bluuebunny/crossref_metadata_2025_split huggingface dataset:
Convolutional neural networks for the classification of glitches in gravitational-wave data streams
Authors: Fernandes Tiago , Vieira Samuel , Onofre Antonio , Calderón Bustillo Juan , Torres-Forné Alejandro , Font José A 
Published: August 2023

Abstract
We investigate the use of convolutional neural networks (including the modern ConvNeXt network family) to classify transient noise signals (i.e. glitches) and gravitational waves (GWs) in data from the Advanced LIGO detectors. First, we use models with a supervised learning approach, both trained from scratch using the Gravity Spy dataset and employing transfer learning by fine-tuning pre-trained models in this dataset. Second, we also explore a self-supervised approach, pre-training models with automatically generated pseudo-labels. Our findings are very close to existing results for the same dataset, reaching values for the F1 score of 97.18% (94.15%) for the best supervised (self-supervised) model. We further test the models using actual GW signals from LIGO-Virgo’s O3 run. Although trained using data from previous runs (O1 and O2), the models show good performance, in particular when using transfer learning. We find that transfer learning improves the scores without the need for any training on real signals apart from the less than 50 chirp examples from hardware injections present in the Gravity Spy dataset. This motivates the use of transfer learning not only for glitch classification but also for signal classification.
Quasinormal modes from Penrose limits
Authors: Fransen Kwinten 
Published: August 2023

AbstractWe use Penrose limits to approximate quasinormal modes (QNMs) with large real frequencies. The Penrose limit associates a plane wave to a region of spacetime near a null geodesic. This plane wave can be argued to geometrically realize the geometrical optics approximation. Therefore, when applied to the bound null orbits around black holes, the Penrose limit can be used to study QNMs. For instance, this Penrose limit point of view makes manifest the symmetry that emerges in the geometrical optics approximation of QNMs in terms of isometries of the resulting plane wave spacetime. We apply the procedure to warpedAdS3, Schwarzschild black holes and Kerr black holes. In the former we show explicitly how the symmetry algebra contracts to that of the limiting plane wave while in the latter we find the expected agreement with numerically computed QNMs for large (real) frequencies.
Semiclassical dynamics of Hawking radiation
Authors: Lowe David A , Thorlacius Lárus 
Published: August 2023

Abstract
We consider gravity in 3+1 spacetime dimensions coupled to N scalar matter fields in a semiclassical limit where

N
→
∞

. The dynamical evolution of a black hole including the back-reaction of the Hawking radiation on the metric is formulated as an initial-value problem. The quantum stress-energy tensor is evaluated using a point-splitting regularization along spacelike geodesics. To account for the quantum entanglement of the matter fields, they are treated as a set of bilocal collective fields defined on spacelike hypersurfaces. The resulting semiclassical field equations include terms up to fourth order in derivatives that can be treated in a perturbative

ℏ

expansion. The formulation we arrive at should be amenable to numerical simulation of time-dependent semiclassical spacetime.
Bouncing Universe in loop quantum gravity: full theory calculation
Authors: Kisielowski Marcin 
Published: August 2023

Abstract
In loop quantum gravity mathematically rigorous models of full quantum gravity were proposed. In this paper we will study a cosmological sector of one of the models describing quantum gravity with positive cosmological constant coupled to massless scalar field. In our previous research we introduced a method to reduce the model to homogeneous-isotropic sector at the quantum level. In this paper we propose a method to restrict our homogeneous-isotropic model to the spatially flat sector. After this restriction the number of degrees of freedom gets substantially reduced. This allows us to make numerical and analytical calculations. Remarkably, the resulting model shares some structural similarities with the loop quantum cosmological models and therefore sheds some new light on the relation between loop quantum gravity and loop quantum cosmology. According to our model the evolution of the Universe is periodic. The quantum gravity effects resolve the Big Bang singularity leading to a Big Bounce and cause the Universe to contract after a classical expansion phase.
Cryogenic mechanical loss of amorphous germania and titania-doped germania thin films
Authors: Khadka S , Markosyan A , Prasai K , Dana A , Yang L , Tait S C , Martin I W , Menoni C S , Fejer M M , Bassiri R 
Published: August 2023

