation under MR Imaging Guidance: Evaluation of Safety in Vivo at 1.5T

PubMed Central

Hetts, S.W.; Saeed, M.; Martin, A.J.; Evans, L.; Bernhardt, A.F.; Malba, V.; Settecase, F.; Do, L.; Yee, E.J.; Losey, A.; Sincic, R.; Roy, S.; Arenson, R.L.; Wilson, M.W.

2013-01-01

BACKGROUND AND PURPOSE: Endovascular navigation under MR imaging guidance can be facilitated by a catheter with steerable microcoils on the tip. Not only do microcoils create visible artifacts allowing catheter tracking, but also they create a small magnetic moment permitting remote-controlled catheter tip deflection. A side product of catheter tip electrical currents, however, is the heat that might damage blood vessels. We sought to determine the upper boundary of electrical currents safely usable at 1.5T in a coil-tipped microcatheter system. MATERIALS AND METHODS: Alumina tubes with solenoid copper coils were attached to neurovascular microcatheters with heat shrink-wrap. Catheters were tested in carotid arteries of 8 pigs. The catheters were advanced under x-ray fluoroscopy and MR imaging. Currents from 0 mA to 700 mA were applied to test heating and potential vascular damage. Postmortem histologic analysis was the primary endpoint. RESULTS: Several heat-mitigation strategies demonstrated negligible vascular damage compared with control arteries. Coil currents ≤300 mA resulted in no damage (0/58 samples) compared with 9 (25%) of 36 samples for > 300-mA activations (P = .0001). Tip coil activation ≤1 minute and a proximal carotid guide catheter saline drip > 2 mL/minute also had a nonsignificantly lower likelihood of vascular damage. For catheter tip coil activations ≤300 mA for ≤1 minute in normal carotid flow, 0 of 43 samples had tissue damage. CONCLUSIONS: Activations of copper coils at the tip of microcatheters at low currents in 1.5T MR scanners can be achieved without significant damage to blood vessel walls in a controlled experimental setting. Further optimization of catheter design and procedure protocols is necessary for safe remote control magnetic catheter guidance. PMID:23846795

Two-slot coiled coaxial cable resonator: reaching critical coupling at a reduced number of coils.

PubMed

Hefferman, Gerald; Chen, Zhen; Wei, Tao

2014-11-01

This paper reports the experimental demonstration of a coiled coaxial cable resonator capable of meeting the critical coupling condition using a reduced number of coils relative to previously reported coiled resonators. By introducing a second slot along the length of the device, a two-slot coiled coaxial cable resonator was fabricated and critical coupling observed at 22 turns. An additional device with one-slot, but otherwise identically constructed, was also fabricated. After 44 turns, the one-slot device had yet to reach critical coupling. An ultrahigh signal-to-noise ratio (greater than 70 dB) was observed at critical coupling of the two-slot device. This reduction in number of slots necessary to reach critical coupling, and the corresponding reduction of physical length of the device, makes this demonstration of the control of critical coupling a potentially important step towards the successful application of coiled coaxial cable resonators to microwave communication and robust sensing applications.

An accurate real-time model of maglev planar motor based on compound Simpson numerical integration

NASA Astrophysics Data System (ADS)

Kou, Baoquan; Xing, Feng; Zhang, Lu; Zhou, Yiheng; Liu, Jiaqi

2017-05-01

To realize the high-speed and precise control of the maglev planar motor, a more accurate real-time electromagnetic model, which considers the influence of the coil corners, is proposed in this paper. Three coordinate systems for the stator, mover and corner coil are established. The coil is divided into two segments, the straight coil segment and the corner coil segment, in order to obtain a complete electromagnetic model. When only take the first harmonic of the flux density distribution of a Halbach magnet array into account, the integration method can be carried out towards the two segments according to Lorenz force law. The force and torque analysis formula of the straight coil segment can be derived directly from Newton-Leibniz formula, however, this is not applicable to the corner coil segment. Therefore, Compound Simpson numerical integration method is proposed in this paper to solve the corner segment. With the validation of simulation and experiment, the proposed model has high accuracy and can realize practical application easily.

Comprehensive Survey on Improved Focality and Penetration Depth of Transcranial Magnetic Stimulation Employing Multi-Coil Arrays.

PubMed

Wei, Xile; Li, Yao; Lu, Meili; Wang, Jiang; Yi, Guosheng

2017-11-14

Multi-coil arrays applied in transcranial magnetic stimulation (TMS) are proposed to accurately stimulate brain tissues and modulate neural activities by an induced electric field (EF). Composed of numerous independently driven coils, a multi-coil array has alternative energizing strategies to evoke EFs targeting at different cerebral regions. To improve the locating resolution and the stimulating focality, we need to fully understand the variation properties of induced EFs and the quantitative control method of the spatial arrangement of activating coils, both of which unfortunately are still unclear. In this paper, a comprehensive analysis of EF properties was performed based on multi-coil arrays. Four types of planar multi-coil arrays were used to study the relationship between the spatial distribution of EFs and the structure of stimuli coils. By changing coil-driven strategies in a basic 16-coil array, we find that an EF induced by compactly distributed coils decays faster than that induced by dispersedly distributed coils, but the former has an advantage over the latter in terms of the activated brain volume. Simulation results also indicate that the attenuation rate of an EF induced by the 36-coil dense array is 3 times and 1.5 times greater than those induced by the 9-coil array and the 16-coil array, respectively. The EF evoked by the 36-coil dispense array has the slowest decay rate. This result demonstrates that larger multi-coil arrays, compared to smaller ones, activate deeper brain tissues at the expense of decreased focality. A further study on activating a specific field of a prescribed shape and size was conducted based on EF variation. Accurate target location was achieved with a 64-coil array 18 mm in diameter. A comparison between the figure-8 coil, the planar array, and the cap-formed array was made and demonstrates an improvement of multi-coil configurations in the penetration depth and the focality. These findings suggest that there is a tradeoff between attenuation rate and focality in the application of multi-coil arrays. Coil-energizing strategies and array dimensions should be based on an adequate evaluation of these two important demands and the topological structure of target tissues.

Study on Dynamic Alignment Technology of COIL Resonator

NASA Astrophysics Data System (ADS)

Xiong, M. D.; Zou, X. J.; Guo, J. H.; Jia, S. N.; Zhang2, Z. B.

2006-10-01

The performance of great power chemical oxygen-iodine laser (COIL) beam is decided mostly by resonator mirror maladjustment and environment vibration. To improve the performance of light beam, an auto-alignment device is used in COIL resonator, the device can keep COIL resonator collimating by adjusting the optical components of resonator. So the coupling model of COIL resonator is present. The multivariable self study fuzzy uncoupling arithmetic and six-dimensional micro drive technology are used to design a six-input-three-output uncoupling controller, resulting in the realization of the high precision dynamic alignment. The experiments indicate that the collimating range of this system is 8 mrad, precision is 5 urad and frequency response is 20Hz, which meet the demand of resonator alignment system.

QUICK RELEASABLE DRIVE

DOEpatents

Dickson, J.J.

1958-07-01

A quick releasable mechanical drive system suitable for use in a nuclear reactor is described. A small reversible motor positions a control rod by means of a worm and gear speed reducer, a magnetic torque clutch, and a bell crank. As the control rod is raised to the operating position, a heavy coil spring is compressed. In the event of an emergency indicated by either a''scram'' signal or a power failure, the current to the magnetic clutch is cut off, thereby freeing the coil spring and the bell crank positioner from the motor and speed reduction gearing. The coil spring will immediately act upon the bell crank to cause the insertion of the control rod. This arrangement will allow the slow, accurate positioning of the control rod during reactor operation, while providing an independent force to rapidly insert the rod in the event of an emergency.

Modelling controlled VDE's and ramp-down scenarios in ITER

NASA Astrophysics Data System (ADS)

Lodestro, L. L.; Kolesnikov, R. A.; Meyer, W. H.; Pearlstein, L. D.; Humphreys, D. A.; Walker, M. L.

2011-10-01

Following the design reviews of recent years, the ITER poloidal-field coil-set design, including in-vessel coils (VS3), and the divertor configuration have settled down. The divertor and its material composition (the latter has not been finalized) affect the development of fiducial equilibria and scenarios together with the coils through constraints on strike-point locations and limits on the PF and control systems. Previously we have reported on our studies simulating controlled vertical events in ITER with the JCT 2001 controller to which we added a PID VS3 circuit. In this paper we report and compare controlled VDE results using an optimized integrated VS and shape controller in the updated configuration. We also present our recent simulations of alternate ramp-down scenarios, looking at the effects of ramp-down time and shape strategies, using these controllers. This work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

High-Speed, High-Power Active Control Coils for HBT-EP

NASA Astrophysics Data System (ADS)

Debono, Bryan

2010-11-01

We report the performance of a newly installed high-speed, high-power active control system for the application of non-symmetric magnetic fields and the study of rotating MHD and resistive wall modes in the HBTEP tokamak. The new control system consists of an array of 120 modular control coils and 40 solid-state, high-power amplifiers that can apply non-symmetric control fields that are more than 10 times larger than previous studies in HBT-EP and exceed 5% of the equilibrium poloidal field strength. Measurements of the current and field response of the control system are presented as a function of frequency and control coil geometry, and these demonstrate the effectiveness of the system to interact with both growing RWM instabilities and long-wavelength modes rotating with the plasma. We describe a research plan to study the interaction of both kink and tearing mode fluctuations with applied static and rotating magnetic perturbations while systematically changing the plasma rotation with a biased molybdenum electrode inserted into the edge plasma.

Endocavitary thermal therapy by MRI-guided phased-array contact ultrasound: experimental and numerical studies on the multi-input single-output PID temperature controller's convergence and stability.

PubMed

Salomir, Rares; Rata, Mihaela; Cadis, Daniela; Petrusca, Lorena; Auboiroux, Vincent; Cotton, François

2009-10-01

Endocavitary high intensity contact ultrasound (HICU) may offer interesting therapeutic potential for fighting localized cancer in esophageal or rectal wall. On-line MR guidance of the thermotherapy permits both excellent targeting of the pathological volume and accurate preoperatory monitoring of the temperature elevation. In this article, the authors address the issue of the automatic temperature control for endocavitary phased-array HICU and propose a tailor-made thermal model for this specific application. The convergence and stability of the feedback loop were investigated against tuning errors in the controller's parameters and against input noise, through ex vivo experimental studies and through numerical simulations in which nonlinear response of tissue was considered as expected in vivo. An MR-compatible, 64-element, cooled-tip, endorectal cylindrical phased-array applicator of contact ultrasound was integrated with fast MR thermometry to provide automatic feedback control of the temperature evolution. An appropriate phase law was applied per set of eight adjacent transducers to generate a quasiplanar wave, or a slightly convergent one (over the circular dimension). A 2D physical model, compatible with on-line numerical implementation, took into account (1) the ultrasound-mediated energy deposition, (2) the heat diffusion in tissue, and (3) the heat sink effect in the tissue adjacent to the tip-cooling balloon. This linear model was coupled to a PID compensation algorithm to obtain a multi-input single-output static-tuning temperature controller. Either the temperature at one static point in space (situated on the symmetry axis of the beam) or the maximum temperature in a user-defined ROI was tracked according to a predefined target curve. The convergence domain in the space of controller's parameters was experimentally explored ex vivo. The behavior of the static-tuning PID controller was numerically simulated based on a discrete-time iterative solution of the bioheat transfer equation in 3D and considering temperature-dependent ultrasound absorption and blood perfusion. The intrinsic accuracy of the implemented controller was approximately 1% in ex vivo trials when providing correct estimates for energy deposition and heat diffusivity. Moreover, the feedback loop demonstrated excellent convergence and stability over a wide range of the controller's parameters, deliberately set to erroneous values. In the extreme case of strong underestimation of the ultrasound energy deposition in tissue, the temperature tracking curve alone, at the initial stage of the MR-controlled HICU treatment, was not a sufficient indicator for a globally stable behavior of the feedback loop. Our simulations predicted that the controller would be able to compensate for tissue perfusion and for temperature-dependent ultrasound absorption, although these effects were not included in the controller's equation. The explicit pattern of acoustic field was not required as input information for the controller, avoiding time-consuming numerical operations. The study demonstrated the potential advantages of PID-based automatic temperature control adapted to phased-array MR-guided HICU therapy. Further studies will address the integration of this ultrasound device with a miniature RF coil for high resolution MRI and, subsequently, the experimental behavior of the controller in vivo.

Opposing effects of pericentrin and microcephalin on the pericentriolar material regulate CHK1 activation in the DNA damage response.

PubMed

Antonczak, A K; Mullee, L I; Wang, Y; Comartin, D; Inoue, T; Pelletier, L; Morrison, C G

2016-04-14

Genotoxic stresses lead to centrosome amplification, a frequently-observed feature in cancer that may contribute to genome instability and to tumour cell invasion. Here we have explored how the centrosome controls DNA damage responses. For most of the cell cycle, centrosomes consist of two centrioles embedded in the proteinaceous pericentriolar material (PCM). Recent data indicate that the PCM is not an amorphous assembly of proteins, but actually a highly organised scaffold around the centrioles. The large coiled-coil protein, pericentrin, participates in PCM assembly and has been implicated in the control of DNA damage responses (DDRs) through its interactions with checkpoint kinase 1 (CHK1) and microcephalin (MCPH1). CHK1 is required for DNA damage-induced centrosome amplification, whereas MCPH1 deficiency greatly increases the amplification seen after DNA damage. We found that the PCM showed a marked expansion in volume and a noticeable change in higher-order organisation after ionising radiation treatment. PCM expansion was dependent on CHK1 kinase activity and was potentiated by MCPH1 deficiency. Furthermore, pericentrin deficiency or mutation of a separase cleavage site blocked DNA damage-induced PCM expansion. The extent of nuclear CHK1 activation after DNA damage reflected the level of PCM expansion, with a reduction in pericentrin-deficient or separase cleavage site mutant-expressing cells, and an increase in MCPH1-deficient cells that was suppressed by the loss of pericentrin. Deletion of the nuclear export signal of CHK1 led to its hyperphosphorylation after irradiation and reduced centrosome amplification. Deletion of the nuclear localisation signal led to low CHK1 activation and low centrosome amplification. From these data, we propose a feedback loop from the PCM to the nuclear DDR in which CHK1 regulates pericentrin-dependent PCM expansion to control its own activation.

Parametric design of tri-axial nested Helmholtz coils

NASA Astrophysics Data System (ADS)

Abbott, Jake J.

2015-05-01

This paper provides an optimal parametric design for tri-axial nested Helmholtz coils, which are used to generate a uniform magnetic field with controllable magnitude and direction. Circular and square coils, both with square cross section, are considered. Practical considerations such as wire selection, wire-wrapping efficiency, wire bending radius, choice of power supply, and inductance and time response are included. Using the equations provided, a designer can quickly create an optimal set of custom coils to generate a specified field magnitude in the uniform-field region while maintaining specified accessibility to the central workspace. An example case study is included.

Parametric design of tri-axial nested Helmholtz coils.

PubMed

Abbott, Jake J

2015-05-01

This paper provides an optimal parametric design for tri-axial nested Helmholtz coils, which are used to generate a uniform magnetic field with controllable magnitude and direction. Circular and square coils, both with square cross section, are considered. Practical considerations such as wire selection, wire-wrapping efficiency, wire bending radius, choice of power supply, and inductance and time response are included. Using the equations provided, a designer can quickly create an optimal set of custom coils to generate a specified field magnitude in the uniform-field region while maintaining specified accessibility to the central workspace. An example case study is included.

Parametric design of tri-axial nested Helmholtz coils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbott, Jake J., E-mail: jake.abbott@utah.edu

This paper provides an optimal parametric design for tri-axial nested Helmholtz coils, which are used to generate a uniform magnetic field with controllable magnitude and direction. Circular and square coils, both with square cross section, are considered. Practical considerations such as wire selection, wire-wrapping efficiency, wire bending radius, choice of power supply, and inductance and time response are included. Using the equations provided, a designer can quickly create an optimal set of custom coils to generate a specified field magnitude in the uniform-field region while maintaining specified accessibility to the central workspace. An example case study is included.

Switching Circuit for Shop Vacuum System

NASA Technical Reports Server (NTRS)

Burley, R. K.

1987-01-01

No internal connections to machine tools required. Switching circuit controls vacuum system draws debris from grinders and sanders in machine shop. Circuit automatically turns on vacuum system whenever at least one sander or grinder operating. Debris safely removed, even when operator neglects to turn on vacuum system manually. Pickup coils sense alternating magnetic fields just outside operating machines. Signal from any coil or combination of coils causes vacuum system to be turned on.

Reluctance apparatus for flywheel energy storage

DOEpatents

Hull, John R.

2000-01-01

A motor generator for providing high efficiency, controlled voltage output or storage of energy in a flywheel system. A motor generator includes a stator of a soft ferromagnetic material, a motor coil and a generator coil, and a rotor has at least one embedded soft ferromagnetic piece. Control of voltage output is achieved by use of multiple stator pieces and multiple rotors with controllable gaps between the stator pieces and the soft ferromagnetic piece.

Method for providing slip energy control in permanent magnet electrical machines

DOEpatents

Hsu, John S.

2006-11-14

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

Magnetic stage with environmental control for optical microscopy and high-speed nano- and microrheology

NASA Astrophysics Data System (ADS)

Aprelev, Pavel; McKinney, Bonni; Walls, Chadwick; Kornev, Konstanin G.

2017-07-01

A novel design of a low-field magnetic stage for optical microscopy of droplets and films within a controlled environment is described. The stage consists of five magnetic coils with a 3D magnetic sensor in a feedback control loop, which allows one to manipulate magnetic nano- and microprobes with microtesla fields. A locally uniform time-dependent field within the focal plane of the microscope objective enables one to rotate the probes in a precisely set manner and observe their motion. The probe tracking protocol was developed to follow the probe rotation in real time and relate it with the viscosity of the host liquid. Using this magnetic stage, a method for measuring mPa s-level viscosity of nanoliter droplets and micron thick films in a 10-20 s timeframe is presented and validated. The viscosity of a rapidly changing liquid can be tracked by using only a few visible probes rotating simultaneously. Vapor pressure and temperature around the sample can be controlled to directly measure viscosity as a function of equilibrium vapor pressure; this addresses a significant challenge in characterization of volatile nanodroplets and thin films. Thin films of surfactant solutions undergoing phase transitions upon solvent evaporation were studied and their rheological properties were related to morphological changes in the material.

Improved efficiency and precise temperature control of low-frequency induction-heating pure iron vapor source on ECR ion source

NASA Astrophysics Data System (ADS)

Kato, Y.; Takenaka, T.; Yano, K.; Kiriyama, R.; Kurisu, Y.; Nozaki, D.; Muramatsu, M.; Kitagawa, A.; Uchida, T.; Yoshida, Y.; Sato, F.; Iida, T.

2012-11-01

Multiply charged ions to be used prospectively are produced from solid pure material in an electron cyclotron resonance ion source (ECRIS). Recently a pure iron source is also required for the production of caged iron ions in the fullerene in order to control cells in vivo in bio-nano science and technology. We adopt directly heating iron rod by induction heating (IH) because it has non-contact with insulated materials which are impurity gas sources. We choose molybdenum wire for the IH coils because it doesn't need water cooling. To improve power efficiency and temperature control, we propose to the new circuit without previously using the serial and parallel dummy coils (SPD) for matching and safety. We made the circuit consisted of inductively coupled coils which are thin-flat and helix shape, and which insulates the IH power source from the evaporator. This coupling coils circuit, i.e. insulated induction heating coil transformer (IHCT), can be move mechanically. The secondary current can be adjusted precisely and continuously. Heating efficiency by using the IHCT is much higher than those of previous experiments by using the SPD, because leakage flux is decreased and matching is improved simultaneously. We are able to adjust the temperature in heating the vapor source around melting point. And then the vapor pressure can be controlled precisely by using the IHCT. We can control ±10K around 1500°C by this method, and also recognize to controlling iron vapor flux experimentally in the extreme low pressures. Now we come into next stage of developing induction heating vapor source for materials with furthermore high temperature melting points above 2000K with the IHCT, and then apply it in our ECRIS.

Structure of bacteriophage T4 fibritin: a segmented coiled coil and the role of the C-terminal domain.

PubMed

Tao, Y; Strelkov, S V; Mesyanzhinov, V V; Rossmann, M G

1997-06-15

Oligomeric coiled-coil motifs are found in numerous protein structures; among them is fibritin, a structural protein of bacteriophage T4, which belongs to a class of chaperones that catalyze a specific phage-assembly process. Fibritin promotes the assembly of the long tail fibers and their subsequent attachment to the tail baseplate; it is also a sensing device that controls the retraction of the long tail fibers in adverse environments and, thus, prevents infection. The structure of fibritin had been predicted from sequence and biochemical analyses to be mainly a triple-helical coiled coil. The determination of its structure at atomic resolution was expected to give insights into the assembly process and biological function of fibritin, and the properties of modified coiled-coil structures in general. The three-dimensional structure of fibritin E, a deletion mutant of wild-type fibritin, was determined to 2.2 A resolution by X-ray crystallography. Three identical subunits of 119 amino acid residues form a trimeric parallel coiled-coil domain and a small globular C-terminal domain about a crystallographic threefold axis. The coiled-coil domain is divided into three segments that are separated by insertion loops. The C-terminal domain, which consists of 30 residues from each subunit, contains a beta-propeller-like structure with a hydrophobic interior. The residues within the C-terminal domain make extensive hydrophobic and some polar intersubunit interactions. This is consistent with the C-terminal domain being important for the correct assembly of fibritin, as shown earlier by mutational studies. Tight interactions between the C-terminal residues of adjacent subunits counteract the latent instability that is suggested by the structural properties of the coiled-coil segments. Trimerization is likely to begin with the formation of the C-terminal domain which subsequently initiates the assembly of the coiled coil. The interplay between the stabilizing effect of the C-terminal domain and the labile coiled-coil domain may be essential for the fibritin function and for the correct functioning of many other alpha-fibrous proteins.

Concept of a Cryogenic System for a Cryogen-Free 25 T Superconducting Magnet

NASA Astrophysics Data System (ADS)

Iwai, Sadanori; Takahashi, Masahiko; Miyazaki, Hiroshi; Tosaka, Taizo; Tasaki, Kenji; Hanai, Satoshi; Ioka, Shigeru; Watanabe, Kazuo; Awaji, Satoshi; Oguro, Hidetoshi

A cryogen-free 25 T superconducting magnet using a ReBCO insert coil that generates 11.5 T in a 14 T background field of outer low-temperature superconducting (LTS) coils is currently under development. The AC loss of the insert coil during field ramping is approximately 8.8 W, which is difficult to dissipate at the operating temperature of the LTS coils (4 K). However, since a ReBCO coil can operate at a temperature above 4 K, the ReBCO insert coil is cooled to about 10 K by two GM cryocoolers, and the LTS coils are independently cooled by two GM/JT cryocoolers. Two GM cryocoolers cool a circulating helium gas through heat exchangers, and the gas is transported over a long distance to the cold stage located on the ReBCO insert coil, in order to protect the cryocoolers from the leakage field of high magnetic fields. The temperature difference of the 2nd cold stage of the GM cryocoolers and the insert coil can be reduced by increasing the gas flow rate. However, at the same time, the heat loss of the heat exchangers increases, and the temperature of the second cold stage is raised. Therefore, the gas flow rate is optimized to minimize the operating temperature of the ReBCO insert coil by using a flow controller and a bypass circuit connected to a buffer tank.

An improved current potential method for fast computation of stellarator coil shapes

NASA Astrophysics Data System (ADS)

Landreman, Matt

2017-04-01

Several fast methods for computing stellarator coil shapes are compared, including the classical NESCOIL procedure (Merkel 1987 Nucl. Fusion 27 867), its generalization using truncated singular value decomposition, and a Tikhonov regularization approach we call REGCOIL in which the squared current density is included in the objective function. Considering W7-X and NCSX geometries, and for any desired level of regularization, we find the REGCOIL approach simultaneously achieves lower surface-averaged and maximum values of both current density (on the coil winding surface) and normal magnetic field (on the desired plasma surface). This approach therefore can simultaneously improve the free-boundary reconstruction of the target plasma shape while substantially increasing the minimum distances between coils, preventing collisions between coils while improving access for ports and maintenance. The REGCOIL method also allows finer control over the level of regularization, it preserves convexity to ensure the local optimum found is the global optimum, and it eliminates two pathologies of NESCOIL: the resulting coil shapes become independent of the arbitrary choice of angles used to parameterize the coil surface, and the resulting coil shapes converge rather than diverge as Fourier resolution is increased. We therefore contend that REGCOIL should be used instead of NESCOIL for applications in which a fast and robust method for coil calculation is needed, such as when targeting coil complexity in fixed-boundary plasma optimization, or for scoping new stellarator geometries.

Optically controlled switch-mode current-source amplifiers for on-coil implementation in high field parallel transmission

PubMed Central

Gudino, Natalia; Duan, Qi; de Zwart, Jacco A; Murphy-Boesch, Joe; Dodd, Stephen J; Merkle, Hellmut; van Gelderen, Peter; Duyn, Jeff H

2015-01-01

Purpose We tested the feasibility of implementing parallel transmission (pTX) for high field MRI using a radiofrequency (RF) amplifier design to be located on or in the immediate vicinity of a RF transmit coil. Method We designed a current-source switch-mode amplifier based on miniaturized, non-magnetic electronics. Optical RF carrier and envelope signals to control the amplifier were derived, through a custom-built interface, from the RF source accessible in the scanner control. Amplifier performance was tested by benchtop measurements as well as with imaging at 7 T (300 MHz) and 11.7 T (500 MHz). The ability to perform pTX was evaluated by measuring inter-channel coupling and phase adjustment in a 2-channel setup. Results The amplifier delivered in excess of 44 W RF power and caused minimal interference with MRI. The interface derived accurate optical control signals with carrier frequencies ranging from 64 to 750 MHz. Decoupling better than 14 dB was obtained between 2 coil loops separated by only 1 cm. Application to MRI was demonstrated by acquiring artifact-free images at 7 T and 11.7 T. Conclusion An optically controlled miniaturized RF amplifier for on-coil implementation at high field is demonstrated that should facilitate implementation of high-density pTX arrays. PMID:26256671

Grapple fixture for use with electromagnetic attachment mechanism

NASA Technical Reports Server (NTRS)

Monford, Jr., Leo G. (Inventor)

1995-01-01

An electromagnetic attachment mechanism for use as an end effector of a remote manipulator system. A pair of electromagnets 15A,15B, each with a U-shaped magnetic core with a pull-in coil 34 and two holding coils 35,36 are mounted by a spring suspension system 38,47 on a base plate 25 of the mechanism housing 30 with end pole pieces 21,22 adapted to move through openings in the base plate when the attractive force of the electromagnets is exerted on a strike plate 65 of a grapple fixture 20 affixed to a target object 14. The pole pieces are spaced by an air gap from the strike plate when the mechanism first contacts the grapple fixture. An individual control circuit and power source is provided for the pull-in coil and one holding coil of each electromagnet. A back-up control circuit connected to the two power sources and a third power source is provided for the remaining holding coils. When energized, the pull-in coils overcome the suspension system and air gap and are automatically de-energized when the pole pieces move to grapple and impose a preload force across the grapple interface. A battery back-up 89A,89B is a redundant power source for each electromagnet in each individual control circuit and is automatically connected upon failure of the primary power source. A centerline mounted camera 31 and video monitor 70 are used in cooperation with a target pattern 19 on the reflective surface 67 of the strike plate to effect targeting and alignment.

Shape-specific nanostructured protein mimics from de novo designed chimeric peptides.

PubMed

Jiang, Linhai; Yang, Su; Lund, Reidar; Dong, He

2018-01-30

Natural proteins self-assemble into highly-ordered nanoscaled architectures to perform specific functions. The intricate functions of proteins have provided great impetus for researchers to develop strategies for designing and engineering synthetic nanostructures as protein mimics. Compared to the success in engineering fibrous protein mimetics, the design of discrete globular protein-like nanostructures has been challenging mainly due to the lack of precise control over geometric packing and intermolecular interactions among synthetic building blocks. In this contribution, we report an effective strategy to construct shape-specific nanostructures based on the self-assembly of chimeric peptides consisting of a coiled coil dimer and a collagen triple helix folding motif. Under salt-free conditions, we showed spontaneous self-assembly of the chimeric peptides into monodisperse, trigonal bipyramidal-like nanoparticles with precise control over the stoichiometry of two folding motifs and the geometrical arrangements relative to one another. Three coiled coil dimers are interdigitated on the equatorial plane while the two collagen triple helices are located in the axial position, perpendicular to the coiled coil plane. A detailed molecular model was proposed and further validated by small angle X-ray scattering experiments and molecular dynamics (MD) simulation. The results from this study indicated that the molecular folding of each motif within the chimeric peptides and their geometric packing played important roles in the formation of discrete protein-like nanoparticles. The peptide design and self-assembly mechanism may open up new routes for the construction of highly organized, discrete self-assembling protein-like nanostructures with greater levels of control over assembly accuracy.

REACTOR HAVING NaK-UO$sub 2$ SLURRY HELICALLY POSITIONED IN A GRAPHITE MODERATOR

DOEpatents

Rodin, M.B.; Carter, J.C.

1962-05-15

A reactor utilizing 20% enriched uranium consists of a central graphite island in cylindrical form, with a spiral coil of tubing fitting against the central island. An external graphite moderator is placed around the central island and coil. A slurry of uranium dioxide dispersed in alkali metal passes through the coil to transfer heat externally to the reactor. There are also conventional controls for regulating the nuclear reaction. (AEC)

Controlled self-assembly of conjugated rod-coil block copolymers for applications in organic optoelectronics

NASA Astrophysics Data System (ADS)

Tao, Yuefei

Organic electronics are of great interest in manufacturing light weight, mechanical flexible, and inexpensive large area devices. While significant improvements have been made over the last several years and it is now clear that morphology on the lengthscale of exciton diffusion (10nm) is of crucial importance, a clear relationship between structure and device properties has not emerged. This lack of understanding largely emerges from an inability to control morphology on this lengthscale. This thesis will center around an approach, based on block copolymer self-assembly, to generate equilibrium nanostructures on the 10 nm lengthscale of exciton diffusion and study their effects on device performance. Self-assembly of semiconducting block copolymers is complicated by the non-classical chain shape of conjugated polymers. Unlike classical polymers, the chains do not assume a Gaussian coil shape which is stretched near block copolymer interfaces, instead the chains are elongated and liquid crystalline. Previous work has demonstrated how these new molecular interactions and shapes control the phase diagram of so-called rod-coil block copolymers. Here, we will focus on controlling domain size, orientation, and chemical structure. While domain size can be controlled directly through molecular weight, this requires significant additional synthesis of domain size is to be varied. Here, the domain size is controlled by blending homopolymers into a self-assembling rod-coil block copolymer. When coil-like blocks are incorporated, the domains swell, as expected. When rod-like blocks are incorporated, they interdigitate with the rods of the block copolymers. This results in an increase in interfacial area which forces the coils to rearrange and an overall decrease in domain size with increasing rod content. Control over lamellar orientation is crucial in order to design and control charge transport pathways and exciton recombination or separation interfaces. While numerous techniques have been demonstrated for classical block copolymers, the pi conjugation in the rod blocks allow for additional control mechanisms. Liquid crystals are traditionally aligned in magnetic fields. Here, it is demonstrated that if the rod-like blocks are aligned unidirectionally, the block copolymer interfaces follow to create macroscopic alignment of the nanostructures. Organic Light Emitting Diodes (OLEDs) are generally composed of electron transporting and hole transporting moieties to balance charge recombination. Here, a new multifunctional bipolar rod-coil block copolymer containing the hole transporting and electron transporting materials is synthesized. Self-assembly of this new block copolymer results in 15nm lamellae oriented in grains both parallel and perpendicula to the anode. The self-assembled block copolymer shows superior device performance to controls consisting of a luminescent, analogous homopolymer, and a blend of the two component homopolymers. The effects of the morphologies and chemical structure on photovoltaics is explored with a rod-coil block copolymer, (poly(3-hexylthiophene-b-acrylic perylene)). By varying the kinetics of self-assembly through processing, the block copolymer can be disordered, ordered with only short range registry between the nanodomains, or with long-range order. The short range ordered samples showed the best device performance suggesting that the connectivity that is a biproduct of poor order is beneficial for device performance.

Embolization of a High-Output Postnephrectomy Aortocaval Fistula with Gianturco Coils and Cyanoacrylate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cekirge, Saruhan; Oguzkurt, Levent; Saatci, Isil

1996-11-15

The authors describe the endovascular treatment of a high-output, large-caliber, postnephrectomy aortocaval fistula using a mixture of cyanoacrylate and lipiodol combined with Gianturco coil embolization. Thirty-nine coils were used to decrease the flow through the fistula so that a fast-polymerizing glue mixture could be injected into the fistula. During rapid polymerization, the N-butyl-2-cyanoacrylate (NBCA) mixture was trapped within the coils, providing an easily controllable glue cast in the fistula, thereby preventing inadvertent embolization into the lungs. This approach can be of considerable benefit for the endovascular treatment of central high-output fistulas.

Demonstration of a stand-alone cylindrical fiber coil for optical amplifiers

NASA Astrophysics Data System (ADS)

Laxton, Steven R.; Bravo, Tyler; Madsen, Christi K.

2015-08-01

The design, fabrication and measurement of a cylindrical fiber coil structure is presented that has applications for compact fiber-optic amplifiers. A multimode fiber is used as a surrogate for a dual clad, rare-earth doped fiber for coil fabrication and optical testing. A ray trace algorithm, written in Python, was used to simulate the behavior of light travelling along the waveguide path. An in-house fabrication method was developed using 3D printed parts designed in SolidWorks and assembled with Arduino-controlled stepper motors for coil winding. Ultraviolet-cured epoxy was used to bind the coils into a rigid cylinder. Bend losses are introduced by the coil, and a measurement of the losses for two coil lengths was obtained experimentally. The measurements confirm that bend losses through a multimode fiber, representative of pump light propagating in a dual-clad rare-earth doped fiber, are relatively wavelength independent over a large spectral range and that higher order modes are extinguished quickly while lower order modes transmit through the windings with relatively low loss.

Neuropsychological function after endovascular and neurosurgical treatment of subarachnoid hemorrhage: a systematic review and meta-analysis.

PubMed

Egeto, Peter; Loch Macdonald, R; Ornstein, Tisha J; Schweizer, Tom A

2018-03-01

OBJECTIVE Subarachnoid hemorrhage (SAH) is treated with either surgical clipping or endovascular coiling, though the latter is the preferred treatment method given its more favorable functional outcomes. However, neuropsychological functioning after treatment is rarely taken into account. In this meta-analysis, the authors synthesized relevant data from the literature and compared neuropsychological functioning in patients after coiling and clipping of SAH. They hypothesized that the coiled patients would outperform the clipped patients; that group differences would be greater with higher posterior circulation rupture rates, in older patients, and in more recent publications; that group differences would be smaller with greater rates of middle cerebral artery (MCA) rupture; and that anterior communicating artery (ACoA) rupture rates would not influence effect sizes. METHODS The MEDLINE, Embase, and PsycINFO databases were searched for clinical studies that compared neuropsychological functioning after either endovascular coiling or surgical clipping for SAH. Hedge's g and 95% confidence intervals were calculated using random effects models. Patients who had undergone coiling or clipping were compared on test performance in 8 neuropsychological domains: executive functions, language, attention/processing speed, verbal memory, visual memory, spatial memory, visuospatial functions, and intelligence. Patients were also compared with healthy controls, and meta-regressions were used to explore the relation between effect sizes and publication year, delay between treatment and neuropsychological testing, mean patient age, and rates of posterior circulation, ACoA, and MCA ruptures. RESULTS Thirteen studies with 396 clipped cases, 314 coiled cases, and 169 healthy controls were included in the study. The coil-treated patients outperformed the clip-treated patients on executive function (g = 0.17, 95% CI 0.08-0.25) and language tests (g = 0.23, 95% CI 0.07-0.39), and all patients were impaired relative to healthy controls (g ranged from -0.93 to -0.29). Coiled patients outperformed clipped patients to a greater degree in more recent publications, over longer posttreatment testing delays, and among older patients. Higher rates of posterior circulation and MCA aneurysms were associated with smaller group differences, while ACoA rupture rates did not influence effect sizes. CONCLUSIONS Coiling of SAH may promote superior neuropsychological functioning under certain circumstances and could have applications for the specialized care of SAH patients.

Effects of a PID Control System on Electromagnetic Fields in an nEDM Experiment

NASA Astrophysics Data System (ADS)

Molina, Daniel

2017-09-01

The Kellogg Radiation Laboratory is currently testing a prototype for an experiment that hopes to identify the electric dipole moment of the neutron. As part of this testing, we have developed a PID (proportional, integral, derivative) feedback system that uses large coils to fix the value of local external magnetic fields, up to linear gradients. PID algorithms compare the current value to a set-point and use the integral and derivative of the field with respect to the set-point to maintain constant fields. We have also developed a method for zeroing linear gradients within the experimental apparatus. In order to determine the performance of the PID algorithm, measurements of both the internal and external fields were obtained with and without the algorithm running, and these results were compared for noise and time stability. We have seen that the PID algorithm can reduce the effect of disturbance to the field by a factor of 10.

Double-null divertor configuration discharge and disruptive heat flux simulation using TSC on EAST

NASA Astrophysics Data System (ADS)

Bo, SHI; Jinhong, YANG; Cheng, YANG; Desheng, CHENG; Hui, WANG; Hui, ZHANG; Haifei, DENG; Junli, QI; Xianzu, GONG; Weihua, WANG

2018-07-01

The tokamak simulation code (TSC) is employed to simulate the complete evolution of a disruptive discharge in the experimental advanced superconducting tokamak. The multiplication factor of the anomalous transport coefficient was adjusted to model the major disruptive discharge with double-null divertor configuration based on shot 61 916. The real-time feed-back control system for the plasma displacement was employed. Modeling results of the evolution of the poloidal field coil currents, the plasma current, the major radius, the plasma configuration all show agreement with experimental measurements. Results from the simulation show that during disruption, heat flux about 8 MW m‑2 flows to the upper divertor target plate and about 6 MW m‑2 flows to the lower divertor target plate. Computations predict that different amounts of heat fluxes on the divertor target plate could result by adjusting the multiplication factor of the anomalous transport coefficient. This shows that TSC has high flexibility and predictability.

Stellarator Saddle Coils

NASA Astrophysics Data System (ADS)

Boozer, Allen H.

