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SDCC: software-defined collective communication for distributed training

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Science China(Information Sciences) 2024年第9期67卷 105-125页

作者： Xin JIN Zhen ZHAng yunshan JIA yun MA Xuanzhe liu School of Computer Science Peking University Department of Computer Science and Technology Johns Hopkins University

Communication is crucial to the performance of distributed training. Today's solutions tightly couple the control and data planes and lack flexibility, generality, and performance. In this study, we present SDCC, a software-defined collective communication framework for distributed training. SDCC is based on the principle of modern systems design to effectively decouple the control plane from the data *** abstracts the operations for collective communication in distributed training with dataflow operations and unifies computing and communication with a single dataflow graph. The abstraction, together with the unification, is powerful: it enables users to easily express new and existing collective communication algorithms and optimizations, simplifies the integration with different computing engines(e.g., Py Torch and Tensor Flow) and network transports(e.g., linux TCP and kernel bypass), and allows the system to improve performance by exploiting parallelism exposed by the dataflow graph. We further demonstrate the benefits of SDCC in four use cases.

关键词： machine learning systems distributed training deep learning collective communication software-defined networking

The corrosion characteristic and mechanism of Mg-5y-1.5Nd-xZn-0.5Zr(x=0,2,4,6 wt.%)alloys in marine atmospheric environment

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Journal of Magnesium and Alloys 2024年第1期12卷 139-158页

作者： Quantong Jiang Dongzhu Lu liren Cheng Nazhen liu Baorong Hou CAS Key Laboratory of Marine Environmental Corrosion and Bio-fouling Institute of OceanologyChinese Academy of SciencesNo.7 Nanhai RoadQingdao 266071PR China State Key laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesNo.5625 Renmin StreetChangchun 130022PR China Open Studio for Marine Corrosion and Protection Pilot National Laboratory for Marine Science and Technology(Qingdao)No.1 Wenhai RoadQingdao 266071PR China Sanya Institute of Oceanology South China Sea Institute of OceanologyChinese Academy of SciencesZhenzhou RoadSanya 572000PR China

The microstructure and precipitated phases of as-cast Mg-5y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were investigated by optical microscopy,scanning electron microscopy,energy-dispersive spectrometry and X-ray *** exposure corrosion experiment of these magnesium alloys was tested in South China Sea and KEXUE vessel atmospheric *** corrosion characteristic and mechanism of magnesium alloys of Mg-5y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were analyzed by weight loss rate,corrosion depth,corrosion products and corrosion *** electrochemical corrosion tests were also measured in the natural *** comprehensive results showed that Mg-5y-1.5Nd-4Zn-0.5Zr magnesium alloy existed the best corrosion resistance whether in the marine atmospheric environment and natural seawater *** depended on the microstructure,type and distribution of precipitated phases in Mg-5y-1.5Nd-4Zn-0.5Zr magnesium *** quantity anodic precipitated phases in the microstructure of Mg-5y-1.5Nd-4Zn-0.5Zr alloy played the key role in the corrosion resistance.

关键词： Marine atmospheric environment Exposure corrosion Magnesium alloy Corrosion rate Corrosion mechanism

Numerical study of a bi-directional in-band pumped dysprosium-doped fluoride fiber laser at 3.2μm

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Frontiers of Information Technology & Electronic Engineering 2024年第7期25卷 1017-1024页

作者： lingjing li Chuny.ng MA Nian ZHAO Jie PEng Bin liu Haining JI yuchen WAng Pinghua TAng School of Physics and Optoelectronics Xiangtan UniversityXiangtan 411105China Research Center of Circuits and Systems Peng Cheng LaboratoryShenzhen 518055China Shanghai Institute of Optics and Fine Mechanics Chinese Academy of SciencesShanghai 201899China

Dy^(3+)-doped fluoride fiber lasers have important applications in environment monitoring,real-time sensing,and polymer *** present,achieving a high-efficiency and high-power Dy^(3+)-doped fluoride fiber laser in the mid-infrared(mid-IR)region over 3μm is a scientific and technological ***,Dy^(3+)-doped fluoride fiber lasers use a unidirectional pumping method,which suffers from the drawback of high thermal loading density on the fiber tips,thus limiting power *** this study,a bi-directional in-band pumping scheme,to address the limitations of output power scaling and to enhance the efficiency of the Dy^(3+)-doped fluoride fiber laser at 3.2μm,is investigated numerically based on rate equations and propagation *** simulation results reveal that the optical‒optical efficiency of the bi-directional in-band pumped Dy^(3+)-doped fluoride fiber laser can reach 75.1%,approaching the Stokes limit of 87.3%.The potential for further improvement of the efficiency of the Dy^(3+)-doped fluoride fiber laser is also *** bi-directional pumping scheme offers the intrinsic advantage of mitigating the thermal load on the fiber tips,unlike unidirectional pumping,in addition to its high *** a result,it is expected to significantly scale the power output of Dy^(3+)-doped fluoride fiber lasers in the mid-IR regime.

