Short Rise Time Research Articles

The Circumstellar Material around the Type IIP SN 2021yja

The majority of Type II-plateau supernovae (SNe IIP) have light curves that are not compatible with the explosions of stars in a vacuum; instead, the light curves require the progenitors to be embedded in circumstellar matter (CSM). We report on the successful fitting of the well-observed SN IIP 2021yja as a core-collapse explosion of a massive star with an initial mass of ∼15 M ⊙ and a pre-explosion radius of 631 R ⊙. To explain the early-time behavior of the broadband light curves, the presence of 0.55 M ⊙ CSM within ∼2 × 1014 cm is needed. Like many other SNe IIP, SN 2021yja exhibits an early-time flux excess including ultraviolet wavelengths. This, together with the short rise time (<2 days) in the gri bands, indicates the presence of a compact component in the CSM, essentially adjacent to the progenitor. We discuss the origin of the preexisting CSM, which is most likely a common property of highly convective red supergiant envelopes. We argue that the difficulty in fitting the entire light curve with one spherical distribution indicates that the CSM around the SN 2021yja progenitor was asymmetric.

Transient Response of ESD Protection Devices for a High-Speed I/O Interface

System-efficient electrostatic discharge (ESD) design (SEED) models of a diode and transient voltage suppressor (TVS) were developed to study their transient response in a high-speed input/output interface. Previously reported SEED models were improved to strengthen their convergence stability and facilitate accurate predictions over a wide range of conditions. These improvements were required to accurately capture the race conditions between the TVS and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -chip diode, where the diode's turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> may prevent turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> of the TVS. Simulations and measurements were performed to demonstrate the impact of the ESD pulse's rise time on race conditions. During a race, results showed the worst-case quasi-static diode current could be twice as high for long rise-time pulses than for short rise-times where the TVS does not turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> , and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -chip diode current may be larger at low test voltages than at high test voltages where the TVS does turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> . Adding a small passive impedance between the external TVS and the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -chip diode helps the TVS turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and reduce the current through the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -chip diode by more than 50%. Similarly, lengthening the trace between the TVS and diode could reduce <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -chip diode current by up to a factor of two.

Fuzzy Neural Network PID Strategy Based on PSO Optimization for pH Control of Water and Fertilizer Integration

In the process of crop cultivation, the application of a fertilizer solution with appropriate pH value is more conducive to the absorption of nutrients by crops. If the pH of the irrigation water and fertilizer solution is too high, it will not only be detrimental to the absorption of nutrients by the crop, but will also damage the structure of the soil. Therefore, the precise regulation of pH in water and fertilizer solutions is very important for agricultural production and saving water and fertilizer. Firstly, the article investigates the hybrid control of fertilizer and water conditioning systems, then builds a fuzzy preprocessing controller and a neural network proportional–integral–differential controller, and optimizes the neural network parameters by means of an improved particle swarm algorithm. The effectiveness of the controller was verified by comparison with the common proportional–integral–differential control and fuzzy algorithm control for fertilizer control and fuzzy preprocessing neural network control. Simulation experiments for this study were designed through the MATLAB/Simulink simulation platform, and the simulation results show that the algorithm has good tracking and regulation capabilities in the system. Finally, the four control algorithms are experimentally validated under different pH regulations using designed field experiments. The results show that, compared with other control algorithms, the control algorithm in this paper has a smaller overshoot and good stability with a shorter rise time, which can achieve the purpose of better regulating the fertilizer application system.

A Novel Embedded Sensor for Partial Discharge Detection in Inverter-Fed Machines

This article presents a novel ring-shaped hybrid fractal antenna for detection of partial discharge (PD) in inverter-fed machines. PD is known as a source of degradation and lifetime reduction in the machines winding insulation. PD activity is becoming a major concern in high performance drives, especially due to the increased use of repetitive impulse voltage with short rise-time (high <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> ) from pulsewidth modulation-controlled inverters. The proposed hybrid fractal antenna is designed and experimentally demonstrated to show a high sensitivity in the ultrahigh-frequency bandwidth of interest for PD detection as well as an ability to discriminate PD signals from other sources of high-frequency disturbances. Additionally, the proposed PD sensing solution features a unique ring-shape geometry that facilitates its physical integration into a live machine, making it suitable as a noninvasive solution for online condition monitoring and PD detection of any inverter-fed electrical machine.