1999-11-01

Modern stellarators are designed using J. Nuehrenberg’s method of varying Fourier coefficients in the shape of the plasma boundary to maximize a target function. The matrix of second derivatives of the target function at the optimum determines a quality matrix. This matrix gives the degradation in the quality of the configuration as the normal magnetic field is varied on a control surface, which lies on or outside the plasma surface. The task is finding saddle coils that produce the desired configuration in the presence of a given toroidal field. An eigenvector of the quality matrix can be important for two reasons: (1) the normal field that must be produced by the saddles is large or (2) the eigenvalue is large (an island-causing resonant perturbation). The rank of the important part of the quality matrix is the number of important eigenvectors. The current in each saddle coil produces a normal field on the control surface, which can be described by an inductance matrix. The relevant part of the inductance matrix has large eigenvalues. The coils can produce the configuration if the rank of the important part of the quality matrix and its product with the relevant part of the inductance matrix are the same. Existing coil design codes, pioneered by P. Merkel, approximate the quality matrix by the unit matrix. Stellarator flexibility could be enhanced by using a more realistic quality matrix and by using trim coils to balance large eigenvalues.

Characteristics of chiral plasma plumes generated in the absence of external magnetic field

NASA Astrophysics Data System (ADS)

Nie, LanLan; Liu, FengWu; Zhou, XinCai; Lu, XinPei; Xian, YuBin

2018-05-01

A chiral plasma plume has recently been generated inside a dielectric tube without the use of an external magnetic field. In this paper, we seek to further study the key properties of such a chiral plume to improve our understanding of how this interesting structure is generated and controlled. The chiral plume is generated by externally mounting a stainless steel helical coil or a ring onto the dielectric tube. By changing the pitch of the helical coil, the pitch of the plasma plume can be controlled, with the shape of the plume following the shape of the helical coil. The addition of the helical coil significantly expands the range of parameters under which the chiral plasma plume appears. When the frequency of the applied voltage increases, additional stable discharge channels appear between the adjacent helices. The addition of two helical coils results in the formation of two chiral plasma plumes, which follow the shape of the helical coils. When a metal ring is placed on the outside of the tube, there is no chiral plasma plume between the high voltage electrode and the ring; however, a chiral plasma plume appears on the right side of the ring if the distance between the ring and the high voltage electrode is small. These findings suggest that the chiral plasma can be effectively modulated and guided using an externally mounted helical coil, which acts as the floating/actual ground to reduce the impedance of the discharge and as such contributes to the emergence of the chiral plasma plume behavior.

A systematic review of mosquito coils and passive emanators: defining recommendations for spatial repellency testing methodologies.

PubMed

Ogoma, Sheila B; Moore, Sarah J; Maia, Marta F

2012-12-07

Mosquito coils, vaporizer mats and emanators confer protection against mosquito bites through the spatial action of emanated vapor or airborne pyrethroid particles. These products dominate the pest control market; therefore, it is vital to characterize mosquito responses elicited by the chemical actives and their potential for disease prevention. The aim of this review was to determine effects of mosquito coils and emanators on mosquito responses that reduce human-vector contact and to propose scientific consensus on terminologies and methodologies used for evaluation of product formats that could contain spatial chemical actives, including indoor residual spraying (IRS), long lasting insecticide treated nets (LLINs) and insecticide treated materials (ITMs). PubMed, (National Centre for Biotechnology Information (NCBI), U.S. National Library of Medicine, NIH), MEDLINE, LILAC, Cochrane library, IBECS and Armed Forces Pest Management Board Literature Retrieval System search engines were used to identify studies of pyrethroid based coils and emanators with key-words "Mosquito coils" "Mosquito emanators" and "Spatial repellents". It was concluded that there is need to improve statistical reporting of studies, and reach consensus in the methodologies and terminologies used through standardized testing guidelines. Despite differing evaluation methodologies, data showed that coils and emanators induce mortality, deterrence, repellency as well as reduce the ability of mosquitoes to feed on humans. Available data on efficacy outdoors, dose-response relationships and effective distance of coils and emanators is inadequate for developing a target product profile (TPP), which will be required for such chemicals before optimized implementation can occur for maximum benefits in disease control.

Magnetic Control of Locked Modes in Present Devices and ITER

NASA Astrophysics Data System (ADS)

Volpe, F. A.; Sabbagh, S.; Sweeney, R.; Hender, T.; Kirk, A.; La Haye, R. J.; Strait, E. J.; Ding, Y. H.; Rao, B.; Fietz, S.; Maraschek, M.; Frassinetti, L.; in, Y.; Jeon, Y.; Sakakihara, S.

2014-10-01

The toroidal phase of non-rotating (``locked'') neoclassical tearing modes was controlled in several devices by means of applied magnetic perturbations. Evidence is presented from various tokamaks (ASDEX Upgrade, DIII-D, JET, J-TEXT, KSTAR), spherical tori (MAST, NSTX) and a reversed field pinch (EXTRAP-T2R). Furthermore, the phase of interchange modes was controlled in the LHD helical device. These results share a common interpretation in terms of torques acting on the mode. Based on this interpretation, it is predicted that control-coil currents will be sufficient to control the phase of locking in ITER. This will be possible both with the internal coils and with the external error-field-correction coils, and might have promising consequences for disruption avoidance (by aiding the electron cyclotron current drive stabilization of locked modes), as well as for spatially distributing heat loads during disruptions. This work was supported in part by the US Department of Energy under DE-SC0008520, DE-FC-02-04ER54698 and DE-AC02-09CH11466.

Numerical optimization of perturbative coils for tokamaks

NASA Astrophysics Data System (ADS)

Lazerson, Samuel; Park, Jong-Kyu; Logan, Nikolas; Boozer, Allen; NSTX-U Research Team

2014-10-01

Numerical optimization of coils which apply three dimensional (3D) perturbative fields to tokamaks is presented. The application of perturbative 3D magnetic fields in tokamaks is now commonplace for control of error fields, resistive wall modes, resonant field drive, and neoclassical toroidal viscosity (NTV) torques. The design of such systems has focused on control of toroidal mode number, with coil shapes based on simple window-pane designs. In this work, a numerical optimization suite based on the STELLOPT 3D equilibrium optimization code is presented. The new code, IPECOPT, replaces the VMEC equilibrium code with the IPEC perturbed equilibrium code, and targets NTV torque by coupling to the PENT code. Fixed boundary optimizations of the 3D fields for the NSTX-U experiment are underway. Initial results suggest NTV torques can be driven by normal field spectrums which are not pitch-resonant with the magnetic field lines. Work has focused on driving core torque with n = 1 and edge torques with n = 3 fields. Optimizations of the coil currents for the planned NSTX-U NCC coils highlight the code's free boundary capability. This manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the U.S. Department of Energy.

Method and apparatus for sensing a target characteristic by measuring both impedance and resonant frequency of a tank circuit

NASA Technical Reports Server (NTRS)

Laskowski, Edward L. (Inventor)

1995-01-01

An apparatus for sensing a target characteristic, such as relative distance between the apparatus and target, target thickness, target material, or lateral position between the apparatus and the target, includes a coil for directing an electro-magnetic field at the target. A voltage controlled oscillator energizes the coil at a resonant frequency which is functionally related to the target characteristic. The coil has an effective impedance value at resonance functionally related to the target characteristic. A frequency monitor measures the resonant frequency. An impedance monitor determines the impedance value when the drive frequency is at the resonant value. A PROM or controller determines the target characteristic in response to the measured resonant frequency and the determined impedance value. The PROM or controller provides a signal responsive to the determined target characteristic.

Experimental evaluation of a high performance superconducting torquer

NASA Astrophysics Data System (ADS)

Goldie, James H.; Avakian, Kevin M.; Downer, James R.; Gerver, Michael; Gondhalekar, Vijay; Johnson, Bruce G.

The high performance superconducting torquer (HPSCT) was designed to slew a large inertia in one degree of freedom with a double versine torque profile, a profile used for pointing applications which minimizes the exciting of structural resonances. The program culminated with the successful demonstration of closed loop torque control, following a desired double versine torque profile to an accuracy of approximately 1 percent of the peak torque of the profile. The targeted double versine possessed a peak torque which matches the torque capacity of the Sperry M4500 CMG (controlled moment gyro). The research provided strong evidence of the feasibility of an advanced concept CMG which would use cryoresistive control coils in conjunction with an electromagnetically suspended rotor and superconducting source coil. The cryoresistive coils interact with the superconducting solenoid to develop the desired torque and, in addition, the required suspension forces.

Invited review the coiled coil silk of bees, ants, and hornets.

PubMed

Sutherland, Tara D; Weisman, Sarah; Walker, Andrew A; Mudie, Stephen T

2012-06-01

In this article, we review current knowledge about the silk produced by the larvae of bees, ants, and hornets [Apoidea and Vespoidea: Hymenoptera]. Different species use the silk either alone or in composites for a variety of purposes including mechanical reinforcement, thermal regulation, or humidification. The characteristic molecular structure of this silk is α-helical proteins assembled into tetrameric coiled coils. Gene sequences from seven species are available, and each species possesses a copy of each of four related silk genes that encode proteins predicted to form coiled coils. The proteins are ordered at multiple length scales within the labial gland of the final larval instar before spinning. The insects control the morphology of the silk during spinning to produce either fibers or sheets. The silk proteins are small and non repetitive and have been produced artificially at high levels by fermentation in E. coli. The artificial silk proteins can be fabricated into materials with structural and mechanical properties similar to those of native silks. Copyright © 2011 Wiley Periodicals, Inc.

A pilot study of planar coil based magnetic stimulation using acute hippocampal slice in mice.

PubMed

Park, H J; Kang, H K; Wang, M; Jo, J; Chung, E; Kim, S

2017-07-01

Micromagnetic stimulation using small-sized implantable coils has recently been studied. The main advantage of this method is that it can provide sustainable stimulation performance even if a fibrotic encapsulation layer is formed around the implanted coil by inflammation response, because indirectly induced currents are used to induce neural responses. In previous research, we optimized the geometrical and control parameters used in implantable magnetic stimulation. Based on those results, we fabricated the planar coil and studied the LTP effect in the hippocampal slice by two different magnetic stimulation protocols using the quadripulse stimulation (QPS) pattern. We found that direct magnetic stimulation (DMS) induced insignificant LTP effect and priming magnetic stimulation (PMS) occluded LTP effect after tetanic stimulation, when QPS patterned magnetic stimulation with 1 A current pulse was applied to the planar coil.

3 Tesla MRI of patients with a vagus nerve stimulator: initial experience using a T/R head coil under controlled conditions.

PubMed

Gorny, Krzysztof R; Bernstein, Matt A; Watson, Robert E

2010-02-01

To assess safety of clinical MRI of the head in patients with implanted model 100, 102, and 103 vagus nerve stimulation (VNS) Therapy Systems (Cyberonics, Inc., Houston, TX) in 3.0 Tesla MRI (GE Healthcare, Milwaukee, WI). The distributions of the radiofrequency B(1) (+)-field produced by the clinically used transmit/receive (T/R) head coil (Advanced Imaging Research Incorporated, Cleveland, OH) and body coil were measured in a head and shoulders phantom. These measurements were supplemented by temperature measurements on the lead tips and the implantable pulse generator (IPG) of the VNS devices in a head and torso phantom with the same two coils. Clinical 3T MRI head scans were then acquired under highly controlled conditions in a series of 17 patients implanted with VNS. Phantom studies showed only weak B(1) (+) fields at the location of the VNS IPG and leads for MRI scans using the T/R head coil. The MRI-related heating on a VNS scanned in vitro at 3T was also found to be minimal (0.4-0.8 degrees C at the leads, negligible at the IPG). The patient MRI examinations were completed successfully without any adverse incidents. No patient reported any heating, discomfort, or any other unusual sensation. Safe clinical MRI head scanning of patients with implanted VNS is shown to be feasible on a GE Signa Excite 3T MRI system using one specific T/R head coil. These results apply to this particular MRI system configuration. Extrapolation or generalization of these results to more general or less controlled imaging situations without supporting data of safety is highly discouraged.

Sliding-mode control combined with improved adaptive feedforward for wafer scanner

NASA Astrophysics Data System (ADS)

Li, Xiaojie; Wang, Yiguang

2018-03-01

In this paper, a sliding-mode control method combined with improved adaptive feedforward is proposed for wafer scanner to improve the tracking performance of the closed-loop system. Particularly, In addition to the inverse model, the nonlinear force ripple effect which may degrade the tracking accuracy of permanent magnet linear motor (PMLM) is considered in the proposed method. The dominant position periodicity of force ripple is determined by using the Fast Fourier Transform (FFT) analysis for experimental data and the improved feedforward control is achieved by the online recursive least-squares (RLS) estimation of the inverse model and the force ripple. The improved adaptive feedforward is given in a general form of nth-order model with force ripple effect. This proposed method is motivated by the motion controller design of the long-stroke PMLM and short-stroke voice coil motor for wafer scanner. The stability of the closed-loop control system and the convergence of the motion tracking are guaranteed by the proposed sliding-mode feedback and adaptive feedforward methods theoretically. Comparative experiments on a precision linear motion platform can verify the correctness and effectiveness of the proposed method. The experimental results show that comparing to traditional method the proposed one has better performance of rapidity and robustness, especially for high speed motion trajectory. And, the improvements on both tracking accuracy and settling time can be achieved.

Design Of Combined Stochastic Feedforward/Feedback Control

NASA Technical Reports Server (NTRS)

Halyo, Nesim

1989-01-01

Methodology accommodates variety of control structures and design techniques. In methodology for combined stochastic feedforward/feedback control, main objectives of feedforward and feedback control laws seen clearly. Inclusion of error-integral feedback, dynamic compensation, rate-command control structure, and like integral element of methodology. Another advantage of methodology flexibility to develop variety of techniques for design of feedback control with arbitrary structures to obtain feedback controller: includes stochastic output feedback, multiconfiguration control, decentralized control, or frequency and classical control methods. Control modes of system include capture and tracking of localizer and glideslope, crab, decrab, and flare. By use of recommended incremental implementation, control laws simulated on digital computer and connected with nonlinear digital simulation of aircraft and its systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perez, A.; Acero, J.; Alberdi, B.

High precision coil current control, stability and ripple content are very important aspects for a stellarator design. The TJ-II coils will be supplied by network commutated current converters and therefore the coil currents will contain harmonics which have to be kept to a very low level. An analytical investigation as well as numerous simulations with EMTP, SABER{reg_sign} and other softwares, have been done in order to predict the harmonic currents and to verify the completion with the specified maximum levels. The calculations and the results are presented.

The Mechanochemical Cycle of Mammalian Kinesin-2 KIF3A/B under Load.

PubMed

Andreasson, Johan O L; Shastry, Shankar; Hancock, William O; Block, Steven M

2015-05-04

The response of motor proteins to external loads underlies their ability to work in teams and determines the net speed and directionality of cargo transport. The mammalian kinesin-2, KIF3A/B, is a heterotrimeric motor involved in intraflagellar transport and vesicle motility in neurons. Bidirectional cargo transport is known to result from the opposing activities of KIF3A/B and dynein bound to the same cargo, but the load-dependent properties of kinesin-2 are poorly understood. We used a feedback-controlled optical trap to probe the velocity, run length, and unbinding kinetics of mouse KIF3A/B under various loads and nucleotide conditions. The kinesin-2 motor velocity is less sensitive than kinesin-1 to external forces, but its processivity diminishes steeply with load, and the motor was observed occasionally to slip and reattach. Each motor domain was characterized by studying homodimeric constructs, and a global fit to the data resulted in a comprehensive pathway that quantifies the principal force-dependent kinetic transitions. The properties of the KIF3A/B heterodimer are intermediate between the two homodimers, and the distinct load-dependent behavior is attributable to the properties of the motor domains and not to the neck linkers or the coiled-coil stalk. We conclude that the force-dependent movement of KIF3A/B differs significantly from conventional kinesin-1. Against opposing dynein forces, KIF3A/B motors are predicted to rapidly unbind and rebind, resulting in qualitatively different transport behavior from kinesin-1. Copyright © 2015 Elsevier Ltd. All rights reserved.

The mechanochemical cycle of mammalian kinesin-2 KIF3A/B under load

PubMed Central

Andreasson, Johan O.L.; Shastry, Shankar; Hancock, William O.; Block, Steven M.

2015-01-01

Summary The response of motor proteins to external loads underlies their ability to work in teams and determines the net speed and directionality of cargo transport. The mammalian kinesin-2, KIF3A/B, is a heterotrimeric motor involved in intraflagellar transport and vesicle motility in neurons. Bidirectional cargo transport is known to result from the opposing activities of KIF3A/B and dynein bound to the same cargo, but the load-dependent properties of kinesin-2 are poorly understood. We used a feedback-controlled optical trap to probe the velocity, run length and unbinding kinetics of mouse KIF3A/B under various loads and nucleotide conditions. The kinesin-2 motor velocity is less sensitive than kinesin-1 to external forces, but its processivity diminishes steeply with load, and the motor was observed occasionally to slip and reattach. Each motor domain was characterized by studying homodimeric constructs, and a global fit to the data resulted in a comprehensive pathway that quantifies the principal force-dependent kinetic transitions. The properties of the KIF3A/B heterodimer are intermediate between the two homodimers, and the distinct load-dependent behavior is attributable to the properties of the motor domains, and not to the neck-linkers or the coiled-coil stalk. We conclude that the force-dependent movement of KIF3A/B differs significantly from conventional kinesin-1. Against opposing dynein forces, KIF3A/B motors are predicted to rapidly unbind and rebind, resulting in qualitatively different transport behavior from kinesin-1. PMID:25866395

Magnetic control of magnetohydrodynamic instabilities in tokamaks

DOE PAGES

Strait, Edward J.

2014-11-24

Externally applied, non-axisymmetric magnetic fields form the basis of several relatively simple and direct methods to control magnetohydrodynamic (MHD) instabilities in a tokamak, and most present and planned tokamaks now include a set of non-axisymmetric control coils for application of fields with low toroidal mode numbers. Non-axisymmetric applied fields are routinely used to compensate small asymmetries ( δB/B ~ 10 -3 to 10 -4) of the nominally axisymmetric field, which otherwise can lead to instabilities through braking of plasma rotation and through direct stimulus of tearing modes or kink modes. This compensation may be feedback-controlled, based on the magnetic responsemore » of the plasma to the external fields. Non-axisymmetric fields are used for direct magnetic stabilization of the resistive wall mode — a kink instability with a growth rate slow enough that feedback control is practical. Saturated magnetic islands are also manipulated directly with non-axisymmetric fields, in order to unlock them from the wall and spin them to aid stabilization, or position them for suppression by localized current drive. Several recent scientific advances form the foundation of these developments in the control of instabilities. Most fundamental is the understanding that stable kink modes play a crucial role in the coupling of non-axisymmetric fields to the plasma, determining which field configurations couple most strongly, how the coupling depends on plasma conditions, and whether external asymmetries are amplified by the plasma. A major advance for the physics of high-beta plasmas ( β = plasma pressure/magnetic field pressure) has been the understanding that drift-kinetic resonances can stabilize the resistive wall mode at pressures well above the ideal-MHD stability limit, but also that such discharges can be very sensitive to external asymmetries. The common physics of stable kink modes has brought significant unification to the topics of static error fields at low beta and resistive wall modes at high beta. Furthermore, these and other scientific advances, and their application to control of MHD instabilities, will be reviewed with emphasis on the most recent results and their applicability to ITER.« less

Thermal Sensitivity Of Sensing Coils For Fibre Gyroscopes

NASA Astrophysics Data System (ADS)

Mohr, F.; Kiesel, P.

1984-11-01

This contribution reports on investigations of the rotation rate error, which occurs at a fibre gyroscope output when its sensing coil is subjected to dynamic temperature variations. The severity of the problem is best illustrated by the fact that the tempera-ture nonuniformity of the sensor coil must be less than 0,01 °C if the system is to resolve rotation rates of 0,01 °/h /1/. This requirement can easily be met in the lab by use of sophisticated control and shielding techniques. However, for a system to be usable under common environmental conditions, special coiling and encapsulating techniques must be developed in order to achieve immunity versus thermal effects.

Combination radial and thrust magnetic bearing

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A. (Inventor)

2002-01-01

A combination radial and thrust magnetic bearing is disclosed that allows for both radial and thrust axes control of an associated shaft. The combination radial and thrust magnetic bearing comprises a rotor and a stator. The rotor comprises a shaft, and first and second rotor pairs each having respective rotor elements. The stator comprises first and second stator elements and a magnet-sensor disk. In one embodiment, each stator element has a plurality of split-poles and a corresponding plurality of radial force coils and, in another embodiment, each stator element does not require thrust force coils, and radial force coils are replaced by double the plurality of coils serving as an outer member of each split-pole half.

Voluntarily controlled but not merely observed visual feedback affects postural sway

PubMed Central

Asai, Tomohisa; Hiromitsu, Kentaro; Imamizu, Hiroshi

2018-01-01

Online stabilization of human standing posture utilizes multisensory afferences (e.g., vision). Whereas visual feedback of spontaneous postural sway can stabilize postural control especially when observers concentrate on their body and intend to minimize postural sway, the effect of intentional control of visual feedback on postural sway itself remains unclear. This study assessed quiet standing posture in healthy adults voluntarily controlling or merely observing visual feedback. The visual feedback (moving square) had either low or high gain and was either horizontally flipped or not. Participants in the voluntary-control group were instructed to minimize their postural sway while voluntarily controlling visual feedback, whereas those in the observation group were instructed to minimize their postural sway while merely observing visual feedback. As a result, magnified and flipped visual feedback increased postural sway only in the voluntary-control group. Furthermore, regardless of the instructions and feedback manipulations, the experienced sense of control over visual feedback positively correlated with the magnitude of postural sway. We suggest that voluntarily controlled, but not merely observed, visual feedback is incorporated into the feedback control system for posture and begins to affect postural sway. PMID:29682421

An Experimental Design of Bypass Magneto-Rheological (MR) damper

NASA Astrophysics Data System (ADS)

Rashid, MM; Aziz, Mohammad Abdul; Raisuddin Khan, Md.

2017-11-01

The magnetorheological (MR) fluid bypass damper fluid flow through a bypass by utilizing an external channel which allows the controllability of MR fluid in the channel. The Bypass MR damper (BMRD) contains a rectangular bypass flow channel, current controlled movable piston shaft arrangement and MR fluid. The static piston coil case is winding by a coil which is used inside the piston head arrangement. The current controlled coil case provides a magnetic flux through the BMRD cylinder for controllability. The high strength of alloy steel materials are used for making piston shaft which allows magnetic flux propagation throughout the BMRD cylinder. Using the above design materials, a Bypass MR damper is designed and tested. An excitation of current is applied during the experiment which characterizes the BMRD controllability. It is shown that the BMRD with external flow channel allows a high controllable damping force using an excitation current. The experimental result of damping force-displacement characteristics with current excitation and without current excitation are compared in this research. The BMRD model is validated by the experimental result at various frequencies and applied excitation current.

Embolization with Tornado coils to control bleeding from an arterioureteral fistula.

PubMed

Jacobs, Bruce L; Maranchie, Jodi K

2007-12-01

Arterioureteral fistulae are rare, but potentially life-threatening causes of bleeding. We present a case of an 82 year-old woman with refractory, transfusion-dependent bleeding from an arterial fistula to her right ureteral stump, following right radical nephrectomy for advanced renal cell carcinoma. Cystoscopy with retrograde ureteral stump embolization using Tornado (Cook Medical, Bloomington, Indiana, USA) coils plus a slurry of thrombin-soaked Gelfoam (Pfizer Inc., New York, New York, USA) was performed, which led to prompt resolution of the patient's hematuria requiring no further hospitalizations or transfusions. Retrograde insertion of coils and injection of thrombin-soaked Gelfoam can be a minimally invasive, safe, and durable alternative for controlling hemorrhage from an arterioureteral fistula to a ureteral stump.

Coil-On-Plug Ignition for Oxygen/Methane Liquid Rocket Engines in Thermal-Vacuum Environments

NASA Technical Reports Server (NTRS)

Melcher, John C.; Atwell, Matthew J.; Morehead, Robert L.; Hurlbert, Eric A.; Bugarin, Luz; Chaidez, Mariana

2017-01-01

A coil-on-plug ignition system has been developed and tested for Liquid Oxygen (LOX)/liquid methane (LCH4) rocket engines operating in thermal vacuum conditions. The igniters were developed and tested as part of the Integrated Cryogenic Propulsion Test Article (ICPTA), previously tested as part of the Project Morpheus test vehicle. The ICPTA uses an integrated, pressure-fed, cryogenic LOX/LCH4 propulsion system including a reaction control system (RCS) and a main engine. The ICPTA was tested at NASA Glenn Research Center's Plum Brook Station in the Spacecraft Propulsion Research Facility (B-2) under vacuum and thermal vacuum conditions. A coil-on-plug ignition system has been developed to successfully demonstrate ignition reliability at these conditions while preventing corona discharge issues. The ICPTA uses spark plug ignition for both the main engine igniter and the RCS. The coil-on-plug configuration eliminates the conventional high-voltage spark plug cable by combining the coil and the spark plug into a single component. Prior to ICPTA testing at Plum Brook, component-level reaction control engine (RCE) and main engine igniter testing was conducted at NASA Johnson Space Center (JSC), which demonstrated successful hot-fire ignition using the coil-on-plug from sea-level ambient conditions down to 10(exp -2) torr. Integrated vehicle hot-fire testing at JSC demonstrated electrical and command/data system performance. Lastly, hot-fire testing at Plum Brook demonstrated successful ignitions at simulated altitude conditions at 30 torr and cold thermal-vacuum conditions at 6 torr. The test campaign successfully proved that coil-on-plug technology will enable integrated LOX/LCH4 propulsion systems in future spacecraft.

Coil-On-Plug Ignition for LOX/Methane Liquid Rocket Engines in Thermal Vacuum Environments

NASA Technical Reports Server (NTRS)

Melcher, John C.; Atwell, Matthew J.; Morehead, Robert L.; Hurlbert, Eric A.; Bugarin, Luz; Chaidez, Mariana

2017-01-01

A coil-on-plug ignition system has been developed and tested for Liquid Oxygen (LOX) / liquid methane rocket engines operating in thermal vacuum conditions. The igniters were developed and tested as part of the Integrated Cryogenic Propulsion Test Article (ICPTA), previously tested as part of the Project Morpheus test vehicle. The ICPTA uses an integrated, pressure-fed, cryogenic LOX/methane propulsion system including a reaction control system (RCS) and a main engine. The ICPTA was tested at NASA Glenn Research Center's Plum Brook Station in the Spacecraft Propulsion Research Facility (B-2) under vacuum and thermal vacuum conditions. In order to successfully demonstrate ignition reliability in the vacuum conditions and eliminate corona discharge issues, a coil-on-plug ignition system has been developed. The ICPTA uses spark-plug ignition for both the main engine igniter and the RCS. The coil-on-plug configuration eliminates the conventional high-voltage spark plug cable by combining the coil and the spark-plug into a single component. Prior to ICPTA testing at Plum Brook, component-level reaction control engine (RCE) and main engine igniter testing was conducted at NASA Johnson Space Center (JSC), which demonstrated successful hot-fire ignition using the coil-on-plug from sea-level ambient conditions down to 10(exp.-2) torr. Integrated vehicle hot-fire testing at JSC demonstrated electrical and command/data system performance. Lastly, Plum Brook testing demonstrated successful ignitions at simulated altitude conditions at 30 torr and cold thermal-vacuum conditions at 6 torr. The test campaign successfully proved that coil-on-plug technology will enable integrated LOX/methane propulsion systems in future spacecraft.

Combined magnetic and kinetic control of advanced tokamak steady state scenarios based on semi-empirical modelling

NASA Astrophysics Data System (ADS)

Moreau, D.; Artaud, J. F.; Ferron, J. R.; Holcomb, C. T.; Humphreys, D. A.; Liu, F.; Luce, T. C.; Park, J. M.; Prater, R.; Turco, F.; Walker, M. L.

2015-06-01

This paper shows that semi-empirical data-driven models based on a two-time-scale approximation for the magnetic and kinetic control of advanced tokamak (AT) scenarios can be advantageously identified from simulated rather than real data, and used for control design. The method is applied to the combined control of the safety factor profile, q(x), and normalized pressure parameter, βN, using DIII-D parameters and actuators (on-axis co-current neutral beam injection (NBI) power, off-axis co-current NBI power, electron cyclotron current drive power, and ohmic coil). The approximate plasma response model was identified from simulated open-loop data obtained using a rapidly converging plasma transport code, METIS, which includes an MHD equilibrium and current diffusion solver, and combines plasma transport nonlinearity with 0D scaling laws and 1.5D ordinary differential equations. The paper discusses the results of closed-loop METIS simulations, using the near-optimal ARTAEMIS control algorithm (Moreau D et al 2013 Nucl. Fusion 53 063020) for steady state AT operation. With feedforward plus feedback control, the steady state target q-profile and βN are satisfactorily tracked with a time scale of about 10 s, despite large disturbances applied to the feedforward powers and plasma parameters. The robustness of the control algorithm with respect to disturbances of the H&CD actuators and of plasma parameters such as the H-factor, plasma density and effective charge, is also shown.

A Novel Transcranial Magnetic Stimulator Inducing Near Rectangular Pulses with Controllable Pulse Width (cTMS)

PubMed Central

Jalinous, Reza; Lisanby, Sarah H.

2013-01-01

A novel transcranial magnetic stimulation (TMS) device with controllable pulse width (PW) and near rectangular pulse shape (cTMS) is described. The cTMS device uses an insulated gate bipolar transistor (IGBT) with appropriate snubbers to switch coil currents up to 7 kA, enabling PW control from 5 μs to over 100 μs. The near-rectangular induced electric field pulses use 22–34% less energy and generate 67–72% less coil heating compared to matched conventional cosine pulses. CTMS is used to stimulate rhesus monkey motor cortex in vivo with PWs of 20 to 100 μs, demonstrating the expected decrease of threshold pulse amplitude with increasing PW. The technological solutions used in the cTMS prototype can expand functionality, and reduce power consumption and coil heating in TMS, enhancing its research and therapeutic applications. PMID:18232369

Application of horizontal spiral coil heat exchanger for volatile organic compounds (VOC) emission control.

PubMed

Deshpande, P M; Dawande, S D

2013-04-01

The petroleum products have wide range of volatility and are required to be stored in bulk. The evaporation losses are significant and it is a economic as well as environmental concern, since evaporative losses of petroleum products cause increased VOC in ambient air. Control of these losses poses a major problem for the storage tank designers. Ever rising cost of petroleum products further adds to the gravity of the problem. Condensation is one of the technologies for reducing volatile organic compounds emissions. Condensation is effected by condenser, which is basically a heat exchanger and the heat exchanger configuration plays an important role. The horizontal spiral coil heat exchanger is a promising configuration that finds an application in VOC control. This paper attempts to understand underlying causes of emissions and analyse the option of horizontal spiral coil heat exchanger as vent condenser.

Error field optimization in DIII-D using extremum seeking control

DOE PAGES

Lanctot, M. J.; Olofsson, K. E. J.; Capella, M.; ...

2016-06-03

A closed-loop error field control algorithm is implemented in the Plasma Control System of the DIII-D tokamak and used to identify optimal control currents during a single plasma discharge. The algorithm, based on established extremum seeking control theory, exploits the link in tokamaks between maximizing the toroidal angular momentum and minimizing deleterious non-axisymmetric magnetic fields. Slowly-rotating n = 1 fields (the dither), generated by external coils, are used to perturb the angular momentum, monitored in real-time using a charge-exchange spectroscopy diagnostic. Simple signal processing of the rotation measurements extracts information about the rotation gradient with respect to the control coilmore » currents. This information is used to converge the control coil currents to a point that maximizes the toroidal angular momentum. The technique is well-suited for multi-coil, multi-harmonic error field optimizations in disruption sensitive devices as it does not require triggering locked tearing modes or plasma current disruptions. Control simulations highlight the importance of the initial search direction on the rate of the convergence, and identify future algorithm upgrades that may allow more rapid convergence that projects to convergence times in ITER on the order of tens of seconds.« less

Effects of pulsed electromagnetic field vibration on tooth movement induced by magnetic and mechanical forces: a preliminary study.

PubMed

Darendeliler, M Ali; Zea, A; Shen, G; Zoellner, H

2007-12-01

This study was designed to determine whether or not high-frequency and low-magnitude vibration affects orthodontic tooth movement caused by magnetic or/and mechanical forces. Forty-four 7-week-old Wistar rats were randomly divided into four groups, with each group further divided into experimental and control subgroups. Neodymium-Iron-Boron (Nd-Fe-B) magnets and Sentalloy closed coil springs were placed between maxillary or mandibular first molars and incisors to activate tooth movement. The animals of experimental subgroups were exposed to the vibration induced by pulsed electromagnetic fields (PEMF) whilst the control subgroups were under normal atmosphere. The experiment lasted for 14 days and all of the animals were sacrificed for examination. The changes in the space between the molar and incisor were measured to indicate the amount of tooth movement. The coil springs, either with sham or active magnets, move molar much more than magnets alone, regardless of absence or presence of PEMF (p < 0.001). Under PEMF, the coil spring moved significantly more amount of tooth movement than that of coil-magnet combination (p < 0.01), as did the magnets compared to sham magnets (p < 0.019). Under a non-PEMF scenario, there was no significant difference in tooth movement between coil spring and coil-magnets combination, nor was there difference between magnets and sham magnets. It is suggested that the PEMF-induced vibration may enhance the effect of mechanical and magnetic forces on tooth movement.

PspF-binding domain PspA1-144 and the PspA·F complex: New insights into the coiled-coil-dependent regulation of AAA+ proteins.

PubMed

Osadnik, Hendrik; Schöpfel, Michael; Heidrich, Eyleen; Mehner, Denise; Lilie, Hauke; Parthier, Christoph; Risselada, H Jelger; Grubmüller, Helmut; Stubbs, Milton T; Brüser, Thomas

2015-11-01

Phage shock protein A (PspA) belongs to the highy conserved PspA/IM30 family and is a key component of the stress inducible Psp system in Escherichia coli. One of its central roles is the regulatory interaction with the transcriptional activator of this system, the σ(54) enhancer-binding protein PspF, a member of the AAA+ protein family. The PspA/F regulatory system has been intensively studied and serves as a paradigm for AAA+ enzyme regulation by trans-acting factors. However, the molecular mechanism of how exactly PspA controls the activity of PspF and hence σ(54) -dependent expression of the psp genes is still unclear. To approach this question, we identified the minimal PspF-interacting domain of PspA, solved its structure, determined its affinity to PspF and the dissociation kinetics, identified residues that are potentially important for PspF regulation and analyzed effects of their mutation on PspF in vivo and in vitro. Our data indicate that several characteristics of AAA+ regulation in the PspA·F complex resemble those of the AAA+ unfoldase ClpB, with both proteins being regulated by a structurally highly conserved coiled-coil domain. The convergent evolution of both regulatory domains points to a general mechanism to control AAA+ activity for divergent physiologic tasks via coiled-coil domains. © 2015 John Wiley & Sons Ltd.

Final Technical Report for DOE DE-FG02-05ER54831 "Laboratory Studies of Dynamos."

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forest, Cary B.

Laboratory Studies of Dynamos: Executive Summary. The self-generation of magnetic fields by astrophysical bodies like planets, stars, accretion disks, galaxies, and even galaxy clusters arises due to a mechanism referred to as a homogeneous dynamo. It is quite simple to demonstrate the generation of a magnetic fi eld from a rotating copper disk coupled with a coil of wire, a device known as the homopolar dynamo. The device works like a magnetic fi eld ampli er with a feedback circuit: the differential rotation of a metal disk past an infinitesimally small seed magnetic field induces currents in the disk which,more » when coupled to a coil winding, can amplify the field until it becomes strong enough to slow the rotation of the disk. What is remarkable is that the same type of circuit may be achieved in a flowing conducting fluid such as a liquid metal in the case of planetary dynamos or a plasma in the case of astrophysical dynamos. The complexity of describing planetary and stellar dynamos despite their ubiquity and the plethora of observational data from the Earth and the Sun motivates the demonstration of a laboratory homogenous dynamo. To create a homogenous dynamo, one first needs a su fficiently large, fast flow of a highly conducting fluid that the velocity shear in the fluid can bend magnetic field lines. With a high Rm-flow, the magnetic fi eld can be ampli ed by the stretching action provided by di fferential rotation. The other critical ingredient is a flow geometry that provides feedback so that the ampli ed eld reinforces the initial in nitesimal seed field - a mechanism that recreates the feedback provided by the coil of wire in the homopolar dynamo. In the Madison Dynamo Experiment, this combination of magnetic ampli cation and feedback is feasible in the simple geometry of two counter-rotating helical vortices in a 1 meter-diameter spherical vessel lled with liquid sodium. For an optimal helical pitch of the flow the threshold for exciting a dynamo is predicted from laminar flow modeling to be at peak flow speeds of 5 m/s. Liquid metals tend to have viscosities similar to that of water yielding inviscid flows. Whereas the timescale for the dynamo instability is on the resistive dissipation time, the timescale for hydrodynamic instability of the shear layer is quite short meaning that the shear layer required to generate the magnetic eld is broken up by Kelvin-Helmholtz instabilities. The eddies generated by large-scale flow drive instabilities at progressively smaller scale giving rise to a cascade of turbulent eddies driven at the largest scale of the experiment. The major contribution of the Madison Dynamo Experiment has been quantifying the role this turbulence plays in the generation of magnetic elds. Overall, the Madison Dynamo Experiment has now operated for about 1 decade and carried out experiments related to magnetic fi eld generation by turbulent flows of liquid metal. The principle thrust of research and indeed the main scienti fic outcomes are related to how turbulent flows create and transport magnetic fi elds.« less

Multiplexing Readout of TES Microcalorimeters Based on Analog Baseband Feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takei, Y.; Yamasaki, N.Y; Mitsuda, K.

