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Testing Regression Coefficients in High-Dimensional and Sparse Settings

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Acta Mathematica Sinica,English Series 2021年第10期37卷 1513-1532页

作者： kai xu Yan TIAN Qing CHENG School of Mathematics and Statistics Anhui Normal UniversityWuhu 241002P.R.China Center for Quantitative Medicine Duke-NUS Medical SchoolNational University of SingaporeSingapore 169856

In the high-dimensional setting,this article considers a canonical testing problem in multivariate analysis,namely testing coefficients in linear regression *** tests for highdimensional regression coefficients have been proposed in the recent ***,these tests are based on the sum of squares type statistics,that perform well under the dense alternatives and suffer from low power under the sparse *** order to attack this issue,we introduce a new test statistic which is based on the maximum type statistic and magnifies the sparse *** limiting null distribution of the test statistic is shown to be the extreme value distribution of type I and the power of the test is *** particular,it is shown theoretically and numerically that the test is powerful against sparse *** studies are carried out to examine the numerical performance of the test and to compare it with other tests available in the literature.

关键词： Extreme value distribution high-dimensional linear models maximum-type-test

数据中心多能互补分布式能源系统设计与运行优化研究

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西安交通大学学报 2025年第1期59卷 93-104页

作者：任效效李小龙薛凯吴炫韩小渠王进仕严俊杰西安交通大学动力工程多相流国家重点实验室西安710049 中国电力工程顾问集团西北电力设计院有限公司西安710075

为实现数据中心的低碳转型和能效提升,提出了一种集成多种可再生能源和储能设备的多能互补分布式能源系统作为其供能系统。建立了包含生命周期成本、碳排放、能耗、电网购电率和热量浪费率等指标的优化目标体系。制定了两种考虑负荷特... 详细信息

为实现数据中心的低碳转型和能效提升,提出了一种集成多种可再生能源和储能设备的多能互补分布式能源系统作为其供能系统。建立了包含生命周期成本、碳排放、能耗、电网购电率和热量浪费率等指标的优化目标体系。制定了两种考虑负荷特征的运行策略,采用改进的多目标蝗虫优化算法对系统容量配置进行求解。为了分析优化目标和运行策略对系统优化的影响,通过组合不同优化目标和运行策略形成了多种优化设计方案,采用层次分析法和熵权法确定评价指标的权重,并利用多准则妥协解排序法进行评价排序。针对青海省某数据中心的案例,获得其能源系统的优化设计与运行方案。研究表明:运行策略主要影响吸收式制冷机和地源热泵的容量,而优化目标主要影响储能设备的容量;在相同的运行策略下,增加优化目标可提升系统的综合性能;对于不同的方案,生命周期成本、碳排放、能耗等基础优化目标值变化较小,而电网购电率和热量浪费率变化较大;通过实施五目标优化,即在基础优化目标的基础上增加热量浪费率、电网购电率,系统的综合性能得到了显著提升,其中热量浪费率和电网购电率分别降低了62.30%和25.92%,可再生能源发电占比增加了2%。

关键词：数据中心多能互补分布式能源系统优化设计运行策略多目标蝗虫优化算法

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High-entropy FeNiCoCr alloys with improved mechanical and tribological properties by tailoring composition and controlling oxidation

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Journal of Materials Science & Technology 2021年第23期82卷 207-213页

作者： Jie xu xuan Kong Minghui Chen Qunchang Wang Fuhui Wang Shenyang National Laboratory for Materials Science Northeastern UniversityShenyang110819China

Many metal matrix self-lubricating composites possess excellent comprehensive properties of high strength and wear resistance after incorporating various lubricants that usually belong to ceramic ***,this improvement is always obtained at the cost of notable decrease in *** order to break through this toughness-tribological properties trade-off,self-lubricating composite alloys based on the matrix of Fe NiCoCr_(0.5) high entropy alloy(HEA)were prepared by milling addition of element Co or Cr and then spark plasma sintering(SPS).Co or Cr is added into the base HEA with the aim of tailoring oxidation behavior,mechanical properties as well as tribological *** no ceramic lubricants are used,the alloy composites remain high *** or Cr element addition leads to the precipitation of a hard phase of a-Cr and grain refinement,both of which contribute to the increase of mechanical *** sliding,oxidation of Fe and Ni is ***,the oxides of cobalt and chromium are formed upon the Co-and Cr-modified HEAs,*** oxidation products,especially the oxides of cobalt that are easy to be sintered on sliding,are in favor of the formation of a lubricating glaze layer at 400℃on the worn surface,and thus the decrease in friction coefficient and wear rate,which are 0.33 and 4.0×10^(-5) mm^(3)/(N m),respectively.

