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On the Dirichlet form of three-dimensional Brownian motion conditioned to hit the origin

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Science China Mathematics 2019年第8期62卷 1477-1492页

作者： Patrick j. Fitzsimmons Liping Li Department of Mathematics University of California at San Diego San Diego CA 92093-0112 USA RCSDS HCMS Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

Our concern in this paper is the energy form induced by an eigenfunction of a self-adjoint extension of the restriction of the Laplace operator to C_c^∞(R^3\{0}).We will prove that this energy form is a regular Diric... 详细信息

Our concern in this paper is the energy form induced by an eigenfunction of a self-adjoint extension of the restriction of the Laplace operator to C_c^∞(R^3\far).We will prove that this energy form is a regular Dirichlet form with core C_c^∞(R^3).The associated diffusion X behaves like a 3-dimensional Brownian motion with a mild radial drift when far from 0,subject to an ever-stronger push toward 0 near that *** particular,faris not a polar set with respect to *** diffusion X is rotation invariant,and admits a skew-product representation before hittingfar:its radial part is a diffusion on(0,∞)and its angular part is a time-changed Brownian motion on the sphere S^*** radial part of X is a"reflected"extension of the radial part of X^0(the part process of X before hittingfar).Moreover,X is the unique reflecting extension of X^0,but X is not a semi-martingale.

关键词： Dirichlet form reflected extension rotationally invariant process Fukushima’s decomposition

Deformation kinking and highly localized nanocrystallization in metastableβ-Ti alloys using cold forging

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journal of Materials Science & Technology 2022年第25期120卷 53-64页

作者： Keer Li W.Chen G.X.Yu j.Y.Zhang S.W.Xin j.X.Liu X.X.Wang j.Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China Northwest Institute for Nonferrous Metal Research Xi’an 710016China Baoji Titanium Industry Co. Ltd.Baoji 721014China

Deformation kinking as an uncommon plastic deformation mechanism has been reported in several materials while the relevant microstructure evolution and grain refinement behavior at a large strain remain unclear so *** this study,the issue was systematically investigated by utilizing cold forging to impose severe plastic deformation(SPD)on Ti-11 V metastableβ-Ti *** is found that the formation of kink bands experiences dislocation gliding,pre-kinking and the ripening of pre-kinks in *** kink bands are subsequently thickened through the coalescence of multiple kink bands in a manner of high *** dislocation slip is developed as a dominant deformation mechanism when deformation kinking is *** resulting grain refinement involves transverse breakdown and longitudinal splitting of dislocation walls and cells,which fragment kink bands into smallβ-*** refinement of theβ-blocks is still governed by dislocation activities,and finally nanograins with a diameter of~15 nm are produced at a large strain of ***,it is revealed that nanocrystallization is highly localized inside kink bands while the outer microstructure maintains original coarse *** localized refinement characterization is ascribed to the intrinsic soft nature of kink bands,shown as low hardness in nanoindentation *** intrinsic softening of kink bands is uncovered to originate from the inner degraded dislocation density evidenced by both experimental measurement and theoretical *** findings enrich fundamental understanding of deformation kinking,and shed some light on exploring the deformation accommodation mechanisms for metal materials at large strains.

关键词： Metastableβ-Ti alloys Deformation kinking Microstructural evolution Grain refinement Dislocations

Maximal number of distinct H-eigenpairs for a two-dimensional real tensor

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Frontiers of Mathematics in China 2013年第1期8卷 85-105页

作者： Kelly j. PEARSON Tan ZHANG Department of Mathematics and Statistics Murray State University Murray KY 42071-0009USA

Based on the generalized characteristic polynomial introduced by j. Canny in Generalized characteristic polynomials [j. Symbolic Comput., 1990, 9（3）： 241-250], it is immediate that for any m-order n-dimensional real tensor, the number of distinct H-eigenvalues is less than or equal to n（m-1）n-1. However, there is no known bounds on the maximal number of distinct H- eigenvectors in general. We prove that for any m ~〉 2, an m-order 2-dimensional tensor sd exists such that d has 2（m - 1） distinct H-eigenpairs. We give examples of 4-order 2-dimensional tensors with six distinct H-eigenvalues as well as six distinct H-eigenvectors. We demonstrate the structure of eigenpairs for a higher order tensor is far more complicated than that of a matrix. Further- more, we introduce a new class of weakly symmetric tensors, called p-symmetric tensors, and show under certain conditions, p-symmetry will effectively reduce the maximal number of distinct H-eigenveetors for a given two-dimensional tensor. Lastly, we provide a complete classification of the H-eigenvectors of a given 4-order 2-dimensional nonnegative p-symmetric tensor. Additionally, we give sufficient conditions which prevent a given 4-order 2-dimensional nonnegative irreducible weakly symmetric tensor from possessing six pairwise distinct H-eigenveetors.