2009-12-16

A TES microcalorimeter array is a promising spectrometer with excellent energy resolution and a moderate imaging capability. To realize a large format array in space, multiplexing the TES signals at the low tempersture stage is mandatory. We are developing frequency division multiplexing (FDM) based on baseband feedback technique. In FDM, each TES is AC-biased with a different carrier frequency. Signals from several pixels are summed and then read out by one SQUID. The maximum number of multiplexed pixels are limited by the frequency band in which the SQUID can be operated in a flux-locked loop, which is {approx}1 MHz withmore » standard flux-locked loop circuit. In the baseband feedback, the signal ({approx}10 kHz band) from the TES is once demodulated. Then a reconstructed copy of the modulated signal with an appropriate phase is fed back to the SQUID input coil to maintain an approximately constant magnetic flux. This can be implemented even for large cable delays and automatically suppresses the carrier. We developed a prototype electronics for the baseband feedback based on an analog phase sensitive detector (PSD) and a multiplier. Combined with Seiko 80-SSA SQUID amp, open-loop gain of 8 has been obtained for 10 kHz baseband signal at 5 MHz carrier frequency, with a moderate noise contribution of 27pA/{radical}(Hz) at input.« less

Seismometer using a vertical long natural-period rotational pendulum with magnetic levitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Otake, Yuji; Araya, Akito; Hidano, Kazuo

We have demonstrated a highly sensitive/wideband vertical-component seismometer using an astatic rotational pendulum to obtain a long natural period. This seismometer employs magnetic levitation for removing any parasitic resonances of a spring to support a weight due to gravity and the thermal dependence of the spring constant. The pendulum has a cylindrical plunger-type permanent magnet that has a weight at one side of its end edge. The plunger magnet is inserted into a uniform magnetic field generated by a window-frame-type permanent magnet, and attached to two crossed-leaf spring hinges as a rotational axis outside of the bore of the magnet.more » Magnetic forces applied to the plunger magnet counterbalance the gravitational force at the weight. To realize stable operation of the rotational pendulum without any unnecessary movements of the plunger magnet, a tilt of lines of the magnetic force in the bore of the window-frame magnet was compensated by a tilted magnetic-pole surface near to its opening. The field uniformity reached 10{sup -4} owing to this compensation. The thermal dependence of a magnetic field strength of about 10{sup -3}/K was also compensated by as much as 9x10{sup -5}/K by Ni-Fe metal having a negative permeability coefficient. The metal was attached along the sidewalls of the window-frame magnet. To determine the feedback control parameters for a feedback control seismometer, the natural period of a prototype rotational pendulum was measured. It was more than 8 s, and was able to be changed from 5 to 8 s by using an additional magnetic spring, similar to the voice coil actuator of a speaker. This change was in accordance with theoretical calculations, and showed that the pendulum movement did not include a big nonlinearity caused by the tilt of the lines of the magnetic force. No parasitic resonances were found during experiments. A velocity feedback-control circuit and a capacitance position detector to measure the weight position were applied to the rotational pendulum for building a feedback control seismometer. Observations showed that the noise level of the seismometer was less than about 10{sup -8} m/s at 1 Hz. This fruitful value is close to the specifications of the most sensitive seismometer, such as STS-I. However, low-frequency noise of about 10{sup -7} m/s, caused by a buoyancy change at the pendulum weight arising from atmospheric pressure variation, could be recognized. To decrease the noise, a vacuum chamber to isolate the atmospheric pressure variation should be employed in the next step of the study.« less

Treating Clinical Depression with Repetitive Deep Transcranial Magnetic Stimulation Using the Brainsway H1-coil.

PubMed

Feifel, David; Pappas, Katherine

2016-10-04

Repetitive transcranial magnetic stimulation (rTMS) is an emerging non-pharmacological approach to treating many brain-based disorders. rTMS uses electromagnetic coils to stimulate areas of the brain non-invasively. Deep transcranial magnetic stimulation (dTMS) with the Brainsway H1-coil system specifically is a type of rTMS indicated for treating patients with major depressive disorder (MDD) who are resistant to medication. The unique H1-coil design of this device is able to stimulate neuronal pathways that lie deeper in the targeted brain areas than those reached by conventional rTMS coils. dTMS is considered to be low-risk and well tolerated, making it a viable treatment option for people who have not responded to medication or psychotherapy trials for their depression. Randomized, sham-control studies have demonstrated that dTMS produces significantly greater improvement in depressive symptoms than sham dTMS treatment in patients with major depression that has not responded to antidepressant medication. In this paper, we will review the methodology for treating major depression with dTMS using an H1-coil.

A super-cusp divertor configuration for tokamaks

DOE PAGES

Ryutov, D. D.

2015-08-26

Our study demonstrates a remarkable flexibility of advanced divertor configurations created with the remote poloidal field coils. The emphasis here is on the configurations with three poloidal field nulls in the divertor area. We are seeking the structures where all three nulls lie on the same separatrix, thereby creating two zones of a very strong flux expansion, as envisaged in the concept of Takase’s cusp divertor. It turns out that the set of remote coils can produce a cusp divertor, with additional advantages of: (i) a large stand-off distance between the divertor and the coils and (ii) a thorough controlmore » that these coils exert over the fine features of the configuration. In reference to these additional favourable properties acquired by the cusp divertor, the resulting configuration could be called ‘a super-cusp’. General geometrical features of the three-null configurations produced by remote coils are described. Furthermore, issues on the way to practical applications include the need for a more sophisticated control system and possible constraints related to excessively high currents in the divertor coils.« less

Active combustion flow modulation valve

DOEpatents

Hensel, John Peter; Black, Nathaniel; Thorton, Jimmy Dean; Vipperman, Jeffrey Stuart; Lambeth, David N; Clark, William W

2013-09-24

A flow modulation valve has a slidably translating hollow armature with at least one energizable coil wound around and fixably attached to the hollow armature. The energizable coil or coils are influenced by at least one permanent magnet surrounding the hollow armature and supported by an outer casing. Lorentz forces on the energizable coils which are translated to the hollow armature, increase or decrease the flow area to provide flow throttling action. The extent of hollow armature translation depends on the value of current supplied and the direction of translation depends on the direction of current flow. The compact nature of the flow modulation valve combined with the high forces afforded by the actuator design provide a flow modulation valve which is highly responsive to high-rate input control signals.

Rice Cellulose SynthaseA8 Plant-Conserved Region Is a Coiled-Coil at the Catalytic Core Entrance1[OPEN

PubMed Central

Rushton, Phillip S.; Olek, Anna T.; Makowski, Lee; Badger, John

2017-01-01

The crystallographic structure of a rice (Oryza sativa) cellulose synthase, OsCesA8, plant-conserved region (P-CR), one of two unique domains in the catalytic domain of plant CesAs, was solved to 2.4 Å resolution. Two antiparallel α-helices form a coiled-coil domain linked by a large extended connector loop containing a conserved trio of aromatic residues. The P-CR structure was fit into a molecular envelope for the P-CR domain derived from small-angle X-ray scattering data. The P-CR structure and molecular envelope, combined with a homology-based chain trace of the CesA8 catalytic core, were modeled into a previously determined CesA8 small-angle X-ray scattering molecular envelope to produce a detailed topological model of the CesA8 catalytic domain. The predicted position for the P-CR domain from the molecular docking models places the P-CR connector loop into a hydrophobic pocket of the catalytic core, with the coiled-coil aligned near the entrance of the substrate UDP-glucose into the active site. In this configuration, the P-CR coiled-coil alone is unlikely to regulate substrate access to the active site, but it could interact with other domains of CesA, accessory proteins, or other CesA catalytic domains to control substrate delivery. PMID:27879387

The effect of winding and core support material on the thermal gain dependence of a fluxgate magnetometer sensor

NASA Astrophysics Data System (ADS)

Miles, David M.; Mann, Ian R.; Kale, Andy; Milling, David K.; Narod, Barry B.; Bennest, John R.; Barona, David; Unsworth, Martyn J.

2017-10-01

Fluxgate magnetometers are an important tool in geophysics and space physics but are typically sensitive to variations in sensor temperature. Changes in instrumental gain with temperature, thermal gain dependence, are thought to be predominantly due to changes in the geometry of the wire coils that sense the magnetic field and/or provide magnetic feedback. Scientific fluxgate magnetometers typically employ some form of temperature compensation and support and constrain wire sense coils with bobbins constructed from materials such as MACOR machinable ceramic (Corning Inc.) which are selected for their ultra-low thermal deformation rather than for robustness, cost, or ease of manufacturing. We present laboratory results comparing the performance of six geometrically and electrically matched fluxgate sensors in which the material used to support the windings and for the base of the sensor is varied. We use a novel, low-cost thermal calibration procedure based on a controlled sinusoidal magnetic source and quantitative spectral analysis to measure the thermal gain dependence of fluxgate magnetometer sensors at the ppm°C-1 level in a typical magnetically noisy university laboratory environment. We compare the thermal gain dependence of sensors built from MACOR, polyetheretherketone (PEEK) engineering plastic (virgin, 30 % glass filled and 30 % carbon filled), and acetal to examine the trade between the thermal properties of the material, the impact on the thermal gain dependence of the fluxgate, and the cost and ease of manufacture. We find that thermal gain dependence of the sensor varies as one half of the material properties of the bobbin supporting the wire sense coils rather than being directly related as has been historically thought. An experimental sensor constructed from 30 % glass-filled PEEK (21.6 ppm°C-1) had a thermal gain dependence within 5 ppm°C-1 of a traditional sensor constructed from MACOR ceramic (8.1 ppm°C-1). If a modest increase in thermal dependence can be tolerated or compensated, then 30 % glass-filled PEEK is a good candidate for future fluxgate sensors as it is more economical, easier to machine, lighter, and more robust than MACOR.

Vibration and shape control of hinged light structures using electromagnetic forces

NASA Astrophysics Data System (ADS)

Matsuzaki, Yuji; Miyachi, Shigenobu; Sasaki, Toshiyuki

2003-08-01

This paper describes a new electromagnetic device for vibration control of a light-weighted deployable/retractable structure which consists of many small units connected with mechanical hinges. A typical example of such a structure is a solar cell paddle of an artificial satellite which is composed of many thin flexible blankets connected in series. Vibration and shape control of the paddle is not easy, because control force and energy do not transmit well between the blankets which are discretely connected by hinges with each other. The new device consists of a permanent magnet glued along an edge of a blanket and an electric current-conducting coil glued along an adjoining edge of another adjacent blanket. Conduction of the electric current in a magnetic field from the magnet generates an electromagnetic force on the coil. By changing the current in the coil, therefore, we may control the vibration and shape of the blankets. To confirm the effectiveness of the new device, constructing a simple paddle model consisting eight hinge- panels, we have carried out a model experiment of vibration and shape control of the paddle. In addition, a numerical simulation of vibration control of the hinge structure is performed to compare with measured data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirtley, John R., E-mail: jkirtley@stanford.edu; Rosenberg, Aaron J.; Palmstrom, Johanna C.

Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ{sub 0}/Hz{sup 1/2}. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes themore » spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.« less

Scanning SQUID sampler with 40-ps time resolution

NASA Astrophysics Data System (ADS)

Cui, Zheng; Kirtley, John R.; Wang, Yihua; Kratz, Philip A.; Rosenberg, Aaron J.; Watson, Christopher A.; Gibson, Gerald W.; Ketchen, Mark B.; Moler, Kathryn. A.

2017-08-01

Scanning Superconducting QUantum Interference Device (SQUID) microscopy provides valuable information about magnetic properties of materials and devices. The magnetic flux response of the SQUID is often linearized with a flux-locked feedback loop, which limits the response time to microseconds or longer. In this work, we present the design, fabrication, and characterization of a novel scanning SQUID sampler with a 40-ps time resolution and linearized response to periodically triggered signals. Other design features include a micron-scale pickup loop for the detection of local magnetic flux, a field coil to apply a local magnetic field to the sample, and a modulation coil to operate the SQUID sampler in a flux-locked loop to linearize the flux response. The entire sampler device is fabricated on a 2 mm × 2 mm chip and can be scanned over macroscopic planar samples. The flux noise at 4.2 K with 100 kHz repetition rate and 1 s of averaging is of order 1 mΦ0. This SQUID sampler will be useful for imaging dynamics in magnetic and superconducting materials and devices.

Scanning SQUID sampler with 40-ps time resolution.

PubMed

Cui, Zheng; Kirtley, John R; Wang, Yihua; Kratz, Philip A; Rosenberg, Aaron J; Watson, Christopher A; Gibson, Gerald W; Ketchen, Mark B; Moler, Kathryn A

2017-08-01

Scanning Superconducting QUantum Interference Device (SQUID) microscopy provides valuable information about magnetic properties of materials and devices. The magnetic flux response of the SQUID is often linearized with a flux-locked feedback loop, which limits the response time to microseconds or longer. In this work, we present the design, fabrication, and characterization of a novel scanning SQUID sampler with a 40-ps time resolution and linearized response to periodically triggered signals. Other design features include a micron-scale pickup loop for the detection of local magnetic flux, a field coil to apply a local magnetic field to the sample, and a modulation coil to operate the SQUID sampler in a flux-locked loop to linearize the flux response. The entire sampler device is fabricated on a 2 mm × 2 mm chip and can be scanned over macroscopic planar samples. The flux noise at 4.2 K with 100 kHz repetition rate and 1 s of averaging is of order 1 mΦ 0 . This SQUID sampler will be useful for imaging dynamics in magnetic and superconducting materials and devices.

Coilgun Acceleration Model Containing Interactions Between Multiple Coils

NASA Technical Reports Server (NTRS)

Liu, Connie; Polzin, Kurt; Martin, Adam

2017-01-01

Electromagnetic (EM) accelerators have the potential to fill a performance range not currently being met by conventional chemical and electric propulsion systems by providing a specific impulse of 600-1000 seconds and a thrust-to-power ratio greater than 200 mN/kW. A propulsion system based on EM acceleration of small projectiles has the traditional advantages of using a pulsed system, including precise control over a range of thrust and power levels as well as rapid response and repetition rates. Furthermore, EM accelerators have lower power requirements than conventional electric propulsion systems since no plasma creation is necessary. A coilgun is a specific type of EM device where a high-current pulse through a coil of wire interacts with a conductive projectile via an induced magnetic field to accelerate the projectile. There are no physical or electrical connections to the projectile, which leads to less system degradation and a longer life expectancy. Multi-staging a coilgun by adding multiple turns on a single coil or on the projectile increases the inductance, thus permitting acceleration of the projectile to higher velocities. Previously, a simplified problem of modeling an inductively-coupled, single-coil coilgun using a circuit-based analysis coupled to the one-dimensional momentum equation through Lenz's law was solved; however, the analysis was only conducted on uncoupled coils. The problem is significantly more complicated when multiple, independently-powered coils simultaneously operate and interact with each other and the projectile through induced magnetic fields. This paper presents a multi-coil model developed with the magnetostatic finite element solver QuickField. In the model, mutual inductance values between pairs of conductors were found by first computing the magnetic field energy for different cases where individual coils or multiple coils carry current, then integrating over the entire finite element domain for each case, and finally using the definition of inductive energy storage to solve for the self and mutual inductance. The electric circuit model is coupled to the projectile through Lenz's law, with the coils coupled through mutual inductance but able to be independently triggered at different times to optimize the acceleration profile. This initial model to predict the behavior of a projectile's acceleration through a coupled, multi-coil coilgun increases the potential of building a highly efficient coilgun thruster with key advantages over other EM thruster systems, thus making it a promising candidate for satellite main propulsion or attitude control thrusters.

A size-adjustable radiofrequency coil for investigating plants in a Halbach magnet

NASA Astrophysics Data System (ADS)

Oligschläger, Dirk; Rehorn, Christian; Lehmkuhl, Sören; Adams, Michael; Adams, Alina; Blümich, Bernhard

2017-05-01

A radio-frequency coil with adjustable distance has been developed and tested for in-situ examination of growing plants. The Helmholtz-based coil design reduces laborious tuning and matching efforts encountered with solenoids wound around a growing stem or branch. Relaxation experiments were performed on tomato plants and winter wheat under controlled light irradiation. Changes in signal amplitude and in relaxation times T2 were recorded over day and night cycles. Peaks in distributions of relaxation times were attributed to different tissue components of two different plants.

Superconducting flat tape cable magnet

DOEpatents

Takayasu, Makoto

2015-08-11

A method for winding a coil magnet with the stacked tape cables, and a coil so wound. The winding process is controlled and various shape coils can be wound by twisting about the longitudinal axis of the cable and bending following the easy bend direction during winding, so that sharp local bending can be obtained by adjusting the twist pitch. Stack-tape cable is twisted while being wound, instead of being twisted in a straight configuration and then wound. In certain embodiments, the straight length should be half of the cable twist-pitch or a multiple of it.

Management of a traumatic hepatic artery pseudoaneurysm and arterioportal fistula with a combination of a stent graft and coil embolization using flow control with balloon remodeling.

PubMed

Flum, Andrew S; Geiger, James D; Gemmete, Joseph J; Williams, David M; Teitelbaum, Daniel H

2009-10-01

We describe a child who presented with a traumatic hepatic artery pseudoaneurysm and arterioportal fistula, which were subsequently managed with an endovascular stent graft and coil embolization using flow control with balloon remodeling. This case demonstrates a rarely seen condition in the pediatric population and a novel management strategy, which should be considered in the management of this complex injury.

Rapid control and feedback rates enhance neuroprosthetic control

PubMed Central

Shanechi, Maryam M.; Orsborn, Amy L.; Moorman, Helene G.; Gowda, Suraj; Dangi, Siddharth; Carmena, Jose M.

2017-01-01

Brain-machine interfaces (BMI) create novel sensorimotor pathways for action. Much as the sensorimotor apparatus shapes natural motor control, the BMI pathway characteristics may also influence neuroprosthetic control. Here, we explore the influence of control and feedback rates, where control rate indicates how often motor commands are sent from the brain to the prosthetic, and feedback rate indicates how often visual feedback of the prosthetic is provided to the subject. We developed a new BMI that allows arbitrarily fast control and feedback rates, and used it to dissociate the effects of each rate in two monkeys. Increasing the control rate significantly improved control even when feedback rate was unchanged. Increasing the feedback rate further facilitated control. We also show that our high-rate BMI significantly outperformed state-of-the-art methods due to higher control and feedback rates, combined with a different point process mathematical encoding model. Our BMI paradigm can dissect the contribution of different elements in the sensorimotor pathway, providing a unique tool for studying neuroprosthetic control mechanisms. PMID:28059065

Rapid control and feedback rates enhance neuroprosthetic control

NASA Astrophysics Data System (ADS)

Shanechi, Maryam M.; Orsborn, Amy L.; Moorman, Helene G.; Gowda, Suraj; Dangi, Siddharth; Carmena, Jose M.

2017-01-01

Brain-machine interfaces (BMI) create novel sensorimotor pathways for action. Much as the sensorimotor apparatus shapes natural motor control, the BMI pathway characteristics may also influence neuroprosthetic control. Here, we explore the influence of control and feedback rates, where control rate indicates how often motor commands are sent from the brain to the prosthetic, and feedback rate indicates how often visual feedback of the prosthetic is provided to the subject. We developed a new BMI that allows arbitrarily fast control and feedback rates, and used it to dissociate the effects of each rate in two monkeys. Increasing the control rate significantly improved control even when feedback rate was unchanged. Increasing the feedback rate further facilitated control. We also show that our high-rate BMI significantly outperformed state-of-the-art methods due to higher control and feedback rates, combined with a different point process mathematical encoding model. Our BMI paradigm can dissect the contribution of different elements in the sensorimotor pathway, providing a unique tool for studying neuroprosthetic control mechanisms.

Kinetically controlled transition from disordered aggregates to ordered lattices of a computationally designed peptide sequence.

NASA Astrophysics Data System (ADS)

Tian, Yu; Zhang, Huixi; Kiick, Kristi; Saven, Jeffrey; Pochan, Darrin

Peptides with well-defined secondary-structures have the ability to exhibit specific, local shapes, which enables the design of complex nanostructures through intermolecular assembly. Our computationally designed coiled-coil homotetrameric peptide building block can self-assemble into 2-D nanomaterial lattices with predetermined symmetries by control of the coiled-coil bundle exterior amino acid residues. And the assemblies can be controlled kinetically. Firstly, the solution pH influences the assembly by affecting the external charged state of peptide bundles which can lead the bundles to be either repulsive or attractive to each other. At room temperature when peptides are under the least charged pH conditions, disordered aggregates are formed that slowly transformed into the desired 2-D lattice structures over long periods of time (weeks). Around neutral pH, even subtle charge differences that come from small pH changes can have an influence on the thickness of afterwards formed plates. Secondly, the solution temperature can largely eliminate the formation of disordered aggregates and accelerate the assembling of matured, desired nanomaterial plates by providing extra energy for the organization process of assembly building blocks. The ability to control the assembly process kinetically makes our peptide plate assemblies very promising templates for further applications to develop inorganic-organic hybrid materials. Funding acknowledged from NSF DMREF program under awards DMR-1234161 and DMR-1235084.

Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry.

PubMed

Wang, G; Wu, K; Hu, H; Li, G; Wang, L J

2016-10-01

To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry

NASA Astrophysics Data System (ADS)

Wang, G.; Wu, K.; Hu, H.; Li, G.; Wang, L. J.

2016-10-01

To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

Miniature Scroll Pumps Fabricated by LIGA

NASA Technical Reports Server (NTRS)

Wiberg, Dean; Shcheglov, Kirill; White, Victor; Bae, Sam

2009-01-01

Miniature scroll pumps have been proposed as roughing pumps (low - vacuum pumps) for miniature scientific instruments (e.g., portable mass spectrometers and gas analyzers) that depend on vacuum. The larger scroll pumps used as roughing pumps in some older vacuum systems are fabricated by conventional machining. Typically, such an older scroll pump includes (1) an electric motor with an eccentric shaft to generate orbital motion of a scroll and (2) conventional bearings to restrict the orbital motion to a circle. The proposed miniature scroll pumps would differ from the prior, larger ones in both design and fabrication. A miniature scroll pump would include two scrolls: one mounted on a stationary baseplate and one on a flexure stage (see figure). An electromagnetic actuator in the form of two pairs of voice coils in a push-pull configuration would make the flexure stage move in the desired circular orbit. The capacitance between the scrolls would be monitored to provide position (gap) feedback to a control system that would adjust the drive signals applied to the voice coils to maintain the circular orbit as needed for precise sealing of the scrolls. To minimize power consumption and maximize precision of control, the flexure stage would be driven at the frequency of its mechanical resonance. The miniaturization of these pumps would entail both operational and manufacturing tolerances of <1 m. Such tight tolerances cannot be achieved easily by conventional machining of high-aspect-ratio structures like those of scroll-pump components. In addition, the vibrations of conventional motors and ball bearings exceed these tight tolerances by an order of magnitude. Therefore, the proposed pumps would be fabricated by the microfabrication method known by the German acronym LIGA ( lithographie, galvanoformung, abformung, which means lithography, electroforming, molding) because LIGA has been shown to be capable of providing the required tolerances at large aspect ratios.

Phased Array Technology with Phase and Amplitude Controlled Magnetron for Microwave Power Transmission

NASA Astrophysics Data System (ADS)

Shinohara, N.; Matsumoto, H.

2004-12-01

We need a microwave power transmitter with light weight and high DC-RF conversion efficiency for an economical SSPS (Space Solar Power System). We need a several g/W for a microwave power transmission (MPT) system with a phased array with 0.0001 degree of beam control accuracy (=tan-1 (100m/36,000km)) and over 80 % of DC-RF conversion efficiency when the weight of the 1GW-class SPS is below a several thousand ton - a several tens of thousand ton. We focus a microwave tube, especially magnetron by economical reason and by the amount of mass-production because it is commonly used for microwave oven in the world. At first, we have developed a phase controlled magnetron (PCM) with different technologies from what Dr. Brown developed. Next we have developed a phase and amplitude controlled magnetron (PACM). For the PACM, we add a feedback to magnetic field of the PCM with an external coil to control and stabilize amplitude of the microwave. We succeed to develop the PACM with below 10-6 of frequency stability and within 1 degree of an error in phase and within 1% of amplitude. We can control a phase and amplitude of the PACM and we have developed a phased array the PCMs. With the PCM technology, we have developed a small light weight MPT transmitter COMET (Compact Microwave Energy Transmitter) with consideration of heat radiation for space use and with consideration of mobility to space.

Parameter estimation and statistical analysis on frequency-dependent active control forces

NASA Astrophysics Data System (ADS)

Lim, Tau Meng; Cheng, Shanbao

2007-07-01

The active control forces of an active magnetic bearing (AMB) system are known to be frequency dependent in nature. This is due to the frequency-dependent nature of the AMB system, i.e. time lags in sensors, digital signal processing, amplifiers, filters, and eddy current and hysteresis losses in the electromagnetic coils. The stiffness and damping coefficients of these control forces can be assumed to be linear for small limit of perturbations within the air gap. Numerous studies have also attempted to estimate these coefficients directly or indirectly without validating the model and verifying the results. This paper seeks to address these issues, by proposing a one-axis electromagnetic suspension system to simplify the measurement requirements and eliminate the possibility of control force cross-coupling capabilities. It also proposes an on-line frequency domain parameter estimation procedure with statistical information to provide a quantitative measure for model validation and results verification purposes. This would lead to a better understanding and a design platform for optimal vibration control scheme for suspended system. This is achieved by injecting Schroeder Phased Harmonic Sequences (SPHS), a multi-frequency test signal, to persistently excite all possible suspended system modes. By treating the system as a black box, the parameter estimation of the "actual" stiffness and damping coefficients in the frequency domain are realised experimentally. The digitally implemented PID controller also facilitated changes on the feedback gains, and this allowed numerous system response measurements with their corresponding estimated stiffness and damping coefficients.

System and method of adjusting the equilibrium temperature of an inductively-heated susceptor

DOEpatents

Matsen, Marc R; Negley, Mark A; Geren, William Preston

2015-02-24

A system for inductively heating a workpiece may include an induction coil, at least one susceptor face sheet, and a current controller coupled. The induction coil may be configured to conduct an alternating current and generate a magnetic field in response to the alternating current. The susceptor face sheet may be configured to have a workpiece positioned therewith. The susceptor face sheet may be formed of a ferromagnetic alloy having a Curie temperature and being inductively heatable to an equilibrium temperature approaching the Curie temperature in response to the magnetic field. The current controller may be coupled to the induction coil and may be configured to adjust the alternating current in a manner causing a change in at least one heating parameter of the susceptor face sheet.

Coiled-Coil Antagonism Regulates Activity of Venus Flytrap-Domain-Containing Sensor Kinases of the BvgS Family

PubMed Central

Lesne, Elodie; Dupré, Elian; Lensink, Marc F.; Locht, Camille

2018-01-01

ABSTRACT Bordetella pertussis controls the expression of its virulence regulon through the two-component system BvgAS. BvgS is a prototype for a family of multidomain sensor kinases. In BvgS, helical linkers connect periplasmic Venus flytrap (VFT) perception domains to a cytoplasmic Per-Arnt-Sim (PAS) domain and the PAS domain to the dimerization/histidine phosphotransfer (DHp) domain of the kinase. The two linkers can adopt coiled-coil structures but cannot do so simultaneously. The first linker forms a coiled coil in the kinase mode and the second in the phosphatase mode, with the other linker in both cases showing an increase in dynamic behavior. The intervening PAS domain changes its quaternary structure between the two modes. In BvgS homologues without a PAS domain, a helical “X” linker directly connects the VFT and DHp domains. Here, we used BvgS as a platform to characterize regulation in members of the PAS-less subfamily. BvgS chimeras of homologues with natural X linkers displayed various regulation phenotypes. We identified two distinct coiled-coil registers in the N- and C-terminal portions of the X linkers. Stable coil formation in the C-terminal moiety determines the phosphatase mode, similarly to BvgS; in contrast, coil formation in the N-terminal moiety along the other register leads to the kinase mode. Thus, antagonism between two registers in the VFT-DHp linker forms the basis for activity regulation in the absence of the PAS domain. The N and C moieties of the X linker play roles similar to those played by the two independent linkers in sensor kinases with a PAS domain, providing a unified mechanism of regulation for the entire family. PMID:29487240

Automatic Frequency Controller for Power Amplifiers Used in Bio-Implanted Applications: Issues and Challenges

PubMed Central

Hannan, Mahammad A.; Hussein, Hussein A.; Mutashar, Saad; Samad, Salina A.; Hussain, Aini

2014-01-01

With the development of communication technologies, the use of wireless systems in biomedical implanted devices has become very useful. Bio-implantable devices are electronic devices which are used for treatment and monitoring brain implants, pacemakers, cochlear implants, retinal implants and so on. The inductive coupling link is used to transmit power and data between the primary and secondary sides of the biomedical implanted system, in which efficient power amplifier is very much needed to ensure the best data transmission rates and low power losses. However, the efficiency of the implanted devices depends on the circuit design, controller, load variation, changes of radio frequency coil's mutual displacement and coupling coefficients. This paper provides a comprehensive survey on various power amplifier classes and their characteristics, efficiency and controller techniques that have been used in bio-implants. The automatic frequency controller used in biomedical implants such as gate drive switching control, closed loop power control, voltage controlled oscillator, capacitor control and microcontroller frequency control have been explained. Most of these techniques keep the resonance frequency stable in transcutaneous power transfer between the external coil and the coil implanted inside the body. Detailed information including carrier frequency, power efficiency, coils displacement, power consumption, supplied voltage and CMOS chip for the controllers techniques are investigated and summarized in the provided tables. From the rigorous review, it is observed that the existing automatic frequency controller technologies are more or less can capable of performing well in the implant devices; however, the systems are still not up to the mark. Accordingly, current challenges and problems of the typical automatic frequency controller techniques for power amplifiers are illustrated, with a brief suggestions and discussion section concerning the progress of implanted device research in the future. This review will hopefully lead to increasing efforts towards the development of low powered, highly efficient, high data rate and reliable automatic frequency controllers for implanted devices. PMID:25615728

Impaired Feedforward Control and Enhanced Feedback Control of Speech in Patients with Cerebellar Degeneration

PubMed Central

Agnew, Zarinah; Nagarajan, Srikantan; Houde, John; Ivry, Richard B.

2017-01-01

The cerebellum has been hypothesized to form a crucial part of the speech motor control network. Evidence for this comes from patients with cerebellar damage, who exhibit a variety of speech deficits, as well as imaging studies showing cerebellar activation during speech production in healthy individuals. To date, the precise role of the cerebellum in speech motor control remains unclear, as it has been implicated in both anticipatory (feedforward) and reactive (feedback) control. Here, we assess both anticipatory and reactive aspects of speech motor control, comparing the performance of patients with cerebellar degeneration and matched controls. Experiment 1 tested feedforward control by examining speech adaptation across trials in response to a consistent perturbation of auditory feedback. Experiment 2 tested feedback control, examining online corrections in response to inconsistent perturbations of auditory feedback. Both male and female patients and controls were tested. The patients were impaired in adapting their feedforward control system relative to controls, exhibiting an attenuated anticipatory response to the perturbation. In contrast, the patients produced even larger compensatory responses than controls, suggesting an increased reliance on sensory feedback to guide speech articulation in this population. Together, these results suggest that the cerebellum is crucial for maintaining accurate feedforward control of speech, but relatively uninvolved in feedback control. SIGNIFICANCE STATEMENT Speech motor control is a complex activity that is thought to rely on both predictive, feedforward control as well as reactive, feedback control. While the cerebellum has been shown to be part of the speech motor control network, its functional contribution to feedback and feedforward control remains controversial. Here, we use real-time auditory perturbations of speech to show that patients with cerebellar degeneration are impaired in adapting feedforward control of speech but retain the ability to make online feedback corrections; indeed, the patients show an increased sensitivity to feedback. These results indicate that the cerebellum forms a crucial part of the feedforward control system for speech but is not essential for online, feedback control. PMID:28842410

Radial magnetic resonance imaging (MRI) using a rotating radiofrequency (RF) coil at 9.4 T.

PubMed

Li, Mingyan; Weber, Ewald; Jin, Jin; Hugger, Thimo; Tesiram, Yasvir; Ullmann, Peter; Stark, Simon; Fuentes, Miguel; Junge, Sven; Liu, Feng; Crozier, Stuart

2018-02-01

The rotating radiofrequency coil (RRFC) has been developed recently as an alternative approach to multi-channel phased-array coils. The single-element RRFC avoids inter-channel coupling and allows a larger coil element with better B 1 field penetration when compared with an array counterpart. However, dedicated image reconstruction algorithms require accurate estimation of temporally varying coil sensitivities to remove artefacts caused by coil rotation. Various methods have been developed to estimate unknown sensitivity profiles from a few experimentally measured sensitivity maps, but these methods become problematic when the RRFC is used as a transceiver coil. In this work, a novel and practical radial encoding method is introduced for the RRFC to facilitate image reconstruction without the measurement or estimation of rotation-dependent sensitivity profiles. Theoretical analyses suggest that the rotation-dependent sensitivities of the RRFC can be used to create a uniform profile with careful choice of sampling positions and imaging parameters. To test this new imaging method, dedicated electronics were designed and built to control the RRFC speed and hence positions in synchrony with imaging parameters. High-quality phantom and animal images acquired on a 9.4 T pre-clinical scanner demonstrate the feasibility and potential of this new RRFC method. Copyright © 2017 John Wiley & Sons, Ltd.

Static Measurements on HTS Coils of Fully Superconducting AC Electric Machines for Aircraft Electric Propulsion System

NASA Technical Reports Server (NTRS)

Choi, Benjamin B.; Hunker, Keith R.; Hartwig, Jason; Brown, Gerald V.

2017-01-01

The NASA Glenn Research Center (GRC) has been developing the high efficiency and high-power density superconducting (SC) electric machines in full support of electrified aircraft propulsion (EAP) systems for a future electric aircraft. A SC coil test rig has been designed and built to perform static and AC measurements on BSCCO, (RE)BCO, and YBCO high temperature superconducting (HTS) wire and coils at liquid nitrogen (LN2) temperature. In this paper, DC measurements on five SC coil configurations of various geometry in zero external magnetic field are measured to develop good measurement technique and to determine the critical current (Ic) and the sharpness (n value) of the super-to-normal transition. Also, standard procedures for coil design, fabrication, coil mounting, micro-volt measurement, cryogenic testing, current control, and data acquisition technique were established. Experimentally measured critical currents are compared with theoretical predicted values based on an electric-field criterion (Ec). Data here are essential to quantify the SC electric machine operation limits where the SC begins to exhibit non-zero resistance. All test data will be utilized to assess the feasibility of using HTS coils for the fully superconducting AC electric machine development for an aircraft electric propulsion system.

Space-coiling fractal metamaterial with multi-bandgaps on subwavelength scale

NASA Astrophysics Data System (ADS)

Man, Xianfeng; Liu, Tingting; Xia, Baizhan; Luo, Zhen; Xie, Longxiang; Liu, Jian

2018-06-01

Acoustic metamaterials are remarkably different from conventional materials, as they can flexibly manipulate and control the propagation of sound waves. Unlike the locally resonant metamaterials introduced in earlier studies, we designed an ultraslow artificial structure with a sound speed much lower than that in air. In this paper, the space-coiling approach is proposed for achieving artificial metamaterial for extremely low-frequency airborne sound. In addition, the self-similar fractal technique is utilized for designing space-coiling Mie-resonance-based metamaterials (MRMMs) to obtain a band-dispersive spectrum. The band structures of two-dimensional (2D) acoustic metamaterials with different fractal levels are illustrated using the finite element method. The low-frequency bandgap can easily be formed, and multi-bandgap properties are observed in high-level fractals. Furthermore, the designed MRMMs with higher order fractal space coiling shows a good robustness against irregular arrangement. Besides, the proposed artificial structure was found to modify and control the radiation field arbitrarily. Thus, this work provides useful guidelines for the design of acoustic filtering devices and acoustic wavefront shaping applications on the subwavelength scale.

Flow control techniques for Onyx embolization of intracranial dural arteriovenous fistulae.

PubMed

Shi, Zhong-Song; Loh, Yince; Gonzalez, Nestor; Tateshima, Satoshi; Feng, Lei; Jahan, Reza; Duckwiler, Gary; Viñuela, Fernando

2013-07-01

Experience of flow control techniques during endovascular treatment of intracranial dural arteriovenous fistulas (DAVFs) using the Onyx liquid embolic system is reported, with an emphasis on high flow shunts. Data were evaluated in patients with DAVFs treated endovascularly with Onyx. Adjunctive techniques with coils, acrylics and balloon assistance were utilized to reduce the rate of flow with transarterial and transvenous approaches. The following types of adjunctive techniques were used in 58 patients who underwent a total of 84 embolization sessions with Onyx: transvenous coiling with transvenous or transarterial Onyx embolization in 36 patients, transarterial coiling with transarterial Onyx embolization in eight patients, arterial or venous balloon assisted technique with transarterial or transvenous Onyx embolization in 11 patients, transarterial high concentration acrylics with transarterial Onyx embolization in one patient and staged transarterial or transvenous coiling and Onyx embolization in two patients. Complete obliteration of the fistulae was achieved in 41 patients (70.7%) and 27 patients (65.9%) with high flow fistulae after endovascular treatment alone. Periprocedural complications were encountered in 16 patients, and 13 complications were associated with the adjunctive techniques. There were four neurologic and two non-neurologic clinical sequelae. Distal Onyx migration occurred in four, microcatheter retention in three and cranial neuropathy in three patients. There was one instance each of cerebellar hemorrhage, thromboembolism, coil stretching and retention, and dissection. 56 survivors experienced complete resolution or significant improvement of their symptoms on follow-up. Flow control techniques are safe and effective adjunctive methods in primary endovascular Onyx embolization of high flow DAVFs.

Driver electronics design and control for a total artificial heart linear motor.

PubMed

Unthan, Kristin; Cuenca-Navalon, Elena; Pelletier, Benedikt; Finocchiaro, Thomas; Steinseifer, Ulrich

2018-01-27

For any implantable device size and efficiency are critical properties. Thus, a linear motor for a Total Artificial Heart was optimized with focus on driver electronics and control strategies. Hardware requirements were defined from power supply and motor setup. Four full bridges were chosen for the power electronics. Shunt resistors were set up for current measurement. Unipolar and bipolar switching for power electronics control were compared regarding current ripple and power losses. Here, unipolar switching showed smaller current ripple and required less power to create the necessary motor forces. Based on calculations for minimal power losses Lorentz force was distributed to the actor's four coils. The distribution was determined as ratio of effective magnetic flux through each coil, which was captured by a force test rig. Static and dynamic measurements under physiological conditions analyzed interaction of control and hardware and all efficiencies were over 89%. In conclusion, the designed electronics, optimized control strategy and applied current distribution create the required motor force and perform optimal under physiological conditions. The developed driver electronics and control offer optimized size and efficiency for any implantable or portable device with multiple independent motor coils. Graphical Abstract ᅟ.

Control of Recombination Directionality by the Listeria Phage A118 Protein Gp44 and the Coiled-Coil Motif of Its Serine Integrase.

