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The I-mode is a promising tokamak operational regime characterized by a high energy confinement and the absence of type-I edge localized modes (ELMs). However, I-mode plasmas occasionally exhibit small ELM-like events known as pedestal relaxation events (PREs), transiently elevating the heat flux on the divertor targets. These PREs have been observed on ASDEX Upgrade (AUG) and Alcator C-Mod. In this work, BOUT++ simulation using the AUG experimental equilibrium and profiles are conducted. The three-field simulation yields a stable outcome, indicating that the PRE profile is peeling and ballooning (P-B) mode stable. In the six-field nonlinear simulations, an I-mode PRE was successfully reproduced in both a qualitative and near-quantitative sense, with PRE characteristics, including time scales, weakly coherent mode (WCM) frequency, and four eigenfrequencies of precursor oscillations (75, 50, 35 and 16 kHz), all exhibiting excellent agreement with experimental observations. Based on the dominant toroidal mode numbers, the entire evolution can be divided into three phases. The first phase is dominated by drift-wave, exhibiting clear WCM characteristics. During the second phase, when the collapse begins to develop, cross-phase analysis reveals a value close to π / 2 between the potential and electron temperature perturbations, indicating that the interchange mode acts as the direct trigger of the PRE. Further analysis of turbulence and transport confirms that the triggering region is located within the area of WCM turbulence. This work proposes a physical picture of the PRE in which drift-wave turbulence evolves into interchange modes, ultimately leading to a pedestal collapse.

This paper reports the recent observation of a weakly coherent mode (WCM) within a conventional reflectometer on EAST and successfully determines its poloidal wavenumber range. During the transition from the L-mode to I-mode, the line-averaged density remains nearly unchanged while a significant change is observed in the electron cyclotron emission (ECE) signals at the boundary. The difference between the signals for the two channels at the edge increased, coinciding with the appearance of the WCM and a simultaneous rise in the boundary electron temperature. Further investigation unveiled the modulating role of edge temperature ring oscillation (ETRO) (Liu et al 2020 Nucl. Fusion 60 126016) on high-frequency density fluctuations. Statistical results unveil an inverse relationship between the centeral frequency of the WCM and q 95. Simulation results provide additional insights, demonstrating that the simulated ‘WCM’ in the density fluctuations aligns with experimental data in terms of center frequency. Additionally, the radial distribution of the simulated ‘WCM’ closely corresponds to regions with the strongest electron temperature gradients. Finally, through a cross-correlation analysis of the simulated fluctuations, the following phase relationship for the wavenumber range of ‘WCM’ was observed: αT~e>αn~i∼αϕ~>αT~i .

The improved energy confinement mode (I-mode) is widely considered as an important operation regime for ITER. I-mode implementation depends on the specified basic plasma parameters and certain operation conditions, which are discovered by statistical plasma characteristics from a large number of I-mode discharges on a tokamak. The extraction process of I-mode plasma characteristics is complicated, time-consuming, and limited to the sampling rate of the measured signals. Experimental observation of the I-mode is accompanied by the appearance of a weakly coherent mode (WCM). However, it takes much time to accurately scan and quantify WCM characteristics when analyzing many I-mode discharges. Recently, a neural network identification method was developed as an I-mode detector to traverse a whole database as a replacement for manual identification. Two fully connected neural network models were trained with the spectrum of propagation velocity of density perturbation from Doppler backward scattering and the electron density measured by a polarimeter-interferometer system with the experimental advanced superconducting tokamak I-mode database. An accuracy of 98.30% in identifying WCMs in I-mode discharges is achieved with the WCM classification model. In addition, the regime classification model was also utilized to successfully distinguish between the low confinement mode (L-mode), I-mode, and high confinement mode (H-mode) with 96.03% accuracy. Finally, ablation experiments were performed on the regime classifiers, showing that there is potential for further performance improvement with future use of RNN model.

