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A Multigrid Method for a Model of the Implicit Immersed Boundary Equations

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Communications in Computational Physics 2012年第7期12卷 378-400页

作者： robert d.guy Bobby Philip department of Mathematics University of California DavisDavisCA 95616USA Oak Ridge National Laboratory Oak RidgeTN 37831USA

Explicit time stepping schemes for the immersed boundary method require very small time steps in order to maintain *** the equations that arise from an implicit discretization is ***,several different approaches have been proposed,but a complete understanding of this problem is still emerging.A multigrid method is developed and explored for solving the equations in an implicittime discretization of a model of the immersed boundary *** model problem consists of a scalar Poisson equation with conformation-dependent singular forces on an immersed *** model does not include the inertial terms or the incompressibility *** method is more efficient than an explicit method,but the efficiency gain is *** multigrid method alone may not be an effective solver,but when used as a preconditioner for Krylov methods,the speed-up over the explicit-time method is *** example,depending on the constitutive law for the boundary force,with a time step 100 times larger than the explicit method,the implicit method is about 15-100 times more efficient than the explicit method.A very attractive feature of this method is that the efficiency of the multigrid preconditioned Krylov solver is shown to be independent of the number of immersed boundary points.

关键词： Preconditioning implicit methods fluid-structure interaction

An Interface-Capturing Regularization Method for Solving the Equations for Two-Fluid Mixtures

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Communications in Computational Physics 2013年第10期14卷 1322-1346页

作者： Jian du robert d.guy Aaron L.Fogelson Grady B.Wright James P.Keener department of Mathematical Science Florida Institute of TechnologyMelbourneFL 32901USA department of Mathematics University of UtahSalt Lake CityUT 84112USA department of Bioengineering University of UtahSalt Lake CityUT 84112USA department of Mathematics University of California DavisDavisCA 95616USA department of Mathematics Boise State UniversityBoiseID 83725USA

Many problems in biology involve gels which are mixtures composed of a polymer network permeated by a fluid solvent(water).The two-fluid model is a widely used approach to described gel mechanics,in which both network and solvent coexist at each point of space and their relative abundance is described by their volume *** phase is modeled as a continuum with its own velocity and constitutive *** some biological applications,free boundaries separate regions of gel and regions of pure solvent,resulting in a degenerate network momentum equation where the network volume fraction *** overcome this difficulty,we develop a regularization method to solve the two-phase gel equations when the volume fraction of one phase goes to zero in part of the computational domain.A small and constant network volume fraction is temporarily added throughout the domain in setting up the discrete linear equations and the same set of equation is solved *** equations are very poorly conditioned for small values of the regularization parameter,but the multigrid-preconditioned GMRES method we use to solve them is efficient and produces an accurate solution of these equations for the full range of relevant regularization parameter values.

关键词： Gel swelling preconditioner two-fluid model

水分和热胁迫处理对4种针叶树苗木气体交换和水分利用效率的影响

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林业科学 2004年第2期40卷 38-44页

作者：喻方圆徐锡增 robert d.guy 南京林业大学森林资源与环境学院南京210037 加拿大不列颠哥伦比亚大学

以杉木、马尾松、花旗松和北美乔柏为研究对象 ,研究了水分和热胁迫对生长期间苗木的气体交换、瞬间水分利用效率和稳定碳同位素组成 (δ1 3C值 )等生理生态指标的影响 ,结果如下 :(1 )水分胁迫使杉木、马尾松、花旗松和北美乔柏 4个树... 详细信息