PubMed

Mandali, Sridhar; Gupta, Kushol; Dawson, Anthony R; Van Duyne, Gregory D; Johnson, Reid C

2017-06-01

The serine integrase of phage A118 catalyzes integrative recombination between attP on the phage and a specific attB locus on the chromosome of Listeria monocytogenes , but it is unable to promote excisive recombination between the hybrid attL and attR sites found on the integrated prophage without assistance by a recombination directionality factor (RDF). We have identified and characterized the phage-encoded RDF Gp44, which activates the A118 integrase for excision and inhibits integration. Gp44 binds to the C-terminal DNA binding domain of integrase, and we have localized the primary binding site to be within the mobile coiled-coil (CC) motif but distinct from the distal tip of the CC that is required for recombination. This interaction is sufficient to inhibit integration, but a second interaction involving the N-terminal end of Gp44 is also required to activate excision. We provide evidence that these two contacts modulate the trajectory of the CC motifs as they extend out from the integrase core in a manner dependent upon the identities of the four att sites. Our results support a model whereby Gp44 shapes the Int-bound complexes to control which att sites can synapse and recombine. IMPORTANCE Serine integrases mediate directional recombination between bacteriophage and bacterial chromosomes. These highly regulated site-specific recombination reactions are integral to the life cycle of temperate phage and, in the case of Listeria monocytogenes lysogenized by A118 family phage, are an essential virulence determinant. Serine integrases are also utilized as tools for genetic engineering and synthetic biology because of their exquisite unidirectional control of the DNA exchange reaction. Here, we identify and characterize the recombination directionality factor (RDF) that activates excision and inhibits integration reactions by the phage A118 integrase. We provide evidence that the A118 RDF binds to and modulates the trajectory of the long coiled-coil motif that extends from the large carboxyl-terminal DNA binding domain and is postulated to control the early steps of recombination site synapsis. Copyright © 2017 American Society for Microbiology.

Structure and non-structure of centrosomal proteins.

PubMed

Dos Santos, Helena G; Abia, David; Janowski, Robert; Mortuza, Gulnahar; Bertero, Michela G; Boutin, Maïlys; Guarín, Nayibe; Méndez-Giraldez, Raúl; Nuñez, Alfonso; Pedrero, Juan G; Redondo, Pilar; Sanz, María; Speroni, Silvia; Teichert, Florian; Bruix, Marta; Carazo, José M; Gonzalez, Cayetano; Reina, José; Valpuesta, José M; Vernos, Isabelle; Zabala, Juan C; Montoya, Guillermo; Coll, Miquel; Bastolla, Ugo; Serrano, Luis

2013-01-01

Here we perform a large-scale study of the structural properties and the expression of proteins that constitute the human Centrosome. Centrosomal proteins tend to be larger than generic human proteins (control set), since their genes contain in average more exons (20.3 versus 14.6). They are rich in predicted disordered regions, which cover 57% of their length, compared to 39% in the general human proteome. They also contain several regions that are dually predicted to be disordered and coiled-coil at the same time: 55 proteins (15%) contain disordered and coiled-coil fragments that cover more than 20% of their length. Helices prevail over strands in regions homologous to known structures (47% predicted helical residues against 17% predicted as strands), and even more in the whole centrosomal proteome (52% against 7%), while for control human proteins 34.5% of the residues are predicted as helical and 12.8% are predicted as strands. This difference is mainly due to residues predicted as disordered and helical (30% in centrosomal and 9.4% in control proteins), which may correspond to alpha-helix forming molecular recognition features (α-MoRFs). We performed expression assays for 120 full-length centrosomal proteins and 72 domain constructs that we have predicted to be globular. These full-length proteins are often insoluble: Only 39 out of 120 expressed proteins (32%) and 19 out of 72 domains (26%) were soluble. We built or retrieved structural models for 277 out of 361 human proteins whose centrosomal localization has been experimentally verified. We could not find any suitable structural template with more than 20% sequence identity for 84 centrosomal proteins (23%), for which around 74% of the residues are predicted to be disordered or coiled-coils. The three-dimensional models that we built are available at http://ub.cbm.uam.es/centrosome/models/index.php.

Comparison of radiofrequency body coils for MRI at 3 Tesla: a simulation study using parallel transmission on various anatomical targets

PubMed Central

Wu, Xiaoping; Zhang, Xiaotong; Tian, Jinfeng; Schmitter, Sebastian; Hanna, Brian; Strupp, John; Pfeuffer, Josef; Hamm, Michael; Wang, Dingxin; Nistler, Juergen; He, Bin; Vaughan, J. Thomas; Ugurbil, Kamil; Van de Moortele, Pierre-Francois

2015-01-01

The performance of multichannel transmit coil layouts and parallel transmission (pTx) radiofrequency (RF) pulse design was evaluated with respect to transmit B1 (B1+) homogeneity and Specific Absorption Rate (SAR) at 3 Tesla for a whole body coil. Five specific coils were modeled and compared: a 32-rung birdcage body coil (driven either in a fixed quadrature mode or a two-channel transmit mode), two single-ring stripline arrays (with either 8 or 16 elements), and two multi-ring stripline arrays (with 2 or 3 identical rings, stacked in the z-axis and each comprising eight azimuthally distributed elements). Three anatomical targets were considered, each defined by a 3D volume representative of a meaningful region of interest (ROI) in routine clinical applications. For a given anatomical target, global or local SAR controlled pTx pulses were designed to homogenize RF excitation within the ROI. At the B1+ homogeneity achieved by the quadrature driven birdcage design, pTx pulses with multichannel transmit coils achieved up to ~8 fold reduction in local and global SAR. When used for imaging head and cervical spine or imaging thoracic spine, the double-ring array outperformed all coils including the single-ring arrays. While the advantage of the double-ring array became much less pronounced for pelvic imaging with a substantially larger ROI, the pTx approach still provided significant gains over the quadrature birdcage coil. For all design scenarios, using the 3-ring array did not necessarily improve the RF performance. Our results suggest that pTx pulses with multichannel transmit coils can reduce local and global SAR substantially for body coils while attaining improved B1+ homogeneity, particularly for a “z-stacked” double-ring design with coil elements arranged on two transaxial rings. PMID:26332290

Double row loop-coil configuration for high-speed electrodynamic maglev suspension, guidance, propulsion and guideway directional switching

DOEpatents

He, Jianliang; Rote, Donald M.

1996-01-01

A stabilization and propulsion system comprising a series of loop-coils arranged in parallel rows wherein two rows combine to form one of two magnetic rails. Levitation and lateral stability are provided when the induced field in the magnetic rails interacts with the superconducting magnets mounted on the magnetic levitation vehicle. The loop-coils forming the magnetic rails have specified dimensions and a specified number of turns and by constructing differently these specifications, for one rail with respect to the other, the angle of tilt of the vehicle can be controlled during directional switching. Propulsion is provided by the interaction of a traveling magnetic wave associated with the coils forming the rails and the super conducting magnets on the vehicle.

Double row loop-coil configuration for high-speed electrodynamic maglev suspension, guidance, propulsion and guideway directional switching

DOEpatents

He, J.; Rote, D.M.

1996-05-21

A stabilization and propulsion system are disclosed comprising a series of loop-coils arranged in parallel rows wherein two rows combine to form one of two magnetic rails. Levitation and lateral stability are provided when the induced field in the magnetic rails interacts with the superconducting magnets mounted on the magnetic levitation vehicle. The loop-coils forming the magnetic rails have specified dimensions and a specified number of turns and by constructing differently these specifications, for one rail with respect to the other, the angle of tilt of the vehicle can be controlled during directional switching. Propulsion is provided by the interaction of a traveling magnetic wave associated with the coils forming the rails and the superconducting magnets on the vehicle. 12 figs.

Simplified Hybrid-Secondary Uncluttered Machine And Method

DOEpatents

Hsu, John S [Oak Ridge, TN

2005-05-10

An electric machine (40, 40') has a stator (43) and a rotor (46) and a primary air gap (48) has secondary coils (47c, 47d) separated from the rotor (46) by a secondary air gap (49) so as to induce a slip current in the secondary coils (47c, 47d). The rotor (46, 76) has magnetic brushes (A, B, C, D) or wires (80) which couple flux in through the rotor (46) to the secondary coils (47c, 47d) without inducing a current in the rotor (46) and without coupling a stator rotational energy component to the secondary coils (47c, 47d). The machine can be operated as a motor or a generator in multi-phase or single-phase embodiments. A method of providing a slip energy controller is also disclosed.

Combination induction plasma tube and current concentrator for introducing a sample into a plasma

DOEpatents

Hull, Donald E.; Bieniewski, Thomas M.

1988-01-01

An induction plasma tube in combination with a current concentrator. The rent concentrator has a substantially cylindrical body having an open end and a partially closed end which defines an aperture. A first slot extends the longitudinal length of the cylindrical body and a second slot extends radially outward from the aperture. Together the first and second slots form a single L-shaped slot. The current concentrator is disposed within a volume bounded by an induction coil substantially along the axis thereof, and when power is applied to the induction coil a concentrated current is induced within the current concentrator aperture. The concentrator is moveable relative to the coil along the longitudinal axis of the coil to control the amount of current which is concentrated at the aperture.

MAGNETOMETER

DOEpatents

Leavitt, M.A.

1958-11-18

A magnetometer ls described, partlcularly to a device which accurately indicates the polarity and intensity of a magnetlc field. The main feature of the invention is a unique probe construction in combinatlon wlth a magnetic fleld detector system. The probe comprises two coils connected in series opposition for energization with an a-c voltage. The voltage lnduced in a third coll on the probe, a pick-up coil, is distorted by the presence of an external field to produce even harmonic voltages. A controlled d-c current is passed through the energized coils to counter the dlstortlon and reduce tbe even harmonic content to a null. When the null point is reached, the d-c current is a measure of the external magnetic field strength, and the phase of the pickup coil voltage indicates tbe field polarlty.

Direct current superconducting quantum interference device spectrometer for pulsed nuclear magnetic resonance and nuclear quadrupole resonance at frequencies up to 5 MHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

TonThat, D.M.; Clarke, J.

1996-08-01

A spectrometer based on a dc superconducting quantum interference device (SQUID) has been developed for the direct detection of nuclear magnetic resonance (NMR) or nuclear quadrupole resonance (NQR) at frequencies up to 5 MHz. The sample is coupled to the input coil of the niobium-based SQUID via a nonresonant superconducting circuit. The flux locked loop involves the direct offset integration technique with additional positive feedback in which the output of the SQUID is coupled directly to a low-noise preamplifier. Precession of the nuclear quadrupole spins is induced by a magnetic field pulse with the feedback circuit disabled; subsequently, flux lockedmore » operation is restored and the SQUID amplifies the signal produced by the nuclear free induction signal. The spectrometer has been used to detect {sup 27}Al NQR signals in ruby (Al{sub 2}O{sub 3}[Cr{sup 3+}]) at 359 and 714 kHz. {copyright} {ital 1996 American Institute of Physics.}« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lackner, Friedrich; Ferracin, Paolo; Todesco, Ezio

The High luminosity LHC upgrade target is to increase the integrated luminosity by a factor 10, resulting in an integrated luminosity of 3000 fb-1. One major improvement foreseen is the reduction of the beam size at the collision points. This requires the development of 150 mm single aperture quadrupoles for the interaction regions. These quadrupoles are under development in a joint collaboration between CERN and the US-LHC Accelerator Research Program (LARP). The chosen approach for achieving a nominal quadrupole field gradient of 132.6 T/m is based on the Nb3Sn technology. The coils with a length of 7281 mm will bemore » the longest Nb3Sn coils fabricated so far for accelerator magnets. The production of the long coils was launched in 2016 based on practise coils made from copper. This paper provides a status of the production of the first low grade and full performance coils and describes the production process and applied quality control. Furthermore an outlook for the prototype assembly is provided.« less

Design Features and Commissioning of the Versatile Experiment Spherical Torus (VEST) at Seoul National University

NASA Astrophysics Data System (ADS)

J. Chung, K.; H. An, Y.; K. Jung, B.; Y. Lee, H.; C., Sung; S. Na, Y.; S. Hahm, T.; S. Hwang, Y.

2013-03-01

A new spherical torus called VEST (Versatile Experiment Spherical Torus) is designed, constructed and successfully commissioned at Seoul National University. A unique design feature of the VEST is two partial solenoid coils installed at both vertical ends of a center stack, which can provide sufficient magnetic fluxes to initiate tokamak plasmas while keeping a low aspect ratio configuration in the central region. According to initial double null merging start-up scenario using the partial solenoid coils, appropriate power supplies for driving a toroidal field coil, outer poloidal field coils, and the partial solenoid coils are fabricated and successfully commissioned. For reliable start-up, a pre-ionization system with two cost-effective homemade magnetron power supplies is also prepared. In addition, magnetic and spectroscopic diagnostics with appropriate data acquisition and control systems are well prepared for initial operation of the device. The VEST is ready for tokamak plasma operation by completing and commissioning most of the designed components.

Vector sensor for scanning SQUID microscopy

NASA Astrophysics Data System (ADS)

Dang, Vu The; Toji, Masaki; Thanh Huy, Ho; Miyajima, Shigeyuki; Shishido, Hiroaki; Hidaka, Mutsuo; Hayashi, Masahiko; Ishida, Takekazu

2017-07-01

We plan to build a novel 3-dimensional (3D) scanning SQUID microscope with high sensitivity and high spatial resolution. In the system, a vector sensor consists of three SQUID sensors and three pick-up coils realized on a single chip. Three pick-up coils are configured in orthogonal with each other to measure the magnetic field vector of X, Y, Z components. We fabricated some SQUID chips with one uniaxial pick-up coil or three vector pick-up coils and carried out fundamental measurements to reveal the basic characteristics. Josephson junctions (JJs) of sensors are designed to have the critical current density J c of 320 A/cm2, and the critical current I c becomes 12.5 μA for the 2.2μm × 2.2μm JJ. We carefully positioned the three pickup coils so as to keep them at the same height at the centers of all three X, Y and Z coils. This can be done by arranging them along single line parallel to a sample surface. With the aid of multilayer technology of Nb-based fabrication, we attempted to reduce an inner diameter of the pickup coils to enhance both sensitivity and spatial resolution. The method for improving a spatial resolution of a local magnetic field image is to employ an XYZ piezo-driven scanner for controlling the positions of the pick-up coils. The fundamental characteristics of our SQUID sensors confirmed the proper operation of our SQUID sensors and found a good agreement with our design parameters.

DOE Office of Scientific and Technical Information (OSTI.GOV)

C. Priniski, T. Dodson, M. Duco, S. Raftopoulos, R. Ellis, and A. Brooks

In support of the National Compact Stellerator Experiment (NCSX), stellerator assembly activities continued this past year at the Princeton Plasma Physics Laboratory (PPPL) in partnership with the Oak Ridge National Laboratory (ORNL). The construction program saw the completion of the first two Half Field-Period Assemblies (HPA), each consisting of three modular coils. The full machine includes six such sub-assemblies. A single HPA consists of three of the NCSX modular coils wound and assembled at PPPL. These geometrically-complex threedimensional coils were wound using computer-aided metrology and CAD models to tolerances within +/- 0.5mm. The assembly of these coils required similar accuracymore » on a larger scale with the added complexity of more individual parts and fewer degrees of freedom for correction. Several new potential positioning issues developed for which measurement and control techniques were developed. To accomplish this, CAD coordinate-based computer metrology equipment and software similar to the solutions employed for winding the modular coils was used. Given the size of the assemblies, the primary tools were both interferometeraided and Absolute Distance Measurement (ADM)-only based laser trackers. In addition, portable Coordinate Measurement Machine (CMM) arms and some novel indirect measurement techniques were employed. This paper will detail both the use of CAD coordinate-based metrology technology and the techniques developed and employed for dimensional control of NSCX subassemblies. The results achieved and possible improvements to techniques will be discussed.« less

Study on a linear relationship between limited pressure difference and coil current of on/off valve and its influential factors.

PubMed

Zhang, Junzhi; Lv, Chen; Yue, Xiaowei; Li, Yutong; Yuan, Ye

2014-01-01

On/off solenoid valves with PWM control are widely used in all types of vehicle electro-hydraulic control systems respecting to their desirable properties of reliable, low cost and fast acting. However, it can hardly achieve a linear hydraulic modulation by using on/off valves mainly due to the nonlinear behaviors of valve dynamics and fluid, which affects the control accuracy significantly. In this paper, a linear relationship between limited pressure difference and coil current of an on/off valve in its critical closed state is proposed and illustrated, which has a great potential to be applied to improve hydraulic control performance. The hydraulic braking system of case study is modeled. The linear correspondence between limited pressure difference and coil current of the inlet valve is simulated and further verified experimentally. Based on validated simulation models, the impacts of key parameters are researched. The limited pressure difference affected by environmental temperatures is experimentally studied, and the amended linear relation is given according to the test data. © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Flexible helical-axis stellarator

DOEpatents

Harris, Jeffrey H.; Hender, Timothy C.; Carreras, Benjamin A.; Cantrell, Jack L.; Morris, Robert N.

1988-01-01

An 1=1 helical winding which spirals about a conventional planar, circular central conductor of a helical-axis stellarator adds a significant degree of flexibility by making it possible to control the rotational transform profile and shear of the magnetic fields confining the plasma in a helical-axis stellarator. The toroidal central conductor links a plurality of toroidal field coils which are separately disposed to follow a helical path around the central conductor in phase with the helical path of the 1=1 winding. This coil configuration produces bean-shaped magnetic flux surfaces which rotate around the central circular conductor in the same manner as the toroidal field generating coils. The additional 1=1 winding provides flexible control of the magnetic field generated by the central conductor to prevent the formation of low-order resonances in the rotational transform profile which can produce break-up of the equilibrium magnetic surfaces. Further, this additional winding can deepen the magnetic well which together with the flexible control provides increased stability.

Impaired Feedforward Control and Enhanced Feedback Control of Speech in Patients with Cerebellar Degeneration.

PubMed

Parrell, Benjamin; Agnew, Zarinah; Nagarajan, Srikantan; Houde, John; Ivry, Richard B

2017-09-20

The cerebellum has been hypothesized to form a crucial part of the speech motor control network. Evidence for this comes from patients with cerebellar damage, who exhibit a variety of speech deficits, as well as imaging studies showing cerebellar activation during speech production in healthy individuals. To date, the precise role of the cerebellum in speech motor control remains unclear, as it has been implicated in both anticipatory (feedforward) and reactive (feedback) control. Here, we assess both anticipatory and reactive aspects of speech motor control, comparing the performance of patients with cerebellar degeneration and matched controls. Experiment 1 tested feedforward control by examining speech adaptation across trials in response to a consistent perturbation of auditory feedback. Experiment 2 tested feedback control, examining online corrections in response to inconsistent perturbations of auditory feedback. Both male and female patients and controls were tested. The patients were impaired in adapting their feedforward control system relative to controls, exhibiting an attenuated anticipatory response to the perturbation. In contrast, the patients produced even larger compensatory responses than controls, suggesting an increased reliance on sensory feedback to guide speech articulation in this population. Together, these results suggest that the cerebellum is crucial for maintaining accurate feedforward control of speech, but relatively uninvolved in feedback control. SIGNIFICANCE STATEMENT Speech motor control is a complex activity that is thought to rely on both predictive, feedforward control as well as reactive, feedback control. While the cerebellum has been shown to be part of the speech motor control network, its functional contribution to feedback and feedforward control remains controversial. Here, we use real-time auditory perturbations of speech to show that patients with cerebellar degeneration are impaired in adapting feedforward control of speech but retain the ability to make online feedback corrections; indeed, the patients show an increased sensitivity to feedback. These results indicate that the cerebellum forms a crucial part of the feedforward control system for speech but is not essential for online, feedback control. Copyright © 2017 the authors 0270-6474/17/379249-10$15.00/0.

Rack protection monitor

DOEpatents

Orr, Stanley G.

2000-01-01

A hardwired, fail-safe rack protection monitor utilizes electromechanical relays to respond to the detection by condition sensors of abnormal or alarm conditions (such as smoke, temperature, wind or water) that might adversely affect or damage equipment being protected. When the monitor is reset, the monitor is in a detection mode with first and second alarm relay coils energized. If one of the condition sensors detects an abnormal condition, the first alarm relay coil will be de-energized, but the second alarm relay coil will remain energized. This results in both a visual and an audible alarm being activated. If a second alarm condition is detected by another one of the condition sensors while the first condition sensor is still detecting the first alarm condition, both the first alarm relay coil and the second alarm relay coil will be de-energized. With both the first and second alarm relay coils de-energized, both a visual and an audible alarm will be activated. In addition, power to the protected equipment will be terminated and an alarm signal will be transmitted to an alarm central control. The monitor can be housed in a separate enclosure so as to provide an interface between a power supply for the protected equipment and the protected equipment.

Suppression of radiating harmonics Electro-Impulse Deicing (EIDI) systems

NASA Astrophysics Data System (ADS)

Zieve, Peter; Ng, James; Fiedberg, Robert

1991-10-01

The electromagnetic compatibility (EMC) of two different configurations of electromagnetic deicing systems is discussed. Both Electro-Impulse Deicing (EIDI) and Eddy Current Repulsion Deicing Strip (EDS) are investigated. With EIDI, rigid coils are mounted behind the wing; while with EDS, the impulse coils are built thin and flexible with printed circuit board technology. An important consideration in the certification of electromagnetic impulse deicing systems is electromagnetic compatibility (EMC). When the capacitor bank discharges, a large current pulse travels down a transmission line to the coil. The coil is one source of radiation. Another source is the cabling and connections to the coil. In work conducted for the FAA in 1988, it was found that excessive electromagnetic emissions resulted from the operation of a Low Voltage Electro-Impulse Deicer (LVEID) in conjunction with a composite wing. The goal of this project was to investigate and develop techniques for controlling emissions without the benefit of shielding. In this study it was determined that both EIDI and EDS could be brought within the RTCA/DO-160B standards through proper shielding and termination of the pulse power cable. An alternative topology of EDS with the impulse coil on the wing exterior surface did not meet the standard.

Superconducting magnetic energy storage for asynchronous electrical systems

DOEpatents

Boenig, Heinrich J.

1986-01-01

A superconducting magnetic energy storage coil connected in parallel between converters of two or more ac power systems provides load leveling and stability improvement to any or all of the ac systems. Control is provided to direct the charging and independently the discharging of the superconducting coil to at least a selected one of the ac power systems.

The Monocyte Chemotactic Protein-1 — Interleukin-6 — Osteopontin Pathway of Intra-Aneurysmal Tissue Healing

PubMed Central

Hosaka, Koji; Rojas, Kelley; Fazal, Hanain Z; Schneider, Matheus B; Shores, Jorma; Federico, Vincent; McCord, Matthew; Lin, Li; Hoh, Brian

2017-01-01

Background and Purpose We have previously demonstrated that the local delivery of monocyte chemotactic protein-1 (MCP-1) via a MCP-1-releasing poly(lactic-co-glycolic acid) (PLGA) -coated coil promotes intra-aneurysmal tissue healing. In this study, we demonstrate that interleukin-6 (IL-6) and osteopontin (OPN) are downstream mediators in the MCP-1-mediated aneurysm healing pathway. Methods Murine carotid aneurysms were created in C57BL/6 mice. Drug-releasing coils (MCP-1, IL-6 and OPN) and control PLGA coils were created and then implanted into the aneurysms in order to evaluate their intra-aneurysmal healing capacity. In order to investigate the downstream mediators for aneurysm healing, blocking antibodies for IL-6 receptor and OPN were given to the mice implanted with the MCP-1-releasing coils. A histological analysis of both murine and human aneurysms was utilized to cross-validate the data. Results We observed increased expression of IL-6 in MCP-1-coil treated aneurysms and not in control-PLGA-only treated aneurysms. MCP-1-mediated intra-aneurysmal healing is inhibited in mice given blocking antibody to IL-6 receptor. MCP-1-mediated intra-aneurysmal healing is also inhibited by blocking antibody to OPN. The role of IL-6 in intra-aneurysmal healing is in recruiting of endothelial cells and fibroblasts. Local delivery of OPN to murine carotid aneurysms via OPN-releasing coil significantly promotes intra-aneurysmal healing, but IL-6-releasing coil does not, suggesting that IL-6 cannot promote aneurysm healing independent of MCP-1. In the MCP-1-mediated aneurysm healing, OPN expression is dependent on IL-6; inhibition of IL-6 receptor significantly inhibits OPN expression in MCP-1-mediated aneurysm healing. Conclusions Our findings suggest that IL-6 and OPN are key downstream mediators of MCP-1-mediated intra-aneurysmal healing. PMID:28292871

Local Delivery Is Critical for Monocyte Chemotactic Protein-1 Mediated Site-Specific Murine Aneurysm Healing.

PubMed

Hourani, Siham; Motwani, Kartik; Wajima, Daisuke; Fazal, Hanain; Jones, Chad H; Doré, Sylvain; Hosaka, Koji; Hoh, Brian L

2018-01-01

Local delivery of monocyte chemotactic protein-1 (MCP-1/CCL2) via our drug-eluting coil has been shown to promote intrasaccular aneurysm healing via an inflammatory pathway. In this study, we validate the importance of local MCP-1 in murine aneurysm healing. Whether systemic, rather than local, delivery of MCP-1 can direct site-specific aneurysm healing has significant translational implications. If systemic MCP-1 is effective, then MCP-1 could be administered as a pill rather than by endovascular procedure. Furthermore, we confirm that MCP-1 is the primary effector in our MCP-1 eluting coil-mediated murine aneurysm healing model. We compare aneurysm healing with repeated intraperitoneal MCP-1 versus vehicle injection, in animals with control poly(lactic-co-glycolic) acid (PLGA)-coated coils. We demonstrate elimination of the MCP-1-associated tissue-healing response by knockout of MCP-1 or CCR2 (MCP-1 receptor) and by selectively inhibiting MCP-1 or CCR2. Using immunofluorescent probing, we explore the cell populations found in healed aneurysm tissue following each intervention. Systemically administered MCP-1 with PLGA coil control does not produce comparable aneurysm healing, as seen with MCP-1 eluting coils. MCP-1-directed aneurysm healing is eliminated by selective inhibition of MCP-1 or CCR2 and in MCP-1-deficient or CCR2-deficient mice. No difference was detected in M2 macrophage and myofibroblast/smooth muscle cell staining with systemic MCP-1 versus vehicle in aneurysm wall, but a significant increase in these cell types was observed with MCP-1 eluting coil implant and attenuated by MCP-1/CCR2 blockade or deficiency. We show that systemic MCP-1 concurrent with PLGA-coated platinum coil implant is not sufficient to produce site-specific aneurysm healing. MCP-1 is a critical, not merely complementary, actor in the aneurysm healing pathway.

TEM Systems Design: Using Full Maxwell FDTD Modelling to Study the Transient Response of Custom-madeTx and Rx Coils.

NASA Astrophysics Data System (ADS)

Chevalier, A.; Rejiba, F.; Schamper, C.; Thiesson, J.; Hovhannissian, G.

2016-12-01

From airborne applications to field scale measurements of Transient Electromagnetic Methods(TEM), an accurate knowledge of the sensitivity of the inductive coil sensors (system response) is aprerequisite to interpret the measured transient magnetic flux density into a subsurface distributionof conductivity. The system response is a term that refers to the cumulative effect of inductive andcapacitive couplings (cross-talks) between each component constituting a TEM apparatus and thenearby conductive structures. As a result, the frequency sensitivity of the voltage coil sensor (Rx)along with the emitted current waveform in the current emitting coil (Tx) are controlled by thegeometry and electronic characteristic of the set-up as well as the near surface electromagneticproperties. During the early development of an innovative airborne TEM solutions (French nationalTEMas project), determining the coil geometries and the impedance matching between all parts ofthe transmission link (electronic parts and coils) for various environmental set-ups, has been a majorissue. In this study, we review the required theoretical framework and propose a versatile numericalmethodology to ease the coil design and impedance matching process while extending ourunderstanding of short-time transient that operates from DC to moderately high frequencies (0 to 20Mhz). We used a full Maxwell equations FDTD model along with a semi-analytical 1D modeler to infercoils emitting and receiving properties, for various coil geometries and site-dependent conditions.Results highlight the influence of the environment on the emitting and sensing properties. Theincreasing effects of cross-talks between the Tx and the Rx coils depending on their size is shown.Strategies regarding the impedance adaptation between the electronical components and the coilsensors are then discussed for different geophysical specifications.

Magnetic reconnection launcher

DOEpatents

Cowan, M.

1987-04-06

An electromagnetic launcher includes a plurality of electrical stages which are energized sequentially in the launcher with the passage of a projectiles. Each stage of the launcher includes two or more coils which are arranged coaxially on either closed-loop or straight lines to form gaps between their ends. The projectile has an electrically conductive gap-portion that passes through all the gaps of all the stages in a direction transverse to the axes of the coils. The coils receive an electric current, store magnetic energy, and convert a significant portion of the stored magnetic energy into kinetic energy of the projectile moves through the gap. The magnetic polarity of the opposing coils is in the same direction, e.g. N-S-N-S. A gap portion of the projectile may be made from aluminum and is propelled by the reconnection of magnetic flux stored in the coils which causes accelerating forces to act upon the projectile and at the horizontal surfaces of the projectile near its rear. The gap portion of the projectile may be flat, rectangular and longer than the length of the opposing coils. The gap portion of the projectile permits substantially unrestricted distribution of the induced currents so that current densities are only high where the useful magnetic force is high. This allows designs which permit ohmic oblation from the rear surfaces of the gap portion of the projectile allowing much high velocities to be achieved. An electric power apparatus controls the electric power supplied to the opposing coils until the gap portion of the projectile substantially occupies the gap between the coils, at which time the coils are supplied with peak current quickly. 8 figs.

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method.

PubMed

Chen, Xinyuan; Dai, Jianrong

2018-05-01

Magnetic Resonance Imaging (MRI) simulation differs from diagnostic MRI in purpose, technical requirements, and implementation. We propose a semiautomatic method for image acceptance and commissioning for the scanner, the radiofrequency (RF) coils, and pulse sequences for an MRI simulator. The ACR MRI accreditation large phantom was used for image quality analysis with seven parameters. Standard ACR sequences with a split head coil were adopted to examine the scanner's basic performance. The performance of simulation RF coils were measured and compared using the standard sequence with different clinical diagnostic coils. We used simulation sequences with simulation coils to test the quality of image and advanced performance of the scanner. Codes and procedures were developed for semiautomatic image quality analysis. When using standard ACR sequences with a split head coil, image quality passed all ACR recommended criteria. The image intensity uniformity with a simulation RF coil decreased about 34% compared with the eight-channel diagnostic head coil, while the other six image quality parameters were acceptable. Those two image quality parameters could be improved to more than 85% by built-in intensity calibration methods. In the simulation sequences test, the contrast resolution was sensitive to the FOV and matrix settings. The geometric distortion of simulation sequences such as T1-weighted and T2-weighted images was well-controlled in the isocenter and 10 cm off-center within a range of ±1% (2 mm). We developed a semiautomatic image quality analysis method for quantitative evaluation of images and commissioning of an MRI simulator. The baseline performances of simulation RF coils and pulse sequences have been established for routine QA. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Dynamic stabilization of the magnetic field surrounding the neutron electric dipole moment spectrometer at the Paul Scherrer Institute

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afach, S.; Fertl, M.; Franke, B., E-mail: beatrice.franke@psi.ch, E-mail: bernhard.lauss@psi.ch

The Surrounding Field Compensation (SFC) system described in this work is installed around the four-layer Mu-metal magnetic shield of the neutron electric dipole moment spectrometer located at the Paul Scherrer Institute. The SFC system reduces the DC component of the external magnetic field by a factor of about 20. Within a control volume of approximately 2.5 m × 2.5 m × 3 m, disturbances of the magnetic field are attenuated by factors of 5–50 at a bandwidth from 10{sup −3} Hz up to 0.5 Hz, which corresponds to integration times longer than several hundreds of seconds and represent the important timescale for the neutron electric dipole moment measurement.more » These shielding factors apply to random environmental noise from arbitrary sources. This is achieved via a proportional-integral feedback stabilization system that includes a regularized pseudoinverse matrix of proportionality factors which correlates magnetic field changes at all sensor positions to current changes in the SFC coils.« less

Design of multichannel laser interferometry for W7-X

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kornejew, P.; Hirsch, M.; Bindemann, T.

2006-10-15

An eight channel interferometer is developed for density feedback control and the continuous measurement of electron density profiles in the stellarator W7-X. An additional sightline is launched in the geometry of the Thomson scattering for cross calibration. Due to the W7-X coil geometry access is strongly restricted. This motivates the optimization of the sightline geometry and design studies for supplementary chords. In-vessel retroreflectors will be used and inserted in the first wall elements. To cope with associated mechanical vibrations and thermal drifts during the discharges with envisaged duration of 30 min either two-color or second harmonic interferometry techniques must bemore » applied. Optimum wavelengths are found to be about 10 and 5 {mu}m. A CO{sub 2}/CO interferometer (10 {mu}m/5 {mu}m) will be tested and compared with an existing CO{sub 2}/HeNe test interferometer. A special difficulty of remotely operated diagnostics is the need of long transmission lines with a path length of about 60 m required from the diagnostics location to the torus hall and back. Different arrangements will be compared.« less

Self-controlled video feedback on tactical skills for soccer teams results in more active involvement of players.

PubMed

van Maarseveen, Mariëtte J J; Oudejans, Raôul R D; Savelsbergh, Geert J P

2018-02-01

Many studies have shown that self-controlled feedback is beneficial for learning motor tasks, and that learners prefer to receive feedback after supposedly good trials. However, to date all studies conducted on self-controlled learning have used individual tasks and mainly relatively simple skills. Therefore, the aim of this study was to examine self-controlled feedback on tactical skills in small-sided soccer games. Highly talented youth soccer players were assigned to a self-control or yoked group and received video feedback on their offensive performance in 3 vs. 2 small-sided games. The results showed that the self-control group requested feedback mostly after good trials, that is, after they scored a goal. In addition, the perceived performance of the self-control group was higher on feedback than on no-feedback trials. Analyses of the conversations around the video feedback revealed that the players and coach discussed good and poor elements of performance and how to improve it. Although the coach had a major role in these conversations, the players of the self-control group spoke more and showed more initiative compared to the yoked group. The results revealed no significant beneficial effect of self-controlled feedback on performance as judged by the coach. Overall, the findings suggest that in such a complex situation as small-sided soccer games, self-controlled feedback is used both to confirm correct performance elements and to determine and correct errors, and that self-controlled learning stimulates the involvement of the learner in the learning process. Copyright © 2017 Elsevier B.V. All rights reserved.

Combined rTMS treatment targeting the Anterior Cingulate and the Temporal Cortex for the Treatment of Chronic Tinnitus

PubMed Central

Kreuzer, Peter M.; Lehner, Astrid; Schlee, Winfried; Vielsmeier, Veronika; Schecklmann, Martin; Poeppl, Timm B.; Landgrebe, Michael; Rupprecht, Rainer; Langguth, Berthold

2015-01-01

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a tinnitus treatment option. Promising results have been obtained by consecutive stimulation of lateral frontal and auditory brain regions. We investigated a combined stimulation paradigm targeting the anterior cingulate cortex (ACC) with double cone coil rTMS, followed by stimulation of the temporo-parietal junction area with a figure-of-eight coil. The study was conducted as a randomized, double-blind pilot trial in 40 patients suffering from chronic tinnitus. We compared mediofrontal stimulation with double-cone-coil, (2000 stimuli, 10 Hz) followed by left temporo-parietal stimulation with figure-of-eight-coil (2000 stimuli, 1 Hz) to left dorsolateral-prefrontal-cortex stimulation with figure-of-eight-coil (2000 stimuli, 10 Hz) followed by temporo-parietal stimulation with figure-of-eight-coil (2000 stimuli, 1 Hz). The stimulation was feasible with comparable dropout rates in both study arms; no severe adverse events were registered. Responder rates did not differ in both study arms. There was a significant main effect of time for the change in the TQ score, but no significant time x group interaction. This pilot study demonstrated the feasibility of combined mediofrontal/temporoparietal-rTMS-stimulation with double cone coil in tinnitus patients but failed to show better outcome compared to an actively rTMS treated control group. PMID:26667790

Very Fast Current Diagnostic for Linear Pulsed Beams

NASA Astrophysics Data System (ADS)

Nassisi, Vincenzo; Delle Side, Domenico; Turco, Vito

2018-01-01

Fast current pulses manage lasers and particle accelerators and require sophisticate systems to be detected. At today Rogowski coils are well known. They are designed and built with a toroidal structure. In recently application, flat transmission lines are imploded and for this reason we develop a linear Rogowski coil to detect current pulses inside flat conductors. To get deep information from the system, it was approached by means of the theory of the transmission lines. The coil we build presents a resistance but it doesn't influence the rise time of the response, instead the integrating time. We also studied the influence of the magnetic properties of coil support. The new device was able to record pulses of more hundred nanoseconds depending on the inductance, load impedance and resistance of the coil. Furthermore, its response was characterized by a sub-nanosecond rise time ( 100 ps), The attenuation coefficient depends mainly on the turn number of the coil, while the quality of the response depends both on the manufacture quality of the coil and on the magnetic core characteristics. In biophysical applications often, a double line is employed in order to have a sample as control and a sample stressed by a light source. So, in this case we build two equal plane lines by 100 Ω characteristic resistance connected in parallel. We diagnosed the current present in a line. The attenuation factor resulted to be 11,5 A/V.

Hybrid-secondary uncluttered permanent magnet machine and method

DOEpatents

Hsu, John S.

2005-12-20

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

What we don't know may hurt us: urinary drainage system tubing coils and CA-UTIs-A prospective quality study.

PubMed

Kubilay, Zeynep; Archibald, Lennox K; Kirchner, H Lester; Layon, A Joseph

2013-12-01

Catheter-associated urinary tract infections account for >30% of infections in acute care hospitals. We hypothesized that coiling of/kinks in the indwelling urinary bladder catheter (IUBC) drainage bag tubing would increase the occurrence of infection/bacteriuria. Ninety-one patient events were evaluated over 60 days. All outcome variables trended with greater frequency among those with a coil in the IUBC tubing; only fever (temperature > 38.1°C) correlated significantly between groups (P = .003). If IUBC is unavoidable, strategies such as keeping collection bag below the level of bladder and avoiding any coiling in the drainage system should be employed. Further study of these phenomena is needed. Copyright © 2013 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.

The mode of action of spatial repellents and their impact on vectorial capacity of Anopheles gambiae sensu stricto.

