Input Pulse Research Articles

Non-ideal program-time conservation in charge trap flash for deep learning

Training deep neural networks (DNNs) is computationally intensive, but arrays of non-volatile memories such as charge trap flash (CTF) can accelerate DNN operations using in-memory computing. Specifically, the resistive processing unit (RPU) architecture uses a voltage-threshold program with stochastic encoded pulse trains and analog memory features to accelerate vector-vector outer product and weight update for gradient descent algorithms. Although CTF, offering high precision, has been regarded as an excellent choice for implementing RPU, the accumulation of charge due to the applied stochastic pulse trains is ultimately of critical significance in determining the final weight update. In this paper, we report on the non-ideal program-time conservation in CTF through pulsing input measurements. We experimentally measure the effect of pulse width and pulse gap, keeping the total ON-time of the input pulse train constant, and report three non-idealities: (1) the cumulative shift reduces when total ON-time is fragmented into a larger number of shorter pulses, (2) the cumulative shift drops abruptly for pulse widths <2 s, (3) the cumulative shift depends on the gap between consecutive pulses and the shift reduction recovers for smaller gaps. We present an explanation based on a transient tunneling field enhancement due to blocking oxide trap-charge dynamics to explain these non-idealities. Identifying and modeling the responsible mechanisms and predicting their system-level effects during learning is critical. This non-ideal accumulation is expected to affect algorithms and architectures relying on devices for implementing mathematically equivalent functions for in-memory computing-based acceleration.

A novel algorithm to determine the input energy for soliton generation in a media with a patterned property

Estimation of input pulse or beam energy is crucial for soliton generation. It is rather easier for conventional solitons that are generated in isotropic media but difficult for anisotropic media, wherein a certain property of the media follows a pattern. This article presents a novel algorithm that can estimate and optimize the initial pulse energy to ensure a stable optical soliton in an anisotropic medium having a patterned property. For demonstration, local nonlinear media with periodic dispersion, diffraction, and nonlinearity as well as nonlocal nonlinear media with periodic diffraction are considered separately. This algorithm can be applied to media with any kind of dispersion map, including an irregular one. It can also be used for media with patterned diffraction, patterned nonlinearity, and multi-layered composite materials.

Contamination and dissolution-crystallisation textures of granite relics in xenolith-rich composite Coral Island Dike of the Paraná-Etendeka Magmatic Province

The Coral Island Xenolithic Dike (CIXD) is a composite intrusion with mafic borders and apophyses (Pulse 1) and a felsic centre with a high amount of granitic xenoliths and xenocrysts (Pulse 2). The xenoliths, most abundant in the dike core, are granitic and vary from millimetres up to 1.5 m in size. The xenolithic composite dike is low-TiO2 Gramado-type. The xenoliths are concentrated in the dacitic core, partially molten and accompanied by relict feldspar and partly resorbed quartz xenocrysts. Field, petrographic and geochemical data attest to contamination by assimilation processes in the central part. Flowage differentiation (Bagnold Effect) has concentrated the large xenoliths in the dacitic core. Evidence of xenolith partial melting comprises spherulitic K-feldspar/albite intergrowths and polycrystalline quartz aggregates. Coronas around the pyroxenes in the dacite and the absence of mesostasis in the dike magmas attest to supercooling of the system at shallow-level conditions. The ascent of the central part of the dike (dacite + xenoliths + relict xenocrysts) was only possible due to the proximity of the magma reservoir to the emplacement site and chamber recharging with hot basic magma input (Pulse 1) that prevents the system from cooling and crystallising.

Nonlinear self-action of ultrashort guided exciton–polariton pulses in dielectric slab coupled to 2D semiconductor

Recently reported large values of exciton–polariton nonlinearity of transition metal dichalcogenide (TMD) monolayers coupled to optically resonant structures approach the values characteristic for GaAs-based systems in the regime of strong light-matter coupling. Contrary to the latter, TMD-based polaritonic devices remain operational at ambient conditions and therefore have greater potential for practical nanophotonic applications. Here, we present the study of the nonlinear properties of Ta2O5 slab waveguide coupled to a WSe2 monolayer. We confirm that the hybridization between the waveguide mode and the exciton resonance in WSe2 gives rise to the formation of guided exciton–polaritons with Rabi splitting of 36 meV. By measuring transmission of ultrashort optical pulses through this TMD-based polaritonic waveguide, we demonstrate the strong nonlinear dependence of the output spectrum on the input pulse energy. We develop a theoretical model that shows agreement with the experimental results and gives insights into the dominating microscopic processes which determine the nonlinear pulse self-action: Coulomb exciton–exciton interaction and scattering to an incoherent excitonic reservoir. Based on the numerical simulation of nonlinear phenomena in our polariton system, we conclude that it may support a quasi-stationary solitonic regime of pulse propagation at intermediate pump energies. Our results provide an important step for the development of nonlinear on-chip polaritonic devices based on 2D semiconductors.

