233 results about "Very low frequency" patented technology

Methods and systems are provided for determining a condition of an organ, or epithelial or stromal tissue, for example in the human breast. The methods incorporate sonophoresis, the application of ultrasonic energy, in order to condition tissue for testing and enhance test measurements. A plurality of electrodes are used to measure surface and transepithelial electropotential and impedance of breast tissue at one or more locations and at several frequencies, particularly very low frequencies. An agent may be introduced into the region of tissue to enhance electrophysiological characteristics. Pressure, drugs and other agents can optionally be applied for enhanced diagnosis. Tissue condition is determined based on the electropotential and impedance profile at different depths of the epithelium, stroma, tissue, or organ, together with an estimate of the functional changes in the epithelium due to altered ion transport and electrophysiological properties of the tissue. Devices for practicing the disclosed methods are also provided.

An apparatus and method are disclosed for imaging a diffraction grating with a very high depth of focus, using a highly accurate code plate position measurement system. Positions may be measured to an accuracy of 1 nm or even smaller. The system may be used in fields such as manufacturing integrated circuits, and low- and very-low-frequency geophones, and other low- and very-low-frequency acoustic detectors.

The invention provides an underground low-frequency wireless communication system based on a low-power small electric antenna. The underground low-frequency wireless communication system comprises a transmitting end FPGA (Field Programmable Gate Array) digital control module, a power amplification and impedance matching module, a small-sized very low frequency transmitting antenna, a small-sized very low frequency receiving antenna, a receiving end filtering and amplifying module, a receiving end FPGA digital control module and an upper computer which are sequentially connected with one another. The underground low-frequency wireless communication system can be used for overcoming the detects of large size and high transmitting power of a conventional very low frequency antenna by using a magnetic induction manner for replacing an electromagnetic wave communication manner and completing the directional wireless communication between the undergrounds and between the underground and the ground surface and can also be used as an independent module to complete the middle and short-distance wireless transmission of underground sensor data to a ground surface receiving device.

The invention relates to a full-lightning positioning system with combination of very-low frequency and very-high frequency (VHF). The full-lightning positioning system is characterized by comprising at least four lightning positioning monitoring stations which are respectively provided with a very-low frequency lightning radiation receiver, a very-high frequency lightning radiation receiver, a GPS receiver and an industrial computer; the station utilizes time reference provided by the GPS receiver and obtains the time and waveform that the change pulse of a lightning electric field and VHF radiation pulse reach all the stations, utilizes the industrial computer to preprocess the obtained waveform data, then transmits the obtained data in real time to the industrial computer for analyzing and processing the pulse waveform by an internet, and realizes real-time monitoring and three-dimensional positioning to lightning discharge events. Under the matching of the above hardware and software, the system can be used for determining the quantity, types, characteristic parameters and statistical characteristics of lightning discharge events occurring in a specified area, and carries out monitoring and early warning to the activities of thunder and lightning.

The invention relates to DAS observation has been proven to be useful for monitoring hydraulic fracturing operations. While published literature has shown focus on the high-frequency components (>1 Hz) of the data, this invention discloses that much of the usable information may reside in the very low frequency band (0-50 milliHz). Due to the large volume of a DAS dataset, an efficient workflow has been developed to process the data by utilizing the parallel computing and the data storage. The processing approach enhances the signal while decreases the data size by 10000 times, thereby enabling easier consumption by other multi-disciplinary groups for further analysis and interpretation. The polarity changes as seen from the high signal to noise ratio (SNR) low frequency DAS images are currently being utilized for interpretation of completions efficiency monitoring in hydraulically stimulated wells.

Apparatus and methods for eliminating DC offset in a wireless communication device operable on a continuous basis or on a sampled basis. In a receive channel, the output of a forward variable gain amplifier is fed back to an RC circuit to charge the capacitor (C) to a voltage dependent on the DC offset in the variable gain amplifier output. The voltage on the capacitor is amplified and summed with the input to the variable gain amplifier. The RC circuit is configured to provide a high gain feedback at DC and very low frequencies, but very low gain at signal frequencies. Preferably the output of the forward variable gain amplifier is fed back to the RC circuit with a gain that is inversely proportional to the forward gain. Disconnection of the capacitor and feedback of the capacitor voltage provides sampled operation. Various embellishments and sample applications are disclosed.

