Cycle Pulse Research Articles

Studies on Pulse Wave Model Based on Multiple Gaussian Decomposition

The characteristics of pulse waveform reflect the physiological and pathological state of the human beings. However, it faces a lack of a comprehensive and detailed understanding. In this pursuit, the present research envisages to propose a new method of pulse waveform analysis based on the traditional method of pulse wave analysis. In this study, the data of 932 subjects were studied that included the pulse wave of the finger vein volume and the pulse wave of the radial artery pressure. The pulse wave was re-analyzed in combination with the physiological process of the heart. Pulse wave data processing was done using the Gaussian function decomposition fitting method to make up for the lost information in the pulse wave. The performance evaluation of this method was compared with the traditional pulse wave fitting. It was found that the difference of k value of pulse wave after normalization was increased by 0.1%, the absolute value of average residuals was increased, and the variance of all data increased by three times. This method could fully reflect the characteristics of the pulse wave, and was found to be an effective characteristic analysis method of pulse wave, thereby providing a scientific basis for the comprehensive analysis of the characteristics of the whole cardiac cycle pulse wave.

Spatiotemporal Assessment of the Cellular Safety of Cavitation-Based Therapies by Passive Acoustic Mapping

Many useful therapeutic bio-effects can be generated using ultrasound-induced cavitation. However, cavitation is also capable of causing unwanted cellular and vascular damage, which should be monitored to ensure treatment safety. In this work, the unique opportunity provided by passive acoustic mapping (PAM) to quantify cavitation dose across an entire volume of interest during therapy is utilised to provide setup-independent measures of spatially localised cavitation dose. This spatiotemporally quantifiable cavitation dose is then related to the level of cellular damage generated. The cavitation-mediated destruction of equine red blood cells mixed with one of two types of cavitation nuclei at a variety of concentrations is investigated. The blood is placed within a 0.5-MHz ultrasound field and exposed to a range of peak rarefactional pressures up to 2 MPa, with 50 to 50,000 cycle pulses maintaining a 5% duty cycle. Two co-planar linear arrays at 90° to each other are used to generate 400-µm-resolution frequency domain robust capon beamforming PAM maps, which are then used to generate estimates of cavitation dose. A relationship between this cavitation dose and the levels of haemolysis generated was found which was comparable regardless of the applied acoustic pressure, pulse length, cavitation agent type or concentration used. PAM was then used to monitor cellular damage in multiple locations within a tissue phantom simultaneously, with the damage–cavitation dose relationship being similar for the two experimental models tested. These results lay the groundwork for this method to be applied to other measures of safety, allowing for improved ultrasound monitoring of cavitation-based therapies.

Measurement of Infrared Photoluminescence Spectra by Gated Integration with Active Baseline Subtraction

On the basis of Fourier transform infrared (FTIR) spectroscopy, a method is implemented that enables measurements of infrared (IR) photoluminescence with a high reverse duty cycle of pump pulses, which decreases the uncontrolled heating of semiconductor structures by an excitation laser. The method was used to record IR photoluminescence spectra of test narrow-gap low-dimensional heterostructures in the wavelength range of 1–5 µm. It is determined that, at high reverse duty cycles of the reference pulse (greater than 20), the developed gated integration method has a better signal-to-noise ratio in the measured spectra than does the conventionally used synchronous detection (lock-in) method.

Особенности импульсного нагрева излучением субтерагерцевого гиротрона при получении нанопорошков оксидов металлов

The paper describes the features of the metal oxide nanopowder obtaining by an evaporation-condensation method with pulsed heating of the material by focused subterahertz radiation. It has been experimentally shown that optimal conditions for the rapid evaporation of a substance are achieved at the highest possible pulse power and the lowest possible duty cycle at a fixed average power. Under these conditions, it is possible to realize the heating and evaporation of a substance in a focused radiation beam in a relatively short time, while the adjacent layers of the substance maintain a relatively low thermal conductivity. A linear increase in the evaporation rate with a decrease in the duty cycle of heating pulses was demonstrated, the increase reached 5 times relative to the continuous heating mode.

