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Constrained multi-degree reduction of triangular Bézier surfaces

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Applied Mathematics(A Journal of Chinese Universities) 2009年第4期24卷 417-430页

作者： zhou lian WANG Guo-jin Department of Mathematics Zhejiang University Hangzhou 310027 China State Key Laboratory of CAD＆CG Zhejiang University Hangzhou 310027 China

This paper proposes and applies a method to sort two-dimensional control points of triangular Bezier surfaces in a row vector. Using the property of bivariate Jacobi basis functions, it further presents two algorithms for multi-degree reduction of triangular Bezier surfaces with constraints, providing explicit degree-reduced surfaces. The first algorithm can obtain the explicit representation of the optimal degree-reduced surfaces and the approximating error in both boundary curve constraints and corner constraints. But it has to solve the inversion of a matrix whose degree is related with the original surface. The second algorithm entails no matrix inversion to bring about computational instability, gives stable degree-reduced surfaces quickly, and presents the error bound. In the end, the paper proves the efficiency of the two algorithms through examples and error analysis.

关键词： triangular Bezier surface explicit boundary curve constraint corner constraint degree reduction Jacobi polynomial

Microstructures and mechanical properties of a new titanium alloy for surgical implant application

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International Journal of Minerals,Metallurgy and Materials 2010年第2期17卷 185-191页

作者： Jun Li lian zhou Zuo-chen Li School of Materials Engineering Shanghai University of Engineering Science Shanghai 201620 China Northwest Institute for Nonferrous Metal Research Xi＇an 710016 China

A new titanium alloy Ti12.5Zr2.5Nb2.5Ta（TZNT） for surgical implant application was synthesized and fully annealed at 700℃for 45 *** microstructure and the mechanical properties such as tensile properties and fatigue properties were *** results show that TZNT mainly consists of a lot of lamellaα-phase clusters with different orientations distributed in the originalβ-phase grain boundaries and a small amount ofβphases between the lamella a *** alloy exhibits better ductility,lower modulus of elasticity,and lower admission strain in comparison with Ti6A14V and Ti6A17Nb,indicating that it has better biomechanical compatibility with human *** fatigue limit of TZNT is 333 MPa,at which the specimen has not failed at 10^7 cycles.A large number of striations present in the stable fatigue crack propagation area,and many dimples in the fast fatigue crack propagation area are observed,indicating the ductile fracture of the new alloy.

关键词： titanium alloy surgical implant microstructure mechanical properties fatigue

Interdecadal Variability in Large and Small Warm Pools in Western Pacific and Their Association with Rainfall Anomalies

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Atmospheric and Oceanic Science Letters 2014年第1期7卷 56-61页

作者： zhou lian-Tong Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of Sciences Key Laboratory of Global Change and Marine-Atmospheric Chemistry

This study investigated interdecadal variability of June–October(JJASO) the large and small warm pools in western Pacific and their association with rainfall anomalies using station and reanalysis data from 1958 to *** results indicated that the large and small warm pools in western Pacific showed an interdecadal shift around *** large warm pool years over western Pacific were found after 1986,whereas the small warm pool years were often seen throughout the periods before *** analysis results also showed that there were obvious interdecadal variability in JJASO rainfall in Southeast China and warm pool in western *** 1958–1985(small warm pool years),the decrease in rainfall was associated with tropospheric moisture divergence and sinking motion over Southeast China and warm pool in western ***,during 1986–2008(large warm pool years),the increase in rainfall was associated with tropospheric moisture convergence and ascending *** analysis showed that large warm pool contributed to the increase in surface latent heat fluxes over warm pool in the western ***,there was an increase in the amount of water vapor over Southeast China and warm pool in western Pacific,which contributed to increased rainfall in these regions.

