Pulse Burst Research Articles

Etch the borosilicate glass to form a straight through-glass-via based on the FLACE technology

Interposers will become in demand for advanced electronic systems and through the substrate, vias are essential for 3D integration. A straight via is necessary because a tapered hole is accompanied by large signal loss. This article reports a straight through-glass-via (TGV) fabricated by femtosecond laser-assisted chemical etching (FLACE). The femtosecond laser was used to modify the glass substrates, and the modified glass samples were etched with hydrofluoric acid (HF) solution to form TGV. The effects of key processing parameters, including laser pulse energy, the number of burst pulses, and the HF solution concentration, on the TGV taper profile, were systematically investigated. It was found that The TGV taper sidewall angle decreases with increasing laser pulse energy and increases with increasing HF solution concentration. The number of bursts should be optimized because more than 10 bursts would prevent TGV formation. The study shows via etched in 3 wt% HF after irradiation with 3 bursts of 60 μJ can become approximately vertical. Among the three processing parameters, HF concentration was found to be the most crucial parameter. This work can serve as a critical reference for applications of TGV in high-performance 3D integrated circuits.

Context-dependent and seasonal fluctuation in bottlenose dolphin (Tursiops truncatus) vocalizations.

A fundamental question in animal behaviour is the role of vocal communication in the regulation of social interactions in species that organise themselves into social groups. Context dependence and seasonality in vocalizations are present in the communication of many species, although very little research has addressed this dependence in marine mammals. The study presented here examined variations in the rate at which free-ranging dyads of bottlenose dolphins emit social-signals in an effort to better understand the relationship between vocal communication and social context. The results demonstrate that changes in the social-signal production in bottlenose dolphins are related to the sex of the partner, mating season and social affiliation between the components of the dyad. In a context of foraging behaviour on the same feeding ground, mixed (male-female) dyads were found to emit more pulsed burst sounds during the mating season. Another relevant aspect of the study seems to be the greater production of agonistic social-signals in the dyads formed by individuals with a lower degree of social affiliation. Overall, this study confirms a clear relationship between dyad composition and context-specific social-signals that could reflect the motivational state of individuals linked to seasonal changes in vocal behaviour.

Experimental investigation into ultrafast laser ablation of polypropylene by burst and single pulse modes

Experimental investigation into ultrashort laser ablation by burst and Single Pulse (SP) modes on Polypropylene was performed. Isolated craters with different set of laser parameters were produced on flat polymer samples to assess the influence of the temporal separation between pulses on surface quality, removal rate (time needed to remove a certain volume) and ablation efficiency (pulse energy needed to remove a certain volume). The laser parameters that allow the development of structures with minimum redeposited material splashed around them and maximum removal rates were identified. Pulse energies of 2.5 μJ and 6 μJ were identified as the removal pulse energy threshold and the value from which a structure depth saturation starts, respectively.The use of bursts provides improved quality and higher removal rates compared to the Single Pulse mode when the same number of pulses of identical pulse energies were emitted in both cases, even though the total eliminated volume is higher in the SP mode. The advantages of using bursts of 3 pulses are reported. Increasing the number of pulses per burst to 4 do not increase the removal rate when compared to bursts of 3 pulses.

Time-resolved measurements of HO2 radical in a heated plasma flow reactor

Time-resolved, absolute HO2 number density in diluted H2O2-Ar, CH4O2-Ar, and C2H4O2-Ar mixtures excited by a repetitive ns pulse discharge in a heated plasma flow reactor is measured by Cavity Ringdown Spectroscopy (CRDS). The experimental results are obtained at T = 300–600 K and P = 130 Torr, both during the discharge pulse burst and in the afterglow. The HO2 number density is inferred from the CRDS data using a spectral model exhibiting good agreement with previous measurements of absolute HO2 absorption cross sections. In the room-temperature H2O2 mixture, as well as in CH4O2 and C2H4O2 mixtures over the entire temperature range studied, HO2 is generated only during the discharge burst and decays in the afterglow. However, in the H2O2 mixture at elevated temperatures, T = 400–600 K, HO2 persists in the afterglow up to 10 ms after the discharge burst, comparable with the flow residence time in the reactor. Comparison with kinetic modeling shows that the sustained reactivity after the source of radicals is turned off is due to a chain propagation/ hydrogen oxidation process, which dominates the radical recombination reactions. The kinetic modeling predictions are in good agreement with the relative HO2 number density measured in all three mixtures, although the model underpredicts the absolute number densities in H2O2 at T = 400–600 K by up to a factor of two. Detection of the sustained low-temperature reactivity in H2O2, initiated by the radical generation in the plasma, suggests that the plasma excitation may also affect kinetics of oxidation and reforming of fuels exhibiting low-temperature chemistry below hot ignition point.

