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不同连栽代次桉树人工林土壤团聚体中有机碳组分的积累和转化

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北京林业大学学报 2024年第10期46卷 42-52页

作者：崔宇鸿叶绍明卢志锋燕羽蒋晨阳广西大学林学院广西壮族自治区国有雅长林场

【目的】探究不同连栽代次桉树人工林土壤中有机碳组分的积累与转化特征，以期揭示环境因素对土壤有机碳组分积累和转化过程的影响，进而为提高桉树生产力和土壤管理提供科学依据。【方法】以广西博白县博白林场第1、2、3代桉树人工林... 详细信息

【目的】探究不同连栽代次桉树人工林土壤中有机碳组分的积累与转化特征，以期揭示环境因素对土壤有机碳组分积累和转化过程的影响，进而为提高桉树生产力和土壤管理提供科学依据。【方法】以广西博白县博白林场第1、2、3代桉树人工林为研究对象，采用干筛法将收集的0～40 cm土壤分为> 2 mm、1～2 mm、0.25～1 mm和<0.25 mm粒径的团聚体以评估土壤团聚体稳定性，并测量不同团聚体中有机碳组分（包括活性有机碳、缓性有机碳和惰性有机碳）的含量和储量，利用冗余分析和偏最小二乘法结构方程模型揭示影响土壤有机碳积累和转化的关键因素。【结果】（1）连栽显著降低了土壤团聚体的稳定性和各有机碳组分的含量和储量。（2）土壤各有机碳组分含量随团聚体粒径的增加而下降，而储量的分布规律则相反。（3）冗余分析和偏最小二乘法结构方程模型证明，土壤团聚体稳定性是影响土壤有机碳积累的主要因素，连栽抑制了惰性有机碳向活性有机碳的转化，导致土壤有机碳总体有效性下降。【结论】连栽主要通过改变土壤团聚体的分布和稳定性，进而调控桉树人工林土壤有机碳组分的积累和转化。研究结果有助于理解桉树人工林土壤有机碳的积累和转化过程中土壤团聚体调控机制。

关键词：桉树连栽土壤团聚体有机碳组分碳组分转化

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中等职业教育发展水平测度与时空演变

继续教育研究 2024年第6期 40-45页

作者：单怡崔宇红北京理工大学教育学院北京100081 北京理工大学图书馆北京100081

中等职业教育担负着培养全面发展的高素质技能型人才的重要职责和任务,是落实科教兴国战略和人才强国战略的重要途径。通过以2012—2019年全国31个省份的中等职业教育为研究对象,综合国内外职业教育研究成果,构建中等职业教育发展水平... 详细信息

中等职业教育担负着培养全面发展的高素质技能型人才的重要职责和任务,是落实科教兴国战略和人才强国战略的重要途径。通过以2012—2019年全国31个省份的中等职业教育为研究对象,综合国内外职业教育研究成果,构建中等职业教育发展水平综合评价指标体系,运用组合赋权法、自然断裂法、空间自相关法分析我国中等职业教育发展的时空演变特征。结果表明:一是2012—2019年我国中等职业教育整体发展态势良好,但区域间存在明显的差异性且呈现出“头轻脚重”结构;二是教育资源作为影响中等职业教育发展的核心要素,主要体现在师资配置和办学条件方面,我国中等职业教育发展在时间序列上呈现“波浪型”的稳定上升趋势且具有明显的阶段特征;三是在空间格局上呈现出由“双核式”向“带状式”演变特征,并且表现出明显的梯度格局特征和区域集聚效应。

关键词：中等职业教育发展水平测度时空格局空间自相关

Mode Ⅲ fracture analysis by Trefftz boundary element method

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Acta Mechanica Sinica 2007年第2期23卷 173-181页

作者： yuhong cui Juan Wang Manicka Dhanasekar Qinghua Qin Department of Mechanics Tianjin UniversityTianjin 300072 China Centre for Railway Engineering Central Queensland UniversityNorth Rockhampton QLD 4702 Australia Department of Engineering Australian National UmversltyCanberra ACT 0200 Australia

This paper presents a hybrid Trefftz （HT） boundary element method （BEM） by using two indirect techniques for mode III fracture problems. Two Trefftz complete functions of Laplace equation for normal elements and a special purpose Trefftz function for crack elements are proposed in deriving the Galerkin and the collocation techniques of HT BEM. Then two auxiliary functions are introduced to improve the accuracy of the displacement field near the crack tips, and stress intensity factor （SIF） is evaluated by local crack elements as well. Furthermore, numerical examples are given, including comparisons of the present results with the analytical solution and the other numerical methods, to demonstrate the efficiency for different boundary conditions and to illustrate the convergence influenced by several parameters. It shows that HT BEM by usingthe Galerkin and the collocation techniques is effective for mode III fracture problems.

