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Variational Solution of Coral Reef Stability Due to Horizontal Wave Loading

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Journal of Ocean University of China 2022年第3期21卷 647-655页

作者： ZHANG Qiyi LONG Quan li xiaowu Department of Ocean Engineering College of EngineeringOcean University of ChinaQingdao266100China Key Laboratory of Ocean Engineering of Shandong Province Ocean University of ChinaQingdao266100China

This paper proposes a theoretical method that can be used in calculating the stability of coral reefs or artificial *** this work,we employ the variational limiting equilibrium procedure to theoretically determine the slope stability of coral reefs covered with hard reef shells as a result of horizontal wave loads.A reasonable functional is proposed and its extremum is calculated based on the conservation of ***,we deduce the stability factor Ns of coral reefs under combined vertical self-gravity and horizontal wave loads,which is consistent with the published *** compare some classic examples of homogeneous slopes without hard shells in order to analyze the accuracy of results generated by this variational *** variational results are accurate and reliable according to the results of a series of detailed calculations and ***,some other influence parameters on the reef stability,including the top-layer tensile strength of coral reef,the amplitude of wave loading,and the tensile crack,are calculated and discussed in *** analysis results reveal that the existence of a hard reef shell could enhance the stability of reef slope and that there is a nonlinear relationship between the stability factor Ns,the shear strength,and the thickness Ds of the covered coral reef ***,the emergence of top-layer tensile cracks on the coral reefs reduces their stability,and the action of horizontal wave loads greatly decreases the stability of coral ***,the hard shell strength and its thickness Ds,surface tensile crack,and wave loading require more careful attention in the field of practical engineering.

关键词： coral reef stability tensile crack variational solution horizontal wave loading

Improving Fatigue Properties of 316L Stainless Steel Welded Joints by Surface Spinning Strengthening

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Acta Metallurgica Sinica(English Letters) 2024年第5期37卷 840-854页

作者： Dongqiqiong Wang Qiang Wang xiaowu li Zhefeng Zhang Department of Materials Physics and Chemistry School of Materials Science and Engineeringand Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education)Northeastern UniversityShenyang 110819China Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China College of light Industry Liaoning UniversityShenyang 110036China

The surface spinning strengthening(3S)mechanism and fatigue life extension mechanism of 316L stainless steel welded joint were systematically elucidated by microstructural analyses and mechanical *** indicate that surface gradient hardening layer of approximately 1 mm is formed in the base material through grain fragmentation and deformation twin strengthening,as well as in the welding zone composed of deformedδ-phases and *** fatigue strength of welded joint after 3S significantly rises by 32%(from 190 to 250 MPa),which is attributed to the effective elimination of surface geometric defects,discrete refinement ofδ-Fe phases and the appropriate improvement in the surface strength,collectively mitigating strain localization and surface fatigue damage within the gradient strengthening *** redistributed fineδ-Fe phases benefited by strong stress transfer of 3S reduce the risk of surface weak phase cracking,causing the fatigue fracture to transition from microstructure defects to crystal defects dominated by slip,further suppressing the initiation and early propagation of fatigue cracks.

关键词： 316L stainless steel Welded joint Surface spinning strengthening Nanotwin Fatigue life

Growth Ring-dependent Fracture Toughness of Sea Urchin Spines Estimated by Boundary Effect Model

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Journal of Bionic Engineering 2022年第5期19卷 1472-1480页

作者： Xiaona liu Simin liang Yingying li Hongmei Ji xiaowu li Department of Materials Physics and Chemistry School of Material Science and EngineeringNortheastern UniversityShenyang 110819China Key Laboratory for Anistropy and Texture of Materials Ministry of EducationNortheastern UniversityShenyang 110819China State key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Although the fracture behavior of sea urchin spines has been extensively investigated,there is as yet a lack of quantitative estimation on the effect of growth rings on the fracture properties of sea urchin *** sea urchin spines,much denser pores present in growth rings rather than porous *** tensile strength and fracture toughness of sea urchin spine samples with different numbers of growth rings are measured by the Boundary Effect Model(BEM).The experimental results of single-edge notched three-point bending tests indicate that the BEM is an appropriate method to estimate the fracture toughness of the present porous sea urchin spines,and the number of growth rings plays an important role in the fracture properties of ***,the tensile strength and fracture toughness of sea urchin spines can be significantly improved with the increase in the number of growth rings,and their fracture toughness can even reach a relatively high value compared with some other porous materials with an identical *** present research findings are expected to provide a fundamental insight into the design of high-performance bionic materials with a highly porous structure.