Toward Dependable Internet of Medical Things: IEEE 802.15.6 Ultra-Wideband Physical Layer Utilizing Superorthogonal Convolutional Code

Wireless body area networks (WBANs) are attracting attention as a very important technology for realizing an Internet of Medical Things (IoMT). IEEE 802.15.6 is well known as one of the international standards for WBANs for the IoMT. This article proposes the combination of the IEEE 802.15.6 ultra-wideband (UWB) physical layer (PHY) with a super orthogonal convolutional code (SOOC) and evaluates its performance as a dependable WBAN. Numerical results show that sufficient dependability cannot be obtained with the error-correcting code specified in IEEE 802.15.6 when applying the single pulse option, while both high energy efficiency and dependability can be obtained by applying an SOCC. In addition, it is confirmed that higher dependability can be obtained by combining an SOCC with a Reed–Solomon (RS) code with a coding rate that is almost the same as the error correction code specified in the standard. Furthermore, the results indicate that high dependability and energy efficiency can be obtained by adjusting the SOCC coding rate and UWB PHY parameters, even in the burst pulse option. The SOCC-applied UWB PHY of this research satisfies the high requirements of the IoMT.

Burst pulse generation in Cr:ZnSe laser with mid-infrared tunability

We demonstrated a nanosecond pulsed Cr:ZnSe laser with both wavelength tunability and burst pulse operation in the mid-infrared (IR) region. The burst pulse operation of the Cr:ZnSe laser was achieved using a pulse-on-demand Tm:YAG laser as a pump source. The number of pulse shots and the repetition rate in a packet were controlled. A tuning range of 2.32 to 2.56 μm was also achieved using a birefringent filter. Our results show that the pulse-on-demand Tm:YAG laser is an attractive pump source for the burst-pulse-operated Cr:ZnSe laser, which paves the way for various mid-IR laser applications.

Enhancement of hydrogen radical density in atmospheric pressure plasma jet by a burst of nanosecond pulses at 1 MHz

The generation and enhancement of active species in non-thermal plasmas are always decisive issues with respect to their successful applications. In this work, an atmospheric pressure plasma jet (APPJ) is generated in Ar + 1% CH4 gas flow by a bipolar nanosecond high-voltage (HV) source with a maximum pulse repetition rate up to 1 MHz (i.e. minimum pulse interval ΔT = 1 μs) in burst mode. The absolute density of hydrogen atom at ground state is measured by the two-photon absorption laser-induced fluorescence method. It is observed that with ΔT = 1 μs, the H atom density keeps increasing during the first eight HV pulses and later on, the H atom density is maintained at a quasi-stable value while more HV pulses are applied. When decreasing ΔT from 10 to 1 μs, while keeping the total number of HV pulses the same (with similar coupled energy), the peak H atom density increases by a factor of more than four times, but the decay of H atom density after the pulse burst with ΔT = 1 μs is faster. Another effect of short ΔT is to extend the axial distribution of the H atom outside the APPJ’s nozzle, and the ΔT = 2 μs case has the highest averaged H atom density when taking its temporal evolution and axial distribution into consideration. In this work, we propose that the intensive nanosecond HV burst is an efficient approach to enhance the active species density in non-thermal plasmas when a rapid response is required.

Hectowatt-level GHz burst-mode all-fiber laser based on dissipative soliton resonance.

We demonstrate a high power Yb-doped burst-mode all-fiber laser system operating at GHz intra-burst repetition rate. To our knowledge, it is the first report utilizing dissipative soliton resonance (DSR) to generate tunable burst-mode rectangular pulses. Due to the tunable duration and the rapid rise/fall time for DSR pulses, a 1-10 ns adjustable burst pulse duration is achieved. The intra-burst with sinusoidal waveform can be tuned from 0.8 GHz to 1.5 GHz and actively modulated by an electro-optic modulator (EOM). Amplified by a three-stage Yb-doped fiber amplifier (YDFA), the output power achieves 304 W at 10 ns of burst duration, and the maximum peak power reaches over 50 kW at 2 ns of burst duration. This laser system is anticipated to be applied to generate high power arbitrary microwave signal.