以杉木、马尾松、花旗松和北美乔柏为研究对象 ,研究了水分和热胁迫对生长期间苗木的气体交换、瞬间水分利用效率和稳定碳同位素组成 (δ1 3C值 )等生理生态指标的影响 ,结果如下 :(1 )水分胁迫使杉木、马尾松、花旗松和北美乔柏 4个树种的净光合速率显著下降。但热胁迫只影响杉木和北美乔柏的净光合速率 ,对马尾松的净光合速率影响不大。 (2 )对针叶气孔导度的研究发现 ,水分和热胁迫均对马尾松苗木针叶气孔导度有显著影响 ,但对杉木和北美乔柏苗木针叶的气孔导度只有轻微影响。 (3)水分和热胁迫处理对马尾松苗木的瞬间水分利用效率有显著影响 ,但对杉木和北美乔柏的瞬间水分利用效率无显著影响。 (4 )水分胁迫处理对杉木、马尾松、花旗松和北美乔柏 4个树种的稳定碳同位素组成 (δ1 3C值 )均有显著影响 ,随着水分胁迫程度的加深 ,4个树种苗木针叶的δ1 3C值增大 (负值绝对值变小 ) ,说明其永久水分利用效率更高。 (5 )热胁迫对杉木和北美乔柏苗木针叶的δ1 3C值有显著影响 ,且在热胁迫下 ,两树种苗木针叶的δ1 3C值减小 (负值绝对值增大 ) ,即永久水分利用效率下降。但热胁迫对马尾松和花旗松苗木的δ1

关键词：水分胁迫热胁迫针叶树苗木气体交换瞬间水分利用效率稳定碳同位素组成

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水分和热胁迫对5种苗木生长及生物量的影响

南京林业大学学报（自然科学版） 2003年第4期27卷 10-14页

作者：喻方圆徐锡增 robert d.guy 南京林业大学江苏南京210037 加拿大不列颠哥伦比亚大学

以杉木、马尾松、花旗松、北美乔柏和扭叶松为对象,研究了水分和热胁迫对苗木生长期间生长和生物量的影响。结果表明:(1)水分胁迫对杉木、马尾松、花旗松、北美乔柏和扭叶松5个树种的苗高增长量和增长率均有显著影响,但影响的程度因树... 详细信息

以杉木、马尾松、花旗松、北美乔柏和扭叶松为对象,研究了水分和热胁迫对苗木生长期间生长和生物量的影响。结果表明:(1)水分胁迫对杉木、马尾松、花旗松、北美乔柏和扭叶松5个树种的苗高增长量和增长率均有显著影响,但影响的程度因树种而异;(2)热胁迫对苗高增长量和增长率也有一定影响,但不如水分胁迫的影响大。热胁迫对北美乔柏和花旗松的苗高增长量及增长率有显著影响,对其它树种的影响较小;(3)水分胁迫对杉苗生物量的影响不大,热胁迫对杉苗生物量指标的各部分干重有显著影响;热和水分胁迫对马尾松苗木3个生物量指标均有显著影响;热胁迫对花旗松、北美乔柏和扭叶松苗木生物量指标的影响均大于水分胁迫;(4)5个受试树种的根茎比受热和水分胁迫的影响都不大。

关键词：水分热胁迫苗木生长生物量影响因素

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水分和热胁迫对苗木针叶可溶性糖含量的影响

南京林业大学学报（自然科学版） 2004年第5期28卷 1-5页

作者：喻方圆徐锡增 robert d.guy 南京林业大学江苏南京210037 加拿大不列颠哥伦比亚大学

以杉木、马尾松、花旗松和北美乔柏为对象,研究了在水分和热胁迫下,苗木生长期间针叶内可溶性糖含量的变化。结果表明:(1)水分和热胁迫处理对杉木针叶果糖含量的影响不明显,但对杉木针叶葡萄糖和蔗糖的含量却有显著影响。水分胁迫和热... 详细信息

