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Multiple Constraints (multiple + constraint)
Selected AbstractsMultiple Constraints and Hicksian Complementarity: A Generalization and an Application to Portfolio ChoiceMETROECONOMICA, Issue 1 2003Christian E. WeberArticle first published online: 19 MAR 200 Ian Steedman (Consumption Takes Time: Implications for Economic Theory, Routledge, London, 2001) has shown, among other things, that when a household chooses amounts of time to allocate to competing consumption activities subject to both a money income constraint and a time constraint, at least two consumption activities must have at least one compensated complement each. This paper generalizes Steedman's result in several directions and uses the generalized version to study compensated complementarity among state,dependent consumption levels and asset purchases in a model of portfolio choice under uncertainty. [source] An augmented Lagrange multiplier approach to continuum multislip single crystal thermo,elasto,viscoplasticityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2005C. C. Celigoj Abstract The material and structural behaviour of single crystals is going to be investigated. On the constitutive level the concept of ,generalized standard materials (gsm)' is used to set up the equations for finite deformation multislip single crystal thermo,elasto,viscoplasticity within a continuum slip theory. The only two scalar quantities needed are a thermodynamic potential and a dissipation potential. The resulting evolution equations for the internal (viscoplastic) variables are discretized in time and solved via a backward Euler scheme, using an ,augmented Lagrange multiplier method' for satisfying the multiple constraints, thus circumventing the cumbersome and less robust ,active set strategies'. As a computational reference frame serves the Eulerian setting. The structural behaviour (non-linear coupled thermomechanics) is solved in a staggered algorithm: in an isothermal mechanical phase via q1(displacements)/p0(pressure)/j0(jacobian)-finite elements and in an isogeometric thermal phase via q1(temperatures)-finite elements, followed by an isogeometric and isothermal update phase of the internal variables. Numerical results of the simple isothermal shear test of a single face-centred cubic (fcc) crystal and of the thermomechanical behaviour of a geometrically imperfect strip consisting of initially equally oriented (0/45/30 in Euler angles) fcc-crystals under tension and plane strain conditions are given. Copyright © 2005 John Wiley & Sons, Ltd. [source] Enhancing diversity of species-poor grasslands: an experimental assessment of multiple constraintsJOURNAL OF APPLIED ECOLOGY, Issue 1 2007RICHARD F. PYWELL Summary 1Many grasslands in north-west Europe are productive but species-poor communities resulting from intensive agriculture. Reducing the intensity of management under agri-environment schemes has often failed to increase botanical diversity. We investigated biotic and abiotic constraints on diversification by manipulating seed and microsite availability, soil fertility, resource competition, herbivory and deficiencies in the soil microbial community. 2The effectiveness of 13 restoration treatments was investigated over 4 years in a randomized block experiment established in two productive grasslands in central-east and south-west England. 3Severe disturbance involving turf removal followed by seed addition was the most effective and reliable means of increasing grassland diversity. Disturbance by multiple harrowing was moderately effective but was enhanced by molluscicide application to reduce seedling herbivory and by sowing the hemiparasite Rhinanthus to reduce competition from grasses. 4Low-level disturbance by grazing or slot-seeding was ineffective in increasing diversity. Inoculation with soil microbial communities from species-rich grasslands had no effect on botanical diversity. Nitrogen and potassium fertilizer addition accelerated off-take of phosphorus in cut herbage but did not cause a reduction in soil phosphorus or increase botanical diversity. 5Different grazing management regimes had little impact on diversity. This may reflect the constraining effect of the July hay cut on species dispersal and colonization. 