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51.
Artificial added mass instabilities in sequential staggered coupling of nonlinear structures and incompressible viscous flows 总被引:1,自引:0,他引:1
Christiane Förster Wolfgang A. Wall 《Computer Methods in Applied Mechanics and Engineering》2007,196(7):1278-1293
Within this paper the so-called artificial added mass effect is investigated which is responsible for devastating instabilities within sequentially staggered Fluid-structure Interaction (FSI) simulations where incompressible fluids are considered.A discrete representation of the added mass operator MA is given and ‘instability conditions’ are evaluated for different temporal discretisation schemes. It is proven that for every sequentially staggered scheme and given spatial discretisation of a problem, a mass ratio between fluid and structural mass density can be found at which the coupled system becomes unstable. The analysis is quite general and does not depend upon the particular spatial discretisation schemes used. However here special attention is given to stabilised finite elements employed on the fluid partition. Numerical investigations further highlight the results. 相似文献
52.
Kammrath Lara K.; Mendoza-Denton Rodolfo; Mischel Walter 《Canadian Metallurgical Quarterly》2005,88(4):605
Three studies investigated conditions in which perceivers view dispositions and situations as interactive, rather than independent, causal forces when making judgments about another's personality. Study 1 showed that perceivers associated 5 common trait terms (e.g., friendly and shy) with characteristic if...then... (if situation a, then the person does x, but if situation b, then the person does y) personality signatures. Study 2 demonstrated that perceivers used information about a target's stable if...then... signature to infer the target's motives and traits; dispositional judgments were mediated by inferences about the target's motivations. Study 3 tested whether perceivers draw on if...then... signatures when making judgments about Big Five trait dimensions. Together, the findings indicate that perceivers take account of person-situation interactions (reflected in if...then... signatures) in everyday explanations of social behavior and personality dispositions. Boundary conditions are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
53.
The mechanisms governing the solubilizing interactions between zwitterionic/anionic mixed surfactant systems at different
molar fractions of the zwitterionic surfactant (Xzwitter) and neutral or electrically charged unilamellar liposomes were investigated. The mixed systems were formed by N-dodecyl-N,N-dimethylbetaine
and sodium dodecyl sulfate in the presence of piperazine-1,4-bis-(2-ethanesulfonic acid) buffer at pH 7.20. Unilamellar liposomes formed by egg phosphatidylcholine, in some cases together
with stearylamine or phosphatidic acid, were used. Solubilization was detected as a decrease in static light-scattering of
liposomes. Two parameters were regarded as corresponding to the effective surfactant/lipid molar ratios (Re) at which the
surfactant system (i) saturated the liposomes, Resat, and (ii) led to a total solubilization of liposomes, Resol. From these parameters the bilayer/aqueous medium surfactant partition coefficients for the saturation (Ksat) and complete bilayer solubilization (Ksol) were determined. When Xzwitter was 0.40, The Re and K parameters showed a maximum, whereas the critical micellar concentration (CMC) of these systems exhibited
a minimum, regardless of the electrical charge of bilayers. Given that the ability of the surfactant systems to saturate or
solubilize liposomes is inversely related to the Resat and Resol parameters, these capacities appear to be directly correlated with the CMC of the mixed systems. The similarity of both Ksat and Ksol (particularly for Xzwitter=0.2–0.8) suggests that a similar partition equilibrium governs both the saturation and the complete solubilization of bilayers,
the free surfactant concentration (Sa,Sb), remaining almost constant with similar values to the CMC for each mixed system studied. 相似文献
54.
桩土物理模型及结构—桩—土相互作用 总被引:10,自引:1,他引:9
本文将工程中常用的密集打桩土体模拟为正交各向异性弹性体。建立了刚性基础-桩-土这一空间相互作用系统的模型。根据圆柱体柱坐标的极点条件。分别选取了两组位移函数来表征桩基和土的位移,并用子区间法分析了结构-桩-土系统的相互作用地震反应。 相似文献
55.
