Abstract: The present disclosure discloses a Beidou signal tracking system with a nonlinear phase-locked loop. A nonlinear element and a low-pass filter are added behind a loop filter to adapt to an output from control of the loop filter, and then to control a phase of an output signal. An in-phase branch pre-filtering link is added before the loop filter to smoothly processing an input signal, and a loop filter of a third-order phase-locked loop assisted by a second-order frequency-locked loop is selected to ensure basic performance index of an algorithm. The in-phase branch pre-filtering link controls signal change of an in-phase branch signal within a reasonable range. The nonlinear element and the low-pass filter behind the loop filter, after proper selection of parameters, can make the phase-locked loop quickly lock within the range where the phase-locked loop could not be locked originally.

Abstract: Provided is a BeiDou navigation satellite B1C signal capturing method, including: mixing a digital intermediate frequency signal with a local intermediate frequency carrier signal to obtain a baseband signal; obtaining a local BOC-like signal on a data channel and a local BOC-like signal on a pilot channel; processing the local BOC-like signal on the data channel and the local BOC-like signal on the pilot channel to obtain a cross-correlation result of the data channel and a cross-correlation result of the pilot channel; performing a linear operation on the cross-correlation result of each of the two channels through a pseudo-correlation function generator to eliminate a secondary peak in the cross-correlation result of each of the two channels, and obtain an optimized cross-correlation result of each of the two channels; and capturing a satellite signal based on the optimized cross-correlation result of each of the two channels.

Abstract: A method for extracting f wave from a single-lead electrocardiography signal is provided. The method includes: establishing a two-channel temporal convolutional neural network model, including two coding submodules, two mask estimation submodules, an information fusion module and two decoding submodules; constructing a training data set of ECG signals; training the two-channel temporal convolutional neural network model, and saving the trained model. The two-channel temporal convolution neural network encodes and decodes a QRST complex and the f wave respectively, and uses a mask of information fusion to estimate and construct regular items to restrict a distribution difference of QRST component coding features, so as to reduce the distortion of the QRST complex, select potential features of a QRST complex and f wave with high signal-to-noise ratio, and thus improve a detection accuracy of the f wave.

Abstract: A method for extracting f wave from a single-lead electrocardiography signal is provided. The method includes: establishing a two-channel temporal convolutional neural network model, including two coding submodules, two mask estimation submodules, an information fusion module and two decoding submodules; constructing a training data set of ECG signals; training the two-channel temporal convolutional neural network model, and saving the trained model. The two-channel temporal convolution neural network encodes and decodes a QRST complex and the f wave respectively, and uses a mask of information fusion to estimate and construct regular items to restrict a distribution difference of QRST component coding features, so as to reduce the distortion of the QRST complex, select potential features of a QRST complex and f wave with high signal-to-noise ratio, and thus improve a detection accuracy of the f wave.

Abstract: Provided is an optical interference light source device of a current-temperature controlled semiconductor laser, including a heat dissipation plate, a ring-shaped semiconductor refrigerating sheet, a semiconductor laser, a PCB board, a thermal sensor and a fixed plate. The first circular window copper area of the PCB is in contact with the second circular copper area through a via. A lower end of a housing of the semiconductor laser is connected to the first circular windowed copper area through a thermally conductive silicone grease. The ring-shaped semiconductor refrigerating sheet is connected to the first circular window copper area through a thermally conductive silicone grease connected to the heat dissipation plate. The thermal sensor is configured to detect a temperature of the first circular windowed copper area. The present disclosure has beneficial effects of simple structures, good thermal conductivities, high temperature control precisions, and stable output wavelengths of the laser.

Abstract: Provided is a device for measuring a lens three-dimensional profile based on laser wavenumber scanning, including: a semiconductor laser for emitting coherent light; a beam splitter for dividing the coherent light into two parts; an optical wedge; a CCD camera for capturing an interference image; a computer for processing image information; a laser controller for adjusting an operating temperature and an operating current of the semiconductor laser; and a bilateral telecentric lens. The coherent light is reflected by the optical wedge and then reaches the bilateral telecentric lens through the beam splitter, to form a first reflected light path. The coherent light is reflected by the measured lens, and then reaches the bilateral telecentric lens through the beam splitter, to form a second reflected light path. The first reflected light path and the second reflected light path form an interference image after passing through the bilateral telecentric lens.

