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Additive manufactured osseointegrated screws with hierarchical design

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Bio-Design and Manufacturing 2024年第2期7卷 206-235页

作者： Wenbo yang Hao Chen Haotian Bai Yifu Sun Aobo zhang yang liu Yuchao Song Qing Han Jincheng Wang department of Orthopedics Second Hospital of Jilin UniversityChangchun 130022China College of Biological and Agricultural Engineering Jilin UniversityChangchun 130022China School of Materials Science and Engineering Jilin UniversityChangchun 130022China

Bone screws are devices used to fix implants or bones to ***,conventional screws are mechanically fixed with thread and often face long-term failure due to poor *** improve osseointegration,screws are evolving from solid and smooth to porous and *** manufacturing(AM)offers a high degree of manufacturing freedom,enabling the preparation of predesigned screws that are porous and *** paper provides an overview of the problems currently faced by bone screws:long-term loosening and screw ***,advances in osseointegrated screws are summarized hierarchically(sub-micro,micro,and macro).At the sub-microscale level,we describe surface-modification techniques for enhancing *** the micro level,we summarize the micro-design parameters that affect the mechanical and biological properties of porous osseointegrated screws,including porosity,pore size,and pore *** addition,we highlight three promising pore shapes:triply periodic minimal surface,auxetic structure with negative Poisson ratio,and the Voronoi *** the macro level,we outline the strategies of graded design,gradient design,and topology optimization design to improve the mechanical strength of porous osseointegrated ***,this paper outlines advances in AM technology for enhancing the mechanical properties of porous osseointegrated *** osseointegrated screws with hierarchical design are expected to provide excellent long-term fixation and the required mechanical strength.

关键词： Bone screws Additive manufacturing Architecture design Surface modification

Balanced Subeulerian Signed Graphs and Signed Line Graphs

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Journal of Mathematical Research with Applications 2024年第1期44卷 7-17页

作者： Juan liu Hong yang Xindong zhang Hongjian LAI College of Big Data statistics Guizhou University of Finance and Economics College of Mathematics and System Sciences Xinjiang University department of Mathematics West Virginia University

A signed graph S =(Su, σ) has an underlying graph Suand a function σ : E(Su)-→{+,-}. Let E-(S) denote the set of negative edges of S. Then S is eulerian signed graph(or subeulerian signed graph, or balanced eulerian signed graph, respectively) if Suis eulerian(or subeulerian, or eulerian and |E-(S)| is even, respectively). We say that S is balanced subeulerian signed graph if there exists a balanced eulerian signed graph S′ such that S′ is spanned by *** signed line graph L(S) of a signed graph S is a signed graph with the vertices of L(S) being the edges of S, where an edge eiej is in L(S) if and only if the edges ei and ej of S have a vertex in common in S such that an edge eiej in L(S) is negative if and only if both edges ei and ej are negative in S. In this paper, two families of signed graphs S and S ′ are identified, which are applied to characterize balanced subeulerian signed graphs and balanced subeulerian signed line graphs. In particular, it is proved that a signed graph S is balanced subeulerian if and only if S?S, and that a signed line graph of signed graph S is balanced subeulerian if and only if S?S ′.

关键词： signed graph signed line graph balanced eulerian balanced subeulerian

Bounds on the maximum numbers of clear two-factor interactions for 2^((n1+n2)-(k1+k2)) fractional factorial split-plot designs

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Science china Mathematics 2006年第12期49卷 1816-1829页

作者： ZI Xuemin zhang runchu liu minqian department of statistics School of Mathematical Sciences and LPMCNankai UniversityTianjin 300071China Department of StatisticsSchool of Mathematical Sciences and LPMCNankai UniversityTianjin 300071China Department of StatisticsSchool of Mathematical Sciences and LPMCNankai UniversityTianjin 300071China

Fractional factorial split-plot (FFSP) designs have an important value of investigation for their special *** are two types of factors in an FFSP design: the whole-plot (WP) factors and sub-plot (SP) factors,which can form three types of two-factor interactions:WP2fi,WS2fi and *** paper considers FFSP designs with resolution Ⅲ or Ⅳ under the clear effects *** derives the upper and lower bounds on the maximum numbers of clear WP2fis and WS2fis for FFSP designs,and gives some methods for constructing the desired FFSP *** further examines the performance of the construction methods.

关键词： fractional factorial design,split-plot,clear effects criterion,resolution.

Unbiased Quasi-regression

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Chinese Annals of Mathematics,Series B 2007年第2期28卷 177-186页

作者： guijun yang Lu LIN runchu zhang department of statistics Tianjin University of Finance and Economics Tianjin 300222 China School of Mathematics and System Sciences Shandong University Jinan 250100 China. LPMC and School of Mathematical Sciences Nankai University Tianjin 300071 China.