PubMed

Ogoma, Sheila B; Ngonyani, Hassan; Simfukwe, Emmanuel T; Mseka, Antony; Moore, Jason; Maia, Marta F; Moore, Sarah J; Lorenz, Lena M

2014-01-01

Malaria vector control relies on toxicity of insecticides used in long lasting insecticide treated nets and indoor residual spraying. This is despite evidence that sub-lethal insecticides reduce human-vector contact and malaria transmission. The impact of sub-lethal insecticides on host seeking and blood feeding of mosquitoes was measured. Taxis boxes distinguished between repellency and attraction inhibition of mosquitoes by measuring response of mosquitoes towards or away from Transfluthrin coils and humans. Protective effective distance of coils and long-term effects on blood feeding were measured in the semi-field tunnel and in a Peet Grady chamber. Laboratory reared pyrethroid susceptible Anopheles gambiae sensu stricto mosquitoes were used. In the taxis boxes, a higher proportion of mosquitoes (67%-82%) were activated and flew towards the human in the presence of Transfluthrin coils. Coils did not hinder attraction of mosquitoes to the human. In the semi-field Tunnel, coils placed 0.3 m from the human reduced feeding by 86% (95% CI [0.66; 0.95]) when used as a "bubble" compared to 65% (95% CI [0.51; 0.76]) when used as a "point source". Mosquitoes exposed to coils inside a Peet Grady chamber were delayed from feeding normally for 12 hours but there was no effect on free flying and caged mosquitoes exposed in the semi-field tunnel. These findings indicate that airborne pyrethroids minimize human-vector contact through reduced and delayed blood feeding. This information is useful for the development of target product profiles of spatial repellent products that can be used to complement mainstream malaria vector control tools.

Healing of Saccular Aneurysms Following Platinum Coil Embolization: Lack of Improved Efficacy with Vitamin C Supplementation

PubMed Central

Dai, Daying; Ding, Yong-Hong; Rezek, Issa; Lewis, Debra A.; Kallmes, David F.; Kadirvel, Ramanathan

2013-01-01

BACKGROUND AND PURPOSE To test the hypothesis that systemic administration of vitamin C, through its action of stimulating collagen synthesis and cross-linking, would decrease the recurrence and improve the occlusion experimental aneurysms treated with platinum coil embolization. METHODS Nineteen experimental aneurysms in female rabbits were embolized with platinum coils (>30% packing density). The animals were divided into three groups: Group 1 (n=6) rabbits served as controls, Group 2 (n=5) rabbits were fed with a vitamin C-supplemented feed and Group 3 (n=8) rabbits were medicated with vitamin C pills. Digital subtraction angiography was used to evaluate stability after embolization. Subjects were euthanized at 12 weeks after coil implantation, and serum vitamin C levels were then measured. Histological samples were examined with a grading system (range, 0-12) based on the neck and dome features. Masson Trichrome staining was employed to evaluate collagen deposition. Parametric data were analyzed with one-way analysis of variance and non-parametric data were examined using a Kruskal-Wallis test. RESULTS There were no significant differences between groups in mean aneurysm size. Mean serum vitamin C concentration was significantly higher in Group 3 and Group 2 compared to Group 1, while vitamin C levels between Group 2 and Group 3 were statistically comparable. Coil compaction was noted in one of six subjects in Group 1 and three of eight subjects in Group 3. All the remaining aneurysms in the test and control groups showed stable occlusion. There were no significant differences in histological scores or collagen deposition among groups. CONCLUSION Vitamin C supplementation following platinum coil embolization does not demonstrate improvement of long-term occlusion rates of aneurysms. PMID:22914744

Healing of saccular aneurysms following platinum coil embolization: lack of improved efficacy with vitamin C supplementation.

PubMed

Dai, Daying; Yong-Hong, Ding; Rezek, Issa; Lewis, Debra A; Kallmes, David F; Kadirvel, Ramanathan

2013-11-01

To test the hypothesis that systemic administration of vitamin C, through its action of stimulating collagen synthesis and crosslinking, would decrease the recurrence and improve the occlusion of experimental aneurysms treated with platinum coils. Experimental aneurysms were created in female rabbits and were embolized with platinum coils (>30% packing density). The animals were divided into three groups: group 1 (n=6) rabbits served as controls, group 2 (n=5) rabbits were fed with a vitamin C supplemented feed and group 3 (n=8) rabbits were medicated with vitamin C pills. Digital subtraction angiography was used to evaluate stability after embolization. Subjects were euthanized at 12 weeks after coil implantation, and serum vitamin C levels were then measured. Histological samples were examined with a grading system (range 0-12) based on the neck and dome features. Masson Trichrome staining was used to evaluate collagen deposition. Parametric data were analyzed with one way analysis of variance and non-parametric data were examined using a Kruskal-Wallis test. There were no significant differences between groups in mean aneurysm size. Mean serum vitamin C concentration was significantly higher in group 3 and group 2 compared with group 1, while vitamin C levels between group 2 and group 3 were statistically comparable. Coil compaction was noted in one of six subjects in group 1 and in three of eight subjects in group 3. All of the remaining aneurysms in the test and control groups showed stable occlusion. There were no significant differences in histological scores or collagen deposition among groups. Vitamin C supplementation following platinum coil embolization does not demonstrate improvement of long term occlusion rates of aneurysms.

Feedback-Equivalence of Nonlinear Systems with Applications to Power System Equations.

NASA Astrophysics Data System (ADS)

Marino, Riccardo

The key concept of the dissertation is feedback equivalence among systems affine in control. Feedback equivalence to linear systems in Brunovsky canonical form and the construction of the corresponding feedback transformation are used to: (i) design a nonlinear regulator for a detailed nonlinear model of a synchronous generator connected to an infinite bus; (ii) establish which power system network structures enjoy the feedback linearizability property and design a stabilizing control law for these networks with a constraint on the control space which comes from the use of d.c. lines. It is also shown that the feedback linearizability property allows the use of state feedback to contruct a linear controllable system with a positive definite linear Hamiltonian structure for the uncontrolled part if the state space is even; a stabilizing control law is derived for such systems. Feedback linearizability property is characterized by the involutivity of certain nested distributions for strongly accessible analytic systems; if the system is defined on a manifold M diffeomorphic to the Euclidean space, it is established that the set where the property holds is a submanifold open and dense in M. If an analytic output map is defined, a set of nested involutive distributions can be always defined and that allows the introduction of an observability property which is the dual concept, in some sense, to feedback linearizability: the goal is to investigate when a nonlinear system affine in control with an analytic output map is feedback equivalent to a linear controllable and observable system. Finally a nested involutive structure of distributions is shown to guarantee the existence of a state feedback that takes a nonlinear system affine in control to a single input one, both feedback equivalent to linear controllable systems, preserving one controlled vector field.

Control theory for scanning probe microscopy revisited.

PubMed

Stirling, Julian

2014-01-01

We derive a theoretical model for studying SPM feedback in the context of control theory. Previous models presented in the literature that apply standard models for proportional-integral-derivative controllers predict a highly unstable feedback environment. This model uses features specific to the SPM implementation of the proportional-integral controller to give realistic feedback behaviour. As such the stability of SPM feedback for a wide range of feedback gains can be understood. Further consideration of mechanical responses of the SPM system gives insight into the causes of exciting mechanical resonances of the scanner during feedback operation.

The "Guidewire-Coil"-Technique to prevent retrograde stone migration of ureteric calculi during intracorporeal lithothripsy.

PubMed

Dreger, Nici Markus; von Rundstedt, Friedrich Carl; Roth, Stephan; Brandt, Alexander Sascha; Degener, Stephan

2017-01-05

Stone retropulsion represents a challenge for intracorporeal lithotripsy of ureteral calculi. The consequences are an increased duration and cost of surgery as well as decreased stone-free rates. The use of additional tools to prevent proximal stone migration entails further costs and risks for ureteral injuries. We present the simple technique of using a coil of the routinely used guidewire to prevent stone retropulsion. We retrospectively evaluated all patients with mid-to-proximal ureteral stones in 2014, which were treated by ureteroscopic lithotripsy (Ho: YAG and/or pneumatic lithotripsy). The preoperative stone burden was routinely assessed using low dose CT scan (if available) and/or intravenous pyelogram. The study population consisted of 55 patients with 61 mid-to-proximal calculi. Twentyseven patients underwent semirigid ureterorenoscopy using the "Guidewire-Coil-Technique", the second group (n = 28) served as control group using the guidewire as usual. There has been a statistically significant reduction of accidental stone retropulsion (2/27 vs. 8/28, p < 0.05) as well as a decreased use of auxiliary procedures (p < 0.05) compared to the control group. No difference was observed in operative time. One ureteral injury in the control group required a prolonged ureteral stenting. The "Guidewire-Coil-Technique" is a simple and safe procedure that may help to prevent proximal calculus migration and therefore may increase stone-free rates without causing additional costs.

A voice coil actuator driven active vibration isolation system with the consideration of flexible modes.

PubMed

Park, Kyihwan; Choi, Dongyoub; Ozer, Abdullah; Kim, Sangyoo; Lee, Yongkwan; Joo, Dongik

2008-06-01

We develop a four-mount active vibration isolation system (AVIS) using voice coil actuators. The flexible body modes in the upper plate of the AVIS can cause an instability problem due to control signal whose frequency is close to the resonant frequency of the flexible modes. The loop shaping technique is applied to reduce the amplitude of the control signal. We investigate the performances of the active vibration isolation system proposed in the word in the time domain and frequency domain by comparing to the passive isolation system.

Solid State Welding Development at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Ding, Robert J.; Walker, Bryant

2012-01-01

What is TSW and USW? TSW is a solid state weld process consisting of an induction coil heating source, a stir rod, and non-rotating containment plates Independent heating, stirring and forging controls Decouples the heating, stirring and forging process elements of FSW. USW is a solid state weld process consisting of an induction coil heating source, a stir rod, and a non-rotating containment plate; Ultrasonic energy integrated into non-rotating containment plate and stir rod; Independent heating, stirring and forging controls; Decouples the heating, stirring and forging process elements of FSW.

Broadband and stable acoustic vortex emitter with multi-arm coiling slits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Xue; Liang, Bin, E-mail: liangbin@nju.edu.cn, E-mail: eleqc@nus.edu.sg, E-mail: jccheng@nju.edu.cn; Zou, Xin-ye

2016-05-16

We present the analytical design and experimental realization of a scheme based on multi-arm coiling slits to generate the stable acoustic vortices in a broadband. The proposed structure is able to spiral the acoustic wave spatially and generate the twisted acoustic vortices with invariant topological charge for a long propagation distance. Compared with conventional methods which require the electronic control of a bulky loudspeaker, this scheme provides an effective and compact solution to generate acoustic vortices with controllable topological charge in the broadband, which offers more initiatives in the demanding applications.

Direct interactions between the coiled-coil tip of DksA and the trigger loop of RNA polymerase mediate transcriptional regulation

USDA-ARS?s Scientific Manuscript database

E. coli DksA is in a class of transcription factors that modify RNA polymerase (RNAP) in all three kingdoms of life. DksA potentiates the effects of the global regulator ppGpp and the initiating NTP, controlling transcription initiation without binding to DNA. Incorporating benzoyl-phenylalanine (Bp...

Direct EPR irradiation of a sample using a quartz oscillator operating at 250 MHz for EPR measurements.

PubMed

Yokoyama, Hidekatsu

2012-01-01

Direct irradiation of a sample using a quartz oscillator operating at 250 MHz was performed for EPR measurements. Because a quartz oscillator is a frequency fixed oscillator, the operating frequency of an EPR resonator (loop-gap type) was tuned to that of the quartz oscillator by using a single-turn coil with a varactor diode attached (frequency shift coil). Because the frequency shift coil was mobile, the distance between the EPR resonator and the coil could be changed. Coarse control of the resonant frequency was achieved by changing this distance mechanically, while fine frequency control was implemented by changing the capacitance of the varactor electrically. In this condition, EPR measurements of a phantom (comprised of agar with a nitroxide radical and physiological saline solution) were made. To compare the presented method with a conventional method, the EPR measurements were also done by using a synthesizer at the same EPR frequency. In the conventional method, the noise level increased at high irradiation power. Because such an increase in the noise was not observed in the presented method, high sensitivity was obtained at high irradiation power. Copyright © 2011 Elsevier Inc. All rights reserved.

Design and model for the giant magnetostrictive actuator used on an electronic controlled injector

NASA Astrophysics Data System (ADS)

Xue, Guangming; Zhang, Peilin; He, Zhongbo; Li, Ben; Rong, Ce

2017-05-01

Giant magnetostrictive actuator (GMA) may be a promising candidate actuator to drive an electronic controlled injector as giant magnetostrictive material (GMM) has excellent performances as large output, fast response and high operating stability etc. To meet the driving requirement of the injector, the GMA should produce maximal shortening displacement when energized. An unbiased GMA with a ‘T’ shaped output rod is designed to reach the target. Furthermore, an open-hold-fall type driving voltage is exerted on the actuator coil to accelerate the response speed of the coil current. The actuator displacement is modeled from establishing the sub-models of coil current, magnetic field within GMM rod, magnetization and magnetostrictive strain sequentially. Two modifications are done to make the model more accurate. Firstly, consider the model fails to compute the transient-state response precisely, a dead-zone and delay links are embedded into the coil current sub-model. Secondly, as the magnetization and magnetostrictive strain sub-models just influence the change rule of the transient-state response the linear magnetostrictive strain-magnetic field sub-model is introduced. From experimental results, the modified model with linear magnetostrictive stain expression can predict the actuator displacement quite effectively.

Realizing actual feedback control of complex network

NASA Astrophysics Data System (ADS)

Tu, Chengyi; Cheng, Yuhua

2014-06-01

In this paper, we present the concept of feedbackability and how to identify the Minimum Feedbackability Set of an arbitrary complex directed network. Furthermore, we design an estimator and a feedback controller accessing one MFS to realize actual feedback control, i.e. control the system to our desired state according to the estimated system internal state from the output of estimator. Last but not least, we perform numerical simulations of a small linear time-invariant dynamics network and a real simple food network to verify the theoretical results. The framework presented here could make an arbitrary complex directed network realize actual feedback control and deepen our understanding of complex systems.

Learning feedback and feedforward control in a mirror-reversed visual environment.

PubMed

Kasuga, Shoko; Telgen, Sebastian; Ushiba, Junichi; Nozaki, Daichi; Diedrichsen, Jörn

2015-10-01

When we learn a novel task, the motor system needs to acquire both feedforward and feedback control. Currently, little is known about how the learning of these two mechanisms relate to each other. In the present study, we tested whether feedforward and feedback control need to be learned separately, or whether they are learned as common mechanism when a new control policy is acquired. Participants were trained to reach to two lateral and one central target in an environment with mirror (left-right)-reversed visual feedback. One group was allowed to make online movement corrections, whereas the other group only received visual information after the end of the movement. Learning of feedforward control was assessed by measuring the accuracy of the initial movement direction to lateral targets. Feedback control was measured in the responses to sudden visual perturbations of the cursor when reaching to the central target. Although feedforward control improved in both groups, it was significantly better when online corrections were not allowed. In contrast, feedback control only adaptively changed in participants who received online feedback and remained unchanged in the group without online corrections. Our findings suggest that when a new control policy is acquired, feedforward and feedback control are learned separately, and that there may be a trade-off in learning between feedback and feedforward controllers. Copyright © 2015 the American Physiological Society.

Learning feedback and feedforward control in a mirror-reversed visual environment

PubMed Central

Kasuga, Shoko; Telgen, Sebastian; Ushiba, Junichi; Nozaki, Daichi

2015-01-01

When we learn a novel task, the motor system needs to acquire both feedforward and feedback control. Currently, little is known about how the learning of these two mechanisms relate to each other. In the present study, we tested whether feedforward and feedback control need to be learned separately, or whether they are learned as common mechanism when a new control policy is acquired. Participants were trained to reach to two lateral and one central target in an environment with mirror (left-right)-reversed visual feedback. One group was allowed to make online movement corrections, whereas the other group only received visual information after the end of the movement. Learning of feedforward control was assessed by measuring the accuracy of the initial movement direction to lateral targets. Feedback control was measured in the responses to sudden visual perturbations of the cursor when reaching to the central target. Although feedforward control improved in both groups, it was significantly better when online corrections were not allowed. In contrast, feedback control only adaptively changed in participants who received online feedback and remained unchanged in the group without online corrections. Our findings suggest that when a new control policy is acquired, feedforward and feedback control are learned separately, and that there may be a trade-off in learning between feedback and feedforward controllers. PMID:26245313

The Helicity Injected Torus Program

NASA Astrophysics Data System (ADS)

Jarboe, T. R.; Nelson, B. A.; Jewell, P. D.; Liptac, J. E.; McCollam, K. J.; Raman, R.; Redd, A. J.; Rogers, J. A.; Sieck, P. E.; Shumlak, U.; Smith, R. J.; Nagata, M.; Uyama, T.

1999-11-01

The Helicity Injected Torus--II (HIT--II) spherical torus is capable of both Coaxial Helicity Injection (CHI) and transformer action current drive. HIT--II has a major radius R = 0.3, minor radius a = 0.2, aspect ratio A = R/a = 1.5, with an on axis magnetic field of up to Bo = 0.67 T. HIT--II provides equilibrium control, CHI flux boundary conditions, and transformer action using 28 poloidal field coils, using active flux feedback control. HIT--II has driven up to 200 kA of plasma current, using either CHI or transformer drive. An overview and recent results of the HIT--II program will be presented. The development of a locked-electron current drive model for HIT and HIT--II has led to the design of a constant inductive helicity injection method for spherical torii. This method is incorporated in the design of the Helicity Injected Torus -- Steady Inductive (HIT-- SI)(T.R. Jarboe, Fusion Technology, 36) (1), p. 85, 1999 experiment. HIT--SI can form a high-beta spheromak, a low aspect ratio RFP, or a spherical tokamak in a steady-state manner without using electrodes. The HIT--SI design and methodology will be presented.

Electromagnetic containerless processing requirements and recommended facility concept and capabilities for space lab

NASA Technical Reports Server (NTRS)

Frost, R. T.; Bloom, H. L.; Napaluch, L. J.; Stockhoff, E. H.; Wouch, G.

1974-01-01

Containerless melting, reaction, and solidification experiments and processes which potentially can lead to new understanding of material science and production of new or improved materials in the weightless space environment are reviewed in terms of planning for spacelab. Most of the experiments and processes discussed are amenable to the employment of electromagnetic position control and electromagnetic induction or electron beam heating and melting. The spectrum of relevant properties of materials, which determine requirements for a space laboratory electromagnetic containerless processing facility are reviewed. Appropriate distributions and associated coil structures are analyzed and compared on the basis of efficiency, for providing the functions of position sensing, control, and induction heating. Several coil systems are found capable of providing these functions. Exchangeable modular coils in appropriate sizes are recommended to achieve the maximum power efficiencies, for a wide range of specimen sizes and resistivities, in order to conserve total facility power.

Effect of vibrotactile feedback on an EMG-based proportional cursor control system.

PubMed

Li, Shunchong; Chen, Xingyu; Zhang, Dingguo; Sheng, Xinjun; Zhu, Xiangyang

2013-01-01

Surface electromyography (sEMG) has been introduced into the bio-mechatronics systems, however, most of them are lack of the sensory feedback. In this paper, the effect of vibrotactile feedback for a myoelectric cursor control system is investigated quantitatively. Simultaneous and proportional control signals are extracted from EMG using a muscle synergy model. Different types of feedback including vibrotactile feedback and visual feedback are added, assessed and compared with each other. The results show that vibrotactile feedback is capable of improving the performance of EMG-based human machine interface.

Study of Globus-M Tokamak Poloidal System and Plasma Position Control

NASA Astrophysics Data System (ADS)

Dokuka, V. N.; Korenev, P. S.; Mitrishkin, Yu. V.; Pavlova, E. A.; Patrov, M. I.; Khayrutdinov, R. R.

2017-12-01

In order to provide efficient performance of tokamaks with vertically elongated plasma position, control systems for limited and diverted plasma configuration are required. The accuracy, stability, speed of response, and reliability of plasma position control as well as plasma shape and current control depend on the performance of the control system. Therefore, the problem of the development of such systems is an important and actual task in modern tokamaks. In this study, the measured signals from the magnetic loops and Rogowski coils are used to reconstruct the plasma equilibrium, for which linear models in small deviations are constructed. We apply methods of the H∞-optimization theory to the synthesize control system for vertical and horizontal position of plasma capable to working with structural uncertainty of the models of the plant. These systems are applied to the plasma-physical DINA code which is configured for the tokamak Globus-M plasma. The testing of the developed systems applied to the DINA code with Heaviside step functions have revealed the complex dynamics of plasma magnetic configurations. Being close to the bifurcation point in the parameter space of unstable plasma has made it possible to detect an abrupt change in the X-point position from the top to the bottom and vice versa. Development of the methods for reconstruction of plasma magnetic configurations and experience in designing plasma control systems with feedback for tokamaks provided an opportunity to synthesize new digital controllers for plasma vertical and horizontal position stabilization. It also allowed us to test the synthesized digital controllers in the closed loop of the control system with the DINA code as a nonlinear model of plasma.

Simulation and design of feedback control on resistive wall modes in Keda Torus eXperiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chenguang; Liu, Wandong; Li, Hong

2014-12-15

The feedback control of resistive wall modes (RWMs) in Keda Torus eXperiment (KTX) (Liu et al., Plasma Phys. Controlled Fusion 56, 094009 (2014)) is investigated by simulation. A linear model is built to describe the growth of the unstable modes in the absence of feedback and the resulting mode suppression due to feedback, given the typical reversed field pinch plasma equilibrium. The layout of KTX with two shell structures (the vacuum vessel and the stabilizing shell) is taken into account. The feedback performance is explored both in the scheme of “clean mode control” (Zanca et al., Nucl. Fusion 47, 1425more » (2007)) and “raw mode control.” The discrete time control model with specific characteristic times will mimic the real feedback control action and lead to the favored control cycle. Moreover, the conceptual design of feedback control system is also presented, targeting on both RWMs and tearing modes.« less

Quasistationary magnetic field generation with a laser-driven capacitor-coil assembly.

PubMed

Tikhonchuk, V T; Bailly-Grandvaux, M; Santos, J J; Poyé, A

2017-08-01

Recent experiments are showing possibilities to generate strong magnetic fields on the excess of 500 T with high-energy nanosecond laser pulses in a compact setup of a capacitor connected to a single turn coil. Hot electrons ejected from the capacitor plate (cathode) are collected at the other plate (anode), thus providing the source of a current in the coil. However, the physical processes leading to generation of currents exceeding hundreds of kiloamperes in such a laser-driven diode are not sufficiently understood. Here we present a critical analysis of previous results and propose a self-consistent model for the high current generation in a laser-driven capacitor-coil assembly. It accounts for three major effects controlling the diode current: the space charge neutralization, the plasma magnetization between the capacitor plates, and the Ohmic heating of the external circuit-the coil-shaped connecting wire. The model provides the conditions necessary for transporting strongly super-Alfvenic currents through the diode on the time scale of a few nanoseconds. The model validity is confirmed by a comparison with the available experimental data.

Magnetic suspension and balance system advanced study

NASA Technical Reports Server (NTRS)

Boom, R. W.; Eyssa, Y. M.; Mcintosh, G. E.; Abdelsalam, M. K.

1985-01-01

An improved compact design for a superconducting magnetic suspension and balance system for an 8 ft. x 8 ft. transonic wind tunnel is developed. The original design of an MSBS in NASA Cr-3802 utilized 14 external superconductive coils and a superconductive solenoid in the airplane test model suspended in a wind tunnel. The improvements are in the following areas: test model solenoid options, dynamic force limits on the model, magnet cooling options, structure and cryogenic designs, power supply specifications, and cost and performance evaluations. The improvements are: MSBS cost reduction of 28%, weight; reduction of 43%, magnet system ampere-meter reduction of 38%, helium liquifier capacity reduction by 33%, magnet system stored energy reduction by 55%, AC loss to liquid helium reduced by 76%, system power supply reduced by 68%, test coil pole strength increased by 19%, wing magnetization increased by 40%, and control frequency limit increased by 200% from 10 Hz to 30 Hz. The improvements are due to: magnetic holmium coil forms in the test model, better rare earth permanent magnets in the wings, fiberglass-epoxy structure replacing stainless steel, better coil configuration, and new saddle roll coil design.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rushton, Phillip S.; Olek, Anna T.; Makowski, Lee

The crystallographic structure of a rice (Oryza sativa) cellulose synthase, OsCesA8, plant-conserved region (P-CR), one of two unique domains in the catalytic domain of plant CesAs, was solved to 2.4 Å resolution. Two antiparallel α-helices form a coiled-coil domain linked by a large extended connector loop containing a conserved trio of aromatic residues. The P-CR structure was fit into a molecular envelope for the P-CR domain derived from small-angle X-ray scattering data. The P-CR structure and molecular envelope, combined with a homology-based chain trace of the CesA8 catalytic core, were modeled into a previously determined CesA8 small-angle X-ray scattering molecularmore » envelope to produce a detailed topological model of the CesA8 catalytic domain. The predicted position for the P-CR domain from the molecular docking models places the P-CR connector loop into a hydrophobic pocket of the catalytic core, with the coiled-coil aligned near the entrance of the substrate UDP-glucose into the active site. In this configuration, the P-CR coiled-coil alone is unlikely to regulate substrate access to the active site, but it could interact with other domains of CesA, accessory proteins, or other CesA catalytic domains to control substrate delivery.« less

Conductor analysis of the ITER FEAT poloidal field coils during a plasma scenario

NASA Astrophysics Data System (ADS)

Nicollet, S.; Hertout, P.; Duchateau, J. L.; Bleyer, A.; Bessette, D.

2002-05-01

In the framework of the ITER (International Thermonuclear Experimental Reactor) FEAT (Fusion Energy Advanced Tokamak) project, a fully superconducting PF (Poloidal Field) system has been designed in detail. The Central Solenoid and the 6 equilibrium coils constituting the PF system provide the magnetic fields which develop, shape and control the 15 MA plasma during the 1800 s of a typical plasma scenario. The 6 PF coils will be wound two-in-hand from a 45 kA niobium-titanium CICC (Cable-In-Conduit-Conductor). These coils will experience severe heat loads specially during the 400 s of the plasma burn: nuclear heating due to the 400 MW of fusion power, thermal radiation and AC losses (30 to 300 kJ). The AC losses along the PF coil pancakes are deduced from accurate magnetic field computations performed with a 3D magnetostatic code, TRAPS. The nuclear heating and the thermal radiation are assumed to be uniform over a given face of the PF coils. These heat loads are used as input to perform the thermal and hydraulic analysis with a finite element code, GANDALF. The temperature increases (0.1 to 0.4 K) are computed, the margins and performances of the conductor are evaluated.

Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

DOEpatents

Petrini, Richard R.; Van Lue, Dorin F.

1983-01-01

A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment (12) with a probe coil (11), and associated coaxial coil cable (13), coil energizing means (21), and circuit means (21, 12) responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube 17 of fiberoptic scope 10. The scope 10 is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means (19, 20) for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

DOEpatents

Petrini, R.R.; Van Lue, D.F.

1983-10-25

A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, coil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signaling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level. 5 figs.

Performance of Upgraded Cooling System for Lhd Helical Coils

NASA Astrophysics Data System (ADS)

Hamaguchi, S.; Imagawa, S.; Obana, T.; Yanagi, N.; Moriuchi, S.; Sekiguchi, H.; Oba, K.; Mito, T.; Motojima, O.; Okamura, T.; Semba, T.; Yoshinaga, S.; Wakisaka, H.

2008-03-01

Helical coils of the Large Helical Device (LHD) are large scale superconducting magnets for heliotron plasma experiments. The helical coils had been cooled by saturated helium at 4.4 K, 120 kPa until 2005. An upgrade of the cooling system was carried out in 2006 in order to improve the cryogenic stability of the helical coils and then it has been possible to supply the coils with subcooled helium at 3.2 K, 120 kPa. A designed mass flow of the supplied subcooled helium is 50 g/s. The subcooled helium is generated at a heat exchanger in a saturated helium bath. A series of two centrifugal cold compressors with gas foil bearing is utilized to lower the helium pressure in the bath. The supplied helium temperature is regulated by rotational speed of the cold compressors and power of a heater in the bath. The mass flow of the supplied helium is also controlled manually by a supply valve and its surplus is evaporated by ten heaters at the outlet above the coils. In the present study, the performance of the cooling system has been investigated and a stable operating method has also developed. As the result, it was confirmed that the performance of the upgraded cooling system satisfies the requirements.

2D tilting MEMS micro mirror integrating a piezoresistive sensor position feedback

NASA Astrophysics Data System (ADS)

Lani, S.; Bayat, D.; Despont, M.

2015-02-01

An integrated position sensor for a dual-axis electromagnetic tilting mirror is presented. This tilting mirror is composed of a silicon based mirror directly assembled on a silicon membrane supported by flexible beams. The position sensors are constituted by 4 Wheatstone bridges of piezoresistors which are fabricated by doping locally the flexible beams. A permanent magnet is attached to the membrane and the scanner is mounted above planar coils deposited on a ceramic substrate to achieve electromagnetic actuation. The performances of the piezoresistive sensors are evaluated by measuring the output signal of the piezoresistors as a function of the tilt of the mirror and the temperature. White light interferometry was performed for all measurement to measure the exact tilt angle. The minimum detectable angle with such sensors was 30µrad (around 13bits) in the range of the minimum resolution of the interferometer. The tilt reproducibility was 0.0186%, obtained by measuring the tilt after repeated actuations with a coil current of 50mA during 30 min and the stability over time was 0.05% in 1h without actuation. The maximum measured tilt angle was 6° (mechanical) limited by nonlinearity of the MEMS system.

A magnetic resonance image-guided breast needle intervention robot system: overview and design considerations.

PubMed

Park, Samuel Byeongjun; Kim, Jung-Gun; Lim, Ki-Woong; Yoon, Chae-Hyun; Kim, Dong-Jun; Kang, Han-Sung; Jo, Yung-Ho

2017-08-01

We developed an image-guided intervention robot system that can be operated in a magnetic resonance (MR) imaging gantry. The system incorporates a bendable needle intervention robot for breast cancer patients that overcomes the space limitations of the MR gantry. Most breast coil designs for breast MR imaging have side openings to allow manual localization. However, for many intervention procedures, the patient must be removed from the gantry. A robotic manipulation system with integrated image guidance software was developed. Our robotic manipulator was designed to be slim, so as to fit between the patient's side and the MR gantry wall. Only non-magnetic materials were used, and an electromagnetic shield was employed for cables and circuits. The image guidance software was built using open source libraries. In situ feasibility tests were performed in a 3-T MR system. One target point in the breast phantom was chosen by the clinician for each experiment, and our robot moved the needle close to the target point. Without image-guided feedback control, the needle end could not hit the target point (distance = 5 mm) in the first experiment. Using our robotic system, the needle hits the target lesion of the breast phantom at a distance of 2.3 mm from the same target point using image-guided feedback. The second experiment was performed using other target points, and the distance between the final needle end point and the target point was 0.8 mm. We successfully developed an MR-guided needle intervention robot for breast cancer patients. Further research will allow the expansion of these interventions.

Counterbalance of cutting force for advanced milling operations

NASA Astrophysics Data System (ADS)

Tsai, Nan-Chyuan; Shih, Li-Wen; Lee, Rong-Mao

2010-05-01

The goal of this work is to concurrently counterbalance the dynamic cutting force and regulate the spindle position deviation under various milling conditions by integrating active magnetic bearing (AMB) technique, fuzzy logic algorithm and an adaptive self-tuning feedback loop. Since the dynamics of milling system is highly determined by a few operation conditions, such as speed of spindle, cut depth and feedrate, therefore the dynamic model for cutting process is more appropriate to be constructed by experiments, instead of using theoretical approach. The experimental data, either for idle or cutting, are utilized to establish the database of milling dynamics so that the system parameters can be on-line estimated by employing the proposed fuzzy logic algorithm as the cutting mission is engaged. Based on the estimated milling system model and preset operation conditions, i.e., spindle speed, cut depth and feedrate, the current cutting force can be numerically estimated. Once the current cutting force can be real-time estimated, the corresponding compensation force can be exerted by the equipped AMB to counterbalance the cutting force, in addition to the spindle position regulation by feedback of spindle position. On the other hand, for the magnetic force is nonlinear with respect to the applied electric current and air gap, the characteristics of the employed AMB is investigated also by experiments and a nonlinear mathematic model, in terms of air gap between spindle and electromagnetic pole and coil current, is developed. At the end, the experimental simulations on realistic milling are presented to verify the efficacy of the fuzzy controller for spindle position regulation and the capability of the dynamic cutting force counterbalance.

Stabilization of model-based networked control systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miranda, Francisco; Instituto Politécnico de Viana do Castelo, Viana do Castelo; Abreu, Carlos

2016-06-08

A class of networked control systems called Model-Based Networked Control Systems (MB-NCSs) is considered. Stabilization of MB-NCSs is studied using feedback controls and simulation of stabilization for different feedbacks is made with the purpose to reduce the network trafic. The feedback control input is applied in a compensated model of the plant that approximates the plant dynamics and stabilizes the plant even under slow network conditions. Conditions for global exponential stabilizability and for the choosing of a feedback control input for a given constant time between the information moments of the network are derived. An optimal control problem to obtainmore » an optimal feedback control is also presented.« less

Magnet Design with High B0 Homogeneity for Fast-Field-Cycling NMR Applications

NASA Astrophysics Data System (ADS)

Lips, O.; Privalov, A. F.; Dvinskikh, S. V.; Fujara, F.

2001-03-01

The design, construction, and performance of a low-inductance solenoidal coil with high B0 homogeneity for fast-field-cycling NMR is presented. It consists of six concentric layers. The conductor width is varied to minimize the B0 inhomogeneity in the volume of the sample. This is done using an algorithm which takes the real shape of the conductor directly into account. The calculated coil geometry can be manufactured easily using standard computerized numeric control equipment, which keeps the costs low. The coil is liquid cooled and produces a B0 field of 0.95 T at 800 A . The field inhomogeneity in a cylindrical volume (diameter 5 mm, length 10 mm) is about 10 ppm, and the inductance is 190 μH. Switching times below 200 μs can be achieved. During 6 months of operation the coil has shown good stability and reliability.

Kilotesla Magnetic Field due to a Capacitor-Coil Target Driven by High Power Laser

PubMed Central

Fujioka, Shinsuke; Zhang, Zhe; Ishihara, Kazuhiro; Shigemori, Keisuke; Hironaka, Youichiro; Johzaki, Tomoyuki; Sunahara, Atsushi; Yamamoto, Naoji; Nakashima, Hideki; Watanabe, Tsuguhiro; Shiraga, Hiroyuki; Nishimura, Hiroaki; Azechi, Hiroshi

2013-01-01

Laboratory generation of strong magnetic fields opens new frontiers in plasma and beam physics, astro- and solar-physics, materials science, and atomic and molecular physics. Although kilotesla magnetic fields have already been produced by magnetic flux compression using an imploding metal tube or plasma shell, accessibility at multiple points and better controlled shapes of the field are desirable. Here we have generated kilotesla magnetic fields using a capacitor-coil target, in which two nickel disks are connected by a U-turn coil. A magnetic flux density of 1.5 kT was measured using the Faraday effect 650 μm away from the coil, when the capacitor was driven by two beams from the GEKKO-XII laser (at 1 kJ (total), 1.3 ns, 0.53 or 1 μm, and 5 × 1016 W/cm2). PMID:23378905

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng,Y.; Liu, J.; Zheng, Q.

Entry of SARS coronavirus into its target cell requires large-scale structural transitions in the viral spike (S) glycoprotein in order to induce fusion of the virus and cell membranes. Here we describe the identification and crystal structures of four distinct a-helical domains derived from the highly conserved heptad-repeat (HR) regions of the S2 fusion subunit. The four domains are an antiparallel four-stranded coiled coil, a parallel trimeric coiled coil, a four-helix bundle, and a six-helix bundle that is likely the final fusogenic form of the protein. When considered together, the structural and thermodynamic features of the four domains suggest amore » possible mechanism whereby the HR regions, initially sequestered in the native S glycoprotein spike, are released and refold sequentially to promote membrane fusion. Our results provide a structural framework for understanding the control of membrane fusion and should guide efforts to intervene in the SARS coronavirus entry process.« less

Rho-associated coiled-coil kinase (ROCK) protein controls microtubule dynamics in a novel signaling pathway that regulates cell migration.

PubMed

Schofield, Alice V; Steel, Rohan; Bernard, Ora

2012-12-21

The two members of the Rho-associated coiled-coil kinase (ROCK1 and 2) family are established regulators of actin dynamics that are involved in the regulation of the cell cycle as well as cell motility and invasion. Here, we discovered a novel signaling pathway whereby ROCK regulates microtubule (MT) acetylation via phosphorylation of the tubulin polymerization promoting protein 1 (TPPP1/p25). We show that ROCK phosphorylation of TPPP1 inhibits the interaction between TPPP1 and histone deacetylase 6 (HDAC6), which in turn results in increased HDAC6 activity followed by a decrease in MT acetylation. As a consequence, we show that TPPP1 phosphorylation by ROCK increases cell migration and invasion via modulation of cellular acetyl MT levels. We establish here that the ROCK-TPPP1-HDAC6 signaling pathway is important for the regulation of cell migration and invasion.

Evaluating Internal Model Strength and Performance of Myoelectric Prosthesis Control Strategies.

PubMed

Shehata, Ahmed W; Scheme, Erik J; Sensinger, Jonathon W

2018-05-01

On-going developments in myoelectric prosthesis control have provided prosthesis users with an assortment of control strategies that vary in reliability and performance. Many studies have focused on improving performance by providing feedback to the user but have overlooked the effect of this feedback on internal model development, which is key to improve long-term performance. In this paper, the strength of internal models developed for two commonly used myoelectric control strategies: raw control with raw feedback (using a regression-based approach) and filtered control with filtered feedback (using a classifier-based approach), were evaluated using two psychometric measures: trial-by-trial adaptation and just-noticeable difference. The performance of both strategies was also evaluated using Schmidt's style target acquisition task. Results obtained from 24 able-bodied subjects showed that although filtered control with filtered feedback had better short-term performance in path efficiency ( ), raw control with raw feedback resulted in stronger internal model development ( ), which may lead to better long-term performance. Despite inherent noise in the control signals of the regression controller, these findings suggest that rich feedback associated with regression control may be used to improve human understanding of the myoelectric control system.

A high-precision miniaturized rotating coil transducer for magnetic measurements

DOE PAGES

Arpaia, P.; Buzio, M.; De Oliveira, R.; ...

