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First-principles study of electronic and magnetic properties of Fe atoms on Cu_(2)N/Cu(100)

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Chinese Physics B 2024年第8期33卷 498-503页

作者：陈佳乐胡军 Institute of high Pressure Physics School of Physical Science and TechnologyNingbo UniversityNingbo 315211China

First-principles calculations were conducted to investigate the structural,electronic,and magnetic properties of single Fe atoms and Fe dimers on Cu_(2)N/Cu(100).Upon adsorption of an Fe atom onto Cu_(2)N/Cu(100),robust Fe-N bonds form,resulting in the incorporation of both single Fe atoms and Fe dimers within the surface Cu_(2)N *** partial occupancy of Fe-3d orbitals lead to large spin moments on the Fe ***,both single Fe atoms and Fe dimers exhibit in-plane magnetic anisotropy,with the magnetic anisotropy energy(MAE)of an Fe dimer exceeding twice that of a single Fe *** magnetic anisotropy can be attributed to the predominant contribution of the component along the x direction of the spin-orbital coupling ***,the formation of Fe-Cu dimers may further boost the magnetic anisotropy,as the energy levels of the Fe-3d orbitals are remarkably influenced by the presence of Cu *** study manifests the significance of uncovering the origin of magnetic anisotropy in engineering the magnetic properties of magnetic nanostructures.

关键词： magnetic nanostructures magnetic anisotropy spin–orbital coupling ultrathin substrate

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Perception field based imitation learning for unlabeled multi-agent pathfinding

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Science China(Information Sciences) 2024年第5期67卷 115-135页

作者： Wenjie CHU Ailun YU Wei ZHANG Haiyan ZHAO Zhi JIN school of Computer Science Peking University Key Laboratory of high-Confidence Software Technologies (Peking University) Ministry of Education

This paper proposes an imitation learning method to learn a universal agent policy for unlabeled multi-agent pathfinding(unlabeled MAPF) in grid environments. The method transforms the unlabeled MAPF problem into a series of temporal-independent homogeneous classification problems for each *** on this transformation, a neural network is designed to imitate a distance-optimal expert *** neural network consists of two successive modules: perception field learner and field integrating *** former refines and encodes the current system state into a perception field for each agent by combining a set of learnable field-generating functions. The latter takes an agent's perception field as input and decides the agent's next action based on a triplet cross-attention mechanism. We evaluate our method on a diverse set of unlabeled MAPF tasks. Compared with state-of-the-art counterparts, the experimental results manifest the superiority of the proposed method in both generalization ability and scalability.

关键词： unlabeled multi-agent pathfinding perception field triplet cross-attention multi-agent imitation learning learning-based planning

Magnetic Switching Dynamics and Tunnel Magnetoresistance Effect Based on Spin-Splitting Noncollinear Antiferromagnet Mn_(3)Pt

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Chinese Physics Letters 2024年第4期41卷 132-138页

作者：朱蒙董建艇李新录郑凡星周晔吴琨张佳 school of Physics and Wuhan National high Magnetic Field Center Huazhong University of Science and TechnologyWuhan 430074China

In comparison to ferromagnets,antiferromagnets are believed to have superior advantages for applications in next-generation magnetic storage devices,including fast spin dynamics,vanishing stray fields and robust against external magnetic field,***,unlike ferromagnetic orders,which could be detected through tunneling magnetoresistance effect in magnetic tunnel junctions,the antiferromagnetic order(i.e.,Néel vector)cannot be effectively detected by the similar mechanism due to the spin degeneracy of conventional *** discovered spin-splitting noncollinear antiferromagnets,such as Mn_(3)Pt with momentum-dependent spin polarization due to their special magnetic space group,make it possible to achieve remarkable tunneling magnetoresistance effects in noncollinear antiferromagnetic tunnel *** first-principles calculations,we demonstrate that the tunneling magnetoresistance ratio can reach more than 800% in Mn_(3)Pt/perovskite oxides/Mn_(3)Pt antiferromagnetic tunnel *** also reveal the switching dynamics of Mn_(3)Pt thin film under magnetic fields using atomistic spin dynamic *** study provides a reliable method for detecting Néel vector of noncollinear antiferromagnets through the tunnel magnetoresistance effect and may pave its way for potential applications in antiferromagnetic memory devices.