Subhi K. Hassun Suham H. F. Al-Madfai Mustafa M. F. Al-Jarrah 《Polymer International》1985,17(4):330-333
Ultrasonic absorption, velocity, adiabatic compressibility, relaxation time and relaxation amplitude measurements are reported on poly(vinyl chloride) (PVC) solution in tetrahydrofuran (THF) using pulsed ultrasonic apparatus operating at 2 MHz and 313 K. Results show a linear increase of velocity. density, viscosity, absorption coefficient, relaxation time and relaxation amplitude values with the increase of PVC concentration in THF. In contrast the compressibility decreases with increasing PVC concentration. This suggests interaction between PVC and THF molecules. 相似文献
56.
Building a knowledge-based system is like developing a scientific theory. Although a knowledge base does not constitute a theory of some natural phenomenon, it does represent a theory of how a class of professionals approaches an application task. As when scientists develop a natural theory, builders of expert systems first must formulate a model of the behavior that they wish to understand and then must corroborate and extend that model with the aid of specific examples. Thus there are two interrelated phases of knowledge-base construction: (1) model building and (2) model extension. Computer-based tools can assist developers with both phases of the knowledge-acquisition process. Workers in the area of knowledge acquisition have developed computer-based tools that emphasize either the building of new models or the extension of existing models. The PROTÉGÉ knowledge-acquisition system addresses these two activities individually and facilitates the construction of expert systems when the same general model can be applied to a variety of application tasks. 相似文献
57.
Fatigue at high temperature is a complex phenomenon as it is influenced by a number of time-dependent processes which become
important at elevated temperatures. These processes include creep, oxidation, phase instabilities and dynamic strain ageing
(DSA), acting either independently or synergistically influence fatigue behaviour, often lowering the fatigue life. Current
design approaches employ linear summation of fatigue and creep damage with suitable factors on permissible damage to take
care of uncertainties in interaction between cyclic and time-dependent processes. It is, therefore, important to develop a
deeper understanding of the processes that occur during high temperature fatigue so that realistic life predictions could
be made.
Results on the high temperature fatigue behaviour of austenitic stainless steels, ferritic steels and nickel base alloys are
presented here. The important mechanisms of interaction of high temperature time-dependent processes with fatigue under various
conditions are discussed in detail. Emphasis is placed on cyclic stress response, fatigue life, deformation substructure and
fracture behaviour. This is followed by a review of important life prediction techniques under combined creep-fatigue loading
conditions. Life prediction techniques considered here include linear damage summation, strain range partitioning, ductility
exhaustion approach, frequency modified and frequency separation methods, techniques based on hysteresis energy and damage
rate models, and methods based on crack-cavitation interation models. 相似文献
58.
环境伴随着经济的发展越来越体现了它的重要性,全社会应重视环境、保护环境,以预防为主,加强综合治理,使我们的天更蓝、水更净、草更绿,到处充满着春的意境. 相似文献
59.
地基基础与上部结构共同作用和结构次生应力问题 总被引:1,自引:0,他引:1
本文考虑到上部结构与地基基础共同作用的事实,着重分析上部结构参与共同作用导致的内力重分布——次生应力问题。通过多个理论与实验的结果,对不同地基和基础条件下的次生应力进行了定量分析,探讨了造成次生应力的各种因素以及对建筑结构带来的危害。 相似文献
60.
在互联网发展的基础上,物联网可将信息的交流与沟通扩展到任何物体与物体之间,故其将成为新媒体时代改变人类生活的新变量。在探索智能化信息交互与设计的过程中,文章紧跟物联网的发展趋势,不断思索物联网的崛起给新媒体时代的文化、生产与生活带来的需求、挑战与可能性,同时指出了在这样的背景下,物联网这个新媒体时代的新形势对信息设计所带来的新启示。 相似文献