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Self-assembled Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) Z-scheme heterojunction by pH adjustment with efficient photocatalytic performance

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Journal of Advanced Ceramics 2022年第11期11卷 1789-1800页

作者： Yan XING Xichuan LU Yi LI Bozhi YANG Yujia HUANG Mengfei ZHANG Jing CHENG Xin MIN Wei PAN New Energy Technology Engineering Lab of Jiangsu Province College of ScienceNanjing University of Posts and TelecommunicationsNanjing 210023China State Key Laboratory of New Ceramics&Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China College of Mathematics and Physics Beijing University of Chemical TechnologyBeijing 100029China Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid Wastes National Laboratory of Mineral MaterialsSchool of Materials Science and TechnologyChina University of Geosciences(Beijing)Beijing 100083China School of Materials Science and Hydrogen Energy Foshan UniversityFoshan 528000China

Semiconductor heterojunction plays a pivotal role in ***,the construction of a heterojunction with a fine microstructure usually requires complex synthetic ***,a pH-adjusted one-step method was employed to controllably synthesize Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction with a well-tuned 0D/1D hierarchical structure for the first *** is noteworthy that the ordered stacking of vanadium oxide tetrahedron(VO_(3)-)guided by the pH value wisely realizes the in-situ growth of Ag_(4)V_(2)O_(7) nanoparticles on the surface of Ag_(3)VO_(4) ***,comprehensive characterization and calculation decipher the electronic structures of Ag_(4)V_(2)O_(7) and Ag_(3)VO_(4) and the formation of Z-scheme heterojunction,benefiting the visible light harvesting and carrier *** a new Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction exhibits remarkable photocatalytic activity and excellent *** degradation of Rhodamine B(RhB)can be achieved in 10 min by the Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) heterojunction under visible light irradiation,demonstrating an outstanding reaction rate of 0.35 min^(−1) that is up to 84-fold higher than those of other silver *** importantly,this integration of synthesis technology and heterojunction design,based on the intrinsic crystal and electronic structures,could be inspiring for developing novel heterostructured materials with advanced performance.

关键词： Ag_(4)V_(2)O_(7)/Ag_(3)VO_(4) self-assembly heterojunction Z scheme photocatalysis

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Multi-scale finite element simulation on large deformation behavior of wood under axial and transverse compression conditions

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Acta Mechanica Sinica 2021年第7期37卷 1136-1151,I0002页

作者： Weizhou Zhong Zexiong Zhang Xiaowei Chen Qiang Wei Gang Chen Xicheng Huang Institute of Systems Engineering China Academy of Engineering PhysicsMianyang Sichuan621999China Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province Mianyang 621999China College of Engineering Science University of Science and Technology of ChinaHefei 230026China Advanced Research Institute for Multidisciplinary Science Beijing Institute of TechnologyBeijing100081China The State Key Lab of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

Multi-scale finite element method is adopted to simulate wood compression behavior under axial and transverse loading. Representative volume elements (RVE) of wood microfibril and cell are proposed to analyze orthotropic mechanical behavior. Lignin, hemicellulose and crystalline-amorphous cellulose core of spruce are concerned in spruce nanoscale model. The equivalent elastic modulus and yield strength of the microfibril are gained by the RVE simulation. The anisotropism of the crystalline-amorphous cellulose core brings the microfibril buckling deformation during compression loading. The failure mechanism of the cell-wall under axial compression is related to the distribution of amorphous cellulose and crystalline cellulose. According to the spruce cell observation by scanning electron microscope, numerical model of spruce cell is established using simplified circular hole and regular hexagon arrangement respectively. Axial and transverse compression loadings are taken into account in the numerical simulations. It indicates that the compression stress-strain curves of the numerical simulation are consistent with the experimental results. The wood microstructure arrangement has an important effect on the stress plateau during compression process. Cell-wall buckling in axial compression induces the stress value drops rapidly. The wide stress plateau duration means wood is with large energy dissipation under a low stress level. The numerical results show that loading velocity affects greatly wood microstructure failure modes in axial loading. For low velocity axial compression, shear sliding is the main failure mode. For high velocity axial compression, wood occur fold and collapse. In transverse compression, wood deformation is gradual and uniform, which brings stable stress plateau.