On-target delivery of intense ultrafast laser pulses through hollow-core anti-resonant fibers.

We report the flexible on-target delivery of 800 nm wavelength, 5 GW peak power, 40 fs duration laser pulses through an evacuated and tightly coiled 10 m long hollow-core nested anti-resonant fiber by positively chirping the input pulses to compensate for the anomalous dispersion of the fiber. Near-transform-limited output pulses with high beam quality and a guided peak intensity of 3 PW/cm2 were achieved by suppressing plasma effects in the residual gas by pre-pumping the fiber with laser pulses after evacuation. This appears to cause a long-term removal of molecules from the fiber core. Identifying the fluence at the fiber core-wall interface as the damage origin, we scaled the coupled energy to 2.1 mJ using a short piece of larger-core fiber to obtain 20 GW at the fiber output. This scheme can pave the way towards the integration of anti-resonant fibers in mJ-level nonlinear optical experiments and laser-source development.

Ballistic dynamics of emergent soliton from Airy pulse in a medium with linear optical potential

We numerically investigate the propagation dynamics of Airy pulse in dispersive and nonlinear medium with time-dependent external optical potential. These time-dependent optical potentials are created by the co-propagating strong pump wave. In the presence of linear optical potential, soliton shedding from signal Airy pulse is observed, which demonstrates ballistic motion. However, emergent soliton can either be advanced or delayed depending upon the sign of the potential and the extent of temporal advancement or delay is directly proportional to the magnitude of the potential strength. In addition, the temporal shift of the emergent soliton is found to be dependent on the input pulse power. Moreover, we show ballistic motion of the emergent soliton by incorporating an initial linear phase as well as linear chirp (quadratic phase) parameters in the input Airy pulse. Furthermore, the effect of truncation factor on the propagation dynamics is explored. These results provide new insights on the manipulation of the signal Airy pulse dynamics in dispersive and nonlinear media.

Computationally assessing diamond as an ultrafast pulse shaper for high-power ultrawideband radar

Diamond holds promise to reshape ultrafast and high-power electronics. One such solid-state device is the diode avalanche shaper (DAS), which functions as an ultrafast closing switch where closing is caused by the formation of the streamer traversing the diode much faster than 107 cm/s. One of the most prominent applications of DAS devices is in ultrawideband (UWB) radio/radar. Here, we simulate a diamond-based DAS and compare the results to a silicon-based DAS. All DASs were simulated in mixed mode as ideal devices using the drift-diffusion model. The simulations show that a diamond DAS promises to outperform an Si DAS when sharpening the kV nanosecond input pulse. The breakdown field and streamer velocity (∼10 times larger in diamond than Si) are likely to be the major reasons enabling kV sub-50 ps switching using a diamond DAS.

Maxwell–Bloch equations without spectral broadening: the long-time asymptotics of an input pulse in a long two-level laser amplifier

We study the problem of propagation of an input electromagnetic pulse through a long two-level laser amplifier under trivial initial conditions. In this paper, we consider an unstable model described by the Maxwell–Bloch equations without spectral broadening. Previously, this model was studied by Manakov in (1982 Zh. Eksp. Teor. Fiz. 83 68–75) and together with Novokshenov in (1986 Teor. Mat. Fiz. 69 40–54). We consider this model in a more natural formulation as an initial-boundary (mixed) problem using a modern version of the inverse scattering transform method in the form of a suitable Riemann–Hilbert (RH) problem. The RH problem arises as a result of applying the Fokas–Its method of simultaneous analysis of the corresponding spectral problems for the Ablowitz–Kaup–Newell–Segur equations. This approach makes it possible to obtain rigorous asymptotic results at large times, which differ significantly from the previous ones. Differences take place both near the light cone and in the tail region, where a new type of solitons is found against an oscillating background. These solitons are physically relevant, their velocities are smaller than the speed of light. The number of such solitons can be either finite or infinite (in the latter case, the set of zeros has a condensation point at infinity). Such solitons cannot be reflectionless, they are generated by zeros of the reflection coefficient of the input pulse (and not by poles of the transmission coefficient). Thus our approach shows the presence of a new phenomenon in soliton theory, namely, the boundary condition (input pulse) of a mixed problem under trivial initial conditions can generate solitons due to the zeros of the reflection coefficient, while the poles of the transmission coefficient do not contribute to the asymptotics of the solution.