Investigations of transient sloshing induced impulsive hydrodynamics

Sloshing-induced impulsive pressures may be extremely high and of short rise time duration. A compressible Volume of Fluid (VoF) method was adopted to study these pressures in a partially filled three-dimensional tank with various oblique tank ceiling angles. Comparative available experimental model test measurements of free surface profiles and velocity and pressure time histories validated this numerical method. To obtain a sufficiently fine grid to yield converging predictions, grid sensitivity studies were performed. The influence of the oblique tank ceiling angle on sloshing-induced impulsive pressures was examined. Results demonstrated that the VoF method obtained accurate predictions of sloshing phenomena. The oblique tank ceiling angle dampened impulsive pressure and, therefore, this angle had to be accounted for in the design of the tank.

SN 2020acat: an energetic fast rising Type IIb supernova

ABSTRACT The ultraviolet (UV) and near-infrared (NIR) photometric and optical spectroscopic observations of SN 2020acat covering ∼250 d after explosion are presented here. Using the fast rising photometric observations, spanning from the UV to NIR wavelengths, a pseudo-bolometric light curve was constructed and compared to several other well-observed Type IIb supernovae (SNe IIb). SN 2020acat displayed a very short rise time reaching a peak luminosity of $\mathrm{{\rm Log}_{10}}(L) = 42.49 \pm 0.17 \, \mathrm{erg \, s^{-1}}$ in only ∼14.6 ± 0.3 d. From modelling of the pseudo-bolometric light curve, we estimated a total mass of 56Ni synthesized by SN 2020acat of MNi = 0.13 ± 0.03 M⊙, with an ejecta mass of Mej = 2.3 ± 0.4 M⊙ and a kinetic energy of Ek = 1.2 ± 0.3 × 1051 erg. The optical spectra of SN 2020acat display hydrogen signatures well into the transitional period (≳ 100 d), between the photospheric and the nebular phases. The spectra also display a strong feature around 4900 Å that cannot be solely accounted for by the presence of the Fe ii 5018 line. We suggest that the Fe ii feature was augmented by He i 5016 and possibly by the presence of N ii 5005. From both photometric and spectroscopic analysis, we inferred that the progenitor of SN 2020acat was an intermediate-mass compact star with an MZAMS of 15–20 M⊙.

Prompt acceleration of a μ + beam in a toroidal wakefield driven by a shaped steep-rising-front Laguerre–Gaussian laser pulse

Recent experimental data for anomalous magnetic moments strongly indicates the existence of new physics beyond the Standard Model. Energetic μ + bunches are relevant to μ + rare decay, spin rotation, resonance and relaxation (μSR) technology, future muon colliders, and neutrino factories. In this paper, we propose prompt μ + acceleration in a nonlinear toroidal wakefield driven by a shaped steep-rising-front Laguerre–Gaussian (LG) laser pulse. An analytical model is described, which shows that a μ + beam can be focused by an electron cylinder at the centerline of a toroidal bubble and accelerated by the front part of the longitudinal wakefield. A shaped LG laser with a short rise time can push plasma electrons, generating a higher-density electron sheath at the front of the bubble, which can enhance the acceleration field. The acceleration field driven by the shaped steep-rising-front LG laser pulse is about four times greater than that driven by a normal LG laser pulse. Our simulation results show that a 300 MeV μ + bunch can be accelerated to 2 GeV and its transverse size is focused from an initial value of w 0 = 5 μm to w = 2 μm in the toroidal bubble driven by the shaped steep-rising-front LG laser pulse with a normalized amplitude of a = 22.

Efficient metrics for the detection of partial discharges under steep-fronted voltage pulses

The increasing use of power electronic inverters in electrical drives is leading to the unexpected inception of partial discharges (PD) within the insulation system of electric machine stator windings. Unfortunately, the short rise and fall times of such voltages, below 100 nanoseconds in most cases, create high-magnitude conducted and radiated interferences that affect the measurements. Detecting partial discharges in these systems with inductive or electromagnetic sensors turns to be an important challenge, especially when interference and partial discharges share the same bandwidth. In this work, the authors propose a technique to detect the occurrence of PD in such systems, even when they are masked by disturbances. The proposed technique combines an analog high-pass filter stage and a digital band-pass to select a proper spectral interval. The resulting signal is converted to the base-band, where two metrics based on the peak-to-average power ratio are proposed. Experimental results obtained with the signals acquired with two antennas show that both proposed metrics exhibit a significant increase, about ten times greater, when the applied voltage exceeds the PD inception voltage. These contributions define new markers for the detection of PD events created by pulsed voltages with overlapped overshoots with promising results.

