47 results about "Ac field" patented technology

In a method and apparatus for adjusting a composite electric field to be applied to an ion trap to accommodate switching the operation of the ion trap between a positive ion mode and a negative ion mode, the composite electric field includes a plurality of component fields including at least one AC trapping field and one or more supplemental AC fields. A phase of one or more of the component fields is adjusted such that a force imparted by the composite field to a negative ion in the ion trap will be substantially the same as the force imparted by the composite field to a positive ion in the ion trap.

A liquid crystal smectic A composition that can be switched by the application of different electric fields across it between a first stable state (left hand block in FIG. 4) and at least one second stable state (right hand block in FIG. 4) in which the composition is less ordered than in the first state. The radiation transmission properties of the first and second states are different. The composition comprises: (A) a liquid crystal material that has a positive dielectric anisotropy and that is a uniformly aligned smectic A structure when in the first state; (B) an ionic dopant giving a negative conductivity anisotropy in the liquid crystal material so that it is capable of disrupting the smectic A structure of the first state when subject to an electric field that causes the dopant to migrate through the composition, thereby causing the composition to switch into said at least one second state, and (C) optically anisotropic pigment particles having positive dielectric anisotropy dispersed in the composition, the largest dimension of the pigment particles being in the range of 10 nm to 1 μm. The composition, when in the first relatively stable state, is capable of undergoing smectic dynamic scattering due to electro-hydrodynamic instability under the influence of a sufficiently low frequency AC field, thereby disordering the liquid crystals and the pigment particles and thereby discouraging the pigment particles from aggregating together. The composition is suitable for use in displays and is especially resistant to degradation by ambient light and so can be used in outside applications.

This is a membrance electrode process method for fuel cell or eletrolysis. The membrance electrode includes a structure of three-layer or five-layer. The three-layer structure is composed by cathode catalytic layer-polymer electrolyte membrance-anode catalytic layer. The process method is as: loading cathode and anode catalytic ink to the two sides of the polymer electrolyte membrance and dry in AC field. The five-layer structure is composed by cathode diffusing layer-cathode catalytic layer-polymer electrolyte membrance-anode catalytic layer-anode diffusing layer. The process method is as: loading cathode and anode catalytic ink to cathode and anode diffusing layer separately and dry in AC field; heat compressing the cathode and anode to the polymer electrolyte membrance.

The invention relates to a test method for evaluating oxidation stability of transformer oil under a high-voltage alternating current (AC) or direct current (DC) field, and the method can be applied in evaluation and actual measurement of transformer oil oxidation stability. The method comprises: under a high-temperature and high-voltage AC or AC field and in the presence of a metal catalyst, introducing air or oxygen for accelerated oxidation of transformer oil, using an oil dielectric loss factor measuring electrode cup built in an analog device for on-line monitoring of the dielectric loss factor change, and taking the time needed for the monitored dielectric loss factor to reach the specified value 0.02 as an index for investigating the oxidation stability of transformer oil. The method provided in the invention can evaluate the oxidation stability of transformer oil under a high-temperature and high-voltage AC or AC field and with the presence of oxygen as well as a metal catalyst.

Method for nondestructive and noncontact detection of faults in a test piece, with a transmitter coil arrangement with at least one transmitter coil that transmits periodic electromagnetical AC fields to a test piece, a receiver coil arrangement with at least one receiver coil for detecting a periodic electrical signal having a carrier oscillation whose amplitude and/or phase is modulated by a fault in the test piece. A signal processing unit produces a useful signal from the receiver coil signal, and an evaluation unit evaluates the useful signal to detect a fault in the test piece. A self-test unit undertakes systematic quantitative checking of signal processing functions of the signal processing unit and/or of the transmitter coil arrangement and/or of the receiver coil arrangement and/or upon external request undertakes calibration of the signal processing unit using a calibration standard which replaces the transmitter coil arrangement and/or of the receiver coil arrangement.

