Pulsed Detection Research Articles

Light shift suppression with pulsed light detection in magnetic-state-selected cesium beam clocks.

Light detection is widely used in atomic clocks. The simple detecting structure induces the light shift which influences the clock's long-term stability. We introduce a new method to suppress light shift by using pulsed light instead of continuous light to detect atomic states. Under a suitable pulsed sequence, the part of the atoms which do not simultaneously interact with light and microwave field are detected. We demonstrate the validity of our approach in a magnetic-state-selected cesium beam clock. Using a well-tuned sequence, the light shift coefficient is reduced by a factor of about 10, in comparison with the continuous light detection scheme. In a clock stability test with extra light power noise, the result shows good immunity of the method to laser power fluctuations. We also analyze the sources of the clock short-term stability degradation, including the Dick effect and the fact that a reduced number of atoms is detected in the pulsed detection case.

Abstract 199: Femoral Artery Doppler Ultrasound Blood Flow Patterns Predict Intrinsic Pulsatility In Cardiac Arrest Patients Receiving Active Chest Compressions

Introduction: Pulse detection requires chest compression interruption, which is associated with poor outcomes in cardiac arrest. Currently no modality can reliably identify return of spontaneous circulation with ongoing chest compressions. Hypothesis We hypothesized that patients with intrinsic pulsatility have anterograde dominant blood flow (ADF) on arterial Doppler ultrasound; whereas those with intrinsic pulselessness have bidirectional blood flow moving antero/retrograde during chest compression/decompression. Methods: We conducted a prospective, diagnostic accuracy study on a convenience sample of adult Emergency Department (ED) cardiac arrest patients with a femoral arterial line in place. Immediately prior to a pulse check, pulsed-wave Doppler ultrasound of the common femoral artery was performed during active chest compressions. Bidirectional flow was present when the anterograde flow waveform was equal in peak systolic velocity to the retrograde flow waveform. All other Doppler waveforms were ADF. A pulse was present when there was an arterial line waveform. Sensitivity, specificity, and accuracy of ADF versus bidirectional flow for predicting pulsatility was assessed. Results: We enrolled 42 patients and performed 104 pulse checks: a pulse was present for 73 (70.2%) and absent in 31 (29.8%). ADF was present in 82 (78.9%) and bidirectional flow was present in 22 (21.2%). Sensitivity of ADF for detecting a pulse was 95.9% (95% CI: 91.3%-100.0%). Specificity of bidirectional flow for detecting pulselessness was 61.3% (95% CI: 44.1-78.4%) and accuracy was 85.6% (95% CI: 77.3-91.7%). Patients with ADF have 36.9 times the odds of having an arterial line pulse compared with patients with bidirectional flow (OR: 36.9; 95% CI: 9.5-144.4). Conclusion: In ED cardiac arrest patients, ADF on Doppler ultrasound has high sensitivity for detecting an arterial line pulse. Further studies are needed to further evaluate this novel finding.

Determination of a High-Power THz Detector for EA-FEL Radiation Using Optical Sampling of GaAs and ZnTe Crystals

This paper presents a diagnostic method for THz pulses produced by EA-FEL. Experimental results present a comparison between ZnTe and GaAs crystals for the detection of a single terahertz pulse using electro-optic sampling. In order to match an electro-optic detector for the EA-FEL radiation, the THz pulse from a source was simultaneously detected by ZnTe and GaAs electro-optic detectors. The GaAs detection system was found to have a shorter response time but low signal-to-noise ratio (SNR) compared to the ZnTe system. The GaAs crystal is suitable for the detection of short THz pulses due to fiber coupling, and the SNR of the GaAs system can be improved using a faster and more sensitive photodetector.

