Frequency Pulse Signal Research Articles

Ultrasensitive and Wash-Free Detection of Tumor Extracellular Vesicles by Aptamer-Proximity-Ligation-Activated Rolling Circle Amplification Coupled to Single Particle ICP-MS.

Tumor-derived extracellular vesicles (TEVs) are rich in cellular information and hold great promise as a biomarker for noninvasive cancer diagnosis. However, accurate measurement of TEVs presents challenges due to their low abundance and potential interference from a high number of EVs derived from normal cells. Herein, an aptamer-proximity-ligation-activated rolling circle amplification (RCA) method for EV membrane recognition, coupled with single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) for the quantification of TEVs, is developed. When DNA-labeled ultrasmall gold nanoparticle (AuNP) probes bind to the long chains formed by RCA, they aggregate to form large particles. Notably, small AuNPs scarcely produce pulse signals in sp-ICP-MS, thereby detecting TEVs in a wash-free manner. By leveraging the strong binding affinity of aptamers, dual aptamers for EpCAM and PD-L1 recognition, and the sp-ICP-MS technique, this method offers remarkable sensitivity and selectivity in tracing TEVs. Under optimized conditions, the present method shows a favorable linear relationship between the pulse signal frequency of sp-ICP-MS and TEV concentration within the range of 105-107 particles/mL, along with a detection limit of 1.1 × 104 particles/mL. The pulse signals from sp-ICP-MS combined with machine learning algorithms are used to discriminate cancer patients from healthy donors with 100% accuracy. Due to its simple and fast operation and excellent sensitivity and accuracy, this approach holds significant potential for diverse applications in life sciences and personalized medicine.

Experimental research on signal sensing of distributed acoustic sensing optical fiber based on Φ-OTDR in shallow water

The distributed acoustic sensing (DAS) technology based on phase-sensitive optical time domain reflectometry (Φ-OTDR) has been widely and well applied on land. Meanwhile, the distributed acoustic sensing optical fiber (DASF) based on Φ-OTDR, as a new type of sensor, is still in the initial stage of research, gets much attention in recent years because of its long-distance monitoring, high sensitivity, anti-electromagnetic interference, good concealment and so on. Performances of DASF in sensing different kinds of acoustic source signals were given by experiments in shallow water, which included single frequency pulse signal in the fixed position, the moving single frequency continuous pulse signal, the moving broadband signal, and the signal generated by the sailing surface target. Depth of the active sound source was changed to examine the performance of DASF in sensing signals in different depths. The specific experimental process was given, and the experimental results were processed and analyzed. Additionally, wave components of data generated from of the sailing surface vessel were explored with the time delay difference between the equivalent array elements of DASF. Results show that DASF can sense the above varieties of underwater acoustic signals well, and the physical field generated by the sailing surface vessel in shallow water include acoustic field and flow field, in which the propagation velocity of the former is faster than that of the latter.

Geoacoustic Inversion Using Modal Dispersion Curves

This paper presents a broadband geoacoustic inversion method based on matching the estimated dispersion curves extracted from low frequency pulse signal by warping transform and the simulated dispersion curves. The single receiver broadband inversion of the geoacoustic parameters is implemented using the first three orders of the dispersion curves, and the results are assessed using the parameter distribution and propagation loss deviation. The simulation outcomes demonstrate the method’s broad applicability for inverting geoacoustic parameters and the warping transform’s relative accuracy for dispersion curves estimation in waveguide environments with significant vertical sound speed modification.

Detection of Low Frequency Pulse Signal in LSI Based on Deep Self Coding Algorithm

In order to detect the pulse of LSI with high accuracy and efficiency, a new detection method of low frequency pulse signal of LSI based on deep self coding algorithm is proposed in this paper. Firstly, Radon transform is used to reduce the dimension of the time-frequency diagram of the pulse signal of the integrated circuit, and the short-time Fourier transform of the pulse signal is completed according to the Hamming window. Secondly, the principle of the depth self encoder is analyzed, and the pulse signal after the short time Fourier transform processing is input into the depth self encoder. Finally, according to the distance function, the gradient descent algorithm is used to update the parameters. Through iterative calculation, the detection of low frequency pulse signal of LSI is completed. The experimental results show that, compared with the traditional low-frequency pulse signal detection method, the detection accuracy of this method is greatly improved, up to 99.79%, and can shorten the overall detection time.