Quasi-regression, motivated by the problems arising in the computer experiments, focuses mainly on speeding up evaluation. However, its theoretical properties are unexplored systemically. This paper shows that quasi-regression is unbiased, strong convergent and asymptotic normal for parameter estimations but it is biased for the fitting of curve. Furthermore, a new method called unbiased quasi-regression is proposed. In addition to retaining the above asymptotic behaviors of parameter estimations, unbiased quasi-regression is unbiased for the fitting of curve.

关键词： Computer experiment Quasi-regression Unbiasedness Fitting of curve Asymptotic normality

Some results on 4~m2~n designs with clear two-factor interaction components

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Science china Mathematics 2008年第7期51卷 1297-1314页

作者： ZHAO ShengLi zhang runchu liu minqian School of Mathematical Sciences Qufu Normal UniversityQufu 273165China department of statistics School of Mathematical Sciences and Key Laboratory of Pure Mathematics and CombinatoricsNankai UniversityTianjin 300071China

Clear effects criterion is one of the important rules for selecting optimal fractional factorial designs,and it has become an active research issue in recent *** et *** upper and lower bounds on the maximum number of clear two-factor interactions(2fi's) in 2n-(n-k) fractional factorial designs of resolutions III and IV by constructing a 2n-(n-k) design for given k,which are only restricted for the symmetrical *** paper proposes and studies the clear effects problem for the asymmetrical *** improves the construction method of Tang et *** 2n-(n-k) designs with resolution III and derives the upper and lower bounds on the maximum number of clear two-factor interaction components(2fic's) in 4m2n designs with resolutions III and *** lower bounds are achieved by constructing specific *** show that the number of clear 2fic's in the resulting design attains its maximum number in many cases,which reveals that the construction methods are satisfactory when they are used to construct 4m2n designs under the clear effects criterion.

关键词： clear mixed levels resolution two-factor interaction component 62K15

Who Are the Elites in the Venture Capital Industry?-Investigation of Elite-Club Boundary in a Co-Investment Network

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Journal of Social Computing 2024年第2期5卷 145-164页

作者： Yu zhang Hu yang the department of Sociology Tsinghua UniversityBeijing 100084China the School of Information Central University of Finance and EconomicsBeijing 102206China

Existing research suggests that elite clubs exist in venture capital markets,but a standard for determining their size and composition is *** paper addresses this challenge by using the weighted k-means sorting algorithm to construct a research framework for elite *** the framework with investment events data from china’s venture capital market(2001-2018),intriguing findings *** ranking of Venture Capitalists(VCs)follows a power-law distribution,providing evidence for elite clubs’*** analysis identifies a turning point in the score curve,serving as a valuable indicator for club *** clubs demonstrate relatively high stability,maintaining advantages and elite status in future *** validation confirms the proposed framework’s superior stability compared to existing ***,elite club members outperform non-elites *** paper effectively identifies elite clubs in the Chinese venture capital market,helping other VCs recognize potential partners,access high-quality information,and enhance investment performance.

关键词： venture capital co-investment network elite club boundary ranking

Linear EV model with replicate observations on independent variables

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Science china Mathematics 2006年第6期49卷 752-769页

作者： liu Jixue, zhang Sanguo & CHEN Xiru department of statistics and finance, university of Science and Technology of china, Hefei 230026, china department of Mathematics, Graduate School of Chinese Academy of Sciences, Beijing 100049, china 1. department of statistics and finance University of Science and Technology of China Hefei 230026 China 2. department of Mathematics Graduate School of Chinese Academy of Sciences Beijing 100049 China

This paper studies the linear EV model when replicate observations are made only on independent variables. We construct the estimates of regression coefficients and prove the consistency and asymptotic normality under some proper conditions. Results obtained reveal the difference between the case where the independent and dependent variables are observed repeatedly and simultaneously and the case studied in this article.

关键词： linear EV model, consistency, asymptotic normality.

UNIFORM OPTIMAL-ORDER ESTIMATES FOR FINITE ELEMENT METHODS FOR ADVECTION-DIFFUSION EQUATIONS

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Journal of Systems Science & Complexity 2009年第4期22卷 555-559页

作者： Qun LIN Hong WANG Shuhua zhang Institute of Computational Mathematics and Scientific/Engineering Computing Chinese Academy of SciencesBeijing 100190 China. department of Mathematics University of South Carolina Columbia South Carolina 29208 USA. Research Center for Mathematics and economics Tianjin University of Finance and Economics Tianjin300222 China.

This article summarizes our recent work on uniform error estimates for various finite elementmethods for time-dependent advection-diffusion equations.

关键词： Advection-diffusion equation bilinear finite element method linear triangular elementmethod nonconforming finite element method.

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期权定价问题的数值方法

系统科学与数学 2004年第1期24卷 10-16页

作者：刘棠张盘铭天津财经学院基础部天津财经学院科研处天津300222

本文研究以股票为标的资产的美式看跌期权定价问题的数值方法,即有限元方法。通过将所考虑的问题转化为等价的变分不等式,并利用积分恒等式与超逼近分析技术,得到了半离散有限元方法的最优L^2-模与L~∞-模的误差估计。

关键词：期权定价股票市场积分恒等式超逼近分析技术误差估计有限元法