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Distribution by Scientific Domains

Business, Economics, Finance and Accounting	33%

Selected Abstracts

Two-dimensional modeling for stability analysis of two-phase stratified flow

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2010
Ghassem Heidarinejad
Abstract The effect of wavelength and relative velocity on the disturbed interface of two-phase stratified regime is modeled and discussed. To analyze the stability, a small perturbation is imposed on the interface. Growth or decline of the disturbed wave, relative velocity, and surface tension with respect to time will be discussed numerically. Newly developed scheme applied to a two-dimensional flow field and the governing Navier,Stokes equations in laminar regime are solved. Finite volume method together with non-staggered curvilinear grid is a very effective approach to capture interface shape with time. Because of the interface shape, for any time advancement, a new grid is performed separately on each stratified field, liquid, and gas regime. The results are compared with the analytical characteristics method and one-dimensional modeling. This comparison shows that solving the momentum equation including viscosity term leads to physically more realistic results. In addition, the newly developed method is capable of predicting two-phase stratified flow behavior more precisely than one-dimensional modeling. It was perceived that the surface tension has an inevitable role in dissipation of interface instability and convergence of the two-phase flow model. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A mass-conservative version of the semi-implicit semi-Lagrangian HIRLAM

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 635 2008
P. H. Lauritzen
Abstract A mass-conservative version of the semi-implicit semi-Lagrangian High-Resolution Limited-Area Model (HIRLAM) is presented. The explicit continuity equation is solved with the so-called cell-integrated semi-Lagrangian (CISL) method. To allow for long time steps, the CISL scheme is coupled with a recently developed semi-implicit time-stepping scheme that involves the same non-complicated elliptic equation as in HIRLAM. Contrarily to the traditional semi-Lagrangian method, the trajectories are backward in the horizontal and forward in the vertical, i.e. cells moving with the flow depart from model layers and arrive in a regular column, and their vertical displacements are computed from continuity of mass and hydrostatic balance in the arrival column. This involves just two-dimensional upstream integrals and allows for a Lagrangian discretization of the energy conversion term in the thermodynamic equation. Preliminary validation of the new model version is performed using an idealized baroclinic wave test case. The accuracy of the new formulation of HIRLAM is comparable to the reference version though it is slightly more diffusive. A main finding is that the new discretization of the energy conversion term leads to more accurate simulations compared to the traditional ,Eulerian' treatment. Copyright © 2008 Royal Meteorological Society [source]

Indefinite oscillators and black-hole evaporation

ANNALEN DER PHYSIK, Issue 10-11 2009
C. Kiefer
Abstract We discuss the dynamics of two harmonic oscillators of which one has a negative kinetic term. This model mimics the Hamiltonian in quantum geometrodynamics, which possesses an indefinite kinetic term. We solve for the time evolution in both the uncoupled and coupled case. We use this setting as a toy model for studying some possible aspects of the final stage of black-hole evaporation. We assume that one oscillator mimics the black hole, while the other mimics Hawking radiation. In the uncoupled case, the negative term leads to a squeezing of the quantum state, while in the coupled case, which includes back reaction, we get a strong entangled state between the mimicked black hole and the radiation. We discuss the meaning of this state. We end by analyzing the limits of this model and its relation to more fundamental approaches. [source]

Indefinite oscillators and black-hole evaporation

Short-term versus Long-term Impact of Managers: Evidence from the Football Industry

BRITISH JOURNAL OF MANAGEMENT, Issue 2 2010
Mathew Hughes
Studies into the impact of top manager change on organization performance have revealed inconsistent findings. Using longitudinal data over a 12-year period on football organizations, we test for the short-term and long-term effects of manager change in comparison to the tenures of incumbent top managers. We find that long incumbent tenures are associated with performance far above the average. But when looking at change events, contrary to theoretical expectations, we find that change in the short term leads to a brief reprieve in poor performance only for performance to deteriorate in the long term as underlying weaknesses once again take hold. Our findings reveal the illusion of a short-term reprieve and the long-term consequences of this illusion. We map several implications for research and practice from our work. [source]

How price increases affect future purchases: The role of mental budgeting, income, and framing

PSYCHOLOGY & MARKETING, Issue 1 2010
Christian Homburg
This article suggests that mental budgeting processes provide afurther understanding of how and to what degree price increases negatively affect a customer's future purchase behavior in a particular category of expenses. Furthermore, the authors analyze how customer income and different price presentation tactics alter this reaction. Results of two experimental studies using both students and non-students show that customer income attenuates the negative effect of a price increase on the likelihood of a future purchase in a particular expense category. As an underlying mechanism, the influence of customer income on future purchase behavior is partially mediated by the degree to which customers engage in mental budgeting. Moreover, mental budgeting strengthens the negative effect of a price increase on a future purchase in the same category of expenses, whereas it does not alter the effect of a price increase on a future purchase in another category. Finally, the framing of a price increase as a percentage versus in absolute terms leads to a lower likelihood of a future category purchase. © 2009 Wiley Periodicals, Inc. [source]