Electrical and optical characterization of multi-hollow surface dielectric barrier discharge in configuration with the air-exposed electrode

In this paper, multi-hollow surface dielectric barrier discharge generated by a perforated ceramic substrate in a configuration with the air-exposed electrode was investigated. The electrical characteristics (discharge power, peak, and average amplitude of current pulses) and optical characteristics (emission intensity) of the discharge were evaluated under various conditions of applied voltage (peak voltage 3–6 kV, frequency 200–2000 Hz), air flow rate (0.5–2.4 L/min), and air relative humidity (0%–80%). Temperature of ceramic substrate was also monitored. Statistical analysis of current pulses was also performed, and histograms of amplitudes of current pulses were calculated. The results showed that discharge characteristics strictly depend on given working conditions. The analysis of current pulses showed opposite trends in average overall number of positive and negative pulses with an increase of discharge power: number of positive current pulses gradually increased, while number of negative current pulses slightly decreased. The highest peak currents were found at 4 kV (1.8 W). With further increase of peak voltage, peak current decreased and beginning of detection of current pulses upon a rising (declining) slope of applied voltage was slightly shifted toward earlier times. At the highest applied peak voltage, pulses appeared even before polarity of applied voltage reversed. Therefore, we suppose that a residual charge accumulated on dielectric surface plays a crucial role in characteristics of the current pulses. Significant influence on current pulses and discharge emission intensity was also found with a change of air relative humidity, while the effect of air flow rate was found weaker.

Temperature-adaptable pressure sensors based on MXene-coated GO hierarchical aerogels with superb detection capability

With the broader application of intelligent sensors in various complex conditions, sensing materials with better mechanical and conductive properties as well as higher temperature adaptability are required. For this purpose, a GO/PVA/MXene (GPM) composite aerogel was designed and prepared via a two-step strategy, including self-assembly and vacuum-assisted dip-coating processes. The as-prepared GPM has a unique structure composed of hierarchical GO network skeleton and MXene coating, endowing it with high Young's modulus (11.2 kPa) and compressibility (90%). Demonstrated with the finite element (FE) simulation, the elasticity and toughness of the GPM are originated from the hierarchical microstructure and the improved thickness of shells. Besides, the GPM exhibits a long-term durability of 5,000 compression cycles at 50% strain, a high sensitivity of 1.744 kPa−1, and a rapid response time of 4.5 ms. Further application examples reveal that the pressure sensor based on GPM has superior physiological signal capture capability, realizing fingertip pulse and temporal artery detections. Moreover, the GPM aerogel possesses high thermal insulation efficiency, resulting in good temperature adaptability in harsh environments from −196 °C to 300 °C. The sensitive pressure sensors should have the potential application in many fields of intelligent factories, complex militaries, and space discoveries.

BaTiO3-Refined NiCuZn Ferrites Towards Enhanced Pulse Detection Sensitivity for a High-Frequency Current Transformer

BaTiO3-Refined NiCuZn Ferrites Towards Enhanced Pulse Detection Sensitivity for a High-Frequency Current Transformer

Identification Friend or Foe Mode Code Detection Using Deep Pulse Detector Network

Identification friend or foe, or its civilian variant known as secondary surveillance radar, is a cooperative airborne identification system that uses coded pulses for providing identity information via an interrogation–response mechanism. The major challenge in this mechanism is the difficulty in correctly decoding the IFF mode code data from the received responses, especially at low signal-to-noise ratios. Due to the high tolerances allowable (as per the Standardization Agreement 4193 and International Civil Aviation Organization Annex 10 aeronautical telecommunication standards for pulse width, pulse positions, and frame width), the statistical variations in the replies are high, which makes the rule-based algorithms complex and less robust. Also, the decoding becomes increasingly difficult due to the garbling of pulses from multiple close-by transponders. To address these challenges of IFF reply processing, this paper proposes modular blocks based on a deep neural network for end-to-end reply processing in the IFF system. IFF pulse detection and degarbling are performed using a convolutional neural-network-based approach, followed by code detection using a recurrent neural-network-based approach, and code tracking using a fully connected network. Because the network is trained to learn the statistical variations in data, it outperforms the conventional rule-based signal processing in terms of probabilistic code detection.

