116 results about "Critical frequency" patented technology

A Wide Area Sensor Network (WASN) is disclosed that utilizes wideband software defined radios (SDRs) to monitor RF energy over a wide frequency range, detect when critical frequencies are being jammed or otherwise interfered with, and locate the source of the interference so that the interference can be eliminated. The WASN may use one or more geolocation techniques In addition, the WASN may detect and locate unauthorized transmitters as well as estimate the transmitted power of authorized transmitters to assure they are not transmitting more power than authorized.

A frequency-dependent phase pre-distortion technique is applied to an input signal in order to reduce spurious emissions resulting from subsequent amplification of the signal. In preferred embodiments, the frequency-dependent phase pre-distortion of the present invention is implemented in combination with the (frequency-independent) magnitude and phase pre-distortion technique described in U.S. patent application Ser. No. 09/395,490 (“the '490 application”), where one or more frequency-dependent phase pre-distortion signals are either advanced or delayed relative to the main pre-distorted signal generated in accordance with the '490 application. Each frequency-dependent phase pre-distortion signal is preferably based on a 180° phase difference between a pair of (critical) frequencies located outside (e.g., one on each side) of the signal channel. The magnitude of the frequency difference between the pair of critical frequencies dictates the magnitude of the desired advancement or delay in time of the frequency-dependent pre-distortion signal relative to the main pre-distorted signal. Embodiments of the present invention may be implemented in either the baseband domain or the RF domain. Implementations may also be based on look-up tables that are adaptively updated to ensure optimal performance over time.

A computing device-controlled system is described for the generation of amplitude-modulated pulse-width modulation (AMPWM) signals for use in treating neurological dysfunction via cranial neurostimulation, where the AMPWM signal is specifically designed to minimize the electrical impedance of the tissues of the head. A low-frequency carrier signal is determined for the AMPWM signal by measuring EEG activity at a reference site or sites, generally corresponding with the location of suspected brain dysfunction. Carrier signal frequency is variably related to critical frequency components of the EEG power spectral density, determined from statistical analysis of amplitudes and variability, and dynamically changed as a function of time to prevent entrainment. The AMPWM signal is presented to a subject via a plurality of neurostimulation delivery modes for therapeutic use.

The application relates to a method of improving a user's perception of an input sound. The application further relates to an audio processing device and to its use. The object of the present application is to increase the sound quality of a sound signal as perceived by a user, e.g. a hearing impaired user. The method comprises a) Defining a critical frequency f_crit between a low frequency range and a high frequency range; b) Analyzing an input sound in a number of frequency bands below and above said critical frequency; c) Defining a cut-off frequency f_cut below said critical frequency f_crit; d) Identifying a source frequency band above said cut-off frequency f_cut; e) Extracting the envelope of said source band; f) Identifying a corresponding target band below said critical frequency f_crit; g) Extracting the phase of said target band; h) Combining the envelope of said source band with the phase of said target band. This has the advantage of increasing the sound quality, and the potential to further improve speech intelligibility in frequency transposition, e.g. frequency lowering systems. The invention may e.g. be used in communication devices, such as telephones, or listening devices, e.g. hearing instruments, headsets, head phones, active ear protection devices or combinations thereof.

Provided are a method and apparatus for effectively encoding/decoding remaining difference signals excluding sinusoidal components, from input audio signals. In the method and apparatus for encoding audio signals, sinusoidal analysis is performed on low frequency signals of less than a predetermined critical frequency in order to extract sinusoidal signals and then, an encoding operation is performed on the remaining difference signals excluding the sinusoidal signals, from input audio signals, by using linear prediction coding (LPC) analysis.

The invention relates to a method of controlling running of a modularized multi-level converter in a low frequency model, which belongs to the technical field of controlling multi-level power electronic converters. The method comprises the following steps: setting high frequency common mode voltage and high frequency ring current both required to be superimposed, revising a switching function of a submodule and bridge arm current, obtaining an expression of capacitance voltage differential coefficient of the submodule according to volt-ampere characteristics of capacitance of the submodule, and in order to allow the capacitance voltage of the submodule to only have high-frequency component, assuming high frequency common mode voltage is known to obtain a expression of the high frequency circular current; comparing a running frequency with a critical frequency to obtain frequency model selection signals, combining an energy control and a circular current control of a phase unit of the modularized multi-level converter, determining whether the high frequency common mode voltage and the high frequency circular current are required to be superimposed to an original instruction or not according to the frequency model selection signals, and generating voltage required to be superimposed in the bridge arm of the phase unit of the high frequency circular current by controlling. The method is easy to realize and strong in universality, and provides reference for low frequency application of the modularized multi-level converter.