A technique for de-gaussing the pole tips and yoke of a write transducer in a perpendicular magnetic recording system is provided. An oscillator in the read channel is configured to produce an adjustable signal pattern output to the preamplifier when a write operation ends for a given time and at a predetermined frequency, such that as the preamplifier write current decays, it decays with transitions (polarity reversals). This results in a decaying AC field being applied to the write transducer at the end of a media write operation, effectively de-gaussing it and reducing the effects of remanent magnetization remaining in the poles and yoke of the magnetic recording head after a write current is turned off. This defeats a potential pole tip lockup or yoke lockup circumstance in the magnetic recording media which can result in an inability to write further data or a possible erasure of valid data on the hard disk with which the write head is associated.

The source coil drive circuit section (31) of an endoscope profile detector (3) comprises an oscillator (110) generating a sine wave, and an amplifier (111) for amplifying the sine wave and generating (driving) an AC field in a source coil (14i) through a switch section (112). The switch section (112) can supply a DC current to the source coil (14i) while switching to the output of the amplifier (111). The source coil drive circuit section (31) is provided with a DC resistance detecting section (113) for measuring the DC resistance of the source coil (14i) from a potential drop when the switch section (112) is supplying a DC current to the source coil (14i).

Methods of detecting anomalies in ambient alternating current (AC) fields are provided. An exemplary embodiment of such a method includes the steps of placing an AC field sensor in an ambient AC field, generating a signal representative of the ambient AC field received by the sensor, and processing the signal to determine if the ambient AC field includes any anomalies. Various applications for the methods are also provided.

The invention provides a resonant cavity magnetic field sensing system for enhancing DC field sensing precision of a wide-temperature-zone AC field, and the system is characterized in that the outputcenter frequency of a laser is locked on the transmission spectrum of a resonant cavity, and a magnetostrictive medium is embedded in the resonant cavity, or the resonant cavity is pasted on the magnetostrictive medium; an alternating magnetic field is arranged on the outer side of the resonant cavity, the change rule of alternating magnetic field signal intensity caused by direct-current magneticfields with different intensities when the wavelength of the laser is locked at the lowest point or the highest point of the transmission spectrum of the resonant cavity is observed, and alternatingmagnetic field enhanced direct-current magnetic field detection is realized; the system has the advantages of wide temperature range, low cost, low power consumption, electromagnetic interference resistance, high-precision direct-current magnetic field detection capability and the like.

A direct electrostatic printing device includes a printhead structure with apertures and control electrodes associated with the apertures for delivering toner from a toner source to a substrate in accordance with image data. A first voltage source is provided to establish a flow of toner particles from the toner source to the substrate. A second voltage source is provided to establish a control voltage between the toner source and the control electrodes to control toner flow in accordance with the image data. The second voltage source provides a first AC field between a toner source and the control electrodes to permit toner flow and a second, diminished, AC field between the toner source and the control electrodes in order to stop the toner flow.

The tandem differential mobility spectrometer (DMS)-ion modulator instrument provides improved resolution relative to traditional DMS for molecules with larger masses. The instrument includes an ion-bunching electrode with an AC field synchronized to the transit time of the ion flow which is positioned downstream of a DMS. The ion bunching electrode produces a mobility-dependent modulation of the ion current. The ratio of AC to DC current provides a measure of the mobility of a large ion, even if it has little differential mobility, thereby extending the useful range of mobility characterization of a DMS system. The instrument is more compact than a larger traditional ion mobility spectrometer and does not require high voltages or high frequencies. Modulation before DMS separation or between tandem DMS separations produces a variable range of analyte and reactant ion densities as well as spatially separating negative and positive ions to reduce ion recombination.

An EMF detecting safety shovel has electromagnetic field (EMF) detection circuitry operably coupled to a blade thereof for measuring changes in EMF over time (AC fields) which may be used by spotters during excavation work for detection of subsurface power supply cables. The safety shovel may be further configured for classifying different types of subsurface power cables wherein the EMF detector circuit may be configured for discriminating between low and high voltage subsurface power cables when the edge of the blade is within a certain distance thereof, and the EMF detector circuit may be adjusted to adjust the distance for use with differing conduit diameters. The EMF detector circuit may also employ bandpass filtering to discriminate between single and three phase power supplies. In this way, the present safety shovel may provide indication of the presence of subsurface power supply cables and also the type thereof.