关键词： Multi-scale model Representative volume element Spruce Energy dissipation Wood cell

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label Attention Network for Temporal Sets Prediction: You Were Looking at a Wrong Self-Attention

arXiv

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arXiv 2023年

作者： Kovtun, Elizaveta Boeva, Galina Shulga, Andrey Zaytsev, Alexey Skolkovo Institute of Science and Technology Russia Sber AI Lab Moscow Institute of Physics and Technology Russia Sber

Most user-related data can be represented as a sequence of events associated with a timestamp and a collection of categorical labels. For example, the purchased basket of goods and the time of buying fully characterize the event of the store visit. Anticipation of the label set for the future event called the problem of temporal sets prediction, holds significant value, especially in such high-stakes industries as finance and e-commerce. A fundamental challenge of this task is the joint consideration of the temporal nature of events and label relations within sets. The existing models fail to capture complex time and label dependencies due to ineffective representation of historical information initially. We aim to address this shortcoming by presenting the framework with a specific way to aggregate the observed information into time- and set structure-aware views prior to transferring it into main architecture blocks. Our strong emphasis on input arrangement facilitates the subsequent efficient learning of label interactions. The proposed model is called label-Attention NETwork, or LANET. We conducted experiments on four different datasets and made a comparison with four established models, including SOTA, in this area. The experimental results suggest that LANET provides significantly better quality than any other model, achieving an improvement up to 65% in terms of weighted F1 metric compared to the closest competitor. Moreover, we contemplate causal relationships between labels in our work, as well as a thorough study of LANET components’ influence on performance. We provide an implementation of LANET to encourage its wider usage. © 2023, CC BY.

关键词： Spatio-temporal data

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Accelerating ab initio real-space electronic structure calculations for low-dimensional materials using an atom-sphere grid truncation method

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Physical Review B 2024年第15期110卷 155157页

作者： Lantian Xue Qiang Xu Cheng Ma Wenhui Mi Yanchao Wang Yu Xie Yanming Ma Key Laboratory of Material Simulation Methods & Software of Ministry of Education College of Physics State Key Lab of Superhard Materials College of Physics International Center of Future Science Key Laboratory of Physics and Technology for Advanced Batteries of Ministry of Education College of Physics

In recent decades, the real-space finite-difference implementations of Kohn–Sham density functional theory have exhibited substantial improvements in computational efficiency for large-scale systems. However, the substantial memory consumption arising from the numerous grid points has begun to limit the widespread adoption of this method. In this study, a general method is presented—applicable to both periodic and Dirichlet boundary conditions—to reduce the number of real-space grids. This approach introduces a truncation of the real-space grids based on atomic positions, which reduces memory requirements and enables a more efficient real-space scheme tailored for simulating low-dimensional and porous materials with uneven spatial distributions. By testing the method on zero-dimensional clusters, one-dimensional tubes, two-dimensional clusters adsorbed on graphene, and three-dimensional metal-organic framework materials, a 30–73% reduction in grid points and a 36–71% reduction in computational time per step are observed for simulations with a 2 meV/atom energy difference.

关键词： Electronic structure Density functional theory development First-principles calculations Numerical techniques

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R/Q Measurements of Multi-Gap Metamaterial Extended Interaction Resonant Cavity Using Perturbation Method

R/Q Measurements of Multi-Gap Metamaterial Extended Interact...

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International Conference on vacuum Electronics

作者： Ning Li Xuanming Zhang Shaozhe Wang Jianjun Zou Junjie Huang Shifeng Li Yongming Li Yurong Liu Huarong Gong Yubin Gong Zhaoyun Duan National Key Laboratory of Science and Technology on Vacuum Electronics in Chengdu School of Electronic Science and Engineering University of Electronic Science and Technology of China Chengdu China Guoli Vacuum (GLVAC) Industrial Technology Research Institute of High Power Devices Co. Ltd. Suzhou China Institute of Applied Electronics China Academy of Engineering Physics Mianyang China

In this paper, the $\boldsymbol{R/Q}$ measurement method of a metamaterial extended interaction resonant cavity (MEIRC) is investigated using the perturbation method. The $\boldsymbol{R/Q}$ expression for MEIRC is accordingly given, which depends on the natural frequency $\boldsymbol{f_{0}}$ of the MEIRC, the perturbation frequency shift $\Delta f$ , and the structural parameters. The $\boldsymbol{R/Q}$ expression is verified by CST simulation where a PTFE dielectric cylinder is considered as the perturbed body. After fabrication and assembly of the MEIRC, the measured natural frequency $\boldsymbol{f_{0}}$ of the double-gap MEIRC is 2.427 GHz, with an $\boldsymbol{R/Q}$ of 182.5 $\Omega$ and an $\boldsymbol{R/Q}$ error of 1.5% relative to the simulated one. In addition, the measured natural frequency $\boldsymbol{f_{0}}$ of the three-gap MEIRC is 2.443 GHz, $\boldsymbol{R/Q}$ is 286.0 $\boldsymbol{\Omega}$ , and the $\boldsymbol{R/Q}$ error is 5.7% relative to the simulated one. The measurements reported here pave the path for developing the metamaterial extended interaction devices.