以杉木、马尾松、花旗松和北美乔柏为对象,研究了在水分和热胁迫下,苗木生长期间针叶内可溶性糖含量的变化。结果表明:(1)水分和热胁迫处理对杉木针叶果糖含量的影响不明显,但对杉木针叶葡萄糖和蔗糖的含量却有显著影响。水分胁迫和热胁迫的交互作用对杉苗针叶的蔗糖含量也有显著影响。随着水分胁迫程度的加深,葡萄糖含量提高了11.80%,蔗糖含量提高幅度达318.86%。随着热胁迫程度的加深,葡萄糖含量提高了16.54%,蔗糖含量提高幅度为169.83%;(2)水分胁迫处理对马尾松苗木针叶葡萄糖和蔗糖含量的影响显著,而热胁迫则对葡萄糖和果糖含量影响显著。水分和热胁迫处理对马尾松苗木针叶3种可溶性糖含量的影响均呈上升趋势,其中水分胁迫条件下葡萄糖含量提高了45.92%,果糖含量提高了34.01%,蔗糖含量提高了138.32%。热胁迫条件下葡萄糖含量提高了36.07%,果糖含量提高了28.01%,蔗糖含量提高了22.82%;(3)水分和热胁迫尽管对花旗松苗木针叶的3种可溶性糖含量均有较显著影响,但随着水分胁迫程度的加深,3种可溶性糖含量均未表现出明显的上升趋势。只有随着热胁迫程度的加深,花旗松苗木针叶的3种可溶性糖含量才呈现出上升趋势;(4)水分和热胁迫对北美乔柏苗木针叶可溶性糖含量均有显著影响。其中随着水分胁迫程度的加深,?

关键词：水分胁迫热胁迫可溶性糖含量苗木

水分和热胁迫处理对三个针叶树种苗木叶绿素荧光的影响(英文)

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Journal of Forestry Research 2004年第1期15卷 24-28,J001-J002页

作者：喻方圆 robert d.guy 南京林业大学森林资源与环境学院南京210037 加拿大不列颠哥伦比亚大学林学系

本文测定了三个周期水分和热胁迫处理对杉木、马尾松和北美乔柏苗木叶绿素荧光的影响。结果表明:三个树种的可变荧光与最大荧光之比值(Fv/Fm)对水分胁迫的反应不同。水分胁迫处理后北美乔柏的(Fv/Fm)值大大降低,而杉木的(Fv/Fm)值只有... 详细信息

本文测定了三个周期水分和热胁迫处理对杉木、马尾松和北美乔柏苗木叶绿素荧光的影响。结果表明:三个树种的可变荧光与最大荧光之比值(Fv/Fm)对水分胁迫的反应不同。水分胁迫处理后北美乔柏的(Fv/Fm)值大大降低,而杉木的(Fv/Fm)值只有轻微下降,马尾松的(Fv/Fm)值则没有显著变化。实验结果还表明:热胁迫处理对三个树种的(Fv/Fm)值都有显著影响。就三个水分和热胁迫周期而言,研究发现:在每个水分和热胁迫周期结束时测定的杉木和马尾松(Fv/Fm)值没有显著差异。但随着胁迫时间的延长,北美乔柏的(Fv/Fm)值显著下降。图4表4参20。

关键词：水分胁迫热胁迫针叶树种苗木叶绿素荧光北美乔柏马尾松杉木

不同种源北美香脂杨苗木碳水化合物积累差异分析

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西南林业大学学报（自然科学） 2014年第1期34卷 27-30页

作者：白婷喻方圆 robert d.guy 南京林业大学森林资源与环境学院江苏南京210037 加拿大不列颠哥伦比亚大学

对9个不同种源的北美香脂杨在加拿大温哥华扦插繁殖的苗木枝条进行分析,分别测定带芽枝条可溶性糖、淀粉、糖组分的含量,扦插后萌发的叶干质量和根干质量。结果表明:不同种源枝条的可溶性糖和淀粉含量差异极显著;扦插生根和叶的干质量... 详细信息

对9个不同种源的北美香脂杨在加拿大温哥华扦插繁殖的苗木枝条进行分析,分别测定带芽枝条可溶性糖、淀粉、糖组分的含量,扦插后萌发的叶干质量和根干质量。结果表明:不同种源枝条的可溶性糖和淀粉含量差异极显著;扦插生根和叶的干质量与淀粉含量间呈现正相关关系,与各地的地理位置(纬度、经度、海拔)无显著相关性;不同种源枝条内淀粉含量与其扦插生根特性呈正相关关系。

