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Cavity optomechanical systems have received widespread attentions because they provide a novel platform for metrology, sensing, hybrid systems and quantum information processing. Their nonlinear dynamics has rich physics and plays an important role in the application scenarios. Previous works devoted to this subject have usually focused on the self-induced oscillation and chaos, whereas other parts of the rich nonlinear-dynamics picture are almost uncharted waters. In this study, we fill this gap and report the first experimental observation of limit-torus attractor, whose dynamics exhibits a torus-like trajectory in phase space. Moreover, we investigate the sharp decrease of oscillating amplitude along the up scanning transmission spectrum, referred to as catastrophe point, for the first time. The location of catastrophe point is independent of the pump power and the coupling distance. Our findings enrich the nonlinear dynamics in optomechanical systems, and open up new ways towards exploiting these systems as versatile building blocks in various applications including communication, quantum information processing, sensing and metrology. [ABSTRACT FROM AUTHOR]

The origin of an extraordinary X-ray burst (XRB) associated with a fast radio burst (FRB) such as FRB 20200428 is still unclear, though several models, such as the emission of a trapped fireball modified by resonant cyclotron scattering, the outflow from a polar trapped-expanding fireball, and the synchrotron radiation of a far-away relativistic shock, have been proposed. To determine which model is true, we study the possible X-ray polarization signature for each model, inspired by the importance of radio polarization in identifying the FRB origin. We first numerically simulate or calculate the XRB spectrum for each model and fit it to the observed data, then compute the corresponding polarization signal based on the fit. We find that these three models predict different polarization patterns in terms of phase/time and energy variations. The differences can be used to test the models with future X-ray polarization observations. [ABSTRACT FROM AUTHOR]

Reliable photonuclear reaction rates in stellar conditions are essential for understanding the origin of the heavy stable neutron-deficient isotopes between 74Se and 196Hg, i.e., p -nuclei. However, many reaction rates of relevance still have to rely on the Hauser–Feshbach (HF) model due to the rarity of experimental progress. One such case is in the mass range of 160 for Dy, Er, Ho, and Tm isotopes. In this work we attempt to constrain the HF model in the TALYS package by reproducing the available experimental data on 160Dy(p, γ)161Ho and 162Er(p, γ)163Tm in the A ∼ 160 mass region, and examine the effects of level density, gamma strength function, and the optical model potential. The constrained model then allows us to calculate the reaction rates of 157,159Ho(γ, p) and 163,165Tm(γ, p) for the γ -process nucleosynthesis in a carbon-deflagration model for Type Ia supernovae. Our recommended rates differ from the JINA REACLIB by more than one order of magnitude in the temperature range 2–3 GK. This results in changes in the final abundance of p -nuclei in the A ∼ 160 mass range by −5.5% to 3% from those with JINA, which means that the uncertainty of (γ, p) reactions is not predominant for the synthesis of these nuclei. [ABSTRACT FROM AUTHOR]

The foreshock region filled with turbulences is a natural lab for studying interactions between plasma and waves. The underlying processes are vital for dissipating the energy carried by the solar wind into the Martian environment. In this study, we analyze an ultralow-frequency wave observed on 2015 August 14 by Mars Atmosphere and Volatile Evolution upstream of the Martian bow shock. The wave properties match with those of 30 s waves; the dispersion calculation shows that the upstream plasma was capable of generating the observed waves. The analysis of the ion behaviors implies the wave generated without a field-aligned beam, while the growth rate of waves seems to be modulated by the interplanetary magnetic field conditions. These results indicate the unique role of the Martian foreshock in the interaction between the solar wind and the planet. [ABSTRACT FROM AUTHOR]

With the intelligent development of magnetic particle inspection, the quality of magnetic indications formed at cracks is closely related to the accuracy of magnetic particle inspection image analysis results. The concentration of magnetic suspension is a key process parameter affecting the quality of magnetic indication formation. Hence, this study presents an online detection method based on machine vision for measuring magnetic suspension concentration. The method initially enhances the contrast of images of the pear-shaped measuring tube containing magnetic suspension and then extracts scale lines through feature analysis and morphological processing. A method for extracting the magnetic particle sedimentation area of magnetic suspension based on a dual-threshold segmentation algorithm is proposed. The contour filtering algorithm and pixel calibration method are used to obtain the magnetic particle concentration of the non-estimation and estimation areas based on scale line extraction, ultimately forming an online accurate detection method for magnetic suspension concentration values. Experiments were conducted to validate the method against different concentrations, turbidity levels, tilting angles of the pear-shaped measuring tube, and ambient brightness. The results show that the error in magnetic suspension concentration detection based on this method is within 5%. This has certain reference value for the stable control of magnetic suspension concentration and for enhancing the reliability of intelligent decision-making results in magnetic particle inspection. [ABSTRACT FROM AUTHOR]

