8,265 research outputs found
Asymmetric long memory GARCH: a reply to Hwang's model
Hwang (2001) proposes the FIFGARCH model to represent long memory asymmetric conditional variance. Although he claims that this model nests many previous models, we show that it does not and that the model is badly specified. We propose and alternative specification
Asymmetric long memory garch: a reply to hwang's model
Hwang (Econom. Lett. 71 (2001) 1) proposes the FIFGARCH model to represent long memory asymmetric conditional variances. However, the model is badly specified and does not nest some fractionally integrated heteroskedastic models previously proposed. We suggest an alternative specification and illustrate the results with simulated data.Publicad
The 2-D and 3-D time marching transonic potential flow method for propfans
Recent efforts concentrated on the development of aerodynamic tools for the analysis of rotors at transonic speeds and of configurations involving relative rotation. Three distinct approaches were taken: (1) extension of the lifting surface method of Williams and Hwang (1986) to relative rotation; (2) development of a time marching linear potential method for counter rotation; and (3) development of 2 and 3 dimensional finite volume potential flow schemes for single rotation. Results from each of these approaches are described
Modern Cosmology: Assumptions and Limits
Physical cosmology tries to understand the Universe at large with its origin
and evolution. Observational and experimental situations in cosmology do not
allow us to proceed purely based on the empirical means. We examine in which
sense our cosmological assumptions in fact have shaped our current cosmological
worldview with consequent inevitable limits. Cosmology, as other branches of
science and knowledge, is a construct of human imagination reflecting the
popular belief system of the era. The question at issue deserves further
philosophic discussions. In Whitehead's words, "philosophy, in one of its
functions, is the critic of cosmologies". (Whitehead 1925)Comment: 4 pages, published in JKAS, 45, 65 (2012
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