Understanding the ion acceleration mechanism in bipolar HiPIMS: the role of the double layer structure developed in the after-glow plasma

The physical vapor deposition techniques are nowadays widely used at industrial scale to produce thin films and surface coatings. Despite their proven utilities and benefits, these techniques still need to be improved in order to build other exigent and innovative coating systems, able to satisfy the market demand and to meet modern society’s needs. In this context, the bipolar high power impulse magnetron sputtering (BP-HiPIMS) technology is gaining ground and popularity due to its extraordinary ability to control the energy of the incoming ion flux to the growing film, enabling an energy-enhanced deposition process thanks to the existence of a dynamic double layer (DL) structure which develops in the after-glow plasma. In this work, the HiPIMS discharge was operated in bipolar mode, in which the negative pulses are followed by positive pulses whose amplitude, duration and delay can be independently controlled. The temporal and spatial evolutions of the plasma potential in BP-HiPIMS discharge were investigated using an emissive probe. Energy-resolved mass spectrometry was used to study the influence of the pulsing configuration (positive/negative pulse duration) on the energy distribution and flux of the ionic species bombarding the substrate. It was found that the ion energy distributions and ion flux were mainly determined by the specific time-and-space evolution of the plasma potential throughout the cycle of the voltage pulses applied to the target and the spatial distribution of the ions at the onset of the positive pulse. The ion propagation dynamics is strongly related to the potential drop across the DL structure whose characteristic features are mainly influenced by the amplitude and duration of the positive pulse. Short negative HiPIMS pulses followed by short and highly positive reverse pulses are favorable for an efficient acceleration mechanism of the metal ions in the potential drop of the DL.

33 W OPCPA at 10 kHz repetition rate with four cycle pulse duration at 2.1µm based on a single pump laser

33 W OPCPA at 10 kHz repetition rate with four cycle pulse duration at 2.1µm based on a single pump laser

Регистрация спектров инфракрасной фотолюминесценции методом стробируемого интегрирования в режиме активного вычитания фонового сигнала

A method based on the Fourier-transform infrared (FTIR) spectrometer has been implemented allowing infrared photoluminescence measurements with a low duty cycle of pump pulses. It reduces the uncontrolled heating of semiconductor structures by pump laser. The method was used to record the infrared photoluminescence spectra of test narrow-gap low dimensional heterostructures in the wavelength range of 1–5 μm. It was determined that for large reverse duty cycle (more then 20) the developed gated integration method has a better signal-to-noise ratio in the measured spectra compared to the traditionally used synchronous detection method (Lock-in amplification).

Исследование свойств наноструктур оксида цинка, полученных методом импульсного электрохимического осаждения

The properties of zinc oxide nanostructures allow it to be used in various fields of science and technology. The increased interest in this compound is caused by a rare combination of optical and electrophysical properties. The films of this compound have good piezoelectric and electroluminescent properties, due to which zinc oxide can be used as functional layers in surface acoustic waves, elements of nonlinear optics. This allows the oxide to pass visible radiation. In this paper, we study the influence of the conditions for obtaining a coating by pulsed electrochemical deposition on the forbidden zones and the power of a coating based on zinc oxide. It was shown that the temperature and duty cycle of pulses are of great importance in the formation of the coating, which is explained by the kinetics of the electrochemical reaction. The Urbach energy increases with a decrease in crystalline size and increased by almost 3 times, compared with a coarse-grained sample.

Estimating the ultrasound attenuation coefficient using complementary Golay codes

Accurate evaluation of ultrasonic wave attenuation is important in many medical applications of ultrasound. The aim of this work is to present a thorough analysis of the effectiveness of using complementary Golay coded sequences (CGCS) during the evaluation of ultrasound attenuation in tissue-like materials, especially at greater depths or at high attenuation. In order to compare the results of the attenuation measurement with the use of CGCS transmission and a short two sine cycles pulse, ultrasound backscattered from medium with predefined attenuation of 0.3, 0.7 and 2 dB/[MHz × cm] were simulated. Also for the same transmission signals, measurements of ultrasound echoes scattered in the tissue phantom with an attenuation of 0.5 dB/[MHz × cm] were performed.In the case of numerically simulated data, for the CGCS excitation, the maximum depth for which the attenuation was correctly determined increased from 55 mm to 80 mm for the 0.7 dB/[MHz × cm] phantom and from 20 mm to 50 mm for the 2 dB/[MHz × cm] phantom compared to excitation of the transducer with a short two sine cycles pulse. When the measurement data obtained using the tissue phantom was used to estimate the attenuation coefficient, the relative error was determined to be 6% and 16% for the depths of 10 mm and 40 mm for the short two sine cycles pulse excitation, respectively. Corresponding values for CGCS excitation and considered depths were 2% and 4%.The use of CGSC sequence during attenuation measurements increases measurement accuracy and can improve medical diagnostic techniques.