关键词：北美香脂杨种源碳水化合物含量

Natural parasites in conjunction with behavioral and color traits explain male agonistic behaviors in a lizard

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Current Zoology 2024年第1期70卷 59-69页

作者： Rodrigo Megia-Palma dhanashree Paranjpe robert d.Cooper Pauline Blaimont Barry Sinervo department of Biomedicine and Biotechnology Parasitology UnitUniversidad de Alcala(UAH)E-28805Alcala de HenaresSpain CIBio Centro de Investigagao em Biodiversidade e Recursos GeneticosInBIO Laboratorio AssociadoCampus de VairaoUniversidade do PortoP-4485-661 VairaoPortugal BIOPOLIS Program in Genomics Biodiversity and Land PlanningCIBIOCampus de VairaoP-4485-661 VairaoPortugal Rupa Rahul Bajaj Center for Environment and Art Empress Botanical GardensKavade MalaPuneIndia department of Ecology and Evolutionary Biology University of CaliforniaLos AngelesCA 90095USA department of Biology University of Houston Downtown1Main St.HoustonTX 77002USA department of Ecology and Evolutionary Biology University of CaliforniaSanta CruzCA 95064USA

Male competition conforms to a cost-benefit model,because while aggression may increase reproductive prospects,it can also increase the risk of *** hypothesize that an additional cost in aggressive males would be an increase in parasite load associated with a high energy investment into sexual *** of these infections,in turn,may downmodulate the level of host aggression via energetic *** staged dyadic male contests in the lab to investigate the relationships of multiple parasites with the agonistic behavior of lizard hosts,Sceloporus *** also included both color and behavioral traits from opponents in the analyses because(1)color patches of lizards may serve as intraspecific signals used by conspecifics to assess the quality of opponents,and(2)contests between male lizards fit classical models of escalated aggression,where lizards increase aggression displays in response to an opponent's *** results conform to our hypothesis because male lizards displayed more pushups when they had more ***,some parasites may modulate the levels of aggression because lizards infected by hematic coccidians performed fewer ***,lizards also displayed fewer pushups when both the chroma and size of the opponent's blue patch were *** results thus also supported the role of the blue patch of *** as a sexual armament,because it contributed to the deterrence of aggression from opponent *** revealed that natural parasitic infections in lizard hosts can contribute to their agonistic *** encourage future studies to account for parasites in behavioral testswithlizards.

关键词： Ixodes pacificus Lankesterella sexual selection social interactions ticks

Projection Preconditioner for Solving the Implicit Immersed Boundary Equations

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Numerical Mathematics(Theory,Methods and Applications) 2014年第4期7卷 473-498页

作者： Qinghai Zhang robert d.guy Bobby Philip department of Mathematics University of UtahSalt Lake CityUT 84112USA department ofMathematics University of California DavisDavisCA 95616USA Oak Ridge National Laboratory Oak RidgeTN 37831USA

This paper presents a method for solving the linear semi-implicit immersed boundary equations which avoids the severe time step restriction presented by explicit-time *** Lagrangian variables are eliminated via a Schur complement to form a purely Eulerian saddle point system,which is preconditioned by a projection operator and then solved by a Krylov subspace *** the viewpoint of projection methods,we derive an ideal preconditioner for the saddle point problem and compare the efficiency of a number of simpler preconditioners that approximate this perfect *** low Reynolds number and high stiffness,one particular projection preconditioner yields an efficiency improvement of the explicit IB method by a factor around *** speed-ups over explicit-time method are achieved for Reynolds number below *** speedup increases as the Eulerian grid size and/or the Reynolds number are further reduced.

关键词： Fluid-structure interaction immersed boundary method projection method preconditioning