The invention provides a generator set multivariable system identification method based on normal operating data. The method comprises the steps that the step response test is carried out on a generator set multivariable system running normally to obtain input and output signals of loops of the generator set multivariable system, the signal decomposition and the spectral analysis are carried out to obtain the maximum critical frequency of all the loops of the generator set multivariable system, the frequency characteristics of the generator set multivariable system on a plurality of frequency points are calculated according to the maximum critical frequency, and a transfer function matrix model of the generator set multivariable system is established according to the frequency characteristics. According to the technical scheme, the identification process of the strongly-coupled generator set multivariable system is divided into the identification processes of a plurality of single-input and single-output systems, the frequency characteristics of the system in the important frequency bands are determined through the step response test carried out when the systems run normally under the normal running state of the generator set multivariable system, the identification process is simple, the anti-interference capability is high, and the identification precision is high.

The invention discloses a speech signal time delay estimation method and system used for echo cancellation. The method comprises the following steps of respectively obtaining a far-end signal and a near-end signal of a voice signal received by a microphone in a call and generating a corresponding far-end frequency domain signal and a corresponding near-end frequency domain signal; adopting a critical band based on the auditory masking effect to respectively carry out sub-band decomposition in the frequency band on the far-end frequency domain signal and the near-end frequency domain signal and obtaining a power spectrum of each critical frequency point of the far-end frequency domain signal and a power spectrum of each critical frequency point of the near-end frequency domain signal; respectively extracting local binary features of the power spectrum of each critical frequency point of the far-end frequency domain signal and the power spectrum of each critical frequency point of the near-end frequency domain signal, respectively matching and generating and outputting a time delay estimation result. According to the method and the system, the correlation between the far-end signal and the near-end signal is counted based on the auditory masking effect, the computation is simple, and the accurate time delay estimation can be obtained to bring great convenience for echo cancellation.

The invention discloses a method for detecting the abnormal sound of an air-conditioning indoor set, and the method comprises the steps: collecting a first sound signal of a to-be-detected air-conditioning indoor set during operation; taking a to-be-detected frequency point as the central frequency, and calculating a first critical frequency band noise value and a first single-frequency noise value, which are corresponding to a first sound signal; determining a reference abnormal sound detection threshold value corresponding to the to-be-detected frequency point; determining that the abnormal detection result of the to-be-detected air-conditioning indoor set is qualified when the difference between the first critical frequency band noise value and the first single-frequency noise value is greater than the reference abnormal sound detection threshold value, or else, determining that the abnormal detection result of the to-be-detected air-conditioning indoor set is not qualified. The invention discloses a device for detecting the abnormal sound of the air-conditioning indoor set. During the detection of abnormal sound, an evaluator does not participate each time, and just needs to detect the abnormal sound according to the abnormal sound detection threshold value, thereby effectively unifying the evaluation standard of abnormal sound detection and reducing the manpower cost.

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 discloses a three-dimensional display asthenopia detection system and method. The three-dimensional display asthenopia detection system comprises three-dimensional display equipment, flicker fusion critical frequency (CFF) measuring equipment, near point distance (NPD) measuring equipment and a data processing unit, wherein the CFF measuring equipment is used for collecting a CFF when a user watches three-dimensional display and transmitting the CFF to the data processing unit, the NPD measuring equipment is used for collecting a NPD when the user watches the three-dimensional display and transmitting the NPD to the data processing unit, the data processing unit comprises a three-dimensional asthenopia prediction model, and the three-dimensional asthenopia prediction model predicates the three-dimensional asthenopia of the user according to the input CFF and the NPD. The three-dimensional display asthenopia detection system and method can rapidly detect the asthenopia degree caused by three-dimensional display, and can be used for evaluating three-dimensional display equipment and content and guiding equipment to produce and manufacture comfortable three-dimensional resources and the like.