High purity copper nanoparticles via sonoelectrochemical approach

Synthesis of monodisperse, uniform sized and high purity copper nanoparticles has always been difficult due to copper’s tendency for oxidation. The objective of this work to describes the synthesization of copper nanoparticles with high purity at different potentials and different current densities at fixed potential by ultrasonic electroplating (sonoelectrochemical) approach. Effects of sonication parameters such as sonication power, duty cycle and ultrasonic pulse time are also investigated. It has been observed that size and morphology of the copper nanoparticles (Cu NPs) are very closely related with deposition potential, current density at fixed potential. Sonication power, duty cycle and ultrasonic pulse time also influence the particles morphology and sizes. Copper powders having particles with uniform morphology were obtained at deposition potential −2V by sonoelectrochemical approach using amperometric I-t curve technique. Poly (vinylpyrrolidone) (PVP) was used as capping agent. The role of PVP in reducing the particle size and against oxidation is demonstrated by some important techniques. This facile synthetic process can be useful to fabricate copper nanoparticles with high purity in order to explore its true potentials and applications in nano-regime scale.

Holographic interference in atomic photoionization from a semiclassical standpoint

A theoretical study of the interference pattern imprinted on the doubly differential momentum distribution of the photoelectron due to atomic ionization induced by a short laser pulse is developed from a semiclassical standpoint. We use the semiclassical two-step model of Shvetsov-Shilovski et al. (Phys. Rev. A 94, 013415) to elucidate the nature of the holographic structure. Three different types of trajectories are characterized during the ionization process by a single cycle pulse with three different types of interferences. We show that the holographic interference arises from the ionization yield only during the first half cycle of the pulse, whereas the coherent superposition of electron trajectories during the first half cycle and the second half cycle gives rise to two other kinds of intracycle interference. Although the picture of interference of a reference beam and a signal beam is adequate, we show that our results for the formation of the holographic pattern agree with the glory rescattering theory of Xia et al. (Phys. Rev. Lett. 121, 143201). We probe the two-step semiclassical model by comparing it to the numerical results of the time dependent Schr\"odinger equation.

Generation of 1.5 cycle pulses at 780 nm at oscillator repetition rates with stable carrier-envelope phase.

We demonstrate a spectral broadening and compression setup for carrier-envelope phase (CEP) stable sub-10-fs Ti:sapphire oscillator pulses resulting in 3.9 fs pulses spectrally centered at 780 nm. Pulses from the oscillator with 2 nJ energy are launched into a 1 mm long all-normal dispersive solid-core photonic crystal fiber and spectrally broadened to more than one octave. Subsequent pulse compression is achieved with a phase-only 4f pulse shaper. Second harmonic frequency resolved optical gating with a ptychographic reconstruction algorithm is used to obtain the spectral phase, which is fed back as a phase mask to the shaper display for pulse compression. The compressed pulses are CEP stable with a long term standard deviation of 0.23 rad for the CEP noise and 0.32 rad for the integrated rms phase jitter. The high total throughput of 15% results in a remaining pulse energy of about 300 pJ at 80 MHz repetition rate. With these parameters and the ability to tailor the spectral phase, the system is well suited for waveform sensitive photoemission experiments with needle tips or nanostructures and can be easily adapted to other sub-10 fs ultra-broadband Ti:sapphire oscillators.