Major and minor flares on Cygnus X-3 revisited

ABSTRACT Intense flares at cm wavelengths reaching levels of tens of Jy have been observed from Cygnus X-3 for many years. This active high-mass X-ray binary also has periods of quenching before major outbursts, and has minor flares at levels of a few hundred mJy. In this paper, we show that the minor flares have much shorter rise times and durations suggesting more rapid expansion of the synchrotron radiation emitting material than in the strong flares. They also appear closer to the binary, whereas the large flares form a more developed jet. Calculations of physical conditions show that the minor outbursts have lower minimum power but have larger magnetic fields and energy densities than the major flares. Minor flares can occur while a major flare is in progress, suggesting an indirect coupling between them. The spectral evolution of the minor flares can be explained by either an expanding synchrotron source or a shock model. The possibility that there is a brightening zone as in SS433 is explored.

High performance self-powered UV–visible photodetectors based on TiO2/graphene/ZnIn2S4/electrolyte heterojunctions

TiO2 nanorods (TNRs)/graphene (G)/ZnIn2S4 (ZIS)/electrolyte heterojunction arrays were synthesized via a three-step synthesis method and applied as an ultraviolet (UV)-visible self-powered photodetector (SPPD). At zero bias, the SPPD exhibited high responsivities of 13.79 mA/W for UV light and 0.39 mA/W for visible light, respectively. Under UV irradiation, the SPPD showed a short rise time of 5 ms and a decay time of 10 ms. TNRs offered an effective pathway for electron transport, and the type-II energy band structure formed by ZIS stacking improved the response of TNRs to UV and visible light significantly. Furthermore, the graphene intermediate layer accelerated the separation and transfer of carriers due to excellent charge collection ability. Therefore, the TNRs/G/ZIS/electrolyte heterojunction arrays have great potential for application in UV–visible SPPD.

A WC/WO star exploding within an expanding carbon-oxygen-neon nebula.

The final fate of massive stars, and the nature of the compact remnants they leave behind (black holes and neutron stars), are open questions in astrophysics. Many massive stars are stripped of their outer hydrogen envelopes as they evolve. Such Wolf-Rayet stars1 emit strong and rapidly expanding winds with speeds greater than 1,000 kilometres per second. A fraction of this population is also helium-depleted, with spectra dominated by highly ionized emission lines of carbon and oxygen (types WC/WO). Evidence indicates that the most commonly observed supernova explosions that lack hydrogen and helium (types Ib/Ic) cannot result from massive WC/WO stars2,3, leading some to suggest that most such stars collapse directly into black holes without a visible supernova explosion4. Here we report observations of SN 2019hgp, beginning about a day after the explosion. Its short rise time and rapid decline place it among an emerging population of rapidly evolving transients5-8. Spectroscopy reveals a rich set of emission lines indicating that the explosion occurred within a nebula composed of carbon, oxygen and neon. Narrow absorption features show that this material is expanding at high velocities (greater than 1,500 kilometres per second), requiring a compact progenitor. Our observations are consistent with an explosion of a massive WC/WO star, and suggest that massive Wolf-Rayet stars may be the progenitors of some rapidly evolving transients.

АНАЛИЗ РАСПРОСТРАНЕНИЯ ИМПУЛЬСНЫХ СИГНАЛОВ С МАЛЫМ ВРЕМЕНЕМ НАРАСТАНИЯ ФРОНТА С ПОМОЩЬЮ ЧИСЛЕННЫХ МЕТОДОВ

This paper presents the results of studies of transient characteristics of extended cable transmission lines. A technique for obtaining the propagation characteristics of pulse signals with a short rise time of the front based on the numerical reversal of the Laplace transform is considered. Formulas for calculating transient characteristics and reflectograms are presented. An assessment of the accuracy of the formulas used is given. Recommendations for improving the accuracy of the analysis are given. Graphs of characteristics are presented.

