共查询到20条相似文献，搜索用时 27 毫秒
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Steven J. Sackett James M. Kelley Peter P. Gillis 《Journal of The Franklin Institute》1977,304(1):47-63
Using our constitutive theory for polycrystalline plasticity, we have calculated characteristic yield conditions for several sample materials in which the dependence of the dislocation velocity on stress is given by an empirical power function. The shape of the yield surfaces for these materials varies resembling that of von Mises when the stress exponent is small and that of Tresca when the exponent is large. Additional examples illustrate the ability of the proposed theory to model such phenomena as the development of anisotropy during plastic deformation, material hardening and softening, the occurrence of upper and lower yield points, and a Bauschinger effect. 相似文献
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综述了高温高压条件下岩石和矿物流变性的实验研究结果 ,总结了影响橄榄石集合体流变性能的各种物理和化学因素 .岩石和矿物在高温高压条件下变形的微观机制主要有 2种 :扩散蠕变和位错蠕变 .橄榄石集合体在扩散蠕变机制作用下 ,应变率 ε和差应力之间的关系为线性 ;在位错蠕变机制作用下 ,差应力指数n约等于 3.在相同差应力作用下 ,温度、熔融组分与橄榄石集合体的应变率是正相关的 .含水条件下 ,橄榄石集合体的强度显著降低 .颗粒度对差应力和应变率的影响比较复杂 ,低应变率和小颗粒度对应的差应力指数约等于 1 ;高应变率和粗糙颗粒度时 ,n为 3左右 . 相似文献
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G.E. Pettengill 《Journal of The Franklin Institute》1946,241(6):449-458
The linear logarithmic relations between deformation and temperature and pressure, previously empirical, have been directly derived from the defining equations for compressibility and thermal expansivity and shown to apply to all three stages of every deformation.Gibbs' thermodynamic potential function is shown to lead directly to simple and exact expressions for the energy of change of phase and of deformation within any one phase. The latter, a general equation of state, amounts to a simple relation between the four internal pressures.The derived deformation and energy functions are applied to some experimental data on steel tape which included thermal and relaxation observations.Thermodynamic relations governing both elastic and viscous behavior are developed. Plastic behavior involves both single phase and multiple phase applications of the second law. Precise thermal measurements should give the constants. 相似文献
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慢地震研究中的一些问题 总被引：16，自引：0，他引：16
对慢地震研究中一些问题的研究现状进行了综述 ,包括 :慢地震的定义及特征、慢地震的识别和定位、慢地震孕育的地质构造背景和产生的物理机制、慢地震孕育和发生过程的数值模拟等 ,也涉及到长周期前兆与慢地震的关系、慢地震与应力触发、地震活动性的关系 .笔者认为 ,在中国起动慢地震研究 ,首先应解决慢地震识别、定位和震源机制问题 ,确切验证中国大陆是否存在慢地震 .为此需要加强各个地区的台网观测密度和发展宽频带地震仪、应变仪、GPS、InSAR的综合观测 ,并应加强对多种资料的综合理论分析及模拟的能力 . 相似文献
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E.E. Gdoutos 《Journal of The Franklin Institute》1981,312(5):361-371
An analysis of the plastic enclaves developed around the end points of rigid fiber inclusions embedded in an elastic plate is undertaken. The plate is subjected to a uniform uniaxial stress at any angle of inclination with the axis of the fiber. It is assumed that the material of the plate is elastic-perfectly plastic and that the deformations are small. A singular solution of the stress field in the vicinity of the end points of the fiber is used in conjunction with the Mises yield criterion to obtain the radius of the plastic zone under conditions of plane strain and generalized plane stress. The dependence of the size and shape of the plastic deformation on the orientation of the fiber, the Poisson's ratio of the plate and the state of stress (plane strain or generalized plane stress) is established. 相似文献
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When two selection environments operate upon each other, mutual shaping in a co-evolution along a particular trajectory is one possible outcome. When three selection environments are involved, more complex dynamics can be expected as a result of interactions involving bi-lateral and tri-lateral relations. Three selection environments are specified in the Triple Helix model: (1) wealth generation (industry), (2) novelty production (academia), and (3) public control (government). Furthermore, this model somewhat reduces the complexity by using university-industry-government relations for the specification of the historical conditions of the non-linear dynamics. Whereas the historical analysis informs us about how institutions and institutional arrangements carry certain functions, the evolutionary analysis focuses on the functions of selection environments in terms of outputs. One can no longer expect a one-to-one correspondence between institutions and functions; a statistics is needed for the evaluation of how, for how long, and to what extent institutional arrangements enhance synergies among different selection environments. The empirical contributions to this Triple Helix issue point in the direction of “rich ecologies”: the construction of careful balances between differentiation and integration among the three functions. 相似文献
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W.H. Ingram 《Journal of The Franklin Institute》1925,200(6):757-765