Effect of Modulated TENS on Corticospinal Excitability in Healthy Subjects

Conventional transcutaneous electrical nerve stimulation (TENS) has been reported to effectively alleviate chronic pain, including phantom limb pain (PLP). Recently, literature has focused on modulated TENS patterns, such as pulse width modulation (PWM) and burst modulation (BM), as alternatives to conventional, non-modulated (NM) sensory neurostimulation to increase the efficiency of rehabilitation. However, there is still limited knowledge of how these modulated TENS patterns affect corticospinal (CS) and motor cortex activity. Therefore, our aim was to first investigate the effect of modulated TENS patterns on CS activity and corticomotor map in healthy subjects. Motor evoked potentials (MEP) elicited by transcranial magnetic stimulation (TMS) were recorded from three muscles before and after the application of TENS interventions. Four different TENS patterns (PWM, BM, NM 40 Hz, and NM 100 Hz) were applied. The results revealed significant facilitation of CS excitability following the PWM intervention. We also found an increase in the volume of the motor cortical map following the application of the PWM and NM (40 Hz). Although PLP alleviation has been reported to be associated with an enhancement of corticospinal excitability, the efficiency of the PWM intervention to induce pain alleviation should be validated in a future clinical study in amputees with PLP.

In vitro study of cataract extraction by bursts of microsecond 1.54-μm laser pulses

Laser extraction of a model porcine eye cataract has been performed for the first time in an in vitro experiment using a 1.54-μm Yb, Er : glass laser generating bursts of microsecond pulses. We used effective pulse repetition rates from 36 to 75 Hz and average laser output powers from 3.9 to 5.25 W. The results demonstrate for the first time that, at an effective pulse repetition rate of 45 Hz, burst repetition rate of 15 Hz, three microsecond pulses per burst, and a burst energy from 260 to 265 mJ, the laser step duration in cataract extraction is 130 ± 10 s, which is comparable to the ultrasonic phacoemulsification and laser extraction time in the case of a Nd : YAG laser emitting at 1.44 μm. Acoustometry and high speed video recording of hydroacoustic processes accompanying interaction of water with 1.54-μm radiation from the Yb, Er : glass laser generating bursts of microsecond pulses have made it possible for the first time to detect overlap of hydroacoustic processes at the pulse spacing in bursts reduced to under 700 μs. In the case of overlap of hydroacoustic processes, despite the increase in average power and effective pulse repetition rate, acoustic wave generation is ineffective because pulses propagate through bubbles formed in the water. Laser cataract extraction is shown to be most effective at a lower average power, lower effective pulse repetition rate, and burst pulse spacing of 850 ± 10 μs.

Pulsed laser ablation of a ceramic electrolyte for all-solid-state batteries

Ion-conducting ceramics are considered to be promising materials for separator layers and hosts for cathode materials in all-solid-state batteries. While most research is dedicated to the electrochemical performance of such ceramics, literature discussing their industrial processability is scarce. Within this work, the laser ablation of the ceramic solid electrolyte Li1+xAlxTi2-x(PO4)3 (LATP) was studied experimentally using short and ultrashort laser pulses. The ablation efficiencies and the ablation rates were compared for nanosecond and picosecond pulse durations. Additionally, the impact of MHz pulse bursts with up to 5 pulses was investigated. The surface quality was analyzed by scanning electron microscopy showing melt formation at high fluences, especially when applying pulse bursts. The different process regimes are discussed regarding an implementation for structuring and cutting in all-solid-state battery production.

Effect of temporal distance in the ultrashort pulse range on the ablation of polypropylene with single pulses and burst pulses

This research focuses on the ablation process of Polypropylene by femtosecond pulses. Single Pulses and bursts of 2, 3 and 4 pulses have been used to ablate squared cavities with side lengths of 2 mm. The pulse overlap and hatch distance have been adapted to the different pulse emitting modes used in the present study to ensure that the same fluence have reached the cavity in each case. A comprehensive study was performed to assess the effect of the temporal distance between pulses and bursts on the cavity depth and morphology, ablation efficiency and recast layer height.The laser parameters that provide the best results in terms of minimum redeposited material and maximum ablation efficiency have been obtained.