关键词： Mid-infrared laser Fiber laser Bi-directional pumping

Low-permittivity liLn(PO_(3))_(4)(Ln=La,Sm,Eu)dielectric ceramics for microwave/millimeter-wave communication

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Journal of Advanced Ceramics 2024年第5期13卷 602-620页

作者： Huanrong Tian Xiaohan Zhang Zidong Zhang yao liu Haitao Wu Key Laboratory for liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China School of Materials Science and Engineering Shandong UniversityJinan 250061China School of Environmental and Material Engineering Yantai UniversityYantai 264005China

The development of dielectric materials with low permittivity and low loss is a great challenge in wireless *** this study,liLn(PO_(3))_(4)(Ln=La,Sm,Eu)ceramic systems were successfully prepared using the traditional solid-state method.X-ray diffraction analysis indicated that the liLn(PO_(3))_(4)ceramics crystallized in a monoclinic structure when sintered at 850–940℃.The characteristic peak shifted to higher angles with variations in the Ln element,which was ascribed to a reduction in the cell *** analysis by structure refinement revealed that the reduction in the cell volume resulted from the decrease in chemical bond lengths and the compression of[liO_(4)]and[PO_(4)]***,the liLn(PO_(3))_(4)ceramic system displayed exceptional performance at low sintering temperatures(910–925℃),including a high quality factor(Q·f)of 41,607–75,968 GHz,low temperature coefficient of resonant frequency(τ_(f))ranging from−19.64 to−47.49 ppm/℃,low permittivity(ε_(r))between 5.04 and 5.26,and low density(3.04–3.26 g/cm^(3)).The application of Phillips–van Vechten–Levine(P–V–L)theory revealed that the increased Q·f value of the liLn(PO_(3))_(4)systems can be attributed to the enhanced packing fraction,bond covalency,and lattice energy,and the stability of τ_(f) was associated with the increase in the bond ***,a prototype microstrip patch antenna using liEu(PO_(3))_(4) ceramics was *** measurement results demonstrated excellent antenna performance with a bandwidth of 360 MHz and a peak gain of 5.11 dB at a central frequency of 5.08 ***,low-εr liLn(PO_(3))_(4)ceramic systems are promising candidates for microwave/millimeter-wave communication.

关键词： low permittivity liLn(PO_(3))_(4) microwave dielectric properties Phillips-van Vechten-Levine(P-V-L)theory microstrip patch antenna

Sensitivity analyses of random cave groups on karst tunnel stability based on water–rock interaction using a novel contact dynamic method

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Underground Space 2024年第5期18卷 162-186页

作者： Chengzhi Xia Zhenming Shi Huanjia Kou Shaoqiang Meng Maomao liu College of Civil Engineering Tongji UniversityShanghai 200092China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China

This paper concentrates on the sensitivity and dynamic simulation of randomly distributed karst cave groups on tunnel stability and connectivity extended ratio based on water–rock interaction using a novel contact dynamic method(CDM).The concept of karst cave group connectivity extended ratio during tunneling and water inrush is *** effects of cave shape and spatial distribution on Qiyueshan tunnel are *** deformation and damage index,and connectivity extended ratio with uniform random karst cave groups are *** results demonstrate that the connectivity extended ratio is verified as a crucial judgment in predicting the safe distance and assessing the stability of the tunnel with the karst cave *** model captures the fracture propagation and contact behavior of rock mass,surface flow,as well as the bidirectional water–rock interaction during the water inrush of Qiyueshan tunnel with multiple caves.A larger cave radius and smaller minimum distance between the cave and tunnel increase the deformation and damage index of the surrounding *** the cave radius and cave area ratio increase,the failure pattern shifts from overall to local *** findings potentially have broad applications in various surface and subsurface scenarios involving water–rock interactions.

关键词： Karst tunnel stability Contact dynamic method Connectivity extended ratio Karst cave groups Qiyueshan tunnel Water-rock interaction

Stress-corrosion coupled damage localization induced by secondary phases in bio-degradable Mg alloys:phase-field modeling

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Journal of Magnesium and Alloys 2024年第1期12卷 361-383页

作者： Chao Xie Shijie Bai Xiao liu Minghua Zhang Jianke Du The Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211P.R.China Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 411201P.R.China

In this study,a phase-field scheme that rigorously obeys conservation laws and irreversible thermodynamics is developed for modeling stress-corrosion coupled damage(SCCD).The coupling constitutive relationships of the deformation,phase-field damage,mass transfer,and electrostatic field are derived from the entropy *** SCCD localization induced by secondary phases in Mg is numerically simulated using the implicit iterative algorithm of the self-defined finite *** quantitative evaluation of the SCCD of a C-ring is in good agreement with the experimental *** capture the damage localization,a micro-galvanic corrosion domain is defined,and the buffering effect on charge migration is *** cases are investigated to reveal the effect of localization on corrosion acceleration and provide guidance for the design for resistance to SCCD at the crystal scale.