关键词： Sea urchin spine Growth ring Boundary Effect Model Porous structure Tensile strength Fracture toughness

Microstructural Characterization and Hardness Behavior of a Biological Saxidomus purpuratus Shell

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Journal of Materials Science & Technology 2011年第2期27卷 139-146页

作者： Wen Yang Guangping Zhang Huasai liu xiaowu li Institute of Materials Physics and Chemistry College of SciencesNortheastern UniversityShenyang 110004China Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Key Laboratory for Anisotropy and Texture of Materials Ministry of EducationNortheastern UniversityShenyang 110004China

The microstructures of the Saxidomus purpuratus shell were *** was found that the inner and middle layers of the shell are composed of crossed lamellae,while the outer layer exhibits porous *** the characteristic structure of each layer,the hardness of inner layer with narrow domains in crossed lamellar structure is the highest,and that of middle layer with wide domains is lower,while the outer layer has the lowest *** damage morphologies of the indentations change a lot,depending not only upon the magnitude of the indentation load,but also upon the orientation between the indentation direction and the crossed lamellae in the microstructure of the shell,which illustrates the anisotropy in mechanical properties of such shells.

关键词： Saxidomus purpuratus shell Microstructure Hardness Crossed lamellar Indentation

Optimization of Grain Boundary Character Distribution in Fe-18Cr-18Mn-0.63N High-Nitrogen Austenitic Stainless Steel

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Acta Metallurgica Sinica(English Letters) 2013年第5期26卷 497-502页

作者： Feng SHI xiaowu li Yutong HU Chuan SU Chunming liU Institute of Materials Physics and Chemistry College of Sciences Northeastern University School of Materials and Metallurgy Northeastern University

Grain boundary engineering（GBE） is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice（CSL） grain boundaries（special grain boundaries） in the grain boundary character distribution（GBCD）. The GBCD in a cold rolled and annealed Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel was analyzed by electron back scatter difraction（EBSD）. The results show that the optimization process of GBE in the conventional austenitic stainless steel cannot be well applied to this high-nitrogen austenitic stainless steel. The percentage of low ΣCSL grain boundaries could increase from 47.3% for the solid solution treated high-nitrogen austenitic stainless steel specimen to 82.0% for the specimen after 5% cold rolling reduction and then annealing at 1423 K for 10 *** special boundaries of high proportion efectively interrupt the connectivity of conventional high angle grain boundary network and thus achieve the GBCD optimization for the high-nitrogen austenitic stainless steel.

关键词： High nitrogen austenitic stainless steel Grain boundary character distri-bution CSL grain boundary EBSD

Processing, microstructure and mechanical properties of biomedical magnesium with a specific two-layer structure

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Progress in Natural Science:Materials International 2013年第2期23卷 183-189页

作者： Xue Zhang xiaowu li Jiguang li Xudong Sun Institute of Materials Physics and Chemistry College of Sciences Northeastern University Key Laboratory for Anisotropy and Texture Engineering of Materials Ministry of Education Northeastern University

A novel magnesium based scaffold with a two-layer structure was synthesized by powder metallurgical process using salt particles as space holder. The outer layer of the scaffold shows an interconnected porous structure and the inner layer presents a compact structure reinforced by the salt particles. Such a specific structure is introduced primarily for the purpose of a better combination of biocompatibility and mechanical compatibility. Experimental results demonstrate that the structural features and mechanical properties of the magnesium based scaffold with a salt content of 30 wt% prepared by the current method are quite compatible with the cancellous bone. Such a novel Mg-based scaffold has the potential to act as degradable implants for bone substitute application.

关键词： Magnesium Salt particle Scaffold material Porous structure Mechanical property

Design, synthesis, and fungicidal activity of novel 1,3,4-oxadiazole derivatives

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Chinese Chemical Letters 2018年第6期29卷 915-918页

作者： Fuqiang Yu Aiying Guan Mengru li Lan Hu xiaowu li Department of Materials Physics and Chemistry School of Material Science and Engineering and Key Laboratory for Anisotropy and Texture of MaterialsMinistry of Education Northeastern University State Key Laboratory of the Discovery and Development of Novel Pesticide Shenyang Sinochem Agrochemicals R&D Co.Ltd.