关键词： Symmetric tensor H-eigenpairs

Effects of far-off and close-up transition cow feeding on uterine health,postpartum anestrous interval,and reproductive outcomes in pasture-based dairy cows

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journal of Animal Science and Biotechnology 2020年第2期11卷 493-503页

作者： S.Meier j.K.Kay B.Kuhn-Sherlock A.Heiser M.D.Mitchell M.A.Crookenden M.Vailati Riboni j.j.Loor j.R.Roche DairyNZ Limited Private Bag 3221Hamilton 3240New Zealand AgResearch Hopkirk Research InstituteGrasslands Research CentrePalmerston North 4442New Zealand Centre for Children’s Health Research Queensland University of TechnologyLevel 662 Graham StreetSouth BrisbaneQueensland 4101Australia DairyNZ Limited c/o University of Auckland3A Symonds StAuckland 1010New Zealand Department of Animal Sciences University of IllinoisUrbana 61801USA Ministry for Primary Industries-ManatūAhu Matua Charles Ferguson TowerPipiteaWellington 6140New Zealand School of Biological Sciences University of AucklandPrivate Bag 92019Auckland 1142New Zealand

Background:In seasonal,pasture-based,dairy production systems,cows must recover from calving and become pregnant within two to 3 *** achieve this,the uterus must involute and ovulation must occur and continue at regular *** these processes are affected by the cows’nutritional or metabolic status post-calving,the objective of this study was to evaluate the effect of cow feeding strategies on uterine health,the length of postpartum anestrous interval,and reproductive *** treatments consisted of two feeding strategies during late-lactation and early dry period(far-off period;starting 4-month pre-calving)and three close-up dry period feeding regimes(1-month pre-calving)in a 2×3 factorial *** randomly assigned 150 cows to one of two far-off *** late lactation,the herds(n=75 cows per herd)were either control-fed(Controlfed)or over-fed(Overfed)to achieve a low or high body condition score(4-month pre-calving;BCS;~4.25 and^4.75;10-point scale)at cessation of *** each of these treatments,three feeding levels were applied during the close-up period(1-month pre-calving):~65%(Feed65),~90%(Feed90),or^120%(Feed120)of metabolizable energy(ME)intakes relative to pre-calving ***:Uterine health improved(***(PMN)cells declined)with increased feeding during the close-up period for cows in the Overfed *** reverse was evident for the Controlfed group with the greatest PMN at the highest intakes during the close-up *** postpartum anoestrous interval(PPAI)was shorter in cows from the Overfed group when moderately fed(Feed90)during the close-up period;in comparison,the PPAI was shorter in the Controlfed group,when those cows were overfed in the close-up period(Feed120).The cows in the Overfed treatment had greater conception and pregnancy rates if cows had moderate dry matter intakes(Feed90)during the close-up period;these reproductive variables were less under excessive feed inta

关键词： Close-up Dairy cows far-off Reproduction Transition period

When and how did plate tectonics begin?Theoretical and empirical considerations

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Chinese Science Bulletin 2007年第5期52卷 578-591页

作者： R. j. STERN Geosciences Department University of Texas at Dallas Box 830688 Richardson TX 75083-0688 USA

板 tectonics 在对流传热的披风(岩流圈) 上是地球的热界面层(岩石圈) 的水平运动并且被岩石圈 inking 主要在 subduction 地区驾驶。板 tectonics 是组织的自我的一个突出的例子，远离平衡建筑群系统(SOFFECS ) ，由热界面层的否定快... 详细信息

