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Phonon vibrational and transport properties of SnSe/SnS superlattice at finite temperatures

Physical Review B 2025年第14期111卷 144314-144314页

作者： Feng-ning Xue Wei Li Zi Li Yong Lu College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 People's Republic of China State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 People's Republic of China School of Electronic Information Engineering Lanzhou Institute of Technology Lanzhou 730050 People's Republic of China Institute of Applied Physics and Computational Mathematics and National Key Laboratory of Computational Physics Beijing 100088 People's Republic of China

The structural stability and phonon properties of SnSe/SnS superlattices at finite temperatures have been studied using machine learning force field molecular dynamics and the anharmonic phonon approach. The vertical SnSe/SnS superlattice undergoes a phase transition from the Pnma phase to a P4/nmm phase at finite temperatures, which is different from the high-temperature Cmcm phase of the SnSe and SnS systems. The stability of P4/nmm phase is determined by molecular dynamics trajectories and anharmonic phonon dispersion relations. The TO modes at the q=Γ(0,0,0) and q=M(1/2,1/2,0) points in the P4/nmm phase exhibit imaginary frequencies in the harmonic approximation but stabilize at elevated temperatures. An analysis of phonon power spectra upon temperature also confirms the dynamic stabilization. The P4/nmm phase has higher symmetry than the Pnma phase, and the phase transition between them is accompanied by competition between the Jahn-Teller effect and phonon anharmonicity. Unlike the anisotropic distribution of Sn-Se/S bonds in the Pnma phase, the P4/nmm phase forms chemical bonds with similar bond lengths both in plane and interlayer, and their resonance effect can significantly enhance phonon scattering. The calculated phonon density of states and lifetime are strongly temperature dependent, demonstrating the heavy anharmonicity in the SnSe/SnS system. The P4/nmm phase has an extremely low lattice thermal conductivity, close to the experimental values of SnSe and SnS. Moreover, with the reduction of band gap and the enhancement of band degeneracy near the Fermi level, the P4/nmm phase exhibits superior electronic transport properties and significantly enhanced response to infrared and visible light. This makes it show great potential in thermoelectric and photovoltaic applications.

关键词： Bond length

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Electronic state reconfiguration of NiMoCox boosts electrocatalytic upcycling of polyethylene terephthalate plastic wastes for simultaneous production of formate and green hydrogen

引用

Chemical Engineering Journal 2025年 515卷

作者： Wang, Shaofeng Li, Shuaidong Li, Yutong Xu, Yue Wu, Zhaomeng He, Yingjian Zhao, Yongwei An, Zheer Lan, Ying Hu, Yanxiao Zhang, Jingzi Huang, Yan Jeong, Samuel Cai, Zeyun Lin, Xi Hu, Kailong School of Materials Science and Engineering and Institute of Materials Genome & Big Data Harbin Institute of Technology Shenzhen518055 China Institute of Special Environments Physical Sciences Harbin Institute of Technology Shenzhen518055 China School of Computer Science and Technology Harbin Institute of Technology Shenzhen518055 China Institute of Applied Physics of Pure and Applied Sciences University of Tsukuba Tsukuba305-8573 Japan

The electrocatalytic upcycling of polyethylene terephthalate (PET) plastic wastes into formate represents a sustainable approach to address the growing PET waste volume, while simultaneously generating valuable hydrogen. The key challenge is to develop highly active electrocatalysts for accelerating the sluggish conversion kinetics of the PET hydrolysate (i.e., ethylene glycol, EG). Herein, the bifunctional and noble-metal-free NiMoCox alloys are synthesized to catalyze both the EG-to-formate oxidation at anode and hydrogen evolution reaction (HER) at cathode, achieving a one-stone-two-birds process for PET upcycling paired with hydrogen production. The NiMoCo0.3 catalyst exhibits a remarkable Faradaic efficiency of 93.5 % for EG-to-formate at an electrode potential as low as 1.4 V vs. reversible hydrogen electrode (RHE). In situ spectral measurements and theoretical simulations demonstrate that Ni acts as the active site for EG oxidation, whereas Co induces electron redistribution around Ni sites, thereby optimizing the adsorptions of intermediates. Furthermore, an anion exchange membrane (AEM) electrolyzer, when processing real PET waste with NiMoCo catalysts, produces high-purity terephthalic acid (TPA) and potassium diformate (KDF) alongside H2 gas. This work provides novel insights into upcycling PET waste for the production of value-added chemicals and green hydrogen. © 2025 Elsevier B.V.