QCA-Based Pulse/Bit Sequence Detector Using Low Quantum Cost D-Flip Flop

In this paper, a Quantum-Dot Cellular Automata (QCA)-based [Formula: see text]-flip flop is designed with low quantum cost to propose a 3-bit sequence detector which detects a bit pattern 101 in both overlapping and non-overlapping forms. Initially, a level to edge-triggered clock converter is proposed to convert clock signal levels into edge defining signals. Later, [Formula: see text]-flip flops of both level and edge triggered clock inputs are developed. Compared with the recently reported designs in the literature, it is observed that the quantum cost of the proposed [Formula: see text]-flip flops is decreased by more than 28% with a cell count of 34, which in turn defines the low area too. Also, latency of the same is reduced by one-fourth with a value of [Formula: see text] s. As far as the sequence detector is concerned, it is smaller in size at 0.16[Formula: see text][Formula: see text]m2 than the existing sequential circuits with a reduction in area and quantum cost by 30%. Further, from the bit stream it detects, the proposed sequence detector can also be used as negative pulse detector and interrupt handler circuit in the future QCA-based digital systems to detect the external interrupts.

Development of Pressure Sensor Based Wearable Pulse Detection Device for Radial Pulse Monitoring.

Wearable pulse detection devices can be used for daily human healthcare monitoring; however, the relatively poor flexibility and low sensitivity of the pulse detection devices are hindering the scrutiny of pulse information during pulse diagnosis of different pulse positions. This paper developed a novel and wearable pulse detection device based on three flexible pressure sensors using synthetic graphene and silver composites as the pressure sensing material. The structural design of the pulse detection device is firstly presented; the core component of pressure sensors is using the sawtooth protrusions to convert pressure induced by radial pulse vibrations into localized deformation of graphene composites. The fabricated pulse detection device is characterized by high pressure sensing performance, including relatively high sensitivity (8.65% kPa−1), broad sensing range (12 kPa), and good dynamic response with a response time of about 100 ms. Then, the pulse detection device is worn on a human wrist to detect the pulses from three pulse positions, namely, ‘Cun’, ‘Guan’, and ‘Chi’, and the results demonstrated the capability of using our device to detect pulse signals. The physical conditions of the subject, such as arterial stiffness index, can be further analyzed through the characteristics of the acquired pulse signals, demonstrating the potential application of using wearable pulse detection devices for human health monitoring.

Pushchino multibeam pulsar search – II. Long-term variability of rotating radio transients

ABSTRACT Pulses from 16 previously known rotating radio transients (RRATs) have been searched for with the 111 MHz daily monitoring program for 4 to 5.5 yr using the Large Phased Array (LPA) at Pushchino. The total number of pulses detected in such a long observation interval is only 90 for RRAT J0640+07, but is as high as 10 751 for RRAT J0302+22. The number and amplitude of pulses vary on time-scales from 6 to 20 months for RRATs J1336+33, J1404+11, J1848+15, J2051+12 and J2105+22, and the pulse number can increase by one or two orders of magnitude in active phases. Long-term trends are found for RRATs J0139+33 and J0302+22, which show a 2–3 times increase in detected pulse number over 1959 d. Some RRATs show annual variations in both pulse number and pulse amplitude. It is hard to explain all these variation time-scales by refractive scintillation on the interstellar medium. The annual and semi-annual variations are probably caused by scintillations on the inhomogeneous interplanetary plasma. Our data show that the number of observational sessions with no pulse detection over the threshold decreases exponentially with the length of pulse silence.

Highly Sensitive Zwitterionic Hydrogel Sensor for Motion and Pulse Detection with Water Retention, Adhesive, Antifreezing, and Self-Healing Properties.

The design and synthesis of conductive hydrogels with antifreezing, long-term stable, highly sensitive, self-healing, and reusable is a critical procedure to enable applications in flexible electronics, medical monitoring, soft robotics, etc. Herein, a novel zwitterionic composite hydrogel possessing antifreezing, fast self-healing performance, water retention, and adhesion was synthesized via a simple one-pot method. LiCl, as an electrolyte and antifreeze, was promoted to dissociate under the electrostatic interaction with zwitterions, resulting in the composite hydrogels with high electrical conductivity (7.95 S/m) and excellent antifreeze ability (-45.3 °C). Meanwhile, the composite hydrogels could maintain 97% of the initial water content after exposed to air (25 °C, 55% RH) for 1 week due to the presence of salt ions. Moreover, the active groups of zwitterions could form conformal adhesion between the composite hydrogels and skin, which was particularly crucial for the stable signal output of the sensor. The dynamic borate ester bonds, active group of zwitterions, and the hydrogen bond between different components could achieve rapid self-healing (2 h, self-healing efficiency to 97%) without any external intervention. Notably, the developed PBAS-Li (poly(vinyl alcohol) Borax/acrylamide/zwitterionic-LiCl) hydrogel not only succeeded in sensitively detecting human motions but also could precisely captured handwritings signals and subtle pulse waves on the neck and wrist. The above findings demonstrated the great potential of PBAS-Li hydrogels in the field of flexible electronic devices.

