Plastic multipliers as driving variables of numerical simulation in elastoplasticity

Statics of elasto-plastic media is stated in terms of eigenstrains acting upon a background elastic problem with fixed (initial) stiffness. In order to minimize the number of unknowns and to provide computationally cheap algorithms plastic multipliers are used as main driving variables. Fixed-point type iterations are suggested for computing plastic multipliers within the load increment. Numerical experiments results are shown to be in good correlation with other software results. A range of problems is outlined where the usage of the proposed algorithms can be advantageous.     

受压矩形截面柱在塑性阶段的缺陷敏感性分析

对加载到塑性阶段的矩形截面柱，本文研究了几何缺陷对屈曲的影响，在分析中考虑了弹性卸载的影响，求出了荷载、缺陷大小及分叉模态幅值之间的精确渐近关系式，结果表明在塑性阶段最大承载力对小缺陷非常敏感，但当缺陷大小达到某一值后，可能不存在最大载荷。     

IMPERFECTION SENSITIVITY ANALYSIS OF A RECTANGULAR COLUMN COMPRESSED INTO THE PLASTIC RANGE

I.IntroductionSinceelasticunloadingoccursinthedeformationprocess,theimperfectionsensitivityanalysisofstructuresloadedintotheplasticrangeismuchcomplicated.TheproblemisfirststudiedintheorybyHutchinson(1973,1974)l"ZI.HeusedKoiter'stheorytoanalysethebehaviorpriortotheonsetofelasticunloadingandtoobtaintheloadandthedisplacementatwhichelasticunloadingbegins.NeedlemanandTvergaard(1982)l'jpresentedananalysisofimperfeCtionsensitivityintheplasticrangethatignoreselasticunloading,thatis,substituteshypo-…     

Fracture under initial stresses acting along cracks: Approach, concept and results

The problems of fracture under initial stresses acting along cracks in [A.N. Guz’, Mechanics of Brittle Fracture of Materials with Initial Stresses, Naukova Dumka, Kiev, 1983 (in Russian)] is studied. Other approaches and concepts are also briefly discussed. Results for isolated and near-the-surface cracks are given.     

一类半线性积分微分方程初边值问题的爆破解和全局解

本文研究初边值问题的爆破解和全局解，证明了在ｆ的凸性假设和一定的增长性假定下解在有限时刻爆破，而在ｆ的其他假设下证明了全局解的存在性。     

A proposed complementary pairing mode between single-stranded nucleic acids and β-stranded peptides: A possible pathway for generating complex biological molecules

A structure for a heterologous double-stranded molecule consisting of an oligoribonucleotide and a β-stranded oligopeptide, paired through complementary Watson-Crick-type hydrogen bonding, is proposed. The basis for such complementary pairings between oligoribonucleotides and oligopeptides is the close correspondence of the distances between the side-chains attached to the backbones of the two molecules. Both inter-nucleotide spacing and inter-amino acid side-chain spacing are approximately 3.4 Å. These kinds of interactions may have implications in protein-mediated-RNA splicing. Formation of a heterologous duplex through such a pairing mode could provide a simple coding mechanism for a reciprocal information transfer between oligonucleotides and oligopeptides. Because of its simplicity and versatility, allowing both specific and nonspecific coding, interactions via these kinds of pairing may have been relevant for prebiotic molecular evolution and for generating complex biological molecules.     

On the choice of the initial value of a quadratic spline in positive interpolation

Any quadratic spline with coinciding interpolating points and breakpoints can be uniquely determined by one initial condition. We examine how to choose the initial value in positive interpolation by using a norm of the spline. Monotone interpolation is also considered. The results are illuminated by numerical examples and by an application.     

非线性伪双曲方程初边值问题整体广义解

本文证明了一类非线性伪双曲方程初边值问题整体广义解的存在唯一性．     

一类三阶拟线性发展方程的整体解

本文研究一类三阶拟线性发展方程ｕｔｔ－Δｕｔ＋ｕｔ＝ｎｉ＝１ｘｉσｉ（ｕｘｉ），（ｘ，ｔ）∈Ω×（０，Ｔ）的初边值问题，其中ΩＲｎ（ｎ≥１）为一有界域．证明了只要σｉ（ｓ）∈Ｃ１，σ′ｉ（ｓ）（ｉ＝１，…，ｎ）有界并且初始函数满足一定的条件，则上述问题存在唯一的整体弱解．     

An analysis of the order of Runge-Kutta methods that use an iterative scheme to compute their internal stage values

We employ B-series to analyze the order of Runge-Kutta (RK) methods that use simple iteration, modified Newton iteration or full Newton iteration to compute their internal stage values. Our assumptions about the initial guess for the internal stage values cover a wide range of practical schemes. Moreover, the analytical techniques developed in this paper can be applied in many other similar contexts.This work was supported in part by the Natural Sciences and Engineering Research Council of Canada, the Information Technology Research Centre of Ontario, and the Norwegian Research Council for Science and Humanities.