6Synthesis and applications. Three alternative approaches to grassland diversification, with different outcomes, are recommended. (i) High intervention deturfing, which would create patches with low competitive conditions for rapid and reliable establishment of the target community. For reasons of cost and practicality this can only be done over small areas but will form source populations for subsequent spread. (ii) Moderate intervention (harrowing or slot-seeding) over large areas, which would establish a limited number of desirable, generalist species that perform well in restoration. This method is low cost and rapid but the increases in biodiversity are less predictable. (iii) Phased restoration, which would complement the above approaches. Productivity and competition are reduced over 3,5 years using Rhinanthus or fertilizers to accelerate phosphorus off-take. After this time harrowing and seeding should allow a wide range of more specialist species to establish. However, further research is required to determine the long-term effectiveness of these approaches. [source] Adaptive evolution of baker's yeast in a dough-like environment enhances freeze and salinity toleranceMICROBIAL BIOTECHNOLOGY, Issue 2 2010Jaime Aguilera Summary We used adaptive evolution to improve freeze tolerance of industrial baker's yeast. Our hypothesis was that adaptation to low temperature is accompanied by enhanced resistance of yeast to freezing. Based on this hypothesis, yeast was propagated in a flour-free liquid dough model system, which contained sorbitol and NaCl, by successive batch refreshments maintained constantly at 12°C over at least 200 generations. Relative to the parental population, the maximal growth rate (µmax) under the restrictive conditions, increased gradually over the time course of the experiment. This increase was accompanied by enhanced freeze tolerance. However, these changes were not the consequence of genetic adaptation to low temperature, a fact that was confirmed by prolonged selection of yeast cells in YPD at 12°C. Instead, the experimental populations showed a progressive increase in NaCl tolerance. This phenotype was likely achieved at the expense of others traits, since evolved cells showed a ploidy reduction, a defect in the glucose derepression mechanism and a loss in their ability to utilize gluconeogenic carbon sources. We discuss the genetic flexibility of S. cerevisiae in terms of adaptation to the multiple constraints of the experimental design applied to drive adaptive evolution and the technologically advantageous phenotype of the evolved population. [source] A bicriterion approach for routing problems in multimedia networksNETWORKS: AN INTERNATIONAL JOURNAL, Issue 4 2003Joćo C. N. Clķmaco Abstract Routing problems in communication networks supporting multiple services, namely, multimedia applications, involve the selection of paths satisfying multiple constraints (of a technical nature) and seeking simultaneously to "optimize" the associated metrics. Although traditional models in this area are single-objective, in many situations, it is important to consider different, eventually conflicting, objectives. In this paper, we consider a bicriterion model dedicated to calculating nondominated paths for specific traffic flows (associated with video services) in multiservice high-speed networks. The mathematical formulation of the problem and the bicriterion algorithmic approach developed for its resolution are presented together with computational tests regarding an application to video-traffic routing in a high-speed network. The algorithmic approach is an adaptation of recent work by Ernesto Martins and his collaborators, namely, the MPS algorithm. © 2003 Wiley Periodicals, Inc. [source] Electrifying diagrams for learning: principles for complex representational systemsCOGNITIVE SCIENCE - A MULTIDISCIPLINARY JOURNAL, Issue 6 2002Peter C.-H. Abstract Six characteristics of effective representational systems for conceptual learning in complex domains have been identified. Such representations should: (1) integrate levels of abstraction; (2) combine globally homogeneous with locally heterogeneous representation of concepts; (3) integrate alternative perspectives of the domain; (4) support malleable manipulation of expressions; (5) possess compact procedures; and (6) have uniform procedures. The characteristics were discovered by analysing and evaluating a novel diagrammatic representation that has been invented to support students' comprehension of electricity,AVOW diagrams (Amps, Volts, Ohms, Watts). A task analysis is presented that demonstrates that problem solving using a conventional algebraic approach demands more effort than AVOW diagrams. In an experiment comparing two groups of learners using the alternative approaches, the group using AVOW diagrams learned more than the group using equations and were better able to solve complex transfer problems and questions involving multiple constraints. Analysis of verbal protocols and work scratchings showed that the AVOW diagram group, in contrast to the equations group, acquired a coherently organised network of concepts, learnt effective problem solving procedures, and experienced more positive learning events. The six principles of effective representations were proposed on the basis of these findings. AVOW diagrams are Law Encoding Diagrams, a general class of representations that have been shown to support learning in other scientific domains. [source] | ||||||||||