Versatile self-assembled electrospun micropyramid arrays for high-performance on-skin devices with minimal sensory interference

On-skin devices that show both high performance and imperceptibility are desired for physiological information detection, individual protection, and bioenergy conversion with minimal sensory interference. Herein, versatile electrospun micropyramid arrays (EMPAs) combined with ultrathin, ultralight, gas-permeable structures are developed through a self-assembly technology based on wet heterostructured electrified jets to endow various on-skin devices with both superior performance and imperceptibility. The designable self-assembly allows structural and material optimization of EMPAs for on-skin devices applied in daytime radiative cooling, pressure sensing, and bioenergy harvesting. A temperature drop of ~4 °C is obtained via an EMPA-based radiative cooling fabric under a solar intensity of 1 kW m–2. Moreover, detection of an ultraweak fingertip pulse for health diagnosis during monitoring of natural finger manipulation over a wide frequency range is realized by an EMPA piezocapacitive-triboelectric hybrid sensor, which has high sensitivity (19 kPa−1), ultralow detection limit (0.05 Pa), and ultrafast response (≤0.8 ms). Additionally, EMPA nanogenerators with high triboelectric and piezoelectric outputs achieve reliable biomechanical energy harvesting. The flexible self-assembly of EMPAs exhibits immense potential in superb individual healthcare and excellent human-machine interaction in an interference-free and comfortable manner.

MISSING PULSE DETECTOR

As a signal goes through a rapid shift from base to higher value and after some period returns back to base value from higher value. It is considered as a pulse signal. A Missing Pulse Detector Circuit is needed to identify such missed pulses when any of the pulses in this pulse chain do not occur that have the predefined interval duration. The detector circuit is capable of delivering notification of missed pulses.

Research on two-dimensional laser warning integrated detection technology

Laser weapons are playing an increasingly important role in modern warfare. To address the growing laser threat, it is necessary to study high-performance two-dimensional laser warning integrated detection technology to achieve simultaneous measurement of two-dimensional directional angle, wavelength and pulse width of incoming laser. This is of great importance for rapid response to security threats. To this end, the paper investigates a two-dimensional laser warning integrated detection system. The measurement principle of the system is as follows: under the condition that the optical system is known, the incidence angle and wavelength of the incoming laser can be judged by the position of the zero-level and first-level diffraction spots, and the mathematical relationship is theoretically derived, so that the principle of laser pulse width measurement based on time-to-digital conversion can be analyzed. For this purpose, firstly, the pulsed laser detection system was designed, the photoelectric conversion of the pulsed laser signal and the time interval measurement were completed, and the pulse width measurement and control unit were experimentally verified. Secondly, the imaging control system of the surface array detector was designed and the imaging effect was verified, and the spot images of lasers with different central wavelengths incident from different angles were collected and the extracted spot center coordinate data were analyzed. Thirdly, the assembly and testing of the two-dimensional laser warning integrated detection system were completed, and the measured wavelength, azimuth, pitch angle and pulse width multi-parameters were tested, and the measurement results were analyzed. The test results show that the system has an azimuth angle of 95°, a pitch angle of 75°, an angular measurement resolution of ≤ 0.5°, a spectral measurement range of 400–1700 nm, and a minimum measurement pulse width of 5 ns, and the two-dimensional laser warning integrated detection system can meet the practical application requirements.

