29,669 research outputs found

    Compositional Model Repositories via Dynamic Constraint Satisfaction with Order-of-Magnitude Preferences

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    The predominant knowledge-based approach to automated model construction, compositional modelling, employs a set of models of particular functional components. Its inference mechanism takes a scenario describing the constituent interacting components of a system and translates it into a useful mathematical model. This paper presents a novel compositional modelling approach aimed at building model repositories. It furthers the field in two respects. Firstly, it expands the application domain of compositional modelling to systems that can not be easily described in terms of interacting functional components, such as ecological systems. Secondly, it enables the incorporation of user preferences into the model selection process. These features are achieved by casting the compositional modelling problem as an activity-based dynamic preference constraint satisfaction problem, where the dynamic constraints describe the restrictions imposed over the composition of partial models and the preferences correspond to those of the user of the automated modeller. In addition, the preference levels are represented through the use of symbolic values that differ in orders of magnitude

    Axisymmetric stability criterion for two gravitationally coupled singular isothermal discs

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    Using the two-fluid formalism with the polytropic approximation, we examine the axisymmetric stability criterion for a composite system of gravitationally coupled stellar and gaseous singular isothermal discs (SIDs).Comment: 12 pages, 11 figures, accepted by MNRA

    NΩN\Omega and ΔΩ\Delta\Omega dibaryons in SU(3) chiral quark model

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    The binding energy of the six quark system with strangeness s=-3 is investigated under the chiral SU(3) constituent quark model in the framework of RGMRGM. The calculations of the single NΩN\Omega channel with spin S=2 and the single ΔΩ\Delta\Omega channel with spin S=3 are performed. The results show that both systems could be dibaryons and the interaction induced by the chiral field plays a very important role on forming bound states in the systems considered. The phase shifts and scattering lengths in corresponding channels are also given.Comment: LaTex file with 5 figure

    Theory for solvent, momentum, and energy transfer between a surfactant solution and a vapor atmosphere

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    We develop a complete set of equations governing the evolution of a sharp interface separating a volatile-solvent/nonvolatile-surfactant solution from a vapor atmosphere. In addition to a sorption isotherm equation and the conventional balances for mass, linear momentum, and energy, these equations include a counterpart of the Hertz???Knudsen???Langmuir equation familiar from conventional theories of evaporation-condensation. This additional equation arises from a consideration of configurational forces within a thermodynamical framework. While the notion of configurational forces is well-developed and understood for the description of materials, like crystalline solids, that possess natural reference configurations, very little has been done regarding their role in materials, such as viscous fluids, that do not possess preferred reference states. We therefore provide a comprehensive discussion of configurational forces, the balance of configurational momentum, and configurational thermodynamics that does not require a choice of reference configuration. The general evolution equations arising from our theory account for the thermodynamic structure of the solution and the interface and for sources of dissipation related to the transport of surfactant, momentum, and heat in the solution, the transport of surfactant and momentum within the interface, and the transport of solute, momentum, kinetic energy, and heat across the interface. Due to the complexity of these equations, we provide approximate equations which we compare to relations that appear in the literature.published or submitted for publicationis peer reviewe
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