关键词： Hybrid Trefftz method. Galerkin technique .Point-collocation technique .Mode III fracture

APPLICATION OF TREFFTZ BEM TO ANTI-PLANE PIEZOELECTRIC PROBLEM

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Acta Mechanica Solida Sinica 2006年第4期19卷 352-364页

作者： Wang Juan cui yuhong Qin Qinghua Jia Jiangying Department of Mechanics Tianjin University Tianjin 30072 China Department of Engineering Australian National University Canberra ACT 0200 Australia

Anti-plane electroelastic problems are studied by the Trefftz boundary element method （BEM） in this paper. The Trefftz BEM is based on a weighted residual formulation and indirect boundary approach. In particular the point-collocation and Galerkin techniques, in which the basic unknowns are the retained expansion coefficients in the system of complete equations, are considered. Furthermore, special Trefftz functions and auxiliary functions which satisfy exactly the specified boundary conditions along the slit boundaries are also used to derive a special purpose element with local defects. The path-independent integral is evaluated at the tip of a crack to determine the energy release rate for a mode Ⅲ fracture problem. In final, the accuracy and efficiency of the Trefftz boundary element method are illustrated by an example and the comparison is made with other methods.

关键词： Trefftz boundary element, point-collocation technique, Galerkin technique, special trial function anti-plane fracture, piezoelectric medium

Helical Fiber Pull-out in Biological Materials

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Acta Mechanica Solida Sinica 2016年第3期29卷 245-256页

作者： Lixin Wang yuhong cui Qinghua Qin Hui Wang Jianshan Wang Tianjin Key Laboratory of Modern Engineering Mechanics & Department of Mechanics Tianjin University Research School of Engineering Australian National University Department of Engineering Mechanics Henan University of Technology

Many biological materials, such as wood and bone, possess helicoid microstructures at microscale, which can serve as reinforcing elements to transfer stress between crack surfaces and improve the fracture toughness of their composites. Failure processes, such as fiber/matrix inter- face debonding and sliding associated with pull-out of helical fibers, are responsible mainly for the high energy dissipation needed for the fracture toughness enhancement. Here we present systemic analyses of the pull-out behavior of a helical fiber from an elastic matrix via the finite element method （FEM） simulation, with implications regarding the underlying toughening mechanism of helicoid microstructures. We find that, through their uniform curvature and torsion, helical fibers can provide high pull-out force and large interface areas, resulting in high energy dissipation that accounts, to a large extent, for the high toughness of biological materials. The helicity of fiber shape in terms of the helical angle has significant effects on the force-displacement relationships as well as the corresponding energy dissipation during fiber pull-out.

关键词： biological materials helicoid microstructures fiber pull-out energy dissipation,toughness

Synthesis of surface imprinted polymers based on wrinkled flower-like magnetic graphene microspheres with favorable recognition ability for BSA

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Journal of Materials Science & Technology 2021年第15期74卷 203-215页

作者： Zuoting Yang Ke Yang yuhong cui Tariq Shah Mudasir Ahmad Qiuyu Zhang Baoliang Zhang School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi'an710129China Xi'an Key Laboratory of Functional Organic Porous Materials Northwestern Polytechnical UniversityXi'an710072China Sunresins New Materials Co.Ltd. Xi'an710072China

Nowadays,the employing of molecular imprinting technique in the analysis and separation of proteins from complex biological samples has been widely favored by *** enrich the types of surface protein imprinted materials and expand the application fields of graphene materials,novel surface molecular imprinted polymers(MIPs)based on magnetic graphene microspheres Fe_(3)O_(4)@r GO@MIPs are first synthesized in this ***_(3)O_(4)@r GO@MIPs are prepared by oxidative self-polymerization of dopamine on the surface of magnetic graphene(Fe_(3)O_(4)@r GO)composite *** serum albumin(BSA)is selected as protein ***_(3)O_(4)@r GO microspheres with wrinkled flower-like structure are obtained by compounding Fe_(3)O_(4)and graphene oxide in an appropriate ratio via the method of high-temperature reduction *** microspheres exhibit promising dispersibility,high external surface area,rich pore structure,and sufficient magnetic *** advantages not only prevent the agglomeration of imprinted microspheres in the aqueous phase,which is conducive to contact and static adsorption,but also increase the amount of protein ***,sufficient magnetic properties ensure fast and effective separation of the *** the adsorption capacity is increased,the separation procedure becomes *** binding capacity of Fe_(3)O_(4)@r GO@MIPs for BSA can reach 317.58 mg/g within 60 min,and the imprinting factor(IF)is *** importantly,Fe_(3)O_(4)@r GO@MIPs can specifically recognize the target BSA from the mixed proteins and the actual *** is no significant decrease in the adsorption amount,IF,and magnetic properties after eight *** is promising to be used in the separation of proteins from the actual biological samples.