Frequency performance analysis of proportional integral-type active disturbance rejection generalized predictive control for time delay systems

To improve the performance of the Active Disturbance Rejection Control (ADRC) in systems which have large time delay, reduce online computation for Proportional Integral-type Generalized Predictive Control (PI-GPC) method, the Proportional Integral-type Active Disturbance Rejection Generalized Predictive Control (PI-ADRGPC) based on Controlled Auto Regression and Moving Average (CARMA) model is designed. The frequency domain analysis method is used to analyse the stability of the PI-ADRGPC based on CARMA model. By using the open-loop transfer function of the PI-GPC discrete form, the influence of parameter changes on the PI-ADRGPC performance is analysed. The performance of the PI-ADRGPC and ADRC algorithm is compared through the application in a second-order time delay system and distillation column system. The research results show that compared with the ADRC algorithm, the PI-ADRGPC method has a shorter rise time and better performance.

A self-powered photoelectrochemical ultraviolet photodetector based on Ti3C2T x /TiO2 in situ formed heterojunctions

Transition metal carbides and nitrides (MXenes), as a large family of emerging two-dimensional materials, have demonstrated extraordinary performance in many fields such as electronics, optics and energy storage. However, their susceptibility to oxidation during preparation and storage in ambient air environment is undesirable for long-term and stable applications. Here, we have demonstrated that the spontaneous oxidation of Ti3C2T x can be harnessed ingeniously to prepare Ti3C2T x /TiO2 in situ formed heterojunctions. Furthermore, a self-powered ultraviolet photodetector was constructed based on the photoelectrochemical performance of Ti3C2T x /TiO2 heterojunctions. Since the highly conductive Ti3C2T x can promote the separation and transfer of photogenerated carriers in TiO2, the prepared photodetector exhibits high responsivity (2.06 mA W−1), short rise and decay times (45 and 69 ms) and long-term stability. This work demonstrates the controllable synthesis of Ti3C2T x /TiO2 heterojunctions and provides a new promising potential of MXenes for photodetection applications.

High-voltage pulse rise time decreasing using transmission coaxial and spiral lines with ferrite

This article presents the results of a study of the formation of a short rise time of a powerful nanosecond 410 kV pulse. Ferrite filled coaxial transmission lines with standard inner conductor and construction in the form of a spiral are designed. The sharpening of the pulse occurs due to the appearance of an electromagnetic shock wave in the ferrite. The value of the rise time at the level of 0.1 - 0.9 has been decreased from 4.5 to 2.5 ns.

A Ga2O3/AlN heterojunction for self-powered solar-blind photodetection with high photo-to-dark current ratio and fast response speed

In this work, the Ga2O3 film was deposited on sapphire substrate by magnetron sputtering technique, then the AlN film was spin-coated onto the Ga2O3 film for constructing the lateral Ga2O3/AlN heterojunction in order to performing solar-blind photodetection. At zero bias, the device could achieve dark current (I dark ), UV light switching ratio, linear dynamic region (LDR), photo responsivity (R), and specific detectivity (D*) of 1.45 × 10−13 A, 2.14 × 104, 86.74 dB, 95.95 μA W−1 and 5.98 × 1010 Jones, respectively. Moreover, the photodetector displayed short rise and decay time of 90 and 116 ms, suggesting fast response speed. The self-powered operation is owing to the formation of built-in electric field and open-circuit voltage (Voc) of 0.4 V for separating electron-hole pairs, profiting from the successful establishment of the Ga2O3/AlN heterojunction with staggered type-II band alignment with large enough conduction band offset.

Temporal and spectral study of PKS B1222 + 216 flares in 2014

ABSTRACT We report on a temporal and spectral study of a flat-spectrum radio quasar, PKS B1222 + 216, in a flare state to get insight into the acceleration and emission mechanisms inside the jet. It is one of the brightest and highly active blazars in the MeV–GeV regime. The long-term multiwaveband light curves of this object showed flaring activity in 2014, with two distinct flares. The work presented here includes the study of flux-index variation, flare fitting, and hardness ratio, and the spectral modelling of X-ray and γ-ray data. The flux-index correlation found in the MeV–GeV regime indicates a ‘softer when brighter’ feature. The modelling of γ-ray light curves suggests that low-energy particles initiate both the flares, followed by the injection of high-energy particles. The short rise time indicates the presence of Fermi first-order acceleration. A single-zone leptonic model is used to fit the multiwaveband spectral energy distributions generated for both flares. The spectral energy distribution modelling shows that inverse Compton scattering of the photon field reprocessed from the broad-line region primarily accounts for the GeV emission. In addition, we have reported a shift in the break energy in the soft X-ray regime during flares, which is due to a rapid change in the injection spectrum.