关键词： Anodes

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A composite ansatz for the calculation of dynamical structure factor

arXiv

引用

arXiv 2023年

作者： Zhang, Yupei Mo, Chongjie Zhang, Ping Kang, Wei HEDPS Center for Applied Physics and Technology School of Physics Peking University Beijing100871 China Beijing Computational Science Research Center Beijing100193 China Institute of Applied Physics and Computational Mathematics Beijing100088 China HEDPS Center for Applied Physics and Technology College of Engineering Peking University Beijing100871 China

We propose an ansatz without adjustable parameters for the calculation of dynamical structure factor. The ansatz combines quasi-particle Green’s function, especially the contribution from the renormalization factor, and the exchange-correlation kernel from time-dependent density functional theory together, verified for typical metals and semiconductors from plasmon excitation regime to Compton scattering regime. It has the capability to reconcile both small-angle and large-angle x-ray scattering (IXS) signals with much improved accuracy, which can be used, as the theoretical base model, in inversely inferring electronic structures of condensed matter from IXS experimental signals directly. It may also used to diagnose thermal parameters, such as temperature and density, of dense plasmas in x-ray Thomson scattering experiments. Copyright © 2023, The Authors. All rights reserved.

关键词： Electronic structure

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ON THE EXISTENCE OF MINIMIZERS IN SHALLOW RESIDUAL RELU NEURAL NETWORK OPTIMIZATION LANDSCAPES

arXiv

引用

arXiv 2023年

作者： Dereich, Steffen Jentzen, Arnulf Kassing, Sebastian Institute for Mathematical Stochastics Faculty of Mathematics and Computer Science University of Münster Germany School of Data Science Shenzhen Research Institute of Big Data The Chinese University of Hong Kong CUHK-Shenzhen Shenzhen China Applied Mathematics: Institute for Analysis and Numerics Faculty of Mathematics and Computer Science University of Münster Germany Faculty of Mathematics University of Bielefeld Germany

In this article, we show existence of minimizers in the loss landscape for residual artificial neural networks (ANNs) with multi-dimensional input layer and one hidden layer with ReLU activation. Our work contrasts earlier results in [GJL22] and [PRV21] which showed that in many situations minimizers do not exist for common smooth activation functions even in the case where the target functions are polynomials. The proof of the existence property makes use of a closure of the search space containing all functions generated by ANNs and additional discontinuous generalized responses. As we will show, the additional generalized responses in this larger space are suboptimal so that the minimum is attained in the original function *** Codes Primary 68T07, Secondary 68T05, 41A50 Copyright © 2023, The Authors. All rights reserved.

关键词： Multilayer neural networks

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Voltage Induced Fluid Mixing Video data based Volumetric Ratio Modelling using Fractional Order Time Series Methods

Voltage Induced Fluid Mixing Video Data based Volumetric Rat...

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Women in data science at Prince Sultan University (WiDS PSU), International Conference of

作者： Saptarshi Das Salwa Al Garea Moutushi Dutta Choudhury Centre for Environmental Mathematics Faculty of Environment Science and Economy University of Exeter Cornwall United Kingdom Department of Physics Amity Institute of Applied Sciences Amity University Kolkata India