The invention provides a communicator inside and outside conduits based on very low frequency power electromagnetic pulse and relates to the communication field. The invention solves the problem of shielding of electromagnetic signals by metallic layers. A very low frequency power electromagnetic pulse emitter provided by the invention and the transmitting terminal of a microcontroller (3) transmit a very low frequency power electromagnetic pulse signal; a magnetic induction receiving antenna group (4) receives the very low frequency power electromagnetic pulse signal, and converts the very low frequency power electromagnetic pulse signal into a voltage signal, and transmits the voltage signal to a signal processing and transmission device (5). The signal processing and transmission device (5) filters and magnifies the voltage signal, extracts the signal components which are the same with the frequency of the emitter, and transmits the signal components to a computer (6) for data analysis and resolving communication instructions. The invention can communicate reliably inside and outside in the environment of metallic conduits. By adopting the invention, when a signal is transmitted in metal, silt, soil and briny environment, the electromagnetic signal attenuation factor is small. By comparing the signal transmitted by the invention with high frequency electromagnetic wave signals, the propagation length of the signal in a lossy medium is significantly improved.

A method for determining electrical properties of a submarine petroleum fluid-bearing formation (1) under overburden geological layers (2) of thickness (s) under a seafloor (3) of a sea (4),

said method comprising the following steps:

• • arranging one or more transmitter antennas (9) in said sea (4), and
  • arranging one or more electromagnetic receivers (8) in said sea (4),
  • said sea having a shallow sea depth (d) of 50-350 meters;
  • using said transmitter antenna (9) transmitting electromagnetic signals (10) of one or more pulses (11) having frequency of very low frequency between 0.01 Hz and 0.10 Hz;
  • using said receiver antennas (8) having an offset from said transmitter (9), for receiving propagated electromagnetic signals (12) due to said emitted; electromagnetic signals (10);
  • analysing one or more components of said received signals (12) from receivers (8) having offsets between about 1 km and 12 km, whether said signals (12) differ significantly from a corresponding signal that would occur from a water-bearing formation (1), indicating a petroleum fluid-bearing formation (1).

Physiological condition monitors utilizing very low frequency acoustic signals and signals indicative of body orientation are disclosed. The physiological condition monitors comprise a sensor that is capable of detecting low frequency acoustic signals in the frequency range of one tenth Hertz to thirty Hertz. The sensor comprises a chamber having portions that form a cavity and a low frequency microphone placed within the cavity. An alternate embodiment of the invention comprises a chamber having portions that form a resonant cavity, a microphone mounted in the resonant cavity, and a membrane that covers the resonant cavity. Low frequency acoustic signals that are incident on the membrane cause the membrane to move and amplify the acoustic signals within the resonant cavity. The sensor provides information concerning physiological conditions, such as respiration and cardiac activity. The sensor in a physiological condition monitor does not need to be directly coupled to the skin of the person being monitored. The physiological condition monitor simultaneously provides information concerning cardiac activity, and respiration activity, and the movement and position orientation of the monitored person's body.

There is disclosed a sensor and method for detecting very low frequency acoustic signals. The sensor is capable of detecting low frequency acoustic signals in the frequency range of one tenth Hertz to thirty Hertz. The sensor comprises a chamber having portions that form a cavity and a low frequency microphone placed within the cavity. An alternate embodiment of the invention comprises a chamber having portions that form a resonant cavity, a low frequency microphone placed within the resonant cavity, and a membrane that covers the resonant cavity. Low frequency acoustic signals that are incident on the membrane cause the membrane to move and amplify the acoustic signals within the resonant cavity.

A communication device transmits very low frequency signals in order to help diagnose the cause of a communication problem in a DSL communication system. The communication problem may be, for example, the inability of a remote data transceiver unit (DTU-R) to successfully train-up with a central data transceiver unit (DTU-C). The very low frequency signals may be used to communicate the status or settings of the remote transceiver unit to the DTU-C, to download settings parameters or executable code to the DTU-R, or to coordinate the transmission of testing signals.

