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Structural design and mechanical performance of composite vascular grafts

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Bio-Design and Manufacturing 2022年第4期5卷 757-785页

作者： Abdul Wasy Zia Rong liu Xinbo Wu School of Fashion and Textiles The Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SARChina

This study reviews the state of the art in structural design and the corresponding mechanical behaviours of composite vascular grafts. We critically analyse surface and matrix designs composed of layered, embedded, and hybrid structures along the radial and longitudinal directions;materials and manufacturing techniques, such as tissue engineering and the use of textiles or their combinations;and the corresponding mechanical behaviours of composite vascular grafts in terms of their physical–mechanical properties, especially their stress–strain relationships and elastic recovery. The role of computational studies is discussed with respect to optimizing the geometrics designs and the corresponding mechanical behaviours to satisfy specialized applications, such as those for the aorta and its subparts. Natural and synthetic endothelial materials yield improvements in the mechanical and biological compliance of composite graft surfaces with host arteries. Moreover,the diameter, wall thickness, stiffness, compliance, tensile strength, elasticity, and burst strength of the graft matrix are determined depending on the application and the patient. For composite vascular grafts, hybrid architectures are recommended featuring multiple layers, dimensions, and materials to achieve the desired optimal flexibility and function for complying with user-specific requirements. Rapidly emerging artificial intelligence and big data techniques for diagnostics and the threedimensional(3D) manufacturing of vascular grafts will likely yield highly compliant, subject-specific, long-lasting, and economical vascular grafts in the near-future.

关键词： Vascular grafts Surface design Structural design Composite materials Mechanical properties

Impact of Carbon Chain Structures in the Backbone on the Flexibility of Modified Polyarylene Sulfide Resins: Molecular Dynamics Simulations and Mesoscopic Analysis

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Chinese Journal of Polymer Science 2024年第4期42卷 544-557页

作者： Chi Zhang Rong liu Jing-Yuan liu Wen-Wei Jiang Key Laboratory of Fine Chemical Engineering and Functional Materials School of Chemical EngineeringSichuan UniversityChengdu610065China

In the domain of high-performance engineering polymers, the enhancement of mechanical flexibility in poly(phenylene sulfide) (PPS) resins has long posed a significant challenge. A novel molecular structure, designated as PP-He-IS, wherein imide rings and an aliphatic hexylene chain are covalently incorporated into the PPS backbone to enhance its flexibility, is introduced in this study. Molecular dynamics (MD) simulations are employed to systematically explore the effects of diversifying the backbone chain structures by substituting phenyl units with alkyl chains of varying lengths, referred to as PP-A-IS where “A” signifies the distinct intermediary alkyl chain configurations. Computational analyses reveal a discernable decrement in the glass transition temperature (Tg) and elastic modulus, counterbalanced by an increment in yield strength as the alkyl chain length is extended. Notably, the PP-He-IS variant is shown to exhibit superior yield strength while simultaneously maintaining reduced elastic modulus and Tg values, positioning it as an advantageous candidate for flexible PPS applications. Mesoscopic analyses further indicate that structures such as PP-He-IS, PP-Pe-IS, and PP-Bu-IS manifest remarkable flexibility, attributable to the presence of freely rotatable carbon-carbon single bonds. Experimental validation confirms that a melting temperature of 504 K which is lower than that of conventional PPS, and lower crystallinity are exhibited by PP-He-IS, thereby affording enhanced processability without compromising inherent thermal stability. Novel insights into the strategic modification of PPS for mechanical flexibility are thus furnished by this study, which also accentuates the pivotal role played by molecular dynamics simulations in spearheading high-throughput investigations in polymer material modifications.

关键词： Molecular dynamics simulations Polyarylene Sulfide Main-chain modifications Flexibility Aliphatic hexylene chain

The Spread Speed of Multiple Catalytic Branching Random Walks

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Acta Mathematicae Applicatae Sinica 2023年第2期39卷 262-292页

作者： rong-li liu School of Mathematics and Statistics Beijing Jiaotong UniversityBeijing 100044China

In this paper we study the asymptotic behavior of the maximal position of a supercritical multiple catalytic branching random walk(X_(n))on Z.If M_(n) is its maximal position at time n,we prove that there is a constantα>0 such that M_(n)/n converges toαalmost surely on the set of infinite number of visits to the set of catalysts.We also derive the asymptotic law of the centered process M_(n)-αn as n→∞.Our results are similar to those in[13].However,our results are proved under the assumption of finite L log L moment instead of finite second moment.We also study the limit of(X_(n))as a measure-valued Markov process.For any function f with compact support,we prove a strong law of large numbers for the process X_(n)(f).

