Triangular Pulse Research Articles

Time-domain Vander-Lugt filters for in-fiber complex (amplitude and phase) optical pulse shaping.

The time-domain counterpart of spatial Vander-Lugt filters is proposed for the first time, to the best of our knowledge. The concept enables reshaping an ultrashort optical pulse into a desired complex (amplitude and phase) arbitrary temporal pulse waveform using a setup configuration similar to that of previously demonstrated fiber-optic time-domain pulse-intensity shapers, i.e., using a single temporal amplitude modulator between two opposite-dispersive all-fiber media. The proposal is experimentally validated through reconfigurable generation of two complex-valued pulse shapes, namely, a 60ps asymmetrical triangular pulse with controlled parabolic phase and a 4-symbol 16-QAM picosecond pulse code sequence.

Discharge current shape control method and experiment in wire EDM

In order to study the effect of discharge current shape on surface roughness and processing speed in wire EDM process, a pulse power generator of adjustable current shape was developed. Based on half-bridge topology of pulse power generator, the various current shapes were generated by the control method of single-arm intermittent turn-on power tubes, regulating the gap discharge current raising time and falling time. The comparison experiment between rectangular waveform and triangular waveform indicated that the processing speed of rectangular waveform was high and the surface roughness of triangular waveform was good. To avoid the contradiction between the processing speed and surface roughness, the narrow triangular pulse combination waveform was investigated. According to the rectangular waveform and triangular waveform machining features, a multiple cutting strategy was discussed that rectangular waveform was used to rough cutting and the triangular waveform was used to trim cutting. The experiment shows that the cutting strategy can obtain a good processing effect.

ID 213 – Comparative study between intra-epidermal electric stimulation and laser stimulation for C-fiber activation. Do we stimulate the same C-fibers?

Objective Intra-epidermal stimulation (IES) has firstly been introduced for A™-fiber activation, but it has recently been utilized by Japanese researchers for C-fiber activation. We aimed to carefully examine the feasibility of IES in comparison to the laser stimulation. Methods IES was delivered as train stimuli (50 Hz; duration 200 ms; inter-trial interval 10 ± 2 s; approximately 15 trains) consisted of square-wave pulse of 0.6 ms duration (triangular pulse is theoretically ideal, but we prioritized the feasibility). Intensity was adjusted to above pain threshold (could be 2 mA) for practical use. Event-related potentials were evaluated in comparison to laser stimuli in both A-delta and C-warmth mode. Results Despite the square-wave pulse and relatively unstable sensation, IES elicited a vertex-positive component at around 1000 ms in parallel with motor response, which was therefore consistent with a selective activation of C-fibers, at least in glabrous skin. Latencies of the IES-elicited and laser-driven C-responses significantly differed, suggesting that the two stimulation methods activate a different pool of C-fibers. Should this be confirmed, it could provide interesting application to differentiate sub-system alteration in clinical settings. Conclusions/Key message The pool of C-fibers activated by IES appears different from that activated by warm-laser stimuli.

Photonic Generation of Triangular Pulses Based on Phase Modulation and Spectrum Manipulation

A photonic triangular pulse generation method based on spectrum manipulation of phase-modulated signals is proposed and experimentally demonstrated. A light wave is first phase modulated by a sinusoidal signal to generate optical sidebands. Then, the optical spectra are manipulated by attenuating the optical carrier and one of the first-order sidebands with the same suppression ratio. By choosing a proper modulation index, a full-duty-cycle triangular pulse train with a repetition rate equal to the frequency of the drive signal can be generated. To improve the practical feasibility and the repetition-rate tunability, the spectrum manipulation is realized using a Sagnac loop and a fiber Bragg grating (FBG). In the experiment, four full-duty-cycle triangular pulse trains with different repetition rates (3–6 GHz) are successfully generated, and the repetition rate can be further improved if larger bandwidth measuring instruments are used. In addition to the large and tunable repetition rate, the proposed scheme also features the advantages of simple structure, low cost, and freedom from bias drift.

