Increasing Pulse Width Research Articles

Evaluation and assessment of clique arrangements for the estimation of omnipolar electrograms in high density electrode arrays: an experimental animal model study

High-density catheters combined with Orientation Independent Sensing (OIS) methods have emerged as a groundbreaking technology for cardiac substrate characterisation. In this study, we aim to assess the arrangements and constraints to reliably estimate the so-called omnipolar electrogram (oEGM). Performance was evaluated using an experimental animal model. Thirty-eight recordings from nine retrospective experiments on isolated perfused rabbit hearts with an epicardial HD multielectrode were used. We estimated oEGMs according to the classic triangular clique (4 possible orientations) and a novel cross-orientation clique arrangement. Furthermore, we tested the effects of interelectrode spacing from 1 to 4 mm. Performance was evaluated by means of several parameters that measured amplitude rejection ratios, electric field loop area, activation pulse width and morphology distortion. Most reliable oEGM estimations were obtained with cross-configurations and interelectrode spacings le 2 mm. Estimations from triangular cliques resulted in wider electric field loops and unreliable detection of the direction of the propagation wavefront. Moreover, increasing interelectrode distance resulted in increased pulse width and morphology distortion. The results prove that current oEGM estimation techniques are insufficiently accurate. This study opens a new standpoint for the design of new-generation HD catheters and mapping software.

Processing and Analysis of Micro-Arc Oxidation Coating on 319S Aluminum Alloy

In this study, a high-hardness and wear-resistant ceramic coating was prepared on the surface of 319S aluminum alloy using the micro-arc oxidation (MAO) technique. The effects of pulse width, negative voltage, and KOH concentration on the MAO coating were investigated, and the microhardness and surface roughness of the coating were measured. The morphology, elemental distribution, and phase composition of the coating were analyzed using SEM, EDS, XRD, and digital microscopy. The influence of the MAO coating on the wear of the 319S aluminum alloy was evaluated using a friction-wear tester. The results showed that in the sodium silicate solution system, with an increase in pulse width, the thickness of the coating gradually increased and the surface hardness initially increased and then decreased. With an increase in negative voltage, the density of the coating first increased and then decreased, the thickness of the dense layer initially increased and then decreased, and the surface hardness initially increased and then decreased. With an increase in the KOH concentration, the coating thickness increased and the roughness initially decreased and then increased. When the pulse width was 3000 ms, the negative voltage was 130 V, and the KOH concentration was 1 g/L, the coating exhibited the best density, with the highest surface hardness of 1426.8 HV and the thickest dense layer of 55 μm. The reduction in surface cracks and improvement in density indicated an enhancement in the hardness and wear resistance of the coating. The decrease in width and depth of the wear scars demonstrated the excellent wear resistance of the coating.

Laser parameters affecting the asymmetric radiation of the electron in tightly focused intense laser pulses

The nonlinear radiation of the electron is a distinctive feature of the action of tightly focused linearly polarized lasers. In this paper, from the perspective of radiation symmetry, the effect of laser parameters on the electron radiation power in the time domain is studied systematically. An asymmetric bimodal structure is found in the time domain in the direction of the maximum radiation. For this special structure, an explanation is given based on the electron dynamics perspective. The structure is compared with the symmetric bimodal structure in the classical theory. The increase in laser intensity, while significantly increasing the radiated power of the electron, exacerbates the asymmetry of the electron radiation. The variation in the initial phase of the laser leads to a periodic variation in the electron motion, which results in a periodic extension of the electron spatial radiation with a period of π. Moreover, the existence of jump points with a phase difference of π in the range of 0–2π is found. The increase in pulse width reduces the radiated power, extends the radiation range, and alleviates the radiation asymmetry. The results in this paper contribute to the study of electron radiation characteristics in intense laser fields.