Optimization of process parameters and performance for machining Inconel 718 in renewable dielectrics

In this study, the optimization of processing parameters of Inconel 718 using electrical discharge machining (EDM) with three kinds of renewable dielectrics (soybean oil, sunflower seed oil, and rapeseed oil) was studied. As input process parameters, pulse current, pulse duration, duty ratio, and dielectric type were all utilized. The machining performance indices of EDM were material removal rate (MRR), surface roughness (Ra), energy pulse ratio per volume (EEV), and exhaust emission characteristics (EEC). The response surface method (RSM) was used to carry out the central composite design of the EDM experiment, and it looked into how process parameters affected machining performance. In addition, the extreme learning machine (ELM)-improved integrated beta-distribution cuckoo search (IBCS) algorithm was used to optimize the EDM process, and the optimization results were verified by experiments. The research results demonstrate that the predicted results are generally better than the experimental results, and the maximum and average deviations of the experimental results are within the acceptable range (maximum deviation <20%, average deviation <15%). The effectiveness of the optimization algorithm was proved, which was helpful in improving the performance of EDM, reducing energy consumption and emissions, and improving the sustainability of EDM.

Infinitesimal phase response functions can be misleading

Phase response functions are the central tool in the mathematical analysis of pulse-coupled oscillators. When an oscillator receives a brief input pulse, the phase response function specifies how its phase shifts as a function of the phase at which the input is received. When the pulse is weak, it is customary to linearize around zero pulse strength. The result is called the infinitesimal phase response function. These ideas have been used extensively in theoretical biology, and also in some areas of engineering. I give examples showing that the infinitesimal phase response function may predict that two oscillators, as they exchange pulses back and fourth, will converge to synchrony, yet this is false when the exact phase response function is used, for all positive interaction strengths. For short, the analogue of the Hartman–Grobman theorem that one might expect to hold at first sight is invalid. I give a condition under which the prediction derived using the infinitesimal phase response function does hold for the exact phase response function when interactions are sufficiently weak but of positive strength. However, I argue that this condition may often fail to hold.

Selection of an appropriate tracer to measure the residence time distribution (RTD) of continuous powder blending operations

Residence time distributions (RTDs) are quickly becoming an important component of the quality control strategy for continuous manufacturing (CM) of pharmaceutical products. However, methodologies for determining RTDs, including appropriate selection of tracers and proper processing of RTD data, have not been fully developed, and there is potential to improve current methods.This work aims to implement protocols for tracer selection and establish a methodology for the determination and quantitative comparison of RTD curves obtained by the pulse method. We used an extensive material property data library and multivariate analyses to select appropriate tracers for active pharmaceutical ingredient (API) of interest. Tracer performance was evaluated in two continuous blenders using pulse input experiments. The equivalence of RTDs obtained from the API and the tracer was examined for formulations with widely different blend flow properties.For the most suitable tracer candidate, material properties were determined for mixtures with different API concentrations to ensure that blend properties containing varying amounts of tracer along the RTD profile remained similar to those of the target formulation. It was observed that even small changes in the physical properties of the target formulation would result in a different tracer RTD. This observation emphasized the importance of preserving the physical properties of the blend when characterizing the dynamical behavior of a unit operation.Further, the RTD of the tracer and the API in the blender were characterized under three different base flow properties. The outcome of these experiments enabled a fair side-by-side comparison of RTDs obtained using pulses of either API or tracer for powders with a varying range of properties. In finding an appropriate tracer, RTD profiles were compared quantitively using different methods. Multivariate analysis of variance (MANOVA) was shown to be a suitable tool for RTD profile comparisons.

Experimental research and optimization of a thermoelectric generator excited by pulsed combustion mode under limited heat dissipation for combined heat and power supply

In this paper, a scheme of pulse combustion mode with pulse input of gas is proposed to solve the problems of low output electrical performance and energy conversion efficiency of combustion-based thermoelectric systems under limited heat dissipation conditions, which is based on experiments. The characteristics of the thermoelectric system show that pulse combustion mode can increase the instantaneous temperature difference, so as to achieve the excitation effect on the output power. The relationships among output power, system efficiency, excitation intensity and pulse input parameters, and the geometry of thermoelectric modules are obtained. The influence of pulse input parameters on the excitation intensity is interactive, and top dead center of pulse inlet power is the parameter that has the greatest influence on the performance. Compared to the constant combustion mode, the pulse combustion mode can increase the output power by up to 28.3%. A maximum output power of 7.15 W with air-cooled heat dissipation and a maximum system efficiency of 3.26% were experimentally obtained, which is a 30% increase in efficiency over current air-cooled heat dissipation thermoelectric systems. Therefore, this paper can provide solutions for more practical power supply, provide effective and feasible guidance for the study of thermoelectric systems, and provide useful insights into the electrical properties of thermoelectric systems.

