Pulse Interval Research Articles

High repetition rate step acousto-optic Q-switched laser with three nanosecond equal-interval and amplitude pulses

A compact, high repetition rate pulse group laser with three nanosecond equal-interval and equal-amplitude sub-pulses has been demonstrated in this paper. Under three-step nanosecond continuous acousto-optic control, a laser pulse group containing three nanosecond interval sub-pulses can be realized. The three sub-pulses have a pulse width of 15 ns, 23 ns, and 25 ns and minimum pulse intervals of 119 ns at a repetition rate of 30 kHz. The corresponding optical-optical conversion efficiency is 29.2 %.

Building ultra-thin Inconel 718 sheet joints using low-frequency PLBW scheme: Weld bead quality, keyhole dynamics, and solidification characteristics

Low-frequency pulsed laser beam welding (PLBW) was employed in building 0.32 mm-thick Inconel 718 superalloy butt joints which are frequently applied in manufacturing high-temperature functional units in the aviation industry. Several process parameter combinations concerning peak laser power, welding speed, and pulse frequency were implemented to explore the macro morphology, microstructure, and mechanical properties of the welded joints. Examinations exhibit that the resulting weld beads possess high continuity at the surface with an overlap factor ranging from 0.58 to 0.73. The cross-sectional profile changes from a V-shape to an H-shape with increasing heat input. Finer grain structures composed of γ matrix and γ/Laves eutectic penetration are observed within the FZ center, as compared to that near the fusion line. Excellent performance is achieved in microhardness and tensile tests. Numerical simulation based on an integrated mathematic model reveals periodic keyhole and weld pool dynamics depending on the pulsing laser power. During a typical pulse interval, keyhole geometry collapses within a fraction of a millisecond, leading to a sharp cooling stage at ∼4 × 106 K/s, and then, the melt cools due to the thermal convection with a normal cooling rate of 105 K/s. The full growth of the adjacent weld spot results in the secondary melting zone (SMZ), wherein the columnar dendrites can be refined mainly due to the heterogeneous nucleation as compared to the primary melting zone (PMZ).

Investigation of Machining Characteristics in Electrical Discharge Machining Using a Slotted Electrode with Internal Flushing.

In die-sinking electrical discharge machining (EDM), it is challenging to implement internal flushing, mainly because it is easy to produce residual material columns on the workpiece cavity's bottom surface, affecting the processing quality and efficiency. In order to solve this problem, the internal flushing slotted electrode EDM technology was proposed. The slotted electrode was designed, and its preparation method was described. The influence of pulse width, pulse interval, and flushing pressure on the performance of the internal flushing slotted electrode EDM was studied using single-factor experiments. The experimental results indicate that, with the increase in pulse width, the material removal rate (MRR) increases first and then decreases, while the electrode wear rate (EWR) and the relative electrode wear rate (REWR) decrease gradually; with the increase in pulse interval, the MRR decreases, while the EWR and the REWR increase gradually; with the increase in flushing pressure, the MRR increases first and then decreases, while the EWR and the REWR increase gradually. When the slotted electrode is used for continuous internal flushing EDM, the appropriate pulse width, flushing pressure, and smaller pulse interval can improve the MRR and reduce the EWR and the REWR.

Meteorology of ‘ridging high’ rainfall over the KwaZulu‐Natal coastal plains

AbstractThe meteorology of ridging highs on the coast of KwaZulu‐Natal (KZN) South Africa was studied using Principal Component (pc) analysis of daily ERA5 sea level air pressure (SLP) fields 1980–2021. The second pc mode time score representing ridging highs, was associated with rain‐showers moving northeast‐ward along the KZN coast. Temporal analysis revealed an Oct‐Dec peak occurrence and 12‐day pulse intervals induced by the eastward migration of atmospheric Rossby waves in early summer. From a ranking of SLP pc2 and associated daily time series, a case study emerged: 14–18 Nov. 2009. This ridging high weather scenario had cold southerly winds subsiding over the warm Agulhas Current. Surface moisture fluxes >350 W/m2 create a buoyant airmass that slows and lifts over the coastal plains, inducing shallow clouds that reduce net solar radiation and potential evaporation. Interannual variability of ridging highs was studied by filtering the daily SLP pc2 time score to retain seasonal fluctuations and correlating with regional fields of SST. This revealed warming in the SW Indian Ocean associated with positive phase Indian Ocean Dipole (IOD). The atmospheric circulation forms a NW trough over Madagascar which deforms eastward moving mid‐latitude anticyclones. Thus, ridging highs that bring beneficial Oct‐Dec rains to the coast of KZN depend on downstream climate coupling with the IOD. Long‐term trends from a coupled model simulation 1980–2100 suggest a poleward retreat of the anticyclonic ridge, consistent with declining Durban‐area river flow in early summer.