Abstract: The present disclosure discloses a dual-channel optical three-dimensional interference method based on underdetermined blind source separation, which blindly separates out, through interference data collected by a CCD camera, interference signals between surfaces of a slide under test, to solve interference signal parameters, including an interference signal amplitude-frequency and an interference signal phase-frequency. Based on a dual-channel optical three-dimensional Michelson-type interference experiment, estimation of a mixed matrix is obtained by a K-means clustering algorithm, and recovery of a source signal is achieved by a L1 norm shortest path method. It is finally achieved that laser wavenumber scanning can accurately and blindly separate out the interference signals of the four surfaces based on light intensity values collected by the CCD camera, to achieve the blind separation of the interference signals of the four surfaces.

Abstract: The present disclosure discloses a dual-channel optical three-dimensional interference method based on underdetermined blind source separation, which blindly separates out, through interference data collected by a CCD camera, interference signals between surfaces of a slide under test, to solve interference signal parameters, including an interference signal amplitude-frequency and an interference signal phase-frequency. Based on a dual-channel optical three-dimensional Michelson-type interference experiment, estimation of a mixed matrix is obtained by a K-means clustering algorithm, and recovery of a source signal is achieved by a L1 norm shortest path method. It is finally achieved that laser wavenumber scanning can accurately and blindly separate out the interference signals of the four surfaces based on light intensity values collected by the CCD camera, to achieve the blind separation of the interference signals of the four surfaces.

Abstract: Provided is an optical interference light source device of a current-temperature controlled semiconductor laser, including a heat dissipation plate, a ring-shaped semiconductor refrigerating sheet, a semiconductor laser, a PCB board, a thermal sensor and a fixed plate. The first circular window copper area of the PCB is in contact with the second circular copper area through a via. A lower end of a housing of the semiconductor laser is connected to the first circular windowed copper area through a thermally conductive silicone grease. The ring-shaped semiconductor refrigerating sheet is connected to the first circular window copper area through a thermally conductive silicone grease connected to the heat dissipation plate. The thermal sensor is configured to detect a temperature of the first circular windowed copper area. The present disclosure has beneficial effects of simple structures, good thermal conductivities, high temperature control precisions, and stable output wavelengths of the laser.

Abstract: Provided is a device for measuring a lens three-dimensional profile based on laser wavenumber scanning, including: a semiconductor laser for emitting coherent light; a beam splitter for dividing the coherent light into two parts; an optical wedge; a CCD camera for capturing an interference image; a computer for processing image information; a laser controller for adjusting an operating temperature and an operating current of the semiconductor laser; and a bilateral telecentric lens. The coherent light is reflected by the optical wedge and then reaches the bilateral telecentric lens through the beam splitter, to form a first reflected light path. The coherent light is reflected by the measured lens, and then reaches the bilateral telecentric lens through the beam splitter, to form a second reflected light path. The first reflected light path and the second reflected light path form an interference image after passing through the bilateral telecentric lens.

Abstract: The present disclosure provides a method for measuring an ambient brightness value, including: obtaining an exposure value of a photographing device during an automatic exposure process and an image brightness value corresponding to the exposure value; and determining an ambient brightness value based on the exposure value, the image brightness value, and an automatic exposure enhancement coefficient of the photographing device.

Abstract: A method for controlling an infrared illuminator and a related image-recording device are provided. The method for controlling an infrared illuminator includes: turning on the infrared illuminator in a filming environment to provide light; filtering out light-reflection interference caused by the light to obtain an actual visible illuminance value; and controlling on and off states of the infrared illuminator based on the actual visible illuminance value.