Abstract
The mechanical loss of amorphous thin films of germania (GeO2) and titania-doped germania (Ti:GeO2) deposited by ion-beam sputtering onto silicon double-paddle oscillators was studied from 10 K to 290 K. Undoped germania was found to show a wide cryogenic mechanical loss peak centered at

∼

60

K with

ϕ
=
3.1
×

10

−
3

, which decreases to

1.1
×

10

−
3

as Ti-concentration increases to 44%. In addition to decreasing the height of this low-temperature peak, Ti-doping increases its width, and shifts its position toward lower temperatures. Annealing reduces the room temperature mechanical loss of Ti:GeO2 and increases its cryogenic mechanical loss, which is consistent with trends observed in most amorphous oxides.
Are the oscillations found in magnetized collisional electronegative warm plasma artifact during plasma-surface interaction?
Authors: Dhawan Rajat , Malik Hitendra K 
Published: August 2023

Abstract
The formation of the sheath and its characteristics are investigated in an electronegative plasma under the impact of an oblique and constant magnetic field. Specifically, the role of the magnetic field and initial conditions of positive ion velocity on the sheath characteristics are uncovered by adopting the Sagdeev potential approach for the determination of the modified Bohm’s criterion. At the sheath edge, the upper and lower components of the positive ion velocity perpendicular to the probe/wall are determined and examined in greater detail. The sheath structure is found to be modified considerably by the initial conditions. If the magnetic field is strong near the sheath edge, then the profile of the positive ion density shows a pulse-like structure for the case when we neglect the x-component (parallel to the wall) of positive ion velocity at the sheath edge. This pulse-like structure disappears when all the components of the positive ion velocity at the sheath edge are included, i.e. the ions are considered to move in any direction but towards the probe. The occurrence or disappearance of pulse-like structures or oscillations completely depend upon the initial conditions. Since in real situations the ions are expected to move in any direction (carrying all their velocity components) and are not aligned only in the direction perpendicular to the wall, these oscillations are artifact in nature. The sheath thickness is observed to be reduced with increasing magnetic field strength and its inclination. In order to better understand the phenomenon, isothermal and adiabatic cases are also discussed.
All-dielectric metasurface refractive index sensor with high figure of merit based on quasi-bound states in the continuum
Authors: Yin Xiangyu , Wang Qi , Yang Ning , Yan Xin , Wang Lei 
Published: August 2023

Abstract
All-Dielectric metasurfaces are widely used in the field of sense due to their small size, freedom of design, and low radiation loss. However, the optical sensor still has the problem of wide full width at half maximum (FWHM), which leads to a low figure of merit (FOM). In order to solve this problem, an all-dielectric metasurface based on quasi-bound states in the continuum (q-BIC) was proposed for refractive index sensing. The sensor structure consisted of a prism/metasurface/analyte, where the metasurface was composed of periodically arranged subwavelength asymmetric silicon gratings. The asymmetry of the structure led to the coupling of the tangential and radiative field components in the superficial layer at the resonance position, which formed a q-BIC resonance peak with a narrow FWHM in the reflection spectrum. We explained the causes of the q-BIC resonance peak generation by finite element analysis, and analyzed the factors affecting the FWHM, and also simulated the machining errors. The results showed that by reducing the asymmetry of the sensor, it could have a high FOM, with a FOM of 1.35 × 107 RIU−1. In addition, simulated machining errors within ±5 nm showed that small machining errors did not lead to the disappearance of q-BIC, which proved that the sensor had good robustness. These findings had provided ideas for the accurate detection of trace substances.
Atomistic simulation of brittle-to-ductile transition in silicon carbide embedded with nano-sized helium bubbles
Authors: Pan Chenglong , Zhang Limin , Jiang Weilin , Wang Rongshan , Chen Liang , Wang Tieshan 
Published: August 2023