Study of temporal pulse shape effects on W using simulations and laser heating

Transient heat pulses with triangular, square, and ELM-like temporal shapes are investigated in order to further understand how transient plasma instabilities will affect plasma facing components in tokamaks. A solution to the 1D heat equation for triangular pulses allows the peak surface temperature to be written analytically for arbitrary rise times. The solution as well as ANSYS simulations reveal that a positive ramp (maximum rise time) triangular pulse has a higher peak surface temperature by a factor of compared to that from a negative ramp (rise time = 0) pulse shape with equal energy density, peak power, and pulse width. Translating the results to ITER, an ELM or disruption pulse with the shortest rise time is the most benign compared to other pulse shapes with the same peak heat flux and same energy density.

Thermal behavior analysis of PWR fuel during RIA at various fuel burnups using modified theatre code

The fuel irradiation and burnup causes geometrical and dimensional changes in the fuel rod which affects its thermal resistance and ultimately affects the fuel rod behavior during steady-state and transient conditions. The consistent analysis of fuel rod thermal performance is essential for precise evaluation of reactor safety in operational transients and accidents. In this work, analysis of PWR fuel rod thermal performance is carried out under steady-state and transient conditions at different fuel burnups. The analysis is performed by using thermal hydraulic code, THEATRe. The code is modified by adding burnup dependent fuel rod behavior models. The original code uses as-fabricated fuel rod dimensions during steady-state and transient conditions which can be modified to perform more consistent reactor safety analysis. AP1000 reactor is considered as a reference reactor for this analysis. The effect of burnup on steady-state fuel rod parameters has been investigated. For transient analysis, hypothetical reactivity initiated accident was simulated by considering a triangular power pulse of variable pulse height (relative to the full power reactor operating conditions) and pulse width at different fuel burnups which corresponds to fresh fuel, low and medium burnup fuels. The effect of power pulse height, pulse width and fuel burnup on fuel rod temperatures has been investigated. The results of reactivity initiated accident analysis show that the fuel failure mechanisms are different for fresh fuel and fuel at different burnup levels. The fuel failure in fresh fuel is expected due to fuel melting as fuel temperature increases with increase in pulse energy (pulse height). However, at relatively higher burnups, the fuel failure is expected due to cladding failure caused by strong pellet clad mechanical interaction, where, the contact pressure increases beyond the cladding yield strength.

Studying complex chemistries using PLASIMO's global model

The Plasimo simulation software is used to construct a Global Model of a CO2 plasma. A DBD plasma between two coaxial cylinders is considered, which is driven by a triangular input power pulse. The plasma chemistry is studied during this power pulse and in the afterglow. The model consists of 71 species that interact in 3500 reactions. Preliminary results from the model are presented. The model has been validated by comparing its results with those presented in Kozák et al. (Plasma Sources Science and Technology 23(4) p. 045004, 2014). A good qualitative agreement has been reached; potential sources of remaining discrepancies are extensively discussed.

A photonic-assisted periodic triangular-shaped pulses generator based on FWM effect in an SOA

We propose a photonic-assisted triangular-shaped pulse train generator based on four-wave mixing effect (FWM) in a semiconductor optical amplifier (SOA). A dual-parallel Mach–Zehnder operated at quadrupling RF modulation is employed to generate two primary sidebands (±2nd) in spectrum of the triangular-shaped pulse. Then the FWM effect leads to generation of two new frequency components. By setting the modulation index and bias current of the SOA properly, the generated harmonics of optical intensity can be corresponding to the Fourier components of typical periodic triangular pulses. Finally, a triangular pulse train with tunable repetition rate can be obtained. Numerical simulations have been taken to evaluate the impact of several key parameters to make the scheme more practical.

80 GHz waveform generated by the optical Fourier synthesis of four spectral sidebands

Using the linear phase shaping of a simple four-line optical frequency comb, we experimentally demonstrate the generation of various optical waveforms such as parabolic, triangular or flat-top pulse trains at a repetition rate of 80 GHz. The initial 80 GHz comb is obtained through the nonlinear spectral broadening of a 40 GHz carrier-suppressed sinusoidal beating in a highly nonlinear fiber. Proof-of-principle experiments are reported for two distinct configurations of the waveform generated: continuous trains and bunches of shaped pulses.