Analysis of Electromagnetic Interference Effect of the Pulse Interference on the Navigation Receiver

Aiming at the problem that satellite navigation signals are easily interfered by the radio frequency (RF) pulse signal, the electromagnetic interference effect of RF pulse on the navigation receiver is studied in this paper. A mathematical model of the pulse interference signal is established, and we choose the bit error rate (BER) as an indicator of the quality of the BDS signal. It is found that the BER is proportional to the duty cycle of the pulse signal and inversely proportional to the equivalent carrier-to-noise ratio (C/N0) through simulation. Then, an experiment of electromagnetic injection on the BDS receiver has been carried out, which studied the influence of the pulse interference parameters, such as repetition frequency and duty cycle on the C/N0 of the BDS signal and the electromagnetic sensitivity threshold of the receiver. The comparative experiment between the pulse interference and the single-frequency continuous wave (CW) interference was also carried out, and we found that the effect of the pulse interference is better than that of single-frequency CW interference. The former is the correlation interference, and the latter is the blocking interference. Combined with the experiment phenomenon, the interference mechanism was further analyzed according to the relationship between the pulse period and the ranging code period of the navigation signal.

A homogeneous nucleic acid assay for simultaneous detection of SARS-CoV-2 and influenza A (H3N2) by single-particle inductively coupled plasma mass spectrometry

In recent years, single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) has become a powerful tool for biological quantitative analysis. Homogeneous analysis method requires no separation and washing steps, which is suited for the analysis of highly infectious pathogens, so as to reduce the risk of infection during the operation. SARS-CoV-2 spreads all over the world, and its early infection symptoms are similar to influenza, which brings inconvenience to triage. Therefore, developing novel analytical method for simultaneous detection of multiple viral nucleic acids is essential. Taking the advantages of SP-ICP-MS and homogeneous analysis strategy, a SP-ICP-MS homogeneous nucleic acid assay by using gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs) probes was established for simultaneous sensitive analysis of SARS-CoV-2 and influenza A (H3N2). In the present of target SARS-CoV-2 or H3N2 nucleic acids, corresponding Au NPs or Ag NPs probes form larger aggregates, resulting in increased pulse signal intensity and reduced pulse signal frequency of the corresponding NPs in SP-ICP-MS measurement. In this assay, the reaction system of Au NPs and Ag NPs probes does not interfere with each other, and there was no separation and washing procedure, which facilitates operation, saves the analysis time, and improves the analysis efficiency. The linear range of this method is 5–1000 pmol L−1, with low-level limits of quantification of target nucleic acid. The developed SP-ICP-MS simultaneous homogeneous detection method has a good potential for detecting nucleic acid, protein, cell and other biological samples by changing different modification sequences on the NPs probes.

An Optimized Design Method of PSWFs Pulse Group Based on DFT Precoding

Aiming at the problems of non-sinusoidal time-domain multiple quadrature modulation signals based on Prolate Spheroidal Wave Functions (PSWFs), as the number of pulses increases, the bandwidth efficiency of the modulation signal frequency band decreases, the Peak-to-Average Power Ratio (PAPR) and the implementation complexity are high, a method for optimal design of PSWFs pulse groups based on DFT precoding is proposed. The PSWFs pulse signal frequency domain generation method is adopted. By introducing the precoding matrix, the multi-channel PSWFs pulse group signals are optimized and designed, and then the input data is redistributed to obtain new PSWFs pulse group signals. Experimental results show that this method can further improve the power efficiency of the modulated signal and effectively reduce the peak-to-average power ratio of the modulated signal without changing the orthogonality of the original PSWFs subcarriers. As the number of carriers increases, the suppression effect on the peak-to-average power ratio becomes more obvious.