ISBN: (数字)9798350395839

ISBN: (纸本)9798350395846

Fluid mixing process under direct current (DC) voltage stress is a complex phenomenon when the physical and chemical properties of the two streams are different. We experimentally investigate two streams of fluid flow one with added ink, changing its density and electro-chemical properties, followed by the application of different DC voltage levels. In this experiment, we found that as the applied voltage increases, volumes of the two fluids – with and without ink keep oscillating. Using the state-of-the-art image segmentation methods based on k-means clustering on the transformed La*b* colour image space, we carry out the pixel counting based volume calculation in the voltage induced fluid mixing experiments. Here, each frame of the video is considered as a separate image, undergoing segmentation process yielding estimated pixel numbers in each cluster. Repeating this frame-by-frame clustering-based image segmentation process on the whole video data yields a fluctuating time-series data, showing the ratio of the two fluids within the closed chamber. Due to the high complexity of the noisy fluctuating time series data, we then apply the autoregressive fractionally integrated moving average (ARFIMA) model to quantify the two-fluid volumetric ratio fluctuation data in compact and simple discrete time models. The hyperparameter tuning of the ARFIMA models have also been demonstrated. The efficacy of the fractional order discrete time models or estimators change with the length of data being modelled which may be useful in getting better insights into the stability of fluid mixing process using the volumetric ratio data analysis, irrespective of the timescale of the experiments.

关键词： Image segmentation Analytical models Fluids Fluctuations Time series analysis Ink data models

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Swin-TCNet: A vision transformer-based method for automated chromosomal object detection

Swin-TCNet: A vision transformer-based method for automated ...

引用

2022 IEEE International Conference on Big data, Big data 2022

作者： Kuo, Chih-En Lu, Chien-Hsing Huang, Li-Yuan National Chung Hsing University Department of Applied Mathematics Taichung Taiwan Taichung Veterans General Hospital Department of Obstetrics and Gynecology Taichung Taiwan National Chung Hsing University Institute of Data Science and Information Computing Taichung Taiwan

ISBN: (纸本)9781665480451

Chromosomes are intracellular aggregates carrying genetic information in genes, which are major objects of study in biological cytogenetics. An abnormal number or structure of chromosome causes chromosome disorders. Chromosome screening is an important part of prenatal the care. However, manual analysis of chromosomes is time-consuming. With the increasing popularity of prenatal diagnosis, manpower becomes overstretched. Therefore, an automatic approach for chromosome detection and recognition is urgently needed. Here, we proposed a vision transformer-based method for automated chromosomal object detection on metaphase cell images. The proposed method, named Swin Transformer Chromosomes Net (Swin-TCNet), that was mainly composed of Swin Transformer, region proposal network (RPN) and, multi-intersection over union (IoU) strategy. A large database formed by 5,000 metaphase cell images consisting of a total of 229,852 chromosomes was used to develop and evaluate the proposed method. The method uses the original cell meta images without pre-processing as input because that is clinically more friendly. The evaluation method used is the COCO API's mAP50, the testing set is up to 1250 original cell meta images (57,484 chromosomes in total), which is much more than the existing related literature. The accuracy and F1-score of our proposed method are 98.9% and 99.1%, respectively. Moreover, the practicality and robustness of Swin-TCNet in clinical practice can also be confirmed through a large amount of validation data. © 2022 IEEE.

关键词： Object detection

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Confronting global 21-cm signal with Z3 symmetric dark matter models

arXiv

引用

arXiv 2023年

作者： Paul, Debarun Dey, Antara Banik, Amit Dutta Pal, Supratik Physics and Applied Mathematics Unit Indian Statistical Institute 203 B.T. Road Kolkata700108 India Technology Innovation Hub on Data Science Big Data Analytics and Data Curation Indian Statistical Institute 203 B.T. Road Kolkata700108 India

While the Z3 symmetric dark matter models have shown tremendous prospects in addressing a number of (astro-)particle physics problems, they can leave interesting imprints on cosmological observations as well. We consider two such promising models: semi-annihilating dark matter (SADM) and Co-SIMP 2 → 3 interaction, and investigate their effects on the global 21-cm signal. SADM alone cannot address the EDGES dip but can perform better with the aid of an excess radio background, whereas Co-SIMP can naturally explain the EDGES absorption feature by virtue of an intrinsic cooling effect without invoking any such excess radiation. Hence, the latter model turns out to be a rare model within the domain of CDM, that uses leptophilic interaction to achieve the EDGES dip. Further, keeping in mind the ongoing debate between EDGES and SARAS 3 on the global 21-cm signal, we demonstrate that our chosen models can still remain viable in this context, even if the EDGES data requires reassessment in future. We then extend our investigation to possible reflections on the Dark Ages, followed by a consistency check with the CMB and BAO observations via Planck 2018(+BAO) datasets. This work thus presents a compelling case of exploring these interesting particle physics models in the light of different cosmological observations. Copyright © 2023, The Authors. All rights reserved.