Generation of Triangular Pulses Based on an Optoelectronic Oscillator

A novel scheme for the generation of full-duty-cycle triangular pulses based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The fundamental tone corresponding to the repetition rate of the pulses is generated by the OEO. Biasing the Mach-Zehnder modulator at the quadratic point, the small-signal gain of the OEO is maximized, while even-order harmonics in the optical intensity are suppressed. By properly setting the gain of the OEO loop, the amplitude of the first-order harmonic is nine times that of the third-order harmonic. After a 90° electrical phase shifter adjusts the phase of the electrical signal at the output of the photodetector, triangular pulses are obtained in the time domain. The oscillating frequency is tuned from 2 to 10 GHz by the yttrium-iron-garnet filter, and the phase noise of generated signal is also investigated. Triangular pulses with repetition rates of 3 and 6 GHz are successfully generated. The root-mean-square errors between the generated and the ideal triangular waveforms are 6.4927e-4 and 9.0932e-4 at 3 and 6 GHz, respectively.

Range Resolution Improvement of a 24 GHz ISM Band Pulse Radar—A Feasibility Study

An approach to improve the range resolution of a 24-GHz industrial, scientific, and medical (ISM) band pulse radar is presented for the automotive short-range radars. The resolution of the range profile was improved by applying the regularized least squares method to a discrete baseband signal at the receiver. For a 24-GHz ISM band pulse radar adopting a regularized least square method, a triangular pulse was identified as the optimal pulse shape under the regulations and in terms of cost effectiveness. To resolve multiple adjacent pulses with a constant false alarm rate, MATLAB simulations based on the least absolute shrinkage and selection operator (LASSO) algorithm were used to derive additional threshold values for output signals after the LASSO operation and the required signal-to-noise ratio (SNR). The simulated and measured values of the required SNR were 20.5 and 21.1 dB, respectively, for the two-target detection with a range resolution of 30 cm, at the detection and false alarm probabilities of 0.9 and $10^{-3}$ , respectively.

Photonic generation of microwave triangular waveform based on polarization-dependent modulation efficiency of a single-drive Mach–Zehnder modulator

A new photonic approach for triangular waveform generation by making full use of the polarization sensitive characteristic of the single-drive Mach–Zehnder modulator (MZM) is proposed and experimentally demonstrated. In this method, the MZM is biased at minimum transmission point and its best modulation axis has an angle with the polarization direction of injection continuous wave (CW). Due to the polarization dependent modulation efficiency of a MZM, the odd-order modulation sidebands can be generated on the parallel polarization component but only the optical carrier is presented on the orthogonal direction. After a polarizer, the required Fourier components can be projected on the same polarization direction, which contribute a triangular pulse stream by photodetection. In the experimental demonstration, triangular waveforms with repetition frequencies of 8, 10, and 12GHz are successfully generated, respectively.

Strength-Duration Curves of the Common Fibular Nerve Show Hypoexcitability in People With Functional Ankle Instability

BackgroundSome motor impairments, such as decreased reaction of peroneal muscles, altered kinematics, or poor postural control, have been described in people with functional ankle instability. Evidence shows a possible relationship between fibular nerve impairments and functional ankle instability. ObjectiveTo investigate the electrophysiologic excitability of the common fibular nerve, as measured by strength-duration curves, in subjects with functional ankle instability compared with a control group without ankle impairment. DesignA cross-sectional study. SettingUniversity Research laboratory. ParticipantsFifty subjects with functional ankle instability (35 men, 15 women; ages 24.36 ± 5.01 years) and 63 uninjured control patients (44 men, 19 women; ages 22.67 ± 4.85 years) were recruited by convenience sampling. InterventionsNot applicable. Main Outcome MeasuresStrength-duration curves of the common fibular nerve were made in all participants. Rheobase, chronaxie, Bawen index, accommodation index, galvano-tetanic threshold, and intensity thresholds for different pulse durations were obtained and compared between the 2 groups. ResultsSubjects with functional ankle instability show increased values of chronaxie (0.58 ± 0.24 ms versus 0.47 ± 0.16 ms; P = .004), Bawen index (1.53 ± 0.24 versus 1.39 ± 0.21; P = .002), and intensity thresholds for pulse durations ≤2 ms both for rectangular and triangular pulse wave forms. The accommodation index was smaller in subjects with functional ankle instability than controls (3.7 ± 0.72 versus 4.05 ± 0.98; P = .036). The remaining parameters did not show significant differences between groups. ConclusionsThese findings suggest that subjects with functional ankle instability show a decreased excitability in their common fibular nerve when compared with subjects without ankle injuries.