Abstract
The tensile response of cubic silicon carbide (SiC) bulk containing cavities (voids and He bubbles) has been investigated using molecular dynamic simulations. The formation of cavities in SiC leads to a significant degradation in the mechanical properties of SiC with more influence on material fracture than initial elastic deformation. The brittle-to-ductile transition occurs in cavity-embedded SiC as the pressure in He bubbles increases. This is associated with the deformation mechanism that bond breaking at a low He bubble pressure transfers to extensive dislocation activities at a higher He bubble pressure. The cavities can effectively concentrate stress around them in the direction perpendicular to the tension, which leads to preferred cracking in the region with a higher tensile stress. The failure mechanism as revealed by this study improves understanding of property degradation in SiC that may be useful for applications of SiC in advanced nuclear energy systems.
Out-of-plane polarization modulated band alignments in β-In2X3/α-In2X3 (X = S and Se) vdW heterostructures
Authors: Xiong Rui , Xiao Fengpeng , Wen Jiansen , Xiong Hao , Jiang Linqin , Qiu Yu , Wen Cuilian , Wu Bo , Sa Baisheng 
Published: August 2023

Abstract
The construction of two-dimensional (2D) van der Waals (vdW) heterostructures is an effective strategy to overcome the intrinsic disadvantages of individual 2D materials. Herein, by employing first-principles calculations, the electronic structures and potential applications in the photovoltaic field of the β-In2X3/α-In2X3 (X = S and Se) vdW heterostructures have been systematically unraveled. Interestingly, the band alignments of β-In2S3/α-In2S3, β-In2Se3/α-In2Se3, and β-In2Se3/α-In2S3 heterostructures can be transformed from type-I to type-II by switching the polarization direction of α-In2X3 layers. It is highlighted that the light-harvesting ability of the β-In2X3/α-In2X3 vdW heterostructures is significantly higher than the corresponding monolayers in nearly the entire visible light region. Interestingly, type-II β-In2S3/α-In2Se3↓ heterostructure can achieve the power conversion efficiency of 17.9%, where the α-In2Se3 layer acts as a donor and the β-In2S3 layer displays as the acceptor. The present research not only provides an in-depth understanding that the out-of-plane polarization of α-In2X3 monolayers can efficiently modulate the band edge alignment of the β-In2X3/α-In2X3 vdW heterostructures, but also paves the way for the application of these heterostructures in the field of photovoltaics and optoelectronics.
The development of a novel apparatus to measure the emissivity of high-roughness materials at 82 K
Authors: Dewasi Avijit , Gangradey Ranjana , Mukherjee Samiran Shanti , Gupta Vishal , Dutta Rohan , Desai Abhinav B , Mishra Jyoti S , Panchal Paresh , Nayak Pratik A , Agravat Hemang S 
Published: August 2023

Abstract
The emissivity of a material changes with temperature. The knowledge of emissivity plays an important role in the estimation of radiation heat load in cryogenic systems. As the emissivity values of different materials at cryogenic temperatures are scarcely available in the literature, room-temperature emissivity values have been extensively used to estimate the radiation heat load in cryogenic systems. This may lead to a significant deviation between the predicted and actual radiation properties at cryogenic temperatures. Therefore, in the present work, an apparatus is developed based on a calorimetric technique for measuring the emissivity of an opaque material around 82 K. The novelties of the apparatus are its compact size, ease of sample handling, shorter time required to reach thermal equilibrium and, most importantly, capacity to measure the emissivity of a sample of high roughness. To understand the effectiveness of low and high emissivity-coated heat radiators for the system, a theoretical and an experimental approach has been followed. It is found that the high-emissivity heat radiator leads to a significant reduction in the time required to reach thermal equilibrium compared to a low-emissivity heat radiator. To verify and validate this setup, the emissivities of Aeroglaze Z306 (high emissivity) and Cu (low emissivity) are measured and compared with the values reported in the literature. Finally, this work has been extended to measure emissivity at cryogenic temperature for the first time for PU1, SG121FD and indigenously developed novel materials, such as black paints, adhesive and activated charcoals of different granule sizes.
An improved single-stage convolutional neural network for rail transit obstacle detection
Authors: Qin Yuliang , He Deqiang , Sun Haimeng , Liu Qi , Li Xianwang , Ren Chonghui 
Published: August 2023