Analysis of partial discharge sources in stator insulation system using variable excitation frequency

Identification of partial discharge (PD) sources in stator insulation is an important and challenging task. Distinct phase-resolved PD (PRPD) pattern of different PD sources are well established at power frequency (50/60 Hz) and can help to identify each source. In this study, different sources of PD commonly found in stator insulation were created on a 6.6 kV epoxy-mica stator coil. Each PD source was experimentally investigated at a variable excitation frequency in the range of 50-0.1 Hz. PRPD pattern and PD parameters such as integrated charge per cycle and number of discharge pulses per cycle of each discharge source were compared at different frequencies. The comparison suggests that the parameter of each PD source was dependent on excitation frequency. Some discharge sources have shown a distinct variation in their characteristics with excitation frequency. These distinct characteristics are additional information to the existing ones, which will help to correlate PD characteristics with the source of PD in stator insulation.

Novel High-Power, High Repetition Rate Laser Diode Pump Modules Suitable for High-Energy Class Laser Facilities

The latest generation of high-energy-class pulsed laser facilities, under construction or planned, such as EuPRAXIA, require reliable pump sources with high power (many kW), brightness (>1 MW/cm2/sr) and electro-optical conversion efficiency (>50%). These new facilities will be operated at high repetition rates (around 100 Hz) and only diode lasers are capable of delivering the necessary performance. Commercial (quasi-continuous wave, QCW) diode laser pulse-pump sources are, however, constructed as low-cost passively cooled stacked arrays that are limited either in brightness, efficiency or repetition rate. Commercial continuous wave diode laser pumps constructed using microchannel coolers (as used in high-value industrial machine tools) can fulfil all requirements, but are typically not preferred, due to their cost and complexity and the challenges of preventing cooler degradation. A custom solution is shown here to fill this gap, using advanced diode lasers in a novel passive side-cooling geometry to realize 100 … 200 Hz pump modules (10%–20% duty cycle) that emit peak power of 6 kW at wavelength = 940 nm. The latest performance of these modules is summarized and compared to literature. We show that a brightness >1 MW/cm2/sr can be efficiently delivered across a wide range of laser pulse conditions with 10% duty cycle (pulse width: 100 µs … 100 ms … cw, repetition rate up to 1 kHz). Furthermore, we describe how these pumps have been used to construct and reliably operate (>109 pulses without degradation) in high-energy-class regenerative and ring amplifiers at the Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI). We also show first results on 100 Hz pumping of cryogenically cooled solid-state Yb:YAG slab amplifiers, as anticipated for use in the EuPRAXIA laser, and note that peak temperature is disproportionately increased, indicating that improved cooling and more detailed studies are needed.

Limit cycles in relay systems with fractional order plants

In this paper, limit cycle frequency, pulse width and stability analysis are examined using different methods for relay feedback nonlinear control systems with integer or fractional order plant transfer functions. The describing function (DF), A loci, a time domain method formulated in state space notation and Matlab/Simulink simulations are used for the analysis. Comparisons of the results of using these methods are given in several examples. In addition, the work has been extended to fractional order systems with time delay. Programs have been developed in the Matlab environment for all the theoretical methods. In particular, Matlab programs have been written to obtain a graphical solution for the A loci method, which can precisely calculate the limit cycle frequency. The developed solution methods are shown in various examples. The major contribution is to look at finding limit cycles for relay feedback systems having plants with a fractional order transfer function (FOTF). However, en route to this goal new assessments of limit cycle stability have been done for a rational plant transfer function plus a time delay.

Methodical inaccuracy of the Z-scan method for few-cycle terahertz pulses

Modern sources of THz radiation generate high-intensity pulses allowing to observe nonlinear effects in this spectral range. To describe many nonlinear effects theoretically, it is necessary to know the nonlinear refractive index coefficient of optical materials. The work studies the applicability of the Z-scan method to determine the nonlinear refractive index coefficient in the THz frequency range for few-cycle pulses. We have discussed the correctness of the known Z-scan method for calculating the nonlinear refractive index coefficient for broadband THz radiation regarding number of cycles pulses have. We have demonstrated that the error in determining the nonlinear refractive index coefficient is always greater than 70% for true single-cycle pulses. With the increase in the number of oscillations to the measurement error shows strong dependence on the sample thickness and can vary from 2% to 90% regarding the parameters chosen. The fact that such radiation dispersion length is commensurate with the nonlinear length or even less than the latter results in the discrepancy mentioned. It is demonstrated that the decrease in the sample thickness leads to the reduction of the nonlinear refractive index coefficient determination error, and this error is <2% when the ratio between the sample thickness and the pulse longitudinal spatial size is ≤1. This can relate to the fact that the nonlinear effects in such a thin sample occur faster than the dispersion ones.

