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Hua's Theorem on Five Almost Equal Prime Squares

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Acta Mathematica Sinica,English Series 2006年第3期22卷 907-916页

作者： guang shi l Department of Mathematics Shandong University

In this paper we sharpen Hua＇s result by proving that each sufficiently large integer N congruent to 5 modulo 24 can be written as N=p1^2＋p2^2＋p3^2＋p4^2＋p5^2,with │pj-√N/5│≤U=N^1/2-1/28＋ε,where pj are primes.

关键词： Additive theory of prime numbers Circle method iterative method

Healing Process of Casting Pores in a Ni-based Superalloy by Hot Isostatic Pressing

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Journal of Materials Science & Technology 2015年第11期31卷 1151-1157页

作者： X.g.Zheng Y.-N.shi l.H.lou Shenyang National laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Superalloy Division Institute of Metal Research Chinese Academy of Sciences

Hot isostatic pressing （HIP） with a pressure of 180 MPa at a temperature of 1170 ℃ was introduced to an investment cast Ni-based superalloy （Mgl） turbocharger blade to explore the healing process of casting pores generated during investment casting. Optical micrograph and scanning electron naicroscopy （SEM） observations indicate that eutectic pores are the main cast defects in the as-cast blade before HIP. These pores normally locate at the solidification front of γ/γ＇ eutectic with a size of a few micrometers to a few tens of micrometers. After HIP for 4 h, most of the pores were closed. Based on phase characteristics, these pores were healed by the formation of γ matrix with finer and irregular-shaped γ＇ precipitates. Healing interface can be easily distinguished by SEM. line scan by using energy dispersive X-ray spectroscopy （EDS） reveals a much higher Ti and Al concentration in the healing interface. It is proposed that solute diffusion toward the casting pores during HIP results in the formation of γ, and the much higher concentration of γ＇-forming elements Al and Ti near the healing interface contributes to the precipitation of γ＇ in the healed region in the succeeding cooling process after HIP.

关键词： Superalloy Hot isostatic pressing (HIP) Healing

Cobalamin-dependent radical S-adenosyl-l-methionine protein functions with a partner to successively methylate tricyclic indole alkaloid for chuangxinmycin maturation and derivatization

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Science China Chemistry 2025年第1期 308-316页

作者： Sili Wang Jiancheng Huang Yanan Du Wei Huang Yufeng Xue Xiaokun Xu guannan Zhong Yuanyuan shi Bin Hong Xiaoying Bian Wen liu State Key laboratory of Chemical Biology Shanghai Institute of Organic Chemistry University of Chinese Academy of SciencesChinese Academy of Sciences State Key laboratory of Microbial Technology Shandong University National Health Commission (NHC) Key laboratory of Biotechnology for Microbial Drugs Institute of Medicinal BiotechnologyChinese Academy of Medical Science & Peking Union Medical College

Cobalamin(Cbl)-dependent radical S-adenosyl-l-methionine(SAM) proteins constitute the largest collection of the radical SAM superfamily that has hundreds of thousands of individual members. Many of these proteins are involved in the biosynthesis of pharmaceutically important natural products to catalyze chemically demanding reactions. In the biosynthetic pathway of chuangxinmycin(CXM), a unique indole alkaloid antibiotic with potent anti-infective activity, functionalization of the characteristic thiopyrano[4,3,2-cd]indole scaffold by regio-and stereoselective C3-methylation is believed to rely on a Cbl-dependent radical process, which, however, remained to be reconstituted biochemically. We here report the dissection of this enzymatic process, which requires the incorporation of Cxm8, a Cbl-dependent radical SAM protein, with Cxm9, a DUF5825family protein that shares no homology to any proteins of known functions. Cxm8 and Cxm9 function together by forming an unexpected heterodimeric complex that selectively catalyzes C3-methylation of the tricyclic indole-S-hetero ring system in a successive manner, achieving CXM and a recently identified, C3-dimethylated congener. Detailed biochemical characterization,isotope labeling, structural simulation and bioinformatics analysis rationalized the catalysis of the Cxm8/Cxm9 complex and particularly the necessity of the DUF5825 protein for C3-methylase activity. This is the first example that a Cbl-dependent protein acts with a partner to exhibit radical SAM activity.