关键词： Dark Matter

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A BLOW-UP CRITERION OF STRONG SOLUTIONS TO THE QUANTUM HYDRODYNAMIC MODEL

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Acta Mathematica Scientia 2020年第3期40卷 795-804页

作者： Guangwu WANG Boling GUO School of Mathematics and Information Science Guangzhou UniversityGuangzhou 510006China Institute of Applied Physics and Computational Mathematics China Academy of Engineering PhysicsBeijing 100088China

In this article,we focus on the short time strong solution to a compressible quantum hydrodynamic *** establish a blow-up criterion about the solutions of the compressible quantum hydrodynamic model in terms of the gradient of the velocity,the second spacial derivative of the square root of the density,and the first order time derivative and first order spacial derivative of the square root of the density.

关键词： Compressible quantum hydrodynamic model blow-up criterion strong solution

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Revisiting coupled CDM-massive neutrino perturbations in diverse cosmological backgrounds

arXiv

引用

arXiv 2023年

作者： Pal, Sourav Samanta, Rickmoy Pal, Supratik Physics and Applied Mathematics Unit Indian Statistical Institute 203 B.T. Road Kolkata700108 India Department of Physics Birla Institute of Technology and Science Pilani Hyderabad500078 India Technology Innovation Hub on Data Science Big Data Analytics and Data Curation Indian Statistical Institute 203 B.T. Road Kolkata700108 India

Massive neutrinos are well-known to cause a characteristic suppression in the growth of structures at scales below the neutrino free-streaming length. A detailed understanding of this suppression is essential in the era of precision cosmology we are entering into, enabling us to better constrain the total neutrino mass and possibly probe (beyond)ΛCDM cosmological model(s). Instead of the usual N-body simulation or Boltzmann solver, in this article we consider a two-fluid framework at the linear scales, where the neutrino fluid perturbations are coupled to the CDM (+ baryon) fluid via gravity at redshifts of interest. Treating the neutrino mass fraction fν as a perturbative parameter, we find solutions to the system with redshift-dependent neutrino free-streaming length in ΛCDM background via two separate approaches. The perturbative scale-dependent solution is shown to be in excellent agreement with numerical solution of the two-fluid equations valid to all orders in fν, and also agrees with results from CLASS to a good accuracy. We further generalize the framework to incorporate different evolving dark energy backgrounds and found sub-percent level differences in the suppression, all of which lie within the observational uncertainty of BOSS-like surveys. We also present a brief discussion on the prospects of the current analysis in the context of upcoming missions. Copyright © 2023, The Authors. All rights reserved.

关键词： Cosmology

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Negative result about the construction of genuinely entangled subspaces from unextendible product bases

arXiv

引用

arXiv 2022年

作者： Demianowicz, Maciej Institute of Physics and Applied Computer Science Faculty of Applied Physics and Mathematics Gdansk University of Technology Narutowicza 11/12 Gdansk80-233 Poland

Unextendible product bases (UPBs) provide a versatile tool with various applications across different areas of quantum information theory. Their comprehensive characterization is thus of great importance and has been a subject of vital interest for over two decades now. An open question asks about the existence of UPBs, which are genuinely unextendible, i.e., they are not extendible even with biproduct vectors. In other words, the problem is to verify whether there exist genuinely entangled subspaces (GESs), subspaces composed solely of genuinely multiparty entangled states, complementary to UPBs. We solve this problem in the negative for many sizes of UPBs in different multipartite scenarios. In particular, in the all-important case of equal local dimensions, we show that there are always forbidden cardinalities for such UPBs, including the minimal ones corresponding to GESs of the maximal dimensions. Copyright © 2022, The Authors. All rights reserved.

关键词： Vectors

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