关键词： catalytic branching random walk invariant measure martingale change of measure spine decomposition

Numerical Investigation of Three-dimensional Aeroacoustic Characteristics of Owl-inspired Trailing-edge Fringes

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Journal of Bionic Engineering 2023年第3期20卷 1103-1120页

作者： Jiaxin rong Hao liu Shanghai Jiao Tong University and Chiba University International Cooperative Research Center(SJTU-CU ICRC) Shanghai200240China Graduate School of Engineering Chiba University1-33Yayoi-choInage-kuChiba263-8522Japan

Owls are widely known for their silent flight,which is attributed to their unique wing morphologies comprising leading-edge(LE)serrations,trailing-edge(TE)fringes,and a velvety surface.The aeroacoustic characteristics of owl-inspired TE fringes have been widely investigated through two-dimensional(2D)modeling,but remain yet poorly studied in association with their three-dimensional(3D)effects.Here,we present a numerical study of the 3D aeroacoustic characteristics of owl-inspired TE fringes in which we combined large-eddy simulations(LES)with the Ffowcs Williams‒Hawkings analogy.We constructed a clean wing model and three wing models with TE fringes that were distributed differently spanwise.The aerodynamic forces and 3D acoustic characteristics reveal that,like the 2D results of our previous studies,the 3D TE fringes enable remarkable sound reduction spatially while having aerodynamic performance comparable to the clean model.Visualizations of the near-field 3D flow structures,vortex dynamics,and flow fluctuations show that TE fringes can robustly alter the 3D flow by breaking 3D TE vortices into small eddies and mitigating 3D flow fluctuations.Particularly,it is verified that TE fringes alter spanwise flows,thus dominating the 3D aeroacoustic characteristics in terms of passive flow control and flow stabilizations,whereas the fringes are inefficient in suppressing the acoustic sources induced by wingtip vortices.Moreover,the TE fringes distributed at midspan have better acoustic performance than those in the vicinity of the wingtip,indicating the importance of a spanwise distribution in enhancing aeroacoustic performance.

关键词： Owl Three-dimensional trailing-edge fringes Aeroacoustics Large-eddy simulation Ffowcs Williams‒Hawkings equation

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共享经济:传统经济模式的颠覆者

经济学家 2017年第5期 97-104页

作者：刘根荣厦门大学经济学院福建厦门361005

云计算、移动互联网、物联网以及大数据技术的运用催生了信息技术时代的新经济形态,即共享经济模式,将深刻地改变人类社会的传统经济形态。共享经济的出现与发展有着必然的经济与社会成因,其带来了对传统经济的一系列的颠覆性影响:促进... 详细信息

云计算、移动互联网、物联网以及大数据技术的运用催生了信息技术时代的新经济形态,即共享经济模式,将深刻地改变人类社会的传统经济形态。共享经济的出现与发展有着必然的经济与社会成因,其带来了对传统经济的一系列的颠覆性影响:促进企业职能转换、促进服务升级、促进行业竞争、引导生产变革、提升社会诚信、实现灵活就业,等等。而针对共享经济的发展面临的边界问题、法律困境以及政府管制问题,本文提出了相应的政策建议。

关键词：共享经济信息技术新经济形态

Local Government Borrowing’s Expansionary Monetary Effect and Its Policy Synergy

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China Finance and Economic Review 2022年第3期11卷 46-65页

作者： Na Li Rong liu School of Public Finance and Taxation Southwest University of Finance and Economics