关键词： large and small warm pools interdecadal variability surface latent heat flux

A Pulsar Wind Nebula Origin of the Ultra-high-energy Source 1LHAASO J1929+1846

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Research in Astronomy and Astrophysics 2023年第10期23卷 218-223页

作者： Qi Xia lian-Cheng zhou Jun Fang Department of Astronomy Yunnan UniversityKunming 650091China

1LHAASO J1929+1846 is one of the ultra-high-energy(UHE,E>0.1 PeV)sources in the first catalog ofγ-ray sources detected by the Large High Altitude Air Shower *** has been detected fluxes at 3 TeV for2.48±0.11×10^(-13)TeV^(-1)cm^(-2)s^(-1)with the Water Cherenkov Detector Array and at 50 TeV for0.64±0.06×10^(-16)TeV^(-1)cm^(-2)s^(-1)with the Kilometer Squared Array,but the origin of its UHE emission remains *** pulsar wind nebula(PWN)G54.1+0.3,which is powered by the pulsar PSR 1930+1852with a period of 136 ms and it is detected within a 0°.29 region around the centroid of 1LHAASO J1929+*** explore whether G54.1+0.3 is capable of producing the UHE radiation of 1LHAASO J1929+***,the data with Fermi Large Area Telescope for the PWN is analyzed to obtain the GeV ***,the multiband nonthermal fluxes for the nebula are investigated based on a one-zone time-dependent *** the model,we assume the spin-down energy of the pulsar is persistently injected into particles(electrons and positrons)and magnetic field in the PWN,and these high-energy particles produce multiband non-thermal radiation from radio toγ-rays via synchrotron radiation and inverse Compton *** reproduce the spectral energy distribution of PWN G54.1+0.3 with reasonable *** result indicates that the UHEγ-ray source 1LHAASO J1929+1846possibly originates from PWN G54.1+0.3.

关键词： radiation mechanisms:non-thermal ISM:supernova remnants gamma-rays:stars

Anisotropic Porous Ti6Al4V Alloys Fabricated by Diffusion Bonding:Adaption of Compressive Behavior to Cortical Bone Implant Applications

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Journal of Materials Science & Technology 2016年第9期32卷 937-943页

作者： Fuping Li Jinshan Li Hongchao Kou lian zhou State Key Laboratory of Solidification Processing Northwestern Polytechnical University

In this work, porous Ti6Al4V alloys with 30%-70% porosity for biomedical applications were fabricated by diffusion bonding of alloy meshes. Pore structure was characterized by Micro-CT and SEM. Compressive behavior in the out-of-plane direction and biocompatibility with cortical bone were studied. The results reveal that the fabricated porous Ti6Al4V alloys possess anisotropic structure with square pores in the in-plane direction and elongated pores in the out-of-plane direction. The average pore size of porous Ti6Al4V alloys with 30%-70% porosity is in the range of 240-360 Bin. By tailoring diffusion bonding temperature, aspect ratio of alloy meshes and porosity, porous Ti6Al4V alloys with different compressive properties can be obtained, for instance, Young＇s modulus and yield stress in the ranges of 4-40 GPa and 70-500 MPa, respectively. Yield stress of porous Ti6Al4V alloys fabricated by diffusion bonding is close to that of alloys fabricated by rapid prototyping, hut higher than that of fabricated by powder sintering and space-holder method. Diffusion bonding temperature has some effects on the yield stress of porous Ti6Al4V alloys, but has a minor effect on the Young＇s modulus. The relationship between compressive properties and relative density conforms well to the Gibson-Ashby model. The Young＇s modulus is linear with the aspect ratio, while the yield stress is linear with the square of aspect ratio of alloy meshes. Porous Ti6Al4V alloys with 60%-70% porosity have potential for cortical bone implant applications.

关键词： Porous biomaterials Titanium alloys Diffusion bonding Compressive behavior Bioadaption

Can Rawls＇ Constructivism Avoid the Euthyphro Dilemma？ In Reply to Shafer-Landau

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Frontiers of Philosophy in China 2015年第4期10卷 568-578页

作者： zhou lian School of Philosophy Renmin University of China Beijing 100872 China

In this essay, I consider two challenges implicit in Russ Shafer-Landau’s criticism of constructivists: the realism challenge and the relativism challenge, respectively. I do not try to offer a decisive set of objections to the challenges; instead I argue that some objective versions of constructivism, especially Rawls’s constructivism, are not susceptible to the criticisms.