Microscale mixing efficiency of ultrasound-assisted synergistic microreactors

Microscopic mixing characteristics within a Y-shaped microchannel reactor are explored using the iodide-iodate parallel competition reaction. The impact of operational parameters and ultrasound synergy on the segregation index (a mixing efficiency measure) is assessed. Factors including channel angle, outlet tube length, hydrogen ion concentration, volume flow ratio, and ultrasound parameters were analyzed for their influence on the segregation index. The findings indicate that mixing efficiency is significantly influenced by the choice of microchannel angle, outlet tube length, and other operational parameters. Furthermore, a notable improvement in micro-mixing was demonstrated through ultrasound intervention, with increased power levels and shorter pulse intervals enhancing efficiency. This comprehensive analysis underscores the potential of ultrasound-enhanced microscale mixing within Y-shaped microchannels, providing insights into the precise control of microfluidic systems for various applications.

Superlow Power Consumption Memristor Based on Borphyrin-Deoxyribonucleic Acid Composite Films as Artificial Synapse for Neuromorphic Computing.

Memristor synapses based on green and pollution-free organic materials are expected to facilitate biorealistic neuromorphic computing and to be an important step toward the next generation of green electronics. Metalloporphyrin is an organic compound that widely exists in nature with good biocompatibility and stable chemical properties, and has already been used to fabricate memristors. However, the application of metalloporphyrin-based memristors as synaptic devices still faces challenges, such as realizing a high switching ratio, low power consumption, and bidirectional conductance modulation. We developed a memristor that improves the resistive switching (RS) characteristics of Zn(II)meso-tetra(4-carboxyphenyl) porphine (ZnTCPP) by combining it with deoxyribonucleic acid (DNA) in a composite film. The as-fabricated ZnTCPP-DNA-based device showed excellent RS memory characteristics with a sufficiently high switching ratio of up to ∼104, super low power consumption of ∼39.56 nW, good cycling stability, and data retention capability. Moreover, bidirectional conductance modulation of the ZnTCPP-DNA-based device can be controlled by modulating the amplitudes, durations, and intervals of positive and negative pulses. The ZnTCPP-DNA-based device was used to successfully simulate a series of synaptic functions including long-term potentiation, long-term depression, spike time-dependent plasticity, paired-pulse facilitation, excitatory postsynaptic current, and human learning behavior, which demonstrates its potential applicability to neuromorphic devices. A two-layer artificial neural network was used to demonstrate the digit recognition ability of the ZnTCPP-DNA-based device, which reached 97.22% after 100 training iterations. These results create a new avenue for the research and development of green electronics and have major implications for green low-power neuromorphic computing in the future.

Optimizing pump-probe reflectivity measurements of ultrafast photoacoustics with modulated asynchronous optical sampling.

Time-resolved optical pump-probe experiments enable the study of complex light-matter interactions on ultrafast timescales, provided that they reach sufficient sensitivity. For instance, with pump-induced ultrafast photoacoustics, probing the typically small changes in optical properties requires a high signal-to-noise ratio. Asynchronous optical sampling (ASOPS), using two separate pulsed lasers at slightly different repetition rates, can be effective at removing noise by averaging many rapidly acquired traces. However, the pump-probe delay scan with ASOPS is always as long as the pump pulse interval, which is inefficient if the delay-time range of interest is shorter. Here, we demonstrate two modified ASOPS schemes that optimize measurement efficiency by only scanning the range of interest. The modification based on frequency modulated ASOPS (MASOPS) is most efficient, especially in the presence of low-frequency flicker noise. We provide a proof-of-concept measurement of ultrafast photoacoustics in which we use MASOPS to scan a time delay of 1/20 of the pump pulse interval. The resulting noise floor is 20 times lower compared to conventional ASOPS, allowing for 20 times faster measurements. Furthermore, we show that by taking experimental noise characteristics into account, more traditional pump-probe methods can also be optimized.