Quantum secure direct communication (QSDC) guarantees both the security and reliability of information transmission using quantum states. One-photon-interference QSDC (OPI-QSDC) is a technique that enhances the transmission distance and ensures secure point-to-point information transmission, but it requires complex phase locking technology. This paper proposes a mixed-encoding one-photon-interference QSDC (MO-QSDC) protocol that removes the need for phase locking technology. Numerical simulations demonstrate that the MO-QSDC protocol could also beat the PLOB bound. [ABSTRACT FROM AUTHOR]

We study the spectral properties of the black hole X-ray transient binary 4U 1630–472 during its 2022 and 2023 outbursts with Insight-HXMT observations. We find that the outbursts are in peculiar soft states. The effect of the hardening factor on the disk temperature is taken into account by the kerrbb model, and the flux and temperature of the disk are found to follow F ∝ T eff 3.92 ± 0.13 and F ∝ T eff 4.91 ± 1.00 for the two outbursts, respectively. The flux–temperature relation is roughly consistent with a standard disk. By fitting with a p -free model, the p -value, the exponent of the radial dependence of the disk temperature, is found to have an anticorrelation with disk temperature. Combining a joint diagnostic analysis with a diagram of the relation between the nonthermal fraction and luminosity, we find a possible scenario that the disk evolves from 2022 to 2023 toward a slim one with a decreasing radiation efficiency, where such an evolution may depend on the fraction of the nonthermal emission in the high soft state. [ABSTRACT FROM AUTHOR]

The impact of flow channel design on mass transport and drainage in proton exchange membrane fuel cells (PEMFCs) is significant, thereby influencing the reaction rate. Based on conventional wavy design, this study introduces two novel hybrid zigzag flow channels (asynchronous and synchronous) with both zigzag sidewalls and bottom wall, aiming in further improving mass and heat transfer, as well as drainage capacity to achieve better fuel cell performance. Numerical simulations demonstrate that the net power densities of both asynchronous and synchronous hybrid zigzag channels show a 28.7% and 44.4% improvement at low voltage, respectively. The implementation of the asynchronous hybrid zigzag flow channel has been observed to result in a notable reduction in pressure drop, amounting to 9.2%, while concurrently enhancing power output by 10.7% in comparison to a conventional zigzag channel. Additionally, the novel hybrid zigzag designs improve mass transfer efficiency at high current density and exhibits better temperature distribution uniformity. Moreover, the volume of fluid simulations illustrate that hybrid zigzag channels are highly effective in removing accumulated water, surpassing the straight channel with a drainage rate exceeding 54%, as well as a lower surface liquid coverage. [ABSTRACT FROM AUTHOR]

In this paper, the robustness of a junction temperature sensing method using the peak of the turn-on current slope for enhanced p-GaN high-electron-mobility transistors is investigated in detail. With the help of a repetitive hard-switching test platform, compared to other temperature-sensitive electrical parameters, it is found that the maximum slope of the flowing current at the turn-on transition shows no trend in degradation, regardless of the applied switching stress. This parameter decreases solely with the increase in junction temperature, showing excellent temperature-dependent linearity. Furthermore, the applicability of this method to the detection of junction temperature under different external gate resistances and drain voltages is verified. The sensed junction temperatures are carried over to calculate the thermal resistance, which is also extracted by advanced thermal characterization test equipment as a reference. Therefore, based on the versatility, convenience and accuracy, the peak of the rising drain current slope has been proven to be the preferred alternative in system applications to detect junction temperatures. [ABSTRACT FROM AUTHOR]

A variety of strategies have been developed to enhance the cycling stability of Si-based anodes in lithium-ion batteries. Although significant progress has been made in enhancing the cycling stability of Si-based anodes, the low initial Coulombic efficiency (ICE) remains a significant challenge to their commercial application. Herein, pitch-based carbon (C) coated Si nanoparticles (NPs) were wrapped by graphene (G) to obtain Si@C/G composite with a small specific surface area of 11.3 m2 g−1, resulting in a high ICE of 91.2% at 500 mA g−1. Moreover, the integrated utilization of graphene and soft carbon derived from the low-cost petroleum pitch strongly promotes the electrical conductivity, structure stability, and reaction kinetics of Si NPs. Consequently, the synthesized Si@C/G with a Si loading of 54.7% delivers large reversible capacity (1191 mAh g−1 at 500 mA g−1), long cycle life over 200 cycles (a capacity retention of 87.1%), and superior rate capability (952 mAh g−1 at 1500 mA g−1). When coupled with a homemade LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode in a full cell, it exhibits a promising cycling stability for 200 cycles. This work presents an innovative approach for the manufacture of Si-based anode materials with commercial application. [ABSTRACT FROM AUTHOR]