Machinability of AA 2024 aluminum alloy by fiber laser engraving process

AbstractThe main objective of the present study is to investigate the machinability of AA 2024‐T351 aluminum alloy by laser beam‐assisted engraving process. The surface in a defined area was machined with the engraving process parameters of scan speed, frequency, and pulse width. While surface roughness measurements were performed to characterize the texture of the processed surface with laser engraving parameters, machining depth measurements were carried out to determine the material removal capacity. In addition, a mathematical relation was built for engraving depth and surface roughness using the response surface methodology. An increase in scan speed and pulse width led to a decrease in engraving depth and surface roughness. Unlike the scan speed and pulse width, any increase in frequency led to increased surface roughness and decreased engraving depth. After processing with lower pulse width and scan speed, a chaotic topography was formed on the surface. The effects of process parameters on engraving depth and surface roughness were analyzed statistically using factorial analysis. Except for the frequency, all parameters for surface roughness were statistically significant, whereas all parameters for engraving depth were statistically significant.

Investigation of continuous pulse current source on the performance of phase change material-thermoelectric cooler system

In this particle, the influence of phase change materials (PCM) on the property of thermoelectric cooler (TEC) is studied by numerical simulation. The heat sink integrated with PCM is placed on the hot side of TEC to reduce the fluctuation of temperature under a continuous pulse current source. The performance of a single-layer PCM-TEC system with that of a single TEC system under continuous pulse current source is firstly compared. Based on this, the effects of current source type, PCM layer, pulse width, cooling load and pulse amplitude on the cooling performance of TEC are investigated in depth. The results show that, compared to a single TEC system, PCM is able to considerably enhance the cooling performance of the TEC during the phase transition period. Besides, increasing PCM layer or decreasing cooling load improves the phase change interval, which increases threefold when the cooling load increases from 0.02 W to 0.06 W. In addition, it is found that lower temperature can be achieved by increasing pulse width or pulse amplitude.

Corrosion resistance of CrN film deposited by high-power impulse magnetron sputtering on SS304 in a simulated environment for proton exchange membrane fuel cells

Insufficient corrosion resistance and conductivity are two major problems hindering the wide application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells. This study explores the use of CrN monolayer and multilayer films to improve the performance of SS304 bipolar plates, which are realized by high-power impulse magnetron sputtering with single pulse width or alternating pulse width. The effect of pulse width on the film structure and composition was characterized by various characterization techniques. Furthermore, corrosion and interfacial contact resistance (ICR) test results show that monolayer CrN film using a single long pulse of 40 μs has the lowest corrosion current density of 0.08 μA/cm2 (0.6 V vs. Ag/AgCl) and ICR of 3.15 mΩ cm2 in all coated samples. As the pulse width increases, vacancy-like defects in film decrease and the density increases, which is attribute to high bombardment flux and high average power of long pulse during deposition.

Quantitative simulation of photothermal effect in laser therapy of hypertrophic scar.

Laser technology has been widely used in the treatment of hypertrophic scar (HPS). Due to the lack of effective quantitative relationship between laser doses and thermal effect of lesion tissue, the selection of laser doses in clinical laser treatment of HPS is blind, which cannot guarantee the best treatment effect. The photothermal model of HPS was established by using finite element method. The effects of laser dose parameters such as laser energy density, pulse width, and spot diameter on the thermal effects of laser treatment were analyzed. According to tissue temperature threshold and thermal damage degree of the simulation results, the optimal laser doses of HPS were selected for the laser treatment experiments of rabbit ear HPSs to verify the rationality of the quantitative photothermal model. The temperature rise and thermal damage degree of HPS following laser treatment were directly correlated to the laser doses, which grew with the increase of energy density and laser pulse width. For the different spot diameters, the temperature rise decreased with the increase of spot diameter, whereas the thermal damage degree worsened with the increase of spot diameter. Both simulation and experimental results show that the optimal treatment parameters of HPS were as follows: The laser energy density was 7.5J/cm3 , the pulse width was 4ms, and the spot diameter was 7mm. The laser dose parameters optimized by the photothermal model have achieved good therapeutic effects in the rabbit ear HPS, indicating that the model can be used for quantitative evaluation of laser doses before clinical treatment.