Low-Power Energy Harvesting Solutions for Wiegand Transducers

This paper proposes the use of Wiegand magnetic sensors as energy harvesters for low-power electronic equipments. When subject to an external, time-varying magnetic field, a Wiegand device releases a triangular voltage pulse several volts wide and of the duration of a few tens of microseconds. Due to the sharpness of the magnetic transition, pulse generation occurs regardless of how slowly the magnetic field variation occurs, an attractive feature which enables its use as an energy harvester even in the presence of low-frequency sources. In this paper, commercial Wiegand sensors are first experimentally characterized, with the purpose of devising a simple electrical model and derive the conditions for maximum energy extraction. Next, the use of Wiegand devices is discussed in the context of two modes of operation, namely, one-shot and battery-charging. In the former, the energy delivered by the Wiegand pulse is entirely utilized by the load circuitry in a one-shot fashion. In the latter, the Wiegand device is periodically excited so as to continuously deliver charge to an on-board rechargeable battery. Harvesting circuits are presented for both cases, and simulations and experimental results are provided supporting the developed theory and the effectiveness of the proposed implementations. With proof-of-concept harvesting prototypes based on discrete components, experimental figures of the extracted energy per pulse amount to $\mathrm {24~ \text {n} \text {J} }$ /pulse in one-shot operation and $\mathrm {30~ \text {n} \text {J} }$ /pulse in the battery-charging case.

Evaluation of Motor Neuron Excitability by CMAP Scanning with Electric Modulated Current.

Introduction. Compound Muscle Action Potential (CMAP) scan is a noninvasive promissory technique for neurodegenerative pathologies diagnosis. In this work new CMAP scan protocols were implemented to study the influence of electrical pulse waveform on peripheral nerve excitability. Methods. A total of 13 healthy subjects were tested. Stimulation was performed with an increasing intensities range from 4 to 30 mA. The procedure was repeated 4 times per subject, using a different single pulse stimulation waveform: monophasic square and triangular and quadratic and biphasic square. Results. Different waveforms elicit different intensity-response amplitude curves. The square pulse needs less current to generate the same response amplitude regarding the other waves and this effect is gradually decreasing for the triangular, quadratic, and biphasic pulse, respectively. Conclusion. The stimulation waveform has a direct influence on the stimulus-response slope and consequently on the motoneurons excitability. This can be a new prognostic parameter for neurodegenerative disorders.

High-voltage pulse waveform modulator based on solid-state Marx generator

Many research fields need special high-voltage pulses in pulsed power applications, which are different from typical rectangular pulses. In this paper, a high-voltage waveform modulator of two methods using a solid-state Marx generator has been developed and tested. Instead of manufacturing a generator with a specialized structure, the modulator can control a general Marx generator by low-voltage programmable logic devices to produce an irregular but controllable high-voltage triangular pulse with pulse length of ~4.5 μs and peak voltage of ~123 kV.

Studies of sub-millisecond domain dynamics in periodically poled Rb-doped KTiOPO(4), using online in situ second harmonic generation.