板 tectonics 在对流传热的披风(岩流圈) 上是地球的热界面层(岩石圈) 的水平运动并且被岩石圈 inking 主要在 subduction 地区驾驶。板 tectonics 是组织的自我的一个突出的例子，远离平衡建筑群系统(SOFFECS ) ，由热界面层的否定快活开车并且由在弯曲岩石圈的驱散控制并且粘滞披风。板 tectonics 是一个不平常的方法让一个硅酸盐行星失去热，当它存在在上仅仅之一大在内部太阳系的五硅酸盐身体。构造活动和热损失的这个模式什么时候开始了，不被知道在地球上。所有硅酸盐行星可能经历了一个短命岩浆海洋阶段。在这团结的、停滞的盖行为是行星的热损失的普通模式以后，与内部，热被融化在更热的早地球中的火山作用和浅 *** 产生了的分层和“热点”正在失去一个不同岩石圈比今天，与更厚的海洋的外壳和更薄的披风岩石圈；如此的岩石圈将比花更长时间目前变得否定地快活，在早地球上建议那板 tectonics 偶发地发生了如果根本。板 tectonics 变得持续(现代风格) 当土足够地冷却了时，融化在散布山脉下面的那解压缩做了薄海洋的外壳，允许海洋的岩石圈在百万年中的一些十个以后变得否定地快活。板 tectonics 什么时候开始了的 Ultimatelythe 问题必须被从地质的记录检索的信息回答。标准因为板 tectonics 的操作包括 ophiolites，蓝片岩 andultra 高的压力变形的带， eclogites，被动边缘，变换差错，不同 cratons 的不同运动的 paleomagneticdemonstration，和在火的岩石中的诊断 geochemicaland 同位素示踪剂的存在。这个记录必须个别地被解释；我解释记录在锝? 从活跃太古代的 tectonics 和类似于板 tectonics 的 magmatismto 一些东西显示构造式样的前进 9 Ga 到有深 subduction 的持续、现代风格板 tectonics—并且强大的平板拉—在 Neoproterozoic 时间开始。

关键词：板块构造形成时间形成机制俯冲前寒武纪地球动力学岩浆作用

An Efficient Real Space Method for Orbital-Free Density-Functional Theory

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Communications in Computational Physics 2007年第2期2卷 334-357页

作者： Carlos j.Garcıa-Cervera Department of Mathematics University of CaliforniaSanta BarbaraCA 93106USA.

We consider the Thomas-Fermi-von Weizsacker energy functional,with the Wang-Teter correction,and present an efficient real space method for Orbital-Free Density Functional *** is proved that the energy minimizer satisfies a second order quasilinear elliptic equation,even at the points where the electron density *** information is used to construct an efficient energy minimization method for the resulting constrained problem,based on the truncated Newton method for unconstrained *** Wang-Teter kernel is analyzed,and its behavior in real space at short and far distances is determined.A second order accurate discretization of the energy is obtained using finite *** efficiency and accuracy of the method is illustrated with numerical simulations in an Aluminium FCC lattice.

关键词： Density functional theory truncated Newton method constrained optimization.

Many public urban parks, but who profits from them? The example of Tabriz, Iran

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Ecological Processes 2015年第1期4卷 72-86页

作者： jürgen Breuste Akbar Rahimi Research Group for Urban and Landscape Ecology Department of Geography and GeologyUniversity of SalzburgSalzburgAustria Department of Landscape Engineering University of TabrizBolvare 29 BahmanTabrizIran

Introduction:Public urban parks are accessible to everyone in a *** time people need to reach a public park influences the accessibility of the *** far away from home are less accessible because of time to spend to reach them than those in the *** green urban infrastructure aims to provide different types of parks(by size and structure)to all urban *** network of parks should allow all inhabitants to have access to parks within close proximity to their ***:This paper aims to investigate the accessibility of parks as related to the social status of the *** was investigated using the example of a clearly socially stratified city(Tabriz,Iran),in which a part of the urban society(by total number and social status)has better or worse access to urban *** example of urban parks shows which services are supplied on site and who the potential users are within an accessible *** services are qualified by structural park indicators and quantified by the quantity of these *** distances are calculated on the basis of the size of the *** distance circles around the parks indicate from where most of the users are coming,depending on park category.A quantification of population as related to potential users by social status in different distances to the parks shows the accessibility of parks for different quantities of inhabitants and different social *** classification of social status(high,middle,and low)was carried out by General Census of statistical center in 2005,informal settlement project data,statistical blocks data,land price in Tabriz municipality,and master and detailed plan ***:Many households do not enjoy government recommended levels of access to public green spaces in Tabriz,and the results highlight the social segregation in park distribution and their ***:The best parks are located in the high social status areas,and the acce