Experimental study on positive corona discharge characteristics in plane-single/double earthed rods air gaps under negative DC voltage

In order to analyze the corona discharge characteristics at the grounding object tip under the thundercloud electric field environment, scaled simulation test has been conducted on corona discharge in the plane-single/double earthed rods air gap. Five gap configurations with three different grounding rods were built during experiments. Factors as rod tip curvature, voltage and gap configuration have been considered in detail. Corona voltage, corona current and the number of ultraviolet photons were all recorded. The grounding rod tip curvature radius can affect corona discharge processes at grounding rod tip. With increasing applied negative DC voltage, five typical corona processes of dark discharge, burst streamer corona, periodic streamer corona, glow corona and brush discharge occurred at conical and spherical grounding rod tip (r=0.75cm), but under d=5cm and d=10cm no glow corona and brush corona appeared at spherical grounding rod tip (r=1.25cm). It is much easier for grounding rod tip with smaller curvature to form glow corona phenomenon. The mean value Iav of periodic streamer corona current pulse amplitude decreases with grounding rod tip curvature radius, while the mean corona current pulse width and pulse interval increases. For grounding rod with conical tip, there is little difference of average current pulse amplitude between periodic streamer corona and brush corona; for grounding rod with spherical tip (r=0.75cm), the mean value Iav of brush corona pulse amplitude increases to 3595.8 μA which has increased by a factor of about 36. The photon number at conical grounding rod tip is larger than that at spherical grounding rod tip at low voltage but the relation reverses as the applied voltage exceeds a critical value. The shielding effect of two grounding rods in plane-double rods air gaps increased with spherical grounding rod curvature radius and decreases with the lateral gap distance between two grounding rods.

Impacts of pulse conditions on endurance behavior of ferroelectric thin-film transistor non-volatile memory

In this work, the ferroelectric thin-film transistor (Fe-TFT) with polycrystalline-silicon (poly-Si) channel and HfZrO x gate dielectric is fabricated to study the characteristics of non-volatile memory (NVM). Significant threshold voltage (V TH) modulation can be achieved with low pulse voltages less than ±3.5 V and pulse widths within 1 μs. In order to achieve the NVM characteristics of low voltage and high speed operation, the impact of the program/erase (PRG/ERS) pulse voltage (V PRG/V ERS) and pulse width on endurance is a critical consideration. In the study of the pulse width effect on endurance, it can be observed that the V TH in PRG-state exhibits the wake-up effect at both short and long pulse widths. In addition, with the increase of pulse width, the V TH in the PRG-state exhibits significant fatigue effect and subthreshold swing (SS) degradation effect. For V TH in the ERS-state, the increase of the pulse width also exhibits the fatigue effect and the SS degradation effect, which is dominated by the SS degradation effect at long pulse widths. In the study of the pulse voltage effect on endurance, the increase of V PRG shows the imprint effect that the V TH in either PRG- or ERS-state reveals a decreasing trend. When the V ERS increases, the SS of the PRG- and ERS-states is degraded, and the fatigue effect of the PRG-state is enhanced. Moreover, the retention characteristics of poly-Si Fe-TFTs exhibit stable characteristics at both room temperature and 50 °C.

High efficiency NOx synthesis and regulation using dielectric barrier discharge in the needle array packed bed reactor

High efficiency NOx synthesis by plasma technology is the key objective in the field of nitrogen fixation currently. In this paper, a needle array packed bed reactor excited by nanosecond pulse voltage is employed to synthesize NOx efficiently with α-Al2O3 and γ-Al2O3 packed materials. The pulse width, pulse rising time, pulse repetition rate, and oxygen content are adjusted to regulate the NOx synthesis results, such as NOx concentration, product selectivity, and energy cost. The discharge power, key reactive species, and the rate coefficient are calculated to provide clear insight into the NOx synthesis pathways. It is found that the NOx can be synthesized efficiently in this needle-tubes array packed bed reactor, the highest NOx concentration of 1.12% and 0.97% are obtained in unfilled reactor and γ-Al2O3 packed bed reactor, respectively, which are nearly-two times higher than the results reported in previous works under the same energy cost and the same type of discharge. In addition, increasing pulse width and pulse repetition rate can significantly enhance the NOx concentrations because of the increased energy input and rate coefficient.