Basically, the present invention is directed to a new and improved system for the therapeutic use of currents which includes conducting direct electrical current through the skin of a body being treated, and periodically reversing the electrical current and conducting the current through the skin in the opposite direction, to effectively deliver very low frequency AC current, substantially in the critical range of approximately 0.0027 Hz to 20 Hz. It has been discovered that, within this substantially critical frequency window between approximately six minutes per full cycle and approximately ten cycles per second, a dramatic cancellation of skin damaging ions takes place. At frequencies higher than approximately 20 Hz, the effect is to diminish its DC-like blood stimulation. At frequencies lower than approximately 0.0027 Hz, the risk of skin injury increases substantially. It is well known that the positive electrode unfortunately produces skin damaging hydrochloric acid. Likewise, the negative electrode unfortunately also produces skin damaging sodium hydroxide. However, within the aforementioned frequency range of the present invention, either polarity stimulates blood circulation, but also cancels the undesired skin damaging ions with the reverse portion of the electrical cycle. The reason for neutralization of the harsh injury producing chemicals, i.e., hydrochloric acid and sodium hydroxide, is that both of these chemicals require a finite period of time on the skin to cause damage. Hence, these damaging chemicals are made to cancel each other before damage takes place, by critical frequency selection, in accordance with the invention, of the AC driving signal. Therefore, optimization of a long sought electrotherapeutic device with reduced side effects has been achieved. Another use of the safe AC currents cited above and/or a DC signal with charged membranes preventing injury is its application to wound healing. The conductive electrodes for these devices may take either of two forms, i.e., one may be non-metallic carbon-filled silicone or, preferably of powdered carbon particles. A second form may be a metallic electrode preferably of aluminum, copper, zinc and/or magnesium as examples of metallic electrodes but not necessarily limited to these metals. These metals are preferably in powdered form and contained within a porous membrane with a small opening to attach a conductive lead to a battery source. Still other applications of the innovative use in electrotherapy of charged membranes and/or powdered metal electrodes is its use for drug delivery and diagnostic purposes. For instance, a membrane enclosed stainless steel powdered negative electrode may be used in the pickup probe for glucose detection. Charged membranes would surround the probe as an intervenor between skin and the electrode.

The invention relates to a method and a device for monitoring a lightning coincident with photo-electric signals. The method comprises the steps of synchronously sampling a radiated optical signal and a very low frequency electromagnetic signal when a lightning occurs in the manner of multi-station detection, synchronously recording a lightning time and a detection station position, sending the lightning data to a system host machine through a network, identifying the lightning through the system host machine, removing an interference signal, positioning, computing the lightning time and position, establishing a lightning information database, and providing an inquiry and statistics function. The device of the invention comprises a plurality of probes and one system host machine, wherein the probes comprise an optical signal amplification module, an electromagnetic signal amplification module, a GPS module, an AD module and a DSP module and the system host machine comprises hardware and software. The method and device of the invention can synchronously record the lightning optical signal and electromagnetic signal, can synchronously analyze through the photo-electric signal, are in favor of removing the interference signal, and can promote the precision of lightning identification and positioning. The monitoring step is simple and the positioning is accurate.

The invention discloses a satellite-borne very low frequency solar radio observation system. The system is used for observing a low frequency solar radio signal of 20-100 MHz. The system comprises three electric field sensors, three sets of analog receivers, a data acquisition and processing module,a time frequency module, a power module and a storage module, wherein the three electric field sensors are respectively connected with the three sets of analog receivers; the three sets of analog receivers and the time frequency module are respectively connected with the data acquisition and processing module; the data acquisition and processing module is connected with the storage module; and the data acquisition and processing module and the three sets of analog receivers are respectively connected with the power module. The system disclosed by the invention can judge the motion of coronal projectiles, predict and anticipate the future space weather event.

A system and method for measuring the speed of a fan is presented. The duty cycle of a pulse width modulated (PWM) power signal may control speed of the fan. The fan may generate tachometer pulses used for monitoring RPM of the fan. Very low frequency test pulses may be generated and provided via a test signal multiplexed with the PWM signal to obtain tachometer pulses present even when the PWM signal is deasserted. The frequency of the test signal may be determined based on the duty cycle of the PWM signal and may be dynamically updated using frequency divider values stored in a user programmable look-up table. The tachometer pulses may be used to reset a flip-flop whose data input is held high and a down counter, which may be operated at a frequency slightly lower than the frequency of the test signal, with the output of the down counter clocking the flip-flop. The output of the flip-flop may provide recreated tachometer pulses to a pulse counter that counts the number of pulses within a determined period of time, providing a measured RPM of the fan.