The temporal evolution of in situ second-harmonic generation was employed to study domain dynamics during periodic poling in Rb-doped KTP. With this method we investigated the influence of various poling parameters, including electric-field pulse shape, pulse magnitude, and number of pulses, on the quality of the QPM structure. It was found that the grating formation can be a sub-millisecond process and the benefits of using symmetric triangular electric-field pulse shape over square pulse shape in the single-pulse poling regime were demonstrated. Multiple-pulse poling with triangular pulses was shown to have a detrimental effect on the QPM structure quality, while multiple square pulses can provide additional flexibility to the structuring process.

Optimizing stimulation parameters in functional electrical stimulation of denervated muscles: a cross-sectional study.

BackgroundTo counteract denervation atrophy long-term electrical stimulation with a high number of muscle contractions has to be applied. This may lead to discomfort of the patient and negative side effects like burns. A functional effective muscle contraction induced by the lowest possible stimulation intensity is desirable. In clinical practice a selective stimulation of denervated muscles with triangular pulses is used.The aim of the study was to evaluate the influence of polarity and pulse duration on the stimulation intensity of triangular pulses in denervated muscles in patients with peripheral nerve lesions.MethodsTwenty-four patients with denervated extensor digitorum communis muscle and twenty-four patients with denervated tibialis anterior muscle due to peripheral nerve lesions were included. Four different combinations of triangular pulses with various duration and polarity were delivered randomly to the denervated muscles. The threshold intensity to induce a functional effective muscle contraction was noted. One-way within subject ANOVA was used to assess changes in intensity. An alpha level of p less than or equal to 0.05 was the criterion for statistical significance.ResultsPatients with a denervated tibialis anterior muscle presented significant lower intensities inducing a functional effective muscle contraction in favor of the stimulation with a duration of 200 ms and a polarity with the cathode proximally applied. No significant differences could be shown between the different stimulation protocols in case of denervated extensor digitorum communis muscle.ConclusionsWe recommend electrical stimulation of the denervated tibialis anterior muscle with triangular current with a duration of 200 ms and a polarity with the cathode proximally applied.

Research of photonic-assisted triangular-shaped pulses generation based on quadrupling RF modulation

We propose an approach to generate optical triangular-shaped pulse train with tunable repetition rate using quadrupling radio frequency (RF) modulation and optical grating dispersion-induced power fading. In this work, a piece of chirped fiber Bragg grating (FBG) is employed as the dispersive media to remove the undesired 8th harmonic in optical intensity. Thus, the generated harmonics of optical intensity can be corresponding to the first two Fourier components of typical periodic triangular pulses. This work also analyzes the impacts of the extinction ratio and the bias voltage drift on the harmonic distortion suppression ratio. After that, the value of the extinction ratio and the range of the bias voltage drift can be obtained. The advantage of this proposal is that it can generate high order frequency-multiplexed optical pulses train which can be applied in all optical signal processing and other fields.

Production of layer by layer Zn–Fe compositional multilayer alloy coatings using triangular current pulses for better corrosion protection

Multiple-layer coatings of Zn–Fe alloy having alternatively the same compositions have been developed galvanostatically on mild steel (MS) from a single plating bath using triangular current pulses. Thiamine hydrochloride (THC) and citric acid (CA) were used as additives. Multiple-layer coatings were developed under different conditions of cyclic cathode current density (CCCD) and number of layers. Cyclic voltammetry demonstrated that the addition of THC and CA improves the deposit character by increasing the Ni content (through suppressing the deposition of Zn) via preferential adsorption on the cathode surface. The corrosion behaviours of the coatings were evaluated by electrochemical AC and DC methods. The optimum multiple-layer coating, represented as (Zn–Fe)3.0/5.0/300, was found to exhibit about four to five times better corrosion resistance when compared with monolayer (Zn–Fe)3.0 alloy, developed from the same bath for the same duration. Distinct phase structures responsible for interface formation between successive layers (which changes alternatively) were confirmed by X-ray diffraction analysis. Better corrosion resistance afforded by multiple-layer coating was attributed to the increased specific surface area of the coating because of layering. A synergistic effect of both structural difference between layers and individual layer thickness is responsible for enhanced corrosion resistance of the multiple-layer coatings. The formation of multiple layers and corrosion mechanism were analysed by scanning electron microscopy.