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Monotone Chains in Modulus of Two Classes of Dirichlet Coefficients

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Acta Mathematica Sinica,English Series 2023年第6期39卷 1101-1114页

作者： guang shi lü Qiang MA School of Mathematics Shandong UniversityJi'nan 250100P.R.China

let f1,...,fkand g1,...,qkbe non-CM newforms of square-free *** byλ_(sym)jf_(i)(n)the coefficients of the Dirichlet expansion of l(sym^(j)f_(i),s)andν1,...,νkthe distinct positive integers such thatλ_(sym)jf_(i)(νi)≠*** this paper,we obtain that there exist infinitely many positive integers m such that 0let expansion of l(sym^(j1)f×sym^(j2)g,s),we have a similar result.

关键词： Dirichlet coefficients Sato-Tate conjecture

Totally homogeneous networks

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National Science Review 2019年第5期6卷 962-969页

作者： Dinghua shi linyuan lü guanrong Chen Department of Mathematics College of Science Shanghai University Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Department of Electronic Engineering City University of Hong Kong

In network science, the non-homogeneity of node degrees has been a concerning issue for ***, with today’s modern web technologies, the traditional social communication topologies have evolved from node-central structures into online cycle-based communities, urgently requiring new network theories and *** the focus from node degrees to network cycles could reveal many interesting properties from the perspective of totally homogenous networks or sub-networks in a complex network, especially basic simplexes(cliques) such as links and ***, compared with node degrees, it is much more challenging to deal with network *** studying the latter, a new clique vector-space framework is introduced in this paper, where the vector space with a basis consisting of links has a dimension equal to the number of links, that with a basis consisting of triangles has the dimension equal to the number of triangles and so *** two vector spaces are related through a boundary operator, for example mapping the boundary of a triangle in one space to the sum of three links in the other *** the new framework,some important concepts and methodologies from algebraic topology, such as characteristic number,homology group and Betti number, will play a part in network science leading to foreseeable new research *** immediate applications, the paper illustrates some important characteristics affecting the collective behaviors of complex networks, some new cycle-dependent importance indexes of nodes and implications for network synchronization and brain-network analysis.

关键词： boundary operator clique vector space cycle homology group totally homogenous network

MICROSTRUCTURE AND PROPERTIES OF Zl201 AllOY OBTAINED BY NEAR-lIQUIDUS ElECTROMAgNETIC CASTINg

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Acta Metallurgica Sinica(English letters) 2005年第5期18卷 653-658页

作者： P. Wang l.F. shi g.M. lu J.Z. Cui The Key laboratory of Electromagnetic Processing of Material Ministry of Education Northeastern University Shenyang 110004 China

The microstructures of Zl201 alloy slurry prepared by near-liquidus electromagnetic casting （NlEMC）, electromagnetic casting（EMC）, and near-liquidus casting（NlC） were investigated by means of electron microscopy and image analysis. Mechanical properties of as-cast alloys were determined. The results show that the NlEMC induces a fine, uniform, and equiaxed grain structure with a mean equal-area-circle grain diameter of 32.8μm. The as-cast aUoy has a hardness of HV122.8 and a tensite strength of 368MPa. Both of them are betterthan those of the alloys prepared by EMC and by NlC. The mechanism of grain refinement in the NlEMC alloy slurry was discussed.

关键词： near-liquidus casting electromagnetic casting rheocasting,microstructure property

Formability of Materials with Small Tools in Incremental Forming

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Chinese Journal of Mechanical Engineering 2020年第4期33卷 150-158页

作者： Hongyu Wei g.Hussain X.shi B.B.l Isidore Mohammed Alkahtani Mustufa Haider Abidi College Mechanical&Electrical Engineering Nanjing University of Aeronautics&AstronauticsNanjingPeople’s Republic of China Faculty of Mechanical Engineering GIK Institute of Engineering Sciences&TechnologyTopi 23460Pakistan College of Mechanical Engineering Shanghai University of Engineering ScienceShanghaiPeople’s Republic of China Bradenburg University of Technology CottbusGermany Industrial Engineering Department College of EngineeringKing Saud UniversityRiyadh 11421Saudi Arabia Advanced Manufacturing Institute King Saud UniversityRiyadh 11421Saudi Arabia