Value of Quantitative Contrast-Enhanced Ultrasonography in Distinguishing Asymptomatic Subacute Thyroiditis from Papillary Thyroid Carcinoma

Background: Asymptomatic subacute thyroiditis (aSAT) without inflammatory features is often difficult to distinguish from papillary thyroid carcinoma (PTC), even with ultrasonography. Under certain circumstances, a fine-needle aspiration biopsy (FNAB) is performed, which is known to increase the patient’s physical pain. Objectives: To investigate the value of quantitative contrast-enhanced ultrasonography (CEUS) in discriminating aSAT from PTC nodules. Patients and Methods: A total of 30 aSAT and 23 PTC patients were systematically reviewed. Quantitative CEUS parameters, including the rise time (RT), time to peak (TTP), maximum intensity (IMAX), as well as their extension indicators (ΔRT and ΔTTP), were determined in various nodule areas (total, central, peripheral, and control regions of nodules). Chi-square test and independent-samples t-test were performed to compare significant differences between PTC and aSAT. A receiver operating characteristics (ROC) curve analysis was also performed to assess the diagnostic efficacy of each parameter, as well as diagnostic efficacy indices, including sensitivity and specificity, in discriminating aSAT from PTC nodules. Results: Compared to the PTC group, patients with aSAT had a longer ∆RT1 (RT of the control area − RT of the whole area; 0.12 ± 0.69 vs. -0.2 ± 0.57, P = 0.03) and ∆RT3 (RT of the control area − RT of the central area; 0.43 ± 0.72 vs. 0.04 ± 0.94, P = 0.049). Besides, compared to the PTC group, the aSAT group had a shorter RT in the total area (RT1: 4.05 ± 1.56 vs. 4.91 ± 2.09, P = 0.045); a shorter TTP in the total (TTP1: 4.91 ± 1.76 vs. 7.30 ± 3.92, P = 0.005), peripheral (TTP2: 5.06 ± 1.97 vs. 7.00 ± 3.48, P = 0.01), and central (TTP3: 4.90 ± 1.68 vs. 7.57 ± 4.41, P = 0.004) areas; and a lower IMAX in the peripheral area (IMAX2: 0.74 ± 0.36 vs. 1.09 ± 0.57, P = 0.009). Based on the ROC curve analysis, the area under the curve was significantly larger for TTP1 as compared to RT1 (P = 0.027). Conclusion: Conventional ultrasound and CEUS examinations were inadequate in distinguishing PTC from aSAT. Overall, a quantitative analysis may indicate more biological characteristics of nodules, which can be helpful in the differential diagnosis.

Study of anti‐windup pi controllers with different coupling–decoupling tuning gains in motor speed

AbstractProportional‐integral (PI) controller is still a widely used closed‐loop controller in industrial applications due to its simplicity. PI controllers experience difficulty in having both non‐overshoot with short rise time. Such unfavorable response is due to its coupled tuning‐gains and the integral windup, which eventually leads to system instability. Various anti‐windup techniques have been proposed. However, similar to the conventional PI controllers, most of these techniques have coupled proportional and integral tuning gains that affect one another. The controllers contain adaptive switching between the conventional and its designated integral control depending on the saturation state. This paper proposes a robust non‐switching anti‐windup PI controller with semi‐decoupling tuning gain. Speed control simulation and experimental testing are conducted to investigate the impact of the various tuning gain dependency. The proposed controller shows a fast response with no overshoot as compared to the conventional and other non‐switching anti‐windup PI controllers with coupling and decoupling tuning gain at certain loading conditions.

Visible-blind and flexible metal-semiconductor-metal ultraviolet photodetectors based on sub-10-nm thick silver interdigital electrodes.

We propose and experimentally demonstrate a distinct visible-blind and flexible metal-semiconductor-metal ultraviolet (UV) photodetector (PD) based on sub-10-nm thick silver interdigital electrodes. The transparent PD with 7-nm thick electrodes shows enhanced visible transmittance (80%) in average and achieves greatly improved responsivity (60.5 mA/W), and detectivity (1.75×1010 Jones) at 5 V under 380-nm illumination, compared with its opaque counterpart. It is as fast as the opaque PD with short rise and fall times (22.4 and 11.5 ms) and shows good flexibility. All the properties are comparable or superior to many reported transparent UV PDs, mainly attributed to the broad high UV-visible transmittance and the high conductivity of the ultrathin silver film.