Assessment of trapping layer control in IGZO/Al2O3/Ga2O3 synaptic transistor for neuromorphic computing

We conducted research to create reverse synapse plasticity using metal oxide semiconductor-based field-effect transistors. Specifically, we used IGZO as the channel, Al2O3 as the tunneling layer, and Ga2O3 as the trapping layer. We adjusted the thickness of the Ga2O3 trapping layers and examined changes in roughness and density. Through this examination, we confirmed the variations and mechanisms of synaptic behaviors with respect to the properties of Ga2O3. We found that controlling the charge traps as functions of pulse time, input voltage, and initialization is key to approaching optimal device conditions. As a result of our research, we obtained a maximum nonlinearity factor of ν = 0.27 for G of synaptic plasticity. This high degree of linearity, particularly near zero nonlinearity, is significant for neuromorphic research in pattern recognition.

A study on cell viability based on thermal inkjet three-dimensional bioprinting

Thermal inkjet three-dimensional (3D) bioprinting (TIJ) is a biological additive manufacturing technology with high cell viability, fast printing speeds, and low costs. It is widely used in biology, chemistry, and pharmaceuticals. In recent years, remarkable results have been achieved in the printing of biological tissues using TIJ. However, few studies have reported on the relationship between TIJ and cell viability. In particular, there have been no reports relating cell viability and the TIJ input energy. In this work, we aim to determine the relationship between the input pulse, printing frequency, and cell viability from the TIJ working principle and find an optimized pulse waveform to improve cell viability. We propose a novel approach to study cell viability. The state of the droplet is observed while controlling the printing pulse and frequency, and then, the corresponding cell viability is determined. The results show that an increase in the pulse increases the shear stress and temperature in the bio-ink, which reduces the viability of the cells. The shear stress and viability of the printed cells show a corresponding piecewise functional relationship. The cell viability is significantly reduced when the ambient temperature is higher than 40 °C. Increasing the printing frequency reduces the rate of printing heat loss, thereby raising the ambient temperature and impairing cell viability. Finally, the optimized input waveform can increase cell viability by up to about 95%.

Frequency-Separating Devices for Secondary Surveillance Radar Systems

A frequency-separating device (FSD) with low insertion losses has been developed that provides electrical strength at high input power and combines the functions of several typical elements of the feeder path of a secondary surveillance radar (SSR): a receive/transmit switch, a harmonic filter, and a receiving band-pass filter. The issues of synthesis, analysis, and optimization of filters for the receiving and transmitting channels of the FSD are considered. Two options for the implementation of an FSD with insertion loss in the channel bandwidths within 0.7 dB, a harmonic suppression level of more than 40 dB, channel isolation, and attenuation at a deviation of ±60 MHz from the center frequencies of the passbands of at least 50 dB are proposed, the devices operate at frequencies of the FSD and of the seventh range of SSR systems with input pulse power up to 12 kW. The main dimensions of the FSD design, the results of numerical simulation, and the data of experimental verification of the characteristics are given. A comparative analysis of theoretical and experimental results is given.

Experimental Study on Effect of Process Characteristics during Electronic Discharge Machining of Titanium Alloy Using Multi Hole Tool Electrode

Due to outstanding material qualities such as higher strength to weight ratio, resistance to corrosion and resistance to fatigue, titanium alloys (Ti-6Al-4V) are widely applied in aerospace industries. Such a challenging to machine and necessary expensive convenctional machinery materials can cut using Electrical Discharge Machining (EDM). This work involves the study of influence of process characteristics on the performance quality of EDM during machining of Ti-6Al-4V. The process characteristics that are considered in this study are Current (9-15amps) or Input power (I.P. of 3-5 kVA), pulse on (60-80 μsec) and pulse off (20-40μsec) times, the pressure of dielectric fluid (6-10 MPa). The effectiveness of the EDM is measured using rate of tool wear (TWR) and rate of material removal (MRR) during machining, taper angle and surface roughness (SR). Dry brass multi hole tool electrode is used along with deionized water as the dielectric medium. Taguchi L18 orthogonal design is used for experimentation. The optimal combination of process characteristics is determined.