关键词： Wrinkled Flower-like Magnetic graphene microspheres Dopamine BSA Surface protein imprinting

Numerical Study on Helical Fiber Fragmentation in Chiral Biological Materials

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Transactions of Tianjin University 2018年第1期24卷 51-58页

作者： Jianshan Wang Li Yuan Lixin Wang yuhong cui Qinghua Qin Department of Mechanics Tianjin UniversityTianjin 300054China China Automotive Technology and Research Center Tianjin 300300China Research School of Engineering Australian National UniversityCanberra ACT 0200Australia

Chiral microstructures exist widely in natural biological materials such as wood, bone, and climbing tendrils. The helical shape of such microstructures plays an important role in stress transfer between fiber and matrix,and in the mechanical properties of biological materials. In this paper, helical fiber fragmentation behavior is studied numerically using the finite-element method(FEM), and then, the effects of helical shape on fiber deformation and fracture,and the corresponding mechanical mechanisms are investigated. The results demonstrate that, to a large degree, the initial microfibril angle(MFA) determines the elastic deformation and fracture behavior of fibers. For fibers with a large MFA, the interfacial area usually has large values, inducing a relatively low fragment density during fiber fragmentation. This work may be helpful in understanding the relationship between microstructure and mechanical property in biological materials, and in the design and fabrication of bio-inspired advanced functional materials.

关键词： Chiral biological materials Helical fiber Fiber fragmentation Deformation Dissipated energy

Distribution Regularity of Debris Flow and Its Hazard in Upper Reaches of Yangtze River and Other Rivers of Southwestern China

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Wuhan University Journal of Natural Sciences 2007年第4期12卷 619-626页

作者： WEI Fangqiang JIANG yuhong cui Peng DING Mingtao Key Laboratory of Mountain Hazards and Surface Process Chinese Academy of Sciences / Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 Sichuan China

In the upper reaches of Yangtze River and other rivers of southwestern China, the debris flows develop and lead to most serious disasters because of the various landforms, complex geological structures and abundant rainfall. The distribution of debris flows has regularity in the regions with different landform, geological structure, and precipitation. The regularities of distribution of debris flows are as following：（1） distributed in transition belts of different morphologic regions; （2） distributed in the area with strong stream trenching; （3） distributed along fracture zones and seismic belts：（4） distributed in the area with abundant precipitation; （5） distribution of debris flow is azonal. The activity of abundant debris flows not only brings harm to Towns, Villages and Farmlands, Main Lines of Communication, Water-Power Engineering, Stream Channels etc., but also induces strong water and soil loss. According to the present status of debris flow prevention, the problems in disasters mitigation and soil conservancy are found out, and the key works are brought up for the future disasters prevention and soil conservancy.

关键词： upper reaches of Yangtze River southwestern China debris flow water and soil loss distribution and hazards of debris flow

Flow field analyses of a porous membrane-separated,double-layered microfluidic chip for cell co-culture

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Acta Mechanica Sinica 2020年第3期36卷 754-767页

作者： Shenbao Chen Jian Xue Jinrong Hu Qihan Ding Luwen Zhou Shiliang Feng yuhong cui Shouqin Lu Mian Long Center of Biomechanics and Bioengineering Key Laboratory of Microgravity(National Microgravity Laboratory)Beijing Key Laboratory of Engineered Construction and Mechanobiologyand CAS Center for Excellence in Complex System MechanicsInstitute of MechanicsChinese Academy of SciencesBeijing100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Nonlinear Mechanics(LNM) Institute of MechanicsChinese Academy of SciencesBeijing 100190China Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211ZhejiangChina Department of Mechanics Tianjin UniversityTianjin 300072China

Organs-on-chips composed of a porous membrane-separated,double-layered channels are used widely in elucidating the effects of cell co-culture and flow shear on biological *** the diversity of channel geometry and membrane permeability is applied,their quantitative correlation with flow features is still *** boundary methods(IBM)simulations and theoretical modelling were performed in this *** simulations showed that channel length,height and membrane permeability jointly regulated the flow features of flux,penetration velocity and wall shear stress(WSS).Increase of channel length,lower channel height or membrane permeability monotonically reduced the flow flux,velocity and WSS in upper channel before reaching a *** the flow flux in lower channel monotonically increased with the increase of each factor,the WSS surprisingly exhibited a biphasic pattern with first increase and then decrease with increase of lower channel ***,the transition threshold of maximum WSS was sensitive to the channel length and membrane *** modeling,integrating the transmembrane pressure difference and inlet flow flux with chip geometry and membrane permeability,was in good agreement with IBM *** analyses provided theoretical bases for optimizing flow-specified chip design and evaluating flow microenvironments of in vivo tissue.

关键词： Immersed boundary method Porous membrane Wall shear stress Penetration velocity Microfluidic chip