2018-02-08

A miniaturized Printed Circuit Board (PCB) sensing coil, jointly developed by CERN and Fermilab for measuring the field of small-gap (less than 10 mm) accelerator magnets, is illustrated. A sensing coil array, with a scheme for compensating the main field when measuring the harmonic error components, hosted on a synthetic sapphire-based transducer, is presented. Key innovating features are (i) very-small size, both for the sensing coil array (thickness of 1.380 mm) and for the transducer (overall diameter of 7.350 mm), (ii) metrological performance, namely accuracy (more than five times better than state of the art), and 1-sigma repeatability (ten timesmore » better on harmonics with amplitude less than 100 ppm), and (iii) manufacturing technology of both the coil array (13 double layers aligned within 10 μm), and the sapphire support (concentricity, the most important uncertainty source for rotating coils, 3 μm of uncertainty, namely one order of magnitude better than fiberglass support). After stating the measurement problem, the design of the transducer and a case study of a two-layer PCB sensor array are also illustrated. Then, the prototyping and quality control of both the sensor and the transducer are discussed. Furthermore, the calibration and the results obtained with a prototype setup at Fermilab are presented. Finally, in the appendix, the theory of the rotating coil, the sensor geometry, and the harmonic compensation are briefly reviewed for the reader easiness.« less

A high-precision miniaturized rotating coil transducer for magnetic measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arpaia, P.; Buzio, M.; De Oliveira, R.

A miniaturized Printed Circuit Board (PCB) sensing coil, jointly developed by CERN and Fermilab for measuring the field of small-gap (less than 10 mm) accelerator magnets, is illustrated. A sensing coil array, with a scheme for compensating the main field when measuring the harmonic error components, hosted on a synthetic sapphire-based transducer, is presented. Key innovating features are (i) very-small size, both for the sensing coil array (thickness of 1.380 mm) and for the transducer (overall diameter of 7.350 mm), (ii) metrological performance, namely accuracy (more than five times better than state of the art), and 1-sigma repeatability (ten timesmore » better on harmonics with amplitude less than 100 ppm), and (iii) manufacturing technology of both the coil array (13 double layers aligned within 10 μm), and the sapphire support (concentricity, the most important uncertainty source for rotating coils, 3 μm of uncertainty, namely one order of magnitude better than fiberglass support). After stating the measurement problem, the design of the transducer and a case study of a two-layer PCB sensor array are also illustrated. Then, the prototyping and quality control of both the sensor and the transducer are discussed. Furthermore, the calibration and the results obtained with a prototype setup at Fermilab are presented. Finally, in the appendix, the theory of the rotating coil, the sensor geometry, and the harmonic compensation are briefly reviewed for the reader easiness.« less

Strategies in probabilistic feedback learning in Parkinson patients OFF medication.

PubMed

Bellebaum, C; Kobza, S; Ferrea, S; Schnitzler, A; Pollok, B; Südmeyer, M

2016-04-21

Studies on classification learning suggested that altered dopamine function in Parkinson's Disease (PD) specifically affects learning from feedback. In patients OFF medication, enhanced learning from negative feedback has been described. This learning bias was not seen in observational learning from feedback, indicating different neural mechanisms for this type of learning. The present study aimed to compare the acquisition of stimulus-response-outcome associations in PD patients OFF medication and healthy control subjects in active and observational learning. 16 PD patients OFF medication and 16 controls were examined with three parallel learning tasks each, two feedback-based (active and observational) and one non-feedback-based paired associates task. No acquisition deficit was seen in the patients for any of the tasks. More detailed analyses on the learning strategies did, however, reveal that the patients showed more lose-shift responses during active feedback learning than controls, and that lose-shift and win-stay responses more strongly determined performance accuracy in patients than controls. For observational feedback learning, the performance of both groups correlated similarly with the performance in non-feedback-based paired associates learning and with the accuracy of observed performance. Also, patients and controls showed comparable evidence of feedback processing in observational learning. In active feedback learning, PD patients use alternative learning strategies than healthy controls. Analyses on observational learning did not yield differences between patients and controls, adding to recent evidence of a differential role of the human striatum in active and observational learning from feedback. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

CONTROLLED NUCLEAR FUSION REACTOR

DOEpatents

Tuck, J.L.; Kruskal, M.; Colgate, S.A.; Rosenbluth, M.N.

1962-01-01

A plasma generating and heating device is described which comprises a ceramic torus with exterior layers of a thick metal membrane and a metallic coil. In operation, the coil generates a B/sub z/ field prior to the formation of an enclosing plasma sheath. Diffusion of the trapped magnetic field outward through the plasma sheath causes enhanced heating, particularly after the sheath has been pinched. (D.L.C.)

Patient and Partner Feedback Reports to Improve Statin Medication Adherence: A Randomized Control Trial.

PubMed

Reddy, Ashok; Huseman, Tiffany L; Canamucio, Anne; Marcus, Steven C; Asch, David A; Volpp, Kevin; Long, Judith A

2017-03-01

Simple nudges such as reminders and feedback reports to either a patient or a partner may facilitate improved medication adherence. To test the impact of a pill bottle used to monitor adherence, deliver a daily alarm, and generate weekly medication adherence feedback reports on statin adherence. Three-month, three-arm randomized clinical trial (ClinicalTrials.gov identifier: NCT02480530). One hundred and twenty-six veterans with known coronary artery disease and poor adherence (medication possession ratio <80 %). Patients were randomized to one of three groups: (1) a control group (n = 36) that received a pill-monitoring device with no alarms or feedback; (2) an individual feedback group (n = 36) that received a daily alarm and a weekly medication adherence feedback report; and (3) a partner feedback group (n = 54) that received an alarm and a weekly feedback report that was shared with a friend, family member, or a peer. The intervention continued for 3 months, and participants were followed for an additional 3 months after the intervention period. Adherence as measured by pill bottle. Secondary outcomes included change in LDL (mg/dl), patient activation, and social support. During the 3-month intervention period, medication adherence was higher in both feedback arms than in the control arm (individual feedback group 89 %, partner feedback group 86 %, control group 67 %; p < 0.001 and = 0.001). At 6 months, there was no difference in medication adherence between either of the feedback groups and the control (individual feedback 60 %, partner feedback 52 %, control group 54 %; p = 0.75 and 0.97). Daily alarms combined with individual or partner feedback reports improved statin medication adherence. While neither an individual feedback nor partner feedback strategy created a sustainable medication adherence habit, the intervention itself is relatively easy to implement and low cost.

Robust design of feedback feed-forward iterative learning control based on 2D system theory for linear uncertain systems

NASA Astrophysics Data System (ADS)

Li, Zhifu; Hu, Yueming; Li, Di

2016-08-01

For a class of linear discrete-time uncertain systems, a feedback feed-forward iterative learning control (ILC) scheme is proposed, which is comprised of an iterative learning controller and two current iteration feedback controllers. The iterative learning controller is used to improve the performance along the iteration direction and the feedback controllers are used to improve the performance along the time direction. First of all, the uncertain feedback feed-forward ILC system is presented by an uncertain two-dimensional Roesser model system. Then, two robust control schemes are proposed. One can ensure that the feedback feed-forward ILC system is bounded-input bounded-output stable along time direction, and the other can ensure that the feedback feed-forward ILC system is asymptotically stable along time direction. Both schemes can guarantee the system is robust monotonically convergent along the iteration direction. Third, the robust convergent sufficient conditions are given, which contains a linear matrix inequality (LMI). Moreover, the LMI can be used to determine the gain matrix of the feedback feed-forward iterative learning controller. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed schemes.

Control system for a small fission reactor

DOEpatents

Burelbach, J.P.; Kann, W.J.; Saiveau, J.G.

1985-02-08

A system for controlling the reactivity of a small fission reactor includes an elongated, flexible hollow tube in the general form of a helical coiled spring axially positioned around and outside of the reactor vessel in an annular space between the reactor vessel and a surrounding cylindrical-shaped neutron reflector. A neutron absorbing material is provided within the hollow tube with the rate of the reaction controlled by the extension and compression of the hollow tube, e.g., extension of the tube increases reactivity while its compression reduces reactivity, in varying the amount of neutron absorbing material disposed between the reactor vessel and the neutron reflector. Conventional mechanical displacement means may be employed to control the coil density of the hollow tube as desired.

Digital control system for space structure dampers

NASA Technical Reports Server (NTRS)

Haviland, J. K.

1985-01-01

A digital controller was developed using an SKD-51 System Design Kit, which incorporates an 8031 microcontroller. The necessary interfaces were installed in the wire wrap area of the SKD-51 and a pulse width modulator was developed to drive the coil of the actuator. Also, control equations were developed, using floating-point arithmetic. The design of the digital control system is emphasized, and it is shown that, provided certain rules are followed, an adequate design can be achieved. It is recommended that the so-called w-plane design method be used, and that the time elapsed before output of the up-dated coil-force signal be kept as small as possible. However, the cycle time for the controller should be watched carefully, because very small values for this time can lead to digital noise.

Feedback is the breakfast of champions: the significance of self-controlled formal feedback for autonomous task engagement.

PubMed

Meng, Liang; Yang, Zijing

2018-01-03

With the aim of examining the positive effect of the formal feedback mechanism itself beyond its informational aspect, we engaged participants in the stopwatch task and recorded their electroencephalogram throughout the experiment. This task requires a button press to stop the watch within a given time interval, the completion of which is simultaneously accompanied by adequate information on task performance. In the self-controlled feedback mode, participants could freely choose whether to request formal feedback after completing the task. In another mode, additional feedback was not provided. The 'non-choice' cue was found to elicit a more negative cue-elicited feedback negativity compared with 'choice', suggesting that the opportunity to solicit formal feedback was perceived as more desirable. In addition, a more enhanced stimulus-preceding negativity was observed prior to the task initiation cue in the self-controlled feedback condition, indicating that participants paid more sustained anticipatory attention during task preparation. Taken together, these electrophysiological results suggested an inherent reward within the formal feedback mechanism itself and the significance of self-controlled formal feedback for autonomous task engagement.

Observer-Based Adaptive Neural Network Control for Nonlinear Systems in Nonstrict-Feedback Form.

PubMed

Chen, Bing; Zhang, Huaguang; Lin, Chong

2016-01-01

This paper focuses on the problem of adaptive neural network (NN) control for a class of nonlinear nonstrict-feedback systems via output feedback. A novel adaptive NN backstepping output-feedback control approach is first proposed for nonlinear nonstrict-feedback systems. The monotonicity of system bounding functions and the structure character of radial basis function (RBF) NNs are used to overcome the difficulties that arise from nonstrict-feedback structure. A state observer is constructed to estimate the immeasurable state variables. By combining adaptive backstepping technique with approximation capability of radial basis function NNs, an output-feedback adaptive NN controller is designed through backstepping approach. It is shown that the proposed controller guarantees semiglobal boundedness of all the signals in the closed-loop systems. Two examples are used to illustrate the effectiveness of the proposed approach.

Low-to-Medium Power Single Chip Digital Controlled DC-DC Regulator for Point-of-Load Applications

NASA Technical Reports Server (NTRS)

Adell, Philippe C. (Inventor); Bakkaloglu, Bertan (Inventor); Vermeire, Bert (Inventor); Liu, Tao (Inventor)

2015-01-01

A DC-DC converter for generating a DC output voltage includes: a digitally controlled pulse width modulator (DPWM) for controlling a switching power stage to supply a varying voltage to an inductor; and a digital voltage feedback circuit for controlling the DPWM in accordance with a feedback voltage corresponding to the DC output voltage, the digital voltage feedback circuit including: a first voltage controlled oscillator for converting the feedback voltage into a first frequency signal and to supply the first frequency signal to a first frequency discriminator; a second voltage controlled oscillator for converting a reference voltage into a second frequency signal and to supply the second frequency signal to a second frequency discriminator; a digital comparator for comparing digital outputs of the first and second frequency discriminators and for outputting a digital feedback signal; and a controller for controlling the DPWM in accordance with the digital feedback signal.

Servo control booster system for minimizing following error

DOEpatents

Wise, William L.

1985-01-01

A closed-loop feedback-controlled servo system is disclosed which reduces command-to-response error to the system's position feedback resolution least increment, .DELTA.S.sub.R, on a continuous real-time basis for all operating speeds. The servo system employs a second position feedback control loop on a by exception basis, when the command-to-response error .gtoreq..DELTA.S.sub.R, to produce precise position correction signals. When the command-to-response error is less than .DELTA.S.sub.R, control automatically reverts to conventional control means as the second position feedback control loop is disconnected, becoming transparent to conventional servo control means. By operating the second unique position feedback control loop used herein at the appropriate clocking rate, command-to-response error may be reduced to the position feedback resolution least increment. The present system may be utilized in combination with a tachometer loop for increased stability.

Role of measurement in feedback-controlled quantum engines

NASA Astrophysics Data System (ADS)

Yi, Juyeon; Kim, Yong Woon

2018-01-01

In feedback controls, measurement is an essential step in designing protocols according to outcomes. For quantum mechanical systems, measurement has another effect; to supply energy to the measured system. We verify that in feedback-controlled quantum engines, measurement plays a dual role; not only as an auxiliary to perform feedback control but also as an energy supply to drive the engines. We consider a specific engine cycle exploiting feedback control followed by projective measurement and show that the maximum bound of the extractable work is set by both the efficacy of the feedback control and the energy change caused by projective measurement. We take a concrete example of an engine using an immobile spin-1/2 particle as a working substance and suggest two possible scenarios for work extraction.

Design, simulation and evaluation of uniform magnetic field systems for head-free eye movement recordings with scleral search coils.

PubMed

Eibenberger, Karin; Eibenberger, Bernhard; Rucci, Michele

2016-08-01

The precise measurement of eye movements is important for investigating vision, oculomotor control and vestibular function. The magnetic scleral search coil technique is one of the most precise measurement techniques for recording eye movements with very high spatial (≈ 1 arcmin) and temporal (>kHz) resolution. The technique is based on measuring voltage induced in a search coil through a large magnetic field. This search coil is embedded in a contact lens worn by a human subject. The measured voltage is in direct relationship to the orientation of the eye in space. This requires a magnetic field with a high homogeneity in the center, since otherwise the field inhomogeneity would give the false impression of a rotation of the eye due to a translational movement of the head. To circumvent this problem, a bite bar typically restricts head movement to a minimum. However, the need often emerges to precisely record eye movements under natural viewing conditions. To this end, one needs a uniform magnetic field that is uniform over a large area. In this paper, we present the numerical and finite element simulations of the magnetic flux density of different coil geometries that could be used for search coil recordings. Based on the results, we built a 2.2 × 2.2 × 2.2 meter coil frame with a set of 3 × 4 coils to generate a 3D magnetic field and compared the measured flux density with our simulation results. In agreement with simulation results, the system yields a highly uniform field enabling high-resolution recordings of eye movements.

State feedback controller design for the synchronization of Boolean networks with time delays

NASA Astrophysics Data System (ADS)

Li, Fangfei; Li, Jianning; Shen, Lijuan

2018-01-01

State feedback control design to make the response Boolean network synchronize with the drive Boolean network is far from being solved in the literature. Motivated by this, this paper studies the feedback control design for the complete synchronization of two coupled Boolean networks with time delays. A necessary condition for the existence of a state feedback controller is derived first. Then the feedback control design procedure for the complete synchronization of two coupled Boolean networks is provided based on the necessary condition. Finally, an example is given to illustrate the proposed design procedure.

Servo control of an optical trap.

PubMed

Wulff, Kurt D; Cole, Daniel G; Clark, Robert L

2007-08-01

A versatile optical trap has been constructed to control the position of trapped objects and ultimately to apply specified forces using feedback control. While the design, development, and use of optical traps has been extensive and feedback control has played a critical role in pushing the state of the art, few comprehensive examinations of feedback control of optical traps have been undertaken. Furthermore, as the requirements are pushed to ever smaller distances and forces, the performance of optical traps reaches limits. It is well understood that feedback control can result in both positive and negative effects in controlled systems. We give an analysis of the trapping limits as well as introducing an optical trap with a feedback control scheme that dramatically improves an optical trap's sensitivity at low frequencies.

High Accuracy Attitude Control of a Spacecraft Using Feedback Linearization

DTIC Science & Technology

1992-05-01

High Accuracy Attitude Control of a Spacecraft Using Feedback Linearization A Thesis Presented by Louis Joseph PoehIman, Captain, USAF B.S., U.S. Air...High Accuracy Attitude Control of a Spacecraft Using Feedback Linearization by Louis Joseph Poehlman, Captain, USAF Submitted to the Department of...31 2-4 Attitude Determination and Control System Architecture ................. 33 3-1 Exact Linearization Using Nonlinear Feedback

Modular coils and finite-β operation of a quasi-axially symmetric tokamak

NASA Astrophysics Data System (ADS)

Drevlak, M.

1998-09-01

Quasi-axially symmetric tokamaks (QA tokamaks) are an extension of the conventional tokamak concept. In these devices the magnetic field strength is independent of the generalized toroidal magnetic co-ordinate even though the cross-sectional shape changes. An optimized plasma equilibrium belonging to the class of QA tokamaks has been proposed by Nührenberg. It features the small aspect ratio of a tokamak while allowing part of the rotational transform to be generated by the external field. In this article, two particular aspects of the viability of QA tokamaks are explored, namely the feasibility of modular coils and the possibility of maintaining quasi-axial symmetry in the free-boundary equilibria obtained with the coils found. A set of easily feasible modular coils for the configuration is presented. It was designed using the extended version of the NESCOIL code (Merkel, P., Nucl. Fusion 27 (1987) 867). Using this coil system, free-boundary calculations of the plasma equilibrium were carried out using the NEMEC code (Hirshman, S.P., Van Rij, W.I., Merkel, P., Comput. Phys. Commun. 43 (1986) 143). It is observed that the effects of finite β and net toroidal plasma current can be compensated for with good precision by applying a vertical magnetic field and by separately adjusting the currents of the modular coils. A set of fully three dimensional (3-D) auxiliary coils is proposed to exert control on the rotational transform in the plasma. Deterioration of the quasi-axial symmetry induced by the auxiliary coils can be avoided by adequate adjustment of the currents in the primary coils. Finally, the neoclassical transport properties of the configuration are examined. It is observed that optimization with respect to confinement of the alpha particles can be maintained at operation with finite toroidal current if the aforementioned corrective measures are used. In this case, the neoclassical behaviour is shown to be very similar to that of a conventional tokamak.

Numerically simulated exposure of children and adults to pulsed gradient fields in MRI.

PubMed

Samoudi, Amine M; Vermeeren, Gunter; Tanghe, Emmeric; Van Holen, Roel; Martens, Luc; Josephs, Wout

2016-11-01

To determine exposure to gradient switching fields of adults and children in a magnetic resonance imaging (MRI) scanner by evaluating internal electric fields within realistic models of adult male, adult female, and child inside transverse and longitudinal gradient coils, and to compare these results with compliance guidelines. Patients inside x-, y-, and z-gradient coils were simulated using anatomically realistic models of adult male, adult female, and child. The induced electric fields were computed for 1 kHz sinusoidal current with a magnitude of 1 A in the gradient coils. Rheobase electric fields were then calculated and compared to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2004 and International Electrotechnical Commission (IEC) 2010 guidelines. The effect of the human body, coil type, and skin conductivity on the induced electric field was also investigated. The internal electric fields are within the first level controlled operating mode of the guidelines and range from 2.7V m -1 to 4.5V m -1 , except for the adult male inside the y-gradient coil (induced field reaches 5.4V m -1 ).The induced electric field is sensitive to the coil type (electric field in the skin of adult male: 4V m -1 , 4.6V m -1 , and 3.8V m -1 for x-, y-, and z-gradient coils, respectively), the human body model (electric field in the skin inside y-gradient coil: 4.6V m -1 , 4.2V m -1 , and 3V m -1 for adult male, adult female, and child, respectively), and the skin conductivity (electric field 2.35-4.29% higher for 0.1S m -1 skin conductivity compared to 0.2S m -1 ). The y-gradient coil induced the largest fields in the patients. The highest levels of internal electric fields occurred for the adult male model. J. Magn. Reson. Imaging 2016;44:1360-1367. © 2016 International Society for Magnetic Resonance in Medicine.

Solid-state circuit breaker with current-limiting characteristic using a superconducting coil

DOEpatents

Boenig, H.J.

1982-08-16

A thyristor bridge interposes an ac source and a load. A series connected DC source and superconducting coil within the bridge biases the thyristors thereof so as to permit bidirectional ac current flow therethrough under normal operating conditions. Upon a fault condition a control circuit triggers the thyristors so as to reduce ac current flow therethrough to zero in less than two eyeles and to open the bridge thereafter. Upon a temporary overload condition the control circuit triggers the thyristors so as to limit ac current flow therethrough to an acceptable level.

Solid-state circuit breaker with current limiting characteristic using a superconducting coil

DOEpatents

Boenig, Heinrich J.

1984-01-01

A thyristor bridge interposes an ac source and a load. A series connected DC source and superconducting coil within the bridge biases the thyristors thereof so as to permit bidirectional ac current flow therethrough under normal operating conditions. Upon a fault condition a control circuit triggers the thyristors so as to reduce ac current flow therethrough to zero in less than two cycles and to open the bridge thereafter. Upon a temporary overload condition the control circuit triggers the thyristors so as to limit ac current flow therethrough to an acceptable level.

On the interaction structure of linear multi-input feedback control systems. M.S. Thesis; [problem solving, lattices (mathematics)

NASA Technical Reports Server (NTRS)

Wong, P. K.

1975-01-01

The closely-related problems of designing reliable feedback stabilization strategy and coordinating decentralized feedbacks are considered. Two approaches are taken. A geometric characterization of the structure of control interaction (and its dual) was first attempted and a concept of structural homomorphism developed based on the idea of 'similarity' of interaction pattern. The idea of finding classes of individual feedback maps that do not 'interfere' with the stabilizing action of each other was developed by identifying the structural properties of nondestabilizing and LQ-optimal feedback maps. Some known stability properties of LQ-feedback were generalized and some partial solutions were provided to the reliable stabilization and decentralized feedback coordination problems. A concept of coordination parametrization was introduced, and a scheme for classifying different modes of decentralization (information, control law computation, on-line control implementation) in control systems was developed.

Temperature feedback control for long-term carrier-envelope phase locking

DOEpatents

Chang, Zenghu [Manhattan, KS; Yun, Chenxia [Manhattan, KS; Chen, Shouyuan [Manhattan, KS; Wang, He [Manhattan, KS; Chini, Michael [Manhattan, KS

2012-07-24

A feedback control module for stabilizing a carrier-envelope phase of an output of a laser oscillator system comprises a first photodetector, a second photodetector, a phase stabilizer, an optical modulator, and a thermal control element. The first photodetector may generate a first feedback signal corresponding to a first portion of a laser beam from an oscillator. The second photodetector may generate a second feedback signal corresponding to a second portion of the laser beam filtered by a low-pass filter. The phase stabilizer may divide the frequency of the first feedback signal by a factor and generate an error signal corresponding to the difference between the frequency-divided first feedback signal and the second feedback signal. The optical modulator may modulate the laser beam within the oscillator corresponding to the error signal. The thermal control unit may change the temperature of the oscillator corresponding to a signal operable to control the optical modulator.

A novel field generator for magnetic stimulation in cell culture experiments.

PubMed

Vogt, G; Schrefl, A; Mitteregger, R; Falkenhagen, D

1997-06-01

A novel field generator specially designed to examine the influence of low frequency magnetic fields on specific cell material was constructed and characterized. The exposure unit described in this paper consists of a controller unit and three sets of coils. The field generator permits a precious definition of the revelant signal parameters and allows the superposition of alternating current (AC) and direct current (DC) magnetic fields. Critical system parameters were monitored continuously. The three sets of coils, each arranged in the Helmholtz Configuration were characterized. After data processing and visualization the results showed a constant and homogeneous field within the experimental area. The special coil design also allows their use in an incubator.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozeki, H.; Isono, T.; Uno, Y.

JAEA successfully completed the manufacture of the toroidal field (TF) insert coil (TFIC) for a performance test of the ITER TF conductor in the final design in cooperation with Hitachi, Ltd. The TFIC is a single-layer 8.875-turn solenoid coil with 1.44-m diameter. This will be tested for 68-kA current application in a 13-T external magnetic field. TFIC was manufactured in the following order: winding of the TF conductor, lead bending, fabrication of the electrical termination, heat treatment, turn insulation, installation of the coil into the support mandrel structure, vacuum pressure impregnation (VPI), structure assembly, and instrumentation. Here in this presentation,more » manufacture process and quality control status for the TFIC manufacturing are reported.« less

Genome-Wide Identification of Arabidopsis Coiled-Coil Proteins and Establishment of the ARABI-COIL Database1

PubMed Central

Rose, Annkatrin; Manikantan, Sankaraganesh; Schraegle, Shannon J.; Maloy, Michael A.; Stahlberg, Eric A.; Meier, Iris

2004-01-01

Increasing evidence demonstrates the importance of long coiled-coil proteins for the spatial organization of cellular processes. Although several protein classes with long coiled-coil domains have been studied in animals and yeast, our knowledge about plant long coiled-coil proteins is very limited. The repeat nature of the coiled-coil sequence motif often prevents the simple identification of homologs of animal coiled-coil proteins by generic sequence similarity searches. As a consequence, counterparts of many animal proteins with long coiled-coil domains, like lamins, golgins, or microtubule organization center components, have not been identified yet in plants. Here, all Arabidopsis proteins predicted to contain long stretches of coiled-coil domains were identified by applying the algorithm MultiCoil to a genome-wide screen. A searchable protein database, ARABI-COIL (http://www.coiled-coil.org/arabidopsis), was established that integrates information on number, size, and position of predicted coiled-coil domains with subcellular localization signals, transmembrane domains, and available functional annotations. ARABI-COIL serves as a tool to sort and browse Arabidopsis long coiled-coil proteins to facilitate the identification and selection of candidate proteins of potential interest for specific research areas. Using the database, candidate proteins were identified for Arabidopsis membrane-bound, nuclear, and organellar long coiled-coil proteins. PMID:15020757

Investigating Cell-Material Interactions of Magnetospirillum magneticum as an Approach for Probing Submerged Surface Structural Integrity

DTIC Science & Technology

2012-07-01

developed a microscope- based , offset Helmholtz coil system with a custom-designed microcontroller. We have developed a microfabrication approach for...implemented an experimental model system using ferromagnetic beads. We have applied direct and frequency based magnetic fields for controlling magnetotactic...fields. Expanded Accomplishments We have developed a microscope- based , offset Helmholtz coil system with a custom- designed microcontroller. To be

Bias-field equalizer for bubble memories

NASA Technical Reports Server (NTRS)

Keefe, G. E.

1977-01-01

Magnetoresistive Perm-alloy sensor monitors bias field required to maintain bubble memory. Sensor provides error signal that, in turn, corrects magnitude of bias field. Error signal from sensor can be used to control magnitude of bias field in either auxiliary set of bias-field coils around permanent magnet field, or current in small coils used to remagnetize permanent magnet by infrequent, short, high-current pulse or short sequence of pulses.

Algorithms for output feedback, multiple-model, and decentralized control problems

NASA Technical Reports Server (NTRS)

Halyo, N.; Broussard, J. R.

1984-01-01

The optimal stochastic output feedback, multiple-model, and decentralized control problems with dynamic compensation are formulated and discussed. Algorithms for each problem are presented, and their relationship to a basic output feedback algorithm is discussed. An aircraft control design problem is posed as a combined decentralized, multiple-model, output feedback problem. A control design is obtained using the combined algorithm. An analysis of the design is presented.

Autonomous benthic algal cultivator under feedback control of ecosystem metabolism

USDA-ARS?s Scientific Manuscript database

An autonomous and internally-controlled techno-ecological hybrid was developed that controls primary production of algae in a laboratory-scale cultivator. The technoecosystem is based on an algal turf scrubber (ATS) system that combines engineered feedback control programming with internal feedback...

Non-Linear Signal Detection Improvement by Radiation Damping in Single-Pulse NMR Spectra

PubMed Central

Schlagnitweit, Judith; Morgan, Steven W; Nausner, Martin; Müller, Norbert; Desvaux, Hervé

2012-01-01

When NMR lines overlap and at least one of them is affected by radiation damping, the resonance line shapes of all lines are no longer Lorentzian. We report the appearance of narrow signal distortions, which resemble hole-burnt spectra. This new experimental phenomenon facilitates the detection of tiny signals hidden below the main resonance. Theoretical analysis based on modified Maxwell–Bloch equations shows that the presence of strong transverse magnetization creates a feedback through the coil, which influences the magnetization of all spins with overlapping resonance lines. In the time domain this leads to cross-precession terms between magnetization densities, which ultimately cause non-linear behavior. Numerical simulations corroborate this interpretation. PMID:22266720

Movement goals and feedback and feedforward control mechanisms in speech production

PubMed Central

Perkell, Joseph S.

2010-01-01

Studies of speech motor control are described that support a theoretical framework in which fundamental control variables for phonemic movements are multi-dimensional regions in auditory and somatosensory spaces. Auditory feedback is used to acquire and maintain auditory goals and in the development and function of feedback and feedforward control mechanisms. Several lines of evidence support the idea that speakers with more acute sensory discrimination acquire more distinct goal regions and therefore produce speech sounds with greater contrast. Feedback modification findings indicate that fluently produced sound sequences are encoded as feedforward commands, and feedback control serves to correct mismatches between expected and produced sensory consequences. PMID:22661828

Movement goals and feedback and feedforward control mechanisms in speech production.

PubMed

Perkell, Joseph S

2012-09-01

Studies of speech motor control are described that support a theoretical framework in which fundamental control variables for phonemic movements are multi-dimensional regions in auditory and somatosensory spaces. Auditory feedback is used to acquire and maintain auditory goals and in the development and function of feedback and feedforward control mechanisms. Several lines of evidence support the idea that speakers with more acute sensory discrimination acquire more distinct goal regions and therefore produce speech sounds with greater contrast. Feedback modification findings indicate that fluently produced sound sequences are encoded as feedforward commands, and feedback control serves to correct mismatches between expected and produced sensory consequences.

Effect of Hot Rolling Process on Microstructure and Properties of Low-Carbon Al-Killed Steels Produced Through TSCR Technology

NASA Astrophysics Data System (ADS)

Paul, S. K.; Ahmed, U.; Megahed, G. M.

2011-10-01

Low-carbon Al-killed hot rolled strips for direct forming, cold rolling, and galvanizing applications are produced from the similar chemistry at Ezz Flat Steel (EFS) through thin slab casting and rolling (TSCR) technology. The desired mechanical and microstructural properties in hot bands for different applications are achieved through control of hot rolling parameters, which in turn control the precipitation and growth of AlN. Nitrogen in solid solution strongly influences the yield strength (YS), ductility, strain aging index (SAI), and other formability properties of steel. The equilibrium solubility of AlN in austenite at different temperatures and its isothermal precipitation have been studied. To achieve the formability properties for direct forming, soluble nitrogen is fixed as AlN by coiling the strip at higher temperatures. For stringent cold forming, boron was added below the stoichiometric ratio with nitrogen, which improved the formability properties dramatically. The requirements of hot band for processing into cold rolled and annealed deep drawing sheets are high SAI and fine-grain microstructure. Higher finish rolling and low coiling temperatures are used to achieve these. Fully processed cold rolled sheets from these hot strips at customer's end have shown good formability properties. Coil break marks observed in some coils during uncoiling were found to be associated with yielding phenomenon. The spike height (difference between upper and lower yield stresses) and yield point elongation (YPE) were found to be the key material parameters for the break marks. Factors affecting these parameters have been studied and the coiling temperature optimized to overcome the problem.

Effects of Hesel-coil deep transcranial magnetic stimulation for depression - a systematic review.

PubMed

Nordenskjöld, Axel; Mårtensson, Björn; Pettersson, Agneta; Heintz, Emelie; Landén, Mikael

2016-10-01

One third of the depressed patients are not improved by antidepressant drugs and psychological treatments, and there is a need for additional treatments. Repetitive transcranial magnetic stimulation (rTMS) is being developed towards an alternative in treatment-resistant depression. Deep transcranial stimulation (dTMS) with the Hesel-coil (H-coil) is a further development of rTMS aiming to enhance the effect by getting the magnetic pulses to penetrate deeper into the brain. This report aims to assess the evidence-base for dTMS for depression. The report also includes an assessment of the ethical and economic aspects involved. A systematic review of the effects of H-coil dTMS on depression was conducted and the scientific support was evaluated using GRADE (Grading of Recommendations Assessment, Development and Evaluation). Only one controlled study was identified. In the sham-controlled randomized study, 212 participants with major depression that had not responded to antidepressant medication were enrolled. A two-point superiority in Hamilton Depression Rating Scale was observed in the dTMS arm vs the sham-arm at 4 weeks, but the difference was not statistically significant. No serious adverse events were reported apart from rare cases of epileptic seizures. The existing scientific support for H-coil dTMS therapy for depression is insufficient. The clinical implication is that the use of dTMS in depression should be restricted to the framework of clinical trials pending further studies. Fortunately, additional studies are underway and the evidence base should presumably improve over the next several years.

B1-control receive array coil (B-RAC) for reducing B1+ inhomogeneity in abdominal imaging at 3T-MRI

NASA Astrophysics Data System (ADS)

Kaneko, Yukio; Soutome, Yoshihisa; Habara, Hideta; Bito, Yoshitaka; Ochi, Hisaaki

2018-02-01

B1+ inhomogeneity in the human body increases as the nuclear magnetic resonance (NMR) frequency increases. Various methods have thus been developed to reduce B1+ inhomogeneity, such as a dielectric pad, a coupling coil, parallel transmit, and radio-frequency (RF) shimming. However, B1+ inhomogeneity still remains in some cases of abdominal imaging. In this study, we developed a B1-control receive array coil (B-RAC). Unlike the conventional receive array coil, B-RAC reduces B1+ inhomogeneity by using additional PIN diodes to generate the inductive loop during the RF transmit period. The inductive loop can generate dense and sparse regions of the magnetic flux, which can be used to compensate for B1+ inhomogeneity. First, B-RAC is modeled in the numerical simulation, and the spatial distributions of B1+ in a phantom and a human model were analyzed. Next, we fabricated a 12-channel B-RAC and measured receive sensitivity and B1+ maps in a 3T-MRI experiment. It was demonstrated that B-RAC can reduce B1+ inhomogeneity in the phantom and human model without increasing the maximum local specific absorption rate (SAR) in the body. B-RAC was also found to have almost the same the receive sensitivity as the conventional receive coil. Using RF shimming combined with B-RAC was revealed to more effectively reduce B1+ inhomogeneity than using only RF shimming. Therefore, B-RAC can reduce B1+ inhomogeneity while maintaining the receive sensitivity.

Effects of Hesel-coil deep transcranial magnetic stimulation for depression – a systematic review

PubMed Central

Nordenskjöld, Axel; Mårtensson, Björn; Pettersson, Agneta; Heintz, Emelie; Landén, Mikael

2016-01-01

Abstract Background: One third of the depressed patients are not improved by antidepressant drugs and psychological treatments, and there is a need for additional treatments. Repetitive transcranial magnetic stimulation (rTMS) is being developed towards an alternative in treatment-resistant depression. Deep transcranial stimulation (dTMS) with the Hesel-coil (H-coil) is a further development of rTMS aiming to enhance the effect by getting the magnetic pulses to penetrate deeper into the brain. Aims: This report aims to assess the evidence-base for dTMS for depression. The report also includes an assessment of the ethical and economic aspects involved. Methods: A systematic review of the effects of H-coil dTMS on depression was conducted and the scientific support was evaluated using GRADE (Grading of Recommendations Assessment, Development and Evaluation). Results: Only one controlled study was identified. In the sham-controlled randomized study, 212 participants with major depression that had not responded to antidepressant medication were enrolled. A two-point superiority in Hamilton Depression Rating Scale was observed in the dTMS arm vs the sham-arm at 4 weeks, but the difference was not statistically significant. No serious adverse events were reported apart from rare cases of epileptic seizures. Conclusions: The existing scientific support for H-coil dTMS therapy for depression is insufficient. The clinical implication is that the use of dTMS in depression should be restricted to the framework of clinical trials pending further studies. Fortunately, additional studies are underway and the evidence base should presumably improve over the next several years. PMID:27093104

Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications

PubMed Central

Pérez, Ramón José; Álvarez, Ignacio; Enguita, José María

2016-01-01

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10−5 °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results. PMID:27128924

Theoretical Design of a Depolarized Interferometric Fiber-Optic Gyroscope (IFOG) on SMF-28 Single-Mode Standard Optical Fiber Based on Closed-Loop Sinusoidal Phase Modulation with Serrodyne Feedback Phase Modulation Using Simulation Tools for Tactical and Industrial Grade Applications.

PubMed

Pérez, Ramón José; Álvarez, Ignacio; Enguita, José María

2016-04-27

This article presents, by means of computational simulation tools, a full analysis and design of an Interferometric Fiber-Optic Gyroscope (IFOG) prototype based on a closed-loop configuration with sinusoidal bias phase- modulation. The complete design of the different blocks, optical and electronic, is presented, including some novelties as the sinusoidal bias phase-modulation and the use of an integrator to generate the serrodyne phase-modulation signal. The paper includes detailed calculation of most parameter values, and the plots of the resulting signals obtained from simulation tools. The design is focused in the use of a standard single-mode optical fiber, allowing a cost competitive implementation compared to commercial IFOG, at the expense of reduced sensitivity. The design contains an IFOG model that accomplishes tactical and industrial grade applications (sensitivity ≤ 0.055 °/h). This design presents two important properties: (1) an optical subsystem with advanced conception: depolarization of the optical wave by means of Lyot depolarizers, which allows to use a sensing coil made by standard optical fiber, instead by polarization maintaining fiber, which supposes consequent cost savings and (2) a novel and simple electronic design that incorporates a linear analog integrator with reset in feedback chain, this integrator generating a serrodyne voltage-wave to apply to Phase-Modulator (PM), so that it will be obtained the interferometric phase cancellation. This particular feedback design with sawtooth-wave generated signal for a closed-loop configuration with sinusoidal bias phase modulation has not been reported till now in the scientific literature and supposes a considerable simplification with regard to previous designs based on similar configurations. The sensing coil consists of an 8 cm average diameter spool that contains 300 m of standard single-mode optical-fiber (SMF-28 type) realized by quadrupolar winding. The working wavelength will be 1310 nm. The theoretical calculated values of threshold sensitivity and dynamic range for this prototype are 0.052 °/h and 101.38 dB (from ±1.164 × 10(-5) °/s up to ±78.19 °/s), respectively. The Scale-Factor (SF) non-linearity for this model is 5.404% relative to full scale, this value being obtained from data simulation results.