Synopsis We present an ab initio quantum study of below-threshold harmonic generation (BTHG) from H2+ molecules in the presence of an intense laser field by solving the time-dependent Schrödinger equation accurately in space and time. We find that multiple channels contribute to BTHG of H2+ molecules, which are related to the electron driven initially at specific time of the laser pulse from one nuclear core to another nuclear core or back to the parent core itself. The distinct contributions of these channels are distinguished by using a novel synchro squeezing time-frequency analysis.

Synopsis We present an efficient scheme for the generation of broadband supercontinuum harmonics and isolated utrashort attosecond pulse by the optimized three-color laser fileds. The optimized laser pulse is synthesized by three one-color laser pulses with proper relative phases. The broadband supercontinuum harmonics are obtained by solving accurately the time-dependent Schrödinger equation using the time-dependent generalized pseudospectral method. Our scheme proposed produces a broadband supercontinuum spectrum with the photon energies near 0.3 keV. As a result, an isolated 17 as pulse can be obtained directly by superposing the supercontinuum harmonics.

Synopsis We calculate the low-order harmonic generation (LOHG) by solving three-dimensional time-dependent Schrödinger equation with an accurate model potential of helium (He) atom in an intense laser fields. The satellite-peak structures of the LOHG are obtained in the harmonic spectra of He atom. We analyze the emission properties of the LOHG by employing a synchrosqueezing transform technique. Our results show that the satellite-peak structures contain the information of the bound states and the Stark shift of He atom in an intense laser fields.

Abstract This paper provides a review of advanced algorithms for ultrasound image formation and signal processing that are based on aperture-domain data (i.e. the data recorded by individual channels prior to beam summation). First aperture-domain data are defined and their properties described, then two specific examples of phase-aberration correction and vector velocity estimation are presented. For phase-aberration correction, sidelobe-reduction techniques based on the coherence of the received aperture-domain data were tested with clinical breast data; the mean improvements in the contrast and contrast-to-noise ratios were 6.9 dB and 23.2 per cent, respectively. For flow estimation, a conventional scanner can only estimate the flow velocity parallel to the beam axis. The proposed flow estimation technique uses aperture-domain data for two-dimensional flow-velocity estimation. The experimental results demonstrate that the estimation errors for the proposed technique are 2.18 per cent and 18.11 per cent in the axial and lateral velocity components, respectively. Other applications in which aperture-domain data can be used are also discussed.

High-intensity noises are a health hazard for industrial workers, and hearing protection is necessary to prevent hearing loss. Passive methods, such as ear muffs, are ineffective against low-frequency noise. Moreover, many hearing-impaired workers must wear hearing aids to enable communication at their workplace, and such aids can amplify ambient noise. To overcome this problem, the present study developed a headset equipped with a digital signal processing system to implement adaptive-feedback active noise cancellation (AFANC) to reduce low-frequency noise. The proposed AFANC headset was effective against wideband industrial noise, with a maximum noise spectrum power reduction of 30 dB. Furthermore, when used with a hearing aid, it improved the speech signal-to-noise ratio by up to 14 dB. These results suggest that a headset with AFANC would be useful for hearing protection in workplaces with high levels of low-frequency industrial noise, especially for hearing-impaired workers.

This paper presents an analytical solution of two-dimensional poroelasticity in the case of constant point sink and closed boundaries. The studied problem is coupled pore fluid flow and solid deformation due to a point sink within a twodimensional finite rectangular domain. In this study, poroelastic theory takes the form of Biot’s consolidation model. Porous media is assumed to be isotropic, linear elastic and saturated by single-phase fluid. On the basis of the author’s previous work, the analytical solution is obtained by use of integral transform method, and compared with the existing exact solution in the literature. The results show that they are completely identical, which verifies the accuracy of the presented analytical solution. The presented analytical solution can be used to validate two-dimensional poroelasticity related numerical solutions. Besides, it can provide us further insights into the flow (pore fluid pressure) and deformation (stress) coupling in porous materials.

THE power supply system from the sixth to the 13th floors of Yee Shan Mansion (T 16) in Taikoo Shing, failed three times during a 17-day...