Determination of sarin and soman in industrial emissions by gas-chromatographic method using pulsating flame-photometric detector

Methods of gas chromatographic determination of trace amounts of sarin and soman in industrial emissions at a level of 1.0 × 10–6 mg/m3 have been developed. The capture and concentration of the target analyte was carried out using a specially designed sampling fluoroplastic cartridge filled with a pre-prepared sorbent Tenax TA with a grain size of 60/80 mesh and a volume of 8 cm3. The extraction of concentrated substances from the sampling cartridge was carried out using a modified and improved method of thermal desorption which consists in involving hot vapors of the solvent (resulted from the introduction of a liquid solvent into the cavity of the sampling cartridge with subsequent heating to 200°C) into desorption process in addition to the inert carrier gas. The substantially higher efficiency of the modified method of thermal desorption compared to the classical methods of extracting target substances from sorbents has been experimentally proved. Data on the quantitative content of sarin and soman were obtained by gas chromatographic method using a Varian CP-3800 gas chromatograph equipped with a pulsating flame-photometric detector, the mixture was separated on a VF-5ms capillary column. The sensitivity of a classical flame photometric detector and a pulsed flame photometric detector to sarin and soman has been studied. The developed methods have a relative error of determination about 27 %, and the duration of analysis of one sample is 3 h 30 min. The methods were tested on the real objects of control, appropriately certified and implemented in practice.

Analysis of impurity profiling of arbekacin sulfate by ion-pair liquid chromatography coupled with pulsed electrochemical detection and online ion suppressor-ion trap-time off light mass spectrometry

Ion-pair liquid chromatography with pulsed electrochemical detection (LC-PED) was established for the analysis of impurities in arbekacin (ABK) sulfate. APursuit pentafluorophenylpropyl (PFP) column was used as stationary phase. This novel method showed greater separation and sensitivity ability. In a representative ABK sample, 24 impurity peaks were detected in LC-PED, where of only 9 were monitored by a post-column derivatization method prescribed by the Japanese Pharmacopoeia (JP). For identification of the chemical structures of the impurities detected by LC-PED, LC-Mass Spectrometry (MS) was used. Two challenges had to be overcome in this work. The first was the transfer of the MS incompatible mobile phase to an MS compatibleone while maintaining the elution order of the peaks in the chromatograms. Previously reported approaches such as two-dimensional (2D)LC were hardly applicable in this case due to the lack of ultraviolet (UV) absorbing chromophores in ABK and its impurities. The sodium hydroxide solution was replaced by aqueous ammonia to adjust the pH of the mobile phase used in LC-PED. The other challenge encountered was the ion suppression effect caused by trifluoroacetic acid (TFA) and pentafluoroproponic acid (PFPA) in the mobile phase. Some strategies such as “TFA-fixed” and its modifications were tried, but they were inconvenient and severe contamination of the MS was observed. A cationself-regenerating suppressor (CSRS), which was originally designed for increasing analyte conductivityof ammonia and amines analysis in ion chromatography (IC), was coupled between the LC and Ion Trap-Time of Flight (IT-TOF)-MS and almost all TFA and PFPA in the mobile phase were removed. The limit of detection (LOD) of ABK in this integrated system improved significantly to 20 ng/mL. The chemical structures of the 28 impurities were elucidated and 15 impurities were reported for the first time.

Heart Rate Detection using a Piezoelectric Ceramic Sensor: Preliminary results

Real-time vital signs monitoring, particularly heart rate, is essential in today's medical practice and research. Heart rate detection allows the doctor to monitor the patient's health status to provide immediate action against possible cardiovascular diseases. We present a possible alternative to traditional heart rate signal monitoring systems, a cardiac pulse system using low-cost piezoelectric signal identification. This system could benefit health care and develop continuous pulse waveform monitoring systems. This paper introduces a heartbeat per minute (BPM) cardiac pulse detection system based on a low-cost piezoelectric ceramic sensor (PCS). The PCS is placed under the wrist and adjusted with a silicone wristband to measure the pressure exerted by the radial artery on the sensor and thus obtain the patient's BPM. We propose a signal conditioning stage to reduce the sensor's noise when acquiring the data and make it suitable for real-time BPM visualization. As a comparison, we performed a statistical test to compare the low-cost PCS with types of traditional sensors, along with the help of 21 volunteers. Experimental results show that the data collected by the PCS, when used for heart rate detection, is highly accurate and close to traditional sensor measurements. Therefore, we conclude that the system efficiently monitors the cardiac pulse signal in BPM. Keywords: Heart rate; Piezoelectric, BPM; Pulse Detection.