All governments face increasingly frequent issues arising from aggregate supply and demand against currency circulation and financial stability,and public finance and banking authorities employ a variety of policy instruments to keep the economy stable and coordinated.How to avoid policy conflicts and maximize effectiveness in policy portfolio of local government borrowing,which is taken as a major macro-control instrument,is a subject that needs in-depth study.This paper probes into local government borrowing’s monetary effect and transmission mechanism and its best synergistic model with monetary policy by the construction of a NK-DSGE model covering financial frictions,multi-period bonds and borrowing rules.The findings are as follows.(1)The shocks of one-percent local government borrowing(bond duration=5 years)push up the money multiplier by 0.39%to produce expansionary monetary effect,and the longer the bond duration,the greater the effect.(2)In the context of physical and financial shocks,monetary policy adopts a moderately tight reverse synergy with local government borrowing,effectively restraining its expansionary monetary effect for better economic stability and recovery.(3)For bonds with longer maturities,raising the risk sensitivity of local government borrowing rules benefits the improvement of welfare.

关键词： local government borrowing monetary policy money supply expansionary monetary effect

A Uniqueness Theorem of a System of Nonlinear Equations and Its Applications

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Acta Mathematicae Applicatae Sinica 2015年第1期31卷 111-120页

作者： Rong liu College of Computer and Information Science Fujian Agriculture and Forestry University College of Mathematics and Computer Science Hunan Normal University

A uniqueness theorem of a solution of a system of nonlinear equations is given. Using this result uniqueness theorems for power orthogonal polynomials, for a Gaussian quadrature formula of an extended Chebyshev system... 详细信息

关键词： uniqueness theorems power orthogonal polynomials Gaussian quadrature formula extendedChebyshev system Gaussian Birkhoff quadrature formula

Empirical likelihood for spatial cross-sectional data models with matrix exponential spatial specification

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Applied Mathematics(A Journal of Chinese Universities) 2024年第1期39卷 125-139页

作者： liu Yan rong Jian-rong QIN Yong-song Nanning University Nanning 530200China Center for Applied Mathematics of Guangxi and College of Mathematics and Statistics Guangxi Normal UniversityGuilin 541004China

In this paper,we study spatial cross-sectional data models in the form of matrix exponential spatial specification(MESS),where MESS appears in both dependent and error terms.The empirical likelihood(EL)ratio statistics are established for the parameters of the MESS model.It is shown that the limiting distributions of EL ratio statistics follow chi-square distributions,which are used to construct the confidence regions of model parameters.Simulation experiments are conducted to compare the performances of confidence regions based on EL method and normal approximation method.

关键词： MESS empirical likelihood con dence region

Selenium-doped cathode materials with polyaniline skeleton for lithium-organosulfur batteries

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Journal of Energy Chemistry 2023年第4期79卷 148-157页

作者： rong Zou Wenwu liu Fen Ran State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals School of Materials Science and EngineeringLanzhou University of TechnologyLanzhou 730050GansuChina

Sulfur-containing polymer(SCP)is considered as an outstanding cathode material for lithium-sulfur batteries.However,undesirable soluble polysulfides may shuttle in electrolyte,concluding long-chain Li_(2)S_(n)(n>4)and short-chain Li2Sn(n≤4),as well as the sluggish conversion kinetics are yet to be solved to enhance the performance of lithium-sulfur batteries.Here Se-doped sulfurized polyaniline with adjusted sulfur-chain-S_(x)-(x≤6)contribute to ensure the absence of long-chain polysulfides,and the skeleton with quinoid imine can endow strongly adsorption towards short-chain polysulfides by the reversible transition between deprotonated/protonated imine(-NH^(+)=and-N=),which offer double insurance against suppressing“shuttle effect”.Furthermore,Se atoms are doped into sulfurized polysulfides to accelerate the redox conversion and take a frontier orbital theory-oriented view into catalytic mechanism.Se-doped sulfurized polyaniline as active materials for lithium-organosulfur batteries delivers good electrochemical performance,including high rate,reversible specific capacity(680 mA h g^(-1)at 0.1 A g^(-1)),and lower capacity decay rate only of 0.15%with near 100%coulomb efficiency during long-term cycle.This work provides a valuable guiding ideology and promising solution for the chemistry-oriented structure design and practical application for lithium-organosulfur batteries.

关键词： Lithium-organosulfur batteries Selenium-doped Cathode materials Sulfur-containing polymer Frontier orbital theory