Prof K C Dube Poster Award

Background:Auditory verbal hallucinations (AVH) are one of the core features of schizophrenia. In approximately 25% of patients with schizophrenia, AVH are refractory to psychotropic drug treatment and can chronically persist. Superior temporal cortex is implicated in AVH. Continuous Theta Burst Stimulation (cTBS) can be one of the add on treatment for auditory hallucination in refractory cases. Accelerated cTBS protocols have the advantage of shorter application time and lower stimulation intensity. In addition use of robotized neuronavigation will improve the accuracy of coil placement and thus localization of the stimulation site.Aim:We aimed to evaluate the efficacy of accelerated cTBS over left superior temporal cortex (STC) in improvement of AVH in schizophrenia, using neuronavigation and robotic arm.Methods:40 patients of schizophrenia with AVH, were enrolled for this randomized, sham controlled, double-blind trial. Each participant in the active group received cTBS comprising of 900 pulses (bursts of 3 stimuli at 50 Hz repeated at 5 Hz frequency), twice a day for 5 days per week for 3 consecutive weeks. AVH were assessed with PSYRATS(AHRS), PANSS & CGI. Assessments were carried out at baseline,1st,3rd & 6th weeks.Results:The improvement in AVH in active group at 1st 3rd & 6th week was not statistically significant at 0.05 (p-value) as compared to sham group. Stimulation was well tolerated.Conclusion:Results suggest that accelerated robotized neuronavigated cTBS does not appear to have substantial potential in the treatment of auditory hallucinations and further research should investigate individualised MRI guided neuronavigation with higher sample size.

Photon energy transfer on titanium targets for laser thrusters

Abstract Using two infrared pulsed lasers systems, a picosecond solid-state Nd:YAG laser with tuneable repetition rate (400 kHz–1 MHz) working in the burst mode of a multi-pulse train and a femtosecond Ti:sapphire laser amplifier with tuneable pulse duration in the range of tens of femtoseconds up to tens of picoseconds, working in single-shot mode (TEWALASS facility from CETAL-NILPRP), we have investigated the optimal laser parameters for kinetic energy transfer to a titanium target for laser-thrust applications. In the single-pulse regime, we controlled the power density by changing both the duration and pulse energy. In the multi-pulse regime, the train’s number of pulses (burst length) and the pulse energy variation were investigated. Heat propagation and photon reflection-based models were used to simulate the obtained experimental results. In the single-pulse regime, optimal kinetic energy transfer was obtained for power densities of about 500 times the ablation threshold corresponding to the specific laser pulse duration. In multi-pulse regimes, the optimal number of pulses per train increases with the train frequency and decreases with the pulse power density. An ideal energy transfer efficiency resulting from our experiments and simulations is close to about 0.0015%.

Generation of pulse bursts in an Yb-doped all-normal dispersion passively mode-locked fiber laser with Raman scatting

Pulse bursts are generated in an Yb-doped all-normal dispersion (ANDi) passively mode-locked fiber laser with Raman scatting based on nonlinear polarization rotation (NPR). The number of pulses can be continuously adjusted from 1 to 8 by adjusting the pump power. The output power varies stepwise with linearly increasing of input power and pulse numbers in the bursts. We explain that the pulse bursts in ANDi fiber laser are formed by the clamping of pulse width and peak power. The energy evolution of the pulses burst with Raman component is experimentally realized in Yb-doped fiber laser, which is excepted to benefit energy controlling in applications such as laser material ablation and so on.

Contour variations and acoustic characteristics of whistle sounds emitted by Pacific white‐sided dolphins in shallow coastal waters of the Sea of Japan

AbstractPacific white‐sided dolphins, Lagenorhynchus obliquidens (PWSDs), migrate along the coast of Japan. PWSDs rarely emit whistles, instead utilizing pulses, unlike many other delphinid species that frequently emit whistle sounds. In the present study, we aimed to clarify the acoustic characteristics and repertoire of the whistle of PWSDs, which have not been reported so far. We analyzed PWSD whistle sound systems (e.g., acoustic parameters and contours) during boat surveys and using passive acoustic monitoring in shallow coastal waters in the northern Sea of Japan. PWSDs in Shakotan rarely emitted whistles, while the burst pulse frequently was as reported in previous studies in other waters. The PWSD whistle vocalization rates were higher during traveling than during foraging. The frequency and duration of their whistles did not appear to change between behaviors. Although complex multiloop whistles were not recorded, whistle contours were classified into seven types. Whistles are often recorded intensively in a short period as a sequence or bout. Considering the extremely low whistle vocalization rates, dolphins may choose whistles instead of pulsed sounds in limited contexts. Our results shed light on the differences in whistle sound usage within odontocete species.