High-power microwave pulse induced failure on InGaP/GaAs heterojunction bipolar transistor

With the development of microwave technology, the reliability of semiconductor devices under high-power microwave (HPM) interference has become one of the huge challenges. On this basis, the damage effect of InGaP/GaAs heterojunction bipolar transistor (HBT) under HPM interference is studied by simulation and experiment. We first establish the experimental platform and obtain the damage threshold of InGaP/GaAs HBT under HPM injection with different pulse widths. The change of S Parameters indicates that permanent damage occurs on the HBT when the input power is 46.1 dBm with the pulse width of 50 ns. In addition, the experimental results show that with the increase pulse width, the damage power threshold decreases while the damage energy threshold increases. Besides, the damage power threshold does not change when the pulse width is more than 500 ns. The simulation model for analyzing the damage mechanism of HBT is established. Simulation results show that hot spots appear in the center of the emitter region under HPM injection, indicating that this region may be burned out and cause the malfunction of HBT.

Generation of h–Shaped pulse in a mode–Locked erbium-doped fiber laser

In this paper, the generation of h-shaped pulse is demonstrated in a nonlinear polarization rotation mode-locked erbium-doped fiber laser (MLEDFL). The length of the entire cavity is about 2506 m to enhance the nonlinear effect in the cavity. The multi-pulse state is obtained firstly under the certain pump power and polarization state. By further adjusting the polarization controller the h-shaped pulse with sharp top and flat bottom is generated under the pump power of ∼100 mW. And the duration of pulse is tuned with a range of 54.63–470 ns. The width and intensity of pulse trailing part vary differently during the process of increasing pulse width. The results indicate that the peak power clamping effect and weak birefringence effect dominate in different h-shaped pulse forming process.

Effects of frequency and pulse width on electron density, hydrogen peroxide generation, and perfluorooctanoic acid mineralization in a nanosecond pulsed discharge gas-liquid plasma reactor

Plasma electron density and temperature were characterized in a continuous flowing gas-liquid film reactor with argon carrier gas by time-resolved optical emission spectroscopy. The plasma parameters were studied as a function of time for varying pulse widths and frequencies. Pulse frequency was varied between 1 and 10 kHz at 16 kV (input voltage) and 40 ns (pulse width) using an Eagle Harbor Technologies, Inc. (EHT) power supply and 5–100 kHz using an Airity Technologies, LLC (AT) power supply. The pulse width was varied between 40 and 200 ns at 16 kV, 2 kHz with the EHT power supply. Optimal frequencies of 5 and 20 kHz were observed for peak electron density with EHT and AT power supplies, respectively. The peak electron density increased with increasing pulse width between 40 and 200 ns using the EHT power supply. Hydrogen peroxide exiting the reactor in the liquid phase increased with discharge power irrespective of the power supply or pulse parameters. Mineralization of 12.5, 50, and 200 ppm perfluorooctanoic acid (PFOA) dissolved in DI water to fluoride (F−) correlated to the peak electron density. Glycerol, a liquid-phase hydroxyl radical scavenger, depleted hydrogen peroxide but did not affect PFOA mineralization. CO, a gas-phase hydroxyl radical scavenger, led to a reduction in the formation of F− production, suggesting hydroxyl radicals in the gas-liquid film play a necessary, but not singular, role in mineralization of PFOA.