Bubble pulse arrival time calculations to determine SUS charge detonation depths

As part of the New England Seamount Acoustics (NESMA) project in 2023, experiments were conducted over the Atlantis II Seamount. A total of 216 Signal Underwater Sound (SUS) broadband explosives (150 1.1 oz and 66 1.8 lb net explosive weight) were deployed at multiple locations and two different design depths around the seamount. An acoustic recorder (SoundTrap ST4300), with four hydrophone channels of varying sensitivities, was deployed during each of the SUS events to record the signals generated by the explosives. The recorded signals include arrivals corresponding to the shock wave, subsequent bubble pulses and reflections from the sea surface and sea floor. The time between the first arrival and the bubble pulse was used to calculate the depth at which each SUS charge detonated. The resulting SUS detonation depths from the bubble pulse calculation were compared with depths obtained from surface and bottom reflections to assess the accuracy of the bubble pulse method. A comparison of the results from the two methods shows that using the bubble pulse interval to calculate the SUS detonation depth is reasonable and can be used in propagation models. [Work supported by Office of Naval Research Code 322OA and TFO.]

Optimal Treatment Strategy for Cancer Based on Mathematical Modeling and Impulse Control Theory

Adaptive therapy is a new type of cancer treatment in which time and dose are dynamically changed according to different individuals, which is very different from conventional cancer treatment strategies that use the maximum dose to kill the tumor cells. However, how to determine the time and dose of drug treatment is a challenging problem. In this paper, a competition model between drug-sensitive cells and drug-resistant cells was established, in which pulse intervention was introduced. In addition, based on the theory of pulse optimal control, three pulse optimal control strategies are proposed in the process of cancer treatment by controlling the pulse interval and dose, minimizing the number of tumor cells at the end of the day at minimal cost. Finally, three optimization strategies were compared, using numerical simulation, in terms of tumor burden and the effect on drug-resistant cells. The results show that the hybrid control strategy has the best effect. This work would provide some new ideas for the treatment of cancer.

VDIU: VLC-Based Debugging Information Upload Method for Self-Powered Sensor Nodes

Currently, more and more self-powered sensor nodes have been deployed in remote and inaccessible areas, and thus online debugging of sensor nodes becomes more necessary and important. However, the existing sensor online debugging approaches mainly rely on original network infrastructure (such as Zigbee or NB-IoT). Once the communication infrastructure is invalid, it is almost impossible to retrieve debugging information and repair the lost self-powered sensor nodes. To this end, in our previous study, we employed the onboard optical modules of the self-powered sensor node to realize a Visible Light Communication(VLC)-based hybrid communication debugging system(VHCDS). In this paper, to improve the efficiency of uploading debugging information, we propose VDIU to optimize the digital pulse interval modulation applied in the uplink of VHCDS. This method reasonably groups and sorts the origin data to reduce the number of empty time slots (unused time slots) and complete data compression in source coding for saving energy. To improve the reliability of the uplink, we also design two frame synchronization mechanisms suitable for the receiver-side optical cameras of the uplink. One mechanism considers lightweight synchronization design via restricting the position of the frame header; the other one focuses on reducing the occupation of the downlink of VHCDS via predicting the position of the frame header using a temporal convolutional network (TCN). Experiments results illustrate that the upload efficiency using VDIU is higher 78% and 28% than DPIM and DH-PIM. Both synchronization mechanisms can arrive the similar performance, but the predicting mechanism reduces the 93% occupation on the downlink.