The antenna system with signal polarization separation

The results of the study of the electrical characteristics of the waveguide-coaxial structure of the polarization separator (orthoplexer) loaded by the waveguide irradiator under the influence of harmonic radiation in the frequency band and pulse signal are presented. The antenna system is designed to study partially-non-reciprocal backscattering of electromagnetic waves.

A reliable initial rotor position estimation method for sensorless control of interior permanent magnet synchronous motors

In this paper, a novel initial rotor position estimation method for reliable start-up of the IPMSM is presented. The proposed method combines the improved high frequency pulse signal injection with positive and negative d-axis current bias injection. Differing from the conventional initial rotor position detection scheme, the injection and the field-oriented control periods are separated in the proposed method. Therefore, the filters are not needed in the process of high-frequency response current and fundamental current extraction. The magnet polarity can be estimated by exciting the positive and negative d-axis currents. Afterwards, the peak values of d-axis current during the voltage injection period are accumulated to detect the rotor magnetic polarity. The proposed method can improve the reliability of the magnet polarity detection. Moreover, it is suitable for both the standstill rotor application and the free-running rotor application. The effectiveness of the proposed method is verified on a 1.5 kW IPMSM drive platform.

Characterization of concentrated and distributed cracks in concrete using a harmonic wave modulation technique

In this work, the damage progression of concrete cracks presented in concentrated form caused by mechanical load and presented in distributed form caused by chemical attack is characterized by a harmonic wave modulation technique. The relative amplitude of sidebands in frequency domain due to the modulation effect of two propagating ultrasonic waves is considered as the damage index for concrete samples. The low frequency signal in this research is a harmonic wave produced by an electromagnetic exciter to avoid the uncertainty of man-made influence previously where the low frequency pulse signal was generated by the instrumented hammer. Both the first order sideband corresponding to classical nonlinearity effect and the second order sideband corresponding to hysteresis nonlinearity effect are simultaneously analyzed through the ultrasonic experiments for damaged samples induced by the sulfate attack and bending tests. The nonlinear parameters present a good distinction between damaged and intact samples for both concentrated cracks and distributed cracks and have an increase in orders of magnitude, showing the well-round feasibility of developed nonlinear wave modulation technique. Furthermore, the nonlinear parameters in the wave modulation technique present an excellent correlation with the nonlinear parameter obtained by the second harmonic generation method for bending cracks of the same reinforced concrete, indicating that the wave modulation method is capable of discriminating different state of damage presented in concentrated cracking form.

The use of a static electrical energy meter as a transducer of active power to a pulse frequency signal

The use of a static electrical energy meter as a transducer of active power to a pulse frequency signal

Electromagnetic pulses bone healing booster

Posttraumatic bone restoration triggered by the need to assist and stimulate compensatory bone growth in periodontal condition. Recent studies state that specific electromagnetic stimulation can boost the bone restoration, reaching up to 30% decrease in recovery time. Based on the existing data on the electromagnetic parameters, a digital electronic device is proposed for intra oral mounting and bone restoration stimulation in periodontal condition. The electrical signal is applied to an inductive mark that will create and impregnate magnetic field in diseased tissue. The device also monitors the status of the electromagnetic field. Controlled wave forms and pulse frequency signal at programmable intervals are obtained with optimized number of components and miniaturized using surface mounting devices (SMD) circuits and surface mounting technology (SMT), with enhanced protection against abnormal current growth, given the intra-oral environment. The system is powered by an autonomous power supply (battery), to limit the problems caused by powering medical equipment from the main power supply. Currently the device is used in clinical testing, in cycles of six up to twelve months.Basic principles for the electrical scheme and algorithms for pulse generation, pulse control, electromagnetic field control and automation of current monitoring are presented, together with the friendly user interface, suitable for medical data and patient monitoring.