Coherent feedback control of a single qubit in diamond

NASA Astrophysics Data System (ADS)

Hirose, Masashi; Cappellaro, Paola

2016-04-01

Engineering desired operations on qubits subjected to the deleterious effects of their environment is a critical task in quantum information processing, quantum simulation and sensing. The most common approach relies on open-loop quantum control techniques, including optimal-control algorithms based on analytical or numerical solutions, Lyapunov design and Hamiltonian engineering. An alternative strategy, inspired by the success of classical control, is feedback control. Because of the complications introduced by quantum measurement, closed-loop control is less pervasive in the quantum setting and, with exceptions, its experimental implementations have been mainly limited to quantum optics experiments. Here we implement a feedback-control algorithm using a solid-state spin qubit system associated with the nitrogen vacancy centre in diamond, using coherent feedback to overcome the limitations of measurement-based feedback, and show that it can protect the qubit against intrinsic dephasing noise for milliseconds. In coherent feedback, the quantum system is connected to an auxiliary quantum controller (ancilla) that acquires information about the output state of the system (by an entangling operation) and performs an appropriate feedback action (by a conditional gate). In contrast to open-loop dynamical decoupling techniques, feedback control can protect the qubit even against Markovian noise and for an arbitrary period of time (limited only by the coherence time of the ancilla), while allowing gate operations. It is thus more closely related to quantum error-correction schemes, although these require larger and increasing qubit overheads. Increasing the number of fresh ancillas enables protection beyond their coherence time. We further evaluate the robustness of the feedback protocol, which could be applied to quantum computation and sensing, by exploring a trade-off between information gain and decoherence protection, as measurement of the ancilla-qubit correlation after the feedback algorithm voids the protection, even if the rest of the dynamics is unchanged.

Magnetic field alignment of coil-coil diblock copolymers and blends via intrinsic chain anisotropy

NASA Astrophysics Data System (ADS)

Rokhlenko, Yekaterina; Majewski, Pawel; Larson, Steven; Yager, Kevin; Gopalan, Padma; Avgeropoulos, Apostolos; Chan, Edwin; Osuji, Chinedum

Magnetic fields can control alignment of self-assembled soft materials such as block copolymers provided there is a suitably large magnetic susceptibility anisotropy present in the system. Recent results have highlighted the existence of a non-trivial intrinsic anisotropy in coil-coil diblock copolymers, specifically in lamellar-forming PS-b-P4VP, which enables alignment at field strengths of a few tesla in systems lacking mesogenic components. Alignment is predicated on correlation in the orientation of end-end vectors implied by the localization of block junctions at the microdomain interface and is observed on cooling across the order-disorder transition in the presence of the field. For appropriate combinations of field strength and grain size, we can leverage intrinsic chain anisotropy to magnetically direct self-assembly of many non-mesogenic systems, including other coil-coil BCPs like PS-b-PDMS and PS-b-PMMA, blends of BCPs of disparate morphologies and MWs, and blends of BCPs with homopolymers. This is noteworthy as blends of PS-b-P4VP with PEO provide a route to form functional materials such as nanoporous films by dissolution of PEO, or aligned ion conduction materials. We survey these various systems using TEM and in-situ X-ray scattering to study the phase behavior and temperature-, time- and field- dependent dynamics of alignment.

Development of model for studies on momentum transfer in electrochemical cells with entry region coil as turbulence promoter

NASA Astrophysics Data System (ADS)

Penta Rao, Tamarba; Rajendra Prasad, P.

2018-04-01

Entry region swirl promoters gain importance in industry because of its effectiveness in augmentation of mass and heat transfer augmentation. Design of equipment needs momentum transfer data along with mass or heat transfer data. Hence an experimental investigation was carried out with coaxially placed entry region spiral coil as turbulence promoters on momentum transfer in forced convection flow of electrolyte in circular conduits. Aqueous solution of sodium hydroxide and 0.01 M equimolal Ferri-ferro cyanide system was chosen for the study. The study covered parameters like effect of pitch of the coil, effect of length of the coil, diameter of the coil, diameter of the coil wire, diameter of the annular rod. The promoter is measured by limiting current technique using diffusion controlled electrochemical reactions. The study comprises of evaluation of momentum transfer rates at the outer wall of the electrochemical cell. Pressure drop measurements were also made to obtain the energy consumption pattern. Within the range of variables covered. The results are correlated by the momentum transfer similarity function. Momentum transfer coefficients were evaluated from measured limiting currents. Effect of each parameter was studied in terms of friction factor. A model was developed for momentum transfer. The experimental data on momentum transfer was modeled in terms of momentum transfer function and Reynolds number, geometric parameters.

Rugged, portable tungsten coil atomic emission spectrometer.

PubMed

Gu, Jiyan; Oliveira, Silvana R; Donati, George L; Gomes Neto, José Anchieta; Jones, Bradley T

2011-04-01

Tungsten coil atomic emission spectrometry is an ideal technique for field applications because of its simplicity, low cost, low power requirement, and independence from cooling systems. A new, portable, compact design is reported here. The tungsten coil is extracted from an inexpensive 24 V, 250 W commercial light bulb. The coil is housed in a small, aluminum cell. The emission signal exits from a small aperture in the cell, while the bulk of the blackbody emission from the tungsten coil is blocked. The resulting spectra exhibit extremely low background signals. The atomization cell, a single lens, and a hand-held charge coupled device (CCD) spectrometer are fixed on a 1 × 6 × 30 cm ceramic base. The resulting system is robust and easily transported. A programmable, miniature 400 W solid-state constant current power supply controls the temperature of the coil. Fifteen elements are determined with the system (Ba, Cs, Li, Rb, Cr, Sr, Eu, Yb, Mn, Fe, Cu, Mg, V, Al, and Ga). The precision ranges from 4.3% to 8.4% relative standard deviation for repetitive measurements of the same solution. Detection limits are in the 0.04 to 1500 μg/L range. Accuracy is tested using standard reference materials for polluted water, peach leaves, and tomato leaves. For those elements present above the detection limit, recoveries range from 72% to 147%.

The N-terminal Part of Arabidopsis thaliana Starch Synthase 4 Determines the Localization and Activity of the Enzyme.

PubMed

Raynaud, Sandy; Ragel, Paula; Rojas, Tomás; Mérida, Ángel

2016-05-13

Starch synthase 4 (SS4) plays a specific role in starch synthesis because it controls the number of starch granules synthesized in the chloroplast and is involved in the initiation of the starch granule. We showed previously that SS4 interacts with fibrillins 1 and is associated with plastoglobules, suborganelle compartments physically attached to the thylakoid membrane in chloroplasts. Both SS4 localization and its interaction with fibrillins 1 were mediated by the N-terminal part of SS4. Here we show that the coiled-coil region within the N-terminal portion of SS4 is involved in both processes. Elimination of this region prevents SS4 from binding to fibrillins 1 and alters SS4 localization in the chloroplast. We also show that SS4 forms dimers, which depends on a region located between the coiled-coil region and the glycosyltransferase domain of SS4. This region is highly conserved between all SS4 enzymes sequenced to date. We show that the dimerization seems to be necessary for the activity of the enzyme. Both dimerization and the functionality of the coiled-coil region are conserved among SS4 proteins from phylogenetically distant species, such as Arabidopsis and Brachypodium This finding suggests that the mechanism of action of SS4 is conserved among different plant species. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Shaped magnetic field pulses by multi-coil repetitive transcranial magnetic stimulation (rTMS) differentially modulate anterior cingulate cortex responses and pain in volunteers and fibromyalgia patients

PubMed Central

2013-01-01

Background Repetitive transcranial magnetic stimulation (rTMS) has shown promise in the alleviation of acute and chronic pain by altering the activity of cortical areas involved in pain sensation. However, current single-coil rTMS technology only allows for effects in surface cortical structures. The ability to affect activity in certain deep brain structures may however, allow for a better efficacy, safety, and tolerability. This study used PET imaging to determine whether a novel multi-coil rTMS would allow for preferential targeting of the dorsal anterior cingulate cortex (dACC), an area always activated with pain, and to provide preliminary evidence as to whether this targeted approach would allow for efficacious, safe, and tolerable analgesia both in a volunteer/acute pain model as well as in fibromyalgia chronic pain patients. Methods Part 1: Different coil configurations were tested in a placebo-controlled crossover design in volunteers (N = 16). Tonic pain was induced using a capsaicin/thermal pain model and functional brain imaging was performed by means of H215O positron emission tomography – computed tomography (PET/CT) scans. Differences in NRS pain ratings between TMS and sham treatment (NRSTMS-NRSplacebo) which were recorded each minute during the 10 minute PET scans. Part 2: 16 fibromyalgia patients were subjected to 20 multi-coil rTMS treatments over 4 weeks and effects on standard pain scales (Brief Pain Inventory, item 5, i.e. average pain NRS over the last 24 hours) were recorded. Results A single 30 minute session using one of 3 tested rTMS coil configurations operated at 1 Hz consistently produced robust reduction (mean 70% on NRS scale) in evoked pain in volunteers. In fibromyalgia patients, the 20 rTMS sessions also produced a significant pain inhibition (43% reduction in NRS pain over last 24 hours), but only when operated at 10 Hz. This degree of pain control was maintained for at least 4 weeks after the final session. Conclusion Multi-coil rTMS may be a safe and effective treatment option for acute as well as for chronic pain, such as that accompanying fibromyalgia. Further studies are necessary to optimize configurations and settings as well as to elucidate the mechanisms that lead to the long-lasting pain control produced by these treatments. PMID:23819466

Servo control booster system for minimizing following error

DOEpatents

Wise, W.L.

1979-07-26

A closed-loop feedback-controlled servo system is disclosed which reduces command-to-response error to the system's position feedback resolution least increment, ..delta..S/sub R/, on a continuous real-time basis, for all operational times of consequence and for all operating speeds. The servo system employs a second position feedback control loop on a by exception basis, when the command-to-response error greater than or equal to ..delta..S/sub R/, to produce precise position correction signals. When the command-to-response error is less than ..delta..S/sub R/, control automatically reverts to conventional control means as the second position feedback control loop is disconnected, becoming transparent to conventional servo control means. By operating the second unique position feedback control loop used herein at the appropriate clocking rate, command-to-response error may be reduced to the position feedback resolution least increment. The present system may be utilized in combination with a tachometer loop for increased stability.

Research on Precision Tracking on Fast Steering Mirror and Control Strategy

NASA Astrophysics Data System (ADS)

Di, Lin; Yi-ming, Wu; Fan, Zhu

2018-01-01

Fast steering mirror is a device used for controlling the beam direction precisely. Due to the short travel of the push-pull FSM, a compound fast steering mirror system driven by both limited-angle voice coil motor and push-pull FSM together is proposed. In the compound FSM system, limited-angle voice coil motor quickly swings at wide angle, while the push-pull FSM do high frequency movement in a small range, which provides the system with the high bandwidth and long travel. In the control strategy, the method of combining feed-forward control in Kalman filtering with auto-disturbance rejection control is used to improve trajectory tracking accuracy. The simulation result shows that tracking accuracy measured by the compound method can be improved by more than 5 times than that of the conventional PID.

Comparison of Coil Designs for Transcranial Magnetic Stimulation on Mice

NASA Astrophysics Data System (ADS)

Rastogi, Priyam; Hadimani, Ravi; Jiles, David

2015-03-01

Transcranial magnetic stimulation (TMS) is a non-invasive treatment for neurological disorders using time varying magnetic field. The electric field generated by the time varying magnetic field is used to depolarize the brain neurons which can lead to measurable effects. TMS provides a surgical free method for the treatment of neurological brain disorders like depression, post-traumatic stress disorder, traumatic brain injury and Parkinson's disease. Before using TMS on human subjects, it is appropriate that its effects are verified on animals such as mice. The magnetic field intensity and stimulated region of the brain can be controlled by the shape, position and current in the coils. There are few reports on the designs of the coils for mice. In this paper, different types of coils are developed and compared using an anatomically realistic mouse model derived from MRI images. Parameters such as focality, depth of the stimulation, electric field strength on the scalp and in the deep brain regions, are taken into account. These parameters will help researchers to determine the most suitable coil design according to their need. This should result in improvements in treatment of specific disorders. Carver Charitable Trust.

Using finite element modelling and experimental methods to investigate planar coil sensor topologies for inductive measurement of displacement

NASA Astrophysics Data System (ADS)

Moreton, Gregory; Meydan, Turgut; Williams, Paul

2018-04-01

The usage of planar sensors is widespread due to their non-contact nature and small size profiles, however only a few basic design types are generally considered. In order to develop planar coil designs we have performed extensive finite element modelling (FEM) and experimentation to understand the performance of different planar sensor topologies when used in inductive sensing. We have applied this approach to develop a novel displacement sensor. Models of different topologies with varying pitch values have been analysed using the ANSYS Maxwell FEM package, furthermore the models incorporated a movable soft magnetic amorphous ribbon element. The different models used in the FEM were then constructed and experimentally tested with topologies that included mesh, meander, square coil, and circular coil configurations. The sensors were used to detect the displacement of the amorphous ribbon. A LabView program controlled both the displacement stage and the impedance analyser, the latter capturing the varying inductance values with ribbon displacement. There was good correlation between the FEM models and the experimental data confirming that the methodology described here offers an effective way for developing planar coil based sensors with improved performance.

Eddy current inspection tool. [Patent application

DOEpatents

Petrini, R.R.; Van Lue, D.F.

1980-10-29

A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, oil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of a fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator for generating audible signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

Trends in tungsten coil atomic spectrometry

NASA Astrophysics Data System (ADS)

Donati, George L.

Renewed interest in electrothermal atomic spectrometric methods based on tungsten coil atomizers is a consequence of a world wide increasing demand for fast, inexpensive, sensitive, and portable analytical methods for trace analysis. In this work, tungsten coil atomic absorption spectrometry (WCAAS) and tungsten coil atomic emission spectrometry (WCAES) are used to determine several different metals and even a non-metal at low levels in different samples. Improvements in instrumentation and new strategies to reduce matrix effects and background signals are presented. Investigation of the main factors affecting both WCAAS and WCAES analytical signals points to the importance of a reducing, high temperature gas phase in the processes leading to atomic cloud generation. Some more refractory elements such as V and Ti were determined for the first time by double tungsten coil atomic emission spectrometry (DWCAES). The higher temperatures provided by two atomizers in DWCAES also allowed the detection of Ag, Cu and Sn emission signals for the first time. Simultaneous determination of several elements by WCAES in relatively complex sample matrices was possible after a simple acid extraction. The results show the potential of this method as an alternative to more traditional, expensive methods for fast, more effective analyses and applications in the field. The development of a new metallic atomization cell is also presented. Lower limits of detection in both WCAAS and WCAES determinations were obtained due to factors such as better control of background signal, smaller, more isothermal system, with atomic cloud concentration at the optical path for a longer period of time. Tungsten coil-based methods are especially well suited to applications requiring low sample volume, low cost, sensitivity and portability. Both WCAAS and WCAES have great commercial potential in fields as diverse as archeology and industrial quality control. They are simple, inexpensive, effective methods for trace metal determinations in several different samples, representing an important asset in today's analytical chemistry.

An Adaptive Impedance Matching Network with Closed Loop Control Algorithm for Inductive Wireless Power Transfer

PubMed Central

Miao, Zhidong; Liu, Dake

2017-01-01

For an inductive wireless power transfer (IWPT) system, maintaining a reasonable power transfer efficiency and a stable output power are two most challenging design issues, especially when coil distance varies. To solve these issues, this paper presents a novel adaptive impedance matching network (IMN) for IWPT system. In our adaptive IMN IWPT system, the IMN is automatically reconfigured to keep matching with the coils and to adjust the output power adapting to coil distance variation. A closed loop control algorithm is used to change the capacitors continually, which can compensate mismatches and adjust output power simultaneously. The proposed adaptive IMN IWPT system is working at 125 kHz for 2 W power delivered to load. Comparing with the series resonant IWPT system and fixed IMN IWPT system, the power transfer efficiency of our system increases up to 31.79% and 60% when the coupling coefficient varies in a large range from 0.05 to 0.8 for 2 W output power. PMID:28763011

An Adaptive Impedance Matching Network with Closed Loop Control Algorithm for Inductive Wireless Power Transfer.

PubMed

Miao, Zhidong; Liu, Dake; Gong, Chen

2017-08-01

For an inductive wireless power transfer (IWPT) system, maintaining a reasonable power transfer efficiency and a stable output power are two most challenging design issues, especially when coil distance varies. To solve these issues, this paper presents a novel adaptive impedance matching network (IMN) for IWPT system. In our adaptive IMN IWPT system, the IMN is automatically reconfigured to keep matching with the coils and to adjust the output power adapting to coil distance variation. A closed loop control algorithm is used to change the capacitors continually, which can compensate mismatches and adjust output power simultaneously. The proposed adaptive IMN IWPT system is working at 125 kHz for 2 W power delivered to load. Comparing with the series resonant IWPT system and fixed IMN IWPT system, the power transfer efficiency of our system increases up to 31.79% and 60% when the coupling coefficient varies in a large range from 0.05 to 0.8 for 2 W output power.

Phase shifting interferometry based on a vibration sensor - feasibility study on elimination of the depth degeneracy

NASA Astrophysics Data System (ADS)

Lee, Seung Seok; Kim, Ju Ha; Choi, Eun Seo

2017-04-01

We proposed novel phase-shifting interferometry using a fiber-optic vibration sensor. The Doppler shift in the coiled fiber caused by vibrations can be used to detect the vibrations by using a fiber-optic interferometer. The principle can be applied to induce phase shifts. While applying vibrations to the coiled fiber at various vibration frequencies, we recorded the variations in the interference fringes. The interference fringe moved to longer wavelengths when a vibration frequency was increased from 38.00 to 38.40 kHz. Phase variations of 3.59 rad/kHz were obtained. The ability to accurately control the phase by using the vibrations in the coiled fiber was demonstrated by the elimination of the depth degeneracy using the complex signal generated by the phase-shifted interference fringes. Using vibrations to control phase shifting can be an acceptable alternative to conventional methods and can be applied to resolve the depth ambiguity in Fourier domain optical coherence tomography.

A combined stochastic feedforward and feedback control design methodology with application to autoland design

NASA Technical Reports Server (NTRS)

Halyo, Nesim

1987-01-01

A combined stochastic feedforward and feedback control design methodology was developed. The objective of the feedforward control law is to track the commanded trajectory, whereas the feedback control law tries to maintain the plant state near the desired trajectory in the presence of disturbances and uncertainties about the plant. The feedforward control law design is formulated as a stochastic optimization problem and is embedded into the stochastic output feedback problem where the plant contains unstable and uncontrollable modes. An algorithm to compute the optimal feedforward is developed. In this approach, the use of error integral feedback, dynamic compensation, control rate command structures are an integral part of the methodology. An incremental implementation is recommended. Results on the eigenvalues of the implemented versus designed control laws are presented. The stochastic feedforward/feedback control methodology is used to design a digital automatic landing system for the ATOPS Research Vehicle, a Boeing 737-100 aircraft. The system control modes include localizer and glideslope capture and track, and flare to touchdown. Results of a detailed nonlinear simulation of the digital control laws, actuator systems, and aircraft aerodynamics are presented.

Geometric foundations of the theory of feedback equivalence

NASA Technical Reports Server (NTRS)

Hermann, R.

1987-01-01

A description of feedback control is presented within the context of differential equations, differential geometry, and Lie theory. Work related to the integration of differential geometry with the control techniques of feedback linearization is summarized. Particular attention is given to the application of the theory of vector field systems. Feedback invariants for control systems in state space form are also addressed.

Cross-entropy optimization for neuromodulation.

PubMed

Brar, Harleen K; Yunpeng Pan; Mahmoudi, Babak; Theodorou, Evangelos A

2016-08-01

This study presents a reinforcement learning approach for the optimization of the proportional-integral gains of the feedback controller represented in a computational model of epilepsy. The chaotic oscillator model provides a feedback control systems view of the dynamics of an epileptic brain with an internal feedback controller representative of the natural seizure suppression mechanism within the brain circuitry. Normal and pathological brain activity is simulated in this model by adjusting the feedback gain values of the internal controller. With insufficient gains, the internal controller cannot provide enough feedback to the brain dynamics causing an increase in correlation between different brain sites. This increase in synchronization results in the destabilization of the brain dynamics, which is representative of an epileptic seizure. To provide compensation for an insufficient internal controller an external controller is designed using proportional-integral feedback control strategy. A cross-entropy optimization algorithm is applied to the chaotic oscillator network model to learn the optimal feedback gains for the external controller instead of hand-tuning the gains to provide sufficient control to the pathological brain and prevent seizure generation. The correlation between the dynamics of neural activity within different brain sites is calculated for experimental data to show similar dynamics of epileptic neural activity as simulated by the network of chaotic oscillators.

Hybrid Feedforward-Feedback Noise Control Using Virtual Sensors

NASA Technical Reports Server (NTRS)

Bean, Jacob; Fuller, Chris; Schiller, Noah

2016-01-01

Several approaches to active noise control using virtual sensors are evaluated for eventual use in an active headrest. Specifically, adaptive feedforward, feedback, and hybrid control structures are compared. Each controller incorporates the traditional filtered-x least mean squares algorithm. The feedback controller is arranged in an internal model configuration to draw comparisons with standard feedforward control theory results. Simulation and experimental results are presented that illustrate each controllers ability to minimize the pressure at both physical and virtual microphone locations. The remote microphone technique is used to obtain pressure estimates at the virtual locations. It is shown that a hybrid controller offers performance benefits over the traditional feedforward and feedback controllers. Stability issues associated with feedback and hybrid controllers are also addressed. Experimental results show that 15-20 dB reduction in broadband disturbances can be achieved by minimizing the measured pressure, whereas 10-15 dB reduction is obtained when minimizing the estimated pressure at a virtual location.

Delay-based virtual congestion control in multi-tenant datacenters

NASA Astrophysics Data System (ADS)

Liu, Yuxin; Zhu, Danhong; Zhang, Dong

2018-03-01

With the evolution of cloud computing and virtualization, the congestion control of virtual datacenters has become the basic issue for multi-tenant datacenters transmission. Regarding to the friendly conflict of heterogeneous congestion control among multi-tenant, this paper proposes a delay-based virtual congestion control, which translates the multi-tenant heterogeneous congestion control into delay-based feedback uniformly by setting the hypervisor translation layer, modifying three-way handshake of explicit feedback and packet loss feedback and throttling receive window. The simulation results show that the delay-based virtual congestion control can effectively solve the unfairness of heterogeneous feedback congestion control algorithms.

Comprehensive joint feedback control for standing by functional neuromuscular stimulation-a simulation study.

PubMed

Nataraj, Raviraj; Audu, Musa L; Kirsch, Robert F; Triolo, Ronald J

2010-12-01

Previous investigations of feedback control of standing after spinal cord injury (SCI) using functional neuromuscular stimulation (FNS) have primarily targeted individual joints. This study assesses the potential efficacy of comprehensive (trunk, hips, knees, and ankles) joint feedback control against postural disturbances using a bipedal, 3-D computer model of SCI stance. Proportional-derivative feedback drove an artificial neural network trained to produce muscle excitation patterns consistent with maximal joint stiffness values achievable about neutral stance given typical SCI muscle properties. Feedback gains were optimized to minimize upper extremity (UE) loading required to stabilize against disturbances. Compared to the baseline case of maximum constant muscle excitations used clinically, the controller reduced UE loading by 55% in resisting external force perturbations and by 84% during simulated one-arm functional tasks. Performance was most sensitive to inaccurate measurements of ankle plantar/dorsiflexion position and hip ab/adduction velocity feedback. In conclusion, comprehensive joint feedback demonstrates potential to markedly improve FNS standing function. However, alternative control structures capable of effective performance with fewer sensor-based feedback parameters may better facilitate clinical usage.

Comprehensive Joint Feedback Control for Standing by Functional Neuromuscular Stimulation – a Simulation Study

PubMed Central

Nataraj, Raviraj; Audu, Musa L.; Kirsch, Robert F.; Triolo, Ronald J.

2013-01-01

Previous investigations of feedback control of standing after spinal cord injury (SCI) using functional neuromuscular stimulation (FNS) have primarily targeted individual joints. This study assesses the potential efficacy of comprehensive (trunk, hips, knees, and ankles) joint-feedback control against postural disturbances using a bipedal, three-dimensional computer model of SCI stance. Proportional-derivative feedback drove an artificial neural network trained to produce muscle excitation patterns consistent with maximal joint stiffness values achievable about neutral stance given typical SCI muscle properties. Feedback gains were optimized to minimize upper extremity (UE) loading required to stabilize against disturbances. Compared to the baseline case of maximum constant muscle excitations used clinically, the controller reduced UE loading by 55% in resisting external force perturbations and by 84% during simulated one-arm functional tasks. Performance was most sensitive to inaccurate measurements of ankle plantar/dorsiflexion position and hip ab/adduction velocity feedback. In conclusion, comprehensive joint-feedback demonstrates potential to markedly improve FNS standing function. However, alternative control structures capable of effective performance with fewer sensor-based feedback parameters may better facilitate clinical usage. PMID:20923741

Optimal feedback scheme and universal time scaling for Hamiltonian parameter estimation.

PubMed

Yuan, Haidong; Fung, Chi-Hang Fred

2015-09-11

Time is a valuable resource and it is expected that a longer time period should lead to better precision in Hamiltonian parameter estimation. However, recent studies in quantum metrology have shown that in certain cases more time may even lead to worse estimations, which puts this intuition into question. In this Letter we show that by including feedback controls this intuition can be restored. By deriving asymptotically optimal feedback controls we quantify the maximal improvement feedback controls can provide in Hamiltonian parameter estimation and show a universal time scaling for the precision limit under the optimal feedback scheme. Our study reveals an intriguing connection between noncommutativity in the dynamics and the gain of feedback controls in Hamiltonian parameter estimation.

Initial development of the DIII–D snowflake divertor control

NASA Astrophysics Data System (ADS)

Kolemen, E.; Vail, P. J.; Makowski, M. A.; Allen, S. L.; Bray, B. D.; Fenstermacher, M. E.; Humphreys, D. A.; Hyatt, A. W.; Lasnier, C. J.; Leonard, A. W.; McLean, A. G.; Maingi, R.; Nazikian, R.; Petrie, T. W.; Soukhanovskii, V. A.; Unterberg, E. A.

2018-06-01

Simultaneous control of two proximate magnetic field nulls in the divertor region is demonstrated on DIII–D to enable plasma operations in an advanced magnetic configuration known as the snowflake divertor (SFD). The SFD is characterized by a second-order poloidal field null, created by merging two first-order nulls of the standard divertor configuration. The snowflake configuration has many magnetic properties, such as high poloidal flux expansion, large plasma-wetted area, and additional strike points, that are advantageous for divertor heat flux management in future fusion reactors. However, the magnetic configuration of the SFD is highly-sensitive to changes in currents within the plasma and external coils and therefore requires complex magnetic control. The first real-time snowflake detection and control system on DIII–D has been implemented in order to stabilize the configuration. The control algorithm calculates the position of the two nulls in real-time by locally-expanding the Grad–Shafranov equation in the divertor region. A linear relation between variations in the poloidal field coil currents and changes in the null locations is then analytically derived. This formulation allows for simultaneous control of multiple coils to achieve a desired SFD configuration. It is shown that the control enabled various snowflake configurations on DIII–D in scenarios such as the double-null advanced tokamak. The SFD resulted in a 2.5×  reduction in the peak heat flux for many energy confinement times (2–3 s) without any adverse effects on core plasma performance.

Post-traumatic hepatic artery pseudo-aneurysm combined with subphrenic liver abscess treated with embolization

PubMed Central

Sun, Long; Guan, Yong-Song; Wu, Hua; Pan, Wei-Min; Li, Xiao; He, Qing; Liu, Yuan

2006-01-01

A 23-year-old man with post-traumatic hepatic artery pseudo-aneurysm and subphrenic liver abscess was admitted. He underwent coil embolization of hepatic artery pseudo-aneurysm. The pseudo-aneurysm was successfully obstructed and subphrenic liver abscess was controlled. Super-selective trans-catheter coil embolization may represent an effective treatment for hepatic artery pseudo-aneurysm combined with subphrenic liver abscess in the absence of other therapeutic alternatives. PMID:16718774

Post-traumatic hepatic artery pseudo-aneurysm combined with subphrenic liver abscess treated with embolization.

PubMed

Sun, Long; Guan, Yong-Song; Wu, Hua; Pan, Wei-Min; Li, Xiao; He, Qing; Liu, Yuan

2006-05-07

A 23-year-old man with post-traumatic hepatic artery pseudo-aneurysm and subphrenic liver abscess was admitted. He underwent coil embolization of hepatic artery pseudo-aneurysm. The pseudo-aneurysm was successfully obstructed and subphrenic liver abscess was controlled. Super-selective trans-catheter coil embolization may represent an effective treatment for hepatic artery pseudo-aneurysm combined with subphrenic liver abscess in the absence of other therapeutic alternatives.

Method for neural network control of motion using real-time environmental feedback

NASA Technical Reports Server (NTRS)

Buckley, Theresa M. (Inventor)

1997-01-01

A method of motion control for robotics and other automatically controlled machinery using a neural network controller with real-time environmental feedback. The method is illustrated with a two-finger robotic hand having proximity sensors and force sensors that provide environmental feedback signals. The neural network controller is taught to control the robotic hand through training sets using back- propagation methods. The training sets are created by recording the control signals and the feedback signal as the robotic hand or a simulation of the robotic hand is moved through a representative grasping motion. The data recorded is divided into discrete increments of time and the feedback data is shifted out of phase with the control signal data so that the feedback signal data lag one time increment behind the control signal data. The modified data is presented to the neural network controller as a training set. The time lag introduced into the data allows the neural network controller to account for the temporal component of the robotic motion. Thus trained, the neural network controlled robotic hand is able to grasp a wide variety of different objects by generalizing from the training sets.

Feedback control of flow vorticity at low Reynolds numbers.

PubMed

Zeitz, Maria; Gurevich, Pavel; Stark, Holger

2015-03-01

Our aim is to explore strategies of feedback control to design and stabilize novel dynamic flow patterns in model systems of complex fluids. To introduce the control strategies, we investigate the simple Newtonian fluid at low Reynolds number in a circular geometry. Then, the fluid vorticity satisfies a diffusion equation. We determine the mean vorticity in the sensing area and use two control strategies to feed it back into the system by controlling the angular velocity of the circular boundary. Hysteretic feedback control generates self-regulated stable oscillations in time, the frequency of which can be adjusted over several orders of magnitude by tuning the relevant feedback parameters. Time-delayed feedback control initiates unstable vorticity modes for sufficiently large feedback strength. For increasing delay time, we first observe oscillations with beats and then regular trains of narrow pulses. Close to the transition line between the resting fluid and the unstable modes, these patterns are relatively stable over long times.

Robust Frequency-Domain Constrained Feedback Design via a Two-Stage Heuristic Approach.

PubMed

Li, Xianwei; Gao, Huijun

2015-10-01

Based on a two-stage heuristic method, this paper is concerned with the design of robust feedback controllers with restricted frequency-domain specifications (RFDSs) for uncertain linear discrete-time systems. Polytopic uncertainties are assumed to enter all the system matrices, while RFDSs are motivated by the fact that practical design specifications are often described in restricted finite frequency ranges. Dilated multipliers are first introduced to relax the generalized Kalman-Yakubovich-Popov lemma for output feedback controller synthesis and robust performance analysis. Then a two-stage approach to output feedback controller synthesis is proposed: at the first stage, a robust full-information (FI) controller is designed, which is used to construct a required output feedback controller at the second stage. To improve the solvability of the synthesis method, heuristic iterative algorithms are further formulated for exploring the feedback gain and optimizing the initial FI controller at the individual stage. The effectiveness of the proposed design method is finally demonstrated by the application to active control of suspension systems.

Optimization of Closed Loop Eigenvalues: Maneuvering, Vibration Control, and Structure/Control Design Iteration for Flexible Spacecraft.

DTIC Science & Technology

1986-05-31

Nonlinear Feedback Control 8-16 for Spacecraft Attitude Maneuvers" 2. " Spacecraft Attitude Control Using 17-35... nonlinear state feedback control laws are developed for space- craft attitude control using the Euler parameters and conjugate angular momenta. Time... Nonlinear Feedback Control for Spacecraft Attitude Maneuvers," to appear in AIAA J. of Guidance, Control, and Dynamics, (AIAA Paper No. 83-2230-CP,

A novel method of sensing temperatures of magnet coils of SINP-MaPLE plasma device

NASA Astrophysics Data System (ADS)

Pal, A. M.; Bhattacharya, S.; Biswas, S.; Basu, S.; Pal, R.

2014-03-01

A set of 36 magnet coils is used to produce a continuous, uniform magnetic field of about 0.35 Tesla inside the vacuum chamber of the MaPLE Device, a linear laboratory plasma device (3 m long and 0.30 m in diameter) built for studying basic magnetized plasma physics phenomena. To protect the water cooled-coils from serious damage due to overheating temperatures of all the coils are monitored electronically using low cost temperature sensor IC chips, a technique first being used in similar magnet system. Utilizing the Parallel Port of a Personal Computer a novel scheme is used to avoid deploying microprocessor that is associated with involved circuitry and low level programming to address and control the large number of sensors. The simple circuits and a program code to implement the idea are developed, tested and presently in operation. The whole arrangement comes out to be not only attractive, but also simple, economical and easy to install elsewhere.

Numerical optimization of three-dimensional coils for NSTX-U

DOE PAGES

Lazerson, S. A.; Park, J. -K.; Logan, N.; ...

2015-09-03

A tool for the calculation of optimal three-dimensional (3D) perturbative magnetic fields in tokamaks has been developed. The IPECOPT code builds upon the stellarator optimization code STELLOPT to allow for optimization of linear ideal magnetohydrodynamic perturbed equilibrium (IPEC). This tool has been applied to NSTX-U equilibria, addressing which fields are the most effective at driving NTV torques. The NTV torque calculation is performed by the PENT code. Optimization of the normal field spectrum shows that fields with n = 1 character can drive a large core torque. It is also shown that fields with n = 3 features are capablemore » of driving edge torque and some core torque. Coil current optimization (using the planned in-vessel and existing RWM coils) on NSTX-U suggest the planned coils set is adequate for core and edge torque control. In conclusion, comparison between error field correction experiments on DIII-D and the optimizer show good agreement.« less

Why self-controlled feedback enhances motor learning: Answers from electroencephalography and indices of motivation.

PubMed

Grand, Kirk F; Bruzi, Alessandro T; Dyke, Ford B; Godwin, Maurice M; Leiker, Amber M; Thompson, Andrew G; Buchanan, Taylor L; Miller, Matthew W

2015-10-01

It was tested whether learners who choose when to receive augmented feedback while practicing a motor skill exhibit enhanced augmented feedback processing and intrinsic motivation, along with superior learning, relative to learners who do not control their feedback. Accordingly, participants were assigned to either self-control (Self) or yoked groups and asked to practice a non-dominant arm beanbag toss. Self participants received augmented feedback at their discretion, whereas Yoked participants were given feedback schedules matched to Self counterparts. Participants' visual feedback was occluded, and when they received augmented feedback, their processing of it was indexed with the electroencephalography-derived feedback-related negativity (FRN). Participants self-reported intrinsic motivation via the Intrinsic Motivation Inventory (IMI) after practice, and completed a retention and transfer test the next day to index learning. Results partially support the hypothesis. Specifically, Self participants reported higher IMI scores, exhibited larger FRNs, and demonstrated better accuracy on the transfer test, but not on the retention test, nor did they exhibit greater consistency on the retention or transfer tests. Additionally, post-hoc multiple regression analysis indicated FRN amplitude predicted transfer test accuracy (accounting for IMI score). Results suggest self-controlled feedback schedules enhance feedback processing, which enhances the transfer of a newly acquired motor skill. Copyright © 2015 Elsevier B.V. All rights reserved.

Motivation in vigilance - Effects of self-evaluation and experimenter-controlled feedback.

NASA Technical Reports Server (NTRS)

Warm, J. S.; Kanfer, F. H.; Kuwada, S.; Clark, J. L.

1972-01-01

Vigilance experiments have been performed to study the relative efficiency of feedback operations in enhancing vigilance performance. Two feedback operations were compared - i.e., experimenter-controlled feedback in the form of knowledge of results (KR) regarding response times to signal detections, and subject-controlled feedback in the form of self-evaluation (SE) of response times to signal detections. The subjects responded to the aperiodic offset of a visual signal during a 1-hr vigil. Both feedback operations were found to enhance performance efficiency: subjects in the KR and SE conditions had faster response times than controls receiving no evaluative feedback. Moreover, the data of the KR and SE groups did not differ significantly from each other. The results are discussed in terms of the hypothesis that self-evaluation is a critical factor underlying the incentive value of KR in vigilance tasks.

Advanced Manufacturing of Superconducting Magnets

NASA Technical Reports Server (NTRS)

Senti, Mark W.

1996-01-01

The development of specialized materials, processes, and robotics technology allows for the rapid prototype and manufacture of superconducting and normal magnets which can be used for magnetic suspension applications. Presented are highlights of the Direct Conductor Placement System (DCPS) which enables automatic design and assembly of 3-dimensional coils and conductor patterns using LTS and HTS conductors. The system enables engineers to place conductors in complex patterns with greater efficiency and accuracy, and without the need for hard tooling. It may also allow researchers to create new types of coils and patterns which were never practical before the development of DCPS. The DCPS includes a custom designed eight-axis robot, patented end effector, CoilCAD(trademark) design software, RoboWire(trademark) control software, and automatic inspection.

Electronic circuit provides accurate sensing and control of dc voltage

NASA Technical Reports Server (NTRS)

Loftus, W. D.

1966-01-01

Electronic circuit used relay coil to sense and control dc voltage. The control relay is driven by a switching transistor that is biased to cutoff for all input up to slightly less than the threshold level.

Effect of Concurrent Visual Feedback Frequency on Postural Control Learning in Adolescents.

PubMed

Marco-Ahulló, Adrià; Sánchez-Tormo, Alexis; García-Pérez, José A; Villarrasa-Sapiña, Israel; González, Luis M; García-Massó, Xavier

2018-04-13

The purpose was to find better augmented visual feedback frequency (100% or 67%) for learning a balance task in adolescents. Thirty subjects were divided randomly into a control group, and 100% and 67% feedback groups. The three groups performed pretest (3 trials), practice (12 trials), posttest (3 trials) and retention (3 trials, 24 hours later). The reduced feedback group showed lower RMS in the posttest than in the pretest (p = 0.04). The control and reduced feedback groups showed significant lower median frequency in the posttest than in the pretest (p < 0.05). Both feedback groups showed lower values in retention than in the pretest (p < 0.05). Even when the effect of feedback frequency could not be detected in motor learning, 67% of the feedback was recommended for motor adaptation.

Verbal communication improves laparoscopic team performance.