关键词： Ecological services Urban parks Social status Park accessibility

A Comparative in vitro Study on Biomedical Zr-2.5X(X=Nb,Sn) Alloys

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journal of Materials Science & Technology 2014年第4期30卷 299-306页

作者： F.Y.Zhou K.j.Qiu D.Bian Y.F.Zheng j.P.Lin Centre for Biomedical Materials and Engineering Harbin Engineering University Department of Materials Science and Engineering College of EngineeringPeking University State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

Nb and Sn are major alloying elements in Zr alloys. In this study, the microstructure, mechanical properties, corrosion behavior, cytocompatibility and magnetic resonance imaging （MRI） compatibility of Zr-2.5X （X = Nb, Sn） alloys for biomedical application are comparatively investigated. It is found that Zr-2.5Nb alloy has a duplex structure of ~ and ~ phase and Zr-2.5Sn alloy is composed of α phase. Both separate addition of Nb and Sn can strengthen Zr but Nb is more effective in strengthening Zr than Sn. The studied Zr-2.5X （X = Nb, Sn） alloys show improved corrosion resistance compared to pure Zr as indicted by the decreased corrosion current density. The alloying addition of Nb enhances the pitting resistance of Zr, whereas the addition of Sn decreases the pitting resistance of Zr. The extracts of Zr-2.5X alloys produce no significant deleterious effect on fibroblast cells （L-929） and osteoblast-Iike cells （MG 63）, indicating good in vitro cytocompatibility. The Zr-2.5X （X = Nb, Sn） alloys show decreased magnetic susceptibility compared to pure Zr and their magnetic susceptibility is far lower than that of pure Ti and Ti-6AI-4V alloy. Based on these facts, Zr-2.5Nb alloy is more suitable for implant material than Zr-2.5Sn alloy. Sn is not suitable as individual alloying addition for Zr because Sn addition decreases the pitting resistance in physiological solution.

关键词： Zr alloys Mechanical properties Corrosion resistance Cytocompatibility Magnetic susceptibility

A new strategy for ionospheric remote sensing using the 130.4/135.6 nm airglow intensity ratios

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Earth and Planetary Physics 2023年第4期7卷 445-459页

作者： XiaoHan Yin jianQi Qin Larry j.Paxton School of Earth and Space Sciences Peking UniversityBeijing 100871China Applied Physics Laboratory Johns Hopkins UniversityLaurelMD 20723USA

We demonstrate here that global-scale determination of a key ionospheric parameter,the peak height of the F_(2)region(h_(m)F_(2)),can be obtained by making a simple ratio measurement of the atomic oxygen 130.4 and 135.6 nm emissions in the far-ultraviolet nightglow with a nadir-viewing system such as a pair of photometers suitable for flight on a *** further demonstrate that measurements from an altitude that is within the typical range of nighttime h_(m)F_(2)250−450 km can provide the ratios that are needed for retrieval of the h_(m)F_(2).Our study is conducted mostly through numerical simulations by using radiative transfer models of the two emissions coupled with empirical models of the atmosphere and *** results show that the relationship between the h_(m)F_(2)and the intensity ratio is sensitive to the altitude from which the emissions are observed,primarily because of the distinctly different degrees of resonant scattering of the two emissions in the atmosphere.A roughly quadratic relationship can be established for observations from an orbit of~400 km,which enables h_(m)F_(2)*** analysis indicates that the relationship can be affected by the ambient atmospheric conditions through resonant scattering and O2 *** typical nighttime conditions with h_(m)F_(2)250−450 km,retrieval of the h_(m)F_(2)from synthetic observations shows that the typical errors are only a few kilometers(up to~20 km),depending on the accuracy of the ambient conditions predicted by the empirical *** findings pave the way for use of the 130.4/135.6 nm intensity ratios for global-scale monitoring of the nighttime ionosphere at mid to low latitudes.

关键词： nighttime ionosphere far-ultraviolet remote sensing 130.4/135.6 nm airglow intensity ratio peak height of the F_(2)region(h_(m)F_(2)) TIMED observation