Study on Pulse-Signal Detection Methods Using Wavelet Transform and Hilbert Huang Transform

The practical wrist pulse of the healthy person and the coronary heart disease patient were analyzed by wavelet transform (WT) and hilbert huang transform ( HHT), and the characteristic information (percentage of energy density) of the pulse signal was discussed. The simulation results show that both WT and HHT are efficient ways in analyzing and processing pulse signal, and can draw main characteristic information from pulse signal. However the basis function is preselected in WT, it doesnt need to be preselected in HHT. In HHT the intrinsic mode function (IMF) is obtained by empirical mode decomposition (EMD), it can reflect the instantaneous frequency of pulse signal, and has the actual physical meaning. The resolving power of time and frequency in WT is restricted by Heisenberg uncertainty principle, and is restricted by each other. While the resolving power of time and frequency in HHT is adaptively changed according to signal intrinsic characteristics. The HHT is more adaptive than WT in analyzing pulse signal. The HHT can offer a new idea to diagnose cardiovascular disease by wrist pulse signal.

Application Research of the Power Spectrum Estimation in the Ankle-Brachial Index Detection

The key of ankle-brachial index (ABI) measurement is accurately measurement of upper and lower extremities systolic pressure. When the blood flow is blocked, blood flow will resume a normal beat and the corresponding cuff pressure of the first trough starting point is the systolic pressure. First it detects the pulse signal main frequency by spectral analysis of the pulse signal which based on the power spectrum estimation. Regarding pulse signal frequency as the basic standard, it achieves power spectrum estimation of blood flow signal with a sliding window. Last it achieves locating the position of systolic pressure by detecting whether the blood flow signal frequency and the pulse signal frequency are the same. Through simulation and experiments, it can achieve accurate detection of systolic pressure and automatic measurement of ankle-brachial index by application of this method.

Phase Locked Loop Pulse Signal Frequency Multiplication Circuit Design Based on FPGA

Phase locked loop pulse interpolation technique requires for the input pulse signal frequency multiplication processing. With FPGA as the core, by detecting the edge of the input pulse signal the separate frequency factor was generated, then frequency division of the system clock was realized according to the separate frequency factor, thus phase locked loop frequency multiplication processing of the input pulse signal was completed. The simulation results show that this method has the advantages of high precision and short frequency response time, etc.

Multi-port voltage-subtracting circuit based on resonant switched-capacitor

This study presents a novel multi-port power convert circuit. In order to facilitate description, the circuit is introduced as a multi-input voltage-subtracting converter. The multiple input sources are shared on a common neutral, and the output voltage is the subtraction operation of the multiple inputs. The converter is only composed by switches, diodes, capacitors and small resonant inductor. All switches only need a pair of complementary fixed frequency pulse signal with fixed duty ratio to control. The detailed circuit analysis of three-input voltage-subtracting circuits, the structure variation and characteristics of multi-input voltage-subtracting converter are summarised in the study. First, the basic switching-capacitor cell of this converter is presented; the converters with different input sources therefore can be easily designed. The small resonant inductors are used to facilitate zero-current switching, and their sizes therefore are very small and do not affect the size of circuit. At the end of this study, an energy distribution system and a multi-colour light modulation circuit based on this circuit are presented.

Effects of random bottom bathymetry on temporal and spatial coherence in shallow water propagation

Fixed system measurements for three experimental shallow water sites reveal systematic dependence of temporal and spatial coherence of individual mode arrivals on frequency and mode number that cannot be fully explained with internal wave variability. Here random fluctuations in bottom bathymetry are introduced to propagation models. Mode structures are randomized and coherence times and lengths decrease with increasing amplitude of bathymetry fluctuations for the same internal wave variations. Distinct mode features blur as frequency of pulse signals increased. Mode coupling and eventually a smearing of continuous modes are observed with increasing frequency and magnitude of bathymetry variations. For low frequencies and bathymetry variations constrained a small fraction of a wavelength, the bottom appears flat and nearly perfect discrete modes are formed. Modes are reinforced by specular reflections all along the path of propagation. Coherence depends entirely on internal wave fluctuations. All mode arrivals have nearly the same coherence times. But modes break up as height of bathymetry fluctuations become comparable to acoustic wavelength. Then sensitivity to sound speed fluctuation increases and coherence is reduced. Two dimensional bathymetry fluctuations account for observation out to 10–20 km and three-dimensional effects become important at longer ranges.