Abstract
Obstacles that intrude into the rail area can lead to serious rail accidents, so obstacle detection technology is an essential guarantee for the safe operation of fully automatic trains. To meet the high-performance requirements of onboard obstacle detection, an efficient feature-aware convolutional neural network (EFA-Net) is proposed in this paper. The multi-scale aware feature pyramid network (MA-FPN) is designed as feature fusion network to extract multi-scale context information. In the detection head, the dynamic awareness block is used to refine the features. A joint representation branch and the generalized focal loss function are introduced to optimize the training effect. The experiments are based on the dataset of real-world rail transit environment. The results show that EFA-Net can achieve a detection accuracy of 90.4% mAP at a detection speed of 20.4 frames per second, and the lightweight design significantly reduces the computational complexity of the proposed model. Compared with other classical detectors, EFA-Net has the best comprehensive performance.
Reconstructing echoes completely submerged in background noise by a stacked denoising autoencoder method for low-power EMAT testing
Authors: Zhou Jinjie , Yu Dianrui , Li Xiang , Zheng Yang , Liu Yao 
Published: August 2023

Abstract
Low-power electromagnetic-acoustic transducer (EMAT) is crucially important for safety-critical equipment in industry, especially for potential explosives and inflammable petrochemical equipment and facilities. When the excitation power is very low, the corresponding echoes are overwhelmed in noise and related measurement would be inaccurate. To solve this problem, this paper presents a new echo reconstruction method based on a deep stacked denoising autoencoder (DSDAE) for nondestructive evaluation. First, the uses of reference signals and new data structure are to improve the training efficiency. A hybrid method based on variational mode decomposition and wavelet transform is used to obtain clean reference signals as inputs of the deep network. Then, the modified network structure and loss function aim to improve the ability of feature extraction and reconstruct clean echoes from low-power EMAT signals. To validate the effectiveness of the proposed method, the experiments of self-excitation and receiving A-scan inspections of stepped specimens with different thicknesses are conducted at some excitation voltages, as low as 25 V. The results indicate that the proposed DSDAE shows better and more stable denoising performance than some popular processing methods for different specimens and excitation voltages. It greatly improves the signal-to-noise ratio of the reconstructed signal to 20 dB. When applying to thickness measurement of specimens, its relative error is lower than 0.3%, which provides a practical and accurate tool for low-power EMAT testing.
Adaptive iterative optimization method for spectral calibration based on deep learning
Authors: Qu Dingran , Song Jun , Lin Yandan 
Published: August 2023

Abstract
The miniature fiber optic spectrometer is smaller, cheaper and has a wide range of applications. However, the measurement error is larger. In order to solve this problem, the adaptive iterative optimization method for spectral calibration is proposed. In this study, a trinity neural network model is built based on spectral wavelength segmentation to improve the calibration degree. Based on the ‘pseudo-label’, a self-optimization method for spectral calibration is proposed to reduce the amount of data required. This study optimizes the measurement accuracy without changing the structure of the spectrometer. And the self-optimization of calibration model in practical application is realized. After experiment, the calibration degree of the calibration model can reach 75.72%. After a self-optimization, it can be increased to 87.45%. The calibration time of 401 spectral values (380 nm–780 nm) is less than 0.01 s. The results show that the operator can use this method to calibrate spectral data without having optical knowledge. This method has low cost, high calibration speed, good reliability and application value.
Nano-Ni/Co-PBA as high-performance cathode material for aqueous sodium-ion batteries
Authors: Zeng Yunshu , Wang Yuyuan , Huang Zhen , Luo Hongyu , Tang Han , Dong Shijie , Luo Ping 
Published: August 2023