关键词： Euthyphro dilemma moral realism moral constructivism relativism

Influence of Lithium Oxide Addition on the Sintering Behavior and Electrical Conductivity of Gadolinia Doped Ceria

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Journal of Materials Science & Technology 2011年第5期27卷 460-464页

作者： Minfang Han Ze Liu Su zhou lian Yu Union Research Center of Fuel Cell School of Chemical & Environment Engineering University of Mining & Technology(CUMTB) Beijing 100083 China

Ceria-based electrolytes have been widely researched in intermediate-temperature solid oxide fuel cell （SOFC）, which might be operated at 500-600℃. Sintering behavior with lithium oxide as sintering additive and electrical conductivity of gadolinia doped ceria （GdonCe0.902-σ, GDC10） electrolyte was studied in this paper by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical impedance spectroscopy （EIS）. As the results,, the fully dense GDC10 electrolytes are obtained at a low temperature of 800℃ with 2.5 mol% Li20 as sintering additive （called 5LiGDCS00）. During sintering process, lithium oxides adsorbed by around GDC10 surface help to sinter at 800~C and are kept at the grain boundary of GDC10 in the end. The fine grains of 100-400 nm and high electrical conductivity of 0.014 S/cm at 600~C in 5LiGDC800 were achieved, which contributed to the lower sintering temperature and enhanced grain boundary conductivity, respectively. Lithium, staying at grain boundary, reduces the depletion of oxygen vacancies in the space charge layers and increases the oxygen vacancy concentration in the grain boundary, which leads to improve the total electrical conductivity of 5LiGDC800.

关键词： Gadolinia doped ceria Sintering additive Electrical conductivity

In-situ SEM Observation of Monotonic and Cyclic Deformed Structure in Ti-2A1-2.5Zr Alloy

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Journal of Materials Science & Technology 2001年第1期17卷 37-38页

作者： Zhentao YU lian zhou Haichen GU Ju DENG Northwest institute for Nonferrous Metal Research P.O.Box 51Xi’an 710016China Materials Science and Engineering College Xi’an Jiaotong UniversityXi’an 710049China

The SEM observation in situ of monotonic and cyclic deformed structure in Ti-ZA1-2.5Zr alloy was performed. The regularity of slippage, crack nucleation, propagation and the typical dislocation configuration were also investigated. The twin and twist play an important role in maintaining homogeneous deformation in the final plastic deformation stage.

关键词： plastic deformation in situ

Modelling and mapping soil erosion potential in China

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Journal of Integrative Agriculture 2019年第2期18卷 251-264页

作者： TENG Hong-fen HU Jie zhou Yue zhou lian-qing SHI zhou College of Environmental and Resource Sciences Zhejiang UniversityHangzhou 310058P.R.China State Key Laboratory of Soil and Sustainable Agriculture Chinese Academy of SciencesNanjing 210008P.R.China

Soil erosion is an important environmental threat in ***,quantitative estimates of soil erosion in China have rarely been reported in the *** this study,soil loss potential in China was estimated by integrating satellite images,field samples,and ground observations based on the Revised Universal Soil Loss Equation(RUSLE).The rainfall erosivity factor was estimated from merged rainfall data using Collocated CoKriging(ColCOK)and downscaled by geographically weighted regression(GWR).The Random Forest(RF)regression approach was used as a tool for understanding and predicting the relationship between the soil erodibility factor and a set of environment *** results show that the average erosion rate in China is 1.44 t ha^(–1) yr^(–1).More than 60%of the territory in China is influenced by soil erosion limitedly,with an average potential erosion rate less than 0.1 t ha^(–1) yr^(–1).Other unused land and other forested woodlands showed the highest erosion *** estimates are comparable to those of runoff plot *** results provide a useful tool for soil loss assessments and ecological environment protections.

关键词： soil erosion potential RUSLE mapping modelling