The equations connecting the winding current and diaphragm motion of a telephone receiver under impressed simple harmonic electromotive and mechanical forces are formulated under: (I) The Maxwell flux theory; (2) the magnetizing-winding theory; (3) the Ampèrean resistanceless fixed molecular circuit theory of permanent magnetism; and (4) a general molecular orbital theory of ferromagnetism. On the latter theory it is found that the coupling coefficients M and N in the equations in question are in general different, in counter-distinction to the other three theories as hitherto formulated. The flux theory is shown not to be inconsistent with this result when certain dynamical phase relations are introduced into the static flux-magnetomotive force formula (Ohm's Law analog) always employed in this theory. The Ampèrean rigid circuit theory is criticized as an inadequate dynamical representation of ferromagnetism. The magnetizing-winding theory (dynamical) is reproduced in slightly generalized form. 相似文献
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M. Farshad 《Journal of The Franklin Institute》1978,305(3):125-135
A two-dimensional theory for the incremental deformations of an initially stressed continuum with couple stresses is established in this paper. As applications of theory, the problems of internal instability and wave propagation are studied. It is found that the otherwise non-dispersive waves become dispersive, and additional local modes of buckling and vibratory motion are observed. To complete the theory, a stress function formulation of equations is also presented. 相似文献
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I. Opatowski 《Journal of The Franklin Institute》1942,234(3):239-249
The bases for a theoretical study of wear by friction were given by Th. Reye. Starting from the obvious assumption that the more work done by the friction forces the more material is removed from the worn surface, he was able first to investigate theoretically the mechanics of different types of bearings. The importance of wear by friction is in some mechanical organs, particularly brakes, so great, that the ideas which Reye published 80 years ago still form today the theoretical basis for their design. The present paper is an attempt to go further in these investigations by taking into account two factors which up to now have been neglected: (1) the elastic deformation of the body subjected to wear and (2) the continuous change of its shape in consequence of the wear. The study, which is carried out in a case where the wear effect is particularly evident, the case of brakes, leads to formulas for the determination of the working features of this organ. It explains also in a very clear manner why a certain geometric position of the braking organs is necessary in order to obtain a progressive braking action and why this becomes worse as the wear goes on. 相似文献
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本文采用国家知识产权局专利数据库,基于2006-2015年发明专利合作申请数据,构建了我国发明专利合作网络,测度了发明专利合作网络的网络中心度、结构洞、集聚系数和小世界性等特征指标,分析了我国发明专利合作网络的演化趋势。研究结果表明:我国发明专利合作网络规模扩张迅速,网络合作关系日益增多,连通性越来越强,高等院校和大型国有企业在网络中占据核心位置,发明专利合作网络中的最强连接子网具备明显的小世界特征。 相似文献
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这篇文章通过一些典型例子讨论了在用启示性方法时从原偏微分方程推导来的稳定性条件与从差分方程展开式推导来的稳定性条件间的不同点。结果表明，对于部分有限差分方程，在用启示性方法分析其计算稳定性的过程中最好采用从差分方程推导来的展开式以期得到较合理的结果。在文章的另一部分，反证法的运用表明了从启示性方法推导来的稳定性条件并非全都是必要条件，在应用中应引起注意。 相似文献
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基于共词分析的学科主题演化方法改进研究 总被引：2，自引：0，他引：2
学科主题演化是情报分析人员采用一定的信息技术方法观察主题在时间维度上的发展、变化趋势以及不同主题之间的交互作用,它已成为情报研究的一项重要内容。基于词频或共现词频的共词分析方法难以反映主题词对间更层次的语义关系,针对这一情况,提出一种改进的共词分析方法,该方法体现主题词、主题和文档间的层次语义关系,以更微观、精确的语义层面展现主题演化过程。 相似文献
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绿色供应链中供应商与核心企业的演化博弈模型分析 总被引：2，自引：0，他引：2
为探究绿色供应链中供应商与核心企业的合作关系,在分析供应商和核心企业在不同策略下各自的成本和收益的基础上,运用演化博弈理论构建一个供应商与核心企业的演化博弈模型,模型分析结果显示：系统的演化呈现出“路径依赖”的特征,系统的演化结果与合作成本和收益存在密切关系。核心企业和供应商积极主动实施绿色供应链管理,加强合作与交流,是双方实现长期共赢的唯一途径。 相似文献
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In this paper, a biological economic system which considers a prey-predator system with Holling type II functional response and harvest effort on prey is proposed. By using the differential-algebraic system theory and Hopf bifurcation theory, Hopf bifurcation of the proposed system is investigated. Different from previous researches on the dynamic behaviors of predator-prey systems, our model is described by differential-algebraic equations due to the economic factor. The economic profit is chosen as a positive bifurcation parameter here. It is found that a phenomenon of Hopf bifurcation occurs as the economic profit increases beyond a certain threshold. Lastly, with the help of Matlab software, numerical simulations are carried out to demonstrate the effectiveness of our results. 相似文献
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Robins R 《Social studies of science》2002,32(1):7-35
This paper examines the material relations of risk within a dispute about the hazards of manufacturing human insulin using gene technology, and the r?le played by the referent 'real risk' in the technical performance of risk in that dispute. It draws on recent work in science and technology studies that extends actor-network theory to examine the performance of reality in scientific practice. The multiplicity of risks in the dispute, and the links made and unmade between them, are examined. I argue that in the dispute, risks were contingently linked and separated around a referent 'real risk' that emerged within the recombinant DNA debate of the late 1970s. I contrast my account of risk with realist and relativist accounts, each of which values risk as an abstract entity. In my account, risk's value is contingent upon sets of material relations that link hazards and procedures for their minimization. Risk's realness emerges as some risks are linked and others separated, working a multiple/singular relation in an ontological politics of risk. 相似文献
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