关键词： tunneling magnetoresistance momentum

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Formal Verification of Data Modifications in Cloud Block Storage Based on Separation Logic

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Chinese Journal of Electronics 2024年第1期33卷 112-127页

作者： Bowen ZHANG Zhao JIN Hanpin WANG Yongzhi CAO Key Laboratory of high Confidence Software Technologies (MOE) School of Computer Science Peking University school of Computer and Artificial Intelligence Zhengzhou University school of Computer Science and Cyber Engineering Guangzhou University

Cloud storage is now widely used, but its reliability has always been a major concern. Cloud block storage(CBS) is a famous type of cloud storage. It has the closest architecture to the underlying storage and can provide interfaces for other types. Data modifications in CBS have potential risks such as null reference or data *** verification of these operations can improve the reliability of CBS to some extent. Although separation logic is a mainstream approach to verifying program correctness, the complex architecture of CBS creates some challenges for verifications. This paper develops a proof system based on separation logic for verifying the CBS data modifications. The proof system can represent the CBS architecture, describe the properties of the CBS system state, and specify the behavior of CBS data modifications. Using the interactive verification approach from Coq, the proof system is implemented as a verification tool. With this tool, the paper builds machine-checked proofs for the functional correctness of CBS data modifications. This work can thus analyze the reliability of cloud storage from a formal perspective.

关键词： Cloud computing Behavioral sciences Reliability Formal verification

Deep learning for code generation: a survey

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Science China(Information Sciences) 2024年第9期67卷 5-40页

作者： Huangzhao ZHANG Kechi ZHANG Zhuo LI Jia LI Jia LI Yongmin LI Yunfei ZHAO Yuqi ZHU Fang LIU Ge LI Zhi JIN Key Lab of high Confidence Software Technologies (Peking University) Ministry of Education school of Computer Science Peking University school of Computer Science and Engineering Beihang University

In the past decade, thanks to the powerfulness of deep-learning techniques, we have witnessed a whole new era of automated code generation. To sort out developments, we have conducted a comprehensive review of solutions to deep learning-based code generation. In this survey, we generally formalize the pipeline and procedure of code generation and categorize existing solutions according to taxonomy from perspectives of architecture, model-agnostic enhancing strategy, metrics, and tasks. In addition, we outline the challenges faced by current dominant large models and list several plausible directions for future research. We hope that this survey may provide handy guidance to understanding, utilizing, and developing deep learning-based code-generation techniques for researchers and practitioners.

关键词： code generation automated software engineering deep learning large model artificial intelligence

Enhanced quality of Al2O3/SiC gate stack via microwave plasma annealing

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Rare Metals 2024年第10期43卷 5362-5371页

作者： Nan-Nan You Xin-Yu Liu Qian Zhang Zhen Wang Jia-Yi Wang Yang Xu Xiu-Yan Li Yu-Zheng Guo Sheng-Kai Wang high-Frequency high-Voltage Device and Integrated Circuits R&D Center Institute of Microelectronics of the Chinese Academy of Sciences school of Integrated Circuits University of Chinese Academy of Sciences school of Electrical Engineering and Automation Wuhan University Department of Micro/Nano Electronics School of Electronic Information and Electrical EngineeringShanghai Jiao Tong University

The high-quality gate dielectric on silicon carbide （SiC） surface is critical to fabricate high-performance SiC metal-oxide-semiconductor field-effect transistors（MOSFETs）.This research employs microwave plasma annealing （MPA） to obtain high-quality Al2O3/SiC gate *** designing MPA atmosphere and optimizing the plasma power,the SiC MOS capacitor with a Al2O3dielectric film shows the enhanced *** interface state density is reduced by 1 order of magnitude to 6×1011cm-2·eV-1,the breakdown electric field is increased,and the voltage shift is effectively suppressed Besides,the mechanism of MPA process is discussed in terms of the thermal effect and reactant species.X-ray photoelectron spectroscopy （XPS） results unveil oxygen plasma plays the main *** plasma power during the MPA process results in defect repairs of the firstneighbor Al-O bonding and partial removal of Al-O-H bond from the interface *** study demonstrates that MPA process is an effective option to realize highquality dielectric and interface on SiC.

关键词： Al2O3 Defect repairs Metal–oxide–semiconductor Microwave plasma annealing Silicon carbide X-ray photoelectron spectroscopy

Enhanced Grain Refining Effect of Mg–Zr Master Alloy on Magnesium Alloys via a Synergistic Strategy Involving Heterogeneous Nucleation and Solute‑Driven Growth Restriction

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Acta Metallurgica Sinica(English Letters) 2024年第8期37卷 1354-1366页

作者： Gang Zeng Hong Liu Jing‑Peng Xiong Jian‑Long Li Yong Liu Key Laboratory of Lightweight and high Strength Structural Materials of Jiangxi Province School of Advanced ManufacturingNanchang UniversityNanchang 330031China