关键词： Phase field Mg alloys Stress-corrosion coupled damage Damage localization Finite element method

In situ reduction strategy towards high conductivity,anti-freezing and super-stretchable rGO based hydrogel for diverse flexible electronics

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Nano Research 2024年第5期17卷 4016-4022页

作者： Xin Zhang Junhao Wang Mengyan Wang Dongxu liu Zhuo Wang College of Resources and Environment University of Chinese Academy of SciencesBeijing 101408China Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of ScienceBeijing 101400China

Hydrogels electrolytes with flexibility and high conductivity have been widely used in kinds of flexible ***,hydrogels always suffer from the inevitable freezing of water at subzero temperatures,which results in the sacrificing of their electrical ***,an anti-freezing,flexible hydrogel based on in situ reduction of graphene oxide(GO)and laponite has been developed as electrolyte for high performance supercapacitor and sensitive *** crosslinked GO and laponite in polyacrylamide(PAM)resulted in an enhanced mechanical property,while the in-situ reduction of GO in the hydrogel enhanced the conductivity and diminishes the aggregated of *** features guarantee a reliable electro signal as sensor and a high performance of the ***,in the process of preparation of reduced graphene oxide(rGO)hydrogel,the addition of ethylene glycol(EG)and KOH,endows the hydrogel antifreeze *** anti-freezing electrolyte can be stretched to a strain of 1600%and maintained a specific capacitance of 37.38 F·g^(-1) at-20℃.In addition,the photothermal conversion character of rGO in the hydrogel,endows it’s the potential application in wound *** overall merits of the hydrogel will open up a new avenue for sensitive sensor and energy storage device in practical applications.

关键词： hydrogel in-situ reduction flexible electronics low temperature tolerance photothermal therapy

Role of polarization evolution in the hysteresis effect of Pb-based antiferroelecrtics

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Chinese Chemical Letters 2024年第4期35卷 516-519页

作者： Botao Gao He Qi Hui liu Jun Chen Beijing Advanced Innovation Center for Materials Genome Engineering Department of Physical ChemistryUniversity of Science and Technology BeijingBeijing 100083China Shanghai Institute of Ceramics Chinese Academy of SciencesShanghai 201899China Hainan University Haikou 570228China

The electric field-induced irreversible domain wall motion results in a ferroelectric(FE) hysteresis. In antiferroelectrics(AFEs), the irreversible phase transition is the main reason for the hysteresis effects, which plays an important role in energy storage performance. Compared to the well-demonstrated FE hysteresis,the structural mechanism of the hysteresis in AFE is not well understood. In this work, the underly.ng correlation between structure and the hysteresis effect is unveiled in Pb(Zr,Sn,Ti)O_(3) AFE system by using in-situ electrical biasing synchrotron X-ray diffraction. It is found that the AFE with a canting dipole configuration, which shows a continuous polarization rotation under the electric field, tends to have a small hysteresis effect. It presents a negligible phase transition, a small axis ratio, and electric field-induced lattice changing, small domain switching. All these features together lead to a slim hysteresis loop and a high energy storage efficiency. These results offer a deep insight into the structure-hysteresis relationship of AFEs and are helpful for the design of energy storage material.

关键词： Antiferroelectric Hysteresis effect Structure refinement Perovskite In situ synchrotron radiation

Iron single-atom/clusters catalysts derived from iron-rich Enteromorpha after urea-saturation for Fenton-like reaction

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Chinese Chemical Letters 2024年第3期35卷 149-152页

作者： yujie Zhang Siyi liu Dongdong Chen Xing Xu School of Environmental Science and Engineering Shandong UniversityQingdao 266237China

Fabrication of single atom catalysts(SACs)by a green and gentle method is important for their practical Fenton-like *** this work,a high effective iron-based catalyst was prepared from the iron-rich Enteromorpha for NPX degradation via peroxymonosulfate(PMS).Both Fe-SACs and iron-clusters was fabricated from the intrinsic iron element in Enteromorpha after the urea *** Fe-SACs/clusters can achieve 100%of NPX oxidation within 20 min with the k_(obs)of 0.282 min^(-1).Quenching tests indicated that the radical pathways were not dominated in the catalytic systems,and strong electron transfer process can be induced in the Fe-SACs/clusters+PMS system by using the NPX as electron donor and FeSACs/clusters/PMS^*complexes as electron *** result was consistent with the phenomenon observed in the galvanic oxidation *** addition,the Fe-SACs/clusters was deposited onto the ceramic membrane(CM)by the spray.ng-crosslinking process to form a Fe-SACs/clusters@CM,which showed an effective and continuous NPX degradation in a heterogeneous PMS system.

关键词： SACs Iron Clusters Fenton-like reaction Enteromorpha