Abstract
Prussian blue analogues (PBAs) are reliable and promising cathode materials for aqueous sodium-ion batteries (ASIBs) owing to their open three-dimensional frameworks, outstanding stability, and low production costs. However, PBAs containing only a single type of transition-metal ion often have limited charge-storage capacities in aqueous systems. This study reports the first example of K0.11Ni0.39Co0.79[Fe(CN)6]·2.04H2O nanoparticles (Ni/Co-PBA) being used as a high-capacity cathode material for ASIBs. Owing to multi-electron redox reactions involving Co and Fe ions, Ni/Co-PBA has an initial capacity of 65 mAh g−1 and a capacity retention rate of 80% after 1000 cycles at 1.0 A g−1, indicating its outstanding cycle performance and capacity retention. Ex-situ x-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and the galvanostatic intermittent titration technique were used to analyze the redox mechanisms and kinetics of Ni/Co-PBA. Ni/Co-PBA-based ASIBs are among the most promising energy-storage technologies for large-scale fixed energy-storage systems because of their outstanding electrochemical performance, low costs, and high efficiency.
Strongly intermittent far scrape-off layer fluctuations in Alcator C-Mod plasmas close to the empirical discharge density limit
Authors: Ahmed Sajidah , Erik Garcia Odd , Q Kuang Adam , LaBombard Brian , L Terry James , Theodorsen Audun 
Published: August 2023

Abstract
Intermittent plasma fluctuations in the boundary region of the Alcator C-Mod device were comprehensively investigated using data time-series from gas puff imaging and mirror Langmuir probe diagnostics. Fluctuations were sampled during stationary plasma conditions in ohmically heated, lower single null diverted configurations with scans in both line-averaged density and plasma current, with Greenwald density fractions up to 0.85. Utilizing a stochastic model, we describe the plasma fluctuations as a super-position of uncorrelated pulses, with large-amplitude events corresponding to blob-like filaments moving through the scrape-off layer (SOL). A deconvolution method is used to estimate the pulse arrival times and amplitudes. The analysis reveals a significant increase of pulse amplitudes and waiting times as the line-averaged density approaches the empirical discharge density limit. Broadened and flattened average radial profiles are thus accompanied by strongly intermittent and large-amplitude fluctuations. Although these filaments are arriving less frequently at high line-averaged densities, we show that there are significant increases in radial far-SOL particle and heat fluxes which will further enhance plasma–wall interactions. The stochastic model has been used as a framework for study of the scalings in the intermittency parameter, flux and mean amplitude and waiting times, and is being used to inform predictive capability for the effects of filamentary transport as a function of Greenwald fraction.
Homoepitaxial growth of
1ˉ02
β-Ga2O3 by halide vapor phase epitaxy
Authors: Oshima Yuichi , Oshima Takayoshi 
Published: August 2023

Abstract
We demonstrated halide vapor phase epitaxy of β-Ga2O3 on a native

1
ˉ

02

substrate, which should be scalable and useful for the formation of vertical fins and trenches with smooth (100)-faceted sidewalls using plasma-free microfabrication techniques, e.g., selective area growth and gas etching, for use in power device applications. No misoriented domains were detected in the epiwafer during x-ray pole figure measurements. The full width at half maximum values of the x-ray rocking curves of the epiwafer were virtually the same as those of the bare substrate. No domain boundaries were found using scanning transmission electron microscopy at the film/substrate interface. The growth rate was as high as 23 μm h−1, which was comparable to the rate for a (001) epilayer that was grown simultaneously.
Tunable electromechanical properties of double-layer stacked anisotropic dielectric elastomer actuators
Authors: Zuo Yuchen , Zhang Junshi , Liu Lei , Zhu Jihong , Zhang Weihong 
Published: August 2023

Abstract
The current reported anisotropic dielectric elastomer (DE) actuators have some potential limitations for widespread application, such as the inability to adjust the anisotropic direction, and the related relatively complicated fabrication process. In this work, we propose a method to realize tunable direction and magnitude of electromechanical deformation of DE membranes. Two sheets of unequal-biaxial prestretched VHB 4905 membranes are attached at different rotation angles, forming an anisotropic DE actuator (DEA) with utilization of carbon grease electrodes. Experimental results demonstrate that, the direction and magnitude of the voltage-induced displacement of DEs is adjustable by tuning the unequal-biaxial prestretch ratio and rotation angle. In addition, the dielectric constant and maximum displacement at breakdown of the anisotropic DEA are also related to the rotation angle. The designed anisotropic DEA realizes the diversity of electromechanical actuation in both the planar 2D and the spatial 3D structures, which can be utilized to help design the practical soft actuators.