Technical evaluation of a simulator for accurate reproduction of oscillometric blood pressure pulses, providing traceability for automated oscillometric sphygmomanometers

Oscillometric blood pressure measurement devices are not directly traceable to primary standards. Currently, device accuracy is measured by comparison between a sample device and reference measurements in a clinical trial. We researched in this study the potential for an alternative evaluation with a simulator. Our research simulator was studied for repeatability and accuracy in delivering simulated blood pressure pulses. Clinical cuff pressure measurements were obtained, along with simultaneous recordings of oscillometric pulse waveforms, spanning the clinical range of cuff pressures, pulse intervals and pulse shapes. Oscillometric pulse peak amplitudes ranged from 1.1 to 3.6 mmHg. Simulated repeatability results showed an average Standard Deviation (SD) for pulse peaks of 0.018 mmHg; 1.0% of peak amplitudes. Comparing simulated pulse shapes, the average repeat SD was 0.015 mmHg; 0.8% of the normalised pulse shapes. The simulated accuracy results had a mean error of − 0.014 ± 0.042 mmHg with a mean accuracy of 97.8%. For pulse shape the corresponding values were − 0.104 ± 0.071 mmHg with a mean accuracy of 95.4%. The correlation between the reference and simulated pulse shapes ranged from 0.991 to 0.996 (all p < 0.00003), with a mean 0.994. We conclude that oscillometric pulses can be reproduced with high repeatability and high accuracy with our research simulator. The extended uncertainty U(p sim ) = 0.3 mmHg for the simulated pulses is dominated by the uncertainty (64%) of the clinical reference data. These results underpin the potential of the simulator to become a secondary standard for millions of oscillometric sphygmomanometers.

Development of transient [formula omitted]SR method for high-flux pulsed muons

In order to expand the applicability of muon spin rotation, relaxation, and resonance (μSR) experiments with pulsed muons and to make effective use of the high-flux beam, we have developed a new experimental method “transient μSR”. In this method, μSR data for each muon pulse are tagged with external parameters such as temperature and magnetic field in real time, allowing the sample environment to be changed without interrupting data collection. As a result, continuous μSR measurements under sample conditions that vary on a time scale longer than the beam pulse interval (40 ms) are realized, and efficient beam utilization is achieved by eliminating the lag time associated with moving between discrete measurement points. The transient μSR method was applied to the study of the magnetic properties of cupric oxide (CuO) and the observation of level-crossing resonance relaxation in copper, and the method was successfully established by confirming that the results reproduce those in the previous reports.

Effect of HBr additive on the performance of all-inorganic Cs3Bi2Br9 halide perovskite resistive switching memory

Non-toxic, stable Cs3Bi2Br9 halide perovskite films prepared using a one-step solution method have become the active layer of resistive switching memory. Here, we control the nucleation and growth of Cs3Bi2Br9 perovskite by introducing an appropriate amount of HBr to adjust the supersaturation of the perovskite precursor solution, thus improving the film formation quality and optimizing the device performance. The memory prepared for this film has a significant bipolar resistive behavior with a high switching ratio of 105, a cycle time of 300 and a retention time of 104 s. In addition, the current transient response of the device under pulsed voltage is investigated. By different the pulse voltage parameters (pulse amplitude, duration and time interval) to study the variation of the device current value, the term "TJUT" is finally encoded and decoded using different the number of pulses and repetitions.

Performance Analysis of Underwater Optical Communication System in Turbulent Link

Underwater wireless optical communication (UWOC) systems have been identified as a suitable replacement technology with high data rates over relatively medium transmission ranges for underwater communication. In the research, we propose a new optical hybrid modulation format for carrying the letters over underwater wireless optical communication (UWOC) system. This hybrid modulation format combines pulse position modulation (PPM) with digital pulse interval modulation (DPIM) to increase the transporting speed. The proposed UWOC system is experimentally investigated in the laboratory over a clean and turbulent water channel. The message was electrically modulated in the transmitter with PPM-DPIM format and then applied to a laser diode. The laser diode emitted light at a wavelength of 650 nm with a power of 60 mW. At the receiver, the photodiode, with its amplifier circuits, sends the received signal to the microprocessor to restore the origin message. The results showed that the received power and signal-to-noise ratio (SNR) decreased with elongating the transmission distance. In addition, the attenuation is raised with increasing distance. The bubbles source is also situated at distances of 25 cm, 50 cm, and 75 cm from the transmitter in turbulent waters. The results showed that locating the bubble source decreases the system's performance. The best results were obtained when the bubble source was 75 cm away from the transmitter. Finally, the hybrid modulation formats (PPM-DPIM) can increase the speed of letter transmission, reduce the bit error rate (BER), and minimize the effect of scattering and attenuation in water channels.