Employing the intermediate derivatization method（IDM）, twenty novel 1,3,4-oxadiazole derivatives containing arylpyrazoloxyl moiety were designed and synthesized. The structures of the title compounds were identified by1 H NMR,13 C NMR, MS and elemental analyses, compound 4 was further identified by single-crystal X-ray diffraction. Antifungal activities against rice sheath blight（RSB） and sorghum anthracnose（SA） were evaluated by the mycelium linear growth rate method. Compounds 4, 16 and 20 displayed significant activities against RSB（EC50= 0.88 mg/L, 0.91 mg/L and 0.85 mg/L, respectively）,higher than the reference tebuconazole; While compound 3 exhibited higher activity against SA（EC50= 1.03 mg/L）, equal to commercial pyraclostrobin（EC50= 1.06 mg/L）. The study showed that compound 20 is a promising fungicide for further development.

关键词： 1,3,4-Oxadiazole derivatives Intermediate derivatization method Rice sheath blight Sorghum anthracnose Structure-activity relationship

Microstructural Dependence of Friction and Wear Behavior in Biological Shells

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Journal of Renewable Materials 2023年第8期11卷 3297-3308页

作者： Xin Wang Ying Yan Hongmei Ji xiaowu li Department of Materials Physics and Chemistry School of Material Science and EngineeringNortheastern UniversityShenyang110819China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang110819China Key Laboratory for Anisotropy and Texture ofMaterials Ministry of EducationNortheastern UniversityShenyang110819China

As an essential renewable mineral resource,mollusk shells can be used as handicrafts,building materials,adsor-bents,***,there are few reports on the wear resistance of their *** Vicker’s hardness and friction,and wear resistance of different microstructures in mollusk shells were comparatively studied in the pre-sent *** hardness of prismatic structures is lower than that of cross-lamellar and nacreous ***-ever,the experimental results of sliding tests indicate that the prismatic structure exhibits the best anti-wear ability compared with foliated,crossed-lamellar,and nacreous *** anti-wear and hardness do not present a positive correlation,as the wear resistance properties of different microstructures in mollusk shells are governed jointly by organic matrix,structural arrangement,and basic building block *** present researchﬁndings are expected to provide fundamental insight into the design of renewable bionic materials with high wear resistance.

关键词： Mollusk shells microstructure hardness friction wear

A Geometric Strategy Algorithm for Orthogonal Pro jection onto a Parametric Surface

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Journal of Computer Science & Technology 2019年第6期34卷 1279-1293页

作者： xiaowu li Zhinan Wu Feng Pan Juan liang Jiafeng Zhang linke Hou College of Data Science and Information Engineering Guizhou Minzu UniversityGuiyang 550025China School of Mathematics and Computer Science Yichun UniversityYichun 336000China School of Software Engineering South China University of TechnologyGuangzhou 510006China Department of Science Taiyuan Institute of TechnologyTaiyuan 030008China Center for Economic Research Shandong UniversityJinan 250100China

In this paper, we investigate how to compute the minimum distance between a point and a parametric surface, and then to return the nearest point (foot point) on the surface as well as its corresponding parameter, which is also called the point projection problem of a parametric surface. The geometric strategy algorithm (hereafter GSA) presented consists of two parts as follows. The normal curvature to a given parametric surface is used to find the corresponding foot point firstly, and then the Taylor's expansion of the parametric surface is employed to compute parameter increments and to get the iteration formula to calculate the orthogonal projection point of test point to the parametric surface. Our geometric strategy algorithm is essentially dependent on the geometric property of the normal curvature, and performs better than existing methods in two ways. Firstly, GSA converges faster than existing methods, such as the method to turn the problem into a root-finding of nonlinear system, subdividing methods, clipping methods, geometric methods (tangent vector and geometric curvature) and hybrid second-order method, etc. Specially, it converges faster than the classical Newton's iterative method. Secondly, GSA is independent of the initial iterative value, which we prove in Theorem 1. Many numerical examples confirm GSA's robustness and efficiency.

关键词： point projection problem point inversion problem normal curvature normal curvature sphere convergence analysis