Effect of current pulse duration in recovering quantitative induced polarization models from time-domain full-response and integral chargeability data

The signal level and shape of induced polarization responses are significantly affected by the current pulse duration and waveform. If not accounted for, this data dependency on the current will propagate trough the inversion to results rendering unquantifiable subsurface models. While this problem has been addressed in full-response induced polarization modelling, questions remain as to how to accurately retrieve quantitative induced polarization inversion models from the types of apparent integral chargeability data often used in data interpretation. Although several methodologies have been proposed for handling and inverting apparent resistivity and integral chargeability, these cannot compensate for the data dependency on the current waveform and pulse duration. This paper presents a novel inversion method for such data. The method considers current waveform and receiver transfer functions for retrieving quantitative IP models unbiased by transmitter waveform. The method uses the constant phase angle model, expressed in terms of the medium resistivity and phase. Specifically, four field data sets for the same profile but with different 100 per cent duty cycle pulse durations (4, 2, 1 and 0.5 s) serve as examples of data sets giving models dependant on current waveform when inverted with standard approaches. The novel inversion method presented here gives quantifiable models independent on the current waveform and pulse duration. These results resemble models retrieved with existing, full-response induced polarization inversions. The results still contain some degree of uncertainty in relation to underlying assumptions and parametrizations. Managing this source of uncertainty is considered in terms of full-response induced polarization inversions with constant phase angle and maximum phase angle inversions. (Less)

WITHDRAWN: Treatment with 3 cycle pulses of high‐dose dexamethasone (HD -DXM) in adults with Primary Immune thrombocytopenia : a prospective randomized clinical trial

Ahead of Print article withdrawn by publisher.

Scattering of a short electromagnetic pulse from a Lorentz–Duffing film: Theoretical and numerical analysis

We combine scattering theory, Fourier, traveling wave and asymptotic analyses together with numerical simulations to present interesting and practically useful properties of femtosecond pulse interaction with thin films. The dispersive material is described by a single resonance Lorentz model and its nonlinear extension with a cubic Duffing-type nonlinearity. A key feature of the Lorentz dielectric function is that its real part becomes negative between its zero and its pole, generating a forbidden region. We illustrate numerically the linear interaction of the pulse with the film using both scattering theory and Fourier analysis. Outside this region we show the generation of a sequence of pulses separated by round trips in the Fabry–Perot cavity due to multiple reflections. When the pulse spectrum is inside the forbidden region, we observe total reflection. Near the pole of the dielectric function, we demonstrate the slowing down of the pulse (group velocity tending to zero) in the medium that behaves as a high-Q cavity. We use the combination of analysis and simulations in the linear regime to validate the delta function approximation of the thin layer; this collapses the forbidden region to a single resonant point of the spectrum. We also study the single cycle pulse interaction with a thin film and show three distinct types of reflection: half-pulse, sinusoidal wave train and cosine wavelet. Finally we analyze the influence of a strong nonlinearity and observe that the film switches from reflecting to transparent.

Generating few-cycle radially polarized pulses

A radially polarized beam is axially symmetric and is able to produce tightly focused light fields beyond the Gaussian beam diffraction limit. However, with the current technology, its duration is limited by the relatively narrow bandwidth that the generation techniques can support. Using a 10 cycle pulse with a central wavelength of 1.8 μm, we show that radially polarized beams can be compressed to the few-cycle regime, while still maintaining their radially polarized nature. Therefore, it seems feasible, using only well-developed methods, to reach focused intensities of ∼1019 W/cm2. Conversion via high-harmonic generation will also open a route for applications in attosecond science, especially for a wide range of optical measurements and optical control that require high spatial and high temporal resolution.