Optimising low-energy defibrillation in 2D cardiac tissue with a genetic algorithm.

Sequences of low-energy electrical pulses can effectively terminate ventricular fibrillation (VF) and avoid the side effects of conventional high-energy electrical defibrillation shocks, including tissue damage, traumatic pain, and worsening of prognosis. However, the systematic optimisation of sequences of low-energy pulses remains a major challenge. Using 2D simulations of homogeneous cardiac tissue and a genetic algorithm, we demonstrate the optimisation of sequences with non-uniform pulse energies and time intervals between consecutive pulses for efficient VF termination. We further identify model-dependent reductions of total pacing energy ranging from ∼4% to ∼80% compared to reference adaptive-deceleration pacing (ADP) protocols of equal success rate (100%).

Inhibition of Dust Re-Deposition for Filter Cleaning Using a Multi-Pulsing Jet

The re-deposition of detached dust during online pulse-jet cleaning is an important issue encountered during filter regeneration. To reduce dust re-deposition, multi-pulsing jet cleaning schemes were designed and experimentally tested. A pilot-scale pulse-jet cleaning dust collector was built with one vertically installed pleated filter cartridge. The effects of pulse duration and interval on the pulse pressure were tested, and the dust re-deposition rate and mechanism were studied and analyzed. It was found that, for the single-pulsing jet, the pulse duration had a critical value of approximately 0.080 s in this test, above which the pulse pressure remained at approximately 0.75 kPa and did not increase further. For the multi-pulsing jet with a small pulse interval (less than approximately 0.10 s), the pulse flows superimposed and reached a higher pulse pressure with a slight inhibition of dust re-deposition. For the multi-pulsing jet with a long pulse interval (over 0.15 s), dust re-deposition was clearly inhibited. The re-deposition rate decreased from 63.8% in the single-pulsing scheme to 24.4% in the multi (five)-pulsing scheme with the same total pulse duration of 0.400 s. The multi-pulsing scheme lengthens the duration of reverse pulse flow, resulting in more elapsed time for the detached dust to freely fall, and inhibiting the re-deposition of dust. The elapsed time in the five-pulsing jet scheme with the recommended pulse duration of 0.080 s and interval of 0.25 s was 2.8 times higher than that of the single-pulsing jet with the same total pulse duration.

Tissue Ablation Using Irreversible Electrolytic Electroporation with Reduced Voltage

Thermal tissue ablation may damage surrounding healthy tissue and cause pain. In this study, tissue ablation with the sequential application of electrical energy-inducing irreversible electroporation (IRE) and electrolysis (EL) (IRE + EL = IREEL) was investigated. An IREEL device was designed to control five output pulse parameters: voltage level (VL), pulse width (PW), pulse interval (PI), pulse number (PN), and pulse tail time (PTT). IREEL experiments were conducted on vegetable tissue. The results indicated that by increasing the VL and PTT, the ablation area increased, whereas the impedance was reduced significantly. Almost no ablation area was observed when only EL or IRE at 500 V and 1000 V, respectively, were applied. The ablation area observed with IRE alone at 1500 V was defined as 100%. In the case of IREEL at 500 V and 1000 V, ablation was induced even with the use of micro-second level PTT, and ablation areas of 91% and 186% were achieved, respectively. For IREEL at a voltage of 1500 V, the ablation area expanded to 209% and the maximum temperature was 48.7 °C, whereas the temperature did not exceed 30 °C under other conditions. A change in pH was also observed in an agar-gel phantom experiment which was conducted to examine and confirm whether IREEL induced electrolysis. IREEL was able induce ablation at low voltages owing to the synergistic effect of applying IRE and EL sequentially. Moreover, the ablation areas at high voltages could be increased compared to the areas observed when IRE and EL were applied independently.