Single point incremental forming(SPIF)is an innovative sheet forming process with a high economic *** formability in this process can be maximized by executing forming with a tool of specific small radius,regarded as threshold critical *** value has been reported as 2.2 mm for 1 mm thick sheet ***,with a change in the forming conditions specifically in the sheet thickness and step size,the critical radius is likely to alter due to a change in the bending *** main aim of the present study is to undertake this point into account and develop a relatively generic *** study is composed of experimental and numerical *** maximum wall angle(θmax)without sheet fracturing is regarded as sheet formability.A number of sheet materials are formed to fracture and the trends correlating formability with normalized radius(i.e.,R/To where R is the tool-radius and To is the sheet thickness)are *** trends confirm that there is a critical tool-radius(Rc)that maximizes the formability in ***,it is found that the critical radius is not fixed rather it shows dependence on the sheet thickness such that Rc=βTo,whereβvaries from 2.2 to 3.3 as the thickness increases from 1 mm to 3 *** critical radius,however,remains insensitive to variation in step size ranging from 0.3 mm to 0.7 *** is also observed that the selection of tool with Rlity window not only on the higher side but also on the lower *** higher limit,as revealed by the experimental and FEA results,diminishes due to excessive shearing because of in-plane biaxial compression,and the lower limit reduces due to pillowing in the bottom of *** new tool-radius condition proposed herein study would be helpful in maximizing the formability of materials in SPIF without performing experimental trials.

关键词： Incremental forming Critical tool-radius Formability curve Finite element analysis

Cost effective approach to identify multiple influential spreaders based on the cycle structure in networks

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Science China(Information Sciences) 2023年第9期66卷 184-193页

作者： Wenfeng shi Shuqi XU Tianlong FAN linyuan lü Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Institute of Dataspace Hefei Comprehensive National Science Center Department of Physics University of Fribourg Alibaba Research Center for Complexity Sciences Hangzhou Normal University

Identifying influential spreaders has theoretical and practical significance in complex *** centrality methods can efficiently find a single spreader, but it could lead to influence redundancy and high initializing costs when used to identify a set of multiple spreaders. A cycle structure is one of the most crucial reasons for the complexity of a network and the cornerstone of the feedback effect. From this novel perspective, we propose a new method based on basic cycles in networks to identify multiple influential spreaders with superior spreading performance and low initializing costs. Experiments on six empirical networks show that the spreaders selected by the proposed method are more scattered in the network and yield the best spreading performance compared with those on seven well-known methods. Importantly, the proposed method is the most cost effective under the same spreading performance. The cycle-based method has the advantage of generating multiple solutions. Our work provides new insights into identifying multiple spreaders and hence can benefit wide applications in practical scenarios.

关键词： multiple spreaders basic cycle complex network cycle structure spreading dynamics

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文档级神经机器翻译综述

软件学报 2025年第1期36卷 152-183页

作者：吕星林李军辉陶仕敏杨浩张民苏州大学计算机科学与技术学院华为翻译中心

机器翻译(machine translation, MT)研究旨在构建一个自动转换系统,将给定源语言序列自动地转换为具有相同语义的目标语言序列.由于机器翻译广阔的应用场景,使其成为自然语言理解领域乃至人工智能领域的一个重要的研究方向.近年来,端到... 详细信息

机器翻译(machine translation, MT)研究旨在构建一个自动转换系统,将给定源语言序列自动地转换为具有相同语义的目标语言序列.由于机器翻译广阔的应用场景,使其成为自然语言理解领域乃至人工智能领域的一个重要的研究方向.近年来,端到端的神经机器翻译(neural machine translation, NMT)方法显著超越了统计机器翻译(statistical machine translation, SMT)方法,成为目前机器翻译研究的主流方法.然而,神经机器翻译系统通常以句子为翻译单位,在面向文档的翻译场景中,将文档中每个句子独立地进行翻译,会因脱离文档的篇章语境引起一些篇章级的错误,如词语错翻、句子间不连贯等.因此将文档级的信息融入到翻译的过程中去解决跨句的篇章级错误是更加自然和合理的做法,文档级的神经机器翻译(document-level neural machine translation, DNMT)的目标正是如此,成为机器翻译研究的热门方向.调研了近年来在文档级神经机器翻译研究方向的主要工作,从篇章评测方法、使用的数据集和模型方法等方面系统地对当前研究工作进行了归纳与阐述,目的是帮助研究者们快速了解文档级神经机器翻译研究现状以及未来的发展和研究方向.同时在文中也阐述了在文档级神经机器翻译的一些展望、困难和挑战,希望能带给研究者们一些启发.

关键词：神经机器翻译 Transformer模型文档上下文篇章评测