Origins of Rydberg-Atom Electrometer Transient Response and Its Impact on Radio-Frequency Pulse Sensing

Rydberg atoms show significant promise as the basis for highly sensitive detectors of continuous radio-frequency (rf) electric fields (E fields). Here, we study their time-dependent response to pulse-modulated rf E fields at 19.4 GHz using a cesium vapor cell at room temperature. We use density-matrix simulations to explain the timescales that shape the transient atomic response under different laser conditions, finding them to be limited by dephasing mechanisms, including transit-time broadening, Rydberg-Rydberg collisions, and ionization. Using a matched filter, we demonstrate the detection of individual pulses with durations from 10 \textmu{}s down to 50 ns and amplitudes from 15 000 \textmu{}V ${\mathrm{cm}}^{\ensuremath{-}1}$ down to about 170 \textmu{}V ${\mathrm{cm}}^{\ensuremath{-}1}$, corresponding to a sensitivity of about 240 nV ${\mathrm{cm}}^{\ensuremath{-}1}$ ${\mathrm{Hz}}^{\ensuremath{-}1/2}$. Finally, we highlight the potential of a Rydberg vapor cell as a receiver by detecting pulse trains from a rotating emitter on a simulated passing aircraft.

Optimization of COVID-19 prevention and control measures during the Beijing 2022 Winter Olympics: a model-based study

BackgroundThe continuous mutation of severe acute respiratory syndrome coronavirus 2 has made the coronavirus disease 2019 (COVID-19) pandemic complicated to predict and posed a severe challenge to the Beijing 2022 Winter Olympics and Winter Paralympics held in February and March 2022.MethodsDuring the preparations for the Beijing 2022 Winter Olympics, we established a dynamic model with pulse detection and isolation effect to evaluate the effect of epidemic prevention and control measures such as entry policies, contact reduction, nucleic acid testing, tracking, isolation, and health monitoring in a closed-loop management environment, by simulating the transmission dynamics in assumed scenarios. We also compared the importance of each parameter in the combination of intervention measures through sensitivity analysis.ResultsAt the assumed baseline levels, the peak of the epidemic reached on the 57th day. During the simulation period (100 days), 13,382 people infected COVID-19. The mean and peak values of hospitalized cases were 2650 and 6746, respectively. The simulation and sensitivity analysis showed that: (1) the most important measures to stop COVID-19 transmission during the event were daily nucleic acid testing, reducing contact among people, and daily health monitoring, with cumulative infections at 0.04%, 0.14%, and 14.92% of baseline levels, respectively (2) strictly implementing the entry policy and reducing the number of cases entering the closed-loop system could delay the peak of the epidemic by 9 days and provide time for medical resources to be mobilized; (3) the risk of environmental transmission was low.ConclusionsComprehensive measures under certain scenarios such as reducing contact, nucleic acid testing, health monitoring, and timely tracking and isolation could effectively prevent virus transmission. Our research results provided an important reference for formulating prevention and control measures during the Winter Olympics, and no epidemic spread in the closed-loop during the games indirectly proved the rationality of our research results.Graphical

A Generalized Transformer-Based Pulse Detection Algorithm.

Pulse-like signals are ubiquitous in the field of single molecule analysis, e.g., electrical or optical pulses caused by analyte translocations in nanopores. The primary challenge in processing pulse-like signals is to capture the pulses in noisy backgrounds, but current methods are subjectively based on a user-defined threshold for pulse recognition. Here, we propose a generalized machine-learning based method, named pulse detection transformer (PETR), for pulse detection. PETR determines the start and end time points of individual pulses, thereby singling out pulse segments in a time-sequential trace. It is objective without needing to specify any threshold. It provides a generalized interface for downstream algorithms for specific application scenarios. PETR is validated using both simulated and experimental nanopore translocation data. It returns a competitive performance in detecting pulses through assessing them with several standard metrics. Finally, the generalization nature of the PETR output is demonstrated using two representative algorithms for feature extraction.