Effect of temperature on heavy ion-induced single event transient on 16-nm FinFET inverter chains

The variations of single event transient (SET) pulse width of high-LET heavy ion irradiation in 16-nm-thick bulk silicon fin field-effect transistor (FinFET) inverter chains with different driven strengths are measured at different temperatures. Three-dimensional (3D) technology computer-aided design simulations are carried out to study the SET pulse width and saturation current varying with temperature. Experimental and simulation results indicate that the increase in temperature will enhance the parasitic bipolar effect of bulk FinFET technology, resulting in the increase of SET pulse width. On the other hand, the increase of inverter driven strength will change the layout topology, which has a complex influence on the SET temperature effects of FinFET inverter chains. The experimental and simulation results show that the device with the strongest driven strength has the least dependence on temperature.

Internal structure and conductivity of laser-induced graphitized wires inside diamond

The paper considers nanostructured interior and conductive characteristics of graphitized wires formed inside single-crystal diamond by laser microstructuring. A series of wires was formed by using different laser pulsewidths (from 150 fs to 10 ns) and varying spatial orientation of the laser beam in the crystal. Electrical resistance of the wires was measured and quasi-longitudinal sections of the wires were studied with scanning electron microscopy. Turning the laser beam inside the diamond crystal results in considerable modification of the mutual arrangement of the laser-induced sp2 nanoplates oriented along the {111} crystallographic diamond planes, however, this has a weak influence on the macroscopic conductivity of the wires. In contrast, increase in the laser pulsewidth in the range studied increases both the wire conductivity and the thickness of the sp2 inclusions. The wires formed by ultrashort (150 fs–5 ps) laser pulses contain numerous quasi-parallel sp2 nanoplates with rare intersections, the actual path of the charge transport along the wires remaining unknown. With increasing pulse width to 10 ns the number of the sp2 nanoplates becomes much smaller, but they form an uninterrupted conductive chain.

Research on transient thermal behavior of semiconductor lasers under pulse current excitation by thermoreflection technique

We measured the response of the facet temperature of the semiconductor laser to a single pulse current with a magnitude of microseconds by using transient thermoreflection method, and then calculated the thermal time constants of the laser. The thermoreflection technique measures the reflectivity of facet which is affected by temperature in real time and thus only measures the thermal parameter. In addition, we select the falling edge of the pulse current where current and light dissipate immediately during the heat decline as the starting point for the study of the thermal response. Therefore, the electro-optical-thermal characteristics of the laser are decoupled in the measurement process. The transient thermal response is formulated as a second-order exponential function of time. The two time constants, i.e τ1 and τ2, represent thermal conductivity performance of laser chip and device package, respectively. We studied the transient thermal behavior of the laser under unsteady state based on the evolution trends of the thermal time constants with amplitude and width of the pulse current. When the pulse is narrow, the heat of the device is concentrated in the active region, even if the current amplitude is relatively large; With the increase of pulse width, the heat generated in the active region diffuses outward to other layers of the chip and heat sink. We also observed the mechanical deformation of the facet in the active region which results from heat accumulation, and the heat generation is related to light intensity.

Perception thresholds and qualitative perceptions for electrocutaneous stimulation

Our long-term goal is the development of a wearable warning system that uses electrocutaneous stimulation. To find appropriate stimulation parameters and electrode configurations, we investigate perception amplitude thresholds and qualitative perceptions of electrocutaneous stimulation for varying pulse widths, electrode sizes, and electrode positions. The upper right arm was stimulated in 81 healthy volunteers with biphasic rectangular current pulses varying between 20 and 2000,upmu hbox {s}. We determined perception, attention, and intolerance thresholds and the corresponding qualitative perceptions for 8 electrode pairs distributed around the upper arm. For a pulse width of 150,upmu hbox {s}, we find median values of 3.5, 6.9, and 13.8 mA for perception, attention, and intolerance thresholds, respectively. All thresholds decrease with increasing pulse width. Lateral electrode positions have higher intolerance thresholds than medial electrode positions, but perception and attention threshold are not significantly different across electrode positions. Electrode size between 15 times 15,hbox {mm}^{2} and 40times 40,hbox {mm}^{2} has no significant influence on the thresholds. Knocking is the prevailing perception for perception and attention thresholds while mostly muscle twitching, pinching, and stinging are reported at the intolerance threshold. Biphasic stimulation pulse widths between 150,upmu hbox {s} and 250,upmu hbox {s} are suitable for electric warning wearables. Within the given practical limits at the upper arm, electrode size, inter-electrode distance, and electrode position are flexible parameters of electric warning wearables. Our investigations provide the basis for electric warning wearables.