Computational and Experimental Modeling in Magnetoplasma Aerodynamics and High-Speed Gas and Plasma Flows (A Review)

This paper provides an overview of modern research on magnetoplasma methods of influencing gas-dynamic and plasma flows. The main physical mechanisms that control the interaction of plasma discharges with gaseous moving media are indicated. The ways of organizing pulsed energy input, characteristic of plasma aerodynamics, are briefly described: linearly stabilized discharge, magnetoplasma compressor, capillary discharge, laser-microwave action, electron beam action, nanosecond surface barrier discharges, pulsed spark discharges, and nanosecond optical discharges. A description of the physical mechanism of heating the gas-plasma flow at high values of electric fields, which are realized in high-current and nanosecond (ultrafast heating) electric discharges, is performed. Methods for magnetoplasma control of the configuration and gas-dynamic characteristics of shock waves arising in front of promising and advanced aircraft (AA) are described. Approaches to the control of quasi-stationary separated flows, laminar–turbulent transitions, and static and dynamic separation of the boundary layer (for large PA angles of attack) are presented.

Wide bandwidth THz emission based on two color chirped laser plasma interaction

This study examined the impact of chirping the input pulses on the amplification of a wide bandwidth THz wave emitted from a plasma slab within a range of input wavelengths from 800 nm to 3.9 µm. It was found that in a normal case of interaction when the injected pulses are highly chirped, flowerthorn-like fluctuations raised in the transverse current density of the plasma, and a THz emission with a higher amplitude within a wide band of 50 THz could be reached. Employing the cross-focusing scheme, the amplitude of the THz wave at 3.9 µm is further enhanced to about 43 times the ones obtained at 800 nm when the two-color pulses are weakly chirped down to 3 × 10−4 rad/s2. A significant increase of 233 times received in THz radiation when a weakly-chirped regime of delayed cross-focusing interaction is established and the intensity of the delayed pulse is increased to 1015 W/cm2, beyond the ionization threshold of Argon gas. The profile change of the fundamental and its second-harmonic waves indicated that a flat-top form is capable of enhancing the THz amplitude approximately by 8 times compared to the case when an ordinary Gaussian profile is used. The obtained results have confirmed that a combination of the type of interaction, chirp value, and the profile of inputs is crucial for enlarging the THz magnitude and domain.

Tailored supercontinuum generation using genetic algorithm optimized Fourier domain pulse shaping.

We report the generation of a spectrally tailored supercontinuum using Fourier-domain pulse shaping of femtosecond pulses injected into a highly nonlinear fiber controlled by a genetic algorithm. User-selectable spectral enhancement is demonstrated over the 1550-2000-nm wavelength range, with the ability to both select a channel with target central wavelength and bandwidth in the range of 1-5 nm. The spectral enhancement factor relative to unshaped input pulses is typically ∼5-20 in the range 1550-1800 nm and increases for longer wavelengths, exceeding a factor of 160 around 2000 nm. We also demonstrate results where the genetic algorithm is applied to the enhancement of up to four spectral channels simultaneously.

Low peak power broadband supercontinuum spectra generated in a square lattice toluene-core photonic crystal fiber with different air hole diameters

This study shows that it is possible to achieve a very large supercontinuum spectral broadening with a peak power hundreds of times lower than in previous publications. We can achieve by using a square lattice toluene-core photonic crystal fiber. With the heterogeneity in the diameter of air holes, our new design allows simultaneous optimization of characteristic quantities to ensure flat near-zero dispersion, small effective mode area, and low attenuation for efficient spectral broadening. Supercontinuum generation (SC) of proposed PCFs has been numerically simulated and studied under different pump source parameters. The first fiber with a lattice constant of 1.0 μm and filling factor of 0.65 operates in all-normal dispersion. It generates broadband of 1.045 μm by a pump pulse with a central wavelength of 1.3 μm, 40 fs duration, and energy of 18 pJ (corresponding peak power of 0.45 kW). Besides, two octave-spanning of the SC spectrum in the wavelength range of 0.775–4.3 μm are formed in the second fiber with an input pulse whose optical properties are 1.55 μm wavelength, 100 fs duration, and energy of 55 pJ (0.45 kW of the peak power). The lattice constant of second fiber is 2.0 μm and the filling factor is 0.3. They would be good candidates for all-fiber SC sources operating with low-power pump lasers. This would be a as cost-effective alternatives to glass core fibers.