The invention discloses a variable frequency centrifuge and a control method of a hot gas bypass valve in the variable frequency centrifuge. The variable frequency centrifuge includes a compressor, and the hot gas bypass valve is disposed between an air suction pipe and an air exhaust pipe of the compressor. The method comprises the following steps of when the variable frequency centrifuge is in an operating state, obtaining a guide vane opening degree, an operating pressure ratio and the upper limit of the operating frequency of the compressor, wherein the operating pressure ratio is a ratioof an air exhaust absolute pressure value to an air suction absolute pressure value of the compressor; calculating the critical frequency of the variable frequency centrifuge according to the guide vane opening degree and the operating pressure ratio; controlling the opening degree of the hot gas bypass valve according to the critical frequency and the upper limit of the operating frequency. By controlling the opening degree of the hot gas bypass valve, the variable frequency centrifuge can safely operate with a small load under high ambient temperature and large pressure ratio, and at the same time, the compressor surging phenomenon does not occur under small load operation, so that the operation reliability of the variable frequency centrifuge is improved.

The invention discloses a wireless communication method of a TDD OFDM wireless communication system, and a physical layer frame structure for realizing the communication method. During conducing wireless transmission, each sub-frame in the physical layer frame sends a downlink service control message by using a regular time slot, receives uplink service by using one or more regular time slots after pausing for a period of time, and sends downlink service by using one or more regular time slots after pausing for a period of time. Considering the adjacent frequency coexistence problem of the TDD OFDM system and the TD-SCDMA system, the sub-frame conducts mutual switching between the uplink and the downlink during pausing periods, so as to ensure alignment of the same type of uplink and downlink switching points in the two communication systems, including the alignment of downlink/uplink switching points and the alignment of uplink/downlink switching points. The inventive method conducts wireless service transmission by using the alignment of the uplink and downlink switching points, thereby eliminating intersystem interference and improving the utilization ratio of system resources.

A hard disk drive that includes a wave stringer. The wave stringer can attenuate energy which propagates through a base plate of the disk drive. The wave stringer may be designed by initially analyzing propagation patterns of both acoustic and shock waves applied to the drive. The wave stringer is then designed, constructed and assembled to the disk drive to attenuate critical frequencies at weak points of the disk drive. The wave stringer may have a plurality of ribs designed to vary the mechanical impedance of the drive to attenuate the propagated energy.

Briefly, a preferred embodiment of the present invention includes an apparatus for tuning a regulator in a process controller. The digitized output from a standard relay and a parasitic relay are fed through digital to analog converter providing signals at 0.5omegac, omegac and 1.5omegac to the process, where omegac is the process critical frequency. The apparatus records the digitized relay output u' and the digitized process output y' until stationary oscillations are reached. The outputs u' and y' are then used to calculate the process frequency response at 0.50omegac, omegac and 1.5omegac. This data is then used to design the regulator, the output of which is converted to analog form and inputted to control the process.

The present invention provides a method for inverting Es layer parameters based on backscattered ionograms, which includes the following steps: Step A: using the established Es layer model to invert the Es layer parameters according to the measured backscattered ionograms' steep front information QPS parameters include the critical frequency, peak height, and half-thickness of Es; Step B: Calculate the elevation angle corresponding to the flat leading and trailing edges of the backscatter ionogram according to the determined QPS parameters to determine the area where Es exists. The present invention uses the inferred Es parameters to synthesize the front and rear edges of the backscattered ionization map Es, which can well conform to the measured Es front and back edges, and can better obtain the vertical distribution and horizontal distribution of the electron concentration in the ES layer, overcoming the traditional definition that considers the electron concentration alone The lack of vertical distribution or spatial distribution of electron concentration can better meet engineering needs.

