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High mechanical strength Si anode synthesis with interlayer bonded expanded graphite structure for lithium-ion batteries

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Journal of Energy Chemistry 2024年第6期93卷 253-263,I0007页

作者： Wenhui Lai Jong Hak Lee Lu Shi Yuqing Liu Yanhui Pu Yong Kang Ong Carlos Limpo Ting Xiong Yifan Rao Chorng Haur Sow Barbaros Ozyilmaz Department of Material Science&Engineering National University of SingaporeSingapore 117575Singapore Center for Advanced 2D Materials National University of SingaporeSingapore 117546Singapore Department of Physics National University of SingaporeSingapore 117551Singapore Institute forFunctional Intelligent Materials National University of SingaporeSingapore 117544Singapore

Despite advancements in silicon-based anodes for high-capacity lithium-ion batteries,their widespread commercial adoption is still hindered by significant volume expansion during cycling,especially at high active mass loadings crucial for practical *** root of these challenges lies in the mechanical instability of the material,which subsequently leads to the structural failure of the ***,we present a novel synthesis of a composite combining expanded graphite and silicon *** composite features a unique interlayer-bonded graphite structure,achieved through the application of a modified spark plasma sintering ***,this innovative structure not only facilitates efficient ion and electron transport but also provides exceptional mechanical strength(Vickers hardness:up to658 MPa,Young's modulus:11.6 GPa).This strength effectively accommodates silicon expansion,resulting in an impressive areal capacity of 2.9 mA h cm^(-2)(736 mA h g^(-1)) and a steady cycle life(93% after 100cycles).Such outsta nding performance is paired with features appropriate for large-scale industrial production of silicon batteries,such as active mass loading of at least 3.9 mg cm^(-2),a high-tap density electrode material of 1.68 g cm^(-3)(secondary clusters:1.12 g cm^(-3)),and a production yield of up to 1 kg per day.

关键词： Lithium-ion battery Silicon anode Spark plasma sintering Interlayer bonding Mechanical strength Tap density

Multiscale observation in wide-spatial radar surveillance based on coherent FDA design

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Science China(Information Sciences) 2024年第2期67卷 232-252页

作者： Lei YU Feng HE Yi SU College of Electronics Science National University of Defense Technology

Wide-spatial radar surveillance missions are challenging tasks, requiring an increased power budget and agility in transmission aimed at extracting information from multiple targets in different environments. These requirements necessitate high transmitting degrees of freedom(DOF) to achieve the objective of multiscale observation for specific tasks in specialized regions of interest. Herein, we exploit the multiscale observation ability in wide-spatial radar surveillance based on frequency diverse array(FDA)radar. The proposed method facilitates spatial anisotropic control of multiple radar resources, including the transmitting waveforms, beampattern, and bandwidth. By utilizing a coherent FDA radar, we offer principles for the selection of baseband waveforms, in addition to the quantitative design of the beampattern gain and optimal bandwidth from the perspective of detection. The feasibility of the proposed method is validated through numerical experiments, thus indicating the potential in wide-spatial radar surveillance. Moreover,this work can be regarded as a preliminary attempt to gauge the efficacy of the computational array, a novel academic concept.

关键词： multi-scale observation wide-spatial surveillance frequency diverse array (FDA) beampattern synthesis frequency diversity gain computational array

Brightness enhancement on random-distributed-feedback Raman fiber lasers pumped by multimode diodes

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High Power Laser Science and Engineering 2024年第3期12卷 69-76页

作者： Xiulu Hao Chenchen Fan Yang Li Zhiyong Pan Jinyong Leng Tianfu Yao Bing Lei Pu Zhou College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangshaChina Nanhu Laser Laboratory National University of Defense TechnologyChangshaChina

The power scaling on short wavelength(SW)fiber lasers operating around 1μm are in significant demand for applications in energy,environment and *** challenge for performance scalability of high-power SW lasers based on rare-earth-doped fiber primarily lies in the physical limitations,including reabsorption,amplified spontaneous emission and parasitic laser ***,we demonstrate an all-fiberized,purely passive SW(1018 nm)randomdistributed-feedback Raman fiber laser(RRFL)to validate the capability of achieving high-power output at SWs based on multimode laser diodes(LDs)direct *** pumped by multimode LDs,the high-brightness RRFL delivers over 656 W,with an electro-optical efficiency of 20%relative to the *** slope efficiency is 94%.The beam quality M2factor is 2.9(which is~20 times that of the pump)at the maximum output signal power,achieving the highest brightness enhancement of 14.9 in *** the best of our knowledge,this achievement also represents the highest power record of RRFLs utilizing multimode diodes for direct *** work may not only provide a new insight into the realization of high-power,high-brightness RRFLs but also is a promising contender in the power scaling of SWs below 1μm.