V2CTx gas sensor based on memristive effect with ultrafast SO2 detection

As a commonly harmful product produced in industrial production, the sensitive detection of SO2 is a crucial safety consideration with adverse impacts on human health. However, constructing MXene-based gas sensors for rapid detection at room temperature is still challenging. In this work, we demonstrate a V2CTx gasistor (gas memristor) with a millisecond-level cycle (360 ms) for SO2 ultrafast detection, and meanwhile, the function of gas response and memory is realized. Specifically, the synaptic plasticity of paired-pulse facilitation (PPF) behavior has been applied to identify the different types of gases instead of gas sensitivity. Consistent with gas response performance, the gasistor displays the highest pulse-controlled PPF ratio (210.4%) under 10 ms electric pulse interval for 10 ppm SO2, 1.34 times that under air. Also, the V2CTx gasistor exhibits excellent repeatability and good stability. Furthermore, this strategy provides a great application prospect in rapid detection and medical treatment for toxic gases and artificial sensing memory.

Design and implementation of a novel dust collector controller for powder production industry

Industries those work with powder either in production or processing always left a portion of industrial dust in the air. By releasing this air directly in the surrounding environment of the industry pollution occurs. Therefore air filtration system is mandatory in these industries and usually bag filter dust collector controller is used. To control and maintain the proper functionality of the bag filtration system PLC based control system or a modular control board is used. In this paper, a novel dust collector controller is designed which can be installed by any user without having any programming knowledge. The main control keys of the control board are the pulse duration and pulse interval which drive the solenoid valves to release air pressure on the filter bags sequentially. Pulse duration can be controlled in the range of 0.01-0.9 seconds and pulse interval can be varied in the range of 1-99 seconds to control 10 rows of pulse jet simultaneously connected with the solenoid valve. The Number of rows can be adjusted and expanded if required. Moreover, noiseless switching provides silent operational functionalities and switching durability as well as the addition of surge controller ensures a complete protection from any sudden high electrical surge. The finally developed prototype was tested in different industries and provides maximum operational efficiency, which can effectively control online bag filter dust collector to separate micro dust particles from the polluted air.

Sprague-Dawley rats differ in responses to medial perforant path paired pulse and tetanic activation as a function of sex and age.

Network plasticity in the medial perforant path (MPP) of adult (5-9 mo) and aged (18-20 mo) urethane-anesthetized male and female Sprague-Dawley rats was characterized. Paired pulses probed recurrent networks before and after a moderate tetanic protocol. Adult females exhibited greater EPSP-spike coupling suggesting greater intrinsic excitability than adult males. Aged rats did not differ in EPSP-spike coupling but aged females had larger spikes at high currents than males. Paired pulses suggested lower GABA-B inhibition in females. Absolute population spike measures were larger post-tetani in female rats than male rats. Relative population spike increases were greatest in adult males relative to females and to aged males. EPSP slope potentiation was detected with normalization in some post-tetanic intervals for all groups except aged males. Tetani shortened spike latency across groups. Tetani-associated NMDA-mediated burst depolarizations were larger for the first two trains in each tetanus in adult males than other groups. EPSP slopes over 30 min post-tetani predicted spike size in female rats, but not in males. Replicating newer evidence MPP plasticity in adult males was mediated by increased intrinsic excitability. Female MPP plasticity was related to synaptic drive increases, not excitability increases. Aged male rats were deficient in MPP plasticity.SIGNIFICANCE STATEMENTThe medial perforant path (MPP)-dentate gyrus (DG) granule cell synapse was the site of discovery of long-term potentiation in the mammalian nervous system but considering the current interest in sex and aging, surprisingly few studies have directly examined these variables in relation to tetanus-induced long-term and short-term (paired pulse) plasticity. Using an interleaved current-paired pulse interval protocol and moderate tetanic protocol young (5-9mo) and old (18-20mo) male and female urethane anesthetized rats were found to differ in levels of granule cell intrinsic excitability, E-S coupling, GABA-B inhibition, and tetanic NMDA current contributions to post-tetanic population spike potentiation. This study provides a platform or future examination of sex- and age-related changes in MPP-DG function.