The invention discloses a double-frequency liquid crystal material having low critical frequency. The double-frequency liquid crystal material comprises 20.0-25.0% of an ingredient A, 20.0-25.0% of an ingredient B, 17.5-22.5% of an ingredient C, 7.5-12.5% of an ingredient D, 7.5-12.5% of an ingredient E, 5.0-10.0% of an ingredient F and 5.0-10.0% of an ingredient G, and the above material are melt and mixed. The ingredient A comprises a series of derivatives having cyclohexylfluorodiphenylacetylene skeleton structures, the ingredient B comprises a series of derivatives having fluorodiphenylacetylene skeleton structures, the ingredient C comprises a series of derivatives having cyclohexylbenzene ring skeleton structures, the ingredient D comprises a series of derivatives having diphenylacetylene skeleton structures, the ingredient E comprises a series of derivatives having three-ring monoester lateral fluoro-group-containing cyano-terminated skeleton structures, and the ingredient F comprises a series of derivatives having three-ring diester lateral dicyano-containing skeleton structures. The double-frequency liquid crystal material has low critical frequency, wide liquid crystalline phase temperature and low viscosity and can be used for preparation of a double-frequency driven liquid crystal device having low work voltage and fast response rate.

The invention discloses a measuring device for impulse speed and impulse times in well-drilling mud pumps, and comprises: An acceleration transducer, a signal acquisition and process circuit, a vibration frequency spectrum ananysis circuit, a signal output interface, and a final output for average impulse speed. The invention also discloses a measuring method for impulse speed and impulse times of the well-drilling mud pumps; the measuring device is characterized by the following composition: Measure vibration frequency spectrum signals of a mud pump piston, and perform acquisition, amplification and filtering for the vibration frequency spectrum signals; provide a critical frequency spectrum point; select a time window according to the critical frequency points, and perform wavelet ananysis, and maintain low-frequency signals from the ananysis; conver the low-frequency signals from time domain to frequency domain; determine whether the low-frequency domain signals are steady waves; if yes, take the frequency and calculate to gain the average impulse speed, and then, calculate impulse times in accordance with the average impulse speed and corresponding time segments; then, go back to Step III; if the low-frequency domain signals are not steady waves, re-select a critical frequency spectrum point before returning to Step III; and after that, output the impulse times and average impulse speed that are received.

The invention relates to a super-capacitor configuration method adaptive to pulse load power fluctuation stabilization. The super-capacitor configuration method includes firstly acquiring industrial production pulse load data, and analyzing the characteristics of the pulse load to obtain typical daily pulse load impact sample data; secondly, determining relevant optimization goals and constraints of the pulse load stabilization; subjecting typical daily pulse load data frequency domain signals after time-frequency conversion to critical frequency search to obtain the critical frequency of the maximum impact limit; finally, considering the optimization goals and the constraints to determine the rated power, the rated capacity and the initial load capacity of an energy storage system of a super-capacitor. By configuring energy storage to alleviate the impact of the pulse load of the industrial production on the power grid, theoretical basis can be provided for the energy storage configuration of the super-capacitor of the pulse load.

The invention discloses a pile foundation dynamic stability analysis and calculation method under the action of a wave load, which comprises the following steps: sorting to obtain a Mathieu equation in a non-homogeneous form, and solving to obtain a critical frequency and an unstable load of parameter resonance; verifying the correctness of theoretical derivation by comparing an analytical solution with a calculation result of finite element simulation. Calculation result analysis shows that the pile top load P0 and the pile body water entry depth have great influence on the instability load,but the instability load is also influenced by the resonance frequency; the influence of the pile side soil body resistance coefficient m on the parameter resonance frequency is maximum, the instability frequency of parameter resonance is rapidly increased along with the increase of m, the stability of the pile body can be effectively improved, and the relative influence of the pile body mass M and the soil body shearing rigidity G on the instability frequency of the pile body is small and cannot be ignored; influences of factors such as pile diameter, wavelength and wave height on amplitude are different and can be adjusted according to specific engineering practice, so that the stability of a pile body is improved.

A buoyant cable antenna element is taught that employs a specific double-negative meta-material sheath with a negative permeability. The double-negative meta-material sheath is disposed over the insulated wire portion of the buoyant cable antenna element. The double-negative meta-material sheath enables a deliberate reduction in the antenna wire inductance to a zero value at a desired critical frequency. Reducing the antenna wire inductance to zero creates a traveling wave structure antenna having enhanced bandwidth.