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Operando reconstruction-induced CO_(2)reduction activity and selectivity for cobalt-based photocatalysis

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Nano Research 2023年第4期16卷 4812-4820页

作者： Kun Zhao Weiying Pang Shuaiyu Jiang Canyu Hu Porun Liu Dandan Cui Xuefei An Baojuan Tian Chao Gao Pan Zhang Meng Tian Dong Fu Huijun Zhao Hebei Key Lab of Power Plant Flue Gas Multi-Pollutants Control School of Environmental Science and EngineeringNorth China Electric Power UniversityBaoding 071003China Interdisciplinary Center for Fundamental and Frontier Sciences Nanjing University of Science and TechnologyJiangyin 214443China Centre for Catalysis and Clean Energy Griffith University Gold Coast CampusLD 4222Australia Hefei National Laboratory for Physical Sciences at the Microscale Collaborative Innovative Center of Chemistry for Energy MaterialsSchool of Chemistry and Materials Scienceand National Synchrotron Radiation LaboratoryUniversity of Science and Technology of ChinaHefei 230026China School of Physics and BUAA-UOW Joint Research Centre Beihang UniversityBeijing 100191China

The oxygen atom coordination inducing the structure reconstruction of the catalytic site is identified and recognized ambiguously,which is related to accurately declare the mechanism in a dynamic catalytic ***,we demonstrated that the reconstructed catalytic sites would lead to a remarkable performance for photocatalytic CO_(2)*** the initial 4-cycles testing,the in-situ formation of CoOx active sites on the Co(CoP)surface performed an increasing transient activity and selectivity toward CO *** formation of reconstructive Co-O bond and the appearance of intermediate specie CO were simultaneously observed by the pre-operando Raman,revealing the dynamic relationship between catalytic site structure and the photocatalytic ***,density functional theory calculations showed that the electronic structure of the reconstructive surface sites could modulate the ability of CO_(2)adsorption and CO *** reduced barrier energy for the rate-determining step finally improved the activity and selectivity of CO_(2)reduction.

关键词： surface reconstruction unsaturated Co-Ox catalytic site balanced relationship photocatalytic CO_(2)reduction

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SPARSE AND TRANSFERABLE UNIVERSAL SINGULAR VECTORS ATTACK

arXiv

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arXiv 2024年

作者： Kuvshinova, Kseniia Tsymboi, Olga Oseledets, Ivan Sber AI Lab Moscow Russia Moscow Institute of Physics and Technology Moscow Russia Moscow Russia Skolkovo Institute of Science and Technology Moscow Russia

The research in the field of adversarial attacks and models’ vulnerability is one of the fundamental directions in modern machine learning. Recent studies reveal the vulnerability phenomenon, and understanding the mechanisms behind this is essential for improving neural network characteristics and interpretability. In this paper, we propose a novel sparse universal white-box adversarial attack. Our approach is based on truncated power iteration providing sparsity to (p, q)-singular vectors of the hidden layers of Jacobian matrices. Using the ImageNet benchmark validation subset, we analyze the proposed method in various settings, achieving results comparable to dense baselines with more than a 50% fooling rate while damaging only 5% of pixels and utilizing 256 samples for perturbation fitting. We also show that our algorithm admits higher attack magnitude without affecting the human ability to solve the task. Furthermore, we investigate that the constructed perturbations are highly transferable among different models without significantly decreasing the fooling rate. Our findings demonstrate the vulnerability of state-of-the-art models to sparse attacks and highlight the importance of developing robust machine learning systems. © 2024, CC BY.

关键词： Jacobian matrices

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LISTENING TO THE WISE FEW: SELECT-AND-COPY ATTENTION HEADS FOR MULTIPLE-CHOICE QA

arXiv

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arXiv 2024年

作者： Tulchinskii, Eduard Kushnareva, Laida Kuznetsov, Kristian Voznyuk, Anastasia Andriiainen, Andrei Piontkovskaya, Irina Burnaev, Evgeny Barannikov, Serguei Skolkovo Institute of Science and Technology Russia AI Foundation and Algorithm Lab Moscow Institute of Physics and Technology Russia CNRS Université Paris Cité France

A standard way to evaluate the abilities of LLM involves presenting a multiple-choice question and selecting the option with the highest logit as the model’s predicted answer. However, such a format for evaluating LLMs has limitations, since even if the model knows the correct answer, it may struggle to select the corresponding letter simply due to difficulties in following this rigid format. To address this, we introduce new scores that better capture and reveal model’s underlying knowledge: the Query-Key Score (QK-score), derived from the interaction between query and key representations in attention heads, and the Attention Score, based on attention weights. These scores are extracted from specific select- and-copy heads, which show consistent performance across popular Multi-Choice Question Answering (MCQA) datasets. Based on these scores, our method improves knowledge extraction, yielding up to 16% gain for LLaMA2-7B and up to 10% for larger models on popular MCQA benchmarks. At the same time, the accuracy on a simple synthetic dataset, where the model explicitly knows the right answer, increases by almost 60%, achieving nearly perfect accuracy, therefore demonstrating the method’s efficiency in mitigating MCQA format limitations. To support our claims, we conduct experiments on models ranging from 7 billion to 70 billion parameters in both zero- and few-shot setups. © 2024, CC BY.