关键词： High entropy alloys Oxidation behavior Self-lubricating composite Cobalt oxide

In-situ evolution process understanding from a salan-ligated manganese cluster to supercapacitive application

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Nano Research 2022年第1期15卷 346-351页

作者： xu Zhang kai Zhao xu Peng Mohamedally Kurmoo Ming-Hua Zeng Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials Ministry-of-Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules&College of Chemistry&Chemical EngineeringHubei UniversityWuhan 430062China Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources School of Chemistry and Pharmaceutical SciencesGuangxi Normal UniversityGuilin 541004China Institut de Chimie de Strasbourg CNRS-UMR7177Universite de Strasbourg4 rue Blaise Pascal67070 Strasbourg CedexFrance

The goal of material chemistry is to study the relationship among hierarchical structure,chemical reaction and precision preparation for materials,yet tracking pyrolysis process on multi-dimensional scale is still at primary *** we propose packing mode analysis to understand evolution process in high temperature *** a proof of concept,we first design a salan-ligated Mn3(Mn3(3-MeOsalophen)_(2)(Cl)_(2))cluster and pyrolyze it under an inert atmosphere directly to a mixed valence MnOx embedded in a porous N-doped carbon skeleton(MnOx/C).Meanwhile,combining thermogravimetry-mass spectrometry(TG-MS)with other characterization techniques,its pyrolysis process is precisely tracked real-time and Mn^(2+)/Mn^(3+)ratios in the resulting materials are deduced,ensuring excellent electrochemical *** a result,the as-preferred MnOVC-900 sample reaches 943 F/g at 1 A/g,maintaining good durability under 5,000 cycles with 90%*** highlight of packing mode analysis strategy in this work would provide a favorable approach to explore the potential relationship between structure and performance in the future.

关键词： evolution process understanding thermogravimetry-mass spectrometry salan-ligated manganese cluster packing mode analysis supercapacitive performance

Non-isothermal Crystallization Kinetics and Isothermal Crystallization Kinetics in Supercooled Liquid Region of Cu–Zr–Al–Y Bulk Metallic Glass

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Acta Metallurgica Sinica(English Letters) 2018年第3期31卷 290-298页

作者： Ke Yang Xin-Hui Fan Bing Li Yan-Hong Li Xin Wang xuan-xuan xu School of Material and Chemical Engineering Xi'an Technological University

The crystallization kinetics of Cu43Zr48Al9 and（Cu43Zr48Al9）98Y2 bulk metallic glasses in non-isothermal and isothermal conditions was studied by differential scanning *** the non-isothermal and isothermal modes,the average activation energy of（Cu43Zra8Al9）98Y2 is larger than that of Cu43Zr48Al9,meaning the higher stability against crystallization of（Cu43Zr48Al9）*** addition,the average activation energies for Cu43Zr48Al9 and（Cu43Zr48Al9）98Y2 calculated using Arrhenius equation in isothermal mode are larger than the values calculated by Kissinger-Akahira-Sunose method in non-isothermal mode,indicating that the energy barrier is higher in isothermal *** Johnson-Mehl-Avrami model was used to analyze the crystallization kinetics in the non-isothermal and isothermal *** Avrami exponent n for Cu43Zr48Al9 is above 2.5,indicating that the crystallization is mainly determined by a diffusion-controlled three-dimensional growth with an increasing nucleation rate,while the Avrami exponent n for（Cu43Zr48Al9）98Y2 is in the range of 1.5-2.5 in the non-isothermal mode,implying that the crystallization is mainly governed by diffusion-controlled three-dimensional growth with decreasing nucleation ***,the Avrami exponents n for Cu43Zr48Al9 and（Cu43Zr48Al9）98Y2 are different in the non-isothermal and isothermal conditions,which imply different nucleation and growth behaviors during the crystallization processes.