Zirconium(Zr)emerges as the most effective grain refiner for magnesium(Mg)alloys incorporating ***,Zr is introduced in the form of an Mg–Zr master ***,within Mg–Zr master alloys,Zr predominantly exists in a particle form,which tends to aggregate due to attractive van der Waals *** clustered Zr is prone to settling,thereby reducing its refining impact on Mg *** this work,a combined pretreatment process for Mg–Zr master alloys was proposed,encompassing the introduction of a physical field to intervene the agglomeration of particle Zr and the employ of high-temperature dissolution and peritectic reactions to promote the solid solution of *** results demonstrate that the particle Zr within the pretreated Mg–Zr master alloy is effectively dispersed and refined,and greater solute Zr levels can be *** subsequent grain refinement ability was studied on a typical Mg–6Zn–0.6Zr(wt%)*** outcome highlights that an improvement in the grain refinement efficacy(32.4%)of Mg–Zr master alloys was obtained with a holding time of 60 *** pretreated Mg–Zr master alloy significantly augments the efficiency of grain refinement for Mg alloys through a synergistic strategy involving heterogeneous nucleation and solute-driven growth *** crucial factor in achieving effective grain refinement of Zr in Mg alloys lies in regulating the presence and morphology of Zr in the Mg–Zr master alloy,distinguishing between particle Zr and solute *** study introduces a novel method for developing more efficient Mg–Zr refiners.

关键词： Magnesium alloy Mg-Zr master alloy Grain refinement Heterogeneous nucleation Solute-driven growth restriction Synergistic strategy

Recycling of spent lithium-ion batteries to resynthesize high-performance cathode materials for sodium-ion storage

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Tungsten 2024年第3期6卷 574-584页

作者： Hai-Qiang Gong Xing-Yuan Wang Long Ye Bao Zhang Xing Ou National Engineering Laboratory for high-Efficiency Recovery of Refractory Nonferrous Metals School of Metallurgy and Environment Central South University

The spent lithium-ion batteries recovery has been brought into focus widely for its environmental imperatives and potential profits from the metal components,such as lithium,cobalt,nickel and ***,the weaker pollution and fewer profits of LiMn2O4cathode dispel the enthusiasm and responsibility of industry ***,a simplified and efncient method to regenerate the sodium-ion cathode materials and separate Li from spent LiMn2O4materials for the profit improvement is *** detail,adjusting the parameters of carbothermal reduction process appropriately,the LiMn2O4spinel structure is destroyed within a short period time and transformed into simple metal *** anticipated,nearly 95 wt.%lithium can be obtained and recovered during the water leaching,while 99 wt.% of manganese can be extracted in acid *** that the leaching residue can return to the carbothermic reduction,leading to a closed-loop economic recycling *** regenerated Na0.67Ni0.3Mn0.7O2cathode displays excellent electrochemical performance with superior cycling stability(the initial capacity reaches 95.9 mAh·g-1,and the retention rate reached 98.3% after 100 cycles at 1 C).The delicate strategy of sodium-ion cathode material regenerated from spent LiMn2O4aims to realize lithium separation and material utilization of manganese simultaneously,providing the instructive suggestion to rise up the recycling profits of spent batteries.

关键词： Manganese Spent battery LiMn 2 O 4 cathode Recycling Regenerated Na 0.67 Ni 0.3 Mn 0.7 O 2 Sodium-ion storage

Hole mobility enhancement in monolayer WSe2 p-type transistors through molecular doping

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Science China(Information Sciences) 2024年第6期67卷 207-213页

作者： Shiyuan LIU Xiong XIONG Xin WANG Xinhang SHI Ru HUANG Yanqing WU school of Integrated Circuits and Beijing Advanced Innovation Center for Integrated Circuits Peking University Wuhan National high Magnetic Field Center and school of Integrated Circuits Huazhong University of Science and Technology

Two-dimensional （2D） transition metal dichalcogenide （TMDC） semiconductor materials exhibit extraordinary electrical properties,holding promise for the realization of next-generation complementary metal-oxide-semiconductor （CMOS） devices at ultimate ***,constrained by effective device doping strategies,the hole mobility and device performance of tungsten diselenide （WSe2） p-type transistors,especially monolayer chemical vapor deposition （CVD）-grown WSe2,have not met *** this paper,an effective performance enhancement of monolayer WSe2p-type transistor was achieved through a molecular doping *** monolayer WSe2directly on SiO2back-gated substrates and leveraging energy band alignment design,4-nitrobenzenediazonium tetrafluoroborate （4-NBD） molecular dopant with a concentration of 10 m M was utilized to modulate the Fermi level position of monolayer WSe2for hole *** devices demonstrated a more than 98%increase in hole mobility,reaching up to 97 cm2·V-1·s-1while maintaining the current on/off ratio of *** p-type WSe2transistors with 1μm channel length exhibit a high drive current surpassing 176μA·μm-1,exceeding previous CVD-WSe2devices with similar channel *** straightforward and effective approach to improving the electrical performance of WSe2transistors paves the way for advanced logic technologies based on transition metal dichalcogenide semiconductors.

关键词： CVD-grown WSe$_2$ molecular doping 4-NBD p-type transistors hole mobility