关键词： fiber laser purely passive gain random distributed feedback stimulated Raman scattering

A nerve-like self-healable conductive wire

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national Science Review 2024年第6期11卷 89-90页

作者： Xuemei Fu Benjamin C.K.Tee Department of Materials Science and Engineering National University of Singapore Institute for Health Innovation and Technology National University of Singapore

In wearables and robotics, it is often required to deploy electronic devices at different spatially distributed locations for multi-functionality [1–3]. Thus, conductive wires for efficient interconnection of various electronic devices are ***, in practical applications, the frequent motion of wearers and robots will result in high-strain deformations of these wires, which could cause irreparable damage.

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A Single-Event-Transient Hardened Phase Locked Loop for Clock and Data Recovery

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Chinese Journal of Electronics 2024年第2期33卷 353-361页

作者： Hengzhou YUAN Bin LIANG Hao SANG Weixia XU Yang GUO Xi CHEN national university of Defense Technology

A radiation-hardened phase-locked loop is proposed for phase interpolator clock and data recovery purposes. A sensitive node-compressed charge pump and multi-node cross coupling voltage-controlled oscillators are proposed in this phase-locked loop with the goal of achieving good jitter performance and improving anti-SET（SET,single-event transient） capability. The root mean square（RMS） jitter of the phase-locked loop is reduced from 3.7 ps to 2.58 ps at 2 GHz, while the laser threshold is improved from 120 p J to 370 p J compared to the unhardened phaselocked loop. The hardened phase-locked loop also does not lose its lock state from linear energy transfers（LETs） of 3.3 to 37.3 Me V·cm2/mg.

关键词： Charge pumps Voltage-controlled oscillators Energy exchange Noise Lasers Jitter Phase locked loops

Beamforming design for covert broadcast communication with hidden adversary

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Science China(Information Sciences) 2024年第6期67卷 384-398页

作者： Weiyu CHEN Haiyang DING Shilian WANG Junshan LUO Fengkui GONG College of Electronic Science and Technology National University of Defense Technology College of Information and Communication National University of Defense Technology State Key Laboratory of Integrated Service Networks Xidian University

This paper explores covert broadcast communication in a challenging situation in which the transmitter, Alice, faces uncertainty regarding the position of the passive adversary, Willie. In this situation,controlling the signal exposure becomes difficult. Specifically, this paper focuses on the cases where Alice can delimit the suspicious areas where Willie may be located. The suspicious areas can have arbitrary number and shapes. Under the Rician fading model, the analytical expression of Willie's detection performance is derived. Then, the transmit power, the beamforming direction, and the number of channel uses are jointly designed to minimize the optimal Willie's detection performance among all the possible positions of Willie, on the premise of satisfying receivers' quality-of-service requirements. To tackle the formulated knotty problem with an infinite number of irregular and discontinuous Willie's possible positions, the continuous nature of the antenna pattern is exploited to convert the original problem into the one with a finite number of possible positions, by sampling the suspicious areas. Then, different algorithms are developed to address the resultant non-convex optimization problem for single-antenna Willie and multi-antenna Willie, respectively. Numerical results demonstrate significant performance gains of the proposed scheme over the widely-adopted maximum ratio transmission scheme, which indicates that simply adjusting the main lobe towards the receiver is indeed far away from optimum and shows the importance of leveraging Alice's limited knowledge of Willie's position.

关键词： low-probability-of-detection communication multiple antennas covertness performance uncertain position parameters optimization

Implicit policy constraint for offline reinforcement learning

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CAAI Transactions on Intelligence Technology 2024年第4期9卷 973-981页

作者： Zhiyong Peng Yadong Liu Changlin Han Zongtan Zhou national university of Defense Technology ChangshaChina

Offline reinforcement learning(RL)aims to learn policies entirely from passively collected datasets,making it a data‐driven decision *** of the main challenges in offline RL is the distribution shift problem,which causes the algorithm to visit out‐of‐distribution(OOD)*** distribution shift can be mitigated by constraining the divergence between the target policy and the behaviour ***,this method can overly constrain the target policy and impair the algorithm's performance,as it does not directly distinguish between in‐distribution and OOD *** addition,it is difficult to learn and represent multi‐modal behaviour policy when the datasets are collected by several different behaviour *** overcome these drawbacks,the au-thors address the distribution shift problem by implicit policy constraints with energy‐based models(EBMs)rather than explicitly modelling the behaviour *** EBM is powerful for representing complex multi‐modal distributions as well as the ability to distinguish in‐distribution samples and *** results show that their method significantly outperforms the explicit policy constraint method and other *** addition,the learnt energy model can be used to indicate OOD visits and alert the possible failure.