关键词： Question answering

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In Situ Monitoring the Potassium‑Ion Storage Enhancement in Iron Selenide with Ether‑Based Electrolyte

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Nano-Micro Letters 2021年第11期13卷 294-307页

作者： Xiaodan Li Jinliang Li Wenchen Zhuo Zhibin Li Liang Ma Zhong Ji Likun Pan Wenjie Mai Siyuan Laboratory Guangzhou Key Laboratory of Vacuum Coating Technologies and New Energy MaterialsGuangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New MaterialsDepartment of PhysicsJinan UniversityGuangzhouGuangdong 510632People’s Republic of China Shanghai Key Laboratory of Magnetic Resonance School of Physics and Electronic ScienceEast China Normal UniversityShanghai 200241People’s Republic of China

As one of the promising anode materials,iron selenide has received much attention for potassium-ion batteries(KIBs).Nevertheless,volume expansion and sluggish kinetics of iron selenide result in the poor reversibility and stability during potassiation–depotassiation *** this work,we develop iron selenide composite matching ether-based electrolyte for KIBs,which presents a reversible specific capacity of 356 mAh g^(−1) at 200 mA g^(−1) after 75 *** to the measurement of mechanical properties,it is found that iron selenide composite also exhibits robust and elastic solid electrolyte interphase layer in ether-based electrolyte,contributing to the improvement in reversibility and stability for *** further investigate the electrochemical enhancement mechanism of ether-based electrolyte in KIBs,we also utilize in situ visualization technique to monitor the potassiation–depotassiation *** comparison,iron selenide composite matching carbonate-based electrolyte presents vast morphology change during potassiation–depotassiation *** changing to ether-based electrolyte,a few minor morphology changes can be *** phenomenon indicates an occurrence of homogeneous electrochemical reaction in ether-based electrolyte,which results in a stable performance for potassium-ion(K-ion)*** believe that our work will provide a new perspective to visually monitor the potassium-ion storage process and guide the improvement in electrode material performance.

关键词： Iron selenide Ether-based electrolyte In situ visualization technique Potassium-ion batteries

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Ultra-high strength yet superplasticity in a hetero-grain-sized nanocrystalline Au nanowire

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Journal of Materials science & technology 2022年第6期101卷 95-106页

作者： Libo Fu Deli Kong Chengpeng Yang Jiao Teng Yan Lu Yizhong Guo Guo Yang Xin Yan Pan Liu Mingwei Chen Ze Zhang Lihua Wang Xiaodong Han Beijing Key Lab of Microstructure and Properties of Advanced Materials Beijing University of TechnologyBeijing 100124China Department of Material Physics and Chemistry University of Science and Technology BeijingBeijing 100083China School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Department of Materials Science and Engineering Johns Hopkins UniversityBaltimoreMD 21218United States School of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China

Nanocrystalline metals often display a high strength up to the gigapascal level,yet they suffer from poor *** studies have shown that the development of hetero-sized grains can efficiently overcome the strength-ductility trade-off of nanocrystalline ***,whether this strategy can lead to the fabrication of nanocrystalline nanowires exhibiting both high strength and superplasticity is unclear,similar to the atomistic deformation *** this paper,we show that ultra-small nanocrystalline Au nanowires comprising grains in both the Hall–Petch and inverse Hall–Petch grain-size regions can exhibit extremely high uniform elongation(236%)and high strength(2.34 gigapascals)at room *** situ atomic-scale observations revealed that the plastic deformation underwent two *** the first stage,the super-elongation ability originated from the intergrain plasticity of small grains via mechanisms such as grain boundary migration and grain *** intergrain plasticity caused the grains in the heterogeneous-structured nanowires to grow very *** the second stage,the superelongation ability originated from intragrain plasticity accompanied by the diffusion of surface *** results show that the hetero-grain-sized nanocrystalline nanowires,comprising grains with sizes both in the strongest Hall–Petch effect region and the inverse Hall–Petch effect region,were simultaneously ultrastrong and *** displayed neither a strength-ductility trade-off nor plastic instability.

关键词： In situ Mechanical property Metallic nanowires Transmission electron microscopy Plastic deformation

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