PubMed

Shiliang Chang; Waid, Erin; Martinec, Danny V; Bin Zheng; Swanstrom, Lee L

2008-06-01

The impact of verbal communication on laparoscopic team performance was examined. A total of 24 dyad teams, comprised of residents, medical students, and office staff, underwent 2 team tasks using a previously validated bench model. Twelve teams (feedback groups) received instant verbal instruction and feedback on their performance from an instructor which was compared with 12 teams (control groups) with minimal or no verbal feedback. Their performances were both video and audio taped for analysis. Surgical backgrounds were similar between feedback and control groups. Teams with more verbal feedback achieved significantly better task performance (P = .002) compared with the control group with less feedback. Impact of verbal feedback was more pronounced for tasks requiring team cooperation (aiming and navigation) than tasks depending on individual skills (knotting). Verbal communication, especially the instructions and feedback from an experienced instructor, improved team efficiency and performance.

Open-loop characteristics of magnetic suspension systems using electromagnets mounted in a planar array

NASA Technical Reports Server (NTRS)

Groom, Nelson J.; Britcher, Colin P.

1992-01-01

The open-loop characteristics of a Large-Gap Magnetic Suspension System (LGMSS) were studied and numerical results are presented. The LGMSS considered provides five-degree-of-freedom control. The suspended element is a cylinder that contains a core composed of permanent magnet material. The magnetic actuators are air core electromagnets mounted in a planar array. Configurations utilizing five, six, seven, and eight electromagnets were investigated and all configurations were found to be controllable from coil currents and observable from suspended element positions. Results indicate that increasing the number of coils has an insignificant effect on mode shapes and frequencies.

Feedback power control strategies in wireless sensor networks with joint channel decoding.

PubMed

Abrardo, Andrea; Ferrari, Gianluigi; Martalò, Marco; Perna, Fabio

2009-01-01

In this paper, we derive feedback power control strategies for block-faded multiple access schemes with correlated sources and joint channel decoding (JCD). In particular, upon the derivation of the feasible signal-to-noise ratio (SNR) region for the considered multiple access schemes, i.e., the multidimensional SNR region where error-free communications are, in principle, possible, two feedback power control strategies are proposed: (i) a classical feedback power control strategy, which aims at equalizing all link SNRs at the access point (AP), and (ii) an innovative optimized feedback power control strategy, which tries to make the network operational point fall in the feasible SNR region at the lowest overall transmit energy consumption. These strategies will be referred to as "balanced SNR" and "unbalanced SNR," respectively. While they require, in principle, an unlimited power control range at the sources, we also propose practical versions with a limited power control range. We preliminary consider a scenario with orthogonal links and ideal feedback. Then, we analyze the robustness of the proposed power control strategies to possible non-idealities, in terms of residual multiple access interference and noisy feedback channels. Finally, we successfully apply the proposed feedback power control strategies to a limiting case of the class of considered multiple access schemes, namely a central estimating officer (CEO) scenario, where the sensors observe noisy versions of a common binary information sequence and the AP's goal is to estimate this sequence by properly fusing the soft-output information output by the JCD algorithm.

Comparing the Effects of Self-Controlled and Examiner-Controlled Feedback on Learning in Children With Developmental Coordination Disorder.

PubMed

Zamani, Mohamad Hosein; Fatemi, Rouholah; Soroushmoghadam, Keyvan

2015-12-01

Feedback can improve task learning in children with developmental coordination disorder (DCD). However, the frequency and type of feedback may play different role in learning and needs to more investigations. The aim of this study was to evaluate the acquisition and retention of new feedback skills in children with DCD under different frequency of self-control and control examiner feedback. In this quasi-experimental study with pretest-posttest design, participants based on their retention were divided into four feedback groups: self-controlled feedback groups with frequencies of 50% and75%, experimenter controls with frequencies of 50% and 75%. The study sample consisted of 24 boys with DCD aged between 9 to 11 years old in Ahvaz City, Iran. Then subjects practiced 30 throwing (6 blocks of 5 attempts) in eighth session. Acquisition test immediately after the last training session, and then the retention test were taken. Data were analyzed using the paired t-test, ANOVA and Tukey tests. The results showed no significant difference between groups in the acquisition phase (P > 0.05). However,in the retention session, group of self-control showed better performance than the control tester group (P < 0.05). Based on the current findings, self-control feedback with high frequency leads to more learning in DCD children. The results of this study can be used in rehabilitation programs to improve performance and learning in children with DCD.

Short- and Long-Term Learning of Feedforward Control of a Myoelectric Prosthesis with Sensory Feedback by Amputees.

PubMed

Strbac, Matija; Isakovic, Milica; Belic, Minja; Popovic, Igor; Simanic, Igor; Farina, Dario; Keller, Thierry; Dosen, Strahinja

2017-11-01

Human motor control relies on a combination of feedback and feedforward strategies. The aim of this study was to longitudinally investigate artificial somatosensory feedback and feedforward control in the context of grasping with myoelectric prosthesis. Nine amputee subjects performed routine grasping trials, with the aim to produce four levels of force during four blocks of 60 trials across five days. The electrotactile force feedback was provided in the second and third block using multipad electrode and spatial coding. The first baseline and last validation block (open-loop control) evaluated the effects of long- (across sessions) and short-term (within session) learning, respectively. The outcome measures were the absolute error between the generated and target force, and the number of force saturations. The results demonstrated that the electrotactile feedback improved the performance both within and across sessions. In the validation block, the performance did not significantly decrease and the quality of open-loop control (baseline) improved across days, converging to the performance characterizing closed-loop control. This paper provides important insights into the feedback and feedforward processes in prosthesis control, contributing to the better understanding of the role and design of feedback in prosthetic systems.

Robust high-performance control for robotic manipulators

NASA Technical Reports Server (NTRS)

Seraji, H.

1989-01-01

A robust control scheme to accomplish accurate trajectory tracking for an integrated system of manipulator-plus-actuators is proposed. The control scheme comprises a feedforward and a feedback controller. The feedforward controller contains any known part of the manipulator dynamics that can be used for online control. The feedback controller consists of adaptive position and velocity feedback gains and an auxiliary signal which is simply generated by a fixed-gain proportional/integral/derivative controller. The feedback controller is updated by very simple adaptation laws which contain both proportional and integral adaptation terms. By introduction of a simple sigma modification to the adaptation laws, robustness is guaranteed in the presence of unmodeled dynamics and disturbances.

49 CFR 236.555 - Repaired or rewound receiver coil.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and Cab Signal Systems Rules and Instructions; Locomotives § 236.555 Repaired...

49 CFR 236.555 - Repaired or rewound receiver coil.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES Automatic Train Stop, Train Control and Cab Signal Systems Rules and Instructions; Locomotives § 236.555 Repaired...

V/STOL tilt rotor aircraft study. Volume 7: Tilt rotor flight control program feedback studies

NASA Technical Reports Server (NTRS)

Alexander, H. R.; Eason, W.; Gillmore, K.; Morris, J.; Spittle, R.

1973-01-01

An exploratory study has been made of the use of feedback control in tilt rotor aircraft. This has included the use of swashplate cyclic and collective controls and direct lift control. Various sensor and feedback systems are evaluated in relation to blade loads alleviation, improvement in flying qualities, and modal suppression. Recommendations are made regarding additional analytical and wind tunnel investigations and development of feedback systems in the full scale flight vehicle. Estimated costs and schedules are given.

Walking Flexibility after Hemispherectomy: Split-Belt Treadmill Adaptation and Feedback Control

ERIC Educational Resources Information Center

Choi, Julia T.; Vining, Eileen P. G.; Reisman, Darcy S.; Bastian, Amy J.

2009-01-01

Walking flexibility depends on use of feedback or reactive control to respond to unexpected changes in the environment, and the ability to adapt feedforward or predictive control for sustained alterations. Recent work has demonstrated that cerebellar damage impairs feedforward adaptation, but not feedback control, during human split-belt treadmill…

Design of beta-domain swapping, alpha/beta-protein, environmentally sensitive coiled coil and peptide functionalized titania materials

NASA Astrophysics Data System (ADS)

Nagarkar, Radhika P.

2009-12-01

The objective of this dissertation is to apply rational peptide design to fabricate nanomaterials via self-assembly. This has been demonstrated in structurally diverse systems with an aim of deciphering the underlying principles governing how sequence affects the peptide's ability to adopt a specific secondary structure and ultimate material properties that are realized from the association of these secondary structural elements. Several amyloidogenic proteins have been shown to self-assemble into fibrils using a mechanism known as domain swapping. Here, discreet units of secondary structure are exchanged among discreet proteins during self-assembly to form extended networks with precise three dimensional organization. The possibility of using these mechanisms to design peptides capable of controlled assembly and fibril formation leading to materials with targeted properties is explored. By altering the placement of a beta-turn sequence that varies the size and location of the exchanged strand, twisting, non-twisting and laminated fibrillar nanostructures are obtained. Hydrogels prepared from these strand swapping beta-hairpins have varied rheological properties due to differences in their fibrillar nanostructures. In a second distinct design, alpha/beta-proteins are used to prepare environmentally sensitive hydrogels. Here, multiple distinct motifs for structural integrity and dynamic response within a single self-assembling peptide allow the amyloid-like fibrils formed to controllably alter their nano-topography in response to an external stimulus such as temperature. The development of these self-assembling alpha/beta-protein motifs also necessitated the design of pH sensitive antiparallel coiled coils. Exploring the basic principles responsible for pH dependent conformational changes in coiled coils can lead to new insights in the control of protein structure and function. Lastly, this dissertation discusses the interface between biomolecules and inorganic materials. Here, a new methodology of functionalizing titania nanoparticles with peptides is developed. In all of these different material forming systems, extensive biophysical characterization by circular dichroism spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction and analytical ultracentrifugation is performed to understand peptide folding and self-assembly. Careful nanostructural characterization by electron and force microscopies is performed to elucidate self-assembly mechanisms and has proved to be vital in applying the iterative design process to develop responsive nanomaterials.

Dynamics of nonlinear feedback control.

PubMed

Snippe, H P; van Hateren, J H

2007-05-01

Feedback control in neural systems is ubiquitous. Here we study the mathematics of nonlinear feedback control. We compare models in which the input is multiplied by a dynamic gain (multiplicative control) with models in which the input is divided by a dynamic attenuation (divisive control). The gain signal (resp. the attenuation signal) is obtained through a concatenation of an instantaneous nonlinearity and a linear low-pass filter operating on the output of the feedback loop. For input steps, the dynamics of gain and attenuation can be very different, depending on the mathematical form of the nonlinearity and the ordering of the nonlinearity and the filtering in the feedback loop. Further, the dynamics of feedback control can be strongly asymmetrical for increment versus decrement steps of the input. Nevertheless, for each of the models studied, the nonlinearity in the feedback loop can be chosen such that immediately after an input step, the dynamics of feedback control is symmetric with respect to increments versus decrements. Finally, we study the dynamics of the output of the control loops and find conditions under which overshoots and undershoots of the output relative to the steady-state output occur when the models are stimulated with low-pass filtered steps. For small steps at the input, overshoots and undershoots of the output do not occur when the filtering in the control path is faster than the low-pass filtering at the input. For large steps at the input, however, results depend on the model, and for some of the models, multiple overshoots and undershoots can occur even with a fast control path.

Characterization of a linear device developed for research on advanced plasma imaging and dynamicsa)

NASA Astrophysics Data System (ADS)

Chung, J.; Lee, K. D.; Seo, D. C.; Nam, Y. U.; Choi, M. C.

2010-10-01

Within the scope of long term research on imaging diagnostics for steady-state plasmas and understanding of edge plasma physics through diagnostics with conventional spectroscopic methods, we have constructed a linear electron cyclotron resonance (ECR) plasma device named Research on Advanced Plasma Imaging and Dynamics (RAPID). It has a variety of axial magnetic field profiles provided by eight water-cooled magnetic coils and two dc power supplies. The positions of the magnetic coils are freely adjustable along the axial direction and the power supplies can be operated with many combinations of electrical wiring to the coils. Here, a 6 kW 2.45 GHz magnetron is used to produce steady-state hydrogen, helium, and argon plasmas with central magnetic fields of 875 and/or 437.5 G (second harmonic). In order to achieve the highest possible plasma performance within the limited input parameters, wall conditioning experiments were carried out. Chamber bake-out was achieved with heating coils that were wound covering the vessel, and long-pulse electron cyclotron heating discharge cleaning was also followed after 4 days of bake-out. A uniform bake-out temperature (150 °C) was achieved by wrapping the vessel in high temperature thermal insulation textile and by controlling the heating coil current using a digital control system. The partial pressure changes were observed using a residual gas analyzer, and a total system pressure of 5×10-8 Torr was finally reached. Diagnostic systems including a millimeter-wave interferometer, a high resolution survey spectrometer, a Langmuir probe, and an ultrasoft x-ray detector were used to provide the evidence that the plasma performance was improved as we desired. In this work, we present characterization of the RAPID device for various system conditions and configurations.

Choosing Sensor Configuration for a Flexible Structure Using Full Control Synthesis

NASA Technical Reports Server (NTRS)

Lind, Rick; Nalbantoglu, Volkan; Balas, Gary

1997-01-01

Optimal locations and types for feedback sensors which meet design constraints and control requirements are difficult to determine. This paper introduces an approach to choosing a sensor configuration based on Full Control synthesis. A globally optimal Full Control compensator is computed for each member of a set of sensor configurations which are feasible for the plant. The sensor configuration associated with the Full Control system achieving the best closed-loop performance is chosen for feedback measurements to an output feedback controller. A flexible structure is used as an example to demonstrate this procedure. Experimental results show sensor configurations chosen to optimize the Full Control performance are effective for output feedback controllers.

Feedforward/feedback control synthesis for performance and robustness

NASA Technical Reports Server (NTRS)

Wie, Bong; Liu, Qiang

1990-01-01

Both feedforward and feedback control approaches for uncertain dynamical systems are investigated. The control design objective is to achieve a fast settling time (high performance) and robustness (insensitivity) to plant modeling uncertainty. Preshapong of an ideal, time-optimal control input using a 'tapped-delay' filter is shown to provide a rapid maneuver with robust performance. A robust, non-minimum-phase feedback controller is synthesized with particular emphasis on its proper implementation for a non-zero set-point control problem. The proposed feedforward/feedback control approach is robust for a certain class of uncertain dynamical systems, since the control input command computed for a given desired output does not depend on the plant parameters.

Electromagnetic receiver with capacitive electrodes and triaxial induction coil for tunnel exploration

NASA Astrophysics Data System (ADS)

Kai, Chen; Sheng, Jin; Wang, Shun

2017-09-01

A new type of electromagnetic (EM) receiver has been developed by integrating four capacitive electrodes and a triaxial induction coil with an advanced data logger for tunnel exploration. The new EM receiver can conduct EM observations in tunnels, which is one of the principal goals of surface-tunnel-borehole EM detection for deep ore deposit mapping. The use of capacitive electrodes enables us to record the electrical field (E-field) signals from hard rock surfaces, which are high-resistance terrains. A compact triaxial induction coil integrates three independent induction coils for narrow-tunnel exploration applications. A low-time-drift-error clock source is developed for tunnel applications where GPS signals are unavailable. The three main components of our tunnel EM receiver are: (1) four capacitive electrodes for measuring the E-field signal without digging in hard rock regions; (2) a triaxial induction coil sensor for audio-frequency magnetotelluric and controlled-source audio-frequency magnetotelluric signal measurements; and (3) a data logger that allows us to record five-component MT signals with low noise levels, low time-drift-error for the clock source, and high dynamic range. The proposed tunnel EM receiver was successfully deployed in a mine that exhibited with typical noise characteristics. [Figure not available: see fulltext. Caption: The new EM receiver can conduct EM observations in tunnels, which is one of the principal goals of the surface-tunnel-borehole EM (STBEM) detection for deep ore deposit mapping. The use of a capacitive electrode enables us to record the electrical field (E-field) signals from hard rock surfaces. A compact triaxial induction coil integrated three induction coils, for narrow-tunnel applications.

Innovative Free-range Resonant Electrical Energy Delivery system (FREE-D System) for a ventricular assist device using wireless power.

PubMed

Waters, Benjamin H; Smith, Joshua R; Bonde, Pramod

2014-01-01

Technological innovation of a smaller, single moving part has an advantage over earlier large pulsatile ventricular assist devices (VADs) prone to mechanical failure. Drivelines limit the potential for extended patient survival durations with newer pumps and act as source for infection, increased morbidity, rehospitalizations, and reduced quality of life. The Free-range Resonant Electrical Energy Delivery (FREE-D) wireless power system uses magnetically coupled resonators to efficiently transfer power. We demonstrate the efficiency over distance of this system. The experimental setup consists of an radiofrequency amplifier and control board which drives the transmit resonator coil, and a receiver unit consisting of a resonant coil attached to a radiofrequency rectifier and power management module. The power management module supplies power to the axial pump, which was set at 9,600 rpm. To achieve a seamless wireless delivery in any room size, we introduced a third relay coil. This relay coil can be installed throughout a room, whereas a single relay coil could be built into a jacket worn by the patient, which would always be within range of the receive coil implanted in the patient's body. The power was delivered over a meter distance without interruptions or fluctuations with coil, rectifier, and regulator efficiency more than 80% and overall system efficiency of 61%. The axial pump worked well throughout the 8 hours of continuous operation. Having same setup on the opposite side can double the distance. A tether-free operation of a VAD can be achieved by FREE-D system in room-size distances. It has the potential to make the VAD therapy more acceptable from the patient perspective.

Inferential modeling and predictive feedback control in real-time motion compensation using the treatment couch during radiotherapy

NASA Astrophysics Data System (ADS)

Qiu, Peng; D'Souza, Warren D.; McAvoy, Thomas J.; Liu, K. J. Ray

2007-09-01

Tumor motion induced by respiration presents a challenge to the reliable delivery of conformal radiation treatments. Real-time motion compensation represents the technologically most challenging clinical solution but has the potential to overcome the limitations of existing methods. The performance of a real-time couch-based motion compensation system is mainly dependent on two aspects: the ability to infer the internal anatomical position and the performance of the feedback control system. In this paper, we propose two novel methods for the two aspects respectively, and then combine the proposed methods into one system. To accurately estimate the internal tumor position, we present partial-least squares (PLS) regression to predict the position of the diaphragm using skin-based motion surrogates. Four radio-opaque markers were placed on the abdomen of patients who underwent fluoroscopic imaging of the diaphragm. The coordinates of the markers served as input variables and the position of the diaphragm served as the output variable. PLS resulted in lower prediction errors compared with standard multiple linear regression (MLR). The performance of the feedback control system depends on the system dynamics and dead time (delay between the initiation and execution of the control action). While the dynamics of the system can be inverted in a feedback control system, the dead time cannot be inverted. To overcome the dead time of the system, we propose a predictive feedback control system by incorporating forward prediction using least-mean-square (LMS) and recursive least square (RLS) filtering into the couch-based control system. Motion data were obtained using a skin-based marker. The proposed predictive feedback control system was benchmarked against pure feedback control (no forward prediction) and resulted in a significant performance gain. Finally, we combined the PLS inference model and the predictive feedback control to evaluate the overall performance of the feedback control system. Our results show that, with the tumor motion unknown but inferred by skin-based markers through the PLS model, the predictive feedback control system was able to effectively compensate intra-fraction motion.

Protective link for superconducting coil

DOEpatents

Umans, Stephen D [Belmont, MA

2009-12-08

A superconducting coil system includes a superconducting coil and a protective link of superconducting material coupled to the superconducting coil. A rotating machine includes first and second coils and a protective link of superconducting material. The second coil is operable to rotate with respect to the first coil. One of the first and second coils is a superconducting coil. The protective link is coupled to the superconducting coil.

The clinical relevance of advanced artificial feedback in the control of a multi-functional myoelectric prosthesis.

PubMed

Markovic, Marko; Schweisfurth, Meike A; Engels, Leonard F; Bentz, Tashina; Wüstefeld, Daniela; Farina, Dario; Dosen, Strahinja

2018-03-27

To effectively replace the human hand, a prosthesis should seamlessly respond to user intentions but also convey sensory information back to the user. Restoration of sensory feedback is rated highly by the prosthesis users, and feedback is critical for grasping in able-bodied subjects. Nonetheless, the benefits of feedback in prosthetics are still debated. The lack of consensus is likely due to the complex nature of sensory feedback during prosthesis control, so that its effectiveness depends on multiple factors (e.g., task complexity, user learning). We evaluated the impact of these factors with a longitudinal assessment in six amputee subjects, using a clinical setup (socket, embedded control) and a range of tasks (box and blocks, block turn, clothespin and cups relocation). To provide feedback, we have proposed a novel vibrotactile stimulation scheme capable of transmitting multiple variables from a multifunction prosthesis. The subjects wore a bracelet with four by two uniformly placed vibro-tactors providing information on contact, prosthesis state (active function), and grasping force. The subjects also completed a questionnaire for the subjective evaluation of the feedback. The tests demonstrated that feedback was beneficial only in the complex tasks (block turn, clothespin and cups relocation), and that the training had an important, task-dependent impact. In the clothespin relocation and block turn tasks, training allowed the subjects to establish successful feedforward control, and therefore, the feedback became redundant. In the cups relocation task, however, the subjects needed some training to learn how to properly exploit the feedback. The subjective evaluation of the feedback was consistently positive, regardless of the objective benefits. These results underline the multifaceted nature of closed-loop prosthesis control as, depending on the context, the same feedback interface can have different impact on performance. Finally, even if the closed-loop control does not improve the performance, it could be beneficial as it seems to improve the subjective experience. Therefore, in this study we demonstrate, for the first time, the relevance of an advanced, multi-variable feedback interface for dexterous, multi-functional prosthesis control in a clinically relevant setting.

Comparing the effects of positive and negative feedback in information-integration category learning.

PubMed

Freedberg, Michael; Glass, Brian; Filoteo, J Vincent; Hazeltine, Eliot; Maddox, W Todd

2017-01-01

Categorical learning is dependent on feedback. Here, we compare how positive and negative feedback affect information-integration (II) category learning. Ashby and O'Brien (2007) demonstrated that both positive and negative feedback are required to solve II category problems when feedback was not guaranteed on each trial, and reported no differences between positive-only and negative-only feedback in terms of their effectiveness. We followed up on these findings and conducted 3 experiments in which participants completed 2,400 II categorization trials across three days under 1 of 3 conditions: positive feedback only (PFB), negative feedback only (NFB), or both types of feedback (CP; control partial). An adaptive algorithm controlled the amount of feedback given to each group so that feedback was nearly equated. Using different feedback control procedures, Experiments 1 and 2 demonstrated that participants in the NFB and CP group were able to engage II learning strategies, whereas the PFB group was not. Additionally, the NFB group was able to achieve significantly higher accuracy than the PFB group by Day 3. Experiment 3 revealed that these differences remained even when we equated the information received on feedback trials. Thus, negative feedback appears significantly more effective for learning II category structures. This suggests that the human implicit learning system may be capable of learning in the absence of positive feedback.

Superresolution parallel magnetic resonance imaging: Application to functional and spectroscopic imaging

PubMed Central

Otazo, Ricardo; Lin, Fa-Hsuan; Wiggins, Graham; Jordan, Ramiro; Sodickson, Daniel; Posse, Stefan

2009-01-01

Standard parallel magnetic resonance imaging (MRI) techniques suffer from residual aliasing artifacts when the coil sensitivities vary within the image voxel. In this work, a parallel MRI approach known as Superresolution SENSE (SURE-SENSE) is presented in which acceleration is performed by acquiring only the central region of k-space instead of increasing the sampling distance over the complete k-space matrix and reconstruction is explicitly based on intra-voxel coil sensitivity variation. In SURE-SENSE, parallel MRI reconstruction is formulated as a superresolution imaging problem where a collection of low resolution images acquired with multiple receiver coils are combined into a single image with higher spatial resolution using coil sensitivities acquired with high spatial resolution. The effective acceleration of conventional gradient encoding is given by the gain in spatial resolution, which is dictated by the degree of variation of the different coil sensitivity profiles within the low resolution image voxel. Since SURE-SENSE is an ill-posed inverse problem, Tikhonov regularization is employed to control noise amplification. Unlike standard SENSE, for which acceleration is constrained to the phase-encoding dimension/s, SURE-SENSE allows acceleration along all encoding directions — for example, two-dimensional acceleration of a 2D echo-planar acquisition. SURE-SENSE is particularly suitable for low spatial resolution imaging modalities such as spectroscopic imaging and functional imaging with high temporal resolution. Application to echo-planar functional and spectroscopic imaging in human brain is presented using two-dimensional acceleration with a 32-channel receiver coil. PMID:19341804

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, T.F.; Lee, A.Y.; Ruck, G.W.

A feasible compact poloidal divertor system has been designed as an impurity control and vacuum vessel first-wall protection option for the TNS tokamak. The divertor coils are inside the TF coil array and vacuum vessel. The poloidal divertor is formed by a pair of coil sets with zero net current. Each set consists of a number of coils forming a dish-shaped washer-like ring. The magnetic flux in the space between the coil sets is compressed vertically to limit the height and to expand the horizontal width of the particle and energy burial chamber which is located in the gap betweenmore » the coil sets. The intensity of the poloidal field is increased to make the pitch angle of the flux lines very large so that the diverted particles can be intercepted by a large number of panels oriented at a small angle with respect to the flux lines. They are carefully shaped and designed such that the entire surfaces are exposed to the incident particles and are not shadowed by each other. Large collecting surface areas can be obtained. Flowing liquid lithium film and solid metal panels have been considered as the particle collectors. The power density for the former is designed at 1 MW/m/sup 2/ and for the latter 0.5 MW/m/sup 2/. The major mechanical, thermal, and vacuum problems have been evaluated in sufficient detail so that the advantages and difficulties are identified. A complete functional picture is presented.« less

Control Theory Perspective of Effects-Based Thinking and Operations: Modelling Operations as a Feedback Control System

DTIC Science & Technology

2007-11-01

Control Theory Perspective of Effects-Based Thinking and Operations Modelling “Operations” as a Feedback Control System Philip S. E... Theory Perspective of Effects-Based Thinking and Operations Modelling “Operations” as a Feedback Control System Philip S. E. Farrell...Abstract This paper explores operations that involve effects-based thinking (EBT) using Control Theory techniques in order to highlight the concept’s

Magnetic field transfer device and method

DOEpatents

Wipf, S.L.

1990-02-13

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

Magnetic field transfer device and method

DOEpatents

Wipf, Stefan L.

1990-01-01

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180.degree. from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180.degree. from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils.

Grip force control during virtual object interaction: effect of force feedback,accuracy demands, and training.

PubMed

Gibo, Tricia L; Bastian, Amy J; Okamura, Allison M

2014-03-01

When grasping and manipulating objects, people are able to efficiently modulate their grip force according to the experienced load force. Effective grip force control involves providing enough grip force to prevent the object from slipping, while avoiding excessive force to avoid damage and fatigue. During indirect object manipulation via teleoperation systems or in virtual environments, users often receive limited somatosensory feedback about objects with which they interact. This study examines the effects of force feedback, accuracy demands, and training on grip force control during object interaction in a virtual environment. The task required subjects to grasp and move a virtual object while tracking a target. When force feedback was not provided, subjects failed to couple grip and load force, a capability fundamental to direct object interaction. Subjects also exerted larger grip force without force feedback and when accuracy demands of the tracking task were high. In addition, the presence or absence of force feedback during training affected subsequent performance, even when the feedback condition was switched. Subjects' grip force control remained reminiscent of their employed grip during the initial training. These results motivate the use of force feedback during telemanipulation and highlight the effect of force feedback during training.

Combined Auditory and Vibrotactile Feedback for Human-Machine-Interface Control.

PubMed

Thorp, Elias B; Larson, Eric; Stepp, Cara E

2014-01-01

The purpose of this study was to determine the effect of the addition of binary vibrotactile stimulation to continuous auditory feedback (vowel synthesis) for human-machine interface (HMI) control. Sixteen healthy participants controlled facial surface electromyography to achieve 2-D targets (vowels). Eight participants used only real-time auditory feedback to locate targets whereas the other eight participants were additionally alerted to having achieved targets with confirmatory vibrotactile stimulation at the index finger. All participants trained using their assigned feedback modality (auditory alone or combined auditory and vibrotactile) over three sessions on three days and completed a fourth session on the third day using novel targets to assess generalization. Analyses of variance performed on the 1) percentage of targets reached and 2) percentage of trial time at the target revealed a main effect for feedback modality: participants using combined auditory and vibrotactile feedback performed significantly better than those using auditory feedback alone. No effect was found for session or the interaction of feedback modality and session, indicating a successful generalization to novel targets but lack of improvement over training sessions. Future research is necessary to determine the cognitive cost associated with combined auditory and vibrotactile feedback during HMI control.

Intermittent compared to continuous real-time fMRI neurofeedback boosts control over amygdala activation.

PubMed

Hellrung, Lydia; Dietrich, Anja; Hollmann, Maurice; Pleger, Burkhard; Kalberlah, Christian; Roggenhofer, Elisabeth; Villringer, Arno; Horstmann, Annette

2018-02-01

Real-time fMRI neurofeedback is a feasible tool to learn the volitional regulation of brain activity. So far, most studies provide continuous feedback information that is presented upon every volume acquisition. Although this maximizes the temporal resolution of feedback information, it may be accompanied by some disadvantages. Participants can be distracted from the regulation task due to (1) the intrinsic delay of the hemodynamic response and associated feedback and (2) limited cognitive resources available to simultaneously evaluate feedback information and stay engaged with the task. Here, we systematically investigate differences between groups presented with different variants of feedback (continuous vs. intermittent) and a control group receiving no feedback on their ability to regulate amygdala activity using positive memories and feelings. In contrast to the feedback groups, no learning effect was observed in the group without any feedback presentation. The group receiving intermittent feedback exhibited better amygdala regulation performance when compared with the group receiving continuous feedback. Behavioural measurements show that these effects were reflected in differences in task engagement. Overall, we not only demonstrate that the presentation of feedback is a prerequisite to learn volitional control of amygdala activity but also that intermittent feedback is superior to continuous feedback presentation. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

The Roles of Feedback and Feedforward as Humans Learn to Control Unknown Dynamic Systems.

PubMed

Zhang, Xingye; Wang, Shaoqian; Hoagg, Jesse B; Seigler, T Michael

2018-02-01

We present results from an experiment in which human subjects interact with an unknown dynamic system 40 times during a two-week period. During each interaction, subjects are asked to perform a command-following (i.e., pursuit tracking) task. Each subject's performance at that task improves from the first trial to the last trial. For each trial, we use subsystem identification to estimate each subject's feedforward (or anticipatory) control, feedback (or reactive) control, and feedback time delay. Over the 40 trials, the magnitudes of the identified feedback controllers and the identified feedback time delays do not change significantly. In contrast, the identified feedforward controllers do change significantly. By the last trial, the average identified feedforward controller approximates the inverse of the dynamic system. This observation provides evidence that a fundamental component of human learning is updating the anticipatory control until it models the inverse dynamics.

Design study of a feedback control system for the Multicyclic Flap System rotor (MFS)

NASA Technical Reports Server (NTRS)

Weisbrich, R.; Perley, R.; Howes, H.

1977-01-01

The feasibility of automatically providing higher harmonic control to a deflectable control flap at the tip of a helicopter rotor blade through feedback of selected independent parameter was investigated. Control parameters were selected for input to the feedback system. A preliminary circuit was designed to condition the selected parameters, weigh limiting factors, and provide a proper output signal to the multi-cyclic control actuators. Results indicate that feedback control for the higher harmonic is feasible; however, design for a flight system requires an extension of the present analysis which was done for one flight condition - 120 kts, 11,500 lbs gross weight and level flight.

Feedback linearization for control of air breathing engines

NASA Technical Reports Server (NTRS)

Phillips, Stephen; Mattern, Duane

1991-01-01

The method of feedback linearization for control of the nonlinear nozzle and compressor components of an air breathing engine is presented. This method overcomes the need for a large number of scheduling variables and operating points to accurately model highly nonlinear plants. Feedback linearization also results in linear closed loop system performance simplifying subsequent control design. Feedback linearization is used for the nonlinear partial engine model and performance is verified through simulation.

Indirect Identification of Linear Stochastic Systems with Known Feedback Dynamics

NASA Technical Reports Server (NTRS)

Huang, Jen-Kuang; Hsiao, Min-Hung; Cox, David E.

1996-01-01

An algorithm is presented for identifying a state-space model of linear stochastic systems operating under known feedback controller. In this algorithm, only the reference input and output of closed-loop data are required. No feedback signal needs to be recorded. The overall closed-loop system dynamics is first identified. Then a recursive formulation is derived to compute the open-loop plant dynamics from the identified closed-loop system dynamics and known feedback controller dynamics. The controller can be a dynamic or constant-gain full-state feedback controller. Numerical simulations and test data of a highly unstable large-gap magnetic suspension system are presented to demonstrate the feasibility of this indirect identification method.

Self-Controlled Feedback Facilitates Motor Learning in Both High and Low Activity Individuals

PubMed Central

Fairbrother, Jeffrey T.; Laughlin, David D.; Nguyen, Timothy V.

2012-01-01

The purpose of this study was to determine if high and low activity individuals differed in terms of the effects of self-controlled feedback on the performance and learning of a movement skill. The task consisted of a blindfolded beanbag toss using the non-preferred arm. Participants were pre-screened according to their physical activity level using the International Physical Activity Questionnaire. An equal number of high activity (HA) and low activity (LA) participants were assigned to self-control (SC) and yoked (YK) feedback conditions, creating four groups: Self-Control-High Activity; Self-Control-Low Activity; Yoked-High Activity; and Yoked-Low Activity. SC condition participants were provided feedback whenever they requested it, while YK condition participants received feedback according to a schedule created by their SC counterpart. Results indicated that the SC condition was more accurate than the YK condition during acquisition and transfer phases, and the HA condition was more accurate than the LA condition during all phases of the experiment. A post-training questionnaire indicated that participants in the SC condition asked for feedback mostly after what they perceived to be “good” trials; those in the YK condition indicated that they would have preferred to receive feedback after “good” trials. This study provided further support for the advantages of self-controlled feedback when learning motor skills, additionally showing benefits for both active and less active individuals. The results suggested that the provision of self-controlled feedback to less active learners may be a potential avenue to teaching motor skills necessary to engage in greater amounts of physical activity. PMID:22969745

Effectiveness of a smartphone app in increasing physical activity amongst male adults: a randomised controlled trial.

PubMed

Harries, Tim; Eslambolchilar, Parisa; Rettie, Ruth; Stride, Chris; Walton, Simon; van Woerden, Hugo C

2016-09-02

Smartphones are ideal for promoting physical activity in those with little intrinsic motivation for exercise. This study tested three hypotheses: H1 - receipt of social feedback generates higher step-counts than receipt of no feedback; H2 - receipt of social feedback generates higher step-counts than only receiving feedback on one's own walking; H3 - receipt of feedback on one's own walking generates higher step-counts than no feedback (H3). A parallel group randomised controlled trial measured the impact of feedback on steps-counts. Healthy male participants (n = 165) aged 18-40 were given phones pre-installed with an app that recorded steps continuously, without the need for user activation. Participants carried these with them as their main phones for a two-week run-in and six-week trial. Randomisation was to three groups: no feedback (control); personal feedback on step-counts; group feedback comparing step-counts against those taken by others in their group. The primary outcome measure, steps per day, was assessed using longitudinal multilevel regression analysis. Control variables included attitude to physical activity and perceived barriers to physical activity. Fifty-five participants were allocated to each group; 152 completed the study and were included in the analysis: n = 49, no feedback; n = 53, individual feedback; n = 50, individual and social feedback. The study provided support for H1 and H3 but not H2. Receipt of either form of feedback explained 7.7 % of between-subject variability in step-count (F = 6.626, p < 0.0005). Compared to the control, the expected step-count for the individual feedback group was 60 % higher (effect on log step-count = 0.474, 95 % CI = 0.166-0.782) and that for the social feedback group, 69 % higher (effect on log step-count = 0.526, 95 % CI = 0.212-0.840). The difference between the two feedback groups (individual vs social feedback) was not statistically significant. Always-on smartphone apps that provide step-counts can increase physical activity in young to early-middle-aged men but the provision of social feedback has no apparent incremental impact. This approach may be particularly suitable for inactive people with low levels of physical activity; it should now be tested with this population.

Microelectromechanical accelerometer with resonance-cancelling control circuit including an idle state

DOEpatents

Chu, Dahlon D.; Thelen, Jr., Donald C.; Campbell, David V.

2001-01-01

A digital feedback control circuit is disclosed for use in an accelerometer (e.g. a microelectromechanical accelerometer). The digital feedback control circuit, which periodically re-centers a proof mass in response to a sensed acceleration, is based on a sigma-delta (.SIGMA..DELTA.) configuration that includes a notch filter (e.g. a digital switched-capacitor filter) for rejecting signals due to mechanical resonances of the proof mass and further includes a comparator (e.g. a three-level comparator). The comparator generates one of three possible feedback states, with two of the feedback states acting to re-center the proof mass when that is needed, and with a third feedback state being an "idle" state which does not act to move the proof mass when no re-centering is needed. Additionally, the digital feedback control system includes an auto-zero trim capability for calibration of the accelerometer for accurate sensing of acceleration. The digital feedback control circuit can be fabricated using complementary metal-oxide semiconductor (CMOS) technology, bi-CMOS technology or bipolar technology and used in single- and dual-proof-mass accelerometers.

Virtual grasping: closed-loop force control using electrotactile feedback.

PubMed

Jorgovanovic, Nikola; Dosen, Strahinja; Djozic, Damir J; Krajoski, Goran; Farina, Dario

2014-01-01

Closing the control loop by providing somatosensory feedback to the user of a prosthesis is a well-known, long standing challenge in the field of prosthetics. Various approaches have been investigated for feedback restoration, ranging from direct neural stimulation to noninvasive sensory substitution methods. Although there are many studies presenting closed-loop systems, only a few of them objectively evaluated the closed-loop performance, mostly using vibrotactile stimulation. Importantly, the conclusions about the utility of the feedback were partly contradictory. The goal of the current study was to systematically investigate the capability of human subjects to control grasping force in closed loop using electrotactile feedback. We have developed a realistic experimental setup for virtual grasping, which operated in real time, included a set of real life objects, as well as a graphical and dynamical model of the prosthesis. We have used the setup to test 10 healthy, able bodied subjects to investigate the role of training, feedback and feedforward control, robustness of the closed loop, and the ability of the human subjects to generalize the control to previously "unseen" objects. Overall, the outcomes of this study are very optimistic with regard to the benefits of feedback and reveal various, practically relevant, aspects of closed-loop control.

Improving Instruction Using Statistical Process Control.

ERIC Educational Resources Information Center

Higgins, Ronald C.; Messer, George H.

1990-01-01

Two applications of statistical process control to the process of education are described. Discussed are the use of prompt feedback to teachers and prompt feedback to students. A sample feedback form is provided. (CW)