关键词： artificial intelligence artificial neural network learning(artificial intelligence) planning(artificial intelligence)

Associations between the use of red yeast rice preparations and adverse health outcomes:An umbrella review of meta-analyses of randomized controlled trials

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Journal of Integrative Medicine 2024年第2期22卷 126-136页

作者： Zhen-yu Ma Shu-ping Yang Ying Li Tian-tian Xu Ya-lin Yang Hui-yong Yang Heng-bing Li Le-jin Zhou Yong Diao Su-yun Li School of Medicine Huaqiao UniversityQuanzhou 362021Fujian ProvinceChina College of Traditional Chinese Medicine Shandong University of Traditional Chinese MedicineJinan 250355Shandong ProvinceChina Second Clinical Medical College Nanjing Medical UniversityNanjing 211166Jiangsu ProvinceChina

Background:Red yeast rice(RYR),a natural lipid-lowering agent,is widely used in clinical ***,the existing meta-analyses concerning the safety of RYR preparations have yielded inconsistent results,and the credibility of the evidence has not been ***:This study was designed to evaluate the existing evidence and offer a comprehensive understanding of the associations between the use of RYR preparations and various adverse health *** strategy:Seven literature databases were searched from inception to May 5,2023,using medical subject headings and free-text terms(e.g.,“red yeast rice,”“Xuezhikang,”and“Zhibitai”).Inclusion criteria:Meta-analyses that investigated and quantitatively estimated associations between the use of RYR preparations and adverse health outcomes were included in this *** extraction and analysis:Two researchers independently extracted data using a standardized data collection table;any disagreements were resolved by consulting a third *** on the participant,intervention,comparator and outcome(PICO)framework in each eligible meta-analysis,a series of unique associations between the use of RYR preparations and adverse health outcomes were *** associations’effect estimates were re-evaluated using random-effect ***:Fifteen meta-analyses,comprising 186(164 unique)randomized controlled trials,were *** on A Mea Surement Tool to Assess Systematic Reviews version 2,3(20%)and 12(80%)of these meta-analyses had low and critically low confidence,respectively.A total of 61 unique associations between the use of RYR preparations and adverse health outcomes were extracted from eligible *** on the random-effect models,10(16.4%)associations indicated a significant protective effect of RYR preparations against adverse health outcomes,while 5(8.2%)indicated an increased risk of adverse health outcomes related to uric acid,alanine transaminase and aspartate trans

关键词： Red yeast rice Safety Adverse health outcomes Umbrella review Meta-analysis Systematic review

Challenges and Opportunities in Preserving Key Structural Features of 3D-Printed Metal/Covalent Organic Framework

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Nano-Micro Letters 2024年第8期16卷 362-381页

作者： Ximeng Liu Dan Zhao John Wang Department of Materials Science and Engineering National University of SingaporeSingapore 117574Singapore Department of Chemical and Biomolecular Engineering National University of SingaporeSingapore 117585Singapore national university of Singapore(Chongqing)Research Institute Chongqing 401123People’s Republic of China

Metal-organic framework(MOF)and covalent organic framework(COF)are a huge group of advanced porous materials exhibiting attractive and tunable microstructural features,such as large surface area,tunable pore size,and functional surfaces,which have significant values in various application *** emerging 3D printing technology further provides MOF and COFs(M/COFs)with higher designability of their macrostructure and demonstrates large achievements in their performance by shaping them into advanced 3D ***,the currently available 3D printing M/COFs strategy faces a major challenge of severe destruction of M/COFs’microstructural features,both during and after 3D *** is envisioned that preserving the microstructure of M/COFs in the 3D-printed monolith will bring a great improvement to the related *** this overview,the 3D-printed M/COFs are categorized into M/COF-mixed monoliths and M/COF-covered *** differences in the properties,applications,and current research states are *** up-to-date advancements in paste/scaffold composition and printing/covering methods to preserve the superior M/COF microstructure during 3D printing are further discussed for the two types of 3D-printed M/*** the analysis of the current states of 3D-printed M/COFs,the expected future research direction to achieve a highly preserved microstructure in the 3D monolith is proposed.

关键词： Metal-organic frameworks Covalent organic frameworks 3D printing Microstructure Monolith