Abstract: The present disclosure discloses a blind separation based high accuracy perspective detection method for a multilayer complex structure material. The method is achieved through blind separation of single channel periodic signals and frequency modulation interference of laser wave numbers. In this method, time series interference images captured by a photodetector are subjected to zero mean normalization; a vector ? of amplitude, frequency and phase field, which is to be solved and reflects characteristics of each interface in the multilayer complex-structure material, is created and is solved using a mathematical optimization method; a phase field distribution of the vector ? is finally extracted and is subjected to phase unwrapping, to realize high accuracy detection on an internal distribution of the multilayer complex structure material.

Abstract: A method for automatically adapting to a Wi-Fi network with hidden service set identifier (SSID) is provided. The method includes a wireless access point (AP) hiding an SSID of the wireless AP and receiving a probe request frame containing request information for automatically adapting to a Wi-Fi network of the wireless AP within coverage of the wireless AP. The method also includes the wireless AP determining whether the probe request frame contains the request information for automatically adapting to the Wi-Fi network of the wireless AP and the wireless AP sending a probe response frame when the probe request frame contains the request information for automatically adapting to the Wi-Fi network of the wireless AP. Further, the method includes the wireless AP receiving a connection request sent by at least one Wi-Fi terminal, such that the at least one Wi-Fi terminal is connected to the Wi-Fi network wirelessly.

Abstract: The present disclosure provides a method for measuring an ambient brightness value, including: obtaining an exposure value of a photographing device during an automatic exposure process and an image brightness value corresponding to the exposure value; and determining an ambient brightness value based on the exposure value, the image brightness value, and an automatic exposure enhancement coefficient of the photographing device.

Abstract: A method for controlling an infrared illuminator and a related image-recording device are provided. The method for controlling an infrared illuminator includes: turning on the infrared illuminator in a filming environment to provide light; filtering out light-reflection interference caused by the light to obtain an actual visible illuminance value; and controlling on and off states of the infrared illuminator based on the actual visible illuminance value.

Abstract: The present disclosure relates to medical monitoring and provides a method and an apparatus for detecting an instantaneous fetal heart rate of a Doppler fetal heart sound based on time-frequency analysis.

Abstract: The present disclosure discloses an apparatus for measuring an internal strain field of a dental resin, comprising: an optical measurement system, a probe and a data processor, wherein an optical fiber coupler in the optical measurement system has one input terminal connected to a light source, one output terminal connected to the probe, the other output terminal provided with an optical component including a reflective element for forming reference light and the other input terminal provided with an photoelectric imaging apparatus for receiving interference light formed by object light and the reference light. The probe is configured to irradiate detection light outputted from the optical fiber to a measured tooth and receive object light which is reflected by the tooth; and the data processor is configured to obtain a measurement result of the internal strain field of the measured dental resin according to an interference spectrum obtained through imaging by the photoelectric imaging apparatus.

Abstract: Methods and systems for multiple Wireless Fidelity (Wi-Fi) devices automatically connecting to a specified access point (AP) are provided. The method includes defining an encryption field in a beacon frame. The encryption field contains connection information of the specified AP defined by a vendor and each of the multiple Wi-Fi devices is from the same vendor. The method also includes assigning respectively a key that decrypts the connection information of the specified AP contained in the encryption field to each Wi-Fi device, and broadcasting the connection information of the specified AP contained in the encryption field of the beacon frame by any AP containing the encryption field. Further, the method includes decrypting the connection information of the specified AP contained in the encryption field of the beacon frame by the multiple Wi-Fi devices having the key, such that the multiple Wi-Fi devices are connected to the specified AP.

Abstract: The present disclosure provides a method for scalable transmission of a video track. In the method, a video source is compressed and encoded by using a scalable video coding scheme and information related to the encoding process is recorded. A video track file is generated for describing importance and address information for the respective code stream block. During the video transmission process, a code stream selection unit selects and organizes a code stream based on the video track file and an available network bandwidth for transmission. A video receiver receives and decodes the code stream and estimates the available network bandwidth and feeds information on the available network bandwidth back to the video transmitter. With the method according to the present disclosure, the smoothness of the video can be guaranteed even if the network environment deteriorates, despite some degradation in video quality.