Characteristics of Regular Pulse Bursts Generated From Lightning Discharges

In this work, we studied the waveforms of all lightning discharges from about 15 min. Eighty-three percent of all lightning discharges contain particular waveforms called regular pulse bursts (RPBs), which have regular microsecond-scale electric or magnetic field pulses. Maximum proportion of RPBs occur in middle or rear of lightning discharges. Prior to or after RPBs, there is always a chaotic pulse period. The analysis indicated that RPBs are caused by a secondary discharge in the fractured old breakdown channel, likeness to dart-stepped leader occuring in negative cloud-to-ground discharge (-CG). Four types of RPBs, namely, category of normal RPBs, category of back RPBs, category of symmetric RPBs, and category of reversal RPBs, were sorted in the light of the evolution of the pulse amplitude, interval between neighboring pulses and pulse polarity. In addition, the difference between normal RPBs and back RPBs was considered to be caused by the distance between neighboring charge pockets and the magnitude of the charge in every charge pocket. The symmetric RPBs were considered to be caused by a discharge channel with a large central charge area. Reversal RPBs were considered to be caused by a bending channel or superposition of two or more RPBs. We located some RPBs in a typical intra-cloud flash (IC) in three-dimensional. The analysis showed that the developing velocity of RPBs ranged from approximately 1.2 × 106 m/s to 3.0 × 106 m/s, which slower less than both of the dart leader or dart-stepped leader process from previous studies. And we found it is several meters to dozens of meters that the lengths range of discharge step which between two adjacent pulses.

Comprehensive Analysis of a Dense Sample of FRB 121102 Bursts

Abstract We present an analysis of a densely repeating sample of bursts from the first repeating fast radio burst, FRB 121102. We reanalyzed the data used by Gourdji et al. and detected 93 additional bursts using our single-pulse search pipeline. In total, we detected 133 bursts in three hours of data at a center frequency of 1.4 GHz using the Arecibo telescope, and develop robust modeling strategies to constrain the spectro-temporal properties of all of the bursts in the sample. Most of the burst profiles show a scattering tail, and burst spectra are well modeled by a Gaussian with a median width of 230 MHz. We find a lack of emission below 1300 MHz, consistent with previous studies of FRB 121102. We also find that the peak of the log-normal distribution of wait times decreases from 207 to 75 s using our larger sample of bursts, as compared to that of Gourdji et al. Our observations do not favor either Poissonian or Weibull distributions for the burst rate distribution. We searched for periodicity in the bursts using multiple techniques, but did not detect any significant period. The cumulative burst energy distribution exhibits a broken power-law shape, with the lower- and higher-energy slopes of −0.4 ± 0.1 and −1.8 ± 0.2, with the break at (2.3 ± 0.2) × 1037 erg. We provide our burst fitting routines as a Python package burstfit 4 4 https://github.com/thepetabyteproject/burstfit that can be used to model the spectrogram of any complex fast radio burst or pulsar pulse using robust fitting techniques. All of the other analysis scripts and results are publicly available. 5 5 https://github.com/thepetabyteproject/FRB121102

Compact High-Voltage AC Generator with Pulse Transformer for High-Frequency Irreversible Electroporation (H-FIRE)

This paper is focused on a design of a high-voltage (HV) generator, which is proposed for a high-frequency irreversible electroporation (H-FIRE). The generator produces bursts of bipolar symmetrical pulses. Most HV sources used for cell electroporation are based on a controlled discharge of a capacitor into a resistive load. This solution is very simple, but it is associated with a certain risk of an uncontrolled discharge of the capacitor. We present a different type of the generator, where a DC-AC inverter with pulse transformer is used and where the mentioned risk is eliminated. Our generator is able to deliver bursts with variable length from 50 to 150 μs and a gap between bursts can be set from 0.5 to 1.5 s. Pulse frequency can be varied from 65 to 470 kHz and the output voltage is controlled in two ranges from 0 to 1.3 kV or from 0 to 2.5 kV. Results are presented with resistive load and with tissue impedance load.

Localized time accurate sampling of nonequilibrium and unsteady hypersonic flows: methods and horizons

Modern “non-intrusive” optical methods are providing revolutionary capabilities for diagnostics of hypersonic flow fields. They generate accurate information on the performance of ground test facilities and provide local time accurate measurements of near-wall and off-body flow fields surrounding hypersonic test articles. They can follow the true molecular motion of the flow and detect nonequilibrium states and gas mixtures. They can be used to capture a wide range of turbulent scales and can produce highly accurate velocity, temperature and density measurements as well as time-frozen images that provide intuitive understanding of flow phenomena. Recent review articles address many of these methods and their applications. The methods highlighted in this review are those that have been enabled or greatly improved by new, versatile laser systems, particularly including kHz rate femtosecond lasers and MHz rate pulse burst lasers. Although these methods can be applied to combusting environments, the focus of this review is on external high Mach number flows surrounding test articles and wind tunnel core flow properties. The high repetition rates enable rapid time evolving flows to be analyzed and enable the collection of large data sets necessary for statistical analysis. Future capabilities based on the use of atomic vapor filters and on frequency tunable, injection locked MHz rate lasers are promising.