A Reconfigurable Picosecond Pulse Generator in Non-linear Transmission Line for Impulse Radar Ultrawideband Applications

This letter presents a reconfigurable picosecond (ps) pulse generator (PG) having Gaussian and monocycle pulse shapes for impulse radar ultrawideband (IR-UWB) applications. A mixed step recovery diode (SRD) topology is used in combination with a non-linear transmission line (NLTL) and pulse-shaping circuit to realize the PG. The pulse-shaping network comprises an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</i> differentiator embedded with a single p-i-n diode to provide two different switchable states. This PG is capable of directly switching from a Gaussian to a monocycle pulse without resorting to the increase in pulsewidth twice of the original Gaussian pulse as deployed in the previous reconfigurable PGs. The PG based on the proposed technique has a pulse duration of almost 70 ps with a promising ringing level in both cases (Gaussian and monocycle). Moreover, not only is the implementation of this technique easy, but it can also modify the pulse into other important shapes, such as the doublet and higher order Gaussian pulses. The proposed reconfigurable PG is measured in both cases, and the results are presented in each case.

Hole Morphology and Keyhole Evolution during Single Pulse Laser Drilling on Polyether-Ether-Ketone (PEEK).

Polyether-ether-ketone (PEEK), with its superior mechanical, chemical, and thermal properties, as well as high biocompatibility, has been used in aerospace, electronics, and biomedical applications. In this paper, a large number of experiments of single-pulse laser drilling on PEEK were performed to analyze the hole morphology and keyhole evolution, which were characterized by an optical microscope, charge-coupled device (CCD), and high-speed camera. A novel method is proposed to observe and measure the dimension of the processed hole rapidly right after laser drilling for special polymer materials with wear-resistance and non-conductivity. Morphological characteristics of holes are presented to illustrate the effect of pulse width and peak power on hole depth, hole diameter, and aspect-ratio. The obtained maximum drilling depth was 7.06 mm, and the maximum aspect-ratio was 23. In situ observations of the dynamic process of laser drilling, including the keyhole evolution together with ejection and vaporization behavior, were also carried out. The keyhole evolution process can be divided into three stages: rapid increment stage (0–2 ms) at a rate of 2.1 m/s, slow increment stage (2–4 ms) at a rate of 0.3 m/s, and stable stage (>4 ms). Moreover, the variation of dimensionless laser power density with the increase in pulse width was calculated. The calculated maximum drilling depth based on energy balance was compared with the experimental depth. It is proven that the laser–PEEK interaction is mainly influenced by a photothermal effect. Ejection is the dominant material-removal mechanism and contributes to over 60% of the depth increment during the rapid increment stage, while vaporization is dominant and contributes to about 80% of the depth increment during the slow increment stage. The results reveal the material removal mechanism for single-pulse laser drilling on PEEK, which is helpful to understand the dynamic process of keyhole evolution. This not only provides a processing window for future laser drilling of PEEK but also gives a guide for the manufacturing of other polymers.

Two-Photon Absorption Effect on Pseudorandom Bit Sequence for High-Speed Operation

Study of two-photon absorption (TPA) has been carried out for all-optical logic operation based on quantum-dot semiconductor optical amplifier (QD-SOA). XOR gate, AND gate and pseudo-random bit sequence (PRBS) were all modeled with the TPA effect on the existing rate equation. Inclusion of TPA induced pumping has increased the output Q-factor (quality). The output result demonstrates that the quality of the output is dependent on the input pulse width and the operation speed. The PRBS system modeled with TPA shows that it can operate at 250 Gb/s and 320 Gb/s and increase in pulse width decrease the Q-factor.