关键词： Bulk metallic glass Yttrium addition Crystallization behavior Activation energy

Generation of microfluidic gradients and their effects on cells behaviours

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Bio-Design and Manufacturing 2020年第4期3卷 427-431页

作者： Qiangqiang Tang Xiran Yang Chengkai xuan kai Wu Chen Lai xuetao Shi Peking University Shenzhen Institute Peking UniversityShenzhenPeople’s Republic of China School of Materials Science and Engineering South China University of TechnologyGuangzhou 510640People’s Republic of China National Engineering Research Center for Tissue Restoration and Reconstruction South China University of TechnologyGuangzhou 510006People’s Republic of China Guangzhou Regenerative Medicine and Health Guangdong Laboratory Guangzhou 510005China

Introduction The concept of“gradients”has been widely demonstrated and applicated in *** example,concentration gradients and potential gradients in the body can regulate the homeostasis as well as the balance of phy... 详细信息

关键词： migration. homeostasis fluid

Study on constant-pressure specific heat of non-equilibrium phase change process in gas-liquid two-phase flow system

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Chinese Science Bulletin 2007年第22期52卷 3162-3167页

作者： xu kai LU WenQiang College of Physical Sciences Graduate University of the Chinese Academy of Sciences Beijing 100049 China

In this paper,the air-water vapor-water system is taken as an example,and the formula of constant-pressure specific heat during non-equilibrium phase change process in the two-phase flow system is deduced using the theory of two-phase flow and thermophysics. The constant-pressure specific heat of non-equilibrium phase change process is calculated with the corresponding numerical model,and the numerical results are compared to those of the equilibrium phase change process. It is shown that in evaporation process,the variational rate of the non-equilibrium specific heat increases with increasing initial fluid temperature and particle mass fraction. The smaller particle radius is,the faster the varia-tional rate is. Meanwhile,the constant-pressure specific heat of equilibrium process is higher than that of the non-equilibrium process all the time.

关键词：平衡相空气水汽热物理学

Characterization of the Topological Features of Catalytic Sites in Protein Coevolution Networks

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Chinese Physics Letters 2020年第6期37卷 127-131页

作者： Xiu-Lian xu Jin-xuan Shi School of Physics Science and Technology Yangzhou UniversityYangzhou 225002China

The knowledge of sequence and structural properties of residues in the catalytic sites of enzymes is important for understanding the physiochemical basis of enzymatic *** reveal new features of the catalytic sites by analyzing the coevolutionary behavior of amino acid *** performing direct coupling analysis of the sequences of homologous proteins,we construct the coevolution networks at the residue *** on the analysis of the topological features of the coevolution networks for a dataset including 20 enzymes,we show that there is significant correlation between the catalytic sites and topological features of protein coevolution *** at the catalytic center often correspond to the nodes with high values of centralities in the networks as characterized by the degree,betweenness,closeness,and Laplacian *** results of this work provide a possible way to extract key coevolutionary information from the sequences of enzymes,which is useful in the prediction of catalytic sites of enzymes.

关键词： evolution networks catalytic

Design of novel NiSiAlY alloys in marine salt-spray environment:PartⅠ.Al-Si-Y and Ni-Si-Y subsystems

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Journal of Materials Science & Technology 2021年第29期88卷 66-78页

作者： kai xu Keke Chang Yong Du Liping Wang Key Laboratory of Marine Materials and Related Technologies Zhejiang Key Laboratory of Marine Materials and Protective TechnologiesNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo315201China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing100049China State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083China

MCrAlY(M=Ni,Co,NiCo)alloys have been widely used as a bond layer for thermal barrier coatings(TBCs).However;oxides form discontinuously on MCrAlY surface in the marine environment since Cr_(2)O_(3)can react with NaCl and H_(2)O at temperatures above 500℃.Replacing Cr with other alloying elements(such as Si)might prevent severe salt-spray corrosion *** save time and efforts in materials design of the Ni-Si-Al-Y system;we obtained the thermodynamic descriptions of the ternary compounds by coupling the CALPHAD(CALculation of PHAse Diagrams)approach and first-principles *** and eighteen ternary compounds were evaluated and calculated in the Al-Si-Y and Ni-Si-Y systems;*** diagrams of the two systems were depicted after a series of experimental Al/Ni-Si-RE(RE denotes rare earth elements,including La,Ce,Pr,Nd,Sm,Gd,Dy,Ho,and Er)systems being *** is found that the RE elements with the same reference states tend to form ternary compounds with the same crystal *** model-based descriptions are the basis for the research and development of novel NiSiAlY alloys in resisting high-temperature corrosion.

关键词： Ternary compounds NiSiAlY CALPHAD Formation enthalpy Rare earth elements