The Pig Tracking System Based on AVR Microcontroller and GPS/GSM

Oil and gas pipelines must be cleaned regularly to ensure their normal operation. It is significant to track the pig when it’s working in the pipeline. With the GPS and GSM technology, this paper introduces a kind of intelligent pig tracking system, The system uses ultra-low frequency electromagnetic wave with strong penetrating to transmit data. It concludes two parts: transmitter part and receiving part. The transmitter part which connects with the pig is controlled by SCM, interval transmitting ultra-low frequency pulse signal. The receiving part uses AVR SCM as its core controller and is mainly composed of magnetic pulse signal receiving module, GSM module, GPS module and LCD module. When the pig is working, the transmitting part interval transmits ultra-low frequency pulse signal. After receiving the right signal, the receiving part will send the location information to the designated GSM handsets. This system makes pig remote monitoring come true.

Variability of Pulse Signal Frequency Obtained Using Nocturnal Pulse Oximetry in Patients with Sleep Apnoea/Hypoapnoea Syndrome

IntroductionThe measurement of central tendency (MCT) is a non-linear analysis technique which applied to second order differences diagrams enables the degree of variability to be quantified in a data series. In the present study an attempt is made to quantify and characterise the changes in heart rate obtained by pulse oximetry in patients with a clinical suspicion of sleep apnoea/hypoapnoea syndrome (SAHS) using the MCT and to evaluate its diagnostic use. Patients and MethodsA total of 187 patients were included in the study, on whom a nocturnal polysomnographic and pulse oximetry study was performed. To evaluate the variability of the heart rate the MCT applied to graphs of second order differences obtained from the heart rate record. ResultPatients with SAHS had a higher heart rate variablity than patients without SAHS (0.449 vs 0.666, P<.001). In the multivariate analysis, the heart rate, the minimum saturation and the desaturation index of 4% were independently associated with the heart rate variability. As a diagnostic method, the MCT of the heart rate gives a sensitivity of 69.3%, a specificity of 77.6% and a diagnostic precision of 72.7%. ConclusionsPatients with SAHS have a greater variabilityin heart rate during the night, evaluated by applying the MCT of the heart rate to diagrams of second order differences. As a screening method, the MCT applied to the heart rate has a moderate sensitivity and specificity.

A Mathematical Model of a Neuron with Synapses based on Physiology

AbstractThe neuron, when considered as a signal processing device, itsinputs are the frequency of pulses received at the synapses, and its output is the frequency of action potentials generated- in essence, a neuron is a pulse frequency signal processing device. In comparison, electrical devices use either digital or analog signals for communication or processing, and the mathematics behind these subjects is well understood. However, in regards to pulse frequency processing devices, there has not yet been a clear and persuasive mathematical model to describe the functions of neurons. It goes without saying that such a model is very important, not only for understanding neuron and neural system behavior, but also for undeveloped potential applications in industry. This paper proposes a method for obtaining the mathematical relationship between the input and output signals of a neuron based on physiological facts. The proposed method focuses on the currents across the postsynaptic membrane of each synapse, and the key is to recognize that the net charge across the whole membrane of a neuron over each action potential cycle must equal to zero. By analyzing the relationship between the input of a synapse and the currents across the postsynaptic membranes, a dynamic pulse frequency model of the neuron can be obtained. Here, we show that the transfer function of a neuron depends on the function of thepostsynaptic current of each synapse in resting state, which can be found by detecting the postsynaptic current when a pulse is received at the synapse. The transfer function of a typical neuron generally includes addition and subtraction of feedthrough terms and/or first order lag functions. To focus on the most basic characteristics of a neuron, accommodation, adaptation, learning, etc. are not discussed in this paper.